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Materials, Volume 3, Issue 8 (August 2010) – 17 articles , Pages 4080-4509

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207 KiB  
Article
Influence of the Structural Properties of Mesoporous Silica on the Adsorption of Guest Molecules
by Hanna Ritter, Jan Hinrich Ramm and Dominik Brühwiler
Materials 2010, 3(8), 4500-4509; https://doi.org/10.3390/ma3084500 - 25 Aug 2010
Cited by 25 | Viewed by 9012
Abstract
Amino-functionalized mesoporous silica of different pore sizes and pore system dimensionalities is used as a host material for the inclusion of fluorescein (non-covalent host-guest interaction) and fluorescein isothiocyanate (covalent host-guest interaction). The parameters determining the achievable guest loading depend on the type of [...] Read more.
Amino-functionalized mesoporous silica of different pore sizes and pore system dimensionalities is used as a host material for the inclusion of fluorescein (non-covalent host-guest interaction) and fluorescein isothiocyanate (covalent host-guest interaction). The parameters determining the achievable guest loading depend on the type of host-guest interaction. For covalent interaction, the loading is mainly determined by the accessibility of the adsorption sites, while a more complex situation was encountered in case of non-covalent interactions. In addition to the accessibility of the adsorption sites, an interpretation of the results needs to take into account the confinement of the included guests, as well as the distribution of the adsorption sites. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Pore size distributions (BJH, desorption isotherm) of parent and amino-functionalized mesoporous silicas.</p> Full article ">Figure 2
<p>X-ray diffraction patterns of parent MCM-41(s) (left panel), MCM-41(middle panel), and MCM-48(right panel).</p> Full article ">Figure 3
<p>Amount of included FITC (left) and fluorescein (right) relative to the amount of surface-grafted amino groups for low (hatched bars) and high (black bars) amino contents.</p> Full article ">Figure 4
<p>Schematic snapshots illustrating the reaction of FITC with amino-functionalized MCM-41(s) and MCM-41.</p> Full article ">
617 KiB  
Review
New Trends in Reaction and Resistance to Fire of Fire-retardant Epoxies
by Caroline Gérard, Gaëlle Fontaine and Serge Bourbigot
Materials 2010, 3(8), 4476-4499; https://doi.org/10.3390/ma3084476 - 25 Aug 2010
Cited by 55 | Viewed by 11168
Abstract
This paper focuses on current trends in the flame retardancy of epoxy-based thermosets. This review examines the incorporation of additives in these polymers, including synergism effects. Reactive flame-retardants—which are incorporated in the polymer backbone—are reported and the use of fire-retardant epoxy coatings for [...] Read more.
This paper focuses on current trends in the flame retardancy of epoxy-based thermosets. This review examines the incorporation of additives in these polymers, including synergism effects. Reactive flame-retardants—which are incorporated in the polymer backbone—are reported and the use of fire-retardant epoxy coatings for materials protection is also considered. Full article
(This article belongs to the Special Issue Flame Retardants)
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Figure 1
<p>Number of publications per year for different keyword combinations (Scifinder, April 2010).</p> Full article ">Figure 2
<p>Structure of cage hexahedral silsesquioxane (RSiO<sub>3/2</sub>)<sub>8</sub>.</p> Full article ">Figure 3
<p>SEM micrographs of POSS composites cured with and without Al. (a) Epoxy/POSS, (b) Epoxy/POSS [Al], (c) higher magnification of (b) [<a href="#B28-materials-03-04476" class="html-bibr">28</a>].</p> Full article ">Figure 4
<p>SEM micrographs of residues for Epoxy/POSS[Al] (left) and Epoxy/POSS (right).</p> Full article ">Figure 5
<p>Chemical structures of octaphenyl POSS (left), glycidoxypropyl heptaphenyl POSS (middle) and glycidoxypropylheptaisobutyl POSS (right) [<a href="#B31-materials-03-04476" class="html-bibr">31</a>].</p> Full article ">Figure 6
<p>Mass loss rate <span class="html-italic">versus</span> time for different CNT-containing epoxies (heat flux: 50 kW/m², N<sub>2</sub> atmosphere) [<a href="#B35-materials-03-04476" class="html-bibr">35</a>].</p> Full article ">Figure 7
<p>Monophosphorylated phloroglucinol (left), partially (K4P4OH, middle) and fully (K8P, right) phosphorylated C-methylcalix [<a href="#B4-materials-03-04476" class="html-bibr">4</a>] resorcinarene [<a href="#B52-materials-03-04476" class="html-bibr">52</a>].</p> Full article ">Figure 8
<p>Spiroorthoester containing silicon[<a href="#B56-materials-03-04476" class="html-bibr">56</a>].</p> Full article ">
660 KiB  
Article
Fluorescence and FTIR Spectra Analysis of Trans-A2B2-Substituted Di- and Tetra-Phenyl Porphyrins
by Pınar Şen, Catherine Hirel, Chantal Andraud, Christophe Aronica, Yann Bretonnière, Abdelsalam Mohammed, Hans Ågren, Boris Minaev, Valentina Minaeva, Gleb Baryshnikov, Hung-Hsun Lee, Julien Duboisset and Mikael Lindgren
Materials 2010, 3(8), 4446-4475; https://doi.org/10.3390/ma3084446 - 23 Aug 2010
Cited by 49 | Viewed by 17686
Abstract
A series of asymmetrically substituted free-base di- and tetra-phenylporphyrins and the associated Zn-phenylporphyrins were synthesized and studied by X-ray diffraction, NMR, infrared, electronic absorption spectra, as well as fluorescence emission spectroscopy, along with theoretical simulations of the electronic and vibration structures. The synthesis [...] Read more.
A series of asymmetrically substituted free-base di- and tetra-phenylporphyrins and the associated Zn-phenylporphyrins were synthesized and studied by X-ray diffraction, NMR, infrared, electronic absorption spectra, as well as fluorescence emission spectroscopy, along with theoretical simulations of the electronic and vibration structures. The synthesis selectively afforded trans-A2B2 porphyrins, without scrambling observed, where the AA and BB were taken as donor- and acceptor-substituted phenyl groups. The combined results point to similar properties to symmetrically substituted porphyrins reported in the literature. The differences in FTIR and fluorescence were analyzed by means of detailed density functional theory (DFT) calculations. The X-ray diffraction analysis for single crystals of zinc-containing porphyrins revealed small deviations from planarity for the porphyrin core in perfect agreement with the DFT optimized structures. All calculated vibrational modes (2162 modes for all six compounds studied) were found and fully characterized and assigned to the observed FTIR spectra. The most intense IR bands are discussed in connection with the generic similarity and differences of calculated normal modes. Absorption spectra of all compounds in the UV and visible regions show the typical ethio type feature of meso-tetraarylporphyrins with a very intense Soret band and weak Q bands of decreasing intensity. In diphenyl derivatives, the presence of only two phenyl rings causes a pronounced hypsochromic shift of all bands in the absorption spectra. Time-dependent DFT calculations revealed some peculiarities in the electronic excited states structure and connected them with vibronic bands in the absorption and fluorescence spectra from associated vibrational sublevels. Full article
(This article belongs to the Special Issue Fluorescent Metal-Ligand Complexes)
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Figure 1

Figure 1
<p>Molecular structures of the di- and tetra-phenyl porphyrins.</p> Full article ">Figure 2
<p>ORTEP view of complex <b>4</b> (top) and <b>5</b> (lower), with thermal ellipsoids at the 50% probability level. H-atoms have been removed for clarity (note: the atom numbering is different from <a href="#materials-03-04446-f003" class="html-fig">Figure 3</a> and refers to the bond distances and angles of <a href="#app1-materials-03-04446" class="html-app">Table S2</a>).</p> Full article ">Figure 3
<p>Labeling diagram of 10,20-bis(4-hexoxyphenyl)-porphyrin in TD DFT calculations for FTIR analysis. <span class="html-italic">m</span><sub>α</sub>, <span class="html-italic">m</span><sub>β</sub>, <span class="html-italic">m</span><sub>γ</sub>, <span class="html-italic">m</span><sub>δ</sub> – are numbers for <span class="html-italic">meso-</span>carbon (<span class="html-italic">m</span>) atoms, accepted for all studied porphyrin derivatives, C<sub>α</sub>, C<sub>β</sub> refer to all pyrrole rings.</p> Full article ">Figure 4
<p>A comparison of the experimental and calculated IR spectra of the investigated tetra- and di-phenyl porphyrins (compounds <b>1–3</b>).</p> Full article ">Figure 5
<p>A comparison of the experimental and calculated IR spectra of investigated tetra-and di-phenyl porphyrins complexes with Zink ion (compounds <b>4–6</b>).</p> Full article ">Figure 6
<p>Absorption and emission spectra of the compounds in THF solution. The absorption and fluorescence maxima are collected in <a href="#materials-03-04446-t002" class="html-table">Table 2</a>.</p> Full article ">Figure 7
<p>Fluorescence decay of <b>4</b> in THF solution for two emission wavelengths: Red 607 nm; Blue 657 nm. Excitation at 405 nm.</p> Full article ">Figure 8
<p>HOMO and LUMO molecular orbitals of compound <b>2</b> and <b>5</b>: a) HOMO of <b>2</b>; b) LUMO of <b>2</b>; c) HOMO of <b>5</b>; d) LUMO of <b>5</b>.</p> Full article ">Figure 9
<p>A schematic detailing the ground and first excited singlet state potential curves of compound <b>2</b>.</p> Full article ">
4093 KiB  
Article
Stability Criteria of Fullerene-like Nanoparticles: Comparing V2O5 to Layered Metal Dichalcogenides and Dihalides
by Roi Levi, Maya Bar-Sadan, Ana Albu-Yaron, Ronit Popovitz-Biro, Lothar Houben, Yehiam Prior and Reshef Tenne
Materials 2010, 3(8), 4428-4445; https://doi.org/10.3390/ma3084428 - 18 Aug 2010
Cited by 12 | Viewed by 10624
Abstract
Numerous examples of closed-cage nanostructures, such as nested fullerene-like nanoparticles and nanotubes, formed by the folding of materials with layered structure are known. These compounds include WS2, NiCl2, CdCl2, Cs2O, and recently V2O [...] Read more.
Numerous examples of closed-cage nanostructures, such as nested fullerene-like nanoparticles and nanotubes, formed by the folding of materials with layered structure are known. These compounds include WS2, NiCl2, CdCl2, Cs2O, and recently V2O5. Layered materials, whose chemical bonds are highly ionic in character, possess relatively stiff layers, which cannot be evenly folded. Thus, stress-relief generally results in faceted nanostructures seamed by edge-defects. V2O5, is a metal oxide compound with a layered structure. The study of the seams in nearly perfect inorganic "fullerene-like" hollow V2O5 nanoparticles (NIF-V2O5) synthesized by pulsed laser ablation (PLA), is discussed in the present work. The relation between the formation mechanism and the seams between facets is examined. The formation mechanism of the NIF-V2O5 is discussed in comparison to fullerene-like structures of other layered materials, like IF structures of MoS2, CdCl2, and Cs2O. The criteria for the perfect seaming of such hollow closed structures are highlighted. Full article
(This article belongs to the Special Issue Progress in Nanomaterials Preparation)
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<p>Crystal structures of <b>(a)</b> α-V<sub>2</sub>O<sub>5</sub> [<a href="#B25-materials-03-04428" class="html-bibr">25</a>]. <b>(b)</b> γ -V<sub>2</sub>O<sub>5</sub> [<a href="#B21-materials-03-04428" class="html-bibr">21</a>] (<span class="html-italic"><span class="underline">a</span></span> = 11.51 Å, <span class="html-italic"><span class="underline">b</span></span> = 4.37 Å, <span class="html-italic"><span class="underline">c</span></span> = 3.56 Å; <span class="html-italic"><span class="underline">a</span></span> = 9.94 Å, <span class="html-italic"><span class="underline">b</span></span> = 10.04 Å and <span class="html-italic"><span class="underline">c</span></span> = 3.58 Å, respectively). Black arrows mark the vdW gap.</p> Full article ">Figure 2
<p>Pulsed laser ablation scheme <b>(1)</b> Laser beam. <b>(2)</b> Quartz tube. (<b>3)</b> V<sub>2</sub>O<sub>5</sub> pellet. <b>(4)</b> Recoiling plume. <b>(5)</b> Furnace. <b>(6)</b> Oxygen carrier gas inlet. <b>(7)</b> Cooled collection plate.</p> Full article ">Figure 3
<p>Typical NIF-V<sub>2</sub>O<sub>5</sub> produced by PLA at a furnace temperature of 300 °C <b>(a)</b> Scanning electron microscope (SEM) image. <b>(b)</b> Transmission electron image (TEM) image. (<b>c)</b> A single NIF-V<sub>2</sub>O<sub>5</sub>. <b>(d)</b> Close-up. The dotted frames highlight short defective domains between facets. The dashed frames highlight amorphous-appearing sections of the NIF-V<sub>2</sub>O<sub>5</sub>. The arrow marks the vdW spacing (4.4 Å).</p> Full article ">Figure 4
<p>Schematic formation mechanism of NIF-V<sub>2</sub>O<sub>5</sub> <b>(a)</b> Molten V<sub>2</sub>O<sub>5</sub> nanodroplet <b>(b)</b> Amorphous V<sub>2</sub>O<sub>5</sub> nanoparticle (NP) <b>(c)</b> Partially crystallized amorphous V<sub>2</sub>O<sub>5</sub> nanoparticle with individual facets growing laterally and radially (<b>d)</b> Fully crystalline NIF-V<sub>2</sub>O<sub>5</sub> NP with defective domains between facets.</p> Full article ">Figure 5
<p>TEM images of NP tilted at <b>(a)</b> +30°, <b>(b)</b> 0° and <b>(c)</b> −30° with the frames in close-up <b>(d,e,f)</b>. The blue dashed frame highlights fringes which appear at specific tilt angles. The spacing corresponds to that of the vdW gap (4.4 Å).</p> Full article ">Figure 6
<p>TEM images of PLA products at <b>(a)</b> 50 °C where only small compact V<sub>2</sub>O<sub>5</sub> NP are observed. <b>(b)</b> 50 °C—a cluster of compact V<sub>2</sub>O<sub>5</sub> NP forming a hollow core. (<b>c)</b> 340 °C—highly faceted NIF-V<sub>2</sub>O<sub>5</sub>. <b>(d)</b> Close-up of (c). The dotted frames highlight the short defective domains seaming adjacent facets.</p> Full article ">Figure 7
<p>TEM images of PLA products after a PRT of three hours <b>(a)</b> T = 300 °C, O<sub>2</sub> flow rate-40 mL/min—a collapsed NIF-V<sub>2</sub>O<sub>5</sub> <b>(b)</b> T = 500 °C, O<sub>2</sub> flow rate-40 mL/min - V<sub>2</sub>O<sub>5</sub> platelet (<b>c)</b> T = 300 °C, O<sub>2</sub> flow rate-200 mL/min—a large NIF-V<sub>2</sub>O<sub>5</sub> <b>(d)</b> T = 500 °C, O<sub>2</sub> flow rate-200 mL/min - V<sub>2</sub>O<sub>5</sub> needles.</p> Full article ">Figure 8
<p><b>(a)</b> IF-Cs<sub>2</sub>O close-up [<a href="#B7-materials-03-04428" class="html-bibr">7</a>] <b>(b)</b> Large IF-CdCl<sub>2</sub> [<a href="#B8-materials-03-04428" class="html-bibr">8</a>]. (<b>c)</b> Small IF-CdCl<sub>2</sub> [<a href="#B8-materials-03-04428" class="html-bibr">8</a>] (All figures are reproduced with permission. Copyright Wiley-VCH Verlag GmbH &amp; Co. KGaA).</p> Full article ">Figure 9
<p>Rendering of an Archimedean solid with a Rhombicuboctahedron structure. The triangular facets are highlighted in red.</p> Full article ">Figure 10
<p><b>(a)</b> NT-WS<sub>2</sub>. <b>(b)</b> NT-NiCl<sub>2</sub> [<a href="#B41-materials-03-04428" class="html-bibr">41</a>]. (<b>c)</b> NT-VO<sub>x</sub> [<a href="#B54-materials-03-04428" class="html-bibr">54</a>] (Copyright Wiley-VCH Verlag GmbH &amp; Co. KGaA. Reproduced with permission).</p> Full article ">
3455 KiB  
Review
Carbon Nanotubes Filled with Ferromagnetic Materials
by Uhland Weissker, Silke Hampel, Albrecht Leonhardt and Bernd Büchner
Materials 2010, 3(8), 4387-4427; https://doi.org/10.3390/ma3084387 - 13 Aug 2010
Cited by 124 | Viewed by 15151
Abstract
Carbon nanotubes (CNT) filled with ferromagnetic metals like iron, cobalt or nickel are new and very interesting nanostructured materials with a number of unique properties. In this paper we give an overview about different chemical vapor deposition (CVD) methods for their synthesis and [...] Read more.
Carbon nanotubes (CNT) filled with ferromagnetic metals like iron, cobalt or nickel are new and very interesting nanostructured materials with a number of unique properties. In this paper we give an overview about different chemical vapor deposition (CVD) methods for their synthesis and discuss the influence of selected growth parameters. In addition we evaluate possible growth mechanisms involved in their formation. Moreover we show their identified structural and magnetic properties. On the basis of these properties we present different application possibilities. Some selected examples reveal the high potential of these materials in the field of medicine and nanotechnology. Full article
(This article belongs to the Special Issue Synthesis of Carbon Nanotube)
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Figure 1
<p>The image presents an empty CNT with spherical catalyst (left) bundles of SWCNT (middle) partially Fe-filled MWCNT (right).</p> Full article ">Figure 2
<p>Setup of a typical SSCVD experiment. Ferrocene is sublimated in the preheater zone A at temperature T<math display="inline"> <msub> <mrow/> <mrow> <mi>p</mi> <mi>r</mi> <mi>e</mi> </mrow> </msub> </math>. The decomposition of the precursor and the formation of CNT occurs in the reaction zone B at temperature T<math display="inline"> <msub> <mrow/> <mrow> <mi>r</mi> <mi>e</mi> <mi>a</mi> <mi>c</mi> </mrow> </msub> </math>.</p> Full article ">Figure 3
<p>Setup of an aerosol experiment. The precursor solution is introduced by a nozzle and diluted by a transport gas flow. The solution evaporates in the preheater zone at temperature T<math display="inline"> <msub> <mrow/> <mrow> <mi>p</mi> <mi>r</mi> <mi>e</mi> </mrow> </msub> </math>. In the reaction zones both the hydrocarbon and the metallocene decompose at temperature T<math display="inline"> <msub> <mrow/> <mrow> <mi>r</mi> <mi>e</mi> <mi>a</mi> <mi>c</mi> </mrow> </msub> </math> to form the CNT.</p> Full article ">Figure 4
<p>Setup of a LSCVD experiment. The precursor is prepared in device A. The solvent is evaporated at T<math display="inline"> <msubsup> <mrow/> <mrow> <mi>p</mi> <mi>r</mi> <mi>e</mi> </mrow> <mn>1</mn> </msubsup> </math> in zone Z<math display="inline"> <msub> <mrow/> <mn>1</mn> </msub> </math> and the ferrocene is sublimated at T<math display="inline"> <msubsup> <mrow/> <mrow> <mi>p</mi> <mi>r</mi> <mi>e</mi> </mrow> <mn>2</mn> </msubsup> </math> in zone Z<math display="inline"> <msub> <mrow/> <mn>2</mn> </msub> </math>. The ferrocene mass flow is diluted by additional transport gas flow. In device B the reaction takes place at the temperature T<math display="inline"> <msub> <mrow/> <mrow> <mi>r</mi> <mi>e</mi> <mi>a</mi> <mi>c</mi> </mrow> </msub> </math>. A moving tape allows for the continuous deposition of CNT on substrates.</p> Full article ">Figure 5
<p>The sketch represents three types of filled CNT that possess different degree and distribution of the filling. All types are found in literature, however a long and continuous filling (C) is reported for iron by, e.g., [<a href="#B12-materials-03-04387" class="html-bibr">12</a>,<a href="#B35-materials-03-04387" class="html-bibr">35</a>,<a href="#B41-materials-03-04387" class="html-bibr">41</a>,<a href="#B47-materials-03-04387" class="html-bibr">47</a>,<a href="#B48-materials-03-04387" class="html-bibr">48</a>], cobalt [<a href="#B13-materials-03-04387" class="html-bibr">13</a>,<a href="#B49-materials-03-04387" class="html-bibr">49</a>] and nickel [<a href="#B33-materials-03-04387" class="html-bibr">33</a>,<a href="#B50-materials-03-04387" class="html-bibr">50</a>]. Type A and B are especially interesting for applications where the cavity shall be filled with foreign material.</p> Full article ">Figure 6
<p>Ferrocene molecule as a representative of the general structure of metallocenes. Two cyclic organic molecules (ligands) bind to the central metal atom. In the center is the iron atom (blue), the carbon atoms are black and hydrogen atoms are white respectively.</p> Full article ">Figure 7
<p>The substrate most often consists of a silicon wafer that is covered with a thin oxide layer. One or more interlayers such as alumina, tantalum, copper or tungsten can be employed. On top a thin layer of catalyst is deposited. If needed, the catalyst can be structured. For the formation of alloys more than one catalyst layer can be deposited. Multilayers also do enhance the activity of the catalyst.</p> Full article ">Figure 8
<p>In the graph the mean outer diameter and the diameter distribution of CNT is sketched. Curve (A): small diameter and distribution of unfilled CNT grown on substrates with catalyst. The other curves (B,C,D) represent CNT grown by the floating catalyst method. Curve (B): almost unfilled CNT, Curve (C): well filled CNT, Curve (D): well filled CNT grown by the combination of catalyst supported substrates and floating catalyst. In principle the CNT possess a broader diameter distribution for the floating catalyst method. The given mean diameters are typical values for multi-walled CNT.</p> Full article ">Figure 9
<p>Base growth mode: The metal particles on the surface are exposed to gaseous hydrocarbons, which decompose catalytically on the surface of the catalyst particle. An exothermic decomposition is assumed and a carbon concentration as well as a temperature gradient form [<a href="#B99-materials-03-04387" class="html-bibr">99</a>]. After its decomposition the carbon diffuses from the hot area with a higher concentration to the colder region of the particle and precipitates to form the graphitic structure of the CNT wall. The particle remains attached to the substrate.</p> Full article ">Figure 10
<p>Tip growth mode: The metal particle is only weakly bound to the substrate surface. The decomposition of the hydrocarbons takes place at the upper side of the particle. Again an exothermic decomposition is assumed and the temperature and carbon concentration increases at the top of the particle which gets deformed during this process and detaches from the substrate. The carbon now diffuses to the colder side of the particle and precipitates to form the CNT shells.</p> Full article ">Figure 11
<p>The figure presents the growth process of <span class="html-italic">in-situ</span> filled CNT after [<a href="#B38-materials-03-04387" class="html-bibr">38</a>]. (A) shows the slow growth stage. The carbon shells at the open tip react with carbon clusters from the gas phase. In (B) a larger catalyst particle attaches to the open tip and the fast growth stage starts. The CNT grows fast and the pressure caused by the shells deforms the catalyst particle. In this stage (C) a filling section is formed. If the supply with catalyst material stops the slow growth stage continues.</p> Full article ">Figure 12
<p>The figure shows three schematic cases for the tip of a growing CNT. Case (A) shows a closed tip since each shell is closed by a fullerene-like cap. Case (C) represents an open tip whereas this situation is only favorable under certain conditions. An open tip can be either stabilized by lip-lip-interaction [<a href="#B101-materials-03-04387" class="html-bibr">101</a>] or as result of the so called “scooter” mechanism [<a href="#B102-materials-03-04387" class="html-bibr">102</a>]. The case (B) is sometimes called open [<a href="#B103-materials-03-04387" class="html-bibr">103</a>] because of the missing fullerene cap but it is also regarded as closed due to the particle.</p> Full article ">Figure 13
<p>Open tip base growth: The filling of the cavity results from the diffusion of small metal clusters that are produced in the gas phase. The clusters diffuse a certain distance, eventually forming a continuous filling.</p> Full article ">Figure 14
<p>Steps of the combined growth mechanism. In step A a catalyst particle is formed. Step B describes the decomposition of hydrocarbons on the particle surface. Due to the floating catalyst method catalytic processes occur also in the gas phase forming metal and carbon clusters. In step C the deposition of iron particles at the growing site takes place continuously, thereby the growth mode changes from base to tip growth mode (step C→D). When further material deposits from the gas phase the growth continues (step E) until a stable cap is formed. If the cap is closed so called secondary growth might occur. This is often tip growth since the wettability of the metal catalyst is low and the particles easily detach (step F and G). According to [<a href="#B108-materials-03-04387" class="html-bibr">108</a>]</p> Full article ">Figure 15
<p>(A) Shows a SEM of an as grown sample of iron-filled CNT. In (B) a TEM micrograph of the filling and the carbon shells is presented. In (C) the corresponding diffraction pattern of the iron filling is visible.</p> Full article ">Figure 16
<p>Raman spectra of Fe-CNT [<a href="#B12-materials-03-04387" class="html-bibr">12</a>]. The crystallinity of the CNT structure increases with increasing reaction temperature. The intensity of the D-band decreases relatively to the intensity of the G-band.</p> Full article ">Figure 17
<p>X-Ray diffraction spectra of Fe-CNT. The <span class="html-italic">α</span>-Fe and <span class="html-italic">γ</span>-Fe are found [<a href="#B12-materials-03-04387" class="html-bibr">12</a>].</p> Full article ">Figure 18
<p>Typical Mössbauer spectra of aligned iron-filled CNT on a substrate. Spectra A results from TMS and spectra B from CEMS.</p> Full article ">Figure 19
<p>SEM and AGM of a bulk sample [<a href="#B12-materials-03-04387" class="html-bibr">12</a>]. A large hysteresis and anisotropy can be observed.</p> Full article ">
2064 KiB  
Review
Nanoscale Hollow Spheres: Microemulsion-Based Synthesis, Structural Characterization and Container-Type Functionality
by Henriette Gröger, Christian Kind, Peter Leidinger, Marcus Roming and Claus Feldmann
Materials 2010, 3(8), 4355-4386; https://doi.org/10.3390/ma3084355 - 12 Aug 2010
Cited by 32 | Viewed by 13757
Abstract
A wide variety of nanoscale hollow spheres can be obtained via a microemulsion approach. This includes oxides (e.g., ZnO, TiO2, SnO2, AlO(OH), La(OH)3), sulfides (e.g., Cu2S, CuS) as well as elemental metals (e.g., Ag, Au). [...] Read more.
A wide variety of nanoscale hollow spheres can be obtained via a microemulsion approach. This includes oxides (e.g., ZnO, TiO2, SnO2, AlO(OH), La(OH)3), sulfides (e.g., Cu2S, CuS) as well as elemental metals (e.g., Ag, Au). All hollow spheres are realized with outer diameters of 10-60 nm, an inner cavity size of 2-30 nm and a wall thickness of 2-15 nm. The microemulsion approach allows modification of the composition of the hollow spheres, fine-tuning their diameter and encapsulation of various ingredients inside the resulting “nanocontainers”. This review summarizes the experimental conditions of synthesis and compares them to other methods of preparing hollow spheres. Moreover, the structural characterization and selected properties of the as-prepared hollow spheres are discussed. The latter is especially focused on container-functionalities with the encapsulation of inorganic salts (e.g., KSCN, K2S2O8, KF), biomolecules/bioactive molecules (e.g., phenylalanine, quercetin, nicotinic acid) and fluorescent dyes (e.g., rhodamine, riboflavin) as representative examples. Full article
(This article belongs to the Special Issue Progress in Nanomaterials Preparation)
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Figure 1
<p>Scheme exploiting the synthesis of hollow spheres via: a) hard-template techniques and b) Kirkendall ripening.</p> Full article ">Figure 2
<p>Synthesis of massive nanoparticles via microemulsion techniques with, e.g.,: a) mixing and coalescence of two different <span class="html-italic">w/o</span>-micellar systems, each of them containing a starting material A and B; b) thermal initiation of particle nucleation in a single <span class="html-italic">w/o</span>-micellar system containing two reactants A and B.</p> Full article ">Figure 3
<p>Synthesis of nanoscale hollow spheres via the microemulsion approach at the liquid-to-liquid phase boundary of a <span class="html-italic">w/o</span>-microemulsion due to a first reactant (A) inside the polar micellar phase and a second reactant (B) added to the non-polar dispersant phase.</p> Full article ">Figure 4
<p>Overview of nanoscale hollow spheres with various compositions gained via the microemulsion approach (modified reproduction from [<a href="#B24-materials-03-04355" class="html-bibr">24</a>]).</p> Full article ">Figure 5
<p>Scheme of hollow sphere formation applying <span class="html-italic">w/o</span>- and <span class="html-italic">o/w</span>-microemulsions with AlO(OH) and Au as concrete examples.</p> Full article ">Figure 6
<p>Mean diameter of micelles containing 0.1 M KF-solution in <span class="html-italic">w/o</span>-microemulsions consisting of CTAB, <span class="html-italic">1</span>-hexanol and <span class="html-italic">n</span>-dodecane (left) and size distribution of La(OH)<sub>3</sub> hollow spheres prepared via microemulsion-based synthesis with different volumes and concentration of aqueous KF solution as the polar phase: A) 1 ml of 0.2 M KF; B) 1 ml of 0.1 M KF; C) 2 ml of 0.1 M KF (modified reproduction from [<a href="#B56-materials-03-04355" class="html-bibr">56</a>]).</p> Full article ">Figure 7
<p>STEM and HRTEM images of La(OH)<sub>3</sub> hollow spheres prepared in <span class="html-italic">w/o</span>-microemulsions with different volumes of the water-phase and different amounts of dissolved KF: A) 1 mL of 0.2 M KF; B) 1 mL of 0.1 M KF; C) 2 mL of 0.1 M KF (reproduction from [<a href="#B56-materials-03-04355" class="html-bibr">56</a>]).</p> Full article ">Figure 8
<p>DLS and SEM/STEM overview images showing size and size distribution of as-prepared AlO(OH) and Ag hollow spheres (modified reproduction from [<a href="#B55-materials-03-04355" class="html-bibr">55</a>,<a href="#B61-materials-03-04355" class="html-bibr">61</a>]).</p> Full article ">Figure 9
<p>XRD and HRTEM of AlO(OH) and Ag hollow spheres showing crystallinity and composition of a manifold of particles as well as of selected single hollow spheres (modified reproduction from [<a href="#B55-materials-03-04355" class="html-bibr">55</a>,<a href="#B61-materials-03-04355" class="html-bibr">61</a>]).</p> Full article ">Figure 10
<p>SEM images of partly destroyed SnO<sub>2</sub> hollow spheres with a scheme exploiting the different contrast and charging of destroyed and intact hollow spheres (reproduction from [<a href="#B24-materials-03-04355" class="html-bibr">24</a>]).</p> Full article ">Figure 11
<p>Destruction of hollow spheres under TEM conditions: a−c) Au, 15−20 nm in diameter; (d−f) Au, 40−60 nm in diameter; (g−i) La(OH)<sub>3</sub>, 30−35 nm in diameter (modified reproduction from [<a href="#B54-materials-03-04355" class="html-bibr">54</a>,<a href="#B56-materials-03-04355" class="html-bibr">56</a>]).</p> Full article ">Figure 12
<p>Scanning transmission electron microscopy (STEM) of CuS and TiO<sub>2</sub> hollow spheres [<a href="#B71-materials-03-04355" class="html-bibr">71</a>].</p> Full article ">Figure 13
<p>Scheme showing the encapsulation of compounds (X) prior to hollow sphere formation via reaction of the starting materials (A and B) at the liquid-to-liquid phase boundary of <span class="html-italic">w/o</span>-micelles.</p> Full article ">Figure 14
<p>FT-IR spectra of KSCN@AlO(OH) with the vibration of [SCN]<sup>−</sup> indicated by arrows (spectra obtained with 1 mg and 10 mg (10x) of sample per 400 mg of KBr; spectra of nonfilled AlO(OH) hollow spheres and pure KSCN as references; modified reproduction from [<a href="#B24-materials-03-04355" class="html-bibr">24</a>]).</p> Full article ">Figure 15
<p>Photos of KSCN@AlO(OH) before and after reaction with Fe(NO<sub>3</sub>)<sub>3</sub> and time-dependent increase of Fe(SCN)<sub>3</sub> absorption (at 470 nm) during the reaction (modified reproduction from [<a href="#B24-materials-03-04355" class="html-bibr">24</a>]).</p> Full article ">Figure 16
<p>Photos of K<sub>2</sub>S<sub>2</sub>O<sub>8</sub>@AlO(OH) before and after reaction with MnAc<sub>2</sub> (similar reaction with pure K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> as a reference) and FT-IR spectra of K<sub>2</sub>S<sub>2</sub>O<sub>8</sub>@AlO(OH) (with nonfilled AlO(OH) hollow spheres and pure K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> as references).</p> Full article ">Figure 17
<p>Watch glass prior and subsequent to etching with KF@La(OH)<sub>3</sub> (reproduction from [<a href="#B56-materials-03-04355" class="html-bibr">56</a>]).</p> Full article ">Figure 18
<p>Photos of Phe@AlO(OH) before and after reaction with ninhydrine and FT-IR spectra of Phe@AlO(OH) (vibrations of Phe indicated by arrows; nonfilled AlO(OH) hollow spheres and pure phenylalanine as references; modified reproduction from [<a href="#B24-materials-03-04355" class="html-bibr">24</a>]).</p> Full article ">Figure 19
<p>UV-Vis and FT-IR spectra of Que@AlO(OH) (vibrations of quercetin indicated by arrows; nonfilled AlO(OH) hollow spheres and pure quercetine as references).</p> Full article ">Figure 20
<p>FT-IR spectra of Nic@AlO(OH) (vibrations of nicotinic acid indicated by arrows; nonfilled AlO(OH) hollow spheres and nicotinic acid as references).</p> Full article ">Figure 21
<p>Proving the fluorescence of R6G@AlO(OH) subsequent to the destabilization of the micellar system and advanced washing procedures performed by centrifugation/resuspension from/in isopropanol as well as from/in water (λ<sub>excitation</sub> = 480 nm).</p> Full article ">Figure 22
<p>Course of the R6G photoluminescence intensity upon addition of hydrochloric acid: (1) R6G@AlO(OH); (2) AlO(OH) suspension with R6G added to the outside of the hollow spheres; (3) solution of R6G (modified reproduction from [<a href="#B55-materials-03-04355" class="html-bibr">55</a>]). Only for (1) the complete sequence of emission spectra is shown; for (2) and (3) only the course of the integrated emission intensities is extracted and shown.</p> Full article ">Figure 23
<p>FT-IR spectra of FMN@AlO(OH) (vibrations of FMN indicated by arrows; nonfilled AlO(OH) hollow spheres and NaH(FMN) as references) as well as excitation and emission spectra of FMN@AlO(OH) (λ<sub>emission</sub> = 500 nm, λ<sub>excitation</sub> = 350 nm).</p> Full article ">Figure 23 Cont.
<p>FT-IR spectra of FMN@AlO(OH) (vibrations of FMN indicated by arrows; nonfilled AlO(OH) hollow spheres and NaH(FMN) as references) as well as excitation and emission spectra of FMN@AlO(OH) (λ<sub>emission</sub> = 500 nm, λ<sub>excitation</sub> = 350 nm).</p> Full article ">Figure 24
<p>Future perspectives of nanoscale hollow spheres: properties and potential areas of application.</p> Full article ">
546 KiB  
Review
Emission Spectroscopy as a Probe into Photoinduced Intramolecular Electron Transfer in Polyazine Bridged Ru(II),Rh(III) Supramolecular Complexes
by Travis A. White, Shamindri M. Arachchige, Baburam Sedai and Karen J. Brewer
Materials 2010, 3(8), 4328-4354; https://doi.org/10.3390/ma3084328 - 11 Aug 2010
Cited by 15 | Viewed by 10751
Abstract
Steady-state and time-resolved emission spectroscopy are valuable tools to probe photochemical processes of metal-ligand, coordination complexes. Ru(II) polyazine light absorbers are efficient light harvesters absorbing in the UV and visible with emissive 3MLCT excited states known to undergo excited state energy and [...] Read more.
Steady-state and time-resolved emission spectroscopy are valuable tools to probe photochemical processes of metal-ligand, coordination complexes. Ru(II) polyazine light absorbers are efficient light harvesters absorbing in the UV and visible with emissive 3MLCT excited states known to undergo excited state energy and electron transfer. Changes in emission intensity, energy or band-shape, as well as excited state lifetime, provide insight into excited state dynamics. Photophysical processes such as intramolecular electron transfer between electron donor and electron acceptor sub-units may be investigated using these methods. This review investigates the use of steady-state and time-resolved emission spectroscopy to measure excited state intramolecular electron transfer in polyazine bridged Ru(II),Rh(III) supramolecular complexes. Intramolecular electron transfer in these systems provides for conversion of the emissive 3MLCT (metal-to-ligand charge transfer) excited state to a non-emissive, but potentially photoreactive, 3MMCT (metal-to-metal charge transfer) excited state. The details of the photophysics of Ru(II),Rh(III) and Ru(II),Rh(III),Ru(II) systems as probed by steady-state and time-resolved emission spectroscopy will be highlighted. Full article
(This article belongs to the Special Issue Fluorescent Metal-Ligand Complexes)
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Figure 1
<p>State diagram for [Ru(bpy)<sub>3</sub>]<sup>2+</sup> (bpy = 2,2’-bipyridine). GS = ground state, MLCT = metal-to-ligand charge transfer excited state, <span class="html-italic">k<sub>isc</sub></span> = intersystem crossing rate constant, <span class="html-italic">k<sub>r</sub></span> = radiative decay rate constant, <span class="html-italic">k<sub>nr</sub></span> = non-radiative decay rate constant, <span class="html-italic">k<sub>rxn</sub></span> = photochemical reaction rate constant.</p> Full article ">Figure 2
<p>Polyazine bridging ligands.</p> Full article ">Figure 3
<p>Schematic representation of ED-BL-EA orbital energetics showing excitation followed by intramolecular electron transfer. ED = electron donor, BL = bridging ligand, EA = electron acceptor.</p> Full article ">Figure 4
<p>Polyazine terminal ligands.</p> Full article ">Figure 5
<p>Schematic representation of the orbital energetics within a photoinitiated electron collector of the ED-BL-EC-BL-ED design. ED = electron donor, BL = bridging ligand, EC = electron collector, et = intramolecular electron transfer.</p> Full article ">Figure 6
<p>State diagram for Ru(II),Rh(III) supramolecular assemblies. GS = ground state, MLCT = metal-to-ligand charge transfer excited state, MMCT = metal-to-metal charge transfer excited state, <span class="html-italic">k<sub>isc</sub></span> = intersystem crossing rate constant, <span class="html-italic">k<sub>r</sub></span> = radiative decay rate constant, <span class="html-italic">k<sub>nr</sub></span> = non-radiative decay rate constant, <span class="html-italic">k<sub>et</sub></span> = intramolecular electron transfer rate constant, <span class="html-italic">k<sub>rxn</sub></span> = photochemical reaction rate constant.</p> Full article ">Figure 7
<p>Ru(II),Rh(III) bimetallic complexes containing an aliphatic-linked BL.</p> Full article ">Figure 8
<p>State diagram of [(Me<sub>2</sub>phen)<sub>2</sub>Ru(Mebpy-CH<sub>2</sub>CH<sub>2</sub>-Mebpy)Rh(Me<sub>2</sub>bpy)<sub>2</sub>]<sup>5+</sup> displaying possible excited state deactivating pathways. <span class="html-italic">k<sub>isc</sub></span> = intersystem crossing rate constant, <span class="html-italic">k<sub>r</sub></span> = radiative decay rate constant, <span class="html-italic">k<sub>nr</sub></span> = non-radiative decay rate constant, <span class="html-italic">k<sub>et</sub></span> = electron transfer rate constant, <span class="html-italic">k<sub>en</sub></span> = energy transfer rate constant. Adapted from reference 35.</p> Full article ">Figure 9
<p>Ru(II),Rh(III) bimetallic complexes containing a phenylene-linked polyazine BL.</p> Full article ">Figure 10
<p>Ru(II),Rh(III) bimetallic complexes containing a pyrazine-linked BL.</p> Full article ">Figure 11
<p>Relative E<sup>0-0</sup> energies of excited states associated with mono- and bimetallic species. Values of E<sup>0-0</sup> taken from 77 K emission measurements in 4:1 EtOH/MeOH glass. dpp = 2,3-bis(2-pyridyl)pyrazine, IL = intraligand excited state, LF = ligand field excited state, MLCT = metal-to-ligand charge transfer excited state. Adapted from [<a href="#B40-materials-03-04328" class="html-bibr">40</a>].</p> Full article ">Figure 12
<p>Polyazine-bridged Ru(II),Rh(III),Ru(II) supramolecular complexes with varying components. TL = terminal ligand.</p> Full article ">Figure 13
<p>State diagram of Ru(II),Ru(II) bimetallic (left) and Ru(II),Rh(III),Ru(II) trimetallic (right). GS = ground state, MLCT = metal-to-ligand charge transfer excited state, MMCT = metal-to-metal charge transfer excited state, <span class="html-italic">k<sub>isc</sub></span> = intersystem crossing rate constant, <span class="html-italic">k<sub>r</sub></span> = radiative decay rate constant, <span class="html-italic">k<sub>nr</sub></span> = non-radiative decay rate constant, <span class="html-italic">k<sub>et</sub></span> = intramolecular electron transfer rate constant, <span class="html-italic">k<sub>rxn</sub></span> = photochemical reaction rate constant.</p> Full article ">Figure 14
<p>Emission spectra of the trimetallic complex [{(phen)<sub>2</sub>Ru(dpp)}<sub>2</sub>RhCl<sub>2</sub>]<sup>5+</sup> (<b>―</b>) and the corresponding [(phen)<sub>2</sub>Ru(dpp)Ru(phen)<sub>2</sub>]<sup>4+</sup> model (<b>―</b>) at room temperature in acetonitrile (phen = 1,10-phenanthroline, dpp = 2,3-bis(2-pyridyl)pyrazine). Emission spectra are corrected for PMT response.</p> Full article ">
431 KiB  
Review
Recent Developments in Halogen Free Flame Retardants for Epoxy Resins for Electrical and Electronic Applications
by Muriel Rakotomalala, Sebastian Wagner and Manfred Döring
Materials 2010, 3(8), 4300-4327; https://doi.org/10.3390/ma3084300 - 11 Aug 2010
Cited by 477 | Viewed by 24476
Abstract
The recent implementation of new environmental legislations led to a change in the manufacturing of composites that has repercussions on printed wiring boards (PWB). This in turn led to alternate processing methods (e.g., lead-free soldering), which affected the required physical and chemical properties [...] Read more.
The recent implementation of new environmental legislations led to a change in the manufacturing of composites that has repercussions on printed wiring boards (PWB). This in turn led to alternate processing methods (e.g., lead-free soldering), which affected the required physical and chemical properties of the additives used to impart flame retardancy. This review will discuss the latest advancements in phosphorus containing flame retardants for electrical and electronic (EE) applications and compare them with commercially available ones. The mechanism of degradation and flame retardancy of phosphorus flame retardants in epoxy resins will also be discussed. Full article
(This article belongs to the Special Issue Flame Retardants)
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<p>Application of glass-fibre reinforced composites in Europe (2009) [<a href="#B3-materials-03-04300" class="html-bibr">3</a>].</p> Full article ">Figure 2
<p>Commonly used epoxy resins for EE applications.</p> Full article ">Figure 3
<p>Newly formed bonds during curing of epoxy resins using: <b>(a)</b> amine, <b>(b)</b> phenol-novolac, or <b>(c)</b> anhydride as hardeners.</p> Full article ">Figure 4
<p>Regularly used hardeners for epoxy resins.</p> Full article ">Figure 5
<p>Halogenated flame retardants used for PWB.</p> Full article ">Figure 6
<p>Melamine polyphosphate.</p> Full article ">Figure 7
<p>9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.</p> Full article ">Figure 8
<p>Commercially available aluminium phosphinates.</p> Full article ">Figure 9
<p>Commercially available phosphates.</p> Full article ">Figure 10
<p>Rendering a novolac epoxy resin flame retardant via chemical incorporation of DOPO [<a href="#B54-materials-03-04300" class="html-bibr">54</a>].</p> Full article ">Figure 11
<p>2-(6-Oxido-6H-dibenzo[c,e][1,2]oxa-phosphorin-6-yl)1,4-benzenediol.</p> Full article ">Figure 12
<p>Fyrol PMP.</p> Full article ">Figure 13
<p>Bisphenol A and diaminodiphenylmethane bridged derivatives of DOPO.</p> Full article ">Figure 14
<p>T<sub>g</sub> <span class="html-italic">vs.</span> phosphorus content of DEN438 samples cured with DICY/Fenuron [<a href="#B52-materials-03-04300" class="html-bibr">52</a>].</p> Full article ">Figure 15
<p>Tris(2-hydroxyethyl) isocyanurate and resorcinol bridged derivatives of DOPO and DDPO.</p> Full article ">Figure 16
<p>2,8-dimethyl-phenoxaphosphin-10-oxide.</p> Full article ">Figure 17
<p>DOPO-NQ.</p> Full article ">Figure 18
<p>DOPO and DPPO adducts with terphathaldialdehyde.</p> Full article ">Figure 19
<p>2-(5,5-dimethyl-4-phenyl-2-oxy-1,3,2-dioxaphosphorin-6-yl)-1,4-benzenediol.</p> Full article ">Figure 20
<p>DOPO substituted chain elongator.</p> Full article ">Figure 21
<p>5,10-Dihydrophosphosazine-10-oxide.</p> Full article ">Figure 22
<p>Hardeners used to cure epoxy resins (c<span class="html-italic">f.</span> <a href="#materials-03-04300-t005" class="html-table">Table 5</a>).</p> Full article ">Figure 23
<p>Assembly fabrication of FR-4 printed wiring boards.</p> Full article ">Figure 24
<p>Thermal degradation paths of an amine cured epoxy resin.</p> Full article ">Figure 25
<p>Combustion cycle of a polymer fire. Red marks represent the main approaches to extinguish a fire scenario.</p> Full article ">Figure 26
<p>Gas phase reaction of halogenated flame retardants (X = Cl, Br).</p> Full article ">Figure 27
<p>Market shares of different flame retardants for EE applications (2007) [<a href="#B5-materials-03-04300" class="html-bibr">5</a>].</p> Full article ">Figure 28
<p>Elementary steps of the gas phase flame retardation by triphenylphosphine oxide and Exolit OP. The frame is highlighting the process of hydrogen scavenging. M is a third body species [<a href="#B40-materials-03-04300" class="html-bibr">40</a>].</p> Full article ">Figure 29
<p>Proposed mechanism for flame retardant reactivity of <b>DOPO</b> in the gas phase.</p> Full article ">
324 KiB  
Article
Preparation of Fast Dissolving Films for Oral Dosage from Natural Polysaccharides
by Yoshifumi Murata, Takashi Isobe, Kyoko Kofuji, Norihisa Nishida and Ryosei Kamaguchi
Materials 2010, 3(8), 4291-4299; https://doi.org/10.3390/ma3084291 - 9 Aug 2010
Cited by 38 | Viewed by 12946
Abstract
Fast-dissolving films (FDFs) were prepared from natural polysaccharides, such as pullulan, without heating, controlling the pH, or adding other materials. The release profiles of model drugs from the films were investigated. In the absence of a drug, the casting method and subsequent evaporation [...] Read more.
Fast-dissolving films (FDFs) were prepared from natural polysaccharides, such as pullulan, without heating, controlling the pH, or adding other materials. The release profiles of model drugs from the films were investigated. In the absence of a drug, the casting method and subsequent evaporation of the solvent resulted in the polysaccharide forming a circular film. The presence of drugs (both their type and concentration) affected film formation. The thickness of the film was controllable by adjusting the concentration of the polysaccharide, and regular unevenness was observed on the surface of 2% pullulan film. All films prepared with polysaccharides readily swelled in dissolution medium, released the incorporated compound, and subsequently disintegrated. The release of dexamethasone from the films was complete after 15 min, although this release rate was slightly slower than that of pilocarpine or lidocaine. Therefore, FDFs prepared from polysaccharides could be promising candidates as oral dosage forms containing drugs, and would be expected to show drug dissolution in the oral cavity. Full article
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<p>Pictures of FDFs prepared with polysaccharides containing various model compounds.</p> Full article ">Figure 2
<p>Surface structure of FDFs observed using a three-dimensional profilemeter. Figures show the center of the FDF (square area; 5 × 5 mm). Each color represents the depth of unevenness.</p> Full article ">Figure 3
<p>Release profiles of PC (a) and LD (b) from FDFs in physiological saline.</p> Full article ">Figure 4
<p>Release profiles of DM from FDFs in physiological saline.</p> Full article ">Figure 5
<p>Release profiles of LD and DM from FDFs in phosphate-buffered saline (pH 7.4).</p> Full article ">Figure 6
<p>Release profiles of LF from FDFs in physiological saline.</p> Full article ">
2737 KiB  
Article
Metal Dependence of Signal Transmission through MolecularQuantum-Dot Cellular Automata (QCA): A Theoretical Studyon Fe, Ru, and Os Mixed-Valence Complexes
by Ken Tokunaga
Materials 2010, 3(8), 4277-4290; https://doi.org/10.3390/ma3084277 - 6 Aug 2010
Cited by 15 | Viewed by 9760
Abstract
Dynamic behavior of signal transmission through metal complexes [L5M-BL-ML5]5+ (M=Fe, Ru, Os, BL=pyrazine (py), 4,4’-bipyridine (bpy), L=NH3), which are simplified models of the molecular quantum-dot cellular automata (molecular QCA), is discussed from the viewpoint of one-electron theory, density functional [...] Read more.
Dynamic behavior of signal transmission through metal complexes [L5M-BL-ML5]5+ (M=Fe, Ru, Os, BL=pyrazine (py), 4,4’-bipyridine (bpy), L=NH3), which are simplified models of the molecular quantum-dot cellular automata (molecular QCA), is discussed from the viewpoint of one-electron theory, density functional theory. It is found that for py complexes, the signal transmission time (tst) is Fe(0.6 fs) < Os(0.7 fs) < Ru(1.1 fs) and the signal amplitude (A) is Fe(0.05 e) < Os(0.06 e) < Ru(0.10 e). For bpy complexes, tst and A are Fe(1.4 fs) < Os(1.7 fs) < Ru(2.5 fs) and Os(0.11 e) < Ru(0.12 e) <Fe(0.13 e), respectively. Bpy complexes generally have stronger signal amplitude, but waste longer time for signal transmission than py complexes. Among all complexes, Fe complex with bpy BL shows the best result. These results are discussed from overlap integral and energy gap of molecular orbitals. Full article
(This article belongs to the Special Issue SPM in Materials Science)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(a) Two degenerate states of QCA cell, "0" and "1". Some applications of QCA cell: (b) QCA logic gate (AND gate) and (c) QCA signal transmission wire. Charge of open circles and triangles is more positive relative to that of filled circles and triangles.</p> Full article ">Figure 2
<p>Simplified two site model of QCA cell and schematic picture of signal transmission between two units, unit 1 (U1) and unit 2 (U2). <span class="html-italic">A</span>, <span class="html-italic">T</span>, and <math display="inline"> <msub> <mi>t</mi> <mi>st</mi> </msub> </math> are the signal amplitude, the signal period, and the signal transmission time, respectively.</p> Full article ">Figure 3
<p>Schematic structures of <b>py</b> and <b>bpy</b> complexes. Input <span class="html-italic">q</span> is placed at a distance <math display="inline"> <msub> <mi>r</mi> <mrow> <mi>q</mi> <mo>-</mo> <mi mathvariant="normal">M</mi> </mrow> </msub> </math> = 10 Å.</p> Full article ">Figure 4
<p>HOMO and LUMO with <span class="html-italic">β</span> spin of <b>py</b> complex when <math display="inline"> <mrow> <mi>q</mi> <mo>=</mo> <mo>+</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> <mspace width="0.166667em"/> </mrow> </math>e (left) and <math display="inline"> <mrow> <mi>q</mi> <mo>=</mo> <mo>-</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> <mspace width="0.166667em"/> </mrow> </math>e (right).</p> Full article ">Figure 5
<p>HOMO and LUMO with <span class="html-italic">β</span> spin of <b>bpy</b> complex when <math display="inline"> <mrow> <mi>q</mi> <mo>=</mo> <mo>+</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> <mspace width="0.166667em"/> </mrow> </math>e (left) and <math display="inline"> <mrow> <mi>q</mi> <mo>=</mo> <mo>-</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> <mspace width="0.166667em"/> </mrow> </math>e (right).</p> Full article ">Figure 6
<p>Dynamic behaviors of <b>py</b> complex upon the switch of input (<span class="html-italic">q</span> = <math display="inline"> <mrow> <mo>+</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> <mspace width="0.166667em"/> </mrow> </math>e → <span class="html-italic">q</span> = <math display="inline"> <mrow> <mo>-</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> <mspace width="0.166667em"/> </mrow> </math>e).</p> Full article ">Figure 7
<p>Dynamic behaviors of <b>bpy</b> complex upon the switch of input (<span class="html-italic">q</span> = <math display="inline"> <mrow> <mo>+</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> <mspace width="0.166667em"/> </mrow> </math>e → <span class="html-italic">q</span> = <math display="inline"> <mrow> <mo>-</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> <mspace width="0.166667em"/> </mrow> </math>e).</p> Full article ">
1755 KiB  
Review
Molecular Dynamics in Two-Dimensional Supramolecular Systems Observed by STM
by Shinobu Uemura, Ryota Tanoue, Neval Yilmaz, Akihiro Ohira and Masashi Kunitake
Materials 2010, 3(8), 4252-4276; https://doi.org/10.3390/ma3084252 - 6 Aug 2010
Cited by 50 | Viewed by 12277
Abstract
Since the invention of scanning tunneling microscopy (STM), 2D supramolecular architectures have been observed under various experimental conditions. The construction of these architectures arises from the balance between interactions at the medium-solid interface. This review summarizes molecular motion observed in 2D-supramolecular structures on [...] Read more.
Since the invention of scanning tunneling microscopy (STM), 2D supramolecular architectures have been observed under various experimental conditions. The construction of these architectures arises from the balance between interactions at the medium-solid interface. This review summarizes molecular motion observed in 2D-supramolecular structures on surfaces using nanospace resolution STM. The observation of molecular motion on surfaces provides a visual understanding of intermolecular interactions, which are the major driving force behind supramolecular arrangement. Full article
(This article belongs to the Special Issue SPM in Materials Science)
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<p>Thermodynamic equilibriums between a homogeneous solution, an air–liquid interface and a solid–liquid interface.</p> Full article ">Figure 2
<p>Four isothermal adsorption states against adsorption strength.</p> Full article ">Figure 3
<p>Molecular motion of fullerene C<sub>60</sub> on various substrates. Adapted with permission from reference [<a href="#B18-materials-03-04252" class="html-bibr">18</a>]. Copyright 2004 American Chemical Society.</p> Full article ">Figure 4
<p><span class="html-italic">In situ</span> STM images and corresponding models of the self-ordering process of TMPyP on I/Au(111) captured at each step of adsorption and ordering. Adapted with permission from reference [<a href="#B12-materials-03-04252" class="html-bibr">12</a>]. Copyright 1995 American Chemical Society.</p> Full article ">Figure 5
<p>Sequential STM images (A-C) of a phenylene ethynylene derivative (D) at the solution–HOPG interface. Reproduced with permission from reference [<a href="#B25-materials-03-04252" class="html-bibr">25</a>]. Copyright Wiley-VCH Verlag GmbH &amp; Co. KGaA.</p> Full article ">Figure 6
<p><span class="html-italic">In-situ</span> STM images and a schematic illustration of CyDs at the aqueous solution–Au(111) interface controlled by electrochemical potential. Reprinted with permission from reference [<a href="#B32-materials-03-04252" class="html-bibr">32</a>]. Copyright 2003 American Chemical Society.</p> Full article ">Figure 7
<p>Chemical structure (A), STM images (B and D) and schematic illustrations (C and E) of TMA order-order transitions at the aqueous solution–Au(111) interface under the electrochemical control. Reproduced from reference [<a href="#B33-materials-03-04252" class="html-bibr">33</a>] by permission of The Royal Society of Chemistry.</p> Full article ">Figure 8
<p>STM image and tentative model of coronene and iodine co-adsorption at the aqueous solution–Au(111) interface under the electrochemical potential control. Reproduced from reference [<a href="#B40-materials-03-04252" class="html-bibr">40</a>] by permission ECS―The Electrochemical Society.</p> Full article ">Figure 9
<p>Dynamic processes during co-adsorption of perfluorinated and non-fluorinated isophthalic acid derivatives on HOPG. Reproduced with permission from reference [<a href="#B41-materials-03-04252" class="html-bibr">41</a>]. Copyright Wiley-VCH Verlag GmbH &amp; Co. KGaA.</p> Full article ">Figure 10
<p>Dynamic processes of a hexapod molecule at the solution–HOPG interface. Reprinted with permission from reference [<a href="#B43-materials-03-04252" class="html-bibr">43</a>]. Copyright 2009 American Chemical Society.</p> Full article ">Figure 11
<p>STM images (A and B) and tentative models (C and D) of self-assembled structures of guanines. Without (A and C) and with (B and D) potassium. Reproduced with permission from reference [<a href="#B45-materials-03-04252" class="html-bibr">45</a>]. Copyright Wiley-VCH Verlag GmbH &amp; Co. KGaA.</p> Full article ">Figure 12
<p>STM images of fullerene C<sub>60</sub> adlayers on Au(111). (A) The adlayers were prepared by the transfer of L films. STM observation was in aqueous electrolyte solution at room temperature. (B) The adlayers were prepared by the sublimation. STM was conducted in UHV at 4.5 K. The observation at room temperature is shown as the inset. Reprinted with permission from reference [<a href="#B58-materials-03-04252" class="html-bibr">58</a>]. Copyright Springer.</p> Full article ">Figure 13
<p>UHV-STM images (A-D) and tentative models (E and F) of propeller-shaped hexa-<span class="html-italic">tert</span>-butyl decacyclene on Cu(100) at room temperature. Reproduced from reference [<a href="#B63-materials-03-04252" class="html-bibr">63</a>] by permission of the American Association for the Advancement of Science.</p> Full article ">Figure 14
<p>Sequential STM images (A, C-I) and the schematic illustration (B) of a porphyrin derivative on Cu(111) at different temperatures. Reproduced with permission from reference [<a href="#B64-materials-03-04252" class="html-bibr">64</a>]. Copyright Wiley-VCH Verlag GmbH &amp; Co. KGaA.</p> Full article ">Figure 15
<p>STM images of double-decker complexes at the solution–HOPG interface. Reprinted with permission from reference [<a href="#B74-materials-03-04252" class="html-bibr">74</a>]. Copyright 2009 American Chemical Society.</p> Full article ">
815 KiB  
Review
Charge-Transfer Interactions in Organic Functional Materials
by Hsin-Chieh Lin and Bih-Yaw Jin
Materials 2010, 3(8), 4214-4251; https://doi.org/10.3390/ma3084214 - 5 Aug 2010
Cited by 18 | Viewed by 11526
Abstract
Our goal in this review is three-fold. First, we provide an overview of a number of quantum-chemical methods that can abstract charge-transfer (CT) information on the excited-state species of organic conjugated materials, which can then be exploited for the understanding and design of [...] Read more.
Our goal in this review is three-fold. First, we provide an overview of a number of quantum-chemical methods that can abstract charge-transfer (CT) information on the excited-state species of organic conjugated materials, which can then be exploited for the understanding and design of organic photodiodes and solar cells at the molecular level. We stress that the Composite-Molecule (CM) model is useful for evaluating the electronic excited states and excitonic couplings of the organic molecules in the solid state. We start from a simple polyene dimer as an example to illustrate how interchain separation and chain size affect the intercahin interaction and the role of the charge transfer interaction in the excited state of the polyene dimers. With the basic knowledge from analysis of the polyene system, we then study more practical organic materials such as oligophenylenevinylenes (OPVn), oligothiophenes (OTn), and oligophenylenes (OPn). Finally, we apply this method to address the delocalization pathway (through-bond and/or through-space) in the lowest excited state for cyclophanes by combining the charge-transfer contributions calculated on the cyclophanes and the corresponding hypothetical molecules with tethers removed. This review represents a step forward in the understanding of the nature of the charge-transfer interactions in the excited state of organic functional materials. Full article
(This article belongs to the Special Issue Organic Electronic Materials)
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<p>Distance dependence of the calculated <b>(a)</b> local exciton (LE) and charge-transfer exciton (CTE) energies <b>(b)</b> exciton coupling (2V) and <b>(c)</b> interaction energies of the electron transfer (t<sub>e</sub>) and hole transfer (t<sub>h</sub>) of various polyene dimers, with N = 6 (black), 10 (blue), 20 (red), and 40 (green) based on the four-orbital CM model (model 2 in <a href="#materials-03-04214-f011" class="html-scheme">Scheme 1</a>) [<a href="#B46-materials-03-04214" class="html-bibr">46</a>]. (Note that although we provide a detail distance dependence data, the van der Waals radius of carbon is 1.7 Å). Reproduced with permission from American Chemical Society.</p> Full article ">Figure 2
<p>Distance dependence of the two low-lying excited states of various polyene dimers, with N = 6 <b>(a)</b>, 10 <b>(b)</b>, 20 <b>(c)</b>, 40 <b>(d)</b> calculated by model 1 (black), model 2 (blue) and model 3 (red line). The insets show the evolution of the energy gap of the two transitions as a function of the intermolecular distance (calculated by model 1). For clarity the data calculated by model 3, we specify the exact values at 3.0 and 5.0 Å for N = 6 (S<sub>1</sub>:4.657 eV, 4.827 eV; S<sub>2</sub>:5.264 eV, 5.098 eV), 10 (S<sub>1</sub>:3.580 eV, 3.722 eV; S<sub>2</sub>:4.174 eV, 4.037 eV), 20 (S<sub>1</sub>:2.814 eV, 2.893 eV; S<sub>2</sub>:3.227 eV, 3.153 eV), 40 (S<sub>1</sub>:2.558 eV, 2.596 eV; S<sub>2</sub>:2.784 eV, 2.748 eV) [<a href="#B46-materials-03-04214" class="html-bibr">46</a>]. Reproduced with permission from American Chemical Society.</p> Full article ">Figure 3
<p>Dependence of the CT wave function (percentage) of lowest excited-state (blue) and second excited-state (red) as a function of chain size, with interchain distance d = 3.6 Å (upper), 3.8 Å (middle), 4.0 Å (lower), calculated by the CM model [<a href="#B46-materials-03-04214" class="html-bibr">46</a>]. Reproduced with permission from American Chemical Society.</p> Full article ">Figure 4
<p>Contour polts of the CT exciton (in percentage) as a function of interchain distance (x axis) and chain size (y axis) of the first (right) and second (left) excited states in polyene dimers calculated using model 1 [<a href="#B46-materials-03-04214" class="html-bibr">46</a>]. Reproduced with permission from American Chemical Society.</p> Full article ">Figure 5
<p>Chain size dependence of the three low-lying excited states of polyene dimers with interchain distance of 3.8 Å (calculated by model 1).</p> Full article ">Figure 6
<p>Dependence of the CT wave function (percentage) of lowest excited-state (blue) and second excited-state (red) for <b>(a)</b> PV<sub>n</sub> <b>(b)</b> T<sub>n</sub> and <b>(c)</b> P<sub>n</sub> systems as a function of chain size, with interchain distance d = 3.6 Å (upper), 3.8 Å (middle), 4.0 Å (lower), calculated by the CM model.</p> Full article ">Figure 7
<p>Various truncated CM model for molecule <b>4</b> with different optimized geometries for AM1 geometry (blue) and DFT geometry (red) [<a href="#B47-materials-03-04214" class="html-bibr">47</a>]. Reproduced with permission from American Chemical Society.</p> Full article ">Figure 8
<p>Orbital diagram for “through-space’’ and “through-bond’’ interaction in the class I/II cyclophandienes with C<sub>2</sub> symmetry element [<a href="#B47-materials-03-04214" class="html-bibr">47</a>]. Reproduced with permission from American Chemical Society.</p> Full article ">Figure 9
<p>Hückel MO’s of the J-aggregated biphenylenes, their energies, perimeter labels, and the five singly excited configurations responsible for the S<sub>1</sub>, N<sub>1</sub>, N<sub>2</sub>, P<sub>1</sub>, and P<sub>2</sub> states. [<a href="#B51-materials-03-04214" class="html-bibr">51</a>]. Reproduced with permission from American Chemical Society.</p> Full article ">Figure 10
<p>State correlation diagrams of biphenylene, H-aggregrated biphenylene dimer (d = 4 Å), and J-aggregrated biphenylene dimer (d = 4 Å). [<a href="#B51-materials-03-04214" class="html-bibr">51</a>]. Reproduced with permission from American Chemical Society.</p> Full article ">Figure 11
<p>CM Hamiltonian matrix (model 1), truncated four-orbital CM model (model 2) and truncated CM model when CT transitions are omitted from the calculation (model 3) [<a href="#B46-materials-03-04214" class="html-bibr">46</a>]. Reproduced with permission from American Chemical Society.</p> Full article ">Figure 12
<p>The truncated MIM model with symmetry constraint [<a href="#B47-materials-03-04214" class="html-bibr">47</a>]. Reproduced with permission from American Chemical Society.</p> Full article ">Figure 13
<p>Energy diagram of the interactions between two ethylenes based on simple Hückel model [<a href="#B46-materials-03-04214" class="html-bibr">46</a>]. Reproduced with permission from American Chemical Society.</p> Full article ">Figure 14
<p>Simplified configuration interactions in the excited state for a dimer based on four-orbital model. The definition of all symbols is described in <a href="#sec2-materials-03-04214" class="html-sec">Section 2</a>.</p> Full article ">Figure 15
<p>Three types of dimeric cyclophandienes with various dihedral angles between chromophores and tethered double bonds [<a href="#B47-materials-03-04214" class="html-bibr">47</a>]. Reproduced with permission from American Chemical Society.</p> Full article ">Figure 16
<p>Molecular structures of cyclophandiene <b>1-4</b> [<a href="#B47-materials-03-04214" class="html-bibr">47</a>]<b>.</b> Reproduced with permission from American Chemical Society.</p> Full article ">
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Article
STM, SECPM, AFM and Electrochemistry on Single Crystalline Surfaces
by Holger Wolfschmidt, Claudia Baier, Stefan Gsell, Martin Fischer, Matthias Schreck and Ulrich Stimming
Materials 2010, 3(8), 4196-4213; https://doi.org/10.3390/ma3084196 - 5 Aug 2010
Cited by 22 | Viewed by 17123
Abstract
Scanning probe microscopy (SPM) techniques have had a great impact on research fields of surface science and nanotechnology during the last decades. They are used to investigate surfaces with scanning ranges between several 100 mm down to atomic resolution. Depending on experimental conditions, [...] Read more.
Scanning probe microscopy (SPM) techniques have had a great impact on research fields of surface science and nanotechnology during the last decades. They are used to investigate surfaces with scanning ranges between several 100 mm down to atomic resolution. Depending on experimental conditions, and the interaction forces between probe and sample, different SPM techniques allow mapping of different surface properties. In this work, scanning tunneling microscopy (STM) in air and under electrochemical conditions (EC-STM), atomic force microscopy (AFM) in air and scanning electrochemical potential microscopy (SECPM) under electrochemical conditions, were used to study different single crystalline surfaces in electrochemistry. Especially SECPM offers potentially new insights into the solid-liquid interface by providing the possibility to image the potential distribution of the surface, with a resolution that is comparable to STM. In electrocatalysis, nanostructured catalysts supported on different electrode materials often show behavior different from their bulk electrodes. This was experimentally and theoretically shown for several combinations and recently on Pt on Au(111) towards fuel cell relevant reactions. For these investigations single crystals often provide accurate and well defined reference and support systems. We will show heteroepitaxially grown Ru, Ir and Rh single crystalline surface films and bulk Au single crystals with different orientations under electrochemical conditions. Image studies from all three different SPM methods will be presented and compared to electrochemical data obtained by cyclic voltammetry in acidic media. The quality of the single crystalline supports will be verified by the SPM images and the cyclic voltammograms. Furthermore, an outlook will be presented on how such supports can be used in electrocatalytic studies. Full article
(This article belongs to the Special Issue SPM in Materials Science)
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<p>EC-STM, SECPM and AFM of Au(111) single crystalline electrode: (A1) EC-STM (150 nm × 150 nm, h<sub>max</sub> = 1.5 nm, Inset: 5 nm × 5 nm) U<sub>S</sub> = 500mV <span class="html-italic">vs.</span> NHE, (A2) SECPM (150 nm × 150 nm, h<sub>max</sub> = 1.5 nm) image of Au(111) single crystal electrode in 0.1 M HClO<sub>4</sub>, U<sub>S</sub> = 500 mV <span class="html-italic">vs.</span> NHE; (A3) Contact Mode AFM in air of a (111) fibre textured gold film (2 µm × 2 µm, U<sub>max </sub>= 0.1V , Inset: 5 nm × 5 nm). Imaging conditions: STM: I<sub>T</sub> = 1 nA, U<sub>Bias</sub> = +100 mV, SECPM: ∆U = 5 mV. The insets show atomic resolution.</p> Full article ">Figure 2
<p>EC-STM, SECPM, AFM and CV of Ru(0001): (A) EC-STM (500 nm × 500 nm, h<sub>max</sub> = 12.17 nm), U<sub>S</sub> = 500mV <span class="html-italic">vs.</span> NHE, (B) SECPM (500 nm × 500 nm, h<sub>max</sub> = 17.22 nm) image of Ru(0001) in 0.1 M HClO<sub>4</sub> at U<sub>S</sub> = 500 mV <span class="html-italic">vs.</span> NHE,<b> (C)</b> Contact mode AFM in air (5 µm × 5 µm, h<sub>max</sub> = 40 nm, Inset: atomic resolution, 12 nm × 12 nm) and <b>(D)</b> CVs obtained in 1 M H<sub>2</sub>SO<sub>4</sub> (black curve) and 0.1 M HClO<sub>4</sub> (red curve) with a scan rate of 100 mV∙s<sup>-1</sup> and 200 mVs<sup>-1</sup>, respectively. Imaging conditions: STM: I<sub>T</sub> = 1 nA, U<sub>bias</sub> = 100 mV, SECPM: ∆U = 5 mV.</p> Full article ">Figure 3
<p>EC-STM, SECPM and CV of Rh(111): (A) <span class="html-italic">In situ</span> EC-STM (500 nm × 500 nm, h<sub>max</sub> = 10 nm) U<sub>S</sub> = 500mV <span class="html-italic">vs.</span> NHE, (B) SECPM (200 nm × 200 nm, h<sub>max</sub> = 4 nm) and image of Rh(111) in 0.1 M HClO<sub>4</sub> at U<sub>S</sub> = 500 mV <span class="html-italic">vs.</span> NHE (C) CVs obtained in 0.1 M HClO<sub>4</sub> (black curve) and 1 M H<sub>2</sub>SO<sub>4</sub> (red curve) with a scan rate of 100 mVs<sup>-1</sup>. Imaging conditions: STM: I<sub>T</sub> = 1 nA, U<sub>bias</sub> = 100 mV, SECPM: ∆U = 5 mV.</p> Full article ">Figure 4
<p>SECPM, AFM and CV of Ir(111) and Ir(100): (A1) SECPM image of Ir(111) (500 nm × 500 nm, h<sub>max</sub> = 5.5 nm) in 0.1M HClO<sub>4</sub> at U<sub>S</sub> = 500 mV <span class="html-italic">vs.</span> NHE and (A2) Contact mode AFM image of Ir(111) obtained in air (1000 nm × 1000 nm, h<sub>max</sub> = 5 nm) image of Ir(111) (B1) STM image of Ir(100) in air (500 nm × 500 nm, h<sub>max</sub> = nm) and (B2) CVs of Ir(111) and Ir(100) in 1 M HClO<sub>4</sub> and 0.01 M HClO4 obtained with a scan rate of 100 mVs<sup>-1</sup> and 50 mVs<sup>-1</sup> . Imaging conditions: STM: I<sub>T</sub> = 1 nA, U<sub>bias</sub> = 100 mV, SECPM: ∆U = 5 mV.</p> Full article ">
569 KiB  
Review
Hydrothermal Synthesis of Nanostructured Vanadium Oxides
by Jacques Livage
Materials 2010, 3(8), 4175-4195; https://doi.org/10.3390/ma3084175 - 2 Aug 2010
Cited by 192 | Viewed by 18393
Abstract
A wide range of vanadium oxides have been obtained via the hydrothermal treatment of aqueous V(V) solutions. They exhibit a large variety of nanostructures ranging from molecular clusters to 1D and 2D layered compounds. Nanotubes are obtained via a self-rolling process while amazing [...] Read more.
A wide range of vanadium oxides have been obtained via the hydrothermal treatment of aqueous V(V) solutions. They exhibit a large variety of nanostructures ranging from molecular clusters to 1D and 2D layered compounds. Nanotubes are obtained via a self-rolling process while amazing morphologies such as nano-spheres, nano-flowers and even nano-urchins are formed via the self-assembling of nano-particles. This paper provides some correlation between the molecular structure of precursors in the solution and the nanostructure of the solid phases obtained by hydrothermal treatment. Full article
(This article belongs to the Special Issue Progress in Nanomaterials Preparation)
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<p>V(V) solute species in aqueous solutions as a function of pH and concentration.</p> Full article ">Figure 2
<p>Hydrolysis ratio 'h' of V(V) precursors [V(OH)<sub>h</sub>(OH<sub>2</sub>)<sub>6-h</sub>]<sup>(5-h)+</sup> as a function of pH.</p> Full article ">Figure 3
<p>Molecular structure of V<sup>V</sup> precursors in the pH range 2-8.</p> Full article ">Figure 4
<p>Structure of (a) (TMA)<sub>4</sub>[H<sub>2</sub>V<sub>10</sub>O<sub>28</sub>] synthesized at room temperature and (b) TMA[V<sub>4</sub>O<sub>10</sub>] obtained under hydrothermal conditions.</p> Full article ">Figure 5
<p><sup>51</sup>V NMR spectra of a vanadate solution recorded at different temperatures: V<sub>10</sub> = [H<sub>2</sub>V<sub>10</sub>O<sub>28</sub>]<sup>4-</sup>, V<sub>4</sub> = [V<sub>4</sub>O<sub>12</sub>]<sup>4-</sup>.</p> Full article ">Figure 6
<p>Polyoxovanadate clusters formed in the presence of X<sup>-</sup> anions [V<sub>15</sub>O<sub>36</sub>Cl]<sup>6-</sup> and [H<sub>3</sub>V<sub>18</sub>O<sub>42</sub>I]<sup>10-</sup>.</p> Full article ">Figure 7
<p>Formation of VOx nanotubes upon hydrothermal treatment of V<sub>2</sub>O<sub>5</sub> gels at 180C: (a) after 8h (b) after 66h ( c) after 120 h.</p> Full article ">Figure 8
<p>Nanostructured vanadium oxides obtained via the self-assembling of nanoparticles: a) and b) Nano-urchin from VOx nanotubes, c) and d) nanospheres from platelets hexavanadate nanoparticles Cs<sub>2</sub>V<sub>6</sub>O<sub>16</sub>.</p> Full article ">
1331 KiB  
Review
Large-Scale Synthesis of Carbon Nanomaterials by Catalytic Chemical Vapor Deposition: A Review of the Effects of Synthesis Parameters and Magnetic Properties
by Xiaosi Qi, Chuan Qin, Wei Zhong, Chaktong Au, Xiaojuan Ye and Youwei Du
Materials 2010, 3(8), 4142-4174; https://doi.org/10.3390/ma3084142 - 30 Jul 2010
Cited by 52 | Viewed by 12404
Abstract
The large-scale production of carbon nanomaterials by catalytic chemical vapor deposition is reviewed in context with their microwave absorbing ability. Factors that influence the growth as well as the magnetic properties of the carbon nanomaterials are discussed. Full article
(This article belongs to the Special Issue Synthesis of Carbon Nanotube)
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<p><b>(a)</b> Formation of single-walled nanotubes (SWNTs) by rolling a graphene sheet along a chiral vector c [<a href="#B17-materials-03-04142" class="html-bibr">17</a>] and <b>(b)</b> Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) (inset) micrographs of SWNTs grown on Ag [<a href="#B15-materials-03-04142" class="html-bibr">15</a>].</p> Full article ">Figure 2
<p><b>(a)</b> Formation of multi-walled nanotubes (MWNT) by rolling up a stack of graphene sheets into concentric cylinders; straight MWNTs <b>(b)</b> <math display="inline"> <semantics> <mrow> <mi>θ</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math> and <b>(c)</b> <math display="inline"> <semantics> <mrow> <mi>θ</mi> <mo>≠</mo> <mn>0</mn> </mrow> </semantics> </math> [<a href="#B30-materials-03-04142" class="html-bibr">30</a>].</p> Full article ">Figure 3
<p><b>(a)</b> TEM image of helical carbon nanotubes (HCNTs) and <b>(b)</b> FE-SEM image of double carbon nanocoils (CNCs) [<a href="#B34-materials-03-04142" class="html-bibr">34</a>].</p> Full article ">Figure 4
<p>Schematic of a typical plasma-enhanced chemical vapor deposition (PECVD) setup [<a href="#B30-materials-03-04142" class="html-bibr">30</a>].</p> Full article ">Figure 5
<p>Schematic of a typical thermal CVD apparatus.</p> Full article ">Figure 6
<p>Typical <b>(a)</b> TEM and <b>(b)</b> FE-SEM image of helical carbon nanofibers (HCNFs) synthesized in a stainless steel reactor over Fe nanoparticles generated by a combined sol-gel/reduction method [<a href="#B60-materials-03-04142" class="html-bibr">60</a>].</p> Full article ">Figure 7
<p>Typical <b>(a)</b> FE-SEM and <b>(b)</b> TEM images of helical carbon nanofibers (HCNTs) synthsized in a quartz reactor over Fe nanoparticles generated by a combined sol-gel/reduction method [<a href="#B57-materials-03-04142" class="html-bibr">57</a>].</p> Full article ">Figure 8
<p>FE-SEM images of plait-like carbon nanocoils (CNCs) collected inside a quartz reactor: <b>(a)</b> Low magnification with white arrows indicating openings of tubes; <b>(b)</b> plait-like CNC with two CNCs fused together in opposite handedness; the left one is left-handed while the right one right-handed [<a href="#B61-materials-03-04142" class="html-bibr">61</a>].</p> Full article ">Figure 9
<p><b>(a)</b> FE-SEM and <b>(b)</b> TEM image of twin carbon nanocoils (T-CNCs) collected inside a quartz tube that was placed inside a stainless steel tube (the arrow indicates the catalyst nanoparticle) [<a href="#B62-materials-03-04142" class="html-bibr">62</a>].</p> Full article ">Figure 10
<p><b>(a)</b> FE-SEM and <b>(b)</b> TEM images of helical carbon nanotubes (HCNTs) synthesized over Fe nanoparticles generated by means of combined coprecipitation/hydrogen reduction method. Note: the arrows in <a href="#materials-03-04142-f010" class="html-fig">Figure 10</a>a indicate the opening of HCNTs and the arrow in <a href="#materials-03-04142-f010" class="html-fig">Figure 10</a>b indicates the catalyst nanoparticle [<a href="#B34-materials-03-04142" class="html-bibr">34</a>].</p> Full article ">Figure 11
<p>Photo of X<sub>400</sub> and Y<sub>400</sub> deposited on a ceramic plate [<a href="#B175-materials-03-04142" class="html-bibr">175</a>].</p> Full article ">Figure 12
<p>(<b>a-b</b>) FE-SEM images of X<sub>400</sub> at different magnifications (the arrows indicate the opening of HCNTs) [<a href="#B175-materials-03-04142" class="html-bibr">175</a>].</p> Full article ">Figure 13
<p>(a-b) FE-SEM images of Y<sub>400</sub> at different magnifications [<a href="#B175-materials-03-04142" class="html-bibr">175</a>].</p> Full article ">Figure 14
<p>Photo of X<sub>450</sub> and Y<sub>450</sub> [<a href="#B175-materials-03-04142" class="html-bibr">175</a>].</p> Full article ">Figure 15
<p>Photo of X<sub>500</sub> and Y<sub>500</sub> [<a href="#B175-materials-03-04142" class="html-bibr">175</a>].</p> Full article ">Figure 16
<p><b>(a)</b> Low and <b>(b)</b> high magnification of FE-SEM images of samples synthesized at 350 °C. The arrows indicate the “clear-cut” ends of CNRs [<a href="#B192-materials-03-04142" class="html-bibr">192</a>].</p> Full article ">
1328 KiB  
Review
Thin Film Deposition Using Energetic Ions
by Darina Manova, Jürgen W. Gerlach and Stephan Mändl
Materials 2010, 3(8), 4109-4141; https://doi.org/10.3390/ma3084109 - 29 Jul 2010
Cited by 77 | Viewed by 15055
Abstract
One important recent trend in deposition technology is the continuous expansion of available processes towards higher ion assistance with the subsequent beneficial effects to film properties. Nowadays, a multitude of processes, including laser ablation and deposition, vacuum arc deposition, ion assisted deposition, high [...] Read more.
One important recent trend in deposition technology is the continuous expansion of available processes towards higher ion assistance with the subsequent beneficial effects to film properties. Nowadays, a multitude of processes, including laser ablation and deposition, vacuum arc deposition, ion assisted deposition, high power impulse magnetron sputtering and plasma immersion ion implantation, are available. However, there are obstacles to overcome in all technologies, including line-of-sight processes, particle contaminations and low growth rates, which lead to ongoing process refinements and development of new methods. Concerning the deposited thin films, control of energetic ion bombardment leads to improved adhesion, reduced substrate temperatures, control of intrinsic stress within the films as well as adjustment of surface texture, phase formation and nanotopography. This review illustrates recent trends for both areas; plasma process and solid state surface processes. Full article
(This article belongs to the Special Issue Advances in Surface Coatings)
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<p>Typical energy ranges for different PVD processes. PIIID = plasma immersion ion implantation and deposition; IBAD = ion beam assisted deposition; PLD = pulsed laser deposition; VAD = vacuum arc deposition; IBA-MBE = ion beam assisted molecular beam epitaxy; MS = magnetron sputtering; MBE = molecular beam epitaxy.</p> Full article ">Figure 2
<p>Morphology of pure Mg films deposited by magnetron sputtering (MS; left panel), ion beam sputtering (IBS; middle panel) and cathodic (vacuum) arc deposition (VAD; right panel) [<a href="#B37-materials-03-04109" class="html-bibr">37</a>].</p> Full article ">Figure 3
<p>Cross section transmission electron microscopy (TEM) bright field images of (a) an MBE (without) and (b) an IBA-MBE (with additional ion assistance) grown GaN (0001) thin film on 6H-SiC (0001) [<a href="#B48-materials-03-04109" class="html-bibr">48</a>].</p> Full article ">Figure 4
<p>Schematic presentation of the self-sputtering process in high power impulse magnetron sputtering (HIPIMS), with loss terms and interactions with secondary electrons (SE).</p> Full article ">Figure 5
<p>Cross section of TiO<sub>2</sub> thin film with prominent macroparticle, subsequently partially coated at later stages of the deposition process.</p> Full article ">Figure 6
<p>Variation of the growth rate for TiN thin films produced by ion beam assisted deposition (IBAD) with nitrogen ions of different energies at fixed titanium evaporation rate. As the sputter rate increases with ion energy in the range of interest, a higher ion energy leads to a reduced growth rate. The triangles indicate measured data points, the lines are from simulations using calculated sputter yields from Reference [<a href="#B79-materials-03-04109" class="html-bibr">79</a>].</p> Full article ">Figure 7
<p>Presentation of a plasma immersion ion implantation and deposition (PIIID) system with filtered cathodic arc, auxiliary plasma source and high voltage pulse generator.</p> Full article ">Figure 8
<p>TEM image of the interface of a TiO<sub>2</sub> sample deposited with (a) 1 kV voltage pulses on Si(100) and (b) 10 kV bias voltage [<a href="#B86-materials-03-04109" class="html-bibr">86</a>].</p> Full article ">Figure 9
<p>Structure zone diagram applicable to energetic deposition as a function of the generalized temperature <span class="html-italic">T*</span> and the normalized energy flux <span class="html-italic">E*</span>; <span class="html-italic">t*</span> represents the net thickness. The boundaries between zones are gradual and for illustration only. Reprinted from [<a href="#B22-materials-03-04109" class="html-bibr">22</a>], Copyright 2010, with permission from Elsevier.</p> Full article ">Figure 10
<p>Depiction of TiN {110} and {200} fiber texture, as obtained from {111} pole figures, for plasma immersion ion implantation and deposition (PIIID) at different pulse voltages of (a) 1 kV and (b) 10 kV at fixed duty cycle of 9% [<a href="#B100-materials-03-04109" class="html-bibr">100</a>].</p> Full article ">Figure 11
<p>Observed texture evolution as a function of pulse voltage and frequency for the formation of TiN by PIIID [<a href="#B101-materials-03-04109" class="html-bibr">101</a>]. The data points show the measured texture for thin film produced at different voltage/frequency combinations, the thin lines show the approximate texture transitions boundaries when assuming that the average energy alone is the dominating factor to determine the texture.</p> Full article ">Figure 12
<p>{111} TiN pole figure indicating a medium to weak biaxial texture with the (200) orientation tilted by about 20–30° from the surface normal, as seen in the shift of the center of the ring-like structure towards χ = 20–30° and the formation of four, more or less pronounced pole density maxima inside the ring structure, in contrast to <a href="#materials-03-04109-f010" class="html-fig">Figure 10</a>b.</p> Full article ">Figure 13
<p>Evolution of intrinsic stress as a function of deposited energy. Typical energy regions for different processes are indicated.</p> Full article ">Figure 14
<p>Identification of process window to obtain different phases as a function of substrate temperature and particle energy. Additionally, the region allowing photoactive thin films is indicated by the blue shaded region [<a href="#B124-materials-03-04109" class="html-bibr">124</a>].</p> Full article ">Figure 15
<p>Transmission electron microscopy (TEM) dark field viewgraphs of three different samples, deposited at 5 kV pulse voltage at (a) room temperature, (b) 200 °C and (c) 300 °C.</p> Full article ">Figure 16
<p>Cross-section TEM micrograph of a Mo/Si multilayer stack formed by dual ion beam assisted deposition. The inset shows in detail the thickness of the Si-layer (dark), the Mo-layer (bright) and the interface between Si and Mo. Reprinted from [<a href="#B34-materials-03-04109" class="html-bibr">34</a>], Copyright 2002, with permission from Elsevier.</p> Full article ">Figure 17
<p>Real time spectroscopic <span class="html-italic">in situ</span> ellipsometry experimental (points) and model (solid lines) spectra of Mo layer growth in the (a) Xe sputter regime (E<sub>ion</sub> = 0.8 keV, f<sub>Xe</sub> = 1.6 sccm) and (b) Ar sputter regime (E<sub>ion</sub> = 0.8 keV, f<sub>Ar</sub> = 3.2 sccm). The different lines refer to different wavelengths [<a href="#B134-materials-03-04109" class="html-bibr">134</a>].</p> Full article ">Figure 18
<p>Film stress <span class="html-italic">versus</span> pulse length modulation of the assisting ion beam for <b>(a)</b> TiO<sub>2</sub> and <b>(b)</b> SiO<sub>2</sub> films grown with an ion energy of 1.2 keV of the assist ion beam. PLM indicates the pulse length modulation of the assist ion beam [<a href="#B135-materials-03-04109" class="html-bibr">135</a>].</p> Full article ">Figure 19
<p>15°-tilted cross-sectional SEM micrographs of Si nanocolumns: (a) without template pattern, (b) honeycomb pattern, and (c) hcp pattern. Reprinted with permission from [<a href="#B151-materials-03-04109" class="html-bibr">151</a>]. Copyright 2008, American Institute of Physics.</p> Full article ">Figure 20
<p>Surface topography after ion bombardment: (a) Si surface, 1200 eV Ar<sup>+</sup>, 15° off-normal; the arrow indicates the projected ion beam direction. (b) Ge surface, 2000 eV Xe<sup>+</sup>, 20° off-normal [<a href="#B164-materials-03-04109" class="html-bibr">164</a>].</p> Full article ">
898 KiB  
Review
Emission Properties, Solubility, Thermodynamic Analysis and NMR Studies of Rare-Earth Complexes with Two Different Phosphine Oxides
by Hiroki Iwanaga
Materials 2010, 3(8), 4080-4108; https://doi.org/10.3390/ma3084080 - 26 Jul 2010
Cited by 26 | Viewed by 11898
Abstract
The paper proposes novel molecular designs for rare-earth complexes involving the introduction of two different phosphine oxide structures into one rare-earth ion. These designs are effective for improving solubility and emission intensity. Additionally, the complexes are indispensable for realizing high performances in LEDs [...] Read more.
The paper proposes novel molecular designs for rare-earth complexes involving the introduction of two different phosphine oxide structures into one rare-earth ion. These designs are effective for improving solubility and emission intensity. Additionally, the complexes are indispensable for realizing high performances in LEDs and security media. The thermodynamic properties of Eu(III) complexes are correlated with the solubility. Correlations between coordination structures and emission intensity were explained by NMR analysis. The luminous flux of red LED devices with Eu(III) complexes is very high (20 mA, 870 m lumen). A new white LED has its largest spectra intensity in the red region and a human look much more vividly under this light. Full article
(This article belongs to the Special Issue Luminescent Materials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The first concept for the molecular design of a novel rare-earth complex with two different phosphine oxides.</p> Full article ">Figure 2
<p>The second concept for the molecular design of novel rare-earth complex with non-symmetric bis-phosphine oxides.</p> Full article ">Figure 3
<p>Emission spectra of the mixtures of Eu(III) complexes and phosphine oxides in a fluorinated solvent (2, 3-dihydrodecafluoropentane).</p> Full article ">Figure 4
<p><sup>31</sup>P-NMR spectra (298 K) of a mixture of Eu(III) complex <b>1</b>, TOPO, and TPPO in fluorinated solvent, CDCl<sub>3</sub>, and DMSO-d<sub>6</sub>.</p> Full article ">Figure 5
<p>Temperature dependence of <sup>31</sup>P NMR spectra of a mixture of Eu(III) complex <b>1</b> and two phosphine oxides in CDCl<sub>3</sub> (A relates to TOPO in <b>4</b>, D relates to TPPO in <b>3</b>, B relates to TOPO in <b>2</b>, and C relates to TPPO in <b>2</b>).</p> Full article ">Figure 6
<p>The emission intensities of a mixture of Eu(III) complex <b>1</b> (1.5 × 10<sup>−2</sup> M), TOPO (1.0 equation), and TPPO (1.0 equation) in fluorinated solvent (2,3-dihydrodecafluoropentane), CDCl<sub>3</sub>, and DMSO-d<sub>6</sub> excited at 395 nm at room temperature.</p> Full article ">Figure 7
<p>Comparison of three types of solid-state <sup>31</sup>P NMR spectra of the mixture of Eu(III) complex <b>1</b>, TOPO, and TPPO.</p> Full article ">Figure 8
<p>Eu(III) complexes with β-diketonates and phosphine oxides used in this study.</p> Full article ">Figure 9
<p>Emission spectra of the mixtures of Eu(III) complex <b>1</b> and phosphine oxides in the fluorinated solvent (2, 3-dihydrodecafluoropentane).</p> Full article ">Figure 10
<p><sup>31</sup>P NMR spectrum of the mixture of Eu(III) complex <b>1</b> and non-symmetric bis-phosphine oxide <b>11</b>.</p> Full article ">Figure 11
<p>Molecular structures of Eu(III) complexes with non-symmetric bis-phosphine oxides.</p> Full article ">Figure 12
<p>Comparison of the excitation spectra of Eu(III) complexes <b>17</b> and <b>18</b>, which have thienyl groups in non-symmetric phosphine oxides, with the spectra of complexes <b>14</b> and <b>15</b>, which have phenyl groups (measured in CCl<sub>4</sub>, 2 × 10<sup>−4</sup> M, room temperature, excited at 336 nm light).</p> Full article ">Figure 13
<p>The molecular structures of Tb(III) complexes with the phosphine oxides used in this study.</p> Full article ">Figure 14
<p>Excitation spectra of Tb(III) complexes <b>1</b><b>9</b>~<b>22</b> (2 × 10<sup>−4</sup> M) in ethyl acetate.</p> Full article ">Figure 15
<p>Molecular structures of Tb(III) complexes without phosphine oxide.</p> Full article ">Figure 16
<p>The emission spectra of Tb(III) complexes <b>19</b>, <b>20</b>, <b>21</b>, <b>24</b>, and <b>25</b> in ethyl acetate (normalized with respect to the transition “from <sup>5</sup>D<sub>4</sub> to <sup>7</sup>F<sub>5</sub>”, which corresponds to the magnetic-dipole transition).</p> Full article ">Figure 17
<p>Two optimized geometries for Eu(III) complexes (structures A and B) in the molecular structure shown in <a href="#materials-03-04080-f001" class="html-fig">Figure 1</a>, M1: R<sup>1</sup>=R<sup>2</sup>=Ph, R<sup>3</sup>=R<sup>4</sup>=H; M2: R<sup>1</sup>=R<sup>2</sup>=Me, R<sup>3</sup>=R<sup>4</sup>=H; M3: R<sup>1</sup>=Me, R<sup>2</sup>=Ph, R<sup>3</sup>=R<sup>4</sup>=H.</p> Full article ">Figure 18
<p>The optimized geometry of simplified Eu(III) complexes with three β-diketonates and non-symmetric phosphine oxides (H atoms are excluded).</p> Full article ">Figure 19
<p>Colorless and transparent emission materials produced by dissolving Eu(III) complexes and/or Tb(III) complexes in a polymer. (a) block, (b) flexible sheet, (c) print on glass.</p> Full article ">Figure 20
<p>LED devices containing novel Eu(III) complexes in the fluorescent layer.</p> Full article ">Figure 21
<p>The emission spectra of white LED devices using Eu(III) complexes with two different phosphine oxides.</p> Full article ">Figure 22
<p>(a) and (b) show a stainless steel sheet and a paper printed via ink jet systems with transparent ink that contains the novel Eu(III) complex. The printed transparent material is invisible under daylight and appears clearly under ultraviolet light. Many applications are expected because any pattern of images can be created on various materials by ink jet systems.</p> Full article ">
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