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Nanomaterials
Volume 3
Issue 4
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Nanomaterials, Volume 3, Issue 4 (December 2013) – 8 articles , Pages 572-673

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668 KiB  
Article
Effect of Nanotube Film Thickness on the Performance of Nanotube-Silicon Hybrid Solar Cells
by Daniel D. Tune and Joseph G. Shapter
Nanomaterials 2013, 3(4), 655-673; https://doi.org/10.3390/nano3040655 - 17 Dec 2013
Cited by 25 | Viewed by 6861
Abstract
The results of measurements on solar cells made from randomly aligned thin films of single walled carbon nanotubes (SWCNTs) on n-type monocrystalline silicon are presented. The films are made by vacuum filtration from aqueous TritonX-100 suspensions of large diameter arc-discharge SWCNTs. The [...] Read more.
The results of measurements on solar cells made from randomly aligned thin films of single walled carbon nanotubes (SWCNTs) on n-type monocrystalline silicon are presented. The films are made by vacuum filtration from aqueous TritonX-100 suspensions of large diameter arc-discharge SWCNTs. The dependence of the solar cell performance on the thickness of the SWCNT film is shown in detail, as is the variation in performance due to doping of the SWCNT film with SOCl2. Full article
(This article belongs to the Special Issue Nanomaterials in Energy Conversion and Storage)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>UV-vis-NIR spectra of thin vacuum filtration films of single walled carbon nanotubes (SWCNTs) on glass, made from aqueous TritonX-100 suspensions of large diameter arc-discharge material.</p> Full article ">Figure 2
<p>(<b>a</b>) Dependence of the SWCNT films’ average optical depth on the volume of SWCNT suspension used per square centimeter of filtration membrane. The different symbols represent different treatments and show very that there is very little effect on the baseline visible absorption; (<b>b</b>) Variation of the sheet resistance with film transmission for as prepared (♦), HCl treated (●), SOCl<sub>2</sub> treated (■) and HCl retreated (▲) devices. Inset shows the two regions of differing resistance for the doped films and the threshold transmittance (<span class="html-italic">T</span><sub>th</sub>) and corresponding sheet resistance (<span class="html-italic">R</span><sub>th</sub>).</p> Full article ">Figure 3
<p>(<b>a</b>) Device schematic; (<b>b</b>) JV curve of a typical SWCNT-Si solar cell.</p> Full article ">Figure 4
<p>Solar cell parameters extracted from as-prepared SWCNT-Si devices with varying SWCNT film thickness.</p> Full article ">Figure 5
<p>Solar cell parameters extracted from HF treated SWCNT-Si devices with varying SWCNT film thickness, 1 h after treatment.</p> Full article ">Figure 6
<p>Solar cell parameters extracted from SOCl<sub>2</sub> treated SWCNT-Si devices with varying SWCNT film thickness.</p> Full article ">Figure 7
<p>Solar cell parameters extracted from HF treated (second treatment) SWCNT-Si devices with varying SWCNT film thickness, 1 h after treatment.</p> Full article ">Figure 8
<p>Solar cell parameters extracted from HF treated (second treatment) SWCNT-Si devices with varying SWCNT film thickness, 4 h after treatment.</p> Full article ">
3437 KiB  
Article
Study of the Effect of Grafting Method on Surface Polarity of Tempo-Oxidized Nanocellulose Using Polycaprolactone as the Modifying Compound: Esterification versus Click-Chemistry
by Abdelhaq Benkaddour, Khalil Jradi, Sylvain Robert and Claude Daneault
Nanomaterials 2013, 3(4), 638-654; https://doi.org/10.3390/nano3040638 - 12 Dec 2013
Cited by 26 | Viewed by 10859
Abstract
Esterification and click-chemistry were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONC) using Polycaprolactone-diol (PCL) as modifying compound in order to improve the dispersion of nanofibers in organic media. These two grafting strategies were analyzed and compared. The first consists of grafting [...] Read more.
Esterification and click-chemistry were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONC) using Polycaprolactone-diol (PCL) as modifying compound in order to improve the dispersion of nanofibers in organic media. These two grafting strategies were analyzed and compared. The first consists of grafting directly the PCL onto TONC, and was carried out by esterification between hydroxyl groups of PCL and carboxyl groups of TONC. The second strategy known as click-chemistry is based on the 1,3-dipolar cycloaddition reaction between azides and alkyne terminated moieties to form the triazole ring between PCL and TONC. The grafted samples were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Thermogravimetry analysis (TGA). Further, the effects of the two treatments on the surface hydrophobization of TONC were investigated by contact angle measurements. The results show that both methods confirm the success of such a modification and the click reaction was significantly more effective than esterification. Full article
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<p>Strategy of TEMPO-oxidized nanocelluloses (TONC) modification adopted in this study.</p> Full article ">Figure 2
<p>Fourier transform infrared spectroscopy (FTIR) spectra of Kraft pulp (<b>a</b>); Tempo-oxidized nanocelluloses (TONC) alone (<b>b</b>) and TONC-Undecynoate (<b>c</b>).</p> Full article ">Figure 3
<p>FTIR spectra of PCL (<b>a</b>) and azido-polycaprolactone (PCL-N3) (<b>b</b>).</p> Full article ">Figure 4
<p>FTIR spectra of PCL (<b>a</b>) and azido-polycaprolactone (PCL-N3) (<b>b</b>).</p> Full article ">Figure 5
<p>X-ray photoelectron spectroscopy (XPS) spectrum of TONC and deconvolution of its C<sub>1s</sub> peak.</p> Full article ">Figure 6
<p>X-ray photoelectron spectroscopy (XPS) spectrum of TONC-g-PCL via esterification method and deconvolution of its C<sub>1s</sub> peak.</p> Full article ">Figure 7
<p>X-ray photoelectron spectroscopy (XPS) spectrum of TONC-g-PCL via click-Chemistry method and deconvolution of its C<sub>1s</sub> peak.</p> Full article ">Figure 8
<p>Transmission electron micrographs of: (<b>A</b>) TONC; (<b>B</b>) (TONC-g-PCL)<sub>ester</sub> and (<b>C</b>) (TONC-g-PCL)<sub>click</sub>.</p> Full article ">Figure 9
<p>Thermogravimetry analysis (TGA) (<b>A</b>) and differential thermogravimetry (<b>B</b>) curves of PCL (red curve), TONC (black curve), TONC-g-PCL via esterification reaction (blue curve) and TONC-g-PCL via click reaction (green curve).</p> Full article ">Figure 10
<p>Contact angle <span class="html-italic">vs.</span> time performed with water for grafted TOCN samples.</p> Full article ">Figure 11
<p>Profiles of water contact angles on TONC-g-PCL via esterification and TONC-g-PCL via click-chemistry 25 s after drop deposition.</p> Full article ">Figure 12
<p>Strategies adopted for the grafting of polycaprolactone-diol onto TONC by direct esterification and click chemistry.</p> Full article ">
776 KiB  
Review
Molecularly Imprinted Nanomaterials for Sensor Applications
by Muhammad Irshad, Naseer Iqbal, Adnan Mujahid, Adeel Afzal, Tajamal Hussain, Ahsan Sharif, Ejaz Ahmad and Muhammad Makshoof Athar
Nanomaterials 2013, 3(4), 615-637; https://doi.org/10.3390/nano3040615 - 26 Nov 2013
Cited by 57 | Viewed by 9951
Abstract
Molecular imprinting is a well-established technology to mimic antibody-antigen interaction in a synthetic platform. Molecularly imprinted polymers and nanomaterials usually possess outstanding recognition capabilities. Imprinted nanostructured materials are characterized by their small sizes, large reactive surface area and, most importantly, with rapid and [...] Read more.
Molecular imprinting is a well-established technology to mimic antibody-antigen interaction in a synthetic platform. Molecularly imprinted polymers and nanomaterials usually possess outstanding recognition capabilities. Imprinted nanostructured materials are characterized by their small sizes, large reactive surface area and, most importantly, with rapid and specific analysis of analytes due to the formation of template driven recognition cavities within the matrix. The excellent recognition and selectivity offered by this class of materials towards a target analyte have found applications in many areas, such as separation science, analysis of organic pollutants in water, environmental analysis of trace gases, chemical or biological sensors, biochemical assays, fabricating artificial receptors, nanotechnology, etc. We present here a concise overview and recent developments in nanostructured imprinted materials with respect to various sensor systems, e.g., electrochemical, optical and mass sensitive, etc. Finally, in light of recent studies, we conclude the article with future perspectives and foreseen applications of imprinted nanomaterials in chemical sensors. Full article
(This article belongs to the Special Issue Nanomaterials in Sensors)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic diagram of molecular imprinting.</p> Full article ">Figure 2
<p>Schematic representation of synthetic route for magnetic imprinted nanoparticles (Imp-NPs). Adopted from [<a href="#B33-nanomaterials-03-00615" class="html-bibr">33</a>].</p> Full article ">Figure 3
<p>Selectivity comparison of Au-NPs/MIP/GCE (glassy carbon electrode), adopted from [<a href="#B59-nanomaterials-03-00615" class="html-bibr">59</a>]. Use parenthesis for µA.</p> Full article ">Figure 4
<p>Current responses of the chlortetracycline-imprinted and non-imprinted polymer (NIP) for different analytes, adopted from [<a href="#B65-nanomaterials-03-00615" class="html-bibr">65</a>].</p> Full article ">Figure 5
<p>Comparison of different imprinted and non-imprinted polymers (NIP) to evaluate the adsorption selectivity for lysozyme (Lys), cytochrome C (Cyc), ribonuclease A (RNase A) and bovine serum albumin (BSA), respectively, at a concentration of 0.5 mg mL<sup>−1</sup> for all. Adopted from [<a href="#B73-nanomaterials-03-00615" class="html-bibr">73</a>].</p> Full article ">Figure 6
<p>Comparison of the QCM sensor responses for the imprinted titania layer and nanoparticles to different capric acid concentrations. The inside graph shows the frequency responses when shifted from fresh oil to waste oil; nanoparticle electrode offers a better response. Adopted from [<a href="#B82-nanomaterials-03-00615" class="html-bibr">82</a>].</p> Full article ">
1371 KiB  
Article
Fabrication and Characterization of SnO2/Graphene Composites as High Capacity Anodes for Li-Ion Batteries
by Abirami Dhanabalan, Xifei Li, Richa Agrawal, Chunhui Chen and Chunlei Wang
Nanomaterials 2013, 3(4), 606-614; https://doi.org/10.3390/nano3040606 - 15 Nov 2013
Cited by 42 | Viewed by 8119
Abstract
Tin-oxide and graphene (TG) composites were fabricated using the Electrostatic Spray Deposition (ESD) technique, and tested as anode materials for Li-ion batteries. The electrochemical performance of the as-deposited TG composites were compared to heat-treated TG composites along with pure tin-oxide films. The heat-treated [...] Read more.
Tin-oxide and graphene (TG) composites were fabricated using the Electrostatic Spray Deposition (ESD) technique, and tested as anode materials for Li-ion batteries. The electrochemical performance of the as-deposited TG composites were compared to heat-treated TG composites along with pure tin-oxide films. The heat-treated composites exhibited superior specific capacity and energy density than both the as-deposited TG composites and tin oxide samples. At the 70th cycle, the specific capacities of the as-deposited and post heat-treated samples were 534 and 737 mA·h/g, respectively, and the corresponding energy densities of the as-deposited and heat-treated composites were 1240 and 1760 W·h/kg, respectively. This improvement in the electrochemical performance of the TG composite anodes as compared to the pure tin oxide samples is attributed to the synergy between tin oxide and graphene, which increases the electrical conductivity of tin oxide and helps alleviate volumetric changes in tin-oxide during cycling. Full article
(This article belongs to the Special Issue Nanomaterials in Energy Conversion and Storage)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>SEM images of (<b>a</b>) as-deposited tin oxide; (<b>b</b>) as-deposited grapheme; (<b>c</b>) as-deposited Tin oxide/graphene (TG) deposited; (<b>d</b>) heat-treated tin-oxide; (<b>e</b>) heat-treated grapheme; (<b>f</b>) heat treated TG composite.</p> Full article ">Figure 2
<p>X-ray diffraction patterns of (<b>a</b>) tin oxide—the peaks for tin oxide powder obtained from sol-gel, the as-deposited and heat-treated tin oxide are shown; and (<b>b</b>) tin oxide/graphene composites—both as-deposited and heat-treated are shown.</p> Full article ">Figure 3
<p>Charge-discharge profiles of (<b>a</b>) TG composites at 195 °C (as deposited); and (<b>b</b>) TG composites at 280 °C (post-heat treated).</p> Full article ">Figure 4
<p>Comparison of (<b>a</b>) cycle performance and (<b>b</b>) energy density of tin oxide/graphene (TG) composites and tin oxide samples for both as-deposited and heat treated samples.</p> Full article ">Figure 5
<p>(<b>a</b>) Rate capability of TG composites—as-deposited and heat-treated; and (<b>b</b>) Normalized capacity <span class="html-italic">vs</span><span class="html-italic">.</span> the rate of discharge of TG composites—as-deposited and heat treated.</p> Full article ">
1848 KiB  
Article
Formation of Gold Microparticles by Ablation with Surface Plasmons
by Quincy Garner and Pal Molian
Nanomaterials 2013, 3(4), 592-605; https://doi.org/10.3390/nano3040592 - 28 Oct 2013
Cited by 4 | Viewed by 5508
Abstract
The formation of gold microparticles on a silicon substrate through the use of energetic surface plasmons is reported. A laser-assisted plasmonics system was assembled and tested to synthesize gold particles from gold thin film by electrical field enhancement mechanism. A mask containing an [...] Read more.
The formation of gold microparticles on a silicon substrate through the use of energetic surface plasmons is reported. A laser-assisted plasmonics system was assembled and tested to synthesize gold particles from gold thin film by electrical field enhancement mechanism. A mask containing an array of 200 nm diameter holes with a periodicity of 400 nm was prepared and placed on a silicon substrate. The mask was composed of 60 µm thick porous alumina membrane sputter-coated with 100 nm thin gold film. A Nd:YAG laser with 1064 nm wavelength and 230 µs pulse width (free-running mode) was then passed through the mask at an energy fluence of 0.35 J/cm2. The extraordinary transmission of laser light through alumina/gold micro-hole optical antenna created both extended and localized surface plasmons that caused the gold film at the bottom of the mask to fragment into microparticles and deposit on the silicon substrate that is in direct contact with the mask. The surface plasmon method is simpler, quicker, more energy efficient, and environmentally safer than existing physical and chemical methods, as well as being contamination-free, and can be extended to all types of materials that will in turn allow for new possibilities in the formation of structured surfaces. Full article
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Figure 1

Figure 1
<p>The coordinate system used for the description of surface plasmons.</p> Full article ">Figure 2
<p>Schematic diagram of experimental excitation of surface plasmons and the resulting formation of microparticles.</p> Full article ">Figure 3
<p>SEM image of porous alumina membrane.</p> Full article ">Figure 4
<p>Gold nanoparticles on the surface of silicon substrate (setup 5). (<b>a</b>) Optical image, (<b>b</b>) SEM image and (<b>c</b>) AFM image.</p> Full article ">Figure 5
<p>SEM image of the mask after laser irradiation.</p> Full article ">Figure 6
<p>Size distribution of gold nanoparticles on the silicon substrate.</p> Full article ">
581 KiB  
Article
Tuning NaYF4 Nanoparticles through Alkaline Earth Doping
by Xian Chen, Dengfeng Peng and Feng Wang
Nanomaterials 2013, 3(4), 583-591; https://doi.org/10.3390/nano3040583 - 24 Oct 2013
Cited by 25 | Viewed by 8608
Abstract
Phase and size of lanthanide-doped nanoparticles are the most important characteristics that dictate optical properties of these nanoparticles and affect their technological applications. Herein, we present a systematic study to examine the effect of alkaline earth doping on the formation of NaYF4 [...] Read more.
Phase and size of lanthanide-doped nanoparticles are the most important characteristics that dictate optical properties of these nanoparticles and affect their technological applications. Herein, we present a systematic study to examine the effect of alkaline earth doping on the formation of NaYF4 upconversion nanoparticles. We show that alkaline earth doping has a dual function of tuning particle size of hexagonal phase NaYF4 nanoparticles and stabilizing cubic phase NaYF4 nanoparticles depending on composition and concentration of the dopant ions. The study described here represents a facile and general strategy to tuning the properties of NaYF4 upconversion nanoparticles. Full article
(This article belongs to the Special Issue Current Trends in Up-Converting Nanoparticles)
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Figure 1
<p>A comparison of the crystal site for the metal ions in the (<b>a</b>) cubic and (<b>b</b>) hexagonal phase NaYF<sub>4</sub>.</p> Full article ">Figure 2
<p>X-ray diffraction (XRD) patterns of the NaYF<sub>4</sub>:Yb/Er (18/2 mol %) nanoparticles obtained in the presence of different amount of Sr<sup>2+</sup> dopant ions. The bottom line spectra are literature data for cubic phase SrF<sub>2</sub> (JCPDS file number 06-0262 [<a href="#B40-nanomaterials-03-00583" class="html-bibr">40</a>]), cubic phase NaYF<sub>4</sub> (JCPDS file number 77-2042 [<a href="#B41-nanomaterials-03-00583" class="html-bibr">41</a>]) and hexagonal phase NaYF<sub>4</sub> (JCPDS file number 16-0334 [<a href="#B39-nanomaterials-03-00583" class="html-bibr">39</a>]), respectively.</p> Full article ">Figure 3
<p>Transmission electron microscopy (TEM) images of the NaYF<sub>4</sub>:Yb/Er (18/2 mol %) nanoparticles obtained in the presence of (<b>a</b>) 0 mol %, (<b>b</b>) 20 mol %, and (<b>c</b>) 50 mol % of Sr<sup>2+</sup> dopant ions, respectively.</p> Full article ">Figure 4
<p>Upconversion emission spectra of the NaYF<sub>4</sub>:Yb/Er (18/2 mol %) nanoparticles obtained in the presence of different amount of Sr<sup>2+</sup> dopant ions. Inset: amplified spectra of the nanoparticles comprising high dopant concentration of Sr<sup>2+</sup>.</p> Full article ">Figure 5
<p>TEM images of the NaYF<sub>4</sub>:Yb/Er (18/2 mol %) nanoparticles obtained in the presence of (<b>a</b>) 0 mol %, (<b>b</b>) 20 mol %, (<b>c</b>) 40 mol %, and (<b>d</b>) 60 mol % of Ca<sup>2+</sup> dopant ions, respectively.</p> Full article ">
1524 KiB  
Article
Susceptibility of CoFeB/AlOx/Co Magnetic Tunnel Junctions to Low-Frequency Alternating Current
by Yuan-Tsung Chen and Zu-Gao Chang
Nanomaterials 2013, 3(4), 574-582; https://doi.org/10.3390/nano3040574 - 15 Oct 2013
Cited by 2 | Viewed by 6435
Abstract
This investigation studies CoFeB/AlOx/Co magnetic tunneling junction (MTJ) in the magnetic field of a low-frequency alternating current, for various thicknesses of the barrier layer AlOx. The low-frequency alternate-current magnetic susceptibility (χac) and phase angle (θ) of the [...] Read more.
This investigation studies CoFeB/AlOx/Co magnetic tunneling junction (MTJ) in the magnetic field of a low-frequency alternating current, for various thicknesses of the barrier layer AlOx. The low-frequency alternate-current magnetic susceptibility (χac) and phase angle (θ) of the CoFeB/AlOx/Co MTJ are determined using an cac analyzer. The driving frequency ranges from 10 to 25,000 Hz. These multilayered MTJs are deposited on a silicon substrate using a DC and RF magnetron sputtering system. Barrier layer thicknesses are 22, 26, and 30 Å. The X-ray diffraction patterns (XRD) include a main peak at 2θ = 44.7° from hexagonal close-packed (HCP) Co with a highly (0002) textured structure, with AlOx and CoFeB as amorphous phases. The full width at half maximum (FWHM) of the Co(0002) peak, decreases as the AlOx thickness increases; revealing that the Co layer becomes more crystalline with increasing thickness. χac result demonstrates that the optimal resonance frequency (fres) that maximizes the χac value is 500 Hz. As the frequency increases to 1000 Hz, the susceptibility decreases rapidly. However, when the frequency increases over 1000 Hz, the susceptibility sharply declines, and almost closes to zero. The experimental results reveal that the mean optimal susceptibility is 1.87 at an AlOx barrier layer thickness of 30 Å because the Co(0002) texture induces magneto-anisotropy, which improves the indirect CoFeB and Co spin exchange-coupling strength and the χac value. The results concerning magnetism indicate that the magnetic characteristics are related to the crystallinity of Co. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
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<p>X-ray diffraction patterns of CoFeB(75 Å)/AlO<span class="html-italic"><sub>x</sub></span>(<span class="html-italic">d</span> Å)/Co(75 Å) magnetic tunneling junction (MTJ).</p> Full article ">Figure 2
<p>Full width at half maximum (FWHM) (<span class="html-italic">B</span>) as a function of thickness (<span class="html-italic">d</span>) of AlO<span class="html-italic"><sub>x</sub></span> layer.</p> Full article ">Figure 3
<p>(<b>a</b>) The perpendicular χ<sub>ac</sub>signal of MTJ sample when the external field is 30 mOe; (<b>b</b>) The perpendicular χ<sub>ac</sub>signal of MTJ sample when the external field is 50 mOe; (<b>c</b>) The in-plane χ<sub>ac</sub>signal of MTJ sample when the external field is 30 mOe; (<b>d</b>) The in-plane χ<sub>ac</sub>signal of MTJ sample when the external field is 50 mOe.</p> Full article ">Figure 4
<p>Susceptibility (χ<sub>ac</sub>) of CoFeB/AlO<span class="html-italic"><sub>x</sub></span> (<span class="html-italic">d</span> = 22, 26 and 30 Å)/Co MTJs as a function of frequency, 10–25,000 Hz.</p> Full article ">Figure 5
<p>Mean optimal susceptibility and average phase angle as functions of AlO<span class="html-italic"><sub>x</sub></span> barrier thickness.</p> Full article ">
114 KiB  
Editorial
Nanomaterials in Sensors
by Joseph J. BelBruno
Nanomaterials 2013, 3(4), 572-573; https://doi.org/10.3390/nano3040572 - 14 Oct 2013
Cited by 15 | Viewed by 4908
Abstract
This Special Issue of Nanomaterials is focused on the continuing implementation of nanomaterials and nanostructures in the development of more sensitive and more specific sensing devices. As a result, these new devices employ smaller sensing elements and provide more “real time” capability. Often, [...] Read more.
This Special Issue of Nanomaterials is focused on the continuing implementation of nanomaterials and nanostructures in the development of more sensitive and more specific sensing devices. As a result, these new devices employ smaller sensing elements and provide more “real time” capability. Often, the inclusion of nanomaterials leads to sensing elements for targets that were previously inaccessible. [...] Full article
(This article belongs to the Special Issue Nanomaterials in Sensors)
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