Nanomaterials

4291 KiB

Open AccessArticle

Effects of Atomization Injection on Nanoparticle Processing in Suspension Plasma Spray

by Hong-bing Xiong, Cheng-yu Zhang, Kai Zhang and Xue-ming Shao

Nanomaterials 2016, 6(5), 94; https://doi.org/10.3390/nano6050094 - 20 May 2016

Cited by 13 | Viewed by 8201

Liquid atomization is applied in nanostructure dense coating technology to inject suspended nano-size powder materials into a suspension plasma spray (SPS) torch. This paper presents the effects of the atomization parameters on the nanoparticle processing. A numerical model was developed to simulate the [...] Read more.

Liquid atomization is applied in nanostructure dense coating technology to inject suspended nano-size powder materials into a suspension plasma spray (SPS) torch. This paper presents the effects of the atomization parameters on the nanoparticle processing. A numerical model was developed to simulate the dynamic behaviors of the suspension droplets, the solid nanoparticles or agglomerates, as well as the interactions between them and the plasma gas. The plasma gas was calculated as compressible, multi-component, turbulent jet flow in Eulerian scheme. The droplets and the solid particles were calculated as discrete Lagrangian entities, being tracked through the spray process. The motion and thermal histories of the particles were given in this paper and their release and melting status were observed. The key parameters of atomization, including droplet size, injection angle and velocity were also analyzed. The study revealed that the nanoparticle processing in SPS preferred small droplets with better atomization and less aggregation from suspension preparation. The injection angle and velocity influenced the nanoparticle release percentage. Small angle and low initial velocity might have more nanoparticles released. Besides, the melting percentage of nanoparticles and agglomerates were studied, and the critical droplet diameter to ensure solid melting was drawn. Results showed that most released nanoparticles were well melted, but the agglomerates might be totally melted, partially melted, or even not melted at all, mainly depending on the agglomerate size. For better coating quality, the suspension droplet size should be limited to a critical droplet diameter, which was inversely proportional to the cubic root of weight content, for given critical agglomerate diameter of being totally melted. Full article

(This article belongs to the Special Issue Plasma Nanoengineering and Nanofabrication)

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3075 KiB

Open AccessArticle

Mechanochemical Synthesis of TiO₂ Nanocomposites as Photocatalysts for Benzyl Alcohol Photo-Oxidation

by Weiyi Ouyang, Ewelina Kuna, Alfonso Yepez, Alina M. Balu, Antonio A. Romero, Juan Carlos Colmenares and Rafael Luque

Nanomaterials 2016, 6(5), 93; https://doi.org/10.3390/nano6050093 - 18 May 2016

Cited by 45 | Viewed by 8356

Abstract

TiO₂ (anatase phase) has excellent photocatalytic performance and different methods have been reported to overcome its main limitation of high band gap energy. In this work, TiO₂-magnetically-separable nanocomposites (MAGSNC) photocatalysts with different TiO₂ loading were synthesized using a simple [...] Read more.

TiO₂ (anatase phase) has excellent photocatalytic performance and different methods have been reported to overcome its main limitation of high band gap energy. In this work, TiO₂-magnetically-separable nanocomposites (MAGSNC) photocatalysts with different TiO₂ loading were synthesized using a simple one-pot mechanochemical method. Photocatalysts were characterized by a number of techniques and their photocatalytic activity was tested in the selective oxidation of benzyl alcohol to benzaldehyde. Extension of light absorption into the visible region was achieved upon titania incorporation. Results indicated that the photocatalytic activity increased with TiO₂ loading on the catalysts, with moderate conversion (20%) at high benzaldehyde selectivity (84%) achieved for 5% TiO₂-MAGSNC. These findings pointed out a potential strategy for the valorization of lignocellulosic-based biomass under visible light irradiation using designer photocatalytic nanomaterials. Full article

(This article belongs to the Special Issue Nanoparticles for Catalysis)

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Reaction system: (1) lamp cooling system; (2) double-walled immersion well reactor; (3) photoreactor; (4) port for taking samples; (5) 125 W ultraviolet (UV) lamp; (6) mother solution; and (7) magnetic stirrer. Full article ">Figure 2
X-ray diffraction (XRD) pattern of 5% TiO2-magnetically-separable photocatalysts (MAGSNC) photocatalysts. (PDF 21-1272 and PDF 39-1346 are the card numbers for the crystalline structures in the data base, while Anatase, syn and Maghemite-C, syn are the corresponding structure names.) Full article ">Figure 3
N2 absorption-desorption isotherm of 5% TiO2-MAGSNC photocatalysts. P: partial vapor pressure of adsorbate gas in equilibrium with the surface at 77.4 K; P0: saturated pressure of adsorbate gas. Full article ">Figure 4
Diffuse reflectance (DR) Ultraviolet-Visible (UV-VIS) absorption spectra of different TiO2-MAGSNC photocatalysts. P25: pure commercial TiO2 from Evonik Industries. Full article ">Figure 5
X-ray photoelectron spectroscopy (XPS) spectra of 5% TiO2-MAGSNC photocatalysts: (a) Ti 2p; and (b) Fe 2p. Full article ">Figure 6
Scanning electron microscopy (SEM) images: (a) 5% TiO2-MAGSNC photocatalysts; (b) 2% TiO2-MAGSNC nanocomposites; and elements mapping of 2% TiO2-MAGSNC photocatalysts: (c) Si; (d) Fe; (e) Ti. Full article ">Figure 7
Transmission electron microscopy (TEM) images of 5% TiO2-MAGSNC photocatalysts. Full article ">

3159 KiB

Open AccessArticle

PDE5 Inhibitors-Loaded Nanovesicles: Physico-Chemical Properties and In Vitro Antiproliferative Activity

by Roberta F. De Rose, Maria Chiara Cristiano, Marilena Celano, Valentina Maggisano, Ada Vero, Giovanni Enrico Lombardo, Martina Di Francesco, Donatella Paolino, Diego Russo and Donato Cosco

Nanomaterials 2016, 6(5), 92; https://doi.org/10.3390/nano6050092 - 18 May 2016

Cited by 21 | Viewed by 5603

Abstract

Novel therapeutic approaches are required for the less differentiated thyroid cancers which are non-responsive to the current treatment. In this study we tested an innovative formulation of nanoliposomes containing sildenafil citrate or tadalafil, phosphodiesterase-5 inhibitors, on two human thyroid cancer cell lines (TPC-1 [...] Read more.

Novel therapeutic approaches are required for the less differentiated thyroid cancers which are non-responsive to the current treatment. In this study we tested an innovative formulation of nanoliposomes containing sildenafil citrate or tadalafil, phosphodiesterase-5 inhibitors, on two human thyroid cancer cell lines (TPC-1 and BCPAP). Nanoliposomes were prepared by the thin layer evaporation and extrusion methods, solubilizing the hydrophilic compound sildenafil citrate in the aqueous phase during the hydration step and dissolving the lipophilic tadalafil in the organic phase. Nanoliposomes, made up of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine monohydrate (DPPC), cholesterol, and N-(carbonyl-methoxypolyethylene glycol-2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE-mPEG2000) (6:3:1 molar ratio), were characterized by a mean diameter of ~100 nm, a very low polydispersity index (~0.1) and a negative surface charge. The drugs did not influence the physico-chemical properties of the systems and were efficiently retained in the colloidal structure. By using cell count and MTT assay, we found a significant reduction of the viability in both cell lines following 24 h treatment with both nanoliposomal-encapsulated drugs, notably greater than the effect of the free drugs. Our findings demonstrate that nanoliposomes increase the antiproliferative activity of phosphodiesterase-5 inhibitors, providing a useful novel formulation for the treatment of thyroid carcinoma. Full article

(This article belongs to the Special Issue Nanomaterials for Cancer Therapies)

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Transmission electron microscopy (TEM) micrographs of empty nanoliposomes (A); SIL-nanoliposomes (B) and TAD-nanoliposomes (C). Bar: 200 nm. Full article ">Figure 2
Release profile of SIL and TAD from nanoliposomes. Experiments were carried out at room temperature. Values were the mean of three independent experiments in triplicate ± standard deviation (SD). Full article ">Figure 3
Nanoliposomes containing PDE5 inhibitors reduced proliferation of TPC-1 cells. After 24 h of treatment, proliferation was evaluated by cell count assay (A) and MTT assay (B), as described in Materials and Methods. Results are mean ± SD of three experiments performed in triplicate. *, **, ***, p < 0.05, 0.01, 0.001 vs. control (ctrl); °, °°, °°°, SIL-nlip vs SIL; #, ##, ###, p < 0.05, 0.01, 0.001 TAD-nlip vs. TAD. Full article ">Figure 4
Nanoliposomes containing PDE5 inhibitors reduced proliferation of BCPAP cells. After 24 h of treatment, proliferation was evaluated by cell count assay (A) and MTT assay (B), as described in Materials and Methods. Results are mean ± SD of three experiments performed in triplicate. *, **, ***, p < 0.05, 0.01, 0.001 vs. control (ctrl); #, ##, p < 0.05, 0.01 TAD-nlip vs. TAD. Full article ">Figure 5
Confocal laser scanning microscopy (CLSM) micrographs of TPC-1 cells treated with rhodamine-labelled nanoliposomes after 3 h incubation: panel A, Hoechst filter; panel B, TRITC filter; and panel C, overlay. A representative example of three independent experiments. Full article ">Figure 6
Z-stack analysis by CLSM of TPC-1 cells treated with rhodamine-labelled nanoliposomes after 3 h incubation: panel A, Hoechst filter; panel B, TRITC filter; and panel C, overlay. A representative example of three independent experiments. Full article ">

5490 KiB

Open AccessArticle

Post-Plasma SiO_x Coatings of Metal and Metal Oxide Nanoparticles for Enhanced Thermal Stability and Tunable Photoactivity Applications

by Patrick Post, Nicolas Jidenko, Alfred P. Weber and Jean-Pascal Borra

Nanomaterials 2016, 6(5), 91; https://doi.org/10.3390/nano6050091 - 13 May 2016

Cited by 16 | Viewed by 6639

Abstract

The plasma-based aerosol process developed for the direct coating of particles in gases with silicon oxide in a continuous chemical vapor deposition (CVD) process is presented. It is shown that non-thermal plasma filaments induced in a dielectric barrier discharge (DBD) at atmospheric pressure [...] Read more.

The plasma-based aerosol process developed for the direct coating of particles in gases with silicon oxide in a continuous chemical vapor deposition (CVD) process is presented. It is shown that non-thermal plasma filaments induced in a dielectric barrier discharge (DBD) at atmospheric pressure trigger post-DBD gas phase reactions. DBD operating conditions are first scanned to produce ozone and dinitrogen pentoxide. In the selected conditions, these plasma species react with gaseous tetraethyl orthosilicate (TEOS) precursor downstream of the DBD. The gaseous intermediates then condense on the surface of nanoparticles and self-reactions lead to homogeneous solid SiO_x coatings, with thickness from nanometer to micrometer. This confirms the interest of post-DBD injection of the organo-silicon precursor to achieve stable production of actives species with subsequent controlled thickness of SiO_x coatings. SiO_x coatings of spherical and agglomerated metal and metal oxide nanoparticles (Pt, CuO, TiO₂) are achieved. In the selected DBD operating conditions, the thickness of homogeneous nanometer sized coatings of spherical nanoparticles depends on the reaction duration and on the precursor concentration. For agglomerates, operating conditions can be tuned to cover preferentially the interparticle contact zones between primary particles, shifting the sintering of platinum agglomerates to much higher temperatures than the usual sintering temperature. Potential applications for enhanced thermal stability and tunable photoactivity of coated agglomerates are presented. Full article

(This article belongs to the Special Issue Plasma Nanoengineering and Nanofabrication)

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3459 KiB

Open AccessArticle

Aggregation and Colloidal Stability of Commercially Available Al₂O₃ Nanoparticles in Aqueous Environments

by Julie Mui, Jennifer Ngo and Bojeong Kim

Nanomaterials 2016, 6(5), 90; https://doi.org/10.3390/nano6050090 - 13 May 2016

Cited by 52 | Viewed by 8259

Abstract

The aggregation and colloidal stability of three, commercially-available, gamma-aluminum oxide nanoparticles (γ-Al₂O₃ NPs) (nominally 5, 10, and 20–30 nm) were systematically examined as a function of pH, ionic strength, humic acid (HA) or clay minerals (e.g., montmorillonite) concentration using dynamic [...] Read more.

The aggregation and colloidal stability of three, commercially-available, gamma-aluminum oxide nanoparticles (γ-Al₂O₃ NPs) (nominally 5, 10, and 20–30 nm) were systematically examined as a function of pH, ionic strength, humic acid (HA) or clay minerals (e.g., montmorillonite) concentration using dynamic light scattering and transmission electron microscopy techniques. NPs possess pH-dependent surface charges, with a point of zero charge (PZC) of pH 7.5 to 8. When pH < PZC, γ-Al₂O₃ NPs are colloidally stable up to 100 mM NaCl and 30 mM CaCl₂. However, significant aggregation of NPs is pronounced in both electrolytes at high ionic strength. In mixed systems, both HA and montmorillonite enhance NP colloidal stability through electrostatic interactions and steric hindrance when pH ≤ PZC, whereas their surface interactions are quite limited when pH > PZC. Even when pH approximates PZC, NPs became stable at a HA concentration of 1 mg·L⁻¹. The magnitude of interactions and dominant sites of interaction (basal planes versus edge sites) are significantly dependent on pH because both NPs and montmorillonite have pH-dependent (conditional) surface charges. Thus, solution pH, ionic strength, and the presence of natural colloids greatly modify the surface conditions of commercial γ-Al₂O₃ NPs, affecting aggregation and colloidal stability significantly in the aqueous environment. Full article

(This article belongs to the Special Issue Engineered Nanomaterials in the Environment)

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X-ray diffraction (XRD) patterns of commercial γ-Al2O3 nanoparticles (NPs) in size of: (a) 5 nm; (b) 10 nm; and (c) 20–30 nm. Note that 20–30 nm γ-Al2O3 NPs have a trace amount of boehmite (γ-AlOOH) (PDF 04-010-5683) marked with *, as an impurity. Full article ">Figure 2
Bright field transmission electron microscopy (TEM) images of γ-Al2O3 NPs in size of: (a) 5 nm; (b) 10 nm; and (c) 20–30 nm. Full article ">Figure 3
Z-average (Zave) hydrodynamic diameter (○) and ζ potential (●) of: (a) 5 nm; (b) 10 nm; and (c) 20–30 nm γ-Al2O3 NP aggregates, as a function of pH. Full article ">Figure 4
(a) Zave hydrodynamic diameter of 5 nm (□), 10 nm (○), and 20–30 nm (△) γ-Al2O3 NP aggregates, as a function of ionic strength (NaCl); (b) Zave hydrodynamic diameter of 5 nm (□), 10 nm (○), and 20–30 nm (△) γ-Al2O3 NP aggregates, as a function of ionic strength (CaCl2); (c) ζ potential of 5 nm (■), 10 nm (●), and 20–30 nm (▲) γ-Al2O3 NP aggregates, as a function of ionic strength (NaCl); and (d) ζ potential of 5 nm (■), 10 nm (●), and 20–30 nm (▲) γ-Al2O3 NP aggregates, as a function of ionic strength (CaCl2). Full article ">Figure 5
(a) Zave hydrodynamic diameter (○) and ζ potential (●) of 10 nm of γ-Al2O3 NPs as a function of HA concentration at pH close to the point of zero charge (PZC) of Al2O3; and (b) bright field TEM images of 10 nm γ-Al2O3 NPs with 10 mg·L−1 of HA at pH close to PZC of Al2O3. Full article ">Figure 6
Bright field TEM images of 10 nm γ-Al2O3 NPs with montmorillonite at pH < PZC of Al2O3 NPs. Full article ">Figure 7
Bright field TEM images of 10 nm γ-Al2O3 NPs with montmorillonite at PZC of Al2O3 NPs. Full article ">Figure 8
Bright field TEM images of 10 nm γ-Al2O3 NPs with montmorillonite at pH > PZC of Al2O3 NPs. Full article ">

3760 KiB

Open AccessArticle

Modification of the Interfacial Interaction between Carbon Fiber and Epoxy with Carbon Hybrid Materials

by Kejing Yu, Menglei Wang, Junqing Wu, Kun Qian, Jie Sun and Xuefeng Lu

Nanomaterials 2016, 6(5), 89; https://doi.org/10.3390/nano6050089 - 12 May 2016

Cited by 30 | Viewed by 5821

Abstract

The mechanical properties of the hybrid materials and epoxy and carbon fiber (CF) composites were improved significantly as compared to the CF composites made from unmodified epoxy. The reasons could be attributed to the strong interfacial interaction between the CF and the epoxy [...] Read more.

The mechanical properties of the hybrid materials and epoxy and carbon fiber (CF) composites were improved significantly as compared to the CF composites made from unmodified epoxy. The reasons could be attributed to the strong interfacial interaction between the CF and the epoxy composites for the existence of carbon nanomaterials. The microstructure and dispersion of carbon nanomaterials were characterized by transmission electron microscopy (TEM) and optical microscopy (OM). The results showed that the dispersion of the hybrid materials in the polymer was superior to other carbon nanomaterials. The high viscosity and shear stress characterized by a rheometer and the high interfacial friction and damping behavior characterized by dynamic mechanical analysis (DMA) indicated that the strong interfacial interaction was greatly improved between fibers and epoxy composites. Remarkably, the tensile tests presented that the CF composites with hybrid materials and epoxy composites have a better reinforcing and toughening effect on CF, which further verified the strong interfacial interaction between epoxy and CF for special structural hybrid materials. Full article

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4198 KiB

Open AccessArticle

Investigation of the Structural, Electrical, and Optical Properties of the Nano-Scale GZO Thin Films on Glass and Flexible Polyimide Substrates

by Fang-Hsing Wang, Kun-Neng Chen, Chao-Ming Hsu, Min-Chu Liu and Cheng-Fu Yang

Nanomaterials 2016, 6(5), 88; https://doi.org/10.3390/nano6050088 - 10 May 2016

Cited by 33 | Viewed by 7325

Abstract

In this study, Ga₂O₃-doped ZnO (GZO) thin films were deposited on glass and flexible polyimide (PI) substrates at room temperature (300 K), 373 K, and 473 K by the radio frequency (RF) magnetron sputtering method. After finding the deposition [...] Read more.

In this study, Ga₂O₃-doped ZnO (GZO) thin films were deposited on glass and flexible polyimide (PI) substrates at room temperature (300 K), 373 K, and 473 K by the radio frequency (RF) magnetron sputtering method. After finding the deposition rate, all the GZO thin films with a nano-scale thickness of about 150 ± 10 nm were controlled by the deposition time. X-ray diffraction patterns indicated that the GZO thin films were not amorphous and all exhibited the (002) peak, and field emission scanning electron microscopy showed that only nano-scale particles were observed. The dependences of the structural, electrical, and optical properties of the GZO thin films on different deposition temperatures and substrates were investigated. X-ray photoemission spectroscopy (XPS) was used to measure the elemental composition at the chemical and electronic states of the GZO thin films deposited on different substrates, which could be used to clarify the mechanism of difference in electrical properties of the GZO thin films. In this study, the XPS binding energy spectra of Ga2p_3/2 and Ga2p_1/2 peaks, Zn2p_3/2 and Zn2p_1/2 peaks, the Ga3d peak, and O₁_s peaks for GZO thin films on glass and PI substrates were well compared. Full article

(This article belongs to the Special Issue Nanomaterials for Flexible and Stretchable Devices: Synthesis, Processes, and Applications)

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Surface morphologies of the Ga2O3-doped ZnO (GZO) thin films as a function of substrate and deposition temperature. (a) Glass; (b) polyimide (PI); (c) 373 K-Glass; (d) 373 K-PI; (e) 473 K-Glass; and (f) 473 K-PI, respectively. Full article ">Figure 2
Atomic force microscopy (AFM) analysis of the GZO thin films as a function of substrate at room temperature. (a) Glass and (b) PI, respectively. Full article ">Figure 3
X-ray diffraction (XRD) patterns of the undoped ZnO thin films and GZO thin films as a function of deposition temperature and on different substrates: (a) glass and (b) PI. a.u.: arbitrary unit. Full article ">Figure 4
Transmittance spectra of the undoped ZnO thin films and GZO thin films deposited as a function of deposition temperature and different substrates: (a) glass and (b) PI. Full article ">Figure 5
The (αhν)2 vs. hν-Eg plots of the GZO thin films deposited as a function of deposition temperature and on different substrates: (a) glass and (b) PI. Full article ">Figure 6
Variations of the (a) Hall mobility; (b) carrier concentration; and (c) resistivity of the GZO thin films as a function of used substrates and deposition temperature. Full article ">Figure 7
Typical widescan spectrum of the GZO thin films as a function of used substrates. (a): glass; (b): PI. Full article ">Figure 8
Binding energy spectra of (a) Ga2p3/2 and Ga2p1/2 peaks; (b) Zn2p3/2 and Zn2p1/2 peaks; and (c) Ga3d peak for the undoped ZnO thin films and GZO thin films on different substrates. Full article ">Figure 9
Binding energy spectra of O1s peaks for GZO thin films on different substrates: (a) glass and (b) PI. Full article ">

4376 KiB

Open AccessArticle

Graphene FETs with Low-Resistance Hybrid Contacts for Improved High Frequency Performance

by Chowdhury Al-Amin, Mustafa Karabiyik, Phani Kiran Vabbina, Raju Sinha and Nezih Pala

Nanomaterials 2016, 6(5), 86; https://doi.org/10.3390/nano6050086 - 10 May 2016

Cited by 3 | Viewed by 5684

Abstract

This work proposes a novel geometry field effect transistor with graphene as a channel—graphene field-effect transistor (GFET), having a hybrid contact that consists of an ohmic source/drain and its extended part towards the gate, which is capacitively coupled to the channel. The ohmic [...] Read more.

This work proposes a novel geometry field effect transistor with graphene as a channel—graphene field-effect transistor (GFET), having a hybrid contact that consists of an ohmic source/drain and its extended part towards the gate, which is capacitively coupled to the channel. The ohmic contacts are used for direct current (DC) biasing, whereas their capacitive extension reduces access region length and provides the radio frequency (RF) signal a low impedance path. Minimization of the access region length, along with the paralleling of ohmic contact’s resistance and resistive part of capacitively coupled contact’s impedance, lower the overall source/drain resistance, which results in an increase in current gain cut-off frequency, f_T. The DC and high-frequency characteristics of the two chosen conventional baseline GFETs, and their modified versions with proposed hybrid contacts, have been extensively studied, compared, and analyzed using numerical and analytical techniques. Full article

(This article belongs to the Special Issue 2D Nanomaterials: Graphene and Beyond Graphene)

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4050 KiB

Open AccessArticle

Rapamycin Loaded Solid Lipid Nanoparticles as a New Tool to Deliver mTOR Inhibitors: Formulation and in Vitro Characterization

by Alice Polchi, Alessandro Magini, Jarosław Mazuryk, Brunella Tancini, Jacek Gapiński, Adam Patkowski, Stefano Giovagnoli and Carla Emiliani

Nanomaterials 2016, 6(5), 87; https://doi.org/10.3390/nano6050087 - 9 May 2016

Cited by 34 | Viewed by 7266

Abstract

Recently, the use of mammalian target of rapamycin (mTOR) inhibitors, in particular rapamycin (Rp), has been suggested to improve the treatment of neurodegenerative diseases. However, as Rp is a strong immunosuppressant, specific delivery to the brain has been postulated to avoid systemic exposure. [...] Read more.

Recently, the use of mammalian target of rapamycin (mTOR) inhibitors, in particular rapamycin (Rp), has been suggested to improve the treatment of neurodegenerative diseases. However, as Rp is a strong immunosuppressant, specific delivery to the brain has been postulated to avoid systemic exposure. In this work, we fabricated new Rp loaded solid lipid nanoparticles (Rp-SLN) stabilized with polysorbate 80 (PS80), comparing two different methods and lipids. The formulations were characterized by differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), wide angle X-ray scattering (WAXS), cryo-transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS) and particle tracking. In vitro release and short-term stability were assessed. Biological behavior of Rp-SLN was tested in SH-SY5Y neuroblastoma cells. The inhibition of mTOR complex 1 (mTORC1) was evaluated over time by a pulse-chase study compared to free Rp and Rp nanocrystals. Compritol Rp-SLN resulted more stable and possessing proper size and surface properties with respect to cetyl palmitate Rp-SLN. Rapamycin was entrapped in an amorphous form in the solid lipid matrix that showed partial crystallinity with stable Lβ, sub-Lα and Lβ′ arrangements. PS80 was stably anchored on particle surface. No drug release was observed over 24 h and Rp-SLN had a higher cell uptake and a more sustained effect over a week. The mTORC1 inhibition was higher with Rp-SLN. Overall, compritol Rp-SLN show suitable characteristics and stability to be considered for further investigation as Rp brain delivery system. Full article

(This article belongs to the Special Issue Nanomaterials for Tissue Engineering)

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2190 KiB

Open AccessArticle

Rapid Nanoparticle Synthesis by Magnetic and Microwave Heating

by Viktor Chikan and Emily J. McLaurin

Nanomaterials 2016, 6(5), 85; https://doi.org/10.3390/nano6050085 - 5 May 2016

Cited by 71 | Viewed by 9227

Abstract

Traditional hot-injection (HI) syntheses of colloidal nanoparticles (NPs) allows good separation of the nucleation and growth stages of the reaction, a key limitation in obtaining monodisperse NPs, but with limited scalability. Here, two methods are presented for obtaining NPs via rapid heating: magnetic [...] Read more.

Traditional hot-injection (HI) syntheses of colloidal nanoparticles (NPs) allows good separation of the nucleation and growth stages of the reaction, a key limitation in obtaining monodisperse NPs, but with limited scalability. Here, two methods are presented for obtaining NPs via rapid heating: magnetic and microwave-assisted. Both of these techniques provide improved engineering control over the separation of nucleation and growth stages of nanomaterial synthesis when the reaction is initiated from room temperature. The advantages of these techniques with preliminary data are presented in this prospective article. It is shown here that microwave assisted heating could possibly provide some selectivity in activating the nanomaterial precursor materials, while magnetic heating can produce very tiny particles in a very short time (even on the millisecond timescale), which is important for scalability. The fast magnetic heating also allows for synthesizing larger particles with improved size distribution, therefore impacting, not only the quantity, but the quality of the nanomaterials. Full article

(This article belongs to the Special Issue Current Trends in Colloidal Nanocrystals)

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(a) LaMer diagram for the nucleation an growth of nanocrystals. (b) Dependence of nucleation and growth rate of crystallization on monomer oversaturation S (S = 1 is the solubility of the monomer at any given temperature). Full article ">Figure 2
Typical heating rates of magnetic, microwave and traditional heating methods. The heating rates depend on the power absorbed by the reaction mixture or contents. Full article ">Figure 3
Drawing of two extremes of microwave-assisted reactions. The vial on the left contains a solution with a large tan δ (such as water). Upon microwave irradiation, the microwaves minimally penetrate the reaction volume due to efficient absorption by the solvent. On the right, a reaction with a solvent with a small tan δ (such as an alkane) is shown, and the microwaves can penetrate further into the reaction solution. The reactants in the solution have a larger tan δ, and can interact, increasing temperature. Full article ">Figure 4
Photographs of a typical 10 mL microwave reaction vessel with a stir-bar and fiber-optic thermometer insert (left) and the fiber-optic thermometer (right). The glass insert provides values of the internal temperature, but is limited by response time and heat transfer through the insert. Full article ">Figure 5
Temperature vs time plots of microwave heating of water (blue) and mineral spirits (orange) to 150 °C at 800 W. The dashed lines indicate the temperatures recorded by the internal fiber-optic thermometer and the solid lines are the temperatures read by the external infrared (IR) sensor. Full article ">Figure 6
White light emission of ultrasmall quantum dots (QDs) produced in magnetic/microwave heating vs. other competing light sources (a). Absorption spectra of CdSe QDs synthesized when magnetic heating (b) is combined with traditional heating methods. The initial rapid magnetic heating provides a positive impact on the size distribution of the CdSe QDs. Full article ">

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Open AccessReview

Biosynthesis of Metal Nanoparticles: Novel Efficient Heterogeneous Nanocatalysts

by Jose M. Palomo and Marco Filice

Nanomaterials 2016, 6(5), 84; https://doi.org/10.3390/nano6050084 - 5 May 2016

Cited by 58 | Viewed by 7653

Abstract

This review compiles the most recent advances described in literature on the preparation of noble metal nanoparticles induced by biological entities. The use of different free or substituted carbohydrates, peptides, proteins, microorganisms or plants have been successfully applied as a new green concept [...] Read more.

This review compiles the most recent advances described in literature on the preparation of noble metal nanoparticles induced by biological entities. The use of different free or substituted carbohydrates, peptides, proteins, microorganisms or plants have been successfully applied as a new green concept in the development of innovative strategies to prepare these nanoparticles as different nanostructures with different forms and sizes. As a second part of this review, the application of their synthetic ability as new heterogonous catalysts has been described in C–C bond-forming reactions (as Suzuki, Heck, cycloaddition or multicomponent), oxidations and dynamic kinetic resolutions. Full article

(This article belongs to the Special Issue Nanoparticles for Catalysis)

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5217 KiB

Open AccessArticle

Noise Removal with Maintained Spatial Resolution in Raman Images of Cells Exposed to Submicron Polystyrene Particles

by Linnea Ahlinder, Susanne Wiklund Lindström, Christian Lejon, Paul Geladi and Lars Österlund

Nanomaterials 2016, 6(5), 83; https://doi.org/10.3390/nano6050083 - 29 Apr 2016

Cited by 8 | Viewed by 5283

Abstract

The biodistribution of 300 nm polystyrene particles in A549 lung epithelial cells has been studied with confocal Raman spectroscopy. This is a label-free method in which particles and cells can be imaged without using dyes or fluorescent labels. The main drawback with Raman [...] Read more.

The biodistribution of 300 nm polystyrene particles in A549 lung epithelial cells has been studied with confocal Raman spectroscopy. This is a label-free method in which particles and cells can be imaged without using dyes or fluorescent labels. The main drawback with Raman imaging is the comparatively low spatial resolution, which is aggravated in heterogeneous systems such as biological samples, which in addition often require long measurement times because of their weak Raman signal. Long measurement times may however induce laser-induced damage. In this study we use a super-resolution algorithm with Tikhonov regularization, intended to improve the image quality without demanding an increased number of collected pixels. Images of cells exposed to polystyrene particles have been acquired with two different step lengths, i.e., the distance between pixels, and compared to each other and to corresponding images treated with the super-resolution algorithm. It is shown that the resolution after application of super-resolution algorithms is not significantly improved compared to the theoretical limit for optical microscopy. However, to reduce noise and artefacts in the hyperspectral Raman images while maintaining the spatial resolution, we show that it is advantageous to use short mapping step lengths and super-resolution algorithms with appropriate regularization. The proposed methodology should be generally applicable for Raman imaging of biological samples and other photo-sensitive samples. Full article

(This article belongs to the Special Issue Nanoparticles in Bioimaging)

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3888 KiB

Open AccessArticle

Application of L-Aspartic Acid-Capped ZnS:Mn Colloidal Nanocrystals as a Photosensor for the Detection of Copper (II) Ions in Aqueous Solution

by Jungho Heo and Cheong-Soo Hwang

Nanomaterials 2016, 6(5), 82; https://doi.org/10.3390/nano6050082 - 27 Apr 2016

Cited by 10 | Viewed by 5790

Abstract

Water-dispersible ZnS:Mn nanocrystals (NCs) were synthesized by capping the surface with polar L-aspartic acid (Asp) molecules. The obtained ZnS:Mn-Asp NC product was optically and physically characterized using the corresponding spectroscopic methods. The ultra violet-visible (UV-VIS) absorption spectrum and photoluminescence (PL) emission spectrum of [...] Read more.

Water-dispersible ZnS:Mn nanocrystals (NCs) were synthesized by capping the surface with polar L-aspartic acid (Asp) molecules. The obtained ZnS:Mn-Asp NC product was optically and physically characterized using the corresponding spectroscopic methods. The ultra violet-visible (UV-VIS) absorption spectrum and photoluminescence (PL) emission spectrum of the NCs showed broad peaks at 320 and 590 nm, respectively. The average particle size measured from the obtained high resolution-transmission electron microscopy (HR-TEM) image was 5.25 nm, which was also in accordance with the Debye-Scherrer calculations using the X-ray diffraction (XRD) data. Moreover, the surface charge and degree of aggregation of the ZnS:Mn-Asp NCs were determined by electrophoretic and hydrodynamic light scattering methods, respectively. These results indicated the formation of agglomerates in water with an average size of 19.8 nm, and a negative surface charge (−4.58 mV) in water at ambient temperature. The negatively-charged NCs were applied as a photosensor for the detection of specific cations in aqueous solution. Accordingly, the ZnS:Mn-Asp NCs showed an exclusive luminescence quenching upon addition of copper (II) cations. The kinetic mechanism study on the luminescence quenching of the NCs by the addition of the Cu²⁺ ions proposed an energy transfer through the ionic binding between the two oppositely-charged ZnS:Mn-Asp NCs and Cu²⁺ ions. Full article

(This article belongs to the Special Issue Current Trends in Colloidal Nanocrystals)

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Dye-Doped Fluorescent Silica Nanoparticles for Live Cell and In Vivo Bioimaging

by Wen-Han Zhang, Xiao-Xiao Hu and Xiao-Bing Zhang

Nanomaterials 2016, 6(5), 81; https://doi.org/10.3390/nano6050081 - 27 Apr 2016

Cited by 67 | Viewed by 11135

Abstract

The need for novel design strategies for fluorescent nanomaterials to improve our understanding of biological activities at the molecular level is increasing rapidly. Dye-doped fluorescent silica nanoparticles (SiNPs) emerge with great potential for developing fluorescence imaging techniques as a novel and ideal platform [...] Read more.

The need for novel design strategies for fluorescent nanomaterials to improve our understanding of biological activities at the molecular level is increasing rapidly. Dye-doped fluorescent silica nanoparticles (SiNPs) emerge with great potential for developing fluorescence imaging techniques as a novel and ideal platform for the monitoring of living cells and the whole body. Organic dye-containing fluorescent SiNPs exhibit many advantages: they have excellent biocompatibility, are non-toxic, highly hydrophilic, optically transparent, size-tunable and easily modified with various biomolecules. The outer silica shell matrix protects fluorophores from outside chemical reaction factors and provides a hydrophilic shell for the insoluble nanoparticles, which enhances the photo-stability and biocompatibility of the organic fluorescent dyes. Here, we give a summary of the synthesis, characteristics and applications of fluorescent SiNPs for non-invasive fluorescence bioimaging in live cells and in vivo. Additionally, the challenges and perspectives of SiNPs are also discussed. We prospect that the further development of these nanoparticles will lead to an exciting breakthrough in the understanding of biological processes. Full article

(This article belongs to the Special Issue Nanoparticles in Bioimaging)

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Nanomaterials, Volume 6, Issue 5 (May 2016) – 14 articles

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