Abstract: In this work, the effects of Ag nanoparticles or Ag-PVP nanocomposites on the fluorescence properties of rhodamine B and fluorescein were investigated. The fluorescence intensities of the dyes could be largely enhanced by Ag nanoparticles with various concentrations. Moreover, the intensities were further increased by Ag-PVP nanocomposites. The results show that the maximum enhancement ratio of 36.5 fold is achieved for rhodamine B in the presence of 2% Ag-PVP nanocomposites, as well as 4.37 fold for fluorescein with 5% Ag-PVP nanocomposites. The enhancement is believed to mainly be originated from the increased excitation rate of the dyes due to the local electromagnetic field which is improved by the interaction of light with Ag nanoparticles. The further fluorescence enhancement of the dyes by Ag-PVP nanocomposites is attributed to the effective separation of Ag nanoparticles from the dyes by PVP molecules. Additionally, the difference in the enhancement ratio of two dyes was also discussed. The lower quantum yield of the dye, as well as higher overlapped degree between Ag nanoparticles and the absorption of dye result in the larger enhancement ratio. The research could be meaningful for improving the sensitivity of rapidly medical or biological assays.
Abstract: Synthesis and immobilization of Au nanoparticles (AuNPs) was performed on transparent fluorine-doped tin oxide (FTO) substrate by pulse electrodeposition method. The method was cost effective, simple and capable of producing nanoparticles strongly attached to the substrate. Effects of several influencing factors such as duty cycle, pulse frequency, current density, solution concentration, deposition period and annealing procedure on the optical properties of AuNPs-FTO electrode were investigated. AuNPs-FTO electrodes were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and UV-Vis absorption analysis. Controllability of the plasmon absorption of the electrodeposited film by tuning of the electrodeposition conditions and thermal annealing procedure was important achievements helpful to the progress of the AuNP film applications in the tunable localized surface plasmon resonance spectroscopy (LSPR) manufacturing industry.
Abstract: This study aims to describe the preparation and characterization of SiO2/TiO2 core-shell particles. In order to prepare the homogenous SiO2/TiO2 inorganic compounds by sol-gel process, SiO2 particles were used as the core, AcAc served as a chelating agent to chelate with TTIP (which was used as the precursor to TiO2), and PEG was added to stabilize the hydrolysis/condensation process. In addition, the ionic surfactant (SDS) and the nonionic surfactant (PVP) dispersed the core-shell particles. In order to improve the crystal structure, a high temperature was used to calcine the core-shell particles. The influence of various reaction parameters on the size, morphology and composition of the particles was also investigated. The properties of the particles were analyzed by electron microscopy, fourier transform infrared analysis, thermogravimetric analysis and powder X-ray diffraction.
Abstract: Single crystalline high quality α-Mn2O3 nanorods and sea-urchins assembled with pen-type nanoneedles have been successfully synthesized by template-free hydrothermal route. The variation in hydrothermal temperature has affected the morphology of the α-Mn2O3 sea-urchin assembled with the nanoneedles noticeably. The influence of temperature change on the thickness, crystallinity, surface morphology and optical properties of α-Mn2O3 has been characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HRTEM), Raman Spectroscopy (RS) and UV-visible Spectroscopy. The results showed that in our experimental conditions, single crystalline nanorods of the α-Mn2O3 were obtained at a low temperature of 180 °C, while single crystalline sea-urchin assembled with pen-type nanoneedles were obtained by increasing the temperature to 280 °C. Nanorods and sea-urchin assembled with pen-type nanoneedles obtained had the well defined morphology and crystalline quality. The sea-urchin synthesized at 280 °C exhibited more than 90% absorption in UV-visible spectrum.
Abstract: PbWO4 crystals with different morphologies were readily induced by duck egg membrane via biomimetic synthesis at room temperature. The size and morphologies of the PbWO4 crystals could be controlled by outer or inner surface of duck egg membrane, the reactant concentration and the reaction time. The results show that spherical, flower-like and spindle-like crystals were obtained on the inner surface of membrane while rhombic, hexagon-like and chrysanthemum-like crystals were gained on the outer surface with the concentration of Pb2+ and WO42- increases. Room-temperature fluorescence spectra indicate the products on the inner surface of the duck egg membrane have a slight blue shift compared to that on the outer surface at the same condition. The PbWO4 crystals with small size obtained at a lower reactant concentration present a better fluorescence performance. The exploration of the reaction mechanism reveals that the interaction between Pb2+ ions and the proteins on the surface of duck egg membrane can make the conformation of the proteins more ordered. In general, the present synthesis route may be extended to prepare other inorganic functional micro-materials.
Abstract: Curcuminoids are a mixture of phenolic compounds isolated from Curcuma longa L. (turmeric) rhizomes that possess antioxidant, anti-inflammatory, anti-Alzheimer and anticancer activities. However, curcuminoids have poor solubility in acid and neutral solutions, rapid decomposition in neutral and alkaline solutions, and low bioavailability that limits their use as therapeutic agents. To overcome these problems, statistical design for preparation and characterization of poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles as a carrier for curcuminoids was evaluated in this study. The curcuminoid-loaded PLGA nanoparticles were prepared by a modified spontaneous emulsification solvent diffusion method using polyvinyl alcohol (PVA) as a stabilizer. The formulations were optimized using three-factor, three-level Box-Behnken experimental design. The independent variables in the formulations were the lactide/glycolide (LA/GA) molar ratio of PLGA (50:50 to 85:15), the curcuminoid concentration (2%-10%, w/v), and the PVA concentration (3%-7%, w/v). The dependent variables were particle size, loading capacity and entrapment efficiency. Statistical evaluation showed that the LA/GA molar ratio of PLGA and the curcuminoid and PVA concentrations all affected the characteristics of the PLGA nanoparticles. To achieve a minimum particle size and maximum loading capacity and entrapment efficiency, the optimal formulation of the curcuminoid-loaded PLGA nanoparticles had a LA/GA molar ratio of PLGA of 50:50, 10% (w/v) curcuminoids, and 3% (w/v) PVA. A sustainable in vitro release profile of curcuminoids was obtained from this optimal formulation.
Abstract: Magnetic nanoparticles of manganese doped ZnS has been synthesized with different molar ratios of manganese and zinc by co-precipitation method. Structure of the prepared nanocomposite was investigated using FT-IR, XRD, TEM and VSM. The most excellent photodegradation efficiency of Reactive Blue 198 (RB198) was observed with the molar ratio of Mn-doped ZnS/Fe3O4 and it was 1:1 in which molar percentage of Mn2+ was 9%. The experiments of dye degradation were carried out under visible light and UV radiation. Results shown that the degradation efficiency of RB198 was up to 100% at the concentration of 200 ppm for 10 minutes when the amount of catalyst was 0.2g/l. Additionally, the effect of various parameters including initial concentration, illumination time and pH to the photodegradation efficiency of dye was also carried out. More interestingly, the reusable experiments showed that the nanocomposited exhibited high photodegradation capacity after three cycles and can be recycled conveniently from water with the assist of an external magnet because of its exceptional properties.
Abstract: NaYbF4: Yb3+, Tm3+ nanoparticles (UCNPs) capped with oleic acid (OA) have been synthesized via high-temperature solvent reaction. The optimization sample of NaYb0.96Er0.02Tm0.02F4 nanoparticles possess spectral purity (the Snw value is bigger than 0.7) and intense near infrared to near infrared (NIR-to-NIR) upconversion luminescence (UCL) (the power of laser is as low as 3.8 W), which makes them ideal and promising platforms for high contrast bioimaging.
Abstract: An Atomic Finite Element Analysis is developed in this paper. At atomic scale, the interatomic bonding forces of Van der Waals and the covalent chemical bond are taken into account. The methodology is applied to study the behavior of carbon nanotubes, whose development has experienced strong growth in recent years and that can be used for quality mechanical reinforcement. These carbon nanotubes are formed by repeating zigzag carbon-carbon bonds. Development of atomic finite element method (AFEM) methodology can be traced back to the homogenized elastic properties of various graphene structures (single-layer graphene sheet, Zig-zag single-walled carbon nanotubes, triple-layer graphene sheet).
Abstract: Dye sensitized solar cells based on TiO2 nanorod suffers from low dye loading and poor light scattering ability, both of which obstacle the improvement of energy conversion efficiency. In this paper, we have successfully synthesized TiO2 rutile nanostructures with tunable morphology on FTO substrates with a one-step hydrothermal synthesis by changing the Ti concentration in the precursor solution. Three different photoanodes, namely, nanorod layer, nanorod layer with flower-like clusters and nanorod layer with densely packed spheres, are obtained without using any surfactants. The photoanode of nanorod layer with densely packed spheres exhibits improved dye loading and enhanced light reflection from 600-800 nm. DSSCs based on such a photoanode exhibits an energy conversion efficiency of 4.08%, achieving a nearly three-fold enhancement compared with dye sensitized solar cells based on TiO2 nanorod array.