Photocatalytic degradation of phenol over novel rod shaped Graphene@BiPO4 nanocomposite

Graphene@BiPO₄ nanocomposite with unique rod shape morphology of BiPO₄ has been successfully fabricated by the simple microwave assisted hydrothermal method. The crucial role of graphene oxide in the growth of rod shaped BiPO₄ crystals has been attempted to explain in this article. Graphene oxide acts as a structure-directing and morphology-controlling agent in the nucleation and growth of nanocrystals. The as prepared organic–inorganic hybrid Graphene@BiPO₄ nanocomposite photocatalyst was characterized by various techniques i.e. X-ray diffraction, scanning electron microscopy, UV–vis diffuse reflectance spectroscopy, Raman spectroscopy and photoluminescence (PL) spectroscopy. The results were promising and shown enhanced photocatalytic activity than pure BiPO₄ for phenol degradation. The effect of graphene loading on the rates of photocatalytic degradation of phenol in solution is investigated. The result shows that the optimum photocatalytic activity of Graphene@BiPO₄ composite at 5 wt% of graphene under visible light is almost three times higher than pure BiPO₄.     

Synthesis and electrochemical performance of LiNi0.6Co0.2Mn0.2O2/reduced graphene oxide cathode materials for lithium-ion batteries

A LiNi_0.6Co_0.2Mn_0.2O₂/reduced graphene oxide (RGO) composite with RGO content of 1.2 % was prepared by a simple spray-drying method instead of high-energy ball milling method. The composite has been characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy, energy dispersive spectroscopy, and charge/discharge test. The X-ray diffractometry result showed that composite possessed a typical hexagonal structure. The RGO sheets served as efficient electronically conductive frameworks benefitting from its 2D structure and outstanding electronic conductivity. The scanning electron microscope and transmission electron microscopy verified that LiNi_0.6Co_0.2Mn_0.2O₂ particles were wrapped with RGO sheets, which facilitated electronic conductivity between particles. The electrochemical results indicated that composite delivered a higher discharge capacity at various discharge rates. The cycling performance was also evaluated. The composite exhibited better cycling performance than pristine sample. Electrochemical impedance spectroscopy showed that the RGO can greatly reduce the charge transfer resistance. The results here gave clear evidence of RGO to improve electrochemical performance.     

Synthesis, structural, optical and electrical properties of metal nanoparticle–rare earth ion dispersed in polymer film

Cu-nanoparticles have been prepared by ablating a copper target submerged in benzene with laser pulses of Nd:YAG (wavelength: 355, 532 nm and 1,064 nm). Colloidal nanoparticles have been characterized by UV–Vis spectroscopy and transmission electron microscopy. The obtained radius for the nanoparticles prepared using 1,064 nm irradiation lies in the range 15–30 nm, with absorption peak at 572 nm. Luminescence properties of Tb³⁺ ions in the presence and absence of Cu-nanoparticles have been investigated using 355 nm excitation. An enhancement in luminescence of Tb³⁺ by local field effect causing increase in lifetime of ⁵D₄ level of Tb³⁺ ion has been observed. Frequency and temperature-dependent conductivity of Tb³⁺ doped PVA thin films with and without Cu-nanoparticles have been measured in the frequency range 20 Hz–1 MHz and in the temperature range 318–338 K (well below its melting temperature). Real part of the conductivity spectra has been explained in terms of power law. The electrical properties of the thin films show a decrease in dc conductivity on incorporation of the Cu-nanoparticles.     

Magnetic ionic liquid-assisted synthesis of polyaniline/AgCl nanocomposites by interface polymerization

A simple strategy for the one-step synthesis of polyaniline/AgCl nanocomposites at the water/magnetic ionic liquid interface was reported. By controlling the reactive conditions, highly dispersed polyaniline/AgCl nanocomposites with their size ranging around 50–80 nm were obtained with magnetic ionic liquid as the oxidant. Transmission electron microscopy was used to show the morphology of the nanocomposites. The nanocomposites were also characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Moreover, polyaniline/AgCl nanocomposites on a glassy carbon electrode showed strong electrocatalytic activity for H₂O₂ and could be used to construct a H₂O₂ biosensor.     

Time-dependent growth of crystalline Au0-nanoparticles in cyanobacteria as self-reproducing bioreactors: 1. Anabaena sp.

In the experiments, multifunctional nanocomposites with fluorescence, superparamagnetism, and bioactivity were synthesized to isolate and detect bacteria. Fluorescent-magnetic nanocomposites (FMNPs) (Fe₃O₄@SiO₂@FITC–SiO₂, core/shell) were first synthesized. Then, FMNPs were conjugated with N-hydroxysuccinimide-activated 4-oxo-4-(prop-2-ynyloxy) butanoic acid (NHS-activated ester) by the linker of 3-aminopropyltriethoxysilane, and alkyne-functionalized fluorescent-magnetic nanocomposites (FMNPs-alkyne) were produced. After 3′-azidopropyl-O-α-d-manno-pyranoside was grafted on the surface of FMNPs-alkyne by click chemistry, the final product—mannose derivatives-grafted fluorescent-magnetic nanocomposites (FMNPs-mannose) were obtained. Common techniques (Nuclear magnetic resonance, ESI mass spectra, etc.) indicated the successful synthesis of the target products. The results of scanning electron microscopy, transmission electron microscopy, and dynamic light scattering showed that FMNPs with one or more magnetic cores have regular structure with a diameter around 100 nm. Fluorescence spectra and fluorescence microscopy indicated that those nanocomposites exhibited strong and stable fluorescence property. FMNPs-mannose have a saturation magnization of 6.88 emu/g at room temperature. FMNPs-mannose were applied to adhere to Escherichia coli ATCC25722 and Staphylococcus aureus ATCC6538. The results showed that FMNPs-mannose were able to specifically adhere to E. coli ATCC25722. However, it had no effect with S. aureus ATCC6538. The obtained FMNPs-mannose will find its application in bacteria detection and separation.     

Photoluminescence and optical characterization of CdS nanoparticles prepared by solid-state method at low temperature

The photoluminescence (PL) and optical properties of CdS nanoparticles prepared by the solid-state method at low temperature have been discussed. The effects of NaCl and anionic surfactant SDBS (sodium dodecylbenzene sulfonate) on the luminescent properties of CdS nanophosphors prepared using this method, without the inert gas or the H₂S environment, were studied separately. The synthesized products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscope (FESEM), and energy dispersive X-ray spectroscopy (EDAX). UV–VIS absorption and PL spectra were also studied. XRD studies confirmed the single-phase formation of CdS nanoparticles. TEM micrograph revealed the formation of nearly spherical nanoparticles with a diameter of 2.5 nm. The PL emission for the CdS shows the main peak at 560 nm with a shoulder at 624 nm, with an increase in the PL intensity after the addition of SDBS. The effect of Mn doping on PL intensity has also been investigated. The PL spectra show that the emission intensity decreases as the dopant concentration increases.     

Fabrication and characterization of MoO3 clusters-coated TiO2 nanotubes showing charge-transferred photoluminescence

MoO₃ clusters-coated TiO₂ nanotubes were synthesized wet-chemically and characterized by measuring photoluminescence spectra and kinetic profiles as well as extinction spectra and electron microscope images. TiO₂ nanotubes having an average outer diameter of 30 nm and an average thickness of 8 nm are surrounded by MoO₃ clusters with an average thickness of 4 nm. The excitation of both the TiO₂ cores and the MoO₃ shells of the type-II nanocomposites suspended in water yields charge-transferred junction photoluminescence having a long lifetime of 2.3 ns at 460 nm.     

Grain size effects on dynamics of Li-ions in Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> glass-ceramic nanocomposites

Li₃V₂(PO₄)₃ glass-ceramic nanocomposites, based on 37.5Li₂O-25V₂O₅-37.5P₂O₅ mol% glass, were successfully prepared via heat treatment (HT) process. The structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD patterns exhibit the formation of Li₃V₂(PO₄)₃ NASICON type with monoclinic structure. The grain sizes were found to be in the range 32–56 nm. The effect of grain size on the dynamics of Li⁺ ions in these glass-ceramic nanocomposites has been studied in the frequency range of 20 Hz–1 MHz and in the temperature range of 333–373 K and analyzed by using both the conductivity and modulus formalisms. The frequency exponent obtained from the power law decreases with the increase of temperature, suggesting a weaker correlation among the Li⁺ ions. Scaling of the conductivity spectra has also been performed in order to obtain insight into the relaxation mechanisms. The imaginary modulus spectra are broader than the Debye peak-width, but are asymmetric and distorted toward the high frequency region of the maxima. The electric modulus data have been fitted to the non-exponential Kohlrausch–Williams–Watts (KWW) function and the value of the stretched exponent β is fairly low, suggesting a higher ionic conductivity in the glass and its glass-ceramic nanocomposites. The advantages of these glass-ceramic nanocomposites as cathode materials in Li-ion batteries are shortened diffusion paths for Li⁺ ions/electrons and higher surface area of contact between cathode and electrolyte.     

Effect of the particle size on the electrochemical performance of nano-Li2FeSiO4/C composites

Nano-Li₂FeSiO₄/C composites were prepared from three kinds of nano-SiO₂ (their particle sizes are 15?±?5, 30?±?5, and 50?±?5 nm, respectively) by a traditional solid-state reaction method. The as-prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), elementary analyzer, Brunauer–Emmett–Teller (BET) analysis, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy. XRD results reveal that nano-Li₂FeSiO₄ composites fabricated from nano-SiO₂ (smaller than 30 nm) have less impurity. SEM results indicate that the particle size of nano-Li₂FeSiO₄ composites is nearly accord with the particle size of nano-SiO₂. BET analysis indicates that the specific surface areas of LFS15, LFS30, and LFS50 are 35.10, 35.27, and 26.68 m² g, respectively, and the main pore size distribution of LFS15, LFS30, and LFS50 are 1.5, 5.5, and 10 nm, respectively. Electrochemical measurements indicate that nano-Li₂FeSiO₄ composites prepared from nano-SiO₂ of 30?±?5 nm have the best electrochemical performance among the three samples.     

Propylene oxide-assisted fast sol–gel synthesis of mesoporous and nano-structured LiFePO4/C cathode materials

LiFePO₄/C nanocomposites are synthesized by a propylene oxide-assisted fast sol–gel method using FeCl₃, LiNO₃, NH₄H₂PO₄, and sucrose as the starting materials. It was found that after adding propylene oxide into the solution containing the starting materials, a monolithic jelly-like FePO₄ gel containing lithium and carbon source is generated in a few minutes without controlling the pH value of the solution and a time-consuming heating process. Propylene oxide plays a key role in the fast generation of the precursor gel. The final products of LiFePO₄/C are obtained by sintering the dry precursor gel. The structures, micro-morphologies, and electrochemical properties of the LiFePO₄/C composites are investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption–desorption analysis, electrochemical impedance spectrum, and charge–discharge cycling tests. The results indicate that the LiFePO₄/C composite prepared by sintering the precursor gel at 680 °C for 5 h is about 30 nm in size with a meso-porous structure (the main pore size distribution is around 3.4 nm). It delivers 166.7 and 105.8 mAh g^?1 at 0.2 and 30 C, respectively. The discharge specific capacity is 97.8 mAh g^?1 even at 40 C. The cycling performance of the prepared LiFePO₄/C composite is stable. The excellent electrochemical performance of the LiFePO₄/C composite is attributed to the nano-sized and mesoporous structure of LiFePO₄/C and the in-situ surface coating of the carbon. It was also found that propylene oxide is crucial for the generation of mesoporous and nano-structured LiFePO₄/C.