Structure and Optical Behavior of Nanocomposite Hybrid Films of Well Monodispersed ZnO Nanoparticles into Poly (vinylpyrrolidone)

We fabricated an inorganic-polymeric photoluminescent thin film based on ZnO nanoparticles, which were grown directly in the poly（vinylpyrrolidone） （PVP） matrix. The microstructure, composition, thermal stability, and the temperature-dependent photoluminescence of the thin film were investigated. X-ray diffraction （XRD） and transmission electron microscopy （TEM） results indicated that all the ZnO nanoparticles with a polycrys talline hexagonal wurzite structure were well separated from each other and were dispersed in the polymeric matrix homogeneously and randomly. Raman spectrum （Raman） showed a typical resonant multi-phonon process within the hybrid thin film. The shifts of infrared bands for PVP in the hybrid film should be attributed to strong coulombic interaction between ZnO and polymeric matrix. The stability of the hybrid film and the effect of the perturbation of ZnO on the stability were determined by means of the thermogravimetric analysis （TG） and differential thermal analysis （DTA）. The ultraviolet-visible adsorption （UV-vis） showed distinct excitonic features. The photoluminescent spectrum （PL） of the ZnO nanoparticles modified by PVP molecules showed markedly enhanced ultraviolet emission and significantly reduced green emission, which was due to the Perfect surface passivation of ZnO nanoparticles. Temperature dependent photoluminescent spectrum studies suggested that the ultraviolet emission was associated with bound exciton recombination.

Recoverable Palladium（O） on Poly（vinylpyrrolidone） Catalyzed Ligand-free Suzuki Reaction in Water

In the absence of any ligand, a recoverable palladium（O） on poly（vinylpyrrolidone） （PVP） catalyzed Suzuki reaction of aryl iodide and bromide with potassium aryltrifluoroborate was developed. The reaction conditions involved the use of water as the solvent, potassium carbonate as the base, and PVP supported palladium metal colloids as the catalyst. The palladium metal could be recovered and recycled for eight consecutive trials without significant loss of its activity.

Convenient synthesis of silver nanoplates with adjustable size through seed mediated growth approach

Silver nanoplates,with average thickness about 5 nm and average tunable size from 40 to 500 nm,were synthesized via a simple room-temperature solution-phase chemical reduction method in the presence of appropriate concentration of trisodium citrate and silver seeds.The optical in-plane dipole plasmon resonance bands of these silver plates could be tuned from 520 to 1100 nm.Control experiments were explored for understanding of the growth mechanism.It is found that both the amount of citrate ions and the small silver seeds added to the growth solution are the key to controlling the silver nanoplates without changing their thickness and crystal structure.Small silver seeds are found to play an important role in the formation of large thin silver nanoplates when poly（vinylpyrrolidone）（PVP） are used as capping agent.

Controlled Synthesis and Characterization of Nobel Metal Nanoparticles

In this work, monodispersed, well-shaped platinum (3.2 - 6.4 nm), rhodium (2.4 - 5.1 nm), palladium (3.2 - 5.3 nm) nanoparticles capped with poly(vinylpyrrolidone) were synthesized by a polyol reduction method in an ethylene glycol solution at temperature of 190℃. The influences of synthetic parameters on the size and morphology of the noble metal nanoparticles have been systematically investigated. The noble metal nanoparticles were characterized by means of UV-vis, laser scattering particle size distribution analysis (LSPSDA) and transmission electron microscopy (TEM). The experimental results showed that the particle size of metals nanoparticles, the morphology of which was spherical, increased with the raise of metal precursor concentration as well as the amount of PVP. The optimal molar ratio of PVP/metal and metal precursor concentration for the fabrication of Pt, Rh, and Pd nanoparticles with uniform distribution were 10 and 0.1 mM, respectively. The morphologies of the Rh nanoparticles with the size of 5.1 nm were polygons, including hexagons, pentagons, and triangles.

A Facile Method for Synthesis of Polygonal Silver Nanopartilces

The synthesis of nanosized powders and their assembly is of considerable importance to the microelectronics industry because of the pervasive drive to miniaturize components. In this work, silver (Ag) nanoparticls was syntheized. Polygonal silver nanoparticls were synthesized by reacting AgNO3 with hydroquinone, in the presence of poly-(vinylpyrrolidone) (PVP) and an ionic liquid 1-n-butyl-3-methylimidazolium hexafluoroborate ([BMIM]·PF6) at ambient temperature. XRD shows that the crystal structure of the nanoparticles is face-centered cubic. TEM measurements display the silver particles with uniform size and narrow particle size distributions. The UV-Vis spectra of the nanoplates distinguish from those of the samples prepared in the absence of PVP and/or ILs. This method is facile and the as-prepared silver nanoparticls are also stable in some solvents, such as ethanol and water.

A Solvothermal Route to Cu_2O Nanocubes and Cu Nanoparticles

Cu2O nanocubes and Cu nanoparticles were prepared by reducing Cu（ Ⅱ ） salt with ethanol as the reducing agent and solvent in the presence of multidentate ligand poly（vinylpyrrolidone） （PVP） under different conditions. The morphologies and the crystalline structures of the products were characterized by using scanning electron microscopy （SEM）, transmission electron microscopy（TEM）, selected-area electron diffraction（ SAED）, and powder X-ray diffraction（XRD）. In particular, the influences of the solvothennal reaction temperature and alkalinity on the products were investigated. A lower temperature and a lower alkali concentration favor the formation of the Cu2O phase, whereas a higher temperature and a higher alkali concentration generally lead to the formation of the Cu phase.

Synthesis and Characterization of Novel Organic/Inorganic Hybrid Polymers Containing Polyhedral Oligosilsesquioxanes

Hybrid polymers, poly(vinyl pyrrolidone-co-isobutyl styryl polyhedral oligomeric silsesquioxanes)s (PVP-POSS) were synthesized by one step polymerization and characterized using GPC and DSC. Addition of POSS significantly increases the Tg of polyvinylpyrrolidone at a fair high POSS content and obtained high molecular weight polymers with very narrow molecular distribution. The POSS content in the resulted hybrids can be controlled by varying the POSS feed ratio.

Floating silver film： A flexible surface-enhanced Raman spectroscopy substrate for direct liquid phase detection at gas-liquid interfaces

In recent years, surface-enhanced Raman spectroscopy （SERS） has developed rapidly and is used for the detection of molecules and biomolecules in liquids. However, few studies have focused on SERS using a water surface as the substrate. A floating metal film on water is desirable for an enhanced SERS performance. In this work, silver nanopartides （Ag NPs） encased in poly（vinylpyrrolidone） films （Ag-PVP films） were synthesized on the surface of an aqueous solution by room temperature electron reduction. A floating silver film on a water surface was thereby achieved and is reported for the first time. The synthesized Ag-PVP film is an excellent flexible substrate for SERS and has other potential appli- cations. Using the floating silver film as a flexible SERS substrate, 10-11 M of 4-aminothiophenol, 10^-6 M of riboflavin, 10^-9 M of 4-mercaptobenzoic acid, 10^-7 M of 4-mercaptophenol, and 10^-7 M of 4-aminobenzoic acid are identified, demonstrating potential use for the floating substrate in the liquid-phase detection of molecules.

Layer-controlled Pt-Ni porous nanobowls with enhanced electrocatalytic performance

Hollow and porous Pt-based nanomaterials are promising catalysts with applications in many sustainable energy technologies such as fuel cells. Economical and green synthetic routes are highly desirable. Here, we report a facile approach to prepare double- and single-layered Pt-Ni nanobowls （DLNBs and SLNBs） with porous shells. Microstructural analysis revealed that the shells were constructed of alloyed Pt-Ni nanocrystals and small amounts of Ni compounds. X-ray photoelectron spectra showed that their Pt 4f binding energies shifted in the negative direction compared to those of the commercial Pt/C catalyst. Furthermore, the DLNBs contained greater contents of oxidized Ni species than the SLNBs. The layer-controlled growth processes were confirmed by microscopy, and a formation mechanism was proposed based on the assistance of citrate and poly（vinylpyrrolidone） （PVP）. For the methanol oxidation reaction, the DLNBs and SLNBs exhibited 2.9 and 2.5 times higher mass activities than that of the commercial Pt/C catalyst, respectively. The activity enhancements were attributed to electronic effects and a bifunctional mechanism. Chronoamperometry and prolonged cyclic voltammetry indicated that the Pt-Ni bowl-like structures had better electrochemical properties and structural stability than the commercial Pt/C catalyst, thus making the Pt-Ni nanobowls excellent electrocatalysts for use in direct methanol fuel cells.