Reduction Reaction Of P-nitrophenol Research Articles

Preparation of Au@silica Janus nanosheets and their catalytic application

We report the preparation of the Au@silica Janus nanosheets by materialization of the emulsion interface and further functionalization with Au nanoparticles. The amphiphilicity and emulsification property of Au@silica Janus nanosheets were not affected by the grown Au nanoparticles. The catalytic performance of the Au@silica Janus nanosheets was explored using the reduction reaction of p-nitrophenol and p-nitroanisol as model reactions in homogenous reaction and emulsion interfacial reaction, respectively. The results indicated that the Au@silica Janus nanosheets exhibited excellent catalytic activity for the reduction reaction of p-nitrophenol in the homogenous reaction. In emulsion interface, the conversion of p-nitroanisol was 16-fold higher than that of the two-phase interface, which could attribute to the expanded active areas and the favorable mass transfer at the emulsion interface. The recovery of the Au@silica Janus nanosheets was simply realized and could be reused with 100 % catalytic activity. Compared with the particle-like Janus catalyst, the Au@silica Janus nanosheets could achieve better catalytic efficiency with a more low content. The conception of emulsion interfacial catalysis with Janus catalysts provides an avenue for conventional heterogeneous reactions.

Difunctional Cu-doped carbon dots: catalytic activity and fluorescence indication for the reduction reaction of p-nitrophenol

The reduction reaction ofp-nitrophenol was catalyzed and monitored using the fluorescence of Cu-doped CDs.

Ionic Liquid-Assisted Synthesis and Catalytic Properties of AuPd Bimetallic Particles

Ionic liquid-assisted synthesis of inorganic materials has been demonstrated to be an efficient synthesis route in the inorganic community. Here AuPd alloy particles are successfully synthesized with the assistance of the ionic liquid 1-octyl-3-methylimidazolium chloride ([OMIM]Cl) at room temperature. The p-nitrophenol reduction reaction using the synthesized metal particles as the catalysts indicates that the synthesized Au(1)Pd(1) particles exhibit the highest catalytic activity in comparison with the studied AuPd particles, the Au and the Pd particles. Therefore, the present synthesis route could be used as an efficient synthesis strategy for fabrication of metal alloy particles with interesting catalytic properties.

Gold Incorporated Mesoporous Silica Thin Film Model Surface as a Robust SERS and Catalytically Active Substrate.

Ultra-small gold nanoparticles incorporated in mesoporous silica thin films with accessible pore channels perpendicular to the substrate are prepared by a modified sol-gel method. The simple and easy spin coating technique is applied here to make homogeneous thin films. The surface characterization using FESEM shows crack-free films with a perpendicular pore arrangement. The applicability of these thin films as catalysts as well as a robust SERS active substrate for model catalysis study is tested. Compared to bare silica film our gold incorporated silica, GSM-23F gave an enhancement factor of 103 for RhB with a laser source 633 nm. The reduction reaction of p-nitrophenol with sodium borohydride from our thin films shows a decrease in peak intensity corresponding to –NO2 group as time proceeds, confirming the catalytic activity. Such model surfaces can potentially bridge the material gap between a real catalytic system and surface science studies.

Bromide ion mediated modification to digestive ripening process: Preparation of ultra-small Pd, Pt, Rh and Ru nanoparticles

Nanoparticles of catalytically important transition metals, such as Pd, Pt, Rh, and Ru have been prepared by the well-known “digestive ripening” (DR) and “modified digestive ripening” (mDR) methods. In the traditional DR process, a polydisperse colloidal dispersion is refluxed in the presence of a surface-active molecule, such as alkanethiol. The mDR method involved a small modification in the procedure, wherein refluxing was performed with an alkanethiol and a tetra-alkylammonium bromide surfactant. This minor modification led to a dramatic change in the final particle size distributions, giving access to nanoparticles in the <3 nm size regime; this was not possible with the traditional DR process. Bromide ions, which are present during refluxing, proved to be an important ingredient in the modification process. These bromide ions are revealed to act as etchants, resulting in ultra-small nanoparticles. All transition metal nanoparticles investigated displayed catalytic activity in the reduction reaction of p-nitro phenol. Pd nanoparticles, synthesized by a modified digestive ripening method, exhibited the best catalytic activity among the systems investigated.

Evaluation of the catalytic activity of the composite track-etched membranes for p-nitrophenol reduction reaction

The catalytic properties of composite materials produced by electroless deposition of gold and silver into nanosized channels of polyethylene terephthalate (PET) track-etched membranes (TeMs) have been addressed. Applying the activation solution with sodium potassium tartrate as a reducing agent makes it possible to prepare PET/Ag/Au composites. The dimension (wall thickness), the structure, and the composition of the deposited metallic nanotubes have been determined by scanning electron microscopy and energy dispersive X-ray diffraction analysis. Liquid-phase reduction of p-nitrophenol as a model system has been used to examine the catalytic activity of the composites, and catalytic ability has been studied as a function of the nanotube wall thickness. It has been found that the mixed PET/Ag/Au composite can mediate the reaction to the most complete extent at the highest rate, with the catalytic activity remaining quite high for five consecutive test cycles.

Kinetics of p-Nitrophenol Reduction Catalyzed by PVP Stabilized Copper Nanoparticles

Copper nanoparticles (CuNPs) in aqueous medium were prepared with alkaline hydrazine hydrate as the reductant and PVP as the stabilizing agent without any inert gas protection. Careful variation in the amount of reductant resulted in formation of two stable CuNPs dispersions with different average sizes and consequently different localized surface plasmon resonance absorbances. These two as-synthesized CuNPs dispersions were used to catalyze the model p-nitrophenol reduction reaction. The kinetics of reduction was monitored as a function of concentration and temperature of reactants. Using this we determined the activation energy, pre-exponential factor and the entropy of activation for the two types of CuNPs samples. Catalytic activities of the CuNPs were found to be affected mainly by their activation energies.

Thermal and pH Dual Responsive Copolymer and Silver Nanoparticle Composite for Catalytic Application

AbstractN‐Isopropylacrylamide and vinyl imidazole copolymer, P(NIPAM‐co‐VI), was synthesized by free radical emulsion polymerization. Then, the copolymer and silver nanoparticle composite, P(NIPAM‐co‐VI)‐Ag, was prepared by in situ reduction of AgNO3 with NaBH4. Due to the coexistence of thermal‐responsive PNIPAM and pH‐responsive PVI, P(NIPAM‐co‐VI) and P(NIPAM‐co‐VI)‐Ag exhibited both thermal and pH responsibility, their size would change while altering the temperature or pH of the circumvent. Their thermal and pH dual responsive properties were studied by dynamic light scattering (DLS). P(NIPAM‐co‐VI)‐Ag could be stably dispersed in water at a pH range from 3.0 to 9.3, which is favorable to use P(NIPAM‐co‐VI)‐Ag as a catalyst in the reduction reaction of p‐nitrophenol. The reaction rate constant (kapp) increased with the decrease of pH or the increase of VI content in the copolymer.

Chitosan stabilised nanozero‐valent iron for the catalytic reduction of p‐nitrophenol

Chitosan stabilised nanozero-valent iron (CNZVI) is proposed as a catalyst because of its simple preparation and high activity. The catalytic activity of CNZVI was investigated using the reduction reaction of p-nitrophenol (p-NP) by NaBH4. The result indicated that CNZVI possessed good catalytic activity, and the rate constant (k) was 2.45 × 10−3 s−1. In addition, CNZVI can be easily separated by an external magnetic field from aqueous solution, and it could also be repeatedly applied for the reduction of p-NP for at least five successive cycles with stable catalytic activity. All of these results suggest that CNZVI could be used as an excellent catalyst for the catalytic reduction of p-NP by NaBH4.

Carbon-protected Au nanoparticles supported on mesoporous TiO2 for catalytic reduction of p-nitrophenol

With the introduction of carbon on Au/TiO2, the reaction rate of C/Au/TiO2 increased by 29% and the stability enhanced by about 3 times more than Au/TiO2 in the p-nitrophenol reduction reaction. Carbon species enhanced the stability of Au nanoparticles and also increase the organic reactants adsorptive ability.

PEO-b-P4VP/Yttrium Hydroxide Hybrid Nanotubes as Supporter for Catalyst Gold Nanoparticles

The adsorption of poly (ethylene oxide)-b-poly(4-vinylpyridine)(PEO-b-P4VP) micelles onto the surface of yttrium hydroxide nanotubes (YNTs) resulted in the hybrid nanotubes with a dense P4VP inner layer and a stretched PEO outer layer surrounding YNTs. The dense P4VP layer was further stabilized by the crosslinking using 1,4-dibromobutane as the crosslinker. Then, the crosslinked hybrid nanotubes (CHNTs) were used as a novel nano supporter for loading the catalyst gold nanoparticles (GNPs) within the crosslinked P4VP layer. The resultant GNPs/CHNTs (GNTs loaded on CHNTs) were applied to catalyze the reduction reaction of p-nitrophenol. The results indicate that this novel nano supporter has advantages such as good dispersity in the suspension, high capacity in loading GNPs (0.87 mmol/g), high catalytic activity of the loaded GNPs (12.9 μmol−1min−1), and good reusability of GNTs/CHNTs.

Water-soluble Au–CeO2 hybrid nanosheets with high catalytic activity and recyclability

A facile one-pot aqueous method has been fabricated for synthesis of Au-CeO(2) hybrid nanosheets. L-Lysine molecules are employed as the junctor to connect the two components of Au and CeO(2) nanoparticles. The obtained catalysts exhibited high catalytic activity, stability, and recyclability for the reduction reaction of p-nitrophenol into p-aminophenol by NaBH(4).

Preparation and electrocatalytic activity of hollow global tungsten carbide with mesoporosity

Tungsten carbide (WC) has an important advantage—a unique to resist very strong catalytic poisons, such as carbon monoxide, hydrocarbons, and hydrogen sulfide, but its catalytic activity is much less than that of platinum metal. How to improve its catalytic activity is the key problem for realization in practical usage and replacement of platinum catalyst in catalysis. Hollow global WC with mesoporosity was fabricated by spray drying sphere miniaturation-gas-solid reaction, used ammonium metatungstate and carbon monoxide as precursors. The samples were characterized by XRD, SEM and EDS, respectively. The results show that the particle of the sample is hollow global WC with mesoporosity. Its crystal phase is WC of hexagonal structure with minor tungsten oxides. The electrocatalytic activity of the sample was analyzed by the approach of powder microelectrode. Hollow global WC with mesoporosity and WC are catalytic active for p-nitrophenol reduction reaction in basic solution. The catalytic activity of hollow global WC with mesoporosity is higher than that of nanosized sphere WC, and much higher than that of sphere WC at the same size of hollow global WC with mesoporosity. It is an efficacious way to improve the catalytic activity of WC by adjusting its morphology and structure with mesoporous hollow globe.