Gold catalysis: Effect of particle size on reactivity towards various substrates

Integration of Gold Nanoparticles into Crosslinker-Free Polymer Particles and Their Colloidal Catalytic Property

This work demonstrates the incorporation of gold nanoparticles (AuNPs) into crosslinker-free poly(N-isopropylacrylamide), PNIPAM, particles in situ and the examination of their structural and catalytic properties. The formation process of the AuNPs across the crosslinker-free PNIPAM particles are compared to that of crosslinked PNIPAM particles. Given the relatively larger free volume across the crosslinker-free polymer network, the AuNPs formed by the in situ reduction of gold ions are detectably larger and more polydisperse, but their overall integration efficiency is slightly inferior. The structural features and stability of these composite particles are also examined in basic and alcoholic solvent environments, where the crosslinker-free PNIPAM particles still offer comparable physicochemical properties to the crosslinked PNIPAM particles. Interestingly, the crosslinker-free composite particles as a colloidal catalyst display a higher reactivity toward the homocoupling of phenylboronic acid and reveal the importance of the polymer network density. As such, the capability to prepare composite particles in a controlled polymer network and reactive metal nanoparticles, as well as understanding the structure-dependent physicochemical properties, can allow for the development of highly practical catalytic systems.

ZnO nanoparticles supported on dendritic fibrous nanosilica as efficient catalysts for the one-pot synthesis of quinazoline-2,4(1H,3H)-diones

The transmutation of waste into valuable materials has a special place in green chemistry. Herein, we report the preparation of quinazoline-2,4(1H,3H)-diones from 2-iodoaniline, isocyanides, and carbon dioxide in the presence of ZnO NPs stably placed on the surface of dendritic fibrous nanosilica by cellulose (DFNS/cellulose-ZnO) as a catalyst. This is a great economic strategy to create three bonds in a one-pot multicomponent reaction step employing functional groups. To prepare the catalyst, the dendritic fibrous nanosilica surface was first activated using cellulose as a substrate to support ZnO NPs. Cellulose acts as a stabilizing and reducing agent for the ZnO nanocatalyst and eliminates the need for a reducing agent. The structure of the prepared DFNS/cellulose-ZnO was examined by various methods, including thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP). The largest amount of quinazoline-2,4(1H,3H)-diones was obtained under ideal situations in the presence of 5 mg of DFNS/cellulose-ZnO under carbon dioxide (1 atm) utilizing a balloon set at 70 °C for 3 hours. The substance was reused for ten consecutive runs and the quinazoline-2,4(1H,3H)-dione content was more than 92% each time. This indicates the potential for application in the green and economic production of quinazoline-2,4(1H,3H)-diones, especially from low-cost feedstocks.

The transmutation of waste into valuable materials has a special place in green chemistry.

Characterization of Nanoparticles: Advances

Over the past two decades, the unique properties of engineered nanoparticles (NPs) have placed them at the centre of revolutionary advancements in many sectors of science, technology and commerce. Multi-technique and multi-disciplinary analytical approaches are required to identify, quantify, and characterize the chemical composition, size and size distribution, surface properties and the number and concentration of NPs. In this chapter, an overview of the recent advances in the characterization of NPs will be presented.

Photooxidation of triarylphosphines under aerobic conditions in the presence of a gold(iii) complex on cellulose extracted from Carthamus tinctorius immobilized on nanofibrous phosphosilicate

Triarylphosphines were converted to the corresponding oxides via photooxidation as a novel method.

Gas sensitivity and sensing mechanism studies on Au-doped TiO₂ nanotube arrays for detecting SF₆ decomposed components

The analysis to SF₆ decomposed component gases is an efficient diagnostic approach to detect the partial discharge in gas-insulated switchgear (GIS) for the purpose of accessing the operating state of power equipment. This paper applied the Au-doped TiO₂ nanotube array sensor (Au-TiO₂ NTAs) to detect SF₆ decomposed components. The electrochemical constant potential method was adopted in the Au-TiO₂ NTAs' fabrication, and a series of experiments were conducted to test the characteristic SF₆ decomposed gases for a thorough investigation of sensing performances. The sensing characteristic curves of intrinsic and Au-doped TiO₂ NTAs were compared to study the mechanism of the gas sensing response. The results indicated that the doped Au could change the TiO₂ nanotube arrays' performances of gas sensing selectivity in SF₆ decomposed components, as well as reducing the working temperature of TiO₂ NTAs.

A review on catalytic applications of Au/TiO2 nanoparticles in the removal of water pollutant

Nanomaterials are showing great potential for the improvement of water treatment technologies. In recent years, catalysis and photocatalysis processes using gold nanoparticles (Au-NPs) have received great attention due to their effectiveness in degrading and mineralizing organic compounds. This paper aims to review and summarize the recently published works and R & D progress in the field of photocatalytic oxidation of various water pollutants such as toxic organic compounds (i.e. azo dyes and phenols) by Au-NPs/TiO2 under solar, visible and UV irradiation. Extensive research which has focused on the enhancement of photocatalysis by modification of TiO2 employing Au-NPs is also reviewed. Moreover, the effects of various operating parameters on the photocatalytic activity of these catalysts, such as size and loading amount of Au-NPs, pH and calcination, are discussed. The support type, loading amount and particle size of deposited Au-NPs are the most important parameters for Au/TiO2 catalytic activity. Our study showed in particular that the modification of TiO2, including semiconductor coupling, can increase the photoactivity of Au/TiO2. In contrast, doping large gold NPs can mask or block the TiO2 active sites, reducing photocatalytic activity. The optimized loading amount of Au-NP varied for each experimental condition. Finally, research trends and prospects for the future are briefly discussed.