Gold (Au) nanoparticles supported on alumina (Al 2 O 3 ) were prepared at several pH levels via the deposition-precipitation (DP) method. The effects of pH at below and above the isoelectric point (IEP) of Al 2 O 3 as well as the pH adjustment before and after the addition of the support into the gold chloride solution were investigated. The results revealed the formation of cationic, clusters and metallic Au on alumina. The catalytic activity of these species was tested in the reduction of p-nitrophenol (p-NP) using hydrazine as a reductant. The catalytic reaction was monitored spectrophotometerically and the highest rate constant (k) achieved based on pseudo first order kinetic model was 12.7´10 -3 s -1 . Structural and elemental characterizations of the supported gold nanoparticles were carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-rays (EDX), atomic absorption spectrometry (AAS), and ultraviolet-visible spectroscopy (UV-Vis).Keywords: Gold; Alumina; Nanoparticles; Catalysis; Kinetics; Nitrophenol; Hydrazine. INTRODUCTIONMany methods for the preparation of metal and metal oxides nanoparticles are known.1 Supported Au nanoparticles prepared by the deposition-precipitation (DP) method were first proposed by Haruta and co-workers. 13 are reported to produce highly active catalysts in many reactions. However, when alumina was used as the support (IEP = 8-9), the resulted catalysts was found to be either very active or inactive under certain conditions during CO oxidation at room temperature. 14-16p-Nitrophenol is among the most common organic pollutants in agricultural wastewaters and industrial. The released of p-nitrophenol into the environment causes harmful effect particularly to biological systems due to its toxicity. As a result, many methods have been developed to remove the hazardous p-nitrophenol such as by photocatalytic degradation, 17 The Au/Al 2 O 3 obtained were analyzed by diffuse reflectance UV-visible (DRS UV-Vis) spectrometer -Perkin Elmer Lambda 35 with KBr powder as reference, powder X-ray diffraction (XRD) using PANanalytical diffractometer (diffraction patterns were compared using the standard database from International Centre Diffraction Data (ICDD)), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM observation was performed for the samples dried on carbon-coated copper grids. The size distribution of the Au nanoparticles was determined from at least about 200 particles. The elemental composition of Au was analyzed using a Perkin Elmer AAnalyst 200 atomic absorption spectrometer at a wavelength of 243 nm. 26 The Au loading of the samples is ex- Catalytic testA mixture of 1 mg gold nanocatalyst, 1.5 mL hydrazine (0.3 mM) and 1.5 mL solution of p-nitrophenol (0.1 mM) was added into a 3 mL cuvette at room temperature. The catalytic activity was determined using UV-Vis spectrophotometer (Perkin Elmer Lambda 25 UV-Vis) by measuring the change in absorbance at 400 nm...

No abstract

Nanoporous materials with straight channels have attracted considerable interest due to their unique physical properties and many potential applications such as separation, sensing, biomedical and electronics. For the last few decades, nanoporous alumina or anodic aluminium oxide (AAO) membrane is gaining attention due to its broad applicability in various applications. The unique properties of AAO membrane coupled with tunable surface modification and properties is playing an increasingly important platform in a diverse range of applications such as separation, energy storage, drug delivery and template synthesis, as well as biosensing, tissue engineering and catalytic studies. This chapter aims to introduce the recent advances and challenges for surface manipulation of AAO following the 'soft' and 'hard' modification strategies. The functions of these modified nanostructures materials and latest important applications are evaluated with respect to improved performance and possible implications of those strategies for the future trends of surface engineering are discussed.

No abstract