Query: gold,Au,Material parameter

title: Sorption desorption profile of Au(III) onto silica modified quaternary amines (SMQA) in gold mining effluent
abstract: This work aim to study sorption desorption of Au(III) onto silica modified quaternary amines (SMQA) in gold mining effluent. Synthesis SMQA was conducted by methylation silica modified ammine (SMA) that synthesized by sol gel process of silica gel (SG) from rice hull ash and APTMS. Characterizations this material by FT IR, XRD, SEM EDS and GSA analyzer show that the material has characteristic parameter of SMQA. Sorption study of sorption Au(III) on SMQA was carried out by batch system with optimum pH 5. Sorption capacity was 74.47 mg/g (Langmuir) with 24 kJ/mole sorption energy (electrostatic interaction) Kinetics sorption studies by Lagergren, Ho, and RBS models shows that the sorption Au(III) in this research have the suitable condition with RBS models. Sorption study reveal that N+(CH3)3 is the most responsible site for Au(III) sorption. Desorbed Au(III) in batch system using Na2S2O3, SC(NH2)2, and KSCN as desorption agent in HCl solution was there are no significant different value (Na2S2O3 94.2 SC(NH2)2 95.2 KSCN 95.2 However, for safer eluent it was recommend to use Na2S2O3 or SC(NH2)2. The reusability of SMQA was four times sorption desorption cycle before at fifth cycle desorbed Au(III) was decreased. The application of SMQA in gold mining effluent by column system (SPE) sample in Sarolangun, Jambi, Indonesia shows that recovered Au(III) was 0.000593 in 2 g sample.

title: Enhanced acetone detection using Au doped ZnO thin film sensor
abstract: Zinc oxide (ZnO) thin films are prepared using sol gel method for acetone vapor sensing. Zinc acetate dihydrate (Zn(CH3COO)2*2H2O) was taken as starting material and a stable and homogeneous solution was prepared in ethanol by deliquescing the zinc acetate and distinct amount of monoethanolamine as a stabilizing agent. The prepared solution was then coated on silicon substrates by spin coating method and then annealed at 650 degC for preparing ZnO thin films. The thickness of the film was maintained at 410 nm. The structural, morphological and optical studies were done for the synthesized ZnO thin films. The operating temperature and sensor response is considered to be an important parameter for the gas sensing behavior of any material. Therefore, the present study examined the effect of sensing behavior of 3% v/v gold (Au) doped ZnO thin films as a sensor. The response characteristics of 410 nm ZnO thin film for temperature ranging from 180 to 360 degC were determined for the acetone vapors. The reported study provides a significant development towards acetone sensors, where a very high sensitivity with rapid response and recovery times are reported with lowered optimal operating temperature as compared to bare ZnO nano chains like structured thin films. In comparison to the bare ZnO thin films giving a response of 63 at an operating temperature of 320 degC, a much better response of 132.3 was observed for the Au doped ZnO thin films at an optimised operating temperature of 280 degC for a concentration of 500 ppm of acetone vapors.

title: Alloying effects at bicomponent Au Cu and In Sn particle arrays formation by vacuum thermal evaporation
abstract: Method of vacuum thermal evaporation of small amounts of material was used for the formation of nanoparticles in Au Cu and In Sn bicomponent systems. The obtained arrays were investigated by Transmission Electron Microscopy. It was found that after the sequential deposition of copper on gold there was formed an array of Au Cu alloy particles. The lattice parameter of this alloy occupies an intermediate position between the parameters of Au and Cu. Sequential deposition of In and Sn and annealing of the resulting structure do not lead to the formation of In Sn alloy. The array is the mixture of particles of two types: some contain In, and others contain Sn. In case of co evaporation of In and Sn in eutectic proportion the resulting array is the mixture of In3Sn b phase particles and InSn4 g phase particles.

title: Reaction Relevant Gold Structures in the Low Temperature Water Gas Shift Reaction on Au CeO2
abstract: Combined in situ X ray absorption near edge structure (XANES) and extended X ray absorption fine structure (EXAFS) studies have been conducted to follow gold structural changes of low content <1%Au) gold ceria catalysts in water gas shift (WGS) reaction tests at 100 and 200 degC; and after heating the used catalysts in oxygen gas at 150 degC. Gold in the fresh (400 degC calcined) material was atomically dispersed in cerium oxide. Under WGS reaction conditions, reduction of the oxidized gold species was observed, accompanied by gradual gold aggregation. The Au Au coordination number is zero for the fresh material, but increases with the reaction temperature, to 6.5 2.4 (after use at 100 degC) and to 8.7 1.5 (after 200 degC) in a gas mixture containing 5% CO 3% H2O in helium. The second important parameter is the reaction gas composition which determines the extent of Au O reduction. The lower the reduction potential of the reaction gas mixture, the more oxidized the gold is in the used catalyst, and the higher.

title: Polyamide 66 microspheres metallised with in situ synthesised gold nanoparticles for a catalytic application
abstract: A simple concept is proposed to metallise polyamide 66 (PA66) spherulite structures with in situ synthesised gold nanoparticles (Au NPs) using a wet chemical method. This cost effective approach, applied to produce a PA66/Au NP hybrid material, offers the advantages of controlling the nanoparticle size, the size distribution and the organic inorganic interactions. These are the key factors that have to be controlled to construct consistent Au nanostructures which are essential for producing the catalytic activities of interest. The hybrid materials obtained are characterised by means of scanning electron microscopy, transmission electron microscopy, attenuated total reflection Fourier transform infrared spectrometry and X ray diffraction spectrometry. The results show that PA66 microspheres obtained via the crystallisation process are coated with Au NPs of 13 nm in size. It was found that controlling the metal coordination is the key parameter to template the Au NPs on the spherulite surfaces. The preparation processes and the key factors leading to the formation of PA66 spherulites coated with Au NPs are discussed. Moreover, the efficiency of the coated spherulites as a potential catalyst is proved by demonstrating the reduction of methylene blue via UV visible spectrometry.

title: In situ electrical modulation and monitoring of nanoporous gold morphology.
abstract: The ability to fine tune feature size in nanostructured thin films is critical, as many desirable properties of these materials are dictated by their nanostructure. Accordingly, there is a need for techniques that allow for modifying nanostructure while monitoring the morphological changes in situ. Here, we demonstrate a closed loop electro annealing system which enables in situ monitoring of morphology evolution in sub micron nanoporous gold (np Au) thin films. Np Au is produced by a microfabrication compatible self assembly process that produces a network of interconnected ligaments with tunable diameter (10 s to 100 s of nanometers) making it a desirable material for numerous applications and fundamental studies alike. We specifically investigate the relationship between np Au morphology (i.e. ligament diameter) and electrical resistance of the thin film. A strong correlation emerges between ligament size and electrical resistance, which puts forward resistance as an effective parameter for monitoring morphology evolution. Surprisingly, np Au films with thicker ligaments lead to an increase in electrical resistance, which is unexpected since the extent of charge carrier scattering at the ligament surface should decrease with increasing ligament size. Further examination of np Au morphology with high resolution electron microscopy revealed grain growth on the ligaments in highly annealed np Au thin films. This suggests that grains act as scattering centers for charge carriers and this becomes the dominant mechanism in dictating electrical resistance in a percolated network of thin conductive ligaments.

title: Effect of thermal treatments on the morphology, chemical state and lattice structure of gold nanoparticles deposited onto carbon structured monoliths
abstract: Gold nanoparticles (GNPs) were deposited onto carbon monoliths through direct chemical reduction of cationic gold sources. Colloidal gold particles were also deposited onto the same type of support to prepare a reference material. The Au/C structured materials were subjected to thermal treatment (annealing) up to 600 degC. Transformations in size, shape, chemical state and possible modifications in the lattice structure of GNPs due to thermal effects were evaluated by field emission gun (FEG) scanning electron microscopy (SEM) X ray diffraction, X ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) Evolution in size and shape of GNPs is compared with some of the models described in the bibliography for the melting of nanoparticles. No modification to either the lattice parameter or atomic structure in gold crystals was detected following annealing. The sintering process among gold nanoparticles could be observed in situ through HRTEM showing the aggregation mechanism for these particles.

title: High resolution continuum source graphite furnace atomic absorption spectrometry for the monitoring of Au nanoparticles
abstract: This work investigates the possibility of obtaining information on the chemical form (ionic or as Au nanoparticles (NPs) in which Au is found in solutions by means of high resolution continuum source graphite furnace atomic absorption spectrometry (HR CS GFAAS) without the need to use any additional separation step or any extra technique. It is demonstrated that proper optimization of the temperature program, using a very slow heating ramp (150 degC s 1) during the atomization step and a sufficiently high atomization temperature (2200 degC) in the absence of chemical modifiers, enables a fast and simple screening to be performed, since the signal profiles obtained for solutions/suspensions of ionic Au and AuNPs are very dissimilar. Moreover, in the case of finding NPs, it is possible to estimate the average particle size, because this parameter appears to be directly related with the time of appearance of the maximum peak height (a value of 27.7 nm 8.8 nm was estimated for NIST Reference Material 8012 Gold nanoparticles, nominal 30 nm diameter) The proposed procedure offers a limit of detection of 5.5 pg (0.55 mg L 1) and a linear range up to 10 ng (1000 mg L 1) and was further validated by spiking a natural water certified reference material (CRM KEJIM 02) The occurrence of mixtures of ionic Au and AuNPs seems to be more complicated to resolve if quantitative information is aimed at (e.g. calculating the exact amount found in each form) because, even though the mixture behaves as predicted by summing the individual signals of ionic Au and AuNPs, signal overlaps can be anticipated and, thus, proper signal deconvolution should be carried out.

title: CeO2 modified Au/TiO2 catalysts with outstanding stability under harsh CO oxidation conditions
abstract: The 1.5 wt% Au/TiO2 World Gold Council catalyst (WGC) was modified by depositing on its surface a 5.4 wt% CeO2 loading by incipient wetness impregnation. Calcination at 673 K of the resulting, surface modified, catalyst yielded a material in which the system of gold particles was not significantly modified with respect to that of the starting 1.5% Au/TiO2 WGC catalyst, neither in terms of its size distribution or metallic dispersion. The latter parameter remained, as in the catalyst prior to CeO2 deposition, in a value about 36% Both catalysts, Au(1.5%/TiO2 WGC and CeO2(5.4%/Au(1.5%/TiO2, were tested in consecutive CO oxidation reaction loops at increasing final temperatures. In these cycles, the ceria modified catalyst showed not only a higher activity but, more importantly, a largely enhanced stability against deactivation. Scanning Transmission Electron Microscopy (STEM) studies clearly revealed the presence of nanometer sized ceria rafts, less than 1 nm thick, on the surface of the fresh CeO2(5.4%/Au(1.5%/TiO2 catalysts. After the CO oxidation test at the highest temperature, 1223 K, the WGC catalyst suffered from a very severe Au nanoparticle sintering whereas Au nanoparticle growth was very much limited in the ceria modified catalyst after the same aging test. STEM results reveal that a major fraction of the Au nanoparticles (75% comprising all the smaller ones

title: Novel porous silica encapsulated Au nanoreactors as peroxidase mimic for one pot glucose detection
abstract: The peroxidase family of natural enzymes facilitate H2O2 reduction by one electron transfer through aromatic substrates, if chromogenic, they can be used in the colorimetric detection of H2O2 and subsequently glucose in tandem with glucose oxidase. Au nanoparticles encapsulated within porous silica exhibited peroxidase mimetic activity and kinetic parameter evaluation indicates an excellent affinity for H2O2. It is also shown to have a detection capability for glucose in very low concentrations and could be used for glucose detection in a one pot assay. The material is synthesised by using cation ended thiol stabilised ultra small gold clusters as precursors. Removal of the thiols creates micropores within the silica, making this material unique in that the active centres are protected inside the silica, yet are accessible to reactant molecules. This characteristic makes the material ideal as a detection tool where attrition resistance will be advantageous.