Gold Doped Research Articles

Syntheses of gold supported on metal oxides and their application in organic transformations

Herein, we report a general and straightforward synthesis method for gold supported on mesoporous and microporous metal oxides. Supported materials, in general, show higher crystallinity compare to unsupported systems as verified through powder X-ray diffraction (XRD). Also, through XRD, most of the metal is observed to be in its oxide form, whereas the gold support was found to be in its metallic state, which has been further confirmed from TEM. In terms of surface area, the catalyst was not found to follow any trend. Morphology wise, there are no changes observed after doping except in few cases. Combined results from XRD, X-ray fluorescence spectroscopy, Auger, and X-ray photoelectron spectroscopy suggest that gold is mainly in the bulk and very little (0.04% in case of gold doped calcium oxide) or non (in case of gold doped mixed manganese-cerium oxide) on the surface. The presence of Au (0) 4f peaks in XPS further confirms the metallic state of the gold. Oxides of indium, magnesium and calcium have been studied for the organic transformation reactions. An enhancement in activity and product selectivity was observed in the case of the gold supported catalysts. Indium serves as a great catalyst for C–C coupling and electrophilic aromatic substitution reactions and gives >99% conversion. Interestingly, 88% selectivity for C–C coupling and >99% selectivity for aromatic substitution have been achieved at 100 °C and room temperature respectively. Magnesium and calcium give Knoevenagel condensation products. At room temperature with very low catalyst loading, >99% conversion and selectivity were observed for the Knoevenagel reaction with as high as 35.30 TOF. A mechanism for the C–C coupling reaction has been proposed based on these results. The general and straightforward synthesis of gold promoted mesoporous and microporous metal oxides were templated using Pluronic P123 surfactant via inverse micelle formation. These catalysts were scanned for the various organic transformation reactions and enhanced activity was shown in the case of gold promoted catalysts. • A general and straightforward synthesis method for gold support mesoporous and microporous metal oxides. • An improvement in metal oxide crystallinity as a result of gold doping. • An enhancement in activity and product selectivity due to the gold supported catalysts. • Indium based C–C coupling and electrophilic aromatic substitution reactions that give >99% conversion. • High selectivity and high conversion for Knoevenagel ester condensation with very low catalyst loading.

Physical Properties of Pure Gold Nanoparticles and Gold Doped ZnO Nanoparticles Using Laser Ablation in Liquid For Sensor Applications

In this paper, the effect of using laser ablation of pure gold targets to obtain gold Nano rods and for pure zinc targets to obtain zinc oxide nanoparticles was studied separately in ethanol using an Nd:YAG laser tattoo removal (nanosecond pulses) and then mixing the resulting mixtures to obtain gold dopant with zinc oxide. Transmission electron microscopy (TEM), (XRD) X-Ray Diffraction and the optical properties were used to characterize the pure gold Nano rods, ZnO nanoparticles, and Au doped ZnO nanoparticles. Based on XRD and TEM, the results revealed the properties of the produced gold Nano roads. The obtained results indicated that the gold Nano rods produced by the 1064nm laser have superior optical, structural, and morphological properties and can be used in different sensors.

A Facile Synthesis of Nano Gold Doped TiO2 and Its Photocatalytic Activity toward Citric Acid

A Facile Synthesis of Nano Gold Doped TiO2 and Its Photocatalytic Activity toward Citric Acid

Gas sensor using gold doped copper oxide nanostructured thin films as modified cladding fiber

We investigate the spectral response of nanostructured copper oxides thin film. Gold was doped in two different concentrations (2% and 4%) using the spray method. A novel ammonia gas sensor at various concentrations (0–500 ppm) was fabricated by replacing CuO films with a clad region. In addition, the effect of gold doping on structural, optical, and morphological properties has been demonstrated. The study shows that the spectral intensity increases linearly with ammonia concentration. The 4% Au doped CuO presents higher sensitivity compared with 2% doped and pure copper oxides. Time response characteristics of the sensor are also reported.

Palladium oxide nanoparticles supported on reduced graphene oxide and gold doped: Preparation, characterization and electrochemical study of supercapacitor electrode

Electrochemical supercapacitors could be thought of as a major energy storage instrument for electrical devices. Nano metal oxides supercapacitors as materials with high electro-activity are attracting supreme consideration due to the best electrochemical efficiency. In this project, synthesis of pure and gold doped PdO-reduced graphene oxide nanocomposites by sonochemical and deposition-precipitation process was performed. The characterization of synthesized un-doped and Au doped PdO-RGO composites were performed by using X-ray photoelectron and Raman spectroscopy, transmission electronic microscopy, and X-ray diffraction method. The characterization results demonstrated PdO particles are embedded into the interlayer of RGO sheets. The electrochemical supercapacitive efficiency of the nanosamples was evaluated by different electrochemical analysis. Au-doped PdO-RGO nanocomposite shows enhanced specific capacitance of 253.0Fg−1 at 5mVs−1 and its high excellent effect was collated with PdO-RGO. The high cyclic stability and specific capacitance of Au doped PdO-RGO demonstrates to the doping of gold and good dispersion of PdO particles on RGO.

Electrochemical in-situ dissolution study of structurally ordered, disordered and gold doped PtCu3 nanoparticles on carbon composites

Abstract Commercial deployment of low-temperature-fuel cells is still hugely restricted by platinum alloy catalysts corrosion. Extensive research of the last years is focused on increasing stability of the catalyst composite, however a comprehensive understanding is still lacking. In pursuing this fundamentally and practically very important objective we present a comparative corrosion study of a PtCu 3 nano-alloy system by investigating the effects of structural ordering and gold doping. For that purpose a recently developed electrochemical flow cell (EFC) coupled to inductively coupled plasma mass spectrometer (ICP-MS) is employed. This approach provides potential- and time-resolved insight into dissolution process at extremely low concentrations (ppb level). Our results show a structure-dependent copper corrosion, where ordering and gold-doping significantly improve copper retention in the native alloy. Two assumptions can be drawn from the measured Pt dissolution profiles: (i) a better Pt re-deposition efficiency in catalysts with higher porosity and (ii) the beneficial effect of Au surface doping that lowers the amount of dissolved Pt amount and shifts the Pt cathodic dissolution to lower potentials. A 2.6 nm Pt/C standard catalyst with the same carbon loading shows a much lower stability which is due to the well-known particle size effect.

Antibacterial Activity and Electrical Properties of Gold Nanoparticle Doped Ceria-Rice Husk Silica (Au/Ce-Silica) Nanocomposites Derived From Biomass

The present study deals with synthesis and characterization of gold doped in ceria-silica, derived from rice husk silica biomass materials. Large amount of silica recovered from waste rice husk silica was utilized. The silica materials derived from waste product can be used as low cost supporting material for potential applications such as catalytic oxidations and low-k dielectric material development. Gold doping on ceria-mixed silica derived from rice husk is carried out by an in situ method (Au/Ce-Silica-A) as well as by co-precipitation method (Au/Ce-Silica-B). The physicochemical characterization and antibacterial activity of as prepared material have been studied.

Nano Gold Doped Nano TiO<sub>2</sub> – An Efficient Solar Photocatalyst for the Degradation of Persistent Organic Pollutants

Novel nanogold doped TiO2nanoparticles are found to be highly efficient for the photocatalytic degradation of organic pollutants. TiO2nanoparticles were synthesized from titanium (IV) isopropoxide through hydrothermal route. Gold nanoparticles were prepared by chemical reduction and stabilization employing D-glucosamine, and were doped in TiO2nanoparticles. The analysis revealed that the diameter of gold nanoparticles used for doping is around 5 nm. Undoped and gold doped samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, UV-Vis diffuse reflectance spectra (DRS) and field emission scanning electron microscopy (SEM). DRS study showed that nanogold doping in titania nanoparticles induces a shift of absorption edge to the visible range and reduces the band gap. Complementing our earlier finding that noble metal doping in titania nanoparticles enable photocatalytic activity in the visible region, it is showed that gold doping enhances photocatalytic activity of the titania nanoparticles. This was confirmed by the degradation of the dye methylene blue repeatedly using gold doped nanoparticles under direct sunlight. Further, the nanoparticles were used to study the degradation of the persistent organic pollutant, β endosulfan, and near complete degradation were observed in an hour. Regenerated nanoparticles were found effective for the degradation of the pesticide for more than three cycles.

Enhanced UV absorbance and photoluminescence properties of ultrasound assisted synthesized gold doped ZnO nanorods

Au doped ZnO (ZnO:Au) nanostructures were synthesized by ultrasound assisted wet chemical method. The concentration of dopant was varied and both structural and optical properties of ZnO:Au were investigated. The crystal structure and morphology of the samples were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). These results showed the formation of nanorods of ZnO:Au having wurtzite structure and c-axis orientation. Gradual increase in crystallite size and bond length was also observed with the increase in gold concentration in ZnO intending the expansion of lattice after gold doping. The optical absorption measurements showed high ultraviolet (UV) absorbance property of ZnO:Au with sharp and intense absorption band in this region as compared to pristine ZnO. Photoluminescence (PL) measurements showed excitonic emission band of ZnO around 390nm for both undoped and Au doped ZnO nanoparticles. Further, a strong emission around 467nm was observed in the PL spectra of ZnO/ZnO:Au which was attributed to the transitions related to excess of oxygen vacancies. Interestingly, a new band was observed at 582nm for doped ZnO samples which grew in intensity with doping concentration. This band was ascribed to the gold nanoparticle adsorbed on the surface of ZnO.

Synthesis and characterisation of gold nanoparticle doped ceria-rice husk silica nanocomposites derived from biomass

To realise high performance in IC devices, it is necessary to reduce the RC delay, cross talk, and power consumption. An effective method to make these reductions is to decrease the parasitic capacitance by employing a low dielectric constant (low-k) material in the intermetal dielectrics (IMD). The present research topic deals with the synthesis and characterisation of gold doped in ceria-silica, derived from rice husk biomass materials. Large amount of silica recovered from waste rice husk silica, hence the silica materials derived from waste product can be the low cost and used for potential application such as low-k dielectric material development. Gold doping on ceria-mixed silica derived from rice husk is carried out by insitu method (Au/Ce-silica-A) and deposition-co precipitation method (Au/Ce-silica-B). Au/Ce-silica-A and Au/Ce-silica-B shown the low-k dielectric constant compared to bulk ceria-silica.

Electrical Transport in Oxide Glasses Containing Gold Nanoparticles

Abstract Gold doped ruby glasses are classical examples of metal-glass nanocomposites that have been investigated for their striking optical properties. For their multifunctional applications, we have explored the nature of the electrical response of two oxide glasses containing a small amount (<0.1mol%) of gold. Gold-doped lithium borate (LBO) and lanthanum borogermanate (LBGO) glasses are studied using ac conductivity as a function of frequency and temperature in relation to their structure as determined by electron microscopy. For ionically conducting LBO, Au doping produces a noticeable increase of the electrical conductivity. For poorly conducting LBGO, gold doping introduces a dielectric loss peak indicative of dipolar relaxation. The heat treatment of both glasses introduces a new mechanism of dc conduction or dipolar loss, which has about one third the activation energy of the untreated samples. This unexpected behavior is attributed to an ionic-to-electronic conductivity transition in gold doped glasses.

Thermoluminescence, optical absorption and ESR studies in [formula omitted] mixed alkali halide crystals doped with gold

Mixed crystals of KCl–KBr of different compositions were grown with Czochralski technique. Crystals were doped with gold. Both the undoped and gold doped crystals were γ -irradiated using 60 Co source. All the irradiated samples were subjected to thermoluminescence, optical absorption and ESR studies. The present study shows the composition dependence of the parameters and enhancement in the luminescence intensity as well as the absorption coefficient with gold doping. Non-linear variation of color center peak position and half band width of F-center with composition has been observed. The results of the above studies are presented in this paper.

Suppression of irradiation effects in gold-doped silicon detectors

Two sets of silicon detectors were irradiated with 1 MeV neutrons to different fluences and then characterized. The first batch were ordinary p - i - n photodiodes fabricated from high-resistivity silicon, while the second batch were gold-doped power diodes fabricated from silicon material initially of low resistivity . The increase in reverse leakage current after irradiation was found to be more in the former case than in the latter. The fluence dependence of the capacitance was much more pronounced in the p - i - n diodes than in the gold-doped diodes. Furthermore, photo current generation by optical means was less in the gold doped devices. All these results suggest that gold doping in silicon somewhat suppresses the effects of neutron irradiation.

Gamma-induced trapping levels in si with and without gold doping

Because gold doping can be used to suppress ionization-induced photocurrents in Si devices exposed to radiation environments, it is of interest to know whether or not radiation-induced mobile defects interact with Au to form deep level defect complexes. Trapping level studies have been undertaken using the technique of deep level transient spectroscopy (DLTS) prior to and following Co-60 gamma irradiation and thermal annealing of p+/n Si junctions doped with 3-6 × 1014 Au/cm3 and 1-3 × 1013 Au/cm3 , and of non-Au doped p+ /n and n+ /p junctions. Prior to irradiation, the Au acceptor level at Ec - 0.57 eV is observed in the gold doped junctions. During irradiation, five additional levels at Ec - 0.18 eV, Ec - 0.20 eV, Ec - 0.46 eV, Ev +0.17 eV, and Ev + 0.39 eV grow in linearly with gamma dose. None of these levels are associated with Au because they are observed at equal concentrations in the non-Au doped and Audoped junctions, and because the Au concentration as monitored by the Ec - 0.57 eV level does not change even when defect concentrations are of the same order. Isochronal annealing studies also indicate that the Au acceptors are inert to defect re-ordering effects which occur during annealing.