花岗斑岩类岩石中Au、Pd溶解性状的实验研究

研究花岗斑岩类岩石中Au、Pd的溶解性状 ,对于研究其溶解、迁移、沉淀条件有着重要的理论价值。研究结果表明 ,花岗斑岩中Au、Pd地球化学性状明显不同 ,Au活性显著 ,Pd惰性特征明显。在T =2 5 0℃、P =2 0× 10 5～ 30× 10 5Pa、pH =7.5 6的条件下 ,Au浸出率最低 ,易于沉淀成矿 ;在T =10 0℃、P =10 0× 10 5Pa、pH =8.2时 ,Au浸出率高 ,最易被活化溶解 ;当T =5 0 0℃ ,P =5 0 0× 10 5Pa ,pH =8.5时 ,Au浸出率中等 ,易被搬运、迁移。Pd易于沉淀成矿的条件是T =10 0℃ ,P =5 0 0× 10 5Pa ,pH =8.2 ;Pd易于活化溶解的条件是T =2 5 0℃ ,P =10× 10 5Pa ,pH =8.5 ;在T =30 0℃、P =(2 0～ 30 )× 10 5Pa、pH =6条件下发生搬运迁移。     

Step-Directed Deposition of Au Nanostructures By Electron Beam Evaporation

Au atoms were vaporized by electron beam evaporation, and their subsequent growths on Si (111 ) and highly ordered pyrolytic graphite (HOPG) substrates were studied using atomic force microscopy. Results show that Au nanoparticles tend to nucleate and grow regularly along the step edges of HOPG, however, nanoparticles are distributed homogeneously over the whole Si substrate. The possibility of controlled growth of Au in ultrahigh vacuum with peculiar surface structures was preseuted.     

A theoretical study of the ability of 2D monolayer Au (111) to activate gas molecules

The adsorption and activation of gas molecules are investigated substantially in solid-gas heterogeneous catalysis. Here we investigated the interaction between gas molecules and unique two-dimensional monolayer Au (111) structure using density functional theory. It is found that CO₂, H₂O, N₂ and CH₄ molecules are weakly adsorbed on the surface with the adsorption energies between ?0.150 and ?0.250 eV due to van der Waals interaction. While CO, NO, NO₂, and NH₃ molecules are adsorbed more stably with the adsorption energies between ?0.300 and ?0.470 eV. Especially, the bond length of CO is stretched by 0.038 Å and the bond angle of NO₂ is obviously enlarged by 10.460°. The activation originates from the rearrangement of molecule orbitals and the orbitals hybridization between the partial orbitals of gas molecules and Au-5d orbitals. The fundamental analyses of adsorption mechanism and electronic properties may provide guidance for the applications of two-dimensional monolayer metal catalysis.PACSnumbers 73.22.-f, 73.61.-r     

Preparation of gold nanoparticles and carbon dots by hydrothermal reaction of bovine haemoglobin with chloroauric acid and energy band bending in carbon dots

ABSTRACT

The incubation and hydrothermal reaction under alkaline condition of bovine haemoglobin with chloroauric acid were investigated. The products in the supernatant from the centrifuge were found to be gold nanoparticles and carbon dots. Greigite (Fe₃S₄) was found as a byproduct in the precipitation. In the incubation process, the reduction ability of bovine haemoglobin molecules was activated under alkaline condition (pH ≈ 12), and Au(III) ions underwent progressive reduction to form Au nanoparticles in situ. In the hydrothermal reaction, denatured bovine haemoglobin molecules underwent biomineralisation to form carbon dots and greigite. Photoluminescence was used as a measurement of the energy band bending of as-prepared carbon dots. The effects of the acceptor 4-nitrotoluene and donor N,N-diethylaniline molecules on the photoluminescence intensity imply that oxygen-contained surface groups induce the upward band bending of carbon dots.     

Au nanoparticles decorated on magnetic nanocomposite (GO-Fe3O4/Dop/Au) as a recoverable catalyst for degradation of methylene blue and methyl orange in water

In the present research, magnetically recyclable graphene oxide (GO)/dopamine hydrochloride/AuNPs nanocatalyst are prepared by a green path with Acorus calamus seeds extract as a stabilizing and reducing agent and its catalytic efficiency was used for the reduction of methylene blue (MB) and methyl orange (MO) in the presence of NaBH₄ as a reducing agent in the aqueous medium in the ambient conditions. The prepared nanocatalyst was characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR) spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and UV–Vis spectroscopy. The prepared nanocatalyst has good catalytic activity and can be regain by an external magnet and recycled several times without considerable loss of its catalytic activity in the process of reduction of organic dyes.     

Functionalized conjugated polymer with plasmonic Au nanoalloy for photocatalytic hydrogen generation under visible-NIR

Gold based multimetallic nanoalloys decorated on conjugated polymer nanofibers have been prepared using a greener approach without using any reducing agent. The as-prepared nanohybrids exhibited superior catalytic activity for solar hydrogen production under visible light (λ > 420 nm) irradiation and near infrared light irradiation. The UV–Visible diffuse reflectance spectra displayed strong absorption in the visible region which significantly favours the photocatalytic performance. Furthermore, the efficient charge separation suggested by electrochemical impedance measurement and photocurrent response curves for Au₅₀Pt₂₄Pd₂₆/PPy nanohybrids which exhibited significant enhancement in H₂ generation rate compared to Au/PPy nanohybrids. The strong interface contact between Au nanoalloys and PPy nanofibers play an important role for the migration of electron during catalysis. The Mott–Schottky plot revealed that photo generated charge carrier concentration has been increased for Au₅₀Pt₂₄Pd₂₆/PPy nanohybrids (7.93 × 10¹¹cm⁻³) compare to pure PPy (1.43 × 10¹¹ cm⁻³). The present study provides a new prospect for using conducting polymer based hybrid as photocatalysts for efficient solar hydrogen production.     

Tunable morphological evolution of in situ gold catalysts mediated silicon nanoneedles

Achieving tunable growth of high quality Silicon (Si) nanoneedles (NNs) is challenging. We report the optimized morphology of in situ gold (Au) catalysts assisted SiNNs grown via very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) method. The vapor-liquid-solid (VLS) mechanism mediated morphological evolution is tuned using hydrogen (H₂) and silane (SiH₄) gas flow. Au-coated Si(100) substrates are treated using H₂ plasma to create in situ Au nanoparticles (NPs) with high catalytic activity. FESEM images manifested the existence of mono-dispersed Au NPs and high yield of SiNNs having diameter ranging from 80 to 140 nm and lengths up to 2.31±0.3 µm. Furthermore, these NNs gradually became thinner to form sharp tips of diameter as small as 4 nm. XRD pattern confirmed the diamond (cubic) crystalline phases of SiNNs. HRTEM images revealed the occurrence of Au NPs at the crystalline SiNNs tips. Raman spectrum of as-grown SiNNs exhibited the TO phonon mode accompanied by a red-shift (~23.59 cm⁻¹). Synthesized SiNNs displayed extremely low reflectance (~8%) at short wavelengths (λ<700 nm), indicating excellent antireflection properties. Our controllable and optimized growth method may constitute a basis to achieve high quality SiNN arrays, which are beneficial for various applications.     

Chemically Synthesized 58‐mer LysM Domain Binds Lipochitin Oligosaccharide

Recognition of carbohydrates by proteins is a ubiquitous biochemical process. In legume–rhizobium symbiosis, lipochitin oligosaccharides, also referred to as nodulation (nod) factors, function as primary rhizobial signal molecules to trigger root nodule development. Perception of these signal molecules is receptor mediated, and nod factor receptor 5 (NFR5) from the model legume Lotus japonicus is predicted to contain three LysM domain binding sites. Here we studied the interactions between nod factor and each of the three NFR5 LysM domains, which were chemically synthesized. LysM domain variants (up to 58 amino acids) designed to optimize solubility were chemically assembled by solid‐phase peptide synthesis (SPPS) with microwave heating. Their interaction with nod factors and chitin oligosaccharides was studied by isothermal titration calorimetry and circular dichroism (CD) spectroscopy. LysM2 showed a change in folding upon nod factor binding, thus providing direct evidence that the LysM domain of NFR5 recognizes lipochitin oligosaccharides. These results clearly show that the L. japonicus LysM2 domain binds to the nod factor from Mesorhizobium loti, thereby causing a conformational change in the LysM2 domain. The preferential affinity for nod factors over chitin oligosaccharides was demonstrated by a newly developed glycan microarray. Besides the biological implications, our approach shows that carbohydrate binding to a small protein domain can be detected by CD spectroscopy.     

Synthesis of AuPd alloyed nanoparticles via room-temperature electron reduction with argon glow discharge as electron source

Argon glow discharge has been employed as a cheap, environmentally friendly, and convenient electron source for simultaneous reduction of HAuCl₄ and PdCl₂ on the anodic aluminum oxide (AAO) substrate. The thermal imaging confirms that the synthesis is operated at room temperature. The reduction is conducted with a short time (30 min) under the pressure of approximately 100 Pa. This room-temperature electron reduction operates in a dry way and requires neither hydrogen nor extra heating nor chemical reducing agent. The analyses using X-ray photoelectron spectroscopy (XPS) confirm all the metallic ions have been reduced. The characterization with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) shows that AuPd alloyed nanoparticles are formed. There also exist some highly dispersed Au and Pd monometallic particles that cannot be detected by XRD and transmission electron microscopy (TEM) because of their small particle sizes. The observed AuPd alloyed nanoparticles are spherical with an average size of 14 nm. No core-shell structure can be observed. The room-temperature electron reduction can be operated in a larger scale. It is an easy way for the synthesis of AuPd alloyed nanoparticles.