Surface Morphology Of Au Research Articles

NIR Laser Integration of Photodetector on 3D Printed Chamber for Colorimetric Biosensing

AbstractIn this work, gold nanoparticles (Au NPs)/indium‐zinc‐oxide (IZO) nanocomposite visible photodetector (PD) is directly prepared by near‐infrared (NIR) laser‐annealing on a 3D‐printed substrate to form an integrated colorimetric sensor. After a surface planarization process, using a low power laser treatment without damaging the substrate, Au NPs are formed from the Au thin layer (6 nm) on 3D‐printed resin substrate by laser‐assisted dewetting process. Also, the UV–vis photoresponsivity is compared by tuning different NIR laser power intensity for sol‐gel IZO curing. By investigating the temperature profile of each laser annealing process and the surface morphology of Au NPs/IZO nanocomposite film, the optimized PD is then integrated with a 3D‐printed sensing chamber for successfully demonstrating urea detection varied from 1, 5, 10, 25 and 50 × 10−3 m, which refer to the salivary urea concentrations for healthy and chronic kidney disease groups.

Formation of Au nanostructures on the surfaces of annealed [formula omitted] thin films

One of the promising methods for high-throughput fabrication of nanostructures is the spontaneous dewetting of an as-deposited thin film. The formation process of Au nanostructures (AuNS) on TiO2 thin films consisted of two steps: formation of Au thin films and post-deposition annealing at 500∘C temperature in Ar gas environment for 60 minutes. TiO2 thin films were deposited using reactive magnetron sputtering method on SiO2 and fused quartz substrates and soaked at 500∘C and 900∘C temperatures to understand the influence of crystalline structure and surface morphology of Au and TiO2 thin films on the formation of AuNS. Properties of the deposited thin films were investigated using XRD, SEM, AFM, and RAMAN. The mean diameter (Dmean), mean area of AuNS (Amean), and mean distance between centroids of nearest neighbor AuNS (NNDcentr) increased exponentially when thicker nanocrystalline Au films were annealed. Standard deviation from Dmean and coefficient of variation also increased indicating higher dispersion of AuNS diameter. It was found that the influence of surface roughness increased by annealing thicker nanocrystalline Au thin films. Dmean, Amean, and NNDcentr increased and the density of AuNS (n) decreased (hAu: 10 nm and 15 nm) with decreasing Rq of TiO2 thin films. The peaks of absorbance (500 nm- 750 nm) were broad and not symmetrical indicating multiple localized surface plasmon resonance (LSPR) from various size AuNS. The position of peak shifted to the longer wavelengths when Dmean and NNDcentr was larger.

Role of Annealing Temperature, Time, and Composition on the Fabrication of Aux Pd1−x Nanostructures on c-Plane Sapphire by the Solid-State Dewetting of Bimetallic Thin Films

Bimetallic nanostructures (BNSs) are important components in various applications due to their elemental composition and morphology dependent catalytic, electronic and optical properties. In this paper, the systematic evolution of Au x Pd1− x (gold–palladium) BNSs on sapphire (0001) is studied via the solid-state dewetting of sequentially deposited Au–Pd bilayers along with the systematic control of elemental composition, annealing temperature, and time. Through the annealing of Au x Pd1− x bilayers at various temperatures between 400 and 900 °C, the fabrication of nanoparticles (NPs) on bilayer, voids, and Au–Pd BNSs are observed with various compositions (Au0.25Pd0.75, Au0.5Pd0.5, and Au0.75Pd 0.25). The evolution process of Au x Pd1− x BNSs is systematically analyzed based on the interdiffusion of Au and Pd and surface energy minimization mechanism. Along with the increased Au composition, the rate of dewetting is enhanced, which resulted in the significantly larger layer- top bimetallic NPs, voids, and BNSs. Furthermore, with the control of annealing time between 0 and 3600 s, the shape of Au–Pd BNSs is transform from the elongated to the round NPs due to the gradually enhanced diffusion. The reflectance (UV–VIS–NIR) spectra show the tight correlation with the surface morphology of Au x Pd1− x BNSs and the average reflectance is gradually decreased along with the increased annealing temperature and time. The dipolar resonance peaks in the NIR region reveal a gradual blue-shift along with the increased annealing time due to the NP size reduction.

Synthesis and Characterization of Au:CuO Nanocomposite by Laser Soldering on Porous Silicon for Photodetector

This work aimed to the synthesize of composite Au:CuO (NPs) by pulsed laser solderingprocess. The optical properties, stability, structural properties and surface morphology of Au:CuOnanocomposite were characterized by UV–VIS spectrophotometer, Zeta potential measurement, XRayDiffraction pattern and Atomic Force Microscope respectively. The band gap of Au dopedCuO is about 1.95 eV. The amount of zeta potential is -54 mV, its indicating that the negativelycharged of Au: CuO nanocomposite in deionized water and the colloid is good stability against aggregation. Surface morphology of Au:CuO nanocomposite show a large number of particles have diameter about 55nm. Au: CuO nanocomposite deposited on porous silicon by drop casting technique for preparationof silicon photodetector, the electrical properties prove that band gap alignment between Au: CuO nanocomposite and PS facilitates the electron transfer and further increases the photoresponsitivity and Quantum efficiency.

Mechanistic Insights into Electro-Oxidation of Solution CO on the Polycrystalline Gold Surface as Seen by in Situ IR Spectroscopy

Carbon monoxide (CO) adsorption and electro-oxidation on a gold (Au) ultrathin film deposited onto a silicon prism infrared (IR) window in a CO-saturated (≈1 mM) 0.1 M HClO4 supporting electrolyte were investigated by in situ electrochemical attenuated-total-reflection (ATR) surface-enhanced IR reflection absorption spectroscopy (SEIRAS). By varying the reaction environment with sequential (CO and N2) purging of the supporting electrolyte and the Au surface morphology with CO annealing, we were able to assign adsorbed CO to terrace-like and step-like sites to deconvolute the corresponding time- and potential-dependent IR spectra. The results of these spectral deconvolutions suggest strongly that in the CO-saturated supporting electrolyte the weakly bound CO interacted mainly with the strongly adsorbed CO on the step-like sites and likely formed a dipolar-coupled weak interacting pair with the latter. Model ab initio density functional theory (DFT) calculations confirm the existence of the weakly bound CO ...

Tuning of size and shape of Au–Pt nanocatalysts for direct methanol fuel cells

In this article, we report the precise control of the size, shape, and surface morphology of Au–Pt nanocatalysts (cubes, blocks, octahedrons, and dogbones) synthesized via a seed-mediated approach. Gold “seeds” of different aspect ratios (1–4.2), grown by a silver-assisted approach, were used as templates for high-yield production of novel Au–Pt nanocatalysts at a low temperature (40 °C). Characterization by electron microscopy (SEM, TEM, HRTEM), energy dispersive X-ray analysis, UV–Vis spectroscopy, zeta-potential (surface charge), atomic force microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry were used to better understand their physico-chemical properties, preferred reactivities and underlying nanoparticle growth mechanism. A rotating disk electrode was employed to evaluate the Au–Pt nanocatalysts electrochemical performance in the oxygen reduction reaction (ORR) and the methanol oxidation reaction of direct methanol fuel cells. The results indicate the Au–Pt dogbones are partially and in some cases completely unaffected by methanol poisoning during the evaluation of the ORR. The ORR performance of the octahedron particles in the absence of MeOH is superior to that of the Au–Pt dogbones and Pt-black; however, its performance is affected by the presence of MeOH.

Pattern formation induced by Ar + sputtering on Au(1 1 1)

Ion sputtering is employed to produce structures on the nanometer scale. The surface morphology of Au(1 1 1) after sputtering with 500 eV Ar + ions at various sputtering temperatures (from room temperature (RT) to 150 °C with variation of 25 °C) has been investigated by scanning tunneling microscopy (STM). It is shown that the sputtering temperature can be used to determine the final surface morphology. At all sputtering temperatures, the surface is characterized by random distribution of pits. The shape and size are briefly discussed. The obtained surface morphology is explained with diffusion processes at various sputtering temperatures. The final surface morphology is the result of the diffusion processes.

Si(111)-(6$times;6)Au surface morphology and nucleation of Pb at low temperature

Si(111)-(6$times;6)Au surface morphology and nucleation of Pb at low temperature

Si(1 1 1)-(6 × 6)Au surface morphology and nucleation of Pb at low temperature

The morphologies of the Si(1 1 1)-(6 × 6)Au surface and the nucleation of Pb have been investigated at temperatures below room temperature using scanning tunnelling microscopy (STM). The STM scans of the clean Si(1 1 1)-(6 × 6)Au surface revealed exceptionally rich and strongly bias-dependent details within the unit cell. After deposition of about 0.01 ML of Pb(1 1 1), at temperatures above 180 K, the single Pb atoms formed a two-dimensional mesh with (6 × 6)-Au periodicity. In this early stage of deposition, the Pb atoms occupied predominantly one specific site of the (6 × 6) unit cell. The local symmetry of this site determined the further growth of the Pb layer. As a consequence, the structure of the Pb layer on Si(1 1 1)-(6 × 6)Au is rotated of 30° relative to that of the Pb layer on Si(1 1 1)-(7 × 7).

In situ vibrational spectroscopy analysis of adsorbed phosphate species on gold single crystal electrodes

The adsorption of phosphate species on Au(100) electrode at different pHs is studied by using in situ Fourier Transform Infrared Spectroscopy. The results are compared with those published previously for Au(111) and also for polycrystalline gold. H 2PO 4 − ions present two spectral features at 1000 and 1120 cm −1, consistent with a C 2v symmetry, as expected. At pH 12.6 for the adsorption of PO 4 3− on Au(100) an abrupt change in the band intensity is observed which is consistent with the lifting of the surface reconstruction. This change in the intensity coincides with a current peak observed in the cyclic voltammogram and has been related to the surface lifting of the reconstruction. The PO 4 3− and H 2PO 4 − ions when adsorbed on Au(100) show the same characteristic bands compared to Au(111). The bands of the adsorbed species are located at ca. 1120 cm − and 1050 and 1085 cm −1 for HPO 4 2− and PO 4 3−, respectively. At Au(100) surfaces the three-fold coordination for both PO 4 3− and HPO 4 2− is very unlikely due to the mismatch between the oxygen-oxygen distances and the atomic distances at the (100) surface. For PO 4 3−, where the bands for the solution and adsorbate phosphate species do not overlap, it is possible to identify a consistent difference in the band half-width, when compared with PO 4 3− adsorbed on Au(111). This difference in band width is tentatively assigned to a different surface morphology of Au(100) after the lifting of the reconstruction.