Surface plasmonic resonance (SPR) is a new paradigm in photoelectrochemical (PEC) research that realizes the persistent supply of green energy in a sustainable manner. However, typical approaches for decorating surfaces Au nanoparticles (NPs), such as the colloidal chemical method, nanolithography, and in situ photo/thermal reduction, involve multiple complex steps and often introduce unwanted surface/interface chemicals that jeopardize the SPR effect and charge transport. Herein, we report a largely enhanced PEC performance achieved by decorating Au NPs onto 3D titanium dioxide (TiO2) nanorod architectures grown by surface-reaction-limited pulsed chemical vapor deposition through a one-step sputtering process. The Au NP size and amount could be manipulated in a controlled manner. Compared to pristine TiO2, the Au–TiO2 electrodes achieved high photocurrent density enhancements of 42% and 267% under simulated sunlight and visible-light illumination, respectively. When amorphous aluminum oxide (Al2O3) films...

Surface-Plasmon-Resonance-Enhanced Photoelectrochemical Water Splitting from Au-Nanoparticle-Decorated 3D TiO2 Nanorod Architectures

Extremely thin gold layers were sputter deposited on glass and silicon substrates, and their thickness and morphology were studied by Rutherford backscattering (RBS) and atomic force microscopy (AFM) methods. The deposited layers change from discontinuous to continuous ones for longer deposition times. While the deposition rate on the silicon substrate is constant, nearly independent on the layer thickness, the rate on the glass substrate increases with increasing layer thickness. The observed dependence can be explained by a simple kinetic model, taking into account different sticking probabilities of gold atoms on a bare glass substrate and regions with gold coverage. Detailed analysis of the shape of the RBS gold signal shows that in the initial stages of the deposition, the gold layers on the glass substrate consist of gold islands with significantly different thicknesses. These findings were confirmed by AFM measurements, too. Gold coverage of the silicon substrate is rather homogeneous, consisting of tiny gold grains, but a pronounced worm-like structure is formed for the layer thickness at electrical continuity threshold. On the glass substrate, the gold clusters of different sizes are clearly observed. For later deposition stages, a clear tendency of the gold atoms to aggregate into larger clusters of approximately the same size is observed. At later deposition stages, gold clusters of up to 100 nm in diameter are formed.

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Early stages of growth of gold layers sputter deposited on glass and silicon substrates

Study on antibacterial activity of chemically synthesized PANI-Ag-Au nanocomposite

Polyaniline (PANI) and Ag/PANI nanoporous composite were prepared by an oxidative polymerization method. The oxidation process of PANI nanoparticles was occurred using (NH4)2S2O8 while the oxidation process of Ag/PANI nanoporous composite was occurred using AgNO3 under the effect of artificial radiation. The structural, morphological, and optical properties of the PANI and Ag/PANI nanoporous structures were studied using different characterization tools. The results confirm the formation of polycrystalline nanoporous PANI and spherical nanoporous composite of Ag/PANI particles. Antibacterial activity tests against gram-positive bacteria, Bacillus subtilis and Staphylococcus aureus, and gram-negative bacteria, Escherichia coli, and Salmonella species were carried out using different concentrations of PANI nanoparticles and Ag/PANI nanoporous composites. PANI has not antibacterial effect against all studied pathogens. In contrast, Ag/PANI nanoporous composites possessed antibacterial activity that is identified by the zone of inhibition. The inhibition zones of bacteria are in order; Salmonella species > S. aureus > B. subtilis > E. coli. The inhibition zones of all bacteria increased with increasing concentrations of Ag/PANI nanoporous composites from 200 to 400 ppm then decreased with further increasing of the dose concentrations to 600 ppm. Finally, a simplified mechanism based on the electrostatic attraction is presented to describe the antimicrobial activity of Ag/PANI nanoporous composite.

Preparation and Characterization of Polyaniline and Ag/ Polyaniline Composite Nanoporous Particles and Their Antimicrobial Activities

The paper is focused on the preparation and surface characterization of gold coatings and nanostructures deposited on glass substrate. Different approaches for the layer preparation were applied. The gold was deposited on the glass with (i) room temperature, (ii) glass heated to 300°C, and (iii) the room temperature-deposited glass which was consequently annealed to 300°C. The sheet resistance and concentration of free carriers were determined by the van der Pauw method. Surface morphology was characterized using an atomic force microscopy. The optical properties of gold nanostructures were measured by UV–vis spectroscopy. The evaporation technique combined with simultaneous heating of the glass leads to change of the sheet resistance, surface roughness, and optical properties of gold nanostructures. The electrically continuous layers are formed for significantly higher thickness (18 nm), if the substrate is heated during evaporation process. The annealing process influences both the structure and optical properties of gold nanostructures. The elevated temperature of glass during evaporation amplifies the peak of plasmon resonance in the structures, the surface morphology being significantly altered.

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Gold nanolayer and nanocluster coatings induced by heat treatment and evaporation technique

Ultrathin gold layers with different thickness of (10–100 nm) on the glass substrate were obtained by Ar plasma-assisted sputtering. The effects of annealing on gold structures sputtered onto glass substrate were studied using AFM, SEM, UV–Vis methods and electrical measurements. Concentration of free charge carriers were determined from the measured resistance and the Hall constant measured by the Van der Pauw method. We have shown that post-deposition thermal treatment leads in significant change in surface morphology of the sputtered Au structures. Our results suggest that the annealing affects electrical properties of the Au coverage namely electrical sheet resistance, free carriers volume concentration, the saturation of which is in comparison with as-sputtered samples shifted towards thicker structures. While semi-conductive character of as-sputtered samples diminishes close to the Au structure thickness of ca 20 nm, in the case of the annealed structures zero-level saturation is achieved for the thickness of 60 nm.

J. Náhlík

Papers

Structural, electrical and optical studies of gold nanostructures formed by Ar plasma-assisted sputtering