Surface enhanced Raman scattering from porous gold nanofibers of different diameters

Porous gold nanofibers of different diameters from 43 to 219 nm were fabricated using electrochemical deposition techniques. Gold-silver alloy were electrochemically deposited in the form of nanofibers within the porous alumina templates of various diameters and only a silver phase was chemically removed using nitric acid. Field-emission scanning electron microscope images of the resulting nanofibers show a high-quality nanoporous network with homogeneous pores. A notable surface-enhanced Raman scattering (SERS) has been observed for all porous gold nanofibers of which scattering efficiencies are distinctly higher than that of the smooth solid gold nanofibers without porosity. As the diameter of porous gold nanofibers decreases, the observed SERS efficiency gradually increases. Controlled fabrication of lateral width of gold nanofibers reveals promising application for high efficient and stable molecular sensing platforms.     

Helix-coiled gold nanowires for molecular sensing

Helix-coiled gold nanowires were fabricated by a templating route using unique composite templates consisting of anodic aluminum oxide (AAO) nanotubular membrane and confined mesoporous silica therein. A different degree of confinement energy induces a different degree of helix curvature of confined porous silica nanochannels in an AAO, which works as a hard template for the electrochemical deposition of gold, thereby rationally enabling a different degree of helix curvature of gold nano-replicas. From surface-enhanced Raman scattering experiments, we first found that helix-coiled gold nanowires show more distinctly enhanced molecule sensing efficiency than those from simple smooth gold nanowires, and gold nanowires with the narrower lateral width show more enhanced molecule sensing efficiency than those of thicker width helix nanowires.     

Photocatalytic degradation of organic pollutants and inactivation of pathogens under visible light via CoOx surface-modified Rh/Sb-doped SrTiO3 nanocube

Visible light-active rhodium and antimony-co-doped SrTiO₃ nanocubes (Rh/Sb:SrTiO₃ NCs) were synthesized at low temperatures from Rh/Sb:TiO₂ nanorods by the molten salt flux method. The effects of different calcination temperatures (700, 800, and 900 °C) and addition of transition metal oxides (NiO_x, CoO_x, and CuO_x) on the photocatalytic properties of the Rh/Sb:SrTiO₃ NCs were studied. The phase composition and morphology of the Rh/Sb:SrTiO₃ NC photocatalysts (after calcination) were characterized using standard analytical techniques. The synergistic effect of the metal oxides and Rh/Sb:SrTiO₃ NCs boosted the photocatalytic degradation of orange II dye and bisphenol A as well as the inactivation of bacteria. 2 wt% CoO_x-loaded Rh/Sb:SrTiO₃ photocatalyst showed higher photocatalytic performance for the degradation of orange II (96.3%) and bisphenol A (87%) in aqueous solution than Ni (2 wt%) and Cu (2 wt%)-loaded Rh/Sb:SrTiO₃ NC composites. In addition, inactivation of Escherichia coli (96%) and Staphylococcus aureus (97.1%) was achieved over CoO_x (2 wt%)-loaded Rh/Sb:SrTiO₃ for 2 h under visible light irradiation (λ?≥?420 nm). Further, scavenging experiments confirmed that superoxide anion radicals (^·O₂^?) and holes (h⁺) are the major active species and OH^· is a minor species responsible for the photocatalytic degradation of the studied organic pollutants. The synthetic strategy presented here offers a novel approach to the design of highly active visible light active photocatalysts for the removal of organic pollutants and inactivation of bacteria in wastewater.

Graphical abstract