Zhiqiang Cheng,Shengzhe Zhao,Zhaolian Han,Yingying Zhang,Xiaodong Zhao,Lijuan Kang
Hollow TiO2 nanotubes have been produced by combining electrospinning with a soaking process and controlled calcination method. Silver was successfully coated on the surface of the TiO2 tubes through the immersion burning method. Structure and components of TiO2 and Ag/TiO2 tubes were characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). Morphology was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocatalysis properties were verified by degradation of methyl orange (MO) dye. From the results, the Ag/TiO2 hollow tubes could degrade methyl orange efficiently under UV light irradiation, showing excellent photocatalytic activity over pure TiO2. The synthesis mechanism of the Ag/TiO2 tubes and the mechanism for silver-enhanced photocatalytic activity have been conjectured.
In the present paper, we report on the design and fabrication of a recyclable microfluidic SERS chip with an integrated Au@Ag/TiO2 NTs (gold core silver shell nanoparticles (NPs) with decorated TiO2 nanotube arrays (NTs)) composite SERS substrate. The stripped TiO2 NTs with regularly arranged pore structures were prepared on a Ti foil by easy tape lithography followed by anodic oxidation. The Au@Ag NPs were fabricated on the mouth surface and the inner walls of the TiO2 NTs within a microchannel without clogging via a facile self-assembly chemical plating composite method. Under optimized conditions, the microfluidic SERS chip provided excellent sensitivity to R6G molecules with a detection limit of 10−10 M and a SERS enhancement factor (EF) of 1.15 × 108. Versus single Au NPs, Au@Ag NPs and the Au@Ag/TiO2 plate, the optimized Au@Ag/TiO2 NTs showed improved SERS peak intensities for the C–C–C bending (613 cm−1) of 20, 2.3 and 1.6 times enhancement, respectively. The enhancement effect was attributed to both electromagnetic and chemical enhancement. The photocatalytic performance of the Au@Ag/TiO2 NTs was exploited to recycle the microfluidic SERS chip through UV light photocatalytic purification. The experimental result shows that the microfluidic SERS chip featured high reproducibility and could be used as an efficient SERS detector for many biochemical molecules.
Yuan Yao,Mingxuan Sun,Zihan Zhang,Xiaojing Lin,Bowen Gao,Sambandam Anandan,Wei Liu
A ternary composites of MoO 3 /Ag/TiO 2 nanotube arrays were synthesized by in-situ annealing of TiO 2 nanotube arrays impregnated with AgNO 3 over MoO 3 powders. During the annealing process , the crystallization of the TiO 2 nanotubes, the thermo-decomposition of AgNO 3 to Ag nanoparticles , and the sublimation of MoO 3 occur jointly. The photoelectrochemical measurements of the resultants indicate that MoO 3 /Ag/TiO 2 nanotube arrays present better photoelectrochemical properties compared with Ag/TiO 2 nanotube arrays and pristine TiO 2 nanotube arrays. Especially, the highest photocurrent and open circuit voltage are up to 21.29 μA/cm 2 and 0.058 V under visible light irradiation , whereas 1.77 and 3.87 times larger than those of TiO 2 nanotube arrays, respectively. Superior photoelectrochemical stability and larger photo-conversion efficiency of the ternary composites are also demonstrated. The improved photoelectrochemical properties are related to the close interfacial contact among MoO 3 , Ag, and TiO 2 as well as the surface plasma resonance of Ag in the ternary composites, which broaden the range of light response and enhance the efficiency of charge separation. This study provides a skillful solution to construct TiO 2 -based composite materials and demonstrates it is an unique architecture to promote the visible light driven photocatalytic application of TiO 2 .
Electrocatalytic conversion of biomass-derived platform molecules is regarded as an emerging approach to obtain high-value fuels and chemicals. Herein, a heterostructured design strategy involving dispersed Ag nanoparticles immobilized on one-dimensional TiO2 nanotubes (Ag-TiO2 NTs) for the electroreduction of 5-hydroxymethylfurfural (HMF) into 2,5-dihydroxymethylfuran (DHMF) was reported. The optimal electrode exhibited an 82.2% FE, 89.8% selectivity, and DHMF productivity value of 0.1 mmol cm−2 h−1. Electrochemical measurements combined with density functional theory (DFT) calculations manifested that the superior performance was derived from the heterojunction-induced metal–semiconductor interactions at the interface, by which the TiO2 NTs and Ag bring complementary advantages inhibiting the hydrogen evolution reaction (HER) and facilitating charge transfer. Moreover, the catalytic activity of the Ag sites on Ag-TiO2 NTs was considered separately. The mass activity of Ag on Ag-TiO2 NTs reached 5.8 mol L−1 g−1, which was far more than that of Ag mesh (0.038 mol L−1 g−1), indicating the significantly enhanced activity of Ag with high utilization. This could be attributed to the controllable nucleation of Ag through the confinement effect of TiO2 NTs, acquiring dispersed Ag nanoparticles. The design scheme for the heterostructured Ag-TiO2 NTs electrocatalyst displays prospective applications for developing highly efficient electrocatalysts for the electrochemical reduction of HMF.
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