Sensitive photoelectric sensing for 5-HMF detection

5-Hydroxymethylfurfural (5-HMF) is a heterocyclic compound with six carbons commonly found in heat-treated carbohydrate-rich foods. 5-HMF exceeding the specified limit is cytotoxic to the human body, and will be converted into carcinogenic substances (5-sulfoxide methyl furfural) after long-term accumulation in the body. Therefore, it is highly necessary to develop a sensitive and accurate detection method for 5-HMF in the field of food safety. In this study, a photoelectric sensing method was developed for the highly sensitive detection of 5-HMF using hollow TiO2 nanospheres successfully synthesized by template, sol-gel and lye etching methods. The structure and composition of the materials were studied by XRD, XPS, SEM and TEM. The electrochemical and photoelectrochemical properties of an h-TiO2 electrode probe based on indium tin oxide (ITO) slides were investigated. The results indicated that the linear relationship of 5-HMF is good in the concentration range of 10-11-10-7 M, and the detection limit of 5-HMF is 0.001 nM. Moreover, the PEC sensor shows high accuracy in the detection of actual samples.

N-Doped Yellow TiO2 Hollow Sphere-Mediated Visible-Light-Driven Efficient Esterification of Alcohol and N-Hydroxyimides to Active Esters

Herein we report a simple synthetic protocol for N-doped yellow TiO₂ (N-TiO₂ ) hollow spheres as an efficient visible-light-active photocatalyst using aqueous titanium peroxocarbonate complex (TPCC) solution as precursor and NH₄ OH. In the developed strategy, the ammonium ion of TPCC and NH₄ OH acts as nitrogen source and structure-directing agent. The synthesized N-TiO₂ hollow spheres are capable of promoting the synthesis of active esters of N-hydroxyimide and alcohol through simultaneous selective oxidation of alcohol to aldehyde followed by cross-dehydrogenative coupling (CDC) under ambient conditions upon irradiation of visible light. It is possible to develop a novel and cost-effective one-pot strategy for the synthesis of important esters and amides on gram scale using the developed strategy. The catalytic activity of N-TiO₂ hollow spheres is much superior to that of other reported N-TiO₂ samples as well as TiO₂ with varying morphology.

Design of Morphology-Controllable ZnO Nanorods/Nanopariticles Composite for Enhanced Performance of Dye-Sensitized Solar Cells

A facile one-pot approach was developed for the synthesis of ZnO nanorods (NRs)/nanoparticles (NPs) architectures with controllable morphologies. The concrete state of existence of NPs and NRs could rationally be controlled through reaction temperature manipulation, i.e., reactions occured at 120, 140, 160, and 180 °C without stirring resulted in orderly aligned NRs, disordered but connected NRs/NPs, and relatively dispersed NRs/NPs with different sizes and lengths, respectively. The as-obained ZnO nanostructures were then applied to construct photoanodes of dye-sensitized solar cells, and the thicknesses of the resultant films were controlled for performance optimization. Under an optimized condition (i.e., with a film thickness of 14.7 µm), the device fabricated with the material synthesized at 160 °C exhibited the highest conversion efficiency of 4.30% with an elevated current density of 14.50 mA·cm-2 and an open circuit voltage of 0.567 V. The enhanced performance could be attributed to the coordination effects of the significantly enhanced dye absorption capability arising from the introduced NPs and the intrinsic fast electron transport property of NRs as confirmed by electrochemical impedance spectroscopy (EIS) and ultraviolet-visible (UV-vis) absorption.