Enhanced catalysis of a vanadium-substituted Keggin-type polyoxomolybdate supported on the M3O4/C (M = Fe or Co) surface enables efficient and recyclable oxidation of HMF to DFF.

In the reaction of oxidizing 5-hydroxymethylfurfural (HMF), attaining high efficiency and selectivity in the conversion of HMF into DFF presents a challenge due to the possibility of forming multiple products. Polyoxometalates are considered highly active catalysts for HMF oxidation. However, the over-oxidation of products poses a challenge, leading to decreased purity and yield. In this work, metal-organic framework-derived Fe3O4/C and Co3O4/C were designed as carriers for the vanadium-substituted Keggin-type polyoxomolybdate H5PMo10V2O40·35H2O (PMo10V2). In this complex system, spinel oxides can effectively adsorb HMF molecules and cooperate with PMo10V2 to catalyze the aerobic oxidation of HMF. As a result, the as-prepared PMo10V2@Fe3O4/C and PMo10V2@Co3O4/C catalysts can achieve efficient conversion of HMF into DFF with almost 100% selectivity. Among them, PMo10V2@Fe3O4/C exhibits a higher conversion rate (99.1%) under milder reaction conditions (oxygen pressure of 0.8 MPa). Both catalysts exhibited exceptional stability and retained their activity and selectivity even after undergoing multiple cycles. Studies on mechanisms by in situ diffuse reflectance infrared Fourier transform spectroscopy and X-ray photoelectron spectroscopy revealed that the V5+ and Mo6+ in PMo10V2, together with the metal ions in the spinel oxides, act as active centers for the catalytic conversion of HMF. Therefore, it is proposed that PMo10V2 and M3O4/C (M = Fe, Co) cooperatively catalyze the transformation of HMF into DFF via a proton-coupled electron transfer mechanism. This study offers an innovative approach for designing highly selective and recyclable biomass oxidation catalysts.

SERS investigation of ciprofloxacin drug molecules on TiO2 nanoparticles.

In this paper, TiO2 nanoparticles (NPs) with different crystallinity served as SERS-active substrates for SERS detection of ciprofloxacin (CIP) drug molecules for the first time. CIP is close to the surface of the TiO2 substrate through the carboxyl group. The mutual SERS enhancement behaviors between CIP molecules and TiO2 NPs were discovered, which are attributed to the contribution of the TiO2-to-molecule charge-transfer mechanism. The crystallinity of TiO2 NPs, the pH value of adsorption solution and the adsorption time have significant influences on the interaction and the SERS behavior between CIP and TiO2. When the calcination temperature of TiO2 NPs is 450 °C, the pH value of adsorption solution is 6 and the adsorption time is 9 h, the CIP molecules on TiO2 NPs exhibit the largest SERS enhancement.

Rapid monitoring of benzylpenicillin sodium using Raman and surface enhanced Raman spectroscopy.

At present, fluorescence spectroscopy, ultraviolet spectroscopy and infrared spectroscopy are usually used to detect drug molecules, however the information about using Raman spectroscopy to detect drug molecules is very few. In this work normal Raman spectroscopy and surface-enhanced Raman spectroscopy were utilized to study benzylpenicillin sodium (NaBP). The results show that NaBP is close to the surface of silver substrate through the carboxyl group, and the detection limit of NaBP is reduced to 1×10(-7) mol/L. Accordingly, the quantitative analysis of NaBP can be carried out in the range of 1×10(-4)-1×10(-7) mol/L concentration. And it is proved that NaBP is not stable in acid and alkali conditions and the decomposition reaction is very complex.

Improving surface-enhanced Raman scattering properties of TiO(2) nanoparticles by metal Co doping.

In this paper, pure and different amount Co ions doped TiO2 nanoparticles were synthesized by a sol-hydrothermal method and were served as SERS-active substrate. The effect of metal Co doping on SERS properties of TiO2 nanoparticles was mostly investigated. The results indicate that abundant metal doping energy levels can be formed in the energy gap of TiO2 by an appropriate amount Co ions doping, which can promote the charge transfer from TiO2 to molecule, and subsequently enhance SERS signal of adsorbed molecule on TiO2 substrate, and improve remarkably SERS properties of TiO2 nanoparticles.