Unravelling the essential difference between TiOx and AlOx interface layers on Ta3N5 photoanode for photoelectrochemical water oxidation

Tantalum nitride(Ta₃N₅)is a very promising photoanode material due to its narrow band gap(2.1 eV)and suitable band alignment for solar water splitting.However,it suffers from severe photocorrosion during water oxidation.In this work,it was found that surface passivation by AlO_x and TiO_x layers results in dramatically different PEC performance of Ta₃N₅ photoanode for water oxidation.The mechanism study indicates that the negative charges on AlO_x can generate additional field to promote separation of photogenerated charges,while the positive charges on TiO_x layer show the opposite effect.As a result,the Ta₃N₅ based photoanode modified with AlO_x layer gives a high photocurrent of 12.5 mA cm^-2 for 24 h at 1.23 V versus the reversible hydrogen electrode(RHE).Dynamic analysis implies that the hole extraction and transfer are significantly improved by the modification with the AlO_x layer.This work reveals the importance of the charges on surface passivation layer in interface engineering of photoelectrodes.     

Intrinsic catalytic role of mesoporous silica in preferential oxidation of carbon monoxide in excess hydrogen

We have studied the intrinsic catalytic role of MCM-41 mesoporous silica in preferential oxidation of CO in excess H(2) (PROX). Two types of MCM-41 supports (MCM-41A and MCM-41B) were obtained from the same pristine as-synthesized materials by using different procedures for surfactant removal: one-step calcination or two-step extraction-calcination. Although two kinds of Pt catalysts prepared from the MCM-41 supports exhibit high similarity in apparent physicochemical parameters such as Pt morphology, particle-size distribution, electronic states, support architecture, and pore-size distribution, they show a dramatic difference in catalytic activity (ca. 100?% versus 10?% CO conversions at 298?K). This feature motivated us to investigate the catalytic role of MCM-41 in the PROX reaction. By means of infrared experiments with the isotope tracer technique, it was revealed that the reactive microenvironment at the interface between Pt and the MCM-41A support is the origin of the high activity. On the highly active Pt/MCM-41A catalyst, interfacial silanols play a decisive role in the ignition of CO oxidation, and gaseous O(2) and H(2) are dissociated on CO-free Pt sites created by the interfacial reaction. The dissociated oxygen and hydrogen are proposed to sustain the catalytic cycle in the form of regenerated silanols on the support, which is catalyzed by the Pt surface in the presence of H(2).     

Enantioselective activation of stable carboxylate esters as enolate equivalents via N-heterocyclic carbene catalysts

The first N-Heterocyclic Carbene (NHC) mediated activation of stable carboxylate esters to generate enolate intermediates is disclosed. The catalytically generated arylacetic ester enolates undergo enantioselective reactions with α,β-unsaturated imines.     

Quantitative structure-retention relationship of curcumin and its analogues

The natural product curcumin is widely used in Asian countries for the treatment of several diseases. However, the clinical potential of curcumins remains limited due to their relatively poor bioavailability and no experimental data about their lipophilicity for bioavailability prediction. To evaluate the retention and lipophilicity of curcumin and its 31 newly synthesized analogues, they were subjected to 3D quantitative structure-retention relationship studies by RP-HPLC. Superior than the classical four-variant quantitative structure-retention relationship model (conventional r(2) =0.734), the 3D comparative molecular similarity index analysis model with combined steric, electrostatic, and H-bond donor fields, resulted in a robust structure-retention correlation (cross-validated q(2) =0.613 and r(2) =0.979). The statistical analyses indicate that the electrostatic and H-bond donor fields have a primary influence on the chromatographic retention of analytes. The predictive power and robustness of the derived comparative molecular similarity index analysis model was further confirmed by the test-set validation (q(2) =0.702, r(2) =0.905, and the slope K=1.016) and Y-randomization examination. Statistically significant and physically meaningful 3D-quantitative structure-retention relationship provided better insight into understanding the retention behaviors of curcumin and its analogues, and their separation mechanism in a given RP-HPLC system.     

Spectroscopic study on the interaction between[Hg（SCN）4]2- and hemoglobin

The interaction between[Hg（SCN）₄]^2- and hemoglobin（Hb） under conditions that simulate a physiological environment was investigated by UV-vis spectroscopy,fluorescence spectroscopy,resonance Rayleigh scattering（RRS） spectroscopy and circular dichroism（CD） spectroscopy.The results obtained from the change of UV-vis and CD spectra,the quenching of Hb fluorescence and the enhancement of RRS intensity proved that a 10:1 type complex was formed between[Hg（SCN）₄]^2- and Hb.The possible mechanism suggested for the interaction was that ten Hg（SCN）₄]^2- anions entered the four subunits of a Hb molecule to react with some residues to form an adduct by coordination and electrostatic forces.The coordination of[Hg（SCN）₄]^2- with Trp was the major cause of the fluorescence quenching of Hb.     

An ethanol biosensor based on a bacterial cell-immobilized eggshell membrane

An ethanol biosensor was fabricated based on a Methylobacterium organophilium-immobilized eggshell membrane and an oxygen（O₂） electrode.A linear response for ethanol was obtained in the range of 0.050-7.5 mmol/L with a detection limit of 0.025 mmol/L（S/N= 3） and a R.S.D.of 2.1%.The response time was less than 100 s at room temperature and ambient pressure. The optimal loading of bacterial cells on the biosensor membrane is 40 mg（wet weight）.The optimal working conditions for the microbial biosensor are pH 7.0 phosphate buffer（50 mmol/L） at 20-25℃.The interference test,operational and storage stability of the biosensor are studied in detail.Finally,the biosensor is applied to determine the ethanol contents in various alcohol samples and the results are comparable to that obtained by gas chromatographic method and the results are satisfactory.Our proposed biosensor provides a convenient,simple and reliable method to determine ethanol content in alcoholic drinks.     

Preparation of amphiphilic graft copolymer with polyisoprene backbone by combination of anionic polymerization and “click” reaction

A novel graft copolymer consisting of polyisoprene backbone and hydrophilic side chain with carbamic acid ester functional group was prepared via thiol-ene"click"reaction and alcohol-isocyanate reactions.Polyisoprene was synthesized by anionic polymerization using n-butyl lithium as initiator,and the pendant hydroxyl groups were introduced by the thiol-ene reaction of mercaptoethanol with the double bond of 1,2-addition units of PI backbone in the presence of radical initiator azobisisobutyronitrile. Isocyanate end group capped poly(ethylene glycol)(mPEG-NCO) was grafted onto the PI backbone through alcoholisocyanate reaction between the pendant hydroxyl groups and isocyanate group of mPEG-NCO.The structure of the graft copolymer were characterized and confirmed by means of size-exclusion chromatography,~1H NMR and FTIR spectroscopy.     

固相萃取-高效液相色谱法同时测定食品塑料包装材料中9种光稳定剂

建立了同时测定食品塑料包装材料中9种紫外光稳定剂含量的高效液相色谱方法。样品用甲醇-乙酸乙酯混合溶剂超声提取,经固相萃取小柱净化后,以ZORBAX SB-C18柱(250 mm×4.6 mm, 5 μm)为分离色谱柱,甲醇和水为流动相,梯度洗脱,以310 nm为检测波长进行定性、定量分析。该方法前处理简单、易操作,9种紫外光稳定剂分离效果良好。9种紫外光稳定剂在0.2～10 mg/L范围内呈良好的线性关系,线性相关系数大于0.999;方法检出限为0.05～0.1 mg/L;实际样品中的加标回收率为70.2%～89.0%,相对标准偏差为0.4%～4.5%。该方法简单、准确,能够满足食品塑料包装材料中紫外光稳定剂的检测要求。     

粒度分析及粒度标准物质研究进展

综述了当前粒度分析测试方法的研究进展,并简单介绍了各种测试方法的基本原理以及包括美国、欧洲、中国在内的国家和地区在粒度标准物质方面的研究概况。