A Blinking Mesoporous TiO2−x Composed of Nanosized Anatase with Unusually Long‐Lived Trapped Charge Carriers

A mesoporous TiO_2?x material comprised of small, crystalline, vacancy‐rich anatase nanoparticles (NPs) shows unique optical, thermal, and electronic properties. It is synthesized using polymer‐derived mesoporous carbon (PDMC) as a template. The PDMC pores serve as physical barriers during the condensation and pyrolysis of a titania precursor, preventing the titania NPs from growing beyond 10 nm in size. Unlike most titania nanomaterials, during pyrolysis the NPs undergo no transition from the anatase to rutile phase and they become catalytically active reduced TiO_2?x. When exposed to a slow electron beam, the NPs exhibit a charge/discharge behavior, lighting up and fading away for an average period of 15 s for an extended period of time. The NPs also show a 50 nm red‐shift in their UV/Vis absorption and long‐lived charge carriers (electrons and holes) at room temperature in the dark, even long after UV irradiation. The NPs as photocatalysts show a good activity for CO₂ reduction.     

A twofold interpenetrating two‐dimensional zinc(II) coordination polymer: synthesis,crystal structure and physical properties

A novel twofold interpenetrating two‐dimensional (2D) Zn^II coordination framework, poly[[(μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene‐κ²N³:N³)(μ‐naphthalene‐2,6‐dicarboxylato‐κ²O²:O⁶)zinc(II)] dimethylformamide monosolvate], {[Zn(C₁₂H₆O₄)(C₁₄H₁₄N₄)]·C₃H₇NO}_n or {[Zn(1,3‐BMIB)(NDC)]·DMF}_n (I), where H₂NDC is naphthalene‐2,6‐dicarboxylic acid, 1,3‐BMIB is 1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene and DMF is dimethylformamide, was prepared and characterized through IR spectroscopy, elemental analysis, thermal analysis and single‐crystal X‐ray diffraction. Single‐crystal X‐ray diffraction analysis revealed that (I) exhibits an unusual twofold interpenetrating 2D network. In addition, it displays strong fluorescence emissions and a high photocatalytic activity for the degradation of Rhodamine B (RhB) under UV‐light irradiation.     

Self-assembly of rutile (α-TiO<Subscript>2</Subscript>) nanoclusters into nanorods in microemulsions at low temperature and their photocatalytic performance

A novel method – inverse microemulsion has been developed not only for synthesizing low cost TiO₂ nanocrystals but also for the first time making these nanocrystals self-assemble into various nanoparticles at 85°C. By variation of the volume ratios of oil to water in reverse microemulsions, the morphologies of obtained samples turned from nanoclusters to nanospherules, then grew into nanodumbbells, and became nanorods at last. It could be observed by transmission electron microscope (TEM) directly. The resulting materials were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscope (HRTEM). The photocatalytic activity of TiO₂ was tested with photodegradation of Methyl Orange (MO) in water. The catalyst consisting of nanorods showed the highest photocatalytic activity, which is due to its large surface area. Furthermore, the mechanism of self-assembly of TiO₂ nanocrystals was discussed in detail.     

Acid‐treated g‐C3N4‐Cu2O composite catalyst with enhanced photocatalytic activity under visible‐light irradiation

Acid‐treated g‐C₃N₄‐Cu₂O was prepared by hydrothermal reduction followed by high temperature calcination and acid exfoliation. The structures and properties of as‐synthesized samples were characterized using a range of techniques, such as X‐ray photoelectron spectroscopy, scanning electron microscopy, Photoluminescence Spectroscopy and the Brunauer–Emmett–Teller (BET) theory. The photocatalytic activity was evaluated by measuring the photodegradation of methyl orange under visible‐light irradiation. Based on the results of TEM, XPS, EPR and other techniques, it was verified that a heterojunction was formed. The acid treatment process can increase the specific surface area to form abundant heterojunction interfaces as channels for photo‐generated carrier separation, thereby enhancing its light utilization and quantum efficiency. Results indicate that acid‐treated g‐C₃N₄‐Cu₂O possesses a large specific surface area, which provides plentiful activated sites for heterojunctions to form; in addition, it showed a high visible light effect and the minimum charge‐transfer resistance. Furthermore, the g‐C₃N₄‐Cu₂O material exhibits high levels of effectiveness and stability. Electron paramagnetic resonance and a series of radical trapping experiments demonstrate that the holes and ?O₂^? could be the main active species in methyl orange photodegradation. This work could provide new insights into the fabrication of composite materials as high‐performance photocatalysts, and facilitate their application in addressing environmental protection issues.     

二氧化钛紫外光在线消解测定COD的研究

以TiO2-K2Cr2O7协同光催化氧化体系为基础，结合流动注射分析方法建立了一种快速测定水样中化学需氧量（COD）的简便方法．该方法测试速度快，不需有毒、昂贵的试剂，具有广阔的应用前景．COD含量在10～100mg·L^-1和100～1000mg·L^-1范围内，吸光度与COD含量均呈良好的线性关系；测定30mg·L^-1和300mg·L^-1的COD标准溶液，RSD≤5．1％（n=7）；将本系统应用于实际环境水样测定，与国家标准分析方法测定结果相符．     

Photoinduced electron transfer in some photosensitive molecules-incorporated semiconductor/zeolites: New photocatalytic systems

An intramolecular charge transfer (ICT) molecule,p-N,N-dimethyl-aminobenzoic acid (DMABA) has been studied in zeolite and colloidal media. The ratio of ICT to normal emission (ICT/LE) is greatly enhanced in zeolites compared to that in polar solvents. The ICT emission of DMABA was quenched by increasing the concentration of TiO₂ colloids, while the normal emission was slightly enhanced. Upon illumination of the heteropoly acid (HPA) incorporated TiO₂ colloids, interfacial electron transfer takes place from the conduction band of TiO₂ to the incorporated HPA which is also excited to catalyze the photoreduction of Methyl Orange. It is found that the interfacial electron transfer mechanism of HPA/TiO₂ is quite analogous to the Z-scheme mechanism for plant photosynthetic systems. In DMABA-adsorbed TiO₂/Y-zeolite the ICT/LE ratio of DMABA is quite small implying that electron transfer takes place from DMABA to the conduction band of TiO₂. This results in drastic enhancement in the photocatalytic activity of DMABA-adsorbed TiO₂/Y-zeolite compared to free TiO₂/Y-zeolite.     

原位低场核磁共振弛豫法定量监测光催化Cr(Ⅵ)还原反应

本文利用原位低场核磁共振（LF-NMR）技术在真实固液反应环境中对光催化还原Cr（Ⅵ）反应进行了定量研究,并对Ag纳米颗粒负载量不同的Ag担载石墨相氮化碳复合光催化剂（Ag/g-C₃N₄）在可见光照射下催化Cr（Ⅵ）还原为Cr（Ⅲ）的性能进行了研究.研究发现,Ag纳米颗粒负载（负载量分别为1 wt.%、2 wt.%、5 wt.%和10 wt.%）可以有效提高g-C₃N₄的光催化性能;且负载量为5 wt.%时光催化性能最优,为无Ag负载的g-C₃N₄的4倍.此外,本文还通过横向弛豫时间（T₂）定量分析了反应体系中顺磁性Cr（Ⅲ）离子的浓度,证实了采用LF-NMR弛豫法评价光催化Cr（Ⅵ）还原反应性能的可行性.     

Two copper(II)-bbtz modified Keggin and β-octamolybdate compounds captured in one-pot under hydrothermal conditions

Under hydrothermal conditions two compounds based on Keggin and β-octamolybdate, respectively, [Cu₂(bbtz)₄(SiMo₁₂O₄₀)] (1) and [Cu₂(bbtz)₄(Mo₈O₂₆)]_1/2·H₂O (2) (bbtz = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene), were synthesized in one-pot and characterized by single-crystal X-ray diffraction, elemental analyses, and IR spectroscopy. In compound 1, two adjacent wave-like Cu^II-bbtz lines are connected by SiMo₁₂ anions and bbtz to generate a ladder-like chain. Adjacent chains share the same Cu^II ions to build a three-dimensional (3-D) framework. In compound 2, the β-Mo₈ anions link Cu₃(bbtz)₂ subunits alternately to form a one-dimensional (1-D) chain. These chains connect each other through sharing Cu^II ions and a 3-D network is constructed. Moreover, we studied the electrocatalytic and photocatalytic activities of these two compounds. The results indicate that 1 and 2 show good electrocatalytic performance for the reduction of nitrite and bromate; they also exhibit photocatalytic properties for degradation of MB and RhB.