A novel ferroceneylazobenzene self-assembled monolayer on an ITO electrode: photochemical and electrochemical behaviors

A novel ferroceneylazobenzene self-assembled monolayer (SAM) has been constructed on an indium-tin oxide (ITO) electrode via the covalent attachment of 4-(4'-11-ferrocenyl-undecanoxyphenylazo)benzoic acid ( FcAzCOOH) onto a silanized ITO substrate surface and verified by reflectance infrared spectroscopy and water contact angle. Atomic force microscopy (AFM) and cyclic voltammogram (CV) indicated that the FcAzCOOH formed a uniform and reproducible SAM on the ITO electrode with a surface coverage of ca. 1.9 x 10 (-10) mol/cm (2) (87 A (2)/molecule). The reversible photoisomerization behavior of the SAM was characterized by UV-vis spectra. The azo pi-pi* transition band intensity of the SAM gradually decreased with UV (365 nm) irradiation and was almost recovered again when subsequent exposure to ambient room light (400-800 nm). The increased tilt angle of the molecules on the ITO substrate after UV irradiation further confirmed the trans-to- cis isomerization of azobenzene moieties. The CV of the trans- FcAzCOOH modified ITO electrode showed a pair of waves due to redox of the ferrocene groups in the potential range of 0 to +800 mV (vs SCE), and the peak separation of the redox wave became larger after UV irradiation and almost returned to its original value after subsequent exposure to the visible light. Rate-dependent CV curves indicated that the charge transfer rate between the ferrocene species in the SAM and the ITO electrode was slowed down after UV irradiation due to the smaller porosity of the monolayer film and the more compact barrier layer between the redox species and the ITO electrode. It is the first time to directly observe the influence of photoisomerization of the azobenzene moiety on the redox behavior of redox species in the ferroceneylazobenzene-functionalized SAM. The present results provide profound insight into the role of redox microenvironment on electron transfer kinetics and also provide a simple and facile approach to the preparation of photocontrollable electrodes.     

镧系元素钼系双11系列杂多蓝的离析和性质研究

本文首次报道了镧系元素钼系双11系列两电子杂多蓝K_yH_z[Ln(XMo_(11)O_(39)_2]·nH_2O(X=P,Ln=La、Ce、Pr、Nd、Sm、Gd;X=Si,Ln=Ce、Pr、Sm、Tb、Dy;X=Ge、Ln=Dy)的制备和离析方法.并通过元素分析、红外光谱、可见-紫外光谱、极谱、循环伏安、热分析、ESR、~(31)P NMR、XPS对产物进行了表征及性质研究.结果表明:杂多蓝阴离子结构较之还原前发生了轻微畸变,还原电子具有一定的离域性.在溶液中杂多蓝较还原前的杂多酸(盐)具有略强的氧化能力.溶液中杂多蓝的氧化能力Ln-P(2)>Ln-Si(2).热稳定性Ln-P(2)>Ln-Si(2).该系列杂多蓝还具有较好的抗碱解能力.     

TiO2/carbon nanotube hybrid nanostructures: Solvothermal synthesis and their visible light photocatalytic activity

MWCNT/TiO₂ hybrid nanostructures were prepared via solvothermal synthesis and sol-gel method with benzyl alcohol as a surfactant. As-prepared hybrid materials were characterized by X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectra and X-ray photoelectron spectroscopy. The results showed that MWCNTs were uniformly decorated with anatase nanocrystals in solvothermal condition, but MWCNTs were embedded in a majority of TiO₂ nanoparticles by sol-gel method. When the weight ratio of MWCNTs to TiO₂ was 20%, MWCNT/TiO₂ hybrid nanostructures prepared by solvothermal synthesis exhibited higher visible-light-driven photocatalytic activity than that prepared by sol-gel method. Post-annealing of MWCNT/TiO₂ nanostructures at 400 °C resulted in the formation of the carbonaceous Ti-C bonds on the interface between TiO₂ and MWCNTs, which enhanced the photoabsorbance of the hybrid materials in the visible light region and improved the visible-light degradation efficiency of methylene blue.     

Determination of marker pteridines in urine by HPLC with fluorimetric detection and second-order multivariate calibration using MCR-ALS

A liquid chromatographic method has been developed, in combination with the multivariate curve resolution-alternating least squares algorithm (MCR-ALS), for the simultaneous determination of marker pteridines in urine samples. A central composite design has been applied to optimize the factors influencing the separation (buffer concentration, buffer pH, flow rate, oven temperature, mobile-phase composition). A set of 15 calibration samples were randomly prepared, in a concentration range of 0.5–10.5 ng mL⁻¹ for neopterin, biopterin, and pterin; 4.0–8.0 ng mL⁻¹ for xanthopterin; and 0.5–4.5 ng mL⁻¹ for isoxanthopterin. The validation was carried out with fortified urine samples from healthy adults. The optimized conditions were a mobile-phase composition of 10 mM citric buffer at pH 5.44 and acetonitrile (94.5/5.5, v/v), a flow rate of 1.0 mL min⁻¹, and an oven temperature of 25 °C. The detection system consisted of a fast-scanning spectrofluorimeter, which allows obtaining of second-order data matrices containing the fluorescence intensity as a function of retention time and emission wavelength. In this work, MCR-ALS was used to cope with coeluting interferences, on account of the second-order advantage inherent to this algorithm which, in addition, is able to handle data sets deviating from trilinearity, like the high-performance liquid chromatography data analyzed in the present report. The developed approach enabled us to determine five pteridines, some of them with overlapped profiles, reducing the experimental time and reagent consumption. Ratio values for pteridines/creatinine in urine, for infected children with different pathologies, are reported in this work.     

经由MOFs煅烧制得多孔Fe2O3表面修饰十二烷基磺酸钠:一种高活性且易回收的燃油脱氮光催化剂（英文）

化石燃料燃烧的排放物是目前最严重的环境污染源,其中含氮有机物燃烧产生的NOx等是污染大气和形成雾霾的主要污染物.伴随石油存量的不断减少、重质石油的更多利用以及机动车的大规模增加,由此引起的污染问题日趋严重,因此发展高效的燃油脱氮技术对保护环境意义重大.光催化氧化是近几十年发展起来的新型高级氧化还原技术,由于其可以利用太阳光且在室温下进行,成本低易于进行,是一类理想的燃油脱氮技术.在众多光催化材料中,α-Fe2O3无毒、廉价且具有合适的带隙(2.3 eV),是目前公认较好的光催化材料.然而,在光催化过程中α-Fe2O3较快的电子-空穴复合速度以及过低的比表面积极大降低了其效率.通常,选择性地设计高比表面的多孔半导体金属氧化物被认为是一种简单且实效的提高光催化反应效率的方法.近年来,以金属有机框架结构(MOFs)为硬模板制备多孔金属氧化物的方法逐渐获得了科学家们的关注,这主要得益于热稳定性差的MOFs本身可以通过调控金属离子以及配体种类从而实现原位均匀的调节和修饰半导体金属氧化物,而且可以作为获得多孔性材料的基底.本文通过水热法合成了一种典型的MOFs即MIL-100(Fe).利用MIL-100(Fe)材料自身多孔性及热不稳定性,采用自模板法煅烧制备成多孔Fe2O3.制得的多孔Fe2O3亲油性较差,进行模拟燃油脱氮光催化反应时相互之间容易聚集成团,无法均匀分散于燃油体系中,导致光催化脱氮效率较低.因此,若能对所得多孔Fe2O3进行表面修饰使其亲油性增强并可均匀分散于于燃油体系中,无疑将促进底物的吸附,从而提高光催化燃油脱氮效果.Fe2O3表面带有正电荷,因此我们巧妙地选用一种阴离子表面活性剂十二烷基磺酸钠(SDS)作为修饰剂,采用简单的静电自组装方法制备了SDS/Fe2O3光催化剂.选用吡啶脱氮作为探针反应,考察了SDS/Fe2O3复合光催化剂的可见光光催化性能.结果表明,与未使用修饰剂的Fe2O3相比,SDS/Fe2O3中长链烷基的存在使其表面亲油性增强,能够在模拟燃油溶液中更加均匀地分散进而提高了脱氮效率.其中煅烧温度为450 C且修饰0.25%SDS的样品活性最佳,可见光(λ≥420 nm)照射240 min后吡啶的脱氮率接近100%.     

同步辐射X射线微探针研究石榴石中元素分布

北京正负电子对撞机(BEPC)提供同步辐射(SR)白光做激发源,束斑尺寸50μm×50μm,计数时间20s,位移200μm/步,扫描测量石榴石中元素(Fe,Mn,Ca)分布.得到清晰的元素分布图。     

动态磁涂覆混合固定相开管毛细管电色谱中电渗流的特征

将表面分别被改性成C18和氨基的磁性纳米颗粒按照不同比例混合,制备成具有不同分离选择性的混合固定相,进一步采用动态磁涂覆的方法制备开管毛细管电色谱柱。通过考察这种色谱柱中不同种类固定相表面物理化学性质对电渗流的综合影响,从理论上说明了其电渗流的特征。分别在不同固定相配比及不同涂覆长度条件下进行实验,理论与实验结果相符,证实通过调节固定相配比或磁铁对数可以便捷地调节电渗流的大小。     

Enhanced MCR-ALS modeling of HPLC with fast scan fluorimetric detection second-order data for quantitation of metabolic disorder marker pteridines in urine

This work presents the development of a liquid chromatographic method based on modeling entire fast scan fluorimetric detection second-order data with the multivariate curve resolution alternating least squares algorithm, for the simultaneous determination of five marker pteridines in urine samples.The modeling strategy involves the building of a single MCR-ALS model composed of matrices augmented in the spectral mode, i.e. time profiles remain invariant while spectra may change from sample to sample. This approach allowed us to separate and determine the whole analytes at once.The developed approach enabled us to determine five of the most important metabolic disorder marker pteridines: biopterin, neopterin, isoxanthopterin, pterin and xanthopterin, three of them presenting emission spectra with the same emission wavelength maxima. In addition, some of these analytes present overlapped time profiles. As a consequence of using the entire data sets, a considerable reduction of the data processing experimental time can be achieved. Results are compared with a previous strategy in which data were split in five different regions, and information about the figures of merit of the new strategy compared with the previously reported strategy is reported.     

Reconstructing Hydrogen Bond Network Enables High Voltage Aqueous Zinc-Ion Supercapacitors

High-voltage aqueous rechargeable energy storage devices with safety and high specific energy are hopeful candidates for the future energy storage system. However, the electrochemical stability window of aqueous electrolytes is a great challenge. Herein, inspired by density functional theory (DFT), polyethylene glycol (PEG) can interact strongly with water molecules, effectively reconstructing the hydrogen bond network. In addition, N, N-dimethylformamide (DMF) can coordinate with Zn²⁺, assisting in the rapid desolvation of Zn²⁺ and stable plating/stripping process. Remarkably, by introducing PEG400 and DMF as co-solvents into the electrolyte, a wide electrochemical window of 4.27 V can be achieved. The shift in spectra indicate the transformation in the number and strength of hydrogen bonds, verifying the reconstruction of hydrogen bond network, which can largely inhibit the activity of water molecule, according well with the molecular dynamics simulations (MD) and online electrochemical mass spectroscopy (OEMS). Based on this electrolyte, symmetric Zn cells survived up to 5000 h at 1 mA cm⁻², and high voltage aqueous zinc ion supercapacitors assembled with Zn anode and activated carbon cathode achieved 800 cycles at 0.1 A g⁻¹. This work provides a feasible approach for constructing high-voltage alkali metal ion supercapacitors through reconstruction strategy of hydrogen bond network.     

In Situ Observation of C−C Coupling and Step Poisoning During the Growth of Hydrocarbon Chains on Ni(111)

The synthesis of high-value fuels and plastics starting from small hydrocarbon molecules plays a central role in the current transition towards renewable energy. However, the detailed mechanisms driving the growth of hydrocarbon chains remain to a large extent unknown. Here we investigated the formation of hydrocarbon chains resulting from acetylene polymerization on a Ni(111) model catalyst surface. Exploiting X-ray photoelectron spectroscopy up to near-ambient pressures, the intermediate species and reaction products have been identified. Complementary in situ scanning tunneling microscopy observations shed light onto the C−C coupling mechanism. While the step edges of the metal catalyst are commonly assumed to be the active sites for the C−C coupling, we showed that the polymerization occurs instead on the flat terraces of the metallic surface.