Various shaped-ZnO nanocrystals via low temperature synthetic methods: Surfactant and pH dependence

ZnO nanocrystals, rod-, carnation-, and flower-like structures, have been synthesized in a high yield through low-temperature synthetic methods. Well-aligned ZnO nanorods having hexagonal wurtzite structure were grown on the ZnO thin films assembled by a spin-coating method. The morphologies of ZnO seed films are affected by pHs of sol–gel solutions, resulting smaller sizes and homogeneous roughness at higher pHs and higher number of spin-coating times. The carnation-like structures, average size of about 2–3 μm, were assembled by tens of uniform ZnO nanosheet petals of ∼50 nm in thickness when a different volume ratio of the precursory solution was used. ZnO nanocrystals on the facets of the compact ZnO nanorods have grown to linear nanorods having an average diameter of ∼500 nm and length of ∼2 μm. Furthermore, a noticeable difference in the growth of ZnO nanocrystals in the presence of various surfactants, polyvinylpyrrolidone, polyvinylsulphonic acid, and polyethyleneimine, has been observed and discussed.     

Environmentally Benign and Efficient Ag2S‐ZnO Nanowires as Photoanodes for Solar Cells: Comparison with CdS‐ZnO Nanowires

In this work, we develop a low‐temperature, facile solution reaction route for the fabrication of quantum‐dot‐sensitized solar cells (QDSSCs) containing Ag₂S‐ZnO nanowires (NWs), simultaneously ensuring low manufacturing costs and environmental safety. For comparison, a CdS‐ZnO NW photoanode was also prepared using the layer‐by‐layer growth method. Ultraviolet photoelectron spectroscopy analysis revealed type‐II band alignments for the band structures of both photoanodes which facilitate electron transfer/collection. Compared to CdS‐ZnO QDSSCs, Ag₂S‐ZnO QDSSCs exhibit a considerably higher short‐circuit current density (J_sc) and a strongly enhanced light‐harvesting efficiency, but lower open‐circuit voltages (V_oc), resulting in almost the same power‐conversion efficiency of 1.2 %. Through this work, we demonstrate Ag₂S as an efficient quantum‐dot‐sensitizing material that has the potential to replace Cd‐based sensitizers for eco‐friendly applications.     

Characterizing the Role of Iodine Doping in Improving Photovoltaic Performance of Dye‐Sensitized Hierarchically Structured ZnO Solar Cells

We report two novel types of hierarchically structured iodine‐doped ZnO (I? ZnO)‐based dye‐sensitized solar cells (DSCs) using indoline D205 and the ruthenium complex N719 as sensitizers. It was found that iodine doping boosts the efficiencies of D205 I? ZnO and N719 I? ZnO DSCs with an enhancement of 20.3 and 17.9 %, respectively, compared to the undoped versions. Transient absorption spectra demonstrated that iodine doping impels an increase in the decay time of I? ZnO, favoring enhanced exciton life. Mott–Schottky analysis results indicated a negative shift of the flat‐band potential (V_fb) of ZnO, caused by iodine doping, and this shift correlated with the enhancement of the open circuit voltage (V_oc). To reveal the effect of iodine doping on the effective separation of e^?‐h⁺ pairs which is responsible for cell efficiency, direct visualization of light‐induced changes in the surface potential between I? ZnO particles and dye molecules were traced by Kelvin probe force microscopy. We found that potential changes of iodine‐doped ZnO films by irradiation were above one hundred millivolts and thus significantly greater. In order to correlate enhanced cell performance with iodine doping, electrochemical impedance spectroscopy, incident‐photon‐current efficiency, and cyclic voltammetry investigations on I? ZnO cells were carried out. The results revealed several favorable features of I? ZnO cells, that is, longer electron lifetime, lower charge‐transfer resistance, stronger peak current, and extended visible light harvest, all of which serve to promote cell performance.     

M2+(M=Cu、Cd、Ag、Fe)掺杂氧化锌纳米粉晶的抗菌性能

采用柠檬酸溶胶-凝胶法制备了ZnO及M²⁺掺杂ZnO纳米粉晶(M=Cu、Cd、Ag、Fe),用现代测试技术表征了样品的组成、结构和形貌,以大肠杆菌(Escherichia coli)、金黄色葡萄球菌(Staphylococcus aureus)和白色念珠菌(Candida albicans)为测试菌株,用抑菌圈、最小抑菌浓度和最小杀菌浓度等方法研究了样品在日光照射下的抗菌活性。结果表明,与母体ZnO相比,Cu、Ag、Cd掺杂样品的抗菌性能明显地增强,这可能是由于掺杂金属离子置换Zn²⁺生成了晶格缺陷和电荷缺陷,阻止了光生电子和光生空穴对的复合从而增强了光催化活性和抗菌活性。     

水稳定的镁掺杂ZnO量子点:一锅法合成及细胞成像应用

一锅法合成了镁掺杂的ZnO量子点, 利用APTES对其进行表面包覆, 并采用XRD、TEM、UV-Vis、PL和FTIR等对材料进行了表征。结果表明镁掺杂能明显增强荧光发光强度, 在合适的掺杂浓度(30%)下其量子产率由11%增加到33%。通过APTES的表面包覆使镁掺杂的ZnO量子点具有良好的水溶性和荧光稳定性, 可用于MCF-7细胞成像研究。     

溶胶凝胶辅助水热可控合成ZnO不同形貌分级结构光催化剂

以Zn(NO₃)₂·6H₂O、柠檬酸和NaOH为原料,采用溶胶凝胶(sol-gel)辅助水热法,仅通过改变水热时间,就可得到片花、棒花及梭状3种不同形貌ZnO分级结构。利用XRD、SEM、UV-Vis DRS、光致发光光谱(PL)和氮低温吸附-脱附等手段对合成的ZnO样品进行了表征。推测了合成条件下不同形貌ZnO分级结构形成的机理。以活性翠兰(KGL)为模拟印染废水,考察了其光催化活性。结果表明,虽然所合成的不同形貌的ZnO样品在光照120 min后均能使KGL降解78%以上,但其中水热4 h得到的片花状ZnO光催化性能最好,可降解99%的KGL,这与其片花状的形貌、较大的比表面积、较多的表面氧缺陷和极性面有关。     

微波诱导燃烧法合成类花状ZnO纳米材料及其晶体结构、荧光性质研究

以硝酸锌[Zn(NO3)2.6H2O]和尿素[CO(NH2)2]作前驱体,通过微波诱导燃烧技术可控合成具有不同形貌的ZnO纳米晶体,并用热重分析和差热分析进行了研究。对各种生长条件:微波功率,辐射时间和尿素/Zn2+物质的量的比对ZnO纳米晶体形貌的影响作了分析。结果表明:尿素/Zn2+物质的量的比对ZnO纳米材料的形貌具有显著影响。X衍射图表明合成的ZnO纳米结构呈六角形。傅里叶变换红外光谱图中400~500 cm-1处明显的峰为Zn-O的振动峰。ZnO纳米结构的发光光谱在366 nm的带边发射,因缺陷又由许多可见光发射峰组成。用扫描电子显微镜、透射电子显微镜、选区电子衍射研究了花状ZnO纳米结构的增长机理。本方法仅需几分钟就获得的了ZnO纳米结构。     

Enantiomeric separations by means of nano‐LC

Enantiomers represent a class of compounds extensively investigated since they can show totally different behaviors when they interact with a chiral environment. Because of their identical chemical structure (they differ only in the spatial arrangement of the atoms in the molecule), the separation of optical isomers is a challenging task of analytical chemistry. So far employed methods for the separation of enantiomers are mainly based on chromatography. CE as well was considered as an analytical technique suitable for chiral separations, characterized by high efficiency and low consumption of reagent. Recently, miniaturization was introduced in LC to answer the needs to perform analyses in the minimum time, to use the smallest amount of samples and to reduce environmental pollution. Nano‐LC represents nowadays a valid alternative to the abovementioned conventional analytical techniques, and can be advantageously exploited for enantiomeric separation especially because it needs minute amounts of the chiral material necessary to carry out enantiomeric separations. This review describes the development and applications of nano‐LC in the field of chiral separations. The data reported in literature show its relevance for the study enantiomers‐chiral selectors interaction, as well as for application in pharmaceutical and clinical research.     

Photografting as a versatile,localizable, and single‐step surface functionalization of silica‐based monoliths dedicated to microscale separation techniques

In this work, we developed a surface functionalization way of silica monoliths with a rapid, simple, versatile, and localizable photografting step. The elaboration of a photoreactive layer at the surface of monoliths was first optimized. The functionalization with [γ‐(methacryloyloxy)propyl]trimethoxysilane at 80°C in a hydro‐organic solution containing triethylamine as catalyst allows reachng the highest density of methacrylate photoactive moieties on silica surfaces. These methacrylate reactive surfaces were subsequently photografted within few minutes with acrylate monomers bearing alkyl chains (C₁₂ and C₁₈). The photografting efficiency was determined by monitoring the retentive properties of monoliths in the RP mode. The retention factors are of the same order of magnitude as highly retentive columns obtained by modification of silica surface with long‐alkyl chain silanes or by thermal polymerization of long‐alkyl chain monomers. It was also verified that such grafting neither impaired the efficiency of the monolithic stationary phase (H_min = 6–8 μm in nano‐LC) nor its permeability (about 6 × 10^?14 m²). Further, it was also demonstrated that photografting is localizable in nonmasked defined areas. Results obtained in anion‐exchange chromatography after photopolymerization of [2‐(methacryloyloxy)ethyl]trimethylammonium chloride are presented as well to demonstrate the versatility of the developed approach.