Synthesis of dendritic silver nanostructures and their application in hydrogen peroxide electroreduction

Well-defined silver (Ag) dendritic nanostructures were successfully synthesized by electrodeposition without the use of any template or surfactant. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to investigate the as-prepared Ag nanomaterials. These dendrites are aggregates of Ag nanoparticles, which are highly crystalline in nature. The concentration of AgNO₃ affects the shape of the nanoparticles. In addition, the electrochemical properties of the Ag dendrite-modified glassy carbon electrode (Ag/GC) were characterized by cyclic voltammetry and chronoamperometry. Results indicated that the as-obtained Ag dendrites exhibited favorable electroreduction activity towards oxygen (O₂) and hydrogen peroxide (H₂O₂). When used as a sensor, the Ag/GC electrode exhibited a wide linear range of 0.005–12 mM H₂O₂, with a remarkable sensitivity of 7.39 μA/mM, a detection limit of 0.5 μM, estimated at a signal-to-noise ratio of 3, and a rapid response time (within 5 s). Moreover, the electrode showed good reproducibility, anti-interferant ability and long-term stability.     

Long-term corrosion of copper in a dilute anaerobic sulfide solution

The mechanism of corrosion of oxygen-free copper has been studied in stagnant aqueous sulfide solutions using corrosion potential and electrochemical impedance spectroscopy (EIS) measurements. Film structure and composition were examined on surfaces and on cross-sections prepared by focused ion beam (FIB) milling using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Experiments were conducted in anaerobic 5 × 10⁻⁵ mol dm⁻³ Na₂S + 0.1 mol dm⁻³ NaCl solutions for exposure periods up to 4000 h (∼167 days) to mimic (at least partially) the conditions that could develop on a copper nuclear fuel waste container in a deep geologic repository. The corrosion film formed was a single cellular Cu₂S layer with a non-uniform thickness. The film thickness increased approximately linearly with immersion time, which implied that the sulfide film formed on the Cu surface is non-protective under these conditions up to this exposure time. The film growth process was controlled by HS⁻ diffusion partially in the aqueous solution in the pores in the cellular sulfide film and partially in the bulk of the aqueous solution.     

食品专业化学动力学创新实验教学探索

针对传统化学动力学实验项目难以满足食品专业教学需求的实际情况,我们通过龙葵红色素热降解反应,开展食品专业化学动力学创新实验教学探索。通过实验教学,学生了解了天然食品色素的热稳定性,掌握了色素热降解动力学参数的测定方法,加深了对化学动力学知识的理解,实现了实验项目与专业问题的有机结合,有效地调动了学习积极性。教改在培养学生创造性思维和解决专业实际问题能力方面,收到了十分理想的效果。     

超临界C02干燥法工艺条件对氧化锆气凝胶结构性质的影响

以无机盐ZrOCl2·8H2O为原料,采用溶胶-凝胶过程结合超临界CO2干燥法制备了ZrO2气凝胶.采用BET、TG/DTA、XRD、TEM以及SEM等手段对样品进行了表征分析.考察了超临界CO2干燥过程中,操作压力、操作温度、CO2流率及干燥时间等工艺条件对样品比表面积、孔性质等的影响.结果表明利用本方法制备的ZrO...     

广州增城市增塘水库从水生生态良性循环趋向富营养化原因分析

广州增城市石滩镇增塘水库面积2＋53km^2。为浅水型水库,自1958～2003年水草丛生,透明度150cm以上,为水生态良性循环示范水库,但2004年,改投入草鱼（鲩）,至2010年水草几乎被吃光,氮磷元素迅增而使藻类、浮游动物丰长,变成了趋向富营养化的水库。建议停放草鱼,恢复水草群落方能稳定为水生生态良性循环的水库。     

A general deposition method for ZnO porous films: Occlusion electrosynthesis

In this paper, a modified electrodeposition method, occlusion electrosynthesis (OE), was used to prepare ZnO porous films. The processes of OE were similar to those of electrodeposition except the addition of ZnO nanoparticles in electrolyte. The ZnO porous film prepared by OE (OE-ZnO) was highly porous with considerable thickness (55 μm). The quantum dots-sensitized solar cell based on OE-ZnO porous film showed superior photoelectrochemical performance to that based on the ZnO porous film prepared by doctor-blade (DB) method at the suitable concentrations of ZnO nanoparticles in electrolyte, about 16–32 g/L. In addition to the ZnO porous film constructed with ZnO nanoparticles, the ZnO porous film constructed with ZnO nanorods, ZnO/multi-walls carbon nanotubes and ZnO/TiO₂ composite porous films have also been successfully synthesized by OE, which were expected to be widely applied in various fields. The low temperature (60 °C) processes without post treatment made OE more promising for preparing ZnO porous films than DB, especially the ZnO porous films for flexible devices.     

论明代青花瓷鸟纹的审美特征与文化内涵

鸟纹是明代青花瓷装饰题材中的重要组成部分,在明代各时期有着不同的发展轨迹,具有丰富的审美特征和文化内涵。从审美特征来看,明代青花瓷鸟纹具有装饰之美、神韵之美、自然之美三大特征;从文化内涵来看,明代青花瓷鸟纹具有吉祥寓意、文人旨趣、时代思潮等内涵。     

论汪野亭新粉彩山水瓷画的地位与影响

汪野亭是民国著名新粉彩流派珠山八友之一,在新粉彩山水瓷画领域独树一帜,成就卓然,在粉彩山水瓷画发展史中占有极重要地位,对当代发展亦产生非常显著的影响。     

层次分析法(AHP)在军团菌杀灭方法评判中的应用

该文利用层次分析法(AHP)对军团菌杀灭方法进行综合评判。以中央空调循环冷却水系统为例,建立评价指标系统,对军团菌控制效果以及化学杀生剂进行综合评价,由此得到化学法是最适于中央空调循环冷却水系统的杀菌方法。其中军团菌特效杀菌剂的杀菌性能最佳,可作为应急处理药剂,二氧化氯、2,5-二溴海因、二氯异氰尿酸可作为日常处理药剂。在条件允许的情况下,可使用臭氧作为处理药剂。     

Ethanolic Extract of Propolis Promotes Reverse Cholesterol Transport and the Expression of ATP-Binding Cassette Transporter A1 and G1 in Mice

The ethanolic extract of propolis (EEP) is beneficial in increasing high density lipoprotein (HDL) cholesterol (HDL-C) and diminishing risks of atherosclerosis. In this study, we examined the effects of EEP on reverse cholesterol transport in mice. ³H -cholesterol laden macrophage was injected intraperitoneally into mice fed by gastric gavage with EEP. Plasma lipid level was determined and ³H-cholesterol was traced in plasma, liver and feces. The effects of EEP on ATP-binding cassette transporter A1 and G1 (ABCA1 and ABCG1) and scavenger receptor BI (SR-BI) in mice liver and in cultured cells were also investigated. EEP administration led to a significant increase in HDL-C and peritoneal macrophage-original ³H-cholesterol in plasma, liver and feces. Liver protein expressions of ABCA1 and ABCG1 were increased but SR-B1 was not. In vitro experiments with HepG2 and Raw264.7 cell lines confirmed the above results. The finding of these studies shows that EEP-enhanced reverse cholesterol transport may have resulted from EEP stimulated plasma HDL level and hepatic ABCA1 and ABCG1 expression.