纳米材料对普洱茶浸提特性的影响

研究了纳米材料对普洱茶浸提特性的影响规律。首先,对纳米材料的平均粒径及分布进行了表征;对比研究了加入纳米材料前后蒸馏水的阴阳离子组成与浓度、pH值和可溶解性固体总量(TDS)及不同水样的17 ONMR半高峰宽等物化性能;其次,在室温(25℃)考察了不同纳米材料添加量下,普洱茶茶汤中茶多酚含量、氨基酸含量和水浸出物含量随浸提时间的变化关系。实验结果表明:纳米材料平均粒径为95.5nm,阳离子组成主要为Ca2+。加入纳米材料后,蒸馏水的17 O-NMR半高峰宽由113Hz减小至53Hz。加入纳米材料后,茶多酚、氨基酸和水浸出物含量较未加入纳米材料显著提高,且浸出速率明显增加,快速达到动态平衡。

超声解析生活饮用水中消毒副产物

三卤甲烷(trihalomethanes,THMs)、四氯化碳(carbon tetrachloride)被世界卫生组织国际防癌症研究所(IARC)列为2B类致癌物,去除或降低生活饮用水中这两类物质显得尤为重要。目前,我国家用水处理器基本都采用多级滤芯、活性炭吸附的方法达到去除目的。试验突破传统方法,采用超声净水技术,通过对水流空化、雾化、聚能冲击波微射流作用,有效降低水中挥发性有机物(三氯甲烷、四氯化碳)浓度。结果表明,超声水流量为3、4、5 L/h时总解析率平均值分别达(三氯甲烷)96.56%、(四氯化碳)95.28%,试验效果良好。

Simulated Annealing Study on Structures and Energetics of CO2 in Argon Clusters

The minimum-energy configurations and energetic properties of the ArN-CO2 （N=1-19） van der Waals clusters were investigated by a simulated annealing algorithm. A newly developed Ar-CO2 potential energy surface together with the Aziz Ar-Ar interaction potential was employed to construct the high dimensional potential functions by pairwise additive approximation. The global minimal conformations were optimized by sampling the glassy phase space with a circumspectively formulated annealing schedule. Unlike the lighter agg-CO2 clusters, the size-dependent structural and energetic characteristics of ArN-CO2 exhibit a different behavior. The dramatically variations with number of solvent were found for small clusters. After the completion of the first solvation shell at N=17, the clusters were evolved more smoothly.

Density functional investigation on structural and electronic properties of small bimetallic Pb_(n)Ag_(n)(n=2–12)clusters

Structural and electronic properties of PbnAgn(n=2–12)clusters were investigated by density functional theory with generalized gradient approximation at BLYP level in DMol3 program package.The optimized bimetallic PbnAgn(n=2–12)clusters were viewed as the initial structures,then,those were calculated by ab initio molecular dynamics(AIMD)to search possible global minimum energy structures of PbnAgn clusters,finally,the ground state structures of PbnAgn(n=2–12)clusters were achieved.According to the structural evolution of lowest energy structures,Ag atoms prefer gather in the central sites while Pb atoms prefer external positions in PbnAgn(n=2–12)clusters,which is in excellent agreement with experimental results from literature and the application in metallurgy.The average binding energies,HOMO-LUMO gaps,vertical ionization potentials,vertical electron affinities,chemical hardnessη,HOMO orbits,LUMO orbits and density of states of PbnAgn(n=2–12)clusters were calculated.The results indicate that the values of HOMO-LUMO gaps,vertical ionization potentials,vertical electron affinities and chemical hardnessηshow obvious odd-even oscillations when n≤5,PbnAgn(n=2–12)clusters become less chemically stable and show insulator-to-metal transition with the variation of cluster size n,PbnAgn(n≥9)cluster are good candidates to study the properties of PbAg alloys.Those can be well explained by the density of states(DOS)distributions of Pb atoms and Ag atoms between–0.5 Ha and 0.25 Ha in PbnAgn(n=2–12)clusters.

导数荧光法研究异丙醇-水配合物的团簇性质

实验获得了异丙醇-水配合物的激发光谱和发射光谱,分析了其荧光发射机理,并用波长为220和232 nm的紫外光激发不同体积百分比的配合溶液得到了荧光光谱,在FFT低通滤波和平滑处理基础上运用导数荧光分析法对其进行优化,进而研究了异丙醇-水配合物的分子团簇性质。结果表明,配合物中异丙醇分子与水分子在H键作用下,以不同方式结合可以形成7种能发荧光的团簇分子,其发射荧光的中心波长分别为277、284、293、309、328、345和362 nm,并根据相对峰位强度得到了各团簇分子数量随溶液浓度变化的规律。