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表面分散过程的分形研究 总被引:5,自引:0,他引:5
盐类和氧化物等活性组分在一定条件下,可在高比表面载体上自发分散。研究这些过程对多相催化剂、吸附剂的制备过程理解和控制无疑是重要的。这类分散过程已被系统地研究,并提出了单层分散模型,对CuCl_2/γ-Al_2O_3、HgCl_2/活性炭等多种体系,测定了单层分散阈值。表面化学习惯上理解为就是二维的化学。早在1931年Tayor就指出表面是不均匀的,但这种不均匀性是作为对理想二维表面的修正而引入的,如TLK模型。表面科学的这些基本概念其数学基础是欧基里德几何学,其物理背景是晶体结构,不规则性就是指晶体结 相似文献
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为将单分散金纳米棒的纵向局域表面等离子体共振(LSPR)波长从近红外光区调节到可见光区,通过表面原位还原反应合成了以银为壳层的单分散双金属核壳复合纳米棒(Au@AgNRs),其Ag壳层厚度可由Ag NO3的用量进行调节。用高分辨透射电镜和X射线能量色散谱仪确证了Au@AgNRs的形态结构、单分散性和化学组成。随着Ag壳层厚度的增加,Au@AgNRs的LSPR效应逐渐增强,纵向LSPR吸收峰由近红外光区蓝移到可见光区。Ag壳层厚度每增加1 nm,Au@AgNRs的纵向LSPR波长减小约12 nm。制得的Au@AgNRs在可视化传感器上有良好的应用前景。 相似文献
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乙烯等离子体处理的云母表面结构及表面性质 总被引:5,自引:0,他引:5
用元素分析、色-质谱、裂解气相色谱和顺磁共振等方法研究了经乙烯等离子体处理的云母表面化学结构及处理过程。结果表明,云母颗粒表面形成了厚数十埃的等离子体聚乙烯膜,其化学结构与反应体系中无云母时得到的等离子体聚乙烯膜相同。通过扫描电镜观察到云母片表面的聚合膜具有规则的海星状花样,随处理时间的延长花样按比例长大。水与云母表面的接触角数据说明,乙烯等离子体处理使云母表面的疏水性提高到聚乙烯的水平,比氩气等离子体、硅烷偶联剂及钛酸酯偶联剂处理的效果均更为显著。 相似文献
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硅表面有机单层膜 :微印章、微加工与微阵列 总被引:1,自引:0,他引:1
总结了作者的实验室在将有机物结合到硅表面方面的研究进展.发现并发展了将有机单层膜组装到硅、氧化硅和相关材料表面的新方法.这些方法简单、可重复,并可得到物理、化学性能良好的致密单层膜.这些单层膜在许多方面有令人鼓舞的应用,包括(a)应用于软印刷术,特别是微接触印章法; (b)用作硅的微加工(微机电系统,MEMS)的单层膜润滑剂; (c)用作DNA和蛋白质微阵列功能分子固定的基底. 相似文献
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利用X射线光电子能谱(XPS)、X射线衍射(XRD)及扩展的X射线精细结构谱(EXAFS)对氧化钴在二氧化钛表面的分散及结构进行了系统研究。结果表明:氧化钴能够在二氧化钛表面实现单层分散,其分散阈值为每平方纳米的二氧化钛分布1.4个钴原子。当负载量小于分散阈值时,钴以二价存在并形成分立的钴氧六配位[CoO6];而当负载量大于分散阈值时,晶体Co3O4在二氧化钛表面形成,钴以两种形式存在,即分散态的钴氧六配位[CoO4]和晶态的Co3O4。实验还表明二氧化钛对二价钴具有明显的稳定作用。 相似文献
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Exciton coupling may arise when chromophores are brought into close spatial proximity. Herein the intra‐nanocrystal exciton coupling of the surface complexes formed by coordination of 8‐hydroxyquinoline to ZnS nanocrystals (NCs) is reported. It is studied by absorption, photoluminescence (PL), PL excitation (PLE), and PL lifetime measurements. The exciton coupling of the surface complexes tunes the PL color and broadens the absorption and PLE windows of the NCs, and thus is a potential strategy for improving the light‐harvesting efficiency of NC solar cells and photocatalysts. 相似文献
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Cyanide, a pseudohalide ion,is a very important anion with both practical and fundamental significance. It is advantageous to employ pseudohalide ions as specific adsorbates on an electrode surface to provide a wider double layer region, and it therefore becomes easier to probe the potential-dependent dynamics of the interface in the absence of complications from electrode-mediated reactions. 相似文献
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In this paper we report on our study of the surface chemical composition, surface energy and acid-base characteristics of plantation eucalypt pulps obtained using the kraft, neutral sulphite semichemical (NSSC) and cold soda processes. X-ray photoelectron spectroscopy (XPS) was used to quantify the surface coverages of extractives and lignin. Inverse gas chromatography (IGC) was used to analyse the dispersive component and the acid-base characteristics of the pulp samples. The pulp yield and the total lignin and extractives in the pulp increased in the sequences of kraft, NSSC and cold soda. The relative surface concentrations of extractives and lignin on the pulps (expressed in terms of the ratios of the pulp surface coverage to the total content of these materials in the pulp) did not increase in the same sequence. The relative surface concentrations of lignin and extractives on the kraft pulps were found to be distinctively higher than those of the NSSC and cold soda pulps. The dispersive components of the surface energy of all pulps were similar before extraction, but increased by different degrees after extraction, with that of the cold soda pulp showing the lowest degree of increase. The acid-base characteristics of the pulps were evaluated using the method of acceptor and donor constants described by Schultz and Lavielle and the method of work of adhesion described by Lundqvist and Ödberg. A comparison of these methods has been made. The acidity of all pulps was found to increase after extraction. The degree of increase in pulp acidity is negatively correlated with the surface lignin concentration on the pulps. The low relative acidity of the cold soda pulp is probably associated with its high surface lignin coverage. An experimental model was established to test this hypothesis. 相似文献
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应用表面光电压谱研究固体表面酸度 总被引:1,自引:0,他引:1
测量与亚带隙辐射相关的表面光电压谱可极其灵敏地得到固体表面态信息。固体表面酸与受体表面态相关。本文用近红外光辐射测试了分子筛和杂多酸的表面光电压,观察到在900~1500 nm光谱区有表面光电压响应。不同的峰位对应不同受体表面态位置,代表不同酸的强度;峰强度对应态密度,反映了酸总量。对初步结果也进行了理论分析。 相似文献
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Pt/CdS光催化剂表面修饰和表面结构 总被引:1,自引:0,他引:1
Pt/CdS光催化剂表面修饰和表面结构张虎勤陈开勋*金振声(西北大学化工系西安710069)(中国科学院兰州化学物理研究所兰州)关键词光催化剂,半导体,表面组成,表面修饰1996-05-20收稿,1996-09-28修回近年来对在Pt/CdS催化剂上... 相似文献
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