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Understanding the mechanisms of reaction and release of acid-baseindicators entrapped in hybrid gels
Wu, Zhijian; Jiang, Yan; Xiang, Hong; You, Laijiang
2006
发表期刊JOURNAL OF NON-CRYSTALLINE SOLIDS
ISSN0022-3093
卷号352期号:52-54页码:5498-5507
摘要The reactivity and release of acid-base indicators entrapped in silica and hybrid silica gels were studied. Methyl orange (MO), methyl red (MR), and phenyl red (PR) were used as the indicators. Tetraethoxysilane (TEOS), n-propyltriethoxysilane (PTES), and bis(trimethoxysilyl)hexane (TSH) were used as gel precursors. HCl (0.01 M) and NaOH (0.01 M) solutions were used as the media for acid-base reaction and release in the experiments. The effects of organosilane addition were examined to understand the processes and mechanisms of reaction and release of the indicators entrapped in the gels. The experimental results suggest that adding the organosilanes lowers the pore size and pore volume of the gels, and therefore suppresses the indicator release, but does not present any obvious effects on the acidbase reactivity of the entrapped indicators. MR entrapped in the gels has no acid-base response, while MO and PR entrapped in the gels can present acid-base response without definite acid-base indicating pH ranges. Only the color change pH values can be determined, which present a 'lag effect' or 'hysteresis' compared with the cases of the free indicators in solutions. The reactivity of the entrapped indicators is suggested to be mainly determined by their chemical nature, the interactions between the indicators and the gel matrices, and the possible involvement of the indicators in the sol-gel process. In general more indicators were found to release in basic solutions than in acidic solutions. For all the entrapped indicators, in acidic solutions through the whole release process, and in basic solutions at the beginning of the release, the indicator release was found to follow the sequence of TEOS Gel > TEOS/PTES Gel > TEOS/TSH Gel. The overall release process is diffusion-controlled, and the release is mainly affected by the textural properties of the gels, the interactions between the gel matrices and the indicators, and the indicator solubility. (c) 2006 Elsevier B.V. All rights reserved. The reactivity and release of acid-base indicators entrapped in silica and hybrid silica gels were studied. Methyl orange (MO), methyl red (MR), and phenyl red (PR) were used as the indicators. Tetraethoxysilane (TEOS), n-propyltriethoxysilane (PTES), and bis(trimethoxysilyl)hexane (TSH) were used as gel precursors. HCl (0.01 M) and NaOH (0.01 M) solutions were used as the media for acid-base reaction and release in the experiments. The effects of organosilane addition were examined to understand the processes and mechanisms of reaction and release of the indicators entrapped in the gels. The experimental results suggest that adding the organosilanes lowers the pore size and pore volume of the gels, and therefore suppresses the indicator release, but does not present any obvious effects on the acidbase reactivity of the entrapped indicators. MR entrapped in the gels has no acid-base response, while MO and PR entrapped in the gels can present acid-base response without definite acid-base indicating pH ranges. Only the color change pH values can be determined, which present a 'lag effect' or 'hysteresis' compared with the cases of the free indicators in solutions. The reactivity of the entrapped indicators is suggested to be mainly determined by their chemical nature, the interactions between the indicators and the gel matrices, and the possible involvement of the indicators in the sol-gel process. In general more indicators were found to release in basic solutions than in acidic solutions. For all the entrapped indicators, in acidic solutions through the whole release process, and in basic solutions at the beginning of the release, the indicator release was found to follow the sequence of TEOS Gel > TEOS/PTES Gel > TEOS/TSH Gel. The overall release process is diffusion-controlled, and the release is mainly affected by the textural properties of the gels, the interactions between the gel matrices and the indicators, and the indicator solubility. (c) 2006 Elsevier B.V. All rights reserved.
其他摘要英文摘要
收录类别SCI
文献类型期刊论文
条目标识符http://ir.isl.ac.cn/handle/363002/2296
专题青海盐湖研究所知识仓储
推荐引用方式
GB/T 7714
Wu, Zhijian,Jiang, Yan,Xiang, Hong,et al. Understanding the mechanisms of reaction and release of acid-baseindicators entrapped in hybrid gels[J]. JOURNAL OF NON-CRYSTALLINE SOLIDS,2006,352(52-54):5498-5507.
APA Wu, Zhijian,Jiang, Yan,Xiang, Hong,&You, Laijiang.(2006).Understanding the mechanisms of reaction and release of acid-baseindicators entrapped in hybrid gels.JOURNAL OF NON-CRYSTALLINE SOLIDS,352(52-54),5498-5507.
MLA Wu, Zhijian,et al."Understanding the mechanisms of reaction and release of acid-baseindicators entrapped in hybrid gels".JOURNAL OF NON-CRYSTALLINE SOLIDS 352.52-54(2006):5498-5507.
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