Growth and in situ transformation of TiO2 and HTiOF3 crystals on chitosan-polyvinyl alcohol co-polymer substrates under vapor phase hydrothermal conditions  

作　　者：Tianxing Wu Guozhong Wang Xiaoguang Zhu Porun Liu Xian Zhang Haimin Zhang Yunxia Zhang Huijun Zhao 

机构地区：[1]Key Laboratory of Materials Physics, Centre for Environmental and Energy Nanomaterials, Anhui Key Laboratory of Nanomaterials and Nanostructures, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China [2]Centre for Clean Environment and Energy, Gold Coast Campus, Griffith University, Queensland 4222, Australia

出　　处：《Nano Research》2016年第3期745-754,共10页纳米研究（英文版）

基　　金：This work was financially supported by the Natural Science Foundation of China （No. 51372248 and 51432009）, the CAS/SAFEA International Partnership Program for Creative Research Teams of Chinese Academy of Sciences, China, and the CAS Pioneer Hundred Talents Program.

摘　　要：A chitosan-polyvinyl alcohol （CS/PVA） co-polymer substrate possessing a large number of amino and hydroxyl groups is used as a substrate to induce the direct growth and in situ sequential transformation of fitanate crystals under HF vapor phase hydrothermal conditions. The process involves four distinct formation/ transformation stages. HTiOF3 crystals with well-defined hexagonal shapes are formed during stage I, and are subsequently transformed into {001} faceted anatase TiO2 crystal nanosheets during stage II. Interestingly, the formed anatase TiO2 crystals are further transformed into cross-shaped and hollow square- shaped HTiOF3 crystals during stages III and IV, respectively. Although TiO2 crystal phases and facet transformations under hydrothermal conditions have been previously reported, in situ crystal transformations between different titanate compounds have not been widely reported. Such crystal formation/ transformations are likely due to the presence of large numbers of amino groups in the CS/PVA substrate. When celluloses possessing only hydroxyl groups are used as a substrate, the direct formation of {001} faceted TiO2 nanocrystal sheets is observed （rather than any sequential crystal transformations）. This substrate organic functional group-induced crystal formation/transformation approach could be applicable to other material systems.A chitosan-polyvinyl alcohol （CS/PVA） co-polymer substrate possessing a large number of amino and hydroxyl groups is used as a substrate to induce the direct growth and in situ sequential transformation of fitanate crystals under HF vapor phase hydrothermal conditions. The process involves four distinct formation/ transformation stages. HTiOF3 crystals with well-defined hexagonal shapes are formed during stage I, and are subsequently transformed into {001} faceted anatase TiO2 crystal nanosheets during stage II. Interestingly, the formed anatase TiO2 crystals are further transformed into cross-shaped and hollow square- shaped HTiOF3 crystals during stages III and IV, respectively. Although TiO2 crystal phases and facet transformations under hydrothermal conditions have been previously reported, in situ crystal transformations between different titanate compounds have not been widely reported. Such crystal formation/ transformations are likely due to the presence of large numbers of amino groups in the CS/PVA substrate. When celluloses possessing only hydroxyl groups are used as a substrate, the direct formation of {001} faceted TiO2 nanocrystal sheets is observed （rather than any sequential crystal transformations）. This substrate organic functional group-induced crystal formation/transformation approach could be applicable to other material systems.

关 键 词：vapor phasehydrothermal synthesis crystal transformation titanate compounds 

分 类 号：TQ325.9[化学工程—合成树脂塑料工业] TB383[一般工业技术—材料科学与工程]