基于硅烷聚合物原位还原及Sol-gel化学调控合成纳米银贯穿功能材料

Compared with that of usual glasses and ceramics,the sol-gel science and technology is a young and new field for preparation of materials. However, controllable fabrication of high-performance functional materials is the frontier of the sol-gel science and technology. It was demonstrated from our previous studies that various organic-inorganic hybrid composites with tailored functionalities and textural characteristics could be facilely prepared using an PMHS-assisted sol-gel pathway, in which commercially available and inexpensive polymeric PMHS molecules simultaneously behaved as structure-tailoring agent and skeleton precursor by virtue of the task-specific Si-H bonds and non-active -CH3 groups,along with other traditional organosilica precursors. On a natural continuation of the previous work,this project is concerned with the exploration of a novel sol-gel synthesis pathway toward nanosilver embedded porous hybrid materials with homogeneous dispersion and narrow size distribution using polymethylhydrosiloxane (PMHS),tetraethoxysilane (TEOS) and 3-mercapto- propyltrimethoxysilane (MPTMS)as co-precursors and AgNO3 as resource of Ag+ ions,without using any extra reducing agent.It is inferred that several parallel reactions as that complexation of Ag+ for MPTMS and release of H+,in-situ reduction of Ag+ into Ag0 and accordingly transformation of Si-H into Si-OH for PMHS molecules and stabilization of newly formed Ag nanoparticles (AgNPs) by MPTMS are ongoing along with the sol-gel reaction of the whole system, which has never been found in reported literatures.The emphasis is on the investigation of the factors affecting the size distribution and dispersion of AgNPs and textrual properties of resultant hybrid composites empolying detailed characterization techniques as UV-vis,TEM,XRD,DLS,N2 physisorption,FT-IR,XPS,NMR, SAXS,EDS, etc.,and it is thus expected to outline the plausible synthesis mechanism behind the proposed sol-gel pathway and the optimum preparation parameters towards hybrid materials with tailored structural features and catalytic performance.In this respect, the as-prepared AgNPs embedded hybrid materials will be accordingly used as solid phase catalysts for the reduction of 4-nitrophenol (4-NP) in the presence of sodium borohydride; and the reduction of other nitrophenols such as 2-nitrophenol (2-NP) and 3-nitrophenol (3-NP) would be also tested using the materials as catalysts,to investigate the combined effects of tailored interface propreties and size-dependence and stability of AgNPs of hybrid materials under aqueous conditions. .In summary,this sol-gel synthesis method is specific,sensitive and generally applicable to other metals or alloys embedded hybrid materials,and hence the detailed mechanism warrants to be fully explored.

利用"化学裁剪"调控合成功能材料是sol-gel研究领域的前沿课题；含氢硅烷聚合物(PMHS)因分子结构及反应活性可设计化及柔软分子链构型可调的特点，在sol-gel化学路线合成功能材料中显示出独特的应用特性。基于前期研究，本申请提出PMHS原位还原及sol-gel化学相结合以调控合成功能材料的构想；即通过室温sol-gel体系中PMHS原位还原Ag+离子、调变自身基团反应参与能力并协同正硅酸乙酯(TEOS)和3-巯丙基三甲氧基硅(MPTMS)组装纳米银贯穿功能材料并研究其形成过程机制。系统考察sol-gel化学体系中组分含量对功能材料结构性能、网络骨架组成和纳米银颗粒尺寸、分布与稳定性的影响，以及Ag+与-SH耦合释放H+对硅物种水解程度、PMHS含氢量对Ag+还原速率的影响规律；以合成材料对对硝基苯酚的催化还原反应为探针，建立纳米银尺寸/分布、稳定性及界面特性与催化性能间的关联规律。

利用线型有机硅聚合物PMHS富含活泼硅氢键的组成结构特点，本项目申请提出了一种调控合成纳米银镶嵌有机-无机杂化材料的研究路线，结合结构性能测试和硝基苯酚液相还原反应并尝试建立线型PMHS聚合物在组装过程中的调控作用机制。. 基于项目研究内容和目标，项目执行期间系统考察了溶胶-凝胶合成过程中PMHS用量对纳米银颗粒尺寸、分布状态及材料结构性能的影响规律，借助TEM、SEM、N2-吸附-脱附等温线、DRS UV-vis和FT-IR等手段跟踪研究了相应过程变化；同时利用液相对硝基苯酚还原反应确立了纳米银尺寸及分布和材料结构性能。. 基于项目研究目标及要解决的科学问题，项目研究期间共发表研究论文5篇，较好完成了项目预期成果。