n-p异质型空心微纳结构的构筑与气敏特性优化

This project is aimed at employing solution chemistry to design and fabricate novel, thermally-stable n-p composite hollow micro/nano-heterostructures, in an attempt to solve the problems such as deactivation at high temperature and poor selectivity. N-type semiconductor metal oxide SnO2 hollow micro/nanostructures (or TiO2/WO3) will be utilized as a host to support or decorate p-type semiconductor metal oxide Co3O4 (or NiO/Cr2O3) as a guest to form a series of n-p composite micro/nano-heterostructures. The hollow structure will reduce the contact between nanoparticles, thus retarding the aggregation and growth of nanoparticles. Through optimal selection and assembly of the host/guest materials to study the growth mechanism of n-p heterostructures; the synergic effect between the two components will be investigated, aiming at improving the sensor selectivity to particular gases. The content ratio, dimension, distribution of p-type guest on n-type host will be subject to systematic study to examine their influence on the sensor sensitivity, operating temperature, and stability. Particular attention will be focused on finding out the function rules behind the superior sensing performances of the n-p micro/nano-heterostructures. It is expected that this project will deliver several useful perspectives including the establishment of a successful methodology and synthesis route to composite micro/nano-heterostructure materials, exploring the Structure-Property relationship between hollow micro/nanostructures and gas sensing performance and revealing the sensing mechanism of the n-p heterostructures. The outcome of this project, including both experimental and theoretical innovation, will contribute to the development of fundamental study in both composite material chemistry and gas sensing materials.

本项目旨在利用液相法设计合成一种新颖的具有良好热稳定性的n-p异质型金属氧化物空心微纳结构，针对目前半导体气敏材料的高温失活和选择性不佳等科学问题进行探索和给出解决方案。主要以n型半导体金属氧化物SnO2为主体，通过设计空心结构降低纳米粒子间的接触，阻止其高温条件下聚集长大，从而提高气敏材料的热稳定性；在其表面组装或修饰p型金属氧化物Co3O4客体（还将尝试n型TiO2/WO3/和p型NiO/Cr2O3），制备一系列n-p异质型复合气敏材料，探索n-p异质结构的生长机制；通过合理搭配主客体，提高气敏材料针对特定气体的选择性；系统研究n-p异质复合材料中p型客体的含量、分布状态、维度等对气体传感器的灵敏度、操作温度、选择性和稳定性等参数的影响，明确n-p异质结构对气敏特性的增强效用，获得调控n-p异质结构气敏性能的规律。本项目的研究结果将促进复合材料化学和气敏材料研究的实验和理论创新。

半导体气体传感器在有害气体快速检测和环境保护等方面拥有广泛的应用前景。本项目从材料结构的角度出发，利用液相化学和气相化学为制备手段，研制了一些列具有高灵敏度和高选择性的气敏材料。（1）p-n异质结构。在W18O49空心球表面生长p 型Co3O4，构筑 p-n异质结，同时负载Au纳米粒子，利用Au的催化溢流效应来进一步增强气敏性能，对2ppm三乙胺响应值达到16.7，同时灵敏度达到0.87ppm-1，最低检测限为81ppb。此外，制备了SnO2/Co3O4异质纳米球，主体为n型SnO2，富有大量的晶界活性位，客体为p型Co3O4，能够促进表面氧负离子的吸附。纳米球表面具有大量p-n异质结，调控界面的电子输运，促进电子空间耗尽层的形成，对丙酮具有较高的响应和优良的选择性，检测限低至103ppb。（2）n-n异质结构。利用水热法制备n-n型Fe2O3/W18O49异质空心球。系统考察了Fe2O3含量对于气敏性能的影响，发现含量为6.3 wt%的Fe2O3/W18O49对丙酮具有最高灵敏度，检测限低至86 ppb。（3）贵金属负载型气敏材料。利用原子层沉积技术在W18O49空心球表面生长0.2-1 nm的Pt纳米粒子。由于Pt粒子的催化性能，相对于W18O49 (200 oC)，Pt/W18O49空心球具有更低的工作温度，为180 oC。Pt/W18O49空心球的检测灵敏度得到了显著提升，对20 ppm丙酮的响应值为85，而W18O49为2.12，提高了40倍；Pt/W18O49的检测限为52 ppb，远远低于W18O49的252 ppb。提出了氧化还原反应策略，利用W18O49中低价态W离子的弱还原性同贵金属盐发生氧化还原反应，将贵金属还原到材料表面从而形成异质结构，实现两种贵金属（Ag和Pt）同时负载，研究了双重增敏机制对于气敏性能的促进作用。对2ppm的三乙胺响应值达到20.28，同时灵敏度达到1.13ppm-1，最低检测限为71ppb。本项目的研究结果为制备气敏材料和研制高性能气体传感器及VOCs气体检测应用提供了实验借鉴。本项目正式发表SCI论文10篇；申请发明专利3项，授权1项；参与撰写英文专著一个章节；参加国内外学术会议6次，做邀请报告3次，口头报告3次；2017年5月，作为召集人举办了国内首届气湿敏青年学术论坛，增强了国内传感器领域青年学者之间的交流与合作。