量子点掺杂介孔氧化钛薄膜的制备及其光增强传感研究
发布时间：2019-03-05 09:36
【摘要】：易挥发有机化合物(Volatile organic compounds,VOCs)作为空气污染的重要成分,不仅会对人体产生危害,而且是疾病甚至是癌症的诱因。然而,目前,用来检测VOCs气体的传统化学传感器稳定性差、可持续性短。本文研究的金属氧化物半导体(TiO2)因其环境友好、选择性良好、可靠稳定和响应快等优点获得广泛的关注。但是,在实际运用中却受到其低量子效应和宽禁带宽度的限制,使其具有高的光生电子空穴复合率以及无法吸收可见光的缺陷。为了延长TiO2中光生电子空穴对的寿命和窄化其禁带宽度,提高材料及相关器件的响应,本文利用石墨烯基材料与TiO2的协同作用和紫外光激发传感材料,使传感材料表面产生光生电子-空穴对,增加载流子浓度,有效地提高TiO2基传感器的响应。我们的主要工作分为以下部分:(1)利用溶胶-凝胶法制得Pt/GQDs-TiO2溶胶溶液以及Pt/GQDs-TiO2介孔复合薄膜。(2)对制得Pt/GQDs-TiO2介孔复合薄膜进行处理和表征。主要从后蒸处理和焙烧两个方面进行研究。其中,后蒸处理研究中,考虑了分温度和时间的改变;研究焙烧是,主要考虑了温度的改变。材料的表征研究主要包括利用紫外-可见分光光度计(UV-vis)分析、荧光光谱(PL)分析、X射线衍射仪(XRD)、透射电子显微镜(TEM)以及原子力显微镜(AFM)对焙烧之后的样品进行结构和形貌的表征。表征结果表明:GQDs被成功地均匀地掺入介孔复合材料;该介孔复合材料的晶粒平均尺寸约为10 nm,介孔TiO2晶相为锐钛矿;同时可以清晰地看到TiO2晶粒良好的结晶度以及有序的孔道。(3)将获得的Pt/GQDs-TiO2介孔复合材料薄膜制备成传感器,并在室温下研究紫外光照射下对多种VOCs气体的传感性能增强,主要包括(ⅰ)考虑检测气体不变,对传感器进行周期性和稳定性的研究;(ⅱ)利用传感器对不同浓度的多种VOCs进行检测。实验结果表明紫外辐照对增强介孔复合材料传感器的检测性能有巨大的提高,特别是在对苯的检测中,如果无紫外光照射,传感器对浓度为25 ppM苯几乎没有电阻响应;在有紫外辐照时,同样的薄膜传感器对浓度为25 ppm苯展现出了良好的电阻响应,响应和回复时间分别为8s和23s。综合对多种VOCs气体(乙醚、苯和乙醇等)的检测分析,我们发现紫外辐照对整个传感系统的电阻响应都有了较大的增强效应。此外,当紫外光照射原本对VOCs没有电阻响应的n型未焙烧的Pt/GQDs-TiO2介孔复合材料时,Pt/GQDs-TiO2介孔复合材料不仅由n型半导体转换成了 p型半导体,而且还对乙醚展现出了良好的电阻响应以及选择性。此时,Pt/GQDs-TiO2介孔复合材料对25ppm的苯有电阻响应,响应时间和回复时间分别为11 s和9 s。
[Abstract]:Volatile organic compound (Volatile organic compounds,VOCs (volatile organic compound), as an important component of air pollution, is not only harmful to human body, but also an inducement of disease and even cancer. However, at present, the traditional chemical sensors used to detect VOCs gas have poor stability and short sustainability. Metal oxide semiconductors (TiO2) have attracted much attention due to their friendly environment, good selectivity, reliability, stability and fast response. However, it is limited by its low quantum effect and wide bandgap width in practical application, which makes it have high photogenerated electron hole recombination ratio and the defect of unable to absorb visible light. In order to prolong the lifetime and narrow the band gap of photogenerated electron hole pairs in TiO2, and to improve the response of materials and related devices, the synergetic effect of graphene-based materials with TiO2 and UV-excited sensing materials were used in this paper. The photogenerated electron-hole pairs are produced on the surface of the sensing materials, the carrier concentration is increased, and the response of the TiO2-based sensors is improved effectively. Our main work is as follows: (1) Pt/GQDs-TiO2 sol solution and Pt/GQDs-TiO2 mesoporous composite thin films were prepared by sol-gel method. (2) Pt/GQDs-TiO2 mesoporous composite films were prepared by treatment and characterization. The study was mainly carried out from two aspects: post-steaming treatment and roasting. The change of temperature and time is taken into account in the study of post-steaming, and the change of temperature is mainly considered in the study of roasting. The characterization of the materials mainly includes ultraviolet-visible spectrophotometer (UV-vis) analysis, fluorescence spectrum (PL) analysis, X-ray diffractometer (XRD),. The structure and morphology of the calcined samples were characterized by transmission electron microscope (TEM) and atomic force microscope (AFM). The results showed that GQDs was successfully and uniformly doped into the mesoporous composites, the average grain size of the mesoporous composites was about 10 nm, and the mesoporous TiO2 phase was anatase. At the same time, we can clearly see the good crystallinity of TiO2 grains and the ordered pore channels. (3) the Pt/GQDs-TiO2 mesoporous composite films were fabricated as sensors. The enhancement of sensing performance of various VOCs gases under UV irradiation is studied at room temperature, including (I) the periodic and stable study of the sensors considering the invariance of the detected gases; (II) using sensors to detect a variety of VOCs in different concentrations. The experimental results show that the detection performance of the enhanced mesoporous composite sensor is greatly improved by ultraviolet irradiation, especially in the detection of benzene, without UV irradiation, the sensor has almost no resistance response to the concentration of 25 ppM benzene. Under UV irradiation, the same thin film sensor showed a good resistance response to the concentration of 25 ppm benzene. The response and recovery time were 8s and 23s, respectively. Based on the analysis of various VOCs gases (ether, benzene and ethanol, etc.), it is found that the resistance response of the whole sensing system is greatly enhanced by ultraviolet irradiation. In addition, when ultraviolet light irradiates the n-type unbaked Pt/GQDs-TiO2 mesoporous composites which have no response to VOCs, the Pt/GQDs-TiO2 mesoporous composites are not only converted from n-type semiconductors to p-type semiconductors. It also shows good resistance response and selectivity to ether. At this time, the Pt/GQDs-TiO2 mesoporous composites have resistance response to benzene of 25ppm, the response time and recovery time are 11 s and 9 s, respectively.
【学位授予单位】：南京信息工程大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O484
本文编号：2434768
[Abstract]:Volatile organic compound (Volatile organic compounds,VOCs (volatile organic compound), as an important component of air pollution, is not only harmful to human body, but also an inducement of disease and even cancer. However, at present, the traditional chemical sensors used to detect VOCs gas have poor stability and short sustainability. Metal oxide semiconductors (TiO2) have attracted much attention due to their friendly environment, good selectivity, reliability, stability and fast response. However, it is limited by its low quantum effect and wide bandgap width in practical application, which makes it have high photogenerated electron hole recombination ratio and the defect of unable to absorb visible light. In order to prolong the lifetime and narrow the band gap of photogenerated electron hole pairs in TiO2, and to improve the response of materials and related devices, the synergetic effect of graphene-based materials with TiO2 and UV-excited sensing materials were used in this paper. The photogenerated electron-hole pairs are produced on the surface of the sensing materials, the carrier concentration is increased, and the response of the TiO2-based sensors is improved effectively. Our main work is as follows: (1) Pt/GQDs-TiO2 sol solution and Pt/GQDs-TiO2 mesoporous composite thin films were prepared by sol-gel method. (2) Pt/GQDs-TiO2 mesoporous composite films were prepared by treatment and characterization. The study was mainly carried out from two aspects: post-steaming treatment and roasting. The change of temperature and time is taken into account in the study of post-steaming, and the change of temperature is mainly considered in the study of roasting. The characterization of the materials mainly includes ultraviolet-visible spectrophotometer (UV-vis) analysis, fluorescence spectrum (PL) analysis, X-ray diffractometer (XRD),. The structure and morphology of the calcined samples were characterized by transmission electron microscope (TEM) and atomic force microscope (AFM). The results showed that GQDs was successfully and uniformly doped into the mesoporous composites, the average grain size of the mesoporous composites was about 10 nm, and the mesoporous TiO2 phase was anatase. At the same time, we can clearly see the good crystallinity of TiO2 grains and the ordered pore channels. (3) the Pt/GQDs-TiO2 mesoporous composite films were fabricated as sensors. The enhancement of sensing performance of various VOCs gases under UV irradiation is studied at room temperature, including (I) the periodic and stable study of the sensors considering the invariance of the detected gases; (II) using sensors to detect a variety of VOCs in different concentrations. The experimental results show that the detection performance of the enhanced mesoporous composite sensor is greatly improved by ultraviolet irradiation, especially in the detection of benzene, without UV irradiation, the sensor has almost no resistance response to the concentration of 25 ppM benzene. Under UV irradiation, the same thin film sensor showed a good resistance response to the concentration of 25 ppm benzene. The response and recovery time were 8s and 23s, respectively. Based on the analysis of various VOCs gases (ether, benzene and ethanol, etc.), it is found that the resistance response of the whole sensing system is greatly enhanced by ultraviolet irradiation. In addition, when ultraviolet light irradiates the n-type unbaked Pt/GQDs-TiO2 mesoporous composites which have no response to VOCs, the Pt/GQDs-TiO2 mesoporous composites are not only converted from n-type semiconductors to p-type semiconductors. It also shows good resistance response and selectivity to ether. At this time, the Pt/GQDs-TiO2 mesoporous composites have resistance response to benzene of 25ppm, the response time and recovery time are 11 s and 9 s, respectively.
【学位授予单位】：南京信息工程大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O484
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