【摘要】：易揮發(fā)有機(jī)化合物(Volatile organic compounds,VOCs)作為空氣污染的重要成分,不僅會(huì)對(duì)人體產(chǎn)生危害,而且是疾病甚至是癌癥的誘因。然而,目前,用來(lái)檢測(cè)VOCs氣體的傳統(tǒng)化學(xué)傳感器穩(wěn)定性差、可持續(xù)性短。本文研究的金屬氧化物半導(dǎo)體(TiO2)因其環(huán)境友好、選擇性良好、可靠穩(wěn)定和響應(yīng)快等優(yōu)點(diǎn)獲得廣泛的關(guān)注。但是,在實(shí)際運(yùn)用中卻受到其低量子效應(yīng)和寬禁帶寬度的限制,使其具有高的光生電子空穴復(fù)合率以及無(wú)法吸收可見(jiàn)光的缺陷。為了延長(zhǎng)TiO2中光生電子空穴對(duì)的壽命和窄化其禁帶寬度,提高材料及相關(guān)器件的響應(yīng),本文利用石墨烯基材料與TiO2的協(xié)同作用和紫外光激發(fā)傳感材料,使傳感材料表面產(chǎn)生光生電子-空穴對(duì),增加載流子濃度,有效地提高TiO2基傳感器的響應(yīng)。我們的主要工作分為以下部分:(1)利用溶膠-凝膠法制得Pt/GQDs-TiO2溶膠溶液以及Pt/GQDs-TiO2介孔復(fù)合薄膜。(2)對(duì)制得Pt/GQDs-TiO2介孔復(fù)合薄膜進(jìn)行處理和表征。主要從后蒸處理和焙燒兩個(gè)方面進(jìn)行研究。其中,后蒸處理研究中,考慮了分溫度和時(shí)間的改變;研究焙燒是,主要考慮了溫度的改變。材料的表征研究主要包括利用紫外-可見(jiàn)分光光度計(jì)(UV-vis)分析、熒光光譜(PL)分析、X射線衍射儀(XRD)、透射電子顯微鏡(TEM)以及原子力顯微鏡(AFM)對(duì)焙燒之后的樣品進(jìn)行結(jié)構(gòu)和形貌的表征。表征結(jié)果表明:GQDs被成功地均勻地?fù)饺虢榭讖?fù)合材料;該介孔復(fù)合材料的晶粒平均尺寸約為10 nm,介孔TiO2晶相為銳鈦礦;同時(shí)可以清晰地看到TiO2晶粒良好的結(jié)晶度以及有序的孔道。(3)將獲得的Pt/GQDs-TiO2介孔復(fù)合材料薄膜制備成傳感器,并在室溫下研究紫外光照射下對(duì)多種VOCs氣體的傳感性能增強(qiáng),主要包括(ⅰ)考慮檢測(cè)氣體不變,對(duì)傳感器進(jìn)行周期性和穩(wěn)定性的研究;(ⅱ)利用傳感器對(duì)不同濃度的多種VOCs進(jìn)行檢測(cè)。實(shí)驗(yàn)結(jié)果表明紫外輻照對(duì)增強(qiáng)介孔復(fù)合材料傳感器的檢測(cè)性能有巨大的提高,特別是在對(duì)苯的檢測(cè)中,如果無(wú)紫外光照射,傳感器對(duì)濃度為25 ppM苯幾乎沒(méi)有電阻響應(yīng);在有紫外輻照時(shí),同樣的薄膜傳感器對(duì)濃度為25 ppm苯展現(xiàn)出了良好的電阻響應(yīng),響應(yīng)和回復(fù)時(shí)間分別為8s和23s。綜合對(duì)多種VOCs氣體(乙醚、苯和乙醇等)的檢測(cè)分析,我們發(fā)現(xiàn)紫外輻照對(duì)整個(gè)傳感系統(tǒng)的電阻響應(yīng)都有了較大的增強(qiáng)效應(yīng)。此外,當(dāng)紫外光照射原本對(duì)VOCs沒(méi)有電阻響應(yīng)的n型未焙燒的Pt/GQDs-TiO2介孔復(fù)合材料時(shí),Pt/GQDs-TiO2介孔復(fù)合材料不僅由n型半導(dǎo)體轉(zhuǎn)換成了 p型半導(dǎo)體,而且還對(duì)乙醚展現(xiàn)出了良好的電阻響應(yīng)以及選擇性。此時(shí),Pt/GQDs-TiO2介孔復(fù)合材料對(duì)25ppm的苯有電阻響應(yīng),響應(yīng)時(shí)間和回復(fù)時(shí)間分別為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.
【學(xué)位授予單位】：南京信息工程大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：O484

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