一維ZnO納米材料甲醛光電氣敏性能的研究
發(fā)布時(shí)間：2018-09-18 12:39
【摘要】：氣體傳感器技術(shù)在工業(yè)自動(dòng)化控制過程、汽車排放控制系統(tǒng)以及家庭、公共場(chǎng)所氣體泄漏檢測(cè)中發(fā)揮了重要的作用,特別是基于金屬氧化物半導(dǎo)體熱阻式氣體傳感器在檢測(cè)H2、CO、Volatile Organic Compounds(VOCs)等氣體方面取得了顯著的成果。熱阻式的金屬氧化物半導(dǎo)體氣體傳感主要是利用其暴露在還原或者氧化性氣氛中電阻的變化來檢測(cè)氣體濃度。由于該種類型的氣體傳感器具有較高的靈敏度,并且價(jià)格便宜,被認(rèn)為是很有前景的傳感器。然而,低的選擇性和相對(duì)較高的工作溫度使熱阻式氣體傳感器在使用過程中穩(wěn)定性較差、能耗高,而且不適合在易燃易爆的環(huán)境中使用。更重要的是,由于工作中需要額外消耗能量,使器件的小型化受到限制。因此,發(fā)展能夠在室溫下工作、低能便攜的新型傳感器對(duì)研究人員來說依然是個(gè)嚴(yán)峻的挑戰(zhàn)。近來已經(jīng)被實(shí)驗(yàn)證實(shí)光激發(fā)可以增加半導(dǎo)體材料光生載流子濃度,促進(jìn)半導(dǎo)體材料表面氣體的吸附脫附,因此,對(duì)金屬氧化物半導(dǎo)體材料來說,使用光激發(fā)代替加熱是可以實(shí)現(xiàn)在室溫下對(duì)目標(biāo)氣體檢測(cè)的。而Zn O作為n型寬帶隙、氣體敏感的半導(dǎo)體材料是構(gòu)建光電氣體傳感器的理想材料。但是,目前光電氣體傳感器對(duì)氣體的響應(yīng)度、選擇性能相比于熱阻式氣體傳感器是有一定差距的,這是目前極需要解決的問題,同時(shí),為了提高Zn O材料光電氣體傳感的性能,深入了解在氣體檢測(cè)過程中材料的光物理過程,即光照后,光生載流子的分離、傳輸以及復(fù)合過程是十分必要。本文選用Zn O作為氣敏材料,氣敏響應(yīng)測(cè)試采用的是在室溫下選用紫外光為激發(fā)光源的表面光電流系統(tǒng)。通過貴金屬修飾、金屬離子摻雜的手段改善Zn O氣敏材料的光電性能,借助于表面光電壓技術(shù)(SPV)深入討論了光生電荷對(duì)光電氣敏的微觀的影響�；谝陨蟽�(nèi)容,本文的工作從以下幾個(gè)方面展開:1.采用水熱方法合成了貴金屬Ag修飾的Zn O納米棒光電氣敏材料。TEM測(cè)試證實(shí)Ag單質(zhì)成功沉積在Zn O納米棒表面,光電氣敏測(cè)試的結(jié)果說明一定Ag修飾量的Zn O材料展現(xiàn)出良好的HCHO氣敏性能,對(duì)40 ppm濃度的HCHO響應(yīng)度是純Zn O氣敏材料的5.3倍。Ag修飾在Zn O表面,一方面是由于Ag具有催化作用,可以加速氧氣在Zn O表面的吸附;另一方面Ag作為電子受體能夠捕獲Zn O導(dǎo)帶中的電子,會(huì)使Zn O表面富集更多的氧負(fù)離子基團(tuán),也會(huì)在光照下促進(jìn)光生電子-空穴的分離,我們用表面光電壓技術(shù)論證了這一解釋。但是多的修飾量并不利于材料的光電氣敏性能,可能是由于過多的Ag單質(zhì)會(huì)占據(jù)Zn O表面活性位點(diǎn),不利于氧氣吸附,也會(huì)阻礙材料對(duì)光的吸收,不利于光生電荷分離,因此,表面修飾要有一個(gè)最佳量。2.采用靜電紡絲的方法合成了Ni2+離子摻雜的Zn O納米纖維光電氣敏材料。通過系統(tǒng)地表征證明了Ni2+離子存在于Zn O的晶格中,有Ni-O-Zn鍵的形成。熒光測(cè)試結(jié)果證明適量的Ni2+離子摻雜可以增加氣敏材料的給體缺陷密度,促進(jìn)更多的氧氣分子吸附,有利于表面催化氧化反應(yīng)。表面光電壓和瞬態(tài)光電壓譜圖直觀的表明了適量的Ni2+離子摻雜能有效的促進(jìn)Zn O納米纖維光生電荷的分離和傳輸,抑制其復(fù)合,使更多的光生空穴參與到氣敏反應(yīng)中,提高了材料對(duì)HCHO的光電氣敏響應(yīng)。3.采用靜電紡絲的方法合成了Al3+離子摻雜的Zn O納米纖維光電氣敏材料。一系列的表征證實(shí)了Al3+離子取代Zn2+進(jìn)入到Zn O晶格中。根據(jù)O 1s的XPS測(cè)試結(jié)果,說明Al3+離子摻雜增加了材料的表面氧空位,促使更多的氧氣分子在其表面的吸附。表面光電壓測(cè)試證實(shí)了多的氧負(fù)離子有助于樣品光生電荷的分離以及促進(jìn)更多的光生空穴向表面遷移。氣敏測(cè)試表明Al3+離子摻雜Zn O氣敏材料對(duì)低濃度(1 ppm)HCHO有很好的響應(yīng),其最低檢測(cè)限為0.14 ppb。另外,我們?cè)跉饷魴z測(cè)過程中選用365 nm的UV-LED燈珠為光源,成功的簡(jiǎn)化了光電氣敏測(cè)試系統(tǒng),這將有利于器件的集成化發(fā)展。
[Abstract]:Gas sensor technology plays an important role in industrial automation control process, automotive emission control system and gas leakage detection in households and public places. Especially, metal oxide semiconductor thermal resistance gas sensor has made remarkable achievements in detecting H2, CO, Volatile Organic Compounds (VOCs) and other gases. Thermal resistive metal oxide semiconductor gas sensors are mainly used to detect gas concentration by changing the resistance of the gas exposed to reductive or oxidative atmosphere. Due to their high sensitivity and low cost, these sensors are considered to be promising sensors. However, they have low selectivity and relatively high selectivity. The working temperature makes the thermistor gas sensor unstable, high energy consumption and unsuitable for use in flammable and explosive environments. More importantly, the miniaturization of the device is limited because of the need for additional energy consumption in the work. Therefore, the development of new low-energy and portable sensors that can work at room temperature will be studied. Recently, it has been proved that photoexcitation can increase the concentration of photogenerated carriers in semiconductor materials and promote the adsorption and desorption of gases on the surface of semiconductor materials. As an n-type wide-band gap, gas-sensitive semiconductor material is an ideal material for constructing photoelectric gas sensors. However, the response and selectivity of photoelectric gas sensors to gases are different from those of thermal resistive gas sensors. This is a problem that needs to be solved at present. At the same time, in order to improve the photoelectric properties of Zn O materials. The performance of gas sensing, in-depth understanding of the material in the process of gas detection photophysical process, that is, after illumination, photogenerated carrier separation, transmission and recombination process is very necessary. Noble metal modification and metal ion doping are used to improve the photoelectric properties of Zn O gas sensing materials. The micro-effects of photoinduced charges on the photoelectric properties of Zn O gas sensing materials are discussed by means of surface photovoltaic technique (SPV). TEM test confirmed that Ag was successfully deposited on the surface of Zn O nanorods. The results showed that Zn O with a certain amount of Ag modified exhibited good HCHO gas sensing properties. The HCHO responsiveness to 40 ppm concentration was 5.3 times higher than that of pure Zn O. Ag modified on the surface of Zn O was due to the catalysis of Ag. On the other hand, Ag as an electron acceptor can capture electrons in the conduction band of Zn O, enrich more oxygen anion groups on the surface of Zn O, and promote the separation of photogenerated electrons and holes under light. We have demonstrated this explanation by surface photovoltaic technique. However, the amount of modification is not favorable. It may be that too much Ag will occupy the active sites on the surface of Zn O, which is not conducive to oxygen adsorption, but also hinder the absorption of light and the separation of photogenerated charges. Therefore, the surface modification should have an optimum amount. 2. Ni2+ doped Zn O nanofibers were synthesized by electrospinning. Gas sensitive materials. It is proved by systematic characterization that Ni2+ ions exist in the lattice of Zn O and form Ni-O-Zn bonds. Fluorescence measurements show that appropriate doping of Ni2+ ions can increase the density of donor defects, promote more oxygen molecules adsorption and facilitate surface catalytic oxidation. Surface photovoltage and transient photovoltage The spectra show that the appropriate amount of Ni2+ ion doping can effectively promote the separation and transmission of photogenerated charge of Zn O nanofibers, inhibit their recombination, make more photogenerated holes participate in the gas-sensitive reaction, and improve the material's photoelectric response to HCHO. 3. Al3+ ion doped Zn O nanofibers were synthesized by electrospinning method. Electrical sensitive materials. A series of characterizations confirm that Al 3+ ions replace Zn 2+ into the Zn O lattice. According to the XPS results of O 1s, it is shown that Al 3+ ion doping increases the surface oxygen vacancy of the material and promotes the adsorption of more oxygen molecules on its surface. Gas sensing tests show that Al 3+ doped Zn O gas sensing materials have a good response to low concentration (1 ppm) HCHO, and the minimum detection limit is 0.14 ppb. In addition, we choose 365 nm UV-LED beads as the light source in the gas sensing process, which simplifies the photoelectric gas sensing testing system successfully. It will facilitate the integrated development of devices.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：O614.241;TP212
本文編號(hào)：2247957
[Abstract]:Gas sensor technology plays an important role in industrial automation control process, automotive emission control system and gas leakage detection in households and public places. Especially, metal oxide semiconductor thermal resistance gas sensor has made remarkable achievements in detecting H2, CO, Volatile Organic Compounds (VOCs) and other gases. Thermal resistive metal oxide semiconductor gas sensors are mainly used to detect gas concentration by changing the resistance of the gas exposed to reductive or oxidative atmosphere. Due to their high sensitivity and low cost, these sensors are considered to be promising sensors. However, they have low selectivity and relatively high selectivity. The working temperature makes the thermistor gas sensor unstable, high energy consumption and unsuitable for use in flammable and explosive environments. More importantly, the miniaturization of the device is limited because of the need for additional energy consumption in the work. Therefore, the development of new low-energy and portable sensors that can work at room temperature will be studied. Recently, it has been proved that photoexcitation can increase the concentration of photogenerated carriers in semiconductor materials and promote the adsorption and desorption of gases on the surface of semiconductor materials. As an n-type wide-band gap, gas-sensitive semiconductor material is an ideal material for constructing photoelectric gas sensors. However, the response and selectivity of photoelectric gas sensors to gases are different from those of thermal resistive gas sensors. This is a problem that needs to be solved at present. At the same time, in order to improve the photoelectric properties of Zn O materials. The performance of gas sensing, in-depth understanding of the material in the process of gas detection photophysical process, that is, after illumination, photogenerated carrier separation, transmission and recombination process is very necessary. Noble metal modification and metal ion doping are used to improve the photoelectric properties of Zn O gas sensing materials. The micro-effects of photoinduced charges on the photoelectric properties of Zn O gas sensing materials are discussed by means of surface photovoltaic technique (SPV). TEM test confirmed that Ag was successfully deposited on the surface of Zn O nanorods. The results showed that Zn O with a certain amount of Ag modified exhibited good HCHO gas sensing properties. The HCHO responsiveness to 40 ppm concentration was 5.3 times higher than that of pure Zn O. Ag modified on the surface of Zn O was due to the catalysis of Ag. On the other hand, Ag as an electron acceptor can capture electrons in the conduction band of Zn O, enrich more oxygen anion groups on the surface of Zn O, and promote the separation of photogenerated electrons and holes under light. We have demonstrated this explanation by surface photovoltaic technique. However, the amount of modification is not favorable. It may be that too much Ag will occupy the active sites on the surface of Zn O, which is not conducive to oxygen adsorption, but also hinder the absorption of light and the separation of photogenerated charges. Therefore, the surface modification should have an optimum amount. 2. Ni2+ doped Zn O nanofibers were synthesized by electrospinning. Gas sensitive materials. It is proved by systematic characterization that Ni2+ ions exist in the lattice of Zn O and form Ni-O-Zn bonds. Fluorescence measurements show that appropriate doping of Ni2+ ions can increase the density of donor defects, promote more oxygen molecules adsorption and facilitate surface catalytic oxidation. Surface photovoltage and transient photovoltage The spectra show that the appropriate amount of Ni2+ ion doping can effectively promote the separation and transmission of photogenerated charge of Zn O nanofibers, inhibit their recombination, make more photogenerated holes participate in the gas-sensitive reaction, and improve the material's photoelectric response to HCHO. 3. Al3+ ion doped Zn O nanofibers were synthesized by electrospinning method. Electrical sensitive materials. A series of characterizations confirm that Al 3+ ions replace Zn 2+ into the Zn O lattice. According to the XPS results of O 1s, it is shown that Al 3+ ion doping increases the surface oxygen vacancy of the material and promotes the adsorption of more oxygen molecules on its surface. Gas sensing tests show that Al 3+ doped Zn O gas sensing materials have a good response to low concentration (1 ppm) HCHO, and the minimum detection limit is 0.14 ppb. In addition, we choose 365 nm UV-LED beads as the light source in the gas sensing process, which simplifies the photoelectric gas sensing testing system successfully. It will facilitate the integrated development of devices.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：O614.241;TP212
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