Study Of Chemistry Sensors About Dealing With The Attack Of Chemicals And Microbe

Nowadays,terrorism,political corruption and environmental pollution are considered as the three biggest questions which threaten the human safety.The international terrorism has become the social effects of pollution on the international peace and development.In the past few years,horrific things happened in succession,for example,the 11 September attacked on the United States,the anthrax things happened in the United States at the same year.The terrorists used the sarin to poison the people in the Japanese.The governments of the world think it important to defend and beat the terrorist.They think that exploration and elimination of the explosives and poisons should be the important content.We should adopt the effective technology which can recognize and check up the explosives and poisons before the terrorists harm the people.Traditional examining technical equipment on poisons and explosives have some disadvantage.The price is dearly,the sensitivity is low and the volume is bulky.So we should develop the technology that they have the high sensitivity ,small volume,low cost,and they had better be used in the locale.The dissertation uses the luminescent bacteria and the nano oxide as the sense organ to recognize and check up the poisons and explosives .The following is the work in this dissertation.Chapter one: Critical reviewsA critical review of present development in related fields was presented in this pait:microbial sensors ,the luminescent bacteria used on the examination of poisons,the study of sensors dealing with the attack on the chemistry and biology.Chapter two: Study of the microbiosensors(luminescent bacteria) about dealing with the attack of Chemicals and Microbe.In this chapter,a microbiosensor was set up by the utilization of Vibrio— Qinghaiensis, which can produce bioluminescence. Toxic chemicals such as tetramine and cyanide will effect the viability of Vibrio-Qinghaiensis, which can supress the bioluminescence and decrease the current. This biosensor can response quickly to the attack of chemicals and microbial with the advantage of high sensitivity, simplicity and convenience.Chapter three: study of the MAA-CdS-TiO₂ self assemblied membrane and its application in the detection of nitro-compoundThe MAA-CdS-TiO₂ modified electrode was prepared in this chapter. The ITO electrode was immersed into the sol-gel of TiO₂ and then the quantum dots of CdS were formed on the film of TiO₂. The ITO/TiO₂/CdS modified electrode showed high sensitivity for the detection of 2,4,6-trinitrotoluene (TNT), which can be detected according to the potential changes under the current of 6mA. The potential responds of the sensor were linearly to the concentration of the TNT from 15ppb to 1500ppb with the detection limit of 7ppb. The results showed that the ITO/TiO₂/CdS modified electrode open news ways for fast, simple and sensitive analysis of TNT.Chapter four: Study of CdS/TiO₂/ITO composite photocatalysis gas sensor and its application in the detection of trinitro-toluene.The CdS/TiO₂/ITO composite film modified electrode was prepared in this chapter by the methods of sol-gel and monolayer self assembly respectively. A large amount of holes in valence bond (h_VB⁺) and hydroxyl radicals were produced in the presence of UV illumination. Under the potential of +50mV, TNT can be oxidized by the holes and hydroxyl radicals. The photocatalysis responds to different concentrations of TNT vapor were in the linear range of 1.8μg/L— 140μg/L with the detection limit of 0.9μg/L (S/N=3). The photocatalysis mechanism of the CdS/TiO₂gas sensor and its electrochemical characteristics were also investigated in this chapter. The response of the sensor was linearly to the concentration of the TNT from 18μg/L to 720μg/L with the detection limit of 0.9μg/L(S/N) =3. The CdS/TiO₂ gas sensor has the advantages of easy preparation, high sensitivity, simple and rapid to perform and so on. This proposed method will also be applied to determine TNT vapor in site.