| An organophosphate is the general name for esters of phosphoric acid.Organophosphate compounds (OPs) are the most widely used group of insecticides andpotent nerve agents, due to the ability of these compounds to inhibitacetylcholinesterase at cholinergic junctions of the nervous system. Therefore, it isdefinitely need to develop new devices for organophosphate compounds detection. Agreat deal of attention has been paid to chemical sensors recently, for effectiveminiaturized low cost smart gas analytical chemical systems that can be utilized for OPsmonitoring. And these chemical sensors become sensitive and selective gas detectorswhen coated with suitable sensitive materials. Accordingly, a great variety of coatingsensitive polymer materials and architectures have been developed for the application ofdetecting chemical vapors or Ops detection.Among those coating sensitive materials, the linear siloxane polymers, conductivepolymers and small molecules sensitive materials have been paid much more attentionsin this dissertation. In this study, a series of sensitive materials for organophosphatecompounds detection were prepared. These sensitive materials were characterized, andcoated onto the AT-cut8MHz QCM sensor to investigate their gas sensitive propertiesto the organophosphorus nerve agent stimulant dimethyl methylphosphonate (DMMP)vapor. And the main research results were as follows.1. A series of new fluorinated phenolic functional groups functionalized linearsiloxane polymer for quartz crystal microbalance sensor (QCMs) application weresynthesized with phenol and its derivatives, via O-alkylation, Claisen rearrange,hydrosilylation and hexafluoroacetone groups (HFA) electrophilic addition reactions.These siloxane polymers include poly{methyl[3-(2-hydroxy)phenyl]propylsiloxane},poly{methyl[3-(2-hydroxy-4-trifluoromethyl)phenyl]propylsiloxane}, poly{methyl[3-(2-hydroxy-4,6-bistrifluoromethyl)phenyl]propylsiloxane}, poly{methyl[3-(2-hydroxy-5-hexafluoroisopropanol)phenyl]propylsiloxane}, and poly{methyl[3-(2-hydroxy-5-triflu-oroisopropanol)phenyl]propylsiloxane}. They were characterized, and coated onto theAT-cut8MHz QCM sensor to investigate their gas sensitive properties to DMMP. The results indicated that these new siloxane polymers exhibited excellent performance onthe detection of dimethyl methylphosphonate (DMMP) vapor, and the frequencychanges of these functionalized siloxane polymer based QCM sensors to the DMMPvapor were completely linear in the concentration range of10-50ppm, and theyexhibited fairly fast response, negligible baseline drift and excellent reversibility andselectivity for DMMP vapor. Especially, the sensitivity of bistrifluoromethyl-substitutedphenol groups functionalized siloxane polymer to DMMP was up to27.01Hz/ppm, andit is much higher than that of the other sensitive materials under the same circumstances,the detection limits (LODs) of the QCM sensor was obtained as low as0.11ppm.2. A series of hydroxyl-group functionalized thiophene polymers were preparedwith thiophene and derivatives, via oxidizing polymerization process, these thiophenepolymers were poly(3,4-dihydroxythiophene) and poly(3,4-diethoxylthiophene). Thenthe thiophene polymers were characterized, and coated onto the AT-cut8MHz QCMsensor to investigate their gas sensitive properties to DMMP. The results indicated thatboth thiophene polymers based QCM sensors to DMMP vapor were completely linearin the concentration range of10-50ppm, and they exhibited fairly fast response, whilewith poor performance on the frequency changes of DMMP. The selectivity of thesensors was tested in several organic vapors and good selectivity to DMMP wasconfirmed. Furthermore, these thiophene polymers were also spinned on the interdigitaltransducer to test the gas sensitive properties. The result showed that the polymers havegood conductivity, and the conductivity was affected by adsorbing the DMMP vapors.3. Polyaniline, poly(o-aminophenol) and the copolymer of aniline ando-aminophenol, were synthesized from o-aminophenol and aniline, through electro-chemical polymerization by cyclic voltammetry. The cyclic-voltammogram presentedthat copolymer of o-aminophenol and aniline was obtained through electrochemicalpolymerization, and the conductivity of these aniline polymers was pretty good.Additionally, these aniline polymers were also coated onto the AT-cut8MHz QCMsensor to investigate their gas sensitive properties to DMMP, and the sensitivities ofthem to DMMP were compared in the related part.4. A group of hexafluoroisopropanol groups functionalized small moleculeorganosilicon compounds were synthesized from benzene, naphthalene and its derivatives, via hydrosilylation and hexafluoroacetone groups (HFA) electrophilicaddition reactions. They were hexafluoroisopropanol groups functionalizedphenpropyl-naphthylsilane, hexafluoroisopropanol groups functionalized tetraphenyl-silicane, hexafluoroisopropanol groups functionalized hexaphenylcyclotrisiloxane andhexafluoroisopropanol groups functionalized octaphenylcyclotetrasiloxane. Then theywere characterized, and coated onto the AT-cut8MHz QCM sensor to investigate theirgas sensitive properties to DMMP. The results indicated these small moleculeorganosilicon compounds exhibited excellent performance on the detection of dimethylmethylphosphonate (DMMP) vapor, and the frequency changes of these fabricatedQCM sensors to the DMMP vapor were completely linear in the concentration range of10-50ppm, and they exhibited fairly fast response, negligible baseline drift andexcellent reversibility and selectivity for DMMP vapor. Interestingly, the sensitivity ofthe hexafluoroisopropanol groups functionalized octaphenylcyclotetrasiloxane toDMMP was up to19.68Hz/ppm, and that is much higher than the other small moleculesensitive materials under the same circumstances, the detection limits (LODs) of thefabricated QCM sensor was obtained as low as0.15ppm. Therefore, this kind newsmall molecule siloxane may be a kind of very promising sensitive material for DMMPvapor detection in chemical sensor applications. |
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