Application Of Quaternary Excited - Enhanced Raman Spectroscopy In The Detection Of Chemical Warfare Agent And Its Related Compounds

Chemical warfare agents (CWAs) are a great threat to humans due to its ease ofproduction, extremely high toxicity and mass destruction. In deal with public safetyemergencies involving CWAs, a rapid, sensitive, reliable field-testing method isparticularly important. Surface-enhanced Raman spectroscopy (SERS) has manyunique features that can meet the demand of CWAs field-testing, such as providingmolecule spectrum with fingerprints information, single-molecule level sensitivity,simple or none sample pre-treatment, fast response, enabling non-contact,non-destructive inspection, etc. The application of SERS in the detection of CWAsand related agents has been studied in several research works, but the LODs are all atppm level or above, so more effort should be put to achieve the on-site detection ofCWAs at trace level. Plasmon-enhanced Raman spectroscopy (PERS) broadens theworking mode of SERS. The core technique of PERS, shell-isolatednanoparticle-enhance Raman spectroscopy (SHINERS), uses the new shell-isolatedworking mode, which greatly improves the stability and universality of the substrateswhile maintains high enhancing activity.This thesis focuses on developing new field-testing methods for CWAs and relatedagents based on PERS technique. We established different detection methods for threemost concerned types of CWAs, blood agents, organophosphorus agents (OPs) andblister agents, depending on their chemical or biological natures. These methods aresimple, fast, highly sensitive and very consistent with field-testing needs. Moreover,we also constructed a RS and SERS spectra database containing a variety of CWAsand related agents, which laid a preliminary data foundation for the field-testing ofCWAs. This thesis includes five chapters.The first chapter is the introduction part. We first elaborated the species,characteristics and potential threats of CWAs. After a brief review on the currentfield-testing techniques, the features and advantages of Raman spectroscopy (RS) onthe field-testing of CWAs were declared. Secondly we gave a brief introduction ofSERS from the aspects of discovery, enhancement mechanism, active substrates,enhancement factor and "hot spots". Then we gave the concept of PERS and lookedinto the development and application of the core technique of PERS--SHINERS.Finally, the basis and main work of this this thesis were summarized. In chapter2, we developed a simple, rapid and sensitive method for the on-sitedetection of cyanide based on pinhole SHIENRS technique. The characterizationresult showed that the pinhole SHINs were composed of an Au core and an ultrathinsilica shell with pinholes. The pinholes can provide binding sites for cyanide anions toAu surface so as to enhance SERS signals, while the shell outside can protect the Aucore from the dissolution by cyanide. After the optimization of pH and other testingconditions, cyanide in clean water samples can be directly measured with an LOD of1ppb, and a good linearity at the range of1-100ppb was achieved. The pinholeSHINs showed excellent stability in cyanide and could obtain reproducible signals in24h. Most common anions and cations, including thiocyanite, did not interfere withcyanide measurement at the10-fold concentration. This method can be directly usedin the measurement of cyanide in simple matrices such as tap water, mineral waterand lake water and good recoveries were obtained. For the detection of cyanide incomplex matrices, we designed an on-line hydrogen generation device to be coupledwith pinhole SHINERS and achieved the trace detection of cyanide in industrialpolluted water and orange juice samples. In all, this method is portable, simple, rapidand sensitivity, with good stability and selectivity, showing great potential in theon-site detection of cyanide in various matrices.In chapter3, we developed a rapid and ultra-sensitive method for the on-sitedetection of sulfur mustard (SM) and related agents based on pinhole SHINERStechnique. The pinhole SHINs could be directly used for the detection of SM at100ppb level due to the Au-S interaction. In order to gain higher sensitivity, we adoptedan agglomeration approach by introducing salt into the pinhole SHINs to induce thegeneration of more “hot spots”. We chose0.1M MgSO4as agglomeration agent inSM detection and a LOD of10ppb was achieved on a portable Raman spectrometer,which was hundreds times or more sensitive than other methods. With goodsensitivity and reproducibility, the established method was directly used in themeasurement of SM in environmental water samples, and the recovery was between88-114%. Based on this method, we obtained good differentiation of four SM relatedagents, CEES, TDG, SM sulphoxide and SM sulphone, and revealed that the SERSresponses of these agents were in correlation with the steric hindrance and electrondistribution around the sulphur atom. This simple, rapid, sensitive and reproduciblemethod provides a new and effective way for the field-testing of SM and relatedagents. In chapter4, we designed and tested three different strategies for the detection ofOPs. The strategies based on Au@ZrO2core-shell nanoparticles (NPs) andacetylcholine esterase (AChE) did not achieve the expected results, then wedeveloped a chemical transformation method and successfully achieved the rapid andsensitive detection of OPs. This method based on the chemical reaction between OPsand ketoxime under alkaline condition in which the ketoxime is quantitativelydecomposed into cyanide ion (CN-) and carboxylic acid. In this way, the measurementof OPs can be transformed into the measurement of CN-with the established pinholeSHINERS method. We applied this chemical transformation method in the detectionof diethyl chlorophosphite and achieved a LOD of10ppb. Then we tested itsapplication on NAs. The result showed that all the G-series agents exhibited the goodSERS response while the V-series agent VX had no response of cyanide signal.Therefore, this method can achieve the rapid and sensitive detection of G-series NAsand other OPs, as well as the differentiation between G-series and V-series NAs.In chapter5, we constructed a RS and SERS spectra database containing a varietyof CWAs and related agents. The Raman spectra of GA, GB, GD,VX,SM and theirhydrolysates were collected with a portable Raman spectrometer. The bands of thespectra were analyzed and classified according to references. The characteristic bandsof NAs and related agents were in the region of720-780cm-1, which could beattributed to the P-C stretching mode. The featured bands of SM and related agentsappeared in the region of600-700cm-1, which were due to the C-S，C-Cl or C-S-Cstretching modes. Based on the developed methods for cyanide and blister agents(chapter2and4), we obtained the SERS spectra of NaCN, SM, TDG, CEES, SMsulphoxide and SM sulphone using pinhole SHINERS, and gave a brief attributionanalysis of the featured bands for each agent. This RS and SERS spectra database laida preliminary data foundation for the field-testing of CWAs.