Study On Novel Electrochemical Sensor And Its Applications For The Detection Of Nitroaromatic Compounds

Since the World Warâ…¡,long-term manufacturing of explosives and cumulative use of land and marine firing ranges,as well as military conflicts,have all resulted in severe contamination from unexplored ordnance and mines worldwide.The nitro aromatic compounds(NACs)in explosive,such as 2,4,6-trinitrotoluene(TNT), 1,3,5-trinitrobenzene(TNB),2,4-dinitrotoluene(DNT)and 1,3-dinitrobenzene(DNB), are toxic and cause health problems in both animals and human beings,including anemia, abnormal liver function,cataract development and skin irritation.Even after degradations, the by-products of the common explosives in environment are still toxic and carcinogenic. Therefore,environmental applications havecompounds(NACs).The detection of traces of explosive materials is of utmost importance and there is a necessity for accurate, sensitive,rapid,easy-to-use and portable method to facilitate the detection,quantification and remediation of these NACs.This dissertation research focuses on developing modified electrodes based on new materials,which is one of most active areas in electroanalytical chemisty of the detection of NACs.The mesoporous materials can greatly enhance the surface available for NACs binding over the geometrical area,and the active centers on the materials accelerate the electron transfer between the surface of the modified electrode and the NACs molecules. In addition,the modified MIP materials further improve the selectivity of the electrode. The specific molecular recognition sites in solid polymer,which are complementary to the shape,size,and functional group of the template exhibite an improved response to the target molecule,making the selective detection of NACs possible.We are adhering to an organic combination of electoanalytical chemistry,material science and sensors.All the three modified electrodes we construct provide fast,simple and sensitive methods and will have wide application in national security and environmental monitoring.Of course, it is a new area worthy of attention and it is also helpful to set up new methods,new techniques and new theories.The details are given as follows: 1.Trace detection of nitroaromatic compounds with layer-by-layer assembled {SBA/PSS}n/PDDA modified electrode(Chapter 2)The {SBA/PSS}n/PDDA films modified electrode was prepared by layer-by-layer (LBL)assembly with mesoporous SiO₂(SBA),poly(sodium4-styrene-sulfonate)(PSS) and poly(diallyldimethylammonium chloride)(PDDA)in this paper.SBA is a large pore-size mesoporous material with highly ordered hexagonally arranged mesochannels and high thermal stability etc.The electrochemical characteristics of the {SBA/PSS}_n/PDDA films have been studied by electrochemical impedance spectroscopy in 0.1MKCl solution containing 5.0mM Fe(CN)₆^3-/Fe(CN)₆^4-at the formal potential of 0.230V.The ultratrace nitroaromatic compounds(NACs)such as TNT,TNB,DNT and DNB were determined by differential pulse voltammetry(DPV)measurement.The sensitivities for NACs determination with {SBA/PSS}n/PDDA modified electrode were dependent on the number of layers,pH and ionic strength of electrolyte,based on which a set of optimized conditions for film fabrication was inferred.The current responses were linear with NACs ranging from 10^-9to 10^-7mol/l.The results showed that the {SBA/PSS}_n/PDDA modified electrode established a new way for fast,simple and sensitive analysis of NACs.2.Electrochemical Sensor Prepared from PAMAM G3-Encapsulated Pt Nanoparticles for the Detection of Nnitroaromatic Compounds(NACs)(Chapter 3)In this paper,electrochemistry,sensing technology and nanotechnology are combined organically.PAMAM encapsulated with Pt nanoparticles is synthesized;then it was modified on the surface of glassy carbon electrode followed by carbon nanotubes. Through electrochemical analytic methods such as Square Wave Voltammetry(SWV) and A.C.Impedance,electrochemical reactions of explosive molecules such as TNT,TNB,DNB and DNT were researched on the surface of modified electrode,and electron passing process and electrochemical reaction mechanism of explosive molecules were discussed.The scientific theoretical foundations were provided for the explosive detectors with small volume,quick reaction time,high sensitivity and convenient to carry.3.Electrochemical Sensor Prepared from Molecular Imprinted Polymer for Recognition of 1,3-Dinitrobenzene(DNB)(Chapter 4)This paper reports an electrochemical sensor modified with multi-wall carbon nanotubes(MWMWCNTs)and molecular imprinted polymer(MIP)material synthesized with acrylamide and ethylene glycol dimethacrylate(EGDMA)in the presence of 1, 3-dinitrobenzene(DNB)as the template molecule.The MWMWCNTs and MEP layers are successively modified on the surface of glassy carbon electrode(GCE),of which the MIP film works as an artificial receptor due to its specific molecular recognition sites. The MIP material is characterized by FT-IR and electrochemical methods of Square Wave Voltammetry(SWV).The interferences of other nitroaromatic compounds(NACs)such as 2,4,6-trinitrotoluene(TNT),1,3,5-trinitrobenzene(TNB)and 2,4-dinitrotoluene(DNT) to DNB are also investigated by MIP/MWMWCNTs electrode.Compared with other traditional sensors,the MIP/MWMWCNTs modified electrode shows better selectivity and sensitivity.In addition,the current responses of DNB are linear with the concentration ranging from 4.5×10^-8mol/L to 8.5×10^-6mol/L with the detection limits of 2.5×10^-8mol/L(-0.58 V)and 1.5×10^-8mol/L(-0.69 V)(S/N=3).The construction process of MIP/MWMWCNTs modified electrode is also studied as well in this paper.All results indicate that the MIP/MWMWCNTs modified electrode establishs an improving way for simple,fast and selective analysis of DNB.