Design And Synthesis Of Fluorescent Chemosensors For Rapid And Selective Detection Of Nerve Agents

Chemosensors are those organic compounds containing active sites that can produce indicative signal upon binding with specific analytes.The action results in change of photopysical properties such as emission and excitation bands,redox potential,fluorescence quantum yield,color,pKa and so on.Establishing rapid and reliable fluorescent chemosensors for selcetive detection of toxic chemicals especialy nerve agents is challenging in current research.Nerve agents(NAs)are classes of the most feared and toxic chemical warfare agents(CWAs)used mostly on the battlefield since WWI.In this work,we have designed two types of fluorescent chemosensors based on quinoline and BODIPY fluorophores.In our first work,two aminoquinline probes namely AQmol-1 and AQmol-2 were developed,for selective sensing of nerve agent simulants especially diisopropylfluorophosphate(DFP)and diethylchlorophosphate(DCP)in preference to organophosphate intereferences.In this sensing reaction,the hydroxy group of two sensors is phosphorylated by DFP/DCP and simultaneous protonation of nitrigen of the quinoline to form a stronger electron donor-acceptor(D-A)molecule over the sensor molecule,giving corresponding fluorescence response.Therein,AQmol-2 diplays ratiometirc fluorescence response towards DFP and DCP with limit of detection(LOD)value of 0.18 μM and 0.16 μM respectively.Furthermore,two AQmol-2 embedded solid polymers,membrane and fibers(the diameter<1 μm),were fabricated for detection of DFP/DCP vapor.Both AQmol-2-embedded solid-state polymers can detect DFP/DCP vapor more rapidly over those(about 30 min)in solutions.The polymer fibers from an electrospaning technology give more rapid response toward DCP(within 20 sec)over that(3 min)of the membrane.In our second work,three meso piperazin BODIPYs(BPA-1,BPA-2 and BPA-3),have been prepared as fluorescent chemosensors for rapid and selective detection of nerve agent mimics(DCP and DFP)in solutions and in gaseous phase like that of quinoline probes.In these probes,secondary amine was phosphorylated with nerve agent simulants(DCP and DFP)resulting in protonation of tertiary amine.From the three chemosensors,BPA-2 displayed the best fluorescence sensing performance toward DFP/DCP with LOD values of 34.7 for DFP and 15.4 nM for DCP in solutions respectively.In order to examine the response times towards DCP/DFP vapor,tow BPA-2 embedded polymers mainly polymer film and fiber have been prepared.Accordingly,polymer have shown rapid response over polymer film for DCP vapor.Generally,both types of fluorescent chemosensors are promising way of detecting nerve agent mimics(DCP and DFP)either in solution or gaseous states.Especially,polymer fibers are the best methods for rapid detection of nerve agent simulants(DCP and DFP)in gaseous phase.