A new derivative of naphthalene diimide (NDMI) was synthesized that displayed optical, electrical, and visual changes exclusively for the most widespread nitroexplosive and highly water-soluble toxicant picric acid (PA) due to strong π-π interactions, dipole-charge interaction, and a favorable ground state electron transfer process facilitated by Coulombic attraction. The sensing mechanism and interaction between NDMI with PA is demonstrated via X-ray diffraction analysis, (1)H NMR studies, cyclic voltammetry, UV-visible/fluorescence spectroscopy, and lifetime measurements. Single crystal X-ray structure of NDMI revealed the formation of self-assembled crystalline network assisted by noncovalent C-H···I interactions that get disrupted upon introducing PA as a result of anion exchange and strong π-π stacking between NDMI and PA. Morphological studies of NDMI displayed large numbers of single crystalline microrods along with some three-dimensional (3D) daisy-like structures which were fabricated on Al-coated glass substrate to construct a low-cost two terminal sensor device for realizing vapor mode detection of PA at room temperature and under ambient conditions. Furthermore, an economical and portable electronic prototype was developed for visual and on-site detection of PA vapors under exceptionally realistic conditions.
Considering the vital need to strengthen the national security emanating from chemical threats, a low-cost, portable ultrasensitive electrical sensor for real-time monitoring of diethylchlorophosphate (DCP) (nerve gas mimic) has been developed. The device consists of a "simple to be fabricated" two-terminal resistor and an electronic combinational circuit for rapid onsite detection of lethal nerve gas vapors with high degree of accuracy in milliseconds. This device is a smart readout electronic model that detects ultratrace DCP vapors by bright visual alerts from light-emitting diode (LED) and loud alarm signal without the need for employing a sophisticated instrument. To obtain high sensitivity and discriminating response, a novel amine-functionalized conjugated polymer (CP) is designed as a sensory channel material for two-terminal sensor. The low-powered poly(3-(9,9-dioctyl-9H-fluoren-2-yl)benzene-1,2-diamine) (PFPDA) fabricated two-terminal electrical sensor is tested at ambient conditions, which shows excellent sensitivity toward nerve gas mimic DCP, with a rapid response in 3 s and a very low limit of detection (LOD) of 5.88 ppb. The amine moiety of PFPDA CP plays a vital role in redox interaction between the semiconductor CP and organophosphates, which ultimately leads to the amplified current signal. The redox interactions occurring among the organophosphate analytes and the amine functional group on the PFPDA backbone provided insights into the mechanism of sensing, which formed the basis of the excellent sensitivity and discriminating ability of this sensor device. The newly designed PFPDA CP-based portable electrical sensor device demonstrates a key contribution in the field of portable electronics for defense safety and environmental monitoring applications.
This paper reports a novel electrochemical method for detection of Glutathione (GSH) using Glutathione-S-Transferase (GST) - ZnO composite nanoparticles to investigate the prospects of the method for detection of cancer at an early stage. The purified GST enzyme was bound with ZnO nanoparticles by electrostatic interactions and the nanocomposite was dropcast on a silicon dioxide wafer. The GST functionalized deposited layer was then used as a chemiresistive channel to detect conjugation reaction between GSH and 1-Chloro-2, 4-Dinitrobenzene (CDNB). The zeta potential values of the ZnO nanoparticles and the GST were found to be 13.4 mV and-6.21 mV, respectively. Around 73.8% binding was observed between the enzyme and ZnO nanoparticles. I - V analysis of the chemiresistive channel showed an increase in conductivity of the channel due to conjugation reaction between GSH and CDNB as compared with that of GSH or CDNB alone. I - V characterization of the GST functionalized layer was performed at various concentrations of GSH and a sensitivity and limit of detection of 5.68 nA/ [Formula: see text] and 41.9 nM were obtained, respectively. Thus from I - V analysis of the chemiresistivechannel, the detectionand quantification of GSH could be obtained. The kinetic parameters of both GST and nanoconjugate of ZnO nanoparticles andGSTwere determinedwith respect to its substrates, GSH and CDNB, using Michaelis-Mentenmodel. This novel approach of detection of GSH bymeans of ZnO nanoparticle and GST enzyme composite can be further analyzed for in vitro experiments, which will lead us to a new and efficient way of detecting certain types of cancers at an early stage.
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