Supercritical CO2 mediated synthesis and characterization of nano hybrids for electrochemical sensing of organophosphates

Abstract

Present thesis demonstrates development of NHs based working electrodes newline(WEs) for electrochemical sensing of OPs extracted from soil samples of selected newlinevegetable crops. For this purpose, a series of electrically conducting electrode materials newlinewas synthesized through SCC mediated dispersion of h-BN at selected weight fractions newline(3 to 7 wt%) over c-MWCNT at 85 ±1°C, 1800 psi over 1 hr. Formation of NHs was newlineascertained through diverse spectral, morphological and thermogravimetric methods. newlineFESEM along with elemental mapping and EDS spectra reveals uniform dispersion of newlineh-BN over surface of c-MWCNT in NHs. NHs (crystallite size 11 nm and Eg 3.34 eV) newlineinvolving h-BN (5 wt %) was identified as potential electrode material for newlineelectrochemical sensing of OPs. Electrical behavior of WEs derived from c-MWCNT, newlineh-BN and NHs in presence of polyvinyl butyral binder in NMP medium was newlineinvestigated and compared at variable voltages and environmental conditions. WEs newlinederived from NHs (5 wt% h-BN) i.e.WE-II has rendered enhanced and#963;DC (0.93 mS/cm), newlinestability in thermal, humid and photochemical environments over 9 hrs. WE-II selected newlinefor electrochemical quantification of OPs in soil samples of cabbage, potato and brinjal. newlineCyclic voltammetry in coherence with electrochemical impedance spectroscopy reveals newlineenhanced redox behavior and EC stability of WEs in KCl (0.1 M) at 7.2 pH. WEs was newlineutilized for EC quantification of OPs through square wave voltammetry (SWV) and newlinedifferential pulse voltammetry (DPV) at compatible pH in KCl (0.1M). For newlineChloropyriphos (CPS) limits of detection (LOD) and limit quantification (LOQ) in newlineng/L were found to be 2.62 and 7.96 by SWV and 2.08 and 6.31 by DPV respectively newlineat WEs. PF has rendered LOD and LOQ (ng/L) by DPV as 2.28 and 6.91 respectively newlineat WEs. Present thesis delivers SCC mediated synthesis of NHs as potential electrode newlinematerials providing highly sensitive, selective and reproducible estimation of OPs in newlinesoil samples of vegetable crops down to nano molar level. newline