DensityFunctional Theoretical Modeling, ElectrostaticSurface Potential and Surface Enhanced Raman Spectroscopic Studieson Biosynthesized Silver Nanoparticles: Observation of 400 pM Sensitivityto Explosives.

Interaction of adsorbate on chargedsurfaces, orientation of theanalyte on the surface, and surface enhancement aspects have beenstudied. These aspects have been explored in details to explain thesurface-enhanced Raman spectroscopic (SERS) spectra of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(HNIW or CL-20), a well-known explosive, and 2,4,6-trinitrotoluene(TNT) using one-pot synthesis of silver nanoparticles via biosyntheticroute using natural precursor extracts of clove and pepper. The biosynthesizedsilver nanoparticles (bio Ag Nps) have been characterized using UV–visspectroscopy, scanning electron microscopy and atomic force microscopy.SERS studies conducted using bio Ag Nps on different water insolubleanalytes, such as CL-20 and TNT, lead to SERS signals at concentrationlevels of 400 pM. The experimental findings have been corroboratedwith density functional computational results, electrostatic surfacepotential calculations, Fukui functions and ζ potential measurements. [ABSTRACT FROM AUTHOR]