Probing the interaction of glutathione with different shape of silver-nanoparticles by optical spectroscopy

Abstract

To understand the influence of the shape of the particles on assay sensitivity using surface plasmon resonance phenomenon (SPR), three different types of silver nanoparticles spherical (SAgNPs), triangular (TAgNPs), and octahedral (OAgNPs) of around 20 nm in size and similar aspect ratio were analyzed after interaction with glutathione (GSH). FTIR peak of Ag-S peak at 2312 cm−1and 2305 cm−1, 2312 cm−1 in SAgNPs, TAgNPs, and OAgNPs respectively confirming interactions. DLS and TEM studies agglomeration of SAgNPs and TAgNPs but not in OAgNPs due to the interaction. Detailed SPR analysis showed interaction of GSH with nanoparticles resulted in alteration of three characteristic features namely changes a decrease in peak height at (506 nm and 398 nm) an increase in peak height (987 nm and 987 nm) and bathochromic shift of absorption peak in 600−700 nm range in the case of SAgNPs and TAgNPs, but no such changes were observed for OAgNPs. To understand the physical phenomenon Marquardt-Levenberg algorithm based non-linear curve fitting analysis where done. In the fitting analysis, GSH concentration-dependent changes of the AS characteristics were fitted to polynomials of different orders, and from the weighted residuals and 95 % prediction interval of the fits, the best models are suggested that describe the changes in the AS of the triangular AgNPs (TAgNPs). The probable reason for the phenomenon lies in surface protection and accessibility of the interaction surface. Unlike SAgNPs, in TAgNPs and OAgNPs the edges of each side are loosely protected with Polyvinylpyrrolidone (PVP) allowing enhanced interaction with GSH from the edges and linear joining. Further, the majority of the ridge of the surface of OAgNPs are not accessible to the other particles which reduce the stability of interaction and joining. As a cumulative result TAgNPs are the best choice for GSH titration among these 3 types of particles.