Molecular scale insights from NMR studies of hybrid systems formed via doping silver QDs in 6CHBT liquid crystal: a quantitative investigation of their optoelectronic properties

Abstract

ABSTRACT We have successfully synthesised silver quantum dots (Ag QDs) via chemical method. We have studied Ag QDs doped 4-(trans-4-n hexylcyclohexyl) isothiocyanatobenzoate (6CHBT) LC hybrid system and their associated structural and optoelectronic properties using both experimental and theoretical methods. The QDs with sizes 4.27 nm−9.56 nm self-assemble to form nano-micro scale hierarchical structures. Theoretical NMR study has been performed using three different methods HF, B3LYP, and wB97XD for pure and Ag NPs doped LC system. NMR data greatly helps us to explore the phenomenological description of the hybrid system by giving us molecular scale insights. Optical microscope, RAMAN, UV, FTIR, HR-XRD, FESEM-EDX, and Fluorescence data confirm the structural and physio-chemical properties of QDs, LC molecules and as well as their hybrid system. We use a nanoscale predictive model to estimate the effective size to which the bandgap value of Ag QDs in a hybrid system corresponds. The bandgap value of pure Ag QDs is found to be 5.32 eV, whereas upon doping these Ag QDs in LC media, their bandgap falls to a value of 4.08 eV. The estimated size (i.e. corresponding to effective confinement) using a hexahedral or octahedral-shaped particle model comes out to be ~15 nm.