Nematic to smectic texture transformation in MBBA by in situ synthesis of silver nanoparticles

Abstract

The present study describes the texture changes in ‘nematic’ N-(4-methoxybenzylidene)-4-butylaniline (MBBA) by in situ synthesis of silver nanoparticles in the system without any external reducing or stabilizing agents. Optical polarizing microscopy (OPM), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and scanning and transmission electron microscopy (SEM and TEM) were utilized to understand the mechanistic details of the texture transformation in MBBA. The experimental results collectively suggest that the silver nanoparticles are generated through the reduction of silver ions by MBBA upon heat treatment, followed by a clear texture transformation from ‘nematic’ to ‘smectic’. The ‘smectic’ MBBA–Ag NP conjugate forms a stable luminescent glassy phase on rapid cooling, with an emission maximum of 500 nm upon photo-excitation at the silver plasmon absorption.