Tuning the optical properties of gold nanoparticles via photoactive liquid crystalline azo ligands

Abstract

In the field of modern nanoscience, the ability to tailor the properties of nanoparticles is essential for advancing their applications. A key approach for achieving this control involves manipulating surface plasmon resonance (SPR) to modify optical properties. This study introduces a novel method for synthesizing gold nanoparticles capped with photoactive liquid crystalline azo ligands, accomplished without reducing agents. Comprehensive structural characterization was performed using Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), ultraviolet-visible (UV-Vis) spectroscopy, powder X-ray diffraction (PXRD), and high-resolution transmission electron microscopy (HRTEM). Photophysical investigations, including time-dependent UV-Vis and fluorescence spectroscopy, provided insights into the modulation of SPR. The mesomorphic behavior of the azo ligands was examined through polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD), revealing a chiral lamellar superstructure confirmed by circular dichroism (CD) spectroscopy. Notably, the photoactive azo ligands demonstrated significant control over SPR peak modulation, enabling precise manipulation of nanoparticle size and arrangement. This research highlights the potential of photoactive ligands in the design of nanoparticles with tailored optical properties, paving the way for innovative applications in various fields.