Textural, electro-optical, dielectric and fluorescence studies of citrate buffer stabilized gold nanoparticles doped in polymer-dispersed liquid crystals composites

ABSTRACT

This work demonstrates the effect of citrate buffer stabilised gold nanoparticles (AuNPs) on the morphological, optical and dielectric properties of polymer-dispersed liquid crystal (PDLC) composites prepared by polymerisation-induced phase separation method. The effect of voltage and temperature on liquid crystal (LC) droplet configurations, transmission, permittivity, conductivity and transition temperatures are studied. The relative transmission and contrast were improved by 22% and 54%, respectively, after the dispersion of AuNPs in PDLC composites as compared to undoped PDLC. The threshold voltage (V_th) of the doped composite was reduced by 13.34% as compared to the undoped composite. The increasing concentration of AuNPs has a minor effect on the (V_th) and transmission as well. Moreover, the low concentration of AuNPs also has better optical responses. The size of LC droplets was found in the range of 35–53 µm and almost independent of voltage and temperature. Beyond threshold voltage, maltese type LC droplet occurred. The photoluminescence spectra reveal that the intensity of AuNPs (1.5 µl) doped sample is higher and a blue shift is seen at 3.0 µl AuNPs-doped sample than others. With increasing AuNPs concentration, the energy bandgap also increases and is reported in the range of 3.4 eV at a higher concentration of AuNPs.

Graphical abstract

KEYWORDS:

• Citrate buffer stabilised gold nanoparticle
• maltese
• permittivity
• conductivity
• fluorescence

Highlights

• Citrate buffer stabilized gold nanoparticles, doped in polymer-dispersed liquid crystals composites have been prepared and studied.

• LCs droplet changes their configuration from bipolar to maltese type configuration with an externally applied voltage and their sizes are more or less independent of temperature and voltage.

• Improvement in relative transmission and contrast ratio by 22% and 54%, respectively. V_sat reduced by 5.6% for the 1.5 µl AuNPs doped PDLC sample.

• Fluorescence spectroscopy reveals that there is an increment in emission intensity of AuNPs doped PDLC whereas the increasing concentration of NPs reduces the intensity of the nanocomposite due to concentration quenching.

• At greater AuNPs (3 µl) concentrations, the E_g increases and found ~ 3.4 eV.

Acknowledgments

The authors are grateful to the Council of Scientific and Industrial Research (CSIR), New Delhi, for providing financial assistance to carry out this work through the CSIR Sanction No. 03(1451)/18/EMR-II Scheme.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Council of Scientific and Industrial Research [03(1451)/18/EMR-II].