Exploring the formation of plasmonic silver nanoparticles and wide range optical energy bandgaps in ion conducting EG–SiO2/AgNO3 hybrid nanofluids for broader functionalities

Abstract

Multifunctional nanofluids are cutting edge materials of high interest in emerging soft device technologies. In this research, silver ion conducting hybrid nanofluids (NFs) comprising ethylene glycol (EG) base fluid, silicon dioxide (SiO₂) nanoparticles, and silver nitrate (AgNO₃) salt with 0.2–2.0 wt% concentrations, are prepared through a state-of-the-art two-step method and characterized for exploration of their broader functionalities. Ultraviolet-visible (UV-Vis) absorbance spectra of these EG–SiO₂/AgNO₃ NFs exhibited three characteristic bands. The surface plasmon resonance band with maximum intensity at 425 nm signifies the formation of plasmonic silver nanoparticles (AgNPs) through the polyol ions reduction process which transformed these materials to SiO₂-AgNPs nanosuspended hybrid NFs. A relatively intense band at 300 nm evidenced coordinative interactions of silver ions with EG molecules. A strong absorption band having onset at about 265 nm is attributed to electronic transitions from the EG molecules. Distinct energy bandgaps, ranges 4.77–4.55, 3.75–3.60, and 2.22–1.96 eV marginally altered with salt concentrations, categorized these soft plasmonic materials of wide bandgap semiconductors. Optical characterization revealed the applicability of these hybrid NFs in photo-sensing, UV shielding, and the design of bandgap tunable optoelectronics. High static dielectric permittivity range 40.30–41.44 and ionic conductivity orders 10^–3–10^–4 S/cm, at 298.15 K, characterizes these materials as polar liquid electrolytes which could be used as energy storage, antibacterial agent, and in developing ion sensitive next technology biomedical devices. Newtonian flow behaviour with high dynamic viscosity additionally explains the utilization of these NFs in heat management and high-performance mass transfer systems.