Highly creditable optical properties through SPR coupling of in situ growing Ag nanoparticles with ZnO in ethylene glycol based plasmonic hybrid nanofluids: Towards a real time growth mechanism

Plasmonic silver (Ag) and zinc oxide (ZnO) nanoparticles (NPs) and their nanohybrid (Ag-ZnO) dispersed a variety of plasmonic nanofluids confirmed a wide range of applications in the areas of energy harvesting/ storage, sensors, biomedical processes, environmental remediation, heat transfer systems, sustainable agriculture, and in the cutting edge photonic and optoelectronic devices. In the advances of such plasmonic nanofluids, herein, the ZnO nanomaterial (0.01 wt%) dispersed ethylene glycol (EG) based semiconductor nanofluid is hybridized with in situ growth of Ag NPs through the polyol ion reduction and nucleation process, on the addition of 1.0 wt% silver nitrate (AgNO 3 ). Such a state-of-the-art prepared Ag-ZnO/EG plasmonic hybrid nanofluid was characterized by ultraviolet-visible (UV-Vis) wavelength range absorbance measurements with a real time ageing (reaction time) of 1, 3, 24, 48, and 72 hr. The changes observed in the intensity of surface plasmonic resonance (SPR) peak of nano ZnO at 375 nm, and also absorbance enhancement up to 340 % at 800 nm with widening of spectral width over the entire visible region, the Ag NPs growth mechanism and their strength of SPR coupling with ZnO at various real time ageings are explained. After measurement at 72 hr, a 1.0 wt% amount of poly(vinyl pyrrolidone) (PVP) was instantly added to this nanofluid as a stabilizing agent to the Ag NPs, and then the UV-Vis absorption spectra of formulated Ag-ZnO/EG/PVP hybrid nanofluid were recorded at time ageing of 1, 24, and 72 hr. Interestingly, the absorbance is further enhanced progressively up to about 54 % over the entire spectral range with time ageing, and the SPR peak of Ag NPs appeared at 440 nm with appreciable increasing intensity, explaining the stabilization of un-nucleated Ag metal into Ag NPs having their distinct characteristics from those already coupled with ZnO nanoparticles. The results of these plasmonic hybrid nanofluids were analyzed concerning the increased concentration of Ag NPs, their SPR coupling with ZnO, and energy bandgap variations of the constituents which found in the range of 2.0–4.4 eV. Potential applications of these plasmonic metal-semiconductor hybrid nanofluids are highlighted with the consideration of their multifunctional features of creditable optical properties. • In situ grown Ag NPs in ZnO/EG nanofluid are characterized by UV-Vis measurements. • Ag-ZnO SPR coupling enhanced absorbance and spectral width in visible range. • PVP stabilizer realized Ag-ZnO/EG/PVP plasmonic hybrid nanofluid more promising. • Bandgap range 2.0–4.4 eV confirmed semiconductor behaviour of the nanofluids. • Optical features demonstrate optoelectronics, biomedical and other wide range uses.