Nanosecond Laser–Assisted Tuning of the Plasmon Band of Triangular-Shaped Ag Nanostructures and Development of a Broadband Visible-Near Infrared Light Absorber

Abstract

Most of the outstanding applications of silver nanoparticles (Ag NPs) have arisen from their tunable localized surface plasmon resonance (LSPR). In this report, we have systematically studied the photothermal transformation of morphology of triangular-shaped Ag NPs (TSNP) under irradiation of a nanosecond (ns)-pulsed laser of 1064-nm wavelength with the pulse duration of 10 ns at different laser fluence and irradiation time. Interestingly, at a typical value of fluence of 104–174 J/cm2 both the triangular and plate-like Ag NPs are transformed into spherical Ag NPs of size ~ 5 nm in just 20–40 min of irradiation that is found to be very much faster when it is compared with the results of well-known chemically etching–based reshaping process in the presence of KBr. We have also demonstrated the possible use of the plasmonic absorption properties of the triangular, plate-like and transformed spherical Ag NPs for the development of a broad-band visible-NIR light absorber by just mixing these Ag NPs of three different morphologies. We have got almost 20% average (overall below 35%) transmission in the wavelength range from 400 to 800 nm in the liquid phase and 57% (overall below 65%) when NPs are put into PVA matrix in 16 vol%. The applicability of the prepared broadband absorber is being verified by monitoring the current response of a light-dependent resistor and degradation process of rhodamine 6G dye in sunlight.