Effect of liquid type on optical absorption and emission features of pulsed laser ablated colloidal gold-copper nanoshells

Abstract Lately, the demand of pure, stable and enviro-friendly hybrid nanostructures of diverse noble metals with controlled physical and chemical properties are growing in the field of optoelectronics, bioelectronics and biomedicine. However, the large-scale synthesis of these nanohybrids with tunable size, stability and high-tech compatible performance remains challenging. Thus, we used Nd-YAG pulse laser (at optimum laser fluence of 4.4 J/cm 2 ) to ablate the solid target of copper (Cu) and gold (Au) independently to make tiny spherical AuNPs and CuNPs in two types of growth medium including deionized water (DIW) and ethanol (ET). Various techniques were used to analyse the obtained colloidal suspensions enclosing AuNPs, CuNPs, and Au-Cu nanoshells (Au-CuNSs). The optical absorption, emission, morphology and structure of the nanostructures produced in these liquids were compared. TEM and SAED images verified the formation of spherical nanocrystallites with face-centred cubic structure of lattice planer growth along (111). The mean diameter of Au-CuNSs made in DIW and ET corresponded to 6.22 ± 2.44 nm and 5.51 ± 1.64 nm. The optical absorbance of Au-CuNSs prepared in DIW and ET exhibited the plasmon peaks around 519-574 nm and 523 to 619 nm, respectively. The photoluminescence spectra of the Au-CuNSs revealed intense blue peak around 458-475 nm and weak red peak around 680-754 nm. The mechanism for the formation of these distinct nanostructures by the pulse laser ablation in liquid approach and their strong optical response was understood, unravelling the influence of growth medium on different properties. It was demonstrated that the overall attributes of the pulse laser ablated nanostructures can be tailored by suitably selecting the liquid medium (pH and electronegativity). These stable, pure and biocompatible nanostructures with desirable characteristics produced by the enviro-affable method can contribute towards varied functional applications, thus leading to sustainable development.