An Investigation of Two Distinct Borate-Based Reddish Ruby Glasses Containing Gold Nanoparticles

Objective: To overcome the limitation seen in the method of synthesis of Gold (Au) Nano Particles (AuNPs) in the ruby glasses by choosing the special binary borate-based glass composition without the need of adding any reducing agents and to produce reddish-ruby color in the glasses containing AuNPs. Methods: Two distinct binary borate glass compositions 30BaO-70B2O3 and 30Li2O–70B2O3 with HAuCl4.3H2O (gold chloride) as a dopant are used to prepare ruby glasses by the melt quenching synthesis method. Without adding any reducing agents and heat treatment, the samples are formed in reddish ruby color containing AuNPs. The samples have been characterized by advanced techniques such as Optical absorption, XRD-analysis, SEM, and ESR analysis. Findings: Ruby-reddish color has been observed in both distinct binary borate-based glasses due to the Surface Plasmon Resonance (SPR) of the AuNPs homogeneously embedded in the glass matrix. The deepness of the color increases with the increase of Au dopant concentration. The characteristic absorption peak seen at around ~560nm in the spectral observation of optical absorption studies gives strong evidence for the existence of AuNPs in the prepared glasses. The average gold particles size was found to be around 20-30 nm from the characteristic Bragg’s reflection sharp peaks in XRD of lithium-borate. SEM studies confirm that the addition of Au dopant increases the kinetics of growth and crystallization partially in both binary glass samples. The ESR analysis reveals that the electronic state of gold in the glass samples is either Au0 or Au+. Novelty: For the first time, the investigation of reddish-ruby colored binary borate-based glasses embedded with AuNPs is achieved without the aid of heat treatment and the need to add any reducing agents. Keywords: XRD, SEM, Gold Nanoparticles, Borate Glass, Optical Absorption, ESR