Eco-friendly AgInS2/ZnS quantum dot nanohybrids with tunable luminescent properties modulated by pH-sensitive biopolymer for potential solar energy harvesting applications

Abstract

Semiconductor quantum dots (QDs) are very interesting candidates for the development of green-energy based nanomaterials and devices. However, currently they present serious concerns because the large majority of efficient QDs have been synthesized using organometallic routes with toxic heavy metals. Herein, we designed and produced novel fluorescent ternary and quaternary QD nanostructures based on AgInS2 (AIS) core and ZnS (ZAIS) shell stabilized with carboxymethyl cellulose (CMC) polymer ligand for potential applications in green solar energy harvesting. Colloidal AgInS2 QDs were prepared by co-precipitation process using a one-pot aqueous green route directly stabilized by CMC at room temperature and varying pH conditions. Then, an outlayer of ZnS was grown and thermally annealed to improve and tune their optical properties and split the emission range, leading to core–shell alloyed nanostructures. Their physicochemical and optical properties were extensively characterized, demonstrating that photoluminescent monodispersed AIS and ZAIS QDs were produced with size typically ranging from 8.5 ± 2.4 nm and 3.2 ± 1.1 nm under acidic or alkaline media, respectively. Therefore, by adjusting the parameters of synthesis, the QD nanohybrids showed tunable optical properties ranging from UV to NIR, with maxima absorption/emission in the visible-range of the light spectrum (from λ = 650 to 750 nm). More importantly, the optical properties demonstrated remarkable enhancement of quantum yield of over one order of magnitude due to the combination of processing parameters and engineered core–shell nano-architecture of AgInS2–ZnS. Thus, these luminescent nanomaterials offer great perspectives for developing innovative broad spectral converters for a wide range of applications in solar energy harvesting.