Synthesis of magnetofluorescence Gd-doped CuInS2/ZnS quantum dots with enhanced longitudinal relaxivity

Abstract

In this paper, we describe the rapid microwave-assisted synthesis of Gd³⁺-doped CuInS₂ (Gd:CIS) quaternary quantum dots (q-dots), which integrate the functions of optical fluorescence and magnetic resonance imaging. Through passivation of ZnS shells around Gd:CIS cores, high-quality and robust photostable Gd:CIS/ZnS core/shell q-dots with enhanced quantum yields were obtained. The intensity and peak-to-peak linewidth of the electron spin resonance (EPR) signal were found to vary depending on the Gd³⁺ concentration of Gd:CIS/ZnS. Benefiting from the incorporation of paramagnetic Gd³⁺ ions, the formed q-dots exhibited well-resolved and strong signals of electron paramagnetic resonance and provided significant contrast enhancement in T₁-weighted images owing to the remarkably high longitudinal relaxivity (r₁ = 55.90 mM⁻¹ s⁻¹) and low r₂/r₁ ratio (1.42), which are significantly higher than those of commercially available T₁ contrast agents. We expect that this facile one-pot synthetic strategy can be extended to the preparation of other Cu-based sulfide quaternary nanomaterials.