Lead-Free Cobalt Halide Perovskite Nanocrystals for Bioimaging and Electrochemical Sensing

Lead-free perovskites are ecofriendly and highly engineered materials of great interest to researchers for their versatile crystal structure and tunable composition, which contribute to exceptional electronic, optical, and catalytic properties. Herein, we have synthesized two different lead-free cobalt halide perovskites (CHPs), 0D-Cs4Co2Cl6 and 2D-Cs4Co2Cl8 nanocrystals, using a simple ultrasonication method (US) and a modified ligand-assisted reprecipitation method (LARP), respectively. In the LARP method, interestingly, a polar solvent (methanol) was employed here with a mixture of coordinating ligands such as oleic acid (OA) and oleylamine (OLA). The crystal formation and morphology of these CHP nanocrystals were confirmed by single-crystal X-ray diffraction (Sc-XRD) and high-resolution transmission electron microscopy (HR-TEM) analyses, respectively. Furthermore, these CHPs exhibited luminescent properties with a variable quantum yield (QY) of 6.11% for 0D- CHP and a QY of 7.23% for 2D- CHP, respectively. These characteristics enable their evaluation in bioimaging and apoptosis assays using HT-29 human colon carcinoma cells. Furthermore, as versatile materials, these two CHP nanocrystals were also investigated for the electrochemical determination of dopamine (DA), a neurotransmitter whose depletion is directly implicated in Parkinson’s disease, with a comparable limit of detection (LOD) of 0.76 μM (US) and 1.2 μM (LARP), respectively.