Enhanced Luminescence of a Quantum Dot Complex Following Interaction with Protein for Applications in Cellular Imaging, Sensing, and White-Light Generation

Herein, we report the sustainable, cost-effective, and greener surface modification strategy of a quantum dot complex (QDC)—comprised of zinc chalcogenide quantum dot (Qdot; for example, undoped ZnS and Mn2+-doped ZnS) and surface zinc quinolate (ZnQ2) complexes—following interaction with bovine serum albumin (BSA) protein. The interaction of BSA with QDC led to an enhancement in their luminescence properties (such as the quantum yield and emission lifetime), solubility, and stability (in water), compared to their bare form. The enhanced luminescence properties of BSA coupled with QDC—also termed herein as the BSA–QDC nanocomposite—are due to the BSA-induced structural rigidity of the ZnQ2 complex (being present on the surface of zinc chalcogenide Qdot). The highly green luminescent nontoxic BSA–QDC nanocomposite—consisting of undoped ZnS and the ZnQ2 complex—showed better imaging capability of HeLa cells in comparison to only QDC and sensing ability of an enzyme (trypsin) with a detection limit of 0.06 μM. Interestingly, the interaction of BSA to a dual-emitting QDC (consisting of orange-emitting Mn2+-doped ZnS Qdot and a green-emitting surface ZnQ2 complex) resulted in the generation of white light (which is hard to achieve from only dual-emitting QDC at λex = 330 nm), with chromaticity coordinates of (0.33, 0.35) and (0.29, 0.35), color rendering indexes of 86 and 80, and correlated color temperatures of 5646 and 7377 K, in liquid and solid phases, respectively. This may open up a new paradigm toward sustainable and user-friendly surface modification strategies for the fabrication of advanced nanoscale materials, with anticipated uses in imaging, sensing, and light-emitting applications.