Thiolactone ring dynamics in dimeric lipids enable pH-switchable supramolecular tuning in surface-engineered quantum dots

Abstract

Surface functionalization of semiconductor nanocrystals with stimuli-responsive ligands provides a powerful platform for designing adaptive nanomaterials for biomedical and optoelectronic applications. In this work, we present a novel strategy for engineering quantum dot (QD) surfaces using thiolactone ring-opening and closing chemistry to enable reversible, pH-sensitive assembly. Gemini-type dimeric lipids, palmitoyl homocysteine (diPHC or GPHC), were employed as ligands that engage in dynamic thiolactone interactions with CdSe/ZnS core–shell and CuInZnS₂ (CIZS) alloyed QDs. These pH-dependent thiolactone bonds undergo intramolecular cyclization and cleavage, leading to reversible surface reorganization and tunable supramolecular self-assembly of lipidated QDs (LQDs). The resulting LQDs maintain excellent colloidal and photostability under aqueous and serum-rich conditions, with consistent fluorescence retention across pH cycles. Compared to monomeric lipid coatings, diPHC-functionalized QDs exhibit enhanced stability and responsiveness, attributed to cooperative multivalent interactions and improved membrane-like packing. Transmission electron microscopy confirms reversible aggregation without compromising nanocrystal core integrity. Dynamic light scattering validates pH-modulated size transitions. This thiolactone-mediated approach enables dynamic, modular, and environmentally responsive nanomaterials for sensing, delivery, diagnostics, and energy applications.