Modulation of Intermolecular Electrostatic Interactions by Anchoring Groups for Enhanced Upconversion Luminescence

Organic dye sensitization can enhance the upconversion luminescence of lanthanide‐doped nanoparticles, but dye aggregation on the nanoparticle surface often limits both loading capacity and energy transfer efficiency. In this study, we systematically compared the roles of carboxylic acids and sulfates anchoring groups in modulating dye aggregation and upconversion luminescence. Using core‐shell structured nanoparticles NaYF 4 :20%Yb 3+ ,2%Er 3+ @NaYF 4 :10%Nd 3+ /10%Yb 3+ (CS‐UNs) as carriers, we demonstrated that the carboxylic acid‐modified dye CyCO effectively inhibited H‐aggregation. Compared to the sulfate‐modified CySO, CyCO enabled a 3.5‐fold increase in the optimal loading ratio with CS‐UNs, leading to a 3.6‐fold enhancement in upconversion luminescence intensity. Spectroscopic analyses revealed that the carboxylic acid group weakened intermolecular electrostatic interactions, thereby reducing the aggregation tendency. This work offers a rational anchoring‐group strategy for designing high‐performance dye‐sensitized upconversion nanomaterials.