Ir775

We purchased commercially available NIR dye (2-[2-[2-Chloro-3-[2-(1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)-ethylidene]-1-cyclohexen-1-yl]-ethenyl]-1,3,3-trimethyl-3H-indolium chloride), commonly known as IR775 from Sigma-Aldrich (USA, Inc.) and used it as received. Molecular structure of the dye is shown in Figure 1. Spectroscopic grade MeOH and CHCl₃ were purchased from Rankem, India. They were used without further purification. All the binary mixtures with IR775 dye were prepared by mixing these two solvents volume wise. We kept the solutions of IR775 in the binary mixture, in a cool and dark place before our steady-state and time-resolved study. All experimental data were recorded at room temperature (295 K).

Hybrid magnetic polymer nanoparticles were synthesized by the “oil-in-water” microemulsion method followed by solvent evaporation based on the method previously described by us with modifications [40 (link),41 (link),42 (link)]. A total of 12 mg PLGA (RG 858 S, lactide/glycolide 85:15, MW 190–240 kDa, Sigma, Darmstadt, Germany), 100 µL of oleate-stabilized magnetite, and 250 µg IR775 (Sigma, Darmstadt, Germany) in 300 µL of dichloromethane were added to 3 mL of 3% aqueous PVA (Mowiol 4-88, Sigma, Darmstadt, Germany) supplemented with chitosan oligosaccharide lactate with a final concentration of 1 g/L (5 kDa, Sigma, Darmstadt, Germany). The mixture was treated with ultrasound for 1 min. After solvent evaporation, the particles were washed thrice with centrifugation for 5 min at 5000× g and finally resuspended in 10 mM HEPES (pH 7.0).