Research on chalcogenide-based quantum dots (QDs) has advanced significantly over recent decades, largely due to their excellent optical properties, particularly photoluminescence, and relatively low toxicity. Among these, Cu₂S and CuS quantum dots have demonstrated notable photothermal effects and antibacterial activity, making them promising candidates for various biomedical applications, including cancer treatment. This study focuses on the synthesis of CuS and Cu₂S quantum dots functionalized with bovine serum albumin (BSA), marking an important step toward their potential biomedical use. The functionalization was achieved through a one-pot synthesis method, characterized by its ability to offer higher chemical yield, elimination of toxic solvents, and provide a method that is simple, economical, and well-controlled. This synthesis produced four samples with varying BSA concentrations. Due to the lower protein concentration, which provides fewer nucleation sites, sample A (BSA concentration 5 mg ml⁻¹) showed a particle size distribution over 100 nm and low stability over time. Sample B (25 mg ml⁻¹ BSA) and C (50 mg ml⁻¹ BSA) showed excellent stability and particle sizes within the expected range for Cu₂S and CuS quantum dots (<2.4 nm). Sample D was synthesized with lower BSA concentration (2.5 mg ml⁻¹) and was used only for comparison in few analyses. Fourier-transform infrared (FTIR) spectroscopy confirmed the structural integrity of BSA after functionalization, while x-ray diffraction (XRD) analysis verified the formation of CuS and Cu₂S crystals. Additional tests, including fluorescence and UV–vis spectroscopy, validated the optical properties of the quantum dots. Transmission electron microscopy (TEM) confirmed crystalline structure of the CuS and Cu₂S quantum dots, with particle size measurements aligning with expectations. Finally, MTT assays confirmed that the synthesized quantum dots are non-toxic, further supporting their potential for biomedical applications.

Silver sulfide quantum dots (Ag₂S QDs) are promising nanomaterials for biomedical applications due to their near-infrared emission and biocompatibility. In this study, Ag₂S QDs were synthesized using bovine serum albumin (BSA) as a stabilizing and reducing agent to assess their potential in targeted photothermal therapy. The QDs showed an average size of 1.06 ± 0.38 nm by DLS and 4.42 nm by TEM. Conjugation to an anti-PSG1 monoclonal antibody was performed via EDC/Sulfo-NHS chemistry and confirmed by FTIR spectroscopy, a decrease in zeta potential, and a redshift in emission. The conjugate exhibited an average size of 22.82 ± 9.7 nm and a zeta potential of +85.7 mV, indicating high colloidal stability. Fluorescence studies showed that the conjugate emits at 590 nm when excited at 560 nm, whereas the BSA-Ag₂S QDs (non-conjugated) emit at 480 nm upon excitation at 400 nm, reflecting changes in optical properties due to conjugation. Thermal imaging under 808 nm laser irradiation revealed efficient photothermal conversion, with temperature increases up to 13.6 °C at 200 μg/mL and a conversion efficiency of 11.41 ± 0.04%. The conjugate was non-cytotoxic to fibroblasts but induced selective cytotoxicity in HeLa cells after laser exposure, with a selectivity index of 3.0. These findings suggest that Ag₂S-BSA QDs conjugated with anti-PSG1 represent promising candidates for further investigation in cancer nanotheranostics.

Black titanium dioxide nanoparticles (bTiO₂ NPs) have emerged as promising materials for light-driven applications due to their extended optical absorption and reduced environmental concerns compared with heavy-metal-based quantum dots. In this work, bTiO₂ NPs were synthesized via a simple, low-cost, and environmentally friendly one-pot aqueous method. X-ray diffraction analysis confirmed the formation of the anatase TiO₂ phase. Transmission electron microscopy (TEM) was used to determine the particle size finding a value of 10.3 ± 3.4 nm. The colloidal dispersion exhibited a positive zeta potential of +47.5 mV, indicating favorable electrostatic stabilization. Optical characterization revealed strong UV absorption at 280 nm, together with a pronounced NIR absorption band centered at approximately 804 nm, consistent with optical transitions associated with sub-band gap electronic states. The analysis of X-ray photoelectron spectroscopy (XPS) to the Ti 2p core-level confirmed the presence of 7.3% of Ti³⁺ species that can explain the NIR absorption. Photoluminescence analysis showed an emission band at 430–433 nm. Under 808 nm NIR irradiation, with an initial temperature of 37 °C, the bTiO₂ NPs exhibited pronounced photothermal heating, reaching a maximum temperature increase of 30.2 °C and a photothermal conversion efficiency of 21.6%. The photothermal response increased with nanoparticle concentration under the evaluated experimental conditions, demonstrating concentration-dependent NIR photothermal heating. In vitro cytotoxicity assays showed high cell viability at the lower concentration tested, exceeding 100% at 50 µg/mL, whereas cell viability decreased to approximately 60% at 500 µg/mL. Overall, these results indicate that the synthesized bTiO₂ NPs exhibit extended NIR absorption, concentration-dependent photothermal heating, and concentration-dependent effects on cell viability, supporting their potential for further investigation as photothermal nanomaterials.