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Gd 3+ - free carbon dots (CDs) were synthesized by one-step solvothermal method using urea, citric acid and 3-(trifluoromethyl)aniline as precursors. Additionally, Gd 3+ -doped CDs were prepared by incorporating gadolinium chloride (Gd 3+ ions) into the synthesis. Size selection of the purified CDs was achieved through filter membranes ranging from 3 kDa to 100 kDa. The chemical composition and optical properties of the obtained samples were characterized by Energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR), Dynamic Light Scattering (DLS), proton relaxation time measurements, Ultraviolet-visible (UV-vis) and fluorescence spectroscopies. A comparative analysis revealed a strong size-dependent behavior in the optical properties of both Gd 3+ -doped and Gd 3+ -free CDs. Furthermore, in vitro tests confirmed the non-cytotoxicity of Gd 3+ -doped CDs, indicating their potential applicability in biomedicine for magnetic resonance imaging (MRI) and red fluorescence-based cell and tissue imaging., Competing Interests: Declarations Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Hybrid nanopowder based on silicon nanoparticles (Si NPs) decorated with carbon NPs was prepared by high-temperature treatment of the oxidized surface of porous Si NPs impregnated with a carbonaceous precursor. The Si NPs decorated by carbon NPs and carbon nanostructures (CNs) were studied with TEM. The surface chemistry for hybrid NPs was characterized by the TPD MS method, and carboxyl, lactone, and phenol groups were found. The CNs and carbon NPs influence the electric response of a sandwich structure that was prepared using the hybrid NPs modified with palladium NPs and then was tested to measure the concentration of hydrogen in nitrogen-hydrogen gas mixtures. The sandwich structure showed reasonable stability of the electrical response, presumably due to the formation of a specific sensitive layer. [ABSTRACT FROM AUTHOR]

A novel sensing system was designed for pH measurements based on the enhanced and quenched photoluminescence (PL) and UV–Vis absorption of the diluted water solutions of F-, O-, and N-containing carbon nanoparticles (FON-CNPs). These FON-CNPs were solvothermally synthesized, dissolved, ultra-filtrated, and separated by thin-layer chromatography. The total fluorine content in them was found to be 1.2–1.5 mmol per gram. Their TGA showed a total weight loss of 52.7% because of the thermal decomposition and detachment of the surface groups and the partial burning of the functionalized shell on the carbon core at temperatures below 1200 °C. TEM and Raman data confirmed the presence of graphitic structures in the carbon core. From the results of ATR FTIR and UV–Vis spectroscopies, we showed that a carbon shell incorporates different functional groups covering the carbon core. The surface groups of the carbon shell include carboxyl, phenolic, and carbonyl groups. Heterocyclic N-containing and amino groups and trifluoromethyl groups supporting the hydrophobicity were also found. We suggested the possible reasons for the pH responses obtained with the sensing system considering them dependent on the de-protonation of functional groups with pH change. [ABSTRACT FROM AUTHOR]