In-situ green synthesis of nitrogen-doped carbon dots for bioimaging and TiO2 nanoparticles@nitrogen-doped carbon composite for photocatalytic degradation of organic pollutants

Abstract

As an efficient photocatalytic titanium dioxide nanoparticles@nitrogen-doped carbon (TiO2 NPs@C) nanocomposite and bright fluorescent with good biocompatible nitrogen-doped carbon dots (N-CDs) were synthesized at once by an affordable hydrothermal method. Physicochemical properties of the synthesized materials were examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) with energy dispersive X-ray (EDX) and elemental mapping analysis, high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), ultraviolet–visible (UV–vis) spectroscopy and fluorescence spectroscopy. The photocatalytic efficiency of synthesized TiO2 NPs@C nanocomposite was evaluated in the degradation of methylene blue (MB) under UV-light irradiation. The degradation efficiency of TiO2 NPs@C nanocomposite is about 90% when extending the irradiation time to 40 min, the rate constant is 5 times higher than that of bare TiO2 NPs. The augmentation of photocatalytic activity of TiO2 NPs@C nanocomposite was attributed to the synergistic effect between TiO2 NPs and graphene-like carbon within the nanocomposite. The recycling studies were conducted and the photodegradation efficiency of TiO2 NPs@C nanocomposite did not show any significant changes up to three cycles, suggesting that the synthesized photocatalyst has good repeatability and the considerable stability. In addition, the carbon derived from a natural green source possesses the hydroxyl and nitrogen-containing functional groups on the surface which resulting TiO2 NPs @C nanocomposite with high photocatalytic activity. Also, the obtained N-CDs displays almost zero toxicity towards the Candida albicans cells even at high concentrations which can be utilized as a powerful in-vitro label-free fluorescent probe for live cell imaging. Based on their bright with stable fluorescence and cellular imaging with good biocompatibility, N-CDs would offer a great potential for a wide range of applications in the biomedical and clinical applications in the near future.