Green approach to synthesize functional carbon nanoparticles at low temperature

•Carbon nanoparticles were synthesized with tomato extract.•Carbon nanoparticles were formed at 60 °C and under atmospheric pressure.•The mild reaction conditions reduce the energy consumption desired in green synthesis.•The particles detected zinc and presented infrared photothermal response. Carbon nanoparticles have demonstrated their potential to develop materials with advanced applications in which their luminescence and biocompatibility are exploited. In the search for sustainable methods to produce these nanoparticles, natural carbon sources such as plant- and animal-based products and by-products have been used. However, the existing procedures are still performed with high temperature, high pressure, and long reaction times. This report proposes a method to synthesize carbon nanoparticles using a tomato extract as the carbon source, followed by precipitation and calcination at a maximum of 60 °C under atmospheric pressure. This calcination temperature is the lowest reported and contributes to establishing a greener synthesis route. The detected fluorescence of these particles covers the entire region of the visible spectrum. The emission intensity is sensitive to zinc cations, demonstrating that this green method produces useful particles in detecting heavy metals similar to those reported by traditional methods. Furthermore, the aqueous solutions of these particles are photothermic when they are irradiated with red light, also showing their usefulness in biomedical developments. Therefore, this green synthesis at a very low temperature contributes to improving the green methods and boosts the sustainable development of advanced functional materials. [Display omitted]