Optimization of Preparation Technology for PET-Based Carbon Dots by Response Surface Method and Its Application.

The preparation of polyethylene terephthalate(PET)-based Carbon Dots (PET-CDs) using one-step hydrothermal method with PET waste, pyromellitic acid (PMA) and ammonia (NH·HO) as precursors is a high-value utilization strategy for PET waste, offering significant application potential. To achieve efficient recycling of PET waste, response surface methodology was adopted for to optimize the precursor ratio during the synthesis of PET-CDs with fluorescence quantum yield (QY) as the key performance indicator. The optimal preparation conditions were determined to be: 1.180 g of PET, 3.287 g of PMA, 8.969 mL of NH·HO, a reaction temperature of 260 °C, and a reaction time of 12 h. The as-prepared PET-CDs exhibit excitation-independent emission properties in the range from 360 nm to 440 nm, with the optimal excitation wavelength of 410 nm and the optimal emission wavelength was 485 nm, resulting in a QY of 83.34%. Structurally, PET-CDs exhibit a spherical morphology, featuring amino and carboxyl groups on their surface, with the particle size ranging from 1.61 to 4.92 nm and an average particle size of 2.88 nm. The prepared PET-CDs can be utilized in light-blocking films (LBFs) and fluorescence anti-counterfeiting technologies. The intensity of light passing through the LBFs significantly is decreased in the ultraviolet and blue light wavelength ranges, with performance comparable to commercial anti-blue light glasses. Additionally, the PET-CDs solution can be adopted for printing patterns that are visible under ultraviolet excitation and are not visible in visible light, demonstrating that PET-CDs can be employed in fluorescence anti-counterfeiting measures.