Ultra-fast synthesis of carbon dots using the wasted coffee residues for environmental remediation

Currently, the coffee residues are one of waste resources which become a problem because the coffee consumption has increased. This is a worldwide problem due to the increase in disposal costs and environmental problems. Therefore, we use the wasted coffee residue which contains caffeine as starting material of carbon dot for solving disposal costs and environmental problems. The carbon dots were synthesized from coffee residues with different firing times by a facile and fast method. The emission peak of carbon dot is about 445 nm (cyan color) under 360 nm. The transmittance of the prepared carbon dot film reaches 90% which is high transparency. These results represent that carbon dot and carbon dot film can be applied for flexible display and optical application through recycling waste coffee residues. [Display omitted] •The structural and morphological properties of the prepared carbon dot using coffee residue were investigated.•The average size of the prepared carbon dots is about 6–7 nm.•The carbon dots show the intense green emission (532 nm) under excitation at 420 nm.