Synthesis of multi colour emissive tunable carbon dots: anti-counterfeit and optoelectronic applications

Abstract

The tunable photoluminescence (PL) carbon dots (CDs) are synthesized using one-pot solvothermal techniques by varying the –NH2, -COOH, and –CH2- ration on the precursor. The carbon dots were synthesized by using 1, 2, 3, 4- butanetetracarboxylic acid (BTC) along with two groups of reagents: (group 1) aromatic compound by varying the NH2: COOH ratio, (group 2): By varying the –CH2- on the non-aromatic compound. These carbon dots show white (ABA-CD, ED CD), purple (AIA-CD), blue (PPD-CD, HYD-CD), and cyan (DBA-CD) colour fluorescence under a single wavelength UV light. The as-obtained carbon dots are further characterized by using 1H NMR, 13C-NMR, MS, FTIR, UV-Vis, and PL. The synthesized carbon dots show an optimal fluorescence quantum yield of 37.41% for purple colour emitting carbon dot AIA-CD. The red shift photoluminescence emission behaviour of purple (AIA-CD), blue (PPD-CD), and cyan colour (DBA-CD) emitting carbon dots can be attributed to the reduction in the bandgap energy from 4.14 to 3.52 to 3.46 eV respectively. Further, the ESI-MS, and 13C-NMR shows that carbon dots can possibly have polymeric structure, and are formed by condensation, and dehydration reactions, along with that carbon dots formed with group 2 precursors have more percentage of sp3 carbon domains as compared to the carbon dots from group 1. The synthesized carbon dots are further used to manufacture a UV Converting torch which is first of its own kind including white light. Further, due to stability, invisibility under daylight, and low cost these carbon dots are further used for anti-counterfeiting, and information storage applications.