Synthesis of Dual Emissive Carbon Quantum Dots for Sensing Applications

Abstract

Carbon quantum dots (CQDs), a new class of nano-material with unique optical property and have great potential in various applications. This work demonstrated the possibility of tuning the emission wavelength of CQDs by simply changing the acid type used during synthesis. In particular, a mixture of sulfuric and phosphoric acids were used to carbonize the same starting precursor, sucrose. This resulted in the isolation of CQDs with green (434 nm) and yellow (520 nm) emission when excited at 350 nm. Solvatochromic effects was studied systematically using photoluminescence spectra (PL) and the origin of PL shifts of the CQDs in different solvents was discussed in regard to the contribution from hydrogen bonding and dipole–dipole interactions. A turn-on/off strategy was proposed for specific recognition of melamine. Initially on the basis of energy transfer process, selectivity of the CQDs was investigated towards different cations. CQDs were found selective only for Fe3+ ions. The sensitivity of CQDs-Fe3+ ions system was also evaluated for melamine detection and found that CQDs-Fe3+ ions mixture was selective for melamine.