Solvent Assisted Synthesis of Nitrogen and Sulfur Doped Blue and Yellow Emissive Carbon Dots and Their Applications as a Selective Cr(VI) Sensor and Patterning Agent

摘要

Preparation of heteroatom doped fluorescent carbon dots (CDs) and their applications in sensing and bio-imaging are showing growing interest. Herein, we report microwave-assisted preparation of CDs using citric acid as carbon source and cysteine as nitrogen and sulfur source using water and formamide as solvent. CDs obtained using water as solvent exhibited blue emission (B-CDs), whereas formamide as solvent yielded yellow emissive CDs (Y-CDs). Doping of nitrogen and sulfur in CDs enhanced their fluorescence intensity substantially. The ion sensing study revealed that B-CDs detect Cr(VI) with high selectivity and sensitivity in water, it has also been successfully tested with real samples following spiked method. The mechanistic study suggests that the 'Inner Filter Effect' is the main reason of fluorescence quenching of B-CDs in presence of Cr(VI). For field application, agarose based sensing strips were prepared using B-CDs and successfully tested. The CDs are also successfully tested as patterning agent.