Development of graphitic-N-based carbon dots using solid-state synthesis for fingerprinting, LEDs, and anticounterfeiting

Abstract

Red-color emitting carbon dots (CDs) are of tremendous interest in the field of materials discipline owing to their promising applications in the domains of forensic applications, lighting, fingerprinting, imaging, sensing, etc. However, the unavailability of mass production of red-emitting CDs restricts their potential uses. As a result, we used a solid-state approach for producing red-color emitting CDs. The benefits of synthesized CDs include large-scale manufacturing, red-color fluorescence in the aggregated state, and afterglow emission. Surprisingly, the developed CDs showed phosphorescence without aggregating any matrix. The fluorescence and phosphorescence emissions were observed at 574 and 585 nm, respectively. The presence of graphitic-N is responsible for red-color emission; simultaneously, it seems that nitrogen helps in extending the sp²-conjugation. Mutually, the CN bond and strong π–π interactions in the aggregated form are responsible for stabilizing the excited triplet state. The carbon dot powder displayed unchanging phosphorescence with a lifespan of 43.71 ms. Further, the produced CDs have been used in anticounterfeiting, latent fingerprint detection, and in solid-state lighting. It is worth noticing that synthesized carbon dots detect even the third level of fingerprint patterning. In lighting, the obtained CIE coordinate is (0.40, 0.37) with a CRI of 98.