Environmentally friendly g-C3N4/carbon quantum dots nanocomposites as fluorescent and anti-spoofing inks

Abstract

The major goal of this research is to examine fluorescence (FL) features and application of graphitic carbon nitride/carbon quantum dots (GCN/CQD) nanocomposites as invisible and anti-spoofing inks. GCN/CQD nanocomposites were used for an environmentally friendly synthesis method. To achieve this, starch and urea were, respectively, applied as a natural source of carbon and a nitrogen resource. The mixtures of starch and urea with a weight ratio of 1:5 and 1:10 were synthesized using a two-step pyrolysis and microwave-assisted method. FL behavior of the GCN/CQD aqueous colloids indicated that a change in the urea concentration could result in FL emission in the various areas of visible light. FL emission spectra of the synthesized sample with low amount urea and in the sample including extra urea were, respectively, observed at blue and green regions. Anti-spoofing function of these nanocomposites as inks were confirmed via optical spectroscopy testing and digital photos taken from UV cabinet. The photos and patterns taken from the ink made of GCN/CQD nanocomposites are nearly invisible under daylight but clear and observable open to UV, as a result one could conclude that these are potentially usable in anti-spoofing function of the secure inks.