Latent fingerprints identification and ink-free printing of fluorescent lignin-derived CDs/PVA nanocomposite with multi-stimuli responsive shape memory behavior

The development and comparison of latent fingerprint (LFP) are crucial for the detection and identification of LFP. However, research on stable, clear, and no background interference’s fluorescent materials for LFP recognition are scarce. In this study, lignin-derived carbon dots (CDs) with orange red emission were synthesized and combined with polyvinyl alcohol (PVA) matrix for identification of LFP and ink-free printing. The physicochemical and microstructure of the CDs and CDs/PVA nanocomposite have been precisely elucidated by TEM, FT-IR, XPS, SEM, and TGA to verify the reaction of CDs with PVA forming hydrogen bonds. The effect of CDs on the mechanical properties of PVA nanocomposite was studied. The tensile strength and elongation at break of PVA nanocomposite were increased by 113.01 % and 175.26 %, respectively. The shape memory and fluorescence properties of CDs/PVA nanocomposite were studied under different conditions such as water, acid, alkali and heat. The fluorescence intensity of CDs/PVA nanocomposites was enhanced due to the deprotonation of CDs surface under alkaline conditions. By coating CDs/PVA solution on LFP, a stable fluorescent fingerprint with clear ridge details was formed on the composite film, and it is applied to letterpress printing and gravure printing, enabling personal identification and ink-free printing. Obviously, the nanocomposite film prepared herein has multiple functions, providing potential for the design and manufacture of advanced all-round personal information identification and encryption applications in extremely harsh high temperature and strong alkaline environments.