Red-Emissive Carbon Dots for Fingerprints Detection by Spray Method: Coffee Ring Effect and Unquenched Fluorescence in Drying Process

Abstract

Brightly red fluorescent carbon dots are synthesized hydrothermally and dissolved in diluted hydrochloric acid solution. Such carbon dots exhibit excitation-independent emission at about 620 nm with quantum yield over 10%, which is visible in daylight. After the carbon dots solution is sprayed to the fingerprints on various solid substrates and dried in air, clear fingerprints can be seen under an ultraviolet lamp and stay stable for 1 day. Detailed characterizations suggest that during the drying process, the coffee-ring effect and the electrostatic interactions between the carbon dots and the fingerprint residues prevent the typical aggregation-induced fluorescence quenching of carbon dots.

One‐Step Hydrothermal Synthesis of Nitrogen‐Doped Conjugated Carbonized Polymer Dots with 31% Efficient Red Emission for In Vivo Imaging

“…Interest in carbon dots (CDs) has increased in recent years due to their simple manufacturing process and unique properties, such as high quantum yield (QY), low toxicity, excellent water solubility, small size, high photostability, and so on . Therefore, they have wide potential applications in many fields, including fluorescent ink, bioimaging, antibacterial activity, optoelectronic devices, and more . However, most of the known CDs show blue light to green light emission under the excitation of ultraviolet (UV) light or blue light, which restrict their further applications in biomedicine and in optoelectronic devices.…”

Orange‐Emissive Carbon Quantum Dots: Toward Application in Wound pH Monitoring Based on Colorimetric and Fluorescent Changing

“…Despite the lower intensities, another absorption band appeared in the high‐energy region at 238 nm was related to the π–π* transition of the aromatic sp 2 bond . In addition, a distinct absorption band from 375 to 485 nm was also observed in the lower‐energy region; such absorption characteristic is usually considered to originate from the defect states caused by the functional groups on the CDs surfaces; the presence of defect states within the structures of O‐CDs can also be confirmed by the size independent PL emission. The excitation spectrum obtained at 575 nm was recorded to verify the possible luminescent centers; it is clear that the O‐CDs possess two distinct optimum excitation bands.…”

“…Unlike the semiconductor quantum dots with size‐dependent PL emission, the O‐CDs behaving an excitation‐independent orange emission could be highly related to the surface state rather than the size effect, because the O‐CDs had a relatively wide size distribution. This size independent emission behavior is very common for the CDs synthesized following “bottom‐up” route using carbon‐contained small molecules . Furthermore, the superior optical properties of O‐CDs in aqueous solution were examined from UV–vis absorption spectrum, as displayed in Figure B.…”

Nanoparticles used for fingermark detection—A comprehensive review

“…Instead of immersing the substrate into a solution, two different groups tried to spray the C‐dots (J. Chen et al, ; C. Wang, Zhou, et al, ). Chen et al used red‐emitting C‐dots in a 0.1 M hydrochloric acid solution (J. Chen, Wei, et al, ). Luminescent fingermarks were obtained on glass, aluminum, leather, and plastic, but no information was provided regarding the type and age of the detected impressions.…”