Preparation Of Fluorescent Ink Based On Graphene Quantum Dots And Its Application In Fluorescent Anti-counterfeiting

With the rapid development of science and technology,people gradually realize the importance of information authenticity and safe storage,and the demand for developing new anti-counterfeiting materials and technologies is becoming increasingly urgent.Fluorescent anti-counterfeiting is the most widely used anti-counterfeiting technology.It has the advantages of simple operation,time-saving and strong anti-counterfeiting performance.Graphene quantum dots?GQDs?,as a new type of carbon-based fluorescent nanomaterials,have the advantages of strong surface modification,low toxicity,low pollution,low cost and good photostability compared with traditional photoluminescent semiconductor quantum dots and organic fluorescent dyes,and have potential application value in the field of fluorescent ink.In this paper,one or more fluorescent colors of GQDs were prepared into fluorescent ink,and various anti-counterfeiting patterns were obtained by writing or printing.The anti-counterfeiting pattern provided a convenient anti-counterfeiting method by showing fluorescent information at a specific excitation wavelength,so as to achieve the purpose of simple anti-counterfeiting.In addition,nitrogen-sulfur co-doped graphene quantum dots?N,S-GQDs?were used as fluorescent anti-counterfeiting materials to design stimuli-responsive information storage and anti-counterfeiting technologies.The composite fluorescent ink was prepared by combining N,S-GQDs and rare earth lanthanum complexes to achieve a more advanced multi-anti-counterfeiting effect.Specific research contents were summarized as following:?1?One-step preparation method of N-doped graphene quantum dots?N-GQDs?was established based on molecular fusion with 1,3,6-trinitropyrene and triethylamine in a solvothermal process.N-GQDs had good salt resistance,photostability and solubility in ethanol,so oily fluorescent ink had been successfully prepared by us,and their applications in fluorescent anti-counterfeiting were investigated.The written or printed words and patterns with N-GQDs based oily fluorescent ink could be dried instantaneously,and bright fluorescent pattern with good light stability displayed under UV light irradiation.In addition,N-GQDs were further used in the preparation of fluorescent powders and fluorescent hydrogels,exhibiting great fluorescence.?2?Using nitrogen-doped graphene quantum dots?N-GQDs?as blue fluorescent ink,hydroxy-graphene quantum dots?OH-GQDs?as green fluorescent ink,and nitrogen-doped carbon dots?N-CDs?as red fluorescent ink,we designed a multicolor fluorescent printing anti-counterfeiting technology based on three kinds of carbon quantum dots.Fluorescent inks made of three carbon quantum dots were used for inkjet printing,and the obtained fluorescent pattern could achieve color encryption in daylight,and a bright fluorescent pattern displayed under 365 nm UV light to realize color decryption.Therefore,the fluorescent anti-counterfeiting performance and visual aesthetics were further improved.In addition,a variety of color fluorescent patterns were printed by using the three fluorescent inks,and exhibited good fluorescence stability for long-term storage.?3?Using Nitrogen-sulfur co-doped graphene quantum dots?N,S-GQDs?as fluorescent material,we investigated its applications in information security storage and fluorescent anti-counterfeiting.Invisible N,S-GQDs/Cu²⁺fluorescent ink was prepared by the combination of N,S-GQDs and its fluorescent quencher Cu²⁺.The fluorescence of N,S-GQDs could be restored by using the stimulant cysteine?Cys?through forming complex with Cu²⁺.Based on this principle,a stimuli-responsive information storage and anti-counterfeiting technology was designed.In addition,N,S-GQDs/Cu²⁺/Eu³⁺DP composite fluorescent inks were prepared by incorporating rare earth Eu³⁺DP complex emitting red fluorescence into N,S-GQDs/Cu²⁺ink.Using Cys as a stimulator,citric acid?CA?that could quench the red fluorescence of Eu³⁺DP was introduced as a second stimulator.With the input sequence of the stimulant as the input signal and the corresponding trace of fluorescent color change path as the output signal,a fluorescent anti-counterfeiting technology similar to the password lock function could be realized,presenting a more advanced multi-anti-counterfeiting effect.