Preparation of Multicolor Biomass Carbon Dots Based on Solvent Control and Their Application in Cr(VI) Detection and Advanced Anti-Counterfeiting

Abstract

Multicolor fluorescent carbon dots (CDs) have received widespread attention due to their excellent fluorescence performance and promising prospects in anti-counterfeiting and sensing detection. To date, most of the multicolor CDs synthesized are derived from chemical reagents; however, the overuse of chemical reagents during the synthesis process will pollute the environment and limit their application. Herein, multicolor fluorescent biomass CDs (BCDs) were prepared by a one-pot ecofriendly solvothermal method, with spinach as the raw material based on solvent control. The as-obtained BCDs can emit blue, crimson, grayish white, and red luminescence, and their quantum yields (QYs) are 8.9, 12.3, 10.8, and 14.4%, respectively. The results of the characterization of BCDs reveal that the regulating mechanism for multicolor luminescence is mainly ascribed to the change of the boiling point and polarity of solvents, which changes the carbonization process of polysaccharides and chlorophyll in spinach, resulting in the altered particle size, surface functional groups, and porphyrin luminescence properties. Further research reveals that blue BCDs (BCD1) show an excellent sensitive and selective response to Cr(VI) in a concentration scale of 0–220 μM with a detection limit (LOD) of 0.242 μM. More importantly, the intraday and interday relative standard deviation (RSD) values were less than 2.99%. The recovery rate of the Cr(VI) sensor for tap water and river water is 101.52–107.51%, which indicates that the sensor has the advantages of high sensitivity, selectivity, rapidity, and reproducibility. Consequently, different multicolor patterns are obtained by using the obtained four BCDs as fluorescent inks, which exhibit beautiful landscape and advanced anti-counterfeiting effects. This study provides a low-cost and facile green synthesis strategy for multicolor luminescent BCDs and proves that BCDs have broad application prospects in ion detection and advanced anti-counterfeiting.

Carbon Dots: A Bright Future as Anticounterfeiting Encoding Agents

“…As the excitation was removed, due to the different fast and slow lifetimes of the blue emission on composites, some of the word letters disappeared, and after only 25 s the final word "on" was revealed, corresponding to the slower blue emitting composites (CDs@SiO 2 -600, and CDs@SiO 2 -550). A similar strategy was applied to a QR code, in which the composites (CDs@SiO 2 -600, and CDs@SiO 2 -550) were used only in certain areas of the code, to produce an unreadable code, which turned into a complete code after 20 s. [85] In another work with a green approach scheme, Wang et al [101] prepared a CDs solution by a solvothermal treatment of spinach as carbon precursor in water (BCD1), ethanol (BCD2), acetone (BCD3), and a mixture of the last two (BCD4). The four samples exhibited strong absorption bands in the UV region (240-280 nm) corresponding to the 𝜋→𝜋* electronic transition of the C═C bond.…”

“…Reproduced under terms of the CC‐BY‐NC‐ND 4.0 license. [ 101 ] Copyright 2023, American Chemical Society. E) Anticounterfeiting patterns (left under sunlight; right under UV light) Reproduced with permission.…”

“…D) Digital photographs of security patterns with CDs-based inks under 254 and 365 nm UV light. Reproduced under terms of the CC-BY-NC-ND 4.0 license [101]. Copyright 2023, American Chemical Society.…”

Comprehensive advances in the synthesis, fluorescence mechanism and multifunctional applications of red-emitting carbon nanomaterials

“…The team used the as-synthesized carbon dots for the anticounterfeiting and the sensing of Cr 6+ . 109 Tariq et al reported microwave-assisted fig biomass extracted red emissive carbon dots, which exhibited excellent antibacterial properties and were used as a antibacterial agent for the diagnosis of bacterial infection. 110 Yang et al developed glutathione-supported waste tobacco leaf-derived red emissive fluorescent carbon dots via a simple hydrothermal method.…”

One-step solvothermal synthesis of full-color fluorescent carbon dots for information encryption and anti-counterfeiting applications

“…Using three natural biomasses, honeysuckle, turmeric and perilla leaves, respectively, as precursors, Zhao et al 40 prepared blue, green and red carbon nanodots by an ultrasound-assisted method at room temperature, which can be used effectively in bacterial imaging. Wang et al 41 synthesized four biomass CDs (BCDs), blue, crimson, grayish white, and red, with QYs of 8.9%, 12.3%, 10.8%, and 14.4%, respectively, by varying the reaction solvents using green spinach leaves as the carbon source. The results revealed that changes in the boiling point and polarity of solvents altered the carbonation process of polysaccharides and chlorophylls in spinach, which further led to changes in particle size, surface functional groups and porphyrin luminescence properties.…”