Green Synthesis of Carbon Dots toward Anti-Counterfeiting

Abstract

The synthesis of carbon dots (CDs) from green precursors has received considerable attention recently. However, most of the natural biomass-derived products without further surface treatment usually have quite low quantum yield (QY) varying in the range of 2–30%. Herein, we report the sustainable fabrication of highly fluorescent CDs from food waste, turtle shells, and demonstrate their applications in the fields of multisignal coding and anti-counterfeiting with a combination of colloidal photonic crystals (CPCs). We utilized turtle shells as precursors to synthesize fluorescent CDs via a simple pyrolysis method. The resultant CDs without further surface treatment have an absolute photoluminescence (PL) QY of 45% and high dispersibility in various solvents. Then, we realized collective optical properties with a combination of CDs and CPCs, including diffractive light abilities and fluorescence. CPC/CD bead codes with a structural color and fluorescence were prepared via a microfluidic device. CPC/CD patterned films with PL and angular dependence of structural colors were also constructed via a 3D microfluidic printing technique, which are useful for multisignal anti-counterfeiting and various optoelectronic applications.

Earth abundant colloidal carbon quantum dots for luminescent solar concentrators

“…56,76,[93][94][95] Many precursors from biomass have been used to produce C-dots via pyrolysis reactions. 56,76,[93][94][95] For instance, Martindale's group reported the synthesis of C-dots by pyrolyzing CA at 180 1C with a yield of 45% and a size of 6.8 AE 2.3 nm. 93 Wang et al reported the large-scale and controllable synthesis of C-dots with a yield of 15% from rice husk.…”

Fabrication of Structural-Coloured Carbon Fabrics by Thermal Assisted Gravity Sedimentation Method

“…The bandgap derived from highly ordered periodic structures is responsible for uniformly reflected colours in the visible spectrum. Accordingly, a variety of techniques, like photolithography [ 4 ], screen printing [ 5 ], atomisation deposition [ 6 ], inkjet printing [ 7 , 8 ], spray coating [ 9 , 10 ], gravity sedimentation [ 11 , 12 ], and electrophoretic deposition [ 13 , 14 ], have been proposed for the adhibition by applying photonic crystals onto substrates in several applications, including paints and inks [ 5 ], smart windows [ 3 ], energy-saving devices [ 15 ], night-time traffic safety and advertisement display [ 16 ], anti-counterfeiting security [ 4 , 17 , 18 ], eyeglasses and photographic lenses [ 19 ], and information storage [ 20 ]. To realise such promising industrial applications, the studies on the large-area scalable fabrication technique of photonic crystals have been conducted, including melt-shear organization method [ 21 ] and oscillatory shear technique [ 22 ].…”

“…In this work, we propose the use of a novel material for traffic warning displays in both sunny and rainy days. The previously published literatures have provided evidence that Poly(St-MMA-AA) copolymer photonic crystal arrays exhibited brilliant structural colours after a self-assembly process [ 18 , 26 , 27 , 28 , 29 ], which was generally synthesised by emulsion polymerisation that was based on the kinetic principles of free radical-initiated vinyl addition polymerisation [ 30 ]. There have been a few attempts at the study of achieving the stimuli-responsive behaviour of the photonic crystal films for amplifying their potential applications as sensing materials [ 31 , 32 , 33 ].…”

Carbon Dots Derived from Facile Tailoring of Shaerhu Lignite as a Novel Fluorescence Sensor with High‐Selectivity and Sensitivity for Cu2+ Detection

“…Coals contain both nanoscale aromatic carbon (NSAC) and aliphatic amorphous carbon . So, coals can be the ideal source of carbon for preparing carbon quantum dots if these domains exfoliate in an efficient way to form a carbon quantum dot …”

“…Synthetic ways including “bottom‐up” or “top‐down” approaches have been used to prepare FCDs from small organic molecules and other carbon‐containing precursors. The “top down” approach is effective for low cost carbon sources such as graphite, fullerene, graphene oxide, carbon nanotubes, and carbohydrates . This method uses H 2 SO 4 , HNO 3 , KMnO 4 , and other strong acids and oxidantsto exfoliate FCDs, and suits large‐scale solution‐processing from easily‐acquired cheap carbon sources .…”