The formation mechanism and chirality evolution of chiral carbon dots prepared via radical assisted synthesis at room temperature

Abstract

We report on a Cu(II) catalyzed process for the production of cysteine based chiral carbon dots, the process does not require any thermal treatment and the carbon dots formation is...

Chiral carbon dots: synthesis, optical properties, and emerging applications

“…Achievements of synthetic chemistry combined with the rapid development of nanotechnology opened up an opportunity to produce a wide range of artificial chiral objects at nanoscale 6 , 9 , 87 , 88 . Among them, chiral semiconductor quantum dots 89 , 90 , perovskite nanocrystals 91 , 92 , metal nanoparticles 93 , 94 as well as chiral carbon dots and chiral graphene quantum dots 53 , 95 have been reported. In these nanostructures, optical activity can be introduced via several pathways.…”

“…Branzi et al studied the formation mechanism of cysteine-based chiral carbon dots produced at room temperature in a reaction catalyzed by copper(II) salts 95 . The formation process of chiral carbon dots was claimed to be influenced by several features of cysteine molecules: free thiol groups took part in redox reactions and resulted in the formation of radical species; amine and carboxylic functional groups enhanced stability of the oxidized state; and hydrogen atoms assisted in radical hydrogen transfer reactions forming carbon-centered radicals.…”

“…Figure 5f shows that the synthesis of chiral carbon dots from either L- or D-cysteine indeed resulted in formation of both enantiomers as can be seen from opposite signs of the CD signal, as well as an increased ratio of the chiral precursor (cysteine) to citric acid precursor leading to stronger signals. Branzi et al studied the influence of the reaction time on the chiral signal of carbon dots synthesized at room temperature in a copper-catalyzed process 95 . Peaks in CD spectra were observed at 220 and 250 nm, whose intensity reached their maximum after 2 h of synthesis, followed by a gradual decrease.…”

Natural deep eutectic solvent assisted synthesis and applications of chiral carbon dots

“…With the increase of preparation time and temperature, the new chiral CD signal at 220 nm reaches a maximum at 160 °C for 3 h, which could be ascribed to the formation of the maximum number of the chiroptical active chromophores present in the CCDs. 34,35 Furthermore, the CD spectra of each DES raw material, DESs, and CCDs are also compared in Fig. S9A-C The redshift of this signal may be due to the interaction of the carbon skeleton and NADES.…”

Physical Mechanism of Fluorescence and Chirality of Functionalized Graphene Quantum Dots

“…The chirality in carbon-based semiconductor nanomaterials is an exciting class that shows promising applications in optoelectronics, catalysis, bioanalysis, and drug delivery. − The chiral GQDs could be produced in chiral forms as mirror images of each other using edge modification with amino acids, and the origin of the chiroptical properties was considered as “it is all in the twist” . Thus, chirality of GQDs can be controlled via surface modification. − Without surface modification, bilayer GQDs can also produce chirality by twist. , GQDs can be used for the chiral fluorescent materials. , Further information on chirality of GQDs, one can refer recent reviews. − Though the formation mechanism and chirality evolution of chiral carbon dots have been discussed, − more detailed physical mechanisms of chiroptical properties of GQDs are not very clear, such as the delocalized charge transfer and charge distributions on center or edge in GQDs, magnetic field occurrence, distribution of magnetic field in GQDs, and so on.…”