Synthesis Of Multicolor Carbon Dots Research Articles

Electrochemical synthesis of multicolor carbon dots with room temperature phosphorescence to thermally activated delayed fluorescence via surface state modulation

Solid-state multicolor carbon dots (CDs) have attracted tremendous attention due to their wide applications. However, the fluorescence quenching of solid-state CDs occurs due to the π-π stacking or energy transfer between adjacent carbon dots. In addition, it is difficult to observe the afterglow of solid-state CDs due to their self-quenching and deliquescence. Here, electrochemically prepared multicolor CDs emit the solid-state fluorescence and afterglow emission with lifetimes up to 657 ms by embedding the CDs into urea matrix. More importantly, the surface amino groups and C = O bonds regulate the afterglow emission of CDs from phosphorescence and thermally activated delayed fluorescence at room temperature. Surface amino groups of multicolor CDs can enhance the spin–orbit coupling, increase the intersystem crossing (ISC) and reverse intersystem crossing (RISC). Thus it can promote the generation of triple excited states and regulate the singlet–triplet energy gap value from 0.384 to 0.026 eV. The formation of covalent bonds stabilizes the single and triple excited states and inhibits the non-radiative recombination, which achieves the enhanced fluorescence and visual afterglow of multicolor CDs. The fluorescence and afterglow CDs can be applied to dual signal imaging and anti-counterfeiting, which broadens the practical applications for solid-state CDs via surface state modulation.

Synthesis of Multicolor Carbon Dots Catalyzed by Inorganic Salts with Tunable Nonlinear Optical Properties.

The nonlinear optical properties of carbon dots have been in the spotlight in recent years. In light of the complexity and diversity of factors affecting the nonlinear optical properties of carbon dots, how to reveal the origin and physical mechanism of the nonlinear optical properties of carbon dots accurately has become a problem. In this work, a template-free method was designed to prepare carbon dots via solid-phase reaction with phloroglucinol as a single carbon source and sodium bisulfate as the catalyst. This method is simple, green, safe, and easy to be prepared on a large scale. Three carbon dots with different luminous colors were obtained by simply adjusting the reaction temperature. The rise of reaction temperature affects the surface functional groups, and then hinders the luminescence of surface states, leading to the change of luminescence properties. The nonlinear optical properties of carbon dots were analyzed by the Z-scan technique. Surprisingly, all carbon dots have nonlinear optical responses, but there are differences in performance. Results prove the increase in sp2 domains may contribute to the significant improvement of the nonlinear optical properties of carbon dots, indicating a direction to improve the nonlinear optical properties of carbon dots.

Reaction Time-Controlled Synthesis of Multicolor Carbon Dots for White Light-Emitting Diodes

Reaction Time-Controlled Synthesis of Multicolor Carbon Dots for White Light-Emitting Diodes

The Emerging Development of Multicolor Carbon Dots.

As a relatively new type of fluorescent carbon-based nanomaterials, multicolor carbon dots (MCDs) have attracted much attention because of their excellent biocompatibility, tunable photoluminescence (PL), high quantum yield, and unique electronic and physicochemical properties. The multicolor emission characteristics of carbon dots (CDs) obviously depend on the carbon source precursor, reaction conditions, and reaction environment, which directly or indirectly determines the multicolor emission characteristics of CDs. Therefore, this review is the first systematic classification and summary of multiple regulation methods of synthetic MCDs and reviews the recent research progress in the synthesis of MCDs from a variety of precursor materials such as aromatic molecules, small organic molecules, and natural biomass, focusing on how different regulation methods produce corresponding MCDs. This review also introduces the innovative applications of MCDs in the fields of biological imaging, light-emitting diodes (LEDs), sensing, and anti-counterfeiting due to their excellent PL properties. It is hoped that by selecting appropriate adjustment methods, this review can inspire and guide the future research on the design of tailored MCDs, and provide corresponding help for the development of multifunctional MCDs.

Controlled Synthesis of Multicolor Carbon Dots Assisted by Machine Learning

AbstractCarbon dots (CDs) have received extensive attention and applications in recent years due to their remarkable characteristics of tunable emission wavelength, high stability, and a variety of synthetic raw materials. Since the formation process and photoluminescence properties of CDs are affected by multiple factors, the luminescence regulation of CDs has always been a troublesome problem. Furthermore, it is still a lack of appropriate approaches to reveal the hidden rules between the synthesis conditions and the luminescence properties of CDs. Inspired by machine learning (ML) applications in molecular and materials science, herein, a data‐driven ML strategy is proposed to multi‐dimensionally investigate the correlation between reaction parameters and the photoluminescence properties of CDs. Meanwhile, it is demonstrated that reaction parameters and solvent properties have different influences on the fluorescence properties of CDs, and the intelligently optimizing synthesis route of CDs is achieved using ML algorithms. CDs with excellent luminescent properties screened by ML are further applied to high‐capacity colorful information encryption. This study provides an efficient ML‐assisted strategy to guide the synthesis of multicolor CDs, helping researchers to quickly and easily obtain CDs according to experimental requirements.

Synthesis of Multicolor Carbon Dots Based on Solvent Control and Its Application in the Detection of Crystal Violet.

The adjustment of the emitting wavelength of carbon dots (CDs) is usually realized by changing the raw materials, reaction temperature, or time. This paper reported the effective synthesis of multicolor photoluminescent CDs only by changing the solvent in a one-step solvothermal method, with 1,2,4,5-tetraaminobenzene as both the novel carbon source and nitrogen source. The emission wavelengths of the as-prepared CDs ranged from 527 to 605 nm, with quantum yields (QYs) reaching 10.0% to 47.6%, and it was successfully employed as fluorescence ink. The prepared red-emitting CDs (R-CDs, λem = 605 nm) and yellow-emitting CDs (Y-CDs, λem = 543 nm) were compared through multiple characterization methods, and their luminescence mechanism was studied. It was discovered that the large particle size, the existence of graphite Ns, and oxygen-containing functional groups are beneficial to the formation of long wavelength-emitting CDs. Y-CDs responded to crystal violet, and its fluorescence could be quenched. This phenomenon was thus employed to develop a detection method for crystal violet with a linear range from 0.1 to 11 µM and a detection limit of 20 nM.

Solvent-controlled and solvent-dependent strategies for the synthesis of multicolor carbon dots for pH sensing and cell imaging

Solvent-controlled, pH-dependent and solvent-dependent strategies are proposed to obtain multicolor carbon dots using the same precursor.

Inorganic Salt Incorporated Solvothermal Synthesis of Multicolor Carbon Dots, Emission Mechanism, and Antibacterial Study

Enriching the synthetic routes of functionalized carbon dots (C dots) and expanding their application are necessary for promoting research into carbon-based nanomaterials. In this study, we develop a one-step and efficient method to prepare excitation-dependent multicolor emissive carbon dots (M-C dots) with quaternary ammonium functional groups via a solvothermal reaction of chloroform, diethylamine, and ammonium carbonate. Through detailed structural characterizations and further reactions of surface functional groups (such as reduction, oxidation, and hydrolysis) on M-C dots, the excitation-dependent tunable photoluminescence behaviors are proposed to come from the multiple emission domains on the surface. The prepared M-C dots possess antibacterial activity against Gram-positive bacteria and Gram-negative bacteria. And the antibacterial effects of M-C dots were investigated by destroying the bacterial cell walls/membranes via strongly electrostatic interactions between positively charged M-C dots and ...