Recent Advances in Synthesis, Modification, Characterization, and Applications of Carbon Dots

Abstract

Although there is significant progress in the research of carbon dots (CDs), some challenges such as difficulty in large-scale synthesis, complicated purification, low quantum yield, ambiguity in structure-property correlation, electronic structures, and photophysics are still major obstacles that hinder the commercial use of CDs. Recent advances in synthesis, modification, characterization, and applications of CDs are summarized in this review. We illustrate some examples to correlate process parameters, structures, compositions, properties, and performances of CDs-based materials. The advances in the synthesis approach, purification methods, and modification/doping methods for the synthesis of CDs are also presented. Moreover, some examples of the kilogram-scale fabrication of CDs are given. The properties and performance of CDs can be tuned by some synthesis parameters, such as the incubation time and precursor ratio, the laser pulse width, and the average molar mass of the polymeric precursor. Surface passivation also has a significant influence on the particle sizes of CDs. Moreover, some factors affect the properties and performance of CDs, such as the polarity-sensitive fluorescence effect and concentration-dependent multicolor luminescence, together with the size and surface states of CDs. The synchrotron near-edge X-ray absorption fine structure (NEXAFS) test has been proved to be a useful tool to explore the correlation among structural features, photophysics, and emission performance of CDs. Recent advances of CDs in bioimaging, sensing, therapy, energy, fertilizer, separation, security authentication, food packing, flame retardant, and co-catalyst for environmental remediation applications were reviewed in this article. Furthermore, the roles of CDs, doped CDs, and their composites in these applications were also demonstrated.

Comparison of carbon dots prepared from collagen peptides using conventional hydrothermal and microwave methods

“…The difference is related to particle size, domain size, and surface state of the two CDs. 29,30 The photoluminescence spectra of the two CDs are shown in Fig. 1C and D.…”

Supramolecular structures from structurally persistent and surface active carbon dots in water

“…This feature makes pyrolysis highly flexible to produce CDs with varying surface chemistries and intriguing photoluminescent (PL) properties. [4][5][6][7] To date, research on CDs is largely restricted to their PL properties and related applications. Being a new type of nanomaterial, they are also attractive building blocks for supramolecular chemistry, which has, however, received trace attention.…”

“…This feature makes pyrolysis highly flexible to produce CDs with varying surface chemistries and intriguing photoluminescent (PL) properties. 4–7…”

Emerging and Versatile Platforms of Metal‐Ion‐Doped Carbon Dots for Biosensing, Bioimaging, and Disease Therapy

“…In comparison with fluorescent dyes and semiconductor quantum dots (SQDs), CDs have the merits of facile preparation, easy surface modification, chemical inertness, excellent photostability, as well as low cytotoxicity and good biocompatibility [8–13] . As a result, they have been applied in diverse fields like sensing, bioimaging, catalysis, biomedicine, optoelectronic devices, and so on [14–22] …”

“…[8][9][10][11][12][13] As a result, they have been applied in diverse fields like sensing, bioimaging, catalysis, biomedicine, optoelectronic devices, and so on. [14][15][16][17][18][19][20][21][22] Since the first synthesis of CDs by Scrivens et al in 2004, [23] great efforts have been made to regulate their structures and properties, aiming at improving the photoluminescent quantum yield, broadening the photoluminescence spectral coverage, and endowing CDs with special applications. [24][25][26][27][28][29] Metal iondoping is an effective approach to tune the physicochemical properties of nanomaterials due to the extensive free electrons, unoccupied orbitals, and large atomic radius of metal ions.…”