Multicolor Afterglow from Carbon Dots: Preparation and Mechanism

Abstract

Carbon dots (CDs), as emerging long afterglow luminescent material, have attracted the attention of researchers and become one of the hot topics in long afterglow materials. In recent years, researchers have obtained a series of CDs‐based long afterglow materials with different properties utilizing matrix‐assisted and self‐protective methods. To meet diverse application needs, the development of multicolor CDs‐based long afterglow materials is a focus and challenge in this field. Most of the previously reported CDs‐based long afterglow materials generally emit blue or green afterglow. Recently, some multicolor systems have been discovered, and the emission range can extend from ultraviolet to near‐infrared. However, there is a lack of systematic and in‐depth analysis regarding the preparation strategy and luminescence mechanism of multicolor afterglow from CDs‐based long afterglow materials. Based on this, this review summarizes the preparation strategies of multicolor afterglow from raw materials and reaction parameters. Then, the luminescence mechanisms of multicolor afterglow are analyzed from seven factors, including carbonization degree, surface state, aggregation degree, temperature dependence, excitation dependence, multi‐emission center, and energy transfer. Moreover, the applications of multicolor afterglow from CDs‐based long afterglow materials are introduced. Finally, the problems and challenges in this field are discussed, and the future development directions are analyzed.

Visualizing Motion Trail via Phosphorescence Carbon Nanodots-Based Delay Display Array

“…Carbon nanodots (CNDs), as a new type of luminescent nanomaterials, have been receiving great attention due to their outstanding luminous properties, eco-friendly nature, and facile preparation . Especially, the phosphorescence resulting from the radiation recombination of triplet excitons in CNDs greatly enhances their potential applications in optoelectronic devices, time-resolved bioimaging, and information security. − However, CNDs do not exhibit phosphorescence or have a low quantum yield due to their unstable triplet excitons. Great effort has been devoted to enhancing spin–orbit coupling, stabilizing triplet excitons of CNDs through introducing heteroatom atoms with unpaired lone pair electrons (such as N and P atoms), and confining them into various matrices (such as silica, zeolite, and sodium cyanate) in order to achieve phosphorescence, given their easy quenched property. − Although the single-dimension confinement matrix can stabilize triplet excitons and enable CNDs to achieve phosphorescence emission through suppressing the intermolecular vibration, they still suffer from a relatively short lifetime and a low quantum efficiency.…”

Host–Guest Metal–Organic Frameworks-Based Long-Afterglow Luminescence Materials

“…Inorganic long-afterglow materials are composed of either transition metals compounds [6] or rare-earth metal compounds [7], mainly including rare-earth-doped aluminate [8,9], silicate [10][11][12], stannite [13], phosphate [14,15], gallate [16,17] and germanate [18,19], which usually require high-temperature calcination to obtain. Organic materials with long afterglows include carbon-based materials [20,21], organic dyes [22,23], polymer-based materials, [24][25][26][27], etc. However, it is the high cost and relatively complex synthesis that have limited the applications of those materials.…”

Photoinduced absorption and linear/nonlinear emission of assembled carbon dot–silica nanocomposites for cellular imaging

“…1 CDs are advantageous in biological applications including bio-imaging in vitro and in vivo , 2–4 cancer diagnosis and biotherapy, 5–8 and gene/drug delivery and bio-sensing 4,8–10 due to their excellent properties of bright-light emission and wide-emitting range, facile preparation process, low/no toxicity, cheap source, etc. 8,11–13 The most widely investigated photoluminescence property for CD-based nanomaterials is the common fluorescence, that is the one-photon excited fluorescence (1PEF). In a bio-spectral window, the 1PEF usually shows obvious shortcomings in the bio-imaging field, whereas multi-photon excited fluorescence or phosphorescence imaging can overcome those defects to show higher resolution, weaker photo-cytotoxicity, stronger resistance to the interference from the background/excitation light, and deeper penetration depth compared with 1PEF imaging.…”

“…In a bio-spectral window, the 1PEF usually shows obvious shortcomings in the bio-imaging field, whereas multi-photon excited fluorescence or phosphorescence imaging can overcome those defects to show higher resolution, weaker photo-cytotoxicity, stronger resistance to the interference from the background/excitation light, and deeper penetration depth compared with 1PEF imaging. 12,14–16…”