At present, the actual mechanism of the photoluminescence （PL） of fluorescent carbon dots （CDs） is still an open debate among researchers. Because of the variety of CDs, it is highly important to summarize the PL ...At present, the actual mechanism of the photoluminescence （PL） of fluorescent carbon dots （CDs） is still an open debate among researchers. Because of the variety of CDs, it is highly important to summarize the PL mechanism for these kinds of carbon materials; doing so can guide the development of effective synthesis routes and novel applications. This review will focus on the PL mechanism of CDs. Three types of fluorescent CDs were involved： graphene quantum dots （GQDs）, carbon nanodots （CNDs）, and polymer dots （PDs）. Four reasonable PL mechanisms have been confirmed： the quantum confinement effect or conjugated 7x-domains, which are determined by the carbon core; the surface state, which is determined by hybridization of the carbon backbone and the connected chemical groups; the molecule state, which is determined solely by the fluorescent molecules connected on the surface or interior of the CDs; and the crosslink- enhanced emission （CEE） effect. To give a thorough summary, the category and synthesis routes, as well as the chemical/physical properties for the CDs, are briefly introduced in advance.展开更多
Carbon dots(CDs) are potentially useful in many areas such as bioimaging, light-emitting diodes, and sensing because of their excellent optical properties, high biocompatibility, and low toxicity.Knowledge of their ph...Carbon dots(CDs) are potentially useful in many areas such as bioimaging, light-emitting diodes, and sensing because of their excellent optical properties, high biocompatibility, and low toxicity.Knowledge of their photoluminescence(PL) mechanisms, which have been widely studied, is of significance in guiding the synthesis and promoting applications of CDs with tunable PL emissions. However,the intrinsic mechanism of PL emission remains unclear, and a unified mechanism has not been found because of differences in particle structures. This review generalizes the categories of CDs, noting their structural diversity. Three types of PL mechanism pertaining to structural differences are outlined: internal factors dominated emission(including the conjugation effect, the surface state, and the synergistic effect), external factors dominated emission(including the molecular state and the environment effect),and crosslink-enhanced emission. Optical applications of CDs are also briefly mentioned. Finally, the prospects for research into PL mechanisms are discussed, noting the remaining challenges and directions for future work.展开更多
文摘At present, the actual mechanism of the photoluminescence （PL） of fluorescent carbon dots （CDs） is still an open debate among researchers. Because of the variety of CDs, it is highly important to summarize the PL mechanism for these kinds of carbon materials; doing so can guide the development of effective synthesis routes and novel applications. This review will focus on the PL mechanism of CDs. Three types of fluorescent CDs were involved： graphene quantum dots （GQDs）, carbon nanodots （CNDs）, and polymer dots （PDs）. Four reasonable PL mechanisms have been confirmed： the quantum confinement effect or conjugated 7x-domains, which are determined by the carbon core; the surface state, which is determined by hybridization of the carbon backbone and the connected chemical groups; the molecule state, which is determined solely by the fluorescent molecules connected on the surface or interior of the CDs; and the crosslink- enhanced emission （CEE） effect. To give a thorough summary, the category and synthesis routes, as well as the chemical/physical properties for the CDs, are briefly introduced in advance.
基金financially supported by the National Natural Science Foundation of China(21905253,51973200)the China Postdoctoral Science Foundation(2018M640681,2019T120632)。
文摘Carbon dots(CDs) are potentially useful in many areas such as bioimaging, light-emitting diodes, and sensing because of their excellent optical properties, high biocompatibility, and low toxicity.Knowledge of their photoluminescence(PL) mechanisms, which have been widely studied, is of significance in guiding the synthesis and promoting applications of CDs with tunable PL emissions. However,the intrinsic mechanism of PL emission remains unclear, and a unified mechanism has not been found because of differences in particle structures. This review generalizes the categories of CDs, noting their structural diversity. Three types of PL mechanism pertaining to structural differences are outlined: internal factors dominated emission(including the conjugation effect, the surface state, and the synergistic effect), external factors dominated emission(including the molecular state and the environment effect),and crosslink-enhanced emission. Optical applications of CDs are also briefly mentioned. Finally, the prospects for research into PL mechanisms are discussed, noting the remaining challenges and directions for future work.
