The various luminescent properties of carbon nanodots (CDs) reveal fascinating applications in several areas. Here, bright and multicolor chemiluminescence (CL) is realized from CDs, whose CL quantum yield can be optimized by adjusting the energy level alignment between the CDs and 1,2‐dioxetanedione intermediate generated from the reaction of peroxalate and hydrogen peroxide. A CL quantum yield of 9.32 × 10 −3 Einsteins mol −1 , maximal luminance of 3.28 cd m −2 , and lifetime of 186.4 s are achieved in red CDs, all of which are the best values ever reported for CDs. As a proof‐of‐concept prototype, a high‐quality information encryption strategy is established via CD based CL imaging techniques by virtue of the high brightness and multicolor CL.

the ROS molecules, hydrogen peroxide (H 2 O 2 ) is prime reactive species, whose overproduction is closely related to various diseases, including inflammation, cancer, or neurological diseases. [5][6][7][8][9] Thus it is of great importance in monitoring the concentration of H 2 O 2 in living specimens. To this end, a number of mapping tools including "dark" biological processes and radiative recombination mechanism have been developed. Chemiluminescence (CL), a kind of light emission induced by energy transfer from chemical reactions, has evoked considerable interest as one ultrasensitive chemical analysis method with quantification and localization. [10][11][12] Without auto-fluorescent interference and phototoxicity from high-energy excitation light, CL shows high signal-to-noise ratio and low perturbation in sensing H 2 O 2 in vivo compared to photoluminescence (PL) method. [13][14][15] Moreover, unlike the bioluminescence probe requiring the activation of bioactive enzyme, CL imaging of H 2 O 2 is a process of nonenzymatic reaction employing a H 2 O 2 -responsive peroxalate that can transfer chemical energy to the CL emitter. Nevertheless, current CL reporters on H 2 O 2 concentrate mainly on small-molecular dyes, semiconducting polymer, and aggregation induced emission nanoparticles, which suffer from low efficiency, short emission wavelength, and low chemical stability in highly oxidative ROS. [16,17] Thereby, it is meaningful to develop new class of CL nanosensors for the imaging and detecting ROS in vitro and in vivo.Carbon nanodots (CDs), which are considered as discrete quasi-spherical nanoparticles with sizes less than 10 nm, are one kind of promising nanomaterials in bioimaging, photocatalysis, optoelectronics, and sensing owing to its unique properties such as high emission efficiency, good biocompatibility, high photo-stability, and tunable luminescence. [18][19][20][21][22][23][24][25][26][27][28] Recently, the CL properties of CDs in peroxlate-H 2 O 2 system have been investigated, and it has been found that multicolor bright and persistent CL can be obtained from CDs. [29] Therefore, it is practicable to develop versatile CL probes based on CDs to detect ROS via in vivo or in vitro imaging. In general, there are several advantages for CDs as the CL imaging probes: (i) CDs exhibit excellent light emission ability and the luminescence property can be tuned by different methods; [30,31] (ii) CDs with emission Reactive oxygen species (ROS) are generated in the body and related to many pathophysiological processes. Hence, detection of ROS is indispensable in understanding, diagnosis, and treatment of many diseases. Here, near-infrared (NIR) chemiluminescent (CL) carbon nanodots (CDs) are fabricated for the first time and their CL quantum yield can reach 9.98 × 10 −3 einstein mol −1 , which is the highest value ever reported for CDs until now. Nanointegration of NIR CDs and peroxalate (P-CDs) through the bridging effect of amphiphilic triblock copolymer can serve as turn-on probes for the detection an...

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quantum yield (PL QY) of 93.3%; the highest yield to date among the blue-emitting CDs. [21] Sun and co-workers developed a CD synthesis technique using multicolored emission through controlled graphitization and surface functionalization. [1] They found the CD emission band to be tunable from 430 nm to 630 nm, which covers the blue and red region.Despite such large progress achieved for CD synthesis, plenty of barriers still exist to CD commercialization. Typically, CDs with great performance are primarily prepared through solvothermal routes, meaning at least several hours are needed to prepare CDs at milligram levels. [1,3,4,6,[19][20][21][22][23] Nevertheless, expensive precursors and complex purification processes will no doubt enlarge the construction costs and increase the preparation time. [3][4][5][6] In another way, CDs suffer from aggregation-causedquenching (ACQ) due to π-π stacking in the solid state, which has shown to greatly hinder the application of CDs in light-emitting fields. [24][25][26][27][28] To overcome this deficiency, efforts have been targeted to develop solid CDs with efficient fluorescence by way of CD monomer separation from direct contact, including CD implantation inside polymer matrices and combining them with inorganic salts as composites. [29][30][31][32][33][34][35][36][37][38] Although this effectively prevents the ACQ of CDs in solid state by the dispersal of CDs into various matrices, only CDs at lower loading fractions (i.e., <0.2 wt%) have the ability to achieve high PL QY. [39] While most white LEDs (WLEDs) are created using the one-step synthesis of white light-emitting CDs, the down-conversion fluorescent powders usually suffer from low luminous efficiency or color instability. [40][41][42] Therefore, it is paramount to develop solid CDs with high fluorescence efficiency and stability in facile, low cost, and high-output ways in order to satisfy scale-up industrial production and application.In this study, we report a facile one-step microwave-assisted heating method to prepare solid CDs with strong green emissions. Here, citric acid, urea, and sodium hydroxide (NaOH) have been used as precursors. The CDs were also made to be resistant to self-quenching by in situ embedding the CD into the crystal matrix of NaOH, so that the PL QY could reach 75.9% in the solid state. To the best of our knowledge, this is the highest value attained for solid CDs having green emission. [8,32,[35][36][37][38] Moreover, powdered CD (CDPs) would also have the potential to be prepared on a much larger scale in several minutes It still remains a challenge to synthesize solid-state carbon dots (CDs) with high emission efficiency; a hurdle that has hindered the application of CDs in many fields. In this work, efficient fluorescent CDs have been prepared through a one-step microwave-assisted heating method. Experimental data show strong green emissions produced from the CD powders (CDPs), carrying an unprecedented 75.9% quantum yield due to both spatial confinement and defect reduction with the ...

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