Designing efficient room-temperature phosphorescence (RTP) carbon dots (C-dots) without the need of an additional matrix is important for various applications. Herein, matrix-free and highly efficient C-dots with yellowgreen RTP emission have been successfully synthesized towards information encryption and decryption. Phytic acid (PA) and triethylenetetramine are used as molecular precursors, and a facile microwave-assisted heating method is selected as synthesis method. The obtained C-dots exhibit a maximum phosphorescence emission at around 535 nm under an excitation wavelength of 365 nm and a long average lifetime up to 750 ms (more than 9 s to the naked eye). PA containing six phosphate groups and serving as P source plays a significant role in producing the RTP C-dots. Furthermore, potential applications of the RTP C-dots in the field of information encryption and decryption are successfully demonstrated.[a] Dr.

Multiple-color emissive carbon dots (C-dots) are gaining increasing attention in various fields. Herein, we report a facile solvothermal method for the synthesis of multiple-color emissive C-dots with the aim of white-light emission. Under single ultraviolet-light excitation, three C-dots emit a easily controlled fluorescent emission wavelength at 440 nm, 500 nm and 610 nm by using different three amines (either ammonium hydroxide, ethylenediamine or p-phenylenediamine, respectively) and pyromellitic dianhydride as molecular precursors while another three C-dots emit a controllable fluorescent emission wavelength at 500 nm, 550 nm and 585 nm by using same three amines and naphthalene-1,4,5,8-tetracarboxylic dianhydride as molecular precursors. The maximum fluorescence wavelength of these C-dots is red-shifted by changing three different amines molecular precursors from ammonium hydroxide, ethylenediamine, to p-phenylenediamine. Furthermore, these C-dots have shown promising applications in the fields of white-light-emitting diodes devices and color printing.

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We report the rational design of the matrix-free carbon dots (C-dots) with long wavelength and wavelengthtunable room-temperature phosphorescence (RTP). Taking advantage of microwave-assisted heating treatment, three RTP C-dots in boric acid (BA) composites are synthesized by using diethylenetriaminepentakis (methylphosphonic acid) as a multiple-sites crosslink agent, a moderately acid catalyst and P source; phenylenediamines (either o-PD, m-PD, or p-PD, respectively) as building block while BA as a carbon-ization-retardant matrix. After the water-soluble BA matrix is removed by dialysis, three matrix-free C-dots are obtained with RTP emission at 540, 550 and 570 nm under an excitation wavelength of 365 nm. Alterations of RTP emission of three matrix-free C-dots are ascribed to the difference in their particle size and band gap from n-π* transition. Furthermore, the application of three matrix-free C-dots are successfully performed in information encryption and decryption.

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