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Carbon quantum dots (CQDs) with multi-color emission are synthesized through hydrothermal method by varying the ratio of citric acid (CA) and urea, the solvent (water, ethyl alcohol, and dimethylformamide), the hydrothermal temperature, and reaction time. The CQDs emit bright fluorescence which can be gradually tuned from blue to red continuously, almost covering the whole visible spectrum. The emission peaks of the CQDs shift from 450 nm to 650 nm with the surface groups and structures changing. Importantly, all solid state CQDs@SiO 2 nanophosphors are successfully synthesized by reversed-phase micromulsion method. Based on these solid state phosphors, multi-color CQDs@SiO 2 phosphors-based light-emitting diodes (LED) and white light-emitting diode (WLED) with a Commission Internationale de L' Eclairage (CIE) value of (0.3497, 0.3045) are fabricated in a low-cost, environment-friendly way. [ABSTRACT FROM AUTHOR]

PbS quantum dot (QD)‐doped glasses were fabricated through melt‐quenching method. After heat treatment schedule, uniform QDs were precipitated in the glasses and near‐infrared emission covering 900‐1700 nm was obtained under excitation. From photoluminescence (PL) spectra and lifetime decay curves, the whole emission band of QD‐doped glasses consisted of emission from the 1S‐1S state and the trap state. While using excitation with higher energy, the full width at half maximum (FWHM) of QD‐doped glasses broadened because smaller QDs were excited. Energy transfer process among QDs was revealed by measuring the lifetime of different emission bands in PL spectrum and the energy transferred from smaller QDs with broader bandgap to bigger QDs with narrow bandgap. Temperature‐dependent PL and the corresponding lifetime decay curves of PbS QD‐doped glasses were analyzed. Temperature‐dependent bandgap structure of PbS QDs was obtained by using density functional theory (DFT) calculations. The results here give deep insight into optical properties of PbS QD‐doped glasses and it is beneficial to design and develop high‐performance QD‐based optoelectronic devices in theory. [ABSTRACT FROM AUTHOR]

Polymeric g‐C3N4 with controllable photoluminescence emission wavelength in the whole visible light range (450–650 nm) is synthesized through the one‐step molecular doping during the thermal condensation process of g‐C3N4 conjugated framework, which opens up its application beyond the conventional catalysis scopes. By adjusting the doped content of hetero‐molecules, the modified g‐C3N4 with the optical properties controlled according to the demand of practical applications can be facilely and largely obtained. It overcomes the limitation of the narrow adjusting range of conventional g‐C3N4 on optical properties and makes it become more promising for applications in solid‐state displays. The corresponding multiple‐color g‐C3N4‐based LED devices and the white‐light LEDs with high quality can be obtained as supported by experiments and theoretical calculations. Moreover, the effect of doped molecule on the π‐conjugated system of g‐C3N4 is systematically studied here, and the tunable luminescence mechanism is proposed. [ABSTRACT FROM AUTHOR]