A facile method is developed to synthesize intrinsically fluorescent carbon dots by hydrothermal treatment of glucose in the presence of monopotassium phosphate. The fluorescence emission of the carbon dots thus produced is tunable by simply adjusting the concentration of monopotassium phosphate.

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The exciton radiative lifetime in ZnO nanorods is studied. It is found that the exciton radiative lifetime increases with temperature as T2. Furthermore, the spectral linewidth of the photoluminescence of the ZnO nanorods also increases with temperature as T2, suggesting a linear dependence of exciton radiative lifetime on the spectral linewidth. The physics behind is that the oscillator strength of excitons at k=0 is shared equally among all the states within the spectral linewidth and the coherence extension of an exciton decreases with temperature due to the scattering by phonons, defects, or impurities.

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