Dear Shuijian,

to measure lifetime, instrument like Time correlated single photon counting can be used.

Both powder and liquid sample can be done with this instrument.

Visit the following link

https://www.youtube.com/watch?v=BbqsNDfCPQU

Thank you very much, Rupesh.

Dear Shuijian,

To correctly measure lifetime the main difficulty in case of solutions and powders is correct preparation of the samples. In the fluorescence spectra of solutions and powders, reabsorption should not occur. To do this, it is necessary to use as low as possible dye concentrations: between 10^(-4) and 10^(-5) M (D < 0.05). The powder is placed in an extremely thin layer between the quartz plates. Thin polymer films should have an optical density D < 0.05. Perhaps the following article will be helpful:

Article Photophysical Properties of Nanodiamonds Covalently Bonded t...

Vladimir

Thank you very much, Vladimir. I learn a lot from your answer.