Ahsanul Habib If you have a powder, then it's a laser diffraction experiment, not DLS. There are no free, independent, discrete particles < 100 nm in a powder. For more information, then see (free registration required):

Dispersion and nanotechnology

https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat

To disperse ZnO nanoparticles powder in DMSO (dimethyl sulfoxide), you can follow these steps:

Remember, the successful dispersion of ZnO nanoparticles in DMSO depends on several factors, including nanoparticle properties, concentration, and processing conditions. It is essential to optimize the dispersion process based on your specific requirements and consult relevant literature or expert advice if needed.

Dear Ahsanul Habib,

Sonication or a high-quality vortex mixer is an important step in DLS when your result is not good. It breaks up the powder into small particles and disperses them evenly in the DMSO.

Here are the steps on how to disperse ZnO NPs powder in DMSO for DLS:

Hope this will help you, best of luck