Hi, the best place you can buy is segmma aldrich. Or the are other websites if you search. If you want a large quantity, then go to alibaba.

It is better to prepare it.

http://www.ijnnonline.net/article_3924_b4ac68c17c06b9e45f86f61a4fc0aa97.pdf

Regards

Some industries such as electrochemical, environmental, optical, and engineered materials also rely on the production of nanoparticles. Wherever nanotechnology is found, freeze drying has become a vital processing tool

Hi Mohammad,

You may make an inquiry at Alfa Chemistry, they offer kinds of good-quality nanomaterials.

https://nanomaterials.alfa-chemistry.com/inquiry

Dear Mohammad,

just in case that your interesting technical question is still of interest to you: My personal suggestion would be to prepare the CuO / water nanofluid yourself. That way you have a better control over the chemical and physical properties. According to the article cited below (citation"): "The CuO-water nanofluids are relatively easy to be prepared by using the two-steps method, which provides a reasonable stability and particle dispersion." Thus please have a closer look at the paper and the references cited therein:

A review on thermal performance of CuO-water nanofluids applied to heat pipes and their characteristics

Conference Paper A review on thermal performance of CuO-water nanofluids appl...

The article is freely accessible as public full text on RG and can be downloaded as pdf file. In addition, please see the following relevant paper which has been published Open Access:

Preparation and thermal conductivity of CuO nanofluid via a wet chemical method

Article Preparation and thermal conductivity of CuO nanofluid via a ...

You will find that the synthetic method is surprisingly simple. Good luck with your research!