The green synthesis method of production of copper nanoparticles by tomato aqueous extract is cheap and environmental friendly. Biosynthesis is a recent strategy for production of copper nanoparticles. Lycopersicon esculentum contain ascorbic acid which is a powerful reducing agent and stabilizing agent.

Reema Aftab you can use following protocol, may be beneficial for you.

Preparation of extract

The fresh leaves of A. vasica were properly cleaned with tap water to avoid dust and other contaminated particles and were cleaned many times by double distilled water. The leaves were shade dried for three weeks and made into a fine powder using a grinder. The crushed leaves were weighed and dispersed in double-distilled deionized water in the ratio 1g: 100 ml. The dispersion was sonicated for half an hour and then centrifuged. The supernatant solution was kept in a refrigerator and again centrifuged after 24 h. Then the solution was purified using a Whatmann No.1 filter paper to avoid all the plant residues in it.

Synthesis of CuO/C nanocomposites

The solution of copper sulphate pentahydrate (CuSO4.5H2O) was used as the source for the CuO and the leaf extract as the reducing agent, capping agent and source of carbon. In double distilled water 0.01 M copper sulphate solution was made and added to the supernatant solution of leaves extract in 5:4 volume ratio followed by constant stirring and in a nitrogen atmosphere. The experiment was repeated for different volume ratios. But the maximum yield was obtained in the ratio 5:4. So the ratio was fixed to 5:4. The reaction mixture was continued to be stirred for half an hour. Then a cloudy cluster of particles was formed. The formation of nanostructures was observed with a notable colour change. The pH of the precursor solution, plant extract and the mixture solution were noted during the experiment. Then the nanocomposite solution was incubated for 24 h to complete the reaction and the residue obtained was cleaned five times with deionized water and centrifuged. The purified particles were air-dried and used for further study.

This depends on the method of extracting the plant ..... The best method for extracting the plant must be adopted, even if it is necessary to use an organic solvent.

Try to synthesized you CuNPs in nitrogen environment. As copper is readily oxidized to Copper Oxide.

Read the article

https://www.degruyter.com/view/journals/gps/8/1/article-p135.xml

Dear Reema Aftab

The limitations of the green method for nanoparticles preparation located where; in some cases, we have to use a high concentration of the plant extract that contains a low concentration of the bioactive molecules; in another word the selected plant does not have enough content of the bioconstituents that work as a reducing, capping and stabilizing agent at the same time. So, we have to modify the reaction conditions like pH, temperature, time, and sometimes the reaction should be conducted under nitrogen gas to prevent the formation of the undesirable oxides nanomaterials. Besides, we can't predict the type of resultant nanomaterial at first till we make a suitable and convenient characterization technique for investigation and identification.

Maybe these papers help you in the process flow of nanoparticles via green chemistry

1- Article Biogenic copper nanoparticles and their applications: A review

2- Article Biosynthesis, Characterization, and Wound-Healing Activity o...

3- Article Biosynthesis of copper nanoparticles using aqueous Tilia ext...

4- Article A review of green methods for phyto-fabrication of hematite ...

The green synthesis method of production of copper nanoparticles by tomato aqueous extract is cheap and environmental friendly. Biosynthesis is a recent strategy for production of copper nanoparticles. Lycopersicon esculentum contain ascorbic acid which is a powerful reducing agent and stabilizing agent.