We prepare a powder mixture of oxygen deficient zinc oxide (ZnO1-x) and carbon dots from zinc nitrate and citric acid precursor. Actually, we aim to prepare ZnO1-x only but carbon dots also appear in the final product. Now, we want to separate and collect only ZnO1-x to measure its optical properties. In addition, I do not want to fully oxidize the ZnO1-x to ZnO. I want it in the same ZnO1-x form with the same oxygen deficiency (that we measure using XPS). Please let me know if there is any method to do the same. Thanks.
you can give heat treatment to your ZnO 1-x powders in different ambients
like annealing in vacuum at different temperatures, or
a reducing atmosphere (with hydrgen atmosphere) - a dangerous experiement,
or find out other methods of creating a reducing atmosphere.
If elemental carbon is present, I think may be it will not be affected.
K. Sreenivas
In what kind of optical properties are you interested in?
form my point of view only local resolved measurements are reasonable. I guess you can use a (Raman) microscope for Raman 🙂 and (UV) vis spectroscopy.
Thank you Dr. Sreenivas for your answer. We tried annealing in air, elemental carbon oxidizes to CO2 and release, but ZnO1-x also oxidizes and sample color also changes from grey (of ZnO1-x/C composite) to white (of ZnO). Annealing in reduced environment is a dangerous experiment because of release of methane and I am also not sure if it will change ZnO1-x or not (eg. create more oxygen deficiency). We will try this after we are sure of safety. Thank you.
Thank you Dr. Schmitt for the post. We are interested in finding the band gap and band positions of ZnO1-x. Well established in literature that oxygen deficient metal oxides (TiO2 or ZnO) can absorb visible light because of the existence of sub energy level between conduction and valance band and also because of the change in the band gap. We are interested in finding the position of the sub energy level. Our synthesis technique generates ZnO1-x hollow spheres but also results in small carbon particle (like carbon dots). Therefore, we want to separate them (or remove carbon from the composite) to characterize the optical properties of ZnO1-x hollow sphere only.
Have you tried separations using solvents? I'm thinking of organic solvents that do not contain oxygen... if there is solvent that could dissolve the carbon dots, they could be washed out of the powder. If the carbon dots do not dissolve readily in the solvents you have available, would there be a sufficient difference in density between the ZnO1-x spheres and the carbon dots to separate them into different layers in the solvent? Just a couple of thoughts....
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