Turning Carbon Quantum Dots into solid

Hello everyone, I am a highschool student researching quantum dots. I am just wondering how I can turn my liquid quantum dots into solid form so I can put it for testing or in any way I can improve my methodology.

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I am making quantum dots using ground Arabica coffee beans. Here is my methodology:

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I am using 1.5 grams of ground Arabica coffee beans then I mixed it with 200 mL of distilled water. After that, it was microwaved at 600 watts for 5 minutes where it was then centrifuged at 3000rpm for 30 minutes. Lastly, it was filtered through a No.1 Whatman filter paper.

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The result after the filtration was still a brownish liquid but the top of the liquid displayed Fluorescence when under a UV light.

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The other part of my research is to compare it with a CQD still made from arabica coffee grounds but now with urea.

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The tests we are planning to do are SEM, XRD, FTIR, and Photoluminescence Spectroscopy.

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Does anyone have any suggestions or ideas on what to do? I would greatly appreciate it. Thank you so much

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