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Caption : figure s1. effect of reaction temperature on the fluorescence intensity of wcs-cds.

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Caption : figure s2. influence of reaction time on the fluorescence intensity of wcs-cds.

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Caption : figure s3. fluorescence intensity of wcs-cds at various concentrations of water caltrop shells.

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Caption : figure s4. (a) the fluorescence spectra of wcs-cds at different emission wavelengths; (b) the fluorescence spectra of wcs-cds at different excitation wavelengths; (c) the optimum excitation and emission wavelength of wcs-cds; (d) the ultraviolet absorption spectrum of wcs-cds.

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Caption : figure s5. the fluorescence decay curve of aqueous wcs-cds.