A simple one-pot hydrothermal approach has been demonstrated for the preparation of highly water soluble and photoluminescent carbon nanodots (C-dots) from low-cost organic compounds. We found that the compounds incorporating amino and carboxylic acid groups are suitable for the preparation of highly photoluminescent and water-soluble C-dots.

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Highly water-soluble, biocompatible, and photoluminescent carbon nanodots (C-dots) having an average diameter 3.4 AE 0.8 nm and a quantum yield 4.3% are obtained from used green tea through grinding, calcination and centrifugation. The as-prepared C-dots are stable in high-ionic-strength media (e.g. 500 mM NaCl) and under light irradiation, allowing images of MCF-10A, MCF-7 and MDA-MB-231 cells to be recorded. The C-dots are mostly localized in the cell membranes and cytoplasms, with evidence of excitation-wavelength cell images. Relative to catechin, the C-dots provide greater inhibition efficiency of the growth of MCF-7 and MDA-MB-231 cancer cells, with lower toxicity for the MCF-10A normal cells. The inhibitory activity of C-dots is associated with the generation of greater amounts of reactive oxygen species. A prothrombin time (PT) assay of plasma samples reveals excellent biocompatibility of the C-dots. To the best of our knowledge, for the first time the C-dots provide inhibition efficiencies up to 80% and 82% for MCF-7 and MDA-MB-231 cancer cells, respectively, showing their high potential as cancer inhibitors.

Organosilane-functionalized carbon dots (SiC-dots) were prepared by a simple one-pot hydrothermal approach. The photoluminescence (PL) properties of the SiC-dots revealed a reversible response toward the temperature (293-343 K). Through Si-O-Si bonding, temperature-sensitive PL SiC-dot films could be easily fabricated on glass substrates.

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