Luminescent ZnO-Carbon Hybrid Nanomaterials: Synthesis, Characterization, Emission Mechanism, and Applications

In this study, hybrid zinc-oxide–carbon nanomaterials (ZnO–C-NMs) with 2–5 nm ZnO nanoparticles embedded in a C nanomatrix were developed through a facile one-pot solvothermal synthesis method. Under UV excitation (355 nm), ZnO–C-NMs emit weak blue luminescence, but under visible light excitation (405 nm), they present a bright green emission. Such luminescence properties are much different from those of C-NMs (synthesized under the same conditions as ZnO–C-NMs, except without the addition of Zn precursors). Through optical characterization and comparison of these materials, the luminescence mechanism of ZnO–C-NMs was discussed; the unique luminescence properties can be attributed to the interaction between the electronic structures of the ZnO nanoparticles and the C matrix. It was also found that ZnO–C-NMs possess excellent luminescence stability in water even under harsh conditions (e.g., high salinity, high concentrations of reactive oxygen species, or wide pH ranges). The observed phenomena may be rooted in a hydration layer on the surface of ZnO–C-NMs through the electrostatic absorption of water molecules. Based on their physiochemical merits, ZnO–C-NMs were successfully employed to detect trace amounts of water in commonly used low-polarity organic solvents with high sensitivities. We believe that such hybrid ZnO–C-NMs have potential for broader applications in sensing, imaging, photocatalysis, and others due to their unique luminescence properties or electronic structures.