We have synthesized biocompatible fluorescent carbon dots (CDs) by a one-step hydrothermal method using Solanum tuberosum (potato) as a raw material. The CDs were characterized by UV-visible, fluorescence, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), dynamic light scattering (DLS) and high-resolution transmission electron microscopic (HR-TEM) techniques. We found that the carbonization of potato at ∼170 °C for 12 h produces highly fluorescent CDs of 0.2–2.2 nm size. The synthesized CDs are well dispersed in water and exhibited strong blue and bright blue emissions under UV illumination (λ_ex = 302, 365 nm). The CDs showed a strong emission peak at 455 nm at an excitation wavelength of 374 nm. The CDs acted as fluorescent probes for multicolor (blue, green and red) imaging of HeLa cells and the CDs did not induce cell death, which indicates that the CDs are biocompatible and nontoxic to HeLa cells. Therefore, the CDs can be used as probes for cell-imaging applications in vitro and in vivo.

Zinc is an essential element that is also renowned for widespread contamination and toxicity at high concentrations. The present study was carried out to analyze the responses induced by lower, as well as higher, doses of zinc (0–200 mg/L), in the form of zinc oxide nanoparticles (ZnO NPs) in wheat and maize, for a period of 21 days. Accumulation of zinc increases with increasing Zn doses in both wheat and maize, with higher doses being in wheat (121 mg/kg in root and 66 mg/kg in shoot) than in maize (95 mg/kg in root and 48 mg/kg in shoot). The activity of alpha-amylase showed increase, while that of dehydrogenase decline, in response to ZnO NPs. The length and biomass of plants and photosynthetic pigments increased slightly upon ZnO NPs supply. Malondialdehyde content showed a progressive increase in root and shoot of both plants. However, in response, antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, and catalase) showed increase up to lower concentrations (100 mg/L) of ZnO NPs but decline variably at higher levels (150–200 mg/L) in wheat and maize. The results suggest that lower supply of ZnO NPs (100 mg/L) could be stimulatory to the growth of plants and can be recommended as a Zn fertilizer source for crop production.

In this work, fluorescent carbon dots (C-dots) were synthesized using a hydrothermal method with Punica granatum (pomegranate) fruits as precursors, and were then used as probes for imaging of bacterial (Pseudomonas aeruginosa) and fungal (Fusarium avenaceum) cells. The C-dots showed a strong emission at 453 nm when excited at 383 nm. Rapid internalization of the C-dots by these cells was confirmed by two color (green and red) images that were obtained using confocal fluorescence microscopy.