Advanced carbon dots via plasma-induced surface functionalization for fluorescent and bio-medical applications.

Multifunctional carbon-based nanodots (C-dots) are synthesized using atmospheric plasma treatments involving reactive gases (oxygen and nitrogen). Surface design was achieved through one-step plasma treatment of C-dots (AC-paints) from polyethylene glycol used as a precursor. These AC-paints show high fluorescence, low cytotoxicity and excellent cellular imaging capability. They exhibit bright fluorescence with a quantum yield twice of traditional C-dots. The cytotoxicity of AC-paints was tested on BEAS2B, THLE2, A549 and hep3B cell lines. The in vivo experiments further demonstrated the biocompatibility of AC-paints using zebrafish as a model, and imaging tests demonstrated that the AC-paints can be used as bio-labels (at a concentration of <5 mg mL-1). Particularly, the oxygen plasma-treated AC-paints (AC-paints-O) show antibacterial effects due to increased levels of reactive oxygen species (ROS) in AC-paints (at a concentration of >1 mg mL-1). AC-paints can effectively inhibit the growth of Escherichia coli (E. coli) and Acinetobacter baumannii (A. baumannii). Such remarkable performance of the AC-paints has important applications in the biomedical field and environmental systems.

High-Efficiency Double Absorber PbS/CdS Heterojunction Solar Cells by Enhanced Charge Collection Using a ZnO Nanorod Array.

The device architecture of solar cells remains critical in achieving high photoconversion efficiency while affordable and scalable routes are being explored. Here, we demonstrate a scalable, low cost, and less toxic synthesis route for the fabrication of PbS/CdS thin-film solar cells with efficiencies as high as ∼5.59%, which is the highest efficiency obtained so far for the PbS-based solar cells not involving quantum dots. The devices use a stack of two band-aligned junctions that facilitates absorption of a wider range of the solar spectrum and an architectural modification of the electron-accepting electrode assembly consisting of a very thin CdS layer (∼10 nm) supported by vertically aligned ZnO nanorods on a ∼50 nm thick ZnO underlayer. Compared to a planar electrode of a 50 nm thick CdS film, the modified electrode assembly enhanced the efficiency by ∼39% primarily due to a significantly higher photon absorption in the PbS layer, as revealed by a detailed three-dimensional finite difference time-domain optoelectronic modeling of the device.

Advanced nanoporous TiO2 photocatalysts by hydrogen plasma for efficient solar-light photocatalytic application.

We report an effect involving hydrogen (H2)-plasma-treated nanoporous TiO2(H-TiO2) photocatalysts that improve photocatalytic performance under solar-light illumination. H-TiO2 photocatalysts were prepared by application of hydrogen plasma of assynthesized TiO2(a-TiO2) without annealing process. Compared with the a-TiO2, the H-TiO2 exhibited high anatase/brookite bicrystallinity and a porous structure. Our study demonstrated that H2 plasma is a simple strategy to fabricate H-TiO2 covering a large surface area that offers many active sites for the extension of the adsorption spectra from ultraviolet (UV) to visible range. Notably, the H-TiO2 showed strong ·OH free-radical generation on the TiO2 surface under both UV- and visible-light irradiation with a large responsive surface area, which enhanced photocatalytic efficiency. Under solar-light irradiation, the optimized H-TiO2 120(H2-plasma treatment time: 120 min) photocatalysts showed unprecedentedly excellent removal capability for phenol (Ph), reactive black 5(RB 5), rhodamine B (Rho B) and methylene blue (MB) - approximately four-times higher than those of the other photocatalysts (a-TiO2 and P25) - resulting in complete purification of the water. Such well-purified water (>90%) can utilize culturing of cervical cancer cells (HeLa), breast cancer cells (MCF-7), and keratinocyte cells (HaCaT) while showing minimal cytotoxicity. Significantly, H-TiO2 photocatalysts can be mass-produced and easily processed at room temperature. We believe this novel method can find important environmental and biomedical applications.