Green Synthesis of Nickel Oxide NPs Incorporating Carbon Dots for Antimicrobial Activities.

A biosynthesis composite using the green synthesis of titled metal nanoparticles (nickel oxide nanoparticles, NiO NPs, and carbon dots, C-dots) was produced, characterized, and then applied for antimicrobial activities. NiO NPs were produced using the Croton macrostachyus (Bakkannisa) plant leaf extract and nickel nitrate (III) hexahydrate [Ni(NO3)2·2H2O] as precursors, while C-dots were produced using citric acid and o-phenylenediamine (o-OPD). The distribution of the average particle size of the NiO NPs and NiO NPs@C-dots was 25.34 ± 0.12 and 24.95 ± 0.22 nm, respectively. The antimicrobial effects of the prepared materials were tested against the selected bacterial and fungal strains. Based on the outcomes of the bioassay, it was realized that both the bare and composite materials were effective against all bacterial strains. The composite's high surface area with strong inhibitive effective antimicrobial effects against bacterial and fungal strains were observed. Therefore, strong inhibitive effects of 21-24 and 22-26 mm were observed with NiO NPs and NiO NPs@C-dots, respectively.

Modification of Flexible Electrodes for P-Type (Nickel Oxide) Dye-Sensitized Solar Cell Performance Based on the Cellulose Nanofiber Film.

The preparation of flexible electrode, including working electrode (WE) and counter electrode (CE), for dye-sensitized solar cells (DSSCs) utilizing metal oxides using environmentally friendly sustainable TEMPO-oxidized cellulose nanofibers (TOCNFs) is reported in this work. A new type of flexible electrode for the DSSCs, which were made of cellulose nanofiber composites with nickel hydroxide [CNF/Ni(OH)2] substrate films and cellulose nanofiber composites with polypyrrole (CNF/PPY). Nickel hydroxide, Ni(OH)2, has been prepared hydrothermally in the presence of TOCNFs, [TOCNF@Ni(OH)2]. Similarly, the conductive polymer substrate has also been prepared from a composite consisting of TOCNF and PPY, TOCNF@ PPY film, by means of polymerization for the CE. Overall, the prepared electrodes both WE from CNF/Ni(OH)2 substrates and CE from the TOCNF@PPY substrate film were revealed as the novelty of this work and which no one has introduced previously. Although NiO nanoparticles (NPs) coated on the Ni(OH)2/TOCNF electrode also produced a good power conversion efficiency, PCE (0.75%); nevertheless, the NiO NP treatment with carbon dots boosted the efficiency up to 1.3%.

Hybridization of nickel oxide nanoparticles with carbon dots and its application for antibacterial activities.

A nickel oxide nanoparticle (NiO NP) composite with carbon dots (C-dots), (NiO NPs@C-dots) was synthesized, characterized, and then its antibacterial activity was evaluated. NiO NPs were prepared using Buddleja polystachya Fresen leaf extract and Ni(NO3 )2 .6H2 O as precursors. The C-dots were synthesized from benzene-1,4-diamine and citric acid. The cubic structure of the NiO NPs and NiO NPs@C-dots was in phase with their average particle size distributions of 21.47 ± 0.56 and 21.61 ± 0.34 nm, respectively. The surface morphology of the NiO NPs@C-dots was characterized using field emission scanning electron microscopy and also revealed a large surface area, which is advantageous for the specified application. The X-ray diffraction result indicated a cubic face wurtzite structure and the crystalline nature of the NiO NPs. Carbon-doped compounds had no influence on the crystal structure of the NiO compound and no new peaks were observed. The antibacterial activity of a composite made up of NiO NPs@C-dots was tested, as well as the antibacterial activities of compounds produced against human photogenic bacterial strains. Both NiO NPs and NiO NPs@C-dots were found to be powerful against all bacterial strains, based on the bioassay results. NiO NPs and NiO@C-dots appeared to display strong to inhibitory effects of 14-20 mm and 17-23 mm, respectively.

Enhanced Photosensitization by Carbon Dots Co-adsorbing with Dye on p-Type Semiconductor (Nickel Oxide) Solar Cells.

In this work, the effect of carbon dots (C-dots) on the performance of NiO-based dye-sensitized solar cells (DSSCs) was explored. NiO nanoparticles (NPs) with a rectangular shape (average size: 11.4 × 16.5 nm2) were mixed with C-dots, which were synthesized from citric acid (CA) and ethylenediamine (EDA). A photocathode consisting of a composite of C-dots with NiO NPs (NiO@C-dots) was then used to measure the photovoltaic performance of a DSSC. A power conversion efficiency (PCE) of 9.85% (430 nm LED@50 mW/cm2) was achieved by a DSSC fabricated via the adsorption of N719 sensitizer with a C-dot content of 12.5 wt % at a 1.5:1 EDA/CA molar ratio. This PCE value was far larger than the PCE value (2.44 or 0.152%) obtained for a NiO DSSC prepared without the addition of C-dots or N719, respectively, indicating the synergetic effect by the co-adsorption of C-dots and N719. This synergetically higher PCE of the NiO@C-dot-based DSSC was due to the larger amount of sensitizer adsorbed onto the composites with a larger specific surface area and the faster charge transfer in the NiO@C-dot working electrode. In addition, the C-dots bound to the NiO NPs shorten the band gap of the NiO NPs due to energy transfer and give rise to faster charge separation in the electrode. The most important fact is that C-dots are the main sensitizer, while N719 tightly adsorbs on C-dots and NiO behaves as an accelerator of a positive electron transfer and a restrainer of the electron-hole recombination. These results reveal that C-dots are a remarkable enhancer for NiO NPs in DSSCs and that NiO@C-dots are promising photovoltaic electrode materials for DSSCs.