The use of plasmonic nanoparticles (NPs) in dye-sensitized solar cells (DSSCs) in an effort to enhance their power conversion efficiencies (PCEs) increases light absorbance of the cells but also affect their electron dynamics. This has contributed to the failure of plasmonic NPs to make the expected high impact of PCE enhancement. Herein, we investigated the wide range effects of plasmonic NPs on the performance of DSSCs, using extended characterization and a systematic approach. We prepared DSSCs using Ag@TiO2 NPs-doped TiO2 photoanodes. Using a wide range doping concentration, we obtained panchromatic enhancement effect with two optimal doping concentrations (0.1 and 1 wt. %).They enhanced PCE via mainly: a) optimal band alignment for efficient charge injection; and b) a balance of the negative and positive effects of plasmonic NPs on cell performance parameters (open circuit voltage, fill factor, charge transfer resistance against recombination, electron life time and charge collection efficiency); respectively. The PCE of the pristine sample increased from 4.66 to 4.88 and 5.00% via these 2 routes, respectively. The major cause of not obtaining very high PCE was charge recombination from high charge density. Thus, these observations might serve as invaluable guidance for the preparation of highly efficient plasmonic DSSCs.
The market demand for elastomeric‐graphene/derivatives nanosheets (GDS) materials is high nowadays, due to their excellent physico‐mechanical properties over traditional composites. However, the curing behavior of elastomeric‐GDS which influences the overall properties and also determines the cost of related products has not been well investigated. Previously, the curing properties of NBR‐graphene oxide (GO) and NBR‐reduced graphene oxide (rGO) was studied and the curatives (accelerator and activators) were suspected to have influence on their curing behavior. This study explores the curing behavior of NBR‐GO and NBR‐rGO in the absence of tetramethylthiuram disulfide (TMTD) accelerator. The virgin NBR exhibited shorter curing periods with higher curing rates (CRI) than the composites. The measured CRI showed close correlation with the activation energy Ea, deduced from Ozawa and Kissinger kinetics models. The NBR‐rGO composites showed shorter scorch time and lowered Ea at higher temperatures, with increased tensile properties than NB‐GO composites. Despite the delay, the composites exhibited high strength over the virgin NBR, due to tighter networks introduced by rGO and GO sheets within NBR. Therefore, future design of elastomer‐GDS‐based composites must involve a careful control of the amounts of the accelerator‐/co‐accelerator‐like TMTD in the mixtures for improved physico‐mechanical properties of the final product.
The synergistic effects of transition metal based nanocomposites are known to possess enhanced antibacterial activities. However, in-depth analysis of the relative antibacterial performance of some of the prominent nanocomposites remains unavailable. This study compares the antibacterial activity of two separate nanocomposites, which are copper oxide with silver (CuO/Ag) and zinc oxide with silver (ZnO/Ag). The individual CuO/Ag and ZnO/Ag nanocomposites were synthesised by a mixed wet-chemical method. The resulting particles were analysed by XRD, XRF, TEM, UV-Vis spectrophotometer, BET, and FTIR. The antibacterial activity of the nanoparticles were tested on Gram-negative and Gram-positive bacteria, Escherichia coli (ATCC25922) and Staphylococcus aureus (ATCC25923), respectively, using the Kirby–Bauer disc diffusion and the microdilution methods. The Kirby–Bauer disc diffusion test results had the same minimum inhibition concentration (MIC) value for both CuO/Ag and ZnO/Ag against E. coli and S. aureus, which was 0.25 mg/ml. The applied nanocomposites using microdilution showed that CuO/Ag had approximately 98.8% and 98.7% efficiency on the respective Gram-positive and Gram-negative bacterial species, while ZnO/Ag achieved 91.7% and 89.3% efficiency, respectively, against the Gram-positive and Gram-negative bacterial species. This study presents a novel approach for relative analysis of the performance efficiency of transition metal based nanocomposites.
Demand for low-cost, environmentally friendly alternative renewable energy sources makes the dye-sensitized solar cell (DSSC) a viable alternative. DSSCs have a high but competitively challenged power conversion efficiency (PCE) of 11.9%. Plasmonic DSSCs is one approach with extreme enhancement of light absorption to increasing the PCE. The highest PCE of plasmonic DSSCs is still <11% however, due to secondary effects which are not yet well understood. In this study, we used a complex composite of plasmonic nanoparticles (PNPs) with extended characterization and wide ranging PNP loadings, combined with a systematic approach to obtain synergistic effects and a deeper understanding of the effects of plasmonic nanostructures on DSSC performance. The results showed two optimal loading amounts of PNPs with enhanced PCEs of 4.26 and 4.36% (from 3.54%), with enhancement effects obtained mainly from efficient charge injection and a balance of the negative and positive effects of the PNPs, respectively. An increase in the photoanode thickness from 5.5 to 9¯m resulted in PCE enhancement from 4.39 to 4.58%, mainly via efficient charge injection. The PNPs had both positive and negative effects on key DSSC performance parameters: decreased photoanode surface area but with panchromatic enhancement of light absorbance; increased short circuit current up to a point followed by a decrease due to poor charge injection; increased open circuit voltage and fill factor; enhanced charge transfer resistance against charge recombination; improved electron lifetime and charge collection efficiency; lowered enhancement of cell performance in the near infra-red region; and induced abundantly generated electrons augmented charge recombination. These results contribute significantly to understanding of the effects of plasmonic nanostructures and can serve as a useful guide to the study of plasmonic DSSCs and related fields.
A layer of TiO nanotube (TNT) arrays with a thickness of 13 μm is synthesized by a two-step anodic oxidation from Ti metal foil. Surface charged Ag nanoparticles (NPs) are prepared by chemical reduction. After a pretreatment of the TNT arrays by acetone vapor, Ag NP filled TNT arrays can be achieved by electrophoretic deposition (EPD). Effects of the applied voltage during EPD such as DC-AC difference, frequency and waveform are investigated by quantitative analysis using atomic absorption spectroscopy. The results show that the best EPD condition is using DC 2 V + AC 4 V and a square wave of 1 Hz as the applied voltage. Back illuminated dye-sensitized solar cells are fabricated from TNT arrays with and without Ag NPs. The efficiency increased from 3.70% to 5.01% by the deposition of Ag NPs.
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