Detection of Exotoxins and Antimicrobial Susceptibility Pattern in Clinical Pseudomonas Aeruginosa Isolates

Background: Pseudomonas aeruginosa is a common opportunistic pathogen that causes nosocomial infection in immunocompromised patients. Among different virulence factors, the type III secretion system (TTSS) is an important agent in virulence and development of antimicrobial resistance in P. aeruginosa. Objectives: Previous studies have shown that production of type III secretion system proteins was correlated with increasing virulence and resistance to several antibiotics. In this study we determined the exotoxins genes (exoU and exoS) and pattern of antimicrobial susceptibility in clinical P. aeruginosa isolates. Methods: A total of 175 P. aeruginosa isolates were collected from patients hospitalized in educational hospitals of Shahrekord and Chamran hospital of Isfahan, Iran from April to December 2015. Antimicrobial susceptibility test was performed by disk diffusion test. The presence of exotoxins genes was detected using multiplex PCR of exoU and exoS genes. Results: The antibiotic resistance rate was higher than 70% to many antibiotics. The highest rate of resistance was related to Levofloxacin and Meropenem (155 (88.6%), 148 (84.6%)) respectively. The exoU gene was found in 75 (42.9%) isolates and 136 (77.7%) of the isolates carried the exoS. In addition, 36(20.6%) of the isolates carried the both of gens. A statistical significance was detected between the presence of exoU gene and resistance to pipracillin (P = 0.01). Conclusions: The result of this study was indicated a high resistance rate to the most antibiotic classes and a specific relationship between the virulence genotype and antimicrobial resistance especially more virulent genotype of exoU+ . In order to prevent the spread of more virulent strains in health care facilities, molecular methods alongside antimicrobial susceptibility tests is suggested

Enhancing Efficiency of Perovskite Solar Cells via N-doped Graphene: Crystal Modification and Surface Passivation

Controlling the morphology and surface passivation in perovskite solar cells is paramount in obtaining optimal opto-electronic properties. This study incorporates N-doped graphene nanosheets in the perovskite layer, which simultaneously induces an improved morphology and surface passivation at the perovskite/spiro interface, resulting in enhancement in all photovoltaic parameters

Hole-Transport Material Engineering in Highly Durable Carbon-Based Perovskite Photovoltaic Devices

Despite the fast-developing momentum of perovskite solar cells (PSCs) toward flexible roll-to-roll solar energy harvesting panels, their long-term stability remains to be the challenging obstacle in terms of moisture, light sensitivity, and thermal stress. Compositional engineering including less usage of volatile methylammonium bromide (MABr) and incorporating more formamidinium iodide (FAI) promises more phase stability. In this work, an embedded carbon cloth in carbon paste is utilized as the back contact in PSCs (having optimized perovskite composition), resulting in a high power conversion efficiency (PCE) of 15.4%, and the as-fabricated devices retain 60% of the initial PCE after more than 180 h (at the experiment temperature of 85 °C and under 40% relative humidity). These results are from devices without any encapsulation or light soaking pre-treatments, whereas Au-based PSCs retain 45% of the initial PCE at the same conditions with rapid degradation. In addition, the long-term device stability results reveal that poly[bis(4–phenyl) (2,4,6–trimethylphenyl) amine] (PTAA) is a more stable polymeric hole-transport material (HTM) at the 85 °C thermal stress than the copper thiocyanate (CuSCN) inorganic HTM for carbon-based devices. These results pave the way toward modifying additive-free and polymeric HTM for scalable carbon-based PSCs

Greener, Nonhalogenated Solvent Systems for Highly Efficient Perovskite Solar Cells

All current highest efficiency perovskite solar cells (PSCs) use highly toxic, halogenated solvents, such as chlorobenzene (CB) or toluene (TLN), in an antisolvent step or as solvent for the hole transporter material (HTM). A more environmentally friendly antisolvent is highly desirable for decreasing chronic health risk. Here, the efficacy of anisole (ANS), as a greener antisolvent for highest efficiency PSCs, is investigated. The fabrication inside and outside of the glovebox showing high power conversion efficiencies of 19.9% and 15.5%, respectively. Importantly, a fully nonhalogenated solvent system is demonstrated where ANS is used as both the antisolvent and the solvent for the HTM. With this, state-of-the-art efficiencies close to 20.5%, the highest to date without using toxic CB or TLN, are reached. Through scanning electron microscopy, UV-vis, photoluminescence, and X-ray diffraction, it is shown that ANS results in similar mixed-ion perovskite films under glovebox atmosphere as CB and TLN. This underlines that ANS is indeed a viable green solvent system for PSCs and should urgently be adopted by labs and companies to avoid systematic health risks for researchers and employees

Perovskite solar cell - electrochemical double layer capacitor interplay

We demonstrate that by a proper design of a system comprising a perovskite solar cell (PSC) coupled to an electrochemical double-layer capacitor (EDLC), it is possible to simultaneously improve both the PSC and EDLC performance and outperform each single unit behavior. Specifically, we propose a parallel connection of PSC and EDLC of different size. The EDLC buffers PSC fluctuations by storing the converted solar energy permitting for very high power output (increased by 1 order of magnitude). At the same time, the PSC improves the capacitive response of the EDLC that can be downsized towards system miniaturization. (C) 2017 Elsevier Ltd. All rights reserved

Photoelectrochemical Water‐Splitting Using CuO‐Based Electrodes for Hydrogen Production: A Review

The cost-effective, robust, and efficient electrocatalysts for photoelectrochemical (PEC) water-splitting has been extensively studied over the past decade to address a solution for the energy crisis. The interesting physicochemical properties of CuO have introduced this promising photocathodic material among the few photocatalysts with a narrow bandgap. This photocatalyst has a high activity for the PEC hydrogen evolution reaction (HER) under simulated sunlight irradiation. Here, the recent advancements of CuO-based photoelectrodes, including undoped CuO, doped CuO, and CuO composites, in the PEC water-splitting field, are comprehensively studied. Moreover, the synthesis methods, characterization, and fundamental factors of each classification are discussed in detail. Apart from the exclusive characteristics of CuO-based photoelectrodes, the PEC properties of CuO/2D materials, as groups of the growing nanocomposites in photocurrent-generating devices, are discussed in separate sections. Regarding the particular attention paid to the CuO heterostructure photocathodes, the PEC water splitting application is reviewed and the properties of each group such as electronic structures, defects, bandgap, and hierarchical structures are critically assessed

Effect of cation composition on the mechanical stability of perovskite solar cells

Photoactive perovskite semiconductors are highly tunable, with numerous inorganic and organic cations readily incorporated to modify optoelectronic properties. However, despite the importance of device reliability and long service lifetimes, the effects of various cations on the mechanical properties of perovskites are largely overlooked. In this study, the cohesion energy of perovskites containing various cation combinations of methylammonium, formamidinium, cesium, butylammonium, and 5-aminovaleric acid is reported. A trade-off is observed between the mechanical integrity and the efficiency of perovskite devices. High efficiency devices exhibit decreased cohesion, which is attributed to reduced grain sizes with the inclusion of additional cations and PbI2 additives. Microindentation hardness testing is performed to estimate the fracture toughness of single-crystal perovskite, and the results indicated perovskites are inherently fragile, even in the absence of grain boundaries and defects. The devices found to have the highest fracture energies are perovskites infiltrated into a porous TiO2/ZrO2/C triple layer, which provide extrinsic reinforcement and shielding for enhanced mechanical and chemical stability