Structural, Optical and Photocatalytic Activity of Multi-heterojunction Bi2O3/Bi2O2CO3/(BiO)4CO3(OH)2 Nanoflakes Synthesized via Submerged DC Electrical Discharge in Urea Solution

In this research, a novel ternary multi-heterojunction Bi₂O₃/Bi₂O₂CO₃/(BiO)₄CO₃(OH)₂ photocatalyst is fabricated via submerged DC electrical arc discharge in urea solution. FT-IR, XRD, EDS and PL results confirm the formation of Bi₂O₃/Bi₂O₂CO₃/(BiO)₄CO₃(OH)₂ multi-heterojunction. Formation of nanoflake morphology is revealed by FE-SEM and TEM images. The optical properties and intense absorption edge of Bi₂O₃/Bi₂O₂CO₃/(BiO)₄CO₃(OH)₂ reveal the proper visible light absorbing ability. The photocatalytic performance of the sample is investigated via the degradation of methylene orange (MeO) and rhodamine B (RB) under visible light irradiation. The photocatalytic activity of Bi₂O₃/Bi₂O₂CO₃/(BiO)₄CO₃(OH)₂ is compared with the synthesized sample in water, Bi₂O₃/Bi/Bi(OH)_3, which exhibits much higher photocatalytic activity. Also, the stable photodegradation efficiency of Bi₂O₃/Bi₂O₂CO₃/(BiO)₄CO₃(OH)₂ after four cycles reveals the long-term stability and reusability of the synthesized photocatalyst. The PL intensity of Bi₂O₃/Bi₂O₂CO₃/(BiO)₄CO₃(OH)₂ shows an improved separation rate of electron-hole pairs and so enhanced photocatalytic performance. The improved photocatalytic activity can be ascribed to the formation of multi-heterojunctions, flake morphology and intrinsic internal electric field (IEF). Multi-heterojunction nanoflakes enhance the absorbance of visible light and facilitate the separation and transport of photogenerated electron holes through large IEF. Our work offers an effective method for the production of innovative bismuth-based photocatalyst with excellent prospects for the degradation of environmental pollutants and light harvesting for renewable energy generation under visible light.

Enhancing the efficiency and stability of perovskite solar cells based on moisture-resistant dopant free hole transport materials by using a 2D-BA2PbI4 interfacial layer

In this work, the photovoltaic performance and stability of perovskite solar cells (PSCs) based on a dopant-free hole transport layer (HTL) are efficiently improved by inserting a two-dimensional (2D) interfacial layer. The benzyl ammonium lead iodide (BA₂PbI₄) 2D perovskite is used as an interfacial layer between the 3D CH₃NH₃PbI₃ perovskite and two moisture-resistant dopant-free HTLs including poly[[2,3-bis(3-octyloxyphenyl)-5,8-quinoxalinediyl]-2,5-thiophenediyl] (TQ1) and poly(3-hexylthiophene) (P3HT). TQ1 with a facile synthesis procedure has a higher moisture resistivity compared to P3HT which can improve the stability of PSCs. The 2D BA₂PbI₄ perovskite with a less-volatile bulkier organic cation efficiently passivates the defects at the perovskite/HTL interface, leading to 11.95% and 15.04% efficiency for the modified TQ1 and P3HT based cells, respectively. For a better understanding, the structural, optical, and electrical properties of PSCs comprising P3HT and TQ1 HTLs with and without interface modification are studied. The interface modified PSCs show slower open-circuit voltage decay and longer carrier lifetimes compared to unmodified cells. In addition, impedance spectroscopy reveals lower charge transport resistance and higher recombination resistance for the modified devices, which could be associated with the modification of the interface between the 3D CH₃NH₃PbI₃ perovskite and HTL caused by the 2D interfacial layer. Also after aging under ambient conditions for about 800 hours, the modified PCSs retain more than 80% of their initial PCEs. These results give us the hope of achieving simpler, cheaper, and more stable PSCs with dopant-free HTLs through 2D interfacial layers, which have great potential for commercialization.

Photoelectrochemical properties of single-grain hematite films grown by electric-field-assisted liquid phase deposition

This article reports a modification of the conventional liquid phase deposition (C-LPD) method for the single-grain deposition of α-Fe2O3 (hematite) films into an electric-field-assisted liquid phase deposition (EA-LPD).

Efficacy of green synthesized silver nanoparticles via ginger rhizome extract against Leishmania major in vitro

INTRODUCTION

Leishmaniasis is a major public health problem that causes by parasite of the genus Leishmania. The pentavalent antimonial compounds that used for treatment are not safe or effective enough. The aim of the present study was preparation and evaluation of the efficacy of green synthesized silver nanoparticles against Leishmania major (L. major) in vitro.

METHODS

To synthesis silver (Ag) nanoparticles (NPs), ginger extract was added to the 0.2mM AgNO3 aqueous solution (1:20). Effects of different concentrations of Ag-NPs on the number of L. major promastigotes were investigated using counting assay. The MTT test was applied to determine the toxicity of Ag-NPs on promastigotes of L. major, as well as, macrophage cells. Then, to evaluate the anti-amastigotes effects of Ag-NPs, parasites within the macrophages were counted by light microscope. Furthermore, to determine the induced apoptosis and necrotic effects of Ag-NPs on promastigotes, flow cytometry method was employed using annexin staining.

RESULTS

The effect of Ag-NPs on promastigotes and amastigotes of L. major was effective and has a reverse relationship with its concentration. According to the results of anti-amastigote assay, the IC50 value of this nanoparticle was estimated 2.35 ppm after 72h. Also, Ag-NPs caused Programmed Cell Death (PCD) in promastigotes of L. major and showed 60.18% of apoptosis.

DISCUSSION

Based on the mentioned results, it can be concluded that Ag NPs has a beneficial effect on promastigote and amastigote forms of L. major in vitro. Hence, these nanoparticles could be applied as promising antileishmanial agents for treatment of Leishmania infections.

The effect of silver oxidation on the photocatalytic activity of Ag/ZnO hybrid plasmonic/metal-oxide nanostructures under visible light and in the dark

A new synergetic hybrid Ag/ZnO nanostructure was fabricated which is able to cause photocatalytic degradation (in high yields) of methylene blue under visible light as well as in the dark. In this nanostructure, ZnO was synthesized using the arc discharge method in water and was coupled with Ag via a chemical reduction method. X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy results confirmed the existence of defects in ZnO in the hybrid nanostructures; these defects act as electron traps and inhibit the recombination of electron-hole pairs. The absorption edge of the hybrid nanostructure shifts toward the visible region of the spectrum due to a combination of the Ag plasmonic effect and the defects in ZnO. Band-edge tuning causes effective visible light absorption and enhances the dye degradation efficiency of Ag/ZnO nanostructures. Silver oxidation in the hetero-structure changed the metal-semiconductor interface and suppressed the plasmonic enhancement. Nevertheless, the synthesized Ag/ZnO decomposed methylene blue in visible light, and the silver oxidation only affected the catalytic activity in the dark. This work provides insight into the design of a new and durable plasmonic-metal oxide nanocomposite with efficient dye degradation even without light illumination.

Green synthesis of silver nanoparticles using Zingiber officinale and Thymus vulgaris extracts: characterisation, cell cytotoxicity, and its antifungal activity against Candida albicans in comparison to fluconazole

Fluconazole (FLZ) application as a highly successful commercial antifungal azole agent to treat the fungal infections is limited due to emergence of FLZ-resistant candida. In this study, the potential of green synthesised silver nanoparticles (NPs) as an antifungal agent against Candida albicans fungal pathogen is investigated. The extract of ginger (Zingiber officinale) and thyme (Thymus vulgaris) plays as reducing agent, capping agent and antifungal agent. The UV-visible spectroscopy shows the peak of surface plasmon resonance of synthesised Ag NPs after a period of time. The synthesised Ag NPs are spherical, with average sizes of 12 and 18 nm based on ginger and thyme extract, respectively. Fourier transform infrared spectroscopy confirms the adsorption of the plant extract on the surface of the as-prepared Ag NPs. Based on the minimum inhibitory concentration (MIC) method against Candida albicans, the antifungal activity of as-prepared green synthesised Ag NPs shows higher inhibitory in comparison to FLZ. Finally, the Ag NPs synthesised via thyme extract shows no cytotoxicity with concentration below 3.5 ppm, which can be considered as an appropriate candidate instead of FLZ to treat the superficial fungal infections.

Can earthworms biosynthesize highly luminescent quantum dots?

Band gap tunable cadmium selenide (CdSe) quantum dots (QDs) were synthesized within earthworms that emit in the middle of the visible spectrum. We demonstrated that this luminescence emission is a combination of the earthworm's protein and QD luminescence, such that the contribution of QDs in the luminescence was negligible. Eisenia fetida earthworms were used for QD biosynthesis and were exposed to different concentrations of CdCl₂ and Na₂ SeO₃ in standard soil for an adequate exposure time. The size of the CdSe QDs based on the effective mass model was in agreement with the size measured from the transmission electron microscopy analysis, with an average diameter of 7 nm. Ultraviolet-visible and photoluminescence analyses confirmed the synthesis of CdSe QDs with unique absorption and luminescence at 430 nm and 605 nm, respectively.

Liquid phase deposition of iron phosphate thin films

Liquid phase deposition (LPD) has been applied for the synthesis of iron phosphate thin films as an example of an effective methodology for the thin film growth of other polyanionic compounds.

Chitosan coated tungsten trioxide nanoparticles as a contrast agent for X-ray computed tomography

Recent advances have shown that inorganic nanoparticles (NPs) based on heavy elements are highly appropriate for X-ray computed tomography (CT). In this contribution, tungsten trioxide NPs are prepared by the electrical arc discharge (EAD) method in DI water. The effect of chitosan (CTS) and glutaraldehyde (GTA) as coating and cross-linking agent, respectively, on the hydrodynamic size and zeta potential of prepared tungsten trioxide NPs is investigated. It is found that zeta potential increases by increasing the amounts of CTS. Meanwhile, by increasing the volume of glutaraldehyde (GTA), the final particle size increases whereas the zeta potential deceases. Chitosan coated tungsten trioxide demonstrated no significant cytotoxicity at concentration up to 5mg/mL after 24h. Finally, the X-ray attenuation of prepared chitosan coated tungsten trioxide NPs are higher than Iohexol as the commercially available iodinated contrasting agent at the same concentrations.