Light-enhanced Activity Research Articles

Investigation of the influence for S-ions incorporated into the Ag2ZnSnSe4 photoelectrodes on their light-enhanced activities in aqueous salt-water solution

BackgroundLarge-scale application in solar salt-water splitting is an important way to reduce the influence of environmental problem without any decrease in the usage of energy. To develop the photoelectrochemical (PEC) salt-water splitting is thus a promising way for further industrial application. MethodsThe Ag2ZnSnSe4 (AZTSe) and their S-ions incorporating samples were produced by the post selenization/sulfurization of Ag/Sn/Zn sandwich metal precursors with the suitable amount of sulfur + selenium powder mixtures at 410 ℃ for 90 min under nitrogen atmosphere. The PEC tests using samples as photoelectrode were then carried out. Significant findingsThe maximum light-enhanced activity of pristine AZTSe and their S-ions incorporated samples was 3.65 and 2.37 mA/cm2 as the applied voltage of 1.23 V vs. RHE (relative hydrogen electrode) in a 0.5 M sodium chloride electrolyte, respectively. Electrochemical impedance and intensity-modulated photocurrent spectra of samples represented that the S-ions incorporated into AZTSe sample could reduce the photo-corrosion reaction on sample surface because of the decrease in the number of light-induced holes occupied on sample surface. Our report proposed the systemic evaluation on the influence of S-ions incorporated into AZTSe sample for light-enhanced salt-water splitting.

Sulfated and Oxygenated Imidazoline Derivatives: Synthesis, Antioxidant Activity and Light-Mediated Antibacterial Activity.

Imidazoline derivatives with different exocyclic substituents were simply prepared from common starting materials. The procedures were carried out in an eco-friendly manner. The antioxidant activity of these derivatives was explored by different experimental assays, such as ABTS.+ and DPPH. scavenging assay, as well as reducing power assay. The structural differences are discussed in terms of the results. Sulfur analogs showed higher antioxidant activity than their oxygenated counterparts. The same tendency was observed in microbiological studies, in which the same imidazoline compounds were assayed for light-mediated activity against of Staphylococcus aureus and Escherichia coli strains. A light-enhanced activity was observed for almost all the sulfated imidazolines after exposure to UV-A (400-320 nm) light.

Antimicrobial and Light-Enhanced Antimicrobial Activities, Cytotoxicity and Chemical Variability of All Tunisian Eryngium Species.

This study was performed on all Eryngium species growing in Tunisia in order to evaluate their intra and interspecies variabilities and to investigate their biological activities. These species are used in traditional medicine, and literature about the phytochemical investigations of most of them is scarce. Antimicrobial and light-enhanced activities were tested against multiresistant microorganisms and extended spectrum beta-lactamase producing bacteria (ESBL). All studied species showed antimicrobial effect with several MIC values lower than 70 μg/ml. Tested Eryngium species have proven to be a promising source of photoactive compounds, while light-enhanced activity offers an alternative for the inactivation of pathogenic microorganisms which is currently subjected to a great interest. This is the first report of this activity in genus Eryngium. A significant improvement of antimicrobial activity with UV irradiation was observed, mainly for E. dichotomum, E. ilicifolium and E. triquetrum. Cytotoxicity, studied for the first time for the most species, was evaluated against cancer (J774) and non-cancer (WI38) human cell lines. Chemical composition of volatile compounds presented in the most active crude extracts (petroleum ether extracts) of the aerial parts was investigated using GC/MS analysis and was submitted to statistical analyses. It revealed their high content of bioactive phytochemicals, particularly oxygenated sesquiterpenes like spathulenol, ledol and α-bisabolol but also hydrocarbon sesquiterpenes such as β-bisabolene and copaene, as well as polyacetylene derivatives such as falcarinol. Statistical analyses permitted to evaluate the interrelations between all Tunisian Eryngium species.

In vitro phototoxic activity of Eugenia jambolana L. and Hyptis martiusii Benth

Ethanol extracts from Hyptis martiusii and Eugenia jambolana were assayed for light-mediated activity against strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Duplicate assays were conducted with and without exposure to UV-A radiation to test for light-activated or light-enhanced activity. Both extracts showed activity against at least two bacterial strains, but H. martiusii was the most active extract, being active against all strains of S. aureus and E. coli. The results represent a first report of the light-mediated antimicrobial activities of H. martiusii and E. jambolana and suggest that phytochemical investigations may be warranted.

Antimicrobial activities of southern Nepalese medicinal plants

In an ethnopharmacological screening of selected medicinal plants used in Nepal, methanol extracts from 20 plant species were assayed for activity against eleven strains of bacteria and four strains of fungi. Duplicate assays were conducted with and without exposure to ultraviolet (UV)-A radiation to test for light-activated or light-enhanced activity. Fifteen of the extracts showed activity against bacteria and fourteen showed activity against fungi. Five extracts were active only when exposed to UV-A light, and the antibiotic or antifungal effect of five extracts was enhanced upon exposure to light. Two of the most active extracts were from plants used to treat diarrhoea and dysentery. Bark from both Terminalia alata (Combretaceae) and Mallotus phillppensis (Euphorbiaceae) was active against Gram-positive and Gram-negative bacteria.

Screening of selected medicinal plants of Nepal for antimicrobial activities

In an ethnopharmacological screening of selected medicinal plants used in Nepal, methanol extracts from 21 plant species were assayed for activity against 8 strains of bacteria and 5 strains of fungi. Duplicate assays were conducted with and without exposure to UV-A radiation to test for light-activated or light-enhanced activity. All 21 of the extracts showed activity against at least 2 bacterial strains, and 20 showed activity against at least 2 fungi. Six extracts were active only when exposed to UV-A light, and the antibiotic or antifungal effect of 14 extracts was enhanced upon exposure to light.

Effects of Light on Chlorophyll Formation in Cultured Tobacco Cells II. Blue Light Effect on 5-Aminolevulinic Acid Formation1

5-Aminolevulinic acid (ALA) accumulation in dark-grown tobacco callus cells in the presence of levulinic acid (LA) was followed under blue or red light or in continuous darkness. Significant formation of ALA continued in the dark. The protochlorophyll- (ide) (Pchl) content of dark-incubated cells remained low because of its turnover. We inferred that the feedback inhibition of ALA synthesis by Pchl would not occur in darkincubated callus cells. ALA formation was enhanced by blue light, and this effect reached saturation at an intensity of about 800 mW.m−2. Neither weak nor strong red light affected ALA formation. Full enhancement of ALA formation by blue light was attained after fairly long continuous illumination of the callus cells. This blue lightenhanced activity of ALA synthesis declined very slowly during the subsequent dark incubation. The blue light enhancement of ALA formation was observed in callus cells supplied with sucrose over a wide range of concentrations. Pchl regeneration in carbon-starved callus cells, supplied with glutamate at various concentrations, was also markedly enhanced by blue light. Respiration of the callus cells was not enhanced by blue light. A possible role of blue light in regulating ALA formation in callus cells is discussed.