Optoelectronics applications of electrodeposited p- and n-type Al2Se3 thin films

In this paper, energy band gaps and electrical conductivity based on aluminum selenide (Al2Se3) thin films are synthesized electrochemically using cathodic deposition technique, with graphite and carbon as cathode and anode, respectively. Synthesis is done at 353 K from an aqueous solution of analytical grade selenium dioxide (SeO2), and aluminum chloride (AlCl2·7H2O). Junctions-based Al2Se3 thin films from a controlled medium of pH 2.0 are deposited on fluorine-doped tin oxide (FTO) substrate using potential voltages varying from 1,000 mV to 1,400 mV and 3 minutes −15 minutes respectively. The films were characterized for optical properties and electrical conductivity using UV-vis and photoelectrochemical cells (PEC) spectroscopy. The PEC reveals a transition in the conduction of the films from p-type to n-type as the potential voltage varies. The energy band gap reduces from 3.2 eV to 2.9 eV with an increase in voltage and 3.3 eV to 2.7 eV with increase in time. These variations indicate successful fabrication of junction-based Al2Se3 thin films with noticeable transition in the conductivity type and energy band gap of the materials. Consequently, the fabricated Al2Se3 can find useful applications in optoelectronic devices.

Foliar Nourishment with Nano-Selenium Dioxide Promotes Physiology, Biochemistry, Antioxidant Defenses, and Salt Tolerance in Phaseolus vulgaris

Novel strategic green approaches are urgently needed to raise the performance of plants subjected to stress. Two field-level experimental attempts were implemented during two (2019 and 2020) growing seasons to study the possible effects of exogenous nourishment with selenium dioxide nanoparticles (Se-NPs) on growth, physio-biochemical ingredients, antioxidant defenses, and yield of Phaseolus vulgaris (L.) plant growing on a salt-affected soil (EC = 7.55–7.61 dS m−1). At 20, 30, and 40 days from seeding, three foliar sprays were applied to plants with Se-NPs at a rate of 0.5, 1.0, or 1.5 mM. The experimental design was accomplished in randomized complete plots. The data indicate noteworthy elevations in indicators related to growth and yield; pigments related to effective photosynthesis, osmoprotectant (free proline and soluble sugars), nutrient and Se contents, K+/Na+ ratio, cell integrity (water content and stability of membranes), all enzyme activities; and all features related to leaf anatomy induced by Se-NPs foliar spray. Conversely, marked lowering in markers of Na+ content-induced oxidative stress (superoxide radical and hydrogen peroxide) and their outcomes in terms of ionic leakage and malondialdehyde were reported by foliar nourishment with Se-NPS compared to spraying leaves with water as an implemented control. The best results were recorded with Se-NPs applied at 1.0 mM, which mitigated the negative effects of soil salinity (control results). Therefore, the outcomes of this successful study recommend the use of Se-NPs at a rate of 1.0 mM as a foliar spray to grow common beans on saline soils with EC up to 7.55–7.61 dS m−1.

7-Bromo-[1,2,5]selenadiazolo[3,4-d]pyridazin-4(5H)-one

New heterocyclic systems containing 1,2,5-chalcogenadiazoles are of great interest for the creation of organic photovoltaic materials and biologically active compounds. In this communication, 3,6-dibromopyridazine-4,5-diamine was investigated in reaction with selenium dioxide in order to obtain 4,7-dibromo-[1,2,5]selenadiazolo[3,4-d]pyridazine. We found that 7-bromo-[1,2,5]selenadiazolo[3,4-d]pyridazin-4(5H)-one, the first representative of the new heterocyclic system, was isolated as a hydrolysis product of the corresponding 4,7-dibromoderivative. The structure of the newly synthesized compound was established by means of elemental analysis, high-resolution mass spectrometry, 1H, 13C NMR, IR and UV spectroscopy, and mass spectrometry.

SELENIUM AS A VERSATILE REAGENT IN ORGANIC SYNTHESIS: MORE THAN ALLYLIC OXIDATION

: For many years since its discovery, Selenium has played the role of a bad boy who became a hero in organic transformations. Selenium dioxide, for instance, is one of the most remembered reagents in allylic oxidations, having been applied in the synthesis of several naturally occurring products. The main goal of this review is to show the recent advances in the use of classical and new selenium reagents in organic synthesis. As demonstrated through around 60 references discussed in this study, selenium can go even forward as a versatile reagent. We bring a collection of selenium reagents and their transformations that are still hidden from most synthetic organic chemists.

Oxidative Dimerization of 1Н-Benzo[f]chromenes: Synthesis of Benzannulated Analogues of Spirobiflavonoids Welwitschins E and F

A new oxidative transformation of 1H-benzo[f]chromenes into spirodimers under the action of selenium dioxide was discovered, leading to spirodimers, which are dibenzannulated analogues of naturally occurring welwitschins E and F. In the reaction, both MnO2 and I2O5 can also be used as an oxidant. The protocol has advantages of mild reaction conditions and simple operation. At the same time, oxidation of 1H-benzo[f]chromenes with (diacetoxyiodo)benzene is accompanied by the formation of 3,3′-bibenzo[f]chromene as a dimer of a different structure. It was also found that 4H-chromenes under the action of various oxidants are cleaved to give chalcone.

ELECTROCHEMICAL OBTAINING AND MORPHOLOGY OF ALLOYS’ NANOCOVERINGS IN SYSTEM Re-Сu-Se

Electrochemical obtaining of nano-coatings in the system Re-Cu-Se on platinum electrode during voltammetric cycling was studied. The research was carried out using sulphate solution containing selenium dioxide, potassium perrenate and copper chloride. For obtaining nano coatings in the Re-Cu-Se system, we used an electrolyte of the following composition (mol/l): 6.9 ∙ 10-4 – 6.9 ∙ 10-3 KReO4 + 9 ∙ 10-4 – 1.8 ∙ 10-2 SeO2 + 6 ∙ 10-4 – 1.2 ∙ 10-2 CuCl2 ∙ 2H2O +2 H2SO4, t = 80 ºC; V = 0.005VS-1; pH = 0.1, electrode - Pt. Based on the studying of the volt-ampere dependences during the joint electroreduction of rhenium (VII), selenium (IV) and copper (II) ions from sulfate electrolytes on a PT electrode, the conditions for the deposition of alloys nanocoatings in the Re-Cu-Se system were established. To study the morphology of films on platinum and copper substrates, the electrode surface was studied using a JEOL JSM7600F scanning electron microscope at various magnifications, and was accordingly subjected to elemental analysis using an Oxford X-MAX 50 detector. The sample has been scanned in the mode of secondary electrons at an accelerating voltage ~ 15 keV. It has been found that agglomerates are observed on the electrode surface, mainly consisting of sphere-shaped particles with an average size of ~ 20-25 nm. The spectrum of characteristic X-ray radiation indicates the presence of these components of the system, allows quantitative analysis of samples. Based on the presented distribution diagram by weight percent, the content of system components is represented by the following ratio: Re-12%, Cu-5%, Se-10%. The presence of characteristic peaks of carbon and oxygen in the spectrum is explained by residual phenomena during obtaining.