Synthesis and antiprotozoal activity of pyridine thioaryl ethers

By reaction of pyridine nitro derivatives containing a mobile halogen atom with thiols of the benzene series, twelve thioaryl ethers of nitropyridine were obtained. However, 2-chloro-3-nitropyridine and 2-chloro-5-nitropyridine were used as reactive pyridine compounds. The reaction was carried out in dimethylformamide (DMFA) or dimethyl sulfoxide (DMSO) in the presence of bases: sodium ethylate, potash, sodium hydride. Generally, the yields exceeded 90%. The sulfur containing derivatives of aromatic series were 2-mercaptobenzoic acid (compound 1 of Table 1), methyl ester of 2-mercaptobenzoic acid (compounds 2 and 3 of Table 1), compound 3 being obtained by reduction of nitro group of compound 2. Also the amides of 2-mercaptobenzoic acid were used: 3-dimethylaminopropylamide of 2-mercaptobenzoic acid (compound 4 of Table 1), and also the reduction product of compound 4 to 3-aminopyridine derivative (compound 5 of Table 1) and morfolide of 2-mercaptobenzoic acid (compound 6 of Table 1). To make the water-soluble a sodium salt of 2-mercaptobenzoic acid was obtained (compound 7 of Table 1). A number of compounds with the pyridine ring nitrogroup reduced to amine (compounds 8, 10 of Table 1), as well as a number of derivatives containing both free (compounds 9, 10 of Table 1) and acylated amino group (compound 11 of Table 1) were also obtained. We also prepared compound 12 representing a product of interaction of 2-chloro-3-nitropyridine with 2-mercapto-3-acetylpyridine. We should note that the best nitrogroup reductant for the synthesis of compounds 3, 5, 7, and 10 is powdered iron in alcohol medium containing both inorganic and organic acids (hydrochloric or acetic acid). The application of other reducing agents (sodium sulfide and ammonium sulfide) led to strong resinification of the reaction mixture. The compounds were recrystallized from organic solvents (ethyl acetate, benzene, ethanol) for purification. Significant antiprotozoic activity was found in 7 of 12 compounds (58%), with 3-nitro-2-chloropyridine being the most active (7.8 and 3.9 ?g/ml). To enhance the activity, the synthesis of compounds with an amino group in the benzene ring as well as the introduction of both donor and acceptor substituents into the benzene ring is recommended.

Impact of GaAs(100) surface preparation on EQE of AZO/Al2O3/p-GaAs photovoltaic structures

In order to effectively utilize the photovoltaic properties of gallium arsenide, its surface/interface needs to be properly prepared. In the experiments described here we examined eight different paths of GaAs surface treatment (cleaning, etching, passivation) which resulted in different external quantum efficiency (EQE) values of the tested photovoltaic (PV) cells. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) examinations were conducted to obtain structural details of the devices. X-ray photoelectron spectroscopy (XPS) with depth profiling was used to examine interface structure and changes in the elemental content and chemical bonds. The photoluminescence (PL) properties and bandgap measurements of the deposited layers were also reported. The highest EQE value was obtained for the samples initially etched with a citric acid-based etchant and, in the last preparation step, either passivated with ammonium sulfide aqueous solution or treated with ammonium hydroxide solution with no final passivation. Subsequent I–V measurements, however, confirmed that from these samples, only the sulfur-passivated ones provided the highest current density. The tested devices were fabricated by using the ALD method.

Оптические и электронные свойства пассивированных поверхностей InP(001)

The effect of chemical passivation in solutions of ammonium sulfide (NH4)2S on the optical and electronic properties of the n-InP (001) surface has been studied. It has been shown that treatment in a 4% aqueous solution of (NH4)2S leads to a decrease of surface band bending and localized charges in near-surface region in the 2 times. Processing in a 4% alcoholic solution of (NH4)2S leads to a decrease in these parameters in 3 times, and moreover, the barrier photovoltage and also reduces in three times.

Novel Low Temperature Route to Produce CdS/ZnO Composite Nanofibers as Effective Photocatalysts

In this work, CdS/ZnO composite nanofibers (NFs) were prepared by the electrospinning of a sol–gel comprised of poly(caprolactone), zinc acetate dihydrate, cadmium acetate dihydrate, and ammonium sulfide. The electrospun NF mats were calcined under vacuum in an argon (Ar) atmosphere at 200 °C for 1 h. Standard physiochemical analysis techniques demonstrated the formation of the crystalline hexagonal phase of CdS and ZnO. Composite NFs showed good photocatalytic degradation of methylene blue (MB) dye under visible light irradiation compared to their counterparts. CdS nanoparticles, ZnO nanofibers, and composite NFs photodegraded 35.5%, 47.3%, and 90% of the MB dye, respectively, within 100 min. The reaction kinetics of MB photodegradation using the composite NFs followed the pseudo-first-order relation. Owing to their facile preparation and good photodegradation ability, the proposed method can be used to prepare various photocatalysts for wastewater treatment.