2-arylfuro [2,3-b] quinoxalines

2-Arylfuro[2,3-b]quinoxalines were obtained by cyclization of 2-phenacyl-3-quinoxalones in the presence of polyphosphoric acid or a mixture of phosphorus oxychloride and phosphorus pentachloride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 259–260, February, 1973.     

Chemistry of esters of keto acids of the acetylene series. X. Addition of amines to 3-phenylethynyl-1-quinoxalone

The reaction of 3-phenylethynyl-2-quinoxalones with aliphatic and aromatic amines gives alkyl(aryl)imines of 3-phenacylidene-2-quinoxalone, the structures of which were proved by alternative synthesis from 3-phenacylidene-2-quinoxalone and the appropriate amines.See [1] for communication IX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 276–277, February, 1976.     

Modified solid electrodes for stripping voltammetric determination of tin

The paper describes the determination of tin by ASV using modified thick film electrodes. Three different types of electrodes were developed: One modified with a mixture of Nafion and mercury(II)acetate, one modified with diethyldithiocarbamate (DDC) or pyrrolidinedithiocarbamate (PDC) and mercury(II)acetate, and one modified with calomel. The analyte was accumulated on the electrode surface after special electrochemical pretreatment of the modified electrode. After recording the voltammogram the electrodes were electrochemically regenerated. By virtue of their lifetime and their measurement reproducibility, we preferred the DDC and PDC modified electrodes. They can be used for months without changing their chemical characteristics. The linear range for tin determination with these electrodes is between 1 and 100 μg/L; the detection limit was calculated as 0.9 μg/L. The electrodes were applied to the direct determination of tin in different canned fruit juices without special sample pretreatment. Received: 20 December 1996 / Revised: 11 March 1997 / Accepted: 13 March 1997     

Enzymeless determination of cholesterol using gold and silver nanoparticles as electrocatalysts

We present the results of synthesis and study of the electrocatalytic activity of gold and silver nanoparticles of different composition (individual metals, core–shell particles, nanoalloys, and particles synthesized electrochemically), immobilized on the surface of a glassy carbon electrode, with respect to cholesterol. A surfactant (cetyltrimethylammonium bromide) is selected to create an aqueous–organic emulsion of cholesterol. It is demonstrated that nanoparticles with a gold core and a silver shell with the regression equation of I = 1.4 × 10^–5 c _chol + 5.8 × 10^–5 (R ² = 0.97) and silver nanoparticles synthesized electrochemically with the regression equation of I = 1.0 × 10^–5 c _chol + 3.0 × 10^–4 (R ² = 0.95) possess optimal electrocatalytic characteristics.     

Multifunctional Sulfur-Hyperdoped Silicon Nanoparticles with Engineered Mid-Infrared Sulfur-Impurity and Free-Carrier Absorption

Si nanoparticles (NPs), which are innovative promising light-harvesting components of thin-film solar cells and key-enabling biocompatible theranostic elements of infrared-laser and radiofrequency hyperthermia-based therapies of cancer cells in tumors and metastases, are significantly advanced in their near/mid-infrared band-to-band and free-carrier absorption via donor sulfur-hyperdoping during high-throughput facile femtosecond-laser ablative production in liquid carbon disulfide. High-resolution transmission electron microscopy and Raman microscopy reveal their mixed nanocrystalline/amorphous structure, enabling the extraordinary sulfur content of a few atomic percents and very minor surface oxidation/carbonization characterized by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. A 200-nm thick layer of the nanoparticles exhibits near−mid-infrared absorbance, comparable to that of the initial 380-micron thick n-doped Si wafer (phosphor-dopant concentration ≈10¹⁵ cm⁻³), with the corresponding extinction coefficient for the hyperdoped NPs being 4–7 orders higher over the broadband spectral range of 1–25 micrometers. Such ultimate, but potentially tunable mid-IR structured, multi-band absorption of various sulfur-impurity clusters and smooth free-carrier absorption are break through advances in mid-infrared (mid-IR) laser and radiofrequency (RF) hyperthermia-based therapies, as envisioned in the RF-heating tests, and in fabrication of higher-efficiency thin-film and bulk photovoltaic devices with ultra-broad (UV−mid-IR) spectral response.     

One-Step Nanosecond-Laser Microstructuring,Sulfur-Hyperdoping,and Annealing of Silicon Surfaces in Liquid Carbon Disulfide

We perform a single-shot IR nanosecond laser processing of commercial silicon wafers in ambient air and under a 2 mm thick carbon disulfide liquid layer. We characterize the surface spots modified in the liquid ambient and the spots ablated under the same conditions in air in terms of its surface topography, chemical composition, band-structure modification, and crystalline structure by means of SEM and EDX microscopy, as well as of FT-IR and Raman spectroscopy. These studies indicate that singlestep microstructuring and deep (up to 2–3% on the surface) hyperdoping of the crystalline silicon in its submicron surface layer, preserving via pulsed laser annealing its crystallinity and providing high (10⁴ cm^?1) spectrally flat near- and mid-IR absorption coefficients, can be obtained in this novel approach, which is very promising for thin-film silicon photovoltaic devices.