New Fluorescent Sensors Based on 1<Emphasis Type="Italic">H</Emphasis>-pyrazolo[3,4-<Emphasis Type="Italic">b</Emphasis>]quinoline Skeleton

Novel fluorescing dyes 1,3,4-triphenyl-6-(1,4,7,10-tetraoxa-13-aza-cyclopentadec-13-ylmethyl)-1H-pyrazolo[3,4-b]quinoline (K1) and 2-[(2-hydroxyethyl)-(1,3,4-triphenyl-1H-pyrazolo[3,4-b]quinolin-6-ylmethyl)-amino]ethanol (L1) have been synthesized and investigated by the means of steady state and time-resolved fluorescence techniques. These compounds act as sensors for the fluorescence detection of small inorganic cations (lithium, sodium, barium, magnesium and calcium) in solvents of different polarities (THF and acetonitrile). The mechanism, which allows application of these compounds as sensors, is an electron transfer from the electro-donative part of molecule to the acceptor part (fluorophore), which is retarded upon complexation of the electro-donative part by inorganic cations. We found that crown ether-containing compound is very sensitive to the addition of any investigated ions but amino alcohol-containing one exhibits better selectivity to the addition of two-valued cations. Two kinds of the complexes (LM⁺ and L₂M⁺) were found in the investigated systems. In addition, the dyes may be used as fluorescence indicators in solvents of lower polarity like tetrahydrofuran.     

Synthesis and properties of cationic polyelectrolyte with regioregular polyalkylthiophene backbone and ionic‐liquid like side groups

High‐regioregular poly{3‐[6‐(1‐methylimidazolium‐3‐yl)hexyl]thiophene‐2,5‐diyl bromide}, PMHT‐Br, has been prepared by reaction of high‐regioregular (above 92%) poly[3‐(6‐bromohexyl)thiophene‐2,5‐diyl] with 1‐methylimidazole. PMHT‐Br is soluble in water and water miscible solvents such as methanol, DMSO and shows solvatochromism; λ_max (nm): 423 (H₂O); 435 (MeOH); 452 (DMSO). Increased absorption band broadening observed for aqueous solution as well as NMR spectra in D₂O suggests a micelle‐like structure of PMHT‐Br molecules in these solutions: poly(3‐hexylthiophene) core and 1‐methylimidazolium bromide shell. Despite the disturbing effect of ionic groups, the solid‐state PMHT‐Br shows absorption maximum at 520 nm, the band edge at 660 nm (ca. 1.9 eV), and fluorescence emission with maximum at 635 nm, in a good agreement with the polymer regioregularity. Fluorescence emission maxima: λ_em (nm): 598 (H₂O); 562 (MeOH); 574 (DMSO), occur in a vicinity of corresponding adsorption band edges. Plot of electrical conductivity of PMHT‐Br (measured under the dynamic vacuum conditions, 5 × 10^?5 Pa) versus 1/T shows a break at about 70 °C same as the temperature dependence of λ_max of the solid PMHT‐Br. These breaks indicate an increase in the mobility of polymer segments and ions within PMHT‐Br; however, a thermal analysis did not provide solid evidence for it. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3073–3081, 2010     

Silicon solar cells with Al2O3 antireflection coating

The paper presents the possibility of using Al₂O₃ antireflection coatings deposited by atomic layer deposition ALD. The ALD method is based on alternate pulsing of the precursor gases and vapors onto the substrate surface and then chemisorption or surface reaction of the precursors. The reactor is purged with an inert gas between the precursor pulses. The Al₂O₃ thin film in structure of the finished solar cells can play the role of both antireflection and passivation layer which will simplify the process. For this research 50×50 mm monocrystalline silicon solar cells with one bus bar have been used. The metallic contacts were prepared by screen printing method and Al₂O₃ antireflection coating by ALD method. Results and their analysis allow to conclude that the Al₂O₃ antireflection coating deposited by ALD has a significant impact on the optoelectronic properties of the silicon solar cell. For about 80 nm of Al₂O₃ the best results were obtained in the wavelength range of 400 to 800 nm reducing the reflection to less than 1%. The difference in the solar cells efficiency between with and without antireflection coating was 5.28%. The LBIC scan measurements may indicate a positive influence of the thin film Al₂O₃ on the bulk passivation of the silicon.     

Hydrolysis of carboxylate and phosphate esters using monopyridinium oximes in cationic micellar media

The reactions of p‐nitrophenyl acetate (PNPA) with a series of monopyridinium oximes, viz. 2‐PAM (2‐hydroxyiminomethyl‐1‐methylpyridinium iodide), 3‐PAM (3‐hydroxyiminomethyl‐1‐methylpyridinium iodide), and 4‐PAM (4‐hydroxyiminomethyl‐1‐methylpyridinium iodide) have been studied in the presence of cationic surfactants of same hydrophobic chain length (C₁₆) within the concentration range of 0.5–6.0 mM at pH 8.0 under the pseudo‐first‐order condition. The observed rate constant (k_obs) increases with increasing surfactant concentration culminating into a maximum, and this has been analyzed in detail following the concepts of micellar catalysis. The structure–activity relationship of the investigated oximes has been discussed, and 2‐PAM was found to be the most reactive among all the three investigated oximes for the cleavage of PNPA. Esterolytic decomposition of p‐nitrophenyldiphenyl phosphate with oximate ions (? CH?NO^?) was followed in cetyltrimethylammonium bromide micelles at pH 9.0, and 4‐PAM was the most reactive oxime for the micellar hydrolysis of phosphate ester. The apparent acid dissociation constants (pK_a) of the investigated oximes have been determined spectrophotometrically. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 569–578, 2011     

New approach to solution of photorefractive transport equations

In our work we propose a novel method of analysis of photorefractive transport equations. The method based on a perturbative approach can be used in the case of two wave mixing and four wave mixing geometry, i.e. for the samples illuminated by interference patterns. Presented approach can be employed for a broad range of material and experimental parameters, particularly for arbitrary depth of light modulation pattern. The approximate analytical solution is compared with results of numerical calculations and a good agreement practically in every case was found. Presented at 9-th International Workshop on Nonlinear Optics Applications, NOA 2007, May 17–20, 2007, Šwinoujście, Poland     

Pion suppression in nuclear collisions

The pion multiplicity per participating nucleon in central nucleus–nucleus collisions at the energies 2–15 AGeV is significantly smaller than in nucleon–nucleon interactions at the same collision energy. This effect of pion suppression is argued to appear due to the evolution of the system produced at the early stage of heavy–ion collisions towards a local thermodynamic equilibrium and further isentropic expansion. Received: 21 July 1997 / Revised version: 12 November 1997 / Published online: 26 February 1998