Ge:Ga photoconductor arrays: Design considerations and quantitative analysis of prototype single pixels

We have conducted a series of experiments on Ge:Ga photoconductors to quantitatively understand how monolithic two-dimensional arrays of this material will perform. Various single pixel prototypes were built and tested in terms of responsivity and detective quantum efficiency, and the results are plotted and compared with the expected absorption efficiency for these devices. All tests were conducted at 89.9 μm. wavelength (bandwidth = 11.9 μm), using standard transimpedence amplifiers and low background conditions. The best performance was obtained for a 2 mm long “longitudinally-contacted” detector that was not mounted inside of an integrating cavity: RESPONSIVITY = 5.2 A/W, and detective quantum EFFICIENCY = 7.7%. The configuration of this device is easily expanded into a two-dimensional format.     

Influence of the Sb dopant distribution on far infrared photoconductivity in Ge:Sb blocked impurity band detectors

Extended long wavelength response to 200 μm (50 cm⁻¹) has been observed in Ge:Sb blocked impurity band (BIB) detectors with N_D1×10¹⁶ cm⁻³. The cut-off wavelength increases from 150 μm (65 cm⁻¹) to 200 μm (50 cm⁻¹) with increasing bias. The responsivity at long wavelengths was lower than expected. This can be explained by considering the observed Sb diffusion profile in a transition region between the blocking layer and active layer. BIB modeling is presented which indicates that this Sb concentration profile increases the electric field in the transition region and reduces the field in the blocking layer. The depletion region consists partially of the transition region between the active and blocking layer, which could contribute to the reduced long wavelength response. The field spike at the interface is the likely cause of breakdown at a lower bias than expected.     

High performance antimony-doped germanium photoconductors

We have produced two new single crystals of antimony-doped germanium that were specifically designed for far-infrared photoconductor applications. Variable-temperature Hall effect analysis shows that these materials are well suited for photoconductor use in terms of majority and minority dopant concentration. We have fabricated sample detectors from these materials and compared their performance to state-of-the-art high sensitivity gallium-doped germanium detectors under low-background and dark conditions. Test results indicate that these devices are nearly identical in sensitivity to the best Ge:Ga in terms of responsivity, detective quantum efficiency, and dark current, and may be favored in some applications that require longer wavelength spectral response.     

Complexation versus micelle formation: α-Cyclodextrin + n-decyltrimethylammonium bromide aqueous solutions

Ultrasonic attenuation spectra as well as dependencies upon surfactant concentration of the specific electric conductivity, the sound velocity, and the density have been measured for aqueous solutions of α-cyclodextrin with different amounts of n-decyltrimethylammonium bromide added. In addition to cyclodextrin isomerization the spectra reveal cyclodextrin–surfactant complexation and, above a critical association concentration, the monomer exchange between surfactant micelles and the suspending liquid. The data are evaluated assuming most α-cyclodextrin to form complexes, predominantly with 1:1 but also with 2:1 cyclodextrin–surfactant stoichiometry.     

Total synthesis and bioactivity of 18(R)-hydroxyeicosapentaenoic acid

Resolvins are family of lipid mediators derived from omega-3 polyunsaturated fatty acids, which are generated during the resolution phase of acute inflammation. Resolvin E1 is biosynthesized from eicosapentaenoic acid via 18(R)-hydroxyeicosapentaenoic acid (18R-HEPE) in the Cox-2 and lipoxygenase mediated pathway and has proven to exhibit potent anti-inflammatory activity. We report herein the first total chemical synthesis of 18R-HEPE and demonstrate that this compound displays in vivo bioactivity by blocking neutrophil infiltration in a murine model of zymosan-induced peritonitis.     

ChemInform Abstract: Polychloride Monoanions from [Cl3]‐ to [Cl9]‐: A Raman Spectroscopic and Quantum Chemical Investigation.

Polychloride monoanions [Cl_n]^‐ (n = 3, 5, 7, 9) stabilized by quaternary ammonium salts are obtained through the addition or condensation of an excess of dry chlorine to [NMe₄]Cl, [NEt₄]Cl, [NPr₄]Cl, or [NBu₄]Cl and characterized by Raman spectroscopy and state‐of‐the‐art quantum chemical calculations up to the CCSD(T) level.