Electronic structure and luminescence of [AuS2PPh(OCH2CHCH2)]2 complex

The complex [AuS₂PPh(OCH₂CHCH₂)]₂ (1) presents an Au(I)–Au(I) intramolecular and intermolecular bonding with luminescence properties. To understand the nature of these features, fully optimized geometries were obtained by three computational methods, DFT/B3LYP, MPW1B95 and MP2. An Au(I)–Au(I) intramolecular bond was found in the ground state, at the three levels of theory, exhibiting an aurophilic interaction between the two gold atoms. Two molecules of the complex were optimized using DFT/B3LYP, in order to analyze the intermolecular interaction between them. The resulting intermolecular bonding distance between the two adjacent gold atoms on each molecule is 3.16 Å, indicating a strong aurophilic attraction. Time dependent calculations indicate that the first excited state with nonzero oscillator strength is a singlet, with an excitation energy equal to 3.16 eV. This should correspond to the absorption band seen experimentally at 3.10 eV. The lowest energy emission of (1) was obtained at 2.73 eV, which corresponds to the emission peak resulting from phosphorescence and located at 2.53 eV. This transition comes from an excited electron on the p orbitals of the ligands that is transferred to the d orbitals of the gold atoms on the HOMO. This interaction may be attributed to Ligand to Ligand–Metal Charge Transfer (LL–MCT).     

Properties of Hg1‐xCdxTe epitaxial films grown on (211)CdTe and (211)CdZnTe

Hg_1‐xCd_xTe (MCT) epitaxial films have been grown employing single crystalline substrates of CdTe and Cd_0.96Zn_0.04Te with (211)Cd and (211)Te crystalline orientations. The Isothermal Vapor Phase Epitaxy (ISOVPE) technique without Hg overpressure has been used for the epitaxial growth. Substrates and films were characterized by optical microscopy, chemical etching and x ray diffraction (Laue technique). The electrical properties were determined by Hall effect measurements. The characterization results allowed to evaluate the crystalline quality of MCT films. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

碲镉汞异质结能带结构的优化设计

分别对带隙较宽(较窄)的p型材料在带隙较窄(较宽)的n型材料之上的碲镉汞(MCT)异质结的能带结构进行了理论分析.在应用的理论模型中提出了一个简单的载流子浓度近似模型用于计入载流子简并效应和导带非抛物线性，同时还考虑到了价带失配的影响.就p-n结位置(z_B)和界面电荷密度(Q)两个参数对MCT异质结能带结构的影响进行了系统分析，发现这些影响是不可忽略的.根据这些影响特征，进一步得出了z_B和Q参数之间的优化设计规律. 关键词： 碲镉汞(MCT) 异质结 载流子浓度近似     

In vivo measurement of normal rat intracellular pyruvate and lactate levels after injection of hyperpolarized [1-(13)C]alanine

Hyperpolarized technology utilizing dynamic nuclear polarization has enabled rapid and high-sensitivity measurements of ¹³C metabolism in vivo. The most commonly used in vivo agent for hyperpolarized ¹³C metabolic imaging thus far has been [1-¹³C]pyruvate. In preclinical studies, not only is its uptake detected, but also its intracellular enzymatic conversion to metabolic products including [1-¹³C]lactate and [1-¹³C]alanine. However, the ratio of ¹³C-lactate/¹³C-pyruvate measured in this data does not accurately reflect cellular values since much of the [1-¹³C]pyruvate is extracellular depending on timing, vascular properties, and extracellular space and monocarboxylate transporter activity. In order to measure the relative levels of intracellular pyruvate and lactate, in this project we hyperpolarized [1-¹³C]alanine and monitored the in vivo conversion to [1-¹³C]pyruvate and then the subsequent conversion to [1-¹³C]lactate. The intracellular lactate-to-pyruvate ratio of normal rat tissue measured with hyperpolarized [1-¹³C]alanine was 4.89±0.61 (mean±S.E.) as opposed to a ratio of 0.41±0.03 when hyperpolarized [1-¹³C]pyruvate was injected.     

In situ infrared spectroscopy at electrochemical interfaces

An insight into the in situ FTIR spectroscopy method as applied in Electrochemistry is given. The particular aspects inherent to the electrochemical method are described in a concise form. Selected examples cover the results of about the last 8 years, on a variety of systems including carbon monoxide, small organic molecules and double-layer components (hydrogen, anions and water). The experimental data refer mostly to adsorption on well-defined single-crystal surfaces. Analogies and differences with data from the metal/gas interface are discussed.     

QWIP or other alternative for third generation infrared systems

Choosing the right detector technology for third generation thermal imaging systems is directly derived from the requirements of these new generation infrared imaging systems.

It is now evident that third generation thermal imager will still need the higher resolution capabilities as well as capabilities in multispectral detection and polarization sensitivity. Four technologies candidates are analyzed; the field-proved HgCdTe (MCT), uncooled microbolometer technology, antimonide based materials and quantum well infrared photodetectors (QWIP). Taking into account the risks, maturity and technologies barrier of each technology, we claim that for non-strategic applications (not low background conditions), QWIP technology is the most favorite. The ternary and superlattice antimonide based materials group seems to be theoretically the best alternative, but are not recommended due to its immaturity and the high risk involved in this technology (passivation, doping control, etc.). We anticipate large penetration of the uncooled detectors to the low-end and medium-end market. The HgCdTe will still be in progress due to the inertia of the large funding and the strategic importance of this detectors technology.     

4×288 readouts and FPAs properties

Analysis of four types 4×288 designed and manufactured readouts is presented. All the readouts have the direct injection input circuit with the circuits incorporated that allows testing procedure of readouts without the photodiodes attached to readout circuits. TDI registers have three delay elements between neighbouring inputs. Some characteristics of 4×288 FPAs with mercury-cadmium-telluride (MCT) arrays are presented too. Analysis have shown that in spite of different constructions of four readout types, different numbers of outputs and external service, rather similar parameters of FPAs have been obtained. Detectivity values measured for all 4×288 FPAs at operation temperature T ≈ 78 K with skimming mode included and background temperature T_b ≈295 K were in the range D*_λ ≅ (1.2−1.7)×10¹¹ cmHz^1/2/W.     

MCT探测器Franz-Keldysh效应有效强度的一种表征方法

通常只有使用较为昂贵、精密的实验设备才能获得 MCT探测器响应波长的偏移量 ,才可确定 MCT探测器 Franz- Keldysh(以下简写为 F- K)效应的强度。提出一种表征 MCT探测器 F- K效应有效强度的简易方法 ,即用 MCT探测器在零偏压及反偏压时的输出电压比来表征其 F- K效应有效强度的强弱。实验结果证实了这种方法有效、可行。     

Directing Traffic: Halogen-Bond-Mediated Membrane Transport

The plasma membrane regulates the transport of molecules into the cell. Small hydrophobic molecules can diffuse directly across the lipid bilayer. However, larger molecules require specific transporters for their entry into the cell. Regulating the cellular entry of small molecules and proteins is a challenging task. The introduction of halogen, particularly iodine, to small molecules and proteins is emerging to be a promising strategy to improve the cellular uptake. Recent studies reveal that a simple substitution of hydrogen atom with iodine not only increases the cellular uptake, but also regulates the membrane transport. The strong halogen-bond-forming ability of iodine atoms plays a crucial role in the transport and the introduction of iodine may provide an efficient strategy for studying membrane activity and cellular functions and improving the delivery of therapeutic agents. This Concept article does not provide a comprehensive picture of membrane transport but highlights halogen-substitution as a novel strategy for understanding and regulating the cell-membrane traffic.     

High operating temperature SWIR p+–n FPA based on MBE-grown HgCdTe/Si(0 1 3)

The characteristics of SWIR (1.6–3 μm) 320 × 256 and 1024 × 1024 focal plane arrays (FPA’s) based on n-type In-doped HgCdTe heteroepitaxial layers are reported. The HgCdTe layers were grown by molecular beam epitaxy on silicon substrates with ZnTe and CdTe buffer layers. p–n junctions were formed by arsenic ion implantation into HgCdTe film. Reverse current in the temperature range from 210 to 330 K was found to be limited by the diffusion mechanism. At the same time in the temperature range from 140 to 210 K the reverse current was dominated by the thermal generation of charge carriers through deep traps located in the middle of the band gap. At 170 K NETD was less than 40 mK.