Simultaneous observation of current oscillations and porous film growth during anodization of InP

The observation of spontaneous oscillations in current during the anodization of InP in relatively high concentrations of KOH electrolytes is reported. Oscillations were observed under potential sweep and constant potential conditions. Well-defined oscillations are observed during linear potential sweeps of InP in 5 mol dm(-)(3) KOH to potentials above approximately 1.7 V (SCE) at scan rates in the range of 50 to 500 mV s(-)(1). The oscillations observed exhibit an asymmetrical current versus potential profile, and the charge per cycle was found to increase linearly with potential. More complex oscillatory behavior was observed under constant potential conditions. Periodic damped oscillations are observed in high concentrations of electrolyte whereas undamped sinusoidal oscillations are observed in relatively lower concentrations. In both cases, the anodization of InP results in porous InP formation, and the current in the oscillatory region corresponds to the cyclical effective area changes due to pitting dissolution of the InP surface with the coincidental growth of a thick porous In(2)O(3) film.     

吡啶气相分子的共振多光子电离谱

本工作观测了双光子能量在35180-36002cm^-^1范围内吡啶分子的共振多光子电离谱。对电子跃迁S~1(^1B~1)→S~0(^1A~l)的振动带做了归属, 首次在^1B~1态观察到7个新的振动模。讨论了N原子取代对分子结构及振动模的影响。     

Investigation of silver binding to polyamidoamine (PAMAM) dendrimers by ESI tandem mass spectrometry

Electrospray ionization tandem mass spectrometry (ESI-MS/MS) was used to probe the binding of silver ions and reduced silver species with polyamidoamine generation 1 amine-terminated (PAMAMG1NH2) and generation 2 hydroxyl-terminated (PAMAMG2OH) dendrimers. At Ag(+)/PAMAMG2OH molar ratios of 1, 2:1 and low abundance 3:1 complexes emerge. Similar results were observed for PAMAMG1NH2. The collisional activated dissociation (CAD) patterns of the dendrimer ions are characterized by losses of amidoamine branches resulting largely from hydrogen migration and cleavage reactions. Ag+/dendrimer complexes are characterized by the loss of a dendrimer branch from the complex, with the silver ion remaining bound to a dendrimer fragment. When the Ag+-bound dendrimer complexes are reduced by hydrazine, low abundance complexes, whose m/z values are consistent with ones containing zerovalent silver species, are observed in the mass spectra. Complexes with three silver atoms are observed in the spectrum containing PAMAMG1NH2, and complexes with four and five silver atoms are observed with PAMAMG2OH. The CAD fragmentation patterns of the complexes formed after the silver reduction are different than those observed for complexes containing one silver ion and are characterized by the ejection of all silver species, possibly as a cluster, leaving the intact dendrimer ion. Experiments with Cu+, Cu2+, and Pt2+ binding to PAMAMG2OH were also done, but reduced metal clusters were not observed in the mass spectra after the addition of hydrazine.     

Effect of water on the formamide-intercalation of kaolinite

The molecular structures of low defect kaolinite completely intercalated with formamide and formamide-water mixtures have been determined using a combination of X-ray diffraction, thermoanalytical techniques, DRIFT and Raman spectroscopy. Expansion of the kaolinite to 10.09 A was observed with subtle differences whether the kaolinite was expanded with formamide or formamide-water mixtures. Thermal analysis showed that greater amounts of formamide could be intercalated into the kaolinite in the presence of water. New infrared bands were observed for the formamide intercalated kaolinites at 3648, 3630 and 3606 cm(-1). These bands are attributed to the hydroxyl stretching frequencies of the inner surface hydroxyls hydrogen bonded to formamide with water, formamide and interlamellar water. Bands were observed at similar positions in the Raman spectrum. At liquid nitrogen temperature, the 3630 cm(-1) Raman band separated into two bands at 3633 and 3625 cm(-1). DRIFT spectra showed the hydroxyl deformation mode at 905 cm(-1). Changes in the molecular structure of the formamide are observed through both the NH stretching vibrations and the amide 1 and 2 bands. Upon intercalation of kaolinite with formamide, bands are observed at 3460, 3344, 3248 and 3167 cm(-1) attributed to the NH stretching vibration of the NH involved with hydrogen bonded to the oxygens of the kaolinite siloxane surface. In the DRIFT spectra of the formamide intercalated kaolinites bands are observed at 1700 and 1671 cm(-1) and are attributed to the amide 1 and amide 2 vibrations.     

Conformational behaviour of fluorinated ethylamines

The infrared and Raman spectra of various flourinated ethylamines have been obtained for different phases. Emphasis has been put on the conformational behaviour in inert gas matrices. Some preliminary results for 2-fluoroethylamine and 2,2,2-trifluoroethylamine are given in the present communication. The two gauche conformers of 2-fluoroethylamine which are observed in the vapour phase are also present in the argon and nitrogen matrices. A conformational change, possibly to an anti conformer, is observed after a few hours in the argon matrix. For 2,2,2-trifluoroethylamine no conformational change is observed in the matrices.     

Emission spectra of HCN/HNC in the 2-5 microm range of astrophysical interest

Emission from H12C14N observed with a Fourier transform spectrometer from a radio-frequency excited plasma is reported in the 2400-3400 cm(-1) spectral range of astrophysical interest. The molecular constants, for 21 vibration-rotation bands are given, as well as estimates of the first-order Herman-Wallis coefficients for 11 bands. These constants are derived from about 900 observed transitions in HCN, and are used to generate a sequential linelist of about 1400 calculated line positions, within a standard deviation equal to 3 x 10(-4) cm(-1). The relative intensities of the observed lines are also reported, as well as those for the nu1 band of H14N12C, at 3650 cm(-1), simultaneously observed from the same plasma.     

Jet-cooled laser spectroscopy of the cyclohexoxy radical

The laser-induced fluorescence and laser-excited dispersed fluorescence spectra of the cyclohexoxy radical has been observed under two sets of free-jet-cooling conditions, characterized by rotational temperatures of approximately 1 and 100 K. Although five conformers of cyclohexoxy are possible, it appears that all presently observed spectral bands can be accounted for by a single one. All cold spectral bands are assigned to the B-X electronic transition of the cyclohexoxy radical. Transitions to both a' and a" B state vibrational levels are observed and allowed due to a substantial pseudo-Jahn-Teller effect in the X state. Hot bands are also observed, which we attributed to transitions to the B state from the low-lying A electronic state. Analysis of the spectra yields vibrational frequencies for the X, A, and B states as well as the energy separations of their vibrationless levels.     

聚环氧乙烷球晶的带状结构与球晶内部的环形裂纹

聚环氧乙烷球晶的带状结构与球晶内部的环形裂纹丁建东，朱军祥，杨玉良（复旦大学高分子科学系、国家教委聚合物分子工程开放实验室，上海，２００４３３）关键词聚合物，带状球晶，裂纹聚环氧乙烷（ＰＥＯ）具有高度的柔顺性，易于结晶，因而被人们选作研究聚合物结晶的...     

The mass spectra of N-phenylphosphoramidate esters

The mass spectra of diethyl and diphenyl N-phenylphosphoramidate are reported. Their electron-impact behavior is similiar to that observed for the corresponding phosphate esters. High resolution mass measurements are used to confirm the elemental composition of all the peaks in the spectra. Some interesting rearrangement fragments are observed in the spectrum of the diphenyl N-phenylphosphoramidate ester.     

O3势能面和振动激发态的理论研究

由于O3在大气化学中的重要作用，近年来针对它的实验和理论研究皆较活跃．尽管对O3的高振动激发态已进行过广泛的研究［“］，得到过多种由实验光谱定出的势能面［‘，’］或由从头算得到的势能函数【‘］，但由于近年来又增加了一些新的高精度的振转光谱实验数据k，’」，而以     

The Modification of Hydroxyl Surfaces of Formamide-Intercalated Kaolinites Synthesized by Controlled Rate Thermal Analysis

Controlled rate thermal analysis (CRTA) technology made possible the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites. X-ray diffraction shows that the CRTA-treated formamide-intercalated kaolinites remain expanded after CRTA treatment. The Raman spectra of the CRTA-treated formamide-intercalated kaolinites are significantly different from those of the intercalated kaolinites with both intercalated and adsorbed formamide. An intense band is observed at 3629 cm(-1), attributed to the inner surface hydroxyls hydrogen bonded to the formamide. Broad bands are observed at 3600 and 3639 cm(-1) and are attributed to the inner surface hydroxyls, which are hydrogen bonded to the adsorbed water molecules. The hydroxyl stretching band of the inner hydroxyl is readily observed at 3621 cm(-1) in the Raman spectra of the CRTA-treated formamide-intercalated kaolinites. The results of thermal analysis show that the amount of intercalated formamide between the kaolinite layers is independent of the presence of water. The Raman bands of the formamide in the CRTA-treated intercalated kaolinites are readily observed. Copyright 2001 Academic Press.     

Drying dissipative structure of sodium salts of hyaluronic acid

Macroscopic and microscopic patterns during the course of dryness of aqueous solution in sodium salts of hyaluronic acid (NaHLA) were observed on a cover glass, a watch glass, and a Petri glass dish. Dendritic and rod-like microscopic patterns, which are similar to those of sodium salts of carboxymethyl cellulose, were observed for NaHLA especially on a cover glass and a watch glass. The microscopic patterns of NaHLA are supported to be originated from the hexose groups of polysaccharides, though the similar dendritic patterns are also observed for some of polynucleotides, sodium salts of deoxyribonucleic acid, and potassium salts of poly (riboadenylic acid), for example. Macroscopic broad ring size decreased substantially from the initial size of liquid and decreased slightly as polymer concentration decreased. These observations are consistent with existence of the rather strong interpolymer affinitive forces during the course of dryness. In the coexistence of sodium chloride, microscopic dendritic patterns grew large especially on a cover glass and a watch glass, which was so often observed for polysaccharides examined hitherto. Drying patterns are clarified to be formed by the successive and cooperative processes of evaporation, convection, sedimentation, and solidification.     

Novel structures of a smectic C* phase with high spontaneous polarization in free-standing films

New stable structures of the liquid crystalline smectic C* phase are observed in free standing films of a material with high spontaneous polarization. A stable configuration of thick films is a stripe of state with an in-plane rotation of the director. In ultra-thin films an anisotropic state was observed. The director fields of the observed structures are modelled and compared with theoretical predictions.     

Aspect ratio dependence of the enhanced fluorescence intensity of gold nanorods: experimental and simulation study

Experimental observations and theoretical treatments are carried out for the band shape and relative intensity of the emission from gold nanorods of various aspect ratios in the range between 2.25 (1.5 theory) and 6.0 (9 theory). The calculation of the fluorescence spectra requires knowledge of the nanorod size distribution, the enhancement factors, and the shape of the unenhanced fluorescence spectrum. The size distribution is determined from the fit of the observed absorption spectrum for each value of aspect ratio studied to the theoretical model of Gans. The theory by Boyd and Shen is used for calculating the enhancement of the fluorescence spectrum of the previously observed weak emission of bulk gold, which originates from the interband transition. This is carried out for nanorods of different aspect ratios. To compare theory to the observed nanorod fluorescence spectra, which suffer from self-absorption, the calculated nanorod fluorescence spectra are corrected for this effect using the observed absorption spectra. The comparison between the observed and the calculated fluorescence band shapes is found to be good. The calculated changes in the relative intensities upon changing the aspect ratios are found to be much greater than that observed. This is due to the fact that for the observed emission of all the nanorods studied nonradiative processes dominate the relaxation mechanism of the excited state, a fact that was not included in the theoretical treatments.     

Thermodynamics of the adsorption of organic molecules on graphitized carbon black modified with a monolayer of 5-hydroxy-6-methyluracil

Thermodynamic characteristics of the adsorption of alkanes, alcohols, arenes, and esters on graphitized carbon black with a deposited monolayer (0.17%) of 5-hydroxy-6-methyluracil are studied by means of inverse gas chromatography at infinite dilution. It is established that size effects (violation of the additivity of molar changes in internal energy and the entropy of adsorption for pairs of molecules of one homologous series that differ by one methyl group) are observed when organic molecules are adsorbed on the surface of the resulting adsorbent. The size effects are similar to those observed when 1% 5-hydroxy-6-methyluracil is deposited on graphitized carbon black. It is concluded that the observed violation of additivity is associated with cavities in the supramolecular structure.     

Classical trajectory simulations of photoionization dynamics of tryptophan: intramolecular energy flow, hydrogen-transfer processes and conformational transitions

One-photon and two-photon ionization dynamics of tryptophan is studied by classical trajectory simulations using the semiempirical parametric method number 3 (PM3) potential surface in "on the fly" calculations. The tryptophan conformer is assumed to be in the vibrational ground state prior to ionization. Initial conditions for the trajectories are weighted according to the Wigner distribution function computed for that state. Vertical ionization in the spirit of the classical Franck-Condon principle is assumed. For the two-photon ionization process the ionization is assumed to go resonantively through the first excited state. Most trajectories are computed, and the analysis is carried out for the first 10 ps. A range of interesting effects are observed. The main findings are as follows: (1) Multiple conformational transitions are observed in most of the trajectories within the ultrafast duration of 10 ps. (2) Hydrogen transfer from the carboxyl group to the amino group and back has been observed. A zwitterion is formed as a transient state. (3) Two new isomers are formed during the dynamics, which have apparently not been previously observed. (4) Fast energy flow between the ring modes and the amino acid backbone is observed for both one- and two-photon ionization. However, the effective vibrational temperatures only approach the same value after 90 ps. The conformation transition dynamics, the proton-transfer processes and the vibrational energy flow are discussed and analyzed.     

First experimental observation of IR emission from Rydberg Matter: detection of light from a deexciting layer

The first successful experiment with IR light emission from the condensed excited material called Rydberg Matter (RM) is reported. RM is formed by desorption from a K doped emitter and deposited on the vacuum side of a reflecting window. The four main emission bands are well fitted by a procedure used previously to match the so called unidentified infrared bands observed in space. The bands are mainly due to transitions n≈50→5, 7, 8, 9 and 10 in RM. Two series belonging to different species are probably observed. RM is thus observed by ordinary optical spectroscopy.     

Freezing of a liquid marble

In this study, we present for the first time the observations of a freezing liquid marble. In the experiment, liquid marbles are gently placed on the cold side of a thermo-electric cooler (TEC), and the morphological changes are recorded and characterized thereafter. These liquid marbles are noticed to undergo a shape transition from a spherical to a flying-saucer-shaped morphology. The freezing dynamics of liquid marbles is observed to be very different from that of a freezing water droplet on a superhydrophobic surface. For example, the pointy tip appearing on a frozen water drop could not be observed for a frozen liquid marble. In the end, we highlight a possible explanation of the observed morphology.     

Time-resolved luminescence spectroscopy of self-trapped excitons in ladder type Br-bridged Pt complexes

The out-of-phase and in-phase ladder type Br-bridged Pt complexes are investigated by time-resolved luminescence spectroscopy in pico- and femtosecond time regions. The observed luminescence spectra have peaks at 0.87 and 0.94 eV in out-of-phase and in-phase materials, respectively, and are assigned to self-trapped excitons. The wave-packet oscillations in self-trapped excitons (STE) are observed in both materials. The time-evolution curves are analyzed in terms of the secondary radiation theory of strongly coupled electron-phonon system. The period and dephasing time of oscillations as well as the lifetime and spectral shape of the STE luminescence are determined. The fast dephasing or cooling of the wave-packet motion observed in the in-phase type complex is ascribed to inter-chain interactions within the ladder.     

Pyrolysis—gas chromatography of quaternary phosphonium compounds

Following studies on the pyrolytic behaviour of quaternary ammonium salts, the work described here throws light on the pyrolysis of the phosphorus analogues. Major differences are observed, particularly in the products formed, and attempts are made to explain the observed differences in behaviour.