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1.
Infrared and Raman spectra of CO[dbnd] 3 ions are different in the two crystallographic forms of CaCO3 Calcite and Aragonite owing to their different site symmetries. Due to this fact, i.r. has been used to assess the reversible Calcite ← → Aragonite transformation which occurs upon grinding of CaCO3, and much work has been done in this field in the last few years(1-4). In the present paper data are reported on Raman spectra of Calcite and Aragonite forms of CaCO3 produced by the above mechanical procedure. 相似文献
2.
Compositional changes induced by 3.5 keV Ar+ sputtering in TiO2, NiO, NiTiO3 and a (TiO2 + NiO) mixture have been quantitatively studied by XPS. Although all the samples show important changes in their stoichiometry, the extent of the decomposition depends on the compound. The stability of Ti4+ appears to be enhanced by the presence of Nisu2+ cations which, on the other hand, are more easily reduced to Ni0 than in pure NiO. To explain these results a redox solid state reaction between the intermediate phases formed during sputtering is proposed, which tends to preserve the most stable phases. 相似文献
3.
CM Silva MF Duarte ML Mira MH Florêncio K Versluis AJ Heck 《Rapid communications in mass spectrometry : RCM》1999,13(12):1098-1103
Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
4.
We present here a new approach based on high resolution scanning force microscopy that permits molecular determination and frictional discrimination between coexisting molecular configurations of alkanethiols on Au(111). The method has allowed visualizing in real time a phase transition between two differently ordered self-assembled configurations, which spontaneously takes place with time at constant coverage and under ambient conditions. Frictional force measurements indicate that the molecular rearrangement observed occurs via an order-disorder-order process. 相似文献
5.
Catarina IV Ramos Flávio Figueira Marcelo D Polêto Francisco ML Amado Hugo Verli João PC Tomé M Graça PMS Neves 《Journal of mass spectrometry : JMS》2016,51(5):342-349
Electrospray mass spectrometry/mass spectrometry was used to investigate the gas‐phase properties of protonated expanded porphyrins, in order to correlate those with their structure and conformation. We have selected five expanded meso‐pentafluorophenyl porphyrins, respectively, a pair of oxidized/reduced fused pentaphyrins (22 and 24 π electrons), a pair of oxidized/reduced regular hexaphyrins (26 and 28 π electrons) and a regular doubly N‐fused hexaphyrin (28 π electrons). The gas‐phase behavior of the protonated species of oxidized and reduced expanded porphyrins is different. The oxidized species (aromatic Hückel systems) fragment more extensively, mainly by the loss of two HF molecules. The reduced species (Möbius aromatic or Möbius‐like aromatic systems) fragment less than their oxidized counterparts because of their increased flexibility. The protonated regular doubly fused hexaphyrin (non‐aromatic Hückel system) shows the least fragmentation even at higher collision energies. In general, cyclization through losses of HF molecules decreases from the aromatic Hückel systems to Möbius aromatic or Möbius‐like aromatic systems to non‐aromatic Hückel systems and is related to an increase in conformational distortion. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
6.
Torrelles X Barrena E Munuera C Rius J Ferrer S Ocal C 《Langmuir : the ACS journal of surfaces and colloids》2004,20(21):9396-9402
The c(4 x 2) structure of C16H33SH alkanethiol monolayers self-assembled on Au(111) has been studied by grazing incidence X-ray diffraction. This structure coexists on the surface with the (radical3x radical3)R30 degrees phase. The structural refinement of the c(4 x 2) phase has been accomplished by omitting the fractional order reflections common to both structures. The surface unit cell consists of four symmetry-independent molecules with atomic displacements related by couples, such that only two nonequivalent chains are present in the surface cell. The stability between neighbor chains is due to van der Waals interactions. The substrate plays an important and non-negligible role in the c(4 x 2) reconstruction. The lateral and normal substrate relaxations to the surface plane are small, and gold atom displacements are lower than 0.25 angstroms but contribute very strongly to the fractional order intensities. The molecular chains form a close packed structure tilted by 37 degrees from the surface normal with no indications of dimer formation between closest S atoms. 相似文献
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8.
F. Jiménez-Villacorta C. Munuera C. Ocal C. Prieto 《Journal of nanoparticle research》2010,12(4):1117-1127
A combined study of the surface nanostructure and electrical characteristics of iron thin films prepared on naturally passivated
silicon wafers is presented. By means of conductive-scanning force microscopy, the influence of the substrate temperature
during film preparation on both surface morphology and conductivity response is investigated. In addition, magnetic properties
of these films are reported and correlated with the nanostructural properties. Films prepared at 200 K show granular core–shell
magnetic behaviour exhibiting exchange bias. Both conductive and magnetic data indicate that samples prepared at low temperature
behave as a percolated network of nanometric metallic iron clusters (with typical sizes of 20 nm) interconnected by oxidized
chains (of 10 nm in diameter), showing an excellent system for nanotechnological exchange bias applications. 相似文献
9.
A simple and rapid method for in situ preconcentration of inorganic and organic mercury compounds in water samples, based on solid phase extraction using dithizone immobilised on a reversed-phase C18 cartridge, has been developed. The adsorbed complexes were stable on the cartridge for at least 2 weeks. The speciation analysis of methylmercury (MeHg), phenylmercury (PhHg) and inorganic mercury (Hg (II)) were done by reversed-phase high performance liquid chromatography. The calibration graphs of MeHg, PhHg and Hg (II) were linear (r>0.999) from the detection limits (0.58, 0.66 and 0.54 ng) to 38, 25 and 26 ng of Hg, respectively. The average recoveries of MeHg, PhHg and Hg (II) from spiked samples (0.3-48.0 mug l(-1) Hg) were 98+/-3, 99+/-1 and 100+/-7%, respectively. By applying SPE procedure a 200-fold concentration of the sample was obtained. 相似文献
10.