Search results for "Spectroscopy"

Radical salts of TTF derivatives with the metal-metal bonded [Re2Cl8]2- anion

2008

Abstract Four new salts of the radical cations of TMTSF (tetramethyltetraselenafulvalene), TMTTF (tetramethyltetrathiafulvalene), BEDT-TTF (bisethylenedithiotetrathia-fulvalene) (ET) and o-Me2TTF (o-4,4′-dimethyltetrathiafulvalene) with the metal–metal bonded dianion [Re2Cl8]2− were synthesized, and their structures and physical properties investigated. The structures of these semiconducting salts feature one-dimensional stacking of the donor molecules interleaved with [Re2Cl8]2− anions and interstitial solvent molecules.

2019

Glycoprotein A repetition predominant (GARP), a specific surface molecule of activated regulatory T cells, has been demonstrated to significantly contribute to tolerance in humans by induction of peripheral Treg and regulatory M2-macrophages and by inhibition of (tumorantigen-specific) T effector cells. Previous work identified GARP on Treg, and also GARP on the surface of several malignant tumors, as well as in a soluble form being shedded from their surface, contributing to tumor immune escape. Preliminary results also showed GARP expression on brain metastases of malignant melanoma. On the basis of these findings, we investigated whether GARP is also expressed on primary brain tumors. We…

2021

The presence and interaction of immune cells in the tumor microenvironment is of significant importance and has a great impact on disease progression and response to therapy. Hence, their identification is of high interest for prognosis and treatment decisions. Besides detailed phenotypic analyses of immune, as well as tumor cells, spatial analyses is an important parameter in the complex interplay of neoplastic and immune cells—especially when moving into focus efforts to develop and validate new therapeutic strategies. Ex vivo analysis of tumor samples by immunohistochemistry staining methods conserves spatial information is restricted to single markers, while flow cytometry (disrupting t…

Frequency-modulation spectroscopy with blue diode lasers

2000

Frequency-modulation spectroscopy provides ultrasensitive absorption measurements. The technique is especially adaptable to diode lasers, which can be modulated easily, and has been used extensively in the near-infrared and infrared spectral regions. The availability of blue diode lasers now means that the accessible wavelength region can be increased. We successfully demonstrate wavelength-modulation spectroscopy and two-tone frequency-modulation spectroscopy for the weak second resonance line of potassium at 404.8 nm and for the transition at 405.8 nm in lead, starting from the thermally populated 6p(2) P-3(2) metastable level, information on the modulation parameters is obtained with a f…

Subpicosecond Laser Spectroscopy of Blue-Light-Induced Absorption in KNbO3 and LiNbO3

2000

Pulses of 427-nm light from am amplified Ti:sapphire frequency-doubled laser are absorbed in two-photon band-gap excitations of KNbO3 and LiNbO3. Induced absorption spectra measured in the visible and recently extended in the infrared have been recorded as a function of delay from 0 to 250 ps after two-photon blue excitation. Samples include stoichiometric as well as congruent LiNbO3. Comparison is made to transient absorption in the nanosecond and longer time range induced by electron pulses of~10 ns width and 270 keV energy. Parts of the absorption can be attributed to bound and free polarons, including the intrinsic electron polaron.

Violet Diode Laser in Time-Resolved Stored-Ion Spectroscopy

2004

Lifetime measurements of the metastable 3d D-2(3/2) level in singly charged calcium were performed using the newly developed violet diode laser operated in an external cavity arrangement. The laser was employed on stored ions at the CRYRING facility to optically pump the resonance line at 397 nm. In combination with laser probing at 866 nm this detection scheme gave the possibility to record the lifetime of this level. which has a radiative lifetime of about 1 s.

Surface Defects as a Tool to Solubilize and Functionalize WS 2 Nanotubes

2017

Layered transition metal dichalcogenides contain a number of crystal defects which significantly change their properties may be beneficial or detrimental for a specific application. We have prepared defect-rich multiwalled WS2 nanotubes by reductive sulfidization of W18O49 nanowires that were obtained solvothermally from tungsten chloride in different alcohols. The synthesis of the W18O49 nanowires was monitored and their morphological characteristics (e. g. length, rigidity and aspect ratio) are described in detail. The effect of morphology of the nanowires on the synthesis of WS2 nanotubes was investigated in order to obtain WS2 nanotubes that are highly solvent dispersible. Dispersions o…

From tungsten hexacarbonyl adsorption on TiO2(1 1 0) surface to supported tungsten oxide phases.

2008

Abstract Synchrotron-based photoemission spectroscopies were used to study the adsorption of tungsten hexacarbonyl on (1 1 0) TiO 2 surfaces: experiments using W4f and Ti2p intensities variations show that, at 140 K, the hexacarbonyl growth proceeds via a layer-by-layer mode. Moreover, it was evidenced using both core levels and valence band experiments that, after back to room temperature, W(CO) 6 desorbs without significant decomposition. However, low energy (500 eV) ion (Ar + ) irradiation can allow partial decomposition of tungsten hexacarbonyl molecules leading to sub-carbonyl tungsten molecules. The bonding of sub-carbonyl species to the TiO 2 surface was then stronger than the one of…

A tungsten oxide–lutetium bisphthalocyanine n–p–n heterojunction: from nanomaterials to a new transducer for chemo-sensing

2019

We report on a new hybrid heterojunction gas-sensitive device by combining a molecular material with a metal oxide. WO3 was synthesised via an aerosol-assisted chemical vapour deposition technique from a tungsten hexacarbonyl precursor. Onto an inorganic film, LuPc2 was vacuum evaporated. The morphology of the WO3–LuPc2 hybrid films is dominated by the morphological features of the tungsten oxide film, as shown by scanning electron microscopy and atomic force microscopy. Raman spectroscopy of the device confirms the presence of both materials. The non-linear I–V characteristics demonstrate the existence of an energy barrier at the interface between the inorganic and molecular materials. The…

Probing the electronic states of high-TMR off-stoichiometric Co2MnSi thin films by hard x-ray photoelectron spectroscopy

2014

The tunnel magnetoresistance ratio (TMR) of fully epitaxial magnetic tunnel junctions with an off-stoichiometric Co${}_{2}$MnSi Heusler alloy has been shown to exhibit a systematic dependence on Mn content, reaching 1135% at 4.2 K for Co${}_{2}$Mn${}_{1.29}$Si. In this paper, we explain the behavior of the observed TMR ratio using ab initio calculations and hard x-ray photoelectron spectroscopy (HAXPES). For the Mn-deficient samples, we show that the the drop of the TMR is caused by Co antisite atoms, which impose extra states into the minority-spin band gap. On the other hand, Mn-excess composition shows nearly half-metallic behavior. This result can be intuitively understood since both Co…