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111.
112.
Norman Scholz Amol Jadhav Milind Shreykar Thomas Behnke Nithiya Nirmalananthan Ute Resch-Genger Nagaiyan Sekar 《Journal of fluorescence》2017,27(6):1949-1956
A comprehensive systematic study of absorption and fluorescence properties in solvents of varying viscosity and polarity of three novel and red-emitting coumarin-rhodamine hybrid derivatives with differences in the rigidity of their substituents is presented. This includes ethanol-polyethylene glycol, toluene-polyethylene glycol, and toluene-paraffin mixtures. Moreover, protonation-induced effects on the spectroscopic properties are studied. A viscosity-induced emission enhancement was observed for all coumarin-rhodamine hybrid derivatives. MCR2 bearing a julolidine donor showed the expected low sensitivity to viscosity whereas MCR3 with its freely rotatable diphenylamino substituent revealed a particularly pronounced sensitivity to this parameter. Moreover, MCR2 shows an enhancement in emission in the open, i.e., protonated form in conjunction with a largely Stokes shift fluorescence in the deep red spectral region. This enables the application of these dyes as viscosity sensors and as far red emitting pH-sensitive probes. 相似文献
113.
G.M. Prinz A. Ladenburger M. Feneberg M. Schirra S.B. Thapa M. Bickermann B.M. Epelbaum F. Scholz K. Thonke R. Sauer 《Superlattices and Microstructures》2006,40(4-6):513
Strained AlN layers grown by MOVPE on sapphire and nominally unstrained AlN single crystals were studied employing photoluminescence, cathodoluminescence, and reflectance spectroscopy in the near-band edge range. The data allow one to determine fundamental optical parameters such as the band edge energy with its crystal field splitting and strain dependence which are still under discussion. Reflection measurements performed on crystal facets with different orientations and subjected to varying selection rules serve to assign the observed transitions to valence band states with specific symmetries.Near-band edge excitonic luminescence at around 6 eV was recorded as a function of temperature (). Fits to the data using standard models from the literature yield the temperature dependence Eg(T) of the band gap. 相似文献
114.
C. Jeyabharathi P. Ahrens U. Hasse F. Scholz 《Journal of Solid State Electrochemistry》2016,20(11):3025-3031
The electrochemical oxidation of single-crystal gold surfaces has been well studied, and the exposed crystal planes can be reliably distinguished based on the peak potentials of oxide formation. However, the multiple oxidation peaks of polycrystalline gold have not yet been unambiguously related to crystal planes. In this work, we used cyclic voltammetric responses of activated polycrystalline gold electrodes recorded in sulfuric acid solutions to allow constructing relationships between crystal planes and oxide peaks. The studies of oxide formation were complemented by measuring double-layer non-faradaic currents, lead underpotential deposition (Pb-upd), the oxygen reduction reaction (ORR), and the hydrogen evolution reaction (HER). 相似文献
115.
K. Jakubowska W. Skrzeczanowski M. Paduch M. Scholz E. Zielińska 《Applied physics. B, Lasers and optics》2014,117(1):389-394
Principal Component Analysis has been employed in order to find correlations between different quantities (related to spectroscopy in visible range, neutron yield and the time derivative of the current) describing Z-pinch plasma in the PF-1000 installation. Set of measurements in various plasma conditions has been taken into account. Strong correlation between level of impurity content and neutron yield has been found. 相似文献
116.
C Fritz G Scholz M Feist E Kemnitz 《Dalton transactions (Cambridge, England : 2003)》2012,41(37):11351-11360
For the first time, aluminium fluorides in liquid phase are available for optical applications. By modifying the conditions of the fluorolytic sol-gel synthesis of aluminium fluorides transparent sols with low viscosities were obtained. These sols consist mainly of small oligomeric or cluster units of aluminium fluoride which are not measurable by DLS, WAXS, SAXS and show unusual narrow signals in solid state NMR. Isolated particles with diameters up to five nanometers can be identified by TEM measurements and allow the use of their sols in optical and anti reflecting coatings. The sol particles were modified by trifluoroacetic acid to prevent agglomeration, and as a result, the obtained xerogels can be re-dispersed transparently in organic solvents. 相似文献
117.
Ray L. Frost Yunfei Xi Ricardo Scholz Fernanda M. Belotti 《Transition Metal Chemistry》2012,37(8):777-782
In this research, we have used vibrational spectroscopy to study the phosphate mineral kosnarite KZr2(PO4)3. Interest in this mineral rests with the ability of zirconium phosphates (ZP) to lock in radioactive elements. ZP have the capacity to concentrate and immobilize the actinide fraction of radioactive phases in homogeneous zirconium phosphate phases. The Raman spectrum of kosnarite is characterized by a very intense band at 1,026?cm?1 assigned to the symmetric stretching vibration of the PO4 3? ??1 symmetric stretching vibration. The series of bands at 561, 595 and 638?cm?1 are assigned to the ??4 out-of-plane bending modes of the PO4 3? units. The intense band at 437?cm?1 with other bands of lower wavenumber at 387, 405 and 421?cm?1 is assigned to the ??2 in-plane bending modes of the PO4 3? units. The number of bands in the antisymmetric stretching region supports the concept that the symmetry of the phosphate anion in the kosnarite structure is preserved. The width of the infrared spectral profile and its complexity in contrast to the well-resolved Raman spectrum show that the pegmatitic phosphates are better studied with Raman spectroscopy. 相似文献
118.
J. Scholz T. Wiersbinski P. Ruhnau D. Kondermann C. S. Garbe R. Hain V. Beushausen 《Experiments in fluids》2008,45(4):583-593
A concept for dynamic mixture formation investigations of fuel/air mixtures is presented which can equally be applied to several
other laser induced fluorescence (LIF) applications. Double-pulse LIF imaging was used to gain insight into dynamic mixture
formation processes. The setup consists of a modified standard PIV setup. The "fuel/air ratio measurement by laser induced
fluorescence (FARLIF)" approach is used for a quantification of the LIF images in order to obtain pairs of 2D fuel/air ratio
maps. Two different evaluation concepts for LIF double pulse images are discussed. The first is based on the calculation of
the temporal derivative field of the fuel/air ratio distribution. The result gives insight into the dynamic mixing process,
showing where and how the mixture is changing locally. The second concept uses optical flow methods in order to estimate the
motion of fluorescence (i.e., mixture) structures to gain insight into the dynamics, showing the distortion and the motion
of the inhomogeneous mixture field. For this "fluorescence motion analysis" (FMA) two different evaluation approaches—the
"variational gradient based approach" and the "variational cross correlation based approach"—are presented. For the validation
of both, synthetic LIF image pairs with predefined motion fields were generated. Both methods were applied and the results
compared with the known original motion field. This validation shows that FMA yields reliable results even for image pairs
with low signal/noise ratio. Here, the "variational gradient based approach" turned out to be the better choice so far. Finally,
the experimental combination of double-pulse FARLIF imaging with FMA and simultaneous PIV measurement is demonstrated. The
comparison of the FMA motion field and the flow velocity field captured by PIV shows that both results basically reflect complementary
information of the flow field. It is shown that the motion field of the fluorescence structures does not (necessarily) need
to represent the actual flow velocity and that the flow velocity field alone can not illustrate the structure motion in any
case. Therefore, the simultaneous measurement of both gives the deepest insight into the dynamic mixture formation process.
The examined concepts and evaluation approaches of this paper can easily be adapted to various other planar LIF methods (with
the LIF signal representing, e.g., species concentration, temperature, density etc.) broadening the insight for a wide range
of different dynamic processes.
相似文献
J. Scholz (Corresponding author)Email: Email: |
V. BeushausenEmail: |
119.
We have studied the mineral kaliborite. The sample originated from the Inder B deposit, Atyrau Province, Kazakhstan, and is part of the collection of the Geology Department of the Federal University of Ouro Preto, Minas Gerais, Brazil. The mineral is characterized by a single intense Raman band at 756 cm?1 assigned to the symmetric stretching modes of trigonal boron. Raman bands at 1229 and 1309 cm?1 are assigned to hydroxyl in-plane bending modes of boron hydroxyl units. Raman bands are resolved at 2929, 3041, 3133, 3172, 3202, 3245, 3336, 3398, and 3517 cm?1. These Raman bands are assigned to water stretching vibrations. A very intense sharp Raman band at 3597 cm?1 with a shoulder band at 3590 cm?1 is assigned to the stretching vibration of the hydroxyl units. The Raman data are complimented with infrared data and compared with the spectrum of kaliborite downloaded from the Arizona State University database. Differences are noted between the spectrum obtained in this work and that from the Arizona State University database. This research shows that minerals stored in a museum mineral collection age with time. Vibrational spectroscopy enhances our knowledge of the molecular structure of kaliborite. 相似文献
120.