共查询到20条相似文献,搜索用时 31 毫秒
1.
N. G. Kozlov S. L. Bondarev E. D. Skakovsky A. V. Baranovsky V. N. Knyukshto L. I. Basalaeva 《Journal of Applied Spectroscopy》2012,79(4):527-534
Hydrobenzophenanthrolinone derivatives were synthesized by three-component condensation of 8-aminoquinoline, aromatic aldehydes, and dimedone. The structures of the obtained substances were confirmed by NMR and IR spectroscopy and mass spectrometry. Spectral-luminescent investigations of the synthesized compounds showed that they were characterized by high oscillator strengths for allowed electronic transitions S n ← S 0 (n = 1–3). Low fluorescence quantum yields in EtOH (Φfl ~ 10–4–10–3) and an increase of the Φfl values in toluene (~10–2) at room temperature and with lowering the temperature to 77 K (Φfl ~ 10–1) for a number of the compounds under study were satisfactorily explained within the framework of Marcus theory. 相似文献
2.
Suspensions of oligophenylenevinylene (nPV) nanoparticles withn = 2 vinylene units are doped with nPVs of longer chainlengths,n = 3–5. Absorption and fluorescence spectroscopy and steady-state and time-resolved fluorescence anisotropy measurements
are used to determine the photo-physical properties of the suspensions. Undoped nanoparticles form highly oriented H-aggregates
with low fluorescence quantum yields (ΦF ≈ 0.1). Introduction of bulky substituents into the particle constituting molecules perturbs the intermolecular orientation.
Upon doping, efficient energy transfer to the dopants is found, changing the color and leading to enhancement of the fluorescence
quantum yields up to ΦF = 0.6. The intermolecular orientation is not changed upon doping. 相似文献
3.
E. Birckner U.-W. Grummt H. Rost A. Hartmann S. Pfeiffer H. Tillmann H.-H. Hörhold 《Journal of fluorescence》1998,8(1):73-80
The absorption and fluorescence of substituted distyrylbenzene (DSB) derivatives and segmented poly(phenylene vinylene) (PPV)
derivatives are characterized by long-wavelength absorption maxima and absorption coefficients of λa = 380–450 nm, ε = 20,000–60,000 M−1 cm1 and fluorescence maxima, quantum yields, and decay times of λr = 440–530 nm, Φf = 0.2–0.9, and Τ = 0.8–2.5 ns, respectively. Alkoxy substituents at the central phenylene ring of DSB groups increase the
bathochromic shift in the spectra in comparison to DSB, without a significant decrease in the high DSB fluorescence quantum
yield. Both phenyl and cyano substitutions at the vinylene bridge lead to a further bathochromic shift of the fluorescence
and a decrease in the quantum yield to ca. 0.4. The DSB derivatives and the related segmented PPV derivatives show nearly
the same absorption spectra, fluorescence spectra, and radiative rate constantsk
f= Φf/Τ, indicating the efficacy of the segmentation of the polymer chain. The radiative rate constants determined by the Φf and Τ values and by the Strickler/Berg formula are in reasonable agreement. This supports the possibility of interpreting
the properties of the polymers in terms of their DSB units. The decrease in the emission anisotropy can be ascribed to multistep
energy transfer processes between different oriented segments. 相似文献
4.
S. L. Bondarev V. N. Knyukshto S. A. Tikhomirov A. N. Pyrko 《Optics and Spectroscopy》2003,94(6):928-933
The spectral-luminescent properties and electronic-level structure of a derivative of oxotetrahydrobenzo[c]phenanthridine—3,3-dimethyl-1,2,3,4-tetrahydrobenzo[c]phenanthridine-1-one
(DTP)—in polar and nonpolar solutions are studied by the luminescence and picosecond spectroscopy techniques at 293 and 77
K. It is shown that DTP exhibits ππp* fluorescence only in polar proton-containing methanol, ethanol, and n-propanol and that this fluorescence is associated with a chromophore + alcohol complex. Solutions of DTP in n-propanol and the nonpolar mixture methylcyclohexane + toluene (6:1) at 77 K display ππp* phosphorescence with a quantum yield
ΦPh=0.1, a lifetime τPh=1.9 s, and a frequency of the 0-0 transition equal to 21550 cm−1. The fact that DTP fluorescence is absent in aprotic solvents and exists in alcohols is explained by the inversion of the
energy levels of the S
ππ* and T
n
π* states, as a result of which the energy level of the fluorescing S
ππ* state in alcohol becomes the lowest. The picosecond spectra and kinetics of the inducedS
n
(ππ*) ← S
1(π π*) and T
k
(ππ*) ← T
1(ππ*) absorption made it possible to estimate the lifetime of the S
1(ππ*) state of DTP in n-propanol at 293 K (20±10 ps) and the position of the triplet-triplet absorption peak (495 nm).
__________
Translated from Optika i Spektroskopiya, Vol. 94, No. 6, 2003, pp. 993–998.
Original Russian Text Copyright ? 2003 by Bondarev, Knyukshto, Tikhomirov, Pyrko. 相似文献
5.
The value of intrinsic chlorophyll fluorescence polarization, and the intensity in emission spectrum were investigated in
leaf segments of Alocasia macrorrhiza under several stress conditions including different temperatures (25–50°C), various concentrations of NaCl (0–250 mM), methyl
viologen (MV, 0–25 μM), SDS (0–1.0%) and NaHSO3 (0–80 μM). Fluorescence emission spectrum of leaves at wavelength regions of 500–800 nm was monitored by excitation at 436 nm.
The value of fluorescence polarization (P value), as result of energy transfer and mutual orientation between chlorophyll molecules, was determined by excitation at
436 nm and emission at 685 nm. The results showed that elevated temperature and concentrations of salt (NaCl), photooxidant
(MV), surfactant (SDS) and simulated SO2 (NaHSO3) treatments all induced a reduction of fluorescence polarization to various degrees. However, alteration of the fluorescence
spectrum and emission intensity of F685 and F731 depended on the individual treatment. Increase in temperature and concentration of NaHSO3 enhanced fluorescence intensity mainly at F685, while an increase in MV concentration led to a decrease at both F685 and F731. On the contrary, NaCl and SDS did not cause remarkable change in fluorescence spectrum. Among different treatments, the
negative correlation between polarization and fluorescence intensity was found with NaHSO3 treatments only. We concluded that P value being measured with intrinsic chlorophyll fluorescence as probe in leaves is a susceptible indicator responding to
changes in environmental conditions. The alteration of P value and fluorescence intensity might not always be shown a functional relation pattern. The possible reasons of differed
response to various treatments were discussed. 相似文献
6.
V. I. Bogdan A. E. Koklin Ya. A. Pokusaeva V. B. Kazansky 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(7):1085-1091
The skeleton isomerization of n-butane, n-hexane, and n-heptane was studied under supercritical conditions on H-forms of zeolites mordenite, beta, and ZSM-5 over the temperature
and pressure ranges 260–450°C and 80–130 atm. The isomerization of n-hexane and n-heptane was accompanied by side processes such as oligomerization and cracking. The selectivity of formation of branched
isomers of these hydrocarbons did not exceed 70 and 30%, respectively. The catalyst with the most stable operation was pentasil
ZSM-5, but the selectivity of formation of branched isomers on it did not exceed 30% even at 260–280°C and decreased to 3%
as the reaction temperature increased to 400–450°C. The fraction of aromatization products was then more than 15%. A study
of the influence of C6–C7
n-alkane additives on the isomerization of n-pentane on mordenite in the H-form under supercritical conditions at 260°C and 120 atm showed that a gradual decrease in
the activity of this catalyst in the isomerization of n-pentane was related to the formation of heavier hydrocarbons. 相似文献
7.
E. S. Itskevich 《Journal of Experimental and Theoretical Physics》1998,86(4):805-810
A study is made of the properties of the homologous series of mercury HTSC-cuprates HgBa2Can−1CunO2n
+2+δ with n=1–8. Experiments are conducted under pressure for samples with n=1–5. The Hg-1223 and Hg-1234 phases were synthesized using a controlled high pressure chamber. The oxygen content of an initial
mixture corresponding to the Hg-1234 phase was varied by changing the composition of the initial BaO/BaO2 oxides. The dependence of the superconducting transition temperature T
c
on the lattice constant a (and, therefore, on the oxygen content) and of T
c
max
and dT
c
max
/dp on n are convex upward up to n=4, 5. The maximum values always correspond to the Hg-1223 phase. Experimental T
c
max
(n) curves for the phases with n=1–6 and dT
c
max
/dp curves for n=1–5 are compared with Anderson’s theory (the so-called RVB model). A general analysis of these results indicates that the
mercury cuprates have an ideal structure for HTSC. The Hg-1223 phase is the “champion” in this ideal structure and the critical
temperature corresponding to this phase (T
c
=135 K) is the highest at atmospheric pressure.
Zh. éksp. Teor. Fiz. 113, 1474–1483 (April 1998) 相似文献
8.
S. N. Morozov U. Kh. Rasulev 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(7):902-905
The mass spectra of secondary cluster ions Bi
n
+ (n = 1–9) from bismuth sputtered by (6–21) keV Au
m
− (m = 1–9) and Bi
m
− (m = 1–5) cluster ions have been investigated. New features of manifestation of dense nonlinear cascades and thermal spikes
have been revealed. It is concluded that the thermal spike regime makes a significant contribution to the mechanism of formation
of small cluster ions, containing up to seven atoms for a bismuth target. 相似文献
9.
In a suitable pH buffer solutions, sodium diethyldithiocarbamate (DDTC) reacts with some divalence metal ions M(II) to form
(M–DDTC)
n
chelate complex nanoparticles, which exhibit different luminescence properties. There is a strongest luminescence peak at
470 nm for the Co(II)–DDTC system, three peaks at 330, 470, and 630 nm for the Cu(II)–DDTC system, three peaks at 420, 470,
and 630 nm for the Cd(II)–DDTC system, four peaks at 350, 400, 435, and 470 nm for the Ni(II)–DDTC system, two peaks at 408
and 470 nm for the Pb(II)–DDTC system, two peaks at 415 and 470 nm for the Fe(II)–DDTC system. The different luminescence
properties of (M–DDTC)
n
chelate complex nanoparticles was explained. Under the optimal conditions, the luminescence intensity of (Co–DDTC)
n
chelate complex nanoparticles at 470 nm (F
470 nm) is linear to Co(II) concentration in the range of 0.012–1.44 μg/mL. The detection limit is 0.0023 μg/mL. A novel luminescence method has been proposed for the determination of cobalt in Vitamin B12 samples, with satisfactory results. 相似文献
10.
X. J. Kuang X. Q. Wang G. B. Liu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(1):71-80
An all-electron scalar relativistic calculation on
Au
n
NO (n = 1–10) clusters has been performed by using density functional
theory with the generalized gradient approximation at the PW91 level. The
small gold cluster would like to bond with nitric and the nitric monoxide
molecule prefers to occupy the on-top and single fold coordination site. The
Au
n
structures in all Au
n
NO clusters are only distorted slightly
and still keep the planar structures. With the bend of Au-N-O bond, the
structures of Au
n
NO clusters evolve from the 2D structure to 3D
structure. The most favorable adsorption between small gold cluster and
nitric monoxide molecule takes place in the case that nitric monoxide
molecule is adsorbed onto an odd-numbered pure Au
n
cluster and becomes
odd-numbered Au
n
NO cluster with even number of valence electrons. The
scalar relativistic effect strengthens the Au–Au, Au–N interaction and
weakens the N–O interaction, appearing as the shorter Au–Au, Au–N
bond-length and the longer N–O bond-length. The differences between our work
and previous work are believed to be the reflection of the scalar
relativistic effect. 相似文献
11.
The relationship between the diffusivity D
n
and the mobility μ
n
of chemically doped organic n-type semiconductors exhibiting a disordered band structure is presented. These semiconductors
have a Gaussian-type density of states. So, calculations have been performed to elucidate the dependence of D
n
/μ
n
on the various parameters of this Gaussian density of states. Y. Roichman and N. Tessler (Appl. Phys. Lett. 80:1948, 2002), and subsequently Peng et al. (Appl. Phys. A 86:225, 2007), conducted numerical simulations to study this diffusivity–mobility relationship in organic semiconductors. However, almost
all other previous studies of the diffusivity–mobility relationship for inorganic semiconductors are based on Fermi–Dirac
integrals. An analytical formulation has therefore been developed for the diffusivity/mobility relationship for organic semiconductors
based on Fermi–Dirac integrals. The D
n
/μ
n
relationship is general enough to be applicable to both non-degenerate and degenerate organic semiconductors. It may be an
important tool to study electrical transport in these semiconductors. 相似文献
12.
N. Kh. Dzhemilev S. F. Kovalenko L. F. Lifanova S. E. Maksimov Sh. T. Khozhiev 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(7):910-914
The spectra of kinetic energies of positive Si
n
O
m
+ cluster ions (n = 2–5, m = 2–7) have been measured using a double focusing ion microanalyzer with reverse geometry at instants 10−5 to 10−4 s after emission. The dissociation energies have been determined within the evaporative ensemble model and the theory of
unimolecular decay reactions. The results obtained are compared with the binding energies of neutral Si
n
O
m
clusters. 相似文献
13.
Amol Rahane Mrinalini Deshpande Ravindra Pandey 《Journal of nanoparticle research》2010,12(3):727-736
Structures, electronic and magnetic properties of Mn and Mn2 doped stoichiometric (GaO)
n
clusters with n = 1−7 are studied in the framework of density functional theory. Doping of a Mn atom is found to be energetically favorable
in (GaO)
n
clusters and the equilibrium configurations are found to be determined by the metal–oxygen interactions. Mn prefers to maximize
the number of Mn–O bonds by selecting a Ga site in the cluster which increases its coordination with oxygen. Addition of a
Mn atom in Mn(GaO)
n
clusters results into the ground state to be either ferromagnetic or antiferromagnetic depending on the Mn coordination number
and the Mn–Mn bond-length in the given Mn2(GaO)
n
cluster. 相似文献
14.
A. V. Voitsekhovskii V. V. Vasil’ev D. V. Grigor’ev I. V. Romanov 《Russian Physics Journal》2009,52(5):441-447
The process of reconstuction of the distribution profile of hole concentration in the p
+–n structure by the method of differential Hall measurements upon implantation of ions As+ (Е = 190 keV, D = 3.1014 cm-2, j = 0.025 μA/cm2) into epitaxial films Cd
x
Hg1–x
Te for x ~ 0.2, with the initial electron concentration and mobility n = 1014 cm-3 and μ = 2∙105 cm2∙V–1∙s–1 is numerically simulated. The dependences of degree of reconstruction of the hole-concentration distribution profile on the
depth of a shunting n-layer and magnitude of the magnetic field, at which the electrophysical parameters of the p
+–n structure are measured, are calculated. The dependence of the limiting magnetic field determining the magnetic-field range
for measurements on the n-layer depth is found. It is shown that in calculations one should use the conduction values measured
at the same magnetic fields as the Hall coefficients for determination of the holeconcentration distribution profile using
the Petritz model. 相似文献
15.
V. A. Kutasov L. N. Luk’yanova P. P. Konstantinov G. T. Alekseeva 《Physics of the Solid State》1997,39(3):419-422
A study has been made of the thermoelectric and galvanomagnetic properties of n-Bi2Te3−x
Sex solid solutions (x=0.3 and 0.36) in the temperature range 80–300 K. The lowest carrier concentrations, (0.8–1)×1018 cm−3, were obtained by displacing the solid solution from the stoichiometric to a Te-rich composition. At such carrier concentrations,
the second subband in the conduction band of n-Bi2Te3−x
Sex is not filled, which results in a growth of mobility because of the absence of interband scattering, and brings about an
increase of thermoelectric efficiency in the 80–120-K range.
Fiz. Tverd. Tela (St. Petersburg) 39, 483–487 (March 1997) 相似文献
16.
F. Assenmacher M. Gutmann F. Noack V. Stert W. Radloff 《Applied physics. B, Lasers and optics》2000,71(3):385-390
The photodissociation dynamics of HNO3 in the electronic S3 (2 1
A
′
) state leading to the fragments OH and NO2 was investigated in real time. HNO3 was prepared either in a fluorescence cell at room temperature (LIF probing of OH) or rotationally cold in a molecular beam
(probing of NO2 by three-photon ionization). A 2 1
A
′
lifetime of 60–80 fs could be obtained from the experimental results, indicating essentially barrierless dissociation. In
addition, secondary dissociation of internally excited nascent fragments NO2
* leading to products NO(X 2
Π) and O(3
P) with a characteristic dissociation time of 2.3 ps was observed. This time is surprisingly long when compared with dissociation
lifetimes of NO2 from the literature, obtained after direct photoexcitation. The discrepancy is explained by differences in the preparation
conditions of the dissociative state of NO2.
Received: 12 November 1999 / Published online: 13 July 2000 相似文献
17.
T. Matsuzaki K. Nagamine K. Ishida N. Kawamura S. N. Nakamura M. Kato H. Sugai M. Tanase K. Kudo N. Takeda G. H. Eaton 《Hyperfine Interactions》2001,138(1-4):295-305
We have measured X-rays and neutrons associated with the muon catalyzed t–t fusion process at the RIKEN-RAL Muon facility.
In the X-ray measurement, we observed Kα and Kβ X-rays originating from the muon sticking process in muon catalyzed t–t fusion, and obtained the Kα X-ray yield and the Kβ/Kα intensity ratio. An average recoil energy of the (μ−α) atoms in a solid T2 medium was determined from the observed Doppler broadening width of the Kα X-ray line. The obtained t–t fusion neutron has shown an exponential time spectrum with a single component and a continuous
energy spectrum with a maximum energy of 9 MeV. We have determined the t–t fusion neutron yield, the t–t fusion cycling rate
and the muon sticking probability from the neutron data. The obtained maximum neutron energy is a very peculiar value from
the view point of the reaction Q value (11.33 MeV) with the three-particle decay mode at the exit channel: t + t → α + n + n + Q. The obtained neutron energy distribution was analyzed by a simple model with two neutron energy components; reasonable agreement
has been obtained, suggesting a strong (n–α) correlation in the exit channel of the t–t muon catalyzed fusion reaction.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
Liu Wei Chen Shifu Zhang Sujuan Zhao Wei Zhang Huaye Yu Xiaoling 《Journal of nanoparticle research》2010,12(4):1355-1366
In this article, the p-type CuBi2O4 powder was prepared by the solid-state reaction method. The p–n heterojunction photocatalyst p-CuBi2O4/n-TiO2 was prepared by ball milling. The photocatalyst was characterized by X-ray powder diffraction (XRD), UV–Vis diffuse reflectance
spectroscopy, scanning electron microscopy (SEM), and photoluminescence emission spectra. The photocatalytic activity of the
photocatalyst was evaluated by photocatalytic reduction of Cr2O7
2− and photocatalytic oxidation of methyl orange (MO). The results showed that the photocatalytic activity of the p–n heterojunction photocatalyst p-CuBi2O4/n-TiO2 was much higher than that of TiO2 and the mixture of p-CuBi2O4–n-TiO2 without ball milling under visible and UV light irradiation. The optimal percentage of doped p-CuBi2O4 is 20 wt%. Compared with pure TiO2, the photoabsorption wavelength range of the photocatalyst is extended greatly toward visible light and improves the utilization
of the total spectrum. The effect of ball milling time on the photocatalytic activity of the photocatalyst was also investigated.
The optimum ball milling time is 6 h. The mechanisms of influence of p-CuBi2O4 on the photocatalytic activity of p-CuBi2O4/n-TiO2 were also discussed by the p–n junction principle and the valance band theory. 相似文献
19.
Alla P. Toropova Andrey A. Toropov Emilio Benfenati Giuseppina Gini Danuta Leszczynska Jerzy Leszczynski 《Molecular diversity》2011,15(1):249-256
Quantitative structure–property relationships (QSPRs) between the molecular structure of [C60] and [C70] fullerene derivatives and their solubility in chlorobenzene (mg/mL) have been established by means of CORAL (CORrelations
And Logic) freeware. The CORAL models are based on representation of the molecular structure by simplified molecular input
line entry system (SMILES). Three random splits into the training and the external validation sets have been examined. The
ranges of statistical characteristics of these models are as follows: n = 18, r
2 = 0.748–0.815, s = 15.1 –17.5 (mg/mL), F = 47–71 (training set); n = 9, r
2 = 0.806–0.936, s = 12.5–17.5 (mg/mL), F = 29–103 (validation set). 相似文献
20.
Richard S. Ellis Jonathan Machta Peter Tak-Hun Otto 《Journal of statistical physics》2008,133(1):101-129
The purpose of this paper is to prove connections among the asymptotic behavior of the magnetization, the structure of the
phase transitions, and a class of polynomials that we call the Ginzburg–Landau polynomials. The model under study is a mean-field
version of a lattice spin model due to Blume and Capel. It is defined by a probability distribution that depends on the parameters
β and K, which represent, respectively, the inverse temperature and the interaction strength. Our main focus is on the asymptotic
behavior of the magnetization m(β
n
,K
n
) for appropriate sequences (β
n
,K
n
) that converge to a second-order point or to the tricritical point of the model and that lie inside various subsets of the
phase-coexistence region. The main result states that as (β
n
,K
n
) converges to one of these points (β,K),
. In this formula γ is a positive constant, and
is the unique positive, global minimum point of a certain polynomial g. We call g the Ginzburg–Landau polynomial because of its close connection with the Ginzburg–Landau phenomenology of critical phenomena.
For each sequence the structure of the set of global minimum points of the associated Ginzburg–Landau polynomial mirrors the
structure of the set of global minimum points of the free-energy functional in the region through which (β
n
,K
n
) passes and thus reflects the phase-transition structure of the model in that region. This paper makes rigorous the predictions
of the Ginzburg–Landau phenomenology of critical phenomena and the tricritical scaling theory for the mean-field Blume–Capel
model. 相似文献