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1.
Wenfang Zhang P. Schmidt-Zhang G. Kossmehl W. Plieth 《Journal of Solid State Electrochemistry》1999,3(3):135-140
Photocurrent and differential capacity measurements have been carried out at polybithienyl (PBT) and poly(3-butylthiophene)
(PBuT) films on platinum. The photocurrents are cathodic, similar to inorganic p-type semiconductors. The band gap energy
was determined from the photocurrent spectra (E
g=1.7 eV for PBT and E
g=1.9 eV for PBuT). The dependence of the differential capacity on the potential could be presented as Mott-Schottky plot,
at least in a limited potential region. The flatband potential was determined (E
fb= 0.67 V for PBT and E
fb=0.58 V for PBuT).
Received: 9 June 1998 / Accepted: 22 August 1998 相似文献
2.
The mechanism of the electrosynthesis of poly(3-butylthiophene) (PBuT) was studied by cyclic voltammetry and potential step
methods in comparison with polybithienyl. The anodic oxidation polymerization of the 3-butylthiophene underwent two steps:
oligomer formation and further polymerization to form the polymer. The doping level of the PBuT increases with the cycle number
of the potential sweeps during polymerization. The current responses to the potential steps indicate a nucleation and nuclei
growth process which is repeated layer to layer. The differential capacity (C
d) and photocurrent were measured at the PBuT films in the aqueous electrolyte solution. The C
d
−2 vs. E plot shows two regions of linearity, one with a negative slope and the other with a positive slope in different potential
regions, which give the same flat-band potential. This indicates that the PBuT film exhibits both p-type and n-type features
of a semiconductor at differrent potential regions. The cathodic photocurrent spectrum was analysed by the (j
ph
hν)2/
n
vs. hν plots, giving band gap energies of 2.41 eV for n=1 and and 2.01 eV for n=4.
Received: 29 July 1999 / Accepted: 15 November 1999 相似文献
3.
On analyzing the topological structures of the three types of tetrahedral fullerenes (which consist only of triangles and
hexagons), (1) C
n
(T
d
,n=12h
2; h=1,2,…), (2) C
n
(T
d
,n=4h
2;h=1,2,…), and (3) C
n
(T,n=4(h
2+hk+k
2);h>k,h,k=1,2,…), we have obtained theoretically the Infrared and Raman active modes by means of the derived formulas for the decomposition
of their nuclear motions into irreducible representations, and the 13C NMR spectra with natural abundance for 13C by using the distribution functions for all of the tetrahedral (T
d
and T) fullerenes, respectively.
Received: 25 May 1998 / Accepted: 30 July 1998 / Published online: 23 November 1998 相似文献
4.
Arvydas Survila Jolanta Pileckien? Stas? Kanapeckait? Putinas Kalinauskas Giedrius Stalnionis 《Journal of Solid State Electrochemistry》2012,16(2):521-527
In accordance with thermodynamic analysis, cuprous oxide layers are formed spontaneously in the Cu|Cu(II), gluconic acid system
at pH > 3.7 under open-circuit conditions. A current peak of Cu2O reduction is observed on cathodic voltammograms at ca −0.7 V, its height being dependent on the exposure time. The analysis
of the charge transferred in this region yields the rate of Cu2O formation equal to 1.25 × 10−10 mol cm−2 s−1. The light perturbation of Cu electrode under open-circuit conditions results in the generation of a negative photopotential,
which is indicative of n-type conductivity. The threshold wavelength is equal to ∼590 nm and is consistent with a band gap of ∼2.1 eV. Anodic photocurrents,
which are observed near the open-circuit potential, decrease with cathodic polarization and change their sign at ∼0.05 V.
Analysis of impedance data was performed, invoking the equivalent circuit that accounts for the two-step charge transfer.
In the presence of Cu2O, some retardation of Cu(II) reduction was found to occur with a slight increase in the admittance of the double layer. The
suggestion has been made that oxide layers formed in Cu(II) gluconate solutions cannot be compact and uniformly distributed
over the entire electrode surface. Relevant investigations of surface morphology support this conclusion. 相似文献
5.
Graham A. Bowmaker Paul A. Kilmartin Graham A. Wright 《Journal of Solid State Electrochemistry》1999,3(3):163-171
Stable, yellow anodic films of parathiocyanogen (SCN)
x
were formed on a platinum electrode from 2.8 M KSCN in methanol at 45 °C at a constant current of 20–40 mA cm−2 for 15–30 min. Loosely bound orange crystals of a more amorphous character were removed by rinsing to leave an adherent yellow
film with sharp Raman bands under 647.1 nm laser excitation at 627 cm−1 (vCS), 1152 cm−1 and 1236–1261 cm−1 (vNN and vCN). The lack of electroactivity and short-lived photocurrents pointed to an insulating film at potentials up to 1.0 V (SHE).
At more positive potentials, longer-lasting photocurrents were obtained, consistent with breakdown of the insulating film.
XPS scans confirmed N:C:S ratios close to 1:1:1, with a deficiency of S of some 10% due to S lost as sulfate at the film surface.
Oxidation of SeCN− in neutral aqueous solution led to the formation of a less-stable orange paraselenocyanogen film with a Raman band at 1256–1267 cm−1, which decomposed within a day to grey selenium.
Received: 12 December 1997 / Accepted: 23 March 1998 相似文献
6.
Željka Petrović Nushe Lajçi Mirjana Metikoš-Huković Ranko Babić 《Journal of Solid State Electrochemistry》2011,15(6):1201-1207
The study of barrier and semiconducting properties of anodically formed oxide films on chromium in an acid solution was carried
out using the Cr-quartz crystal electrode. The oxide film formation and growth occur through an anion vacancies transport
via a low-field-assisted mechanism (H = 106 V cm−1). The anion diffusion coefficient, which quantitatively describes the transport of point defects within the growing film,
was calculated from capacitance data using the Nernst-Planck equation for low-field limit approximation and Mott-Schottky
analysis. The depletion region in the passive film, close to the film|electrolyte interface, dominates the semiconducting
properties. The passive film on Cr in an acid solution behaves as an n-type semiconductor. An energy-band structure model
of the passive film is given. 相似文献
7.
Lang SM Claes P Neukermans S Janssens E 《Journal of the American Society for Mass Spectrometry》2011,22(9):1508-1514
Structural information on free transition metal doped aluminum clusters, Al
n
TM
+ (TM = Ti, V, Cr), was obtained by studying their ability for argon physisorption. Systematic size (n = 5 – 35) and temperature (T = 145 – 300 K) dependent investigations reveal that bare Al
n
+ clusters are inert toward argon, while Al
n
TM
+ clusters attach one argon atom up to a critical cluster size. This size is interpreted as the geometrical transition from
surface-located dopant atoms to endohedrally doped aluminum clusters with the transition metal atom residing in an aluminum
cage. The critical size, n
crit
, is found to be surprisingly large, namely n
crit = 16 and n
crit = 19 – 21 for TM = V, Cr, and TM = Ti, respectively. Experimental cluster–argon bond dissociation energies have been derived as function of cluster size from
equilibrium mass spectra and are in the 0.1–0.3 eV range. 相似文献
8.
CuCrO2 single crystal, elaborated by the flux method, is a narrow-band-gap semiconductor crystallizing in the delafossite structure
with an indirect optical transition at 2.12 eV. The relatively longer Cu–Cu is consistent with the semi-conducting behavior.
The conductivity in the (001) plans is thermally activated and occurs predominantly by small polaron hopping through mixed-valence
states Cu+/2+ in conformity with a classical dielectric behavior. The activation energy (0.05 eV) gave an effective mass of 9 m
o, indicating that the levels in the vicinity of the Fermi level E
f are strongly localized. The oxide shows an excellent chemical stability over the whole pH range; the semi-logarithmic plot
gave an exchange current density of 0.7 mA cm−2 and a corrosion potential of 0.18 V/SCE in KOH (0.5 M) electrolyte. The electrochemical study is confined in (001) plans, and reversible oxygen intercalation is
evidenced from the cyclic voltammetry. The Mott–Schottky plot (C−2-V) is characteristic of p type conduction and exhibits a linear plot from which a flat band potential of +0.21 V/SCE and a holes density N
A
of 5.06 × 1014 cm−3 were obtained. The photocurrent is due to Cu+: d → d transition and the valence band is positioned at 5.34 eV below vacuum. 相似文献
9.
During the investigation of n-type HfSe2 (ΔEg = 1.13 eV, with n = 1.2 × 1019 cm?3) in contact with aqueous electrolytes, both anodic and cathodic photocurrents were detected. This inversion of the polarity of the photocurrents is only observed during illumination with photon energies larger than hν = 2.5 eV. For photons with hν<2.5 eV only anodic photocurrents were found. These results are interpreted in terms of two narrow d-conduction bands placed at different distances from the Fermi level, the existence of which is compatible with data on optical transmission. Additional results obtained concern the photocorrosion of HfSe2 to Hf(IV) and elemental selenium, as well as a very characteristic transient photocurrent response arising at potentials considerably negative of the flat-band potential on a newly cleaved surface. The latter effect is interpreted as a photo-deintercalation phenomenon arising from hafnium atoms pushed on to intercalation or adsorption sites during cleavage, and released as ions during illumination. 相似文献
10.
Ortega-Algar S Ramos-Martos N Molina-Díaz A 《Analytical and bioanalytical chemistry》2008,391(2):715-719
A single optosensing device based on lanthanide-sensitized luminescence was developed for determination of p-aminobenzoic acid (PABA). The method is based on the formation of a complex between PABA and Tb(III) immobilized on the solid
phase (QAE A-25 resin) placed inside the flow cell. NaCl (1 M) was used as carrier solution and HCl (0.05 M) as eluent. The
sample solutions of PABA (100 μL) containing Tb(III) and buffered at pH = 6.0 were injected into the carrier stream and the
luminescence was measured at λ
ex = 290 nm and λ
em = 546 nm. The method shows a linear range from 0.2 to 6.0 μg mL−1 with an RSD of 1.2% (n = 10) and a sampling frequency of 22 h−1. A remarkable characteristic of the method is its high selectivity which allows it to be satisfactorily applied to the analysis
of PABA in pharmaceutical samples without prior treatment.
Figure Typical emission bands of Tb(III) in a solid-phase PABA–Tb(III) luminescence spectrum 相似文献
11.
Mahmoud M. Khader Mahmoud M. Saleh Emad M. El-Naggar 《Journal of Solid State Electrochemistry》1998,2(3):170-175
Active ferric tungstate was prepared by fusing an equimolar mixture of tungsten oxide and ferric oxide at 1100 °C and annealing
at 800 °C for 20 h. Analysis of the electrode material by X-ray diffraction showed that its composition was Fe2WO6. When this material was illuminated by visible light in 0.1 M NaOH solution, an anodic photocurrent at a positive potential
of 0.5 V (SCE) was obtained. Therefore, this material is considered as an n-type semiconductor. The d.c. conductivity of this
material at 25 °C was 4 × 10−6 Ω−1 cm−1. In the dark, unexpectedly high anodic currents were observed at positive potentials of 0.8 V (SCE) in 0.1 M NaOH. These
currents are attributed to the existence of a high density of electron-hole recombination centers within the band-gap of ferric
tungstate. When dimethyl viologen (DMV) was used as an electroactive compound in the electrolyte, the anodic photocurrents
increased significantly. The oxidation of DMV is thus expected to compete with the electron-hole recombination process. Furthermore,
the process of electron-hole recombination was also predicted from the shape of the photocurrent transients under interrupted
illumination. These transients exhibited first-order relaxation effects in the region of the onset time of the photocurrents.
The band-gap energy of Fe2WO6 was found to be about 1.5 eV and its flat-band potential in 0.1 M NaOH was about −0.3 V (SCE). The photoelectrochemical properties
of ferric tungstate are explained according to the formalism of the band model of the semiconductor/electrolyte interface.
Received: 16 July 1997 / Accepted: 26 September 1997 相似文献
12.
A number of configurations of NLi
n
Na2 (n = 1–4) species were optimized using the B3LYP–density functional theory method; the 6-31G* basis set was used in this calculation. In order to study all possible dissociation energies, some related species such as
NLi2Na, NLi
n
(n = 1–4), Li
n
(n = 1, 2) and Na
n
(n = 1, 2) were also considered. Optimizations of these species were followed by fundamental frequency calculations at the same
level. Global minima of these species were shown to adopt C
2
v
(NLi4Na2, NLi2Na2), D
3
h
(NLi3Na2) and C
s
(NLiNa2 and NLi2Na) configurations. All possible dissociation energies were obtained.
Received: 30 November 1998 / Accepted: 15 October 1999 / Published online: 14 March 2000 相似文献
13.
Razika Brahimi Mohamed Trari Aïssa Bouguelia Yassine Bessekhouad 《Journal of Solid State Electrochemistry》2010,14(7):1333-1338
The delafossite CuAlO2 single crystal, prepared by the flux method, is a low mobility p-type semiconductor with a hole mobility of 1.2 × 10−5 cm−2 V−1 s−1. The chronoamperometry showed an electrochemical O2− insertion with a diffusion coefficient D
303K of 3.3 × 10−18 cm2 s−1. The thermal variation of D in the range 293–353 K gave an enthalpy of diffusion (ΔH) of 44.7 kJ mol−1. CuAlO2 is photoactive, and the Mott–Schottky plot indicates a flat band potential of +0.42 V vs saturated calomel electrode and
a holes density (N
A) of 1016 cm−3. The photocurrent spectra have been analyzed by using the Gartner model from which the absorption coefficients and diffusion
lengths were determined. An optical transition at 1.66 eV, indirectly allowed, has been obtained. The spectral photoresponse
provides a high absorption at 480 nm. The low quantum yield (η) is attributed to a small depletion length (440 nm) and a hole diffusion width (271 nm) compared to a very large penetration
depth (12 μm). 相似文献
14.
Torsten Barfels Bernd Schmidt Andreas von Czarnowski Hans-Joachim Fitting 《Mikrochimica acta》2002,139(1-4):11-16
For investigation of the luminescent center profile cathodoluminescence measurements are used under variation of the primary
electron energy E
0 = 2…30 keV. Applying a constant incident power regime (E
0·I
0 = const), the depth profiles of luminescent centers are deduced from the range of the electron energy transfer profiles dE/dx.
Thermally grown SiO2 layers of thickness d = 500 nm have been implanted by Ge+-ions of energy 350 keV and doses (0.5–5)1016 ions/cm2. Thus Ge profiles with a concentration maximum of (0.4 – 4) at% at the depth of dm≅240 nm are expected. Afterwards the layers have been partially annealed up to T
a = 1100 °C for one hour in dry nitrogen. After thermal annealing, not only the typical violet luminescence (λ = 400 nm) of
the Ge centers is strongly increased but also the luminescent center profiles are shifted from about 250 nm to 170 nm depth
towards the surface. This process should be described by Ge diffusion processes, precipitation and finally Ge nanocluster
formation. Additionally, a Ge surface layer is piled-up extending to a depth of roughly 25 nm. 相似文献
15.
J. Pablo Tomba Daniel Portinha Walter F. Schroeder Mitchell A. Winnik Willie Lau 《Colloid and polymer science》2009,287(3):367-378
This paper describes experiments that investigate the use of low glass transition temperature (T
g) latex particles consisting of oligomer to promote polymer diffusion in films formed from high molar mass polymer latex.
The chemical composition of both polymers was similar. Fluorescence resonance energy transfer (FRET) was used to follow the
rate of polymer diffusion for samples in which the high molar mass polymer was labeled with appropriate donor and acceptor
dyes. In these latex blends, the presence of the oligomer (with M
n = 24,000 g/mol, M
w/M
n = 2) was so effective at promoting the interdiffusion of the higher molar mass poly(butyl acrylate-co-methyl methacrylate; PBA/MMA = 1:1 by weight) polymer (with M
n = 43,00 g/mol, M
w/M
n = 3) that a significant amount of interdiffusion occurred during film drying. Additional polymer diffusion occurred during
film aging and annealing, and this effect could be described quantitatively in terms of free-volume theory.
This paper is dedicated to Professor Haruma Kawaguchi to honor his many contributions to the field of latex particles and
their applications. 相似文献
16.
Timothy J. Johnson Robert L. Sams Sarah D. Burton Thomas A. Blake 《Analytical and bioanalytical chemistry》2009,395(2):377-386
We report quantitative infrared spectra of vapor-phase hydrogen peroxide (H2O2) with all spectra pressure-broadened to atmospheric pressure. The data were generated by injecting a concentrated solution
(83%) of H2O2 into a gently heated disseminator and diluting it with pure N2 carrier gas. The water vapor lines were quantitatively subtracted from the resulting spectra to yield the spectrum of pure
H2O2. The results for the ν6 band strength (including hot bands) compare favorably with the results of Klee et al. (J Mol. Spectrosc. 195:154, 1999) as well as with the HITRAN values. The present results are 433 and 467 cm-2 atm−1 (±8 and ±3% as measured at 298 and 323 K, respectively, and reduced to 296 K) for the band strength, matching well the value
reported by Klee et al. (S = 467 cm−2 atm−1 at 296 K) for the integrated band. The ν1 + ν5 near-infrared band between 6,900 and 7,200 cm−1 has an integrated intensity S = 26.3 cm−2 atm−1, larger than previously reported values. Other infrared and near-infrared bands and their potential for atmospheric monitoring
are discussed. 相似文献
17.
A. Zaidi S. Lahmar Z. Ben Lakhdar P. Rosmus M. Hochlaf 《Theoretical chemistry accounts》2005,114(4-5):341-349
For the most stable linear isomer of C3S in its X1Σ+ state a six-dimensional potential energy surface (PES) has been calculated ab initio by coupled cluster – connected triples
(CCSD(T)) method. The analytic form of the PES has been transformed in a quartic force field in dimensionless normal coordinates
and employed in calculations of spectroscopic constants using second-order perturbation theory. The PES and the full kinetic
energy operator in internal coordinates have been used to calculate variationally the anharmonic ro-vibrational energies for
J=0 and J=1. The two experimental band origins of C3S observed in the gas phase, ν1 and ν1+ν5−ν5, agree very well with the theoretical values. The anharmonic ro-vibrational levels, including the bending modes up to 2200
cm−1, are reported. The singlet ground state PES has a saddle point at about 1.25 eV above the linear minimum and two other higher
lying cyclic local minima. The only dipole- and spin-allowed electronic transition between 0 and 5 eV is calculated to be
the 1Π−X1Σ+ transition with a vertical transition energy of 353.2 nm in good agreement with the matrix value of 378 nm. The dissociative
paths C + C2S, C2 + CS and C3 + S of low lying singlet and triplet states have been investigated.
Electronic Supplementary Material: Supplementary material is available in the online version of this article at dx.doi.org/10.1007/s00214-005-0683-7
Dedicated to Professor H. Stoll. 相似文献
18.
Relativistic energy-consistent small-core lanthanide pseudopotentials of the Stuttgart–Bonn variety and extended valence
basis sets have been used for the investigation of the dimers La2 and Lu2. It was found that the ground states for La2 and Lu2 are most likely 1∑
g
+ (σ
g
2π
u
4) and 3∑
g
− (4f
144f
14σ
g
2σ
u
2πu
2), respectively. The molecular constants including error bars were derived from multireference configuration interaction as
well as coupled-cluster calculations, taking into account corrections for atomic spin–orbit splitting as well as possible
basis set superposition errors. The theoretical values for La2 (R
e=2.70±0.03 ?, D
e=2.31±0.13 eV, ωe=186±13 cm−1) show good agreement with the experimental binding energy (D
e=2.52±0.22 eV), but the experimental vibrational constant in an Ar matrix (ωe=236±0.8 cm−1) is significantly higher. For Lu2 the theoretical values (R
e=3.07±0.03 ?, D
e=1.40±0.12 eV, ωe=123±1 cm−1) are in overall excellent agreement with experimental data (D
e=1.43±0.34 eV, ωe=122± 1 cm−1). The electronic structures of La2 and Lu2 are compared to those other lanthanide dimers and trends in the series are discussed.
Received: 25 March 2002 / Accepted: 2 June 2002 / Published online: 21 August 2002 相似文献
19.
New divalent transition metal 3,5-pyrazoledicarboxylate
hydrates of empirical formula Mpz(COO)2(H2O)2,
where M=Mn, Co, Ni, Cu, Zn and Cd (pz(COO)2=3,5-pyrazoledicarboxylate),
metal hydrazine complexes of the type Mpz(COO)2N2H4
where M=Co, Zn or Cd and Mpz(COO)2nN2H4·H2O,
where n=1 for M=Ni
and n=0.5 for M=Cu
have been prepared and characterized by physico-chemical methods. Electronic
spectroscopic data suggest that Co and Ni complexes adopt an octahedral geometry.
The IR spectra confirm the presence of unidentate carboxylate anion (Δν=νasy(COO–)–νsym(COO–)>215
cm–1) in all the complexes and bidentate
bridging hydrazine (νN–N=985–950 cm–1)
in the metal hydrazine complexes. Both metal carboxylate and metal hydrazine
carboxylate complexes undergo endothermic dehydration and/or dehydrazination
followed by exothermic decomposition of organic moiety to give the respective
metal oxides as the end products except manganese pyrazoledicarboxylate hydrate,
which leaves manganese carbonate. X-ray powder diffraction patterns reveal
that the metal carboxylate hydrates are isomorphous as are those of metal
hydrazine complexes of cobalt, zinc and cadmium. 相似文献
20.
Mirjana Mladenović Peter Botschwina Peter Sebald Stuart Carter 《Theoretical chemistry accounts》1998,100(1-4):134-146
The results of various ab initio calculations are reported for the electronic ground state of the acetylide anion. An “Eyring's
lake” in the T-shaped configuration is identified with six different methods (SCF, MP2, CCSD, CCSD-T, CCSD(T), and CEPA–1).
The equilibrium bond lengths of HCC− are estimated to be r
e
(CH)=1.0689(3) ? and R
e
(CC)=1.2464(2) ?, and the ground-state rotational constant is predicted to be B
0=41636(20)MHz. The large permanent dipole moment of μ0=−3.093D should facilitate detection of the anion by microwave spectroscopy. The band centers are predicted to be 3211.3cm−1(ν1), 511.1cm−1(ν2), and 1805.0cm−1(ν3). A large transition dipole moment of 0.477 D is calculated for the ν2 band. Rovibrational levels of HCC− up to approximately 20 000 cm−1 above equilibrium are calculated with DVR-DGB and FBR methods on the basis of a previous CEPA–1 potential energy surface.
Different energy patterns are found and discussed, for which anharmonic and Coriolis resonances are shown to play an important
role.
Received: 27 July 1998 Accepted: 12 August 1998 / Published online: 19 October 1998 相似文献