Enhancing Electron Collection Efficiency and Effective Diffusion Length in Dye‐Sensitized Solar Cells

Intensity‐modulated photocurrent spectroscopy and intensity‐modulated photovoltage spectroscopy are employed to measure the dynamics of electron transport and recombination in the ZnO nanowire (NW) array‐ZnO/layered basic zinc acetate (LBZA) nanoparticle (NP) composite dye‐sensitized solar cells (DSSCs). The roles of the vertical ZnO NWs and insulating LBZA in the electron collection and transport in DSSCs are investigated by comparing the results to those in the TiO₂–NP, horizontal TiO₂–NW and vertical ZnO–NW‐array DSSCs. The electron transport rate and electron lifetime in the ZnO NW/NP composite DSSC are superior to those in the conventional TiO₂–NP cell due to the existence of the vertical ZnO NWs and insulating LBZA. It indicates that the ZnO NW/NP composite anode is able to sustain efficient electron collection over much greater thickness than the TiO₂–NP cell does. Consequently, a larger effective electron diffusion length is available in the ZnO composite DSSC.     

Asymptotic electromagnetic fields in non-relativistic QED: The problem of existence revisited

This paper is devoted to the scattering of photons by charged particles in models of non-relativistic quantum mechanical matter coupled minimally to the soft modes of the quantized electromagnetic field. We prove existence of scattering states involving an arbitrary number of asymptotic photons of arbitrarily high energy. Previously, upper bounds on the photon energies seemed necessary in the case of n>1 asymptotic photons and non-confined, non-relativistic charged particles.     

Influence of ZnO Nanoparticles on the Behavior of the Short-Lived Products of the Pulse Photolysis of Fluorescein and Its Halogen Derivatives in Isopropanol

Rapid processes, which occur on photoexcitation of fluorescein and a series of its halogen derivatives in the presence of ZnO nanoparticles in isopropanol, have been studied by pulse photolysis. The short-lived intermediates have been identified and the kinetics of their destruction have been studied. It is shown that photoinduced transfer of an electron from the singlet and triplet excited molecules of the dyestuffs into the conduction zone of the semiconductor occurs in the presence of ZnO nanoparticles.     

Distribution of odd electrons in ground-state molecules

A density function D(r) = 2(r, r) – tS(r, r)(r, r) dr, where (r, r) is a spinless first-order density matrix, has been proposed as fundamental formula representing the spatial distribution of odd electrons in molecules. The bonding properties of electrons in some representative triatomic species have been examined in the light of D(r). The density function can also be used successfully to assess the diradical character of unstable singlet ground-state molecules.     

The alternant hydrocarbon pairing theorem and all-valence electrons theory. An approximate LCOAO theory for the electronic absorption and MCD spectra of conjugated organic compounds, part 2

An approximate linear combination of orthogonalized atomic orbitals (LCOAO) all-valence electrons theory is described, based on a previously suggested partitioning of the Fock operator. Kinetic energy and penetration terms are evaluated explicitly in a L?wdin OAO basis, while two-electron repulsion terms are treated according to the conventional neglect of differential overlap (NDO) approximation. One-electron and penetration integrals are parameterized explicitly to predict approximate alternant pairing symmetry for the π-systems of benzene and napthalene. Application of the resulting LCOAO theory to a variety of alternant and non-alternant hydrocarbons demonstrates significant improvements in the prediction of MCD B-terms and transition moment directions, particularly for alternant (4N+2)- or 4N-perimeter π-systems for which traditional NDO procedures fail. Received: 27 May 1997 / Accepted: 28 August 1997     

Resonance capture of electrons by molecules of substituted pyrans

Negative-ion mass spectrometry in the mode of resonance capture of electrons and photoelectron spectroscopy in combination with quantum-chemical calculations showed that the formation of the resonance states of negative molecular ions in the reaction of electrons with molecules of the mechanism of intershell Feshbach resonance with the consecutive excitation of an electron from several higher occupied MO to one vacant MO. In a low-energy region, the resonance at 1.4 eV is a resonance of form and the resonance at 3–4 eV is the usual electron exciting Feshbach resonance with a parent triplet state (π.π*)³. The one and the same vacant π*_CC MO is “active” in all the resonances mentioned. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1892–1894, October, 1997.     

室温离子液体中银纳米微粒的制备与结构表征

利用化学还原方法在室温离子液体1-甲基-3-丁基咪唑四氟硼酸盐中制备了金属银纳米微粒,采用X射线衍射,透射电子显微镜,傅立叶红外光谱和热分析对所制备的样品进行了结构表征.结果表明,所制备的银纳米微粒具有立方相结构,粒径约为20 nm.离子液体不但作为反应的溶剂而且作为修饰剂修饰在银纳米微粒的表面,从而有效地阻止了银纳米微粒的团聚.     

Electrochemical behavior of electrodes containing nanostructured carbon of various morphology in the cathodic region of potentials

Voltammograms for electrodes containing nanostructured carbon of various morphology (single-walled carbon nanotubes, filament, columnar structures) are obtained in neutral aqueous electrolytic solutions. Experimental proofs for the existence of injection of solvated electrons into electrolytic solutions at moderate cathodic potentials are presented for all the electrodes. It is established that this effect is connected with the presence of atomically sharp areas on the electrode surfaces. It is assumed that the reason for the appearance of solvated electrons is the autoelectron emission at the interface between the conducting surface of the carbon material and the electrolytic solution. By studying the nitrate anion reduction it is shown that the reduction over-voltage of stable compounds may be lowered by substituting a fast homogeneous reaction of solvated electrons with the initial substance for the hindered heterogeneous stage of the first electron transfer.     

Solvated and Stabilized Electrons in Radiation-Chemical Processes

The electrons solvated in metal-ammonia solutions are relatively stable; by contrast, hydrated electrons are very unstable and have been discovered only recently during radiolysis of water. They can be regarded as the simplest radicals. Radiation chemical production of solvated electrons has proved to be a particularly elegant method for the qualitative and quantitative investigation of the reactions between these electrons and numerous compounds, whose rates are partly controlled by diffusion. It has been possible in some cases to identify optically and ESR-spectroscopically the resulting short-lived products (radical-anions). The similarity between the physical and chemical properties of electrons solvated in solutions and those of electrons stabilized in the solid phase suggests that the two species are identical.     

Evolution of lone pair of excess electrons inside molecular cages with the deformation of the cage in e2@C60F60 systems

For unusual e(2)@C(60)F(60)(I(h), D(6h), and D(5d)) cage structures with two excess electrons, it is reported that not only the lone pair in singlet state but also two single excess electrons in triplet state can be encapsulated inside the C(60)F(60) cages to form single molecular solvated dielectrons. The interesting relationship between the shape of the cage and the spin state of the system has revealed that ground states are singlet state for spherical shaped e(2)@C(60)F(60)(I(h)) and triplet states for short capsular shaped e(2)@C(60)F(60)(D(6h)) and long capsular shaped e(2)@C(60)F(60)(D(5d)), which shows a spin evolution from the singlet to triplet state with the deformation of the cage from spherical to capsular shape. For these excess electron systems, the three ground state structures have large vertical electron detachment energies (VDEs (I) of 1.720-2.283 eV and VDEs (II) of 3.959-5.288 eV), which shows their stabilities and suggests that the large C(60)F(60) cage is the efficient container of excess electrons.