超细碳化硅中游离碳的测定

通过加热氧化并电位滴定产生的ＣＯ２，分析超细碳化硅粉中游离碳，对部分碳化硅和游离硅同时被氧化的干扰，提出了新的校正方法和计算式，测定精度ＲＳＤ≤５．１％相对误差≤６．２％。     

Electrical Methods to Elucidate Charge Transport in Hybrid Perovskites Thin Films and Devices

The panchromatic light absorption and excellent charge carrier transport properties in organo lead halide perovskites allowed to achieve an unprecedented power conversion efficiency in excess of 25 % for thin film photovoltaics fabrication. To understand the underlying phenomena, various comprehensive set of optical and electrical techniques have been employed to investigate the charge carrier dynamics in such devices. In this perspective, we aim to summarize the electrical transport properties of perovskite thin films by using (i) impedance spectroscopy (IS), (ii) space charge limited current (SCLC), (iii) field‐effect transistors (FETs) and (iv) time‐of‐flight (TOF) methods. We have deliberated various equivalent circuit used to model the perovskite solar cells by means of IS. The SCLC technique provide vital electrical parameters such as mobility, activation energy, traps density and distribution, carrier concentration, density of states, etc. The TOF technique measures mobility as a primary parameter while the FETs configuration provide a valuable insight into the in‐plane charge transport in perovskites thin films. We believe that these notable understanding will provide insights into charge carrier dynamics in perovskite materials and devices.     

密度泛函理论研究边链对苯并菲电荷传输的影响

采用密度泛函理论在B3LYP/6-31G**水平上,根据电子转移的半经典模型对含有炔基的不同软链的苯并菲化合物分子的电荷传输性质进行研究。研究表明,所有目标化合物均有利于苯并菲的电荷传输。其中,直接在苯并菲刚性环上引入酰胺基（-CO-NH-）有利于提高正电荷的传输,而间隔基为酯基的单取代化合物的正负电荷传输性质均比较良好。在苯并菲上单取代的分子明显比其双取代、三取代的分子正电荷传输性质好。     

Effect of Crystallization Kinetics on Microstructure and Charge Transport of Polythiophenes

We have examined the effects of crystallization kinetics of poly(3‐hexylthiophene) and poly[2,5‐bis(3‐hexadecylthiophen‐2‐yl)thieno(3,2‐b)thiophene] on microstructure and charge transport. Rapid crystallization increases the density of tie molecules in polythiophenes. As a consequence, ordered regions are better connected resulting in higher charge carrier mobilities. Our results suggest that controlling the crystallization kinetics might be an important factor for maximizing the charge mobility in semicrystalline polythiophene thin films.     

CdS敏化对TiO2纳米薄膜电极光生电荷转移特性的影响

1991年Gratzel等[1]以敏化的TiO2纳米薄膜电极组成的液体结光电化学太阳能电池(PEC),其光电转换效率(IPCE)达到10%. 最近,选用固态电解质使这种PEC的IPCE达到33%[2].于是用有机染料[3,4]及窄带隙半导体纳米微粒[5]敏化的电极受到了广泛关注.     

The Influence of Charge Transport and Recombination on the Performance of Dye‐Sensitized Solar Cells

Electrochemical impedance spectroscopy (EIS) and transient voltage decay measurements are applied to compare the performance of dye sensitized solar cells (DSCs) using organic electrolytes, ionic liquids and organic‐hole conductors as hole transport materials (HTM). Nano‐crystalline titania films sensitized by the same heteroleptic ruthenium complex NaRu(4‐carboxylic acid‐4′‐carboxylate) (4,4′‐dinonyl‐2,2′‐bipyridyl)(NCS)₂ , coded Z‐907Na are employed as working electrodes. The influence of the nature of the HTM on the photovoltaic figures of merit, that is, the open circuit voltage, short circuit photocurrent and fill factor is evaluated. In order to derive the electron lifetime, as well as the electron diffusion coefficient and charge collection efficiency, EIS measurements are performed in the dark and under illumination corresponding to realistic photovoltaic operating conditions of these mesoscopic solar cells. A theoretical model is established to interpret the frequency response off the impedance under open circuit conditions, which is conceptually similar to photovoltage transient decay measurements. Important information on factors that govern the dynamics of electron transport within the nanocrystalline TiO₂ film and charge recombination across the dye sensitized heterojunction is obtained.     

Investigation of the Effect of Substituents on Electronic and Charge Transport Properties of Benzothiazole Derivatives

A series of new benzothiazole-derived donor–acceptor-based compounds (Comp1–4) were synthesized and characterized with the objective of tuning their multifunctional properties, i.e., charge transport, electronic, and optical. All the proposed structural formulations (Comp1–4) were commensurate using FTIR, ¹H NMR, ¹³C NMR, ESI-mass, UV–vis, and elemental analysis techniques. The effects of the electron-donating group (-CH₃) and electron-withdrawing group (-NO₂) on the optoelectronic and charge transfer properties were studied. The substituent effect on absorption was calculated at the TD-B3LYP/6-31+G** level in the gas and solvent phases. The effect of solvent polarity on the absorption spectra using various polar and nonpolar solvents, i.e., ethanol, acetone, DMF, and DMSO was investigated. Light was shed on the charge transport in benzothiazole compounds by calculating electron affinity, ionization potential, and reorganization energies. Furthermore, the synthesized compounds were used to prepare thin films on the FTO substrate to evaluate the charge carrier mobility and other related device parameters with the help of I-V characteristic measurements.     

碱熔-电感耦合等离子体原子发射光谱法（ICP-OES）测定高碳高硅钢中的硅含量

研究了过氧化钠碱熔-ICP-OES法测定高碳高硅钢样品中的硅含量分析方法。样品经过氧化钠熔融和盐酸浸取后,选择了合适的分析谱线,以信号的稳定性为原则,优化了仪器最佳测定参数,实现了电感耦合等离子体原子发射光谱法对高碳高硅钢中硅含量的测定。通过实验探讨了钠离子、钢中基体元素铁等对硅含量测定干扰情况,测定结果的相对标准偏差不大于2%(n=6)。     

Charge Carrier Transport Mechanism in Ta2O5, TaON,and Ta3N5 Studied by Applying Polaron Hopping and Bandlike Models

TaON and Ta₃N₅ are considered promising materials for photocatalytic and photoelectrochemical water splitting. In contrast, their counterpart Ta₂O₅ does not exhibit good photocatalytic performance. This may be explained with the different charge carrier transport mechanisms in these materials, which are not well understood yet. Herein, we investigate the charge transport properties in Ta₂O₅, TaON, and Ta₃N₅ by polaron hopping and bandlike models. First, the polaron binding energies were calculated to evaluate whether the small polaron occurs in these materials. Then we performed calculations to localize the excess carriers as small polarons using a hybrid density functional. We find that the small polaron hopping is the charge transfer mechanism in Ta₂O_5, whereas our calculations indicate that this mechanism may not occur in TaON and Ta₃N₅. We also investigated the bandlike model mechanism by calculating the charge carrier mobility of these materials using the effective mass approximation, but the calculated mobility is not consistent with experimental results. This study is a first step towards understanding charge transport in oxynitrides and nitrides and furthermore establishes a simple rule to determine whether a small polaron occurs in a material.     

Charge Fluctuations and Ethylene‐Group‐Ordering Transition in β′′‐(BEDT‐TTF)4[(H3O)Fe(C2O4)3]⋅Y Molecular Charge‐Transfer Salts

The polarized infrared reflectance and Raman spectra of the three quasi‐two‐dimensional β′′‐(BEDT‐TTF)₄[(H₃O)Fe(C₂O₄)₃]?Y bifunctional charge‐transfer salts, where BEDT‐TTF=bis(ethylenedithio)tetrathiafulvalene and Y=C₆H₅Br, (C₆H₅CN)_0.17(C₆H₅Br)_0.83, (C₆H₅CN)_0.4(C₆H₅F)_0.6, have been measured as a function of the temperature. Signatures of charge inhomogenity have been found in both Raman and infrared spectra of the β′′‐(BEDT‐TTF)₄[(H₃O)Fe(C₂O₄)₃]?Y superconductors. A 100 K transition to a mixed insulating/metallic state is clearly seen for the first time in the temperature dependence of the electronic spectra of superconducting β′′‐(BEDT‐TTF)₄[(H₃O)Fe(C₂O₄)₃]?C₆H₅Br. We suggest that this phase transition is due to subtle changes in the ethylene groups ordering, which are related to a structural phase transition in the anionic layer. The infrared and Raman spectra of quasi‐two‐dimensional metal α‐′pseudo‐κ′‐(BEDT‐TTF)₄[(H₃O)Fe(C₂O₄)₃]C₆H₄Br₂ are also investigated.     

Theoretical Study on the Charge Transport Properties of Coronene and Its Derivatives

Molecular structures, reorganization energies and charge transport matrix elements of coronene and its fluoro-, hydroxyl- and sulfhydryl-substituted derivatives have been studied at the B3LYP/6-31G＊＊ level. Based on the semi-classical model of electron transfer, charge transport rate constants of the title molecules have been calculated. The results indicate that the coronene molecule is helpful to the transport of negative charge, and the transport rate of positive charge is between those of hexaazatriphenylene and triphenylene.     

Capacitive and Charge Transfer Effects of Single-Walled Carbon Nanotubes in TiO2 Electrodes

The transfer of nanoscale properties from single-walled carbon nanotubes (SWCNTs) to macroscopic systems is a topic of intense research. In particular, inorganic composites of SWCNTs and metal oxide semiconductors are being investigated for applications in electronics, energy devices, photocatalysis, and electroanalysis. In this work, a commercial SWCNT material is separated into fractions containing different conformations. The liquid fractions show clear variations in their optical absorbance spectra, indicating differences in the metallic/semiconducting character and the diameter of the SWCNTs. Also, changes in the surface chemistry and the electrical resistance are evidenced in SWCNT solid films. The starting SWCNT sample and the fractions as well are used to prepare hybrid electrodes with titanium dioxide (SWCNT/TiO₂). Raman spectroscopy reflects the optoelectronic properties of SWCNTs in the SWCNT/TiO₂ electrodes, while the electrochemical behavior is studied by cyclic voltammetry. A selective development of charge transfer characteristics and double-layer behavior is achieved through the suitable choice of SWCNT fractions.     

Formation of the Charge-Localized Dimer Radical Cation of 2-Ethyl-9,10-dimethoxyanthracene in Solution Phase

Although dimer radical ions of aromatic molecules in the liquid-solution phase have been intensely studied, the understanding of charge-localized dimers, in which the extra charge is localized in a single monomer unit instead of being shared between two monomer units, is still elusive. In this study, the formation of a charge-localized dimer radical cation of 2-ethyl-9,10-dimethoxyanthracene (DMA), (DMA)₂^.+ is investigated by transient absorption (TA) and time-resolved resonance Raman (TR³) spectroscopic methods combined with a pulse radiolysis technique. Visible- and near-IR TA signals in highly concentrated DMA solutions supported the formation of non-covalent (DMA)₂^.+ by association of DMA and DMA^.+. TR³ spectra obtained from 30 ns to 300 μs time delays showed that the major bands are quite similar to those of DMA except for small transient bands, even at 30 ns time delay, suggesting that the positive charge of non-covalent (DMA)₂^.+ is localized in a single monomer unit. From DFT calculations for (DMA)₂^.+, our TR³ spectra showed the best agreement with the calculated Raman spectrum of charge-localized edge-to-face T-shaped (DMA)₂^.+, termed DT^.+, although the charge-delocalized asymmetric π-stacked face-to-face (DMA)₂^.+, termed DF3^.+, is the most stable structure of (DMA)₂^.+ according to the energetics from DFT calculations. The calculated potential energy curves for the association between DMA^.+ and DMA showed that DT^.+ is likely to be efficiently formed and contribute significantly to the TR³ spectra as a result of the permanent charge-induced Coulombic interactions and a dynamic equilibrium between charge localized and delocalized structures.     

Effect on Charge Transfer and Charge Recombination by Insertion of a Naphthalene‐Based Bridge in Molecular Dyads Based on Borondipyrromethene (Bodipy)

The photophysical properties of two related dyads based on a N,N‐dimethylaniline donor coupled to a fully‐alkylated boron dipyrromethene (Bodipy) acceptor are described. In one dyad, BD1 , the donor unit is attached directly to the Bodipy group, whereas in the second dyad, BD2 , a naphthalene spacer separates the two units. Cyclic voltammograms recorded for the two dyads in deoxygenated MeCN containing a background electrolyte are consistent with the reversible one‐electron oxidation of the N,N‐dimethylaniline group and the reversible one‐electron reduction of the Bodipy nucleus. There is a reasonable driving force (ΔG_CT) for photoinduced charge transfer from the N,N‐dimethylaniline to the Bodipy segment in MeCN. The charge‐transfer state is formed for BD1 extremely fast (1.5 ps), but decays over 140 ps to partially restore the ground state. On the other hand, the charge‐transfer state for BD2 is formed more slowly, but it decays extremely rapidly. Charge recombination for both dyads leads to a partial triplet formation on the Bodipy group. The naphthalene spacer group is extremely efficient at promoting back electron transfer.     

Hall-effect Measurements and Transport Properties of Heterostructures in the Model System NiTe2-Sn12Sb2Te15

In composite materials of NaCl-type Sn₁₂Sb₂Te₁₅ with x equivalents of CdI₂-type NiTe₂ (x = 0.2; 1; 2), both phases are stable from room temperature up to 500 °C without a significant extent of mutual doping. The thermoelectric properties of this model system, complemented by Hall measurements, show clear trends with increasing x. Both electrical and thermal conductivities increase significantly whilst Seebeck coefficients decrease due to an increase in charge carrier concentrations. The overall Figure of merit zT is slightly impaired upon heterostructuring with NiTe₂. However, the good reproducibility and cyclability of the measurements renders these composites an intriguing model system to qualitatively examine the applicability of a simple single parabolic band (SPB) model based on Hall-effect data to rather metallic heterostructures. This model is best applicable to composites with lower fractions of NiTe₂ and gives the direction for tuning the charge carrier concentrations toward the optimum upon heterostructuring. These findings are in accordance with B-factor analysis and classical effective medium theory for spheroidal precipitates.     

Electrochemical Characterization of a Pyrolytic Carbon Film Electrode and the Effect of Anodization

A pyrolytic carbon (PC) film electrode was fabricated by the chemical vapor deposition (CVD) method. This report deals with the preparation, characterization and electrochemical behavior of this carbon film. Cyclic voltammetry, linear sweep voltammetry, Raman spectroscopy and scanning electron microscopy were employed to characterize the electrode. Low background current and capacitance were observed and the rate of charge transfer for Fe(CN) redox couple was determined via cyclic voltammetry. Also the effect of the anodic activation on the electrochemical activity was evaluated and characterized with respect to the sequence of voltage applied to the electrode. The excellent electrochemical activity and low background current are the reasons why this electrode is attractive for electroanalysis measurements with lower detection limit.     

Effects of Spatial Constraints and Brønsted Acid Site Locations on para‐Terphenyl Ionization and Charge Transfer in Zeolites

The locations of Brønsted acid sites (BAS) in the channels of medium‐pore zeolites have a significant effect on the spontaneous ionization of para‐terphenyl (PP₃) insofar as spatial constraints determine the stability of transition states and charge‐transfer complexes relevant to charge separation. The ionization rates and ionization yield values demonstrate that a strong synergy exists between the H⁺ polarization energy and spatial constraints imposed by the channel topology. Spectroscopic and modeling results show that PP₃ incorporation, charge separation, charge transfer and charge recombination differ dramatically among zeolites with respect to channel structure (H‐FER, H‐MFI, H‐MOR) and BAS density in the channel. Compartmentalization of ejected electrons away from the initial site of ionization decreases dramatically the propensity for charge recombination. The main mode of PP₃^.+ decay is hole transfer to form AlO₄H^.+ ??? PP₃ charge‐transfer complexes characterized by intense absorption in the visible range. According to the nonadiabatic electron‐transfer theory, the small reorganization energy in constrained channels explains the slow hole‐transfer rate.     

A Study on the Effects of Carrier Gases on the Structure and Morphology of Carbon Nanotubes Prepared by Pyrolysis of Ferrocene and C2H2 Mixture

Carbon nanotubes （CNTs） were prepared using different carrier gases, with ferrocene as the catalyst precusor and acetylene as the carbon source. The effects of ammonia and nitrogen as carrier gases on the structure and morphology of CNTs were investigated. Transmission electron microscope （TEM）, high-resolution electron microscope （HRTEM）, scanning electron microscope （SEM） and X-ray diffraction （XRD） were employed to characterize the products and the catalyst. Experiment results show that the CNTs grown in N2 gas exhibited cylindrical and tubular structure, while a bamboo-like structure was observed for the CNTs grown in NH3 gas. Moreover, vertically aligned CNTs were obtained on an A12O3 disk when NH3 was used as the carrier gas. The carrier gas also exerted influence on the shape of the catalyst. Based on the theory of active centers of catalysis and combined with the particle shape of the catalyst, a growth model for the vertically aligned CNTs on the substrate is given.