The photophysical and electrochemical properties of a new series of Ru complexes adsorbed onto P25 TiO2 films and their performance in dye-sensitized solar cells (DSSCs) are reported, in order to examine the effects of their various structural differences. The dyes are all homoleptic tridentate Ru(II) complexes differing in the nature of the tridentate chromophore, being either terpyridine (tpy) or 2,6-dipyrazinylpyridine (dpp), in the nature of the anchoring group, either carboxylic acid or ester groups, and in the presence or absence of a phenylene spacer between the chromophore and the anchoring group. The dpp dyes performed poorest, largely due to too-low excited state energies, and phenylene spacers were found to be deleterious to loading levels, while ester anchoring groups led to lower loading levels even after heating to promote transesterification. Further, tert-butylpyridine in the electrolyte inhibited their performance. The best dye in the series was bis(4′-carboxy-2,2′:6′,2″-terpyridine)ruthenium(II) bis(hexafluorophosphate) (H2) for which a total solar energy conversion efficiency of 1.56% was achieved under the best-measured conditions.

In this paper, an inductively coupled plasma (ICP) enhanced magnetron sputtering (MS) method was utilized to deposit silver (Ag) nanoparticles embedded inside of simultaneously polymerized poly(ethylene oxide) (PEO) thin film. Ex situ transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS) have been employed to elucidate the Ag nanoparticle structure, shape, and growth process during ICP enhanced MS deposition. The results showed that, when capped by polymer PEO film, the Ag nanocrystals were shaped in multiple-twinned particles (MTP) and further transformed into decahedrons held five-twinning structure with distinct twinning boundaries. The formation of particle size of Ag nanocrystalline on Si (100) surfaces was found unambiguously dependent on the ICP power, and the estimated particle size of Ag nanoparticles was in the range of 5-10 nm. From the results, it was assumed that PEO coating was the reason for inducing the, formation of Ag NITP and nanodecahedron structures.

Network coordinate algorithm provides anefficient way to predict communication latency between hosts withlimited measurements. Hosts are embedded into a coordinate space andassigned a set of coordinates which reflect their positions in thegeometric space. The distance between the coordinates of two hostscan be a predictor of the actual communication latency between them.How to improve the prediction accuracy is a problem which challengesthe practical applications of network coordinate algorithm. In orderto improve the short distance prediction accuracy of traditionalnetwork coordinate algorithm such as Vivaldi, we propose a newhierarchical network coordinate algorithm based on communitystructure detection. The whole network is organized into N-levelhierarchies without any requirement of fixed nodes asinfrastructure. Each host is assigned multiple coordinatescorresponding to the N-level hierarchies so that different sets ofcoordinates satisfy different ranges of distance prediction.Simulation results show that the new hierarchical network coordinatealgorithm provides more accurate short distance predictions withoutdegrading the accuracy of long distance predictions. Internetapplications such as the nearest server selection will benefit fromthe more accurate prediction of short distance using this newhierarchical network coordinate algorithm.

TiO2 dye-sensitized solar cells were built using new polypyridine Ru(II) complexes as dyes, and the solar energy conversion efficiencies were measured. Here, we present results for two of our dyes, which carry ester and carboxyl anchoring groups as well as a phenylene spacer between the anchoring group and a terpyridine ligand Electrochemical, UV-visible, and FTIR measurements were employed to investigate the extent and nature of the surface binding. Dye- sensitized solar cell (DSSC) performance will be discussed with respect to the surface concentration of chemisorbed dyes, the electronic properties of the photoanodes and the electrochemical properties of adsorbed dyes.

A novel electrodeposited CdS nanoparticle-modified highly-ordered TiO2 nanotube-array photoelectrode and its application to photoelectrochemical cells is reported. Results show formation of a thin, nanoparticulate CdS layer, comprised of sphere-like 10–20nm diameter nanoparticles, on the anodic synthesized TiO2 nanotube-array (inner diameter of 70nm, wall thickness 25nm and ca. 400nm length) electrode. The resulting CdS–TiO2 photoelectrode has an as-fabricated bandgap of 2.53, and 2.41eV bandgap after sintering at 350°C in N2 ambient. Photoelectrochemical properties are described in detail.

Molecular modification of dye-sensitized, mesoporous TiO2 electrodes changes their electronic properties. We show that the open-circuit voltage (V(oc)) of dye-sensitized solar cells varies linearly with the dipole moment of coadsorbed phosphonic, benzoic, and dicarboxylic acid derivatives. A similar dependence is observed for the short-circuit current density (I(sc)). Photovoltage spectroscopy measurements show a shift of the signal onset as a function of dipole moment. We explain the dipole dependence of the V(oc) in terms of a TiO2 conduction band shift with respect to the redox potential of the electrolyte, which is partially followed by the energy level of the dye. The I(sc) shift is explained by a dipole-dependent driving force for the electron current and a dipole-dependent recombination current.

An in-depth study of n-type doping in a crystalline perylene diimide organic semiconductor (PPEEB) reveals that electrostatic attractions between the dopant electron and its conjugate dopant cation cause the free carrier density to be much lower than the doping density. Measurements of the dark currents as a function of field, doping density, electrode spacing, and temperature are reported along with preliminary Hall-effect measurements. The activation energy of the current, E(aJ), decreases with increasing field and with increasing dopant density, n(d). It is the measured change in E(aJ) with n(d) that accounts primarily for the variations between PPEEB films; the two adjustable parameters employed to fit the current-voltage data proved to be almost constants, independent of n(d) and temperature. The free electron density and the electron mobility are nonlinearly coupled through their shared dependences on both field and temperature. The data are fit to a modified Poole-Frenkel-like model that is shown to be valid for three important electronic processes in organic (excitonic) semiconductors: excitonic effects, doping, and transport. At room temperature, the electron mobility in PPEEB films is estimated to be 0.3 cm(2)/Vs; the fitted value of the mobility for an ideal PPEEB crystal is 3.4 +/- 2.7 cm(2)/Vs. The modified Poole-Frenkel factor that describes the field dependence of the current is 2 +/- 1 x 10(-4) eV (cm/V)(1/2). The analytical model is surprisingly accurate for a system that would require a coupled set of nonlinear tensor equations to describe it precisely. Being based on general electrostatic considerations, our model can form the requisite foundation for treatments of more complex systems. Some analogies to adventitiously doped materials such as pi-conjugated polymers are proposed.

Doping a perylene diimide organic semiconductor with a one-electron reduced perylene diimide containing a covalently bound counterion provides a well-characterized system for understanding doping in organic semiconductors. We obtain insight into the doping process by electron paramagnetic resonance (EPR) measurements of the dopant solutions, the dopant plus host solutions from which thin films are spin-coated, and the resulting solid films. After correction for some trace impurities in the solutions, the spin density incorporated into the solid films is linearly proportional to the added dopant density. Nevertheless, the film conductivity increases superlinearly with dopant concentration. Although neither pure dopant nor host aggregate in solution, they aggregate when combined. This is presumably a result of the delocalization of the dopant electron over a number of host molecules. Angle-dependent EPR measurements on thin films suggest that the g-tensor symmetry axis is close to the pi-pi stacking axis, consistent with relatively delocalized electrons in this crystal direction. Nevertheless, most electrons are not entirely free, but still bound in the vicinity of the dopant cation by Coulomb attraction. At low concentration, dopants appear to segregate primarily to crystallite grain boundaries, while at higher concentration they are incorporated into the bulk of the crystallites. About half of the spins are paired in the solid at room temperature, and more at lower temperature.

We show that the same factors that cause exciton formation in organic (excitonic) semiconductors, the low dielectric constant and the localized wave functions of the charge carriers, also control their doping processes. We compare doping in organic and inorganic semiconductors and show that the superlinear increase in conductivity with doping density should be a universal characteristic of excitonic semiconductors. The binding energy of the dopant electron to its conjugate cation in highly ordered perylene diimide films controls the free carrier density. The binding energy decreases with increasing dopant concentration because the neutral dopants increase the polarizability of the film.

A new method for the immobilization of enzyme in microfluidic channel on the integrated chip for proteomic analysis was reported. The PDMS film immersing in the acrylic acid solution was irradiated under UV lamp to produce active free radicals and then immersed alternatively into the PDDA solution and trypsin solution for self-assemble. The monomer solution of the produced chip was characterized with the reflectance IR technique, contact angle determination and SEM observations. A standard protein BSA was selected to test the performance of the product. It was verified that CE and MALDI-TOF/TOF-MS detection can be on-line carried out in a single, successive running.

A heuristic approach to describing excitonic processes, doping, and transport is developed for all organic semiconductors but with an emphasis on crystalline molecular semiconductors. A simple equation is proposed that semiquantitatively defines "excitonic" semiconductors, XSCs, a classification that includes most organic semiconductors and some inorganic materials. The same electrostatic and spatial factors that cause exciton formation upon light absorption in XSCs, as opposed to the formation of free electron-hole pairs, also control the doping process and carrier transport. Doping studies of XSCs are reviewed with an emphasis on the more recent, quantitative investigations. One conclusion is that most added charge carriers in doped XSCs are not free but rather are electrostatically bound to their conjugate dopant counterions. A superlinear increase in conductivity with doping density is thus expected to be, and apparently is, a universal attribute of XSCs. The interactions between the crystal structure, its dielectric properties, and the doping efficiency are probed via two substitutional dopant molecules in two different crystalline host lattices. An analogy is drawn between purposely doped XSCs and adventitiously doped XSCs such as pi-conjugated polymers: in both cases the number of free carriers is a small, and field-dependent, fraction of the total carrier density. The Poole-Frenkel mechanism accounts naturally for the expected interactions between carriers bound in a Coulomb well and an applied electric field. Together with a field-dependent mobility, this mechanism is expected to semiquantitatively describe the conductivity in doped XSCs.

Hexagonal CdSe and hexagonal CdS nanoparticles have been prepared using Cd(Ac)2 and less hazardous elemental Se or S as precursors, respectively, with the aid of ultrasound irradiation under an atmosphere of H2/Ar (5/95, V/V). The products consist of 7–10nm nanocrystallites which aggregated in the form of polydispersive nanoclusters with sizes in the range 30–40nm in the case of CdSe, and near monodispersive nanoclusters with a mean size of about 40nm in the case of CdS. X-ray diffraction, high-resolution TEM and SAED patterns (selected area electron diffraction patterns) show that the as-prepared particles are well crystallized. X-ray photoelectron spectroscopy (XPS) measurements further confirm the formation of CdSe and CdS. Diffuse reflection spectra indicate that both the CdSe and the CdS nanocryslallites are direct band-gap semiconductors with band-gap values of about 1.83 and 2.62eV, respectively. Control experiments demonstrate that the hydrogen is the reducing agent, and the extreme high temperature induced by the collapse of the bubble accelerates the reduction of elemental Se or S by hydrogen. An ultrasound assisted in situ reduction/combination mechanism is proposed.

Nanoporous TiO2 electrodes coated with a thin layer of various wide band gap materials were tested in dye sensitized solar cells (DSSCs). Using Nb2O5, ZnO, SrTiO3, ZrO2, Al2O3 and SnO2 as shell materials, we find that the mechanism by which the shell affects the electrode properties depends on the coating material. In the exceptional case of Nb2O5, the coating forms a surface energy barrier, which slows the recombination reactions. The other shell materials each form a surface dipole layer that shifts the conduction band potential of the core TiO2. The shift direction and magnitude depend on the dipole parameters which are induced by the properties of the two materials at the core–shell interface. The results show that either the shell acidity or the electron affinity of the shell are the shift controlling parameters, although the former seems more likely. This new tool for the modification of the electronic properties of the nanoporous electrodes allows for optimization towards a wide range of applications.

Brief UV illumination of dye-sensitized solar cells can result in a remarkable increase in their photoconversion efficiency (Ferrere, S; Greg, B. A. J. Phys. Chem. B 2001. 105, 7602). Further investigation of this phenomenon reveals that a major effect of UV illumination is to reversibly create a high concentration of photoactive surface states continuously distributed below the conduction bandedge in the nanoporous TiO2 films. The ability to create, and then eliminate, surface states allows, for the first time, a clear assessment of the influence of these states on the dye-sensitization process. Positive conduction bandedge (mobility edge) shifts apparently also result from UV illumination, and the difficulties in quantifying such shifts in functioning cells are discussed. We conclude that the major cause of the increased efficiency is the photoproduction of surface states that may improve photoinjection and carrier transport while possibly slowing the recombination rate. The creation of these surface states is strongly inhibited by the presence in the electrolyte solution of the Li+ ion, which is known to specifically adsorb to TiO2 surfaces. We present an in-depth characterization of the UV-induced changes in the dye-sensitized solar cell through comparisons of otherwise identical cells in LiI-containing solution and in tetrabutylammonium iodide-containing solution, before and after UV illumination. The "UV effect" is also observed in hydroquinone/benzoquinone solutions thus, it is not dependent on the presence of the I-/I-2, redox couple. Although surface states are usually deleterious for planar semiconductor electrodes, we show that a high density of surface states may be beneficial for the photoconversion process in nanoporous solar cells.

This paper describes the synthesis and characterization of a core-shell nanoporous electrode consisting of an inner SnO2 matrix and a thin shell of TiO2. The coating is characterized as a very thin rutile TiO2 layer whose conduction band level is located between the levels of bare SnO2 and TiO2. The TiO2 shell acts as an energy barrier at the electrode-electrolyte interface, thus slowing the interaction between the electrons in the electrode and the electrolyte ions. When applied in a dye-sensitized solar cell, the coated electrode is significantly superior to a bare SnO2 electrode. The increase of all cell parameters improves the conversion efficiency by a factor of 2.2. The combination of improved electron collection efficiency with respect to bare SnO2 and a more positive conduction band with respect to bare TiO2 should make dyes having a relatively positive excited-state potential usable in dye-sensitized systems.

利用电化学、表面光电压、荧光光谱、FTIR和X射线衍射, 研究了5-（-4-十二烷氧基苯乙烯基）-（1H,3H）-2,4,6-嘧啶三酮（PB12）与4-氨基-2,6-二-十二烷基胺基-1,3,5-三嗪（M12）之间的自组装过程. 结果发现, 在室温等摩尔PB12与M12在氯仿中混合后不仅通过三重互补氢键形成氢键超分子, 而且氢键超分子之间通过π-π相互作用进行进一步组装. 在氢键超分子之间的组装过程中,π-π相互作用是通过M12的HOMO与PB12的LUMO之间的HOMO-LUMO非定域化作用实现的. 氢键超分子之间PB12与M12交替排列, 形成层间距为0.41 nm的纳米管.

ADVERTISEMENT RETURN TO ISSUEPREVAddition & Corre...Addition & CorrectionORIGINAL ARTICLEThis notice is a correctionControlling the Particle Size of Calcined SnO2 NanocrystalsGuangsheng Pang, Siguang Chen, Yuri Koltypin, Arie Zaban, Shouhua Feng, and Aharon GedankenCite this: Nano Letters 2002, 2, 1, 79Publication Date (Web):December 15, 2001Publication History Published online15 December 2001Published inissue 1 January 2002https://doi.org/10.1021/nl0100926Copyright © 2002 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views474Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (6 KB) Get e-AlertsSUBJECTS:Mixtures,Nanocrystals,Particle size,Thermogravimetric analysis Get e-Alerts

A novel method for shortening the synthesis time of mesoporous TiO2 to 6 h is reported. Low-angle XRD and TEM showed that mesoporous TiO2 with short-range ordered structures was synthesized when octadecylamine was used as a structure-directing agent and when Ti(OPri)(4) was used as a precursor. The highest surface area (853 m(2) g(-1)) was obtained after extraction with a dilute solution of nitric acid. The material maintained a high surface area (467 m(2) g(-1)) after calcination at 350 degreesC, but the short-range ordered structures collapsed. XPS showed the interaction between TiO2 and octadecylamine, while DSC, TGA, and FT-IR spectra showed the removal of octadecylamine by extraction and calcination. A mechanism for the fast formation of mesoporous TiO2 is proposed. It is attributed to the formation of mesoporous material at high temperatures formed in the interface between the gas and bulk solutions resulting from ultrasound irradiation. Electrodes made from the mesoporous TiO2 were tested in a dye-sensitized solar cell. The short-circuit photocurrent, open-circuit photovoltage and fill factor increased with an increase in the sintering temperature, having a performance threshold at 450 degreesC, showing that the more ordered structures are required for high solar cell conversion efficiencies.

Self-assembly of a pair of complementary molecular components, 5-(4-dodecyloxyben-zylidene)-(1H,3H)-2, 4,6-pyrimidinetrione (PB 12 )and 4-amino-2,6-didodecylamino-1, 3, 5-triazine (M 12 ) was studied by cyclic voltammogram, surface photovoltage spectroscopy, fluorescence spectroscopy, FTIR and X-ray diffraction. It is found that after mixing equimolar amount of PB 12 and M 12 at room temperature, not only triply complementary hydrogen bonds are formed between PB 12 and M 12 but also further self-assembly of the supermolecules based on network of hydrogen bonds occurs via π-π interactions. During the self-assembly of the supermolecules, π -π interactions are induced by delocalized interactions between the HOMO of M 12 and the LUMO of PB 12 , resulting in the formation of a supramolecular nanotube with a layered structure bearing a d value of 0.41 nm and PB 12 and M 12 are arranged alternatively between adjacent supermolecules.

A novel method for large-scale preparation of yttria-stabilized zirconia (YSZ) nanocrystals is presented. The hydrous YSZ colloidal nanoparticles are self-assembled on the surface of SrCO3 nanoparticles by a sonochemical method. After calcination, fully crystalline monodispersed YSZ nanoparticles are obtained, and the SrCO3 is washed out by 10% HNO3 solution. The agglomeration of YSZ particles is inhibited as the crystallization occurs on the surface and interface of SrCO3 nanoparticles. The nanocrystals are monodispersed with an average particle size of 4.7 nm and a high surface area of 165 m(2)/g. The quantum confinement effect is observed: the band gap increases from 4.13 eV for the agglomerated sample to 5.44 eV for the monodispersed YSZ nanocrystals.