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In heterojunction photovoltaic devices of ITO/TiO2/poly(3-alkylthiophene)/Au, the photocurrent was characterized at different temperatures for different alkyl chain lengths and regioregularities: regiorandom, regioregular poly(3-hexylthiophene), and regioregular poly(3-dodecylthiophene). The regioregularity and alkyl chain length affected the photovoltaic characteristics due to differences in hole-carrier transportation. The drift charge mobilities of these devices were analyzed by the space-charge-limited current theory using the relation between the dark current and the bias voltage. The photocurrent in the devices based on poly(3-alkylthiophene)s decreased rapidly below the temperature at which the drift charge mobility was 10−5 cm2/V·s.

New 4- and 4,4‘-oligophenylenevinylene-functionalized Ru(II)-bipyridine sensitizers were synthesized and used in dye-sensitized TiO2 solar cells (DSSCs) to study their sensitizing properties relative to those of the usual N3 dye. Among those studied, two sensitizers, denoted as D5 and D6, have rendered considerably higher photocurrents and efficiencies for their cells, compared to those of a cell using the conventional N3 dye. The short-circuit photocurrent densities for N3, D5, and D6 are 9.8, 10.8, and 11.7 mA/cm2, and the efficiencies are 4.1, 4.6, and 4.8%, respectively. The enhanced photocurrents are correlated with the increased molar absorption coefficients of the D5 and D6 dyes over the entire visible spectra region, relative to those of the N3 dye. Corresponding enhancements in IPCE values are attributed to the oligophenylenevinylene groups of D5 and D6 that consist of conjugated double bonds. Analysis of the absorption spectra of the sensitizer-coated TiO2 films and the desorbed dyes in an aqueo...

Plasma source ion implantation (PSII) technique was used for the ion implantation and deposition of copper film on the polyimide. In PSII–EIAMAD (energetic ion assisted mixing and deposition) process, a polyimide film was immersed in a plasma, and high negative voltage pulses were applied to accelerate ions into the substrate resulting in the mixing effect of copper atoms with polyimide layers. This method was used to improve the adhesion between Cu layer and polyimide film depending on ion species, ion energy, and treatment time. The adhesion strength was determined by the 90° peel test. The deposited-copper surface was investigated by SEM and AFM, and the interface between Cu film and polyimide was characterized by AES. Enhancement of adhesion for PSII–EIAMAD treated copper film was observed and its interface was very gradient in AES depth profile. The Cu-deposited layers are adherent and reasonably stable after heat treatment of 24 h at 100 °C.

We report successful development of both discrete ultraviolet (UV) photodiodes and UV imagers consisting of 8×8 backside-illuminated AlGaN p-i-n photodiode arrays. The discreteAlGaN p-i-n photodiodes showed a responsivity of 0.1A∕W, a cutoff wavelength of 350nm, an external quantum efficiency of 35%, and a response time of 4.1ns. Then, 8×8 AlGaN p-i-n photodiode arrays were fabricated, followed by hybridizations with readout integrated circuits manufactured using a 0.5μm 2poly-3metal N-well complementary metal-oxide semiconductor process by gold stud bumping. The 8×8 focal plane array UV imagers operated successfully by sensing radiation in the 300–350nm spectral bands.

Anatase TiO2 nanorods and nanotubes were produced from hydrolyzed TiCl4 using an anodic alumina membrane (AAM) as template. SEM analysis indicated that the form of nanostructures depends on the pore size of the membrane, and their diameters are almost same regardless of nominal pore sizes. When the nanorods were incorporated at about 10 wt% level in a P25 TiO2 film electrode of a dye-sensitized solar cell, its solar energy conversion efficiency was enhanced by about 42% as a result of a higher short-circuit photocurrent, compared with that of a cell fabricated with bare P25. The nanostructures were characterized by SEM, energy dispersive X-ray spectroscopy and Raman spectroscopy. Reasons for the invariance of sizes of nanostructures, and for the enhancement of the solar energy conversion efficiency are discussed. These explanations are supported by SEM, dye-adsorption measurements and light scattering findings.

A new type of hybrid gel electrolyte matrix based on tetraethyl orthosilicate (TEOS) and poly(ethylene glycol) (Mw 200, PEG200) was developed for dye-sensitized solar cells (DSSCs). The quasi-solid-state DSSC containing the hybrid gel electrolyte rendered an open-circuit voltage of 0.74 V, a short-circuit photocurrent density of 9.2 mA cm−2 and a fill factor of 0.61 at 100 mW cm−2, and consequently an overall solar energy conversion efficiency of 4.1%. TiO2 films and gels were characterized by FE-SEM and FT-IR, and the assembled DSSCs by photocurrent density–voltage and incident photon-to-current conversion efficiency measurements.

Three saponins were extracted and isolated from starfish by reversed-phase high performance liquid chromatography (HPLC), and analyzed by fast atom bombardment mass spectrometry (FAB-MS). Their molecular weight information could be obtained by the presence of abundant [M+Na]+ ions and weak [M+H]+ ions in FAB-MS spectra. Moreover, high resolution mass measurements of their [M+Na]+ ions were performed at the resolution of 10000 to elucidate the element composition of extracted saponins. The collision-induced dissociation (CID) of sodium-adducted molecules [M+Na]+ yielded diverse product ions via dissociated processes. In the collision-induced dissociation (CID)-MS/MS analysis of [M+Na]+ ion, the sulfate-containing saponins produced characteristic ions such as SO4Na+, [NaHSO4+Na]+, [M+Na-sugar]+ and [M+Na-2sugar]+ ions, whereas the sulfate-free compound showed characteristic ions produced by cleavage of sugar moiety and side chain of aglycone. The fragmentation patterns could provide information on the linkage position of sugar groups in aglycone and sulfate groups.

An efficient flexible dye-sensitized solar cells (DSSCs) using stainless steel supporting substrate for fabricating nanocrystalline TiO2 film electrodes were developed, intending to improve the photoelectrochemical properties of plastic substrate-based DSSCs. The most important advantage of a stainless steel-based TiO2 film electrode over a plastic-based electrode lies in its high-temperature sinterability. Optimal photovoltaic properties were obtained with a cell where the TiO2 film was coated on both ITO- and SiOx-sputtered stainless steel (denoted as TiO2/ITO/SiOx/StSt). The photocurrent of the flexible cells with a TiO2/ITO/SiOx/StSt electrode increased significantly, leading to a much higher overall solar conversion efficiency η of 4.2% at 100 mW/cm2, based on short-circuit photocurrent density, open-circuit voltage and fill factor of 11.2 mA/cm2, 0.61 and 0.61 V, respectively, than those reported for cells with plastic substrates.

Three cyclitol derivatives were isolated from the marine sponge Sarcotragus sp. by reversed-phase high-performance liquid chromatography and analyzed by fast-atom bombardment mass spectrometry (FAB-MS). Their structural elucidation was carried out with FAB tandem mass spectrometry (FAB-MS/MS). FAB-MS spectra produced a significant abundance of the sodium adducts [M+Na]+ and [M+2Na-H]+ from a mixture of m-NBA and NaI. In addition, trifluoroacetylation of the cyclitol derivatives was used for confirmation of the presence of the cyclitol ring. High abundance [M-5H+5CF3CO+Na]+ ions were observed in the FAB-MS spectra of the trifluoroacetyl-cyclitol derivatives. Collision-induced dissociation (CID) of the [M+Na]+ ions produced diverse product ions via a series of dissociative processes. Charge-remote fragmentation (CRF) patterns of [M+Na]+ ions were very useful for the identification of product ions which are characteristic for the cyclitol ring and long hydrocarbon chains substituted at the glycerol backbone. Moreover, the CID-MS/MS spectra of the [M+Na]+ ions yielded characteristic product ions at m/z 53, 83, 113, 155 and 171 for the cyclitol moiety, and at m/z 213, 229 and 245 for the glycerol backbone attached to the cyclitol ring.

We report a record high continuous wave (CW) output power of 250 mW for the 780 nm band AlGaAs laser. The selectively buried ridge (SBR) structure was used and each layer of the laser was designed to have the lowest defect density by using the deep level transient spectroscopy (DLTS) analyses. The laser operated at a peak wavelength of 783 nm with a threshold current of 38 mA. The stable fundamental transverse mode was observed at 100 mW, 70 °C for more than 3000 h. The far-field aspect ratio, a ratio of far-field vertical angle over far-field parallel angle to the junction plane, was measured to be 1.8, which is small enough for the high density CD-R system.

A new strategy involving the introduction of the common cationic surfactant cetyltrimethylammonium bromide (CTAB) for the cathodic deposition of titanium dioxide from hydrolyzed TiCl4 and TiCl3 solutions by cyclic voltammetry has been developed. Crack-free and non-transparent anatase TiO2 films were obtained for the first time and characterized with the aid of Raman spectra and SEM. Selection of TiCl4 as the precursor for the electrodeposition is quite a novel approach for the research in the area of dye-sensitized solar cells (DSSCs). It is noted that NO3− ion is essential for such a deposition. Under the same conditions, a thicker TiO2 film was obtained by adding CTAB into KNO3 electrolyte, compared with the case without it. The CTAB-promoted film led to an increased energy conversion efficiency of the corresponding DSSC. Mechanisms are proposed for the electrochemical deposition and the beneficial role of CTAB.

An analytical method has been developed for measuring 24 chlorinated pesticides in fish tissue samples. Extraction of chlorinated pesticides was carried out by ultrasonication using an acetone-n-hexane (5:2, v/v) mixture. Most of the lipids in the extract were eliminated by freezing-lipid filtration, prior to solid-phase extraction (SPE) cleanup. During freezing-lipid filtration, about 90% of the lipids extracted from the fish samples were easily removed without any significant losses of chlorinated pesticides. For purification, SPE using Florisil was shown to be more effective than silica. Quantification was performed using gas chromatography-mass spectrometry in the selected ion monitoring mode. Spiking experiments were carried out to determine the recovery, precision, and limits of detection (LODs) of the method. The overall recovery was above 80% in the spiked fish tissue sample at 100 ng/g level. The detection limits for chlorinated pesticides were ranged from 0.5 to 5 ppb, except for endosulfan I and II which was 20 ppb. The newly developed method is demonstrated to give efficient recoveries and LODs for detecting chlorinated pesticides spiked into fish tissue with high lipid content.

The effects of using indium zinc oxide (IZO) as a conducting substrate in dye-sensitized TiO2 solar cells (DSC) on their photocurrent−voltage characteristics are studied. We have found that both short-circuit photocurrent (Jsc) and open-circuit voltage (Voc) of IZO-based cells are substantially improved by about 40% and 10%, respectively, when compared with those of cells based on fluoride-doped tin oxide (FTO). The Jsc increase is correlated to the improved contact between IZO and TiO2 and enriched conduction band electrons in the TiO2-on-IZO electrode, due to the blocking of surface states by the evaporated metallic components of the substrate. The combined effects of the negative shift of flat band potential and the reduction in recombination explain the Voc increase. Our experimental finding suggests that IZO-coated substrate makes more efficient DSC than a FTO-coated one.

Composite anatase TiO2 nanostructure, consisting of both tubules and rods, has been synthesized by precipitation from hydrolyzed TiCl4 solution using an anodic alumina membrane (AAM). SEM analyses show that the structure consists of rods of 200−250-nm diameter and tubules of about 500-nm diameter. Each tubule may be visualized as a single sheet of 60−80 nm thickness rolled into a cylinder of diameter about 2.5 times the pore size of the AAM. The thus-prepared TiO2 nanomaterial is characterized and a possible mechanism of its formation is discussed.

Single-wall carbon nanotubes (SWCN) were integrated in TiO 2 film and the beneficial influence on the dye-sensitized solar cells in terms of improved photocurrent was studied in the light of static J-V characteristics obtained both under illumination and in the dark, photocurrent transients, IPCE spectra and impedance spectra. Compared with a solar cell without SWCN, it is established that the photocurrent density of the modified cell increases at all applied potentials. The enhanced photocurrent density is correlated with the augmented concentration of electrons in the conduction band of TiO 2 and with increased electrical conductivity. Explanations are additionally corroborated with the help of SEM, Raman spectra and dye-desorption measurements.

The promotional effect of CO 2 in the liquid phase oxidation of ethylbenzene to acetophenone (AP) with the Co/Mn/Br (MC-type) catalyst system has been investigated. Significant enhancement of catalytic activity was found in the presence of CO 2 and thus selectivity toward acetophenone was increased as well. UV-visible investigations of the MC-type catalyst system in the oxidation of ethylbenzene reveal that Mn(III) is more easily formed in the presence of CO 2 ; such formation would be associated with the CO 2 promotional effect.

The surface resistivity of several polymers such as poly(styrene/butadiene copolymer), modified poly(phenyleneoxide), poly(ethylene terephthalate), and polyimide was improved by the argon gas plasma source ion implantation (Ar-PSII) technique equipped with a mesh-type conducting grid. With the grid, the surface resistivities of the modified polymers decreased up to 11 orders of magnitudes at a high ion dose, and remained nearly at the same values after 3 months. The PSII treated polymer sample with the grid provided more uniformly modified surface and lower surface resistivity than that treated without the grid. The extent of the decrease in surface resistivity depended on the polymer structures and physical properties. However, the surface resistivity was independent of the sample thickness, the grid size, and the grid height. Surface analyses using scanning electron microscopy, time-of-flight secondary ion mass spectrometry, and Raman spectroscopy provided the useful information on modified surfaces.

Time-dependent change in the concentrations of some aromatic hydrocarbons with TiO2-based catalysts under irradiation was monitored by absorption spectroscopy. Titanium silicalite-2 with higher crystallinity (TS-2h) showed greater photodegradation efficiency than titanium silicalite-2 (TS-2). The greater efficiency was attributed to the increased adsorptivity based on the larger distribution coefficient arising from the more hydrophobic nature in the TS-2h cavity than in TS-2. The distribution coefficient correlates well with the slope of the Langmuir–Hinshelwood equation, and can be a useful index for the relative photodegradation efficiency of the aromatic hydrocarbon.

The effect of annealing temperature on the properties of TiO2 films prepared from hydrolyzed TiCl4 solutions was characterized by X-ray diffraction (XRD) and photoelectrochemical measurements. It is found that the amount of rutile in the TiO2 films increases from room temperature to 250 °C. Above 250 °C, the amount of crystalline rutile material did not change. Analysis of XRD data suggests that a noncrystalline phase is converted to the rutile phase of TiO2 by heat treatment of the films. Furthermore, the analysis indicates that the size of the rutile crystallites increases with temperature from about 100 to 400 °C. The photocurrent and conversion efficiency of the cells improved substantially with annealing temperature. The higher photocurrent appears to correlate with the increased crystallinity of the film. The TiO2 material displayed a photochromic effect.

The mechanism of photocurrent decay with time of illumination of PbS-coated TiO2 (PbS/TiO2) photoelectrochemical cells in S2− and SO32− solution was investigated. The photocurrent decay at short circuit can primarily be attributed to the formation of PbSO4 on the surface of PbS, followed by the dissolution of PbSO4 into the aqueous solution. In the presence of pyridine or ethanol in the solution, the Jsc decay with time of illumination is reduced due to the suppression of the PbSO4 formation.

Poly(methylmethacrylate) (PMMA), poly(2-hydroxyethyl methacrylate (PHEMA), and poly(2-hydroxypropyl methacrylate) (PHPMA) were modified to improve the wettability by two techniques: plasma and plasma source ion implantation. The modified surfaces were characterized to investigate the dependence of the modification and hydrophobic recovery on the polymer structure. The differences obtained under optimal experiment conditions among the polymers were interpreted in terms of their polymer structures including the glass transition temperature. The surface free energy, calculated from the contact angle measurements, revealed that its polar component was a dominant factor in improving the wettability. The PSII treatment created more functional groups on the surface and extensively modified the polymer layer than the plasma treatment.

Influence of an electrodeposited overlayer and a spin-coated underlayer of TiO 2 electrode on the cell performance was studied. The effect of annealing TiO 2 electrode in O 2 atmosphere was also investigated. XRD analysis made on TiO 2 by the sol-gel method showed a pure anatase phase. Electrodeposited TiO 2 film showed two times larger surface area and O 2 annealed TiO 2 showed three times larger surface area than untreated TiO 2 , Electrodeposition of TiO 2 resulted in sub-particles on base TiO 2 and increased the surface area and the short-circuit current (J sc ) For an underlayer, TiCl 4 treatment caused no noticeable changes in current-voltage characteristics. Annealing in O 2 atmosphere did not cause any apparent changes in bonding characteristics judging from XPS measurement. A conversion efficiency up to 5.8% was obtained.

The effect of Cl− ions on the photodecomposition of 4-chlorophenol (4-CP) was investigated with and without titanium silicalite-2 (TS-2) catalyst as a function of pH by absorption spectroscopy. In the absence of TS-2, chloride ions enhance the photodegradation of 4-CP in acidic and neutral solutions under UV illumination, with a faster photodegradation in acidic solutions. In the presence of TS-2, however, chloride ions enhance the photodegradation only in acidic solutions. The results reveal that chloride ions should be in close proximity to 4-CP in order to enhance photodegradation. The enhancement can be attributed to the reaction of chloride ions with chloride radicals that are abstracted from 4-CP either by absorption of the light or by reaction with hydroxyl radicals.

The photodegradation of pentachlorophenol in water was examined with a high-pressure mercury lamp. A number of photodegradation products of pentachlorophenol, such as less-chlorinated phenols through reductive dechlorination, and catechol and trihydroxylated products via the addition of hydroxyl radicals, were observed as major products. Moreover, polychlorinated biphenylethers, hydroxylated polychlorobiphenylethers and polychlorinated dibenzo-p-dioxins as minor products were also formed by dimerization process during the photolysis of pentachlorophenol. These compounds were identified by gas chromatography-mass spectrometry. The degradation rate of PCP in water was measured against the UV-irradiation time. After the irradiation for 15 min, 75% of PCP was converted into a number of products through reductive dechlorination and oxidation. On the basis of the identified products, the photodegradation pathways of PCP under UV irradiation were proposed.

The photocatalyzed degradation of 4-chlorophenol (4-CP) in water is comparatively examined with TiO 2 powder, TiO 2 /CdS powder, TiO 2 thin film electrodes and TiO 2 /CdS thin film electrodes in the initial stages of the reaction. The apparent intermediates of 4-CP photodegradation with TiO 2 and TiO 2 /CdS powders in suspensions are found to be 1,4-benzoquinone (BQ) and hydroquinone (HQ), with HQ rapidly converting into BQ with TiO 2 and TiO 2 /CdS electrodes at an applied anodic potential of 0.6 V vs Ag/AgCl. The apparent reaction rate constants using the Langmuir–Hinshelwood equation with TiO 2 /CdS powder and the TiO 2 /CdS electrode are obtained to be about 90% and 33% larger than with TiO 2 powder and the TiO 2 electrode, respectively, indicating that the TiO 2 /CdS catalysts have more photocatalytic activities than the TiO 2 catalysts in the initial stages. The adsorption coefficient ( K ) of 4-CP on TiO 2 /CdS powder is one and a half times larger than that on TiO 2 powder. With the electrode catalysts at 0.6 V, the value of K increases several times with respect to the corresponding powder catalysts and shows essentially no difference between the TiO 2 /CdS electrode and the TiO 2 electrode. Thus, the value of K may strongly depend on the electrostatic interaction between 4-CP and the electrode surface, but not very much on the type of electrode surface.

Visible electroluminescence (EL) from cathodically biased n‐Si in an electrolyte solution containing has been studied. EL from the porous n‐Si samples fabricated by photoelectrochemical etching over a wide range of current densities shows both blueshift and peak broadening with increasing , which can be attributed to the progressive participation of more silicon hydride species, , with larger n in the emitting progress. Based on analysis of spectral changes and resolution of the EL peak into components, a revised mechanism of the EL, where silicon hydrides are considered to donate electrons to sulfate radical anions, is proposed. EL is produced by recombination of the resulting radical, , with an accumulated electron in the conduction band. The radicals would lead to competing reactions that strip off hydrogens from the surface silicon hydrides. with larger n is subject to the earlier EL. © 1999 The Electrochemical Society. All rights reserved.

Electrochemical deposition of Cu-doped ZnTe films was investigated as a back contact material for CdTe solar cells. The deposition system consisted of a potentiostat, a substrate (cathode), a Pt counter electrode, and an Ag/AgCl reference electrode. Experimental conditions were pH=2.5∽4, deposition temperature=70 ∽80°C, electrolyte concentration=0.02 M Zn2, 10-4 M TeO2, and deposition potential (Va) = -0.85 ∽ -1.0 V vs Ag/AgCl A cyclic voltammogram obtained from an ITO substrate showed a ZnTe reduction peak at Va = -0 7 ∽ -0 9 V A film obtained at pH=2.5, Va=-0.975 V showed the strongest ZnTe X-ray diffraction peak, but its surface morphology was not as smooth as the films made under the condition of pH=3∽4, Va=-0.950V. Triethanolamine did not form a complex with cu2 in acidic solution as needed for uniform Cu-doping, but oxalate anion and 1,10-phenanthrolme did at pH=2∽3. The efficiency of CdTe solar cells increased from 3.4% to 7.1% when Cu-doped ZnTe film was used as the back contact.

Ultrasonic agitation was applied during the chemical bath deposition of CdS thin films. Ultrasonication resulted in a dramatic difference in surface morphology, growth rate, and optical properties of CdS films. There were virtually no colloidal particles adsorbed on the surface. The surface roughness measured by atomic force microscopy was reduced by a factor of two. Band gap energy increased to 2.39 eV from 2.37 eV. X-ray patterns showed that the preferred orientation changed from hexagonal(002)/cubic(111) to hexagonal(101). Optical transmission improved in the wavelength range longer than 520 nm. The chemical reaction for CdS formation started at a lower temperature under ultrasonication, and dense films were obtained even when the chemical composition of the aqueous solution deviated far from the optimum conditions.

TiO 2 thin films were prepared on electrochemically etched porous Si by anodic oxidative hydrolysis of TiCl 3 for the purpose of solar cell application. We compared electrochemical and photoelectrochemical properties of the TiO 2 -deposited porous Si electrodes (TiO 2 /porous Si) with those of a porous Si electrode. The TiO 2 /porous Si showed prolonged stability of photoluminescence and enhancements of photovoltage and photocurrent by 0.13 V and 67% increase, respectively, in comparison with porous Si due to the reduction of surface traps for charge carriers in the presence of TiO 2 thin layer. Li + and Na + ions exhibited intercalation and deintercalation through the electrodeposited TiO 2 film.

Electrochromism of nanocrystalline TiO{sub 2} films under cathodic bias in propylene carbonate containing LiClO{sub 4} was studied by time-dependent absorption and fluorescence spectroscopies. The absorption spectra revealed two absorption bands near 700 and 420 nm. The absorption band near 700 nm showed a blue shift and an increase in absorbance with time. The blue shift seemed to be due to the progressive involvement of the trapped electrons in the lower energy levels within the shallow surface states. The newly observed band near 420 nm appeared to have originated from the deep surface states which, lying 1.3--1.8 eV below the conduction band, were gradually filled with electrons in the shallow surface states.

The plasma source ion implantation (PSII) was utilized to improve the wettability and the stability of surface layer formed in the modification of polymeric materials. Polystyrene was treated with different kinds of plasma ions to render the surface more hydrophilic or hydrophobic. Hydrophobic recovery of PSII-treated polystyrene was also observed as a function of aging time, aging temperature, and treatment parameters. Treatment parameters involve kinds of gases, pressure, plasma power, pulse frequency, pulse voltage, etc. To study the effect of inert gas on hydrophobic recovery, polystyrene samples were prepared by helium, argon, or gas-mixture treatment. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) has been used to interpret the PSII-treated polystyrene surface and its hydrophobic recovery, with the assistance of x-ray photoelectron spectroscopy and water contact angle measurements. TOF-SIMS spectra of 18O2 PSII-treated samples showed the presence of 18O-containing peaks from the modified ...

Ultrasonic agitation was applied during the chemical bath deposition of CdS thin films. Ultrasonication resulted in a dramatic change in the surface morphology, growth rate, and optical properties of CdS films. There were virtually no colloidal particles adsorbed on the surface. The surface roughness measured by atomic force microscopy was reduced by a factor of two. Band gap energy increased to 2.39 eV from 2.37 eV. X-ray patterns showed that the preferred orientation changed from hexagonal (002)/cubic (111) to hexagonal (101). Optical transmission improved in the wavelength range larger than 520nm. The chemical reaction for CdS formation started at a lower temperature under ultrasonication, and dense films were obtained even when the chemical composition of the aqueous solution deviated far from optimum conditions.

Spectral shifts of visible electroluminescence (EL) from cathodically biased n-Si in electrolyte solution containing persulfate ions are described. The electrochemically etched n-Si cathodes exhibit a blue shift of the EL with the increase of applied potential. It is explained that the blue shift is caused by the formation of an accumulation layer and the Fermi level pinning in the porous Si. A study of the EL as a function of time at a constant potential shows a red shift, which can be attributed to the bandgap lowering caused by the conversion of the predominant surface bonds Si-H to Si-Si. Electro-polymerization of aniline on the porous Si surface enhanced the stability of the EL possibly due to the strengthening of the surface bonds.

The photodegradation of DDT in water was examined with a high-pressure mercury lamp. A total of 17 photodegradation products of DDT including DDD, DDE and DDMU were identified by gas chromatography-mass spectrometry (GC-MS). Mass spectrometric analyses were done with electron impact (EI), methane positive chemical ionization (PCI) and electron capture negative ion chemical ionization (ENCI). The degradation rate of DDT in the presence of acetone was measured against the irradiation time. After the irradiation for 10min, 80% of DDT was converted into a number of products, including DDD, DDE, DDMU and dichlorobenzophenone, through reductive dechlorination, oxidation, isomerization and chlorination. On the basis of the identified products, the photodegradation pathways of DDT are proposed.

Chemiluminescence (CL) from fluorophores generated by the reaction of bis(2,4-dinitrophenyl)oxalate (DNPO), H 2 O 2 , and several bases have been examined for the identification of multiple pathways. When the intensity of PO-CL (peroxyoxalate chemiluminescence) vs. time was measured under low base concentration in acetonitrile, two distinctive emission maxima, a fast decaying peak and a slowly decaying peak, were observed. The fast decaying first peak was predominant over the slowly varying peak at high concentration of DNPO and H 2 O 2 and at low base concentration, and might be formed by the direct reaction of hydroperoxy oxalate ester (X) and fluorophore. When another set of the intensity vs. time was measured at high base concentration in ethylacetate containing 5% tert -butylalcohol, there also appeared two different peaks, a slowly decaying peak and a sharply decaying peak. The slowly decaying peaks in both sets of experiments were produced by base-catalyzed nucleophilic reaction of DNPO with X. The sharply decaying peak in the latter experiment could be dependent on the relative basicity of the donor, X, and acceptor, base. Based on the those observations a scheme is suggested that describes three reaction pathways.

The electrochemical behavior of polypyrrole (PPy) electropolymerized within poly(acrylonitrile-co-butadiene) (PAB) was compared with that of PPy deposited on Pt in terms of cyclic voltammetry, chronoamperometry, and chronopotentiometry in acetonitrile. The PAB coating was not removed after the PPy deposition. The reduction peak potentials of a PPy ¦PAB¦Pc electrode occurred at more negative potentials than those of a PPy ¦ Pt electrode. For both electrodes anodic and cathodic peak currents were proportional to the scan rate below 100 mV s−1, but to the square root of the scan rate beyond 200 mV s−1. The apparent diffusion coefficient of ClO4− in the PPy + PAB was estimated to be 1.6 times larger than that in the PPy. The more porous and rougher structure of the PPy film grown within the PAB layer had higher anodic and cathodic currents, faster charging and discharging rates and a larger capacity.

M N719 dye (Solaronix)ethanol solution for 36 h. The redox electrolyte composed of0.80 M 1,2-dimethyl-3-hexyl-immidazolium iodide (home-made) and 40 mM iodine in 3-methoxypropionitrile (Aldrich).J-V curves were measured with a Keithley 2400 sourcemeter. A 1000 W Xenon lamp (Oriel, 9113) was utilized at100 mW/cm

Current-voltage (J-V) curves of n-GaAs/KOH(aq)-Se{sub 2}{sup 2{minus}}/Se{sup 2{minus}} and n-Si/acetone-LiClO{sub 4}-Fc{sup +/0} (ferrocenium ion/ferrocene) solar cells exhibit sigmoidal shapes near the open-circuit potential. J-V and flatband potential measurements indicate that the deviation of the J-V curves from the ideal square-like shape to S shape is due to the light-induced displacement of the bandedges. Analytical expression describing the dependence of light-induced bandedge shifts on the anodic photocurrent, the density of surface states, and the interfacial charge-transfer velocity are derived and verified experimentally. Application of the expressions to J-V data yields quantitative information on the kinetics of interfacial charge transfer.

The luminescence properties of PSMA-Ln(III) (Ln = Sm, Dy, Tb, Gd, Yb, Eu) in aqueous solution were investigated. Upon excitation of the styrene subunit, energy migrates from the PSMA polymer to Ln 3+ ions, and luminescence enhancements of Tb 3+ , Eu 3+ , Sm 3+ and Dy 3+ were observed. In PSMA-Eu 3+ , the effect of environment around the metal ion largely contributes to the luminescence enhancement. Fluorescence from PSMA in PSMA-Ln 3+ complexes was also measured. PSMA fluorescence intensity was enhanced upon coordination to Ln(III) (Ln = Sm, Dy, Tb, Gd), and λ em,max was blue-shifted due to Ln(III) association to the polymer chain and the reduced chain mobility of PSMA. In the presence of Eu 3+ and Yb 3+ , however, PSMA luminescence intensity was decreased. Compared to Tb 3+ , the unlikely low efficiency of energy transfer from styryl moieties in PSMA−Eu 3+ and diminished PSMA fluorescence intensities are attributed to the possibility of a deactivating charge transfer state due to the low reduction potentials of Eu 3+ and Yb 3+ .

The open-circuit photovoltage (V[sub oc]) of semiconductor/liquid junction solar cells is a critical parameter in determining the energy conversion efficiency. A simple, quantitative relationship between the semiconductor surface recombination velocity (S[sub r]) and the open-circuit photovoltage (V[sub oc]) of photoelectrochemical systems was derived and verified experimentally. Experimental results obtained for the n-Si/acetone-FeCp[sub 2][sup +/0]-LiClO[sub 4] junction indicate that V[sub oc] is controlled by surface recombination. Quantitative analysis of the results using the derived expression yields values of the barrier height and S[sub r] that compare favorably with published data. Application of the equation to other semiconductor/liquid junction cells suggests that the expression may be important in evaluating and understanding the behavior of a wide range of photoelectrochemical systems.

tovisible and near infrared light by adsorbed dye molecules tothe photoanode.Efforts have been focused on improving the solar conver-sion efficiency of presently reported value of about 10%.The conversion efficiency decreases due to recombinationlosses of photoinjected electrons with oxidized dye mole-cules or redox couple at the surface of nanocrystalline TiO

A dye-sensitized solar cell (DSSC) containing a TiO(2) film treated with COOH-functionalized germanium nanoparticles (Ge-COOH Nps) exhibited a higher short-circuit photocurrent density (J(sc); 15.4 mA cm(-2)) compared to the corresponding untreated DSSC (13.4 mA cm(-2)) using N719 and a 12 μm thick TiO(2) film at 100 mW cm(-2). The amount of N719 attached to the treated TiO(2) film was 21% greater than that attached to the untreated TiO(2) film. Enhancement of the J(sc) value by 15% was attributed mostly to an intramolecular charge transfer from N719 attached to the Ge-COOH Nps to the TiO(2) conduction band through the Ge-COOH Nps.

The sensitization of Eu(III) ion emission in tetrahydrofuran by copolymers of styrene-maleic anhydride, styrene-maleic acid(PSMA), and europium salt of PSMA(PSMA-Eu) was studied. When excited at 260 nm in the presence of PSMA, the emission of Eu(III) at 618 nm exhibited large enhancement compared with that in the absence of PSMA. The enhancement was even greater for PSMA-Eu and accompanied by the decrease in monomer and excimer emission of polymers, suggesting that energy is transferred from the excited polymer to Eu(III) ions

An electrospun membrane was prepared from a 16 wt % solution of poly(vinylidenefluoride- co-hexafluoropropylene) (PVdF-HFP) in a mixture of acetone/ N, N-dimethylacetamide (7:3 wt %) at an applied voltage of 12 kV. It was then activated by immersing it in 0.6 M 1-hexyl-2,3-dimethylimidazolium iodide, 0.1 M LiI, 0.05 M I 2, and 0.5 M 4- tert-butylpyridine in ethylene carbonate/propylene carbonate (1:1 wt %) to obtain the corresponding membrane electrolyte with an ionic conductivity of 10 (-5) S cm (-1) at 25 degrees C. On the basis of this electrospun membrane electrolyte, quasi-solid-state dye-sensitized solar cells were fabricated, which showed an open-circuit voltage ( V oc) of 0.76 V, a fill factor of 0.62, and a short-circuit current density ( J sc) of 15.57 mA cm (-2) at an incident light intensity of 100 mW cm (-2). This yields a light-to-electricity conversion efficiency of 7.3%. Moreover, this cell possessed better long-term stability than that fabricated with conventional liquid electrolyte.

Various adsorbents for a solid phase extraction (SPE) method were used to study their ability to separate PCBs from transformer oil to rapidly determine their sub-ppm concentration in the transformer oil. Approximately 90% of the transformer oil could be removed from the PCBs by using a hydrophilic–lipophilic balanced copolymer (HLB) adsorbent, but the recovery of deca-chlorobiphenyl (deca-CB) used as a surrogate was only 24.5% due to lose during this cleanup process. The use of a silica adsorbent gave good results with 89.9% recovery of the deca-CB. The recovery of Aroclor 1242 and 1260 were 95.4 and 90.3% on silica, and 98.9 and 83.5% on HLB, respectively. Acid treatment was an essential step in removing the ambiguous interference peaks to help identify the PCBs. A decreased sensitivity of the electron capture detection (ECD) for PCBs was observed due to the presence of the remaining trace oil after the workup procedure. This loss in sensitivity was allowed for by using tetrachloroxylene as an internal standard, and this was found to be reliable for the criteria of quality control by employing an experiment in which LCS was spiked with 2 mg/l of Aroclor 1260 and analyzed each day over a 25 day period. The MDL for the analytical method established in this study is 0.05 mg/l.

Linking of N3 dye to another TiO2-attached N3 dye rendered an enhanced short-circuit photocurrent and thereby higher efficiency for the dye-sensitized solar cell with the pertinent TiO2 film electrode.

A coordinatively induced length control of W18O49 nanorods has been developed using thermal decomposition of W(CO)6 in octyl ether solutions of single or mixed capping agents, oleic acid (OA), oleic acid/hexadecylamine (HDA), and oleic acid/trioctylphosphine oxide (TOPO). The order of length for nanorods synthesized with different capping agents was OA > OA/HDA > OA/TOPO, which was the opposite of order of their coordinating power. The order of crystalline size (diameter x length) from the TEM image was OA/HDA > OA > OA/TOPO and matched exactly with the order of crystallinity from the XRD pattern. The order of photoluminescence intensity was OA/HDA < OA < OA/TOPO and was the opposite of the order for the crystalline size or crystallinity. The strong coordinating power and steric bulkiness of TOPO is thought to interrupt the growth of the nanorods, the rearrangement of the end face atoms, and the fusion of the lateral faces and, thereby, increase the oxygen defects and the photoluminescence intensity.