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101.
Conjugated PPV-PPE copolymer has been investigated in organic solar cells in combination with twelve different fullerene derivatives. It was shown that the length of solubilizing alkyl chains in the fullerene derivative structures correlates well with the performance of photovoltaic cells.  相似文献   
102.
Strong experimental and theoretical evidence was provided on the controlled formation of the two-dimensional J-aggregates that were assembled in the herringbone morphology. The exciton-band structure formation of 1,1',3,3'-tetraethyl-5,5',6,6'-tetrachlorobenzimidazolocarbocyanine (TTBC) J-aggregates was investigated in ionic (NaOH) aqueous solution at room temperature. The control was achieved by changing the [TTBC] at a given [NaOH], or vice versa, and was monitored through the changes in the absorption, fluorescence excitation, and emission spectra. Specific attention was paid to expose the excited-state structure and dynamics through simulations of the excitonic properties, which included diagonal energetic disorder and phonon-assisted exciton relaxation. Aggregates were characterized by an asymmetrically split Davydov pair, an H-band (approximately 500 nm, 1300 cm(-1) wide, Lorentzian-like) and a J-band (approximately 590 nm, 235 cm(-1) wide, with a band shape typical of a one-dimensional J-aggregate), whose relative intensities showed a strong dependence on the [TTBC]/[NaOH]. The H-band is favored by high [TTBC] or high [NaOH]. An explanation of the control on the aggregate formation was given by correlating the changes in the absorption with the structural modifications and the subsequent changes in the dynamics, which were induced by variations in the dye and NaOH concentrations. The J-band shape/width was attributed to disorder and disorder-induced intraband phonon-assisted exciton relaxation. The intraband processes in both bands were estimated to occur in the same time scale (about a picosecond). It has been suggested that the wide energetic gap between the Davydov split bands (3000 cm(-1)) could get bridged by the excitonic states of the loosely coupled chains, in addition to the monomeric species at low [TTBC]. Phonon-assisted interband relaxation, through the band gap states and/or directly from the H- to the J-band, are suggested for accounting the difference between the bandwidths and shapes of the two bands. Energy transfer between the H-band and the monomeric species is suggested as crucial for tuning the relative strengths of the two bands.  相似文献   
103.
The photoinduced charge-transfer properties of a series of polyalkylthiophene copolymers, carrying anthraquinone substituents covalently linked to the conjugated backbone, have been studied in the solid state by photoinduced absorption (PA) and light-induced electron spin resonance (LESR) spectroscopy. The measurements indicate the formation of metastable charges arising from the photoinduced electron transfer from the polythiophene backbone to the anthraquinone moieties. At low temperatures (below 200 K), long-lived persistent charges are formed, exhibiting lifetimes that extend for several minutes; their recombination kinetics has been studied by following the formation and decay of the PA and LESR signals. The results are rationalized using a model originally proposed to describe the low-temperature recombination kinetics of long-lived photoexcited carriers in amorphous inorganic semiconductors. It is clearly evidenced that, in these polymers, the number of acceptor substituents in the chain, easily tuned by chemical tailoring, plays a key role in the photoexcitation scenario.  相似文献   
104.
[Structure: see text] A novel covalently linked bis([60]fullerene)-phthalocyanine triad is reported, exhibiting long-lived photoinduced charge separation both in solution and in the solid state. The first demonstration of a working solar cell using triad 1 as the active material is also presented.  相似文献   
105.
106.
This contribution presents the synthesis and properties of four thiophene‐containing poly(‐p‐arylene‐ethynylene)/poly(‐p‐arylene‐vinylene)s, PIa‐b and PIIa‐b , whose repeating units (RU) consist either of 1:2 or 2:2 triple bond/double bond ratio, and which bear linear alkoxy side chains not longer than octyloxy and branched 2‐ethylhexyloxy. PIa‐b and PIIa‐b exhibit similar absorption and emission behaviour in dilute solution (λa = 483–486 nm, λe = 540 nm) as well as in solid state (λa = 500, 530 nm, λe = 560 nm), whereby slightly higher fluorescence quantum yields (Φf) were obtained for PI than for PII systems, as a result of higher number of thiophene units within the RU of PII . An enhancement of the Φf‐value from 0% to 3% is obtained after replacing linear octadecyloxy in PIIc‐e by bulky branched 2‐ethylhexyloxy in PIIa‐b . Nonoptimized solar cells of configuration ITO/PEDOT:PSS/polymer: PCBM (1:3 weight ratio)/LiF/Al show open circuit voltages as high as 900 mV for PIa‐b and 800 mV for PIIa‐b . Reducing the size of the side chain from R = 2‐ethylhexyl in PIa to R = methyl in PIb leads to a significant increase of the short circuit current, I SC, from ca. 2.5 mA to ca. 3.7 mA and consequently to an enhancement of the energy conversion efficiency, ηAM1.5, from ca. 1.2% to ca. 1.7%. This is due to an extended donor‐acceptor interfacial area, as evidenced by AFM topology pictures showing smaller nanoscale clusters size in PIb than in PIa active layer. The same change led to minimal effect in PII systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1619–1631, 2007  相似文献   
107.
Retention behaviors of an amide-embedded silica base stationary phase, which was recently developed by our group, were studied by using six different groups of small polar compounds including phenolic compounds, substituted anilines, chlorinated herbicides, Sudan dyes and some nucleotides and nucleosides in HPLC. The chromatographic behaviors of the prepared stationary phase for these analytes were compared with those of a commercially available reversed-phase column ACE C18 under same conditions. Among the six groups of analytes studied, the amide-silica stationary phase showed enhanced selectivity towards phenolic compounds, substituted anilines, Sudan dyes and herbicides under reversed-phase conditions and satisfactory selectivity towards nucleosides and nucleotides which could not be separated with ACE C18 column under HILIC conditions. Experimental data provided some evidence that functional groups on the stationary phases might have certain degrees of influence on selectivity possibly through secondary interactions with the model compounds. The retentions of the moderately polar compounds such as phenolic acids, anilines and herbicides on the stationary phase are higher than highly polar compounds such as nucleotides and nucleosides due to both the hydrophobic and hydrophilic interactions between the stationary phase and analytes. The quantitative determination of Sudan dyes (I, II, III, and IV) in red chilli peppers was performed. Many red chilli peppers were screened and three of them contained Sudans dyes.  相似文献   
108.
This work investigates the photoinduced energy transfer from poly(N‐vinylcarbazole) (PVK), as a donor material, to fac‐(2,2′‐bipyridyl)Re(CO)3Cl, as a catalyst acceptor, for its potential application towards CO2 reduction. Photoluminescence quenching experiments reveal dynamic quenching through resonance energy transfer in solid donor/acceptor mixtures and in solid/liquid systems. The bimolecular reaction rate constant at solution–film interfaces for the elementary reaction of the excited state with the quencher material could be determined as 8.8(±1.4)×1011 L mol?1 s?1 by using Stern–Volmer analysis. This work shows that PVK is an effective and cheap absorber material that can act efficiently as a redox photosensitizer in combination with fac‐(2,2′‐bipyridyl)Re(CO)3Cl as a catalyst acceptor, which might lead to possible applications in photocatalytic CO2 reduction.  相似文献   
109.
Centers for Disease Control and Prevention (CDC) has reported that lower extremity amputation (LEA) rate of per 1000 diabetic patients is 18.4 because of the complications that first appeared in the foot. A second amputation is also required for 9% to 17% of these patients within the same year although LEA may be preventable. Most of the diabetic foot conditions may be prevented and treated by a therapeutic footwear or a medical device such as an insole or an orthotic shoe. Traditional insole manufacturing is a laborious work that requires specific skills. Moreover, traditional approaches contain harmful material particles that may cause respiratory failure. Unfortunately, manufactured insoles may not be suitable for any mass‐produced footwear in all cases. Therefore, patient requires to get insole‐specific footwear. In this study, a diabetic insole was manufactured by means of a fused deposition modeling‐(FDM) based system and a thermoplastic polymer. Biomechanical functionality was determined according to the applied polymer analysis on each produced sample and foam material. Subsequently, finite element analysis (FEA) was performed to target insole geometry to ensure the quality of the final medical product. Additive and traditional manufactured insoles are compared according to the cost and function. As a result, fabrication of an insole, based on the FDM method, was improved down to 8 h and 9 m. The weight of an insole prototype was 74.74 g, and the material cost was $3.44 while total cost of the traditional foam casting was determined as $35.37 and weight of the insole was 72.6 g for this study. Consequently, benefits of the applied method are evaluated.  相似文献   
110.
Natural polymer‐based hydrogel bioinks are widely used in bioprinting due to their suitability for recapitulation of in vivo cellular activities. However, preservation of the target geometry in a cell‐laden hydrogel is difficult to achieve. The aim of this study was to develop a universal sacrificial bioink that allows high cell viability and a better shape fidelity in the cell‐laden construct. A polysaccharide‐based universal sacrificial bioink was developed for microextrusion‐based bioprinting and was optimized to erode in 48 hours in the cell culture medium without formation of any undesired by‐products. The sacrificial hydrogel was prepared from alginate and agarose via a microwave oven assisted method and bioprinted at room temperature to generate microchannels in the cell‐laden hydrogel or to support a tubular structure and its biocompatibility determined by live/dead assay. Bioprinting time was significantly reduced, down to a few minutes for a large‐scale tissue model (1 minute 52 seconds for a 2 cm tubular structure), by means of a high bioprinting speed up to 25 mm/s. After 48 hours in the cell culture, the sacrificial bioink completely detached from the cell‐laden construct without causing any changes in its printed shape. Cell viability in the cell‐laden construct was observed to be more than 95% at the end of 3‐day culture. This novel sacrificial bioink enables bioprinting at room temperature without affecting oxygen and nutrient penetration into the cell‐laden hydrogel and allows retention of high cell viability and shape fidelity.  相似文献   
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