Hydrogen bonding effects on surface structure, photophysical properties, and photoelectrochemistry have been examined in a mixed film of porphyrin and fullerene composites with and without hydrogen bonding on indium tin oxide and nanostructured SnO2 electrodes. The nanostructured SnO2 electrodes modified with the mixed films of porphyrin and fullerene composites with hydrogen bonding exhibited efficient photocurrent generation compared to the reference systems without hydrogen bonding. Atomic force microscopy, infrared reflection absorption, and ultraviolet-visible absorption spectroscopies and time-resolved fluorescence lifetime and transient absorption spectroscopic measurements disclosed the relationship between the surface structure and photophysical and photoelectrochemical properties relating to the formation of hydrogen bonding between the porphyrins and/or the C60 moieties in the films on the electrode surface. These results show that hydrogen bonding is a highly promising methodology for the fabrication of donor and acceptor composites on nanostructured semiconducting electrodes, which exhibit high photoelectrochemical properties. 相似文献
A supramolecular system of a perylene derivative containing bis(2,6-diacylaminopyridine) units and a perylene bisimide bound through three hydrogen-bonds was synthesized and characterized. 1H NMR spectra confirmed the existence of hydrogen-bonding interactions between the perylene derivative (3) and the perylene bisimide (7). The photocurrent generation of the self-assembled 3.7 film was measured, and a cathodic photocurrent response was obtained. SEM images indicated that well-defined long fibers could be fabricated by self-assembly, by exploiting the hydrogen bonding interactions and pi-pi stacking interactions of perylene rings. 相似文献
Detonated nanodiamonds (NDs) exhibit remarkable photocatalytic activity towards the hydrogen gas generation upon 532 nm laser pulse irradiation. Hydrogenation dramatically increases the quantum yield, suggesting that hydrogen-terminated sites work as electron reservoirs. NDs can also be used as effective photocatalysts to reduce graphene oxide. The resulting composites exhibit high and stable photocurrent generation upon visible light irradiation. 相似文献
Hydrogen treatment has been proposed as a simple and effective strategy to enhance the performance of Ti O2 nanostructures for applications such as photocatalysis and photoelectrochemical(PEC) water splitting. While some studies have suggested that the black color can be ascribed to surface disorder, other reports have suggested that it is caused by the "oxygen vacancy" states associated with Ti3+ within the bandgap of the Ti O2. The chemical nature and potential use of the bandgap states responsible for the black color of increased visible absorption is not yet well understood and subject of strong interest. Here we briefly review current understanding of the possible mechanisms behind the black color of hydrogen-treated Ti O2 nanowires and its relevance to photocatalysis and solar water splitting for hydrogen generation. One important conclusion to date is that while hydrogen treatment enhances photocurrent of Ti O2 with UV excitation, no noticeable photocurrent can be detected with visible light, which seems to be due to the very short lifetimes of the bandgap oxygen vacancy states arising from hydrogen treatment. 相似文献
[reaction: see text] A convenient synthesis of monodendrons whose conformation is restricted through the intervention of intramolecular hydrogen bonding and repulsive electrostatic interactions is described. X-ray crystal structure analysis of the second generation dendron shows the presence of a propeller-type secondary structure and indicates that the dendrons have assembled into a symmetrically interdigitated dimer in the solid state. 1H NMR and IR spectral data are in agreement with the presence of intramolecular hydrogen bonding between the amides and the pyridine N throughout the dendron structure in solution. 相似文献
We have developed a metal and halogen-free Friedel–Crafts acylation protocol with virtually no waste stream generation. We propose a hydrogen bonding donor solvent will form a hydrogen bonding network and may provide significant rate enhancement for Friedel–Crafts reactions. Trifluoroacetic acid is one of the strongest H-bond donor solvents, which is also volatile and can be easily recovered by distillation without need for reaction workup. Our protocol is a ‘green’ Friedel–Crafts acylation process: 1) the catalyst can be recovered and reused; 2) using halogen free starting material (carboxylic acids anhydride or carboxylic acids); 3) no need for aqueous reaction work-up; 4) minimum or no waste steam generation. 相似文献
The photosensitive multilayer films from sulfonated metal-free, sulfonated copper-, and sulfonated nickel-phthalocyanines were fabricated with diazoresin layer by layer on a substrate via electrostatic interaction by the self-assembly technique. Under UV irradiation, the linkage nature between the layers of the film is converted from the electrostatic bonding to covalent bonding. The covalently attached multilayer films are very stable towards polar solvents and salt aqueous solutions. The photovoltaic properties of the covalently attached film can be determined by means of a traditional three-electrode photoelectrochemical cell in aqueous solutions with KCI as the supporting electrolyte. The photocurrent determination has shown that the sulfonated copper-containing phthalocyanine films possess a higher photocurrent value than sulfonated metalfree and sulfonated nickel-containing phthaloeyanine films. 相似文献
Given its well‐ordered continuous π stacking of nucleobases, DNA has been considered as a biomaterial for charge transfer in biosensors. For cathodic photocurrent generation resulting from hole transfer in DNA, sensitivity to DNA structure and base‐pair stacking has been confirmed. However, such information has not been provided for anodic photocurrent generation resulting from excess‐electron transfer in DNA. In the present study, we measured the anodic photocurrent of a DNA‐modified Au electrode. Our results demonstrate long‐distance excess‐electron transfer in DNA, which is dominated by a hopping mechanism, and the photocurrent generation is sequence dependent. 相似文献
Light is a common source of energy in sustainable technologies for photocurrent generation. To date, in such light-harvesting applications, the excited electrons generate the photocurrent. Here, we introduce a new mechanism for photocurrent generation that is based on excited state proton transfer (ESPT) of photoacids and photobases that can donate or accept a proton, respectively, but only after excitation. We show that the formed ions following ESPT can either serve as electron donors or acceptors with the electrodes, or modify the kinetics of mass transport across the diffuse layer, both resulting in photocurrent generation. We further show that control of the current polarity is obtained by switching the irradiation between the photoacid and the photobase. Our study represents a new approach in photoelectrochemistry by introducing ESPT processes, which can be further utilized in light-responsive energy production or energy storage. 相似文献
Hematite nanoarrays are important photoanode materials. However, they suffer from serious problems of charge transfer and surface states; in particular, the surface states hinder the increase in photocurrent. A previous strategy to suppress the surface state is the deposition of an Fe-free metal oxide overlayer. Herein, from the viewpoint of atomic bonding energy, it is found that the strength of bonding around Fe atoms in the hematite is the key to suppressing the surface states. By treating the surface of hematite with Se and NaBH4, the Fe2O3 transforms to a double-layer nanostructure. In the outer layer, the Fe−O bonding is reinforced and the Fe−Se bonding is even stronger. Therefore, the surface states are inhibited and the increase in the photocurrent density becomes much faster. Besides, the treatment constructs a nanoscale p–n junction to promote the charge transfer. Improvements are achieved in onset potential (0.25 V shift) and in photocurrent density (5.8 times). This work pinpoints the key to suppressing the surface states and preparing a high-efficiency hematite nanoarray, and deepens our understanding of hematite photoanodes. 相似文献
To establish a semiartificial device for (bio-)hydrogen production utilizing photosynthetic water oxidation, we report on the immobilization of a Photosystem 2 on electrode surfaces. For this purpose, an isolated Photosystem 2 with a genetically introduced His tag from the cyanobacterium Thermosynechococcus elongatus was attached onto gold electrodes modified with thiolates bearing terminal Ni(II)-nitrilotriacetic acid groups. Surface enhanced infrared absorption spectroscopy showed the binding kinetics of Photosystem 2, whereas surface plasmon resonance measurements allowed the amount of protein adsorbed to be quantified. On the basis of these data, the surface coverage was calculated to be 0.29 pmol protein cm(-2), which is in agreement with the formation of a monomolecular film on the electrode surface. Upon illumination, the generation of a photocurrent was observed with current densities of up to 14 microA cm(-2) . This photocurrent is clearly dependent on light quality showing an action spectrum similar to an isolated Photosystem 2. The achieved current densities are equivalent to the highest reported oxygen evolution activities in solution under comparable conditions. 相似文献
Summary: The ability of SuSi to generate microstructures of polymers with hydrogen bonding interactions has been checked. This is a random procedure recently developed to localize independent minima. Calculations were performed on nylon 6, a large number of equilibrated and relaxed atomistic models, i.e. microstructures without torsional strain and atomic overlaps, being generated. Results indicated that the generation algorithm implemented in SuSi underestimates the amount of amide groups involved in hydrogen bonding interactions. This is an expected result since no specific criterion was introduced in it to facilitate the formation of specific interactions. Several modifications have been introduced in the generation algorithm to overcome this limitation. The changes induced by these modifications in the generated microstructures are discussed.
A new computational strategy denoted SuSi generates atomistic models of hydrogen bond forming polymers with very reliable results. 相似文献
Vibrational energy transfer (VET) of proteins at cell membrane plays critical roles in controlling the protein functionalities, but its detection is very challenging. By using a surface‐sensitive femtosecond time‐resolved sum‐frequency generation vibrational spectroscopy with infrared pump, the detection of the ultrafast VET in proteins at cell membrane has finally become possible. The vibrational relaxation time of the N−H groups is determined to be 1.70(±0.05) ps for the α‐helix located in the hydrophobic core of the lipid bilayer and 0.9(±0.05) ps for the membrane‐bound β‐sheet structure. The N−H groups with strong hydrogen bonding gain faster relaxation time. By pumping the amide A band and probing amide I band, the vibrational relaxation from N−H mode to C=O mode through two pathways (direct coupling and through intermediate states) is revealed. The ratio of the pathways depends on the NH⋅⋅⋅O=C hydrogen‐bonding strength. Strong hydrogen bonding favors the coupling through intermediate states. 相似文献
I INTRODUCTION.Ftinctional polymer materials for adsorption and separation are widely used in indtistry,agriculture, hi-tech, national defense and scientific research. Functions of these polymermaterials are displayed through interactions between the materials and small molecules or ions,which include ion bonding, covalent bonding, coordinate bonding and van der Waals forces.FunCtional polymers based on the above interactions are ion exchange resins, polymer supportedreagentS, chelating … 相似文献