Recently, hydrovoltaic technology emerged as a novel renewable energy harvesting method, which dramatically extends the capability to harvest water energy. However, the urgent issue restricting its device performance is poor carrier transport properties of the solid surface if large charged interface is considered simultaneously. Herein, a hydrovoltaic device based on silicon nanowire arrays (SiNWs), which provide large charged surface/volume ratio and excellent carrier transport properties, yields sustained electricity by a carrier concentration gradient induced by evaporation-induced water flow inside nanochannels. The device can yield direct current with a short-circuit current density of over 55 μA cm−2, which is three orders larger than a previously reported analogous device (approximately 40 nA cm−2). Moreover, it exhibits a constant output power density of over 6 μW cm−2 and an open-circuit voltage of up to 400 mV. Our finding may pave a way for developing energy-harvesting devices from ubiquitous evaporation-driven internal water flow in nature with semiconductor material of silicon. 相似文献
We show that a robust molybdenum hydride system can sustain photoelectrocatalysis of a hydrogen evolution reaction at boron‐doped, hydrogen‐terminated, p‐type silicon. The photovoltage for the system is about 600–650 mV and the current densities, which can be sustained at the photocathode in non‐catalytic and catalytic regimes, are similar to those at a photoinert vitreous carbon electrode. The kinetics of electrocatalysed hydrogen evolution at the photocathode are also very similar to those measured at vitreous carbon—evidently visible light does not significantly perturb the catalytic mechanism. Importantly, we show that the doped (1–10 Ω cm) p‐type Si can function perfectly well in the dark as an ohmic conductor and this has allowed direct comparison of the cyclic voltammetric behaviour of the response of the system under dark and illuminated conditions at the same electrode. The p‐type Si we have employed optimally harvests light energy in the 600–700 nm region and with 37 mW cm?2 illumination in this range; the light to electrochemical energy conversion is estimated to be 2.8 %. The current yield of hydrogen under broad tungsten halide lamp illumination at 90 mW cm?2 is (91±5) % with a corresponding chemical yield of (98±5) %. 相似文献
A double hydrophilic block copolymer, poly(ethylene glycol)‐poly(3‐dimethyl (methacryloyloxyethyl) ammonium propane sulfonate) (PEG‐SB), is synthesized by reversible addition‐fragmentation transfer (RAFT) polymerization using PEG methyl ether (4‐cyano‐4‐pentanoate dodecyl trithiocarbonate) as a chain transfer agent. PEG‐SB forms multi‐layered microspheres with dipole‐dipole interactions of the SB side chains as the driving force. The PEG‐SB polymers show an upper critical solution temperature (UCST) and the UCST is controllable by the polymerization degree. The PEG‐SB microspheres are dissociated above the UCST and then monodispersed microspheres (∼1 μm) are obtained when the solution temperature is decreased below the UCST again. The disassociation/association of the microspheres is also controllable using the concentration of NaCl. These multi‐responsive microspheres could be a powerful tool in the field of nano‐biotechnology.
The specific hydrophobic effect involved in the self‐assembly of a bolaamphiphilic perylene bisimide (PBI) dye bearing oligoethylene glycol (OEG) chains has been identified. In pure water, the self‐assembly is entropically driven and enthalpically disfavored, as explored by optical spectroscopy and isothermal titration calorimetry studies. Besides strong π–π interactions between the PBI units that are primarily of enthalpic nature, the major contribution to the self‐assembly is the gain of entropy by release of confined water molecules from the hydration shell of the hydrophilic OEG moieties. Both contributions favor self‐assembly, but their countervailing thermodynamic parameters are reflected in an uncommon temperature dependence, which can be inverted upon gradual addition of an organic cosolvent that makes the π–π interaction increasingly dominant. 相似文献
All the previously reported supramolecular polymers based on crown ether‐based molecular recognition have been prepared in anhydrous organic solvents. This is mainly due to the weakness of crown ether‐based molecular recognition in the presence of water. Here we report a linear supramolecular polymer constructed from a heteroditopic monomer in an aqueous medium driven by crown ether‐based molecular recognition through the introduction of electrostatic attraction. In addition, the reversible transition between the linear supramolecular polymer and oligomers is achieved by adding acid and base. This study realizes the breakthrough of the solvent for supramolecular polymerization driven by crown ether‐based molecular recognition from anhydrous organic solvents to aqueous media. It is helpful for achieving supramolecular polymerization driven by crown ether‐based molecular recognition in a completely aqueous medium. 相似文献
Although the role of intermolecular aromatic π–π interactions in the self‐assembly of di‐l ‐phenylalanine (l ‐Phe‐l ‐Phe, FF), a peptide that is known for hierarchical structure, is well established, the influence of intramolecular π–π interactions on the morphology of the self‐assembled structure of FF has not been studied. Herein, the role of intramolecular aromatic π–π interactions is investigated for FF and analogous alanine (Ala)‐containing dipeptides, namely, l ‐Phe‐l ‐Ala (FA) and l ‐Ala‐l ‐Phe (AF). The results reveal that these dipeptides not only form self‐assemblies, but also exhibit remarkable differences in structural morphology. The morphological differences between FF and the analogues indicate the importance of intramolecular π–π interactions, and the structural difference between FA and AF demonstrates the crucial role of the nature of intramolecular side‐chain interactions (aromatic–aliphatic or aliphatic–aromatic), in addition to intermolecular interactions, in deciding the final morphology of the self‐assembled structure. The current results emphasise that intramolecular aromatic π–π interaction may not be essential to induce self‐assembly in smaller peptides, and π (aromatic)–alkyl or alkyl–π (aromatic) interactions may be sufficient. This work also illustrates the versatility of aromatic and a combination of aromatic and aliphatic residues in dipeptides in the formation of structurally diverse self‐assembled structures. 相似文献
Two water‐soluble para‐xylylene‐connected 4,4′‐bipyridinium (BIPY2+) polymers have been prepared. UV‐Vis absorption, 1H NMR spectroscopy, and cyclic voltammetry experiments support that in water the BIPY2+ units in the polymers form stable 1:1 charge‐transfer complexes with tetrathiafulvalene (TTF) guests that bear two or four carboxylate groups. These charge‐transfer complexes are stabilized by the donor–acceptor interaction between electron‐rich TTF and electron‐deficient BIPY2+ units and electrostatic attraction between the dicationic BIPY2+ units and the anionic carboxylate groups attached to the TTF core. On the basis of UV‐Vis experiments, a lower limit to the apparent association constant of the TTF?BIPY2+ complexes of the mixtures, 1.8×106 m ?1, has been estimated in water. Control experiments reveal substantially reduced binding ability of the neutral TTF di‐ and tetracarboxylic acids to the BIPY2+ molecules and polymers. Moreover, the stability of the charge‐transfer complexes formed by the BIPY2+ units of the polymers are considerably higher than that of the complexes formed between two monomeric BIPY2+ controls and the dicarboxylate‐TTF donor; this has been attributed to the mutually strengthened electron‐deficient nature of the BIPY2+ units of the polymers due to the electron‐withdrawing effect of the BIPY2+ units. 相似文献
The copper complex [(bztpen)Cu](BF4)2 (bztpen=N‐benzyl‐N,N′,N′‐tris(pyridin‐2‐ylmethyl)ethylenediamine) displays high catalytic activity for electrochemical proton reduction in acidic aqueous solutions, with a calculated hydrogen‐generation rate constant (kobs) of over 10000 s?1. A turnover frequency (TOF) of 7000 h?1 cm?2 and a Faradaic efficiency of 96 % were obtained from a controlled potential electrolysis (CPE) experiment with [(bztpen)Cu]2+ in pH 2.5 buffer solution at ?0.90 V versus the standard hydrogen electrode (SHE) over two hours using a glassy carbon electrode. A mechanism involving two proton‐coupled reduction steps was proposed for the dihydrogen generation reaction catalyzed by [(bztpen)Cu]2+. 相似文献
There is an urgent need for the development in the field of the magnetism of topological insulators, owing to the necessity for the realization of the quantum anomalous Hall effect. Herein, we discuss experimentally fabricated nanostructured hierarchical architectures of the topological insulator Bi2Te3 without the introduction of any exotic magnetic dopants, in which intriguing room‐temperature ferromagnetism was identified. First‐principles calculations demonstrated that the intrinsic point defect with respect to the antisite Te site is responsible for the creation of a magnetic moment. Such a mechanism, which is different from that of a vacancy defect, provides new insights into the origins of magnetism. Our findings may pave the way for developing future Bi2Te3‐based dissipationless spintronics and fault‐tolerant quantum computation. 相似文献
The cooperative effects of hydrogen bonding in small water clusters (H2O)n (n=3–6) have been studied by using the partition of the electronic energy in accordance with the interacting quantum atoms (IQA) approach. The IQA energy splitting is complemented by a topological analysis of the electron density (ρ( r )) compliant with the quantum theory of atoms‐in‐molecules (QTAIM) and the calculation of electrostatic interactions by using one‐ and two‐electron integrals, thereby avoiding convergence issues inherent to a multipolar expansion. The results show that the cooperative effects of hydrogen bonding in small water clusters arise from a compromise between: 1) the deformation energy (i.e., the energy necessary to modify the electron density and the configuration of the nuclei of the isolated water molecules to those within the water clusters), and 2) the interaction energy (Eint) of these contorted molecules in (H2O)n. Whereas the magnitude of both deformation and interaction energies is enhanced as water molecules are added to the system, the augmentation of the latter becomes dominant when the size of the cluster is increased. In addition, the electrostatic, classic, and exchange components of Eint for a pair of water molecules in the cluster (H2O)n?1 become more attractive when a new H2O unit is incorporated to generate the system (H2O)n with the last‐mentioned contribution being consistently the most important part of Eint throughout the hydrogen bonds under consideration. This is opposed to the traditional view, which regards hydrogen bonding in water as an electrostatically driven interaction. Overall, the trends of the delocalization indices, δ(Ω,Ω′), the QTAIM atomic charges, the topology of ρ( r ), and the IQA results altogether show how polarization, charge transfer, electrostatics, and covalency contribute to the cooperative effects of hydrogen bonding in small water clusters. It is our hope that the analysis presented in this paper could offer insight into the different intra‐ and intermolecular interactions present in hydrogen‐bonded systems. 相似文献
A visible‐light‐driven radical‐mediated strategy for the in situ generation of aza‐ortho ‐quinone methides from 2‐vinyl‐substituted anilines and alkyl radical precursors is described. This process enables an efficient multicomponent reaction of 2‐vinylanilines, halides, and sulfur ylides, and has a wide substrate scope and good functional group tolerance. Treatment of the cycloaddition products with a base leads to densely functionalized indoles in a single‐flask operation. 相似文献
Hydrophobic reduced graphene oxides (rGOs) were generated in agarose hydrogel beads (AgarBs) by NaBH4 reduction of graphene oxides (GOs) initially loaded in the AgarBs. The resulting rGO‐loaded AgarBs were able to effectively adsorb organic compounds in water as a result of the attractive hydrophobic force between the rGOs in the AgarBs and the organic compounds dissolved in aqueous media. The adsorption capacity of the rGOs was fairly high even toward reasonably water‐soluble organic compounds such as rhodamine B (321.7 mg g?1) and aspirin (196.4 mg g?1). Yet they exhibited salinity‐enhanced adsorption capacity and preferential adsorption of organic compounds with lower solubility in water. Such peculiar adsorption behavior highlights the exciting possibility for adopting an adsorption strategy, driven by hydrophobic forces, in practical wastewater treatment processes. 相似文献