Beta‐Sheet‐Forming,Self‐Assembled Peptide Nanomaterials towards Optical,Energy, and Healthcare Applications

Peptide self‐assembly is an attractive route for the synthesis of intricate organic nanostructures that possess remarkable structural variety and biocompatibility. Recent studies on peptide‐based, self‐assembled materials have expanded beyond the construction of high‐order architectures; they are now reporting new functional materials that have application in the emerging fields such as artificial photosynthesis and rechargeable batteries. Nevertheless, there have been few reviews particularly concentrating on such versatile, emerging applications. Herein, recent advances in the synthesis of self‐assembled peptide nanomaterials (e.g., cross β‐sheet‐based amyloid nanostructures, peptide amphiphiles) are selectively reviewed and their new applications in diverse, interdisciplinary fields are described, ranging from optics and energy storage/conversion to healthcare. The applications of peptide‐based self‐assembled materials in unconventional fields are also highlighted, such as photoluminescent peptide nanostructures, artificial photosynthetic peptide nanomaterials, and lithium‐ion battery components. The relation of such functional materials to the rapidly progressing biomedical applications of peptide self‐assembly, which include biosensors/chips and regenerative medicine, are discussed. The combination of strategies shown in these applications would further promote the discovery of novel, functional, small materials.     

Polymeric Micelle‐Mediated Delivery of DNA‐Targeting Organometallic Complexes for Resistant Ovarian Cancer Treatment

Three half‐sandwich iridium and ruthenium organometallic complexes with high cytotoxicity are synthesized, and their anticancer mechanisms are elucidated. The organometallic complexes can interact with DNA through coordination or intercalation, thereby inducing apoptosis and inhibiting proliferation of resistant cancer cells. The organometallic complexes are then incorporated into polymeric micelles through the polymer‐metal coordination between poly(ethylene glycol)‐b‐poly(glutamic acid) [PEG‐b‐P(Glu)] and organometallic complexes to further enhance their anticancer effects as a result of the enhanced permeability and retention effect. The micelles with particle sizes of ≈60 nm are more efficiently internalized by cancer cells than the corresponding complexes, and selectively dissociate and release organometallic anticancer agents within late endosomes and lysosomes, thereby enhancing drug delivery to the nuclei of cancer cells and facilitating their interactions with DNA. Thus, the micelles display higher antitumor activity than the organometallic complexes alone with a lack of the systemic toxicity in a mouse xenograft model of cisplatin‐resistant human ovarian cancer. These results suggest that the polymeric micelles carrying anticancer organometallic complexes provide a promising platform for the treatment of resistant ovarian cancer and other hard‐to‐treat solid tumors.     

Annealing-induced enhancement of ferromagnetism in SnO2-core/Cu-shell coaxial nanowires

In this study, we have coated tin oxide (SnO₂) nanowires with a Cu shell layer via the sputtering method and subsequently investigated the effects of thermal annealing. The annealing-induced changes in morphologies, microstructures, and compositions of the resulting core-shell nanowires were characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and energydispersive X-ray spectroscopy (EDX). The Cu shell layers were agglomerated to form clusters, which were mainly comprised of the Cu₂O phase. For the first time, a hysteresis loop indicating weak ferromagnetism was observed from the pure SnO₂ nanowires. Both the coercivity and the retentivity in the hysteresis loop were slightly increased by Cu-sputtering, indicating a very slight enhancement of ferromagnetism. Also, the ferromagnetic behavior was significantly enhanced by thermal annealing. We discuss the possible mechanisms of annealing-induced enhancement of ferromagnetism in the SiO₂/Cu core-shell nanowires, which include the generation of Cu₂O phase, Cu-doping into the SnO₂ lattice, and the generation of oxygen vacancies in SnO₂ core nanowires.     

Thermal characteristics of a premixed impinging circular laminar-flame jet with induced swirl

A swirling flow has been induced in a premixed gas-fired impinging circular flame jet by adding two tangential air flows to the main axial air/fuel flow. The flame jet system was considered to be small-scale and operated under low-pressure, laminar flow conditions. The effects of Reynolds number of the air/butane mixture and nozzle-to-plate distance on the heating performance of the flame were studied and compared with the heat-flux distributions on an impingement plate under different operating conditions. The whole investigation was conducted under the stoichiometric air/fuel condition (i.e., equivalence ratio, Φ = 1) with the Reynolds number being varied from 800 to 1700, and nozzle-to-plate distance being selected between 1.5 and 4.0. The introduction of swirl to small-scale, low-pressure, laminar premixed gas-fired impinging circular flame jets is the method for enhancing their thermal performances. The heat-flux distribution on the impingement plate was more uniform and the flame temperatures essentially higher when compared with a similar flame jet system without induced swirl.     

Performance evaluation of photovoltaic–thermosyphon system for subtropical climate application

The rapid development and sales volume of photovoltaic (PV) modules has created a promising business environment in the foreseeable future. However, the current electricity cost from PV is still several times higher than from the conventional power generation. One way to shorten the payback period is to bring in the hybrid photovoltaic–thermal (PVT) technology, which multiplies the energy outputs from the same collector surface area. In this paper, the performance evaluation of a new water-type PVT collector system is presented. The thermal collection making use of the thermosyphon principle eliminates the expense of pumping power. Experimental rigs were successfully built. A dynamic simulation model of the PVT collector system was developed and validated by the experimental measurements, together with two other similar models developed for PV module and solar hot-water collector. These were then used to predict the energy outputs and the payback periods for their applications in the subtropical climate, with Hong Kong as an example. The numerical results show that a payback period of 12 year for the PVT collector system is comparable to the side-by-side system, and is much shorter than the plain PV application. This is a great encouragement in marketing the PVT technology.     

Effect of clamping pressure on the performance of a PEM fuel cell

Examined were the effects of the clamping pressure on the performance of a proton exchange membrane (PEM) fuel cell. The electro-physical properties of the gas diffusion layer (GDL) such as porosity, gas permeability, electrical resistance and thickness were measured using a special-designed test rig under various clamping pressure levels. Correlations for the gas permeability of the GDL were developed in terms of the clamping pressure. In addition, the contact resistance between the GDL and the bipolar (graphite) plate was measured under various clamping pressures. Results showed that at the low clamping pressure levels (e.g. <5 bar) increasing the clamping pressure reduces the interfacial resistance between the bipolar plate and the GDL that enhances the electrochemical performance of a PEM fuel cell. In contrast, at the high clamping pressure levels (e.g. >10 bar), increasing the clamping pressure not only reduces the above Ohmic resistance but also narrows down the diffusion path for mass transfer from gas channels to the catalyst layers. Comprising the above two effects did not promote the power density too much but reduce the mass-transfer limitation for high current density.     

Effect of calcination temperature on morphology,crystallinity and electrochemical properties of nano-crystalline metal oxides (Co3O4, CuO,and NiO) prepared via ultrasonic spray pyrolysis

Nano-crystalline metal oxides (Co₃O₄, CuO, and NiO) are synthesized as anode materials for lithium-ion batteries by an ultrasonic spray pyrolysis method. The effects of calcination temperature on the morphology, crystallite size and electrochemical properties of the metal oxides are investigated. X-ray diffraction (XRD) studies show that the crystallite size varies with the final calcination temperature. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations reveal that the calcination temperature strongly influences the morphology of the prepared metal oxides and this results in different electrochemical performance. The existence of a nano-scale microstructure for the prepared metal oxides has a strong relationship with irreversible capacity and capacity retention.     

Effect of structure on porous gas-diffusion electrodes for phosphoric acid fuel cells

This investigation is concerned with the variation of structure in the catalyst layer for porous gas-diffusion electrodes. The pore-size distribution and the total pore volume of the electrode are measured by a mercury penetration method. A model that accounts for this incomplete wetting electrode is solved by an orthogonal collocation method and matched with experimental observations. The numerical solution indicates that the effectiveness factor drops noticeably under high current density when the agglomerate radius is greater than 40 μm. When the agglomerate radius is smaller than 1.2 μm, however, the effect of ionic transport becomes important. The maximum reaction rate occurs at carbon-paper/ catalyst-layer interface when the effective conductivity of the electrolyte is larger than that of the solid phase. If the effective conductivity of the electrolyte is smaller, then the maximum reaction rate occurs at the electrode/electrolyte interface.