Such future soft wearable electronics or wearable 2.0 products [8] will not be viable unless efficient reliable and skin-conformal power sources are to be developed. Most of the current wearable electronics are powered by rigid and bulky lithium-ion battery. Although paper batteries are emerging as a thinner version candidate, [9] they are still based on conventional metallic materials, which are neither stretchable nor compressive, unable to conformally be attached onto human skin. Typical smart soft electronics including wearable glucose sensors, pressure sensors, and surface electromyography (sEMG) only require a voltage of <100 mV and a power consumption of <20 µW, which could be supplied by different types of energy devices. [10] In this context, a variety of soft energy devices based on nanomaterials including batteries, [11] supercapacitors, [12,13] solar cells, [14] triboelectric nanogenerators, [15] and fuel cells [16-18] have attracted tremendous attention as the potential replacement of the lithium-ion battery to power skin-like electronics. Each type of those energy devices has their own intrinsic pros and cons. Wearable supercapacitors cannot provide continuous long-term energy supplies; [12,13] the performance of wearable photovoltaic devices is highly dependent on the external light source; [14] and the wearable nanogenerators based on piezoelectric and triboelectric devices can only provide intermittent energy and must be integrated with energy storage devices for continuous long-term monitoring. [15] Stretchable enzymatic biofuel cell that uses glucose or lactic acid in the body fluid to generate energy has been considered as an environmentally friendly power source for the next-generation skin-like energy devices. However, its performance is largely dependent on the stability of the enzyme, which may be easily affected by body temperature, pH, and fuel concentrations. [19,20] In contrast, fuel cells that use ethanol or methanol as a model system could offer a much higher power density and stability as they are not influenced by the biological environments. [21] A number of materials including silver nanowires, [22] carbon fibers, [23] graphene paper, [24] nickel foam, [25] vertically aligned gold nanowires (V-AuNWs) [26] have been demonstrated to fabricate flexible or even stretchable fuel cells. Nevertheless, high power output, skin-like device thickness, Skin-like energy devices can be conformally attached to the human body, which are highly desirable to power soft wearable electronics in the future. Here, a skin-like stretchable fuel cell based on ultrathin gold nanowires (AuNWs) and polymerized high internal phase emulsions (polyHIPEs) scaffolds is demonstrated. The polyHIPEs can offer a high porosity of 80% yet with an overall thickness comparable to human skin. Upon impregnation with electronic inks containing ultrathin (2 nm in diameter) and ultrahigh aspect-ratio (>10 000) gold nanowires, skin-like strain-insensitive stretchable electrodes are successfully fabricated. With such designed ...
We have designed and synthesized a series of Schiff base derivatives, and studied their structural features in two-dimensional (2D) and three-dimensional (3D) states by combining scanning tunneling microscopy (STM) and X-ray diffraction experiments. The Schiff-base derivatives with short alkyl chains crystallize easily, which allows a detailed structural analysis by X-ray diffraction. Due to the strong adsorbate-substrate interactions, those bases with long alkyl chains easily form 2D assemblies on highly oriented pyrolytic graphite (HOPG). The STM images indicate also that the introduction of two methoxy groups into the molecule can change the structure of these 2D assemblies as a result of the increased steric hindrances, for example: the Schiff-base derivative, bearing both methoxy groups and C16H33 tails, forms 2D Moiré patterns, and an alignment of pairing Schiff-base molecules may be easily resolved. Conversely, the Schiff base derivative, bearing solely C16H33 tails, forms 2D non-Moiré patterns. It is demonstrated that the 3D structural features result from the compromise of intermolecular interactions of different molecular moieties. However, there is one more factor, which also governs the 2D structure: the adsorbate-substrate interaction. The 3D crystal structure may thus help to understand many factors involved in the formation of 2D structures, and would be helpful for designing new molecular assemblies with tailoring functions.
Understanding crystallization and its correlations with liquid dynamics is relevant for developing robust amorphous pharmaceutical solids. Herein, nimesulide, a classical anti-inflammatory agent, was used as a model system for studying the correlations between crystallization kinetics and molecular dynamics. Kinetic parts of crystal growth (ukin) of nimesulide exhibited a power law dependence upon the liquid viscosity (η) as ukin~η−0.61. Bulk molecular diffusivities (DBulk) of nimesulide were predicted by a force-level statistical–mechanical model from the α-relaxation times, which revealed the relationship as ukin~Dbulk0.65. Bulk crystal growth kinetics of nimesulide in deeply supercooled liquid exhibited a fragility-dependent decoupling from τα. The correlations between growth kinetics and α-relaxation times predicted by the Adam–Gibbs–Vogel equation in a glassy state were also explored, for both the freshly made and fully equilibrated glass. These findings are relevant for the in-depth understanding and prediction of the physical stability of amorphous pharmaceutical solids.
We report here a simple and cost-effective autologous growth method to prepare a NiFe-based integrated electrode for efficient electrocatalytic water oxidation.
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