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991.
Efficient Hydrogen Evolution Reaction Catalysis in Alkaline Media by All‐in‐One MoS2 with Multifunctional Active Sites 下载免费PDF全文
Mohsin Ali Raza Anjum Hu Young Jeong Min Hee Lee Hyeon Suk Shin Jae Sung Lee 《Advanced materials (Deerfield Beach, Fla.)》2018,30(20)
MoS2 becomes an efficient and durable nonprecious‐metal electrocatalyst for the hydrogen evolution reaction (HER) when it contains multifunctional active sites for water splitting derived from 1T‐phase, defects, S vacancies, exposed Mo edges with expanded interlayer spacings. In contrast to previously reported MoS2‐based catalysts targeting only a single or few of these characteristics, the all‐in‐one MoS2 catalyst prepared herein features all of the above active site types. During synthesis, the intercalation of in situ generated NH3 molecules into MoS2 sheets affords ammoniated MoS2 (A‐MoS2) that predominantly comprises 1T‐MoS2 and exhibits an expanded interlayer spacing. The subsequent reduction of A‐MoS2 results in the removal of intercalated NH3 and H2S to form an all‐in‐one MoS2 with multifunctional active sites mentioned above (R‐MoS2) that exhibits electrocatalytic HER performance in alkaline media superior to those of all previously reported MoS2‐based electrocatalysts. In particular, a hybrid MoS2/nickel foam catalyst outperforms commercial Pt/C in the practically meaningful high‐current region (>25 mA cm?2), demonstrating that R‐MoS2‐based materials can potentially replace Pt catalysts in practical alkaline HER systems. 相似文献
992.
Natural double‐layered structures observed in living organisms are known to exhibit asymmetric volume changes with environmental triggers. Typical examples are natural roots of plants, which show unique self‐organized bending behavior in response to environmental stimuli. Herein, light‐ and electro‐active polymer (LEAP) based actuators with a double‐layered structure are reported. The LEAP actuators exhibit an improvement of 250% in displacement and hold an object three times heavier as compared to that in the case of conventional electro‐active polymer actuators. Most interestingly, the bending motion of the LEAP actuators can be effectively locked for a few tens of minutes even in the absence of a power supply. Further, the self‐locking LEAP actuators show a large and reversible bending strain of more than 2.0% and require only 6.2 mW h cm?2 of energy to hold an object for 15 min at an operating voltage of 3 V. These novel self‐locking soft actuators should find wide applicability in artificial muscles, biomedical microdevices, and various innovative soft robot technologies. 相似文献
993.
Nondestructive Real‐Time Monitoring of Enhanced Stem Cell Differentiation Using a Graphene‐Au Hybrid Nanoelectrode Array 下载免费PDF全文
Jin‐Ho Lee Hye Kyu Choi Letao Yang Sy‐Tsong Dean Chueng Jeong‐Woo Choi Ki‐Bum Lee 《Advanced materials (Deerfield Beach, Fla.)》2018,30(39)
Stem cells have attracted increasing research interest in the field of regenerative medicine because of their unique ability to differentiate into multiple cell lineages. However, controlling stem cell differentiation efficiently and improving the current destructive characterization methods for monitoring stem cell differentiation are the critical issues. To this end, multifunctional graphene–gold (Au) hybrid nanoelectrode arrays (NEAs) to: (i) investigate the effects of combinatorial physicochemical cues on stem cell differentiation, (ii) enhance stem cell differentiation efficiency through biophysical cues, and (iii) characterize stem cell differentiation in a nondestructive real‐time manner are developed. Through the synergistic effects of physiochemical properties of graphene and biophysical cues from nanoarrays, the graphene‐Au hybrid NEAs facilitate highly enhanced cell adhesion and spreading behaviors. In addition, by varying the dimensions of the graphene‐Au hybrid NEAs, improved stem cell differentiation efficiency, resulting from the increased focal adhesion signal, is shown. Furthermore, graphene‐Au hybrid NEAs are utilized to monitor osteogenic differentiation of stem cells electrochemically in a nondestructive real‐time manner. Collectively, it is believed the unique multifunctional graphene‐Au hybrid NEAs can significantly advance stem‐cell‐based biomedical applications. 相似文献
994.
Light‐Emitting Diodes: Monolithic Flexible Vertical GaN Light‐Emitting Diodes for a Transparent Wireless Brain Optical Stimulator (Adv. Mater. 28/2018) 下载免费PDF全文
995.
Carrier Dynamics: Transient SHG Imaging on Ultrafast Carrier Dynamics of MoS2 Nanosheets (Adv. Mater. 14/2018) 下载免费PDF全文
996.
Gi Dae Park Jeong Hoo Hong Jae Hun Choi Jong‐Heun Lee Yang Soo Kim Yun Chan Kang 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(24)
Multicomponent materials with various double cations have been studied as anode materials of lithium‐ion batteries (LIBs). Heterostructures formed by coupling different‐bandgap nanocrystals enhance the surface reaction kinetics and facilitate charge transport because of the internal electric field at the heterointerface. Accordingly, metal selenites can be considered efficient anode materials of LIBs because they transform into metal selenide and oxide nanocrystals in the first cycle. However, few studies have reported synthesis of uniquely structured metal selenite microspheres. Herein, synthesis of high‐porosity CoSeO3 microspheres is reported. Through one‐pot oxidation at 400 °C, CoSex–C microspheres formed by spray pyrolysis transform into CoSeO3 microspheres showing unordinary cycling and rate performances. The conversion mechanism of CoSeO3 microspheres for lithium‐ion storage is systematically studied by cyclic voltammetry, in situ X‐ray diffraction and electrochemical impedance spectroscopy, and transmission electron microscopy. The reversible reaction mechanism of the CoSeO3 phase from the second cycle onward is evaluated as CoO + xSeO2 + (1 ? x)Se + 4(x + 1)Li++ 4( x + 1)e? ? Co + (2x + 1)Li2O + Li2Se. The CoSeO3 microspheres show a high reversible capacity of 709 mA h g?1 for the 1400th cycle at a current density of 3 A g?1 and a high reversible capacity of 526 mA h g?1 even at an extremely high current density of 30 A g?1. 相似文献
997.
A desirability function method for optimizing mean and variability of multiple responses using a posterior preference articulation approach 下载免费PDF全文
Dong‐Hee Lee In‐Jun Jeong Kwang‐Jae Kim 《Quality and Reliability Engineering International》2018,34(3):360-376
A desirability function approach has been widely used in multi‐response optimization due to its simplicity. Most of the existing desirability function‐based methods assume that the variability of the response variables is stable; thus, they focus mainly on the optimization of the mean of multiple responses. However, this stable variability assumption often does not apply in practical situations; thus, the quality of the product or process can be severely degraded due to the high variability of multiple responses. In this regard, we propose a new desirability function method to simultaneously optimize both the mean and variability of multiple responses. In particular, the proposed method uses a posterior preference articulation approach, which has an advantage in investigating tradeoffs between the mean and variability of multiple responses. It is expected that process engineers can use this method to better understand the tradeoffs, thereby obtaining a satisfactory compromise solution. 相似文献
998.
Miniaturized,Battery‐Free Optofluidic Systems with Potential for Wireless Pharmacology and Optogenetics 下载免费PDF全文
Kyung Nim Noh Sung Il Park Raza Qazi Zhanan Zou Aaron D. Mickle Jose G. Grajales‐Reyes Kyung‐In Jang Robert W. Gereau IV Jianliang Xiao John A. Rogers Jae‐Woong Jeong 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(4)
Combination of optogenetics and pharmacology represents a unique approach to dissect neural circuitry with high specificity and versatility. However, conventional tools available to perform these experiments, such as optical fibers and metal cannula, are limited due to their tethered operation and lack of biomechanical compatibility. To address these issues, a miniaturized, battery‐free, soft optofluidic system that can provide wireless drug delivery and optical stimulation for spatiotemporal control of the targeted neural circuit in freely behaving animals is reported. The device integrates microscale inorganic light‐emitting diodes and microfluidic drug delivery systems with a tiny stretchable multichannel radiofrequency antenna, which not only eliminates the need for bulky batteries but also offers fully wireless, independent control of light and fluid delivery. This design enables a miniature (125 mm3), lightweight (220 mg), soft, and flexible platform, thus facilitating seamless implantation and operation in the body without causing disturbance of naturalistic behavior. The proof‐of‐principle experiments and analytical studies validate the feasibility and reliability of the fully implantable optofluidic systems for use in freely moving animals, demonstrating its potential for wireless in vivo pharmacology and optogenetics. 相似文献
999.
Asymmetric Fullerene Nanosurfactant: Interface Engineering for Automatic Molecular Alignments 下载免费PDF全文
Dae‐Yoon Kim Sang‐A Lee Soeun Kim Changwoon Nah Seung Hee Lee Kwang‐Un Jeong 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(1)
Since the molecular self‐assembly of nanomaterials is sensitive to their surface properties, the molecular packing structure on the surface is essential to build the desired chemical and physical properties of nanomaterials. Here, a new nanosurfactant is proposed for the automatic construction of macroscopic surface alignment layer for liquid crystal (LC) molecules. An asymmetric nanosurfactant (C60NS) consisted of mesogenic cyanobiphenyl moieties with flexible alkyl chains and a [60]fullerene nanoatom is newly designed and precisely synthesized. The C60NS directly introduced in the anisotropic LC medium is self‐assembled into the monolayered protrusions on the surface because of its amphiphilic nature originated by asymmetrically programmed structural motif of LC‐favoring moieties and LC‐repelling groups. The monolayered protrusions constructed by the phase‐separation and self‐assembly of asymmetric C60NS nanosurfactant in the anisotropic LC media amplify and transfer the molecular orientational order from surface to bulk, and finally create the automatic vertical molecular alignment on the macroscopic length scale. The asymmetric C60NS nanosurfactant and its self‐assembly described herein can offer the direct guideline of interface engineering for the automatic molecular alignments. 相似文献
1000.
Super‐Absorbent Polymer Valves and Colorimetric Chemistries for Time‐Sequenced Discrete Sampling and Chloride Analysis of Sweat via Skin‐Mounted Soft Microfluidics 下载免费PDF全文
Sung Bong Kim Yi Zhang Sang Min Won Amay J. Bandodkar Yurina Sekine Yeguang Xue Jahyun Koo Sean W. Harshman Jennifer A. Martin Jeong Min Park Tyler R. Ray Kaitlyn E. Crawford Kyu‐Tae Lee Jungil Choi Rhonda L. Pitsch Claude C. Grigsby Adam J. Strang Yu‐Yu Chen Shuai Xu Jeonghyun Kim Ahyeon Koh Jeong Sook Ha Yonggang Huang Seung Wook Kim John A. Rogers 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(12)
This paper introduces super absorbent polymer valves and colorimetric sensing reagents as enabling components of soft, skin‐mounted microfluidic devices designed to capture, store, and chemically analyze sweat released from eccrine glands. The valving technology enables robust means for guiding the flow of sweat from an inlet location into a collection of isolated reservoirs, in a well‐defined sequence. Analysis in these reservoirs involves a color responsive indicator of chloride concentration with a formulation tailored to offer stable operation with sensitivity optimized for the relevant physiological range. Evaluations on human subjects with comparisons against ex situ analysis illustrate the practical utility of these advances. 相似文献