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991.
992.
Nano Research - The contributions of the first two authors were unfortunately misrepresented on the first page and the first page of the ESM. 相似文献
993.
Ultrastretchable Conductor Fabricated on Skin‐Like Hydrogel–Elastomer Hybrid Substrates for Skin Electronics 下载免费PDF全文
Sun Hong Kim Sungmook Jung In Seon Yoon Chihak Lee Youngsu Oh Jae‐Min Hong 《Advanced materials (Deerfield Beach, Fla.)》2018,30(26)
Printing technology can be used for manufacturing stretchable electrodes, which represent essential parts of wearable devices requiring relatively high degrees of stretchability and conductivity. In this work, a strategy for fabricating printable and highly stretchable conductors are proposed by transferring printed Ag ink onto stretchable substrates comprising Ecoflex elastomer and tough hydrogel layers using a water‐soluble tape. The elastic modulus of the produced hybrid film is close to that of the hydrogel layer, since the thickness of Ecoflex elastomer film coated on hydrogel is very thin (30 µm). Moreover, the fabricated conductor on hybrid film is stretched up to 1780% strain. The described transfer method is simpler than other techniques utilizing elastomer stamps or sacrificial layers and enables application of printable electronics to the substrates with low elastic moduli (such as hydrogels). The integration of printed electronics with skin‐like low‐modulus substrates can be applied to make wearable devices more comfortable for human skin. 相似文献
994.
Sunkook Kim Jesse Maassen Jiyoul Lee Seung Min Kim Gyuchull Han Junyeon Kwon Seongin Hong Jozeph Park Na Liu Yun Chang Park Inturu Omkaram Jong‐Soo Rhyee Young Ki Hong Youngki Yoon 《Advanced materials (Deerfield Beach, Fla.)》2018,30(12)
Thin‐film transistors (TFTs) based on multilayer molybdenum diselenide (MoSe2) synthesized by modified atmospheric pressure chemical vapor deposition (APCVD) exhibit outstanding photoresponsivity (103.1 A W?1), while it is generally believed that optical response of multilayer transition metal dichalcogenides (TMDs) is significantly limited due to their indirect bandgap and inefficient photoexcitation process. Here, the fundamental origin of such a high photoresponsivity in the synthesized multilayer MoSe2 TFTs is sought. A unique structural characteristic of the APCVD‐grown MoSe2 is observed, in which interstitial Mo atoms exist between basal planes, unlike usual 2H phase TMDs. Density functional theory calculations and photoinduced transfer characteristics reveal that such interstitial Mo atoms form photoreactive electronic states in the bandgap. Models indicate that huge photoamplification is attributed to trapped holes in subgap states, resulting in a significant photovoltaic effect. In this study, the fundamental origin of high responsivity with synthetic MoSe2 phototransistors is identified, suggesting a novel route to high‐performance, multifunctional 2D material devices for future wearable sensor applications. 相似文献
995.
Efficient Solid‐State Photoluminescence of Graphene Quantum Dots Embedded in Boron Oxynitride for AC‐Electroluminescent Device 下载免费PDF全文
Minsu Park Hyewon Yoon Jaeho Lee Jungmo Kim Jinho Lee Seong‐Eui Lee Seunghyup Yoo Seokwoo Jeon 《Advanced materials (Deerfield Beach, Fla.)》2018,30(38)
Emerging graphene quantum dots (GQDs) have received much attention for use as next‐generation light‐emitting diodes. However, in the solid‐state, π‐interaction‐induced aggregation‐caused photoluminescence (PL) quenching (ACQ) in GQDs makes it challenging to realize high‐performance devices. Herein, GQDs incorporated with boron oxynitride (GQD@BNO) are prepared from a mixture of GQDs, boric acid, and urea in water via one‐step microwave heating. Due to the effective dispersion in the BNO matrix, ACQ is significantly suppressed, resulting in high PL quantum yields (PL‐QYs) of up to 36.4%, eightfold higher than that of pristine GQD in water. The PL‐QY enhancement results from an increase in the spontaneous emission rate of GQDs due to the surrounding BNO matrix, which provides a high‐refractive‐index material and fluorescence energy transfer from the larger‐gap BNO donor to the smaller‐gap GQD acceptor. A high solid‐state PL‐QY makes the GQD@BNO an ideal active material for use in AC powder electroluminescent (ACPEL) devices, with the luminance of the first working GQD‐based ACPEL device exceeding 283 cd m?2. This successful demonstration shows promise for the use of GQDs in the field of low‐cost, ecofriendly electroluminescent devices. 相似文献
996.
Donghun Lee Haeli Park Soo Deok Han Su Han Kim Woong Huh Jae Yoon Lee Yoon Seok Kim Myung Jin Park Won Il Park Chong‐Yun Kang Chul‐Ho Lee 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(2)
Ultralow power chemical sensing is essential toward realizing the Internet of Things. However, electrically driven sensors must consume power to generate an electrical readout. Here, a different class of self‐powered chemical sensing platform based on unconventional photovoltaic heterojunctions consisting of a top graphene (Gr) layer in contact with underlying photoactive semiconductors including bulk silicon and layered transition metal dichalcogenides is proposed. Owing to the chemically tunable electrochemical potential of Gr, the built‐in potential at the junction is effectively modulated by absorbed gas molecules in a predictable manner depending on their redox characteristics. Such ability distinctive from bulk photovoltaic counterparts enables photovoltaic‐driven chemical sensing without electric power consumption. Furthermore, it is demonstrated that the hydrogen (H2) sensing properties are independent of the light intensity, but sensitive to the gas concentration down to the 1 ppm level at room temperature. These results present an innovative strategy to realize extremely energy‐efficient sensors, providing an important advancement for future ubiquitous sensing. 相似文献
997.
Jeong-Hoon Song Yao Fu Tae-Yeon Kim Yeong-Cheol Yoon John G. Michopoulos Timon Rabczuk 《International Journal of Mechanics and Materials in Design》2018,14(4):491-509
This paper presents the development of a strong form-based collocation method called the particle difference method (PDM), capable of predicting the spatiotemporal evolution of polycrystalline material solidification through coupling of multi-phase and temperature fields. Cross coupled phase field evolution and heat transfer equations are discretized via the PDM to obtain the interface kinematics of polycrystalline boundary during solidification. A distinct feature of the PDM is its ability to represent derivative operators via a moving least-square approximation of the Taylor expansion through point-wise computations at collocation points. The method discretizes directly the strong forms using the pre-computed derivative operators at each collocation point and elegantly overcomes the topological difficulty in modeling intricate moving interfaces. To verify the efficacy of the PDM, numerical results are compared with those obtained from the conventional finite difference method for uniform and irregular distributions of the collocation points. The scalability of the parallelized PDM is tested by measuring its efficiency with increasing the number of processors. We also provide a solidification simulation with two ellipsoidal inclusions to demonstrate the capability of the PDM in complex moving interface problems with high curvature. 相似文献
998.
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
999.
Se Youn Cho Minjee Kang Jaewon Choi Min Eui Lee Hyeon Ji Yoon Hae Jin Kim Cecilia Leal Sungho Lee Hyoung‐Joon Jin Young Soo Yun 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(17)
Na‐ion cointercalation in the graphite host structure in a glyme‐based electrolyte represents a new possibility for using carbon‐based materials (CMs) as anodes for Na‐ion storage. However, local microstructures and nanoscale morphological features in CMs affect their electrochemical performances; they require intensive studies to achieve high levels of Na‐ion storage performances. Here, pyrolytic carbon nanosheets (PCNs) composed of multitudinous graphitic nanocrystals are prepared from renewable bioresources by heating. In particular, PCN‐2800 prepared by heating at 2800 °C has a distinctive sp2 carbon bonding nature, crystalline domain size of ≈44.2 Å, and high electrical conductivity of ≈320 S cm?1, presenting significantly high rate capability at 600 C (60 A g?1) and stable cycling behaviors over 40 000 cycles as an anode for Na‐ion storage. The results of this study show the unusual graphitization behaviors of a char‐type carbon precursor and exceptionally high rate and cycling performances of the resulting graphitic material, PCN‐2800, even surpassing those of supercapacitors. 相似文献
1000.
The incremental Virtual Fields Method and prestretching method applied to rubbers under uniaxial medium‐strain‐rate loading 下载免费PDF全文
Conventional dynamic experiments on rubbers have several limitations including low signal‐to‐noise ratio and a long time period during which the specimen is not in static equilibrium, which causes difficulties separating constitutive material behaviour from specimen response. In order to overcome these limitations, we build on previous research in which the Virtual Fields Method (VFM) is applied to dynamic tensile experiments. A previous study has demonstrated that the VFM can be used to identify the material parameters of a hyperelastic model for a given rubber based on optical measurements of wave propagation in the rubber, eliminating the need for force measurements by instead using acceleration fields as a “virtual load cell.” In order for us to successfully characterise the strain hardening in the material, large deformations are required, and these were achieved by applying static preloads to the specimen before the dynamic loading. In order for us to then apply the VFM, measurements of the static force, or strain, or both, are required. This paper explores different methods for applying the VFM, in particular, comparing the use of a static force measurement, as in the previous research, to methods that only require strain fields in order to apply the incremental equation of motion. Finite element method simulations were conducted to compare the identification sensitivity to experimental error sources between the 2 VFM implementations; the experimental data used in the previous studies were then applied to the incremental VFM. A further experimental comparison is provided between constitutive parameters obtained in tensile experiments using the VFM and compressive measurements from a modified split Hopkinson bar technique equipped with a piezoelectric force transducer. Finally, there is a discussion of the effects of preloading and relaxation in the material. 相似文献