Publications by authors named "Chaoyi Yan"

42 Publications

Disintegrable, transparent and mechanically robust high-performance antimony tin oxide/nanocellulose/polyvinyl alcohol thermal insulation films.

Carbohydr Polym 2021 Aug 7;266:118175. Epub 2021 May 7.

State Key Lab of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, China. Electronic address:

Polymer-based thermal insulation films are widely utilized to reduce the influence of solar radiation. However, current thermal insulation films face several challenges from poor thermal insulation performance and severe environmental pollution, which are caused by the non-disintegratability of polymer substrates. Here, cellulose nanofiber (CNF)/antimony tin oxide (ATO) hybrid films with and without polyvinyl alcohol (PVA) are presented and they can be used as window thermal barrier films and personal thermal management textiles. The hybrid films exhibit prominent thermal insulation performance, blocking 91.07% ultraviolet(UV) light, reflecting 95.19% near-infrared(NIR) light, and transmitting 44.89% visible(VIS) light. Meanwhile, the hybrid films demonstrate high thermal stability, high anti-UV aging stability, and robust mechanical properties. Moreover, the used-up hybrid films based on natural cellulose are of high disintegratability and recyclability. Our present work is anticipated to open up a new avenue for the fabrication of next-generation high-performance thermal insulation films with sustainable and environmentally friendly processes.
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http://dx.doi.org/10.1016/j.carbpol.2021.118175DOI Listing
August 2021

Record-Low Subthreshold-Swing Negative-Capacitance 2D Field-Effect Transistors.

Adv Mater 2020 Nov 12;32(46):e2005353. Epub 2020 Oct 12.

State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China.

Power consumption is one of the most challenging bottlenecks for complementary metal-oxide-semiconductor integration. Negative-capacitance field-effect transistors (NC-FETs) offer a promising platform to break the thermionic limit defined by the Boltzmann tyranny and architect energy-efficient devices. However, it is a great challenge to achieving ultralow-subthreshold-swing (SS) (10 mV dec ) and small-hysteresis NC-FETs simultaneously at room temperature, which has only been reported using the hafnium zirconium oxide system. Here, based on a ferroelectric LiNbO thin film with great spontaneous polarization, an ultralow-SS NC-FET with small hysteresis is designed. The LiNbO NC-FET platform exhibits a record-low SS of 4.97 mV dec with great repeatability due to the superior capacitance matching characteristic as evidenced by the negative differential resistance phenomenon. By modulating the structure and operating parameters (such as channel length (L ), drain-sourse bias (V ), and gate bias (V )) of devices, an optimized SS from ≈40 to ≈10 mV dec and hysteresis from ≈900 to ≈60 mV are achieved simultaneously. The results provide a new potential method for future highly integrated electronic and optical integrated energy-efficient devices.
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http://dx.doi.org/10.1002/adma.202005353DOI Listing
November 2020

Highly Thermally Stable, Green Solvent Disintegrable, and Recyclable Polymer Substrates for Flexible Electronics.

Macromol Rapid Commun 2020 Oct 24;41(19):e2000292. Epub 2020 Aug 24.

State Key Lab of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510640, China.

Flexible electronics require its substrate to have adequate thermal stability, but current thermally stable polymer substrates are difficult to be disintegrated and recycled; hence, generate enormous electronic solid waste. Here, a thermally stable and green solvent-disintegrable polymer substrate is developed for flexible electronics to promote their recyclability and reduce solid waste generation. Thanks to the proper design of rigid backbones and rational adjustments of polar and bulky side groups, the polymer substrate exhibits excellent thermal and mechanical properties with thermal decomposition temperature (T ) of 430 °C, upper operating temperature of over 300 °C, coefficient of thermal expansion of 48 ppm K , tensile strength of 103 MPa, and elastic modulus of 2.49 GPa. Furthermore, the substrate illustrates outstanding optical and dielectric properties with high transmittance of 91% and a low dielectric constant of 2.30. Additionally, it demonstrates remarkable chemical and flame resistance. A proof-of-concept flexible printed circuit device is fabricated with this substrate, which demonstrates outstanding mechanical-electrical stability. Most importantly, the substrate can be quickly disintegrated and recycled with alcohol. With outstanding thermally stable properties, accompanied by excellent recyclability, the substrate is particularly attractive for a wide range of electronics to reduce solid waste generation, and head toward flexible and "green" electronics.
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http://dx.doi.org/10.1002/marc.202000292DOI Listing
October 2020

Ultrabroadband Photodetectors up to 10.6 µm Based on 2D Fe O Nanosheets.

Adv Mater 2020 Jun 13;32(25):e2002237. Epub 2020 May 13.

State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China.

The ultrabroadband spectrum detection from ultraviolet (UV) to long-wavelength infrared (LWIR) is promising for diversified optoelectronic applications of imaging, sensing, and communication. However, the current LWIR-detecting devices suffer from low photoresponsivity, high cost, and cryogenic environment. Herein, a high-performance ultrabroadband photodetector is demonstrated with detecting range from UV to LWIR based on air-stable nonlayered ultrathin Fe O nanosheets synthesized via a space-confined chemical vapor deposition (CVD) method. Ultrahigh photoresponsivity (R) of 561.2 A W , external quantum efficiency (EQE) of 6.6 × 10 %, and detectivity (D*) of 7.42 × 10 Jones are achieved at the wavelength of 10.6 µm. The multimechanism synergistic effect of photoconductive effect and bolometric effect demonstrates the high sensitivity for light with any light intensities. The outstanding device performance and complementary mixing photoresponse mechanisms open up new potential applications of nonlayered 2D materials for future infrared optoelectronic devices.
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http://dx.doi.org/10.1002/adma.202002237DOI Listing
June 2020

Multicolored Cathodically Coloring Electrochromism and Electrofluorochromism in Regioisomeric Star-Shaped Carbazole Dibenzofurans.

ACS Appl Mater Interfaces 2020 May 12;12(21):24156-24164. Epub 2020 May 12.

School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China.

In this work, a series of fluorescent cathodically coloring electrochromic (EC) small molecules , , and with 3,5-di(9-carbazol-9-yl)benzene (DCz) linked to dibenzofuran (DBF) at different substitutional positions were synthesized and fully characterized. These compounds are electroactive and undergo quasi-reversible two-step single-electron reduction generating radical anions and dianions. The absorptions of , , and in the neutral states lie in the UV region (λ ≈ 350 nm), showing high transparency, while the absorption of their reduced states can be largely tuned across the visible region through driving voltage and substitutional positions. Initially generated spectroelectrochemically radical anions show absorption in the short-wavelength region of ∼380-500 nm with weak broad absorptions at longer wavelengths. On further reduction, these bands disappear on the cost of growing intense bands from dianions at longer wavelengths of 500-700 nm with some tail absorptions in the shorter-wavelength region. This renders the colors of the EC devices based on these materials, which are changed from green to red, yellow to magenta, and light to deep blue for , , and , respectively, covering four legs of the *** color space. Besides excellent optical contrast (>90%) and high coloration efficiency (up to 504 cm C), the fluorescence observed in solution of neutral , , and can be modulated between the fluorescence and quenched states by direct electrochemical redox reactions. Both EC and electrofluorochromic (EFC) processes are reversible on cycling. This research demonstrates the feasibility of developing multifunctional EC/EFC materials with multicolored electrochromism through exploiting electrochemical properties of traditional fluorescent small molecules.
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http://dx.doi.org/10.1021/acsami.0c00883DOI Listing
May 2020

Trifluoromethyl Group-Modified Non-Fullerene Acceptor toward Improved Power Conversion Efficiency over 13% in Polymer Solar Cells.

ACS Appl Mater Interfaces 2020 Mar 28;12(10):11543-11550. Epub 2020 Feb 28.

School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China.

Herein, we report a new molecule structure modification strategy for non-fullerene small-molecule electron acceptors (NFAs) for solar cells through trifluoromethylation of end-capping groups. The synthesized trifluoromethylated acceptor ITCF3 exhibits narrower band gap, stronger light absorption, lower molecular energy levels, and better electron transport property compared to the reference NFA without the trifluoromethyl group (ITIC). Bulk heterojunction solar cells based on ITCF3 combined with the PM6 polymer donor exhibit a significantly improved power conversion efficiency of 13.3% compared with the ITIC-based device (8.4%). This work reveals great potential of trifluoromethylation in the design of efficient photovoltaic acceptor materials.
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http://dx.doi.org/10.1021/acsami.9b20544DOI Listing
March 2020

Self-Confined Growth of Ultrathin 2D Nonlayered Wide-Bandgap Semiconductor CuBr Flakes.

Adv Mater 2019 Sep 24;31(36):e1903580. Epub 2019 Jul 24.

State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China.

2D planar structures of nonlayered wide-bandgap semiconductors enable distinguished electronic properties, desirable short wavelength emission, and facile construction of 2D heterojunction without lattice match. However, the growth of ultrathin 2D nonlayered materials is limited by their strong covalent bonded nature. Herein, the synthesis of ultrathin 2D nonlayered CuBr nanosheets with a thickness of about 0.91 nm and an edge size of 45 µm via a controllable self-confined chemical vapor deposition method is described. The enhanced spin-triplet exciton (Z , 2.98 eV) luminescence and polarization-enhanced second-harmonic generation based on the 2D CuBr flakes demonstrate the potential of short-wavelength luminescent applications. Solar-blind and self-driven ultraviolet (UV) photodetectors based on the as-synthesized 2D CuBr flakes exhibit a high photoresponsivity of 3.17 A W , an external quantum efficiency of 1126%, and a detectivity (D*) of 1.4 × 10 Jones, accompanied by a fast rise time of 32 ms and a decay time of 48 ms. The unique nonlayered structure and novel optical properties of the 2D CuBr flakes, together with their controllable growth, make them a highly promising candidate for future applications in short-wavelength light-emitting devices, nonlinear optical devices, and UV photodetectors.
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http://dx.doi.org/10.1002/adma.201903580DOI Listing
September 2019

SnS hollow nanofibers as anode materials for sodium-ion batteries with high capacity and ultra-long cycling stability.

Chem Commun (Camb) 2019 Jan;55(4):505-508

Key Laboratory of Textile Science and Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, 201620, China.

In this study, a novel anode material of SnS hollow nanofibers (SnS HNFs) was rationally synthesized by a facile process and demonstrated to be a promising anode candidate for sodium-ion batteries. The synergetic effect of unique hollow and porous microstructures of SnS HNFs led to high capacity and ultra-long cycling stability.
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http://dx.doi.org/10.1039/c8cc07332eDOI Listing
January 2019

Electrospun Kraft Lignin/Cellulose Acetate-Derived Nanocarbon Network as an Anode for High-Performance Sodium-Ion Batteries.

ACS Appl Mater Interfaces 2018 Dec 14;10(51):44368-44375. Epub 2018 Dec 14.

Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science , North Carolina State University , Raleigh , North Carolina 27695-8301 , United States.

An innovative nanocarbon network material was synthesized from electrospun kraft lignin and cellulose acetate blend nanofibers after carbonization at 1000 °C in a nitrogen atmosphere, and its electrochemical performance was evaluated as an anode material in sodium-ion batteries. Apart from its unique network architecture, introduced carbon material possesses high oxygen content of 13.26%, wide interplanar spacing of 0.384 nm, and large specific surface area of 540.95 m·g. The electrochemical test results demonstrate that this new nanocarbon network structure delivers a reversible capacity of 340 mA h·g at a current density of 50 mA·g after 200 cycles and exhibits a high rate capacity by delivering a capacity of 103 mA h·g at an increased current density of 400 mA·g. The present work rendered an innovative approach for preparing nanocarbon materials for energy-storage applications and could open up new avenues for novel nanocarbon fabrication from green and environmentally friendly raw materials.
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http://dx.doi.org/10.1021/acsami.8b13033DOI Listing
December 2018

Carbon-enhanced centrifugally-spun SnSb/carbon microfiber composite as advanced anode material for sodium-ion battery.

J Colloid Interface Sci 2019 Feb 30;536:655-663. Epub 2018 Oct 30.

Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, College of Textiles, North Carolina State University, Raleigh, NC 27695-8301, USA. Electronic address:

Antimony tin (SnSb) based materials have become increasingly attractive as a potential anode material for sodium-ion batteries (SIBs) owing to their prominent merit of high capacity. However, cyclic stability and rate capability of SnSb anodes are currently hindered by their large volume change during repeated cycling, which results in severe capacity fading. Herein, we introduce carbon-coated centrifugally-spun [email protected] microfiber (CMF) composites as high-performance anodes for SIBs that can maintain their structural stability during repeated charge-discharge cycles. The centrifugal spinning method was performed to fabricate [email protected] due to its high speed, low cost, and large-scale fabrication features. More importantly, extra carbon coating by chemical vapor deposition (CVD) has been demonstrated as an effective method to improve the capacity retention and Coulombic efficiency of the [email protected] anode. Electrochemical test results indicated that the as-prepared [email protected]@C anode could deliver a large reversible capacity of 798 mA h∙g at the 20th cycle as well as a high capacity retention of 86.8% and excellent Coulombic efficiency of 98.1% at the 100th cycle. It is, therefore, demonstrated that [email protected]@C composite is a promising anode material candidate for future high-performance SIBs.
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http://dx.doi.org/10.1016/j.jcis.2018.10.101DOI Listing
February 2019

Modulating Electronic Structures of Inorganic Nanomaterials for Efficient Electrocatalytic Water Splitting.

Angew Chem Int Ed Engl 2019 Mar 4;58(14):4484-4502. Epub 2019 Feb 4.

State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China.

Electrocatalytic water splitting is one of the most promising sustainable energy conversion technologies, but is limited by the sluggish electrochemical reactions. Inorganic nanomaterials have been widely used as efficient catalysts for promoting the electrochemical kinetics. Several approaches to optimize the activities of these nanocatalysts have been developed. The electronic structures of the catalysts play a pivotal role in governing the activity and thus have been identified as an essential descriptor. However, the underlying working mechanisms related to the refined electronic structures remain elusive. To establish the structure-electronic-behavior-activity relationship, a comprehensive overview of the developed strategies to regulate the electronic structures is presented, emphasizing the surface modification, strain, phase transition, and heterostructure. Current challenges to the fundamental understanding of electron behaviors in the nanocatalysts are fully discussed.
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http://dx.doi.org/10.1002/anie.201810104DOI Listing
March 2019

High-Performance SERS Substrate Based on Hierarchical 3D Cu Nanocrystals with Efficient Morphology Control.

Small 2018 09 26;14(38):e1802477. Epub 2018 Aug 26.

State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China.

Cu nanocrystals of various shapes are synthesized via a universal, eco-friendly, and facile colloidal method on Al substrates using hexadecylamine (HDA) as a capping agent and glucose as a reductant. By tuning the concentration of the capping agent, hierarchical 3D Cu nanocrystals show pronounced surface-enhanced Raman scattering (SERS) through the concentrated hot spots at the sharp tips and gaps due to the unique 3D structure and the resulting plasmonic couplings. Intriguingly, 3D sword-shaped Cu crystals have the highest enhancement factor (EF) because of their relatively uniform size distribution and alignment. This work opens new pathways for efficiently realizing morphology control for Cu nanocrystals as highly efficient SERS platforms.
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http://dx.doi.org/10.1002/smll.201802477DOI Listing
September 2018

Cytomembrane-Structure-Inspired Active Ni-N-O Interface for Enhanced Oxygen Evolution Reaction.

Adv Mater 2018 Sep 22;30(39):e1803367. Epub 2018 Aug 22.

State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China.

Surface/interface design is one of the most significant and promising motivations to develop high-performance catalysts for electrolytic water splitting. Here, the nature of cytomembrane having the most effective and functional surface structure is mimicked to fabricate a new configuration of Ni-N-O porous interface nanoparticles (NiNO INPs) with strongly interacting nanointerface between the Ni N and NiO domains, for enhancing the electrocatalytic oxygen evolution reaction (OER) performance. The combination of transmission electron microscopy and electrochemical investigations, tracking the correlation between microstructure evolution and catalytic activity, demonstrate the strongly coupled nanointerface for an approximately sixfold improvement of electrolytic efficiency. Density functional theory simulates the electrocatalytic process with a maximum of 85% reduction of the energy barrier. Further investigations find that the real active site for the OER in the NiNO INPs is the strongly coupled Ni-N-O nanointerface, not the derived amorphous hydroxide, during the OER process. The determination of the correlation of constructed nanointerface with catalytic properties suggests a significant strategy toward the rational design of catalysts for efficient water electrocatalysis.
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http://dx.doi.org/10.1002/adma.201803367DOI Listing
September 2018

Self-Assembly-Assisted Facile Synthesis of MoS-Based Hybrid Tubular Nanostructures for Efficient Bifunctional Electrocatalysis.

ACS Appl Mater Interfaces 2018 Jul 6;10(28):23731-23739. Epub 2018 Jul 6.

School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore.

In this work, MoS-based hybrid tubular nanostructures are facilely synthesized via a self-assembly-assisted process and evaluated as a bifunctional electrocatalyst for hydrogen evolution reactions (HERs) and oxygen reduction reactions (ORRs). By simply mixing the reactants under ambient conditions, (NH)MoS/polydopamine (PDA) hybrid nanospheres are formed. The protonated dopamine is linked to tetrahedral [MoS] via weak N-H···S and O-H···S interactions, causing the PDA nanospheres merging together and forming nanorods under stirring-induced shear force. Moreover, the oxidative polymerization of dopamine proceeds on the surface of the nanorods, whereas it is prohibited inside the nanorods owing to lack of oxygen, leading to outward diffusion of dopamine and hence cavitation. After annealing, the tubular morphology is perfectly retained, while ultrafine MoS monolayers are formed due to the confinement of the framework. Benefiting from these unique structural features, the MoS/C hybrid nanotubes possess abundant active sites and high surface area, as well as boost electronic and ionic transport, remarkably enhancing their electrocatalytic activities. The onset and half-wave potentials are 0.91 and 0.82 V, respectively, for ORR, close to those of Pt/C. Moreover, low onset potential and small Tafel slope are also observed for HER, demonstrating the potential of the hybrid nanotubes as a promising non-noble metal bifunctional electrocatalyst.
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http://dx.doi.org/10.1021/acsami.8b04140DOI Listing
July 2018

Direct Printing of Stretchable Elastomers for Highly Sensitive Capillary Pressure Sensors.

Sensors (Basel) 2018 Mar 28;18(4). Epub 2018 Mar 28.

School of Advanced Materials, Shenzhen Graduate School, Peking University, Shenzhen 518055, China.

We demonstrate the successful fabrication of highly sensitive capillary pressure sensors using an innovative 3D printing method. Unlike conventional capacitive pressure sensors where the capacitance changes were due to the pressure-induced interspace variations between the parallel plate electrodes, in our capillary sensors the capacitance was determined by the extrusion and extraction of liquid medium and consequent changes of dielectric constants. Significant pressure sensitivity advances up to 547.9 KPa were achieved. Moreover, we suggest that our innovative capillary pressure sensors can adopt a wide range of liquid mediums, such as ethanol, deionized water, and their mixtures. The devices also showed stable performances upon repeated pressing cycles. The direct and versatile printing method combined with the significant performance advances are expected to find important applications in future stretchable and wearable electronics.
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http://dx.doi.org/10.3390/s18041001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5948908PMC
March 2018

Reduced Graphene Oxide-Incorporated [email protected] Composites as Anodes for High-Performance Sodium-Ion Batteries.

ACS Appl Mater Interfaces 2018 Mar 9;10(11):9696-9703. Epub 2018 Mar 9.

Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science , North Carolina State University , Raleigh , North Carolina 27695-8301 , United States.

Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries because of the low cost and natural abundance of sodium resources. Nevertheless, low energy density and poor cycling stability of current SIBs unfavorably hinder their practical implementation for the smart power grid and stationary storage applications. Antimony tin (SnSb) is one of the most promising anode materials for next-generation SIBs attributing to its high capacity, high abundance, and low toxicity. However, the practical application of SnSb anodes in SIBs is currently restricted because of their large volume changes during cycling, which result in serious pulverization and loss of electrical contact between the active material and the carbon conductor. Herein, we apply reduced graphene oxide (rGO)-incorporated [email protected] nanofiber ([email protected]@CNF) composite anodes in SIBs that can sustain their structural stability during prolonged charge-discharge cycles. Electrochemical performance results shed light on that the combination of rGO, CNF, and SnSb alloy led to a high-capacity anode (capacity of 490 mAh g  at the 10th cycle) with a high capacity retention of 87.2% and a large Coulombic efficiency of 97.9% at the 200th cycle. This work demonstrates that the [email protected]@CNF composite is a potential and attractive anode material for next-generation, high-energy SIBs.
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http://dx.doi.org/10.1021/acsami.7b18921DOI Listing
March 2018

3D printed stretchable capacitive sensors for highly sensitive tactile and electrochemical sensing.

Nanotechnology 2018 May 15;29(18):185501. Epub 2018 Feb 15.

School of Advanced Materials, Shenzhen Graduate School, Peking University, Shenzhen 518005, People's Republic of China.

Developments of innovative strategies for the fabrication of stretchable sensors are of crucial importance for their applications in wearable electronic systems. In this work, we report the successful fabrication of stretchable capacitive sensors using a novel 3D printing method for highly sensitive tactile and electrochemical sensing applications. Unlike conventional lithographic or templated methods, the programmable 3D printing technique can fabricate complex device structures in a cost-effective and facile manner. We designed and fabricated stretchable capacitive sensors with interdigital and double-vortex designs and demonstrated their successful applications as tactile and electrochemical sensors. Especially, our stretchable sensors exhibited a detection limit as low as 1 × 10 M for NaCl aqueous solution, which could have significant potential applications when integrated in electronics skins.
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http://dx.doi.org/10.1088/1361-6528/aaafa5DOI Listing
May 2018

A New Member of Electrocatalysts Based on Nickel Metaphosphate Nanocrystals for Efficient Water Oxidation.

Adv Mater 2018 Feb 11;30(5). Epub 2017 Dec 11.

State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China.

High-performance electrocatalysts are desired for electrochemical energy conversion, especially in the field of water splitting. Here, a new member of phosphate electrocatalysts, nickel metaphosphate (Ni P O ) nanocrystals, is reported, exhibiting low overpotential of 270 mV to generate the current density of 10 mA cm and a superior catalytic durability of 100 h. It is worth noting that Ni P O electrocatalyst has remarkable oxygen evolution performance operating in basic media. Further experimental and theoretical analyses demonstrate that N dopant boosts the catalytic performance of Ni P O due to optimizing the surface electronic structure for better charge transfer and decreasing the adsorption energy for the oxygenic intermediates.
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http://dx.doi.org/10.1002/adma.201705045DOI Listing
February 2018

Effects of p-(Trifluoromethoxy)benzyl and p-(Trifluoromethoxy)phenyl Molecular Architecture on the Performance of Naphthalene Tetracarboxylic Diimide-Based Air-Stable n-Type Semiconductors.

ACS Appl Mater Interfaces 2016 Jul 7;8(28):18277-83. Epub 2016 Jul 7.

School of Advanced Materials, Peking University Shenzhen Graduate School, Peking University , Shenzhen 518055, China.

N,N'-Bis(4-trifluoromethoxyphenyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-POCF3) and N,N'-bis(4-trifluoromethoxybenzyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-BOCF3) have similar optical and electrochemical properties with a deep LUMO level of approximately 4.2 eV, but exhibit significant differences in electron mobility and molecular packing. NDI-POCF3 exhibits nondetectable charge mobility. Interestingly, NDI-BOCF3 shows air-stable electron transfer performance with enhanced mobility by increasing the deposition temperature onto the octadecyltrichlorosilane (OTS)-modified SiO2/Si substrates and achieves electron mobility as high as 0.7 cm(2) V(-1) s(-1) in air. The different mobilities of those two materials can be explained by several factors including thin-film morphology and crystallinity. In contrast to the poor thin-film morphology and crystallinity of NDI-POCF3, NDI-BOCF3 exhibits larger grain sizes and improved crystallinities due to the higher deposition temperature. In addition, the theoretical calculated transfer integrals of the intermolecular lowest unoccupied molecular orbital (LUMO) of the two materials further show that a large intermolecular orbital overlap of NDI-BOCF3 can transfer electron more efficiently than NDI-POCF3 in thin-film transistors. On the basis of fact that the theoretical calculations are consistent with the experimental results, it can be concluded that the p-(trifluoromethoxy) benzyl (BOCF3) molecular architecture on the former position of the naphthalene tetracarboxylic diimides (NDI) core provides a more effective way to enhance the intermolecular electron transfer property than the p-(trifluoromethoxy) phenyl (POCF3) group for the future design of NDI-related air-stable n-channel semiconductor.
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http://dx.doi.org/10.1021/acsami.6b04753DOI Listing
July 2016

Flexible, solid-state, ion-conducting membrane with 3D garnet nanofiber networks for lithium batteries.

Proc Natl Acad Sci U S A 2016 06 15;113(26):7094-9. Epub 2016 Jun 15.

University of Maryland Energy Research Center, University of Maryland, College Park, MD 20742; Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742

Beyond state-of-the-art lithium-ion battery (LIB) technology with metallic lithium anodes to replace conventional ion intercalation anode materials is highly desirable because of lithium's highest specific capacity (3,860 mA/g) and lowest negative electrochemical potential (∼3.040 V vs. the standard hydrogen electrode). In this work, we report for the first time, to our knowledge, a 3D lithium-ion-conducting ceramic network based on garnet-type Li6.4La3Zr2Al0.2O12 (LLZO) lithium-ion conductor to provide continuous Li(+) transfer channels in a polyethylene oxide (PEO)-based composite. This composite structure further provides structural reinforcement to enhance the mechanical properties of the polymer matrix. The flexible solid-state electrolyte composite membrane exhibited an ionic conductivity of 2.5 × 10(-4) S/cm at room temperature. The membrane can effectively block dendrites in a symmetric Li | electrolyte | Li cell during repeated lithium stripping/plating at room temperature, with a current density of 0.2 mA/cm(2) for around 500 h and a current density of 0.5 mA/cm(2) for over 300 h. These results provide an all solid ion-conducting membrane that can be applied to flexible LIBs and other electrochemical energy storage systems, such as lithium-sulfur batteries.
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http://dx.doi.org/10.1073/pnas.1600422113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4932948PMC
June 2016

Electroluminescent Devices: Extremely Stretchable Electroluminescent Devices with Ionic Conductors (Adv. Mater. 22/2016).

Adv Mater 2016 Jun;28(22):4489

School of Materials Science and Engineering, 50 Nanyang Avenue, Nanyang Technological University, Singapore, 639798, Singapore.

An extremely stretchable electroluminescent device is fabricated by P. S. Lee and co-workers, as described on page 4490. The stretchable alternating-current electroluminescent (ACEL) device possesses extremely high stretchability, and can be linearly stretched to 700% with the luminance being maintained at 70% of the initial value before stretching. The device can be repeatedly stretched to 400% with stable emission behavior. The presented device will provide new opportunities in stretchable lighting, volumetric 3D displays, interactive readout systems, and other unprecedented applications.
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http://dx.doi.org/10.1002/adma.201670152DOI Listing
June 2016

Three-Dimensional Printable High-Temperature and High-Rate Heaters.

ACS Nano 2016 05 10;10(5):5272-9. Epub 2016 May 10.

Department of Materials Science and Engineering, University of Maryland College Park , College Park, Maryland 20742, United States.

High temperature heaters are ubiquitously used in materials synthesis and device processing. In this work, we developed three-dimensional (3D) printed reduced graphene oxide (RGO)-based heaters to function as high-performance thermal supply with high temperature and ultrafast heating rate. Compared with other heating sources, such as furnace, laser, and infrared radiation, the 3D printed heaters demonstrated in this work have the following distinct advantages: (1) the RGO based heater can operate at high temperature up to 3000 K because of using the high temperature-sustainable carbon material; (2) the heater temperature can be ramped up and down with extremely fast rates, up to ∼20 000 K/second; (3) heaters with different shapes can be directly printed with small sizes and onto different substrates to enable heating anywhere. The 3D printable RGO heaters can be applied to a wide range of nanomanufacturing when precise temperature control in time, placement, and the ramping rate are important.
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http://dx.doi.org/10.1021/acsnano.6b01059DOI Listing
May 2016

Graphene Oxide-Based Electrode Inks for 3D-Printed Lithium-Ion Batteries.

Adv Mater 2016 Apr 2;28(13):2587-94. Epub 2016 Feb 2.

Department of Materials Science and Engineering, University of Maryland College Park, College Park, MD, 20742, USA.

All-component 3D-printed lithium-ion batteries are fabricated by printing graphene-oxide-based composite inks and solid-state gel polymer electrolyte. An entirely 3D-printed full cell features a high electrode mass loading of 18 mg cm(-2) , which is normalized to the overall area of the battery. This all-component printing can be extended to the fabrication of multidimensional/multiscale complex-structures of more energy-storage devices.
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http://dx.doi.org/10.1002/adma.201505391DOI Listing
April 2016

Extremely Stretchable Electroluminescent Devices with Ionic Conductors.

Adv Mater 2016 Jun 4;28(22):4490-6. Epub 2015 Dec 4.

School of Materials Science and Engineering, 50 Nanyang Avenue, Nanyang Technological University, Singapore, 639798, Singapore.

An extremely stretchable electroluminescent device is fabricated based on alternating-current electroluminescent (ACEL) materials and ionic conductors. The stretchable ACEL device possesses extremely high stretchability, and can be linearly stretched to 700% with the luminance being maintained at 70% of the initial value before stretching. The ACEL device can be repetitively stretched to 400% with stable emission behavior.
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http://dx.doi.org/10.1002/adma.201504187DOI Listing
June 2016

Nickel cobalt oxide nanowire-reduced graphite oxide composite material and its application for high performance supercapacitor electrode material.

J Nanosci Nanotechnol 2014 Sep;14(9):7104-10

In this paper, we report a facile synthesis method of mesoporous nickel cobalt oxide (NiCo2O4) nanowire-reduced graphite oxide (rGO) composite material by urea induced hydrolysis reaction, followed by sintering at 300 degrees C. P123 was used to stabilize the GO during synthesis, which resulted in a uniform coating of NiCo2O4 nanowire on rGO sheet. The growth mechanism of the composite material is discussed in detail. The NiCo2O4-rGO composite material showed an outstanding electrochemical performance of 873 F g(-1) at 0.5 A g(-1) and 512 F g(-1) at 40 A g(-1). This method provides a promising approach towards low cost and large scale production of supercapacitor electrode material.
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http://dx.doi.org/10.1166/jnn.2014.8982DOI Listing
September 2014

Highly stretchable and self-deformable alternating current electroluminescent devices.

Adv Mater 2015 May 18;27(18):2876-82. Epub 2015 Mar 18.

School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798.

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http://dx.doi.org/10.1002/adma.201405486DOI Listing
May 2015

Stretchable graphene thermistor with tunable thermal index.

ACS Nano 2015 Feb 11;9(2):2130-7. Epub 2015 Feb 11.

School of Materials Science and Engineering, Nanyang Technological University , 50 Nanyang Avenue, Singapore 639798.

Stretchable graphene thermistors with intrinsic high stretchability were fabricated through a lithographic filtration method. Three-dimensional crumpled graphene was used as the thermal detection channels, and silver nanowires were used as electrodes. Both the detection channel and electrodes were fully embedded in an elastomer matrix to achieve excellent stretchability. Detailed temperature sensing properties were characterized at different strains up to 50%. It is evident that the devices can maintain their functionalities even at high stretched states. The devices demonstrated strain-dependent thermal indices, and the sensitivity of the thermistors can be effectively tuned using strain. The unique tunable thermal index is advantageous over conventional rigid ceramic thermistors for diverse and adaptive applications in wearable electronics.
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http://dx.doi.org/10.1021/nn507441cDOI Listing
February 2015

Stretchable energy storage and conversion devices.

Small 2014 Sep;10(17):3443-60

Stretchable electronics are a type of mechanically robust electronics which can be bended, folded, crumpled and stretched and represent the emerging direction towards next-generation wearable and implantable devices. Unlike existing electronics based on rigid Si technologies, stretchable devices can conform to the complex non-coplanar surfaces and provide unique functionalities which are unreachable with simple extension of conventional technologies. Stretchable energy storage and conversion devices are the key components for the fabrication of complete and independent stretchable systems. In this review, we present the recent progresses in the developments of stretchable power sources including supercapacitors, batteries and solar cells. Representative structural and material designs to impart stretchability to the originally rigid devices are discussed. Advantages and drawbacks associated with the fabrication methods are also analysed. Summaries of the research progresses along with future development directions for this exciting field are also presented.
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http://dx.doi.org/10.1002/smll.201302806DOI Listing
September 2014

High-efficiency transfer of percolating nanowire films for stretchable and transparent photodetectors.

Nanoscale 2014 Sep 6;6(18):10734-9. Epub 2014 Aug 6.

School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798.

Stretchable devices with good transparency offer exciting new applications over the existing technologies, but remarkable difficulties remain in the fabrication of transparent and stretchable devices. In this paper, we report an effective method to fabricate transparent elastic photodetectors which combines the merits of the transparent polydimethylsiloxane (PDMS) polymer with its stretchability and the Zn₂SnO₄ nanowire (NW) with its photodetection functionality. Zonyl fluorosurfactant is found to be critical which improves the bonding between the functional NWs and the PDMS matrix, thus enabling the high efficient transfer of NW structures into PDMS. Highly conductive and thin percolating AgNW films were successfully embedded into PDMS mixed with ∼11% Zonyl which are otherwise not achievable with pure PDMS. Transparent and stretchable photodetectors were fabricated with the developed method. The photocurrent was found to be reciprocal to the square of the channel length, Iph∼ 1/l(2). The chemically bonded sensing materials in the PDMS matrix allow more NW exposure to air. This lead to a fast switching operation of the photodetectors with a response time below 0.8 s and a reset time around 3 s, which is significantly improved compared to reported stretchable NW photodetectors fully embedded in the polymer matrix.
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http://dx.doi.org/10.1039/c4nr02462aDOI Listing
September 2014

Rational design of MnO/carbon nanopeapods with internal void space for high-rate and long-life li-ion batteries.

ACS Nano 2014 Jun 19;8(6):6038-46. Epub 2014 May 19.

Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology , 130 Meilong Road, Shanghai 200237, China.

Searching the long-life MnO-based materials for lithium ion batteries (LIBs) is still a great challenge because of the issue related to the volumetric expansion of MnO nanoparticles (NPs) or nanowires (NWs) during lithiation. Herein, we demonstrate an unexpected result that a peapod-like MnO/C heterostructure with internal void space can be facilely prepared by annealing the MnO precursor (MnO-P) NW/polydopamine core/shell nanostructure in an inert gas, which is very different from the preparation of typical MnO/C core/shell NWs through annealing MnO NW/C precursor nanostructure. Such peapod-like MnO/C heterostructure with internal void space is highly particular for high-performance LIBs, which can address all the issues related to MnO dissolution, conversion, aggregation and volumetric expansion during the Li(+) insertion/extraction. They are highly stable anode material for LIBs with a very high reversible capacity (as high as 1119 mAh g(-1) at even 500 mA g(-1)) and fast charge and discharge capability (463 mAh g(-1) at 5000 mA g(-1)), which is much better than MnO NWs (38 mAh g(-1) at 5000 mA g(-1)) and MnO/C core/shell NWs (289 mAh g(-1) at 5000 mA g(-1)). Such nanopeapods also show excellent rate capability (charged to 91.6% in 10.6 min using the constant current mode). Most importantly, we found that MnO/C nanopeapods show no capacity fading even after 1000 cycles at a high current density of 2000 mA g(-1), and no morphology change. The present MnO/C nanopeapods are the most efficient MnO-based anode materials ever reported for LIBs.
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http://dx.doi.org/10.1021/nn501310nDOI Listing
June 2014
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