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Department of Chemistry
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1.Hydrogen and methane storage in ultrahigh surface area Metal-Organic Frameworks

Author:Ding, Lifeng ; Yazaydin, A. Ozgur

Source:Microporous and Mesoporous Materials,2013,Vol.182

Abstract:In this work we computationally studied eight Metal-Organic Frameworks (MOFs) which showed or is expected to have ultrahigh surface areas (NU-100, NU-108, NU-109, NU-110, MOF-180, MOF-200, MOF-210 and MOF-399). Successful activation for some of these MOFs have not been possible since their synthesis, and for most of them experimental surface area, pore volume and hydrogen and methane adsorption data do not exist. Geometric surface areas and pore volumes of these eight MOFs were calculated, and in order to assess their hydrogen and methane storage capacities adsorption isotherms were computed using grand canonical Monte Carlo simulations. Our results reveal that if it can be successfully activated MOF-399 will have the highest gravimetric surface area and pore volume (exceeding 7100 m2/g and 7.55 cm3/g) among all MOFs synthesized until now. Thanks to its substantially large pore volume MOF-399 is predicted to store much more hydrogen and methane in gravimetric terms compared to other ultrahigh surface area MOFs. © 2013 Elsevier Inc. All rights reserved.

2.Functionalization of diketopyrrolopyrrole with dendritic oligothiophenes: Synthesis, photophysical properties, and application in solar cells

Author:Gao, W;Wang, JK;Lin, Y;Luo, Q;Ma, YC;Dou, JY;Tan, HW;Ma, CQ;Cui, Z


Abstract:Diketopyrrolopyrrole (DPP) is one of the most widely used organic dye moieties in conjugated organic semiconductors for use in organic electronics. To enrich the library of DPP based organic semiconductors and to further understand the structure-property-performance relationship of this type materials, in this paper, the diketopyrrolopyrrole moiety was functionalized with three-dimensional (3D) pi-conjugated dendritic oligothiophenes (DOTs), and four diketopyrrolopyrrole compounds decorated with dendritic oligothiophenes (DOT-c-DPPs) were obtained and characterized in detailed. Results show that all these four compounds are monodisperse with defined molecular structure. Spectroscopy and cyclic voltammetry measurement results showed that the introduction of dendritic oligothiophene unit on the DPP unit improves the light absorption ability over 350-500 nm, and decreases the optical band gap slightly, which are in good accordance with theoretical calculation results that the frontier molecular orbitals are mainly located at the central DPP unit. Solution processed organic solar cells using these DOT-c-DPPs as the electron donor were fabricated and tested. Improved device performance was found for the bigger molecule for its less aggregation tendency. (C) 2017 Elsevier B.V. All rights reserved.

3.Growth of WS2 flakes on Ti3C2Tx Mxene Using Vapor Transportation Routine

Author:Su, WT;Wang, SG;Fu, L;Chen, F;Song, KX;Huang, XW;Yang, L


Abstract:Two-dimensional dichalcogenides (TMDs) and mxene junctions had been predicted to possess distinct tunable electronic properties. However, direct synthesis of WS2 on Ti3C2Tx mxene is still challenging. Herein, we successfully deposited WS2 onto the surface of Ti3C2Tx mxene by employing the vapor transportation (VT) routine. By modulating pressure and source-sample distance, multilayer and monolayer (1 L) WS2 flakes were deposited onto the lateral side and top surface of Ti3C2Tx flakes. The 1 L WS2 flakes growing on lateral side of Ti3C2Tx flake have much higher photoluminescence (PL) intensity than 1 L flakes growing on the top surface. Our study has the potential to benefit the design and preparation of novel electronic and electrochemical devices based on TMDs/mxene junctions.

4.Development of Solid-Phase RPA on a Lateral Flow Device for the Detection of Pathogens Related to Sepsis

Author:Heeroma, AJ;Gwenin, C


Abstract:Population extended life expectancy has significantly increased the risk of septic shock in an ageing population. Sepsis affects roughly 20 million people every year, resulting in over 11 million deaths. The need for faster more accurate diagnostics and better management is therefore paramount in the fight to prevent these avoidable deaths. Here we report the development of a POC device with the ability to identify a broad range of pathogens on a lateral flow platform. Namely Gram-positive and Gram-negative bacteria. The simple to use laboratory device has the potential to be automated, thus enabling an operator to carry out solid-phase lysis and room temperature RPA in situ, providing accurate results in hours rather than days. Results show there is a potential for a fully automated device in which concepts described in this paper can be integrated into a lateral flow device.

5.Improved Resistive Switching Behavior in Solution-processed AlOx based RRAM

Author:Qi, YF;Zhao, CZ;Zhao, C;Mitrovic, IZ;Xu, WY;Yang, L;Shen, ZJ;He, JH


Abstract:In this study, a comprehensive comparison in light of the switching behavior has been made to the AlOx dielectrics in Resistive Random Access Memory (RRAM) devices, which were fabricated with solution-processed (SP) and atomic-layer-deposition (ALD) based techniques under the same temperature (250 degrees C). The improved resistive switching properties such as smaller V-set/V-reset (1.2 similar to 1.8 V/-0.9 similar to-1.3 V), a narrower RHRs/RLRs distribution (2 similar to 80 k Omega/0.8 similar to 1 k Omega) and a higher resistance ratio (8 similar to 230) under 5 mA compliance current (CC) have been achieved with SP method. The conduction mechanisms of the ON and OFF state for both devices are the ohmic conduction and Frenkel-Poole emission, respectively. Therefore, the solution-based fabrication method has the potential application for the flexible memory, due to the fabrication merits of the low-temperature, low cost, large area implementation and being environmental-friendly.

6.Four supramolecular isomers of dichloridobis(1,10-phenanthroline)cobalt(II): synthesis, structure characterization and isomerization

Author:Chen, XC;Han, SM;Wang, RY;Li, Y


Abstract:Crystal engineering can be described as the understanding of intermolecular interactions in the context of crystal packing and the utilization of such understanding to design new solids with desired physical and chemical properties. Free-energy differences between supramolecular isomers are generally small and minor changes in the crystallization conditions may result in the occurrence of new isomers. The study of supramolecular isomerism will help us to understand the mechanism of crystallization, a very central concept of crystal engineering. Two supramolecular isomers of dichloridobis(1,10-phenanthroline-k(2) N, N') cobalt(II), [CoCl2(C12H8N2)(2)], i.e. (IA) (orthorhombic) and (IB) (monoclinic), and two supramolecular isomers of dichloridobis(1,10-phenanthroline-k(2) N, N') cobalt(II) N, N-dimethylformamide monosolvate, [CoCl2(C12H8N2)(2)]center dot C3H7NO, i.e. (IIA) (orthorhombic) and (IIB) (monoclinic), were synthesized in dimethylformamide (DMF) and structurally characterized. Of these, (IA) and (IIA) have been prepared and structurally characterized previously [Li et al. (2007). Acta Cryst. E63, m1880-m1880; Cai et al. (2008). Acta Cryst. E64, m1328-m1329]. We found that the heating rate is a key factor for the crystallization of (IA) or (IB), while the temperature difference is responsible for the crystallization of (IIA) or (IIB). Based on the crystallization conditions, isomerization behaviour, the KPI (Kitajgorodskij packing index) values and the density data, (IB) and (IIA) are assigned as the thermodynamic and stable kinetic isomers, respectively, while (IA) and (IIB) are assigned as the metastable kinetic products. The 1,10-phenanthroline (phen) ligands interact with each other through offset face-to-face (OFF) pi-pi stacking in (IB) and (IIB), but by edge-to-face (EF) C-H center dot center dot center dot pi interactions in (IA) and (IIA). Meanwhile, the DMF molecules in (IIB) connect to neighbouring [CoCl2(phen)(2)] units through two C-H center dot center dot center dot Cl hydrogen bonds, whereas there are no obvious interactions between DMF molecules and [CoCl2(phen)(2)] units in (IIA). Since OFF pi-pi stacking is generally stronger than EF C-H center dot center dot center dot pi interactions for transition-metal complexes with nitrogen-containing aromatic ligands, (IIA) is among the uncommon examples that are stable and densely packed but that do not following Etter's intermolecular interaction hierarchy.

7.Plasma-Enhanced Combustion-Processed Al2O3 Gate Oxide for In2O3 Thin Film Transistors

Author:Liu, QH;Zhao, C;Zhao, CZ;Mitrovic, IZ;Hall, S;Xu, WY;Yang, L;Lim, EG;Wang, QN;Wei, YL;Cao, YX


Abstract:In this study, we describe how to obtain high-quality Al2O3 dielectric thin films and their implementation in In2O3 thin film transistors by combining plasma treatment and combustion process at low temperatures (250 degrees C). The single layer Al2O3 dielectric formed by this technique exhibited a higher areal capacitance and a lower leakage level compared with those of conventional solution-processed Al2O3. The resulting TFTs presented a superior electrical performance at a low operating voltage of 2 V, with a positive threshold voltage of 0.39 V, a subthreshold swing of 0.V/decade, an On/Off ratio of 1.8x10(4), and a superior mobility of 136 cm(2) V-1 s(-1).

8.Plasmonic enhanced Cu2O-Au-BFO photocathodes for solar hydrogen production

Author:Cheng, XR;Gu, SL;Centeno, A;Dawson, G


Abstract:A novel Cu2O-Au-BFO heterostructure photocathode was constructed which significantly improved the efficiency of photo-generated carrier transfer for solar hydrogen production. A BiFeO3 (BFO) ferroelectric film was synthesized on top of a Cu2O layer by a sputtering process. The BFO layer acted to protect the Cu2O layer from photochemical corrosion, increasing photoelectrochemical (PEC) stability. The p-n heterojunction between Cu2O and BFO layers enhanced the PEC properties by suppressing charge recombination and improved interfacial charge transfer efficiency. When Cu2O and BFO are interfaced by Au Nanoparticles (NPs) the PEC performance was further enhanced, due to hot-electron transfer at the plasmonic resonance. After positive poling, the depolarization field across the whole volume of BFO film drove electrons into the electrolyte solution, inducing a significant anodic shift, V-op of 1.01 V vs. RHE, together with a significantly enhanced photocurrent density of -91 mu A/cm(2) at 0 V vs. RHE under 100 mW/cm(2) illumination. The mechanism was investigated through experimental and theoretivcal calculations.

9.Effects of Rapid Thermal Annealing on the Structural, Electrical, and Optical Properties of Zr-Doped ZnO Thin Films Grown by Atomic Layer Deposition

Author:Wu, JJ;Zhao, YC;Zhao, CZ;Yang, L;Lu, QF;Zhang, Q;Smith, J;Zhao, YM


Abstract:The 4 at. %% zirconium-doped zinc oxide (ZnO: Zr) films grown by atomic layer deposition (ALD) were annealed at various temperatures ranging from 350 to 950 degrees C. The structural, electrical, and optical properties of rapid thermal annealing (RTA) treated ZnO: Zr films have been evaluated to find out the stability limit. It was found that the grain size increased at 350 degrees C and decreased between 350 and 850 degrees C, while creeping up again at 850 degrees C. UV-vis characterization shows that the optical band gap shifts towards larger wavelengths. The Hall measurement shows that the resistivity almost keeps constant at low annealing temperatures, and increases rapidly after treatment at 750 degrees C due to the effect of both the carrier concentration and the Hall mobility. The best annealing temperature is found in the range of 350-550 degrees C. The ZnO: Zr film-coated glass substrates show good optical and electrical performance up to 550 degrees C during superstrate thin film solar cell deposition.

10.Impacts of filler covalent and non-covalent modification on the network structure and mechanical properties of carbon-silica dual phase filler/natural rubber

Author:Wang, JY;Jia, HB;Ding, LF;Xiong, X


Abstract:The carbon-silica dual phase filler (CSDPF) was modified by bis (3-triethoxy-silylpropyl) tetrasulphane (Si69) and 1-allyl-3-methyl-imidazolium chloride (AMI), respectively. The natural rubber (NR) vulcanizates filled with modified CSDPF were fabricated through mechanical mixing followed by a high-temperature cure process. The impacts of filler surface modification on the curing characters, crosslinked junctions, network structure, and mechanical properties of NR vulcanizates were investigated. The results showed that the Si69 interacted with CSDPF through covalent bond, while the interaction between AMI and CSDPF was hydrogen bond. Both modifications increased the cure rate of CSDPF/NR compounds as well as the crosslinked degree, compared with those of pristine CSDPF/NR compound. The modifications improved the dispersion of CSDPF in NR matrix. The covalent modification by Si69 caused a limited movement of NR chains in the CSDPF surface, which contributed to a greater tensile modulus of Si69-modified CSDPF/NR. However, the higher content of mono-sulfidic crosslink and the poorer content of strain-induced crystallization in the NR matrix led to a slight increase of tensile strength and tear strength of Si69-modified CSDPF/NR, compared with those of CSDPF/NR. The tensile modulus of AMI-modified CSDPF/NR had a lower value due to a faster polymer chain motion on the CSDPF surface. However, the tensile and tear strength of AMI-modified CSDPF/NR increased significantly because of the increase of mono-sulfidic crosslink, strain-induced crystallization, and the existed hydrogen bond between CSDPF and NR. Copyright (c) 2015 John Wiley & Sons, Ltd.

11.Phosphinic acids: current status and potential for drug discovery

Author:Abdou, MM;O'Neill, PM;Amigues, E;Matziari, M


Abstract:Phosphinic acid derivatives exhibit diverse biological activities and a high degree of structural diversity, rendering them a versatile tool in the development of new medicinal agents. Pronounced recent progress, coupled with previous research findings, highlights the impact of this moiety in medicinal chemistry. Here, we highlight the most important breakthroughs made with phosphinates with a range of pharmacological activities against many diseases, including anti-inflammatory, anti-Alzheimer, antiparasitic, antihepatitis, antiproliferative, anti-influenza, anti-HIV, antimalarial, and antimicrobial agents. We also provide the current status of the corresponding prodrugs, drug-delivery systems, and drug applications of phosphinic acids in the clinical stage

12.Polymer nanocomposites for lithium battery applications

Author:Ferrari, S. ; Nair, J.R. ; Zhou, Y. ; Wan, C.

Source:Polymer-based Nanocomposites for Energy and Environmental Applications A volume in Woodhead Publishing Series in Composites Science and Engineering,2018,Vol.

13.Compressive and flexural strength of Ultra-High Performance Fibre Reinforced Concrete containing recycled rubber crumb

Author:Wang, X;Xia, J;Li, Y


Abstract:Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) has excellent mechanical properties and good durability. However, the embodied energy of UHPFRC is much higher than that of ordinary concrete due to the high usage of cement. In order to reduce the adverse environmental impact of utilizing UHPFRC, recycled rubber crumb is used as an additional component or as a replacement for fine aggregates. Cube specimens with two different mix design schemes were investigated during this study. The reduction of compressive strength was investigated. UHPFRC prisms were also cast and loaded in four point bending tests to check the reduction of flexural strength. The mixing procedure and temperature variation during the casting process was recorded. Some cube specimens were heat cured in hot water at 90 degree Celsius for forty-eight hours. Those cubes were tested following curing at around 7 days to obtain the early age strength, while other cubes are normally cured in water at around 20 degree Celsius with the prisms until 28 days.

14.Symmetry Effects on Attenuation Factors in Graphene-Based Molecular Junctions

Author:Zhang, Q;Tao, SH;Yi, RW;He, CH;Zhao, CZ;Su, WT;Smogunov, A;Dappe, YJ;Nichols, RJ;Yang, L


Abstract:The unique structural and electronic characteristics of graphene make it an attractive contact for fundamental single-molecule electrical studies. With this in mind, we have probed here the electrical conductance of a molecular junction based on alpha,omega-diaminoalkane chains sandwiched between a gold and a graphene electrode. Using an STM based I(s) method combined with density functional theory-based transport calculations, we demonstrate that the resulting attenuation factor turns out to be much lower when compared to the standard molecular junction between two gold electrodes. This effect is attributed to asymmetric coupling of the molecule through strong chemisorption at the gold electrode and weaker van der Waals contact at graphene. Moreover, this asymmetric coupling induces higher conductance than that in the same hybrid metal graphene molecular junction using standard thiol anchoring groups.

15.Body Sensor Networks: Overview of Hardware Framework and Design Challenges

Author:Nanjappan, V;Wang, W;Lau, K;Man, KL;Liang, HN;Lee, JK;Kim, KK


Abstract:Internet of Everything (IoE), embedded with microcontrollers and wireless technologies onto a single system on a chip (SoC), are able to be connected with other devices in the cloud. Wearable sensors and RFID are core technologies in IoE. Energy efficiency and miniaturization are the two most critical technical challenges for the hardware implementation of microelectronic systems enabling Internet of Everything. Low-power smart systems on a chip are the key enabling solutions. In this paper, we outline the key hardware components and design challenges of BSN.

16.Versailles Project on Advanced Materials and Standards Interlaboratory Study on Measuring the Thickness and Chemistry of Nanoparticle Coatings Using XPS and LEIS

Author:Belsey, NA;Cant, DJH;Minelli, C;Araujo, JR;Bock, B;Bruner, P;Castner, DG;Ceccone, G;Counsell, JDP;Dietrich, PM;Engelhard, MH;Fearn, S;Galhardo, CE;Kalbe, H;Kim, JW;Lartundo-Rojas, L;Luftman, HS;Nunney, TS;Pseiner, J;Smith, EF;Spampinato, V;Sturm, JM;Thomas, AG;Treaty, JPW;Veith, L;Wagstaffe, M;Wang, H;Wang, ML;Wang, YC;Werner, W;Yang, L;Shard, AG


Abstract:We report the results of a Versailles Project on Advanced Materials and Standards (VAMAS) interlaboratory study on the measurement of the shell thickness and chemistry of nanoparticle coatings. Peptide-coated gold particles were supplied to laboratories in two forms: a colloidal suspension in pure water and particles dried onto a silicon wafer. Participants prepared and analyzed these samples using either X-ray photoelectron spectroscopy (XPS) or low energy ion scattering (LEIS). Careful data analysis revealed some significant sources of discrepancy, particularly for XPS. Degradation during transportation, storage, or sample preparation resulted in a variability in thickness of 53%%. The calculation method chosen by XPS participants contributed a variability of 67%%. However, variability of 12%% was achieved for the samples deposited using a single method and by choosing photoelectron peaks that were not adversely affected by instrumental transmission effects. The study identified a need for more consistency in instrumental transmission functions and relative sensitivity factors since this contributed a variability of 33%%. The results from the LEIS participants were more consistent, with variability of less than 10%% in thickness, and this is mostly due to a common method of data analysis. The calculation was performed using a model developed for uniform, flat films, and some participants employed a correction factor to account for the sample geometry, which appears warranted based upon a simulation of LEIS data from one of the participants and comparison to the XPS results.

17.Synthesis, structure and electrochemistry of ruthenium(II) and (III) mono-and bis-oxalato complexes

Author:Elnajjar, FO;Wang, RY;Aquino, MAS


Abstract:Using trans- [NH2Me2][Ru(eta(2)-ox)(2)(H2O)(2)]center dot 4H(2)O 1 as starting material, as well as its original preparation as a guide, the synthesis of trans-[NH2Me2][Ru(eta(2)-ox)(2)(PPh3)(2)] 2, trans-[pyH] [Ru(eta(2)-ox)(2)(H2O)(2)]center dot 4H(2)O 3, trans-[PyH] [Ru(eta(2) -ox)(2)(py)(2)]center dot 2.5H(2)O 4, [Ru(eta(2)-ox)(py)(4)]center dot 4CHCl(3) 5 and fac-[Ru(eta(2)-ox)(DMSO-S)(3) (DMSO-O)]center dot 1.34H(2)O 6 are outlined. Complexes 2-6 have been characterized using elemental analysis, IR, UV-visible, H-1 NMR, and X-ray diffraction. In addition, their electrochemical behaviour has been analyzed using cyclic and Osteryoung square-wave voltammetries with complex 6 displaying linkage isomerization.

18.Al/GO/Si/Al RRAM with Solution-processed GO dielectric at Low Fabrication Temperature

Author:Shen,Z. J.;Zhao,C.;Zhao,C. Z.;Mitrovic,I. Z.;Yang,L.;Xu,W. Y.;Lim,E. G.;Luo,T.;Huang,Y. B.

Source:2019 Joint International EUROSOI Workshop and International Conference on Ultimate Integration on Silicon, EUROSOI-ULIS 2019,2019,Vol.

Abstract:© 2019 IEEE. In this work, the Al/GO/Si/Al RRAM device was fabricated with solution-processed graphene oxide (GO) thin film at low temperature (50 ?). A superior electrical performance and stable operation of the device has been achieved showing typical bipolar resistive switching characteristics with operation voltage lower than 3 V, retention property sustained over 104 s and endurance over 102 cycles. The results suggest that the solution-processed GO thin films exhibit great potential for use in the flexible device.

19.Design of Interactions for Handheld Augmented Reality Devices Using Wearable Smart Textiles: Findings from a User Elicitation Study

Author:Nanjappan, V;Shi, RK;Liang, HN;Xiao, HR;Lau, KKT;Hasan, K


Abstract:Advanced developments in handheld devices' interactive 3D graphics capabilities, processing power, and cloud computing have provided great potential for handheld augmented reality (HAR) applications, which allow users to access digital information anytime, anywhere. Nevertheless, existing interaction methods are still confined to the touch display, device camera, and built-in sensors of these handheld devices, which suffer from obtrusive interactions with AR content. Wearable fabric-based interfaces promote subtle, natural, and eyes-free interactions which are needed when performing interactions in dynamic environments. Prior studies explored the possibilities of using fabric-based wearable interfaces for head-mounted AR display (HMD) devices. The interface metaphors of HMD AR devices are inadequate for handheld AR devices as a typical HAR application require users to use only one hand to perform interactions. In this paper, we aim to investigate the use of a fabric-based wearable device as an alternative interface option for performing interactions with HAR applications. We elicited user-preferred gestures which are socially acceptable and comfortable to use for HAR devices. We also derived an interaction vocabulary of the wrist and thumb-to-index touch gestures, and present broader design guidelines for fabric-based wearable interfaces for handheld augmented reality applications.

20.Evaluating the component contribution to nonlinear optical performances using stable [Ni4O4] cuboidal clusters as models

Author:Hao, ZM;Chao, MY;Liu, Y;Song, YL;Yang, JY;Ding, LF;Zhang, WH;Lang, JP


Abstract:Five stable clusters sharing the cuboidal [Ni4O4] skeleton are subjected to third-order nonlinear optical (NLO) property measurements. Preliminary results suggest that the NLO property is largely defined by the cluster core skeleton and the directly coordinated atoms, with limited contribution from the heavy atoms peripherally attached to the aromatic ligands.
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