ORCID Profile
0000-0001-8466-0257
Current Organisation
Queensland University of Technology
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In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Materials engineering | Nanotechnology | Electronic and Magnetic Properties of Condensed Matter; Superconductivity | Nanoelectronics | Nanoelectronics | Functional materials | Electronic and magnetic properties of condensed matter; superconductivity | Condensed matter modelling and density functional theory | Surfaces and Structural Properties of Condensed Matter | Organic semiconductors | Polymers and plastics | Nanomaterials |
Expanding Knowledge in the Physical Sciences | Integrated Circuits and Devices | Expanding Knowledge in Engineering | Expanding Knowledge in Technology
Publisher: Wiley
Date: 14-06-2023
Abstract: It is well known that electrocatalytic oxygen evolution reaction (OER) activities primarily depend on the active centers of electrocatalysts. In some oxide electrocatalysts, high‐valence metal sites (e.g., molybdenum oxide) are generally not the real active centers for electrocatalytic reactions, which is largely due to their undesired intermediate adsorption behaviors. As a proof‐of‐concept, molybdenum oxide catalysts are selected as a representative model, in which the intrinsic molybdenum sites are not the favorable active sites. Via phosphorus‐modulated defective engineering, the inactive molybdenum sites can be regenerated as synergistic active centers for promoting OER. By virtue of comprehensive comparison , it is revealed that the OER performance of oxide catalysts is highly associated with the phosphorus sites and the molybdenum/oxygen defects. Specifically, the optimal catalyst delivers an overpotential of 287 mV to achieve the current density of 10 mA cm −2 , accompanied by only 2% performance decay for continuous operation up to 50 h. It is expected that this work sheds light on the enrichment of metal active sites via activating inert metal sites on oxide catalysts for boosting electrocatalytic properties.
Publisher: AIP Publishing
Date: 08-2012
DOI: 10.1063/1.4740455
Abstract: We demonstrate that the interfacial hole injection barrier Δh between p-type organic materials (i.e., CuPc and pentacene) and Co substrate can be tuned by the insertion of a MoO3 buffer layer. Using ultraviolet photoemission spectroscopy, it was found that the introduction of MoO3 buffer layer effectively reduces the hole injection barrier from 0.8 eV to 0.4 eV for the CuPc/Co interface, and from 1.0 eV to 0.4 eV for the pentacene/Co interface, respectively. In addition, by varying the thickness of the buffer, the tuning effect of Δh is shown to be independent of the thickness of MoO3 interlayer at both CuPc/Co and pentacene/Co interfaces. This Fermi level pinning effect can be explained by the integer charge-transfer model. Therefore, the MoO3 buffer layer has the potential to be applied in p-type organic spin valve devices to improve the device performance via reducing the interfacial hole injection barrier.
Publisher: Springer Science and Business Media LLC
Date: 03-05-2022
DOI: 10.1007/S40820-022-00862-0
Abstract: Bismuth-based materials (e.g., metallic, oxides and subcarbonate) are emerged as promising electrocatalysts for converting CO 2 to formate. However, Bi o -based electrocatalysts possess high overpotentials, while bismuth oxides and subcarbonate encounter stability issues. This work is designated to exemplify that the operando synthesis can be an effective means to enhance the stability of electrocatalysts under operando CO 2 RR conditions. A synthetic approach is developed to electrochemically convert BiOCl into Cl-containing subcarbonate (Bi 2 O 2 (CO 3 ) x Cl y ) under operando CO 2 RR conditions. The systematic operando spectroscopic studies depict that BiOCl is converted to Bi 2 O 2 (CO 3 ) x Cl y via a cathodic potential-promoted anion-exchange process. The operando synthesized Bi 2 O 2 (CO 3 ) x Cl y can tolerate − 1.0 V versus RHE, while for the wet-chemistry synthesized pure Bi 2 O 2 CO 3 , the formation of metallic Bi o occurs at − 0.6 V versus RHE. At − 0.8 V versus RHE, Bi 2 O 2 (CO 3 ) x Cl y can readily attain a FE HCOO - of 97.9%, much higher than that of the pure Bi 2 O 2 CO 3 (81.3%). DFT calculations indicate that differing from the pure Bi 2 O 2 CO 3 -catalyzed CO 2 RR, where formate is formed via a * OCHO intermediate step that requires a high energy input energy of 2.69 eV to proceed, the formation of HCOO − over Bi 2 O 2 (CO 3 ) x Cl y has proceeded via a * COOH intermediate step that only requires low energy input of 2.56 eV.
Publisher: Elsevier BV
Date: 04-2021
Publisher: AIP Publishing
Date: 26-03-2007
DOI: 10.1063/1.2719033
Abstract: Energy level alignment of rubrene adsorbed on Au(111) was studied by photoemission spectroscopy. After rubrene adsorption, the work function is reduced from 5.24eV for clean Au to 4.31eV, suggesting the invalidity of vacuum level alignment and the presence of a strong interfacial dipole. The frontier molecular orbital energies of rubrene are modified by electrode surface polarization in the submonolayer regime. As a consequence, the hole injection barrier is thickness dependent and varies from about 0.4eV for a monolayer of rubrene to 0.9eV for a thick layer.
Publisher: AIP Publishing
Date: 25-01-2016
DOI: 10.1063/1.4940749
Abstract: Surface transfer doping of hydrogen-terminated diamond has been achieved utilising V2O5 as a surface electron accepting material. Contact between the oxide and diamond surface promotes the transfer of electrons from the diamond into the V2O5 as revealed by the synchrotron-based high resolution photoemission spectroscopy. Electrical characterization by Hall measurement performed before and after V2O5 deposition shows an increase in hole carrier concentration in the diamond from 3.0 × 1012 to 1.8 × 1013 cm−2 at room temperature. High temperature Hall measurements performed up to 300 °C in atmosphere reveal greatly enhanced thermal stability of the hole channel produced using V2O5 in comparison with an air-induced surface conduction channel. Transfer doping of hydrogen-terminated diamond using high electron affinity oxides such as V2O5 is a promising approach for achieving thermally stable, high performance diamond based devices in comparison with air-induced surface transfer doping.
Publisher: American Chemical Society (ACS)
Date: 12-06-2007
DOI: 10.1021/JA072133R
Publisher: American Chemical Society (ACS)
Date: 28-02-2006
DOI: 10.1021/JP056785I
Abstract: The adsorption of allyl alcohol, acrylic acid, and allyl chloride, as well as unsaturated organic molecules such as acetylene and 1,3 butadiene, on reconstructed diamond (100) 2 x 1 have been investigated using high-resolution electron energy loss (HREELS) spectroscopy and synchrotron radiation spectroscopy. The cycloadditions of these organic molecules produce chemically adsorbed adlayers with varying degree of coverages on the clean diamond. The organic adsorbed surface has a lowered electron affinity and shows a secondary electron yield that varies between 12 and 40% of the yield obtained from a fully hydrogenated diamond surface. The diamond surface can be functionalized with hydroxyl, carboxylic, and chlorine functionalities by the adsorption of these allyl organics. The [2 + 2] adduct of acetylene on the diamond (100) 2 x 1 surface can be observed. 1,3-butadiene attains a higher coverage as well as forms a thermally more stable adlayer on the diamond surface compared to the other organic molecules, due to its ability to undergo [4 + 2] cycloaddition.
Publisher: Elsevier BV
Date: 06-2018
Publisher: American Physical Society (APS)
Date: 19-04-2011
Publisher: Elsevier BV
Date: 07-2007
Publisher: Wiley
Date: 08-10-2021
Abstract: 2D black phosphorus (BP) is one promising electrocatalyst toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysis. The too strong adsorption of oxygen intermediates during OER, while the too weak adsorption of hydrogen intermediate during HER, however, greatly compromise its practical water splitting applications with overpotentials as high as 450 mV for OER and 420 mV for HER to achieve 10 mA cm −2 under alkaline conditions. Herein, by rationally introducing the nanosized iridium (Ir) modifier together with optimized exposing surface toward electrolytes, an efficient Ir‐modified BP electrocatalyst with much favorable adsorption energies toward catalytic intermediates possesses an outstanding pH‐universal water splitting performance, surpassing the nearly all reported BP‐based catalysts and the commercial noble‐metal catalysts. The Ir‐modified BP catalyst with the optimized exposed surfaces only requires an overall cell voltage of 1.54 and 1.57 V to achieve 10 mA cm −2 in acidic and alkaline electrolysers, respectively. This design uncovers the potential applications of 2D BP in practical electrocatalysis fields via decreasing reaction intermediate adsorption energy barriers and promoting the interfacial electron coupling for heterostructured catalysts, and offers new insights into the surface‐dependent activity enhancement mechanism.
Publisher: American Physical Society (APS)
Date: 10-08-2011
Publisher: MDPI AG
Date: 09-06-2010
DOI: 10.3390/MA3063642
Publisher: American Chemical Society (ACS)
Date: 03-02-2007
DOI: 10.1021/JP066600N
Publisher: American Chemical Society (ACS)
Date: 04-2021
Publisher: Springer Science and Business Media LLC
Date: 06-2020
Publisher: Wiley
Date: 04-2014
Abstract: Organic semiconductor materials have important applications in organic electronics and other novel hybrid devices. In these devices, the transport of charge carriers across the interfaces between organic molecules and electrodes plays an important role in determining the device performance. Charge transfer dynamics at the organic/electrode interface usually occurs at the several femtoseconds timescale, and quantitative charge transfer dynamics data can been inferred using synchrotron-based core-hole clock (CHC) spectroscopy. In this research news, we have reviewed recent progress in the applications of CHC spectroscopy on the quantitative characterization of charge transfer dynamics at organic/electrode interfaces. By examining charge transfer dynamics at different types of interface, from weakly interacting van der Waals-type interfaces to interfaces with strong covalent bonds, we discuss a few factors that have been found to affect the charge transfer dynamics. We also review the application of CHC spectroscopy to quantify through-bonds and through-space charge transport in organic molecules.
Publisher: Wiley
Date: 30-11-2022
Abstract: Recently it is discovered that molecular junctions can be pushed into the Marcus Inverted region of charge transport, but it is unclear which factors are important. This paper shows that the mechanism of charge transport across molecular wires can be switched between the normal and Marcus Inverted regions by fine‐tuning the molecule–electrode coupling strength and the tunneling distance across oligophenylene ethynylene (OPE) wire terminated with ferrocene (Fc) abbreviated as S‐OPE n Fc ( n = 1–3). Coherent tunneling dominates the mechanism of charge transport in junctions with short molecules ( n = 1), but for n = 2 or 3 redox reactions become important. By weakening the molecule—electrode interaction by interrupted conjugation, S‐CH 2 ‐OPE n Fc, intramolecular orbital gating can occur pushing the junctions completely into the Marcus Inverted region. These results indicated that weak molecule—electrode coupling is important to push junctions into the Marcus Inverted Region.
Publisher: Elsevier BV
Date: 10-2017
Publisher: MDPI AG
Date: 11-04-2022
DOI: 10.3390/NANO12081303
Abstract: Recently, two-dimensional (2D) materials and their heterostructures have attracted considerable attention in gas sensing applications. In this work, we synthesized 2D MoS2@MoO3 heterostructures through post-sulfurization of α-MoO3 nanoribbons grown via vapor phase transport (VPT) and demonstrated highly sensitive NO2 gas sensors based on the hybrid heterostructures. The morphological, structural, and compositional properties of the MoS2@MoO3 hybrids were studied by a combination of advanced characterization techniques revealing a core-shell structure with the coexistence of 2H-MoS2 multilayers and intermediate molybdenum oxysulfides on the surface of α-MoO3. The MoS2@MoO3 hybrids also exhibit room-temperature ferromagnetism, revealed by vibrating s le magnetometry (VSM), as a result of the sulfurization process. The MoS2@MoO3 gas sensors display a p-type-like response towards NO2 with a detection limit of 0.15 ppm at a working temperature of 125 °C, as well as superb selectivity and reversibility. This p-type-like sensing behavior is attributed to the heterointerface of MoS2-MoO3 where interfacial charge transfer leads to a p-type inversion layer in MoS2, and is enhanced by magnetic dipole interactions between the paramagnetic NO2 and the ferromagnetic sensing layer. Our study demonstrates the promising application of 2D molybdenum hybrid compounds in gas sensing applications with a unique combination of electronic and magnetic properties.
Publisher: American Chemical Society (ACS)
Date: 10-03-2021
Publisher: American Chemical Society (ACS)
Date: 05-08-2009
DOI: 10.1021/NN9005335
Abstract: Size and ligand effects are the basis for the novel properties and applications of metallic nanoparticles (NPs) in nanoelectronics, optoelectronics, and biotechnology. This work reports the first observation of enhanced photoelectron emission from metallic Au NPs ligated by alkanethiols. The enhancement is based on a conceptually new mechanism: the AuNP provides electrons while the alkane ligand emits electrons due to its low or negative electron affinity. Moreover, the AuNP-ligand chemical bonding is found to significantly facilitate the transmission of photoexcited electrons from the AuNP to the ligand emitter. Consequently the smooth NP film, which is a typical low-aspect-ratio two-dimensional structure, exhibits strong and stable field emission behavior under photoillumination conditions. The photoenhanced field emission is related to the interband and surface plasmon transitions in AuNPs, and a photoenhancement factor of up to approximately 300 is observed for the AuNP-based field emission. This is highly remarkable because field emission is often based on one-dimensional, high-aspect-ratio nanostructures (e.g., nanotubes and nanowires) with geometrical field enhancement effect. The chemical linkage of electron-supplying AuNP and electron-emitting alkane ligand represents a fundamentally new mechanism for efficient photoexcitation and emission. Being low-temperature/solution processable, and inkjet printable, AuNPs may be a flexible material system for optoelectronic applications such as photodetection and photoenhanced field emission.
Publisher: World Scientific Pub Co Pte Lt
Date: 28-04-2021
DOI: 10.1142/S0218625X21400096
Abstract: The discovery of two-dimensional (2D) materials with single or a few-atom-thick layers has presented unprecedented opportunities to study, control and harness the properties of van der Waals (vdW) materials at their 2D limit. It also offers a platform that allows the arbitrary creation of heterostructures in a materials-by-design approach with properties tailored by the constituting components. Combining organic molecules with 2D materials to form hybrid heterointerfaces has recently emerged as a facile and versatile approach to engineer the electronic, optical, magnetic and chemical properties of 2D materials for new or optimized device applications. Underpinning the development of organic–2D materials heterostructures is the ability to interrogate the interfacial electronic structures and properties at multiple dimensions. This review provides a timely update on the application of synchrotron-based soft X-ray spectroscopies (SR-SXS) in the characterization of organic–2D materials interfaces. By harnessing the unparalleled high energy resolution, tunable energy, high brilliance and tunable polarization inherent to synchrotron radiation, electronic structures, charge transfer dynamics, molecular orientations and spin configurations at the hybrid interfaces can be examined, which helps us to formularize a coherent understanding of the organic–2D materials interfaces that will guide the design of new hybrid vdW structures and devices. We also offer our perspective on the future application of SR-SXS in the exploration of organic–2D materials heterostructures.
Publisher: AIP Publishing
Date: 05-06-2014
DOI: 10.1063/1.4878675
Abstract: The optical conductivity (σ1) of SrTiO3 for various vacancies has been systematically studied using a combination of ultraviolet-vacuum ultraviolet reflectivity and spectroscopic ellipsometry. For cation (Ti) vacancies, σ1 shows large spectral weight transfer over a wide range of energy from as high as 35 eV to as low as 0.5 eV and the presence of mid-gap states, suggesting that strong correlations play an important role. Meanwhile, for anion (O) vacancies, σ1 shows changes from 7.4 eV up to 35 eV.
Publisher: American Chemical Society (ACS)
Date: 06-08-2021
Abstract: Layered sodium titanates (NTO), one of the most promising anode materials for advanced sodium-ion batteries (SIBs), feature high theoretical capacity and no serious safety concerns. The pristine NTO electrode, however, has unfavorable Na
Publisher: American Chemical Society (ACS)
Date: 23-11-2006
DOI: 10.1021/JP065821Q
Abstract: Self-assembled functionalized aromatic thiols (oligophenylenes composed of building blocks of dimethoxy-substituted phenylenes, perfluoro-substituted phenylenes, and a terminal thiol group) were used to tune the hole injection barrier (Delta(h)) of copper(II) phthalocyanine (CuPc) on Au(111). Synchrotron-based high-resolution photoemission spectroscopy study reveals a significant reduction of Delta(h) by as much as 0.75 eV from Delta(h) = 0.9 eV for CuPc/Au(111) to Delta(h) = 0.15 eV for CuPc/BOF/Au(111), where BOF represents 4-pentafluorophenyl-1-(p-thiophenyl)-2,5-dimethoxybenzene. The delocalized pi orbitals of these functionalized aromatic thiols greatly facilitate effective charge transfer (hole or electron) across the SAM interface as compared to alkanethiols, hence making this novel interface modification scheme a simple and effective way to tune the hole injection barrier. This method has potential applications in molecular electronics, organic light-emitting diodes (OLED), organic field-effect transistors (OFETs), and organic solar cells.
Publisher: AIP Publishing
Date: 17-08-2009
DOI: 10.1063/1.3206654
Abstract: In this work, we demonstrate room temperature ferromagnetism of ZnO nanocrystals (NCs) embedded in alumina-based amorphous matrix. Our study has shown that solid solution occurred for lower Al concentration [≤x=0.09 for (Zn1−x,Alx)O]. No ferromagnetism appears in Al-doped ZnO with x≤0.09. With higher Al concentration, alumina-based amorphous structure appeared and fully amorphous was found in the composition of (Zn0.30,Al0.70)O. Ferromagnetism was found in (Zn1−x,Alx)O with a threshold of 16 mol % of Al. The room temperature ferromagnetism was found to be attributed to ZnO NCs in an alumina-based amorphous ZnO–Al2O3 matrix. Ferromagnetism reached a maximum with a volume percentage of ZnO NCs to be ∼27 vol %. The detailed investigations (transmission electron microscopy, x-ray photoelectron spectroscopy, and superconducting quantum interference device) show that the optimized size of these NCs is in the range of 4–5 nm. No ferromagnetism appears if the s le contains a fully amorphous structure.
Publisher: Wiley
Date: 02-2021
Publisher: Elsevier BV
Date: 10-2021
Publisher: AIP Publishing
Date: 29-07-2019
DOI: 10.1063/1.5108561
Abstract: Spin relaxation properties of π-conjugated organic semiconductors are key indicators of the performance of organic spintronic devices. However, reliable determination of spin relaxation parameters in organic materials is hindered by complex interfacial phenomena at organic/ferromagnetic metal interfaces that couple spin injection with charge injection. Here, we study the spin pumping induced pure spin transport in Permalloy/rubrene/Pt trilayers and determine the spin diffusion length λs = 132 ± 9 nm and the spin relaxation time τs = 3.8 ± 0.5 ms in rubrene films at room temperature by using the inverse spin Hall effect. The determined spin diffusion length λs is found to be almost two times larger than that of ∼46.3 nm at 100 K extracted from rubrene spin valve devices in which charge carrier injection/detection occurs at organic/ferromagnetic metal interfaces. Our results demonstrate experimentally that the efficiency and the rate of spin polarized charge transport through the organic/ferromagnetic metal interface play a dominant role in determining the spin relaxation process of spin valve devices in which charge and spin currents are coupled.
Publisher: American Chemical Society (ACS)
Date: 02-02-2006
DOI: 10.1021/JA0577241
Abstract: We report the creation of polymeric micro/nanostructures which exhibit distinct chemical and physical characteristics from the matrix poly(N-vinyl carbazole) (PVK). The structure formation is based on atomic force microscopy (AFM) facilitated cross-linking and oxygenation. The reaction of PVK with AFM lithographically induced nanoscale discharge produces raised structures in which bridge oxygen links neighboring carbazole groups. The cross-linking by bridge oxygen converts the initially insulating PVK matrix to chemically modified conducting patterns through the formation of extended pi-conjugations. A comprehensive AFM, PES (photoelectron spectroscopy), FTIR (Fourier transform infrared spectroscopy), and DFT (density functional theory) analysis is presented to address the chemophysical identity of the patterned structures. Our results demonstrate new capabilities of AFM nanolithography in generating heterogeneous functional structures in a polymer matrix.
Publisher: Elsevier BV
Date: 08-2020
Publisher: Wiley
Date: 31-05-2022
Abstract: 2D heterostructures provide another exciting opportunity for extending the application of 2D materials in energy conversion and storage devices, due to their flexibility in electronic structure modulations and surface chemistry regulations. Herein, by coupling liquid‐exfoliated and mildly oxidized black phosphorus nanosheets (BP‐NSs) with wet‐chemically synthesized 2D nickel Ni(OH) 2 nanosheets (NH‐NSs), 2D/2D heterostructured nanosheets (BNHNSs) are rationally constructed with a favorable transition of electron structure and desired intermediate adsorptions for alkaline oxygen evolution reaction (OER) catalysis. When used as an OER catalyst, to reach a current density of 10 mA cm −2 , the overpotential of 2D/2D BNHNSs is only 297 mV, corresponding to a considerable decrease of 22% and 34% compared with the in idual 2D NH‐NSs and 2D BP‐NSs, respectively. The structural tracking at the initial reconstruction stage via time‐dependent Raman spectra confirms that the phosphorus oxidization into the P–OH and the phase transformation into oxyhydroxide (NiOOH) significantly promote the electron transfer and electrocatalytic efficiency and thus endow the 2D/2D BNHNSs with much enhanced OER catalytic activity. This work offers new insights on the electron structure modulation of 2D‐based heterostructures and opens new avenues for regulating the adsorption of emerging phosphorene‐based materials for electrocatalysis.
Publisher: Wiley
Date: 26-08-2021
Abstract: Interface plays a critical role in determining the physical properties and device performance of heterostructures. Traditionally, lattice mismatch, resulting from the different lattice constants of the heterostructure, can induce epitaxial strain. Over past decades, strain engineering has been demonstrated as a useful strategy to manipulate the functionalities of the interface. However, mismatch of crystal symmetry at the interface is relatively less studied due to the difficulty of atomically structural characterization, particularly for the epitaxy of low symmetry correlated materials on the high symmetry substrates. Overlooking those phenomena restrict the understanding of the intrinsic properties of the as‐ determined heterostructure, resulting in some long‐standing debates including the origin of magnetic and ferroelectric dead layers. Here, perovskite LaCoO 3 ‐SrTiO 3 superlattice (SL) is used as a model system to show that the crystal symmetry effect can be isolated by the existing interface strain. Combining the state‐of‐art diffraction and electron microscopy, it is found that the symmetry mismatch of LaCoO 3 ‐SrTiO 3 SL can be tuned by manipulating the SrTiO 3 layer thickness to artificially control the magnetic properties. The work suggests that crystal symmetry mismatch can also be designed and engineered to act as an effective strategy to generate functional properties of perovskite oxides.
Publisher: American Chemical Society (ACS)
Date: 30-11-2011
DOI: 10.1021/JP2083924
Publisher: American Chemical Society (ACS)
Date: 11-02-2014
DOI: 10.1021/JP4103542
Publisher: Springer Science and Business Media LLC
Date: 06-09-2024
Publisher: AIP Publishing
Date: 23-03-2020
DOI: 10.1063/5.0005170
Abstract: TiS2 has been intensively studied as an electrode material and a thermoelectric material for energy storage and conversion applications due to its high electrical conductivity. Understanding the influence of defects on electrical transport is of importance not only to resolve the long-standing question concerning the nature of TiS2, but also for the rational design of TiS2 based devices for energy scavenging applications. In this study, we integrate photoemission spectroscopy, Raman spectroscopy, and electrical transport measurements to determine the chemical compositions dominated by defects and their influence on the doping and electrical properties. Our results demonstrate that TiS2 is a heavily self-doped semiconductor with the Fermi level close to the conduction band, which serves as the conclusive experimental evidence regarding the semiconducting nature of TiS2. The doping effect is sensitive to the (subtle) changes in the chemical composition. The electron donation from the Ti interstitials (Tii) to the TiS2 host explains the high carrier concentration. The Ti Frenkel pair (TiF) acting as the acceptor is responsible for the decrease in the electron carrier concentration and electrical conductivity. High conductivity maintains upon partial oxidization, indicating the oxidization-tolerance in terms of the electronic structure. Our results provide valuable insight into the evolution of electronic properties modulated by defects that reveal unambiguously the self-doped semiconducting nature of TiS2 and chemical- and environment-tolerance of TiS2 as an advanced energy scavenging material.
Publisher: AIP Publishing
Date: 27-04-2020
DOI: 10.1063/5.0005690
Abstract: Hydrogen-terminated (H-terminated) diamond, when surface transfer doped, can support a sub-surface two-dimensional (2D) hole band that possesses a strong Rashba-type spin–orbit interaction. By incorporating a V2O5/Al2O3 bilayer gate dielectric in a diamond-based metal–oxide–semiconductor architecture, metallic surface conductivity can be maintained at low temperature, avoiding the carrier freeze out exhibited by devices with an Al2O3 gate dielectric alone. Hole densities of up to 2.5 × 1013 cm−2 are achieved by the electrostatic gating of the device, and the spin–orbit interaction strength can be tuned from 3.5 ± 0.5 meV to 8.4 ± 0.5 meV, with a concurrent reduction in the spin coherence length from 40 ± 1 nm to 27 ± 1 nm. The demonstration of a gated device architecture on the H-terminated that avoids the need to cycle the temperature, as is required for ionic liquid gating protocols, opens a pathway to engineering practical devices for the study and application of spin transport in diamond.
Publisher: American Physical Society (APS)
Date: 03-06-2013
Publisher: American Chemical Society (ACS)
Date: 17-08-2021
Publisher: AIP Publishing
Date: 09-05-2011
DOI: 10.1063/1.3589970
Abstract: We report room temperature ferromagnetism in partially hydrogenated epitaxial graphene grown on 4HSiC(0001). The presence of ferromagnetism was confirmed by superconducting quantum interference devices measurements. Synchrotron-based near-edge x-ray absorption fine structure and high resolution electron energy loss spectroscopy measurements have been used to investigate the hydrogenation mechanism on the epitaxial graphene and the origin of room temperature ferromagnetism. The partial hydrogenation induces the formation of unpaired electrons in graphene, which together with the remnant delocalized π bonding network, can explain the observed ferromagnetism in partially hydrogenated epitaxial graphene.
Publisher: American Chemical Society (ACS)
Date: 23-01-2019
Publisher: American Chemical Society (ACS)
Date: 28-10-2019
Abstract: Being a metallic transition-metal dichalcogenide, monolayer vanadium diselenide (VSe
Publisher: Elsevier BV
Date: 09-2009
Publisher: American Chemical Society (ACS)
Date: 24-06-2009
DOI: 10.1021/JP903139Q
Publisher: Elsevier BV
Date: 08-2020
Publisher: Elsevier BV
Date: 03-2020
Publisher: Elsevier BV
Date: 06-2021
Publisher: Wiley
Date: 06-06-2019
Abstract: Metal halide perovskites represent a family of the most promising materials for fascinating photovoltaic and photodetector applications due to their unique optoelectronic properties and much needed simple and low-cost fabrication process. The high atomic number (Z) of their constituents and significantly higher carrier mobility also make perovskite semiconductors suitable for the detection of ionizing radiation. By taking advantage of that, the direct detection of soft-X-ray-induced photocurrent is demonstrated in both rigid and flexible detectors based on all-inorganic halide perovskite quantum dots (QDs) synthesized via a solution process. Utilizing a synchrotron soft-X-ray beamline, high sensitivities of up to 1450 µC Gy
Publisher: Elsevier BV
Date: 08-2022
Publisher: American Chemical Society (ACS)
Date: 11-08-2023
Publisher: Wiley
Date: 19-06-2021
Abstract: This paper describes the transition from the normal to inverted Marcus region in solid‐state tunnel junctions consisting of self‐assembled monolayers of benzotetrathiafulvalene (BTTF), and how this transition determines the performance of a molecular diode. Temperature‐dependent normalized differential conductance analyses indicate the participation of the HOMO (highest occupied molecular orbital) at large negative bias, which follows typical thermally activated hopping behavior associated with the normal Marcus regime. In contrast, hopping involving the HOMO dominates the mechanism of charge transport at positive bias, yet it is nearly activationless indicating the junction operates in the inverted Marcus region. Thus, within the same junction it is possible to switch between Marcus and inverted Marcus regimes by changing the bias polarity. Consequently, the current only decreases with decreasing temperature at negative bias when hopping is “frozen out,” but not at positive bias resulting in a 30‐fold increase in the molecular rectification efficiency. These results indicate that the charge transport in the inverted Marcus region is readily accessible in junctions with redox molecules in the weak coupling regime and control over different hopping regimes can be used to improve junction performance.
Publisher: American Chemical Society (ACS)
Date: 26-12-2018
Publisher: American Chemical Society (ACS)
Date: 29-03-2021
Publisher: Elsevier BV
Date: 06-2022
Publisher: Wiley
Date: 04-09-2023
DOI: 10.1002/EEM2.12668
Publisher: American Chemical Society (ACS)
Date: 25-08-2023
Publisher: American Physical Society (APS)
Date: 22-09-2008
Publisher: AIP Publishing
Date: 15-04-2011
DOI: 10.1063/1.3573779
Publisher: American Physical Society (APS)
Date: 08-11-2010
Publisher: American Chemical Society (ACS)
Date: 05-07-2019
DOI: 10.1021/ACS.NANOLETT.9B01796
Abstract: Practical applications of two-dimensional (2D) black phosphorus (BP) are limited by its fast degradation under ambient conditions, for which many different mechanisms have been proposed however, an atomic level understanding of the degradation process is still hindered by the absence of bottom-up methods for the growth of large-scale few-layer black phosphorus. Recent experimental success in the fabrication of single-layer blue phosphorus provides a model system to probe the oxidation mechanism of two-dimensional (2D) phosphorene down to single-layer thicknesses. Here, we report an atomic-scale investigation of the interaction between molecular oxygen and blue phosphorus. The atomic structure of blue phosphorus and the local binding sites of oxygen have been precisely identified using qPlus-based noncontact atomic force microscopy. A combination of low-temperature scanning tunneling microscopy and X-ray photoelectron spectroscopy measurements reveal a thermally reversible oxidation process of blue phosphorus in a pure oxygen atmosphere. Our study clearly demonstrates the essential role of oxygen in the initial oxidation process, and it sheds further light on the fundamental pathways of the degradation mechanism.
Publisher: American Chemical Society (ACS)
Date: 26-11-2021
DOI: 10.1021/JACS.1C09549
Publisher: AIP Publishing
Date: 15-11-2010
DOI: 10.1063/1.3514553
Abstract: We demonstrate that the electron injection barrier (Δe) between Co and C60 can be tuned by inserting a thin Alq3 interlayer. Using ultraviolet photoemission spectroscopy, Δe of C60 on Alq3-predecorated Co (Δe=0.3 eV) was found to be reduced by 0.3 eV compared with that of C60 deposited directly on the bare Co metal surface (Δe=0.6 eV). Due to Fermi level pining at the Alq3/Co interface, this tuning effect is independent of the thickness of Alq3 interlayer from multilayer to monolayer. Based on the experimental results, band level alignment diagrams are proposed for C60/Co and C60/Alq3/Co interfaces with two different Alq3 thicknesses. Our findings could have potential applications for the reduction in the carrier injection barrier in organic spin valves.
Publisher: American Chemical Society (ACS)
Date: 22-06-2020
Publisher: AIP Publishing
Date: 19-07-2010
DOI: 10.1063/1.3466914
Abstract: The electronic properties of rubrene films exposed to oxygen have been studied by photoemission and x-ray absorption spectroscopies. Oxygen incorporation causes the highest occupied molecular orbital of rubrene to shift to a ∼1.0 eV deep level due to chemical bonds formed by the oxygen atoms with the carbon atoms within the tetracene backbone of rubrene molecules. Deformation of the molecular backbone induced by the C–O bonds destroys the delocalized nature of the molecular orbitals. The oxidized rubrene molecules in a single crystal are proposed to act as point defects that disturb the long-range periodicity and produce localized acceptor states.
Publisher: Springer Science and Business Media LLC
Date: 20-02-2018
DOI: 10.1038/S41598-018-21579-4
Abstract: We report on optimisation of the environmental stability and high temperature operation of surface transfer doping in hydrogen-terminated diamond using MoO 3 and V 2 O 5 surface acceptor layers . In-situ annealing of the hydrogenated diamond surface at 400 °C was found to be crucial to enhance long-term doping stability. High temperature sheet resistance measurements up to 300 °C were performed to examine doping thermal stability. Exposure of MoO 3 and V 2 O 5 transfer-doped hydrogen-terminated diamond s les up to a temperature of 300 °C in ambient air showed significant and irreversible loss in surface conductivity. Thermal stability was found to improve dramatically however when similar thermal treatment was performed in vacuum or in ambient air when the oxide layers were encapsulated with a protective layer of hydrogen silsesquioxane (HSQ). Inspection of the films by X-ray diffraction revealed greater crystallisation of the MoO 3 layers following thermal treatment in ambient air compared to the V 2 O 5 films which appeared to remain amorphous. These results suggest that proper encapsulation and passivation of these oxide materials as surface acceptor layers on hydrogen-terminated diamond is essential to maximise their environmental and thermal stability.
Publisher: American Chemical Society (ACS)
Date: 08-09-2020
Publisher: Elsevier BV
Date: 10-2020
Publisher: American Chemical Society (ACS)
Date: 15-11-2011
DOI: 10.1021/JP208645F
Publisher: American Chemical Society (ACS)
Date: 06-12-2022
Publisher: American Chemical Society (ACS)
Date: 04-06-2012
DOI: 10.1021/AM300887J
Abstract: We demonstrate the use of chemical-vapor-deposited (CVD) graphene as an effective indium-tin-oxide (ITO) electrode surface modifier to engineer the organic donor-acceptor heterojunction interface properties in an inverted organic solar cell device configuration. As revealed by in situ near-edge X-ray adsorption fine structure measurement, the organic donor-acceptor heterojunction, comprising copper-hexadecafluoro-phthalocyanine (F16CuPc) and copper phthalocyanine (CuPc), undergoes an obvious orientation transition from a standing configuration (molecular π-plane nearly perpendicular to the substrate surface) on the bare ITO electrode to a less standing configuration with the molecular π-plane stacking adopting a large projection along the direction perpendicular to the electrode surface on the CVD graphene-modified ITO electrode. Such templated less-standing configuration of the organic heterojunction could significantly enhance the efficiency of charge transport along the direction perpendicular to the electrode surface in the planar heterojunction-based devices. Compared with the typical standing organic-organic heterojunction on the bare ITO electrode, our in situ ultraviolet photoelectron spectroscopy experiments reveal that the heterojunction on the CVD graphene modified ITO electrode possesses better aligned energy levels with respective electrodes, hence facilitating effective charge collection.
Publisher: Elsevier BV
Date: 05-2020
Publisher: Wiley
Date: 13-06-2008
Abstract: We investigate the interface between a C(60) fullerite film, C(60)F(36), and diamond (100) by using core-level photoemission spectroscopy, cyclic voltammetry (CV), and high-resolution electron energy loss spectroscopy (HREELS). We show that C(60) can be covalently bonded to reconstructed C(100)-2x1 and that the bonded interface is sufficiently robust to exhibit characteristic C(60) redox peaks in solution. The bare diamond surface can be passivated against oxidation and hydrogenation by covalently bound C(60). However, C(60)F(36) is not as stable as C(60) and desorbs below 300 degrees C (the latter species being stable up to 500 degrees C on the diamond surface). Neither C(60) fullerite nor C(60)F(36) form reactive interfaces on the hydrogenated surface-they both desorb below 300 degrees C. The surface transfer doping process of hydrogenated diamond by C(60)F(36) is the most evident one among all the adsorbate systems studied (with a coverage-dependent band bending induced by C(60)F(36)).
Publisher: Elsevier BV
Date: 04-2018
Publisher: American Chemical Society (ACS)
Date: 23-08-2006
DOI: 10.1021/LA060974Q
Abstract: The information depth of near-edge X-ray absorption fine structure spectroscopy in the total electron yield mode (TEY-NEXAFS) is given by the escape depth of the TEY electrons z(TEY). This is determined by the effective ranges both of the inelastically scattered secondary electrons and of the primary excited electron before they thermalize below the vacuum level. For regioregular poly(3-hexylthiophene) (rreg-P3HT) thin films, we have measured the total electron emission efficiency to be 0.028 +/- 0.005 e h at an incident photon energy of 320 eV. The range of the primary electron was computed using optical dielectric-loss theory to be 7.5 nm. The range of the secondary electrons was then found by modeling to be 3.0 nm. This gives z(TEY) to be 2.5 nm, which is considerably less than the often-assumed value of 10 nm in the literature. It is also considerably smaller than the computed electron-electron scattering inelastic mean free path in the material, which suggests the predominance of electron-phonon scattering. Thus, TEY-NEXAFS has sufficient surface sensitivity to probe the frontier molecular layers of these organic conjugated polymers. In a second aspect of this report, the rreg-P3HT films have been characterized by in-situ core and valence photoemission spectroscopies and by ex-situ microattenuated total-reflection vibrational spectroscopy as a function of irradiation dose. No damage was observed in composition, bonding, orientation, and surface morphology under typical TEY-NEXAFS spectral acquisition conditions. For an integrated TEY that exceeds 2 x 10(-3) C cm(-2), however, the material degrades via alkyl side-chain dehydrogenation to unsaturated units, cross linking, ring opening of the backbone, and sulfur extrusion. Given that secondary electrons are the dominant cause of radiation damage, this exposure threshold measured by integrated TEY should also be valid at other X-ray energies.
Publisher: Elsevier BV
Date: 02-0005
Publisher: Springer Science and Business Media LLC
Date: 06-01-2013
Abstract: One of the main goals of organic and molecular electronics is to relate the performance and electronic function of devices to the chemical structure and intermolecular interactions of the organic component inside them, which can take the form of an organic thin film, a self-assembled monolayer or a single molecule. This goal is difficult to achieve because organic and molecular electronic devices are complex physical-organic systems that consist of at least two electrodes, an organic component and two (different) organic/inorganic interfaces. Singling out the contribution of each of these components remains challenging. So far, strong π-π interactions have mainly been considered for the rational design and optimization of the performances of organic electronic devices, and weaker intermolecular interactions have largely been ignored. Here, we show experimentally that subtle changes in the intermolecular van der Waals interactions in the active component of a molecular diode dramatically impact the performance of the device. In particular, we observe an odd-even effect as the number of alkyl units is varied in a ferrocene-alkanethiolate self-assembled monolayer. As a result of a more favourable van der Waals interaction, junctions made from an odd number of alkyl units have a lower packing energy (by ∼0.4-0.6 kcal mol(-1)), rectify currents 10 times more efficiently, give a 10% higher yield in working devices, and can be made two to three times more reproducibly than junctions made from an even number of alkyl units.
Publisher: American Chemical Society (ACS)
Date: 29-04-2015
DOI: 10.1021/ACS.NANOLETT.5B00290
Abstract: An atomic-scale understanding of gas adsorption mechanisms on metal-porphyrins or metal-phthalocyanines is essential for their practical application in biological processes, gas sensing, and catalysis. Intensive research efforts have been devoted to the study of coordinative bonding with relatively active small molecules such as CO, NO, NH3, O2, and H2. However, the binding of single nitrogen atoms has never been addressed, which is both of fundamental interest and indeed essential for revealing the elementary chemical binding mechanism in nitrogen reduction processes. Here, we present a simple model system to investigate, at the single-molecule level, the binding of activated nitrogen species on the single Mn atom contained within the manganese phthalocyanine (MnPc) molecule supported on an inert graphite surface. Through the combination of in situ low-temperature scanning tunneling microscopy, scanning tunneling spectroscopy, ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations, the active site and the binding configuration between the activated nitrogen species (neutral nitrogen atom) and the Mn center of MnPc are investigated at the atomic scale.
Publisher: AIP Publishing
Date: 15-09-2007
DOI: 10.1063/1.2778636
Abstract: The conformation degree and molecular orientation during the growth of rubrene films on Si(111) and Au(111) have been studied by in situ x-ray absorption spectroscopy. The backbones of rubrene molecules on Au(111) are twisted at the first few layers in contrast, no appreciable twisting is observed on Si(111) even at a thickness of approximately 1.5 nm. The planarization of the backbone in the first few layers is due to strong molecule–substrate interactions between rubrene and Si(111). The rubrene molecules on Au(111) have a backbone tilt angle of 41° and a phenyl side group tilt of 64° with respect to the substrate surface, suggesting the crystalline nature of the films. Ex situ atomic force microscopy measurements confirm that the rubrene film grown on Au(111) is crystalline and the growth direction is along its crystallographic c axis.
Publisher: American Chemical Society (ACS)
Date: 22-11-2013
DOI: 10.1021/JP4099733
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0SC04555A
Abstract: Herein, we report the first room temperature switchable Fe( iii ) molecular spin crossover (SCO) tunnel junction.
Publisher: Elsevier BV
Date: 2022
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0MA00123F
Abstract: Coordination crosslinking of oligoamide nanorods yields two dimensional metallosupramolecular framework.
Publisher: American Chemical Society (ACS)
Date: 18-11-2009
DOI: 10.1021/LA901204X
Abstract: The molecular orientations of copper phthalocyanine (CuPc) organic semiconductor molecules on hydrogenated and bare diamond (001)-2 x 1 surfaces are studied using synchrotron-based photoemission spectroscopy (PES) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Angular-dependent NEXAFS reveals that the CuPc molecular assemblies are orientationally ordered and lying down on hydrogenated diamond, whereas they undergo a molecular reorientation on bare diamond from lying down at submonolayer coverage to standing up in multilayers. The molecular film on bare diamond also exhibits an order-disorder-order transition in the molecular orientations. The distinct molecular orientation within the CuPc films on both diamond (001) surfaces is explained in terms of the interplay between intermolecular interactions and molecule-substrate interactions.
Publisher: Wiley
Date: 08-12-2010
Abstract: Organic–organic heterojunctions (OOHs) are critical features in organic light‐emitting diodes, ambipolar organic field‐effect transistors and organic solar cells, which are fundamental building blocks in low‐cost, large‐scale, and flexible electronics. Due to the highly anisotropic nature of π‐conjugated molecules, the molecular orientation of organic thin films can significantly affect the device performance, such as light absorption and charge‐carrier transport, as well as the energy level alignment at OOH interfaces. This Feature Article highlights recent progress in the understanding of interface energetics at small molecule OOH interfaces, focusing on the characterization and fabrication of OOH with well‐defined molecular orientations using a combination of in situ low‐temperature scanning tunneling microscopy, synchrotron‐based high‐resolution ultraviolet photoelectron spectroscopy and near‐edge X‐ray absorption fine structure measurements. The orientation dependent energy level alignments at the OOH interfaces will be discussed in detail.
Publisher: The Royal Society
Date: 28-10-2012
Abstract: We report room-temperature ferromagnetism (FM) in highly conducting, transparent anatase Ti 1− x Ta x O 2 ( x ∼0.05) thin films grown by pulsed laser deposition on LaAlO 3 substrates. Rutherford backscattering spectrometry (RBS), X-ray diffraction, proton-induced X-ray emission, X-ray absorption spectroscopy (XAS) and time-of-flight secondary-ion mass spectrometry indicated negligible magnetic contaminants in the films. The presence of FM with concomitant large carrier densities was determined by a combination of superconducting quantum interference device magnetometry, electrical transport measurements, soft X-ray magnetic circular dichroism (SXMCD), XAS and optical magnetic circular dichroism, and was supported by first-principles calculations. SXMCD and XAS measurements revealed a 90 per cent contribution to FM from the Ti ions, and a 10 per cent contribution from the O ions. RBS/channelling measurements show complete Ta substitution in the Ti sites, though carrier activation was only 50 per cent at 5 per cent Ta concentration, implying compensation by cationic defects. The role of the Ti vacancy ( V Ti ) and Ti 3+ was studied via XAS and X-ray photoemission spectroscopy, respectively. It was found that, in films with strong FM, the V Ti signal was strong while the Ti 3+ signal was absent. We propose (in the absence of any obvious exchange mechanisms) that the localized magnetic moments, V Ti sites, are ferromagnetically ordered by itinerant carriers. Cationic-defect-induced magnetism is an alternative route to FM in wide-band-gap semiconducting oxides without any magnetic elements.
Publisher: Wiley
Date: 16-02-2018
Publisher: American Chemical Society (ACS)
Date: 06-2007
DOI: 10.1021/JA071658G
Abstract: Epitaxial graphene thermally grown on 6H-SiC(0001) can be p-type doped via a novel surface transfer doping scheme by modifying the surface with the electron acceptor, tetrafluoro-tetracyanoquinodimethane (F4-TCNQ). Synchrotron-based high-resolution photoemission spectroscopy reveals that electron transfer from graphene to adsorbed F4-TCNQ is responsible for the p-type doping of graphene. This novel surface transfer doping scheme by surface modification with appropriate molecular acceptors represents a simple and effective method to nondestructively dope epitaxial graphene for future nanoelectronics applications.
Publisher: Wiley
Date: 16-07-2021
Abstract: Although the carbon‐supported single‐atom (SA) electrocatalysts (SAECs) have emerged as a new form of highly efficient oxygen reduction reaction (ORR) electrocatalysts, the preferable sites of carbon support for anchoring SAs are somewhat elusive. Here, a KOH activation approach is reported to create abundant defects/vacancies on the porous graphitic carbon nanosphere (CNS) with selective adsorption capability toward transition‐metal (TM) ions and innovatively utilize the created defects/vacancies to controllably anchor TM–SAs on the activated CNS via TMN x coordination bonds. The synthesized TM‐based SAECs (TM‐SAs@N‐CNS, TM: Cu, Fe, Co, and Ni) possess superior ORR electrocatalytic activities. The Cu‐SAs@N‐CNS demonstrates excellent ORR and oxygen evolution reaction (OER) bifunctional electrocatalytic activities and is successfully applied as a highly efficient air cathode material for the Zn–air battery. Importantly, it is proposed and validated that the N‐terminated vacancies on graphitic carbons are the preferable sites to anchor Cu‐SAs via a Cu(NC 2 ) 3 (NC) coordination configuration with an excellent promotional effect toward ORR. This synthetic approach exemplifies the expediency of suitable defects/vacancies creation for the fabrication of high‐performance TM‐based SAECs, which can be implemented for the synthesis of other carbon‐supported SAECs.
Publisher: IOP Publishing
Date: 20-01-2010
Publisher: Elsevier BV
Date: 05-2023
Publisher: Elsevier BV
Date: 09-2007
Publisher: Elsevier BV
Date: 12-2019
Publisher: American Physical Society (APS)
Date: 17-06-2022
Publisher: Elsevier BV
Date: 04-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8TA12070F
Abstract: CuWO 4 is an n-type oxide semiconductor with a bandgap of 2.2 eV which exhibits great potential for photoelectrochemical (PEC) conversion of solar energy into chemical fuels.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NA00107G
Abstract: Understanding the influence of structural properties on the electronic structure will pave the way for optimization of charge transport properties of SAM devices.
Publisher: Wiley
Date: 08-07-2022
Abstract: 2D tin diselenide and its derived 2D heterostructures have delivered promising potentials in various applications ranging from electronics to energy storage devices. The major challenges associated with large‐scale fabrication of SnSe 2 crystals, however, have hindered its engineering applications. Herein, a tin‐extraction synthetic method is proposed for producing large‐size SnSe 2 bulk crystals. In a typical synthesis, a Sn‐containing MAX phase (V 2 SnC) and a Se source are heat‐treated under a reducing atmosphere, by which Sn is extracted from the V 2 SnC phase as a rectified Sn source to form SnSe 2 crystals in the cold zone. After the following liquid exfoliation, the obtained 2D SnSe 2 nanosheets have a lateral size of a few centimeters and an atomic thickness. Furthermore, by coupling with 2D graphene to form 2D/2D SnSe 2 /graphene heterostructured electrodes, as validated by theoretical calculation and experimental studies, the superior Li‐/Na‐ion storage performance with ultralow surface/interface ion transport barriers are achieved for rechargeable Li‐/Na‐ion batteries. This innovative synthetic strategy opens a new avenue for the large‐scale synthesis of selenides and offers more options into the practical application of emerging 2D/2D heterostructure for electrochemical energy storage.
Publisher: Royal Society of Chemistry (RSC)
Date: 24-07-2014
DOI: 10.1039/C4NR02933J
Abstract: This study describes that the current rectification ratio, R ≡ |J|(-2.0 V)/|J|(+2.0 V) for supramolecular tunneling junctions with a top-electrode of eutectic gallium indium (EGaIn) that contains a conductive thin (0.7 nm) supporting outer oxide layer (Ga2O3), increases by up to four orders of magnitude under an applied bias of >+1.0 V up to +2.5 V these junctions did not change their electrical characteristics when biased in the voltage range of ±1.0 V. The increase in R is caused by the presence of water and ions in the supramolecular assemblies which react with the Ga2O3/EGaIn layer and increase the thickness of the Ga2O3 layer. This increase in the oxide thickness from 0.7 nm to ∼2.0 nm changed the nature of the monolayer-top-electrode contact from an ohmic to a non-ohmic contact. These results unambiguously expose the experimental conditions that allow for a safe bias window of ±1.0 V (the range of biases studies of charge transport using this technique are normally conducted) to investigate molecular effects in molecular electronic junctions with Ga2O3/EGaIn top-electrodes where electrochemical reactions are not significant. Our findings also show that the interpretation of data in studies involving applied biases of >1.0 V may be complicated by electrochemical side reactions which can be recognized by changes of the electrical characteristics as a function voltage cycling or in current retention experiments.
Publisher: American Chemical Society (ACS)
Date: 20-07-2023
Publisher: Wiley
Date: 31-07-2021
Abstract: The detection and monitoring of nitrogen dioxide (NO 2 ) plays a vital role in the environmental, healthcare, farming, and industrial sectors. However, the development of NO 2 gas sensors with simultaneously high sensitivity, reversibility, low detection limit, and excellent selectivity remains challenging. In this work, an ultrasensitive NO 2 gas sensor with superb selectivity and reversibility is demonstrated based on α‐phase molybdenum trioxide (α‐MoO 3 ). Nanoribbons of α‐MoO 3 are synthesized via vapor phase transport (VPT) and systematically characterized using a combination of advanced characterization probes. At an optimal operating temperature of 125 °C, the α‐MoO 3 ‐based sensor shows a very high sensitivity toward NO 2 with a detection limit as low as 24 ppb, while also exhibiting excellent selectivity and reversibility. Such impressive performance originates from the layered nature of the α‐MoO 3 nanoribbons as well as the hierarchical assembly of the nanoribbons as the sensing layer. The study demonstrates a facile sensing platform based on α‐MoO 3 for ultrasensitive and selective NO 2 gas sensing.
Publisher: American Physical Society (APS)
Date: 23-09-2021
Publisher: American Chemical Society (ACS)
Date: 09-06-2022
Publisher: Elsevier BV
Date: 05-2003
Publisher: IOP Publishing
Date: 07-04-2008
Publisher: American Chemical Society (ACS)
Date: 30-06-2007
DOI: 10.1021/LA063165F
Abstract: Evaporated pentacene thin films with thicknesses from several nm to 150 nm on gold and silver substrates have been studied by ultraviolet photoelectron spectroscopy (UPS), near-edge X-ray absorption fine structure (NEXAFS), scanning tunneling microscopy (STM), and atomic force microscopy (AFM). It was found that pentacene thin-film structures, particularly their molecular orientations, are strongly influenced by the metal substrates. UPS measurements revealed a distinct change in the valence band structures of pentacene on Au compared to those on Ag, which is attributed to the different packing between adjacent molecules. Using NEXAFS, we observed 74+/-5 degrees and 46+/-5 degrees molecular tilt angles on Ag and Au, respectively, for all measured thicknesses. We propose that pentacene molecules stand up on the surface and form the "thin-film phase" structure on Ag. On Au, pentacene films grow in domains with molecules either lying flat or standing up on the substrate. Such a mixture of two crystalline phases leads to an average tilt angle of 46 degrees for the whole film and the change in valence band structures. STM and distance-voltage (z-V) spectroscopy studies confirm the existence of two crystalline phases on Au with different conducting properties. z-V spectra on the low conducting phase clearly indicate its nature as "thin-film phase".
Publisher: Springer Science and Business Media LLC
Date: 21-11-2022
DOI: 10.1038/S41563-022-01402-2
Abstract: To realize molecular-scale electrical operations beyond the von Neumann bottleneck, new types of multifunctional switches are needed that mimic self-learning or neuromorphic computing by dynamically toggling between multiple operations that depend on their past. Here, we report a molecule that switches from high to low conductance states with massive negative memristive behaviour that depends on the drive speed and number of past switching events, with all the measurements fully modelled using atomistic and analytical models. This dynamic molecular switch emulates synaptic behavior and Pavlovian learning, all within a 2.4-nm-thick layer that is three orders of magnitude thinner than a neuronal synapse. The dynamic molecular switch provides all the fundamental logic gates necessary for deep learning because of its time-domain and voltage-dependent plasticity. The synapse-mimicking multifunctional dynamic molecular switch represents an adaptable molecular-scale hardware operable in solid-state devices, and opens a pathway to simplify dynamic complex electrical operations encoded within a single ultracompact component.
Publisher: Wiley
Date: 28-03-2013
Publisher: Elsevier BV
Date: 06-2004
Publisher: American Chemical Society (ACS)
Date: 28-04-2015
Publisher: American Chemical Society (ACS)
Date: 06-11-2015
DOI: 10.1021/ACS.NANOLETT.5B03520
Abstract: The reversible selective hydrogenation and dehydrogenation of in idual manganese phthalocyanine (MnPc) molecules has been investigated using photoelectron spectroscopy (PES), low-temperature scanning tunneling microscopy (LT-STM), synchrotron-based near edge X-ray absorption fine structure (NEXAFS) measurements, and supported by density functional theory (DFT) calculations. It is shown conclusively that interfacial and intramolecular charge transfer arises during the hydrogenation process. The electronic energetics upon hydrogenation is identified, enabling a greater understanding of interfacial and intramolecular charge transportation in the field of single-molecule electronics.
Publisher: Wiley
Date: 09-08-2020
Publisher: IOP Publishing
Date: 12-02-2016
DOI: 10.1088/0953-8984/28/9/094006
Abstract: Understanding the charge transport properties in general of different molecular components in a self-assembled monolayer (SAM) is of importance for the rational design of SAM molecular structures for molecular electronics. In this study, we study an important aspect of the charge transport properties, i.e. the charge transfer (CT) dynamics between the active molecular component (in this case, the ferrocenyl moieties of a ferrocenyl-n-alkanethiol SAM) and the electrode using synchrotron-based core-hole clock (CHC) spectroscopy. The characteristic CT times are found to depend strongly on the character of the ferrocenyl-derived molecular orbitals (MOs) which mediate the CT process. Furthermore, by systemically shifting the position of the ferrocenyl moiety in the SAM, it is found that the CT characteristics of the ferrocenyl MOs display distinct dependence on its distance to the electrode. These results demonstrate experimentally that the efficiency and rate of charge transport through the molecular backbone can be modulated by resonant injection of charge carriers into specific MOs.
Publisher: AIP Publishing
Date: 14-05-2007
DOI: 10.1063/1.2737908
Abstract: MnSb nanoparticles with average lateral diameters ⟨d⟩ from 5to30nm are synthesized on ultra thin silicon nitride covered Si(111) by codeposition of Mn and Sb. These MnSb particles possess sharp interfaces and a NiAs-type lattice. The Mn 2p x-ray absorption spectroscopy analysis shows broad line shapes due to the itinerant Mn 3d states. The particles with ⟨d⟩=5 and 8.5nm are superparamagnetic at room temperature, while those of ⟨d⟩=15 and 30nm exhibit ferromagnetic behavior.
Publisher: AIP Publishing
Date: 11-02-2008
DOI: 10.1063/1.2857460
Abstract: In situ synchrotron-based near-edge x-ray absorption fine structure measurements and photoemission spectroscopy have been used to investigate the effect of molecular orientation on the interfacial dipole and the energy level alignment at the interfaces of organic heterojunctions comprising copper-hexadecafluoro-phthalocyanine (F16CuPc) on both standing-up and lying-down copper(II) phthalocyanine (CuPc) thin films. It is found that F16CuPc thin films adopt the same molecular orientation of the underlying CuPc thin films. An interfacial dipole of 0.45eV forms at the interface of lying-down F16CuPc∕CuPc on highly ordered pyrolytic graphite. In contrast, a much larger interfacial dipole of 1.35eV appears at the interface of standing-up F16CuPc∕CuPc on octane-1-thiol terminated Au(111).
Publisher: American Chemical Society (ACS)
Date: 29-01-2008
DOI: 10.1021/JP0726337
Publisher: Wiley
Date: 03-04-2007
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0TC05773H
Abstract: This work gives new insights in the conduction mechanisms across biomolecular junctions and demonstrates that proteins can reversibly change between in- and coherent tunnelling pathways defined by the protein cage and the amount of co-factor.
Publisher: AIP Publishing
Date: 29-08-2011
DOI: 10.1063/1.3629812
Abstract: Chemical vapor deposition (CVD) graphene has been used as an effective structural template to manipulate molecular orientation of organic thin film of chloroaluminium phthalocyanine (ClAlPc) on indium tin oxide (ITO) electrode. As revealed by in-situ near-edge x-ray adsorption fine structure measurement, ClAlPc molecules on the CVD graphene modified ITO electrode adopt a well-aligned lying-down configuration with their molecular π-plane nearly parallel to the electrode surface, in contrast to the random orientation of ClAlPc molecules on the bare ITO electrode. This lying-down configuration results in an optimized stacking of the molecular π-plane perpendicular to the electrode surface and hence facilitates efficient charge transport along this direction.
Publisher: American Chemical Society (ACS)
Date: 17-08-2007
DOI: 10.1021/LA701285H
Abstract: The tuning of electron affinity and secondary electron emission on diamond (100) surfaces due to cycloaddition with 1,3-butadiene is investigated by photoemission experiments and density functional theory (DFT) calculations. A significant reduction in electron affinity up to 0.7 eV and enhancement of secondary electron emission were observed after 1,3-butadiene adsorption. The lowering of vacuum level via 1,3-butadiene adsorption is supported by DFT calculations. The C-H bonds in the covalently bonded organics on diamond contribute to the enhanced secondary electron emission and reduced electron affinity in a mechanism similar to that of C-H bonds on hydrogenated diamond surfaces. This combination of strong secondary emission and low electron affinity by the organic functionalization of diamond has potential applications in diamond-based molecular electronic devices.
Publisher: American Physical Society (APS)
Date: 08-07-2010
Publisher: Elsevier BV
Date: 2023
Publisher: Elsevier BV
Date: 04-2006
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9TA13313E
Abstract: Hole for faster OER: The hole state induced by Fe 4+ promotes the OER process. It reduces the energy barrier for electron transfer at the interface and facilitates a faster electron transfer from reaction intermediates to the catalyst.
Publisher: AIP Publishing
Date: 27-09-2021
DOI: 10.1063/5.0058989
Abstract: Metal-insulator transition (MIT), an intriguing correlated phenomenon induced by the subtle competition of the electrons' repulsive Coulomb interaction and kinetic energy, is of great potential use for electronic applications due to the dramatic change in resistivity. Here, we demonstrate a reversible control of MIT in VO2 films via oxygen stoichiometry engineering. By facilely depositing and dissolving a water-soluble yet oxygen-active Sr3Al2O6 capping layer atop VO2 at room temperature, oxygen ions can reversibly migrate between VO2 and Sr3Al2O6, resulting in a gradual suppression and a complete recovery of MIT in VO2. The migration of the oxygen ions is evidenced in a combination of transport measurement, structural characterization, and first-principles calculations. This approach of chemically induced oxygen migration using a water-dissolvable adjacent layer could be useful for advanced electronic and iontronic devices and studying oxygen stoichiometry effects on the MIT.
Publisher: Elsevier BV
Date: 03-2015
Publisher: American Chemical Society (ACS)
Date: 08-10-2008
DOI: 10.1021/CM801752J
Publisher: Wiley
Date: 13-01-2022
Abstract: Rechargeable aqueous zinc‐ion batteries (ZIBs) are promising in stationary grid energy storage due to their advantages in safety and cost‐effectiveness, and the search for competent cathode materials is one core task in the development of ZIBs. Herein, the authors design a 2D heterostructure combining amorphous vanadium pentoxide and electrochemically produced graphene oxide (EGO) using a fast and scalable spray drying technique. The unique 2D heterostructured xerogel is achieved by controlling the concentration of EGO in the precursor solution. Driven by the improved electrochemical kinetics, the resultant xerogel can deliver an excellent rate capability (334 mAh g −1 at 5 A g −1 ) as well as a high specific capacity (462 mAh g −1 at 0.2 A g −1 ) as the cathode material in ZIB. It is also shown that the coin cell constructed based on spray‐dried xerogel can output steady, high energy densities over a broad power density window. This work provides a scalable and cost‐effective approach for making high performance electrode materials from cheap sources through existing industrialized materials processing.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6NR08311K
Abstract: We report a detailed investigation of elementary catalytic decomposition of ammonia on the Pt-Ni-Pt(111) bimetallic surface using in situ near ambient pressure X-ray photoelectron spectroscopy. Under the near ambient pressure (0.6 mbar) reaction conditions, a different dehydrogenation pathway with a reduced activation energy barrier for recombinative nitrogen desorption on the Pt-Ni-Pt(111) bimetallic surface is observed. The unique surface catalytic activity is correlated with the downward shift of the Pt 5d band states induced by the Ni subsurface atoms via charge redistribution of the topmost Pt layer. Our results provide a practical understanding of the unique chemistry of bimetallic catalysts for facile ammonia decomposition under realistic reaction conditions.
Publisher: Elsevier BV
Date: 06-2021
Publisher: Wiley
Date: 03-02-2021
Publisher: American Chemical Society (ACS)
Date: 04-05-2009
DOI: 10.1021/JP810804T
Publisher: AIP Publishing
Date: 10-09-2018
DOI: 10.1063/1.5037624
Abstract: Here, we report the electronic structures at the N, N′-dipentyl-3,4,9,10-perylenedicarboximide (PTCDI-C5)/CH3NH3PbI3 interface identified in-situ by X-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy. Strong chemical reactions are found to occur upon the deposition of PTCDI-C5 molecules on CH3NH3PbI3. Electron donation from PTCDI-C5 molecules to CH3NH3PbI3 leads to the filling of surface states and the emergence of an interfacial gap state with its onset tailed to the Fermi level. As a consequence, the downward surface band bending resulting from surface states acting as donor states at the pristine perovskite surface is reduced by 0.2 eV. After the energy level alignment at the interface is established, the perovskite conduction band minimum is found to be in line with the lowest unoccupied molecular orbital favoring the electron extraction with a moderate valence band maximum-highest occupied molecular orbital offset of ∼0.7 eV. The present results demonstrate that interfacial chemical reactions can dictate energetics at organic erovskite interfaces. Understanding the chemical interaction and resultant electronic structures at those interfaces is crucial for efficient and long-term stable perovskite-based devices when passivation of chemical active sites and matched energy level could be readily reached.
Publisher: AIP Publishing
Date: 16-03-2020
DOI: 10.1063/1.5141775
Abstract: A hydrogen-terminated diamond (H-terminated diamond) surface supports a two-dimensional (2D) p-type surface conductivity when exposed to the atmosphere, as a result of the surface transfer doping process. The formation of reliable Ohmic contacts that persist to cryogenic temperature is essential for the exploration of quantum transport in the diamond 2D conducting channel. Herein, the contact properties of Pd on H-terminated diamond have been fully investigated down to 4 K using transmission line method measurements. Pd is shown to form an Ohmic contact on H-terminated diamond with linear I–V characteristics and low specific contact resistance in the range of (8.4 ± 1) ×10−4 Ω·cm2 to (1.3 ± 0.2) ×10−3 Ω·cm2 for the temperature range of 300 K–4 K. This is in stark contrast to reference devices with Au/Pt/Ti contacts, which exhibit a significant temperature dependence and non-Ohmic behavior at low temperature. Using 2D thermionic emission theory, a negative Schottky barrier height (SBH), − 23 ± 1 meV, between Pd and H-terminated diamond has been determined, in comparison to a positive SBH of 42 ± 1 meV for the Au/Pt/Ti/H-terminated diamond interface. These results show that Pd serves as an excellent candidate for forming reliable Ohmic contacts on H-terminated diamond for enabling precise electrical transport measurements at cryogenic temperature.
Publisher: American Physical Society (APS)
Date: 03-09-2019
Publisher: American Chemical Society (ACS)
Date: 12-05-2020
Publisher: AIP Publishing
Date: 09-09-2013
DOI: 10.1063/1.4811758
Abstract: We report on the emerging and admixture of Frenkel and charge transfer (CT) excitons near the absorption onset in pentacene single crystals. Using high energy-resolution spectroscopic generalized ellipsometry with in-plane polarization dependence, the excitonic nature of three lowest lying excitations is discussed. Their distinct polarization dependence strongly indicates the presence of both Frenkel and CT types of excitons near the excitation onset. In particular, the peculiar polarization behavior of the second excitation can only be rationalized by taking into account the inherent CT transition dipole moment. This observation has important implications for the pentacene-based optoelectronic devices.
Publisher: Wiley
Date: 15-02-2011
Publisher: AIP Publishing
Date: 21-01-2011
DOI: 10.1063/1.3546034
Abstract: The electronic structures at the MoO3/Co interface were investigated using synchrotron-based ultraviolet and x-ray photoelectron spectroscopy. It was found that interfacial chemical reactions lead to the reduction of Mo oxidation states and the formation of Co-O bonds. These interfacial chemical reactions also induce a large interface dipole, which significantly increases the work function of the cobalt substrate. In addition, two interface states located at 1.0 and 2.0 eV below the Fermi level are identified. These two states overlap at film thickness of between 2–4 nm, which suggests the MoO3 intermediate layer may facilitate ohmic charge transport.
Publisher: Elsevier BV
Date: 03-2011
Publisher: IOP Publishing
Date: 06-2017
Publisher: Elsevier BV
Date: 09-2020
Publisher: AIP Publishing
Date: 15-09-2009
DOI: 10.1063/1.3225918
Abstract: Molecular orientation-controlled charge transfer has been observed at the organic-organic heterojunction interfaces of copper-hexadecafluoro-phthalocyanine (F16CuPc) or copper(II) phthalocyanine (CuPc) on both standing-up and lying-down CuPc or F16CuPc thin films. In situ synchrotron-based photoemission spectroscopy reveals that the charge transfer at the standing F16CuPc/CuPc or CuPc/F16CuPc interface is much larger than that at the lying F16CuPc/CuPc or CuPc/F16CuPc interface. This can be explained by the orientation-dependent ionization potentials of well-ordered organic thin films, which place the highest-occupied molecular orbital of the standing CuPc film much closer to the lowest-unoccupied molecular orbital of the standing F16CuPc film, facilitating stronger charge transfer as compared to that at the lying OOH interfaces. Our results suggest the possibility of manipulating interfacial electronic structures of organic heterojunctions by controlling the molecular orientation, in particular for applications in ambipolar organic field transistors and organic photovoltaics.
Publisher: Wiley
Date: 05-08-2020
Publisher: Wiley
Date: 03-2021
Abstract: Aliovalent doping is widely adopted to tune the electronic structure of transition‐metal oxides for design of low‐cost, active electrocatalysts. Here, using single‐crystalline thin films as model electrocatalysts, the structure‐activity relationship of Fe states doping in perovskite LaNiO 3 for oxygen evolution reaction (OER) is studied. Fe 4+ state is found to be crucial for enhancing the OER activity of LaNiO 3 , dramatically increasing the activity by six times, while Fe 3+ has negligible effect. Spectroscopic studies and DFT calculations indicate Fe 4+ states enhance the degree of Ni/Fe 3 d and O 2 p hybridization, and meanwhile produce down‐shift of the unoccupied density of states towards lower energies. Such electronic features reduce the energy barrier for interfacial electron transfer for water oxidization by 0.2 eV. Further theoretical calculations and H/D isotope experiments reveal the electronic states associated with Fe 4+ ‐O 2− ‐Ni 3+ configuration accelerate the deprotonation of *OH to *O (rate‐determining step), and thus facilitate fast OER kinetics.
Publisher: Wiley
Date: 20-01-2007
Publisher: IOP Publishing
Date: 23-05-2016
DOI: 10.1088/0957-4484/27/27/275201
Abstract: A combination of synchrotron-based x-ray spectroscopy and contact potential difference measurements have been used to examine the electronic structure of the (3 × 1) silicon terminated (100) diamond surface under ultra high vacuum conditions. An occupied surface state which sits 1.75 eV below the valence band maximum has been identified, and indications of mid-gap unoccupied surface states have been found. Additionally, the pristine silicon terminated surface is shown to possess a negative electron affinity of -0.86 ± 0.1 eV.
Publisher: American Chemical Society (ACS)
Date: 12-01-2012
DOI: 10.1021/JP210533N
Publisher: American Chemical Society (ACS)
Date: 31-08-2011
DOI: 10.1021/NN202910T
Abstract: We demonstrated a novel method to obtain charge neutral quasi-free-standing graphene on SiC (0001) from the buffer layer using fluorine from a molecular source, fluorinated fullerene (C(60)F(48)). The intercalated product is stable under ambient conditions and resistant to elevated temperatures of up to 1200 °C. Scanning tunneling microscopy and spectroscopy measurements are performed for the first time on such quasi-free-standing graphene to elucidate changes in the electronic and structural properties of both the graphene and interfacial layer. Novel structures due to a highly localized perturbation caused by the presence of adsorbed fluorine were produced in the intercalation process and investigated. Photoemission spectroscopy is used to confirm these electronic and structural changes.
Publisher: Elsevier BV
Date: 02-2014
Publisher: American Association for the Advancement of Science (AAAS)
Date: 02-08-2019
Abstract: The erasable and recreatable 2D electron gas at SrTiO 3 -based heterointerface paves the way towards future novel electronics.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0TA05130F
Abstract: A novel in situ polymerization approach is developed for the synthesis of well-defined FeN 4 -based single-atom catalysts (SACs) on carbon nanotubes with superior catalytic activity in the ORR and Zn–oxygen batteries.
Publisher: AIP Publishing
Date: 05-2006
DOI: 10.1063/1.2201615
Abstract: Core-hole clock spectroscopy and near-edge x-ray-absorption fine structure measurements have been used to investigate the ultrafast electron transfer dynamics at the Copper(II) phthalocyanine (CuPc)∕Au(111) interface. It was found that the strong electronic coupling between the first layer of CuPc molecules and Au(111) substrate favors ultrafast electron transfer from the lowest unoccupied molecular orbital of the CuPc molecules to the conduction band of Au(111) in the time scale of ∼6fs. In contrast, the intermolecular electron transfer within multilayers of CuPc molecules via the weak van der Waals interaction was much slower.
Publisher: AIP Publishing
Date: 02-2020
DOI: 10.1063/1.5142999
Abstract: Gallium oxide (Ga2O3) is an emerging wide bandgap semiconductor that has attracted a large amount of interest due to its ultra-large bandgap of 4.8 eV, a high breakdown field of 8 MV/cm, and high thermal stability. These properties enable Ga2O3 a promising material for a large range of applications, such as high power electronic devices and solar-blind ultraviolet (UV) photodetectors. In the past few years, a significant process has been made for the growth of high-quality bulk crystals and thin films and device optimizations for power electronics and solar blind UV detection. However, many challenges remain, including the difficulty in p-type doping, a large density of unintentional electron carriers and defects/impurities, and issues with the device process (contact, dielectrics, and surface passivation), and so on. The purpose of this article is to provide a timely review on the fundamental understanding of the semiconductor physics and chemistry of Ga2O3 in terms of electronic band structures, optical properties, and chemistry of defects and impurity doping. Recent progress and perspectives on epitaxial thin film growth, chemical and physical properties of defects and impurities, p-type doping, and ternary alloys with In2O3 and Al2O3 will be discussed.
Publisher: AIP Publishing
Date: 20-04-2009
DOI: 10.1063/1.3122940
Abstract: The molecular orientation of copper(II) phthalocyanine (CuPc) thin films on monolayer C60 on Ag(111) was studied by in situ near-edge x-ray absorption fine structure measurements and low-temperature scanning tunneling microscopy. It is found that in densely packed thin films, CuPc molecules adopt a standing-up configuration with the molecular π-plane tilting slightly from the surface normal on monolayer C60.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2TB01135B
Abstract: Nanoceria prepared with different Ce 3+ /Ce 4+ ratios show different oxidase mimetic activities. The activity is enhanced selectively in presence of fluoride ions and used for glutathione detection.
Publisher: Elsevier BV
Date: 2021
Publisher: Wiley
Date: 04-11-2019
Abstract: The ability to use mechanical strain to steer chemical reactions creates completely new opportunities for solution- and solid-phase synthesis of functional molecules and materials. However, this strategy is not readily applied in the bottom-up on-surface synthesis of well-defined nanostructures. We report an internal strain-induced skeletal rearrangement of one-dimensional (1D) metal-organic chains (MOCs) via a concurrent atom shift and bond cleavage on Cu(111) at room temperature. The process involves Cu-catalyzed debromination of organic monomers to generate 1,5-dimethylnaphthalene diradicals that coordinate to Cu adatoms, forming MOCs with both homochiral and heterochiral naphthalene backbone arrangements. Bond-resolved non-contact atomic force microscopy imaging combined with density functional theory calculations showed that the relief of substrate-induced internal strain drives the skeletal rearrangement of MOCs via 1,3-H shifts and shift of Cu adatoms that enable migration of the monomer backbone toward an energetically favorable registry with the Cu(111) substrate. Our findings on this strain-induced structural rearrangement in 1D systems will enrich the toolbox for on-surface synthesis of novel functional materials and quantum nanostructures.
Publisher: American Chemical Society (ACS)
Date: 21-07-2020
Publisher: AIP Publishing
Date: 11-05-2020
DOI: 10.1063/5.0006447
Abstract: The surfaces of Sb2Te3 topological insulator crystals were implanted using a 40 keV chromium ion beam. To facilitate uniform doping, the Sb2Te3 was passivated with a thin TiO2 film before the implantation step. The resulting chemical structure was studied using atomic-resolution transmission electron microscopy. A fluence of 7 × 1015 ions/cm2 at 40 keV lead to amorphization of the Sb2Te3 surface, with chromium predominantly incorporated in the amorphous layer. Heating to 200 °C caused the amorphous region to recrystallize and led to the formation of a thin chromium-rich interfacial layer. Near-edge x-ray absorption spectroscopy indicates a uniform valence state of Cr3+ throughout, with no evidence of metallic clustering. High-temperature superparamagnetic behavior was detected up to 300 K, with an increased magnetic moment below 50 K.
Publisher: AIP Publishing
Date: 03-01-2020
DOI: 10.1063/1.5124373
Abstract: The ability to tune magnetic orders, such as magnetic anisotropy and topological spin texture, is desired to achieve high-performance spintronic devices. A recent strategy has been to employ interfacial engineering techniques, such as the introduction of spin-correlated interfacial coupling, to tailor magnetic orders and achieve novel magnetic properties. We chose a unique polar–nonpolar LaMnO3/SrIrO3 superlattice because Mn (3d)/Ir (5d) oxides exhibit rich magnetic behaviors and strong spin–orbit coupling through the entanglement of their 3d and 5d electrons. Through magnetization and magnetotransport measurements, we found that the magnetic order is interface-dominated as the superlattice period is decreased. We were able to then effectively modify the magnetization, tilt of the ferromagnetic easy axis, and symmetry transition of the anisotropic magnetoresistance of the LaMnO3/SrIrO3 superlattice by introducing additional Mn (3d) and Ir (5d) interfaces. Further investigations using in-depth first-principles calculations and numerical simulations revealed that these magnetic behaviors could be understood by the 3d/5d electron correlation and Rashba spin–orbit coupling. The results reported here demonstrate a new route to synchronously engineer magnetic properties through the atomic stacking of different electrons, which would contribute to future applications in high-capacity storage devices and advanced computing.
Publisher: AIP Publishing
Date: 15-07-2020
DOI: 10.1063/5.0009713
Abstract: Artificial iconic memories, also called photomemories, are new types of nonvolatile memory that can simultaneously detect and store light information in a monolithic device. Several approaches have been proposed to construct artificial iconic memories, such as three-terminal field effect transistors, which can achieve an effective control of the gate voltage and external light terminals. The drawbacks in constructing these memories involve complicated fabrication processes, and the resulting performance of, for ex le, perovskite transistor-type photomemories is limited by the low carrier mobilities and poor ambient stabilities, whereas architectures based on floating gate modulations entail strict interface engineering and poor device reliability. In this paper, we propose a novel monolithic artificial iconic memory with a multilayer architecture of indium tin oxide erovskite/gold erovskite/silver, which combines the memory and photodetector functionalities of perovskites in an integrated device. The bottom perovskite layer plays the role of a photodetector, modulating the voltage bias on the top perovskite layer that serves as a resistive switching memory. This multilayer perovskite device can store photo-sensing data in its resistive states, with a memory retention of 5 × 103 s and ambient stability longer than sixty days. As a prototype demonstration, a 7 × 7 artificial iconic memory array is constructed to detect and store data on light intensity distribution, enabling a nonvolatile imaging functionality. Our work provides a new platform for designing perovskite-based architectures with simultaneous light detection and data storage capabilities.
Publisher: Wiley
Date: 14-09-2022
Abstract: In biomolecular electronics, the role of structural order in charge transport (CT) is poorly understood. It has been reported that the metal oxide cores of protein cages (e.g., iron oxide and ferrihydrite nanoparticles (NPs) present in ferritin and E2-LFtn, which is E2 protein engineered with an iron-binding sequence) play an important role in the mechanism of CT. At the same time, the NP core also plays a major role in the structural integrity of the proteins. This paper describes the role of structural order in CT across tunnel junctions by comparing three iron-storing proteins. They are (1) DNA binding protein from starved cells (Dps, diameter (∅) = 9 nm) (2) engineered archaeal ferritin (AfFtn-AA, ∅ = 12 nm) and (3) engineered E2 of pyruvate dehydrogenase enzyme complex (E2-LFtn, ∅ = 25 nm). Both holo-Dps and apo-Dps proteins undergo CT by coherent tunneling because their globular architecture and relative structural stability provide a coherent conduction pathway. In contrast, apo-AfFtn-AA forms a disordered structure across which charges have to tunnel incoherently, but holo-AfFtn-AA retains its globular structure and supports coherent tunneling. The large E2-LFtn always forms disordered structures across which charges incoherently tunnel regardless of the presence of the NP core. These findings highlight the importance of structural order in the mechanism of CT across biomolecular tunnel junctions.
Publisher: Elsevier BV
Date: 12-2005
Publisher: American Chemical Society (ACS)
Date: 05-01-2010
DOI: 10.1021/NN901476M
Abstract: The template-directed assembly of two planar molecules (copper phthalocyanine (CuPc) and pentacene) on SiC nanomesh has been studied by scanning tunneling microscopy and photoelectron spectroscopy, respectively. Both molecules are trapped as single molecules in the cells of SiC nanomesh at low coverage. At high coverage, CuPc forms a highly ordered single-molecular array with identical symmetry and periodicity as the substrate, whereas pentacene forms a quasi-amorphous layer due to the random mixture of three different adsorption configurations. This difference in adsorption behavior is attributed to differences in molecular geometries. The measured changes of work functions reveal weak charge transfer between the molecules and substrate. Both molecules are preferentially adsorbed on the SiC nanomesh rather than on graphene. The CuPc single-molecular array possesses good long-range order, large area coverage, and a molecular density of over 3.0 x 10(13) molecules/cm(2).
Publisher: AIP Publishing
Date: 11-2011
DOI: 10.1063/1.3656834
Abstract: Charge transfer dynamics across the lying-down 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) organic semiconductor molecules on Au(111) interface has been investigated using the core-hole clock implementation of resonant photoemission spectroscopy. It is found that the charge transfer time scale at the PTCDA/Au(111) interface is much larger than the C 1s core-hole lifetime of 6 fs, indicating weak electronic coupling between PTCDA and the gold substrate due to the absence of chemical reaction and/or bonding.
Publisher: Research Square Platform LLC
Date: 20-01-2022
DOI: 10.21203/RS.3.RS-1156230/V1
Abstract: To realise molecular scale electrical operations beyond the von Neumann bottleneck, new types of multi-functional switches are needed that mimic self-learning or neuromorphic computing by dynamically toggling between multiple operations that depend on their past. Here we report a molecule that switches from high to low conductance states with massive negative memristive behaviour that depends on the drive speed and number of past switching events, with all measurements fully modelled using atomistic and analytical models. This dynamic molecular switch (DMS) emulates synaptic behaviour and Pavlovian learning, all within a 2.4 nm thick layer that is three orders of magnitude thinner than a neuronal synapse. The DMS provides all fundamental logic gates necessary for deep learning because of its time-domain and voltage-dependent plasticity. The synapse-mimicking multi-functional DMS represents adaptable molecular scale hardware operable in solid-state devices opening a pathway to simplify dynamic complex electrical operations encoded within a single ultra-compact component.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6CP07592D
Abstract: The promising rubrene-based PSC device performance demonstrates the potential of rubrene as a suitable hole transport material in PSCs due to an optimal energy level alignment at the rubrene/CH 3 NH 3 PbI 3 interface.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NR07832K
Abstract: The Fe 0.1 Ni 0.9 S 2 catalyst can maintain its own metallic phase as a conductive channel for fast electron transfer and a thin layer of Fe 0.1 Ni 0.9 OOH serves as an active catalytic phase for the OER.
Start Date: 2015
End Date: 2017
Funder: Australian Research Council
View Funded ActivityStart Date: 2016
End Date: 2019
Funder: Australian Research Council
View Funded ActivityStart Date: 2018
End Date: 2018
Funder: Australian Research Council
View Funded ActivityStart Date: 06-2017
End Date: 05-2022
Amount: $652,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 12-2023
End Date: 12-2026
Amount: $520,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2023
End Date: 12-2025
Amount: $470,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2015
End Date: 12-2017
Amount: $266,300.00
Funder: Australian Research Council
View Funded ActivityStart Date: 05-2018
End Date: 06-2021
Amount: $205,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 07-2023
End Date: 08-2024
Amount: $586,779.00
Funder: Australian Research Council
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