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Kingo Itaya - One of the best experts on this subject based on the ideXlab platform.
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effect of sulfuric acid concentration on the structure of sulfate Adlayer on au 1 1 1 electrode
Electrochemistry Communications, 2006Co-Authors: Kazuhiro Sato, Soichiro Yoshimoto, Junji Inukai, Kingo ItayaAbstract:Abstract The adsorption of sulfate on Au(1 1 1) single-crystal electrode was examined in sulfuric acid solutions of various concentrations (0.5–7.5 M) by cyclic voltammetry and in situ scanning tunneling microscopy (STM). The well-known sulfate Adlayer with (√3 × √7) unit cell was found in 0.5 M sulfuric acid by in situ STM. In 2.5 and 5.0 M sulfuric acid, a new order–disorder phase transition, from the (√3 × √7) Adlayer to a disordered structure, was found to take place at ca. 1.1 V vs. Ag∣AgCl∣KCl(sat.). In 7.5 M sulfuric acid, no current spikes were seen in the CV profile, and in situ STM showed that the sulfate Adlayer was disordered.
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dependence of molecular recognition of fullerene derivative on the Adlayer structure of zinc octaethylporphyrin formed on au 100 surface
Journal of Physical Chemistry B, 2005Co-Authors: Soichiro Yoshimoto, Yosuke Honda, Yasujiro Murata, Michihisa Murata, Koichi Komatsu, Kingo ItayaAbstract:Adlayers of ZnOEP were prepared on reconstructed Au(100)-(hex) and unreconstructed Au(100)-(1 x 1) surfaces by immersing into a benzene solution containing ZnOEP molecules, and the Adlayer structures were characterized byscanning tunneling microscopy (STM). A hexagonally arranged ZnOEP array was formed on an Au(100)-(hex) surface, whereas a rectangularly arranged ZnOEP array was found on an Au(100)-(1 x 1) surface. The Adlayer structure of ZnOEP was dependent upon the underlying Au atomic arrangements. Furthermore, an investigation of the spuramolecular assembly for these modified surfaces was carried out by using an open-cage C 6 0 derivative (opened C 6 0 ). A supramolecular assembled Adlayer with a 1:1 composition of opened C 6 0 /ZnOEP was formed on Au(100)-(hex), whereas aggregates of opened C 6 0 were found on the ZnOEP-modified Au(100)-(1 x 1) surface. Electrochemical responses of opened C 6 0 were significantly influenced by underlying ZnOEP arrays. This finding suggests that precise control of underlying ZnOEP Adlayers with the Au atomic structure is important to recognize the opened C 6 0 on them.
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electrochemical redox control of ferrocene using a supramolecular assembly of ferrocene linked c60 derivative and metallooctaethylporphyrin array on a au 111 electrode
Langmuir, 2004Co-Authors: Soichiro Yoshimoto, Akira Saito, Eishi Tsutsumi, Francis Dsouza, Osamu Ito, Kingo ItayaAbstract:Supramolecular assembled layers of ferrocene-linked C60 derivative (C60Fc) and various metal ions coordinated to octaethylporphyrin (MOEP) were formed on the surface of a Au(111) single-crystal electrode by immersing the Au substrate successively into a benzene solution containing MOEP and one containing C60Fc molecules. The MOEPs used were zinc(II) (ZnOEP), cobalt(II) (CoOEP), copper(II) (CuOEP), and iron(III) chloride (FeClOEP) of OEP (2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine). The molecules of C60Fc directly attached to the Au(111) electrode showed poorly defined electrochemical redox response, whereas a clear electrochemical redox reaction of the ferrocene group in the C60Fc molecule was observed at 0.78 V versus reversible hydrogen electrode on ZnOEP, CoOEP, and CuOEP Adlayers, but not on the FeClOEP Adlayer. Adlattices of the underlying layer and the top layer of C60Fc were determined by in situ scanning tunneling microscopy. Adlayer structures of MOEP were independent of the central metal ion...
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effect of Adlayer structure on the host guest recognition between calcium and crown ether substituted phthalocyanine arrays on au single crystal surfaces
Journal of the American Chemical Society, 2004Co-Authors: Soichiro Yoshimoto, Akinori Tada, Koji Suto, Nagao Kobayashi, Kingo ItayaAbstract:Adlayers of 15-crown-5-ether-substituted cobalt(II) phthalocyanine (CoCRPc) were prepared by immersion of either Au(111) or Au(100) substrate into benzene−ethanol (9:1 v/v) mixed solutions containing CoCRPc. In situ STM imaging was carried out after transferring the CoCRPc-modified Au crystals into aqueous HClO4 solution. The packing arrangement of the CoCRPc array on Au(111) was determined to be p(8 × 4√3R − 30°), and the internal structure was clearly observed by high-resolution STM. Two Adlayer structures of CoCRPc, (8 × 9) and (4√5 × 4√5)R26.7°, were found on the Au(100)−(1 × 1) terrace. In the presence of 1 mM Ca2+, two Ca2+ ions were trapped in two diagonally located 15-crown-5-ether moieties of each CoCRPc molecule on Au(111), whereas encapsulation of Ca2+ ions was not seen in the CoCRPc arrays on the Au(100)−(1 × 1) surface. The present study demonstrates that the relationship between crown moieties of CRPc and the underlying Au lattice is important in the trapping of Ca2+ ions in crown rings.
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two dimensional supramolecular organization of copper octaethylporphyrin and cobalt phthalocyanine on au 111 molecular assembly control at an electrochemical interface
Journal of the American Chemical Society, 2004Co-Authors: Soichiro Yoshimoto, Norihito Higa, Kingo ItayaAbstract:Mixed Adlayers of 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine copper(II) (CuOEP) and cobalt(II) phthalocyanine (CoPc) were prepared by immersing Au(111) substrate in a benzene solution containing CuOEP and CoPc molecules, and they were investigated in 0.1 M HClO4 by cyclic voltammetry (CV) and in-situ scanning tunneling microscopy (STM). The composition of the mixed Adlayer consisting of CuOEP and CoPc molecules was found to vary depending on the immersion time. CoPc molecules displaced CuOEP molecules during the modification process with increasing immersion time, and the CuOEP molecules were completely replaced with CoPc molecules in the mixed solution after a long modification time. The two-component Adlayer consisting of CuOEP and CoPc, which has a structure with the constituent molecules arranged alternately, was found to form either a p(9 × 3√7R − 40.9°) or a p(9 × 3√7R − 19.1°) structure, each involving two molecules on the Au(111) surface. The surface mobility and the molecular reorganization o...
Michael J Weaver - One of the best experts on this subject based on the ideXlab platform.
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infrared spectroscopy of carbon monoxide and nitric oxide on palladium 111 in aqueous solution unexpected Adlayer structural differences between electrochemical and ultrahigh vacuum interfaces
Journal of Electroanalytical Chemistry, 1999Co-Authors: Shouzhong Zou, Roberto Gomez, Michael J WeaverAbstract:Abstract Coverage-dependent infrared reflection-absorption spectra (IRAS) measured for carbon monoxide and nitric oxide Adlayers dosed onto Pd(111) in acidic aqueous solution are examined in comparison with IRAS and other Adlayer structural data available on Pd(111) in ultrahigh vacuum (UHV). Unlike most other ordered Pt-group surfaces, the coverage-dependent spectral fingerprints for both electrochemical Adlayers on Pd(111) are markedly different from their UHV-based counterparts. These disparities are magnified after allowance is made for the differences in surface potentials, and hence interfacial electrostatic fields, between the electrochemical and UHV-based systems. Specifically, at low dosed CO coverages ( θ CO ν CO) band is obtained at ca. 1830–1880 cm −1 , consistent with threefold-hollow coordination, which is replaced at higher coverages up to saturation ( θ CO =0.75) by a pair of bands at 1940–1960 and 1890–1920 cm −1 , suggestive of ‘bridging-like’ along with hollow CO binding. Unusually similar θ CO -dependent infrared spectra were obtained upon sequential partial electrooxidation of a saturated layer, indicating that any CO islands thereby forming are largely dissipated. While the infrared spectra are qualitatively similar to the behavior in UHV at low coverages, the electrochemical ν CO frequencies are significantly (30–40 cm −1 ) higher than expected, and the higher-frequency ν CO feature seen for θ CO >0.4 has no obvious counterpart at the Pd(111)/UHV interface. These behavioral differences can be partly, yet not entirely, rationalized in terms of water coadsorption. Dosed NO Adlayers exhibit largely a single NO stretching ( ν NO ) band blueshifting by ca. 30 cm −1 up to ca. 1750 cm −1 at saturation, suggestive of largely atop NO coordination. The absence of the markedly lower-frequency ν NO bands seen at low dosages on Pd(111) in UHV is ascribed to partial segregation of NO and coadsorbed water, yielding higher local NO coverages. These unexpected ν CO and ν NO spectral properties at Pd(111) electrodes with respect to the corresponding UHV-based systems are also discussed in comparison with corresponding IRAS behavior for CO and NO Adlayers on other low-index Pt-group surfaces. The coadsorption of CO and NO on Pd(111) is also briefly considered. The form of the ν CO / ν NO spectra indicate the presence of some CO segregation as well as CO/NO molecular intermixing.
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validity of double layer charge corrected voltammetry for assaying carbon monoxide coverages on ordered transition metals comparisons with Adlayer structures in electrochemical and ultrahigh vacuum environments
Surface Science, 1998Co-Authors: Roberto Gomez, Juan M. Feliu, A Aldaz, Michael J WeaverAbstract:Abstract A coulometric procedure enabling the reliable and accurate evaluation of saturated CO coverages, θ sat CO , on Pt-group transition-metal electrodes is outlined, and applied to CO Adlayers on ordered low-index platinum, rhodium, and iridium surfaces in acidic aqueous media. Along with voltammetric data, the method utilizes previously described measurements of the charge displaced upon CO adsorption. The reverse of this charge, Q dis , together with the “background” charge Q b flowing between a suitable pair of electrode potentials in the absence of CO, constitutes the overall “double-layer” correction Q dl to the total voltammetric charge Q tot measured for the electrooxidation of adsorbed CO between the same potentials. Significantly, the Q dis as well as the Q b component of Q dl typically constitutes moderate or even large corrections to Q tot , so that the deduced θ sat CO values are noticeably (20–30%) smaller than some voltammetric-based estimates reported earlier. However, the revised coulometric θ sat CO values are in consistently good agreement with the corresponding coverages obtained by means of an infrared spectrophotometric procedure. These θ sat CO values are compared with Adlayer structural information obtained recently from in situ scanning tunneling microscopy along with infrared spectroscopy, and also with structural data for corresponding Adlayers in ultrahigh vacuum (UHV). In most cases, the electrochemical and UHV-based θ sat CO values are not greatly different (within 5–10%), even though the CO binding site arrangements are often dissimilar in these two environments. The role of the electrode potential in affecting θ sat CO under some conditions via alterations in binding-site energetics, however, is noted for the Pt(111)/CO system.
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the adsorption of sulfate on gold 111 in acidic aqueous media Adlayer structural inferences from infrared spectroscopy and scanning tunneling microscope
Journal of Electroanalytical Chemistry, 1994Co-Authors: Gregory J Edens, Michael J WeaverAbstract:The potential-dependent adsorption of sulfate on ordered Au(111) from acidic aqueous electrolytes has been examined in situ by means of IR reflection-absorption spectroscopy (IRAS) and by atomic-resolution scanning tunneling microscopy (STM) in order to explore further the nature of the adsorbate bonding and the structural changes attending the formation of the ordered Adlayer at high potentials, as observed recently using STM. Solution conditions that encompassed aqueous sulfuric acid, sulfuric acid/sulfate electrolytes of varying pH and dilute sulfate in excess perchloric acid were selected in order to facilitate comparisons with recent adsorbate compositional data extracted from chronocoulometric and radiotracer measurements which utilized the last mentioned type of electrolyte. Essentially the same ordered Adlayer structures were deduced by STM to form at suitably high potentials (≳ 0.8 V/SCE) in both sulfuric acid and the mixed sulfate/excess perchloric acid media. The Adlayer, which exhibits a (√3 × √7) symmetry, involves a fractional sulfate coverage of 0.2, in accordance with chronocoulometic and radiotracer data. The possibility that the ordered sulfate Adlayer incorporates coadsorbed hydronium cations is discussed; such coadsorption is suggested by the presence of additional tunneling maxima in the STM images. The IRAS data display a prominent SO stretching band νso at 1155–1220 cm−1, the potential-dependent intensity of which correlates with sulfate surface concentrations reported earlier. The appearance of this νso feature is also insensitive to the electrolyte conditions, including pH, consistent with its assignment to adsorbed sulfate rather than bisulfate. The νso frequency exhibits only a slight (ca. 5 cm−1) downshift upon forming the ordered Adlayer, indicating that adsorbate ordering incurs no marked changes in sulfate speciation or surface bonding.
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carbon monoxide Adlayer structures on platinum 111 electrodes a synergy between in situ scanning tunneling microscopy and infrared spectroscopy
Journal of Chemical Physics, 1994Co-Authors: Ignacio Villegas, Michael J WeaverAbstract:The spatial structure of compressed carbon monoxide Adlayers on Pt(111) in aqueous acidic solution has been explored by means of in‐situ scanning tunneling microscopy (STM) along with infrared reflection–absorption spectroscopy (IRAS). Besides offering a detailed structural picture of this electrochemical interface in comparison with the well‐studied Pt(111)/CO system in ultrahigh vacuum (uhv) environments, the real‐space structural information provided by STM allows an assessment of the obfuscating influence of dynamic dipole coupling upon IRAS binding‐site assignments. In turn, the latter data provide an important crosscheck on the validity of binding‐site assignments deduced from the STM images. Emphasis is placed on the structures formed from near‐saturated CO solutions, encouraged by the electrode potential‐induced Adlayer phase transition at ca. 0 V vs SCE observed previously under these conditions by IRAS. At potentials below 0 V, a hexagonal close‐packed (2×2)–3CO Adlayer is observed, with a CO co...
Soichiro Yoshimoto - One of the best experts on this subject based on the ideXlab platform.
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effect of sulfuric acid concentration on the structure of sulfate Adlayer on au 1 1 1 electrode
Electrochemistry Communications, 2006Co-Authors: Kazuhiro Sato, Soichiro Yoshimoto, Junji Inukai, Kingo ItayaAbstract:Abstract The adsorption of sulfate on Au(1 1 1) single-crystal electrode was examined in sulfuric acid solutions of various concentrations (0.5–7.5 M) by cyclic voltammetry and in situ scanning tunneling microscopy (STM). The well-known sulfate Adlayer with (√3 × √7) unit cell was found in 0.5 M sulfuric acid by in situ STM. In 2.5 and 5.0 M sulfuric acid, a new order–disorder phase transition, from the (√3 × √7) Adlayer to a disordered structure, was found to take place at ca. 1.1 V vs. Ag∣AgCl∣KCl(sat.). In 7.5 M sulfuric acid, no current spikes were seen in the CV profile, and in situ STM showed that the sulfate Adlayer was disordered.
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dependence of molecular recognition of fullerene derivative on the Adlayer structure of zinc octaethylporphyrin formed on au 100 surface
Journal of Physical Chemistry B, 2005Co-Authors: Soichiro Yoshimoto, Yosuke Honda, Yasujiro Murata, Michihisa Murata, Koichi Komatsu, Kingo ItayaAbstract:Adlayers of ZnOEP were prepared on reconstructed Au(100)-(hex) and unreconstructed Au(100)-(1 x 1) surfaces by immersing into a benzene solution containing ZnOEP molecules, and the Adlayer structures were characterized byscanning tunneling microscopy (STM). A hexagonally arranged ZnOEP array was formed on an Au(100)-(hex) surface, whereas a rectangularly arranged ZnOEP array was found on an Au(100)-(1 x 1) surface. The Adlayer structure of ZnOEP was dependent upon the underlying Au atomic arrangements. Furthermore, an investigation of the spuramolecular assembly for these modified surfaces was carried out by using an open-cage C 6 0 derivative (opened C 6 0 ). A supramolecular assembled Adlayer with a 1:1 composition of opened C 6 0 /ZnOEP was formed on Au(100)-(hex), whereas aggregates of opened C 6 0 were found on the ZnOEP-modified Au(100)-(1 x 1) surface. Electrochemical responses of opened C 6 0 were significantly influenced by underlying ZnOEP arrays. This finding suggests that precise control of underlying ZnOEP Adlayers with the Au atomic structure is important to recognize the opened C 6 0 on them.
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electrochemical redox control of ferrocene using a supramolecular assembly of ferrocene linked c60 derivative and metallooctaethylporphyrin array on a au 111 electrode
Langmuir, 2004Co-Authors: Soichiro Yoshimoto, Akira Saito, Eishi Tsutsumi, Francis Dsouza, Osamu Ito, Kingo ItayaAbstract:Supramolecular assembled layers of ferrocene-linked C60 derivative (C60Fc) and various metal ions coordinated to octaethylporphyrin (MOEP) were formed on the surface of a Au(111) single-crystal electrode by immersing the Au substrate successively into a benzene solution containing MOEP and one containing C60Fc molecules. The MOEPs used were zinc(II) (ZnOEP), cobalt(II) (CoOEP), copper(II) (CuOEP), and iron(III) chloride (FeClOEP) of OEP (2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine). The molecules of C60Fc directly attached to the Au(111) electrode showed poorly defined electrochemical redox response, whereas a clear electrochemical redox reaction of the ferrocene group in the C60Fc molecule was observed at 0.78 V versus reversible hydrogen electrode on ZnOEP, CoOEP, and CuOEP Adlayers, but not on the FeClOEP Adlayer. Adlattices of the underlying layer and the top layer of C60Fc were determined by in situ scanning tunneling microscopy. Adlayer structures of MOEP were independent of the central metal ion...
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effect of Adlayer structure on the host guest recognition between calcium and crown ether substituted phthalocyanine arrays on au single crystal surfaces
Journal of the American Chemical Society, 2004Co-Authors: Soichiro Yoshimoto, Akinori Tada, Koji Suto, Nagao Kobayashi, Kingo ItayaAbstract:Adlayers of 15-crown-5-ether-substituted cobalt(II) phthalocyanine (CoCRPc) were prepared by immersion of either Au(111) or Au(100) substrate into benzene−ethanol (9:1 v/v) mixed solutions containing CoCRPc. In situ STM imaging was carried out after transferring the CoCRPc-modified Au crystals into aqueous HClO4 solution. The packing arrangement of the CoCRPc array on Au(111) was determined to be p(8 × 4√3R − 30°), and the internal structure was clearly observed by high-resolution STM. Two Adlayer structures of CoCRPc, (8 × 9) and (4√5 × 4√5)R26.7°, were found on the Au(100)−(1 × 1) terrace. In the presence of 1 mM Ca2+, two Ca2+ ions were trapped in two diagonally located 15-crown-5-ether moieties of each CoCRPc molecule on Au(111), whereas encapsulation of Ca2+ ions was not seen in the CoCRPc arrays on the Au(100)−(1 × 1) surface. The present study demonstrates that the relationship between crown moieties of CRPc and the underlying Au lattice is important in the trapping of Ca2+ ions in crown rings.
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two dimensional supramolecular organization of copper octaethylporphyrin and cobalt phthalocyanine on au 111 molecular assembly control at an electrochemical interface
Journal of the American Chemical Society, 2004Co-Authors: Soichiro Yoshimoto, Norihito Higa, Kingo ItayaAbstract:Mixed Adlayers of 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine copper(II) (CuOEP) and cobalt(II) phthalocyanine (CoPc) were prepared by immersing Au(111) substrate in a benzene solution containing CuOEP and CoPc molecules, and they were investigated in 0.1 M HClO4 by cyclic voltammetry (CV) and in-situ scanning tunneling microscopy (STM). The composition of the mixed Adlayer consisting of CuOEP and CoPc molecules was found to vary depending on the immersion time. CoPc molecules displaced CuOEP molecules during the modification process with increasing immersion time, and the CuOEP molecules were completely replaced with CoPc molecules in the mixed solution after a long modification time. The two-component Adlayer consisting of CuOEP and CoPc, which has a structure with the constituent molecules arranged alternately, was found to form either a p(9 × 3√7R − 40.9°) or a p(9 × 3√7R − 19.1°) structure, each involving two molecules on the Au(111) surface. The surface mobility and the molecular reorganization o...
E. Carry - One of the best experts on this subject based on the ideXlab platform.
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High-overtone bulk-acoustic resonator gravimetric sensitivity: Towards wideband acoustic spectroscopy
Journal of Applied Physics, 2015Co-Authors: David Rabus, Eric Lebrasseur, Thierry Baron, Sylvain Ballandras, JEAN-MARIA FRIEDT, E. CarryAbstract:In the context of direct detection sensors with compact dimensions, we investigate the gravimetric sensitivity of High-overtone Bulk Acoustic Resonators, through modeling of their acoustic characteristics and experiment. The high frequency characterizing such devices is expected to induce a significant effect when the acoustic field boundary conditions are modified by a thin Adlayer. Furthermore, the multimode spectral characteristics is considered for wideband acoustic spectroscopy of the Adlayer, once the gravimetric sensitivity dependence of the various overtones is established. Finally, means of improving the gravimetric sensitivity by confining the acoustic field in a low acoustic-impedance layer is theoretically established.
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High-overtone Bulk-Acoustic Resonator gravimetric sensitivity: towards wideband acoustic spectroscopy
Journal of Applied Physics, 2015Co-Authors: David Rabus, Eric Lebrasseur, Sylvain Ballandras, JEAN-MARIA FRIEDT, Thomas Baron, E. CarryAbstract:In the context of direct detection sensors with compact dimensions, we investigate the gravimetric sensitivity of high-overtone bulk acoustic resonators, through modeling of their acoustic characteristics and experiment. The high frequency characterizing such devices is expected to induce a significant effect when the acoustic field boundary conditions are modified by a thin Adlayer. Furthermore, the multimode spectral characteristics are considered for wideband acoustic spectroscopy of the Adlayer, once the gravimetric sensitivity dependence of the various overtones is established. Finally, means of improving the gravimetric sensitivity by confining the acoustic field in a low acoustic-impedance layer is theoretically established.
Dong Wang - One of the best experts on this subject based on the ideXlab platform.
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the structural details and substituent effects on biphenyls Adlayers with halogen pseudohalogen substituents on au 1 1 1 an stm investigation
Journal of Electroanalytical Chemistry, 2013Co-Authors: Dong WangAbstract:Abstract The substituent effect on the adsorption behaviors of four halogen/pseudohalogen-terminated biphenyls (X–BP–X, with X = F, Br, I and CN) on a Au(1 1 1) surface in 0.1 M HClO4 solution has been investigated by electrochemical scanning tunneling microscopy (ECSTM) and cyclic voltammetry (CV). All the four molecules could form ordered Adlayers at adsorption potentials. From F–BP–F, Br–BP–Br to I–BP–I, the molecular adsorption configuration varies from upright, alternating upright and flat-lying to totally flat-lying. In contrast, a trimer motif connected via CN–Au coordination interaction is found as the building unit for the Adlayer of CN–BP–CN on Au(1 1 1) electrode. The Adlayer structures and configurations are regulated by the properties of the substituted groups.
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molecular Adlayer and photo induced structural transformation of a diarylethene derivative on au 1 1 1 investigated with scanning tunneling microscopy
Journal of Electroanalytical Chemistry, 2011Co-Authors: Xu Zhang, Dong Wang, Lijun Wan, Hui Lin, Daoben ZhuAbstract:Abstract The self-assembly and photo-induced structural transformation of a diarylethene derivative 1,2-bis(3,5-dimethyl dithioene [3,2-b:2′,3′-d]thiophene-2-yl) perfluorocyclopentene (BDDTP) have been investigated by cyclic voltammetry and electrochemical scanning tunneling microscopy (EC-STM) on a Au(1 1 1) substrate. BDDTP was found to form two ordered Adlayer structures on Au(1 1 1) surface. STM observation revealed that the original ordered structures transformed into disordered Adlayers after ex situ and in situ ultraviolet (UV) irradiation. Such a dramatic difference in the self-assembly behavior of BDDTP before and after UV irradiation results from the conformational transformation induced by photo-irradiation and the associated molecule–substrate interaction change. The result provides useful information to understand the self-assembly behavior and photochromic reaction of diarylethenes compounds on solid supports.
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formation and structure of p nitrobenzoic acid Adlayer on au 111 surface in hclo4 investigated by in situ scanning tunneling microscopy
Journal of Nanoscience and Nanotechnology, 2011Co-Authors: Liu Yang, Dong Wang, Ting Chen, Lijun WanAbstract:The adsorption and Adlayer structure of p-nitrobenzoic acid (pNBA) on a Au(111) surface in 0.1 M HCIO4 are investigated by in-situ scanning tunneling microscopy (STM) and cyclic voltammetry. The pNBA Adlayer is prepared by dipping Au(111) into a saturated pNBA aqueous solution. The cyclic voltammogram (CV) of the so-prepared Au(111) electrode shows an irreversible cathodic peak at 0.24 V, which corresponds to the electro-reduction reaction from pNBA to hydroxylamine, and a pair of reversible peaks at ca. 0.7 V, corresponding to redox reaction of hydroxylamine to nitrosobenzoic acid. STM is employed to investigate the pNBA Adlayer structure. The molecules form ordered Adlayers in (16 x 2 square root of 3), (7 x 4 square root of 3) and (9 x 6 square root of 3) structures at the double layer potential region. High resolution STM image reveals the details of the molecular arrangement in the Adlayers. On the basis of the STM image and the chemical structure of pNBA, structural models for three Adlayers are proposed. In all three structures, pNBA molecules adsorb perpendicularly with the carboxylic groups contacting with the Au(111) substrate. The effect of dipping time on the Adlayer formation is investigated. Upon shifting the electrode potentials in negative direction to induce the electroreduction reaction, the bright dots corresponding to the molecular aggregations start emerging on the surface and selectively locate at the elbow position along Au(111) reconstruction lines. The results provide direct evidence for the adsorption and electrochemical behavior of nitro-benzene derivatives.
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Substitution effect on the Adlayer formation of tetrachloroperylene bisimides on HOPG surface
Surface Science, 2010Co-Authors: Qing Chen, Dong Wang, Ting Chen, Xu Zhang, Hualei Qian, Zhaohui Wang, Lijun WanAbstract:Abstract Di-perylene-3,4,9,10-tetracarboxylic acid bisimides (diPBI) is an n-type graphene molecule with nonplanar conformation. The controllable assembly and molecular Adlayer structures of tetrachlorinated diPBI derivatives with different alkyl chains substitutions on highly oriented pyrolytic graphite were studied by scanning tunneling microscopy. When the molecule was substituted by butyl, the formation of multilayer or monolayer can be regulated by the solution concentration. When the molecule was substituted by 2-ethylhexyl, however, it can only form monolayer assembly. The unit cell of 2-ethylhexyl substituted diPBI Adlayer was expanded to a rectangular shape compared to that of the butyl substituted diPBI. The steric repulsion of the alkyl chains (straight or branched) substitution is proposed as the key factor to control the Adlayer structures of diPBI derivatives. The result is helpful to the design and fabrication of the organic film of chemically synthesized graphene type materials.
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electrochemical scanning tunneling microscopy Adlayer structure and reaction at solid liquid interface
Journal of Physical Chemistry C, 2007Co-Authors: Dong WangAbstract:The Adlayer structure and reaction at the solid/liquid interface has been intensively investigated due to its importance in many physical chemistry and life processes. The emergence of electrochemical scanning tunneling microscopy (ECSTM) provides a new opportunity to study this subject at the atomic and molecular level in aqueous solution. This feature article summarizes some of the latest progress in ECSTM application for the understanding of the structure and reactions taking place at the solid/liquid interface. The adsorption of atoms and organic molecules is clearly revealed, and the knowledge of the underlying molecule/substrate and intermolecular reactions governing the Adlayer formation on the surface is deduced. In addition, the effect of external stimuli, such as electrode potential and UV light, on the Adlayer structure is demonstrated. Finally, the prospects of future development in this exciting field are outlined.