Shuehlin Yau - Academia.edu (original) (raw)
Papers by Shuehlin Yau
The Journal of Physical Chemistry C
Journal of the Chinese Chemical Society
Journal of Materials Chemistry A, 2017
New branched alkyl tetrathienothiophene (TTAR)-based organic sensitizers with power conversion ef... more New branched alkyl tetrathienothiophene (TTAR)-based organic sensitizers with power conversion efficiency up to 11%.
Journal of the American Chemical Society, Jan 13, 2015
A new series of metal-free organic chromophores (TPA-TTAR-A (1), TPA-T-TTAR-A (2), TPA-TTAR-T-A (... more A new series of metal-free organic chromophores (TPA-TTAR-A (1), TPA-T-TTAR-A (2), TPA-TTAR-T-A (3), and TPA-T-TTAR-T-A (4)) are synthesized for application in dye sensitized solar cells (DSSC) based on a donor-π-bridge-acceptor (D-π-A) design. Here a simple triphenylamine (TPA) moiety serves as the electron donor, a cyanoacrylic acid as the electron acceptor and anchoring group, and a novel tetrathienoacene (TTA) as the π-bridge unit. Due to the extensively conjugated TTA π-bridge, these dyes exhibit high extinction coefficients (4.5-5.2 × 10(4) M(-1) cm(-1)). By strategically inserting a thiophene spacer on the donor or acceptor side of the molecules, the electronic structures of these TTA-based dyes can be readily tuned. Furthermore, addition of a thiophene spacer has a significant influence on the dye orienta-tion and self-assembly modality on TiO2 surfaces. The insertion of a thiophene between the π-bridge and the cyanoacrylic acid anchoring group in TPA-TTAR-T-A (dye 3) promot...
Journal of The Electrochemical Society
In situ scanning tunneling microscopy was used to examine the spatial structures of lead (Pb) ada... more In situ scanning tunneling microscopy was used to examine the spatial structures of lead (Pb) adatom and carbon monoxide (CO) molecule adsorbed onto an ordered Pt(111) electrode in 0.1 M perchloric acid (HClO4) containing 1 mM Pb(ClO4)2 under potential control. Ordered Pb structures were not seen until the potential was made more negative to 0 V (vs. Ag/AgCl), where a quasi-square array (7 57) was seen. Shifting the potential more negative substantiated Pb deposition, which triggered restructuring of the Pb adlayer into (21 21)R11 and (3 23)rect ( = 0.62 and 0.67) at -0.1 V. Pb adatom reduced the poisoning effect of CO on the Pt(111) electrode by blocking the adsorption of CO and by forcing CO molecule to asymmetric sites. An ordered (7 3) – Pb + CO structure was imaged at 0 V in 0.1 M HClO4 + 1 mM Pb(ClO4)2, from which the surface coverage and binding sites of CO molecule were inferred.
Journal of the Electrochemical Society, 2013
In situ scanning tunneling microscopy (STM) was used to study copper deposition at vacancy defect... more In situ scanning tunneling microscopy (STM) was used to study copper deposition at vacancy defects on a copper thin film underpotentiostatic conditions at −0.20 V (vs. Ag/AgCl) in a formula containing sulfuric acid, chloride, polyethylene glycol (PEG), andbis-3-sodiumsulfopropyl-disulfide (SPS) – the widely used mixture to facilitate Cu superfilling at recessed features in semiconductorprocessing. The vacancy island measuring ∼70 nm wide and 12 nm deep sat in the middle of a facetted surface structure at thebeginning. Cu deposit nucleated mainly at the rim of the vacancy and grew into stacked Cu(111) facets. These local pyramidal Custacks could restructure into wider Cu(111) terraces by transferring Cu atoms rapidly from higher to lower planes. Voltammetricresults showed that Cu deposition was suppressed in a plating bath containing 1 mM KCl + 88 μM PEG8000 + 10−7 M SPS.Steps with sharp edges bunched in the course of Cu deposition. The vacancy island was filled with Cu deposit assuming smoothterraces with sharp step edges aligned mainly in the 121 directions of the Pt(111) electrode, suggesting crystalline packing in theCu deposit. Atomic-resolution STM imaging revealed a hexagonal array presumed to be the (√3 × √3)R30◦ – Cl− adlattice
Journal of Electroanalytical Chemistry
The Journal of Physical Chemistry C, 2017
A bioderived zwitterionic molecule, cysteine betaine (Cys-b), can be used as a biomaterial coatin... more A bioderived zwitterionic molecule, cysteine betaine (Cys-b), can be used as a biomaterial coating to evade fouling and damage by light radiation. In situ scanning tunneling microscopy (STM) has been used to study the structures of the cysteine betaine (Cys-b) molecule adsorbed on an Au(111) electrode in 0.1 M HClO4 and H2SO4. A number of Cys-b structures have been identified in 0.1 M HClO4 before adsorbed Cys-b is irreversibly oxidized, including (4 × 8), (6 × 6), and (√19 × 3√3). By contrast, very different Cys-b structures, including (√7 × 4), which is an incommensurate structure, and disordered structures, are seen in the same potential region in H2SO4. These results are reconciled by a coadsorption scheme involving the Cys-b cation and ClO4– (or HSO4–). The coverages of Cys-b are 1.31 × 1014 and 2.32 × 1014 molecules/cm2 at the same potential in HClO4 and H2SO4. Although Cys-b molecules are tethered to the Au(111) substrate via their S-ends, their spatial structures are influenced greatly by the inte...
The Journal of Physical Chemistry C
Department of Chemistry, National Centr E-mail: mcchen@ncu.edu.tw Materials Research Institute, N... more Department of Chemistry, National Centr E-mail: mcchen@ncu.edu.tw Materials Research Institute, Northwestern Department of Chemical Engineering, Nat Taiwan. E-mail: kcho@ntu.edu.tw Department of Physics, Astronomy and Research Center, Northwestern University, E Department of Chemistry, PSG College of Ar Research Center for New Generation Pho Chung-Li 32054, Taiwan Institute of Chemistry, Academia Sinica, Na Department of Materials Science and Engi Energy Research Center, Northwestern Univ Department of Chemistry, The Materials Re Solar Energy Research Center, Northwestern E-mail: t-marks@northwestern.edu † Electronic supplementary informa 10.1039/c7ta01825h ‡ These authors contributed equally. Cite this: J. Mater. Chem. A, 2017, 5, 12310
The Journal of Physical Chemistry C
Electrodes modified by thiol molecules with conjugated heterocycles can lead to improved activiti... more Electrodes modified by thiol molecules with conjugated heterocycles can lead to improved activities in electroanalysis and electrodeposition. However, the intricate interactions among thiol molecul...
ECS Meeting Abstracts
In situ scanning tunneling microscopy (STM) was used to examine the ordered microstructures of pl... more In situ scanning tunneling microscopy (STM) was used to examine the ordered microstructures of platinum (Pt) deposited on Au(111) substrate in aqueous Na2PtCl6 solution saturated with carbon monoxide (CO) without potential control at room temperature. PtCl6 2- complexes were reduced by CO molecules and deposited on Au(111) in a hexagonal array without potential control. At the same time, we introduced electron spectroscopy for chemical analysis (ESCA) to prove the Pt adatoms were reduced to metallic state after the CO was oxidized in air. According to the results of CV and STM, the coverage of Pt on Au(111) substrate increased sharply with the time passed initially and finally had the value of 0.87monolayer (ML) after 200min dosing. After 5min dosing, the adsorption of CO molecules first mobilized and rearranged Pt adatoms on Au(111) from disordered Pt aggregates to 0.9 nm wide tortuous stripes, and finally to patches of ordered Pt adatoms at 0.1 V (versus reversible hydrogen electr...
Electrochemistry Communications
Abstract The use of copper single-crystal electrodes (CSCEs) has revealed the crucial role of ele... more Abstract The use of copper single-crystal electrodes (CSCEs) has revealed the crucial role of electrode structure in electrocatalysis and corrosion. CSCEs, although commercially available, can be prepared in-house by melting the end of a Cu wire to form a single crystal bead (SCB) in ambient air. Unlike the conventional torch used for making Pt and Au SCBs, the torch used in this study allows the Cu bead to cool down to room temperature in a nitrogen stream. The resulting Cu bead is subsequently fabricated into a CSCE with a desired orientation. Copper’s propensity for oxidation does not pose a problem for our method as long as the H2 and O2 fluxes to the flame are well-controlled. The bulk oxide in the Cu SCB prepared as above is below the detection limit of our X-ray photoelectron spectrometer. The devised method opens up an avenue toward the study of electrochemistry at well-defined Cu and possibly other non-noble transition metal electrodes. Moreover, this method can also be used to make alloyed SCBs, as illustrated by the successful fabrication of a Cu/Ni (98.5/1.5) bead. The resulting Cu(1 1 1) and Cu98.5Ni1.5(1 1 1) electrodes are examined by cyclic voltammetry and in situ scanning tunneling microscopy in 0.1 M sulfuric acid. The trace amount of Ni in the Cu(1 1 1) electrode affects the potential, but not the structure, of specific adsorption of the (bi)sulfate anion. A (√3 × √7)–HSO4− structure and the Cu(1 1 1) lattice are imaged by STM at positive and negative potentials.
Langmuir : the ACS journal of surfaces and colloids, Jan 23, 2018
Surface modification for biosensors has focused attention for improvement of their sensitivity an... more Surface modification for biosensors has focused attention for improvement of their sensitivity and specificity, particularly for the detection in complex medium. In this work, we have synthesized zwitterionic carboxybetaine-thiols (CB-thiols) and sulfobetaine-thiols (SB-thiols) for modification of gold substrates to form a functional self-assembled monolayer (SAM) for the immunoassay in a surface plasmon resonance (SPR) biosensor. X-ray photoelectron spectroscopy (XPS), contact angle goniometer, and cyclic voltammetry were applied for characterizations of elemental composition, surface wettability, and packing density, respectively. The antifouling properties of the SAMs were accessed by quantitative analysis of protein and bacterial adsorption. The results from the SAMs with a single component indicated that the SB-thiol SAM provides better surface hydrophilicity, fouling resistance, and packing density as compared to the CB-thiol SAM, likely due to the ionic association of CB moie...
Journal of The Electrochemical Society
The Journal of Physical Chemistry C
The role of step defects on an electrode is a central issue in the modern study of electrocatalys... more The role of step defects on an electrode is a central issue in the modern study of electrocatalysis. Although scanning tunneling microscopy (STM) has been used to characterize the electrified interfaces of low Miller-indexed single-crystal electrodes, there has been little progress in the STM study of stepped Pt electrodes. Herein, the structures of Pt(332) and Pt(997), two vicinal surfaces to the (111) plane, are examined by high-resolution STM under potential control in 0.5 M H2SO4 solution containing iodide or carbon monoxide. These electrodes are annealed by a hydrogen flame and quenched in Millipore water, giving rise to rough step edges with poorly defined atomic structures at 0.1 V (vs reversible hydrogen electrode) in 0.5 M H2SO4. However, step edges are sharpened and aligned in the ⟨110⟩ direction after adsorption of CO on both electrodes. In contrast, seesaw-like step lines are produced by iodine adsorption. Therefore, the step structure and mobility of Pt atoms are markedly influenced by the ad...
Journal of the Electrochemical Society
The Journal of Physical Chemistry C
Journal of the Chinese Chemical Society
Journal of Materials Chemistry A, 2017
New branched alkyl tetrathienothiophene (TTAR)-based organic sensitizers with power conversion ef... more New branched alkyl tetrathienothiophene (TTAR)-based organic sensitizers with power conversion efficiency up to 11%.
Journal of the American Chemical Society, Jan 13, 2015
A new series of metal-free organic chromophores (TPA-TTAR-A (1), TPA-T-TTAR-A (2), TPA-TTAR-T-A (... more A new series of metal-free organic chromophores (TPA-TTAR-A (1), TPA-T-TTAR-A (2), TPA-TTAR-T-A (3), and TPA-T-TTAR-T-A (4)) are synthesized for application in dye sensitized solar cells (DSSC) based on a donor-π-bridge-acceptor (D-π-A) design. Here a simple triphenylamine (TPA) moiety serves as the electron donor, a cyanoacrylic acid as the electron acceptor and anchoring group, and a novel tetrathienoacene (TTA) as the π-bridge unit. Due to the extensively conjugated TTA π-bridge, these dyes exhibit high extinction coefficients (4.5-5.2 × 10(4) M(-1) cm(-1)). By strategically inserting a thiophene spacer on the donor or acceptor side of the molecules, the electronic structures of these TTA-based dyes can be readily tuned. Furthermore, addition of a thiophene spacer has a significant influence on the dye orienta-tion and self-assembly modality on TiO2 surfaces. The insertion of a thiophene between the π-bridge and the cyanoacrylic acid anchoring group in TPA-TTAR-T-A (dye 3) promot...
Journal of The Electrochemical Society
In situ scanning tunneling microscopy was used to examine the spatial structures of lead (Pb) ada... more In situ scanning tunneling microscopy was used to examine the spatial structures of lead (Pb) adatom and carbon monoxide (CO) molecule adsorbed onto an ordered Pt(111) electrode in 0.1 M perchloric acid (HClO4) containing 1 mM Pb(ClO4)2 under potential control. Ordered Pb structures were not seen until the potential was made more negative to 0 V (vs. Ag/AgCl), where a quasi-square array (7 57) was seen. Shifting the potential more negative substantiated Pb deposition, which triggered restructuring of the Pb adlayer into (21 21)R11 and (3 23)rect ( = 0.62 and 0.67) at -0.1 V. Pb adatom reduced the poisoning effect of CO on the Pt(111) electrode by blocking the adsorption of CO and by forcing CO molecule to asymmetric sites. An ordered (7 3) – Pb + CO structure was imaged at 0 V in 0.1 M HClO4 + 1 mM Pb(ClO4)2, from which the surface coverage and binding sites of CO molecule were inferred.
Journal of the Electrochemical Society, 2013
In situ scanning tunneling microscopy (STM) was used to study copper deposition at vacancy defect... more In situ scanning tunneling microscopy (STM) was used to study copper deposition at vacancy defects on a copper thin film underpotentiostatic conditions at −0.20 V (vs. Ag/AgCl) in a formula containing sulfuric acid, chloride, polyethylene glycol (PEG), andbis-3-sodiumsulfopropyl-disulfide (SPS) – the widely used mixture to facilitate Cu superfilling at recessed features in semiconductorprocessing. The vacancy island measuring ∼70 nm wide and 12 nm deep sat in the middle of a facetted surface structure at thebeginning. Cu deposit nucleated mainly at the rim of the vacancy and grew into stacked Cu(111) facets. These local pyramidal Custacks could restructure into wider Cu(111) terraces by transferring Cu atoms rapidly from higher to lower planes. Voltammetricresults showed that Cu deposition was suppressed in a plating bath containing 1 mM KCl + 88 μM PEG8000 + 10−7 M SPS.Steps with sharp edges bunched in the course of Cu deposition. The vacancy island was filled with Cu deposit assuming smoothterraces with sharp step edges aligned mainly in the 121 directions of the Pt(111) electrode, suggesting crystalline packing in theCu deposit. Atomic-resolution STM imaging revealed a hexagonal array presumed to be the (√3 × √3)R30◦ – Cl− adlattice
Journal of Electroanalytical Chemistry
The Journal of Physical Chemistry C, 2017
A bioderived zwitterionic molecule, cysteine betaine (Cys-b), can be used as a biomaterial coatin... more A bioderived zwitterionic molecule, cysteine betaine (Cys-b), can be used as a biomaterial coating to evade fouling and damage by light radiation. In situ scanning tunneling microscopy (STM) has been used to study the structures of the cysteine betaine (Cys-b) molecule adsorbed on an Au(111) electrode in 0.1 M HClO4 and H2SO4. A number of Cys-b structures have been identified in 0.1 M HClO4 before adsorbed Cys-b is irreversibly oxidized, including (4 × 8), (6 × 6), and (√19 × 3√3). By contrast, very different Cys-b structures, including (√7 × 4), which is an incommensurate structure, and disordered structures, are seen in the same potential region in H2SO4. These results are reconciled by a coadsorption scheme involving the Cys-b cation and ClO4– (or HSO4–). The coverages of Cys-b are 1.31 × 1014 and 2.32 × 1014 molecules/cm2 at the same potential in HClO4 and H2SO4. Although Cys-b molecules are tethered to the Au(111) substrate via their S-ends, their spatial structures are influenced greatly by the inte...
The Journal of Physical Chemistry C
Department of Chemistry, National Centr E-mail: mcchen@ncu.edu.tw Materials Research Institute, N... more Department of Chemistry, National Centr E-mail: mcchen@ncu.edu.tw Materials Research Institute, Northwestern Department of Chemical Engineering, Nat Taiwan. E-mail: kcho@ntu.edu.tw Department of Physics, Astronomy and Research Center, Northwestern University, E Department of Chemistry, PSG College of Ar Research Center for New Generation Pho Chung-Li 32054, Taiwan Institute of Chemistry, Academia Sinica, Na Department of Materials Science and Engi Energy Research Center, Northwestern Univ Department of Chemistry, The Materials Re Solar Energy Research Center, Northwestern E-mail: t-marks@northwestern.edu † Electronic supplementary informa 10.1039/c7ta01825h ‡ These authors contributed equally. Cite this: J. Mater. Chem. A, 2017, 5, 12310
The Journal of Physical Chemistry C
Electrodes modified by thiol molecules with conjugated heterocycles can lead to improved activiti... more Electrodes modified by thiol molecules with conjugated heterocycles can lead to improved activities in electroanalysis and electrodeposition. However, the intricate interactions among thiol molecul...
ECS Meeting Abstracts
In situ scanning tunneling microscopy (STM) was used to examine the ordered microstructures of pl... more In situ scanning tunneling microscopy (STM) was used to examine the ordered microstructures of platinum (Pt) deposited on Au(111) substrate in aqueous Na2PtCl6 solution saturated with carbon monoxide (CO) without potential control at room temperature. PtCl6 2- complexes were reduced by CO molecules and deposited on Au(111) in a hexagonal array without potential control. At the same time, we introduced electron spectroscopy for chemical analysis (ESCA) to prove the Pt adatoms were reduced to metallic state after the CO was oxidized in air. According to the results of CV and STM, the coverage of Pt on Au(111) substrate increased sharply with the time passed initially and finally had the value of 0.87monolayer (ML) after 200min dosing. After 5min dosing, the adsorption of CO molecules first mobilized and rearranged Pt adatoms on Au(111) from disordered Pt aggregates to 0.9 nm wide tortuous stripes, and finally to patches of ordered Pt adatoms at 0.1 V (versus reversible hydrogen electr...
Electrochemistry Communications
Abstract The use of copper single-crystal electrodes (CSCEs) has revealed the crucial role of ele... more Abstract The use of copper single-crystal electrodes (CSCEs) has revealed the crucial role of electrode structure in electrocatalysis and corrosion. CSCEs, although commercially available, can be prepared in-house by melting the end of a Cu wire to form a single crystal bead (SCB) in ambient air. Unlike the conventional torch used for making Pt and Au SCBs, the torch used in this study allows the Cu bead to cool down to room temperature in a nitrogen stream. The resulting Cu bead is subsequently fabricated into a CSCE with a desired orientation. Copper’s propensity for oxidation does not pose a problem for our method as long as the H2 and O2 fluxes to the flame are well-controlled. The bulk oxide in the Cu SCB prepared as above is below the detection limit of our X-ray photoelectron spectrometer. The devised method opens up an avenue toward the study of electrochemistry at well-defined Cu and possibly other non-noble transition metal electrodes. Moreover, this method can also be used to make alloyed SCBs, as illustrated by the successful fabrication of a Cu/Ni (98.5/1.5) bead. The resulting Cu(1 1 1) and Cu98.5Ni1.5(1 1 1) electrodes are examined by cyclic voltammetry and in situ scanning tunneling microscopy in 0.1 M sulfuric acid. The trace amount of Ni in the Cu(1 1 1) electrode affects the potential, but not the structure, of specific adsorption of the (bi)sulfate anion. A (√3 × √7)–HSO4− structure and the Cu(1 1 1) lattice are imaged by STM at positive and negative potentials.
Langmuir : the ACS journal of surfaces and colloids, Jan 23, 2018
Surface modification for biosensors has focused attention for improvement of their sensitivity an... more Surface modification for biosensors has focused attention for improvement of their sensitivity and specificity, particularly for the detection in complex medium. In this work, we have synthesized zwitterionic carboxybetaine-thiols (CB-thiols) and sulfobetaine-thiols (SB-thiols) for modification of gold substrates to form a functional self-assembled monolayer (SAM) for the immunoassay in a surface plasmon resonance (SPR) biosensor. X-ray photoelectron spectroscopy (XPS), contact angle goniometer, and cyclic voltammetry were applied for characterizations of elemental composition, surface wettability, and packing density, respectively. The antifouling properties of the SAMs were accessed by quantitative analysis of protein and bacterial adsorption. The results from the SAMs with a single component indicated that the SB-thiol SAM provides better surface hydrophilicity, fouling resistance, and packing density as compared to the CB-thiol SAM, likely due to the ionic association of CB moie...
Journal of The Electrochemical Society
The Journal of Physical Chemistry C
The role of step defects on an electrode is a central issue in the modern study of electrocatalys... more The role of step defects on an electrode is a central issue in the modern study of electrocatalysis. Although scanning tunneling microscopy (STM) has been used to characterize the electrified interfaces of low Miller-indexed single-crystal electrodes, there has been little progress in the STM study of stepped Pt electrodes. Herein, the structures of Pt(332) and Pt(997), two vicinal surfaces to the (111) plane, are examined by high-resolution STM under potential control in 0.5 M H2SO4 solution containing iodide or carbon monoxide. These electrodes are annealed by a hydrogen flame and quenched in Millipore water, giving rise to rough step edges with poorly defined atomic structures at 0.1 V (vs reversible hydrogen electrode) in 0.5 M H2SO4. However, step edges are sharpened and aligned in the ⟨110⟩ direction after adsorption of CO on both electrodes. In contrast, seesaw-like step lines are produced by iodine adsorption. Therefore, the step structure and mobility of Pt atoms are markedly influenced by the ad...
Journal of the Electrochemical Society