Supramolecular aggregation of inorganic molecules at Au(111) electrodes under a strong ionic atmosphere.

Neutral inorganic molecules are generally weak in surface adsorption and intermolecular interactions. Self-assembly of such types of molecule would provide valuable information about various interactions. At electrochemical interfaces, the relative strength of these interactions may be modified through control of electrode potential and electrolyte, which may lead to the discovery of new structures and new phenomena. However, studies of this nature are as yet lacking. In this work, we consider the covalent-bound semimetal compound molecules, XCl(3) (X = Sb, Bi), as model systems of neutral inorganic molecules to investigate their self-assembly at electrochemical interfaces under a high ionic atmosphere. To fulfill such investigations, in situ STM and cyclic voltammetry are employed, and comparative experiments are performed on Au(111) in ionic liquids as well as aqueous solutions with high ionic strength. In the room temperature ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF(4)), potential-dependent partial charge transfer between the Au surface and XCl(3) molecules creates a molecule-surface interaction and provides the driving force for adsorption of the molecules. Supramolecular aggregations of adsorbed XCl(3) are promoted through chlorine-based short-range intermolecular correlation under crystallographic constraint, while repulsive Coulombic interactions created between the partially charged aggregations facilitate their long-range ordering. For SbCl(3) molecules, hexagonally arranged 6- or 7-member clusters are formed at 0.08 to -0.2 V (vs Pt), which assemble into a secondary ( radical31 x radical31)R8.9 degrees structure. For BiCl(3) molecules, both the 6-membered hexagonal and 3-membered trigonal clusters are formed in the narrow potential range -0.3 to -0.35 V, and are also arranged into an ordered secondary structure. Comparative studies were performed with SbCl(3) in concentrated aqueous solutions containing 2 M HCl to simulate the strong ionic strength of the ionic liquid. Almost identical 6-/7-member clusters and long-range ( radical31 x radical31)R8.9 degrees structure are observed at -0.1 V, demonstrating the crucial role of strong ionic strength in such supramolecular aggregations. However, such supramolecular structures are modified and eventually destroyed as ionic strength is further increased by addition of NaClO(4) up to 6 M. The destructive changes of the supramolecular structures are attributed to the alteration of ion distribution in the double layer from cation-rich to anion-rich at increasing NaClO(4) concentration. This modifies and eventually breaks the balance of intermolecular and molecule-electrolyte interactions. Finally, the dynamic behavior of the SbCl(3) assembly is investigated down to molecular level. It has been demonstrated that the initial stage of assembly follows a two-dimensional nucleation and growth mechanism and has a potential-dependent rate that is closely related to the surface mobility of the SbCl(3) clusters. There is a probability that clusters can escape from an existing assembly domain or insert into a vacancy in such a domain while they can also relax with central or ring members in a dynamic fashion. These phenomena indirectly reflect the dynamic properties of cations from electrolytes at the interface. The rich information contained in the self-assembly behavior of SbCl(3) and BiCl(3) demonstrates that neutral inorganic molecules can be employed for fundamental studies of a variety of interesting issues, especially the interplay of various interfacial interactions.

[1]  B. Mao,et al.  Extending the capability of STM break junction for conductance measurement of atomic-size nanowires: an electrochemical strategy. , 2008, Journal of the American Chemical Society.

[2]  C. Lagrost,et al.  Electrochemical reactivity in room-temperature ionic liquids. , 2008, Chemical reviews.

[3]  L. Wan,et al.  Electrochemical Scanning Tunneling Microscopy: Adlayer Structure and Reaction at Solid/liquid Interface , 2007 .

[4]  K. Ariga,et al.  Real-time STM observation of molecular dynamics on a metal surface , 2007 .

[5]  Jiawei Yan,et al.  In Situ STM Studies on the Underpotential Deposition of Antimony on Au(111) and Au(100) in a BMIBF4 Ionic Liquid , 2007 .

[6]  F. Endres,et al.  Ionic liquids: the link to high-temperature molten salts? , 2007, Accounts of chemical research.

[7]  Alexei A Kornyshev,et al.  Double-layer in ionic liquids: paradigm change? , 2007, The journal of physical chemistry. B.

[8]  C. Czeslik Bunsen Colloquium: Controlling Protein Adsorption at Materials Surfaces , 2007 .

[9]  Xin Xu,et al.  Self-assembly of alkanols on Au(111) surfaces. , 2006, Chemistry.

[10]  L. Wan Fabricating and controlling molecular self-organization at solid surfaces: studies by scanning tunneling microscopy. , 2006, Accounts of chemical research.

[11]  R. Salvarezza,et al.  Self-assembled monolayers of alkanethiols on Au(111): surface structures, defects and dynamics. , 2005, Physical chemistry chemical physics : PCCP.

[12]  C. Wakai,et al.  How polar are ionic liquids? Determination of the static dielectric constant of an imidazolium-based ionic liquid by microwave dielectric spectroscopy. , 2005, The journal of physical chemistry. B.

[13]  K. Minato,et al.  Molecular to ionic transition of BiCl3 in LiCl–KCl eutectic melt , 2005 .

[14]  L. Wan,et al.  Supramolecular nanostructures of 1,3,5-benzene-tricarboxylic acid at electrified Au(111)/0.05 M H2SO4 interfaces: an in situ scanning tunneling microscopy study. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[15]  C. Jung,et al.  Atomic rearrangements during the electrochemical treatments of Au(111) covered with irreversibly adsorbed Sb. , 2005, The journal of physical chemistry. B.

[16]  G. Whitesides,et al.  Self-assembled monolayers of thiolates on metals as a form of nanotechnology. , 2005, Chemical reviews.

[17]  F. D. Schryver,et al.  Self-assembly at the liquid/solid interface: STM reveals. , 2005, The journal of physical chemistry. B.

[18]  C. Jung,et al.  Initial adsorption stage of irreversibly adsorbing Sb on Au(1 1 1) , 2004 .

[19]  Xin Xu,et al.  Self-assembly of normal alkanes on the Au (111) surfaces. , 2004, Chemistry.

[20]  G. Wipff,et al.  M3+ Lanthanide Chloride Complexes in “Neutral” Room Temperature Ionic Liquids: A Theoretical Study , 2004 .

[21]  Jiawei Yan,et al.  An in situ STM study on the long-range surface restructuring of Au(1 1 1) in a non-chloroaluminumated ionic liquid , 2003 .

[22]  N. Oxtoby,et al.  Controlling molecular deposition and layer structure with supramolecular surface assemblies , 2003, Nature.

[23]  Jiawei Yan,et al.  An in situ STM study on Sb electrodeposition on Au(1 1 1): irreversible adsorption and reduction, underpotential deposition and mutual influences , 2003 .

[24]  T. Ye,et al.  Porphyrin self-assembly at electrochemical interfaces: role of potential modulated surface mobility. , 2002, Journal of the American Chemical Society.

[25]  D. Kolb,et al.  Initial stages of Pt deposition on Au(111) and Au(100) , 2002 .

[26]  O. Magnussen Ordered anion adlayers on metal electrode surfaces. , 2002, Chemical reviews.

[27]  H. Güntherodt,et al.  Time evolution analysis of a 2D solid gas equilibrium: a model system for molecular adsorption and diffusion , 2001 .

[28]  D. Kolb Electrochemical Surface Science , 2001 .

[29]  F. Schreiber Structure and growth of self-assembling monolayers , 2000 .

[30]  D. Kolb,et al.  The adsorption of sulfate and phosphate on Au(111) and Au(100) electrodes: an in situ STM study , 2000 .

[31]  V. Climent,et al.  Electrocatalysis of formic acid and CO oxidation on antimony-modified Pt(111) electrodes , 1998 .

[32]  Aicheng Chen,et al.  Ionic adsorption at the Au(111) electrode , 1998 .

[33]  S. Yau,et al.  Direct Observation of Complexation of Alkali Cations on Cyanide-Modified Pt(111) by Scanning Tunneling Microscopy , 1996 .

[34]  Tao,et al.  Surface charge induced order-disorder transition in an organic monolayer. , 1995, Physical review letters.

[35]  I. Bae,et al.  Solvent effects in metal underpotential deposition on single crystal metal surfaces , 1995 .

[36]  M. Tosi Structure of covalent liquids , 1994 .

[37]  B. Ocko,et al.  Electrodeposited bismuth monolayers on gold (111) electrodes: comparison of surface x-ray scattering, scanning tunneling microscopy, and atomic force microscopy lattice structures , 1993 .

[38]  A. Gewirth,et al.  Correlation of electrode surface structure with activity toward peroxide electroreduction for bismuth monolayers on gold(111) , 1992 .

[39]  A. Aldaz,et al.  New observations of a structure sensitive electrochemical behaviour of irreversibly adsorbed arsenic and antimony from acidic solutions on Pt (111) and Pt (100) orientations , 1988 .

[40]  Shigang Sun,et al.  Electrochemical adsorption behaviour of platinum stepped surfaces in sulphuric acid solutions , 1986 .

[41]  Clarke,et al.  Structural phase transitions in SbCl5-intercalated graphite. , 1985, Physical review. B, Condensed matter.

[42]  G. Mamantov,et al.  Raman spectra of molten bismuth trichloride and antimony trichloride and of their mixtures with potassium chloride or aluminum trichloride , 1973 .