Langmuir-Blodgett films of a Mo-blue nanoring [Mo(142)O(429)H(10)(H(2)O)(49)(CH(3)CO(2))(5)(CH(3)CH(2)CO(2))](30)(-) (Mo(142)) by the semiamphiphilic method

Langmuir monolayers and LB films of the ring-shaped mixed-valence polyoxomolybdate [Mo142O429H10(H2O)49(CH3CO2)5(CH3CH2CO2)](30-) (Mo142) dissolved in the aqueous subphase have been successfully fabricated by using the adsorption properties of a DODA monolayer. Infrared and ultraviolet-visible spectroscopy of the LB films indicates that Mo142 and DODA molecules are incorporated within these LB films. X-ray reflectivity experiments indicate that the LB films exhibit a well-defined lamellar structure formed by bilayers of DODA molecules alternating with monolayers of Mo142. Using behenic acid-modified hydrophobic quartz substrate is critical for the formation of the well-defined lamellar structure. From the values of the periodicity obtained by these experiments it is clear that the Mo142 clusters lie flat along the charged organic layers. AFM images also showed the flat and homogeneous films on the quartz substrates treated with behenic acid. Cyclic voltammograms of Mo142-LB films deposited on ITO substrates showed quasi-reversible oxidation/reduction waves with positive shift of the potential compared to the case of solution.     

In situ spectroscopic characterization of rectifying molecular monolayers self-assembled on gold.

We report visible, Raman, and infrared spectra of self-assembled monolayers (SAMs) formed by the donor-(pi-bridge)-acceptor chromophore, Z-beta-[N-(omega-acetylthioalkyl)-4-quinolinium]-alpha-cyano-4-styryldicyanomethanide (CH3CO-S-CnH2n-Q3CNQ where n=8, 10), on gold-coated substrates. The data are compared with the spectra collected for the same compound in solution and in the solid state, and with those obtained for a Langmuir-Blodgett (LB) monolayer of C16H33-Q3CNQ deposited on gold. Spectral analysis confirms that in solution, in the solid state and in the LB film the chromophore has a zwitterionic (D+-pi-A-) ground state. At variance with this well-known result, our data show that in SAMs deposited on gold the chromophore has a more neutral, quinoid ground state. We relate this difference to the different packing of the molecules in the two different films: in SAMs in fact the chromophores stand almost vertical with respect to the substrate, whereas in LB films they make an angle of about 45 degrees. The Q3CNQ molecule is a well-known molecular rectifier, and for SAMs we were able to check the direction of electron flow at forward bias on the same samples that have been characterized spectroscopically, shedding light on the rectification mechanism.     

Interfacial supramolecular self-assembled monolayers of C(60) by thiolated beta-cyclodextrin on gold surfaces via monoanionic C(60)

The supramolecular self-assembled monolayers (SAMs) of C(60) by thiolated beta-cyclodextrin (CD) on gold surfaces were constructed for the first time using C(60) monoanion. The results indicate that monoanionic C(60) plays a crucial role in the formation of the C(60)-containing self-assembled monolayers. The generation of C(60) monoanion and the formation process of C(60) SAMs were monitored in-situ by UV-visible and near-IR spectroscopy. The resulting C(60) SAMs were fully characterized by spectroscopic ellipsometry (SE), cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and water contact angle measurements. After the immobilization of C(60) by the SAMs of thiolated beta-CD, the film thickness increased by approximately 1 nm from 0.8 to 1.8 nm as determined by SE, demonstrating the formation of the supramolecular self-assembled monolayers of thiolated beta-CD/C(60). The new C(60) SAMs exhibited one quasi-reversible redox couple at half wave potential of -0.57 V vs SCE in aqueous solution containing 0.1 M KCl. The surface coverage of C(60) on the gold surfaces was estimated to be 1.1 x 10(-10) mol cm(-2). The XPS showed the assembly of C(60) over the thiolated beta-CD SAMs. The surface hydrophobicity increased greatly upon the formation of the C(60)-containing SAMs as analyzed by water contact angle measurements. The results are in agreement with the formation of 1:1 complex of C(60) and cyclodextrin on gold surfaces, though it also reveals some non-homogeneous features of the monolayers.     

Synthesis,structural analysis,and self-assembly of phenylene ethynylene oligomers and their ?F, ?CF3, and ?CH3 substituted derivatives

Oligomers consisting of aromatic building blocks separated by alkynyl units were synthesized by Sonogashira cross-coupling of aryl halides with terminal acetylenes. Strong electron acceptors such as  F and  CF₃ and weak electron donors like  CH₃ were placed as substituents on one of the benzene rings. Acetyl-protected sulfhydryl groups were attached to one end of these molecules to promote their self-organization on gold surfaces. The electron-transport properties of such self-assembled monolayers (SAMs) are highly sensitive to the local order of the molecules in the solid state. Single crystals were analyzed by X-ray diffraction experiments that revealed structural details that could lead to a better understanding of the electron-transport properties. The unsymmetrical substitution of the aromatic rings by electron-active groups in the ortho-, meta-, or para positions resulted in changes of such molecular parameters as bonding and torsion angles and planarity. These parameters, in turn, can affect the angle of the molecular attachment to a gold substrate and the density of the resulting SAMs. Patterned SAMs of some of these molecules and comparison alkane thiols were obtained on gold by microcontact printing or flooding. The SAM thickness was determined by spectroscopic ellipsometry. Surface potential differences between adjacent SAMs or between SAMs and the gold substrate were measured by scanning surface potential microscopy under ambient conditions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 541–550, 2004     

Quantifying electron transfer during hyperthermal scattering of C60+ from Au(111) and n-alkylthiol self-assembled monolayers

A tandem time-of-flight mass spectrometer with an intermediate surface was used to quantify electron transfer during glancing incidence scattering of hyperthermal C(60) (+) (E(coll)=250-500 eV, theta(in)=75 degrees ) from (i) self-assembled monolayers of n-alkylthiols on gold (of various chain lengths), (ii) partly fluorinated alkylthiols on gold, as well as (iii) clean gold surfaces. Self-assembled monolayers (SAMs) behave as insulating layers with their thicknesses determining the electron tunneling probability during collision. Correspondingly, a roughly exponential dependence of the neutralization probability on the chain length n was found. A pronounced dependence of the neutral yield on the primary beam kinetic energy indicates that dynamic SAM deformation and associated projectile penetration depth also play a role in determining electron transfer efficiency. Results are consistent with the molecular deformability of SAMs as determined with other experimental methods.     

Self-assembly of C(60) pi-extended tetrathiafulvalene (exTTF) dyads on gold surfaces

The first self-assembly of a C60 pi-extended tetrathiafulvalene (exTTF) dyad on a gold surface is reported. Four fullerene derivatives, two of them containing p-quinonoid pi-extended tetrathiafulvalenes (exTTFs), have been synthesized, and their solution electrochemistry has been investigated by means of cyclic voltammetry. Fullerene-containing SAMs of thioctic acid derivatives 3 and 6 have also been investigated by cyclic voltammetry. The cyclic voltammograms of both compounds exhibit three reversible reduction waves, and for compound 6, one irreversible oxidation process corresponding to the oxidation of the exTTF subunit is observed. Stable self-assembled monolayers (SAMs) of fullerene derivative 3 were formed on gold surfaces, whereas dyad 6 does not present a very clear electrochemical response, most probably as a result of structural rearrangements on the monolayer or charge transfer between the C60 and exTTF moieties.     

Directionally oriented LB films of an OPE derivative: assembly, characterization, and electrical properties

Langmuir films have been fabricated from 4-[4'-(4'-thioacetyl-phenyleneethynylene)-phenyleneethynylene]-aniline (NOPES) after cleavage of the thioacetyl protecting group. Characterization by surface pressure vs area per molecule isotherms and Brewster angle microscopy reveal the formation of a high quality monolayer at the air-water interface. One layer Langmuir-Blodgett (LB) films were readily fabricated by the transfer of the NOPES Langmuir film onto solid substrates. X-ray photoelectron spectroscopy (XPS), surface polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS), and quartz crystal microbalance (QCM) experiments conclusively demonstrate the formation of one layer LB films in which the functional group associated with binding to the substrate can be tailored by the film transfer conditions. Using LB methods this molecule could be transferred to gold samples with either the amine or thiol group attached to the gold surface. The amine group is directly attached to the gold substrate (Au-NH(2)-OPE-SH) when the substrate is initially immersed in the subphase and withdrawn during the transfer process; in contrast, monomolecular films in which the thiolate group is attached to the gold substrate (Au-S-OPE-NH(2)) are obtained when the substrate is initially out of the subphase and immersed during the transfer process. The morphology of these films was analyzed by atomic force microscopy (AFM), showing the formation of homogeneous layers. Film homogeneity was confirmed by cyclic voltammetry, which revealed a large passivation of gold electrodes covered by NOPES monolayers. Electrical properties for both polar orientated junctions have been investigated by scanning tunnelling microscopy (STM), with both orientations featuring a nonrectifying behavior.     

Preparation and functions of self‐assembled monolayers of helix peptides

Self‐assembled monolayers (SAMs) of helix peptides oriented vertically to a gold surface were prepared. Negative surface potentials of a few hundred millivolts were observed for the helix peptide SAMs when they were immobilized on gold through the N terminal of the peptides. However, positive surface potentials were generated in the helix peptide SAMs when the N terminal of the peptides was directed the opposite way. The large dipole moment of the helical peptide was thought to be the major factor for generation of the surface potential. The effect of the dipole moment on the electron transfer through the helix peptide SAMs was investigated. Photocurrent generation by photoexcitation of the N‐ethylcarbazolyl group of the peptide SAMs was accelerated by the dipole moment directed toward the gold substrate. Helical peptides were thus shown to be a suitable medium for electron transfer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4826–4831, 2000     

硒杂环化合物(4,5-苯并苤硒脑)在金表面上的自组装

为了寻求新的自组装单分子膜体系,构建新的功能膜,研究了具备平面型的大环共轭硒杂环化合物-- 4,5-苯并苤硒脑(苯并[c]硒二唑,简称苤硒脑)在金表面的自组装单分子膜.通过X射线光电子能谱(XPS)和电化学手段对其进行表征.XPS研究结果表明,自组装形成单分子膜后,苤硒脑分子中Se3d结合能从57.4 eV下降到57.1 eV;表明硒杂环化合物是通过金硒键固定在金表面上的;电化学循环伏安法实验表明,金电极表面上自组装该有机硒后, Fe(CN)63-/4-的氧化还原峰几乎完全消失;以四硼酸钠为底液,测得该化合物自组装在金表面上时,其还原电位在-0.66 V,与在溶液中用裸金电极测得的还原峰电位基本一致.     

Facile synthesis of chlorophyll analog possessing a disulfide bond and formation of self-assembled monolayer on gold surface

A chlorophyll analog forming self-assembled monolayers (SAMs) on a gold surface was synthesized for the first time. 13(2)-(Demethoxycarbonyl)pheophorbide-a, which was converted from naturally occurring chlorophyll-a, was condensed with 2-hydroxyethyl disulfide to give a chlorin dyad linked by a disulfide bond. The chlorin analog was spontaneously immobilized on a gold substrate by soaking in an acetone solution of the dyad for 24 h. The resulting gold plate exhibited a visible absorption spectrum with about 420- and 675-nm maxima as the Soret and Qy peaks, respectively, indicating that chlorin pi-conjugates were modified on the gold substrate through Au-S bonding. Both visible absorption and fluorescence emission bands of the chlorin chromophores on the gold substrate were red-shifted compared with those of the synthesized chlorin dyad in a homogeneous acetone solution. The measured absorbance at the Soret maximum suggests that the chlorin chromophores on the gold plate were densely packed on a gold surface to form a SAM. Cathodic photocurrents were generated from SAMs of the chlorins on a gold substrate with irradiation of visible-lights above 400 nm. Photoinduced electron transfer from chlorins on the gold substrate to oxygen molecules in an electrolyte solution were attributed to the cathodic photocurrent generation.     

多巴胺在2-氨基-5-巯基-[1,3,4]三氮唑自组装膜电极上的准可逆行为研究及分析应用

利用新合成的巯基试剂2-氨基-5-巯基-[1，3，4]三氮唑在金电极表面进行了首次自组装，用电化学法和扫描电子显徽镜对自组装膜电极进行了表征。研究了多巴胺在该自组装膜电极上的电化学行为，发现该自组装膜能有效促进多巴胺在电极与溶液之间的电子传递．表现为二电子传递的准可逆行为，电极反应速率常数为0．105cm／s。该自组装膜电极用于多巴胺注射液含量的测定，结果满意。     

Surface stress, kinetics, and structure of alkanethiol self-assembled monolayers

The surface stress induced during the formation of alkanethiol self-assembled monolayers (SAMs) on gold from the vapor phase was measured using a micromechanical cantilever-based chemical sensor. Simultaneous in situ thickness measurements were carried out using ellipsometry. Ex situ scanning tunneling microscopy was performed in air to ascertain the final monolayer structure. The evolution of the surface stress induced during coverage-dependent structural phase transitions reveals features not apparent in average ellipsometric thickness measurements. These results show that both the kinetics of SAM formation and the resulting SAM structure are strongly influenced both by the surface structure of the underlying gold substrate and by the impingement rate of the alkanethiol onto the gold surface. In particular, the adsorption onto gold surfaces having large, flat grains produces high-quality self-assembled monolayers. An induced compressive surface stress of 15.9 +/- 0.6 N/m results when a c(4x2) dodecanethiol SAM forms on gold. However, the SAMs formed on small-grained gold are incomplete and an induced surface stress of only 0.51 +/- 0.02 N/m results. The progression to a fully formed SAM whose alkyl chains adopt a vertical (standing-up) orientation is clearly inhibited in the case of a small-grained gold substrate and is promoted in the case of a large-grained gold substrate.     

Synthesis and self-assembly of 2,9,16-tri(tert-butyl)-23-(10-mercaptodecyloxy)phthalocyanine and the application of its self-assembled monolayers in organic light-emitting diodes

2,9,16-Tri(tert-butyl)-23-(10-mercaptodecyloxy)phthalocyanine (8) and its disulfide (9) have been synthesized and characterized, and their self-assembling behaviors on gold substrates have been studied. Characteristic Q-bands were observed at about 630 nm in the UV/visible spectra of the self-assembling monolayers (SAMs). They were broadened and blue-shifted relative to those observed in solution. Binding energies for S2p have the same values (161.70 eV) and are in accord with those for gold thiolates. The application of the SAMs in organic light-emitting diode was investigated. It shows that the SAM promotes the hole injection process from the anode.     

Molecular rectification: self-assembled monolayers in which donor-(pi-bridge)-acceptor moieties are centrally located and symmetrically coupled to both gold electrodes

Self-assembled monolayers (SAMs) obtained from 1-(10-acetylsulfanyldecyl)-4-[2-(4-dimethylaminophenyl)vinyl]quinolinium iodide exhibit asymmetric current-voltage (I-V) characteristics. The rectification may be reversibly switched: it is suppressed when the film is exposed to HCl vapor, the intramolecular charge-transfer axis being inhibited by protonation, but restored when exposed to NH(3). The behavior is intrinsic to the donor-(pi-bridge)-acceptor moiety, and ambiguity in the assignment has been excluded by matching the alkyl tails on the substrate and contacting STM tip to locate the chromophore midway between the electrodes: Au-S-C(10)H(21)//D-pi-A-C(10)H(20)-S-Au. Films contacted by gold tips exhibit rectification ratios of ca. 18 at +/-1 V, whereas those contacted by pentanethiolate (Au-S-C(5)H(11))- and decanethiolate (Au-S-C(10)H(21))-coated tips have corresponding ratios of ca. 11 and 5, respectively. The I-V curves are different, but when adjusted for thickness the current versus electric field dependence is indistinguishable. Seven dyes are reported: SAMs with sterically hindered D-pi-A moieties, in which the donor and acceptor are twisted out of plane, exhibit rectification, whereas those that are planar or have a weak donor-acceptor combination do not.     

Structure-dependent charge transport and storage in self-assembled monolayers of compounds of interest in molecular electronics: effects of tip material, headgroup, and surface concentration

The electrical properties of self-assembled monolayers (SAMs) on a gold surface have been explored to address the relation between the conductance of a molecule and its electronic structure. We probe interfacial electron transfer processes, particularly those involving electroactive groups, of SAMs of thiolates on Au by using shear force-based scanning probe microscopy (SPM) combined with current-voltage (i-V) and current-distance (i-d) measurements. Peak-shaped i-V curves were obtained for the nitro- and amino-based SAMs studied here. Peak-shaped cathodic i-V curves for nitro-based SAMs were observed at negative potentials in both forward and reverse scans and were used to define the threshold tip bias, V(TH), for electric conduction. For a SAM of 2',5'-dinitro-4,4'-bis(phenylethynyl)-1-benzenethiolate, VII, V(TH) was nearly independent of the tip material [Ir, Pt, Ir-Pt (20-80%), Pd, Ni, Au, Ag, In]. For all of the SAMs studied, the current decreased exponentially with increasing distance, d, between tip and substrate. The exponential attenuation factors (beta values) were lower for the nitro-based SAMs studied here, as compared with alkylthiol-based SAMs. Both V(TH) and beta of the nitro-based SAMs also depended strongly on the molecular headgroup on the end benzene ring addressed by the tip. Finally, we confirmed the "memory" effect observed for nitro-based SAMs. For mixed SAMs of VII and hexadecanethiol, I, the fraction of the charge collected in the negative tip bias region that can be read out at a positive tip bias on reverse scan (up to 38%) depended on the film composition and decreased with an increasing fraction of I, suggesting that lateral electron hopping among molecules of VII occurs in the vicinity of the tip.     

Self-assembled monolayers (SAMs) with photo-functionalities

Self-assembled monolayers (SAMs) of alkylthiol on metals, especially on gold, with photo-functionalities, such as photo-induced electron transfer, control of photo-electrochemical properties, control of electron transfer by photoisomerization, luminescence, and photo-patterning, are reviewed.     

New dialkyldithiophosphinic acid self-assembled monolayers (SAMs): influence of gold substrate morphology on adsorbate binding and SAM structure

We report the fabrication and characterization of new self-assembled monolayers (SAMs) formed from dihexadecyldithiophosphinic acid [(C(16))(2)DTPA] molecules on gold substrates. In these SAMs, the ability of the (C(16))(2)DTPA headgroup to chelate to the gold surface depends on the morphology of the gold substrate. Gold substrates fabricated by electron-beam evaporation (As-Dep gold) consist of ～50-nm grains separated by deep grain boundaries (～10 nm). These grain boundaries inhibit the chelation of (C(16))(2)DTPA adsorbates to the surface, producing SAMs in which there is a mixture of monodentate and bidentate adsorbates. In contrast, gold substrates produced by template stripping (TS gold) consist of larger grains (～200-500 nm) with shallower grain boundaries (<2 nm). On these substrates, the low density of shallow grain boundaries allows (C(16))(2)DTPA molecules to chelate to the surface, producing SAMs in which all molecules are bidentate. The content of bidentate adsorbates in (C(16))(2)DTPA SAMs formed on As-Dep and TS gold substrates strongly affects the SAM properties: Alkyl chain organization, wettability, frictional response, barrier properties, thickness, and thermal stability all depend on whether a SAM has been formed on As-Dep or TS gold. This study demonstrates that substrate morphology has an important influence on the structure of SAMs formed from these chelating adsorbates.     

Isostructural self-assembled monolayers. 2. Methyl 1-(3-mercaptopropyl)-oligo(ethylene oxide)s

The structural order and ordering conditions of the self-assembled monolayers (SAMs) of HSCH2CH2CH2O(EO)xCH3, where EO = CH2CH2O and x = 3-9, on polycrystalline gold (Au) were determined by reflection-absorption infrared spectroscopy (RAIRS), spectroscopic ellipsometry (SE), and electrochemical impedance spectroscopy. For x = 5-7, RAIRS and SE data show that the oligo(ethylene oxide) [OEO] segments adopt the near single phase, 7/2 helical conformation of the folded-chain crystal polymorph of crystalline poly(ethylene oxide), oriented normal to the substrate. These SAMs exhibit OEO segment structure and orientation identical to that found in a previous isostructural series [HS(CH2CH2O)6-8C18H37 SAMs. Vanderah, D. J., et al. Langmuir 2003, 19, 3752] and are anisotropic films for surface science metrology where structure is constant and thickness increases in 0.30 nm increments. In addition, this is the first example of OEO SAMs to attain this highly ordered, helical conformation where the (EO)x segment is separated from the Au-sulfur headgroup by a polymethylene chain. For x = 4, 8, and 9, the SAMs are largely helical but show evidence of nonhelical conformations and establish the upper and lower limits of the isostructural set. For x = 3, the SAMs are largely disordered containing some all-trans conformation. SAM order as a function of immersion time from 100% water and 95% ethanol indicates that the HSCH2CH2CH2O(EO)5-7CH3 SAMs order faster and under a wider range of conditions than omega-alkyl 1-thiaolio(ethylene oxide) [HS(EO)xCH3] SAMs, reported earlier (Vanderah, D. J., et al. Langmuir 2002, 18, 4674 and Vanderah, D. J., et al. Langmuir 2003, 19, 2612).     

Self-assembly of alkanols on Au(111) surfaces

Self-assembled monolayers (SAMs) of alkanols (1-C(N)H(2N+1)OH) with varying carbon-chain lengths (N = 10-30) have been systematically studied by means of scanning tunneling microscopy (STM) at the interfaces between alkanol solutions (or liquids) and Au(111) surfaces. The carbon skeletons were found to lie flat on the surfaces. This orientation is consistent with SAMs of alkanols on highly oriented pyrolytic graphite (HOPG) and MoS2 surfaces, and also with alkanes on reconstructed Au(111) surfaces. This result differs from a prior report, which claimed that 1-decanol molecules (N = 10) stood on their ends with the OH polar groups facing the gold substrate. Compared to alkanes, the replacement of one terminal CH3 group with an OH group introduces new bonding features for alkanols owing to the feasibility of forming hydrogen bonds. While SAMs of long-chain alkanols (N > 18) resemble those of alkanes, in which the aliphatic chains make a greater contribution, hydrogen bonding plays a more important role in the formation of SAMs of short-chain alkanols. Thus, in addition to the titled lamellar structure, a herringbone-like structure, seldom seen in SAMs of alkanes, is dominant in alkanol SAMs for values of N < 18. The odd-even effect present in alkane SAMs is also present in alkanol SAMs. Thus, the odd N alkanols (alkanols with an odd number of carbon atoms) adopt perpendicular lamellar structures owing to the favorable interactions of the CH3 terminal groups, similar to the result observed for odd alkanes. In contrast to alkanes on Au(111) surfaces, for which no SAMs on an unreconstructed gold substrate were observed, alkanols are capable of forming SAMs on either the reconstructed or the unreconstructed gold surfaces. Structural models for the packing of alkanol molecules on Au(111) surfaces have been proposed, which successfully explain these experimental observations.     

Self-assembled monolayers of CH3COS- terminated surfactant-encapsulated polyoxometalate complexes

Self-assembled monolayers (SAMs) on gold surfaces based on three kinds of acetylthio-surfactant-encapsulated polyoxometalate clusters (thio-SECs) terminated with multiple CH(3)COS- groups, (NC(26)H(55)S(CO)CH(3))(6)H(2)[Co(H(2)O)CoW(11)O(39)], (NC(26)H(55)S(CO)CH(3))(13)H(3)[Co(4)(H(2)O)(2)(P(2)W(15)O(56))(2)], and (NC(26)H(55)S(CO)CH(3))(13)[Fe(4)(H(2)O)(2)(P(2)W(15)O(56))(2)]Br, have been prepared, which is representative of a general methodology to fabricate polyoxometalate-based SAMs. Thio-SECs self-assembled into monolayers on gold surfaces through the hydrolysis of CH(3)COS- groups and the subsequent formation of S-Au bonds, which was confirmed by grazing angle infrared spectroscopy, X-ray photoelectron spectroscopy, and ellipsometric and scanning tunneling microscopy (STM) measurements. Furthermore, the SAMs of the thio-SECs possess closely packed structures, and the local short-range order is clearly observed in the magnified STM image. We have also investigated the electrochemical behavior of SAMs of thio-SECs by cyclic voltammetry in detail, and the redox potential of the original polyoxometalates has been well retained. The electrochemical signals of the SAMs are very weak because of the small moiety of thio-SECs that are electrochemically accessible in the cyclic voltammetry experiments. The polyoxometalate-modified electrodes that we prepared are not only highly ordered in the local short range but also stable in electrochemical cycling because of the multiple S-Au bonds of thio-SECs on the gold substrates that aid in the construction of functional materials such as electrochemical and electrocatalytic devices.