Self-assembled monolayers of benzenethiol and benzenemethanethiol on Au(111): Influence of an alkyl spacer on the structure and thermal desorption behavior

Noh, Jaegeun; Ito, Eisuke; Hara, Masahiko

doi:10.1016/j.jcis.2009.10.076

Cited by 47 publications

(45 citation statements)

References 39 publications

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“…161 eV can be assigned to S atoms of TMMPP physorbed (unbounded) on Au(111). 72,73 No signals with the higher energy due to the S atoms produced by C-S cleavage were observed. Thus, the peak due to the desorption of the thiolate of TMMPP from the Au(111) surface can be assigned to be the most positive peak observed around ¹0.85 V. This peak potential was more negative than those observed at the benzenethiol SAM, 67,70 revealing that each TMMPP molecule exactly interacted with Au atoms through four thiolate groups.…”

Section: Electrochemical Reductive Desorptionmentioning

confidence: 98%

Self-Assembly Process of Flatly Adsorbed Porphyrin Self-Assembled Monolayer on a Au(111) Surface Studied by ex situ Scanning Tunneling Microscopy and Electrochemical Reductive Desorption Measurements

et al. 2014

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Self-assembly process of a porphyrin derivative [5,10,15,20-tetra-(m-mercapto-p-methoxyphenyl) porphyrin; TMMPP], which was designed and synthesized to be flatly adsorbed on a gold substrate surface, on a Au(111) single crystal surface was investigated by ex situ scanning tunneling microscopy (STM) and electrochemical reductive desorption measurements. A small number of TMMPP molecules were randomly but flatly adsorbed on the Au(111) surface when the deposition time was less than 1 h as the initial stage of the self-assembly process. When the deposition time was more than 20 h as the final stage of the self-assembly process, the densely-packed and flatly adsorbed TMMPP SAM formed on the Au(111) surface via a phase transition from a random to an ordered structure. These results indicated that we succeeded in the formation of the flatly adsorbed and well-defined porphyrin selfassembled monolayer (SAM) on the Au(111) surface.

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Section: Electrochemical Reductive Desorptionmentioning

confidence: 98%

Self-Assembly Process of Flatly Adsorbed Porphyrin Self-Assembled Monolayer on a Au(111) Surface Studied by ex situ Scanning Tunneling Microscopy and Electrochemical Reductive Desorption Measurements

et al. 2014

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“…The similar structure was often observed for other aromatic thiol SAMs. 9,10,12,15 It was suggested that the formation of gold adatom islands is due to a low mobility of gold adatoms emerged from the first gold layer during the chemisorption of aromatic thiols on gold surfaces. Therefore, higher deposition temperature can increase a mobility of gold adatoms and a diffusion rate of adsorbing molecules on the gold surfaces, resulting in the formation of high quality SAMs with a structural order and without such gold a datom islands.…”

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confidence: 99%

“…[6][7][8][9][10][11][12][13][14][15][16] However, there have been very few reports on the structure and orientation of SAMs of 4-alkylbenzenethiols with a nonpolar sustituent.…”

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confidence: 99%

Structural Investigation of 4-Methylbenzenethiol Self-Assembled Monolayers on Au(111) by Scanning Tunneling Microscopy

Kang¹,

Noh²

2014

Bulletin of the Korean Chemical Society

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Self-assembled Monolayers (SAMs) Formed by the Spontaneous Adsorption of Organic Thiols on Metal Surfaces offer a powerful route for potential applications in a variety of fields such as corrosion inhibition, lubrication, sensors, biointerface, and nanopatterning. [1][2][3][4] Recently, SAMs of aromatic thiols have drawn considerable attention due to their practical applications in molecular electronic devices. 5,6 It has been demonstrated that the work function of metal electrodes in electronic devices can be easily tuned by introducing the SAMs of ω-functionalized aromatic thiols with different functional group 5-8 and the performance of SAMmodified devices was strongly dependent on the molecular orientation of adsorbed molecules.8 Therefore, it is essential to understand the surface structure and molecular orientation of aromatic thiol SAMs as well as to control two-dimensional (2D) structure of SAMs for the development of electronic devices. Structural order of aromatic thiol SAMs on Au(111) was considerably enhanced by increasing the number of phenyl ring in the molecular backbone 9-11 and by inserting the alkyl spacer between the phenyl ring and the sulfur atom.12,13 High-resolution scanning tunneling microscopy (STM) imaging revealed that the adsorption of benzenethiol (BT) on Au(111) at 50°C led to the formation of well-ordered SAMs showing the (2 × 3√2)R30° structure, 9,12 while fluorinated benzenethiol SAMs have quite different packing strcutures.14,15 So far, numerous reports have mainly focused on the surface structure, molecular orientation, self-assembled process and physical property of SAMs formed by various aromatic thiols. 6-16 However, there have been very few reports on the structure and orientation of SAMs of 4-alkylbenzenethiols with a nonpolar sustituent. 17The main purpose of this work is to elucidate how much the alkyl substituent of benzenethiol at 4-position affects the formation and structure of SAMs. To explore this question, we examined 4-methylbenzenethiol (4-MBT) SAMs prepared in a 1 mM ethanol solution using STM, and revealed for the first time that 4-MBP molecules on Au(111) at 75 ºC form 2D ordered SAMs describing a (2√3 × √11.5)R30°s tructure.Atomically flat Au(111) substrates were prepared by thermal evaporation of gold onto mica as described previously.10 4-MBT SAMs were prepared by dipping the Au(111) substrate in a 1 mM ethanol solution of 4-MBT at room temperature or 75 °C for 2 h. STM measurements were carried out using a NanoScope E (Veeco, Santa Barbara, CA) with a commercial Pt/Ir (80:20) tip under ambient conditions. Imaging parameters were in the range of 300-500 mV for the bias voltage and in the range of 0.30-0.60 nA for the tunneling current between the tip and the sample.STM images in Figure 1 show the surface structures of 4-MBT SAMs on Au(111) formed after immersion in a 1 mM ethanol solution at room temperature and 75 °C for 2 h. The adsorption of 4-MBT molecules on Au(111) at room temperature yielded to the disordered SAMs containing gold adatom islands (bri...

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“…To understand these fundamental issues, STM has been used as one of the very powerful tools for visualizing the atomic-and molecular-scale surface structures of SAMs on metal surfaces, as demonstrated in many previous reports. [1][2][3][4][6][7][8][9][10][11][12][13][14][15][16][20][21][22][23][24][25][26][27][28][29][30][31][32][33] Additionally, thermal desorption spectroscopy (TDS) 10,11,32,[34][35][36][37] and electrochemical measurements [38][39][40][41][42][43] are very useful techniques to investigate the adsorption conditions, thermal stability, and the electrochemical behavior and stability of SAMs. TDS measurements revealed that alkanethiol SAMs exist as a form of monomer (alkanethiolate), not dimers (dialkyl disulfides) derived from associa-tive reactions of the sulfur headgroups, 10,11,34,…”

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Influence of Thiol Molecular Backbone Structure on the Formation and Reductive Desorption of Self-Assembled Aromatic and Alicyclic Thiol Monolayers on Au(111) Surface

Kang¹,

Noh²

2013

Bulletin of the Korean Chemical Society

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The surface structure and electrochemical behavior of self-assembled monolayers (SAMs) prepared from benzenethiol (BT), cyclohexanethiol (CHT), and cyclopentanethiol (CPT) on Au(111) surface were examined by scanning tunneling microscopy (STM) and cyclic voltammetry (CV) to understand the influence of thiol molecular backbone structure on the formation and reductive desorption behavior of SAMs. STM imaging showed that BT and CPT SAMs on Au(111) surface formed at room temperature were mainly composed of disordered domains, whereas CHT SAMs were composed of well-ordered domains with three orientations. From these STM results, we suggest that molecule-substrate interaction is a key parameter for determining the structural order and disorder of simple aromatic and alicyclic thiol SAMs on Au(111). In addition, the reductive desorption peak potential for BT SAMs with aromatic rings was observed at a less negative potential of -566 mV compared to CHT SAMs (-779 mV) or CPT SAMs (-775 mV) with aliphatic cyclic rings. This reductive desorption behavior for BT SAMs is due to the presence of p-orbitals on the aromatic rings, which promote facile electron transfer from the Au electrode to BT as compared to CHT and CPT. We also confirmed that the reductive desorption behavior for simple alicyclic thiol SAMs such as CHT and CPT SAMs on Au electrodes was not significantly influenced by the degree of structural order.

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Self-assembled monolayers of benzenethiol and benzenemethanethiol on Au(111): Influence of an alkyl spacer on the structure and thermal desorption behavior

Cited by 47 publications

References 39 publications

Self-Assembly Process of Flatly Adsorbed Porphyrin Self-Assembled Monolayer on a Au(111) Surface Studied by ex situ Scanning Tunneling Microscopy and Electrochemical Reductive Desorption Measurements

Self-Assembly Process of Flatly Adsorbed Porphyrin Self-Assembled Monolayer on a Au(111) Surface Studied by ex situ Scanning Tunneling Microscopy and Electrochemical Reductive Desorption Measurements

Structural Investigation of 4-Methylbenzenethiol Self-Assembled Monolayers on Au(111) by Scanning Tunneling Microscopy

Influence of Thiol Molecular Backbone Structure on the Formation and Reductive Desorption of Self-Assembled Aromatic and Alicyclic Thiol Monolayers on Au(111) Surface

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