Mixed Self-Assembled Monolayers of Semirigid Tetrahydro-4H-thiopyran End-Capped Oligo(cyclohexylidenes)
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Abstract:
Single-component and mixed self-assembled monolayers (SAMs) of one- and three-ring semirigid tetrahydro-4H-thiopyran end-capped oligo(cyclohexylidenes)that is, thiopyran (1), 4-(4-cyclohexylidene-cyclohexylidene)tetrahydro-4H-thiopyran (2), and 4-(tetrahydro-4H-thiopyran-4-cyclohexylidene-4'-ylidene)tetrahydro-4H-thiopyran (3)on Au(111) substrates have been prepared and studied by cyclic voltammetry (CV), atomic force microscopy (AFM), and scanning tunneling microscopy (STM). It was found that the shortest adsorbate 1 more readily forms a SAM than 2 or 3. Notwithstanding, the SAMs of 2 or 3 are thermodynamically more stable due to favorable intermolecular attractions. Holes were made with the AFM tip establishing tilt angles of 30−50° with respect to the surface normal for all SAMs. STM imaging showed well-ordered, line-shaped packing patterns with molecular resolution for the SAM of 2. Similar patterned structures were not observed for 1 and 3. Mixed SAMs were prepared by exposing a SAM of 1 to ethanol solutions of either 2 or 3. STM imaging revealed that domains of molecules of 2 or 3 amidst a monolayer of 1 are formed in both cases. Whereas in the mixed SAM of 1 and 2 the domains are irregularly shaped, circular islands of uniform size are found in the mixed SAM of 1 and 3.Keywords:
Thiopyran
Self-assembled monolayer
Self-assembled monolayer
Thioether
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The alkyltrichorosilane(OTS) monolayers are prepared by self assembled technique. The topographies of self assembled OTS monolayers are characterized and analyzed by atomic force microscopy. The results indicate that the topographies of self assembled OTS monolayers are functions of the time of formation. The topographies of monolayers become constant with the time increasing. In the meantime, the topographies are also dependant on the composition of solvent.
Self-assembled monolayer
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Self-assembled monolayer(SAM) of 3-mercaptopropyltrimethoxysilane(MPS) absorbed on the surface of silver was constructed and electrochemical characteristics and compact extent of the monolayer was studied by cyclic voltammetry(CV) and contact angle.The results indicated that SAM by MPS can be obtained and can inhibit electrons from transferring across the thin film according to the decrease of peak current,the negative-moving reductive peak potential and the increase of peak potential difference of CV on the modified electrode.MPS assembled concentration and assembled time can affect compact extent of the monolayer and the best efficacious MPS assembled concentration in ethanol was 0.1 mmol/L for 6 h.An analysis of contact angle of the monolayer showed that self-polymeric extent of the end-group in MPS can increase with the increase of hydrolysis time and the compact extent of the monolayer can be markedly improved by prolonging hydrolysis time.
Self-assembled monolayer
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Self-assembled monolayer
Component (thermodynamics)
Scanning Probe Microscopy
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Self-assembled monolayer
Ellipsometry
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Using a scanning tunneling microscope (STM), we demonstrated the tip-height-controlled removal of self-assembled monolayers (SAMs) on an Au(111) surface in air. The monolayer films were selectively removed by the mechanical tip contact while scanning. By controlling tunneling current at a constant sample bias voltage, the appropriate tip height was investigated for the removal of different alkanethiol SAMs: octanethiol, decanethiol and dodecanethiol. The tip height for the removal of alkanethiol SAMs was dependent on the film thickness. This result indicated that selective molecular removal of SAMs on the Au(111) surface could be accomplished by controlling the tip height.
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This study analyzed the behaviour of organization molecular chemically modified tetraether lipids caldarchaeol-PO4 on the modification of the solid surface-supported wafer silicon to amino-silanised using Langmuir-Blodgett films, Self Assembling Monolayers (SAMs), ellipsometry, and atomic force microscopy (AFM). On the silicon wafer with an amino-silaned surface, the monolayers of caldarchaeol-PO4 remained stable. By using the Langmuir-Blodgett technique and SAMs, the organisations of molecular monolayers of caldarchaeol-PO4 have been examined. In the Langmuir-Blodgett procedure, surface pressure is carried out in monolayers of more flat, inhomogeneous caldarchaeol-PO4. A large flat domain is displayed by another way of monolayers caldarchaeol-PO4 using SAMs. Monolayers caldarchaeol-PO4 by the Langmuir-Blodgett method appears to be stable and chemically resistant after washing with organic solvent and an additional treatment ultrasonification with various lipid thicknesses of about 2 nm to 6 nm. Conversely monolayers caldarchaeol-PO4 by SAMs appear less than monolayers caldarchaeol-PO4 by the Langmuir-Blodgett method, thicknesses varying from 1 nm to 3 nm.
Self-assembled monolayer
Ellipsometry
Surface pressure
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The immobilization of surface-derivatized gold nanoparticles onto methyl-terminated self-assembled monolayers (SAMs) on gold surface was achieved by the cooperation of hydrophobic and electrophoretic forces. Electrochemical and scanning probe microscopy techniques were utilized to explore the influence of the SAM's structure and properties of the nanoparticle/SAM/gold system. SAMs prepared from 1-decanethiol (DT) and 2-mercapto-3-n-octylthiophene (MOT) were used as hydrophobic substrates. The DT SAM is a closely packed and organized monolayer, which can effectively block the underlying gold and inhibit a variety of solution species including organic and inorganic molecules from penetrating, whereas the MOT monolayer is poorly packed or disorganized (because of a large difference in dimension between the thiophene head and the alkylchain tail) and permeable to many organic probes in aqueous solution but not to inorganic probes. Thus, the MOT monolayer provides a more energetically favorable hydrophobic surface for the penetration and adsorption of organic species than the DT monolayer. This hypothesis is supported by experiments in which the density of hydrophobically immobilized nanoparticles on the MOT SAM is much larger than that on the DT SAM. The results also suggest new approaches for modification of macroscopic surfaces with nanoscopic particles.
Self-assembled monolayer
Hydrophobic effect
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Self-assembled monolayer
Trichlorosilane
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