Silanes, self-assembled monolayers

Fig. 10.27). A fluorinated silane self-assembled monolayer was first applied to the master to aid in the separation of master and stamp. The stamp was formed using one of the following procedures. For thinner stamps, PDMS (Sylgard 184) pre-polymer mixture (1 10) was poured over the PR master and a 250 pm thick, 13-inch x 13-inch Mylar film was placed on top of the liquid PDMS. The prepolymer was evenly spread to less than 50 pm in thickness by rolling a Meyer rod over the surface of the Mylar backing film. 

Composites of PANI-NFs, synthesized using a rapid mixing method, with amines have recently been presented as novel materials for phosgene detection [472]. Chemiresistor sensors with nanofibrous PANI films as a sensitive layer, prepared by chemical oxidative polymerization of aniline on Si substrates, which were surface-modified by amino-silane self-assembled monolayers, showed sensitivity to very low concentration (0.5 ppm) of ammonia gas [297]. Ultrafast sensor responses to ammonia gas of the dispersed PANI-CSA nanorods [303] and patterned PANI nanobowl monolayers containing Au nanoparticles [473] have recently been demonstrated. The gas response of the PANI-NTs to a series of chemical vapors such as ammonia, hydrazine, and triethylamine was studied [319,323]. The results indicated that the PANI-NTs show superior performance as chemical sensors. Electrospun isolated PANI-CSA nanofiber sensors of various aliphatic alcohol vapors have been proven to be comparable to or faster than those prepared from PANI-NF mats [474]. An electrochemical method for the detection of ultratrace amount of 2,4,6-trinitrotoluene with synthetic copolypeptide-doped PANI-NFs has recently been reported [475]. PANI-NFs, prepared through the in situ oxidative polymerization method, were used for the detection of aromatic organic compounds [476]. 

W. Zheng, C.-Y. Chiang, I. Underwood, Hybrid molecular orientation of sandwich-type structure discogen hexaalkoxydibenzo[a, c]phenazine on the surfaces modified using silane self-assembled monolayers. Mol. Cryst. Liq. CrysL 540, 94-101 (2011)... 

Tbworfe GK, Composto RJ, Shapiro IM, Ducheyne P. (2006) Nucleation and growth of calcium phosphate on amine-, carboxyl- and hydioxyl-silane self-assembled monolayers. Biomater 27 631 42. 

Luderer F, Walschus U (2005) Immobilization of Oligonucleotides for Biochemical Sensing by Self-Assembled Monolayers Thiol-Organic Bonding on Gold and Silanization on Silica Surfaces. 260 37-56... 

The nse of self-assembled monolayers of proteins by direct chemical attachment of the peptide to a modified snrface obviates some of the protein orientation difficnlties observed in the construction of LB mono-layers. An initial report of the construction of peptide SAMs on silanized qnartz was pnblished in early 1998 (185). Pilloud et al. have utilized the covalent ligation of protein cysteine thiols to thiol-terminated silanized... 

Flowever, the focus of the major part of the chapters lies on the couphng chemistry used for DNA immobilization. Successful immobihzation techniques for DNA appear to either involve a multi-site attachment of DNA (preferentially by electrochemical and/or physical adsorption) or a single-point attachment of DNA (mainly by surface activation and covalent immobihzation or (strept)avidin-biotin linkage). Immobilization methods described here comprise physical or electrochemical adsorption, cross-linking or entrapment in polymeric films, (strept)avidin-biotin complexation, a surface activation via self-assembled monolayers using thiol linker chemistry or silanization procedures, and finally covalent coupling strategies. 

A recent study by DePalma and Tillman [ 10] also demonstrates the potential of surface modification by self-assembled monolayers of low surface energy fiuoroalkyl-containing silanes. Fatty acids, amines and alcohols have long been known to adsorb as monomolecular films on metals. Silane coupling agents have featured strongly in new studies to develop more robust films, covalently bound together and to the metal substrate. 

DePalma and Tillman investigated self-assembled monolayer films from three silanes, tridecafluorooctyltrichlorosilane, undecyltrichlorosilane, and octadecyl-trichlorosilane, on silicon, a popular model substrate for such studies with great relevance to potential semiconductor coating applications. They characterized the films by ellipsometry and contact angle measurements (data for trideca-fluorooctyltrichlorosilane are included in Table 1), but more usefully from an applicational viewpoint, they carried out friction and wear measurements with a pin-on-disk device where the silicon wafer substrate, coated with monolayer, is moved under a spherical glass slider. Optical microscopy was used to assess wear. Table 2 summarizes DePalma and Tillman s data and their comparison with the classical self-assembled monolayer friction studies of Levine and Zisman [18]. 

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