Mixed silane monolayers

Similar to thiol SAMs, nonspecific interactions can be reduced by mixing PEG-terminated silanes into the monolayer. Another simple method is rinsing of the silanized surface with Tween 80 after the preparation [29]. 

P. Silberzan, D. Ausserr and J.J. Benattar, Silanation of silica surfaces, a new method of constructing pure or mixed monolayers, Langmuir, 1, 1647-1651 (1991). 

Quite another type of imprinting on the surface of silica was used by Sagiv (102). Mixed monolayers of n-octadecyltrichlorosilane and surfactant dyes are absorbed and chemically bound to glass. The dye molecules are then removed, leaving holes entrapped within a stable network of chemisorbed and polymerized silane molecules. These layers show a preferred adsorption of Che dyes used as templates. Problems are encountered with Che kinetics of the sorption-desorption process which has to proceed through a channel formed from the dense arrangement of long alkyl chains in the monolayer. 

In diffuse reflectance IR spectroscopy (DRIFT) light impinges on a solid powdered sample and is scattered in all directions. This light is collected and redirected to a detector. The powder must be very fine and is mixed with or dispersed in a suitable matrix, such as KCl or KBr with a particle size of less than 10 pm. It is not suitable for large powders or lumps. By using special sample preparation techniques, e.g., by placing the KBr powder over the sample, monolayers of adsorbed silanes have been studied [55], or water adsorbed on polymer surfaces has been detected [56]. 

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]. 

M. Mansueto, S. Sauer, M. Butschies, M. Kaller, A. Baro, R. Woerner, N.H. Hansen, G. Tovar, J. Pflaum, S. Laschat, Triphenylene silanes for direct surface anchoring in binary mixed self-assembled monolayers. Langmuir 28, 8399-8407 (2012)... 

Many standard proteins lacking sufficient aromatic amino acids and thiols on their surface as e.g. urease need reactive photo cross-linking. For that purpose the protein stock solutions 5% (w/v in distilled water) is mixed with a solution of 3% (w/v) 4,4 -diazidostilbene-2,2 disulfonic acid disodiumsalt tetrahydrate (DIAS) in a ratio of 10 1 (v / v). The mixture is spin-coated onto the mirror and activated with a monolayer l-(3-aminopropyl)-methyl-diethoxysilane. Amino-silane, an efficient adhesion promoter, is applied via vapor silanization as described above. Finally the spin-coated protein film is cross-linking via irradiation with UV-light for 30 seconds (350 nm, 60 W), The application of wavelength less than 350 nm will lead to considerable DIAS decomposition, therefore DNA cross-linker devices as used above are not recommended for this method. 

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