Monolayers chemical sensors

There are three advantages to study molecular recognition on surfaces and interfaces (monolayers, films, membranes or soHds) (175) (/) rigid receptor sites can be designed (2) the synthetic chemistry may be simplified (J) the surface can be attached to transducers which makes analysis easier and may transform the molecular recognition interface to a chemical sensor. And, which is also a typical fact, this kind of molecular recognition involves outside directed interaction sites, ie, exo-receptor function (9) (see Fig. 5b). 

The first report of surface-immobilized dendrimers was in 1994 [54]. Subsequently, our research group showed that the amine-terminated PAMAM and PPl dendrimers could be attached to an activated mercaptoimdecanoic acid (MUA) self-assembled monolayer (SAM) via covalent amide linkages [55, 56]. Others developed alternative surface immobilization strategies involving metal com-plexation [10] and electrostatic binding [57]. These surface-confined dendrimer monolayers and multilayers have found use as chemical sensors, stationary phases in chromatography, and catalytic interfaces [41,56,58,59]. Additional applications for surface-confined dendrimers are inevitable, and are dependent only on the synthesis of new materials and the development of clever, new immobilization strategies. 

Mirsky, V. M. Vasjari, M. Novotny, I. Rehacek, V. Tvarozek, V. Wolfbeis, O. S., Self-assembled monolayers as selective filters for chemical sensors, Nanotechnology 2002, 13, 1-4... 

In conclusion, the advantages of microfluidic devices, parallel synthesis, and combinatorial approaches can be merged to integrate a fluorescent chemical sensor array in a microfluidic chip. Fluorescent microchannel array can be produced by parallel synthesis of fluorescent monolayers covalent attached to the walls of glass microchannels. 

Paolesse R., Di Natale C., Macagnano A., Davide E., Boschi T., and D Amico A., Self-assembled monolayers of mercaptoporphyrins as sensing material for quartz crystal microbalance chemical sensors. Sens. Actuators B, B47, 70-76, 1998. 

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]. 

Over the last decades, there have been a lot of efforts to fabricate polymer thin film. However, it is difficult to obtain a conducting polymer in thin film or monolayer owing to lack of processabihty and solubility. Among the conducting polymers, PANI thin film has a great potential to apply for chemical sensor due to its sensing ability and conductivity. Similar to PPy, there have been several methods to fabricate PANI thin film LB technique, self-assembly, electropolymerization, evaporation, and plasma-mediated polymerization. 

Tisch U, Haick H (2010) Sensors based on monolayer-capped metallic nanoparticles. In Korotcenkov G (ed) Chemical sensors fundamentals of sensing materials. Vol. 2. Nanostructured materials. Momentum, New York, pp 141-202 Turkevich J, Stevenson PC, HilUer J (1951) A study of the nucleation and growth processes in the synthesis of coUoidal gold. Discuss Faraday Soc 11 55-56... 

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