Thin films sol-gel

Fig. 19. Schematic representation of a typical sol-gel thin film coating. Diagram adapted from Ref. 95. ...

J. Di, S. Bi, and M. Zhang, Third-generation superoxide anion sensor based on superoxide dismutase directly immobilized by sol-gel thin film on gold electrode. Biosen. Bioelectron. 19, 1479-1486 (2004). 

Mainly, three approaches have been used to immobilize the enzyme on transducer or electrode surface, single layer, bilayer, and sandwich configurations [69, 98], In some studies enzymes are covalently linked with sol-gel thin films [99], Sol-gel thin films are highly convenient for fast, large, and homogeneous electron transfer [17]. With an increase in gel thickness the signal decays and diffusion of analytes to biomolecule active site becomes difficult eventually these factors lead to poor response. By employing thin films various biosensors such as optical and electrochemical biosensors have been reported. 

U. Narang, P.N. Prasad, and F.V. Bright, A novel protocol to entrap active urease in a tetraethoxysi-lane-derived sol-gel thin-film architecture. Chem. Mater. 6, 1596—1598 (1994). 

B. Wang, B. Li, Z. Wang, G. Xu, Q. Wang, and S. Dong, Sol-gel thin-film immobilized soybean peroxidase biosensor for the amperometric determination of hydrogen peroxide in acid medium. Anal. Chem. 71, 1935-1939 (1999). 

Watkins, A. N. Ligler, F. S. 2000. Patterned deposition of sol-gel thin films using an airbrush. Anal. Lett. 33 1899-1912. 

Working with the University of Padua s Professor Sandro Campes-trini and Dr Massimo Carraro has been (and is) as fruitful as it is pleasant. And similarly joyful is the research with Professor Laura M. Ilharco and Dr Alexandra Fidalgo at Lisboa Polytechnic. We thank the University of Poitiers Professor Eric Le Bourhis and Madrid s CSIC senior researcher Marisa Ferrer for rewarding shared work on sol gel thin films and on photochemical and biomaterials, respectively. 

Nguyen, T., McNamara, K. P., and Rosenzweig, Z. (1999). Optochemical sensing by immobilizing fluorophore-encapsulating liposomes in sol-gel thin films. Anal. Chim. Acta 400 45-54. 

Nishida, F. McKieman, J. M. Dunn, B. Zink, J. I. Brinker, C. J. Hurd, A. J., In situ fluorescence probing of the chemical changes during sol-gel thin film formation. Journal of the American Ceramic Society 1995, 78(6), 1640-1648... 

Fireman-Shoresh S, Avnir D, Marx S (2003) General method for chiral imprinting of sol-gel thin films exhibiting enantioselectivity. Chem Mater 15( 19) 3607—3613... 

In this work a combination of polymeric and colloidal sol techniques has been investigated as an alternative method to fabricate electrolyte layers on warm-pressed anode substrates. Sol-gel thin film deposition is applied on dense or very fine porous substrates. Therefore, multilayer structure electrolyte layers are manufactured. Gas-tightness and the electrochemical performance were tested. 

Capone, S., Siciliano, E, Quaranta, E, Rella, R., Epifani, M. and Vasanelli, L., Moisture infiuence of geometry effect of Au and Pt electrodes on CO sensing response of SnOj microsensors based on sol-gel thin film . Sensor Actual B, 2001, 77,503-11. 

Higgins, D. A. Collinson, M. M., Gaining Insight into the Nanoscale Properties of Sol-Gel Thin Films by Single-Molecule Spectroscopy. Langmuir 2005, 21,9023-9031. 

Experiments have shown that other types of gas sensors can also use mesoporous silicas as the sensing layer. For example, selective sensing of nitric oxide has been accomplished in the presence of carbon monoxide through the application of quartz crystal microbalance technology employing a cobalt phthalocyanine-modified sol-gel thin film (Palaniappan et al. 2006,2008). Electrochemical detection of nitrite has been accomplished using a metalloporphyrin-modified silicate material... 

Brinker CJ, Hurd AJ, Schunk P-R, Ashley CS (1992) Review of sol-gel thin film formation. J Non-Cryst Sohds... 

Fireman-Shoresh S, Popov I, Avnir D et al (2005) Enantioselective, chirally templated sol-gel thin films. J Am Chem Soc 127 2650-2655... 

Patel, A.K. Sharma, P.S. Prasad, B.B. (2009). Electrochemical sensor for uric acid based on a molecularly imprinted polymer brush grafted to tetraethoxysilane derived sol-gel thin film graphite electrode. Materials Science and Engineering C, 29,1545-1553. 

Reisfeld showed that nonlinear sol-gel glasses, and especially sol-gel thin films, form an interesting class of optoelectronic devices, and investigated the origin of strong nonlinearities on a millisecond to nanosecond scale of glasses doped with fluorescein, acridine and methyl orange. 

Stress that generates during firing is the origin of the aacks in gel-derived films, which also provides substrate bending (Hu, 1988 Atkinson, 1991 Scherer, 1992 Drinker, 1992). Properties of the films, for example. Curie point of ferroelectric thin films, could also be affected by stress in films (Desu, 1994 Lee, 1994 Rossetti, 1991). Therefore, scientific understanding is quite important on stress evolution in gel-derived films in the field of sol-gel thin film deposition techniques. 

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