Coating processes – Electrical product produced – Carbon coating
Reexamination Certificate
1998-10-29
2001-05-15
Parker, Fred J. (Department: 1775)
Coating processes
Electrical product produced
Carbon coating
C427S282000, C427S287000
Reexamination Certificate
active
06231920
ABSTRACT:
This invention relates to a novel process for preparing sol-gel graphite composite electrodes, and to the composite electrodes produced therefrom.
Carbon paste and graphite composites with their unique properties of easy and bulk modification, renewable surface and low background currents have found wide applications in electrocatalysis and electroanalysis. Carbon inks are commonly and commercially used for the microfabrication of electrochemical sensors and biosensors based on thick-film technologies. The selectivity of these surfaces is enhanced by their modification with a recognition entity chosen according to the analytes to be determined. The simple mixing of the surface modifier with the graphite before the electrode assembly has always presented the problem of modifiers leaching with concomitant detrimental effects on the electrochemical response. Recently, sol-gel graphite composite electrodes have been reported for biosensors and chemical sensors and procedures for screen-printed electrodes with these composites. Sol-gel networks are promising encapsulation matrices because mild polymerization conditions and low gelation temperatures can be used allowing the encapsulation of fragile biological molecules. Furthermore, properties such as porosity, hydrophilicity and matrix chemical modification can be controlled in the preparation process to avoid the leaching problem and enhance the analyte diffusion and selectivity.
Generally, sol-gel reactions proceed by hydrolysis of an alkoxide precursor under acidic or basic conditions, and subsequent condensation of the hydroxylated monomers to form a porous gel. The addition of a co-solvent is necessary to mix the alkoxide with water.
SUMMARY OF THE INVENTION
To avoid the previously discussed problems, the present invention is directed to a novel process for preparing sol-gel graphite composite electrodes, which comprises introducing a surfactant into the process and thus avoiding the need for a co-solvent, a catalyst, a cellulose binder and thermal curing. This process is more environmentally friendly and compatible for organics and biomolecules immobilization, and offers an economical one-step fabrication of screen-printed modified electrodes. Additionally, composite electrodes produced from this novel process exhibit improved properties previously not taught in the prior art. Specifically, the resulting composite electrodes have a fine texture, and exhibit excellent adhesion and mechanical strength when exposed to both aqueous and non-aqueous solutions.
Because composites generally have low electrical resistance and good adhesion to various substrates (e.g., PVC, ceramics, metals, glass), this procedure offers an economical, one-step and low cost fabrication of screen-printed modified electrodes. Therefore, a further object of the present invention is to demonstrate electroanalytical applications of this composite in electrocatalysis and electroanalysis, specifically for composite electrodes in chemical sensors and biosensors.
Biosensors have been in the market place for several years, of which glucose sensors have prevailed, creating a large and stand-alone business. Disposable single-use sensors are one of the main products used by diabetic patients. However, to be more competitive with the existing methodologies on a large scale, many aspects should be improved to make them less expensive, user and environment friendly, and more easily manufactured (less complex to readily control quality and cut costs). Printing inks are obviously one of the critical components determining the products' performance and acceptance. And many efforts have been made in this field. UV-polymerizable screen-printable composites have been produced for more durable enzyme sensors. Screen-printable sol-gel enzyme-containing carbon inks offer a one-step fabrication of disposable enzyme strips obviating the need for thermal curing.
Besides the low cost and easy fabrication, the mediated glucose sensor that can be prepared in accordance with the present invention possesses excellent characteristics such as low operation potential (+0.3 V) and therefore less interferences, a wide working range (up to 30 mM) with a linear range up to 15 mM, a short response time (around 10 seconds) and long-term stability and shelf time.
In accordance with the present invention, disposable complexing (pre-concentrating) screen-printed strip electrodes for trace nickel have been fabricated by doping a sol-gel graphite composite with ligand dimethylglyoxime. Optimum quantitation procedures and parameters have been identified. A short (1 minute) accumulation period using open-circuit condition yielded a detection limit of 2 &mgr;g/L nickel. Fabrication of screen-printed environmental sensors by incorporation of ligands into carbon inks holds promise in routine trace metal speciation and quantitation based on the conventional pre-concentration/voltammetric strategy. For example, cobalt phthalocyanine (CoPC) modified composite electrode shows a behavior different from previous studies, indicating differences in charge and mass transport of species in these composite electrodes compared to traditional carbon paste electrodes. In addition, the surfactant-induced sol-gel polymerization that occurs in accordance with the present invention allows the encapsulation of fragile molecules under relatively mild conditions. This polymerization beneficially results in a mechanically and chemically stable surface for organic solvents.
Additional features and advantages of the present invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the present invention will be realized and attained by means of the elements and combinations particularly pointed out in the written description and appended claims.
REFERENCES:
patent: 4229490 (1980-10-01), Frank et al.
patent: 5160418 (1992-11-01), Mullen
patent: 5403462 (1995-04-01), Lev et al.
patent: 5494562 (1996-02-01), Maley et al.
patent: 5529676 (1996-06-01), Maley et al.
patent: 5573647 (1996-11-01), Maley et al.
patent: 5582698 (1996-12-01), Flaherty et al.
patent: 5601694 (1997-02-01), Maley et al.
patent: 5616222 (1997-04-01), Maley et al.
patent: 5711868 (1998-01-01), Maley et al.
patent: 5770028 (1998-06-01), Maley et al.
Kalcher, K.; Kaufmann, J. M.; Wang, J.; Vytras, K.; Neuhold, C.; Yang, Z.Electroanalysis1995, 7, No. 1, pp. 5-22.
Bilitewski, U.; Ruger, P.; Schmid, R. D.,Biosens.&Bioelectron.1991, 6, pp. 369-373.
Ikegami, A.; Arima, H.; Iwanaga, S.; Kaneyasu, M.,Proceedings of the 4th European Hybrid Microelectronic Conference,Copenhagen, May 18-20, 1983, pp. 211-218.
Alvarez-Icaza, M.; Bilitewski, U.,Anal. Chem.Jun. 1993, vol. 65, No. 11, pp. 525A-533A.
Kalcher, K.,Electroanalysis1990, 2, pp. 419-433.
Tsionsky, M.; Lev. O.,Anal. Chem.1995, 67, pp. 2409-2414.
Tsionsky, M.; Gun. G.; Glezer, V.; Lev, O.Anal. Chem.1994, 66, pp. 1747-1753.
Sampath, S.; Lev. O.Anal. Chem.1996, 68, pp. 2015-2021.
Iosefzon-Kuyavskaya, B; Gigozin, I.; Ottolenghi, M.; Avnir, D.; Lev. O.,J.Non-Cryst, Solids1992, 147 & 148, pp. 808-812 (North Holland).
Dunuwila, D.C.; Torgerson, B.A.; Chang, C.K.; Berglund, K.A..,Anal. Chem.1994, 66, pp. 2739-2744.
Dunbar, R.A.; Jordan, J.D.; Bright, F.V.Anal. Chem.1996, 68, pp. 604-610.
Petit-Dominguez, M.D.; Shen, H.; Heineman, W.R.; Seliska, C.J.,Anal. Chem.1997, 69, pp. 703-710.
Wang, J.; Pamidi, P.V.A.; Park, D.S.,Anal. Chem.1996, 68, pp. 2705-2708.
Avnir, D.,Acc. Chem. Res.1995, 28, pp. 328-334.
Avnir, D.; Braun S.; Lev. O.; Ottolenghi, M.,Chem. Mater1994, 6, pp. 1605-1614.
Zink, J. I.; Yamanaka, S. A.; Ellerby, L. M.; Valontine, J. S.; Nishida, F.; Dunn, B. J.,Sol-Gel Sci. Technol.1994, 2, pp. 791-795.
Hench, L. L.; West, J. K.,Chem. Rev.1990, 90, pp. 33-72.
Brinker, C. J.; Hurd, A. J.; Schunk, P. R.; Frye, G. C.; Ashley, C. S.,J. Non-Cryst, Solids1992, 147 & 148, pp. 424-436.
Cardosi, M.F.; Birch, S.W.,Anal. Chim. Acta1993, 276, pp. 69-74.
Avnir, D.; Kaufman
Guadalupe Ana R.
Guo Yizhu
Parker Fred J.
Patent Law Office of Heath W. Hoglund
University of Puerto Rico
LandOfFree
Electroanalytical applications of screen-printable... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electroanalytical applications of screen-printable..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electroanalytical applications of screen-printable... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2523984