Chemistry: analytical and immunological testing – Optical result – Spectrum analysis
Reexamination Certificate
2000-01-12
2001-06-05
Soderquist, Arlen (Department: 1743)
Chemistry: analytical and immunological testing
Optical result
Spectrum analysis
C422S068100, C422S082010, C422S082020, C422S082030, C422S082050, C422S082080, C422S082090, C436S086000, C436S164000, C436S501000, C436S514000, C436S525000
Reexamination Certificate
active
06242264
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to self-assembled metal colloid monolayers, methods of preparation, and use thereof.
In surface enhanced Raman scattering (SERS), million-fold enhancements in Raman scattering can be obtained for molecules adsorbed at suitably rough surfaces of Au, Ag, and Cu. Although many approaches have been reported, preparation of well-defined, stable SERS substrates having uniform roughness on the critical 3 to 100 nm scale has proven difficult. Because colloidal Au can be synthesized as monodisperse solutions throughout most of this size regime, and because molecules adsorbed to closely spaced colloidal Au and Ag exhibit enhanced Raman scattering, these particles are excellent building blocks for SERS-active substrates. The key issue is whether colloidal Au and Ag particles can be organized into macroscopic surfaces that have a well-defined and uniform nanometer-scale architecture. Indeed, controlling nanostructure is currently a central focus throughout materials research. Progress in self assembly of organic thin films on metal surfaces [C. D. Bain and G. M. Whitesides,
Angew. Chem. Int. Ed Engl.
28, 506 (1989); A. Ulman,
An Introduction to Ultrathin Organic Films, from Langmuir-Blodgett to Self-Assembly
(Academic Press, Boston, 1991)] led us to explore the reverse process: self assembly of colloidal Au and Ag particles onto supported organic films. As detailed below, this approach has yielded surfaces that are SERS-active, characterizable at both the macroscopic and microscopic levels, highly reproducible, electrochemically addressable, and simple to prepare in large numbers. Moreover, these substrates have a surface roughness that is defined by the colloid diameter (which is tunable) and an average interparticle spacing that is continuously variable. As such, self-assembled Au, Ag and Ag-coated colloid monolayers are likely to have extraordinary utility for SERS.
In the nearly twenty years since the discovery of surface enhanced Raman scattering (SERS) of molecules adsorbed at roughened Ag electrodes, and the accompanying theoretical work demonstrating the need for surface roughness, there have been numerous reports of new architectures for SERS substrates. See, for instance, Liao, P. F.; Bergman, J. G.; Chemla, D. S.; Wokaun, A.; Melngailis, J.; Hawyrluk, A. M.; Economou, N. P.
Chem. Phys. Lett.
1981, 82, 355-9; Creighton, J. A.; Blatchford, C. G.; Albrecht, M. G.
J. Chem. Soc., Faraday Trans.
2 1979, 75, 790-8; Blatchford, C. G.; Campbell, J. R.; Creighton, J. A.
Surf Sci.
1982, 120, 435-55; Tran, C. D.
Anal. Chem.
1984, 56, 824-6; Soper, S. A.; Ratzhlaff, K. L.; Kuwana, T.
Anal. Chem.
1990, 62, 143844; Sequaris, J.-M.; Koglin, E.
Fresenius J Anal. Chem.
1985, 321, 758-9; Aroca, R.; Jennings, C.; Kovacs, G. J.; Loutfy, R. O.; Vincett, P. S.
J. Phys. Chem.
1985, 89, 4051-4; Moody, R. L.; Vo-Dinh, T.; Fletcher, W. H.
Appl. Spectrosc.
1987, 41, 966-70; Ni, F.; Cotton, T. M.
Anal. Chem.
1986, 58, 3159-63; Yogev, D.; Efrima, S.
J. Phys. Chem.
1988, 92, 5761-5; Goudonnet, J. P.; Bijeon, J. L.; Warmack, R. J.; Ferrell, T. L.
Phys. Rev. B: Condensed Matter
1991, 43, 4605-12; Murray, C. A.; Allara, D. L.
J. Chem. Phys.
1982, 76, 1290-1303; Brandt, E. S.
Appl. Spectrosc.
1993, 47, 85-93; Alsmeyer, Y. W.; McCreery, R. L.
Anal. Chem.
1991, 63, 1289-95; Mullen, K.; Carron, K.
Anal. Chem.
1994, 66, 478-83; Beer, K. D.; Tanner, W.; Garrell, R. L.
J. Electroanal Chem.
1989, 258, 313-25; Dawson, P.; Alexander, K. B.; Thompson, J. R.; Haas III, J. W.; Ferrell, T. L.
Phys. Rev. B: Condens. Matter
1991, 44, 6372-81; Roark, S. E.; Rowlen, K. L.
Appl. Spectrosc.
1992, 46, 1759-61; Roark, Shane E.; Rowlen, K. L.
Chem. Phys. Lett.
1993, 212, 50; Roark, Shane E.; Rowlen, K. L.
Anal. Chem.
1994, 66, 261-70; Walls, D.; Bohn, P.
J. Phys. Chem.
1989, 93, 2976-82; Dutta, P. K.; Robins, D.
Langmuir
1991, 7, 2004-6; Sheng, R.-S.; Zhu, L.; Morris, M. D.
Anal. Chem.
1986, 58,1116-9.
These surfaces span a wide range of assembly principles and encompass similarly broad levels of complexity. Examples of SERS-active surfaces include electrochemically-roughened electrodes, microlithographically-prepared elliptical Ag posts, aggregates of colloidal Au or Ag particles—both in solution and associated with chromatographic media, evaporated thin films, Ag-coated latex particles, substrates prepared by chemical reduction of Ag
+
, and liquid Ag films. The motivation for this work stems from several intrinsically attractive aspects of SERS as a vibrational spectroscopy-based structural tool and/or analytical method: million fold signal enhancements compared to solution Raman spectra, adsorption-induced fluorescence quenching, a lack of interference from H
2
O, and molecular generality. However, while SERS has been invaluable for certain narrowly defined applications, most spectroscopists would agree that the technique has not lived up to its enormous potential.
The problem has been the inability of any previous surface to meet all, or even most, of the essential criteria that would define a truly useful SERS substrate: strongly enhancing, reproducible, uniformly rough, easy to fabricate, and stable over time. Biocompatibility is also extremely important, insofar as previous studies demonstrating partial or full protein denaturation upon adsorption to SERS-active substrates [Holt, R. E.; Cotton, T. M.
J: Am. Chem. Soc.
1989, 111, 2815-21; Lee, N.-S.; Hsieh, Y.-Z.; Morris, M. D.; Schopfer, L. M.
J. Am. Chem. Soc.
1987, 109, 1353-63] have proven to be a major setback to the use of SERS in biological systems. Other desirable characteristics include electromagnetic tunability (i.e. the ability to control the wavelength where optimal enhancement occurs, so as to match the substrate to the photon source), electrochemical addressability—to control the extent of adsorption and the redox state of adsorbed species, a lack of surface “activation” steps, and a low cost per substrate. This last feature is particularly important for applications involving large numbers of routine measurements, such as in environmental monitoring, airport security, and clinical medicine.
SUMMARY OF THE INVENTION
Detailed embodiments of the present invention are disclosed herein. However, it is understood that certain preferred embodiments are merely illustrative of the invention which may be embodied in various forms and applications. Specific compositional and functional details disclosed herein are not meant to be interpreted as limiting, but merely as support for the invention as claimed and as appropriate representations for teaching those skilled in the art to variously employ the present invention in any appropriate embodiment.
We report here a new approach to SERS substrates that meets all of the criteria delineated above. Our strategy involves assembly of colloidal Au, Ag, or other suitable metal particles into macroscopic two-dimensional arrays on polymer-immobilized substrates (FIG.
1
). In the first, covalent approach, reactive hydroxyl/oxide groups are generated on a substrate. For many substrates (glass, metal, etc.), such functional groups are already present in high concentration. A second step involves surface-initiated polymerization of bifunctional organosilanes such as (RO)
3
Si(CH
2
)
3
A. The alkoxysilane forms covalent attachments to the surface via hydrolysis. The pendant functional group A (FIG.
1
B), chosen for its high affinity toward noble metal surfaces, extends out into solution. In the final step, the polymer-derivatized substrate is immersed into a solution of colloidal Au particles, where surface assembly spontaneously occurs. An alternate approach based on high affinity binding of streptavidin to biotin can also be used (FIG.
1
C). See Wilchek, M.; Bayer, E. A.
Anal. Biochem.
1988, 171, 1 and Anzai, J.; Hoshi, T.; Osa, T
Trends Anal. Chem.
1994, 13, 205-10. Here, a biotinylated surface is reacted with a colloidal Au-streptavidin conjugate to form a colloid-based surface held together
Baker Bonnie E.
Natan Michael J.
Soderquist Arlen
Swanson & Bratschun LLC
The Penn State Research Foundation
LandOfFree
Self-assembled metal colloid monolayers having size and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Self-assembled metal colloid monolayers having size and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Self-assembled metal colloid monolayers having size and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2448735