Measuring and testing – Gas analysis – Detector detail
Reexamination Certificate
2001-11-05
2003-06-17
Niebling, John F. (Department: 2812)
Measuring and testing
Gas analysis
Detector detail
C073S031030, C073S031060, C438S049000, C438S029000
Reexamination Certificate
active
06578406
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to molecular electronics, and, more particularly, to vapor-sensitive, molecular light emitting diodes based on thin films of certain platinum complexes.
BACKGROUND ART
The inventors have recently published reports that have enucleated and explained the unusual “vapochromic” changes in absorption and emission spectra that result when certain stacked platinum complexes are exposed to organic vapors; see, e.g., C. L. Exstrom et al,
Chemical Materials,
Vol. 7, pp. 15-17 (1995) and C. A. Daws et al,
Chemical Materials,
Vol. 9, pp. 363-368 (1997).
A typical experiment involves a solution, crystal or solid film of material, such as tetrakis(p-decylphenylisocyano)platinum tetracyanoplatinate (I) (see
FIG. 1
, which depicts the chemical formula of the compound, where the dashed vertical line indicates the c-axis) that forms stacks of alternating cations and anions with strong interplatinum interactions. These salts exhibit an intense absorption band in the visible region. Exposing the stacks to small molecule vapors, such as acetone or chloroform, leads to sorption of the vapor molecules in the free volume between the stacks, and produces shifts in the absorption and emission spectra. These “vapochromic” or “vapoluminescent” changes are usually reversible so that the original spectrum is regained quickly after the vapor is removed. Such an effect has potential application for sensor technology.
Molecular LEDs are under intense investigation; see, e.g., R. H. Friend in
Conjugated Polymers and Related Materials,
W. R. Salaneck et al, Eds., Chapter 21, Oxford University Press (1993); A. J. Heeger, in Conjugated Polymers and Related Materials, W. R. Salaneck et al, Eds., Chapter 4, Oxford University Press (1993); R. H. Friend et al, in “Physical Properties of Polymers Handbook”, J. E. Mark, Ed., AIP Press, New York (1996); Y. Yang,
MRS Bulletin,
pp. 31-38 (June 1997); T. Tsutsui,
MRS Bulletin,
p. 39-45 (June 1997); and W. R. Salaneck et al,
MRS Bulletin,
p. 46-51 (June 1997). However, to the best of the inventors' knowledge, there is only one unspecific report from the patent literature which describes this type of LED sensor; see, U.S. Pat. No. 5,629,533, issued to D. E. Ackley et al on May 13, 1997.
Vapochromic platinum complexes and salts have been the subject of a patent; see, U.S. Pat. No. 5,766,952, issued to Kent R. Mann et al on Jun. 16, 1998. Such complexes change color when exposed to certain organic vapors.
DISCLOSURE OF INVENTION
In accordance with the present invention, a molecular light emitting diode is provided. The molecular LED employs an organic complex that acts as both a sensor to certain organic molecules, or analyte vapors, and as an active light emitter. The molecular LED of the present invention comprises:
(a) a first electrode;
(b) a hole transport layer formed on the first electrode;
(c) a sensing/emitting layer formed on the hole transport layer, the sensing layer comprising a material that changes color upon exposure to the analyte vapors;
(d) an electron conductor layer formed on the sensing layer; and
(e) a second electrode formed on the electron conductor layer, wherein the hole transport layer emits light at a shorter wavelength than the sensing/emitting layer and wherein at least the first electrode comprises an optically transparent material. The device is preferably formed on a transparent dielectric substrate, on which the first electrode is formed.
Also in accordance with the present invention, a method is provided for detecting analyte vapors. The method comprises:
(a) providing the above-described vapochromic LED;
(b) introducing the analyte vapors to the sensing layer; and
(c) biasing the first electrode positive with respect to the second electrode.
Further in accordance with the present invention, methods are provided for forming the vapochromic LED.
Other objects, features, and advantages of the present invention will become apparent upon consideration of the following detailed description and accompanying drawings, in which like reference designations represent like features throughout the FIGURES. The drawings referred to in this description should be understood as not being drawn to scale except if specifically noted.
REFERENCES:
patent: 5629533 (1997-05-01), Ackley et al.
patent: 5766952 (1998-06-01), Mann et al.
C.L. Exstrom et al, “Inclusion of Organic Vapors by Crystalline, Solvatochromic [Pt(aryl isonitrile)4][Pd(CN)4] Compounds”,Chemical Materials, vol. 7, pp. 15-17 (1995).
C.A. Daws et al, “Vapochromic Compounds as Environmental Sensors”Chemical Materials, vol. 9, pp. 363-368 (1997).
R.H. Friend, “Conjugated Polymers and Related Materials”, W.R. Salaneck et al, Eds., Chapter 21, Oxford University Press (1993).
A.J. Heeger, “Conjugated Polymers and Related Materials”, W.R. Salnaeck et al, Eds., Chapter 4, Oxford university Press (1993).
R.H. Friend et al, “Conjugated Polymer Electroluminescence”,Physical Properties of Polymers Handbook, J.E. Mark, Ed., AIP Press, New York (1996).
Y. Yang, “Polymer Electroluminescent Devices”,MRS Bulletin, pp 31-38 (Jun. 1997).
T. Tsutsui, “Progress in Electroluminescent Devices Using Molecular Thin Films”,MRS Bulletin, pp. 39-45 (Jun. 1997).
W.R. Salaneck et al, “Conjugated Polymer Surfaces and Interfaces for Light-Emitting Devices”,MRS Bulletin, pp. 46-51 (Jun. 1997).
C.L. Exstrom, “Structural Characterization of Iridium 1,8-Diisocyanomenthane Complexes and the Effects of Guest Molecule Inclusion on the Structure and Spectroscopy of Organometallic Stacking Materials”, Ph.D. Dissertation, University of Minnesota, 1995.
Kunugi et al, “Light-emitting Diodes Based on Linear and Starburst Electro-Oligomerized Thienyltriphenylamines”,Synthetic Metals, 89, pp. 227-229 (1997).
John P. Wheeler, “Light-Emitting Polymers Are Ready For Prime Time”,Photonics Spectra, pp. 130-134, Apr. 1997.
Kunugi et al, “A Vapochromic LED”,J. A. Chem. Soc.,vol. 120, pp. 589-590 (1998).
Exstrom Christopher L.
Kunugi Yoshihito
Mann Kent R.
Miller Larry L.
Collins David W.
Niebling John F.
Regents of the University of Minnesota
Simkovic Viktor
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