Abstract:
A nuclear powered quantum dot light source, having a holder having at least a portion that is a radiolucent and a mixture of quantum dots, a radionuclide, and a radiolucent binder material into which the quantum dots and radionuclide are located. Alpha and/or beta particles from the radionuclide energize the quantum dots and cause them to give off light at one or more predetermined wavelengths.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of provisional patent application No. 60/673,158, filed on Apr. 20, 2005. 
    
    
     BACKGROUND 
     Quantum dots are semiconductor nanocrystals ranging from nanometers in size to a few microns. The size controls the number of electrons contained in the dot. Each quantum dot can contain from one to several thousand electrons. Since quantum dots are so small, quantum mechanical effects force the electron energy levels to be quantized. Quantum dots have sometimes been called artificial atoms because the electron quantum levels contained within a dot are similar to the electron orbitals in an atom. 
     This quantization allows distinct wavelength (colors) of light to be emitted. Light or electric current typically excites them. The light emitted ranges from ultraviolet to visible to infrared, depending on the material and the size. This is a wavelength span of 350 to 2300 nanometers. The emission has a very narrow bandwidth of 30 nanometers, full width at half maximum (FWHM). Work is being conducted on using quantum dots as a replacement for LEDs. 
     In addition to semiconductors, quantum dots can be made from metal. Presently, quantum dots are made by vacuum techniques such as molecular beam epitaxy (MBE) or chemical vapor deposition (CVD), or in aqueous solutions where a colloid is formed. Other techniques may be developed. Cadmium selenide (CdSe) is a common material for visible light quantum dots. A 3 nanometer CdSe dot emits 520-nanometer light that is green. Increasing the diameter to 5.5 nanometers increases the wavelength to 630 nanometers, the wavelength of red light. Quantum dots can be “tuned” by controlling their size to have any desired pure color of a desired wavelength. Other phosphors suitable for quantum dots include doped zinc sulfide (ZnS) compounds. Gold quantum dots have also been made. CdSe quantum dots may be coated with ZnS as a protective layer. 
     Quantum dots are commercially available from companies such as Evident Technologies of Troy, N.Y. Quantum dots have a myriad of applications, including medical applications for tagging proteins and antibodies. The quantum dots fluoresce to map the proteins and antibodies. Other uses of quantum dots include photovoltaic solar cells, electroluminescent devices, the phosphorous of LED lights, thermoelectrics, inks, pigments and anti-counterfeiting materials, to mention just a few areas of current research and development. 
     Quantum dots have been proven to be radiation resistant. It would therefore be advantageous if energy, namely alpha or beta particles from nuclear sources, could be utilized as the energy source to energize quantum dots for use in light sources having precise wavelengths and intensities, which precise light sources could be used, for example, to calibrate light sources. Other uses of these quantum dots include their uses in calibrating detector equipment such as ATP luminometers used for measuring the presence of ATP in swab samples, etc. 
     SUMMARY OF THE INVENTION 
     The company Isotope Products Laboratories, of Valencia, Calif., currently supplies light sources using alpha and beta emitters as light calibration sources. Presently, scintillator manufacturers have a limited choice of wavelengths available. Quantum dots excited by alpha particles or beta particles would provide a light source with precise wavelengths ranging from the infrared to ultraviolet light. Besides permitting light sources to be made having a predetermined, single wavelength, such light sources could also, for example, allow multiple wavelengths of light to be emitted by using combinations of quantum dots. This is not currently available. 
     Such light sources could be used as calibration sources for instruments using photomultiplier tubes or PIN photodiodes. Scintillator light sources are used in bacteria contamination detection systems, such as in ATP luminometers. Brighter light sources can be used to illuminate gun sights replacing fragile glass tubes containing tritium. 
     The use of scintillator material limits the available plastic matrix to polyvinyltoluene (PVT). PVT is a delicate plastic whose surface is damaged by finger prints. However, with quantum dots, other plastics such as epoxy, various resins, and silicone can be used. Quantum dots can even be embedded in glasses. Light sources can be made using techniques such as spray coating or screen-printing. Spin or dip coating can also form films. Ink jet systems can also be used for film deposition. 
     Quantum dots having desired qualities, (e.g., selected wavelength of light produced and intensity) can be combined in close association or proximity with one or more types of radionuclides in a matrix of optically translucent or transparent material. 
     More particularly, one or more types of quantum dots that produce light of one or more desired wavelengths, respectively, are mixed into a translucent or transparent matrix, e.g., cured UV resin, air cured resins, along with one or more types of radionuclides. The radionuclides emit either alpha or beta particles. Examples of beta radiation emitting radionuclides include, but are not limited to, hydrogen 3 (tritium, or  3 H), carbon 14 ( 14 C), silicon 32 ( 32 Si), nickel 63 ( 63 Ni), and thallium 204 ( 204 Tl). Examples of alpha radiation emitting radionuclides include, but are not limited to, polonium 210 ( 210 Po), americium 241 ( 241 Am) and thorium 232 ( 232 Th). The radionuclide(s) will provide energy, in the form of emitted alpha or beta particles, which will energize the quantum dots and cause them to emit light at the desired wavelength(s) and intensity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings. 
         FIG. 1  is a side view of an exemplary nuclear powered quantum dot light source. 
         FIG. 2  is a diagrammatic representation of an exemplary matrix containing quantum dots and radionuclides. 
         FIG. 3  is a side view of another exemplary nuclear powered quantum dot light source. 
         FIG. 4 . is a side view of yet another exemplary nuclear powered quantum dot light source. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning first to  FIG. 1 , there is shown a side view of an exemplary nuclear powered quantum dot light source  10 . The exemplary nuclear powered quantum dot light source  10  preferably has a container  12  in which is located a quantum dot and radionuclide containing matrix  14 . The container  12  can be formed in a desired size and shape, e.g., disk shaped, box shaped, etc., and of a desired material, such as metal, plastic, glass, etc. The container  12  has at least one side  16  which is open or light transmissive, with other sides  18  being opaque if desired. The sides  18  could be made to be reflective (e.g. mirrored) so that the light generated by the energized quantum dots is more efficiently reflected out of the container. A layer of material  20  not containing radioisotopes or quantum dots can optionally be provided over the at least one side  16 . The layer of material  20  is made of clear or light transmissive material, such as a UV curable resin and can be provided to help ensure that physical human contact with any radioisotopes is eliminated. In addition or alternately, the entire container  12  can be encapsulated within a nonradioactive envelope. 
       FIG. 2  is a diagrammatic and simplified representation of the exemplary matrix  14  containing quantum dots  30  and radionuclides  32  contained in a matrix material  34 , such as a UV cured resin. Some other materials can include thermal sol-gel hybrids, UV sol-gel hybrids and plastic resins such as polycarbonate, polystyrene, PMMA (polymethylmethacrylate), and polyethylene. 
     The ratio of the quantum dots  30  to radionuclide(s)  32  in the matrix material  34  can be determined as is required. The quantum dots are sized and engineered to produce light with a wavelength span of 350 to 2300 nanometers (ultraviolet to visible to infrared), with the size and material of the quantum dots determining the wavelength emitted. One or more different types of quantum dots can be used to provide either light at a single wavelength, or if desired, multiple wavelengths. The radionuclides  32  can be selected from radionuclides that emit either alpha or beta particles. Examples of beta radiation emitting radionuclides include, but are not limited to hydrogen 3 (tritium, or  3 H), carbon 14 ( 14 C), silicon 32 ( 32 Si), nickel 63 ( 63 Ni), and thallium 204 ( 204 Tl). Examples of alpha radiation emitting radionuclides include, but are not limited to, polonium 210 ( 210 Po), americium 241 ( 241 Am) and thorium 232 ( 232 Th). The radionuclide(s) will provide energy, in the form of emitted alpha or beta particles, that will energize the quantum dots and cause them to emit light at the desired wavelength(s) and intensity.  FIG. 2  is provided as a simplified representation, but in actual construction, the amount of radionuclides relative to the number of quantum dots, and the concentrations of the radionuclides and radionuclides in the matrix will be selected so that the quantum dots are adequately energized and emit light of the proper wavelength and intensity. 
       FIG. 3  is a side view of another exemplary nuclear powered quantum dot light source  50 . In this embodiment, the nuclear powered quantum dot light source  50  is adapted for use in devices such as ATP luminometers, and comprises a test tube shaped holder  52  which contains a quantum dot containing matrix  54 . The test tube shaped holder  52  has a sealed bottom  56  and an open top  58 . A cap  60  is made of a radiolucent transparent material, such as most plastics and some glasses, and is used to seal off the holder  52  with the quantum dot containing matrix  54  contained therein, and prevents direct human contact with the quantum dot containing matrix  54 . 
       FIG. 4  is a side view of yet another exemplary nuclear powered quantum dot light source  70  that is similar to holder  50  of  FIG. 3 . This embodiment of nuclear powered quantum dot light source  70  comprises a test tube shaped holder  72  which contains a quantum dot containing matrix  74 . The test tube shaped holder  72  has a sealed bottom  76  and a top  78  that is sealed off with a cap  80 . Depending on the requirements, the cap  80  can be made of a radiolucent material and will seal off the holder  52  with the quantum dot containing matrix  54  therein, and thereby prevent direct human contact with the quantum dot containing matrix  54 . 
     With respect to all the holders discussed above, if desired, it is possible for the holders to have walls formed entirely of radiolucent material. 
     Lastly, although all the embodiments are shown having a holder, it is possible to form the light source without a holder, such as by extruded or cast the material without a container. Such as use might be appropriate, for example, where the light source is placed in another device. 
     Having thus described the exemplary embodiments of the present invention, it should be understood by those skilled in the art that the above disclosures are exemplary only and that various other alternatives, adaptations, and modifications may be made within the scope of the present invention. The presently disclosed embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.