Patent Application
20080157039
Chemiluminescence is the production of light from a non-heat-generating chemical reaction; in short, light without fire. The firefly's biochemical chemiluminescent reaction is highly efficient, approaching the theoretical limit of one photon produced for each molecule involved in the reaction, producing 88 photons for each 100 molecules for a yield of 88%. The current man-made chemiluminescence uses chemical reactions that require a fluorescent molecule, a key intermediate, and a catalyst; and produce sustainable, instantaneous, highly visible light, which specific doping can allow differing colors and intensities. Commercially valuable, man-made chemiluminescent reactions have efficiencies as high as 23%, which is far less than the 88% efficiency of the firefly.
Man-made chemiluminescence combines two kinds of chemistry. First is fluorescence. Chemiluminescence includes the fluorescent process as a product of a chemical reaction (as opposed to photonic absorption and re-emission). The second type of chemistry is what (when mixed with the fluorescer) actually produces the excited state. This excitation process is the heart of chemiluminescence. Certain decomposition reactions of organic peroxides are currently used to produce excited products with the described limited efficiency.
The excitation process must generate at least 40 to 70 kilocalories/mole of energy to reach the energy range of visible light. This is a substantial amount of energy in chemical terms; only highly energetic molecules meet this requirement. Furthermore this energy must both be available, and must be provided in a single chemical step, essentially instantaneously. Just as in an incandescent light bulb, atoms in the materials are excited, causing electrons to rise to a higher and then return to a normal energy level. When the electrons return to their normal levels, they release energy as light.
Rauhut and Laszlo J. Bollyky developed a series of oxalate esters and produced the first commercial chemiluminescent reaction with a quantum yield of 5%. Hardly as efficient as a firefly, but still useful. Rauhut designed a phenyl oxalate ester that when mixed with hydrogen peroxide and a dye produced light, as shown by
The mechanism is that first the phenyl oxalate ester and hydrogen peroxide (H2O2) react in the presence of a salicylate catalyst forming a peroxy acid ester and phenol; and then the peroxy acid ester decomposes to form more phenol and a highly energetic intermediate, presumed to be a cyclic compound containing four-membered ring dimer of CO2. As the cyclic dimer decomposes into two CO2 molecules, it gives up its energy to a waiting dye molecule, which then fluoresces.
The chemical reaction taking place includes a solution of a phenyl oxalate ester (commonly bis(2,4,5-trichlorophenyl-6-carbopentoxyphenyl)oxalate (CPPO), a fluorescent dye that determines the color of light, and hydrogen peroxide. The hydrogen peroxide (H2O2) is separated from the other two chemicals until chemiluminescence is desired, when they are combined. Then the hydrogen peroxide reacts with the phenyl oxalate ester producing carbon dioxide, a phenol and, most importantly, releasing energy. This energy is absorbed by the dye, exciting electrons in the dye's molecules to a higher energy level. Once at the higher energy level, the electrons immediately lose the energy they absorbed and fall to lower energy levels. As the electrons fall back to lower energy levels, the energy that is lost is transformed into electromagnetic radiation, some of which is visible light.
The dye must gain energy from the breakdown of the CPPO. For light to be seen in the visible spectrum, the radiation emitted must be between 400 nm and 700 nm. This range of wavelengths has a corresponding range of energy required between 170 kJ/mol and 300 kJ/mol. This energy is released from a high energy intermediate that forms during the reaction and is transferred to the dye. The intermediate that forms when the CPPO is oxidized by hydrogen peroxide is called 1,2-dioxetane-3,4-dione. This compound is a four membered ring structure. As in most four membered rings, the compound is considered high in energy because of the strain on the bonds of the molecule forcing them into the ring. Although the compounds are different, they all share the common trait of being highly conjugated systems. This conjugation allows electrons to move easily because of the small gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The energy produced as the four-membered ring structure decomposes into two CO2 molecules is enough to move the electrons across the gap.
Because the fluorescer is separate from the energy-producing components of the reaction, it can be varied without changing the basic chemistry. Since the color of the light depends on the fluorescer selected, peroxyoxalate chemiluminescence can be formulated in many desired colors. Blue color can be produced using 9,10 diphenylanthracene, green color can be produced using 9,10-bis(phenylethynyl)anthracene, yellow can be produced using either of 1-chloro-9,10-bis(phenylethynyl)anthracene or Rubrene [5,6,11,12-tetraphenylnaphthacene], orange can be produced using 5,12-bis(phenylethynyl)-napthacene and red can be produced using Rhodamine B. However, Rhodamine B is rarely used because it will break down when mixed with the phenyl oxalate ester and shorten the shelf life of the product.
Once the reaction has been activated, it cannot be stopped until the reaction is complete. Under normal conditions when sufficient materials are present the reaction will emit light for hours before running its course. After the reaction has been initiated, reducing the temperature will extend the life into days. The cold temperatures cause the reaction rate to slow down drastically. Raising the temperature affects the rate of the reaction. It causes the rate to increase and the light that is emitted more intense and last for only tens of minutes.
Omniglow, which produces a line of chemiluminescent light sticks (for emergency use when power is not available) and novelty items, uses the preparation described immediately below for the oxalate and the peroxide component for chemiluminescent light sticks, achieving a reaction efficiency of 17%.
The invention is a method for controlling the rate at which a chemiluminescence reaction takes place by encapsulating a key reactant in a moisture-sensitive, nano-polymeric structure which has an average particle diameter of about from 10 nanometers (0.01 micron) to 1000 nanometers (1 micron). By producing a paint that incorporates a reactant, a solvent, a catalyst, and a dye, wherein one or any combination of these ingredients is encapsulated in moisture-sensitive, nano-polymeric structures with progressive sensitivity, then by controlling the humidity or, for a given humidity, the degree of sensitivity of the moisture-sensitive, nano-polymeric structures, the necessary excitation and fluorescing reactions can be made controllable through a first-order responsiveness to the ambient humidity rather than the ambient temperature.
In a chemiluminescent paint, a combination of the reactant of phenyl oxalate ester and the solvent of hydrogen peroxide (H2O2) will react in the presence of the catalyst of sodium salicylate to form a peroxy acid ester and phenol in Step One of the chemiluminescent reaction as follows:
The completion of the chemiluminescence reaction to florescence is accomplished in Step Two, when the intermediate product of peroxy acid ester first decomposes to form more phenol and a highly energetic intermediate, presumed to be a cyclic compound containing four-membered ring dimer of CO2. Then, as the cyclic dimer decomposes into two CO2 molecules, it gives up its energy to a waiting dye molecule, which then fluoresces.
In a first instantiation of the invention, the solvent, typically hydrogen peroxide (H2O2), is encapsulated.
In a second instantiation of the invention, the catalyst, typically sodium salicylate, is encapsulated.
In a third instantiation of the invention, the reactant, typically phenyl oxalate ester, is encapsulated.
In a fourth instantiation of the invention, some combination of the proportions of the separate components, the solvent, typically hydrogen peroxide (H2O2), the catalyst, typically sodium salicylate, and the reactant, typically phenyl oxalate ester, are each encapsulated.
In a fifth instantiation the salicylate is used in the cationic form as sodium salicylate for the catalyst.
The best method uses a formulation of reactant phenyl oxalate ester 50 mg, catalyst of sodium salicylate in a range from 5 to and including 10 g, the dye of 10 mg, and solvent 5 to 10 ml of hydrogen peroxide of 3 to 5% by weight hydrogen peroxide.
The present invention uses moisture-sensitive nano-polymeric structures and materials combined with chemiluminescence and excitation reactions for florescence paint to produce the unexpected result of reducing the dependence of the life of the actively fluorescing (chemiluminescent) paint on ambient temperature.
According to a feature of the invention the activating ingredient for the chemo-fluorescent reaction is encapsulated into progressive nano-polymeric structures. This nano-polymeric structure uses humidity to control duration of the reaction, by progressively releasing the activating ingredient on exposure to humidity over time.
According to another feature of the invention a dual-aerosol, spray-can system is used to store and apply chemo-fluorescent marking paint with one aerosol stream containing the encapsulated activating ingredient and the other containing the other chemical reactants, wherein the contents of the two streams are mixed just prior to applying the chemo-fluorescent marking paint, thereby only beginning the chemiluminescence upon mixture and application of the two streams.
According to still another feature of the invention the full progression of the chemo-fluorescent reaction to completion and the cessation of chemiluminescence in a shortened time in accordance with an external, intended act, is enabled by using the moisture-sensitive nano-polymeric structures and materials combined with chemiluminescence and excitation reactions for florescence paint that has a neutral, background, or transparent color value in the absence of chemiluminescence, by spraying water on the surface marked by the actively fluorescing (chemiluminescent) paint.
Varying the degree of encapsulation of the polymeric structure is well known in the current art, as can be seen in the general-market ads for ‘micro-encapsulated’ over-the-counter medications (also known as timed-release medications). The preferred method uses a ozokerite silicon copolymer, whose nano-polymeric structure has an average particle diameter of about from 10 nanometers (0.01 micron) to 1000 nanometers (1 micron).
In an instantiation of the invention the paint incorporates structures with a progressive range of relative volumes devoted to structure and contents. Incorporating a combination of structures with progressive encapsulation allows for limited reaction intensity, controlling it differentially through varying the amount of the reactant, solvent, and catalyst as the humidity gradually terminates the encapsulation of the activating ingredient. The lifespan is a function of the amount of moisture present rather than temperature in the instant invention because the encapsulation unwinds in a time-moisture concentration relationship. Therefore the selection of the encapsulation material used can be tailored to the expectation of the relative humidity present to obtain the life of the light. For use in arid climates where the relative humidity is say 20% it is necessary to select an encapsulation material more sensitive to moisture then for use in a tropical climate with say 80% humidity to get the same desired life.
This method allows the production of a chemiluminescent paint that can have a more controllable time period. Under ordinary circumstances, at standard humidity ranges, the chemiluminescent period may be tens of hours as the chemicals combine once released. But if a shortened period is desired—after an accident scene has been investigated, or after power has been restored—this period can be accelerated and shortened to its limit by simply washing the paint with water (thereby increasing the humidity locally to 100%).
Contrariwise, the storage period can be extended, by using separate containers for the chemicals that are to be combined, and only starting the excitation and fluorescent reactions when the streams of the encapsulated and non-encapsulated chemicals (reactant, solvent, and catalyst) are combined. One of the current problems with the existing art is the need to produce containers with frangible separating portions that must not break before the chemiluminescent reaction is to begin, yet must also be readily breakable (often by weak, ill, or young individuals with less than adult strength or physical capability). If improperly moved or stored—such that the containers are unduly jostled or even just shaken—the separating walls may break, allowing the chemiluminescence to begin. This can be particularly troublesome when an emergency light source is reached for when an emergency arrives, only to find that a minor upset sometime in the past has already exhausted the chemical reactant's capability to produce the chemiluminescence. As a further instantiation of the invention, various methods for preparing the oxalate and peroxide components is further described in the following paragraphs. The best glow result may be obtained by mixing the oxalate and peroxide components in 1:3 ratios.
In a first embodiment, wherein the preferable concentration of hydrogen peroxide is 1.6M, the oxalate component and peroxide components are respectively prepared as follows.
In a further embodiment, while the peroxide component is prepared using the procedure described immediately above, the oxalate component is prepared by choosing a solvent that will dissolve the oxalate ester at room temperature. The advantage of using a solvent to dissolve the oxalate ester at room temperature is the potential it provides for large-scale production in a short period of time with resulting lower cost.
In yet a further embodiment increasing the chemiluminescent efficiency is obtained by, immediately after mixing the oxalate and peroxide precursors, encapsulating the activating ingredient or the dye fluorescer with nano-polymeric compounds. This is done not just to control the rate of chemiluminescent reaction but also to
In a further embodiment, immediately after mixing oxalate and peroxide precursors, the reaction mixture (being any of the key reactants and chemiluminescent liquid) is encapsulated with at least one nano-polymeric compound to control the rate of chemiluminescent reaction, to increase the chemiluminescence efficiency.
In a further embodiment, additional material is chosen and added to enhance the reflective light intensity of the paint. Gold or silver nanoparticles can be used to enhance the perceived intensity of the chemiluminescence reaction, increasing the emitted light intensity linearly with an increasing concentration of the gold or silver nanoparticles. In this method, a colloidal form of gold or silver nanoparticles, each nanoparticle averaging less than 40 nm size in any dimension, is mixed with desired fluorescer. The internal reflectivity and thus total emitted light from the paint will increase through the provision of these incorporated nano-reflectors.
The scope of this invention includes any combination of the steps from the different embodiments disclosed in this specification, and is not limited to the specifics of the preferred embodiment or any of the alternative embodiments mentioned above. Individual embodiments of this invention may contain all, or less than all, of the steps disclosed in the specification. The claims stated herein should be read as including those steps which are not necessary to the invention yet are in the prior art and are necessary to the overall function of that particular claim, and should be read as including, to the maximum extent permissible by law, known functional equivalents to the steps disclosed in the specification, even though those functional equivalents are not exhaustively detailed herein.
