The Science of GLOW

When man first realized that the cold light of the firefly was different from the hot light of a campfire, an interest in chemical light was born.

How was it different? What made it work? And what created that GLOW?

After much research these questions were answered. It was discovered that chemical light, or chemiluminescence, converts the energy released in a chemical reaction directly to light without the involvement of heat or flame. The biochemical reaction that occurs within the firefly is the most efficient example we know: in principle, it is possible for each molecule of a chemiluminescent reactant to produce one photon of light. The firefly approaches this theoretical limit by producing 88 photons for each 100 molecules for a quantum yield of 88%.

Early research into chemical light was not nearly as efficient. While more than 50 chemiluminescent reactions have been discovered, the quantum yields were no better than 0.1%. Clearly, the firefly was way ahead.

Slowly. however, we are catching up. Today we have invented new reactions having efficiencies as high as 23%, and it is reasonable to anticipate that further research will produce reactions that will, at some point, rival the firefly.

Manmade chemiluminescence requires a combination of two special kinds of chemistry. The first is called fluorescence.

In regular fluorescence, a molecule absorbs light, creating an electronic excited state. After its lifespan (as short as one billionth of a second) the energetic excited state releases its energy as light.

Chemiluminescence includes this fluorescent process, except that the necessary excited state is produced as a product of chemical reaction rather than by light absorption. The second type of chemistry required is what (when mixed with the fluorescer) actually produces the excited state. This is called the excitation process and is the heart of chemiluminescence. We now know that certain decomposition reaction of organic peroxides can produce excited products efficiently.

How does this happen? We believe an excitation process must be capable of generating at least 40 to 70 kilocalories/mole of energy, the energy range of visible light. This is a substantial amount of energy in chemical terms, and only highly energetic molecules are capable of meeting the requirement. Not only must energy be available, but it must be provided essentially instantaneously in a single chemical step.

In addition to substantial instantaneous energy release and the formation of a fluorescent product, other requirements must also be met, which involve the distribution of energy released from a reaction between light-emitting (electronic) excited states and heat-emitting (vibrational) excited states.

Since all of these requirements must be met together in an efficient chemiluminescent reaction, and since none of the requirements are commonly met individually, it is understandable that efficient chemiluminescence is rare.

But it is possible.

The first step comes from basic chemistry that produces the key intermediate (K1). The second step is the critical excitation process wherein the chemical energy of K1 is converted and transferred to electronic excitation energy in a separate fluorescent chemical molecule (fluorescer). The third step is the basic fluorescent emission.

The critical feature in the process, of course, is the structure of K1.

Its efficiency is believed to result in part from:

- Its high energy content
- Its ability to release its energy instantaneously through a concerted peroxide decomposition reaction
- The quantum mechanical reluctance of a small molecule like carbon dioxide to accept a large amount of chemical energy as heat
- The inability of carbon dioxide itself to become electronically excited by the available energy.

Since K1 does not have a favorable pathway by which it can get rid of its unwanted energy, it has an appreciable lifespan. On the other hand, because of its energy content, it can quickly decompose when it encounters a fluorescer with the ability to accept its energy. The FLUORESCER thus acts as a CATALYST for the decomposition of K1, and this catalyst is an important factor in the efficiency of this chemical reaction.

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 GLOW depends on the fluorescer selected, peroxyoxalate chemiluminescence can be formulated in any color desired.

Chemical light products are now molded into different shapes and sizes including Lightsticks, Jewelry, and numerous configurations for everything from novelty and toy items to commercial and industrial safety accessories, military products, sporting goods, agricultural, and biomedical applications. The chemical reactants are sealed within each configuration and are separated by a capsule. Activation is accomplished with a bend, snap, and shake. Duration and intensity of the GLOW varies with each type of product.

Chemical light is especially beneficial because it is non-toxic and nonflammable, cannot cause fire or explosion, can be used in wind or rain, and does not require batteries.