The Effects of Various Solvents and Reagents on the Chemiluminescence of Luminol

From crime scenes to birthday parties to battlegrounds, chemiluminescence is a beautiful, yet useful phenomenon. The reaction of chemiluminescent molecules such as luminol can be used to detect bloodstains not visible to the naked eye or create long lasting, easily concealable light sources such as glow sticks. The goal of this experiment was to find the most appropriate solvent in which to dissolve luminol and examine the effects of adding reagents such as sodium hydroxide, bleach, and hydrogen peroxide to the solution, aiming to find the concentrations that caused the luminol to glow for the longest period of time. Although a rather complicated reaction, the luminol reacted best with a comparatively simple solution.

Introduction

Chemiluminescence is the production of light from a chemical reaction. This phenomenon is caused by the fall of an electron from a higher energy shell back to its ground state, its normal, lower energy shell. An electron is promoted to a higher energy level when it absorbs energy, causing the electron to be in an excited state. When the electron falls back down, the absorbed energy is released as a photon, a packet of energy in the form of electromagnetic energy. If the wavelength of this energy is within the visible spectrum, it is seen as light.

This process of exciting an electron to a higher energy state and then dropping it back to its ground state is what causes light to be produced in the reaction of luminol. Luminol, C8H7N3O2, is not a compound found in nature . However, related compounds called luciferins can be found in organism such as fireflies and luminescent jellyfish. Luminol is a manufactured compound that is most well-known for its use in crime scene investigations. Lumin...

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...p water/luminol solution were added to each of four wells. Five drops of the reagents were then added to each well. Chemiluminescence was not observed in any well.

Trial 5 was the last trial performed on the first day of the experiment. In the period between the next lab session, chemiluminescence and luminol were researched, with findings encouraging the use of distilled water as a solvent and hydrogen peroxide or bleach as a reagent, with the reagents also dissolved in the distilled water.

In the second lab session, trials were carried out in test tubes rather than in well plates. In the first test tube, a small amount of luminol was mixed with a specified amount of solvent. In the second tube, a reagent or reagents were combined with a solvent. One tube was then poured into the other to initiate the reaction. The trials and the results are shown in Table 2.