The key difference between fluorescence and phosphorescence and luminescence is the way they emit light. In fluorescence, a substance can immediately reemit the absorbed radiation, while in phosphorescence, the substance does not reemit the radiation immediately after the absorption. Luminescence, on the other hand, is the emission of light from a non-heated substance due to some other cause such as a chemical reaction, electrical energy, etc.
All fluorescence, phosphorescence and luminescence are related to the emission of an absorbed light from a source material.
CONTENTS
1. Overview and Key Difference
2. What is Fluorescence
3. What is Phosphorescence
4. What is Luminescence
5. Fluorescence vs Phosphorescence vs Luminescence in Tabular Form
6. Summary – Fluorescence vs Phosphorescence vs Luminescence
What is Fluorescence?
Fluorescence can be defined as the emission of light from a substance that has absorbed energy previously. This type of substance has to absorb light or any other electromagnetic radiation to emit light as fluorescence. Furthermore, this emitted light is a type of luminescence, meaning it emits spontaneously. The emitted light often has a longer wavelength than the absorbed light. That means the emitted light energy is lower than absorbed energy.
In fluorescence, light is emitted as a result of the excitation of atoms in the substance. The absorbed energy is often released as luminescence in a very short time period, about 10-8 seconds. That means we can observe fluorescence as soon as we remove the source of radiation that causes excitation.
There are many applications of fluorescence in different fields, such as mineralogy, gemology, medicine, chemical sensors, biochemical research, dyes, biological detectors, fluorescent lamp production, etc. Moreover, we can find this process as a natural process as well; for example, in some minerals.
What is Phosphorescence?
Phosphorescence is a type of photoluminescence in which a substance exposed to the light of a short wavelength can cause the substance to glow. This happens by the absorption of the light and reemission of that light at a longer wavelength. The material tends to absorb some of the energy from the radiation to reemit it for a longer time after removing the radiation source.
There are two possible mechanisms from which phosphorescence can happen: triplet phosphorescence and persistent phosphorescence. Triplet phosphorescence occurs when an atom absorbs a high-energy photon while persistent phosphorescence occurs when a high-energy photon is absorbed by an atom, which causes it to trap its electrons in a defect in the lattice of the crystalline or amorphous material.
What is Luminescence?
Luminescence is the emission of light by a substance that has not been heated. It is the spontaneous emission of light from a substance. We can call it “cold light” because the light does not emit from a heated substance. The causes for this emission can include chemical reactions, electrical energy, subatomic motions, or stress on a crystal. Therefore, we can easily distinguish luminescence from incandescence, because in incandescence, light emits from a heated source. There are different types of luminescence such as bioluminescence, chemiluminescence, electroluminescence, photoluminescence, and thermoluminescence.
Types of Luminescence
Chemiluminescence is the emission of light as a result of a chemical reaction. Here, the emitted light is called luminescence. This means the light emits as spontaneous emission, not by heat or cold light. However, heat may also be formed. Then, the reaction becomes exothermic.
Bioluminescence indicates the biochemical emission of light by living organisms. It is a type of chemiluminescence. This emission mainly occurs in marine vertebrates and invertebrates. However, we can observe bioluminescence in some fungi species, microorganisms such as bioluminescent bacteria, terrestrial arthropods (fireflies), etc.
Photoluminescence is a form of luminescence that occurs with a photoexcitation via photon absorption. This light emission occurs when a substance absorbs electromagnetic radiation and re-emits the radiation. This process initiates with photoexcitation. This means the electrons of the substance undergo excitations when the substance absorbs photons, and electrons move to higher energy states from lower energy states. Following these excitations, there are relaxation processes as well. In the relaxation step, photons are re-radiated or emitted. The time period between the absorption and emission of photons may vary depending on the substance.
Electroluminescence indicates a chemical phenomenon in which a material emits light as a response to the passage of an electric current. We can abbreviate it as EL. This is both an optical phenomenon and an electrical phenomenon. It can occur in the presence of an electric current or in the presence of a strong electric field. This feature is distinct from black body light emission that results from one of the following causes: heat, a chemical reaction, sound, and other mechanical action.
Thermoluminescence can be described as the emission of light from some mineral forms and some crystalline materials. This emission occurs due to the electron displacement within the crystal lattice of these substances. Some examples for substances that can undergo thermoluminescence include ceramic, brick, fire pits, etc.
What is the Difference Between Fluorescence and Phosphorescence and Luminescence?
Fluorescence is the emission of light from a substance that has absorbed energy previously. The key difference between fluorescence and phosphorescence and luminescence is their emissions. In fluorescence, a substance can immediately reemit the absorbed radiation, while in phosphorescence, the substance does not reemit the radiation immediately after the absorption. Luminescence, on the other hand, is the emission of light from a non-heated substance due to some other cause such as a chemical reaction, electrical energy, etc.
Below is a summary of the difference between fluorescence and phosphorescence and luminescence in tabular form for side by side comparison.
Summary – Fluorescence vs Phosphorescence vs Luminescence
Fluorescence, phosphorescence, and luminescence are related to the emission of an absorbed light from a source material. The key difference between fluorescence and phosphorescence and luminescence is that in fluorescence, a substance can immediately reemit the absorbed radiation but, in phosphorescence, the substance does not reemit the radiation immediately after the absorption. Whereas, luminescence refers to the emission of light from a non-heated substance due to some other cause such as a chemical reaction, electrical energy, etc.
Reference:
1. “Fluorescence.” Chemistry LibreTexts.
2. “Photoluminescence.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “Black light theatre Prague HILT 13” By Black light theatre Prague – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Phosphorescence” By Lưu Ly – Own work, Public Domain) via Commons Wikimedia
3. “Luminescence material” By Vishal Garasia vish – Own work (CC BY-SA 4.0) via Commons Wikimedia