Quantum Dots Explained

Quantum dots or QDs are nanocrystalline semiconducting materials that have optical and electrical properties. Their sizes range from two to fifty nanometers. Most types of quantum dots have either photoluminescent or electroluminescent properties. In other words, they emit light when excited by light or electricity.

What Are Quantum Dots? What Are Their Properties?

It is important to highlight the fact that a photoluminescent or photo-emissive quantum dot emits light upon exposure to a light source. An electroluminescent or electro-emissive quantum dot emits light via the passage of electric current or a strong electric field.

The frequency of light emitted by a quantum dot depends on its size, shape, and/or material composition. With regard to dimension, smaller ones emit blues while larger ones emit reds. Thus, each quantum dot can be finely tuned to emit a particular frequency of light and therefore, produce a specific color.

It is also worth reiterating that QDs are semiconductors. They operate like a single electron transistor. They also have atom-like energy states that contribute to their optical properties. Hence, in addition to their optical properties, QDs have several potential optical-electrical applications.

What Are the Applications of Quantum Dots?

Below are some of the current and potential applications:

• Display Technology: Researchers and manufacturers have developed introduced quantum dot or QD displays such as the QLEDs from Samsung that take advantage of the photo-emissive or electro-emissive properties of quantum dots to produce light and thus, produce color. QD technology can be integrated with existing display technologies such as IPS LCD technology and OLED technology.

• Medical Imaging: The fact that QDs emit light has made them applicable in advanced biological and medical imaging such highly sensitive cellular imaging. Their size, brightness, and stability make them more advantageous over organic dyes.

• Medicine: QDs can have antibacterial properties by impairing the anti-oxidative systems of bacteria and directly damage their cell walls, among others. QDs have shown to be effective against gram-positive and gram-negative bacteria.

• Solar Energy: Quantum dots can increase the efficiency of photovoltaic cells, thus leading to a decrease in cost. Remember that these materials can absorb light and that they have tunable absorption spectrum and high extinction coefficient.

• Photocatalysts: The optical properties of QDs also make them photocatalysts that give them more specific applications such as conversion of water to hydrogen gas, sanitation and disinfection, conversion of carbon dioxide into gaseous hydrocarbons, and decomposition, among others.

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