Recently, the Nobel Prize for chemistry was awarded to three US-based scientists for their development of quantum dots. So, what exactly are these quantum dots, how are they being used outside of fancy QLED TV screens, and where might we see them in the engineering landscape?
Understanding quantum dots
A quantum dot is a tony semiconductor particle, typically on the nanometre scale, that exhibits quantum mechanical properties. These properties arise from the confinement of electrons within the three-dimensional boundaries of the quantum dot.
Quantum dots have a few key characteristics that can be readily utilised:
- Size-tuneable bandgap: Quantum dots have a size-dependent bandgap, which means that by controlling their size, the energy levels of the electrons within the dot can be finely tuned. This property allows quantum dots to emit or absorb light at specific wavelengths, making them useful in various optical applications.
- Quantum confinement: Electrons within quantum dots are confined in a way that restricts their motion to discrete energy levels, similar to the behaviour of electrons in atoms. This confinement results in discrete electronic states, leading to unique optical and electronic properties.
- Optical properties: Quantum dots can emit light at specific, well-defined wavelengths when excited with energy, a property known as quantum confinement. This property is valuable for applications like display technology, lighting, and biomedical imaging.
- High surface area: Quantum dots have a high surface-to-volume ratio due to their small size, making them suitable for various applications in catalysis, sensors, and biomedical research.
- Versatile materials: Quantum dots can be made from a variety of semiconductor materials, allowing engineers and scientists to tailor their properties for specific applications by selecting the appropriate materials and size parameters.
Quantum dots in the realm of engineering
Quantum dot technology has a wide range of potential applications across many different fields, engineering and industry stand out, however, as one of the most promising due to the unique properties of quantum. Quantum mechanical effects such as size-tuneable bandgaps or quantum confinement are great examples of these properties. Here are some ways in which quantum dot technology can be applied to engineering:
- Display technology – By far the most known application of quantum dots, display technologies are a major application of the technology, particularly in LCD and LED screens. By using quantum dots as a colour conversion layer, manufacturers can achieve a wider colour gamut and improved colour accuracy in displays. This results in more vibrant and realistic images. These, of course, are used in QLED TVs, such as those made popular by Samsung, but not limited to.
- Lighting: Quantum dot-based LEDs can produce high-quality, energy-efficient lighting. Quantum dots can be used to tune the emission spectrum of LEDs to match the desired lighting colour, making them suitable for various applications, including general lighting and specialised lighting in horticulture or healthcare.
- Solar cells: Quantum dots can be incorporated into solar cells to improve their efficiency. Quantum dots can be engineered to absorb specific wavelengths of light effectively, which allows for more efficient energy conversion in photovoltaic devices.
- Biomedical imaging: Quantum dots can be used as contrast agents in biomedical imaging. Their unique optical properties, including tuneable emission wavelengths and resistance to photobleaching, make them valuable for applications like fluorescent labelling in microscopy and tracking biological molecules.
- Sensors: Quantum dots can serve as sensitive detectors in various sensor applications. For example, they can be employed in environmental sensors to detect specific pollutants or in biological sensors for detecting biomolecules with high sensitivity and selectivity.
- Quantum computing: Quantum dots are being explored for use in quantum computing due to their ability to trap and manipulate individual electrons’ quantum states. Quantum dots can serve as qubits (quantum bits) in quantum computers, potentially enabling faster and more powerful computation for certain tasks.
- Quantum communication: Quantum dots can be integrated into quantum communication systems for secure and long-distance communication. Quantum dots can be used as single-photon sources or for entanglement generation, which is critical in quantum cryptography and quantum key distribution.
- Energy storage: Quantum dot-based materials can be used in energy storage devices, such as batteries and supercapacitors, to improve energy density, charge/discharge rates, and overall performance.
- Catalysis: Quantum dots can be used as catalysts in chemical reactions, particularly for catalysing reactions involving energy conversion or environmental remediation. Their high surface area and unique electronic properties make them promising candidates for catalytic applications.
- Quantum dot lasers: Quantum dots can be employed in semiconductor lasers for various applications, including telecommunications, optical data storage, and medical devices. Their size-tuneable emission wavelengths and high-efficiency properties are advantageous for laser technologies.
Atomic-scale material engineering
One of the most exciting potential applications of quantum dots lies within material engineering and atomic-scale manipulation of materials. This side of the technology is still only at the emergence of its true potential but that isn’t to say that it isn’t already showing promising signs. The ability to engineer materials on the atomic level is owed to quantum dots’ capabilities of precisely manipulating and controlling nanoscale semiconductor particles.
Achieving atomic-scale engineering with quantum dots involves a complex process that utilises the full capabilities of the technologies. Quantum dot nanoscale particles must be synthesised and tailored so that they can used as building blocks for atomic structures, catalysts, or enhancers in various materials and structures. From here, precise analytical methods can be used to study and control the engineered atomic-scale properties. This level of control enables the development of novel materials and technologies with tailored atomic arrangements and properties for specific applications.
