Quantum dots – background briefing
Quantum dots are tiny particles, or “nanoparticles”, of a semiconductor material, traditionally chalcogenides (selenides or sulfides) of metals like cadmium or zinc (CdSe or ZnS, for example), which range from 2 to 10 nanometers in diameter (about the width of 50 atoms).
Because of their small size, quantum dots display unique optical and electrical properties that are different in character to those of the corresponding bulk material. The most immediately apparent of these is the emission of photons under excitation, which are visible to the human eye as light. Moreover, the wavelength of these photon emissions depends not on the material from which the quantum dot is made, but its size.
The ability to precisely control the size of a quantum dot enables the manufacturer to determine the wavelength of the emission, which in turn determines the colour of light the human eye perceives. Quantum dots can therefore be “tuned” during production to emit any colour of light desired. The ability to control, or “tune” the emission from the quantum dot by changing its core size is called the “size quantisation effect”.
The smaller the dot, the closer it is to the blue end of the spectrum, and the larger the dot, the closer to the red end. Dots can even be tuned beyond visible light, into the infra-red or into the ultra-violet.
At the end of the production process, quantum dots appear physically either as a powder or in a solution. Because of their tiny size, the ability to produce even a relatively “small” volume of quantum dots (e.g. one kilo) will yield enough actual quantum dots for industrial scale applications. Nanoco Technologies has patented a molecular seeding process which enables such “large scale” production to occur.
Now, the ability to mass-produce consistently high quality quantum dots enables product designers to envisage their use in consumer products and a wide range of other applications for the first time, and then bring these superior, next-generation products to market. Together with our partners, this is what Nanoco Technologies does.
Our research and development department is also constantly engaged in the creation of new quantum dots with additional properties sought by the market, such as our RoHS-compliant heavy metal-free quantum dots.