Quantum dots can be defined as semiconductor nanostructures which are artificial in nature and ranges from 2-10 nm in size. These tiny nanocrystals become excited under illumination and emits colors of different wavelength. Quantum dots possess unique properties determined by their structure (hollow or solid), size, shape and composition. Fabrication of Quantum dots is achieved by several methods such as electron beam lithography, epitaxy or by means of colloidal synthesis.
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Copyright © 2019 Nida Tabassum Khan, et al.
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The word ‘Quantum’ itself is derived from a Latin word meaning ‘amount’ and can be defined as small unit of physical property like energy or matter 1. In 1900 physicist Max Planck discovered that like matter radiation existed in discrete units of energy, hence named these units as “quanta” 2. Similarly, quantum dots can be defined as semiconductor nanostructures which are artificial in nature and ranges from 2-10 nm in size 3, 4.These tiny nanocrystals become excited under illumination and emits colors of different wavelength 5. Quantum dots possess unique properties determined by their structure (hollow or solid), size, shape and composition 6.Sometimes these are also referred as artificial atoms 7. Quantum dots have different crystalline lattice structures so when pressure is applied they form very thin semiconductor films 8. As a result, the flat film later due to stress tends to separate into dots in three dimensions 9.
Physiochemical Properties of Quantum dots is mentioned in Table 1.Table 1. Physiochemical Properties of Quantum dots
|1||Size||Microscopic, 2-10nm (10-50 atoms) 10|
|2||Configuration||Confined in three-dimensions 11|
|3||Highly tunable||Variable core sizes make them give off different colors by tuning/changing the characteristic wavelength of emitted light 12.|
|4||Excitable||Can excite to higher energy level to emit light of respective wavelength 13|
|5||Shapes||Various including cubes, spheres and pyramids 14|
|6||Resistance||Resistance to photo-bleaching, photo-degradation and chemical- degradation 15, 16.|
Types of Quantum Dots
There are 3 types of Quantum dots on the basis of their composition and structure 17.
Core-Typed Quantum Dots
Core-shell Quantum Dots
Also known as Core-Shell semi-conducting nanoparticles having variable photophysical properties e.g ZnS20
Alloyed Quantum Dots
Multicomponent semiconductor nanoparticles e.g. CdS-Se/ZnS 21
Applications of Quantum Dots
Used in Solar cells and photo-voltaic e.g. Graphene quantum dots 26.
Used as fluorophores which helps in bio-sensing and bio-tagging 27.
Used as a catalyst to form hydrocarbons 28
Luminescent quantum dots (LQD) are used in high quality displays and lighting systems 29
Quantum computing uses quantum computer that store information in quantum bits 30.
Magnetic quantum particles are used in memory chips 31
Used in communication devices like lasers 32.
Quantum dots have many exceeding rewards, but they do have drawbacks like they are costly, toxic, may cause environmental pollution etc 37.
Due to their excellent intrinsic and extrinsic properties, Quantum dots continues to amaze researchers with their immense applications.