JAN Journal of Advances in Nanotechnology 2689-2855 Open Access Pub United States 10.14302/issn.2689-2855.jan-19-3012 JAN-19-3012 in-brief Quantum Dots- Tiny Semiconductor Nanodots Nida Tabassum Khan 1 * Muhammad Jibran Khan 1 Department of Biotechnology, Faculty of Life Sciences and Informatics, Balochistan University of Information Technology Engineering and Management Sciences, (BUITEMS), Quetta, Pakistan corresponding author Muhammad Humayun 1 Huazhong University of Science and Technology, China. Nida Tabassum Khan, Department of Biotechnology, Faculty of Life Sciences and Informatics, Balochistan University of Information Technology Engineering and Management Sciences, (BUITEMS), Quetta, Pakistan, Email: nidatabassumkhan@yahoo.com

The authors have declared that no competing interests exist.

 19 09 2019 1 2 1 4 04 09 2019 18 09 2019 19 09 2019 © 2019 Nida Tabassum Khan, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://openaccesspub.org//jan/article/1166

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.

 DNA assays Crystalline lattice structures Luminescence Photo-bleaching Semi-conducting nanoparticles. Introduction

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 34.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.

Physiochemical Properties of Quantum dots
S.no Physiochemical Properties  
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 1516.
Types of Quantum Dots

There are 3 types of Quantum dots on the basis of their composition and structure 17.

Core-Typed Quantum Dots

Quantum dots that have internally uniform structures which is composed of a single material 18. They have variable electro/photo luminescence e.g. Metal chalcogenides 19.

 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

 Fabrication of Quantum Dots

There are 3 main approaches through which quantum dots can be prepared

1. Electron beam lithography 22

2. Colloidal synthesis 23

3. Epitaxy such as Vapor Phase epitaxy, liquid phase epitaxy,molecular beam epitaxy etc 2425

 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.

Have biological applications including in vivo and invitro imaging, DNA assays and microarrays,labelling tumors , diagnosis /treatment of cancer , drug delivery 33343536

Quantum dots have many exceeding rewards, but they do have drawbacks like they are costly, toxic, may cause environmental pollution etc 37.

Conclusion

Due to their excellent intrinsic and extrinsic properties, Quantum dots continues to amaze researchers with their immense applications.

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