Nanotechnology

Nanotechnology can be expounded as a vast field of research and development concerned with constructing and reorganizing atoms and molecules on a compact nanometer scale. When considering the unit nanometer, one nanometer is one-billionth of a meter which is extremely small where ordinary rules of physics and chemistry no longer apply(1).At this juncture, nanotechnology has numerous applications in various types of fields regarding its unique properties(2). This article intends to illuminate the fundamentals of nanotechnology.

History

The use of the field of nanotechnology can be traced back to the fourth century AD, where Romans used to design a color changing cup that has two different colors in certain lighting conditions: which was named as the “Lycurgus cup”(3). This phenomenon was observed due to the presence of silver 66.2%, 31.2% gold and 2.6% copper particles in the nano-scale which is disseminated in glass(4). The red color was observed as a result of the absorption of light (∼520 nm) by the gold particles and the purple color was due to the absorption by the larger particles while the green color is attributed to the light scattering by colloidal dispersions of silver particles with size >40 nm. This is considered as one of the oldest synthetic nanomaterials(3).In late medieval church windows, the same occurrence can be observed due to spherical gold nanoparticles of 25 nanometers and silver nanoparticles of 100 nanometers(3). Some of the pre-modern examples for using nanotechnology can be found in;the copper and silver nanoparticles in Islamic ceramic glazes called “lusterware” that date back to the 9th to 17th centuries ;stained glass windows in European cathedrals from the 6th-15th centuries that consist of various metallic nanoparticles ; and13^th-18^th century “Damascus” saber blades that show traces of the use of carbon nanotubes long before the advancement of modern science. However, although these ancient artifacts show that such nanoparticles were used for various applications, there is no reason to believe that these people possessed an understanding of the science at the nanoscale.

Modern Era

The first systematic study of nanoparticle behaviour is reported to have been carried out by Michael Faraday in the mid-1850s.

The speech“There’s Plenty of Room at the Bottom” by physicist Richard Feynman can be considered as the milestone which gave birth to modern nanotechnology. Although he did not directly develop the field, due to his visionary ideas  he is considered as the father of nanoscience and nanotechnology. Feynman delivered his speech about nanotechnology at the California Institute of Technology (Caltech) on December 29, 1959, where he described a process in which scientists would be able to manipulate atoms and molecules over their sizes but there he didn’t specify a term for it. Later the term nanotechnology was coined by a Japanese scientist named Norio Taniguchi in 1974 during a conference to provide the idea of building small things on an even smaller scale.In the year 1986 twelve years after the introduction of the term “Nanotechnology” British scientist K. Eric Drexler published “Engines of Creation: The Coming Era of Nanotechnology” which is considered as the first book on nanoscience(3).
The invention of the Scanning Electron Microscope (SEM) in the 1930s’ with later improvements, enabled scientists to “see” the nanoscale for the first time. Thereafter with the invention of Scanning Tunneling Microscopy (STM), scientists were able to capture an image of a surface at an extremely small scale – down to individual atoms. These inventions lead to other types of techniques such as the atomic force microscope (AFM) and scanning probe microscopes (SPM), which are the instruments of choice for nanotechnology researchers today(3). Nano structures such as Fullerenes and Carbon nanotubes are allotropes of carbon which is characterized by a hollow structure where fullerenes have a spherical structure while nanotubes have a cylindrical structure. They were discovered in 1985 and 1990 respectively. By the 21^st century, nanotechnology has been developed in a way such that nanoparticles are used to target drug delivery to cancer cells(5).

Basic Concept

 There are two main types of concepts used in the engineering process of nanomaterials and nanostructures: which are Top-down and Bottom-up approaches. A Top-down approach is where nanostructures are synthesized by removing crystal planes that are present on the substrate and the Bottom-up approach is where nanostructures are synthesized onto the substrate by mounting atoms onto each other(6). The Top-down concept is good for producing materials with long-range order and for making macroscopic connections while the Bottom-up concept is best for manufacturing structures with short-range order at Nano scales. Since both approaches have their distinct features neither the bottom-up nor top-down approach is superior; each has its own merits and demerits(Table 01)(7).

Table01:Summary of the Advantages and Disadvantages for the Top‐Down and Bottom‐Up Approaches

Basic Structures and properties

Nanoparticles are unique candidates for certain scientific processes due to their astounding properties that arise out of aspects such as surface area, particle size, and quantum effects. When particles are made with 1-100 nm scale properties which they own at a larger scale change significantly where we call it a quantum effect. For instance, opaque substances become transparent, inert materials become catalysts, etc.. Nanomaterials have a comparably larger surface area when compared with their bulk material which has the same mass, and this makes  nanoscale materials more chemically reactive. Shape, size, inner structure, and surface characteristics can be considered as principal parameters of Nanoparticles and it can be observed in the forms of aerosols, suspensions or, emulsions.

Some physical and chemical properties related to nanomaterials can be listed as,

• High surface-to-volume ratio
• Low percolation threshold
• Increasing hardness/wear resistance with decreasing grain size
• Increasing resistivity with decreasing grain size
• Improved atomic transport kinetics
• Low melting and sintering temperatures
• Improved reliability and fatigue resistance

Nanomaterials can be classified into two main categories based on the type of material used and the dimension (Fig 05).

Fullerene, graphene, carbon nanotubes are carbon-based nanomaterials made from carbon atoms. Nanomaterials that are made from metals and metal oxides are inorganic nanomaterials. TiO2, MnO2, and ZnO are some examples. Organic nanomaterials are synthesized from organic matter while composite nanomaterials are synthesized by combining with other nanoparticles or more complex materials.

Classification according to dimension is done by considering the number of dimensions in the nanometer scale. It can be classified as below.

Applications

There are numerous commercial products that we use daily which wouldn’t exist in the same way without the manipulations done using nanotechnology and also it has a huge impact on fields like Medicine, Electronic/It industry, Energy sector, and many more. Nanotechnology has a huge contribution toward making our lives easy and more sufficient.

Medicine

Nanotechnology involves medicine regarding applications such as drug delivery, antibacterial treatments, diagnostic techniques, and many more. Nanoparticles have been developed to carry out delivery of certain drugs, light, heat, or other required substances to specified cells and at the same time, it reduces the damage to healthy cells in the body especially in the case of drug delivery to cancer cells(8).In the process of manufacturing diagnostic detectors and devices with high sensitivity nanomaterials like nanotubes, quantum dots, nanowires have been used over the years(9). For Instance, in the detection of kidney damage, gold nanorods have been functionalized to identify damaged kidney cells.

Energy

A wide range of energy-related applications is associated with nanotechnology where nanomaterials have been used to produce energy more efficiently and effectively. Some applications and their distinctive Nano features can be listed below.

Table 02: Applications of nanotechnology in the Energy sector

Electronics and IT Industry

Today computer devices and electronic devices are much smaller but faster thanks to the contribution of nanomaterials. Nano transistors, nano diodes, Organic Light Emitting Diodes(OLED) are used in the manufacturing process of many electronic and computing device parts such as Screens of digital devices, flash memory chips, digital sensors, antimicrobial coatings, random access memory(RAM) cards, anti-reflective films, water-resistant films, etc.

Environmental Industry

Globally, levels of environmental pollution are increasing at an alarming state where ecosystems and people around are likely to be affected by it. Nanotechnological products come as a good candidate to contribute widely to environmental protection by saving raw materials, removing hazardous gases and waste but still it plays a subordinate role in the purpose where some applications are still at the research basis. Some specific applications can be listed as,

• Radioactive waste clean(Using Titanate Nanofibers as absorbents)
• Oil spill removal(Still in the research level)
• water and wastewater treatment (Using nano adsorbents, nanocatalysts, nanomembranes)

  Consumer Products

Consumer manufacturing processes were hugely benefited by introducing nanomaterials into their products where it is used in many ways such as food packaging, adhesive and lubricant production, surface treatments, personal care production, smart fabric production and many more. Also,  nanotechnology is being applied in the processing, producing, and packaging of food items where nanocomposite coating is meant to improve food packaging by increasing the heat resistance and mechanical properties. There are several uses in the automotive sector where nanoparticles are used as fillers in tires to reduce vehicles being slip in wet conditions and light nanomaterials are suitable as substitute car body parts.

 Diverse Effects

Under some situations, nanomaterials may cause harm to human health and the environment around us(10). Nanoparticles can enter the human body through many routes due to their nano-scale. If nanoparticles enter the human body their toxicity depends on their surface properties, structure, size and it may lead to the release of cytokine since nanoparticles are foreign materials in the sense of the human body where it could affect lungs, and in extreme situations can trigger cardiac arrests. Quantum dots are used in drug delivery systems where it is supposed to carry a specific medicine to a certain cell or a system. But these nanoparticles could spread within the body and their effects on the living system are the same as the medicine it carries(10). Since nanoparticles do not degrade readily or dissolve easily it could be toxic to living organisms. Also, it has been found that certain carbon-based nanoparticles cause lung and DNA damage due to high exposure. Few studies have been conducted on the direct or indirect adverse effects of nanomaterials on the environment, and there are no clear shreds of evidence that suggest that nanoparticles are toxic to the environment(11).

Future

This emerging frontier technology will be able to create many new materials and devices with the use of technological advancements in the near future where we might be able to see nanosystems included in nanorobotics, artificial organs, and molecular level nanomaterials. Even though nanotechnology has shown exponential growth over the last few decades still we are currently experiencing the second generation of nanomaterials where it is predicted to have four distinct generations of advancements. As with any other new technology, nanotechnology has raised several questions regarding its health impact on living organisms and the environment. But in the coming decades regardless of the field nanotechnology will have a huge impact on every human on the planet due to its potential mind-boggling features.

References

1. Bawa R, Bawa SR, Maebius SB, Flynn T, Wei C. Protecting new ideas and inventions in nanomedicine with patents. Nanomedicine Nanotechnology, Biol Med. 2005 Jun;1(2):150–8.
2. Nasrollahzadeh M, Sajadi SM, Sajjadi M, Issaabadi Z. An Introduction to Nanotechnology. In: Interface Science and Technology. Elsevier B.V.; 2019. p. 1–27.
3. Bayda S, Adeel M, Tuccinardi T, Cordani M, Rizzolio F. The history of nanoscience and nanotechnology: From chemical-physical applications to nanomedicine [Internet]. Vol. 25, Molecules. MDPI AG; 2020 [cited 2020 Oct 27]. p. 112. Available from: /pmc/articles/PMC6982820/?report=abstract
4. Sabu Thomas, Nandakumar Kalarikkal, Oluwatobi Samuel Oluwafemi SMB, editor. Lycurgus Cup – an overview | ScienceDirect Topics. In: Synthesis of Inorganic Nanomaterials [Internet]. Elsevier; 2018 [cited 2020 Oct 27]. Available from: https://www.sciencedirect.com/topics/engineering/lycurgus-cup
5. Niska K, Zielinska E, Radomski MW, Inkielewicz-Stepniak I. Metal nanoparticles in dermatology and cosmetology: Interactions with human skin cells. Vol. 295, Chemico-Biological Interactions. Elsevier Ireland Ltd; 2018. p. 38–51.
6. Waqar Ahmed NA, editor. (PDF) Fabrication of Nanomaterials by Pulsed Laser Synthesis. In: Manufacturing Nanostructures [Internet]. One Central Press (OCP); 2014 [cited 2020 Nov 1]. Available from: https://www.researchgate.net/publication/270583669_Fabrication_of_Nanomaterials_by_Pulsed_Laser_Synthesis
7. Iqbal P, Preece JA, Mendes PM. Nanotechnology: The “Top-Down” and “Bottom-Up” Approaches. In: Supramolecular Chemistry [Internet]. Chichester, UK: John Wiley & Sons, Ltd; 2012 [cited 2020 Nov 2]. Available from:
8. Ochubiojo M, Chinwude I, Ibanga E, Ifianyi S. Nanotechnology in Drug Delivery. In: Recent Advances in Novel Drug Carrier Systems [Internet]. InTech; 2012 [cited 2020 Nov 7]. Available from: https://dx.doi.org/10.5772/51384
9. Laroui H, Rakhya P, Xiao B, Viennois E, Merlin D. Nanotechnology in diagnostics and therapeutics for gastrointestinal disorders [Internet]. Vol. 45, Digestive and Liver Disease. NIH Public Access; 2013 [cited 2020 Nov 7]. p. 995–1002. Available from: /pmc/articles/PMC3970315/?report=abstract
10. Hardman R. A toxicologic review of quantum dots: Toxicity depends on physicochemical and environmental factors [Internet]. Vol. 114, Environmental Health Perspectives. Environ Health Perspect; 2006 [cited 2020 Nov 21]. p. 165–72. Available from: https://pubmed.ncbi.nlm.nih.gov/16451849/
11. Taghavi SM, Momenpour M, Azarian M, Ahmadian M, Souri F, Taghavi SA, et al. Effects of Nanoparticles on the Environment and Outdoor Workplaces. Electron physician [Internet]. 2013 [cited 2020 Nov 23];5(4):706–70612. Available from: /pmc/articles/PMC4477780/?report=abstract