Monthly Engineering Horizons

NANO MATERIALS AND NANO TECHNOLOGY

NANO MATERIALS AND NANO TECHNOLOGY

October 23
18:43 2019

By:Dr. Muneeb Asim, Chief Scientific Officer and Dr. Sadia Khalid, Assistant Prof. (HEC IPFP Fellow) Nano Sciences and Technology Department, National Centre for Physics, Islamabad

1.                   NANOMATERIALS

Nanomaterials (NMs) have at least one of dimensions < 100 nm.  Everything is comprised of combinations of atoms and molecules bound together either by shape or electronic charge. Theoretically and computationally humans can manipulate atoms on a nano-scale for numerous applications from food to space technology. Nanotechnology has guided to develop and engineer synthesis methods and tools for preparing variety of nanomaterials with unique size (dimensions), shape (morphology) and structures (compositions). Nanomaterials offer unique properties for use almost in all types of daily life applications. The size of nanomaterials can be imagined from the Fig.1. interestingly, when the size of molecule reduces to nano-level, not only its surface area to volume increase enormously, its chemical activity, reaction time, permeability, etc. also increases by many folds. 

Figure 1 Nanomaterials have a characteristic dimension in the size range.1

Nanomaterials can be classified on their basic chemistry (inorganic, organic, or carbon nanomaterials). Furthermore, they are also categorized based on composition, morphology, dimensionality, agglomerated states, and uniformity. State-of-the-art in-situ characterisation plays a crucial role in order to elucidate the importance of individual growth parameters for the controlled formation and the study of structure properties relationships of these novel nanomaterials. Nanotechnology offers a spectrum of solutions to applications by exploitation of nano-powders, dispersed solutions, polymer nanocomposites, coatings of nanomaterials, monoliths, etc. The design and development of nanotechnologies is considered as an interdisciplinary area of research which brings together theoretical and experimental researchers from various fields.2 There are two approaches to synthesise nanomaterials; (a) bottom-up approach (atom by atom) and (b) top-down approach (slicing or successive cutting). The fabrication methods for nanomaterials include:

  • Solution based growth
  1. Wet chemical approach
  2. Colloidal synthesis
  3. Hydrothermal/solvothermal synthesis
  • Vapour phase growth
  1. Physical vapour deposition (PVD)
  2. Chemical vapour deposition (CVD)
  • Exfoliation
  1. Mechanical/physical
  2. Electrochemical
  3. Intercalation

A wide range of characterization tools used for nanomaterials include, X-ray diffraction (XRD), scanning tunneling microscope (STM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force (AFM) and X-ray photoelectron spectroscopy (XPS) etc.

Figure 2 Basic nanomaterials classification: a inorganic nanomaterials, b organic nanomaterials, c carbon-based materials.2

At NS&TD, researchers are working on designing and synthesis of wide range of materials e.g., polymers, inorganic nanocrystals (metal oxides, metal sulfides, etc.), hybrid composites, thin films and studying their structural and basic properties using state-of-the-art characterization methods like XRD, SEM, TEM, XPS etc. to understand their behaviour at the nanometer scale. These nanomaterials have been applied in diverse areas such as catalysis, solar cells, batteries, supercapacitors, nanomedicines, magnetic, piezoelectric, electrochromic and photonic devices and environmental applications. The commonly used nanomaterial in our labs include;

  • Carbon nanomaterials (CNTs, graphene, nanodiamonds etc.)
  • Polymers and ionic liquids
  • Metals nanoparticles (silver, gold, copper, iron etc.)
  • Metal oxides (titanium oxide, iron oxide, cobalt oxide, copper oxide, zinc oxide, ceria, ferrites etc.)
  • Metal sulfides
  • 2D layered materials (e.g., MnO2, VO2, MoS2, WS2)

 

2.                   BRIEF HISTORY OF NANOTECHNOLOGY

In 1959, physicist Richard Feynman predicted a future in which scientists would, by manipulating atoms and molecules, be able to build materials and structures of higher strength, lighter weight, increased control of the light spectrum, and greater chemical reactivity. “There’s Plenty of Room at the Bottom: An Invitation to Enter a New Field of Physics” was an after-dinner lecture given by a Nobel Prize winning physicist Richard Feynman at the annual American Physical Society (APS) meeting “Winter Meeting in the West” at Caltech on December 29, 1959. In this lecture, Feynman discussed the importance of “manipulating and controlling things on a small scale” and how they could “tell us much of great interest about the strange phenomena that occur in complex situations.” The term ‘nanotechnology’ was used first by the Japanese scientists Norio Taniguchi (1912-1999) in a 1974 paper on production technology that creates objects and features on the order of a nanometer. 

The invention of scanning tunneling microscope in the 1980s by IBM Zurich scientists and then the atomic force microscope allowed scientists to see materials at an unprecedented atomic level. Significant progress in nanotechnology was obtained by IBM in 1990 when a team of physicists had spelled out the letters “IBM” using 35 individual atoms of xenon. Another breakthrough came in 1985 with the discovery of round shaped 60 carbon atoms well known as buckyball or fullerenes. This led to the discovery of carbon nanotubes in 1991. Carbon nanotubes (CNTs) are about 100 times stronger than steel with the excellent thermal and electrical conductivity. In parallel, studies of semiconductor nanocrystals led to the development of quantum dots (QDs) that have unique properties as compared to bulk semiconductors and discrete molecules.

3.                   APPLICATIONS OF NANOMATERIALS

NMs have diverse applications in water purification and remediation, groundwater and soil remediation, as delivery systems in agriculture, as biosensors, and medical and cosmetics. Fig.3 shows some of the nanomaterials and their wide range of applications.

Figure 3 Nanomaterials and their applications

3.1 ENERGY AND ENVIRONMENT

Nanotechnology is considered to have particular potential in photovoltaics (PV). In nano engineered solar cells, smaller particles and materials with different molecular structures facilitate higher energy absorption. Photovoltaics brought a revolution when world was facing a lot of challenges in energy sector. The sun provides 1 kWm-2 of free power for several hours every day. PV based on Si needs alternative due to its more fabrication cost. Hybrid perovskite has become a new attractive PV material due to its astonishing properties and simple processability. Perovskites may find use in many applications including solar cells, light emitting diodes and photo detectors. More complex applications, such as lasers and electro-optic modulators, require the use of single crystalline perovskite materials to reach their ultimate performance levels. The solar spectrum contains sufficient energy to split water (H2O), because of the low absorption coefficient of water (~10-2 m-1) in the UV-visible region of the electromagnetic spectrum. NS&TD has also developed efficient photo-anodes for hydrogen production from water splitting using composite of reduced Graphene oxide (rGO) and hematite nanoparticles.

Aside from solar, nanotech is being applied in storage devices e.g., lithium ion batteries (LIBs), sodium ion batteries (SIBs) and supercapacitors (SCs). There are a number of materials investigated in order to find appropriate anode for LIBs and SIBs which can be classified as, carbon-based materials, transition metal oxides, phosphides, sulfides, phosphorous based compounds, alloys, and organic compounds. There is urgent need to exploit novel anode materials e.g., carbon based-metal oxide composites for lithium and sodium ion batteries. Alongside, development of metal sulfides, metal oxides/polymer-based supercapacitor electrodes with improved specific capacitance and energy density of supercapacitor device is underway.

Biofuel production from solid wastes, biomass waste & non-edible oils by using nano catalytic gasification/ pyrolysis/ fermentation. The synthesis of synthetic fuel is another hot topic of the present-day scenario as the fossil fuels resources are depleting day by day. To search an alternative to fossil fuel, researchers are focusing to produce fuel grade hydrocarbons from CO2 present in larger quantity in air. In this regard, researchers at NS&TD are able to prepare highly active and selective nanocatalysts to convert CO2 to methanol, ethanol, dimethyl ether and other fuel grade hydrocarbons. Treatment of textile waste water by nano-photocatalyst is another field of interest for the green clean environment.

3.2   NANO-MEDICINES AND PHARMACEUTICAL

Using nanoscale carrier systems, drugs can be delivered in a much more targeted and efficient way. Photoactive nanomaterials have been developed for cancer therapy. Nanomedicine combines chemical and mechanical properties to help patients and practitioners, seeking to manufacture drugs that reach the intended area much faster than traditional injections or pills. Unlike existing medicines, nanoparticles can cross certain biological barriers within the body. For example, long-term usage or over dosage of non-steroidal anti-inflammatory drugs (NSAIDs) has severe side effects such as gastrointestinal bleeding, peptic ulceration, renal toxicity, heart failure and hypertension. Nanoformulation can be one of the solutions to overcome these side effects by improving the therapeutic efficacy of NSAIDs.

3.3   MANUFACTURING AND INDUSTRY

Carrying out processes at nanoscale reduces costs, improves efficiency, and improves the quality of materials. For example, CNTs/epoxy/polymer nano composites have been synthesised and applied to manufacture light weight durable and inexpensive sports products. Industrialists are consulting various new techniques, materials and technologies to achieve their goals. In this aspect, NS&TD preparing high quality CNTs and after purification and functionalization these CNTs are used in the synthesis of various sports goods like field hockey sticks, paddle racket, ice hockey stick and tennis rackets in collaboration with Sialkot industry.

3.4   ELECTRONICS AND TELECOMMUNICATION

In a world dominated by data, it is vital to handle information quickly and at scale. Luckily, when it comes to electronics, nanotechnology can deliver the smaller, faster, and more powerful chips needed to meet big data demands. For example, IBM’s 7 nm test chip using Silicon Germanium (SiGe) as the channel material in the transistor and holds 20 billion transistors four times as many transistors in the same area as a 14 nm chip for the most advanced commercial CPUs. It also employed Extreme Ultraviolet (EUV) lithography to etch the microscopic patterns into each chip and gearing up for the development of a next-generation transistor type at 3 nm.

3.5   FOOD AND AGRICULTURE

Nanotechnology is helping to solve the global issue of food waste by making food and food packaging more durable and resistant to bacteria. For example, nano food affects the fish growth. Nanopesticides could reduce the chemical impact on plants by activating only once ingested by an insect. Nanofertilizers evolution as sustainable alternative to commercial fertilizers for higher yields and improving land reclamation.

4.       CHALLENGES IN NANOTECHNOLOGY:

The fascinating innovations of nanotechnology also have unresolved queries of various level.  Researchers across the world are meticulously studying how atoms fit together to form larger structures and how quantum mechanics impact substances at the nanoscale, as the elements at nanoscale behave differently than they do in bulk form. In medical science applications, the concern becomes more fearful as nanoparticles are so small, that they could easily cross the blood-brain barrier, which is a membrane that protects the brain from harmful chemicals in the bloodstream. The use of nanoparticles in applications ranging from our clothing to highways, we need to be sure that they won’t poison us. Nanotechnology may also lead to create more powerful and lethal weapons than conventional ones. Some organizations urge scientists and politicians to examine carefully all the possibilities of nanotechnology before designing increasingly powerful weapons. As the molecular manufacturing is becoming a reality, it will impact the world’s economy? What will happen to the manufacturing jobs? Perhaps the questions arose is a matter of debate and nanotechnology will definitely continue to impact us as we learn more about the enormous potential of the nanoscale.

REFERENCES

  1. B. Ward. Development, synthesis and characterization of multifunctional nanomaterials: KU Leuven, Belgium, 2014.
  2. N. Kumar and S. Sinha Ray, Synthesis and Functionalization of Nanomaterials, in Processing of Polymer-based Nanocomposites: Introduction, Sinha Ray S., Editor. 2018, Springer International Publishing: Cham. p. 15-55.

 

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Engineering Horizons

Engineering Horizons

“Engineering Horizons” is the first & leading technical magazine of Pakistan covering Process, Mechanical, Metallurgical, Mining, Electrical & Electronics field under a single cover. We also feel pleasure in saying that this is the only magazine of its own kind & style, which is widely circulated in all Engineering Sectors of Pakistan.

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As you know, monthly “Engineering Horizons” is the first & Leading Technical Magazine of Pakistan covering Process, Mechanical, Metallurgical, Mining, Electrical & Electronics fields under a single cover. We also feel pleasure in saying that this is the only magazine of its own kind & style, which is widely circulated in all Engineering Sectors of Pakistan.