Unit IV Nanotechnology 2024 PDF

Nano particles& New engineering materials Dr Anita Nehra Dept of Chemistry JECRC University, Jaipur  Syllabus Nano particles& New engineering materials: Terminology- scales of nano- systems- nanoparticles: introduction-atoms to molecules-quantum dots-...

Nano particles& New engineering materials Dr Anita Nehra Dept of Chemistry JECRC University, Jaipur  Syllabus Nano particles& New engineering materials: Terminology- scales of nano- systems- nanoparticles: introduction-atoms to molecules-quantum dots-shrinking of bulk materials to quantum dots. Different types of nanoparticles. Various approaches in nanoparticle synthesis Characterisation of nanomaterials : Important methods for the characterisation of nanomaterials Applications of nanomaterials :Catalysis, Electronics & Telecommunication, Medicines, Composites, Energy sciences Molecular electronic devices, An Introduction to polymers for electronic industry, Organic conducting polymers Nanoscale/nano-range: Dimensions between approximately 1 and 100 nanometers  Terminology- scales of nanosystems Human hair: 100,000 nm RBC: 2000–5000 nm Human DNA: 2.5 nm CNT: 1.0–1.3 nm Water: 0.3 nm An ant: 4 million nm big! https://chembam.com/definitions/nanotechnology/ T E R M I N O L O G Y Mater. Adv., 2021, 2, 1821  Classification of Nanomaterials 0 D : all three dimensions in the nanoscale (nanoparticles, quantum dots) 1 D : two dimensions in nanoscale and one macroscale ( nanofibers, nanowires) 2 D : one dimensions in nanoscale and the two other in the macroscale ( nano sheets, thin films) 3 D : no dimensions at the nanoscale, all are in the macroscale (nanostructures with nanomaterials) Quantum dots https://ion2.upm.edu.my/article/properties_and_classification_of_nanomaterials-69062 Difference between nanomaterial and bulk material Environmental Technology & Innovation, 2020, 20, 101067 Synthesis of nanomaterials  Ball milling method: Top-down approach Mater. Adv., 2021, 2, 1821  Mechanical milling A cost-effective method for producing materials at the nanoscale level from bulk materials It is helpful in the production of nanocomposites. Mechanical milling is used to produce oxide- and carbide-strengthened aluminum alloys, wear-resistant spray coatings, aluminum/nickel/magnesium/copper-based nanoalloys, and many other nanocomposite materials. Ball-milled carbon nanomaterials are considered a novel class of nanomaterial, providing the opportunity to satisfy environmental remediation, energy storage, and energy conversion demands. Grinding carbon materials and nitrogenous materials in a high-speed rotating jar with some grinding media. The solid particles can be destroyed to small particles and activated by collision from the grinding media  Sol gel process: Bottom-up approach It is used for the preparation of oxide nanomaterials The sol–gel process involves hydrolysis followed by condensation. A metal or metalloid employed as a precursor is dispersed in acid or water to form a sol. Gel is obtained from this sol by the removal of water. MOR + H2O → MOH + ROH (hydrolysis). Metal alkoxide MOH + ROM → MOM + ROH (condensation) http://www.wikiwand.com/it/Processo_sol-gel  Sol gel process 1. First the solvated solution of the alkoxide or metal is formed. 2. Solvation is followed by polycondensation due to the formation of oxide or alcohol- bridged network. This leads to gelation and increases the viscosity of the solution dramatically. 3. Gradually, the gel solidifies and the smaller particles aggregate to form larger particles, a process called coarsening. 4. This is followed by drying of the gel where water and volatile liquids are removed from the gel network. 5. After this the surface-bound M-OH groups are removed so that the gel is stabilised against rehydration. 6. It is essential to control the growth of the agglomerating particles.  Techniques for characterization of nanomaterials Techniques i. Raman & Infrared spectroscopy (FT-IR), Structure and Functional group (FG) ii. Nuclear magnetic resonance (NMR) analysis, Purity Conformational change iii. UV-visible spectroscopy Optical properties iv. Electron dispersive X-ray spectroscopy Elemental and chemical composition at v. X-ray photoelectron spectroscopy (XPS) the surface vi. Scanning electron microscopy (SEM) Size and size distribution, Shape, vii. Scanning tunneling microscopy (STM) Aggregation, surface morphology viii. Transmission electron microscopy (TEM) ix. Atomic force microscopy (AFM) x. Dynamic light scattering (DLS) Hydrodynamic size distribution xi. Zeta potential Stability referring to surface charge xii. Mass spectrometry (MS) Molecular weight, Composition Characterization of NPs by TEM  UV-visible spectroscopy, UV lamp Size dependent Ag nanoparticels showing various colors Ultraviolet-visible (UV-vis) spectroscopy: Spectrum of different size Ag nanoparticles  SEM and fluorescence microscope SEM images of the oil-soluble CdSe/ZnS quantum dots TEM image a) SEM images of the quantum dot-labeled molecularly imprinted polymer and (b) true-color fluorescence image of the quantum dot-labeled molecularly imprinted polymer. Analytical Letters, 2017, 51, 921-934.  Fullerene Fullerene is any molecule in the form of a hollow sphere, ellipsoid or tubular structure composed entirely of carbon. They are commonly referred to as “Buckyballs” – named after Buckminster Fuller who designed geodesic physical structures and buildings based on this geometry. Discovered in 1985 by Smalley, Curl and Kroto., it is the roundest and most symmetrical large molecule known to man. The canonical structure, C60, has iscosahedral symmetry and an electronic structure similar to that of graphene. Using a laser to vapourise graphite rods in an atmosphere of helium gas, these chemists obtained cage like molecules composed of 60 carbon atoms joined together by single and double bonds to form a hollow sphere with 12 pentagonal and 20 hexagonal faces. The C60 molecule undergoes a wide range of novel chemical reactions. It readily accepts and donates electrons, a behaviour that suggests applications in batteries and advanced electronic devices.  Graphene It is one-atom-thick planar sheet of sp2 -bonded carbon atoms that are densely packed in a honeycomb (hexagonal) crystal lattice. It can be viewed as an atomic-scale chicken wire made of carbon atoms and their bonds. The carbon-carbon bond length in graphene is about 0.142 nm. Graphene is the basic structural element of some Graphene carbon allotropes including graphite, carbon nanotubes and fullerenes. It has the ability to conduct electrons and is transparent. Those qualities make graphene an alternative for use as a transparent conductor, the sort now found in everything from computer displays and flat panel TVs to ATM touch screens and solar cells.  Carbon Nano tubes (CNT) Graphene is the basic structural building block of carbon nanotubes. Carbon nanotubes (CNT) also known as ‘buckytubes’ have a cylindrical nanostructure in the form of a tube and an engineered CNT typically has a nanoscale thick wall, geometrically shaped similar to a Buckyball, with a nanoscale diameter, and a length that may exceed 100 nm. Carbon nanotubes are manufactured as single wall carbon nanotubes (SWCNT) or multiwall carbon nanotubes (MWCNT). They are synthesized in a variety of ways, including arc discharge, laser ablation and chemical vapor deposition. With respect to tensile strength, carbon nanotubes are the strongest and stiffest materials yet discovered, more than 5 times stronger than Kevlar. CNTs have a very low density, their specific strength is 300 times greater than stainless steel, though under compression CNTs appear to be a lot weaker.  Nanotubes properties 1. Molecular perfection: essentially nearly free of defects 2. Electrical conductivity: probably the best conductor of electricity on a nanoscale level that can ever be possible 3. Thermal conductivity: comparable to diamond along the tube axis 4. Mechanical: probably the stiffest, strongest, and toughest fiber that can ever exist 5. Chemistry of carbon: can be reacted and manipulated with the richness and flexibility of other carbon molecules. 6. Self-assembly: strong van der Waals attraction leads to spontaneous roping of many nanotubes.  Quantum Dots (QDs) Quantum dots, also known as nanocrystals, are another form of nanomaterial and are a specific type of semiconductor. They are 2-10 nanometers (10-50 atoms) in diameter, and because of their electrical characteristics, they are [electrically] tunable. The electrical conductivity of semiconductors can change due to external stimulus such as voltage or exposure to light, etc. Colloidal quantum dots irradiated with a UV light. Differently sized Sensitivity to different wavelengths of light, can be adjusted quantum dots emit different colors by the number of atoms or size of the quantum dot. Quantum of light due to quantum dots are typically made from CdSe, ZnS or CdTe compounds, confinement. Quantum dots (QD) are semiconductor nanostructures that act as artificial atoms by confining electrons and holes in 3-dimensions. Quantum dots absorb light, then quickly re-emit the light but in a different colour. They have extremely sharp (delta-function-like) density of the available energy states and the strong confinement of electron and hole wave functions inside the dots. As a result, electrons are confined to specific – discrete – energy levels, similar to conditions that resemble those in an individual atom. Main applications: Quantum Dots (QDs) Optical and optoelectronic devices, quantum computing, and information storage. Semiconductors with QDs as Material for Cascade Lasers. Semiconductors with QDs as Material for IR Photodetectors and Injection Lasers with QDs The Nobel Prize in Chemistry 2023 A B C A Massachusetts Institute of Technology (MIT), Cambridge, MA, USA A B C B Columbia University, New York, NY, USA C Nanocrystals Technology Inc., New York, NY, USA  Noble contributions Aleksey Ekimov In the early 1980s, he succeeded in creating size-dependent quantum effects in coloured glass. The colour came from nanoparticles of copper chloride and Ekimov demonstrated that the particle size affected the colour of the glass via quantum effects. Louis Brus The first scientist in the world to prove size-dependent quantum effects in particles floating freely in a fluid. Moungi Bawendi In 1993, he revolutionized the chemical production of quantum dots, resulting in almost perfect particles. This high quality was necessary for them to be utilized in applications. QDs: computer monitors and television screens based on QLED LED lamps, and biochemists and doctors use them to map biological tissue  Properties of nanomaterials Surface to volume ratio: Surface area When a bulk material is subdivided into materials on the nano scale, the total volume remains the same but the collective surface area is increased. This results in increase of surface to volume ratio at nanoscale as compared to bulk materials. The ratio of surface area to volume of a material is given by = surface area/volume 𝑎𝑟𝑒𝑎/volume = 4𝜋𝑟2 /4/3 𝜋𝑟3 = 3/r Thus as the radius of a given material is decreased, its surface to 𝑣𝑜𝑙𝑢𝑚𝑒 ratio increases This results in more number of atoms or molecules on the surface as compared to its number inside the volume in a nanomaterial. The molecules or atoms at the surface of a nanomaterial possess high surface energy and have high reactivity and have greater tendency to agglomerate.  Surface to volume ratio Thus, as the nanomaterials have s significant proportion of atoms existing at the surface, this has profound effect on reactions that occur at the surface such as catalysis reactions and detection reactions. The melting point of nanomaterials are reduced as compared to bulk counterpart due to larger surface atoms present. 8 Optical Properties  Optical Properties Ultraviolet-visible (UV-vis) spectroscopy: Size dependent Ag nanoparticels showing various colors Spectrum of different size Ag nanoparticles  Electrical properties In bulk metals, the valence and conduction bands overlap, while in metal nanoparticles there is a gap between these bands. The gap observed in metal nanoparticles can be similar in size to that seen in semiconductors (< 2 eV) or even insulators (> 2 eV). This results in a metal becoming a semiconductor. For example, carbon nanotubes can be either conductors or semiconductors depending on their nano structure. Another example is super capacitors which has effectively no resistance which disobey ohm’s law.  Magnetic properties The magnetic properties of a magnet are described by its magnetisation curve (called hysteresis curve which is the variation of intensity of magnetisation with applied magnetic field). These curves show the property like whether a magnet can be used as permanent magnet or a electromagnet The size of the material can change the property of a magnet by changing the magnetisation curves. Thus nanostructuring of bulk magnetic materials leads to changes in the curves which can produce soft or hard magnets with improved properties. Mechanical properties Mechanical properties of nanomaterials may reach the theoretical strength, which are one or two orders of magnitude higher than that of single crystals in the bulk form. The enhancement in mechanical strength is simply due to the reduced probability of defects. Carbon nanotubes are 100 times stronger than steel but six times lighter. Applications of nanomaterials Mater. Adv., 2021, 2, 1821  Medicine Nanoparticles are being used for the diagnosis and treatment of various diseases. Nanomaterials are used in medicine as drug carriers. Their large surface area enables them to load the drug on them and their small size helps them to transport these drugs into the cells, nuclei and across the membranes The nanoparticles can be coated on the drug (nanospheres), filled in a cavity surrounded by a polymeric layer (nanocapsules), the drug can be contained in holes inside nanoparticles (nanopores) or in branched-tree-shaped nanoparticles (dendrimers). Catalysis The nanoparticles have large surface area and hence provide higher catalytic activity. Nanoaluminium becomes so reactive that it finds its use as a solid fuel in rocket propulsion  Environmental technologies Nanoparticles on powder supports or on tubular monoliths form a catalytic system used widely in the removal of pollutants such as oxidation of volatile organic compounds (VOCs) in chimneys. Oxidation of flue gases in the catalytic converters of petrol-burning internal combustion engines where CO is oxidised to CO2 (in the presence of Pt catalyst). NOX is removed by reducing it to N2 in the presence of CO (catalyst Rh), and hydrocarbons are oxidised to CO2 and H2O using Pd catalyst. cerium oxide nanoparticles are used in diesel engines for pollution control. They trap the carbon particles (soot) formed because of incomplete combustion, hence are used in filters. Electronics and related fields Nanomaterials are widely used in electronic circuits used in television, radio, telephone, automobiles, aeronautics, etc. Use of nanomaterials helps in reducing the size of these gadgets. Solid-state techniques can also be used to create devices known as nanoelectromechanical system or NEMS that are related to microelectromechanical system or MEMS. Sunscreen Nano titanium oxides are used in cosmetics to prevent the skin from solar radiations (preparation of sun screens). Sensors Magnetic materials Magnets made of nanocrystalline yttrium–samarium–cobalt grains possess exceptional magnetic properties because of their larger grain interface area. These magnets find use in motors, in medical field, in magnetic resonance imaging (MRI) and in microsensors. The luminescent materials that glow when struck by a beam of electrons are called ‘phosphors’. These phosphors are widely used in television screens, for detection of forgery in bank notes, scintillators in medical fields, etc. The reduction in size improves the resolution of monitors. Nano phosphors are also used as fillers in cosmetics, varnishes and technical fibers. Owing to the nanoparticle size of the fillers the visible wavelengths do not interact and light passes easily, thereby maintaining the transparency.  Environmental remediation: water purification Nanotechnology is useful in regards to remediation, desalination, filtration, purification and water treatment. More surface area Small volume The higher the surface area and volume, the particles become stronger, more stable and durable Materials may change electrical, optical, physical, chemical, or biological properties at the nano level Makes chemical and biological reactions easier Cellulose nanocrystals (CNC) and Cellulose nanofibrils (CNF) Nanocellulose based renewable material has a combination of high surface Nanocellulose gel area with high material strength. It is chemically inert and possesses versatile hydrophilic surface chemistry. These properties make them a most promising nanomaterial for usage as a membrane and filter in water purification systems to remove bacterial and chemical contaminants from polluted water. It is noted that nanocellulose material has high potential in water purification technology. https://en.wikipedia.org/wiki/Nanotechnology_for_water_purification TEM image of CNC  Graphene and Carbon Nanotubes (CNT) The graphene embedded with carbon nanotubes to serve as nanofilters is more useful for dye rejection in water effluent, removal of salt ions, and also acts as antifouling agent. Graphene nanofilter membranes possess effective antifouling agent due to its strong bond between graphene sheets and proteins. Also, graphene oxide coated nanofilter membranes helps in dechlorination of water. In addition to this, ultrathin nanofilter coated with graphene is the most potent filter that could be commercialized for water Plant organisms, bacteria purification. and animals (freshwater Graphene oxide membranes can be used in various forms such sponges) have covered (fouled) the sheath of as free, surface modified, and graphene cast in membranes in an electric cable in a the range of micro, nano, or ultrafilters. canal (Mid-Deûle in Lille, https://en.wikipedia.org/wiki/Nanotechnology_for_water_purification END north of France).