Intro to Nanotechnology & its Applications

Definition of Nanotechnology

• Nanotechnology involves research and development at the atomic, molecular, or macromolecular levels
• These developments occur under 100nm
• 10 Hydrogen atoms or 3.5 gold atoms is approximately 1nm (10^-9 m)

Applications of Nano Research

• Passive nanostructures: coatings, nanoparticles, polymers, ceramics
• Active nanostructures: amplifiers, targeted drugs
• Systems of nanosystems: guided assembling, 3D networking, robotics
• Molecular nanosystems: molecular devices by design

Examples of Nanomaterials

• Carbon nanotubes in tennis racquet heads provide greater stiffness, rigidity, lightweight, and responsiveness
• Nanoclay composites in multilayer PET bottles reduce CO2 escape and O2 absorption, increasing shelf life and enhancing mechanical and thermal performance
• Nanosized SiO2 within voids of carbon fibres in Wilson tennis racquets provides greater strength, stability, and power
• Buckyballs (Buckminsterfullerene): spherical structures of 60 carbon atoms arranged in a soccer ball shape, used in drug delivery, lubricants, and reinforcing materials

Properties of Nanomaterials

• Mechanical Properties: high hardness/strength, superplastic behavior of ceramics, ductile ceramics
• Thermal Properties: small heat capacities, responds to infrared radiation, lower sintering temperatures
• Optical Properties: high and selective optical absorption of metal particles, size smaller than a wavelength, reactive to light
• Electrical Properties: small mean free path of electrons in a solid
• Magnetic Properties: single magnetic domain, giant magneto-resistance
• Chemical degradation Properties: reactive to other chemicals, degradation over time
• Particle size: single magnetic domain smaller than wavelength of light, hindered propagation of lattice imperfections
• Large surface area: specific surface area, small heat capacity, heat shield capabilities, high surface area to volume ratio

Future Applications of Nanostructured Materials

• Energy Technologies: New types of solar cells (Grätzel cells), nanostructured semiconductor window layers, high energy density rechargeable batteries, smart windows, better insulation, rocket fuel ignitors, repairable heat-exchangers, magnetic refrigerators, pollutant elimination
• Automobile Industry: Corrosion protection, pollutant elimination in catalytic converters, nanostructured batteries for electric/hybrid cars, smart windows, fuel-efficient engines with nanostructured spark plugs and coatings, scratch-resistant top-coats, simple couplings, engine performance sensors
• Optics: Graded refractive index (GRIN) lenses, scratch-resistant reading aids and car windows, anti-fogging coatings, colored glass, optical filters
• Electronics: Single-electron tunneling transistors, efficient electrical contacts for semiconductors, electrically conducting nanoceramics, conducting electrodes, capacitive materials, magnetic memories, magnetorestrictive materials, soft magnetic alloys, resistors and varistors
• Optoelectronics: High-temperature superconductors, liquid magnetic O-rings, nanophosphors for high-definition displays, electroluminescent nanocrystalline silicon for optoelectronic chips and TVs, efficient light-emitting diodes, plastic lasers, optical switches and fibers, transparent conducting layers, 3D optical memories
• High-Sensitivity Sensors: Gas sensors (Nox, Sox, CO, CO2, CH4), UV and robust optical sensors based on nanostructured silicon carbide (SiC), smoke detectors, ice detectors
• Catalysis: Photocatalytic air and water purifiers, improved activity/selectivity/lifetime in chemical transformations and fuel cells, precursors for new catalysts, stereoselective catalysis

Nanomaterials Case Study: Improved Nanoparticle Platinum-Based Catalyst

• Engineered to enhance catalytic activity
• Platinum used in fuel cell catalysts is combined with ruthenium for efficient catalytic behavior
• CO poisoning is mitigated with new nanocatalysts that show enhanced tolerance
• The new catalysts exhibit good cost-effectiveness

Highly Selective Catalysts

• These enable catalysts to perform reactions without unwanted byproducts
• Nanoparticles allow control of catalytic functions due to their small size
• Nanoparticles must be uniform in size for predictable reactions
• Template surfaces (tungsten or oxides) aid in nanoparticle growth
• Surface faceting directs particle formation and distribution

Gordon Moore – Scaling Law

• The number of transistors on a chip doubles every 18-24 months
• Transistor size decreases by 13% annually, increasing chip size by 16%
• Cost increases as size decreases

Importance of Nanoscience

• Quantum mechanical properties of electrons are influenced at nanoscale
• It's possible to vary micro and macroscopic properties without changing chemical composition
• Man-made objects can be created inside living cells
• High surface-volume ratio is ideal for composite materials and drug delivery
• Higher density allows for new electronic device concepts and reduced power consumption

Types of Nanomaterials

• Carbon nanotubes, nanostructures, quantum confinement, nanophotonics, spintronics, nanoprobes
• Nanoelectronics: Quantum dots, nanowires, single-electron transistors
• Nanoelectromechanical systems: Micromechanical systems to nanoscale
• Nanobiology and nanomedicine

Material Properties

• Mechanical: Deformation to an applied force – elastic modulus, strength
• Thermal: Heat or change in temperature – heat capacity, thermal conductivity
• Optical: Light or electromagnetic radiation – refraction index, reflectivity
• Electrical: Response to an external electric field - electrical conductivity, dielectric constant
• Magnetic: Response to an external magnetic field – magnetic susceptibility, coercivity

Materials

• Metals, ceramics, polymers, composites (natural/synthetic), advanced materials respond/change to external stimuli, nanoengineered carbon nanotubes

Nanoscale Phenomena – Physics

• Electromagnetic forces are predominant
• Wave-particle duality
• Quantum mechanical tunneling is the penetration of electron wavefunction into an energy barrier
• Quantum confinement is the description of electrons in terms of energy levels, and band gaps

Nanoscale Phenomena - Chemistry

• Intramolecular bonding/chemical interactions are important to structure
• Increased surface/volume ratio increases reactivity
• Increased surface energy decreases melting point and increases heat capacity

Bulk objects

• Particles exceed 100nm in all dimensions
• Atoms on the surface have higher energy, and surface energy increases as size decreases
• Specific heat capacity of a nanocrystalline material is higher than bulk due to quantum confinement effects and higher surface energy

Properties of Nanocrystalline Materials vs Bulk Materials

• Grain size: 1-100 nm(Nanocrystalline) to Micrometer to millimeter (Bulk Materials)
• High Surface Area (Nanocrystalline) vs Low Surface Area (Bulk Materials)
• High Surface Energy (Nanocrystalline) vs Low Surface Energy (Bulk Materials)
• High Hardness (Nanocrystalline) vs Low Hardness (Bulk Materials)
• Low Ductility(Nanocrystalline) vs HighDuctility(Bulk Materials)
• Low Thermal Conductivity (Nanocrystalline) vs High Thermal Conductivity (Bulk Materials)
• High Specific Heat Capacity at high temperatures (Nanocrystalline) vs Low Specific Heat Capacity (Bulk Materials)
• Higher Electrical Bandgap (Nanocrystalline) vs Standard Electrical Bandgap (Bulk Materials)
• Size-dependent Optical Properties (Nanocrystalline) vs Bulk-like Optical Properties (Bulk Materials)
• High Diffusivity & Reactivity (Nanocrystalline) vs Low Diffusivity & Reactivity (Bulk Materials)

Microscopes

• Scanning Electron Microscope: Provides info about the surface of a sample and can handle thicker samples
• Transmission Electron Microscope: Shows sample's internal structure

Excitons

• The freeing of electrons is the creation of an exciton

Intentionally Produced Nanomaterials

• Carbon-based materials: hollow spheres, ellipsoids tubes mostly composed of C
• Metal-based materials: quantum dots, nanoparticles, metal oxides

Dendrimers

• Surface that has numerous chain ends for catalysis, can be used to store drug molecules

Composites

• Nanoparticles combined with other nanoparticles or bulk materials, typically used for auto parts, packaging, heat barrier, flame retardant materials

Metal-containing Nanoparticle Classifications

• Bulk: Films or crystals, amorphous or polycrystalline or single-crystalline
• 2D: Quantum wells, superlattices, Langmuir-Blodgett films, membranes
• 1D: Nanotubes, nanowires, nanorods, nanobelts
• 0D: Nano or quantum dots, colloids, nanoparticles
• 3D: Nanocrystals, nanocomposites, cellular, porous materials, hybrids, polymers
• Cluster: Objects with up to ~50 units
• Colloid: Stable liquid phase containing nanoparticles of 1-1000 nm in size
• Nanoparticle: Generally 1-100 nm, amorphous, aggregates of crystallites or crystalline
• Nanocrystal: Single-crystal, nm in size

Materials Synthesis – Solid State

• Combines powders, initiated with heat (no washing or purification)
• Shake & bake – initiate reaction in molten flux/rapidly condensing vapour
• Can be expensive, rxn incomplete, inhomogeneous products, not desired structure

Materials Synthesis – Wet Chemistry

• Combines elements through reaction in solution – promoted by heat and pressure

Materials Synthesis – Reactive Gas Processing

• Used to produce intermediate/final products using reactive gases

Materials Synthesis – Vapor Condensation

• Decomposition/reaction of precursors in low pressure flame, rapid cooling in cool gas

Materials Synthesis – Melt Quenching

• Spray plasma over falling powders, melting, rapid cooling in cold water

Strategies for Making Nanomaterials – Top-Down

• Slicing of bulk material to nanosize, large scale production possible, can have defects/dislocations
• Lithography: capable of producing complex materials

Strategies for Making Nanomaterials – Bottom-Up

• Phase Reactions: Capable of self assembly, Sol-gel, hydrothermal, solvothermal

Specific Methods – Soft Chemistry

• Conducted under 500 degrees, used to modify solids/doping, needs appropriate precursor
• Unstable over time

Specific Methods – Hydrothermal/Solvothermal Synthesis

• At elevated temp and pressure, water is at critical/supercritical state

Specific Methods – Sol-Gel Synthesis

• Formation of a network through polymerization, dispersion of colloidal particles occur
• Aerogel is produced by removing the liquid from a gel, supercritical drying
• Xerogel is formed by standard drying methods

Specific Methods – Electrochemical Cell Design

• Used for nanoparticle deposition
• Current is passed between working and counter electrode
• Working electrode is kept at constant potentia

Electrochemical Deposition

• Used for making thin films - electroplating, easy control of size, needs conductive substrates

Tricks for Synthesis - Templates

• Restrict growth region using well-defined voids in templates

Tricks for Synthesis - Seed Layers

• A pre-deposited layer helps growth in desired morphology

Tricks for Synthesis - Catalysis

• Speeds up the reaction

This covers the fundamentals of nanotechnology, focusing on research and development at the atomic and molecular levels (under 100nm). It also explores various types of nano applications, like coatings and targeted drugs, and provides examples of nanomaterials such as carbon nanotubes and nanoclay composites.