It describes how different properties of materials changes when reduced to nano. Property includes electrical, optical, mechanical, magnetic, thermal etc.
The document summarizes three common methods for synthesizing nanomaterials: solvothermal, photochemical, and electrochemical.
The solvothermal method involves chemical reactions between precursors in a solvent at high temperature and pressure. Key factors like the solvent, temperature, and duration can control the size, morphology, and uniformity of synthesized nanostructures. The photochemical method uses light sources like UV lamps to initiate chemical reactions. The solvent and wavelength of light are important parameters. The electrochemical method applies a voltage between electrodes in an electrolytic solution to reduce metal ions and form nanoparticles. Parameters like voltage, temperature, electrolyte composition and reaction time can influence nanoparticle size and concentration.
Sonochemical method of synthesis of nanoparticles.pptxMuhammadHashami2
for obtaining nanomaterial we use many methods, on of the important method is sonochemical method, this method is cost less and we can obtain nanoparticles simply.
1) Ferrites are magnetic ceramic materials that have a wide variety of applications from microwave to radio frequencies due to their properties like high resistivity and permeability.
2) They are classified based on their crystal structure into spinel, garnet, ortho, and hexagonal ferrites. Soft ferrites are used in transformers while hard ferrites are used in permanent magnets.
3) Ferrites are synthesized using methods like solid state reaction, sol-gel, and precipitation. Their properties can be modified by controlling synthesis parameters.
4) Major applications of ferrites include transformers, inductors, antennas, recording heads, and magnetic shielding due to their advantages over metals.
X-ray photoelectron spectroscopy (XPS) is a surface-sensitive technique that uses X-rays to eject core electrons from the surface of a sample. It can be used to identify the elements present in the sample and provide information about the chemical and electronic states of the elements. In XPS, X-rays eject core electrons, which are then analyzed based on their kinetic energy. This kinetic energy is related to the electron binding energy and can be used to identify the element and chemical environment. XPS requires ultra-high vacuum to avoid surface contamination and provide high-resolution spectra with sharp elemental peaks and broader Auger peaks.
The properties of nanomaterials depend on their small size, with dimensions typically between 1 to 100 nanometers. As size decreases, the surface area to volume ratio increases, altering physical properties like melting point. Nanomaterials also exhibit unique electrical properties due to quantum confinement effects, where energy levels become discrete. Their optical, magnetic, chemical and mechanical properties also change at the nanoscale, making nanomaterials useful in applications like hydrogen storage, catalysis, and superplastic materials.
The document discusses top-down and bottom-up processes for manufacturing structures at the nanoscale. Top-down processes start with bulk material and use techniques like lithography and etching to pattern structures, while bottom-up processes build structures from the atomic or molecular scale using self-assembly. Both approaches are needed as bottom-up is required to make smaller structures than lithography allows, and applications include growing carbon nanotubes, nanodots, and using self-assembled monolayers. Challenges of bottom-up include controlling assembly, but the future will see more integration of both top-down and bottom-up nanomanufacturing.
know more about nanomaterials and its apllication in future as well as current situation, and what wil we reserch on basis of nanomaterials and carbon structure and its aplication in such futuriastic manner.
laser ablation and pyrolysis for micro machining and nano fabricationJAISMON FRANCIS
This document discusses laser ablation and pyrolysis techniques. It begins by introducing lasers and their various types and uses. It then describes laser ablation, which is the process of removing material from a surface using a laser beam. Pulsed laser ablation is discussed as a method to machine materials with high precision without causing heat damage. Laser pyrolysis is then covered, which uses high heat from a laser to decompose mixtures of reactants and gases to produce nanoparticles. Specific techniques like pulsed laser deposition and laser beam interference ablation are also summarized.
The document summarizes three common methods for synthesizing nanomaterials: solvothermal, photochemical, and electrochemical.
The solvothermal method involves chemical reactions between precursors in a solvent at high temperature and pressure. Key factors like the solvent, temperature, and duration can control the size, morphology, and uniformity of synthesized nanostructures. The photochemical method uses light sources like UV lamps to initiate chemical reactions. The solvent and wavelength of light are important parameters. The electrochemical method applies a voltage between electrodes in an electrolytic solution to reduce metal ions and form nanoparticles. Parameters like voltage, temperature, electrolyte composition and reaction time can influence nanoparticle size and concentration.
Sonochemical method of synthesis of nanoparticles.pptxMuhammadHashami2
for obtaining nanomaterial we use many methods, on of the important method is sonochemical method, this method is cost less and we can obtain nanoparticles simply.
1) Ferrites are magnetic ceramic materials that have a wide variety of applications from microwave to radio frequencies due to their properties like high resistivity and permeability.
2) They are classified based on their crystal structure into spinel, garnet, ortho, and hexagonal ferrites. Soft ferrites are used in transformers while hard ferrites are used in permanent magnets.
3) Ferrites are synthesized using methods like solid state reaction, sol-gel, and precipitation. Their properties can be modified by controlling synthesis parameters.
4) Major applications of ferrites include transformers, inductors, antennas, recording heads, and magnetic shielding due to their advantages over metals.
X-ray photoelectron spectroscopy (XPS) is a surface-sensitive technique that uses X-rays to eject core electrons from the surface of a sample. It can be used to identify the elements present in the sample and provide information about the chemical and electronic states of the elements. In XPS, X-rays eject core electrons, which are then analyzed based on their kinetic energy. This kinetic energy is related to the electron binding energy and can be used to identify the element and chemical environment. XPS requires ultra-high vacuum to avoid surface contamination and provide high-resolution spectra with sharp elemental peaks and broader Auger peaks.
The properties of nanomaterials depend on their small size, with dimensions typically between 1 to 100 nanometers. As size decreases, the surface area to volume ratio increases, altering physical properties like melting point. Nanomaterials also exhibit unique electrical properties due to quantum confinement effects, where energy levels become discrete. Their optical, magnetic, chemical and mechanical properties also change at the nanoscale, making nanomaterials useful in applications like hydrogen storage, catalysis, and superplastic materials.
The document discusses top-down and bottom-up processes for manufacturing structures at the nanoscale. Top-down processes start with bulk material and use techniques like lithography and etching to pattern structures, while bottom-up processes build structures from the atomic or molecular scale using self-assembly. Both approaches are needed as bottom-up is required to make smaller structures than lithography allows, and applications include growing carbon nanotubes, nanodots, and using self-assembled monolayers. Challenges of bottom-up include controlling assembly, but the future will see more integration of both top-down and bottom-up nanomanufacturing.
know more about nanomaterials and its apllication in future as well as current situation, and what wil we reserch on basis of nanomaterials and carbon structure and its aplication in such futuriastic manner.
laser ablation and pyrolysis for micro machining and nano fabricationJAISMON FRANCIS
This document discusses laser ablation and pyrolysis techniques. It begins by introducing lasers and their various types and uses. It then describes laser ablation, which is the process of removing material from a surface using a laser beam. Pulsed laser ablation is discussed as a method to machine materials with high precision without causing heat damage. Laser pyrolysis is then covered, which uses high heat from a laser to decompose mixtures of reactants and gases to produce nanoparticles. Specific techniques like pulsed laser deposition and laser beam interference ablation are also summarized.
This document provides an overview of core/shell nanoparticles, including their classes, synthesis mechanisms, and applications. It discusses the four main classes of core/shell nanoparticles: inorganic/inorganic, inorganic/organic, organic/inorganic, and organic/organic. Two common approaches for synthesizing core/shell nanoparticles are described - using pre-synthesized core particles or synthesizing the core in-situ before adding the shell. The document outlines various techniques for synthesizing different types of core/shell nanoparticles and their mechanisms. Applications include modifying material properties, biomedical uses, and controlled drug release.
Lecture 3 Properties of Nanomaterial- Surface to Volume Ratio.pptDivitGoyal2
1. Nanotechnology involves manipulating matter at the nanoscale, between 1 to 100 nanometers.
2. One key difference between bulk and nanoscale materials is their surface area to volume ratio. Nanoparticles have a much higher surface area relative to their volume.
3. This large surface area to volume ratio allows for new material properties and applications. For example, it allows nanoparticles to serve as very effective catalysts by increasing the amount of surface available for chemical reactions.
Solvothermal method mithibai college msc part 1 pradeep jaiswalPradeep Jaiswal
This document discusses the solvothermal method for preparing nanomaterials. The solvothermal method involves conducting chemical reactions in a closed vessel (autoclave) where the solvent is heated above its boiling point. This allows reactions to occur under high temperature and pressure. An example given is the preparation of chromium dioxide nanoparticles by oxidizing chromium oxide in an autoclave with water and chromium trioxide. Advantages of the solvothermal method include precise control over the size, shape and properties of the synthesized nanoparticles. Disadvantages include the need for expensive autoclave equipment and safety issues during high pressure/temperature reactions.
Novel effects can occur in materials when structures are formed with sizes comparable to any one of many possible length scales, such as the de Broglie wavelength of electrons, or the optical wavelengths of high energy photons. In these cases quantum mechanical effects can dominate material properties. One example is quantum confinement where the electronic properties of solids are altered with great reductions in particle size. The optical properties of nanoparticles, e.g. fluorescence, also become a function of the particle diameter. This effect does not come into play by going from macrosocopic to micrometer dimensions, but becomes pronounced when the nanometer scale is reached.
Effects of ionizing radiation on the layered semiconductor tungsten diselenideRoger Walker
This document summarizes research on the effects of ionizing radiation on tungsten diselenide (WSe2), a two-dimensional material with potential applications in space electronics. The research examined how WSe2 is impacted by exposure to x-rays, electrons, protons at different energies, and heavy metal ions like iron and silver. It was found that thin films of WSe2 grown via MOCVD were stable against soft x-rays, but exfoliated WSe2 ionized in response to protons and was destabilized by heavy metal ions. The band alignment of WSe2 on silicon carbide substrates was also modified by ionization. Exposure to air led to oxidation of WSe2 damaged by
Surface modification can be used to alter
or improve these characteristics, and so
surface analysis is used to understand
surface chemistry of material, and
investigate the efficacy of surface
engineering. From non-stick cookware
coatings to thin-film electronics and bioactive
surfaces, X-ray photoelectron
spectroscopy is one of the standard
tools for surface characterization.
This document discusses magnetic properties of ferrites and their applications. It begins by explaining how ferrites exhibit quantum size effects and changes in magnetic behavior at the nanoscale due to increased surface area. It then describes the crystal structure of ferrites and the different types of magnetic ordering they can exhibit. Applications discussed include use of ferrites in transformers, sensors, data storage, and biomedical technologies. Magnesium ferrite is highlighted as a potential humidity sensor due to its porous structure and semiconducting properties.
Core shell nanoparticles and its biomedical applicationsKiran Qamar Kayani
Core-shell nanoparticles consist of an inner core covered by an outer shell. They are classified based on their material properties as inorganic-inorganic, inorganic-organic, organic-inorganic, or organic-organic. Core-shell nanoparticles are widely used in biomedical applications due to their less cytotoxicity, increased dispersibility and biocompatibility, better conjugation with biomolecules, and greater thermal and chemical stability compared to single component nanoparticles. Examples of biomedical uses discussed in the document include using ZnO-DOX@ZIF-8 nanoparticles for pH-responsive drug delivery, hollow carbon spheres for enzyme immobilization in biosensors, and NaYF4:Nd/NaLuF4@PDA nanoparticles
The document discusses the scanning tunneling microscope (STM), which uses quantum tunneling to produce atomic-scale images of surfaces. Key points:
- The STM was invented in 1981 and won the Nobel Prize in Physics in 1986. It allows visualization of individual atoms and manipulation of single atoms.
- The STM works by scanning a sharp conductive tip very close to a sample surface. A bias voltage causes electrons to tunnel between tip and surface, producing a current that varies with atomic topography.
- STM can image in various environments, with resolutions down to 0.1 nm laterally and 0.01 nm vertically. It has found many uses including atomic manipulation and etching.
This document discusses nanotechnology and provides an overview of top-down and bottom-up approaches to nanomaterial synthesis. It describes that the bottom-up approach involves molecular components arranging themselves into more complex structures from the smallest level, while the top-down approach uses larger external tools to shape and assemble materials into the desired nanoscale structures. Characterization techniques for nanomaterials include SEM, TEM, AFM, XRD, FTIR, and NMR. Applications mentioned include medical imaging, disease detection, agriculture, and environmental remediation.
This document discusses carbon nanotubes. It describes carbon nanotubes as having a diameter as small as 1nm and being made of rolled graphene sheets. Carbon nanotubes can be single-walled, multi-walled, or double-walled. They have extraordinary properties including high tensile strength, electrical and thermal conductivity. Potential applications include conductive plastics, structural materials, electronics, and biosensors. Common fabrication methods are electric arc discharge, laser ablation, and chemical vapor deposition.
This document summarizes research manipulating the coercivity of cobalt ferrite nanoparticles by changing particle size. Cobalt ferrite nanoparticles were synthesized with sizes ranging from 6 to 44 nm through calcination of a precursor at temperatures from 300 to 1200 degrees Celsius. X-ray diffraction characterization confirmed the crystal structure and particle sizes calculated using the Scherrer formula. Magnetic characterization using VSM found that coercivity reached a maximum of 645 Oe for 19 nm particles due to thermal effects and magnetic anisotropy in the nano-range. Smaller particles also exhibited lower saturation magnetization attributed to greater surface spin disorder. Future work could further investigate the mechanism of surface spin disorder through magnetic domain imaging.
Auger electron spectroscopy is a technique used to analyze the composition of solid surfaces. It works by bombarding a sample with electrons, which ejects inner shell electrons from atoms. The vacancy is then filled by an electron from a higher energy level, emitting an Auger electron. The kinetic energy of the Auger electron is characteristic of the emitting element and can be used to identify the elements present on the surface. AES provides information about surface composition and chemistry with high sensitivity to light elements. It has various applications in materials science and surface analysis.
This document provides an overview of applied nanochemistry and various nanomaterial classes. It discusses zero-dimensional nanoparticles, quantum dots, molecular electronics, nanotube/nanowire field effect transistors, and nanoporous materials and their applications. It also summarizes different nanomaterial classes based on their dimensionality, including zero-dimensional, one-dimensional, two-dimensional, and three-dimensional nanomaterials. Various types of two-dimensional and three-dimensional nanomaterials are classified and examples are provided.
X-ray photoelectron spectroscopy (XPS) is a surface-sensitive technique that uses X-rays to eject electrons from the surface of a material. An XPS instrument measures the kinetic energy of the ejected electrons to identify the elements present and analyze the chemical and electronic states of the surface. XPS can analyze the top 10-100 angstroms of a material in an ultra-high vacuum environment. The technique works by measuring the binding energy of electrons ejected from a material by X-ray photons, each element has characteristic binding energies that can be used for identification and analysis of oxidation states or impurities in the surface.
Xps (x ray photoelectron spectroscopy)Zaahir Salam
The document provides an overview of X-ray photoelectron spectroscopy (XPS) technology. XPS works by irradiating a sample surface with x-rays and measuring the kinetic energy and number of electrons that escape from the top 1-10 nm of the material. This allows one to determine the sample's elemental composition and chemical/electronic states. Key aspects discussed include the use of ultra-high vacuum conditions to prevent surface contamination and allow for accurate analysis. Characteristic XPS spectra are produced that contain peaks corresponding to different elemental binding energies.
Metallic nanoparticles (MNPs) is a type of nanoparticle which have a metal core composed of inorganic metal or metal oxide that is usually covered with a shell made up of organic or inorganic material or metal oxide.
This document discusses the classification and properties of nanomaterials. It begins by describing the different types of nanomaterials based on dimensionality - zero-dimensional, one-dimensional, two-dimensional, and three-dimensional. It then explains how the physical and chemical properties of nanomaterials, such as melting point, band gap, mechanical strength, and optical absorption, are dependent on their size and shape due to increased surface area and quantum effects. The document concludes by discussing how electrical conductivity and other electronic properties are also influenced by the nanoscale dimensions.
This document provides an overview of core/shell nanoparticles, including their classes, synthesis mechanisms, and applications. It discusses the four main classes of core/shell nanoparticles: inorganic/inorganic, inorganic/organic, organic/inorganic, and organic/organic. Two common approaches for synthesizing core/shell nanoparticles are described - using pre-synthesized core particles or synthesizing the core in-situ before adding the shell. The document outlines various techniques for synthesizing different types of core/shell nanoparticles and their mechanisms. Applications include modifying material properties, biomedical uses, and controlled drug release.
Lecture 3 Properties of Nanomaterial- Surface to Volume Ratio.pptDivitGoyal2
1. Nanotechnology involves manipulating matter at the nanoscale, between 1 to 100 nanometers.
2. One key difference between bulk and nanoscale materials is their surface area to volume ratio. Nanoparticles have a much higher surface area relative to their volume.
3. This large surface area to volume ratio allows for new material properties and applications. For example, it allows nanoparticles to serve as very effective catalysts by increasing the amount of surface available for chemical reactions.
Solvothermal method mithibai college msc part 1 pradeep jaiswalPradeep Jaiswal
This document discusses the solvothermal method for preparing nanomaterials. The solvothermal method involves conducting chemical reactions in a closed vessel (autoclave) where the solvent is heated above its boiling point. This allows reactions to occur under high temperature and pressure. An example given is the preparation of chromium dioxide nanoparticles by oxidizing chromium oxide in an autoclave with water and chromium trioxide. Advantages of the solvothermal method include precise control over the size, shape and properties of the synthesized nanoparticles. Disadvantages include the need for expensive autoclave equipment and safety issues during high pressure/temperature reactions.
Novel effects can occur in materials when structures are formed with sizes comparable to any one of many possible length scales, such as the de Broglie wavelength of electrons, or the optical wavelengths of high energy photons. In these cases quantum mechanical effects can dominate material properties. One example is quantum confinement where the electronic properties of solids are altered with great reductions in particle size. The optical properties of nanoparticles, e.g. fluorescence, also become a function of the particle diameter. This effect does not come into play by going from macrosocopic to micrometer dimensions, but becomes pronounced when the nanometer scale is reached.
Effects of ionizing radiation on the layered semiconductor tungsten diselenideRoger Walker
This document summarizes research on the effects of ionizing radiation on tungsten diselenide (WSe2), a two-dimensional material with potential applications in space electronics. The research examined how WSe2 is impacted by exposure to x-rays, electrons, protons at different energies, and heavy metal ions like iron and silver. It was found that thin films of WSe2 grown via MOCVD were stable against soft x-rays, but exfoliated WSe2 ionized in response to protons and was destabilized by heavy metal ions. The band alignment of WSe2 on silicon carbide substrates was also modified by ionization. Exposure to air led to oxidation of WSe2 damaged by
Surface modification can be used to alter
or improve these characteristics, and so
surface analysis is used to understand
surface chemistry of material, and
investigate the efficacy of surface
engineering. From non-stick cookware
coatings to thin-film electronics and bioactive
surfaces, X-ray photoelectron
spectroscopy is one of the standard
tools for surface characterization.
This document discusses magnetic properties of ferrites and their applications. It begins by explaining how ferrites exhibit quantum size effects and changes in magnetic behavior at the nanoscale due to increased surface area. It then describes the crystal structure of ferrites and the different types of magnetic ordering they can exhibit. Applications discussed include use of ferrites in transformers, sensors, data storage, and biomedical technologies. Magnesium ferrite is highlighted as a potential humidity sensor due to its porous structure and semiconducting properties.
Core shell nanoparticles and its biomedical applicationsKiran Qamar Kayani
Core-shell nanoparticles consist of an inner core covered by an outer shell. They are classified based on their material properties as inorganic-inorganic, inorganic-organic, organic-inorganic, or organic-organic. Core-shell nanoparticles are widely used in biomedical applications due to their less cytotoxicity, increased dispersibility and biocompatibility, better conjugation with biomolecules, and greater thermal and chemical stability compared to single component nanoparticles. Examples of biomedical uses discussed in the document include using ZnO-DOX@ZIF-8 nanoparticles for pH-responsive drug delivery, hollow carbon spheres for enzyme immobilization in biosensors, and NaYF4:Nd/NaLuF4@PDA nanoparticles
The document discusses the scanning tunneling microscope (STM), which uses quantum tunneling to produce atomic-scale images of surfaces. Key points:
- The STM was invented in 1981 and won the Nobel Prize in Physics in 1986. It allows visualization of individual atoms and manipulation of single atoms.
- The STM works by scanning a sharp conductive tip very close to a sample surface. A bias voltage causes electrons to tunnel between tip and surface, producing a current that varies with atomic topography.
- STM can image in various environments, with resolutions down to 0.1 nm laterally and 0.01 nm vertically. It has found many uses including atomic manipulation and etching.
This document discusses nanotechnology and provides an overview of top-down and bottom-up approaches to nanomaterial synthesis. It describes that the bottom-up approach involves molecular components arranging themselves into more complex structures from the smallest level, while the top-down approach uses larger external tools to shape and assemble materials into the desired nanoscale structures. Characterization techniques for nanomaterials include SEM, TEM, AFM, XRD, FTIR, and NMR. Applications mentioned include medical imaging, disease detection, agriculture, and environmental remediation.
This document discusses carbon nanotubes. It describes carbon nanotubes as having a diameter as small as 1nm and being made of rolled graphene sheets. Carbon nanotubes can be single-walled, multi-walled, or double-walled. They have extraordinary properties including high tensile strength, electrical and thermal conductivity. Potential applications include conductive plastics, structural materials, electronics, and biosensors. Common fabrication methods are electric arc discharge, laser ablation, and chemical vapor deposition.
This document summarizes research manipulating the coercivity of cobalt ferrite nanoparticles by changing particle size. Cobalt ferrite nanoparticles were synthesized with sizes ranging from 6 to 44 nm through calcination of a precursor at temperatures from 300 to 1200 degrees Celsius. X-ray diffraction characterization confirmed the crystal structure and particle sizes calculated using the Scherrer formula. Magnetic characterization using VSM found that coercivity reached a maximum of 645 Oe for 19 nm particles due to thermal effects and magnetic anisotropy in the nano-range. Smaller particles also exhibited lower saturation magnetization attributed to greater surface spin disorder. Future work could further investigate the mechanism of surface spin disorder through magnetic domain imaging.
Auger electron spectroscopy is a technique used to analyze the composition of solid surfaces. It works by bombarding a sample with electrons, which ejects inner shell electrons from atoms. The vacancy is then filled by an electron from a higher energy level, emitting an Auger electron. The kinetic energy of the Auger electron is characteristic of the emitting element and can be used to identify the elements present on the surface. AES provides information about surface composition and chemistry with high sensitivity to light elements. It has various applications in materials science and surface analysis.
This document provides an overview of applied nanochemistry and various nanomaterial classes. It discusses zero-dimensional nanoparticles, quantum dots, molecular electronics, nanotube/nanowire field effect transistors, and nanoporous materials and their applications. It also summarizes different nanomaterial classes based on their dimensionality, including zero-dimensional, one-dimensional, two-dimensional, and three-dimensional nanomaterials. Various types of two-dimensional and three-dimensional nanomaterials are classified and examples are provided.
X-ray photoelectron spectroscopy (XPS) is a surface-sensitive technique that uses X-rays to eject electrons from the surface of a material. An XPS instrument measures the kinetic energy of the ejected electrons to identify the elements present and analyze the chemical and electronic states of the surface. XPS can analyze the top 10-100 angstroms of a material in an ultra-high vacuum environment. The technique works by measuring the binding energy of electrons ejected from a material by X-ray photons, each element has characteristic binding energies that can be used for identification and analysis of oxidation states or impurities in the surface.
Xps (x ray photoelectron spectroscopy)Zaahir Salam
The document provides an overview of X-ray photoelectron spectroscopy (XPS) technology. XPS works by irradiating a sample surface with x-rays and measuring the kinetic energy and number of electrons that escape from the top 1-10 nm of the material. This allows one to determine the sample's elemental composition and chemical/electronic states. Key aspects discussed include the use of ultra-high vacuum conditions to prevent surface contamination and allow for accurate analysis. Characteristic XPS spectra are produced that contain peaks corresponding to different elemental binding energies.
Metallic nanoparticles (MNPs) is a type of nanoparticle which have a metal core composed of inorganic metal or metal oxide that is usually covered with a shell made up of organic or inorganic material or metal oxide.
This document discusses the classification and properties of nanomaterials. It begins by describing the different types of nanomaterials based on dimensionality - zero-dimensional, one-dimensional, two-dimensional, and three-dimensional. It then explains how the physical and chemical properties of nanomaterials, such as melting point, band gap, mechanical strength, and optical absorption, are dependent on their size and shape due to increased surface area and quantum effects. The document concludes by discussing how electrical conductivity and other electronic properties are also influenced by the nanoscale dimensions.
This document provides an introduction to fundamentals of nano-biotechnology. It discusses key concepts such as the nanoscale, unique properties of nanomaterials, and applications in various fields including medicine, computing, energy, and more. Some examples highlighted include use of nanoparticles for targeted drug delivery, nanowires as medical sensors, nanoshells for cancer therapy, and nanomaterials in batteries, displays, and implants to increase durability.
Nanotechnology involves creating and manipulating materials at the nanoscale, between 1-100 nanometers. At this scale, materials exhibit unique properties due to increased surface area to volume ratio and quantum mechanical effects. Some examples include enhanced chemical reactivity, color changes with particle size, and size-dependent melting points and conductivity. The document provides background on nanotechnology and an overview of how properties change at the nanoscale.
Nanomaterials are materials with at least one dimension sized between 1 to 100 nanometers. They possess unique properties due to their increased surface area to volume ratio and quantum effects. There are several types of nanomaterials including nanoparticles, nanotubes, nanowires, fullerenes and more. Some key aspects are:
- Nanoparticles have over 50% of their atoms on the surface, increasing reactivity.
- Carbon nanotubes are very strong and can be semiconducting or metallic depending on their structure.
- Nanomaterials can be synthesized through various methods including chemical vapor deposition and laser ablation.
- Their small size gives nanomaterials potential applications in electronics, optics, medicine and more. However more
The document discusses how the surface-to-volume ratio affects the properties of nanomaterials. It explains that nanomaterials have an extremely high surface area to volume ratio compared to larger materials, meaning the surface plays a larger role in determining properties. Different shapes like spheres, cylinders, and cubes are examined, showing how their surface-to-volume ratios change with size. The large increase in surface area for a given volume is demonstrated by reducing a 10 micrometer particle to billions of 10 nanometer particles, increasing the surface area by a factor of 1000. The high surface-to-volume ratio is a key factor making nanomaterial properties dependent on surface effects.
The document discusses several size-dependent properties of nanomaterials. As particle size decreases:
- Surface area to volume ratio increases, increasing surface and quantum effects
- Electronic structure changes from continuous bands to discrete energy levels
- Optical properties like absorption spectra and color are altered
- Reactivity and melting point decrease due to higher surface energy
- Magnetic and wetting properties change, with contact angle decreasing
- Density may increase or decrease depending on changes in cohesion and lattice constants
This document provides an introduction to nanoparticles and nanostructures. It begins with definitions of nanoparticles as having at least one dimension less than 1 micrometer. Examples of different nanoparticle shapes are given such as spheres, rods, and tubes. The document then discusses how the physical properties of nanoparticles can differ from bulk materials due to their high surface area to volume ratio. Properties like size, crystal structure, melting point, and mechanical strength are covered. Later sections explore how optical, electrical, and other properties can be altered at the nanoscale. Health concerns related to nanoparticles are also mentioned. In summary, this document introduces nanoparticles and nanostructures while examining how their physical characteristics can change at the nanoscale.
This document provides an introduction to nanoparticles and nanostructures. It defines nanoparticles as having at least one dimension less than 1 micrometer. Examples include spherical, rod-like, and tube-like particles. The document outlines that physical properties of nanoparticles such as size, crystal structure, melting point, and mechanical strength can differ from bulk materials due to increased surface area to volume ratio at the nanoscale. Optical, electrical, and health properties are also discussed.
1. Nanoparticles have unique properties due to their high surface area to volume ratio, including lower melting points and tunable optical absorption.
2. In semiconductors, quantum confinement results from physically constraining electrons, increasing the energy level spacing and causing absorption and emission spectra to shift to higher energies with decreasing particle size.
3. Nanomaterials exhibit both intramolecular bonding like covalent and ionic bonds, and intermolecular bonding like van der Waals forces, which influence their physical and chemical properties.
This document provides an overview of materials properties and structures. It discusses key properties like strength, toughness, hardness, brittleness, malleability, ductility, creep and fatigue. It also describes different crystal structures including simple cubic, body centered cubic, face centered cubic and hexagonal closed packed. It defines terms like unit cell, space lattice, atomic radius, atomic packing factor, coordination number, Bravais lattice, crystallographic planes and Miller indices for describing material structures.
The document discusses the crystal structures of materials. It begins by explaining that the properties of some materials are directly related to their crystal structures. For example, magnesium and beryllium have different properties than gold and silver due to differences in their crystal structures. It then lists the key learning objectives which include describing different crystal structures, computing densities, and distinguishing between single crystals and polycrystalline materials. The document goes on to explain common metallic crystal structures like body centered cubic and face centered cubic, as well as non-metallic structures like rock salt and cesium chloride. It also discusses factors that determine crystal structure such as the relative sizes of ions to maximize interactions and maintain charge neutrality.
Engineering Physics study materials discusses nanoscience and nanotechnology. It defines nanotechnology as manipulating matter at the atomic or molecular scale to produce novel structures and devices. When matter is reduced to the nanoscale, quantum confinement occurs and energy levels become quantized. This can increase the band gap and surface area to volume ratio. Nanomaterials are classified based on dimensionality (0D, 1D, 2D) and properties (metallic, semiconducting, insulating). Synthesis methods include top-down (milling) and bottom-up (self-assembly) approaches. Carbon nanotubes are discussed in detail, including their unique electrical, mechanical, and thermal properties, and applications in fields like electronics, composites,
This document discusses the chemistry of nanoscale materials including their synthesis, properties, and applications. Key points include:
- Nanoparticles exhibit unusual properties due to their small size such as changes in melting points, optical properties, and surface reactivity.
- Semiconductor nanoparticles known as quantum dots exhibit quantum confinement effects which alter their band gap.
- Common synthetic methods for nanoparticles include chemical reduction, sonochemistry, and electrochemical routes. Stabilization is needed to prevent aggregation.
- Dendrimers can template the synthesis of metal nanoclusters within their cores. Monitoring by UV-vis spectroscopy allows observation of cluster formation.
The document discusses nanotechnology and provides definitions and explanations of key concepts. It begins by defining nanotechnology as the design, characterization, production and application of structures and systems through control of shape and size at the nanometer scale. It then explains that a nanometer is one billionth of a meter and provides examples to illustrate the nanoscale. The document goes on to summarize some of the unique physical properties of nanomaterials compared to bulk materials, including increased surface area to volume ratio and quantum confinement effects. It also briefly outlines some common synthesis methods like sol-gel processing and chemical vapor deposition.
The document discusses several size-dependent properties of nanoparticles including shape, melting point, density, and specific surface area. As particle size decreases below 100nm, melting point decreases rapidly due to a higher percentage of surface atoms. Density may decrease or increase depending on the material. Specific surface area increases significantly with decreasing size. Nanoparticle shape depends strongly on factors like temperature, pressure and crystal structure, and may differ from the bulk material.
This document discusses different states of matter and properties of liquids and solids. It defines key terms like phases, intermolecular forces, and boiling point. It describes different types of solids like ionic, molecular, metallic and network solids. It also discusses properties of liquids like surface tension, capillary action, and viscosity.
This document provides an overview of surfaces and their characterization. It discusses that surfaces have different geometric and electronic structures than bulk materials. Studying surfaces is important for gas-solid and liquid-solid interactions like catalysis. Surfaces are also difficult to study due to their low concentration and need for ultra-high vacuum. Techniques for preparing clean surfaces include cleavage, heating, chemical cleaning, and ion bombardment. Surface structure is described using Miller indices and lattice vectors. The creation of surfaces requires energy in the form of surface free energy due to broken bonds at the surface. Common surface energies are provided for some metals.
This document provides an overview of nanomaterials and their optical properties. It begins with an introduction to nanomaterials and their history. It then discusses how the optical properties of nanomaterials differ from bulk materials due to their small size and large surface area. Specifically, it describes how semiconductor nanomaterials exhibit size-dependent band gaps and excitonic effects. For metallic nanomaterials, it explains surface plasmon resonance and how this results in strong light absorption. Different characterization techniques for studying nanomaterials are also summarized, including electron microscopy methods. Finally, common synthesis routes like colloidal methods are outlined.
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Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdfSelcen Ozturkcan
Ozturkcan, S., Berndt, A., & Angelakis, A. (2024). Mending clothing to support sustainable fashion. Presented at the 31st Annual Conference by the Consortium for International Marketing Research (CIMaR), 10-13 Jun 2024, University of Gävle, Sweden.
The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...Scintica Instrumentation
Targeting Hsp90 and its pathogen Orthologs with Tethered Inhibitors as a Diagnostic and Therapeutic Strategy for cancer and infectious diseases with Dr. Timothy Haystead.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
3. The properties of materials can be different at the Nanoscale for two main
reasons:
First, nanomaterials have a relatively larger surface area when compared to
the same mass of material produced in a larger form.
Nano particles can make materials more chemically reactive and affect
their strength, magnetic or electrical properties.
Second, quantum effects can begin to dominate the behaviour of matter at
the Nanoscale
Reason of Properties Change in Nano
4. Size
• Nanoparticles exhibit unique properties due to their high surface
area to volume ratio.
• A spherical particle has a diameter (D) of 100nm.
– Calculate the volume (V) and surface area (SA)
3
3
-9 3
-22 3
4
3 6
(100 10 )
6
5.24 10
D
V r
V
V x m
2 2
-9 2
-14 2
4
(100 10 )
3.141 10
SA r D
SA
SA m
𝑆𝐴
𝑉
=
3.141 × 10−14𝑚2
5.24 × 10−22𝑚3
𝑆𝐴
𝑉
≈ 6 × 107
5. Surface Area:Volume Ratio
• This gives an approximate surface area to volume ratio of >107:1
which is significantly larger than a macro sized particle.
• As the surface area to volume ratio increases so does the
percentage of atoms at the surface and surface forces become
more dominant.
• Generally accepted material properties are derived from the
bulk, where the percentage of atoms at the surface is miniscule.
These properties change at the nanoscale.
6. Size
Nanoparticle Nanoparticle Volume Surface Area SA:Vol Ratio
Diameter
(nm)
Diameter
(um) (nm3) (nm2) (nm2/nm3)
1 0.001 0.524 3.14 6
10 0.01 524 314 0.6
100 0.1 523598 31416 0.06
1000 1 5.24E+08 3.14E+06 0.006
10000 10 5.24E+11 3.14E+08 0.0006
100000 100 5.24E+14 3.14E+10 0.00006
1000000 1000 5.24E+17 3.14E+12 0.000006
Some example calculations for volume and surface area of
nanoparticles.
These calculations use nm as unit of length.
7. Surface Area:Volume Ratio
In this graph:
SA = nm2
Vol = nm3
SA:Vol Ratio = nm2/nm3
The ratio increases
dramatically when the
nanoparticle diameter drops
below about 100 nm
8. Crystal Structure
• The spatial arrangement of atoms in a crystal lattice is
described by its unit cell.
• The unit cell is the smallest possible volume that
displays the full symmetry of the crystal.
• Many materials have a “preferred” unit cell.
9. Crystal Structure
• In 3 dimensions, unit cells are defined by 3 lattice
constants and 3 angles.
• This leads to 14 Bravais lattices, each having
characteristic restrictions on the lattice constants,
angles, and centering of atoms in the unit cell.
b
a
c
11. Size & Crystal Structure
• Most metals in the solid form close packed lattices
• Ag, Al, Cu, Co, Pb, Pt, Rh are Face Centered Cubic (FCC)
• Mg, Nd, Os, Re, Ru, Y, Zn are Hexagonal Close Packed (HCP)
• Cr, Li, Sr can form Body Centered Cubic (BCC) as well as (FCC) and
(HCP) depending upon formation energy
12. Size & Crystal Structure
• How does crystal structure impact nanoparticles?
• Nanoparticles have a “structural magic number”, that
is, the optimum number of atoms that leads to a stable
configuration while maintaining a specific structure.
• Structural magic number = minimum volume and
maximum density configuration
• If the crystal structure is known, then the number of
atoms per particle can be calculated.
13. Close-Packed Magic Number Clusters
• Number of atoms (y) in shell (n): y = 10n2 + 2 (n = 1,2,3…)
• Maximum number of nearest neighbors (metal-metal hcp packing)
• Decreasing percentage of surface atoms as cluster grows
14. Size & Crystal Structure
• For n layers, the number of atoms N in an
approximately spherical FCC nanoparticle is
given by the following formula:
N = 1/3[10n3 – 15n2 + 11n - 3]
• The number of atoms on the surface Nsurf
NSurf = 10n2 – 20n +12
15. Size & Crystal Structure
Poole, C., Owens, F. Introduction to Nanotechnology.
Wiley, New Jersey. 2003
Example Calculations:
How many atoms (N) are in
idealized Au NP’s with the
following diameters?
5 nm Au NP:
With 9 shells, n = 9 and
NP diameter = 17d = 4.896
nm
N = 1/3[10n3 – 15n2 + 11n - 3] N
= 2057
Other Approximate Values
10 nm = 17,900
20 nm = 137,000
30 nm = 482,000
40 nm = 1.1 million
50 nm = 2.2 million
16. The Nano particles affects many properties such as
Magnetic properties
Electrical properties
Mechanical properties
Thermal properties
Band gap
Optical properties
Dielectric properties
Size Dependence of Properties
18. Mechanical Properties
dislocations
grain boundaries
atomic defects
atomic defects, dislocations and strains
grain boundaries and interfaces
porosity
connectivity and percolation
short range order
connectivity and percolation
porosity
19. Yield strength refers to an
indication of maximum stress that
can be developed in a material
without causing
plastic deformation. It is the stress
at which a material exhibits a
specified permanent deformation
and is a practical approximation of
the elastic limit.
Hardness is a measure of the resistance to localize plastic deformation induced by
either mechanical indentation or abrasion. Macroscopic hardness is generally
characterized by strong intermolecular bonds.
Elastic modulus is the ratio of stress, below the proportional limit, to the
corresponding strain. It is the measure of rigidity or stiffness of a material.
20. 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.
Mechanical Properties
The mechanical properties of nanomaterials increase with decrease in size, because
smaller the size, lesser is the probability of finding imperfections such as dislocations,
vacancies, grain boundaries
• Strength of material improves significantly as the particle size decrease due to
perfect defect free surface.
• Hardness and yield strength of material also increases as particle size is
decreased.
• Elastic modulus and toughness of material also increases as particle size is
decreased.
22. Melting Point (Microscopic Definition): Temperature at which
the atoms, ions, or molecules in a substance have enough energy to
overcome the intermolecular forces (Binding Energy) that hold the
them in a “fixed” position in a solid
Thermal properties
melt at the same temperature.
At macroscopic length scales (Bulk), the melting temperature of
materials is size-independent.
ice cube
glacier
23. Thermal properties
melting point
decreases
Nanocrystal size
decreases
surface energy
increases
Surface atoms require less energy to
move because they are in contact
with fewer atoms of the substance
Example:
10 nm Au NP melts at 964oC
bulk Au at 1064oC
<1.4 nm Au NPs melts below room temperature
3 nm CdSe nanocrystal melts at 700 K bulk CdSe
at 1678 K
In contact
with 3 atoms
In contact with 6 atoms
volume
Binding energy:
2
2/3
1/3 3/4
( 1) ( )
.
cZ Z d N Z
B E aA bA
A A
surface Electrostatic
repulsion Lack of
symmetry
Parity
24. 2
1
surface SL
M M
f
T T
H r
Thermal properties
Melting point of the surface (1st layer)
TM Melting point of bulk materials
SL
Solid-liquid interface energy
f
H
Enthalpy
r Radius of the particle
25. Melting point as a function of size
Source: Nanoscale Materials in Chemistry, Wiley, 2001
26. Melting point as a function of size
Source: Nanoscale Materials in Chemistry, Wiley, 2001
Au
27. Thermal Conductivity
bulk
•Heat is transported in materials by two different mechanisms:
Lattice vibration waves (phonons) and
Free electrons.
• In metals, the electron mechanism of heat transport is 8 significantly more
efficient than phonon processes.
•In the case of nonmetals, phonons are the main mechanism of thermal
transport.
In both metals and nonmetals, as the
system length scale is reduced to the
nanoscale, there are quantum
confinement and classical scattering
effects.
29. Optical Properties
• The size dependence on the optical
properties of nanoparticles is the result of
two distinct phenomena:
a) Surface plasmon resonance (SPR)
-- metal nano-structures
b)Increased energy level spacing due to the
confinement of delocalized energy states.
-- prominent in semiconductors
30. Optical Properties -SPR
• Surface Plasmons
– Recall that metals can be modeled as an arrangement of
positive ions surrounded by a sea of free electrons.
– The sea of electrons behaves like a fluid and will move
under the influence of an electric field
+
-
+ + +
+ + + +
-
-
-
- - -
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- -
-
- -
-
-
-
-
-
-
-
- -
-
-
-
- - - - - -
- -
- - - -
-
-
-
-
-
-
-
+
-
+ + +
+ + + +
-
-
-
- - -
-
-
- -
-
-
-
-
-
-
-
-
-
-
-
-
- -
-
- -
-
-
-
-
-
-
-
- -
-
-
- -
- - - - -
- -
- - - -
-
-
-
-
- -
-
-
-
-
- -
E-field
31. Optical Properties -SPR
Surface Plasmons
– If the electric field is oscillating (like a photon), then the
sea of electrons will oscillate too. These oscillations are
quantized and resonate at a specific frequency. Such
oscillations are called plasmon.
Source: MRS Bulletin 2005, 30(5), 338.
Resonance at a metal surface Resonance in metal NP
32. Optical Properties - SPR
• Surface Plasmons
– Formal definition: Plasmons are the coherent excitation of free
electrons in a metal.
– The plasmon resonance frequency (f) depends on particle size,
shape, and material type. It is related to the plasmon energy
(E) by Planck’s constant. E=h*f
– Surface plasmons are confined to the surface of the material.
– The optical properties of metal nanoparticles are dominated
by the interaction of surface plasmons with incident photons.
If the plasmons oscillation matches with the frequency of
incident radiation, resonance occurs and called surface
plasmon resonance. • It takes place when size of nanoparticle
is smaller than wavelength of incident radiations.
33. Optical Properties -SPR
Surface Plasmons
– Metal nanoparticles like gold and silver have plasmon frequencies in the
visible range.
– When white light impinges on metal nanoparticles the wavelength
corresponding to the plasmon frequency is absorbed.
– The spectral locations, strengths, and number of plasmon resonances for a
given particle depend on the particle’s shape and size.
34. Optical Properties
Optical absorption spectrum of 20- and 80-nm gold nanoparticles embedded in glass.
[Adapted from F. Gonella et al., in Handbook of Nanostructured Material and Nanotechnology,
H. S. Nalwa, ed., Academic Press, San Diego, 2000, Vol. 4, Chapter 2, p.85.]
• Absorption spectra of spherical Au nanoparticles
35. Martin, Olivier J.F. “Spectral response of plasmon resonant nanoparticles with non-regular
shape”. Optics Express Col. 6. No. 11 May 2000
Surface Plasmons: Shape
dependence of absorption spectra
•The amount of light that is scattered
into the far field is described by the
scattering cross section (SCS). The SCS
is plotted against the wavelength of light
used to illuminate a particle from a
specific angle.
•The arrows indicate the illumination
angle, and their colors correspond to the
different plot lines.
Optical Properties
36. Optical Properties- SPR
Martin, Olivier J.F. "Plasmons". Plasmons.
22 Mar. 2006. Ecole Polytechnique Fédérale
de Lausanne. 26 Jan. 2003.
Surface Plasmons:
Shape dependence of
absorption spectra. Resonant
frequency of different shapes
NPs are different.
37. Optical Properties – Band Gap
• Energy levels: from atoms to bulk materials…
– The Pauli Exclusion Principle states that electrons can only exist in unique,
discrete energy states.
– In an atom the energy states couple together through spin-orbit
interactions to form the energy levels .
– When atoms are brought together in a bulk material, the energy states form
nearly continuous bands of states, or in semiconductors and insulators,
nearly continuous bands separated by an energy gap.
N
Energy Energy
Atoms: Discrete Energy Levels Bulk Materials: Band Structures
38. Optical Properties- Band gap
• Energy levels
– In semiconductors and insulators, the valance band corresponds to the ground
states of the valance electrons.
– In semiconductors and insulators, the conduction band corresponds to excited
states where electrons are a free to move about in the material and participate in
conduction.
– In order for conduction to take place in a semiconductor, electrons must be
excited out of the valance band, across the band gap into the conduction band.
This process is called carrier generation.
– Conduction takes place due to the empty states in the valence band (holes) and
electrons in the conduction band.
Ec
Ev
Electron excited into conduction
band
band
gap
39. Optical Properties- Band gap
• Energy level spacing
– In semiconductors and insulators a photon with an energy equal to the band
gap energy is emitted when an electron in the conduction band recombines
with a hole in the valance band.
– The electronic band structure of a semiconductor dictates its optical
properties.
– GaP, a material commonly used for green LEDs, has an intrinsic band gap of
2.26 eV. Carrier recombination across the gap results in the emission of 550
nm light.
Eg = 2.26 eV
λ=550 nm
40. Optical Properties- Band gap
• Energy level spacing and quantum confinement
– The reduction in the number of atoms in a material results in the confinement
of normally delocalized energy states.
– Electron-hole pairs become spatially confined when the dimensions of a
nanoparticle approach the de Broglie wavelength of electrons in the
conduction band.
– As a result the spacing between energy bands of semiconductor or insulator is
increased (Similar to the particle in a box scenario, of introductory quantum
mechanics.)
Energy
Eg
Eg
Bulk Materials
Nano Materials
Increased
band gap
41. Band gap
The band gap is increases with reducing the
size of the particles
Bandgap is the energy needed to promote an electron from the valence band to
the conduction band
In bulk materials, there are 1023
atoms on surface, large no. of atoms
means large energy states, so band gap
is less.
As we go in nanorange, no. of atoms
decrease to 10-1000 atoms, so energy
states decrease, band gap is more.
42. Optical Properties - Band gap
• Energy level spacing and quantum confinement
– As semiconductor particle size is reduced the band gap
is increased.
– Absorbance and luminescence spectra are blue shifted
with decreasing particle size.
CdSe quantum dots
Jyoti K. Jaiswal and Sanford M. Simon. Potentials and pitfalls of fluorescent quantum
dots for biological imaging. TRENDS in Cell Biology Vol.14 No.9 September 2004
43. For semiconductors such as ZnO, CdS, and Si, the bandgap
changes with size
Optical Properties- Band gap
45. Electrical and Electronic Properties
• Effect of structure on conduction
– If nanostructures have fewer defects, one would
expect increased conductivity vs macroscale
• Other electrical effects on the nanoscale:
– Surface Scattering
– Change in Electronic Structure
– Ballistic Conduction
– Discrete Charging
– Tunneling Conduction
– Microstructural Effects
46. Surface Scattering
• Electrons have a mean-free-path (MFP) in solid
state materials.
• MFP is the distance between scattering events as
charge carriers move through the material.
• In metals, the MFP is on the order of 10’s of
nanometers.
• If the dimensions of a nanostructure are smaller
than the electron MFP, then surface scattering
becomes a factor.
47. Source of resistance: scattering
Total resistivity, ρT , of a metal is a
combination of the contribution of individual
and independent scattering, known as
Matthiessen’s rule:
thermal resistivity defect resistivity
Electron collisions with vibrating
atoms (phonons) displaced from their
equilibrium lattice positions are the
source of the thermal or phonon
contribution, which increases linearly
with temperature.
Impurity atoms, defects such as
vacancies, and grain boundaries
locally disrupt the periodic electric
potential of the lattice and
effectively cause electron scattering,
which is temperature independent.
Source
48. Considering individual electrical resistivity directly proportional to the respective
mean free path (λ) between collisions, the Matthiessen’s rule can be written as:
Increase in crystal perfection or reduction
of defects, which would result in a
reduction in defect scattering and, thus, a
reduction in resistivity.
However, the defect scattering makes a
minor contribution to the total electrical
resistivity of metals at room temperature,
and thus the reduction of defects has a very
small influence on the electrical resistivity.
Create an additional contribution to the
total resistivity due to surface
scattering, which plays a very important
role in determining the total electrical
resistivity of nanosized materials.
If the mean free electron path, λS, due
to the surface scattering is the smallest,
then it will dominate the total electrical
resistivity.
In nano, the surface scattering of electrons results in reduction of electrical conductivity.
+ ρs
Nano
49. Reduction in material’s dimensions will increase crystal perfection or reduction
of defects, which would result in a reduction in defect scattering and, thus a
reduction in resistivity and conductivity increases.
In nanowires and thin films, the surface scattering of electrons results in
reduction of electrical conductivity. When the critical dimension is smaller than
the mean free path, motion of electron will undergo elastic and inelastic
scattering.
Elastic scattering: electron reflects same way as photon reflects from mirror.
Both momentum and energy is conserved. Direction of motion of electron is
parallel to surface. Electrical conductivity is same as bulk materials.
Inelastic scattering: In this electron mean free path is terminated by
impinging on surface. The electron loses its kinetic energy and electrical
conductivity decreases.
Electrical and Electronic Properties
Surface scattering:
50. Electrical and Electronic Properties
Change of Electronic Structure:
Reduction in characteristic dimension below a critical size, i.e.
below De Broglie wavelength results in change of electronic
structure, leading to widening of band gap. Such a change
results in reduced electrical conductivity.
Some metal nanowires undergo transition to become
semiconductors and semiconductors might become insulators
when their diameters are reduced below a critical diameter.
52. Electrical and Electronic Properties
Quantum Transport:
It occurs when length of conductor is smaller than electron mean
free path.
In this case, each transverse waveguide
mode or conducting channel contributes
G0 = 2e2h = 12.9kΩ-1
In ballistic transport there is no energy
dissipation and no elastic scattering takes
place.
Ballistic conduction,
Coulomb blockade and
Tunnelling
Ballistic conduction:
53. Electrical and Electronic Properties
It occurs when length of conductor is smaller
than electron mean free path.
Ballistic conduction:
L
2
1
1
h L
R
q M
2
1
h
R
q M
2
h L
R
q
L
Transport of a conductor
Ohm’s law
𝑖 𝐿 << 𝜆𝑚
𝑖𝑖 𝐿 << 𝜆𝜙
55. Electrical and Electronic Properties
Coulomb Blockade & Single Electron Transistor:
It occurs when length of contact resistance is larger than resistance of nanostructures and total
capacitance of object is so small that adding a single electron requires significant energy.
Metal or semiconductor nanocrystals exhibit quantum effects that give rise to discrete charging of
metal particles.
Coulomb Blockade can be observed by making the device very small, like quantum dot (i.e. 3D
confinement). In this 3D confined state, electrons inside the QD will create a strong Coulomb
repulsion preventing other to flow. This, the device will no longer follow Ohms law. It require too
much Coulomb energy to add extra electron. This is called Coulomb blockade.
G
The Coulomb Energy
Ec = e2/2C
Electronic charge – e
Total Capacitance - C
57. Electrical and Electronic Properties
Tunelling:
It involves charge transport through an insulating medium
seperating two conductors that are closely spaced.
This is because electron wave function from two conductors
overlap inside insulator, when thickness is thin.
As thickness of layer increases, electrical conductivity decreases
59. Magnetic Properties
due to the huge
surface energy
bulk materials nanostructured materials
Magnetic properties
are distinctly different
superparamagnetism
Ferromagnetism
Ref: Prof A K Gsnguli slides
60. Magnetic Properties
I
A Magnetic moment, (m or µ) = IA
Origin of Magnetism
Macroscopic Microscopic
(charge current) (atomic scale)
Magnetization (M) =
m
V
Magnetic moment per unit volume
Magnetic field strength (H) measure of the strength of the externally applied
magnetic field.
Magnetic moment
(m or µ)
is the measure of the strength of magnet can the ability to
produce magnetic field.
Magnetic induction /
Magnetic flux density (B)
Magnetic flux per unit area.
0 ( )
B H M
Magnetic Susceptibility ,
M
H
Gives physical idea about the magnetic
material
Energy of the magnetic moment (E) : E= - m.B
61. Magnetic Properties
Origin of Magnetism (atomic)
Nuclear Spin
Orbital motion of
electrons
Electron Spin
(Small effect)
electron nucleus
m m
Magnetic moment arising due to nucleus is
very small compared to electron.
or Am2
Electron
Nucleus
62. Magnetic Properties
Spin
Orbital
motion
Lattice
weak
In bulk, contribution of magnetic
moment due to orbital motion of
crystalline solid is small
In Nano orbital – lattice coupling
decreases due to reduced surface energy
magnetization increases
Side reduced
Fundamental
component of
magnetism
Magnetism
of atom
Magnetism
of Molecule
Magnetism
of solid
Magnetism
of hybrids
64. Spin
Orbital
motion
Lattice
weak
Contribution of magnetic moment due
to orbital motion of crystalline solid is
small in bulk
In Nano orbital – lattice
coupling decreases due to reduced
surface energy magnetization
increases
Side reduced
Increase in Magnetization in nano
68. A Survey of Magnetic Nanoparticle Applications
A method for early diagnosis of brain cancer under development uses magnetic nanoparticles and nuclear magnetic
resonance (NMR) technology. The magnetic nanoparticles attach to particles in the blood stream called
microvesicles which originate in brain cancer cells. NMR is then used to detect these microvesicle/magnetic
nanoparticle clusters, allowing an early diagnosis.
Iron oxide nanoparticles can be used to improve Magnetic Resonance Imaging (MRI) of cancer tumors. The
nanoparticle is coated with a peptide that binds to a cancer tumor. Once the nanoparticles are attached to the tumor,
the magnetic property of the iron oxide enhances the images from the MRI scan.
Researchers at MIT have shown that iron oxide nanoparticles in water can be used to increase the amount of heat
transfer out of a system at localized hot spots. The researchers believe this technique could be applied to cooling
a wide range of devices, from electronics devices to fusion reactors.
Magnetic nanoparticles can attach to cancer cells in the blood stream. These nanoparticles may allow doctors to
remove cancer cells before they can establish new tumors.
Using nanoscavengers, in which a layer of reactive nanoparticles coat a synthetic core which is designed to be easily
magnetized. The nanoparticles, for example silver nanoparticles if bacteria is a problem, attach to or kill the
pollutants. Then when a magnetic field is applied the nanoscavengers are removed from the water.
Nanoparticles containing iron oxide that allows the nanoparticles to be directed, by a magnetic field, to stents.
This could allow drugs to be delivered directly to stents placed in arteries.
Iron oxide nanoparticles can used to improve MRI images of cancer tumors. The nanoparticle is coated with a
peptide that binds to a cancer tumor, once the nanoparticles are attached to the tumor the magnetic property of
the iron oxide enhances the images from the Magnetic Resonance Imagining scan.
Upto now we are discussing about the techniques and methods how we may proceed in a systematic way with nanomaterials. Now, lets see what is the reason behind