Essentials in Nanoscience and Nanotechnology - Narendra Kumar - ebook

Essentials in Nanoscience and Nanotechnology ebook

Narendra Kumar

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This book describes various aspects of nanoscience and nanotechnology. It begins with an introduction to nanoscience and nanotechnology and includes a historical prospective, nanotechnology working in nature, man -made nanomaterial and impact of nanotechnology illustrated with examples. It goes on to describes general synthetic approaches and strategies and also deals with the characterization of nanomaterial using modern tools and techniques to give basic understanding to those interested in learning this emerging area. It then deals with different kinds of nanomaterial such as inorganics, carbon based-, nanocomposites and self-assembled/supramolecular nano structures in terms of their varieties, synthesis, properties etc. In addition, it contains chapters devoted to unique properties with mathematical treatment wherever applicable and the novel applications dealing with information technology, pollution control (environment, water), energy, nanomedicine, healthcare, consumer goods etc.

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Table of Contents

Cover

Title Page

Copyright

Preface

Acknowledgments

About the Authors

Dr. N. Kumar, Former Director, Defence Laboratory, Jodhpur

Dr. S. Kumbhat, Professor, Department of Chemistry, Jai Narain Vyas University, Jodhpur

Chapter 1: Introduction

1.1 Definitions of Nanoscience and Nanotechnologies

1.2 Uniqueness of the Nanoscale

1.3 Nanoscience in Nature

1.4 Historical Perspective

1.5 Nanomaterials

1.6 Strategies for Synthesis of Nanomaterials

1.7 Properties of Nanomaterials

1.8 Significance of Nanoscience

1.9 Commercial Applications

1.10 Potential Health Hazards and Environmental Risks

1.11 Futuristic Outlook

Review Questions

References

Chapter 2: Nanomaterials: General Synthetic Approaches

2.1 Introduction

2.2 Top-Down Approach

2.3 Bottom-Up Approaches

Review Questions

References

Chapter 3: Characterization Tools for Nanomaterials

3.1 Introduction

3.2 Imaging Through Electron Microscopy

3.3 Scanning Probe Microscopy (SPM)

3.4 Characterization Through Spectroscopy

3.5 Scattering Techniques

Review Questions

References

Chapter 4: Nanomaterials

4.1 Introduction

4.2 Inorganic Nanomaterials

4.3 Organic Nanomaterials

4.4 Biological Nanomaterials

4.5 Nanoporous Materials

4.6 Quantum Dots

4.7 Nanoclusters

4.8 Nanomaterials in Different Configurations

Review Questions

References

Chapter 5: Carbon-Based Nanomaterials

5.1 General Introduction

5.2 Fullerene

5.3 Carbon Nanotubes (CNTs)

5.4 Graphene

5.5 Carbon Nano-Onions

5.6 Carbon Nanofibers

5.7 Carbon Black

5.8 Nanodiamond

Review Questions

References

Chapter 6: Self-Assembled and Supramolecular Nanomaterials

6.1 Introduction: Self-Assembly

6.2 Historical Perspective of Supramolecular and Self-Assembled Structures

6.3 Fundamental Aspects of Supramolecular Chemistry

6.4 Self-Assembly Via Non-Covalent Interaction

6.5 Synthetic Strategies for Molecular Self-Assembly

6.6 Biological Self-Assembly

6.7 Templated (Non-Molecular) Self-Assembly

6.8 Self-Assembled Supramolecular Nanostructures

6.9 Self-Folding Nanostructures

6.10 Applications

Review Questions

References

Chapter 7: Nanocomposites

7.1 Introduction

7.2 Ceramic–Matrix Nanocomposites

7.3 Metal–Matrix Nanocomposites

7.4 Polymer–Matrix Nanocomposites

7.5 Nanocoatings

Review Questions

References

Chapter 8: Unique Properties

8.1 Introduction

8.2 Size Effects

8.3 Physical Properties

8.4 Chemical Properties at Nanoscale

8.5 The Concept of Pseudo-Atoms

Review Questions

References

Chapter 9: Applications of Nanotechnology

9.1 Introduction

9.2 Medicine and Healthcare

9.3 Drug Development and Drug Delivery System

9.4 Information and Computer Technologies

9.5 Nanoelectromechanical Systems (NEMS)

9.6 Nanotechnologies in Tags

9.7 Nanotechnology for Environmental Issues

9.8 Energy

9.9 Nanotechnology in Enhancing the Fuel Efficiency

9.10 Chemical and Biosensors Using Nanomaterials (NMs)

9.11 Nanotechnology in Agro Forestry

9.12 Defense Applications

9.13 Nanotechnology

in Space

9.14 Consumer Goods

9.15 Sport Goods

Review Questions

References

Chapter 10: Toxicity and Environmental Issues

10.1 Introduction

10.2 Sources of Nanoparticles and Their Health Effects

10.3 Toxicology of Engineered Nanoparticles

10.4 Positive Health Effects of Nanoparticles

10.5 Environmental Sustainability

10.6 Safe Working with Nanomaterials

10.7 Nanomaterial Waste Management

10.8 Gaps in Knowledge about Health Effects of Engineered Nanoparticles

10.9 Government Standards and Materials Safety Data Sheets

10.10 Risk Management

Review Questions

References

Index

End User License Agreement

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Guide

Cover

Table of Contents

Preface

Begin Reading

List of Illustrations

Chapter 1: Introduction

Figure 1.1 Size comparisons of objects, nanomaterials, and biomolecules.

Figure 1.2 Exponential increases in surface area for cubes ranging from meter to nanosize.

Figure 1.3 Change in optical properties of a semiconductor ranging from bulk to nanosize. Courtesy of Grossman, MIT, USA.

Figure 1.4 Nanotechnology in nature: (a) electron microscopic image of a sensory patch in amphibian ears. http://scinerds.tumblr.com/post/35542105310/stereocilia-stairsteps; (b) peacock feather showing barbules, representing a photonic lattice; (c and d) electron microscopy image of transverse and longitudinal sections of barbules. Zi et al. [2a] © 2003. With permission of National Academy of Sciences, USA.

Figure 1.5 Natural and fabricated antireflective surfaces: (a) schematic of a moth; (b) scanning electron micrograph of antireflective surface of a moth's eye (scale bar = 1 µm); (c) biomimetic replica of a moth eye fabricated with ion- beam etching.

Figure 1.6 (a) Lotus (

Nelumbo nucifera

) plant; (b) spherical water droplet on a nonwettable lotus plant leaf. Blossey [6] © 2003. With permission of Nature Publishing Group. ; (c) self-cleaning: a drop picks up the dirt particles as it rolls off the leaf's surface.

Figure 1.7 Gecko's adhesive system structure: (a) ventral view of a tokay gecko (

Gekko gecko

); (b) sole of the foot showing adhesive lamellae; (c) microstructure: part of a single lamella showing arrays of setae; (d and e) nanostructure: single seta with branched structure at the upper right area, terminating in hundreds of spatular tips. Hansen and Autumn [6], © 2005. With permission of National Academy of Sciences, USA.

Figure 1.8 (a) Lycurgus cups. Courtesy of Trustees of the British Museum. © The Trustees of the British Museum; (b) ancient Maya fresco painting. Reproduced from Sanchez et al. [8] © 2005. With permission of The Royal Society of Chemistry.

Figure 1.9 Richard Feynman.

Figure 1.10 Typical examples showing varied dimensionality in nanomaterials: (a) fullerene; (b) quantum dot; (c) metal cluster; (d) carbon nanotube; (e) metal oxide nanotube; (f) graphene; (g) metal oxide nanobelts; (h) nanodiamond; (i) metal organic frameworks (MOFs).

Chapter 2: Nanomaterials: General Synthetic Approaches

Figure 2.1 “Top-down” and “bottom-up” approaches for the synthesis of nanomaterials.

Figure 2.2 (a) A ball-milling apparatus. Courtesy of PANalytical Inc. (b) Schematic representation of different forms of impact in mechanical ball milling.

Figure 2.3 (a) Set up for etching by electric arc discharge and (b) resultant water stabilization of Au NPs in solution.

Figure 2.4 Setup for laser ablation technique for the synthesis of Fe

2

O

3

nanoparticles from iron wire.

Figure 2.5 Soft lithography with polydimethyl siloxane (PDMS) molds.

Figure 2.6 Schematic of nanoimprint lithography process.

Figure 2.7 Nanosphere lithography. (a) Schematic illustration of the NSL process and (b) SEM image of triangular gold nanoprism as a product of nanosphere lithography.

Figure 2.8 Illustration of dip-pen nanolithography.

Figure 2.9 Schematic of ultrasonic spray pyrolysis setup.

Figure 2.10 (a) Schematic of a basic setup for electrospray. Seul-Gi Kim et al. [11] © 2014, With permission of Japan Society of Applied Physics; (b)–(d) three distinct electrospray.

Figure 2.11 Schematics of electrospinning process for nanofiber synthesis.

Figure 2.12 Schematic representation of chemical vapor deposition: (a) thermal and (b) plasma assisted.

Box 2.5 Preparation of Fe

2

O

3

. Shukla et al. [15] © 2010. With permission of ASPBS.

Figure 2.13 Schematic representation of chemical reduction method for nanosynthesis.

Figure 2.14 Schematic representation different capping agents (a) polymer; (b) organic ligand, and (c) micelle.

Box 2.6 Preparation of Ag NPs by reduction method. Manoth et al. [16] © 2008. With permission of Elsevier.

Figure 2.15 Illustration of the reverse micelle preparation route for hierarchical structuring of TiO

2

.

Figure 2.16 Schematic representation of sol–gel process for the synthesis of a variety of nanostructures.

Figure 2.17 (a) Sonochemical reactor; (b) transient cavitation during sonolysis.

Figure 2.18 Scanning electron micrograph (SEM): (a) magnetotactic bacteria (

Magnetospirillum gryphiswaldense

) cell; (b) magnetite crystals observed at the ends of the chain in magnetotactic bacteria.

Figure 2.19 Plant

Curculigo orchioides

(inset shows dried root) root extract used for nanosynthesis and AFM image of resultant silver nanoparticles. Courtesy, Dr. Sushma Dave, VIET, Jodhpur, India.

Figure 2.20 (a)–(c) Molecular biomimetics (I1, inorganic-1; I2, inorganic-2; P1 and P2, inorganic-specific proteins; LP, linker protein; FP, fusion protein).

Figure 2.21 Schematic illustration: (a) Langmuir balance; (b) deposition of a floating monolayer on a solid substrate.

Chapter 3: Characterization Tools for Nanomaterials

Figure 3.1 Electron beam-induced processes and their relative energies.

Figure 3.2

Schematic of electron gun

: (a) tungsten filament Wehnelt thermionic gun; (b) field emission gun.

Figure 3.3 Electromagnetic lenses.

Figure 3.4 Electron transition path for secondary electron and backscattered electron used in SEM.

Figure 3.5 (

a

,

b

) Principal features of a scanning electron microscope.

Figure 3.6 A secondary electron scintillator–photomultiplier detector.

Figure 3.7 SEM images showing the characteristic depth of field: (a) pollen grains, http://en.wikipedia.org/. ; (b) zinc oxide nanorods arranged as flower.

Figure 3.8 SEM image and EDX spectra. (a) Graphene balls. Adapted from Klajn et al.[12], ©2007 AAAS. (b) Nanoporous material.

Figure 3.9 (a, b) Principal features of a light and transmission electron microscope.

Figure 3.10 TEM image of (a) SnO

2

nanobelts Jiang et al. [14] © 2013. With permission of RSC; (b) CNTs. Wu et al. [15] © 2013. With permission of NPG; (c) graphitized Fe–Co alloy core-shell NPs, (inset, HRTEM image showing Fe–Co core and graphite shell).

Figure 3.11 (a, b) Bright field and dark field modes and the corresponding typical TEM images in bright field and dark field modes.

Figure 3.12 (a–c) TEM images showing the formation of Fe

3

O

4

nanocrystals.

Figure 3.13 Essential components of an STM with a close-up view of the tunneling effect between tip of the probe and the surface atoms.

Figure 3.14 (a) Constant current and (b) constant height imaging modes of an STM.

Figure 3.15 STM images of (a) nano-gold on TiO

2

. Galhenage et al. [17b], © 2013. With permission of ACS; (b) nano-cobalt on TiO

2

surface Galhenage et al. [17b], © 2013. With permission of ACS; (c) graphene on SiO

2

showing grain boundary. Koepke et al. [19], © 2013. With permission of ACS.

Figure 3.16 Schematic representation of AFM, Courtesy of Keysight Technologies.

Figure 3.17 AFM images showing (a) InAs/GaAs QDs grown on a Ge/Si substrate. Chen et al. [21a], © 2015. With permission of licensee MDPI, Basel, Switzerland; (b) Pt nanoparticles coated with Si nanopillars. Li et al. [21b], © 2015. With permission of NPG; (c) cholesterol–B, SA conjugate. Gehlot et al. [22], © 2013. With permission of NISCAIR, CSIR, New Delhi.

Figure 3.18 (a) AFM image of graphene balls with height bar; (b) cross section along the line indicated in (a). Kumar et al. [13], © 2013. With permission from ASP.

Figure 3.19 Spectrum of various electromagnetic radiations.

Figure 3.20 (a, b) UV–vis spectrum of gold nanoparticles with different geometries: spheres (top), decahedra (middle), and rods (bottom).

Figure 3.21 IR spectra and XRD pattern of pure Fe

3

O

4

nanoparticles at: (a) room temperature and after calcination for 2 h at different temperatures; (b) 150 °C; (c) 250 °C; (d) 350 °C; (e) 450 °C; (f) 550 °C.

Figure 3.22 Schematic representation of Raman spectrometer.

Figure 3.23 Energy level diagram showing the states involved in Raman signal.

Figure 3.24 Raman spectra of allotropes of nanocarbon in comparison to amorphous carbon.

Figure 3.25 Working principles of TERS.

Figure 3.26 Schematic electron spectroscopy: (a) X-ray photoelectron spectroscopy; (b) Auger spectroscopy; and (c) X-ray fluorescence spectroscopy.

Figure 3.27 Basic components of XPS/ESCA instrument. https://en.wikipedia.org/wiki/X-ray_photoelectron_spectroscopy.

Figure 3.28 XPS scan survey spectrum for all elements. https://en.wikipedia.org/wiki/X-ray_photoelectron_spectroscopy.

Figure 3.29 C

1s

XPS of carbon nanomaterials: (a) graphene oxide. Huang [30], © 2012. With permission of RSC; (b) fluorinated SWNTs. Dillon et al. [31], © 2008. With permission of ACS; and (c) fullerene. Arie and Lee [32], © 2009. With permission of Hanyang university, Korea.

Figure 3.30 XPS spectra of TiO

2

–WO

3

thin film: (a) survey scan between binding energy 0 and 1200 eV before etching; (b) high-resolution peaks for Ti-2p after etching the film; (c) high-resolution peaks for Ti-2f after etching.

Figure 3.31 AES survey spectrum (upper trace) and differentiated spectrum (lower trace) of an oxidized Fe–Cr–Nb alloy.

Figure 3.32 Schematics: (a) cylindrical mirror analyzer; (b) concentric hemispherical analyzer.

Figure 3.33 Characterization of an Sn–Nb wire by SEM: (a) SEM image; (b) schematic of the elemental distribution; and (c) point analysis giving the percent concentration of Nb and Sn.

Figure 3.34 Process of secondary ion sputtering and the schematic of a dynamical SIMS instrument.

Figure 3.35 Basic features of an XRD spectrometer.

Figure 3.36 A typical XRD pattern of (a) NaCl powder and (b) carbon nanomaterials.

Figure 3.37 (a, b) X-ray diffraction patterns of nanostructured TiO

2

film.

Figure 3.38 Schematic of a typical SAXS setup. www.mrl.ucsb.edu.

Figure 3.39 A typical plots of diffracted intensity versus scattering vector, inset shows centro-symmetric pattern on the 2D detector. www.mrl.ucsb.edu.

Figure 3.40 Basic components and optics for a dynamic light scattering experiment,

Figure 3.41 (a) Electric double layer around a particle; (b) effect of zeta potential on suspension properties.

Figure 3.42 Shift in frequency by a moving particle.

Chapter 4: Nanomaterials

Figure 4.1 Electrostatic and steric stabilization of nanostructure metal colloids.

Figure 4.2 Nanostructured metal colloids obtained via [BEt

3

H–] reduction method (including the mean particle sizes in nanometers).

Figure 4.3 Color variation of gold nanoparticles of different sizes.

Figure 4.4 Influence of size, shape, and composition on the light-scattering and resultant colors of silver nanoparticles (quoted nanoparticle sizes are all approximate).

Figure 4.5 TEM image of nano-titanium flower.

Figure 4.6 TEM micrographs of nanocrystals obtained by sulfuric acid hydrolysis of (a) cotton, (b) avicel, and (c–e) tunicate cellulose.

Figure 4.7 Synthesis of a typical dendrimers involving growth (g) and activation (a, a*) steps.

Figure 4.8 Nanometer-scale pores for biotechnology. (a) Single biological pore model of α-hemolysin. http://www.ipt.arc.nasa.gov/carbonnano.html. (b) Electric field-driven entry of a supramolecular entity through a single α-HL channel.

Figure 4.9 (a) Structure and functionality of a nanogear.

Figure 4.10 Types of possible pores in a porous material.

Figure 4.11 Representative zeolite frameworks (with pore openings): (a) zeolite A:3D, 4.2 Å; (b) zeolite Y:3D, 7.4 Å; (c) zeolite L:1D, 7.1 Å; (d) ZSM-5 (silicalite):2D, 5.3 ×5.6 Å, 5.1 ×5.5 Å. Zheng et al. [27] © 2012.With permission of authors.

Figure 4.12 A typical porous texture of a biomass-based activated carbon.

Figure 4.13 A molecular sieve: A metal-organic framework (MOF) MIL-47 loaded with CuCl

2

.

Figure 4.14 Comparison of band gap energy in a bulk semiconductor, quantum dots, and a molecule. Emission colors in ZnS quantum dots by varying dopants.

Figure 4.15 Schematic of polythiol-coated CdSe-ZnS core–shell quantum dot.

Figure 4.16 Nanocluster from atom/molecule.

Figure 4.17 SEM images of biomimics of natural hierarchical structures: (a) pillared poly(methyl methacrylate) nanofiber.

Figure 4.18 Inorganic nanotube: SEM image of TiO

2

nanotubes.

Figure 4.19 SEM images: (a) SnO

2

nanobelts.

Chapter 5: Carbon-Based Nanomaterials

Figure 5.1 Carbon in different hybridized states: (a) sp

2

with planer geometry as in graphite; (b) sp

3

with tetrahedral geometry as in diamond.

Figure 5.2 Allotropes of carbon nanomaterials in different dimensions.

Figure 5.3 C

60

fullerene.

Figure 5.4 Possible derivatization of C

60

: (a) fullerene salts; (b) exohedral adducts; (c) open-cage fullerenes; (d) quasifullerenes; (e) heterofullerenes; (f) endohedral fullerenes.

Figure 5.5 Schematic of arc discharge process.

Figure 5.6 (a–d) Fullerene derivatives.

Figure 5.7 (a–c) Types of carbon nanotubes.

Figure 5.8 Different structural forms of single-wall carbon nanotubes.

Figure 5.9 Transmission electron micrograph (TEM) of MWCNT.

Figure 5.10 Schematic of the arc discharge procedure in liquid nitrogen.

Figure 5.11 SEM images of MWCNTs synthesized: (a) with and (b) without the magnetic field.

Figure 5.12 Schematic of plasma rotating electrode system.

Figure 5.13 (a) Classical laser ablation apparatus used at Rice University; (b) schematic of ultrafast laser evaporation method.

Figure 5.14 Schematic of the apparatus for magnetic purification of CNTs.

Figure 5.15 (a) Planar structure of 2D graphene; Dai et al.[3], © 2012. With permission of Wiley. (b) Graphene shown as chicken net.

Figure 5.16 Band structure of graphene (a) energy bands near the Fermi level in graphene; (b) conic energy bands in the vicinity of the K and K' points; (c) density of states near the Fermi level with Fermi energy EF.

Figure 5.17 Schematic diagram of CVD reactor for preparing graphene.

Figure 5.18 Schematic representation of graphite exfoliation process resulting in graphene.

Figure 5.19 (a) Oxidation of graphite to graphene oxide and reduction to reduced graphene oxide. (b) A proposed reaction pathway for epoxy reduction by hydrazine.

Figure 5.20 Experimental setup for electrochemical synthesis of graphene: (a) electrochemical cell; (b) exfoliation of chemically modified graphene sheets on graphite anode.

Figure 5.21 Isocyanate treatment of GO.

Figure 5.22 Raman spectra of graphene.

Figure 5.23 (a) Optical image graphene flakes showing one, two, three, and four layers; (b) TEM image of graphene showing hexagonal lattice structure with pentagon–heptagon pairs.

Figure 5.24 Carbon nano-onions (a) FESEM image; (b) EDX spectrum; and (c–e) HRTEM images (inset is the corresponding SAED pattern).

Figure 5.25 HRTEM image along with schematic representation of carbon nanofibers with their graphene sheets in “parallel.”

Figure 5.26 Pyrolysis furnace for the synthesis of carbon black.

Figure 5.27 Nanodiamond: (a) octahedral model. Krueger [42], © 2008. With permission of RSC; (b) meteoritic diamond with multiple twinning. Daulton et al. [40], © 1996. With permission of Elsevier; (c) triamantane, a diamondoid molecule. Krueger [42], © 2008. With permission of RSC.

Figure 5.28 Formation of nanodiamond at near-ambient conditions via microplasma dissociation of ethanol.

Figure 5.29 Surface functionalization of nanodiamond yields various covalently modified derivatives with different terminal groups for further surface modification.

Figure 5.30 Treating drug-resistant cancer with nanodiamond. Moore et al. [42b], © 2013. Reprinted with permission of John Wiley and Sons.

Chapter 6: Self-Assembled and Supramolecular Nanomaterials

Figure 6.1 Rigid triangular structure self-assembled in combination with macrocycle rings in solution to create a supramolecular organic framework (SOF). Zhang et al. [10], © 2013. With permission of ACS.

Figure 6.2 Schematic illustration of nanoscale self-assembly. vdW attraction and steric repulsion may induce the phase separation of rods and spheres into two closely-packed arrangements (top). Alternatively, when the rods are functionalized with positively charged ligands and the spheres with negatively charged ligands, the particles are expected to organize via electrostatic interactions into a binary lattice (bottom).

Figure 6.3 van der Waals forces driven nanoparticle assemblies: (a) 2D hexagonal close-packed structure of 5 nm Ag-NPs. Harfenist et al. [12], © 1996. With permission of ACS; (b) side-by-side self-organized gold nanorods (15 × 200 nm, aspect ratio >5) leading to continuous ribbons. Sau and Murphy [13], © 2005. With permission of ACS; (c) isotropic self-assembly of gold nanorods (15 × 200 nm, aspect ratio 3.2) Sau and Murphy [13], © 2005. With permission of ACS.

Figure 6.4 TEM image of self-assembly of magnetic nanoparticles formed by strong dipole–dipole interactions: (a) linear chains of 20 nm cobalt-NPs. Thomas [14], © 1966. With permission of AIP; (b) parallel chains of 10 nm ϒ-Fe

2

O

3

. Lalatonne et al. [15], © 2004. With permission of NPG.

Figure 6.5 STM images of (a) hexagonal close network of trimesic acid on HOPG. Lackinger et al. [17], © 2005. With permission of ACS; and (b) molecular wires of 4-[

trans

-2-(pyrid-4-yl-vinyl)]benzoic acid on Ag(1 1 1) surface. Smith et al. [18], © 2004. With permission of Wiley, VCH-Verlag.

Figure 6.6 Schematic representation of (a)

n

-dodecanethiolate monolayer, self-assembled on an atomically flat gold substrate. Smith et al. [18], © 2004. With permission of Elsevier; (b) dicarboxylic acid derivatives as spacer.

Figure 6.7 (a) Normal capillary bridge forces, (b) lateral capillary forces.

Figure 6.8 Self-assembled 2D (a and b) and 3D (c and d) structures in systems of macroscopic components interacting via capillary interactions.

Figure 6.9 Thermodynamics of self-assembly.

Figure 6.10 Cross-sectional view of SEM image: (a) dried suspension of V

2

O

5

; (b) polycrystalline silicon templated by 855-nm silica spheres.

Figure 6.11 Nanomotors assembled in ordered arrays: (a–d) Schematic diagrams and snapshot images of a 2 × 2 nanomotor array rotating; (e) overlapped snapshot image of a 1 × 3 nanomotor array.

Chapter 7: Nanocomposites

Figure 7.1 Abalone shell and its structure.

Figure 7.2 Working temperature range for different matrix materials.

Figure 7.3 Types of reinforcements: (a) continuous fibers; (b) whiskers; (c) particulates.

Figure 7.4 (a) Strength and fracture toughness for various Al

2

O

3

/SiC nanocomposites as a function of SiC volume fraction. Nanocomposites derived from the classical powder route are represented by solid symbols and nanocomposites fabricated from an amorphous Si–C–N powder by open symbols; (b) average matrix grain size (

R

) as a function of 1

/V

f

of SiC for Al

2

O

3

/SiC nanocomposites.

Figure 7.5 High magnification SEM images of the 1.5 vol% GPL-Si

3

N

4

nanocomposites (arrows illustrate the location of GPL on the fracture surface).

Figure 7.6 Preparation of CNT–metal matrix composites via chemical routes.

Figure 7.7 Common geometries of reinforcement particle and respective surface-to-volume ratios.

Figure 7.8 A simple route for synthesis of polymer–metal oxide nanocomposites [N. Kumar, Unpublished work].

Figure 7.9 Color fluorescence image of (a) QD-poly(lauryl methacrylate) composite rods excited by a UV Hg-lamp ( = 365 nm). Lee et al. [22], © 2000. With permission of Wiley-VCH; (b) PVA films containing Au nanorods aligned parallel and perpendicular to the electric field of polarized incoming light (P, represents a polarizer). Pérez-Juste et al. [23], ©2005. With permission of Wiley-VCH.

Figure 7.10 Types of composite derived from interaction between clays and polymers: (a) phase-separated microcomposite; (b) intercalated nanocomposite; and (c) exfoliated nanocomposite.

Figure 7.11 Nylon-6 nanocomposite formed through

in situ

polymerization with ADA–MMT.

Figure 7.12 Carbon nanotube/polymer matrix nanocomposite.

Figure 7.13 SEM micrograph of NiCr–WC coatings with (a) single-layer 60% carbide concentration and (b) double-layer graded coating with outer layer 60% WC over inner layer of 15% WC.

Chapter 8: Unique Properties

Figure 8.1 Schematic representation of tunneling.

Figure 8.2 Relationship between size, energy, and energy of states of nanoparticles.

Figure 8.3 Evolution of the band gap and the density of states as the number of atoms in a system increase.

Figure 8.4 Calculated structures of the fullerene C

60

(a) and of the Au

32

(b) nanoclusters, which are both hollow.

Figure 8.5 Size dependence of the dispersion for cubic particles with

n

=

N

1/3

atoms along an edge.

Figure 8.6 Calculated mean coordination number as a function of inverse radius for magnesium clusters of different symmetries (triangles: icosahedra, squares: decahedra, diamonds: hexagonal close packing).

Figure 8.7 (a) Schematic illustration of the excitation of the dipole surface plasmon oscillation. (b) and (c) Characteristic UV–Vis spectra corresponding to the spherical and rod-shaped Au NPs, respectively.

Figure 8.8 Absorption (a) and Fluorescence (b) spectra of longer gold nanorods (230 nm, upper trace) and shorter gold nanorods (30 nm, lower trace) in aqueous solution. Li et al.[12], © 2005. With permission of RSC.

Figure 8.9 Fluorescence in CdSe–CdS core–shell nanoparticles with a diameter of 1.7 nm (blue); 3.7 nm (green) and ∼6 nm (red) giving evidence of the scaling of the semiconductor band gap with particle size. Courtesy of H. Weller, University of Hamburg.

Figure 8.10 The energy levels of valence and conduction bands of core and shell in type I heterostructural QDs.

Figure 8.11 Comparative band gap in (a) metals; (b) insulator; (c) semiconductor.

Figure 8.12 Schematic of the density of states exhibited by bulk metal relative to increasingly smaller nanoclusters. The approximate diameter, nuclearity, and Kubo gap for each size regime are indicated.

Figure 8.13 Voltage endurance characteristics for nanocomposites using 4 µ tip/plane electrodes. (a) Epoxy-TiO

2

, (b) XLPE-SiO

2

.

Figure 8.14 The different magnetic effects in magnetic nanoparticles shown through spin arrangement in (a) ferromagnet; (b) antiferromagnet

D

= diameter,

D

c

= critical diameter; (c) combination of two different ferromagnetic phases; (d) magnetic moments in a superparamagnet; (e) exchange coupling; and (f) pure antiferromagnetic.

Figure 8.15 Calculated electronic orbitals for the core–shell icosahedral cluster AlPb

12

+

.

Chapter 9: Applications of Nanotechnology

Figure 9.1 Nanobiosensor. (a) Silicon nanowires surface modified with avidin molecules (purple stars), which selectively bind a streptavidin-functionalized molecule or nanoparticle. Courtesy of Raj Mohanty, Boston University, USA. (b) Nano-gold surface immobilized with dengue antigen–BSA conjugate for detection of dengue using SPR technique. Kumbhat et al. [4], ©2010. With permission of Elsevier.

Figure 9.2 Optical image of a flexible paper display containing an LED array (25 × 16). Russo et al. [9], ©2011. With permission of Wiley-VCH Verlag Gmbh and Co.

Figure 9.3 Illustration of (a) barcode and (b) the RFID tag.

Figure 9.4 (a) Solar radiations reaching to earth surface; (b) solar spectrum.

Figure 9.5 Typical sandwich-type dye-sensitized TiO

2

nanocrystal solar cell.

Figure 9.6 Schematic illustration of the structure of (a) quantum dot sensitized solar cell (QDSC) and (b) photoinduced charge transfer processes following a laser pulse excitation. Kamat [16], © 2013. With permission of ACS.

Figure 9.7 Nano-architectures of hybrid solar cell materials. (a) Blend of semiconductor nanoparticles and conducting polymer films; (b) blend of semiconductor nanorods and conducting polymer films; (c) blend of semiconductor nano-tetrapods and conducting polymer films. Courtesy of Liu [17].

Figure 9.8 Thermoelectric devices.

Figure 9.9 (a, b) Nanowires made of piezoelectric materials embedded in shoe sole to generate electricity from mechanical motion such as a human walking or running. http://www.mdpi.com/1424-8220/14/7/12497. Used under CC-BY 3.0. http://creativecommons.org/licenses/by/3.0/.

Figure 9.10 Schematic representation of a fuel cell.

Figure 9.11 Schematic representation of facile cycling of Ti-doped LiAlH

4

for high-performance hydrogen storage.

Figure 9.12 Schematic representation of a lithium-ion battery.

Figure 9.13 The complete invisibility system based on metamaterials: (a) Schematic representation of metamaterial showing bending of light. http://www.physics.org. (b) Quantum stealth mock-up using metamaterial. Courtesy of G. Cramer, Hyper Stealth Biotechnology Corp. [27].

Figure 9.14 Space transportation with nanotubes: faster, better, cheaper. [http://www.ipt.arc.nasa.gov/spacetransport.html.]

Figure 9.15 Antibacterial textiles: (a) interaction between bacteria and coating of AgNPs within sol–gel-based silicate material. Hamm et al. [35], © 2012. With permission of ACS; (b) doctor's sterile suit containing nanosilver. http://www.ecouterre.com/.

Figure 9.16 Specific advantages of nanotechnology in sports equipment.

Chapter 10: Toxicity and Environmental Issues

Figure 10.1 Possible pathways of exposure of nanoparticles to human body.

Figure 10.2 Relocation of inhaled NPs after deposition on the alveolar epithelium. Kreyling et al. [6],

©

2013. With permission of ACS.

Figure 10.3 Classification of natural and engineered nanoparticles existing in the environments.

Figure 10.4 Indoor air pollution from cooking.

Figure 10.5 Deposition of inhaled particles in the human respiratory tract versus particle diameter.

Figure 10.6 The risk assessment paradigm integrated with life cycle stages of nanomaterials.

List of Tables

Chapter 1: Introduction

Table 1.1 Bio-Inspired Unique Properties

Table 1.2 Milestones Associated with the Evolution of Nanoscience and Nanotechnology

Table 1.3 Characteristics of Nanomaterial and Their Importance

Table 1.4 Size and Shape-Related Attributes and Properties of nanomaterials

Table 1.5 Summary of Some Commercialized Nano-Based Products and Their Specific Applications

Chapter 2: Nanomaterials: General Synthetic Approaches

Table 2.1 Common Techniques for Synthesis of Nanomaterials

Table 2.2 Substrate–Ink Combinations for DPN

Table 2.3 Extracellular Bionanosynthesis of Nanoparticles

Chapter 3: Characterization Tools for Nanomaterials

Table 3.1 Common Investigation Techniques for the Characterization of Nanoparticles

Table 3.2 Fundamental Properties of Electrons

Table 3.3 Electron Wavelength and Velocity at Different Acceleration Voltage

Table 3.4 Comparative Overview of Characteristics of Different Electron Guns

Table 3.5 Characteristic Features of Optical, Electron, and Scanning Probe Microscopes

Table 3.6 Key Attributes of AFM for the Characterization of Nanoparticles

Table 3.7 Radiations Used in Scattering-Based Characterization Techniques

Chapter 4: Nanomaterials

Table 4.1 Important Metallic Nanomaterials

Chapter 5: Carbon-Based Nanomaterials

Table 5.1 A Comparative Account of Different Methods for Synthesis of CNTs

Table 5.2 Potential Applications of Chemically Modified CNTs

Chapter 6: Self-Assembled and Supramolecular Nanomaterials

Table 6.1 Summary of Supramolecular Interactions

Chapter 7: Nanocomposites

Table 7.1 Critical Size of Reinforcement Applicable to Different Properties

Table 7.2 Classification of Nanocomposites and Typical Examples

Table 7.3 Physical and Mechanical Properties of GPL-Si

3

N

4

Nanocomposites

Table 7.4 Nanoceramic Metal–Matrix Nanocomposites and Associated Properties

Table 7.5 Potential Application Areas and Unique Properties of CNT-Reinforced Metal Matrix Composites

Table 7.6 Classification and Examples of Clay Minerals

Table 7.7 Potential Application Areas of Polymer–Graphene Nanocomposites

Chapter 8: Unique Properties

Table 8.2 Change in Surface Area on Size Reduction

Chapter 9: Applications of Nanotechnology

Table 9.1 Areas of Application of Nanotechnology

Table 9.2 Nanomaterials for Air Pollution Control

Table 9.3 Nanomaterials Based Commercially Available Batteries

Table 9.4 Chemical Sensors and Biosensors Based on Nanomaterials

Table 9.5 Enhanced Properties of Textile Fibers with Inclusion Nanostructure

Table 9.6 Attributes Nanomaterials in Sports Equipments and Its Associated Benefits

Chapter 10: Toxicity and Environmental Issues

Table 10.1 Measured Concentrations of Nanoparticles Resulting from Various Common Indoor Household Activities

Table 10.2 Expected Toxicological Effects of Engineered Nanoparticles

Table 10.3 Best Practices for a Nanotechnology Laboratory

Essentials in Nanoscience and Nanotechnology

Narendra Kumar

Sunita Kumbhat

Copyright © 2016 by John Wiley & Sons, Inc. All rights reserved

Published by John Wiley & Sons, Inc., Hoboken, New Jersey

Published simultaneously in Canada

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permissions.

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Library of Congress Cataloging-in-Publication Data:

Names: Kumar, Narendra (Materials scientist), author. | Kumbhat, Sunita, author.

Title: Essentials in nanoscience and nanotechnology / Narendra Kumar, Sunita Kumbhat.

Description: Hoboken, New Jersey : John Wiley & Sons, Inc. 2016. | Includes bibliographical references and index.

Identifiers: LCCN 2015040306 | ISBN 9781119096115 (cloth)

Subjects: LCSH: Nanotechnology. | Nanoscience.

Classification: LCC T174.7 .K78 2016 | DDC 500–dc23 LC record available at http://lccn.loc.gov/2015040306

Preface

The turn of twenty-first century has witnessed the emergence of three cutting-edge technologies, namely, Information and Communication Technology (ICT), Biotechnology, and Nanotechnology. In 2005, the United Nations Task Force on the Millennium Development Goals touted Nanotechnology as one of three platform technologies that can reduce hunger, promote health, improve water sanitation, develop renewable resources, and improve the environment, and recommended that developing countries should initiate nanotechnology programs at a national level. Inspired by such forecasts, by 2014, over 60 countries followed the United States and established the National Nanotechnology Initiative. These countries range from advanced industrial countries in Europe and Japan to the emerging markets of Russia, China, Brazil, and India.

Physicist Richard Feynman, in his famous speech of 1959, forecasted the development of nanoscience and the punch line “plenty of room at the bottom” became reality by the 1980s when scientists developed techniques and tools to explore and manipulate matter at the atomic scale. The term “nanoscale” defines a size range from 1 to 100 nm, although a scientifically based range goes from the atomic scale (0.2 nm) to 100 nm. The focus on the nanoregime relates to the convenience of some standard definition that can be used to both categorize nanotechnology, nanoscience, and nanoproducts and act as a bridge between quantum mechanical effects and surface area effects.

Nanoscience is not merely about size; it is about the unique physical, chemical, biological, and optical properties that emerge naturally at the nanoscale, whereas nanotechnology is related to the ability to manipulate and engineer such effects. It is a broad new area of science that demolishes boundaries among physics, chemistry, biology, cognitive science, materials science, and engineering at the nanoscale. New technologies, however, are likely to revolutionize the economy and the society only if there is a broader strong National base consisting of trained manpower and infrastructure that allows a new technology to spread and transform to its exciting niche applications, whether civilian or military. To do so, the most important thing is to educate and train the budding manpower at the school and university levels. For that, availability of standard books is necessary, and this book is designed keeping in mind these essential requirements.

Furthermore, keeping in view the unprecedented research and development in the area of nanoscience and nanotechnology and to make the students aware about the latest developments in the field, we have attempted to write this book in a manner as simple as possible while including the latest development in the field. The subject matter of the book, ranging from fundamentals to the latest developments and technological applications, is presented in 10 chapters. The first chapter on introduction gives a historical prospective, provides living examples of nanoscience in nature and artificial nanomaterials, and brings out the likely impact of nanotechnology on human civilization. Chapter 2 describes general synthetic approaches and strategies, while Chapter 3 deals with the characterization of nanomaterials using modern tools and techniques to provide the basic understanding to students who are interested in learning this emerging area. Chapters 4–7 deal with different kinds of nanomaterials such as inorganic, carbon-based nanocomposites, and self-assembled/supramolecular nanostructures, respectively, in terms of their varieties, synthesis, and properties. Following this, Chapters 8 and 9 are devoted to the unique properties and applications of nanotechnology in various disciplines such as information technology, pollution, environment, energy, healthcare, consumer goods, and so on. Finally, the last chapter deals with the toxicological and ethical issues associated with nanotechnology.

We believe this book will generate and promote the basic understanding on the complex and revolutionary disciplines of nanoscience and nanotechnology, which is offered now as a core subject in most of the academic institutions across the globe.

Acknowledgments

Writing a book is always a dedicated effort requiring patience and hidden support of family members, which both the authors have been fortunate to enjoy during the course of writing this book. In this context, Dr. Kumar would like to thank his wife, Mrs. Soma Jain, who supported him at every step and without whom it would have been impossible to accomplish writing this book. She showed immense strength in bearing with little time he could spend with her. Dr. Kumar would like to thank his children and their spouses, Anjali and Vikas; Atul and Parul; Akshaya and Pragati for their support, and his grandchildren Kratyagya, Kritika, and Eshna for always cheering him up. Dr. Kumbhat would like to acknowledge her husband, Air Cmde Jinendra Kumbhat, for being her pillar of strength and standing beside her throughout the course of writing this book. He has been her inspiration and motivation for continuing to improve her knowledge and move her career forward. Dr. Kumbhat would like to thank her children and their spouses, Shruti and Mehul; Kunal and Sonal, who have all been such wonderful and encouraging children.

The authors would like to express their gratitude to a number of distinguished academicians, researchers, and reviewers for their support, discussions, and critical reviews made during the course of writing this book. Dr. Kumar would like to acknowledge the support of students and members of his research group, including Dr. S. R. Vadera, Director, of Defence Laboratory of Jodhpur, Prof. K. Manzoor, Drs Rashi Mathur, A. K. Shukla, M. K. Patra, S. C. Negi, Manoth Mathew, D. R. Sharma, Vivek Kumar Singh, S. Gowda, Vatsana Gupta, Jitendra Singh, and Manoj Dhaka for their ever willing support while Prof. Kumbhat would like to acknowledge the support of Prof. R. P. Singh, Vice Chancellor, of Jai Narain Vyas University, Jodhpur, and her colleagues from the Department of Chemistry for their support in planning and execution of the courses related to nanoscience and nanotechnology. She also acknowledges the ever-willing support of her research students, Drs Urmila Nain, Sushma Dave, Omprakash Khatri, Jaya Jain, Richa Vyas, Kamesh Gangawat, Manjulata Parihar, Rakhee, Kavita, Uravsini Singh, Hema Somani, Ved Prakash, and Menka Khicher.

The authors would like to thank John Wiley & Sons, Inc., for taking up this project and Ms. Anita Lekhwani, Senior Acquisitions Editor, and her team members including Ms. Cecilia Tsai and Ms. Purvi Patel at John Wiley, Hoboken, New Jersey for their consistent interest, timely action in execution of this project, and making the publication of this book a reality.

About the Authors

Dr. N. Kumar, Former Director, Defence Laboratory, Jodhpur

Dr. Narendra Kumar, DRDO fellow, graduated and did his PhD degree in “Organometallic Chemistry” in 1976 from Delhi University. From 1976 to 1981, he served at the National Physical Laboratory, New Delhi, and worked toward the development and application of materials including organometallics, liquid crystals, electrochromics, and electrode materials. He served as a postdoctoral research fellow at Windsor University, Canada, during 1981–1983 and worked in the field of electrochemical synthesis of metallic and organometallic complexes of transition and actinide elements. In 1984, he joined as Scientist at the Defence Laboratory, Jodhpur, and retired from there as its Director in 2012, where he carried out pioneering research work in the development of conducting polymers, liquid loam, nanomaterials, and products based on them for various defence applications. Dr. Kumar has published more than 100 research and review articles in international journals in the areas of Nanoscience, Organometallics, Conducting Polymers, and Electrochemical Synthesis, and also a chapter entitled “Nanotechnology for Sensor and Display Applications” in the Encyclopedia of Nanoscience and Technology published by American Scientific Publication, USA. He has 12 patents to his credit and authored one book entitled Nanotechnology and Nanomaterials in the Treatment of Life Threatening Diseases published by Elsevier (USA) in 2013. He also served as a visiting Research Associate of CSIR, New Delhi, during 1992–1995 and is a recognized supervisor of J. N. V. University, Jodhpur, for PhD and has guided 6 students for their PhD degrees in the area of nanoscience. He has delivered several invited talks on Conducting Polymers and Nanomaterials in several International and national conferences/seminars, as well as at universities in India, Japan, and the United States.

He received the DRDO Technology Cash Award in 1996 for his pioneering research work on conducting polymers, and DRDO Scientist of the Year award in 2005 from the Prime Minister of India for products based on conducting polymers and nanomaterials for defense applications. He is a recipient of the National MRSI-ICSC Super Conductivity and Materials Science Annual Award for the year 2010 by Materials Research Society of India. Dr. Kumar is a member of various scientific societies including the prestigious American Chemical Society.

Dr. S. Kumbhat, Professor, Department of Chemistry, Jai Narain Vyas University, Jodhpur

Dr. Sunita Kumbhat, Professor and Chemistry Department at J.N.V. University, Jodhpur, has graduated in Chemistry and obtained her PhD degree in the field of Electrochemistry in 1985 from J.N.V. University, Jodhpur. She did postdoctoral research in the fields of Photoelectrochemistry and Sonovoltammetry with Prof. R.G. Compton at Oxford University, UK. Dr. Kumbhat joined the Department of Chemistry, J.N.V. University, as permanent faculty member in 1986, and has been serving as a Professor since 2001 where she has been involved in teaching graduate and postgraduate courses on Analytical Chemistry, Electrochemistry, Sensors, and Nanoscience and supervising PhD students. Her areas of interest are Electrochemistry and Biosensors for Biomedical and Environmental Analysis. She has more than 50 research papers in international journals, three educational films, and one patent to her credit. She has supervised 14 research students for their PhD degrees. Her awards and recognition include Commonwealth Academic Staff Fellowship (1994–1995) at Oxford, UK, National Associate (1997) at BARC, Mumbai, and the INSA–JSPS Visiting Fellowship (2005) at Kyushu University, Fukuoka, Japan. Dr. Kumbhat is associated with various Indian and International scientific societies and is also an assessing member of the National Assessment and Accreditation Council, Bangalore, India.

Chapter 1Introduction

1.1 Definitions of Nanoscience and Nanotechnologies

Nanoscience

is a new discipline concerned with the unique properties associated with nanomaterials, which are assemblies of atoms or molecules on a nanoscale. Nanoscience is actually the study of objects/particles and its phenomena at a very small scale, ranging roughly from 1 to 100 nm. “Nano” refers to a scale of size in the metric system. It is used in scientific units to denote one-billionth of the base unit, approximately 100,000 times smaller than the diameter of a human hair. A nanometer is 10

−9

m (1 nm = 10

−9

m), a dimension in the world of atoms and molecules (the size of H atom is 0.24 nm and, for instance, 10 hydrogen atoms lined up measure about 1 nm). Nanoparticles are those particles that contain from 100 to 10,000 atoms. Thus, the particles in size roughly ranging from 1 to 100 nm are the building block of nanomaterials.

Nanomaterials:

These materials are created from blocks of nanoparticles, and thus they can be defined as a set of substances where at least one dimension is approximately less than 100 nm. However, organizations in some areas such as environment, health, and consumer protection favor a larger size range from 0.3 to 300 nm to define nanomaterials. This larger size range allows more research and a better understanding of all nanomaterials and also allows to know whether any particular nanomaterial shows concerns for human health or not and in what size range. Nanocarbons such as fullerenes, carbon nanotubes, and graphene are excellent examples of nanomaterials. A comparison of the size of nanomaterials with some natural and biological species is illustrated in

Figure 1.1

.

Nano-object:

Material confined in one, two, or three dimensions at the nanoscale. This includes nanoparticles (all three dimensions in the nanoscale), nanofibers (two dimensions in the nanoscale), and nanoplates (one dimension in the nanoscale). Nanofibers are further divided into nanotubes (hollow nanofiber), nanorods (solid nanofiber), and nanowire (electrically conducting or semiconducting nanofiber). However, the term nano-object is not very popular.

Particle:

It is a minute piece of matter with defined physical boundaries. A particle can move as a unit. This general particle definition applies to nano-objects.

Nanoparticle:

It is a nano-object with all three external dimensions in the nanoscale. Nanoparticles can have amorphous or crystalline form and their surfaces can act as carriers for liquid droplets or gases.

Nanoparticulate matter:

It refers to a collection of nanoparticles, emphasizing their collective behavior.

Agglomerate:

It is a group of particles held together by weak forces such as van der Waals forces, some electrostatic forces, and surface tension. It should be noted that agglomerate will usually retain a high surface-to-volume ratio.

Aggregate:

It is a group of particles held together by strong forces such as those associated with covalent or metallic bonds. It should be noted that an aggregate may retain a high surface-to-volume ratio.

Nanotechnology

is the construction and use of functional structures designed from atomic or molecular scale with at least one characteristic dimension measured in nanometers. Their size allows them to exhibit novel and significantly improved physical, chemical, and biological properties, phenomena, and processes because of their size. Thus, nanotechnology can be defined as research and development that involves measuring and manipulating matter at the atomic, molecular, and supramolecular levels at scales measured in approximately 1–100 nm in at least one dimension.

Figure 1.1 Size comparisons of objects, nanomaterials, and biomolecules.

When characteristic structural features are intermediate between isolated atoms and bulk materials in the range of approximately 1–100 nm, the objects often display physical attributes substantially different from those displayed by either atoms or bulk materials. The term “nanotechnology” is by and large used as a reference for both nanoscience and nanotechnology especially in the public domain. We should distinguish between nanoscience and nanotechnology. Nanoscience is a convergence of physics, chemistry, materials science, and biology, which deals with the manipulation and characterization of matter on length scales between the molecular and the micron size. Nanotechnology is an emerging engineering discipline that applies methods from nanoscience to create products.

1.2 Uniqueness of the Nanoscale

At nanoscale, the laws of physics operate in an unfamiliar way because of two important reasons: high surface-to-volume ratio and quantum effect. The key reason for nano-sized regime being special is the dramatic increase in the surface-to-volume ratio. When the size of building blocks gets smaller, the surface area of the material increases by six orders of magnitude, as illustrated in Figure 1.2, while the volume remaining the same. For example, dissecting a 1 m3 of any material into 1 nm particles increases the total combined surface area from 6 to 60,000,000 m2, approximately 10 million times larger [1]. Nanomaterials have a wider range of applications such as catalysts, cleanup, and capture of pollution and any other application where chemical reactivity is important such as medicine. This effect occurs at all length scales, but what makes it unique at the nanoscale is that the properties of the material become strongly dependent on the surface of the material since the amount of surface is now at the same level as the amount of bulk. In fact, in some cases such as fullerenes or single-walled nanotubes, the material is entirely the surface.

Figure 1.2 Exponential increases in surface area for cubes ranging from meter to nanosize.

Another important attribute of nanoscale materials is the fact that it is possible for the quantum mechanical properties of matter to dominate over bulk properties. One example of this is in the change in the optical properties, for example, in the photoemission, of many semiconductor materials as they “go nano.” Figure 1.3 illustrates how, a material whose optical properties may be considered uninteresting, simply by changing its size to the nanoscale one can control the color of the material [2]. This effect is due to quantum confinement.

Figure 1.3 Change in optical properties of a semiconductor ranging from bulk to nanosize. Courtesy of Grossman, MIT, USA.

Important consequence of each of these properties is that they offer completely new methods of tuning the properties of materials and devices. Nanotechnology can provide unprecedented understanding about materials and devices and is likely to impact many fields. By using structure at nanoscale as a tunable physical variable, we can greatly expand the range of performance of existing chemicals and materials. Nanoscience and nanotechnology are broad and interdisciplinary areas of research and development activity that have been growing explosively worldwide in the past two decades. Nanoscience has the potential for revolutionizing the methods in which materials and products are created and the range and nature of functionalities that can be accessed; nanotechnology already has a significant commercial impact that will increase exponentially in future.

1.3 Nanoscience in Nature

Nanostructures are plentiful in nature. In the universe, nanoparticles are distributed widely and are considered to be the building blocks in planet formation processes. Indeed, several natural structures including proteins and the DNA diameter of around 2.5 nm, viruses (10–60 nm), and bacteria (30 nm to 10 µm) fit the above definition of nonmaterial, while others are of mineral or environmental origin. For example, these include the fine fraction of desert sand, oil fumes, smog, fumes originating from volcanic activity or from forest fires, and certain atmospheric dusts. Biological systems have built up inorganic–organic nanocomposite structures to improve the mechanical properties or to improve the optical, magnetic, and chemical sensing in living species. As an example, nacre (mother-of-pearl) from the mollusk shell is a biologically formed lamellar ceramic, which exhibits structural robustness despite the brittle nature of its constituents. These systems have evolved and been optimized by evolution over millions of years into sophisticated and complex structures. In natural systems, the bottom-up approach starting from molecules and involving self-organization concepts has been highly successful in building larger structural and functional components. Functional systems are characterized by complex sensing, self-repair, information transmission and storage, and other functions all based on molecular building blocks. Examples of these complex structures for structural purposes are teeth, such as shark teeth, which consist of a composite of biomineralized fluorapatite and organic compounds. These structures result in the unique combination of hardness, fracture toughness, and sharpness. The evolution has worked on much smaller scales too, producing finely honed nanostructures, parts less than a millionth of a meter across, or smaller than 1/20th of the width of a human hair help animals climb, slither, camouflage, flirt, and thrive. Figure 1.4a shows an electron microscopic image of a sensory patch in amphibian ears, which consists of a single bundle of stereo cilia projecting from the epithelium of the papilla, and acts as a nanomechanical cantilevers that measure deflections as small as 3 nm because of sound waves. Many of the shimmering colors in butterfly's wings are produced not with pigments but with nanostructures. The scales on their wings are patterned with nanoscale channels, ridges, and cavities made of chitin, a protein. Unlike pigments, which create color by absorbing some wavelengths of light and reflecting the rest, the nanostructures are shaped so that they physically bend and scatter light in different directions, sending particular colors back to our eyes. This scattering can also make them iridescent (i.e., the color changes with the angle one sees it from. When infrared radiation hits the chitin nanostructures, their shape changes because of expansion, thus changing the colors they display. Figure 1.4b shows glittering colors of peacock feather where barbs project directly from the main feather stem, and barbules (∼0.5 mm long) attached to each side of the barb generate the typical “shimmer” of iridescence. Electron microscopy (Figure 1.4c and d) of barbules reveals a highly ordered structure of melanin rods of high refractive index embedded in keratin of lower refractive index with air tube between each square of melanin rods. The whole array of melanin rods, keratin matrix, and air holes comprises a 2D photonic crystal. There is much interest on mimicking these natural wonders with potential applications in optical engineering and communications. Less seriously, photonic crystal pigment-free paints would not fade, fabrics might be more vibrant.

Figure 1.4 Nanotechnology in nature: (a) electron microscopic image of a sensory patch in amphibian ears. http://scinerds.tumblr.com/post/35542105310/stereocilia-stairsteps; (b) peacock feather showing barbules, representing a photonic lattice; (c and d) electron microscopy image of transverse and longitudinal sections of barbules. Zi et al. [2a] © 2003. With permission of National Academy of Sciences, USA.

The compound eye of arthropods uses nanoscale features to enhance their visual sensitivity. An insect's compound eye has about 50–10,000 individual facets, which are studded with an array of nanoscale protuberances called “corneal nipples” (Figure 1.5a and b), each with its own set of optical machinery. These tiny structures of size ranging from 50 to 300 nm cut down the glare that reflects off the insect eye. The nanoscale nipple pattern on moth eyes has inspired new antireflective coatings (Figure 1.5c) for solar cells. The male silk moth can detect, with single-molecule precision, the pheromones of a female moth emitted up to 2 miles away. Spider silks are some of the toughest materials known to man, stronger than steel, and their webs can withstand gusts of wind. The spider's silks get their strength from just nanometers of thin crystal proteins, which are stacked with hydrogen bonds, allowing the silk to stretch and flex under pressure.

Figure 1.5 Natural and fabricated antireflective surfaces: (a) schematic of a moth; (b) scanning electron micrograph of antireflective surface of a moth's eye (scale bar = 1 µm); (c) biomimetic replica of a moth eye fabricated with ion- beam etching.

Parker & Townley [2c] © 2007. With permission of Nature Publishing Group.

These are only a few of the countless examples of how nature employs nanotechnology in different methods, of course, with the most important technology to us being the human body itself, which contains billions of nanoscale machines! It is both fascinating and humbling to observe that despite all of the phenomenal technological advances in nanoscale synthesis and characterization, in most cases we are still unable to build nanotechnology-based devices that even come close to nature.

1.3.1 Naturally Occurring Nanomaterials

Naturally occurring nanomaterials may originate from one of the following sources:

i.

Natural erosion and volcanic activity

Nanoparticles are part of mineral world since they are naturally produced from erosion and volcanic explosions.

ii.

Clays

Minerals such as clays are a type of layered nanostructured silicate materials that are characterized by a fine 2D crystal structure. Mica, one among them, is the most studied [3]. In mica, a large number of silicate sheets are held together by relatively strong bonds. On the other hand, montmorillonite, a smectic type of clay, has relatively weak bonds between layers. Each layer consists of two sheets of silica held together by cations such as Li+, Na+, K+, and Ca2+