Springer Handbook of Nanomaterials

Graphene is the two-dimensional allotrope of carbon, consisting of a hexagonal arrangement of carbon atoms on a single plane. This chapter explores the history of graphene, as the theoretical building block for other carbon allotropes as well as its rise as a material in its own right in recent years. Graphene can be fabricated by different methods including mechanical exfoliation, chemical vapor deposition, and decomposition of SiC, although bulk-quantity production of pristine graphene remains a challenge. The atomic and electronic structure of graphene is described, highlighting the strong correlation in graphene between structure and properties, as is the case with other carbon allotropes. Graphene exhibits a number of unique and superlative electronic and optical properties. The intrinsic properties of graphene can be tailored by nanofabrication, chemistry, electromagnetic fields, etc. Various applications of graphene have been proposed in electronic, optoelectronic, and mechanical products. In addition, graphene has emerged as a candidate in chemical, biochemical, and biological applications. Derivatives of graphene such as graphene oxide or graphane are also of interest in terms of both fundamental

graphane

graphene

oxide (GO)

properties and applications.

The discovery of buckminsterfullerene 25 years ago opened a new field in materials science in which different disciplines such as physics, chemistry, medicine, mathematics, and engineering came together. This discovery is a clear example of what we now call nanoscience, thus having important implications for several applications in what is known as the nanotechnology of carbon materials. In this chapter, a revision of the most important advances in this area, involving the multidisciplinarity of the field, is given. Special emphasis is given to the geometry, production methods, physicochemical behavior, applications, future perspectives, and the relationship to other layered materials such as graphene,

graphene

boron nitride, and metal chalcogenides.

Single-walled carbon nanotubes (SWCNTs) are hollow, long cylinders with extremely large aspect ratios, made of one atomic sheet of carbon atoms in a honeycomb lattice. They possess extraordinary thermal, mechanical, and electrical properties and are considered as one of the most promising nanomaterials for applications and basic research. This chapter describes the structural, electronic, vibrational, optical, transport, mechanical, and thermal properties of these unusual one-dimensional (1-D) nanomaterials. The crystallographic (Sect.

4.2.1

), electronic (Sect.

4.2.2

), vibrational (Sect.

4.2.3

), optical (Sect.

4.4

), transport (Sect.

4.5

), thermal (Sect.

4.6.1

), and mechanical (Sect.

4.6.2

) properties of these unusual 1-D nanomaterials will be outlined. In addition, we will provide an overview of the various methods developed for synthesizing SWCNTs in Sect.

4.3

.

Even after more than two decades of extensive basic studies since their discovery, carbon nanotubes continue to surprise researchers with potential new applications and interesting discoveries of novel phenomena and properties. Because of an enormous thrust towards finding practical applications, carbon nanotube research is actively being pursued in diverse areas including energy storage, molecular electronics, nanomechanical devices, composites, and chemical and bio-sensing.

Structurally, carbon nanotubes are made up of sp

2

-bonded carbon atoms, like graphite, and can be conceptually viewed as rolled-up sheets of single-layer graphite, or graphene. Their diameter typically lies in the nanometer range while their length

single-layer

graphite

graphite

single-layer

often exceeds microns, sometimes centimeters, thus making them 1-D nanostructures. Depending on the number of

nanostructure

tubes that are arranged concentrically, carbon nanotubes are further classified into single-walled and multi- walled nanotubes.

carbon nanotube (CNT)

Single-walled carbon nanotubes, the subject of this chapter, are especially interesting. They are ideal materials in which to explore one-dimensional physics and strong Coulomb correlations. In addition,

Coulomb

correlation

their cylindrical topology allows them to exhibit nonintuitive quantum phenomena when placed in a parallel magnetic field, due to the Aharonov–Bohm effect. A number of research groups have found exotic many-body effects through a variety of transport,

Aharonov–Bohm effect

optical, magnetic, and photoemission experiments.

Their electronic properties are very sensitive to their microscopic atomic arrangements and symmetry, covering a wide spectrum of energy scales. They can be either metallic or semiconducting with varying band gaps, depending on their diameter and chirality. Semiconducting nanotubes are particularly promising for photonic device applications with their

semiconducting

nanotube

nanotube (NT)

semiconducting

diameter-dependent, direct band gaps, while metallic tubes are considered to be ideal candidates for a variety of electronic applications such as nanocircuit components and power transmission cables.

Multi-walled carbon nanotubes (MWCNTs)

multi-walled carbon nanotube (MWCNT)

are elongated cylindrical nanoobjects made of sp

2

carbon. Their diameter is 3–30 nm and they can grow several cm long, thus their aspect ratio can vary between 10 and ten million. They can be distinguished from single-walled carbon nanotubes on the basis of their multi-walled Russian-doll structure and rigidity, and from carbon nanofibers on the basis of their different wall structure, smaller outer diameter, and hollow interior. This chapter

tube interior

introduces MWCNT synthesis methods, discusses the chemistry and properties of multi-walled carbon nanotubes, and gives examples of their application. References to single-walled carbon nanotubes (SWNT)

single-walled carbon nanotube (SWNT)

are kept at a minimum.

It is well known that carbon nanotubes possess outstanding electrical and mechanical properties, and if they are modified these

carbon nanotube (CNT)

modified

properties can be improved or other novel characteristics can appear. In addition, these modified carbon nanotubes, being different from their pure counterparts, now require additional studies to assess their toxicity and biocompatibility.

Generally speaking, carbon nanotubes can be classified as single-, double- or multi-walled, and each type can be modified; For example, these tubular structures can be doped with foreign atoms, incorporate structural defects, and/or be functionalized with different molecules. These local modifications greatly modify their electronic and chemical properties, and can be understood by using a variety of microscopy and spectroscopy techniques.

In Sect.

6.1

, we describe the general concepts and synthesis for the main doping types. In Sect.

6.2

, we focus on the different types of defects that can be introduced into nanotubes so as to modify their physicochemical properties. Section

6.3

discusses the categories of nanotube chemical functionalization and their resulting effects. The electrochemical properties of modified carbon nanotubes are an important topic that needs further investigation, and Sect.

6.4

reviews the latest advances in this area. The characterization techniques mainly used to study modified carbon nanotubes are reviewed in Sect.

6.5

. Some applications of modified carbon nanotubes are described in Sect.

6.6

. Finally, aspects of the toxicity and biocompatibility of modified carbon nanotubes are presented in Sect.

6.7

. The chapter finally provides an outlook and perspectives in the field.

Carbon nanofibers are sp

2

-based linear, noncontinuous filaments that are different from carbon fibers, which are continuous with diameter of several micrometers. This chapter provides a review on the growth, structural properties, and practical applications of carbon nanofibers as compared with those of conventional carbon fibers. Carbon nanofibers can be produced via catalytic chemical vapor deposition (CVD)

chemical vapor deposition (CVD)

as well as the combination of electrospinning of organic polymer and thermal treatment. The amount of commercially available carbon nanofiber worldwide is ca. 500 t/year. Carbon nanofibers exhibit high specific area, flexibility, and superstrength due to their nanosized diameter, which allows them to be used in electrode materials of energy storage devices, hybrid-type filler in carbon-fiber-reinforced plastics, and bone tissue scaffold. It is envisaged that carbon nanofibers will be key materials of green science and technology through a close combination with carbon fibers and carbon nanotubes.

This chapter presents a brief survey of the different classes of nanodiamond particles and a comparison of their purity, structure, and physical properties. The primary focus of this chapter is on nanodiamond particles produced by detonation shock wave-assisted synthesis, thus harnessing the energy of explosives. Selected applications of nanodiamond particles are discussed, including for polishing, as a filler material for nanocomposites, in drug delivery, and for chemical vapor deposition of diamond films.

Noble metal nanoparticles

noble metal (NM)

nanoparticle

in general and their gold and silver analogs in particular are attracting huge interest from the scientific community owing to their fabulous properties and diversity of applications. Mankind has been fascinated by gold and silver

gold and silver

since prehistoric times, and applications of their nanoparticles have attracted attention for millennia, although understanding phenomena at the nanoscale is very recent. Nanoscale analogs are being explored due to their unusual functional attributes quite unlike the bulk. As research in this area moves forward, scientists are discovering novel application possibilities. Tunability of properties by varying size, shape, composition, or local environment presents them with unusual capabilities. By manipulating the chemical composition of the materials at the nanoscale, their electrical, chemical, optical, and other properties can be manipulated precisely. In this chapter, an overview of their history, diversity, strategies of synthesis, and optical properties is presented. The specialized methods employed for synthesis of anisotropic nanosystems are also discussed. Approaches to modulate the properties of these systems postsynthetically either through chemical reactions or by the formation of superstructures via assembly are also covered. Methodologies for fabricating functionalized nanomaterials are also discussed. Various proposed applications of such materials are pointed out. A glimpse into a newly emerging category of noble metal nanosystems called quantum clusters is also given.

Since nanosized metals

nanosized

metal

with magnetic features, and porous and noble metals, are discussed in other chapters of this handbook, here we present a complementary, comprehensive review on other metal nanostructures. Accordingly, this chapter is devoted to review the strategies of synthesis as well as properties of the most common transition- and post-transition-metal nanoparticles.

metal

nanoparticle (NP)

nanoparticle (NP)

metal

Particular attention is paid to scalable production methods and enabled or foreseen applications of such metals, including low-melting-point lead, bismuth, tin, and indium, some of the refractories including tungsten, molybdenum, tantalum, and titanium, as well as a few more of the very commonly used metals such as copper, aluminum, and zinc. The review is expected to help the readers to get a glance at the state-of-the-art in the field and to foster new studies to overcome chal lenges associated typically with controlled bulk production and exploitation of this family of nanomaterials.

An overview is provided of nanostructured alloy materials as both isolated particles with nanoscale diameter (nanoalloys) and

nanoalloy

bulk materials with nanoscale structure. The methods for preparing and characterizing these systems from both experimental and theoretical modeling points of view are presented, and the basic knowledge on their structural, catalytic, mechanical, optical, and magnetic properties is reviewed. It is shown that, due to the increased freedom associated with composition and chemical ordering, new physical phenomena appear in metal multicomponent nanosystems, as well as novel or profoundly modified properties: For example, new structural motifs can arise depending on the structural and energetic characteristics of the metal components, and

metal

component

the size of the system. Hence, the catalytic activity, mechanical strength, plasmonic and nonlinear optical, as well as magnetic responses exhibit features in multicomponent nanostructured systems which are different and can in principle be finely tuned

nanostructured

system

with respect to their pure counterparts. The challenges associated with full exploitation of these possibilities are outlined.

The chapter starts by defining some concepts and principles specific to the field of nanoalloys which are then used in the next sections (Sect.

11.1

). A brief overview of the methods for preparing (Sect.

11.2

) and characterizing (Sect.

11.3

) nanostructured alloys then follows. The core of the chapter (Sect.

11.4

) presents a discussion of the properties of these

nanostructured

alloy

materials, distinguished into: structural, catalytic, optical, and magnetic. Section

11.5

is devoted to nanostructured bulk alloys. A brief section on applications (Sect.

11.6

) and an outlook (Sect.

11.7

) conclude the chapter.

magnetic nanostructure

characterization techniques

Advances in magnetic nanostructures are rapid in the field of science and technology due to the unique magnetic properties observed at the nanoscale such as superparamagnetism, enhanced magnetic moment, high saturation field, shape anisotropy, etc. The common morphologies of magnetic nanostructures are dots, nanoparticles, nanocrystals, nanowires, nanotubes, and thin films. With the emergence of new synthesis and fabrication techniques, magnetic nanomaterials with diverse shapes and sizes have been fabricated

characterization technique

magnetic nanostructure

and their structure–property relationships established. Characterization techniques such as magnetic

magnetic

force microscopy (MFM)

Lorentz

microscopy

force microscopy (MFM), Lorentz microscopy, magnetometry based on superconducting

superconducting quantum interference device (SQUID)

quantum interference device (SQUID), and small-angle neutron scattering

small angle neutron scattering (SANS)

(SANS) have been utilized to study magnetism in nanostructures.

In this chapter, the magnetism of atoms is discussed and the effect of nanostructuring on magnetic properties is

magnetic

length scale

reviewed. Characteristic magnetic length scales are presented. When the size of magnetic materials, in at least one dimension, becomes comparable to characteristic magnetic length scales, size-specific magnetic properties such as superparamagnetism, remanence enhancement, random anisotropy, and giant

giant magnetoresistance (GMR)

magnetoresistance (GMR) effects are observed. The change in magnetic moment and anisotropy with dimensionality is discussed; e.g., broken symmetry at surfaces and interfaces may increase magnetic moment compared with the bulk counterpart. In nanostructured materials, shape and surface anisotropy is induced and thickness dependence of anisotropy is observed in thin films.

Magnetization reversal mechanisms and the use of micromagnetic modeling in establishing microstructure–property relationships

micromagnetic modeling

magnetization reversal

mechanism

are discussed. Magnetic nanostructures such as particles, nanowires, nanorings, thin films, and molecular nanomagnets are reviewed. Current trends in synthesis

molecular

beam epitaxy (MBE)

by physical (melt spinning, ball milling, sputtering, and molecular beam epitaxy (MBE)) and chemical (reduction, self-assembly, and electrodeposition) processes are outlined. The use of atomic

Mössbauer spectroscopy

force microscopy, Mössbauer spectroscopy, electron holography, scanning electron microscopy, and transmission electron microscopy is discussed. The magnetic properties of hard and soft nanostructured magnets are reviewed. Exchange-coupled nanocomposites and the GMR effect are also

magnetic nanostructure

application

data storage

discussed. Applications of magnetic nanostructures in data storage and biomedical applications are summarized.

Nanoparticles are small clusters of atoms about 1–100 nm long. The term “nano” derives from the Greek word

nanos

, which means dwarf or extremely small. A nanometer is a billionth of a meter or 10

−9

 m. Nanostructured materials have attracted the attention of different types of people such as scientists, engineers, etc. Essentially, the reason is that nanocrystals

nanocrystal

in the 1–10 nm range make up a new realm of matter in which physical and chemical properties change as size changes. Metal oxide nanoparticles

metal oxide nanoparticle

are an important class of materials for their optical, magnetic, and electronic properties and have a wide range of applications such as in catalysts, sensors, optical materials, electrical materials, and magnetic storage. Synthesis routes

synthesis

route

for nanoparticles can be broadly classified into solid-state and soft chemical routes such as gel combustion, coprecipitation, sol–gel, hydrothermal/solvothermal, sonochemical, template synthesis, etc. This chapter deals with the various properties of nanoparticles synthesized using different techniques. The application of nanooxides

nanooxide

as sorbents for environmental remediation is also discussed in this chapter.

Understanding ferroelectricity in perovskite, bulk dense nanograin ceramics

nanograin

ceramics

is a fundamental issue that has remained unsolved for decades. The novel development of an unconventional pressureless two-step sintering strategy featuring densification without grain growth is deemed particularly exciting because it is more desirable for commercial production. Using this technique, high-density pure barium titanate (BT) ceramic samples could be produced, which allowed for better understanding of the size effect in nanometer-scale BT ceramic

barium titanate (BT)

ceramic

ceramic

barium titanate (BT)

systems and to address real industrial applications. In this chapter, we describe the methods for fabrication of highly dense piezoelectric nanoceramics followed by the systemic investigation of the size effect on the microstructures and piezoelectric behavior of (1-

x

)BiScO

3

-

x

PbTiO

3

(BSPT) nanoceramics. BSPT ceramics with average grain size from the micrometer scale down to 10 nm have been prepared by a two-step

sintering

two-step

sintering method. The microstructures and properties of these bulk dense nanocrystalline ceramics were characterized by means of x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), scanning probe microscopy (SPM), and hysteresis-loop and dielectric measurements.

This chapter introduces a peculiar carbon compound previously named as graphitic acid, graphite oxide

graphitic

acid

graphite

oxide (GO)

GO (graphite oxide)

graphene

oxide (GO)

(GO), or more recently, graphene oxide (GO). It is basically a wrinkled two-dimensional carbon sheet with various oxygenated functional groups on its basal plane and peripheries, with thickness of around 1 nm and lateral dimensions varying from a few nanometers to several microns. It was first prepared by the British chemist B.C. Brodie in 1859, and became very popular in the scientific community during the last half decade, simply because it was believed to be an important precursor to graphene (a single atomic layer of graphite, the discovery of which won Andre Geim and Konstantin Novoselov the 2010 Nobel Prize in Physics). Several strategies have been introduced to reduce GO back to graphene; however, in this chapter we mainly focus on GO itself, and more relevantly, its synthesis, chemical structure, physical and chemical properties, and possible applications. We emphasize here that, despite its strong relevance to graphene, GO also has its own scientific significance as a basic form of oxidized carbon and technological importance as a platform for all kinds of derivatives and composites that have already demonstrated various interesting applications. The synthesis recipes include the Brodie and Staudenmaier methods (Sect.

15.1.1

), the Hummers method and its modification (Sect.

15.1.2

), and the Tour method (Sect.

15.1.3

). Section

15.2

covers characterization methods together with chemical structure models as well as physical properties of graphite oxide. In the application section (Sect.

15.3

) several examples are given, followed by concluding remarks in Sect.

15.4

.

Graphite nanoparticles are known to be unstable due to the abundance of rim atoms with dangling bonds, closing into fullerenes and nanotubes under appropriate conditions. It was proposed in 1992 that this property is common also to nanoparticles of inorganic layered materials rather than being limited to carbon. Indeed, inorganic fullerene-like nanoparticles (IF) and inorganic nanotubes (INT) were produced initially from the layered materials WS

2

and MoS

2

, and subsequently from numerous other layered compounds. The state of the art in this field is described briefly in this review.

This chapter reviews the main methods used for IF and INT synthesis and discusses the relations between the different mechanisms and the resulting morphologies. Emphasis is placed on methods reported recently. The main differences between the morphologies are presented using WS

2

and MoS

2

as representatives of the inorganic IF/INT family. The measured properties of W(Mo)S

2

IF and INT are further examined and compared with theoretical calculations.

Finally, current applications of WS

2

and MoS

2

IF and INT are reviewed, highlighting recent advances in the fields of tribology and nanocomposite materials.

Controlling the morphology of nanomaterials

morphology of nanomaterial

nanomaterial

morphology

is important for their fundamental study and practical application. Especially one-dimensional nanowires, nanorods, and nanotubes and two-dimensional nanoplates possess interesting physical and chemical properties due to their structural anisotropy. The key to obtaining these morphologies is to break the symmetry of crystal growth to promote anisotropic growth. In this chapter we discuss the catalyst- and template-free screw-dislocation-driven nanomaterial growth mechanism,

growth

mechanism

in which an axial screw dislocation creates self-perpetuating growth steps upon intersecting with the crystal surface and enables anisotropic crystal growth under low supersaturation conditions. The presence of screw dislocations

screw dislocation

not only alters the growth kinetics

nanomaterial

growth kinetics

of nanomaterials, but also distorts the crystal lattice and generates a strain field, both of which lead to morphology variation of the nanomaterials. The structural characteristics associated with dislocation-driven growth can be readily detected using transmission electron microscopy techniques. A review is presented on a wide range of nanomaterials formed under various conditions whose growth has been confirmed to be driven by screw dislocations, demonstrating the generality of this mechanism. A framework for rationally synthesizing anisotropic nanomaterials

anisotropic

nanomaterial

nanomaterial

anisotropic

via dislocation-driven growth is provided. This will enable large-scale, low-cost production of nanomaterials for various applications.

Homogeneity is supposed to be a particular feature of glasses leading to the well-known isotropic optical properties and

glass

mechanical behavior. However, in some cases heterogeneity can be detected at the molecular scale. Amorphous phase separation, incipient crystallization, and concentration gradients are representative of heterogeneities that can be exploited in the preparation of nanostructured glass-derived materials.

Nuclear magnetic resonance (NMR)

nuclear magnetic resonance (NMR)

is one of the spectroscopic methods widely used for characterization of the structure of glassy materials, and the basis of new NMR techniques for study on the medium range is first presented in Sect.

18.1

. Afterwards, nanoceramics with small crystal volume fractions and crystal dimensions of some nanometers are described, displaying new emerging properties (Sect.

18.2

). Metal nanoparticles, quantum dots, and lanthanide-containing nanocrystals are some of the structures that can be grown in glasses (Sect.

18.2

). Glasses are unique in the sense that they can be obtained in any morphology, and a final perspective is presented for glass waveguides containing these nanoscale heterogeneities (Sect.

18.3

).

This chapter provides insight into the composition, preparation, properties, and applications of composites based on polymer matrix

polymer

matrix material

and different forms of nanosized carbon filler. Carbon nanotube and graphene filler materials are discussed in greater

graphene

carbon nanotube (CNT)

detail. The dispersion and orientation of these fillers and the interfacial adhesion between the filler and the matrix material play important roles in determining the mechanical, electrical, and other properties of the composites created. Accordingly, this chapter describes the role as well as the characterization techniques of these properties.

In particular, it will be shown how Raman spectroscopy is becoming an important noninvasive technique both to characterize the

Raman

spectroscopy

electronic structure and to follow the deformation behavior of carbon-based nanomaterials. Such spectroscopic knowledge reveals the intrinsic properties of these nanomaterials, the interaction of the reinforcement with the surrounding environment, and hence the efficiency of the mechanical reinforcement in these composites.

This chapter aims to provide an insight into the physics and chemistry of nanoparticle–liquid systems. The first part of the chapter discusses parameters and effects that influence dispersion stability (Sect.

20.1

), including particle size and shape as well as the interactions at the interface between the solid and liquid phases. Section

20.2

summarizes the practical aspects of making a dispersion, collecting and listing hundreds of examples from contemporary literature. Because of the broad spectrum of materials in question, the survey is limited to dispersions of inorganic nanoparticles including metals, their oxides/sulfides, some (compound) semiconductors, as well as nanostructured carbon particles such as fullerenes, nanotubes, and graphene/graphite (Sect.

20.3

). Dispersions of polymers of either synthetic or biological origin lie beyond the scope of this work. Since a very large fraction of applications are related to various surface coatings using dispersions as the source of nanoparticles, Sect.

20.4

is devoted to drying phenomena and particle self-ordering.

In this chapter, we mainly describe the fabrication, properties, and potential applications of nanoporous metals (NPMs) with random porous structure. Nanoporous metals represent an interesting type of nanostructured material

nanoporous metal

with nanosized porosity and ultrahigh specific surface area, and thus possess unique mechanical, physical, and chemical properties associated with their nanoporous structure. Based upon the porosity distribution, nanoporous metals can be classified into two categories: one has a random porous structure, and the other has a regular pore distribution. Nanoporous metals with random porous structure can be synthesized by the dealloying strategy, whereas template methods are normally used to fabricate nanoporous metals with more

dealloying

regular pore distribution. Nanoporous metals date back to the days of Raney (1920s) when high specific surface metal catalysts were prepared by dealloying Al-based alloys in alkaline solutions. In the new century, monolithic nanoporous metals received renewed attention due to the observation of a series of very intriguing structural properties. Nanoporous metals made by dealloying exhibit a three-dimensional bicontinuous interpenetrating ligament (metal)–channel (void) structure with a length scale of several

ligament–channel structure

nanometers to hundreds of nanometers, and the characteristic size can be modulated to as large as several microns by treatments such as thermal annealing. In contrast, the template technique can precisely control the pore size and microstructure of nanoporous metals, but dynamic modulation of the dominant length scale is virtually impossible. In addition, nanoporous metals are different from metallic foams, which have a length scale of several microns to more than 1 cm, and are normally used as damping and acoustic materials. Here, we mainly focus on dealloyed nanoporous metals. Firstly, the dealloying method and formation mechanism of nanoporous metals are reviewed based upon previous experimental observations and computer simulation. Secondly, we summarize recent knowledge on microstructures of nanoporous metals and their unique properties (catalytic, electrocatalytic, mechanical, sensing, optical, etc.). Finally, potential applications of nanoporous metals are discussed in the fields of fuel cells, catalysis, sensors, actuators, etc.

Zeolites are natural materials that have surrounded us since the beginnings of the history of mankind. They may have been used by ancient man instinctively; however, their use is only documented from about the middle of the 18th century. They became the wonder materials of the 20th century, and remain so in our time as well. Their secret lies in their porous structure, the wide variety of their three-dimensional channel system, and the diversity of their pore size, reaching nanometer dimensions. Their synthesized varieties have many applications, as described in this chapter, but perhaps the most important is their use as catalysts. Indeed, their use in acid-catalyzed isomerization of straight-chain hydrocarbons to produce high-octane gasoline has shaped our world and generated much wealth. However, this is not their only catalytic application; their tunable structural features and the constrained environment they provide allow their use in catalysis of many types of reactions, tremendously influencing the selectivities of transformations.

Porous anodic aluminum oxide (AAO) is one of the typical self-organized fine structures

anodic aluminum oxide (AAO)

with cylindrical pores of uniform diameter arranged in a hexagonal array. AAO has been commonly used as a template for synthesis of nanostructures with a variety of materials. In this chapter, we first describe the preparation of AAO templates with various pore structures, such as straight, branched, and step-shaped pores. Then, we focus on the use of AAO with different pore structures as templates for construction of nanostructures with various architectures, including one-dimensional

one-dimensional (1-D)

(1-D) nanostructures and nanoheterostructures with linear and complex shapes.

Porous silicon (PS) is a nanoporous material obtained by electrochemical etching of crystalline silicon. Since

crystalline

silicon

silicon

crystalline

nanoporous

material

its discovery in the mid 1950s it has been investigated as an active material in a number of research fields. The complexity of silicon electrochemistry, which is not yet completely understood, enables fine-tuning of etched nanoporous structures from the scale of a few nanometers up to tens of microns in a nearly continuous way (Sects.

24.1

,

24.2

). Historically, porous silicon was investigated for its bright visible luminescence and the possibility of realizing efficient silicon-based light emitters. Later, the shaping of complex photonic crystal (PC) structures led to porous silicon returning to the limelight in the form of silicon-based photonics. In fact, compared with other fabrication technologies (such as physical or chemical deposition methods), electrochemical etching has some fundamental advantages: it is a cheap and fast method that does not require complex facilities; it allows fabrication of complex structures with extremely high optical quality, composed by hundreds of layers; and moreover it enables etching of huge-aspect-ratio (> 100) structures in a short time (Sects.

24.3

–

24.6

). Lastly, applications of porous silicon in optical sensing and drug delivery have maintained interest in porous silicon as an extremely lively field.

Nanomaterials, notable for their extremely small feature size, have the potential for wide-ranging industrial, biomedical, and

nanomaterial

electronic applications. Organic nanomaterials, with the utility of weak noncovalent interactions for the design and self-assembly

organic nanomaterial

of molecules one by one into desired structures, give the potential advantages of constructing building blocks using synthetic chemistry at multiple levels, and open the

bottom-up

route for synthesis of organic and polymeric nanostructures; for example, self-assembly

self-assembly

of organic molecules with the assistance of noncovalent interactions, such as hydrogen bonding, electrostatic interactions, and pi-stacking, provides a powerful strategy for synthesis of molecular nanostructures, which have been attracting particular attention since the 1990s as a

bottom-up

paradigm

bottom-up

paradigm

of nanosciences, and discrete nanoparticles with controlled chemical composition and size distribution are readily synthesized. However, the assembly of well-defined nanostructures in large areas, the tuning of noncovalent interactions for efficient assembly, and the dynamics and model of the self-assembly process remain challenging and demanding tasks. There is still a long way to go to achieve true mastery of the art. It will be attractive to find a simple, efficient, and controllable way to produce organic nanomaterials in large areas (mass production) as well as to bridge their applications in organic optoelectronics. In fact, organic nanomaterials have been projected as active components in optoelectronic devices

optoelectronic device

recently, not to mention the great efforts invested in manipulating their morphologies and tailoring their functions. The overall aim of this chapter is to bring together science and applications on organic nanomaterials with emphasis on synthesis and preparation, processing, characterization, and applications of organic nanomaterials

organic nanomaterial

that enable novel or enhanced properties or functions, including experiments and applications.

The increasing demand for a suitable bone implant material

bone implant

implant

bone

bone implant

material

has been forcing researchers to work on various man-made materials that may be used as a suitable replacement for natural bone and are affordable and easy to fabricate. In the past years, although significant efforts have been made in tissue engineering and regenerative medicine to put forward an ideal bone

regenerative medicine

implant, they are far from meeting the real objective. Recent advances in nanobiotechnology

nanobiotechnology

in the field of therapeutics hold great promise to achieve the objective of an ideal implant in proper synchronization with tissue engineering.

tissue engineering

Nanocomposites, a product of synergistic efforts in nanobiotechnology and tissue engineering towards an ideal orthopedic implant, possess enormous potential for use as suitable bone implant material. Along with discussing the existing/conventional bone implant materials and their shortcomings, the main focus of this chapter is to elucidate nanocomposite as a potential next

conventional

bone implant

bone implant

conventional

generation bone implant material. In this review, attempts have been made to deliver concise and relevant information about various nanofabrication technologies,

nanofabrication

characterization of nanocomposites, and their in vitro and in vivo biocompatibility study. Primary investigations support that nanocomposites are an ideal implant material for orthopedic applications; however, substantial developments are still highly needed to put nanocomposites into real practice, where current leanings in nanobiotechnology foreshadow a bright future through the use of nanocomposites in orthopedics.

orthopedic

use of nanocomposites

After defining the quest for bone implants, Sect.

26.2

gives a brief introduction to bone, and its structure and composition will be discussed. Section

26.3

gives a description and highlights shortcomings of conventional implant materials, followed by Sect.

26.4

describing the challenges posed by conventional and existing implants. In Sect.

26.5

a detailed study of the possible role of nanotechnology for suitable orthopedic implants are presented. Future perspectives in Sect.

26.6

close the chapter.

Since its inception, the field of tissue engineering

tissue engineering

has sought to rebuild the complexity of normal tissues by seeding cells onto scaffolds to support the formation of new tissue. Recently, nanofibers have gained increasing attention because these biomaterials have unique properties and are able to interface with cells at the same scale as native extracellular matrix fibrils. New fabrication technologies provide novel ways to control the nanoscale structure and properties of biomaterials, which is advantageous in the engineering of tissues for in vitro study and in vivo applications in regenerative medicine. This chapter explores the properties of nanofiber biomaterials (diameters <500  nm) and examines the specific advantages relative to other scaffold materials. This includes nanofibers from biopolymers

biopolymer

as well as synthetic polymers, with consideration of relative advantages and disadvantages. A range of fabrication strategies

fabrication

strategy

is discussed that span from fiber spinning techniques, to phase separation in bulk, to directed and self-assembly. Insight is provided as to how synthetic polymers and biopolymers are used to make these nanofibers

nanofiber

and the specific molecular structures that impart the unique mechanical, electrical, chemical, and biological properties. Analysis of these nanofiber biomaterials

nanofiber biomaterial

requires characterization techniques that are able to probe at the nanometer, micrometer, and macroscales. Examples are provided using optical microscopy, electron microscopy, scanning probe microscopy, mechanical characterization, and as sessment of biocompatibility

biocompatibility

and biodegradation.

biodegradation

Finally, nanofiber biomaterials have wide applications in tissue engineering; here we focus on representative examples in cardiac, musculoskeletal, ophthalmic, and neural tissue engineering.

Materials play a key role especially in the field of energy storage and conversion. Design of efficient and cost-effective materials for energy applications is of prime research focus. This chapter presents the recent trends in the energy-related applications of various carbon nanotubes (CNT) and their hybrid nanostructures. Development of CNT-based

carbon nanotube (CNT)

electrocatalysts for proton exchange membrane fuel cells and CNT-based electrodes for supercapacitors and Li-ion batteries are discussed.

manufactured nanomaterial (MNM)

Manufactured nanomaterials (MNMs) with unique physical and chemical properties have attracted a great deal of attention as key materials to underpin future scientific and technological advancements. Applications of MNMs can also provide breakthroughs in the construction industry by reinforcing mechanical properties, decreasing vulnerability to chemical corrosion and accidental damage, and providing supplementary functions such as anti-biofouling and hydrophilicity. With the

material

performance

enhancement of material performance and functionality, use of MNMs enables (partial) nonutility generation, low carbon emission, and self-assessment of structural health to increase the sustainability of buildings and infrastructures. On the other hand, recent research into the safety of MNMs has raised concerns about their adverse biological and environmental effects. There is a high probability that MNMs used in construction will have hazardous effects on human and ecological receptors, considering that MNMs incorporated into construction materials would be released via multiple exposure routes during their entire lifecycle (manufacturing, construction, demolition, and recycling/disposal). Consequently, to responsibly utilize the potential benefits of nanotechnology in construction, multidisciplinary efforts are required to develop proactive strategies to mitigate the environmental release of MNMs and guidelines to manage their environmental risks throughout construction-related activities.

Plasmonic nanoparticles

plasmonic

nanoparticle

nanomedicine

are being researched as a noninvasive tool for ultrasensitive diagnostic,

ultrasensitive diagnostic

spectroscopic, and, recently, therapeutic technologies. With particular antibody coatings on nanoparticles, they attach to abnormal cells of interest (cancer or otherwise). Once attached, nanoparticles can be activated/heated with ultraviolet (UV)/visible/infrared (IR), radiofrequency (RF) or x-ray pulses, damaging the surrounding area of the abnormal cell to the point of death. Here, we describe an integrated approach to improved plasmonic therapy

photodynamic therapy

plasmonic

therapy

composed of nanomaterial optimization and the development of a theory for selective radiation nanophotothermolysis of abnormal biological cells with gold nanoparticles and self-assembled

self-assembled

nanocluster

self-assembled

nanoclusters.

nanocluster

The theory takes into account radiation-induced linear and nonlinear synergistic effects in biological cells containing nanostructures, with focus on optical, thermal, bubble formation, and nanoparticle explosion phenomena. On the basis of the developed models, we discuss new ideas and new dynamic modes for cancer treatment

cancer treatment

by radiation-activated nanoheaters, which involve nanocluster aggregation in living cells, microbubbles

microbubble

overlapping around laser-heated intracellular nanoparticles/clusters, and the laser thermal explosion mode of single nanoparticles (

nanobombs

) delivered to cells.

This chapter provides an overview of different filtration processes (Sect.

31.1

) and the mechanism of nanofiltration (Sect.

31.2

). In the following sections, we focus on nanofiltration based on carbon nanotube membranes. A brief introduction to carbon nanotubes and their structure and properties is given, with an emphasis on the different kinds of synthesis of membranes; their function in nanofiltration in gas–vapor transport, liquid transport, and some other filtration-like techniques for filtration of bacteria and viruses is also discussed in detail (Sect.

31.3

). Finally, an outlook of future research is proposed.

Manufactured nanoparticles

nanoparticle (NP)

manufactured

of different chemical compositions are now widely commercially applied. They are found in places as diverse as food packaging and automotive bumpers, where their special nanoscale properties help to lower cost while improving performance. Given these widespread applications, the unintended effects of manufactured nanomaterials on workers, consumers, and the environment have become a focal point for international research. Initially, the human health effects of nanoscale materials were of most interest, but more recently identification of nanoscale particles in wastewater sludge has turned attention towards their environmental impacts.

environmental impact

Though the topic of nanomaterial safety

nanomaterial

safety

has received substantial attention in the literature, many basic questions about nanoparticle transport, fate, and toxicology remain unanswered. A central challenge for researchers has been the definitive characterization of particular manufactured nanomaterials,

manufactured nanomaterial (MNM)

environmental properties

particularly in commercial products that have significant human or environmental exposure. Careful determination of the physical size, surface chemistry, internal structure, and intermediate stability of manufactured nanomaterials helps investigators compare results, as well as link unwanted biological outcomes to particular material features. This chapter provides an overview of the current exposure and toxicity studies of manufactured (e.g., engineered) nanomaterials. A special emphasis in this chapter is the practice used for nanomaterial characterization

nanomaterial characterization

as it relates to their biological and environmental properties.