22.1 Introduction

The term nanotechnology is the combination of two words: the Greek numerical prefix nano referring to a billionth along with the word technology. As an outcome, nanotechnology or nanoscaled technology is generally considered to be at a size below 100 nm (a nanometer is one billionth of a meter). Nanoscale science (or nanoscience) studies the phenomena, properties, and responses of materials at atomic, molecular, and macromolecular scales, and in general at sizes between 1 and 100 nm. In this scale, and especially below 5 nm, the properties of matter differ significantly (i.e., quantum-scale effect plays an important role) from that at a larger particulate scale. Nanotechnology is thus the design, manipulation, fabrication, production, and application, by controlling the shape and size, the properties, responses and functionalities of structures, devices, and systems on the order of or less than 100 nm [1,2].

Nanotechnology is considered an emerging technology due to the possibility to advance well-established products while developing new products with totally exceptional characteristics and functions with enormous potential in a wide range of applications. In addition to various industrial uses, great innovations are foreseen in the information and communication technology, biology and biotechnology, medicine and medical technology, metrology, and so on. Significant applications of nanosciences and nanoengineering lie in the fields of pharmaceutics, cosmetics, processed food, chemical engineering, high-performance materials, electronics, precision mechanics, optics, energy production, and environmental sciences. Nanotechnology is dynamic field where over 50 000 nanotechnology articles have been published annually worldwide in recent years, and more than 2500 patents have been filed [3].

In 1959, Richard Feynman, a renowned physicist, envisioned the theoretical capability of nanotechnology in his famous and unforgettable talk, “There's plenty of room at the bottom,” in which he specified the possibility of manipulating and controlling objects on a very small scale [4].

The principles of physics, as far as I can see, do not speak against the possibility of manoeuvring things atom by atom. It is not an attempt to violate any laws; it is something, in principle, that can be done; but in practice, it has not been done because we are too big.”

-Richard Feynman, Nobel Prize winner in Physics in 1965.

The term “nanotechnology” was popularized by K. Eric Drexler in 1986 in his book Engines of the Creation: The Coming Era of Nanotechnology. He proposed the idea of self-assembly of particles or molecules to build machines in a few nanometers wide. Now, after almost 50 years, realizing the dream of the nanoworld, nanotechnology has become an accepted concept with the emergence of a simple nanoscale technology. Four generations of nanotechnology products have been identified by Mihail (Mike) Roco of the US National Nanotechnology Initiative with a focus on their manufacturing methods and research [5].

1. First generation (∼2001): Passive nanostructures, such as nanostructured coatings, nanoparticle dispersions, and bulk materials (metals, polymers, and ceramics), with the primary focus on the synthesis and control of nanoscale processes along with tools of measurement.
2. Second generation (∼2005): Active nanostructures (transistors, amplifiers, drugs and chemicals, and actuators) with a focus on novel devices and nanobiosensors as the key area of research.
3. Third generation (∼2010): Three-dimensional nanosystems and systems of nanosystems with various synthesis and assembling techniques with a research focus on heterogeneous nanostructures and supramolecular system engineering.
4. Fourth generation (∼2015): Heterogeneous molecular nanosystems having a molecule with specific structure and a different role to play. Multiscale self-assembly would lead to nanoarchistructures with fundamental new functionalities.

The main question is that what makes nanoparticle so unique? The answer lies in understanding the size, shape, and surface topography of a nanoparticle. Particles in the nanometer range exhibit two distinct properties: (i) Laws of classical physics no longer apply below the 50 nm range; therefore, particles are governed by quantum physics. This means that if there is a reduction in size, the electronic, optical, and magnetic properties are altered as compared to their bulk counterparts. (ii) Ratio between the mass and the surface area changes, that is, the smaller the size, the greater the surface area available, thereby leading to unique properties of nanomaterials.

The availability of exceptional large surface area of nanoparticles enables them to react with other substances. In particular, nanoparticles with a crystalline structure have more surface atoms loosely bonded than the strongly bonded interior atoms. Thus, there are proportionately more atoms on the surface and fewer in the interior [6]. For example, if the particle consists of 13 atoms, then there will be 12 atoms on the surface regardless of which packing scheme has been followed. The fraction of atoms present on the surface (P_s, percentage) can be estimated by a simple relation: P_s = 4N^−1/3 × 100, where N is the total number of atoms in a particle [7]. Many potential application areas become prominent in the nanorange. Gold (Au), which is chemically inert in the bulk phase, serves as an efficient catalyst at the nanoscale [8]. Thus, the emergence of relevant physicochemical properties is a fundamental requirement for the design of novel materials, thereby unraveling the unknowns of nanotechnology, which stem from quantum and surface phenomena of matter at the nanoscale.

Nanotechnology can help in solving serious humanity problems, such as energy adequacy, climate change, or fatal diseases. It is an area that has highly promising prospects for turning fundamental research into successful innovations, not only to boost the competitiveness of actual industry but also to create new products that will make positive changes in our daily life, especially in medicine, environment, electronics, or any other field. Nanoscience and nanotechnology open up new avenues of research and lead to new, useful, and sometimes unexpected applications. Novel materials and new-engineered surfaces allow making products that perform better. New medical treatments are emerging for fatal diseases, such as brain tumors and Alzheimer's disease [9].

Nanotechnology involves two main approaches for the fabrication of materials: (i) the “bottom-up” approach leading to the formation of nanostructured building blocks and then assembling them into a final material by principles of molecular recognition; (ii) the “top-down” approach involves the construction of nanoobjects from larger entities without atomic-level control. The latter is similar to the approach used by the semiconductor industry for the fabrication of devices out of an electronic substrate utilizing pattern formation, such as electron beam lithography and pattern transfer processes (reactive ion etching), thereby creating structures at the nanoscale [10]. Analytical science (chemistry) gives a thrust to nanotechnology by coupling it to the new generation of analytical tools, such as atomic force microscopy (AFM) and scanning tunneling microscopy (STM) with processes such as electron beam lithography and molecular beam epitaxy, which allows the manipulation of nanostructures with novel phenomena [11]. Thus, analytical chemistry is important in the development of structures in the nanoregime and devices. The highly interdisciplinary nature plays a major role in the advancement of nanotechnology. It helps in establishing the principles and methods in the application of nanotechnology with the unusual properties of nanomaterials. Morphology, size, and chemical composition are characterized using analytical sciences' tools. In addition, chemical synthesis leads to the fabrication of new nanomaterials with new analytical possibilities. There is a wide range of applications for nanomaterials in electroanalytical investigations and they have the potential to be used in electrochemical sensors with high sensitivity and selectivity based on different strategies.

Electroanalytical analysis based on nanoscience is coupled with the simplicity, speed, high selectivity, and sensitivity of electrochemistry with unique properties of nanomaterials to become one of the most exciting areas of research [12]. Nanotechnology is the engineering of functional materials at the molecular scale, which involves very advanced concepts. It is an envisioned ability to fabricate materials using a bottom-up approach with the present era techniques and tools to fabricate complete high-performance products. It has come a long way since its inception and has found potential applications in daily consumer products, appliances, and in particular in the field of medicine.

Nanomaterials with unique properties, such as nanoparticles, carbon nanotubes (CNT), fullerenes, quantum dots, quantum wires, nanofibers, and nanocomposites, need to find new application opportunities. Products containing engineered nanomaterials are already in the market. The range of commercial products available today is very broad, including metals, ceramics, polymers, smart textiles, cosmetics, sunscreens, electronics, paints, and varnishes. However, new methodologies and instrumentation have to be developed in order to increase our knowledge and information on their properties. Nanomaterials must be examined both for their possible side effects on health as a matter of precaution and for their possible environmental impacts. The development of specific guidance documents at a global level for the safety evaluation of nanotechnology products is strongly recommended. Ethical and moral concerns also need to be addressed in parallel with such fast new developments [13,14].

Huge aspirations are coupled to nanotechnological developments in modern medicine. The potential medical applications are predominantly in diagnostics (disease diagnosis and imaging), monitoring, availability of more durable and better prosthetics, and new drug-delivery systems for potentially harmful drugs. While products based on nanotechnology are actually reaching the market, sufficient knowledge on the associated toxicological risks is still lacking. Reducing the size of structures to nanolevel results in distinctly different properties. In addition to chemical composition, which largely dictates the intrinsic toxic properties, very small size appears to be a dominant indicator of drastic or toxic effects of particles. From a regulatory point of view, a risk management strategy is already a requirement for all medical technology applications [15–17].

Nanotechnology (“nanotech”) is the science that deals with the engineering and manipulation of functional materials on an atomic, molecular, and supramolecular scale, where significant enhancement in the properties is evident compared to their bulk counterparts. It encompasses the different scientific phenomena that develop along all the dimensions ranging from atom clusters, molecular aggregates, supramolecular structures, polymers, and biomolecules. In the case of “nano,” it is difficult to distinguish between the science and the technology since both complement each other. Science involves theory and experiment, whereas technology involves the development, applications, and commercial implications. A generalized description of nanotechnology has been established by the National Nanotechnology Initiative, which defines it as a science working in the range of 1–100 nm. It is a revolutionary science paving the way for almost all fields in the domain of human activity. As an example, the major potential application of carbon based nanomaterials in environmental sector is shown in Figure 22.1.

In order to discuss the advances of nanotechnology, each of the following sections in this chapter will be presented as follows: (i)carbon nanomaterials (CNMs) for environmental devices and techniques, (ii) the impact of functionalized nanomaterial for environmental techniques and nanotechnology in the field of electronics is presented, (iii) nanoseparation devices for environment, focusing on nanodevices which is based on the nanostructured materials, (iv) nanomagnetics for environment that is currently used to characterize and manipulate nanostructures, (v) nano-lab on a chip for environment, (vi) bionanomaterial-based devices for environment, (vii) toxicity, economy, and legalization of nanotechnology, (viii) nanotechnology, a green and sustainable vision for the future and the increasing instrumentation demands.

22.2 Carbon Nanomaterials for Environmental Devices and Techniques

CNMs, including fullerenes, nanotubes, and graphene as well as their N-doped derivatives, have been studied for a wide range of applications in energy conversion systems, such as solar cells and fuel cells. In the past few years, different studies have shown the excellent potential of carbon nanotubes as sensitive material for detecting the biological and chemical molecules, via the functionalization of CNT sidewalls so that a better chemical bonding between specific chemical species and CNT can be reached and the selectivity of the adsorption process can be enhanced. Some properties of CNTs make them very attractive to produce small and wearable sensors for environmental monitoring [18]. Their intrinsic strength makes them suitable for miniaturized sensors and usable on flexible substrates. Their response at room temperature is optimal for ultralow power, wearable, battery-operated devices. The adsorption of a small quantity of chemical species can result in a dramatic change in CNTs' conductivity. Therefore, CNTs are favorable to detect species at low concentrations (e.g., low parts per billion level). A sensor can be fabricated using a simple transducer (comb electrodes) to monitor the electrical resistance of CNT-based film or, alternatively, CNTs can integrate the channel of a FET device [19,20]. Figure 22.2 represents the structure of carbon atom and carbon-based nanoparticles.

However, several fundamental and technological challenges remain to be addressed before CNT-based biosensors can be fully exploited for real-life applications, such as in medical diagnostics, proteomics arrays, and gene chips. The next generation will require highly miniaturized, arrayable design that can be functionalized and monitored in multiplex approach. Further, a clear understanding of how electrical conductance is affected by protein adsorption is lacking, but essential efforts are being carried out to optimize CNT-based biosensor designs. A mechanism has been proposed that the charges on the surface of proteins exert gating effects or charge transfer to CNTs, thereby causing changes in the electrical conductance of CNT-FETs. This is essentially what has been suggested for nanowire-based biosensors. Another possibility is that the protein adsorption on the devices affects the dielectric constant of the electrical double layer in aqueous solution, thereby changing the gate efficiency of the electrolyte [21].

The global energy consumption has been accelerating at an alarming rate. This, together with the limited supply of today's main energy sources (i.e., oil, coal, and uranium) and their detrimental long-term effects on the environment has made it more important than ever to develop renewable energy sources. The sun does provide us with renewable energy sources, which neither run out nor have any significant harmful environmental effects. Ever since the French scientist Alexandre-Edmond Becquerel discovered the photovoltaic effect in 1839, scientists and engineers have devoted considerable effort to realize the dream that human beings can one day convert the energy of sunlight directly into electricity by fine photovoltaic effect to meet daily energy needs. After more than 170 years, however, this dream is yet to be realized. Nevertheless, tremendous success has been made, since the development of the first single-junction inorganic (Si) solar cell at Bell Laboratories in 1954. Although a power conversion efficiency up to 35% has now been achieved for inorganic (III–V semiconductor) multijunction solar cells in a lab scale, the widespread use of the conventional Si-based photovoltaic devices is still limited, due to the difficulties in modifying the bandgap of Si crystals and the high cost associated with the fabrication processes involving elevated temperature and high vacuum. These inorganic solar cells are still too expensive to compete with the conventional grid electricity. Thus, alternative approaches using organic materials, including organic dyes and conjugated polymeric semiconductors, have received considerable attention in the search for novel photovoltaic cells because of their potential benefits over the inorganic materials, including low cost, lightweight, flexibility, and versatility for fabrication (especially over a large area). In this regard, the photoinduced charge transfer of fullerenes is of importance for the development of polymeric photovoltaic cells, which can be used to store light energy as electron relays for producing electricity [22–24].

Recently, solar cells based on quantum dots (QD solar cells) have attracted great interest because of their potential in exceeding the Shockley–Queissar limit of 32% power conversion efficiency for Si solar cells and achieving size-tunable optical absorption and efficient multiple carrier generation. One of the major challenges in developing high-performance QD solar cells is to effectively separate the photogenerated electron–hole pairs and to facilitate the electron transfer to the electrode. Carbon nanomaterials of suitable band energies, such as fullerenes and SWNTs, have been used in QD solar cells as efficient electron acceptors. Instead of burning fuel to create heat, fuel cells convert chemical energy directly into electricity. Although many different types can be proposed and fabricated depending on the nature of the electrolyte materials used, all work using the same principle based on electrochemical cell consisting of an anode, electrolyte, and cathode. By pumping, for example, hydrogen (H₂) gas onto one electrode (the anode), H₂ dissociates into its constituent electrons and protons. While the protons diffuse through the cell toward a second electrode (the cathode), the electrons flow out of the anode to provide electrical power. Electrons and protons both end up at the cathode to combine with oxygen to form water [25–27].

Supercapacitors (electrochemical capacitors or ultracapacitors) are the electrochemical energy storage devices that combine the high energy storage of conventional batteries with the high power delivery capability of conventional capacitors. Supercapacitors have been realized with three principal types of electrode materials, namely, high-surface-area activated carbons, transition metal oxides, and electroactive conjugated polymers. The properties of electrode materials play an important role in determining the performances of the supercapacitors. The unique electrical, mechanical, and chemical properties of CNTs have made them as intensively studied materials in the field of nanotechnology. A number of device applications of these nanoscale materials have been envisioned. Single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) under special conditions have shown to possess ballistic conduction behavior, which makes them attractive candidates for field-emission devices [28–30].

Current biological sensing techniques commonly rely on optical detection principles that are inherently complex, requiring multiple steps between the actual engagement of the analyte and the generation of a signal, multiple reagents, preparative steps, signal amplification, complex data analysis, and relatively large sample size. The techniques are highly sensitive and specific but more difficult to miniaturize. Electronic detection techniques may offer an alternative, but their potential has not yet been explored fully. Field-effect transistors (FETs) fabricated using semiconducting single-wall carbon nanotubes (nanotube FETs, NTFETs) have been extensively studied. Such devices have been found to be sensitive to various gases, such as oxygen and ammonia, and thus can operate as sensitive chemical sensors [31–33].

According to the IUPAC classification, there are three classes of pore sizes: micropores (<2 nm), mesopores (≈2–50 nm), and macropores (>50 nm). It is known that most of the surface area of activated carbons resides in the scale of micropores. Pores of this scale are generally considered to be poorly or not at all accessible for electrolyte ions (especially for organic electrolytes) and thus are incapable of supporting an electrical double layer. In contrast, mesopores contribute the most to the capacitance in an electrical double-layer capacitor. However, recent experimental and theoretical studies have demonstrated that the charge storage in pores of 0.5–2 nm in size (smaller than the size of solvated electrolyte ions) increased with decreasing the pore size, due to the closer approach of the ion center to the electrode surface in the smaller pores. Pores less than 0.5 nm wide are too small for double layer formation. Currently available activated carbon materials have high surface area, but they unfortunately show low mesoporosity, resulting in their low electrolyte accessibility and thus limited capacitance. This translates to the limited energy density of the resultant supercapacitors. Moreover, along with their poor electrical conductivity, the low electrolyte accessibility of activated carbons produces a high internal resistance and hence a poor power density for the capacitors. Consequently, currently available supercapacitors based on these activated carbon electrodes possess a limited energy density (4–5 Wh kg⁻¹) and a limited power density (1–2 kW kg⁻¹). Therefore, new materials are needed to overcome the drawbacks of activated carbon electrode materials in order to improve the performance of the supercapacitors [34–36].

22.3 Functionalized Nanomaterials for Environmental Techniques

Environmental pollution occurs in various matrices, such as air, water, and soils. Pollutants can have harmful effects on humans and animals, entering them via several routes: the food chain, inhalation, and acute or chronic skin contact. It is well known that pollution has become a serious global problem, and various governments and researchers have started to seriously address this growing problem [37–39]. Environmental pollution has increasingly become one of the most significant issues to address the sustainability of our world. Widespread pollution of soil and water is a serious problem for which environmental remediation is urgently needed. The combination of nanotechnology and environmental science has thus become a hot research topic. With the rapid development of nanotechnology, new nanomaterials have resulted in remarkable achievements in this field. Although nanomaterials have gained success in chemical, biological, biomedical, and material field applications, the application of these materials in the environmental field has only begun very recently. Environmental remediation usually involves degradation, sequestration, or other related approaches that result in removal of pollutants to reduce risks to human beings, animals, and environmental reservoirs impacted by chemical and radiological contaminants [40–42].

Functionalized nanomaterials, composed of both organic and inorganic components, have recently been identified as promising candidates for environmental applications. In recent years, due to the rapid progress of nanotechnology, new nanomaterials with specific properties have become a hot field of research in materials science. The unique physicochemical properties of materials induced by various parameters, such as mean size, shape, purity, crystal structure, and surface characteristics can generate effective solutions to the on-going and future challenging environmental and biomedical problems [43,44].

As a result of this approach, a large number of techniques have been developed that enable obtaining novel functional nanomaterials with unique and desirable properties, such as mechanical, electrical, optical, catalytic, and photonic properties, and in particular their extremely high surface area. As a result of these special features, size effect, surface effect, quantum size effect, and macroscopic quantum tunneling effect emerged. The functionalization process is applied to nanomaterials by coating technique or chemical modifications in order to (1) improve the surface and optical properties, (2) to avoid aggregation, and (3) to eliminate the interaction between the nanomaterials and biological substances [45,46].

The application of nanomaterials in the detection and removal of pathogens provides greater sensitivity, lower cost, shorter turnaround times, smaller sample sizes, in-line and real-time detection, higher throughput, and portability in environmental remediation. In addition, metal and metal oxide nanomaterials can be used to remove organic pollutants and metals by reduction or oxidation of nanomaterials and the degree of removal can be enhanced through functionalization with chemical entities that can capture selectively target pollutants in water and air. This method is effective and promising and can be used in the engineering of water and air improvement. Nanomembranes have found applications in the production of potable water, water reclamation, and the removal of toxic heavy metals, dyes, and pesticides from contaminated water. Further improvements must be made in the application of environmental remediation to selectively remove materials, which have greater resistance to changes in pH and the concentrations of chemicals present in the contaminated water, greater stability for a longer period of time, and cost optimization [47,48].

Nanofibrous media have a low weight, high permeability, and small pore size that make them appropriate for a wide range of filtration applications. In addition, nanofiber-based membranes offer unique properties, such as high specific surface area (depending on the diameter of fibers and intrafiber porosity), good interconnectivity of the pores, and the potential to incorporate active chemistry or functionality at a nanoscale. A high flux could be produced via nanofibrous prefilters with even higher loading capacities. Such prefilters can be used in various applications, such as the removal of microparticles from wastewater and with ultrafiltration or nanofiltration membranes to prolong the life of these membranes. On-going investigations are being carried to develop engineered nanomaterials of various fiber diameters and morphologies and identify their effects on the performance of nanofibers. The environmental applications of polymer-supported nanocomposites in photocatalytic/chemical catalysis degradation, the adsorption of pollutants, and pollutant sensing and detection result in a greener environment. However, the study of the interaction between the host polymers and the encapsulated nanoparticles as well as the effect on the dispersion in polluted air and water is necessary. In addition, the large-scale production of polymer-supported nanocomposites and more practical applications remain open. The extensive application of sorbents in environmental remediation has shown the capability of adsorbing metals and organic pollutants from contaminated water and air. Iron-based nanomaterials, TiO₂ nanomaterials, and polymeric adsorbents have shown high adsorption capacities and selectivities [49–51].

The surface modifications of sorbents are being studied for process optimization. Enhancing the reusability of sorbents and the extension of their life span must be explored to reduce the cost of environmental remediation. Sensors have been developed for sensing gases, chemicals, and volatile organic compounds as well as the detection and identification of bacteria. Further developments of nanomaterials' functional properties are necessary in order to meet the need for trace detection and the treatment of pollutants in water and air. Important fundamental and mechanistic studies are also required in order to fully explore their real potentials. One-dimensional CNTs with single and multiple layers have shown superior adsorption capacities in the removal of a diverse range of biological and chemical contaminants, due to their fibrous nanostructure with high aspect ratio and provision of large external surface area. Nanoscale particles composed of CNTs are difficult to be separated from aqueous solution. Ultracentrifugation separation method is efficient to separate CNTs, which requires high energy. The membrane filtration method is an alternative and efficient technique to separate CNTs from aqueous solutions. However, the membrane can be easily blocked. The CNT/metal oxide or magnetic composites are promising materials in environmental pollution management at a large scale. More efforts for the development of practical applications of these CNT-based composites are required in the future. Dendritic nanopolymers have been developed for low-pressure filtration processes to remove perchlorate and uranium from contaminated water as well as metal ions (e.g., copper, silver, nickel, and zinc) from industrial wastewater. The long-term efficiencies of dendritic nanopolymer composites have not been reported and should be addressed in the future [52–54].

22.4 Nanoseparation Device for Environment

Nanoliquid chromatography is a recently developed microfluidic technique, mainly for analytical purposes, offering some advantages over conventional high-performance liquid chromatography (HPLC). Because of its features, this miniaturized technique has gained more and more interest in various application fields resulting in an alternative and/or complementary to HPLC [55]. Separation and accurate identification of highly valuable biomolecules (nucleic acids, proteins, polysaccharides, etc.) from complex biological fluids (serum, milk, cell extracts, etc.) require utmost importance. Development of a microfluidic device for biomolecular separation requires involvement and knowledge of chemistry and other branches of life sciences [56]. Due to the increasing number of chiral compounds introduced every year, separation processes are facing challenges to develop high environmentally benign and economically feasible separation techniques of chiral pharmaceuticals to enable their availability on a commercial scale [57].

Dielectrophoresis (DEP) is a phenomenon in which a force is exerted on a dielectric particle when it is subjected to a nonuniform electric field. This force does not require the particle to be charged. All particles exhibit dielectrophoretic activity in the presence of electric fields. DEP can be a useful technique both for flow manipulation and for separation of charged and uncharged particles. It was earlier believed that DEP flow manipulation of nanosized particles is not possible, as the dominance of Brownian motion-induced force over the DEP force increases with a decrease in particle size. However, with recent advancements in microfabrication, microdevices with very small features can be fabricated to create very high electric field gradient, thus making DEP feasible for flow manipulation of nanosized particles, while minimizing Joule heating [58]. The distinction between NPs and their ionic species is of particular importance. The current challenges in relation to environmental impacts of nanotechnology are to determine the existence of NPs and also the forms and quantities in which they persist in complex environmental media. The issue of whether metal nanoparticles or their ionic species or both pose high risks to aquatic organisms due to the uptake and bioaccumulation remains to be addressed [59]. Their recovery needs contributions of chemistry of selective extractive systems, since the separation of the mixtures into individual elements is usually a complex and expensive process [60].

Nowadays, ion-imprinted polymers have been investigated as highly selective sorbents for solid-phase extraction in order to concentrate and clean up the samples prior to analysis. One potential application that has recently attracted widespread interest is their use for cleanup and enrichment of low-concentration analytes in complex matrices [61]. High-performance liquid chromatography on micro- and nanocolumns has become a very relevant separation technique. Utilization of micro- and nanocolumns is ideal for all the sample-limited applications. Another important benefit is the flow rate compatibility of micro- and nanocolumns with mass spectrometers and better column temperature control. An application of gradient elution makes this separation technique extremely powerful for the separation of solutes of a wide range of polarity, improves the solute detestability, and increases the speed of analysis [62]. With the development of economy and society, the output of oily wastewater is increasing sharply. The separation of oil–water mixtures is becoming an imperative, due to its serious threat to the environment and human beings. Traditional techniques were employed to remove oil from water, such as in situ burning, gravity separation, air flotation, coalescence and flocculation, bioremediation, and adsorption. But these methods often suffered from limitations including high cost, complex separation instrument, low separation efficiency, and secondary pollutants. More recently, taking inspiration from nature, lotus leaves, desert beetle, and the superwetting materials have been fabricated and used for oil–water separation successfully, which was achieved by fabricating rough surfaces and modifying with low-surface energy materials [63]. Due to their inherent features, alumina-based ceramic membranes can easily separate small gas molecules such as hydrogen. With their gas permeation values larger than polymeric membranes, this kind of membranes offer a wide range of applications in chemical, petrochemical, and energy industry, where hydrogen separation under severe conditions results in increased productivity as well as process efficiency. Consequently, porous alumina-based ceramic membranes covered with a thin selective layer manufactured by chemical vapor deposition and legal methods have attracted great attention for hydrogen separation [64].

22.5 Magnetic Nanomaterials for Environment

In recent years, magnetic nanomaterials (MNMs) have attracted considerable attention because of their unique properties that make them very useful in different fields. MNMs have at least one dimension smaller than 1 µm and are possible to be manipulated under the influence of an external magnetic field [65,66]. In addition, below certain critical dimensions, which vary with material characteristics, s superparamagnetic is observed [65,67,68]; thus, the nanomaterials exhibit no magnetic properties upon the removal of the external field and therefore have no attraction for each other, offering the advantage of reducing risk of particle aggregation, and more importantly, they provide a strong response to an external magnetic field [65,68–70].

Water pollution by inorganic and organic compounds, such as heavy metals and dyes, has become a serious problem because of their extremely hazardous effects on humans and ecological systems. The application of magnetic nanoparticles (MNPs) as adsorbent materials in solving environmental problems has recently received great attention due to their unique physical and chemical properties, which make them superior to traditional adsorbents. The use of MNPs as adsorbent materials for environmental remediation has a great potential due to their superior physical and chemical properties in comparison to bulk materials. The easy functionalization of MNPs allows the synthesis of specific nanoadsorbents to perform selective removal of a large variety of pollutants. However, the regeneration process of loaded MNPs needs another stage for the recovery of MNPs. The final management of both the spent regeneration solution and the exhausted adsorbent are the crucial stages that should be evaluated in order to bring MNP-based adsorption technology a step forward [65].

The ability of functionalization by anchoring specific functional entities on their surface makes it possible for the synthesis of different types of engineered MNPs for the removal of a large number of both organic and inorganic contaminants. However, the successful implementation of MNP-based adsorption technology needs the evaluation and optimization of the magnetic recovery stages, the regeneration process, and the management of both the spent regeneration solution and the exhausted adsorbent [65].

Advances in the synthesis methods over the past decades have led to the availability of superparamagnetic nanoparticles with different shell and surface modifications [65,71–76]. MNPs are generally composed of magnetic elements, such as iron, cobalt, nickel, or their oxides like magnetite (Fe₃O₄), maghemite (γ-Fe₂O₃), nickel ferrite (NiFe₂O₄), cobalt ferrite (CoFe₂O₄), and so on [69]. Usually, MNPs are coated with organic layers (e.g., surfactants or polymers such as dextran and polyethylene glycol) or inorganic components, such as metallic elements (e.g., gold or platinum), metal oxides (aluminum oxide, cobalt oxide, etc.), activated carbon, silica, and so on [67,72–74] in order to make them stable against oxidation and spontaneous aggregation to increase their physicochemical stability and provide a functionalizable surface [66].

The use of engineered MNPs for heavy metals and dyes' removal has numerous benefits including higher adsorption capacities and faster removal rates in comparison to the traditional sorbent materials [65]. Also, the regeneration of MNPs for further reuse can be successfully achieved by adequately contacting MNPs with the proper eluent [65]. Moreover, management alternatives of both solid and liquid wastes generated in the process by either material recovery or final disposal have to be reviewed, promoting the zero-discharge processes for ensuring the environmental welfare. Hence, there is a growing interest in the use of MNPs for environmental remediation. However, the application of MNPs in environmental technologies is still in the early stage and much work is needed for the establishment of such nanotechnologies. Nevertheless, the future problems related to poor water quality and water scarcity in many countries make their future quite promising. In this regard, this chapter aims to provide valuable guidelines to accomplish the successful integration of magnetic nanoadsorbents in water treatment technologies, thus trying to offer useful information for the implementation of the nanotechnologies in a near future.

22.6 Bionanomaterial-Based Devices for Environment

Renewable energies have attracted more and more attention due to the rise in the energy consumption and environmental concerns. Nanobiohybrid materials based upon semiconductor nanostructures and a bioprotein have been successfully used for solar energy conversion systems, such as photovoltaic cells and water splitting photoelectrochemical cells. Biomolecule-sensitized solar cells (BSSCs) have been developed as a promising “green” technology for low-cost photovoltaic power generation [77–79]. The mechanism of BSSCs is very similar to dye-sensitized solar cells (DSSCs). DSSCs appeared as a new generation of photovoltaic device and have attracted much attention as potential alternative to traditional photovoltaic devices [77]. The advantages of DSSCs over Si-based solar cells lie in its simple production method, varieties of material sources, low cost, and possible fabrication of flexible solar cells, even though their performances are still low compared to those of Si-based solar cells [80,81].

The use of different nanoscale materials in various fields, including physics, chemistry, biology, and electronics has grown exponentially over the last decade. In recent years, the incorporation of a unique photoactive protein and nanomaterials, such as metallic and ceramic nanostructures, has been studied to enhance the performance of both protein and nanostructures. This combination offers promising strategies to fabricate novel nanobiomaterials for bioelectronics applications. The application of CNTs in nanobiotechnology has become the subject of intense investigation since its discovery in 1991 [82]. Such considerable interest reflects the unique behavior of CNTs, including their high electrical conductivity, excellent biocompatibility, chemical stability, and mechanical strength [83,84]. CNTs with the advantages of high surface area, fast heterogeneous electron transfer, and long-range electron transfer have been widely used to develop nanobioelectronics in the last decade [85,86]. Biomolecules (e.g., proteins and DNA) can also be electrostatically adsorbed onto the surface of CNTs and can be attached to functional entities on modified CNTs [87]. Bradley et al. demonstrated the integration of bacterioprotein and CNT network transistor as a nanoelectronic device [88]. It was found that both components kept their functionality while interacting with each other. The device provided additional details about some characteristics of bacterioprotein like bacteriorhodopsin has an asymmetry in charge distribution. Also, they suggested that by connecting the living cells directly to these nanoelectronic devices, monitoring of certain cell functions in different environments could be possible [89].

Polymer nanotechnology is a vibrant area, which attempts to develop the materials loaded with specialized particulate in nanoscale [90]. Biopolymer nanobiohybrids were studied extensively earlier for food packaging applications [91]. Chitosan films laden with cellulose nanocrystals improved film permeation properties. Nanobiocomposites are a newer class of biopolymer matrices, which apply polymer nanoparticle physicochemical interactions for superior materials design. High surface area of incorporated particulates helps in the improvement of biopolymer thermal and barrier properties [92]. Noncovalent polymer functional interactions in nanoscale are some of the predictable techniques for remarkable properties enhancement.

The application of micro- and nanotechnology in food industry may represent a solution for the potential bioavailability issues, providing new opportunities to address these challenges [93,94], exhibiting novel material functionalities and applications, compared to those at the macroscale [95]. Due to their reduced size, micro- and nanosystems can improve solubility, bioavailability, and sensorial characteristics (e.g., mask unpleasant flavors), prevent undesirable physical and chemical reactions, and protect bioactive compounds from degradation. This behavior can be related to the large surface area to volume ratio and the effect of physical and chemical interactions between the materials, found at lower sized structures (i.e., at micro- and nanoscale), which have a significant impact on the overall properties of those systems [95]. Among these, the incorporation of bioactive compounds in food and the assurance of their stability during processing, storage, and digestion, until reaching the appropriate delivery point and timing, are the main concerns regarding the controlled release of bioactive compounds [93]. On the other hand, size reduction promotes a great improvement in bioadhesive properties that may include a significant increase in adhesive forces, prolonging gastrointestinal (GI) transit time, thus leading to a higher bioavailability, compared to larger particles [96].

22.7 Nano-Lab on a Chip for Environment

“Lab on a chip” refers to devices and methods for controlling and manipulating the fluid flows at microlevels. Lab on a chip is the science and technology of systems that process or manipulate microscopic amounts (10⁻⁹–10⁻¹⁸ l) of fluids. It uses channels with dimensions of tens to hundreds of micrometers. These microfluidic devices are widespread now, and are used in many scientific and industrial contexts. Lab-on-a-chip systems are growing very fast, replacing laboratory procedures and human work. It not only synthesizes chemicals efficiently but also carries out biological and chemical analyses. It has developed its applications in modern chemistry, clinical chemistry, fabrication, engineering and materials science, biology, physics, electronics, aiding communication and collaboration across disciplines. Most biological applications on lab on a chip are already commercialized in global market, whereas for environmental chemistry, the field is still developing [97].

22.8 Toxicity, Economy, and Legalization of Nanotechnology

The 2016 Nobel Prize for Chemistry was awarded to three researchers for their work on the design of tiny molecular machines. Though, this is the first time that nanotechnology has been awarded a Nobel Prize. But with great promises comes great pitfalls. The critical question is whether this new science harbors destructive powers that, if fully understood, would call for legal restrictions or a ban on the use of nanoparticles. The public and scientists alike have thus far viewed nanotechnology as a tremendous advance in the quest for lighter materials, more effective pharmaceuticals, and better medicine. Exceedingly small nanoparticles are already used in a wide range of consumer products, such as food and food contact items, cosmetics and skin care, varnishes and paints, cleaning products, and communication devices. Silver (Ag) nanoparticles are inserted into fabrics to function as antimicrobials. CNTs are used to strengthen materials. Titanium dioxide (TiO₂) nanoparticles make sunscreens clear.

The next-generation nanotechnology may involve nanoscale structures that change when exposed to light, magnetic or electric fields, or the presence of specific molecules. New applications may include targeted drug and gene delivery, diagnostic devices, “smart” packaging, cloaking devices, and weapons capable of autonomous firing decisions. New technologies that are initially seen as great advances are sometimes later viewed as exceedingly dangerous. There are many examples. Chlorofluorocarbons made refrigeration, air conditioning, and aerosols but seriously damaged Earth's protective ozone layer. Lead additives made paint durable, but poisoned children generations later. Asbestos insulated products but destroyed human respiratory systems. Fossil fuels catalyzed industry and transportation but also sped destructive climate change.

The health, safety, and environmental risks associated with nanotechnology are largely unknown, because the relevant science continues to evolve. Significant knowledge gaps still remain. Research has suggested that some CNTs may cause serious health problems, because they exhibit toxic properties similar to asbestos. However, not all CNTs are equally hazardous. It is unclear how law should respond to uncertain but potentially devastating risks. Most consumers have no ability to intelligently evaluative the dangers caused by nanotechnology products. Tort litigation is unlikely to provide remedies because of the difficulties of proving causation. There are regulations in the United States and Europe that cover chemicals that may be produced in nanoform. However, those regimes are not designed to detect the risks posed by nanotechnology, because they often fail to appreciate what is unique about nanomaterials.

Nanoparticles can pass through membranes and enter the body via unexpected paths. Because of their tube-like or wafer shape, which results in increased surface area in comparison to mass or weight, nanomaterials may have greater toxicity. Nanoparticles sometimes display radically different physical or chemical properties than their bulk counterparts, and may exhibit special optical, electrical, and magnetic behavior. It seems unlikely that the administration of the United States and other countries will act in the near future to effectively address nanotechnology risks, because those risks are uncertain and the potential costs of regulation are high. Every major industrialized country has invested heavily in the development of nanotechnology. Because scientific developments move at a rapid pace, any regulatory interruption has the potential to seriously impede innovation and profitability. Logically, nanotechnology risks should be addressed at the international level because nanomaterials cross borders and pose issues worldwide. Internationally consistent standards would prevent a “race to the bottom” in which countries sacrifice health, safety, and environmental interests in an effort to attract nanotechnology enterprises. Yet, there is little precedent for such regulation. The difficulties of creating a global agreement to address climate change suggest that it will be a long time before any treaty effectively grapples with nanotechnology.

At present, the best course is to develop the “soft law” predicate for later “hard law” regulation. Soft law refers to nonbinding international norms or agreements that can gradually acquire legal value. Soft law instruments include codes of conduct, aspirational guidelines, and statements of best practices, voluntary reporting, risk management systems, and licensing, accreditation, or certification schemes. The basic role of soft law is to create expectations that, once widely endorsed, can be translated into binding legal obligations. Minimizing the health, safety, and environmental risks related to nanotechnology requires raising the visibility of the issue, collecting reliable data, establishing prudent practices, building an international consensus, and eventually enacting and enforcing binding obligations. Great strides in the development of nanotechnology must reflect a prudent balance between the economic progress and the hazard prevention [106].

22.9 Nanotechnology: A Green and Sustainable Vision

As green innovation is not yet clearly defined, there can be no clear definition of what nanotechnology for green innovation – green nanotechnology – should encompass. From some published papers on this issue, one could describe green nanotechnology as a foundation for products and processes that are safe and have a low net environmental impact, being energy efficient, reducing waste, reducing greenhouse gas emissions, and using renewable materials. Green nanotechnology can be seen as supporting the development of sustainable solutions to address the global issues, such as energy shortages, scarcity of clean water, and many other areas of environmental concern. Nanotechnology for green innovation – green nanotechnology – aims for products and processes that are safe, energy efficient, reduce waste, and lessen greenhouse gas emissions. Such products and processes are based on renewable materials and/or have a low net impact on the environment. Green nanotechnology is also about manufacturing processes that are economically and environmentally sustainable. Green nanotechnology is increasingly being referred to in connection with other concepts such as green chemistry and sustainable and green engineering and manufacturing [107].

The principles of green chemistry can be applied to produce safer and more sustainable nanomaterials and more efficient and sustainable nanomanufacturing processes. Conversely, the principles of nanoscience can be used to foster green chemistry by using nanotechnology to make manufacturing more environment-friendly. Green nanotechnology can have multiple roles and impacts across the whole value chain of a product and can be of an enabling nature, being used as a tool to further support technology or product development [108], for example,

• nanotechnology can play a fundamental role in bringing a key functionality to a product,
• nanotechnology may constitute a small percentage of a final product whose key functions hinge on exploiting the size-dependent phenomena of nanotechnology,
• nanotechnology can improve or enable sustainable and green processes that lead to the development and production of a nanotechnology-enabled product without that final product containing any nanomaterials.

Significant advances have been made in the field of nanotechnology in the past decade and more, helping it to move closer to achieve its green potential. However, the economic and environmental sustainability of green solutions involving nanotechnology in many cases is yet unclear and some novel solutions bring with them environmental, health, and safety (EHS) risks (e.g., high-energy manufacturing processes and processes that may rely on toxic materials). These risks must be mitigated in advancing green nanotechnology solutions. Green nanotechnology is expected to increasingly impact on several economic sectors, ranging from food packaging to automotives and from the tire industry to electronics. Nanotechnology is also increasingly being applied in conjunction with other technologies, such as biotechnology and energy technologies, leading to products incorporating multiple green technological innovations. For nanotechnology, a wealth of applications has been proposed. To many scientists and engineers, nanotechnology manufacturing promises less material and energy consumption and less waste and pollution from production. Nanotechnology is also expected to enable new technological approaches that reduce the environmental footprints of existing technologies in industrialized countries or to allow developing countries to harness nanotechnology to address some of their most important needs. Certainly, science and technology, and nanotechnology in particular, cannot provide “magic bullets” that will solve all sustainability problems. But nanoscience and nanotechnology may be of critical enabling component of sustainable development, when they are used wisely and when the social context of their application is considered. Shaping nanotechnology for sustainable development, therefore, has to be carried out under the conditions of uncertain knowledge and of provisional assessments [109].

In many countries, supports for green nanotechnology have been mainstreamed within more general efforts to “green” the trajectory of the economy. Green nanotechnology operates in a complex landscape of fiscal and legislative policies and allied measures for green growth and science, technology, and innovation. Framing conditions, such as regulation, standards, and research, and environmental and enterprise policy strongly influence the development of green nanotechnology for processes or products. Although green nanotechnology is increasingly demonstrating its potential to move out of the laboratory and into concrete solutions for products and processes, there is still a great hesitancy from companies to lead the way [110].

22.10 Conclusions

Nanotechnology is a promising technology with applications in several scientific and research fields, such as information and communication technology, electronics, energy, biology, medical technology, and so on. Novel nanobiomaterials and nanodevices are fabricated and controlled by nanotechnology tools and techniques, which investigate and tune the properties, responses, and functions of living and nonliving matter at sizes below 100 nm. Nanotechnology is a science with huge potential and great expectations. The daily announcements of new discoveries and breakthroughs are going to influence all aspects of human society. Nanomaterials bring new possibilities by tailoring optical, electronic, mechanical, chemical, and magnetic properties.

In recent years, there was a rapid progress in the fabrication and processing of nanostructures. As a result, nanophase materials and applications are already in the market and a large volume of new applications is expected over the next several years. However, the development and commercialization of products containing nanomaterials raises many of the same issues as with the introduction of any new technology, including concerns about the toxicity and environmental impact of nanomaterial exposures. Despite the extensive research in the past decade, the literature on the toxicological risks associated with the application of nanotechnology in medical field is scarce. In order to investigate in depth the complex nanosystems, highly sophisticated nanoscale precision tools are required. The advances in nanomaterials necessitate the parallel progress of the nanometrology tools and techniques.

The above-described methods contribute toward a better and in-depth understanding of several aspects of environmental devices and techniques. The nanoscale precision and the detailed investigation that these techniques offer, there is enormous potential for even more advanced applications for the improvement of the quality of research and of everyday life.