Sustainable Nanotechnology. Группа авторов

that it is inaccessible to some remote areas of the world. With air the situation is different because there is an abundance of breathable air, the only problem is the quality of it. As the global population increases and continues to spread, the result is the settlement of factories and other industrial buildings and an increase in automobile use, which contributes to the poor quality of breathable air.

      Some examples of nanotechnology used in air purification methods are CNTs, GNPs, and nanocatalysts. CNTs have a small pore structure and large surface area of functional groups, which can be manipulated through optimum chemical or thermal treatment. These characteristics allow CNTs to be highly efficient in trapping perilous substances from the air [102]. Unlike CNTs, GNPs have shown to exhibit converting characteristics. For example, when combined with titanium dioxide, GNPs are able to convert sulfur dioxide present in polluted air into sulfur [103]. Nanocatalysts also exhibit converting characteristics. The surface area of these catalysts is large enough for chemical reactions to take place. These reactions are able to convert the harmful gases produced by automobiles and factories into safe gases.

      1.4.3 Energy

      Water and air are essential to the survival of most living beings, but for humans, energy has become as important. As much as we promote the use of alternative sources for energy, most of it is still produced from fossil fuels. This has a huge impact on the environment and is actually a barrier to achieving sustainability. Fossil fuels may have been an excellent source for many of our needs, but it certainly has proved to not be a reliable source. First, fossil fuels are considered to be nonrenewable resources, i.e. at one point we would have to deal with their depletion and find reliable alternative resources for our needs. Additionally, this resource is not readily available to everyone because of its uneven distribution – a huge concern for those who are not able to access it [104, 105]. There are many alternative sources of energy available, most popular being solar energy, but they have not been used at a large scale due to issues with converting nonrenewable sources to renewable energy and minimizing energy loss [106]. The use of nanotechnology in the energy sector is able to provide clean energy in a cost‐effective way by developing both conventional and renewable energy sources.

      1.4.3.1 Energy Conversion

      Even though there are many forms of energy available to us, we cannot directly use them. In everyday life, the most useful forms of energy for us are electrical and heat energy, but they can only be generated through conversion from other forms of energy. In reality, all forms of energy, including nuclear energy, come from the sun, hence solar energy is the common source. This energy can be converted to chemical, heat, wind/hydro, and mechanical energy, all of which can be ultimately converted to electrical energy, the most common form of energy used [107]. Every day, the sun releases a huge amount of energy, making solar energy abundant and cost‐free. This energy is released in the form of heat and radiation. Using photovoltaic cells, sunlight can be converted into solar energy that can then be converted into other forms of energies [108]. Conventional solar cells have two drawbacks; they are expensive to produce and their efficiency is rarely above 20%. This is mainly due to the energy of the photons in the cell being larger than the bandgap energy, the right amount of energy needed for the solar cell to work. To correct this, solar cells are enhanced with quantum dots. Due to their variation in size, quantum dots are able to produce various bandgaps that allow the photons that previously had larger energy to pass through. In addition, solar cells made of nanomaterials, such as nanocrystalline silicon, are capable of increasing the efficiency of solar cells by 40–50% [109].

      1.4.3.2 Energy Production

      Some of the already discussed nanomaterials can be used to make already established energy production mechanisms more effective. To make solar cells more cost‐efficient and effective, organic materials such as CNTs have been used. Organic materials have quite a few advantages over inorganic materials in the case of solar cells. Organic semiconductors exhibit a high absorbance coefficient, which allows the photons to be absorbed within a thin layer of the solar cells. This marginally decreases the cost of solar cell production. Additionally, organic materials have shown to be more efficient with increasing temperature, whereas inorganic materials have exhibited a loss of efficiency when the temperature increases. Even though the use of CNTs in polymer‐based solar cells have very limited efficiency, for commercial use, it is more desirable due to its low cost and various applications [110].

Nanotechnology is utilized in unconventional methods of energy production in many ways. In the case of windmills, nanotechnology can be used to enhance the operation and efficiency of it. The use of CNTs in making rotor blades results in higher fatigue resistance, shear strength, and fracture toughness [111]. Nanocomposites can also be used to coat the blade to prevent it from damage from the weather and other environmental factors. For example, super‐hydrophobic nanocomposites containing titanium power have been shown to reduce water adhesion strength, which means in extremely cold temperatures the water will not stick to the rotor blades and possibly damage them [112]. Nanocoatings and nanocomposites can also be used for corrosion protection in hydropower systems and for drilling equipment of geothermal, oil, and gas systems [113].

      1.4.3.3 Energy Storage

      Sustainability of energy includes more than just safe production and conversion; being able to store it for later use is quite important. Nanotechnology’s influence in energy storage can make it a safe and cost‐effective process in addition to sustainability. The simplest form of energy storage and one that most people are familiar with are batteries [114]. Most of the electronic devices that are used today are portable, which has increased the demand for an energy storage unit that is high density yet lightweight. This can be done by using nanocrystalline separator plates in batteries, which not only allow more storage of energy than conventional methods but also make the battery lightweight due to their foam‐like structure [115].

      A safer alternative to fossil fuel‐generated energy is using hydrogen as an energy carrier. Hydrogen has shown the potential to hold a tremendous amount of energy and can be converted into other energy forms without releasing any harmful emissions. Various nanomaterials, especially carbon based, are good candidates for hydrogen storage due to their high absorbency, high specific area, pores, and low‐mass density [116]. Combination of single‐walled CNTs and BH₃ may work as a reversible hydrogen storage system and allow storage and release of hydrogen. This makes it optimal for hydrogen‐based fuel cells that could be used in vehicles.

1.5 Industry

      Most applications of nanotechnology highlighted in this chapter are somewhat directly related to the health and sustainability of the human body. Industries can contribute to the deteriorating condition of the environment by emitting harmful gasses. It can also have a negative influence on the health of living beings through the emission of harmful gases and particles. Nanotechnology, however, is not limited to just those applications. The use of nanomaterials in various industries can produce safe materials and minimize their negative consequences. It can also increase the cost‐efficiency of the materials and make the industry economically sufficient.

      1.5.1 Automotive

      The data on the ownership of automobiles continues to climb as the influence of industrialization continues to spread. Along with the increase in the automotive industry comes an increase in fuel consumption, greenhouse gases, and resource usage. This in return increases the demand and cost of fuel and resources. Even though car manufacturers do put in the effort to minimize the negative consequences of automobiles and increase its efficiency, measures to achieve sustainability are rarely implemented [117]. With the introduction of nanotechnology, new opportunities to make the industry safe and sustainable have arisen. The combination of car engineering and nanotechnology has influenced change in each part of the car. For instance, the improvisation of nanomaterials such as carbon black and silica in car tires results in lower rolling resistance, abrasion resistance, friction, and extended tire life and safety; decrease in weight; and overall a superior performance. In addition, brominated isobutylene‐co‐para‐methyl