Sustainable Nanotechnology. Группа авторов

also be the focus development of this field. What are the reasons for using nanomaterials? Protection against biological deterioration, chemicals, and enhancement of physical properties can be few of the reasons. Furthermore, the safety of using nanomaterials over conventional materials and methods should be assessed, for example, what are the results of these applications in in vivo and in vitro experiments, or do nano‐enhanced food contribute to food allergies? [78]

      Healthy and sustainable food is certainly a goal for the future, especially to achieve global sustainability. Sustainability of food is a bit tricky because food has a shelf life and for most items, it is not very long. A reason for that is biological pathogens. Silver nanoparticles and nanocomposites have been identified as antimicrobials by the US FDA. The Ag⁺ ions in AgNPs are responsible for binding to cause morphological changes and generation of reactive oxygen species by binding to membrane proteins of bacteria. This causes damage to cells and death due to oxidative stress [80, 81]. Even though some nanomaterials are used to cause oxidative stress, there is some that act as antioxidant carriers. A developed example of this is SiO₂‐gallic acid nanoparticles that contain a high capacity of 2,2‐diphenyl‐1‐picrylhydrazyl radicals, a compound used to measure antioxidant activity [82]. Nano‐delivery materials can also be used to increase the BA of bioactive compounds in food products. Depending on the type of bioactive compound, there are many nano‐carries available. For instance, coenzyme Q10 is a lipophilic compound and is not very soluble in water, which is the cause of its low BA. A lipid‐free nano‐CoQ10 system is modified with various surfactants, which improve the solubility and BA of coenzyme Q10 in oral administration [83].

      1.3.3 Food Packaging

      Similar to its contribution to food science, nanotechnology’s contribution to food packaging focuses on increasing the shelf life of food and improving its safety. Currently, polymer‐based materials, synthetic and organic, are widely used in biomedical sciences and agriculture. However, polymers alone cannot achieve the required performance of an innovative packaging; hence, nanomaterials such as CNTs, nano clay, and biocomposites have been used to manipulate the polymers and improve their performance [83]. In food packaging, the combination of polymers and nanomaterials has developed intelligent and active packaging systems. The basis of each packaging system is the mimicking of biological processes, which preserves the integrity of the package and foods in food chain systems [84].

      1.3.3.1 Intelligent Packaging

      An intelligent packaging system focuses on monitoring the conditions and quality of food products during the distribution and storage stage of the supply chain and intends on delivering this information to the consumer of the product. Intelligent packaging systems can be distributed in four categories: data carriers, quality indicators, sensors, and others such as organic light‐emitting diodes (OLEDs) and holograms [84]. Nano‐based communication devices such as Radio Frequency Identification (RFID) tags and a barcode with wireless sensors could be used to provide product authenticity, anti‐theft, anti‐counterfeiting [85], and product traceability [86]. For instance, a wireless RFID sensor tag consisting of two planar inductor‐capacitor resonators to monitor relative humidity has shown a sensitivity range of 20–70%.

This system could be integrated into the RFID sensors of conventional packaging machines [87]. ZnO nanoparticle and polyvinylpyrrolidone (PVP)‐based luminescent films also showed the capability of sensing the status of food substrates by the intensity of their luminescence [88]. In addition, the use of quantum dots and graphene to develop a chip‐based sensor to detect oil samples exhibits the capability to differentiate between various oil samples in a laboratory setting. Compared to the conventional methods of high‐performance liquid chromatography (HPLC), this system was able to discriminate between eight different unknown oil samples with an accuracy of 92.5% [89].

      1.3.3.2 Active Packaging

      In active packaging systems, food products, packaging materials, and the environment are interacting together to extend the shelf life, quality, and safety of the products [85]. Active packaging systems can be categorized as scavengers, blockers, releasers, and regulators [84]. The focus here is to protect the food products from harmful microbes [90], excess moisture [91], and excess oxygen [92]. Active antimicrobial packaging systems are combinations of antimicrobial agents and nanomaterials. For example, antimicrobial nanofibrous films of polyvinyl alcohol‐b‐cyclodextrin with cinnamon essential oil performed well in suppressing the growth of Staphylococcus aureus and Escherichia coli [93]. Substitution of cinnamon essential oil with lemongrass and oregano essential oils exhibited suppression of Salmonella enteritidis in ground beef placed in a sterile plastic bag for six days [94]. For reduction of the rate of oxygen transmission, ascorbic and iron powders or copper chloride can be used as catalysts for oxygen scavenging thermoplastic starch films. This method reduces the oxygen transmission rate from 20.9% to 1% in 15 days at 80% relative humidity (RH) [93]. Additionally, for the modification of atmosphere packaging, oxygen scavenging polyethylene terephthalate (PET) films, PET‐aluminum oxide coatings, polylactic acid films, and oriented polypropylene (o‐PP) films were deposited with palladium layers through vacuum deposition on the silicon oxide layer. This method was also able to significantly reduce the oxygen transmission rate [91]. Similarly, low‐density polyethylene (LDPE) films combine with activated carbon and sodium erythorbate exhibited the oxygen concentration absorbance rate of 80% [92].

1.4 Human Health and the Environment

      Presently, environmental sustainability is recognized as one of the biggest issues fueled by and affecting humankind. Directly related to the continuous increase in population, the constant deteriorating environmental health is holding us back from achieving global sustainability. Moreover, almost every aspect of sustainability discussed in this chapter either is dependent upon the environment or contributes to its condition [95]. Although there are many aspects of the environment that can be improved to prevent any more damage, the three discussed here are air, water, and energy. The influence of nanotechnology can enhance these three facets of the environment in a safe manner and minimize the effects of any future anthropogenic activities.

      1.4.1 Water Purification

      Clean water is an essential part of global sustainability. The constantly increasing the global human population increases the demand for clean water; however, population increase is also a factor in the growth of industries, a huge factor in the decrease in water quality. Making clean and affordable water accessible to people is still a challenge today [96]. There are various conventional methods used today for water treatment and purification. Nanomaterial‐based water purification methods, however, not only improve the quality of water but also extend purification treatments to remote areas without electricity [97]. Many nanomaterials used in nano oncology and for drug delivery are also utilized in water treatments. For example, CNTs, in this case acting as nano adsorbents, are better alternatives of activated carbon because they are able to absorb organic chemicals more efficiently than activated carbon [98].

      Nanomembranes are another method of removing microparticles from water. These membranes are composed of nanofibers and, when combined with metal oxide nanoparticles, can intensify membrane surface hydrophilicity, water permeability, and fouling resistance [96]. Nanocatalysts, such as zero‐valent metal, semiconductor materials, and bimetallic nanoparticles, are used in purification treatment to amplify reactivity and degradation of contaminants such as pesticides and herbicides [99]. Studies show that silver nanocatalysts, N‐doped TiO₂, and ZrO₂ nanoparticles are successful in the degradation of contaminants in water [100]. Similar to nanocatalysts, nanostructured catalytic membranes also have higher rates of decomposition and selectivity. These membranes require less contact time, can be scaled for commercial purposes, are composed of homogeneous catalytic sites, and allow multiple reactions to take place simultaneously [101].

      1.4.2 Air Purification

Air is a unique essential resource needed by living beings. Unlike water, living without air is quite impossible for aerobic species.