Nanotechnology
1. INTRODUCTION
The Greek prefix “nano” is derived from the word “dwarf” and refers to a reduction in size, or time, of 10− 9, which is 1000 times smaller than a micron. The nanometer (nm) scale is typically defined as one billionth of a meter or three to five atoms in width—equivalent to 10 Å or smaller than one-tenth of a micrometer in at least one dimension. However, the term nanoscale is sometimes used even for materials smaller than 1 μm. Also, 1 nm is 10− 9 m or 10,000 times less than the diameter
Nanotechnology is a broad term that refers to all technologies in nano-scale. Many nano-scale is about 1nm to 100nm. (1 nanometer is a billionth of a meter). Nanotechnology is a field of applied science, and it covers a wide era of science. The essence of nanotechnology is the ability to work at the atomic, molecular,, and supramolecular levels, in the length scale of about 1–100 nanometers (nm) range, to create, manipulate, and use materials, devices, and systems that have novel properties and functions because of the small scale of their structures. In some situations, the length scale under which the novel phenomena and properties develop may be less than 1 nm (for example, manipulation of atom at ∼ 0.1 nm) or larger than 100 nm (for example, nanoparticles reinforced with polymer strings of 200–300 nm). All materials and systems establish their foundation at the nanoscale. A human hair is 10,000 nm thick. (Roco, 1999).
Nanotechnology is connected with systems and materials, the components and structures of which represent novel, significantly improved chemical, physical, and biological properties, processes, and phenomena because of their nanoscale size. The dictionary definition of nanotechnology is “the design, characterization, manufacture and shape and size-controlled application of matters in the nanoscale”. A substitute definition from the same dictionary is “the careful and controlled manipulation, precision placement, modeling, measurement, and production of materials at the nanoscale to make matters, systems, and devices by fundamentally novel properties and functions (Nasrollahzadeh et al., 2019).
The manipulation of materials at the atomic level by utilizing nanotechnology has great potential in the area of cosmeceuticals, opening up new avenues for the cosmetics industry. The incorporation of various nanomaterials during the development of cosmetic/cosmeceutical products results in nanocosmetics/ nanocosmeceuticals, respectively. Prolongation of action, augmented bioavailability, and improved aesthetic appeal of products are a few of the advantages associated with nanotechnology-based cosmeceuticals. These products offer several other benefits over traditionally used cosmeceuticals, such as small size and huge surface-to-volume ratio, which makes them effective adjuvants in cosmeceuticals. Further, the inclusion of nanoparticles in cosmetic formulations does not change the properties of cosmeceuticals but improves their appearance, coverage, and adherence to the skin. Cosmetic manufacturers employ nanosized ingredients to improve UV protection, skin penetration, color, the release of fragrance, finish quality, anti-aging effect, and a variety of other properties. They prolong the duration of action by either controlling the delivery of active ingredients, causing site-specificity, improving biocompatibility, or enhancing the drug-loading capacity. All of these factors make them more popular among consumers, necessitating clinical trials in this area to address their safety concerns. Nanocosmeceuticals have also been highly exploited for formulating various anti-aging formulations. They are successfully marketed as skincare, hair care, and nail care products, among others, claiming to stimulate their growth, protect their structure, and increase hydration power, thus improving their effectiveness as cosmetic products.
The design and production of the encapsulating structure that provides mechanical support, environmental protection, electrical signal,, and a means of heat dissipation for the Si chip, whether digital or analog, processor, or memory. Level two packaging is then the integration of these packaged chips into a board-level system that similarly provides mechanical support, power and signal delivery and interconnections, and thermal dissipation(Morris, 2018).
the paper presents a thorough investigation of the potential for the fabrication of a broad range of flexible microwave electronics and systems, as a first step into assessing the challenges and feasibility of these novel manufacturing technologies for the scalable low-cost production of high-performance wireless passives, sensors, and integrated systems. For this purpose, we will first discuss in Section II the properties and advantages of for the fabrication of flexible wireless electronics. In Section III we will then present various flexible wireless component prototypes fabricated with AMT. Section IV reports preliminary printed sensor modules, such as inkjet-printed nano-carbon-enabled gas and microfluidic sensors. Fully assembled RF nodes and modules (radar, beacon) are presented in Section V, while major challenges and future directions for the implementation of AMT-fabricated “zero-power” green flexible RF systems are discussed in Section VI.(Hester et al., 2015).
1.2 Properties and characteristics of nanotechnology
1.2.1 Nanostructure
Due to the direct pathways for photogenerated carriers, one-dimensional (1-D) semiconductor structures, e.g., nanowires, nanorods, nanotubes, and nanoneedles, can efficiently facilitate the transportation of photoelectrons to FTO and thus suppress the recombination of photogenerated electron-hole pairs. These structures are capable of reducing grain boundaries and defects that result in less recombination of electron-hole pairs, and consequently 1-D WO3 nanostructure photoanodes demonstrated superior PEC properties to nanocrystalline particles (Kafizas et al., 2017).
A large number of grain boundaries in the nanoparticle films increase the resistance and interfacial charge recombination and thus impede the electron transfer to the back-contacted conductive substrate. Different from nanoparticles and similar to 1D semiconductor structures, 2D nanostructures, e.g., nanoplates, nanosheets, and nanoflakes, are favorable for highly efficient and directional transport of electrons and holes. Besides, 2D semiconductors have a bigger surface/volume ratio than the 1D semiconductor. WO3 nanoplates (Zhan et al., 2015).
1.2.1 Cost-effectiveness
With the increase in the number related to the development and study of the antibacterial properties of the copper-polymer nanocomposites, their excellent antibacterial properties, and relatively low production cost, this review presents a comprehensive compilation of research, focused mainly on the antimicrobial activity of copper polymer nanocomposite (Tamayo et al., 2016).
1.2.2 Biocompatibility
Modern bone implants (scaffolds) should have antibacterial properties for counteraction to various bacterial infections. It seems to be the main problem in the process of bone tissue regeneration in orthopedics and dentistry because it provides “implant-associated” infections, which lead to loss of the implant. Treatment of such infections is conducted by applying systemic antibiotics, which are not always effective due to the formation of microbial resistance. One of the possible ways to solve this problem is to create nanostructured materials embedded with particles or apply coatings, which have good biocompatibility, as well as antibacterial properties (Shypylenko et al., 2016).
1.2.3 Nanotechnology in medicine
Regenerative medicine involves the development of methods to repair and replace diseased or damaged cells, tissues, or organs to restore or establish normal tissue functions. Nanotechnology is a powerful strategy in tissue regeneration for recreating the nanoscale features of tissues that can direct cellular adhesion, migration, and differentiation. Nanomaterials also have unique physical, chemical, optical, electrical, and magnetic properties that are different from their bulk-level counterparts. Based on their size and functional advantages, nanomaterials can be used for effective biomolecule delivery, scaffolds for tissue engineering, in vivo cell tracking, and stem cell therapy (Yang et al., 2019).
1.2.4 Nanotechnology in cancer therapy
Nanotechnology in cancer therapy Many conventional treatments do not distinguish between cancerous and healthy tissue, so these methods usually fail. Designing nanoparticles that can distinguish the difference between healthy and cancer cells is important in treatment because chemotherapy drugs do have not such features. Nano-materials are recently used to bind specific ligands to cancer cells. For example, binding nano-materials to monoclonal antibodies, peptides, and other small protein molecules of tumor tissue is important as drug delivery systems (DDS). For this purpose, nano-materials are designed specifically for each cell. Drug resistance is a major obstacle to the success of cancer chemotherapy treatment. It reduces the efficiency of treatment and increases deaths. Many cancer patients are drug-resistant. Tumors use several different mechanisms to reduce accumulating anticancer drugs in tumor tissue. Uses of novel therapeutic approaches to combat these accumulations seem to be needed. The toxicity of drugs for normal tissues is another important reason for the reduced effectiveness of cancer therapy. Because of the increasing rate of drug resistance in cancer patients, the use of nanoparticles as drug carriers to enhance anticancer drug delivery is in progress.(Zare-Zardini et al., 2016) Cancer is a leading cause of death and a global health burden. It was estimated that there would be 18.1 million new cancer cases and 9.6 million cancer-related deaths by 2018(Bray et al., 2018).
1.2.5 Nanotechnology in food and agriculture
From food nanotechnology to marketed products, or from fundamental aspects of nanotoxicity to regulation and legislation, or from knowledge of food nanotechnology to public awareness and acceptance, a huge amount of information and effort is needed and all these aspects are strictly related to each other. nanomaterials may provide an alternative solution to apply novel nanomaterials in the food industry with a relatively “acceptable” negative impact (He et al., 2019).
Fig. 1 Food Packaging Nanotechnology Figure
1.2.6 Food packaging
Foods are highly susceptible to spoilage making them unacceptable for consumers. Food packaging is a critical point in the proper handling and maintenance of food quality. Traditional food packaging has four basic functions: protection or preservation, containment, convenience, and communication. Improvements are made in these basic functions to design improved active, and smart packaging (Gregor-Svetec, 2018). The use of nanoparticles and nanocomposites in food packaging increases the mechanical strength and properties of the
oxygen barrier of packaging and may provide other benefits.
Fig. 2 Bionanomaterials (Primožič et al., 2021)
1.2.6 Nanotechnology in agriculture
This is far below the targeted 4% annual growth in the agricultural sector for 2020. The major concern is food grain production. nanotechnology (NT) has been identified as a potential technology for reviving the agriculture and food industry and can improve the livelihood of the poor. Various sectors like health care, materials, textile, information and communication technology (ITC), and energy can get huge benefits from nanotechnology. In the agricultural sector in particular, nanotechnology plays an important role in crop production(Pramanik et al., 2020)
1.3 Droplet-based micro and nanotechnology synthesis
Droplets are used in micro and nanotechnology for different reasons. Droplets can be used as (i) containers for material transport, (ii) reaction chambers to fabricate nanomaterials, and (iii) building blocks to make structures. One major area of droplet-based nanotechnology involves the transport of liquid cargo in the form of oil-in-water or water-in-oil emulsion droplets. These platforms move the droplets along various types of tracks, including microfluidic channels, and nanotubes. flow in this regime dates to the early 1950s when efforts to dispense sub-nanoliter amounts of liquids were made, providing the basics of current ink-jet technology. The invention of the ink jet was followed by the development of High-Performance Liquid Chromatography (HPLC) and the introduction of microvalves and micropumps during the 1980s. To generate small reaction volumes, the liquid can be split into micro/nano wells(Mashaghi et al., 2016).
1.4 Biological synthesis of nanotechnology
The biological synthesis of nanoparticles is increasingly regarded as a rapid, ecofriendly, and easily scaled-up technology.
Metal nanoparticles produced using microorganisms and plant extracts are stable and can be monodispersed by controlling synthetic parameters, such as pH, temperature, incubation period, and mixing ratio.
Recently, biological nanoparticles were found to be more pharmacologically active than physicochemically synthesized nanoparticles.
Among the various biological nanoparticles, those produced by medicinal plants are the most pharmacologically active, possibly due to the attachment of several pharmacologically active residues(Singh et al., 2016).
1.4.1 Chemical and physical synthesis
Fig. 3 Synthesis of nanotechnology (Ijaz et al., 2020).
1.5 Nanotechnology in Healthcare Sectors
1.5.1 Role of Nanotechnology in Gene Therapy
Gene therapy is a procedure to replace a defective gene in the DNA (which is responsible for causing a disease) with a normal gene. The gene is usually inserted into the stem cells using a vector ](Misra, 2013). Stem cells have a long life and a self-renewal ability; therefore, they are the most suitable targets for gene therapy. The vector used should be highly specific and efficient in releasing the gene or genes of variable sizes. It should not be recognized as an antigen by the host immune system. The vector must have the ability to express the inserted gene throughout the life of that organism (Kay, 2011)When the gene is correctly inserted into the cells, it inhibits and corrects the functions of the mutated gene and induces the normal functioning of cells.
Gene therapy using non-viral nanostructures is safe, as compared to therapy using viral vectors. They are also much less oncogenic and rarely trigger immune responses. Their preparation is much easier than that of viral vectors. There is no risk of virus recombination and no limit on the size of the gene to be loaded. NPs are one of the many nanostructures that are used for non-viral gene delivery. The presence of a positive charge, small size, and high surface-to-volume ratio enables them to penetrate deep into the membranes, thus making them ideal vectors for gene delivery. The major nanosystems used in gene therapy.
Fig. 4 Gene therapy in nanotechnology (Anjum et al., 2021)
1.5.2. Nanotechnology in covid 19
The current impact of COVID-19 on global health is enormous, but in addition, the worldwide impact on the economy, employees, and companies is going to be considerable and may entail deep economic and negative social impacts as well as geopolitical repercussions as a possible consequence. This global emergency requires a response to the COVID-19 pandemic with science and technology means, wherein nanotechnology approaches may contribute to advanced solutions to this crisis. Nanotechnology (Ruiz‐Hitzky et al., 2020).
Fig. 5Affected or infected person (Del Real, G.2020)
Type of nanotechnology
Nanoparticle technology
Nanocomposite technology
Nanocrystal technology
Nanotube technology
Nanowire technology
Nanoelectronics
Nanomedicine
1.6 Nanocomposite
The corresponding polymer nanocomposites can be grouped into the type of layered polymer nanocomposites. In the second type, two dimensions are on a nanometer scale and the third is larger, forming an elongated one-dimensional structure, these nanoscale fillers include nanofibers or nanotubes, e.g., carbon nanofibers and nanotubes or halloysite nanotubes as reinforcing nanofillers to obtain materials with exceptional properties. The third type is the nanocomposites containing nanoscale fillers of three dimensions in the order of nanometers. These nanoscale fillers are iso-dimensional low aspect ratio nanoparticles such as spherical silica, semiconductor nanoclusters, and quantum dots showing schematics of various nanoscale fillers.
Fig. 6: Nanoscale Fillers (Huang et al., 2016).
immiscible systems, typical with many conventional filled polymers, poor physical interaction between inorganic fillers and polymers brings about low mechanical and physical properties. Conversely, strong interactions between layered silicates and polymers may result in nanometer-level dispersion of inorganic nano-phases in polymer matrices.
Consequently, polymer nanocomposites will show unique mechanical and physical properties not shared by micro-composites The layered silicates are usually impermeable to liquids and gases across the layer thickness and hence provide an excellent barrier for polymer nanocomposites to these substances.
Fig.7 Paraffin-type bilayer (Fu et al., 2019)
1.6.1 1Nanofiber (or nanotube)/polymer nanocomposites
The reported exceptional properties of CNTs motivate many researchers to conduct extensive studies on the processing of CNT-reinforced polymer nanocomposites. An interesting way to fabricate these composites is to spin carbon fibers from CNTs dispersed in a surfactant solution followed by recondensation in a stream of a polymer solution. With this method, there is preferential orientation of the nanotubes along the fiber axis. Carbon nanofiber (CNF) reinforced polymer nanocomposites can be prepared by high shearing methods like twin screws. The high shearing method is efficient for preparing a CNF well-dispersed sample. (Lozano & Barrera, 2001)
1.6.2 Nanocomposite For Food Packaging
There is a strong drive-in industry for packaging solutions that contribute to sustainable development by targeting a circular economy, which pivots around the recyclability of the packaging materials. The aim is to reduce traditional plastic consumption and achieve high recycling efficiency while maintaining the desired barrier and mechanical properties. In this domain, packaging materials in the form of polymer nanocomposites (PNCs) can offer the desired functionalities and can be a potential replacement for complex multilayered polymer structures. There has been an increasing interest in nanocomposites for food packaging applications, with a five-fold rise in the number of published articles during the period 2010–2019. The barrier, mechanical, and thermal properties of the polymers can be significantly improved by incorporating low concentrations of nanofillers. Furthermore, antimicrobial and antioxidant properties can be introduced, which are very relevant for food packaging applications.
Fig.8 Barrier properties of nanocomposite (Sarfraz et al., 2020)
1.6.3 Barrier Properties of Polymer Nanocomposites
The improvement in the barrier properties of PNCs is generally explained in the literature in terms of the increased tortuosity with the addition of fillers, as shown in(Nielsen, 1967). The tortuous pathway created by the nanofillers alters the diffusion rate of the molecules, thus resulting in improved barrier properties. However, to achieve the desired improvement, the fillers must be uniformly distributed throughout the polymer matrix, which is often difficult to achieve. Another possible mechanism is the polymer–nanoparticle interaction, which can also influence the barrier properties by immobilizing the polymer strands.
Fig. 9 Migrating substance
Schematic of the gas molecule diffusion through (a) a polymer-only barrier and (b) a polymer composite barrier. Uniformly dispersed nanoplates decrease the permeability by increasing the resistance through tortuosity (Müller et al., 2017).
1.6.4 Bio-Based and Biodegradable Nanocomposite Films
Research on active biopolymer nanocomposite materials is an emerging field that, if successful, may compensate for some of the shortcomings of these bio-based and biodegradable materials in terms of, e.g., oxygen barrier properties. The use of antimicrobial or antioxidative components in combination with nanofillers creates an additional hurdle for spoilage bacteria or oxidative spoilage and may thereby narrow the gap with the performance of conventional plastic packaging materials in terms of the obtained shelf-life of a packaged product. Montmorillonite has been applied in combination with different essential oils in biopolymers, e.g., chitosan/montmorillonite/ginger essential oil (Souza et al., 2018), chitosan/montmorillonite/rosemary essential oil (Souza et al., 2019)and soy protein/montmorillonite/clove essential oil.
1.6.5 Toxicity and Safety Aspect
Currently, according to the “Plastic Food Contact Materials” Regulation (EU) 10/2011, only nanoparticles authorized and specifically mentioned in the specification of Annex I of the regulation can be used in plastic packaging for food. This also applies to nanoparticles that are intended to be used behind a functional barrier. Nanoparticles, which were initially listed in the specifications, and thus authorized, are silica, carbon black, and titanium nitride (Wyser et al., 2016). Titanium nitride nanoparticles are typically used as an additive in PET bottles, for which a concentration of up to 20 mg/kg is allowed. For food contact plastic packaging containing particles/fillers other than the three listed above, an application must be submitted to the European Food Safety Authority (EFSA), which contains specific information regarding the migration, toxicology, and possible exposure for their authorization(Sarfraz et al., 2020).
1.6.6 High thermal-stability polyimide films
The high thermal resistance PI films mean more excellent physical and chemical stability at a high temperature compared to traditional polyimide films. Many aromatic units are located in the polyimide backbone, like benzene rings, phenylimides, or phenylbenzimidazole, which have high bond energy and intermolecular forces that only can be broken at high temperatures, and then the polyimide structure will be destroyed.
Flexibility, lightness, and low cost have great potential applications in flexible optoelectronic devices. However, the PI films with higher thermal stability, and lower CTE containing benzoxazole or benzimidazole structure are required. Therefore, it is important to modify this kind of PI films to further improve their combined properties (Ma et al., 2019).
1.6.7 Nanosized particles of magnetic materials
Nanosized particles of ferromagnetic and ferrimagnetic materials reveal interesting magnetic properties depending on the particle size, shape, and crystal structure. Nanosized particles of numerous magnetic materials have been incorporated into extended matrix materials (i.e., organic or inorganic polymers) to create integrated functional systems with additional magnetic properties. Due to their unique properties (i.e., magnetic moment in combination with good chemical stability and low.
Functional magnetic nanocomposites with organic matrices
Fig. 10 Magnetic nanoparticle (Behrens & Appel, 2016)
Liquid crystals are highly anisotropic organic matrices. Recently, ferromagnetic Sc-doped, single-crystal BaFe12O19 nanoplatelets were suspended in a thermotropic, nematic liquid crystal (i.e., 4-pentyl-4′-cyanobiphenyl (5CB)), forming a stable, ferromagnetic liquid phase as a result of the balanced magnetic interactions between the platelet-shaped particles and the repulsive forces mediated by the nematic liquid crystal. The orientational coupling of the magnetic liquid.
1.6.8 Reinforcing Agents
The aim of reinforcement of metallic materials with nano-particles or fibers is always aimed to improve specific properties (Stark, Stoessel, et al. 2015), typical development goals for composite materials are:
• Increase in yield and tensile strength at room temperature or elevated temperature while maintaining ductility;
• Increase of creep resistance at elevated temperatures;
• Increased fatigue strength;
• Improvement of thermal shock resistance;
• Improvement of wear resistance;
• Increase of the Young’s modulus; or
• Reduction of coefficient of thermal expansion.
Ceramic nanoparticles and carbon-based nanotubes have been available in the last few years at significantly lower prices than in the 1980s or 1990s and have culminated in impressive promotion of the research and development of nanoparticle-reinforced light metals last 25 years.
Carbides, borides, nitrides, and oxides are used to reinforce metallic materials in the nanoparticle form (Lakhi et al., 2017), usually produced industrially at low cost and deployed in the grinding and polishing industry; especially, SiC, B4C, and Al2O3, AlN, BN, and TiB2 are technically and economically relevant examples. shows some relevant properties of the ceramics listed above and lists common ceramic nanoparticles useable for metal matrix nanocomposite production.
One of the greatest challenges in manufacturing metal matrix nanocomposites is to disperse nano-sized ceramic particles uniformly in molten metals. This is usually problematic because nanoparticles tend to agglomerate as clusters due to the high surface energy that leads to high van der Waals attractive forces between nanoparticles. Thus, deagglomerating nanoparticle clusters are of major significance to achieve homogeneous distribution of nanoparticles in the metal matrix. Liquid metal processing assisted by an external ultrasound field has been demonstrated to be an efficient way to homogenize the nanoparticle distribution in molten metal (Xu et al., 2016). This processing is followed by appropriate solidification, e.g., a sufficiently slow cooling rate, which can give rise to homogeneous microstructure in the nanocomposite. Thus, the optimum enhancement effect of nanoparticles on the mechanical properties of nanocomposite can be achieved (Dieringa, 2018).
One is that liquid metals are usually optically opaque and the majority of metal alloys require relatively high temperatures (above a few hundred degrees Celsius) to maintain liquidus structure; special techniques, such as X-ray imaging, are needed to “see” through the liquid metals. In addition, in situ observation requires imaging with nanoscale resolution and extremely high speed (up to on the order of 105 frames per second to be able to capture both activities of nanoparticle clusters and cavitation bubbles (with radii from a few to a few hundred micrometer.(Mirihanage et al., 2016) According to the Minnaert equation, the critical radius of a cavitation bubble in liquid aluminum is around 60–70 µm when the acoustic pressure is sufficiently high (Xu et al., 2016)
Fig. 11 Fragment of nanoparticle
Main mechanisms of ultrasonic deagglomeration of nanoparticle clusters: (a) collapse of cavitation bubble; and (b) acoustic streaming.
The ball milling process of a CNT-reinforced metal matrix bulk composite (i.e., Al/CNT nanocomposite) is shown in where the CNTs are integrated (partially welded) with the matrix powder metal (i.e., aluminum) at various steps; an effective ball milling process shall produce a well-dispersed (homogenized) distribution of reinforcement particles in the metal matrix.
Fig. 12 Reinforcement particle (Mirihanage et al., 2016)
1.6.8 Composition of nanocomposite and structure
Crystalline MoS2 has a typical transition-metal dichalcogenide (MX2) layered sandwich structure. The edge planes of crystalline MoS2 are active sites for HER, whereas their basal planes are chemically inert. Benefitting from wide research, three universal strategies have been suggested to improve the HER activity of crystalline MoS2-based catalysts: (1) increasing the density of active sites; (2) enhancing the intrinsic catalytic activity; (3) improving the conductivity and diffusion properties of the MoS2 materials. During the past decade, significant advances have been achieved in crystalline MoS2-based catalysts(Lu et al., 2017)
conductive supports in MoSx can reduce the aggregation of MoSx nanosheets, as well as provide fast electron transfer channels. Carbon materials, owing to their high conductivity, earth abundant, large specific surface areas, and high stability, have been regarded as ideal supports for electrocatalytic materials. Carbon materials such as porous carbon, and carbon nanotubes. carbon fibers, as well as graphene have been investigated as supports of MoSx. Recently, we found that highly conductive carbon black (CB) can enhance the catalytic activity of amorphous MoS2 obviously(Cao, Peng, Li, et al., 2017). About that CB is active and economic, MoSx/CB composites would have great potential for commercial application in HER. the possible reactions during the process of synthesis are as follows:
HOCH2CH2OH⟶𝛾-rayesol−+H+HOCHC+HOH
MoS42−⟶esol−MoSx+S2
the HER performance of the as-synthesized materials, MoSx, all MoSx/C nanocomposites, and commercial 20% Pt/C were tested in a standard three-electrode system(Cao, Peng, Liu, et al., 2017).
1.7 Nanoparticle
Nanoparticles, in particular gold nanoparticles, have been used for millennia in China and Egypt by women for both curative and aesthetic purposes and by artists for the making and decoration of glasses and ceramics such as the illustrious Lycurgus cup (fifth century AD). Small nanoparticles are usually called nanoclusters or, for those smaller than one nm, subnanoclusters, although there is a continuum of situations from molecules to solid state between small clusters defined by molecular orbitals and larger nanoparticles defined by energy band structures. Decreasing the nanocatalyst size down to a single atom (20−22) has attracted much recent attention because in this case no atoms located at the interior of the nanoparticle are lost. Moreover, supported single-atom catalysts are better defined than sub nanocatalysts that are more or less polydispersed and are therefore less selective. This area recalls single-site organometallic catalysts in which the ligands are present besides the oxide support of the single metal site(Astruc, 2020).
It is also reported that silver nanoparticles can protect some skin diseases like atopic dermatitis The explanation of the protective effects is still not understood. It is suggested that silver can disrupt the bacterial cell wall. At minimal and reasonable concentrations of silver, there are no side effects on human health. Due to the antibacterial properties of silver nanoparticles, it can be used as a preservatives in cosmetics, and in anti-acne preparation. For example, silver nanoparticles, which have antibacterial activity, are also being incorporated into toothpastes and shampoos as preservatives. Kim et al. observed that silver nanoparticles inhibit the growth of dermatophytes, making them a potential anti-infective agent. Nano silver is also used in dietary supplements, because of its antibacterial, anti flu, and cancer-inhibitory effects.(Noorbakhsh et al., 2011).
Acute dermal toxicity studies on silver nanoparticle (SNP) gel formulation (S-gel) in Sprague-Dawley rats showed complete safety for topical application. These results clearly indicate that silver nanoparticles could provide a safer alternative to conventional antimicrobial agents in the form of a topical antimicrobial formulation. Some special tooth creams for the neck of sensitive teeth contain nanoscale calcium phosphate (apatite) which produces a thin layer similar to natural tooth enamel, which is thus supposed to reduce sensitivity to pain. Tiny particles of nanometer-thin pigment can be found in make-up, nanoparticulate gold and silver is used in certain day and night creams to give the skin a fresher appearance. GNS Nanogistnanover TM Premium make up range contains Nano silver, GNS NanogistnanoverTM Q10 Range contains Nano silver. Nano silver is used in soaps, toothpastes, wet wipes, deodorants, lip products, as well as face and body foams(Shende et al., 2020).
1.7 Application of Nanoparticle
1.7.1 Cosmetics
Increasing development of new skin products requires more quality and scientific assessments. Efficacy of skin care products not only depends on the individual active agents, but also on the carrier employed. It is recognized that a proper formulation of skin products adapted to the state of the skin may present many positive effects on hydration and stabilization of the epidermal barrier of the skin. The general formulation with interaction between carrier, active ingredient, and skin influences the preparation and the release of active ingredient as cargo. The aim of current study was to review recent literature about skin-related delivery of cosmetics by nanoparticles. Our main focus was on liquid based nanoparticles due to their importance in skin cargo delivery as well as their vast application in current cosmetic formulations. Data were collected from electronic databases using MeSH keywords such as nanoparticles, lipid particles, cosmetic, dermal delivery, and combinations of these words(Khezri et al., 2018).
Nanoparticles (NPs) are defined as materials with dimensions smaller than 100 nm and presenting various shapes, i.e., spheres, rods, dendritic shapes, etc. (Pidgeon et al., 2004). It should be noted, however, that there exists no uniform definition of nanomaterials. The Environmental Protection Agency (EPA) emphasizes, in its opinion, the unique properties of NPs, which largely differentiate them from equivalent chemical compounds. In turn, the US Food and Drug Administration (USFDA) clearly states that NPs should exhibit dimension-dependent phenomena. The International Organization for Standardization (ISO), as the basic criterion, considers the nanoscale dimension of both the external dimension as well as the internal surface structure.
Complex nanoparticle-support ensembles are often called nanocomposites. The complexification of the nanocatalyst design is sometimes reminiscent to the complexity organized by Mother Nature. For instance, supported subnanoparticles of MoS2 type containing only a few atoms resemble MoS-based nanoclusters serving as cofactors of the nitrogenase enzymes that catalyse N2 fixation. These biomimetic aspects are useful for instance for the design of processes involving nanocatalytic H2O, N2, and CO2 reduction.(Modena et al., 2019).
1.7.2 Conductive nanoparticle
Polystyrene (PS) has been found to be largely used as a coating material in nanocomposites for electrical applications. ZnO as a core material has been investigated. It has certain features that permit its use in transparent electronics, ultraviolet (UV) light emitters, piezoelectric devices, chemical sensors, and spin electronics. A microemulsion polymerisation method was used to coat the ZnO nanoparticles, with oleic acid modified zinc oxide (OA-ZnO) nanoparticles as seeds, and potassium persulphate (KPS) as an initiator in water. The average core + shell size is around 300 nm, considering a core diameter of 20–80 nm. Gold–polystyrene nanoparticles (Kim et al., 2014).
1.7.3 Drug delivery application
Core–shell nanoparticles are widely used in the field of controlled drug delivery, and some of the applications that are going to be described in this section will be mentioned subsequently because several combinations of materials can be used for many other purposes. For the inorganic core, reconnecting with the previous section, magnetic materials such as magnetite and cobalt are investigated. Silica has also been analysed in many scientific articles; gold and upconversion luminescent nanoparticles (UCNPs) (Zhang et al., 2015) and ZnO have been found in use for this pharmaceutical application.
PH-responsive drug delivery system based on chitosan coated mesoporous silica nanoparticles. Starting from the synthesis of phosphonate functionalised mesoporous silica nanoparticles (MSNs), (MCM-41-PO3) nanospheres, the phosphoramidate covalent bonding creates a link between phosphonate groups on the surface of the MSNs and amino groups on chitosan. The spherical nanoparticle synthesis is outlined in fig. with a mean diameter of about 110 nm.
Fig. 13 Spherical nanoparticle (Popat et al., 2012)
1.7.4 Waste water treatment
(Moustakas et al., 2013) a green synthesis of Pd nanoparticles in an apricot kernel shell substrate using Salvia hydrangea extract as an organic reducing agent and proved their catalytic activity for reduction of organic dyes, 4-nitrophenol (4-NP), methyl orange (MO), methylene blue (MB), rhodamine B (RhB), and Congo Red (CR) at room temperature. The modified TiO2 (m-TiO2) nanostructure covered with a shell of carbonaceous type material, which acts as a highly efficient visible light sensitiser, was synthesised using the gel combustion method. The photocatalytic performance of the m-TiO2 powder was tested for the degradation of methylene blue (MB) azo dye under UVA (350–365 nm), visible (440–460 nm) and daylight (350–750 nm) illumination. The particles size is 3–10 nm.
Fig. 14 solution hydrolysis (Khodadadi et al., 2017)
1.7.5 Formation of natural nanoparticle
The classification of NNPs and all possible pathways leading to their formation is a complex and massive task as it covers all spheres of the Earth, chemical elements/species, and a vast number of diverse mechanisms, processes and conditions. Synthesis can also occur via top-down approaches starting from larger precursors, e.g., nano-sized mineral fragments generated by wind erosion on deserts, or the formation of carbon NPs from the combustion of biomass.
On Earth, nano-sized objects are formed and occur within all spheres, thus covering the atmosphere (including the whole troposphere, and some types of NPs can be found at even higher levels), hydrosphere (oceans, lakes and rivers, groundwater, pore water and hydrothermal vents), lithosphere (soils, rocks, lava or magma at certain stages of evolution), and biosphere (mainly in/at microorganisms, but also including higher organisms and even humans).(Hochella et al., 2015) From this burgeoning list of possible NP occurrences, the NPs in the atmosphere and hydrosphere, which are reported to occur at concentrations up to 106–107 particles mL−1 have the major effects on biota due to their close contact/interactions with biota.
Fig. 15 natural nanoparticle (Sharma et al., 2015)
Organisms, particularly microorganisms, extensively generate NPs in the environment. Biological processes (or biomineralization) in nature produce a number of inorganic nanomaterials such as Fe- and Si-based nanominerals, calcium carbonate, and calcium phosphate(Gao et al., 2017).
Fig. 16 formation of natural nanoparticle (Zeytuni et al., 2011)
2.1. COPPER OXIDE
Copper oxide (CUO) is a black solid compound that is a key ingredient in the production of semiconductors, batteries, and other industrial processes. It is also used in the manufacture of coper salts, ceramics, and glass. Compared with other properties such as electrical conductivity and field emission, optical property of CUO nanostructures has been much less investigated and discussed so far. As a p type semiconductor, a narrow bandgap of around 1.2 eV was reported for bulk CUO. In fact, reported values of bandgap for CUO were not in good agreement; for example, bandgap in the range of 1.56 and 1.85 eV was reported for CUO thin films (Cho, 2013). In addition, the variation of bandgap could also relate to quantum size effect in different CUO nanostructure.
CUO first attracted attention of chemists as a good catalyst in organic reactions but recently discovered applications of CUO such as high-Tc superconductors, gas sensors, solar cells, emitters, electronic cathode materials also make this material a hot topic for physicists and materials science engineers. Some of the most interesting applications of CUO nanomaterials are sensing, photocatalyst,
2.2 Crystal Structure and Some Physics Constants
CUO crystal has monoclinic structure and belongs to symmetry. Cupric oxide has four formula units per unit cell. The coordination number of copper atom is, which means that it is linked to four oxygen neighbour atoms in an approximately square planar configuration in the plane. In all crystallized solids, divalent copper surroundings are always very distorted by a strong Jahn-Teller effect which often leads to more stable square planar groups. The Cu-O bond lengths in this plane are 1.88 and 1.96 Å, respectively, which are larger than those in the cuprous oxide (Ching et al., 1989). The next two Cu-O bond lengths perpendicular to the plane are much greater
Fig.17 Crystal structure of CuO (Dai et al., 2021)
COPPER (I) OXIDE (CU2O)
2.3 Physical and chemical properties of copper oxide
Oxidation state: copper oxidation state +1
Appearance: Red or radish -brown solid
Chemical formula: cu2o
Passivation of Copper
Pourbaix diagrams (potential vs. pH diagram) provide key information for understanding the electrochemical oxidation of metals. According to the Pourbaix diagram for copper, it is apparent that the most suitable electrolytes for copper anodization are the alkaline ones (solutions of bases like NaOH, KOH, but also salts with alkaline hydrolysis like carbonates and bicarbonates of potassium and sodium, not researched yet as potential copper anodizing electrolytes).(Beverskog & Puigdomenech, 1997) It is also noticeable that electrochemical oxidation may lead to the formation of oxides like Cu2O (lower potentials) and CUO (greater potentials), as well as cupric hydroxide Cu(OH)2 and water-soluble coordination anions with hydroxyl ligands, namely Cu(OH)3− and Cu(OH)42−. For anodizing, the minimal solubility of Cu2O in water is at a pH range from 7.5 to 8.0. It is also worth noting that the as-obtained anodic oxides formed on copper are crystalline, while other anodic oxides, like titania or alumina, are amorphous. The formation of crystalline phases in anodic alumina or titania requires annealing after the anodization.
Fig.18 crystalline phase of cation
According to the chemical reactions, first copper oxidizes and forms metastable CuOH on the Cu surface:
CU+OH−→CUOH+ CU+OH−→CUOH+ e¯
Next, cuprous hydroxide, CUOH, may react in two ways, either forming solid Cu2O (2):
2CuOH→Cu2O+H2O2CuOH→Cu2O+H2O
Or bonding the hydroxyl group and forming water-soluble Cu2O2H−
2CuOH+OH−→Cu2O2H+H2O2CuOH+OH−→Cu2O2H−+H2O
In an alkaline environment, Cu2O2H− may also transform easily into Cu2O22−, when OH− accepts a proton.
The cuprous oxide, under the influence of hydroxyl anions, may transform into the water-soluble Cu2O22−:
Cu2O+2OH-→Cu2O2+H2OCu2O+2OH-→Cu2O22−+H2O
Furthermore, the formed Cu2O22−, anions are metastable and disproportionate into solid, metallic Cu and water-soluble CuO22−, which can be also considered as [Cu(OH)4]2− (5):
Cu2O2−2→CuO2−2+CuCu2O22−→CuO22−+Cu
Thus, the re-deposited copper may undergo the entire cycle of reactions again, starting from Reaction (1). According to Ambrose et al., and their voltammetric study of Cu in KOH, a water-soluble Cu(I) species may also be formed directly from Cu, due to the formation of a coordination anion(Ambrose et al., 1973).
2.3 Strategies of Copper Anodization
The passivation of copper, due to the abovementioned complexity, triggers numerous topics and needs for fundamental research. The easiest way to passivate electrochemically metal, that has not yet been explored in terms of anodization, is the application of a potentiostatics with a three-electrode system, with which potentiostatic experiments in the passivity field are conducted according to Pourbaix diagram. reported such a study on Cu passivation in 1 M aqueous solution of KOH (Stepniowski et al., 2017). The voltametric study showed without any doubt two distinct oxidation peaks, at ca. −450 and −150 mV vs. Ag|AgCl, responsible for metallic copper oxidation to Cu+ and Cu2+, respectively. Moreover, the morphology of the obtained oxides strongly depends on the applied potential: for low potentials, micron-sized cubes were formed, mainly made of cuprous oxide, while at −200 and −100 mV vs. Ag|AgCl, nanowires were grown that were composed of a mixture of cuprous and cupric oxide
Fig.19 Mixture of cuprous or cupric oxide.
Top-view FE-SEM images of the surface morphology of the oxides formed via copper passivation in 1.0 M KOH at −400 (A); −300 (B); −200 (C); and −100 mV (D). Reproduced with permission from (Stepniowski et al., 2017)Elsevier, 2017.
Top-view FE-SEM images of effects of Cu anodization in: (a) 0.15 M KOH + 0.1 M NH4Cl at 6 V for 300 s; (b) 0.2 M KOH + 0.1 M NH4F at 6 V for 300 s; and (c) aqueous solution of KOH (pH = 11) at 10 V. Reproduced with permission from (Allam & Grimes, 2011) (Stepniowski & Misiolek, 2018)
Chemical properties:
Formula CU2O
Density 6.0g/cm3
Melting point: 1235 c(2255f)
2.4 Use of copper oxide
2.4.1 Hydrogen Sulfide (H2S)
CuO is a well-known sensor material for H2S gas detection, due to its catalytic behavior when exposed to H2S gas. The H2S detectors can be divided into two groups. The first one is focused on high concentrations of H2S, which are very dangerous for human beings (Egondi et al., 2018). The second one is developed to detect low concentrations of ppm and ppb, which is important for medical applications, such as halitosis diagnosis. Recently, Hu et al.(Hu et al., 2018) presented the gas-sensing results of H2S detection utilized by CuFe2O4− and CuO-based gas sensors. The obtained results showed that the response of the optimized CuFe2O4− modified heterostructures to 10 ppm H2S was approximately 20-times higher than that of pure CuO microspheres. The optimal temperature was 240 °C(Rydosz, 2018).
2.5 Application of copper oxide in textile industries
Copper oxide nanoparticles (CUONPS) have various application in the textile industries including.
2.5.1 Dye degradation
Can degrade industrial dyes, addressing environmental concerns. metal oxide nanoparticles have been used effectively for the degradation of organic dyes in wastewater. They are also used for antimicrobial activities. Amongst the metal oxides nanoparticles used for the decontamination of water, copper oxide nanoparticles have shown impressive results. This is because it is relatively cheap, has a narrow bandgap and high catalytic efficiency. toxic chemicals and solvents that are dangerous to human health and the environment are used as reducing/oxidizing agents. Biosynthesis of metal oxides has been used recently to overcome the challenges posed by using chemical methods (Nwanya et al., 2019).
2.5.2. Antibacterial properties
Incorporated into fabrics offer antibacterial benefits Nanostructured materials such as silver, copper, ZnO, MgO, TiO2, CuO, carbon nanotubes (CNTs) and their composites possessing antibacterial properties have recently received much attention. The use of such nanomaterials in medical devices is to prevent bacterial infection. Elemental copper and its compounds have been recognized as antimicrobial materials by the US Environmental Protection agency (EPA). Copper(I and II) oxides in its nanoform (<100 nm) displays enhanced antimicrobial activity towards pathogenic microorganisms. The ability of copper oxides to kill E.coli was confirmed based on the decrease in number of the colonies observed on the agar plates. The suspensions of various concentrations of Cu(I) and (II) oxides were incubated for 18 h and the bactericidal efficacies were monitored.
Fig.20 for bacterial decreases.
Denisov, N. M., Baglov, A. V., Borisenko, V. E., & Drozdova, E. V. (2016). Preparation and antibacterial properties of composite nanostructures from titanium and copper oxides. Inorganic Materials, 52, 523-528.
2.5.3 Photocatalytic activity
Facilitate photocatalytic reaction enhancing textile textile application The photocatalytic activity of titania is also limited by the recombination of the photogenerated electron-hole pairs as typical for all semiconducting materials. Titania exhibits only weak bandgap emission upon the recombination of conduction band electrons with valence band holes, and the irradiative recombination involving trap states is optically allowed. Recombination is generally caused by impurities, defects or other factors, which introduce bulk or surface imperfections into the crystal and, depending on titania properties(Schneider et al., 2014).
The first papers about Cu/TiO2 systems were mainly connected with photodeposition of copper on titania surface as the efficient method for Cu removal from water environments. CuII ions were reduced to metallic copper with the participation of photogenerated electrons (e−) and holes (h+) according to the following Reactions.
TiO2 + hν → e− + h+
Cu2+ + 2e− → Cu
H2O + 2h+ → 0.5O2 + 2H+
the presence of copper ions on the efficiency of photocatalytic oxidation of organic compounds. It was found that addition of dissolved copper ions to TiO2 reaction system improved significantly the rate of photocatalytic oxidation(Okamoto et al., 1985).
2.5.4 Waste water treatment
Aid in treating textile wastewater by degrading dyes. Textile industry is one of the most water consumption industries utilizing large amount of dyes, organic and inorganic chemicals and additives in the production process. Therefore, produced wastewater is a highly colored effluent due to the presence of dyes. Textile wastewater usually has high organic compounds and contains a wide variety of organic pollutants, make a high Chemical Oxygen Demand (COD). These toxic compounds are limiting factors for the use of biological treatment of textile wastewater since microorganism culture may be disturbed due to the toxicity of dyes. Several physico-chemical processes have been conducted for textile wastewater treatment. Coagulation and adsorption are conventional methods for the treatment of textile wastewater but, these processes are not able to mineralize organic compounds and only separate organic pollutants from water environment. Indeed, they convert aqueous pollution to solid pollution. Membrane processes suffers from the production of a concentrate liquid of pollutants which needs further treatment . Advanced Oxidation Processes (AOPs) are effective methods for the treatment of textile wastewater.
2.5.5 Textile finishing
CUONPs improve textile properties such as antimicrobial and UV protection.
Copper oxide (cuo) textile finishing is a process that impart various properties to textiles ,including.
5.5.6 Antimicrobial properties
CUO finishing prevents the growth of bacteria, fungi, and viruses on textile.
5.5.6.1 Antiviral properties:
CUO finishing has been shown to reduce the spread of viruses, such as COVID-19, on textile.
5.5.6.2 UV protection:
CUO finishing provide UV radiation protection, preventing skin damage and fabric degradation.
5.5.6.3 Flame retardancy:
CUO finishing can improve flame retardancy, reducing the reducing the risk textile fires(Khan & Jha, 2018).
2.5.7 Electronics
. Mechanically flexible and optionally Copper oxide nanoparticles have potentials application in electronics devices such as transistor and solar cells stretchable opto-electronic devices integrated with textiles (e-textile) or conformably adaptable to the human body (e-skin) are attracting great interest to create somatosensory systems that are useful for wearable sensors, health monitoring, drug dispensing, and the study of biological function, as well as for technologies that include human–machine interfaces, soft robotics, Electrical characterizations were performed with an Agilent 4155C semiconductor parameter analyzer in ambient (RH = 30–40%). For flexible IGZO FN TFTs, the output curve was measured at a gate voltage sweep from 0 to +10 V and drain source voltage from 0 to +1 V. To characterize the transfer curves, each gate voltage sweeps from 0 to +10 V was applied with a source–drain voltage bias of +1 V. The device was mechanically deformed during electrical characterization by laminating the device on different cylindrical objects having a different radius of curvature (Wang et al., 2020).
Synthesis of copper oxide
The increasing demand for environmentally friendly and sustainable synthesis methods, biogenic synthesis (green synthesis) has become prominent in the fabrication of CuO NPs. This approach utilizes biological entities such as plants and microorganisms to produce CuO NPs, offering advantages in terms of availability, simplicity, cost-effectiveness, and environmental compatibility (Subbaiya et al., 2017).
Biogenic synthesis of copper oxide nanoparticles
The synthesis of CuO NPs using biological methods involves the utilization of plant and microorganism extracts, including bacteria and fungi. This eco-friendly approach is renowned for its simplicity and cost-effectiveness, in contrast to conventional methods that rely on expensive and hazardous chemicals. Biological synthesis eliminates the need for chemical reducing and capping agents. Instead, plant extracts contain phytochemicals such as alkaloids, phenols, flavonoids, and terpenoids, while microorganisms possess enzymes and proteins. These natural components fulfill the dual role of reducing and capping, resulting in the production of nontoxic, biocompatible, and highly stable nanoparticles(Abhimanyu et al., 2023). However, the use of bacteria-based green synthesis has drawbacks, requiring a sterile culture environment, specialized growth media, and meticulous monitoring throughout the entire process. Additionally, the cost of media for bacterial growth can be prohibitive for large-scale commercial production(Agarwal et al., 2017).
Plant-based approaches for the synthesis of CuO NPs
The eco-friendly synthesis of CuO NPs using plant extracts, microorganisms, and other biological derivatives has been reported. Plants as production aggregates for CuO NPs have garnered considerable interest due to their safety, simplicity, and ability to serve as rich resources for stabilizing and reducing agents. Natural extracts from plant components offer a rapid, low-cost, and environmentally benign alternative that does not require expensive equipment, resulting in highly pure and concentrated products free of impurities. The metabolites and phytochemicals present in plant extracts, such as phenolic compounds, alkaloids, terpenoids, saponins, tannins, amino acids, proteins, enzymes, and vitamins, play crucial roles in reducing copper ions in salt solution, leading to the formation of corresponding CuO NPs(Gopinath et al., 2016). Presents the biological synthesis of CuO NPs utilizing diverse plant components, such as flowers, leaves, fruits, and stems, which are briefly discussed in this review. Previous studies have successfully demonstrated the preparation of CuO NPs through a simple approach involving mixing copper salt with plant extract. This mixture undergoes a reaction within minutes to hours under normal laboratory conditions(Priya et al., 2023).
Microbe-mediated green synthesis of CuO NPs
In recent years, microorganisms have emerged as significant nanofactories and have attracted considerable attention due to their reliability, eco-friendliness, and cost-effectiveness. They offer a viable alternative to reduce the use of toxic chemicals and the high energy requirements associated with physical and chemical synthesis. Microbes have the ability to accumulate and detoxify heavy metals while simultaneously reducing metal salts into metal or metal oxide nanoparticles through a range of enzymes. Bacteria, fungi, and yeast have been utilized for intra- or extracellular biosynthesis of metal and metal oxide nanoparticles (ALSHAMI et al., 2023). The extracellular synthesis method, in particular, has advantages over the intracellular approach because it eliminates several synthesis steps, such as sonication for cell wall degradation, multiple centrifugations, and washing steps for nanoparticle purification, increasing the practicality of the approach. Microbes play a crucial role in nanoparticle synthesis by providing enzymes and proteins, reducing cofactors, and organic materials as reducing agents. Additionally, the proteins secreted by microbes act as natural capping agents, preventing nanoparticle aggregation and ensuring long-term stability, thereby providing additional benefits(Mohd Yusof et al., 2019).
Actinomycetes-mediated synthesis of CuO NPs
Actinomycetes are exploited for synthesizing nanoparticles because they can produce secondary metabolites such as enzymes and proteins. These compounds serve as capping and stabilizing agents, enabling the production of nanoparticles with diverse shapes and sizes. For instance, Nabila and Kannabiran were the first to report the synthesis of highly stable spherical CuO NPs with an average size of 61.7 nm using actinomycetes. These nanoparticles demonstrated promising bactericidal potential against various human pathogenic bacteria. Another study described the eco-friendly synthesis of CuO NPs using two endophytic actinomycetes, Streptomyces pseudogriseolus (Acv-11) and Streptomyces zaomyceticus (Oc-5), isolated from Oxalis corniculata leaves. The nanoparticles synthesized from Acv-11 and Oc-5 were spherical with average sizes of 80 nm and 78 nm, respectively. Furthermore, these biosynthesized CuO NPs displayed interesting antibacterial, antifungal, larvicidal, and antioxidant properties(Hassan et al., 2019).
3.1. CALCIUM ALGINATE
alginate has become one of the most preferred materials as an abundant natural biopolymer (Ching et al., 2017) Alginate is a linear polymer polysaccharide composed of β-D-mannuronic acid (M block) and α-L-guluronic acid (G block) jointed by 1,4-linkages, which is extracted from either brown algae or some genera of bacteria. The molecular chain is arranged in an irregular blockwise pattern of varying proportions of G-G, M-G and M-M blocks (Brus et al., 2017) The percentage of M and G blocks and their distribution has an impact on the physicochemical properties of alginate, such as alginate of rich M units displays a flexible structure and better biocompatibility, while alginate of enriched G units exhibits a rigid molecular structure. Alginate is known to be rich in carboxyl and hydroxyl groups distributed along the backbone, making it open to chemical functionalization and cross-linking treatment. Typically, alginate can be cross-linked to form a hydrogel in the presence of divalent or trivalent metal cations, such as Fe3+, Al3+, Cr3+, Cu2+, Ba2+, Sr2+, Ca2+, et al. The gelation mechanism is the coordination between the carboxyl groups of alginate and the metal ions. Taking Ca2+ as an example, each calcium ion forms coordination bonds with two G units of the alginate molecular chain, which is called the egg-box structure (Brus et al., 2017) .
used the alginate to cross-link with cellulose to fabricate the alginate-based composite hydrogel, which was then lyophilized to be the hydrogel porous scaffold. The pore diameter of the scaffold was precisely tuned by adjusting the lyophilization process parameters such as the lyophilization temperature and time. As well known, pores of the lyophilized scaffold can provide the oxygen and nutrient substance for the host cell to facilitate the growth of new tissue. Moreover, the alginate porous scaffold can be acquired without ionic cross-linking, just by the freeze-drying technique. In order to enrich the application properties of the alginate scaffold, some other polymers such as gelatin (Homem et al., 2021). Chitosan and collagen were also incorporated into the alginate polymer to lyophilize and form the hybrid multi-functional lyophilized scaffold(Zhang et al., 2021).
The wet spinning technique is a pioneering approach for preparing the alginate fiber and its schematic diagram is exhibited in. The homogeneous alginate spinning solution extruded from the spinneret is introduced into a coagulation bath consisting of calcium salt solution to induce ion cross-linking and then form the primary fiber. The multiple draft rollers are installed in the coagulation bath to endow the primary fiber with a proper drawing ratio, which is beneficial for the improvement of fibrous mechanical performance. Moreover, to further enrich the application properties of alginate fiber, some researchers combined Ca2+ with other metal ions such as Zn2+, Ba2+, Cu2+, Al3+ and so forth to form the multi-metal ions coagulation bath . There are some differences in terms of the chelation interaction of various metal ions with alginate molecules, resulting in various formation rates of fiber (Zhang et al., 2019) Some other scholars chose other metal cations with better gelation ability to tune the ion exchange rate with alginate polymer, which retarded the Ca–Na cross-linking rate and achieved the homogeneous structure of metal-alginate fiber, following the order of the metal ion exchange rate: Pb2+ > Cu2+ > Cd2+ > Ba2+ > Sr2+ > Ca2+ > Co2+ ≈ Ni2+ ≈ Zn2+ > Mn2+ . These works aimed to decrease calcium ion content for prolonging the formation rate of fiber, but the longer formation time resulted in forming a hierarchical structure in the fiber Alginate is one of the most preferred biomaterials as an abundant natural biopolymer, which was approved by the United States Food and Drugs Administration. Calcium alginate fiber is nontoxic and has high hygroscopicity and biocompatibility, making it a perfect candidate for biomaterials such as wound dressing and tissue engineering scaffolds. Significantly, alginate fiber can imitate the physicochemical environment of tissue and its degradable product in vivo can be efficiently cleared by the renal, which is beneficial for tissue repair and regeneration. As an ideal biomaterial, the hygroscopic properties and biocompatibility of alginate fiber have become the research focus(Yeo & Kim, 2019).
3.2 Application of calcium alginate in Textile Industry
Application of calcium alginate in Textile Industry are given below.
3.2.1Tissue Engineering Scaffold
The other major application of calcium alginate-based fiber is tissue engineering scaffold, as a cost-effective material for cell immobilization and encapsulation. Compared to the wound dressing, the tissue engineering scaffold has additional requirements such as serving as an extracellular medium matrix to support cell growth, migration, differentiation, and eventually cell normal function. Multiple pieces of literature reported alginate hydrogel serving as the tissue engineering scaffold, in a bulky form or as an ink to be printed into a designed form, while investigation on calcium alginate fiber is also underway extensively. The fiber provides a few features that hydrogel does not have. As the assembly of fibers, the space between fibers allows a fast transport of nutrients and oxygen to the regeneration site and quick release of waste. Additionally, the manipulation of fiber orientation into an aligned form mimics the physiological environment, especially for the purpose to cue multiple cells to arrange into an aligned form, including muscle cell or neuron where the pattern is crucial for the activation of normal physiological function(Yeo & Kim, 2019).
3.2.2. Finishing treatments
The textile industry is looking for ecofriendly surface modification process that can be carried out without toxic textile chemicals. Recently, the use of low-environmental impact technologies based on sustainable biopolymers presents a novel possible avenue for large scale development of functional textiles in a green approach. For example, alginate chitosan cyclodextrin propolis and collagen suitable alternative agents have been used for the functional finishing of textile material Calcium alginate is used in finishing treatment to improve the texture and softness of fabrics. The functional finishing of textiles by alginate has been achieved using some techniques such as nanocomposite coating, ionic cross-linking coating, and LBL methods. These finishing methods are simple and have the strong possibility of industrial application. However, there is still a long way to go in research to obtain ideal functional textiles(Li et al., 2017).
3.2.3. Biomedical textile
Calcium alginate is used in biomedical textile due to its biocompatibility, biodegradability, and non- toxicity Biomaterials either natural or synthetic are widely used in biomedical applications to support, enhance, or replace damaged tissues or biological functions. In clinical setting, biomaterials are used as medical implants and devices to promote healing and serve as a carrier for cells during human tissues regeneration process.
The use of alginate in fibre form as biomedical materials has attracted extensive interest because of their high surface area, ease of handling, and its ability to retain mechanical integrity while in wet state. The later properties being crucial given the absorbent nature of alginate, especially when used as dressing for heavily exuding wound. For example, 3M™ Tegaderm™ Alginate High Integrity and High Gelling Alginate Dressing, made from hydro-entangled nonwoven web of calcium alginate fibres(Aderibigbe & Buyana, 2018).
3.2.4. Nanofibers
Coated calcium alginate nonwoven fabric with ZnO nano-particles, using the method of ion exchange. Calcium alginate nonwoven fabrics were first immersed in Zn(NO3)2 solution, in order to obtain zinc calcium alginate fabrics. Indeed, the high-Zn2+ concentration solution allows part of the Ca2+ on the calcium alginate fibers to undergo an ion exchange reaction with Zn2+. Then, the zinc calcium alginate fabric was immersed in amino hyperbranched HBP solutions. Zn2+ was obtained in the solution after an ion exchange of Zn2+ with NH3+. A high temperature of 80 °C can convert Zn2+ into Zn(OH)42−, and then, the ZnO-NPs are obtained. Finally, ZnO-NPs were bonded to the surface of calcium alginate fabrics. Indeed, the force of attraction between the positive groups of the ZnO-NPs and the negative groups of the alginate fabric, and the interactions of the hydrogen bonds between the amino groups on the ZnO-NPS, and the hydroxyl and carboxyl groups on the fabric allow for the attachment of the ZnO-NPs on the alginate fabric.(Dodero et al., 2020)
3.2.5. Silver ion
embedded alginate fibers with silver nano-particles (Ag-NPs) using the method of in situ reduction. First, alginate fibers and a silver nitrate (AgNO3) aqueous solution are mixed together. Ion exchange between the silver ions (Ag+) and the sodium or calcium ions in the alginate allows for the diffusion of Ag+ ions into alginate fibers. The fixation of Ag+ ions is performed thanks to an electrostatic attraction between the negative groups of the alginate and the positively charged Ag+ ions. The silver ions were then reduced in situ, so that the metallic silver generated can adhere to these elaborated fibers. These authors indicate that in an aqueous medium, these elaborated fibers allow for the reduction of 4-nitrophenol 4-NP to 4-aminophenol 4-AP. The catalytic reduction is performed by the Ag-NPs by relaying the electrons from the BH4− donor to the 4-NP acceptor(Zhang et al., 2020).
In the first stage, metal hydride formation was achieved via the adsorption of BH4− and its reaction with the surface of the elaborated alginate/Ag-NPs fibers. Due to the strong adsorption of the alginate/Ag-NPs fibers, 4-nitrophenol 4-NP can transport to the surface of the Ag-NPs. The desorption/adsorption equilibrium of the reactants on the surface of alginate/Ag-NPs fibers is fast. Then, the interaction of the adsorbed 4-NP with the silver nano-particles reduces the 4-NP. The reduction reaction allows the formation of the 4-aminophenol 4-AP (3). A new reduction cycle (4) will take place when the 4-AP reactant is desorbed from the surfaces of the Ag-NPs (Lin et al., 2015).
3.2.6. Textile printing:
three-dimensional (3D) printing, as a versatile layer-by-layer construction method by the direct addition of inks and helping a pre-defined digital model, was presented in 1986. Indeed, the origin of this technology dates back to the late nineteenth century, when technologies such as sculpture were developed. This technology has been used to fabricate a variety of materials such as polymers, composites, glass, metals, and other materials with complex, dense, and porous architectures by employing computer-aided manufacturing. Compared to the conventional engineering technologies, which usually need molds and machines, 3D printing has many advantages such as more flexibility, less consumption of materials during the process, 3D printing technology can be considered as the next universal manufacturing and the industrial revolution. 3D printed materials have been extensive applied in numerous industries like biomedical, water resource sector, food, batteries, Water-soluble alginate can be extracted by using several methods to increase the efficiency of alginate. Alginate-based hydrogels are popularly used for 3D printing technology due to their excellent printability and biocompatibility, relatively low cost, low toxicity, as well as rapid gelation in the presence of Ca2+ cross-linker.
Employing the 3D printed alginate-based materials for the electronics industry:
Various bacteria can be employed electricity for or treating pollutants and generating valuable produces. For example, S. Oneidensis MR-1 bacteria are broadly examined. This bacterium is used in the treatment of wastewater by oxidizing organic pollutants. In the process of oxidizing pollutants, electrons are created that are located on the outer surface of the bacterium. When this bacterium comes in contact with an electrode in a microbial fuel cell.
3.2.6 Wound dressing
Dermal wounds, both acute and chronic, represent significant clinical challenges such as poor vascularisation, protease susceptibility and microbial invasion at wound site which affect the early wound closure. Conventionally, cloth dressings comprising of a sterile pad and cloth gauze are used as wound dressing due to their low cost. However, they are prone to bacterial infection and easily stick to the wound, causing suboptimal wound healing process. Thus, the ability of materials, especially natural polymers such as polysaccharides (e.g., chitosan, chitin, dextran, alginates, chondroitin and heparin), proteoglycans and proteins (e.g., collagen, gelatin, fibrin, silk fibroin and keratin) have been proposed and studied to accelerate wound healing and to control the infection(Parani et al., 2016) .
Alginate dressing has been a well-known commercial wound dressing based on calcium alginate or sodium alginate in a form of absorbent gel-fibre matrices with fluid contact. It can maintain a moist wound environment which facilitates hemostatic effect, atraumatic removal and aids in the control of minor bleeding. However, having alginate hydrogel alone as wound dressing is insufficient for preventing bacterial infection and promoting bioactivities, especially in chronic wound healing. Therefore, recently alginate composite dressings have been increasingly developed(Parani et al., 2016).
3.3 Synthesis of Calcium alginate
Calcium alginate is naturally occurring polymer derived from brown seaweed its synthesis involve following steps.
3.3.1. Extraction of Alginate
Alginate is extracted from brown seaweed through a process involving treatment with sodium carbonate, followed by precipitation with calcium chloride or ethanol. Alginate is a natural occurring biopolymer with complex matrix polysaccharides in the brown seaweed. It exists as an insoluble salt such as calcium, magnesium and sodium. Commercially available sodium alginate’s molecular weight range between 32–400 kDa. Alginate consists of a linear block copolymer sequence of α-L-guluronic acid (G) and β-D-mannuronic acid (M) bonded by 1→4 linkages as shown in. The difference at C-5 in the uronic acids makes guluronic acid and mannuronic acid stereochemically different to each other. Random sequences of M- and G-blocks are distributed, where the proportion of these sequences depends on the source. The physical properties of alginate depend on a number of different key factors in which M and G contents play a crucial part. The M-M block is a relatively straight polymer, linked di-equatorially at C-1 and C-4; whereas the G-G block is buckled, linked from di-axial groups at both C-1 and C-4 stereochemical structure of M-G, G-G, G-M, M-M blocks. Around 200 different categories of alginates have been identified and extracted from nature, the ratio of mannuronate to guluronate (M/G) varies significantly, depending on the source organism and tissue from which it is being isolated and also the season when it was harvested listed the M/G ratios of alginates extracted from typical species of brown seaweed(Saji et al., 2022).
Calcium carbonate (CaCO3) comprises more than 4% of the earth’s crust. It can be found throughout the world in natural forms such as marble and limestone. CaCO3 is used in many industrial applications and mostly extracted by mining or quarrying. However, large scale industrial mining can be a serious risk to the environment. In recent years, microbially induced CaCO3 precipitation has emerged as an alternative approach to conventional CaCO3 extraction by mining. Bacterially induced CaCO3 precipitation has been successfully used for a wide range of applications including strengthening of sand and soil, removal of metal contaminants from the soil and groundwater, removal of calcium ions and polychlorinated biphenyls , remediation of monuments, CO2 sequestration , bio-deposition on porous materials such as limestone and brick, and, more recently, durability improvement of cementitious materials such as concrete (Okyay & Rodrigues, 2015).
The soluble calcium contained in the media was determined using a benchtop photometer. The precipitated CaCO3 was harvested by passing through filter paper (0.2 μm) and washed three times with distilled water. The precipitates were oven dried at 70 °C for 24 h (Seifan et al., 2017).
After extraction, the alginate contains residues, such as heavy metals, protein compounds, toxins, and polyphenols that compromise the biocompatibility of this biopolymer. Therefore, accurate extraction techniques must be performed, eliminating upstream and unnecessary compounds, and purification must be performed to eliminate downstream compounds, avoiding an immunogenic response in biomedical applications. Alginate used in medicine and introduced into the body without purification leads to cell overgrowth around the capsules of this biopolymer, so purification techniques must be used to reduce contaminants such as immunogenic proteins. Unpurified alginate, raw alginate, in a sphere for directed microencapsulation introduced into living organisms, is also known to produce characteristic pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPS) that stimulate the immune response. The viscosity must also be considered within alginate purification, as this parameter is affected after purification. Alginate can be purified by filtration, extractison, and precipitation (Uyen et al., 2020).
Figure. 21 sodium alginate extractionand purification.(Gonzalez-Pujana et al., 2018).
Conclusion
In conclusion, the synthesis and application of calcium alginate and copper oxide nanoparticles and nanocomposites have been discussed. Calcium alginate, a biocompatible and biodegradable polymer, has been explored for its potential in biomedical applications, sustainable textiles, and wound dressings. Copper oxide nanoparticles, with their antimicrobial and catalytic properties, have been investigated for their use in antimicrobial finishes, UV protection, and conductive textiles. The combination of these materials in nanocomposites has shown enhanced properties and potential for various applications. The findings of this research highlight the potential of these materials in addressing various challenges in biomedicine, sustainability, and textile technology.
Future research directions may include:
- Scaling up the synthesis of these materials
- Investigating their toxicity and environmental impact
- Exploring their use in other applications, such as drug delivery and tissue engineering
Overall, this research demonstrates the potential of calcium alginate and copper oxide nanoparticles and nanocomposites to drive innovation in various fields.
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