1 Introduction

Nanomaterials have been the subject of continuous research by researchers since its inception. While some researchers define nanomaterials as materials smaller than a few nanometers, others use the term to describe materials smaller than one micrometer. There is no specific definition of nanomaterials due to their multiple applications in many fields [1]. There are a number of scientific terms used related to nanomaterials, including the following:

Nanotechnology is a term that refers to the existence of material at the nanoscale level. Nanomanufacturing is defined as the use of specific methods to transform materials to the nano-level, and this is done by a group of top-down or bottom-up methods. A scale with a range of 1–100 nm is known as “Nanoscale”. Any substance with at least one dimension that lies in the 1–100 nm nanoscale range is considered a nanomaterial [2]. Nano-object is a discrete portion of matter that exists on the nanoscale and has one, two, or three exterior dimensions. Nanoparticles are the nanoscale state of an object if all its dimensions are within the nanoscale range. The aspect ratio refers to the ratio of the length of the major axis of a nano-object to its width of the minor axis. Nanosphere indicates that the aspect ratio of the nanoparticle is 1. Nanorod is a term used if the aspect ratio of a nanoparticle is greater than 1 [3]. The term "nano-fibers" refers to nano-objects that have two dimensions within the nanoscale range, but the third dimension over the nanoscale. Nanowires are structures that are similar to nanorods but have a greater aspect ratio. Nanotube is a term used if the nanofibers are hollow. Nanostructured materials: This term refers to any material that has molecules, crystals, structural elements, or contains groups with dimensions ranging from 1 to 100 nm. Nanomaterial is a term given to a material if it has at least one dimension ranging between 1 and 100 nm, and it does not differ much from the term nanostructured materials [4]. Engineering nanomaterials are materials that are specially produced to have one or more dimensions in a range not exceeding 100 nm. Nanocomposites: This term refers to materials that are multi-component and have multiple and different phases, provided that any component or phase possesses a nanoscale dimension or more [5].

Chemical, biological, and physical processes are the three main methods for the synthesis of nanomaterials. Nanomaterial production in physical manners is top-down, but in biological and chemical approaches it is bottom-up. Some examples of physical processes are electric arc as well as laser techniques, physical vapor deposition (PVD), mechanical ball milling, and so on. Several examples of chemical procedures are hydrothermal processing, chemical vapor deposition (CVD), the sol–gel technique, and co-precipitation. Plants, microbes (including bacteria, fungi, algae, and actinomycetes), along with biomimetic substances (such as cells, pollen, and enzymes) are all part of the biologic processes [6].

There are several factors that influence the efficiency of different methods for producing nanomaterials, such as the type of materials used (organic, inorganic, metallic, non-metallic, ceramic, polymer, or semiconductor), the concentrations of the reacting materials, the type of method used (physical, chemical, or biological), the reaction time, temperatures, pH, and humidity. We find that the pH directly affects the shape and dimensions of nanoparticles, as very small particles are produced at high pH levels, while at low pH levels, larger particles are produced [7]. The reaction time directly affects the color of the nanomaterials that are produced. The different methods used affect the physic-chemical characteristics of nanoparticles as well as the quantity and type of nanoparticles [8].

The present review provides an overview of the different physical techniques used in the generation of nanomaterials, such as mechanical ball milling, inert gas condensation (IGC), physical vapors deposition (PVD), laser ablation, laser pyrolysis, electrospinning, ion sputtering, pulsed wire discharge, and Arc discharge method. In addition, advantages and disadvantages of each method. Types of nanomaterials like carbon, metal, ceramic, lipid, semiconductor, and polymer nanomaterials. Characterization analysis of nanomaterials including Ultraviolet–visible (UV–V) spectroscopy, XRD (X-ray diffraction), BET (Brunauere emmette teller), FESEM (Field emission scanning electron microscopy), FTIRS (Fourier transform infrared spectroscopy), TEM (Transmission electron microscopy) and Zeta size analysis. Different uses of nanomaterials, such as environmental applications, agricultural applications, and military applications.

2 Types of nanomaterials

The following categories of nanomaterials are defined regarding to their size, shape, physical characteristics, as well as chemical composition [9]:

2.1 Carbon-based nanomaterials

The group of carbon-based nanomaterials includes two main groups: fullerenes and carbon nanotubes, in addition to other sub-groups like graphene, carbon nanofibers, as well as carbon black. These groups differ from each other in their shapes, sizes, physical properties, and chemical properties [10].

2.1.1 Fullerenes

Fullerenes are sphere molecules of carbon made up of various numbers of carbon atoms ranging in number from 28 to 1500 carbon atoms linked together by sp2 hybridization. The chemical symbol for fullerene is (C60). The size of single layers of fullerene ranges from 8.2 nm, and the size of multilayer fullerenes ranges from 4 to 36 nm [11]. Fullerene is characterized by its high electrical conductivity, which is why it has applied importance in electronic devices and commercial importance as well [12].

2.1.2 Carbon nanotubes (CNT)

Graphene nano foils are used in hollow coils to produce carbon nanotubes using the laser or electric arc method. Nanotubes are small in size about 0.7 nm in the case of single-layer carbon nanotubes and to a maximum of 100 nm in the case of multi-layer carbon nanotubes. Nanotubes can be anywhere from a couple of micrometers to several millimeters in length. The nanotubes' ends might be filled with fullerene molecules or left empty. One type of nanotube, known as a single-wall carbon nanotube (SWCNT), consists of two walls, called Double wall carbon nanotubes (DWCNTs), or consists of several walls, called Multi-wall carbon nanotubes (MWCNTs) [13, 14].

2.1.3 Graphene

A hexagonal lattice of planar, two-dimensional carbon atoms makes up graphene. The graphene sheet has a thickness of roughly 1 nm [15].

2.1.4 Carbon nanofibers

Carbon nanofibers are coiled fibers with a cone shape that are produced in the same method as graphene and carbon nanotubes [16].

2.1.5 Carbon black

Carbon black is an amorphous carbon substance with a spherical shape. The diameters of carbon black range from 20 to 70 nm [17].

2.2 Metal-based nanomaterials

To create nanoparticles based on metals, scientists use a variety of physical, chemical, as well as biological techniques [18, 19]. Metallic elements such as iron, copper, lead, aluminum, zinc, cadmium, cobalt, gold, as well as silver are usually utilized in the production of nanomaterials [20, 21]. The size range of metallic nanomaterials is 10–100 nm, which is one of the physical and chemical characteristics that define them. Characteristics of the material's outer layer, including its density, surface charge, size of pores, crystal structure, spherical form, as well as reaction rate [22, 23]. Nanomaterials made of copper, silver, as well as gold are characterized by a broad absorption capacity of the solar electromagnetic spectrum in the visible range. These metals have unique photoelectric properties as a result of the existence of confined surface plasmon resonance (SPR) [24]. Nanometal oxides made of silver and copper are used as biocides due to their very toxic effect on bacteria [25].

Many metal oxide nanomaterials have been produced, like zinc-, nickel-, manganese-, titanium-, iron- and cobalt-oxide nanomaterials. Metal-oxide nanomaterials have unique properties that qualify them for scientific and commercial applications. For instance, copper nanoparticles are utilized in remote sensing devices, antibacterial, catalysts, paint industry, and textile industry because they are characterized by a large surface area-to-volume ratio and interaction with other nanomaterials [26, 27].

Cerium oxide nanomaterials (CeO2) are added to diesel fuel to improve combustion efficiency [28]. Iron oxide nanoparticles are characterized by being highly crystalline, soluble in water, mono-disperse, and good biocompatibility [29].

The size of superparamagnetic iron oxide (USPIO) nanomaterials ranges from 50 to 100 nm and is widely used in medical applications such as MRI (magnetic resonance imaging), drug carriers, and gene delivery vectors [30].

2.3 Ceramic nanomaterials

Ceramic nanomaterials are small solid particles composed of inorganic and non-metallic materials. It is produced by heat treatment and cooled in specific methods to obtain certain physical and chemical properties. Ceramic nanomaterials are characterized by different shapes and sizes, amorphous, and polycrystalline, with good porosity, high density, and heat resistance. Ceramic nanomaterials are utilized in numerous uses like chemical catalysts, photocatalysts, battery manufacturing, coating materials, photo-analysis of dyes, and imaging fields [31, 32].

2.4 Lipid-based nanomaterials

Lipid-based nanomaterials are solid-lipid cores composed of lipophilic molecules in the form of lipid-soluble matrices. The diameter of lipid nanomaterials ranges from 10 to 1000 nm and is characterized by its spherical shape. It is usually used in biological applications [33].

2.5 Semiconductor nanomaterials

Semiconductors are metallic materials located between metals and nonmetals. Semiconductor nanomaterials have physical and chemical properties similar to metallic nanomaterials, such as different sizes and shapes, which gives them a wide range of different applications. Semiconductor nanomaterials were used in photocatalysis and photonic optics, so they were widely used in the manufacture of solar cells, transistors, LEDs (light emitting diodes), and water-splitting applications [34, 35].

2.6 Polymer nanomaterials

Polymer nanomaterials are produced from various organic materials. It is characterized by nano-spherical shapes or nano-capsules whose size ranges between 1 and 1000 nm. Nanospheres are a mass of solid particles in the form of a matrix. Nano-capsules forms of polymeric materials are fully encapsulated solid nanoparticles. Polymer nanomaterials are used to produce lipid nanoparticles and have medical applications such as the pharmaceutical industry and cancer treatment [36, 37]. Table 1 summarizes the sizes and shapes of several kinds of nanomaterials.

Table 1 Sizes and shapes of different types of nanomaterials
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3 Physical methods for the preparation of nanomaterials

Physical methods depend in their working principle to produce nanomaterials on the use of thermal energy, radiation on energy, and mechanical pressure forces, which results in the condensation, dissolution, evaporation or abrasion of the materials. Physical methods for producing nanomaterials are distinguished from chemical methods in that they are environmentally friendly, do not cause pollution, produce homogeneous nanoparticles and chemical solvents are never used in these methods [7].

Nanomaterials are usually produced by physical methods from fragmentation of bulk materials in top-down methods [4]. Among the physical methods used to produce nanomaterials and nanoparticles are the following:

3.1 Mechanical ball milling

The basic principle of working in this method is based on the use of ball milling to reduce particle size with high energy. This method was developed by John Benjamin (1970). Reducing the particle size leads to modifying the surface properties of the material. The mechanical milling process is classified into high-energy mechanical milling and low-energy mechanical milling. The mechanical milling process is depended on the properties of milling powder and the mechanical energy used. This technique is commonly employed for the synthesis of metal nanoparticles [38].

In this method, the material to be converted into nanoparticles is placed in a container containing solid balls were made of steel or carbide in the presence of an inert gas, taking into account that the ratio of the balls to the material used is 2:1. The container gets rapid rotation around its central axis, causing the material to be squeezed between the solid balls and the container wall (Fig. 1). The container rotation speed and milling duration affect the production rate and size of nanomaterials [39].

Fig. 1
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Mechanical ball milling method [4]

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Different types of milling containers, including attrition ball mill, planetary ball mill, vibrating ball mill, low energy rolling mill, and high energy ball mill are utilized [38, 40]. The sizes of nanomaterials produced by ball milling range between 3 and 25 nm. The morphological and physical properties of nanomaterials produced using ball milling are influenced by multiple factors, such as the type of material, the type of mill, the speed of rotation of the mill, the duration of the grinding processes, the high energy used, the ratio of solid balls to the powder ratio, and the type of inert gas used in the grinding medium [41].

Advantages: It is extensively utilized for the production of nanomaterials with better physical characteristics like high purity and solubility. An environmentally friendly method does not result in any type of pollution [42].

Disadvantages: It requires high energy during the process of producing nanomaterials. The grinding time is very long. Nanomaterial contamination may occur during the grinding process. It is possible for grinding to occur due to the microstructure of the material, which may be very sensitive. The size of the resulting nanomaterials cannot be controlled [43].

3.2 Inert gas condensation (IGC)/molecular condensation

The Inert gas condensation technique is used to produce a wide range of nanomaterials, including metallic materials, alloys, semiconductors, metal nanoparticles, and their oxide nanoparticles [7]. The molecular or inert gas condensation method depends on compressing metal materials using an inactive or inert gas such as neon, argon, or helium inside a pressure chamber container, which results in the evaporation of the particles of the metal material. Then the metal vapors are cooled using liquid nitrogen. Cooling metal vapors causes the atom to quickly lose its energy and form nanoparticles with sizes ranging from 2 to 100 nm. For Example copper nanoparticles were produced by evaporating them with an inert gas and then cooling the vapors using liquid nitrogen [44].

Several factors affect the size of nanoparticles generated produced by this technique, such as the type of inert gas injected into the pressure chamber, temperature and pressure in chamber. It was found that the evaporation temperature and inert gas pressure have a clear impact on the size, shape, and crystallization of nanoparticles [45].

Advantages: This method was used to produce multi-core metallic nanomaterials. It is characterized by the production of ultrafine nanoparticles [46].

Disadvantages: This method requires special conditions of gas pressure and temperature [46].

3.3 Physical vapors deposition (PVD)

One of the physical methods used to produce nanomaterials is by transferring the materials to the atomic level using the material evaporation method. It results in nanoparticles in the form of very thin layers. It is an environmentally friendly method that does not result in pollution at all. Also it is called evaporative condensation method. This method is used to increase the efficiency of metal hardness and resistance to oxidation or corrosion by depositing thin films in the form of nanoparticles on the surface of these metals. It was utilized to generate silver nanoparticles and germanium nanoparticles for use in electronic and optical devices. This technique is also utilized to deposit metal nanoparticles and thin films on carbon nanotubes [47].

Advantages: The temperature used in the PVD method is relatively low. A simple and easy method was used to produce thin metal nano-films. The size of nanoparticles can be controlled. Nanoparticles have a good crystal structure [48].

Disadvantage: Production costs are very high. It is Low productivity [38].

3.4 Laser ablation (LA)

Nanomaterials are produced using a strong laser beam. This method is called laser ablation (LA) or Pulsed laser deposition (PLD). In this method, evaporation or removal of particles from the solid surface of the original material or primary material occurs as a result of its exposure to a high-intensity laser beam, which leads to the production of nanoparticles. A 106 μm Nd: YAG (neodymium coated yttrium aluminum garnet) laser, harmonic lasers of Ti: Sapphire (titanium-coated sapphire), and copper vapor lasers are utilized (Fig. 2). This method is widely used for the synthesis of carbon nanomaterials, metal nanomaterials, oxide composites, and ceramics [49].

Fig. 2
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Laser ablation (LA) method [53]

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The researchers used the laser ablation method to prepare lead sulfide nanoparticles on a Si substrate and produce silver nanoparticles on nanosheets of nickel hydroxide. This method can also be used in the preparation of carbon nanotubes. The type of laser beam, the wavelength of the laser beam, pulse time, and type of solvent are very important factors influencing the size and formulation of nanoparticles [50].

Advantages: An effective and easy method was used to produce nanoparticles in the form of a suspension. Nanoparticles are produced in liquid-media without the need to add surfactants. It is used to prepare silicon nanoparticles and Al2O3 nanoparticles coating. The purity of nanoparticles is about 90%. It is environmentally friendly technology [7, 51].

Disadvantages: This method is characterized by its low productivity in addition to its high cost [52].

3.5 Laser pyrolysis

Magnetic nanoparticles are produced using the laser pyrolysis technique. In this technique, a beam is utilized to high-power from carbon dioxide, where the reacting gaseous or liquid materials are excited and then quenched again. A salt solution is also used to spray the reactants, where the reactants evaporate and produce particles that are then dried and converted into concentrated particles at higher temperatures [54].

A high-energy infrared carbon dioxide laser that is absorbed by the reactants with sulfur hexafluoride (It is an inert photosensitizer). Nanomaterials are produced when the reactants reach saturation and become condensable during the evaporation stag. This method can also be used for produce molybdenum sulfide nanoparticles, silicon carbide nanoparticles, silicon nanoparticles, composite nanoparticles, ceramic nanoparticles, ternary nanocomposites, and metal oxide nanoparticles [55].

Advantages: Clean, environmentally friendly. It is used to produce nanoparticles of uniform size. The size of the resulting nanoparticles can be adjusted. A simple method is used for producing large quantities of nanomaterials and nanostructures with different dimensions [40].

Disadvantages: This method can be used to produce large quantities of nanomaterials, but this requires very sophisticated and expensive equipment [7].

3.6 Electrospinning

Coaxial electrospinning is considered one of the most important physical achievements for the production of nanomaterials. It follows a top-down approach and is a simple and effective technique for producing nanofibers from polymers [28]. The electro-spindle consists mainly of a blunt injection needle, a high-voltage electrical source, a tank containing the solution, a pump, and a collector [56]. Figure 3 depicts a diagram of the working principle of coaxial electrospinning to produce nanofibers.

Fig. 3
figure 3

Electrospinning method [57]

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Several factors affect the electrospinning processes to produce nanofibers: (1) the thickness of the injection needle. (2) Polymer composition and molecular weight. (3) Viscosity and surface tension of the solution (4) Electrolytic flow rate and concentration (5) Capillary distance (6) The size and movement of the collector (7) The room temperature, relative humidity, and air velocity inside the room. This technique has been employed to develop the production of core–shell nanomaterials, hollow polymers, organic, inorganic, and hybrid nanomaterials. The nanofibers produced in this method are characterized by a strong and specific nanostructure and a high surface-to-volume ratio [57]. A variety of polymers, like natural polymers, synthetic polymers, specialized polymers, as well as biodegradable polymers are used in the coaxial electrospinning process. These polymers must be soluble in solvents and have a high molecular weight [58].

3.7 Ion sputtering

This method is called several names, including sputtering, ion sputtering, ion beam deposition, ionizing mass beam deposition (IBD), and Ion sputtering. This technique was developed in 1985 to produce high-quality single-crystalline nanofilms [59]. The ion spraying process is carried out inside a vacuum chamber while maintaining the chamber pressure between 0.05 and 0.1 mbar. A high electrical potential is used and directed at the target material, causing evaporation of molecules from the surface of the material. An electron beam is used and the free electrons are moved through a spiral path using magnetic poles, which leads to the electrons colliding with the atoms of the inert gas (argon), and thus ionization of the gas occurs. As the process continues, due to the accelerating electrical voltage a state of ignition (plasma) occurs, which leads to the attraction of positively charged gas ions and their continuous collision with the surface of the target substance. This process is repeated using energy higher than the binding energy between the molecules of the substrate. A continuous collision occurs between the gas molecules and the atoms of the substrate, which leads to the dispersion of the atoms and the formation of vapors in the form of a cloud. The cloud consisting of matter atoms is deposited in the form of thin nano-films (Fig. 4) [7, 40].

Fig. 4
figure 4

Ion sputtering method [7, 40]

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Advantages: It does not affect the composition of the material after completing the process. It is not necessary to choose heat-resistant metals or intermetallic compounds as in other methods such as laser ablation. An economical method, as spraying equipment is inexpensive. The possibility of forming impurities is less compared to chemical methods. It is used to generate ionic nanoparticles of different sizes and compositions. The size, composition, and charge of ions can be controlled [60].

Disadvantages: Ionized gases can affect the structure, appearance, and optical properties of nanocrystalline metal oxide films [40].

3.8 Pulsed wire discharge technique

It is among the most used physical processes that generate metallic nanoparticles. In this technique, a metal wire is vaporized via a pulsating electric current passing through two electrodes. The vapors are then cooled by the surrounding gas to form nanoparticles. Figure 5 shows the pulsed wire discharge method to produce metallic nanomaterials. It is an environmentally friendly method that has been used to produce nitride nanoparticles [44, 61].

Fig. 5
figure 5

Pulsed wire discharge method [61]

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3.9 Arc discharge technique

The arc discharge method is divided into two methods: a method that takes place in a gaseous medium and is called the Electric Arc Discharge in Aerosol Dielectrics method in air insulators, and another method that takes place in a liquid medium and is called the Electric Arc Discharge with Liquid Dielectric method [6].

3.9.1 The electric arc discharge in aerosol dielectrics

The Electric Arc Discharge in Aerosol Dielectrics method is one of the most important methods used to produce nanomaterials with different structures. They are most commonly used to produce carbon-based nanomaterials such as fullerene, Few-layer graphene (FLG), carbon nano-horns (CNHs), and amorphous spherical carbon nanoparticles and carbon nanotubes (CNTs) [62].

In this method, the electric arc is created at atmospheric pressure using electrodes while maintaining a critical distance between the electrodes. When the electric potential between the electrodes reaches the threshold point, the gas ionizes and the current passing through the electrodes expands, leading to the formation of a plasma column. This is followed by the scattering of the electrodes, and then the metal evaporates and crystallizes in the form of small particles with a diameter of about a few nanometers, called elementary particles. These particles mix with the gas and are known as aerosols. Thus, nanoparticles are formed [63].

It's a simple process that needs inexpensive equipment. The shape, size, and production rate of nanoparticles using this method are affected by several factors, including: the type of electrodes, the critical distance between the electrodes, the discharge energy, and the chemical structure of the aerosol particles [64].

3.9.2 The electric arc discharge with liquid dielectric

The basic principle of the arc discharge method in an insulating liquid medium is to produce thermal energy by a series of electrical discharges from the electrical energy used between the electrodes. The temperature of the electrodes during this process may reach several thousand degrees Celsius. This leads to melting and then evaporation of the electrode material. The resulting vapors are then condensed in an insulating liquid medium; leading to form nanoparticles. This method is used to produce gold nanoparticles and silver nanoparticles [65].

Figure 6 shows the method of discharging an electric arc using a direct current. The electrical discharge unit in a dielectric liquid medium consists of two electrodes, an electrical power source and an operating tank containing the dielectric liquid. Mono or bimetallic electrodes can be used. Organic liquids and inorganic liquids are used as dielectric medium [63].

Fig. 6
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Electric arc discharge with liquid dielectric method [63]

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Many factors affect nanoparticle shapes and sizes that are produced using the electric arc discharge method with a liquid dielectric, including the intensity of the electrical current, the type of electrodes, the distance between the electrodes, the type of insulating liquid medium, and the temperature resulting from the electrical discharge process [66].

4 Characterization analysis of nanomaterials

Nanomaterials technology is currently widely used in many applied, research and scientific fields. Consequently, knowledge of the morphological, chemical, and physical aspects is essential, and this is done through the analysis and characterization of nanomaterials. Many modern techniques provide us with the characterization analysis of nanomaterials, such as: [7]

4.1 Ultraviolet–visible (UV–V) spectroscopy analysis

UV–V spectroscopy is a method employed to analyze the composition of substances or nanoparticles. It is a straightforward and cost-effective approach to characterization. The idea of its work is based on measuring the intensities of light reflection in the samples to be characterized and comparing it with measuring the light intensity in the material resulting from it (the reference material). The process of measuring the optical absorption spectra of the sample signifies the creation of nanoparticles, as shown in Fig. 7. Characterizing the sample's transport and absorption characteristics is made possible by the UV–V spectroscopy approach [7].

Fig. 7
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UV–Vis absorption spectra and wavelength of Zn (NO3)2 nanoparticle [67]

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Optical properties, refractive index, shape, size, and stability evaluation of colloidal solutions are the most important features of the sample nanoparticles. Therefore, UV–V spectroscopy is used as an effective and important tool in characterizing, analyzing, identifying, and examining nanomaterials. The information obtained from the use of UV–V spectroscopy indicates that a maximum wavelength of 300 nm for Zn (NO3)2 changes to 340–370 nm when it is converted into nano-zinc oxides [67].

4.2 XRD (X-ray diffraction)

Among the most commonly techniques employed approaches to characterize and analyze nanomaterials is X-ray diffraction (XRD). They are extensively utilized to characterize a wide range of nanomaterials such as crystals, powders, and liquids. XRD was utilized to confirm the crystalline nature of the nanomaterials, stress measurement, phase analysis, chemical characterization, structural analysis, size, and shape of the nanoparticles [67].

It is a distinctive technique for studying and analyzing crystalline, amorphous, and polycrystalline materials at the molecular and atomic levels of the material. XRD refers to the phenomenon of elastic scattering of X-rays through material atoms. Elastic scattering is the loss of energy by rays when they collide with atoms of matter. The working principle of XRD relies on the disparity in distance (either in phase or angle) transmitted by the waves interfering with the atomic structure of the material. The XRD device consists of (1) an Electron beam tube to produce X-rays. (2) Collimator used to make the rays in parallel lines before they reach and collide with the sample. (3) Where to place the samples. (4) Detector: (or counter) used to detect neutral rays. (5) Computer to plot the XRD data (2θ vs. reflection intensity). Figure 8 [68]

Fig. 8
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Components and working principles of XRD [68]

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4.3 BET (Brunauere Emmette Teller) analysis

It is utilized to calculate the surface area of nanomaterials. The idea of its work is based on using nitrogen to analyze the surface area of BET. Due to the presence of a weak connection between the gaseous phase and its solid phase, liquid nitrogen is used to cool the surface, which leads to the production of quantities that can be detected by adsorption. This method is characterized by high efficiency, great interaction with most metallic nanomaterials and gives accurate results. This method was used to detect the crystalline structure of metal ions and their oxides, such as zinc oxide. Figure 9 Shows that zinc oxide has a porous structure as a result of the adsorption of N2 [7].

Fig. 9
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Zn (NO3)2 nanoparticles analysis by BET [67]

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4.4 FESEM (field emission scanning electron microscopy) analysis

Morphological analysis of nanomaterials (at the nanoscale) depends on the FESEM (field emission scanning electron microscopy) technology usage. This technique is done by directing a beam of electrons using the electron gun at the top of the device to hit the sample. The magnetic field and lenses in the sample chamber are used to control the path of the electron beam [69].

The electron beam is projected successively and rapidly onto the sample, which leads to the scattering of electrons. Some of the scattered electrons are transferred to the sample and others become scattered electrons. The detector is used to track scattered electrons and secondary electrons by the device's computer (Fig. 10).

Fig. 10
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The different parts of the SEM [70]

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A much magnified, high-resolution image is taken by the device's computer to determine and analyze the properties of the nanoparticles of the sample. Figure 11 shows the basic signals resulting from by primary electrons interacting with the sample in the SEM [70]. Figure 12 shows FESEM images of silver-doped zinc oxide nanoparticles.

Fig. 11
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The basic signals resulting from by primary electrons interacting with the sample in the SEM [71]

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Fig. 12
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FESEM images of silver-doped Zn (NO3)2 nanoparticles [72]

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4.5 FTIR (Fourier transform infrared) spectroscopy

Inorganic and organic molecular bonding can be investigated with this method. The infrared (IR) spectrum encompasses electromagnetic waves with wavelengths between 700 nm and 1 mm, which fall on the red end of the visible light spectra. This method relies on exposing the sample to infrared radiation to form a spectrum. The sample absorbs a portion of infrared radiation depending on the molecular bonding characteristics of the substance. The samples’ molecular fingerprint is determined from infrared transmission and absorption. This method provides a set of information that determines the characteristics, quality, and number of individual components of the sample [73]. Figure 13 shows a schematic diagram of the operation of FTIR instrument with an FTIR spectrum.

Fig. 13
figure 13

Schematic diagram of the operation of an FTIR instrument with an FTIR spectrum [74]

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4.6 TEM (transmission electron microscopy) analysis

The morphological characteristics of nanomaterials are established using TEM analysis. The concept of the study revolves around utilizing the principle of electron permeability within the sample. Consequently, electrons are emitted into the device by a part called a filament. Electrons are emitted from the filament in the form of thermal filaments or emission filaments. The electrode is used to accelerate the production of electrons to obtain high energy. Pictures of the samples are taken using an electromagnetic lens [7].

The crystal structure and interatomic distance of the nanomaterials were investigated utilizing high-resolution transmission electron microscopy (HRTEM). In TEM analysis, the SAED type shows the natural characteristics of the sample, whether it has a crystalline or amorphous structure. The images obtained from the device regarding the study of the sample indicate that the presence of a concentric ring indicates that the sample has an amorphous structure, while the presence of systematically arranged points indicates that the sample is crystalline. Figure 14 shows an image of the shapes of silver-doped Zn (NO3)2 nanoparticles taken by TEM the natural structure of the sample is crystalline [72].

Fig. 14
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Image type SAED by TEM of silver-doped Zn (NO3)2 nanoparticles [72]

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4.7 Zeta size

To study the surface charge, particle size characteristics, and molecular weight of colloidal nanoparticles in liquid media, a group of nanoscale tools is used, called the Zeta size, particle size analyzer, or Zeta potential. Particle size analysis (Zeta size) is a colloidal chemistry technique that is useful in understanding the physical stability of nanomaterials while they are in dispersion. The concept of the work is based on whether the nanoparticles have a positive or negative charge on their surfaces. It works to attract charged ions to their surface and produce an interfacial double layer around them (Fig. 15).

Fig. 15
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Zeta size and ionic concentration of charged particles suspended in a liquid medium [74]

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The nanoparticles disperse throughout the solution in the first layer, known as the Stern layer, which is encased in an ionic layer. An electrical potential that describes the double layer is called the Zeta potential. It represents the potential diametrically opposed to the liquid's ionic double layer and the dispersion medium. For colloidal nanoparticles, the optimum Zeta potential value falls somewhere between 100 mV and (− 100 mV) [75].

The large value of the Zeta potential (positive/negative) expresses the better stability of the particles through the electro-static repulsive forces of the particles. If the Zeta value is greater than ± 30 mV, the repulsive forces are sufficient to maintain the identity of the individual particles. If the Zeta value is smaller than ± 30 mV, the particles aggregate due to the existance of van der Walls forces, which leads to the lack of physical stability of the substance [76].

5 Applications of nanomaterials

5.1 Environmental applications

5.1.1 Bioremediation

Nanomaterials are utilized to remove environmental pollutants as well as organic pollutants from water and soil, such as heavy metals. Silver nanoparticles were used to analyze some organic compounds and dyes found in wastewater. The nanomaterials that have been used to remove organic pollutants include metal oxides, nanoscale zeolites, carbon nanofibers, and carbon nanotubes [77].

Nano zero-valent iron (nZVI) has been widely used for removing heavy metals like cadmium, lead, mercury, thallium, as well as arsenic from water and soil. Due to the extreme toxicity of these elements, their presence beyond the permissible limit results in harm to human, animal, and plant health. Supermagnetic iron oxide nanoparticles are an effective material and have the ability to absorb heavy metals from water and soil [78].

5.1.2 Environmental sensors

Nanoparticles and materials have already been used as biosensors to monitor pollutants in soil and water and improve their quality. Certain properties of nanoparticles are used to bind directly to some kinds of organic pollutants as well as heavy metals in water and soil, thus detecting and treating them. For instance, gold nanoparticles have been used as environmental sensors to detect mercury compounds in water. Nanomaterials have also been utilized to detect bacterial and fungal diseases and biological compounds in the soil that infect plants [79].

5.1.3 Environmental catalysts

Nanomaterials have been effectively utilized as environmental catalysts in chemical reactions, including catalyzing the conversion of biomass for biofuel production and various environmental remediation processes. Platinum nanoparticles showed their efficiency in catalyzing the conversion of biomass into biodiesel. It was also used to measure the amount of mercury ions in groundwater (47.3 nm), tap water (26 nm), and MilliQ samples (16.9 nm). In general, nanomaterials have unique properties and distinct capabilities that allow them to be utilized in many environmental uses [80].

5.2 Medical industry applications

5.2.1 Medical drug delivery

Currently, there is a growing fascination with the utilization of silver nanoparticles in biomedical applications because of their optical properties, chemical stability, ease of synthesis and production. Researchers turned their attention to using silver nanoparticles in treating cancer, and satisfactory results were obtained. It has also been used in chemical sensing of drug side effects and as drug carriers. Sun et al. [81] presented two methods for subjecting the use of nanomaterials to pharmaceutical control, which are: (1) sustainable materials and their use can be controlled (2) catalytic materials, that is, materials that are sensitive to pH, light, enzymes, and temperatures.

Nanomaterials used in the pharmaceutical industry have proven their ability to deliver medications to specific areas of the body with high efficiency, which allows the medications to be more effective. Zinc oxide nanoparticles have also been utilized to deliver drugs and their ability to effectively target cancer cells. Copper nanoparticles have antimicrobial properties. They have therefore been used in medicines to treat bacterial infections [82].

5.2.2 Diagnosis of diseases

Nanomaterials are used in the manufacture of medical devices such as CT scan machines. For instance, iron oxide nanoparticles were utilized as contrast agents in a magnetic resonance imaging (MRI) device to detect tissues and organs inside the human body. Silver nanoparticles have electrical, optical, and catalytic properties in their ability to detect tumors resulting from cancer cells [83].

5.2.3 Tissue engineering

Due to the tremendous progress in nanomaterials are used in the medical field. Nanoparticles have been used as stimulators of the repair and growth of tissues as well as organs. For instance, titanium dioxide nanoparticles were used in tissue culture engineering to stimulate bone cell growth [84].

5.2.4 Antimicrobials

Copper nanoparticles and silver nanoparticles have highly toxic properties to microorganisms. These nanoparticles have been utilized in medical and therapeutic products, including medical devices and wound dressings. In general, nanomaterials have great potential that allows them to be used in medical industries. It is necessary to study them well in terms of the benefits and risks that arise from their use and the extent of their security and safety on human public health [85].

5.3 Agricultural applications

5.3.1 Pesticides and herbicides

Nanomaterials are used in the manufacture of agricultural pesticides, insecticides, and herbicides, which reduces the use of chemical pesticides and thus reduces environmental pollution. Copper nanoparticles and silver nanoparticles have anti-fungal, anti-bacterial, anti-viral, and anti-algae properties, allowing them to be used in managing pests and diseases that affect agricultural crops. They can also be utilized as transport and delivery systems for the active components in biological compounds, which leads to a more targeted application [85, 86]. Using metal nanoparticles in the field of agricultural pesticides is still in its early stages, so it is necessary to study their side effects on human health.

5.3.2 Fertilizer industry

Nanomaterials usage in the fertilizer industries (nanofertilizers) has improved mineral nutrition for plants. Recent investigation has demonstrated that the application of nanomaterials may yield greater efficacy in comparison to chemical fertilizers. The nanomaterials usage in agricultural fertilizers has led to controlling the release of soil elements and the ability of plants to benefit from them. This may reduce the loss of elements in irrigation water without the plant benefiting from them. It is possible shortly that fertilizers based on nanomaterials will be replaced to reduce chemical fertilizers usage and the risks resulting from them. In contrast, other studies have found that nanomaterials are as effective as other agricultural fertilizers, or even less effective. Nanoparticles of metals including silver, zinc, copper, gold, aluminum, and iron are the most widely used in fertilizing, promoting plant growth, and improving agricultural productivity [87].

5.3.3 Safety of agricultural crops

Nanomaterials have been used to detect and eliminate pathogens that affect agricultural crops through their use in agricultural pesticides and fertilizers. This resulted in the safety of agricultural food products and reduced the risk of foodborne diseases [77].

5.3.4 Water purification

Nanomaterials have been used to purify irrigation water through their ability to get rid of organic pollutants and remove heavy metals that may accumulate in plants. It reduces the chances of crop contamination, improves their productivity, and thus improves the safety and quality of agricultural products [77].

5.4 Food industry applications

5.4.1 Processing and preservation food

Nanomaterials have been utilized to enhance the efficiency of food processing and manufacturing processes, including grinding, drying, and mixing processes. For example, silver nanoparticles have been used as natural preservatives in food preservation processes as antibacterial agents. Nanomaterials have also been used in the manufacture of materials used to wrap food, which makes them resistant to heat, humidity, gases, and pollutants [86].

5.4.2 Fortification of food

Nanomaterials can be used to improve the quality of foodstuffs, and this is done by adding the necessary vitamins and minerals to the product. For example, iron oxide nanoparticles and copper nanoparticles were used to add iron and copper to the product according to the prescribed proportions. Copper is a vital component in numerous metabolic processes. Additionally, iron is an essential nutritional element [88].

5.4.3 Quality of food

Nanomaterials are used as sensors to detect the quality and safety of foodstuffs. In general, the use of nanomaterials in the food industry leads to improving the nutritional values, quality and safety of products [87].

5.5 Electronics industry applications

5.5.1 Display and storage technologies

Silver nanoparticles and gold nanoparticles have been used to improve image contrast by enhancing the brightness and conductivity performance of display screens such as LCD and OLED displays. Nanomaterials have been utilized in energy storage devices, such as capacitors and batteries, to enhance energy density and accelerate charging. Zinc oxide nanoparticles (ZnO NPs) are utilized in capacitors because of their capacity to store and dissipate energy [89].

5.5.2 Data storage

Nanomaterials play a crucial role in enhancing the capacity, speed, and efficiency of electronic data storage devices, especially flash drives and hard drives. Magnetic nanoparticles have been employed in hard drives for their capacity to store and recover data through their magnetic characteristics. Magnetic nanoparticles consist of iron, nickel, or cobalt components that possess the ability to be readily magnetized and demagnetized. This characteristic enables them to effectively store or retrieve data. Utilizing nanoparticles is advantageous for enhancing the performance and efficiency of electronic devices and systems [90].

5.5.3 Sensors

Sensors are considered one of the important applications of nanomaterials in electronic devices. Sensors are used to detect changes in a particular substance in a particular environment. Nanomaterial-based sensors have high sensitivity and broad exploratory limits. Sensors are used in many applied fields, such as sensing humidity, toxic gases, engines, energy storage devices, medical devices, and military defense devices. They are also used in air navigation devices (aviation and space sciences) and many other applied fields [91].

Examples of nanomaterials used in sensors include ZnFe2O4 nanoparticles for sensing humidity due to the small size of the nanoparticles, their large surface area, and their ability to absorb water vapor. CoFe2O4, CuFe2O4, and NiFe2O4 nanoparticles are also used to sense oxidizing gases such as chlorine. Figure 16 shows the role of nanoarchitectonics and its contributions to multiple scientific disciplines in the design and fabrication of sensors [92].

Fig. 16
figure 16

Design and fabrication of sensors using nanoarchitectonics [92]

Full size image

5.6 Chemical applications

Nanomaterials have proven to be highly effective catalysts for chemical processes, enabling the performance of chemical reactions at reduced temperatures. Several nanomaterials have been employed as catalysts in the chemical industry: the use of platinum nanoparticles (PtNPs) in fuel cell reactions and palladium nanoparticles in hydrogenation reactions, oxidation reactions, and cross-coupling reactions.

Iron nanoparticles have also been used in hydrolysis and oxygen reduction reactions, and nickel nanoparticles have been utilized in hydrogenation and hydrolysis reactions [93].

Nanoparticles have been used based on their ultrafine size properties in the separation and purification of liquids, gases, and chemicals, such as the use of iron oxide nanoparticles to remove pollutants from water. Silver nanoparticles and gold nanoparticles have also been used to purify water and remove bacterial and viral pollutants and heavy metals. Aluminum nanoparticles have been used to purify gases and remove pollutants from water, such as oils and fuels [94].

5.7 Military industry applications

5.7.1 Remote sensing equipment

Nanomaterials possess distinct physical and chemical characteristics that make them suitable for enhancing the sensitivity of sensors employed in defense systems, including those used in chemical, biological, and radioactive warfare [95].

5.7.2 Protective coatings

To preserve military equipment, it is coated with materials that protect against chemical or biological agents, so nanomaterials are utilized to enhance the properties of coating materials. Metal nanomaterials have been used to improve the chemical properties and durability of coating materials. For example, aluminum nanoparticles, zinc nanoparticles, nickel nanoparticles, or chromium nanoparticles have been added to the polymer coating to improve its corrosion resistance [96].

5.7.3 Weapons

Nanomaterials have an important and effective role in military applications, especially in the manufacture of weapons, military equipment and in the field of biological weapons. Ceramic nanoparticles, metal nanoparticles, and polymer nanoparticles have been utilized to develop protective shields and masks against toxic gases for soldiers. Adding nanoparticles improves the mechanical properties of substances used in manufacturing and makes them more resistant to damage. It is also used in developing sensors, radars and other detecting systems for defense uses [97].

5.7.4 Manufacturing

Adding aluminum nanoparticles, copper nanoparticles and nickel nanoparticles to polymers improved the mechanical properties, electrical conductivity, and thermal stability, which improves the efficiency, performance and durability of substances usage in the manufacture of weapons and equipment, like armor or structural materials. Gold nanoparticles and platinum nanoparticles can also be used to manufacture functional materials as sensors and chemical catalysts due to their ability to absorb reactants and their large surface area [93].

5.7.5 Energy storage

Batteries and fuel cells are utilized as energy storage systems in military equipment, so nanoparticles were utilized as a cathode electrode in batteries to increase the energy density, capacity and stability rate of the battery. For instance, lithium cobalt oxide nanoparticles (LiCoO2) have been utilized as cathodes in lithium-ion batteries. Iron oxide nanoparticles (Fe2O3) and manganese oxide nanoparticles (MnO2) have also been utilized as cathodes in rechargeable lithium batteries. Metal nanoparticles were used as active materials to increase the electrode area in supercapacitors. The use of various nanomaterials in military industries improves the performance, efficiency, and safety of defense systems [98].

6 Future challenges and perspectives

There are many different methods for preparing nanomaterials, and this review is devoted to studying physical methods with their advantages and disadvantages. Nanomaterials are used in many applications in various fields such as the environment, agriculture, industry, medicine, military defense systems, electronics, and energy storage. However, there are many challenges and potential future directions for researchers and scholars to develop methods for preparing nanomaterials and applying them on a large scale. These challenges include the following:

One of the main challenges is the production of nanomaterials while controlling the size and shape to suit their use in different applications. This depends on the choice of preparation method and control of production factors. In addition, the size and shape of nanomaterials affect their physical and chemical properties and thus their potential applications. Therefore, the appropriate and most efficient method must be chosen to produce nanomaterials with appropriate sizes and shapes for their practical applications.

Disadvantages of the methods used in the production of nanomaterials can affect the production of nanomaterials with low efficiency. For example, carbon nanotubes are one of the well-known nanomaterials. However, the presence of impurities and intermittent tube lengths, diameters, and cavities lead to a significant weakening of the tensile strength of carbon nanotubes.

One of the very important challenges is to produce nanomaterials at a low cost. In general, highly efficient nanomaterials are produced using advanced tools and under very special conditions, which limits their production in large quantities. We find that most of the nanomaterials that were produced on a large scale were done by low-cost methods, which led to the production of low-quality materials that contain many impurities.

We also find that one of the challenges facing the production of nanomaterials is their impact on the environment. For example, we find that silver nanoparticles have a toxic effect on aquatic organisms, but they have other beneficial environmental effects. Therefore, we find that need more research on the impact of nanomaterials on the environment and the development of environmentally friendly production methods.

Regarding future trends, it is the use of nanomaterials in energy storage devices, electronics, environmental protection, and renewable energy production. For example, the use of nanomaterials in developing solar cell systems. Nanomaterials will be used to improve the efficiency of electrodes in energy storage batteries, hydrogen production as a renewable energy source, delivering medicines and treating chronic diseases such as cancer. From the above, the future of advanced technology is closely linked to progress in the field of nanomaterials technology engineering.

7 Conclusion

Various research studies have dealt with nanomaterials on a wide scale. Nanomaterials have been classified in terms of shape, size, and source into nanomaterials based on carbon, metals, ceramics, lipids, semiconductors, and polymers. Ultrafine materials (1–100 nm) that have different dimensions are classified as nanomaterials. Two main methods are utilized to synthesize and prepare nanomaterials: top-down as well as bottom-up. Three main techniques are included under these methods: physical methods, chemical methods, and biological methods. This review focused on different physical methods for producing nanomaterials. Different properties of nanomaterials are determined using different analysis and characterization techniques. Nanomaterials have been studied in scientific research across various disciplines like physics, materials science, engineering, and chemistry, which led to the contribution of nanomaterials to the development of various applied fields.