**4.5 Solar cell optimisation**

*Silver Micro-Nanoparticles - Properties, Synthesis, Characterization, and Applications*

electronics through ink-jet printing [42].

**4.4 Fillers**

homes in winter.

*4.4.1 AgNPs as inorganic filler*

the electrical conductivity [45].

acetone and deionised water to remove the particles and organic contaminants present on the surface; after cleaning the film, it was treated with ozone by UVO-100 UV ozone for 30 min. These AgNPs suspensions were spin-coated with 500 rpm, 15 seconds on the polyimide substrate and dried at room temperature to remove the solvent. The resulting AgNPs on the polyimide substrate was heated from 100 to 200 °C and held at 200 °C for 1 h to convert to silver films. The synthesised AgNPs were sintered at different temperatures, and it was shown that the resistivity of the silver film sintered at 150 °C for 1 h was close to the resistivity of bulk silver. Upon the results, the prepared nanoparticles showed a low sintering temperature. Therefore, silver nanoparticles would be used to construct the

The micro-sized silver particle fillers are seen as full density silver flakes; they had demonstrated to be highly porous agglomerates. Conjugated polymers with different nanoscale filler inclusions **have been investigated for** sensor applications, including gas sensors, biosensors, and chemical sensors. **Nanofill**ers used include nanowires of metal oxide, nanotubes of **carbon and nanoscale** silver [43]. In the coming decades, nanofiller-based silver nanoparticles and their related products are very promising. In the future, we will face many risks and challenges, in particular energy problems, and research into sustainable energy conversion is expected to explode, both theoretically and experimentally, and polymer nanocomposites will not stand out from this trend, such as self-cleaning or "easyto-clean" coatings, coated on the surface of a building, protective substrates and glass can help to save energy and water in facility cleaning. In contrast, insulating nanocomposite coatings can help save billions of dollars in energy savings to keep

Mineral or metallic fillers are reviewed as inorganic fillers. Clay, nano clay [montmorillonite (MMT)], silver nanoparticles (AgNPs), and calcium carbonate (CaCO3) are the most common inorganic reinforcement material-based composites. AgNPs is also a popular metallic filler due to its physicochemical properties, including optical, electrical, catalytic, antimicrobial, and therapeutic properties. It can be synthesised either chemically or biologically. Conventional physical and chemical methods are more costly and toxic than biological methods that can produce nanoparticles in high yields, with good solubility and stability [44]. The biological method is most preferred and very simple, cost-effective, fast, environmentally friendly, and non-toxic. The green approach is preferred for synthesising AgNPs because it uses bacteria, plant extracts, fungi, vitamins, and amino acids far from chemical methods. Few researchers had analysed these nanoparticles via TEM. The resistivity was also evaluated through various levels of filler loading. The AgNPs prepared and synthesised were spheres and nano-sized approximately 50–150 nm in diameter and micro-sized particles with diameters of 5–8 μm, and flakes of silver of 10 μm in length. The data concluded that it was not easy to find the cross-linkage of particles, and there are very lesser chances of different contact and contact area. Through the resistivity measurements, it has been demonstrated that the conductivity of micro-sized silver particle-filled adhesive is influenced by constriction resistance, the AgNPs-containing adhesive is controlled by tunnelling and even thermionic emission. Therefore the particular AgNPs were succeeded to increase

**226**

In recent years, the emerging technology in plasmonic effects in thin-film silicon solar cell is widely studied. It has been a promising application in solar cell fabrication industries due to the nanoscale properties of the silver nanoparticles established in the interface between the metal and dielectric contacts which in turn enhance the light-trapping properties of thin-film silicon solar cells through an increase in absorbance capacity and production of hot electrons that enhance the photocurrents in the solar cell [46]. Silver indium sulphide quantum dots (QD) supported by glutathione (GSH) and polyethylene (PET) as dual-ligands have been synthesised by [47] using an environmentally friendly and reproducible aqueous method. The resulting silver indium sulphide quantum dots present surprisingly long lifespans of 3.69 ls, excellent fluorescent stability and low cytotoxicity, making them the ideal candidate for real-time bioimaging. Thus, they can effectively passivate the surface trap centres and thus reduce non-radiative emissions in **Figure 5**.

### **4.6 Biosensor fabrication**

Few groups have tried to fabricate nano-enzymatic glucose biosensors by depositing AgNPs using the in-situ chemical reduction method on TiO2 nanotubes, which is synthesised using an anodic oxidation process. Scanning electron microscopy was used to determine the structure, morphology, and mechanical activity of the electrode. It was present both inside and outside of TiO2 nanotubes whose length and diameter were about 1.2 μm and 120 nm. The composition was constructed and used as an electrode of a non-enzymatic biosensor for glucose oxidation. The electrocatalytic properties of the prepared electrodes for glucose oxidation were investigated by cyclic voltammetry (CVs) and differential pulse voltammetry (DPV). Nano enzymatic glucose biosensors have exciting applications in catalysis and sensor areas [48].

In [49] work, their silver nanostructures were significantly stabilised by the Mercaptopropionic Acid (MPA), and Self Assembled Monolayer (SAM) biosensor detection limit for endotoxin *E.coli* was estimated at 340 pg./ml. We investigated biosensor selectivity in different experiments, taking endotoxin *B.abortus* as the second form of endotoxin contamination in our target samples (HBs-ag developed

#### **Figure 5.**

*Silver indium sulphide QDs stabilised by GSH and PET have been successfully prepared using an environmentally friendly and reproducible aqueous route. The resulting QDs have an absolute quantum yield (QY) photoluminescence (PL) of up to 37.2 percent [47].*

at the Institute Pasteur, Iran). Overall, this study suggests that Localised Surface Plasmon Resonance (LSPR) biosensing can be considered in quality control laboratories as a sensitive, simple, and label-free method for detecting endotoxins. They showed that this biosensor could selectively detect both forms of endotoxins compared to other biological organisms. The construction of a silver-based LSPR biosensor for endotoxin detection was described. They used the Glancing Angle Deposition (GLAD) method to obtain reproducible nanocolumns of silver.

#### **5. Environmental impacts, toxicity and disposal**

The cytotoxicity of AgNPs must also be taken into account, particularly if used to treat chronic wounds. The wound healing and tissue repair mechanisms appear to be complex, and it is unknown if there is a temporary window on the exposure of AgNPs [15]. The toxicity of AgNPs depends on a variety of factors, such as concentration, duration, dosage and particle size. In comparison to (Michigan Cancer Foundation) MCF-7 cell culture, toxicity is dose-dependent and to cause cell damage in Human Epidermoid Larynx (Hep-2) cell line by Reactive Oxygen Species (ROS) formation. AgNPs biogenically synthesised from *Podophyllum hexandrum* leaf extract showed cytotoxicity and apoptotic influence, possibly through caspacecascade activation and loss of mitochondrial integrity [50].

Metallic nanoparticles in general and AgNPs, in particular, are growing warning triggers for human and environmental managers due to the growing introduction of AgNPs into consumer goods. The enormous use of AgNPs in the products points out so many questions about the toxicity and safety [13]. Release of AgNPs from consumer goods is required to shift in land-based environments, but their fate and transition are very complicated and little are understood about their effect on the climate. AgNPs textile and cosmetic compounds in Europe have the highest environmental exposure when washing and rinsing water in wastewater treatment plants is treated. The resulting silver release from these plants is predicted to be low in the soil and surface waters.

However, owing to the widespread use of silver-based goods, the public is concerned about various aquatic lives when AgNPs reach the sea. Another concern with AgNPs is that they do not differentiate between helpful and harmful microorganisms. Free silver or AgNPs found in urban wastewater have been greatly converted into Ag2S during the wastewater treatment process. There are several techniques available to regulate and reduce their toxicity by surface alteration. Surface modification is helpful in stabilising nanoparticles against agglomeration and keeping these nanostructures compliant with another step. The WHO has estimated 50% of the biological pollution indoor air is created by air handling systems and the production of harmless microorganisms such as bacterial and fungal pathogens has been observed in air filters. Most of these pathogens develop mycotoxin, which is harmful to human health, decreasing microbial growth in air filter by incorporating antimicrobial Ag-NPs through air filters.

The antimicrobial effect of Ag-NPs on bacterial contamination of activated carbon filters (ACFs) was investigated by [51]. The study found that Ag-deposited "ACF filters" effectively eliminated bioaerosols. Analysis of the antibacterial activity of the Ag-coated "ACF filters" revealed that there were two bacteria called "*Bacillus subtilis*" and *E. coli* is completely inhibited within 10 and 60 minutes, respectively. Polymer air filters made of polypropylene and silver nitrate (AgNO3) were examined for bacterial survival [52]. The results indicated that the addition of antibacterial agent AgNO3 to filter effectively prevented bacteria from colonised filter. The presence of the antimicrobial compound AgNO3 in the filtration systems reduces the number of

**229**

**oxidise and easily mix in solutions** [57]**.**

Nevertheless, more research is still needed to explore the potential risks of inorganic metallic filler (e.g., AgNPs) towards ecological, human, and animal activities. Inorganic fillers are not biodegradable, and it varies with different synthesis approaches and methods for the quality. Hence, clay and calcium carbonate is the most common inorganic fillers used in research since they are usually environmen-

**5.1 Future concerns**

tal-friendly and inexpensive.

*Silver Nanoparticles in Various New Applications DOI: http://dx.doi.org/10.5772/intechopen.96105*

bacteria observed in Gram-negative and Gram-positive bacterial strains *Micrococcus* 

has made the antimicrobial filters therapy technology quite important for the future. Water is one of the most valuable substances on Earth and is necessary for all living beings. About 70 percent of the world is saturated with water, but just 0.6 per cent is suitable for human use. Access to clean water is a major health and social challenge in many developed countries. There has been considerable interest in water disinfection using AgNPs. Chemicals formed by nanosilver (chem-Ag-NPs) can be uniformly decorated on porous ceramic materials to form Ag-NPs-porous ceramic, composite materials using 3-aminopropyltriethoxysilane (APTES) as a molecule interaction [53]. Since silver and AgNP are commonly used in clinical fields, more study is required into the cytotoxic effects of normal cells and cancer cells. AgNPs have been observed as toxic to some of their mammalian cells. The IC50 was of 5 lg/mL (GT-AgNP) and 272.14 ± 0.09 lg/mL (C-AgNP), for example, in AgNPs (C-AgNP and GT-AgNP), synthesised with coffee and green tea extract. Besides, the susceptibility of NIH/3 T3 to the AgNPs was improved from cervical cancer, with IC50, 14.26 ± 0.05 lg/mL (GT-AgNP). AgNPs demonstrated cytotoxic effects by cell line and by the exposure concentration. Significantly cytotoxic activity against the cells of B16F10 (mouse melanoma; IC501/26.43 ± 3.4108 g/mL), SKOV3 (human ovarian, carcinoma; IC501/416.24 ± 2.4808 g/mL), A549 (human lung adenocarcinoma; IC501/43 ± 33978 g/mL) and PC3 (human prostate cancer; IC501/41 ± 28 g/mL) were observed in AgNPs synthesised with fungal *Pestalotiopsis microspora* (mL) [54]. The silver accumulation's major organs are the liver and kidney, irrespective of whether the AgNPs are intravenous, oral or nasal [36]. AgNPs from diverse resources has different impacts on the wellbeing of mammals. In vivo experiments in rats treated with 10 mg/kg AgNPs synthesised with *Ficus religiosa* leaf extract showed an accumulation of silver in the liver, brain and lungs at a concentration of 4.77, 3.94 and 3.043 μg/g of tissue respectively (In **Figure 6**) [55]. AgNPs are not only detrimental to humans; they are also harmful to fish. The toxicity in Zebrafish is measured. Suggested findings The LD50 for silver nitrate was 100 lg/L, but the LD50 was 80 and 400 lg/L for chemical and plant synthesis AgNPs, respectively [36]. Fungal-derived AgNPs did not significantly impact *Poecilia reticulate* after 48 h of exposure to 3.41 mg/L. This may mean that fungal-derived AgNPs are the least toxic among the numerous AgNPs, whereas chemical-derived AgNPs are usually more toxic than silver nitrates. AgNPs also possess size-dependent toxicity to Zebrafish. For example, smaller size AgNPs appear to cause higher mortality rates and lower hatchability rates, resulting in higher embryotoxicity than larger particle sizes [56]. The cytotoxicity of AgNPs is influenced by many factors, including shape, size, composition, surface charge, and capping molecule or coating. **Uncoated Ag NPs are more harmful than Ag NPs, which are coated. AgNPs should be kept in the dark at a temperature of 4 °C as they are photosensitive. AgNPs that are not properly stabilised can rapidly** 

The significant reduction in bacterial pathogens' growth in silver-treated filters

*luteus, Micrococcus roseus, Bacillus subtilis* and *Pseudomonas luteola*.

*Silver Nanoparticles in Various New Applications DOI: http://dx.doi.org/10.5772/intechopen.96105*

*Silver Micro-Nanoparticles - Properties, Synthesis, Characterization, and Applications*

**5. Environmental impacts, toxicity and disposal**

cascade activation and loss of mitochondrial integrity [50].

in the soil and surface waters.

antimicrobial Ag-NPs through air filters.

at the Institute Pasteur, Iran). Overall, this study suggests that Localised Surface Plasmon Resonance (LSPR) biosensing can be considered in quality control laboratories as a sensitive, simple, and label-free method for detecting endotoxins. They showed that this biosensor could selectively detect both forms of endotoxins compared to other biological organisms. The construction of a silver-based LSPR biosensor for endotoxin detection was described. They used the Glancing Angle Deposition (GLAD) method to obtain reproducible nanocolumns of silver.

The cytotoxicity of AgNPs must also be taken into account, particularly if used to treat chronic wounds. The wound healing and tissue repair mechanisms appear to be complex, and it is unknown if there is a temporary window on the exposure of AgNPs [15]. The toxicity of AgNPs depends on a variety of factors, such as concentration, duration, dosage and particle size. In comparison to (Michigan Cancer Foundation) MCF-7 cell culture, toxicity is dose-dependent and to cause cell damage in Human Epidermoid Larynx (Hep-2) cell line by Reactive Oxygen Species (ROS) formation. AgNPs biogenically synthesised from *Podophyllum hexandrum* leaf extract showed cytotoxicity and apoptotic influence, possibly through caspace-

Metallic nanoparticles in general and AgNPs, in particular, are growing warning triggers for human and environmental managers due to the growing introduction of AgNPs into consumer goods. The enormous use of AgNPs in the products points out so many questions about the toxicity and safety [13]. Release of AgNPs from consumer goods is required to shift in land-based environments, but their fate and transition are very complicated and little are understood about their effect on the climate. AgNPs textile and cosmetic compounds in Europe have the highest environmental exposure when washing and rinsing water in wastewater treatment plants is treated. The resulting silver release from these plants is predicted to be low

However, owing to the widespread use of silver-based goods, the public is concerned about various aquatic lives when AgNPs reach the sea. Another concern with AgNPs is that they do not differentiate between helpful and harmful microorganisms. Free silver or AgNPs found in urban wastewater have been greatly converted into Ag2S during the wastewater treatment process. There are several techniques available to regulate and reduce their toxicity by surface alteration. Surface modification is helpful in stabilising nanoparticles against agglomeration and keeping these nanostructures compliant with another step. The WHO has estimated 50% of the biological pollution indoor air is created by air handling systems and the production of harmless microorganisms such as bacterial and fungal pathogens has been observed in air filters. Most of these pathogens develop mycotoxin, which is harmful to human health, decreasing microbial growth in air filter by incorporating

The antimicrobial effect of Ag-NPs on bacterial contamination of activated carbon filters (ACFs) was investigated by [51]. The study found that Ag-deposited "ACF filters" effectively eliminated bioaerosols. Analysis of the antibacterial activity of the Ag-coated "ACF filters" revealed that there were two bacteria called "*Bacillus subtilis*" and *E. coli* is completely inhibited within 10 and 60 minutes, respectively. Polymer air filters made of polypropylene and silver nitrate (AgNO3) were examined for bacterial survival [52]. The results indicated that the addition of antibacterial agent AgNO3 to filter effectively prevented bacteria from colonised filter. The presence of the antimicrobial compound AgNO3 in the filtration systems reduces the number of

**228**

bacteria observed in Gram-negative and Gram-positive bacterial strains *Micrococcus luteus, Micrococcus roseus, Bacillus subtilis* and *Pseudomonas luteola*.

The significant reduction in bacterial pathogens' growth in silver-treated filters has made the antimicrobial filters therapy technology quite important for the future. Water is one of the most valuable substances on Earth and is necessary for all living beings. About 70 percent of the world is saturated with water, but just 0.6 per cent is suitable for human use. Access to clean water is a major health and social challenge in many developed countries. There has been considerable interest in water disinfection using AgNPs. Chemicals formed by nanosilver (chem-Ag-NPs) can be uniformly decorated on porous ceramic materials to form Ag-NPs-porous ceramic, composite materials using 3-aminopropyltriethoxysilane (APTES) as a molecule interaction [53]. Since silver and AgNP are commonly used in clinical fields, more study is required into the cytotoxic effects of normal cells and cancer cells. AgNPs have been observed as toxic to some of their mammalian cells. The IC50 was of 5 lg/mL (GT-AgNP) and 272.14 ± 0.09 lg/mL (C-AgNP), for example, in AgNPs (C-AgNP and GT-AgNP), synthesised with coffee and green tea extract. Besides, the susceptibility of NIH/3 T3 to the AgNPs was improved from cervical cancer, with IC50, 14.26 ± 0.05 lg/mL (GT-AgNP). AgNPs demonstrated cytotoxic effects by cell line and by the exposure concentration. Significantly cytotoxic activity against the cells of B16F10 (mouse melanoma; IC501/26.43 ± 3.4108 g/mL), SKOV3 (human ovarian, carcinoma; IC501/416.24 ± 2.4808 g/mL), A549 (human lung adenocarcinoma; IC501/43 ± 33978 g/mL) and PC3 (human prostate cancer; IC501/41 ± 28 g/mL) were observed in AgNPs synthesised with fungal *Pestalotiopsis microspora* (mL) [54]. The silver accumulation's major organs are the liver and kidney, irrespective of whether the AgNPs are intravenous, oral or nasal [36]. AgNPs from diverse resources has different impacts on the wellbeing of mammals. In vivo experiments in rats treated with 10 mg/kg AgNPs synthesised with *Ficus religiosa* leaf extract showed an accumulation of silver in the liver, brain and lungs at a concentration of 4.77, 3.94 and 3.043 μg/g of tissue respectively (In **Figure 6**) [55].

AgNPs are not only detrimental to humans; they are also harmful to fish. The toxicity in Zebrafish is measured. Suggested findings The LD50 for silver nitrate was 100 lg/L, but the LD50 was 80 and 400 lg/L for chemical and plant synthesis AgNPs, respectively [36]. Fungal-derived AgNPs did not significantly impact *Poecilia reticulate* after 48 h of exposure to 3.41 mg/L. This may mean that fungal-derived AgNPs are the least toxic among the numerous AgNPs, whereas chemical-derived AgNPs are usually more toxic than silver nitrates. AgNPs also possess size-dependent toxicity to Zebrafish. For example, smaller size AgNPs appear to cause higher mortality rates and lower hatchability rates, resulting in higher embryotoxicity than larger particle sizes [56]. The cytotoxicity of AgNPs is influenced by many factors, including shape, size, composition, surface charge, and capping molecule or coating. **Uncoated Ag NPs are more harmful than Ag NPs, which are coated. AgNPs should be kept in the dark at a temperature of 4 °C as they are photosensitive. AgNPs that are not properly stabilised can rapidly oxidise and easily mix in solutions** [57]**.**

#### **5.1 Future concerns**

Nevertheless, more research is still needed to explore the potential risks of inorganic metallic filler (e.g., AgNPs) towards ecological, human, and animal activities. Inorganic fillers are not biodegradable, and it varies with different synthesis approaches and methods for the quality. Hence, clay and calcium carbonate is the most common inorganic fillers used in research since they are usually environmental-friendly and inexpensive.

**Figure 6.**

*No histopathological changes have been observed in the kidneys, brain, heart, lungs, and spleen from rats treated with FRAgNPs of 5 and 10 mg/kg b.w on day 29 as well as on day 89 [55].*
