Pure Starch Films Research Articles

Investigation of physio-mechanical, antioxidant and antimicrobial properties of starch–zinc oxide nanoparticles active films reinforced with Ferula gummosa Boiss essential oil

The production of surface compounds coated with active substances has gained significant attention in recent years. This study investigated the physical, mechanical, antioxidant, and antimicrobial properties of a composite made of starch and zinc oxide nanoparticles (ZnO NPs) containing various concentrations of Ferula gummosa essential oil (0.5%, 1%, and 1.5%). The addition of ZnO NPs improved the thickness, mechanical and microbial properties, and reduced the water vapor permeability of the starch active film. The addition of F. gummosa essential oil to the starch nanocomposite decreased the water vapor permeability from 6.25 to 5.63 g mm−2 d−1 kPa−1, but this decrease was significant only at the concentration of 1.5% of essential oils (p < 0.05). Adding 1.5% of F. gummosa essential oil to starch nanocomposite led to a decrease in Tensile Strength value, while an increase in Elongation at Break values was observed. The results of the antimicrobial activity of the nanocomposite revealed that the pure starch film did not show any lack of growth zone. The addition of ZnO NPs to the starch matrix resulted in antimicrobial activity on both studied bacteria (Staphylococcus aureus and Escherichia coli). The highest antimicrobial activity was observed in the starch/ZnO NPs film containing 1.5% essential oil with an inhibition zone of 340 mm2 on S. aureus. Antioxidant activity increased significantly with increasing concentration of F. gummosa essential oil (P < 0.05). The film containing 1.5% essential oil had the highest (50.5%) antioxidant activity. Coating also improved the chemical characteristics of fish fillet. In conclusion, the starch nanocomposite containing ZnO NPs and F. gummosa essential oil has the potential to be used in the aquatic packaging industry.

Improving water resistance and mechanical properties of starch-based films by incorporating microcrystalline cellulose in a dynamic network structure

The widespread use of starch-based films is hindered by inadequate tensile strength and high water sensitivity. To address these limitations, a novel starch film with a dynamic network structure was produced via the dehydration-condensation reaction of N, N′-methylene diacrylamide (MBA) and microcrystalline cellulose (MCC). The improvement in mechanical properties was enhanced by the incorporation of MCC, which was achieved through intermolecular hydrogen bonding and chemical crosslinking. To verify the interactions among MCC, MBA, and starch, x-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), and x-ray diffraction (XRD) were conducted. The results established the predicted interactions. The dynamic network structure of the film reduced the water absorption capacity (WAC) of starch and MCC hydroxyl groups, as confirmed by differential scanning calorimeter (DSC) and dynamic mechanical thermal analysis (DMTA). These analyses showed a restriction in the mobility of starch chains, resulting in a higher glass transition temperature (Tg) of 69.26 °C. The modified starch films exhibited excellent potential for packaging applications, demonstrating a higher contact angle (CA) of 89.63°, the lowest WAC of 4.73 g/g, and the lowest water vapor transmission rate (WVTR) of 13.13 g/m2/d, along with improved mechanical properties and identical light transmittance compared to pure starch films.

Development of active packaging film reinforced with nano cellulose extracted from Palmyra palm (Borassus flabellifer) residues for prolonging the shelf life of chicken meat

SummaryThe development of new packaging materials with biodegradability is gaining more importance nowadays. The packaging materials produced using cellulose can reduce the environmental pollution caused by synthetic polymers. The nanocellulose was extracted from the Borassus flabellifer husk by combining TEMPO (2,2,6,6‐tetramethylpiperidine 1‐oxyl radical)‐mediated oxidation and ultrasonication. The packaging film was developed by the combination of arrowroot starch (5 g), glycerol (2 g), nanocellulose suspension (5%) and neem oil (1 mL) using the solution casting technique. The film was then analysed for different properties, including tensile strength, contact angle measurement, antioxidant properties and antimicrobial properties. The active packaging film showed improved mechanical, antimicrobial and optical properties than the normal starch film. The application study of the active films showed that the chicken meat packed in pure starch films spoiled faster with greater changes in pH, weight loss and hardness than the chicken packed in active films. The incorporation of neem oil in the film prevented the lipid oxidation of chicken meat due to the antioxidant activity of phenolic compounds present in neem oil and resulted in lower peroxide values.

Incorporation of oxidized debranched starch/chitosan nanoparticles for enhanced hydrophobicity of corn starch films

Starch films have superior advantages owing to the renewability and low cost of starch; however, their strong inherent hydrophilic character greatly limits their practical application. This study aimed to improve the hydrophobicity of corn starch films by adding a new type of covalently formed, oxidized debranched starch/chitosan nanoparticles (SC-NPs). SC-NPs were obtained by a Schiff-base crosslinking reaction between the aldehyde group of dialdehyde debranched starch and the amino group of chitosan. Corn starch films reinforced with SC-NPs were obtained using a casting method. A mass ratio of dialdehyde debranched starch and chitosan of 3–5 yielded mainly spherical nanoparticles ranging from 50 to 150 nm in diameter determined by transmission electron microscopy. The water contact angle (WCA) of the pure starch film was only 19.4°, whereas the WCA values of the films reinforced with 3 % SC-NPs were greater than 70°, indicating that SC-NPs efficiently improved the hydrophobicity of corn starch films. The ultraviolet and visible light barrier property of starch films with 3 % SC-NPs were significantly enhanced in comparison with pure starch film. The water vapor permeability, water solubility, and swelling ratio were markedly lower in films with 3 % SC-NPs than in neat starch films.

Structure and properties of flexible starch-based double network composite films induced by dopamine self-polymerization

Starch-based packaging materials are being developed to alleviate environmental pollution and greenhouse gas emissions associated with plastic-based ones. However, the high hydrophilicity and poor mechanical properties of pure-starch films limit their widespread application. In this study, dopamine self-polymerization was used as a strategy to improve the performance of starch-based films. Spectroscopy analysis showed that strong hydrogen bonding occurred between polydopamine (PDA) and starch molecules within the composite films, which significantly altered their internal and surface microstructures. The composite films had a greater water contact angle (> 90°), which indicated that the incorporation of PDA reduced their hydrophilicity. Additionally, the elongation at break of the composite films was 11-fold higher than pure-starch films, indicating that PDA improved film flexibility, while the tensile strength decreased to some extent. The composite films also exhibited excellent UV-shielding performance. These high-performance films may have practical applications in food and other industries as biodegradable packaging materials.

Preparation and properties of biodegradable films made of cationic potato-peel starch and loaded with curcumin

The purpose of this study was to develop biodegradable films made of cationic potato starch-derivatives and loaded with curcumin. Potato starch was recovered from potato peel waste (PW). Cationic starch (CS) was obtained by modifying potato starch, mixed with curcumin and used to prepare composite films. Curcumin at low concentration was compatible with CS and was uniformly distributed in the CS matrix of the composite films. Compared with the pure cationic starch film, the incorporation of 5% curcumin increased the elongation at break (18%) and hydrogen-bonding interactions and reduced the water-vapor permeability (WVP) (21%) of the CS films. In addition, the mechanical properties of CS films were slightly improved, whereas the thermal stability of the CS films was unchanged. The CS/curcumin films showed excellent ultraviolet (UV) barrier performance and the addition of 5% of curcumin improved the UV blocking effect by 53.33%, but reduced the transparency by 47.74%. The composite films also had good antioxidant activity and the highest scavenging activity of DPPH and ABTS was 86.77% and 98.09% in the composite film containing 5% curcumin, and curcumin was rapidly released. In conclusion, this study shows that CS/curcumin composite films are potential bioactive packaging material for foods and can alleviate the problem of agricultural waste disposal. • The active biodegradable CS/curcumin composite film was prepared by solution casting method. • The addition of curcumin improved the UV barrier and mechanical properties of CS films. • The addition of curcumin improved the water vapor barrier and surface hydrophobicity of CS films. • The CS/curcumin composite films showed strong antioxidant activity. • The composite film had potential application value in the field of food packaging.

Improving the properties of corn starch films for application as packaging material via reinforcement with microcrystalline cellulose synthesized from elephant grass

Nowadays, the development of biodegradable packaging materials from natural renewable sources has attained great attraction in the research field to mitigate environmental problems and the depletion of resources. In this regard, starch-based films are effective for food packaging due to their low cost and eco-friendliness. In the present study, microcrystalline cellulose (MCC) was synthesized from elephant grass biomass and characterized using XRD, FTIR, FESEM, and TGA analysis. The prepared E-MCC was then employed as reinforcement in corn starch films to improve their properties, and the fabricated films were characterized using FTIR, FESEM, TGA, water contact angle, moisture content, and tensile strength testing. The addition of 1% E-MCC significantly enhanced the thermal stability of the films by increasing the peak degradation temperature from 312.3 (neat starch film) to 321 °C. The water contact angle value of the pure starch film was 19.52°, which increased to 98.83° with the incorporation of 5% E-MCC. The mechanical strength of the film increased from 6.03 MPa (neat film) to 22.33 MPa (5% E-MCC). The findings in the study reveal that MCC synthesized from elephant grass is a promising reinforcing agent that can considerably enhance the various properties of corn starch films for food packaging applications.

Post‐harvest quality and shelf life assessment of Agaricus bisporus influenced by nanocellulose/nanohemicellulose loaded starch based packaging

AbstractThe post‐harvest shelf life and quality of Agaricus bisporus can be prolonged by effective packaging and storage. This work is an attempt to extend the shelf life and preserve the quality of Agaricus b. through nanocellulose and nanohemicellulose reinforced starch based packaging material. Spherical shaped nanocellulose and nanohemicellulose were isolated from corn cob. Starch nanocomposites were prepared using 0.25%, 0.5%, 0.75%, and 1 wt% of nanocellulose and nanohemicellulose and were characterized. Tailor improved mechanical and reduced water vapor permeability were achieved along with biodegradability. Tensile strength increased to 8.17 ± 0.75 Mpa for nanocellulose and 5.45 ± 0.17 MPa for nanohemicellulose reinforced films. Young's modulus increased significantly to 445.39 ± 8.39 and 106.45 ± 4.55 MPa and a significant decrease in elongtion of the film to 21.30 ± 4.89% and 38.25 ± 1.87% in 0.75% cellulose nanoparticles (CNP) and 0.75% hemicellulose nanoparticles (HNP) reinforced films respectively. Fabricated films were thermally stable with onset degradation at 260 and 280°C for nanocellulose and nanohemicellulose reinforced films. Developed films were used for packing button mushrooms. The results showed that mushrooms packed in fabricated nanoparticle loaded biobased films retained the quality of mushrooms and exhibited better retention in pH, color, firmness than the pure starch film and can be used to preserve the quality of mushroom in refrigerated condition for upto 6 days.

Effect of Psyllium Husk Addition on the Structural and Physical Properties of Biodegradable Thermoplastic Starch Film.

The research subject was the analysis of the microstructure, barrier properties, and mechanical resistance of the psyllium husk (PH)-modified thermoplastic starch films. The tensile tests under various static loading conditions were not performed by researchers for this type of material before and are essential for a more precise assessment of the material’s behavior under the conditions of its subsequent use. The film samples were manufactured by the casting method. PH addition improved starch gelatinization and caused a decrease in failure strain by 86% and an increase in failure stress by 48% compared to pure films. Fourier transform infrared spectroscopy results showed the formation of additional hydrogen bonds between polysaccharides in starch and PH. An increase in the number of hydrophilic groups in the modified films resulted in a faster contact angle decrease (27.4% compared to 12.8% for pure ones within the first 5 s); however, it increased the energy of water binding and surface complexity. The modified films showed the opacity at 600 nm, 43% higher than in the pure starch film, and lower transmittance, suggesting effectively improving barrier properties to UV light, a potent lipid-oxidizing agent in food systems.

Isolation and characterization of lignin-rich particles as byproducts of bioethanol production from wheat straw to reinforce starch composite films

Bioethanol was produced from wheat straw by a concentrated alkali pretreatment at specific conditions with a yield of 88 g ethanol per 1 kg of dry straw. To economically improve the bioethanol production process and valorize residual waste, the lignin-rich solid waste particles were isolated from the pretreatment waste liquid and characterized, and finally employed to reinforce starch-based biodegradable film. The solid waste particles were characterized by chemical analysis, dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). As bioethanol byproducts, they have mainly contained 88 wt% lignin. The average diameter of the uniform spherical shape extracted particles was determined to be 160 nm by DLS and FESEM. The presence of syringyl and guaiacyl rings were conducted by FTIR. Due to their suitable mechanical performance and thermal resistance, the lignin nanoparticles were employed as reinforcement for green biodegradable starch films. To prepare films, suspensions containing starch, glycerol, and different concentrations of lignin (0–30 wt%) were molded by the solution casting process. The starch-lignin composite films were analyzed by mechanical tensile tests, crystallinity analysis, FESEM, and thermal analysis. From the results, it was found that by adding 20 wt% lignin particles, the tensile strength and modulus of the pure starch film were increased from 4.8 and 0.9–8 and 2.4 MPa which can be partially explained due to crystallinity enhancement of film from 29 % to 48.3 %. In addition, the thermal resistance and the hydrophilic property of the composite films were enhanced due to lignin nanoparticle presence. It can be concluded that the isolation of lignin nanoparticles as waste solid in bioethanol production could be considered as a promising stage in the sustainability of second-generation products from the bioethanol production process.

Effect of polymer blending on mechanical and barrier properties of starch-polyvinyl alcohol based biodegradable composite films

The study was aimed to improve the properties of starch-based biodegradable films by the way of polymer blending. The composite films were prepared by incorporating various proportions of PVA (10, 30, 50, 70, and 90% of starch wt.) to the starch using the solvent casting method. All films were analyzed for their mechanical behavior, barrier properties, water solubility, water contact angle, and biodegradability. Incorporation of PVA to starch polymer significantly (p < 0.05) improved the mechanical and barrier properties of composite films. The highest improvement in mechanical behavior was observed for the SP90 composite film, having a higher content of PVA. SP90 film showed 1.93 fold increase in TS, 3.74 fold increase in E and 1.72 fold increase in BS over the pure starch film. On the other hand, maximum PVA incorporation resulted in 52% and 57% decrease in WVP and OP of composite films respectively, depicting a good barrier against water vapour and oxygen gas. Fourier-transform infrared spectroscopy and scanning electron microscopy of films confirmed the excellent compatibility between starch and PVA polymer. Interestingly, the composite films degraded rapidly in moistened soil within 3 weeks of burial. Biodegradability study showed a promising potential of starch-PVA composite films for the development of eco-friendly food packaging material.

Barrier, Mechanical and Morphological Properties of Biodegradable Films Based on Corn Starch Incorporated with Cellulose Obtained from Pineapple Crowns

ABSTRACT This work aimed to develop biodegradable composites formed from corn starch-based films and cellulose extracted from pineapple crown residue. Fibers obtained from the crowns underwent alkaline treatment, followed by bleaching. Cellulose was characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). These analyses verified that the process was effective in isolating cellulose fibers. The biocomposites were then produced via casting and with cellulose of different concentrations (5%, 10%, 15%). These biocomposites were less soluble in water than the pure starch film, and the film with 15% cellulose had lower water vapor permeability rate (WVPR) compared to pure starch film. In terms of the thermal characterization, there were no significant variations in the melting and gelatinization temperatures of the films. When analyzing the mechanical properties, it was seen that the Young’s modulus of the biocomposites increased in relation to the starch film, in which the composite with a 15% increase of 377.76%. Regarding the tensile strength, there were no differences between preferences, probably due to the dispersion of the fibers.

A study of films based on starch and Na‐montmorillonite designed for prolonged release of oxytetracycline hydrochloride

AbstractFunctional starch‐based nanocomposite films containing Na‐montmorillonite (MMT) and oxytetracycline hydrochloride (OTC) are prepared by the casting method; their structure and transport properties are analyzed. The results of X‐ray difraction and fourier transform infrared spectroscopy measurements show that MMT and OTC participates in the formation of a hydrogen bond network in the starch matrix, leading to a decrease in the film crystallinity degree. The MMT incorporation in the nanocomposites lowers their swelling degree. It is established, that the OTC release from the pure starch film is controlled by the Fickian diffusion mechanism. The MMT particles act as containers capable of holding OTC, as well as crystallite obstacles, limiting the OTC movement within the starch matrix structure. An increase in the MMT concentration from 1 to 5 wt% (based on dry starch) in the films leads to prolonged OTC release. The data on the OTC release from the films with a 3% and 5% MMT content best fits the linear superimposition model. The MMT and OTC have opposite effects on the tensile strength of the starch films.

Obtaining plasticized starch and microfibrillated cellulose from oil palm empty fruit bunches: Preparation and properties of the pure materials and their composites

Starch and celluloses are biodegradable resources of great importance in terms of marketing. These biopolymers can be used to generate films with interesting mechanical, optical, and thermal properties, which can substitute for plastic films in certain applications, e.g., packaging materials. This study describes the preparation of pure plasticized starch films, prepared from soluble starch and glycerol, and the preparation of microfibrillated cellulose films from oil palm empty fruit bunches fabricated via casting. Composites made of plasticized starch were also prepared with microfibrillated cellulose added in 10% increments. The density, color difference, opacity, morphology, water activity, water affinity, and thermal and mechanical characteristics of the films were investigated. Plasticized starch is a translucent material with contact transparency; it is fragile and has relatively high water and glycerol contents. The thermogravimetric analysis of materials displayed up to four stages of weight loss related to water evaporation, glycerol, starch, and cellulose thermal degradation. As a consequence, the materials with higher cellulose content exhibited better thermal resistance. The composites with 90% of microfibrillated cellulose resulted in increased tensile strength when compared to the pure materials. The pure microfibrillated cellulose presented the highest values of Young modulus. The addition of plasticized starch to microfibrillated cellulose improved the maximum strain of the composites.

Corn starch/PVA bioplastics—The properties and biodegradability study using Chlorella vulgaris cultivation

AbstractIn this study, a biodegradable alternative to synthetic plastics was explored, where gelatinized corn starch was blended with polyvinyl alcohol (PVA) using the solution casting method at different ratios. Tensile tests showed that films made of only starch exhibited the lowest tensile strength at 3.66 MPa, which increased as the ratio of PVA in the blend was raised. The water vapor transmission rate was similar even when the starch content was changed. PVA was shown to increase the solubility of the film in water, and starch demonstrated a better ability to absorb water than that of PVA, with the pure starch film swelled up to 167% of its original weight. Fourier transform infrared (FTIR) analysis revealed that there was no significant chemical interaction between the starch and PVA which could alter their respective functional groups. Bioplastic films made of only starch showed the least amount of degradation after 3 days when buried in soil, while water uptake in films made of PVA caused it to turn into a sticky gel‐like substance. Chlorella vulgaris exhibited a higher preference for PVA as the substrate when compared to starch. This revealed that C. vulgaris showed promise as a candidate for breaking down the bioplastic films when grown as a heterotroph.

Formulation of edible films from fenugreek mucilage and taro starch

In this research communication, taro starch and fenugreek mucilage were used, in four combination ratios, 1:1 (T1),1:2 (T2),1:3 (T3),2:1 (T4), one pure taro starch (To) and one pure fenugreek mucilage (Fo) to develop total six edible films. Films were evaluated on the basis of optical,textural, morphological, microbiological, color and thermal properties. The optical properties such as transparency and opacity found better results in higher taro concentration films i.e. T1 and T4. In color analysis, the chroma values were found in the range of 66.17–78.80 and hue angle values were found in the range of 22.67–33.85, for all the films. Films of pure fenugreek (Fo) and higher concentration ratio of fenugreek (T2 and T3) found highest rupture strength when compared with another film. Thermal conductivity of the films was founded in the range of 0.049–0.099 W/m°K. A least microbial growth of 1.0 × 102 ± 0.03 cfu/ml was found in Fo film and maximum microbial growth of 1.5 × 102 ± 0.03 cfu/ml was found pure taro starch film (To). SEM (Scanning Electron Microscopy) analysis of films found smooth surface for (To) and (Fo) films when compared to other films. Higher values of water vapour permeability indicated the porous structure,which allowed the water to penetrate inside the films, it was in the range of 1.53–2.79 mg/Pa.s.m2 × 10–11. The film (To and Fo) found better results for most of the properties. This edible films can be used as a primary packaging material for food products.

Preparation and Properties of Corn Starch/Chitin Composite Films Cross-Linked by Maleic Anhydride.

To improve the functional properties of starch-based films, chitin (CH) was prepared from shrimp shell powder and incorporated into corn starch (CS) matrix. Before blending, maleic anhydride (MA) was introduced as a cross-linker. Composite CS/MA-CH films were obtained by casting-evaporation approach. Mechanical property estimation showed that addition of 0–7 wt % MA-CH improved the tensile strength of starch films from 3.89 MPa to 9.32 MPa. Elongation at break of the films decreased with the addition of MA-CH, but the decrease was obviously reduced than previous studies. Morphology analysis revealed that MA-CH homogeneously dispersed in starch matrix and no cracks were found in the CS/MA-CH films. Incorporation of MA-CH decreased the water vapor permeability of starch films. The water uptake of the films was reduced when the dosage of MA-CH was below 5 wt %. Water contact angles of the starch films increased from 22° to 86° with 9 wt % MA-CH incorporation. Besides, the composite films showed better inhibition effect against Escherichia coli and Staphylococcus aureus than pure starch films.

Nanoarchitectonics Composites of Thermoplastic Starch and Montmorillonite Modified with Low Molecular Weight Polylactic Acid.

Nano montmorillonite (MMT) was modified by low molecular weight polylactic acid (PLA), then, the PLA modified MMT and raw MMT were added into thermoplastic starch (TPS) to prepare biodegradable nanocomposite films, respectively. For both nanocomposite films with raw MMT and modified MMT, the Tmax of degradation was enhanced and the mechanical properties were improved. The composite films containing 4 wt.% MMT displayed tensile strength of 5.06 MPa, approximately 1.4 times of that for the pure TPS films. The tensile strength of composite films containing 4 wt.% modified MMT is 6.74 MPa approximately 2 times of those for pure starch films. On the other hand, the composite film containing 4 wt.% modified MMT displayed elongation at break as high as 34.25%, which is 1.3 times of that of the pure starch film, while the composite films containing raw MMT had reduced elongation at break. This study showed that the MMT modified with PLA could significantly enhance the mechanical properties of TPS, and provides a new method to prepare fully biodegradable starch-based nanocomposites.

Robust Starch/Regenerated Cellulose All‐Polysaccharides Bilayer Films with Excellent Mechanical Properties

AbstractStarch‐regenerated cellulose bilayer films containing cellulose nanofibers in the casted regenerated cellulose layer are obtained by using a dissolution‐regeneration‐suction filtration approach. Scanning electron micrograph, thermogravimetric analysis, differential scanning calorimetry, and X‐ray diffraction are used to characterize the properties of the composite films. The tensile strength and modulus of the nanocomposite containing 40 wt% regenerated cellulose are increased by 156% and 111%, respectively, compared with pure starch film. Additionally, the obtained films displayed low water absorption, excellent thermal stability, and optical performance. More importantly, the film fabrication process adopted is environmentally benign, cost‐effective, and easy to operate. The all‐polysaccharides bilayer films can be used as a renewable material for industrial applications such as packaging to substitute petroleum‐based polymers in a wide range of applications.

Physical, mechanical, and antibacterial characteristics of bio-nanocomposite films loaded with Ag-modified SiO2 and TiO2 nanoparticles.

In this study, starch-based films incorporating metal oxide (MO2 ) nanoparticles (NPs) of TiO2 and SiO2 (at a concentration of 1 to 4wt. %) were produced by solution casting method. In order to exhibit antimicrobial properties, MO2 NPs were modified by synthesizing silver (Ag) ions over the NPs using cationic adsorption method. Ag ions were then reduced to metallic Ag by sodium borohydride solution. Scanning electron microscopy showed a smooth surface for the pure starch film. Incorporating MO2 @Ag NPs in the films increased surface roughness with agglomerated NPs within starch matrix. Energy dispersive X-ray analysis exhibited a uniform dispersion of Ag-loaded MO2 NPs, which increases surface contact between these NPs and the biopolymer matrix leading to improved physical and mechanical properties of the resulting films. With increasing in the NPs concentrations, the tensile strength and elongation at break % of the films increased and decreased, respectively. Incorporating MO2 @Ag NPs into starch matrix decreased solubility in water and water vapor permeability of the obtained films, and significantly inhibited the growth of Escherichia coli and Staphylococcus aureus. The most antibacterial effect was obtained for the films containing higher weight concentrations of Ag-loaded SiO2 -NPs.