1 Introduction

Polymer blends have been a prominent subject of research and development in polymers for about 50 years. The academic and industrial focus on polymer blends experienced a significant surge in the late 1960s, although it had been of interest before that time [1, 2]. In recent decades, numerous chemical and physical combinations of diverse polymers have been produced using random, block, and graft copolymerization techniques and mixing. The potential of polymer blends to meet emerging market demands has rapidly captured the attention of scientists, prompting further advancements in this field [3, 4]. The utilization of polymeric thermoplastics has experienced a significant surge in the previous 40 years. Applications encompass a wide range of products such as supermarket items, commerce, garbage bags, drink cups, caps and closures, culinary utensils, food containers, household appliances, plastic fuel tanks, construction materials, and children’s toys, among several others. Water-soluble polymers, such as PEG and PVA, and their blends are widely used in various applications, emulsifiers, cosmetics, packaging, and adhesives [5, 6]. Polyvinyl alcohol (PVA) polymer is highly preferred in several sectors because of its semi-crystalline form and favorable physical properties. PVA is a polymer consisting of hydroxyl groups linked by a carbon backbone. The presence of OH groups in polymer blends can facilitate the formation of hydrogen bonding. Due to its exceptional physico-chemical characteristics, PVA is commonly used in polymeric blends. It possesses excellent skills to create a film and is not carcinogenic. Additionally, it has the properties of emulsification, biocompatibility, and biodegradability [7, 8]. Polyvinyl alcohol (PVA) possesses numerous exceptional characteristics that render it a promising candidate as a host material for additions [9]. The properties encompass dielectric strength, water solubility, nontoxicity, thermal stability, chemical resistance, environmental friendliness, and mechanical strength. The solubility conditions are contingent upon various elements, such as hydrolysis, molecular weight, particle size, and crystallinity. Because of its diverse attributes, such as compatibility, abundance, and affordability, it finds multiple applications in everyday life [10, 11]. Polyethylene glycol, or poly(ethylene glycol) or PEG, is a chemical molecule composed of repeated units of ethylene glycol O-CH2-CH2. PEG’s chemical properties contribute to its biocompatibility, making it highly advantageous in a wide range of life-related applications. The substance can be injected into media, chemically combined with molecules, and affixed to surfaces without interfering with cellular processes [12, 13]. Due to its extensive medical and biological use, this polymer is highly sought after as it has received authorization from the FDA. The polymer’s lack of toxicity, inability to trigger an immune response, compatibility with living organisms, and ability to dissolve in many different solvents make it highly versatile and explain the extensive research conducted on this material [14, 15]. Transition metal oxides (TMOs) are a prevalent group of materials that exhibit a diverse range of stability and charge transfer characteristics. Their versatility stems from their inherent malleability, enabling them to be easily modified with different atoms and surface treatments. Additionally, their capacity to be shaped into minuscule particles gives rise to a substantial surface-to-volume ratio [16, 17]. Copper oxide is regarded as a favorable option among these oxides of transition metals due to its advantageous characteristics, including increased stability, improved electrochemical activity, and excellent redox capabilities [18, 19]. Copper oxide is a semiconducting metal with distinctive optical, electrical, and magnetic characteristics. It has found utility in diverse applications, including the creation of supercapacitors and near-infrared filters, semiconductors, microelectromechanical systems, field effect transistors, electrochemical cells, gas sensors, magnetic storage media, solar cells, field emitters, and nanodevices for catalysis [20, 21]. Silicon dioxide, or silica, existing as a natural and synthetic material today, is required in many industries, as given further [22]. Silicon oxide nanoparticles (SiO2 NPs) possess distinct physical, chemical, and optical characteristics, making them suitable for various applications across multiple domains [23]. It’s a pleasant material with a wide range of applications in semiconductor devices. By acting as a solid plasticizer, the SiO2 particulates enhance the dimensional stability and the composite polymer’s chemical and mechanical properties [24, 25]. SiO2 nanoparticles have received significant attention in electrochemical sensing analysis due to their excellent biocompatibility and good dispersion. The unique characteristics of the polymers above and nanomaterials were used in this work to produce nanocomposites with very distinctive features. Metal oxide and polymer nanocomposites possess remarkable dielectric properties, making them extensively used as capacitors in the electronics sector [26, 27]. The addition of nano-sized metal oxide creates substantial interfacial regions between the matrix and the nanofillers. The host matrix’s enhancement in dielectric and magnetic properties mostly depends on the presence of large interfacial areas and a high concentration of metal nanoparticles. These materials have a critical role in altering the distribution of space charges and enhancing the routes of carriers [28, 29].

To the best of our knowledge, to date, no attempt has been made at synthesizing nanocomposites containing PVA–PEG polymer blend, and hybrids nanoparticles (SiO2–CuO). On the other hand, SiO2–CuO nanoparticles have high sensitivity for pressure. Hence, the purpose of this study is to the presentation of the low-cost, easy synthesis process, and an eco-friendly by PVA–PEG–SiO2/CuO nanocomposites for pressure sensors.

2 Materials and Methods

Nanocomposites (NCs) films were fabricated using the casting technique, incorporating polyvinyl alcohol (PVA), Polyethylene Glycol (PEG), silicon oxide (SiO2), and copper oxide (CuO) NMs. The process involved dissolving a mixture of pure PVA and PEG (70/30 ratio) in 50 ml of distilled water for 45 min at a temperature of 55 °C while continuously stirring with a magnetic stirrer to achieve a homogeneous solution. After undergoing a 4-day air drying period at room temperature (RT), the observed result was the successful creation of polymer nanocomposites (NCs). The (PVA–PEG–SiO2/CuO) nanocomposites were obtained from the Petri plate and used for measurement. The optical characteristics of nanocrystals (NCs) consisting of PVA–PEG–SiO2/CuO were analyzed using a U.V./1800/Shimadzu spectrophotometer in the 200–800 nm wavelength range. The samples were tested at various concentrations utilizing an Olympus (model/Nikon/73346) optical microscope equipped with a 10 × magnification capability and a camera specifically intended for microscopic photography. FTIR is used to evaluate nanocomposites (NCs) from samples containing (PVA–PEG–SiO2/CuO). The dielectric characteristics of NCs were assessed using an LCR meter (HIOKI/3532/50/LCR/HI/TESTER/model). In order to evaluate the performance of the pressure sensor nanocrystals (NCs), the parallel capacitance between the two poles positioned above and below the specimen was calculated using an LCR meter. The computation was performed over various pressure intervals within the range of 80 to 160 bars.

Absorbance (A), transmittance (\({\text{T}}_{r}\)) and absorption coefficient (α) are calculated by the equations [30, 31]

$$A=\frac{{I}_{o}}{{I}_{A}}$$
(1)
$${T}_{r}=\frac{{I}_{{T}_{r}}}{{I}_{o}}$$
(2)
$$\alpha =\frac{2.303\times A}{d}$$
(3)

where IA (the intensity of absorbed light), Io (the intensity of incident light), ITr (the intensity of transmitted light), d (sample thickness), and A (absorption).

From Eq. (4), calculated material non-direct transition model [32, 33]

$$ \alpha {\text{h}}\upsilon = {\text{B}}\left( {{\text{h}}\upsilon - {\text{E}}_{\text{g}} } \right)^{\text{r}} $$
(4)

r, hυ, B, and Eg depict allowed/forbidden indirect transitions (2 and 3, respectively), photon energy, constant, and energy band gap.

The extinction coefficient (K) and refractive index (n) are calculated from equations [34, 35]

$$ K = \frac{\alpha \lambda }{{4\pi }}\quad \left( {\lambda \,{\text{is the wavelength}}} \right) $$
(5)
$$ n = \sqrt {{4R - \frac{k2}{{\left( {R - 1} \right)2}}}} -\frac{{\left( {R + 1} \right)}}{(R - 1)}\quad \left( {\text{R is the reflectance}} \right) $$
(6)

The dielectric constants (ε1 and ε2) and optical conductivity were calculated from the following equations [36, 37]

$$ {{\upvarepsilon }}_{1} = {\text{ n}}^{2} - {\text{k}}^{2} $$
(7)
$$ {{\upvarepsilon }}_{2} = {\text{2nk}} $$
(8)
$$ \sigma_{{\text{op}}} = \alpha {\text{nc}}/{4}\pi $$
(9)

c: the light speed (3 × 108 m/s).

Dielectric [constant (ɛ′) and loss (ε")] and Alternating current electrical conductivity (σa.c) are given by [38, 39]

$$ \varepsilon {\prime} = \frac{C_p }{{C_o }} $$
(10)
$$ \varepsilon^{{\prime} {\prime} } = \frac{C_p }{{C_o }}\,{\text{D}} $$
(11)
$$ \sigma_{{\text{a}}.{\text{c}}} = \omega \varepsilon_o {\text{D}}\,\frac{C_p }{{C_o }} $$
(12)

Co, Cp, ω, and D vacuum capacitors signify capacitance, angular frequency, and displacement.

3 Results and Discussion

3.1 FTIR Analysis of (PVA–PEG–SiO2/CuO) NCs

FT-IR spectroscopy is an effective method for studying the interactions and complexation of produced films (PVA–PEG–SiO2/CuO) NCs. Figure 1 displays the FT-IR transmittance spectra of the pure PVA–PEG blend and its films containing varying amounts (0, 2, 4, and 6) of SiO2/CuO by weight percentage. The spectra were scanned across a wavenumber range of 500–4500 cm−1. The FT-IR spectra of pure PVA–PEG exhibit a broad absorption band in the range of 3000–3500 cm−1, similar to the stretching vibration mode (hydroxyl groups OH). Additional absorption peaks are observed at the following wavenumbers: 2848, 1380, 1252, 1192, 1014, 866, and 743 cm−1. These peaks correspond to the following molecular vibrations: CH2 (asymmetric stretching mode), C=O (stretching mode), CH2 (symmetric bending mode), C–H (bending mode), CH2 (rocking), C–C (stretching mode), and OH (wagging mode), respectively [40]. Figure 1 illustrates the plots of the FT-IR spectra of the filled samples to provide a clear understanding of how the varying concentrations of SiO2/CuO affect the structure of the PVA–PEG blend. The FT-IR spectrum of the (PVA–PEG–SiO2/CuO) NCs does not exhibit any additional peaks compared to the pure PVA–PEG film. Furthermore, noticeable discrepancies in the intensities of absorption peaks can be observed in the FT-IR transmittance spectra of (PVA–PEG–SiO2/CuO) NCs compared to pure PVA–PEG film. The results indicate that (SiO2/CuO) NMs have been effectively incorporated into the PVA–PEG polymer, resulting in the formation of a uniform host material called (PVA–PEG–SiO2/CuO) NCs [41, 42].

Fig. 1
figure 1

FTIR spectra for (PVA–PEG–SiO2/CuO) NCs

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3.2 Optical Microscope of (PVA–PEG–SiO2/CuO) NCs

The Optical Microscope (OM) images of the pure polymer and polymer doped with (SiO2/CuO) NMs films at magnification (10X) with different ratios are (0, 2, 4, and 6)wt% of (SiO2/CuO) NMs are shown in Fig. 2, A planar surface of the PVA–PEG matrix and uniform distribution of starch particles were observed under the optical microscope in the mix film containing 2%, 4%, and 6% by weight of the (SiO2/CuO) NMs. The nanoparticles form a continuous network within the polymer matrix reaching 6 wt% (SiO2/CuO) NMs; this network contains nano paths that allow the passage of charge carriers [7, 43].

Fig. 2
figure 2

Microscopic images (10 ×) for (PVA–PEG–SiO2/CuO) NCs: A-pure PVA–PEG, B-2 wt% SiO2/CuO, C-4 wt% SiO2/CuO, D-6 wt% SiO2/CuO

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3.3 The Optical Properties of (PVA–PEG–SiO2/CuO) NCs

The utilization of a material in optoelectronic devices necessitates a thorough comprehension of its optical absorption. This information offers critical insights into the material’s capacity to efficiently convert light. Figures 3 and 4 display the PVA–PEG blend’s optical absorbance and transmittance spectra filled with SiO2/CuO across a wavelength range of 190–1200 nm. The produced samples exhibit distinct absorption peaks at 200 nm, indicating the presence of π → π* electronic transitions in the PVA–PEG blend. As the SiO2/CuO concentration is increased to 6%, there is a noticeable rise in the absorption of the (PVA–PEG–SiO2/CuO) NCs, accompanied by a redshift towards longer wavelengths. This finding suggests that the filled composite blends have a lower optical bandgap than the pure PVA–PEG. The transmittance spectra exhibit an opposite performance pattern, as depicted in Fig. 4. By analyzing the transmittance spectra, it is evident that the transmittance drops as the weight percentage of the filler increases from 0 to 6%. This characteristic makes the composite blends suitable for a range of optical applications. At an incident wavelength of 540 nm, the optical transmittance of the produced samples drops from 0.96 (PVA–PEG) to 0.49 (2% SiO2/CuO), 0.39 (4% SiO2/CuO), and 0.33 (6% SiO2/CuO) as depicted in the insert of Fig. 4. The results we obtained are consistent with the findings in the literature [44, 45]

Fig. 3
figure 3

Wavelength-dependent (PVA–PEG–SiO2/CuO) NCs absorption spectra

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Fig. 4
figure 4

The wavelength dependence of the transmission spectra of (PVA–PEG–SiO2/CuO) NCs

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Figure 5 illustrates the absorption coefficient α of (PVA–PEG–SiO2/CuO) nanocomposite films about photon energy. The absorption coefficient exhibited a steady rise in values with increasing photon energy, ultimately reaching a threshold of 3.9 eV. This behavior can be explained by the electron’s lower transition, where the energy of the incoming photon is insufficient to enable the electron to jump from the valence band to the conduction band. When the energy level reaches 3.9 eV, all samples’ absorption coefficient increases significantly. The notable electron transitions occurring within the conductive band can elucidate the occurrence [46]. At an energy level of 3.9 electron volts (eV), the absorption coefficient increased significantly by 1683%, 2117%, and 2492% (at a wavelength of 540 nm) as the concentrations of (SiO2/CuO) in the NCs increased to 2, 4, and 6 weight percent (wt. %), respectively. The gathered outcomes resemble the conclusions posited by the researchers [47, 48].

Fig. 5
figure 5

Photon energy-dependent (PVA–PEG–SiO2/CuO) NCs absorption coefficient

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The study investigated the impact of the weight percentage of the filler on the optical bandgap (Eg) of the (PVA–PEG–SiO2/CuO) nanocomposites. The optical bandgap, denoted as Eg, signifies the disparity in energy levels between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals. The samples’ optical absorption coefficient (α) values were determined based on the absorbance (A) readings using Eq. 3. Plots of the (αhυ)1/2 (allowed) and (αhυ)1/3 (forbidden) values of the produced films and the incident energy (hv) are shown in Figs. 6 and 7. The permissible energy gap (Eg) values were determined by projecting the linear segments of the shown curves to an incident photon energy of zero. These values are also displayed in Table 1. The obtained Eg values for each film appear to be compatible. The PVA–PEG film’s calculated bandgap energy (Eg) is approximately 4.37 electron volts (eV).

Fig. 6
figure 6

Variation of (αhυ)1/2 for (PVA–PEG–SiO2/CuO) NCs with photon energy

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Fig. 7
figure 7

Variation of (αhυ)1/3 of (PVA–PEG–SiO2/CuO) NCs with photon energy

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Table 1 (PVA–PEG–SiO2/CuO) NCs energy gaps for indirect allowed/forbidden transitions
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Additionally, the inclusion of 6 wt% of SiO2/CuO in PVA–PEG to create (PVA–PEG–SiO2/CuO) NCs results in a reduction of the Eg value of the NCs to 2.80 eV, as compared to pure PVA–PEG. The drop is attributed to the formation of secondary energy levels within the bandgap of the pure PVA–PEG. An evident reduction in the forbidden energy values is observed due to the inclusion of (SiO2/CuO) in the PVA–PEG blend, as depicted in the image in Fig. 6. The observed fluctuation in Eg (3.69–1.68 eV) is mainly attributed to the development of energy states inside the energetic bandgaps of the host mix. The rise in the number of voids, disorganization, and faults in the composite mixes resulting from the filling process is an additional component contributing to the fall in the Eg value [49, 50].

Figure 8 displays K plots illustrating the relationship between the pure PVA–PEG and (PVA–PEG–SiO2/CuO) NCs as a function of the wavelength of incident photons. The K values align with the absorbance values, as K is influenced by the optical absorption coefficient, as indicated in Eq. 5. Specifically, the K value increases as the (SiO2/CuO) content in the host matrix rises at any wavelength. The primary cause of this outcome can be attributed to the heightened dampening nature of the incoming electromagnetic waves, which is a result of the augmented quantity of SiO2/CuO) NMs that were added. Our findings are consistent with the existing literature [51, 52].

Fig. 8
figure 8

Difference of extinction coefficient for (PVA–PEG–SiO2/CuO) NCs with wavelength

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Figure 9 illustrates the relationship between the refractive index and the wavelength for polymer nanocomposite (PVA–PEG–SiO2/CuO) films. The relationship between the concentration of (SiO2/CuO) NMs and the increase in n values is observable. The high density of (SiO2/CuO) NMs in the pure polymer is the reason for this association. When 6 wt% (SiO2/CuO) NMs are added to the PVA–PEG, the refractive index of the pure PVA–PEG increases from 1.37 to 3.04 at a wavelength of 460 nm. As the wavelength increases within the visible region, the refractive index diminishes until it attains a value of 460 nm. The refractive index then remains extremely stable between 460 and 780 nm. The increase in refractive index is caused by the interaction between the incoming light and the polymer containing (SiO2/CuO) NMs. This interaction results in a more excellent bending of light and, as a result, an elevation in the refractivity of the films [53, 54].

Fig. 9
figure 9

(PVA–PEG–SiO2/CuO) NCs’ wavelength-dependent n

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Analysing the dielectric performance of NCs materials is a useful method to examine both relaxation and conducting processes in polymeric materials. Figure 10 depicts the correlation between the real component of the dielectric constant (ε1) and the wavelength. As the frequencies increase, the value decreases for all samples. The decrease in value may be attributed to a reduction in the number of dipoles responsible for polarisation or the incapacity of the dipole structure to respond to the applied electric field. Figure 11 depicts the influence of (SiO2/CuO) NMs on the imaginary component of the dielectric constant. The diagram represents the relationship between the concentration of (SiO2/CuO) nanoparticles and the imaginary part of the dielectric constant in (PVA–PEG–SiO2/CuO) nanocomposites. The result clearly shows a positive connection, demonstrating that when the concentration of SiO2/CuO NMs grows, the imaginary component of the dielectric constant of the NCs similarly increases. The phenomenon under investigation can be further explained by the increased electrical polarization caused by the high concentration of nanoparticles in the sample. Consequently, an increase in charges ensues within the polymers. The correlation between the imaginary component of the dielectric constant and the extinction coefficient is particularly conspicuous over the visible light to near-infrared wavelength range. Within these specified regions, the refractive index remains generally stable, whereas the extinction coefficient progressively rises with the increase in wavelength [55, 56].

Fig. 10
figure 10

Shows the wavelength-dependent ε1 for (PVA–PEG–SiO2/CuO) NCs

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Fig. 11
figure 11

shows the wavelength-dependent ε2 for (PVA–PEG–SiO2/CuO) NCs

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Figure 12 shows the change in optical conductivity in comparison to wavelength. The purified PVA–PEG material exhibited a robust positive correlation between the concentrations of (SiO2/CuO) and optical conductivity according to the experiment. The conductivity experienced a substantial increase until it reached a concentration of 5 wt%. The observed increase in conductivity may be attributed to the phenomenon of generating additional energy levels within the band gap. By facilitating the transition of electrons from the valence band to specific energy levels and ultimately enabling their movement into the conduction band, the development of these new energy levels enhances electron mobility. Consequently, the conductivity of a material increases as the band gap decreases. The researcher’s conclusions are substantially supported by these data [57, 58].

Fig. 12
figure 12

Shows the wavelength-dependent σop for (PVA–PEG–SiO2/CuO) NCs

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3.4 The AC Electrical Properties of (PVA–PEG–SiO2/CuO) NCs

The dielectric loss (ε″) and the dielectric constant (ε′) are frequency-dependent properties. The initial term refers to the energy that has been stored within a system. In contrast, the latter term denotes the dissipative energy of a material in response to an external electric field. Figure 13 shows the effect of the (SiO2/CuO) NMs addition on the dielectric constant of the pure PVA–PEG. The dielectric constant increases with increasing concentration of the (SiO2/CuO) NMs. The reason for this increase is the formation of a cluster of the (SiO2/CuO) NMs inside NCs at low concentrations of the (SiO2/CuO) NMs; hence, the dielectric constant becomes low, and at high concentrations (SiO2/CuO) NMs form a continuous network inside NCs and so value of the dielectric constant increases with high concentrations of (SiO2/CuO) NMs [59]. Variation of the dielectric constant of (PVA–PEG–SiO2/CuO) NCs with the frequency is shown in Fig. 14. The figure shows that all of the dielectric constants of nanocomposite samples decrease as the frequency of the field applied increases; this can be due to the inclination of the dipole in the nanocomposite of samples to the orient themselves in directions of the electrical fields applied and to decrease the polarization of the space charge to absolute polarization [60, 61].

Fig. 13
figure 13

Influence of (SiO2/CuO) NMs content on the ε′ of (PVA–PEG–SiO2/CuO) NCs at 100 Hz

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Fig. 14
figure 14

Behavior of ɛ′ with frequency of (PVA–PEG–SiO2/CuO) NCs

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The variation of dielectric loss for (PVA–PEG–SiO2/CuO) NCs with frequency at room temperature with different concentrations of (SiO2/CuO) NMs is shown in Fig. 15. The graph demonstrates that as frequency increases, the loss decreases. This phenomenon occurs because the dipoles of composite molecules cannot rotate in parallel to quickly respond to the periodic phase changes of the electric field. Consequently, a temporal lag exists between the dipole’s and electric field’s frequencies. This finding suggests that no ions are scattering and electric charge buildup. The higher value of the dielectric loss for (PVA–PEG–SiO2/CuO) NCs at the higher concentration of (SiO2/CuO) NMs can be understood regarding electrical conductivity, which is related to the dielectric loss [62, 63]. The dielectric loss rises as the concentration of (SiO2/CuO) NMs increases, as shown in Fig. 16. A perpetual web of particles forms in the nanocomposite when the concentration reaches 6 wt%.

Fig. 15
figure 15

Behavior of ε″ with a frequency of (PVA–PEG–SiO2/CuO) NCs

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Fig. 16
figure 16

Influence of (SiO2/CuO) NMs content on the ε″ of (PVA–PEG–SiO2/CuO) NCs at 100 Hz

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Figures 17 and 18 illustrate the relationship between the frequency (f) and the concentration of (SiO2/CuO) NMs in the (PVA–PEG–SiO2/CuO) NCs, specifically in terms of the A.C. electrical conductivity performance. The graph illustrates a positive correlation between A.C. electrical conductivity and the electric field frequency in all nanocomposite samples. This behavior can be attributed to the migration of ions within the clusters and the movement of electrically charged particles. At lower frequencies, a more significant charge accumulation occurs at the interface between the electrode and electrolyte; this leads to a decrease in the amount of ions that can move around and, consequently, a drop in electrical conductivity. The conductivity rises as the concentration of (SiO2/CuO) NMs increases. The rise in electric charge results from the creation of fully saturated nanoparticles. Table 2 displays the ɛ′, ε", and σa.c values for (PVA–PEG–SiO2/CuO) nanocomposites at a frequency of 100 Hz [64], as shown in Table 2.

Fig. 17
figure 17

Difference of conductivity for (PVA–PEG–SiO2/CuO) NCs with frequency (f)

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Fig. 18
figure 18

Difference of conductivity for (PVA–PEG–SiO2/CuO) NCs with (SiO2/CuO) NMs contents

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Table 2 Influence of (SiO2/CuO) NMs content on the electrical characteristics of (PVA–PEG–SiO2/CuO) NCs at 100 Hz
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3.5 Application of (PVA–PEG–SiO2/CuO) NCs for Pressure Sensors

Figure 19 illustrates the change in parallel capacitance for (PVA–PEG–SiO2/CuO) nanocomposites under different applied pressures, considering different weight percentages of (SiO2/CuO) nanoparticles. As depicted in the diagram, the capacitance positively correlates with the magnitude of the applied pressure. The relationship between the parallel capacitance and the applied pressure can be clarified by examining the nanocomposite samples for crystalline regions with an intrinsic dipole moment. When no external mechanical or electrical stimulus is applied to this system, the dipole moments undergo a stochastic orientation, resulting in an overall dipole moment of zero. Applying stress on the samples can induce an electric field by altering the local distribution of the dipole moments. Attractive forces are generated by the electric field around the charges at the specimen’s upper and lower regions [65].

Fig. 19
figure 19

Difference of parallel capacitance for (PVA–PEG–SiO2/CuO) NCs with pressure

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Figure 20 illustrates the impact of (SiO2/CuO) NMs on the electrical capacitance (Cp) of (PVA–PEG–SiO2/CuO) NCs under a pressure of 80 bars. The graph demonstrates a direct relationship between the concentration of (SiO2/CuO) NMs and the electrical capacitance of NCs. The observed phenomenon could be attributed to a rise in the density of charge carriers in NCs, as suggested by previous research [66].

Fig. 20
figure 20

At 80 bar, the influence of (SiO2/CuO) NMs concentration on parallel capacitance for (PVA–PEG–SiO2/CuO) NCs

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The concentration of (SiO2/CuO) NMs in the sensitive layer has a significant influence on the performance of (PVA–PEG–SiO2/CuO) NCs sensors, which in turn governs the pressure sensing range, leading to various applications that require shuttle to higher forces. The influence of (SiO2/CuO) NMs on sensitivity for (PVA–PEG–SiO2/CuO) NCs is shown in Fig. 21. The graph demonstrates a direct relationship between the concentration of (SiO2/CuO) NMs and the electrical capacitance of NCs; this is due to internal dipole moment [67].

Fig. 21
figure 21

The influence of (SiO2/CuO) NMs concentration on sensitivity for (PVA–PEG–SiO2/CuO) NCs

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4 Conclusion

The objective of this study was to investigate the structural, electrical, and optical characteristics of nanostructures composed of a composite material comprising polyvinyl alcohol (PVA), Polyethylene Glycol (PEG), Silicon dioxide (SiO2), and copper oxide (CuO). The Fourier Transform Infrared (FTIR) spectra indicate a tangible interaction between the original polymer and nanoparticles of (SiO2/CuO). The optical microscope images demonstrate that incorporating (SiO2/CuO) additions resulted in a uniform distribution, with the nanoparticles forming a cohesive network inside the polymer blend. The optical parameters of the PVA–PEG–SiO2/CuO nanocomposites were significantly enhanced compared to the base materials. The absorption coefficient (α) increased by 2207% (from 14 to 310 cm−1), the refractive index (n) by 121% (from 1.35 to 3), the extinction coefficient (k) by 1900% (from 0.00005 to 0.001), the real part of the dielectric constant (ε1) by 416% (from 2 to 9), the imaginary part of the dielectric constant (ε2) by 6053% (from 0.0001 to 0.008), and the optical conductivity (σop) by 5874% (from 4 × 1010 to 220 × 1010). These improvements were observed at a wavelength of 540 nm. These results indicate that the PVA–PEG–SiO2/CuO nanocomposites are highly promising for applications in electronic and optical fields. Incorporating a nanofiller composed of 6 wt% of (SiO2/CuO) led to a reduction in the energy gap for both indirect transitions. The energy gap for permitted transitions fell from 4.37 to 2.80 electron volts (eV), while the energy gap for forbidden transitions reduced from 3.69 to 1.68 eV. The nanocomposites (NCs) made of polyvinyl alcohol (PVA), polyethylene glycol (PEG), silicon dioxide (SiO2), and copper oxide (CuO) demonstrate exceptional sensitivity to pressure while retaining a lightweight, flexible, and highly effective characteristic.