Morphological,thermal,optical,and electronic characteristics of PVA/PVP filled WO 3 nanocomposites

Abstract

PVA/PVP filled Tungsten oxide (WO₃) nanoparticles hybrid polymer nanocomposites are fabricated using a simple solution casting technique. The XRD, FTIR, and SEM images signify the effective incorporation of WO₃ nanoparticles (NPs) in the PVA/PVP mix host matrix. PXRD study indicated that the incorporation of WO₃ nanoparticle concentrations up to 3 wt. percent in the host matrix mix upsurges the crystallinity of the polymer nanocomposites. FTIR spectroscopy confirms the existence of intermolecular hydrogen bond formation amongst nanoparticles and the PVA/PVP matrix. SEM analysis demonstrates the WO₃ nanoparticles were evenly distributed in the PVA/PVP mix matrix. The tangent loss curve's characteristics for different WO₃ doping concentrations indicate that PVP-PVA/(x)WO₃ nanocomposites represent both relaxations and non-relaxation dipoles. The tangent loss has a relatively steady value above 0.1 MHz, with a minimal value of 0.09208 at x = 3 wt% loading concentration. The result suggests that the nanocomposite functions as a substance with no loss. The capacitance (Cp) among two electrodes on the bottom and top sides of the nanocomposites was evaluated at pressures varying from 80 to 200 bar to explore the application of the pressure sensor. Thermal evaporation of PVA/PVP:WO₃ nanocomposites yielded the changing oxygen vacancy percentage as the WO3 level rose. The moisture-resistant performance of PVA/PVP: WO₃ nanocomposites ranged from negative to positive. The PVA/PVP:WO₃ nanocomposites has shown its significance in fabricating material for optoelectronic devices including humidity sensors. The nanocomposite for x = 3 wt% is thermally stable in all test ranges up to 890 °C. The findings indicate that WO₃ in the produced films improved their thermal stability.

Keywords

PVA PVP nanocomposites nanoparticles XRD

Introduction

Polymer nanocomposites have become emerging materials in the recent decade because of their prospective involvement in various fields. These polymeric nanocomposites have acquired the highest degree of attention due to their appealing characteristics, such as flexibility, abundance, and economic features.^1,2 Furthermore, their flexibility to adjust with their attributes equips them to be a prominent material in industrial applications. The tailoring of nanocomposites is accomplished by combining different homopolymers or filling or doping them with fillers to achieve specific applications in areas such as optoelectronics, supercapacitor, antireflection coatings, bio, and medical applications are among them.^3–5 Out of many polymers, polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) in especially are highly valued owing to their unique properties, which include eco-environmental, biodegradability, non-toxicity, and water solubility.^6,7 The presence of hydroxyl groups in the PVA backbone provides polarity, which binds the added nanofillers well. The relatively high optical transmittance for the visible and infrared bands and its semi-crystalline properties make PVA a potential candidate for many device applications.^8,9

On the other hand, another host PVP polymer promotes stable adherence and miscibility due to its carbonyl groups and pyrrolidone rings.¹⁰ The advantages of these appealing properties of PVP and PVA polymers may be considered by combining them in a suitable ratio. This miscible mix of PVP and PVA is suitable for sophisticated applications such as optoelectronic devices, energy storage devices, and nanoelectronics.¹¹ In recent years, many filler metal oxide nanomaterials have proven their significance in enhancing the physical properties of nanocomposites. Transition metal oxide, such as tungsten oxide (WO₃), an n-type semiconductor substance with a band gap value of 2.6–3.0 eV, has garnered considerable interest.¹² Apart from these, WO₃ nanoparticles exist in cubic, triclinic, monoclinic, orthorhombic, tetragonal, and hexagonal forms, which makes it a viable contender for optoelectronics applications. The high melting temperature, photo electrochromic, tensile, and mechanical strength make the WO₃ nanoparticles ideal nanofillers in enhancing the physical properties of PVA/PVP nanocomposites.¹³ The combination of the PVA/PVP blend with WO₃ gives the advantages of physical properties of both the blends with the added nanoparticle.

Nevertheless, few research papers have been published that focus solely on filling nanostructured WO₃ in PVA/PVP to explore optical and electrical device applications. In this current research, we have regulated the nanocomposite's structural, thermal, optical, electrical and dielectric properties by varying the percentage filling of WO₃ nanofillers. The influence of WO₃ nanofillers on the physical properties of PVA/PVP:(x)WO₃ nanocomposites was investigated using XRD, FTIR, UV-Vis spectrophotometers, TGA and LCR meter.

Materials and method

Preparation of tungsten oxide (WO₃) nanoparticles

The ammonium tungstate hydrate (H₄₂N₁₀O₄₂W_12−x H₂O) initially mixed in deionized water and then heated at 90˚C with gentle agitation at 750 rpm. After full dissolution, nitric acid (HNO₃) was injected drop by drop to the tungstate solution, which was held at a constant agitation speed of 750 rpm. Furthermore, while maintaining the same swirling rate, the combined solution was held at 90˚C for 1 h to test the effect of the time necessary for the development of the WO₃ precursor. After this period, the precipitates were settled at room temperature for 24hrs. After decanting the acquired aqueous solution, deionizing water was poured with constant agitation, and the sedimentation process of the produced precipitates was continued until the pH of the solution turns neutral. The precipitates were dried at 80˚Ccelsius to eliminate the surplus moisture. The obtained precursors were then degraded by heat processing at 400˚C for 4 h to create WO₃ nanoparticles. XRD and SEM were used to determine the crystalline nature and shape of WO₃ powder.¹⁴

Preparation of PVA/PVP/(x)WO₃ nanocomposites

A visible liquid was formed after dissolving equal amounts of Mowiol 4–88 (PVA, average molecular weight ∼31000, Sigma Aldrich Germany) and Poly (vinyl pyrrolidone) (PVP, average molecular weight ∼40000, Sigma Aldrich Germany) in 40 ml of deionized water and stirring with a magnetic stirrer for an hour at 90 °C. After that, the thick solution concoction is split into four identical portions.

PVA/PVP/(x)WO₃ nanocomposites with different (tungsten oxide) WO₃ filler levels (‘x’) are produced by combining a weight (‘Wd’) of the nanofillers with a weight (‘Wp’) of PVA/PVP. Therefore, the weight fraction percentage (%) of the nanofillers is determined using:

x % = \frac{W_{d}}{W_{d} + W_{p}} \times 100

(1)

Synthesized WO₃ nanofillers with weight percentages of x = 0, 1, 2, and 3% are introduced to respective component of the solution. Additionally, WO₃-filled PVA/PVP mix components are sonicated for 10 min using a probe ultrasonicator to ensure that all of the nanofillers are evenly dispersed. After filling each PVA/PVP(x) WO₃ solution, it is placed on a petri dish and heated to 50 °C for a nighttime drying period. For additional characterization, each composite film is peeled off, encased in silver foil, and stored in vacuum desiccators.

Experimental results

XRD studies

Figure 1 explicates the XRD profile of combined PVA/PVP filled with WO₃ nanofillers at various filler levels. Significant peaks for the crystalline planes (011), (002), (020), (200), (120), (112), (022), (202), (220), (232), (114), and (50) degrees (JCPDS card N 83–0950) at 2θ= 19.1°, 22.9°, 23.4°, 24.1°, 26.4°, 28.1°, 32.8°, 33.9°, 41.6°, 49.82°, 50,43°) attest to the existence of WO₃ in the host framework. PVA molecules are implied by the spikes at 19° to 20° degrees, while the PVP molecule is typified by the peaks at 13° and 21° degrees.^15,16

Figure 1.

XRD spectra of pure PVA/PVP/WO₃ nanocomposites.

The semicrystalline character of PVA/PVP nanocomposites is supported by their conspicuous peaks. With the increase of WO₃ nanofillers, the diffraction peaks at PVA and PVP blend slightly richer. For x = 3 wt percent filler concentration, the PVA/PVP:(x) WO₃ nanocomposites’ diffraction peaks exhibited highest value, indicating organized distributions and intricate particle production. The amorphous area of the PVA/PVP mix and the added WO3 nanofillers generate a complex that increases the degree of crystallinity.¹⁷ This typically occurs because of interactions among the stuffed WO₃ nanofillers and the PVA/PVP blend main chain, which reduces the intermolecular and co-ordination interactions (inter/intramolecular interactions) among the WO₃ nanofiller and the blended polymer's ether O-H (hydroxyl) group of PVA and C = O (carbonyl) group of PVP. Using the Debye-Scherrer setup, the average crystallite diameters (D) of the infused WO₃ nano additives are measured.¹⁸

D = \frac{k λ}{β \cos θ}

(2)

Where λ refers to the x-ray wavelength, β is the whole width at half maximum of the X-ray profile, and θ indicates the Bragg angle, and k is equivalent to 0.9 and dependent on the form of the crystal and crystallographic planes. The percentage crystallinity of the PVA/PVP:(x) WO₃ polymeric composite is deliberated utilizing the standard relation,¹⁹

% Crystallinity = \frac{(total area of crystalline peaks)}{(total area of all peaks)}

(3)

Average inter-crystallite separation (R) within the PVA/PVP:(x) WO₃ nanocomposites are configured using the relation,

R = \frac{5 λ}{8 \sin θ}

(4)

where ‘λ’ symbolize the x-ray light wavelength, and ‘θ’ signify the angle of diffraction.

The PVA/PVP: (x) WO₃ matrix, the microstrains (ε) produced, is investigated using the relation²⁰

ε = \frac{(β c o s θ)}{4}

(5)

The density of dislocations in WO₃ nanofiller (δ) was envisioned by²⁰

δ = \frac{1}{D^{2}}

(6)

Table 1 explores the crystalline characteristics of the WO₃ nanofillers formed inside the PVA/PMMA matrix. The variance contained in Table 1 illustrates the structural regularity that transpired due to WO₃ nanofillers that resides within the PVA/PVP blend.

Table 1.

Crystalline parameters of PVA/PVP/(x)WO₃ nanocomposites.

Sl.No	Sample Wt%	Percentage of Crystallinity	Average crystallinity size D (nm)	Average intercrystalline separation R (Å)	Micro strain (ε)×10⁻³	δ (10¹⁶ lines/m²)
1	Pure WO₃	92.12	55.11	-	0.628	0.0329
2	0 wt%	56.64	2.56	5.70	13.54	15.258
3	1 wt%	58.95	21.37	5.37	1.622	0.219
4	3 wt%	59.12	23.15	5.21	1.497	0.1866

FTIR spectra

Figure 2 FTIR spectra of WO₃ nanoparticles showsthe bands less than 500 cm⁻¹ signposting WO vibrations. The spectra peaks witness between 500 and 1100 cm⁻¹ refers to W-O-W and O-W-O vibrations. Furthermore, H-O-H vibrations are observed above 1300 cm⁻¹,^21,22 and the bands observed at 1625 and 3444 cm⁻¹ indicate the adsorbed water's O H bending modes. The peaks emerging at 728 and 817 cm⁻¹ represents O-W-O stretching modes.²³ The broad band at 649 cm⁻¹ represents O-W-O stretching and a narrow band at 1408 cm⁻¹ signifies OH stretching. From this vantage point, the spectra suggest the fingerprints of tungsten oxide nanoparticles.

Figure 2.

FTIR spectra of prepared WO₃ nanoparticles.

FT-IR investigates the physico-chemical alterations resulted from the interaction among tungsten trioxide nanoparticles and PVA/PVP nano-composite films. Figure 3 displays the FTIR bands of the PVA/PVP mix both prior to and following integration with WO₃ for x = 1, 2, and 3 wt%. Several distinctive bands in the PVA/PVP blend have the subsequent vibrational frequencies: the OH (hydroxyl function) is measured at 3291 cm⁻¹, the C–H stretching at 2919 cm⁻¹, the C–O stretching at 1705cm⁻¹, and the N–H stretching vibration at 1591 cm⁻¹. The vibrational motion of CH₂ scissoring was attributed to the band at 1421 cm⁻¹.²² The carbonyl group (C = O) of the PVP molecule is the cause of the band seen at 1663 cm⁻¹.²³ These facts articulate that collaboration of PVA /PVP blends with WO₃ through hydrogen bond formation. The tungsten trioxide nanoparticles’ W-O-W stretching vibration is associated with the bands at 617 cm⁻¹ and 942 cm⁻¹.²⁴ Figure 2 also illustrates improvement in band intensities (typical broadband at 3291 cm⁻¹) with nanodopant concentration, particularly at x = 3wt%. For doped films, the intensities of the other bands are either enhanced or altered. Due to these certain interactions and thenotable band alterations resulted in changes to their chemical frameworks.

Figure 3.

FTIR spectra for PVA/PVP filler WO₃nanocomposites.

UV visible spectroscopy

Figure 4 explores the results of UV/Vis spectra for varying filler concentrations of the samples. PVA/PVP molecules exhibit considerable distinctive absorbance in the spectral range 200–400 nm.²⁴ Figure 4 signifies the movement of band edge towards the longer wavelength by dissimilar absorption intensities with the rise in filler level concentration upto x = 5wt%. The shift in band edge implies the creations of a complex through inter/intra molecule H - bonding, primarily between WO₃ ions and the OH groups of the PVA/PVP main chain. The formation of complex by the inter/intra hydrogen bonding between the PVA/PVP backbone and WO₃ nanofillers results in increased absorption. The increased absorption is in accordance to Beer's law, stating that radiation absorption is reliant on the amount of absorbent atoms. In the case of filled PVA/PVP nanocomposites, the displacement in the absorption edge mimics the change in the energy band gap. The drop in optical energy values with the rise in nanofillers concentration may possibly be connected to the production of defects which also alters the optical properties of materials. In the certain spectral range, the absorption bands are associated to π-π * electron transition. The π-electron excitation takes less energy, this transition occurs at longer wavelengths. The π-electron excitation takes less energy, this transition occurs at longer wavelengths. The variance in energy gap is caused by the crystalline formations and existence of unstructured defects inside the PVA/PVP host matrix.

Figure 4.

Tauc plot of PVA/PVP filled WO₃ nanocomposites.

Figures 4 represent the energy difference between permissible indirect transitions of WO₃ nanofillers throughout the PVA/PVP matrix.

Using equation (4) gives the absorption coefficient α of PVA/PVP/WO₃ sample in terms of photon energy,

α = \frac{2 .303 A}{d}

(7)

where A and d represents the absorbance as well as the thickness of prepared sample.

The classical Tauc's formulates the link between the absorption coefficient as well as the optical band gap E_g. The optical energy band gap value is achieved by conversion of UV-visible absorption spectra to Tauc's plot. The frequency sensitive absorption coefficient predicted by Mott and Devis²⁵ transforms the absorption spectrum into Tauc's plot.

α (ν) = \frac{β {(h ν - E_{g})}^{r}}{h ν}

(8)

where β is a constant and the exponent r is an empirical index, and its magnitude is 2 for the indirect allowable transition accountable for optical absorption in the quantum mechanical sense.

The linearity of the curve shows the product of absorption coefficient with photon energy (αhν)^1/2 versus photon energy (hν)at room temperature denotes an authorized indirect transition. Figure 4 explores, the optical energy band gap (E_g) projecting the linear section of this curve to a point (αhν) 0.5=0 for both pure as well as doped PVA films, as shown in Figure 4. The allowable indirect transition between the valence and conduction bands is taken into account.

Figure 5 represents the extinction coefficient which refers to the degree to which a nanocomposite absorbs or reflects radiation or light at a certain wavelength. Extinction coefficient and absorption coefficient are linked by:

K = \frac{α λ}{4 π}

(9)

Figure 5.

Variation of extinction co-efficient with wavelength.

The extinction coefficient shows a dispersion tendency that is consistent with the Sellmeier association. The extinction coefficient results from light absorbance whenever the photon's wavelength is larger than or equivalent to the grain size. The chance of grain scattering, grain size and density of the nanoparticles escalates with the rise in WO₃nanofillers fraction. It also found that extinction coefficient increases with the rise in wavelength. It was found seldom zero at 320 nm owing to secondary transitions that occur alongside the basic transformation.

AC and DC conductivity

The AC conductivity of these films was determined in the frequency range of 50 Hz to 5 MHz with the HIOKI 3532–50 LCR Hi-tester, a device connected to a computer. Conductivity was measured at room temperature. Figure 6 depicts the variation in AC conductivity as a function of frequency for polymer nanocomposites. Figure 3 shows that conductivity raises with increased frequency. The increase in AC conductivity is caused by a rise in the WO₃content in the polymer matrix, which results in a greater number of free ions. This will boost the mobile charge carriers, comparatively more free ions in the polymer framework owing to a boost in salt content, the AC conductivity has increased. Table 2 illustrates the surge in AC conductivity with the rise in filler level.²⁵ As a result of these charge carriers moving inside a framework of semi crystalline polymers, conductivity rises. Therefore, a correlation exists amongst the conductivity and the semicrystalline of the polymer layer. Conductivity often rises with decreasing crystallinity, as previously noted; this is the complement of an upsurge in crystalline nature.²⁶

Figure 6.

Ac conductivity of PVA-PVP/WO₃ nanocomposites.

Table 2.

Dc conductivity values of PVA/PVP:(x)WO₃ nanocomposites for various ‘x’ filler levels.

Sl No	Concentration of WO₃ (wt%)	Conductivity(σ in S/cm)
1	0	0.96×10⁻⁹
2	1	1.26×10⁻⁹
3	2	2.31×10⁻⁹
4	3	3.79 × 10⁻⁹

The DC conductivity of PVP-PVA/WO₃ samples are assessed employing the following equation,

σ_{DC} = \frac{d}{RA}

(10)

where d signposts the thickness of the tester, A the area of the electrode, and R denotes the resistance of the nanocomposite (I–V data)

The DC conductivity of PVA-PVP/(x) WO₃ nanocomposites with distinct nanofiller values of x = 0,1,2, and 3 weight percent is shown in Table 2. The DC conductivity has a greater value when the loading is x = 3wt%. The XRD data indicate that increased crystallinity is the cause of the increase in dc conductivity. This crystallinity rise up to x = 3wt% filler indicates the formation of charge transfer complexes, or CTCs. Polaron and bipolaron generation in the PVA-PVP:(x)WO₃ nanocomposite matrix is identified by the formation of conjugated double bonds in the underlying structure of PVP molecules.²⁷ These findings contribute to the development of charge-transfer complexes, such as the interpolaron hoping model, which involves charge carrier hopping aided by phonons. Enhanced CTCs create a conducting direction in PVA-PVPs but decrease the barrier strength of deceptive sites.²⁸ The conductive nanofillers’ width gets smaller as the amount of WO3 nanofillers rises, unless it achieves the ideal filler level of x = 15 wt percent. By raising contact conductance, it enhances PVA-PVP:(x)WO₃ nanocomposites’ conductivity.²⁹ On the other hand, cations in the PVA-PVP mainchain could benefit from oxygen molecules that bond with W ions.³⁰ Because such complexes reduce the barrier height and increase dc conductivity, they play a crucial role in enabling electrons to hop longitudinally among the insulator functional groups and the barrier. The current-voltage attributes of the PVA/PVP:WO₃ nanocomposites explores the reveal that the rise in bias voltage enhances the oxygen vacancy content allowing the nanocomposites conduction to shifts from volume-limited (space charge-limited) to electrode-limited (Schott Base launch), as described by Yang et al. The resistance switching behavior of WO₃ NWs may be altered by varying the percentage of oxygen deficiencies and even the scanning range of the bias voltage.

Dielectric studies

Figure 7 depicts the capacitance fluctuation of PVA/PVP/WO₃ nanocomposites with x = 0, 1, 2, and 3 wt%. Figure 7 demonstrates resurgence in nanocomposites capacitance with an increase in pressure. Composites have dipoles exhibiting intrinsic dipole moments in their crystalline domain. The net dipole moment is zero in the absence of stress. The mechanical stress changes the local dipole distributions and creates an electric field. This induced electric field accrue the localized charges at both bottom and top sides of the composites their by raising its capacitance.^25,31

Figure 7.

Variation of capacitance for PVA/PVP/WO₃ nanostructures with pressure.

The capacitance (Cp) among two electrodes on the bottom as well as top sides of the nanocomposites were evaluated applying the pressures varying from 80 to 200 bar to explore the application of the pressure sensor. The influence of discrete oxygen vacant positions on the electrical properties of WO₃ has been a matter of contention.³² It was found that as the oxygen vacancies increases the device's conductivity as a result of increased photo generated carrier transit and effective separation. It is critical to explore the electrical properties of tungsten oxides with varying degrees of oxygen vacancy. The PVA/PVP:WO₃ nanocomposites has shown its significance in fabricating material for optoelectronic devices including humidity sensors.

Figure 8 and 9 represents frequency dependence on the real part ε′ and imaginary part ε″ dielectrics of the nanocomposites. The frequency dependent relation shows that the added nanodopant transforms the physical properties of PVA/PVP:WO₃ nanocomposites. The observations suggest that both ε′ and ε″ diminishes with the rise in frequency due to polarization loss persuade by charge accretion. At higher frequency, the values of ε′ and ε″ remains constant. The higher values of ε′ and ε″ found for x = 3wt% loading signposts the accretion of charges due to the polarization in the interaction among WO₃ nanoparticles and PVA/PVP.

Figure 8.

Variation of real dielectric constant of PVA-PVP/WO₃ nanostructures with frequency.

Figure 9.

The imaginary part of complex permittivity of PVA-PVP/WO₃ nanocomposites as a function of frequency.

The dielectric loss factor in terms of real and imaginary parts of permittivity is given by

Tan δ = \frac{ε^{^{″}}}{ε^{'}}

(11)

Figure 10 signifies the deviation of tangent loss with increase in frequency for different ‘x’ doping concentration of PVP-PVA/(x)WO₃. The tangent loss curve's characteristics for different WO₃ doping concentrations indicate that PVP-PVA/(x)WO3 nanocomposites include both relaxation as well as non-relaxation dipoles. The tangent loss has a relatively steady value above 0.1 MHz, with a minimal value of 0.09208 at x = 3 weight percent loading concentration. The result suggests that the nanocomposite functions as a substance with no loss. The graph 10 additional suggests that such PVP-PVA nanocomposite materials may be employed as adjustable dielectric materials for a variety of device applications at lower frequency ranges. Overall, it can be said that the primary PVP-PVA matrix may contain WO₃ nanoparticles, which might decrease energy loss and improve the electrical characteristics of nanocomposites.

Figure 10.

Dielectric loss of PVA/PVP nanocomposites.

Thermal studies

Thermogravimetric investigations reveal tungsten trioxide's influence on the thermal degradation behaviors of the PVP/PVP matrix. Figure 11 depicts the TGA graphs of the PVA/PVP blend combined with WO3 at various laser-ablation times. The observation suggests the initial weight loss for PVA/PVP at 110–300°C in the lack of tungsten-trioxide nanoparticles. In contrast, the initial weight loss for PVA/PVP-WO₃ nanocomposites at 312 °C attributed to the incorporation of WO₃ in the films formed by the breakdown of chains in the PVA/PVP blend. In contrast to other samples, the nanocomposite for x = 3wt% is thermally stable in all test ranges up to 890 °C (Figure 4). The findings indicate that WO₃ in the produced films improved their thermal stability. The thermal disintegration of PVA/PVP blends with various strengths occurs at a greater temperature than the thermal disintegration of the pure PVA/PVP matrix, implying that the specified chemical interaction between tungsten trioxide and the PVA/PVP blend increases the thermal stability of the generated films.³³ Furthermore, increasing the quantity of WO3 in the PVA/PVP combination increased the thermal characteristics of the nanocomposite, notably in the final sample, which remained thermally stable up to 972 °C. Thermal evaporation of PVA/PVP: WO3 nanocomposites yielded a changing oxygen vacancy percentage as the WO3 level rose.³⁴ The moisture-resistant performance of PVA/PVP: WO₃ nanocomposites ranged from negative to positive.

Figure 11.

TGA curves of PVP/PVP and blend filled with WO₃.

Morphological studies

SEM detects the functioning of PVA/PVP matrix material elements by noticing the phase disparities and networks.³⁵ Figure 12 exhibit the SEM microstructure of pure PVA/PVP and WO ions at the optimal infill level, x = 3 wt percent. The pure PVP/PVA film has the smoothest, most stable, and homogeneous surface, indicating a strong hierarchical framework. These PVA/PVP molecules may spread in the soft-segment mechanism while not influence microphase separation, allowing strong and weak segments to mix. When WO₃ is incorporated to unadulterated PVA/PVP polymer films, their surface morphology advances, transforming from smooth to rough. It results from the spontaneous dispersion and detachment of nanofiller WO₃, which might generate topological disturbances in the PVA/PVP host matrix.^6,15 Therefore, the network started developing a crystalline framework, thereby increasing the versatility of the PVP membrane. The homogeneous surface shape of the filler PVA/PVP:(x)WO₃ nanocomposites may be responsible for their increased conductivity.³⁶

Figure 12.

SEM image of (a) Pure PVA/PVP and (b)x = 3wt% of WO₃ nanofillers.

Figure 12 illustrates the Energy Dispersive X-ray (EDS) investigates the chemical composition and uniform percentage variation in PVA/PVP filled with WO₃-based nanocomposites. To prevent particles formed by charging on the mixture's surface, the filled PVA/PVP:(x)WO₃ was covered with gold particles prior to EDS analysis. Figure 13 depicts WO₃ in a continuous section of the fabricatedPVA/PVP frame work.

Figure 13.

EDS spectra of PVA/PVP:(x) WO₃ nanocomposite for x = 3wt% filler level.

SEM-assisted chemical characterization is a technique for confirming the existence of WO₃nanofillers in the PVP/PVA matrix and approving the disbursement of W, C, and O elements on the surface of PVA/PVP:(x)WO₃ nanocomposites. Figure 14 explores the unique impression of mapping of components in diverse hues, such as W (green), O (yellow), and C (red). Furthermore, the elemental mapping reveals even dispersion of WO₃ nanofillers in the PVA/PVP matrix.

Figure 14.

SEM image of the (a) W, (b) O and (c) C elemental composition of PVA/PVP:(x)WO₃ nanocomposite for x = 3wt%.

Conclusions

The outcomes of the study of PVA/PVP-filled WO₃ polymer nanocomposites made by solution casting and coagulation mixing are discussed below.

The XRD analysis reveals that the synthesized WO₃ nanoparticles have an average particle size of 55.11 nm. XRD spectra explore filler interactions with PVA/PVP matrix-forming complexes, resulting in structural differences that alter crystallinity.

FTIR signifies the interaction among WO₃ ions with the OH group of the PVA/PVP backbone, utilizing intra- and intermolecular hydrogen bonding to form a complex.

The UV–visible spectral studies showed that the optical energy gap of PVA/PVP: WO3 decreases with the rise in filler level, and for x = 3%, the value of Eg = 2.756 eV.

The extinction coefficient results in grain scattering, grain size, and density of the nanoparticles escalate with the rise in the WO3 nanofillers fraction.

The variation in AC and DC conductivity of the polymer nanocomposites rises with frequency.

The tangent loss curve's characteristics for different WO₃ doping concentrations indicate that PVP-PVA/(x)WO3 nanocomposites include both relaxations and non-relaxation dipoles. The tangent loss has a relatively steady value above 0.1 MHz, with a minimal value of 0.09208 at x = 3 weight percent loading concentration. The result suggests that the nanocomposite functions as a substance with no loss.

The capacitance (Cp) among two electrodes on the bottom and top sides of the nanocomposites was evaluated at pressures varying from 80 to 200 bar to explore the application of the pressure sensor.

The process of thermal evaporation of PVA/PVP:WO₃ nanocomposites resulted in a variation in the proportion of oxygen vacancies as the quantity of WO₃ increased. The moisture resistance of PVA/PVP: WO₃ nanocomposites varied from negative to positive. The relevance of PVA/PVP:WO₃ nanocomposites lies in their ability to fabricate materials for optoelectronic gadgets, which include humidity sensors.

In contrast to other samples, the nanocomposite for x = 3wt% is thermally stable in all test ranges up to 890 °C. The findings indicate that including WO₃ in the produced films improved their thermal stability.

The Scanning electron microscopy images show the WO₃ flake nanoparticles, their homogenous distribution, and the compatibility between the nanoparticles with the PVA matrix.

Footnotes

ORCID iD

Hassan AH Alzahrani

Declaration of conflicting interests

The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author received no financial support for the research, authorship, and/or publication of this article.

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Morphological,thermal,optical,and electronic characteristics of PVA/PVP filled WO 3 nanocomposites

Abstract

Keywords

Introduction

Materials and method

Preparation of tungsten oxide (WO3) nanoparticles

Preparation of PVA/PVP/(x)WO3 nanocomposites

Experimental results

XRD studies

FTIR spectra

UV visible spectroscopy

AC and DC conductivity

Dielectric studies

Thermal studies

Morphological studies

Conclusions

Footnotes

ORCID iD

Declaration of conflicting interests

Funding

References

Preparation of tungsten oxide (WO₃) nanoparticles

Preparation of PVA/PVP/(x)WO₃ nanocomposites