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Abstract

This work presents the influence and improvement of the properties of linear and non-linear optical polystyrene (PS) nanocomposites by adding lanthanum hydroxide La(OH)₃ NPs at different concentrations (0, 1, 2, and 3 wt%). The solution casting procedure was employed to fabricate the PS/La(OH)₃ nanocomposites. XRD, FTIR, SEM, EDX, and Raman spectroscopy were used to analyze the structure of the prepared samples. The pure PS film exhibits an absorption edge of 3.29 eV, which gradually decreases to 2.80, 2.39, and 2.01 eV with increasing concentrations of La(OH)₃. Additionally, the optical band gap of pure PS is 3.83 eV, respectively, decreased to 3.67, 3.55, and 3.39 eV with increasing La(OH)₃ NPs loading from 1 to 3 wt%. Furthermore, the volume and surface energy loss functions (VELF and SELF) values increased with the increasing content of La(OH)₃ NPs within the PS polymer matrix. Furthermore, the third-order nonlinear optical susceptibility χ⁽³⁾ value increased from 1.03 × 10⁻¹⁴ for the pure PS film to 1.14 × 10⁻⁹ esu for PS/3% La(OH)₃ nanocomposite film. Meanwhile, the nonlinear refractive index n₂ value enhanced from 2.68 × 10⁻¹³ esu for the pure PS film to 1.23 × 10⁻⁹ esu for the PS/3%La(OH)₃ nanocomposite films, respectively.

Keywords

PS polymer nanocomposite polymer composite non-linear optical properties linear optical properties dispersion energy

Introduction

Polymer composite materials have garnered significant interest due to their ability to integrate the beneficial characteristics of nanofillers and polymers, resulting in materials with enhanced functionalities.^1,2 Polymer nanocomposites enriched with metal oxides are utilized for advanced applications, including optoelectronics, radiation shielding, sensors, and energy storage.^3–11 Khasraw et al. reported the development of polyethylene oxide (PEO) nanocomposites doped with V₂O₅ nanoparticles, exhibiting improved structural, optical, and dielectric properties.¹² Similarly, Mamand et al.¹³ investigated PEO nanocomposites incorporating Fe₃O₄ nanoparticles, achieving tailored optical and magnetic characteristics. Additionally, Dyari M. Mamand et al. ¹⁴ reported improved optical properties in chitosan polymer doped with orange peel dye. One of the remarkable polymers that garnered an enormous degree of scientific interest is polystyrene (PS). PS achieved particular attention attributable to its exceptional thermal and chemical stability, as well as its unique optical properties. PS possessed exceptional mechanical durability, low density, outstanding thermal resistance, superior electrical insulation, and simplicity of processing and molding, in addition to its exceptional optical transparency.^15,16 All of these benefits render it suitable for a diverse range of industrial and technological applications, such as electronics, insulation, and packaging.¹⁷ The integration of nanofillers has emerged as a crucial field of research to meet the increasing demand for novel materials with unique properties. Abdelghany et al.¹⁸ reported that adding 5 wt% nanosilica reduced the direct optical band gap of PVC/PS (50/50 wt%) from 3.88 eV to 3.49 eV. Rahimli et al.² have studied the impact of ZnO nanoparticles (NPs) on the dielectric and thermal attributes of PS/ZnO nanocomposites. Abulyazied et al. ¹⁹ reported the radiation shielding, optical, and structural properties of PS/Dy₂O₃ composites.

Lanthanum compounds (lanthanum (III) hydroxide La(OH)₃ and lanthanum (III) oxide La₂O₃) are of significant research interest due to their potential applications across various technological domains.²⁰ R.S. Yadav et al.²⁰ synthesized a Eu, Sm co-doped La(OH)₃ nanocrystalline red-emitting phosphor via a combustion process. Leidinger et al. ²¹ produced (La(OH)₃) hollow spheres by employing a water-in-oil microemulsion technique. Wang et al.²² prepared La(OH)₃ nanorods via a hydrothermal process and evaluated their photocatalytic performance through the degradation of Congo red dye. Khound et al.²³ have synthesized a La₂O₃/polyvinyl phenol thin film for transistor applications. Alhassan et al.²⁴ have outlined the linear/non-linear optical properties of PVC/La₂O₃ nanocomposites. La₂O₃ exhibits high hygroscopicity and readily absorbs water to produce La(OH)₃, which is notably stable.²⁰

The solution casting method is simple and allows reasonable control over film thickness. However, its large-scale use is limited by high solvent consumption, long processing time, and the risk of nonuniform filler distribution due to gravity-driven sedimentation during drying.²⁵

This work presents the influence and improvement of the properties of linear and non-linear optical PS nanocomposites by the addition of La(OH)₃ NPs at different fractions (0, 1, 2, and 3 wt%). The solution casting approach was employed to fabricate PS/La(OH)₃ nanocomposites. The structural characteristics of the samples were evaluated using several characterization techniques, such as EDX. SEM, and XRD. The optical characteristics of the synthesized PS/La(OH)₃ nanocomposites were also examined.

Materials and methods

Polystyrene and lanthanum hydroxide (La(OH)₃) nanopowder were purchased from ADWIC Co. A polystyrene (PS) solution was prepared by dissolving 1 g of PS in 10 mL of toluene and stirring it for 30 min using a magnetic stirrer. La(OH)₃ NPs were added to the PS solution with different concentration ratios (0, 1, 2, and 3 wt%) and stirred via a magnetic stirrer for 45 min. The PS, PS/1% La(OH)₃, PS/2% La(OH)₃, and PS/3% La(OH)₃ nanocomposites were dried in air. The PS, PS/1% La(OH)₃, PS/2% La(OH)₃, and PS/3% La(OH)₃ nanocomposites were renamed as PS, PS/La₁, PS/La₂, and PS/La₃, respectively. The thickness of the PS/La(OH)₃ nanocomposite films was measured to be 350 ± 20 µm. The structural and morphological characterization of PS and PS/La(OH)₃ nanocomposite films was performed using various analytical techniques. The crystal structure was analyzed by X-ray diffraction (XRD) using a Shimadzu 6000 diffractometer. The functional groups were identified using Fourier Transform Infrared (FTIR) spectroscopy with a Nicolet iS10 spectrometer. Surface morphology and elemental composition were investigated by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray analysis (EDX) using an Inspect S instrument (FEI, Holland). Optical properties of the samples were examined using a UV–Vis–NIR spectrophotometer (Jasco V-570).

Results and discussion

Structural analyses

The X-ray diffraction and FTIR spectra of La(OH)₃ NPs are illustrated in Figure 1. The La(OH)₃ NPs’ main crystal structure and purity degrees are revealed by the XRD patterns (Figure 1(a)). The pure hexagonal phase can be identified by the diffraction peaks observed at the (100), (110), (101), (201), (200), (211), and (112) reflection planes (JCPDS card No. 36-1481).²⁶ The high crystallinity of La(OH)₃ NPs was verified by the stronger and identified diffraction peaks of the NPs. The nanostructures of the La(OH)₃ NPs are suggested by the broader character of XRD peaks.²⁷

Figure 1.

(a) X-ray diffraction pattern, (b) FTIR spectra of La(OH)₃ NPs.

Scherrer’s formula was implemented to assess the crystallite size (D) of the La(OH)₃ NPs²⁸:

D = \frac{0.9 x λ}{β \cos (θ)}

(1)

λ denotes the X-ray wavelength, θ corresponds to the diffraction angle, and β refers to the full width at half maximum (FWHM) of the observed peak expressed in radians. The crystallite size of the La(OH)₃ NPs has been determined to be 26.32 nm.

Figure 1(b) illustrates FTIR spectra of La(OH)₃ NPs in the wavenumber range of 3500–400 cm⁻¹. The detection of O–H stretching vibrations resulting from moisture absorption on the surface of the samples has been verified by a wide band observed at 3604 cm⁻¹. The well-defined band appearing at 857 cm⁻¹ is related to C–H bending vibrations, while the peak at 1465 cm⁻¹ was created by the asymmetric stretching of C-O−functional groups. The broadband at 641 cm⁻¹ is attributed to La–O stretching vibrations, whereas the narrow band at 494 cm⁻¹ results from La–O bending vibrations.²⁷

The SEM image of La(OH)₃ NPs is illustrated in Figure 2(a). The figure revealed that the La(OH)₃ NPs have plate-like and rod-shaped particles with an aggregated distribution. Figure 2(b) shows EDX spectra of La(OH)₃ NPs. EDX spectra revealed the elemental composition (La and O elements) and purity of La(OH)₃ NPs.

Figure 2.

(a) SEM image and (b) EDX spectra of La(OH)₃ NPs.

Additionally, Figure 3(a) illustrates the XRD patterns of polystyrene (PS) and PS-based nanocomposites as the concentration of La(OH)₃ increases to 1%, 2%, and 3%. The amorphous structure of pure PS is characterized by a broad peak at approximately 20°. As the content of La(OH)₃ rises, distinct peaks that correspond to La(OH)₃ are observed. As the concentration of La(OH)₃ rises, these peaks become more distinct, suggesting that the La(OH)₃ NPs are effectively incorporated and have an improved crystallinity profile. The FTIR spectra of PS and PS/La(OH)₃ nanocomposite films are illustrated in Figure 3(b). FTIR spectrum of the pure PS film revealed characteristic absorption peaks at 3025 cm⁻¹ and 2919 cm⁻¹, which are attributed to the aromatic C-H and aliphatic C-H stretching vibrations, respectively. The bands identified at 1490 cm⁻¹ were characterized as resulting from C = C bending vibrations. The vibrational phase of CH₂ bending is located at 1448 cm⁻¹.^29,30

Figure 3.

(a) X-ray diffraction patterns and (b) FTIR spectra for the pristine PS and La(OH)₃-mixed PS films.

Impressively, by the addition of a high percentage 3% of La(OH)₃ NPs into the PS, new characteristic bands appeared at a wavenumber of about 3604 and 641 cm⁻¹ owing to O–H group and La–O stretching vibrations of the La(OH)₃ NPs. Moreover, the inclusion of La(OH)₃ NPs into the PS matrix also led to an increase in the intensity of the bands for all nanocomposite films, suggesting an interaction between the polymeric chain and La(OH)₃ NPs. Possible physical and chemical interactions may occur between La(OH)₃ and the PS matrix. La(OH)₃ nanoparticles can interact with PS chains through weak van der Waals forces, and hydrogen bonding may also form between surface oxygen atoms of La(OH)₃ NPs and hydrogen atoms of the PS chains.^31–35 These findings confirm the good preparation of PS/La(OH)₃ nanocomposite films.

Raman analysis is a practical and efficient method to ascribe the structure of nanocomposite films. Figure 4 shows the Raman spectra of PS/La₁ and PS/L₃ films. It can be seen that the spectra present several Raman modes intrinsic to PS, including peaks at 609, 998, 1028, and 1595 cm⁻¹, which correspond to ring deformation, aromatic groups, C-H bending, and C = C aromatic ring stretching, respectively. Moreover, the peaks at 794, 2900, and 3053 cm⁻¹ are related to a weaker single bond C-C, C-H stretching of aromatic, and C-H stretching of aliphatic carbon. Meanwhile, these spectra also present small peaks, which are more pronounced in the case of the PS/L₃ film at 208, 354, and 447 cm⁻¹, assigned to La–O bending vibration, La–O stretching vibration, and Eg_ν1 mode, respectively. These results provide strong evidence of the successful loading of La(OH)₃ on the PS.^36–39

Figure 4.

The Raman spectra of PS/La₁ and PS/L₃ films.

Optical properties

Studying the optical properties, such as absorption, absorption coefficient, energy gap, reflectance, and refractive index, provides insight into the electronic configuration and energy levels of the polymers, which are crucial for understanding their functionality in various applications. The absorbance (A) and reflectance (R) are measured using UV-vis spectroscopy. Figure 5(a) displays optical absorbance spectra for pure PS and La(OH)₃-loaded PS films. All spectra present a strong absorption region in the UV region between 190 and 350 nm, which may be owing to the sufficient photon energy for interacting with atoms.⁴⁰ It can be seen that the pristine PS spectrum exhibits an absorption band at 250 nm, which is attributed to the π→π* electronic transitions of the PS matrix.^41,42 This figure also shows that increasing the amount of La(OH)₃ NPs in the nanocomposite films enhances the absorbance, which is attributed to the nanoparticles aggregating, thereby increasing the number of charge carriers.⁴¹ The enhanced absorbance is beneficial for applications where strong light absorption is essential, such as in optical devices.⁴³ The dependence of reflectance spectra (R) on wavelength (λ) for both pure and doped nanocomposite films is displayed in Figure 5(b). As observed, the reflectance spectra for all films decrease with increasing wavelength, reaching a constant value at higher wavelengths. Moreover, the reflectance values gradually increased as the La(OH)₃ NPs content improved in the PS matrix. Such an increase may stem from enhanced light scattering resulting from the formation of molecular bonds between the polymer and the incorporated filler.²⁴

Figure 5.

(a) The absorbance (A) versus wavelength (λ) and (b) the reflectance (R) versus wavelength (λ) for the pristine PS and La(OH)₃ -mixed PS films.

The linear absorption coefficient (α) of pure PS and PS-doped films by La(OH)₃ can be given from the absorbance values and thickness of films (d) according to the Beer-Lambert expression⁴⁴:

α = (2.303) \frac{A}{t}

(2)

Figure 6(b) reveals changes in linear absorption coefficient (α) with photon energy (hν) for the prepared films. There is a gradual improvement in the absorption coefficient after incorporation of the La(OH)₃ NPs with the polymer matrix. This improvement in the absorption coefficient is attributed to the formation of molecular complexes between the La(OH)₃ NPs and the PS polymer, which creates new energy levels and enhances photon absorption.⁴⁵ Meanwhile, the absorption edge values can be extracted from the pure PS and PS-doped films from the extrapolation of the linear parts of the curves to a point α (cm ^{– 1}) = 0 and were listed in Table 1. According to the table, the pure PS film exhibits an absorption edge of 3.29 eV, which gradually decreases to 2.80, 2.39, and 2.01 eV for the PS/La₁, PS/La₂, and PS/La₃ samples, respectively. This result confirms a red shift of the absorption edge after inserting different amounts of the nanofiller, indicating interactions between the nanoparticles and the polymer matrix and reducing the optical band gap.

Figure 6.

(a) α Vs. hν (b) (αhν)² versus hν for the pristine PS and La(OH)₃-mixed PS films.

Table 1.

The estimated Ee, Eg, and E_U for the pristine PS and La(OH)₃-mixed PS films.

	Absorption edge (E_e) (eV)	Optical bandgap (E_g) (eV)	Urbach tail (E_U) (eV)
PS	3.29	3.83	0.53
PS/La₁	2.80	3.67	0.97
PS/La₂	2.39	3.55	1.25
PS/La₃	2.01	3.39	1.28

According to Mott and Davis, the optical band gap energy (E_g) values of the pure PS and PS-loaded films were computed by considering the following dependence of α on the photon energy (hν)⁴⁶:

{(α . h ν)}^{1 / x} = X (h ν - E_{g})

(3)

The parameter x, known as the band tailing factor, is assigned a value of 1/2 for direct allowed transitions and 2 for indirect allowed transitions. Figure 6(b) presents the Tauc relation between (αhν)² versus hν for the pristine PS and three nanocomposite films of PS/La(OH)₃ with various weight amounts of La(OH)₃. Using this figure and equation (3), the allowed direct optical band gap can be found by extrapolating the linear portion of the obtained curves to the x-axis, where α = 0. The values of the band gap were summarized in Table 1. The optical band gap of pure PS is 3.83 eV, respectively, decreased to 3.67, 3.55, and 3.39 eV with increasing La(OH)₃ NPs loading from 1 to 3 wt%. Specific defects in the films induced this reduction due to the insertion of La(OH)₃ nanoparticles.⁴⁵ This decrease indicates that the additional La(OH)₃ NPs enhance the nanocomposite films’ ability to conduct electricity by creating defects that facilitate charge carrier generation across the nanocomposite’s band gap.

The Urbach energy (E_U), a measure of band tail width, can be calculated from the absorption coefficient spectra based on the following formula.⁴⁷

\ln (α) = \ln (α_{o}) + \frac{h ν}{E_{U}}

(4)

Where α_o equals a constant, and is called the pre-exponential factor. The E_U can be derived from the inverse slope of the straight-line portion of ln(α) versus hν plots (Figure 7). The obtained band tail values are listed in Table 1. The values suggest that increasing the nanofiller concentration led to an increase in the E_U. The results demonstrate that the distribution of La(OH)₃ NPs affects the structural defects in the PS films.⁴⁸

Figure 7.

Ln α versus h $ν$ for the pristine PS and La(OH)₃-mixed PS films.

Based on the wavelength (λ) and absorption coefficient (α), the extinction coefficient (k) can be evaluated using the relation below⁴⁹:

k = \frac{α λ}{4 π}

(5)

The variation of k as a function of λ for the pure PS and La(OH)₃-loaded PS films is disclosed in Figure 8(a). As shown, incorporating La(OH)₃ NPs with an increased ratio gradually increases k, which is explained by the increase in charge carriers and defect states.⁵⁰ The refractive index (n) is a fundamental optical property, indicating the extent to which light slows down in a given medium. The refractive index of the pure and nanocomposite films can be extracted from the Fresnel’s relationship⁵¹:

n = \sqrt{\frac{4 R}{{(1 - R)}^{2}} - k^{2}} + \frac{(1 + R)}{(1 - R)}

(6)

Figure 8.

(a) The extinction coefficient (k) versus wavelength (λ) and (b) the refractive index (n) versus wavelength (λ) for the pristine PS and La(OH)₃-mixed PS films.

Figure 8(b) depicts the refractive index alteration against the wavelength of pure PS and La(OH)₃-doped PS films. The refractive index of virgin PS and PS/La(OH)₃ films declined substantially with increasing wavelengths. Further, as the concentration of La(OH)₃ NPs increases, a higher refractive index is observed, due to the higher dipole and density arising from the cross-linked structure and the presence of La(OH)₃ in the PS matrix.⁵² Meanwhile, incorporating the La(OH)₃ NPs into the PS matrix may lead to the formation of localized states in the band gap area.⁵³ There is a growing need for optical materials with a wide range of refractive indices in various applications, such as filters, optical adhesives, antireflection coatings, and relatively high-reflecting surfaces.⁵⁴

Moreover, dielectric properties demonstrate the materials’ response when interacting with an electric field, resulting in polarization. The real dielectric part (ε_r) and the imaginary part (ε_i) can be deduced from the k and n values by the following formulas⁵⁵:

ε_{r} = n^{2} - k^{2}

(7)

ε_{i} = 2 n k

(8)

Figure 9 shows both the real and imaginary components of the dielectric constant for pure PS and La(OH)₃-loaded PS films. It is noted that the real dielectric constant values are higher than the imaginary dielectric constant. As the La(OH)₃ NPs concentration is increased, both the real and imaginary dielectric constant gradually increase. The increase in dielectric constant can be attributed to the enhanced density of states in the band gap of La(OH)₃/PS films, resulting in greater polarization.⁵⁶

Figure 9.

(a) The real dielectric (ε_r) versus wavelength (λ) and (b) the imaginary dielectric (ε_i) versus wavelength (λ) for the pristine PS and La(OH)₃-mixed PS films.

Fast electron energy loss within a material and at its surface can be quantified by the volume and surface energy loss functions (VELF and SELF), respectively. In which these two functions can be deduced using values of ε_r and ε_i by the following equations⁵⁷:

V E L F = \frac{ε_{2}}{ε_{1}^{2} + ε_{2}^{2}}

(9)

S E L F = \frac{ε_{2}}{{(ε_{1} + 1)}^{2} + ε_{2}^{2}}

(10)

Figure 10(a) and (b) shows the variation in the VELF and the SELF for the pure PS and filled PS by La(OH)₃ NPs. It can be seen that both VELF and SELF have similar behaviors. Furthermore, VELF and SELF exhibited growth with an increase in the amount of La(OH)₃ NPs within the PS polymer matrix, which may be due to improvements in the electronic structure and polarization processes of the polymer molecules under the applied electromagnetic field.⁵⁸ The enhancement of VELF and SELF renders these PS/La(OH)₃ films suitable for electro-optical uses.

Figure 10.

(a) VELF versus hν and (b) SELF versus hν for the pristine PS and La(OH)₃-mixed PS films.

The Wemple–DiDomenico single-oscillator model was applied to describe the wavelength-dependent behavior of the refractive index within the normal dispersion region⁵⁹:

n^{2} = 1 + \frac{E_{d} E_{o}}{E_{o} - {(h ν)}^{2}}

(11)

E_d. refers to the dispersion energy (average strength of interband optical transitions), and E_o denotes oscillator energy. These two parameters can be estimated from the slope and intercept of the linear part of the curves that appeared in the plot between (n²−1)⁻¹ and (hν)² (Figure 11). The numerical values of E_d. and E_o for the pure and filled films are listed in Table 2. The E_o values are approximately equal to 1.05, 1.37, 1.92, and 1.66 times the direct band gap for the pure PS, PS/La₁, PS/La₂, and PS/La₃ nanocomposite films, respectively. Furthermore, the optical transition strength increases as the E_d. rises, particularly with a higher percentage of La(OH)₃ NPs in the PS matrix. This can be explained by the fact that a charge transfer complex develops between the La(OH)₃NPs and the PS matrix.⁶⁰ In addition, the other two factors, including the static refractive index (n_o) and the oscillation strengths (f) for the pure PS and La(OH)₃-filled PS films, can be estimated using the following relations^61,62:

n_{o} = \sqrt{1 + \frac{E_{d}}{E_{O}}}

(12)

f = E_{d} E_{o}

(13)

Figure 11.

(n²-1)⁻¹ versus (hν)² for the pristine PS and La(OH)₃-mixed PS films.

Table 2.

The optical parameters and χ⁽¹⁾, χ⁽³⁾, and n₂ for the pristine PS and La(OH)₃-mixed PS films.

	n _o	f (eV) ²	E _d (eV)	E _o (eV)	χ ⁽¹⁾	χ ⁽³⁾ esu	n ₂ esu
PS	1.45	17.84	4.45	4.01	0.088	1.03 × 10⁻¹⁴	2.69 × 10⁻¹³
PS/La₁	2.08	83.77	16.72	5.01	0.266	8.46 × 10⁻¹³	1.53 × 10⁻¹¹
PS/La₂	2.51	247.72	36.27	6.83	0.423	5.42 × 10⁻¹²	8.14 × 10⁻¹¹
PS/La₃	3.50	355.49	63.97	5.62	0.906	1.14 × 10⁻¹⁰	1.23 × 10⁻⁹

The assessed values of n_o and f were listed in Table 2. The n_o value ranged between 1.45 and 3.50 for PS/La₃ nanocomposite film, and f started from 17.84 (eV)² to 355.49 (eV)². This increase in no and f values is due to new structural defects created by incorporating La(OH)₃NPs with the PS backbone.⁶³

The nonlinear optical characteristics of materials are fundamental to the operation of many advanced optical devices, including all-optical switching and integrated photonic devices. The first-order linear optical susceptibility can be given for the pure PS and doped PS films with La(OH)₃ NPs as follows⁶⁴:

χ^{(1)} = \frac{E_{d}}{4 π E_{O}}

(14)

where χ⁽¹⁾ demonstrates the response of samples to the light. The χ⁽¹⁾ values were obtained for the pure PS film and La(OH)₃-loaded PS nanocomposite films (See Table 2). This parameter increases gradually with increasing concentrations of La(OH)₃ NPs. This increment confirms the interaction between PS and La(OH)₃ NPs, creating a large number of free electrons that can absorb light. Meanwhile, the third order nonlinear optical susceptibility (χ⁽³⁾) and the nonlinear refractive index (n₂) can be expressed as⁶⁴:

χ^{(3)} = 6.82 \times 10^{- 15} {(\frac{E_{d}}{E_{O}})}^{4} e . s . u .

(15)

n_{2} = \frac{12 π X^{(3)}}{n_{o}}

(16)

where n₀ denotes static refractive index at hν → 0. The increase in both χ⁽³⁾ and n₂ can be observed upon adding La(OH)₃ NPs, which introduces high nonlinearity (Table 2) in the nanocomposite films, making them suitable for designing diverse optoelectronic devices and optical communication systems. In which, χ⁽³⁾ value of 1.03 × 10⁻¹⁴ of the pure film increased to 8.46 × 10⁻¹³, 5.42 × 10⁻¹², and 1.14 × 10⁻¹⁰ esu for PS/La₁, PS/La₂, and PS/La₃ nanocomposite films, respectively. Meanwhile, the n₂ value of 2.69 × 10⁻¹³ for the pure film increased to 1.53 × 10⁻¹¹, 8.14 × 10⁻¹¹, and 1.23 × 10⁻⁹ esu for PS/La₁, PS/La₂, and PS/La₃ nanocomposite films, respectively. This rise in non-linear optical properties is interpreted as the reduction in the distance between energy states, resulting from the energy levels created after the insertion of the nanoparticles, which enhances the dipole matrix element and yields stronger and more pronounced susceptibility magnitudes.⁶⁵

Conclusions

Using the solution casting method, novel and flexible optoelectronic nanocomposite films were produced based on PS and La(OH)₃ NPs. XRD analyses reveal that La(OH)₃ NPs are effectively incorporated into the PS matrix, exhibiting a pure hexagonal phase with a crystallite size of ∼26.32 nm. FTIR spectra indicated the functional groups of pristine PS and PS/La(OH)₃ nanocomposite films. From the linear optical characteristics, the absorbance and absorbance coefficient of the PS increased with the increase in the amount of La(OH)₃ NPs in the nanocomposite films. The optical band gap of the virgin PS film is 3.83 eV, respectively, and decreases to 3.67, 3.55, and 3.39 eV with increasing La(OH)₃ NPs loading from 1 to 3 wt%. Additionally, the Urbach energy value of the pure PS increased with the increase in nanofiller concentration in the nanocomposite films. Furthermore, the VELF and SELF values were enhanced with higher amounts of La(OH)₃ NPs within the PS matrix. For the dispersion parameters, the static refractive index (n_o) was boosted from 1.45 of the pure PS to 3.50 for PS/La₃ nanocomposite film, and the oscillation strengths (f) increased from 17.84 (eV)² to 355.49 (eV)². A significant increase was noted in the nonlinear χ⁽³⁾ value of the pure film from 1.03 × 10⁻¹⁴ to 8.46 × 10⁻¹³, 5.42 × 10⁻¹², and 1.14 × 10⁻¹⁰ esu for PS/La₁, PS/La₂, and PS/La₃ nanocomposite films, respectively. The results provide evidence of improved linear and nonlinear optical properties in PS after the addition of La(OH)₃ NPs; therefore, the nanocomposite films are expected to excel in optoelectronic devices.

Footnotes

Authors contributions

A.M. Elbasiony: Writing – review & editing, Conceptualization, Writing – original draft, Funding, and Formal analysis. Nuha Al-Harbi: Data curation, Conceptualization, Writing – review & editing, Software, Resources, and Investigation. M. M. Abdelhamied: Writing – original draft, Methodology, Investigation, Formal analysis, Conceptualization, and Supervision.

Declaration of conflicting interests

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

Funding

The authors extend their appreciation to the Deanship of Scientific Research at Northern Border University, Arar, KSA for funding this research work through the project number “NBU-FFR-2025-3049-11”.

ORCID iD

M.M. Abdelhamied

Data Availability Statement

Data will be made available on request.*

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Influence of lanthanum hydroxide on the structural and optical characteristics of polystyrene films toward optoelectronic applications

Abstract

Keywords

Introduction

Materials and methods

Results and discussion

Structural analyses

Optical properties

Conclusions

Footnotes

Authors contributions

Declaration of conflicting interests

Funding

ORCID iD

Data Availability Statement

References