Enhanced Optical Properties of PAN-PEG Polymer with TiO2 Nanoparticles for Biological Applications

INTRODUCTION
Current research focus on the science and technology applications throughout technical domains. The field of research involves polymer science and technology in different applications including micro-nanoelectronics. Different areas within nanocomposite science include “bactericidal properties, composite reinforcement, barrier properties, cosmetic applications and electro-optical properties [1-4]. Research in this area has included fuel cell electrodes, nanoparticle drug delivery, biomaterials derived from polymers, catalysts attached to polymers, miniemulsion particles, self-assembling polymer films, blends of polymers, and nanocomposites. Nanocomposites exhibit multiple themes which involve bactericidal properties along with composite reinforcement, flame resistance, barrier properties, aesthetic capabilities and electro-optical properties [1, 2, 5, 6]. A special case of composite material is a material constructed such that the interaction between the different materials reinforce one another to create a new substance with properties that exceed the individual ones of either of the ingredients in a given application. Composites, due to their high hardness, high melting point, low density, and high thermal conductivity, offer promising prospects in various industrial fields [7]. In recent years, polymer-based nanocomposites have introduced as highly adaptable and sophisticated materials. The development of polymer nanocomposites has expanded the range of potential applications for coatings and adhesives. The characteristics of polymer nanocomposite coatings are a result of the change of fillers and the methods employed in their manufacture. The polyacrylonitrile (PAN) is a synthetic resin and a product of the polymerization of acrylonitrile. This material is a well-known category of acrylic resins, however it is a strong and durable thermoplastic shape. It has excellent resistance to solvents and chemicals with moderate combustion speed and little gas permeability. The majority of PAN is manufactured in the form of acrylic and modacrylic fibers, which are widely used as alternatives to wool in the production of apparel and home goods. A semicrystalline organic polymer, PAN, with nitrile’s chemical formula of (C3H3N)n, has nitrile (CN) functional group as the unit structure. Nitrile functional groups are excellent hydrogen bonding acceptors because of the nitrogen atom’s lone pair. Additionally, nitriles may be used to produce very strong attractive connections due to the large dipole moment between the electron-poor carbon atom and the electron-rich nitrogen atom. The high strength and resistance of many organic solvents are induced by the strong intermolecular interaction [8-12]. Optical spectroscopy is often regarded as a highly effective method for elucidating the band structure of materials. Very favorable electron transport and mechanical as well as optical features have made polymer-based nanocomposites interesting for a large number of applications in medical and engineering technology [13]. Optical spectroscopy in the modified state may also be used to investigate electronic band structure of the crystal. In order to study functional materials, it is important to possess a comprehensive understanding of the band gap associated with the material. PAN is considered to be a polymer with exceptional versatility, mostly attributed to its elevated carbon content [14-17]. It is highly biostable because of its carbon-carbon backbone and it is resistant to degradation. The polymerization of acrylonitrile monomer ultimately results in the formation of PAN in either granulated or powdered form. This powder, in its natural state, has very few applications in the manufacturing business. Therefore, in order to form polymer, it needs to be treated with a large number of co-monomers in a different form [18].

MATERIAL AND METHODS 
The casting procedure was used to fabricate the polymer blend that consisted of PAN (90% weight) and polyethylene glycol (PEG ,5% weight). Suppressors of nano-composition were made with different weight percentages of titanium oxide (TiO2) nanoparticles (0, 2, 4, 6 and 8). Measurements of absorbance and transmittance spectra of resulting PAN-PEG-TiO2 nanocomposites within a wavelength span of 220-800 nm were studied by the UV/1800/ Shimadzu spectrophotometer. The Eq. 1 [19] can be used to calculate the absorption coefficient (α) of PAN-PEG-TiO2 nanocomposites: 

where, d is the sample thickness. A is the absorbance of the nanocomposites. Eq. 2 [20] establish the electrical transitions model of amorphous semiconductors. 

For an indirect transition, n is 2, and for an indirect transition, n is 3. Here, C is the constant, hυ is the photon energy, and Eg is the optical energy band gap. The Eq. 3 [20] was employed to determine the extinction coefficient (k) of the PAN-PEG-TiO2 nanocomposites: 

When k→0, the Eq. 4 [21] describes the refractive index (n) of the PAN-PEG-TiO2 nanocomposites: 

where, R is the reflectance. The actual (1) and imaginary (2) components of the dielectric constant of the PAN-PEG-TiO2 nanocomposites were ascertained using Eq. 5 and 6 [22]:  

RESULTS AND DISCUSSION
XRD analysis was carried out for better understanding the crystalinity of materials. The XRD pattern of TiO2 (Fig. 1a) clearly demonstrates the presence of pure anatase phase TiO2 nanoparticles with excellent crystalline quality. The dominant peak at 2θ ≈ 25° corresponds to the (101) crystallographic plane of anatase, which is the most characteristic peak for this phase. Additional well-defined peaks at 37-38°, 48°, 54-55°, 62°, 69°, and 75° correspond to the phase purity with no detectable rutile contamination. The intense peaks with low background noise indicate high crystallinity and minimal amorphous content, which are crucial for enhanced optical properties in biological applications. The the pure anatase phase is particularly advantageous for PAN-PEG composite system due to its superior photocatalytic activity, better biocompatibility, and enhanced UV absorption properties as compared to other TiO2 phases, making it ideal for biological sensing and antimicrobial applications. The XRD pattern of resulting PAN-PEG/TiO2 nanocomposite system (Fig. 1b) after the incorporation of TiO2 nanoparticles into the polymer matrix show a dramatic transformation in the diffraction pattern as compared to pure polymer systems. The prominent sharp peak at 2θ ≈ 25° corresponds to the (101) crystallographic plane of anatase TiO2, confirming the successful integration of crystalline TiO2 nanoparticles within the PAN-PEG polymer matrix while maintaining their anatase phase structure. This pattern is characterized by a significantly elevated and broad background signal, which is attributed to the amorphous and semi-crystalline regions of the PAN-PEG polymer blend [23]. The presence of broad peaks in the 15-35° and 40-60° regions, indicates the semi-crystalline nature of polymer matrix and possible polymer-nanoparticle interactions that affect the local molecular ordering. The high signal-to-noise ratio and the retention of the anatase peak intensity demonstrate excellent dispersion of TiO2 nanoparticles throughout the polymer matrix without significant agglomeration, while the interaction between the inorganic nanofillers and the organic polymer chains creates a hybrid material structure that combines the crystalline properties of TiO2 with the flexible characteristics of the PAN-PEG blend, resulting in enhanced optical properties suitable for biological applications [24-28]. 
This FESEM images in Fig. 2(a, b) demonstrates the successful incorporation and uniform dispersion of TiO2 nanoparticles within the PAN-PEG polymer matrix [29-31]. The image clearly shows well-dispersed spherical TiO2 nanoparticles with measured sizes of D1 = 42.81 nm, D2 = 24.78 nm, and D3 = 41.67 nm indicats a relatively narrow size distribution with an average particle size of approximately 35-40 nm. The nanoparticles appear as well-defined spherical components, which are uniformly distributed across the polymer surface without significant agglomeration or clustering. The polymer matrix background shows a textured shape that differs significantly from the smooth morphology of pure PAN-PEG, suggesting strong interfacial interactions between the nanoparticles and polymer chains. This morphological structure is particularly advantageous for biological applications as it provides numerous surface-exposed TiO2 nanoparticles that can interact with high flexibility of the polymer matrix, ultimately contributing to the enhanced optical properties through increased light scattering, photocatalytic activity, and UV absorption capabilities in direction of biological sensing and antimicrobial applications [27, 28, 32-35]. 
The absorbance of the PAN-PEG mixture with wavelength range of 220-800 nm is affected by the addition of TiO2 nanoparticles, as displayed in Fig. 3.
When the proportion of TiO2 nanoparticles is increased, Fig. 4 shows how the absorption coefficient of the PAN-PEG mixture changes with respect to photon energy. According to the data, the free electrons in the TiO2 nanoparticles absorb more of the incident radiation, leading to a higher absorption coefficient for the PAN-PEG blend. 
An indirect energy gap exists in the nanocomposites when the absorption coefficient of the PAN-PEG-TiO2 nanocomposites is below 104 cm-1. When the concentration of TiO2 nanoparticles increases, the energy band gap between the indirect permitted and prohibited transitions decreases [19], as shown in Fig. 5. The high conductivity and narrow band gap are a result of electrons graphically transitioning from the valance band to the conduction band on these local levels. 
The extinction coefficient of the PAN-PEG mixture changes with concentration of TiO2 nanoparticles, as shown in Fig. 6. As the concentration of TiO2 nanoparticles enhances, the extinction coefficient of the blends increases [20].  
Fig. 7 displays the relationship between the incident photon energy and the refractive index of a PAN-PEG blend containing diverse concentrations of TiO2 nanoparticles. Since TiO2 nanoparticles produce a greater packing density, the refractive index of resulting PAN-PEG-TiO2 nanocomposites rises as the TiO2 content increases [20]. 
The wavelength dependence of the real and imaginary components for the dielectric constant of PAN-PEG-TiO2 nanocomposites with different concentrations of TiO2 nanoparticles are depicted in Figs. 8 and 9, respectively. It can be deduced that as the fraction of TiO2 nanoparticles in PAN-PEG-TiO2 nanocomposites increases, the material’s refractive index (n) and extinction coefficient (k) rises [21]. 
The calculation of gamma radiation in PAN-PEG-TiO2 nanocomposites is as follows:

where, N0 is the number of radiation particles recorded at a specific period, N is the number counted at the same time, with a sample thickness of (d), and μ is attenuation coefficient of gamma radiation for PAN-PEG-TiO2 nanocomposites [22]. In order to estimate linear attenuation coefficients, the transmitted gamma ray fluxes of PAN-PEG-TiO2 nanocomposites were measured using the Geiger counter. Figs. 10 and 11 show N/N0 variation of PAN-PEG-TiO2 nanocomposites. The rise of the attenuation radiation reduces transmission radiation as weight percentages of TiO2 nanoparticles increases [36-38]. 

CONCLUSION
The present investigation showed that the absorbance of the PAN-PEG composite rises with the concentration of TiO2 nanoparticles. XRD and FESEM analyses demonstrated the successful synthesis of highly crystalline anatase TiO2 nanoparticles and their excellent dispersion within the PAN-PEG matrix. Results showed that as the concentration of TiO2 nanoparticles rises, PAN-PEG composite’s real and imaginary dielectric constants, extinction coefficient, and absorption coefficient enhances. The energy band gap of the PAN-PEG composite is enhanced by increasing the proportion of TiO2 nanoparticles. Finally, the Lambda capacity of PAN-PEG-TiO2 nanocomposites has also been explored. The PAN-PEG-TiO2 nanocomposites showed improved optical and shielding properties that make them effective for use in applications that involve gamma ray shielding.

CONFLICT OF INTEREST
The authors declare that there is no conflict of interests regarding the publication of this manuscript.