NiO@PAN-SA nanocomposites: a multifunctional material excelling in dye degradation and antimicrobial applications

1 Introduction

Antibiotics are formulated to inhibit bacterial infections, contingent upon the four processes or actions performed by the bacterium. Nonetheless, there are certain limits, including challenges in penetrating bacterial cells and the excretion of these antibiotics from the system. To address these constraints, a novel method has emerged; new anti-bacteria including nanoparticles have been designed based on the established mechanisms of existing antibacterial, and these nanoparticle-loaded antibacterial have demonstrated considerable antibacterial efficacy (Kapoor G et al., 2017).

In recent years, metal oxide nanoparticles have attracted considerable interest across multiple domains due to their distinctive physical and chemical properties, including reactivity, elevated surface area, and optical attributes. These nanoparticles, generally made of materials such as titanium dioxide, copper oxide, zinc oxide, and nickel oxide, are employed in various applications including catalysis, electronics, environmental remediation, drug delivery, and medicinal and pharmaceutical uses (Al-Fakeh and Al-Otaibi, 2022; Ohodnicki et al., 2013; Vangijzegem et al., 2019; Al-Fakeh et al., 2023; Sunarso et al., 2017; Berensmeier, 2006; Al-Fakeh et al., 2024). Their dimensions, typically between 1 and 100 nm, enable superior performance relative to bulk materials, positioning them as a central subject of inquiry and advancement in nanotechnology (Ahangari et al., 2013; Wolf et al., 2001). Nickel oxide nanoparticles are the most commonly employed photocatalysts for the degradation of diverse chemical compounds, bacteria, and viruses, in addition to water purification (Akbari et al., 2020). The efficacy of photocatalysts is significantly influenced by nanotechnology, particularly as the dimensions of NiO nanoparticles diminish (Khalili et al., 2021). Nickel oxide nanoparticles have gained significance in water treatment and the elimination of organic substances (Liu et al., 2017; Al-Kadhi et al., 2023). This is attributable to the higher stability, transparency, availability, and nontoxicity of these materials, alongside their robust photocatalytic activity, which recent studies have demonstrated to surpass that of other photocatalysts (Vyas et al., 2021; Goel et al., 2020; Tsai et al., 2020; Wilson et al., 2017; Singla et al., 2019; Oguz et al., 2018).

Polymer-based particle systems have discovered a wide range of applications in a variety of scientific fields as well as in everyday life (Gatadi et al., 2021). On the other hand, polymeric nanoparticles hold great potential for the development of substances for magnetic resonance tomography, effective media for the magnetic-controlled transfer of pharmaceuticals, agents for the treatment of malignant tumors, and systems for the targeted administration of contrasting and therapeutic agents (Vera et al., 2016). In recent years, polymer nanocomposites have garnered a lot of attention, notably because they possess improved physicochemical, engineering, and drug-conjugating properties. Such nanocomposites have found their vast uses in a variety of disciplines, ranging from the packaging of food (Koilparambil et al., 2016) and the environment (Huang et al., 2016; Talib et al., 2021), including the treatment of water and wastewater (McNeill, 1989), to the field of medicine (Chinthamreddy et al., 2024; Galiatsatou et al., 2002).

Polyacrylonitrile (PAN) is a prevalent synthetic polymer recognized for its superior chemical resistance, thermal stability, and exceptional mechanical strength. It is frequently employed in membrane filtration, adsorption, and the creation of nanocomposites because to its capacity to create porous structures. The incorporation of nitrile (-C≡N) functional groups in PAN facilitates robust interactions with metal oxide nanoparticles, resulting in improved composite stability and performance (Mallakpour and Behranvand, 2016). PAN also offers structural reinforcement to NiO nanoparticles, inhibiting agglomeration and guaranteeing uniform dispersion within the matrix. Sodium Alginate (SA) is a naturally occurring polysaccharide sourced from brown algae, recognized for its biodegradability, hydrophilicity, and biocompatibility. It comprises carboxyl (-COO^-) and hydroxyl (-OH) groups, which promote robust interactions with metal ions and nanoparticles. The integration of SA into the NiO-PAN composite augments its hydrophilicity, flexibility, and metal ion chelation capacity, thus enhancing its adsorption efficacy and biological activity. SA is extensively utilized in biological applications, including wound healing, medication delivery, and tissue engineering. The problem of dye pollution in aquatic habitats has emerged as a considerable environmental issue, alongside its significance in biomedical and antibacterial applications (Ambalgi et al., 2016). Dyes like Rhodamine B (RhB) and Malachite green dye are extensively utilized in the textile, paper, and leather sectors, resulting in the release of hazardous contaminants into aquatic environments (Al-Fakeh and Alsaedi, 2021; Al-Fakeh, 2020; Hendrawan et al., 2019). These colors are non-biodegradable and chemically stable, rendering their extraction from water sources very difficult. Their tenacious presence not only disturbs aquatic ecosystems but also presents significant health hazards to humans and animals, including carcinogenic and mutagenic consequences (Motelica et al., 2021; Salama et al., 2018; Patterson, 1955; N Sujith Benarzee and Kumar, 2023). Catalytic performance of silver (AgNPs), gold (AuNPs), and palladium nanoparticles (PdNPs) synthesized using dextran was evaluated. The nanoparticles exhibited spherical shapes with sizes of 3.4 nm, 8.3 nm, and 17.1 nm. Spectral data indicated the successful synthesis via reduction of dextran’s alcoholic groups. PdNPs showed the highest catalytic activity in reducing aromatic pollutants, with half-lives ranging from 0.34 to 0.49. This study emphasizes a simple, cost-effective green synthesis methodology, offering a reliable comparison of catalytic capabilities and potential for broader applications of nanomaterials (Emam et al., 2019).

The catalytic hydrolysis of prothiofos, an organophosphorus pesticide, using recyclable metal composites like Ag@chitin, Au@chitin, Pd@chitin, and Pd@Au@Ag@chitin. Among these, the Pd@Au@Ag@chitin composite significantly accelerates hydrolysis, achieving 99% in 150 minutes–4.1 times faster than non-catalytic methods. Despite a 22% efficiency reduction after five applications, the catalyst retains effectiveness, indicating the potential of these bio-composites for pesticide degradation and environmental strategies (Emam et al., 2021). The recyclable nano-catalyst made from chitin to encase palladium nanoparticles (Pd NPs), yielding Pd NPs@chitin. Spectral analyses confirmed the successful immobilization within the chitin matrix, enhanced under alkaline conditions. The nano-catalyst exhibited rapid catalytic activity, fully degrading acidic dye 193 within 5 min and retaining high efficiency after five reuse cycles. This method offers significant advantages over traditional catalysts, including excellent recyclability and cost-effective preparation for environmental remediation applications (Ahmed et al., 2021). Pathogenic microorganisms and dyes contribute to water pollution, impacting aquatic life and human health. A multifunctional material using AgI and Ag NPs on bamboo fabrics was developed, demonstrating significant antibacterial (88% against Staphylococcus aureus, 90% against Escherichia coli) and antifungal (82% against C. albicans) activity. The material showed 90% reduction and 93% photodegradation of methylene blue (MB) under UV light, confirming its effectiveness in degrading pollutants (Rehan et al., 2025; Ahmed and Emam, 2020).

Progress in the field of nanocomposite research has undeniably been made, leading to significant advancements in various applications. However, despite these strides, there remains a notable gap in the existing literature regarding the comprehensive documentation of certain specific material incorporations. Specifically, very few studies have meticulously documented the successful integration of nickel oxide (NiO) nanoparticles into a sophisticated dual-polymer matrix. This particular matrix is composed of both polyacrylonitrile (PAN) and sodium alginate (SA), chosen for their distinct and complementary properties. The primary aim of such an incorporation is to achieve a synergistic effect, particularly focusing on concurrent antibacterial activity and efficient dye-degradation capabilities. This dual functionality is of paramount importance given the increasing environmental concerns and the need for advanced materials to address them. A significant observation within the current research landscape is that the majority of previous investigations have tended to focus exclusively on either dye removal processes or the assessment of antibacterial capabilities in isolation. Researchers have often compartmentalized these two critical aspects, dedicating their efforts to optimizing one function without adequately exploring its interplay with the other. Consequently, there is a clear paucity of studies that delve into the intricate details of the synergistic effect that can be achieved through the strategic combination of this hybrid matrix, consisting of PAN and SA, loaded with NiO nanoparticles, and its profound impact on both antibacterial efficacy and dye degradation efficiency. The potential for a hybrid system to offer enhanced performance in both areas simultaneously remains largely unexplored, representing a substantial opportunity for future research and development in the field of advanced functional materials. This study presents a multifunctional NiO@PAN-SA nanocomposite, produced by altering NiO loading (10%–50%) while preserving a 1:1 PAN–SA polymer ratio. The innovation consists of (i) a hybrid organic–inorganic matrix that enhances nanoparticle dispersion and reactivity, (ii) dual functionality that facilitates both microbial suppression and catalytic dye degradation, and (iii) a systematic assessment of NiO content for performance improvement. This study is among the first to investigate concentration-dependent multifunctionality in this particular hybrid nanocomposite system.

2 Experimental

2.1 Chemicals and reagents

All reagents and solvents were of analytical quality and were not subjected to additional purification prior to use. Nickel Nitrate (99% purity), polyacrylonitrile (99% purity), and sodium alginate polymers were acquired from SD Fine Chemicals. Malachite Green (98% purity) and Rhodamine B (95% purity) were procured from Merck India. Sodium hydroxide pellets and ethanol (99% purity) were acquired from BLD Pharma. We acquired nutritious broth, agar-agar, Rhodamine B, and Alizarin Red S from SD Fine Chemicals.

2.2 Synthesis of nickel oxide NPs

Nickel oxide nanoparticles were synthesized using the sol-gel method. Initially, 2 g of nickel nitrate were dissolved in 15 mL of distilled water, whereas 8 g of sodium hydroxide were dissolved in 10 mL of distilled water. The solutions were stirred for approximately 5 minutes each. A sodium hydroxide solution was introduced to the nickel nitrate solution following thorough mixing, with ongoing agitation via a magnetic stirrer for approximately 5 minutes. A burette was filled with 100 mL of ethanol and titrated dropwise into a solution of sodium hydroxide and nickel nitrate. Following the reaction, a light green precipitate was generated, which was subsequently washed thrice with deionized water and ethanol, and then dried at 120 °C in a hot air oven. The anhydrous material was then calcined at 900 °C for 2 hours in a muffle furnace (Mallakpour and Behranvand, 2016).

2.3 Synthesis of NiO @PAN-SA polymer nanocomposites

NiO@PAN-SA polymer nanocomposites were synthesized via an in-situ polymerization technique. Initially, 0.7 mmol of NiO nanoparticles were dispersed in 50 mL of deionized water using ultra sonication for 30 min. Subsequently, an equimolar mixture of PAN and SA was dissolved in the NiO solution under continuous magnetic stirring. The solution was heated to 40 °C and then allowed to cool slowly to room temperature. A series of nanocomposite samples with varying concentrations of NiO nanoparticles (10%, 20%, 30%, 40%, and 50%) were produced, maintaining an equimolar ratio of PAN and SA. The resulting mixture was subjected to centrifugation twice, rinsed with alcohol and deionized water, and then dried overnight in an oven at 60 °C (Ambalgi et al., 2016).

2.4 Biological studies of NiO @PAN-SA polymer nanocomposites

2.4.1 Anti-bacterial activity

2.4.1.1 Bacterial strains

The antibacterial efficiency of the produced NiO-PAN-SA nanocomposites was evaluated against two bacterial strains: Gram-positive: S. aureus (ATCC 25923) and Gram-negative: E. coli (ATCC 25922), Both strains were obtained from the American Type Culture Collection (ATCC) and employed as model microorganisms for antibacterial assessment.

2.4.1.2 Preparation of culture media and inoculum

a) Nutrient agar preparationAvailable for purchase Nutrient Agar (NA) was utilized to manufacture the culture medium. 28.0 g of sodium chloride was dissolved in 1,000 mL of purified water and properly blended. The sterilized media was subjected to autoclaving at 121 °C for 15 min and thereafter utilized for agar plate formation in antibacterial experiments.

b) Preparation of Nutrient Broth

Nutrient Broth (NB) was employed for the preparation of bacterial inoculum. 1.3 g of NB powder was dissolved in 100 mL of distilled water, properly mixed, and sterilized via autoclaving at 121 °C for 15 min. The sterilized broth functioned as the medium for bacterial proliferation and inoculum standardization).

c) Preparation of bacterial stock culture

Stock cultures of bacterial strains for experimental purposes were produced on nutrient agar slants under aseptic conditions. Two sets of inclinations were preserved:One set was preserved at 4 °C for long-term storage as a stock culture. The second set was identified as the operational framework for antibacterial testing. A glycerol stock was created and stored at −20 °C for long-term preservation.

d) Standardization of inoculum

Bacterial suspensions were generated by inoculating S. aureus and E. coli into sterile nutritive broth and incubating at 37 °C for 24 h. The bacterial density was calibrated to approximately 10⁵ CFU/mL to ensure consistency in antibacterial testing.

2.4.2 Antifungal efficacy

2.4.2.1 Fungal strains

The antifungal efficacy of the produced NiO-PAN-SA nanocomposites was assessed against Aspergillus niger (MTCC 183), a therapeutically relevant fungus strain. The strain was obtained from the Microbial Type Culture Collection (MTCC) at the Institute of Microbial Technology (IMTECH) in Chandigarh and utilized for antifungal testing.

2.4.2.2 Preparation of Sabouraud Dextrose Agar (SDA)

Available for purchase Sabouraud Dextrose Agar (SDA) served as the culture medium. 32.5 g of SDA powder was dissolved in 500 mL of purified water and blended thoroughly. The produced medium was sterilized via autoclaving at 121 °C for 15 min and subsequently utilized for agar plate preparation in antifungal activity studies.

2.5 Dye adsorption degradation study

The photocatalytic characteristics of the synthesized NiO@PAN-SA polymer nanocomposites were assessed utilizing Rhodamine B dye and Malachite green. The degradation of Rhodamine B dye was analyzed with the catalyst (NiO@PAN-SA) under solar irradiation. Rhodamine B dye is an organic dye commonly employed in the textile industry for coloring purposes. It exhibits a distinctive absorbance band in the visible spectrum at 553 nm, as observed in UV-visible spectroscopy, while Alizarin Red S shows an absorbance band in the visible spectrum at 365 nm in UV-visible spectroscopy. In this study, 20 mg of synthesized nanoparticles were dispersed in 20 mL of double-distilled water and sonicated for 5 min. The resulting sample solution was then added to 20 mL of Rhodamine B solution (2 × 10-5 M) and 20 mL of Alizarin Red S in a separate conical flask. The mixed solutions were stirred for a few minutes and sonicated for half an hour in a darkroom. An adsorption-desorption equilibrium was established between the nanoparticles and the dyes without solar irradiation. The mixed reaction solution was then exposed to solar light. The experiment took place on a sunny day from 10 a.m. to 5 p.m., with an atmospheric temperature of 31 °C–38 °C. The mixed reaction solution was kept under solar irradiation with constant stirring. A 2 mL aliquot of the reaction mixture was taken at designated time intervals and filtered to remove the solid phase. The resulting filtrate was analyzed by recording the absorbance at 553 nm and 365 nm using a UV-Visible spectrophotometer. The absorbance of the Rhodamine B dye decreased at 553 nm (λ max) as the reaction time increased. Likewise, the absorbance of the Alizarin Red S dye decreased at 365 nm (λ max) with increasing reaction time. The findings demonstrated that Rhodamine B and Alizarin Red S were decolorized and degraded into new intermediate products. The percentage of degradation dyes was calculated using the following equation,

% of Degradation = 100 * A o ‐ A t / A o

Here, Ao = Initial absorption of dye.

A_t = Absorbance of dye at the time, t.

2.6 Photocatalytic degradation kinetic study of dyes

The kinetic study of photocatalytic degradation of dyes was evaluated by using synthesized NiO@PAN-SA (1.0) under solar light irradiation. The Langmuir–Hinshelwood kinetic model can explain the photocatalytic degradation of organic dyes using heterogeneous photocatalyst. The following equation can apply for the photocatalytic reaction of dyes,

Rate r = dC / dt = k KC / 1 + KC

However, for the low concentration of dyes, KC<<1 and then followed by integrating concerning time t, the resultant equation is ln (C_o/C_t) = k Kt = k_app t. It is a pseudo-first-order kinetic model equation.

Then the equation is modified as ln (A_o/A_t) = K_app t.

Here, dC/dt = rate of dye degradation (mg/L.min^-1),

K = the reaction rate constant min ‐ 1 ,

K = the absorption coefficient of the dye on to the photocatalyst ,

Kapp ⁡ min ⁡ ‐ 1 is the apparent rate constant .

2.7 Characterization and techniques

A wide variety of analytical methods were employed to characterize the substance. An Agilent ATR benchtop spectrometer 4,500–400 cm^-1 using a KBr spectrometer was used to obtain the FT-IR spectra, which were recorded in the 400–4,000 cm^-1 range. The Rigaku Ultima IV powder diffractometer, operated at 40 kV with a CuKα radiation source, was used to analyse structural phase parameters using X-ray diffraction (XRD) in the 2θ range of 10°–80°. A scanning electron microscope (ZEIS Evo SEM, Oxford instruments) was used to analyse the morphology and particle size. Particle size assessment through Transmission Electron Microscopy (JOEL. JEM 2100).

2.8 Statistical evolution

The % of degradation of dye, Apparent rate constant, correlation coefficient standard deviation, and relative standard deviation was calculated using Microsoft excel and XL Stat. The study also involved a comprehensive analysis of various kinetic models to accurately describe the degradation process. The goodness of fit for each model was evaluated using statistical parameters such as the correlation coefficient (R ²), which indicated how well the model explained the observed data. The apparent rate constant (k_app) was determined for each degradation condition, providing insight into the speed of the reaction. Furthermore, the standard deviation and relative standard deviation were meticulously calculated for all measured parameters, ensuring the reliability and precision of the experimental results. These statistical analyses, performed using Microsoft Excel and XLStat, were crucial in validating the experimental methodology and in drawing robust conclusions about the efficiency and kinetics of the dye degradation process under different conditions.

3 Results and Discussion

3.1 FTIR analysis

In Figure 1 displays FTIR spectra of multiple distinctive peaks associated with the polymer matrix (Polyacrylonitrile and Sodium Alginate) and the incorporated NiO nanoparticles. The extensive absorption band detected between 3,500 and 3,300 cm^-1 is ascribed to the O-H stretching vibrations of the hydroxyl (-OH) groups in Sodium Alginate (SA) (Salama et al., 2018) (Patterson, 1955). This signifies the existence of hydrophilic capabilities in the composite, potentially facilitating improved dispersion of NiO nanoparticles. A prominent peak at approximately 2,240 cm^-1 indicates the C≡N stretching vibration of Polyacrylonitrile (PAN), so affirming the structural integrity of the polymer backbone. A notable peak of about 1,600 cm^-1 is attributed to the C=O stretching of carboxyl (-COO^-) groups from Sodium Alginate, a defining trait of the polysaccharide. The peaks within the range of 1,000–1,100 cm^-1 correspond to C-O-C stretching vibrations, signifying the existence of glycosidic connections in the alginate (N Sujith Benarzee and Kumar, 2023). This verifies that Sodium Alginate retains its structural integrity within the composite. The primary evidence for the integration of NiO nanoparticles is derived from the vibrational bands in the 500–600 cm^-1 range, which are associated with Ni-O stretching vibrations. The strength of these bands increases with the increase in NiO concentration from 10% to 50%, indicating a heightened level of NiO integration and interaction within the PAN-SA matrix (Emam et al., 2019) (Emam et al., 2021). Additionally, minor broadening and slight shifts were noted in the OH (3,500–3,300 cm^-1) and C=O (∼1,600 cm^-1) bands with increasing NiO content. These subtle spectral variations suggest possible hydrogen bonding or electrostatic interactions between NiO NP’s and the PAN-SA polymer matrix. Although no new peaks indicating covalent bond formation were detected, the observed changes support physical interactions that may enhance NP’s dispersion and composite stability.

3.2 PXRD analysis

Figure 2 illustrates that Powder X-ray diffraction (PXRD) is a crucial instrument for examining the crystalline characteristics of the NiO-PAN-SA nanocomposites. The diffractograms display distinct peaks, predominantly associated with the crystalline NiO phase. The prominent diffraction peaks at 2θ = 37°, 43°, 63°, and 75° correspond to the (111), (200), (220), and (311) planes of the cubic phase of NiO, as indicated in JCPDS Card No. 47–1,049 (Patterson, 1955). The peaks indicate that NiO retains its crystalline structure following its integration into the polymer matrix. At reduced NiO concentrations (10% and 20%), the PXRD patterns exhibit broad peaks, indicating the existence of an amorphous phase, presumably attributable to the polymeric characteristics of PAN and SA. With the increase in NiO concentration (30%, 40%, and 50%), the strength of the diffraction peaks intensifies, signifying enhanced crystallinity. This indicates that increased NiO loading promotes the development of well-defined NiO nanocrystals inside the composite structure. The lack of additional peaks in the PXRD pattern indicates that no substantial secondary phases or contaminants were introduced during the synthesis process.

3.3 FESEM analysis

The high-resolution SEM pictures (Figures 3a-e) illustrate the morphological progression of NiO-PAN-SA nanocomposites as the concentration of NiO nanoparticles increases from 10% to 50%. At the smallest concentration (10%), the composite displays a smooth, stratified shape, signifying the dominant presence of the polymeric matrix (PAN and SA) with negligible NiO deposition. With a rise in NiO content to 20% and 30%, the surface exhibits increased roughness, characterized by significant porosity and flaky structures, indicating progressive integration of NiO. At 40% loading, the composite exhibits a highly nanostructured, rough surface with distributed NiO nanoparticles, resulting in needle-like or fibrous formations that augment surface area and possible functional activity. At the maximum concentration (50%), the morphology transitions to a compact, agglomerated form including discrete spherical NiO nanoparticles, suggesting potential particle clustering. This agglomeration may reduce the effective surface area and hinder the uniform dispersion of active sites. While functional activity still increased, such clustering at high NiO loadings may adversely affect long-term performance. This observation highlights the potential presence of a critical loading threshold beyond which excessive agglomeration could diminish composite functionality. The transition from a smooth polymeriec structure to a porous, NiO-enhanced composite remains a key factor influencing the material’s antibacterial and dye adsorption behaviour.

3.4 TEM analysis

Figures 4a-e illustrates TEM images of NiO@PAN-SA nanocomposites. The TEM image (a) indicated that the synthesized NiO nanoparticles exhibit a spherical morphology with an average particle size of 50 nm. The TEM image (b) of PAN/NiO demonstrated the existence of spherical NiO nanoparticles within the SA matrix, which appear wire like or tubular in shape (c, d, and e), suggesting the coating of PAN and SA on the NiO. The polymerization and growth of SA enveloped the NiO nanoparticles, leading to an increase in particle size within the nanocomposites.

3.5 Antibacterial activity

The antibacterial efficacy of NiO@PAN-SA nanocomposites was assessed against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) via the agar well diffusion technique. The inhibitory zones, assessed at different concentrations (25, 50, 75, and 100 µg), are illustrated in Figure 5 and Table 1. The standard antibiotic demonstrated modest antibacterial efficacy, with inhibition zones measuring 9 mm–13 mm for S. aureus and 9 mm–14 mm for E. coli, providing a benchmark for comparison.

TABLE 1. Depicts the antibacterial activity results of Ni@PAN-SA composites.

At lower concentrations (25 and 50 µg), the majority of NiO@PAN-SA samples shown minimal or no antibacterial action against S. aureus, with the exception of NiO@PAN-SA (0.2) and NiO@PAN-SA (0.8), which displayed slight inhibition (9 mm). As the concentration rose to 75 and 100 μg, the inhibition zones markedly enhanced, with NiO@PAN-SA (1.0) exhibiting the greatest antibacterial efficacy (13 mm and 14 mm, respectively). Escherichia coli exhibited moderate susceptibility to the composites, with NiO@PAN-SA (0.4), (0.8), and (1.0) showing consistent suppression between 10 mm and 13 mm at elevated doses.

The data shown in Figure 4 and Table 1 indicates that the antibacterial activity of NiO@PAN-SA is contingent upon concentration, with increased Ni levels correlating with enhanced bacterial growth inhibition. Figure 6 shown Antimicrobial activity with zone of Inhibition of various microorganisms on Standard Gram and NiO@PAN-SA Ncs. The disparity in activity between S. aureus and E. coli suggests a potential difference in bacterial membrane contacts. Gram-positive bacteria are generally more susceptible due to their thicker peptidoglycan layer, which may enhance interactions with Ni-based nanocomposites. The results underscore the efficacy of NiO@PAN-SA nanocomposites as powerful antibacterial agents for biological applications and water purification systems (Rehan et al., 2025). Future studies will include MIC and MBC (Minimum Bactericidal Concentration) evaluations to allow direct comparison with existing nanocomposite systems in the literature.

NiO@PAN-SA Ncs exhibit potent, dose-dependent antibacterial activity against both Gram-positive S. aureus and Gram-negative E. coli. Increasing nanoparticle concentration consistently reduces bacterial growth. NiO@PAN-SA Ncs effectively combat both Gram-positive and Gram-negative bacteria, as evidenced in Table 2 and Figure 7. Post-incubation, clear zones around disks or wells confirm bacterial growth inhibition. Measure these zones with a ruler or calipers; larger zones signify greater activity. Replicate tests for accuracy, incorporating control samples.

TABLE 2. Results of Zone of inhibition of bacteria by NiO@PAN-SA Ncs and Amoxicillin.

3.6 Antifungal activity

The antifungal efficacy of Ni@PAN-SA nanocomposites was assessed against Aspergillus niger utilizing the well diffusion method, with findings illustrated in Figure 5 and Table 3. The conventional antifungal drug demonstrated considerable inhibition, with inhibition zones varying from 11 mm at 25 μg to 20 mm at 100 µg. The Ni@PAN-SA nanocomposites exhibited concentration-dependent antifungal efficacy, demonstrating significant inhibition at elevated doses ( Figure 8 ). At lower concentrations (25 and 50 µg), the majority of Ni@PAN-SA samples shown no antifungal activity, except Ni@PAN-SA (1.0), which displayed an inhibitory zone of 9 mm at 25 μg and 11 mm at 50 µg. With the concentration rising to 75 and 100 μg, the inhibitory zones grew more pronounced in all samples. Significantly, Ni@PAN-SA (1.0) exhibited the most pronounced antifungal activity, with inhibition zones measuring 13 mm and 15 mm at 75 and 100 μg, respectively. Ni@PAN-SA (0.8) demonstrated notable inhibition, with zones of 12 mm and 14 mm at concentrations of 75 and 100 μg, respectively. The observed trend indicates that increased Ni content improves antifungal efficacy, likely due to the interaction between Ni nanoparticles and fungal cell membranes, resulting in membrane rupture and inhibition of fungal proliferation ( Figure 9). Although Ni@PAN-SA nanocomposites demonstrated limited antifungal efficacy relative to the standard, their potential as antifungal agents is apparent, especially at elevated doses.

TABLE 3. Depicts the Antifungal activity of Ni@PAN-SA composites.

3.7 Dye adsorption study

The adsorption ability of different concentrated Ni@CTAB-SA composites for removing dyes like Rhodamine B, and Malachite green dye finds extensive application in textiles, food coloring, printing, and biological staining and these were removed by using UV-Vis adsorption studies (Chinthamreddy et al., 2024).

3.7.1 Rhodamine B dye adsorption

The degradation of Rhodamine B (1 ppm) was investigated over 5 hours utilizing Ni@PAN-SA nanocomposites at different concentrations (1.0, 0.8, 0.6, 0.4, and 0.2) observed in Figure 10. The absorbance spectra obtained at various time intervals (1HR, 2HR, 3HR, 4HR, and 5HR) demonstrate a significant reduction in peak intensity near 550 nm, indicative of Rhodamine B. The regular decline in absorbance over time indicates the gradual breakdown of the dye molecules. The degree of degradation is contingent upon the concentration of Ni@PAN-SA, with elevated concentrations (Ni@PAN-SA 1.0) exhibiting enhanced dye removal efficacy relative to diminished values (Ni@PAN-SA 0.2). During the early phase (1HR), the decrease in absorbance is very slight, indicating the commencement of the catalytic activity. Over time, a notable decrease in absorbance is evident at 2HR and 3HR, signifying the degradation of Rhodamine B resulting from interactions with the catalyst. At the 5-h point, the absorbance value is markedly reduced, indicating that a considerable portion of Rhodamine B has degraded. The effective degradation noted at elevated Ni@PAN-SA concentrations is due to a greater number of active sites for catalytic activity, resulting in improved adsorption and decomposition of dye molecules. This trend highlights the function of NiO-PAN-SA in enhancing degradation kinetics, rendering it a suitable material for wastewater treatment applications focused on Rhodamine B elimination. The current study did not investigate the reusability and regeneration of the NiO@PAN-SA nanocomposites. However, given the positive results seen in dye breakdown and antibacterial effectiveness, future research will focus on testing how well the material can be reused and how it performs over many cycles of use.

3.7.2 Percentage of degradation of RB dye using NiO@PAN-SA (1.0)

The percentage of degradation ofthe RB efficacy in the presence of NiO@PAN-SA (1.0) was evaluated under solar irradiation, and results are shown in Figure 11 . The mathematical equation, % Degradation = 100*[(A_o-A_t)/A_o], was used to calculated % of degradation of RB dye during the reaction, where A_o and A_t are the absorbance of RB dye (λ_max = 553) at the initial and the time, t. Table 4 shows the calculated % of degradation of RB dye using synthesized NiO@PAN-SA (1.0) under solar irradiations.

TABLE 4. The values of % of degradation of RB dye by using NiO@PAN-SA (1.0) under solar Irradiation.

3.7.3 Photodegradation kinetics of RB dye

The Langmuir–Hinshelwood (L-H) equation can explain the reactivity results and gives the reaction rate values for the degradation of hours during photocatalysis reaction. The reaction rate constant (k)and correlating factor value were calculated for RB dye during the degradationby plotting ln (A_o/A_t) versus irradiation time. Figure 12 shows the reaction rate constant and correlating factor value of this experiment. This photocatalytic degradation of RB dye follows pseudo-first-order kinetic reaction. The ln (A_o/A_t) was calculated based on the absorbance of RB dye during the catalytic reaction. The resultant values are shown in Table 5 .

TABLE 5. The values of Ao/At and In (Ao/At) of RB dye using NiO@PAN-SA (1.0) under solar irradiation.

3.7.4 Malachite green dye adsorption

The degradation of Malachite Green (1 ppm) was seen under the same experimental circumstances as Rhodamine B, with absorbance spectra recorded over a 5-h period ( Figure 13). The distinctive absorption peak of Malachite Green is observed in the 330–400 nm range, and its slight decrease in intensity signifies the progressive degradation of the dye molecules. At 1 h, the decrease in absorbance is negligible, indicating the initial phases of the degradation process. Nonetheless, with time, the absorbance persistently diminishes, especially at 2 h and 3 h, indicating that the Ni@PAN-SA nanocomposite effectively promotes the degradation of Malachite Green molecules.

At 5 h, the absorbance is markedly reduced relative to the initial state, signifying considerable degradation of the dye. Analogous to Rhodamine B, the degradation rate and extent are significantly affected by the concentration of Ni@PAN-SA, with the highest concentration (Ni@PAN-SA 1.0) demonstrating the most efficient removal efficacy. The enhanced performance is due to the increased catalytic activity of Ni@PAN-SA, which offers a greater number of reactive sites for the adsorption and oxidative degradation of Malachite Green. The observed effective degradation indicates that Ni@PAN-SA may serve as a suitable choice for the remediation of industrial dye pollutants in wastewater systems.

3.7.5 Percentage of degradation of malachite green dye using NiO@PAN-SA (1.0)

The percentage of degradation of the Alizarin Red S efficacy in the presence of NiO@PAN-SA (1.0) was evaluated under solar irradiation, and results are shown in Figure 14. The mathematical equation, % Degradation = 100*[(A_o-A_t)/A_o], was used to calculated % of degradation of Alizarin Red S dye during the reaction, where A_o and A_t are the absorbance of Alizarin Red S dye (λ_max = 365) at the initial and the time, t. Table 6 shows the calculated % of degradation of Alizarin Red S dye using synthesized NiO@PAN-SA (1.0) under solar irradiations.

TABLE 6. The values of % of degradation of Malachite green dye by using NiO@PAN-SA (1.0) under solar Irradiation.

3.7.6 Photodegradation kinetics of malachite green

The Langmuir–Hinshelwood (L-H) equation can explain the reactivity results and gives the reaction rate values for the degradation of hours during photocatalysis reaction. The reaction rate constant (k)and correlating factor value were calculated for Alizarin Red S dye during the degradation by plotting ln (A_o/A_t) versus irradiation time. Figure 15 shows the reaction rate constant and correlating factor value of this experiment. This photocatalytic degradation of Alizarin Red S dye follows pseudo-first-order kinetic reaction. The ln (A_o/A_t) was calculated based on the absorbance of Alizarin Red S dye during the catalytic reaction. The resultant values are shown in Table 7 .

TABLE 7. The values of Ao/At and In (Ao/At) of Malachite green dye using NiO@PAN-SA (1.0) under solar irradiation.

3.7.7 Dye degradation mechanism

The investigation of NiO@PAN-SA nanocomposites reveals that dye degradation primarily occurs through catalytic pathways, with surface adsorption and redox-driven generation of reactive oxygen species (ROS) as contributing factors. Although no external light was utilized, ambient or low-intensity visible light can excite NiO to create electron-hole pairs that generate hydroxyl radicals (·OH) and superoxide anions (O₂ ⁻), which facilitate oxidative cleavage of dye molecules. This aligns with published literature that highlights NiO’s capability as a visible-light active semiconductor, its role in ROS-mediated oxidation of dye, and the significance of adsorption in enhancing degradation rates. Key literature emphasizes that NiO not only acts as a catalyst but also helps concentrate dye at active sites, further promoting degradation. Various studies have documented dye removal even in the absence of strong illumination, attributable to adsorption dynamics, surface redox reactions, and the presence of ambient light. Your findings corroborate with this existing body of work, particularly regarding the dual function of NiO as an adsorbent and ROS generator (Koohestani et al., 2026). It would be beneficial to specifically mention the detected ROS (·OH, O₂ ⁻) and any experimental validations such as scavenger tests. Additionally, contrasting your experimental conditions, including light intensity and chemical interactions, with those of cited studies should be made to account for variations in catalytic behaviour (Radjenovic and Sedlak, 2015). The composite’s elevated surface area and porosity facilitate the effective adsorption of dye molecules onto active NiO sites, hence enhancing interaction duration.

3.7.8 Comparative analysis of degradation performance

In comparing the degradation efficiency of the two dyes, it is clear that Rhodamine B demonstrates a more significant reduction in absorbance during the initial hours, while Malachite Green exhibits a steadier deterioration trend. This disparity may be ascribed to variances in molecular structure and interaction with NiO@PAN-SA, together with differences in the adsorption affinity of the nanocomposite for each dye. All dye degradation tests were performed using model solutions in controlled laboratory circumstances. The efficacy of NiO@PAN-SA nanocomposites in actual or synthetic industrial effluents, perhaps comprising a combination of dyes, salts, and organic pollutants, has yet to be investigated. Future research will entail testing in complex matrices to evaluate tolerance, selectivity, and practical performance. Nevertheless, the trend in both instances substantiates that NiO@PAN-SA nanocomposites are integral to dye degradation, positioning them as viable options for wastewater purification applications.

3.7.9 The reusability potential of NiO@PAN-SA nanocomposites during the degradation process

The NiO@PAN-SA nanocomposites show a significant capacity for reusability in the degradation process, indicating their potential for sustainable applications. The reusability of the NiO@PAN-SA nanocomposites in degrading Rhodamine B dye was analyzed over five cycles, each lasting 60 min. After complete degradation, to verify the stability of the photocatalyst, the NiO@PAN-SA nanocomposites were collected, rinsed with distilled water and ethanol, centrifuged, and dried in an oven at 80 °C for 4 h before being reused in the recycling procedure for the photodegradation studies of dye at the same concentration. The degradation efficiency was calculated, and the results were presented as shown in Figure 16. The degradation efficiency of NiO@PAN-SA on Rhodamine B dye was observed to decrease from 60.52% in the first cycle to 31.27% in the fifth cycle. The photodegradation capability of the NiO@PAN-SA nanocomposites showed a slight decline. This is due to some loss of NiO@PAN-SA nanocomposites during the separation and washing processes. To improve the reusability and stability of the NiO@PAN-SA nanocomposites, they can be fixed on inert substrates such as carbon cloth, glass slides, or ceramic supports, which assists in facilitating easier recovery and reducing catalyst loss. The recyclability confirmed in this study indicated that the NiO@PAN-SA nanocomposites maintained strong stability and reusability throughout the photodegradation process.

4 Conclusions

In summary, we successfully synthesized and characterized NiO-PAN-SA nanocomposites, demonstrating their multifunctional properties in antimicrobial activity and dye degradation. The analyses of structure and morphology validated the consistent integration of NiO nanoparticles into the polymer matrix, thereby improving the composite’s overall performance. The studies on antibacterial and antifungal properties revealed that these nanocomposites successfully suppressed the growth of both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, in addition to the fungal strain Aspergillus niger. The effectiveness against microbes was observed to vary with concentration, where increased levels of NiO resulted in enhanced inhibition. Alongside their antimicrobial properties, the NiO-PAN-SA nanocomposites demonstrated remarkable efficiency in degrading dyes such as Rhodamine B and Malachite Green. The consistent reduction in absorbance observed over time suggests a catalytic influence of NiO, promoting the degradation of dye molecules. The enhancement in degradation efficiency was observed with higher concentrations of NiO, highlighting its function as an active element within the composite. The findings underscore the promising uses of NiO-PAN-SA nanocomposites in the realms of biomedical and material sciences, such as in antimicrobial coatings, sterilization materials, and the degradation of organic contaminants. The capacity to efficiently address bacterial and fungal infections, coupled with the ability to degrade dyes, positions these nanocomposites as highly promising candidates for applications in healthcare, biotechnology, and environmental sectors. Additional investigations may delve into the enduring stability, reusability, and possible alterations of these materials to improve their efficacy in practical scenarios. Future research will concentrate on measuring the reusability and regeneration of the nanocomposites, evaluating the cost-effectiveness of their synthesis, and investigating their scalability for industrial manufacturing and practical environmental remediation.

Generative AI statement

The author(s) declared that generative AI was not used in the creation of this manuscript.

Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Footnotes

Edited by: Suresh Babu Naidu Krishna, Durban University of Technology, South Africa

Reviewed by: Hossam Elsayed Emam, National Research Centre, Egypt

Vishwajit Chavda, Kyungpook National University, Republic of Korea