Structural and surface properties of polyvinylpyrrolidone and aloe vera - capped iron oxide nanoparticles: Application in the photocatalytic degradation of methylene blue European Journal of Chemistry 16 (3) (2025) 233-241 European Journal of Chemistry ISSN 2153-2249 (Print) / ISSN 2153-2257 (Online) – Copyright © 2025 The Authors – Atlanta Publishing House LLC – Printed in the USA. This work is published and licensed by Atlanta Publishing House LLC – CC BY NC – Some Rights Reserved. https://dx.doi.org/10.5155/eurjchem.16.3.233-241.2691 European Journal of Chemistry View Journal Online View Article Online Structural and surface properties of polyvinylpyrrolidone and aloe vera - capped iron oxide nanoparticles: Application in the photocatalytic degradation of methylene blue Réné Njiké 1, Adrien Pamen Yepseu 1, Cyrille Ghislain Fotsop 2, Giscard Doungmo 3, Katia Nono Nchimi 1,* and Peter Teke Ndifon 1,* 1 Department of Inorganic Chemistry, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon 2 Faculty of Process and Systems Engineering, Otto von Guericke University, Magdeburg, Germany 3 Institute für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Str. 2, 24118 Kiel, Germany * Corresponding author at: Department of Inorganic Chemistry, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon. e-mail: katia.nchimi@yahoo.fr (K.N. Nchimi); pndifon@facsciences-uy1.cm (P.T. Ndifon). 10.5155/eurjchem.16.3.233-241.2691 Received: 16 April 2025 Received in revised form: 22 June 2025 Accepted: 26 July 2025 Published online: 30 September 2025 Printed: 30 September 2025 Iron oxide nanoparticles were synthesized by the chemical precipitation method at 25 and 80 °C using polyvinylpyrrolidone (PVP) and aloe vera/polyvinyl pyrrolidone (AP) as capping agents. FTIR bands at 1584-1455 and 522-561 cm-1 confirm the formation of PVP- and AP- capped iron oxide nanoparticles. The formation of magnetite and hematite phases was confirmed by powder X-ray Diffraction patterns. The elemental composition of the synthesized particles was confirmed by EDX. SEM analysis revealed a mixed morphology of spherical and irregular-shaped particles of average crystallite sizes ranging from 9 to 58 nm, as estimated from XRD and SEM measurements. Both PVP- and AP-capped nanoparticles were used as catalysts for the photocatalytic degradation of methylene blue under ultraviolet (UV) irradiation. After 180 min of irradiation with 20 mg of photocatalyst, degradation efficiencies of 53-82% were obtained, with AP-capped nanoparticles being more efficient, suggesting their potential as effective materials for the photocatalytic degradation of toxic dyes in wastewater. Aloe vera Iron oxide Photocatalyst Surface properties Polyvinyl pyrrolidone Degradation of methylene blue Cite this: Eur. J. Chem. 2025, 16(3), 233-241 Journal website: www.eurjchem.com 1. Introduction There has been a great deal of recent interest in the design and fabrication of nanomaterials with specific morphologies and crystallite sizes due to their unique electrical, magnetic, optoelectronic, adsorptive and photocatalytic properties [1]. Metal oxide nanoparticles (MONPs) are versatile materials with a wide range of applications that have been extensively studied due to their high stability, ease of preparation, ability to obtain desired size, shape, and porosity, as well as large surface area to allow functionalization and interaction with biological and chemical systems [2]. Despite the effectiveness of metal oxide nanoparticles, these materials still suffer from limitations such as rapid recombination rate, wide band gap, and reusability. Among metal oxide nanoparticles, iron oxide nanoparticles (IONPs) have recently attracted considerable interest due to their biocompatibility, nontoxicity, catalytic activity, low cost, and environmental friendliness [3,4]. Iron oxide nanoparticles have been extensively studied due to their wide range of applications in biomedicine therapy, environmental remedia- tion, catalysis, and other industrial processes due to their low band gap and magnetic properties, which makes them recyclable [4-6]. The degradation of pollutants using these materials depends on their stability and surface area. Several synthetic approaches, including physical [5-7] and chemical [8,9] methods, have been used to prepare iron oxide nano- particles for the removal of dyes from wastewater. Dasgupta et al. synthesized iron (Fe2+/Fe3+) oxide nanoparticles using the chemical precipitation method and evaluated the photo- catalytic activity of the particles obtained in the degradation of methylene blue (MB) [10]. Bachir et al. also reported the synthesis of α-Fe2O3 attached to a polyurethane polymer for photocatalytic degradation of MB dye [11]. Louisah et al. [12] synthesized Fe3O4 and studied its photocatalytic degradation of MB in water, sometimes using toxic solvents, high pressures, and temperatures and producing agglomerated iron oxide nanoparticles with various morphologies [13-15]. Co-precipitation is a wet chemical synthesis method that is easy to implement, cost-effective, and produces small nanoparticles [16]. This method uses synthetic polymers such ABSTRACT RESEARCH ARTICLE KEYWORDS https://dx.doi.org/10.5155/eurjchem.16.3.233-241.2691 https://www.eurjchem.com/ https://dx.doi.org/10.5155/eurjchem.16.3.233-241.2691 mailto:katia.nchimi@yahoo.fr mailto:pndifon@facsciences-uy1.cm http://www.eurjchem.com/ https://crossmark.crossref.org/dialog/?doi=10.5155/eurjchem.16.3.233-241.2691&domain=pdf&date_stamp=2025-09-30 234 Njiké et al. / European Journal of Chemistry 16 (3) (2025) 233-241 2025 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.16.3.233-241.2691 as polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) as capping agents for the preparation of iron oxide nanoparticles. Shaik et al. [17] synthesized iron oxide nanoparticles for hyperthermia using PVP as a sealing agent, resulting in nanoparticles with an average size of 5-9 nm, but very little attention has been given to studying their photocatalytic properties. Although efforts have been made to control the size, morphology, and dispersibility of iron oxide nanoparticles for specific applications, the subject remains a challenge due to the high magnetism of iron oxide nanoparticles, which favors agglomeration and limits their photocatalytic application [8,18]. Plant extracts such as aloe vera extract have been used for the synthesis of IONPs. These extracts which are usually made up of phytochemicals such as flavonoids, alkaloids, and polysaccharides are rich in hydroxyl and carbonyl groups that can act as reducing agents, stabilizing and capping agents, producing small, well-dispersed, and stable IONPs that can easily be used for the degradation of organic dyes [19-22]. Organic pollutants have considerable adverse effects on the environment and human health. Among the various organic pollutants, dyes are the most frequently used and are discharged into aqueous environments [20]. These dyes are dangerous, carcinogenic, and toxic and have harmful effects on human health, the environment, and aquatic ecosystems. Several methods have been used to eliminate these dyes from water sources [10,20]. Most of these methods are associated with secondary pollution problems and complicated procedures; high costs, expensive installation, incessant energy input, low disposal efficiency, and the products cannot be reused. Therefore, it is necessary to develop an efficient and environmentally friendly protocol for the degradation of toxic dyes. The degradation of Methylene blue involves the interac- tion of a photocatalyst (nanoparticles) with light radiation to generate reactive species (hydroxyl radicals (•OH)) that break down the dye into smaller, less harmful compounds like CO2, H2O, and inorganic ions. This process decolorizes and degrades methylene blue in aqueous solutions, making it a potential method for wastewater treatment. The degradation leads to the breakdown of the dye molecule, especially the aromatic rings of MB. Several studies have been reported on the effect of polymers such as PVP or plant extracts such as aloe vera extract on the shape and size of IONPs [23], but, to our knowledge, no studies have been carried out to examine the synergistic effect of encapsulating polymers/plant extracts such as aloe vera on the size, shape, crystallinity, optical and photocatalytic properties of IONPs. In this work, we report the synthesis of recyclable iron oxide nanoparticles using the Co-precipitation method, and we study the synergistic effect of the combination of aloe Vera gel extract and PVP as stabilizing agents on the size, morphology, crystallinity, surface properties, and agglomeration pattern of iron oxide nanoparticles. We also report the effect of temperature on the photocatalytic properties of iron oxide nanoparticles prepared using aloe Vera/PVP as a coating agent. 2. Experimental 2.1. Reagents All reagents used in this study (Iron(III) chloride, 97%; iron(II) chloride, 43%; sodium hydroxide, 97%; ethanol, 95% and polyvinyl pyrrolidone, 100%) were obtained from commercial sources and used without further purification. 2.2. Instrumentation Fourier transform infrared (FTIR) spectroscopy was performed on a Genesis FTIRTM spectrometer (ATI Mattson) equipped with a DTGS (deuterated triglycine sulfate) detector operating in transmission mode in the spectral range of 400 to 4000 cm−1. X-ray diffraction (XRD) measurements were performed using a Rigaku Rint 200 diffractometer with MoKα radiation source (with λ = 0.70930 nm). Scanning electron microscopy (SEM) analyses were performed using a ZEISS EVO scanning electron microscope equipped with energy-dispersive X-ray spectroscopy-EDX (Carl Zeiss Gemini SEM 500, Germany). Optical absorption measurements were conducted using an Ocean Insight FX-VIS-IRS-ES spectrophotometer at room temperature. For N2 sorption measurements, a BELSorp Max instrument was used. Before measurements, the samples were activated for 16-24 h at 100 °C under reduced pressure (< 10–2 kPa). 2.3. Methodology 2.3.1. Preparation of aloe vera extract (AG) Fresh aloe vera leaves were obtained from the Mfoundi market in Yaoundé and washed thoroughly with distilled water before cutting into small pieces. The whitish gel of Aloe Vera was then separated from the green part using a scalpel and macerated to obtain a liquid gel that was stored at 4 °C [23]. 2.3.2. Synthesis of PVP-capped iron oxide nanoparticles (IONPs) A solution of Fe(III): Fe(II) in a 2:1 molar ratio was prepared by dissolving of FeCl2.4H2O and FeCl3.6H2O in 30 mL of distilled water. The solution was then added dropwise to a 30 mL solution of PVP. The resulting mixture was stirred for one hour at 25 °C (room temperature) and the pH was adjusted to pH = 12 by adding NaOH (5M). The resulting mixture was stirred under N2 gas for one hour and the resulting black precipitate was washed with distilled water, centrifuged at 1000rpm and dried in an oven [24]. This precipitate was then calcined at 500°C for 2 hours to obtain the iron oxide nanoparticles. The same procedure was repeated at 80 °C. The resulting nanoparticles were labelled IP-25 and IP-80 for the sample synthesized at 25 and 80°C, respectively. 2.3.3. Synthesis of AG/PVP(AP)-capped IONPs A solution of Fe(III): Fe(II) in a molar ratio of 2:1 was prepared by dissolving FeCl2·4H2O and FeCl3·6H2O in 30 mL of distilled water. The solution was then added dropwise to 60 mL of a freshly prepared extract of aloe vera gel solution to which 0.2 g PVP had previously been added. The mixture was stirred for one hour at room temperature and the pH of the solution adjusted to 12 by adding NaOH (5 M). The resulting mixture was then stirred under N2 gas for one hour and the black precipitate obtained was washed, centrifuged, and dried in an oven at 60 ° C for 48 hours. The precipitate obtained was then calcined at 500 °C for 2 hours to obtain iron oxide nanoparticles. The same procedure was repeated at 80 °C. The resulting nanoparticles were labelled IAP-25 and IAP-80 for the sample synthesized at 25 and 80 °C, respectively. 2.3.4. Photocatalytic studies For each photocatalytic study, 20 mg of nanoparticles as catalyst was added to a solution of methylene blue (MB), (50 mL, 1×10-5 mol/L) as model pollutant while stirring. The adsorption-desorption equilibrium between the nanoparticles and the MB dye solution was established for 90 min in the dark. Once equilibrium was reached, the solution was irradiated with a UV lamp of power 60 W/m2 and λ = 365 nm. Aliquots were collected at 15 min intervals and centrifuged. Njiké et al. / European Journal of Chemistry 16 (3) (2025) 233-241 235 2025 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.16.3.233-241.2691 Figure 1. IR spectra of (a) IP-25, (b) IP-80, (c) IAP-80, and (d) IAP-25. Figure 2. XRD spectra of (a) IP-25, (b) IAP-25, (c) IAP-80, and (d) IP-80. The absorbance of the resulting solutions was analyzed using UV-Vis-NIR spectrophotometer at the maximum wavelength for MB (λ = 662 nm). The efficiency of photodegradation for each time period was calculated using Equation 1 [25] %Removal = 𝐴𝐴𝑡𝑡−𝐴𝐴𝑜𝑜 𝐴𝐴𝑂𝑂 × 100 (1) where At = absorbance of MB at t seconds; Ao = initial absorbance of MB. 3. Results and discussions 3.1. FT-IR studies The IR spectra of iron oxide nanoparticles (IONPs) are shown in Figure 1 and the IR spectra of PVP and aloe vera are shown respectively in Figures S1a and S1b. All samples show the same peak as seen in the spectra. The bands in the range 3362-3458 and 1584-1455 cm-1 correspond to the O-H stretching and H-O bending of adsorbed water on the surface of IAP-25, IP-25, IAP-80 and IP-80, respectively, and can be explained by the presence of PVP in the synthetic media and the probable adsorption of moisture from the atmosphere onto the surface of nanoparticles. The bands at 536, 522, 561 and 549 cm-1 correspond to the Fe-O bond in IAP-25, IP-25, IAP-80 and IP-80, respectively [9,13,24,26,27]. 3.2. Powder XRD studies of PVP-capped iron oxide nanoparticles (IP-25 and IP-80) Powder X-ray diffraction was performed on PVP-capped IONPs (IP-25 and IP-80) and aloe vera/PVP-capped IONPs (IAP- 25 and IAP-80) to determine the phase composition and crystallinity. The results of the p-XRD measurements are shown in Figure 2. For IP-25, peaks were observed at 2θ = 13.6, 16.0, 19.4, 23.8, 25.3, 27.6, 37.8° corresponding to the (220), (311), (400), (422), (511), (440), (731) cubic planes of magnetite phase with reference code ICSD 03-067-3107[9]. For IP-80, peaks were observed at 2θ = 24.0, 33.2, and 35.5° corresponding to the (012), (104), (110) cubic planes of the hematite phase (ICSD 00-024-0072). For IAP-25, peaks were observed at 2θ = 31.7, 35.3 and 42.9° corresponding to the (220), (311), and (400) cubic planes, corresponding to magnetite phase with reference code ICSD 03-067-3107, while for IAP-80, peaks were observed at 2θ = 31.7, 35.0, 45.4, 56.4°, corresponding to (220), (311), (331), (511) cubic planes of magnetite with reference code ICSD 03-067-3107. 236 Njiké et al. / European Journal of Chemistry 16 (3) (2025) 233-241 2025 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.16.3.233-241.2691 (a) (b) (c) (d) Figure 3. SEM images of (a) IP-25, (b) IP-80, (c) IAP-80, and (d) IAP-25. The data obtained were compared with the reference data in the ICSD database, and the peaks in IP-25, IAP-25, and IAP- 80 correspond exactly to the cubic phase of magnetite (ICSD 03- 067-3107) while the peaks in IP-80 correspond to the cubic phase of hematite (ICSD 00-024-0072). The sizes of the nanoparticles were determined using Scherrer Equation 2: D = 𝐾𝐾𝐾𝐾 𝛽𝛽𝛽𝛽𝛽𝛽𝛽𝛽𝛽𝛽 (2) β= Full width at half maximum for the most intense diffraction peak, θ = Angle for the most intense peak. The crystallite sizes of IP-25 and IP-80 were determined to be 19.05 nm, and 17.26 nm, respectively. The sizes obtained in this study are smaller than those obtained by G. Pandey et al. [28] who synthesized magnetite with PVP as capping and obtained a crystallite size of 32 nm. On the other hand, the sizes of IAP-25 and IAP-80 were determined to be 15.28 and 57.52 nm, respectively. These results differ from those obtained in studies using aloe vera or PVP [23,29,30]. Comparing the sizes of PVP-capped IONPs and AP-capped IONPs at both temperatures, we observe that the mixed capping of IONPs with aloe vera and PVP leads to a reduction in crystallite size at low temperature (from 19.05 to 15.28 nm). Thus, we can say that the synergy between aloe vera/PVP affects the crystallite size of the particles, resulting in smaller particles than those of PVP-capped IONPs. This result obtained is comparable to that obtained by Raghad Zein et al. (2022) [31] who studied the influence of PVP on the properties of green synthesized silver nanoparticles. This size reduction can be explained by the synergistic action of phytochemicals in aloe vera (alkaloids, flavonoids and polysaccharides) and the C=O bond in PVP through which PVP bonds to the surface of iron oxide particles, thereby limiting particle growth [10,13,19,32]. The sizes obtained in this study are smaller than those obtained using aloe vera or PVP alone [23,33]. Thus, aloe vera/PVP can be used to synthesize IONPs of small crystallite sizes for photocatalytic applications. 3.3. SEM/EDX analysis The morphology and elemental composition of the particles were determined by SEM and EDX analysis. Images of the synthesized samples are presented in Figure 3. The images show that all samples have a mixed morphology of spherical and irregularly shaped particles. The particles are more agglomerated when aloe vera/PVP is used as the capping agent than when PVP alone was used at both temperatures. This is an indication that the particles may be more dispersed in PVP than in aloe vera/PVP. Thus, the use of a combination of aloe vera/PVP as the capping agent did not improve the disper- sibility of the iron oxide NPs. Furthermore, the grain size of the particles at low temperature was estimated to be 29.2±10.4 nm for IP-25 and 26.5±12.7 nm for IAP-25, while at high temperature, the grain size was estimated to be 9.73±2.80 nm for IP-80 and 32.84±15.19 nm and IAP-80, respectively [18,34]. These results suggest that the synergy between aloe vera and PVP reduces the size of the resulting particles at low temperature while favoring growth and size increase at high temperature. This increase in size can be explained by the denaturation of aloe vera with increasing temperature. Heurta et al. [35] showed that at 53.2 °C, 50% of the aloe vera plant membrane is damaged. This suggests that at 80 °C, the phytochemicals (flavonoids, alkaloids, and polysaccharides) in aloe vera that play an active role in the capping of the nanoparticles are structurally modified; hence, crystallite growth is preferred. The sizes obtained from SEM measure- ments differ from the results obtained from XRD measure- ments, most probably due to the agglomeration of the isolated nanoparticles. From these results, we observe that the mixing of aloe vera/PVP favors reduction in size of the resultant particles at low temperature. The particle size distribution obtained from the SEM images using ImageJ software is shown in Figure 4. Table 1 gives a summary of the crystallite sizes and grain sizes obtained in this study. Njiké et al. / European Journal of Chemistry 16 (3) (2025) 233-241 237 2025 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.16.3.233-241.2691 Table 1. Crystallite size and grain size of IONPs. Samples Size from SEM (nm) (Present work) Size from XRD (nm) (Present work) Size (nm) (Published work) IP-25 29.20 19.05 30.00 [28] IP-80 9.73 17.26 18.02 [30] IAP-25 26.50 15.28 13.00 [31] IAP-80 32.84 57.52 - (a) (b) (c) (d) Figure 4. Particle size distribution of (a) IP-25, (b) IP-80, (c) IAP-8, and (d) IAP-25 The EDX spectra (Figure S2) of the different samples indicate the presence of the main elemental components of the iron oxide nanoparticles (iron (Fe), oxygen (O)) confirming the formation of the iron oxide nanoparticles. Table 2 shows a summary of the weight percentage of iron and oxygen in the different samples. The presence of Cl and Na on the EDX spectra originates from the precursors of the synthesis (Table 2). 3.4. Adsorption studies The surface properties of the synthesized iron oxide nanoparticles were determined by using BET analysis for the specific surface area (S), pore diameter (Dp), and pore volume (V). The PVP-capped samples had specific surface areas of 28.98 m2g-1 and 20.99 m2g-1 for IP-25 and IP-80, respectively (Table 3). The aloe vera/PVP-capped samples had specific surface areas of 35.60 and 25.87 m2g-1 for IAP-25 and IAP-80, respectively (Table 3). The results show that the dual capping of aloe vera and PVP increases the surface area of the synthesized IONPs. Porous volumes were evaluated as 0.021, 0.014, 0.024 and 0.018 cm-3g-1 for IP-25, IP-80, IAP-25, and IAP- 80 respectively. The mean pore diameters were evaluated as 2.89, 2.70, 2.73, 2.78 nm for IP-25, IP-80, IAP-25 and IAP-80, respectively. The results indicate that all materials are mesoporous [12] and can be used effectively as adsorbents and for photocatalytic applications. Table 3 summarizes the BET results. 238 Njiké et al. / European Journal of Chemistry 16 (3) (2025) 233-241 2025 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.16.3.233-241.2691 Table 2. Weight percentages of Fe and O Sample Fe O IO-PVP-25 41.60 21.90 IO-PVP-80 65.60 23.10 IO-AP-25 50.80 22.20 IO-AP-80 39.00 31.60 Table 3. Surface characteristics of iron oxide nanoparticles. Samples Specific surface area (S/m2g-1) Pore diameter (Dp/nm) Pore volume (V/cm-3g-1) IP-25 28.98 2.89 0.021 IP-80 20.99 2.70 0.014 IAP-25 35.60 2.73 0.024 IAP-80 25.87 2.78 0.018 (a) (b) (c) (d) Figure 5. Adsorption-desorption isotherms for (a) IP-25, (b) IP-80, (c) IAP-25, and (d) IAP-80. The adsorption isotherms (Figure 5) of both IP-25 and IP- 80 are more likely to follow the type IV adsorption isotherm and hysteresis loop of type H4, as obtained by Pandey et al. [28]. However, the IONPs capped with aloe vera/PVP are likely to follow the type IV adsorption isotherm with hysteresis loop H3 [36]. This suggests a change in the shape of pores from small slit-shapes to larger slit shapes, increasing the surface area available for light interaction [37]. Therefore, this study shows that the dual capping of aloe vera/polyvinylpyrrolidone (PVP) enhances the surface area and modifies the shape of the pores of IONPs, making them favorable for use in photocatalysis. 3.5. Optical properties of IONPs The optical properties of the IONPs were studied by measuring their UV absorbance (Figure S3-S6) The energy band gaps of the IONPs were determined from the Tauc plots (Figure S7). The energy band gap of 2.40 eV and 1.60 eV was obtained for IP-25 and IP-80, respectively, similar to those reported from previous studies [23,33]. The energy band gaps for IAP-25 and IAP-80 were found to be 2.60 eV and 2.20 eV, respectively. This result indicates that mixing aloe vera and PVP causes a blue shift in the energy band gaps of PVP-capped IONPs. This observed increase in the energy band gap could be due to the reduction in the nanometric size of the nanoparticles, which clearly shows the effect of the addition of aloe vera on the optical properties of the nanoparticles [38]. 3.6. Photocatalytic studies The photocatalytic properties of the synthesized IONPs was examined by photocatalytic degradation of the MB dye using these materials as photocatalysts. Figure S8 shows the photo- catalytic activity of each sample over a 180-minute period. MB was used as a dye to investigate the photocatalytic properties of the synthesized nanoparticles. The initial absorbance of MB (A0) was taken and the absorbance (At) was monitored at 15 minute intervals for 180 minutes. The absorbances were recorded at a maximum wavelength of 662 nm. The degra- dation efficiency of the MB dye was calculated for each prepared sample over the 180-minute period as shown in Figure 6. Njiké et al. / European Journal of Chemistry 16 (3) (2025) 233-241 239 2025 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.16.3.233-241.2691 Table 4. Comparison of MB dye degradation with iron oxides. Dye Source of light and intensity Time of irradiation/mins pH % Degradation Reference MB UV lamp, 150W 60 7 25 [12] MB Sunlight 120 7 34 [42] MB Mercury UV lamp, 250 W 90 7 45 [43] MB Xenon, Visible light 360 7 60 [41] Rhodamine B Sunlight 60 - 24 [44] MB UV lamp, 60W 120 7 81 Present work Figure 6. Photodegradation efficiency of IP-25, IP-80, IAP-25, and IAP-80. Figure 7. Mechanism and schematic diagram of the photodegradation of MB by IONPs. Figure 6 shows that all IONPs synthesized have some photo-catalytic activity. PVP-capped samples have photocatalytic activity lower than that of the synergistically synthesized aloe vera/PVP-capped IONPs. This suggests that the dual capping of aloe vera/PVP enhances the photocatalytic activity of IONPs. This increase in photocatalytic activity can be attributed to the larger surface area of aloe vera/PVP-capped IONPs resulting from a change in the pore shape from small to large slits. The larger slit pores allow for greater adsorption of MB dye before degradation by photoexcited electrons [39]. The study achieved a degradation efficiency of 81 % at pH = 7 using the IAP-25 sample, which is higher than the 25 % achieved by Louisah et al. [12] who used iron oxide nanoparticles synthesized with Burkeana plant extract for photocatalytic degradation of MB at pH = 7. The proposed mechanism of degra- dation of MB by Fe3O4 is as follows [40,41]. UV light strikes bare Fe3O4 inducing the photogeneration electrons and holes. Fe3O4 + hv → e⁻ + h+ (3) The photogenerated electrons are picked up by dissolved oxygen (O2) in water to produce an active radical specie (O2˙¯). e⁻ + O2 → O2˙¯. (4) Photogenerated holes (h+) are picked up by water molecules (H2O) to form OH. h+ + H2O → ˙OH (5) Free radicals (O2˙¯ and ˙OH) are responsible for the degradation of activated MB. h+ +MB → MB+ (6) ˙OH + MB → H2O +CO2 (7) The schematic diagram presented in Figure 7 illustrates the degradation mechanism of MB on IONP photocatalysts. The degradation efficiencies obtained in this study were compared with those of similar studies in the literature (Table 4) and the results show that the catalysts obtained in this study have improved the degradation efficiencies of the dye. 4. Conclusions IONPs were successfully synthesised using only PVP only and combined aloe vera/PVP as capping agents. The aloe vera/PVP-capped IONPs exhibited smaller crystallite sizes as the PVP-capped IONPs, indicating that this method of synthesis is effective in producing small-sized IONPs. An increase in the synthesis temperature favoured the growth of crystallites in the 240 Njiké et al. / European Journal of Chemistry 16 (3) (2025) 233-241 2025 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.16.3.233-241.2691 aloe vera/PVP-capped IONPs. The synthesis approach using combined capping agents (aloe vera/PVP) has a synergistic effect on the size of the IONPs, reducing crystallite growth and hence increasing the surface area of the IONPs, suggesting its potential use to synthesize IONPs with favorable surface properties for photocatalytic degradation of dyes like methylene blue. IONPs capped with aloe vera/PVP and synthe- sized at low temperatures exhibit a higher photocatalytic degradation efficiency, indicating that high temperature has an impact on the photocatalytic degradation efficiency of IONPs on MB using aloe vera/PVP. Acknowledgements We thank the Alexander von Humboldt Foundation for a postdoctoral fellowship to (KNN). The authors also acknowledge the final assistance through the 'Fond de modernization et d’appui a la recherche' allocation to Higher Education Teachers of Cameroon (KNN and PTN). Supporting information The data used to support the findings of this study are included in the article. Any other data are available from the corresponding author upon request. Electronic supplementary information (ESI) available: IR spectra of capping agents, UV spectra of nanoparticles, and photodegradation curves. Disclosure statement Conflict of interest: The authors declare that they have no conflict of interest. Sample availability: Samples of the compounds are available from the author. CRediT authorship contribution statement Conceptualization: Katia Nono Nchimi, Peter Teke Ndifon; Methodology: Réné Njiké, Adrien Pamen Yepseu; Giscard Doungmo; Validation: Katia Nono Nchimi; Formal Analysis: Réné Njiké, Adrien Pamen Yepseu; Giscard Doungmo; Investigation: Réné Njiké, Cyrille Ghislain Fotsop; Resources: Katia Nono Nchimi, Peter Teke Ndifon; Data Curation: Adrien Pamen Yepseu, Cyrille Ghislain Fotsop; Writing - Original Draft: Réné Njiké, Adrien Pamen Yepseu; Writing - Review and Editing: Katia Nono Nchimi, Peter Teke Ndifon; Visualization: Katia Nono Nchimi; Funding acquisition: Katia Nono Nchimi, Peter Teke Ndifon; Supervision: Katia Nono Nchimi, Peter Teke Ndifon; Project Administration: Peter Teke Ndifon. ORCID and Email Réné Njiké rene.njike@facsciences-uy1.cm https://orcid.org/0009-0000-9670-830X Adrien Pamen Yepseu yepseuadrien@gmail.com https://orcid.org/0000-0002-2773-1351 Cyrille Ghislain Fotsop fotsopcyril@yahoo.fr https://orcid.org/0000-0001-6455-2515 Giscard Doungmo gdoungmo@ac.uni-kiel.de https://orcid.org/0000-0002-6332-8260 Katia Nono Nchimi katia.nchimi@yahoo.fr https://orcid.org/0000-0002-5031-6404 Peter Teke Ndifon pndifon@facsciences-uy1.cm https://orcid.org/0000-0001-9331-9034 References [1]. Herlekar, M.; Barve, S.; Kumar, R. Plant-Mediated Green Synthesis of Iron Nanoparticles. J. Nanoparticles 2014, 2014, 1–9. [2]. Sanchez-Moreno, P.; Ortega-Vinuesa, J. L.; Peula-Garcia, J. M.; Marchal, J. A.; Boulaiz, H. Smart Drug-Delivery Systems for Cancer Nanotherapy. CDT. 2018, 19 (4), 339–359. [3]. Jana, T. K.; Pal, A.; Mandal, A. K.; Sarwar, S.; Chakrabarti, P.; Chatterjee, K. Photocatalytic and antibacterial performance of α-Fe2 O3 nanostructures. ChemistrySelect 2017, 2, 3068–3077. [4]. Machala, L.; Zboril, R.; Gedanken, A. Amorphous Iron(III) Oxide — A Review. ChemInform. 2007, 38 (28), 4003–4018 https://doi.org/10.1002/chin.200728192. [5]. Montiel Schneider, M. G.; Martín, M. J.; Otarola, J.; Vakarelska, E.; Simeonov, V.; Lassalle, V.; Nedyalkova, M. Biomedical Applications of Iron Oxide Nanoparticles: Current Insights Progress and Perspectives. Pharmaceutics 2022, 14 (1), 204. [6]. Tharani, K.; Jegatha Christy, A.; Sagadevan, S.; Nehru, L. Photocatalytic and antibacterial performance of iron oxide nanoparticles formed by the combustion method. Chemical. Physics. Letters 2021, 771, 138524. duplicated [7]. Pecharroman, C.; Gonzalez-Carreao, T.; Iglesias, J. The Infrared Dielectric Properties of Maghemite, -Fe2O3, from Reflectance Measurement on Pressed Powders. Phys. Chem. Miner. 1995, 22 (1). https://doi.org/10.1007/BF00202677 [8]. Criveanu, A.; Dumitrache, F.; Fleaca, C.; Gavrila-Florescu, L.; Lungu, I.; Morjan, I. P.; Socoliuc, V.; Prodan, G. Chitosan-coated iron oxide nanoparticles obtained by laser pyrolysis. Applied Surface Science Advances 2023, 15, 100405. [9]. Noqta, O. A.; Aziz, A. A.; Usman, A. I. Synthesis of PVP Coated Superparamagnetic Iron Oxide Nanoparticles with a High Saturation Magnetization. SSP. 2019, 290, 301–306. [10]. Dasgupta, N.; Nayak, M. A.; Gauthier, M. Starch-stabilized iron oxide nanoparticles for the photocatalytic degradation of methylene blue. Polysaccharides 2022, 3, 655–670. [11]. Yaou Balarabe, B.; Illiassou Oumarou, M. N.; Koroney, A. S.; Adjama, I.; Ibrahim Baraze, A. R. Photo-Oxidation of Organic Dye by Fe2O3 Nanoparticles: Catalyst, Electron Acceptor, and Polyurethane Membrane (PU-Fe2O3) Effects. J. Nanotechnology 2023, 2023, 1–12. [12]. Mahlaule-Glory, L. M.; Mapetla, S.; Makofane, A.; Mathipa, M. M.; Hintsho-Mbita, N. C. Biosynthesis of iron oxide nanoparticles for the degradation of methylene blue dye, sulfisoxazole antibiotic and removal of bacteria from real water. Heliyon 2022, 8 (9), e10536. [13]. Silva, M. F.; de Oliveira, L. A.; Ciciliati, M. A.; Lima, M. K.; Ivashita, F. F.; Fernandes de Oliveira, D. M.; Hechenleitner, A. A.; Pineda, E. A. The Effects and Role of Polyvinylpyrrolidone on the Size and Phase Composition of Iron Oxide Nanoparticles Prepared by a Modified Sol- Gel Method. J. Nanomaterials 2017, 2017, 1–10. [14]. Marand, Z. R.; Rashid Farimani, M. H.; Shahtahmasebi, N. Study of magnetic and structural and optical properties of Zn doped Fe3O4 nanoparticles synthesized by co-precipitation method for biomedical application. Nanomed. J. 2014, 1, 238-247. https://doi.org/10.7508/ NMJ.2015.04.004 [15]. Teng, Y.; Li, Y.; Li, Y.; Song, Q. Preparation of Fe3O4/PVP magnetic nanofibers via in situ method with electrospinning. J. Phys.: Conf. Ser. 2020, 1549 (3), 032087. [16]. Fujishima, A.; Honda, K. Electrochemical Photolysis of Water at a Semiconductor Electrode. Nature. 1972, 238 (5358), 37–38. [17]. Fu, C.; Ravindra, N. M. Magnetic iron oxide nanoparticles: synthesis and applications. Bioinspired, Biomimetic Nanobiomaterials 2012, 1 (4), 229–244. [18]. Shaikh, I. A.; Shah, D. V. Synthesis of PVP capped superparamagnetic iron oxide (Fe3O4) nanoparticles in the inert atmosphere - An ideal candidate for hyperthermia. AIP. Conference Proceedings 2019, 2162, 020113. [19]. Jeevanandam, J.; Chan, Y. S.; Danquah, M. K. Biosynthesis of Metal and Metal Oxide Nanoparticles. ChemBioEng. Reviews 2016, 3 (2), 55–67. [20]. Nagajyothi, P. C.; Prabhakar Vattikuti, S. V.; Devarayapalli, K. C.; Yoo, K.; Shim, J.; Sreekanth, T. V. Green synthesis: Photocatalytic degradation of textile dyes using metal and metal oxide nanoparticles- latest trends and advancements. Critical Reviews Environmenta. Science and. Technology 2019, 50 (24), 2617–2723. [21]. Ali, K.; Ahmed, B.; Khan, M. S.; Musarrat, J. Differential surface contact killing of pristine and low EPS Pseudomonas aeruginosa with Aloe vera capped hematite (α-Fe2O3) nanoparticles. Journal of Photochemistry and Photobiology B: Biology 2018, 188, 146–158. [22]. Phumying, S.; Labuayai, S.; Thomas, C.; Amornkitbamrung, V.; Swatsitang, E.; Maensiri, S. Aloe vera plant-extracted solution hydrothermal synthesis and magnetic properties of magnetite (Fe3O4) nanoparticles. Appl. Phys. A 2012, 111 (4), 1187–1193. [23]. Rahmani, R.; Gharanfoli, M.; Gholamin, M.; Darroudi, M.; Chamani, J.; Sadri, K.; Hashemzadeh, A. Plant-mediated synthesis of superparamagnetic iron oxide nanoparticles (SPIONs) using aloe vera and flaxseed extracts and evaluation of their cellular toxicities. Ceramics International 2020, 46 (3), 3051–3058. [24]. Nchimi Nono, K.; Vahl, A.; Terraschke, H. Towards High-Performance Photo-Fenton Degradation of Organic Pollutants with Magnetite- Silver Composites: Synthesis, Catalytic Reactions and in Situ Insights. Nanomaterials (Basel) 2024, 14 (10), 849. [25]. Yepseu, A. P.; Girardet, T.; Nyamen, L. D.; Fleutot, S.; Ketchemen, K. I.; Cleymand, F.; Ndifon, P. T. Copper (II) Heterocyclic Thiosemicarbazone Complexes as Single-Source Precursors for the mailto:rene.njike@facsciences-uy1.cm https://orcid.org/0009-0000-9670-830X mailto:yepseuadrien@gmail.com https://orcid.org/0000-0002-2773-1351 mailto:fotsopcyril@yahoo.fr https://orcid.org/0000-0001-6455-2515 mailto:gdoungmo@ac.uni-kiel.de https://orcid.org/0000-0002-6332-8260 mailto:katia.nchimi@yahoo.fr https://orcid.org/0000-0002-5031-6404 mailto:pndifon@facsciences-uy1.cm https://orcid.org/0000-0001-9331-9034 https://doi.org/10.1002/chin.200728192 https://doi.org/10.1007/BF00202677 https://doi.org/10.7508/%20NMJ.2015.04.004 https://doi.org/10.7508/%20NMJ.2015.04.004 Njiké et al. / European Journal of Chemistry 16 (3) (2025) 233-241 241 2025 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.16.3.233-241.2691 Preparation of Cu9S5 Nanoparticles: Application in Photocatalytic Degradation of Methylene Blue. Catalysts 2022, 12 (1), 61. [26]. Morales Morales, J. A. Synthesis of Hematite α-Fe2O3 Nano Powders by the Controlled Precipitation Method / Síntesis de Nano Polvos de Hematita α-Fe2O3 Por El Método de Precipitación. Cienc. Desarro. 2017, 8 (1), 99–107. [27]. Lassoued, A.; Dkhil, B.; Gadri, A.; Ammar, S. Control of the shape and size of iron oxide (α-Fe2O3) nanoparticles synthesized through the chemical precipitation method. Results in Physics 2017, 7, 3007–3015. [28]. Pandey, G.; Singh, S.; Hitkari, G. Synthesis and characterization of polyvinyl pyrrolidone (PVP)-coated Fe3O4 nanoparticles by chemical co-precipitation method and removal of Congo red dye by adsorption process. Int. Nano. Lett. 2018, 8 (2), 111–121. [29]. Itoh, H.; Sugimoto, T. Systematic Control of Size, Shape, Structure, and Magnetic Properties of Uniform Magnetite and Maghemite Particles. J. Colloid Interface Sci. 2003, 265 (2), 283–295. [30]. Agarwal, T.; A. Gupta, K.; Alam, S.; G. H. Zaidi, M. Fabrication and Characterization of Iron Oxide Filled Polyvinyl Pyrrolidone Nanocomposites. Cmaterials. 2012, 2 (3), 17–21. [31]. Zein, R.; Alghoraibi, I.; Soukkarieh, C.; Ismail, M. T.; Alahmad, A. Influence of Polyvinylpyrrolidone Concentration on Properties and Anti-Bacterial Activity of Green Synthesized Silver Nanoparticles. Micromachines 2022, 13 (5), 777. [32]. Kahramanoğlu, I.; Chen, C.; Chen, J.; Wan, C. Chemical Constituents, Antimicrobial Activity, and Food Preservative Characteristics of Aloe vera Gel. Agronomy 2019, 9 (12), 831. [33]. Mandal, B. K.; Biswas, A.; Barman, S.; Das, R.; Debnath, P. S. Structural study of iron oxide nanoparticles (INPs) synthesized in aloe vera plant extract. AIP. Conference. Proceedings 2020, 2220, 020185. [34]. Yazid, N. A.; Joon, Y. C. Co-precipitation synthesis of magnetic nanoparticles for efficient removal of heavy metal from synthetic wastewater. AIP. Conference. Proceedings 2019, https://doi.org/ 10.1063/1.5117079. [35]. Huerta, C.; Freire, M.; Cardemil, L. Expression of hsp70, hsp100 and ubiquitin in Aloe barbadensis Miller under direct heat stress and under temperature acclimation conditions. Plant. Cell. Rep. 2012, 32 (2), 293–307. [36]. Sing, K. S. W.; Williams, R. T. Physisorption Hysteresis Loops and the Characterization of Nanoporous Materials. Adsorp. Sci. Technol. 2004, 22 (10), 773–782. [37]. AlAbduljabbar, F. A.; Haider, S.; Ali, F. A.; Alghyamah, A. A.; Almasry, W. A.; Patel, R.; Mujtaba, I. M. Efficient Photocatalytic Degradation of Organic Pollutant in Wastewater by Electrospun Functionally Modified Polyacrylonitrile Nanofibers Membrane Anchoring TiO2 Nanostructured. Membranes 2021, 11 (10), 785. [38]. Deotale, A. J.; Nandedkar, R. Correlation between Particle Size, Strain and Band Gap of Iron Oxide Nanoparticles. Materials Today: Proceedings 2016, 3 (6), 2069–2076. [39]. Kumar, A. A Review on the Factors Affecting the Photocatalytic Degradation of Hazardous Materials. Int. J. Mater Sci. Eng. MSEIJ. 2017, 1 (3), https://doi.org/10.15406/mseij.2017.01.00018. [40]. Ahmad, W.; Khan, A. U.; Shams, S.; Qin, L.; Yuan, Q.; Ahmad, A.; Wei, Y.; Khan, Z. U.; Ullah, S.; Rahman, A. U. Eco-benign approach to synthesize spherical iron oxide nanoparticles: A new insight in photocatalytic and biomedical applications. Journal of Photochemistry and Photobiolog. B: Biology 2020, 205, 111821. [41]. Ganeshraja, A. S.; Rajkumar, K.; Zhu, K.; Li, X.; Thirumurugan, S.; Xu, W.; Zhang, J.; Yang, M.; Anbalagan, K.; Wang, J. Facile synthesis of iron oxide coupled and doped titania nanocomposites: tuning of physicochemical and photocatalytic properties. RSC. Adv. 2016, 6 (76), 72791–72802. [42]. Šmitran, A.; Jelić, D.; Pržulj, S.; Vračević, S.; Gajić, D.; Malinović, M.; Božić, L. Study of iron oxide nanoparticles doped with copper: antimicrobal and photocatalytical activity. Contemp. Mater. CM. 2020, 11 (2), 93–101 https://doi.org/10.7251/COMEN2002093J. [43]. Wu, W.; Xiao, X.; Zhang, S.; Ren, F.; Jiang, C. Facile method to synthesize magnetic iron oxides/TiO2 hybrid nanoparticles and their photodegradation application of methylene blue. Nanoscale. Res. Lett. 2011, 6 (1), https://doi.org/10.1186/1556-276X-6-533. [44]. Duy Vu Nguyen, K.; Dang Nguyen Vo, K. Magnetite nanoparticles-TiO2 nanoparticles-graphene oxide nanocomposite: Synthesis, characterization and photocatalytic degradation for Rhodamine-B dye. AIMS. Materials Science 2020, 7 (3), 288–301. Copyright © 2025 by Authors. This work is published and licensed by Atlanta Publishing House LLC, Atlanta, GA, USA. The full terms of this license are available at https://www.eurjchem.com/index.php/eurjchem/terms and incorporate the Creative Commons Attribution-Non Commercial (CC BY NC) (International, v4.0) License (http://creativecommons.org/licenses/by-nc/4.0). By accessing the work, you hereby accept the Terms. This is an open access article distributed under the terms and conditions of the CC BY NC License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited without any further permission from Atlanta Publishing House LLC (European Journal of Chemistry). No use, distribution, or reproduction is permitted which does not comply with these terms. Permissions for commercial use of this work beyond the scope of the License (https://www.eurjchem.com/index.php/eurjchem/terms) are administered by Atlanta Publishing House LLC (European Journal of Chemistry). https://doi.org/%2010.1063/1.5117079 https://doi.org/%2010.1063/1.5117079 https://doi.org/10.15406/mseij.2017.01.00018 https://doi.org/10.7251/COMEN2002093J https://doi.org/10.1186/1556-276X-6-533 https://www.eurjchem.com/index.php/eurjchem/terms http://creativecommons.org/licenses/by-nc/4.0 https://www.eurjchem.com/index.php/eurjchem/terms 1. Introduction 2. Experimental 2.1. Reagents 2.2. Instrumentation 2.3. Methodology 2.3.1. Preparation of aloe vera extract (AG) 2.3.2. Synthesis of PVP-capped iron oxide nanoparticles (IONPs) 2.3.3. Synthesis of AG/PVP(AP)-capped IONPs 2.3.4. Photocatalytic studies 3. Results and discussions 3.1. FT-IR studies 3.2. Powder XRD studies of PVP-capped iron oxide nanoparticles (IP-25 and IP-80) 3.3. SEM/EDX analysis 3.4. Adsorption studies 3.5. Optical properties of IONPs 3.6. Photocatalytic studies 4. Conclusions Acknowledgements Supporting information Disclosure statement CRediT authorship contribution statement ORCID and Email References PrintField10: PrintField11: PrintField12: PrintField13: PrintField14: PrintField15: PrintField16: PrintField17: PrintField18: PrintField20: PrintField21: PrintField22: PrintField23: PrintField24: PrintField25: PrintField26: PrintField27: PrintField28: