Introduction

In the modern domain, the routine usages of cosmetics, dyes, and chemicals are amplified. Thus, global water resources were contaminated via leftover chemicals and dyes. This contamination directly affected all living creatures1,2,3,4,5,6. The existence of dye in water is toxic, and also prevent sunlight passing through water which influences aquatic organisms. Henceforth, appropriate dye removal is essential before its release to water bodies. decomposition of dye pollutants into non-toxic ingredients is a challenge7. Advanced Oxidation Processes (AOPs) for removing pollutants embrace several methods, for instance, ozonation, photocatalysis, and electrochemical oxidation. In this study Methylene blue (MB) dye was decomposed upon Ag/Nd2O3 utilization. The MB dye contamination is spread widely owing to its usage in dyeing and printing textile industries8. The azo functional group (–N=N–) which exists in MB structure is considered carcinogenic9. Additionally, methylene blue (MB) inhalation affects digestive system pains, respiratory system sicknesses, as well nervous systems disorders10. Saravanan et al.11 develop a dye removal Photocatalytic process by replacing UV radiation instead with visible electromagnetic waves. Photocatalytic degradation is influenced by band-gap, surface area, and grain size, and amount of material12. Metallic nano-scale metals possess special physical and chemical activity that push in exploiting them in numerous fields such as electronics, textile, medical, etc. catalytic potential of metals recommends its usage in the degradation of toxic dyes7. Further, metallic insertions belong to exceptional electric, magnetic and optical performances. Semiconductor catalysts are preferred in the process of photocatalytic degradation of wastewater due to several advantages. Firstly, they are cost-effective. Secondly, they are non-toxic. Thirdly, they possess adaptable characterization that could be altered through doping, size adjustment, or sensitizers. Fourthly, they enable a multi-electron relocation process. Lastly, they can be utilized extensively without significant reduction in their photocatalytic efficiency13.

The optical and magnetic characteristics of Neodymium oxide nanoparticles have much attention for numerous usages. Indeed, Nd2O3 is extensively utilized in photonic, luminescent, and thermo luminescent usages9. Moreover, grayish blue hexagonal crystal lattice of neodymium oxide (Nd2O3) offers significant catalytic, electric, coloring, besides additive characteristics14,15. Nd2O3 enhances photocatalytic activity by facilitating the effective separation of photo-generated electrons16. Casillas et al.17, studied the photo-catalytic degradation of diclofenac in aqueous system catalyzed with Al2O3–Nd2O3 oxides and the effectiveness linked to the Nd2O3 contribution. Studying silver doped neodymium oxide nano-composite is favored owing to its inertness, non-toxicity, high surface area10, which are different from their macro-scaled equivalents. Additionally, the energy gap could be narrowed by modifying surface defects by forming nano-composites17. A research revealed that CuO nanoparticles doped with Nd2O3 had a remarkable photocatalytic efficacy, reaching up to 90.8% during a duration of 80 min, accompanied with a degradation rate of 0.0227 min−118. On the other hand, from 90 to 100% degradation was detected for several dyes by silver NPs. Also, the advantage of NPs usage in dye degradation process is time saving with lacking any hazardous chemical7. Such usages strongly depend on the morphological features, and crystal structure of silver NPs19. The incorporation of AgNPs into Nd2O3 improves the efficiency of photocatalysis due to many factors. To begin with, doping involves the incorporation of distinct metallic elements into the structure of the photocatalyst, resulting in a fundamental modification of its physical and chemical characteristics. This allows for the inclusion of a larger quantity of photogenerated electrons and holes, so effectively adjusting the reaction towards visible wavelengths20. Furthermore, AgNPs enhance the photocatalytic activity driven by ultraviolet light by facilitating the separation of electrons and holes. Additionally, AgNPs also stimulate the photocatalytic activity driven by visible light via the localized surface plasma resonance (LSPR) of AgNPs20. Hence, the addition of AgNPs to Nd2O3 doping might augment the photocatalytic efficiency by broadening the spectrum of light absorption and facilitating the segregation of photo-generated charge carriers20,21. Further, the plasmon excitation boosts optical field response19. Lately scientists notify AgNPs as a recommended degradation agent of methylene blue7. Owing to the previous survey; Nd2O3, and Ag NPs are recommended for effective dye removal strategy. The microstructure, optical, and antibacterial behavior is examined.

Bacteria, fungus, and plants are effectively used in biological methods to degrade different textile dyes. In order to harness the capabilities of microbial consortia for improving dye degradation, it is important to consider the wide range of enzyme activation that might occur within a culture. The drawbacks of this approach include the need for prolonged retention times for the conversion of a functional molecule and its complete mineralization. The combination of photocatalysis for dye removal and antibacterial activity for water treatment is more effective and will reduce the cost of the water treatment process22.

The objective of this paper is to illustrate the influence of Photocatalytic properties on the dyes removal capability and assess the adsorption aptitude of Nd2O3 and AgNPs compositions in environmental applications, particularly water decontamination and antibacterial activity. Additionally, the research aims to examine the optical behavior of the pure Nd2O3 composition.

Experimental techniques

Preparation of Ag/Nd2O3 NPs

In the first step, 100.0 mL of 0.1 M silver nitrate (99.9%) was mixed by 100.0 mL of 0.1 M neodymium chloride (99.8%) solution. In the second step, 200 mL of 0.1 M thio-urea solution has been added while manipulating the temperature at 80 °C for 3 h on a magnetic stirrer. Throughout the heating process, 1 M NaOH (99%) has been gradually added to obtain the desired alkaline precipitate. After 3 h, the mixture was cooled down to room temperature and then washed with distilled water and ethanol to dissolve any contaminations. Finally, the precipitate was dried at 70 °C for three days. During the stirring and heating process, the following reactions were predicted: Sodium hydroxide was dissolved, giving aqueous sodium cations and hydroxyl anions, as well as silver nitrate and neodymium chloride13. The following equations were predicted.

$${\text{OH}}^{ - }_{{({\text{aq}})}} + {\text{ Nd}}^{3 + }_{{({\text{aq}})}} + {\text{ Ag}}^{ + }_{{({\text{aq}})}} \to {\text{AgOH}}_{{({\text{aq}})}} + {\text{ Nd}}\left( {{\text{OH}}} \right)_{{3({\text{aq}})}}$$
$${\text{AgOH}}_{{({\text{aq}})}} + {\text{ Nd}}\left( {{\text{OH}}} \right)_{{3({\text{aq}})}} \to {\text{Ag}}/{\text{Nd}}_{2} {\text{O}}_{{3({\text{s}})}} \downarrow \, + \, 2{\text{H}}_{2} {\text{O}}$$

The resultant product is not water soluble as Nd2O3 has a very low solubility in water23,24.

All raw chemicals have been obtained from Sigma Aldrich. The powder of Ag/Nd2O3 NPs was exposed to UV–Vis spectroscopy analysis (Lamda-950, PerkinElmer, Germany). The X-ray diffraction (XRD) pattern was attained by an X-ray diffractometer (XRD, X’Pert Explorer, PANalytical diffractometer) equipped with Cu Kα1 radiation (λ = 1.5406 nm) utilizing a originator voltage of 40 kV and current of 35 mA. FTIR analysis have been executed with a spectrometer (iS50 ATR Spectrum-100 FTIR) gotten from PerkinElmer, Germany. High resolution transmission electron microscope (HRTEM, JEM-2100F) has been utilized for the synthesized samples. Additionally, MB degradation evaluation was executed by a spectrophotometer24.

The concentration of methylene blue (MB) solution was modified to 20 ppm and the pH was 6. The lighting system used a closed box to emit visible light within the spectrum of 500 watts. Following irradiation, a volume of 3 mL was extracted from the (MB) solution at certain time intervals for analysis using a spectrophotometer. The deterioration potential is determined using the mathematical formula25,26. Following the degradation of MB, the resulting precipitated powder was subjected to centrifugation for the purpose of recycling27,28.

Preparation of Bacterial Culture: A bacterial culture is created by cultivating bacteria in a media that is abundant in nutrients, hence facilitating their development and multiplication. The culture is placed in a controlled environment to facilitate bacterial growth. Following the incubation period, the culture is examined. If the antibacterial treatment is effective, there should be a region where bacterial proliferation is impeded. The antibacterial activity may be quantified by measuring and using this zone. The antibacterial activity has been tested against both Gram-negative (Escherichia coli = E. coli) and Gram-positive (Staphylococcus aureus = S. aureus). The experiment begun with 5 mg/ml starting concentration for the synthesized samples to be examined. The inhibition zone has been measured after 24 h of incubation at 37 °C under visible light.

Discussion

XRD

Crystallinity was clarified by XRD analysis that 2θ were introduced in 10–70 scope. For silver, the bands were confirmed its existing, utilizing JCPDS no. 04-0783. Various peaks for silver attained at 2θ = 38.3°, 43.9°, 65.1°, and 77.3°, which corresponds to the Bragg’s reflections of the (111), (200), (220), and (311) crystal planes of the face-centered cubic (fcc) structure of metallic silver29. Figure 1 also marks peaks for Nd2O3 according to JCPDS no. 21-057930. The peaks of Nd2O3 which are at 2θ = 27.8, 29°, 40.2°, 49°, 51.6, and 57° ,can be indexed to the (100), (002), (102), (110), (103), and (112), respectively31. The resultant patterns do not refer to any major disorders owing to the silver nanoparticle's contribution17.

Figure 1
figure 1

XRD of Pure Nd2O3 NPs, and Ag/Nd2O3NPs.

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FTIR

The FTIR spectra are revealed in Fig. 2. It can be observed that the broadband at 3455 cm−1 for pure oxide while adding silver NPs does not cause a noticeable shift that O–H stretching vibration of the –OH group appears at 3448 cm−132. The revealing absorption peak at 3554 cm−1 is assigned to thio-urea residual N–H stretching33. The Neodymium oxide (Nd2O3) NPs strong band centered at 669 cm−1 is attributed to Nd–OH which shows significant diminishing with adding Silver nano-particles32. The centered bands at 588 cm−1 was because of –O stretching of Nd30. The previously mentioned bands confirm Nd2O3, Ag/Nd2O3 chemical composition.

Figure 2
figure 2

FTIR of Pure Nd2O3 NPs, and Ag/Nd2O3NPs.

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TEM

Nd2O3 NPs microstructure is demonstrated in Fig. 3a. Distinct grains for pure Neodymium oxide are appeared, while Silver nanoparticles appeared with well-defined grains upon the Nd2O3 matrix. Silver nano-particles average grain size is 9.2 nm. As well, Nd2O3 introduces significant crystalline portions with distinct grain borders. In addition, the circle inserted in the same figure displays fringes of diffraction points; thus, the presence of well-crystallized Neodymium oxide is approved17. The displayed Fig. 3b micrograph confirms the good distribution of Ag NPs upon Nd2O3, besides the well matching with XRD results. The red circles represent AgNPs which is inside the surface of Nd2O3 which is represented in blue circles. Figure 3c represent saed pattern for Ag/Nd2O3NPs and Fig. 3d obtained the particle size histogram of Ag/Nd2O3NPs.

Figure 3
figure 3

TEM micrographs of (a) Pure Nd2O3 NPs, (b) Ag/Nd2O3NPs, (c) saed pattern for Ag/Nd2O3NPs, (d) particle size histogram of Ag/Nd2O3NPs.

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Optical study

Studying the optical characteristics of nano-composite have an excessive curiosity in order to discover their proper usage. The optical characteristics of Nd2O3 and Ag/Nd2O3 nanoparticles were inspected by UV–Vis spectroscopy in wavelengths ranging from 200 to 1100 nm. The band at 244 nm is for Nd2O3 NPs that allied an interchange of electrons among the valence and conduction orbits32. The optical band gap energy has been assessed by mode suggested by Wood and Tauc. Aiming for optically induced transition understanding, optical band-gaps are obtained from UV absorption spectra. The technique is based on the absorption of a relatively high energetic photon in comparison to bandgap energy. Briefly, there are two types of optical transitions based on absorption edge, they are direct and indirect transitions. Both transition types involve an interaction of the valence band with an electromagnetic wave.

The Optical absorption coefficient (α) is calculated by Beer–Lambert’s equation34. After that, the absorption coefficients (α) plot against (hν) in Fig. 4, showing absorption edge shift was obtained due to silver assimilation. The Eg values were almost 6.8 e.V for pure Neodymium oxide (Nd2O3) NPs32. On the other hand, Ag NPs insertion causes shifting of λ to lower frequency35, besides lowering absorption edge to 6.1 e.V30. this confirms the well spreading of silver NPs36. As well, the band-gap is estimated from \(\alpha hv ={A(hv -Eg)}^{m}\) equation37,38, where (hν) is for photon energy, (Eg) is for band-gap, (A) is for band tailing parameter, and (m) direct transition is at m = 0.5, and indirect transition is at m = 2).

Figure 4
figure 4

Optical behavior of Pure Nd2O3 NPs, and Ag/Nd2O3 NPs.

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Bandgap widened with size shrinkage owing to electron confinement at nano-scale which is famed for the “quantum size effect”. The diminishing of bandgap refers to the perfection in crystallographic ordering by adding Ag NPs that enhance boosting in electronic localization upon nano-composite ingredients39,40. Consequently, these interpretations boost these compositions’ usage in sensors industries.

Finally, The refractive index (n) is computed using Dimitrov and Sakka formula as a function of indirect energy band-gap.

$$\frac{{n^{2} - 1}}{{n^{2} + 1}} = 1 - \sqrt {\frac{{Eg_{i} }}{20}}$$
(1)

In likewise, addition, the refractive index alteration as listed in Table 1 refers to varying packing density36. This specifies Nd2O3 NPs and Ag/Nd2O3 NPs to be utilized in optoelectronic devices.

Table 1 Optical properties of Nd2O3 NPs and Ag/Nd2O3 NPs nano-composite.
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Methylene blue (MB) degradation assessment by Uv–Vis Absorption Analysis

The characteristic absorbance peak of methylene blue dye was centered at 618 nm. Throughout the irradiation step, the crest in both cases (Nd2O3 and Ag/Nd2O3) shows a regular decline in absorbance owing to hypochromic influence. The absorbance of MB solution shows a dwindling pattern with time. this could explain the adsorbing capability of both tested compositions, However, the silver-containing composition exhibits a higher potential for degradation41. This may be explained by Nd2O3 capability to absorb photons that enhance electron excitation, generating positive holes. The electron–hole pairs travel individually to the surface of oxide and lead to redox series with adsorbed species, generating highly reactive oxygen species (ROS). These oxy-species interact with adsorbed contaminations leading to the decomposition process42. However, after short time electrons and holes recombine causing a decline in its photo-degradation potential. Thus, decreasing their recombination is executed by metals that act as cationic dopants42. Further, in this study degradation assessment of pure Nd2O3 and AgNd2O3 nanoparticles Mixed System is executed under visible light. Spectra display a gradual dropping of MB content with irradiation time. The MB degradation efficiency is detected via peak intensity, thus the dye concentration shows a declining pattern with the time that confirms its efficiency in removing the MB dye. Mixed System shows more efficient degradation owing to silver nano-particle insertion that the MB concentration dropped to half of its starting point at 150 min. Also, The photo-conversion capability using pure Nd2O3 as a reference photo-catalyst was lower than those of nano-composite, reaching 33% after 150 min of light irradiation, as obtained in Fig. 517. In conclusion, crystallinity, and ROS generation noticeably persuade the surface area, number of active sites, and decline in the particle size that enhances dye decomposition.

Figure 5
figure 5

The degradation of MB using (a) pristine Nd2O3 NPs, (b) Ag/Nd2O3NPs.

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The process of degrading MB dye by photocatalysis using Ag/Nd2O3 nanocomposite consists of many sequential stages: The photocatalytic process starts upon light absorption by the Ag/Nd2O3 nanocomposite, resulting in the generation of electron–hole pairs. Subsequently, the electrons that are in an excited state undergo a reaction with molecular oxygen, resulting in the formation of superoxide radicals. Simultaneously, the positively charged holes have the ability to directly oxidize the dye or water, leading to the generation of hydroxyl radicals. Subsequently, these radicals exhibit a high level of reactivity, enabling them to break down the dye molecules. Subsequently, the reactive species engage in interactions with the dye molecules, resulting in their fragmentation into smaller, less detrimental constituents43,44,45. This is the first stage at which the perceptible hue of the dye begins to diminish. Ultimately, the ideal outcome is for the dye molecules to undergo full mineralization, resulting in the formation of innocuous chemicals such as water and carbon dioxide43,44,45. The efficacy of this procedure relies on several aspects, such as the characteristics of the nanocomposite, the intensity and wavelength of the light, and the concentration of the dye1. The Ag/Nd2O3 nanocomposite exhibits enhanced efficacy attributed to the inclusion of silver, which facilitates light absorption and facilitates the dissociation of electron–hole pairs46,47.

While previous research mentioned in Table 2 demonstrated significant photocatalytic activity in the removal of MB dye, the composites that were prepared did not exhibit any antibacterial properties. Additionally, the pH of the reaction was not specified in the previous studies. Furthermore, the concentration of dye used was very low. In contrast, our work investigates the photocatalytic activity using a 20 ppm dye concentration and at a pH of 6.

Table 2 comparison from different studies about the removal efficiency of different dyes.
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Anti-bacterial activity

As E. coli, and S. aureus are the two greatest widespread bacterial species, especially after implant surgery. The introduced performance shows almost doubling an antibacterial efficiency with merging silver into pure Neodymium oxide (Nd2O3) nanoparticles. For illustration, as shown in Fig. 6, S. aureus demonstrates an inhibition zone of 9.3 ± 0.5 mm for pure Neodymium oxide (Nd2O3) nanoparticles (NPs), 16.7 ± 0.4 mm for Ag/Nd2O3 nano-composite. E. coli inhibition zones reveal bacterial inhibition capacity under the tested inhibitor, it shows 8.8 ± 0.4 mm for Neodymium oxide and 15.9 ± 0.3 mm for Ag/Nd2O3 nano-composite. The introduced antibacterial pattern is explained by the different nature of gram-positive and gram-negative bacteria, for example, E. coli and S. aureus have a divergent structure with thicker cell wall peptidoglycan layer in gram-positive than that of the gram-negative species54. Derakhshi et al.55 point to the active antibacterial role of silver nanoparticles in gram-negative bacteria with 800 μg/mL. Additionally, antibacterial composite amount and nature affect the subsequent results. The introduced germicidal valuation is performed in dark, neglecting the plasmonic effect of Ag–NPs. Likewise, The mechanism of antimicrobial activity upon using silver NPs has involved the interaction of silver ions with thiol groups in pathogenic enzymes and proteins, resulting in cell death56. Additionally, the effectiveness of released reactive oxy-Species is affected by the inserted silver quantity, size, and distribution57. Further, the released oxonium ions (H3O+) from Nd2O3 mineral trioxide interrupt the cellular pH, thus bacterial reproduction is disturbed, also does not allow drug-resistant phenomenon occurrence58. As well, Wang et al.59 studied mineral trioxide/silver nanoparticles nano-composite, finding significant performance of La2O3 or Ag–La2O3 nanoparticles in inhibiting E. coli and S. aureus growth. Therefore, nanomaterials specially mixed systems are highly recommended for biological applications. Nd2O3 nanoparticles have many mechanisms by which they might impact microorganisms. To begin with, they may cause modifications in the bacterial community's composition by changing the prevalence of uncommon and delicate taxa, therefore reducing the overall effectiveness of the community. In addition, Nd2O3 nanoparticles have the ability to connect with the cell wall of bacteria, especially in Gram-positive bacteria that have a thick peptidoglycan layer60,61,62,63. This interaction has an impact on the integrity and function of the cell wall. Nano-Nd2O3 may disrupt enzyme activity, specifically affecting enzymes that are essential for soil carbon and nitrogen cycle60. These enzymes are critical for bacterial survival and function. In addition, like other metal oxide nanoparticles, Nd2O3 nanoparticles has the capability to produce reactive oxygen species (ROS), which may induce oxidative stress in bacterial cells. Oxidative stress may lead to the impairment of vital cellular molecules and ultimately cause cellular demise64. Moreover, upon contact with bacterial cells, the nanocomposite liberates silver ions (Ag+), which interfere with the integrity of the cell membrane, eventually leading to the demise of the cells61,65,66,67. The Nd2O3 nanocomposite exhibits antibacterial characteristics due to the synergistic effects of these coupled processes.

Figure 6
figure 6

Antibacterial behavior of Pure Nd2O3 NPs, and Ag/Nd2O3NPs.

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Conclusion

Structural, and compositional study of pure Neodymium oxide (Nd2O3 NPs), and Silver (Ag)/Neodymium oxide (Nd2O3) nano-composite, using XRD, FTIR, and TEM techniques. This study emphasizes optical behavior, MB dye degradation potential of pure Nd2O3 NPs, and (Ag/Nd2O3) nano-composite, alongside revealing their antibacterial performance of silver and trioxide mineral interaction with bacterial species. For instance, S. aureus, and E. coli enlargement of inhibition zone under Ag NPs insertion. S. aureus inhibition zone broadened from 9.3 ± 0.5 mm for pure Nd2O3 to 16.7 ± 0.4 mm for Ag/Nd2O3 composition, while E. coli inhibition zones extended from 8.8 ± 0.4 mm for Neodymium oxide to15.9 ± 0.3 mm for Ag/Nd2O3. Also, optical behavior displays band-gap contraction with assimilation with Ag NPs, which improves electronic localization. That direct and indirect transitions dropped from (6.7 to 6.1) and (5.2 to 2.9 e.V), respectively. Concerning the methylene blue degradation, Ag/Nd2O3 shows more efficient Methylene blue degradation than pure Nd2O3 in that the MB concentration dropped to almost 50% of its starting point after 150 min, while pure Nd2O3 reached 33% after 150 min of light irradiation. On the other hand, TEM displays the studied compositions microstructures confirming the good distribution of Ag NPs (average size 9.2 nm) upon Nd2O3. The results interpretations boost usage of such composites in sensors industries, and water treatment. The research team highlights the significance of investigating the prolonged stability and resilience of the Ag/Nd2O3 nano-composite under actual environmental conditions. Assessing the material’s performance under various environmental conditions, such as temperature, pH, and humidity, would provide useful insights for its practical utilization. Moreover, the authors propose investigating the potential of the Ag/Nd2O3 nano-composite in other domains apart from antibacterial applications. For example, exploring its photocatalytic qualities for water treatment or its sensing capabilities for environmental monitoring might provide new opportunities for its use in these domains.