A Review of Iron polyphenol green nanomaterials and their environmental applications

A Review of Iron polyphenol green nanomaterials and their environmental applications

Jinat Aktar

Center for the Environment

Indian Institute of Technology Guwahati, Guwahati, Assam, India 781039

Abstract – Ironpolyphenol green nanomaterials have evolved as a promising class of sustainable materials due to its low toxicity, ecofriendly, and low-cost characteristics. This review investigates the synthesis, characterization, and prospective environmental implications of ironplant polyphenol complexes, with precise prominence on their function as green nanomaterials. Polyphenols developed from plant sources such phenolic acids act as natural antioxidant, and stabilizing agents, allowing formation of iron-based nanostructures under mild and environment friendly conditions. The review also enlightens the basic mechanisms governing ironpolyphenol complexation, including redox interactions, coordination reactions, and antioxidant activity, which mutually control material stability and reactivity.

Moreover, the review also imparts special focus on environmental applications, especially in wastewater treatments, where such nanomaterials validate high efficacy for remediation from heavy metals, dyes, nutrients, and even emerging contaminants through adsorption, and redox transformation. Their versatility goes beyond water treatment to beneficial agricultural applications, where ironpolyphenol complexes enhance bioavailability of micronutrient, soil health, and plant stress resistance. Furthermore, the intrinsic antimicrobial properties of polyphenols, synergistically improves by iron- mediated reactive oxygen species production, are reviewed in the context of bacterial resistance by damaging their cells.

Conclusively, this review highlights the prospectives of iron polyphenol green nanomaterials as economical, biodegradable, and scalable substitutes to conventional synthetic nanomaterials. Current challenges, knowledge gaps, and future research directions related to material optimization, environmental fate, and large-scale implementation are also discussed to facilitate their transition from laboratory research to real-world applications.

Keywords – Adsorption, green synthesis, iron polyphenol, pollutant removal, antimicrobial activity.

1. INTRODUCTION

   In the twenty-first century, the worlds population is confronted with serious water quality challenges. Despite the fact that water is the most vital natural resource, just 1% of it is suitable for human use [1]. Approximately 1.1 billion people do not have access to safe drinking water, according to the World Health Organization (WHO, 2015). The water issue is exacerbated by poor water management, the generation of a massive volume of hazardous waste, and its improper disposal [2]. The inevitability of wastewater treatment reinforces the need to develop sustainable treatment options. Pollutants released in wastewater can be hazardous to aquatic life and able to change the condition of the aquatic ecosystem [3]. Various approaches for purifying wastewater have been developed, such as sedimentation, membrane filtration, flotation, precipitation, adsorption, ion exchange coagulation, oxidation, etc. [46]. Among them, adsorption is a much simpler and attractive procedure in comparison to other methods due to its high efficiency and ease of handling. Besides, it shows good efficiency in low concentrations of pollutants. Traditional methods for removing contaminants from wastewater are not cost- effective, particularly at low pollutant concentrations [7]. Moreover, adsorption has also been in practice for decades in the treatment of wastewater from distinct sources [810]. Additional benefits include the recovery of pure metal for recycling and the reuse of the adsorbent [11]. However, conventional adsorbents are chemically modified, susceptible to secondary effects, and expensive. Therefore, in the current scenario, there is an obvious need for sustainable, cost-effective, energy-efficient, and green adsorbent. This review is an attempt towards contributing to the water treatment process using eco-friendly efficient bio- adsorbent.

   Adsorption by biomaterials, commonly known as biosorption, is a popular approach where different parts of plants, dry leaves, shoot powder, barks, agricultural wastes, fruit shells, and a variety of other biological materials have all been investigated over the years (Figure.1) (Table 1.1).

   Activated carbon from coconut coil Eichhornia crassipes (Water hyacinth)

   Methylene blue [15]

   Phosphorus [16]

   Water hyacinth was modified by citric acid

   Ni (II), Cu (II), and Cr (VI)

   [17]

   Bamboo dust carbon Methylene blue [18]

   Tea extract mediated nanoparticles

   Malachite green, rhodamine B

   [19]

   Figure 1. Schematic representation of green synthesis of nanoparticles

   Bio-adsorbents have been the subject of a recent flurry of research articles due to their simple process, biodegradability, low cost, nontoxic, ecofriendly, and year-round availability. Some of the selected bio-absorbents used for the removal of different kinds of pollutants from wastewater are enlisted in the following table.

   Table 1.1. Selected list of different bio-adsorbent used in

   pollutant removal.

   Adsorbent Pollutant References

   Rice hull ash Lead (II) [1] NaOH treated rice husk Malachite green [2]

   Wheat bran Chromium (VI) [3]

   It can be concluded from the above table that different parts of plants, different agro-waste, water hyacinth, etc., in dry or powder form, in some modified form, after converting in charcoal were used for adsorption of different heavy metals, dyes, and other pollutants present in wastewater. However, in many literatures activated charcoal from different biomaterials were used for water treatment purposes but, energy consumption and air pollution is an adverse side of it. The use of biomaterials extract and different precursor salts for the synthesis of different metal-ligand complexes is another well- known area of study regarding environmental application and environmental chemistry.

   The presence of polyphenol in different parts of plants like root [29], shoot, leaves, seed [30], bulk, etc., acts as a ligand and makes complexation in the presence of different precursor metal salts. The specific components that cause plant-mediated metal complex synthesis and the mechanism of action are still unknown. Different secondary metabolites such as flavonoids, polyphenols, terpenoids, and heterocyclic compounds have been suggested to react with metal salts and produce plant mediated-metal complex [31,32]. Different polyphenols like gallic acid, ellagic acid, quercetin catechol derivatives etc., present in plant extracts are soluble in water, and some organic solvents react with precursor iron salt solutions (Figure 2).

   Polyphenols are chemically interesting due to their redox activity, which is the origin of their function as an antioxidant.

   Ocimum americanum L. seed pods

   Aegle marmelos correa

   (Bael fruit) Okra, pumpkin, grape,

   and squash

   Chromium (VI) [4]

   Chromium (VI) [5]

   Copper ions [6]

   Polyphenols are structurally diverse, and their reactivity depends on pH. The size distribution of these synthesized materials usually belongs within nano ranges [28,33,34]. Due to their high surface-to-volume ratio, nanoparticles are well known for their application in water treatment.

   Sugarcane bagasse Cu2+, Cd2+, and Pb2+ [7]

   Sugarcane bagasse Rhodamine B (RhB) andBasic Blue 9

   [8]

   Iron oxyhydroxide NP coated rice husk Azadirachta indica (Neem)

   Fluoride [9]

   Lead (II) [10]

   Rambutan peel based activated carbon

   Remazol Brilliant Blue R

   [11]

   Phoenix tree leaf powder Methylene blue [12] Pea peels Bismarck brown [13]

   Coconut husk Mercury (Hg0) [14]

   		silver
   Stemona		Gold	4-nitrophenol,	[25]
   tuberosa Lour			methylene blue,
   			methyl orange and
   			methyl red
   Lagerstroemia	Leaf	Gold	methyl orange,	[26]
   speciosa			bromophenol blue
   			and bromocresol
   			green, and 4-
   			nitropheno
   Hibiscus	Flower	Copper	Nitrate	[27]
   sabdariffa
   Citrofortunella	Leaf	Copper	Rhodamin B	[28]
   microcarpa
   Moringa	Leaf	Iron	Nitrate removal,	[29]
   oleifera
   Dodonaea	Leaf	Iron	Antimicrobial	[30]
   viscosa
   Laurus nobilis	Leaf	Iron	Antimicrobial	[31]
   L			against Listeria
   			monocytogenes
   			bacterium.
   Carica papaya	Leaf	Iron	Remazol yellow	[32]
   			RR dye
   			degradation

   Figure 2. Structure of selected plant polyphenols.

   Tea Leaf Iron Malachite green,

   rhodamine B and methylene blue dye removal

   [19]

   Hence, these materials are also well known as green synthesized nanoparticles. The small size ranges of the

   Simmondsia chinensis

   Seed Iron Fluoride removal [33]

   materials possess increased surface area, which helps in the adsorption of pollutants due to increments of active sites. Moreover, the use of plant materials for the green synthesis of nanoparticles is useful for its cost-effectiveness, bulk

   Nettle and

   Thyme Azadirachta indica

   Leaf Iron Cephalexin (CEX)

   antibiotic removal Leaf Iron ammonia nitrogen,

   COD

   [34] [35]

   production, and effective reproducibility process. Table 1.2 represents various plant parts utilized in different literature for synthesizing metal-based nanomaterials.

   Eucalyptus

   teretiornis, Eucalyptus globules

   Leaf Iron Dye removal [36]

   Leaf Iron Chromium [37]

   The production of green nanoparticles provides numerous

   oolong tea Leaf Iron Malachite green [38]

   advantages over traditional methods that include no energy requirement, significant affordability, and eco-friendliness as

   Green tea Iron Methylene blue and methyl orange

   [39]

   no toxic byproducts are produced [35]. The benefit of green produced nanoparticles synthesis is that they do not require

   Lantana

   camara

   Leaf Iron Ni (II) [40]

   synthetic reducing agents, which are detrimental to the environment. Additional benefits of green synthesis over traditional ones include the possibility of bulk scale production, no requirement of external conditions such as high pressure and energy [36].

   Table 1.2. Literature of plant-mediated synthesis of the nanoparticles.

   Oak, mulberry

   and cherry Eichhornia crassipes, Lantana camara and Mimosa pudica

   Leaf Iron Arsenic (III),

   Chromium

   Leaf Iron Nitrate and phosphate

   [41] [42]

   Vaccinium

   Shoot

   Iron Arsenic [43]

   Plant name	Plant part	Metal salt	Application	Refere nces		corymbosum	and leaf
   Benjamina	Leaf	Silver	Cadmium	[20]		Tea extract	Leaf	Iron	Bromothymol blue	[44]
   Trigonella	Leaf	Silver	Reactive blue 19	[21]

   foenum-			and Reactive
   graecum			yellow 186
   Terminalia	Fruit	Silver	Methyl orange,	[22]
   bellerica			Eosin yellow
   kernel
   Palm tree	Leaf	Copper	Methylene blue	[23]
   (Phoenix		silver
   dactylifera)
   Mussaenda	Leaf	Gold	Rhodamine B,	[24]
   glabrata		and	methyl orange

    

   Table 1.2 summarizes the utilization of several plant species for the synthesis of plant-mediated metal nano complexes. Different precursor metal salts like silver, gold, copper, nickel, and iron were used for complexation purposes. Among them, some metal salts are quite costly, which makes the synthesized materials expensive, and some have some toxic effects on the environment. However, the use of iron salt for synthesis makes the material cost-effective and environmentally friendly. Apart from it, iron is a common earth element also very essential for

   the growth of the living body. Iron forms strong bonds with the phenolic OH group of the polyphenols to form a complex. Iron after complexation generally prefers the Fe (III) oxidation state, but in a mixture, some amount of Fe (II) could also be present [60-61].

   Polyphenols can react with iron in various ways depending on pH, iron oxidation state, metal-ligand ratio, and oxygen present. Depending upon pH, polyphenols and polyphenolic- metal complexes can be varied structurally, show different coordination modes [6062]. Iron binds to polyphenol due to the antioxidant actions of polyphenols [64, 71-73].

2. APPLICATION OF IRON-PLANT POLYPHENOL COMPLEXES IN WASTEWATER TREATMENT
   1. Wastewater Treatment

      Zhu et al. (2018) used green tea extract was utilized for the synthesis of zero-valent iron/Cu nanoparticle synthesis at N2 atmosphere and employed for the removal of Cr (VI) from aqueous solutions [74]. At pH 5, zero-valent iron/Cu nanoparticles were capable of 94.7 % removal of 5 mg/L of Cr

      (VI) solution. The material was characterized y FESEM, FTIR, and PXRD (peak is unclear, polyphenol not measured, no iron-polyphenol ratio). Pan et al. (2019) used peanut skin for iron-based nanoparticles synthesis purposes [75]. This study described the core-shell structure of nano complex with Fe (0) in the core, surrounded by the biomolecule layer. The material was characterized using PXRD, FTIR, XPS, and UV- spectroscopy. Moreover, SEM images showed agglomeration of the particle. Materials showed 100% removal of 10 mg/L of Cr (VI) at pH 4.7 and 2 g/L of dose. Similarly, Jin et al. (2018) synthesized zero-valent iron nanoparticles using eucalyptus leaf extract and applied for chromium removal [76]. The experiment was executed with 10 mg/L of chromium solution, at pH 4, nanoparticle dose of 1.4 g/L, 30C. Results showed 86% removal of total chromium.

      Ehrampoush et al. (2015) utilized tangerine peel extract, which acted as a stabilizing agent for the synthesis of iron oxide nanoparticles by co-precipitation method and utilized for cadmium adsorption [77]. The average size of the particles in DLS was 200 nm. Moreover, the removal experiment showed 88% removal of 20 mg/L of Cd at 4 pH, with a material dose of 4 g/L.

      Machado et al. (2017) utilized the oak leaves to synthesize nanoscale zero-valent iron and analyzed the degradation of a popular antibiotic and amoxicillin in wastewater [78]. They studied the degradation of 100% of amoxicillin occurred at 95 min of contact time in an aqueous solution with amoxicillin and nanoparticle in the ratio of 1:15. Apart from these, Lantana camara fruit extract was used by Nithya et al. (2018) for the synthesis of iron oxide nanoparticles and applied for the removal of Ni (II) [34]. With the dose of the nanoparticle of 1.2 g/L, 99% removal of 100 mg/L of the solution was observed at pH 7. Manquián-Cerda et al. (2017) employed the plant leaves and shoots extract of Vaccinium Corymbosum to synthesize iron nanoparticles and apply them for arsenate removal [58]. Nanoparticles were characterized using TEM, SEM (52 nm), BET, PXRD. They reported that the maximum removal of 76% of 200 mg/L arsenates was observed at pH 4, and 120 min of reaction time. Furthermore, Sajadi et al. (2016) utilized the plant seeds of Silybum marianum L. for the synthesis of copper-supported iron nanoparticles and applied them against

      nitrobenzene reduction [79]. Materials were characterized by XRD, TEM, EDS, and UVvis spectroscopy. Maximum removal of 96% was observed for 1 mmol of concentration at

      90 min of reaction time. The following tables show the summary of plant-mediated iron-nano complexes synthesized by using different plants, characterized, and applied to remove pollutants from wastewater.

      Table 1.3. Use of plant-mediated nanoparticles in wastewater treatment.

      Plant name	Application	Condition	Removal or uptake	Comment	Refere nces
      Green tea,	Nitrate	20 mg/L, 1g dose	50 and 35%	Total phenol not measured. EDS only.	[45]
      Eucalyptus				PXRD peak not clear
      leaf Nephrolepis	Chromium	50 mg/L of	90%	XPS, EDS, Fe+3, Fe+2, Fe0	[46]
      auriculata	(VI)			Nitrogen atmosphere for synthesis. The
      				dose is not clear.
      Citrus maxima	Chromium	100 mg/L, 90	99%	TEM, EDS, XPS, IR, DLS.	[47]
      peels	(VI)	min,		Nanoparticles in solution phase. The
      				dose of material is not clear. Removal
      				was not checked with varying conditions.
      Oak, mulberry and	Arsenic (III),		300 mg/g	Polyphenol not measured, no	[41]
      cherry NPs			200 mg/g and	characterization for the state of iron.
      			250 mg/g	Claim Zero valent NPs
      Tangerine peel	Cadmium	4 pH, 4 g/L of	88%	No polyphenol estimation. SEM, DLS	[48]
      extract		dose, 20 mg/L of		only. In removal, no triplicates
      		Cd
      Nettle and Thyme	Cephalexin	25 mg/L, 0.1g	80%	Powder XRD, peaks of different state of	[34]
      leaf	antibiotic	dose		Fe were there. Claim Zero valent NPs
      Cupressus	Methyl	25 mg/L, with	95%	Polyphenol not measured. PXRD	[49]
      sempervirens leaf Hibiscus flower	orange dye Rodamine B	H2O2, 1 g/L dose	20 mg/g	Synthesis and characterization not	[50]
      petals				cleared, EDS done. Claim Zero valent
      				NPs
      Eucalyptus leaf	Acid black		71% and 84%		[51]
      	194		removal	Iron-Polyphenol complex
      	COD, N
      Oolong tea	Malachite	50 mg/L conc,	73%	EDS, PXRD.	[38]
      	green	0.01g dose, in		NP in solution phase
      		40min.
      Iron-polyphenol	Acid red 94	2000 mg/L initial	Uptake is 463	IR, TEM only. NPs in solution used. Not	[52]
      with Eucalyptus	and MB	conc. 24hr contact	mg/g for acid	in powder form. Dose and other
      and 2 other plants		time.	red and 64 mg/g	parameters not clear
      			for MB
      Iron-polyphenol	Acid black	1300 mg/L of	> 80% removal.	UV, IR	[36]
      with Eucalyptus	194	2000 mg/L initial		NPs in solution used. Not in powder
      leaf		conc. 24h contact		form. Dose and other parameters not
      		time.		clear
      		pH 3-9
      Tea leaf	Malachite	0.01 g of dose, 50	Uptake of 190.3	IR, XPS, zeta potential.	[19]
      	green (MG),	mg/L initial conc.	mg/g, 186.93/p>	Only kinetics study
      	methylene		mg/g and 182.4
      	blue (MB),		mg/g, respective
      	and
      	rhodamine B
      	(RB)
      Fe-zero with Guava	MB	50 mg/L conc,	> 94% removal	UV-TEM-IR.	[53]
      leaf		2.4g/L dose.		Claim Zero valent NPs
      Tea leaf-Iron,	Real textile	Initial- 350 mg/L	72% removal	XRD, SEM, EDX, different modeling.	[54]
      NZVI activated	water	conc. dose 0.7g.	for AC, 85%	UV peak not mentioned.
      carbon comparison		pH 5 for NZVI, 8	removal for
      		for AC, and 7 for	green nano. And
      		green nano.	71% for nZVI
      Fe3O4 coated-tea polyphenol	MB removal	3.5 mg/L conc, dose 1g/L, pH >7.	Uptake 5mg/g	ESI mass, PXRD, raman, VSM, BET surface area 126	[55]

      It was observed that no confined protocol was followed for synthesis purposes. In different reports, various kinds of synthesis processes were used. Thus, there exists a scarcity of knowledge regarding detailed analysis of zero-valent iron, irrespective of results reported in various literature. In some literature, the formation of zero-valent iron was claimed without proper characterization of the materials. However, in some literature, iron complexes were separated using centrifugation and applied as a powder form. Whereas, according to some other experimental results, materials were present in the suspension phase. So to say, basically, in all the studies, the efficiency of iron- polyphenol complexes in pollutant removal was studied.

   2. Application in Agriculture

      Iron is an important element for plant growth, photosynthesis capacities, as well as different biochemical processes. It is also crucial for the structure of chloroplasts, as well as Fe-S group is essential to ensure electron flow in the thylakoid membrane [90]. Iron also has an important role in synthesizing chl-b from chl-a [91]. In different literature, iron-based nanomaterials improved plant growth in terms of biomass, root-shoot growth, photosynthesis capacity, productivity, etc. [92,93]. However, some literature reported the negative impact on the plants, like the accumulation of iron nanoparticles in the root surface and cause the suppression of water uptake, suppression on growth, induce stress, etc. [9496]. Table 1.4. Summarizes different studies on the effect of iron-based nanoparticles on plant species.

      Table 1.4. Positive and negative effects of different metal complexes on different plant species.

      Materials	Species	Analysis		Comment	Refere nces
      Iron oxide NPs	Lemna minor	No. of leaves, dry accumulation in chlorophyll, Lipid	weight, Fe the root, peroxidation	At high concentration, chlorophyll content decrease, MDA production increased. Showed toxicity on plant	[56]

      were measured.

      and kill plants within 7 days in all concentration range.

      Iron (III) oxide NPs

      Vigna radiata Dry biomass, root-shoot growth, Fe

      and As analysis, proline test, H2O2 content, total antioxidant capacity, SEM, etc., were measured.

      The effect of Seedlings raised in AsO4 3 and Fe2O3-NPs, and in combined conditions were evaluated in this study. AsO4 3- reduces the seedling growth. Fe2O3-NPs showed resistance to arsenic toxicity.

      [57]

      Micro and nano-sized iron

      Lepidium sativum, Sinapis alba, and Sorghum saccharatum

      Germination index, elongation, biomass, microscopic observation was checked.

      No significant phytotoxicity effects could be detected. Increased seedling length and biomass production were observed.

      [58]

      Fe3O4

      Cucumber and

      Root elongation, germination index,

      Decrease in

      root growth and

      [59]

      nanoparticle

      lettuce

      relative seed germination was checked.

      germination index.

      Zero-valent iron Cattail and

      hybrid poplars plant species

      Root-shoot weight, length were measured. FESEM, EDX, TEM were also checked.

      The result showed the toxic effect on cattail species at >200mg/L of concentration. While at a lower concentration, it enhances plants growth.

      [60]

      FeOx NPs	Lactuca sativa	Germination test, root shoot length	1mg/L dose helped in germination and growth. However, 20mg/L dose suppressed the germination of seeds.	[61]
      Zero-valent iron	Oryza sativa cv	Germination test, growth,	Increased root-shoot length, biomass,	[62]
      nanoparticle		hydrolytic enzyme activities,	and chlorophyll. absence of membrane
      		antioxidant, proline, chlorophyll.	damage, decrease in proline content.
      Zero-valent iron	Peanut	Germination test, growth, TEM	40 and 80 mol/L of dose better of	[63]
      nanoparticle			growth of plants.

      In the above table, it could be seen that iron complexes were able to show positive effects by increasing the plants productivity, growth, and biomass. On the other hand, some literature showed the negative influence of iron complexes on plants, such as the deposition of iron nanoparticles in the root surface, which reduces the water intake, affects growth rate, and induces stress.

   3. Antimicrobial Activity

      The application of iron complexes on nanomaterials has significant potential in the inhibition of various diseases causing bacteria and fungi. Although the mechanism of these metal nano compounds, antimicrobial properties are

      yet to be known. A number of the proposed mechanisms of antimicrobial activities have been suggested, including breakage of the cell membrane, damage of DNA, etc. Lee et al. (2008) studied the effect of zero-valent iron on E. Coli and studied the severe physical disruption of membranes which could have induced oxidative stress and showed the high antimicrobial effects of dissolved iron [104]. However, the absence of a harmful effect of nZVI on the species was observed by Stefaniuk et al. (2016), and further growth of Gram-positive bacteria was found [105]. The following table shows the summary of the inhibition effect of iron polyphenol complexes on different microbes.

      Table 1.5. Antimicrobial activity of iron nanoparticles.

      Materials	Species	Comments	References
      Iron oxide NPs with	E. oli and S. epidermidis	Kirby-Bauer diffusion assay with 70 µL of material.	[64]
      Cynometra ramiflora		<p(dose is not clearly mentioned). The exact area of ZOI
      leaf extract		is not mentioned.
      Gallic-Aluminium and	E. oli	Only iron-gallic acid complex is effective in showing	[65]
      gallic-iron complex		inhibition. ZOI of the iron-gallic complex is 12.00 ±
      		0.25 mm with 50L of genotoxic dose.
      Iron oxide NPs with	Trichothecium roseum,	With 0.5 mg/ml dose of iron nano, the ZOI of the	[66]
      tannic acid	Cladosporium herbarum,	different fungi are as follows:
      	Penicillium chrysogenum,	T. roseum, (22 mm)
      	Alternaria alternata, and	C. erbarum, (18 mm)
      	Aspergillus niger.	P. hrysogenum,(28 mm)
      		A. alternate (21 mm) and A. niger (26 mm).
      Iron oxide magnetic	E. coli, P. mirabilis and B.	8 mm ZOI with 12.5 µg/disc of dose.	[67]
      NPs with Argemone	subtilis
      mexicana L. leaf
      extract
      Iron oxide NPs	Staphylococcus aureus,	With a dose of 0.15 mg/mL of NPs, the ZOI against S.	[68]
      	Escherichia coli, and	aureus, E. coli, and P. aeruginosa is 29,26,28 mm.
      	Pseudomonas
      	aeruginosa
      Iron oxide NPs	Bacillus subtilis and E. coli	Showed antimicrobial activity at > 50 µM. relatively at	[69]
      		high concentrations
      Fe3O4-NPs	Bacillus cereus and Klebsiella pneumoniae	With 5 g/mL of MIC, against K. pneumoniae and B. cereus showed	[70]
      		26 mm and 22 mm zone of inhibitions, respectively.
      		MBC for these strains was observed at 40 g/mL of
      		Fe3O4-NPs, showing 4050% loss in viable bacterial
      		cells and 80 g/mL of concentration exhibiting 9099%
      		loss.

      This table summarizes the capabilities of different types of iron nano-complexed against various microorganisms to check their inhibition. Different kinds of methods were used for the estimation of the antimicrobial activity of iron- based materials. The phytochemicals are capable of showing antimicrobial activity and fight against several pathogenic diseases [113]. Literature showed the formation of reactive oxygen species (ROS) that breaks the DNA stand and also causes the death of the cells [111]. The mechanism of inhibition varies from species to species. Considering the small size of the iron complex, it can easily penetrate the bacterial membrane due to the adhesion and deposition of the materials, as a result of which cytolysis occurs [114].

3. CONCLUSION

   This review consolidates current knowledge on iron plant polyphenol complexes as an emerging category of green nanomaterials with significant environmental relevance. Iron strongly binds with phenolic OH of plants polyphenols. The unique coordination chemistry between iron ions and naturally occurring polyphenols enables the formation of stable, multifunctional nanostructures using environmentally benign synthesis routes. These materials combination of iron with the antioxidant, and antimicrobial properties of polyphenols, resulting in synergistic performance across diverse environmental applications. In wastewater treatment, iron-polyphenol nanomaterials have demonstrated remarkable effectiveness in removing a wide range of contaminants, including heavy metals, synthetic dyes, nutrients, and emerging pollutants. Beyond water remediation, their application in agriculture highlights

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