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A sustainable, affordable, and cost-effective method was developed to synthesize zinc oxide nanoparticles (SB-ZnO-NPs) using leaf extracts of Strobilanthes barbatus. The synthesized SB-ZnO-NPs displayed an absorbance maximum at 359 nm with a band gap of 3.24 eV. The average diameter of the SB-ZnO-NPs, as determined by FESEM analysis, was 84.23 nm. The particles had nearly spherical morphologies. By using FTIR analysis, it was established that functional groups played a part in the formation of SB-ZnO-NPs. Reactive Yellow 86 (RY-86) and Reactive Yellow 145 (RY-145) textile dyes were degraded by SB-ZnO-NPs under the impact of UV irradiation, and the degradation rates were 87.50 and 91.11%, respectively, in 320 min. When dye solutions treated with SB-ZnO-NPs were tested for phytotoxicity, the results showed a sharp decline in the effectiveness of the inhibition compared to dye effluents. The synthesised SB-ZnO-NPs can, therefore, be employed as a substitute potential catalyst for the breakdown of textile colours both before and after release into water bodies.

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  • An environmentally friendly green-synthesized zinc oxide nanoparticle was biosynthesized using Strobilanthes barbatus plant extract.

  • Reactive Yellow industrial textile dyes were found to degrade photocatalytically when exposed to UV radiation.

  • Phytotoxicity research reveals that degraded dyes are less hazardous to aquatic life.

green synthesis, photocatalytic degradation, phytotoxicity, Reactive Yellow dyes, UV radiation, zinc oxide nanoparticles
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A significant factor in the environment's devastation is the leakage of dye pollutants by textile factories. Dye-containing wastewater is a significant contributor to environmental pollution that also negatively affects human health since textile firms produce enormous amounts of colourful wastewater that carries a wide range of persistent pollutants (Al-Tohamy et al. 2022). The main contaminants in textile wastewater include refractory organics, dyes, toxicants and inhibitory chemicals, surfactants, detergents, and salts. The dye in textile wastewater is the greatest challenge for treatment (Doble & Kruthiventi 2007). 80% of all discharges made by manufacturers are caused by the textile industry, which first causes harm by discharging toxic waste that has not been treated into waterways. Organic dyes are toxic, mutagenic, and carcinogenic substances that continue to be major environmental pollutants and persist across entire food chains, giving rise to a biomagnification effect whereby species at advanced trophic levels have more substantial pollution levels than their prey. As a result of their discharge into wastewater, which is frequently used for irrigation in agriculture in developing countries, and the fact that they do not adhere to the fabric during the colouring process, azo-type textile dyes should be noted in this context (Lellis et al. 2019; Ardila-Leal et al. 2021). Azo dyes, which are mutagenic and carcinogenic, can result in genetic changes, abnormal births, hereditary diseases, and allergic reactions (Mahmoud et al. 2015).

Reactive dyes are among the synthetic azo dyes used in garment dyeing that are frequently utilized in industries that pollute the environment (Mahmood et al. 2011). One of the widely used dyes in the cotton and textile dyeing industry is Reactive Yellow 145 (RY-145) and Reactive Yellow 86 (RY-86). It has been discovered that these dyes have negative impacts on human beings and the environment. Their discharge into the environment during the manufacturing and dyeing processes can pollute water bodies, causing aquatic ecosystem anomalies and bioaccumulation in organisms. These textile dyes are poisonous to aquatic life and can harm ecosystems in the long run. RY-86 and RY-145 have been linked to skin irritation, allergic responses, and possible carcinogenicity in humans (Mehta et al. 2010; Gharbani 2018). Traditional methods for eliminating Reactive Yellow dyes from wastewater are difficult and expensive because of their increased solubility in water (Vidhyadevi et al. 2014). They need to be handled before release due to their limited biodegradability and harmful properties, which represent a threat to the environment.

Osmosis, flocculation, and other techniques have been utilized in the past, but each of these procedures has advantages and disadvantages of its own. Effective wastewater colour removal is only possible with a combination of biological and physicochemical treatment methods. Industrial effluents have a complex composition, which requires the employment of a variety of treatment techniques. Advanced oxidation (AO) + hydrolytic acidification + A/O is a popular combination, as is iron-carbon Fenton + ABR + UASB + A/O + Fenton. The AO + hydrolytic acidification + A/O method starts with advanced oxidation to destroy complex organic molecules, then moves on to hydrolytic acidification for breaking down pollutants further, and finally, to an A/O process for aerobic treatment. Fenton chemistry is used for oxidation in the iron-carbon Fenton + ABR + UASB + A/O + Fenton process, ABR and UASB for anaerobic digestion, A/O for aerobic treatment, and Fenton again for further oxidation. These combinations contribute to the reduction of the many contaminants contained in industrial effluents (Tkaczyk et al. 2020; Dohdoh et al. 2021).

When compared to the usage of green-synthesized nanoparticles (NPs), traditional approaches for treating industrial effluents have some drawbacks. Conventional treatment procedures require the use of huge volumes of chemicals, such as coagulants and flocculants, which can be expensive and have adverse ecological effects. Specific contaminants, such as heavy metals or persistent organic pollutants, are frequently difficult to remove using these approaches. Green-synthesized NPs, on the other hand, provide advantages such as high reactivity and selectivity for pollution removal (Magalhães-Ghiotto et al. 2021).

Degradation of organic pollutants utilizing zinc oxide (ZnO) photocatalysts based on nanomaterials that are active at the right light radiations is one of the effective and advantageous options. Zinc oxide nanoparticles (ZnO-NPs), which have broad bandgap energy of less than 3 eV, are believed to exhibit strong photocatalytic capabilities. Many plants have been used to biosynthesize ZnO-NPs, which have degraded a variety of colours with negative effects on both humans and the environment (Gangwar & Sebastian 2021). The green synthesis of ZnO-NPs using Strobilanthes barbatus plant is economically significant. It provides a sustainable and cost-effective alternative to traditional procedures, avoiding the need for costly and dangerous chemicals. This method makes use of S. barbatus plant extracts that are widely available, renewable, and affordable. Green-synthesized ZnO-NPs have a wide range of uses in agriculture, healthcare, cosmetics, wastewater treatment and remediation of the environment. Their economic significance emerges from promoting environmentally responsible practices, lowering manufacturing costs, and stimulating innovation in a variety of industries while minimizing environmental damage (Faisal et al. 2021). According to our knowledge, this is the first attempt to biologically synthesize ZnO-NPs from S. barbatus (SB). Furthermore, the research employs widely used major textile dyes (RY-145and RY-86), which are released accidentally or due to a lack of cost-effective, dependable, and environmentally friendly degradation methods, making this work critical for preventing discharge prior to treatment.

In light of the results, we developed a unique environmentally friendly approach to create ZnO-NPs from S. barbatus leaf extracts and examined their photo-degradation of RY-145 and RY-86 dyes. Terpenoids, flavonoids, phytosterols, phenolic chemicals, and carbohydrates are abundant in the leaves and stems of S. barbatus (Zhu et al. 2022), which makes them useful in the synthesis of ZnO-NPs. In order to degrade Reactive Yellow dyes, the study seeks to produce ZnO-NPs in a single pot to serve as an effective photocatalyst.

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Materials

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Zinc acetate dihydrate was procured from Himedia Laboratories, India. RY-145 and RY-86 were procured from textile industry in Jetpur, India. Fresh leaves of S. barbatus were procured from plants raised in greenhouse conditions.

Plant extract preparation and ZnO-NPs biosynthesis

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On a magnetic stirrer, 10 g of roughly chopped and pulverized leaves were boiled for 20 min at 60 °C in 100 mL of deionized water. Whatman filter Paper No. 1 was used to filter the cooled mixture. S. barbatus extract (1 ml) was treated with a 50 ml (0.1 M) solution of zinc acetate for 10 min at room temperature with vigorous shaking (pH 10). A whitish colour was eventually achieved after the mixture was continually agitated (400 rpm, 60 °C) for 1 h. The slurry that resulted was dried and centrifuged. The acquired sample was calcined in a muffle furnace for 2 h at 500 °C to produce white SB-ZnO-NPs (Figure 1). Previously researchers have reported that ZnO-NPs were biosynthesized using a variety of plants (Gangwar & Sebastian 2021). ZnO-NPs were synthesized in the current work, utilizing S. barbatus leaf extract. The biomolecules present in SB plant extract might aid in the reduction, stabilization, and capping of ZnO-NPs. The colour of the solution of zinc acetate dihydrate and S. barbatus leaf extract altered from light brown to white during the green synthesis of ZnO-NPs. The colour shift suggested the conversion of metallic zinc (Zn+) ions to ZnO-NPs. The reduction of the acetate group of metal salts in the presence of polyphenols may occur by chelation, according to reports (Naseer et al. 2018; Singh et al. 2019). During the calcination process, metal oxide NPs are created when connections between metal salts and hydroxyl groups break, removing the water molecule (Kaur et al. 2018). The white powder synthesized (assumed to be ZnO-NPs) was then used for physical characterization.

Characterization

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Biosynthesis of SB-ZnO-NPS was observed at a wavelength ranging from 200 to 800 nm using a UV-vis spectrophotometer (UV-1800, Shimadzu, Japan). Particle size and zeta potential of SB-ZnO-NPs were initially calculated using a Zetasizer (ZEN3600, Malvern, Germany) using the Dynamic Light Scattering (DLS) method. Structural characteristics of SB-ZnO-NPs were carried out using FESEM (MIRA 3, TESCAN, Czech Republic) and XRD (Miniflex, Rigaku, Japan) analysis. Analysis of crystalline nature was determined using X-ray diffractions at 2θ values obtained at 20°–80° using Cu kα radiations at a wavelength of 1.541 Å and size was calculated from XRD data using the Debye–Scherrer formula.

Image J software (version: 1.53k) was utilized for the calculation of the size of NPs from FESEM images. The functionality of the synthesized SB-ZnO-NPs and plant extract were analyzed using a Fourier-transform infrared spectroscopy (FTIR) (IR spirit -L, Shimadzu, Japan), verified at 4,000–500 cm−1 employing an IR spectrophotometer (IR spirit with single reflectance). Origin Pro 9.4 software was utilized for the preparation of graphs.

Photocatalytic activity

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The azo dyes, RY-145 and RY-86, one of the major dyes in textile industry was utilized for photocatalytic degradation studies. Recent research has reported dye concentration as 1 ppm (Chijioke-Okere et al. 2019) and 5 ppm (Puthukulangara Jaison & Kadanthottu Sebastian 2023) for their dye degradation studies. In this study, SB-ZnO-NPs (1 mg/ml) was dissolved in distilled water and mixed with 1 ppm each of RY-145 and RY-86, respectively. After placing it in the dark for 10–15 min, the mixture was provided with UV light using a photoreactor. Absorbance at the range of 200–800 nm was observed at regular time intervals (0, 10, 20, 40, 80, 160, and 320 min) using a UV-vis spectrophotometer. The maximum absorbance peak was at 408 and 420 nm for RY-145 and RY-86, respectively. The degradation was observed by a decrease as the well hypsochromic shift in peaks. The dye degradation efficiency of SB-ZnO-NPs was calculated using the equation (Meena et al. 2016).
Here A0 and At represent time-dependent concentrations of the dyes, respectively.
Figure 1
Flowchart showing the synthesis of zinc oxide nanoparticles (SB-ZnO-NPs) using Strobilanthus barbatus leaves.
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Flowchart showing the synthesis of zinc oxide nanoparticles (SB-ZnO-NPs) using Strobilanthus barbatus leaves.

Figure 1
Flowchart showing the synthesis of zinc oxide nanoparticles (SB-ZnO-NPs) using Strobilanthus barbatus leaves.
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Flowchart showing the synthesis of zinc oxide nanoparticles (SB-ZnO-NPs) using Strobilanthus barbatus leaves.

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Phytotoxicity studies

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The degradation efficiency and toxicity reduction of SB-ZnO-NPs-treated dyes RY-145 and RY-86 were analyzed using trophic level equivalents. A. cepa root growth inhibition test was performed as previously performed (Vigneshpriya et al. 2019) with slight modifications. A. cepa (onion bulbs) obtained from a nearby vegetable shop was cleaned adequately under running water. Uniformly developed onion roots after 72 h were taken out from distilled water and subjected to treated and untreated dye, and SB-ZnO-NPs solutions. After 48 h, root length (RL) was recorded and percentage inhibition was calculated using the following equation
For assessing V. radiata toxicity, seeds were used in the sprouting test with slight modifications. The seeds were germinated in a Petri dish (10 seeds each, 1 cm spacing) and subjected to treated and untreated dye, and SB-ZnO-NPs solutions, respectively. Seedlings germination percentage, shoot length, and RL toxicity were calculated (Dharshini et al. 2021) after 7 days of treatment.
Brine shrimp (Artemia salina) lethality assay was performed using a previously established method (Bilal et al. 2016) with slight modifications. Eggs hatched in artificial seawater (consist 36 g of non-iodized salt in 1 L of deionized water). 100 nauplii each were cultured for 24 h at RT with treated and untreated dye, and SB-ZnO-NP solutions, respectively. The mortality rate (MR) was calculated by counting the dead nauplii under a binocular microscope and using the equation
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UV–Vis spectroscopy

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Plant phytochemicals help in the reduction and stabilization of zinc ions to zinc oxide. The addition of plant extracts to zinc acetate resulted in the change of suspension colour from green to white, indicating the formation of SB-ZnO-NPs. A characteristic peak at 359 nm was observed by spectral analysis (Figure 2), which was well within 320–380 nm as suggested by earlier studies (Suresh et al. 2015), suggesting an intrinsic band gap associated with ZnO-NPs. This may be attributed to electro transition to conduction band from valance bands (Khorsand Zak et al. 2012). The band gap energy of SB-ZnO-NPs using Wood-Tauc's relation (Khorsand Zak et al. 2011) was determined to be 3.24 eV, which showed a sharp peak, suggesting nanosize particles with a narrow distribution. The band energy was less than that of bulk ZnO (3.45 eV) (Soosen Samuel et al. 2009), suggesting the applicability for wastewater treatment especially with dye effluents (Singh et al. 2019).
Figure 2
UV–Vis spectra of biologically synthesized zinc oxide nanoparticles (SB-ZnO-NPs) using Strobilanthus barbatus leaves.
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UV–Vis spectra of biologically synthesized zinc oxide nanoparticles (SB-ZnO-NPs) using Strobilanthus barbatus leaves.

Figure 2
UV–Vis spectra of biologically synthesized zinc oxide nanoparticles (SB-ZnO-NPs) using Strobilanthus barbatus leaves.
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UV–Vis spectra of biologically synthesized zinc oxide nanoparticles (SB-ZnO-NPs) using Strobilanthus barbatus leaves.

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Dynamic Light Scattering

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NP stability is determined by the particle size and zeta potential. NP hydrodynamic diameter was found to be 91.96 nm (Figure 3(a)). The two sets of particle size distributions in the figure clearly show the NP size is below 100 nm. The zeta potential measurement is an important parameter for investigating NP surface charge and colloidal stability. The zeta potential of the SB-ZnO-NPs was −26.8 mV (Figure 3(b)), clearly suggesting good colloidal stability of the synthesized NPs. The study of DLS is used to determine the stability of colloidal solutions containing NPs. DLS demonstrates a narrow size distribution with a single peak in a stable solution, indicating individual NPs and fast Brownian motion. On the other hand, an unstable solution shows wider size distributions, more peaks, and shorter decay durations in the intensity autocorrelation function, indicating particle aggregation or agglomeration (Raval et al. 2019). The hydrodynamic diameter of NPs with a diameter smaller than 100 nm is significant because it influences stability and agglomeration. Smaller NPs are more stable and have less agglomeration, which enhances their suspension characteristics. Smaller NPs have a higher surface area-to-volume ratio, which improves reactivity and efficiency. Depending on the application, such as medication administration, catalysis, filtration, dye degradation, and others, a desirable range for hydrodynamic particle diameter is 10–100 nm. Catalytic applications, on the other hand, may require a narrower size distribution for maximum performance (Austin et al. 2020). The S. barbatus plant extract used for the surface functionalization and colloidal stability is providing very good help for the synthesized NPs due to the presence of phytochemicals contained in the plant extract. The repulsive interactions between negatively charged particles inhibit agglomeration, resulting in ZnO-NPs stability (Sonia et al. 2017). According to recent papers, the particle diameter of ZnO-NPs synthesized from the Acanthaceae family showed an average particle diameter of 84.7 nm and zeta potential at –11.1 mV, similar to obtained results (Kotakadi et al. 2022).
Figure 3
Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs): (a) particle size and (b) zeta potential.
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Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs): (a) particle size and (b) zeta potential.

Figure 3
Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs): (a) particle size and (b) zeta potential.
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Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs): (a) particle size and (b) zeta potential.

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XRD pattern

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Structure and crystallinity of SB-ZnO-NPs were determined by XRD. The crystalline nature of SB-ZnO-NPs is represented in the intensive diffraction peaks. The peak diffraction measured at 2θ values of 31.78°, 34.44°, 36.26°, 47.54°, 56.60°, 62.84°, 65.9°, 66.39°, and 67.94° conforming to the phases [100], [002], [101], [102], [110], [103], [020], [112], and [201], respectively (Figure 4). The sharper peak observed at 36.26° corresponds to the size of SB-ZnO-NPs. Using the Debye–Scherrer formula, the average diameter of the NPs was determined to be 22.29 nm. The peaks matched with JCPDS number 98-001-1316. SB-ZnO-NPs exhibited a hexagonal structure with lattice parameters a = b = 3.2430 Å and c = 5.1950Å, as previously reported (Vinayagam et al. 2020).
Figure 4
Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs) by XRD analysis to elucidate the crystalline structure.
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Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs) by XRD analysis to elucidate the crystalline structure.

Figure 4
Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs) by XRD analysis to elucidate the crystalline structure.
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Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs) by XRD analysis to elucidate the crystalline structure.

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FESEM analysis

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FESEM images taken at different magnifications showed the shape and size of SB-ZnO-NPs (Figure 5). The surface morphology shows spherical, highly dispersed NPs. The micrograph showed agglomeration of ZnO-NPs, which is due to the NP polarity, surface morphology, relationship in synergistic activity, and electrostatic attraction as previously reported (Peng et al. 2011; Aminuzzaman et al. 2018). The average diameter of the SB-ZnO-NPs was 84.23 nm.
Figure 5
Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs) by SEM analysis.
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Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs) by SEM analysis.

Figure 5
Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs) by SEM analysis.
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Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs) by SEM analysis.

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FTIR analysis

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ZnO bond formation and phytochemicals involved in biosynthesized ZnO-NPs were determined using FTIR analysis. The presence of absorbance peak at 3,302.55, 2,929.09, and 2,861.26 cm−1 corresponds to –OH stretching vibrations. The absorption peaks at 1,605.22, 1,421.68—, and 1,041.83 cm−1 were attributed to C–C stretching, C–H bending, and C–N stretching, respectively (Yulizar et al. 2020). The existence of alkaloid secondary metabolites is confirmed by the C–N stretching vibration. The vibrations of –OH stretching, C–C stretching, and C–H bending are the primary attributes of saponins and flavonoids. The secondary metabolites present in plant extract facilitated the conversion of Zn+2 ions to ZnO-NPs (Ashna et al. 2020). The strong vibrational peak at 682.42 cm−1 by stretching modes leads to the formation of SB-ZnO-NPs (Figure 6). As a result, SB-ZnO-NPs are reduced and stabilized by S. barbatus biomolecules (Sonia et al. 2017).
Figure 6
Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs) by FTIR to measure the functional groups capping the NPs.
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Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs) by FTIR to measure the functional groups capping the NPs.

Figure 6
Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs) by FTIR to measure the functional groups capping the NPs.
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Characterization of biogenic zinc oxide nanoparticles (SB-ZnO-NPs) by FTIR to measure the functional groups capping the NPs.

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Photocatalytic activity

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The degradation efficiency of synthesized SB-ZnO-NPs was examined using RY-86 and RY-145 dyes under UV irradiation. Furthermore, photo-degradation of dyes was determined using the UV-vis spectra of the reaction mixture at 420 and 408 nm for RY-86 and RY-145, respectively. Figures 7 and 8 show time-dependent degradation of RY-86 and RY-145 dyes. The absorbance of RY-86 dye decreased with time from 0 to 320 min indicating a gradual decrease in dye concentration, showing a decrease in dye concentration and degradation efficiency of 87.50% after 320 min (Figure 7(a)). After 320 min, there was a significant hypsochromic shift from 420 to 378 nm, signifying the degradation of the dye (Figure 7(b)). Similarly, RY-145 under UV light showed a decrease in absorbance range and dye concentration from 0 to 320 min at gradual intervals, with a degradation efficiency of 91.11% (Figure 8(a)). RY-145 also showed a hypsochromic shift from 408 to 379 nm, indicating dye degradation (Figure 8(b)). The ability of ZnO-NPs for photocatalytic degradation dyes has been reported in previous studies (Gangwar & Sebastian 2021). When radiations of energy greater than band gap energy falls off the catalyst surface, it may lead to the generation of holes (h+) in the valance band. This causes excitation of electrons (e−) in the conduction band, which is followed by photochemical reactions (Figure 9). The h+ oxidizes H2O to produce OH radicals, which can lead to the formation of reactive oxygen species (ROS) which can include hydroxyl radicals (OH̄) and superoxide ions (⁠⁠). leading to dye degradation (Suresh et al. 2015; Silva et al. 2016; Kaur et al. 2021).
Figure 7
Photocatalytic degradation of RY-86 dye (a) at different time intervals and (b) hypsochromic shift of the degraded dye.
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Photocatalytic degradation of RY-86 dye (a) at different time intervals and (b) hypsochromic shift of the degraded dye.

Figure 7
Photocatalytic degradation of RY-86 dye (a) at different time intervals and (b) hypsochromic shift of the degraded dye.
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Photocatalytic degradation of RY-86 dye (a) at different time intervals and (b) hypsochromic shift of the degraded dye.

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Figure 8
Photocatalytic degradation of RY-145 dye (a) at different time intervals and (b) hypsochromic shift of the degraded dye.
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Photocatalytic degradation of RY-145 dye (a) at different time intervals and (b) hypsochromic shift of the degraded dye.

Figure 8
Photocatalytic degradation of RY-145 dye (a) at different time intervals and (b) hypsochromic shift of the degraded dye.
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Photocatalytic degradation of RY-145 dye (a) at different time intervals and (b) hypsochromic shift of the degraded dye.

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Figure 9
Proposed mechanism of degradation of Reactive Yellow dyes using biogenic zinc oxide nanoparticles (SB-ZnO-NPs).
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Proposed mechanism of degradation of Reactive Yellow dyes using biogenic zinc oxide nanoparticles (SB-ZnO-NPs).

Figure 9
Proposed mechanism of degradation of Reactive Yellow dyes using biogenic zinc oxide nanoparticles (SB-ZnO-NPs).
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Proposed mechanism of degradation of Reactive Yellow dyes using biogenic zinc oxide nanoparticles (SB-ZnO-NPs).

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Phytotoxicity studies

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The untreated and treated dyes were tested for toxicity. Table 1 summarizes the phytotoxicity of the treated and untreated dyes. The RL in A. cepa was monitored for percentage RL inhibition. The RL increased by more than 50% when dyes were treated with SB-ZnO-NPs suggesting a significant reduction in the inhibition and toxic effect of the dye solutions. In V. radiata, seeds showed a significant reduction in the inhibition percentage of dyes treated with SB-ZnO-NPs. ZnO-NPs have been efficient in the reduction of inhibition for seed germination as reported by previous studies (Modi et al. 2022). Artemia serves as an important model for bioassay and toxicity as they serve a central function in the aquatic life cycle (Ozkan et al. 2016). Artemia toxicity assay revealed that SB-ZnO-NPs treatment on dyes is highly efficient in the removal of toxic effects in industrial dye-contaminated waters. Reports suggest that ZnO-NPs are not toxic to artemia species (Ravichandran et al. 2020) and hence can be used in water bodies for the treatment of industrial effluents.

Table 1

Phytotoxicity assessment of untreated and treated textile dyes

Allium cepa toxicity
Vigna radiata toxicity
Brine shrimp mortality
Characters and treatmentAverage root lengths (cm)Percentage of inhibition (%)Germination percentage (%)Average stem toxicity (%)Average root toxicity (%)Average initial number of live naupliiAverage number of dead naupliiPercentage mortality (%)
Distilled water 7.81 ± 0.05 0 100 0 0 172 ± 0.58 1 ± 0.58 0.78 
RY 86 2.69 ± 0.46 65.51 10 64.85 ± 0.28 75.51 ± 0.27 108 ± 2.65 97 ± 2.65 89.81 
RY 145 2.14 ± 0.34 72.56 12 75.74 ± 0.61 50 ± 0 120 ± 5.00 98 ± 2.89 81.94 
ZnO-NPs 5.13 ± 0.46 34.36 90 5.27 ± 0.06 4.30 ± 0.36 153 ± 2.31 2 ± 0.58 1.09 
T-RY 86 6.68 ± 0.29 14.47 95 4.46 ± 0.411 1.35 ± 0.51 138 ± 2.65 4 ± 0.58 3.14 
T-RY 145 6.19 ± 0.09 20.79 90 11.35 ± 0.36 1.62 ± 0.13 153 ± 3.46 5 ± 0.58 3.05 
Allium cepa toxicity
Vigna radiata toxicity
Brine shrimp mortality
Characters and treatmentAverage root lengths (cm)Percentage of inhibition (%)Germination percentage (%)Average stem toxicity (%)Average root toxicity (%)Average initial number of live naupliiAverage number of dead naupliiPercentage mortality (%)
Distilled water 7.81 ± 0.05 0 100 0 0 172 ± 0.58 1 ± 0.58 0.78 
RY 86 2.69 ± 0.46 65.51 10 64.85 ± 0.28 75.51 ± 0.27 108 ± 2.65 97 ± 2.65 89.81 
RY 145 2.14 ± 0.34 72.56 12 75.74 ± 0.61 50 ± 0 120 ± 5.00 98 ± 2.89 81.94 
ZnO-NPs 5.13 ± 0.46 34.36 90 5.27 ± 0.06 4.30 ± 0.36 153 ± 2.31 2 ± 0.58 1.09 
T-RY 86 6.68 ± 0.29 14.47 95 4.46 ± 0.411 1.35 ± 0.51 138 ± 2.65 4 ± 0.58 3.14 
T-RY 145 6.19 ± 0.09 20.79 90 11.35 ± 0.36 1.62 ± 0.13 153 ± 3.46 5 ± 0.58 3.05 

Values are mean ± standard deviation.

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Plant-mediated synthesis is an ecologically safe and sustainable strategy that reduces the usage of toxic chemicals and their environmental effect. Plants serve as natural reducing agents, allowing for the biosynthesis of NPs with excellent purity and stability. The resultant NPs are more biocompatible, making them suitable for biological applications. Overall, plant-mediated production of ZnO-NPs is a potential green nanotechnology route with a wide range of applications. To summarize, a simple, cost-effective, green synthesis method was developed for SB-ZnO-NPs synthesis, which was able to degrade Reactive Yellow industrial textile dyes. Synthesized SB-ZnO-NPs showed spherical, highly dispersed NPs with a size of 84.23 nm. The optical band gap of 3.24 was responsible for the effective photocatalytic activity under UV light. The SB-ZnO-NPs had significant photocatalytic activity for the degradation of Reactive Yellow textile dyes. Phytotoxicity studies also revealed that the degraded products were less toxic to organisms. Thus, owing to this efficient photocatalytic potential, the current study cites toward the development of green strategies for the photocatalysis of industrial textile effluents. The biosynthesis and degradation of ZnO-NPs are still in their early stages, and the treatment of dye combinations as well as other pollutants must be explored before they can be used in large-scale industrial wastewater treatment approaches.

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Authors are thankful to the Centre for Research, CHRIST (Deemed to be University) for financial assistance (MRPDC-1934). Authors are thankful to Common Instrumentation Lab, Materials Research Lab, Department of Physics, CHRIST (Deemed to be University) for providing the instrumentation facilities and major research project (MRP DSC-1830), Centre for Research, CHRIST (Deemed to be University) for providing the DLS analysis facilities. We also thank Department of Materials Engineering, Indian Institute of Science, Bangalore, Karnataka, India for providing the FESEM analysis facilities.

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Authors are thankful to the Centre for Research, CHRIST (Deemed to be University) for financial assistance (MRPDC-1934). J.K.S. has received research support.

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All relevant data are included in the paper or its Supplementary Information.

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The authors declare there is no conflict.

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