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Article

Comparative Study of SnO2 and ZnO Semiconductor Nanoparticles (Synthesized Using Randia echinocarpa) in the Photocatalytic Degradation of Organic Dyes

by
Manuel J. Chinchillas-Chinchillas
1,
Horacio E. Garrafa-Gálvez
1,
Victor M. Orozco-Carmona
2,* and
Priscy A. Luque-Morales
3,*
1
Departamento de Ingeniería y Tecnología, Universidad Autónoma de Occidente (UAdeO), 81048 Guasave, Sinaloa, Mexico
2
Centro de Investigación en Materiales Avanzados (CIMAV), Av. Miguel de Cervantes Saavedra 120, Complejo Industrial Chihuahua, 31136 Chihuahua, Chihuahua, Mexico
3
Facultad de Ingeniería, Arquitectura y Diseño, Universidad Autónoma de Baja California (UABC), 22860 Ensenada, Baja California, Mexico
*
Authors to whom correspondence should be addressed.
Symmetry 2022, 14(10), 1970; https://doi.org/10.3390/sym14101970
Submission received: 14 August 2022 / Revised: 9 September 2022 / Accepted: 16 September 2022 / Published: 22 September 2022
(This article belongs to the Section Chemistry: Symmetry/Asymmetry)
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Abstract

:
Symmetry in nanomaterials is essential to know the behavior of their properties. In the present research, the photocatalytic properties of SnO2 and ZnO nanoparticles were compared for the degradation of the cationic dyes Methylene Blue (MB) and Rhodamine B (RB). The nanoparticles were obtained through a green synthesis process assisted by Randia echinocarpa extracts; they were then analyzed through Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) to characterize their structure. Transmission electron microscopy (TEM) was used to identify the morphology and disclose nanoparticle size, and the optical properties were studied through Ultraviolet–visible spectroscopy (UV–Vis). The results show that the synthesized SnO2 and ZnO nanomaterials have quasispherical morphologies with average sizes of 8–12 and 4–6 nm, cassiterite and wurtzite crystal phases, and band gap values of 3.5 and 3.8 eV, respectively. The photocatalytic activity yielded 100% degradation of the MB and RB dyes in 210 and 150 min, respectively. ZnO performed higher photocatalytic degradation of the cationic dyes than SnO2 due to a higher content of Randia echinocarpa extracts remaining after the green synthesis process.

1. Introduction

Semiconductor nanomaterials have gained significant importance over the past years owing to their relevant properties and potential application in diverse areas [1], with a particular focus on pollutant elimination since it has been widely demonstrated that semiconductor nanomaterials have an excellent capacity for contaminant-removal through different methods such as adsorption, precipitation, nanofiltration, and photocatalysis degradation [2]. To date, photocatalysis has predominated because of its benefits of low cost, its ability to offset contaminant compounds without generating dangerous byproducts, and, most remarkably, its needless catalyst consumption [3]. Plenty of catalyst types have been used, such as films, membranes, nanorods, and nanoparticles, among others [4]. Nanoparticles possess numerous advantages over conventional bulk materials due to their high surface-to-volume ratio resulting in high surface area, which drastically augments photocatalytic degradation efficiency [5]. In addition, there are various crystalline structures that make up the nanoparticles; this atomic symmetry allows this nanomaterial to acquire unique properties. TiO2, CdS, BiVO4, SnO2, and ZnO semiconductor nanoparticles are among the most promising nanoparticles for photocatalytic applications [6,7].
SnO2 is an n-type semiconductor with a high boiling point (1127 °C), an exciton-binding energy of 1300 meV [8], and a wide band gap (~3.6 eV) which is of great relevance for many applications in the electronics and pollutant-elimination fields; it is well known that due to its porous structure, it can help remove or degrade many kinds of contaminants [9]. Likewise, ZnO is also an n-type semiconductor used in the production of cosmetics, lotions, supplements, and electronic devices by virtue of its low toxicity, high stability, and thermal resistance; additionally, it also has antibacterial properties [10] and a wide band gap (~3.3 eV) rendering it an excellent candidate to be used in photocatalysis [11]. Over time, different methodologies have been implemented to obtain semiconductor nanoparticles. The best method known to date is green synthesis because it is an inexpensive method, it is a simple method (easy to operate), it fosters energy-consumption reduction, undergoes shorter processing times, involves organisms such as bacteria, fungi, and plants rather than hazardous chemical reagents, and aids in synthesizing nanoparticles with better control and quality [12]. It has been reported in the literature that plant extracts used in green synthesis contain organic molecules such as flavonoids, polyphenols, enzymes, carbohydrates, vitamins, etc. These organic molecules have an effect on the size of the synthesized nanoparticles and on the reduction of the energy gap. By reducing the band gap of the nanoparticles, the photocatalytic activity increases, since it requires less energy to produce the energetic jump of electrons and initiate a chain reaction (photocatalytic reaction) [13].
Several reports have been published regarding the green synthesis of SnO2 and ZnO; for example, Jadhav et al. demonstrate green synthesis of SnO2 with the aid of Carica papaya leaves, showing control over nanoparticle size which results in a size of ~7.1 nm [14]. Daphne mucronatahas has also been used as a reducing and stabilizing agent during the synthesis process of SnO2 nanoparticles [15], and in the work of Najjarand and colleagues, chitosan was used at different synthesis temperatures to positively avoid agglomeration [16]. In the case of ZnO nanoparticles, there are also several reports; that of Sadiq et al. shows the use of Syzygium Cumini for the elimination of Methylene Blue [17]. Additionally, Selim et al. took advantage of the properties of Deverra tortuosa to obtain ZnO nanoparticles with cytotoxic properties [18]. Moreover, Pillai et al. attained ZnO nanoparticles with antimicrobial and fungicide properties using Beta vulgaris, Cinnamomum tamala, Cinnamomum verum, and Brassica oleracea var. Italica through green synthesis [19].
Although an extensive amount of plants have been used so far for green synthesis, others still provide enormous benefits but have not yet been explored. Among them is Randia echinocarpa, a plant classified as a shrub that can reach up to 3 to 5 m in height, with medium-sized, dark-green leaves and round green fruit with spine-like projections [20]. Randia echinocarpa is a plant endemic to Mexico that grows in warm and mild weather. It has been used to treat otitis, rhinitis, anemia, diabetes, and bronchitis, among other illnesses [21]. Its composition, high in melanins and phenolic groups with antioxidant properties, renders this plant an excellent candidate [22]. Some of the active components of this plant are melanins, linoleic acid, palmitic acid, β-sitosterol, and α-glucosidase [21]. Herein, Randia echinocarpa was utilized as a stabilizing agent in the green synthesis of SnO2 and ZnO nanoparticles further used in the photocatalytic degradation of cationic dyes MB and RB.

2. Materials and Methods

2.1. Extract Obtention

Fruit was collected in its native form and washed with water before peeling to obtain the Randia echinocarpa extracts. The peel was triturated in a blender until a fine powder was acquired; afterwards, 2 g of the Randia echinocarpa powder were added to 50 mL of deionized water, stirred for 2 h at room temperature, and later placed in a warm-water bath at 60 °C for 1 h. Eventually, the solution was filtered through a Whatman #4 filter and the final Randia echinocarpa extract solution was attained.

2.2. Nanoparticles Synthesis

The procedure for the synthesis of both SnO2 and ZnO nanoparticles was the same, 2 g of metal precursor salt (SnCl2•2H2O for SnO2 and Zn(NO3)2•6H2O for ZnO) were added to 50 mL of the Randia echinocarpa extract solution and stirred for 1 h at room temperature; next, the solution was set in a water bath at 60 °C for 12 h until the liquid was evaporated entirely from the solution. The dried product underwent further thermal treatment at 400 °C for 1 h, and the resulting material was ground in an agate mortar (for 10 min) for its subsequent use and characterization.

2.3. Characterization

The as-synthesized nanoparticles were characterized through FT-IR (Perkin Elmer Brand, 0.5 cm−1 resolution, and 4500 to 400 cm−1 measurement range) and XRD (Bruker-D2 Phase, with Cu Ka = 1.541 Å radiation at a 0.022 step from 10 to 80°) to disclose their structure; TEM (JEOL JEM-2010F transmission electron microscope, with 120 kV acceleration) was performed for the morphology analysis and the elucidation of nanoparticle size distribution; and the optical properties, as well as the monitoring of the photodegradation of the cationic dyes, were conveyed through UV–Vis (Perkin Elmer brand spectrophotometer, Lambda 365, 190–800 nm wavelength and 600 nm/min scanning speed) and PL (Horiba, Nanolog, ethanol solvent, 100 ppm concentration).

2.4. Photodegradation

Photodegradation of the MB and RB dyes was performed with UV radiation to evaluate the photocatalytic properties of the synthesized nanoparticles. Dye solutions were prepared at concentrations of 15 ppm. Then, 50 mg of SnO2 and ZnO nanoparticles, respectively and separately, were added to 50 mL of each solution and subsequently stirred in darkness for 30 min. Afterwards, they were placed in a Polaris UVA-1C reactor with a 10 W bulb at 254 nm wavelength for 3 h, while aliquots were taken every 10 min to be analyzed by UV–Vis spectrophotometry.

3. Results and Discussion

3.1. FT-IR

The infrared spectroscopy (FT-IR) analyses of SnO2 and ZnO are shown in Figure 1. Two important bands related to SnO2 are portrayed: one at 1642 cm−1, and another wide band from 760 to 340 cm−1, which can be assigned to Sn–OH and O–Sn–O bonds, respectively; these bands are characteristic of SnO2 nanoparticles, proving their successful synthesis similarly to reports in the literature [23]. In the case of ZnO, a very intense band at 360 cm−1 is displayed, attributed to the Zn–O bond of ZnO nanoparticles, which demonstrates their obtainment [24]. Furthermore, unlike in the SnO2 nanoparticle spectrum, a group of bands ranging from 1600 to 650 cm−1 is disclosed in the ZnO spectrum, owing to the organic content of the Randia echinocarpa extracts [25]. The presence of these bands indicates that the extract’s organic compounds still remain on the ZnO nanoparticles, which is beneficial for the photocatalytic activity [26].

3.2. XRD

X-ray diffraction spectroscopy (XRD) was performed on samples of the synthesized materials to identify their crystallinity. The diffraction patterns of the SnO2 and ZnO nanoparticles are illustrated in Figure 2. In the SnO2 diffractogram, the diffraction peaks located at 2θ with values of 26.6°, 33.8°, 38.0°, 38.9°, 51.7°, 54.7°, 57.9°, 61.7°, 64.6°, and 65.8° are associated to the planes (110), (101), (200), (111), (211), (220), (002), (310), (112), and (301), respectively, which indicates the formation of SnO2 in a cassiterite phase with a tetragonal crystalline structure according to data reported in JCPDS #72-1147 [27]. The ZnO XRD pattern exhibited nine defined peaks at 2θ with values of 31.8°, 34.4°, 36.3°, 47.5°, 56.6°, 62.8°, 66.4°, 67.9°, and 69.0° which correspond to planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively. These diffraction peaks are indexed to the wurtzite phase and a hexagonal crystalline structure of zinc oxide according to JCPDS #36-1451 [28,29]. The well-defined and intense peaks in the diffraction patterns depict the high crystallinity of the SnO2 and ZnO nanoparticles [17]. Crystallite sizes of both as-synthesized materials were calculated by the Scherrer equation, which is defined as D = K λ / β cos θ , where K is the dimensionless shape factor (0.9), λ is the wavelength of Cu Kα (1.54 Ǻ) X rays, β is the full width at half-maximum (FWHM) in radians, and θ is Bragg’s angle in radians [30]. The values of the most intense peaks, ascribed to the (110) and (101) planes of SnO2 and to (100) and (101) of the ZnO nanoparticles, were used for evaluating the crystalline structure factors and for resolving the crystallite sizes. The crystallite sizes were 14.18 and 21.89 nm for SnO2 and ZnO, respectively. These sizes have been reported elsewhere regarding both materials [31,32,33].

3.3. TEM

The as-synthesized nanoparticles were subjected to transmission electron microscopy (TEM) to ascertain their morphology and size. A TEM micrograph of the SnO2 nanoparticles can be seen in Figure 3a. Quasispherical nanoparticles of average size between 8 and 12 nm are observed, as is detailed in the histogram (3a inset), which matches the data reported in the literature [34]. In the HRTEM image (3b), the lattice fringe was measured to be 0.33 nm, which is ascribed to the main crystalline plane (110) of tetragonal SnO2; this proved to be the preferential growth direction [35]. The elemental analysis spectrum of the SnO2 nanoparticles acquired through energy-dispersive X-ray spectroscopy (XEDS) is shown in Figure 3c, which defines solely Sn and O as the main chemical components, indicating the obtainment of SnO2 nanoparticles. Meanwhile, the TEM micrograph in Figure 3d depicts distributed, quasispherical ZnO nanoparticles without any detectable agglomeration. The histogram of size distribution, garnered through the Image J software, is shown in Figure 3 (3d inset) and renders a narrow distribution of nanoparticle average size, 4–6 nm. The HRTEM image of ZnO is disclosed in Figure 3e, where lattice fringes of 0.28, 0.26, and 0.24 nm were identified, corresponding to the planes (100), (002), and (101), respectively. This reveals the preferential growth directions and the high-order arrangement of the ZnO nanoparticles. These results are congruent with those derived from XRD and those found in the literature [36,37]. Additionally, the XEDS spectrum only manifested peaks corresponding to Zn and O (Figure 3f), confirming the successful formation of ZnO nanoparticles.

3.4. Optical Analysis

The optical properties of SnO2 and ZnO were analyzed through the UV–Vis spectroscopy technique, and the results are displayed in Figure 4. A band at 290 nm resulted from the analysis of SnO2, characteristic of SnO2 nanoparticles with a band gap of 3.5 eV. The ZnO sample portrayed a strong signal at 375 nm and a 3.8 eV band gap. The band-gap values of SnO2 and ZnO fall within the UV range, making it possible for them to be used in photocatalytic degradation [38]. It becomes evident that the acquired band-gap values for both materials rise over those reported for conventional nanoparticles [39,40]; this is because the Randia echinocarpa extracts act in a manner analogous to a stabilizing agent during nanoparticle synthesis, avoiding nanoparticle overgrowth [41], which achieves quantic confinement due to the diminished size and, in turn, accomplishes an increase in band-gap value [42].
The optical analyses of the SnO2 and ZnO nanoparticles were supplemented with photoluminescence analyses (PL); the spectra are shown in Figure 5. Firstly, four important signals are disclosed in the SnO2 spectrum within the blue range at 449, 467, 534, and 561 nm [43,44]; the bands are attributed to luminescent centers such as structural defects and other defects generated by the presence of organic molecules from the Randia echinocarpa extracts [45], verifying their presence as was resolved by FT-IR. The ZnO spectrum denotes a strong emission between 385 and 534 nm with a maximum peak at 467 nm, attributable to a high density of surface defect states within the band gap which lead to a strong band flexion and a significant reduction in the rate of exciton recombinations [46,47]. The density of states is caused by defects such as oxygen vacancies and interstitial Zn defects existent in ZnO nanoparticles; these defects can be a consequence of organic molecules from Randia echinocarpa, which indicates their continuance after the synthesis process, as was observed by the FT-IR assay [48,49].

3.5. Formation Mechanism

A proposed mechanism for the formation of SnO2 and ZnO nanoparticles synthesized from SnCl2•2H2O and Zn(NO3)2•6H2O, respectively, aided by Randia echinocarpa extracts, is illustrated in Figure 6. It is suggested that the reaction begins with the hydrolysis of the metal salts (Sn and Zn) stirred into the extract; later, nucleation takes place, followed by agglomeration giving rise to nanoparticle formation. Within the same process, the organic components of the Randia echinocarpa extracts are added onto the nanoparticles through interactions with the OH groups of the organic compounds [50]. These molecules act as stabilizing agents, preventing nanoparticle growth; crystallization occurs with the subsequent thermal treatment of the nanoparticles; thermal stability is conferred to them by interacting with the organic compounds [51], which is why even after thermal treatment, some organic molecules are still present on the nanoparticles. It can be concluded that the use of Randia echinocarpa helps the green synthesis process for the obtainment of better-quality nanoparticles and size control, which is in close correlation with previous reports of plant extracts utilized in the green synthesis of semiconductor nanoparticles [52,53,54].

3.6. Contaminant Photodegradation

The photocatalytic properties of SnO2 and ZnO were evaluated through the photocatalytic degradation of the cationic dyes MB and RB in UV radiation. The MB degradation is disclosed in Figure 7a; SnO2 and ZnO achieved a 5 and 4% dye concentration decrease, respectively, within the first 30 min of reaction in darkness. This decrease is an effect of the dye’s adsorption onto the nanoparticle surface, owing to the affinity between them [55,56]. Once the lamp was lit, SnO2 degraded 95% after 210 min of reaction time, whereas ZnO achieved 100% degradation. It was faster with SnO2 within the first minutes than with ZnO, as is shown by the rate constants in the inset of Figure 7a with values of 0.01421 and 0.01201 min−1 for SnO2 and ZnO, respectively. Similar to the case of MB, since both are cationic dyes, the underlying affinity of RB towards the nanoparticle surface induces a reduction of solution concentration by 2% with SnO2 and ZnO after 30 min in the dark (Figure 7b). Moreover, ZnO achieved the highest efficiency of 100% RB degradation in 150 min, while SnO2 did so in 180 min. Likewise, ZnO had a degradation rate constant of 0.02191 min−1, higher than that of SnO2, equivalent to 0.01437 min−1. The as-synthesized nanoparticles accomplished good photocatalytic activity towards the degradation of dyes MB and RB, where ZnO revealed the best results. Another more-favorable characteristic of ZnO over SnO2 was the smaller nanoparticle size obtained (8–12 nm for SnO2 and 4–6 nm for ZnO), which brings about a larger surface area that, in turn, translates into a larger quantity of active sites over which photodegradation can develop, improving pollutant-dye elimination [57,58,59]. Table 1 shows the degradation results of organic pollutants (MB and RB) from some investigations.

3.7. Photodegradation Mechanism

The photocatalytic degradation mechanisms of both dyes, MB and RB, unfold in a very similar way with SnO2 and ZnO, and the proposal of this work to define it is schematically is shown in Figure 8. The photocatalysis reaction of the organic dyes happens in a homogenous way; this implies that the dye molecules remain adsorbed on the surface of the SnO2 and ZnO nanoparticles (active sites). When UV light is irradiated over the system and its photon energy is greater than the nanoparticle band-gap values (hv ≥ Eg), 3.5 and 3.8 eV for SnO2 and ZnO, respectively, electrons (e−) are generated in the conduction band and holes (h+) in the valence band [68]. The excited e− react with oxygen molecules, forming superoxide anion radicals (•O2−), and the h+ interact with water molecules from the system giving rise to hydroxyl radicals (•OH) [69]. •O2− and •OH are highly powerful oxidating agents with extremely high reactivity, responsible for decomposing the organic dye molecules into depleted, benign subproducts such as CO2, H2O, and ion salts [70].

4. Conclusions

Green synthesis of semiconductor nanoparticles is an up-to-date, economic, and facile approach for obtaining SnO2 and ZnO nanoparticles as proven in the present research; Randia echinocarpa extracts were used as stabilizing agents—avoiding the use of hazardous, chemical reagents—in the syntheses of well-defined SnO2 and ZnO nanoparticles of sizes 8–12 nm and 4–6 nm and cassiterite and wurtzite crystalline phases, respectively. These nanoparticles possess characteristic properties that strongly aid photocatalytic activity. The as-green-synthesized ZnO nanoparticles achieved complete degradation of the dyes MB and RB in a period of 210 and 150 min, respectively, owing to the generation of highly oxidating species, such as •O2− and •OH radicals. The higher photocatalytic activity of ZnO compared to SnO2 in the degradation of the cationic dyes was due to a greater content of Randia echinocarpa extracts remaining after the green synthesis process of the nanoparticles.

Author Contributions

Conceptualization, M.J.C.-C. and H.E.G.-G.; methodology, M.J.C.-C.; software, V.M.O.-C.; validation, P.A.L.-M., and H.E.G.-G.; formal analysis, M.J.C.-C.; investigation, P.A.L.-M.; resources, V.M.O.-C.; data curation, H.E.G.-G.; writing—original draft preparation, H.E.G.-G.; writing—review and editing, M.J.C.-C.; visualization, V.M.O.-C.; supervision, P.A.L.-M.; project administration, P.A.L.-M.; funding acquisition, V.M.O.-C. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

The authors gratefully acknowledge the use of TEM facilities at the TEM Laboratory of Universidad de Sonora.

Conflicts of Interest

The authors declare no conflict of interest.

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Symmetry 14 01970 g001 550
Figure 1. FT-IR spectra of the SnO2 and ZnO nanoparticles synthesized with Randia echinocarpa.
Figure 1. FT-IR spectra of the SnO2 and ZnO nanoparticles synthesized with Randia echinocarpa.
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Figure 2. Diffractograms of the SnO2 and ZnO nanoparticles synthesized with Randia echinocarpa.
Figure 2. Diffractograms of the SnO2 and ZnO nanoparticles synthesized with Randia echinocarpa.
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Figure 3. TEM micrographs of the SnO2 and ZnO nanoparticles synthesized with Randia echinocarpa; (a) TEM micrograph and particle size distribution, (b) HRTEM, and (c) XEDS spectrum of SnO2; (d) TEM micrograph and particle size distribution, (e) HRTEM, and (f) XEDS spectrum of ZnO.
Figure 3. TEM micrographs of the SnO2 and ZnO nanoparticles synthesized with Randia echinocarpa; (a) TEM micrograph and particle size distribution, (b) HRTEM, and (c) XEDS spectrum of SnO2; (d) TEM micrograph and particle size distribution, (e) HRTEM, and (f) XEDS spectrum of ZnO.
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Figure 4. (a) UV–Vis absorbance spectra and (b) band gap of the SnO2 and ZnO nanoparticles synthesized with Randia echinocarpa.
Figure 4. (a) UV–Vis absorbance spectra and (b) band gap of the SnO2 and ZnO nanoparticles synthesized with Randia echinocarpa.
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Figure 5. Photoluminescence spectra of (a) SnO2 and (b) ZnO nanoparticles synthesized with Randia echinocarpa.
Figure 5. Photoluminescence spectra of (a) SnO2 and (b) ZnO nanoparticles synthesized with Randia echinocarpa.
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Figure 6. Proposed formation mechanism for the SnO2 and ZnO nanoparticles synthesized with Randia echinocarpa.
Figure 6. Proposed formation mechanism for the SnO2 and ZnO nanoparticles synthesized with Randia echinocarpa.
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Figure 7. Photocatalytic degradation assays of (a) MB and (b) RB.
Figure 7. Photocatalytic degradation assays of (a) MB and (b) RB.
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Figure 8. Schematic of the proposed dye-degradation mechanism by the SnO2 and ZnO nanoparticles synthesized with Randia echinocarpa.
Figure 8. Schematic of the proposed dye-degradation mechanism by the SnO2 and ZnO nanoparticles synthesized with Randia echinocarpa.
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Table
Table 1. Degradation of MB and RB in other investigations.
Table 1. Degradation of MB and RB in other investigations.
YearMaterialsSynthesis MethodPollutants (Dye)DegradationReference
2022ZnO-doped CCarbonization of zeolitic imidazolate framework-8MB98% in 250 min[60]
2021Cellulose nanofibersCellulose membranes using an automatic sheet formerMB60% in 180 min[61]
2021ZnO NPsGreen synthesis (Syzygium Cumini)MB91.4% in 180 min[17]
2021ZnO NpsGreen synthesis (Ziziphus jujuba)MB37% in 45 min[62]
2022SnO2 NPsHydrothermal synthesisMB97% in 120 min[63]
2021Au-ZnO NPsGreen synthesis (Carya illinoinensis)RB95% in 180 min[64]
2022ZnO NPsGreen synthesis (Sechium edule polysaccharides)RB95% in 75 min[65]
2021SnO2 NPsGreen synthesis (Camellia sinensis)RB100% in 180 min[66]
2022CuO–SiO2 CompositeSol–gel processRB85% in 300 min[67]
2022ZnO NPsGreen synthesis (Randia echinocarpa)MB100% in 210 minThis work
2022SnO2 NPsGreen synthesis (Randia echinocarpa)RB100% in 150 minThis work
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Chinchillas-Chinchillas, M.J.; Garrafa-Gálvez, H.E.; Orozco-Carmona, V.M.; Luque-Morales, P.A. Comparative Study of SnO2 and ZnO Semiconductor Nanoparticles (Synthesized Using Randia echinocarpa) in the Photocatalytic Degradation of Organic Dyes. Symmetry 2022, 14, 1970. https://doi.org/10.3390/sym14101970

AMA Style

Chinchillas-Chinchillas MJ, Garrafa-Gálvez HE, Orozco-Carmona VM, Luque-Morales PA. Comparative Study of SnO2 and ZnO Semiconductor Nanoparticles (Synthesized Using Randia echinocarpa) in the Photocatalytic Degradation of Organic Dyes. Symmetry. 2022; 14(10):1970. https://doi.org/10.3390/sym14101970

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Chinchillas-Chinchillas, Manuel J., Horacio E. Garrafa-Gálvez, Victor M. Orozco-Carmona, and Priscy A. Luque-Morales. 2022. "Comparative Study of SnO2 and ZnO Semiconductor Nanoparticles (Synthesized Using Randia echinocarpa) in the Photocatalytic Degradation of Organic Dyes" Symmetry 14, no. 10: 1970. https://doi.org/10.3390/sym14101970

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