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. 2020 Jul 1;5(27):16386–16394. doi: 10.1021/acsomega.0c00405

Microwave-Assisted Degradation of Paracetamol Drug Using Polythiophene-Sensitized Ag–Ag2O Heterogeneous Photocatalyst Derived from Plant Extract

Jannatun Zia 1, Ufana Riaz 1,*
PMCID: PMC7364436  PMID: 32685801

Abstract

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Ag–Ag2O nanoparticles were synthesized using Osmium sanctum plant extract. The nanoparticles were sensitized with polythiophene (PTh) and were characterized via scanning electron microscopy with energy dispersive X-ray and elemental mapping, transmission electron microscopy, X-ray diffraction (XRD), Fourier-transform infrared, and UV–vis spectroscopy analyses. The elemental mapping results revealed that the samples were composed of C, S, Ag, and O elements which were uniformly distributed in the nanohybrid. XRD analysis confirmed the crystalline nature of Ag–Ag2O nanoparticles, and the average particle size was found to be ranging between 36 and 40 nm. The optical band gap of Ag–Ag2O, PTh, and Ag–Ag2O/PTh was found to be 2.49, 1.1, 1.5, and 0.68 eV. The catalytic activity of Ag–Ag2O, PTh, and Ag–Ag2O/PTh was investigated by degrading paracetamol drug under microwave irradiation. Around 80% of degradation was achieved during 20 min irradiation. All degradation kinetics were fitted to the pseudo-first-order model. A probable degradation pathway for paracetamol degradation was proposed based on liquid chromatography mass spectrometry analysis of degraded fragments.

Introduction

In recent years, huge amounts of pharmaceutical compounds are being discovered in water bodies worldwide.1N-Acetyl-p-amino phenol (acetaminophen) commonly known as paracetamol is a highly prescribed antipyretic drug, and its intermediates are found in wastewater resources, which pose serious environmental concerns.2−5 Several research projects are being funded on the degradation of these toxic pharmaceutical organic pollutants to minimize water pollution. Photocatalytic degradation of paracetamol has been reported by Villota et al.,1 Dalida et al.,2 Moctezuma et al.,5 Jallouli et al.,6 Vogna et al.,7 Gotostos et al.,8 and Abdul-Zahra et al.9 using different heterogeneous photocatalysts under UV and visible light irradiation.

Several photocatalysts such as TiO2,10 ZnO,11 SnO2,12 TiO2–Bi2WO6,13 Ta3N5–Pt,14 Ta3N5–Bi2MoO6,15 g-C3N4,16 and HCN–Au17 have been utilized in waste water remediation which can only be activated under UV irradiation. Hence, studies have dedicated toward designing visible-light-responsive heterogeneous photocatalysts to improve the absorbance and utilization of solar energy. In this regard, Ag-based semiconductors such as Ag3PO4,18 AgVO3,19 Ag2CO3,20 Ag/TiO2,21 Ag/ZnO,22 CS/Ag,23 r-GO/Ag,24 and Fe3O4/Ag3PO4@WO325 have shown excellent photocatalytic properties and antimicrobial activity.26

Ag2O is a p-type semiconductor with a narrow band gap of 1.3–1.4 eV and exhibits enhanced visible-light activity and high photo-oxidative properties.27 However, the photosensitivity and rapid recombination of photo-induced electron–hole pairs largely limit their application as a stable photocatalyst. To improve its performance, the strategy of designing Ag–Ag2O hybrid material has led to the improvement in its catalytic activity and stability as metallic Ag demonstrates strong visible-light absorbance because of strong surface plasmon resonance effect and acts as an electron scavenger, which prevents the reduction of Ag2O.28 Moreover, the utilization of conducting polymers such as polypyrrole, polythiophene (PTh), and polyaniline as photosensitizers can effectively contribute toward improvement in the photocatalytic activity as these polymers have shown to efficiently act as hole transporters and donate electrons, improve the interfacial electron transfer process, and prevent oxidation/reduction of metallic nanoparticles.29,30

Most of the studies based on the synthesis of heterogeneous photocatalysts have reported traditional chemical methods such as hydrothermal, precipitation, solvothermal, sol–gel, and physical vapor deposition techniques for designing these materials which cause serious environmental issues as strong acids/solvents and reducing/stabilizing agents are used to synthesize these metal oxides which lead to the release of considerable amounts of toxic materials as unreacted and non-biodegradable compounds in the environment.31,32

Hence, in this study, we have synthesized Ag–Ag2O nanohybrids via a green route using plant extract of Osmium sanctum (commonly known as holy basil) with the aim to develop an eco-friendly and facile strategy for tailoring such heterocatalysts with minimal utilization of toxic chemicals/reagents. The synthesized Ag–Ag2O nanohybrid was modified with PTh in order to enhance its catalytic properties. The structural, morphological, spectral, and optical properties of the synthesized nanomaterials were investigated using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) with elemental mapping, transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), and UV–vis spectroscopy (UV–vis) techniques. As a great deal of literature is available on the photocatalytic activity of these nanohybrids, we have explored their catalytic activity under microwave irradiation and have compared with the reported photocatalytic performance of such materials so as to establish the high efficiency of microwave-assisted catalytic degradation which could be used to safely degrade these drugs prior to their disposal in water bodies.

Results and Discussion

Confirmation of Morphology via XRD, SEM with Elemental Mapping, and TEM Studies

The XRD profile of Ag–Ag2O, Figure 1, showed intense peaks at 2θ = 27.8, 32.3, 38.1, 46.2, 54.9, 57.6, 64.3, 68, and 76.9° corresponding to (110), (111), (200), (200), (220), (110), (311), (222), and (311) planes of face centered cubic lattice of silver oxide (Ag2O), respectively. The peaks were found to be in agreement with the standard cubic Ag2O (JCPDS 76-1393). The peaks associated with Ag0 particles appeared at 2θ = 27.8 (110), 46.2 (200), 57.6 (110), and 76.9° (311).33−35 The average particle size of Ag–Ag2O calculated using the Scherer formula was found to be 36 nm. The XRD profile of PTh showed peaks at 2θ = 16.5, 17.6, 19.5, 26.4, 28.3, 34.9, 39.4, 54.9, and 67.4°. The peak at 2θ = 26.4 and 28.3° were correlated with PTh which confirmed the semicrystalline morphology of the polymer.36,37 The XRD pattern of Ag–Ag2O/PTh showed characteristic peaks at 2θ = 26.8, 32.2, 46.2, 54.8, 57.4, 67.9, and 77.2°, while the peak at 2θ = 26.4° was associated with PTh which was found to overlap with the Ag–Ag2O peaks. The peaks of PTh appeared to be low in intensity, while some of the peaks appeared to be missing presumably because of encapsulation by the Ag–Ag2O particles which was further confirmed by high-resolution transmission electron microscopy (HR-TEM) studies.

Figure 1.

Figure 1

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XRD patterns of Ag–Ag2O, PTh and Ag–Ag2O/PTh nanocomposites.

The HR-TEM of Ag–Ag2O, Figure 2a, showed the formation of distorted spherical particles ranging between 10 and 15 nm, while the HR-TEM of PTh, Figure 2b, revealed clusters of rodlike aggregates forming a dense bundle like structure. The HR-TEM of Ag–Ag2O/PTh, Figure 2c, showed a mixed morphology of hollow tubular structures of PTh surrounded with distorted spherical Ag–Ag2O nanoparticles. The average particle size was observed to be ranging between 20 and 30 nm. The appearance of mixed morphology in the case of Ag–Ag2O/PTh confirmed the formation of the nanohybrid.

Figure 2.

Figure 2

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TEM micrograph of (a) Ag/Ag2O, (b) PTh, and (c) Ag/Ag2O–PTh nanohybrids.

The field emission SEM (FE-SEM) of Ag–Ag2O, Figure 3a, showed clusters of spherical particles as noticed in the HR-TEM and the EDX results, and Figure 3b revealed the compositions of Ag and O to be 95.10 and 4.90 wt. % and 74.24 and 25.76 at. %, respectively. The percentage values were consistent with optimal stoichiometry 2:1 of Ag2O. The elemental mapping of Ag2O, Figure 3c, showed homogeneous distribution of Ag and O the surface of the synthesized nanoparticles.

Figure 3.

Figure 3

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SEM of (a)Ag–Ag2O, (b) EDX of Ag–Ag2O, (c) elemental mapping of Ag–Ag2O, (d) SEM of PTh, (e) EDX of PTh, (f) elemental mapping of PTh, (g) SEM of Ag–Ag2O/PTh, (h) EDX of Ag–Ag2O/PTh, and (i) elemental mapping of Ag–Ag2O/PTh.

Similarly, the FE-SEM image of PTh, Figure 3d, showed cauliflower like morphology and the EDX spectrum of confirmed the presence of C and S, Figure 3e. The intensity of the peak associated with C content was noticed to be 87.68 at wt % and 12.32 at wt % for S. The elemental mapping image, Figure 3f, revealed homogeneous distribution of C with S particles randomly scattered over the surface. The SEM of Ag–Ag2O/PTh, Figure 3g, exhibited a mixed morphology of spherical particles of Ag2O surrounded by flaky rod like structures of PTh. The loading of PTh and Ag2O was confirmed to be 61 and 39 wt %, respectively, as evident from the EDX spectrum, Figure 3h. The elemental mapping of the nanohybrid, Figure 3i, showed uniformly distributed Ag–Ag2O nanoparticles, while the polymer was observed to encapsulate the surface of metal oxide. The EDX results confirmed the stoichiometry of the metal oxide, while the elemental mapping results clearly depicted formation of nanohybrids.

Thermal Stability of Ag–Ag2O and Its Nanohybrids with PTh

The thermogravimetric analysis (TGA) curve of Ag–Ag2O, Figure 4, showed a four step decomposition curve. The first decomposition event was observed at 181 °C because of moisture and free H2O molecules. The second decomposition event exhibited 10.33 wt % loss at 335 °C because of entrapped H2O present on the surface of Ag–Ag2O, while the third decomposition event was noticed at 718 °C revealing a weight loss of 29.81%. The fourth decomposition took place at 805 °C because of the transformation of Ag2O into Ag, and the residue was calculated to be 67.62%.

Figure 4.

Figure 4

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TGA profile of (a) Ag−Ag2O, (b) PTh, and (c) Ag−Ag2O/PTh nanohybrids.

Thus, Ag−Ag2O was found to exhibit excellent thermal stability. PTh also showed a four step decomposition profile, Figure 4. The first weight loss of almost 36.63% was noticed around 181 °C because of the loss of absorbed H2O molecules, while 71.20 wt % loss occurred at 620 °C because of the decomposition of carbon chains of PTh. The TGA profile of Ag/Ag2O–PTh, showed first decomposition event at 181 °C because of loss of moisture and other volatile compounds, while the second decomposition event took place at 351 °C exhibiting 11.24 wt % loss. Almost 38.66 wt % loss was noticed at 805 °C because of the decomposition of polymer backbone. The loading of PTh was calculated to be 28% from the char content. The thermal stability was found follow the order: Ag–Ag2O > Ag−Ag2O/PTh > PTh.

Spectral Studies of Ag–Ag2O, PTh, and Ag–Ag2O/PTh Nanohybrids

IR spectra of Ag–Ag2O, PTh, and Ag–Ag2O/PTh nanohybrids are shown in Figure 5. A broad hump was observed in the IR spectrum of Ag–Ag2O at 3330 cm–1 because of the O–H stretching vibration of water molecules present on the surface of Ag2O. The band at 1519 cm–1 was assigned to the O–H bending vibrations. The peaks noticed at 1046, 1016, 677, and 621 cm–1 corresponded to the Ag–O antisymmetric and symmetric stretching vibrations, while the band at 621 cm–1 was correlated with the presence of the Ag metal. The IR spectrum of PTh exhibited characteristics peaks at 3367 and 3216 cm–1 because of OH stretching vibrations of water molecules. The peaks at 1640 and 1606 cm–1 were attributed to the C=C stretching vibration of conjugated alkene groups present in PTh. The absorption bands at 1373 and 1036 cm–1 were attributed to the C–H bending vibration and C–H in plane deformation mode in PTh, whereas the absorption peaks at 1178 and 855 cm–1 were assigned to the C–S–C stretching vibrations. The absorption band at 782 cm–1 was associated with the C–H out of plane bending vibrations in PTh.38,39 The IR spectrum of Ag–Ag2O/PTh exhibited a broad hump at 3314 cm–1 because of the presence of O–H stretching vibration, while the peak at 1642 cm–1 was associated with the O–H bending vibration. The absorption bands at 1317 and 1094 cm–1, respectively, were attributed to the C–H bending vibration and C–H in the plane deformation mode of PTh. The peaks at 1195 and 842 cm–1 were assigned to the C–S–C stretching vibrations. The absorption band at 782 cm–1 was associated with the C–H out of plane bending vibration. The peaks noticed at 1042 and 634 cm–1 corresponded to Ag–O symmetric and anti-symmetric stretching vibrations. The pronounced OH peak of Ag–Ag2O was noticed to undergo broadening and a decrease in the intensity in the nanohybrid Ag–Ag2O/PTh. Similarly, the C=C stretching peaks at 1640 and 1606 cm−1 of PTh were noticed to undergo decrease in the intensity which could be attributed to intense interaction of PTh with the Ag–Ag2O.

Figure 5.

Figure 5

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IR spectra of Ag–Ag2O, PTh, and Ag–Ag2O/PTh nanohybrids.

The UV–vis spectrum of Ag/Ag2O showed a peak at 260 nm, Figure 6a.40 The UV–vis spectrum of PTh, Figure 6a, revealed a shoulder ranging between 300 and 400 nm associated with π–π* transitions of PTh, whereas the UV–vis spectrum of Ag–Ag2O/PTh revealed a peak at 260 nm similar to the one noticed in pristine metal oxide and a broad hump at 430 nm. The Tauc plot, Figure 6b, depicted an optical band gap value of 1.1 eV for Ag–Ag2O, while band gap of PTh was noticed to be 1.5 eV. The Ag–Ag2O/PTh revealed a band gap value of 0.68 eV. The UV and visible light response of the hybrid materials was found to be remarkably improved upon modification with PTh because of the sensitization effect of the later which could also help in enhancing the photocatalytic properties.

Figure 6.

Figure 6

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(a) UV–vis spectra of pure Ag–Ag2O, PTh, and Ag–Ag2O/PTh; (b) Tauc’s plot of Ag–Ag2O, PTh, and Ag–Ag2O/PTh nanohybrids.

Microwave-Assisted Degradation of Paracetamol Drug Using Ag–Ag2O, PTh, and Ag–Ag2O/PTh as Catalysts

The performance of Ag−Ag2O, PTh, and Ag−Ag2O/PTh as catalysts was evaluated by degrading paracetamol drug solution under microwave irradiation for 20 min (given in the Supporting Information as Figure S1a–c). Microwave-assisted degradation of paracetamol drug using Ag–Ag2O as catalyst exhibited 26% degradation within 20 min, while in presence of PTh as showed, the drug solution revealed 46% degradation. Almost 80% degradation was achieved using Ag–Ag2O/PTh.

The plots of C/C0 versus time and ln C/C0 versus time for Ag–Ag2O, PTh, and Ag–Ag2O/PTh, (given in the Supporting Information as Figure S2a,b) revealed pseudo-first-order kinetics in all the cases. The catalyst Ag–Ag2O/PTh displayed the highest rate constant value of 0.096 min–1 which was found to be 3 times higher than that of pure PTh and 1.5 times higher than the Ag–Ag2O.

The effect of the drug concentration (50–150 mg/L) was investigated, as is depicted in the Supporting Information as Figure S2c. The degradation efficiency of paracetamol drug was noticed to decrease from 69.77 to 42.43% upon increasing the drug concentration from 50 to 150 mg/L in the presence of Ag–Ag2O as catalyst. Similarly, in the presence of Ag–Ag2O/PTh, the degradation efficiency of paracetamol drug was noticed to decrease from 80.51 to 56.35% (given in the Supporting Information as Figure S2d). The rate of paracetamol degradation was observed to decrease with the increase in its concentration.

Recyclability of Ag–Ag2O/PTh and Confirmation of Its Stability via Spectral and Morphological Studies after Regeneration

To evaluate the reusability of the Ag–Ag2O/PTh catalyst, recyclability experiments were conducted up to four cycles (shown in the Supporting Information as Figure S3). The catalytic activity of the Ag–Ag2O/PTh catalyst revealed a slight decline of 10% after the fourth cycle. The regenerated Ag–Ag2O/PTh catalyst was investigated for the change in its spectral and morphological features. The XRD profile of the recycled Ag–Ag2O/PTh catalyst revealed a similar pattern as that of pristine Ag–Ag2O/PTh (given in the Supporting Information as Figure S4a). The peaks were observed to be sharp and distinct, confirming that the catalyst was able to retain its crystalline nature even after four cycles. The IR spectrum of Ag–Ag2O/PTh also revealed insignificant changes in the functional groups (given in the Supporting Information as Figure S4b), confirming that the catalyst was structurally intact and could be safely used up to four cycles.

Analysis of Degraded Fragments via LCMS and Confirmation of Radical Generation via Scavenging Experiments

The intermediates products obtained after microwave-assisted catalytic degradation of paracetamol drug using Ag–Ag2O/PTh as catalyst were identified using the liquid chromatography mass spectrometry (LCMS) technique, and the chromatographs are provided in the Supporting Information as Figure S5. The degradation mechanism of paracetamol (m/z value 151) was favored by the fission of CH3–C=O group to form aminophenol (P1, m/z—111), Scheme 1. The fission of amide group further led to the formation of cyclohexanol (P2, m/z—100), followed by the formation of phenol via the electron attack on cyclohexanol. The fragmentation of the OH group of phenol generated cyclohexane, which upon rearrangement, transformed to cyclohexene and cyclohexadiene. The diene upon further attack by the reactive species generated nontoxic diols, as shown in Scheme 1.

Scheme 1. Proposed Degradation Pathway of Paracetamol into Its Intermediates.

Scheme 1

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To explore radical generation, three different quenchers, namely, sodium sulfate (Na2SO4) (e-scavenger) benzoquinone (BQ) (•–O2 scavenger), and isopropyl alcohol (IPA) (•OH scavenger) were added into paracetamol drug solution and exposed to microwave irradiation for 20 min in the presence of Ag–Ag2O/PTh as catalyst (given in the Supporting Information as Figure S6). The degradation rate of the paracetamol drug was observed to decrease in the presence of Na2SO4. The degradation rate of paracetamol drug was noticed to be 75% in the absence of any scavenger and 57% in the presence of Na2SO4. Similarly, the degradation rate was noticed to be reduced to 38% in the presence of IPA and 46% in the presence of BQ. The reduction in the degradation rate of paracetamol was noticed to be significantly reduced in the presence of IPA and BQ confirming that—•OH and •–O2 were the active radical species that were involved in microwave-assisted catalytic degradation of the paracetamol using Ag–Ag2O/PTh as catalyst.

Comparison of Various Catalysts Used for the Degradation of Paracetamol under Different Conditions

Degradation of paracetamol has been reported by various kinds of photocatalysts which are briefly discussed in Table 1. Jallouli et al.6 conducted photocatalytic degradation of acetaminophen using TiO2 P25 under UV light and confirmed that more than 90% of 2.65 × 10–4 M solution of the drug degraded under UV irradiation. Vaiano et al.41 prepared TiO2–graphite composites (TiO2–G) which revealed 88% degradation of paracetamol (25 mg/L) under 180 min UV light irradiation. Similarly, Dalida et al.2 explored the degradation of acetaminophen using TiO2 under visible light irradiation and confirmed that 95% of acetaminophen degradation took place after 540 min irradiation in the presence of 1.0 g/L TiO2/KAl(SO4)2 aqueous solution having an acetaminophen concentration of 0.10 mM. Gotostos et al.8 designed novel photocatalyst K3[Fe(CN)6]/TiO2 to degrade acetaminophen under visible light using blue and green LED lights. It was observed that 0.1 mM of acetaminophen was degraded up to 98% under blue LED and 64% under green LED when exposed for 9 h. Yanyan et al.42 utilized TiO2/SiO2 and WO3/TiO2/SiO2 for the degradation of acetaminophen (5 mg/L) under UV–vis irradiation which revealed 95% degradation in the presence of WO3/TiO2/SiO2. Likewise, Nasr et al.43 utilized noble metal-loaded TiO2 photocatalysts, namely, Ag/TiO2, Au/TiO2, and Pt/TiO2 for the degradation of acetaminophen (20 mg/L) using solar light. Almost 78% degradation was achieved within 180 min using Pt/TiO2. Hence, it can be concluded that microwave-assisted degradation of paracetamol using PTh-modified Ag–Ag2O was found to be far superior to UV and visible light irradiation methods reported for the degradation of paracetamol. Moreover, the fragments produced in our case were mainly diols unlike toxic amines and phenols as confirmed by LCMS studies. This technique could therefore be utilized as a green technology for the rapid and eco-friendly mode of degradation of toxic pharmaceuticals.

Table 1. Paracetamol Degradation Using Different Photocatalysts, Exposure Time, and Different Conditions of Light Source.

photocatalysts concentration of drug degradation of paracetamol duration of degradation light source
TiO2 nanoparticles, TiO2/cellulosic fiber6 2.65 × 10–4 M 90% 3.5 h UV and sunlight irradiation
TiO2–graphite composites41 25 mg L–1 88% 180 min UV light
TiO2/KAl(SO4)22 0.10 mM acetaminophen 95% 540 min visible light
K3[Fe(CN)6]/TiO28 0.1 mM of acetaminophen 98% (blue LED), 64% (green LED) 9 h blue LED lamp, green LED lamp
TiO2/SiO2, WO3/TiO2/SiO242 5 mg/L of acetaminophen 42%, 95% 4 h UV–vis irradiation
Ag/TiO2, Au/TiO2, Pt/TiO243 20 mg/L acetaminophen 73.7%, 68.8%, 78.0% 180 min solar light
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Conclusions

Microwave-assisted green synthesis of Ag–Ag2O was carried out using O. sanctum, and the synthesized nanoparticles were sensitized using PTh. XRD studies showed the crystalline morphology of the nanohybrids and TEM analysis showed that average particle size was found to be ranging between 36 and 40 nm. SEM–EDX with elemental mapping confirmed stoichiometry of Ag–Ag2O and the homogeneous distribution of PTh over Ag–Ag2O. UV–vis spectra confirmed the band gap of Ag/Ag2O–PTh to be 0.68 eV. The nanohybrid exhibited enhanced microwave-assisted catalytic activity against the degradation of paracetamol within a very short time span of 20 min. The catalyst was reusable up to four cycles which revealed no change in structural and morphological features as confirmed by IR and XRD studies. The radical scavenging experiments confirmed the formation of •–O2•OH radicals. Based on the LCMS data, the degradation pathway of paracetamol was proposed and revealed formation of low molar mass fragments constituted of mainly dienes. Based on the reported photocatalysts utilized for the degradation of paracetamol under UV and visible light irradiation, Ag–Ag2O/PTh exhibited superior microwave-assisted catalytic properties and could be utilized for rapid degradation of toxic pharmaceutical pollutants. A comparative report on the visible light photocatalysis and microwave-assisted catalytic properties of Ag–Ag2O/PTh is underway in our laboratory and will be published soon.

Experimental Details

O. sanctum (Tulsi) leaves were collected from university campus of Jamia Millia Islamia, New Delhi, India. Silver nitrate (AgNO3), (molar mass: 169.87 g/mol, density: 4.35 g/cm3, melting point: 212 °C, boiling point: 440 °C) (Merck India), thiophene (C4H4S, molar mass: 84.14 g/mol, density: 1.05 g/cm3, boiling point: 84 °C) (Loba Chemie Pvt. Ltd., India), ferric chloride (FeCl3·6H2O, molar mass 270.30 g/mol, assay ≥98%, boiling point: 280–285 °C, melting point: 37 °C, Merck India), chloroform (CHCl3, vapour pressure 211 hPa (20 °C), boiling point 61 °C, melting point −63 °C, solubility: 8.7 g/L, Sigma-Aldrich, USA), and ethanol (Merck India) were used without further purification.

Preparation of O. sanctum Extract

The extract of O. sanctum was prepared using the leaves of the plant which were washed with distilled water to remove dust particles and impurities. The leaves were then dried finely ground into powder. Approximately, 20 g of the powdered leaves was added to a Soxhlet apparatus containing an ethanol:water mixture (50 mL (v/v)) and heated at 50 °C for 1 h. The extract of the leaves was collected and filtered using a Buchner funnel using Whatman paper no. 42. The filtrate was then kept at 4 °C in a refrigerator for 24 h.

Microwave-Assisted Green Synthesis of Ag–Ag2O Nanoparticles

The extract of O. sanctum (30 mL) was added to AgNO3 solution (30 mL, 0.5 M) in a 250 mL Erlenmeyer flask which was subjected to microwave irradiation for 5 min. The color of the reaction mixture turned dark brown, confirming the oxidation of Ag particles. The reaction mixture was kept for 24 h under dark condition 30 °C for complete bioreduction process. The obtained Ag–Ag2O particles were centrifuged at 1000 rpm and washed several times with distilled water and ethanol. The obtained powder was then dried in a vacuum oven at 70 °C for 12 h. The Ag–Ag2O particles were then subjected to calcination at 600 °C to obtain the metal oxide powder.

Polymerization of Thiophene (PTh)

Double distilled thiophene monomer (5 mL) was dissolved in chloroform (30 mL), and FeCl3 dissolved in 30 mL of chloroform was added dropwise to the thiophene solution with continuous stirring at 25 °C for 2 h on a magnetic stirrer equipped with an N2 inlet and a thermometer. The reaction mixture was then filtered and washed with double distilled water to remove the unreacted monomer and oxidant impurities. The obtained polymer was dried in a vacuum oven at 80 °C for 24 h.

Synthesis of Ag−Ag2O/PTh Nanohybrids

Ag–Ag2O nanoparticles (1.39 g) and PTh (1.39 g) were mixed and grinded using a mortar and pestle. The mixed powder was then dissolved in an ethanol:water mixture (50/50 v/v) in a 100 mL conical flask and sonicated for 4 h at 25 °C. The obtained nanocomposite was then centrifuged, washed with distilled water, and dried in an oven at 80 °C before use.

Characterization

Spectral Measurements

FT-IR spectra were recorded on an FT-IR spectrophotometer model Shimadzu Affinity-1. UV–vis–IR diffuse reflectance spectra were recorded on PerkinElmer Lamda 35, USA.28,29

Morphological Studies

FE-SEM–EDX spectra were recorded on FEI, Nova nano SEM 30 KVA, Germany coupled with EDX. XRD patterns were recorded on an X-ray diffractometer (Rigaku Rodafex 200B) using a Ni-filtered Cu Kα radiation source. High resolution electron emission micrographs were taken on FEI, Technai HR-TEM 200 kV, USA.

Thermal Analysis

TGA was recorded on a thermal analyzer model TA/DTA 6300, EXSTAR 6000. The samples were heated between 35 and 810 °C at the rate of 10 °C min–1 under a nitrogen atmosphere.

Microwave-Assisted Catalytic Degradation of Paracetamol and Analysis of Degraded Fragments

The degradation experiments were performed under microwave irradiation using microwave oven model IFB (17PM-MEC2B) equipped with a Teflon magnetic stirrer (Scientific Instruments). Paracetamol drug was used as a model organic pollutant to evaluate the catalytic activity of Ag–Ag2O, PTh and Ag/Ag2O–PTh samples. Approximately, 100 mg photocatalyst (Ag–Ag2O, PTh and Ag/Ag2O–PTh) was added to a 100 mL aqueous suspension of paracetamol (80 mg/L), which was sonicated for 10 min and then kept under dark condition to attain the adsorption–desorption equilibrium. The drug solution (100 mL) was irradiated under microwave oven in the presence of the catalyst (9100 mg) for 20 min. Aliquots of 2 mL were taken out at a fixed time intervals to obtain the supernatant liquid at regular intervals of 5, 10, 15, and 20 min. The concentration of the paracetamol was measured via a UV–vis spectrophotometer model Shimadzu UV-1800 at λmax = 239 nm. The degraded fragments of paracetamol were identified by the LC–MS technique as per method reported in our previous studies.28,29

Confirmation of Scavengers and Recyclability Tests

Radical scavenging experiments were performed by adding 50 mg of the catalyst (Ag–Ag2O, PTh, and Ag−Ag2O/PTh) to drug solution (50 mL, 100 ppm) containing scavengers Na2SO4 (5 mL, 5 Mm), BQ (5 mL, 5 Mm), and IPA (5 mL, 5 Mm). The suspension was sonicated for 10 min and exposed to microwave irradiation for 20 min. Aliquots of suspension (2 mL) were drawn at regular intervals, and the UV spectra were recorded on a UV–visible spectrophotometer (model Shimadzu UV 1800).12,28,29 The recyclability was tested up to four cycles, and in each cycle, 50 mg of Ag−Ag2O/PTh was used to degrade 100 mL of aqueous suspension of paracetamol (80 mg/L) exposed to microwave irradiation for 20 min. The catalyst was recycled by air-drying and reused.

Acknowledgments

The authors also wish to acknowledge the instrumentation facilities utilized at CIF facility under DST-PURSE, JMI, and the SAIF Facility at All India Institute of Medical Sciences (AIIMS) for carrying out the TEM analysis.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.0c00405.

  • UV–visible spectra of paracetamol under microwave irradiation, Ct/Co versus time plots of paracetamol, effect of paracetamol concentration on the degradation efficiency using Ag−Ag2O and Ag−Ag2O/PTh as catalysts, recyclability test of the Ag−Ag2O/PTh nanohybrid, XRD and IR spectrum of Ag−Ag2O/PTh, LC−MS spectrum of intermediates of paracetamol (Calpol), and Ct/Co versus time plots (PDF)

Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. U.R. conceptualized the work and analyzed the results while J.Z. carried out the experimental studies.

The authors declare no competing financial interest.

Supplementary Material

ao0c00405_si_001.pdf (589.2KB, pdf)

References

  1. Villota N.; Lomas J. M.; Camarero L. M. Study of the paracetamol degradation pathway that generates color and turbidity in oxidized wastewaters by photo-Fenton technology. J. Photochem. Photobiol., A 2016, 329, 113–119. 10.1016/j.jphotochem.2016.06.024. [DOI] [Google Scholar]
  2. Dalida M. L. P.; Amer K. M. S.; Su C.-C.; Lu M.-C. Photocatalytic degradation of acetaminophen in modified TiO2 under visible irradiation. Environ. Sci. Pollut. Res. 2014, 21, 1208–1216. 10.1007/s11356-013-2003-4. [DOI] [PubMed] [Google Scholar]
  3. Fan G.; Peng H.; Zhang J.; Zheng X.; Zhu G.; Wang S.; Hong L. Degradation of acetaminophen in aqueous solution under visible light irradiation by Bimodified titanate nanomaterials: morphology effect, kinetics and mechanism. Catal. Sci. Technol. 2018, 8, 5906–5919. 10.1039/c8cy01614c. [DOI] [Google Scholar]
  4. Nunes B.; Antunes S. C.; Santos J.; Martins L.; Castro B. B. Toxic potential of paracetamol to freshwater organisms: a headache to environmental regulators. Ecotoxicol. Environ. Saf. 2014, 107, 178–185. 10.1016/j.ecoenv.2014.05.027. [DOI] [PubMed] [Google Scholar]
  5. Moctezuma E.; Leyva E.; Aguilar C. A.; Lunaa R. A.; Montalvo C. Photocatalytic degradation of Paracetamol: Intermediates and total reaction meachanism. J. Hazard. Mater. 2012, 243, 130–138. 10.1016/j.jhazmat.2012.10.010. [DOI] [PubMed] [Google Scholar]
  6. Jallouli N.; Elghniji K.; Trabelsi H.; Ksibi M. Photocatalytic degradation of paracetamol on TiO2 nanoparticles and TiO2/cellulosic fiber under UV and sunlight irradiation. Arabian J. Chem. 2017, 10, S3640–S3645. 10.1016/j.arabjc.2014.03.014. [DOI] [Google Scholar]
  7. Vogna D.; Marotta R.; Napolitano A.; d’Ischia M. Advanced Oxidation Chemistry of Paracetamol, UV/H2O2 −Induced Hydroxylation/Degradation Pathways and 15N-Aided Inventory of Nitrogenous Breakdown Product. J. Org. Chem. 2002, 67, 6143–6151. 10.1021/jo025604v. [DOI] [PubMed] [Google Scholar]
  8. Gotostos M. J. N.; Su C. C.; De luna M. D. G.; Lu M. C. Kinetics study of acetaminophen degradation by visible light photocatalysis. J. Environ. Sci. Health, Part A 2014, 49, 892–899. 10.1080/10934529.2014.894310. [DOI] [PubMed] [Google Scholar]
  9. Abdul-Zahra A. J.; Mashkour M. S.; Juda A. M.; Al-Sulrani H. A. A. Photocatalytic degradation of paracetamol and procanine. Int. J. ChemTech Res. 2016, 9, 412–425. [Google Scholar]
  10. Kashyap J.; Ashraf S. M.; Riaz U. Highly Efficient Photocatalytic Degradation of Amido Black 10B Dye Using Polycarbazole-Decorated TiO2 Nanohybrids. ACS Omega 2017, 2, 8354–8365. 10.1021/acsomega.7b01154. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Riaz U.; Ashraf S. M.; Budhiraja V.; Aleem S.; Kashyap J. Comparative studies of the photocatalytic and microwave −assisted degradation of alizarin red using ZnO/poly(1- naphthylamine) nanohybrids. J. Mol. Liq. 2016, 216, 259–267. 10.1016/j.molliq.2016.01.018. [DOI] [Google Scholar]
  12. Riaz U.; Zia J. Microwave-assisted rapid degradation of DDT using nanohybrids of PANI with SnO2 derived from Psidium Guajava extract. Environ. Pollut. 2020, 259, 113917. 10.1016/j.envpol.2020.113917. [DOI] [PubMed] [Google Scholar]
  13. Xu P.; Shen X.; Luo L.; Shi Z.; Liu Z.; Chen Z.; Zhu M.; Zhang L. Preparation of TiO2/Bi2WO6 nanostructured heterojunctions on carbon fibers as a weaveable visible-light photocatalyst/photoelectrode. Environ. Sci.: Nano 2018, 5, 327–337. 10.1039/c7en00822h. [DOI] [Google Scholar]
  14. Li S. J.; Zhang L. S.; Wang H. L.; Chen Z. G.; Hu J. Q.; Xu K. B.; Liu J. S. Ta3N5-Pt nonwoven cloth with hierarchical nanopores as efficient and easily recyclable macroscale photocatalysts. Sci. Rep. 2014, 4, 3978. 10.1038/srep03978. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Li S.; Shen X.; Liu J.; Zhang L. Synthesis of Ta3N5/Bi2MoO6 core–shell fiber-shaped heterojunctions as efficient and easily recyclable photocatalysts. Environ. Sci.: Nano 2017, 4, 1155–1167. 10.1039/c6en00706f. [DOI] [Google Scholar]
  16. Cao S.; Low J.; Yu J.; Jaroniec M. Polymeric photocatalysts based on graphitic carbon nitride. Adv. Mater. 2015, 27, 2150–2176. 10.1002/adma.201500033. [DOI] [PubMed] [Google Scholar]
  17. Chang Y.; Liu Z.; Shen X.; Zhu B.; Macharia D. K.; Chen Z.; Zhang L. Synthesis of Au nanoparticle-decorated carbon nitride nanorods with plasmon-enhanced photoabsorption and photocatalytic activity for removing various pollutants from water. J. Hazard. Mater. 2018, 344, 1188–1197. 10.1016/j.jhazmat.2017.10.040. [DOI] [PubMed] [Google Scholar]
  18. Bi Y.; Ouyang S.; Umezawa N.; Cao J.; Ye J. Facet effect of singlecrystalline Ag3PO4 sub-microcrystals on photocatalytic properties. J. Am. Chem. Soc. 2011, 133, 6490–6492. 10.1021/ja2002132. [DOI] [PubMed] [Google Scholar]
  19. Konta R.; Kato H.; Kobayashi H.; Kudo A. Photophysical properties and photocatalytic activities under visible light irradiation of silver vanadates. Phys. Chem. Chem. Phys. 2003, 5, 3061–3065. 10.1039/b300179b. [DOI] [PubMed] [Google Scholar]
  20. Dong H.; Chen G.; Sun J.; Li C.; Yu Y.; Chen D. A novel high-efficiency visible-light sensitive Ag2CO3 photocatalyst with universal photodegradation performances: simple synthesis, reaction mechanism and first-principles study. Appl. Catal., B 2013, 134-135, 46–54. 10.1016/j.apcatb.2012.12.041. [DOI] [Google Scholar]
  21. Petica A.; Florea A.; Gaidau C.; Balan D.; Anicai L. Synthesis and characterization of silver-titania nanocomposites prepared by electrochemical method with enhanced photocatalytic characteristics, antifungal and antimicrobial avtivity. J. Mater. Res. Technol. 2019, 8, 41–53. 10.1016/j.jmrt.2017.09.009. [DOI] [Google Scholar]
  22. Zare M.; Namratha K.; Alghamdi S.; Mohammad Y. H. E.; Hezam A.; Zare M.; Zhang Q. X. Novel Green Biomimetic Approach for Synthesis of ZnO-Ag Nanocomposite; Antimicrobial Activity against Food-borne Pathogen, Biocompatibility and solar Photocatalysis. Sci. Rep. 2019, 9, 8303. 10.1038/s41598-019-44309-w. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Al-Sherbini A.-S. A.; Ghannam H. E. A.; El-Ghanam G. M. A.; El-Ella A. A.; Ahmad A. M. Y. Utilization of chitosan/Ag bionanocomposites as eco-friendly photocatalytic reactor for Bactericidal effect and heavy metals removal. Heliyon 2019, 5, e01980 10.1016/j.heliyon.2019.e01980. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Pratheesya T.; Harish S.; M N.; Sohila S.; Ramesh R. Enhanced antibacterial and photocatalytic activities of silver nanoparticles anchored reduced graphene oxide nanostructure. Mater. Res. Express 2019, 6, 074003. 10.1088/2053-1591/ab1567. [DOI] [Google Scholar]
  25. Gasmalla H. B.; Lu X.; Shinger M. I.; Ni L.; Chishti A. N.; Diao G. Novel magnetically separable of Fe3O4/Ag3PO4@WO3 nanocomposites against Staphylococcus aureus (S. aureus). J. Nanobiotechnol. 2019, 17, 58. 10.1186/s12951-019-0485-z. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Arjunan N.; Kumari H. L. J.; Singaravelu C. M.; Kandasamy R.; Kandasamy J. Physicochemical investigations of biogenic chitosan-silver nanocmposite as antimicrobial and anticancer agent. Int. J. Biol. Macromol. 2016, 92, 77–87. 10.1016/j.ijbiomac.2016.07.003. [DOI] [PubMed] [Google Scholar]
  27. Wang X.; Li S.; Yu H.; Yu J.; Liu S. Ag2O as a new visible-light photocatalyst: Self-stability and high photocatalytic activity. Chem.—Eur. J. 2011, 17, 7777–7780. 10.1002/chem.201101032. [DOI] [PubMed] [Google Scholar]
  28. Zhou W. J.; Leng Y. H.; Hou D. M.; Li H. D.; Li L. G.; Li G. Q.; Liu H.; Chen S. W. Phase transformation and enhanced photocatalytic activity of S-Doped Ag2O/TiO2 heterostructured nanobelts. Nanoscale 2014, 6, 4698–4704. 10.1039/c3nr06565k. [DOI] [PubMed] [Google Scholar]
  29. Zia J.; Rashad P M.; Riaz U. Photoctalytic degradation of anti-inflammatory drug using POPD/Sb2O3 organic-inorganic nanohybrid under solar light. J. Mater. Res. Technol. 2019, 8, 4079–4093. 10.1016/j.jmrt.2019.07.017. [DOI] [Google Scholar]
  30. Zia J.; Ajeer M.; Riaz U. Visible- light driven photocatalytic degradation of bisphenol −A using ultrasonically synthesized polypyrrole/K-birnessite nanohybrids: Experimental and DFT studies. J. Environ. Sci. 2019, 79, 161–173. 10.1016/j.jes.2018.11.021. [DOI] [PubMed] [Google Scholar]
  31. Shah M.; Fawcett D.; Sharma S.; Tripathy S.; Poinern G. Green Synthesis of Metallic Nanoparticles via Biological Entities. Materials 2015, 8, 7278–7308. 10.3390/ma8115377. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Kulkarni N.; Muddapur U. Biosynthesis of Metal nanoparticles: A Review. J. Nanotechnol. 2014, 2014, 510246. 10.1155/2014/510246. [DOI] [Google Scholar]
  33. Sullivan K. T.; Wu C.; Piekiel N. W.; Gaskell K.; Zachariah M. R. Synthesis and reactivity of nano-Ag2O as an oxidizer for energetic systems yielding antimicrobial products. Combust. Flame 2013, 160, 438–446. 10.1016/j.combustflame.2012.09.011. [DOI] [Google Scholar]
  34. Wei N.; Cui H.; Song Q.; Zhang L.; Song X.; Wang K.; Zhang Y.; Li J.; Wen J.; Tian J. Ag2O nanoparticles/TiO2 nanobelt heterostructures with remarkable photo-response and photocatalytic properties under UV, visible and near −infrared irradiation. Appl. Catal., B 2016, 198, 83–90. 10.1016/j.apcatb.2016.05.040. [DOI] [Google Scholar]
  35. Ravichandran S.; Paluri V.; Kumar G.; Loganathan K.; Rao B.; Venkata B. R. K. A novel approach for the biosynthesis of silver oxide nanoparticles using aqueous leaf extract of Callistemon lanceolatus (Myrtaceae) and their therapeutic potential. J. Exp. Nanosci. 2016, 11, 445–458. 10.1080/17458080.2015.1077534. [DOI] [Google Scholar]
  36. Chen J.; Feng J.; Yan W. Facile synthesis of a polythiophene/TiO2 particle composite in aqueous medium and its adsorption performance for Pb(ii). RSC Adv. 2015, 5, 86945–86953. 10.1039/c5ra14614c. [DOI] [Google Scholar]
  37. Khanmohammadi S.; Karimian R.; Hajibonabi F.; Mostafidi E.; Tanomand A.; Edjlali L.; Azami Z. K.; Mehrabani M. G.; Kafil H. S. Polythiophene/TiO2 and polythiophene/ZrO2 nanocomposites: physical and antimicrobial properties against common infections. Biointerface Res. Appl. Chem. 2018, 8, 3457–3462. [Google Scholar]
  38. Murugavel S.; Malathi M. Synthesis and Characterization of polythiophene nanofibers. Int. J. Chem. Sci. 2016, 14, 363–371. [Google Scholar]
  39. Kauser A. Synthesis and Electrical Property of Polythiophene/Sol-gel Silver Nanoparticle-based Polyethylene Composite. Int. J. Compos. Mater. 2016, 6, 43–47. 10.5923/j.cmaterials.20160602.01. [DOI] [Google Scholar]
  40. Arulmoorthy M. P.; Vasudevan S.; Vignesh R.; Rathiesh A. C.; Srinivasan M. Green Synthesis of Silver Nanoparticles using medicall sand dune plant Ipomoea Pescaprae leaf extract. Int. J. Sci. Inven. Today 2015, 4, 384–392. [Google Scholar]
  41. Vaiano V.; Sacco O.; Matarangolo M. Photocatalytic degradation of Paracetamol under UV irradiation using TiO2-graphite composites. Catal. Today 2018, 315, 230–236. 10.1016/j.cattod.2018.02.002. [DOI] [Google Scholar]
  42. Yanyan L.; Kurniawan T. A.; Ying Z.; Albadarin A. B.; Walker G. Enhanced photocatalytic degradation of acetaminophen from wastewater using WO3/TiO2/SiO2 composite under UV–VIS irradiation. J. Mol. Liq. 2017, 243, 761–770. 10.1016/j.molliq.2017.08.092. [DOI] [Google Scholar]
  43. Nasr O.; Mohamed O.; Al-Shirbini A.-S.; Abdel-Wahab A.-M. Photocatalytic degradation of acetaminophen over Ag, Au and Pt loaded TiO2 using solar light. J. Photochem. Photobiol., A 2019, 374, 185–193. 10.1016/j.jphotochem.2019.01.032. [DOI] [Google Scholar]

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