Synthesis of ZnO/MoS2 heterojunction with the green Ag nanoparticles for the efficient sunlight photocatalytic activity

Pristine MoS2 nanosheet/silver nanoparticles (MoS2/Ag NPs) and composites are fabricated via hydrothermal, green synthesis, and chemical methods. Pristine MoS2, Ag, Z/M, and Z/M/Ag nanoparticles and composites are characterized through SEM, FTIR, as well as UV–Vis spectroscopy. The bandgap of materials is reduced effectively which is useful for photocatalytic activity. The photocatalytic decomposition of pharmaceutical drugs in effluent has been researched using metal-oxide or metal-sulfide-based semiconductor nanoparticles as nano-catalysts. The originality of these nano-catalyst substances lies in their relative simplicity of manufacturing, capacity to absorb energy in the UV–visible spectrum, large bandgap, innoxious, and inexpensive. The visible-light photocatalytic activity of Z/M also Z/M/Ag composites were investigated using a test of OTC. Almost degradation of OTC in about 120 min. at different concentrations of composites, Z/M/Ag photocatalyst was attained. This substantial enhancement in the photocatalytic proficiency of Z/M/Ag photo-catalyst below visible light ir-radiation may be ascribed to existence of MoS2 and Ag micro-particles on ZnO micro-particles which significantly improves absorption in an observable scale of the visible range.


Introduction
Through the promotion of industries and agriculture , per annum, thousands of tons of drain water covering pharmaceutical toxins are generated (Umukoro et al. 2018), by way of a consequence, water contamination has become the world's most critical problem (Li et al. 2018). Million tons of large metals, poisonous cleaners, and further wastes are disposed of into the sea (Kumar et al. 2019) through various industries without any cleansing, these pollutants have caused damage to the environment, specifically near humans (Fu et al. 2012). More than 0.78 tons of humans in the globe do not have acquired freshwater, outcomes in serious health issues (Amin et al. 2014). Semiconductor photocatalysis is one of the innovative processes appropriate for the removal of environmental impurities and water toxics (Pant et al. 2013). While other semiconductors, such as ZnO, TiO 2 , Fe 2 O 3 , and ZnS, have been investigated for degradation of various carbon-based impurities, while, ZnO has earned the most interest in recent times (Li et al. 2017a(Li et al. , 2017b. This is due to its non-toxicity, flat band structure, spectrum overlap with sunlight emission, low cost, biological and chemical stability, and ease of use in both ambient and hazardous environments. (Sabouni & Gomaa 2019). Outstanding of its substantial exciton binding energy (60 meV) and direct bandgap, ZnO is a broad bandgap semiconductor material through a direct bandgap of 3.37 eV at ambient temperature, which has interesting applications for optoelectronic devices (Yang 2013;Li et al. 2017aLi et al. , 2017b. ZnO has got a lot of interest as the radiant photocatalyst in the degradation and eventual mineralization of pollutants (Hariharan 2006). Because of its wide bandgap energy, ZnO can just absorb a limited amount of visible radiation in the ultraviolet (UV) range, which corresponds to only 5% of the total ) . Its utilizations are further restricted via frequent recombination of photo-generated electron-hole pairs (Peng et al. 2013). Constructing heterojunction-based photocatalysts with enhanced photocatalytic activity as they can effectively distinct photo-generated electron-hole sets is one technique to solve the restrictions of metal-oxide photocatalysts Zhang et al. 2016). Among the thoroughgoing researched layered transition, metal dichalcogenides are MoS 2 (TMDCs). Molybdenum disulfide has been the focus of much research for non-aqueous batteries, catalyzed hydrodesulfurization of petroleum, and wear resistance, among other applications (Li et al. 2003). A serious review of several conversations of band-edge valley excitons in single layer MoS 2 is conducted out using wideband microsecond temporary absorption spectroscopy with circular polarization compressor lights, in which intravalley cohesive linkage mechanisms are easily noticeable at room temperature (Yue et al. 2022). The semiconductor single-layer MoS 2 has a direct bandgap of 1.8 eV. This remarkable feature of MoS 2 will mainly overcome limitation of contrast metal oxides allowing 2D constituents to be utilized in upcoming generation flipping and optoelectronic strategies (Ganatra and Zhang 2014;Li and Zhu 2015). Van der Waals interactions aggregate the MoS 2 sheets to become MoS 2 material, which can be separated into mono-and very few nanosheets in water or ethanol utilizing ultrasonic energy . The 1T0-MoS 2 also on edge of the surface makes the excitation as well as further slight decrease of *N 2 extra endothermic beneficial than perfectly preserved TiO 2 , that also leads to improved NRR catalytic properties, according to DFT calculations . MoS 2 includes a large variety of energy storage utilization in series, solar cells, micro-wave, and Terahertz utilizations, along with detection which includes optical components, diagnostic devices, and electrolytic diagnostic devices that plays a vital purpose in the identification of diseases such as cancer and Alzheimer's (Samy et al. 2021). Exfoliate with 2-D MoS 2 possesses strong physical and chemical characteristics, as well as a greater surface area, large number of distributed activation sites, and significant in-plane electron mobility, through a monolayer band slit of 1.2 to 2.2 eV (Wu et al. 2020). The MoS 2 nanoparticles have a large number of active sites that can adsorption contaminants and hence optimize photocatalytic performance. Based on the high Strong interaction in proportion to its two-dimensional structure and low electrostatic screen, the PL emissions of MoS 2 is characterized by excitation energy and trions. MoS 2 excited state not just to regulates the emission properties and also enables hard phase difference for significant optic benefit . As a result of its unique features, nanomaterials MoS 2 can be coupled with additional semiconductors like ZnO to generate hetero-junctions that boost photo-catalytic action (Ding et al. 2014;Kumar et al. 2019). The photocatalytic accomplishment of a p-n heterojunction fabrication of n-type ZnO then p-type MoS 2 can be significantly enhanced. To initiate, MoS 2 can begin beneath visible light to boost the p-n heterojunctions light use proficiency. Subsequently, the p-n consequence permits the electrons created by MoS 2 to travel to the conduction band (CB) of ZnO (Fei et al. 2020). Suneel Kumar reported that the nanosheets with triple heterojunctions, ZnO nanoparticles are attached to MoS 2 -RGO nanosheets in this composition, together with photocatalysts for photocatalytic hydrogen (H2) progression with high proficiency (Kumar et al. 2017). In this effort, we magnificently put together a new p-n heterojunction of ZnO/MoS 2 composites with the green Ag nanoparticles by adding Ag constant quantity in the composites of ZnO/MoS 2 with a chemical technique to boost the competence of pharmaceuticals degeneration. Ag nanoparticles improvement, which may facilitate greater dissociation of electron-hole pairs and considerable improvement of the visible region, has resulted in significant growth in photocatalytic activity. Furthermore, Ag nanoparticles are verified to have outstanding antiseptic properties (Phu et al. 2020;Thuc et al. 2016). Moreover, ZnO/MoS 2 with green Ag nanoparticles can successfully suppress the re-combination of photo-generated electrons also holes, manage a great external area, grow pharmaceutical impurities adsorption, and raise the experience of abundant energetic sites used for Oxytetracycline degeneration due to p-n hetero-junction of ZnO/MoS 2 also visible-light-active MoS 2 . Various useful nanomaterials can also be suggested to improve light-matter relations, improving purposes like the spacer, huge quadratic response, highefficiency quantum reference, and solar cell, owing to the quick advancement of current technology and research (Zhou et al. 2021). The chemical configuration, geomorphology structure, optical features too photocatalytic completion of simultaneously planned photocatalysts remained exhaustively measured. Also, the multiple degeneration process was thoroughly examined. The preparation of the unique triple photocatalyst and the degeneration of resistive organic substances had a parameter in this work.

Synthesis of ZnO
0.02 mol Zn (NO 3 )2·6H 2 O mixed in 750 ml distilled water during continuously stirring. 0.15 mol NH 3 ·H 2 O add dropwise to the solution at room temperature. The result is obtained as a white solution and pH is maintained. The final mixture heat at 80 °C and stir continuously. After the reaction, the precipitate filter washes many times through the deionized water than alcohol, then dries at 60 °C in the oven. Products are obtained as white powder. The procedure followed by Zhang is previously reported. (Zhang et al. 2007).

Synthesis of MoS 2
In the representative procedure, 0.8 g of ammonia metavanadate, and 5.12 g of thiourea remained diffuse into 80 ml de-ionized water and stimulated for 2 h. The suspension was very shiny and also have a white color. 10 ml of ethanol was added to the suspension to maintain the P H of the solution. The suspension was shifted into a 100 ml PTFElined stainless-steel autoclave and warmed up at 200 °C for 24 h. The solution dried up at 80 °C for 14 h. The obtained talc was blacked and shiny. The powder is put into the tube for future use.

Synthesis of green Ag nanoparticles
Bitter apples (Citrullus colocynthis) were collected from the Kfueit, RYK. And was used for the Aqueous extract solution. 20 g of a plant organ (seeds) were thoroughly washed in distilled water and soaked in 200 ml distilled water for 24 h at 40 °C. After that, the seeds were separated, the solution saved in a beaker, and covered by aluminum foil.10 ml of Aqueous extract suspension and 90 ml of distilled water were put into a beaker. The 0.08 g silver nitrate was added to this solution, beaker covered with aluminum foil, and was stirred in the whole solution for 15 min at normal temperature. The solution was put into China dishes, Covered China dishes with Aluminum foil, and kept in an oven at 120 °C. Every 15 min, the Solution was checked properly. After 2 h the oven temperature is set at 80 °C beacause the Solution remains safe from burning. The solution was dried completely for 8 h. the powder form of material was collected in the tube for future uses.

Synthesis of ZnO/MoS 2 Composites
In a beaker 50 ml ethanol and 1 g ZnO were added then it is stirred for 20 min. After that, the solution is covered by aluminum foil and kept aside. Secondly, the 0.2 g MoS 2 and 25 ml ethanol were added to the beaker and stirred for the 40mints. Now, for the composites of ZnO/MoS 2 , (2%, 4%, 6%, 8%, 10%) added 10 ml ZnO solution in every composite but the MoS 2 added by the given steps (1 ml in 2%, 2 ml in 4%, 3 ml in 6%, 4 ml in 8%, 5 ml in 10%) whole solution were put into the dish and covered it with aluminum foil. All the solutions were measured by measuring the cylinder. The dishes are kept in the oven and dry solution for 70 °C. after 5 h the solution dried completely and the white-colored powdered was obtained.

Synthesis of ZnO/MoS 2 /Ag
In the beaker 50 ml, ethanol, and 1 g of ZnO were added then it is stirred for 20 min. After that, the solution is covered by aluminum foil and kept on aside. Secondly, the 0.2 g MoS 2 and 25 ml ethanol were added to the beaker and stirred for the 40mints. Now, prepare the solution of Ag, add in beaker 0.01 g powder of Ag in 20 ml ethanol, stirrer for 15 min. Add a constant (4%) quantity of Ag solution in every (2%, 4%, 6%, 8% & 10%) of ZnO/MoS 2 composites. The completed solution is put in china dishes and dray at 80 °C.

Characterization techniques
Characterization allows us to assess the structure and contents of materials, as well as determine whether or not the approach was successful. UV spectroscopy is an optical spectroscopy technique that uses visible, ultraviolet, and near-infrared light. UV-Vis. spectroscopy tells us how much light absorbs the materials and gives the optical properties of the materials such as the bandgap of the materials. FT-IR (Fourier transform infrared spectroscopy) notify which chemical bond and functional group exist in the materials. SEM (Scanning electron microscopy) determined the morphology, size, and shape of the materials.

Photodegradation of Oxytetracycline (OTC) drug under dispersion of visible light
The splitting efficiency of photo-excited electrons and holes can also be enhanced by the heterojunction with MoS 2 and the enabling nanomaterials by limiting the agglomerate of MoS 2 . (Ji et al. 2021). ZnO was utilized as a catalyst for photocatalytic degeneration of OTC drugs (Changanaqui et al. 2020). Photocarriers energized by UV light will interact other ambient molecules to form O 2 and OH ions, resulting in effectively standardized tests the top Sulphur gaps of 1L-MoS 2 in an acidic condition proton (H + ) context (Q. Feng et al. 2021). within a maximum specimen, 5 mg of the synthesized catalyst (ZnO, MoS 2 , Ag, ZnO/MoS 2 , and ZnO/MoS 2 /Ag) was dispersed in the polluted suspension. The suspensions take place in the dark previous to light enhancement to verify that photocatalyst and contaminants be in symmetry. Behind revelations, almost 5 ml of the suspension was collected into vacutainer tubes. This suspension was examined by UV-Vis spectroscopy. Next, to determine the absorbance between 340 and 350 nm, photodegradation of OTC was analyzed. The amputation competence was concluded by the given calculation: The photocatalytic catalyst continuously at the surface of the catalyst is a pseudofirst-order reaction with the following kinetic equation in the solid-liquid reaction: where Co (initial), C t (reaction) concentration of OTC, correspondingly; k is the pseudofirst-order degeneration rate continual or superficial reaction rate continual and t is investigational time (min). (Luo et al. 2015;Nguyen et al. 2020). When measuring drug degradation, the influence of various control factors on photocatalytic activity, which includes photocatalyst concentration, primary P H of a suspension, and original pollutant percentage, was evaluated Triquet et al. 2020).

Structural characterization
SEM differs from traditional light microscopes in that it magnifies images using light waves. When an electron beam strikes a specimen surface in a scanning electron microscope, it interacts with it. The morphology of organized nano-particles and nano-sheets also their nano heterojunctions were calculated by scanning electron microscopy (SEM).
In the current research, the size and shape of pristine MoS 2 and Ag have been analyzed through SEM, as well as various samples, Z/M and Z/M/Ag having varying concentrations. The particle dimensions measured in SEM images are a formation of nanoflowers. The approximately observed particle size is 10 µm. The prepared molybdenum disulfide substance exhibits a nanoflower-like shape built from nanowires, as seen in Fig. 1A,   Lamba et al. 2015). A Band at 780 cm −1 is because of the S-S bond, and that at 1025 cm −1 is due to the S-S bond (Maugé et al. 2001;Kumar et al. 2016). The peaks on round 3197cm −1 fit to feature groups of the O-H stretch set (Maugé et al. 2001;Lamba et al. 2017). Figure 2b displays the FT-IR spectrum, of composed Ag nano-particles. There is wide absorption on 704 cm −1 , 945 cm −1 . The absorbance peak at 1384 cm −1 is noted ably greater signifying a remaining quantity of NO 3 in suspension, respectively. A peak at 1634 cm −1 is linked through stretch vibration of -C=C-. A peak at 1634 cm −1 possibly offered proportional stretching vibrations of -COO-(carboxylate ion) assemblies of amino acid deposits with the permitted carboxylate assemblies in protein. A peak at 3188 cm −1 specifies (alkenyl stretch) C-H at the same time as a peak of 945 cm -1 which signifies aromatic ring C-H vibrations, signifying participation of free catching. The research proposes that certain polyphenolic components be linked to silver nanoparticles. It indicates that polyphenols linked to Ag nanoparticles might be included in at a minimum a single aromatic ring. Endings show that molecules connected to silver nanoparticles have amide groups that are both free and bound. The aromatic rings may also contain amide groups. This suggests that the polyphenols coupled to silver nanoparticles have an aromatic ring and bound amide region (Satyavani et al. 2011). The C=O and C-O absorption bands were indicated by the peaks seen during 1397 cm −1 and 1502 cm −1 , accordingly. Due to the presence of water molecules, a maximum peak at 3398 was detected (Yang et al. 2016;Zhang et al. 2017). In composite MoS 2 /ZnO, entirely spreading peaks that exist in pure MoS 2 and ZnO take exposed. In FT-IR spectra of composite, there remain no strong peaks. The filtering of peak site, spectrum size, and spectrum solidity in the MoS 2 /ZnO samples prove its creation. (Awasthi et al. 2016). Figure 3 indicates FT-IR spectrum of composed Z/M/Ag (2%, 4%, 6%, 8%, 10%) composites. The broad absorption peak at 3372 cm −1 while the mutual peak of ZnO/MoS 2 located on (3370-3380) cm −1 , means that the Z/M/Ag composite verified its formation. The peak at 2352 cm −1 is because of the construction of compound sulfur with active sites in MoS 2 . Absorbance peak at 1379 cm −1 is noted ably improved signifying a remaining quantity of NO 3 in the suspension. A peak at 2970 cm −1 indicates (alkyl stretch) C-H as well as a peak of 1044 cm −1 which indicates aromatic ring C-H vibrations, indicating the participation of free catching. This proposed accessory of approximately polyphenolic components to silver Ag nano-particles. In composite Z/M/Ag, all different peaks that occur in pure MoS 2, ZnO, and Ag have been revealed. The FT-IR spectra of composite, spectrum width and spectrum strength prove the formation of Z/M/Ag.

UV-Vis characterization
The Uv-visible spectroscopy gives the bandgap and the ranges of the materials. Its fundamental way is to predict how much light the material under examination absorbs. It's used to figure out how much absorption is in a solution. MoS 2 , Ag, Z/M, and Z/M/Ag nanoparticles were classified using a UV-Vis. spectrophotometer. Using distilled water for Z/M and ethanol for Z/M/Ag in place of a reference. UV-Vis. absorption ranges of pristine MoS 2 , Ag, Z/M, and Z/M/Ag composite samples are shown in Fig. 4,5,6,7. Absorption peaks of all composites are observed nearly similar range from 340 to 360 nm, which certify, through doping of MoS 2 and Ag at different percent gives the variation in band gap ranges. With the Tauc plot link, the bandgap of pristine MoS 2 , Ag, and samples remained determined.

Photocatalytic efficiency
Because of the potential imaginable in environmental purification also solar energy conversion, semi-conductor photo-catalysts have acquired a lot of research consideration in recent decades. (Zhang et al. 2008). The photocatalytic efficiency of the produced nanomaterials was examined for mortification of the antibiotic oxytetracycline below visible light contact, relative findings are shown in Fig. 8. In photocatalysts under identical reaction conditions, Z/M and Z/M/Ag have the maximum rate of OTC degradation. A standard drug, OTC, was selected as the main contaminant, as well as the research measuring OTC has been performed around below visible light ir-radiation that measures the photocatalytic competence of composites. The time-dependent UV-Vis absorbance graph of OTC suspension with pristine MoS 2 and Ag nano-particles. Predictably, it produces relatively little quantity of OTC mortification because of insufficient light accumulating and efficient carrier re-combination. The assessment of the OTC degradation (%) used for the several photo-catalysts under examination is existing in Fig. 9. Nanocomposite Z/M/Ag are shown in Figures, correspondingly. Under visible-radiance enhancement, photo-generated carriers in MoS 2 start regular photo-degradation of OTC antibiotics, as shown in Figs. 10 and 11. Strangely improved photo-catalytic activity has been attained in the existence Z/M/Ag nanocomposite catalyst, in which OTC antibiotics were putrefied after 120 min lighting. I observed it, photo-catalytic productivities of entirely the Z/M/Ag nano-composites stay markedly greater than those of pristine MoS 2 and Ag NPs, suggesting respected collegial properties created by sample nano-structures. Between entirely the composites, this has been revealed that Z/M/Ag (6%, 8%, 10%) exhibited the finest photo-degradation activity. Consequently, rapid transfer of electrons at the heterojunction, facilitated electron transport due to contaminant band level, and improved contaminant adsorption efficiency of the Nanotechnology heterostructures might all be related to the increased photocatalytic activity of the BZM Nanotechnology heterojunctions (Benavente et al. 2018;Kumar et al. 2016). Importantly, the MoS 2 executes a dual function through the production of heterojunctions and improved photo stability as a result of simultaneous hole transfer. Additionally, generated B-doped ZnO-MoS 2 Nano heterostructures performed comparable nanocomposites in terms of photocatalytic activity, according to published research (Kumar et al. 2019;Kumar et al. 2018). Pristine MoS 2 exhibits only 9% degeneration of OTC, while pristine Ag exhibits only 20% degeneration. Composites Z/M/Ag (6%) exhibits 74% degeneration. Composites Z/M/Ag (8%) exhibits 79% degeneration. Composite Z/M/Ag (10%) exhibits the 85% degeneration. Rate of degeneration of OTC is: Z/M/Ag(10%) > Z/M/ Ag(8%) > Z/M/Ag(6%) > Ag > MoS 2 As shown in graph. There is no important variation in the top figure and the concentration reductions regularly positive the degeneration. The possible reaction of the equation is: