Hydrothermal synthesis of MoO3/ZnO heterostructure with highly enhanced photocatalysis and their environmental interest

https://doi.org/10.1016/j.jece.2021.105040Get rights and content

Highlights

  • The MoO3/ZnO heterostructure show a highly structural exclusivity combined with a large surface area.

  • Photocatalytic degradation of dye with non-hazardous intermediates and removal of heavy metals.

  • The excellent recyclability of MoO3/ZnO for further degradation process.

  • The present study aids as base-line data for future biological studies on MoO3/ZnO heterostructures.

Abstract

A methodological approach has been made in the synthesis of the MoO3/ZnO heterostructure via., superficial hydrothermal route. The synthesized MoO3/ZnO will act as an agent for the photocatalytic destruction of Eosin Blue (EB) in a single step with non-toxic molecular intermediates are attained. Simultaneously Chromium (Cr), Iron (Fe), Lead (Pb), Zinc (Zn), and Copper (Cu), heavy metal are removed under the impact of sunlight. Excellent activity against bacteria like Bacillus subtilis, Staphylococcus aureus, and the biocompatibility studies of Human embryonic kidney (HEK-293) was systematically accomplished. Also, the synthesized heterostructure was used in the treatment of Albino swiss mice administrated with air pollutant (PM 2.5). Later enormous collagen fibers, thickening of elastic fibers and congested pulmonary vessels with collapsed alveoli was observed but in case of mice treated with particulate matter followed by MoO3/ZnO showed very slight increase in the size of interalveolar walls, proving to be an excellent bio-medication. This work offers the opportunity of constructing efficient photocatalyst with admirable bio-compatibility for a safer environment. Among many other metal oxides tested during the experiment, pioneer synthesis of MoO3/ZnO heterostructure was a benchmark for various environmental therapies.

Introduction

The synthetic dyes and heavy metals have major negative impact on environmental life and biological health [1]. Direct and indirect effects of these dyes thrash millions of lives each year as well as builds major health hazards [2]. Also, dye and heavy metal pollution from several industries has a vital damages to environment because of the quick population growth and it has also made a great extent of damage to the aquatic organisms [3], [4], and also in India, exposure to particulate matter air pollution contributed to 1.26 million death in every year (an average). The pollutants primary effect was found in the respiratory system and which caused respiratory infections in lower respiratory tract, known as Chronic Obstructive Pulmonary Disease (COPD). Research work carried out on introduction of various drug for mitigating the air pollution problem is very less, so the property of the metal oxide is helping the research workers to treat the lung infected with air pollutants [5], [6]. Assorted water/wastewater treatment practice has dynamic past, which faced failure many times in achieving complete elimination of contaminants in waste-water counting along toxic organic dyes and heavy metals which is also not safe [7], [8]. The conversion of dyes (non-toxic molecular intermediates) and heavy metals (stabilization) to the form with multi-usage has occupied the research scholars for the 20 years [9]. MoO3/ZnO, which behaves as useful material has promised in gaining extraordinary attention of researchers because of having huge surface area for the activity and flexibility for designing the nanocomposite in desired shape with no change in chemical properties and has unresolved biocompatibility [10], [11]. Currently, mesoporous materials for photocatalysis is a captivating, cost-effective method for waste-water purification as well as biological applications [12], [13]. In addition, solar light-driven works by re-using of abundant energy to encourage dye degradation and heavy metal removal in tremendously low light conditions [14], [15]. The idea is modest having individual purpose based on the earliest method of utilizing metal-based derivatives in wastewater purification as it attains excellent removal and degradation competence [16], [17]. Some researchers had precursors into metal oxides into desired structures of nano carbon-metal and micro carbon-metal based derivatives for its sustainability and for its use in the degradation of dye, removal of heavy metal, medicine, batteries, detecting of biomolecules and also in electricals [18], [19]. The configuration wise organized and tailored heterostructure forms and sesquioxide are fascinating and attracted by many researchers for their distinguished property [20]. A fresh scientific insights about metal oxides to remove the pollutants in water and wastewater showed its significant possibilities as a photocatalyst [21], [22], [23] Till date, many groups has reported in the application of metal oxide as effective photocatalyst by chemical surface modification [24]. These are the improved choices for photocatalysis adding privilege to their substantial competences [25], which has undesirable influences on environment [26]. MoO3/ZnO heterostructure are synthesized by diverse methods, including laser ablation [27], arc discharge [28], electrolysis [29], microwave [30], mechanical grinding [31], and sol-gel dispensation [32]. But these approaches agonize from many problems, including huge cost, temperature. In this disparity, the synthesis of MoO3/ZnO using hydrothermal method, which is flexible cum cost-effective, and suitable technique in the production of high quality and quantity of MoO3/ZnO with reasonably less temperature for synthesis. Hydrothermal method will enable to enhance and fine-tune the physical characteristics like diameters, morphology and size. Many researchers are eagerly working on varied carbon-metal nanomaterials, but only few researches were focused on the biocompatibility features, with less information. An arousing approach was made to mitigate the health problem due to air pollution by employing mice as model organism. Albino swiss mice were administered with air pollutant (PM 2.5) followed by MoO3/ZnO via. intranasal instillation. Exact figure of control animal was treated with physiological saline. After the one-month administration, the animal lung was subject to histopathological scoring. Mice exposed to air pollutant after 30 days histopathological result showing the large concentration of collagen fibers, thickness of elastic fibers and congested pulmonary vessels with collapsed alveoli but in case of mice treated with particulate matter followed by MoO3/ZnO showed reduction in the size of interalveolar walls. Henceforth, it is a thought-provoking assignment to develop a low-cost and effective MoO3/ZnO heterostructure. The reputation of the materials is sensed to be even more if intense research is carried out. Grasping these points, concentration was laid on the material surface modifications using hydrothermal method for the heterostructure synthesis. The study is pioneered by using the synthesized heterostructure MoO3/ZnO for degrading EB dye, and heavy metals like Copper (Cu), Zinc (Zn), Iron (Fe), Lead (Pb), and Chromium (Cr) removal as well as the recyclability of heterostructure. Bacterial with toxicity valuations using HEK-293 cells is carried out.

Section snippets

Synthesis of MoO3/ZnO heterostructure

An entailed amount of 0.1 M NaOH (Loba Chemie, 99%) is dispersed in 20 ml of water with drop-wise addition of 0.1 M Zn (NO3)2·6H2O (Sigma-Aldrich, 99%) solution, both were mixed with 30 ml of DIW at 80 °C under magnetic agitating conditions. Then the solution is moved for hydrothermal synthesis process to a general-purpose stainless-steel autoclave. Later, the autoclaves were placed at 150 °C for 5 h and bought down to room temperature. And now the products from the liners was washed with

Characterization results of synthesized MoO3/ZnO heterostructure

The XRD patterns of MoO3/ZnO heterostructure synthesized by hydrothermal route at 150 °C for 5 h are revealed in (ESI. 1). The crystalline nanostructure was observed with intensive sharp peak. The diffractive peaks at 2θ of 12.11°, 24.01°, 25.41° and 27.11° could be compared to the 020, 110, 040 and 021 crystallographic planes respectively are perfectly indexed to those of hexagonal rod structured α-MoO3 with JCPDS No. 21-0569. The evident diffractive peaks with 2θ at 32.1°, 35.1°, 48.01°,

Conclusion

The present research work features the synthesis, fabrication and characterization of MoO3/ZnO heterostructure under mild hydrothermal conditions, for efficient photocatalysis and their biological applications. It scrutinizes the highly efficient and modified MoO3/ZnO with excellent recyclability which also proves to be the material suitable for the degradation of EB dye with molecular intermediates and heavy metal removal. Additionally, MoO3/ZnO is utilized for multi-tasking biological

CRediT authorship contribution statement

Abhilash Mavinakere Ramesh: Conceptualization, Methodology, Data curation, Writing - original draft, Visualization, Investigation, Software, Validation. Srikantaswamy Shivanna: Supervision, Writing - review & editing.

Funding information

The authors would like to acknowledge the support provided by Department of Science and Technology, Government of India, for awarding the financial assistance through DST – INSPIRE Senior Research Fellow (SRF) to Abhilash M R., award number (IF160104).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The animal welfare and the experimental procedures were carried out in accordance with the regulations for the administration of affairs concerning experimental animals, and the ethical regulations on the care and use of laboratory animals from University of Mysore, Karnataka, India, approved by university committee for animal

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