Novel direct dual-Z-scheme ZnO-Er2O3-Yb2O3 heterostructured nanocomposite with superior photocatalytic and antibacterial activity
Graphical abstract
Introduction
Nowadays, the environmental pollution imputed by carcinogenic organic pigments and dyes are the frontline challenges for the research community. The use of highly toxic and hazardous dyes in medical laboratories and industrial applications have a diverse impact on the environment and public health [1]. On the other hand, infectious diseases due to pathogenic bacterial strains such as E. coli, and S. aureus are among the major sources of public health issues throughout the world [2]. Recently, enormous efforts have been made for developing metal oxides based efficient photocatalysts and antimicrobials agents to overcome these issues [3]. In this regard, solar photocatalytic technology is an efficient green approach for relieving the negative environmental influence of organic pollutants on the ecosystem [4]. The coupling of different functional materials into a single matrix to form a heterojunction is fascinating to achieve superior photocatalytic and antibacterial properties [5]. The double heterojunction interface in the mixed metal oxides may cause an increase in the carrier’s lifetime, charge separation efficiency and charge transferability due to suitable bandgap positions [6], [7]. The ZnO/REO nanocomposites are recently being fabricated to enhance photocatalytic and antibacterial activity. ZnO is one of the most promising candidates for photocatalytic and antibacterial applications because of its wide direct bandgap (3.37 eV), low-cost, high chemical stability, high biocompatibility, low toxicity and eco-friendly characteristics [3], [8]. Among various rare-earth oxides (REO), the Er2O3 and Yb2O3 with energy bandgap 5.3 eV and 4.9 eV along with different oxidation states have widely attracted due to their wide range of applications as heterogeneous catalysis, biosensors, antibacterial agent, and etc. [9], [10].
In this context, a novel ZnO-Er2O3-Yb2O3 heterojunction nanocomposite using the facile co-precipitation method is fabricated for the first time. The photocatalytic activity of grown nanocomposite was evaluated against MB dye under sunlight irradiation and the antibacterial activity against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) bacteria at different concentrations. To study the effect of various operational parameters such as catalyst dose, dye concentrations, pH of reaction along with reusability and radical trapping experiments are carried out. A possible direct dual-Z-scheme and conventional heterojunction schematic model is also proposed to elaborate on the photocatalytic mechanism.
Section snippets
Experimental
All the experimental procedures are provided in Supplementary data and characterization tools were discussed in the previous report [6].
Results and discussion
Fig. 1(a) shows the XRD pattern of as-prepared ZnO-Er2O3-Yb2O3 nanocomposite. All observed diffraction peaks are well indexed to ZnO hexagonal wurtzite, Er2O3 cubic, and Yb2O3 cubic structures, confirming the formation of the nanocomposite. The characteristic diffraction peaks of ZnO, Er2O3, and Yb2O3 are well resolved and no peak relating to impurity could be identified which indicates that heterostructured materials can be grown by facile co-precipitation method at room temperature. The
Conclusion
In summary, the direct dual-Z-scheme ZnO-Er2O3-Yb2O3 heterostructured nanocomposite was successfully prepared via the co-precipitation method. The optical energy bandgap in the visible region (2.9 eV) makes it an efficient photocatalyst for sunlight. The grown nanocomposite has good antibacterial activity for S. aureus but greater for E. coli bacteria. The photodegradation of MB solution under the sunlight illumination at different experimental conditions specified that 25 mg catalyst, 15 μM
Credit author statement
Dr. Muhammad Akram working as Research Officer in “Pakistan Council of Research in Water Resources (PCRWR), Bahawalpur, 63100, Pakistan”. The author added for his contribution in Chemical Oxygen Demand (COD) experiment.
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.
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