The comparison of antibacterial activities of CsPbBr3 and ZnO nanoparticles
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All-inorganic cesium lead bromide (CsPbBr3) perovskite nanoparticles and ZnO nanoparticles were synthesized. The structure, optical properties and the morphology of synthesized nanoparticles were fully characterized using X-ray diffraction (XRD), UV/Vis spectroscopy and transition electron microscopy (TEM). A comparative study was carried out to investigate the antibacterial activity of ZnO and CsPbBr3 perovskite nanoparticles toward Gram-negative, rod-shaped Escherichia coli O157:H7 bacteria cells. Experimental results showed that the antibacterial activity of CsPbBr3 nanoparticles was better than that of ZnO nanoparticles.
KeywordsCsPbBr3 perovskite nanoparticles ZnO nanoparticles Antibacterial activity E. coli
Nanotechnology is one of the most interesting branches of science which could provide materials at the nanoscale size. Nanomaterials have been utilized broadly in various fields such as tissue engineering, drug delivery, bioscience, agriculture and water due to its unique physical and chemical properties [1, 2, 3]. Recently, nanoparticles (NPs) demonstrated a high impact in the antibacterial filed [4, 5]. Among them, zinc oxide (ZnO) is considered for its photocatalytic-driven bacterial activity in which it has a broad direct band gap energy of 3.3 eV and high exciton binding energy of 60 meV . Stability, good biocompatibility, low cost, and easy preparation are some of the advantages of the ZnO nanoparticle that makes it a promising antibacterial agent [4, 7]. Beside these benefits, ZnO nanoparticle also has some important drawbacks that limited its applications as an antibacterial agent such as easily losing the active sites and showing a tendency of aggregation. More importantly, ZnO with a wide band gap (Eg = 3.3 eV) could generate charge carriers only in the UV portion of sunlight. It must be highlighted that to overcome these shortcomings of the ZnO nanoparticle, some simple and efficient strategies have been developed . However, as an alternative, designing and fabrication of new nanomaterials with low band gap energy which is important in antibacterial activities could be considered as another strategy.
Organic–inorganic hybrid perovskite nanostructures (MAPbX3; MA = CH3NH3, X = Br, Cl or I) with tunable optical properties have attracted much attention. Perovskites are one of the wonderful groups of materials which demonstrate some practical properties such as high temperature superconductivity, piezoelectricity, pyroelectricity, ferroelectricity, and catalytic property . Recently, as an alternative, all-inorganic perovskites (CsPbX3, X = Cl, Br, I) have received tremendous consideration due to their enhanced stability and outstanding electronic properties compared to their organic–inorganic counterparts. To the best of our knowledge, there are no reports about antibacterial activity of all-inorganic perovskites. Therefore, for the first time, we investigated and compared the antibacterial activity of inorganic cesium lead bromide (CsPbBr3) perovskite powder with ZnO powder against Gram-negative, rod-shaped Escherichia coli O157:H7 (abbreviated as E. coli). Experimental results showed that CsPbBr3 perovskite agent was more efficient than ZnO for the destruction of bacteria.
Materials and methods
CsPbBr3 perovskite nanoparticles were fabricated through the free-surfactant process. All starting materials used for CsPbBr3 Perovskite NPs including lead bromide (PbBr2) and cesium bromide (CsBr) were obtained from Sigma-Aldrich and used without further purification. In a typical synthesis, in a 250 mL round bottom flask containing 100 mL DMF, 1 mg PbBr2 was dispersed via ultra-sonication. After stirring at 75 °C for 20 min, the appropriate amount of CsBr in ethanol was added dropwise to the mixture solution under vigorous stirring. Reaction temperature was decreased to 50 °C and stirred for 10 min. The obtained solution was centrifuged at 2500 rpm for 10 min and then washed several times with 1-propanol. Finally, collected powders were annealed at 350 °C and dried at 80 °C for 24 h .
In the case of ZnO NPs synthesis, zinc acetate dihydrate [Zn(O2CCH3)2·2H2O], isopropanol and monoethanolamine were purchased from Sigma-Aldrich. ZnO NPs were prepared using the sol–gel pyrolysis method . Typically, 1.1 g zinc acetate dihydrate was added in a mixture of isopropanol (15 mL) and monoethanolamine (0.55 mL). To obtain a clear and homogeneous solution, the mixture was stirred at 75 °C for 2 h. To make gel, the solution was kept for 2 days (aging). The gel was then preheated at 80 °C to evaporate the solvent and remove organic residuals. Finally, the obtained solid powders were annealed at 350 °C for 2 h. Shimadzu UV-1800 model spectrophotometer, SEM/EDX (MIRA3 TESCAN microscope) and TEM (Philips CM120). The agar well diffusion method was utilized to test the antibacterial property of NPs against Escherichia coli O157:H7 bacteria cells .
Results and discussions
Two different types of nanoparticles, ZnO and CsPbBr3 perovskite, were successfully synthesized and characterized. Free-surfactant fabrication of CsPbBr3 perovskite NPs offered a fast, easy and inexpensive approach for the synthesis of nanomaterials, which show potential for antibacterial activity at a large scale. The antibacterial activity of nanoparticles against Escherichia coli O157:H7 was evaluated. Experimental results showed a significant room temperature antibacterial operation of CsPbBr3 perovskite nanoparticles due to its narrower band gap.
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