Microstructural properties and antibacterial activity of Ce doped NiO through chemical method
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The nickel oxide and different concentration of Cerium ions (0.01 M, 0.02 M and 0.03 M) doped NiO nanoparticles (NPs) were synthesized by chemical method. The XRD spectra exhibited the cubic structure of NiO. The average crystalline sizes were observed as 43 nm, 36 nm, 29 nm and 23 nm in NiO and Ce doped NiO NPs, respectively. The Ni (2p), O (1s) and Ce (3d) oxidation states were confirmed by XPS spectra. The FESEM image and TEM image showed the flowers with spherical nanostructure in undoped and doped NiO NPs. The Chemical compositions were identified by EDAX spectra. Metal-oxide (Ni–O) functional groups were found at 439, 435, 445 and 446 cm−1 in undoped and doped samples respectively. The optical studies were carried out using UV–Vis spectra and PL studies. Magnetization values were enhanced in Ce doped NiO NPs as compared to NiO NPs. Antibacterial activities were done by various human pathogens with using NiO and Ce doped NiO NPs.
KeywordsNiO NPs Ce doped NiO NPs XRD PL Oxygen vacancies VSM Antibacterial activity
Rare earth (RE) 3d ion doped with NiO has been intensively studied in the past decade, to obtain better optical and magnetic properties . RE atoms are possessing the special 4f shells. RE atoms are the excellent candidates for the luminescence centers of doped materials due to the transition of intra –4f or 4f–5d narrow emission line. The transition plays the important roles in the absorption of RE atoms in the UV range. An energy transfer process from the excited semiconductor host to doping lanthanide atoms, promoted the doped NPs to circumvent absorption of optical centers with extraordinary improvement of luminescent properties [2, 3]. Cerium as one element of Lanthanide doped semiconductors has been used in the focus of numerous unique potential applications like optical properties and biomedical applications [4, 5, 6, 7, 8]. The NiO NPs are p-type semiconductors and have stable wide band gap (3.4–4.0 eV) . The NiO NPs are one of the promising metal oxides for various potential applications like alkaline batteries, gas sensors, electrochemical capacitors, smart windows, biomedicine, drug delivery, and magnetic bar codes [10, 11, 12, 13, 14, 15].
The mechanism of antibacterial actions of the material states were productions of reactive oxygen species (ROS)  on the surface of these NPs in the light causes oxidative stress in bacterial cells eventually, leading to death of the cells. Reactive oxygen species contain the most reactive hydroxyl radical (OH), the less toxic superoxide anion radical (˙O2−) and hydrogen peroxide with a weaker oxidizer (H2O2). This can damage Deoxyribo nucleic acid (DNA), cell membranes, etc., which lead to cell death . The attachment of the NPs to the bacteria has also been demonstrated. This is attributed to the electrostatic attraction between the negatively charged bacteria and the positively charged NPs. Such a contact may not only inhibit bacterial growth, but also the generated reactive oxygen species may kill the cell . It suggests that both NiO NPs and Ni2+ are toxic, but have different modes of actions which take place in the antibacterial cell death.
In the present investigations, NiO (A1), [cerium] Ce3+ ions (0.01 M (A2), 0.02 M (A3) and 0.03 M (A4)) doped NiO samples are synthesized by chemical method. The Synthesized samples are studied in structural, optical, magnetic and antibacterial properties of A1, A2, A3 and A4 samples and examined.
2 Materials and method
Nickel (II) nitrate hexahydrate (AR), cerium (III) nitrate hexahydrate (AR) and NaOH (AR) were used as precursor materials for the synthesis of Ni1−xCexO (where x = 0.0, 0.01, 0.02 and 0.03) series.
The experimental procedure for the preparation of NiO NPs (A1) sample has been reported in our previous paper . In the case of Ce doped NiO samples, the synthesis of Ni1−xCexO (x = 0.01 M (A2), 0.02 M (A3) and 0.03 M (A4)) of cerium nitrate salt solution was mixed with Nickel nitrate solution. 0.8 M of NaOH solution was added in drops to the homogenous mixed metal solution to form a black precipitate. The black precipitate was washed a number of times with deionized water and ethanol. Further the black precipitate was dried at 120 ◦C for 1 h. The obtained Ce doped NiO samples were annealed at 700 °C for 5 h and used for further studies.
The antibacterial activities of the Ni1−xCexO NPs for x = 0.0 (A1), 0.01 M (A2), 0.02 M (A3) and 0.03 M (A4) were investigated by the well diffusion method. They have been reported in our previous paper .
2.1 Characterization techniques
The NiO NPs were characterized by X-ray (XRD) diffractometer (model: X’PERT PRO PANalytical). The diffraction patterns were recorded in the range of 20°–80°. The monochromatic wavelength of 1.54Å was used. The XPS measurements were performed with an XPS (Carl Zeiss) equipment. The spectra were at a pressure using an ultra high vacuum with Al Kα excitation at 250 W. The samples were analyzed by Field Emission Scanning Electron (FESEM) Microscopy (Carl Zeiss Ultra 55 FESEM) with EDAX (model: Inca). FT-IR spectra were recorded with using Perkin-Elmer spectrometer. The UV–Vis-NIR spectrum was recorded in the wavelength range 190–1110 nm using Lambda 35. The magnetic properties were analyzed by vibrating sample magnetometer (Lakeshore mini VSM 3639).
3 Results and discussion
Atomic percentage of Ce doped NiO NPs
Atom. Con %
Atom. Con %
Atom. Con %
1.24 (Ce 3d)
Elemental composition of NiO and Ce doped NiO NPs
In summary, NiO and Ce doped NiO nanoparticles were prepared through chemical method. The XRD pattern revealed that the synthesized nanoparticles exhibited cubic structure. The oxidation states of Ni (2p) Ce (3d) and O (1s) were identified by x-ray photoelectron spectroscopy spectra for NiO NPs. The morphology were identified through FESEM and TEM analysis. The chemical compositions were identified through EDAX analysis. FT-IR spectra explained Ni–O stretching vibration observed at 439, 435, 445, and 446 cm−1 for respective NiO nanoparticles. The UV–Vis absorption spectra showed the absorption peak edges which are observed at 346, 322, 318 and 328 nm in A1, A2, A3 and A4 samples. The Ce doping of NiO NPs altered the band emission as compared to NiO NPs due to Nickel vacancies, oxygen vacancies and surface defects. The enhanced magnetization values of Ce doped NiO NPs are more than that of NiO NPs, which was due to Ce3+ ions substitution in NiO matrix. The NiO, Ce doped NiO NPs and Erythromycin exhibited antibacterial activity. We suggest that synthesized NiO and Ce doped NiO nanoparticles can be used for the treatment of various human diseases such as pneumonia, bloodstream infection, kidney failure, wound infection and urinary tract infections.
Mr. MAR carried out the preparation of nanoparticles and executes the physical characterization studies and contributed to the main text of the manuscript. Dr. RRK checked the scientific information and flow of the text to maintain a better readability. Further this research work is not funded by any agency.
Compliance with ethical standards
Conflict of interest
The authors declared that they have no conflict of interest.
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