Structural, Optical, and Antibacterial Properties of NiO and BaO Doped NiO Prepared by Co-Precipitation Method

Inorganic Chemistry Inorganic Non-Metallic Materials Nanoscience Chemistry Materials Science Microbiology Materials Chemistry Biochemistry Life Sciences
Nickel Oxide BaO Doping Antibacterial Properties Optical Properties Co-Precipitation Method

Academic Background

Nickel oxide (NiO), as a p-type semiconductor, has garnered significant attention due to its exceptional optical properties, chemical stability, and extensive applications in optoelectronics, photocatalysis, and biosensors. NiO’s high transparency, adjustable electrical conductivity, and wide bandgap make it an ideal material for solar cells, photodetectors, and energy storage systems. However, the antibacterial properties of NiO and its potential in biomedical applications still require further investigation. Although previous studies have shown that NiO can inhibit bacterial growth by generating reactive oxygen species (ROS), its antibacterial efficiency is influenced by factors such as crystallite size, defect density, and surface structure.

In recent years, doping techniques have been widely used to optimize the performance of NiO. Barium oxide (BaO), as a dopant, is believed to enhance the optical properties of NiO, but its impact on the antibacterial performance of NiO has not been thoroughly studied. Therefore, this research aims to synthesize pure NiO and BaO-doped NiO (Ba-NiO) nanoparticles via the co-precipitation method, systematically investigating the effects of BaO doping on the structural, optical, and antibacterial properties of NiO. The study provides a theoretical foundation for optimizing NiO-based materials in biotechnology and related fields.

Source of the Paper

This study was jointly conducted by Sreenivasa Kumar Godlaveeti, N. Rajesh, Mohamed Ouladsmane, Ahmed M. Aljuwayid, K. Riazunnisa, Shaik Mohammed Azharuddin, and Rajababu Chintaparty. The research team is affiliated with the School of Energy and Power Engineering at Dalian University of Technology, the Department of Biotechnology and Bioinformatics at Yogi Vemana University, the Department of Physics at Rajeev Gandhi Memorial College of Engineering and Technology, the Department of Chemistry at King Saud University, and the Department of Physics at Annamacharya University. The paper was accepted on March 25, 2025, by Bionanoscience, a journal under Springer Nature, and published in the same year.

Research Process

1. Material Synthesis

The study employed the co-precipitation method to synthesize pure NiO and BaO-doped NiO nanoparticles. The specific steps are as follows: - Reagent Preparation: Analytical-grade nickel acetate tetrahydrate (Ni(C₂H₃O₂)₂·4H₂O) and barium chloride dihydrate (BaCl₂·2H₂O) were used as raw materials, with sodium hydroxide (NaOH) as the precipitating agent. - Solution Preparation: A 1 M nickel acetate solution and a 4 M NaOH solution were separately dissolved in distilled water, with a molar ratio of 1:4. - Co-precipitation Reaction: The NaOH solution was slowly added to the nickel acetate solution under magnetic stirring to ensure uniform precipitation. The precipitate was filtered, washed, and dried at 90°C for 3 hours. - Calcination Treatment: The dried material was calcined at 800°C for 2 hours to obtain pure NiO. BaO-doped NiO was prepared using the same method, with a doping ratio of 5%.

2. Structural Characterization

  • X-ray Diffraction (XRD) Analysis: XRD analysis was used to examine the crystal structure of pure NiO and Ba-NiO. The results showed that pure NiO has a face-centered cubic (FCC) structure, while BaO doping introduced additional diffraction peaks, indicating the successful incorporation of Ba²⁺ into the NiO lattice.
  • Transmission Electron Microscopy (TEM) Analysis: TEM images revealed that pure NiO nanoparticles are spherical, while Ba-NiO exhibits a mixed morphology of spherical particles and nanorods.
  • Elemental Mapping and Energy-Dispersive Spectroscopy (EDS) Analysis: EDS confirmed the presence of Ba in the doped sample, with an atomic percentage of 0.17% and a weight percentage of 0.72%.

3. Optical Properties Study

  • UV-Vis Absorption Spectroscopy: The absorption edge of pure NiO was located at 313 nm, while Ba-NiO exhibited a redshift in the absorption edge, indicating a reduction in bandgap energy.
  • Tauc Plot Analysis: The bandgap energy was calculated using the Tauc plot. Pure NiO has a bandgap energy of 3.0 eV, while Ba-NiO showed a slight reduction in bandgap energy.

4. Antibacterial Performance Testing

  • Experimental Design: The agar diffusion method was used to evaluate the antibacterial activity of NiO and Ba-NiO nanoparticles against Escherichia coli (E. coli) and Bacillus subtilis (Bacillus subtilis).
  • Result Analysis: Pure NiO exhibited larger inhibition zones at all concentrations, indicating superior antibacterial activity compared to Ba-NiO.

Main Results

1. Structural Analysis

BaO doping significantly altered the crystal structure of NiO, leading to lattice distortions and increased crystallinity. XRD and TEM analyses showed that Ba-NiO has larger crystallite sizes and a morphology transition from spherical to a mix of spherical particles and nanorods.

2. Optical Properties

BaO doping caused a redshift in the absorption edge of NiO, resulting in a reduced bandgap energy. This change is associated with the improved crystallinity and reduced defect density induced by BaO doping.

3. Antibacterial Performance

Pure NiO demonstrated higher antibacterial activity, attributed to its higher defect density and larger specific surface area. Although BaO doping improved optical properties, it slightly reduced antibacterial efficiency.

Research Conclusion

This study successfully synthesized pure NiO and BaO-doped NiO nanoparticles via the co-precipitation method and systematically investigated the effects of BaO doping on the structural, optical, and antibacterial properties of NiO. The results indicate that BaO doping significantly enhances the optical properties of NiO but slightly reduces its antibacterial activity. Pure NiO, with its higher defect density and larger specific surface area, exhibits superior antibacterial performance. These findings provide important insights for optimizing NiO-based materials in biomedical, photocatalytic, and environmental applications.

Research Highlights

  1. Innovative Synthesis Method: The co-precipitation method was employed to efficiently and cost-effectively synthesize pure NiO and BaO-doped NiO nanoparticles.
  2. Systematic Performance Study: This is the first systematic investigation of the effects of BaO doping on the structural, optical, and antibacterial properties of NiO.
  3. Application Potential: The research results provide a theoretical foundation for developing high-performance NiO-based antibacterial and photocatalytic materials.

Research Value

The scientific value of this study lies in revealing the multifaceted effects of BaO doping on the properties of NiO, offering new insights for material design and performance optimization. Its application value lies in providing potential material candidates for developing efficient antibacterial coatings, photocatalytic materials, and energy storage devices. Future research could further explore the performance of different doping concentrations and composite materials to achieve broader applications.

Other Valuable Information

The experimental data and analytical methods from this study provide a reference template for similar material research. Additionally, the research team plans to further investigate the effects of other dopants on the properties of NiO to expand its application scope.