Microstructural, antifungal and photocatalytic activity of NiO–ZnO nanocomposite

The standard antibiotic Flucanazole was used for this study.

With the use of XRD pattern (Figure 1),theNC’s crystal structure is identified. The peaks at angles 37.1°, 43.1°, 62.5°, 75.0°, and 78.9° denote the (111), (200), (220), (311), and (222) planes of NiO(JCPDS # 04-0835), respectively, which belong to the FCC structure of NiO, and, also,the relative intensities of the distinctive peaks are in accordance with the standard pattern. The peaks are also visible at angles 31.7°, 34.44°, 36.2°, 47.5°, 51.8°, 56.5°, 67.8°, 69.0°, and 76.2° in the XRD pattern. These peaks correspond to (100), (002), (101), (100), (102), (110), (200), (201), (112), and (202) reflections, respectively, which denote the ZnO hexagonal structure (JCPDS # 89-1397). The peaks from cubic NiO and hexagonal ZnO are evident in the NiO–ZnO NC sample. For ZnO and NiO NC, no further impurity peaks are seen, and the distinct peaks shown in the XRD pattern attest to the development of highly polycrystalline ZnO and NiO phases. The crystallite size is computed using the Scherer’s formula.

Fig. 1

The (101) reflection of ZnO is used to calculate the crystallite sizeand is found to be 39 nm, while crystallite size of NiO is 23 nm, calculated from the (200) peak of NiO. The results obtained in this work are consistent with the results of Jolaei et al. [14]. The ZnO–NiO NCsare synthesized using the co-precipitation method, and the crystalline structure of ZnO is confirmed as hexagonal (JCPDS File No. 80-0075), while the structure of NiO is cubic (JCPDS File No. 78-0429). The synthesis of the NiO–ZnO NC photocatalyst is achieved by co-precipitation and co-gel formation processes [18]. The XRD pattern exhibit reflections correspond to both pure NiO and ZnO.

The bands corresponding to 416, 1,946, 2,004, 2,025, 2,075, 2,202, 2,181, 2,235, and 3,650 cm⁻¹ are obtained from Fourier transform infrared (FTIR) spectroscopy investigation of NiO–ZnO NC. The peak observed at 2,000–2,235 cm⁻¹ represents the adsorption of ambient CO₂ on the surface of the NC. Figure 2 demonstrates that the hydroxyl group’s stretching vibration is seen in the transmittance band in the 3650 cm⁻¹ range. The peaks at 1946 cm⁻¹ can be attributed to the bending vibration of the OH bond. Nickel and zinc metal oxides can be seen at the maxima at 455 cm⁻¹ and 416 cm⁻¹, respectively [19].

Fig. 2

FESEM is a powerful technique to analyze the surface topography and crystallite size. Figures 3A–3D shows the NiO–ZnONC with different magnifications. The micrographs show formation of crystallites with uniform size with dense structure. The dense structure isformed with specific shape and size. The EDS results are shown in Figure 3E, which reveals the Zn, Ni, and oxygen elements, indicating the presence of ZnO and NiO,with no impurities. Thenickel, zinc, and oxygen, ascertained using EDX analysis, are 9.71%, 39.34%, and 50.95%, (wt%),respectively. The EDX results are determined to be similar to the findings reported by Karthikeyan et al. [12] and Haq et al. [19].

Fig. 3

The absorbance spectra of the NiO–ZnO NC, obtained in the 200–1,000 nm region, are displayed in Figure 4. The sudden absorbance indicates the bandgap of the material. The interaction between the incident photon and the substance has enough energy when the wavelength is smaller, which causes the absorbance to rise. The spectrum shows the absorbance to be about 390 nm. The approximate bandgap can be calculated by means of the equation E (eV) = 1,240/Wavelength (nm) = 3.17 eV. The bandgap of the NiO– ZnO NC is found to be ∼3.17e.V, and this value is comparable with the other reported results. Weldekirstos et al. [13] calculated the bandgap using the Tauc plot and found the value of 2.90 eV. Jolaei et al. [14] calculated the optical bandgap of ZnO–NiO NC,and the value is found to be 2.94 eV.

Fig. 4

The majority of tribal residents frequently suffer from infectious diseases, especially skin and mucosal infections, as a result of poor sanitation, unclean drinking water, and a lack of knowledge about healthy eating practices. Among these skin pathogens, fungus play a significant role. Notable species include Candida spp. and dermatophytes. In the case of A. niger (Table 1), at the drug concentration between 250 μg/mL and 1000 μg/mL, the zone of inhibition for flucanazole was 10 mm, whereas the NC had 10, 10, 11, and 12 mm. In A.flavus, for the drug concentration between 250 μg/mL and 1000μg/mL, the zone of inhibition was 10 mm in flucanazole and 11.4–14 mm range for the NC. In the case of A.fumigatus at the drug concentration between 250 μg/mL and 1000 μg/mL, the zone of inhibition for flucanazole was 8.0 mm and 8 mm, 9 mm, 9 mm, 10 mm for NC. In the case of C. albicans, it was 10 mm in flucanazole, whereas the NC gave 11, 12, 12, and 13 mm for different concentrations. In Mucorspp, at the drug concentration between 250 μg/mL and 1000μg/mL, the zone of inhibition for flucanazole was 10 mm, whereas for the NC, it was 10.2, 10.8, 11, and 12 mm. The present work clearly indicates that the NiO–ZnO NC possesses significant antifungal activity against pathogenic fungi such as A.niger, A.flavus, A.fumigatus, C.albicans, and Mucorspp. Hussein et al. [11] examined the antibacterial properties of NiO–ZnO NCagainst both Gram-positive (G + Ve) bacteria–specifically, S. aureus, and Gram-negative (G-Ve) bacteria– specifically E. coli. The results indicated that the antibacterial activity of the NC was more pronounced against S. aureus compared to E. coli.

Nanoparticlessuch as photocatalystshave significant potential for environmental friendly removal of major pollutants such as organic dyes, heavy metals, and pesticides from industrial waste. Figure 5 depicts the process of photo degradation of MB dye using ZnO–NiO as a catalyst. The studies were conducted to assess the impact of a catalyst on MB dye degradation using visible radiation. The graph illustrates the highest level of intensity reached by the MB dye under dark conditions. Over time, the intensity of absorbance for the MB dye diminishes. The rate of a chemical reaction can be altered by exposing it to specific wavelengths of ultraviolet, visible, and infrared light energy. The catalyst absorbs this energy, leading to the generation of electron–hole pairs (e–h). These pairs then generate highly reactive reducing and/or oxidizing radicals on the conduction and valence bands, respectively. The radicals present in contaminated water undergo secondary reactions to destroy both organic and inorganic pollutants. After a duration of 120 min, the absorbance reaches its lowest point, and the MB dye solution loses its color, showing the breakdown of the pollutant due to radiation. The catalyst exhibited a consistent and proportional rise in the absorption of MB when exposed to visible light.

Fig. 5

Paul et al. [20] synthesized NiO–ZnO NC and analyzed the photocatalytic activity. The photocatalytic reduction of MB exhibited kinetics,indicating the homogeneous adsorption of MB on the NC’s surface. Udayachandran Thampy et al. [9] studied the photocatalytic property of ZnO–NiO NC in breaking down MB dye using sun irradiation. The researchers found that the NC exhibited a much superior photocatalytic performance in comparison to pure ZnO and NiO. The enhanced photocatalytic performance of the composite can be ascribed to the improved separation of charge carriers, facilitated by the internal electric field at the interface of ZnO and NiO. The evaluation of the photocatalytic efficiency of NiO–ZnO NC was conducted by quantifying the degradation of MB dye under a continuous stream of visible radiation [15]. The synthesized ZnO nanoparticles had the capacity to degrade the MB dye by up to 76% at the specified conditions. The transition from a rich blue color to a colorless state can be visibly observed as a result of the breakdown of the MB dye when exposed to radiation. NiO– ZnO NC was prepared using a microwave-assisted approach,and the subsequent experiment utilized a prearranged NC to facilitate the photodegradation of MBdye and Rhodamin B when exposed to UV light [21]. Almost all the researchers used only UV light for the photocatalytic degradation, while the present work utilized the visible light for the photocatalytic degradation,and the work demonstrated that the NC exhibits exceptional photocatalytic efficacy of 75%.