**3.5 FT-IR analysis**

FT-IR stands for Fourier transform Infrared, the method that is used for infrared spectroscopy. Some of the IR radiation is passed through a sample is absorbed by the sample and few are transmitted. The resulting spectrum represents the molecular absorption and transmission, creating a fingerprint of the sample. **Figure 4** shows the typical FT-IR spectra of Zinc copper ferrite nanostructures recorded between 4000 and 400 cm−1. In the range of 1000–400 cm−1, two main absorption bands of ferrite are appearing. The absorption band υ 1 = 580 cm−1 is assigned to the stretching vibration of tetrahedral complexes (Fe3+-O2−), and the absorption band υ2 = 400 cm−1 is attributed to the octahedral complexes (Fe3+-O2−). The peak intensity of υ 1 decreases with increasing Cu2+ contents, while the position band is shifted to lower frequencies. Synchronously, the intensity and position of υ 2 changed

**Figure 4.** *FT-IR spectra of zinc copper ferrite nanostructures annealed sample at 600⁰C.*

slightly with x. Similar results are observed in Zinc copper ferrite nanostructures prepared by the sol–gel combustion method [89, 90]. The difference in band position of υ1and υ2 can be related to the difference in Fe3+-O2 bond lengths at A sites and B sites. It was found that the Fe-O distance at A sites (1.89 Å) is smaller than that of the B sites (2.03 Å) [91, 92]. When Zn2+ ions are replaced by Cu2+ ions, due to charge imbalance some Fe3+ ions shift from A sites to B sites, making the Fe3+-O2 stretching vibration greater in the B domain. So the decrease in peak intensity of υ 1 with increasing Cu2+ content is mainly attributed to the change in Fe3+-O2 bands.

#### **3.6 Magnetic properties**

The most effective technique for analyzing the magnetic properties of ferrite nanoparticles are VSM (vibrating sample magnetometer), magnetization hysteresis (M − H) loop. One can find saturation magnetization, remanent magnetization, and coercivity by using these characterization techniques. The interior of the magnetic substance is normally divided into several domains, as the external magnetic field increases the domain walls may move and the magnetic field rotates within domains, resulting in a single-domain state. The magnetization saturation is attained if the magnetization axis and the external magnetic field direction are similar. The spontaneous magnetization (Ms) was obtained by extrapolating the high-field part of the loop to the zero applied field [93–97]. A similar variation of magnetization of ZnCu ferrite with the increase in Zn2+ concentration up to a particular x value has been reported in the literature [98–100]. Najmoddin et al. [101] observed the highest Ms. value of 52 emu/g at room temperature for x = 0.25 in ZnCu nanoferrites prepared by wet chemical method. Retentivity is the value of magnetization that is retained in the absence of an induced magnetic field. Coercivity is defined as the caliber of a ferromagnetic material to withstand an external magnetic field without demagnetizing it. In the case of a ferromagnetic material, it is defined as the intensity of the applied magnetic field that is required to reduce the magnetization to zero after the saturation state. The materials which have high coercivity are called hard materials and one with a low magnitude are soft materials. Hard materials are preferred for making permanent magnets whereas soft materials are used for making transformers, inductor cores, and microwave devices.

**Figure 5** shows a typical hysteresis loop of all the Zinc copper ferrite nanostructures compositions which are annealed at 600°C. By using a vibrating sample magnetometer, the measurements of magnetization for all the compositions were carried out under the applied magnetic field of range ± 10 k Oe at room temperature. It is observed that the magnetic properties such as saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc) values are closer to the values inscribed in the literature. [102–106]. The structure of spinel ferrite is ferrimagnetic, the magnetic moments of A and B sites are coupled antiparallel to each other. Since there are doubly filled B sites, the net magnetic moment is the difference between the two sites. The magnetization behavior of spinel ferrite can be understood in Neel's model [107, 108]. The composition of Zinc copper ferrite nanostructures and cation distribution among the A and B sites will to a large degree, influence the magnetic properties of samples. According to this, in any ferrite, the magnetic order of tetrahedral clusters (A-site) and octahedral clusters (B-site) was found to be anti-parallel to each other. In this, the A-A and B-B superexchange interaction was predominated by the A-B superexchange interaction. According to Neel's model, the net magnetic moment of the composition per formula is expressed as:

$$
\mu B = \mathbf{M}\_{\mathbb{B}}\left(\mathbf{x}\right) - \mathbf{M}\_{\mathbb{A}}\left(\mathbf{x}\right),
\tag{1}
$$

*The Presented Study of Zn-Cu Ferrites for Their Application in "Photocatalytic Activities" DOI: http://dx.doi.org/10.5772/intechopen.99535*

**Figure 5.** *Magnetic hysteresis loops for zinc copper ferrite nanostructures nanostructures annealed sample at 600⁰C.*

where MB and MA are the magnetic moments of B and A sublattices respectively.

The squareness ratio or remnant ratio (Mr/Ms) of a material is one of the important characteristics which depends on its anisotropy. The values of the squareness ratio represent the random arrangement of uniaxial particles along with the cubic magnetocrystalline anisotropy [109, 110]. In the study, the squareness ratio of pure ZnCuFe2O4 is 0.54, at room temperature. And it has been observed from the literature that the squareness, indicates the presence of non-interacting single domain particles with cubic anisotropy in the respective compositions [111].

The values of Bohr Magneton (μB) of these samples were also evaluated by using the following Equation.

$$\mu B = \frac{\text{MsMw}}{\text{5585}}$$

Where Mw is the molecular weight of the sample and Ms. is saturation magnetization.

5585 = β × N [β is Conversion factor (9.27 × 10–21); N is Avogadro's number].

It is observed that the value of Bohr Magneton is 1.56. One can adapt the composition of ferrite materials by squareness ratio (S) for the development of new electromagnetic materials and as per the need of the hour [112]. In the present work, the variation in the magnetic properties of Zinc copper ferrite nanostructures is obtained.

### **4. Photocatalytic degradation**

The magnetic material ZnCuFe2O4 with the spinel structure has been proven effective in the application of dye removal. The visible light exposes, excellent photochemical stability. ZnCuFe2O4 has grabbed massive attention in the conversion

of solar energy and photochemical hydrogen production from water. Also, the ZnCuFe2O4 magnetic particles possessed intrinsic peroxidase-like activity, which could react with H2O2 to produce •OH. Zinc Copper ferrite is one of the most important ferrites. ZnCuFe2O4 nanoparticles were found to be photo-sensitive in the visible light region (1.92 eV) with exceptional photochemical stability which paves way for them to act as gas sensors and photocatalysts [113, 114]. Photooxidation and photoreduction refer to the initiation of oxidation and reduction reactions by light energy. When irradiated with light energy, an electron (e-) is excited from the valence band (VB) to the conduction band (CB) of the photocatalyst, leaving a photogenerated hole (h+) photogenerated electron and holes are capable of oxidizing/reducing adsorbed substrates. The ZnCuFe2O4 NPs promote a photocatalytic reaction by serving as agents for the charge transfer between two adsorbed molecules. The charge transfer at the semiconductor–electrolyte interface is followed by bandgap excitation of a semiconductor nanoparticle. At the later stage, the nanoparticle quenches the excited state by accepting an electron, either transferring the charge to another substrate or generating photocurrent [115]. In both cases, the sensitivity of the semiconductor is retained which describes it as photocatalytic.

The photo-degradation phenomenon of methylene blue by Zinc copper ferrite nanocrystal is evaluated and the observed absorption spectra are presented in **Figure 6(a)**. It is clearly shown in the figure that the characteristic absorption

#### **Figure 6.**

*Zinc copper ferrite annealed at 600⁰C under UV-light irradiation. (a) Absorption of MB solution during the photo-degradation (b) photo-degradation percentage (c) plots of ln[C/Co] versus irradiation time (d) photocatalytic mechanism of MB in the catalyst.*

*The Presented Study of Zn-Cu Ferrites for Their Application in "Photocatalytic Activities" DOI: http://dx.doi.org/10.5772/intechopen.99535*

peak of the methylene blue (MB) at about 664 nm decay gradually with an enhanced exposure time of 8 hours and almost disappears after the irradiation time. This indicates that the MB dye has almost degraded. The photocatalytic performance of the NPs is observed by plotted (C/Co) as a function of time for MB dye and the same is shown in **Figure 6(b)**. The presence of Zinc copper ferrite nanocrystal emphasis the effective photo-degradation activity for MB, and no degradation of dye molecules was observed in the darkness. However, the Zinc copper ferrite sample exhibited 65% photodegradation. The variation of MB photo-degradation on the crystallite size of Zinc copper ferrite nanocrystals is shown in **Figure 6(c)**. Further, it reveals that the degradation percentage of MB and their kinetics [116, 117]. Photocatalytic reaction mechanisms for oxidation of MB dye by Zinc copper ferrite are presented in **Figure 6(d)**. Photo catalytic activities have been proved to advance by Zinc copper ferrite and it can be ascribed from the photo absorption spreading even up to the visible region, minimizing the electron–hole recombination rate.

## **4.1 ZnCu ferrites for ongoing COVID-19 pandemics**

Nanomaterials are making a global impact on the health system and socioeconomic progress. Nanoparticles of ZnCu have unique physical and chemical features that can be coupled with the development of potential therapeutic drugs, nanomaterial-based antiviral sprays, anti-viral surface coatings, and drug delivery. The study emphasizes the choice of synthesis method which decides the size and charges tunability properties to the ZnCu ferrites. The size tunability ensures that a large amount of drug can be fused into anatomically privileged sites of the virus, while charge tunability would facilitate the entry of the drug into charged parts of the virus. In addition, biosensors for the early detection of viral strains such as the COVID-19 can also be developed with ZnCu ferrites. For instance, ZnCu ferrites can be used to develop Giant magneto resistance-based sensors which have been applied in virus detection, earlier [114].
