Introduction

The increasing number of applications of nanotechnology has led to the development of various synthetic materials with nanoscale properties (Giovanni et al., 2015). Since ancient times, metals have been used as bactericidal agents. Many of these include gold, silver, titanium, chromium, manganese, and zinc (Vanaja et al., 2013).

Cadmium nanocrystals have recently received a lot of attention due to their unique size dependent optical and electrical properties caused by the quantum confinement effect. Their properties can be fine-tuned by affixing them to various suitable materials, which are used for important technological purposes such as antibacterial activity (Demir, Okur, & Şeker, 2012; Li et al., 2011; Qian, Yan, & Xiao, 2012).

Titanium dioxide has a wide range of crystalline structures that are used in solar cells, air purifier catalysts, photovoltaic materials, gas and humidity sensors, and antireflective coatings (Chen, Sun, & Weng, 2006; Han, Li, & Zhang, 2006; Samuel, Pasricha, & Ravi, 2005). Powdered titanium oxide is also commonly used in toothpastes as a whitener (Malarkodi et al., 2013). The antibacterial, antifungal, and antiviral activities of nanoparticles have been roughly investigated in comparison with other metals, but only a few authors have reported the antibacterial activity of metals such as cadmium nanocrystals in recent years (Tabatabaee, Baziari, Nasirizadeh, & Dehghanizadeh, 2013; Zare et al., 2018). Because of their smaller size, highly optical fluorescence property, and ease of tissue functionalization, the development of novel cadmium-based quantum dots or carbon materials has enormous potential in the treatment and identification of cancer, as well as targeted drug delivery (Rzigalinski & Strobl, 2009). It has been reported that doping TiO₂ with various elements significantly improved its receptivity to visible light (Pelaez et al., 2012; Tsutomu, Tetsuya, Sigeru, & Keisuke, 2003). In recent years, there has been a growing interest in Cadmium-Titanium Oxide nanocomposite as a potential new material for optical fibre (Dislich, 1993; Fades, Zelinski, & Uhlmann, 1993; Pettit, Ashley, Reed, & Brinker, 1993). To replace other materials, pure and high quality Cadmium with Titanium Oxide nanocomposite of good optical quality are required. In general, reaction sintering has been found to be difficult to control, especially when a chemically homogeneous, single phase product with high purity, high density, and uniform microstructure is desired. Sol-Gel processing has been investigated extensively as an alternative to conventional processing (Phani et al., 1998). This method entails controlled hydrolysis of an alkoxide, followed by condensation, which results in the formation of a gel. The structure of the final compound or material is extremely sensitive to pH, reactant stability, water content, and impurities. We describe the synthesis of Cadmium with Titanium Oxide (Cd-TiO₂) nanocomposite powders using a Sol-Gel technique, which results in high purity crystalline powders at temperatures lower than solid state reactions. After proper morphological and structural characterization of the prepared sample using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet Spectroscopy (UV), and X‐ray diffraction (XRD). We tested the prepared Cadmium with Titanium Oxide (Cd-TiO₂) nanocomposite against these bacteria to study its antibacterial effect against Gram-negative and Gram-positive bacteria.

Materials and Methods

Chemicals and Materials

Sigma-Aldrich, Inc. provided titanium (IV) isopropoxide (TIP, 97.0 percent), N-dimethylformamide (DMF, 99.8 percent), and 1-butyl-3-methylimidazolium hexafluorophosphate (PF₆, 97.0 percent.(Milwaukee, WI).

In our experiments, we used 99.8 percent Cadmium Sulphate and 99.5 percent acetonitrile. All of these chemicals were used exactly as they were given to us. Except for the antibacterial tests, which used sterilised H₂O, all experiments used deionized water.

Preparation of Cd-TiO₂ Nanocomposite Powders

A solution was prepared with 5 mL of PF6 and 45 mL of DMF, in which the desired amount of CdSO₄ was dissolved. With vigorous stirring, titanium(IV) isopropoxide (9.68 mL) was slowly added to the solution. Dropwise additions of deionized H₂O (2.28 mL) were made to hydrolyze and form a gel. The gel was washed with acetonitrile repeatedly after overnight ageing to remove the entrapped PF₆, vacuum-dried at 80°C, and calcined in air at 600°C for 4 hours to produce Cd-TiO₂ nanocomposite powder.

Characterization of Cd-TiO₂ Nanocomposite

To analyse the chemical compositions of Cd-TiO2, the specific surface area (BET) was also determined. X-ray diffraction (XRD) patterns were recorded on a powder X-ray diffractometer (X'pert Pro) to study the crystalline structure. A Scanning Electron Microscope (SEM, Model JEOL JEM-2010F) was used in conjunction with an energy-dispersive X-ray spectroscopy (EDX) probe to examine the morphology of a Cd-TiO₂ Nanocomposite. The bonds and stretching modes were determined using a Fourier transform infrared (FTIR) spectrometer (BRUKER Vertex-70).

Antibacterial activity

The standard well diffusion method (Azam et al., 2012) was used to test antibacterial susceptibility against gramme negative bacteria such as E. coli, Pseudomonas, and Enterobacter and gramme positive bacteria such as Staphylococcus aureus and Bacillus subtilis. Bacterial cultures were grown for 24 hours in Nutrient broth media. The wells were then filled with a constant volume of Cd-TiO₂ nanocomposite and water as a control. The plates were chilled for 5–10 minutes to allow for successive diffusion before the bacterial strains were incubated at 37°C for 24 hours. The diameter of the inhibition zone was measured and recorded after incubation. The experiments were carried out in triplicate.

Result and Discussion

X-ray Diffraction

For phase identification, X-ray diffraction (XRD) is used, and the diffracted intensities are recorded as a function of 2. Figure 1 depicts the XRD pattern of a Cd-TiO₂ nanocomposite powder calcined at 600°C for 4 hours. The specific diffraction peaks are shown in Figure 1 at 27.1°, 36.0°, 39.0°, 41.1°, 44.0°, 54.5°, 56.5°, 63.0°, 64.5°, and 69.0°. The crystalline size of the phase is indicated by all peaks of Cd-TiO₂ nanocomposite. Sharp and intense peaks, on the other hand, are observed for the sample that was calcined at 600°C for 4h indicating a higher degree of crystallinity in the pure TiO₂ sample, a weak (JCPDS No. 29-1360) peak was observed. Sharp peak represent as (Cd- TiO₂ nanocomposite) Cadmium present from Titanium Oxide nanopowder. For the sample of all the diffraction lines agree with reported values and match with the JCPDS data (card No: 29–277) confirming the formation of rhombohedral structure. The crystallite size is calculated and found to be Scherrer formula applied to the three highest peak such as 27.1°, 36.0°, 54.5° orientation which is the maximum reflection of the rhombohedral structure of Cd-TiO₂ nanocomposite. The particle size of Cd-TiO₂ nanocomposite in 35nm. The increased Cd loading appears to increase the size of the TiO2 crystallites in the powders. The size of the TiO₂ particles is expected to vary similarly (Phani, Passacantando, & Santucci, 2000).

Ultra Violet Spectroscopy

Figure 2 shows that the exhibit UV-Vis spectrophotometer of synthesized Cd-TiO₂ nanocomposite powder by using solgel method. The Cd-TiO₂ nanocomposite The growth phase is critical in the synthesis of nanocomposite materials. For Cd-TiO₂ nanocomposite powder, the broad peak was located between 350 nm.

The absorbance of Cd-TiO₂ nanocomposite that was gradually increased after indicates gradual increase of nanocomposite. Finally, the result shows that the UV-visible absorption spectrum of Cd-TiO₂ nanocomposite shows an absorption onset at 350 nm (band gap = 3.04eV).

Fourier Transform Infrared Spectroscopy

From 4000 to 500cm^-1, several vibration bands of the Cd-TiO₂ Nanocomposite can be observed (Figure 3). The broad peak at around 3638cm^-1 in the higher energy region can be attributed to the stretching vibrations band observed at the O-H bond in the carboxyl group (Zhu, Kumari, Huang, & Achal, 2016).

The bands observed for the C-N bond at 1202cm^-1 and 1126cm^-1 correspond to the stretching vibrations of aliphatic and aromatic amines, respectively. The peak at 531 cm^-1 corresponds to the anatase phase of TiO₂. The Ti–O stretching vibration and the Ti-O-Ti lattice are responsible for the 417cm^-1 decrease in conduction elsewhere (Golobostanfard & Abdizadeh, 2013). The FTIR spectral results revealed possible interactions of the Cd-TiO₂ Nanocomposite, which could be responsible for the nanocomposite's stabilisation (Zhu et al., 2016).

Scanning Electron Microscopy-EDAX

The morphological analysis of the synthesised Cd-TiO₂ Nanocomposite was learned using SEM. The SEM images of Cd-TiO₂ Nanocomposite are shown in Figure 4, and the average size of the Cd-TiO₂ Nanocomposite is determined to be in the range of 35nm. Cd-TiO₂ Nanocomposite shape such as spherical shape and then crystalline nature.

The purity of the synthesised Cd-TiO₂ Nanocomposite was confirmed by the energy dispersive X-ray (EDAX) spectra, which are shown in Figure 4 and Figure 5, respectively, and then C, O, Ti, Cd, and Pt elements are present in Cd-TiO₂ Nanocomposite. As shown in Figure 4, the weight percentage of Cd is 5.8 percent, Ti is 51.03 percent, C is 5.13 percent, and O is 31.75 percent in Cd-TiO₂ Nanocomposite. The EDAX spectra also confirm the doping in Cd nanocrystals. The absence of any additional impurity peaks in the spectra demonstrates the purity of the prepared nanocrystals.

BET Surface Area Analysis

The N₂ adsorption–desorption isotherms and BJH pore size distribution of Cd-TiO₂ nanocomposites are depicted in Figure 5. The N₂ adsorption–desorption isotherms of the as-prepared Cd-TiO₂ nanocomposites demonstration type IV characteristics, which is one of the main characteristics of mesoporous materials. Major pore size distribution of Cd-TiO₂ nanocomposites is ranged from 2.24 nm.

The BET surface area of the prepared Cd-TiO₂ nanocomposites pore volume was 0.01cm³/g. The surface area of Cd-TiO₂ nanocomposites is calculated to be 8.1 m2 g^-1 built on the BET model. The surface area of BET and mesoporous structure improve the Photo generated electrons and holes toward contribute now photocatalytic activity and deliver more channels on behalf of water molecule to go through, which is important to complete high water and photo reduction efficacy (Zhang et al., 2018).

Antibacterial Activity

The antibacterial activity of a synthesised Cd-TiO₂ nanocomposite (Das, Nath, Chakdar, Gope, & Bhattacharjee, 2010) against Gramnegative bacteria was investigated using the well diffusion method (Das, Gang, & Nath, 2011; Das, Gang, Nath, & Bhattacharjee, 2012; Das, Saha, Hussain, & Nath, 2013).

As shown in Figure 6, a prepared solution of Cd-TiO₂ nanocomposite with various concentrations (such as 25, 50, 75, and 100 ml) is placed in the broth against Pseudomonas. In this case, the standard antibiotic ampicillin serves as a reference, while distilled water serves as a control.

The zone of inhibition (ZOI) on bacterial growth was observed and recorded after 24 hours of incubation, as shown in Figure 6. A measuring ruler was used to determine the diameter of the ZOI.

When tested against pathogens such as Pseudomonas, the Cd-TiO₂ nanocomposite demonstrated antibacterial activity (Figure 6).

The zone of minimum inhibition concentration was measured in 25ml at 20mm and 100ml at 30mm.

Conclusion

The Sol-Gel technique, we created a high purity bulk single phase Cd-TiO₂ nanocomposite powder. X-ray diffraction for the crystallite size is calculated and found to be Scherrer formula applied to the three highest peak such as 27.1°, 36.0°, 54.5° orientation which is the maximum reflection of the rhombohedral structure of Cd-TiO₂ nanocomposite. The particle size of Cd-TiO₂ nanocomposite in 35nm. The UV-visible absorption spectrum of Cd-TiO₂ nanocompositeshows an absorption onset at 350 nm (band gap = 3.04eV). The SEM image shows that the Cd-TiO₂ Nanocomposite shape such as spherical shape and then crystalline nature. The energy dispersive X-ray (EDAX) spectra confirmed the purity of the synthesised Cd-TiO₂ Nanocomposite, and then C, O, Ti, Cd, and Pt elements are present in Cd-TiO₂ Nanocomposite. In Cd-TiO₂ Nanocomposite, the weight percentage of Cd is 5.8 percent, Ti is 51.03 percent, C is 5.13 percent, and O is 31.75 percent. BET image shows that the major pore size distribution of Cd-TiO₂ nanocomposites is ranged from 2.24 nm. The BET surface area of the prepared Cd-TiO₂ nanocomposites pore volume was 0.01cm³/g. The surface area of Cd-TiO₂ nanocomposites is calculated to be 8.1 m² g^-1 built on the BET model. The Cd-TiO₂ nanocomposite showed that the antibacterial activity when tested against the pathogens only gram-negative bacteria such as Pseudomonas. The zone of minimum inhibition concentration was measured in a range of 20mm in 25μl and 30mm in 100μl.

Funding Support

The authors declare that they have no funding support for this study.

Conflict of Interest

The authors declare that there is no conflict of interest.