1 Introduction

Nanomaterials belongs to the range of below 100 nm has unique chemical, physical, electrical, and mechanical properties and also diversely utilized in the field of medical, biotechnology, microbiology, pharmaceutics and chemistry, engineering, inexpensive catalyst, cytotoxicity study, etc. [1,2,3]. Owing to its large surface area, nanomaterial synthesis methods are classified into the physical and chemical methods. However, these methods are not suitable for medicinal and biological applications because of its harmful nature to the environment. Therefore, researchers are going for a green synthesis route to prepare nanomaterials because the green synthesis approach is simple, eco-friendly, and cost-effective [4, 5]. Green synthesis is a fascinating method for material science [6,7,8].In the past few decades, metal oxide semiconductors such as ZnO, MgO, CuO, CdO, NiO, etc. were widely used, and it is prepared via physical, chemical, and biological methods. Among them, TiO2 NPs are a well-known semiconductor with a wide bandgap of 3.2 eV for anatase and 3.0 eV for rutile phase [9], but the brookite phase is rare to obtain [10]. The Anatase and rutile phase of TiO2 exhibits a tetragonal crystal structure, but the brookite phase is an orthorhombic structure [11]. The transition metal oxide, mainly TiO2, is widely used in cosmetics, photocatalysts, medicines, sensors, and solar cell applications because of its peculiar properties like interconnected pores and large surface area [12].

Nowadays, the metal and metal oxide nanoparticles are synthesized by chemical as well as physical methods such as the microwave [13], hydrothermal [14], solid-state [15], solution route method [16], sol–gel [17] chemical phase decomposition vapour [18], solvothermal crystallization [19], ultrasonic irradiation and [20], and green synthesis method [21]. Nevertheless, these methods generate heterogeneous NPs with high energy consumption and also the chemicals process involves synthetic capping, reducing, and stabilizing agents which results in the creation of anti-environmentally safe by-products [22]. In recent years researchers are focussed on the green synthesis route to the synthesis of metal and metal oxide nanoparticles. The bio-mediated metal and metal oxide NP's shows potential application on drug delivery, nanocatalyst, nano-medicine, biosensor, biotechnology, and microbiology. The green synthesis method is similar to the chemical reduction process, where the costly chemical reagents are replaced by plant extracts and microorganisms and also reduces the toxicity, which enhances its biomedical applications.

The bio-mediated TiO2 NPs exhibit excellent antibacterial, anti-inflammatory, anti-fungal, anti-microbial, and several biological activities. The decomposition of microorganisms by its photo-semiconductor properties results in the enhancement of biological activities [23]. There are numerous reports on the preparation of TiO2 NPs from Cinnamon Powder [9], Mangifera indica [24] Citrus reticulate [25] Azadirachtaindica leaf [26] Murayakoenigii [27] Curcuma longa [28], Cynodondactylon [1], Annona squamosa [29], Morindacitrifolia [30], Psidium guajava [31], Jatropha curcas [32], Fungus-mediated [33] towards the biological applications. Moreover, the morphology, size, shape, porosity, and crystallinity depend upon the concentration of precursor and temperature [34].

This present study is to investigate the chemical and bio-synthesis of the TiO2 nanoparticles. The phytochemicals present in jasmine flower extracts are alkaloids, coumarins, flavonoids, tannins, terpenoids, glycosides, embodies, steroids, essential oil, and saponins [35]. These phytochemicals are responsible for the reduction of Titanium tetra Isopropoxide to titanium dioxide nanoparticles. The structural, morphological, vibrational, and optical properties of the TiO2 NPs were analyzed. The photodegradation of methylene blue dye were visualized uisng UV-Visible irradiation technique. As well as the antibacterial activity were tested against  both gram-positive and gram-negative strains . The different processes of TiO2 nanoparticles synthesis were studied in detail.

2 Materials and methods

2.1 Materials

Titanium Tetra Isopropoxide (TTIP, C12H28O4Ti, 97%), Ethanol (C2H5OH, 96%), Methylene blue (C16H18CIN3S), and distilled water was purchased from Merck India. Jasmine flowers were collected from the local market. All chemicals and reagents are of analytic grade and used without further purification. Bacterial pathogens, such as Staphylococcus aureus (gram-positive bacteria), Klebsiella pneumonia and E-coli (gram-negative bacteria) were used to study biological activities.

2.2 Synthesis of TiO2 by hydrothermal method

The slight modifications were made on the synthesis of TiO2 NPs from the previously reported literature [36]. Initially, 0.1 N of titanium tetra isopropoxide is dissolved in 20 ml of ethanol solution under continuous stirring for 30 min. After that, add a few drops of distilled water to form the dispersion medium. The product was placed on the ultrasonic bath for 20 min. After sonication, the solution was transferred into an autoclave at 150 °C for 3 h. Then the solution was cool to room temperature, and it was washed and centrifuged with deionized water to remove the impurities. Then it is filtered with Whatman No. 1 Filter paper. The filtered sample was dried oven at 110 °C for 5 h, and it is further annealed at 500 °C for 2 h. The resultant TiO2 NPs was collected and processed with further characterization.

2.3 Green synthesis of TiO2 nanoparticles using jasmine flower extract

TiO2 NPs were synthesized using the facile green synthesis route from Jasmine flower extract acts as a reducing/capping agent. The jasmine flowers were purchased from the local market of Nagercoil, Tamilnadu. The jasmine flower extract was prepared by adding 50 g of jasmine flower in 100 ml distilled water and boiled the mixture with a hotplate for 30 min. Then the aqueous solution has been filtered and stored for further tests. Take 50 ml of titanium tetra isopropoxide (TTIP) in a 100 ml beaker and add 20 ml of flower extract drop by drop to the above TTIP solution. The solution was stirred by 3 h at room temperature. The colour of the solution was changed from pure white to yellowish-grey. A change of colour confirms the formation of titanium dioxide nanoparticles. After that, the solution was Filter and dried at 110 °C for 5 h. Then the dried samples were calcined Muffle furnace at 500 °C for 2 h [37, 38].

2.4 Characterization of TiO2 nanoparticles

X-Ray Diffraction pattern of investigated titanium dioxide nanoparticles was recorded by using PANanalytical XPERT PRO Diffractometer. FT-IR spectrum was recorded by using the Perkin Elmer spectrophotometer recorded from 400 to 4000 cm−1. The Surface morphology of TiO2 nanoparticles was visualized using SEM. EDS spectrum is used to determine its homogeneity and its elemental distribution of elements in the investigated compound. SEM with EDS spectrum was recorded with the help of Quanta FEG-250. UV–Visible Diffuse Reflectance Spectrophotometer (DRS) spectrum was recorded using a Shimadzu 2700 spectrophotometer. The reflectance spectrum was recorded in the range of 200–800 nm. The antibacterial activity of TiO2 nanoparticles was studied for both gram-positive and gram-negative bacteria by the disk diffusion method.

2.5 Antibacterial activity

The antibacterial activity of titanium dioxide nanoparticles was tested by the agar diffusion method. First, the nutrient agar was uniformly spread in the Petri dish plate. Then fix the 6 mm diameter well, which is used to study the inhibition zone. Place 50 μl of TiO2 NPs in 6 mm diameter well. The culture medium was incubated at 37 °C C for 24 h under aerobic conditions. The zone of inhibition layer was measured using the millimeter region. The Zone of inhibition results in the antibacterial activity of TiO2 NPs.

2.6 Photodegradation of Methylene blue

Methylene blue dye is used as a model pollutant for photodegradation. Take 100 mg of TiO2 NPs in 250 ml beaker with contains 100 ml methylene blue solution under ultrasonication for 20 min. Furthermore, the mixed solution was kept in a chamber at the dark condition to attain the absorption desorption equilibrium. The photodegradation of methylene blue dye was recorded with the help of UV–Visible irradiation at every 30 min regular interval from 0 to 120 min. The absorbance of methylene blue dye was recorded using 200 µl volume and 10 cm length quartz cuvette. Then the dye degradation efficiency was calculated.

3 Results and discussion

3.1 X-Ray Diffraction

The X-ray diffraction technique analyzed the crystalline phase, crystal structure, purity, and average crystalline size of the TiO2 NPs. Figure 1 displays the XRD pattern of bio mediated and chemically synthesized TiO2 NPs. The diffraction angle (2ϴ) at 27.45°,36.75°,41.27°, 44.07°, 54.27°, 56.54°, 62.78°, 64.05°, 69.01°, and 69.85° which corresponds to the Braggs reflection plane of (110), (101), (111), (210), (211), (220), (002), and (301) respectively. The observed angle at 27.45° (101) represents the high crystalline nature of TiO2 NPs. The XRD pattern of TiO2 NPs shows good agreement with the JCPDS card number: 89-4920, and it exhibits the tetragonal crystal structure [39]. The average crystalline size of TiO2 NPs was calculated from the XRD pattern using the Debye Scherer formula

$${\text{D}} = {\text{k}}\lambda /\beta \cos \theta ,$$

where D is an average crystalline size, K is a dimensionless shape factor with a value close to unity, λ is the wavelength of the X-ray, β is the full width half the maximum intensity (FWHM) and θ is the Bragg angle [40, 41]. The average crystalline size of TiO2 NPs was found in the range of 31–42 nm. Observed average crystalline size values well-matched with previous reports [42,43,44]. However, there is a small difference in peak strength, phase shift, and average crystalline size due to the synthesis process. The green TiO2 nanoparticles were exhibited higher intensity TiO2 peaks due to the presence of polyphenolic compounds in the plant extract. XRD data were tabulated in Table 1.

Fig. 1
figure 1

Shows XRD pattern of TiO2 nanoparticles

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Table 1 Shows comparison of XRD datas of TiO2 NPs with standard value
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3.2 Fourier transform infrared spectroscopy

The functional group and chemical compound present in the prepared TiO2 NPs were identified using the FT–IR spectrum. Figure 2 shows the FT–IR spectrum of TiO2 NPs. The broadband at 3709–3712 cm−1correlates to the O–H Stretching vibration [45, 46]. The band around 1513–1516 cm−1 reflects the bending vibration of functional groups C–H [47]. The thin band at 1269–1278 cm−1displays the alcohol functional groups [48]. The band assigned at 1057–1055 cm−1 corresponds to C–O groups of aromatic stretching vibration. The strong band at 460 cm−1 and 900 cm−1 reveals the formation of Ti–O and Ti–O-Ti bending vibrations, respectively [49]. Peaks observed at 460–1000 cm−1 may disappear/partially decrease in intensity by annealing temperature [50]. The metal oxide bonds like Ti–O–Ti and Ti–O confirms the existence of TiO2 in the prepared TiO2 NPs. The presence of the Ti–O–Ti bond is due to the strong interaction (capped) of biomolecules with TiO2 NPs which results in the presence of alkaloids, coumarins, flavonoids, tannins, and terpenoids [51]. These phytochemicals are responsible for reducing the bulk of titanium dioxide to stable TiO2 in green synthesis [39]. The hydroxyl groups present at 3709–3712 cm−1 in TiO2 NPs, which enhances the photocatalytic performance. The IR frequency of green synthesized TiO2 NPs are slightly changed compared to chemically prepared TiO2 NPs. The Band assignment corresponds to tentative frequency was tabulated in Table 2.

Fig. 2
figure 2

Shows FT–IR spectra of TiO2 nanoparticles

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Table 2 Shows the FT-IR tentative frequency of TiO2 nanoparticles
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3.3 UV–Visible spectroscopy

The optical behavior of the TiO2 NPs was investigated using the DRS spectrum. The UV–Visible reflectance spectrum of TiO2 NPs was shown in Fig. 3. The spectra of TiO2 NPs at 385 nm indicate the charge coordinated electronic transition between the O 2p state and Ti at 3d state [52]. During the biosynthesis process, the colloidal solution turns from white to yellowish-grey, which indicates the formation of titanium dioxide nanoparticles. The white colour dispersion shows the formation of TiO2 NPs during the chemical process. The sharp absorption peak corresponds to the change in the crystalline phase and the average crystalline size [53]. Hence the investigated nanomaterial is applicable for catalytic application [54, 55]. The sharp absorbance peak around 385–400 nm region confirms the formation of TiO2 NPs. The reflectance spectra of TiO2 NPs were well matched with the previous reports [56].

Fig. 3
figure 3

Shows UV–Visible reflectance spectrum of TiO2 nanoparticles

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3.4 Scanning electron microscope

Figure 4 a, b, c, d shows the SEM images of prepared TiO2 NPs. The SEM image of bio-mediated TiO2 nanoparticles is a spherical shaped structure and the chemical synthesis TiO2 nanoparticles sphere-like surface morphology. The average particle size of a spherical shaped TiO2 NPs was found in the range of 32–48 nm. The Particle size obtained from SEM results is well correlated with the average crystalline size from XRD. In general, the decrease in particle size is inversely proportional to the surface volume of the material. Therefore the lower particle size material quickly penetrates the toxic elements as well as the bacterial surface that led the process of decomposition [57, 58].

Fig. 4
figure 4

Shows SEM images of TiO2 nanoparticles at various magnification a and b Green synthesis method c and d Chemical method

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3.5 Elemental dispersive spectrum

The elemental analysis of the chemical compounds was investigated through EDS spectra. Figure 5 shows the EDS spectra of Bio-mediated TiO2 NPs. The elements present in the synthesized TiO2 NPs are Titanium (Ti), and Oxygen (O) [59]. In bio-mediated TiO2 NPs, the composition of the titanium element is high compared to oxygen content. The atomic and weight percentage of the TiO2 NPs are tabulated in Table 3.

Fig. 5
figure 5

Shows EDS spectra of TiO2 NPs (green synthesis)

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Table 3 Shows the elemental composition of TiO2 nanoparticles green synthesis
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3.6 Anti-bacterial activity

The antibacterial study of TiO2 nanoparticles was examined by gram-positive and gram-negative bacteria. Figure 6a, b shows anti bacterial activity of titanium dioxide nanoparticles.  The cell wall of the gram-negative bacteria is composed of thin peptidoglycan and a thick layer of peptidoglycan in gram-positive bacteria. The zone inhibition layer of the TiO2 NPs was examined against Escherichia coli, Staphylococcus aureus, and Klebsiella pneumoniae, which is measured in mm scale. Microbial pathogens may causes multiple diseases to living species. The zone inhibition layer for gram-negative bacteria such as E-Coli and Klebsiella are 12 and 11 mm for chemical synthesis and, 14 and 12 mm for green synthesis, respectively. At the same time, the zone inhibition layer for gram-positive microbial pathogens like staphylococcus aureus is 8 and 7 mm for green and chemical synthesis process. The high zone inhibition layer was observed in green synthesized TiO2 NPs. The zone inhibition layer of pathogenic bacteria Escherichia coli and Klebsiella pneumonia have strong outcomes relative to Staphylococcus aureus. Thin walls of gram-negative bacteria are quickly broken by a positive ion of TiO2 NPs. The Electrostatic interaction exists between the positive TiO2 NPs and the negatively charged cell wall surface of E.coli and Klebsiella pneumoniaebacteria which leads to a high inhibition region on gram-negative bacteria. Bacterial cell walls induced by reactive oxygen species (ROS), such as hydroxyl group and superoxide result in a rupture on the bacterial cell wall. As the surface area of nanoparticles increases, there is an increase in surface oxide ion concentration and resulted in more effective destruction of the cytoplasm membrane and the cell wall of bacteria [60].

In this present report, gram-negative bacteria are highly potent when compared with gram-positive bacteria. The difference in diameter of zone of inhibition is due to the difference in susceptibility of bacteria, the morphology of nanoparticles, phase formations, particle size, shape, and synthesis method. The effect of inhibition of growth on both positive and negative bacteria owing to its vigorous antibacterial activity [61, 62]. The zone of inhibition (ZOI) of prepared TiO2 NPs shows an excellent antibacterial activity. Thus, the prepared TiO2 NPs are highly applicable to biomedical applications. The efficient antimicrobial agents must be poisonous to pathogens with the capability to be covered as antimicrobial coverings on medical appliances, purity testing devices, wound dressings, textiles, biomaterials, consumer products, food packaging [63].

3.7 Photocatalytic activity

The photodegradation of methylene blue dye was studied with the help of UV–Visible irradiation technique. Figure 7a, b shows the schematic representation of the photodegradation of methylene blue. The Photodegradation efficiency of TiO2 NPs was calculated using the following equation.

$${\text{Dye removal}}\left( \% \right) = \frac{{C_{0} - C_{t} }}{{C_{0} }} \times 100$$

where Ct is the temporal concentration of MB at time t and C0 is the initial concentration of MB [64].

Fig. 6
figure 6

Shows anti-bacterial activity of TiO2 nanoparticles a Green synthesis method, b chemical method

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Photocatalytic activity of chemically and bio-mediated TiO2 NPs were examined by methylene blue. In this study, methylene blue dye is used as a pollutant because it is widely utilized in the textile industry for colouring purposes, and also it is more harmful to human beings. So, the removal of methylene blue from wastewater is a challenging problem [65]. The photodegradation efficiency and the absorption spectra of methylene blue dye with a regular interval of time, as shown in Fig. 7a, b. The UV absorption spectra of methylene blue at 665 nm corresponds to π–π* transition. Absorption peak intensity reduction results indicate the degradation of methylene blue. The Biologically synthesized TiO2 NPs have higher degradation efficiency compared to chemically synthesized TiO2 NPs. The degradation efficiency increases due to the presence of the hydroxyl group in jasmine flower extract. Bio mediated TiO2 NPs results in the maximum degradation of 89% under 120 min of irradiation. When TiO2 NPs undergo UV–Visible irradiation, the electron–hole pair is generated. The positive holes of TiO2 NPs break water molecules to form hydrogen gas/free radical and negative electron react with oxygen molecules to form superoxide anions [66]. The electron–hole pair results in the formation of a hydroxyl group (OH·) and superoxide’s (O2·−). These superoxide’s and hydroxyl groups are responsible for the degradation of methylene blue [67]. During the reduction process, methylene blue is converted to Leuco methylene blue (LMB) [68]. The degradation efficiency of bio-mediated TiO2 and chemically investigated TiO2 NPs are 89% and 82% respectively.

Fig. 7
figure 7

Shows photocatalytic activity of TiO2 NPs Green synthesis method, and chemical synthesis method

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4 Conclusion

In this present work, TiO2 NPs are successfully synthesized by green synthesis and hydrothermal method (chemical method). Colour changes confirmed the reduction of bulk Titanium to nanoparticles. The photodegradation of methylene blue under UV–Visible irradiation results in the degradation of methylene blue to leuco methylene blue. Bio-mediated TiO2 shows maximum degradation efficiency of 89% under 120 min of irradiation. SEM image reveals that a uniform spherical shape surface morphology. The antibacterial activity of TiO2 NPs was visualized by the agar diffusion method. Antibacterial activity of TiO2 NPs was tested against bacterial pathogens such as Staphylococcus aureus (gram-positive bacteria) Escherichia coli and Klebsiella pneumonia (gram-negative bacteria). The bio-mediated TiO2 NPs exhibit a good potent on antibacterial activity. The suggested results have inferred the property of TiO2 nanoparticles is suited for biomedical and wastewater treatment (dye degradation) applications.