Synthesis, Characterization and Surface Properties of Nano-TiO 2 Using a Novel Leaf Extracts

The main focus of research is on the nature of applications in the fields of science and technology, particularly nanotechnology. In this paper, a simple, non-toxic, inexpensive, and environmentally friendly green method was used to synthesize TiO 2 nanoparticles using the extraction of portulacaria afra plant leaves and TiCl 4 as a precursor. The synthesized titanium dioxide nanoparticles were characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction patterns, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis. The SEM image of TiO 2 nanoparticles showed a few spherical, non-agglomerated particles. The average diameter of the nanoparticles, according to the surface topography of TiO 2 -NPs, is 70.24 nm. It was found that the average crystalline size was 18.9 nm by utilizing the Debye-Scherrer equation to calculate the size of the crystals. The vibrational mode of Ti-O-Ti exhibits a distinctive peak in the broad band centered at 578.64, 547.78, and 514.99 cm -1 , which denotes the development of metal-oxygen bonding, confirming the presence of TiO 2 -NPs. The specific surface of the synthesized particles was calculated using the Brunauer-Emmett-Teller BET equation.


Introduction
Nanotechnology aims mainly to improve, develop, and utilize the unique properties of molecules at the nano level in order to enhance materials, instruments, and systems with fundamentally different properties.In all fields of science and technology, innovative ideas continued to be developed in the fields of medical technologies, sensor technology, energy resources, and environmental protection and preservation [1].TiO2 is a semiconductor material with a large band gap that can be crystalline as rutile, anatase, or brookite.It is a great material for chemical sensors, solar cells, photocatalysis, dye-sensitized solar cells, microelectronics, electrochemistry, and charge-spreading devices [2].The anatase phase of TiO2 nanocrystals has recently attracted attention due to their intriguing features as compared to the bulk and because they are essential not just for applications but also from a fundamental standpoint [3].TiO2-NPs can be synthesized chemically or physically using microwave [4], hydrothermal [5], solid state , solution route, sol gel [6], chemical phase breakdown vapor, solvothermal crystallization [7], coprecipitation [8], ultrasonic irradiation, and biologically applicable green synthesis methods [9].
Green synthesis is a simple process that utilizes a variety of biological agents, such as plants, bacteria, fungi, algae, and yeast, with no dangerous products [10].Due to its low cost, simple technique, and scalability for large-scale production, green synthesis has greater advantages over physical and chemical processes.With this technique, expensive equipment, hazardous chemicals, high temperatures, and high pressure are not necessary [11].As a result, plant and herbal extracts are more desirable due to the easier and more cost-effective process and the inclusion of compounds such as flavonoids, terpenoids, and polysaccharides [12].The creation of environmentally safe nanoparticles with a variety of natural features, great stability, and suitable dimensions can be achieved through a one-step green reduction method called nano-TiO2 biosynthesis for the production of biological nanoparticles [13].TiO2-NPs are created from a variety of plants, including the Jatropha curcas plant [14], the glycosmis cochinchinensis plant [15], the Syzygium cumini plant [16], the Moringa oleifera plant [17], the Psidium guajava plant [18], and the Aloe vera plant [11].
In this research, Portulacaria afra (PA) was used to synthesize TiO2-NPs.(PA) is a succulent plant that is native to South Africa and can live in different regions of the world, including Iraq.(PA) is commonly found in semi-arid regions.This plant has small, succulent leaves and is in the form of a tall or small woody tree.The height of this plant can reach 2-5 meters.This plant contains bioactive substances such as alkaloids, amino acids, flavonoids, terpenoids, and other phenolic intermediates that may act as effective reducing agents for the bioreduction of metals into nanoparticles (NPs), which in turn have a variety of biological applications [19].

Materials
Titanium tetrachloride TiCl4, 99.0% was purchased from CDH, Portulacaria afra leaves collected from a local garden in Baghdad, Iraq.

Biosynthesis of TiO2-NPs by Portulacaria afra (PA)
In this method, TiO2-NPs were synthesized using the aqueous extract of (PA) plant leaves.(PA) leaves were removed from the original plant, thoroughly cleaned with tap water to eliminate impurities, then rinsed with distilled water and chopped into little pieces.25 g of chopped plant leaves were added to 100 mL of boiled distilled water and heated for two hours continuously at 90 o C.
The plant extract was filtered using a Whatman No. 1 filter solution.For the synthesis of titanium dioxide nanoparticles, 2.8 mL of titanium tetrachloride as an aprecursor was added to 100 mL of distilled water and shaken well.(PA) leaf extract was added to the titanium tetrachloride solution gradually with continuous stirring.The mixture was continually stirred for 4 hours.Titanium dioxide nanoparticles were synthesized during this process, and they were separated by drying the precipitate for a day at room temperature.Then it was heated in an electric oven for one hour.The precipitate was dried for 24 hours at 100 o C. Then the precipitate was calcined at 500 o C for 4 hours continuously [11].After that, the precipitate was often washed with distilled water to get rid of the impurities.To obtain titanium dioxide nanoparticles as a white precipitate, the precipitate was dried and heated at 700 o C for one hour.Finally, a laboratory mill ground the precipitate and stored it for characterization and application.Figure 1 shows the steps of TiO2-NPs preparation from (PA) plant.

Characterization of TiO2-NPs
For chemical, structural, physical, and morphological evaluations, TiO2 NPs were characterized.Analyses of the morphology of nano-TiO2 were done using scanning electron microscopy (FESEM-EDS, MIRA III, TESCAN, and Czech).The physical assessment was done using atomic force microscopy (AFM 2022, Nanosurf, and Switzerland).Structural assessment of the nanoparticles was characterized using X-ray diffraction XRD (PW1730, Philips, and Holland).Chemical assessment was carried out using Shimadzu IR-Affinity-1 Japan.Brunauer-Emmett and Teller surface area analyzer type BELSORP MINI II, BEL, Japan, was applied to estimate the specific surface area, average pore volume, and pore size distribution [20] .These measurements were used to describe the topography and examine the characteristics of a material at the nanoscale.

Scanning Electron Microscopy (SEM)
SEM measurements were used to obtain the images of samples using the technique of scanning electron microscopy to explore the surface features, porosity morphology [21], and crystalline structure [22].It can be seen from Figure 2 that the sample showed excellent crystallinity.The particle size of TiO2-NPs was 47.580 nm, which was calculated using IMAGE J software.The SEM image of TiO2 nanoparticles revealed that TiO2 has a nanosheet-like structure on its surface and is porous [23].The SEM image showed that the TiO2 nanoparticles had clumped together and took an irregular shape, which was obtained at a magnification of 500 nm.There were a few non-clumping particles that were spherical in shape.So, it can infer that the phytochemicals of Portulacaria afra leaf extract coat the surface of TiO2 nanoparticles, inhibiting their accumulation [15].

Fourier Transform Infrared Spectroscopy (FTIR)
FTIR spectra provide specific data about the chemical bonding and molecular structures of organic compounds and a limited number of inorganic materials.It is useful for the identification of unknown compounds when patterns of IR spectra are available.FTIR spectra were recorded over a wavelength range between 400 and 4000 cm -1 .Figure 5 shows the FTIR spectrum of TiO2-NPs.In this Figure, a wide absorption band at 3421.72 cm -1 is caused by the surface adsorbed moisture of the synthetic TiO2-NPs straining the O-H bond.The weak absorption bands at 2380.16 and 2312.65 cm -1 could be caused by the C=O bond stretching generated by carbon dioxide that was adsorbed to the NPs surface .The O-H bending of water molecules was adsorbed on the particle surface, resulting in the absorption band appearing at 1627.92 cm -1 .The vibrational mode of Ti-O-Ti exhibits a distinctive peak in the broad band centered at 578.64, 547.78, and 514.99 cm -1 , which denotes the development of metal-oxygen bonding [27].The peak at 2879.72, 2831.50 cm -1 confirmed the presence of secondary amines, and the peak at 1643.35 cm −1 was caused by the O-H bending vibration of adsorbed water molecules on the surface of TiO2 which may play a significant role in photocatalytic activity.Strong peaks at 1546.91, 1531.48, and 1517.98 cm -1 indicate aliphatic nitro compounds with stretching of N-O [15].The peaks 1394.53,1342.46, and 1319.31cm −1 related to aliphatic amine-containing and C-N-stretched amines [28].Table 2. FTIR spectrum data for TiO2-NPs.

BET analysis
The characteristic and adsorption capacity of the synthesized TiO2-NPs could be predicted from the surface area and porosity information obtained from the BET equation [29].The specific surface area was calculated from the BET equation and found to be 14.741 m 2 /g, as shown in Figure 6.The total pore volume and mean pore diameter were found to be equal to 0.1191 cm 3 /g and 32.304 nm, respectively.The N2 gas adsorption/desorption isotherm for TiO2-NPs is presented in Figure 7.This figure shows the presence of a cylindrical pore in this sample with a narrow distribution of uniform pores [30].

Conclusion
The environmentally friendly technique for producing TiO2-NPs from PA plant extract compared to other preparation methods could be a promising technology because it uses no hazardous chemicals and is environmentally benign.SEM, AFM, XRD, FTIR, and BET are among the diagnostic methods used to describe the prepared particles.A few spherical, nonagglomerated particles could be seen in the SEM image of TiO2 nanoparticles.When the surface topography of TiO2-NPs was studied, an average diameter of 70.24 nm was observed.Through the use of Debye Scherrer, the crystallite size was calculated.The crystalline size was 18.9 nm on average.The presence of TiO2-NPs is confirmed by the vibrational mode of Ti-O-Ti, which displays a characteristic peak in the broad band centered at 578.64, 547.78, and 514.99 cm -1 .This peak indicates the development of metal-oxygen bonding.According to BET analysis, the specific surface area was 14.741 m 2 / g and the total pore volume was 0.1191 cm 3 / g.Titanium dioxide nanoparticles, especially those prepared by green methods, have many unique features and characteristics that enable them to be used to treat environmental pollution problems.For future work, it is recommended: 1. Study the use of the green synthesized TiO2-NPs to get rid of other contaminants from the environment, such as heavy metals.2. Study the possibility of using these prepared nanomaterials in medical

Figure 3
Figure 3 (a, b).View of AFM image and granularity cumulating distribution chart of TiO2-NPs.

Table 2
shows the FTIR spectrum data for TiO2-NPs.