SYNTHESIS AND CHARACTERIZATION OF STRUCTURAL NANOCOMPOSITE TITANIUM DIOXIDE COPPER-DOPED USING THE IMPREGNATION METHOD

Nanocomposite Titanium Dioxide (TiO 2 ) doped Copper (Cu), Cu-TiO 2 is synthesized by the impregnation method. This study aims to determine the effect of adding Cu to the TiO 2 structure. The 1, 3, and 5 Cu with% TiO 2 dissolved in 50 ml of deionized water, and 3 grams of TiO 2 added. The compound is then stirred for 2 hours at 90 o C and dried in an oven at 110 o C for 30 minutes. Drying samples were calcined at 500 o C for 3 hours. Cu-TiO 2 nanocomposites were characterized by XRD, SEM-EDX Mapping, and FTIR. The XRD analysis results show that Cu-TiO 2 nanocomposite has a high level of crystallinity and has an anatase phase structure. The size of TiO 2 crystals decreased with Cu doping and increased from 49.66 nm to 49.68 nm, with an increase in the composition of the doping mass of Cu. The SEM-EDX Mapping results show that all samples tend to clot, and Cu dopants evenly distributed on the surface of TiO 2 . FTIR analysis explained the presence of hydroxyl ions in the sample marked with the appearance of the absorption peak at 1658.78 cm -1 associated with OH bending of Ti-OH.


INTRODUCTION
Titanium dioxide (TiO2) has many advantages compared to other types of semiconductors, including chemical stability, corrosion resistance, and non-toxic [1]. TiO2 has three different phases, namely, anatase, rutile, and brookite. In general, the anatase phase is formed at 300-600 o C, while rutile formed at high temperatures [2,3]. In its use, TiO2 has the limitation of only being stimulated in some parts of the UV light from the sun. Therefore, surface modification of TiO2 with transition metals [4], and non-metal elements [5,6] becomes very important.
Currently, copper metal, Cu, as one of the TiO2 dopants, is the concern of many researchers. To improve the properties of TiO2 can be done by doping with the element Cu. It is caused by high copper conductivity and low cost. Also, copper has a low level of toxicity [7]. Cu can also affect particle size and optical properties of TiO2, and the amount of oxygen on the surface of TiO2 [8]. Cu-TiO2 has been widely applied in various fields, including environmental remediation, degradation of organic pollutants [9,10], and bacterial disinfection [11].
Xin et al. [12], synthesized Cu-TiO2 with dopant variations of Cu (0 to 3 mol%) made by the sol-gel method. It was found that at 0.06% mol had many electronic traps, such as the voiding of O and Cu (II) ions and compared with pure TiO2, the hydroxyl content on the surface of Cu-TiO2 increased. Heciak et al. [13] studied the effect of modification procedures and copper precursors on the physicochemical and photoactivity on the formation of useful hydrocarbons from acetic acid. The synthesis of Cu-TiO2 was carried out by different methods, namely impregnation, mechanical alloying, and photo deposition.
Reddam et al. [14], synthesized modified TiO2 with cations of Fe, Mn, and Cu. The characterization results confirmed the presence of anatase and rutile phases, and well dispersed on the surface of the catalyst, which was verified by XPS analysis. Mathew et al. [15], synthesized Cu-TiO2 by the sol-gel method and calcined at a temperature range of 500 -700 o C for antimicrobial applications. The characterization results explained the presence of anatase at a temperature of 500-600 o C, and bandgap energy was obtained 2.8 eV. The calcination temperature treatment of 500 o C was too carried out by Heider et al. [16]. They reported that at calcination temperature of 500 o C, an anatase phase was obtained.
In this study, the impregnation method was used for the synthesis of Cu-TiO2 nanocomposites. In the process, this method does not transpire anion or cation exchange. The method depends on the metal cation, which becomes a dopant. Queiroz and Barbosa [17] reported that the synthesis of Cu-TiO2 by the impregnation method could be obtained by anatase phase TiO2. Behnajady and Eskandarloo [18] reported the same thing. Besides, the insertion of dopants by the impregnation method does not change the electronic structure of the catalyst material.
The micro characterization obtained was done by X-ray Diffraction (XRD) and Scanning electron microscopy (SEM) -energy dispersive X-ray (EDX). The functional group investigated by Fourier-transform infrared spectroscopy (FTIR).

METHOD
Cu-TiO2 nanocomposites synthesized using the impregnation method. Copper sulfate, n% (n = 0, 1, 3, and 5) of the weight of TiO2, was dissolved in 50 ml of distilled water as a solution of copper precursors and stirred with magnetic stirrers until homogeneous at room temperature for 30 minutes. After that, 3 g TiO2 was added to the solution. Subsequently evaporated at 90 o C for 2 hours while stirring. The sample was then dried in an oven at 110 o C, crushed and calcined at 500 o C for 3 hours. It is to obtain the anatase phase TiO2 formed in the temperature range 400-500 o C [19]. Also, the calcination temperature of 500 o C can induce OH group deficiencies on the surface [20].
Nanocomposite samples characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM)-energy dispersive X-ray (EDX) Mapping, and Fourier-transform infrared spectroscopy (FTIR).  The average size of the crystallite sample is obtained from the half-width of the full maximum (FWHM) from the highest peak using the Debye-Scherer equation,

RESULT AND DISCUSSION
where t is the size of a crystal grain, k is the Scherrer constant (0.9), λ is the wavelength of Xrays (in Å), β is the width of half the peak (in radians), and θ is the Bragg diffraction angle (in radians). The results are shown in TABLE 2.  FIGURE 2 (a-c) shows the results of the characterization using SEM. The results explained that all Cu-TiO2 samples tended to clot. In FIGURE 2a, small clumps of relatively uniform size appear, and they get more significant with the increasing composition of Cu dopants, as in FIGURE 2b and 2c. It indicated that Cu dopants are dispersed on the surface of TiO2. XRD data confirmed this result. Nankya and Kim [24] reported that clumping particles and TiO2 particle size decreased with the addition of Cu dopants. It is shown that Cu doping affects grain growth. FIGURE 3 shows the EDX Mapping image on a 5%-CTO nanocomposite sample. The elements shown in the image are colored spots. Cu dopants are evenly distributed on the surface of TiO2. Zaid et al. [25] reported that the dispersed metal element indicated that doping Cu on the surface of TiO2 by the method used was successful. Also, it shows that the calcination process influences the distribution of elements of Cu, O, and Ti that is evenly distributed in Cu-TiO2, as reported by Tian [20]. This result was also reported by Singh and Dutta [26] with calcination temperatures of 600 o C. In 1658.78 cm -1 , it was related to the -OH bending of Ti-OH on the surface of TiO2 and the water molecules adsorbed by the catalyst [27]. These results indicate the presence of hydroxyl ions in the sample. It thought that the existence of these peaks is because they are physically adsorbed. The absorption area of TiO2 appears at 600-700 cm -1 and changes with the addition of metals [28].

CONCLUSION
The Cu-TiO2 nanocomposites were prepared using the impregnation method. From the observations, it was found that nanocomposites contain Cu on the surface of TiO2. XRD measurements show that this doping material is an anatase structure phase with a high level of crystallinity and crystalline size ranges from 49.66 nm -49.68 nm and 55.88 nm for TiO2 without doping. SEM/EDX data show that agglomeration is increasing with the addition of Cu dopants and Cu, Ti, O elements evenly distributed on the surface of Cu-TiO2. FTIR data showed that copper, Cu, entered the TiO2 matrix, which was marked by the presence of hydroxyl ions at 1658.78 cm -1 .