Bio activity testing of SnO 2 -TiO 2 nanocomposite synthesis by chemical methods

In this work, SnO 2 :TiO 2 nano composite with silver dopant have been prepared by chemical route method at preparation temperature 100 ℃ , with 6% Ag ratio. Titanium chloride (TiCl 3 ) has been used as the precursors of TiO 2 and tin chloride (SnCl 2 ) were taken as the precursors of SnO 2 in the laboratory. The prepared samples were described by FESEM, X-Ray diffraction and uv-visible spectrophotometer. Results show that compared to pure SnO 2 and pure TiO 2 ,SnO 2 :TiO 2 nano composite calcined 400 ℃ shows a large surface area. The average crystalline size was estimated from XRD analysis by using Debye-Scherrer’s formula and the result shows that the crystalline size increases from (27.78) nm to (29.2354)nm after adding Ag. Bio activity application of the prepared composite has been tested after immersion SnO 2 :TiO 2 nano composite in the simulated body fluid SBF, the morphology and particle size of the prepared immersed samples have been estimated after 20 days by FESEM images. (


Introduction
Metal oxides based on (nano dispersed and nanostructured) are a very important class of materials with Chemical, electronic, and structural characteristics [1].Nano materials based on metal oxide materials becoming interesting popular materials which can be used in many medicine and ecology applications such as diagnosis, drug delivery, tissue culturing, gene therapy, DNA sequencing and in cancer treatment [2,3].Adsorption nanomaterials have a high capacity, fast kinetics and high surface area [4,5].Moreover, metal oxide nanomaterials have considerable interested because of high advantages compare with bulk materials and, they have excellent prospects for getting new materials.However, nanomaterials oxides also have a significant debit their operation as environmental pollution with nanoparticles, photocatalysts and adsorbents as well as for the manufacture of monitoring device [6].It is promising to produce nano composites an incredibly intriguing kind of nanostructures material because of their parcels that could surpass the parcels of its several phases.[7].Also, nano composites due to their structure have occasionally unique, chemical, and physical characteristics, which can be used in many fields, such as product of new accoutrements can used in the fields of drug, ecology and energy [8,9].TiO 2 and SnO 2 are semiconductors materials with different band gap (3.2) eV for TiO 2 and (3.6) eV for SnO 2 [10].These materials have comparable ionic radii.(0.69 Å of Sn4+ and 0.605 Å of Ti4+), this similarity provide these materials an electronic intermixed density states [11].Also, SnO 2 and TiO 2 have same structural (tetragonal structure) and electronic properties and that lead to easily form a composite and doping [12].Coupling such materials to form nano composite is claimed to be a successful method for achieving quantum efficiency.[13].These materials are very good for making nano composites.The extensive use of SnO 2 and TiO 2 as composite increases in the last years compared to other materials because of its special chemical and physical characteristics that make it appropriate for many important field such as, biomedical field, optical emitters, catalysts, electronic conductors, and amplified detection signals attention [14][15][16].When this material irradiated with light, electrons are generated and move from TiO 2 to SnO 2 .As the conduction band of TiO 2 is greater than that of SnO 2 , holes stayed in the valence band of TiO 2 , whereas electrons moved to the conduction band of SnO 2 .[17].Several methods can be used for investigated (SnO 2 -TiO 2 ) nano composite, these include hydrothermal, sol-gel, thermal evaporation, chemical method, electrospinning, chemical vapor deposition (CVD) [18 ].Among these methods, chemical method has been widely used as a low-cost route to prepare nanostructures oxide and good control size, shape and morphology of nanostructures [19]

Experimental part
SnO 2 -TiO 2 nano composite has been synthesized by chemical precipitation method as in the following procedure: Firstly (0.1 M) of SnCl 2 ⋅ 5H 2 O was added to 100 ml deionized water and ethanol (2:1) ratio in a 100 mL beaker.To obtain a homogeneous solution, a continuous magnetic stirring was used for 30 min.Then 10 mL of HCl was added gradually while stirring constantly for 10 min to get a transparent solution.Later NaOH was added dropwise to the solution leading the pH became 8.After that for preparing TiO 2 solution: (0.1M) TiCl 4 was slowly added dropwise into 100 ml of deionized water and 100ml of ethanol for 30 minutes of constant magnetic stirring followed by the dropwise addition of 10 mL of HCl to the mixture.The reaction was performed under a fume hood because of the large amount of Cl2 and HCl gases evolved from this reaction.
SnO 2 :TiO 2 nanocomposite was prepared using chemical route method by mixing the two solution SnO 2(0.50) :TiO 2(0.50) and transfer to 500 mL container with magnetic moving for 30 minute after that the beaker was heated at a temperature of 100 ℃ for 4 h.The result solution washed with deionized water remove the chlorine content.The product was drying on a hot plate and then dried powder was heated at 400℃ for 1 hour.
SnO 2 :TiO 2 nano composite was doped by Ag with 6% ratio by adding AgNO 3 (0.058 wt.%) to the mixture solution with continues stirrer for 15 min.Then, the mixture was heated at 100 ℃ for 4h to achieve a homogeneous material it was left until the second day for dry.Finally, the sample was washed with distilled water and dried.All samples were annealing in electric oven at 400 ℃ for 1h.The optical properties of the samples were investigated using (double beam spectrophotometer UV-210A Shimadzu).The absorbance have been recorded in the wavelength rang (300-900)nm .
Simulated body fluid (SBF) is a solution that has ions that equivalent to those in the solution of human body, Show Table (1).In order to examine the material's bioactivity, all the prepared Samples immersion in this solution for 20 days.To prepare SBF solutions, appropriate quantities of these materials were dissolving in 500 mL deionized water one by one to each material was completely dissolved.

Result and discussion
The X-ray diffraction pattern of SnO 2 -TiO 2 nanocomposite pure and doping with silver (6%wt) are showing in figure (1-a,b,c,d).Figure (1-a) shows poly crystalline structure of SnO 2 with diffraction peaks related to 2Ө = 26.61 0,33.8 0 , 37.83 0 , 51.8 0 and 54.72 0 corresponding to (110),( 101),( 200) , ( 211) and (220) planes All the peaks related to the tetragonal rutile tin dioxide structure JCPDS : (41-1445).While Figure (1-b) shows x-ray diffraction pattern of SnO 2 -TiO 2 nanocomposite, another two peaks related to TiO 2 at 2Ө = (25.27 0) and (48.03 0 ) were identified as matching the hkl (101) and (220) respectively planes.From the sharp peaks it can be indicated the formation of high crystalline TiO 2 -SnO 2 nano composite.Figure (1-c) show the XRD pattern of TiO 2 the diffraction data showed good agreement with the JCPDS card ) and all the peaks can be indexed as anatase phases of TiO 2 .[16].Additionally, diffraction peak changes of silver doped SnO 2 -TiO 2 are observed in figure (1-d).Which 2θ = 32.790 correspond to the crystallographic planes (111) for Ag 2 O and 2θ= 38.05 0 are assigned as (200) (according to (JCPDS) file No. which is because the ions created by doping NPs may have an ionic radius that is lower than Ti+.Notably, characteristic diffraction peaks of Ag 2 O or Ag were detected possibly due to the high content of Ag rate of doping [17].The crystallite size can be estimated for the prepared sample from the XRD pattern using Scherrer equation [20].
where λ is the wavelength of the XRD (equal to 1.5405 Å), k is a constant= 0.9, θ is the reflection angle and β is the FWHM in rad.As shown in Table 2.The relation between the absorbance spectra (A) and wavelength (λ) is shown in figure (3).It can be shown from the figure that the absorbance is low in the visible region, and it decreases sharply between (300 -400)nm region.Also, from the figure the spectra of absorbance were found to increases for SnO 2 -TiO 2 nanocomposite comparing with pure SnO 2 .While figure (4) shows the absorbance spectra of undoped and Ag doped SnO 2 -TiO 2 nanocomposite and it can be notice from the figure that the absorbance spectra increase after doping with Ag and the edge of absorption shifted toward higher wavelength.Bioactivity testing of the prepared samples was performed by taking simulated body fluids (SBF) solution.SBF solution was prepared with the chemical investigations matching those of human bodily fluid and the amounts of ions equal to the inorganic constituents of human blood plasma [21].Figure (5-a,b) shows the FE-SEM image of pure SnO 2 and TiO 2 nanostructures , as seen from the figure agglomeration of Sno 2 and Tio 2 at discrete grains on the surface and unordered crystallites do not adhere to each other.Also, the cavity within the grain increases, that is encouraging for in vitro bioactivity testing.

Conclusion
In summary, pure and Ag doped SnO 2 -TiO 2 nanocomposite were effectively produced via chemical route method.The morphological, optical and structural characteristics of the samples were examined.The result of the XRD revealed that the crystallite size of prepared composite increases after doping with Ag.The obtained nanocomposite displayed a polycrystalline structure, Also the interaction of nanocomposite of with (SBF) solution was successfully achieved.Uniform distribution of spherical NPs on the surface of nanocomposite showed good morphologic effects that provided high efficiencies biomaterial.

Figure ( 2 a
Figure (2 a,b) shows the FE-SEM images of the SnO 2 and TiO 2 samples respectively.The dominate structures obtained from the figure were nanoparticles uniformly distributed with average diameter about (30)nm for SnO 2 and (45)nm for TiO 2 and some pores between them.FE-SEM images of SnO 2 -TiO 2 nanocomposite and Ag doped SnO 2 -TiO 2 nanocomposite are showing in figure (2) c and d respectively, from figure (2-c) the sample content aggregation of nanoparticles with non-uniform distribution while figure (2-d) showed that the samples contained a composition of nanoparticles with diameter from 70 to 90 nm and a small nanoparticles can be shown on the surface of sample.Also, those particles were agglomerated together which can be because of the heat treatment.

Figure ( 5
-c) shows the FE-SEM image of SnO 2 -TiO 2 nanocomposite after 20 days immersion in the SBF solution.The surface morphology of the SnO 2 -TiO 2 nanoparticles is examined by FE-SEM and clearly seen a contact of nanoparticles with each other and the porosity within the grain increases.Compared with the pure SnO 2 -TiO 2 nanocomposite, the size of nanoparticles was enlarged and uniform, so it surfaces area was larger.The growth of the fine particles of Ag in regular pattern is observed on the surface of the sample as show in figure(5-d).