Synthesis and Characterization Co and MgCo-doped TiO₂Nanoparticles

 

Gullipilli Sandhya¹, R.Ravichandra Babu¹*

¹Department of Chemistry, GITAM Institute of Science, (GITAM Deemed to be University), Visakhapatnam, Andhra Pradesh-530045, India

*Corresponding Author E-mail: rrcbabu7@yahoo.in*

This communication deals with newly synthesized Copper and Magnesium co-doped Titania nano particles by Sol gel method and characterized by XRD, FE-SEM, EDX, FT-IR and HR-TEM.X-ray diffraction studies of the Co-Mg/TiO₂ show the presence of anatase phase TiO_2. The FE-SEM images of the Co-Mg/TiO2 show the morphology and decreased size when compared to undoped TiO₂. The particles distribution and elemental data in the sampleswas obtained by different techniques such as SEM, EDAX and HR-TEM.The elemental data of cobalt, magnesium, titanium and oxygen were confirmed by EDAX. From TEM images size is found to be≈10nm which confirms that the dopants Co and Mg reduces the size of nanoparticles. These results suggested that the simple and cost effective method and shows excellent photo catalytic applications.

 

 

INTRODUCTION:

Titanium dioxide or titania (TiO₂) commercial production was initiated from different kinds of ores in 1923. TiO₂ exists in three phases such as anatase, rutile and brookite. TiO₂ most existence in tetragonal anatase and rutile phases compared to brookite is observed. Anatase is stable at low temperature where as rutile is stable at high temperatures having optical energy band gap of 3.2 eV (380nm) and 3.0 eV (415nm) respectively¹.Brookite is rarely studied compared to other 2 polymorphs because of difficulty in preparation and its structure is complicated². All the 3 polymorphs have same Ti-O6 octahedran arrangement where 6 oxygen atoms surrounding central Ti atom, yet they differ significantly in their electronic structure ³.TiO2 Photocatalyst due to its inertness, anti toxic and cost cutting properties is widely used to treat contaminated waters for removal of organic and inorganic pollutants⁴.

 

TiO₂ due to its low cost and photochemical stability can be used as semiconductor, adsorbent, in pigments and catalyst⁵.With the advent of photo catalytic splitting of water on a TiO2 electrode under UV light discovery several preparation methods and applications of TiO2 in environmental, energy and hydrogen storage fields were investigated^6. Recently, fine particles of titania have got attention due to their unique properties as an luminescent material, bacteriocidal action, photocatalyst for photolysis of water and solar cell⁷. Doping TiO2 using transition metals makes it active in higher photo catalytic conversion.Band edge or surface of TiO2 can be changed by metal doping⁸ doped TiO2 nanocrystals are paid much more attention for their enhanced photocatalytic activity⁹. The incorporation of metals leads to new energy level formation between the conduction and valence band ¹⁰. Magnesium due to its ionic radius can replace Ti in bulk. Magnesium doping does not cause structural changes in crystal. Cobalt has several advantages as it is used in magnetic compounds, catalysis, cathodes¹¹ and sensors. Literature survey, reveals the synthesis of different types of metal oxides and doped TiO₂ such as, TiO₂, Ag₂O,ZnO, Fe- TiO₂, Co₃O₄-TiO₂, Mg-TiO₂, Nd-TiO₂, Sn-TiO₂, Cu-TiO₂, Ag-TiO₂ Au-Cu/TiO₂, Ag-Mg/TiO₂^12-25 used for various applicationsIn the present communication the Co/ Mg co-doped TiO₂ nanoparticles are synthesized by a sol–gel route and characterized by XRD, FE-SEM, EDX, FT-IR and HR-TEM.

 

MATERIALSAND METHODS:

Cobalt Nitrate and Magnesium acetate sources for preparing Co-Mg doped TiO₂ photo catalysts and Titanium tetra-n-butoxide [Ti (O-Bu)₄] purchased from Merck, Chinaand anhydrous ethanol were obtained from Hangzhou High-crystal Fine Chemical Co., Ltd., China.

 

Preparation of Cobalt and Magnesium co-doped TiO₂ nanoparticles:

Magnesium acetate and Cobalt nitrate were taken into a 250ml containing 40ml of anhydrous ethanol in appropriate amount and stirred for one hour. To the above solution 4.5ml of ammonium hydroxide is added and stirring is continued for 12hrs.The solution is filtered and residue is washed with ethanol for 3 times. The residue is then dispersed in 40ml ethanol and a solution containing 5ml of Titanium tetra n-butoxide dissolved in 40ml of isopropyl alcohol is added and stirred in orbital shaker at 70ºC for 12hrs. The final product is washed with ethanol and water and dried in oven. The dried product is subjected to calcinations in muffle furnace at 500°C for 2hrs.

 

Characterization of Co and Mg codoped TiO₂ nanoparticles:

XRD data was obtained from X-ray diffraction instrument DX2700, China. The FE-SEM micrographs and EDAX measurements were characterised by using a JEOL 6335F FE-SEM microscope. Fourier transform infrared (FT-IR) spectra for Co and Mg doped TiO₂ nanoparticles was carried out in FT-IR spectro photometer IR-Prestige-21 Shimadzu, by KBr pellet method. The particle size and morphology of the sample was examined by high resolution transmission electron microscopy HR-TEM by instrument JEOL/JEM 2100 respectively.

 

RESULTS AND DISCUSSION:

X-ray Diffraction Studies:

XRD patterns of undoped TiO₂ and Co-Mg/TiO₂ powders are shown in the Fig. 1. From the experimental data it can be predicted that the crystal phase of sample is anatase²⁶. The doped oxide in comparision with undoped oxide shows peak shifting. Furthermore it is observed that the doping of metals caused the increase in the intensity of anatase TiO₂ peaks and no additional peaks related to Co and Mgwere not detected. It may be attributed to homogeneity and well dispersion of co and mg content in TiO₂ particles. The observed 2θ are at about 25^◦, 38^◦, 48^◦, 54^◦, 54^◦, 62^◦, 68^◦, 70^◦, 74^◦, and 82^◦ which are assigned to the (101), (004), (200), (105), (211), (204) (116), (220), (215) and (224) crystal planes, respectively and this characteristic patterns are in correlation with standard JCPDS values of anatase TiO₂ (JCPDS Card No. 21-1272)^27-28.Particles size decrease is observed due to doping that may be ascribed to a broadening effect caused due to incorporation of metals in crystal lattice of TiO₂ ²⁹

 

 

Fig. 1: XRD patterns of (Curve a) Undoped TiO2 (Curve b) Co-Mg/TiO₂ nanoparticles.

 

Fourier Transform Infrared Spectroscopy Study:

The FTIR spectra of the undoped and doped TiO₂ samples are shown in Fig. 2. Stretching and bending vibrations of H–O–H pertaining to 1620 cm-1 can be observed. Furthermore, the peaks between 600 and 400 cm-1, 3400 cm-1 and 1387 cm-1 corresponds to stretching of Ti-O-Ti are noted.^30-33 .Co and Mgpeaks were not observed which suggests that the particles are uniformly distributed.

 

 

Fig. 2 FT-IR spectra of (Curve a) Undoped TiO2 (Curve b) Co-Mg/TiO₂ nanoparticles

 

 

 

Field Emission-Scanning Electron Microscopic study:

Field Emission Scanning Electron Microscopy is shown in Fig. 3. It is used to detect the size of the particles and surface morphology. The surface morphology of the sample contains a mixture of nano particles.The average particle size was found to be~10nm. Co and Mg ions on doping on TiO₂ control the growth of particles. Several observations suggest that spherical structure not only crucial for the surface properties and surface area but also make the spectrum active to show better photo catalytic activity.

 

 

Fig. 3: FE-SEM image of Co-Mg/TiO₂ nanoparticles

 

Energy Dispersive X-ray (EDX) spectra:

The energy dispersive X-ray (EDX) spectra of Co and Mg co-doped TiO₂ are shown in Fig 4. The peaks corresponding to titanium, oxygen and the respective doped metals Cobalt and Magnesium can be clearly seen in these spectra.

 

 

 

 

Fig. 4 EDAX spectra of Co-Mg/TiO₂ nanoparticles

 

 

Transmission Electron Microscopy:

Transmission electron microscopy was used to study the crystallinity, particle size, and morphology of the samples. Individual particle data can be obtained from TEM measurements. Fig. 5 reveals the TEM image showing the high resolution morphology of the anatase TiO₂ particles. Small sized crystallites present in nanotitania can be easily observed. These crystallites show spherical shape. Close observation reveals that the particles are in spherical shape, with average particle size of 6.32-10.39 nm. It can also be observed that patches of doped metals present on the surface of transparent TiO2 nanoparticles.

 

 

Fig. 5: TEM images ofCo-Mg/TiO₂ nanoparticles

 

CONCLUSIONS:

Co and Mg doped TiO₂ was synthesized by sol gel method using cobalt nitrate and magnesium acetate as Co and Mg source.The nano particles were characterized using XRD, FT-IR, FE-SEM, EDS, HR-TEM. The results suggested product was in the form of anatase phase. The particle size of co and mg doped TiO2 is in the range of 6.32-10.39nm, which is considerably less than Co doped TiO2 and Mg doped TiO2. Hence the newly synthesized Co and Mg doped TiO2 is found to be very effective and efficient to degrade organic contaminants and removal of some selected trace metals. Also it can be claimedthat the method is found to besimple and cost effective.

 

ACKNOWLEDGMENTS:

The author is also thankful to Department of chemistry, Gitam (deemed to be university) for providing lab facilities.The author is thankful to Andhra University, Visakhapatnam for providing facilities such as XRD, and FT-IR andSTIC-Cochin for HR-TEM, SEM and EDAX

 

CONFLICT OF INTEREST:

The authors declare no conflict of interest

 

 

 

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Received on 03.04.2018         Modified on 20.04.2018

Accepted on 01.05.2018         © AJRC All right reserved