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Synthesis and characterization of nano tio2 via different methods
- 1. Synthesis and characterization of nano-TiO2 via different methods By TAMKEEN FAROOQ M.Tech VLSI Electronics & Communication Sharda University
- 2. Overview 1. TiO2 Introduction & properties 2. Synthesis Methods 3. Sol-gel Method 4. Sol-gel process & experimental procedure 5. Characterizations for sol-gel method 6. Hydrothermal Method 7. Synthesis via hydrothermal method 8. Characterizations for hydrothermal method 9. Conclusion
- 3. TiO2 Introduction & Properties Titanium dioxide nanoparticles also called ultrafine titanium dioxide Particles of titanium dioxide (TiO2) with diameters less than 100 nm Believed to be one of the three most produced nanomaterials , along with silicon dioxide nanoparticles and zinc oxide nanoparticles Properties TiO2 promising material as semiconductor Produced in the rutile and anatase forms Unlike larger TiO2 particles, TiO2 nanoparticles are transparent rather than white High UV absorbance High photochemical stability
- 4. Synthesis methods Titanium dioxide nanoparticles can be prepared following methods: Sol gel method Hydrothermal method Solvo thermal method Precipitation method Co- Precipitation method
- 5. Sol gel Method o It is a wet chemical technique o One of the well established synthetic approach to prepare novel metal oxide o Involves the evolution of inorganic networks through the formation of a colloidal suspension (sol) and gelation of the sol to form a network in a continuous liquid phase (gel) o The precursors for synthesizing these colloids consist : - metal alkoxides ; e.g: titanium isopropoxide (TTIP) -metal chlorides
- 6. Sol gel Process & Experimental Procedure Hydrolysis of metal oxide precursor Condensation of metal hydroxide Gelation & Ageing of the formed Sol Drying Densification Apparatus used : • Beaker • Measuring Flask • Titanium isopropoxide as preccursor • Absolute Ethanol • Distilled water • Nitric Acid (dil HNO3) • Stirrir with magnetic bit • Hot air oven for drying and Muffle Furnace for Sintering
- 7. Procedure : [Titanium isopropoxide] =10 ml+ [Ethanol = 40 ml] , Stir for 30 minutes [Nitric acid = 10 ml] + [Distilled water =40 ml] Add HNO3 in TTIP solution drop by drop and put the solution for one day Centrifuge and sonicate (add ethanol) three to four times for washing Centrifuge and dry in oven for 2 hours at 50 -60 degree celsius Sintering at 450 degree celsius for two hours to obtain the nanoparticles
- 8. UV-VIS absorption spectra of TiO2 nanoparticles via Sol gel
- 9. XRD pattern of TiO2 nanoparticles synthesized via sol-gel route
- 10. • Crystallite size was obtained by Debye-Scherrer’s formula given by equation: D=Kλ/ (βcosθ) • where D is the crystal size • λ is the wavelength of the X-ray radiation (λ=0.15406 nm) for CuKα • K is usually taken as 0.89 • β is the line width at half-maximum height given by 2θ2 - 2θ1 • The crystallite size obtained using this formula is 7 nm for sol- gel derived particles 17 nm in case of hydrothermal method derived particles.
- 11. TEM images of TiO2 nanoparticles synthesized via sol-gel route • Clear spherical and non- homogenous structures can be seen in the figure having diameter ~ 9nm. • Selected area diffraction clearly indicates that TiO2 nanoparticles are highly crystalline in nature.
- 12. SEM micrographs of TiO2 nanoparticles synthesized via sol-gel route • Clear nanostructures having grain size ~ 30nm. • 1 grain nanoparticle is ~ 3 crystallites. • Nanoparticles seen by SEM image consists of a number of crystallites seen by TEM image.
- 13. Hydrothermal Method • It is wet chemical method • Conducted in steel pressure vessels called autoclaves with or without teflon liners • Under controlled temperature and/or pressure with the reaction in aqueous solution • Widely used for the production of small particles in ceramics industry • Used to prepare nanoparticle of titanium dioxide
- 14. Synthesis of TiO2 nanoparticles Apparatus Required : • Beaker • Measuring flask • Titanium tetrachloride as source material • Titanium isopropoxide (TTIP) • Sodium Hydroxide as mineralizer • Distilled water • Auto Clave vessel
- 15. Procedure: • Mix one molar stoichiometric ratio of TTIP in 50 ml of distilled water • 2 – 3 mol NaOH solution is added • The final volume was adjusted to 90 ml using distilled water • 90 ml sol was transferred to a 100 ml Teflon lined Auto Clave vessel • The sealed vessel was heated to 240 degree celsius for 12 hours • The resultant precipitate was dried at 450 degree celsius for 2 hours to obtain TiO2 nano particles
- 16. UV-VIS absorption spectra of TiO2 nanoparticles via different methods
- 17. XRD pattern of TiO2 nanoparticles synthesized via hydrothermal method
- 18. • The crystallite size obtained using Debye- Scherrer formula is 17 nm. • Average particle size can be calculated • Crystallinity for a particle be it semi crystalline or crystalline • Provides information about structures ; eg , rhombohedral, cubic etc • It gives information about miller indices • Provides information about unit cell dimension
- 19. TEM images of TiO2 nanoparticles synthesized via hydrothermal method • TEM shows particles are crystalline in nature. • No clear spherical structures can be seen. • Nanoparticles obtained are adhering to one another. • Agglomeration of nanoparticle is more. • Average particle size is ~ 19nm.
- 20. SEM micrographs of TiO2 nanoparticles synthesized via hydrothermal method • Grain size is ~ 100nm. • 1 grain in hydrothermal derived nanoparticles consist of approximately 5 crystallites.
- 21. Band gap obtained by extrapolating the linear portion of the (Ahv) versus hv • Band gap energies (Eg) of TiO2 nanoparticles ( 3.54 and 3.43 eV) are larger than the value of 3.2 Ev for the bulk TiO2. • Band gap increases with decreasing particle size. • Absorption edge is shifted to a higher energy with decreasing particle size.
- 22. • The optical absorbance coefficient α can be expressed as: α = A(hʋ- Eg)^n/hʋ where: α is the absorption coefficient Eg is the absorption band gap A is constant n is the number of transitions
- 23. Photoluminiscence of TiO2 nanoparticles obtained via different methods. • The first peak in PL spectra between 320-400 nm corresponds to direct recombination between electrons in conduction band and holes in valence band. • TiO2 nanoparticles prepared by sol-gel method show high luminiscence than hydrothermal derived nanoparticles. • The intensity peak is observed at 354nm.
- 24. Conclusion • TiO2 nanoparticles prepared via sol-gel route were highly cyrstalline and smaller crystallites size as compared to the one prepared by hydrothermal method. • The band gap of synthesized nanoparticles is size dependent.
- 25. References • M.Tomkiiewicz , Catal. Today 58 (2000) 115. • G.Ramakrishna, H.N. Ghosh, Langmuir 19 (2003) 505. • M.M. Rahman, K.M.Krishna, T.Soga, T.Jimbo, M.Umeno, J.Phys.Chem.Solids 60 (1999) 201. • E.Pelizzetti, C.Minero, Elecrochim. Acta 38 (1993) 47. • S.Sahni, S.B.Reddy, B.S.Murty, Materials Science and Engineering A 452-453 (2007) 758. • B.Li, X.Wang, M.Yan, L.Li, Materials Chemistry and Physics 78 (2002) 184. • Yu.V.Kolen ko, B.R.Churagulov, M.Kunst, L.Mazerolles, C.Colbeau-justin, Applied Catalysis B: Environmental 54 (2004) 51.