Abstract— In thisstudy, nanoparticles of undoped titanium dioxide were prepared using precursorTitanium tertbutoxide via Sol geltechnique. Using a single process, Co, Cu, Fe, Ni and Zn doped TiO2nanoparticles were prepared by simply changing the precursor dopant metal salt.The nanostructures were characterised bya Scanning Electron Microscope, XRD, Ultraviolet visible Spectroscopy. SEMconfirmed the size of nanoparticles nearly 9 to 20 nm. XRD analysis proved thatthe position of peaks was not affected by doping. The band gap for undoped anddoped samples are estimated using the (?Ephot)^2 versus Ephot plots. Metaldoping decreases the band gap of anatase titatnium dioxide nanoparticles isconfirmed with our results.
Index Terms— Titanium dioxide nanoparticles, SEM, band gap,transition metal doped I INTRODUCTION Titanium dioxide is very useful because of its resistanceto photochemical erosion. It is convinient to handle and is comparativelycheaper. It is used in photocatalytic application as it can be prepared easily.
Its photostability is high. Its holes have strong oxidizing power. Largesurface area increases amount of photon generated electron hole pairs.
Titaniumdioxide is most suitable catalyst for organic contaminants. Titanium dioxide has been used for the photodegradation oforganic dyes and decolorization of wastewater. Using TiO2 as photocatalyst has one drawback that it has a wide energyband and its band gap (3.2 eV for anatase phase ) falls nearly in the UV rangeof electromagnetic spectrum. Only UV light forms electron hole pair requiredfor photocatalytic process.
Since UV light is only 3-5% of the solar spectrum,scientist are trying to decrease its band gap so that electron hole formationshould occur at the incidence visible light. Undoped titaniumdioxide is sensitive nm, it can be doped with variety of metal and nonmetal impurities 1. One of the way to shift optical response of TiO2 to thevisible range is by adding a transitionmetal oxide such as that of copper, zinc, cobalt, nickel andironin an adequate amount. 1 2 4 6. The recombination of electron holepairs (photo generated) is reduced dueto this doping and causes red shift. II MATERIALS AND METHODS 2.1 Materials: All Analytical grade purity reagents were used without anyfurther purification.
Titanium tert-butoxide (98% purity)was the titaniumprecursor precursor used obtained from Sigma Aldrich. Hydrochloric acid HClwas supplied by Highmedia and Analytical reagent grade ethanol was obtainedfrom Changshu Yangyuan Chemical, China. De-ionized water was used for preparing all standardsolution.
Loba Chemie supplied Anhydrous ferric chloride (FeCl3), coppersulphate pentahydrate (CuSO4.5H2O), Cobalt Chloride hexahydrate (CoCl2.6H2O),Nickel Chloride hexahydrate (NiCl2.
6H2O) and Zinc Acetate dehydrate(Zn(CH3COO)2.2H2O) of 99% purity. 2.
2Method of Preparation : Undoped sample is preparedusing sol gel method described in 1013. Solution A is prepared with 2.5 mLof Titanium tert-butoxide , 25 mL ethanol added together with constantstirring. Solution B is prepared with 1.
25 l. of distilled water ,0.25 mL ofHydrochloric acid and 25 mL ethanol added together with constant stirring.Solution A and B were mixed with continuous stirring for 2 hrs. A sol isallowed to transform into gel which was dried under 80°C for 1 hr. The dry gelwas then sintered at 450°C for 3 hrs. to obtain desired undoped TiO2 Nanocrystalline particles.
Extra solution ‘C’ wasprepared for metal doped TiO2nanoparticles,. Solution C was a 0.73 M solution of the dopant metal precursorsalt in distilled water.
1 mL of solution ‘C’ was added to solution B and restof the procedure is same as above. The amount of metal salt solution used wascalculated for a Ti:Metal atomic ratio of 0.05. 2.3 Characterisation: D8Advance X-ray diffraction meter(Bruker AXS, Germany) was used to characterizethe crystalline structure (room temperature, 30 KV, 30 mA), using Cu Ka radiation (=0.
15406 nm).The crystal Field Emission Scanning Electron Microscopy (JEDL JSM-7600F) wasused to study the morphology and structure of the particles. Size of nanoparticles was measured.UV/Vis spectrophotometer Perkin ElmerLambda XLS+ was used to study the absorption spectra of the TiO2 samples. III RESULTS 3.1 SEMAnalysis: “Fig.
1,” (a) and (f) shows the SEM images along with theparticle size distribution of the synthesized undoped and doped TiO2.SEM imaging of all six samples showedspherical nature of nanoparticles with particle size nearly 11nm to 24nm. Sample1(Undoped), Sample 2(Co doped), Sample3(Cu doped), Sample 4(Fe doped), Sample 4(Fe doped), Sample 5(Ni doped), Sample6(Zn doped) 3.
2UV-Visiblespectra The band gap calculations are done as per procedure 1415. The graphis ploted between (?Ephot)^2versus Ephot for a direct transition which is most suitable for anatseTiO2 paricles, where Ephot is the photon energy, Ephot= (1239/?) eV, ? is the wavelength in nm and ? is theabsorption coefficient . An absorption energy is given by the value of Ephot extrapolated to ? = 0, which corresponds to a bandgap Eg. The bandgaps of all the sixsamples were calculated as tabulated below. Our calculated bandgap values arecompared with values mentioned in the literature.2 The results showed the band gap of Titanium dioxide was narroweddue to metal doping which improves thephoto reactivity of TiO2. Our results matches with the literature i.
e. band gapdecreases due to metal doping.3.3 XRD analysis : JCPDS-84-1286 was referred to compare the peaks of sampleswhich confirmed its anatase structure at 2? = 25.4o.
Also it isnoted that our sample’s diffractograms donot have any peak assigned to rutile phase (2? = 27.36 o). The crystallite size wasdetermined with the help of the Scherrer formula below: G = 0.9? / ?(2?) cos ? where? is the Cu K? radiation wavelength and ?(2?) is peak width athalf-height. The calculated sizes are mentioned below. XRD of all samplesshowed the peaks are occurring at thesame angle that means doping did not cause any effect on anatase nature of TiO2nanoparticles.
eddue to metal doping which improves thephoto reactivity of TiO2. Our results matches with the literature i.e. band gapdecreases due to metal doping.IV CONCLUSIONS: SEM pictures of samples show uniform morphology with spherical particles.
The particle size 11 nm-24 nm which matches with the size calculated using XRD. The prepared TiO2 sample’s absorption spectra exhibited strong absorptions below 370 nm for undoped, Cu doped and Co doped samples, below 380 for Zn doped, below 480 for Fe doped, below 650 for Ni doped. The band gap of 3.4eV of the prepared sample confirmed its nano crystallite size as larger band gap have smaller crystallite size.
Bulk sample of TiO2 has band gap of 3.2 eV. XRD pattern revealed that the prepared titania composed of predominantly anatase phase . The position of peaks was not affected by doping. Band gap decreases due to metal doping in Anatase TiO2 nano particles. ACKNOWLEDGMENT Theauthor is thankful to Mumbai University for funding this project under Minor Research Grant and S.I.
E.S.Graduate School of Technology for supporting this research work.Thanksare due to SAIF, Indian Institute of Technology,Mumbai for helping in characterizing thesamples. REFERENCES 1. AdrianaZaleska: ‘DopedTiO2: A review’, RecentPatents on engineering, Vol.
2(3), 20082. M. Khairy, W.
Zakaria: ‘Effect ofmetal-doping of TiO2 nanoparticles on their photocatalytic activities towardremoval of organic dyes’, Egyptian Journal of Petroleum, Vol. 23(4), 20143. N. Nasralla, M. Yeganeh, Y.
Astuti, S.Piticharoenphun, N. Shahtahmasebi, A.
Kompany, M. Karimipour, B.G. Mendis,N.R.J.Pooltone, L.
Šiller : ‘Structural and spectroscopic study of Fe-dopedTiO2 nanoparticles prepared by sol–gel method’, Sharif University ofTechnology, Vol. 20(3), 20124. Yaqin Wang, Ruirui Zhang, Jianbao Li,Liangliang Li2 and Shiwei Lin: ‘First-principles study on transition metal-dopedanatase TiO2’, Nanoscale Research Letters, Vol. 9(46), 20145.
Konkanok Ubonchonlakat, Lek Sikong andKalayanee Kooptarnond: ‘Effect of Calcinations Temperature on PhotocatalyticActivity of Ag-doped TiO2 Coated on Tile Substrate’, CMU. J.Nat.Sci. Special Issueon Nanotechnology, Vol.
7(1), 20086. R. Jaiswal, N.
Patel, Alpa Dashora, R.Fernandes, M. Yadav, R. Edla, R.S. Varma, D.
C. Kothari, B.L. Ahuja, A.Miotello: ‘Efficient Co-B-codoped TiO2 photocatalyst for degradation of organicwater pollutant under visible light’, Applied Catalysis B: Environmental, Vol.183, 20167. Mukhtar Effendi and Bilalodin: ‘Effect ofDoping Fe on TiO2 Thin Films Prepared bySpin Coating Method’, International Journal of Basic & Applied Sciences,Vol.
12(2), 20128. Thirugnanasambandan Theivasanthi andMarimuthu Alagar: ‘Titanium dioxide (TiO2) Nanoparticles – XRD Analyses – AnInsight’, ArXiv, Vol. 1307.1091, 20139. S. Ramesh: ‘Sol-Gel Synthesisand Characterization of Ag3(2+x)AlxTi4?xO11+? (0.0 ? x ? 1.0) Nanoparticles’,Journal of Nanoscience, Hindawi Publishing Corporation, 2013