Facile method to synthesize magnetic iron oxides/TiO2 hybrid nanoparticles and their photodegradation application of methylene blue
© Wu et al; licensee Springer. 2011
Received: 18 May 2011
Accepted: 30 September 2011
Published: 30 September 2011
Many methods have been reported to improving the photocatalytic efficiency of organic pollutant and their reliable applications. In this work, we propose a facile pathway to prepare three different types of magnetic iron oxides/TiO2 hybrid nanoparticles (NPs) by seed-mediated method. The hybrid NPs are composed of spindle, hollow, and ultrafine iron oxide NPs as seeds and 3-aminopropyltriethyloxysilane as linker between the magnetic cores and TiO2 layers, respectively. The composite structure and the presence of the iron oxide and titania phase have been confirmed by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectra. The hybrid NPs show good magnetic response, which can get together under an external applied magnetic field and hence they should become promising magnetic recovery catalysts (MRCs). Photocatalytic ability examination of the magnetic hybrid NPs was carried out in methylene blue (MB) solutions illuminated under Hg light in a photochemical reactor. About 50% to 60% of MB was decomposed in 90 min in the presence of magnetic hybrid NPs. The synthesized magnetic hybrid NPs display high photocatalytic efficiency and will find recoverable potential applications in cleaning polluted water with the help of magnetic separation.
Extended and oriented nanostructures are desirable for many applications, but facile fabrication of complex nanostructures with controlled crystalline morphology, orientation, and surface architectures remains a significant challenge . Among their various nanostructured materials, magnetic NPs-based hybrid nanomaterials have attracted growing interests due to their unique magnetic properties. These functional composite NPs have been widely used in various fields, such as magnetic fluids, data storage, catalysis, target drug delivery, magnetic resonance imaging contrast agents, hyperthermia, magnetic separation of biomolecules, biosensor, and especially the isolation and recycling of expensive catalysts [2–12]. To this end, magnetic iron oxide NPs became the strong candidates, and the application of small iron oxide NPs has been practiced for nearly semicentury owing to its simple preparation methods and low cost approaches .
Currently, semiconductor NPs have been extensively used as photocatalyst. TiO2 NPs have been used as aphotocatalytic purification of polluted air or wastewater, will become a promising environmental remediation technology because of their high surface area, low cost, nontoxicity, high chemical stability, and excellent degradation for organic pollutants [14–17]. Moreover, TiO2 also bears tremendous hope in helping to ease the energy crisis through effective utilization of solar energy based on photovoltaic and water-splitting devices [18–21]. As comparing with heterogeneous catalysts, many homogenerous catalytic systems have not been commericalized because of one major disadvantage: the difficulty of separation the reaction product from the catalyst and from any reaction solvent for a long and sustained environment protection . In addition, there are two bottleneck drawbacks associated with TiO2 photocatalysis currently, namely, high charge recombination rate inherently and low efficiency for utilizing solar light, which would greatly hinder the commercialization of this technology . Currently, the common methods are metals/non-metals-doping or its oxides-doping to increasing the utilization of visible light and enhancing the separation situation of charge carriers [24–27]. More importantly, the abuse and overuse of photocatalyst will also pollute the enviroment.
Reagents and materials
FeCl3·6H2O, FeCl2·4H2O, FeSO4·7H2O, and KOH were purchased from Tianjin Kermel Chemical Reagent Co., Ltd. (Tianjin, China); KNO3, L(+)-glutamic acid (Gla, C5H9NO4), tetrabutyl titanate (Ti(Bu)4, Bu = OC4H9, CP) and methylene blue were purchased from Sinopharm Chemical Reagent CO., Ltd. (Shanghai, China); cetyltrimethylammmonium bromide (CTAB, C19H42BrN, ultrapure), MB and hexamethylenetetramine (C6H12N4) were purchased from Aladdin Chemical Reagent CO., Ltd. (Shanghai, China); 3-aminopropyltriethyloxysilane (APTES) were purchased from Sigma (St. Louis, MO, USA), and all the reagents are analytical pure and used as received.
Preparation of iron oxide seeds
A. Spindle hematite NPs
According to Ishikava's report , we take a modified method to prepare the monodisperse spindle hematite NPs, in a typical synthesis, 1.8 ml of a 3.7 M FeCl3·6H2O solution was added dropwise into 4.5 × 10-4 M NaH2PO4 solution at 95°C and the mixture was aged at 100°C for 12 h. The resulting precipitates were washed with a 1 M ammonia solution and doubly distilled water and finally dried under vacuum.
B. Hollow magnetite NPs
According to our previous report , in a typical synthesis, solution A was prepared by dissolving 2.02 g KNO3 and 0.28 g KOH in 50 mL double distilled water, solution B was prepared by dissolving 0.070 g FeSO4·7H2O in 50 mL double distilled water. Then the two solution were mixed together under magnetic stirring at a rate of ca. 400 rpm. Two minutes later, solution C (0.18 g Gla in 25 mL double distilled water) was added dropwise into the mixed solution. The reaction temperature was raised increasingly to 90°C and kept 3 h under argon (Ar) atmosphere. Meanwhile, the brown solution was observed to change black. After the mixture was cooled to room temperature, the precipitate products were magnetically separated by MSS, washed with ethanol and water two times, respectively, and then redispersed in ethanol.
C. Ultrafine magnetite NPs
The ultrafine magnetite NPs were prepared through the chemical co-precipitation of Fe(II) and Fe(III) chlorides (FeII/FeIII ratio = 0.5) with 0.5 M NaOH . The black precipitate was collected on a magnet, followed by rinsing with water several times until the pH reached 6 to 7.
Preparation of amino-functionalized iron oxide NPs
A solution of APTES was added into the above seed suspensions, stirred under Ar atmosphere at 25°C for 4 h. The prepared APTES-modified seeds were collected with a magnet, and washed with 50 mL of ethanol, followed by double distilled water for three times .
Preparation of iron oxides/TiO2 hybrid NPs
In a typical synthesis, 0.2 g amino-functionalized seeds, 0.2 g CTAB, and 0.056 g HMTA were dissolved in 25 ml ethanol solution under ultrasonic condition at room temperature. The mixture solution was then transferred into a Teflon-lined tube reactor. Then, 1 ml Ti(Bu)4 dropwise added in the tube, and was kept at 150°C for 8 h.
Photodegradation of MB
The prepared samples were weighed and added into 80 mL of methylene blue solutions (12 mg/L). The mixed solutions were illuminated under mercury lamp (OSRAM, 250 W with characteristic wavelength at 365 nm), and the MB solutions were illuminated under UV light in the photochemical reactor. The solutions were fetched at 10-min intervals by pipette for each solution and centrifuged. Then, the time-dependent absorbance changes of the transparent solution after centrifugation were measured at the wavelength between 500 and 750 nm.
TEM images were performed with a JEOL JEM-2010 (HT) (JEOL, Tokyo, Japan) transmission electron microscope operating at 200 kV, and the samples were dissolved in ethanol and dropped on super-thin cabon coated copper grids. SEM studies were carried out using a FEI Sirion FEG operating at 25 keV, samples were sprinkled onto the conductive substrate, respectively. Powder X-ray diffraction (XRD) patterns of the samples were recorded on a D8 Advance X-ray diffractometer (Germany) using Cu Kα radiation (λ = 0.1542 nm) operating at 40 kV and 40 mA and with a scan rate of 0.05° 2θ s-1. X-ray photoelectron spectroscopy (XPS) measurements were made using a VG Multilab2000X. This system uses a focused Al exciting source for excitation and a spherical section analyzer. The percentages of individual elements detection were determined from the relative composition analysis of the peak areas of the bands. Magnetic measurements were performed using a Quantum Design MPMS XL-7 SQUID magnetometer. The powder sample was filled in a diamagnetic plastic capsule, and then the packed sample was put in a diamagnetic plastic straw and impacted into a minimal volume for magnetic measurements. Background magnetic measurements were checked for the packing material. The diffuse reflectance, absorbance and transmittance spectra, and photodegradation examination of the microspheres was carried out in a PGeneral TU-1901 spectrophotometer.
Results and discussion
Formation mechanism and morphology
Structure and composition
Standard binding energy values
Ti 2p 3/2
Naked Fe3O4 nanoparticles
APTES-coated Fe3O4 nanoparticles
Hybrid nanoparticles (FT-3)
Surface elemental composition and XPS binding energies of FT-1, FT-2, and FT-3
Chemical composition (%); in parentheses, binding energy (eV)
Ti 2 p
Fe 2 p
O 1 s
N 1 s
Si 2 p
Magnetic and magnetic response properties
Optical adsorption and photocatalytic properties
In order to calculate the bandgap of hybrid NPs, the relationship between the absorption coefficient (α) and the photon energy (hν) have been given by equation as follows: α hv = A(hv-E E ) m , where A is a constant, E g is the bandgap energy, hν is the incident photon energy and the exponent m depends on the nature of optical transition. The value of m is 1/2 for direct allowed, 2 for indirect allowed, 3/2 for direct forbidden, and 3 for indirect forbidden transitions . The main mechanism of light absorption in pure semiconductors is direct interband electron transitions. The absorption coefficient α has been calculated from the Lamberts formula , , where T and t are the transmittance (can be directly measured by UV-vis spectra) and path length of the colloids solution (same concentration), respectively. A typical plot of (α hν)2 versus photon energy (hν) for the samples are shown in Figure 9b. The value of FT-1, FT-2, and FT-3 is 2.85, 2.89, and 2.73 eV, respectively.TiO2 is important for its application in energy transport, storage, and for the environmental cleanup due to its well known photocatalytic effect with a bandgap of 3.2 eV . Comparing with the pure TiO2 NPs, the bandgap of hybrid NPs is obviously decreased, and the absorption edge generates obvious red shift. This red shift is attributed to the charge-transfer transition between the electrons of the iron oxide NPs and the conduction band (or valence band) of TiO2. Iron oxide NPs can increase energy spacing of the conduction band in TiO2 and finally lead to the quantization of energy levels and causes the absorption in the visible region. The other is that amino groups can act as a substitutional dopant for the place of titanium and change metal coordination of TiO2 and the electronic environment around them . Similar phenomenon of red shift in the bandgap for iron oxide/TiO2 hybrid NPs were also found by other reports [53, 65–67].
In summary, MRCs have been fabricated via a facile seed-mediate technology. These iron oxide/TiO2 hybrid NPs were synthesized in a stepwise process. First, three different shapes of naked iron oxide NPs were prepared. Next, amino groups encapsulated iron oxide NPs are synthesized by APTES modification. Finally, the iron oxide/TiO2 hybrid NPs can be obtained after the TiO2 coating. The FT-2 and FT-3 hybrid NPs show superparamagnetic and both display good photocatalytic properties. This MRCs combination of the photocatalysis properties of TiO2 and the superparamagnetic property of Fe3O4 NPs endows this material with a bright perspective in purification of polluted wastewater. Additionally, this work also discusses the formation mechanism and potentially provided a general method for synthesizing nanocomposites of magnetic iron oxide NPs and other functional NPs, which may find wider applications besides in photocatalysis.
The authors thank the National Basic Research Program of China (973 Program, no. 2009CB939704), the National Nature Science Foundation of China (nos. 91026014, 10905043, 11005082), the Fundamental Research Funds for the Central Universities and the PhD candidates self-research (including 1 + 4) program of Wuhan University in 2008 (no. 20082020201000008) for financial support. W. Wu thanks L. Lin, L. Zeng, Z. H. Wu, and Prof. Q. G. He of HUT for assistance with the photodegradation measurements.
- Tian ZRR, Voigt JA, Liu J, McKenzie B, McDermott MJ, Rodriguez MA, Konishi H, Xu HF: Complex and oriented ZnO nanostructures. Nat Mater 2003, 2: 821–826. 10.1038/nmat1014View ArticleGoogle Scholar
- Dobson J: Magnetic nanoparticles for drug delivery. Drug Dev Res 2006, 67: 55–60. 10.1002/ddr.20067View ArticleGoogle Scholar
- Wu W, He QG, Jiang CZ: Magnetic iron oxide nanoparticles: synthesis and surface functionalization strategies. Nanoscale Res Lett 2008, 3: 397–415. 10.1007/s11671-008-9174-9View ArticleGoogle Scholar
- Shokouhimehr M, Piao YZ, Kim J, Jang YJ, Hyeon T: A magnetically recyclable nanocomposite catalyst for olefin epoxidation. Angew Chem Int Ed 2007, 46: 7039–7043. 10.1002/anie.200702386View ArticleGoogle Scholar
- Babes L, Denizot B, Tanguy G, Le Jeune JJ, Jallet P: Synthesis of iron oxide nanoparticles used as MRI contrast agents: a parametric study. J Colloid Interface Sci 1999, 212: 474–482. 10.1006/jcis.1998.6053View ArticleGoogle Scholar
- Yao Y, Huang J, Yang J, McIntyre T, Chen J: Multimodality based diagnosis and treatment of breast cancer cells by magnetic nanoparticles coated by a gold shell with hyperthermia and radiation therapy. Radiother Oncol 2007, 84: S78-S78.Google Scholar
- Qian ZY, Men K, Zeng S, Gou ML, Guo G, Gu YC, Luo F, Zhao X, Wei YQ: Preparation of magnetic microspheres based on Poly(epsilon-caprolactone)-Poly(ethylene glycol)-Poly(epsilon-caprolactone) copolymers by modified solvent diffusion method. J Biomed Nanotechnol 2010, 6: 287–292. 10.1166/jbn.2010.1125View ArticleGoogle Scholar
- Arkhis A, Elaissari A, Delair T, Verrier B, Mandrand B: Capture of enveloped viruses using polymer tentacles containing magnetic latex particles. J Biomed Nanotechnol 2010, 6: 28–36. 10.1166/jbn.2010.1093View ArticleGoogle Scholar
- He NY, Liu HN, Li S, Tian L, Liu LS: A novel single nucleotide polymorphisms detection sensors based on magnetic nanoparticles array and dual-color single base extension. J Nanosci Nanotechnol 2010, 10: 5311–5315. 10.1166/jnn.2010.2386View ArticleGoogle Scholar
- Li ZY, He L, He NY, Shi ZY, Wang H, Li S, Liu HN, Dai YB: An applied approach in detecting E. coli O157:H7 using immunological method based on chemiluminescence and magnetic nanoparticles. Acta Chim Sinica 2010, 68: 251–256.Google Scholar
- He NY, Li ZY, He L, Shi ZY, Wang H, Li S, Liu HN, Wang ZF: Preparation of SiO 2 /polymethyl methacrylate/Fe 3 O 4 nanoparticles and its application in detecting E. coli O157:H7 using chemiluminescent immunological method. J Biomed Nanotechnol 2009, 5: 505–510. 10.1166/jbn.2009.1070View ArticleGoogle Scholar
- He NY, Tian L, Li S, Liu HN, Wang ZF: An automated MagStation for high-throughput single nucleotide polymorphism genotyping and the dual-color hybridization. J Biomed Nanotechnol 2009, 5: 511–515. 10.1166/jbn.2009.1066View ArticleGoogle Scholar
- Gupta AK, Gupta M: Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications. Biomaterials 2005, 26: 3995–4021. 10.1016/j.biomaterials.2004.10.012View ArticleGoogle Scholar
- Janus M, Tryba B, Kusiak E, Tsumura T, Toyoda M, Inagaki M, Morawski A: TiO 2 nanoparticles with high photocatalytic activity under visible light. Catal Lett 2009, 128: 36–39. 10.1007/s10562-008-9721-0View ArticleGoogle Scholar
- Hou YD, Wang XC, Wu L, Chen XF, Ding ZX, Wang XX, Fu XZ: N-doped SiO 2 /TiO 2 mesoporous nanoparticles with enhanced photocatalytic activity under visible-light irradiation. Chemosphere 2008, 72: 414–421. 10.1016/j.chemosphere.2008.02.035View ArticleGoogle Scholar
- Wu ZB, Gu ZL, Zhao WR, Wang HQ: Photocatalytic oxidation of gaseous benzene over nanosized TiO 2 prepared by solvothermal method. Chin Sci Bull 2007, 52: 3061–3067. 10.1007/s11434-007-0456-xView ArticleGoogle Scholar
- Wang WJ, Zhang JL, Chen F, He DN, Anpo M: Preparation and photocatalytic properties of Fe 3+ -doped Ag@TiO 2 core-shell nanoparticles. J Colloid Interface Sci 2008, 323: 182–186. 10.1016/j.jcis.2008.03.043View ArticleGoogle Scholar
- Kwak ES, Lee W, Park NG, Kim J, Lee H: Compact inverse-opal electrode using non-aggregated TiO 2 nanoparticles for dye-sensitized solar cells. Adv Funct Mater 2009, 19: 1093–1099. 10.1002/adfm.200801540View ArticleGoogle Scholar
- Liu B, Aydil ES: Growth of oriented single-crystalline rutile TiO 2 nanorods on transparent conducting substrates for dye-sensitized solar sells. J Am Chem Soc 2009, 131: 3985–3990. 10.1021/ja8078972View ArticleGoogle Scholar
- Zhao D, Peng TY, Lu LL, Cai P, Jiang P, Bian ZQ: Effect of annealing temperature on the photoelectrochemical properties of dye-sensitized solar cells made with mesoporous TiO 2 nanoparticles. J Phys Chem C 2008, 112: 8486–8494. 10.1021/jp800127xView ArticleGoogle Scholar
- Baek IC, Vithal M, Chang JA, Yum JH, Nazeeruddin MK, Gratzel M, Chung YC, Seok SI: Facile preparation of large aspect ratio ellipsoidal anatase TiO 2 nanoparticles and their application to dye-sensitized solar cell. Electrochem Commun 2009, 11: 909–912. 10.1016/j.elecom.2009.02.026View ArticleGoogle Scholar
- Cole-Hamilton DJ: Homogeneous catalysis-new approaches to catalyst separation, recovery, and recycling. Science 2003, 299: 1702–1706. 10.1126/science.1081881View ArticleGoogle Scholar
- Wang J, Jing LQ, Xue LP, Qu YC, Fu HG: Enhanced activity of bismuth-compounded TiO 2 nanoparticles for photocatalytically degrading rhodamine B solution. J Hazard Mater 2008, 160: 208–212. 10.1016/j.jhazmat.2008.02.103View ArticleGoogle Scholar
- Lopez T, Recillas S, Guevara P, Sotelo J, Alvarez M, Odriozola JA: Pt/TiO 2 brain biocompatible nanoparticles: GBM treatment using the C6 model in Wistar rats. Acta Biomater 2008, 4: 2037–2044. 10.1016/j.actbio.2008.05.027View ArticleGoogle Scholar
- Lv KL, Zuo HS, Sun J, Deng KJ, Liu SC, Li XF, Wang DY: (Bi, C and N) codoped TiO 2 nanoparticles. J Hazard Mater 2009, 161: 396–401. 10.1016/j.jhazmat.2008.03.111View ArticleGoogle Scholar
- Xu JJ, Ao YH, Fu D, Yuan CW: Synthesis of Gd-doped TiO 2 nanoparticles under mild condition and their photocatalytic activity. Colloid Surf A 2009, 334: 107–111. 10.1016/j.colsurfa.2008.10.017View ArticleGoogle Scholar
- Yue L, Zhang XM: Preparation of highly dispersed CeO 2 /TiO 2 core-shell nanoparticles. Mater Lett 2008, 62: 3764–3766. 10.1016/j.matlet.2008.04.059View ArticleGoogle Scholar
- Li Y, Wu JS, Qi DW, Xu XQ, Deng CH, Yang PY, Zhang XM: Novel approach for the synthesis of Fe 3 O 4 @TiO 2 core-shell microspheres and their application to the highly specific capture of phosphopeptides for MALDI-TOF MS analysis. Chem Commun 2008, (5):564–566.Google Scholar
- Mou F, Guan J, Xiao Z, Sun Z, Shi W, Fan XA: Solvent-mediated synthesis of magnetic Fe 2 O 3 chestnut-like amorphous-core/γ-phase-shell hierarchical nanostructures with strong As(v) removal capability. J Mater Chem 2011, 21: 5414–5421. 10.1039/c0jm03726eView ArticleGoogle Scholar
- Guan JG, Mou FZ, Sun ZG, Shi WD: Preparation of hollow spheres with controllable interior structures by heterogeneous contraction. Chem Commun 2010, 46: 6605–6607. 10.1039/c0cc01044hView ArticleGoogle Scholar
- Guan JG, Tong GX, Xiao ZD, Huang X, Guan Y: In situ generated gas bubble-assisted modulation of the morphologies, photocatalytic, and magnetic properties of ferric oxide nanostructures synthesized by thermal decomposition of iron nitrate. J Nanopart Res 2010, 12: 3025–3037. 10.1007/s11051-010-9897-2View ArticleGoogle Scholar
- Tong G, Guan J, Zhang Q: Goethite hierarchical nanostructures: Glucose-assisted synthesis, chemical conversion into hematite with excellent photocatalytic properties. Mater Chem Phys 2011, 127: 371–378. 10.1016/j.matchemphys.2011.02.021View ArticleGoogle Scholar
- Chen CT, Chen YC: Fe 3 O 4 /TiO 2 core/shell nanoparticles as affinity probes for the analysis of phosphopeptides using TiO 2 surface-assisted laser desorption/ionization mass spectrometry. Anal Chem 2005, 77: 5912–5919. 10.1021/ac050831tView ArticleGoogle Scholar
- Chen WJ, Tsai PJ, Chen YC: Functional Fe 3 O 4 /TiO 2 core/shell magnetic nanoparticles as photokilling agents for pathogenic bacteria. Small 2008, 4: 485–491. 10.1002/smll.200701164View ArticleGoogle Scholar
- Wang CX, Yin LW, Zhang LY, Kang L, Wang XF, Gao R: Magnetic (γ-Fe 2 O 3 @SiO 2 ) n @TiO 2 functional hybrid nanoparticles with actived photocatalytic ability. J Phys Chem C 2009, 113: 4008–4011. 10.1021/jp809835aView ArticleGoogle Scholar
- Yoon TJ, Lee W, Oh YS, Lee JK: Magnetic nanoparticles as a catalyst vehicle for simple and easy recycling. New J Chem 2003, 27: 227–229. 10.1039/b209391jView ArticleGoogle Scholar
- Ishikawa T, Matijevic E: Formation of monodispersed pure and coated spindle-type iron particles. Langmuir 1988, 4: 26–31. 10.1021/la00079a004View ArticleGoogle Scholar
- Wu W, Xiao XH, Zhang SF, Li H, Zhou XD, Jiang CZ: One-pot reaction and subsequent annealing to synthesis hollow spherical magnetite and maghemite nanocages. Nanoscale Res Lett 2009, 4: 926–931. 10.1007/s11671-009-9342-6View ArticleGoogle Scholar
- Massart R: Preparation of aqueous magnetic liquids in alkaline and acidic media. IEEE Trans Magn 1981, 17: 1247–1248. 10.1109/TMAG.1981.1061188View ArticleGoogle Scholar
- Wu W, He Q, Chen H: Silane bridged surface tailoring on magnetite nanoparticles. Bioinformatics and Biomedical Engineering 2007.Google Scholar
- Wu W, He QG, Chen H, Tang JX, Nie LB: Sonochemical synthesis, structure and magnetic properties of air-stable Fe 3 O 4 /Au nanoparticles. Nanotechnology 2007, 18: 145609. 10.1088/0957-4484/18/14/145609View ArticleGoogle Scholar
- Pearson RG: Hard and soft acids and bases. J Am Chem Soc 1963, 85: 3533–3539. 10.1021/ja00905a001View ArticleGoogle Scholar
- Gillet JN, Meunier M: General equation for size nanocharacterization of the core-shell nanoparticles by X-ray photoelectron spectroscopy. J Phys Chem B 2005, 109: 8733–8737. 10.1021/jp044322rView ArticleGoogle Scholar
- Liu SY, Ma YH, Armes SP: Direct verification of the core-shell structure of shell cross-linked micelles in the solid state using X-ray photoelectron spectroscopy. Langmuir 2002, 18: 7780–7784. 10.1021/la020517jView ArticleGoogle Scholar
- Lu LH, Sun GY, Zhang HJ, Wang HS, Xi SQ, Hu JQ, Tian ZQ, Chen R: Fabrication of core-shell Au-Pt nanoparticle film and its potential application as catalysis and SERS substrate. J Mater Chem 2004, 14: 1005–1009. 10.1039/b314868hView ArticleGoogle Scholar
- Remita H, Etcheberry A, Belloni J: Dose rate effect on bimetallic gold-palladium cluster structure. J Phys Chem B 2003, 107: 31–36. 10.1021/jp021277jView ArticleGoogle Scholar
- Toshima N, Yonezawa T, Kushihashi K: Polymer-protected palladium-platinum bimetallic clusters: preparation, catalytic properties and structural considerations. J Chem Soc, Faraday Trans 1993, 89: 2537–2543. 10.1039/ft9938902537View ArticleGoogle Scholar
- Wagner CD, Riggs WW, Davis LE, Moulder JF, Muilenberg GE: Handbook of X-ray Photoelectron Spectroscopy. Eden Prairie: Perkin-Elmer Corporation, Physical Electronics Division; 1979.Google Scholar
- Tung WS, Daoud WA: New approach toward nanosized ferrous ferric oxide and Fe 3 O 4 -doped titanium dioxide photocatalysts. ACS Appl Mater Interfaces 2009, 1: 2453–2461. 10.1021/am900418qView ArticleGoogle Scholar
- Singh H, Laibinis PE, Hatton TA: Rigid, superparamagnetic chains of permanently linked beads coated with magnetic nanoparticles. Synthesis and rotational dynamics under applied magnetic fields. Langmuir 2005, 21: 11500–11509. 10.1021/la0517843View ArticleGoogle Scholar
- Selvan RK, Augustin CO, Sanjeeviraja C, Prabhakaran D: Effect of SnO 2 coating on the magnetic properties of nanocrystalline CuFe 2 O 4 . Solid State Commun 2006, 137: 512–516. 10.1016/j.ssc.2005.12.018View ArticleGoogle Scholar
- Xuan SH, Jiang WQ, Gong XL, Hu Y, Chen ZY: Magnetically separable Fe 3 O 4 /TiO 2 hollow spheres: Fabrication and photocatalytic activity. J Phys Chem C 2009, 113: 553–558. 10.1021/jp8073859View ArticleGoogle Scholar
- He QH, Zhang ZX, Xiong JW, Xiong YY, Xiao H: A novel biomaterial - Fe 3 O 4 :TiO 2 core-shell nanoparticle with magnetic performance and high visible-light photocatalytic activity. Opt Mater 2008, 31: 380–384. 10.1016/j.optmat.2008.05.011View ArticleGoogle Scholar
- Bodker F, Hansen MF, Koch CB, Lefmann K, Morup S: Magnetic properties of hematite nanoparticles. Phys Rev B 2000, 61: 6826–6838. 10.1103/PhysRevB.61.6826View ArticleGoogle Scholar
- Mansilla MV, Zysler R, Fiorani D, Suber L: Annealing effects on magnetic properties of acicular hematite nanoparticles. Physica B-Condensed Matter 2002, 320: 206–209. 10.1016/S0921-4526(02)00683-XView ArticleGoogle Scholar
- Tadic M, Kusigerski V, Markovic D, Milosevic I, Spasojevic V: High concentration of hematite nanoparticles in a silica matrix: structural and magnetic properties. J Magn Magn Mater 2009, 321: 12–16. 10.1016/j.jmmm.2008.07.006View ArticleGoogle Scholar
- More AM, Gujar TP, Gunjakar JL, Lokhande CD, Joo OS: Growth of TiO 2 nanorods by chemical bath deposition method. Appl Surf Sci 2008, 255: 2682–2687. 10.1016/j.apsusc.2008.08.003View ArticleGoogle Scholar
- Park JT, Koh JH, Koh JK, Kim JH: Surface-initiated atom transfer radical polymerization from TiO 2 nanoparticles. Appl Surf Sci 2009, 255: 3739–3744. 10.1016/j.apsusc.2008.10.027View ArticleGoogle Scholar
- Segets D, Gradl J, Taylor RK, Vassilev V, Peukert W: Analysis of optical absorbance spectra for the determination of ZnO nanoparticle size distribution, solubility, and surface energy. Acs Nano 2009, 3: 1703–1710. 10.1021/nn900223bView ArticleGoogle Scholar
- Sciancalepore C, Cassano T, Curri ML, Mecerreyes D, Valentini A, Agostiano A, Tommasi R, Striccoli M: TiO 2 nanorods/PMMA copolymer-based nanocomposites: highly homogeneous linear and nonlinear optical material. Nanotechnology 2008, 19: 205705. 10.1088/0957-4484/19/20/205705View ArticleGoogle Scholar
- Pankove JI: Optical Processes in Semiconductors. Mineola, New York: Courier Dover Publications; 1975.Google Scholar
- Wu W, Xiao XH, Peng TC, Jiang CZ: Controllable Ssynthesis and optical properties of connected zinc oxide nanoparticles. Chem-Asian J 2010, 5: 315–321. 10.1002/asia.200900378View ArticleGoogle Scholar
- Fujishima A, Honda K: Electrochemical photolysis of water at a semiconductor electrode. Nature 1972, 238: 37–38. 10.1038/238037a0View ArticleGoogle Scholar
- Chen X, Mao SS: Titanium dioxide nanomaterials: Synthesis, properties, modifications, and applications. Chem Rev 2007, 107: 2891–2959. 10.1021/cr0500535View ArticleGoogle Scholar
- Song HM, Ko JM, Park JH: Hybrid photoreactive magnet obtained from Fe 3 O 4 /TiO 2 composite nanoparticles. Chem Lett 2009, 38: 612–613. 10.1246/cl.2009.612View ArticleGoogle Scholar
- Sato T, Yamamoto Y, Fujishiro Y, Uchida S: Intercalation of iron oxide in layered H 2 Ti 4 O 9 and H 4 Nb 6 O 17 : visible-light induced photocatalytic properties. J Chem Soc, Faraday Trans 1996, 92: 5089–5092. 10.1039/ft9969205089View ArticleGoogle Scholar
- Kang M, Choung SJ, Park JY: Photocatalytic performance of nanometer-sized Fe x O y /TiO 2 particle synthesized by hydrothermal method. Catal Today 2003, 87: 87–97. 10.1016/j.cattod.2003.09.011View ArticleGoogle Scholar
- Thongsuwan W, Kumpika T, Singjai P: Photocatalytic property of colloidal TiO 2 nanoparticles prepared by sparking process. Curr Appl Phys 2008, 8: 563–568. 10.1016/j.cap.2007.10.004View ArticleGoogle Scholar
- Wu BC, Yuan RS, Fu XZ: Structural characterization and photocatalytic activity of hollow binary ZrO 2 /TiO 2 oxide fibers. J Solid State Chem 2009, 182: 560–565. 10.1016/j.jssc.2008.11.030View ArticleGoogle Scholar
- Xiao Q, Si Z, Zhang J, Xiao C, Zhiming Y, Qiu G: Effects of samarium dopant on photocatalytic activity of TiO 2 nanocrystallite for methylene blue degradation. J Mater Sci 2007, 42: 9194–9199. 10.1007/s10853-007-1919-9View ArticleGoogle Scholar
- Wu W, Xiao X, Zhang S, Zhou J, Ren F, Jiang C: Controllable synthesis of TiO 2 submicrospheres with smooth or rough surface. Chem Lett 2010, 39: 684–685. 10.1246/cl.2010.684View ArticleGoogle Scholar
- Hoffmann MR, Martin ST, Choi W, Bahnemann DW: Environmental applications of semiconductor photocatalysis. Chem Rev 1995, 95: 69–96. 10.1021/cr00033a004View ArticleGoogle Scholar
- Zhang XW, Du AJ, Lee PF, Sun DD, Leckie JO: TiO 2 nanowire membrane for concurrent filtration and photocatalytic oxidation of humic acid in water. J Membr Sci 2008, 313: 44–51. 10.1016/j.memsci.2007.12.045View ArticleGoogle Scholar
- Zhang XW, Pan JH, Du AJ, Xu SP, Sun DD: Room-temperature fabrication of anatase TiO 2 submicrospheres with nanothornlike shell for photocatalytic degradation of methylene blue. J Photochem Photobio A 2009, 204: 154–160. 10.1016/j.jphotochem.2009.03.011View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.