In the present work, electrospray ionization mass spectrometry (ESI-MS) was used to investigate the titanium clusters present during nucleation and growth of sol–gel derived TiO2 nanoparticles. Depending on the alkoxide precursor used, Ti clusters of different sizes were identified [titanium isopropoxide (TTIP) ∼ 11–12 Ti atoms, titanium butoxide (TTB) ∼ 10–11 Ti atoms and titanium tetraethoxide (TTE) ∼ 5–7 Ti atoms]. The Ti–O–Ti backbone/core of the titanium clusters were found to be quite stable after formation and do not easily break up into smaller clusters. The results of this investigation suggest that these clusters are used as building blocks in the growth during the induction period. The h-ratio (nH2O/nalcoxide) and the pH were not found to influence the identity of the Ti clusters present during nucleation of the growth of sol–gel derived TiO2 nano-particles, although the induction period was greatly influenced. The reactivity of the alkoxy group are OEt > OPri > OBu. The difference in reactivity of the alkoxides is generally believed to be due to the increasing size of the alkoxy group which causes sterical hindrance during the nucleophilic substitution reaction.
SimonsenM.E.SøgaardE.G., “Sol-gel reactions of titanium alkoxides and water: Influence of pH and alkoxy group on cluster formation and properties of the resulting products”, J. Sol Gel Sci. Technol.53, 485 (2010). doi: 10.1007/s10971-009-2121-0
2.
CristoniS.ArmelaoL.GrossS.TondelloE.TraldiP., “Electrospray ionization in the study of sol-gel processes: The polycondensation of Ti(O-n-Bu)4 in the presence of Si(OEt)4”, Rapid Commun. Mass Spectrom.15, 386–392 (2001). doi: 10.1002/rcm.240
3.
SeragliaR.ArmelaoL.CristoniS.GrossS.TondelloE.TraldiP., “Matrix-assisted laser desorption/ionisation mass spectrometry in the study of polycondensation of Ti(OBun)4 in the presence of Si(OEt)4”, Rapid Commun. Mass. Spectrom.17, 2649 (2003). doi: 10.1002/rcm.1231
4.
BussianP.SobottF.BrutschyB.SchraderW.SchuthF., “Speciation in solution: Silicate oligomers in aqueous solutions detected by mass spectrometry, Angew. Chem. Int. Ed.39(21), 3901 (2000). doi: 10.1002/1521-3773(20001103)39:21<3901::AID-ANIE3901>3.0.CO;2-D
5.
BlanchardJ., PhD thesis, Universite Pierre et Marie Curie, Paris, France (1997).
6.
SolovievA.TufeuR.SanchezC.KanaevA.V., “Nucleation stage in the Ti(OPri)4 sol–gel process”, J. Phys. Chem. B105(19), 4175 (2001). doi: 10.1021/jp0040190
7.
SolovievA.SogaardE.G., “Application of electrospray ionization mass spectrometry for characterization of titanium polyoxoalkoxides in sol–gel processes”, J. Mater. Sci.41(18), 6159 (2006). doi: 10.1007/s10853-006-0160-2
8.
RozesL.SteunouN.FornasieriG.SanchezC., “Titanium-oxo clusters, versatile nanobuilding blocks for the design of advanced hybrid materials”, Monatsh. Chem.137(5), 501 (2006). doi: 10.1007/s00706-006-0464-6
9.
BlanchardJ.RibotF.SanchezC.BellotP.V.TrokinerA., “Structural characterization of titanium-oxo-polymers synthesized in the presence of protons or complexing ligands as inhibitors”, J. Non Cryst. Solids265(1–2), 83 (2000). doi: 10.1016/S0022-3093(99)00885-6
10.
BlanchardJ.BarbouxdoeuffS.MaquetJ.SanchezC., “Investigation on hydrolysis-condensation reactions of titanium(iv) butoxide”, New J. Chem.19, 929 (1995).
11.
BlanchardJ.InM.SchaudelB.SanchezC., “Hydrolysis and condensation reactions of transition metal alkoxides: Calorimetric study and evaluation of the extent of reaction”, Eur. J. Inorg. Chem.1998(8), 1115 (1998).
12.
SolovievA.IvanovD.TufeuR.KanaevA.V., “Nanoparticle growth during the induction period of the sol–gel process”, J. Mater. Sci. Lett.20(10), 905 (2001). doi: 10.1023/A:1010972615248
13.
CampostriniR.CarturanG.SorarùG.TraldiP., “Hydrolysis and polycondensation of Si(OEt)4 II. Identification of chemical species in condensed phase by mass spectrometry with fast atom bombardment”, J. Non Cryst. Solids108(3), 315 (1989). doi: 10.1016/0022-3093(89)90303-7
14.
CampostriniR.CarturanG.PelliB.TraldiP., “Hydrolysis and polycondensation of Si(OEt)4: A mass spectrometry approach to the definition of reaction intermediates in the presence of acid or basic catalysts. Part 1”, J. Non Cryst. Solids108(2), 143 (1989). doi: 10.1016/0022-3093(89)90576-0
15.
CristoniS.ArmelaoL.TondelloE.TraldiP., “Electrospray ionization in the study of polycondensation of Si(OEt)4”, J. Mass Spectrom.34(12), 1380 (1999). doi: 10.1002/(SICI)1096-9888(199912)34:12
16.
EggersK.EichnerT.WoenckhausJ., “Mass spectrometric investigation of small silicate polyhedra in solution”, Int. J. Mass Spectrom.244(1), 72 (2005). doi: 10.1016/j.ijms.2005.05.001
17.
SchüthF.BussianP.ÅgrenP.SchunkS.LindénM., “Techniques for analyzing the early stages of crystallization reactions”, Solid State Sci.3(7), 801 (2001). doi: 10.1016/S1293-2558(01)01199-2
18.
SimonsenM.E.SøgaardE.G., “ESI-MS investigation of the polymerization of inorganic polymers”, Int. J. Mass Spectrom.285(1–2), 78–85 (2009). doi: 10.1016/j.ijms.2009.04.010
19.
CristoniS.ArmelaoL.GrossS.TondelloE.TraldiP., “Electrospray ionization in the study of the polycondensation of Ti(O-i-C3H7)4 and Ti(O-n-C4H9)4”, Rapid Commun. Mass Spectrom.14(8), 662 (2000). doi: 10.1002/(SICI)1097-0231(20000430)14:8<662::AID-RCM931>3.0.CO;2-V
20.
GuanB.LuW.FangJ.ColeR.B., “Characterization of synthesized titanium oxide nanoclusters by MALDI-ToF mass spectrometry”, J. Am. Soc. Mass Spectrom.18(3), 517 (2007). doi: 10.1016/j.jasms.2006.10.021
SolovievA.JensenH.SogaardE.G.KanaevA.V., “Aggregation kinetics of sol–gel process based on titanium tetraisopropoxide”, J. Mater. Sci.38(15), 3315 (2003). doi: 10.1023/A:1025198323886
23.
BrinkerC.J.SchererG.W., Sol-Gel Science, the Physics and Chemistry of Sol-Gel Processing. Academic Press, San Diego, California, USA (1990).
24.
KallalaM.SanchezC.CabaneB., “SAXS study of gelation and precipitation in titanium-based systems”, J. Non Cryst. Solids147-148, 189 (1992). doi: 10.1016/S0022-3093(05)80616-7
25.
MarchisioD.L.OmegnaF.BarresiA.A.BowenP., “Effect of mixing and other operating parameters in sol-gel processes”, Ind. Eng. Chem. Res.47(19), 7202 (2008). doi: 10.1021/ie800217b
