Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate
Summary
The surfactant mediated sol-gel synthesis of nanosized monosodium titanate is described, along with preparation of the corresponding peroxide modified material. An ion-exchange reaction with Au(III) is also presented.
Abstract
This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the material with Au(III) ions. The synthesis method was derived from a sol-gel process used to produce micron-sized monosodium titanate (MST), with several key modifications, including altering reagent concentrations, omitting a particle seed step, and introducing a non-ionic surfactant to facilitate control of particle formation and growth. The resultant nMST material exhibits spherical-shaped particle morphology with a monodisperse distribution of particle diameters in the range from 100 to 150 nm. The nMST material was found to have a Brunauer-Emmett-Teller (BET) surface area of 285 m2g-1, which is more than an order of magnitude higher than the micron-sized MST. The isoelectric point of the nMST measured 3.34 pH units, which is a pH unit lower than that measured for the micron-size MST. The nMST material was found to serve as an effective ion exchanger under weakly acidic conditions for the preparation of an Au(III)-exchange nanotitanate. In addition, the formation of the corresponding peroxotitanate was demonstrated by reaction of the nMST with hydrogen peroxide.
Introduction
Titanium dioxide and alkali metal titanates are widely used in a variety of applications such as pigments in paint and skin care products and as photocatalysts in energy conversion and utilization.1-3 Sodium titanates have been shown to be effective materials to remove a range of cations over a wide range of pH conditions through cation exchange reactions.4-7
In addition to the applications just described, micron-sized sodium titanates and sodium peroxotitanates have recently been shown to also serve as a therapeutic metal delivery platform. In this application, therapeutic metal ions such as Au(III), Au(I), and Pt(II) are exchanged for the sodium ions of monosodium titanate (MST). In vitro tests with the noble metal-exchanged titanates indicate suppression of the growth of cancer and bacterial cells by an unknown mechanism.8,9
Historically, sodium titanates have been produced using both sol-gel and hydrothermal synthetic techniques resulting in fine powders with particle sizes ranging from a few to several hundred microns.4,5,10,11 More recently, synthetic methods have been reported that produced nanosize titanium dioxide, metal-doped titanium oxides, and a variety of other metal titanates. Examples include sodium titanium oxide nanotubes (NaTONT) or nanowires by reaction of titanium dioxide in excess sodium hydroxide at elevated temperature and pressure,12-14 sodium titanate nanofibers by reaction of peroxotitanic acid with excess sodium hydroxide at elevated temperature and pressure,15 and sodium and cesium titanate nanofibers by delamination of acid-exchanged micron-sized titanates.16
The synthesis of nanosize sodium titanates and sodium peroxotitanates is of interest to enhance ion exchange kinetics, which are typically controlled by film diffusion or intraparticle diffusion. These mechanisms are largely controlled by the particle size of the ion exchanger. In addition, as a therapeutic metal delivery platform, the particle size of the titanate material would be expected to significantly affect the nature of the interaction between the metal-exchanged titanate and the cancer and bacterial cells. For example, bacterial cells, which are typically on the order of 0.5 – 2 µm, would likely have different interactions with micron size particles versus nanosized particles. In addition, non-phagocytic eukaryotic cells have been shown to only internalize particles with a size of less than 1 micron.17 Thus, the synthesis of nanosize sodium titanates is also of interest to facilitate metal delivery and cellular uptake from the titanate delivery platform. Reducing the size of sodium titanates and peroxotitanates will also increase the effective capacity in metal ion separations and enhance photochemical properties of the material.16,18 This paper describes a protocol developed to synthesize nanosize monosodium titanate (nMST) under mild sol-gel conditions.19 The preparation of the corresponding peroxide modified nMST; along with an ion-exchange reaction to load the nMST with Au(III) are also described.
Protocol
Representative Results
Discussion
The presence of extraneous water, for example from impure reagents, can alter the outcome of the reaction, leading to larger or more polydisperse particles. Therefore, care should be taken to ensure dry reactants are used. The titanium isopropoxide and sodium methoxide should be stored in a desiccator when not in use. High purity isopropanol should also be used for the synthesis.
Temperature was found to play a key role in the conversion of the product from a gel to particulate form. TEM image…
Disclosures
The authors have nothing to disclose.
Acknowledgements
The authors thank the Laboratory Directed Research and Development program at the Savannah River National Laboratory (SRNL) for funding. We thank Dr. Fernando Fondeur for collection and interpretation of the FT-IR spectra and Dr. John Seaman of the Savannah River Ecology Laboratory for the use of the DLS instrument for particle size measurements. We also thank the Dr. Daniel Chan of the University of Washington and the National Institute of Health (Grant #1R01DE021373-01), for funding experiments investigating the ion exchange reactions with Au(III). The Savannah River National Laboratory is operated by Savannah River Nuclear Solutions, LLC for the Department of Energy under contract DE-AC09-08SR22470.
Materials
| Titanium(IV) isopropoxide | Sigma Aldrich | 377996 | 99.999% trace metals basis |
| Isopropyl alcholol, 99.9% | Sigma Aldrich | 650447 | HPLC grade (Chomasolv) |
| Sodium methoxide in methanol | Sigma Aldrich | 156256 | 25 wt% |
| Triton X-100 | Sigma Aldrich | T9284 | BioXtra |
| hydrogen tetrachloroaurate(III) trihydrate | Sigma Aldrich | G4022 | ACS reagent grade |
| hydrogen peroxide (30 wt%) | Fisher | H325 | Certified ACS |
| 10-mL syringes | Fisher | 14-823-16E | |
| Dual channel syringe pump | Cole Parmer | EW-74900-10 | Or equivalent programmable dual channel syringe pump |
| Tygon tubing 1/8 inch ID, 1/4 inch OD | Cole Parmer | EW-0640776 | |
| Tygon tubing 1/16 inch ID, 1/8 inch OD | Cole Parmer | EW-0740771 | |
| 0.1-µm Nylon filter | Fisher | R01SP04700 | |
| Labquake shaker rotisserie | Thermo Scientific | 4002110Q |
References
- O’Regan, B., Grätzel, M. A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films. Nature. 353, 737-740 (1991).
- Frank, A. J., Kopidakis, N., van de Lagemaat, J. Electrons in nanostructured TiO2 solar cells: transport, recombination and photovoltaic properties. Coord. Chem. Rev. 248 (13-14), 1165-1179 (2004).
- Mor, G. K., Varghese, O. K., Paulose, M., Shankar, K., Grimes, C. A. A review on highly ordered, vertically oriented TiO2 nanotube arrays: fabrication, material properties, and solar energy applications. Sol. Energy Mater. Sol. Cells. 90 (14), 2011-2075 (2006).
- Dosch, R. G. . Use of titanates in decontamination of defense waste. Report RS-8232-2/50318. , (1978).
- Sylvester, P., Clearfield, A. The removal of strontium from simulated Hanford tank wastes containing complexants. Sep. Sci. Technol. 34 (13), 2539-2551 (1999).
- Manna, B., Dasgupta, M., Ghosh, U. C. Crystalline hydrous titanium(IV) oxide (CHTO): an arsenic(III) scavenger from natural water. J. Water Supply Res. T. 53, 483-495 (2004).
- Elvington, M. C., Click, D. R., Hobbs, D. T. Sorption behavior of monosodium titanate and amorphous peroxotitanate materials under weakly acidic conditions. Sep. Sci. Technol. 45 (1), 66-72 (2010).
- Wataha, J. C., et al. Titanates deliver metal ions to human monocytes. J. Mater. Sci.: Mater. Med. 21 (4), 1289-1295 (2010).
- Chung, W. O., et al. Peroxotitanate- and monosodium metal-titanate compounds as inhibitors of bacterial growth. J. Biomed. Mater. Res., Part A. 97 (3), 348-354 (2011).
- Hobbs, D. T., et al. Strontium and actinide separations from high level nuclear waste solutions using monosodium titanate 1. Simulant testing. Sep. Sci. Technol. 40 (15), 3093-3111 (2005).
- Ramirez-Salgdo, J., Djrado, E., Fabry, P. Synthesis of sodium titanate composites by sol-gel method for use in gas potentiometric sensors. J. Eur. Ceram. Soc. 24 (8), 2477-2483 (2004).
- Yang, J., et al. Study on composition, structure and formation process of nanotube Na2Ti2O4(OH)2. Dalton Trans. 2003 (20), 3898-3901 (2003).
- Chen, W., Guo, X., Zhang, S., Jin, Z. TEM study on the formation mechanism of sodium titanate nanotubes. J. Nanopart. Res. 9 (6), 1173-1180 (2007).
- Meng, X., Wang, D., Liu, J., Zhang, S. Preparation and characterization of sodium titanate nanowires from brookite nanocrystallites. Mater. Res. Bull. 39 (14-15), 2163-2170 (2004).
- Yada, M., Goto, Y., Uota, M., Torikai, T., Watari, T. Layered sodium titanate nanofiber and microsphere synthesized from peroxotitanic acid solution. J. Eur. Ceram. Soc. 26 (4-5), 673-678 (2006).
- Stewart, T. A., Nyman, M., deBoer, M. P. Delaminated titanate and peroxotitanate photocatalysts. Appl. Catal. B. 105 (1-2), 69-76 (2011).
- Rejman, J., Oberle, V., Zuhorn, I. S., Hoekstra, D. Size-dependent internalization of particles via the pathways of clathrin- and caveolae-mediated endocytosis. Biochem. J. 377 (1), 159-169 (2004).
- Hobbs, D. T., Taylor-Pashow, K. M. L., Elvington, M. C. Formation of nanosized metal particles on a titanate carrier. US patent application. , (2015).
- Elvington, M. C., Tosten, M., Taylor-Pashow, K. M. L., Hobbs, D. T. Synthesis and characterization of nanosize sodium titanates. J. Nanopart. Res. 14, 1114 (2012).
- Duff, M. C., Hunter, D. B., Hobbs, D. T., Fink, S. D., Dai, Z., Bradley, J. P. Mechanisms of strontium and uranium removal from high-level radioactive waste simulant solutions by the sorbent monosodium titanate. Environ. Sci. Technol. 38 (19), 5201-5207 (2004).
- Puangpetch, T., Sreethawong, T., Chavadej, S. Hydrogen production over metal-loaded mesoporous-assembled SrTiO3 nanocrystal photocatalysts: effects of metal type and loading. Int. J. Hydrogen Energy. 35 (13), 6531-6540 (2010).
- Fan, X., et al. Facile method to synthesize mesoporous multimetal oxides (ATiO3, A = Sr, Ba) with large specific surface areas and crystalline pore walls. Chem. Mater. 22 (4), 1276-1278 (2010).
- Rossmanith, R., et al. Porous anatase nanoparticles with high specific area prepared by miniemulsion technique. Chem. Mater. 20 (18), 5768-5780 (2008).
- Wu, Y., Zhang, Y., Xu, J., Chen, M., Wu, L. One-step preparation of PS/TiO2 nanocomposite particles via miniemulsion polymerization. J. Colloid Interface Sci. 343 (1), 18-24 (2010).
- Jiang, C., Ichihara, M., Honmaa, I., Zhou, H. Effect of particle dispersion on high rate performance of nano-sized Li4Ti5O12 anode. Electrochim. Acta. 52 (23), 6470-6475 (2007).
- Bouras, P., Stathatos, E., Lianos, P. Pure versus metal-ion-doped nanocrystalline titania for photocatalysis. Appl. Catal. B. 73 (1-2), 51-59 (2007).
- Bonino, R., et al. Ti-Peroxo species in the TS-1/H2O2/H2O system. J. Phys. Chem. B. 108 (11), 3573-3583 (2004).
- Bordiga, S., et al. Resonance Raman effects in TS-1: the structure of Ti(IV) species and reactivity towards H2O, NH3 and H2O2: an in situ study. Phys. Chem. Chem. Phys. 2003 (5), 4390-4393 (2003).
- Vacque, V., Sombret, B., Huvenne, J. P., Legrand, P., Suc, S. Characterization of the O-O peroxide band by vibrational spectroscopy. Spectrochim. Acta Part A. 53 (1), 55-66 (1997).
