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.

1. Synthesis of Nano-monosodium Titanate (nMST)
<ol>
	<li>Prepare 10 ml of solution #1 by adding 0.58 ml of 25 wt % sodium methoxide solution to 7.62 ml of isopropanol followed by 1.8 ml of titanium isopropoxide.</li>
	<li>Prepare 10 ml of solution #2 by adding 0.24 ml of ultrapure water to 9.76 ml of isopropanol.</li>
	<li>Add 280 ml of isopropanol to a 3-neck 500-ml round bottom flask, followed by 0.44 ml of Triton X-100 (average MW: 625 g/mol). Stir the solution well with a magnetic stir bar.</li>
	<li>Prepare a dual channel syringe pump to deliver solutions #1 and #2 at a rate of 0.333&#160;ml/min.</li>
	<li>Load solutions #1 and #2 into two separate 10-ml syringes fitted with a length of tubing that will allow delivery of the solution from the syringe pump to below the solution level in the 500-ml round bottom flask.</li>
	<li>While stirring, add all of solutions #1 and #2 (10 ml each) to the reaction using the syringe pump programmed in step 1.4.</li>
	<li>After the addition is complete, cap the flask and continue to stir for 24 hr at RT.</li>
	<li>Uncap the flask and heat the reaction mixture to ~82 &#176;C (refluxing isopropanol) for 45-90 min, followed by purging with nitrogen while maintaining heating. As isopropanol is evaporated, add ultrapure water intermittently to replace the evaporated isopropanol.</li>
	<li>After most of the isopropanol has evaporated and the volume of water added is approximately 50 ml, remove the heat and allow the reaction mixture to cool.</li>
	<li>Collect the product by filtering through a 0.1-&#181;m nylon filter paper, and wash several times with water to remove the surfactant and any residual isopropanol. Do not filter to dryness. After washing is complete, transfer the slurry from the filter into a pre-weighed bottle or vial, and store as an aqueous slurry.</li>
	<li>Determine the yield by determining the weight percent solids of the slurry. This can be done by measuring the weight of an aliquot of the slurry before and after drying.</li>
</ol>
2. Au(III) Ion Exchange
<ol>
	<li>Transfer 6.50 g of 4.23 wt % nMST slurry to a 50-ml centrifuge tube. This amount may vary based on the actual weight percent of the nMST slurry produced in step 1.10 above, and determined in step 1.11.</li>
	<li>Weigh out 0.0659 g of HAuCl4&#183;3H2O into a 1-dram glass vial. The target Ti:Au mass ratio is 4:1.</li>
	<li>Dissolve the HAuCl4&#183;3H2O in ~ 1 ml of water, then transfer to the centrifuge tube containing the nMST. Rinse the vial several times with additional water to ensure all of the HAuCl4&#183;3H2O is transferred to the centrifuge tube containing the nMST.</li>
	<li>Dilute the suspension with additional water, as necessary, to bring the total volume to 11 ml. Target a final Au(III) concentration of approximately 15 mM.</li>
	<li>Wrap the centrifuge tube in foil to keep the suspension in the dark, and then tumble the suspension on a shaker rotisserie for a minimum of 4 days.</li>
	<li>Collect the product by centrifuging at 3,000 x g for 15 min to isolate the solids. Wash the solids three times with distilled water by redispersing in water, and reisolate by centrifuging at 3,000 x g for 15 min to remove any unexchanged Au(III).</li>
	<li>Store the final product either as an aqueous suspension by redispersing in water, or as a moist solid by decanting off the final wash water and capping the tube. Store the product in the dark.</li>
</ol>
3. Preparation of the Peroxotitanate
<ol>
	<li>Transfer 5 g of a 9.8 wt % slurry of nMST to a small flask.</li>
	<li>Weigh out 0.154 g of 30 wt % H2O2 solution. The target H2O2:Ti molar ratio is 0.25:1.</li>
	<li>While stirring the nMST suspension well add the 0.154 g of H2O2 solution drop-wise. Upon H2O2 addition, the suspension of white solids immediately turns yellow.</li>
	<li>After the addition is complete stir the reaction at ambient temperature for 24 hr.</li>
	<li>Collect the product by filtering through a 0.1-&#181;m nylon filter, and wash several times with water to remove any unreacted H2O2. Do not filter to dryness. After washing is complete, transfer the slurry from the filter into a pre-weighed bottle or vial, and store as an aqueous slurry.</li>
</ol>

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<li>Bonino, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Ti-Peroxo+species+in+the+TS-1%2FH2O2%2FH2O+system%5BTitle%5D)+AND+%22J.+Phys.+Chem.+B%22%5BJournal%5D)">Ti-Peroxo species in the TS-1/H2O2/H2O system.</a> J. Phys. Chem. B. 108 (11), 3573-3583 (2004).</li>
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</ol>

The authors have nothing to disclose.

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 images before and after heating to 82 &#176;C show the product appears as a semi-particulate/semi-gel-like state prior to heating, but after heating the product appears solid and particulate in nature. Thus, the low temperature heating for 45-90 min&#160;is needed to complete particulate formation of the nMST.
As noted in this paper, the addition of a surfactant is critical to control the final size of the monosodium titanate. However, for the MST to serve as an effective ion exchanger, the surfactant must be removed so that all sites are accessible for the ion-exchange reaction. Thus, the choice of a suitable surfactant must consider not only the particle growth properties, but also chemical properties that allow the surfactant to be easily and effectively removed by economical means. In the case of the Triton X series of surfactants, these surfactants are very soluble in water and can be effectively removed by rinsing with water. For other surfactants, effective removal may require rinsing with a non-aqueous liquid.
The technique described in this work has expanded the range of particle sizes of MST that can be prepared, down into the nano regime. This has opened up the possibility for new applications for these materials, including their use as therapeutic metal delivery platforms. The decrease in particle size also increases the sorption kinetics, making the materials more efficient ion-exchangers. Modifications of the conditions used in this technique could further expand the range of particle sizes available, not only to smaller nanomaterials, but also to produce particles of larger size if that is desirable for a particular application.
While this technique is limited to the synthesis of materials that can be prepared using a sol-gel synthesis, it could be applied to other materials beyond MST. Not only could this technique be applied to RT sol-gel syntheses, like the one described, but application to a hydrothermal synthesis could also be envisioned. In the hydrothermal synthesis, the addition of the surfactant to the precursor solution could serve to limit the size of the precursor material formed, leading to faster reaction during the hydrothermal step, and also the possible formation of smaller particles of the final product.

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 &#8211; 2 &#181;m, 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.

<table><tbody><tr><td>Titanium(IV) isopropoxide</td><td>Sigma Aldrich</td><td>377996</td><td>99.999% trace metals basis</td></tr><tr><td>Isopropyl alcholol, 99.9%</td><td>Sigma Aldrich</td><td>650447</td><td>HPLC grade (Chomasolv)</td></tr><tr><td>Sodium methoxide in methanol</td><td>Sigma Aldrich</td><td>156256</td><td>25 wt%</td></tr><tr><td>Triton X-100</td><td>Sigma Aldrich</td><td>T9284</td><td>BioXtra</td></tr><tr><td>hydrogen tetrachloroaurate(III) trihydrate</td><td>Sigma Aldrich</td><td>G4022</td><td>ACS reagent grade</td></tr><tr><td>hydrogen peroxide (30&amp;nbsp;wt%)</td><td>Fisher</td><td>H325</td><td>Certified ACS</td></tr><tr><td>10-ml syringes</td><td>Fisher</td><td>14-823-16E</td><td></td></tr><tr><td>Dual channel syringe pump</td><td>Cole Parmer</td><td>EW-74900-10</td><td>Or equivalent programmable dual channel syringe pump</td></tr><tr><td>Tygon tubing 1/8 inch ID, 1/4 inch OD</td><td>Cole Parmer</td><td>EW-0640776</td><td></td></tr><tr><td>Tygon tubing 1/16 inch ID, 1/8 inch OD</td><td>Cole Parmer</td><td>EW-0740771</td><td></td></tr><tr><td>0.1-&amp;micro;m Nylon filter</td><td>Fisher</td><td>R01SP04700</td><td></td></tr><tr><td>Labquake shaker rotisserie</td><td>Thermo Scientific</td><td>4002110Q</td><td></td></tr></tbody></table>

synthesis and reaction chemistry of nanosize monosodium titanate

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&#160;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.

MST is synthesized using a sol-gel method in which tetraisopropoxytitanium(IV) (TIPT), sodium methoxide, and water are combined and reacted in isopropanol to form seed particles of MST.4 Micron-sized particles are then grown by controlled addition of additional quantities of the reagents. The resultant particles feature an amorphous core and an outer fibrous region having dimensions of about 10 nm wide by 50 nm in length.20
Figure 1A shows a typical particle size distribution, as measured by dynamic light scattering (DLS), for micron-sized MST prepared using the established sol-gel method. This synthesis produces a multimodal distribution of particles, with the majority around 1 &#181;m. Initial attempts to reduce the particle size of the MST investigated eliminating the seed step and using much more dilute reagent concentrations. In the diluted reaction the final solvent:TIPT volume ratio was 165 compared to 5.14 in the micron-sized MST synthesis, representing a reagent dilution of ~32 during the synthesis. As seen in Figure 1B, this resulted in a bimodal distribution with particle sizes centered at 50-100 nm and at 500 nm after 24 hr of reaction. After 48 hr, a trimodal distribution is observed with the appearance of particles measuring 1,000 nm (1 &#181;m) in size (Figure 1C). DLS measurements at shorter reaction times show a bimodal distribution of particle sizes similar to that shown in Figure 1B except the distribution is centered at smaller particle sizes. Thus, we conclude that the reduced reagent concentration and absence of the seed step leads to smaller particles produced initially, but particle growth continues resulting in a mixture of both nano and micron-sized MST.
Over the last decade there have been a number of papers reporting the addition of surfactants in sol&#8211;gel syntheses to control particle size resulting in the production of nanosize titanium dioxide, metal-doped titanium dioxides and multi-metal titanium oxides.21-26 Based on these findings, we initiated a series of tests to determine if the addition of surfactant to the MST synthesis would control particle growth allowing the sole production of nanosize particles. A number of non-ionic surfactants (Brig 52; Merpol A; Triton X series (X-15, X-45, X-100, X-165, X-405); TWEEN 20; 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate; and Zonyl FS300) as well as one anionic surfactant (sodium docusate) and one cationic surfactant (CTAB) were screened.
Initial experiments screened surfactants at a concentration of 0.12 moles of surfactant per mole of TIPT. Products from these reactions were screened using DLS for polydispersity and average particle size. Triton X-100, Triton X-165, Brij 52, and Zonyl FS300 showed a good combination of small particle size (Zave &#60; 150 nm) and monodispersity, with Triton X-100 and Triton X-165 showing the most narrow range of particle sizes. Additional experiments were then performed to examine a range of surfactant concentrations from 0.012 to 1.2 moles of surfactant per mole of TIPT. Higher surfactant concentrations resulted in broader distributions of particle sizes, while lower concentrations resulted in bimodal distributions suggesting that there was insufficient surfactant to limit the growth of particles. Triton X-100 at 0.12 moles per mole of TIPT appeared close to optimal for the synthesis of uniform nMST particles (Figures 2 and 3).
Temperature plays a key role in the conversion of the product from a gel to particulate form. Transmission electron microscopy (TEM) images before and after heating to 82 &#176;C show the product appears as a semi-particulate/semi-gel-like state prior to heating, but after heating the product appears solid and particulate in nature. Thus, the low temperature heating for 45-90 min&#160;is needed to complete particulate formation of the nMST.
Additional characterization of the nMST included determination of surface area and isoelectric point (IEP). Surface area measurements were obtained by Brunauer-Emmett-Teller (BET) analysis of nitrogen absorption isotherms. The BET surface area measured 285 m2g-1 for the nMST compared to only 20 m2g-1 for the micron-sized MST. The higher surface area for the nMST is consistent with the much smaller particle size of the nMST. Zeta potential measurements were performed over a range of pH conditions to determine the IEP for the nano and microtitanates. The IEPs determined are as follows: nMST = 3.34; peroxide-modified nMST = 2.05; MST = 4.46; peroxide-modified MST = 3.43. The nMST exhibited a lower IEP than MST indicating a higher fraction of surface sites available for protonation. This would be expected given the order of magnitude higher surface area of the nMST. Conversion of the nMST to the peroxide-modified nMST form lowered the IEP by more than a pH unit. A similar trend was observed upon conversion of MST to the peroxo form. The lower IEP for the peroxide-modified nMST and peroxide-modified MST materials likely results from the presence of non-bridging peroxo species that can be easily protonated and deprotonated.
The success of the surface modification of the nMST by H2O2 can be immediately observed from the color change from white to yellow. This color change is due to the &#951;2-bound protonated hydroperoxo-titanium ligand-to-metal-charge-transfer absorption band at 385 nm.27,28 Fourier transform infrared spectroscopy (FT-IR) also confirmed the formation of the peroxotitanate species as evidenced by the appearance of an absorption band at 883 cm-1 for the peroxide modified nMST (Figure 4) which is absent in the untreated nMST material. This band is very near the region of 845-875 cm-1 that is reported for the O-O stretching vibration in peroxides.29 TEM and scanning electron microscopy (SEM) analyses indicated that the particle size and morphology were retained after the peroxide reaction.
To determine the extent of the Au(III) ion-exchange, samples of the Au(III)-loaded solids were digested in hot nitric acid, followed by analysis of the diluted solution by inductively coupled plasma &#8211; emission spectroscopy (ICP-ES). The Au(III) loadings range from 71.4 mg Au/g nMST to 128.7 mg Au/g, with an average value of 97.3 mg/g. This represents a 33% increase over Au(III) loading on the micron-sized MST, which ranges from 58.0 mg Au/g MST to 88.6 mg/g, with an average value of 73.3 mg/g. TEM images of the nMST after exchange with Au(III) showed the presence of gold with no observable changes in the particle morphology. We believe that Au(III) is incorporated into the lattice of the micron and nanosize MST by coordinating to the oxygen atoms of titania as was observed in previous studies with MST exchanged with Sr2+ and UO22+.20
<img alt="Figure 1" src="/files/ftp_upload/53248/53248fig1.jpg" /> 
Figure 1. MST and nMST particle size distributions. (A) Particle size distribution of MST, (B) particle size distribution of nMST synthesized using no surfactant after 24 hr, and (C) particle size distribution of nMST synthesized using no surfactant after 48 hr. Reproduced with permission from reference 19. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53248/53248fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/53248/53248fig2.jpg" /> 
Figure 2. Typical particle size distribution of nMST. Particle size distribution for monosodium titanate synthesized in the presence of Triton X-100. Reproduced with permission from reference 19. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53248/53248fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" src="/files/ftp_upload/53248/53248fig3.jpg" /> 
Figure 3. Size and morphology of nMST and MST. (A, B) Transmission electron microscopy images of nMST; (C) scanning electron microscopy image of nMST, and (D) scanning electron microscopy image of MST. Reproduced with permission from reference 19. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53248/53248fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" src="/files/ftp_upload/53248/53248fig4.jpg" /> 
Figure 4. FT-IR absorption spectra of nMST (black) and peroxide-modified nMST (gray). The spectra confirm the formation of the peroxotitanate species as evidenced by the appearance of an absorption band at 883 cm-1 for the peroxide-modified nMST. Reproduced with permission from reference 19. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53248/53248fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate

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.

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the ...

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8.6K Views.  Savannah River Consulting, L.L.C.. 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.

Video: Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan &#948; solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials&#39; morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by St&#246;ber&#39;s methods, which have smooth surfaces.

Silica nanoparticles were prepared using acid-catalysis of a siloxane precursor and microwave-assisted synthetic techniques resulting in the controlled growth of nanomaterials ranging from 30-250 nm in diameter. The growth dynamics can be controlled by varying the initial silicic acid concentration, time of the reaction, and temperature of reaction.

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle ...

Fabrication of Spatially Confined Complex Oxides

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from the inherent strong electron correlations that reside within them. These materials can also possess electronic phase separation in which regions of vastly different resistive and magnetic behavior can coexist within a single crystal alloy material. By reducing the scale of these materials to length scales at and below the inherent size of the electronic domains, novel behaviors can be exposed. Because of this and the fact that spin-charge-lattice-orbital order parameters each involve correlation lengths, spatially reducing these materials for transport measurements is a critical step in understanding the fundamental physics that drives complex behaviors. These materials also offer great potential to become the next generation of electronic devices 1-3. Thus, the fabrication of low dimensional nano- or micro-structures is extremely important to achieve new functionality. This involves multiple controllable processes from high quality thin film growth to accurate electronic property characterization. Here, we present fabrication protocols of high quality microstructures for complex oxide manganite devices. Detailed descriptions and required equipment of thin film growth, photo-lithography, and wire-bonding are presented.

We describe the use of pulsed laser deposition (PLD), photolithography and wire-bonding techniques to create micrometer scale complex oxides devices. The PLD is utilized to grow epitaxial thin films. Photolithography and wire-bonding techniques are introduced to create practical devices for measurement purposes.

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Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material.

Various procedures are outlined to prepare atomically defined templates for epitaxial growth of complex oxide thin films. Chemical treatments of single crystalline SrTiO3 (001) and DyScO3 (110) substrates were performed to obtain atomically smooth, single terminated surfaces. Ca2 Nb3 O10- nanosheets were used to create atomically defined templates on arbitrary substrates.

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain ...

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and reduction half reactions, and fast electron (hole) diffusion and charge separation. Nanowires present suitable architectures to meet these requirements. Axially segmented Ag|ZnO and radially segmented (coaxial) TiO2-Ag nanowires with a diameter of 200 nm and a length of 6-20 &#181;m were made by templated electrodeposition within the pores of polycarbonate track-etched (PCTE) or anodized aluminum oxide (AAO) membranes, respectively. In the photocatalytic experiments, the ZnO and TiO2 phases acted as photoanodes, and Ag as cathode. No external circuit is needed to connect both electrodes, which is a key advantage over conventional photo-electrochemical cells. For making segmented Ag|ZnO nanowires, the Ag salt electrolyte was replaced after formation of the Ag segment to form a ZnO segment attached to the Ag segment. For making coaxial TiO2-Ag nanowires, a TiO2 gel was first formed by the electrochemically induced sol-gel method. Drying and thermal annealing of the as-formed TiO2 gel resulted in the formation of crystalline TiO2 nanotubes. A subsequent Ag electrodeposition step inside the TiO2 nanotubes resulted in formation of coaxial TiO2-Ag nanowires. Due to the combination of an n-type semiconductor (ZnO or TiO2) and a metal (Ag) within the same nanowire, a Schottky barrier was created at the interface between the phases. To demonstrate the photocatalytic activity of these nanowires, the Ag|ZnO nanowires were used in a photocatalytic experiment in which H2 gas was detected upon UV illumination of the nanowires dispersed in a methanol/water mixture. After 17 min&#160;of illumination, approximately 0.2 vol% H2 gas was detected from a suspension of ~0.1 g of Ag|ZnO nanowires in a 50 ml 80 vol% aqueous methanol solution.

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Procedures are outlined to prepare segmented and coaxial nanowires via templated electrodeposition in nanopores. As examples, segmented nanowires consisting of Ag and ZnO segments, and coaxial nanowires consisting of a TiO2 shell and a Ag core were made. The nanowires were used in photocatalytic hydrogen formation experiments.

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Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

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A &#8220;removable ceramic coating method&#8221; is presented in visual format for the synthesis of non-sintered and metal-terminated monometallic and bimetallic early transition metal carbide and nitride nanoparticles with tunable sizes and crystal structures.

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Synthesis and Characterization of Fe-doped Aluminosilicate Nanotubes with Enhanced Electron Conductive Properties

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe aims at lowering the band gap of imogolite, an insulator with the chemical formula (OH)3Al2O3SiOH, and at modifying its adsorption properties towards azo-dyes, an important class of organic pollutants of both wastewater and groundwater.
Fe-doped nanotubes are obtained in two ways: by direct synthesis, where FeCl3 is added to an aqueous mixture of the Si and Al precursors, and by post-synthesis loading, where preformed nanotubes are put in contact with a FeCl3&#8226;6H2O aqueous solution. In both synthesis methods, isomorphic substitution of Al3+ by Fe3+ occurs, preserving the nanotube structure. Isomorphic substitution is indeed limited to a mass fraction of ~1.0% Fe, since at a higher Fe content (i.e., a mass fraction of 1.4% Fe), Fe2O3 clusters form, especially when the loading procedure is adopted. The physicochemical properties of the materials are studied by means of X-ray powder diffraction (XRD), N2 sorption isotherms at -196 &#176;C, high resolution transmission electron microscopy (HRTEM), diffuse reflectance (DR) UV-Vis spectroscopy, and &#950;-potential measurements. The most relevant result is the possibility to replace Al3+ ions (located on the outer surface of the nanotubes) by post-synthesis loading on preformed imogolite without perturbing the delicate hydrolysis equilibria occurring during nanotube formation. During the loading procedure, an anionic exchange occurs, where Al3+ ions on the outer surface of the nanotubes are replaced by Fe3+ ions. In Fe-doped aluminosilicate nanotubes, isomorphic substitution of Al3+ by Fe3+ is found to affect the band gap of doped imogolite. Nonetheless, Fe3+ sites on the outer surface of nanotubes are able to coordinate organic moieties, like the azo-dye Acid Orange 7, through a ligand-displacement mechanism occurring in an aqueous solution.

Here, we present a protocol to synthesize and characterize Fe-doped aluminosilicate nanotubes. The materials are obtained by either sol-gel synthesis upon addition of FeCl3&#8226;6H2O to the mixture containing the Si and Al precursors or by post-synthesis ionic exchange of preformed aluminosilicate nanotubes.

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe ...

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs within the interlayer space of semiconducting layered titania nanosheet (TNS) films was investigated here. Two types of intermediate films (i.e., TNS films containing methyl viologen (TNS/MV2+) and 2-ammoniumethanethiol (TNS/2-AET+)) were prepared. The two intermediate films were soaked in an aqueous tetrachloroauric(III) acid (HAuCl4) solution, whereby considerable amounts of Au(III) species were accommodated within the interlayer spaces of the TNS films. The two types of obtained films were then soaked in an aqueous sodium tetrahydroborate (NaBH4) solution, whereupon the color of the films immediately changed from colorless to purple, suggesting the formation of AuNPs within the TNS interlayer. When only TNS/MV2+ was used as the intermediate film, the color of the film gradually changed from metallic purple to dusty purple within 30 min, suggesting that aggregation of AuNPs had occurred. In contrast, this color change was suppressed by using the TNS/2-AET+ intermediate film, and the AuNPs were stabilized for over 4 months, as evidenced by the characteristic extinction (absorption and scattering) band from the AuNPs.

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Here, we present a protocol for the in situ synthesis of gold nanoparticles (AuNPs) within the interlayer space of layered titanate films without the aggregation of AuNPs. No spectral change was observed even after 4 months. The synthesized material has expected applications in catalysis, photo-catalysis, and the development of cost-effective plasmonic devices.

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The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on Their Photocatalytic NOx Abatement Performance

The chemical bonding of particulate photocatalysts to supporting material surfaces is of great importance in engineering more efficient and practical photocatalytic structures. However, the influence of such chemical bonding on the optical and surface properties of the photocatalyst and thus its photocatalytic activity/reaction selectivity behavior has not been systematically studied. In this investigation, TiO2 has been supported on the surface of SiO2 by means of two different methods: (i) by the in situ formation of TiO2 in the presence of sand quartz via a sol-gel method employing tetrabutyl orthotitanium (TBOT); and (ii) by binding the commercial TiO2 powder to quartz on a surface silica gel layer formed from the reaction of quartz with tetraethylorthosilicate (TEOS). For comparison, TiO2 nanoparticles were also deposited on the surfaces of a more reactive SiO2 prepared by a hydrolysis-controlled sol-gel technique as well as through a sol-gel route from TiO2 and SiO2 precursors. The combination of TiO2 and SiO2, through interfacial Ti-O-Si bonds, was confirmed by FTIR spectroscopy and the photocatalytic activities of the obtained composites were tested for photocatalytic degradation of NO according to the ISO standard method (ISO 22197&#8722;1). The electron microscope images of the obtained materials showed that variable photocatalyst coverage of the support surface can successfully be achieved but the photocatalytic activity towards NO removal was found to be affected by the preparation method and the nitrate selectivity is adversely affected by Ti-O-Si bonding.

The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on Their Photocatalytic NOx Abatement Performance

The focus of the present work is to establish means to generate and quantify levels of Ti-O-Si linkages and to correlate these with the photocatalytic properties of the supported TiO2.

The chemical bonding of particulate photocatalysts to supporting material surfaces is of great importance in engineering more efficient and practical ...

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 &#176;C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications.
In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

Here, we present a protocol for the synthesis of porous barium titanate (BaTiO3) thin film by a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles are used as an organic template.

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its ...

Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of Manganese(II) Acetylacetonate

For biomedical applications, metal oxide nanoparticles such as iron oxide and manganese oxide (MnO), have been used as biosensors and contrast agents in magnetic resonance imaging (MRI). While iron oxide nanoparticles provide constant negative contrast on MRI over typical experimental timeframes, MnO generates switchable positive contrast on MRI through dissolution of MnO to Mn2+ at low pH within cell endosomes to &#8216;turn ON&#8217; MRI contrast. This protocol describes a one-pot synthesis of MnO nanoparticles formed by thermal decomposition of manganese(II) acetylacetonate in oleylamine and dibenzyl ether. Although running the synthesis of MnO nanoparticles is simple, the initial experimental setup can be difficult to reproduce if detailed instructions are not provided. Thus, the glassware and tubing assembly is first thoroughly described to allow other investigators to easily reproduce the setup. The synthesis method incorporates a temperature controller to achieve automated and precise manipulation of the desired temperature profile, which will impact resulting nanoparticle size and chemistry. The thermal decomposition protocol can be readily adapted to generate other metal oxide nanoparticles (e.g., iron oxide) and to include alternative organic solvents and stabilizers (e.g., oleic acid). In addition, the ratio of organic solvent to stabilizer can be changed to further impact nanoparticle properties, which is shown herein. Synthesized MnO nanoparticles are characterized for morphology, size, bulk composition, and surface composition through transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy, respectively. The MnO nanoparticles synthesized by this method will be hydrophobic and must be further manipulated through ligand exchange, polymeric encapsulation, or lipid capping to incorporate hydrophilic groups for interaction with biological fluids and tissues.

Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of ManganeseII Acetylacetonate

This protocol details a facile, one-pot synthesis of manganese oxide (MnO) nanoparticles by thermal decomposition of manganese(II) acetylacetonate in the presence of oleylamine and dibenzyl ether. MnO nanoparticles have been utilized in diverse applications including magnetic resonance imaging, biosensing, catalysis, batteries, and waste water treatment.

For biomedical applications, metal oxide nanoparticles such as iron oxide and manganese oxide (MnO), have been used as biosensors and contrast agents in ...

Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate

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