The authors would like to acknowledge the French ANR (grant ANR-10-BLAN-0810 NEQSON) and CEA/DEN/Marcoule.

1. Measurement&#160;of Uranium Sonoluminescence
The thermostated cylindrical sonoreactor is mounted on top of a high-frequency transducer providing 203 or 607 kHz ultrasound. Ultrasonic irradiation with low frequency ultrasound of 20 kHz is performed with a 1-cm2 titanium horn placed reproducibly on top of the reactor. The emission spectra are recorded in the range 230&#8211;800 nm using a spectrometer coupled to a liquid-nitrogen cooled CCD camera. Hydrogen in the outlet gas is measured simultaneously with the spectroscopic study using a quadrupole mass spectrometer (MS).
<ol>
	<li>Prepare the sonoreactor by tightly attaching the glass part onto the high-frequency transducer and the Teflon lid holding the 20 kHz horn onto the glass part. Put the sonoreactor on the translation stage and adjust its position so as to image with the two mirrors the center of the reactor onto the entrance slit of the emission spectrometer.</li>
	<li>Prepare uranyl solutions in perchloric acid by dissolving weighted UO3 samples, provided by CETAMA/CEA France, in a minimal volume of concentrated HClO4 under heating. Adjust then the volume of solution with diluted HClO4. To prepare uranyl solutions in H3PO4 dissolve UO3 samples in concentrated HClO4, evaporate the obtained solution to the wet salts and dissolve the latter in the desired volume of 0.5 M H3PO4.</li>
	<li>Put the solution to study into the sonoreactor. Tightly replace the 20 kHz horn. Add thermocouple and inlet gas tube onto the sonoreactor and connect the outlet gas tube to the entrance of the mass spectrometer.</li>
	<li>Put on the cryostat at ~0-1 &#176;C. Let argon bubble in the solution at a flow rate of 100 ml/min for at least 30 min and start following Ar and H2 MS signals.</li>
	<li>When MS signals are constant, switch on the ultrasonic generator (either the high-frequency one, at 60-80 W, or the 20 kHz one, at 35 W) and wait approximately 20 min until a steady-state temperature of about 10 &#176;C is reached inside the sonoreactor. The H2 MS signal should increase, indicating cavitation and water sonolysis.</li>
	<li>Close the light-tight box around the sonoreactor and start measuring sonoluminescence spectra, each during 300 sec to ensure good signal intensity. For each wavelength interval make three spectra to increase the signal to noise ratio and put second-order-light filter when necessary.</li>
	<li>After measuring the SL spectra, switch off the ultrasonic generator and keep measuring MS signals until a nice baseline is reached. At the same time, measure emission spectra in the absence of US that will allow to correct SL spectra for parasite light.</li>
</ol>
2. Sonochemical Reduction of Pt(IV) in Aqueous Solutions
<ol>
	<li>Prepare a 5 g/L&#160;Pt(IV) solution starting from H2PtCl6&#183;6H2O salt. Remarks: platinum salts are light and moisture sensitive. Keep the remaining salt under inert atmosphere and if possible, carry out the weighting procedure within a nonreactive gas atmosphere glove box.</li>
	<li>Under a fume hood, set up a 50 ml airtight glass reactor equipped with a double jacket (Figure 6).
	 <img alt="Figure 6" fo:content-width="5in" src="/files/ftp_upload/51237/51237fig6highres.jpg" width="500" /> 
	Figure 6: Experimental set-up for Pt(IV) sonochemical reduction at 20 kHz. 1. Ultrasonic generator of 20 kHz ultrasound with 750 W of maximal electric power, 2. Piezoceramic transducer, 3. Titanium horn, 4. Thermostated reactor, 5. Gas inlet, 6. Sample outlet, 7. Thermocouple, 8. PTFE ring.</li>
	<li>Equip the reactor with a Pt-100 thermocouple, a septum, a PTFE gas inlet and also a gas outlet with flow meters calibrated within the range of 100 ml/min. Connect the gas outlet to a water trap (molecular sieves) and finally to a gas mass spectrometer. CAUTION: Be sure to evacuate the gas within the fume hood since CO is a very harmful compound. A CO gas detector in the laboratory is mandatory.</li>
	<li>At the top of the reactor, fix a 1 cm&#178; titanium probe with a piezoelectric transducer supplied by a 20 kHz generator. Ensure that the sonotrode tip is at around 2 cm from the bottom of the reactor.</li>
	<li>Prior to experiments, start the chiller and set the temperature to -18 &#176;C. In the meantime, introduce 50 ml of deionized water within the reactor and make the Ar/CO (10%) gas bubbling deep within the solution with a flow rate around 100 ml/min. Ensure that there is no major leakage by checking the gas outlet flow rate. Be sure that the sonotrode tip is 1 to 2 centimeters below the surface of the liquid and start the gaseous products monitoring.</li>
	<li>After 10 to 15 min, fix the gas inlet slightly below the liquid surface and once the chiller reaches the setup temperature, start the ultrasonic irradiation with an acoustic power of 17 W/ml.</li>
	<li>After 15 to 20 min of ultrasonic irradiation, check that the temperature reaches a steady state around 40 &#176;C. If not, change the chiller settings to meet this requirement.</li>
	<li>Take a precise amount of the H2PtCl6 solution with the help of a syringe equipped with a stainless steel needle. Carefully introduce the needle through the septum and inject the solution within the cavitation zone below the sonotrode tip. Wash out the syringe by gently pumping the solution in and out and finally take a 1 ml sample. Repeat the sampling procedure at regular time intervals of 15 to 30 min.</li>
	<li>Measure the total concentration evolution of Pt ions in solution by ICP-OES analysis after dilution of the aliquots in 0.3 M HNO3. In the meantime, determine the amount of Pt(IV) ions within the system by following the 260 nm band in UV/Vis spectroscopy.</li>
	<li>As soon as no platinum ions can be detected in solution, switch off the ultrasonic irradiation, turn off the gas bubbling and the chiller. Take the platinum nanoparticle suspension out of the reactor.</li>
	<li>Prior to TEM analysis, try to centrifuge the suspension at high rotation speed (20,414 x g) for at least 20 min. Carefully remove the supernatant and store the deposit after drying at room temperature under vacuum or leave it within a small amount of water.</li>
	<li>Some samples can be very difficult to concentrate and can need longer centrifugation time. If it is not successful, use this procedure only to separate the platinum nanoparticles from the bigger titanium particles released in solution during the ultrasonic irradiation and then keep the supernatant this time.</li>
	<li>Disperse one drop of supernatant or few milligrams of dried products in absolute ethanol or isopropanol. Deposit one drop of the suspension on a carbon coated copper grid and proceed to the HRTEM analysis after total evaporation of the solvent.</li>
</ol>
3. Sonochemical Synthesis of Plutonium Colloids
In Marcoule, the ATALANTE facility is equipped with several hot labs and shielded cell lines dedicated to the research and development for nuclear fuel cycle. One of the glove boxes is devoted to the study of the sonochemical reactions of actinides.
<ol>
	<li>Suspend 200 mg of PuO2 (SBET = 13.3 m2/g) in 50 ml of pure water in the sonochemical reactor located in the glove box.</li>
	<li>Equip the reactor with the tight Teflon ring and the 20 kHz ultrasonic probe. Before each experiment, screw a new tip to ensure maximal effect of cavitation and avoid the accumulation of titanium particles in solution resulting from the tip erosion.</li>
	<li>Set the temperature of the cryostat (Huber CC1) situated outside the glove box low enough to manage the temperature increase in solution after the ultrasound will be switched-on. Note that the cooling system is equipped with a heat exchanger to avoid radioactive contamination outside the barrier. Insert the tight thermocouple into the cell to control the temperature of the solution.</li>
	<li>Allow bubbling the solution with pure argon 20 min before sonication (100 ml/min). Note that the Ar bubbling will be applied during the whole sonication experiments to ensure the maximal effects of acoustic cavitation.</li>
	<li>Set the ultrasonic generator to the appropriate amplitude (~30%) in order to obtain the required acoustic power Pac (17 W/cm2) delivered to the solution. Note that the acoustic power is previously measured using the thermal probe method 22. Using the appropriate conditions, the accumulation of hydrogen peroxide in solution (resulting from the combination of hydroxyl radicals induced by the homolytic dissociation of sonicated water molecules) is previously measured in pure water to calibrate the system and allow the reproducibility of the experiment.</li>
	<li>Switch-on the ultrasonic generator and sonicate the PuO2 solution. Adjust the cryostat settings to obtain a temperature of 30 &#176;C in the solution.</li>
	<li>Once the colloids are formed (after 5-12 hr of irradiation), switch-off the ultrasonic generator, transfer the solution to centrifugation tube, and centrifuge during 10 min (22,000 x g) in order to remove the solid phase.</li>
	<li>UV-Vis spectrometer can thereafter be used for direct analysis and characterization of Pu colloids. During sonication, the kinetics of H2O2 accumulation in solution under ultrasound irradiation can also be measured by the colorimetric method at 410 nm (&#949; = 780 cm-1M-1) after diluting 500 &#181;l of sampled solution with 500 &#181;l TiOSO4 (2 x 10-2 M in 2 M HNO3 &#8211; 0.01 M [N2H5][NO3]) followed by centrifugation.</li>
</ol>

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I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanism+of+Pt(IV)+Sonochemical+Reduction+in+Formic+Acid+Media+and+Pure+Water.">Mechanism of Pt(IV) Sonochemical Reduction in Formic Acid Media and Pure Water.</a> Chem. Eur. J. 18, 3879-3885 (2010).</li><li>Thompson, L. H., Doraiswamy, L. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sonochemistry:+science+and+engineering.">Sonochemistry: science and engineering.</a> Ind. Eng. Chem. Res. 38, 1215-1249 (2012).</li><li>Nikitenko, S. I., Venault, L., Pflieger, R., Chave, T., Bisel, I., Moisy, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential+applications+of+sonochemistry+in+spent+nuclear+fuel+reprocessing:+a+short+review.">Potential applications of sonochemistry in spent nuclear fuel reprocessing: a short review.</a> Ultrason. Sonochem. 17, 1033-1040 (2010).</li><li>Chave, T., Den Auwer, C., Moisy, P., Nikitenko, S. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sonochemical+formation+of+Pu(IV)+colloids.">Sonochemical formation of Pu(IV) colloids.</a> ATALANTE 2012 Nuclear chemistry for sustainable fuel cycles. , (2012).</li><li>Baird, C. P., Kemp, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Luminescence+spectroscopy,+lifetimes+and+quenching+mechanisms+of+excited+states+of+uranyl+and+other+actinide+ions.">Luminescence spectroscopy, lifetimes and quenching mechanisms of excited states of uranyl and other actinide ions.</a> Prog. React. Kinet. 22 (2), 87-139 (1997).</li><li>Marcantonatos, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photochemistry+and+exciplex+of+the+uranyl+ion+in+aqueous+solution.">Photochemistry and exciplex of the uranyl ion in aqueous solution.</a> J. Chem. Soc. Faraday Trans. 76, 1093-1097 (1980).</li><li>Burrows, H. D., Kemp, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photochemistry+of+uranyl+ion.">Photochemistry of uranyl ion.</a> Chem. Soc. Rev. 3, 139-165 (1974).</li><li>Kazakov, V. P., Sharipov, G. L., Sadykov, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Specific+quenching+of+the+radioluminescence+from+UO22++ions+by+the+products+of+radiolysis+in+acidic+solutions.">Specific quenching of the radioluminescence from UO22+ ions by the products of radiolysis in acidic solutions.</a> High Energy Chemistry (Khimiya Vysokikh Energii. 16, 376-377 (1982).</li><li>Katz, J. J., Seaborg, G. T., Morss, L. 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J., Henglein, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasonic+Irradiation+of+Water+in+the+Presence+of+18,18O2:+Isotope+Exchange+and+Isotopic+Distribution+of+H2O2.">Ultrasonic Irradiation of Water in the Presence of 18,18O2: Isotope Exchange and Isotopic Distribution of H2O2.</a> J. Phys. Chem. 90, 1954-1956 (1986).</li><li>Nikitenko, S. I., Martinez, P., Chave, T., Billy, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sonochemical+Disproportionation+of+Carbon+Monoxide+in+Water:+Evidence+for+Treanor+Effect+during+Multibubble+Cavitation.">Sonochemical Disproportionation of Carbon Monoxide in Water: Evidence for Treanor Effect during Multibubble Cavitation.</a> Angew. Chem. Int. Ed. 48, 9529-9532 (2009).</li><li>Surendran, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+self-assembly+of+platinum+nanoparticles+to+nanostructured+materials.">From self-assembly of platinum nanoparticles to nanostructured materials.</a> Small. 1, 964-967 (2005).</li><li>Chave, T., Grunenwald, A., Ayral, A., Lacroix-Desmazes, P., Nikitenko, S. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sonochemical+deposition+of+platinum+nanoparticles+on+polymer+beads+and+their+transfer+on+the+pore+surface+of+a+silica+matrix.">Sonochemical deposition of platinum nanoparticles on polymer beads and their transfer on the pore surface of a silica matrix.</a> J. Colloid Interface Sci. 395, 81-84 (2013).</li><li>Virot, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Catalytic+dissolution+of+ceria+under+mild+conditions.">Catalytic dissolution of ceria under mild conditions.</a> J. Mater. Chem. 22, 14734-14740 (2012).</li><li>Virot, M., Chave, T., Nikitenko, S. I., Shchukin, D. G., Zemb, T., Moehwald, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acoustic+cavitation+at+the+water-glass+interface.">Acoustic cavitation at the water-glass interface.</a> J. Phys. Chem. C. 114, 13083-13091 (2010).</li><li>Virot, M., Pflieger, R., Skorb, E. 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The authors have nothing to disclose.

The most critical parameters for successful observation of sonoluminescence and sonochemistry are: 1) rigorous control of the saturating gas and the bulk temperature during sonication, 2) careful selection of ultrasonic frequency, 3) using an optimal composition of sonicated solution to prevent quenching.
The kinetics of the sonochemical reactions as well as the intensity of sonoluminescence is very sensitive to the temperature of solution submitted to ultrasound: in contrast to the kinetics of most &#34;usual&#34; chemical reactions the rate of the sonochemical processes falls with the temperature of the bulk 1. The sonoluminescence exhibits a similar behavior. This is a direct consequence of the rise in vapor pressure associated with heating the liquid. The higher the vapor pressure the larger amounts of solvent enter inside the bubble that leads to a sonochemical plasma quenching. Therefore, to get maximum sonochemical yield or the maximum intensity of sonoluminescence any experiment should be conducted at as low temperature as is feasible. This principle can be demonstrated by the multibubble sonoluminescence in water saturated with argon: the increase of bulk temperature from 11 &#176;C to 30 &#176;C causes intensity of sonoluminescence to decrease by a factor of 5 4.
The maximum efficiency of acoustic cavitation is reached in the presence of heavy noble gases like Ar, Kr and Xe, and what&#8217;s more, the strongest sonoluminescence is observed in the presence of xenon gas 5, 26. From the point of view of plasmachemical model of cavitation this phenomenon is explained by a lower ionization potential of Xe (12.13 eV) compared to that of Ar (15.76 eV) 5. However, it must be remembered that this dependence on ionization potential is a simplistic view since the sonochemical effects will also depend on other parameters, like noble gas solubility, thermal conductivity etc. In addition, chemical composition of the gas mixture can be very important for the efficiency of the sonochemical reactions. For instance, Ar/CO gas mixture works much better for the sonochemical reduction of Pt(IV) in water compared to pure Ar due to OH&#8226; radical scavenging with carbon monoxide molecules 7.
The best choice of ultrasonic frequency for the sonochemical processing depends on the system to be studied. In general, the chemical effects of ultrasound, such as radical generation, are stronger at high ultrasonic frequencies due to the higher electronic temperature of the nonequilibrium plasma generated during bubble collapse. The sonoluminescence is also more intense at high frequency for the same reason. Besides, the geometry of the active zone is different at high and low frequencies: at high frequency almost the entire reactor is active, whereas at 20 kHz it is only the relatively small zone below the US horn. On the other hand, the cavitation bubbles are much bigger at low-frequency ultrasound. Consequently, their collapse produces much stronger mechanical effects (erosion of solid surfaces, dispersion of aggregates, emulsification, etc.). Therefore, ultrasonic activation of solids (extended surfaces and powders) can be recommended to perform with low-frequency ultrasound. By contrast, the sonochemical redox reactions in homogeneous solutions would be more effective at high frequency. Noteworthy that the highest yield of the chemically reactive species is observed between 200 kHz and 400 kHz. This phenomenon is attributed to the superposition of two opposite effects: (i) increase of vibronic temperatures of the intrabubble sonochemical plasma with ultrasonic frequency and (ii) decrease of the bubble size. Therefore, the optimal ratio &#34;intrabubble conditions/bubble size&#34; is observed in the medium range of frequencies.
Finally, the reaction medium is also important for optimization of both sonochemical and sonoluminescence yields. In most cases the sonochemical reactions of non-volatile species, like metal ions, are not related to the direct action of cavitation bubbles. Instead, cavitation causes a chemical transformation of solvent followed by the interactions of sonolytic products with metal ions. For example, sonolysis of nitric acid aqueous solutions leads to formation of nitrous acid, which is an effective catalyst of numerous redox reactions with actinide ions 9. These catalytic reactions allow control of actinide oxidation states in nitric acid medium without addition of any side chemicals. On the other hand, the products of solvent sonolysis lead to quenching of the sonoluminescence of uranyl 6 and lanthanide 27 ions. Complexation with strong ligands, like phosphate or citrate ions, enhances manifold sonoluminescence of these cations due to reduction of intra- and inner-molecular quenching.

The use of power ultrasound in numerous industrial and research areas, such as the cleaning of solid surfaces, degassing of liquids, material sciences, environmental remediation, and medicine, has received much attention during the last decade 1. The ultrasonic treatment increases the conversion, improves the yield, and initiates the reactions in homogeneous solutions as well as in heterogeneous systems. It is generally accepted that the physical and chemical effects of ultrasonic vibrations in liquids arise from acoustic cavitation or, in other words, to the implosive collapse of microbubbles in fluids irradiated with power ultrasound 2. Violent implosion of the cavitation bubble generates transient extreme conditions in the gas phase of the bubble, which are responsible for the formation of chemically active species and sonoluminescence. Nevertheless, debate still continues over the origin of such extreme conditions. Spectroscopic analysis of the sonoluminescence helps to better understand the processes occurring during the bubble collapse. In water, saturated with noble gases, the sonoluminescence spectra are composed from OH(A2&#931;+-X2&#928;i), OH(C2S+-A2S+) bands and a broad continuum ranging from UV to NIR part of the emission spectra 3. Spectroscopic analysis of OH(A2&#931;+-X2&#928;i) emission bands revealed formation of nonequilibrium plasma during sonolysis of water 4, 5. At low ultrasonic frequency, weakly excited plasma with Brau vibrational distribution is formed. By contrast, at high-frequency ultrasound, the plasma inside collapsing bubbles exhibits Treanor behavior typical for strong vibrational excitation. The vibronic temperatures (Tv, Te) increase with ultrasonic frequency indicating more drastic intrabubble conditions at high-frequency ultrasound.
In principal, each cavitation bubble can be considered as a plasma chemical microreactor providing highly energetic processes at almost room temperature of the bulk solution. The photons and the "hot" particles produced inside the bubble enable to excite the non-volatile species in solutions thus increasing their chemical reactivity. For example, the mechanism of ultrabright sonoluminescence of uranyl ions in acidic solutions is influenced by uranium concentration: photons absorption/re-emission in diluted solutions, and excitation via collisions with "hot" particles contributes at higher uranyl concentration 6. Chemical species produced by cavitation bubbles can be used for the synthesis of metallic nanoparticles without any templates or capping agents. In pure water sparged with argon, the sonochemical reduction of Pt(IV) occurs by hydrogen issued from sonochemical water molecules splitting yielding monodispersed nanoparticles of metallic platinum 7. Sonochemical reduction is accelerated manifold in the presence of formic acid or Ar/CO gas mixture.
Many previous studies have shown the advantages of ultrasound to activate the surface of divided solids due to the mechanical effects in addition to chemical activation 8,9. Small solid particles that are much less in size than the cavitation bubbles do not perturb the symmetry of collapse. However, when a cavitation event occurs near big aggregates or near extended surface the bubble implodes asymmetrically, forming a supersonic microjet leading to the cluster disaggregating and to the solid surface erosion. Ultrasonic treatment of plutonium dioxide in pure water sparged with argon causes formation of stable nanocolloids of plutonium(IV) due to both physical and chemical effects 10.

<table border="0" cellpadding="0" cellspacing="0" width="573">
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			<td height="42" style="height:42px;width:216px;">20 kHz Ultrasound Generator</td>
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			<td height="84" style="height:84px;width:216px;">Multifrequency Generator AG 1006</td>
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			<td height="42" style="height:42px;width:216px;">Spectrometer SP 2356i</td>
			<td style="width:71px;">Roper Scientific</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">CCD camera SPEC10-100BR cooled with liquid nitrogen</td>
			<td style="width:71px;">Roper Scientific</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Quadrupole mass-spectrometer PROLAB 300</td>
			<td style="width:71px;">Thermoscientific</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Centrifuge Sigma 1-14</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">H2PtCl6 6H2O</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ar; Ar/CO gases</td>
			<td style="width:71px;">Air Liquid</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Uranium and Plutonium compounds</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td>Prepared in the laboratories of Marcoule Research Center</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Perchloric acid</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Phosphoric acid</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Formic acid</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

activating molecules, ions, and solid particles with acoustic cavitation

The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic cavitation: the nucleation, growth, and implosive collapse of microbubbles in liquids submitted to power ultrasound. The violent implosion of bubbles leads to the formation of chemically reactive species and to the emission of light, named sonoluminescence. In this manuscript, we describe the techniques allowing study of extreme intrabubble conditions and chemical reactivity of acoustic cavitation in solutions. The analysis of sonoluminescence spectra of water sparged with noble gases provides evidence for nonequilibrium plasma formation. The photons and the "hot" particles generated by cavitation bubbles enable to excite the non-volatile species in solutions increasing their chemical reactivity. For example the mechanism of ultrabright sonoluminescence of uranyl ions in acidic solutions varies with uranium concentration: sonophotoluminescence dominates in diluted solutions, and collisional excitation contributes at higher uranium concentration. Secondary sonochemical products may arise from chemically active species that are formed inside the bubble, but then diffuse into the liquid phase and react with solution precursors to form a variety of products. For instance, the sonochemical reduction of Pt(IV) in pure water provides an innovative synthetic route for monodispersed nanoparticles of metallic platinum without any templates or capping agents. Many studies reveal the advantages of ultrasound to activate the divided solids. In general, the mechanical effects of ultrasound strongly contribute in heterogeneous systems in addition to chemical effects. In particular, the sonolysis of PuO2 powder in pure water yields stable colloids of plutonium due to both effects.

Uranyl ion sonoluminescence is extremely weak in HClO4 solutions: though typical light absorption by UO22+ ions is observed below 500 nm, emission lines from excited (UO22+)* (centered at 512 nm and 537 nm) are hardly seen (Figure 1). The SL of UO22+ is quenched. This quenching can be attributed to reduction of the excited uranyl ion by a coordinated water molecule 11-13:
(UO22+)* + H2O &#8594; UO2+ + H+ + OH&#8226;
<img alt="Figure 1" fo:content-width="5in" src="/files/ftp_upload/51237/51237fig1highres.jpg" width="500" /> 
Figure 1: Sonoluminescence spectra of HClO4 (0.2 M; 65 W) and UO22+ (0.1 M) in HClO4 (0.2 M; 81 W) at 203 kHz, 10 &#176;C, Ar. Black curve shows the emission spectrum of 0.2 M perchloric solution without uranium in the presence of argon. This spectrum consists of OH radical emission centered at 310 nm and a broad continuum spanning from the UV to the near IR spectral range. Blue curve demonstrates the emission spectrum of the same solution but in the presence of uranyl ions (0.1 M). The photons emitted by collapsing bubbles in the range of 250-450 nm are absorbed by UO22+ species almost completely. However, emission lines from excited (UO22+)* at 512 nm and 537 nm are very weak. Moreover, these emission lines can be observed only at 203 kHz which also exhibits the most intense sonoluminescence from sonicated water in the studied range of frequencies. Reproduced with permission from 6.
Besides, the mass spectrometer measures a decrease by 40% in H2 formation rate during the sonolysis of HClO4 solutions when UO22+ concentration is increased from 50 to 100 mM. This decrease indicates that the excited uranyl ions can also be quenched by products of the sonochemical water split (H2 and H2O2):
(UO22+)* + H2 &#8594; UO2+ + H+ + H
(UO22+)* + H &#8594; UO2+ + H+
(UO22+)* + H2O2 &#8594; UO2+ + H+ + HO2&#8226;
This quenching pattern resembles quenching of the radioluminescence of uranyl ions by radiolytical products of water 14.
By contrast, in H3PO4 solutions the SL of UO22+ is intense and, in the right conditions of US frequency and UO22+ concentration, even visible to the naked eye (Figure 2). The light emission zone shows a layered structure arising from the standing acoustic wave field inside the sonochemical reactor: brighter zones correspond to the antinodes of acoustic pressure, where the concentration of cavitation bubbles is highest.
<img alt="Figure 2" fo:content-width="5in" src="/files/ftp_upload/51237/51237fig2highres.jpg" width="500" /> 
Figure 2: Photograph of UO22+ sonoluminescence (3.1 x 10-2 M) in 0.5 M H3PO4 at 203 kHz, 63 W, 10 &#176;C, Ar, exposure time 30 sec. The picture is taken through the quartz window of the sonoreactor. The halo around the major light emission zone originates from light reflection in the reactor's cooling jacket. Scale bar 2.5 cm. The light emission zone is layered indicating that there is a standing acoustic wave field inside the reactor. Reproduced with permission from 6.
The intense SL of UO22+ in H3PO4 (Figure 3) is enabled by strong complexation of UO22+ by phosphate ions 15, which protects uranyl from quenching. Through the formation of uranyl phosphate complexes (UO22+)* lifetime gets almost 200 times longer16 and UO22+ molar extinction coefficient twice as much. These two effects lead to an enhancement of UO22+ sonoluminescence, while the pure acids show similar SL intensities.
<img alt="Figure 3" fo:content-width="5in" src="/files/ftp_upload/51237/51237fig3highres.jpg" width="500" /> 
Figure 3: Sonoluminescence spectra of H3PO4 (0.5 M) and UO22+ (5 x 10-2 M) in H3PO4 (0.5 M) at 203 kHz, 61 W, 10 &#176;C, Ar. The strong emission lines at 496 nm, 517 nm and 540 nm (blue curve) are attributed to (UO22+)* emission. Reproduced with permission from 6.
Excitation of uranyl ions may proceed by two mechanisms, both of which can be provided by ultrasound. In the first excitation pathway, excitation proceeds by absorption of part of the light emitted by cavitation bubbles at collapse. In the second pathway excitation is induced by collisions at the bubble interface with the &#34;hot&#34; particles from the sonochemical plasma, whereby kinetic and excitation energy from the &#8220;hot&#8221; particles may be transferred to uranyl ions. To determine which excitation mechanism prevails, the intensity of uranyl SL is measured for different uranyl concentrations in H3PO4 at 204 kHz. As can be seen in Figure 4, for very dilute solutions ([UO22+] &#60; 1 x 10-4 M) the intensity of uranyl SL increases linearly with UO22+ concentration. For higher concentrations up to 2 x 10-2 M the intensity of uranyl SL is almost independent from UO22+ concentration. These two domains correspond to a photoexcitation mechanism, where the emission is proportional to the number of absorbed photons. It is therefore proportional to UO22+ concentration until absorption of the UV part of the SL spectrum becomes too important. It is then approximately constant.
<img alt="Figure 4" fo:content-width="5in" src="/files/ftp_upload/51237/51237fig4highres.jpg" width="500" /> 
Figure 4: Variation of (UO22+)* relative emission peak heights at 516 nm and 539 nm as a function of UO22+ concentration in H3PO4 (0.5 M) for diluted solutions; at 203 kHz, 82 W, 10 &#176;C, Ar. The seeming maximal intensity of uranium sonoluminescence observed at [UO22+]~0.001 M is related to uranium self-absorption that decreases the intensity at higher concentrations (see Ref. 3).
In more concentrated solutions ([UO22+] &#62; 3 x 10-2 M), when the amount of uranyl ions at the interface of collapsing bubbles becomes high enough, uranyl SL starts to increase again with uranyl concentration. This additional luminescence is due to a second excitation mechanism, namely by collisions with &#8220;hot&#8221; particles formed in the plasma of cavitation bubbles at collapse.
<img alt="Figure 5" fo:content-width="5in" src="/files/ftp_upload/51237/51237fig5highres.jpg" width="500" /> 
Figure 5: Variation of (UO22+)* relative emission peak heights at 516 nm and 539 nm as a function of UO22+ concentration in H3PO4 (0.5 M) for more concentrated solutions; at 203 kHz, 82 W, 10 &#176;C, Ar. Reproduced with permission from 6.
By coupling gas mass spectrometer, UV/Vis spectroscopy and ICP-OES measurement, it's possible to determine the reduction kinetics of platinum ions within our conditions (Figure 7). The results indicate that the Pt(IV) reduction is a two-step mechanism with the subsequent reduction of Pt(IV) ions into Pt(II) and finally in Pt(0) as reported in the literature 17. The sharp increases of CO2 signal in the gas phase (Figure 7) is evidence that the main reducing agent in the system is CO following the equations 1 and 2:
PtCl62- + CO + H2O &#8594; PtCl42- + CO2 + 2H+ + 2Cl- (1)
PtCl42- + CO + H2O &#8594; Pt0 + CO2 + 2H+ + 4Cl- (2)
<img alt="Figure 7" fo:content-width="5in" src="/files/ftp_upload/51237/51237fig7highres.jpg" width="500" /> 
Figure 7: Evolution of the concentrations of platinum(IV) and (II) in solution and estimated percentage of metallic Pt (dash lines). Hydrogen and CO2 emission curves obtained during ultrasonic irradiation in pure water under Ar/CO atmosphere (solid lines). T = 20&#177;1 &#176;C and Pac = 0.35 W/ml. Ultrasonic irradiation was triggered at 10 min on the time axis and platinum solution was added 30 min later. This figure has been modified from 7.
Experiments in pure water under argon atmosphere confirm that the reduction of platinum ions can occur by in situ formed hydrogen. Indeed, acoustic cavitation can induce the homolytic split of water molecules inside cavitation bubbles into H and OH&#176; radicals. Recombination of H atoms and OH&#176; radicals leads respectively to the formation of H2 and hydrogen peroxide into solution&#160;18. The presence of oxidative species namely OH&#176; radicals and/or hydrogen peroxide in the system can be a hindrance for the reduction process. Recently it was reported that the addition of a small amount of CO within the gas phase, can totally scavenge the hydroxyl radicals formed under ultrasonic irradiation (equation 3)&#160;19. Note that this reaction leads also to an increase of H2 formation rate, compared to the sonolysis of pure water under Ar, in agreement with equations 3 and 4 7.
CO + OH&#8226; &#8594; CO2 + H (3)
2H &#8594; H2 (4)
Thus, CO is not only a reducing agent but also plays the role of OH radical scavenger. However bubbling CO into a Pt(IV) solution without ultrasonic irradiation at room temperature doesn't lead to the formation of Pt nanoparticles but to a pink colloidal suspension of platinum carbonyl species 20. Thus, the carbon monoxide ability to reduce platinum ions at room temperature is enhanced due to the local heating in the liquid shell surrounding the bubble during its collapse 7. In these conditions the sonochemical reduction at room temperature could be observed within few hours and lead to the formation of metallic Pt particles within the range of few nanometers as observed in Figure 8. This procedure can be considered for a large array of experimental conditions since only the gas phase has to be changed and no further reagent need to be added within the liquid medium. Noteworthy, the design of a reduction process carried out at low ultrasonic frequency will be of utmost interest for the controllable Pt NP deposition on various specific supports even on thermosensitive materials like polymers 21.
<img alt="Figure 8" fo:content-width="5in" src="/files/ftp_upload/51237/51237fig8highres.jpg" width="500" /> 
Figure 8: High resolution TEM image of Pt nanoparticles obtained under ultrasonic irradiation in pure water with Ar/CO atmosphere. Picture of obtained brown colloid is given as an inset with an overview of Pt nanoparticles at low magnification. This figure has been modified from 7.
The 5 hr sonolysis of a PuO2 suspension in pure water under Ar bubbling leads to the formation of a green colloid solution which remains stable for months after centrifugation (Figure 9). The application of ultrasound in heterogeneous systems is known to generally enhance erosion, fracture, and dispersion of solid surfaces 22-24. However, the same experiment performed with CeO2 or ThO2 as surrogates of PuO2 do not lead to the formation of colloids. A possible reaction between PuO2 and sonochemically generated chemical species could explain this phenomenon. When increasing the duration of ultrasound irradiation from 5 hr to 11 hr, the concentration of colloid is found to be increased. UV-Vis spectra obtained with these conditions are different than the one observed for Pu colloids obtained by conventional techniques (Figure 10), for example by dilution of concentrated Pu(IV) solution 25.
<img alt="Figure 9" fo:content-width="5in" src="/files/ftp_upload/51237/51237fig9highres.jpg" width="500" /> 
Figure 9: Scheme of the experiment leading to the sonochemical formation of Pu colloids.
<img alt="Figure 10" fo:content-width="5in" src="/files/ftp_upload/51237/51237fig10highres.jpg" width="500" /> 
Figure 10: UV-Vis spectra characterizing the Pu colloids obtained from PuO2 with ultrasound under Ar in pure water (brown curve) and by the dilution of Pu(IV) in pure water (blue curve).
Chemical species generated under ultrasound irradiation are attributed to the acoustic cavitation phenomenon 7. Under Ar bubbling, the species detected during the sonication of pure water are H2 and H2O2 in agreement with the following equations:
H2O &#8594; H + OH&#176;
H + H &#8594; H2
HO&#176; + &#176;OH &#8594; H2O2
In order to clarify the chemical mechanism involved in the formation of Pu colloids, the presence of H2O2 can be measured by the TiOSO4 colorimetric method during sonolysis, by determining the generation of Ti(IV)&#183;H2O2 complexes at ~410 nm. Using our experimental settings, the H2O2 formation rate is measured to be ~0.7 &#181;M/min&#160;and follows a zero order kinetic law in agreement with the literature for similar experiments performed with reactors having the same geometry. In the presence of suspended PuO2, analyses reveal that the sonolysis of such a solution do not lead to the accumulation of H2O2 in solution suggesting a chemical mechanism occurring between PuO2 and H2O2. In order to check this hypothesis, the same experiment can be performed in the presence of a 5 x 10-2 M H2O2 in solution. However, these settings do not lead to the formation of Pu colloids according to the UV-Vis absorption spectra.
The sonochemical formation of Pu colloids can therefore be investigated in pure water under experimental conditions that avoid the formation of H2O2. The replacement of Ar atmosphere by Ar/CO (10%) atmosphere allows quenching OH&#176; radicals formed during sonolysis 7. In agreement with the literature, Ar/CO bubbling prevents the accumulation of H2O2 in solution. However, these experimental conditions lead to the formation of Pu colloids having a UV-Vis absorption spectrum that agrees with what observed under Ar atmosphere (Figure 10). Consequently, H2O2 appears to not be the limiting species for the generation of Pu colloids under ultrasound irradiation. Furthermore, Pu colloids can be formed in the absence of H2O2 as well. Note also that the sonolysis of PuO2 suspended in a nitric acid solution do not lead to the formation of Pu colloids. One can conclude that plutonium colloids are formed via Pu(IV) reduction by hydrogen (H2) originated from water sonolysis followed by the re-oxidation of Pu(III) in solution and formation of hydrolyzed Pu(IV) ultrasmall particles.

Watch this Scientific Journal Video about Activating Molecules, Ions, and Solid Particles with Acoustic Cavitation at JoVE.com

Activating Molecules, Ions, and Solid Particles with Acoustic Cavitation

Acoustic cavitation in liquids submitted to power ultrasound creates transient extreme conditions inside the collapsing bubbles, which are the origin of unusual chemical reactivity and light emission, known as sonoluminescence. In the presence of noble gases, nonequilibrium plasma is formed. The "hot" particles and the photons generated by collapsing bubbles are able to excite species in solution.

The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic ...

activating-molecules-ions-and-solid-particles-with-acoustic-cavitation

Nanyang Technological University

Research

JoVE Journal

Chemistry

15.0K Views.  UMR 5257 CEA-CNRS-UM2-ENSCM. Acoustic cavitation in liquids submitted to power ultrasound creates transient extreme conditions inside the collapsing bubbles, which are the origin of unusual chemical reactivity and light emission, known as sonoluminescence. In the presence of noble gases, nonequilibrium plasma is formed. The "hot" particles and the photons generated by collapsing bubbles are able to excite species in solution.

Video: Activating Molecules, Ions, and Solid Particles with Acoustic Cavitation

Origami Inspired Self-assembly of Patterned and Reconfigurable Particles

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two dimensional (2D) structures. These technologies are mature, offer high precision and many of them can be implemented in a high-throughput manner. We leverage the advantages of planar lithography and combine them with self-folding methods1-20 wherein physical forces derived from surface tension or residual stress, are used to curve or fold planar structures into three dimensional (3D) structures. In doing so, we make it possible to mass produce precisely patterned static and reconfigurable particles that are challenging to synthesize.
In this paper, we detail visualized experimental protocols to create patterned particles, notably, (a) permanently bonded, hollow, polyhedra that self-assemble and self-seal due to the minimization of surface energy of liquefied hinges21-23 and (b) grippers that self-fold due to residual stress powered hinges24,25. The specific protocol described can be used to create particles with overall sizes ranging from the micrometer to the centimeter length scales. Further, arbitrary patterns can be defined on the surfaces of the particles of importance in colloidal science, electronics, optics and medicine. More generally, the concept of self-assembling mechanically rigid particles with self-sealing hinges is applicable, with some process modifications, to the creation of particles at even smaller, 100 nm length scales22, 26 and with a range of materials including metals21, semiconductors9 and polymers27. With respect to residual stress powered actuation of reconfigurable grasping devices, our specific protocol utilizes chromium hinges of relevance to devices with sizes ranging from 100 &mu;m to 2.5 mm. However, more generally, the concept of such tether-free residual stress powered actuation can be used with alternate high-stress materials such as heteroepitaxially deposited semiconductor films5,7 to possibly create even smaller nanoscale grasping devices.

We describe experimental details of the synthesis of patterned and reconfigurable particles from two dimensional (2D) precursors. This methodology can be used to create particles in a variety of shapes including polyhedra and grasping devices at length scales ranging from the micro to centimeter scale.

There are numerous techniques such as photolithography, electron-beam lithography and soft-lithography that can be used to precisely pattern two ...

Dynamic Electrochemical Measurement of Chloride Ions

This protocol describes the dynamic measurement of chloride ions using the transition time of a silver silver chloride (Ag/AgCl) electrode. Silver silver chloride electrode is used extensively for potentiometric measurement of chloride ions concentration in electrolyte. In this measurement, long-term and continuous monitoring is limited due to the inherent drift and the requirement of a stable reference electrode. We utilized the chronopotentiometric approach to minimize drift and avoid the use of a conventional reference electrode. A galvanostatic pulse is applied to an Ag/AgCl electrode which initiates a faradic reaction depleting the Cl&#713; ions near the electrode surface. The transition time, which is the time to completely deplete the ions near the electrode surface, is a function of the ion concentration, given by the Nernst equation. The square root of the transition time is in linear relation to the chloride ion concentration. Drift of the response over two weeks is negligible (59 &#181;M/day) when measuring 1 mM [Cl&#713;]using a current pulse of 10 Am-2. This is a dynamic measurement where the moment of transition time determines the response and thus is independent of the absolute potential. Any metal wire can be used as a pseudo-reference electrode, making this approach feasible for long-term measurement inside concrete structures.

Dynamic measurement of chloride ions is presented. Transition time of an Ag/AgCl electrode, during a chronopotentiometric technique, can give the concentration of chloride ions in electrolyte. This method does not require a stable conventional reference electrode.

This protocol describes the dynamic measurement of chloride ions using the transition time of a silver silver chloride (Ag/AgCl) electrode. Silver silver ...

X-ray Powder Diffraction in Conservation Science: Towards Routine Crystal Structure Determination of Corrosion Products on Heritage Art Objects

The crystal structure determination and refinement process of corrosion products on historic art objects using laboratory high-resolution X-ray powder diffraction (XRPD) is presented in detail via two case studies.
The first material under investigation was sodium copper formate hydroxide oxide hydrate, Cu4Na4O(HCOO)8(OH)2&#8729;4H2O (sample 1) which forms on soda glass/copper alloy composite historic objects (e.g., enamels) in museum collections, exposed to formaldehyde and formic acid emitted from wooden storage cabinets, adhesives, etc. This degradation phenomenon has recently been characterized as &#34;glass induced metal corrosion&#34;.
For the second case study, thecotrichite, Ca3(CH3COO)3Cl(NO3)2&#8729;6H2O (sample 2), was chosen, which is an efflorescent salt forming needlelike crystallites on tiles and limestone objects which are stored in wooden cabinets and display cases. In this case, the wood acts as source for acetic acid which reacts with soluble chloride and nitrate salts from the artifact or its environment.
The knowledge of the geometrical structure helps conservation science to better understand production and decay reactions and to allow for full quantitative analysis in the frequent case of mixtures.

Modern high resolution X-ray powder diffraction (XRPD) in the laboratory is used as an efficient tool to determine crystal structures of long-known corrosion products on historic objects.

The crystal structure determination and refinement process of corrosion products on historic art objects using laboratory high-resolution X-ray powder ...

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of Chalcogenidoplumbates(II or IV)

The phases of &#34;PbCh2&#34; (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica glass ampules). Reduction of such phases by elemental alkaline metals in amines affords crystalline chalcogenidoplumbate(II) salts comprised of [PbTe3]2- or [Pb2Ch3]2- anions, depending upon which sequestering agent for the cations is present: crown ethers, like 18-crown-6, or cryptands, like [2.2.2]crypt. Reactions of solutions of such anions with transition-metal compounds yield (poly-)chalcogenide anions or transition-metal chalcogenide clusters, including one with a &#181;-PbSe ligand (i.e., the heaviest-known CO homolog).
In contrast, the solid-state synthesis of a phase of the nominal composition &#34;K2PbSe2&#34; by successive reactions of the elements and by the subsequent solvothermal treatment in amines yields the first non-oxide/halide inorganic lead(IV) compound: a salt of the ortho-selenidoplumbate(IV) anion [PbSe4]4-. This was unexpected due to the redox potentials of Pb(IV) and Se(-II). Such methods can further be applied to other elemental combinations, leading to the formation of solutions with binary [HgTe2]2- or [BiSe3]3- anions, or to large-scale syntheses of K2Hg2Se3 or K3BiSe3 via the solid-state route.
All compounds are characterized by single-crystal X-ray diffraction and elemental analysis; solutions of plumbate salts can be investigated by 205Pb and 77Se or 127Te NMR techniques. Quantum chemical calculations using density functional theory methods enable energy comparisons. They further allow for insights into the electronic configuration and thus, the bonding situation. Molecular Rh-containing Chevrel-type compounds were found to exhibit delocalized mixed valence, whereas similar telluridopalladate anions are electron-precise; the cluster with the &#181;-PbSe ligand is energetically favored over a hypothetical CO analog, in line with the unsuccessful attempt at its synthesis. The stability of formal Pb(IV) within the [PbSe4]4- anion is mainly due to a suitable stabilization within the crystal lattice.

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of ChalcogenidoplumbatesII or IV

The synthesis of chalcogenidoplumbates(II,IV) via the in situ reduction of nominal "PbCh2" (Ch = Chalcogen) and via a solid-state reaction and subsequent solvothermal reactions is presented. Additionally, reactivities of plumbate(II) solutions are portrayed, which yield the heaviest-known CO homolog known to date: the &#181;-PbSe ligand.

The phases of &#34;PbCh2&#34; (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica ...

Measurement of Particle Size Distribution in Turbid Solutions by Dynamic Light Scattering Microscopy

A protocol for measuring polydispersity of concentrated polymer solutions using dynamic light scattering is described. Dynamic light scattering is a technique used to measure the size distribution of polymer solutions or colloidal particles. Although this technique is widely used for the assessment of polymer solutions, it is difficult to measure the particle size in concentrated solutions due to the multiple scattering effect or strong light absorption. Therefore, the concentrated solutions should be diluted before measurement. Implementation of the confocal optical component in a dynamic light scattering microscope1 helps to overcome this barrier. Using such a microscopic system, both transparent and turbid systems can be analyzed under the same experimental setup without a dilution. As a representative example, a size distribution measurement of a temperature-responsive polymer solution was performed. The sizes of the polymer chains in an aqueous solution were several tens of nanometers at a temperature below the lower critical solution temperature (LCST). In contrast, the sizes increased to more than 1.0 &#181;m when above the LCST. This result is consistent with the observation that the solution turned turbid above the LCST.

A protocol for the direct measurement of particle size distribution in concentrated solutions using dynamic light scattering microscopy is presented.

A protocol for measuring polydispersity of concentrated polymer solutions using dynamic light scattering is described. Dynamic light scattering is a ...

Facile Preparation of Ultrafine Aluminum Hydroxide Particles with or without Mesoporous MCM-41 in Ambient Environments

An aqueous suspension of nanogibbsite was synthesized via the titration of aluminum aqua acid [Al(H2O)6]3+ with L-arginine to pH 4.6. Since the hydrolysis of aqueous aluminum salts is known to produce a wide array of products with a wide range of size distributions, a variety of state-of-the-art instruments (i.e., 27Al/1H NMR, FTIR, ICP-OES, TEM-EDX, XPS, XRD, and BET) were used to characterize the synthesis products and identification of byproducts. The product, which was comprised of nanoparticles (10-30 nm), was isolated using gel permeation chromatography (GPC) column technique. Fourier transform infrared (FTIR) spectroscopy and powder X-ray diffraction (PXRD) identified the purified material as the gibbsite polymorph of aluminum hydroxide. The addition of inorganic salts (e.g., NaCl) induced electrostatic destabilization of the suspension, thereby agglomerating the nanoparticles to yield Al(OH)3 precipitate with large particle sizes. By utilizing the novel synthetic method described here, Al(OH)3 was partially loaded inside the highly ordered mesoporous framework of MCM-41, with average pore dimensions of 2.7 nm, producing an aluminosilicate material with both octahedral and tetrahedral Al (Oh/Td = 1.4). The total Al content, measured using energy-dispersive X-ray spectrometry (EDX), was 11% w/w with a Si/Al molar ratio of 2.9. A comparison of bulk EDX with surface X-ray photoelectron spectroscopy (XPS) elemental analysis provided insight into the distribution of Al within the aluminosilicate material. Furthermore, a higher ratio of Si/Al was observed on the external surface (3.6) as compared to the bulk (2.9). Approximations of O/Al ratios suggest a higher concentration of Al(O)3 and Al(O)4 groups near the core and external surface, respectively. The newly developed synthesis of Al-MCM-41 yields a relatively high Al content while maintaining the integrity of the ordered silica framework and can be used for applications where hydrated or anhydrous Al2O3 nanoparticles are advantageous.

An ultrafine aluminum hydroxide nanoparticle suspension was prepared via the controlled titration of [Al(H2O)]3+ with L-arginine to pH 4.6 with and without cage-effect confinement within mesoporous channels of MCM-41.

An aqueous suspension of nanogibbsite was synthesized via the titration of aluminum aqua acid [Al(H2O)6]3+ with L-arginine to pH 4.6. Since the hydrolysis ...

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles

Bicyclic aziridinium ions were generated by the removal of an appropriate leaving group through internal nucleophilic attack by nitrogen atom in the aziridine ring. The utility of bicyclic aziridinium ions, specifically 1-azoniabicyclo[3.1.0]hexane and 1-azoniabicyclo[4.1.0]heptane tosylate highlighted in the aziridine ring openings by the nucleophile with the release of the ring strain to yield the corresponding ring-expanded azaheterocycles such as pyrrolidine, piperidine and azepane with diverse substituents on the ring in regio- and stereospecific manner. Herein, we report a simple and convenient method for the preparation of the stable 1-azabicyclo[4.1.0]heptane tosylate followed by selective ring opening via a nucleophilic attack either at the bridge or at the bridgehead carbon to yield piperidine and azepane rings, respectively. This synthetic strategy allowed us to prepare biologically active natural products containing piperidine and azepane motif including sedamine, allosedamine, fagomine and balanol in highly efficient manner.

Bicyclic aziridinium ions such as 1-azoniabicyclo[4.1.0]heptane tosylate were generated from 2-[4-tolenesulfonyloxybutyl]aziridine, which was utilized for the preparation of substituted piperidines and azepanes via regio- and stereospecific ring-expansion with various nucleophiles. This highly efficient protocol allowed us to prepare diverse azaheterocycles including natural products such as fagomine, febrifugine analogue and balanol.

Bicyclic aziridinium ions were generated by the removal of an appropriate leaving group through internal nucleophilic attack by nitrogen atom in the ...

Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) with a 4.6 nm pore size, and ordered silica porous matrix, SBA-15, with a 5.3 nm pore size. This work describes the surface properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the differently ordered porous materials with similar pore sizes. For this purpose, OMC and SBA-15 with highly ordered nanoporous structures are synthesized via impregnation of the silica matrix by applying a carbon precursor and by the sol-gel method, respectively. The porous structure of investigated systems is characterized by an N2 adsorption-desorption analysis at 77 K. To determine the electrochemical character of the surface of synthesized materials, potentiometric titration measurements are conducted; the obtained results for OMC shows a significant pHpzc shift toward the higher values of pH, relative to SBA-15. This suggests that investigated OMC has surface properties related to oxygen-based functional groups. To describe the surface properties of the materials, the contact angles of liquids penetrating the studied porous beds are also determined. The capillary rise method has confirmed the increased wettability of the silica walls relative to the carbon walls and an influence of the pore roughness on the fluid/wall interactions, which is much more pronounced for silica than for carbon mesopores. We have also studied the melting behavior of D2O confined in OMC and SBA-15 by applying the dielectric method. The results show that the depression of the melting temperature of D2O in the pores of OMC is about 15 K higher relative to the depression of the melting temperature in SBA-15 pores with a comparable 5 nm size. This is caused by the influence of adsorbate/adsorbent interactions of the studied matrices.

Here we report the synthesis and characterization of ordered nanoporous carbon (with a 4.6 nm pore size) and SBA-15 (with a 5.3 nm pore size). The work describes the surface and textural properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the materials.

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) ...

Solid-phase Synthesis of [4.4] Spirocyclic Oximes

A convenient synthetic route for spirocyclic heterocycles is well sought after due to the molecule&#39;s potential use in biological systems. By means of solid-phase synthesis, regenerating Michael (REM) linker strategies, and 1,3-dipolar cycloaddition, a library of structurally similar heterocycles, both with and without a spirocyclic center, can be constructed. The main advantages of the solid-support synthesis are as follows: first, each reaction step can be driven to completion using a large excess of reagents resulting in high yields; next, the use of commercially available starting materials and reagents keep the costs low; finally, the reaction steps are easy to purify via simple filtration. The REM linker strategy is attractive because of its recyclability and traceless nature. Once a reaction scheme is completed, the linker can be reused multiple times. In a typical solid-phase synthesis, the product contains either a part of or the whole linker, which can prove undesirable. The REM linker is &#34;traceless&#34; and the point of attachment between the product and the polymer is indistinguishable. The high diastereoselectivity of the intramolecular 1,3-dipolar cycloaddition is well documented. Limited by the insolubility of the solid support, the reaction progression can only be monitored by a change in the functional groups (if any) via infrared (IR) spectroscopy. Thus, the structural identification of intermediates cannot be characterized by conventional nuclear magnetic resonance (NMR) spectroscopy. Other limitations to this method stem from the compatibilities of the polymer/linker to the desired chemical reaction scheme. Herein we report a protocol that allows for the convenient production of spirocyclic heterocycles that, with simple modifications, can be automated with high-throughput techniques.

Here we present a protocol to demonstrate an efficient method for the synthesis of spirocyclic heterocycles. The five-step process utilizes solid-phase synthesis and regenerating Michael linker strategies. Generally difficult to synthesize, we present a customizable method for the synthesis of spirocyclic molecules otherwise inaccessible to other modern approaches.

A convenient synthetic route for spirocyclic heterocycles is well sought after due to the molecule&#39;s potential use in biological systems. By means of ...

Stable DNA Motifs, 1D and 2D Nanostructures Constructed from Small Circular DNA Molecules

This article presents a detailed protocol for synthesis of small circular DNA molecules, annealing of circular DNA motifs, and construction of 1D and 2D DNA nanostructures. Over decades, the rapid development of DNA nanotechnology is attributed to the use of linear DNAs as the source materials. For example, the DAO (double crossover, antiparallel, odd half-turns) tile is well-known as a building block for construction of 2D DNA lattices; the core structure of DAO is made from two linear single-stranded (ss) oligonucleotides, like two ropes making a right hand granny&#160;knot. Herein, a new type of DNA tiles called cDAO (coupled DAO) are built using a small circular ss-DNA of c64nt or c84nt (circular 64 or 84 nucleotides) as the scaffold strand and several linear ss-DNAs as the staple strands. Perfect 1D and 2D nanostructures are assembled from cDAO tiles: infinite nanowires, nanospirals, nanotubes, nanoribbons; and finite nano-rectangles. Detailed protocols are described: 1) preparation by T4 ligase and purification by denaturing PAGE (polyacrylamide gel electrophoresis) of small circular oligonucleotides, 2) annealing of stable circular tiles, followed by native PAGE analysis, 3) assembling of infinite 1D nanowires, nanorings, nanospirals, infinite 2D lattices of nanotubes and nanoribbons, and finite 2D nano-rectangles, followed by AFM (Atomic Force Microscopy) imaging. The method is simple, robust, and affordable for most labs.

This article presents a detailed protocol for T4 ligation and denaturing PAGE purification of small circular DNA molecules, annealing and native PAGE analysis of circular tiles, assembling and AFM imaging of 1D and 2D DNA nanostructures, as well as agarose gel electrophoresis and centrifugation purification of finite DNA nanostructures.

This article presents a detailed protocol for synthesis of small circular DNA molecules, annealing of circular DNA motifs, and construction of 1D and 2D ...