This study was financially supported by Experimental Technology Innovation Foundation of Institute of Geology and Geophysics, Chinese Academy of Sciences (No. 11890940), and China Ocean Mineral Resources R &#38; D Association Project (No. DY135-S2-2-07).

1. Preparing the sample, reagents, and containers
<ol>
	<li>Clean the fume hood, hotplate and the balance room bench for the chemical experiment with sprayed alcohol or ultrapure water.</li>
	<li>Prepare sub-boiled acids (2 M HCl, 8 M HCl, 7 M HNO3, and 14 M HNO3), clean beakers and any apparatus before sample processed. 
	NOTE: Sulfide samples presented in this study were collected from newly discovered hydrothermal zones in the South Atlantic. Approximately 60 mg of powdered sample was used in this process. Sample was collected into glass vials and put in the sample storage cabinet.</li>
</ol>
2. Weigh the samples
<ol>
	<li>Prepare cleaned 30 mL perfluoroalkoxy (PFA) beakers. Label twice outside the beaker (to prevent erasure).</li>
	<li>Weigh the blank beakers. 
	NOTE: The balance used is accurate to &#177;0.0001 g provided that all the vessels have had their static electricity completely removed.</li>
	<li>Read the weight and record it.</li>
	<li>Pour the sample into the beaker. Cover with a lid and weigh the samples. 
	NOTE: Sample weight depends on the 230Th content. 230Th level varies with the U concentration and age of the sample. In general, a total of 100 ng of total U is sufficient for the sample.</li>
	<li>Add some (~1 mL) ultrapure water using a bottle, rinse the inner wall and shake the beaker carefully. 
	NOTE: Add enough ultrapure water cover all the samples.</li>
</ol>
3. Dissolve and spike the sample
<ol>
	<li>Place the sample-containing beaker in the fume hood.</li>
	<li>Open the beaker lid. Add 3 mL of HNO3 (14 M) or aqua regia into the sample using a pipette.</li>
	<li>Place the beaker on the hotplate, set the hotplate temperature to 170 &#176;C and dissolve the sample completely. 
	NOTE: If there are still insoluble substances in the solution, add 12 M HCl, 22.6 M HF and 10.6 M HClO4, and use a pressurized closed tank to ensure complete dissolution of samples.</li>
	<li>Leave the solution to cool for at least 30 min. Add 0.1&#8211;0.3 g 229Th-233U-236U spike solution of known activity into the solution. 
	NOTE: Generally, the optimal ratio of 235U/233U is ~10&#8211;20:1 in the mixed solution.</li>
	<li>Place the solution onto the hotplate, set the temperature to 170 &#176;C and leave it on the hotplate until it dries. 
	NOTE: Evaporation must be done slowly when the sample approaches dryness.</li>
	<li>Dissolve the sample in 2 drops of HNO3 (0.04 mL, 14 M), and dry it on the hotplate at 170 &#176;C again.</li>
</ol>
4. Ferric hydroxide co-precipitation for U-Th
<ol>
	<li>Prepare cleaned 15 mL centrifuge tubes, label and place them in the tube stand. 
	NOTE: Add approximately 10 mg of Fe(III) (FeCl3 in 12 M HCl) into the centrifugal tube carefully if samples contain almost no Fe.</li>
	<li>Add several drops (0.1 mL) of 2 M HCl into the beaker. Shake the beaker gently and dissolve the sample completely.</li>
	<li>Transfer each sample into a centrifuge tube.</li>
	<li>Add several drops of ammonia (~0.1 mL) until the acid is neutralized; when pH is 7&#8211;8, a reddish-brown precipitate appears. U and Th isotopes are precipitated by the Fe(OH)3. 
	NOTE: The clear solution contains unwanted ions such as metal-elements, Mg2+, NO3- and NH4OH.</li>
	<li>Cap the centrifuge tubes. Centrifuge at 2,340 x g for 7 min. Discard the supernatant</li>
	<li>Add some ultrapure water to wash the precipitate. Centrifuge as above and repeat this step twice more.</li>
	<li>Dissolve the precipitate with 1.5 mL of 7 M HNO3. Transfer it into the corresponding beaker.</li>
	<li>Add 1 drop of HClO4 (to remove organic matter), and dry it on the hotplate at 170 &#176;C for about 30 min.</li>
</ol>
5. Preparation of anion exchange column
<ol>
	<li>Prepare small polytetrafluoroethylene (PTFE) columns (~2.5 mL column size) as shown in Figure 1; insert the frit into each column slowly at the bottom on the bench.</li>
	<li>Pipet cleaned anion-exchange resins into the columns. Put the columns on the holder.</li>
	<li>Fill the whole column with ultrapure water. Add 1 drop of 14 M HNO3. 
	NOTE: This step is performed in order mainly to remove the trace elements in the column.</li>
	<li>Add 2 column volumes (CV) of 7 M HNO3 to remove the trace elements. Then repeat this step.</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/59098/59098fig1.jpg" /> 
Figure 1: Ion-exchange column filling with anionic exchange resin. <a href="https://www.jove.com/files/ftp_upload/59098/59098fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
6. Purification and separation of U and Th fractions
<ol>
	<li>Dissolve the sample in 0.5 mL of 7 M HNO3. Load it onto the column carefully.</li>
	<li>Let it drip across the column into the waste beaker.</li>
	<li>Add 2 CV and 1 CV of 7 M HNO3 successively into the column. Iron and other metal-elements in the sample are removed while U and Th are retained by the resin in this step.</li>
	<li>Add 2 CV and 1 CV of 8 M HCl into the column successively to elute thorium fraction. Collect the thorium fraction using a 7 mL capacity cleaned PFA beaker. Add 1 drop of HClO4 into the beaker and dry the fraction on a hotplate at 170 &#176;C for about 30 min.</li>
	<li>Elute uranium fraction from the resin with 2 CV of 0.1 M HNO3 twice. Collect the eluate in the cleaned PFA beaker. Add 1 drop of HClO4 and dry it on the hotplate at 170 &#176;C for about 30 min.</li>
	<li>Prepare and label 2 mL capacity vials.</li>
	<li>Dissolve each sample in 1 drop HNO3 and dry it on the hotplate at 170 &#176;C for less than 5 min until 0.5 drop is left. Transfer them along with 0.2 mL of 2% HNO3 + 0.1% HF into the corresponding vials for instrument measurement.</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/59098/59098fig2.jpg" /> 
Figure 2: Uranium and thorium fractions of the submarine hydrothermal sulfides. <a href="https://www.jove.com/files/ftp_upload/59098/59098fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
7. MC-ICPMS measurement
<ol>
	<li>Measure the U and Th fractions collected through the above chemical purification process using a high-resolution MC-ICPMS instrument. 
	NOTE: U and Th isotopic ratios can be obtained by using the instrument by applying secondary electron multiplier (SEM)21 technique. The instrument parameters13 are listed in Table 1. Thorium age was calculated using the following equation: 
	<img alt="Equation 1" src="/files/ftp_upload/59098/59098eq1.jpg" /> 
	Initial ratio of 234U to 238U was measured as follows: 
	<img alt="Equation 2" src="/files/ftp_upload/59098/59098eq2.jpg" /></li>
</ol>

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Instrument</td>
			<td>Parameter</td>
			<td>Value</td>
		</tr>
		<tr>
			<td rowspan="5">MC-ICPMS</td>
			<td>RF power</td>
			<td>1325 W</td>
		</tr>
		<tr>
			<td>Cool gas</td>
			<td>16.00 L min-1</td>
		</tr>
		<tr>
			<td>Auxiliary gas</td>
			<td>1.78 L min-1</td>
		</tr>
		<tr>
			<td>Sample gas</td>
			<td>1.00 L min-1</td>
		</tr>
		<tr>
			<td>Low resolution</td>
			<td>300~400</td>
		</tr>
		<tr>
			<td rowspan="5">CETAC Aridus II</td>
			<td>Sample injection rate</td>
			<td>50~60 &#956;L min-1</td>
		</tr>
		<tr>
			<td>Ar Sweep Gas</td>
			<td>2~5 L min-1</td>
		</tr>
		<tr>
			<td>Nitrogen Gas</td>
			<td>2~10 mL min-1</td>
		</tr>
		<tr>
			<td>Spray Chamber Temperature</td>
			<td>110 &#176;C</td>
		</tr>
		<tr>
			<td>Membrane Oven Temperature</td>
			<td>160 &#176;C</td>
		</tr>
	</tbody>
</table>
Table 1: Instrument parameters for measuring U-Th isotopes by MC-ICPMS (using the instrument listed in the Table of Materials).

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L., Brichet, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Actinide-series+disequilibrium+as+a+tool+to+establish+the+chronology+of+deep-sea+hydrothermal+activity.">Actinide-series disequilibrium as a tool to establish the chronology of deep-sea hydrothermal activity.</a> Geochimica et Cosmochimica Acta. 57 (6), 1221-1231 (1993).</li><li>Lalou, C., 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=New+age+data+for+Mid-Atlantic+Ridge+hydrothermal+sites:+TAG+and+Snakepit+chronology+revisited.">New age data for Mid-Atlantic Ridge hydrothermal sites: TAG and Snakepit chronology revisited.</a> Journal of Geophysical Research. 98, 9705-9713 (1993).</li><li>Lalou, C., Reyss, J. L., Brichet, E., Rona, P. 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L., Chen, J. H., Ku, T. -. L., Wasserburg, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precise+timing+of+the+last+interglacial+period+from+mass+spectrometric+analysis+of+230Th+in+corals.">Precise timing of the last interglacial period from mass spectrometric analysis of 230Th in corals.</a> Science. 236 (4808), 1537-1553 (1987).</li><li>Edwards, R. L., Taylor, F. W., Wasserburg, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dating+earthquakes+with+high+precision+thorium-230+ages+of+very+young+corals+[J].">Dating earthquakes with high precision thorium-230 ages of very young corals [J].</a> Earth and Planetary Science Letters. 90 (4), 371-381 (1988).</li><li>Hai, C., Jess, A., Edwards, R. L., Boyle, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=U-Th+dating+of+deep-sea+corals.">U-Th dating of deep-sea corals.</a> Geochimica et Cosmochimica Acta. 64 (14), 2401-2416 (2000).</li><li>Ishibashi, J., 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=Dating+of+Hydrothermal+Mineralization+in+Active+Hydrothermal+Fields+in+the+Southern+Mariana+Trough.">Dating of Hydrothermal Mineralization in Active Hydrothermal Fields in the Southern Mariana Trough.</a> Subseafloor Biosphere Linked to Hydrothermal Systems. , 289-300 (2015).</li><li>Jaffey, A. H., Flynn, K. F., Glendenin, L. E., Bentley, W. C., Essling, A. 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Authors have nothing to disclose.

Some critical steps must be followed to ensure success of this protocol. Ensure that all operations are carried out in clean chemistry room under fume hood with clean air circulation. Purify all regents in this process in advance and clean the apparatus before use. Dissolve the samples completely in the process of making the 7 M HNO3 solution which is then loaded onto the 7 M HNO3-conditioned resins. If there is any insoluble substance in the sample, it will be redissolved after drying. Additional i...

Submarine hydrothermal sulfides have been a steady source of metals like iron, copper, zinc and lead. They are also seen as economically viable resources of silver and gold. The location and size of the deposits are a record of the history of hydrothermal venting on the seafloor. Dating of a hydrothermal sulfide can provide important information regarding the formation and alteration mechanism of the sulfide ore deposit, seafloor hydrothermal activity history, and growth rate of large sulfide deposits1,2,3. 238U-234U-230Th disequilibrium dating is an effective isotopic method of age estimation for hydrothermal sulfides4,5,6,7,8,9,10,11,12, where the purification and separation of U and Th isotopes is necessary. This text describes a protocol for U and Th isotopes separation and 230Th-U dating of sulfides sample by MC-ICPMS.
Geological materials which contain U and Th remain undisturbed for several million years, and a state of secular equilibrium between all the nuclides in the radioactive series is established. However, a combination of chemical solubility and nuclear recoil factors often create disequilibrium, in which the members of the decay series are separated from each other through processes such as deposition, transport and weathering. For example, when a sulfide deposit is formed, the state of 238U, 234U and 230Th is of disequilibrium, and the long-lived 238U can decay gradually towards short-lived 234U and 230Th subsequently. Assuming (i) the system remains closed with respect to U and Th isotopes, and (ii) initial amount of 230Th and 232Th incorporated into sulfide samples is zero, it is possible to determine the time of deposition by measuring the present-day activity ratios of 230Th/238U and 234U/238U. However, the initial amount of Th is not zero in the sample, and we assume the initial 230Th/232Th atomic ratio is 4.4 &#177; 2.2 x 10-6. The applicable dating range of this method is approximately ~10-6 x 105 years13,14. However, the large difference between the abundance of uranium and thorium makes measurement challenging. Hence, it is very important to establish a chemical procedure for U-Th dating by MC-ICPMS.
In the past 30 years, most studies focused more measurements of carbonate materials14,15,16,17 and less on sulfide deposits11,12,18,19. Alpha-particle counting methods have traditionally been used for the study of 230Th/238U disequilibrium of submarine hydrothermal sulfides1. However, analytical uncertainty of 5-17% is a limiting factor that affects the precision of age determination of sulfides1,8,9. These techniques generally suffer from the use of relatively large columns and reagent volumes and the need for multiple column passes for purification and separation U-Th from a sample. Recent developments in MC-ICPMS have greatly improved the precision of U-Th isotopic measurements (&#60;5&#8240; for ages)14 and have significantly reduced the sample size (&#60;0.2 g) required for analysis. In these works, many chemical separation procedures have been developed, and have achieved excellent chemical yields with low chemical background12,13.
Here we present a chemical-based protocol to obtain samples that are sufficiently clean for MC-ICPMS analysis. It is suitable for the dating of hydrothermal sulfide samples of age &#60;6 x 105 years14. With this technique, the separated U and Th isotopic fractions can meet measuring requirements by MC-ICPMS. The age of the hydrothermal sulfide sample can be calculated from the extent of disequilibria between 230Th and 234U and between 234U and 238U by using the described activity decay equation.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>AG 1-X8 anion-exchange resin</td>
			<td>BIO-RAD</td>
			<td>140-1441</td>
			<td>Separating rare elements</td>
		</tr>
		<tr>
			<td>Ammonia solution</td>
			<td>Kanto Chemical CO., INC.</td>
			<td>1336-21-6</td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Glass vials</td>
			<td>BOTEX</td>
			<td>None</td>
			<td>Sample collection</td>
		</tr>
		<tr>
			<td>Hydrochloric acid</td>
			<td>Sinopharem chemical reagent Co. Ltd</td>
			<td>7647-01-0</td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Hydrofluoric acid</td>
			<td>EMD Millipore CO.</td>
			<td>7664-39-5</td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Neptune Plus</td>
			<td>Thermo Fisher Scientific CO.</td>
			<td>None</td>
			<td>Apparatus</td>
		</tr>
		<tr>
			<td>Nitric acid</td>
			<td>Sinopharem chemical reagent Co. Ltd</td>
			<td>7697-37-2</td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Perchloric acid</td>
			<td>Kanto Chemical CO., INC.</td>
			<td>32059-1B</td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Ultrapure water</td>
			<td>Merck Millipore</td>
			<td>None</td>
			<td>Producted by Mill-Q Advantage systerm</td>
		</tr>
		<tr>
			<td>Wipe paper</td>
			<td>Kimberley-Clark</td>
			<td>0123-12</td>
			<td>Wipe and clean</td>
		</tr>
		<tr>
			<td>2 ml vial</td>
			<td>Nelgene</td>
			<td>5000-0020</td>
			<td>Sample collection</td>
		</tr>
		<tr>
			<td>229Th-233U-236U spike</td>
			<td>None</td>
			<td>None</td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>7 ml PFA beaker</td>
			<td>Savillex</td>
			<td>200-007-20</td>
			<td>Sample treatment</td>
		</tr>
		<tr>
			<td>10 ml centrifuge</td>
			<td>Nelgene</td>
			<td>3110-1000</td>
			<td>Sample treatment</td>
		</tr>
		<tr>
			<td>30 ml PFA beaker</td>
			<td>Savillex</td>
			<td>200-007-20</td>
			<td>Sample treatment</td>
		</tr>
	</tbody>
</table>

separation of uranium and thorium for 230th-u dating of submarine hydrothermal sulfides

The age of a submarine hydrothermal sulfide is a significant index for estimating the size of hydrothermal ore deposits. Uranium and thorium isotopes in the samples can be separated for 230Th-U dating. This article presents a method to purify and separate U and Th isotopes in submarine hydrothermal sulfide samples. Following this technique, the separated U and Th fractions can meet measuring requirements by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS). The age of the hydrothermal sulfide sample can be calculated by measuring the present-day activity ratios of 230Th/238U and 234U/238U. A super clean room is necessary for this experiment. Cleaned regents and supplies are used to reduce the contamination during the sample processes. Balance, hotplate, and centrifuge are also used. The sulfide sample is powdered for analysis and less than 0.2 g sample is used. Briefly, the sample is weighed, dissolved, added to 229Th-233U-236U double spike solution, Fe co-precipitated, and separated on an anion-exchange resin extraction column. Approximately 50 ng U is consumed for 230Th-U dating of sulfides sample by MC-ICPMS.

Using this procure, a submarine hydrothermal sulfide sample can be completely dissolved. Following this protocol, the Th fraction was eluted from the hydrothermal sulfide sample using 8 M HCl. Meanwhile, the U fraction of the hydrothermal sulfide sample was eluted with 0.1 M HNO3. U and Th fractions were dissolved in the 2% HNO3 (+0.1% HF) solution (see Figure 2) and stored in 2 mL capacity vials. The mixture was then analyzed by MC-ICPMS.
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Separation of Uranium and Thorium for 230Th-U Dating of Submarine Hydrothermal Sulfides

The protocol describes a method to purify and separate the U and Th nuclide in submarine hydrothermal sulfide sample with Fe co-precipitation and extraction chromatography for 230Th-U disequilibrium dating.

Separation of Uranium and Thorium for 230Th-U Dating of Submarine Hydrothermal Sulfides

The age of a submarine hydrothermal sulfide is a significant index for estimating the size of hydrothermal ore deposits. Uranium and thorium isotopes in ...

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6.4K Views.  Chinese Academy of Sciences. The protocol describes a method to purify and separate the U and Th nuclide in submarine hydrothermal sulfide sample with Fe co-precipitation and extraction chromatography for 230Th-U disequilibrium dating.

Video: Separation of Uranium and Thorium for 230Th-U Dating of Submarine Hydrothermal Sulfides

Formation of Ordered Biomolecular Structures by the Self-assembly of Short Peptides

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control self-assembly and mimicking this process in vitro will bring about major advances in the areas of materials science and nanotechnology. Among the available biological building blocks, peptides have several advantages as they present substantial diversity, their synthesis in large scale is straightforward, and they can easily be modified with biological and chemical entities1,2. Several classes of designed peptides such as cyclic peptides, amphiphile peptides and peptide-conjugates self-assemble into ordered structures in solution. Homoaromatic dipeptides, are a class of short self-assembled peptides that contain all the molecular information needed to form ordered structures such as nanotubes, spheres and fibrils3-8. A large variety of these peptides is commercially available.
This paper presents a procedure that leads to the formation of ordered structures by the self-assembly of homoaromatic peptides. The protocol requires only commercial reagents and basic laboratory equipment. In addition, the paper describes some of the methods available for the characterization of peptide-based assemblies. These methods include electron and atomic force microscopy and Fourier-Transform Infrared Spectroscopy (FT-IR). Moreover, the manuscript demonstrates the blending of peptides (coassembly) and the formation of a &#34;beads on a string&#34;-like structure by this process.9 The protocols presented here can be adapted to other classes of peptides or biological building blocks and can potentially lead to the discovery of new peptide-based structures and to better control of their assembly.

This paper describes the formation of highly ordered peptide-based structures by the spontaneous process of self-assembly. The method utilizes commercially available peptides and common lab equipment. This technique can be applied to a large variety of peptides and may lead to the discovery of new peptide-based assemblies.

In nature, complex functional structures are formed by the self-assembly of biomolecules under mild conditions. Understanding the forces that control ...

Optimization of Synthetic Proteins: Identification of Interpositional Dependencies Indicating Structurally and/or Functionally Linked Residues

Protein alignments are commonly used to evaluate the similarity of protein residues, and the derived consensus sequence used for identifying functional units (e.g., domains). Traditional consensus-building models fail to account for interpositional dependencies &#8211; functionally required covariation of residues that tend to appear simultaneously throughout evolution and across the phylogentic tree. These relationships can reveal important clues about the processes of protein folding, thermostability, and the formation of functional sites, which in turn can be used to inform the engineering of synthetic proteins. Unfortunately, these relationships essentially form sub-motifs which cannot be predicted by simple &#8220;majority rule&#8221; or even HMM-based consensus models, and the result can be a biologically invalid &#8220;consensus&#8221; which is not only never seen in nature but is less viable than any extant protein. We have developed a visual analytics tool, StickWRLD, which creates an interactive 3D representation of a protein alignment and clearly displays covarying residues. The user has the ability to pan and zoom, as well as dynamically change the statistical threshold underlying the identification of covariants. StickWRLD has previously been successfully used to identify functionally-required covarying residues in proteins such as Adenylate Kinase and in DNA sequences such as endonuclease target sites.

Synthetic protein sequences based on consensus motifs typically ignore co-evolving residues, that imply interpositional dependencies (IPDs). IPDs can be essential to activity, and designs that disregard them may result in suboptimal results. This protocol uses StickWRLD to identify IPDs and help inform rational protein design, resulting in more efficient results.

Protein alignments are commonly used to evaluate the similarity of protein residues, and the derived consensus sequence used for identifying functional ...

Chemical Gardens as Flow-through Reactors Simulating Natural Hydrothermal Systems

Here we report experimental simulations of hydrothermal chimney growth using injection chemical garden methods. The versatility of this type of experiment allows for testing of various proposed ocean / hydrothermal fluid chemistries that could have driven reactions toward the origin of life in environments on the early Earth, early Mars, or even other worlds such as the icy moons of the outer planets. We show experiments that include growth of chemical garden structures under anoxic conditions simulating the early Earth, inclusion of trace components of phosphates / organics in the injection solution to incorporate them into the structure, a switch of the injection solution to introduce a secondary precipitating anion, and the measurement of membrane potentials generated by chemical gardens. Using this method, self-assembling chemical garden structures were formed that mimic the natural chimneys precipitated at submarine hydrothermal springs, and these precipitates can be used successfully as flow-through reactors by feeding through multiple successive &#8220;hydrothermal&#8221; injections.

We describe chemical garden formation via injection experiments that allow for laboratory simulations of natural chemical garden systems that form at submarine hydrothermal vents.

Here we report experimental simulations of hydrothermal chimney growth using injection chemical garden methods. The versatility of this type of experiment ...

Preparation of Biopolymer Aerogels Using Green Solvents

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers (gelatin, agar, cellulose), only recently have biomasses been recognized as an abundant source of chemically diverse macromolecules for functional aerogel materials. Biopolymer aerogels (pectin, alginate, chitosan, cellulose, etc.) exhibit both specific inheritable functions of starting biopolymers and distinctive features of aerogels (80-99% porosity and specific surface up to 800 m2/g). This synergy of properties makes biopolymer aerogels promising candidates for a wide gamut of applications such as thermal insulation, tissue engineering and regenerative medicine, drug delivery systems, functional foods, catalysts, adsorbents and sensors. This work demonstrates the use of pressurized carbon dioxide (5 MPa) for the ionic cross linking of amidated pectin into hydrogels. Initially a biopolymer/salt dispersion is prepared in water. Under pressurized CO2 conditions, the pH of the biopolymer solution is lowered to 3 which releases the crosslinking cations from the salt to bind with the biopolymer yielding hydrogels. Solvent exchange to ethanol and further supercritical CO2 drying (10 - 12 MPa) yield aerogels. Obtained aerogels are ultra-porous with low density (as low as 0.02 g/cm3), high specific surface area (350 - 500 m2/g) and pore volume (3 - 7 cm3/g for pore sizes less than 150 nm).

A new way for the production of biopolymer-based aerogels by carbon dioxide (CO2) induced gelation is shown. The technique utilizes pressurized carbon dioxide (5 MPa) for the production of biopolymer hydrogels and supercritical CO2 (12 MPa) to convert gels into aerogels. The only solvents needed besides CO2 are water and ethanol.

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers ...

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, 1,4-benzene-bis(iminoguanidinium) (BBIG), is demonstrated. The ligand is synthesized as the chloride salt (BBIG-Cl) by in situ imine condensation of terephthalaldehyde with aminoguanidinium chloride in water, followed by crystallization as the sulfate salt (BBIG-SO4). Alternatively, BBIG-Cl is synthesized ex situ in larger scale from ethanol. The sulfate separation ability of the BBIG ligand is demonstrated by selective and quantitative crystallization of sulfate from seawater. The ligand can be recycled by neutralization of BBIG-SO4 with aqueous NaOH and crystallization of the neutral bis-iminoguanidine, which can be converted back into BBIG-Cl with aqueous HCl and reused in another separation cycle. Finally, 35S-labeled sulfate and &#946; liquid scintillation counting are employed for monitoring the sulfate concentration in solution. Overall, this protocol will instruct the user in the necessary skills to synthesize a ligand, employ it in the selective crystallization of sulfate from aqueous solutions, and quantify the separation efficiency.

A protocol for in situ aqueous synthesis of a bis(iminoguanidinium) ligand and its utilization in selective separation of sulfate is presented.

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, ...

Capillary Electrophoresis to Monitor Peptide Grafting onto Chitosan Films in Real Time

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. Compared to other analytical separation techniques, such as chromatography, CE is cheap, robust and effectively requires no sample preparation (for a number of complex natural matrices or polymeric samples). CE is fast and can be used to follow the evolution of mixtures in real time (e.g., chemical reaction kinetics), as the signals observed for the separated compounds are directly proportional to their quantity in solution.
Here, the efficiency of CE is demonstrated for monitoring the covalent grafting of peptides onto chitosan films for subsequent biomedical applications. Chitosan&#39;s antimicrobial and biocompatible properties make it an attractive material for biomedical applications such as cell growth substrates. Covalently grafting the peptide RGDS (arginine - glycine - aspartic acid - serine) onto the surface of chitosan films aims at improving cell attachment. Historically, chromatography and amino acid analysis have been used to provide a direct measurement of the amount of grafted peptide. However, the fast separation and absence of sample preparation provided by CE enables equally accurate yet real-time monitoring of the peptide grafting process. CE is able to separate and quantify the different components of the reaction mixture: the (non-grafted) peptide and the chemical coupling agents. In this way the use of CE results in improved films for downstream applications.
The chitosan films were characterized through solid-state NMR (nuclear magnetic resonance) spectroscopy. This technique is more time-consuming and cannot be applied in real time, but yields a direct measurement of the peptide and thus validates the CE technique.

Free solution capillary electrophoresis is a fast, cheap and robust analytical method that enables the quantitative monitoring of chemical reactions in real time. Its utility for rapid, convenient and precise analysis is demonstrated here through analysis of covalent peptide grafting onto chitosan films for improved cell adhesion.

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C60 molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C60/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C60 deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C60 chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C60 molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C60 chain structures to a hexagonal close packed quasi-1D stripe structure.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

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 ...

Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol

The purification of organic compounds is an essential component of routine synthetic operations. The ability to remove contaminants into an aqueous layer by generating a charged structure provides an opportunity to use extraction as a simple purification technique. By combining the use of a miscible organic solvent with saturated sodium bisulfite, aldehydes and reactive ketones can be successfully transformed into charged bisulfite adducts that can then be separated from other organic components of a mixture by the introduction of an immiscible organic layer. Here, we describe a simple protocol for the removal of aldehydes, including sterically-hindered neopentyl aldehydes and some ketones, from chemical mixtures. Ketones can be separated if they are sterically unhindered cyclic or methyl ketones. For aliphatic aldehydes and ketones, dimethylformamide is used as the miscible solvent to improve removal rates. The bisulfite addition reaction can be reversed by basification of the aqueous layer, allowing for the re-isolation of the reactive carbonyl component of a mixture.

Here, we present a protocol to remove aldehydes and reactive ketones from mixtures by a liquid-liquid extraction protocol directly with saturated sodium bisulfite in a miscible solvent. This combined protocol is rapid and facile to perform. The aldehyde or ketone can be re-isolated by the basification of the aqueous layer.

The purification of organic compounds is an essential component of routine synthetic operations. The ability to remove contaminants into an aqueous layer ...

Automated 90Sr Separation and Preconcentration in a Lab-on-Valve System at Ppq Level

A quick, automated and portable system for the separation and determination of radiostrontium in aqueous samples, using Sr-resin and multi sequential flow injection analysis, has been developed. The concentrations of radioactive strontium were determined by flow scintillation counting, allowing for on-line and also on-site determination. The proposed system can determine radioactive strontium at industrial relevant levels without further modification using overall analysis time of less than 10 min per aqueous sample. The limit of the detection is 320 fg&#183;g-1 (1.7 Bq/g).

Automated 90Sr Separation and Preconcentration in a Lab-on-Valve System at Ppq Level

Here, we present the portable autoRAD platform for quick radiometric separation and determination of 90Sr, an important fission product highly pertinent to nuclear waste.

A quick, automated and portable system for the separation and determination of radiostrontium in aqueous samples, using Sr-resin and multi sequential flow ...