Name: surface properties of synthesized nanoporous carbon and silica matrices
Uploaded: 2019-03-27T14:00:00.000+00:00
Duration: 9 min 31 s
Description: Watch this Scientific Journal Video about Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices at JoVE.com

The authors would like to thank the National Center of Science for providing financial support with grant no. DEC-2013/09/B/ST4/03711 and UMO-2016/22/ST4/00092. The authors are also grateful for the partial support from the Poland Operational Program Human Capital PO KL 4.1.1, as well as from the National Centre for Research and Development, under research grant no. PBS1/A9/13/2012. The authors are especially grateful for Prof. L. Ho&#322;ysz from Interfacial Phenomena Division, Faculty of Chemistry, Maria Curie-Sk&#322;odowska University, Lublin, Poland, for her kindness and enabling the measurements of the wettability in the SBA-15 nanopores.

1. Preparation of the OMC Materials
<ol>
	<li>Synthesis of a silica matrix as OMC precursor
	<ol>
		<li>Prepare 360 mL of 1.6 M HCl by adding 50 mL of HCl (36% - 38%) in a 500 mL round-bottom flask and, then, adding 310 mL of ultrapure water (resistivity of 18.2 M&#937;&#183;cm).</li>
		<li>To that, add 10 g of PE 10500 polymer (6.500 g/mol).</li>
		<li>Place the flask in an ultrasonic bath. Heat the solution to 35 &#176;C and stir it until the solid polymer is completely dissolved, making a homogeneous mixture.</li>
		<li>Add 10 g of 1,3,5-trimethylbenzene to the flask and stir the content (at a stirring rate of 220 rpm) by maintaining it at 35 &#176;C in the water bath.</li>
		<li>After stirring for 30 min, add 34 g of tetraethyl orthosilicate (TEOS) to the flask. Add the TEOS slowly and dropwise with constant stirring. Ensure that it takes 10 min to add 34 g of TEOS.</li>
		<li>Stir the solution mixture again for 20 h at the same temperature (35 &#176;C).</li>
		<li>Transfer the contents of the flask into a polytetrafluoroethylene cartridge and place it in an autoclave. Leave the solution for 24 h at 90 &#176;C.</li>
		<li>Filter the resulting precipitate, using a B&#252;chner funnel, and wash it with distilled water, using at least 1 L.</li>
		<li>Dry the obtained solid at room temperature and apply a thermal treatment to the sample at 500 &#176;C, using a muffle furnace in an air atmosphere for 6 h.</li>
	</ol>
	</li>
	<li>Impregnation of the resulting silica matrix, using a carbon precursor
	<ol>
		<li>Prepare impregnation solutions (IS1 and IS2) with appropriate proportions of water, 3 M sulfuric acid (VI), and sugar (glucose), where glucose plays the role of carbon precursor and sulfuric acid acts as catalyst. 
		CAUTION: Sulfuric acid is very toxic, it causes severe skin burns and eye damage.
		<ol>
			<li>Prepare IS1. For each gram of silica, mix 5 g of water, 0.14 g of 3 M sulfuric acid (VI), and 1.25 g of sugar.</li>
			<li>Prepare IS2. For each gram of silica, mix 5 g of water, 0.08 g of 3 M sulfuric acid (VI), and 0.75 g of sugar.</li>
		</ol>
		</li>
		<li>Place the silica material (1 g) and the prepared solution IS1 of the carbon precursor and the catalyst in a 500 mL flask. Heat the mixture in a vacuum dryer at 100 &#176;C for 6 h. 
		NOTE: In this step, use only IS1. IS2 should be applied in the next step.</li>
		<li>Add the IS2 to the mixture in the vacuum dryer (to the solution with the partially carbonized carbon precursor). Heat the mixture again in the vacuum dryer at 160 &#176;C for 12 h.</li>
	</ol>
	</li>
	<li>Tempering/carbonization
	<ol>
		<li>Transfer the obtained composite to a mortar for the fragmentation of the larger particles and a homogenization of the material.</li>
		<li>Place the obtained product into the flow furnace and heat it to 700 &#176;C (at a heating rate of 2.5 &#176;C/min) and heat for 6 h at this temperature. Heat the material in a nitrogen atmosphere.</li>
		<li>Allow the solution to cool before opening the furnace.</li>
	</ol>
	</li>
	<li>Removal of the silica matrix by etching
	<ol>
		<li>Prepare 100 mL of etching solution (ES). Mix 50 mL of 95% ethyl alcohol and 50 mL of water. Add 7 g of potassium hydroxide and stir until it is dissolved.</li>
		<li>Place all obtained carbonized material (at least 1 g) in a 250 mL round-bottom flask and add 100 mL of ES.</li>
		<li>Supply the system with a reflux condenser and magnetic stirrer and heat to a boil while stirring constantly. Boil the mixture for 1 h.</li>
		<li>Transfer the obtained material to the B&#252;chner funnel, wash it with at least 4 L of distilled water, and dry it.</li>
	</ol>
	</li>
</ol>
2. Preparation of the Silica SBA-15 Matrix
<ol>
	<li>Synthesize a silica matrix.
	<ol>
		<li>Prepare 150 mL of 1.6 M HCl.</li>
		<li>Dissolve 4 g of PE 6400 polymer (EO13PO70EO13) in 150 mL of acid solution in a round-bottom flask.</li>
		<li>Place the flask in an ultrasonic bath. Heat the solution to 40 &#176;C and stir it so that the polymer can dissolve (at least for 30 min).</li>
		<li>Slowly add 8.5 g of TEOS to the flask, dropwise, with constant stirring. Stir the solution mixture for 24 h at the same temperature (40 &#176;C).</li>
		<li>Transfer the contents of the flask to a polytetrafluoroethylene cartridge. Leave the solution for 24 h in a 120 &#176;C oven.</li>
		<li>Filter the resulting precipitate, using a B&#252;chner funnel, and wash it with distilled water (at least 1 L).</li>
		<li>Dry the obtained solid at room temperature and calcine for 6 h at 600 &#176; C, using a muffle furnace in an air atmosphere.</li>
	</ol>
	</li>
</ol>
3. Methods of Characterization
<ol>
	<li>Low-temperature nitrogen adsorption/desorption measurements
	<ol>
		<li>Use an automatic sorption analyzer to obtain N2 adsorption/desorption isotherms at 77 K.</li>
		<li>Use an appropriate glass tube for nitrogen sorption measurements. Before adding the porous sample to the glass tube, clean the tube in an ultrasonic washer and rinse it first with distilled water and, next, with anhydrous ethanol.</li>
		<li>Heat the glass tube at 150 &#176;C for 3 h and fill the tube with compressed nitrogen. Weigh the empty glass tube under the nitrogen conditions before the measurement to minimize the weight error.</li>
		<li>Place the sample in the glass tube and weigh the total mass (the mass of the sample with the glass tube).</li>
		<li>Prior to the measurements, degas the sample. Place the glass tube with the sample in the degassing port of the sorption analyzer. Apply the following process conditions: a pressure of at least 0.01 mmHg, a temperature of 423 K, and a duration of 24 h. In the degassing port, connect the sample to the vacuum and heat it to the set temperature (423 K). After degassing, fill the sample with nitrogen and transfer it to the analysis port.</li>
	</ol>
	</li>
	<li>Transmission electron microscopy
	<ol>
		<li>Use the TEM microscope with the 120 kV (for SBA-15) and 200 kV (for the OMC material) accelerating voltages to collect the good quality TEM images.</li>
		<li>For preparing a monodisperse film of the sample, disperse the sample (1 mg) in ethanol (1 mL). Perform the dispersion procedure in a microcentrifuge tube by placing it in an ultrasonic bath for 3 min.</li>
		<li>Place two drops of the dispersion on a TEM copper grid using a micropipette. Transfer the TEM grid to the TEM microscope and start the TEM imaging.</li>
	</ol>
	</li>
	<li>Energy dispersive X-ray spectroscopy
	<ol>
		<li>Use a scanning electron microscope equipped with an X-ray detector to acquire an energy dispersive X-ray spectrum of the samples.</li>
		<li>Apply an acceleration voltage of 15 kV to harvest the spectrum. Select the silicon as the optimization element for SBA-15 and the carbon for the OMC sample.</li>
	</ol>
	</li>
	<li>Potentiometric titration measurement
	<ol>
		<li>Use an automatic burette to perform the potentiometric titration experiment. Add the titrant in small and controlled portions (according to the titration software and procedure). Provide the smallest increment, at least 1 &#956;L, by an automatic dosing intrument.</li>
		<li>Disperse 0.1 g of the sample in 30 mL of an electrolyte solution (water solution of 0.1 M NaCl). Use the magnetic stirrer and isothermal conditions (293 &#177; 0.1 K) during the dispersion procedure.</li>
		<li>Add 1 - 2 mL of titrant (0.1 M NaOH solution) to the suspension. 
		NOTE: Perform the addition in small aliquots (each to be about 0.05 mL). The automatic burette The procedure should provide at least a dozen experimental points in the pH range from 1 to 14.</li>
		<li>Calculate the surface density of the charge Qs, using the following formula. 
		<img alt="Equation 1" src="/files/ftp_upload/58395/58395eq1.jpg" />&#160;(1) 
		Here, 
		&#916;n = the change in H+/OH- balance reduced per mass of sample; 
		SBET = the Brunauer-Emmett-Teller (BET) surface area of the porous solid state; 
		F = the Faraday number.</li>
	</ol>
	</li>
	<li>Capillary rise method for wettability measurements
	<ol>
		<li>To determine the contact angle inside the pores of the studied samples, use the capillary rise method. 
		NOTE: This method is based on the measurement of the mass rise of the liquid, which is penetrating the porous bed, as the function of the time. The main assumption of this method is based on the fact that penetrating liquid is advancing into the porous column and that this column consists of intergranular capillaries with a certain average radius. Thus, every relation derived for single capillary is valid for the layer of the porous powder. In a single vertical capillary, the wetting liquid floats against the gravitational forces as a result of the difference of pressure between the liquid and the vapor in the pores (capillary pressure). In this meaning, the penetration of the liquid into the porous bed allows the determination of the dynamic advancing contact angle inside the pores.</li>
		<li>Apply the modified Washburn&#8217;s equation17,18, expressed as follows. 
		<img alt="Equation 2" src="/files/ftp_upload/58395/58395eq2.jpg" /> (2) 
		Here, 
		m = the mass of the measured liquid; 
		C = the geometric parameter dependent on the distribution, shape, and size of the pores; 
		&#961; = the density; 
		&#947;l = the surface tension; 
		&#951; = the viscosity of the penetrating liquid; 
		&#952; = the contact angle; 
		t = time.</li>
		<li>Using equation (2), estimate the values of the advancing contact angles inside the studied pores.</li>
		<li>Prepare the force tensiometer. For powders, use a glass tube with a diameter of 3 mm and a ceramic sinter; for liquid, use a vessel with a diameter of 22 mm and a maximum volume of 10 mL.</li>
		<li>Measure 0.017 g of the sample.</li>
		<li>Start the computer program connected to the tensiometer. Put a vessel with the liquid on a motor-driven stage and suspend the glass tube with the sample on an electronic balance.</li>
		<li>Start the motor and start approaching the liquid in the vessel with the sample at a low constant rate of 10 mm/min; set the immersion depth of the sample tube into the liquid equal to 1 mm.</li>
		<li>From this moment, the dependence m2 = f(t) registers in the computer program.</li>
		<li>Stop the experiment when the dependence m2 = f(t) starts to show the characteristic plateau.</li>
		<li>Check for accuracy by repeating this procedure 3x - 5x.</li>
	</ol>
	</li>
	<li>Dielectric relaxation spectroscopy
	<ol>
		<li>To describe the melting behavior of confined water inside the studied porous matrices, perform the temperature measurements of electric capacitance C of the sample present in a parallel plate capacitor made of stainless steel19,20,21. To measure the capacitance C as the function of the temperature and the frequency of the applied cyclic electric field, use an impedance analyzer. 
		NOTE: The complex electric permittivity is defined as &#949;* = &#949;` + i&#949;``, where &#949;` = C/C0 is the real, and &#949;`` = tg&#948;&#183;&#949;` is an imaginary part of the permittivity, where C0 is the capacitance of the empty capacitor and tg&#948; are the dielectric losses.</li>
		<li>Put the measured sample into the plate capacitor.</li>
		<li>Select a frequency range from 100 Hz to 1 MHz and a temperature from 140 K to 305 K. Control the rate of temperature change with the temperature controller; set the temperature rate as equal to 0.8 K/min during the cooling and 0.6 K/min during the heating process.</li>
	</ol>
	</li>
</ol>

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K., Kreysa, G., Baselt, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Critical+appraisal+of+the+use+of+nitrogen+adsorption+for+the+characterization+of+porous+carbons.">Critical appraisal of the use of nitrogen adsorption for the characterization of porous carbons.</a> Characterization of Porous Solids V. , 421-427 (2000).</li><li>Sing, K. S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+use+of+gas+adsorption+for+the+characterization+of+porous+solids.">The use of gas adsorption for the characterization of porous solids.</a> Colloids and Surfaces. 38, 113-124 (1989).</li><li>Rouquerol, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recommendations+for+the+characterization+of+porous+solids.">Recommendations for the characterization of porous solids.</a> Pure &amp; Applied Chemistry. 66, 1739-1758 (1994).</li><li>Marega, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+direct+SAXS+approach+for+the+determination+of+specific+surface+area+of+clay+in+polymer-layered+silicate+nanocomposites.">A direct SAXS approach for the determination of specific surface area of clay in polymer-layered silicate nanocomposites.</a> The Journal of Physical Chemistry B. 116, 7596-7602 (2012).</li><li>Tsao, C. S., 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=Neutron+Scattering+Methodology+for+Absolute+Measurement+of+Room-Temperature+Hydrogen+Storage+Capacity+and+Evidence+for+Spillover+Effect+in+a+Pt-Doped+Activated+Carbon.">Neutron Scattering Methodology for Absolute Measurement of Room-Temperature Hydrogen Storage Capacity and Evidence for Spillover Effect in a Pt-Doped Activated Carbon.</a> The Journal of Physical Chemistry Letters. 1, 1569-1573 (2010).</li><li>Mattson, J. S., Mark, H. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Activated Carbon: Surface Chemistry and Adsorption from Solution. , (1971).</li><li>L&#225;szl&#243;, K., Szucs, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+characterization+of+polyethyleneterephthalate+(PET)+based+activated+carbon+and+the+effect+of+pH+on+its+adsorption+capacity+from+aqueous+phenol+and+2,3,4-trichlorophenol+solutions.">Surface characterization of polyethyleneterephthalate (PET) based activated carbon and the effect of pH on its adsorption capacity from aqueous phenol and 2,3,4-trichlorophenol solutions.</a> Carbon. 39, 1945-1953 (2001).</li><li>Garten, V. A., Weiss, D. E., Willis, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+interpretation+of+the+acidic+and+basic+structures+in+carbons.">A new interpretation of the acidic and basic structures in carbons.</a> Australian Journal of Chemistry. 10, 309-328 (1957).</li><li>Boehm, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+oxides+on+carbon+and+their+analysis:+A+critical+assessment.">Surface oxides on carbon and their analysis: A critical assessment.</a> Carbon. 40, 145-149 (2002).</li><li>Menendez, J. A., Phillips, J., Xia, B., Radovic, L. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+modification+and+characterization+of+chemical+surface+properties+of+activated+carbon:+In+the+search+of+carbons+with+stable+basic+properties.">On the modification and characterization of chemical surface properties of activated carbon: In the search of carbons with stable basic properties.</a> Langmuir. 12, 4404-4410 (1996).</li></ol>

The authors have nothing to disclose.

In 1992, ordered nanoporous silica materials were obtained for the first time, using an organic template; since then, a large number of publications related to different aspects of these structures, synthetic methods, the investigation of their properties, their modifications, and different applications have appeared in the literature1,2,3. The interest in SBA-15 nanoporous silica matrix4 is due to their unique quality: a high surface area, wide pores with a uniform pore size distribution, and good chemical and mechanical properties. Nanoporous silica materials with cylindrical pores, such as SBA-155, are often used as a porous matrix for catalysts as they are efficient catalysts in organic reactions6,7. The material can be synthesized with a wide range of methods that can influence their characteristics8,9,10. Therefore, it is crucial to optimize these methods for potential applications in many fields: electrochemical devices, nanotechnology, biology and medicine, drug delivery systems, or in adhesion and tribology. In the present study, two different types of nanoporous structures are presented, namely silica and carbon porous matrices. To compare their properties, the SBA-15 matrix is synthesized using the sol-gel method, and the ordered nanoporous carbon material is prepared by the impregnation of the resulting silica matrix with a carbon precursor.
Porous carbon materials are important in many appliances due to their high surface area and their unique and well-defined physicochemical properties6,11,12. Typical preparation results in materials with randomly distributed porosity and a disordered structure; there is also a limited possibility for the change of the general pore parameters, and thus, structures with relatively broad pore size distributions are obtained13. This possibility is broadened for nanoporous carbon materials with high surface areas and ordered systems of nanopores. More predicted geometry and more control of the physicochemical processes inside the pore space are important in many applications: as catalysts, separation media systems, advanced electronic materials, and nanoreactors in many scientific fields14,15.
To obtain the porous carbon replicas, the ordered silicates can act as a solid matrix to which carbon precursors are directly introduced. The method can be divided into several stages: the selection of ordered silica material; the deposition of a carbon precursor in a silica matrix; carbonization; then, the removal of the silica matrix. Many different types of carbonaceous materials can be obtained by this method, but not all nonporous materials have an ordered structure. An important element of the process is the selection of a suitable matrix whose nanopores must form a stable, three-dimensional structure16.
In this work, the influence of the type of pore walls on the surface properties of synthesized nanoporous matrices is investigated. The surface properties of OMC material are reflected by the surface properties of silica analog (SBA-15) of OMC. The textural and structural properties of both types of materials (OMC and SBA-15) are characterized by low-temperature N2 adsorption/desorption measurements (at 77 K), transmission electron microscopy (TEM), and energy dispersive X-ray analysis (EDX).
Low-temperature gas adsorption/desorption measurement is one of the most important techniques during the characterization of porous materials. Nitrogen gas is used as an adsorbate due to its high purity and the possibility to create a strong interaction with solid adsorbents. Important advantages of this technique are the user-friendly commercial equipment and relatively easy data-processing procedures. The determination of nitrogen adsorption/desorption isotherms is based on the accumulation of the adsorbate molecules on the surface of solid adsorbent at 77 K in a wide range of pressure (P/P0). The Barrett, Joyner, and Halenda (BJH) procedure for calculating the pore size distribution from experimental adsorption or desorption isotherms is applied. The most important assumptions of the BJH method include a planar surface and an even distribution of the adsorbate on the investigated surface. However, this theory is based on the Kelvin equation and it remains the most widely used manner for calculating the pore size distribution in the mesoporous range.
To evaluate the electrochemical character of the samples, a potentiometric titration method is applied. The surface chemistry of the material depends on the surface charge related to the presence of heteroatoms or functional groups on the surface. The surface properties are also investigated by contact angle analysis. The wettability inside the pores provides information about the adsorbate-adsorbent interactions. The influence of the wall roughness on the melting temperature of the water confined in both samples is studied with the dielectric relaxation spectroscopy (DRS) technique. Measurements of the dielectric constant allow the investigation of melting phenomena as the polarizability of the liquid and solid phases are different from each other. A change in the slope of the temperature dependence of the capacitance shows that melting occurs in the system.

<table><tbody><tr><td>1,3,5-trimethylbenzene</td><td>Sigma-Aldrich, Poland</td><td>M7200 Sigma-Aldrich</td><td>Mesitylene, also known as 1,3,5-trimethylbenzene, reagent grade, assay: 98%.</td></tr><tr><td>anhydrous ethanol</td><td>POCH, Avantor Performance Materials Poland S.A.</td><td>396480111</td><td>Assay, min. 99.8 %, analysis-pur (a.p.)</td></tr><tr><td>ASAP 2020. Accelerated Surface Area and Porosimetry System</td><td>Micromeritics Instrument Corporation, Norcross, GA, USA</td><td></td><td>Samples were outgassed before analysis at 120 &lt;sup&gt;o&lt;/sup&gt;C for 24 hours in degas port of analyzer. The dead space volume was measured for calibration on experimental measurement using helium as a adsorbate.</td></tr><tr><td>Automatic burette Dosimat 665</td><td>Metrohm, Switzerland</td><td></td><td>The surface charge properties were experimentally determined by potentiometric titration of the suspension at constant temperature 20&amp;deg;C maintained by the thermostatic device. Prior to potentiometric titration measurements, the solid samples were dried by 24 hours at 120 &lt;sup&gt;o&lt;/sup&gt;C. The initial pH was established by addition of 0.3 cm&lt;sup&gt;3&lt;/sup&gt; of 0.2 mol/L HCl. T The 0.1 mol/L NaOH solution was used as a titrant, added gradually by using automatic burette.</td></tr><tr><td>Digital pH-meter pHm-240</td><td>Radiometer, Copenhagen</td><td></td><td>Device coupled with automatic burette</td></tr><tr><td>ethyl alcohol</td><td>POCH, Avantor Performance Materials Poland S.A.</td><td>396420420</td><td>Assay, min. 96 %.analysis-pur (a.p.)</td></tr><tr><td>glucose</td><td>POCH, Avantor Performance Materials Poland S.A.</td><td>459560448</td><td>assay 99.5%</td></tr><tr><td>Hydrochloric acid</td><td>POCH, Avantor Performance Materials Poland S.A.</td><td>575283115</td><td>Hydrochloric acid, 35 - 38% analysis-pur (a.p.)</td></tr><tr><td>HOPG graphite substrate</td><td>Spi Supplies</td><td>LOT#1170906</td><td>HOPG SPI-2 Grade, 20x20x1 mm</td></tr><tr><td>Impedance analyzer Solartron 1260</td><td>Solartron</td><td></td><td></td></tr><tr><td>Pluronic PE 6400 polymer</td><td>BASF (Polska)</td><td></td><td>(EO&lt;sub&gt;13&lt;/sub&gt;PO&lt;sub&gt;70&lt;/sub&gt;EO&lt;sub&gt;13&lt;/sub&gt;)</td></tr><tr><td>Pluronic PE10500</td><td>BASF Canada Inc.</td><td></td><td>Molar mass 6500 g/mol</td></tr><tr><td>potassium hydroxide</td><td>Sigma-Aldrich, Poland</td><td>P5958 Sigma-Aldrich</td><td>BioXtra, &amp;ge;85% KOH basis</td></tr><tr><td>SEM microscope</td><td>JEOL JSM-7001F</td><td></td><td>Scanning Electron Microscope with EDS detector</td></tr><tr><td>Sigma Force Tensiometer 701</td><td>KSV, Sigma701, Biolin Scientific</td><td></td><td>force tensiometer</td></tr><tr><td>Sulfuric acid (VI)</td><td>POCH, Avantor Performance Materials Poland S.A.</td><td>575000115</td><td></td></tr><tr><td>surface glass type KS 324 Kavalier</td><td>Megan Poland</td><td></td><td>80 % of SiO2 , 11% of Na2O and 9% of CaO</td></tr><tr><td>Tecnai G2 T20 X-TWIN</td><td>FEI, USA</td><td></td><td>Transmission Electron Microscope with EDX detector.</td></tr><tr><td>TEM microscope</td><td>JEOL JEM-1400</td><td></td><td></td></tr><tr><td>temperature controller ITC503</td><td>Oxford Instruments</td><td></td><td></td></tr><tr><td>Tetraethylorthosilicate</td><td>Sigma-Aldrich, Poland</td><td>131903</td><td>Tetraethyl silicate, TEOS, reagent grade, assay 98%</td></tr><tr><td>Ultrapure water</td><td>Millipore, Merck KGaA, Darmstadt, Germany</td><td>SIMSV0001</td><td>Simplicity Water Purification SystemUltrapure Water: 18.2 MegOhm&amp;middot;cm, TOC: &amp;lt;5 ppb</td></tr></tbody></table>

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.

To characterize the porous structure of the investigated samples of OMC and SBA-15, the N2 adsorption-desorption isotherms were recorded at 77 K. The experimental N2 gas adsorption-desorption isotherms characterizing the investigated systems, as well as the pore size distributions (PSD) obtained from the adsorption and desorption data, are presented in Figure 1A-D. The position of the inflection points on the sorption isotherms (Figure 1A, C) indicates the pressure at which the process of mesopore filling starts. This information is needed for the calculation of the mean pore size and the PSD (Figure 1B, D), according to the Kelvin equation.
Figure 2A-C presents the TEM images of the OMC. Figure 2D, E presents the TEM images of the SBA-15 sample. The obtained TEM micrographs were used for evaluating the quality of the synthesized materials and confirming the two-dimensional hexagonal structure. An interpretation of the TEM images allows an estimation of the pore sizes and a comparison of the values with the data obtained from sorption measurements (Figure 1).
Figure 3 shows the surface charge density distribution for carbon and silica material. The properties of surfaces and interfaces of supports and solid matrices have a crucial impact on the characteristics of investigated materials and on the physicochemical processes and phenomena on their surface or in their vicinity. An experimental investigation of the surface properties, such as surface charge densities, seems to be appropriate and valuable for investigating how surface properties (presence and types of functional groups) influence the investigated chemical and physical phenomena. In particular, the surface characteristics related to the surface chemistry of the carbon materials depend on the surface charge defined by heteroatoms (such as oxygen or nitrogen) and influence the wettability, adsorptive properties, electrochemical and catalytic features, and finally, acid-base and hydrophilic-hydrophobic behavior. An analysis of the point-of-zero charge position on the pH scale provides information about the system&#39;s acidity; the lower the pHpzc value, the more acidic the sample is.
Figure 4A, B shows typical TEM-energy dispersive X-ray spectroscopy (EDS) spectra for the OMC sample illustrating the interaction of the incident electron beam with the sample, which generates the X-rays with energies characteristic of an atomic number of elements. TEM-EDS is a powerful tool for the determination of the chemical composition. Figure 4C shows the EDS results for SBA-15 material. The value of the energy of the characteristic radiation coming from the sample allows an identification of the elements contained in the studied sample, while the intensity (the height of the peaks in the spectrum) enables a qualitative analysis of its contents (Figure 4C).
Figure 5 depicts the results of the measurements of contact angles inside the nanopores of OMC (Figure 5A) and SBA-15 (Figure 5B), referenced to the wettabilities on smooth highly oriented pyrolytic graphite (HOPG) and glass substrates, respectively. An ideally smooth silica surface glass and HOPG graphite as a smooth graphite surface were used. The measured contact angles are shown as a function of the microscopic wetting parameter &#945;w for both the smooth planar silica, the graphite surface, and the rough nanoporous materials. Values of &#945;w for the liquids on these silica and graphite substrates (Figure 5A, B) can be found based on the following equation.
<img alt="Equation 3" src="/files/ftp_upload/58395/58395eq3.jpg" />(3)
Here, 
&#949;fw, &#949;ff = the energy depths of the Lennard-Jones potential; 
&#963;fw = the collision length of the Lennard-Jones potential; 
&#961;w = the number of solid atoms per unit volume; 
&#916; = the distance between the separating layers in the substrate.
These values are taken from previously published literature22,23,24. The measurement of wettability allows the characterization of the adsorbate/adsorbent interactions. Together with the potentiometric titration and EDX analysis, the measurement of wettability provides a full description of the surface properties of a given sample. The lower the contact angle, the higher the wettability, which means that the interaction of the penetrating liquid molecule with the studied surface is stronger (Figure 5A, B).
Figure 6 shows the roughness fractions f calculated from the Cassie-Baxter model25&#160;vs. the microscopic wetting parameter for the nanoporous carbon (OMC; Figure 6A) and the silica (SBA-15; Figure 6B) matrix. We assume that the wetting on the rough surfaces occurs according to the Cassie-Baxter mechanism (i.e., the droplet of the liquid does not penetrate the cavities but is on the top of the irregularities [as shown in the insets of Figure 5A, B]). In this model, the contact angle on the rough surface &#952;p is described as:
cos&#952;p = f(1 + cos&#952;) - 1&#160; &#160; &#160; (4)
Here, 
&#952; = the contact angle value on a smooth nonporous substrate (glass); 
f = is the fraction of the porous surface which is in direct contact with the liquid interface.
It is worth evaluating the roughness fractions f (equation 4) which acts as a correction factor for interpreting contact angle measurements for the liquid molecules with the sample surface in the pores.
Figure 7 presents the dielectric spectroscopy results for deuterated water confined in the studied samples of OMC (Figure 7A) and SBA-15 (Figure 7B). These illustrate the temperature dependences of electric capacity C for both samples (Figure 7A, B). In the solid state of the polar substance, their orientational polarization vanishes, and the dielectric constant &#949; is equal to n2, where n is the refractive index of the substance. The sharp increase visible in the C-T curves indicates the melting phase transitions occurring in the system. The temperature of the anomalous increase of the C-T function allows the determination of the melting point of both the bulk liquid and the melting point in the pores of the studied sample.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58395/58395fig1.jpg" /> 
Figure 1: Experimental N2 adsorption/desorption isotherm plot at 77 K and porosity distributions by the Barrett, Joyner, and Halenda method (BJH)7,26,27. For (A and B) nanoporous carbon material and&#160;(C and D) silica SBA-15 material.&#160;The nitrogen isotherms show characteristic hysteresis loops, providing an information about the shape and pore size distributions of the studied pores. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58395/58395fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58395/58395fig2.jpg" /> 
Figure 2: TEM images illustrating the ordered nanoporous channels structure. (A - C) TEM images of the nanoporous carbon along the (001) direction at various magnifications. (D - E) The structure of SBA-15. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58395/58395fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58395/58395fig3.jpg" /> 
Figure 3: Potentiometric titration results for OMC and SBA-15 (pH dependence of the surface charge density). The surface charge density dependence of pH shows the differences in the electrochemical character of both materials; the pzc point provides information about the number of acid sites on the sample surface. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58395/58395fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58395/58395fig4.jpg" /> 
Figure 4: Examples of TEM- EDS spectra and EDS analysis. (A and B) EDS spectra for the OMC sample, recorded from two different areas marked on the TEM image. (C) EDS spectra and quantitative analysis result of the SBA-15 sample. Quantitative results of an EDS analysis give information about the presence of elements in the functional groups responsible for the surface reactivity; this is a technique complementary to the potentiometric titration. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58395/58395fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/58395/58395fig5.jpg" /> 
Figure 5: Contact angles vs. the microscopic wetting parameter measured inside the porous matrices. (A) The nanoporous carbon (OMC) and (B) silica (SBA-15) matrix, referenced to as the contact angles vs. the microscopic wetting parameter function on smooth HOPG and glass substrates, respectively.&#160;The wettability inside the pores refers to the wettability on flat surfaces and provides some information about the influence of the pore roughness on adsorbate/adsorbent interactions. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58395/58395fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/58395/58395fig6.jpg" /> 
Figure 6: The roughness fractions f calculated from the Cassie-Baxter model vs. the microscopic wetting parameter. For (A) the nanoporous carbon (OMC) and (B) silica (SBA-15) matrix. An application of the Cassie-Baxter model of wettability allows the interpretation of contact angles on rough porous substrates. The f fractions calculated from this model describe the percentage of contributions of the porous wall which are in direct contact with the liquid surface. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58395/58395fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/58395/58395fig7.jpg" /> 
Figure 7: Temperature dependences of electric capacitance of D2O water confined inside the OMC and SBA-15 porous matrix. The (A) OMC and the (B) SBA-15 porous matrix. The interpretation of the C-T function allows the identification of the temperature of the phase transition of D2O in pores and in the bulk occurring in the studied system. An increase in C-T function lead to the increase in melting point for both bulk water and confined water inside the pores. The value of the melting point&#39;s shift in pores relative to the bulk is dependent on the host/guest molecular interactions. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58395/58395fig7large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td rowspan="3">Sample</td>
			<td colspan="2">Surface area (SBET)a&#160;</td>
			<td colspan="2">Pore volume</td>
			<td colspan="3">Pore Size distribution</td>
		</tr>
		<tr>
			<td colspan="2">(m2/g)</td>
			<td colspan="2">(cm3/g)</td>
			<td colspan="3">(nm)</td>
		</tr>
		<tr>
			<td>STotal</td>
			<td>Smicb</td>
			<td>VTotalc</td>
			<td>Vmicb</td>
			<td>Dhd</td>
			<td>Dmo (NLDFT)e</td>
			<td>Dmo (BJH)f</td>
		</tr>
		<tr>
			<td>OMC</td>
			<td>757</td>
			<td>23</td>
			<td>0.87</td>
			<td>0.006</td>
			<td>4.6</td>
			<td>0.4</td>
			<td>3.9</td>
		</tr>
		<tr>
			<td>SBA-15</td>
			<td>460</td>
			<td>16</td>
			<td>0.6</td>
			<td>0.004</td>
			<td>5.3</td>
			<td>*</td>
			<td>5.5</td>
		</tr>
	</tbody>
</table>
Table 1: The values of textural parameters describing a porous structure of ordered nanoporous carbon and SBA-15 silica calculated from N2 sorption isotherms.&#160;aBET surface area calculated using experimental points at the relative pressure of (P/P0) 0.035 - 0.31, where P and P0 are denoted as the equilibrium and saturation pressure of nitrogen. bSurface area and pore volume of micropores calculated by the t-plot method with a fitted statistical thickness in the range from 3.56 to 4.86 &#197;. cTotal pore volume calculated by 0,0015468 x the amount of nitrogen adsorbed at P/P0 = 0.99. dHydraulic pore diameters calculated from the BET surface areas and pore volumes according to the equation: Dh = 4V/S. eThe pore diameter estimated from the PSD maximum of the nonlocal density functional theory (NLDFT). NLDFT calculations were performed using a nonnegative regularization of 0.001 and the cylindrical geometry of pores as a model of carbon porosity. fThe pore diameter estimated from the BJH method (the same results for adsorption and desorption data). *The lack of values of pore diameters of SBA-15 estimated from the NLDFT method.

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Surface Properties of Synthesized Nanoporous Carbon and Silica 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]) ...

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Nanyang Technological University

Research

JoVE Journal

Chemistry

9.3K Views.  Adam Mickiewicz University. Dit protocol is belangrijk omdat poreus oppervlaktekenmerk met betrekking tot het opsluitingseffect van vloeistoffen in poreuze matrices een belangrijk probleem is in energie,geneeskunde en milieutoepassing. Een synthese en karakterisering van de nieuwe materialen, koolstof en silica nanoporiën, en de bepaling van de bevochtiging parameters bieden nieuwe informatie over de eigenschappen van de opsluiting nanofases. In nanotechnologie, biologie en geneeskunde is het cruciaal om de synthesemet...

Video: Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques 1, 2, and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. 
Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT microstructures, significantly increases the packing density of CNTs. This process enables directed transformation of vertical CNT microstructures into straight, inclined, and twisted shapes, which have robust mechanical properties exceeding those of typical microfabrication polymers. This in turn enables formation of nanocomposite CNT master molds by capillary-driven infiltration of polymers. The replica structures exhibit the anisotropic nanoscale texture of the aligned CNTs, and can have walls with sub-micron thickness and aspect ratios exceeding 50:1. Integration of CNT microstructures in fabrication offers further opportunity to exploit the electrical and thermal properties of CNTs, and diverse capabilities for chemical and biochemical functionalization 3.

We present methods for fabrication of patterned microstructures of vertically aligned carbon nanotubes (CNTs), and their use as master molds for production of polymer microstructures with organized nanoscale surface texture. The CNT forests are densified by condensation of solvent onto the substrate, which significantly increases their packing density and enables self-directed formation of 3D shapes.

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip ...

Engineering

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

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

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

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

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties of the materials were investigated. We used a one pot sol-gel approach to intercalate gold nano particles in the walls of mesoporous silica. To start with the synthesis, P123 was used as template to form micelles. Then TESPTS was used as a surface modification agent to intercalate gold nano particles. Following this process, TEOS was added in as a silica source which underwent a polymerization process in acid environment. After hydrothermal processing and calcination, the final product was acquired. Several techniques were utilized to characterize the porosity, morphology and structure of the gold intercalated mesoporous silica. The results showed a stable structure of mesoporous silica after gold intercalation. Through the oxidation of benzyl alcohol as a benchmark reaction, the GMS materials showed high selectivity and recyclability.

Here, we present a protocol with a sol-gel process to synthesize gold intercalated in the walls of mesoporous materials (GMS), which is confirmed to possess a mesoporous matrix with gold intercalated in the walls imparting great stability and recyclability.

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties ...

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

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The silica-encapsulated metal oxide nanoparticles are then carburized in a methane/hydrogen atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal carbide nanoparticles. During the carburization process, the silica shells prevent the sintering of adjacent carbide nanoparticles while also preventing the deposition of excess surface carbon. Alternatively, the silica-encapsulated metal oxide nanoparticles can be nitridized in an ammonia atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal nitride nanoparticles. By adjusting the reverse microemulsion parameters, the thickness of the silica shells, and the carburization/nitridation conditions, the transition metal carbide or nitride nanoparticles can be tuned to various sizes, compositions, and crystal phases. After carburization or nitridation, the silica shells are then removed using either a room-temperature aqueous ammonium bifluoride solution or a 0.1 to 0.5 M NaOH solution at 40-60 &#176;C. While the silica shells are dissolving, a high surface area support, such as carbon black, can be added to these solutions to obtain supported early transition metal carbide or nitride nanoparticles. If no high surface area support is added, then the nanoparticles can be stored as a nanodispersion or centrifuged to obtain a nanopowder.

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

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The ...

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

Preparation of Functional Silica Using a Bioinspired Method

The goal of the protocols described herein is to synthesize bioinspired silica materials, perform enzyme encapsulation therein, and partially or totally purify the same by acid elution. By combining sodium silicate with a polyfunctional bioinspired additive, silica is rapidly formed at ambient conditions upon neutralization. 
The effect of neutralization rate and biomolecule addition point on silica yield are investigated, and biomolecule immobilization efficiency is reported for varying addition point. In contrast to other porous silica synthesis methods, it is shown that the mild conditions required for bioinspired silica synthesis are fully compatible with the encapsulation of delicate biomolecules. Additionally, mild conditions are used across all synthesis and modification steps, making bioinspired silica a promising target for the scale-up and commercialization as both a bare material and active support medium.
The synthesis is shown to be highly sensitive to conditions, i.e., the neutralization rate and final synthesis pH, however tight control over these parameters is demonstrated through the use of auto titration methods, leading to high reproducibility in reaction progression pathway and yield. 
Therefore, bioinspired silica is an excellent active material support choice, showing versatility towards many current applications, not limited to those demonstrated here, and potency in future applications.

Here, we present a protocol to synthesize bioinspired silica materials and immobilize enzymes therein. Silica is synthesized by combining sodium silicate and an amine &#39;additive&#39;, which neutralize at a controlled rate. Material properties and function can be altered either by in situ enzyme immobilization or post-synthetic acid elution of encapsulated additives.

The goal of the protocols described herein is to synthesize bioinspired silica materials, perform enzyme encapsulation therein, and partially or totally ...

Multiscale Structures Aggregated by Imprinted Nanofibers for Functional Surfaces

Multiscale surface structures have attracted increasing interest owing to several potential applications in surface devices. However, an existing challenge in the field is the fabrication of hybrid micro-nano structures using a facile, cost-effective, and high-throughput method. To overcome these challenges, this paper proposes a protocol to fabricate multiscale structures using only an imprint process with an anodic aluminum oxide (AAO) filter and an evaporative self-aggregation process of nanofibers. Unlike previous attempts that have aimed to straighten nanofibers, we demonstrate a unique fabrication method for multiscale aggregated nanofibers with high aspect ratios. Furthermore, the surface morphology and wettability of these structures on various liquids were investigated to facilitate their use in multifunctional surfaces.

Presented is an easy method to fabricate nano-micro multiscale structures, for functional surfaces, by aggregating nanofibers fabricated using an anodic aluminum oxide filter.

Multiscale surface structures have attracted increasing interest owing to several potential applications in surface devices. However, an existing ...

Microscopic Visualization of Porous Nanographenes Synthesized through a Combination of Solution and On-Surface Chemistry

On-surface synthesis has recently been regarded as a promising approach for the generation of new molecular structures. It has been particularly successful in the synthesis of graphene nanoribbons, nanographenes and intrinsically reactive and instable, yet attractive species. It is based on the combination of solution chemistry aimed at preparation of appropriate molecular precursors for further ultra-high vacuum surface assisted transformations. This approach also owes its success to an incredible development of characterization techniques, such as scanning tunneling/atomic force microscopy and related methods, which allow detailed, local characterization at atomic scale. While the surface-assisted synthesis can provide molecular nanostructures with outstanding precision, down to single atoms, it suffers from basing on metallic surfaces and often limited yield. Therefore, the extension of the approach away from metals and the struggle to increase productivity seem to be significant challenges toward wider applications. Herein, we demonstrate the on-surface synthesis approach for generation of non-planar nanographenes, which are synthesized through a combination of solution chemistry and sequential surface-assisted processes, together with the detailed characterization by scanning probe microscopy methods.

A combination of solution and surface assisted synthesis opens new directions in the atomically precise synthesis of nanostructures. Scanning tunneling microscopy (STM) supplemented by non-contact atomic force microscopy (nc-AFM) enables detailed characterization of newly designed and generated carbon-based nano-objects.

On-surface synthesis has recently been regarded as a promising approach for the generation of new molecular structures. It has been particularly ...

Synthesis of Metal Nanoparticles Supported on Carbon Nanotube with Doped Co and N Atoms and its Catalytic Applications in Hydrogen Production

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented herein. The novel strategy is based on a facile one-pot pyrolysis treatment of cobalt (II) acetylacetonate and nitrogen-rich organic precursors under Ar atmosphere at 800 &#176;C, resulting in the formation of Co- and N- co-doped carbon nanotube with earthworm-like morphology. The obtained catalyst was found to have a high density of defect sites, as confirmed by Raman spectroscopy. Here, cobalt (II) nanoparticles were stabilized on the atomically dispersed cobalt- and nitrogen-doped carbon nanotubes. The catalyst was confirmed to be effective in the catalytic hydrolysis of ammonia borane, in which the turnover frequency was 5.87 mol H2&#183;molCo-1&#183;min-1, and the specific hydrogen generation rate was determined to be 2447 mL H2&#183;gCo-1&#183;min-1. A synergistic function between the Co nanoparticle and the doped carbon nanotubes was proposed for the first time in the catalytic hydrolysis of ammonia borane reaction under a mild condition. The resulting hydrogen production with its high energy density and minimal refueling time could be suitable for future development as energy sources for mobile and stationary applications such as road trucks and forklifts in transport and logistics.

Here, we present a protocol to synthesize Co nanoparticles supported on carbon nanotubes with Co- and N- dopants for hydrogen productions.

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented ...

Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

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