Name: highly stable, functional hairy nanoparticles and biopolymers from wood fibers: towards sustainable nanotechnology
Uploaded: 2016-07-20T14:00:00
Description: Watch this Scientific Journal Video about Highly Stable, Functional Hairy Nanoparticles and Biopolymers from Wood Fibers: Towards Sustainable Nanotechnology at JoVE.com

Financial support from an Industrial Research Chair funded by FPInnovations and NSERC for a NSERC Discovery grant and from the NSERC Innovative Green Wood Fiber Products Network are acknowledged.

CAUTION: Read the material safety data sheets (MSDS) of all the chemicals before touching them. Many of the chemicals used in this work may cause severe health damages. Using personal protection such as lab coat, gloves, and goggles is a must. Do not forget that safety comes first. The water used throughout the synthesis is distilled water.
1. Preparation of Partially Oxidized Fibers as an Intermediate
<ol>
	<li>Tear 4 g Q-90 softwood pulp sheets into small pieces of approximately 2 x 2 cm<s...

<ol>
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A., Alloin, F., Dufresne, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Review+of+recent+research+into+cellulosic+whisker,+their+Properties+and+their+application+in+nanocomposites+field.">Review of recent research into cellulosic whisker, their Properties and their application in nanocomposites field.</a> Biomacromolecules. 6 (2), 612-626 (2005).</li><li>Sj&#246;str&#246;m, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Wood chemistry: Fundamentals and applications. , (1993).</li><li>Nageli, C., Schwendener, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Das Mikroskop, Theorie und Anwendung desselben. 2. Verbesserte auflage. , (1877).</li><li>Moon, R. 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Polym. 82 (2), 329-336 (2010).</li><li>Liu, D., Chen, X., Yue, Y., Chen, M., Wu, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+and+rheology+of+nanocrystalline+cellulose.">Structure and rheology of nanocrystalline cellulose.</a> Carbohydr. Polym. 84 (1), 316-322 (2011).</li><li>Lam, E., Male, K. B., Chong, J. H., Leung, A. C. W., Luong, J. H. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applications+of+functionalized+and+nanoparticle-modified+nanocrystalline+cellulose.">Applications of functionalized and nanoparticle-modified nanocrystalline cellulose.</a> Trends Biotechnol. 30 (5), 283-290 (2012).</li><li>Kalia, S., Dufresne, A., 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=Cellulose-based+bio-+and+nanocomposites:+A+review.">Cellulose-based bio- and nanocomposites: A review.</a> Int. J. Polym. Sci. 2011, 1-35 (2011).</li><li>Bai, W., Holbery, J., Li, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+technique+for+production+of+nanocrystalline+cellulose+with+a+narrow+size+distribution.">A technique for production of nanocrystalline cellulose with a narrow size distribution.</a> Cellulose. 16 (3), 455-465 (2009).</li><li>Eichhorn, S. J., Dufresne, A., 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=Review:+Current+international+research+into+cellulose+nanofibres+and+nanocomposites.">Review: Current international research into cellulose nanofibres and nanocomposites.</a> J. Mater. Sci. 45 (1), 1-33 (2010).</li><li>Safari, S., Sheikhi, A., van de Ven, T. G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroacoustic+characterization+of+conventional+and+electrosterically+stabilized+nanocrystalline+celluloses.">Electroacoustic characterization of conventional and electrosterically stabilized nanocrystalline celluloses.</a> J. Colloid Interface Sci. 432, 151-157 (2014).</li><li>Yang, H., Tejado, A., Alam, N., Antal, M., Van De Ven, T. G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Films+prepared+from+electrosterically+stabilized+nanocrystalline+cellulose.">Films prepared from electrosterically stabilized nanocrystalline cellulose.</a> Langmuir. 28 (20), 7834-7842 (2012).</li><li>Guthrie, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+&amp;#34;dialdehydes&amp;#34;+from+the+periodate+oxidation+of+carbohydrates.">The &amp;#34;dialdehydes&amp;#34; from the periodate oxidation of carbohydrates.</a> Adv Carbohydr Chem. 16, 105-158 (1961).</li><li>van de Ven, T. G. M., Tejado, A., Alam, M. N., Antal, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+highly+charged+non-water+soluble+cellulose+products,+includes+all+types+of+cellulose+nanostructures+especially+cellulose+nanofibers,+and+method+of+making+them.">Novel highly charged non-water soluble cellulose products, includes all types of cellulose nanostructures especially cellulose nanofibers, and method of making them.</a> U.S. Provisional Patent Application. , (2011).</li><li>Yang, H., Chen, D., van de Ven, T. G. 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Following the chemistry discussed in this visual paper, a spectrum of highly stable cellulose-based nanoparticles with tunable charge bearing both crystalline and amorphous phases (hairy nanocrystalline celluloses) are produced. Depending on the periodate oxidation time, as shown in Table 1, various products are yielded: oxidized fibers (fraction 1), SNCC (fraction 2), and DAMC (fraction 3) each of which providing unique properties, such as defined size, morphology, crystallinity, and aldehyde content. F...

Cellulose, as the most abundant biopolymer in the world, has been served recently as a key raw material to yield crystalline nanoparticles named nanocrystalline cellulose (NCC, also known as cellulose nanocrystals CNC)1. To understand the mechanism of NCC synthesis, the structure of cellulose fibers needs to be explored. Cellulose is a linear and polydispersed polymer comprising poly-beta(1,4)-D-glucose residues2. The sugar rings in each monomer are connected through glycosidic oxygen to form chains of (1-1.5) x 104 glucopyranose units2,3, introducing alternating crystalline parts and disordered, amorphous regions, first reported by Nageli and Schwendener2,4. Depending on the source, crystalline parts of cellulose can adopt various polymorphs5.
If a cellulose fiber is treated with a strong acid, such as sulfuric acid, the amorphous phase can be completely hydrolyzed away to disrupt the polymer and produce crystalline particles of various aspect ratio depending on the source (e.g., wood and cotton yield more than 90% crystalline nanorods of width ~ 5-10 nm and length ~ 100-300 nm, whereas tunicin, bacteria, and algae produce 5-60 nm wide and 100 nm to several micrometer long NCCs)6. Readers are referred to the vast amount of literature available on the scientific and engineering aspects of these nanomaterials2,5,7-16. Despite numerous interesting properties of these nanoparticles, their colloidal stability has always been an issue at high salt concentrations and high/low pH due to their relatively low surface charge content (less than 1 mmol/g)17.
Instead of strong acid hydrolysis, cellulose fibers can be treated with an oxidizing agent (periodate), cleaving C2-C3 linkage in the anhydro D-glucopyranose residues to form 2,3-dialdehyde units with no significant side reactions18,19. These partially oxidized fibers can be used as a valuable intermediate material to produce nanoparticles bearing both amorphous and crystalline regions (hairy nanocrystalline celluloses) using solely chemical reactions without any mechanical shear or ultrasonication20. When the partial oxidation degree DS &#60; 2, heating oxidized fibers results in three batches of products, namely fibrous cellulose, water dispersible dialdehyde cellulose nanowhiskers called sterically stabilized nanocrystalline cellulose (SNCC), and dissolved dialdehyde modified cellulose (DAMC), which can be isolated by precise control over the co-solvent addition and intermittent centrifugation21.
Performing controlled chlorite oxidation on the partially oxidized fibers converts almost all the aldehyde groups to carboxyl units, which can introduce as high as 7 mmol COOH groups per gram of nanocrystalline cellulose depending on the aldehyde content18, acting as stabilizers. These nanoparticles are called electrosterically stabilized nanocrystalline cellulose (ENCC). Furthermore, it has been confirmed that soft layers of charged hair-like protruding chains exist on ENCC17. This material has been used as a highly efficient adsorbent to scavenge heavy metal ions22. The charge of these nanoparticles can be precisely controlled by controlling the periodate reaction time23.
Despite known oxidation reactions of cellulose, the production of SNCC and ENCC has never been reported by any other research groups most probably due to the separation challenges. We have been able to successfully synthesize and isolate various fractions of nanoproducts by precisely designing the reaction and separation steps. This visual article demonstrates with complete detail how to reproducibly prepare and characterize the aforementioned novel nanowhiskers bearing both amorphous and crystalline parts from wood fibers. This tutorial may be an asset for active researchers in the fields of soft material, biological, and medicinal sciences, nanotechnology and nanophotonics, environmental science and engineering, and physics.

<table border="0" cellpadding="0" cellspacing="0" width="947">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Q-90 softwood pulp</td>
			<td style="width:149px;">FPInnovations</td>
			<td style="width:213px;">-</td>
			<td style="width:369px;">-</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sodium periodate</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td style="width:213px;">S1878-500G/CAS7790-28-5</td>
			<td style="width:369px;">Light sensitive, Strong oxidizer, must be kept away from flammable materials</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium chloride</td>
			<td style="width:149px;">ACP Chemicals</td>
			<td style="width:213px;">S2830-3kg/7647-14-5</td>
			<td style="width:369px;">-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">2-Propanol</td>
			<td style="width:149px;">Fisher</td>
			<td style="width:213px;">L-13597/67-63-0</td>
			<td style="width:369px;">Flammable</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ethylene glycol</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td style="width:213px;">102466-1L/107-21-1</td>
			<td style="width:369px;">-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium hydroxide</td>
			<td style="width:149px;">Fisher</td>
			<td style="width:213px;">L-19234/1310-73-2</td>
			<td style="width:369px;">Strong base, causes serious health effects</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sodium chlorite</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td style="width:213px;">71388-250G/7758-19-2</td>
			<td style="width:369px;">Reactive with reducing agents and combustible materials</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hydrogen peroxide</td>
			<td style="width:149px;">Fisher</td>
			<td style="width:213px;">H325-500/7722-84-1</td>
			<td style="width:369px;">Corrosive and oxidizing agent, keep in a cool and dark place</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ethanol</td>
			<td style="width:149px;">Commercial alcohols</td>
			<td style="width:213px;">P016EAAN</td>
			<td style="width:369px;">Flammable</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Hydrochloric acid</td>
			<td style="width:149px;">ACP Chemicals</td>
			<td style="width:213px;">H-6100-500mL/7647-01-0</td>
			<td style="width:369px;">Strong acid, causes serious health effects</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hydroxylamine hydrochloride</td>
			<td style="width:149px;">Sigma-Aldrich</td>
			<td style="width:213px;">159417-100G/5470-11-1</td>
			<td style="width:369px;">Unstable at high temperature and humidity, mutagenic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Centrifuge</td>
			<td style="width:149px;">Beckman Coulter</td>
			<td style="width:213px;">J2</td>
			<td>High rotary speed</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Fixed angle rotor</td>
			<td style="width:149px;">Beckman Coulter</td>
			<td style="width:213px;">JA-25.50</td>
			<td>Tighten the lid carefully</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:216px;">Dialysis tubing</td>
			<td style="width:149px;">Spectrum Labs</td>
			<td style="width:213px;">Spectra (Part No. 132676)</td>
			<td>Cutoff Mw = 12-14 kD, Length ~ 30 cm, width ~ 4.5 cm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Aluminum cup</td>
			<td style="width:149px;">VWR</td>
			<td style="width:213px;">611-1371</td>
			<td>57 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Titrator</td>
			<td style="width:149px;">Metrohm</td>
			<td style="width:213px;">836 Titrando</td>
			<td>-</td>
		</tr>
	</tbody>
</table>

highly stable, functional hairy nanoparticles and biopolymers from wood fibers: towards sustainable nanotechnology

Nanoparticles, as one of the key materials in nanotechnology and nanomedicine, have gained significant importance during the past decade. While metal-based nanoparticles are associated with synthetic and environmental hassles, cellulose introduces a green, sustainable alternative for nanoparticle synthesis. Here, we present the chemical synthesis and separation procedures to produce new classes of hairy nanoparticles (bearing both amorphous and crystalline regions) and biopolymers based on wood fibers. Through periodate oxidation of soft wood pulp, the glucose ring of cellulose is opened at the C2-C3 bond to form 2,3-dialdehyde groups. Further heating of the partially oxidized fibers (e.g., T = 80 &#176;C) results in three products, namely fibrous oxidized cellulose, sterically stabilized nanocrystalline cellulose (SNCC), and dissolved dialdehyde modified cellulose (DAMC), which are well separated by intermittent centrifugation and co-solvent addition. The partially oxidized fibers (without heating) were used as a highly reactive intermediate to react with chlorite for converting almost all aldehyde to carboxyl groups. Co-solvent precipitation and centrifugation resulted in electrosterically stabilized nanocrystalline cellulose (ENCC) and dicarboxylated cellulose (DCC). The aldehyde content of SNCC and consequently surface charge of ENCC (carboxyl content) were precisely controlled by controlling the periodate oxidation reaction time, resulting in highly stable nanoparticles bearing more than 7 mmol functional groups per gram of nanoparticles (e.g., as compared to conventional NCC bearing &#60;&#60; 1 mmol functional group/g). Atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) attested to the rod-like morphology. Conductometric titration, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), dynamic light scattering (DLS), electrokinetic-sonic-amplitude (ESA) and acoustic attenuation spectroscopy shed light on the superior properties of these nanomaterials.

The mass portion and charge content of each fraction during the periodate and chlorite oxidation of pulp depends on the reaction time (Table 1). Moreover, DAC molecular weight depends on heating condition and residence time (Table 2). Once SNCC and DAMC are made, they precipitate out by adding propanol (Figure 1). To measure the charge content of ENCC, conductometric titration is performed (Figure 2). NCC and ENCC colloid...

Watch this Scientific Journal Video about Highly Stable, Functional Hairy Nanoparticles and Biopolymers from Wood Fibers: Towards Sustainable Nanotechnology at JoVE.com

Highly Stable, Functional Hairy Nanoparticles and Biopolymers from Wood Fibers: Towards Sustainable Nanotechnology

Synthesis schemes to prepare highly stable wood fiber-based hairy nanoparticles and functional cellulose-based biopolymers have been detailed.

Nanoparticles, as one of the key materials in nanotechnology and nanomedicine, have gained significant importance during the past decade. While ...

The overall goal of this procedure is to produce a new class of cellulose based nanoparticles and biopolymers, including a unique nanocrystalline cellulose that bears both crystalline and amorphous parts, and is thus called hairy nanocrystalline cellulose. This method can help provide key building blocks to advance the sustainable nanotechnology field. The main advantage of this technique is that through simple chemical reactions, cellulose fibers are converted to highly functional nanoparticles and biopolymers.The invention of hairy nanocrystalline cellulose has introduced a new opportunity to use cellulose, the most abundant biopolymer in the world, for advanced applications such as bionanocomposites, rheology modifiers, use in environmental remediation, hydrogels, and much more. Hairy nanocrystalline cellulose can be prepared as a-ly-nik neutral or ker-kyn-ickle nanoparticles, each of which has its own unique properties. To begin, tear up Q-90 softwood pulp sheets into approximately two centimeter square pieces.Collect four grams and soak the pieces in water for at least 24 hours while stirring. Once soaked, use a mechanical disintegrator for about three minutes to make a near uniform dispersion of pulp in solution. Next, use a vacuum filter composed of a 20 micron nylon filter in a Buchner funnel to separate the disintegrated pulp from the liquid.Then, weight the wet pulp and calculate the amount of adsorbed water. Next, prepare a fresh aqueous periodate oxidizing solution. The required ratio of sodium periodate to sodium chloride depends on the type of fibers being synthesized.Now, add the wet pulp to the oxidizing solution. The total mass of water in the system should be 200 grams for SNCC, or 266 grams for ENCC. Then tightly cover the beaker with aluminum foil to prevent periodate deactivation.Stir the mixture at 105 rpm at room temperature to make a favored aldehyde content, which can take several days. When the reaction is complete, add ethylene glycol to the mixture and continue the stirring for 10 minutes to quench the periodate. Then, collect the oxidized pulp by vacuum filtration as before, and redisperse the oxidized pulp in 500 milliliters of water with stirring for 30 minutes.Then vacuum filter the pulp and repeat the redispersion and filtration process until the pulp has been washed five times. After five water washes, store the pulp at four degrees Celsius. Weigh the wet pulp and divide it by four, and remeasure the mass of stored water.Then disperse one quarter in 100 total grams of water in a round bottom flask. Transfer the round bottom flask to an oil bath set to 80 degrees Celsius, and heat it for six hours with gentle stirring. Be aware that under certain heating conditions and residence time in water, the property of the dialdehyde cellulose can change.Once the solution cools, centrifuge it at 18, 500 gs for 10 minutes. The precipitate is the first fraction of unfibrillated cellulose. Separate it from the supernatant.Next, weigh the supernatant and separate the SNCC from the supernatant by adding 1.7 grams of propanol per gram of supernatant while stirring. This will produce a biphasic solution. Then collect the second fraction of SNCC by centrifugation at 3, 000 gs for 10 minutes.Decant the supernatant and store the SNCC for further analysis. To each gram of supernatant, add precisely 3.5 grams of propanol. The white precipitate that forms is the third fraction, which is made up of DAMC.After centrifugation, the DAMC makes a gel. To purify the SNCC or DAMC, redisperse either precipitate in 10 milliliters of water with vigorous stirring for one hour. Then place the dispersion in dialysis tubing and secure the top and bottom with clips.Place the loaded dialysis bag in about four liters of distilled water and stir it for 24 hours to eject the salts. Change the water at least once throughout the dialysis process. Then collect the dialyzed solution and store it at four degrees Celsius.In advance, prepare 0.5 molar sodium hydroxide and set it aside. Now measure the water content of the one quarter of wet oxidized pulp as with SNCC synthesis and calculate how much water is needed for a total of 50 grams. Into this volume of water, dissolve in 2.93 grams of sodium chloride and 1.41 grams of sodium chlorite.Then add the oxidized pulp, followed by dropwise addition of 1.41 grams of hydrogen peroxide. Stir the suspension for 24 hours at room temperature at 105 rpm while maintaining the pH around five by adding drops of the prepared 0.5 molar sodium hydroxide. Expect the pH to drop rapidly after about 15 minutes.Keep the pH at five for at least four hours before letting the reaction go overnight. In the morning, almost no solid should be observable in the solution. Do not overreact the particles or they may gradually lose their crystalline structure.Next, divide the suspension evenly into two centrifuge tubes and centrifuge them at 27, 000 gs for 10 minutes. The supernatant contains the ENCC and DCC. Separate the microfibrous precipitate from the supernatant and weigh both.To the supernatant, slowly add 0.16 grams of ethanol per gram of supernatant while stirring. The ENCC fraction will form as a white precipitate. Then use a 10 minute centrifugation at 3, 000 gs to separate the transparent gel-like ENCC.Decant the supernatant. From the supernatant, collect the DCC fraction using a co-solvent precipitation. Then use the previously described dialysis procedure to purify both the ENCC and DCC fractions before further analysis.After purifying the ENCC and SNCC particles, they were further analyzed. To measure the charge content of the purified ENCC, conductometric titration was performed. NCC and ENCC colloidal behavior was affected by the ionic strength and pH.Next, their size was analyzed at different potassium chloride concentrations and pH. The circles represent NCC, and the squares ENCC. The stars represent dynamic light scattering size measurements.Because SNCC is a neutral particle, its size was altered by adding propanol. Transmission electron microscopy images of ENCC and SNCC revealed their fundamentally similar structures. Bearing a high carboxyl group content, ENCC is able to separate a high amount of copper ions from aqueous systems.FTIR spectra were used to reveal the chemical structure differences of the three fractions. Liquid phase C13 NMR was used to analyze the third fraction, or DCC. Solid state C13 NMR was used to compare a cellulose pulp, NCC, and SNCC.Once mastered, this technique can be easily implemented in hours if it is performed properly. While attempting this procedure, it's important to remember to pay attention to the reaction times under solvent additions. Following this procedure, other functionizations can be performed, such as a shift based reaction to produce ker-hy-nick hairy nanocrystalline cellulose.After its development, this technique has paved the way for researchers in the field of nanotechnology to explore green, sustainable nanomaterials for advanced applications. Don't forget that working with cellular reagents, such as periodate, hydrogen peroxide, and sodium hydroxide is extremely hazardous, and precautions such as wearing a lab coat, goggles, and gloves should be taken while performing this procedure.

Research

JoVE Journal

Chemistry

Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and ...

Folding and Characterization of a Bio-responsive Robot from DNA Origami

The DNA nanorobot is a hollow hexagonal nanometric device, designed to open in response to specific stimuli and present cargo sequestered inside. Both ...

From Constructs to Crystals &#8211; Towards Structure Determination of &#946;-barrel Outer Membrane Proteins

Membrane proteins serve important functions in cells such as nutrient transport, motility, signaling, survival and virulence, yet constitute only ~1% ...

Layer-by-layer Synthesis and Transfer of Freestanding Conjugated Microporous Polymer Nanomembranes

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in ...

A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like ...

Photochemical Oxidative Growth of Iridium Oxide Nanoparticles on CdSe@CdS Nanorods

We demonstrate a procedure for the photochemical oxidative growth of iridium oxide catalysts on the surface of seeded cadmium selenide-cadmium sulfide ...

Green and Low-cost Production of Thermally Stable and Carboxylated Cellulose Nanocrystals and Nanofibrils Using Highly Recyclable Dicarboxylic Acids

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils ...

Microfluidic Dry-spinning and Characterization of Regenerated Silk Fibroin Fibers

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables ...

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

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

Synthesis and Characterization of Amphiphilic Gold Nanoparticles

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of ...