The authors acknowledge the support of the Air Force Research Labs under UES sub-contract #S-932-19-MR002. The authors further acknowledge equipment support from New York State Graduate Research and Teaching Initiative (GRTI/GR15).

1. Pre-analysis Sample Preparation
<ol>
	<li>Separation of functional particles from ink vehicle: centrifugation
	<ol>
		<li>Based on the initial ink formulation, calculate how much ink sample is needed to obtain a minimum of 2.0 g of particle sediment. For example, if the ink is 10 vol% ceramic and the density of the ceramic is 6.67 g/cm3, then a minimum of 3.0 ml of ink is needed to generate 2.0 g of sediment.</li>
		<li>Pipet at least the minimum required ink quantity into a centrifuge tube. Choice of centrifuge tube should be made based on quantity of ink required and on inertness of tube material to ink solvents.</li>
		<li>Place tube in centrifuge. Choice of centrifuge and rotational rate will be dictated by the gravitational force required to sediment the ink particle. A standard lab centrifuge like the Sorvall ST16 centrifuge with a TX-200 swinging bucket rotor is usually adequate.</li>
		<li>Program centrifuge to spin ink at a rotational rate and time necessary to produce a clear supernatant. For the centrifuge used here, typical rates and times are 3,000 &#8211; 4,000 rpm for between 30 min and 90 min. Arriving at the correct rotational speed and time necessary to sediment the ink may require trial and error because even inks of the same average particle sizes may have different particle size distributions.</li>
	</ol>
	</li>
	<li>Post-separation sample handling: removal of supernatant, sample washing, drying
	<ol>
		<li>Once a clear supernatant has been achieved, remove the centrifuge tube from the centrifuge.</li>
		<li>Decant the supernatant and save in a capped glass sample vial for possible future analysis. The functional particles are now residual in the centrifuge tube.</li>
		<li>After decanting, place the uncapped centrifuge tube upside down on a paper towel and allow additional supernatant to drip out for 1 min.</li>
		<li>Remove the tube from the paper towel and rinse the sedimented particles by adding to the tube approximately 2 ml of fresh solvent of the same composition used in the ink formulation. Note that this solvent will only touch the top most layer of the particles sedimented in the centrifuge tube. Decant solvent. Repeat the rinse cycle three times.</li>
		<li>After the final rinse cycle, place the uncapped centrifuge tube upside down on a paper towel and allow the additional solvent to drip out for approximately 5 min.</li>
		<li>Use a thin metal spatula to remove the sediment from the bottom of the centrifuge tube, and spread onto a clean, dry watch glass. Use a lint-free non-abrasive cotton swab or the tip of a clean spatula to remove excess particles from the spatula tip.</li>
		<li>Place the watch glass into a 50 &#176;C oven and allow the particles to dry for 24 hr. The temperature of the oven should be kept relatively low to minimize the possibility of decomposing adsorbed species. The time required for drying the particles will depend on the vapor pressure of the solvent. 24 hr is typical, but results are usually insensitive to wait times as short as 12 hr and as long as 3 weeks.</li>
	</ol>
	</li>
</ol>
2. Diffuse Reflectance Infrared Spectroscopy Measurement
<ol>
	<li>Preparation of infrared spectrometer: align accessory, purge compartment
	<ol>
		<li>Turn on IR spectrometer.</li>
		<li>To prepare for diffuse reflectance infrared spectroscopy measurements, place the diffuse reflectance sampling accessory into the infrared spectrometer sampling compartment. The infrared spectrometer may be any Fourier transform infrared spectrometer capable of interfacing with a diffuse reflectance sampling apparatus. A Shimadzu IR Prestige 21 spectrometer interfaced with a Pike Technologies EasiDiff accessory was utilized for this protocol. For most ink particles, a standard deuterated, L-alanine doped triglycine sulfate (DLaTGS) detector provides enough sensitivity for measurement. A liquid nitrogen cooled mercury cadmium telluride (MCT) detector provides a four to tenfold increase in sensitivity, but this is not usually necessary for identifying adsorbates on ink particle surfaces.</li>
		<li>Align the diffuse reflectance sampling accessory as per the manufacturer&#8217;s instructions.</li>
	</ol>
	</li>
	<li>After alignment, close the infrared sampling compartment and begin purging with nitrogen or with CO2-free, dry air (purge rate of 10 L/min). A standard Parker Balston FT-IR purge gas generator provides air with less than 1 ppm water and CO2. The amount of purge time necessary to obtain a stable water and CO2 free chamber will depend on the sample compartment configuration and the humidity in the lab. The necessary purge time can be determined experimentally by comparing background spectra taken at 1 or 2 min intervals and assessing the intensities of the water and CO2 bands as a function of time.</li>
	<li>Prepare sample for diffuse reflectance infrared spectroscopy measurement
	<ol>
		<li>Obtain the following sample preparation accessories: small (35 mm) agate mortar and pestle, small metal spatula, straight razor blade, and two diffuse reflectance infrared sample cups. Wipe the accessories clean with ethanol, then acetone, and allow them to dry for 10 min in a 50 &#176;C oven.</li>
		<li>Remove clean, dry sample preparation accessories from the oven, place them on a large Kimwipe, and allow them to cool to RT.</li>
		<li>While the sample preparation accessories are cooling, remove the dried ink particles from the oven, and use an analytical balance to measure 0.025 g of the particle sample. Leave the sample sitting in the analytical balance.</li>
		<li>Return to the sample preparation accessories and pour 0.5 g of KBr into the agate mortar. Always use KBr sold for infrared applications. Pre-measured individual 0.5 g packets of KBr (Thermo Scientific) are recommended because they minimize weighing time and exposure of the hydroscopic KBr to the ambient water vapor. Grind the KBr to a uniform appearance, usually 1 min of continuous manual grinding.</li>
		<li>Completely fill one of the diffuse reflectance infrared sampling cups with the ground KBr powder. Lightly press the powder with the blunt end of the pestle, and top off the sampling cup with KBr.</li>
		<li>Use the side of the razor blade to flatten the top of the KBr in the sample cup. This filled and flattened sample is the reference or background.</li>
		<li>Dispose of any KBr remaining in the mortar, and wipe clean.</li>
		<li>Open a new 0.5 g packet of KBr powder (or add 0.5 g of KBr powder), and pour into the mortar.</li>
		<li>Add the previously weighed 0.025 g of ink particles to the 0.5 g of KBr, and grind with the pestle to form a uniform powder, usually 1 min of continuous manual grinding. This ratio of ink particles to KBr provides a 5 wt% sample during the measurement. This is within the standard range (1 &#8211; 10 wt%), but can be adjusted up or down depending on the absorptivity and signal strength of the sample.</li>
		<li>Follow steps 2.3.5 and 2.3.6 to create a sample cup filled with the particle/KBr mixture.</li>
	</ol>
	</li>
	<li>Infrared spectroscopic measurement
	<ol>
		<li>Place the reference and sample cups into the holder, and place the holder into the diffuse reflectance infrared spectroscopy sampling accessory. Position the holder so that the cup containing the background (pure KBr) material is exposed to the infrared radiation.</li>
		<li>Close the infrared sampling compartment and allow the compartment to purge for 5 min. This purge time may be adjusted depending on the amount of time determined to be necessary in step 2.2.</li>
		<li>After 5 min of purging, obtain an infrared spectrum of the background in the region of interest. The number of scans should be set to maximize the signal to noise ratio while minimizing measurement time. 128 scans at 4 cm-1 resolution is usually adequate.</li>
		<li>After the background scan is completed, open the infrared sample compartment and move the cup containing the particle/KBr mixture so that it is now exposed to the infrared radiation.</li>
		<li>Repeat steps 2.4.2 and 2.4.3 to obtain a spectrum of the particle/KBr mixture.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Wray, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Additive+manufacturing-+Turning+manufacturing+inside+out.">Additive manufacturing- Turning manufacturing inside out.</a> American Ceramic Society Bulletin. 93, (2014).</li><li>Hiemenz, P. C., Rajagopalan, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Principles of Colloid and Surface Chemistry, Third Edition, Revised and Expanded. , (1997).</li><li>B&#246;hnlein-Mau&#223;, 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=The+function+of+polymers+in+the+tape+casting+of+alumina.">The function of polymers in the tape casting of alumina.</a> Advanced Materials. 4, 73-81 (1992).</li><li>Grote, C., Cheema, T. A., Garnweitner, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+Study+of+Ligand+Binding+during+the+Postsynthetic+Stabilization+of+Metal+Oxide+Nanoparticles.">Comparative Study of Ligand Binding during the Postsynthetic Stabilization of Metal Oxide Nanoparticles.</a> Langmuir. 28, 14395-14404 (2012).</li><li>Zhang, Q., 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=Aqueous+Dispersions+of+Magnetite+Nanoparticles+Complexed+with+Copolyether+Dispersants:+Experiments+and+Theory.">Aqueous Dispersions of Magnetite Nanoparticles Complexed with Copolyether Dispersants: Experiments and Theory.</a> Langmuir. 23, 6927-6936 (2007).</li><li>Amstad, E., Gillich, T., Bilecka, I., Textor, M., Reimhult, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrastable+Iron+Oxide+Nanoparticle+Colloidal+Suspensions+Using+Dispersants+with+Catechol-Derived+Anchor+Groups.">Ultrastable Iron Oxide Nanoparticle Colloidal Suspensions Using Dispersants with Catechol-Derived Anchor Groups.</a> Nano Letters. 9, 4042-4048 (2009).</li><li>Wu, N., 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=Interaction+of+Fatty+Acid+Monolayers+with+Cobalt+Nanoparticles.">Interaction of Fatty Acid Monolayers with Cobalt Nanoparticles.</a> Nano Letters. 4, 383-386 (2004).</li><li>Blackman, K., Slilaty, R. M., Lewis, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Competitive+Adsorption+Phenomena+in+Nonaqueous+Tape+Casting+Suspensions.">Competitive Adsorption Phenomena in Nonaqueous Tape Casting Suspensions.</a> Journal of the American Ceramic Society. 84, 2501-2506 (2001).</li><li>Hind, A. R., Bhargava, S. K., McKinnon, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=At+the+solid/liquid+interface:+FTIR/ATR+&#8212;+the+tool+of+choice.">At the solid/liquid interface: FTIR/ATR &#8212; the tool of choice.</a> Advances in Colloid and Interface Science. 93, 91-114 (2001).</li><li>Wang, J., Gao, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+properties+of+polymer+adsorbed+zirconia+nanoparticles.">Surface properties of polymer adsorbed zirconia nanoparticles.</a> Nanostructured Materials. 11, 451-457 (1999).</li><li>Guedes, M., Ferreira, J. M. F., Ferro, A. 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+study+on+the+aqueous+dispersion+mechanism+of+CuO+powders+using+Tiron.">A study on the aqueous dispersion mechanism of CuO powders using Tiron.</a> Journal of Colloid and Interface Science. 330, 119-124 (2009).</li><li>Guedes, M., Ferreira, J. M. F., Ferro, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dispersion+of+Cu2O+particles+in+aqueous+suspensions+containing+4,5-dihydroxy-1,3-benzenedisulfonic+acid+disodium+salt.">Dispersion of Cu2O particles in aqueous suspensions containing 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt.</a> Ceramics International. 35, 1939-1945 (2009).</li><li>Gottlieb, H. E., Kotlyar, V., Nudelman, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NMR+Chemical+Shifts+of+Common+Laboratory+Solvents+as+Trace+Impurities.">NMR Chemical Shifts of Common Laboratory Solvents as Trace Impurities.</a> The Journal of Organic Chemistry. 62, 7512-7515 (1997).</li><li>Amstad, E., 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=Influence+of+Electronegative+Substituents+on+the+Binding+Affinity+of+Catechol-Derived+Anchors+to+Fe3O4+Nanoparticles.">Influence of Electronegative Substituents on the Binding Affinity of Catechol-Derived Anchors to Fe3O4 Nanoparticles.</a> The Journal of Physical Chemistry C. 115, 683-691 (2010).</li><li>Naviroj, S., Koenig, J. L., Ishida, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diffuse+Reflectance+Fourier+Transform+Infrared+Spectroscopic+Study+of+Chemical+Bonding+and+Hydrothermal+Stability+of+an+Aminosilane+on+Metal+Oxide+Surfaces.">Diffuse Reflectance Fourier Transform Infrared Spectroscopic Study of Chemical Bonding and Hydrothermal Stability of an Aminosilane on Metal Oxide Surfaces.</a> The Journal of Adhesion. 18, 93-110 (1985).</li><li>Li, C. -. C., Chang, M. -. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colloidal+stability+of+CuO+nanoparticles+in+alkanes+via+oleate+modifications.">Colloidal stability of CuO nanoparticles in alkanes via oleate modifications.</a> Materials Letters. 58, 3903-3907 (2004).</li><li>Lee, S., Paik, U., Yoon, S. -. M., Choi, J. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dispersant-Ethyl+Cellulose+Binder+Interactions+at+the+Ni+Particle-Dihydroterpineol+Interface.">Dispersant-Ethyl Cellulose Binder Interactions at the Ni Particle-Dihydroterpineol Interface.</a> Journal of the American Ceramic Society. 89, 3050-3055 (2006).</li><li>Lee, S. J., Kim, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diffuse+reflectance+infrared+spectra+of+stearic+acid+self-assembled+on+fine+silver+particles.">Diffuse reflectance infrared spectra of stearic acid self-assembled on fine silver particles.</a> Vibrational Spectroscopy. 18, 187-201 (1998).</li><li>Lee, D. H., Condrate, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FTIR+spectral+characterization+of+thin+film+coatings+of+oleic+acid+on+glasses:+I.+Coatings+on+glasses+from+ethyl+alcohol.">FTIR spectral characterization of thin film coatings of oleic acid on glasses: I. Coatings on glasses from ethyl alcohol.</a> Journal of Materials Science. 34, 139-146 (1999).</li><li>Lee, D. H., Condrate, R. A., Lacourse, W. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FTIR+spectral+characterization+of+thin+film+coatings+of+oleic+acid+on+glasses+Part+II+Coatings+on+glass+from+different+media+such+as+water,+alcohol,+benzene+and+air.">FTIR spectral characterization of thin film coatings of oleic acid on glasses Part II Coatings on glass from different media such as water, alcohol, benzene and air.</a> Journal of Materials Science. 35, 4961-4970 (2000).</li><li>Jay Deiner, ., Piotrowski, L., A, K., Reitz, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+Fatty+Acid+and+Triglyceride+Dispersant+Bonding+in+Non-Aqueous+Dispersions+of+NiO.">Mechanisms of Fatty Acid and Triglyceride Dispersant Bonding in Non-Aqueous Dispersions of NiO.</a> Journal of the American Ceramic Society. 96, 750-758 (2013).</li><li>Young, D., 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=Ink-jet+printing+of+electrolyte+and+anode+functional+layer+for+solid+oxide+fuel+cells.">Ink-jet printing of electrolyte and anode functional layer for solid oxide fuel cells.</a> Journal of Power Sources. 184, 191-196 (2008).</li><li>Nakamoto, 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> Infrared and Raman Spectra of Inorganic and Coordination Complexes. , (1997).</li><li>Fuller, M. P., Griffiths, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diffuse+reflectance+measurements+by+infrared+Fourier+transform+spectrometry.">Diffuse reflectance measurements by infrared Fourier transform spectrometry.</a> Analytical Chemistry. 50, 1906-1910 (1978).</li></ol>

The authors have nothing to disclose.

The two critical factors for generating high quality infrared spectra using this procedure are: 1) minimizing the absolute quantity of water contamination and the differences in the quantity of water contamination between the sample and reference cups; and 2) creating sample and reference cups with uniform flat layers and similar KBr grain sizes. Both of these factors are achieved by paying particular attention to the sample preparation procedures outlined in section 2.3.
In order minimize the...

Additive manufacturing has recently emerged as a promising technique for fabrication of everything from ceramics to semiconductors to medical devices1. As the applications of additive manufacturing expand to printed ceramic, metal oxide, and metal parts, the need to formulate specialized functional inks arises. The question of how to formulate the required functional inks relates to a fundamental issue in surface and colloid science: what are the mechanisms by which particles in colloidal dispersion are stabilized against aggregation? Broadly, stabilization requires modification of the particle surfaces such that close approach of particles (and hence aggregation) is prevented either by Coulombic repulsion (electrostatic stabilization), by the entropic penalty of polymer entanglement (steric stabilization), or by a combination of the Coulombic and entropic forces (electrosteric stabilization)2. In order to achieve any of these mechanisms of stabilization, it is usually necessary to modify the particle surface chemistry through attachment of polymers or shorter chain functional groups. Thus, the rational formulation of stable functional inks demands that we know whether a given chemical additive attaches to the particle surface and what chemical group attaches to the particle surface.
The goal of the method presented in this protocol is to demonstrate rapid characterization of chemical species adsorbed on particle surfaces in functional inks. This goal is particularly important as functional ink formulation transitions from a specialized task for surface and colloid scientists to an activity broadly practiced by the range of scientists and engineers interested in printing ceramic, metal oxide, and metal devices. Achieving this goal requires designing an experiment that overcomes the challenges of characterizing opaque, high solids loadings dispersions. It also requires discriminating between chemical species that are present in the dispersion but not adsorbed on the particles from those that are actually adsorbed. It further requires distinguishing between those species that are chemically adsorbed on the particles from those that are weakly physisorbed. In this experimental protocol, we present the use of diffuse reflectance infrared spectroscopy for characterization of dispersant attachment in functional inks. The diffuse reflectance infrared spectroscopy measurement follows a pre-analysis sample preparation technique necessary to distinguish adsorbed species from those merely present in the dispersion.
A variety of methods are currently used to gain insight into the nature of the interactions between chemical ink components and colloidally dispersed particles. Some of these methods are indirect probes in which measured properties are presumed to correlate with surface functionalization. For example, changes in slurry rheology or sedimentation rates are presumed to correlate with adsorption of surface modifiers3. Particle size distribution, as characterized by dynamic light scattering (DLS), and zeta potential, as characterized by electrophoretic mobility, provide insight into the adsorption of polymers or species with surface charge4,5. Similarly, sample mass loss as probed by thermogravimetric analysis (TGA) relates to the presence of desorbing species and the strength of interaction between the adsorbate and the particle6. The information from the above mentioned indirect probes suggest changes in surface chemistry, but they do not provide direct insight into the identity of the adsorbing species or the mechanism of its adsorption. Direct insight is particularly important for functional inks in which a large number of components are present in the dispersion. To provide detailed molecular level information, X-ray photoelectron spectroscopy (XPS)7, 13C nuclear magnetic resonance (NMR) 4,6, and infrared spectroscopy8-12 have been explored. Of these three options, infrared spectroscopy is particularly promising. In comparison to 13C NMR, infrared spectroscopy does not require that inks be formulated with analytically pure solvents to prevent interferences during measurement13. In comparison to X-ray photoelectron spectroscopy, standard infrared spectroscopy can be conducted at ambient pressure, avoiding the need for ultrahigh vacuum conditions during measurement.
There is literature precedent for the use of infrared spectroscopy to probe the interaction between colloidally dispersed ceramic, metal oxide, and metal nanoparticles. These works can be separated into attempts to measure interfacial chemistry in situ using attenuated total reflectance infrared (ATR-IR)9, and attempts to measure interfacial chemistry ex situ using solid sampling8. While there are advantages to in situ measurements, the uncertainties that arise due to the necessity for spectral manipulation make the method difficult for multi-component inks in which there are solvents and multiple polymeric components. Therefore, this protocol focuses on solid sampling and ex situ measurement. All of the solid sampling methods entail a pre-treatment step where a solid is obtained by separating the particles from the solvent, and an analysis step where infrared measurements are performed on the solid particles. The difference between methods arises in the choice of sample pre-treatment and in the choice of experimental technique used for infrared analysis of the solid. Historically, the traditional way to use infrared spectroscopy to analyze solids was to grind small quantities (&#60; 1%) of the solid sample with potassium bromide (KBr) powder, and then subject the mixture to high pressure sintering. The result is a transparent KBr pellet. This procedure has been attempted successfully with powders derived from aqueous suspensions of zirconia nanoparticles functionalized with polyethyleneamine10, with fatty acid monolayers on cobalt nanoparticles7, and with catechol-derived dispersants on Fe3O4 nanoparticles14. Despite these successful applications of the KBr pelleting technique for detection of adsorbed dispersants, diffuse reflectance infrared spectroscopy provides several advantages. One advantage is simplified sample preparation. In contrast to KBr pelleting, the solid sample in diffuse reflectance can be simply ground by hand. There is no sintering step as the powder itself is loaded into the sample cup and the diffusely scattered infrared light is measured. The other advantage of diffuse reflectance over KBr pelleting is the increased surface sensitivity15. The increase in surface sensitivity is especially useful for the present application in which the critical questions are the presence and nature of adsorbates on the nanoparticle surfaces.
Among works that have used the diffuse reflectance sampling technique to probe the adsorption of chemical species on colloidally dispersed samples, the primary differences arise in the method of separating the nanoparticles from the liquid medium. This step is critical because, without the separation, it would be impossible to distinguish specifically adsorbed dispersants from dispersants simply dissolved in the liquid medium. In several examples, the method of separation is not obvious from the experimental protocol12,16,17. When specified, the most frequently practiced method involves gravitational separation. The rationale is that the ceramic, metal oxide, and metal nanoparticles are all more dense than the surrounding media. When they settle, they will drag down with them only the specifically adsorbed species. Chemical species not interacting with the particles will remain in solution. While dispersions may readily settle under normal gravitational force18, a stable inkjet ink should not observably settle over a time period of less than a year. As such, the method of employing centrifugation for pre-analysis separation is preferred. This has been demonstrated in several studies of dispersant adsorption on glass particles19,20, dispersant binder adsorption on alumina8, and anionic dispersant functionalization of CuO11. Most recently, we have used it to evaluate mechanisms of fatty acid binding in non-aqueous NiO dispersions used for inkjet and aerosol jet printing of solid oxide fuel cell layers21.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>FTIR bench</td>
			<td>Shimadzu Scientific Instruments</td>
			<td>IR_Prestige 21 used in this work; in 2013 IR-Tracer 100 model replaced Prestige-21</td>
			<td>Any research grade FTIR with purgable sample compartment is acceptable</td>
		</tr>
		<tr>
			<td>Purge gas generator for sample compartment</td>
			<td>Parker Balston</td>
			<td>74-5041NA Lab Gas Generator</td>
			<td>Provides air with less than 1ppm CO2 and water; also possible to purge compartment with N2 tank</td>
		</tr>
		<tr>
			<td>Diffuse Reflectance Infrared Accessory</td>
			<td>Pike Technologies</td>
			<td>042-10XX</td>
			<td>Includes sample preparation kit and mortar and pestle (these can also be purchased separately, described below)</td>
		</tr>
		<tr>
			<td>Diffuse Reflectance Sample Preparation kit</td>
			<td>Pike Technologies</td>
			<td>042-3040</td>
			<td>Includes sample holder cups, spatulas, alignment mirror, mirror brush, razor blades</td>
		</tr>
		<tr>
			<td>Agate mortar and pestle</td>
			<td>Pike Technologies</td>
			<td>161-5035</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>ThermoScientific</td>
			<td>Sorvall ST16</td>
			<td>Most benchtop centrifuges capable of ~ 5000 rpm will be acceptable</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Consumables</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Item</td>
			<td>Company</td>
			<td>Catalog #</td>
			<td>Comments/Description</td>
		</tr>
		<tr>
			<td>Centrifuge tubes</td>
			<td>Evergreen Scientific</td>
			<td>222-2470-G8K</td>
			<td>Any centrifuge tube of compatible size and material is acceptable</td>
		</tr>
		<tr>
			<td>KBr powder packets</td>
			<td>ThermoScientific</td>
			<td>50-465-317</td>
			<td>Also possible to use alternative KBr supplier</td>
		</tr>
	</tbody>
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diffuse reflectance infrared spectroscopic identification of dispersant/particle bonding mechanisms in functional inks

In additive manufacturing, or 3D printing, material is deposited drop by drop, to create micron to macroscale layers. A typical inkjet ink is a colloidal dispersion containing approximately ten components including solvent, the nano to micron scale particles which will comprise the printed layer, polymeric dispersants to stabilize the particles, and polymers to tune layer strength, surface tension and viscosity. To rationally and efficiently formulate such an ink, it is crucial to know how the components interact. Specifically, which polymers bond to the particle surfaces and how are they attached? Answering this question requires an experimental procedure that discriminates between polymer adsorbed on the particles and free polymer. Further, the method must provide details about how the functional groups of the polymer interact with the particle. In this protocol, we show how to employ centrifugation to separate particles with adsorbed polymer from the rest of the ink, prepare the separated samples for spectroscopic measurement, and use Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) for accurate determination of dispersant/particle bonding mechanisms. A significant advantage of this methodology is that it provides high level mechanistic detail using only simple, commonly available laboratory equipment. This makes crucial data available to almost any formulation laboratory. The method is most useful for inks composed of metal, ceramic, and metal oxide particles in the range of 100 nm or greater. Because of the density and particle size of these inks, they are readily separable with centrifugation. Further, the spectroscopic signatures of such particles are easy to distinguish from absorbed polymer. The primary limitation of this technique is that the spectroscopy is performed ex-situ on the separated and dried particles as opposed to the particles in dispersion. However, results from attenuated total reflectance spectra of the wet separated particles provide evidence for the validity of the DRIFTS measurement.

The experimental procedure described in this protocol has been applied to gain insight into the mechanism of NiO particle stabilization in an ink used to print the anode of solid oxide fuel cells. This ink is a dispersion of NiO particles in 2-butanol, alpha terpineol, and a range of dispersants and binders22. Representative results are shown here for a simplified dispersion of NiO in 2-butanol with an oleic acid dispersant. In Figure 1A, we show raw diffuse reflectance infrared spectroscopy d...

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Diffuse Reflectance Infrared Spectroscopic Identification of Dispersant/Particle Bonding Mechanisms in Functional Inks

Formulation of stable, functional inks is critical to expanding the applications of additive manufacturing. In turn, knowledge of the mechanisms of dispersant/particle bonding is required for effective ink formulation. Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) is presented as a simple, inexpensive way to gain insight into these mechanisms.

In additive manufacturing, or 3D printing, material is deposited drop by drop, to create micron to macroscale layers.  A typical inkjet ink is a colloidal ...

diffuse-reflectance-infrared-spectroscopic-identification

Research

JoVE Journal

Chemistry

13.6K 조회수.  New York City College of Technology, City University of New York (CUNY). Formulation of stable, functional inks is critical to expanding the applications of additive manufacturing. In turn, knowledge of the mechanisms of dispersant/particle bonding is required for effective ink formulation. Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) is presented as a simple, inexpensive way to gain insight into these mechanisms.

비디오: Diffuse Reflectance Infrared Spectroscopic Identification of Dispersant/Particle Bonding Mechanisms in Functional Inks

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 combination with their outstanding thermal and chemical stability, and low densities. However, their insoluble nature causes problems in their processing since usually applied techniques such as spin coating are not available. Especially for membrane applications, where the processing of CMP as thin films is desirable, the processing problems have hindered their commercial application.
Here we describe the interfacial synthesis of CMP thin films on functionalized substrates via molecular layer-by-layer (l-b-l) synthesis. This process allows the preparation of films with desired thickness and composition and even desired composition gradients.
The use of sacrificial supports allows the preparation of freestanding membranes by dissolution of the support after the synthesis. To handle such ultra-thin freestanding membranes the protection with sacrificial coatings showed great promise, to avoid rupture of the nanomembranes. To transfer the nanomembranes to the desired substrate, the coated membranes are upfloated at the air-liquid interface and then transferred via dip coating.

In this paper we describe the interfacial synthesis of conjugated microporous polymers (CMP) on sacrificial substrates, and the dissolution of the substrate for the preparation of freestanding CMP nanomembranes. In addition, we will describe how the fragile nanomembranes can be transferred to other substrates.

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

A Filter-based Surface Enhanced Raman Spectroscopic Assay for Rapid Detection of Chemical Contaminants

We demonstrate a method to fabricate highly sensitive surface-enhanced Raman spectroscopic (SERS) substrates using a filter syringe system that can be applied to the detection of various chemical contaminants. Silver nanoparticles (Ag NPs) are synthesized via reduction of silver nitrate by sodium citrate. Then the NPs are aggregated by sodium chloride to form nanoclusters that could be trapped in the pores of the filter membrane. A syringe is connected to the filter holder, with a filter membrane inside. By loading the nanoclusters into the syringe and passing through the membrane, the liquid goes through the membrane but not the nanoclusters, forming a SERS-active membrane. When testing the analyte, the liquid sample is loaded into the syringe and flowed through the Ag NPs coated membrane. The analyte binds and concentrates on the Ag NPs coated membrane. Then the membrane is detached from the filter holder, air dried and measured by a Raman instrument. Here we present the study of the volume effect of Ag NPs and sample on the detection sensitivity as well as the detection of 10 ppb ferbam and 1 ppm ampicillin using the developed assay.

A procedure for fabrication and performing the filter-based surface enhanced Raman spectroscopic (SERS) assay for the detection of chemical contaminants (i.e., pesticide ferbam and antibiotic ampicillin) is presented.

We demonstrate a method to fabricate highly sensitive surface-enhanced Raman spectroscopic (SERS) substrates using a filter syringe system that can be ...

Construction of Models for Nondestructive Prediction of Ingredient Contents in Blueberries by Near-infrared Spectroscopy Based on HPLC Measurements

Nondestructive prediction of ingredient contents of farm products is useful to ship and sell the products with guaranteed qualities. Here, near-infrared spectroscopy is used to predict nondestructively total sugar, total organic acid, and total anthocyanin content in each blueberry. The technique is expected to enable the selection of only delicious blueberries from all harvested ones. The near-infrared absorption spectra of blueberries are measured with the diffuse reflectance mode at the positions not on the calyx. The ingredient contents of a blueberry determined by high-performance liquid chromatography are used to construct models to predict the ingredient contents from observed spectra. Partial least squares regression is used for the construction of the models. It is necessary to properly select the pretreatments for the observed spectra and the wavelength regions of the spectra used for analyses. Validations are necessary for the constructed models to confirm that the ingredient contents are predicted with practical accuracies. Here we present a protocol to construct and validate the models for nondestructive prediction of ingredient contents in blueberries by near-infrared spectroscopy.

We present here a protocol to construct and validate models for nondestructive prediction of total sugar, total organic acid, and total anthocyanin content in individual blueberries by near-infrared spectroscopy.

Nondestructive prediction of ingredient contents of farm products is useful to ship and sell the products with guaranteed qualities. Here, near-infrared ...

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels

Ion channel gating is a stimulus-driven orchestration of protein motions that leads to transitions between closed, open, and desensitized states. Fundamental to these transitions is the intrinsic flexibility of the protein, which is critically modulated by membrane lipid-composition. To better understand the structural basis of channel function, it is necessary to study protein dynamics in a physiological membrane environment. Electron Paramagnetic Resonance (EPR) spectroscopy is an important tool to characterize conformational transitions between functional states. In comparison to NMR and X-ray crystallography, the information obtained from EPR is intrinsically of lower resolution. However, unlike in other techniques, in EPR there is no upper-limit to the molecular weight of the protein, the sample requirements are significantly lower, and more importantly the protein is not constrained by the crystal lattice forces. Therefore, EPR is uniquely suited for studying large protein complexes and proteins in reconstituted systems. In this article, we will discuss general protocols for site-directed spin labeling and membrane reconstitution using a prokaryotic proton-gated pentameric Ligand-Gated Ion Channel (pLGIC) from Gloeobacter violaceus (GLIC) as an example. A combination of steady-state Continuous Wave (CW) and Pulsed (Double Electron Electron Resonance-DEER) EPR approaches will be described that will enable a complete quantitative characterization of channel dynamics.

This article describes methods for site-directed spin labeling and reconstitution of pentameric ligand-gated channels for Electron Paramagnetic Resonance studies. This protocol can be adapted for any membrane protein. The reconstitution method described here can also be used for patch-clamp measurements of macroscopic and single-channel currents in a defined lipid system.

Ion channel gating is a stimulus-driven orchestration of protein motions that leads to transitions between closed, open, and desensitized states. ...

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding

Herein, we demonstrate that a bottom-up approach, based on halogen bonding (XB), can be successfully applied for the design of a new type of ionic liquid crystals (ILCs). Taking advantages of the high specificity of XB for haloperfluorocarbons and the ability of anions to act as XB-acceptors, we obtained supramolecular complexes based on 1-alkyl-3-methylimidazolium iodides and iodoperfluorocarbons, overcoming the well-known immiscibility between hydrocarbons (HCs) and perfluorocarbons (PFCs). The high directionality of the XB combined with the fluorophobic effect, allowed us to obtain enantiotropic liquid crystals where a rigid, non-aromatic, XB supramolecular anion acts as mesogenic core.
X-ray structure analysis of the complex between 1-ethyl-3-methylimidazolium iodide and iodoperfluorooctane showed the presence of a layered structure, which is a manifestation of the well-known tendency to segregation of perfluoroalkyl chains. This is consistent with the observation of smectic mesophases. Moreover, all the reported complexes melt below 100 &#176;C, and most are mesomorphic even at room temperature, despite that the starting materials were non-mesomorphic in nature.
The supramolecular strategy reported here provides new design principles for mesogen design allowing a totally new class of functional materials.

A protocol for the synthesis of a new type of mesogens, based on the halogen-bonded supramolecular anion [CnF2n+1-I&#183;&#183;&#183;I&#183;&#183;&#183;I-CnF2n+1]&#8722;, is reported.

Herein, we demonstrate that a bottom-up approach, based on halogen bonding (XB), can be successfully applied for the design of a new type of ionic liquid ...

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

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

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

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

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

Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate

The synthesis of 3,5-lutidine N-oxide dehydrate, 1, was achieved in the synthesis route of 2-amino-pyridine-3,5-dicarboxylic acid. Ochiai first used the methodology for non-substituted pyridines in 1957 in a 12 h process, but no X-ray suitable crystals were obtained. The substituted ring used in the methodology presented here clearly influenced the addition of water molecules into the asymmetric unit, which confers a different nucleophilic strength in 1. The X-ray suitable crystal compound 1 was possible due to the stabilization of the negative charge in the oxygen by the presence of two water molecules where the hydrogen atoms donate positive charge into the ring; such water molecules serve well to construct a supramolecular interaction. The hydrated molecules may be possible for the alkaline system that is reached by adjusting the pH to 10. Importantly, the double methyl substituted ring and a reaction time of 5 h, makes it a more versatile method and with wider chemical applications for future ring insertions.

Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate

Herein, we report the synthesis and crystallization of 3,5-lutidine N-oxide dehydrate by a simple protocol that differs from the classical synthesis of pyridine N-oxide. This protocol utilizes different starting material and involves less reaction time to yield a new solvated supramolecular structure, which crystallizes under slow evaporation.

The synthesis of 3,5-lutidine N-oxide dehydrate, 1, was achieved in the synthesis route of 2-amino-pyridine-3,5-dicarboxylic acid. Ochiai first used the ...

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 ...

Inkjet Printing All Inorganic Halide Perovskite Inks for Photovoltaic Applications

A method for synthesizing photoactive inorganic&#160;perovskite quantum dot inks and an inkjet printer deposition method, using the synthesized inks, are demonstrated. The ink synthesis is based on a simple wet chemical reaction and the inkjet printing protocol is a facile step by step method. The inkjet printed thin films have been characterized by X-ray diffraction, optical absorption spectroscopy, photoluminescent spectroscopy, and electronic transport measurements. X-ray diffraction of the printed quantum dot films indicates a crystal structure consistent with an orthorhombic room temperature phase with (001) orientation. In conjunction with other characterization methods, the X-ray diffraction&#160;measurements show high quality films can be obtained through the inkjet printing method.

A protocol for synthesizing inorganic-lead-halide hybrid perovskite quantum dot inks for inkjet printing and the protocol for preparing and printing the quantum dot inks in an inkjet printer with post characterization techniques are presented.

A method for synthesizing photoactive inorganic&#160;perovskite quantum dot inks and an inkjet printer deposition method, using the synthesized inks, are ...

Characterizing Lewis Pairs Using Titration Coupled with In Situ Infrared Spectroscopy

Lewis acid-activation of carbonyl-containing substrates is a fundamental basis for facilitating transformations in organic chemistry. Historically, characterization of these interactions has been limited to models equivalent to stoichiometric reactions. Here, we report a method utilizing in situ infrared spectroscopy to probe the solution interactions between Lewis acids and carbonyls under synthetically relevant conditions. Using this method, we were able to identify 1:1 complexation between GaCl3 and acetone and a highly ligated complex for FeCl3 and acetone. The impact of this technique on mechanistic understanding is illustrated by application to the mechanism of Lewis acid-mediated carbonyl-olefin metathesis in which we were able to observe competitive binding interactions between substrate carbonyl and product carbonyl with the catalyst.

Here, we present a method for the observation of solution interactions between Lewis acids and bases by employing in situ infrared spectroscopy as a detector for titration under synthetically relevant conditions. By examining solution interactions, this method represents a complement to X-ray crystallography, and provides an alternative to NMR spectroscopy.

Lewis acid-activation of carbonyl-containing substrates is a fundamental basis for facilitating transformations in organic chemistry. Historically, ...