The authors acknowledge constructive discussion with Prof. D.Y.C. Leung and Dr. Y. Chen (The University of Hong Kong), Prof. M.H.K. Leung (City University of Hong Kong), Dr. W. S. Liu (Southern University of Science and Technology), and Mr. Frank H.T. Leung (Techskill [Asia] Limited). The authors acknowledge the financial support of General Research Fund of the Research Grants Council of Hong Kong Special Administrative Region, China, under Award Number 17204516 and 17206518, and Innovation and Technology Fund (Ref: ITS/171/16FX).

1. Preparation of the graphene oxide electrode
<ol>
	<li>Synthesis of graphene oxide via the modified Hummer&#39;s method
	<ol>
		<li>Steps 1.1.2 and 1.1.3 occur at a low temperature (&#60;0 &#176;C). Circulate ice water flowing through the external layer of a double wall glass beaker placed on a magnetic stirrer to create low temperature conditions for the reactants inside.</li>
		<li>Mix 1 g of sodium nitrate (NaNO3) with 100 mL of sulfuric acid (H2SO4, reagent grade, 95-98%) using slow stirring in the beaker.</li>
		<li>Add 1 g of flake graphite into the sulfuric acid and stir for 1 h in the cold bath. Add 6 g of potassium permanganate (KMnO4) gradually to the solution and stir the mixture for another 2 h.</li>
		<li>The next step of the reaction takes place at a middle temperature (~35 &#176;C). Change the ice water to 35 &#176;C water and continue the oxidation of the graphite by stirring for &#189; h.</li>
		<li>The last step of the reaction takes place at a TH (80-90 &#176;C). Add 46 mL of deionized (DI) water (70 &#176;C) into the reaction tank drop by drop. Note that that the reaction is strong. Add 140 mL of DI water and 20 mL of hydrogen peroxide (30% H2O2) in the reaction tank as the last step of the reaction. Make sure that golden particles of GO appear as a result.</li>
		<li>Wash the product thoroughly with dilute hydrochloric acid (HCl) and DI water several times until the GO suspension reaches pH = 7.</li>
		<li>Freeze the washed GO suspension overnight and dry it in a freeze dryer until water evaporates completely.</li>
	</ol>
	</li>
	<li>Preparation of the graphene oxide electrode
	<ol>
		<li>Mix the graphene oxide, carbon black, and PVDF in a mass ratio of 75:15:10 and put them in a glass bottle. Drip the solvent N-methyl-2-pyrrolidone (NMP) into the solid mixture and ensure the weight ratio of solvent and solid mixture is 4:1.</li>
		<li>Prepare the paste by mixing at 2,000 rpm for 13 min and defoaming in 1,200 rpm for 2 min with a mixer.</li>
		<li>Brush coat the paste on carbon paper until the coat is ~8-15 mg/cm2 and dry it for 4 h at 40 &#176;C.</li>
	</ol>
	</li>
</ol>
2. Preparation of the polyaniline (PANI) electrode
<ol>
	<li>Prepare 1 wt% carboxymethyl cellulose (CMC) aqueous solution by dissolving CMC powder in DI water by stirring for 10 h.</li>
	<li>Mix 50 mg of leucoemeraldine-base PANI and 10 mg of carbon black in a beaker. Add 150 &#956;L of 1 wt% CMC solution into the beaker and mix with a magnetic stirrer for 12 h.</li>
	<li>Add 6 &#956;L of 40% styrene-butadiene (SBR) solution into the mixture and stir for another 15 min.</li>
	<li>Place a piece of carbon paper on the doctor blade coater and drop the mixed PANI slurry at the leading edge of the carbon paper.</li>
	<li>Blade coat the slurry to produce a film 400 &#956;m thick on the carbon paper. Dry the coating for 4 h at 50 &#176;C.</li>
</ol>
3. Assembling the pouch cell
<ol>
	<li>Cut titanium foil into the approproate size and then connect each piece to a nickel tab with a 20 kHz ultrasonic spot welding machine.</li>
	<li>Place the porous hydrophilic polypropylene-based separator between the GO electrode and the PANI electrode to avoid short circuits. Each electrode is paired with one current collector.</li>
	<li>Package the electrodes using aluminum laminated film. Seal the sides of the aluminum laminated film with a compact vacuum sealer for 4 s. Set the temperature of the top and bottom sealing parts as 180 &#176;C and 160 &#176;C separately.</li>
	<li>Inject 500 &#956;L of the 1 M KCl electrolyte into the pouch cell and allow to equilibrate for 10 min.</li>
	<li>Extrude the excess electrolyte and seal the last side of the pouch cell in a -80 kPa vacuum chamber.</li>
</ol>
4. Setting up the temperature controlling system
<ol>
	<li>Stack the pouch cell between two thermoelectric modules. Place thermocouples on the top and bottom sides of the cell. Apply thermal paste to all the interfaces to ensure good thermal contact. 
	NOTE: The temperature is controlled with LabVIEW code. Temperatures measured from the thermocouples are compared with the setting temperatures and the output voltage is determined by the difference between the real time temperature and setting temperature via a PID control. The voltage signals are transmitted to the power supply and are connected to the thermoelectric module. The closed-loop control guarantees a temperature measurement accuracy within &#177; 0.5 &#176;C.</li>
</ol>
5. Electrochemical characterization
<ol>
	<li>Perform the electrochemical tests of the cell using a potentiostat. Conduct the thermal charging in open circuit mode while carrying out the electrical discharging process at a constant current.</li>
</ol>

<ol>
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K., Pardemann, R., Meyer, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimating+the+Global+Waste+Heat+Potential.">Estimating the Global Waste Heat Potential.</a> Renewable and Sustainable Energy Reviews. 57, 1568-1579 (2016).</li><li>Gur, I., Sawyer, K., Prasher, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Searching+for+A+Better+Thermal+Battery.">Searching for A Better Thermal Battery.</a> Science. 335 (6075), 1454-1455 (2012).</li><li>He, R., Schierning, G., Nielsch, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoelectric+Devices:+A+Review+of+Devices,+Architectures,+and+Contact+Optimization.">Thermoelectric Devices: A Review of Devices, Architectures, and Contact Optimization.</a> Advanced Materials Technologies. 3 (4), 1700256 (2018).</li><li>Abraham, T. J., MacFarlane, D. R., Pringle, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+Seebeck+Coefficient+Redox+Ionic+Liquid+Electrolytes+for+Thermal+Energy+Harvesting.">High Seebeck Coefficient Redox Ionic Liquid Electrolytes for Thermal Energy Harvesting.</a> Energy &amp; Environmental Science. 6 (9), 2639-2645 (2013).</li><li>Zhang, L., 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=High+Power+Density+Electrochemical+Thermocells+for+Inexpensively+Harvesting+Low-Grade+Thermal+Energy.">High Power Density Electrochemical Thermocells for Inexpensively Harvesting Low-Grade Thermal Energy.</a> Advanced Materials. 29 (12), 1605652 (2017).</li><li>Duan, 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=Aqueous+Thermogalvanic+Cells+with+A+High+Seebeck+Coefficient+for+Low-Grade+Heat+Harvest.">Aqueous Thermogalvanic Cells with A High Seebeck Coefficient for Low-Grade Heat Harvest.</a> Nature Communications. 9 (1), 5146 (2018).</li><li>Im, H., 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=High-Efficiency+Electrochemical+Thermal+Energy+Harvester+Using+Carbon+Nanotube+Aerogel+Sheet+Electrodes.">High-Efficiency Electrochemical Thermal Energy Harvester Using Carbon Nanotube Aerogel Sheet Electrodes.</a> Nature Communications. 7, 10600 (2016).</li><li>Hu, R., 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=Harvesting+Waste+Thermal+Energy+Using+A+Carbon-Nanotube-Based+Thermo-Electrochemical+Cell.">Harvesting Waste Thermal Energy Using A Carbon-Nanotube-Based Thermo-Electrochemical Cell.</a> Nano Letters. 10 (3), 838-846 (2010).</li><li>Poletayev, A. 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W., 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=An+Electrochemical+System+for+Efficiently+Harvesting+Low-Grade+Heat+Energy.">An Electrochemical System for Efficiently Harvesting Low-Grade Heat Energy.</a> Nature Communications. 5, 3942 (2014).</li><li>Yang, Y., 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=Charging-Free+Electrochemical+System+for+Harvesting+Low-Grade+Thermal+Energy.">Charging-Free Electrochemical System for Harvesting Low-Grade Thermal Energy.</a> Proceedings of the National Academy of Sciences. 111 (48), 17011-17016 (2014).</li><li>Yang, Y., 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=Membrane-Free+Battery+for+Harvesting+Low-Grade+Thermal+Energy.">Membrane-Free Battery for Harvesting Low-Grade Thermal Energy.</a> Nano Letters. 14 (11), 6578-6583 (2014).</li><li>Fukuzumi, Y., Amaha, K., Kobayashi, W., Niwa, H., Mortitomo, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prussian+Blue+Analogues+as+Promising+Thermal+Power+Generation+Materials.">Prussian Blue Analogues as Promising Thermal Power Generation Materials.</a> Energy Technology. 6 (10), 1865-1870 (2018).</li><li>Shibata, T., Fukuzumi, Y., Kobayashi, W., Moritomo, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+Power+Generation+During+Heat+Cycle+Near+Room+Temperature.">Thermal Power Generation During Heat Cycle Near Room Temperature.</a> Applied Physics Express. 11 (1), 017101 (2018).</li><li>Shibata, T., Fukuzumi, Y., Moritomo, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+Efficiency+of+A+Thermocell+Made+of+Prussian+Blue+Analogues.">Thermal Efficiency of A Thermocell Made of Prussian Blue Analogues.</a> Scientific Reports. 8 (1), 14784 (2018).</li><li>Takahara, I., Shibata, T., Fukuzumi, Y., Moritomo, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+Thermal+Cyclability+of+Tertiary+Battery+Made+of+Prussian+Blue+Analogues.">Improved Thermal Cyclability of Tertiary Battery Made of Prussian Blue Analogues.</a> ChemistrySelect. 4 (29), 8558-8563 (2019).</li><li>Zhang, F., Liu, J., Yang, W., Logan, B. 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+Thermally+Regenerative+Ammonia-Based+Battery+for+Efficient+Harvesting+of+Low-Grade+Thermal+Energy+as+Electrical+Power.">A Thermally Regenerative Ammonia-Based Battery for Efficient Harvesting of Low-Grade Thermal Energy as Electrical Power.</a> Energy and Environmental Science. 8 (1), 343-349 (2015).</li><li>Zhu, X., Rahimi, M., Gorski, C. A., Logan, 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+Thermally-Regenerative+Ammonia-Based+Flow+Battery+for+Electrical+Energy+Recovery+from+Waste+Heat.">A Thermally-Regenerative Ammonia-Based Flow Battery for Electrical Energy Recovery from Waste Heat.</a> ChemSusChem. 9 (8), 873-879 (2016).</li><li>Zhang, F., LaBarge, N., Yang, W., Liu, J., Logan, B. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancing+Low-Grade+Thermal+Energy+Recovery+in+a+Thermally+Regenerative+Ammonia+Battery+Using+Elevated+Temperatures.">Enhancing Low-Grade Thermal Energy Recovery in a Thermally Regenerative Ammonia Battery Using Elevated Temperatures.</a> ChemSusChem. 8 (6), 1043-1048 (2015).</li></ol>

The authors declare no competing financial interests.

The aTEC converts thermal energy into electricity via a thermal charging process when heating from RT to TH and a successive electrical discharging process at TH. Getting rid of the dependence on a temperature gradient or a temperature cycle like the TGC and TREC, aTEC allows isothermal heating operation during the entire charging and discharging processes. Thermal induced voltage is based on the pseudocapacitive effect of GO because heating facilitates the chemisorption of protons on the oxygen fun...

Ubiquitous low-grade heat energy (&#60;100 &#176;C) could be recycled and converted into electricity1,2 but is instead wasted. Unfortunately, heat recovery is still a great challenge, because converting low-grade heat to electricity is usually inefficient due to the low temperature differential and the distributed nature of the heat sources3. Intensive research has been conducted in solid-state thermoelectric (TE) materials and devices for the past decades, but the scalable application of TE devices in a low-grade heat regime is limited by the low energy conversion efficiency (&#951;E) of &#60;2%4.
Alternative approaches based on the effect of temperature on electrochemical cells have been suggested as a solution to this problem, because the ionic Seebeck coefficient (&#945;) of thermoelectrochemical cells (TECs) is much higher than that of TE semiconductors5,6. Thermogalvanic cells (TGC) utilize redox active electrolytes sandwiched between two identical electrodes to generate a voltage across the cell when a thermal gradient is applied. The commonly used aqueous Fe(CN)63-/Fe(CN)64- electrolyte in TGCs was reported to have an &#945; of -1.4 mV/K and yield an &#951;E of &#60;1%7,8,9,10,11. However, TGCs suffer the drawback of the poor ionic conductivity of the liquid electrolyte, which is around three orders of magnitude smaller than the electronic conductivity in TE materials. The electric conductivity could be improved, but this improvement is always accompanied by a higher thermal conductivity, which leads to a lower temperature gradient. Therefore, the &#951;E of TGCs is inherently limited due to the trade-off between the liquid electrolyte conductance and the temperature requirement for the desired redox reactions in each side of the electrode.
A thermally regenerative electrochemical cycle (TREC)12,13,14 based on a battery system using a solid copper hexacyanoferrate (CuHCF) cathode and a Cu/Cu+ anode was recently reported. TREC is configured as a pouch cell to improve the electrolyte conductance, showing an &#945; of &#8722;1.2 mV/K and reaching a high &#951;E of 3.7% (21% of &#951;carnot) when operated at 60 &#176;C and 10 &#176;C. Nevertheless, one limit of TREC is that external electricity is required at the start of the process to charge the electrodes in each thermal cycle, leading to complicated system designs14. A TREC without this limitation can be achieved, but it suffers from a poor conversion efficiency of &#60;1%13. The TREC system demonstrates that a sodium-ion secondary battery (SIB)-type thermocell consisting of two types of Prussian blue analogues (PBA) with different &#945; values can harvest waste heat. The thermal efficiency (&#951;) increases proportionally with &#916;T. Moreover, &#951; reaches 1.08%, 3.19% at &#916;T = 30 K, 56 K separately. The thermal cyclability is improved using Ni-substituted PBA15,16,17,18.
Alternatively, a thermally regenerative ammonia battery (TRAB) employs copper-based redox couples [Cu(NH3)42+/Cu and Cu(II)/Cu] that operate with the reverse temperature gradient by switching the temperature of electrolyte co-operated with positive and negative electrodes, which produces a &#951;E of 0.53% (13% of &#951;carnot). However, this system is configured with two tanks full of liquid electrolyte, causing sluggish heating and cooling. Also, the ammonia stream in the system creates concerns regarding safety, leakage, and stability19,20,21.
Here we present an asymmetric thermoelectrochemical cell (aTEC) for heat-to-electricity conversion that can be thermally charged and electrically discharged by continuous isothermal heating without maintaining a temperature gradient in a geometric configuration or switching temperatures in a thermal cycle. The aTEC uses asymmetric electrodes, including a graphene oxide (GO) cathode and a polyaniline (PANI) anode, and KCl as the electrolyte. It is thermally charged via the thermo-pseudocapacitive effect of GO and then discharged with the oxidation reaction of PANI. Notably, the aTEC exhibits a high &#945; of 4.1 mV/K and attains a &#951;E of 3.32%, the highest ever achieved at 70 &#176;C (25.3% of &#951;Carnot).

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Alumina laminated film</td>
			<td>Showa Denko</td>
			<td>SPALF C4</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbon black</td>
			<td>Alfa Aesar</td>
			<td>H30253.22</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbon paper</td>
			<td>CeTech Co. Ltd</td>
			<td>W0S1009</td>
			<td></td>
		</tr>
		<tr>
			<td>Carboxymethyl cellulose (CMC)</td>
			<td>Guidechem company</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DC Power supply</td>
			<td>B&#38;K Precision</td>
			<td>Model 913-B</td>
			<td></td>
		</tr>
		<tr>
			<td>Doctor blade coater</td>
			<td>Shining Energy Co. Ltd</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Gamry</td>
			<td>Gamry Instruments</td>
			<td>Reference 3000</td>
			<td></td>
		</tr>
		<tr>
			<td>Graphite</td>
			<td>Sigma-Aldrich</td>
			<td>332461-2.5KG</td>
			<td></td>
		</tr>
		<tr>
			<td>Mixer</td>
			<td>Thinky</td>
			<td>ARE-250</td>
			<td></td>
		</tr>
		<tr>
			<td>Nickel tab</td>
			<td>Tianjin Iversonchem company</td>
			<td></td>
			<td>4 mm width</td>
		</tr>
		<tr>
			<td>N-Methyl-2-pyrrolidone (NMP)</td>
			<td>Sigma-Aldrich</td>
			<td>443778-1L</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyaniline (leucoemeraldine base)</td>
			<td>Sigma-Aldrich</td>
			<td>530670-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>potassium permanganate (KMnO4)</td>
			<td>Sigma-Aldrich</td>
			<td>223468-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Separator</td>
			<td>CLDP</td>
			<td></td>
			<td>25 um thickness</td>
		</tr>
		<tr>
			<td>Sodium nitrate (NaNO3)</td>
			<td>Sigma-Aldrich</td>
			<td>S5506-250G</td>
			<td></td>
		</tr>
		<tr>
			<td>Styrene butadiene</td>
			<td>Tianjin Iversonchem company</td>
			<td>BM400</td>
			<td></td>
		</tr>
		<tr>
			<td>Sulfuric acid</td>
			<td>Sigma-Aldrich</td>
			<td>320501-2.5L</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermoelectric modules</td>
			<td>CUI Inc.</td>
			<td>CP455535H</td>
			<td></td>
		</tr>
		<tr>
			<td>Titanum foil</td>
			<td>Qingyuan metal</td>
			<td></td>
			<td>0.03 mm thickness</td>
		</tr>
	</tbody>
</table>

asymmetric thermoelectrochemical cell for harvesting low-grade heat under isothermal operation

Low-grade heat is abundantly available in the environment as waste heat. The efficient conversion of low-grade heat into electricity is very difficult. We developed an asymmetric thermoelectrochemical cell (aTEC) for heat-to-electricity conversion under isothermal operation in the charging and discharging processes without exploiting the thermal gradient or the thermal cycle. The aTEC is composed of a graphene oxide (GO) cathode, a polyaniline (PANI) anode, and 1M KCl as the electrolyte. The cell generates a voltage due to the pseudocapacitive reaction of GO when heating from room temperature (RT) to a high temperature (TH, ~40-90 &#176;C), and then current is successively produced by oxidizing PANI when an external electrical load is connected. The aTEC demonstrates a remarkable temperature coefficient of 4.1 mV/K and a high heat-to-electricity conversion efficiency of 3.32%, working at a TH = 70 &#176;C with a Carnot efficiency of 25.3%, unveiling a new promising thermoelectrochemical technology for low-grade heat recovery.

The aTEC pouch cell was configured with asymmetric electrodes consisting of a GO cathode, a PANI anode, and filled with the KCl electrolyte. The thickness of the pouch cell shown in Figure 1A is 1 mm, which facilitates isothermal conditions between the two electrodes as well as efficient heat conduction. The scanning electron microscopy (SEM) images of the GO cathode and the PANI anode coated on carbon paper are shown in ...

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Asymmetric Thermoelectrochemical Cell for Harvesting Low-grade Heat under Isothermal Operation

Low-grade heat is abundant, but its efficient recovery is still a great challenge. We report an asymmetric thermoelectrochemical cell using graphene oxide as a cathode and polyaniline as an anode with KCl as the electrolyte. This cell works under isothermal heating, exhibiting a high heat-to-electricity conversion efficiency in low-temperature regions.

Low-grade heat is abundantly available in the environment as waste heat. The efficient conversion of low-grade heat into electricity is very difficult. We ...

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6.8K Views.  University of Hong Kong. Low-grade heat is abundant, but its efficient recovery is still a great challenge. We report an asymmetric thermoelectrochemical cell using graphene oxide as a cathode and polyaniline as an anode with KCl as the electrolyte. This cell works under isothermal heating, exhibiting a high heat-to-electricity conversion efficiency in low-temperature regions.

Video: Asymmetric Thermoelectrochemical Cell for Harvesting Low-grade Heat under Isothermal Operation

Particles without a Box: Brush-first Synthesis of Photodegradable PEG Star Polymers under Ambient Conditions

Convenient methods for the rapid, parallel synthesis of diversely functionalized nanoparticles will enable discovery of novel formulations for drug delivery, biological imaging, and supported catalysis. In this report, we demonstrate parallel synthesis of brush-arm star polymer (BASP) nanoparticles by the &#34;brush-first&#34; method. In this method, a norbornene-terminated poly(ethylene glycol) (PEG) macromonomer (PEG-MM) is first polymerized via ring-opening metathesis polymerization (ROMP) to generate a living brush macroinitiator. Aliquots of this initiator stock solution are added to vials that contain varied amounts of a photodegradable bis-norbornene crosslinker. Exposure to crosslinker initiates a series of kinetically-controlled brush+brush and star+star coupling reactions that ultimately yields BASPs with cores comprised of the crosslinker and coronas comprised of PEG. The final BASP size depends on the amount of crosslinker added. We carry out the synthesis of three BASPs on the benchtop with no special precautions to remove air and moisture. The samples are characterized by gel permeation chromatography (GPC); results agreed closely with our previous report that utilized inert (glovebox) conditions. Key practical features, advantages, and potential disadvantages of the brush-first method are discussed.

Poly(ethylene glycol) (PEG) brush-arm star polymers (BASPs) with narrow mass distributions and tunable nanoscopic sizes are synthesized in via ring opening metathesis polymerization (ROMP) of a PEG-norbornene macromonomer followed by transfer of portions of the resulting living brush initiator to vials containing varied amounts of a rigid, photo-cleavable bis-norbornene crosslinker.

Convenient methods for the rapid, parallel synthesis of diversely functionalized nanoparticles will enable discovery of novel formulations for drug ...

Isolation and Preparation of Bacterial Cell Walls for Compositional Analysis by Ultra Performance Liquid Chromatography

The bacterial cell wall is critical for the determination of cell shape during growth and division, and maintains the mechanical integrity of cells in the face of turgor pressures several atmospheres in magnitude. Across the diverse shapes and sizes of the bacterial kingdom, the cell wall is composed of peptidoglycan, a macromolecular network of sugar strands crosslinked by short peptides. Peptidoglycan&#8217;s central importance to bacterial physiology underlies its use as an antibiotic target and has motivated genetic, structural, and cell biological studies of how it is robustly assembled during growth and division. Nonetheless, extensive investigations are still required to fully characterize the key enzymatic activities in peptidoglycan synthesis and the chemical composition of bacterial cell walls. High Performance Liquid Chromatography (HPLC) is a powerful analytical method for quantifying differences in the chemical composition of the walls of bacteria grown under a variety of environmental and genetic conditions, but its throughput is often limited. Here, we present a straightforward procedure for the isolation and preparation of bacterial cell walls for biological analyses of peptidoglycan via HPLC and Ultra Performance Liquid Chromatography (UPLC), an extension of HPLC that utilizes pumps to deliver ultra-high pressures of up to 15,000 psi, compared with 6,000 psi for HPLC. In combination with the preparation of bacterial cell walls presented here, the low-volume sample injectors, detectors with high sampling rates, smaller sample volumes, and shorter run times of UPLC will enable high resolution and throughput for novel discoveries of peptidoglycan composition and fundamental bacterial cell biology in most biological laboratories with access to an ultracentrifuge and UPLC.

The bacterial cell wall is composed of peptidoglycan, a macromolecular network of sugar strands crosslinked by peptides. Ultra Performance Liquid Chromatography provides high resolution and throughput for novel discoveries of peptidoglycan composition. We present a procedure for the isolation of cell walls (sacculi) and their subsequent preparation for analysis via UPLC.

The bacterial cell wall is critical for the determination of cell shape during growth and division, and maintains the mechanical integrity of cells in the ...

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family of easy accessible, very cheap, and air stable, but highly active and universally applicable C-C cross-coupling catalysts with an excellent functional group tolerance. Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1), the least stable complex within this series towards protons; e.g. in the form of water, allows an eased nanoparticle formation and hence, proved to be the most active Heck catalyst within this series at 100 &#176;C and is a very rare example of an effective and versatile catalyst system that efficiently operates under mild reaction conditions. Rapid and complete catalyst degradation under work-up conditions into phosphonates, piperidinium salts and other, palladium-containing decomposition products assure an easy separation of the coupling products from catalyst and ligands. The facile, cheap, and rapid synthesis of 1,1',1"-(phosphinetriyl)tripiperidine and 1 respectively, the simple and convenient use as well as its excellent catalytic performance in the Heck reaction at 100 &#176;C make 1 to one of the most attractive and greenest Heck catalysts available.
We provide here the visualized protocols for the ligand and catalyst syntheses as well as the reaction protocol for Heck reactions performed at 10 mmol scale at 100 &#176;C and show that this catalyst is suitable for its use in organic syntheses.

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1&#039;,1&#039;&#039;-phosphinetriyltripiperidine]}palladium Under Mild Reaction Conditions

Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1) is an easy accessible, cheap, and air stable, but highly active Heck catalyst with an excellent functional group tolerance that efficiently operates under mild reaction conditions to give the coupling products in very high yields.

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family ...

Hot Biological Catalysis: Isothermal Titration Calorimetry to Characterize Enzymatic Reactions

Isothermal titration calorimetry (ITC) is a well-described technique that measures the heat released or absorbed during a chemical reaction, using it as an intrinsic probe to characterize virtually every chemical process. Nowadays, this technique is extensively applied to determine thermodynamic parameters of biomolecular binding equilibria. In addition, ITC has been demonstrated to be able of directly measuring kinetics and thermodynamic parameters (kcat, KM, &#916;H) of enzymatic reactions, even though this application is still underexploited. As heat changes spontaneously occur during enzymatic catalysis, ITC does not require any modification or labeling of the system under analysis and can be performed in solution. Moreover, the method needs little amount of material. These properties make ITC an invaluable, powerful and unique tool to study enzyme kinetics in several applications, such as, for example, drug discovery.
In this work an experimental ITC-based method to quantify kinetics and thermodynamics of enzymatic reactions is thoroughly described. This method is applied to determine kcat and KM of the enzymatic hydrolysis of urea by Canavalia ensiformis (jack bean) urease. Calculation of intrinsic molar enthalpy (&#916;Hint) of the reaction is performed. The values thus obtained are consistent with previous data reported in literature, demonstrating the reliability of the methodology.

Isothermal titration calorimetry measures heat flow released or absorbed in chemical reactions. This method can be used to quantify enzyme-catalysis. In this paper, the protocol for instrumental setup, experiment running, and data analysis is generally described, and applied to the characterization of enzymatic urea hydrolysis by jack bean urease.

Isothermal titration calorimetry (ITC) is a well-described technique that measures the heat released or absorbed during a chemical reaction, using it as ...

Synthetic Methodology for Asymmetric Ferrocene Derived Bio-conjugate Systems via Solid Phase Resin-based Methodology

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. The most common techniques utilized are imaging modalities such as Magnetic Resonance Imaging (MRI), Positron Emission Topography (PET), and Computed Topography (CT) and are optimal for understanding the physical structure of the disease but can only be performed once every four to six weeks due to the use of imaging agents and overall cost. With this in mind, the development of &#8220;point of care&#8221; techniques, such as biosensors, which evaluate the stage of disease and/or efficacy of treatment in the clinician&#8217;s office and do so in a timely manner, would revolutionize treatment protocols.1 As a means to exploring ferrocene based biosensors for the detection of biologically relevant molecules2, methods were developed to produce ferrocene-biotin bio-conjugates described herein. This report will focus on a biotin-ferrocene-cysteine system that can be immobilized on a gold surface.

The synthesis of asymmetric species of ferrocene is challenging using solution techniques. This report focuses on the methods carried out to produce a ferrocene-biotin bioconjugate using facile and clean reactions accomplished via solid-phase synthesis. Incorporation of a thiolate moiety is shown to impart the ability for immobilization on gold surfaces.

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. ...

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 oligomeric clusters of these yellow nanoparticles of narrow size distribution are synthesized under ambient conditions via two methods. The delay-time method controls the number of subunits in the oligoclusters by varying the time between the addition of HAuCl4 to alkaline solution and the subsequent addition of reducing agent, NaSCN. The yellow oligoclusters produced range in size from ~3 to ~25 nm. This size range can be further extended by an add-on method utilizing hydroxylated gold chloride (Na+[Au(OH4-x)Clx]-) to auto-catalytically increase the number of subunits in the as-synthesized oligocluster nanoparticles, providing a total range of 3 nm to 70 nm. The crude oligocluster preparations display narrow size distributions and do not require further fractionation for most purposes. The oligoclusters formed can be concentrated &#62;300 fold without aggregation and the crude reaction mixtures remain stable for weeks without further processing. Because these oligomeric clusters can be concentrated before derivatization they allow expensive derivatizing agents to be used economically. In addition, we present two models by which predictions of particle size can be made with great accuracy.

We describe a simple method for producing highly stable oligomeric clusters of gold nanoparticles via the reduction of chloroauric acid (HAuCl4) with sodium thiocyanate (NaSCN). The oligoclusters have a narrow size distribution and can be produced with a wide range of sizes and surface coats.

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

Analyzing the Photo-oxidation of 2-propanol at Indoor Air Level Concentrations Using Field Asymmetric Ion Mobility Spectrometry

We demonstrate a versatile protocol to be used for determining the effectiveness of photocatalysts in degrading indoor air concentration (ppb) volatile organic carbons (VOCs), illustrating this with a titanium dioxide based catalyst, and the VOC 2-propanol. The protocol takes advantage of field asymmetric ion mobility spectroscopy (FAIMS), an analysis tool that is capable of continuously identifying and monitoring the concentration of VOCs such as 2-propanol and acetone at the ppb level. The continuous nature of FAIMS allows detailed kinetic analysis, and long-term reactions, offering a significant advantage over gas chromatography, a batch process traditionally used in air purification characterization. The use of FAIMS in photocatalytic air purification has only recently been used for the first time, and with the protocol illustrated here, the flexibility in allowing alternative VOCs and photocatalysts to be tested using comparable protocols offers a unique system to elucidate photocatalytic air purification reactions at low concentrations.

A protocol for determining the effectiveness of photocatalysts in degrading indoor air concentration (ppb) model volatile organic carbons such as 2-propanol is described.

We demonstrate a versatile protocol to be used for determining the effectiveness of photocatalysts in degrading indoor air concentration (ppb) volatile ...

Phase Behavior of Charged Vesicles Under Symmetric and Asymmetric Solution Conditions Monitored with Fluorescence Microscopy

Phase-separated giant unilamellar vesicles (GUVs) exhibiting coexisting liquid-ordered and liquid-disordered domains are a common biophysical tool to investigate the lipid raft hypothesis. Numerous studies, however, neglect the impact of physiological solution conditions. On that account, the current work presents the effect of high-salinity buffer and trans-membrane solution asymmetry on liquid-liquid phase separation in charged GUVs grown from dioleylphosphatidylglycerol, egg sphingomyelin, and cholesterol. The effects were studied under isothermal and varying temperature conditions.
We describe equipment and experimental strategies applicable for monitoring the stability of coexisting liquid domains in charged vesicles under symmetric and asymmetric high-salinity solution conditions. This includes an approach to prepare charged multicomponent GUVs in high-salinity buffer at high temperatures. The protocol entails the option to perform a partial exchange of the external solution by a simple dilution step while minimizing the vesicle dilution. An alternative approach is presented utilizing a microfluidic device that allows for a complete external solution exchange. The solution effects on phase separation were also studied under varying temperatures. To this end, we present the basic design and utility of an in-house built temperature control chamber. Furthermore, we reflect on the assessment of the GUV phase state, pitfalls associated with it and how to circumvent them.

Experiments on phase separated giant unilamellar vesicles (GUVs) frequently neglect physiological solution conditions. This work presents approaches to study the effect of high-salinity buffer on liquid-liquid phase separation in charged multicomponent GUVs as a function of trans-membrane solution asymmetry and temperature.

Phase-separated giant unilamellar vesicles (GUVs) exhibiting coexisting liquid-ordered and liquid-disordered domains are a common biophysical tool to ...

Liquid-cell Transmission Electron Microscopy for Tracking Self-assembly of Nanoparticles

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully understood. We have traced the trajectories of individual nanoparticles using liquid-cell transmission electron microscopy (TEM) to investigate the mechanism of the assembly process. Herein, we present the protocols used for liquid-cell TEM studies of the self-assembly mechanism. First, we introduce the detailed synthetic protocols used to produce uniformly sized platinum and lead selenide nanoparticles. Next, we present the microfabrication processes used to produce liquid cells with silicon nitride or silicon windows and then describe the loading and imaging procedures of the liquid-cell TEM technique. Several notes are included to provide helpful tips for the entire process, including how to manage the fragile cell windows. The individual motions of nanoparticles tracked by liquid-cell TEM revealed that changes in the solvent boundaries caused by evaporation affected the self-assembly process of nanoparticles. The solvent boundaries drove nanoparticles to primarily form amorphous aggregates, followed by flattening of the aggregates to produce a 2-dimensional (2D) self-assembled structure. These behaviors are also observed for different nanoparticle types and different liquid-cell compositions.

Here we introduce experimental protocols for the real-time observation of a self-assembly process using liquid-cell transmission electron microscopy.

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully ...

Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera

Here, we present a sensible method of the acquisition and analysis of time-resolved photoluminescence using an ultrafast iCCD camera. This system enables the acquisition of photoluminescence spectra covering the time regime from nanoseconds up to 0.1 s. This enables us to follow the changes in the intensity (decay) and emission of the spectra over time. Using this method, it is possible to study diverse photophysical phenomena, such as the emission of phosphorescence, and the contributions of prompt and delayed fluorescence in molecules showing thermally activated delayed fluorescence (TADF). Remarkably, all spectra and decays are obtained in a single experiment. This can be done for solids (thin film, powder, crystal) and liquid samples, where the only limitations are the spectral sensitivity of the camera and the excitation wavelength (532 nm, 355 nm, 337 nm, and 266 nm). This technique is, thus, very important when investigating the excited state dynamics in organic emitters for their application in organic light-emitting diodes and other areas where triplet harvesting is of paramount importance. Since triplet states are strongly quenched by oxygen, emitters with efficient TADF luminescence, or those showing room temperature phosphorescence (RTP), must be correctly prepared in order to remove any dissolved oxygen from solutions and films. Otherwise, no long-lived emission will be observed. The method of degassing solid samples as presented in this work is basic and simple, but the degassing of liquid samples creates additional difficulties and is particularly interesting. A method of minimizing solvent loss and changing the sample concentration, while still enabling to remove oxygen in a very efficient and a repeatable manner, is presented in this work.

Here, we present a method of the spectroscopic characterization of organic molecules by means of time-resolved photoluminescence spectroscopy on the nanosecond-to-millisecond timescale in oxygen-free conditions. Methods to efficiently remove oxygen from the samples and, thus, limit luminescence quenching are also described.

Here, we present a sensible method of the acquisition and analysis of time-resolved photoluminescence using an ultrafast iCCD camera. This system enables ...