This work was supported by the Natural Science Foundation of Shanghai, China (No. 18ZR1401000), the Shanghai Pujiang Program (No. 18PJ1400400), and the National Key Research and Development Program of China (No. 2018YFF0215703).

CAUTION: Please carefully read relevant safety data sheets (SDS) of all chemicals and wear proper personal protection equipment (PPE) before use. Some of the chemicals are toxic and irritant. Be careful when handling carbon nanotubes, which may have additional hazards if inhaled or contacted by skin.
1. Preparation of the electroactive titanate-CNT filter
<ol>
	<li>Preparation of titanate nanowires16
	<ol>
		<li>Dissolve 56 g of potassium hydroxide (KOH) in 100 mL of deionized water under vigorous stirring.</li>
		<li>Add 3 g of titanium dioxide (TiO2) powder into the as-dissolved KOH solution.</li>
		<li>Transfer the above solution into a Teflon-lined reactor and keep it at 200 &#176;C for 24 h.</li>
		<li>Wash the obtained white precipitate with 0.1 mol/L hydrochloric acid (HCl) and deionized water until a neutral effluent pH is obtained. Dry the product under vacuum at 60 &#176;C overnight.</li>
		<li>Transfer the products to a tube furnace and heat it to 600 &#176;C for 2 h with a ramp rate of 1 &#176;C/min.</li>
	</ol>
	</li>
	<li>Preparation of titanate-CNT filter17
	<ol>
		<li>Add 20 mg of carbon nanotubes (CNTs) into 40 mL of n-methyl pyrrolidone (NMP). Probe-sonication for 40 min to obtain homogeneous solution.</li>
		<li>Separately, add 20 mg of the as made titanate nanowires into 20 mL of NMP. Perform probe-sonication for 20 min.</li>
		<li>Mix the titanate dispersion solution with the CNT dispersion solution. Filter the mixture solution onto a PTFE membrane, which serves as a support for the titanate-CNT filter.</li>
		<li>Rinse sequentially with 100 mL of ethanol and 200 mL of deionized water. 
		NOTE: A CNT-alone filter can be prepared by a similar route without the addition of titanate nanowires.</li>
	</ol>
	</li>
</ol>
2. Electrochemical filtration of Sb(III)
<ol>
	<li>Description on the experimental apparatus18
	<ol>
		<li>Conduct the sorption experiments in an electrochemistry modified polycarbonate filtration casing (see Figure 1).</li>
		<li>Use a DC power supply to drive the electrochemistry.</li>
		<li>Adopt perforated titanium ring as connector for anodic or cathodic filters.</li>
		<li>Use an insulating silicone rubber as a separator and seal.</li>
	</ol>
	</li>
	<li>Filtration experiments
	<ol>
		<li>Add 2.2 mg of C8H4K2O12Sb2.3H2O into 1000 mL of deionized water to prepare 800 &#956;g/L Sb(III) solution.</li>
		<li>Transfer 100 mL of Sb(III) solution to a 150 mL beaker. Adjust solution pH to 7.</li>
		<li>Place the as-prepared titanate-CNT filter anode into the polycarbonate filtration casing and place another CNT-alone filter as cathode. Seal the casing.</li>
		<li>Pass through the filtration system with Sb(III) solution at a given flow. Apply a DC voltage during filtration.</li>
		<li>Determine the Sbtotal and Sb(III) concentration with atomic fluorescence spectrometer technique17. 
		NOTE: In this process, flow rate and applied voltage can be tuned by a peristaltic pump and a DC power supply, respectively.</li>
	</ol>
	</li>
</ol>

<ol>
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B., 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=Assessments+of+levels,+potential+ecological+risk,+and+human+health+risk+of+heavy+metals+in+the+soils+from+a+typical+county+in+Shanxi+Province,+China.">Assessments of levels, potential ecological risk, and human health risk of heavy metals in the soils from a typical county in Shanxi Province, China.</a> Environmental Science and Pollution Research. 23, 19330-19340 (2016).</li><li>Huang, S. 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P., 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=Three-dimensional+reduced+graphene+oxide+coupled+with+Mn3O4+for+highly+efficient+removal+of+Sb(III)+and+Sb(V)+from+water.">Three-dimensional reduced graphene oxide coupled with Mn3O4 for highly efficient removal of Sb(III) and Sb(V) from water.</a> Acs Applied Materials &amp; Interfaces. 8, 18140-18149 (2016).</li><li>Saleh, T. A., Sari, A., Tuzen, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effective+adsorption+of+antimony(III)+from+aqueous+solutions+by+polyamide-graphene+composite+as+a+novel+adsorbent.">Effective adsorption of antimony(III) from aqueous solutions by polyamide-graphene composite as a novel adsorbent.</a> Chemical Engineering Journal. 307, 230-238 (2017).</li><li>Yan, Y. Z., An, Q. D., Xiao, Z. Y., Zheng, W., Zhai, S. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flexible+core-shell/bead-like+alginate@PEI+with+exceptional+adsorption+capacity,+recycling+performance+toward+batch+and+column+sorption+of+Cr(VI).">Flexible core-shell/bead-like alginate@PEI with exceptional adsorption capacity, recycling performance toward batch and column sorption of Cr(VI).</a> Chemical Engineering Journal. 313, 475-486 (2017).</li><li>Fu, L., Shozugawa, K., Matsuo, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxidation+of+antimony+(III)+in+soil+by+manganese+(IV)+oxide+using+X-ray+absorption+fine+structure.">Oxidation of antimony (III) in soil by manganese (IV) oxide using X-ray absorption fine structure.</a> Journal of Environmental Sciences. 73, 31-37 (2018).</li><li>Liu, 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=Adsorption+of+Pb2+,+Cd2+,+Cu2++and+Cr3++onto+titanate+nanotubes:+competition+and+effect+of+inorganic+ions.">Adsorption of Pb2+, Cd2+, Cu2+ and Cr3+ onto titanate nanotubes: competition and effect of inorganic ions.</a> Science of the Total Environment. 456, 171-180 (2013).</li><li>Wu, B., 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=Dynamic+study+of+Cr(VI)+removal+performance+and+mechanism+from+water+using+multilayer+material+coated+nanoscale+zerovalent+iron.">Dynamic study of Cr(VI) removal performance and mechanism from water using multilayer material coated nanoscale zerovalent iron.</a> Environmental Pollution. 240, 717-724 (2018).</li><li>Shan, C., Ma, Z. Y., Tong, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+removal+of+trace+antimony(III)+through+adsorption+by+hematite+modified+magnetic+nanoparticles.">Efficient removal of trace antimony(III) through adsorption by hematite modified magnetic nanoparticles.</a> Journal of Hazardous Materials. 268, 229-236 (2014).</li><li>Luo, J. M., 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=Removal+of+antimonite+(Sb(III))+and+antimonate+(Sb(V))+from+aqueous+solution+using+carbon+nanofibers+that+are+decorated+with+zirconium+oxide+(ZrO2).">Removal of antimonite (Sb(III)) and antimonate (Sb(V)) from aqueous solution using carbon nanofibers that are decorated with zirconium oxide (ZrO2).</a> Environmental Science &amp; Technology. 49, 11115-11124 (2015).</li><li>Liu, Y. B., 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=Golden+carbon+nanotube+membrane+for+continuous+flow+catalysis.">Golden carbon nanotube membrane for continuous flow catalysis.</a> Industrial &amp; Engineering Chemistry Research. 56, 2999-3007 (2017).</li><li>Ma, B. 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=Enhanced+antimony(V)+removal+using+synergistic+effects+of+Fe+hydrolytic+flocs+and+ultrafiltration+membrane+with+sludge+discharge+evaluation.">Enhanced antimony(V) removal using synergistic effects of Fe hydrolytic flocs and ultrafiltration membrane with sludge discharge evaluation.</a> Water Research. 121, 171-177 (2017).</li><li>Yuan, Z. Y., Zhang, X. B., Su, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Moderate+hydrothermal+synthesis+of+potassium+titanate+nanowires.">Moderate hydrothermal synthesis of potassium titanate nanowires.</a> Applied Physics a-Materials Science &amp; Processing. 78, 1063-1066 (2004).</li><li>Liu, Y. B., 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=Electroactive+modified+carbon+nanotube+filter+for+simultaneous+detoxification+and+sequestration+of+Sb(III).">Electroactive modified carbon nanotube filter for simultaneous detoxification and sequestration of Sb(III).</a> Environmental Science &amp; Technology. 53, 1527-1535 (2019).</li><li>Gao, G., Vecitis, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrochemical+carbon+nanotube+filter+oxidative+performance+as+a+function+of+surface+chemistry.">Electrochemical carbon nanotube filter oxidative performance as a function of surface chemistry.</a> Environmental Science &amp; Technology. 45, 9726-9734 (2011).</li><li>Liu, Y. B., 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=Simultaneous+oxidation+and+sorption+of+highly+toxic+Sb(III)+using+a+dual-functional+electroactive+filter.">Simultaneous oxidation and sorption of highly toxic Sb(III) using a dual-functional electroactive filter.</a> Environmental Pollution. 251, 72-80 (2019).</li></ol>

We have nothing to disclose.

The key to this technology is to fabricate an electroactive conductive and porous hybrid filter with high Sb-specificity. To do this, special care should be paid to the fabrication process. The amount of titanate nanowires need to be precisely controlled due to the "trade-off" effect between the filter's electrical conductivity and surface area.
In addition, it should be also noted that a proper applied voltage is necessary. Once the applied voltage is too high (e.g., &#62;3 V), other competit...

Recently, the environmental pollution caused by emerging antimony (Sb) has attracted much attention1,2. Extensive studies demonstrate that Sb compounds pose high toxicity to human and microorganisms, although present in low concentrations in the environment3,4. Even worse, conventional physicochemical or biological methods are usually ineffective to remove these emerging contaminants due to their low concentrations and high toxicity5. The most abundant species of Sb are Sb(V) and Sb(III), of which the latter form is more toxic.
Among the currently available treatment methods, adsorption is believed to be a promising and feasible alternative due to its high efficiency, low cost, and simplicity6,7. Till now, several nanoscale sorbents with tunable microstructures, large specific surface area and Sb specificity have been developed, such as TiO28, MnO29, titanate10, zerovalent iron11, iron oxides and other binary metal oxides12,13. A common problem when dealing with nanoscale adsorbents is the post-separation issue due to their small particle size. One strategy to address this issue is to load these nano-sorbents onto macro/micro-scale supports14. Another challenging issue restricting the wide application of adsorption technology is the poor mass transport caused by limited concentration of target compounds/molecules15. This issue may be partially addressed by adopting a membrane design and convention could enhance the mass transport significantly. Recent efforts have been devoted to develop advanced treatment systems that combine adsorption and oxidation in a single unit for effective Sb(III) removal. Here, we show how an electroactive titanate-carbon nanotube (titanate-CNT) filter was rationally designed and applied for the simultaneously adsorption and sequestration of toxic Sb(III). By fine-tuning the titanate loading amount, applied voltage, and flow rate, we demonstrate how the Sb(III) oxidation rate and sequestration efficiency can be tailored correspondingly. Although the fabrication and application of the electroactive filter is shown in this protocol, similar designs can also apply to the treatment of other heavy metal ions.
Minor changes in the fabrication process and reagents may cause significant changes in the morphology and performance of the final system. For instance, the hydrothermal time, temperature, and chemical purity have been shown to affect the microstructures of these nanoscale adsorbents. The flow rate of the adsorbate solution also determines the residence time within a flow-through system as well as the removal efficiency of target compounds. With clear identification of these key impacting parameters, a reproducible synthesis protocol can be secured and a stable removal efficiency of Sb(III) can be achieved. This protocol aims to provide detailed experience on the fabrication of dual-functional hybrid filters as well as their applications towards the removal of toxic heavy metal ions in a flow-through manner.

<table><tbody><tr><td>Atomic fluorescence spectrometer</td><td>Ruili Co., Ltd</td><td></td><td></td></tr><tr><td>Carbon nanotubes (CNT)</td><td>TimesNano Co., Ltd</td><td></td><td></td></tr><tr><td>DC power supply</td><td>Dahua Co., Ltd</td><td></td><td></td></tr><tr><td>Ethanol, 96%</td><td>Sinopharm</td><td></td><td></td></tr><tr><td>Hydrochloric acid, 36%</td><td>Sinopharm</td><td></td><td>Corrosive</td></tr><tr><td>L-antimony potassium tartrate</td><td>Sigma-Aldrich</td><td></td><td>Highly toxic</td></tr><tr><td>N-methyl-2-pyrrolidinone (NMP), 99.5%</td><td>Sinopharm</td><td></td><td>Highly toxic</td></tr><tr><td>Potassium hydroxide, 85%</td><td>Sinopharm</td><td></td><td>Corrosive</td></tr><tr><td>Peristaltic pump</td><td>Ismatec Co., Ltd</td><td></td><td></td></tr><tr><td>Titanium dioxide powders</td><td>Sinopharm</td><td></td><td></td></tr></tbody></table>

a dual-functional electroactive filter towards simultaneously sb(iii) oxidation and sequestration

We have designed a facile method to synthesize a dual-functional electrochemical filter consisting of two 1-D materials: titanate nanowires and carbon nanotubes. The hybrid titanate-CNT filter was prepared by a sonication coupled with a post-filtration route. Due to the synergistic effects of the increased number of exposed sorption sites, electrochemical reactivity, small pore size of the titanate-CNT network coupled with a flow-through design, simultaneous Sb(III) oxidation and sequestration can be readily achieved. Atomic fluorescence spectrometer technology demonstrated that the applied electrical field accelerates the Sb(III) conversion rate and the as-obtained Sb(V) were adsorbed effectively by the titanate nanowires due to their Sb specificity. This protocol provides a practical solution for the removal of highly toxic Sb(III) and other similar heavy metal ions.

The electroactive filtration apparatus employed is an electrochemically modified polycarbonate filtration casing (Figure 1). Field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) techniques are employed to characterize the morphology of the titanate-CNT filter (Figure 2). To demonstrate the efficacy of the electrochemical filtration system, the change of Sbtotal and Sb valence state as a function of time is det...

Watch this Scientific Journal Video about A Dual-Functional Electroactive Filter Towards Simultaneously SbIII Oxidation and Sequestration at JoVE.com

A Dual-Functional Electroactive Filter Towards Simultaneously SbIII Oxidation and Sequestration

A protocol for the rational design of a dual-functional electroactive filter consisting of carbon nanotubes and titanate nanowires is reported and their environmental applications towards Sb(III) oxidation and sequestration is presented.

A Dual-Functional Electroactive Filter Towards Simultaneously Sb(III) Oxidation and Sequestration

We have designed a facile method to synthesize a dual-functional electrochemical filter consisting of two 1-D materials: titanate nanowires and carbon ...

a-dual-functional-electroactive-filter-towards-simultaneously-sb-iii

Research

JoVE Journal

Environment

5.4K Views.  Donghua University. Een verwijdering van opkomende verontreinigingsantimoon uit oppervlaktewateren is zeer geëist. De meest voorkomende antimoon soorten zijn antimoon drie en antimoon vijf, en antimoon drie is 10 keer giftiger dan antimoon vijf. Een twee-staps oxidatie neerslag strategie wordt vaak aangenomen voor antimoon drie verwijdering, dat wil zeggen om antimoon drie oxideren tot antimoon vijf in de eerste plaats, gevolgd door chemische neerslag.Maar we kunnen dit binnen één eenheid bereiken. Aan...

Video: A Dual-Functional Electroactive Filter Towards Simultaneously SbIII Oxidation and Sequestration

Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen 1-7. The performance of SOFCs and the rates of many chemical and energy transformation processes in energy storage and conversion devices in general are limited primarily by charge and mass transfer along electrode surfaces and across interfaces. Unfortunately, the mechanistic understanding of these processes is still lacking, due largely to the difficulty of characterizing these processes under in situ conditions. This knowledge gap is a chief obstacle to SOFC commercialization. The development of tools for probing and mapping surface chemistries relevant to electrode reactions is vital to unraveling the mechanisms of surface processes and to achieving rational design of new electrode materials for more efficient energy storage and conversion2. Among the relatively few in situ surface analysis methods, Raman spectroscopy can be performed even with high temperatures and harsh atmospheres, making it ideal for characterizing chemical processes relevant to SOFC anode performance and degradation8-12. It can also be used alongside electrochemical measurements, potentially allowing direct correlation of electrochemistry to surface chemistry in an operating cell. Proper in situ Raman mapping measurements would be useful for pin-pointing important anode reaction mechanisms because of its sensitivity to the relevant species, including anode performance degradation through carbon deposition8, 10, 13, 14 ("coking") and sulfur poisoning11, 15 and the manner in which surface modifications stave off this degradation16. The current work demonstrates significant progress towards this capability. In addition, the family of scanning probe microscopy (SPM) techniques provides a special approach to interrogate the electrode surface with nanoscale resolution. Besides the surface topography that is routinely collected by AFM and STM, other properties such as local electronic states, ion diffusion coefficient and surface potential can also be investigated17-22. In this work, electrochemical measurements, Raman spectroscopy, and SPM were used in conjunction with a novel test electrode platform that consists of a Ni mesh electrode embedded in an yttria-stabilized zirconia (YSZ) electrolyte. Cell performance testing and impedance spectroscopy under fuel containing H2S was characterized, and Raman mapping was used to further elucidate the nature of sulfur poisoning. In situ Raman monitoring was used to investigate coking behavior. Finally, atomic force microscopy (AFM) and electrostatic force microscopy (EFM) were used to further visualize carbon deposition on the nanoscale. From this research, we desire to produce a more complete picture of the SOFC anode.

We present a unique platform for characterizing electrode surfaces in solid oxide fuel cells (SOFCs) that allows simultaneous performance of multiple characterization techniques (e.g. in situ Raman spectroscopy and scanning probe microscopy alongside electrochemical measurements). Complementary information from these analyses may help to advance toward a more profound understanding of electrode reaction and degradation mechanisms, providing insights into rational design of better materials for SOFCs.

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen ...

Engineering

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

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

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

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

Multi-analyte Biochip (MAB) Based on All-solid-state Ion-selective Electrodes (ASSISE) for Physiological Research

Lab-on-a-chip (LOC) applications in environmental, biomedical, agricultural, biological, and spaceflight research require an ion-selective electrode (ISE) that can withstand prolonged storage in complex biological media 1-4. An all-solid-state ion-selective-electrode (ASSISE) is especially attractive for the aforementioned applications. The electrode should have the following favorable characteristics: easy construction, low maintenance, and (potential for) miniaturization, allowing for batch processing. A microfabricated ASSISE intended for quantifying H+, Ca2+, and CO32- ions was constructed. It consists of a noble-metal electrode layer (i.e. Pt), a transduction layer, and an ion-selective membrane (ISM) layer. The transduction layer functions to transduce the concentration-dependent chemical potential of the ion-selective membrane into a measurable electrical signal.
The lifetime of an ASSISE is found to depend on maintaining the potential at the conductive layer/membrane interface 5-7. To extend the ASSISE working lifetime and thereby maintain stable potentials at the interfacial layers, we utilized the conductive polymer (CP) poly(3,4-ethylenedioxythiophene) (PEDOT) 7-9 in place of silver/silver chloride (Ag/AgCl) as the transducer layer. We constructed the ASSISE in a lab-on-a-chip format, which we called the multi-analyte biochip (MAB) (Figure 1).
Calibrations in test solutions demonstrated that the MAB can monitor pH (operational range pH 4-9), CO32- (measured range 0.01 mM - 1 mM), and Ca2+ (log-linear range 0.01 mM to 1 mM). The MAB for pH provides a near-Nernstian slope response after almost one month storage in algal medium. The carbonate biochips show a potentiometric profile similar to that of a conventional ion-selective electrode. Physiological measurements were employed to monitor biological activity of the model system, the microalga Chlorella vulgaris.
The MAB conveys an advantage in size, versatility, and multiplexed analyte sensing capability, making it applicable to many confined monitoring situations, on Earth or in space.
Biochip Design and Experimental Methods
The biochip is 10 x 11 mm in dimension and has 9 ASSISEs designated as working electrodes (WEs) and 5 Ag/AgCl reference electrodes (REs). Each working electrode (WE) is 240 &mu;m in diameter and is equally spaced at 1.4 mm from the REs, which are 480 &mu;m in diameter. These electrodes are connected to electrical contact pads with a dimension of 0.5 mm x 0.5 mm. The schematic is shown in Figure 2.
Cyclic voltammetry (CV) and galvanostatic deposition methods are used to electropolymerize the PEDOT films using a Bioanalytical Systems Inc. (BASI) C3 cell stand (Figure 3). The counter-ion for the PEDOT film is tailored to suit the analyte ion of interest. A PEDOT with poly(styrenesulfonate) counter ion (PEDOT/PSS) is utilized for H+ and CO32-, while one with sulphate (added to the solution as CaSO4) is utilized for Ca2+. The electrochemical properties of the PEDOT-coated WE is analyzed using CVs in redox-active solution (i.e. 2 mM potassium ferricyanide (K3Fe(CN)6)). Based on the CV profile, Randles-Sevcik analysis was used to determine the effective surface area 10. Spin-coating at 1,500 rpm is used to cast ~2 &mu;m thick ion-selective membranes (ISMs) on the MAB working electrodes (WEs).
The MAB is contained in a microfluidic flow-cell chamber filled with a 150 &mu;l volume of algal medium; the contact pads are electrically connected to the BASI system (Figure 4). The photosynthetic activity of Chlorella vulgaris is monitored in ambient light and dark conditions.

Multi-analyte Biochip MAB Based on All-solid-state Ion-selective Electrodes ASSISE for Physiological Research

All-solid-state ion-selective electrodes (ASSISEs) constructed from a conductive polymer (CP) transducer provide several months of functional lifetime in liquid media. Here, we describe the fabrication and calibration process of ASSISEs in a lab-on-a-chip format. The ASSISE is demonstrated to have maintained a near-Nernstian slope profile after prolonged storage in complex biological media.

Lab-on-a-chip (LOC) applications in environmental, biomedical, agricultural, biological, and spaceflight research require an ion-selective electrode (ISE) ...

Bioengineering

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

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

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

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

Chemistry

Self-standing Electrochemical Set-up to Enrich Anode-respiring Bacteria On-site

Anaerobic respiration coupled with electron transport to insoluble minerals (referred to as extracellular electron transport [EET]) is thought to be critical for microbial energy production and persistence in many subsurface environments, especially those lacking soluble terminal electron acceptors. While EET-capable microbes have been successfully isolated from various environments, the diversity of bacteria capable of EET is still poorly understood, especially in difficult-to-sample, low energy or extreme environments, such as many subsurface ecosystems. Here, we describe an on-site electrochemical system to enrich EET-capable bacteria using an anode as a respiratory terminal electron acceptor. This anode is connected&#160;to a cathode capable of&#160;catalyzing abiotic oxygen reduction. Comparing this approach with electrocultivation methods that use a potentiostat for poising the electrode potential, the two-electrode system does not require an external power source. We present an example of our on-site enrichment utilized in an alkaline pond at the Cedars, a terrestrial serpentinization site in Northern California. Prior attempts to cultivate mineral reducing bacteria were unsuccessful, which is likely due to the low-biomass nature of this site and/or the low relative abundance of metal reducing microbes. Prior to implementing our two-electrode enrichment, we measured the vertical profile of dissolved oxygen concentration. This allowed us to place the carbon felt anode and platinum-electroplated carbon felt cathode at depths that would support anaerobic and aerobic processes, respectively. Following on-site incubation, we further enriched the anodic electrode in the laboratory and confirmed&#160;a distinct microbial community compared to the surface-attached or biofilm communities normally observed at the Cedars. This enrichment subsequently led to the isolation of the first electrogenic microbe from the Cedars. This method of on-site microbial enrichment has the potential to greatly enhance the isolation of EET-capable bacteria from low biomass or difficult to sample habitats.

On-site microbial enrichment or in situ cultivation techniques can facilitate the isolation of difficult-to-culture microbial taxa, especially from low-biomass or geochemically extreme environments. Here, we describe an electrochemical set-up without using an external power source to enrich microbial strains that are capable of extracellular electron transport (EET).

Anaerobic respiration coupled with electron transport to insoluble minerals (referred to as extracellular electron transport [EET]) is thought to be ...

Characterizing Electron Transport through Living Biofilms

Here we demonstrate the method of electrochemical gating used to characterize electrical conductivity of electrode-grown microbial biofilms under physiologically relevant conditions.1 These measurements are performed on living biofilms in aqueous medium using source and drain electrodes patterned on a glass surface in a specialized configuration referred to as an interdigitated electrode (IDA) array. A biofilm is grown that extends across the gap connecting the source and drain. Potentials are applied to the electrodes (ES and ED) generating a source-drain current (ISD) through the biofilm between the electrodes. The dependency of electrical conductivity on gate potential (the average of the source and drain potentials, EG = [ED + ES]/2) is determined by systematically changing the gate potential and measuring the resulting source-drain current. The dependency of conductivity on gate potential provides mechanistic information about the extracellular electron transport process underlying the electrical conductivity of the specific biofilm under investigation. The electrochemical gating measurement method described here is based directly on that used by M. S. Wrighton2,3 and colleagues and R. W. Murray4,5,6 and colleagues in the 1980&#39;s to investigate thin film conductive polymers.

A protocol for measuring electrical conductivity of living microbial biofilms under physiologically relevant conditions is presented.

Here we demonstrate the method of electrochemical gating used to characterize electrical conductivity of electrode-grown microbial biofilms under ...

A Protocol for Electrochemical Evaluations and State of Charge Diagnostics of a Symmetric Organic Redox Flow Battery

Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid and deployment of renewable energy technologies. Among the many flow battery chemistries, non-aqueous flow batteries have the potential to achieve high energy density because of the broad voltage windows of non-aqueous electrolytes. However, significant technical hurdles exist currently limiting non-aqueous flow batteries to demonstrate their full potential, such as low redox concentrations, low operating currents, under-explored battery status monitoring, etc. In an attempt to address these limitations, we recently reported a non-aqueous flow battery based on a highly soluble, redox-active organic nitronyl nitroxide radical compound, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO). This redox material exhibits an ambipolar electrochemical property, and therefore can serve as both anolyte and catholyte redox materials to form a symmetric flow battery chemistry. Moreover, we demonstrated that Fourier transform infrared (FTIR) spectroscopy could measure the PTIO concentrations during the PTIO flow battery cycling and offer reasonably accurate detection of the battery state of charge (SOC), as cross-validated by electron spin resonance (ESR) measurements. Herein we present a video protocol for the electrochemical evaluation and SOC diagnosis of the PTIO symmetric flow battery. With a detailed description, we experimentally demonstrated the route to achieve such purposes. This protocol aims to spark more interests and insights on the safety and reliability in the field of non-aqueous redox flow batteries.

We present the protocols for electrochemically evaluating a symmetric non-aqueous organic redox flow battery and for diagnosing its state of charge using FTIR.

Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid ...

Simultaneous Multi-surface Anodizations and Stair-like Reverse Biases Detachment of Anodic Aluminum Oxides in Sulfuric and Oxalic Acid Electrolyte

After reporting on the two-step anodization, nanoporous anodic aluminum oxides (AAOs) have been widely utilized in the versatile fields of fundamental sciences and industrial applications owing to their periodic arrangement of nanopores with relatively high aspect ratio. However, the techniques reported so far, which could be only valid for mono-surface anodization, show critical disadvantages, i.e., time-consuming as well as complicated procedures, requiring toxic chemicals, and wasting valuable natural resources. In this paper, we demonstrate a facile, efficient, and environmentally clean method to fabricate nanoporous AAOs in sulfuric and oxalic acid electrolytes, which can overcome the limitations that result from conventional AAO fabricating methods. First, plural AAOs are produced at one time through simultaneous multi-surfaces anodization (SMSA), indicating mass-producibility of the AAOs with comparable qualities. Second, those AAOs can be separated from the aluminum (Al) substrate by applying stair-like reverse biases (SRBs) in the same electrolyte used for the SMSAs, implying simplicity and green technological characteristics. Finally, a unit sequence consisting of the SMSAs sequentially combined with SRBs-based detachment can be applied repeatedly to the same Al substrate, which reinforces the advantages of this strategy and also guarantees the efficient usage of natural resources.

A protocol for fabricating nanoporous anodic aluminum oxides via simultaneous multi-surfaces anodization followed by stair-like reverse biases detachments is presented. It can be applied repeatedly to the same aluminum substrate, exhibiting a facile, high-yield, and environmentally clean strategy.

After reporting on the two-step anodization, nanoporous anodic aluminum oxides (AAOs) have been widely utilized in the versatile fields of fundamental ...

In Situ Lithiated Reference Electrode: Four Electrode Design for In-operando Impedance Spectroscopy

Extending operating voltage of Li-ion batteries results in higher energy output from these devices. High voltages, however, may trigger or accelerate multiple processes responsible for long-term performance decay. Given the complexity of physical processes occurring inside the cell, it is often challenging to achieve a full understanding of the root causes of this performance degradation. This difficulty arises in part from the fact that any electrochemical measurement of a battery will return the combined contributions of all components in the cell. Incorporation of a reference electrode can solve part of the problem, as it allows the electrochemical reactions of the cathode and the anode to be individually probed. A variation in the voltage range experienced by the cathode, for example, can indicate alterations in the pool of cyclable lithium ions in the full-cell. The structural evolution of the many interphases existing in the battery can also be monitored, by measuring the contributions of each electrode to the overall cell impedance. Such wealth of information amplifies the reach of diagnostic analysis in Li-ion batteries and provides valuable input to the optimization of individual cell components. In this work, we introduce the design of a test cell able to accommodate multiple reference electrodes, and present reference electrodes that are appropriate for each specific type of measurement, detailing the assembly process in order to maximize the accuracy of the experimental results.

The incorporation of reference electrodes in a Li-ion battery provides valuable information to elucidate degradation mechanisms at high voltages. In this article, we present a cell design that accommodates multiple reference electrodes, along with the assembly steps to assure maximum accuracy of the data obtained in electrochemical measurements.

Extending operating voltage of Li-ion batteries results in higher energy output from these devices. High voltages, however, may trigger or accelerate ...

An Efficient Method for Selective Desalination of Radioactive Iodine Anions by Using Gold Nanoparticles-Embedded Membrane Filter

Here, we demonstrate a detail protocol for the preparation of nanomaterials-embedded composite membranes and its application to the efficient and ion-selective removal of radioactive iodines. By using citrate-stabilized gold nanoparticles (mean diameter: 13 nm) and cellulose acetate membranes, gold nanoparticle-embedded cellulose acetate membranes (Au-CAM) have easily been fabricated. The nano-adsorbents on Au-CAM were highly stable in the presence of high concentration of inorganic salts and organic molecules. The iodide ions in aqueous solutions could rapidly be captured by this engineered membrane. Through a filtration process using an Au-CAM containing filter unit, excellent removal efficiency (&gt;99%) as well as ion-selective desalination result was achieved in a short time. Moreover, Au-CAM provided good reusability without significant decrease of its performances. These results suggested that the present technology using the engineered hybrid membrane will be a promising process for the large-scale decontamination of radioactive iodine from liquid wastes.

An efficient method for the rapid and ion-selective desalination of radioactive iodine in several aqueous solutions is described by using gold nanoparticles-immobilized cellulose acetate membrane filters.

A Dual-Functional Electroactive Filter Towards Simultaneously Sb(III) Oxidation and Sequestration

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