The authors would like to thank Lawrence Livermore National Laboratory&#39;s Center for Bioengineering for support during the preparation of this manuscript. Professor Loren Frank is kindly acknowledged for his collaborations with the group that have enabled fabrication and design of the thin-film Pt microarrays discussed in the above work. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by Lab Directed Research and Development Award 16-ERD-035. LLNL IM release LLNL-JRNL-762701.

<ol>
	<li>Fleischmann, M., Hendra, P. J., McQuillan, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Raman+spectra+of+pyridine+adsorbed+at+a+silver+electrode.">Raman spectra of pyridine adsorbed at a silver electrode.</a> Chemical Physics Letters. 26 (2), 163-166 (1974).</li><li>Chung, T., 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=Electrode+modifications+to+lower+electrode+impedance+and+improve+neural+signal+recording+sensitivity.">Electrode modifications to lower electrode impedance and improve neural signal recording sensitivity.</a> Journal of Neural Engineering. 12 (5), 056018 (2015).</li><li>Green, R. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser+patterning+of+platinum+electrodes+for+safe+neurostimulation.">Laser patterning of platinum electrodes for safe neurostimulation.</a> Journal of Neural Engineering. 11 (5), 056017 (2014).</li><li>Arroyo-Curr&#225;s, N., Scida, K., Ploense, K. L., Kippin, T. E., Plaxco, K. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+Surface+Area+Electrodes+Generated+via+Electrochemical+Roughening+Improve+the+Signaling+of+Electrochemical+Aptamer-Based+Biosensors.">High Surface Area Electrodes Generated via Electrochemical Roughening Improve the Signaling of Electrochemical Aptamer-Based Biosensors.</a> Analytical Chemistry. 89 (22), 12185-12191 (2017).</li><li>Weremfo, A., Carter, P., Hibbert, D. B., Zhao, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigating+the+interfacial+properties+of+electrochemically+roughened+platinum+electrodes+for+neural+stimulation.">Investigating the interfacial properties of electrochemically roughened platinum electrodes for neural stimulation.</a> Langmuir. 31 (8), 2593-2599 (2015).</li><li>Ivanovskaya, A. 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=Electrochemical+Roughening+of+Thin-Film+Platinum+for+Neural+Probe+Arrays+and+Biosensing+Applications.">Electrochemical Roughening of Thin-Film Platinum for Neural Probe Arrays and Biosensing Applications.</a> Journal of The Electrochemical Society. 165 (12), G3125-G3132 (2018).</li><li>Cai, W. 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=Investigation+of+surface-enhanced+Raman+scattering+from+platinum+electrodes+using+a+confocal+Raman+microscope:+dependence+of+surface+roughening+pretreatment.">Investigation of surface-enhanced Raman scattering from platinum electrodes using a confocal Raman microscope: dependence of surface roughening pretreatment.</a> Surface Science. 406 (1), 9-22 (1998).</li><li>Tykocinski, M., Duan, Y., Tabor, B., Cowan, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+electrical+stimulation+of+the+auditory+nerve+using+high+surface+area+(HiQ)+platinum+electrodes.">Chronic electrical stimulation of the auditory nerve using high surface area (HiQ) platinum electrodes.</a> Hearing Research. 159 (1-2), 53-68 (2001).</li><li>Liu, Y. C., Wang, C. C., Tsai, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+electrolytes+used+in+roughening+gold+substrates+by+oxidation-reduction+cycles+on+surface-enhanced+Raman+scattering.">Effects of electrolytes used in roughening gold substrates by oxidation-reduction cycles on surface-enhanced Raman scattering.</a> Electrochemistry Communications. 7 (12), 1345-1350 (2005).</li><li>Liu, Z., Yang, Z. L., Cui, L., Ren, B., Tian, Z. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrochemically+Roughened+Palladium+Electrodes+for+Surface-Enhanced+Raman+Spectroscopy:+Methodology,+Mechanism,+and+Application.">Electrochemically Roughened Palladium Electrodes for Surface-Enhanced Raman Spectroscopy: Methodology, Mechanism, and Application.</a> The Journal of Physical Chemistry C. 111 (4), 1770-1775 (2007).</li><li>Rodr&#237;guez, J. M. D., Meli&#225;n, J. A. H., Pe&#241;a, 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=Determination+of+the+Real+Surface+Area+of+Pt+Electrodes.">Determination of the Real Surface Area of Pt Electrodes.</a> Journal of Chemical Education. 77 (9), 1195-1197 (2000).</li><li>Lvovich, V. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Impedance Spectroscopy: Applications to Electrochemical and Dielectric Phenomena. , (2012).</li><li>Tooker, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Towards+a+large-scale+recording+system:+demonstration+of+polymer-based+penetrating+array+for+chronic+neural+recording.">Towards a large-scale recording system: demonstration of polymer-based penetrating array for chronic neural recording.</a> Conference proceedings - IEEE Engineering in Medicine and Biology Society. 2014, 6830-6833 (2014).</li><li>Tooker, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfabricated+polymer-based+neural+interface+for+electrical+stimulation/recording,+drug+delivery,+and+chemical+sensing+development.">Microfabricated polymer-based neural interface for electrical stimulation/recording, drug delivery, and chemical sensing development.</a> Conference proceedings - IEEE Engineering in Medicine and Biology Society. 2013, 5159-5162 (2013).</li></ol>

The authors declare no competing financial interests.

The electrochemical roughening of thin-film macroelectrodes and microelectrodes is possible with oxidation-reduction pulsing. This simple approach does require several key elements to nondestructively roughen thin-film electrodes. Unlike foils, roughening of thin metal films may lead to sample destruction if parameters are not properly chosen. Critical parameters of the roughening procedure are pulse amplitude, duration and frequency. Additionally, ensuring electrode cleanliness and perchloric acid purity prior to the pr...

Nearly five decades ago, the first observation of surface enhanced Raman spectroscopy (SERS) occurred on electrochemically roughened silver1. Electrochemical roughening of metal foils is still attractive today because of its simplicity over other roughening methods2,3 and its usefulness in many applications like improving aptamer sensors4, improving neural probes5, and improving adhesion to metal substrates6. Electrochemical roughening methods exist for many bulk metals1,5,7,8,9,10. Until recently, however, there was no report on the application of electrochemical roughening to thin (hundreds of nanometers thick) metal films6, despite the prevalence of microfabricated thin-film metal electrodes in a number of fields.
Established methods to roughen thick platinum (Pt) electrodes5,8 delaminate thin-film Pt electrodes6. By modulating the frequency of the roughening procedure and the electrolyte used for the for the roughening, Ivanovskaya et al. demonstrated Pt thin-film roughening without delamination. That publication focused on using this new approach to increase the surface area of platinum recording and stimulation electrodes on microfabricated neural probes. The roughened electrodes were demonstrated to improve recording and stimulation performance and improve adhesion of electrochemically deposited films and improve biosensor sensitivity6. But this approach also likely improves surface cleaning of microfabricated electrode arrays and enhances the capabilities of thin-film electrodes for other sensor applications (e.g., aptasensors) as well.
The approach to roughen thin-film macroelectrodes (1.2 mm diameter) and microelectrodes (20 &#181;m diameter) is described in the following protocol. This includes preparation of the electrode surface for roughening and how to characterize the roughness of the electrode. These steps are presented along with tips on how to optimize the roughening procedure for other electrode geometries and the most important factors to ensure an electrode is roughened nondestructively.

<table border="0" cellpadding="0" cellspacing="0" style="width:648px;" width="646">
	<tbody>
		<tr height="62">
			<td height="62" style="height:62px;width:223px;">Acetone</td>
			<td style="width:131px;">Fisher Scientific, Sigma Aldrich or similar</td>
			<td style="width:123px;">n/a</td>
			<td style="width:172px;">Laboratory grade</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">EC-Lab Software</td>
			<td style="width:131px;">Bio-Logic Science Instruments</td>
			<td style="width:123px;">n/a</td>
			<td style="width:172px;">For instrument control and data analysis</td>
		</tr>
		<tr height="125">
			<td height="125" style="height:125px;width:223px;">Leakless Silver/Silver Chloride Reference</td>
			<td style="width:131px;">eDAQ Company, Australia</td>
			<td style="width:123px;">ET069-1</td>
			<td style="width:172px;">Free from chloride anion contamination 
			(or other type of chloride free electrode e.g. Mercury sulfate electrode)</td>
		</tr>
		<tr height="62">
			<td height="62" style="height:62px;width:223px;">Mercury Sulfate &#38; Acid Electrode Kit&#160;</td>
			<td style="width:131px;">Koslow, Scientific Testing Instruments</td>
			<td style="width:123px;">5100A</td>
			<td style="width:172px;">glass, 9mm version</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Milipore DI water</td>
			<td style="width:131px;">MilliporeSigma</td>
			<td style="width:123px;">n/a</td>
			<td style="width:172px;">Certified resistivity of 18.2 M&#937;.cm (at 25&#176;C)&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Perchloric acid, 99.9985%</td>
			<td style="width:131px;">Sigma Aldrich</td>
			<td style="width:123px;">311421</td>
			<td style="width:172px;">High Purity</td>
		</tr>
		<tr height="83">
			<td height="83" style="height:83px;width:223px;">Phosphate-buffered saline</td>
			<td style="width:131px;">Teknova</td>
			<td style="width:123px;">P4007</td>
			<td style="width:172px;">10mM PBS with 100mM NaCl, pH 7 
			or similar product from elsewhere</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Platinum Wire Auxiliary Electrode (7.5 cm)</td>
			<td style="width:131px;">BASi</td>
			<td style="width:123px;">MW-1032</td>
			<td style="width:172px;">Counter electrode</td>
		</tr>
		<tr height="125">
			<td height="125" style="height:125px;width:223px;">Pt macroelectrodes</td>
			<td style="width:131px;">Lawrence Livermore National Laboratory</td>
			<td style="width:123px;">n/a</td>
			<td style="width:172px;">1.2 mm diameter, 250 nm thick Pt disc electrodes insulated in polyimide. More information in Reference 9.</td>
		</tr>
		<tr height="104">
			<td height="104" style="height:104px;width:223px;">Pt microelectrode arrays</td>
			<td style="width:131px;">Lawrence Livermore National Laboratory</td>
			<td style="width:123px;">n/a</td>
			<td style="width:172px;">20 &#181;m diameter 250 nM thick Pt disc electrodes insulated in polyimide. More information in Reference 9.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Sulfuric acid, 99.999%</td>
			<td style="width:131px;">Sigma Aldrich</td>
			<td style="width:123px;">339741</td>
			<td style="width:172px;">High Purity</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">UV &#38; Ozone Dry Stripper</td>
			<td style="width:131px;">Samco</td>
			<td style="width:123px;">UV-1</td>
			<td style="width:172px;">for cleaning electrodes</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">VersaSTAT 4 Potentiostat</td>
			<td style="width:131px;">AMETEK, Inc.</td>
			<td style="width:123px;">n/a</td>
			<td style="width:172px;">Good time resolution for pulsing tests</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">VersaStudio Software</td>
			<td style="width:131px;">AMETEK, Inc.</td>
			<td style="width:123px;">n/a</td>
			<td style="width:172px;">For instrument control</td>
		</tr>
		<tr height="104">
			<td height="104" style="height:104px;width:223px;">VMP-200 Potentiostat&#160;</td>
			<td style="width:131px;">Bio-Logic Science Instruments</td>
			<td style="width:123px;">n/a</td>
			<td style="width:172px;">Low current resolution&#160;option is preferable for measurements with microelectrodes</td>
		</tr>
	</tbody>
</table>

electrochemical roughening of thin-film platinum macro and microelectrodes

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries of the metal. Using this method, a crack free, thin-film macroelectrode surface with up to 40 times increase in active surface area was obtained. The roughening is easy to do in a standard electrochemical characterization laboratory and incudes the application of voltage pulses followed by extended application of a reductive voltage in a perchloric acid solution. The protocol includes the chemical and electrochemical preparation of both a macroscale (1.2 mm diameter) and microscale (20 &#181;m diameter) platinum disc electrode surface, roughening the electrode surface and characterizing the effects of surface roughening on electrode active surface area. This electrochemical characterization includes cyclic voltammetry and impedance spectroscopy and is demonstrated for both the macroelectrodes and the microelectrodes. Roughening increases electrode active surface area, decreases electrode impedance, increases platinum charge injection limits to those of titanium nitride electrodes of same geometry and improves substrates for adhesion of electrochemically deposited films.

A schematic showing the voltage application for roughening both macroelectrodes and microelectrodes is shown in Figure 2. Optical microscopy can be used to visualize the difference in the appearance of a roughened macroelectrode (Figure 3) or microelectrode (Figure 4). In addition, electrochemical characterization of the Pt surface using impedance spectroscopy and cyclic voltammetry can readily show ...

Watch this Scientific Journal Video about Electrochemical Roughening of Thin-Film Platinum Macro and Microelectrodes at JoVE.com

Electrochemical Roughening of Thin-Film Platinum Macro and Microelectrodes

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries. The electrochemical techniques of cyclic voltammetry and impedance spectroscopy are demonstrated to characterize these electrode surfaces.

This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries ...

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7.6K Views.  Lawrence Livermore National Laboratory. This protocol demonstrates a method for electrochemical roughening of thin-film platinum electrodes without preferential dissolution at grain boundaries. The electrochemical techniques of cyclic voltammetry and impedance spectroscopy are demonstrated to characterize these electrode surfaces.

Video: Electrochemical Roughening of Thin-Film Platinum Macro and Microelectrodes

Dynamic Electrochemical Measurement of Chloride Ions

This protocol describes the dynamic measurement of chloride ions using the transition time of a silver silver chloride (Ag/AgCl) electrode. Silver silver chloride electrode is used extensively for potentiometric measurement of chloride ions concentration in electrolyte. In this measurement, long-term and continuous monitoring is limited due to the inherent drift and the requirement of a stable reference electrode. We utilized the chronopotentiometric approach to minimize drift and avoid the use of a conventional reference electrode. A galvanostatic pulse is applied to an Ag/AgCl electrode which initiates a faradic reaction depleting the Cl&#713; ions near the electrode surface. The transition time, which is the time to completely deplete the ions near the electrode surface, is a function of the ion concentration, given by the Nernst equation. The square root of the transition time is in linear relation to the chloride ion concentration. Drift of the response over two weeks is negligible (59 &#181;M/day) when measuring 1 mM [Cl&#713;]using a current pulse of 10 Am-2. This is a dynamic measurement where the moment of transition time determines the response and thus is independent of the absolute potential. Any metal wire can be used as a pseudo-reference electrode, making this approach feasible for long-term measurement inside concrete structures.

Dynamic measurement of chloride ions is presented. Transition time of an Ag/AgCl electrode, during a chronopotentiometric technique, can give the concentration of chloride ions in electrolyte. This method does not require a stable conventional reference electrode.

This protocol describes the dynamic measurement of chloride ions using the transition time of a silver silver chloride (Ag/AgCl) electrode. Silver silver ...

Electrochemical Impedance Spectroscopy as a Tool for Electrochemical Rate Constant Estimation

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). In the case of fast reversible electrochemical processes, current is predominantly affected by the rate of diffusion, which is the slowest and limiting stage. EIS is a powerful technique that allows separate analysis of stages of charge transfer that have different AC frequency response. The capability of the method was used to extract the value of charge transfer resistance, which characterizes the rate of charge exchange on the electrode-solution interface. The application of this technique is broad, from biochemistry up to organic electronics. In this work, we are presenting the method of analysis of organic compounds for optoelectronic applications.

Electrochemical impedance spectroscopy (EIS) of species that undergo reversible oxidation or reduction in solution was used for determination of rate constants of oxidation or reduction.

Electrochemical impedance spectroscopy (EIS) was used for advanced characterization of organic electroactive compounds along with cyclic voltammetry (CV). ...

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity in aqueous CO2 reduction. Different from traditional metal nanocrystals, the synthesis of metal single atoms involves a matrix material that can confine those single atoms and prevent them from aggregation. We report an electrospinning and thermal annealing method to prepare Ni single atoms dispersed and coordinated in a graphene shell, as active centers for CO2 reduction to CO. During the synthesis, N dopants play a critical role in generating graphene vacancies to trap Ni atoms. Aberration-corrected scanning transmission electron microscopy and three-dimensional atom probe tomography were employed to identify the single Ni atomic sites in graphene vacancies. Detailed setup of electrochemical CO2 reduction apparatus coupled with an on-line gas chromatography is also demonstrated. Compared to metallic Ni, Ni single atom catalyst exhibit dramatically improved CO2 reduction and suppressed H2 evolution side reaction.

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Here, we present a protocol for the synthesis and electrochemical testing of transition metal single atoms coordinated in graphene vacancies as active centers for selective carbon dioxide reduction to carbon monoxide in aqueous solutions.

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity ...

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 &#176;C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications.
In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

Here, we present a protocol for the synthesis of porous barium titanate (BaTiO3) thin film by a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles are used as an organic template.

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its ...

Gold Nanoparticle Modified Carbon Fiber Microelectrodes for Enhanced Neurochemical Detection

For over 30 years, carbon-fiber microelectrodes (CFMEs) have been the standard for neurotransmitter detection. Generally, carbon fibers are aspirated into glass capillaries, pulled to a fine taper, and then sealed using an epoxy to create electrode materials that are used for fast scan cyclic voltammetry testing. The use of bare CFMEs has several limitations, though. First and foremost, the carbon fiber contains mostly basal plane carbon, which has a relatively low surface area and yields lower sensitivities than other nanomaterials. Furthermore, the graphitic carbon is limited by its temporal resolution, and its relatively low conductivity. Lastly, neurochemicals and macromolecules have been known to foul at the surface of carbon electrodes where they form non-conductive polymers that block further neurotransmitter adsorption. For this study, we modify CFMEs with gold nanoparticles to enhance neurochemical testing with fast scan cyclic voltammetry. Au3+ was electrodeposited or dipcoated from a colloidal solution onto the surface of CFMEs. Since gold is a stable and relatively inert metal, it is an ideal electrode material for analytical measurements of neurochemicals. Gold nanoparticle modified (AuNP-CFMEs) had a stability to dopamine response for over 4 h. Moreover, AuNP-CFMEs exhibit an increased sensitivity (higher peak oxidative current of the cyclic voltammograms) and faster electron transfer kinetics (lower &#916;EP or peak separation) than bare unmodified CFMEs. The development of AuNP-CFMEs provides the creation of novel electrochemical sensors for detecting fast changes in dopamine concentration and other neurochemicals at lower limits of detection. This work has vast applications for the enhancement of neurochemical measurements. The generation of gold nanoparticle modified CFMEs will be vitally important for the development of novel electrode sensors to detect neurotransmitters in vivo in rodent and other models to study neurochemical effects of drug abuse, depression, stroke, ischemia, and other behavioral and disease states.

In this study, we modify carbon-fiber microelectrodes with gold nanoparticles to enhance the sensitivity of neurotransmitter detection.

For over 30 years, carbon-fiber microelectrodes (CFMEs) have been the standard for neurotransmitter detection. Generally, carbon fibers are aspirated into ...

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.

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 ...

The Effect of Anodization Parameters on the Aluminum Oxide Dielectric Layer of Thin-Film Transistors

Aluminum-oxide (Al2O3) is a low cost, easily processable and high dielectric constant insulating material that is particularly appropriate for use as the dielectric layer of thin-film transistors (TFTs). Growth of aluminum-oxide layers from anodization of metallic aluminum films is greatly advantageous when compared to sophisticated processes such as atomic layer deposition (ALD) or deposition methods that demand relatively high temperatures (above 300 &#176;C) such as aqueous combustion or spray-pyrolysis. However, the electrical properties of the transistors are highly dependent on the presence of defects and localized states at the semiconductor/dielectric interface, which are strongly affected by the manufacturing parameters of the anodized dielectric layer. To determine how several fabrication parameters influence the device performance without performing all possible combination of factors, we used a reduced factorial analysis based on a Plackett-Burman design of experiments (DOE). The choice of this DOE permits the use of only 12 experimental runs of combinations of factors (instead of all 256 possibilities) to obtain the optimized device performance. The ranking of the factors by the effect on device responses such as the TFT mobility is possible by applying analysis of variance (ANOVA) to the obtained results.

Anodization parameters for growth of the aluminum-oxide dielectric layer of zinc-oxide thin-film transistors (TFTs) are varied to determine the effects on the electrical parameter responses. Analysis of variance (ANOVA) is applied to a Plackett-Burman design of experiments (DOE) to determine the manufacturing conditions that result in optimized device performance.

Aluminum-oxide (Al2O3) is a low cost, easily processable and high dielectric constant insulating material that is particularly appropriate for use as the ...

Fabrication of Thin Film Silver/Silver Chloride Electrodes with Finely Controlled Single Layer Silver Chloride

This paper aims to present a protocol to form smooth and well-controlled films of silver/silver chloride (Ag/AgCl) with designated coverage on top of thin film silver electrodes. Thin film silver electrodes sized 80 &#181;m x 80 &#181;m and 160 &#181;m x 160 &#181;m were sputtered on quartz wafers with a chromium/gold (Cr/Au) layer for adhesion. After passivation, polishing and cathodic cleaning processes, the electrodes underwent galvanostatic oxidation with consideration of Faraday&#39;s Law of Electrolysis to form smooth layers of AgCl with a designated degree of coverage on top of the silver electrode. This protocol is validated by inspection of scanning electron microscope (SEM) images of the surface of the fabricated Ag/AgCl thin film electrodes, which highlights the functionality and performance of the protocol. Sub-optimally fabricated electrodes are fabricated as well for comparison. This protocol can be widely used to fabricate Ag/AgCl electrodes with specific impedance requirements (e.g., probing electrodes for impedance sensing applications like impedance flow cytometry and interdigitated electrode arrays).

This paper aims to present a method to form smooth and well-controlled films of silver chloride (AgCl) with designated coverage on top of thin film silver electrodes.

This paper aims to present a protocol to form smooth and well-controlled films of silver/silver chloride (Ag/AgCl) with designated coverage on top of thin ...

Probing Surface Electrochemical Activity of Nanomaterials using a Hybrid Atomic Force Microscope-Scanning Electrochemical Microscope (AFM-SECM)

Scanning electrochemical microscopy (SECM) is used to measure the local electrochemical behavior of liquid/solid, liquid/gas and liquid/liquid interfaces. Atomic force microscopy (AFM) is a versatile tool to characterize micro- and nanostructure in terms of topography and mechanical properties. However, conventional SECM or AFM provides limited laterally resolved information on electrical or electrochemical properties at nanoscale. For instance, the activity of a nanomaterial surface at crystal facet levels is difficult to resolve by conventional electrochemistry methods. This paper reports the application of a combination of AFM and SECM, namely, AFM-SECM, to probe nanoscale surface electrochemical activity while acquiring high-resolution topographical data. Such measurements are critical to understanding the relationship between nanostructure and reaction activity, which is relevant to a wide range of applications in material science, life science and chemical processes. The versatility of the combined AFM-SECM is demonstrated by mapping topographical and electrochemical properties of faceted nanoparticles (NPs) and nanobubbles (NBs), respectively. Compared to previously reported SECM imaging of nanostructures, this AFM-SECM enables quantitative assessment of local surface activity or reactivity with higher resolution of surface mapping.

Probing Surface Electrochemical Activity of Nanomaterials using a Hybrid Atomic Force Microscope-Scanning Electrochemical Microscope AFM-SECM

Atomic force microscopy (AFM) combined with scanning electrochemical microscopy (SECM), namely, AFM-SECM, can be used to simultaneously acquire high-resolution topographical and electrochemical information on material surfaces at nanoscale. Such information is critical to understanding heterogeneous properties (e.g., reactivity, defects, and reaction sites) on local surfaces of nanomaterials, electrodes and biomaterials.

Scanning electrochemical microscopy (SECM) is used to measure the local electrochemical behavior of liquid/solid, liquid/gas and liquid/liquid interfaces. ...