1
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Godeffroy L, Shkirskiy V, Noël JM, Lemineur JF, Kanoufi F. Fuelling electrocatalysis at a single nanoparticle by ion flow in a nanoconfined electrolyte layer. Faraday Discuss 2023; 246:441-465. [PMID: 37427498 DOI: 10.1039/d3fd00032j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
We explore the possibility of coupling the transport of ions and water in a nanochannel with the chemical transformation of a reactant at an individual catalytic nanoparticle (NP). Such configuration could be interesting for constructing artificial photosynthesis devices coupling the asymmetric production of ions at the catalytic NP, with the ion selectivity of the nanochannels acting as ion pumps. Herein we propose to observe how such ion pumping can be coupled to an electrochemical reaction operated at the level of an individual electrocatalytic Pt NP. This is achieved by confining a (reservoir) droplet of electrolyte to within a few micrometres away from an electrocatalytic Pt NP on an electrode. While the region of the electrode confined by the reservoir and the NP are cathodically polarised, operando optical microscopy reveals the growth of an electrolyte nanodroplet on top of the NP. This suggests that the electrocatalysis of the oxygen reduction reaction operates at the NP and that an electrolyte nanochannel is formed - acting as an ion pump - between the reservoir and the NP. We have described here the optically imaged phenomena and their relevance to the characterization of the electrolyte nanochannel linking the NPs to the electrolyte microreservoir. Additionally, we have addressed the capacity of the nanochannel to transport ions and solvent flow to the NP.
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Affiliation(s)
| | | | - Jean-Marc Noël
- Université Paris Cité, CNRS, ITODYS, F-75013 Paris, France.
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2
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Sarkar S, Nieuwenhuis AF, Lemay SG. Integrated Glass Microfluidics with Electrochemical Nanogap Electrodes. Anal Chem 2023; 95:4266-4270. [PMID: 36812004 PMCID: PMC9996602 DOI: 10.1021/acs.analchem.2c04257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
We present a framework for the fabrication of chip-based electrochemical nanogap sensors integrated with microfluidics. Instead of polydimethylsiloxane (PDMS), SU-8 aided adhesive bonding of silicon and glass wafers is used to implement parallel flow control. The fabrication process permits wafer-scale production with high throughput and reproducibility. Additionally, the monolithic structures allow simple electrical and fluidic connections, alleviating the need for specialized equipment. We demonstrate the utility of these flow-incorporated nanogap sensors by performing redox cycling measurements under laminar flow conditions.
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Affiliation(s)
- Sahana Sarkar
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Ab F Nieuwenhuis
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Serge G Lemay
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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3
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Ito K, Inoue KY, Ito-Sasaki T, Ikegawa M, Takano S, Ino K, Shiku H. Highly Sensitive Electrochemical Endotoxin Sensor Based on Redox Cycling Using an Interdigitated Array Electrode Device. MICROMACHINES 2023; 14:327. [PMID: 36838027 PMCID: PMC9960723 DOI: 10.3390/mi14020327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/23/2023] [Accepted: 01/25/2023] [Indexed: 06/18/2023]
Abstract
The Limulus amebocyte lysate (LAL) reaction-based assay, the most commonly used endotoxin detection method, requires a skilled technician. In this study, to develop an easy-to-use and highly sensitive endotoxin sensor, we created an electrochemical endotoxin sensor by using an interdigitated array electrode (IDAE) device with advantages of amplifiable signals via redox cycling and portability. We added Boc-Leu-Gly-Arg-p-aminophenol (LGR-pAP) as an electrochemical substrate for an LAL reaction and detected p-aminophenol (pAP) released from LGR-pAP as a product of an endotoxin-induced LAL reaction via an IDAE device. The IDAE device showed a great redox cycling efficiency of 79.8%, and a 4.79-fold signal amplification rate. Then, we confirmed that pAP was detectable in the presence of LGR-pAP through chronoamperometry with the potential of the anode stepped from -0.3 to 0.5 V vs. Ag/AgCl while the cathode was biased at -0.3 V vs. Ag/AgCl. Then, we performed an endotoxin assay by using the IDAE device. Our endotoxin sensor detected as low as 0.7 and 1.0 endotoxin unit/L after the LAL reaction for 1 h and 45 min, respectively, and these data were within the cut-off value for ultrapure dialysis fluid. Therefore, our highly sensitive endotoxin sensor is useful for ensuring medical safety.
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Affiliation(s)
- Kentaro Ito
- Department of Frontier Science for Advanced Environment, Graduate School of Environmental Studies, Tohoku University, 6-6-11-604 Aramaki Aoba, Sendai 980-8579, Japan
| | - Kumi Y. Inoue
- Center for Basic Education, Faculty of Engineering, University of Yamanashi, 4-3-11 Takeda, Kofu 400-8511, Japan
| | - Takahiro Ito-Sasaki
- Department of Biomedical Engineering for Health and Welfare, Graduate School of Biomedical Engineering, Tohoku University, 6-6-11-604 Aramaki Aoba, Sendai 980-8579, Japan
| | - Miho Ikegawa
- Department of Frontier Science for Advanced Environment, Graduate School of Environmental Studies, Tohoku University, 6-6-11-604 Aramaki Aoba, Sendai 980-8579, Japan
| | - Shinichiro Takano
- Department of Frontier Science for Advanced Environment, Graduate School of Environmental Studies, Tohoku University, 6-6-11-604 Aramaki Aoba, Sendai 980-8579, Japan
| | - Kosuke Ino
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, 6-6-11-604 Aramaki Aoba, Sendai 980-8579, Japan
| | - Hitoshi Shiku
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, 6-6-11-604 Aramaki Aoba, Sendai 980-8579, Japan
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4
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Nguyen LBT, Leong YX, Koh CSL, Leong SX, Boong SK, Sim HYF, Phan-Quang GC, Phang IY, Ling XY. Inducing Ring Complexation for Efficient Capture and Detection of Small Gaseous Molecules Using SERS for Environmental Surveillance. Angew Chem Int Ed Engl 2022; 61:e202207447. [PMID: 35672258 DOI: 10.1002/anie.202207447] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Indexed: 01/13/2023]
Abstract
Gas-phase surface-enhanced Raman scattering (SERS) remains challenging due to poor analyte affinity to SERS substrates. The reported use of capturing probes suffers from concurrent inconsistent signals and long response time due to the formation of multiple potential probe-analyte interaction orientations. Here, we demonstrate the use of multiple non-covalent interactions for ring complexation to boost the affinity of small gas molecules, SO2 and NO2 , to our SERS platform, achieving rapid capture and multiplex detection down to 100 ppm. Experimental and in-silico studies affirm stable ring complex formation, and kinetic investigations reveal a 4-fold faster response time compared to probes without stable ring complexation capability. By synergizing spectral concatenation and support vector machine regression, we achieve 91.7 % accuracy for multiplex quantification of SO2 and NO2 in excess CO2 , mimicking real-life exhausts. Our platform shows immense potential for on-site exhaust and air quality surveillance.
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Affiliation(s)
- Lam Bang Thanh Nguyen
- Division of Chemistry and Biological Chemistry, School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
| | - Yong Xiang Leong
- Division of Chemistry and Biological Chemistry, School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
| | - Charlynn Sher Lin Koh
- Division of Chemistry and Biological Chemistry, School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
| | - Shi Xuan Leong
- Division of Chemistry and Biological Chemistry, School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
| | - Siew Kheng Boong
- Division of Chemistry and Biological Chemistry, School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
| | - Howard Yi Fan Sim
- Division of Chemistry and Biological Chemistry, School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
| | - Gia Chuong Phan-Quang
- Division of Chemistry and Biological Chemistry, School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
| | - In Yee Phang
- Division of Chemistry and Biological Chemistry, School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
| | - Xing Yi Ling
- Division of Chemistry and Biological Chemistry, School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore
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5
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Nguyen LBT, Leong YX, Koh CSL, Leong SX, Boong SK, Sim HYF, Phan-Quang GC, Phang IY, Ling XY. Inducing ring complexation for efficient capturing and detection of small gaseous molecules using SERS for environmental surveillance. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202207447] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
| | - Yong Xiang Leong
- Nanyang Technological University Chemistry and Biological Chemistry SINGAPORE
| | | | - Shi Xuan Leong
- Nanyang Technological University Chemistry and Biological Chemistry SINGAPORE
| | - Siew Kheng Boong
- Nanyang Technological University Chemistry and Biological Chemistry SINGAPORE
| | - Howard Yi Fan Sim
- Nanyang Technological University Chemistry and Biological Chemistry SINGAPORE
| | | | - In Yee Phang
- Nanyang Technological University Chemistry and Biological Chemistry SINGAPORE
| | - Xing Yi Ling
- Nanyang Technological University Division of Chemistry & Biological Chemistry 21 Nanyang Link,Nanyang Technological University, 637371 Singapore SINGAPORE
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6
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Jaugstetter M, Blanc N, Kratz M, Tschulik K. Electrochemistry under confinement. Chem Soc Rev 2022; 51:2491-2543. [PMID: 35274639 DOI: 10.1039/d1cs00789k] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Although the term 'confinement' regularly appears in electrochemical literature, elevated by continuous progression in the research of nanomaterials and nanostructures, up until today the various aspects of confinement considered in electrochemistry are rather scattered individual contributions outside the established disciplines in this field. Thanks to a number of highly original publications and the growing appreciation of confinement as an overarching link between different exciting new research strategies, 'electrochemistry under confinement' is the process of forming a research discipline of its own. To aid the development a coherent terminology and joint basic concepts, as crucial factors for this transformation, this review provides an overview on the different effects on electrochemical processes known to date that can be caused by confinement. It also suggests where boundaries to other effects, such as nano-effects could be drawn. To conceptualize the vast amount of research activities revolving around the main concepts of confinement, we define six types of confinement and select two of them to discuss the state of the art and anticipated future developments in more detail. The first type concerns nanochannel environments and their applications for electrodeposition and for electrochemical sensing. The second type covers the rather newly emerging field of colloidal single entity confinement in electrochemistry. In these contexts, we will for instance address the influence of confinement on the mass transport and electric field distributions and will link the associated changes in local species concentration or in the local driving force to altered reaction kinetics and product selectivity. Highlighting pioneering works and exciting recent developments, this educational review does not only aim at surveying and categorizing the state-of-the-art, but seeks to specifically point out future perspectives in the field of confinement-controlled electrochemistry.
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Affiliation(s)
- Maximilian Jaugstetter
- Analytical Chemistry II, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany.
| | - Niclas Blanc
- Analytical Chemistry II, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany.
| | - Markus Kratz
- Analytical Chemistry II, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany.
| | - Kristina Tschulik
- Analytical Chemistry II, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany.
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7
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Kostiuchenko ZA, Lemay SG. Quasi-One-Dimensional Generator-Collector Electrochemistry in Nanochannels. Anal Chem 2020; 92:2847-2852. [PMID: 31934747 PMCID: PMC7003156 DOI: 10.1021/acs.analchem.9b05396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Mass transport in
fluidic channels under conditions of pressure-driven
flow is controlled by a combination of convection and diffusion. For
electrochemical measurements the height of a channel is typically
of the same order of magnitude as the electrode dimensions, resulting
in complex two- or three- dimensional concentration distributions.
Electrochemical nanofluidic devices, however, can have such a low
height-to-length ratio that they can effectively be considered as
one-dimensional. This greatly simplifies the modeling and quantitative
interpretation of analytical measurements. Here we study mass transport
in nanochannels using electrodes in a generator-collector configuration.
The flux of redox molecules is monitored amperometrically. We observe
the transition from diffusion-dominated to convection-dominated transport
by varying both the flow velocity and the distance between the electrodes.
These results are described quantitatively by the one-dimensional
Nernst–Planck equation for mass transport over the full range
of experimentally accessible parameters.
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Affiliation(s)
- Zinaida A Kostiuchenko
- MESA+ Institute for Nanotechnology and Faculty of Science and Technology , University of Twente , P.O. Box 217, 7500 AE Enschede , The Netherlands
| | - Serge G Lemay
- MESA+ Institute for Nanotechnology and Faculty of Science and Technology , University of Twente , P.O. Box 217, 7500 AE Enschede , The Netherlands
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8
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Ito K, Inoue KY, Ino K, Matsue T, Shiku H. A highly sensitive endotoxin sensor based on redox cycling in a nanocavity. Analyst 2019; 144:3659-3667. [DOI: 10.1039/c9an00478e] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A highly sensitive endotoxin sensor and novel analytical principle using diffusion coefficient difference was developed using a nanocavity device.
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Affiliation(s)
- Kentaro Ito
- Graduate School of Environmental Studies
- Tohoku University
- Sendai
- Japan
| | - Kumi Y. Inoue
- Graduate School of Environmental Studies
- Tohoku University
- Sendai
- Japan
| | - Kosuke Ino
- Department of Applied Chemistry
- Graduate School of Engineering
- Tohoku University
- Sendai 980-8579
- Japan
| | - Tomokazu Matsue
- Graduate School of Environmental Studies
- Tohoku University
- Sendai
- Japan
| | - Hitoshi Shiku
- Department of Applied Chemistry
- Graduate School of Engineering
- Tohoku University
- Sendai 980-8579
- Japan
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9
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Al-Kutubi H, Voci S, Rassaei L, Sojic N, Mathwig K. Enhanced annihilation electrochemiluminescence by nanofluidic confinement. Chem Sci 2018; 9:8946-8950. [PMID: 30647886 PMCID: PMC6301198 DOI: 10.1039/c8sc03209b] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 09/30/2018] [Indexed: 12/30/2022] Open
Abstract
The generation of stable enhanced light emission by electrochemiluminescence in microfabricated nanofluidic electrochemical devices is demonstrated for the first time by exploiting nanogap amplification.
Microfabricated nanofluidic electrochemical devices offer a highly controlled nanochannel geometry; they confine the volume of chemical reactions to the nanoscale and enable greatly amplified electrochemical detection. Here, the generation of stable light emission by electrochemiluminescence (ECL) in transparent nanofluidic devices is demonstrated for the first time by exploiting nanogap amplification. Through continuous oxidation and reduction of [Ru(bpy)3]2+ luminophores at electrodes positioned at opposite walls of a 100 nm nanochannel, we compare classic redox cycling and ECL annihilation. Enhanced ECL light emission of attomole luminophore quantities is evidenced under ambient conditions due to the spatial confinement in a 10 femtoliter volume, resulting in a short diffusion timescale and highly efficient ECL reaction pathways at the nanoscale.
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Affiliation(s)
- Hanan Al-Kutubi
- University of Groningen , Groningen Research Institute of Pharmacy , Pharmaceutical Analysis , P.O. Box 196 , 9700 AD Groningen , The Netherlands .
| | - Silvia Voci
- University of Bordeaux , Bordeaux INP , Institut des Sciences Moléculaires , UMR CNRS 5255 , 33607 Pessac , France .
| | - Liza Rassaei
- Rotterdam School of Management , Erasmus University , Burgemeester Oudlaan 50 , 3062 PA Rotterdam , The Netherlands.,Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Neso Sojic
- University of Bordeaux , Bordeaux INP , Institut des Sciences Moléculaires , UMR CNRS 5255 , 33607 Pessac , France .
| | - Klaus Mathwig
- University of Groningen , Groningen Research Institute of Pharmacy , Pharmaceutical Analysis , P.O. Box 196 , 9700 AD Groningen , The Netherlands .
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10
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Kang S, Nieuwenhuis AF, Mathwig K, Mampallil D, Kostiuchenko ZA, Lemay SG. Single-molecule electrochemistry in nanochannels: probing the time of first passage. Faraday Discuss 2018; 193:41-50. [PMID: 27775135 DOI: 10.1039/c6fd00075d] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The diffusive mass transport of individual redox molecules was probed experimentally in microfabricated nanogap electrodes. The residence times for molecules inside a well-defined detection volume were extracted and the resulting distribution was compared with quantitative analytical predictions from random-walk theory for the time of first passage. The results suggest that a small number of strongly adsorbing sites strongly influence mass transport at trace analyte levels.
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Affiliation(s)
- Shuo Kang
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
| | - Ab F Nieuwenhuis
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
| | - Klaus Mathwig
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
| | - Dileep Mampallil
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
| | - Zinaida A Kostiuchenko
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
| | - Serge G Lemay
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
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11
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Cui J, Mathwig K, Mampallil D, Lemay SG. Potential-Controlled Adsorption, Separation, and Detection of Redox Species in Nanofluidic Devices. Anal Chem 2018; 90:7127-7130. [PMID: 29808992 PMCID: PMC6011178 DOI: 10.1021/acs.analchem.8b01719] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nanoscale channels and electrodes for electrochemical measurements exhibit extreme surface-to-volume ratios and a correspondingly high sensitivity to even weak degrees of surface interactions. Here, we exploit the potential-dependent reversible adsorption of outer-sphere redox species to modulate in space and time their concentration in a nanochannel under advective flow conditions. Induced concentration variations propagate downstream at a species-dependent velocity. This allows one to amperometrically distinguish between attomole amounts of species based on their time-of-flight. On-demand concentration pulse generation, separation, and detection are all integrated in a miniaturized platform.
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Affiliation(s)
- Jin Cui
- MESA+ Institute for Nanotechnology , University of Twente , PO Box 217, 7500 AE Enschede , The Netherlands
| | - Klaus Mathwig
- MESA+ Institute for Nanotechnology , University of Twente , PO Box 217, 7500 AE Enschede , The Netherlands
| | - Dileep Mampallil
- MESA+ Institute for Nanotechnology , University of Twente , PO Box 217, 7500 AE Enschede , The Netherlands
| | - Serge G Lemay
- MESA+ Institute for Nanotechnology , University of Twente , PO Box 217, 7500 AE Enschede , The Netherlands
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12
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Kostiuchenko ZA, Glazer PJ, Mendes E, Lemay SG. Chemical physics of electroactive materials - the oft-overlooked faces of electrochemistry. Faraday Discuss 2017; 199:9-28. [PMID: 28654123 DOI: 10.1039/c7fd00117g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Electroactive materials and their applications are enjoying renewed attention, in no small part motivated by the advent of nanoscale tools for their preparation and study. While the fundamentals of charge and mass transport in electrolytes on this scale are by and large well understood, their interplay can have subtle manifestations in the more complex situations typical of, for example, integrated microfluidics-based applications. In particular, the role of faradaic processes is often overlooked or, at best, purposefully suppressed via experimental design. In this introductory article we discuss, using simple illustrations from our laboratories, some of the manifestations of electrochemistry in electroactive materials.
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Affiliation(s)
- Zinaida A Kostiuchenko
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
| | - Piotr J Glazer
- Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Eduardo Mendes
- Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Serge G Lemay
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
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13
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Zafarani HR, Mathwig K, Sudhölter EJR, Rassaei L. Electrochemical Amplification in Side-by-Side Attoliter Nanogap Transducers. ACS Sens 2017; 2:724-728. [PMID: 28670622 PMCID: PMC5485373 DOI: 10.1021/acssensors.7b00180] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 05/16/2017] [Indexed: 11/30/2022]
Abstract
We report a strategy for the fabrication of a new type of electrochemical nanogap transducer. These nanogap devices are based on signal amplification by redox cycling. Using two steps of electron-beam lithography, vertical gold electrodes are fabricated side by side at a 70 nm distance encompassing a 20 attoliter open nanogap volume. We demonstrate a current amplification factor of 2.5 as well as the possibility to detect the signal of only 60 analyte molecules occupying the detection volume. Experimental voltammetry results are compared to calculations from finite element analysis.
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Affiliation(s)
- Hamid Reza Zafarani
- Laboratory of Organic
Materials and Interfaces, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Klaus Mathwig
- University of Groningen, Groningen Research Institute of Pharmacy, Pharmaceutical Analysis, P.O. Box 196, 9700 AD Groningen, The Netherlands
| | - Ernst J. R. Sudhölter
- Laboratory of Organic
Materials and Interfaces, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Liza Rassaei
- Laboratory of Organic
Materials and Interfaces, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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14
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In-situ Raman spectroscopy to elucidate the influence of adsorption in graphene electrochemistry. Sci Rep 2017; 7:45080. [PMID: 28338094 PMCID: PMC5364475 DOI: 10.1038/srep45080] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 02/17/2017] [Indexed: 11/08/2022] Open
Abstract
Electrochemistry on graphene is of particular interest due to graphene's high surface area, high electrical conductivity and low interfacial capacitance. Because the graphene Fermi level can be probed by its strong Raman signal, information on the graphene doping can be obtained which in turn can provide information on adsorbed atoms or molecules. For this paper, the adsorption analysis was successfully performed using three electroactive substances with different electrode interaction mechanisms: hexaammineruthenium(III) chloride (RuHex), ferrocenemethanol (FcMeOH) and potassium ferricyanide/potassium ferrocyanide (Fe(CN)6). The adsorption state was probed by analysing the G-peak position in the measured in-situ Raman spectrum during electrochemical experiments. We conclude that electrochemical Raman spectroscopy on graphene is a valuable tool to obtain in-situ information on adsorbed species on graphene, isolated from the rest of the electrochemical behaviour.
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15
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Steentjes T, Sarkar S, Jonkheijm P, Lemay SG, Huskens J. Electron Transfer Mediated by Surface-Tethered Redox Groups in Nanofluidic Devices. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2017; 13:1603268. [PMID: 27982518 DOI: 10.1002/smll.201603268] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 11/11/2016] [Indexed: 06/06/2023]
Abstract
Electrochemistry provides a powerful sensor transduction and amplification mechanism that is highly suited for use in integrated, massively parallelized assays. Here, the cyclic voltammetric detection of flexible, linear poly(ethylene glycol) polymers is demonstrated, which have been functionalized with redox-active ferrocene (Fc) moieties and surface-tethered inside a nanofluidic device consisting of two microscale electrodes separated by a gap of <100 nm. Diffusion of the surface-bound polymer chains in the aqueous electrolyte allows the redox groups to repeatedly shuttle electrons from one electrode to the other, resulting in a greatly amplified steady-state electrical current. Variation of the polymer length provides control over the current, as the activity per Fc moiety appears to depend on the extent to which the polymer layers of the opposing electrodes can interpenetrate each other and thus exchange electrons. These results outline the design rules for sensing devices that are based on changing the polymer length, flexibility, and/or diffusivity by binding an analyte to the polymer chain. Such a nanofluidic enabled configuration provides an amplified and highly sensitive alternative to other electrochemical detection mechanisms.
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Affiliation(s)
- Tom Steentjes
- Molecular NanoFabrication, MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE, Enschede, The Netherlands
| | - Sahana Sarkar
- NanoIonics, MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE, Enschede, The Netherlands
| | - Pascal Jonkheijm
- Molecular NanoFabrication, MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE, Enschede, The Netherlands
| | - Serge G Lemay
- NanoIonics, MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE, Enschede, The Netherlands
| | - Jurriaan Huskens
- Molecular NanoFabrication, MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE, Enschede, The Netherlands
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16
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Zafarani HR, Mathwig K, Lemay SG, Sudhölter EJR, Rassaei L. Modulating Selectivity in Nanogap Sensors. ACS Sens 2016. [DOI: 10.1021/acssensors.6b00556] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hamid Reza Zafarani
- Laboratory
of Organic Materials and Interfaces, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Klaus Mathwig
- Pharmaceutical
Analysis, Groningen Research Institute of Pharmacy, University of Groningen, P.O. Box 196, 9700 AD Groningen, The Netherlands
| | - Serge G. Lemay
- MESA+
Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Ernst J. R. Sudhölter
- Laboratory
of Organic Materials and Interfaces, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Liza Rassaei
- Laboratory
of Organic Materials and Interfaces, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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17
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Redox cycling with ITO electrodes separated by an ultrathin silica nanochannel membrane. Electrochem commun 2016. [DOI: 10.1016/j.elecom.2016.08.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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18
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Tan SY, Zhang J, Bond AM, Macpherson JV, Unwin PR. Impact of Adsorption on Scanning Electrochemical Microscopy Voltammetry and Implications for Nanogap Measurements. Anal Chem 2016; 88:3272-80. [PMID: 26877069 DOI: 10.1021/acs.analchem.5b04715] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Sze-yin Tan
- Department
of Chemistry, University of Warwick, Coventry, West Midlands CV4 7AL, United Kingdom
- School
of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - Jie Zhang
- School
of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - Alan M. Bond
- School
of Chemistry, Monash University, Clayton, Victoria 3800, Australia
| | - Julie V. Macpherson
- Department
of Chemistry, University of Warwick, Coventry, West Midlands CV4 7AL, United Kingdom
| | - Patrick R. Unwin
- Department
of Chemistry, University of Warwick, Coventry, West Midlands CV4 7AL, United Kingdom
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19
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Kanno Y, Ino K, Shiku H, Matsue T. A local redox cycling-based electrochemical chip device with nanocavities for multi-electrochemical evaluation of embryoid bodies. LAB ON A CHIP 2015; 15:4404-4414. [PMID: 26481771 DOI: 10.1039/c5lc01016k] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
An electrochemical device, which consists of electrode arrays, nanocavities, and microwells, was developed for multi-electrochemical detection with high sensitivity. A local redox cycling-based electrochemical (LRC-EC) system was used for multi-electrochemical detection and signal amplification. The LRC-EC system consists of n(2) sensors with only 2n bonding pads for external connection. The nanocavities fabricated in the sensor microwells enable significant improvement of the signal amplification compared with the previous devices we have developed. The present device was successfully applied for evaluation of embryoid bodies (EBs) from embryonic stem (ES) cells via electrochemical measurements of alkaline phosphatase (ALP) activity in the EBs. In addition, the EBs were successfully trapped in the sensor microwells of the device using dielectrophoresis (DEP) manipulation, which led to high-throughput cell analysis. This device is considered to be useful for multi-electrochemical detection and imaging for bioassays including cell analysis.
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Affiliation(s)
- Yusuke Kanno
- Graduate School of Environmental Studies, Tohoku University, Japan.
| | - Kosuke Ino
- Graduate School of Environmental Studies, Tohoku University, Japan.
| | - Hitoshi Shiku
- Graduate School of Environmental Studies, Tohoku University, Japan.
| | - Tomokazu Matsue
- Graduate School of Environmental Studies, Tohoku University, Japan. and WPI-Advanced Institute for Materials Research, Tohoku University, Japan
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20
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Abstract
The reference electrode is a key component in electrochemical measurements, yet it remains a challenge to implement a reliable reference electrode in miniaturized electrochemical sensors. Here we explore experimentally and theoretically an alternative approach based on redox cycling which eliminates the reference electrode altogether. We show that shifts in the solution potential caused by the lack of reference can be understood quantitatively, and determine the requirements for accurate measurements in miniaturized systems in the absence of a reference electrode.
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Affiliation(s)
- Sahana Sarkar
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands, ; Fax: +31 53 489 3511; Tel : +31 53 489 2306
| | - Klaus Mathwig
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands, ; Fax: +31 53 489 3511; Tel : +31 53 489 2306
| | - Shuo Kang
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands, ; Fax: +31 53 489 3511; Tel : +31 53 489 2306
| | - Ab. F. Nieuwenhuis
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands, ; Fax: +31 53 489 3511; Tel : +31 53 489 2306
| | - Serge G. Lemay
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands, ; Fax: +31 53 489 3511; Tel : +31 53 489 2306
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21
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Rassaei L, Mathwig K, Kang S, Heering HA, Lemay SG. Integrated biodetection in a nanofluidic device. ACS NANO 2014; 8:8278-84. [PMID: 25105352 DOI: 10.1021/nn502678t] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The sensing of enzymatic processes in volumes at or below the scale of single cells is challenging but highly desirable in the study of biochemical processes. Here we demonstrate a nanofluidic device that combines an enzymatic recognition element and electrochemical signal transduction within a six-femtoliter volume. Our approach is based on localized immobilization of the enzyme tyrosinase in a microfabricated nanogap electrochemical transducer. The enzymatic reaction product quinone is localized in the confined space of a nanochannel in which efficient redox cycling also takes place. Thus, the sensor allows the sensitive detection of minute amounts of product molecules generated by the enzyme in real time. This method is ideally suited for the study of ultra-small-volume systems such as the contents of individual biological cells or organelles.
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22
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Mathwig K, Aartsma TJ, Canters GW, Lemay SG. Nanoscale methods for single-molecule electrochemistry. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2014; 7:383-404. [PMID: 25000819 DOI: 10.1146/annurev-anchem-062012-092557] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The development of experiments capable of probing individual molecules has led to major breakthroughs in fields ranging from molecular electronics to biophysics, allowing direct tests of knowledge derived from macroscopic measurements and enabling new assays that probe population heterogeneities and internal molecular dynamics. Although still somewhat in their infancy, such methods are also being developed for probing molecular systems in solution using electrochemical transduction mechanisms. Here we outline the present status of this emerging field, concentrating in particular on optical methods, metal-molecule-metal junctions, and electrochemical nanofluidic devices.
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Affiliation(s)
- Klaus Mathwig
- MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, the Netherlands; ,
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23
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Mampallil D, Mathwig K, Kang S, Lemay SG. Reversible Adsorption of Outer-Sphere Redox Molecules at Pt Electrodes. J Phys Chem Lett 2014; 5:636-640. [PMID: 26276621 DOI: 10.1021/jz402592n] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Adsorption often dominates the response of nanofluidic systems due to their high surface-to-volume ratios. Here we harness this sensitivity to investigate the reversible adsorption of outer-sphere redox species at electrodes, a phenomenon that is easily overlooked in bulk measurements. We find that even though adsorption does not necessarily play a role in the electron-transfer process, such adsorption is nevertheless ubiquitous for the widely used outer-sphere species. We investigate the physical factors driving adsorption and find that this counterintuitive behavior is mediated by the anionic species in the supporting electrolyte, closely following the well-known Hofmeister series. Our results provide foundations both for theoretical studies of the underlying mechanisms and for contriving strategies to control adsorption in micro/nanoscale electrochemical transducers where surface effects are dominant.
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Affiliation(s)
- Dileep Mampallil
- MESA+ Institute for Nanotechnology, University of Twente, Carre 4409, Achterhorst, 7500AE Enschede, The Netherlands
| | - Klaus Mathwig
- MESA+ Institute for Nanotechnology, University of Twente, Carre 4409, Achterhorst, 7500AE Enschede, The Netherlands
| | - Shuo Kang
- MESA+ Institute for Nanotechnology, University of Twente, Carre 4409, Achterhorst, 7500AE Enschede, The Netherlands
| | - Serge G Lemay
- MESA+ Institute for Nanotechnology, University of Twente, Carre 4409, Achterhorst, 7500AE Enschede, The Netherlands
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24
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Hüske M, Stockmann R, Offenhäusser A, Wolfrum B. Redox cycling in nanoporous electrochemical devices. NANOSCALE 2014; 6:589-598. [PMID: 24247480 DOI: 10.1039/c3nr03818a] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Nanoscale redox cycling is a powerful technique for detecting electrochemically active molecules, based on fast repetitive oxidation and reduction reactions. An ideal implementation of redox cycling sensors can be realized by nanoporous dual-electrode systems in easily accessible and scalable geometries. Here, we introduce a multi-electrode array device with highly efficient nanoporous redox cycling sensors. Each of the sensors holds up to 209,000 well defined nanopores with minimal pore radii of less than 40 nm and an electrode separation of ~100 nm. We demonstrate the efficiency of the nanopore array by screening a large concentration range over three orders of magnitude with area-specific sensitivities of up to 81.0 mA (cm(-2) mM(-1)) for the redox-active probe ferrocene dimethanol. Furthermore, due to the specific geometry of the material, reaction kinetics has a unique potential-dependent impact on the signal characteristics. As a result, redox cycling experiments in the nanoporous structure allow studies on heterogeneous electron transfer reactions revealing a surprisingly asymmetric transfer coefficient.
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Affiliation(s)
- Martin Hüske
- Institute of Bioelectronics (PGI-8/ICS-8) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich, D-52425 Jülich, Germany.
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25
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Kang S, Nieuwenhuis AF, Mathwig K, Mampallil D, Lemay SG. Electrochemical single-molecule detection in aqueous solution using self-aligned nanogap transducers. ACS NANO 2013; 7:10931-10937. [PMID: 24279688 DOI: 10.1021/nn404440v] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Electrochemical detection of individual molecular tags in nanochannels may enable cost-effective, massively parallel analysis and diagnostics platforms. Here we demonstrate single-molecule detection of prototypical analytes in aqueous solution based on redox cycling in 40 nm nanogap transducers. These nanofluidic devices are fabricated using standard microfabrication techniques combined with a self-aligned approach that minimizes gap size and dead volume. We demonstrate the detection of three common redox mediators at physiological salt concentrations.
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Affiliation(s)
- Shuo Kang
- MESA+ Institute for Nanotechnology, University of Twente , PO Box 217, 7500 AE Enschede, The Netherlands
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26
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27
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WEBSTER THADDAEUSA, SISMAET HUNTERJ, GOLUCH EDGARD. AMPEROMETRIC DETECTION OF PYOCYANIN IN NANOFLUIDIC CHANNELS. ACTA ACUST UNITED AC 2013. [DOI: 10.1142/s1793984413400114] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Microfabricated nanofluidic electrode assemblies (NEAs) with integrated palladium references were used to amperometrically monitor changes in pyocyanin concentration. Pyocyanin is an electroactive molecule that is produced by the opportunistic pathogen Pseudomonas aeruginosa and is directly linked to cellular processes that increase both robustness and virulence in this bacterium. This is the first time that pyocyanin has been measured in real time using microfabricated sensors. A linear response in faradaic current (R2= 0.96) was observed over a biomedically relevant range of pyocyanin concentrations (0–100 μM) while continuously measuring the current for 2 h. Measurement of the current that results from the repeated oxidation and reduction of pyocyanin at two closely spaced electrodes inside the device nanochannel yielded a 1.07 μM limit of detection without electrical isolation of the electrochemical cell. Since a reference electrode is integrated inside the nanofluidic channel of these sensors, they can potentially be employed to detect pyocyanin and other redox-active molecules in wide range of medical and environmental settings where space is limited. NEAs were also used with an external Ag/AgCl reference electrode to determine the concentration of pyocyanin in trypticase soy broth samples. This type of analysis is completed in less than 2 min and the detection limit was determined to be 441 nM.
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Affiliation(s)
- THADDAEUS A. WEBSTER
- Department of Chemical Engineering, Northeastern University, 360 Huntington Ave., 313SN, Boston, MA 02115, USA
| | - HUNTER J. SISMAET
- Department of Chemical Engineering, Northeastern University, 360 Huntington Ave., 313SN, Boston, MA 02115, USA
| | - EDGAR D. GOLUCH
- Department of Chemical Engineering, Northeastern University, 360 Huntington Ave., 313SN, Boston, MA 02115, USA
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28
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Pushing the Limits of Electrical Detection of Ultralow Flows in Nanofluidic Channels. MICROMACHINES 2013. [DOI: 10.3390/mi4020138] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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29
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Lemay SG, Kang S, Mathwig K, Singh PS. Single-molecule electrochemistry: present status and outlook. Acc Chem Res 2013; 46:369-77. [PMID: 23270398 DOI: 10.1021/ar300169d] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The development of methods for detecting and manipulating matter at the level of individual macromolecules represents one of the key scientific advancements of recent decades. These techniques allow us to get information that is largely unobtainable otherwise, such as the magnitudes of microscopic forces, mechanistic details of catalytic processes, macromolecular population heterogeneities, and time-resolved, step-by-step observation of complex kinetics. Methods based on optical, mechanical, and ionic-conductance signal transduction are particularly developed. However, there is scope for new approaches that can broaden the range of molecular systems that we can study at this ultimate level of sensitivity and for developing new analytical methods relying on single-molecule detection. Approaches based on purely electrical detection are particularly appealing in the latter context, since they can be easily combined with microelectronics or fluidic devices on a single microchip to create large parallel assays at relatively low cost. A form of electrical signal transduction that has so far remained relatively underdeveloped at the single-molecule level is the direct detection of the charge transferred in electrochemical processes. The reason for this is simple: only a few electrons are transferred per molecule in a typical faradaic reaction, a heterogeneous charge-transfer reaction that occurs at the electrode's surface. Detecting this tiny amount of charge is impossible using conventional electrochemical instrumentation. A workaround is to use redox cycling, in which the charge transferred is amplified by repeatedly reducing and oxidizing analyte molecules as they randomly diffuse between a pair of electrodes. For this process to be sufficiently efficient, the electrodes must be positioned within less than 100 nm of each other, and the analyte must remain between the electrodes long enough for the measurement to take place. Early efforts focused on tip-based nanoelectrodes, descended from scanning electrochemical microscopy, to create suitable geometries. However, it has been challenging to apply these technologies broadly. In this Account, we describe our alternative approach based on electrodes embedded in microfabricated nanochannels, so-called nanogap transducers. Microfabrication techniques grant a high level of reproducibility and control over the geometry of the devices, permitting systematic development and characterization. We have employed these devices to demonstrate single-molecule sensitivity. This method shows good agreement with theoretical analysis based on the Brownian motion of discrete molecules, but only once the finite time resolution of the experimental apparatus is taken into account. These results highlight both the random nature of single-molecule signals and the complications that it can introduce in data interpretation. We conclude this Account with a discussion on how scientists can overcome this limitation in the future to create a new experimental platform that can be generally useful for both fundamental studies and analytical applications.
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Affiliation(s)
- Serge G. Lemay
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - Shuo Kang
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - Klaus Mathwig
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - Pradyumna S. Singh
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
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30
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Xiong J, White HS. The i–V response of an electrochemical cell comprising two polarizable microelectrodes and the influence of impurities on the cell response. J Electroanal Chem (Lausanne) 2013. [DOI: 10.1016/j.jelechem.2012.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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31
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Singh PS, Kätelhön E, Mathwig K, Wolfrum B, Lemay SG. Stochasticity in single-molecule nanoelectrochemistry: origins, consequences, and solutions. ACS NANO 2012; 6:9662-9671. [PMID: 23106647 DOI: 10.1021/nn3031029] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Electrochemical detection of single molecules is being actively pursued as an enabler of new fundamental experiments and sensitive analytical capabilities. Most attempts to date have relied on redox cycling in a nanogap, which consists of two parallel electrodes separated by a nanoscale distance. While these initial experiments have demonstrated single-molecule detection at the proof-of-concept level, several fundamental obstacles need to be overcome to transform the technique into a realistic detection tool suitable for use in more complex settings (e.g., studying enzyme dynamics at single catalytic event level, probing neuronal exocytosis, etc.). In particular, it has become clearer that stochasticity--the hallmark of most single-molecule measurements--can become the key limiting factor on the quality of the information that can be obtained from single-molecule electrochemical assays. Here we employ random-walk simulations to show that this stochasticity is a universal feature of all single-molecule experiments in the diffusively coupled regime and emerges due to the inherent properties of brownian motion. We further investigate the intrinsic coupling between stochasticity and detection capability, paying particular attention to the role of the geometry of the detection device and the finite time resolution of measurement systems. We suggest concrete, realizable experimental modifications and approaches to mitigate these limitations. Overall, our theoretical analyses offer a roadmap for optimizing single-molecule electrochemical experiments, which is not only desirable but also indispensable for their wider employment as experimental tools for electrochemical research and as realistic sensing or detection systems.
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Affiliation(s)
- Pradyumna S Singh
- MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
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32
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Abstract
The response of nanoscale electrodes displays deviations from conventional voltammetry theory that include a reduction in the limiting current and enhanced current fluctuations. We study the power spectra of these fluctuations in well characterized conical electrodes with radii between 2 and 10 nm. The fluctuations are found to display non-trivial power laws. We propose a model based on reversible adsorption of the redox species onto the nanoelectrode. This model is consistent with the non-stationary character of both the limiting current and the adsorption of molecules onto metal electrodes. Our model predicts the electrochemical reaction is nonergodic and sets fundamental limits on the sensitivity of uncoated nanoelectrodes.
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Affiliation(s)
- Diego Krapf
- Electrical and Computer Engineering and School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523, USA.
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33
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Mathwig K, Mampallil D, Kang S, Lemay SG. Electrical cross-correlation spectroscopy: measuring picoliter-per-minute flows in nanochannels. PHYSICAL REVIEW LETTERS 2012; 109:118302. [PMID: 23005685 DOI: 10.1103/physrevlett.109.118302] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 06/27/2012] [Indexed: 06/01/2023]
Abstract
We introduce all-electrical cross-correlation spectroscopy of molecular number fluctuations in nanofluidic channels. Our approach is based on a pair of nanogap electrochemical transducers located downstream from each other in the channel. When liquid is driven through this device, mesoscopic fluctuations in the local density of molecules are transported along the channel. We perform a time-of-flight measurement of these fluctuations by cross-correlating current-time traces obtained at the two detectors. Thereby we are able to detect ultralow liquid flow rates below 10 pL/min. This method constitutes the electrical equivalent of fluorescence cross-correlation spectroscopy.
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Affiliation(s)
- Klaus Mathwig
- MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
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