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Guglielmotti V, Fuhry E, Neubert TJ, Kuhl M, Pallarola D, Balasubramanian K. Real-Time Monitoring of Cell Adhesion onto a Soft Substrate by a Graphene Impedance Biosensor. ACS Sens 2024; 9:101-109. [PMID: 38141037 DOI: 10.1021/acssensors.3c01705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2023]
Abstract
Soft substrates are interesting for many applications, ranging from mimicking the cellular microenvironment to implants. Conductive electrodes on such substrates allow the realization of flexible, elastic, and transparent sensors. Single-layer graphene as a candidate for such electrodes brings the advantage that the active area of the sensor is transparent and conformal to the underlying substrate. Here, we overcome several challenges facing the routine realization of graphene cell sensors on a canonical soft substrate, namely, poly(dimethylsiloxane) (PDMS). We have systematically studied the effect of surface energy before, during, and after the transfer of graphene. Thus, we have identified a suitable support polymer, optimal substrate (pre)treatment, and an appropriate solvent for the removal of the support. Using this procedure, we can reproducibly obtain stable and intact graphene sensors on a millimeter scale on PDMS, which can withstand continuous measurements in cell culture media for several days. From local nanomechanical measurements, we infer that the softness of the substrate is slightly affected after the graphene transfer. However, we can modulate the stiffness using PDMS with differing compositions. Finally, we show that graphene sensors on PDMS can be successfully used as soft electrodes for real-time monitoring of the cell adhesion kinetics. The routine availability of single-layer graphene electrodes on a soft substrate with tunable stiffness will open a new avenue for studies, where the PDMS-liquid interface is made conducting with minimal alteration of the intrinsic material properties such as softness, flexibility, elasticity, and transparency.
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Affiliation(s)
- Victoria Guglielmotti
- Department of Chemistry, School of Analytical Sciences Adlershof (SALSA) & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 10099, Germany
- Instituto de Nanosistemas, Universidad Nacional de General San Martín, San Martín 1650, Provincia de Buenos Aires, Argentina
| | - Emil Fuhry
- Department of Chemistry, School of Analytical Sciences Adlershof (SALSA) & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 10099, Germany
| | - Tilmann J Neubert
- Department of Chemistry, School of Analytical Sciences Adlershof (SALSA) & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 10099, Germany
| | - Michel Kuhl
- Department of Chemistry, School of Analytical Sciences Adlershof (SALSA) & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 10099, Germany
| | - Diego Pallarola
- Instituto de Nanosistemas, Universidad Nacional de General San Martín, San Martín 1650, Provincia de Buenos Aires, Argentina
| | - Kannan Balasubramanian
- Department of Chemistry, School of Analytical Sciences Adlershof (SALSA) & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 10099, Germany
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Plačkić A, Neubert TJ, Patel K, Kuhl M, Watanabe K, Taniguchi T, Zurutuza A, Sordan R, Balasubramanian K. Electrochemistry at the Edge of a van der Waals Heterostructure. Small 2023:e2306361. [PMID: 38109121 DOI: 10.1002/smll.202306361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 10/19/2023] [Indexed: 12/19/2023]
Abstract
Artificial van der Waals heterostructures, obtained by stacking two-dimensional (2D) materials, represent a novel platform for investigating physicochemical phenomena and applications. Here, the electrochemistry at the one-dimensional (1D) edge of a graphene sheet, sandwiched between two hexagonal boron nitride (hBN) flakes, is reported. When such an hBN/graphene/hBN heterostructure is immersed in a solution, the basal plane of graphene is encapsulated by hBN, and the graphene edge is exclusively available in the solution. This forms an electrochemical nanoelectrode, enabling the investigation of electron transfer using several redox probes, e.g., ferrocene(di)methanol, hexaammineruthenium, methylene blue, dopamine and ferrocyanide. The low capacitance of the van der Waals edge electrode facilitates cyclic voltammetry at very high scan rates (up to 1000 V s-1 ), allowing voltammetric detection of redox species down to micromolar concentrations with sub-second time resolution. The nanoband nature of the edge electrode allows operation in water without added electrolyte. Finally, two adjacent edge electrodes are realized in a redox-cycling format. All the above-mentioned phenomena can be investigated at the edge, demonstrating that nanoscale electrochemistry is a new application avenue for van der Waals heterostructures. Such an edge electrode will be useful for studying electron transfer mechanisms and the detection of analyte species in ultralow sample volumes.
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Affiliation(s)
- Aleksandra Plačkić
- L-NESS, Department of Physics, Politecnico di Milano, Via Anzani 42, Como, 22100, Italy
- BioSense Institute, University of Novi Sad, Dr Zorana Đinđića 1, Novi Sad, 21000, Serbia
| | - Tilmann J Neubert
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099, Berlin, Germany
| | - Kishan Patel
- L-NESS, Department of Physics, Politecnico di Milano, Via Anzani 42, Como, 22100, Italy
| | - Michel Kuhl
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099, Berlin, Germany
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Amaia Zurutuza
- Graphenea Semiconductor SLU, Mikeletegi Pasealekua 83, San Sebastián, 20009, Spain
| | - Roman Sordan
- L-NESS, Department of Physics, Politecnico di Milano, Via Anzani 42, Como, 22100, Italy
| | - Kannan Balasubramanian
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099, Berlin, Germany
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Peplau S, Neubert TJ, Balasubramanian K, Polleux J, Börner HG. Statistical Copolymers that Mimic Aspects of Mussel Adhesive Proteins: Access to Robust Adhesive-Domains for Non-Covalent Surface PEGylation. Macromol Rapid Commun 2023; 44:e2300300. [PMID: 37657944 DOI: 10.1002/marc.202300300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 08/24/2023] [Indexed: 09/03/2023]
Abstract
Reconstructing functional sequence motifs of proteins, using statistical copolymers greatly reduces the information content, but simplifies synthesis significantly. Key amino acid residues involved in the adhesion of mussel foot proteins are identified. The side-chain functionalities of Dopa, lysine, and arginine are abstracted and incorporated into acrylate monomers to allow controlled radical polymerization. The resulting Dopa-acrylate (Y*-acr), arginine-acrylate (R-acr), and lysine-acrylate (K-acr) monomers are polymerized in different monomer ratios and compositions by reversible addition fragmentation transfer polymerization with a poly(ethylene glycol) (PEG) macrochain transfer agent. This results in two sets of PEG-block-copolymers with statistical mixtures and different monomer ratios of catechol/primary amine and catechol/guanidine side-chain functionalities, both important pairs for mimicking π-cation interactions. The coating behavior of these PEG-block-copolymers is evaluated using quartz crystal microbalance with dissipation energy monitoring (QCM-D), leading to non-covalent PEGylation of the substrates with clear compositional optima in the coating stability and antifouling properties. The coatings prevent non-reversible albumin or serum adsorption, as well as reduce cellular adhesion and fungal spore attachment.
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Affiliation(s)
- Stefan Peplau
- Department of Chemistry, Laboratory for Organic Synthesis of Functional Systems, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany
| | - Tilmann J Neubert
- Department of Chemistry, Laboratory for Organic Synthesis of Functional Systems, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany
- Department of Chemistry, Micro & Nano Analytical Sciences, School of Analytical Sciences Adlershof (SALSA) and IRIS Adlershof, Humboldt-Universität zu Berlin, Albert-Einstein-Str. 5-9, 12489, Berlin, Germany
| | - Kannan Balasubramanian
- Department of Chemistry, Micro & Nano Analytical Sciences, School of Analytical Sciences Adlershof (SALSA) and IRIS Adlershof, Humboldt-Universität zu Berlin, Albert-Einstein-Str. 5-9, 12489, Berlin, Germany
| | - Julien Polleux
- Research & Innovation Unit, Department of Ophthalmic Optics, Health University of Applied Sciences Tyrol, Innrain 98, Innsbruck, 6020, Austria
| | - Hans G Börner
- Department of Chemistry, Laboratory for Organic Synthesis of Functional Systems, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany
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Wehrhold M, Neubert TJ, Grosser T, Vondráček M, Honolka J, Balasubramanian K. A highly durable graphene monolayer electrode under long-term hydrogen evolution cycling. Chem Commun (Camb) 2022; 58:3823-3826. [PMID: 35234242 DOI: 10.1039/d2cc00220e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Achieving long term stability of single graphene sheets towards repeated electrochemical hydrogen evolution reaction (HER) cycling has been challenging. Here, we show through appropriate electrode preparation that it is possible to obtain highly durable isolated graphene electrodes, which can survive several hundreds of HER cycles with virtually no damage to the sp2-carbon framework and persistently good electron transfer characteristics.
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Affiliation(s)
- Michel Wehrhold
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Germany.
| | - Tilmann J Neubert
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Germany.
| | - Tobias Grosser
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Germany.
| | - Martin Vondráček
- Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, Prague 18221, Czech Republic
| | - Jan Honolka
- Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, Prague 18221, Czech Republic
| | - Kannan Balasubramanian
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Germany.
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Grosser T, Wehrhold M, Neubert TJ, Balasubramanian K. Graphene‐Mercury‐Graphene Sandwich Electrode for Electroanalysis. ChemElectroChem 2021. [DOI: 10.1002/celc.202101290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Tobias Grosser
- Department of Chemistry School of Analytical Sciences Adlershof (SALSA) & IRIS Adlershof Humboldt-Universität zu Berlin Unter den Linden 6 10117 Berlin Germany
| | - Michel Wehrhold
- Department of Chemistry School of Analytical Sciences Adlershof (SALSA) & IRIS Adlershof Humboldt-Universität zu Berlin Unter den Linden 6 10117 Berlin Germany
| | - Tilmann J. Neubert
- Department of Chemistry School of Analytical Sciences Adlershof (SALSA) & IRIS Adlershof Humboldt-Universität zu Berlin Unter den Linden 6 10117 Berlin Germany
| | - Kannan Balasubramanian
- Department of Chemistry School of Analytical Sciences Adlershof (SALSA) & IRIS Adlershof Humboldt-Universität zu Berlin Unter den Linden 6 10117 Berlin Germany
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Neubert TJ, Wehrhold M, Kaya NS, Balasubramanian K. Faradaic effects in electrochemically gated graphene sensors in the presence of redox active molecules. Nanotechnology 2020; 31:405201. [PMID: 32485689 DOI: 10.1088/1361-6528/ab98bc] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Field-effect transistors (FETs) based on graphene are promising devices for the direct sensing of a range of analytes in solution. We show here that the presence of redox active molecules in the analyte solution leads to the occurrence of heterogeneous electron transfer with graphene generating a Faradaic current (electron transfer) in a FET configuration resulting in shifts of the Dirac point. Such a shift occurs if the Faradaic current is significantly high, e.g. due to a large graphene area. Furthermore, the redox shift based on the Faradaic current, reminiscent of a doping-like effect, is found to be non-Nernstian and dependent on parameters known from electrode kinetics in potentiodynamic methods, such as the electrode area, the standard potential of the redox probes and the scan rate of the gate voltage modulation. This behavior clearly differentiates this effect from other transduction mechanisms based on electrostatic interactions or molecular charge transfer doping effects, which are usually behind a shift of the Dirac point. These observations suggest that large-area unmodified/pristine graphene in field-effect sensors behaves as a non-polarized electrode in liquid. Strategies for ensuring a polarized interface are discussed.
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Affiliation(s)
- Tilmann J Neubert
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof and Department of Chemistry, Humboldt-Universität zu Berlin, Berlin, Germany. Institut für Silizium-Photovoltaik, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
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Wehrhold M, Neubert TJ, Yadav A, Vondráček M, Iost RM, Honolka J, Balasubramanian K. Correction: pH sensitivity of interfacial electron transfer at a supported graphene monolayer. Nanoscale 2019; 11:15668. [PMID: 31408079 DOI: 10.1039/c9nr90181g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Correction for 'pH sensitivity of interfacial electron transfer at a supported graphene monolayer' by Michel Wehrhold et al., Nanoscale, 2019, DOI: 10.1039/c9nr05049c.
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Affiliation(s)
- Michel Wehrhold
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Unter den Linden 6, 10117 Berlin, Germany.
| | - Tilmann J Neubert
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Unter den Linden 6, 10117 Berlin, Germany. and Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institut für Silizium-Photovoltaik, Kekuléstr. 5, 12489 Berlin, Germany
| | - Anur Yadav
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Unter den Linden 6, 10117 Berlin, Germany.
| | - Martin Vondráček
- Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague, Czech Republic
| | - Rodrigo M Iost
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Unter den Linden 6, 10117 Berlin, Germany.
| | - Jan Honolka
- Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague, Czech Republic
| | - Kannan Balasubramanian
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Unter den Linden 6, 10117 Berlin, Germany.
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Wehrhold M, Neubert TJ, Yadav A, Vondráček M, Iost RM, Honolka J, Balasubramanian K. pH sensitivity of interfacial electron transfer at a supported graphene monolayer. Nanoscale 2019; 11:14742-14756. [PMID: 31348480 DOI: 10.1039/c9nr05049c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Electrochemical devices based on a single graphene monolayer are often realized on a solid support such as silicon oxide, glassy carbon or a metal film. Here, we show that, with graphene on insulating substrates, the kinetics of the electron transfer at graphene with various redox active molecules is dictated by solution pH for electrode reactions that are not proton dependent. We attribute the origin of this unusual phenomenon mainly to electrostatic effects between dissolved/dissociated redox species and the interfacial charge due to trace amounts of ionizable groups at the supported graphene-liquid interface. Cationic redox species show higher electron transfer rates at basic pH, while anionic species undergo faster electron transfer at acidic pH. Although this behavior is observed on graphene on three different insulating substrates, the strength of this effect appears to differ depending on the surface charge density of the underlying substrate. This finding has important implications for the design of electrochemical sensors and electrocatalysts based on graphene monolayers.
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Affiliation(s)
- Michel Wehrhold
- School of Analytical Sciences Adlershof (SALSA), IRIS Adlershof & Department of Chemistry, Humboldt-Universität zu Berlin, Unter den Linden 6, 10117 Berlin, Germany.
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Yadav A, Iost RM, Neubert TJ, Baylan S, Schmid T, Balasubramanian K. Selective electrochemical functionalization of the graphene edge. Chem Sci 2018; 10:936-942. [PMID: 30774888 PMCID: PMC6346287 DOI: 10.1039/c8sc04083d] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 11/04/2018] [Indexed: 12/23/2022] Open
Abstract
We report the direct exclusive modification of the edge of a single graphene monolayer with nanoparticles or organic functionalities under ambient conditions.
We present a versatile and simple method using electrochemistry for the exclusive functionalization of the edge of a graphene monolayer with metal nanoparticles or polymeric amino groups. The attachment of metal nanoparticles allows us to exploit surface-enhanced Raman scattering to characterize the chemistry of both the pristine and the functionalized graphene edge. For the pristine patterned graphene edge, we observe the typical edge-related modes, while for the functionalized graphene edge we identify the chemical structure of the functional layer by vibrational fingerprinting. The ability to obtain single selectively functionalized graphene edges routinely on an insulating substrate opens an avenue for exploring the effect of edge chemistry on graphene properties systematically.
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Affiliation(s)
- Anur Yadav
- School of Analytical Sciences Adlershof (SALSA) , Humboldt Universität zu Berlin , 10099 Berlin , Germany . nano.anchem-at-hu-berlin.de.,Department of Chemistry , IRIS Adlershof , Humboldt Universität zu Berlin , 10099 Berlin , Germany
| | - Rodrigo M Iost
- School of Analytical Sciences Adlershof (SALSA) , Humboldt Universität zu Berlin , 10099 Berlin , Germany . nano.anchem-at-hu-berlin.de.,Department of Chemistry , IRIS Adlershof , Humboldt Universität zu Berlin , 10099 Berlin , Germany
| | - Tilmann J Neubert
- School of Analytical Sciences Adlershof (SALSA) , Humboldt Universität zu Berlin , 10099 Berlin , Germany . nano.anchem-at-hu-berlin.de.,Department of Chemistry , IRIS Adlershof , Humboldt Universität zu Berlin , 10099 Berlin , Germany.,Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Institut für Silizium-Photovolatik , Kekuléstr. 5 , 12489 Berlin , Germany
| | - Sema Baylan
- School of Analytical Sciences Adlershof (SALSA) , Humboldt Universität zu Berlin , 10099 Berlin , Germany . nano.anchem-at-hu-berlin.de
| | - Thomas Schmid
- School of Analytical Sciences Adlershof (SALSA) , Humboldt Universität zu Berlin , 10099 Berlin , Germany . nano.anchem-at-hu-berlin.de.,BAM , Federal Institute for Materials Research and Testing , Richard-Willstätter-Str. 11 , 12489 Berlin , Germany
| | - Kannan Balasubramanian
- School of Analytical Sciences Adlershof (SALSA) , Humboldt Universität zu Berlin , 10099 Berlin , Germany . nano.anchem-at-hu-berlin.de.,Department of Chemistry , IRIS Adlershof , Humboldt Universität zu Berlin , 10099 Berlin , Germany.,BAM , Federal Institute for Materials Research and Testing , Richard-Willstätter-Str. 11 , 12489 Berlin , Germany
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