Kannan Balasubramanian

Humboldt-Universität zu Berlin

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Klaus Kern

École Polytechnique Fédérale de Lausanne

Marko Burghard

Max Planck Institute for Solid State Research

Tilmann J. Neubert

Humboldt-Universität zu Berlin

Rodrigo M. Iost

Universidade Federal de São Carlos

Anur Yadav

Humboldt-Universität zu Berlin

Roman Sordan

Politecnico di Milano

Tetiana Kurkina

RWTH Aachen University

Alf Mews

Universität Hamburg

Laura Zuccaro

University of Toronto

Michel Wehrhold

Humboldt-Universität zu Berlin

Cooperative Institutions

Max Planck Institute for Solid State Research

Max Planck Society

École Polytechnique Fédérale de Lausanne

Humboldt-Universität zu Berlin

Politecnico di Milano

Centre National de la Recherche Scientifique

Universidade de São Paulo

University of Rome Tor Vergata

Universidade Federal de São Carlos

Federal Institute For Materials Research and Testing

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Applications of the Static Quenching of Rhodamine B by Carbon Nanotubes

ChemPhysChem (2009)

Ashraf Ahmad Tetiana Kurkina Klaus Kern Kannan Balasubramanian

We report here on the interaction of the fluorescent dye rhodamine B (RB) with single-walled carbon nanotubes (SWCNTs). We observe that SWCNTs statically quench the fluorescence of RB by forming a stable ground state complex. Careful spectroscopic analysis indicates that the complex formation is efficient mainly with certain chiral forms. We propose three different applications utilizing this quenching mechanism and the associated complexation. Firstly, the quenching efficiency can be utilized as a measure for the characterization and quantification of nanotube dispersions. Secondly, we demonstrate that the specific complexation of RB can be deployed to enrich certain chiral forms in suspension. Finally, we show that RB can be effectively used to visualize nanotubes deposited on substrates.

Rhodamine B

Rhodamine

Characterization

Suspension

10.1002/cphc.200900246

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Citations (54)

Binding Kinetics of Methylene Blue on Monolayer Graphene Investigated by Multiparameter Surface Plasmon Resonance

ACS Omega (2018)

Nur Selin Kaya Anur Yadav Michel Wehrhold Laura Zuccaro Kannan Balasubramanian

In this paper, we study the interaction of a small dye molecule, namely, methylene blue (MB) with graphene surfaces using surface plasmon resonance (SPR). We show that by utilizing all of the parameters of the SPR angular dip and exploiting the fact that MB absorbs light at the operating wavelength, it is possible to detect the binding of small molecules that would otherwise not give a significant signal. The binding of MB to unmodified graphene is found to be stronger than that for gold. By studying the interaction at modified surfaces, we demonstrate that electrostatic effects play a dominant role in the binding of MB on to graphene. Furthermore, following the binding kinetics at various concentrations allows us to estimate apparent equilibrium binding and rate constants for the interaction of MB with graphene.

Methylene blue

Receptor–ligand kinetics

Self-assembled monolayer

10.1021/acsomega.8b00689

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Citations (21)

Enhanced Detection of Kidney Stones using Level Set Segmentation and Kernel-ELM

Davinder Kumar K. Punnam Chandar Neeru Malik Kannan Balasubramanian D. Suganthi

Kernel (algebra)

10.1109/icdsns62112.2024.10690917

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Citations (1)

Graphene‐Mercury‐Graphene Sandwich Electrode for Electroanalysis

ChemElectroChem (2021)

Tobias Grosser Michel Wehrhold Tilmann J. Neubert Kannan Balasubramanian

Abstract We present a new class of hybrid 2D electrodes, where mercury is incorporated between two graphene monolayers, prepared by bottom‐up assembly. First, the bottom graphene layer is electrochemically modified leading to the creation of fine mercury nanodroplets of variable size on the graphene surface. Although such electrodes show good sensitivity to heavy metal ions, their stability is limited due to the outgassing of mercury over time. After coverage with a top monolayer, the graphene surface is rendered with the favorable properties of mercury such as the high overpotential for hydrogen evolution, the ability to work at a broader cathodic potential range and higher sensitivity towards heavy metal ions such as Cd 2+ and Pb 2+ . Most importantly, the outgassing of mercury is completely hindered by the top layer, which yields a stable mercury‐like electrode but with a carbonaceous non‐toxic interface. We attribute the favorable properties of the sandwich electrode to the subsurface mercury present below the top graphene sheet, which renders it with new electrochemical properties.

Mercury

Overpotential

Outgassing

Graphene foam

10.1002/celc.202101290

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Citations (3)

Self-Assembled Electrical Biodetector Based on Reduced Graphene Oxide

ACS Nano (2012)

Tetiana Kurkina Subramanian Sundaram Ravi S. Sundaram Francesca Re Massimo Masserini

Large-scale fabrication of graphene-based devices is an aspect of great importance for various applications including chemical and biological sensing. Toward this goal, we present here a novel chemical route for the site-specific realization of devices based on reduced graphene oxide (RGO). Electrodes patterned by photolithography are modified with amino functional groups through electrodeposition. The amine groups function as hooks for the attachment of graphene oxide flakes selectively onto the electrodes. Graphene-like electrical behavior is attained by a subsequent thermal annealing step. We show that this anchoring strategy can be scaled-up to obtain RGO devices at a wafer scale in a facile manner. The scalability of our approach coupled with the use of photolithography is promising for the rapid realization of graphene-based devices. We demonstrate one possible application of the fabricated RGO devices as electrical biosensors through the immunodetection of amyloid beta peptide.

10.1021/nn301429k

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Citations (43)

Coulomb blockade phenomena in electromigration break junctions

Applied Physics Letters (2005)

Roman Sordan Kannan Balasubramanian Marko Burghard Klaus Kern

Nanosized gap structures have been fabricated via electromigration-induced breaking of gold-palladium nanowires. The application of low breaking voltages resulted in gap junctions exhibiting single-electron tunneling signatures at low temperature (2K), which are attributed to the formation of metallic nanoclusters during the electromigration process. Strikingly, the I–V characteristics of most samples displayed a close similarity to those typically attributed to electrical transport through single molecules contacted by incorporation into electromigration gaps. The finding that the breaking of bare nanowires alone is sufficient to create rich differential conductance features should be taken into account in future electrical studies on molecular-scale structures.

Electromigration

Nanoclusters

Coulomb blockade

Break junction

10.1063/1.1991988

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Citations (57)

Photocurrent Imaging of Charge Transport Barriers in Carbon Nanotube Devices

Nano Letters (2005)

Kannan Balasubramanian Marko Burghard Klaus Kern Matteo Scolari Alf Mews

The realization of high-performance electrical devices incorporating single-wall carbon nanotubes critically depends on the minimization of charge transport barriers in the tubes and at the contacts. Herein we demonstrate photocurrent imaging as a fast and effective tool to locate such barriers within individual metallic nanotubes contacted by metal electrodes. The locally induced photocurrents directly reflect the existence of built-in electric fields associated with the presence of depletion layers at the contacts or structural defects along the tubes.

Photocurrent

Photoconductivity

Charge carrier

10.1021/nl050053k

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Citations (109)

Bioelectronics and Interfaces Using Monolayer Graphene

ChemElectroChem (2018)

Lucyano J. A. Macedo Rodrigo M. Iost Ayaz Hassan Kannan Balasubramanian Frank N. Crespilho

Abstract Graphene is expected to revolutionize several application areas ranging from portable energy conversion and storage to miniaturized biosensors for medical applications. In this endeavor, the control of surface characteristics is an essential aspect for understanding fundamental phenomena occurring at the graphene‐liquid interface. In this comprehensive review, we address recent progress in the investigation of the interfacial characteristics of monolayer graphene and methods for modulating the physical and chemical properties of this interface. We focus on the electrochemistry and field‐effect measurements in liquid, which provide an improved understanding of the unique graphene‐liquid interface, with due consideration of the influence of the underlying substrate and structural defects in graphene. Finally, we present reported examples of using single graphene monolayers in miniaturized devices for realizing sensors, neural interfaces and batteries.

Bioelectronics

Interface (matter)

10.1002/celc.201800934

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Citations (60)

Photoelectronic transport imaging of individual semiconducting carbon nanotubes

Applied Physics Letters (2004)

Kannan Balasubramanian Yuwei Fan Marko Burghard Klaus Kern Marcel G. Friedrich

Photoconductivity in individual semiconducting single-wall carbon nanotubes was investigated using a confocal scanning optical microscope. The magnitude of the photocurrent was found to increase linearly with the laser intensity, and to be maximum for parallel orientation between the light polarization and the tube axis. Larger currents were obtained upon illuminating the tubes at 514.5 nm in comparison to those at 647.1 nm, consistent with the semiconducting tubes having a resonant absorption energy at the former wavelength. Moreover, the determination of the photoresponse as a function of position along single nanotubes has proven to be a useful tool to monitor local electronic structure effects.

Photoconductivity

Photocurrent

10.1063/1.1688451

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Citations (120)

Selective Enhancement of Carbon Nanotube Photoluminescence by Resonant Energy Transfer

ChemPhysChem (2009)

Ashraf Ahmad Klaus Kern Kannan Balasubramanian

Highly selective: Enhancement of the photoluminescence (PL) emission efficiency of selected chiral forms of semiconducting single-walled carbon nanotubes (SWCNTs) is presented (see figure). Excitation of Nile blue A in the presence of SWCNTs results in the quenching of its fluorescence. The energy is resonantly transferred to the (7,5) SWCNT whereas the (8,7) tube is not in resonance; hence, its PL remains unaffected.We report on a simple method for enhancing the efficiency of photoluminescence (PL) emission from selected chiral forms of semiconducting single-wall carbon nanotubes (SWCNTs). The method is based on the use of a fluorescent dye (Nile blue A) that shows the capability of resonant energy transfer on to nanotubes. The excitation of Nile blue A in the presence of SWCNTs results in the quenching of its fluorescence and the energy is resonantly transferred to certain chiral forms. The PL emission from these chiral forms shows a marked increase in efficiency signifying the occurrence of Förster type resonant energy transfer (FRET). Due to its simplicity, this procedure has widespread implications for the detection of carbon nanotubes as well as for their use as fluorophores in FRET-based in vivo and in vitro biological applications.

Nile blue

Photoluminescence excitation

10.1002/cphc.200800796

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Citations (46)