Carbon nanotube transistors have outstanding potential for electronic detection of biomolecules in solution. The physical mechanism underlying sensing however remains controversial, which hampers full exploitation these promising nanosensors. Previously suggested mechanisms are electrostatic gating, changes gate coupling, carrier mobility changes, and Schottky barrier effects. We argue that each has its characteristic effect on the liquid dependence device conductance. By studying both...

Noble metal nanoparticles can be electrodeposited on carbon nanotubes under potential control. The nanotube sidewalls serve both as the electrodeposition template and wire electrically connecting deposited nanoparticles.

We demonstrate the use of individual single-walled carbon nanotubes (SWNTs) as nanoelectrodes for electrochemistry. SWNTs were contacted by nanolithography, and cyclic voltammetry was performed in aqueous solutions. Interestingly, metallic semiconducting yielded similar steady-state voltammetric curves. clarify this behavior through a model that considers electronic structure SWNTs. Interfacial electron transfer to is observed be very fast but can nonetheless resolved due nanometer critical...

We report charge inversion, the sign reversal of effective surface in presence multivalent counterions, for biologically relevant regimes divalent ions and mixtures monovalent ions. Using streaming currents, pressure-driven transport countercharges diffuse layer, we find that inversion occurs rectangular silica nanochannels at high concentrations Strong screening is found to cancel restoring original polarity. An analytical model based on ion correlations successfully describes our observations.

Individual binding events are observed using amperometric detection. Discrete steps in the microelectrode response correspond to adsorption of single microspheres on electrode surface.

We have directly observed reversal of the polarity charged surfaces in water upon addition tri- and quadrivalent ions using atomic force microscopy. The bulk concentration multivalent at which charge inversion reversibly occurs depends only very weakly on chemical composition, surface structure, size lipophilicity ions, but is dominated by their valence. These results support theoretical proposal that spatial correlations between are driving mechanism behind inversion.

We present a theoretical description of the kinetics electrochemical charge transfer at single-walled carbon nanotube (SWNT) electrodes, explicitly taking into account SWNT electronic band structure. SWNTs have distinct and low density states (DOS), as expressed by small value quantum capacitance. show that this greatly affects alignment occupation in voltammetric experiments thus electrode kinetics. model electrochemistry metallic semiconducting well graphene applying Gerischer−Marcus...

Field-effect transistors based on single-walled carbon nanotubes (SWNTs) and graphene can function as highly sensitive nanoscale (bio)sensors in solution. Here, we compare experimentally how SWNT respond to changes the composition of aqueous electrolyte which they are immersed. We show that conductance SWNTs is strongly affected by ionic strength, pH, type ions present, a manner be qualitatively different for devices. this sensitivity results from combination mechanisms including...

Carbon nanotube transistors show tremendous potential for electronic detection of biomolecules in solution. However, the nature and magnitude sensing signal upon molecular adsorption have so far remained controversial. Here, authors that choice reference electrode is critical resolves much previous controversy. The eliminate artifacts related to by using a well-defined accurately control solution potential. Upon addition bovine serum albumin proteins, measure transistor threshold shift −15mV...

We report the electrochemical detection of individual redox-active molecules as they freely diffuse in solution. Our approach is based on microfabricated nanofluidic devices, wherein repeated reduction and oxidation at two closely spaced electrodes yields a giant sensitivity gain. Single entering leaving cavity are revealed anticorrelated steps faradaic current measured simultaneously through electrodes. Cross-correlation analysis provides unequivocal evidence single molecule sensitivity....

We have developed a chip-based nanofluidic device to amplify the electrochemical signal of catechols by orders magnitude. The amplification is based on rapid redox cycling between plane parallel electrodes inside nanochannel. show that it possible monitor only few hundred molecules residing in active area sensor. Furthermore, due nanochannel design, sensor immune interference undergoing irreversible reactions. demonstrate selectivity detecting catechol presence ascorbic acid, whose oxidized...

We demonstrate that a 50 nm high solution-filled cavity bounded by two parallel electrodes in which electrochemically active molecules undergo rapid redox cycling can be used to determine very fast electron-transfer kinetics. illustrate this capability showing the heterogeneous rate constant of Fc(MeOH)(2) sensitively depends on type and concentration supporting electrolyte. These solid-state devices are mechanically robust stable over time therefore have potential become widespread...

The development of methods for detecting and manipulating matter at the level individual macromolecules represents one key scientific advancements recent decades. These techniques allow us to get information that is largely unobtainable otherwise, such as magnitudes microscopic forces, mechanistic details catalytic processes, macromolecular population heterogeneities, time-resolved, step-by-step observation complex kinetics. Methods based on optical, mechanical, ionic-conductance signal...

Tumor-derived extracellular vesicles (tdEVs) are attracting much attention due to their essential function in intercellular communication and potential as cancer biomarkers. Although tdEVs significantly more abundant blood than other biomarkers, concentration compared components remains relatively low. Moreover, the presence of particles with a similar size that makes selective sensitive detection further challenging. Therefore, highly specific biosensors required for unambiguous tdEV...

We report on the fabrication and characterization of gold nanoelectrodes with carefully controlled nanometer dimensions in a matrix insulating silicon nitride. A focused electron beam was employed to drill nanopores thin nitride membrane. The size shape were studied high-resolution transmission microscopy electron-energy-loss two-dimensional maps. pores subsequently filled gold, yielding conically shaped nanoelectrodes. examined by atomic electrostatic force microscopy. Their applicability...

We report an experimental study of 1/f noise in liquid-gated graphene transistors. show that the gate dependence is well described by a charge-noise model, whereas Hooge's empirical relation fails to describe data. At low carrier density, can be attributed fluctuating charges close proximity graphene, while at high density it consistent with due scattering channel. The charge power scales inversely device area, and bilayer devices exhibit lower than single-layer devices. In air, observed also model.

Charge inversion occurs when the effective charge of a surface exposed to solution reverses polarity due an excess counterions accumulating in immediate vicinity surface. Using atomic force spectroscopy, we have directly measured effect on changing dielectric constant solvent and surface-charge density. Both decreasing increasing bare density lower charge-inversion concentration. These observations are consistent with theoretical proposal that spatial correlations between ions dominant...

ADVERTISEMENT RETURN TO ISSUEPREVFeatureNEXTLithography-Based NanoelectrochemistryLithographically fabricated nanostructures appear in an increasingly wide range of scientific fields, and electroanalytical chemistry is no exception. This article introduces lithography methods provides overview the new capabilities electrochemical phenomena that can emerge nanostructures.Liza Rassaei, Pradyumna S. Singh, Serge G. LemayView Author Information University TwenteCite this: Anal. Chem. 2011, 83,...