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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,(More)
Nanofluidic thin-layer cells count among the most sensitive electrochemical sensors built to date. Here we study both experimentally and theoretically the factors that limit the response time of these sensors. We find that the key limiting factor is reversible adsorption of the analyte molecules to the surfaces of the nanofluidic system, a direct(More)
This paper presents improvements in flow detection by electrical cross-correlation spectroscopy. This new technique detects molecular number fluctuations of electrochemically active analyte molecules as they are transported by liquid flow through a nanochannel. The fluctuations are used as a marker of liquid flow as their time of flight in between two(More)
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(More)
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(More)
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(More)
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(More)
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(More)
Redox cycling between two electrodes separated by a narrow gap allows dramatic amplification of the faradaic current. Unlike conventional electrochemistry at a single electrode, however, the mass-transport-limited current is controlled by the diffusion coefficient of both the reduced and oxidized forms of the redox-active species being detected and,(More)