H. Al-Kutubi, S. Voci, L. Rassaei, N. Sojic and K. Mathwig, Chemical Science, published online. [link]
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.
The Annual Symposium of the Working Group on Electrochemistry of the Royal Netherland Chemical Society will take place in Groningen this November:
Hyphenated Electrochemistry – Combining Electrochemical Methods with Complementary Techniques for Sensing Applications
The capability of electrochemistry is greatly enhanced when used in combination with other methods. The meeting focusses on such hyphenated techniques, which have recently gained more importance in a variety of fields, for example in analytics. Topics include single-molecule detection, electrochemiluminescence, electrochemical transistors, micro- and nanofluidic lab-on-a-chip detection, and diverse
applications such as fuel cells and protein analysis.
Date: Friday 23 November 2018
Location: NH Hotel Groningen, Hanzeplein 132, 9713 GW Groningen
See here for the program, and here for the registration.
P. E. Oomen, Y. Zhang, R. C. Chiechi, E. Verpoorte and K. Mathwig, Lab on a Chip 18 (2018) 2913. [link, pdf]
We suspended a single nanoskived gold nanowire in a microfluidic channel. In this preliminary report, a 200-nm-diameter nanowire was used as an electrode to perform hydrodynamic voltammetry in the center of solution flow. Suspended nanowires exhibit superior current response due to highly efficient mass transport in the area of fastest flow.
Jin Cui, Klaus Mathwig, Dileep Mampallil and Serge G. Lemay, Analytical Chemistry 90 (2018) 7127. [link, pdf]
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.
P. de Haan, M. A. Ianovska, K. Mathwig, H. Bouwmeester and E. Verpoorte, 21st International Conference on Miniaturized Systems for Chemistry and Life Sciences, Savannah, Georgia, USA, Oct. 22-16 (2017) 1593.
Gut-on-a-chip models have gained attention as replacements for other cell-based assays or animal studies in drug development or toxicological studies. These models aim to provide a more accurate representation of the in vivo situation in form and function; however, no digestive processes have been included in these systems so far. This work describes a miniaturized digestive system based on artificial digestive juices that digest liquid samples in a series of three microreactors. After optimization of the pH value of juices and mixtures, samples leading to fluorescent products were digested to demonstrate enzyme functionality and to determine kinetic parameters.
F. Marken and K. Mathwig, Current Opinion in Electrochemistry, 7 (2018) 15. Themed Issue on Physical and Nanoelectrochemistry.
Redox feedback mechanisms can be exploited in electroanalytical detection right to the limit of single molecules being observed. The process relies on anode and cathode being placed extremely close together to minimize diffusion time. In addition to the more complex and expensive nanofabrication tools, there are attempts of “benchtop” microgap and nanogap fabrication to exploit deposition and etch reactions in the assembly. An overview is given summarizing recent methodology development and emerging applications in electroanalysis. One important implication of a very close anode-to-cathode distance is migration of ions in a strong electric field when no electrolyte is used, leading to ion accumulation and a change in signal amplification. Phenomena of this type and geometry/functional implications are considered.