Electrochemical Nanoprobes for Single-Cell Analysis

The measurement of key molecules in individual cells with minimal disruption to the biological milieu is the next frontier in single-cell analyses. Nanoscale devices are ideal analytical tools because of their small size and their potential for high spatial and temporal resolution recordings. Here, we report the fabrication of disk-shaped carbon nanoelectrodes whose radius can be precisely tuned within the range 5–200 nm. The functionalization of the nanoelectrode with platinum allowed the monitoring of oxygen consumption outside and inside a brain slice. Furthermore, we show that nanoelectrodes of this type can be used to impale individual cells to perform electrochemical measurements within the cell with minimal disruption to cell function. These nanoelectrodes can be fabricated combined with scanning ion conductance microscopy probes, which should allow high resolution electrochemical mapping of species on or in living cells

Micro- and nanoelectrochemistry for surface patterning, biosensing and electrocatalysis

Mikro- und Nanoelektroden kommen als elektrochemische Werkzeuge und Sensoren in verschiedenen Anwendungen zum Einsatz. Mikrostrukturierung durch lokale Aktivierung von redox-aktiven Oberflächengruppen wird in einer elektrochemischen Rastertropfenzelle sowie in der elektrochemischen Rastersondenmikroskopie erreicht. Durch gezielte Modifikation mit Preußisch Blau und Platin werden Kohlenstoffnanoelektroden zur chemischen Analyse einzelner Zellen und zur intrazellulären Detektion von reaktiven Sauerstoffspezies, insbesondere H$_{2}O_{2}$, verwendet. Es werden zudem hochsensitive und vielseitige Feldeffekttransistoren auf Basis von dualen Nanoelektroden hergestellt und zur Bestimmung der lokalen $H^{+}$ und ATP Konzentration an Zellen genutzt. Einzelne Nickelhydroxid-Nanopartikel werden elektrochemisch charakterisiert, um den Einfluss der Partikelgröße auf die elektrokatalytische Aktivität der $Ni(OH)_2$ Partikel für die Sauerstoffentwicklung zu ergründe

Size Stability and H₂/CO Selectivity for Au Nanoparticles during Electrocatalytic CO₂ Reduction

In this paper, we show that Au nanoparticles (AuNPs) stabilized with either citrate or by low-generation dendrimers rapidly grow during electrocatalytic reduction of CO₂. For example, citrate-stabilized AuNPs and AuNPs encapsulated within sixth-generation, hydroxyl-terminated, poly­(amidoamine) dendrimers (G6-OH DENs) having diameters of ∼2 nm grow substantially in size (to 6–7 nm) and polydispersity during just 15 min of electrolysis at −0.80 V (vs RHE). This degree of instability makes it impossible to correlate the structure of AuNPs determined prior to electrocatalysis to their catalytic function. In contrast to the G6-OH dendrimer, the higher generation G8-OH analogue stabilizes AuNPs under the same conditions that lead to instability of the other two materials. More specifically, G8-OH DENs having an initial size of 1.7 ± 0.3 nm increase to only 2.2 ± 0.5 nm during electrolysis in 0.10 M NaHCO₃ at −0.80 V (vs RHE). Even when the electrolysis is carried out at −1.20 V, the higher-generation dendrimer stabilizes encapsulated AuNPs. This is presumably due to the compactness of the periphery of the G8-OH dendrimer. Although the G8-OH dendrimer nearly eliminates AuNP growth, the surface of the AuNP is still accessible for electrocatalytic reactions. The smaller, more stable G8-OH DENs strongly favor formation of H₂ over CO. Some previous reports have suggested that AuNPs in the ∼2 nm size range yield primarily CO, but we believe these findings are a consequence of the growth of the AuNPs during catalysis and do not reflect the true function of ∼2 nm AuNPs

Monitoring Cobalt-Oxide Single Particle Electrochemistry with Subdiffraction Accuracy

International audienceBy partially overcoming the diffraction limit, superlocalization techniques have extended the applicability of optical techniques down to the nanometer size-range. Herein, cobalt oxide-based nanoparticles are electrochemically grown onto carbon nanoelectrodes and their individual catalytic properties are evaluated through a combined electrochemical-optical approach. Using dark-field white light illumination, edges superlocalization techniques are applied to quantify changes in particle size during electrochemical activation with down to 20 nm precision. It allows the monitoring of (i) the anodic electrodeposition of cobalt hydroxide material and (ii) the large and reversible volume expansion experienced by the cobalt hydroxide particle during its oxidation. Meanwhile, the particle light scattering provides chemical information such as the Co redox state transformation, which complements both the particle size and the recorded electrochemical current and provides in operando mechanistic information on particle electrocatalytic properties

Monitoring Cobalt-Oxide Single Particle Electrochemistry with Subdiffraction Accuracy

By partially overcoming the diffraction limit, superlocalization techniques have extended the applicability of optical techniques down to the nanometer size-range. Herein, cobalt oxide-based nanoparticles are electrochemically grown onto carbon nanoelectrodes and their individual catalytic properties are evaluated through a combined electrochemical-optical approach. Using dark-field white light illumination, edges superlocalization techniques are applied to quantify changes in particle size during electrochemical activation with down to 20 nm precision. It allows the monitoring of (i) the anodic electrodeposition of cobalt hydroxide material and (ii) the large and reversible volume expansion experienced by the cobalt hydroxide particle during its oxidation. Meanwhile, the particle light scattering provides chemical information such as the Co redox state transformation, which complements both the particle size and the recorded electrochemical current and provides in operando mechanistic information on particle electrocatalytic properties

Doping Level of Boron-Doped Diamond Electrodes Controls the Grafting Density of Functional Groups for DNA Assays

The impact of different doping levels of boron-doped diamond on the surface functionalization was investigated by means of electrochemical reduction of aryldiazonium salts. The grafting efficiency of 4-nitrophenyl groups increased with the boron levels (B/C ratio from 0 to 20 000 ppm). Controlled grafting of nitrophenyldiazonium was used to adjust the amount of immobilized single-stranded DNA strands at the surface and further on the hybridization yield in dependence on the boron doping level. The grafted nitro functions were electrochemically reduced to the amine moieties. Subsequent functionalization with a succinic acid introduced carboxyl groups for subsequent binding of an amino-terminated DNA probe. DNA hybridization significantly depends on the probe density which is in turn dependent on the boron doping level. The proposed approach opens new insights for the design and control of doped diamond surface functionalization for the construction of DNA hybridization assays