Facile electrochemical hydrogenation and chlorination of glassy carbon to produce highly reactive and uniform surfaces for stable anchoring of thiolated molecules

A nickel hydroxide platform prepared on a hydroxyl-enriched screen-printed carbon electrode for oxidative electrocatalysis

We report here the preparation of an activation-free Ni electrode (i.e., eventually the formation of NiOOH) through enrichment of hydroxyl functional groups via a base-catalyzed hydrolysis reaction on a "preanodized" screen printed carbon electrode. The as-prepared Ni electrode exhibits good electroanalytic performance for the flow injection analysis of glucose.

Stable Carboxylate-Terminated Gold Surfaces Produced by Spontaneous Grafting of an Alkyltin Compound

Self-assembled monolayers formed by chemisorption of thiolated molecules on gold surfaces are widely applied for biosensing. Moreover, and due to the low stability of thiol-gold chemistry, contributions to the functionalisation of gold substrates with linkers that provide a more stable platform for the immobilisation of electroactive or biological molecules are highly appreciated. Herein, it is demonstrated that a carboxylated organotin compound can be successfully grafted onto gold substrates to form a highly stable organic layer with reactivity for subsequent binding to an aminated molecule. A battery of techniques were used to characterise the surface chemistry. The grafted layer was used to anchor aminoferrocene and subjected to both thermostability tests and long-term stability studies over a period of one year, demonstrating thermostability up to 90 °C and storage stability for at least 12 months at 4 °C protected from light. The stable surface tethering of molecules on gold substrates can be exploited in a plethora of applications, including molecular techniques, such as solid-phase amplification and solid-phase melting curve analysis, that require elevated temperature stability, as well as biosensors, which require long-term storage stability.

Quantum and electrochemical interplays in hydrogenated graphene

The design of electrochemically gated graphene field-effect transistors for detecting charged species in real time, greatly depends on our ability to understand and maintain a low level of electrochemical current. Here, we exploit the interplay between the electrical in-plane transport and the electrochemical activity of graphene. We found that the addition of one H-sp³ defect per hundred thousand carbon atoms reduces the electron transfer rate of the graphene basal plane by more than five times while preserving its excellent carrier mobility. Remarkably, the quantum capacitance provides insight into the changes of the electronic structure of graphene upon hydrogenation, which predicts well the suppression of the electrochemical activity based on the non-adiabatic theory of electron transfer. Thus, our work unravels the interplay between the quantum transport and electrochemical kinetics of graphene and suggests hydrogenated graphene as a potent material for sensing applications with performances going beyond previously reported graphene transistor-based sensors.

Electrochemically-gated graphene field-effect transistors show promise for sensing of charged species in real time. Here, the authors leverage the interplay between electrical in-plane transport and electrochemical activity to explore the sensing performance of hydrogenated graphene.

Thiol-Ene Modified Amorphous Carbon Substrates: Surface Patterning and Chemically Modified Electrode Preparation

Amorphous carbon (aC) films are chemically stable under ambient conditions or when interfaced with aqueous solutions, making them a promising material for preparing biosensors and chemically modified electrodes. There are a number of wet chemical methods capable of tailoring the reactivity and wettability of aC films, but few of these chemistries are compatible with photopatterning. Here, we introduce a method to install thiol groups directly onto the surface of aC films. These terminal thiols are compatible with thiol-ene click reactions, which allowed us to rapidly functionalize and pattern the surface of the aC films. We thoroughly characterized the aC films and confirmed the installation of surface-bound thiols does not significantly oxidize the surface or change its topography. We also determined the conditions needed to selectively attach alkene-containing molecules to these films and show the reaction is proceeding through a thiol-mediated reaction. Lastly, we demonstrate the utility of our approach by photopatterning the aC films and preparing ferrocene-modified aC electrodes. The chemistry described here provides a rapid means of fabricating sensors and preparing photoaddressable arrays of (bio)molecules on stable carbon interfaces.

Surface functionalisation of carbon for low cost fabrication of highly stable electrochemical DNA sensors

An alternative strategy for surface tethering of DNA probes, where highly reactive glassy carbon (GC) substrates are prepared via electrochemical hydrogenation and electrochemical/chemical chlorination is reported. Thiolated DNA probes and alkanethiols were stably immobilised on the halogenated carbon, with electrochemical chlorination being milder, thus producing less damage to the surface. Electrochemical DNA sensors prepared using this surface chemistry on carbon with electrochemical chlorination providing an improved performance, producing a highly ordered surface and the use of lateral spacers to improve steric accessibility to immobilised probes was not required.

Carbon Substrates: A Stable Foundation for Biomolecular Arrays

Since their advent in the early 1990s, microarray technologies have developed into a powerful and ubiquitous platform for biomolecular analysis. Microarrays consist of three major elements: the substrate upon which they are constructed, the chemistry employed to attach biomolecules, and the biomolecules themselves. Although glass substrates and silane-based attachment chemistries are used for the vast majority of current microarray platforms, these materials suffer from severe limitations in stability, due to hydrolysis of both the substrate material itself and of the silyl ether linkages employed for attachment. These limitations in stability compromise assay performance and render impossible many potential microarray applications. We describe here a suite of alternative carbon-based substrates and associated attachment chemistries for microarray fabrication. The substrates themselves, as well as the carbon-carbon bond-based attachment chemistries, offer greatly increased chemical stability, enabling a myriad of novel applications.

A FeCl₂-graphite sandwich composite with Cl doping in graphite layers: a new anode material for high-performance Li-ion batteries

A composite with FeCl₂ nanocrystals sandwiched between Cl-doped graphite layers has been created via a space-confined nanoreactor strategy. This composite can be used as a new type of anode material for Li-ion batteries, which exhibit high reversible capacity and superior rate capability with excellent cycle life.