Monodispersed Molecular Phthalocyanine with Sulfur-Driven Electron Delocalization for Enhanced Electrochemical Biosensing.

Heterogenizing the molecular catalysts on conductive scaffolds to achieve the isolated molecular dispersion and expected coordination structures is significant yet still challenging. Herein, a sulfur-driving strategy to anchor monodispersed cobalt phthalocyanine on nitrogen and sulfur co-doped graphene (NSG-CoPc) is demonstrated. Experimental and theoretical analysis prove that the incorporation of S dramatically improves the adsorption capability of NSG and evokes the monodispersion of the CoPc molecule, promoting the axial Co─N coordination and the electron delocalization of the Co catalytic center. Benefiting from the reduced activation energy barrier and boosted electron transfer, as well as the maximized active site utilization, NSG-CoPc exhibits outstanding H2O2 oxidization and sensing performance (used as a representative reaction). Moreover, the usage of NSG as a substrate can be readily extended to other metal (Ni, Cu, and Fe) phthalocyanine molecules with molecular-level dispersion. This work clarifies the mechanism of heteroatoms decoration and provides a new paradigm in devising monodispersed molecular catalysts with modulated chemical surroundings for broad applications.

Superhydrophilicity Regulation of Carbon Nanotubes Boosting Electrochemical Biosensing for Real-time Monitoring of H2O2 Released from Living Cells.

Dynamic and accurate monitoring of cell-released electroactive signaling biomolecules through electrochemical techniques has drawn significant research interest for clinical applications. Herein, the functionalized carbon nanotubes (f-CNTs) featuring with gradient surface wettability from hydrophobicity to hydrophilicity, and even to superhydrophilicity, were regulated by thermolysis of an ionic liquid for exploration of the dependence of surface wettability on electrochemical biosensing performance to a cell secretion model of hydrogen peroxide (H2O2). The superhydrophilic f-CNTs demonstrated boosting electrocatalytic reduction activity for H2O2. Additionally, the molecular dynamic (MD) simulations confirmed the more cumulative number density distribution of H2O2 molecules closer to the superhydrophilic surface (0.20 vs 0.37 nm), which would provide a faster diffusional channel compared with the hydrophobic surface. Thereafter, a superhydrophilic biosensing platform with a lower detectable limit reduced by 200 times (0.5 vs 100 µM) and a higher sensitivity over 56 times (0.112 vs 0.002 µA µM cm-2) than that of the hydrophobic one was achieved. Given its excellent cytocompatibility, the superhydrophilic f-CNTs was successfully applied to determine H2O2 released from HeLa cells which were maintained alive after a 30 min real-time monitoring test. The surface hydrophilicity regulation of electrode materials presents a facile approach for real-time monitoring of H2O2 released from living cells and would provide new insights for other electroactive signaling targets at the cellular level.

Controllable assembly of three-dimensional porous graphene-Au dual aerogels and its application for high-efficient bioelectrocatalytic O2 reduction.

Aerogels derived from the colloidal nanoparticles featured with hierarchical interconnected pore-rich networks guarantee their great potentials in various applications. Herein, the controllable assembly of three-dimensional aerogels based on Au nanoparticles (Au NPs) and reduced graphene oxide (rGO) nanosheets as building blocks via a bottom-up approach have been systematically clarified. The difference of building blocks and their assembly sequence were crucially to the final aerogel morphologies and electrochemical properties. Specifically, the highly porous graphene-gold dual aerogels (rGO-Au DAGs) with interconnected rGO nanosheets and Au nanowires showed high conductivity, large surface area and good biocompatibility. Thus, it was employed as an excellent matrix to immobilize enzyme for high-efficient bioelectrocatalysis. Taking bilirubin oxidase as an example, a more positive on-set potential (0.60 V) and a larger catalytic current density (0.77 mA cm-2@0.40 V) than those of other rGO-Au assemblies were achieved for direct bioelectrocatalytic O2 reduction. This study will provide an efficient strategy for unique dual-structural aerogels design and shed light to develop new functional materials for bioelectrocatalytic applications such as biosensors and biofuel cells.