Carbon Nanotubes, Graphene, and Carbon Dots as Electrochemical Biosensing Composites

Carbon nanomaterials (CNMs) have been extensively used as electrochemical sensing composites due to their interesting chemical, electronic, and mechanical properties giving rise to increased performance. Due to these materials’ unknown long-term ecological fate, care must be given to make their use tractable. In this review, the design and use of carbon nanotubes (CNTs), graphene, and carbon dots (CDs) as electrochemical sensing electrocatalysts applied to the working electrode surface are surveyed for various biosensing applications. Graphene and CDs are readily biodegradable as compared to CNTs. Design elements for CNTs that carry over to graphene and CDs include Coulombic attraction of components and using O or N atoms that serve as tethering points for attaching electrocatalytically active nanoparticles (NPs) and/or other additives.

Chemical Upcycling of PET Waste towards Terephthalate Redox Nanoparticles for Energy Storage

Over 30 million ton of poly(ethylene terephthalate) (PET) is produced each year and no more than 60% of all PET bottles are reclaimed for recycling due to material property deteriorations during the mechanical recycling process. Herein, a sustainable approach is proposed to produce redox-active nanoparticles via the chemical upcycling of poly(ethylene terephthalate) (PET) waste for application in energy storage. Redox-active nanoparticles of sizes lower than 100 nm were prepared by emulsion polymerization of a methacrylic-terephthalate monomer obtained by a simple methacrylate functionalization of the depolymerization product of PET (i.e., bis-hydroxy(2-ethyl) terephthalate, BHET). The initial cyclic voltammetry results of the depolymerization product of PET used as a model compound show a reversible redox process, when using a 0.1 M tetrabutylammonium hexafluorophosphate/dimethyl sulfoxide electrolyte system, with a standard redox potential of −2.12 V vs. Fc/Fc+. Finally, the cycling performance of terephthalate nanoparticles was investigated using a 0.1 M TBAPF6 solution in acetonitrile as electrolyte in a three-electrode cell. The terephthalate anode electrode displays good cycling stability and performance at high C-rate (i.e., ≥5C), delivering a stable specific discharge capacity of 32.8 mAh.g−1 at a C-rate of 30 C, with a capacity retention of 94% after 100 cycles. However, a large hysteresis between the specific discharge and charge capacities and capacity fading are observed at lower C-rate (i.e., ≤2C), suggesting some irreversibility of redox reactions associated with the terephthalate moiety, in particular related to the oxidation process.

Protein corona formation around biocatalytic nanomotors unveiled by STORM

The interaction of nanoparticles with biological media is a topic of general interest for drug delivery systems and among those for active nanoparticles, also called nanomotors. Herein, we report the use of super resolu-tion microscopy, in particular stochastic optical reconstruction microscopy (STORM), to characterize the formation of protein corona around active enzyme-powered nanomotors. First, we characterize the distribu-tion and number of enzymes on nano-sized particles and characterized their motion capabilities. Then, we incubated the nanomotors with fluorescently labelled serum proteins. Interestingly, we observed a signifi-cant decrease of protein corona formation (20 %) and different composition, which was studied by a proteo-mic analysis. Moreover, motion was not hindered, as nanomotors displayed an enhanced diffusion regardless of protein corona. Elucidating how active particles interact with biological media and maintain their self-propulsion after protein corona formation will pave the way of the use these systems in complex biological fluids in biomedicine.

Electrochemical Characterization of Graphene–LiMn2O4 Composite Cathode Material for Aqueous Rechargeable Lithium Batteries

A series of graphene– LiMn2O4 composite electrodes were prepared by physical mixing of graphene powder and LiMn2O4 cathode material. LiMn2O4was synthesized by reactions under autogenic pressure at elevated temperature method. CV, galvanostatic charge-discharge experiments and EIS studies revealed that the addition of graphene significantly decreases the charge-transfer resistance of LiMn2O4 electrodes. 5 wt. % graphene–LiMn2O4 composite electrode exhibits better electrochemical performance by increasing the reaction reversibility and capacity compared to that of the pristine LiMn2O4 electrode. Improved electrochemical performances are thus achieved, owing to the synergic effect between graphene and the LiMn2O4 active nanoparticles. The ultrathin flexible graphene layers can provide a support for anchoring well-dispersed active cathode particles and work as a highly conductive matrix for enabling good contact between them. At the same time, the anchoring of active nanoparticles on graphene effectively reduces the degree of restacking of graphene sheets and consequently keeps a highly active surface area which increases the lithium storage capacity and cycling performance.

Non-equilibrium properties of an active nanoparticle in a harmonic potential

Active particles break out of thermodynamic equilibrium thanks to their directed motion, which leads to complex and interesting behaviors in the presence of confining potentials. When dealing with active nanoparticles, however, the overwhelming presence of rotational diffusion hinders directed motion, leading to an increase of their effective temperature, but otherwise masking the effects of self-propulsion. Here, we demonstrate an experimental system where an active nanoparticle immersed in a critical solution and held in an optical harmonic potential features far-from-equilibrium behavior beyond an increase of its effective temperature. When increasing the laser power, we observe a cross-over from a Boltzmann distribution to a non-equilibrium state, where the particle performs fast orbital rotations about the beam axis. These findings are rationalized by solving the Fokker-Planck equation for the particle’s position and orientation in terms of a moment expansion. The proposed self-propulsion mechanism results from the particle’s non-sphericity and the lower critical point of the solution.

Near infrared bioimaging and biosensing with semiconductor and rare-earth nanoparticles: recent developments in multifunctional nanomaterials

Research in novel materials has been extremely active over the past few decades, wherein a major area of interest has been optically active nanoparticles. These structures can overcome some of...