Direct Voltammetric Determination of Redox-Active Iron in Carbon Nanotubes

Electrochemical Investigation of Porosity in Core-Shell Magnetoplasmonic Nanoparticles

Porous core-shell nanoparticles (NPs) have emerged as a promising material for broad ranges of applications in catalysts, material chemistry, biology, and optical sensors. Using a typical Ag core-Fe₃O₄ shell NP, a.k.a., magnetoplasmonic (MagPlas) NP, two porous shell models were prepared: i.e., Ag@Fe₃O₄ NPs and its SiO₂-covered NPs (Ag@Fe₃O₄@SiO₂). We suggested using cyclic voltammetry (CV) to provide unprecedented insight into the porosity of the core-shell NPs caused by the applied potential, resulting in the selective redox activities of the core and porous shell components of Ag@Fe₃O₄ NPs and Ag@Fe₃O₄@SiO₂ NPs at different cycles of CV. The porous and nonporous core-shell nanostructures were qualitatively and quantitatively determined by the electrochemical method. The ratio of the oxidation current peak (μA) of Ag to Ag⁺ in the porous shell to that in the SiO₂ coated (nonporous) shell was 400:3.2. The suggested approach and theoretical background could be extended to other types of multicomponent NP complexes.

Metallic impurities in black phosphorus nanoflakes prepared by different synthetic routes

The allotropes of elementary phosphorus materials, such as black phosphorus and its single layer form phosphorene have recently regained scientific attention due to their outstanding properties suitable for applications in electronics, optical devices, and energy applications. As with many other materials, there is a fundamental question of the presence of impurities in these materials and their influence on the properties. Such impurities are expected to dramatically influence the electronic and electrochemical properties of black phosphorus in a way similar to the way they do in the case of graphene. Here, we synthesize black phosphorus from commercially available red phosphorus via different techniques. We utilize high-pressure conversion of red phosphorus to black phosphorus and vapor phase growth of black phosphorus using a gold/tin alloy-like solvent for red phosphorus. We show that both methods lead to black phosphorus containing a large number of metallic impurities. We show that the classical tin-based method for preparing black phosphorus adds a significant amount of tin and that the metallic impurities present have an observable effect on the electrochemical properties of black phosphorus.