Electrochemical sensors based on metal nanoparticles with biocatalytic activity

Biosensors have attracted a great deal of attention, as they allow for the translation of the standard laboratory-based methods into small, portable devices. The field of biosensors has been growing, introducing innovations into their design to improve their sensing characteristics and reduce sample volume and user intervention. Enzymes are commonly used for determination purposes providing a high selectivity and sensitivity; however, their poor shelf-life is a limiting factor. Researchers have been studying the possibility of substituting enzymes with other materials with an enzyme-like activity and improved long-term stability and suitability for point-of-care biosensors. Extra attention is paid to metal and metal oxide nanoparticles, which are essential components of numerous enzyme-less catalytic sensors. The bottleneck of utilising metal-containing nanoparticles in sensing devices is achieving high selectivity and sensitivity. This review demonstrates similarities and differences between numerous metal nanoparticle-based sensors described in the literature to pinpoint the crucial factors determining their catalytic performance. Unlike other reviews, sensors are categorised by the type of metal to study their catalytic activity dependency on the environmental conditions. The results are based on studies on nanoparticle properties to narrow the gap between fundamental and applied research. The analysis shows that the catalytic activity of nanozymes is strongly dependent on their intrinsic properties (e.g. composition, size, shape) and external conditions (e.g. pH, type of electrolyte, and its chemical composition). Understanding the mechanisms behind the metal catalytic activity and how it can be improved helps designing a nanozyme-based sensor with the performance matching those of an enzyme-based device.

Preparation of copper phthalocyanine/SiO2 composite particles through simple, green one-pot wet ball milling in the absence of organic dispersants

In order to improve the dispersibility, thermal stability and pH adaptability of organic pigments in water, submicrometer copper phthalocyanine (CuPc)/SiO₂ composite particles (CPs) were prepared through a simple one-pot wet ball-milling process under acidic conditions without using any organic surfactant. In the as-obtained CPs, the surface of the CuPc particles was homogeneously decorated with SiO₂ nanoparticles (NPs) through hydrogen bonding interactions. Due to the surface-attached SiO₂ NPs, the CuPc/SiO₂ CPs present a high aqueous dispersibility and a pH-dependent colloidal stability. Furthermore, both the thermal stability and color intensity of CuPc were increased by encapsulation of CuPc particles within SiO₂ NPs.

Submicrometer copper phthalocyanine (CuPc)/SiO₂ composite particles were prepared through a simple one-pot wet ball-milling process under acidic condition without using any organic surfactant.