In recent decades, the attention of scientists has been drawn towards nanoparticles (NPs) of metals and metalloids. Traditional methods for the manufacturing of NPs are now being extensively studied. However, disadvantages such as the use of toxic agents and high energy consumption associated with chemical and physical processes impede their continued use in various fields. In this article, we analyse the relevance of the use of living systems and their components for the development of "green" synthesis of nano-objects with exceptional properties and a wide range of applications. The use of nano-biotechnological methods for the synthesis of nanoparticles has the potential of large-scale application and high commercial potential. Bacteria are an extremely convenient target for green nanoparticle synthesis due to their variety and ability to adapt to different environmental conditions. Synthesis of nanoparticles by microorganisms can occur both intracellularly and extracellularly. It is known that individual bacteria are able to bind and concentrate dissolved metal ions and metalloids, thereby detoxifying their environment. There are various bacteria cellular components such as enzymes, proteins, peptides, pigments, which are involved in the formation of nanoparticles. Bio-intensive manufacturing of NPs is environmentally friendly and inexpensive and requires low energy consumption. Some biosynthetic NPs are used as heterogeneous catalysts for environmental restoration, exhibiting higher catalytic efficiency due to their stability and increased biocompatibility. Bacteria used as nanofactories can provide a new approach to the removal of metal or metalloid ions and the production of materials with unique properties. Although a wide range of NPs have been biosynthetic and their synthetic mechanisms have been proposed, some of these mechanisms are not known in detail. This review focuses on the synthesis and catalytic applications of NPs obtained using bacteria. Known mechanisms of bioreduction and prospects for the development of NPs for catalytic applications are discussed.
Nanoceria (CeO2–x
) is a unique
antioxidant material with the ability to self-regenerate its properties
after interaction with oxidants. In our paper, the dynamics of nanoceria–oxidant
interaction accompanied by reversible Ce3+ ↔ Ce4+ transitions of cerium ions was studied for nanoceria water
colloidal solutions using conventional spectroscopic techniques. We
have shown that interaction of nanoceria with hydrogen peroxide leads
to Ce3+ → Ce4+ oxidation, accompanied
by quenching of Ce3+ luminescence of nanoceria, and the
recovery of initial Ce3+ luminescence intensity occurs
with a sufficient time delay (up to few days). The role of oxygen
transport within ceria nanoparticles in the regeneration of antioxidant
properties of nanoceria after interaction with an oxidant is discussed.
Involvement of oxygen diffusion into recovery of nanoceria antioxidant
properties hampers the redox activity of ceria nanoparticles making
it size- and temperature-dependent.
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