Enzymatic activity of cerium oxide nanoparticles modified by phosphine ligands.

Ligand-functionalized nanoparticles have replaced bare nanoparticles from most biological applications. These applications require tight control over size and stability of nanoparticles in aqueous medium. Understanding the mechanism of interaction of nanoparticle surfaces with functional groups of different organic ligands such as carboxylic acids is confounding despite the two decades of research on nanoparticles because of the inability to characterize their surfaces in their immediate environment. Often the surface interaction is understood by correlating the information available, in a piecemeal approach, from surface sensitive spectroscopic information on ligands and the bulk and surface information on nanoparticles. In present study we report the direct interaction of 5–7 nm cerium oxide nanoparticles surface with acetic acid. An in-situ XPS study was carried out by freezing the aqueous solution of nanoparticles to liquid nitrogen temperatures. Analysis of data collected concurrently from the ligands as well as functionalized frozen cerium oxide nanoparticles show that the acetic acid binds to the ceria surface in both dissociated and molecular state with equal population over the surface. The cerium oxide surface was populated predominantly with Ce4+ ions consistent with the thermal hydrolysis synthesis. DFT calculations reveal that the acetate ions bind more strongly to the cerium oxide nanoparticles as compared to the water molecules and can replace the hydration sphere of nanoparticles resulting in high acetate/acetic surface coverage. These findings reveal molecular level interaction between the nanoparticle surfaces and ligands, giving a better understanding of how materials behave in their immediate solution environment. This study also proposes a simple and elegant methodology to directly study the surface functional groups attached to nanoparticles in their immediate solution environment.

With the threat of increasing SARS‐CoV‐2 cases looming in front of us and no effective and safest vaccine available to curb this pandemic disease due to its sprouting variants, many countries have undergone a lockdown 2.0 or planning a lockdown 3.0. This has upstretched an unprecedented demand to develop rapid, sensitive, and highly selective diagnostic devices that can quickly detect coronavirus (COVID‐19). Traditional techniques like polymerase chain reaction have proven to be time‐inefficient, expensive, labor intensive, and impracticable in remote settings. This shifts the attention to alternative biosensing devices that can be successfully used to sense the COVID‐19 infection and curb the spread of coronavirus cases. Among these, nanomaterial‐based biosensors hold immense potential for rapid coronavirus detection because of their noninvasive and susceptible, as well as selective properties that have the potential to give real‐time results at an economical cost. These diagnostic devices can be used for mass COVID‐19 detection to understand the rapid progression of the infection and give better‐suited therapies. This review provides an overview of existing and potential nanomaterial‐based biosensors that can be used for rapid SARS‐CoV‐2 diagnostics. Novel biosensors employing different detection mechanisms are also highlighted in different sections of this review. Practical tools and techniques required to develop such biosensors to make them reliable and portable have also been discussed in the article. Finally, the review is concluded by presenting the current challenges and future perspectives of nanomaterial‐based biosensors in SARS‐CoV‐2 diagnostics.

Nanoceria has evolved as one of the promising nanomaterials due to its unique enzyme-like properties, including excellent oxidase mimetic activity, which significantly increases in the presence of fluoride ions. However,...

Cerium oxide nanoparticles (CeNPs) depict excellent in vitro and in vivo antioxidant properties, determined by the redox switching of surface cerium ions between its two oxidation states (Ce3+ and Ce4+)....