Creative approaches to the design of catalytic nanomaterials are necessary in achieving environmentally sustainable energy sources. Integrating dissimilar metals into a single nanoparticle (NP) offers a unique avenue for customizing catalytic activity and maximizing surface area. Alloys containing five or more equimolar components with a disordered, amorphous microstructure, referred to as High-Entropy Metallic Glasses (HEMGs), provide tunable catalytic performance based on the individual properties of incorporated metals. Here, we present a generalized strategy to electrosynthesize HEMG-NPs with up to eight equimolar components by confining multiple metal salt precursors to water nanodroplets emulsified in dichloroethane. Upon collision with an electrode, alloy NPs are electrodeposited into a disordered microstructure, where dissimilar metal atoms are proximally arranged. We also demonstrate precise control over metal stoichiometry by tuning the concentration of metal salt dissolved in the nanodroplet. The application of HEMG-NPs to energy conversion is highlighted with electrocatalytic water splitting on CoFeLaNiPt HEMG-NPs.
A holy grail in analytical chemistry is the specific quantification of a single entity, be that entity an atom, a molecule, a nanoparticle, a virus, or a circulating tumor cell. Analytical chemistry is entering an era where this sensitivity can be achieved. In these experiments, the limit of detection is 1, and the limit of quantitation is not only measured in units of concentration but units of time: the waiting time before positively identifying a single entity. Electrochemistry is front and center in single entity experiments with hundreds of publications per year detailing observations of various entities colliding with micro-and nano-electrodes. These types of experiments are referred to as 'stochastic electrochemistry' due to the stochastic nature of the collision of an entity with an electrode surface. If methods of detection can be made specific, simple, inexpensive, and robust, the techniques hold the promise of transforming diagnostics (i.e., the specific detection of a single cancerous cell in blood). This review will critically analyze the stochastic electrochemistry literature and focus on reports detailing methods to ensure the response at the electrode surface is specific to the colliding entity. The topic of specificity, and strategies to achieve it, are highlighted.
We report an indirect method for the effective replacement of ligands on the surface of Au nanocrystals with different morphologies. The method involves the deposition of an ultrathin layer of Ag to remove a strong capping agent such as cetyltrimethylammonium chloride (CTAC), followed by selective etching of the Ag layer in the presence of citrate ions as a stabilizer. Using multiple characterization techniques, we confirm that the surface of the Au nanocrystals is covered by citrate ions after the indirect ligand exchange process, and there is essentially no aggregation during the entire process. We also demonstrate that this method is effective in suppressing the toxicity of Au nanospheres by completely replacing the initially used CTAC with citrate.
While there are numerous publications on laser-assisted fabrication and characterization of Pt nanoelectrodes, the exact replication of those procedures is not as straightforward as following a single recipe across laboratories....
Precise determination of boundaries in co-culture systems is difficult to achieve with scanning electrochemical microscopy alone. Thus, biological scanning electrochemical microscope platforms generally consist of a scanning electrochemical microscope positioner...
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