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Nano Lett ; 22(9): 3591-3597, 2022 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-35439017


Despite the successful control of crystal phase using template-directed growth, much remains unknown about the underlying mechanisms. Here, we demonstrate that the crystal phase taken by the deposited metal depends on the lateral size of face-centered cubic (fcc)-Pd nanoplate templates with 12 nm plates giving fcc-Ru while 18-26 nm plates result in hexagonal closed-packed (hcp)-Ru. Although Ru overlayers with a metastable fcc- (high in bulk energy) or stable hcp-phase (low in bulk energy) can be epitaxially deposited on the basal planes, the lattice mismatch will lead to jagged hcp- (high in surface energy) and smooth fcc-facets (low in surface energy), respectively, on the side faces. As the proportion of basal and side faces on the nanoplates varies with lateral size, the crystal phase will change depending on the relative contributions from the surface and bulk energies. The Pd@fcc-Ru outperforms the Pd@hcp-Ru nanoplates toward ethylene glycol and glycerol oxidation reactions.

Nanopartículas , Oxirredução , Fenômenos Físicos
Nanoscale ; 12(42): 21923-21931, 2020 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-33112348


The structure and phase transformation of a cobalt (Co) catalyst, during single walled carbon nanotube (SWCNT) growth, is elucidated for inactive, active and deactivated nanoparticles by in situ imaging using an environmental transmission electron microscope. During nanotube growth, the structure was analyzed using Miller indices to determine the types of planes that favor anchoring or liftoff of nanotubes from the Co catalyst. Density functional theory was further applied to model the catalyst interactions to compare the work of adhesion of the catalyst's faceted planes to understand the interactions of different Miller planes with the graphene structure. Through in-depth studies of multiple distinct Co nanoparticles, we established a dominant nanoparticle phase for SWCNT growth. In addition, we identified the preferred lattice planes and a threshold for work of adhesion to allow the anchoring and liftoff of SWCNTs.

Adv Healthc Mater ; 3(1): 59-68, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23868871


Stable pH is an established biomarker of health, relevant to all tissues of the body, including the heart. Clinical monitoring of pH in a practical manner, with high spatiotemporal resolution, is particularly difficult in organs such as the heart due to its soft mechanics, curvilinear geometry, heterogeneous surfaces, and continuous, complex rhythmic motion. The results presented here illustrate that advanced strategies in materials assembly and electrochemical growth can yield interconnected arrays of miniaturized IrOx pH sensors encapsulated in thin, low-modulus elastomers to yield conformal monitoring systems capable of noninvasive measurements on the surface of the beating heart. A thirty channel custom data acquisition system enables spatiotemporal pH mapping with a single potentiostat. In vitro testing reveals super-Nernstian sensitivity with excellent uniformity (69.9 ± 2.2 mV/pH), linear response to temperature (-1.6 mV °C(-1) ), and minimal influence of extracellular ions (<3.5 mV). Device examples include sensor arrays on balloon catheters and on skin-like stretchable membranes. Real-time measurement of pH on the surfaces of explanted rabbit hearts and a donated human heart during protocols of ischemia-reperfusion illustrate some of the capabilities. Envisioned applications range from devices for biological research, to surgical tools and long-term implants.

Eletrônica , Miocárdio/metabolismo , Animais , Cateterismo Cardíaco , Desenho de Equipamento , Humanos , Concentração de Íons de Hidrogênio , Íons/química , Íons/metabolismo , Isquemia/metabolismo , Isquemia/patologia , Microeletrodos , Miocárdio/química , Próteses e Implantes , Coelhos , Reperfusão , Temperatura