Developing syntheses of more sophisticated nanostructures comprising late transition metals broadens the tools to rationally design suitable heterogeneous catalysts for chemical transformations. ...Herein, we report a synthesis of Pd–Rh nanoboxes by controlling the migration of metals in a core–shell nanoparticle. The Pd–Rh nanobox structure is a grid-like arrangement of two distinct metal phases, and the surfaces of these boxes are {100} dominant Pd and Rh. The catalytic behaviors of the particles were examined in electrochemistry to investigate strain effects arising from this structure. It was found that the trends in activity of model fuel cell reactions cannot be explained solely by the surface composition. The lattice strain emerging from the nanoscale separation of metal phases at the surface also plays an important role.
The effect of lattice strain on the catalytic properties of Pd nanoparticles is systematically studied. Synthetic strategies for the preparation of a series of shape‐controlled Pd nanocrystals with ...lattice strain generated from different sources has been developed. All of these nanocrystals were created with the same capping agent under similar reaction conditions. First, a series of Pd nanoparticles was synthesized that were enclosed in {111} surfaces: Single‐crystalline Pd octahedra, single‐crystalline AuPd core–shell octahedra, and twinned Pd icosahedra. Next, various {100}‐terminated particles were synthesized: Single‐crystalline Pd cubes and single‐crystalline AuPd core–shell cubes. Different extents of lattice strain were evident by comparing the X‐ray diffraction patterns of these particles. During electrocatalysis, decreased potentials for CO stripping and increased current densities for formic‐acid oxidation were observed for the strained nanoparticles. In the gas‐phase hydrogenation of ethylene, the activities of the strained nanoparticles were lower than those of the single‐crystalline Pd nanoparticles, perhaps owing to a larger amount of cetyl trimethylammonium bromide on the surface.
Shape up and ship out: Shape‐controlled Pd nanocrystals have been synthesized with lattice strain generated from different sources. During electrocatalysis, decreased potentials for CO stripping and increased current densities for formic‐acid oxidation are observed for the strained nanoparticles. In the gas‐phase hydrogenation of ethylene, the activity of the strained nanoparticles was lower than that of single‐crystalline Pd nanoparticles.
The sensitivity of a photonic crystal optical biosensor is greatly enhanced through the incorporation of low refractive index porous dielectric material into the device structure. In this work, ...computer models are used to predict the reflectance spectra and sensitivity performance of a one-dimensional photonic crystal biosensor. A manufacturable replication method is demonstrated that can produce a low-index dielectric periodic surface structure with a 550
nm period over large surface areas. The sensitivity of porous glass biosensors is characterized and compared with sensors incorporating non-porous polymer material. Results for detection of proteins, polymer layers, and bulk liquids indicate up to a four-fold sensitivity increase.
A label-free method for detecting the attachment of human cancer cells to a biosensor surface for rapid screening for biological activity is described, in which attachment of a cell results in highly ...localized increase of the resonant reflected wavelength of a photonic crystal narrowband reflectance filter incorporated into a standard 96-well microplate. An imaging detection instrument is used to determine the spatial distribution of attached cells by mapping the shift in reflected resonant wavelength as a function of position. The method enables monitoring of cancer cell attachment, cell proliferation, and cell detachment that is induced by exposure of the cells to drug compounds. We demonstrate the efficacy of this method as an early screening technique for the rapid quantification of the rate of cancer cell proliferation on the sensor surface, and subsequently as a means for quantifying cell detachment resulting from apoptosis that is induced by exposure of the cells to cytotoxic chemicals.
Protein−DNA interactions are essential for fundamental cellular processes such as transcription, DNA damage repair, and apoptosis. As such, small molecule disruptors of these interactions could be ...powerful tools for investigation of these biological processes, and such compounds would have great potential as therapeutics. Unfortunately, there are few methods available for the rapid identification of compounds that disrupt protein−DNA interactions. Here we show that photonic crystal (PC) technology can be utilized to detect protein−DNA interactions, and can be used in a high-throughput screening mode to identify compounds that prevent protein−DNA binding. The PC technology is used to detect binding between protein−DNA interactions that are DNA-sequence-dependent (the bacterial toxin−antitoxin system MazEF) and those that are DNA-sequence-independent (the human apoptosis inducing factor (AIF)). The PC technology was further utilized in a screen for inhibitors of the AIF−DNA interaction, and through this screen aurin tricarboxylic acid was identified as the first in vitro inhibitor of AIF. The generality and simplicity of the photonic crystal method should enable this technology to find broad utility for identification of compounds that inhibit protein−DNA binding.
Professor Chia-Kuang (Frank) Tsung made his scientific impact primarily through the atomic-level design of nanoscale materials for application in heterogeneous catalysis. He approached this challenge ...from two directions: above and below the material surface. Below the surface, Prof. Tsung synthesized finely controlled nanoparticles, primarily of noble metals and metal oxides, tailoring their composition and surface structure for efficient catalysis. Above the surface, he was among the first to leverage the tunability and stability of metal–organic frameworks (MOFs) to improve heterogeneous, molecular, and biocatalysts. This article, written by his former students, seeks first to commemorate Prof. Tsung’s scientific accomplishments in three parts: (1) rationally designing nanocrystal surfaces to promote catalytic activity; (2) encapsulating nanocrystals in MOFs to improve catalyst selectivity; and (3) tuning the host–guest interaction between MOFs and guest molecules to inhibit catalyst degradation. The subsequent discussion focuses on building on the foundation laid by Prof. Tsung and on his considerable influence on his former group members and collaborators, both inside and outside of the lab.
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