Electrolysis Can Be Used to Resolve Hydrogenation Pathways at Palladium Surfaces in a Membrane Reactor.

For common hydrogenation chemistries that occur at high temperatures (where H is adsorbed and activated at the same surface which the substrate must also adsorb for reaction), there is often little consensus on how the reactions (e.g., hydro(deoxy)genation) actually occur.

Facets and vertices regulate hydrogen uptake and release in palladium nanocrystals.

Crystal facets, vertices and edges govern the energy landscape of metal surfaces and thus the chemical interactions on the surface. The facile absorption and desorption of hydrogen at a palladium surface provides a useful platform for defining how metal-solute interactions impact properties relevant to energy storage, catalysis and sensing. Recent advances in in operando and in situ techniques have enabled the phase transitions of single palladium nanocrystals to be temporally and spatially tracked during hydrogen absorption.

Stabilizing Copper for CO Reduction in Low-Grade Electrolyte.

We demonstrate herein a CO reduction electrocatalyst regeneration strategy based on the manipulation of the Cu(0)/Cu equilibrium with high concentrations of ethylenediaminetetraacetic acid (EDTA). This strategy enables the sustained performance of copper catalysts in distilled and tap water electrolytes for over 12 h. The deposition of common electrolyte impurities such as iron, nickel, and zinc is blocked because EDTA can effectively bind the metal ions and negatively shift the electrode potential of M/M .

Electrocatalytic Alloys for CO Reduction.

Electrochemically reducing CO using renewable energy is a contemporary global challenge that will only be met with electrocatalysts capable of efficiently converting CO into fuels and chemicals with high selectivity. Although many different metals and morphologies have been tested for CO electrocatalysis over the last several decades, relatively limited attention has been committed to the study of alloys for this application. Alloying is a promising method to tailor the geometric and electric environments of active sites.

Simultaneous Enhancement of Photoluminescence, MRI Relaxivity, and CT Contrast by Tuning the Interfacial Layer of Lanthanide Heteroepitaxial Nanoparticles.

Nanoparticle (NP) based exogenous contrast agents assist biomedical imaging by enhancing the target visibility against the background. However, it is challenging to design a single type of contrast agents that are simultaneously suitable for various imaging modalities. The simple integration of different components into a single NP contrast agent does not guarantee the optimized properties of each individual components.

Direct Evidence for Coupled Surface and Concentration Quenching Dynamics in Lanthanide-Doped Nanocrystals.

Luminescence quenching at high dopant concentrations generally limits the dopant concentration to less than 1-5 mol% in lanthanide-doped materials, and this remains a major obstacle in designing materials with enhanced efficiency/brightness. In this work, we provide direct evidence that the major quenching process at high dopant concentrations is the energy migration to the surface (i.e.

Compact Micellization: A Strategy for Ultrahigh T1 Magnetic Resonance Contrast with Gadolinium-Based Nanocrystals.

Paramagnetic gadolinium (Gd(3+))-based nanocrystals (NCs) with a large number of confined gadolinium ions can be expected to heavily enhance the longitudinal (T1) relaxation of water protons compared to clinical gadolinium complexes with only a single paramagnetic center. However, paramagnetic Gd(3+)-NCs reported to date show only a modest T1 relaxivity of ∼10 mM(-1) s(-1) per Gd(3+) at 1.5 T, only about 3-times higher than clinical Gd(3+) complexes.

Enhanced UV upconversion emission using plasmonic nanocavities.

Upconversion of near infrared (NIR) into ultraviolet (UV) radiation could lead to a number of applications in bio-imaging, diagnostics and drug delivery. However, for bare nanoparticles, the conversion efficiency is extremely low. In this work, we experimentally demonstrate strongly enhanced upconversion emission from an ensemble of β-NaYF:Gd/Yb/Tm @NaLuF core-shell nanoparticles trapped in judiciously designed plasmonic nanocavities.

Lanthanide-based heteroepitaxial core-shell nanostructures: compressive versus tensile strain asymmetry.

Heteroepitaxial core-shell nanostructures have been proven advantageous in a wide variety of applications, ranging from luminescence enhancement, band gap engineering, multimodal theranostics, to catalysis. However, precisely tailoring the epitaxial growth is challenging, and a general understanding of the parameters that impact epitaxial growth remains unclear. Here we demonstrate the critical role of the sign of the lattice mismatch of the shell relative to the core (compressed/tensile) in generating lanthanide-based core-shell structures, a parameter conventionally not considered in heteroepitaxial design.

Engineering upconversion emission spectra using plasmonic nanocavities.

We show that the upconversion emission spectra of Tm³⁺ and Yb³⁺ codoped β-NaYF₄-NaYF₄ core-shell nanoparticles can be judiciously modified by means of plasmonic nanocavities. Our analysis indicates that more than a 30-fold increase in conversion efficiency to the UV spectral band can be expected by engineering the NIR absorption and the local density of states. The effect of the nanocavity on the resulting radiation patterns is discussed.

Ln(3+)-doped nanoparticles for upconversion and magnetic resonance imaging: some critical notes on recent progress and some aspects to be considered.

In this feature article we will critically discuss the synthesis and characterisation aspects of Ln(3+)-doped nanoparticles (NPs) that show upconversion, upon 980 nm excitation. Upconversion is a non-linear process that converts two or more low-energy photons, often near-infrared photons, into one of higher energy, e.g.

Self-focusing by Ostwald ripening: a strategy for layer-by-layer epitaxial growth on upconverting nanocrystals.

We demonstrate a novel epitaxial layer-by-layer growth on upconverting NaYF(4) nanocrystals (NCs) utilizing Ostwald ripening dynamics tunable both in thickness and composition. Injection of small sacrificial NCs (SNCs) as shell precursors into larger core NCs results in the rapid dissolution of the SNCs and their deposition onto the larger core NCs to yield core-shell structured NCs. Exploiting this NC size dependent dissolution/growth, the shell thickness can be controlled either by manipulating the number of SNCs injected or by successive injection of SNCs.

NaDyF4 Nanoparticles as T2 Contrast Agents for Ultrahigh Field Magnetic Resonance Imaging.

A major limitation of the commonly used clinical MRI contrast agents (CAs) suitable at lower magnetic field strengths (<3.0 T) is their inefficiency at higher fields (>7 T), where next-generation MRI scanners are going. We present dysprosium nanoparticles (β-NaDyF4 NPs) as T2 CAs suitable at ultrahigh fields (9.

An effective polymer cross-linking strategy to obtain stable dispersions of upconverting NaYF4 nanoparticles in buffers and biological growth media for biolabeling applications.

Ligands on the nanoparticle surface provide steric stabilization, resulting in good dispersion stability. However, because of their highly dynamic nature, they can be replaced irreversibly in buffers and biological medium, leading to poor colloidal stability. To overcome this, we report a simple and effective cross-linking methodology to transfer oleate-stabilized upconverting NaYF(4) core/shell nanoparticles (UCNPs) from hydrophobic to aqueous phase, with long-term dispersion stability in buffers and biological medium.

Facile ligand-exchange with polyvinylpyrrolidone and subsequent silica coating of hydrophobic upconverting beta-NaYF(4):Yb(3+)/Er(3+) nanoparticles.

A facile ligand-exchange strategy with a water-soluble polymer, i.e. polyvinylpyrrolidone (PVP), to replace the surface passivating oleate ligands on the beta-NaYF(4) nanoparticle surface is reported.