Large-Area Near-Infrared Emission Enhancement on Single Upconversion Nanoparticles by Metal Nanohole Array.

Single lanthanide (Ln) ion doped upconversion nanoparticles (UCNPs) exhibit great potential for biomolecule sensing and counting. Plasmonic structures can improve the emission efficiency of single UCNPs by modulating the energy transferring process. Yet, achieving robust and large-area single UCNP emission modulation remains a challenge, which obstructs investigation and application of single UCNPs.

Self-assembled monolayer-based blue perovskite LEDs.

Blue perovskite light-emitting diodes (LEDs) have shown external quantum efficiencies (EQEs) of more than 10%; however, devices that emit in the true blue-those that accord with the emission wavelength required for Rec. 2100 primary blue-have so far been limited to EQEs of ~6%. We focused here on true blue emitting CsPbBr colloidal nanocrystals (c-NCs), finding in early studies that they suffer from a high charge injection barrier, a problem exacerbated in films containing multiple layers of nanocrystals.

Phase-Transition-Driven Regional Distribution of Rare-Earth Ions for Multiplexed Upconversion Emissions.

Phase transition of the polymorphs is critical for controlled synthesis and property modulation of functional materials. Upconversion emissions from an efficient hexagonal sodium rare-earth (RE) fluoride compound, β-NaREF, which is generally obtained from the phase transition of the cubic (α-) phase counterpart, are attractive for photonic applications. However, the investigation of the α → β phase transition of NaREF and its effect on the composition and architecture is still preliminary.

Zwitterions Narrow Distribution of Perovskite Quantum Wells for Blue Light-Emitting Diodes with Efficiency Exceeding 15.

While quasi-two-dimensional (quasi-2D) perovskites have emerged as promising semiconductors for light-emitting diodes (LEDs), the broad-width distribution of quantum wells hinders their efficient energy transfer and electroluminescence performance in blue emission. In particular, the underlying mechanism is closely related to the crystallization kinetics and has yet to be understood. Here for the first time, the influence of bifunctional zwitterions with different coordination affinity on the crystallization kinetics of quasi-2D perovskites is systematically investigated.

Migrating photon avalanche in different emitters at the nanoscale enables 46th-order optical nonlinearity.

A photon avalanche (PA) effect that occurs in lanthanide-doped solids gives rise to a giant nonlinear response in the luminescence intensity to the excitation light intensity. As a result, much weaker lasers are needed to evoke such PAs than for other nonlinear optical processes. Photon avalanches are mostly restricted to bulk materials and conventionally rely on sophisticated excitation schemes, specific for each individual system.

All-Inorganic Manganese-Based CsMnCl Nanocrystals for X-Ray Imaging.

Lead-based halide perovskite nanomaterials with excellent optical properties have aroused great attention in the fields of solar cells, light-emitting diodes, lasing, X-ray imaging, etc. However, the toxicity of lead prompts researchers to develop alternatives to cut down the usage of lead. Herein, all-inorganic manganese-based perovskite derivatives, CsMnCl nanocrystals (NCs), with uniform size and morphology have been synthesized successfully via a modified hot-injection method.

Local Structure Engineering in Lanthanide-Doped Nanocrystals for Tunable Upconversion Emissions.

Upconversion emissions from lanthanide-doped nanocrystals have sparked extensive research interests in nanophotonics, biomedicine, photovoltaics, photocatalysis, . Rational modulation of upconversion emissions is highly desirable to meet the requirements of specific applications. Among the diverse developed methods, local structure engineering is fundamentally feasible, through which the upconversion emission intensity, selectivity, wavelength shift, and lifetime can be tuned effectively.

Lanthanide Upconverted Microlasing: Microlasing Spanning Full Visible Spectrum to Near-Infrared under Low Power, CW Pumping.

The miniaturization of lasers holds promise in ultradense data storage and biosensing, but greater pump power is required to reach the lasing thresholds to overcome increased optical losses with reduced resonant cavity sizes. Here, the whispering galley mode (WGM) of Yb /Tm doped upconversion nanoparticles (UCNPs) coupled with microcavities (≈5 µm) is used to achieve ultralow threshold upconverted lasing at 800 nm with excitation fluences as low as 4 W cm . The continuous-wave (CW) upconverted lasing, with a Q factor on the order of 10 , can remain stable for more than 6 h.

Upconversion Fluorescence Resonance Energy Transfer Aptasensors for H5N1 Influenza Virus Detection.

Influenza A virus (IAV) poses a significant threat to human health, which calls for the development of efficient detection methods. The present study constructed a fluorescence resonance energy transfer (FRET) system based on novel fluorescent probes and graphene oxide (GO) for detecting H5N1 IAV hemagglutinin (HA). Here, we synthesized small (sub-20 nm) sandwich-structured upconversion nanoparticles (UCNPs) (SWUCNPs for short) with a high energy transfer efficiency, which allows for controlling the emitter in a thin shell.

Networking State of Ytterbium Ions Probing the Origin of Luminescence Quenching and Activation in Nanocrystals.

At the organic-inorganic interface of nanocrystals, electron-phonon coupling plays an important but intricate role in determining the diverse properties of nanomaterials. Here, it is reported that highly doping of Yb ions within the nanocrystal host can form an energy-migration network. The networking state Yb shows both distinct Stark splitting peak ratios and lifetime dynamics, which allows quantitative investigations of quenching and thermal activation of luminescence, as the high-dimensional spectroscopy signatures can be correlated to the attaching and de-attaching status of surface molecules.

Lanthanide-Doped Upconversion Nanoparticles for Super-Resolution Microscopy.

Super-resolution microscopy offers a non-invasive and real-time tool for probing the subcellular structures and activities on nanometer precision. Exploring adequate luminescent probes is a great concern for acquiring higher-resolution image. Benefiting from the atomic-like transitions among real energy levels, lanthanide-doped upconversion nanoparticles are featured by unique optical properties including excellent photostability, large anti-Stokes shifts, multicolor narrowband emissions, tunable emission lifetimes, etc.

Desilylation Induced by Metal Fluoride Nanocrystals Enables Cleavage Chemistry In Vivo.

Metal fluoride nanocrystals are widely used in biomedical studies owing to their unique physicochemical properties. The release of metal ions and fluorides from nanocrystals is intrinsic due to the solubility equilibrium. It used to be considered as a drawback because it is related to the decomposition and defunction of metal fluoride nanocrystals.

Design, Identification, and Evolution of a Surface Ruthenium(II/III) Single Site for CO Activation.

Ru compounds are widely used in catalysis, photocatalysis, and medical applications. They are usually obtained in a reductive environment as molecular O can oxidize Ru to Ru and Ru . Here we report the design, identification and evolution of an air-stable surface [bipy-Ru (CO) Cl ] site that is covalently mounted onto a polyphenylene framework.

Adsorption and activation of molecular oxygen over atomic copper(I/II) site on ceria.

Supported atomic metal sites have discrete molecular orbitals. Precise control over the energies of these sites is key to achieving novel reaction pathways with superior selectivity. Here, we achieve selective oxygen (O) activation by utilising a framework of cerium (Ce) cations to reduce the energy of 3d orbitals of isolated copper (Cu) sites.

Intrinsically Active Surface in a Pt/γ-MoN Catalyst for the Water-Gas Shift Reaction: Molybdenum Nitride or Molybdenum Oxide?

Apart from active metals, supports also contribute significantly to the catalytic performance of supported metal catalysts. On account of the formed strain and defects, the heterostructured surface of the support may play a crucial role to activate the reactant molecules, while it is usually neglected. In this work, the Pt/γ-MoN catalyst was prepared via a facile solution method.

Experimental and Simulation Insights into Local Structure and Luminescence Evolution in Eu-Doped Nanocrystals under High Pressure.

Tremendous effort has been devoted to tailoring structure-correlated properties, especially for the luminescence of lanthanide nanocrystals (NCs). High pressure has been demonstrated as a decent way to tune the performance of lanthanide NCs; however, little attention has been paid to the local structure evolution accompanied by extreme compression and its effect on luminescence. Here, we tailor the local structure around lanthanide ions with pressure in β-NaGdF NCs, in which Eu ions were doped as optical probes for local structure for the sensitive electric dipole transition.

Engineering of Upconverted Metal-Organic Frameworks for Near-Infrared Light-Triggered Combinational Photodynamic/Chemo-/Immunotherapy against Hypoxic Tumors.

Metal-organic frameworks (MOFs) have shown great potential as nanophotosensitizers (nPSs) for photodynamic therapy (PDT). The use of such MOFs in PDT, however, is limited by the shallow depth of tissue penetration of short-wavelength light and the oxygen-dependent mechanism that renders it inadequate for hypoxic tumors. Here, to combat such limitations, we rationally designed core-shell upconversion nanoparticle@porphyrinic MOFs (UCSs) for combinational therapy against hypoxic tumors.

Direct Identification of Active Surface Species for the Water-Gas Shift Reaction on a Gold-Ceria Catalyst.

The crucial role of the metal-oxide interface in the catalysts of the water-gas shift (WGS) reaction has been recognized, while the precise illustration of the intrinsic reaction at the interfacial site has scarcely been presented. Here, two kinds of gold-ceria catalysts with totally distinct gold species, <2 nm clusters and 3 to 4 nm particles, were synthesized as catalysts for the WGS reaction. We found that the gold cluster catalyst exhibited a superiority in reactivity compared to gold nanoparticles.

A Eu-Eu ion redox shuttle imparts operational durability to Pb-I perovskite solar cells.

The components with soft nature in the metal halide perovskite absorber usually generate lead (Pb) and iodine (I) defects during device fabrication and operation. These defects serve as not only recombination centers to deteriorate device efficiency but also degradation initiators to hamper device lifetimes. We show that the europium ion pair Eu-Eu acts as the "redox shuttle" that selectively oxidized Pb and reduced I defects simultaneously in a cyclical transition.

Pt-Embedded CuO -CeO Multicore-Shell Composites: Interfacial Redox Reaction-Directed Synthesis and Composition-Dependent Performance for CO Oxidation.

Exploring the state-of-the-art heterogeneous catalysts has been a general concern for sustainable and clean energy. Here, Pt-embedded CuO -CeO multicore-shell (Pt/CuO -CeO MS) composites are fabricated at room temperature via a one-pot and template-free procedure for catalyzing CO oxidation, a classical probe reaction, showing a volcano-shaped relationship between the composition and catalytic activity. We experimentally unravel that the Pt/CuO -CeO MS composites are derived from an interfacial autoredox process, where Pt nanoparticles (NPs) are in situ encapsulated by self-assembled ceria nanospheres with CuO clusters adhered through deposition/precipitation-calcination process.

Composition-Graded Cesium Lead Halide Perovskite Nanowires with Tunable Dual-Color Lasing Performance.

Cesium lead halide (CsPbX ) perovskite has emerged as a promising low-threshold multicolor laser material; however, realizing wavelength-tunable lasing output from a single CsPbX nanostructure is still constrained by integrating different composition. Here, the direct synthesis of composition-graded CsPbBr I nanowires (NWs) is reported through vapor-phase epitaxial growth on mica. The graded composition along the NW, with an increased Br/I from the center to the ends, comes from desynchronized deposition of cesium lead halides and temperature-controlled anion-exchange reaction.

Scalable Direct Writing of Lanthanide-Doped KMnF Perovskite Nanowires into Aligned Arrays with Polarized Up-Conversion Emission.

The use of one-dimensional nano- and microstructured semiconductor and lanthanide materials is attractive for polarized-light-emission studies. Up-conversion emission from single-nanorod or anisotropic nanoparticles with a degree of polarization has also been discussed. However, microscale arrays of nanoparticles, especially well-aligned one-dimensional nanostructures as well as their up-conversion polarization characterization, have not been investigated yet.

Selective Cation Exchange Enabled Growth of Lanthanide Core/Shell Nanoparticles with Dissimilar Structure.

Core/shell nanostructure is versatile for improving or integrating diverse functions, yet it is still limited to homeomorphism with isomorphic core and shell structure. Here, we delineate a selective cation exchange strategy to construct lanthanide core/shell nanoparticles with dissimilar structure. Hexagonal NaLnF, a typical photon conversion material, was selected to grow cubic CaF shell to protect surface exposed Ln.

Unravelling the energy transfer of Er-self-sensitized upconversion in Er-Yb-Er clustered core@shell nanoparticles.

Unravelling upconversion (UC) energy transfer mechanisms is significant for designing novel efficient anti-Stokes phosphors. We have studied the correlation of different lanthanide dopants within Er-self-sensitized core@shell upconversion nanoparticles (UCNPs). Here, our focus will be on high-concentration dopants that are able to sufficiently produce the clustering effect, especially within the interplay between Er and Yb.