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Luminescent solar concentrators (LSCs) have recently emerged as valuable candidates for the realization of aesthetically pleasing solar windows for near-zero-energy consumption buildings. The growing demand by the building-integrated photovoltaic sector is urging the development of sustainable production methods that minimize the use of polluting organic solvents and hazardous materials, while still enabling industrial-grade LSCs. Here, we introduce a new class of benzothieno-benzothiophene (BTBT) derivatives as highly efficient reabsorption-free emitters for transparent LSCs featuring high stability and a solvent-free chemical access with sustainability factor as low as 21, 10 to 50 times lower than conventional LSC emitters. By embedding our BTBT emitters in optical-grade polymeric waveguides, we produced large-area (40 cm × 40 cm) LSCs with optical power efficiency as high as 3% (corresponding to an optical quantum efficiency of 54%). These results represent an important advancement toward sustainable solar glazing systems for green architecture.The growing demand for building-integrated photovoltaic technologies for near-zero-energy buildings is motivating the scientific community to develop devices that meet the functional, energetic, and aesthetic needs for sustainable architecture. Luminescent solar concentrators (LSCs) are emerging as valuable solutions to realize aesthetically pleasing semitransparent photovoltaic windows capable of converting urban buildings into energy generators. In this work, we report on efficient, transparent LSCs based on a novel class of reabsorption-free derivatives synthesized through a solvent-free route that massively improves the sustainability factor with respect to the state of the art. Optical-grade polymeric LSCs are produced via industrial methods with an optical power efficiency as high as 3% despite their transparency in the visible region. These results represent an important step forward for sustainable solar glazing systems for environmentally friendly architecture. Efficient and aesthetically pleasing solar technologies, such as LSC photovoltaic windows, are becoming essential for the widespread of zero-energy buildings. The more the LSC technology gains appeal, the higher the need becomes for efficient and sustainable materials and production routes. Through a new mechanochemical route, we produce efficient, reabsorption-free LSC emitters with a massively increased sustainability factor. The integration of such derivatives into industrial-grade LSCs leads to an optical efficiency of 3% for large-area devices.

Abstract The Chinese Panorpa species without anal horn are normally assigned to the Panorpa davidi group. Here, we taxonomically revise the P. davidi group, which currently includes 17 known species and four new species: P. gaokaii sp. nov., P. huayuani sp. nov., P. uncinata sp. nov. and P. yaoluopingensis sp. nov. Panorpa shanyangensis Chou & Wang, 1981 and P. sexspinosa zhongnanensis Chou & Ran, 1981 are treated as junior synonyms of P. sexspinosa Cheng, 1949. We describe for the first time the male of P. stigmosa Zhou, 2006, and the females of P. curva Carpenter, 1938, P. davidi Navás, 1908, P. difficilis Carpenter, 1938, P. fructa Cheng, 1949, and P. jinchuana Hua, Sun & Li, 2001. A key to species of the group is provided. Phylogenetic analyses of maximum parsimony and maximum likelihood based on 79 morphological characters show that the newly defined P. davidi group is a well-supported monophyletic group and is sister to the genus Cerapanorpa Gao, Ma & Hua, 2016.

We report on design and fabrication of Ni 2+ -doped glass-ceramics from a low-alkali optical glass in Li 2 O-Na 2 O-Ga 2 O 3 -SiO 2 -GeO 2 system by melting technique and subsequent thermally controlled nano-crystallization. The analysis of differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, absorption and fluorescence spectroscopy reveals, for the first time, the real possibility of optimizing the integrated intensity of Ni 2+ near-infrared emission through controlled pre-treatments at temperatures of nanophase nucleation, with the enhancement up to a factor of four with respect to gallium germanosilicate glass-ceramics obtained without pre-treatments. Importantly, the effects on the light emission are shown to be related to the influence of pre-treatment on size and size distribution of the gallium oxide nanocrystals which result from subsequent crystallization at higher temperature.

As a model radio-photodynamic therapy (RPDT) agent, we developed a multicomponent nanomaterial by anchoring conjugated chromophores on the surface of scintillating chrysotile nanotubes. Its ultimate composition makes the system a scintillation-activated photosensitizer for the singlet oxygen production. This nanomaterial shows a remarkable ability to enhance the production of singlet oxygen in an aqueous environment, under X-ray irradiation, boosting its production by almost 1 order of magnitude. Its efficiency as a coadjutant for radiotherapy has been tested in vitro, showing a striking efficacy in enhancing both the prompt cytotoxicity of the ionizing radiation and the long-term cytotoxicity given by radiation-activated apoptosis. Notably, the beneficial activity of the RPDT agent is prominent at low levels of delivered doses comparable to the one employed in clinical treatments. This opens the possibility of effectively reducing the therapy exposure and consequently undesired collateral effects due to prolonged exposure of patients to high-energy radiation.

Scintillators, materials that produce light pulses upon interaction with ionizing radiation, are widely employed in radiation detectors. In advanced medical-imaging technologies, fast scintillators enabling a time resolution of tens of picoseconds are required to achieve high-resolution imaging at the millimetre length scale. Here we demonstrate that composite materials based on fluorescent metal–organic framework (MOF) nanocrystals can work as fast scintillators. We present a prototype scintillator fabricated by embedding MOF nanocrystals in a polymer. The MOF comprises zirconium oxo-hydroxy clusters, high-Z linking nodes interacting with the ionizing radiation, arranged in an orderly fashion at a nanometric distance from 9,10-diphenylanthracene ligand emitters. Their incorporation in the framework enables fast sensitization of the ligand fluorescence, thus avoiding issues typically arising from the intimate mixing of complementary elements. This proof-of-concept prototype device shows an ultrafast scintillation rise time of ~50 ps, thus supporting the development of new scintillators based on engineered fluorescent MOF nanocrystals. Composites of fluorescent metal–organic framework nanocrystals in a polymer are exploited to create fast scintillators with a rise time of about 50 ps.

Photon upconversion assisted by sensitized triplet–triplet annihilation (sTTA-UC) is a wavelength-shifting technique where high-energy photons are emitted from the radiative recombination of high-energy singlets populated through the annihilation of the metastable triplets of two annihilator/emitter molecules. The emitter triplets are previously populated via energy transfer from a light-harvester/sensitizer moiety that absorbs the incident low-energy photons. In solutions, this process is efficient even at low excitation powers, whereas the limited molecular mobility and short exciton lifetimes typically observed in solid matrices hinder the bi-molecular interactions making the sTTA-UC process rather ineffective. We show here that controlling the confinement of the upconverting dye pairs in nanostructured or nanosized materials results in an increased effective local density of the excitation energy. This also activates a specific sTTA-UC kinetics independent of the triplet excitons’ mobility that improves the material performance at low powers. We provide a complete modeling of the sTTA-UC process in confined systems. The results obtained afford useful guidelines for the future development of upconverting photonic devices operating at subsolar irradiances suitable for technological implementation.

We introduce and study a family of spaces of entire functions in one variable that generalise the classical Paley–Wiener and Bernstein spaces. Namely, we consider entire functions of exponential type a whose restriction to the real line belongs to the homogeneous Sobolev space $$\dot{W}^{s,p}$$ W ˙ s , p and we call these spaces fractional Paley–Wiener if $$p=2$$ p = 2 and fractional Bernstein spaces if $$p\in (1,\infty )$$ p ∈ ( 1 , ∞ ) , that we denote by $$PW^s_a$$ P W a s and $${\mathcal {B}}^{s,p}_a$$ B a s , p , respectively. For these spaces we provide a Paley–Wiener type characterization, we remark some facts about the sampling problem in the Hilbert setting and prove generalizations of the classical Bernstein and Plancherel–Pólya inequalities. We conclude by discussing a number of open questions.

Photon upconversion based on sensitized triplet–triplet annihilation (sTTA-UC) is a wavelength-shifting technique with potential use in actuators, sensing, and solar technologies. In sTTA-UC, the upconverted photons are the result of radiative recombination of high-energy singlets, which are created through the fusion of metastable triplets of two annihilator/emitter molecules. The emitter triplets are populated via energy transfer (ET) from a low-energy absorbing light-harvester/sensitizer. The process is highly efficient at low powers in solution but becomes relatively ineffective in solid matrices since the limited molecular mobility precludes bimolecular interactions. The realization of efficient solid-state upconverters that exhibit long-term stability and are compatible with industrial fabrication processes is an open challenge. Here, nanophase-separated polymer systems synthesized under ambient conditions that contain the upconverting dyes in liquid nanodomains is reported. The nanostructured polymers show an excellent optical quality, an outstanding upconversion efficiency of up to ≈23%, and excellent stability in air, with only negligible performance losses over a period of three months. Moreover, the dyes’ confinement in nanosized domains

Low-power photon upconversion (UC) based on sensitized triplet-triplet annihilation (sTTA) is considered as the most promising upward wavelength-shifting technique to enhance the light-harvesting capability of solar devices. Colloidal nanocrystals (NCs) with conjugated organic ligands have been recently proposed to extend the limited light-harvesting capability of molecular absorbers. Key to their functioning is efficient energy transfer (ET) from the NC to the triplet state of the ligands that sensitize free annihilator moieties responsible for the upconverted luminescence. The ET efficiency is typically limited by parasitic processes, above all nonradiative hole-transfer to the ligand highest occupied molecular orbital (HOMO). Here, a new exciton-manipulation approach is demonstrated that enables loss-free ET by electronically doping CdSe NCs with gold impurities that introduce a hole-accepting intragap state above the HOMO energy of 9-anthracene acid ligands. Upon photoexcitation, the NC photoholes are rapidly routed to the Au-level, producing a long-lived bound exciton in perfect resonance with the ligand triplet. This hinders hole-transfer leading to ≈100% efficient ET that translates into an upconversion quantum yield as high as ≈12% (≈24% in the normalized definition), which is the highest performance for NC-based upconverters based on sTTA to date and approaches the record efficiency of optimized organic systems.

Metal clusters with appropriate molecular ligands have been shown to be suitable subnanometer building blocks for supramolecular architectures with controlled secondary interactions, providing access to physical regimes not achievable with conventional intermolecular motifs. An example is the excimer photophysics exhibited by individual cluster-based superstructures produced by top-down etching of gold nanoparticles. Now, a supramolecular architecture of copper clusters is presented with controlled optical properties and efficient non-resonant luminescence produced via a novel bottom-up synthesis using mild green reductants followed by a ligand exchange reaction and spontaneous supramolecular assembly. Spectroscopic experiments confirm the formation of the intercluster network and reveal the permanent nature of their excimer-like behavior, thus extending the potential impact and applicability of metal cluster superstructures as efficient and stable non-resonant single-particle emitters.

In triplet-triplet annihilation based upconversion, high-energy photons are generated through the annihilation of fluorophore triplets, populated via energy transfer from a light-harvesting sensitizer. However, the absorption band of common sensitizers is narrow, limiting the fraction of recoverable photons. We overcome this issue using a third chromophore as an additional light-harvester in the transparency window between the upconverted luminescence and the sensitizer absorption. The third component transfers the extra-collected energy to sensitizers, realizing a cascade-sensitized upconversion that shows a 20% increment of the high-energy photon output and a conversion yield of 10% at solar irradiance.

Luminescent nanoparticles are researched for their potential impact in medical science, but no materials approved for parenteral use have been available so far. To overcome this issue, we demonstrate that Eu3+-doped hafnium dioxide nanocrystals can be used as non-toxic, highly stable probes for cellular optical imaging and as radiosensitive materials for clinical treatment. Furthermore, viability and biocompatibility tests on artificially stressed cell cultures reveal their ability to buffer reactive oxygen species, proposing an anti-cytotoxic feature interesting for biomedical applications.

In this paper we study spaces of holomorphic functions on the Siegel upper half-space $${\mathcal U}$$ and prove Paley–Wiener type theorems for such spaces. The boundary of $${\mathcal U}$$ can be identified with the Heisenberg group $${\mathbb H}_n$$ . Using the group Fourier transform on $${\mathbb H}_n$$ , Ogden and Vagi (Adv Math 33(1):31–92, 1979) proved a Paley–Wiener theorem for the Hardy space $$H^2({\mathcal U})$$ . We consider a scale of Hilbert spaces on $${\mathcal U}$$ that includes the Hardy space, the weighted Bergman spaces, the weighted Dirichlet spaces, and in particular the Drury–Arveson space, and the Dirichlet space $${\mathcal D}$$ . For each of these spaces, we prove a Paley–Wiener theorem, some structure theorems, and provide some applications. In particular we prove that the norm of the Dirichlet space modulo constants $$\dot{{\mathcal D}}$$ is the unique Hilbert space norm that is invariant under the action of the group of automorphisms of $${\mathcal U}$$ .

Metal-organic frameworks (MOFs) are porous hybrid materials built up from organic ligands coordinated to metal ions or clusters by means of self-assembly strategies. The peculiarity of these materials is the possibility, according to specific synthetic routes, to manipulate both the composition and ligands arrangement in order to control their optical and energy-transport properties. Therefore, optimized MOFs nanocrystals (nano-MOFs) can potentially represent the next generation of luminescent materials with features similar to those of their inorganic predecessors, that is, the colloidal semiconductor quantum dots. The luminescence of fluorescent nano-MOFs is generated through the radiative recombination of ligand molecular excitons. The uniqueness of these nanocrystals is the possibility to pack the ligand chromophores close enough to allow a fast exciton diffusion but sufficiently far from each other preventing the aggregation-induced effects of the organic crystals. In particular, the formation of strongly coupled dimers or excimers is avoided, thus preserving the optical features of the isolated molecule. However, nano-MOFs have a very small fluorescence quantum yield (QY). In order to overcome this limitation and achieve highly emitting systems, we analyzed the fluorescence process in blue emitting nano-MOFs and modeled the diffusion and quenching mechanism of photogenerated singlet excitons. Our results demonstrate that the excitons quenching in nano-MOFs is mainly due to the presence of surface-located, nonradiative recombination centers. In analogy with their inorganic counterparts, we found that the passivation of the nano-MOF surfaces is a straightforward method to enhance the emission efficiency. By embedding the nanocrystals in an inert polymeric host, we observed a +200% increment of the fluorescence QY, thus recovering the emission properties of the isolated ligand in solution.

Upconversion is a photon-management process especially suited to water-splitting cells that exploit wide-bandgap photocatalysts. Currently, such catalysts cannot utilize 95% of the available solar photons. We demonstrate here that the energy-conversion yield for a standard photocatalytic water-splitting device can be enhanced under solar irradiance by using a low-power upconversion system that recovers part of the unutilized incident sub-bandgap photons. The upconverter is based on a sensitized triplet-triplet annihilation mechanism (sTTA-UC) obtained in a dye-doped elastomer and boosted by a fluorescent nanocrystal/polymer composite that allows for broadband light harvesting. The complementary and tailored optical properties of these materials enable efficient upconversion at subsolar irradiance, allowing the realization of the first prototype water-splitting cell assisted by solid-state upconversion. In our proof-of concept device the increase of the performance is 3.5%, which grows to 6.3% if concentrated sunlight (10 sun) is used. Our experiments show how the sTTA-UC materials can be successfully implemented in technologically relevant devices while matching the strict requirements of clean-energy production.

The effective incorporation of photovoltaic (PV) elements into the urban environment, specifically in buildings, is a challenging process. Apart from the aesthetic limitations of having black and opaque PV cells when installed in building facades, they are not optimally positioned for high-efficiency electric energy generation because of shadowing effects due to neighboring trees and buildings. Emphasis is given to luminescent solar concentrators (LSCs) that have emerged as an appealing solution for concentrating a large area of sunlight into a small beam of high field intensity. The coupling of PV cells to the edges of LSCs also presents an exciting strategy to PV urban integration. Here, we outline the mechanistic framework for LSCs, review the current experimental state of the art involving optically active centers in various geometrical device configurations, and discuss the performance quantification of LSCs currently in development. For the sake of completeness, a brief discussion of the other spectral converters suitable for PV applications is also reported.

We study the fractional Laplacian and the homogeneous Sobolev spaces on R^d , by considering two definitions that are both considered classical. We compare these different definitions, and show how they are related by providing an explicit correspondence between these two spaces, and show that they admit the same representation. Along the way we also prove some properties of the fractional Laplacian., 17 pages - some new references and comments have been added

Sensitized triplet–triplet annihilation based photon up-conversion (TTA-UC) greatly improves the scope and applicability of fluorescence bioimaging by enabling anti-Stokes detection at low powers, thus eliminating the background autofluorescence and limiting the potential damage of the living tissues. Here the authors present a facile, one-step protocol to prepare dual dye-doped, TTA-UC active nanomicelles starting from the commercially available surfactant Kolliphor EL, a component of several FDA approved preparations. These nanosized micelles show an unprecedented up-conversion yield of 6.5% under 0.1 W cm−2 excitation intensity in an aqueous, nondeaerated dispersion. The supramolecular architecture obtained preserves the embedded dyes from oxygen quenching, allowing satisfactory anti-Stokes fluorescence imaging of 3T3 cells. This is the first example of efficient multicomponent up-converters prepared using highly biocompatible materials approved by the international authority, paving the way for the development of new complex and multifunctional materials for advanced theranostics.

Photon upconversion based on sensitized triplet-triplet annihilation in bi-component systems is a multistep process that involves a triplet-triplet energy transfer (ET) from a donor to an acceptor moiety. This is aimed at sensitizing the population of annihilating optically dark triplets that generates the high energy photoluminescence. A large resonance between the involved triplets is usually recommended because it increases the energy gain between absorbed and emitted upconverted photons. However, it also enables efficient back-ET from acceptor to donor triplets, with potential detrimental consequences on the system performance. Here, we analyze a model system, where the energy difference between donor and acceptor triplets is lower than kBT at room temperature by means of time resolved and steady state photoluminescence spectroscopy, and develop a kinetic model, which describes the iterative loop that transfers the triplet exciton between the donor and acceptor molecules. In such a way, we obtained the guidelines for the optimization of the system composition required to overcome the back-ET effect and maximize the upconversion quantum yield.

The conversion of low-energy light into photons of higher energy based on sensitized triplet-triplet annihilation (sTTA) upconversion is emerging as the most promising wavelength-shifting methodology because it operates efficiently at excitation powers as low as the solar irradiance. However, the production of solid-state upconverters suited for direct integration in devices is still an ongoing challenge owing to the difficulties concerning the organization of two complementary moieties, the triplet sensitizer, and the annihilator, which must interact efficiently. This problem is solved by fabricating porous fluorescent nanoparticles wherein the emitters are integrated into robust covalent architectures. These emitting porous aromatic framework (ePAF) nanoparticles allow intimate interaction with the included metallo-porphyrin as triplet sensitizers. Remarkably, the high concentration of framed chromophores ensures hopping-mediated triplet diffusion required for TTA, yet the low density of the framework promotes their high optical features without quenching effects, typical of the solid state. A green-to-blue photon upconversion yield as high as 15% is achieved: a record performance among annihilators in a condensed phase. Furthermore, the engineered ePAF architecture containing covalently linked sensitizers produces full-fledge solid-state bicomponent particles that behave as autonomous nanodevices.

The sensitized triplet-triplet annihilation-based upconversion in bicomponent systems is currently considered the most promising strategy for increasing the light-harvesting ability of solar cells. Flexible, manageable, inexpensive up-converting devices become possible by implementing this process in elastomers. Here, we report a study combining optical spectroscopy data of the light conversion process with the nano- and macroscopic viscoelastic characterization of the host material embedding the active dyes, in order to find a rationale for the fabrication of efficient solid-state upconverting systems. By using the poly(n-alkyl acrylates) as a model of the monophasic elastomers, we demonstrate that the yield of the bimolecular interactions at the base of the upconversion process, namely, energy transfer and triplet-triplet annihilation, is mainly determined by the glass transition temperature (Tg) of the polymer. By employing the polyoctyl acrylate (Tg = 211 K), we achieved a conversion yield at the solid state larger than 10% at an irradiance of 1 sun, showing the potential of the elastomer-based upconverting materials for developing real-world devices.

In this paper we characterize the closed invariant subspaces for the ($*$-)multiplier operator of the quaternionic space of slice $L^2$ functions. As a consequence, we obtain the inner-outer factorization theorem for the quaternionic Hardy space on the unit ball and we provide a characterization of quaternionic outer functions in terms of cyclicity., Comment: 19 pages. Typos fixed and minor changes

The surface of some minerals when in contact with aqueous environments is observed to develop a layer of electric charges which allows for the formation of stable adducts with foreign chemical species of opposite charge. Due to the increment of the surface-to-volume ratio, this effect is enhanced when the mineral is in the form of nanoparticle. Here, we show the peculiar characteristics of synthetic layered chrysotile mineral nanotubes, which have been used to ionically anchor fluorescent organic dyes and properly modified magnetic nanoparticles, conferring useful functionalities to the so-obtained adduct. Indeed, such composite nanomaterial displays optical and chemical sensitiveness to pH changes in the acidic range and allows for contrast enhancement in magnetic resonance imaging. In combination with a high overall biocompatibility, such functionalized nanotubes are becoming promising platforms for the development of low-impact multimodal diagnostic and therapeutic tools.

Fluoromagnetic systems are recognized as an emerging class of materials with great potential in the biomedical field. Here, it is shown how to fabricate fluoromagnetic nanotubes that can serve as multimodal probes for the imaging and targeting of brain cancer. An ionic self-assembly strategy is used to functionalize the surface of synthetic chrysotile nanotubes with pH-sensitive fluorescent chromophores and ferromagnetic nanoparticles. The acquired magnetic properties permit their use as contrast agent for magnetic resonance imaging, and enable the tracking of tumor cell migration and infiltration responsible for metastatic growth and disease recurrence. Their organic component, changing its fluorescence attitude as a function of local pH, targets the cancer distinctive acidity, and allows localizing and monitoring the tumor occurrence and progression by mapping the acidic spatial distribution within biopsy tissues. The fluoromagnetic properties of nanotubes are preserved from the in vitro to the in vivo condition and they show the ability to migrate across the blood brain barrier, thus spontaneously reaching the brain tumor after injection. The simplicity of the synthesis route of these geomimetic nanomaterials combined with their demonstrated affinity with the in vivo condition strongly highlights their potential for developing effective functional materials for multimodal theranostics of brain cancer.

A novel chromophoric ionic liquid (IL) with two-dimensional (2D) nanostructural order is developed, and its structure-property relationship is investigated by harnessing photon upconversion based on triplet energy migration. An ion pair of 9,10-diphenylanthracene-2-sulphonate (DPAS) and asymmetric quaternary phosphonium ion exhibited both ionic crystal (IC) and supercooled IL phases at room temperature. Single crystal X-ray analysis of the IC phase showed an alternate alignment of polar (ionic) and non-polar (non-ionic) layers, and this layered structure was basically maintained even in the IL phase. The diffusion length of triplet excitons in the IL phase, obtained by the analysis of upconverted emission in succession to triplet-triplet annihilation (TTA), is larger than the domain size estimated from powder X-ray analysis. This suggests that triplet excitons in chromophoric ILs can diffuse over the nanostructured domains.

Metal nanoclusters featuring tunable luminescence and high biocompatibility are receiving attention as fluorescent markers for cellular imaging. The recently discovered ability of gold clusters to scavenge cytotoxic reactive oxygen species (ROS) from the intracellular environment extends their applicability to biomedical theranostics and provides a novel platform for realizing multifunctional luminescent probes with engineered anti-cytotoxic activity for applications in bio-diagnostics and conceivably cellular therapy. This goal could be achieved by using clusters of strongly reactive metals such as silver, provided that strategies are found to enhance their luminescence while simultaneously enabling direct interaction between the metal atoms and the chemical surroundings. In this work, we demonstrate a synergic approach for realizing multifunctional metal clusters combining enhanced luminescence with strong and lasting ROS scavenging activity, based on the fabrication and in situ protection of Ag nanoclusters with a supramolecular mantle of thiolated-Au atoms (Ag/Au-t). Confocal imaging and viability measurements highlight the biocompatibility of Ag/Au-t and their suitability as fluorescent bio-markers. ROS concentration tests reveal the remarkable scavenging activity of Ag-based clusters. Proliferation tests of cells in artificially stressed culture conditions point out their prolonged anti-cytotoxic effect with respect to gold systems, ensuring positive cell proliferation rates even for long incubation time.

We define Hardy spaces Hp(Dβ′), p∈(1,∞), on the non-smooth worm domain Dβ′={(z1,z2)∈C2:|Imz1−log⁡|z2|2|0. Here Wk,p denotes the Sobolev space of order k and underlying Lp norm, p∈(1,∞). As a consequence of the Lp boundedness of S˜, we prove that Hp(Dβ′)∩C(Dβ′‾) is a dense subspace of Hp(Dβ′).

In this work we provide an asymptotic expansion for the Szego kernel associated to a suitably defined Hardy space on the non-smooth worm domain $$D'_{\upbeta }$$ . After describing the singularities of the kernel, we compare it with an asymptotic expansion of the Bergman kernel. In particular, we show that the Bergman kernel has the same singularities of the first derivative of the Szego kernel with respect to any of the variables. On the side, we prove the boundedness of the Bergman projection operator on Sobolev spaces of integer order.

In this paper, we study the regularity of the Szegö projection on Lebesgue and Sobolev spaces on the boundary of the unbounded model worm domain bD'β.We consider the Hardy spaceH2(D'β). Denoting by bD'β.the boundary ofD'β, it is classical thatcan be identified with the closed subspace of L2(D'β, dσ), denoted by H2(D'β), consisting of the boundary values of functions in H2(D'β), where P : L2(D'β, dσ) →H2(D'β) is the induced Lebesgue measure. The orthogonal Hilbert space projection Ws,p (bD'β.) is called the Szegö projection. Letdenote the Lebesgue–Sobolev space on bD'β. We prove that P, initially defined on the dense subspace Wsp(bD'β)∩ L2(D'β, dσ), extends to a bounded operatorP : Wsp(bD'β)→ Wsp(bD'β) and 1 < p < ȡEand s ≥ 0

Sensitized triplet-triplet-annihilation-based photon upconversion (TTA-UC) permits the conversion of light into radiation of higher energy and involves a sequence of photophysical processes between two dyes. In contrast to other upconversion schemes, TTA-UC allows the frequency shifting of low-intensity light, which makes it particularly suitable for solar-energy harvesting technologies. High upconversion yields can be observed for low viscosity solutions of dyes; but, in solid materials, which are better suited for integration in devices, the process is usually less efficient. Here, it is shown that this problem can be solved by using transparent nanodroplet-containing polymers that consist of a continuous polymer matrix and a dispersed liquid phase containing the upconverting dyes. These materials can be accessed by a simple one-step procedure that involves the free-radical polymerization of a microemulsion of hydrophilic monomers, a lipophilic solvent, the upconverting dyes, and a surfactant. Several glassy and rubbery materials are explored and a range of dyes that enable TTA-UC in different spectral regions are utilized. The materials display upconversion efficiencies of up to ≈15%, approaching the performance of optimized oxygen-free reference solutions. The data suggest that the matrix not only serves as mechanically coherent carrier for the upconverting liquid phase, but also provides good protection from atmospheric oxygen.

In this paper we study the regularity of the Szeg\H{o} projection on Lebesgue and Sobolev spaces on the distinguished boundary of the unbounded model worm domain $D_\beta$. We denote by $d_b(D_\beta)$ the distinguished boundary of $D_\beta$ and define the corresponding Hardy space $\mathscr{H}^2(D_\beta)$. This can be identified with a closed subspace of $L^2(d_b(D_\beta),d\sigma)$, that we denote by $\mathscr{H}^2(d_b(D_\beta))$, where $d\sigma$ is the naturally induced measure on $d_b(D_\beta)$. The orthogonal Hilbert space projection $\mathscr{P}: L^2(d_b(D_\beta),d\sigma)\to \mathscr{H}^2(d_b(D_\beta))$ is called the Szeg\H{o} projection on the distinguished boundary. We prove that $\mathscr{P}$, initially defined on the dense subspace $L^2(d_b( D_\beta),d\sigma)\cap L^p(d_b(D_\beta), d\sigma)$ extends to a bounded operator $\mathscr{P}: L^p(d_b(D_\beta), d\sigma)\to L^p(d_b(D_\beta), d\sigma)$ if and only if $\textstyle{\frac{2}{1+\nu_\beta}}\pi$. Furthermore, we also prove that $\mathscr{P}$ defines a bounded operator $\mathscr{P}: W^{s,2}(d_b(D_\beta),d\sigma)\to W^{s,2}(d_b(D_\beta), d\sigma)$ if and only if $0\leq s, Comment: 27 pages

Incorporation of doping ions in nanocrystals is a strategy for providing nanophases with functions directly related to ion features. At the nanoscale, however, doping can also activate more complex effects mediated by perturbation of the nanophase size and structure. Here, we report a paradigmatic case in which we modify grown-in-glass γ-Ga2 O3 nanophases by nickel or titanium doping of the starting glass, so as to control the concentration of oxygen and gallium vacancies responsible for the light emission. Optical absorption and luminescence show that Ni2+ and Ti4+ ions enter into the nanophase, but differential scanning calorimetry and X-ray diffraction indicate that Ni and Ti also work as modifiers of nanocrystal growth. As a result, doping influences nanocrystal size and concentration, which in turn dictate the number of donors and acceptors per nanocrystal. Finally, the chain of effects turns out to control both the intensity and spectral distribution of the light emission.

The technological application of sensitized upconversion based on triplet-triplet annihilation (TTA) requires the transition from systems operating in liquid solutions to solid-state materials. Here, we demonstrate that the high upconversion efficiency reported in hyper-cross-linked nanoparticles does not originate from residual mobility of the embedded dyes as it happens in soft hosts. The hyper-reticulation from one side blocks the dyes in fixed positions, but on the other one, it suppresses the nonradiative spontaneous decay of the triplet excitons, reducing intramolecular relaxations. TTA is thus enabled by an unprecedented extension of the triplet lifetime, which grants long excitons diffusion lengths by hopping among the dye framework and gives rise to high upconversion yield without any molecular displacement. This finding paves the way for the design of a new class of upconverting materials, which in principle can operate at excitation intensities even lower than those requested in liquid or in rubber hosts.

The stimulated emission from an organic dye adsorbed within the void network of a NP 1D (photonic crystals) PC, was studied. The nanoparticle one-dimensional photonic crystals (NP 1DPCs) were assembled by polyelectrolyte-assisted layer-by-layer deposition with subsequent calcination of the films to remove the polymer components. Each layer was prepared by spin-coating a block-copolymer-templated titania- or silica-based sol solution followed by a calcination step. To maximize the photonic-crystal effect, PCs consisting of eleven bilayers, compared to the four-bilayer NP 1D PCs, were fabricated with good structural and optical quality over 2 cm ×2 cm areas. The effective refractive index of the SiO2 and TiO2 layers and the TiO2 layers was determined by spectroscopic ellipsometry to be 1.21 and 1.80 at 598 nm. A central feature of the 1D PC employed in this proof-of-concept study is the nanoparticle-generated porosity, which enables the uptake of a high loading of R6G dye.

Long-life excimer-like structures Metal quantum clusters have ideal properties for medical applications such as imaging. The challenge is to prolong their transient properties for the fabrication of useful devices. Santiago-Gonzalez et al. arranged gold clusters in a supramolecular lattice held together by hydrogen bonding and showed that this material can be used for imaging of fibroblast cells. In the superstructure, the gold molecules can come together in the excited state as excimers and then dissociate to emit radiation. Because they are within a lattice, this behavior shows long-term stability. Furthermore, the lattice superstructure scavenges reactive oxygen species and reduces cell damage. Science , this issue p. 571

We report highly efficient sensitized triplet–triplet annihilation based upconversion in aqueous suspensions of nanoparticles prepared from 9,10-diphenylanthracene-terminated poly(e-caprolactone) and with platinum octaethylporphyrin as the sensitizer. The particles upconversion characteristics are strongly temperature-dependent. This feature gives insights into the mechanisms enabling the process in the nanoparticle environment, and the specific temperature range in which the photophysical parameters change is suitable for live cell and in vivo temperature sensing.

Conventional solar cells exhibit limited efficiencies in part due to their inability to absorb the entire solar spectrum. Sub-band-gap photons are typically lost but could be captured if a material that performs up-conversion, which shifts photon energies higher, is coupled to the device. Recently, molecular chromophores that undergo triplet-triplet annihilation (TTA) have shown promise for efficient up-conversion at low irradiance, suitable for some types of solar cells. However, the molecular systems that have shown the highest up-conversion efficiency to date are ill suited to broadband light harvesting, reducing their applicability. Here we overcome this limitation by combining an organic TTA system with highly fluorescent CdSe semiconductor nanocrystals. Because of their broadband absorption and spectrally narrow, size-tunable fluorescence, the nanocrystals absorb the radiation lost by the TTA chromophores, returning this energy to the up-converter. The resulting nanocrystal-boosted system shows a doubled light-harvesting ability, which allows a green-to-blue conversion efficiency of μ12.5% under 0.5 suns of incoherent excitation. This record efficiency at subsolar irradiance demonstrates that boosting the TTA by light-emitting nanocrystals can potentially provide a general route for up-conversion for different photovoltaic and photocatalytic applications.

Submitted on behalf of EDAA (http://www.edaa.com/); International audience; Designers of factory automation applications increasingly demand for tools for rapid prototyping of hardware extensions to existing systems and verification of resulting behaviors through hardware and software co-simulation. This work presents a framework for the timing-accurate co-simulation of HDL models and their verification against hardware and software running on an actual embedded device of which only a minimal knowledge of the current design is required. Experiments on real-life applications show that early architectural and design decisions can be taken by measuring the expected performance on the models realized using the proposed framework.