Search

In this article, the author examines the concept of truth by M. Heidegger in light of social and epistemological issues. He believes that “truth as unconcealment” is a more productive approach than the theory of correspondence or coherence since it can capture a number of socio-humanitarian concepts where verification is complicated. The author believes that Heidegger’s existential-historical thought about the “essence of truth” receives a logical continuation in the “esoteric initiative” or “sygetics”, which — if it is explicated in relation to the social attitudes and imperatives of the thinker — means the strategy of minimizing the public sphere and returning to one’s own. With regard to the institutional (re)production of knowledge, this means a chance for philosophy and scientific research to start a new existence on the other side of academic, professional education, i.e. outside the modern university. Finally, Heidegger’s concept of truth questions the scientistic image of science and philosophy. It shows that genuine knowledge cannot totally depend on the requirement of rational reconstruction of propositions.

The conversation with Sergey Khoruzhiy took place in March of the year during his visit to the Institute of Human Sciences in Vienna. The questions were asked at that time by the Institute's freelance staff — Kristina Stoeckl and Alexander Mikhailovsky. The conversation was conducted in English. The transcribed text of the interview with abbreviations was published in the journal Studies in East European Thought: Michailowski A., Stoeckl K. Interview with Sergey Horujy / / Studies in East European Thought. — 2016. - Vol. 68, No. 2/3. - P. 1-8. Russian translation by A.V. Mikhailovsky.

The article is an introduction to the first Russian translation of Max Scheler's essay “On Eastern and Western Christianity”, which was published in the collection of articles “War and Reconstruction” (1916) and thus forms part of Scheler's war philosophy. The article presents the polemical context of this essay and establishes a connection with Scheler's axiology and phenomenology as well. Particular attention is paid to the reception of F.M. Dostoevsky among German intellectuals of the early 20th century and the influence of this reception on Scheler's understanding of the ideas of salvation and suffering in the Eastern Church.

Understanding the genetic causes of evolutionary diversification is challenging because differences across species are complex, often involving many genes. However, cases where single or few genetic loci affect a trait that varies dramatically across a radiation of species provide tractable opportunities to understand the genetics of diversification. Here, we begin to explore how diversification of bioluminescent signals across species of cypridinid ostracods ("sea fireflies") was influenced by evolution of a single gene, cypridinid-luciferase. In addition to emission spectra ("colour") of bioluminescence from 21 cypridinid species, we report 13 new c-luciferase genes from de novo transcriptomes, including in vitro assays to confirm function of four of those genes. Our comparative analyses suggest some amino acid sites in c-luciferase evolved under episodic diversifying selection and may be associated with changes in both enzyme kinetics and colour, two enzymatic functions that directly impact the phenotype of bioluminescent signals. The analyses also suggest multiple other amino acid positions in c-luciferase evolved neutrally or under purifying selection, and may have impacted the variation of colour of bioluminescent signals across genera. Previous mutagenesis studies at candidate sites show epistatic interactions, which could constrain the evolution of c-luciferase function. This work provides important steps toward understanding the genetic basis of diversification of behavioural signals across multiple species, suggesting different evolutionary processes act at different times during a radiation of species. These results set the stage for additional mutagenesis studies that could explicitly link selection, drift, and constraint to the evolution of phenotypic diversification.

The design and synthesis of the near-infrared (NIR)-II emissive conjugated oligoelectrolyte COE-BBT are reported. COE-BBT has a solubility in aqueous media greater than 50 mg mL

As in many fields, the most exciting endeavors in photon upconversion research focus on increasing the efficiency (upconversion quantum yield) and performance (anti-Stokes shift) while diminishing the cost of production. In this vein, studies employing metal-free thermally activated delayed fluorescence (TADF) sensitizers have garnered increased interest. Here, for the first time, the strategy of ternary photon upconversion was utilized with the TADF sensitizer 4CzIPN, resulting in a doubling of the upconversion quantum yield in comparison to the binary system employing p-terphenyl as the emitter. In this ternary blend, the sensitizer 4CzIPN is paired with an intermediate acceptor, 1-methylnaphthalene, in addition to the emitter molecule, p-terphenyl yielding a normalized upconversion quantum yield of 7.6% while maintaining the 0.83 eV anti-Stokes shift. These results illustrate the potential benefits of utilizing this strategy of energy-funneling, previously used only with heavy-metal based sensitizers, to increase the performance of these photon upconversion systems. This article is protected by copyright. All rights reserved.

The synthesis of a new conjugated oligoelectrolyte (COE), namely DSAzB, is described, which contains a conjugated core bearing a diazene moiety in the center of its electronically delocalized structure. Similar to structurally related phenylenevinylene-based COEs, DSAzB readily intercalates into model and natural lipid bilayer membranes. Photoinduced isomerization transforms the linear trans COE into a bent or C-shape form. It is thereby possible to introduce DSAzB into the bilayer of a cell and disrupt its integrity by irradiation with light. This leads to controlled permeabilization of membranes, as demonstrated by the release of calcein from DMPG/DMPC vesicles and by propidium iodide influx experiments on S. epidermidis. Both experiments support that the permeabilization is selective for the light stimulus, highly efficient, and repeatable. Target-selective and photoinduced actions demonstrated by DSAzB may have broad applications in biocatalysis and related biotechnologies.

Protein aggregation is associated with numerous devastating diseases such as Alzheimer's, Parkinson's, and prion diseases. Development of therapeutics would benefit from knowledge of the structural organization of protein molecules in these amyloid aggregates, particularly in their aqueous biological milieu. However, detailed structural studies to date have been mainly on the solid state and have required large quantities of purified aggregate. Moreover, these conventional methods require the aggregated assembly to remain structurally stable over days or weeks required to perform the experiment, whereas the pathologically relevant species of in vivo aggregates may be shorter lived. Here, we show the organization of protein chains in dissolved amyloid aggregates can be readily determined spectroscopically using minute quantities of fluorescein-labeled protein segments in a matter of minutes. Specifically, we investigated the possibility of using the ultrafast dynamics of fluorescein to distinguish among three categories of β-sheet geometry: (1) antiparallel in-register, (2) parallel in-register, or (3) antiparallel out-of-register. Fluorescein, the most commonly used staining dye in biology and medicine, was covalently attached to the N-termini of peptide sequences selected from a library of known amyloid crystal structures. We investigated the aggregates in solution using steady-state and time-resolved absorption and fluorescence spectroscopy. We found that the dynamics of fluorescein relaxation from the excited state revealed amyloid structure-specific information. Particularly, the nonfluorescent cation form of fluorescein showed remarkable sensitivity to local environments created during aggregation. We demonstrate that time-resolved absorption is capable of differentiating strand organization in β-sheet aggregates when strong intermolecular coupling between chromophores occurs. This approach can be useful in optical recognition of specific fibril architectures of amyloid aggregates.

Nanophotonic resonators offer the ability to design nanoscale optical elements and engineered materials with unconventional properties. Dielectric-based resonators intrinsically support a complete multipolar resonant response with low absorption, while metallic resonators provide extreme light confinement and enhanced photon–electron interactions. Here, we construct resonators out of a prototypical metal–insulator transition material, vanadium dioxide (VO2), and demonstrate switching between dielectric and plasmonic resonances. We first characterize the temperature-dependent infrared optical constants of VO2 single crystals and thin-films. We then fabricate VO2 wire arrays and disk arrays. We show that wire resonators support dielectric resonances at low temperatures, a damped scattering response at intermediate temperatures, and plasmonic resonances at high temperatures. In disk resonators, however, upon heating, there is a pronounced enhancement of scattering at intermediate temperatures and a substanti...

Understanding the genetic causes of evolutionary diversification is challenging because differences across species are complex, often involving many genes. However, cases where single or few genetic loci affect a feature that varies dramatically across a radiation of species would provide tractable opportunities to understand the genetics of diversification. Here, we show the diversification of bioluminescent signals in cypridinid ostracods (“sea fireflies”) to be strongly influenced by a single gene, cypridinid-luciferase. We find different evolutionary processes, including selection, drift, and constraint, each acted on c-luciferase at different times during evolutionary history and impacted different phenotypes, diversifying behavioral signals across species. In particular, some amino acid sites in c-luciferase evolved under episodic diversifying selection, and are associated significantly with phenotypic changes in both enzyme kinetics and color, which impact signals directly. We also find that multiple other amino acid positions in c-luciferase evolved neutrally or under purifying selection and may have impacted the variation of color of bioluminescent signals across genera. This work provides a rare glimpse into the genetic basis of diversification across many species, showing how multiple evolutionary processes may act at different times during a radiation of species to diversify phenotypes. These results indicate not only selection but also drift and constraint may be important evolutionary drivers of species diversification.Significance statementA hallmark of life is its astounding diversity. While we are beginning to understand the drivers of biodiversity, uncovering the genetic basis remains challenging. As such, how different molecular evolutionary processes act to diversify phenotypes is a major question in biology. Here we show a single gene to be important in a riotous diversity of fantastical behaviors - the bioluminescent signals of sea fireflies - allowing us to demonstrate multiple evolutionary forces including selection, drift, and constraint contributed to diversification. Our work highlights that not only selection but also neutral processes and constraint have each worked at different times to shape phenotypic diversity.

Multiphoton excitation allows one to access high energy excited states and perform valuable tasks in biological systems using tissue penetrating near-infrared (NIR) light. Here, we describe new photoactive manganese tricarbonyl complexes incorporating the ligand 4'-p-N,N-bis(2-hydroxyethyl)amino-benzyl-2,2':6',2″-terpyridine (TPYOH), which can serve as an antenna for two photon NIR excitation. Solutions of Mn(CO)3(TPYOH)X (X = Br- or CF3SO3-) complexes are very photoactive toward CO release under visible light excitation (405 nm, 451 nm). The same responses were also triggered by multiphoton excitation at 750 and 800 nm. In this context, we discuss the potential applications of these complexes as visible/NIR light photoactivated carbon monoxide releasing moieties (photoCORMs). We also report the isolation and crystal structures of the TPYOH complexes Mn(TPYOH)Cl2 and [Mn(TPYOH)2](CF3SO3)2, to illustrate a possible photolysis product(s).

Inorganic phosphor materials play a crucial role in the creation of white light from blue and near-UV solid-state light-emitting diodes. Understanding the intricacies of the phosphor structure is key for setting the stage for improved, more efficient functionality. Average structure and coordination environment analysis of the robust and efficient green-emitting phosphor, β-SiAlON:Eu2+ (β-Si6−zAlzOzN8−zEu0.009), is combined here with a range of property measurements to elucidate the role of Al content (z) in luminescence properties, including the red shift of emission and the thermal quenching of luminescence as a function of increasing Al content z. Average structure techniques reveal changes in polyhedral distortion with increasing z for the 9-coordinate Eu site in β-SiAlON:Eu2+. X-ray absorption near edge structure (XANES) is used to confirm that the majority of the activator Eu is in the Eu2+ state, exhibiting the symmetry-allowed and efficient 4f75d0 → 4f65d1 transitions. Room temperature and temperature-dependent luminescence indicate a curious increase in thermal stability with increasing z over a small range due to an increasing barrier for thermal ionization, which is correlated to an increase in the quantum yield of the phosphor.

Simulation of electronic dynamics in realistically large molecular systems is a demanding task that has not yet achieved the same level of quantitative prediction already realized for its static counterpart. This is particularly true for processes occurring beyond the Born-Oppenheimer regime. Non-adiabatic molecular dynamics (NAMD) simulations suffer from two convoluted sources of error: numerical algorithms for dynamics and electronic structure calculations. While the former has gained increasing attention, particularly addressing the validity of ad hoc methodologies, the effect of the latter remains relatively unexplored. Indeed, the required accuracy for electronic structure calculations to reach quantitative agreement with experiment in dynamics may be even more strict than that required for static simulations. Here, we address this issue by modeling the electronic energy transfer in a donor-acceptor-donor (D-A-D) molecular light harvesting system using fewest switches surface hopping NAMD simulations. In the studied system, time-resolved experimental measurements deliver complete information on spectra and energy transfer rates. Subsequent modeling shows that the calculated electronic transition energies are "sufficiently good" to reproduce experimental spectra but produce over an order of magnitude error in simulated dynamical rates. We further perform simulations using artificially shifted energy gaps to investigate the complex relationship between transition energies and modeled dynamics to understand factors affecting non-radiative relaxation and energy transfer rates.

Amyloid fibrils are a hallmark of neurodegeneration. The structural diversity of amyloids necessitates sensitive methods and probes that can be reliably used to characterize them. Here, we study insulin fibrils and its polymorphs seeded with LVEALYL peptide in context of probing the surface patterns using Thioflavin T (ThT) and polythiophene derivative – Poly[2-(3-thienyl)ethoxy-4-butylsulfonate] (PTEBS) polymer. We investigated the dynamics and lifetimes of these two probes using time-resolved absorption and fluorescence spectroscopy. The photoluminescence emission lifetimes of the probes showed different relaxation times in the presence of structurally different amyloid fibrils. However, only PTEBS revealed sensitivity to the surface patterns of the fibrils that was explained by uneven charge distribution and exposure of different amino acids to the fibril surface where probe is interacting with the fibril. We find that PTEBS binding to distinct amyloid surfaces causes perturbation of the main chain of the polymer creating new conditions for energy distribution in the excited states that favors formation of various emitting species. The results indicate that PTEBS and ThT are comparable in terms of recognition of fibril polymorphs whereas polymer probe provides additional dimension to study fibrils surface patterns that can be revealed using time resolved spectroscopy.

We present a rapid and energy-efficient microwave-assisted approach to prepare a single-phase full-color phosphor based on Ba 3 MgSi 2 O 8 . The samples were prepared using a citric acid based sol–gel preparation pathway with a microwave-assisted heating step, which reduces the time required for the final heat treatment to less than 30 min. Thermogravimetric analysis was utilized to optimize the solution-based preparation prior to microwave heating. The structural properties of the obtained luminescent materials have been thoroughly investigated by means of X-ray powder diffraction and Rietveld analyses. To study the optical behavior, the excitation and emission spectra were recorded. Full-color emission is achieved using Eu 2+ (blue), Tb 3+ (green), and Mn 2+ (red) as the activator ions. The thermally robust emission was investigated using temperature-dependent luminescence spectroscopy. The energy-transfer processes within the samples were studied using time-dependent spectroscopy, and the quantum yield of this true color phosphor as a function of the composition was determined.

This article in the form of “reflections” is devoted mainly to the image-building of Heidegger in Russia as a thinker of Being, a conservative critic of late modernity and a “post” philosopher. On the one hand, due to French post-modernism influence on late Soviet and post-Soviet philosophy Russia has developed a special interest in Heidegger’s deconstruction theory. On the other hand, the reception of Heidegger’s criticism of European nihilism, totalitarianism and machine technology as the manifestations of modernity has shaped significantly the account of the “political”. The specifics of Russian reception of Heidegger can also be traced in the rejection of strict division between the “core” of Heidegger’s philosophy and “accidental” conditions related to social and political aspects of his work in 1930s. The current discussion about recently published “Black notebooks” shows not only the fact of existence of a separate language of description and analysis in Russian philosophical field but also an original tendency to holistic consideration of Heidegger’s thinking including not only his existential and historical reflections but also political passages and criticism of civilizational discourse. In addition to the reviews of “Black notebooks” by N.V. Motroshilova, V.V. Mironov and D. Mironova in the last year’s issues of the magazine “Voprosy filosofii” there are earlier works by N.V. Motroshilova, V.V. Bibikhin and A.V. Gulyga related to the debate on Heidegger’s political and ideological commitment which are in focus of attention.

A membrane-intercalating conjugated oligoelectrolyte (COE), PTTP, was designed and synthesized with the goal of providing red-shifted absorption spectra relative to previously synthesized COE analogs. Specifically, electron-rich and electron-poor subunits were introduced in the conjugated backbone to modulate the band gap. PTTP exhibits maxima of absorption at 507 nm and of emission at 725 nm. PTTP can also efficiently function to generate singlet oxygen in situ (ΦΔ≈20 %) and has appropriate topology and dimensions to interact with lipid membranes. The resulting rapid membrane insertion and sensitizing ability provide PTTP with a highly efficient antibacterial capability under a low light dose (0.6 J cm−2) toward Gram-negative bacteria E. coli, making it a remarkably efficient optically mediated antimicrobial agent.

The article provides a comparison of two intellectual accounts of experiences in the First World War—From the Letters of an Artillery Ensign (1918) by the Russian philosopher and writer Fjodor Stepun and The Storm of Steel by the German essayist Ernst Junger. The aim of this article is to reveal similarities and differences between the “optics” of Junger and Stepun who are reporting one and the same event but deal with two different images of the Great War.

The orthosilicate phosphors SrxBa2–xSiO4:Eu2+ have now been known for over four decades and have found extensive recent use in solid-state white lighting. It is well-recognized in the literature and in practice that intermediate compositions in the solid-solutions between the orthosilicates Sr2SiO4 and Ba2SiO4 yield the best phosphor hosts when the thermal stability of luminescence is considered. We employ a combination of synchrotron X-ray diffraction, total scattering measurements, density functional theory calculations, and low-temperature heat capacity measurements, in conjunction with detailed temperature- and time-resolved studies of luminescence properties to understand the origins of the improved luminescence properties. We observe that in the intermediate compositions, the two cation sites in the crystal structure are optimally bonded as determined from bond valence sum calculations. Optimal bonding results in a more rigid lattice, as established by the intermediate compositions possessing the hi...

Six experimental methods have been used to investigate the exciton diffusion length in materials with systematic chemical modifications. We find that exciton diffusion length correlates with molecular ordering. We discuss situations in which certain experimental techniques are more appropriate.

Addition of low concentrations (

Optical antenna metasurfaces have attracted substantial attention in recent years, as they may enable new classes of planar optical elements. However, actively tuning nanoantenna resonances, whether dielectric or plasmonic, remains an unresolved challenge. In this work, we investigate tuning mid-infrared (MIR) Mie resonances in semiconductor subwavelength particles by directly modulating the permittivity with free charge carriers. Using femtosecond laser ablation, we fabricate spherical silicon and germanium particles of varying sizes and doping concentrations. Single-particle infrared spectra reveal electric and magnetic dipole, quadrupole, and hexapole resonances. We first demonstrate size-dependent Si and Ge Mie resonances spanning the entire mid-infrared (2-16 μm) spectral range. We subsequently show doping-dependent resonance frequency shifts that follow simple Drude models. Taking advantage of the large doping dependence of Si and Ge MIR permittivities, we demonstrate a huge tunability of Mie resonance wavelengths (up to ~ 9 μm) over a broad 2-16 μm MIR range. This tuning range corresponds to changes of permittivity as large as 30 within a single material system, culminating in the emergence of plasmonic modes at high carrier densities and long wavelengths. We also demonstrate dynamic tuning of intrinsic semiconductor antennas using thermo-optic effects. These findings demonstrate the potential for actively tuning infrared Mie resonances, thus providing an excellent platform for tunable metamaterials.

Lanthanide-modified CdSe quantum dots (CdSe(Ln) QDs) have been prepared by heating a solution of Cd(oleate)2, SeO2, and Ln(bipy)(S2CNEt2)3 (bipy = 2,2′-bipyridine) to 180–190 °C for 10–15 min. The elemental compositions of the resulting CdSe(Ln) cores and CdSe(Ln)/ZnS core/shell QDs show this route to be highly reproducible. The optical absorption spectra of these composite materials are similar to those of the unmodified nanocrystals, but the QD-centered band edge photoluminescence (PL) is partially quenched. The time-gated emission and excitation spectra of the CdSe(Ln) cores display sensitized lanthanide-centered PL upon higher energy excitation of the nanocrystal host but not upon excitation at the lowest energy QD absorption band. Growth of the ZnS shell led to the depletion of about 60% of the lanthanide ions present together with depletion of nearly all of the lanthanide-centered PL. On these bases, we conclude that the lanthanide-centered PL from the CdSe(Ln) cores originates with Ln3+-related tra...

Reported are quantitative studies of the energy transfer from water-soluble CdSe/ZnS and CdSeS/ZnS core/shell quantum dots (QDs) to the Cr(III) complexes trans-Cr(N(4))(X)(2)(+) (N(4) is a tetraazamacrocycle ligand, X(-) is CN(-), Cl(-), or ONO(-)) in aqueous solution. Variation of N(4), of X(-), and of the QD size and composition allows one to probe the relationship between the emission/absorption overlap integral parameter and the efficiency of the quenching of the QD photoluminescence (PL) by the chromium(III) complexes. Steady-state studies of the QD PL in the presence of different concentrations of trans-Cr(N(4))(X)(2)(+) indicate a clear correlation between quenching efficiency and the overlap integral largely consistent with the predicted behavior of a Förster resonance energy transfer (FRET)-type mechanism. PL lifetimes show analogous correlations, and these results demonstrate that spectral overlap is an important consideration when designing supramolecular systems that incorporate QDs as photosensitizers. In the latter context, we extend earlier studies demonstrating that the water-soluble CdSe/ZnS and CdSeS/ZnS QDs photosensitize nitric oxide release from the trans-Cr(cyclam)(ONO)(2)(+) cation (cyclam = 1,4,8,11-tetraazacyclotetradecane) and report the efficiency (quantum yield) for this process. An improved synthesis of ternary CdSeS core/shell QDs is also described.

A rapid and energy efficient microwave assisted solid state preparative route for europium-doped Akermanite (Ca{sub 2}MgSi{sub 2}O{sub 7}) has been developed. This method reduces the reaction time and energy needed by more than 90%, compared to the preparation carried out in a conventional furnace. The obtained samples are phase pure as has been determined using synchrotron X-ray powder diffraction data and Rietveld analyses. Scanning electron microscopy was employed to investigate the morphology of the microwave prepared compounds whilst energy dispersive X-ray spectroscopy (EDX) was used to verify the elemental composition of the specimens. A systematic investigation of the influence of the utilized microwave setup is presented. Finally, the microwave prepared materials were subject to temperature dependent photoluminescence measurements in order to investigate the thermal quenching of the luminescence.

Ce3+-substituted aluminum garnet compounds of yttrium (Y3Al5O12) and lutetium (Lu3Al5O12)—both important compounds in the generation of (In,Ga)N-based solid state white lighting—have been prepared using a simple microwave heating technique involving the use of a microwave susceptor to provide the initial heat source. Carbon used as the susceptor additionally creates a reducing atmosphere around the sample that helps stabilize the desired luminescent compound. High quality, phase-pure materials are prepared within a fraction of the time and using a fraction of the energy required in a conventional ceramic preparation; the microwave technique allows for a reduction of about 95% in preparation time, making it possible to obtain phase pure, Ce3+-substituted garnet compounds in under 20 min of reaction time. It is estimated that the overall reduction in energy compared with ceramic routes as practised in the lab is close to 99%. Conventionally prepared material is compared with material prepared using microwav...

Three novel inorganic-organic framework compounds containing the organic chromophore ligand 9-fluorenone-2,7-dicarboxylic acid (abbreviated H(2)FDC) and barium (BaFDC), cadmium (CdFDC) and manganese (MnFDC), respectively, have been synthesized and evaluated for their use as phosphor materials for solid state lighting and other applications. The results are compared with two earlier reported structures containing the same ligand with calcium (CaFDC) and strontium (SrFDC). The barium- and cadmium-containing compounds both show blue excited, yellow photoluminescence, while the manganese structure does not. The trends in luminescent efficiency for the Ba, Cd, Ca, and Sr derivatives are discussed in relation to crystallographic, optical, and low-temperature specific heat considerations.

We report on a study of the overall surface-enhanced Raman scattering (SERS) response from several thiol-terminated molecules located at interstitial sites between Ag nanoparticles. Multiplexing of the SERS signal was demonstrated along with its dependence of the molecular length, regiochemistry, and the number of thiol groups. The data collected establish pathways for the rational design of the SERS reporters and multiplexed sensory applications.

A new, highly efficient green oxyfluoride phosphor family Sr2.975−xBaxCe0.025AlO4F (SBAF:Ce3+) has been developed as a component of solid state white light emitting diodes (LED). The phosphor emits with a maximum at 502 nm when excited by 405 nm excitation, with a quantum efficiency approaching 100%. When SBAF:Ce3+ (x = 1.0) is incorporated with encapsulant on an ultraviolet (405 nm) LED, greenish-white light with a color rendering index of 62 under a forward bias current of 20 mA is obtained. The results suggest that phosphors deriving from SBAF:Ce3+ have potential for incorporation in formulations for white LEDs and related applications. The preparation and structural and optical characterization of the phosphor family is described. Attempts to understand the origins of the high efficiency on the basis of the thermal quenching characteristics of SBAF:Ce3+ in comparison with related compounds are presented.

Two dense inorganic−organic frameworks were prepared using the intrinsically luminescent organic ligand 9-fluorenone-2,7-dicarboxylic acid (H2FDC) in combination with the alkaline earth metals calcium and strontium. Ca(FDC)(H2O)2 (1) and Sr(FDC)(H2O)5·2H2O (2) were prepared hydrothermally and both adopt three-dimensional framework structures. They absorb strongly between 380 and 460 nm and show broad visible emission with peaks at 503 and 526 nm, respectively. Structure 1 shows a quantum yield at room temperature of 7.8% which increases to 15% at −196 °C, while structure 2 shows a room temperature quantum yield of 2.8%, increasing to 3.3% at −196 °C.

Here we report a new approach for the preparation of anode buffer layer for efficient polymer light-emitting devices (PLEDs) by using glycerol to modify relative low conductivity poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). This new type of anode buffer layer allows for a 50–90% increase in device performance for green emitting phosphorescent PLEDs in terms of luminous efficiency, and external quantum efficiency, while 90–150% in power efficiency, as compared to devices fabricated using commercially available PEDOT:PSS. The green emitting phosphorescent PLEDs with this modified anode buffer exhibit very high efficiencies, representing a significant step forward to matching and exceeding the efficiencies reported to date with vacuum-deposited small molecular devices. We anticipate that these findings can provide a simple experimental procedure for improvement of PLEDs.

We have investigated the upconversion properties of the rare-earth doped systems La 2 BaZnO 5 ( I 4/ mcm ) and Gd 2 BaZnO 5 ( Pbnm ). The dependence of the luminescence properties on the identity and the concentration of the dopants, Er 3+ and Er 3+ co-doped with Yb 3+ , as well as on the synthetic route, was examined. Following coherent excitation at 975 nm, strong upconversion emission was observed in the visible region (525, 550 and 660 nm). Power dependence studies revealed a two photon process for these emissions. In the co-doped samples, a blue emission (410 nm) could also be observed. For this emission, the power dependence studies confirmed a three photon process.

Electrostatic interactions between the imidazole-based cationic homopolymer, polyvinylimidazole (PVIm), and anionic polysaccharide, sodium alginate, lead to the formation of colloidal aggregates known as complex coacervates in the pH range 4–6.5. PVIm was labeled with the fluorescent reporter pyrene to investigate the coacervation-induced changes in and around PVIm chains. While the pyrene-tagged PVIm had blue fluorescence in water, the coacervate phase exhibited an additional broad band around 492 nm (green) due to formation of pyrene excimers. Fluorescence spectroscopic investigations point toward aggregation of PVIm chains and desolvation upon coacervation. Highly anisotropic fluorescence emission indicates tight packing of the polymer chains in the coacervate. Confocal microscopy of fluorescein-labeled alginate and rhodamine-labeled PVIm shows coacervates as dense aggregates with uniform distribution of the polymers. Fluorescence spectroscopy offers sensitive and easy investigation into polyelectrolyte interactions.

Conjugated polyelectrolytes (CPEs) have been widely used as light harvesting macromolecules to amplify the signals of fluorescent assays that betray the presence of various biomolecular targets. Electrostatic interactions play an important role in coordinating optical coupling events and lead in the formation of complexes between oppositely charged CPEs and the target species. Here, we combine for the first time optical studies and structural characterization by liquid phase atomic force microscopy (AFM) to provide a picture of aggregate structure and growth dynamics between cationic CPE and DNA as a function of charge ratio. Specifically, poly1 20, a copolymer containing a backbone with 50% fluorene, 30% phenylene, and 20% 2.1.3-benzothiadiazole (BT) units and pendant cationic groups was mixed with single stranded DNA (ssDNA) labeled with the Cy5 acceptor chromophore. Continuous addition of ssDNA Cy5 to poly1 20 leads to a saturation in Cy5 emission due to Cy5-Cy5 self-quenching. Addition of ssDNA to a preformed poly1 20 /ssDNA-Cy5 solution results in increased sensitization by energy transfer and a reduction of Cy5-Cy5 self quenching. Adsorption of aggregates onto negatively charged mica under water allows for direct imaging of the polyelectrolyte complexes as a function of charge ratio. The composite set of observations allows for the development of a model for aggregate growth, which is dynamic and ceases when the surface charge becomes sufficiently negative. This saturation point can be mitigated by addition of unlabeled ssDNA.

The development of one- and two-photon induced polymerization using CdS semiconductor quantum dots (QDs) and amine co-initiators to promote radical generation and subsequent polymerization is presented. Two-photon absorption (TPA) cross-section measurements, linear absorption, and transmission electron microscopy are used to characterize the QDs. The effectiveness of the co-initiators in increasing the efficiency of photopolymerization (polymer chains formed per excitation) is examined. Triethylamine was observed to be most effective, yielding quantum efficiencies of initiation of >5%. The interactions between the co-initiators and QDs are investigated with steady-state photoluminescence and infrared spectroscopies. Possible initiation mechanisms are discussed and supported by electrochemical data. Making use of the surface chemistry developed here and the large QD TPA cross-sections, two-photon induced polymerization is demonstrated. The large TPA cross-sections coupled with modest quantum efficiencies for initiation reveal the unique potential of molecularly passivated QDs as efficient two-photon photosensitizers for polymerization.

We report a novel strategy for writing volume holograms by photoacid generation and subsequent acid-catalyzed degradation leading to increased free volume/refractive index modulation in the exposed regions of a cross-linked rigid polymeric matrix. This strategy offers nondestructive read out and high diffraction efficiency and allows optical-quality, millimeter thick films to be fabricated that possess excellent thermal and dimensional stability. A key feature of this approach is the efficient acid-catalyzed degradation of functional groups in the cross-linked matrix leading to release of volatile products which diffuse readily out of the thick films. Furthermore, the reported data storage material is lightweight and inexpensive and can be easily processed into different shapes, making it an attractive candidate for data storage applications.

Described is the photoluminescence (PL) of water-soluble CdSe/ZnS core/shell quantum dots (QDs) as perturbed by salts of the chromium(III) complexes trans-Cr(cyclam)Cl2+ (1), trans-Cr(cyclam)(ONO)2+ (2), and trans-Cr(cyclam)(CN)2+ (3) (cyclam = 1,4,8,11-tetraazacyclo-tetradecane). The purpose is to probe the characteristics of such QDs as antennae for photosensitized release of bioactive agents (in the present case, the bioregulatory molecule NO) from transition metal centers. Addition of 1 or 2 to a QD solution results in concentration-dependent quenching of the band edge emission, but 3 has a minimal effect. Added KCl strongly attenuates the quenching by 1, and this suggests that the Cr(III) cations and the QDs form electrostatic assemblies via ion pairing on the negatively charged QD surfaces. Quenching by 2, a known photochemical NO precursor, was accompanied by photosensitized NO release. All three, however, do quench the broad red emission ( approximately 650-850 nm) attributed to radiative decay of surface trapped carriers. The effect of various concentrations of 1 on time-resolved PL and absorbance were explored using ultrafast spectroscopic methods. These observations are interpreted in terms of the Förster resonance energy-transfer mechanism for quenching of the band edge PL by multiple units of 1 or 2 at the QD surface, whereas quenching of the low-energy trap emission occurs via a charge-transfer pathway.

Metal-to-ligand charge transfer photolysis of the ruthenium(II) pyrazine complex Ru(NH3)5pz2+ (I) in pH 7.4 oxygenated phosphate buffer solution generates the Ru(III) analog Ru(NH3)5pz3+ plus the reactive oxygen species singlet oxygen and superoxide. Based on the very short MLCT lifetime (re-measured as approximately 250 ps in D2O) of I* and the quantum yield for singlet oxygen formation (0.01 for aerated D2O) the rate constant for oxygen quenching of I* was calculated to be approximately (3+/-1)x10(10) M-1 s-1.

Two water-soluble conjugated polyelectrolytes, poly(9,9′-bis(6-N,N,N-trimethylammoniumhexyl)fluorene-alt-1,4-(2,5-bis(6-N,N,N-trimethylammoniumhexyloxy))phenylene) tetrabromide (P1i) and poly((10,10′-bis(6-N,N,N-trimethylammoniumhexyl)-10H-spiro(anthracene-9,9′-fluorene))-alt-1,4-(2,5-bis(6-N,N,N-trimethylammoniumhexyloxy))phenylene) tetrabromide (P2i) are synthesized, characterized, and used in fluorescence resonance energy transfer (FRET) experiments with fluorescein-labeled single-stranded DNA (ssDNA-Fl). P1i and P2i have nearly identical π-conjugated backbones, as determined by cyclic voltammetry and UV-vis spectroscopy. The main structural difference is the presence of an anthracenyl substituent, orthogonal to the main chain in each of the P2i repeat units, which increases the average interchain separation in aggregated phases. It is possible to observe emission from ssDNA-Fl via FRET upon excitation of P2i. Fluorescein is not emissive within the ssDNA-Fl/P1i electrostatic complex, suggesting Fl emission quenching through photoinduced charge transfer (PCT). We propose that the presence of the anthracenyl “molecular bumper” in P2i increases the distance between optical partners, which decreases PCT more acutely relative to FRET.

We demonstrate tuning of infrared Mie resonances by varying the carrier concentration in doped semiconductor antennas. We fabricate spherical silicon and germanium particles of varying sizes and doping concentrations. Single-particle infrared spectra reveal electric and magnetic dipole, quadrupole, and hexapole resonances. We subsequently demonstrate doping-dependent frequency shifts that follow simple Drude models, culminating in the emergence of plasmonic resonances at high doping levels and long wavelengths. These findings demonstrate the potential for actively tuning infrared Mie resonances by optically or electrically modulating charge carrier densities, thus providing an excellent platform for tunable metamaterials.

Simple procedures are provided for exchanging charge-compensating ions in conjugated polyelectrolytes by progressive dilution of the original species and for determining the degree of ion exchange by using X-ray photoelectron spectroscopy. By using these methods, the bromide ions in poly[(9,9-bis(6'-N,N,N-trimethylammoniumbromide)hexyl)fluorene-co-alt-4,7-(2,1,3-benzothiadiazole)]were exchanged with BF4-, CF3SO3-, PF6-, BPh4-, and B(3,5-(CF3)2C6H3)4- (BArF4-). Absorption, photoluminescence (PL), and PL quantum yields (Phi) were measured in different solvents and in solid films cast from methanol. Examination of the resulting trends, together with the spectral bandshapes in different solvents, suggests that increasing the counteranion (CA) size decreases interchain contacts and aggregation and leads to a substantial increase of Phi in the bulk. Size analysis of polymers containing Br- and BArF4- in water by dynamic light scattering techniques indicates suppression of aggregation by BArF4-. Nanoscale current-voltage measurements of films using conducting atomic force microscopy show that hole mobilities and, more significantly, charge injection barriers are CA dependent. These results show that it is possible to significantly modify the optoelectronic properties of conjugated polyelectrolytes by choosing different counterions. A parent conjugated backbone can thus be fine-tuned for specific applications.

The spectroscopic and near-field scanning optical microscopy (NSOM) studies of phosphorescent films doped with colloidal gold nanoparticles (NPs) are presented. Films with a high concentration of 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum(II) dispersed in a neutral polymer poly[(methyl methacrylate)-co-(ethyl acrylate)] demonstrate a twofold increase of the phosphorescence quantum yield after the addition of aggregated NPs. In materials doped with unaggregated particles, a decrease of the emission yield is observed. Theoretical modeling of the phosphorescence transients suggests a minimization of the triplet–triplet quenching owing to the presence of fast processes that decrease the concentration of chromophores in the excited state and may be both of radiative and non-radiative origin. NSOM examination of the films reveals increased light emission around large NP clusters. This observation demonstrates significant enhancement of the spontaneous emission rates by the large aggregates, although unaggregated NPs introduce mostly phosphorescence quenching sites.

A series of organic- and water-soluble distyrylbenzene-based two-photon absorption (TPA) fluorophores containing dialkylamino donor groups at the termini was designed, synthesized, and characterized. The central core was systematically substituted to modulate intramolecular charge transfer (ICT). These molecules allow an examination of solvent effects on the TPA cross section (delta) and on the TPA action cross section. In toluene, the delta values follow the order of ICT strength. The effect of solvent on delta is nonmonotonic: maximum delta was measured in an intermediate polarity solvent (THF) and was lowest in water. We failed to find a correlation between the observed solvent effect and previous theoretical predictions. Hydrogen bonding to the donor groups and aggregation of the optical units in water, which are not included in calculational analysis, may be responsible for the discrepancies between experimental results and theory.