Exploring contrast-enhancing staining agents for studying adipose tissue through contrast-enhanced computed tomography.

Contrast-enhanced computed tomography offers a nondestructive approach to studying adipose tissue in 3D. Several contrast-enhancing staining agents (CESAs) have been explored, whereof osmium tetroxide (OsO4) is the most popular nowadays. However, due to the toxicity and volatility of the conventional OsO4, alternative CESAs with similar staining properties were desired. Hf-WD 1:2 POM and Hexabrix have proven effective for structural analysis of adipocytes using contrast-enhanced computed tomography but fail to provide chemical information. This study introduces isotonic Lugol's iodine (IL) as an alternative CESA for adipose tissue analysis, comparing its staining potential with Hf-WD 1:2 POM and Hexabrix in murine caudal vertebrae and bovine muscle tissue strips. Single and sequential staining protocols were compared to assess the maximization of information extraction from each sample. The study investigated interactions, distribution, and reactivity of iodine species towards biomolecules using simplified model systems and assesses the potential of the CESA to provide chemical information. (Bio)chemical analyses on whole tissues revealed that differences in adipocyte gray values post-IL staining were associated with chemical distinctions between bovine muscle tissue and murine caudal vertebrae. More specific, a difference in the degree of unsaturation of fatty acids was identified as a likely contributor, though not the sole determinant of gray value differences. This research sheds light on the potential of IL as a CESA, offering both structural and chemical insights into adipose tissue composition.

Palladium-Catalyzed Arylations towards 3,6-Diaryl-1,3a,6a-triazapentalenes and Evaluation of Their Fluorescence Properties.

Methyl 4-(1,3a,6a-triazapentalen-3-yl)benzoate (TAP1) shows interesting properties as a small molecule fluorophore. In the search for post-functionalization methods, palladium-catalyzed arylation reactions were demonstrated. Direct CH arylation reactions of TAP1 with various aryl halides resulted in 3,6-diaryltriazapentalenes TAP4, although mostly in poor yields. Bromination of TAP1 followed by Suzuki coupling, on the other hand, requires a more delicate procedure, but gave arylated products with the same regiochemistry (TAP4) in moderate to good yields. The structure of 6-phenyltriazapentalene TAP4a was confirmed by crystallographic analysis. In addition, the effect of the C6 arylation on the fluorescent properties of 3-aryl-1,3a,6a-triazapentalenes was studied in dichloromethane at room temperature and in 2-methyltetrahydrofuran at 77 K, while the photophysical properties of two saponified derivatives were measured in acetonitrile.

Photophysical Properties of Silver Clusters in Faujasite Zeolites: Does the Crystal Size Matter?

Electrostatic interactions between the zeolite cavity and confined noble-metal nanoparticles govern the photophysical properties of these materials. A better understanding of these interactions can afford new perspectives in optoelectronics applications. We investigated this interplay by revealing the peculiar photophysical properties of Ag clusters embedded in nanosized faujasite zeolite structures. Crystal size and steady state optical properties were characterized via integrated light and electron microscopy (ILEM) and steady state spectroscopy. Extensive time-resolved spectroscopy experiments performed on femtosecond to millisecond time scales revealed excited state dynamics that are intriguingly different from those observed for their micrometer sized counterpart. Multiscale modeling investigations were performed to rationalize the effect of the crystal size on the photophysical properties. Our results indicate that for the nanosized crystals, the emissive properties as well as the radiative and nonradiative processes involving the Ag clusters are dramatically dependent on the surface charge density and surface charge balance.

Weaving Aerogels into 3D Ordered Hyperelastic Hybrid Carbon Assemblies.

The development of a 3D carbon assembly with a combination of extraordinary electrochemical and mechanical properties is desirable yet challenging. Herein, an ultralight and hyperelastic nanofiber-woven hybrid carbon assembly (NWHCA) is fabricated by nanofiber weaving of isotropic porous and mechanical brittle quasi-aerogels. Upon subsequent pyrolysis, metallogel-derived quasi-aerogel hybridization and nitrogen/phosphorus co-doping are integrated into the NWHCA. Finite element simulation indicates that the 3D lamella-bridge architecture of NWHCA with the quasi-aerogel hybridization contributes to resisting plastic deformation and structural damage under high compression, experimentally demonstrated by complete deformation recovery at 80% compression and unprecedented fatigue resistance (>94% retention after 5000 cycles). Due to the superelasticity and quasi-aerogel integration, the zinc-air battery assembled based on NWHCA shows excellent electrochemical performance and flexibility. A proof-of-concept integrated device is presented, in which the flexible battery powers a piezoresistive sensor, using the NWHCA as the air cathode and the elastic conductor respectively, which can detect full-range and sophisticated motions while attached to human skin. The nanofiber weaving strategy allows the construction of lightweight, superelastic, and multifunctional hybrid carbon assemblies with great potential in wearable and integrated electronics.

Single-particle optical study on the effect of chloride post-treatment of MAPbI3 nano/microcrystals.

Surface passivation by post-treatment with methylammonium chloride (MACl) is regarded as a promising strategy to suppress surface defects in organic-inorganic lead halide perovskites and elevate the efficiency of solar cells based on these materials. However, traditional MACl post-treatment methods often impede the performance of the final device, due to the creation of additional unwanted defects. Herein, we report a novel approach for chloride post-treatment by applying a mixed ethanol/toluene solvent and validate its beneficial effect on the structure, composition, and optical properties of methylammonium lead iodide nano/microcrystals and related photosensitive devices. An optimized (mild) Cl content improves the crystallinity, enhances photoluminescence (PL) intensity, provides longer PL lifetimes, and induces brighter and longer ON-states in single-particle emission trajectories. On top of a reduction in the population percentage of crystals showing gradual photodegradation, our Cl-treatment method even leads to photobrightening. Additionally, the extent of carrier communication throughout spatially distant nanodomains enhances after MACl-based post-modification. Our results demonstrate that surface-bound Cl significantly reduces the trap density induced by under-coordinated lead ions or iodide vacancies and reveal the importance of a careful consideration of the applied Cl content to avoid the generation of high-bandgap MAPbCl3 heterojunctions upon excessive Cl treatment. Importantly, significant trap passivation upon MACl treatment translates into a more stable and elevated photocurrent in the corresponding photodetector device. We anticipate these findings will be beneficial for designing durable, high-performance lead halide perovskite photonic devices.

Origin of the polychromatic photoluminescence of zeolite confined Ag clusters: temperature- and co-cation-dependent luminescence.

Zeolite confined silver clusters (AgCLs) have attracted extensive attention due to their remarkable luminescent properties, but the elucidation of the underlying photophysical processes and especially the excited-state dynamics remains a challenge. Herein, we investigate the bright photoluminescence of AgCLs confined in Linde Type A zeolites (LTA) by systematically varying the temperature (298-77 K) and co-cation composition (Li/Na) and examining their respective influence on the steady-state and time-resolved photoluminescence. The observed polychromatic emission of the tetrahedral Ag4(H2O) n 2+ clusters ranges from orange to violet and three distinct emitting species are identified, corresponding to three long-lived triplet states populated consecutively and separated by a small energy barrier. These long-lived species are at the origin of the polychromatic luminescence with high photoluminescence quantum yields. Furthermore, the Li-content dependence of decay times points to the importance of guest-host-guest interactions in tuning the luminescent properties with a 43% decrease of the dominating decay time by increasing Li content. Based on our findings, a simplified model for the photophysical kinetics is proposed that identifies the excited-state processes. The results outlined here pave the way for a rational design of confined metal clusters in various frames and inspire the specified applications of Ag-zeolites.

Synthesis and Spectroscopic Properties of 1,2,3-Triazole BOPAHY Dyes and Their Water-Soluble Triazolium Salts.

Water-soluble BOPAHY fluorophores have not yet been reported. The potential of 1,2,3-triazolium salts for the formation of water-soluble chromophores is explored. 1,2,3-Triazole-substituted pyrroles were synthesized in a metal-free pathway and alkylated to obtain water-soluble 1,2,3-triazolium BOPAHY dyes. High fluorescence quantum yields were observed for triazole-bridged BOPAHY dyes in DCM and moderate fluorescence quantum yields for 1,2,3-triazolium-bridged BOPAHY chromophores in DCM and water. The fluorescence of the freely rotatable 1,2,3-triazolium-linked BOPAHYs is partially quenched in water.

New Metal-Free Route towards Imidazole-Substituted Uridine.

Nucleosides with a bi(hetero)aryl nucleobase have unique potential applications as antiviral drugs and molecular probes. The need for transition metal catalysis to synthesize these nucleosides from pre-functionalized building blocks and the use of nucleobase protection groups results in expensive and tedious syntheses. Herein we report that 5-imidazolyl-uracil can be obtained by scalable Van Leusen imidazole synthesis and regioselectively introduced on ribose to obtain the desired nucleoside in a 5 step synthesis (total yield 55 %). The 5-imidazolyl moiety leads to improved fluorescence properties. The only side-product formed was characterized by 2D-NMR and X-ray crystallography and could be suppressed during synthesis in favor of the desired product.

BOPAHY: a doubly chelated highly fluorescent pyrrole-acyl hydrazone -BF2 chromophore.

New easily functionalisable and highly fluorescent BOPAHY chromophores are synthesised via a one-pot two-step reaction starting from commercially available pyrrole-2-carbaldehydes and respective acyl hydrazides in the presence of BF3·OEt2. Most importantly, all BOPAHY dyes show excellent photophysical properties with quantum yields up to 0.92. Steady-state spectroscopy and quantum chemical calculations provide a first insight into these promising properties.

Bay-Substituted Thiaza[5]helicenes: Synthesis and Implications on Structural and Spectroscopic Properties.

A series of bay-substituted thiaza[5]helicenes was synthesized to investigate the effect of different substituents on the properties of these helicenes. These thiaza[5]helicenes with different substituents were prepared in a straightforward manner through indole- and benzo[b]thiophene synthesis, palladium-catalyzed Suzuki coupling, oxidative cyclization, and functional group interconversion reactions. We investigated the impact of these different bay area substituents compared to the unsubstituted thiaza[5]helicene on the structural parameters and studied the steady-state electronic spectroscopy of these thiaza[5]helicenes in toluene and acetonitrile. We found that different functional groups influence the solid state structure and spectroscopic properties, but a single substituent in the bay area of a thiaza[5]helicene was not enough to prevent enantiomerization at room temperature.

5,10-Dihydrobenzo[ a]indolo[2,3- c]carbazoles as Novel OLED Emitters.

The excited-state dynamics of four 5,10-dihydrobenzo[ a]indolo[2,3- c]carbazoles in solution and in films were studied with stationary and time-resolved spectroscopies. The solvent dependency of the photophysics reveals no appreciable dipole moment in the ground state. In the excited state, electron-withdrawing substituents contribute to an outspoken charge-transfer character. In films, although the molecules are mostly present as monomers, the excited-state dynamics are characterized by a cascade of energy-transfer processes to excited dimers and aggregates which dominate the photoluminescence (PL) spectra. The properties of the aggregates depend on the used substituents. The electroluminescence spectra obtained from single-layer and multilayer devices mostly resemble the PL spectra, but show contributions from other species such as electromers or electroplexes. It is inferred that the different substituents lead to a different packing of the carbazole moieties, each of which has different mobilities and recombination probabilities.

Modelling absorption and emission of a meso-aniline-BODIPY based dye with molecular mechanics.

Absorption and emission spectra of 8-(4-dimethylaminophenyl)-1,3,5,7-tetramethyl-BODIPY have been calculated using Coupled Cluster (CC) approaches, Time-Dependent Density Functional Theory (TD-DFT) and a QM-informed MM approach. In the case of TD-DFT calculations solvent effects were included using the linear-response (LR), corrected linear response (cLR) and state specific (SS) Polarizable Continuum Model (PCM). We show that range-separated functionals give results in reasonable agreement with coupled cluster methods but both tend to overestimate excitation energies. Furthermore, we show that the SS-PCM approach is unable to provide a quantitative description of solvent effects in these systems, especially for the highly challenging charge-separated charge-transfer state. In contrast, the QM-informed MM approach gives results in good agreement with experiment and we propose a scheme which can be used to directly compare theoretically obtained spectra with experimental ones.