Emission in the Biological Window from AIE-Based Carbazole-Substituted Furan-Based Compounds for Organic Light-Emitting Diodes and Random Lasers.

The emission quenching observed in devices utilizing luminescent materials such as solid thin films is a prevalent issue. Consequently, searching for new organic luminescent compounds exhibiting aggregation-induced emission (AIE) behavior and characterized by relatively simple and cost-effective synthesis is of crucial interest among applications from optoelectronics and organic lasing branches. Herein, we report the optical properties of three furan-based carbazole-substituted compounds, namely, tBuCBzSOPh, tBuCBzSPh, and tBuCbzTCF, exhibiting the aforementioned AIE phenomenon.

Preparation of Langmuir-Blodgett Films from Quinoxalines Exhibiting Aggregation-Induced Emission and Their Acidochromism.

The development of aggregation-induced emission (AIE)-exhibiting compounds heavily relies on our evolving comprehension of their behavior at interfaces, an understanding that still remains notably limited. In this study, we explored the preparation of two-dimensional (2D) sensing films from 2,3-diphenylquinoxaline-based diazapolyoxa- and polyazamacrocycles displaying AIE the Langmuir-Blodgett (LB) technique. This systematic investigation highlights the key role of the heteroatom-containing tether of 2,3-diphenylquinoxalines in the successful fabrication of Langmuir layers at the air-water interface and the transfer of AIE-emitting supramolecular aggregates onto solid supports.

Quinoxaline-based azamacrocycles: synthesis, AIE behavior and acidochromism.

The development of luminescent molecular materials has advanced rapidly in recent decades, primarily driven by the synthesis of novel emissive compounds and a deeper understanding of excited-state mechanisms. Herein, we report a streamlined synthetic approach to light-emitting diazapolyoxa- and polyazamacrocycles NCOQ and NCQ ( = 3-10; = 2, 3; = 2-5), incorporating a 2,3-diphenylquinoxaline residue (DPQ). This synthetic strategy based on macrocyclization through Pd-catalyzed amination reaction yields the target macrocycles in good or high yields (46-92%), enabling precise control over their structural parameters.

Imidazo[1,2-]pyridine and Imidazo[1,5-]pyridine: Electron Donor Groups in the Design of D-π-A Dyes.

This work investigates the electron-donating capabilities of two 10-π electron nitrogen bridgehead bicyclic [5,6]-fused ring systems, imidazo[1,2-]pyridine and imidazo[1,5-]pyridine rings. Eight compounds with varying positions of electron-withdrawing moieties (TCF or DCI) coupled to the imidazopyridine ring were synthesized and studied. DCI-containing compounds (-) exhibited a purely dipolar nature with broad absorption bands, weak fluorescence, large Stokes shifts, and strong solvatochromism.

Tuning the Photophysical Properties of Aza-BODIPYs in the Near-Infrared Region by Introducing Electron-Donating Thiophene Substituents.

This study presents the synthesis, the spectroscopic and electrochemical properties of new bis- and tetra-substituted azaboron-dipyrromethene (aza-BODIPY) dyes substituted by different electron donating groups connected to the aza-BODIPY core through a thiophene unit. In line with theoretical calculations, experimental measurements point out the positive impact of the thiophene group that behave as a secondary donor group leading to an enhancement of the intramolecular charge transfer process in comparison to previously reported aza-BODIPY dyes. This heterocycle has also been found to tune the oxidative potential and to stabilize the electro-generated species.

targeting and multimodal imaging of cerebral amyloid-β aggregates using hybrid GdF nanoparticles.

To propose a new multimodal imaging agent targeting amyloid-β (Aβ) plaques in Alzheimer's disease. A new generation of hybrid contrast agents, based on gadolinium fluoride nanoparticles grafted with a pentameric luminescent-conjugated polythiophene, was designed, extensively characterized and evaluated in animal models of Alzheimer's disease through MRI, two-photon microscopy and synchrotron x-ray phase-contrast imaging. Two different grafting densities of luminescent-conjugated polythiophene were achieved while preserving colloidal stability and fluorescent properties, and without affecting biodistribution.

Unveiling the molecular structure and two-photon absorption properties relationship of branched oligofluorenes.

Organic molecules have been intensively studied during the last few decades because of their photonics and biological applications. In this material class, the fluorene molecules present outstanding optical features, for example, high values of two-photon absorption (2PA) cross-sections, visible transparency, and high fluorescence quantum yield. Also, it is possible to improve the nonlinear optical response by modifying the fluorene molecular structure.

Methodology for dyes purification by preparative bidimensional offline reversed-phase high-performance liquid chromatography separation based on mobile phase pH change: Case study of Justicia spicigera.

The extensive characterization of the natural dyes involves the purification of their colored compounds for their structural analysis and stability studies. As most natural compounds being ionizable, herein is presented the optimization of an easy and affordable preparative bidimensional offline reversed-phase high-performance liquid chromatography purification based on mobile phase pH change. At the analytical scale, several combinations of stationary phases and mobile phases at different pH values were investigated first.

Correction: Light-induced chemical activation of a fluorescent probe for monitoring intracellular G-quadruplex structures.

Correction for 'Light-induced chemical activation of a fluorescent probe for monitoring intracellular G-quadruplex structures' by Marco Deiana , , 2021, , 13795-13808, https://doi.org/10.1039/D1NR02855C.

Assembly of Aggregation-Induced Emission Active Bola-Amphiphilic Macromolecules into Luminescent Nanoparticles Optimized for Two-Photon Microscopy In Vivo.

The (Z) and (E)-isomers of an extended tetraphenylethylene-based chromophore with optimized two-photon-induced luminescence properties are separated and functionalized with water-solubilizing pendant polymer groups, promoting their self-assembly in physiological media in the form of small, colloidal stable organic nanoparticles. The two resulting fluorescent suspensions are then evaluated as potential two-photon luminescent contrast agents for intravital epifluorescence and two-photon fluorescence microscopy. Comparisons with previously reported works involving similar fluorophores devoid of polymer side chains illustrate the benefits of later functionalization regarding the control of the self-assembly of the nano-objects and ultimately their biocompatibility toward the imaged organism.

Femtosecond Spectroscopy and Nonlinear Optical Properties of aza-BODIPY Derivatives in Solution.

The fast relaxation processes in the excited electronic states of functionalized aza-boron-dipyrromethene (aza-BODIPY) derivatives (1-4) were investigated in liquid media at room temperature, including the linear photophysical, photochemical, and nonlinear optical (NLO) properties. Optical gain was revealed for nonfluorescent derivatives 3 and 4 in the near infrared (NIR) spectral range under femtosecond excitation. The values of two-photon absorption (2PA) and excited-state absorption (ESA) cross-sections were obtained for 1-4 in dichloromethane using femtosecond Z-scans, and the role of bromine substituents in the molecular structures of 2 and 4 is discussed.

Mimicry can drive convergence in structural and light transmission features of transparent wings in Lepidoptera.

Müllerian mimicry is a positive interspecific interaction, whereby co-occurring defended prey species share a common aposematic signal. In Lepidoptera, aposematic species typically harbour conspicuous opaque wing colour patterns with convergent optical properties among co-mimetic species. Surprisingly, some aposematic mimetic species have partially transparent wings, raising the questions of whether optical properties of transparent patches are also convergent, and of how transparency is achieved.

Effective π-electron number and symmetry perturbation effect on the two-photon absorption of oligofluorenes.

Fluorene-based molecules exhibit significant nonlinear optical responses and multiphoton absorption in the visible region, which, combined with the high fluorescence quantum yield in organic solvents, could make this class of materials potentially engaging in diverse photonics applications. Thus, herein, we have determined the two-photon absorption (2PA) of oligofluorenes containing three, five, and seven repetitive units by employing the wavelength-tunable femtosecond Z-scan technique. Our outcomes have shown that the 2PA cross-section in oligofluorenes presents an enhanced value of around 18 GM per N, in which N is the effective number of π-electrons, for the pure 2PA allowed transition (1A-like → 2A-like).

2D macro-XRF to reveal redacted sections of French queen Marie-Antoinette secret correspondence with Swedish count Axel von Fersen.

During the French Revolution, Marie-Antoinette, queen of France and wife of Louis XVI, maintained a highly secret correspondence with the Swedish count Axel von Fersen, her close friend and rumored lover. An unidentified censor later redacted certain sections of the exchanged letters. This presumably sensitive content has been puzzling historians for almost 150 years.

3D Printing and Pyrolysis of Optical ZrO Nanostructures by Two-Photon Lithography: Reduced Shrinkage and Crystallization Mediated by Nanoparticles Seeds.

Two-photon lithography is a potential route to produce high-resolution 3D ceramics. However, the large shrinkage due to the elimination of an important organic counterpart of the printed material during debinding/sintering remains a lock to further development of this technology. To limit this phenomenon, an original approach based on a composite resin incorporating 45 wt% ultrasmall (5 nm) zirconia stabilized nanoparticles into the zirconium acrylate precursor is proposed to process 3D zirconia microlattices and nanostructured optical surfaces.

On the origin of controlled anisotropic growth of monodisperse gold nanobipyramids.

We elucidate the crucial role of the cetyl trimethylammonium bromide (CTAB) surfactant in the anisotropic growth mechanism of gold nano-bipyramids, nano-objects with remarkable optical properties and high tunability. Atomistic molecular dynamics simulations predict different surface coverages of the CTAB (positively charged) heads and their (bromide) counterions as function of the gold exposed surfaces. High concentration of CTAB surfactant promotes formation of gold nanograins in solution that work as precursors for the smooth anisotropic growth of more elongated nano-bipyramidal objects.

Light-induced in situ chemical activation of a fluorescent probe for monitoring intracellular G-quadruplex structures.

Light-activated functional materials capable of remote control over duplex and G-quadruplex (G4) nucleic acids formation at the cellular level are still very rare. Herein, we report on the photoinduced macrocyclisation of a helicenoid quinoline derivative of binaphthol that selectively provides easy access to an unprecedented class of extended heteroaromatic structures with remarkable photophysical and DNA/RNA binding properties. Thus, while the native bisquinoline precursor shows no DNA binding activity, the new in situ photochemically generated probe features high association constants to DNA and RNA G4s.

Exploring the Concept of Dimerization-Induced Intersystem Crossing: At the Origins of Spin-Orbit Coupling Selection Rules.

Singlet-triplet interconversions (intersystem crossing, ISC) in organic molecules are at the basis of many important processes in cutting-edge photonic applications (organic light-emitting devices, photodynamic therapy, etc.). Selection rules for these transitions are mainly governed by the spin-orbit coupling (SOC) phenomenon.

Near-infrared dyes for two-photon absorption in the short-wavelength infrared: strategies towards optical power limiting.

This work provides an overview of the recent advances in the field of two-photon absorbing chromophores active in the short-wavelength infrared (SWIR) spectral range. Herein the common strategies and main structure-property relationships that lead to near-infrared (NIR) electronic absorption of chromophores are described. A complete review of the molecules that feature two-photon absorption (2PA) beyond 1100 nm is presented for the purpose of further use in optical power limiting applications in the SWIR band.

Spectral characterisation of a traditional Mesoamerican dye: relationship between identification on the 16 century manuscript and composition of plant extract.

Characterisation of vegetal colourants in manuscripts is still a challenging task. Their identification using non-invasive techniques - since sampling is rarely possible - is valid only if there is evidence that the recorded signals are generated by compounds specific to the plant species. Otherwise, more extensive chemical characterisations are required to relate the non-invasive technique signals to the chemical composition of the dye extract and thus avoid misidentification.

Reevaluating the Solution Photophysics of Tetraphenylethylene at the Origin of their Aggregation-Induced Emission Properties.

Although tetraphenylethylene (TPE) and its derivatives have been the most commonly used building blocks in the construction of molecules with aggregation-induced emission (AIE) properties, no absolute consensus exists regarding the mechanisms at the origin of the phenomenon. Restriction of intramolecular rotations (RIR) of peripheral phenyls has historically been a dominant paradigm, which has served as a valuable guideline in the molecular engineering of AIEgens. Yet, an increasing number of recent works have established that photoisomerization or photocyclization may actively participate in the nonradiative dissipation of the excitation energy.

Hybrid multimodal contrast agent for multiscale investigation of neuroinflammation.

Neuroinflammation is a process common to several brain pathologies. Despites its medical relevance, it still remains poorly understood; there is therefore a need to develop new in vivo preclinical imaging strategies to monitor inflammatory processes longitudinally. We here present the development of a hybrid imaging nanoprobe named NP3, that was specifically designed to get internalized by phagocytic cells and imaged in vivo with MRI and bi-photon microscopy.

Benzothiadiazole-Substituted Aza-BODIPY Dyes: Two-Photon Absorption Enhancement for Improved Optical Limiting Performances in the Short-Wave IR Range.

Aza-boron dipyrromethenes (aza-BODIPYs) presenting a benzothiadiazole substitution on upper positions are described. The strong electron-withdrawing effect of the benzothiadiazole moiety permits enhancement of the accepting strength and improves the delocalization of the aza-BODIPY core to attain a significant degree of electronic communication between the lower donating groups and the upper accepting groups. The nature of the intramolecular charge transfer is studied both experimentally and theoretically.

Two-Photon Absorbing AIEgens: Influence of Stereoconfiguration on Their Crystallinity and Spectroscopic Properties and Applications in Bioimaging.

This paper aims at designing chromophores with efficient aggregation-induced emission (AIE) properties for two-photon fluorescence microscopy (2PFM), which is one of the best-suited types of microscopy for the imaging of living organisms or thick biological tissues. Tetraphenylethylene (TPE) derivatives are common building blocks in the design of chromophores with efficient AIE properties. Therefore, in this study, extended TPE AIEgens specifically optimized for two-photon absorption (2PA) are synthesized and the resulting (/) isomers are separated using chromatography on chiral supports.

Impact of Ion-Pairing Effects on Linear and Nonlinear Photophysical Properties of Polymethine Dyes*.

The two-photon absorption (2PA) and photophysics of heptamethine dyes featuring cyanine or dipolar electronic structures have been compared for the first time. The perfectly delocalized cyanine system is classically characterized by a two-photon transition matching the vibronic component of its lower energy absorption band. The dipolar species is generated by ion-pairing with a hard counterion in a non-dissociating solvent and displays significant modifications oft he optical properties, including a significant hypochromic shift of absorption, weaker emission and 2PA matching the lower energy transition, thus revealing symmetry breaking within the polymethine electronic structure.