The Strong Light-Emission Materials in the Aggregated State: What Happens from a Single Molecule to the Collective Group

Advances in aggregation-induced emission luminogens for biomedicine: From luminescence mechanisms to diagnostic applications

Advancements in early detection have demonstrated the significance of biomarkers as indicators of health and disease. Traditional detection methods often face limitations, such as low sensitivity and time consumption. Fluorescence-based techniques are considered promising approaches because of their noninvasiveness and rapid response. However, these conventional methods have some drawbacks, such as low quantum yield, photobleaching, and aggregation-caused quenching. Recently, aggregation-induced emission (AIE) has emerged as a potential alternative, characterized by luminous emission upon aggregation, thus improving detection sensitivity and stability. This review explores the recent advancements in AIE luminogens (AIEgens) in biomedical engineering, with a particular focus on their application in biomarker detection. Here, we discuss the different types of AIE mechanisms and their advantages in disease diagnosis and imaging. In addition, we summarize the development of various AIEgen-based probes for the detection of diverse biomarkers. Finally, we address the remaining challenges and future directions for AIE materials in modern biomedical engineering, emphasizing the potential of AIEgens in biomarker detection and disease diagnosis strategies.

Synthesis of (Z)-Enediynes via Stereoinvertive Nucleophilic Substitution of (E)-Sulfonylethenes with Arylethynide, and Their Aggregation-Induced Optical Properties

(Z)-Enediynes were successfully synthesized from a trio of terminal ethynes through consecutive three-step reactions: iodosulfonylation of ethyne with I2/PhSO2Na, followed by ethynylations of iodo and sulfonyl moieties of the resulting iodosulfonylethene via Sonogashira-Hagihara coupling and nucleophilic addition-elimination, respectively. The molecular structure of the obtained (Z)-enediyne was fully characterized by X-ray crystal structure analysis, revealing that the nucleophilic substitution of (E)-sulfonylethene with arylethynide underwent a selective stereoinversion. The (Z)-enediynes exhibited photoluminescence in both the solution and solid states (crystals and powders). Ph2N-substituted derivatives showed remarkable solvatofluorochromism, and upon replacing the solvent from toluene to acetonitrile, the emission color changed from blue to yellow.

Hydrogen Bond-Mediated Self-Assembly of Carbon Dots Enabling Precise Tuning of Particle and Cluster Luminescence for Advanced Optoelectronic Applications

The effective control over the self-assembly process of carbon dots (CDs) and their cluster luminescence in the aggregated state is of paramount significance and challenge. This study, for the first time, systematically explores the photoluminescent behavior of CDs in their aggregated state, which is less understood compared to their discrete state. By investigating the effects of concentration and solvent environment, it's demonstrated that CDs could exhibit dual emission properties, shifting from blue particle emissions to red cluster emissions as they aggregate. The key to this tunable luminescence lies in hydrogen bonding, which drives the self-assembly of CDs and modulates their photo physical properties. These findings reveal that through precise control of aggregation, CDs can be engineered for advanced optoelectronic applications, including tunable light-emitting diodes (LEDs), secure information encryption, and fingerprint authentication. This report not only deepens the understanding of the underlying mechanisms governing CDs' cluster luminescence but also introduces a novel approach to exploiting their unique properties for technological innovation.

Ammonia and temperature sensing applications using fluorometric and colorimetric microparticles and polymeric films doped with BODIPY-emitters

Four functionalized BODIPY derivatives (BDP1 to BDP4) were synthesized and their optical properties investigated both in solution and when incorporated into a solid matrix. Recognizing the versatility of BODIPY derivatives and the increasing interest in developing new luminescent organic dyes embedded in polymers, the BODIPY derivatives were dispersed into two types of polymeric matrices: Poly(methyl methacrylate) (PMMA) and Thermoplastic Polyurethane (TPU), both as films and microparticles. This resulted in eight new BODIPY-doped polymer films and eight types of BODIPY-doped polymeric microparticles for use in aqueous solutions. The integration of the BODIPY dyes into the polymeric matrices combines the unique properties of the polymer films, such as porosity, flexibility, and elasticity, with the excellent photophysical characteristics of the BODIPYs. Importantly, the dispersion minimized issues such as aggregation-caused quenching commonly observed in solid-state luminescent materials. The thermometric responses of all polymer films were evaluated by studying their solid-state emission spectra in the 25-200 °C temperature range. The reversibility of these temperature-induced changes was also assessed, revealing excellent recovery of luminescence. These promising results suggest these materials could have applications as fluorescent thermometric sensors. Furthermore, we explored the potential of the brominated (BDP3) and chalcogenated (BDP4) BODIPY derivatives as ammonia sensors. The two derivatives produced yellow fluorescent products upon interaction with the analyte. Kinetic studies using solid-state emission spectra of BDP4@TPU and BDP4@PMMA showed significant differences in reaction rates (minutes for BDP4@TPU and hours in the case of BDP4@PMMA) attributable to the higher permeability of TPU when compared with PMMA. Detection and quantification of ammonia concentration were conducted by means of simple photographic analysis, measuring the "R" (red) and "G" (green) components of RGB color parameters. The results from the photographic method correlated well with the results from fluorimetric spectroscopy studies. The photographic analysis is straightforward, portable, and does not require expensive equipment. Finally, we successfully applied polymeric microparticles doped with BODIPYs to detect ammonia in water, demonstrating their effectiveness without the need for organic solvents. This highlights their potential for environmental monitoring and other applications requiring sensitive and selective detection methods.

Charge balanced aggregation: A universal approach to aqueous organic nanocrystals

Organic nanocrystals, particularly those composed of conjugated molecules, hold immense potential for various applications. However, their practical utility is often hindered by the challenge of achieving stable aqueous dispersions, which are essential for biological compatibility and effective delivery. This study introduces a novel and versatile strategy for preparing stable aqueous organic nanocrystals using a modified reprecipitation method. We demonstrate the broad applicability of this approach by successfully preparing a diverse library of nanocrystals from 27 conjugated molecules. Our findings reveal a charge-balanced aggregation mechanism for nanocrystal formation, highlighting the crucial role of surface charge in controlling particle size and stability. Based on this mechanism, we establish a comprehensive molecular combination strategy that directly links molecular properties to colloidal behaviour, enabling the straightforward prediction and preparation of stable aqueous dispersions without the need for excipients. This strategy provides a practical workflow for tailoring the functionality of these nanocrystals for a wide range of applications. To illustrate their therapeutic potential, we demonstrate the enhanced efficacy of these nanocrystals in treating acute ulcerative colitis, myocardial ischemia/reperfusion injury, and cancer in mouse models. This work paves the way for developing next-generation nanomaterials with tailored functionalities for diverse biomedical applications.

Multiscale Materials Engineering via Self-Assembly of Pentapeptide Derivatives from SARS CoV E Protein

Short peptide-based supramolecular hydrogels hold enormous potential for a wide range of applications. However, the gelation of these systems is very challenging to control. Minor changes in the peptide sequence can significantly influence the self-assembly mechanism and thereby the gelation propensity. The involvement of SARS CoV E protein in the assembly and release of the virus suggests that it may have inherent self-assembling properties that can contribute to the development of hydrogels. Here, three pentapeptide sequences derived from C-terminal of SARS CoV E protein are explored with same amino acid residues but different sequence distributions and discovered a drastic difference in the gelation propensity. By combining spectroscopic and microscopic techniques, the relationship between peptide sequence arrangement and molecular assembly structure are demonstrated, and how these influence the mechanical properties of the hydrogel. The present study expands the variety of secondary structures for generating supramolecular hydrogels by introducing the 310-helix as the primary building block for gelation, facilitated by a water-mediated structural transition into β-sheet conformation. Moreover, these Fmoc-modified pentapeptide hydrogels/supramolecular assemblies with tunable morphology and mechanical properties are suitable for tissue engineering, injectable delivery, and 3D bio-printing applications.

Near-Infrared Fluorescent Turn-On Probe for Selective Detection of Hypochlorite in Aqueous Medium and Live Cell Imaging

Hypochlorite, as an important reactive oxygen species (ROS), plays a vital role in many physiological and pathological processes, but an excess concentration of hypochlorite (ClO-) may become toxic to humans and cause disease. Hence, the selective and rapid detection of hypochlorite (ClO-) is necessary for human safety. Here, we report a novel near-infrared (NIR) fluorescence "turn-on" and highly selective benzophenoxazinium chloride-based fluorescent probe, BPH (benzophenoxazinium dihydroxy benzaldehyde), for hypochlorite detection. Due to hypochlorite-induced vicinal diol oxidation to the corresponding ortho benzoquinone derivative, the photoinduced electron transfer (PET) process, which was operating from vicinal diol to the benzophenoxazinium chloride receptor moiety, was suddenly inhibited, as a result of which strong NIR fluorescence "turn-on" emission was observed. The detection limit of BPH was found to be 2.39 × 10-10 M, or 0.23 nM. BPH was successfully applied for exogenous and endogenous hypochlorite detection in live MDA-MB 231 cells.

Ultra-Wide Modulation and Reversible Reconfiguration of a Flexible Organic Crystalline Optical Waveguide Between 645 and 731 nm

Flexible organic crystalline optical waveguides, which deliver input or self-emit light through various dynamic organic crystals, have attracted increasing attention in the past decade. However, the modulation of the waveguide output relies on chemical design and substituent modification, being time-consuming and laborious. Here we report an elastic organic crystal that displays long-distance light transduction up to 2.0 cm and an ultra-wide modulation of crystalline optical waveguides between red (645 nm) and near infrared (731 nm) in both the pristine and the elastically bent states based on a pre-designed self-absorption effect. The flexible organic crystalline optical waveguides can be precisely and reversibly reconfigured by controlling the irradiation point. In addition, deep-red amplified spontaneous emission (ASE) that is able to transduce through a 5.0 mm bent crystal with an ultra-low optical loss coefficient of 0.093 dB/mm has been attained. To the best of our knowledge, this is the first report of flexible organic ASE waveguides. The present study not only provides a simple yet effective strategy to remarkably modulate flexible organic crystalline optical waveguides but also demonstrates the superiority of lasing over normal emission as flexible optical communication elements.

Single-component TADF gels: study of the positional isomer effect on gelation and morphological effect on conductivity

The gelation of two TADF positional isomers, 4BPy-mDTC and BPy-DTC, was explored. Among these emitters, only 4BPy-mDTC forms stable organogels due to the optimized intermolecular interactions. Interestingly, the morphology of the gel can be tuned from fibre to fettuccine by changing the solvents. The electrical conductivity of the self-assembly can also be increased from 8.05 × 10-4 S m-1 to 6.05 × 10-3 S m-1 by tuning the morphology.

A Novel AIE-Active Salicylaldehyde-Schiff Base Probe with Carbazole Group for Al3+ Detection in Aqueous Solution

A donor-acceptor Schiff-base fluorescent probe BKS with chelation enhanced fluorescence (CHEF) mechanism was designed and synthesized via benzophenone(Acceptor), salicylaldehyde and carbazole(Donor) for Al3+ detection, which exhibited typical aggregation-induced emission (AIE) characteristic. BKS probe could provide outstanding selectivity to Al3+ with a prominent fluorescence "turn-on" at 545 nm in a wide pH range from 2 to 11. By the Job's plot, the binding stoichiometry ratio of probe BKS to Al3+ was determined 1:1. The proposed strategy offered a very low limit of detection at 1.486 µM in THF/H2O(V/V = 1:4, HEPBS = 10 mM, pH = 7.40), which was significantly lower than the standard of WHO (Huang et al., Microchem J 151:104195, 2019)-(Yongjie Ding et al., Spectrochim Acta Mol Biomol Spectrosc 167:59-65, 2021) guidelines for drinking water. BKS probe could provide a wider linear detection range of 50 to 500 µM. Furthermore, the probe could hardly be interfered by other examined metal ions. The analysis of Al3+ in real water samples with appropriate recovery (100.72 to 102.85) with a relative standard deviation less than 2.82% indicated the accuracy and precision of BKS probe and the great potential in the environmental monitoring of Al3+.

Responsive Organic Fluorescent Aggregates Based on Ion-π Interactions Away from Fluorescent Conjugated Groups

Responsive organic luminescent aggregates have a wide range of application fields, but currently there is still a lack of reasonable molecular design strategies. Introducing ion-π interactions into molecules can effectively alter their luminescent properties. However, current research typically focuses on ion localization at luminescent conjugated groups with the strong interaction forces. In this work, we introduce the flexible alkoxy chain spacers between fluorescent conjugated groups and ion-π interaction sites, and then adjust the fluorescence performance of the molecule by changing the strength of ion-π interactions. Bromine ion-based molecules with strong ion-π interactions exhibit high and stable fluorescence quantum yields in crystals and amorphous powders under the external stimuli. Hexafluorophosphate ion-based molecules with weak ion-π interactions have the high fluorescence quantum yield in crystals and very low fluorescence quantum yield in amorphous powders, showing variable fluorescence intensities under external stimuli. This demonstrates a new class of responsive organic luminescent solid-state materials.

Designing Dual-State and Aggregation-Induced Emissive Luminogens from Lignocellulosic Biosourced Molecules

Utilizing lignocellulosic biosourced platforms, we synthesized novel cyanostilbene (CS) derivatives featuring the 3,4-dimethoxyphenyl moiety. These derivatives were investigated for their emission properties in both solution and solid states. The two simple CS derivatives exhibit very weak luminescence in solution but significant luminescence in the solid state, indicating distinct Aggregation-Induced Emission (AIE) characteristic. Furthermore, combining these two CS units, without conjugation and with quasi perpendicular orientation, results in a Dual-State Emission (DSE) fluorophore showing luminescence both in solution and solid states. X-ray crystallography studies on the solid-state compounds reveal a structure-emission relationship, demonstrating that the colour emission correlates with the conformations adopted by the molecules in the solid state, which influence the type of stacking.

Recent advances in tunable solid-state emission based on α-cyanodiarylethenes: from molecular packing regulation to functional development

The design and development of organic solid-state luminescent materials stand as crucial pillars within the realm of contemporary photofunctional materials. Overcoming challenges such as concentration quenching and achieving tailored luminescent properties necessitates a judicious approach to molecular structure design and the strategic utilization of diverse stimuli to modulate molecular packing patterns. Among the myriad candidates, α-cyanodiarylethenes (CAEs) emerge with distinctive solid-state luminescent attributes, capable of forming self-assembled packing structures with varying degrees of π-π stacking. This characteristic endows them with potential in the field of intelligent molecular responsive materials and optoelectronic devices. This tutorial review embarks on an exploration of design strategies geared towards attaining tunable solid-state emission through customized packing of CAEs. It explores the utilization of stimuli responses, including such as mechanical forces, light irradiation, solvent interactions, thermal influences, as well as the utilization of co-assembly methodologies. The overarching aim of this review is to provide a widely applicable platform fostering the flourishing development of modern organic photofunctional materials through integrating principles of molecular engineering, organic optoelectronics, and materials science.

Highly Luminescent TCNQ in Melamine

Optical properties of molecules change drastically as a result of interactions with surrounding environments as observed in solutions, clusters, and aggregates. Here, we make 7,7,8,8-tetracyanoquinodimethane (TCNQ) highly luminescent by encapsulating it in crystalline melamine. Colored single crystals are synthesized by slow evaporation of aqueous tetrahydrofuran solutions of melamine and TCNQ. Single-crystal X-ray diffraction reveals the lattice structure of pure melamine, meaning that the color is of impurities. Both mass spectrometry and UV-vis spectroscopy combined with density-functional theory calculations elucidate that the impurity species are neutral TCNQ and its oxidation product, dicyano-p-toluoyl cyanide anion (DCTC-), whose concentrations in a melamine crystal can be controlled by adjusting the molar ratio between melamine and TCNQ in the precursor solution. Fluorescence excitation-emission wavelength mappings on the precursor solutions illustrate dominant emissions from DCTC- while the emission from TCNQ is quenched by the resonance energy transfer to DCTC-. On the contrary, TCNQ in crystalline melamine is a bright fluorophore whose emission wavelength centered at 450 nm with internal quantum yields as high as 19% and slow fluorescence lifetimes of about 2 ns. The method of encapsulating molecules into transparent melamine would make many other molecules fluorescent in solids.

Photoluminescence variations in organic fluorescent crystals by changing the surface energy of the substrate

Organic fluorescent crystals were obtained using single-benzene-based diethyl 2,5-dihydroxyterephthalate (DDT) molecules through crystallization from a droplet of the DDT solution on an Au substrate. To control the size of the DDT crystals, the surface energy of the Au substrate was modified with air plasma treatment, producing a hydrophilic surface and a hydrophobic self-assembled monolayer (SAM) coating. The size of DDT crystals increased as the surface energy of the substrate decreased. The averaged cross-section area of the DDT crystals on the Au substrates increased in the order of the air-plasma-treated substrate (∼23.43 μm2) < pristine substrate (∼225.6 μm2) < hydrophobic SAM-coated substrate (∼2240 μm2). On the other hand, the main emission of the DDT crystals redshifted from blue to green as the crystal size increased, which is related to the aggregation of the DDT crystals. Moreover, the coffee-ring effect during the DDT crystallization was hindered by controlling the solvent evaporation conditions. As examples of the application of the proposed technique, patterned DDT crystals were obtained using selectively patterned hydrophobic and hydrophilic substrates.

Insights into mechanistic interpretation of crystalline-state reddish phosphorescence of non-planar π-conjugated organoboron compounds

Metal-free room-temperature phosphorescent (RTP) materials are attracting attention in such applications as organic light-emitting diodes and bioimaging. However, the chemical structures of RTP materials reported thus far are mostly predominantly based on π-conjugated systems incorporating heavy atoms such as bromine atoms or carbonyl groups, resulting in limited structural diversity. On the other hand, triarylboranes are known for their strong Lewis acidity and deep LUMO energy levels, but few studies have reported on their RTP properties. In this study, we discovered that compounds based on a tetracyclic structure containing boron, referred to as benzo[d]dithieno[b,f]borepins, exhibit strong solid-state reddish phosphorescence even in air. Quantum chemical calculations, including those for model compounds, revealed that the loss of planarity of the tetracyclic structure increases spin-orbit coupling matrix elements, thereby accelerating the intersystem crossing process. Moreover, single-crystal X-ray structural analysis and natural energy decomposition analysis suggested that the borepin compounds without bromine or oxygen atoms, unlike typical RTP materials, exhibit red-shifted phosphorescence in the crystalline state owing to structural relaxation in the T1 state. Additionally, the borepin compounds showed potential application as bioimaging dyes.

Unique Visualization Growth Process of Long-Lived Room Temperature Phosphorescence in Polymer System

Recently, embedding organic phosphors into the polyvinyl alcohol (PVA) matrix has emerged as a convenient strategy to obtain efficient long-lived room temperature phosphorescence (RTP) via forming strong intermolecular hydrogen bonds with organic phosphors to minimize nonradiative relaxations. Regrettably, it is discovered that PVA is unable to trigger RTP emission when a novel functional phosphor THBE containing six extended biphenyl formaldehyde arms is doped into PVA matrix. Surprisingly, the excellent long-lived RTP emission can be easily obtained by doping THBE into PVA analogs, poly(vinyl alcohol-co-ethylene) (PVA-co-PE). The unique visualization growth process (i.e., white streak generation) of long-lived RTP is observed by UV light-driven aggregation of functional molecules THBE in PVA-co-PE matrix. The phosphorescent intensity of the luminescent film is enhanced by 55 times, from 729 to 40,785 a.u., and its phosphorescence lifetime is increased by 38 times, from 37.08 to 1415.41 ms. Due to the dynamically reversible RTP performance, as well as the permeability, flexibility, and wrinkle-free properties of the luminescent film, it can be utilized to create cutting-edge information storage devices.

Machine Learning Prediction of Quantum Yields and Wavelengths of Aggregation-Induced Emission Molecules

The aggregation-induced emission (AIE) effect exhibits a significant influence on the development of luminescent materials and has made remarkable progress over the past decades. The advancement of high-performance AIE materials requires fast and accurate predictions of their photophysical properties, which is impeded by the inherent limitations of quantum chemical calculations. In this work, we present an accurate machine learning approach for the fast predictions of quantum yields and wavelengths to screen out AIE molecules. A database of about 563 organic luminescent molecules with quantum yields and wavelengths in the monomeric/aggregated states was established. Individual/combined molecular fingerprints were selected and compared elaborately to attain appropriate molecular descriptors. Different machine learning algorithms combined with favorable molecular fingerprints were further screened to achieve more accurate prediction models. The simulation results indicate that combined molecular fingerprints yield more accurate predictions in the aggregated states, and random forest and gradient boosting regression algorithms show the best predictions in quantum yields and wavelengths, respectively. Given the successful applications of machine learning in quantum yields and wavelengths, it is reasonable to anticipate that machine learning can serve as a complementary strategy to traditional experimental/theoretical methods in the investigation of aggregation-induced luminescent molecules to facilitate the discovery of luminescent materials.

Precise molecular engineering for the preparation of pyridinium photosensitizers with efficient ROS generation and photothermal conversion

Organic photosensitizers (PSs) with aggregation-induced emission properties have great development potential in the integrated application of multi-mode diagnosis and treatment of photodynamic therapy (PDT) and photothermal therapy (PTT). However, preparing high-quality PSs with both optical and biological properties, high reactive oxygen species (ROS) and photothermal conversion ability are undoubtedly a great challenge. In this work, a series of pyridinium AIE PSs modified with benzophenone have been synthesized. A wide wavelength range of fluorescent materials was obtained by changing the conjugation and donor-acceptor strength. TPAPs5 has a significant advantage over similar compounds, and we have also identified the causes of high ROS generation and high photothermal conversion in terms of natural transition orbitals, excited state energy levels, ground-excited state configuration differences and recombination energy. Interestingly, migration of target sites was also found in biological imaging experiments, which also provided ideas for the design of double-targeted fluorescent probes. Therefore, the present work proposed an effective molecular design strategy for synergistic PDT and PTT therapy.

Controllable π-π coupling of intramolecular dimer models in aggregated states

π-π coupling as a common interaction plays a key role in emissions, transport and mechanical properties of organic materials. However, the precise control of π-π coupling is still challenging owing to the possible interference from other intermolecular interactions in the aggregated state, usually resulting in uncontrollable emission properties. Herein, with the rational construction of intramolecular dimer models and crystal engineering, π-π coupling can be subtly modulated by conformation variation with balanced π-π and π-solvent interactions and visualized by green-to-blue emission switching. Moreover, it can rapidly respond to temperature, pressure and mechanical force, affording a facile way to modulate π-π coupling in situ. This work contributes to a deeper understanding of the internal mechanism of molecular motions in aggregated states.

Abnormal thermally-stimulated dynamic organic phosphorescence

Dynamic luminescence behavior by external stimuli, such as light, thermal field, electricity, mechanical force, etc., endows the materials with great promise in optoelectronic applications. Upon thermal stimulus, the emission is inevitably quenched due to intensive non-radiative transition, especially for phosphorescence at high temperature. Herein, we report an abnormal thermally-stimulated phosphorescence behavior in a series of organic phosphors. As temperature changes from 198 to 343 K, the phosphorescence at around 479 nm gradually enhances for the model phosphor, of which the phosphorescent colors are tuned from yellow to cyan-blue. Furthermore, we demonstrate the potential applications of such dynamic emission for smart dyes and colorful afterglow displays. Our results would initiate the exploration of dynamic high-temperature phosphorescence for applications in smart optoelectronics. This finding not only contributes to an in-depth understanding of the thermally-stimulated phosphorescence, but also paves the way toward the development of smart materials for applications in optoelectronics.

Recent synthetic strategies of small heterocyclic organic molecules with optoelectronic applications: a review

Over the past few years, there have been tremendous developments in the design and synthesis of organic optoelectronic materials with appealing applications in device fabrication of organic light-emitting diodes, superconductors, organic lasers, organic field-effect transistors, clean energy-producing organic solar cells, etc. There is an increasing demand for the synthesis of green, highly efficient organic optoelectronic materials to cope with the issue of efficiency roll-off in organic semiconductor-based devices. This review systematically summarized the recent progress in the design and synthesis of small organic molecules having promising optoelectronic properties for their potential applications in optoelectronic devices during the last 10-year range (2010-early 2021).

AIE-based ratiometric fluorescent probe for mercury ion, medium-dependent fluorescence color change and optimized sensitivity in solid state

A new AIE-based luminogen TPES, as a ratiometric fluorescence probe for mercury(II) was readily synthesized. The probe combined the advantages of the outstanding specificity of Hg2+-triggered deprotection reaction of thioketal and the brilliant emission of AIEgens in aggregated state. Once encountered aqueous Hg2+, fluorescent color of TPES in THF-H2O (fw = 98%) altered from blue to green rapidly, while other metal cations gave no interference to the probe. And the mechanism of this chemosensor was carefully verified by 1H NMR analysis, FTIR and MS spectra. As expected, TPES exhibits excellent selectivity and sensitivity towards Hg2+ in the solid state. When using filter paper as the solid medium, the fabricated test strips could signify Hg2+ ions with the LOD as 1 × 10-5 M (Hg2+ in aqueous solution), accompanied with a distinct emitting altered from blue to green. Furthermore, by changing the medium from filter paper to silica gel plate, a more significant fluorescence alteration from blue to yellow was achieved, and the LOD was further optimized to 1 × 10-6 M as discerned by naked-eye.

Luminescent Properties of β-(hydroxyaryl)-butenolides and Fluorescence Quenching in Water

This work describes the luminescent properties of the new compound β-(hydroxyaryl)-butenolides recently discovered. The compounds were subjected to UV-Vis absorption and fluorescence analyzes when diluted in different solvents. Through the results, it was possible to observe that the β-hydroxyarylutenolides have two absorption bands, one at 289-291 nm and the other with higher intensity at 328-354 nm. The emission band between 385-422 nm is observed under excitation at 324-327 nm. The compounds showed solvatochromism as a function of the analyzed solvent. In water, fluorescence quenching of all compounds occurs. Therefore, studies with compound containing the methylenedioxy group attached in phenyl ring were carried at different concentrations of water in DMSO. The decrease in the fluorescence intensity of this compound is linearly proportional to the increase in the amount of water in the DMSO, with a minimum detection volume of 0.028%. Quantum yields of three compounds were evaluated in different solvents, showing that the relationship between the structure of the compound and the solvent is essential for a high value. The fluorescence quantum yield was also measured by Thermal Lens Spectroscopy (TLS) using DMSO as the solvent, confirming the high value for the analyzed samples. Despite being preliminary, the studies revealed that these compounds have luminescent properties that could be applied in the development of chemical sensors for detecting water in DMSO.

Enhancing the optical properties of [P(MMA-co-AN)/ZrO2]TF by doping fluorescein dye, TD-DFT/DMOl3 simulations and COVID-19 main protease docking

Poly methyl methacrylate-co-acrylonitrile [P(MMA-co-AN)]HB hybrid blend was first synthesized by precipitation polymerization and characterized by static light scattering. With a thickness of 200 ± 5 nm, the hybrid nanocomposite of [P(MMA-co-AN)/ZrO2]HNC thin films were fabricated by spin coating method. X-Ray diffraction studies showed a monoclinic cell structure with an average crystalline size of 180 nm for the fabricated films. An improvement in the optical properties were figured out when fluorescein dye was doped in the hybrid nanocomposite. Where the optical energy gap was decreased from 4.31 to 4.025 eV for fluorescein doped hybrid nanocomposite. While a possible energy transfer between ZrO2 and fluorescein was investigated in the laser photoluminescence spectra. DFT-CASTEP simulations were deployed to calculate the theoretical optical properties for the molecules under consideration. The structural and optical simulations of [P(MMA-co-AN)/ZrO2]HNC were found to match the experimental data. Molecular docking studies of [P(MMA-co-AN)/ZrO2]Iso against the main protease of novel corona virus COVID 19 (PDB code 6LU7 Hormone) showed an interesting interaction.

Investigation of Mechanochromic Luminescence of Pyrene-based Aggregation-Induced Emission Luminogens: Correlation between Molecular Packing and Luminescence Behavior

To better understand the correlation between molecular structure and optical properties such as aggregation-induced emission (AIE) and mechanochromic luminescence (MCL) emission, two new pyrene-based derivatives with substitutions at the 4- and 5-positions (1HH) and at the 4-, 5-, 9-, and 10-positions (2HH) were designed and synthesized. Cyano groups were introduced at the periphery of the synthesized compounds (1HCN, 1OCN, 1BCN, 2HCN, 2OCN, and 2BCN) to investigate the influence of these groups on the emission properties of the pyrene derivatives both in solution and in the solid state. The fluorescence emission performance of these compounds in water/acetone mixtures was simultaneously studied, revealing outstanding aggregation-induced emission properties. The typical shift in emission maxima to higher values was attributed to J-aggregate formation in the aggregate state. Careful investigation of the crystal structures demonstrated abundant and intense intermolecular interactions, such as C-H…π and C-H…N hydrogen bonds, contributing to the remarkable mechanochromic luminescence performance of these compounds. The MCL properties of all the compounds were investigated using powder X-ray diffraction, and the remarkable mechanochromic properties were attributed to J-aggregate phenomena in the solid state. These results provide valuable insights into the structure-property relationship of organic MCL materials, guiding the design of efficient organic MCL materials.

Performance of point charge embedding schemes for excited states in molecular organic crystals

Modeling excited state processes in molecular crystals is relevant for several applications. A popular approach for studying excited state molecular crystals is to use cluster models embedded in point charges. In this paper, we compare the performance of several embedding models in predicting excited states and S1-S0 optical gaps for a set of crystals from the X23 molecular crystal database. The performance of atomic charges based on ground or excited states was examined for cluster models, Ewald embedding, and self-consistent approaches. We investigated the impact of various factors, such as the level of theory, basis sets, embedding models, and the level of localization of the excitation. We consider different levels of theory, including time-dependent density functional theory and Tamm-Dancoff approximation (TDA) (DFT functionals: ωB97X-D and PBE0), CC2, complete active space self-consistent field, and CASPT2. We also explore the impact of selection of the QM region, charge leakage, and level of theory for the description of different kinds of excited states. We implemented three schemes based on distance thresholds to overcome overpolarization and charge leakage in molecular crystals. Our findings are compared against experimental data, G0W0-BSE, periodic TDA, and optimally tuned screened range-separated functionals.

Transcytosis-Inducing Multifunctional Albumin Nanomedicines with Deep Penetration Ability for Image-Guided Solid Tumor Treatment

Transcytosis is an active transcellular transportation pathway that has garnered interest for overcoming the limited deep penetration of nanomedicines in solid tumors. In this study, a charge-convertible nanomedicine that facilitates deep penetration into solid tumors via transcytosis is designed. It is an albumin-based calcium phosphate nanomedicine loaded with IR820 (mAlb-820@CaP) for high-resolution photoacoustic imaging and enhanced photothermal therapy. Biomineralization on the surface stabilizes the albumin-IR820 complex during circulation and provides calcium ions (Ca2+ ) for tissue penetration on degradation in an acidic environment. pH-triggered transcytosis of the nanomedicine enabled by caveolae-mediated endocytosis and calcium ion-induced exocytosis in 2D cellular, 3D spheroid, and in vivo tumor models is demonstrated. Notably, the extravasation and penetration ability of the nanomedicine is observed in vivo using a high-resolution photoacoustic system, and nanomedicine shows the most potent photothermal antitumor effect in vivo. Overall, the strategy provides a versatile theragnosis platform for both noninvasive photoacoustic imaging and high therapeutic efficiency resulting from deep penetration of nanomedicine.

Large-Scale Preparation for Multicolor Stimulus-Responsive Room-Temperature Phosphorescence Paper via Cellulose Heterogeneous Reaction

The large-scale preparation of sustainable room-temperature phosphorescence (RTP) materials, particularly those with stimulus-response properties, is attractive but remains challenging. This study develops a facile heterogeneous B─O covalent bonding strategy to anchor arylboronic acid chromophores to cellulose chains using pure water as a solvent, resulting in multicolor RTP cellulose. The rigid environment provided by the B─O covalent bonds and hydrogen bonds promotes the triplet population and suppresses quenching, leading to an excellent lifetime of 1.42 s for the target RTP cellulose. By increasing the degree of chromophore conjugation, the afterglow colors can be tuned from blue to green and then to red. Motivated by this finding, a papermaking production line is built to convert paper pulp reacted with an arylboronic acid additive into multicolor RTP paper on a large scale. Furthermore, the RTP paper is sensitive to water because of the destruction of hydrogen bonds, and the stimuli-response can be repeated in response to water/heat stimuli. The RTP paper can be folded into 3D afterglow origami handicrafts and anti-counterfeiting packing boxes or used for stimulus-responsive information encryption. This success paves the way for the development of large-scale, eco-friendly, and practical stimuli-responsive RTP materials.

Realizing long range π-conjugation in phenanthrene and phenanthrene-based molecular crystals for anomalous piezoluminescence

Unlike the known aggregation-caused quenching (ACQ) that the enhancement of π-π interactions in rigid organic molecules usually decreases the luminescent emission, here we show that an intermolecular "head-to-head" π-π interaction in the phenanthrene crystal, forming the so-called "transannular effect", could result in a higher degree of electron delocalization and thus photoluminescent emission enhancement. Such a transannular effect is molecular configuration and stacking dependent, which is absent in the isomers of phenanthrene but can be realized again in the designed phenanthrene-based cocrystals. The transannular effect becomes more significant upon compression and causes anomalous piezoluminescent enhancement in the crystals. Our findings thus provide new insights into the effects of π-π interactions on luminescence emission and also offer new pathways for designing efficient aggregation-induced emission (AIE) materials to advance their applications.

Synthesis Strategies, Optical Mechanisms, and Applications of Dual-Emissive Carbon Dots

Tuning the optical properties of carbon dots (CDs) and figuring out the mechanisms underneath the emissive phenomena have been one of the most cutting-edge topics in the development of carbon-based nanomaterials. Dual-emissive CDs possess the intrinsic dual-emission character upon single-wavelength excitation, which significantly benefits their multi-purpose applications. Explosive exploitations of dual-emissive CDs have been reported during the past five years. Nevertheless, there is a lack of a systematic summary of the rising star nanomaterial. In this review, we summarize the synthesis strategies and optical mechanisms of the dual-emissive CDs. The applications in the areas of biosensing, bioimaging, as well as photoelectronic devices are also outlined. The last section presents the main challenges and perspectives in further promoting the development of dual-emissive CDs. By covering the most vital publications, we anticipate that the review is of referential significance for researchers in the synthesis, characterization, and application of dual-emissive CDs.

Effective transport of aggregated hypericin encapsulated in SBA-15 nanoporous silica particles for photodynamic therapy of cancer cells

Photodynamic therapy (PDT) represents an interesting modality for the elimination of damaged biomaterials and cells. This treatment takes advantage of the photosensitizing properties of molecules that are active only when irradiated with light. In the present work, a dual property of hypericin, a hydrophobic molecule with high performance in photodiagnostics and photodynamic therapy, was exploited. The non-fluorescent and photodynamically inactive form of hypericin aggregates was loaded into the nanopores of SBA-15 silica particles. The synthesized particles were characterized by infrared spectroscopy, thermogravimetry, differential thermal analysis, small-angle X-ray scattering and transmission electron microscopy. Hypericin aggregates were confirmed by absorption spectra typical of aggregated hypericin and by its short fluorescence lifetime. Release of hypericin from the particles was observed toward serum proteins, mimicking physiological conditions. Temperature- and time-dependent uptake of hypericin by cancer cells showed gradual release of hypericin from the particles and active cellular transport by endocytosis. A closer examination of SBA-15-hypericin uptake by fluorescence lifetime imaging showed that aggregated hypericin molecules, characterized by a short fluorescence lifetime (∼4 ns), were still present in the SBA-15 particles upon uptake by cells. However, monomerization of hypericin in cancer cells was observed by extending the hypericin fluorescence lifetime by ∼8 ns, preferentially in lipid compartments and the plasma membrane. This suggests a promising prognosis for delayed biological activity of the entire cargo, which was confirmed by effective PDT in vitro. In summary, this work presents an approach for safe, inactive delivery of hypericin that is activated at the target site in cells and tissues.

A Series of Planar Phosphorescent Cyclometalated Platinum(II) Complexes as New Anticancer Theranostic Agents That Induce Oncosis

Herein, four planar cyclometalated platinum(II) complexes with a main ligand of enlarged aromatic rings have been assessed as effective anticancer theranostic agents for the first time. With an increased number of aromatic rings in the N∧N ligand, 1a-1d exhibit increased lipophilicity and cytotoxicity selectivity. The intensity of the Pt-Pt interaction of each complex can be indicated by an enhanced near-infrared (NIR) emission in phosphate-buffered saline (PBS), their binding activity with biomolecules of bovine serum albumin (BSA) is accompanied by a vivid turn-on green emission, and the intensity gradually decreased from 1a to 1d, which is consistent with the docking of two complexes with BSA. Both "turn-on" NIR and green emission of 1d can be mainly observed in nuclei of living cell within 24 h, while two phosphorescence traces of 1b were recorded in lysosomes by confocal imaging. Moreover, 1d shows the highest efficiency in inducing oncosis of Hela cells, and the relative process was investigated.

Formation of Highly Emissive Anthracene Excimers for Aggregation-Induced Emission/Self-Assembly Directed (Bio)imaging

AIEgens have emerged as a promising alternative to molecular rotors in bioimaging applications. However, transferring the concept of aggregation-induced emission (AIE) from solution to living systems remains a challenge. Given the highly heterogeneous nature and the compartmentalization of the cell, different approaches are needed to control the self-assembly within the crowded intricate cellular environment. Herein, we report for the first time the self-assembly mechanism of an anthracene-guanidine derivative (AG) forming the rare and highly emissive T-shaped dimer in breast cancer cell lines as a proof of concept. This process is highly sensitive to the local environment in terms of polarity, viscosity, and/or water quantity that should enable the use of the AG as a fluorescence lifetime imaging biosensor for intracellular imaging of cellular structures and the monitoring of intracellular state parameters. Different populations of the monomer and T-shaped and π-π dimers were observed in the cell membrane, cytoplasm, and nucleoplasm, related to the local viscosity and presence of water. The T-shaped dimer is formed preferentially in the nucleus because of the higher density and viscosity compared to the cytoplasm. The present results should serve as a precursor for the development of new design strategies for molecular systems for a wide range of applications such as cell viscosity, density, or temperature sensing and imaging.

The Key Role of Molecular Packing in Luminescence Property: From Adjacent Molecules to Molecular Aggregates

The luminescence materials act as the key components in many functional devices, as well as the detection and imaging systems, which can be permeated in each aspect of modern life, and attract more and more attention for the creative technology and applications. In addition to the diverse properties of organic luminogens, the multiple molecular packing at aggregated states frequently offers new and/or exciting performance. However, there still lacks comprehensive analysis of molecular packing in these organic materials, resulting in an increased gap between molecular design and practical applications. In this review, from the basic knowledge of organic compounds as single molecules, to the discernable property of excimer, charge transfer (CT) complex or self-assembly systems by adjacent molecules, and finally to the opto-electronic performance of molecular aggregates, the relevant factors to molecular packing and practical applications are discussed.

Orchestrated Strategies for Developing Fluorophores for NIR-II Imaging

Fluorescence imaging (FLI), a non-invasive, real-time, and highly sensitive imaging modality, allows for investigating the molecular/cellular level activities to understand physiological functions and diseases. The emergence of the second near-infrared window (NIR-II, 1000-1700 nm) has endowed fluorescence imaging with deeper tissue penetration and unprecedented clarity. Among the various NIR-II imaging fluorophores, the organic fluorescent probes have occupied a pivotal position in bioimaging due to their higher biocompatibility, safety, and potential for clinical applications compared with those of the inorganic probes. To obtain high-quality organic dyes, diverse strategies have been taken. In this review, different strategies for optimizing NIR-II organic fluorophores are summarized, including traditional chemical modifications, and emerging bioengineering operations, which have not previously been elaborated on and summarized. Moreover, the bioengineering strategies are highlighted using endogenous serum proteins and even exogenous gene-editing proteins, which would provide fresh insights to design good-performance dyes and help develop NIR-II probes with clinical translation potential in the future. A critical perspective on the direction of the design strategies of NIR-II dyes for disease imaging is also proposed.

Fabricating a photochromic benzonitrile Schiff base into a low-cost reusable paper-based wearable sensor for naked-eye dosimetry of UV radiations

We report in this study a photochromic benzonitrile Schiff base, (E)-4-((2-hydroxy-4-methoxybenzylidene)amino)benzonitrile (HMBAB). The molecular design, synthesis, aggregation-induced emission (AIE) as well as the quantum chemical calculations were outlined. In particular, HMBAB would undergo a reversible tautomerism in response to UV exposure, exhibiting remarkable changes in both absorption and emission: the compound shows yellow color and green-yellow luminescence; after UV exposure, the changes into orange-red while the luminescence is dramatically quenched, accompanied by a large bathochromic-shift. In addition, the photochromic state can be fully recovered via thermal treatment. Such reversible dual-channel photochromism was investigated using UV-vis reflectance spectroscopy and colorimeter, wherein a gradient change with time and a high fatigue resistance in cycle use was recorded. The photochromism is quantified by well-established RGB and Lab color space, in which the color change can be accurately analyzed by the chromatic aberration (ΔE*_Lab). Sensitivity test gives a two-stage linear relation between ΔE*_Lab and UV intensity, by which a limit of detection (LOD) as low as 67 μW/cm² is obtained. HMBAB was further fabricated into a paper-based wearable sensor, capable of being integrated into a chest card or a bracelet. It exhibits various degrees of color change in different sunlight environments, which can be readily observed by naked eyes, providing an early warning for high-dose UV radiations.

Tuning the Solid Phase Fluorescence Emission from Long Wavelength Visible to Near-Infrared in Oxazol-5-One Derivatives: Structure-Property Relationship, Theoretical and Experimental Studies

Most of the fluorescent molecules among organic [Formula: see text]-conjugated materials show blue or green emission in the solid phase but few of them emit red-shifted visible and near-infrared light in the material science. To create molecules emitting for this feature, two π-conjugated oxazol-5-one derivatives containing donor (OCH₃) and acceptor groups (NO₂) were synthesized. Their optical and charge-transport properties were investigated through experimental and theoretical methods including the single crystal X-ray crystallography, Hirshfeld Surface Analysis, photophysical studies and Density Functional Theory (DFT), respectively. In addition, FT-IR, ¹H-NMR, ¹³C-NMR spectroscopy, cyclic voltammetry (CV) measurements were performed. According to our results, both molecules may provide the significant pathway of development of long wavelength visible and red emissive features in solid phase with the aggregation induced enhanced emission (AIEE) properties particularly in the fields of OLEDs, optical communication, defence and bioimaging.

Conjugated Aggregation-Induced Fluorescent Materials for Biofluorescent Probes: A Review

The common fluorescent conjugated materials present weak or quenching luminescent phenomena in the solid or aggregate state (ACQ), which limits their applications in medicine and biology. In the last two decades, certain materials, named aggregation-induced emission (AIE) fluorescent materials, have exhibited strong luminescent properties in the aggregate state, which can overcome the ACQ phenomenon. Due to their intrinsic properties, the AIE materials have been successfully used in biolabeling, where they can not only detect the species of ions and their concentrations in organisms, but can also monitor the organisms' physiological activity. In addition, these kinds of materials often present non-biological toxicity. Thus, AIE materials have become some of the most popular biofluorescent probe materials and are attracting more and more attention. This field is still in its early infancy, and several open challenges urgently need to be addressed, such as the materials' biocompatibility, metabolism, and so on. Designing a high-performance AIE material for biofluorescent probes is still challenging. In this review, based on the molecular design concept, various AIE materials with functional groups in the biofluorescent probes are introduced, including tetrastyrene materials, distilbene anthracene materials, triphenylamine materials, and hexaphenylsilole materials. In addition, according to the molecular system design strategy, the donor-acceptor (D-A) system and hydrogen-bonding AIE materials used as biofluorescent probes are reviewed. Finally, the biofluorescent probe design concept and potential evolution trends are discussed. The final goal is to outline a theoretical scaffold for the design of high-performance AIE biofluorescent probes that can at the same time further the development of the applications of AIE-based biofluorescent probes.

High-contrast reversible multiple color-tunable solid luminescent ionic polymers for dynamic multilevel anti-counterfeiting

Dynamic color-tunable luminescent materials, which possess huge potential applications in advanced multilevel luminescence anti-counterfeiting, are of considerable interest. However, it remains challenging to develop simple high-contrast reversible multiple (triple or more than triple) color-tunable high-efficiency solid luminescent materials with low cost, facile synthesis, and good processability. Herein, by simply grafting charged multi-color AIEgen-based chromophores into polymers, a series of high-efficiency multiple color-tunable luminescent single ionic polymers are constructed through tuning feed ratios, counter anions and reaction solvents. Remarkably, some ionic polymers can not only achieve rare high-contrast reversible multiple color-tunable emission in solid states in response to different solvent stimuli, but also could realize excitation-dependent color-tunable emission. To the best of our knowledge, such charming multiple (triple or more than triple) color-tunable solid polymers responding to multiple external stimuli are still rare. Based on comparative studies of emission spectra, excitation spectra and fluorescence lifetimes before and after swelling, it could be inferred that solvent stimuli could induce microstructure changes of these ionic polymers and then change the aggregated-states of their corresponding AIE-active emission centers. Moreover, the different solvent stimuli could induce to produce different degrees of microstructure changes, resulting in their unique multiple color-tunable emission. More significantly, these smart color-tunable ionic polymers show great promise for applications in dynamic multilevel (three-level or even more than three-level) anti-counterfeiting.

Control of Fluorescence of Organic Dyes in the Solid-State by Supramolecular Interactions

Fluorescent organic dyes play an essential role in the creation of new "smart" materials. Fragments and functional groups capable of free rotation around single bonds can significantly change the fluorescent organic dye's electronic structure under analyte effects, phase state transitions, or changes in temperature, pressure, and media polarity. Dependencies between steric and electronic structures become highly important in transition from a solution to a solid-state. Such transitions are accompanied by a significant increase in the dye molecular structure's rigidity due to supramolecular associates' formation such as H-bonding, π···π and dipole-dipole interactions. Among those supramolecular effects, H-bonding interactions, first of all, lead to significant molecular packing changes between loose or rigid structures, thus affecting the fluorescent dye's electronic states' energy and configuration, its fluorescent signal's position and intensity. All the functional groups and heteroatoms that are met in the organic dyes seem to be involved in the control of fluorescence via H-bonding: C-H···N, C-H···π, S = O···H-C, P = O···H, C-H···O, NH···N, C - H···C, C - H···Se, N-H···O, C - H···F, C-F···H. Effects of molecular packing of fluorescent organic dyes are successfully used in developing mechano-, piezo-, thermo- fluorochromes materials for their applications in the optical recording of information, sensors, security items, memory elements, organic light-emitting diodes (OLEDs) technologies.

Solid-state emitting twisted π-conjugate as AIE-active DSE-gen: in vitro anticancer properties against FaDu and 4T1 with biocompatibility and bioimaging

Dual-state emissive fluorogens (DSE-gens) are currently defining their importance as a transpiring tool in biological and biomedical applications. This work focuses on designing and synthesizing indole-anthracene-based solid-state emitting twisted π-conjugates using a metal-free protocol to achieve AIE-active DSE-gens, expanding their scope in biological applications. Special effort has been made to introduce proficient and photo/thermostable DSE-gens that inhibit cancer but not normal cells. Here, the lead DSE-gen initially detects cancer and normal cells by bioimaging; however, it could also confirm and distinguish cancer cells from normal cells by its abated fluorescence signal after killing cancer cells. In contrast, the fluorescence signals for a normal cell remain unscathed. Surprisingly, these molecules displayed decent anticancer properties against FaDu and 4T1 but not MCF-7 cell lines. From a series of newly designed indole-based molecules, we report one single 2,3,4-trimethoxybenzene-linked DSE-gen (the lead), exhibiting high ROS generation, less haemolysis, and less cytotoxicity than doxorubicin (DOX) for normal cells, crucial parameters for a biocompatible in vitro anticancer probe. Thus, we present a potentially applicable anticancer drug, offering a bioactive material with bioimaging efficacy and a way to detect dead cancer cells selectively. The primary mechanism behind the identified outcomes is deciphered with the support of experimental (steady-state and time-resolved fluorescence, biological assays, cellular uptake) and molecular docking studies.

AIEgens Based on Anion-π+ Interactions: Design, Synthesis, Photophysical Properties, and Their Applications in Material Science and Biology

The design of novel aggregation-induced emission luminogens (AIEgens), has generally been facilitated by disrupting the possibility of π-π stacking. The recent literature describes a novel strategy to design AIEgens by introducing anion-π⁺ interactions to prevent the detrimental π-π stacking. This new strategy provides access to intrinsically charged AIEgens whose photophysical properties can be tuned either by incorporating different substituents on the π-molecular scaffold to modulate the acidity for tuning the interaction energy between a π-acceptor and counter-anions. This concept article provides a brief overview of the field, focusing on the synthesis of AIEgens, their photophysical properties, crystallography studies and their applications in live cell fluorescence imaging.

Experimental and TDDFT materials simulation of thermal characteristics and entropy optimized of Williamson Cu-methanol and Al2O3-methanol nanofluid flowing through solar collector

Current investigation emphasizes the evaluation of entropy in a porous medium of Williamson nanofluid (WNF) flow past an exponentially extending horizontal plate featuring Parabolic Trough Solar Collector (PTSC). Two kinds of nanofluids such as copper-methanol (Cu-MeOH) and alumina-methanol (Al₂O₃-MeOH) were tested, discussed and plotted graphically. The fabricated nanoparticles are studied using different techniques, including TDDFT/DMOl³ method as simulated and SEM measurements as an experimental method. The centroid lengths of the dimer are 3.02 Å, 3.27 Å, and 2.49 Å for (Cu-MeOH), (Al₂O₃-MeOH), and (Cu-MeOH-αAl-MOH), respectively. Adequate similarity transformations were applied to convert the partial differential equation (PDEs) into nonlinear ordinary differential equations (ODEs) with the corresponding boundary constraints. An enhancement in Brinkmann and Reynolds numbers increases the overall system entropy. WNF parameter enhances the heat rate in PTSC. The thermal efficiency gets elevated for Cu-MeOH than that of Al₂O₃-MeOH among 0.8% at least and 6.6% in maximum for varying parametric values.

Two Cholesterol-Containing Pyrene Derivatives: Subtle Spacer Difference, Diverse Stimuli-Responsive Luminescence, Chirality, and Self-Assembly Behaviors

Two chiral molecules 1 and 2 were designed and synthesized with a pyrene moiety directly linked to a chiral cholesterol moiety and connected through a methylene spacer, respectively. Influence of the spacer on their stimuli-responsive luminescence, chirality, and self-assembly behaviors was systematically investigated. Molecules 1 and 2 had similar aggregation-induced emission enhancement (AIEE) in solution, because of carrying the same fluorescence moiety. Both molecules displayed mechanochromism (MC) property but with different color contrast, whereas only 2 showed mechanoluminescence (ML) activity. When doping in liquid crystal molecule 5CB, both molecules induced the formation of chiral nematic liquid crystals (N*-LCs) with strong circularly polarized luminescence (CPL). Molecule 2 induced single handedness signal, irrespective of doping ratios, while 1-doped N*-LCs showed an inversion of CPL signal from negative to positive upon the increase of doping ratios. Molecules 1 and 2 also self-assembled into different coassemblies with 5CB. Their distinct behaviors were attributed to the influence of the methylene spacer, which caused different molecular conformation and steric bulkiness; accordingly, it changed intermolecular interactions and molecular packing of the two molecules and led to diverse chirality and luminescence. This work provided important model molecules to better understand the molecular structure-property relationship and guide the design of novel functional molecules.

Combined experimental and TD-DFT/DMOl3 investigations, optical properties, and photoluminescence behavior of a thiazolopyrimidine derivative

We present here the FT-IR, DFT computation, XRD, optical, and photophysical characterization of a heterocyclic compound with thienopyrimidine and pyran moieties. TD-DFT/DMOl³ and TD-DFT/CASTEP computations were used to study the geometry of isolated and dimer molecules and their optical behavior. The indirect (3.93 eV) and direct (3.29 eV) optical energy bandgaps, HOMO-LUMO energy gap (3.02 eV), and wavelength of maximum absorption (353 nm) were determined in the gas phase with M062X/6-31+G (d, p). A thin film of the studied molecule was studied using XRD, FT-IR, and UV-Vis spectroscopy. The average crystallite size was found as 74.95 nm. Also, the photoluminescence spectroscopy revealed that the compound exhibited different emission bands at the visible range with different intensities depending on the degree of molecular aggregation. For instance, solutions with different concentrations emitted blue, cyan, and green light. On the other hand, the solid-state material produced a dual emission with comparable intensities at λ_max = 455, 505, and 621 nm to cover the entire visible range and produce white emission from a single material with CIE coordinates of (0.34, 0.32) that are very similar to the ideal pure white light. Consequently, these findings could lead to the development of more attractive new luminous materials.

Anthracene Single-Crystal Scintillators for Computer Tomography Scanning

X-ray imaging and computed tomography (CT) technology, as the important non-destructive measurements, can observe internal structures without destroying the detected sample, which are always used in biological diagnosis to detect tumors, pathologies, and bone damages. It is always a challenge to find materials with a low detection limit, a short exposure time, and high resolution to reduce X-ray damage and acquire high-contrast images. Here, we described a low-cost and high-efficient method to prepare centimeter-sized anthracene crystals, which exhibited intense X-ray radioluminescence with a detection limit of ∼0.108 μGy s^-1, which is only one-fifth of the dose typically used for X-ray diagnostics. Additionally, the low absorption reduced the damage in radiation and ensured superior cycle performance. X-ray detectors based on anthracene crystals also exhibited an extremely high resolution of 40 lp mm^-1. The CT scanning and reconstruction of a foam sample were then achieved, and the detailed internal structure could be clearly observed. These indicated that organic crystals are expecting to be leading candidate low-cost materials for low-dose and highly sensitive X-ray detection and CT scanning.