Brightening Nonconventional Luminophores by Reconfiguring Hydrogen‐Bond Networks via Pressure Treatment

Si-assisted N, P Co-doped room temperature phosphorescent carbonized polymer Dots: Information Encryption, graphic Anti-counterfeiting and biological imaging

Fluorescence emission spectra and absolute quantum yields have been measured for ten diverse crude oils at various concentrations over a broad range of excitation and emission wavelengths in the visible and the near-infrared. Energy transfer produces large red shifts and large widths in the fluorescence emission spectra for shorter wavelength excitation particularly for heavier crude oils. However, the effects of energy transfer are nearly absent for near-infrared excitation; all crude oils exhibit nearly the same emission spectra for long wavelength excitation. In addition, the fraction of emission resulting from collisional energy transfer relative to nascent emission is almost independent of oil type; it is governed by quantum yield characteristics. Absolute fluorescence quantum yields of ten crude oils (and three rhodamine dyes for validation) were measured with respect to scattering of latex microspheres in distilled water. Fluorescence quantum yields vary systematically with crude oil type as well as excitation wavelength; quantum yields are lower for high fluorophore concentrations (heavy crude oils) and for longer wavelength excitation. Stern-Volmer analyses of the quantum yields indicate that simple models apply and show the relative quenching rates for different excitation wavelengths.

The dependence of the relative luminescence quantum yield on the wavelength of the exciting light has been measured for seven substances in the region from 158 nm to the longwave decrease. The absolute quantum yield has also been measured for exciting wavelengths of 254 and 313 nm by two different methods. Measurements were made on easily reproducible, infinitely thick layers; reabsorption was not taken into account. Sodium salicylate, Lumogen no. 2 and Lumogen Red 640 had the most stable quantum yield and the highest light resistance; they should be considered most suitable for use as standards in luminescence work.

The pressure‐induced blue‐white emission of materials provided possibility of single‐component white light‐emitting diodes (WLEDs). However, the high‐pressure metastable phase with excellent blue‐white emission is very difficult to be stabilized at ambient conditions, seriously limiting the practical applications. Here, we successfully quenched a blue‐white emission in a 0D perovskite (C 9 H 9 N 5 ) 2 ZnCl 4 ·2H 2 O upon decompression, which exhibited a stark increase by a factor of more than 40 and CIE coordinates of (0.248, 0.308). Strengthening of intermolecular hydrogen bonds, increased tetrahedra distortion, and inhibit of the phonon‐assisted non‐radiative decay are highly responsible for the observed emission enhancement. The retention mechanism of enhanced blue‐white emission is associated with large steric hindrance effect of complex organic cation, which contributed to increasing the potential barrier of phase transition. Furthermore, the phosphor‐converted light emitting diode (pc‐LED) is fabricated using pressure‐treated (C 9 H 9 N 5 ) 2 ZnCl 4 ·2H 2 O, which exhibited superior chromaticity. Combined with micro‐nano patterning, diverse patterns of QR codes and butterflies are achieved. The QR codes after pressure treatment can be easily scanned for accessing the homepage of Jilin University with a phone, which considerably enhanced the ability of naked‐eye recognition and visual information encryption. Pressure indeed offers a robust strategy to endow high‐efficiency luminescent materials with great potentials in lighting, display and anti‐counterfeiting.

Synthesis and characterization of blue light emitters based on dimers of fluorene: Effects of different pendant electron-withdrawing moieties

Environmental‐friendly carbon dots (CDs) have found wide applications in the fields of white light emitting diode (WLED), chemical sensor, wide‐gamut display, etc. However, for the aggregation‐caused quenching (ACQ) effect, high dose of CDs immobilization generally suffers from the great fluorescence quenching, hindering their practical uses in many cases. In the present work, a one‐step microwave‐assisted microemulsion process is developed to prepare matrix‐free green CDs powders with absolute fluorescent quantum yield (QY) up to 48.34%. From dilute solution to matrix‐free powder, the QY of CDs decreases only about 20%, significant smaller than the sample prepared without surfactant (74%). Structural characterization and fluorescent lifetime measurements suggest that the passivation of hydrophobic long‐alkyl chains from surfactant Span‐80 is very key for their good solid‐state photoluminescence (PL). For the good solid‐state PL and various solvent‐compatibility, the CDs reported show promising applications in the fabrication of WLED and the measurement of water content of ethanol/water solution. This work provides a new idea to design and simply synthesize desirable CDs‐based luminescent materials with good solid‐state PL.

A biocompatible phosphorescence probe based on iridium(III) solvent complex for monitoring integrin expression in living cells.

Carbon nanodots (CNDs), boasting biocompatibility, structural versatility, and tuneable photoluminescence, are promising candidates in luminescent materials. This study demonstrates how the optical properties of N, S co-doped carbon nanodots can be effectively tuned through variation in solvents. Drastic change is noted in the physico-chemical features of CNDs achieved using sulphuric acid and water through solvothermal route. A red shift in emission is noted in system achieved using sulfuric acid medium. The synthesized CNDs are explored for light emitting diode (LED) application. CNDs achieved using hydrothermal method (MCDs) lead to pure white light (CIE coordinates: 0.33, 0.38) emitting LEDs, and sulfuric acid modification (SMCD) produces LEDs emitting in yellowish-orange light (CIE coordinates: 0.57, 0.42), due to enhanced oxidation of carbon core. Further, the difference in solvents is also reflected in the response of these CNDS toward external analytes. Picric acid induced luminescence quenching of SMCDs enabled selective detection of the analyte among 11 nitroaromatic compounds, highlighting the impact of surface functionalization in tuning the response toward external environments. The sensing mechanism, involving the inner filter effect and static quenching, as well as the selective response to picric acid, was confirmed through optical characterization and frontier molecular orbital (FMO) analysis.

The development of smart circularly polarized luminescence (CPL) materials faces significant challenges, primarily centered on achieving high luminescence dissymmetry factors (glum) alongside broadly tunable responses. Here, we report a chiral scaffold based on covalent organic frameworks (COFs) for high-performance and adaptive photocontrollable time-evolving CPL, enabling identifiable and encrypted chiroptical outputs. Cyclodextrin modified on the COF generates multicolor CPL emission through noncovalent interaction with fluorophores. Blending the modified COF and fluorophores with polyethylene glycol (PEG) yields transparent mixed-matrix films exhibiting a high glum of -0.027 and absolute quantum yield (39%). Subsequently, sulfonato-merocyanine, a photochromic switch, is introduced to modulate the system's emission, endowing the reversible CPL signals with light-fueled tunability and time-dependent dynamic evolution. Notably, we fabricate mixed-matrix films to amplify the light-controllable CPL signals, where the glum varies between -0.009 and -0.044 upon 420 nm irradiation and thermal relaxation. A dynamic modulation range of glum ≈0.035 is achieved, which is a remarkable value reported among dynamic COF-based CPL materials. Furthermore, films featuring photocontrollable, self-erasable vector luminescent signals are achieved for dual-mode anticounterfeiting. This work provides insight into the design of intelligent luminescent materials.

Fluorescent probes are indispensable for cellular imaging and for monitoring pH-dependent biological processes. However, the majority of reported probes are effective only in near-neutral or mildly acidic ranges, with very few functioning reliably in strongly acidic environments (pH < 4). Designing water-soluble, biocompatible probes that can operate efficiently under such extreme conditions remains an important analytical challenge. To address this challenge, two pH-responsive fluorescent probes, Xpy and XpyF, based on a xanthone core, were designed and synthesized. Both probes exhibit excellent water solubility, low cytotoxicity, and strong turn-on fluorescence in acidic environments. The probes display distinct emission changes from blue at neutral to moderately acidic pH (3-7) to green at strongly acidic pH (1-2). Absolute quantum yield and TCSPC studies confirmed significant fluorescence enhancement and lifetime prolongation under acidic conditions, consistent with protonation-induced PET inhibition. Cellular imaging studies revealed efficient internalization and strong nuclear localization with high Pearson's correlation coefficients. Importantly, while Xpy showed consistent nuclear staining across pH values, XpyF demonstrated a unique pH-dependent switch from cytoplasmic localization at pH 7.4 to nuclear accumulation at pH 4.3. Overall, Xpy and XpyF represent reliable nuclear-targeting sensors for strongly acidic media, illustrating how subtle structural modifications can yield distinct functional outcomes in bioimaging.

Glutathione‐capped gold nanoclusters (GSH‐Au NCs) with second near‐infrared (NIR‐II, 1000–1700 nm) fluorescence have received increasing interest in biomedical applications. However, conventional aqueous synthesis of GSH‐Au NCs results in low NIR‐II absolute fluorescence quantum yield (≈0.27%) and limited renal clearance efficiency (≈70%), which restricts its clinical applications. This study reports a GSH‐etching post‐synthesis method to selectively convert nonfluorescent GSH‐Au n NCs ( n &gt; 25) into fluorescent GSH‐Au 25 NCs (eGSH‐Au NCs). This molecular etching process decreases the size of the NCs from 3.3 to 2.0 nm and afforded 37% increase in NIR‐II absolute fluorescence quantum yield and 11.9% enhancement in renal clearance efficiency. The optimized eGSH‐Au NCs facilitates whole cerebrovascular imaging through the scalp and skull, tumor vasculature imaging with a resolution of 40.8 µm, dynamic tumor perfusion imaging with a signal‐to‐background ratio of 10.5, and enhanced lymphatic vessel and lymph node imaging. Additionally, eGSH‐Au NCs exhibit superior photothermal properties, achieving almost 100% tumor growth inhibition in Hepa1‐6 tumor‐bearing mice. This study presents a novel strategy to improve the bioimaging and therapeutic performance of NIR‐II Au NCs, thus advancing their clinical translation.

Upconversion has attracted much attention for the potential applications of nanomaterials and bulk materials. Upconversion nanoprobes and sensors rely on the non-linear emission of the reporters, which present a low efficiency due to their anti-Stokes nature. For these two reasons, the materials require accurate and contrastable efficiency measurements, typically by measuring the absolute upconversion quantum yield (UCQY). The methodology for such measurements will vary from traditional photoluminescence quantum yield techniques that have been applied for downshifting materials [1]. Effects like the scattering, broadband absorption and reemission, inner-filter effects, thickness, self-absorption, and temperature, have to be considered [2].This presentation will focus on some of these effects. The scattering has usually been neglected, however systems with scattering can increase the power density and subsequently the UCQY, as demonstrated both experimentally and via simulations [3]. Furthermore, this energy concentration also provides a new method for identifying the refractive index of phosphors, which is useful since some phosphors cannot be produced in macroscopic sizes. Broadband characterisation enables a route for characterisation exploiting the wide energy levels at the near-infrared. However, it introduces new challenges such as reemission [4]. In the case of applications that use a thick upconverted, the thickness is also a key parameter that can be responsible up to 50% of the emission [5].Finally, one of the applications that is been intensively researched is the use of upconverting and downshifting nanoparticles as temperature reporters. Absolute upconversion photoluminescence quantum yield characterisation for different probes will be presented with a modified integrating sphere that allows in-situ absorption and emission measurements.

We present an integrating hemisphere-based (i.e.,a variant of integrating spheres) implementation of the indirect illumination method for absolute photoluminescence quantum yield measurements, which is a recommended method in the international standard IEC 62607-3-1:2014. We rigorously formulated a mathematical model and a measurement procedure for the absolute photoluminescence quantum yield measurement in the integrating hemisphere-based system. The measurement system was calibrated using an Hg-Ar discharge lamp and spectral irradiance standard lamps for wavelength and relative spectral radiant flux scales, respectively. Furthermore, we identified and evaluated uncertainty components involved in the photoluminescence quantum yield (PLQY) measurement. To validate our measurement system, we applied it to the two de facto standard dyes: quinine bisulfate (QBS) and fluorescein (FLS). Consequently, their PLQY values were determined to be 0.563±0.024 (k=2) and 0.876±0.032 (k=2) for, respectively, QBS and FLS, which are consistent with previous reports.

Tetrasulfone[9]helicene (PTSH) was newly synthesized to improve and evaluate its fluorescence and excited-state dynamics through a single-step oxidation reaction of tetrathia[9]helicene (PTTH). In electrochemical measurements, the reduction potential of PTSH was shifted in a positive direction by approximately 1.0 V when compared to that of PTTH because of its electron-accepting sulfone units. The results of the electrochemical measurements agree with the energy levels calculated by density functional theory (DFT) methods and steady-state spectroscopic measurements. Furthermore, a significant enhancement of the absolute fluorescence quantum yield (ΦFL) was achieved. The absolute fluorescence quantum yield of PTSH attained 0.27, which is approximately 10 times larger than that of PTTH (ΦFL = 0.03). Such an enhancement of ΦFL can be successfully explained by the corresponding kinetic comparison. The reason is mainly the increased energy gap ΔEST between the lowest singlet (S1) and triplet (T1) excited state...

Absolute upconversion quantum yield of β-NaYF4 doped with Er3+ and external quantum efficiency of upconverter solar cell devices under broad-band excitation considering spectral mismatch corrections