Nonradiative Energy Transfer Research Articles

New C-linked diarylheptanoid dimers as potential α-glucosidase inhibitors evidenced by biological, spectral and theoretical approaches.

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by elevated blood glucose levels, generally due to defects of insulin action or secretion. Inhibition of α-glucosidase, an enzyme responsible for carbohydrate degradation, is a promising strategy for managing postprandial hyperglycemia in diabetic patients. In this study, two new C-linked diarylheptanoid dimers, kaemgalanganols A (1) and B (2), were isolated from K. galanga, which showed obvious inhibitory activity on α-glucosidase but weak activity on protein tyrosine phosphatase 1B (PTP1B). Kaemgalanganol B had an IC50 value of 35.1μM against α-glucosidase, obviously more potent than kaemgalanganol A (IC50=78.5μM) and acarbose (IC50=363.0μM). Enzyme kinetic study indicated that 2 was a reversible mixed-type inhibitor of α-glucosidase via non-competitive and anti-competitive inhibition modes. Fluorescence quenching and UV-visible spectroscopic study revealed that fluorescence quenching mechanism of 2 on α-glucosidase is a combination of dynamic quenching and static quenching, accompanied by non-radiative energy transfer. Compound 2 formed complex with α-glucosidase closer to the Tyr residue, and induced changes in both the microenvironment and peptide backbone. Surface hydrophobicity and CD spectra measurement indicated that 2 affected the function of α-glucosidase by decreasing the surface hydrophobicity of α-glucosidase as well as altering the secondary structure instead of the overall three-dimensional framework, which is consistent with the results of fluorescence experiment. Molecular docking manifested that compound 2 had a strong binding affinity (-7.27kcal/mol) with α-glucosidase, higher than 1 (-9.82kcal/mol) and acarbose (-4.48kcal/mol), consistent with the enzyme inhibitory assay. Besides hydrogen bonds, electrostatic interactions and hydrophobic interactions played important roles in the binding of 2 with α-glucosidase. This study disclosed the inhibitory activity and mechanism of 2 against α-glucosidase, which provides a theoretical basis for the development of new antidiabetic drugs form K. galanga.

ВОДОРАСТВОРИМЫЙ ПРЕПАРАТ НА ОСНОВЕ ХЛОРИНА Е6 С ЦИТРАТОМ ЕВРОПИЯ КАК ПОТЕНЦИАЛЬНЫЙ ФОТОСЕНСИБИЛИЗАТОР НОВОГО ПОКОЛЕНИЯ

The present study is directed towards synthesis a water-soluble substance for photodynamic therapy. It is an aqueous solution containing Chlorin e6 as a photosensitizer and europium citrate as a scintillator. The ionic composition of the solution was determined using ESI mass spectrometry. The conclusion was made about the nonradiative energy transfer from europium to Chlorin e6 with subsequent luminescence of the latter based on the analysis of the luminescence spectrum of the solution containing the conjugate [Eu:H2Cit:Chlorin e6=1:1:1]2-We studied dark toxicity «in vitro». It was shown that in the range of introduced PS concentrations from 3.13 to 100 μg/ml, the percentage of viable cells varied from 91.64±4.58% to 24.14±1.21%, which confirms the prospect of further study of the new substance

Förster Resonance Energy Transfer in Metal Halide Perovskite: Current Status and Future Prospects.

Förster Resonance Energy Transfer (FRET) is a non-radiative energy transfer process in a donor-acceptor system and has applications in various fields, such as single-molecule investigations, biosensor creation, and deoxyribonucleic acid (DNA) mechanics research. The investigation of FRET processes in metal halide perovskites has also attracted great attention from the community. The review aims to provide an up-to-date study of FRET in the context of perovskite systems. First, we discuss the fundamentals of FRET process, and then summarize the recent progress of FRET phenomenon in perovskite-perovskite, perovskite-inorganic fluorophores, perovskite-organic fluorophores, and organic fluorophores-perovskite systems. Finally, we speculate on the future prospects of roles of FRET in the implications for the overall performance of optoelectronic devices based on these systems, as well as the challenges in maximizing FRET efficiency.

Insight into the binding mechanism between soy protein isolate-oat β-glucan extrudate and quercetin in nanoparticles by multi-spectroscopic techniques.

Nanoparticles prepared by soy protein isolate (SPI)-oat β-glucan (OG) extrudates (E-SPI-OG) could encapsulate quercetin and improve its bioaccessibility. This study systematically investigated the binding mechanism between E-SPI-OG and quercetin in nanoparticles using multi-spectroscopic techniques. The results revealed that fluorescence quenching via static type occurred during the interaction between E-SPI-OG and quercetin, accompanied by the occurrence of non-radiative energy transfer (binding distance was 2.99nm and less than 7nm). The interaction between E-SPI-OG and quercetin was an endothermic and spontaneous binding process (ΔH>0 and ΔG<0) and mainly driven by hydrophobic interactions (ΔH of 4.92kJ·mol-1 and ΔS of 121.39J·mol-1·K-1). Tryptophan and tyrosine residues of E-SPI-OG were involved in binding to quercetin, resulting in a larger binding constant (2.07-5.48×105L·mol-1) and more binding sites (1.15-1.25). Quercetin altered the secondary structure of E-SPI-OG (α-helix content was reduced from 8.9% to 6.75%), causing its structure to become loose.

Deciphering the biophysical aspects of the interaction of 3,5,4'-trihydroxy-trans-stilbene with ribonuclease A: spectroscopic and computational studies.

Drug-receptor interaction is an important aspect in drug action, drug discovery, and pharmacological aspects. The molecule 3,5,4'-trihydroxy-trans-stilbene known as resveratrol is a natural polyphenol and exhibits diverse biological activities. Ribonuclease A catalyses the degradation of RNA by its ribonucleolytic activity. The report presents the binding interaction of resveratrol with RNase A using experimental and theoretical techniques. Experimental studies revealed the interaction strength of 104M-1 order with a single binding site. Resveratrol quenched the ribonuclease A fluorescence with a quenching constant of 104M-1 range. The accessible fraction of the fluorophore was found to be 0.75 besides non-radiative energy transfer from ribonuclease A to resveratrol. The donor-acceptor distance was 2.14nm from FRET calculations. No visible changes in the protein structure was evident from the circular dichroism studies. The interface residues involved in the interaction were obtained from docking studies. Further, the participation of the active site residues, His 12, His 119, and Lys 41 with interaction indicates the location of resveratrol near to the active site of ribonuclease A and indicates its possible potential to inhibit the ribonuclease A activity. The RMSD of less than 3Å indicates stable conformation of protein in the complex. The protein RMSF value in the complex less than 3Å shows no deviation of protein residues over time and thus suggests no conformational variation in the protein after binding.

Optimization study and luminescence enhancement effect for the determination of moxifloxacin using some rare elements

Moxifloxacin is a potent fluoroquinolone antibiotic and a promising antibacterial drug that significantly reduces skin, pneumonia, and respiratory pathogens. Herein, sensitive fluorescent trivalent lanthanides are desired as a facile, rapid, and effective MOX detection technique using light and heavy rare earth elements, such as Eu3+ and Tb3+, respectively. This spectrofluorometric technique relies on the nonradiative intramolecular energy transfer from MOX to lanthanide ions in the presence of cooperative ligands, for instance, 2,2′-bipyridine, 1,10-phenanthroline, or ethylene diamine, and an anionic surfactant (sodium dodecyl benzene sulfonate SDBS). Optimal fluorescence parameters, for instance, λex, λem, pH, concentrations of MOX, Ln3+, SDBS, and coordinating ligands, were determined based on the extent of sensitization. Micellar-enhanced fluorescence was also studied. The fluorescence intensity of the quaternary MOX-Ln3+-SDBS-phen system dramatically increased with MOX concentrations ranging from 0.4 to 8 µg/mL, with a determination coefficient and detecting limit of 0.9977 and 0.0221 µg/mL, respectively. The emission quantum yields of all systems were calculated, and it was observed that MOX-Tb3+-phen-SDBS has the highest quantum yield (0.26). Furthermore, the performance of this precise technique for detecting MOX was confirmed in pharmaceutical tablets and human serum/urine samples. The satisfactory recoveries% and RSD were found from 99.25 to 100.5 % and 1.6 to 1.8 % in tablets and from 95.33 to 103.35 % with 0.7 to 2.9 % in human samples, respectively.

In-situ oxidative polymerization of dopamine triggered by CuO2 in acidic condition and application in "turn-off" sensing.

Dopamine (DA) is a key neurotransmitter whose concentration affects various neurological disorders. Unlike previous methods that synthesize non-fluorescent polydopamine (NFL-PDA) under alkaline conditions, this study introduces a novel "turn-off" sensing method for DA using NFL-PDA synthesized through a unique reaction pathway. In our approach, CuO2 nanodots, created via a simple reduction method, catalyze the formation of hydroxyl radicals (•OH) in acidic conditions, triggering the oxidative polymerization of DA into NFL-PDA. The reaction between DA and CuO2 nanodots in acidic solution was examined to understand the process. UiO-66-NH2 was then used to test NFL-PDA's fluorescence quenching ability and to further investigate the DA determination mechanism. Results showed that fluorescence quenching was due to enhanced non-radiative energy transfer and Förster resonance energy transfer (FRET) between NFL-PDA and UiO-66-NH2. This led to the development of a simple "turn-off" fluorometric DA determination method with a linear range of 0.1-200μmol/L and a limit of detection (LOD) of 0.0575μmol/L. Although this method does not outperform existing NFL-PDA synthesis methods under alkaline conditions, it provides a new synthesis approach and application for sensing DA, contributing to the basic theory of chemical sensing. Additionally, DA determination in human serum samples was successfully achieved, with results consistent with high-performance liquid chromatography (HPLC).

Intelligent sensing platform based on europium-doped carbon dots for dual-functional detection of ciprofloxacin/Ga3+ and its tracking in vivo

Ciprofloxacin (CIP) and gallium (Ga) are widely used in many fields and their excessive presences will pose serious threats to the environment and life health. Therefore, developing an intelligent detection method for rapidly tracking and determination of CIP and Ga3⁺ concentration in environments and organisms is of great significance. In this work, a europium-doped carbon dots (Eu-CDs) with unique structure and performances was prepared by a one-pot hydrothermal method. Eu-CDs can efficiently overcome the problem of aggregation-induced fluorescence quenching in complex environments to track CIP and Ga3⁺ with highly sensitivity. The "antenna effect" of non-radiative energy transfer is introduced to explain the pathway on fluorescence transition of Eu-CDs through DFT theoretical calculations and mechanism investigations, which provide a theoretical basis for the design and development of novel carbon dots with specific functions. Eu-CDs can successfully be applied to fluorescence imaging in organisms, moreover, it also exhibits excellent application potentials in the field of anti-tumor and antibacterial. In addition, a portable intelligent detection platform based on Eu-CDs-hydrogel device have been developed, which provides a new strategy for rapidly detection of CIP and Ga3⁺ in real samples.

Charge Transfer Donor-Acceptor Guests Confined within Metal-Organic Framework Crystals

Organic donor-acceptor (D-A) co-crystals have emerged as a promising class of semiconductors for photovoltaic applications.1,2 These co-crystals, which are packed through π-stacking interactions, can form charge transfer (CT) excitons within donor-acceptor pairs. These materials can exhibit unique and rare properties such as ambipolar charge transport, room-temperature ferroelectricity, and non-linear optical properties. Confinement of such D-A pairs within crystalline porous host materials such as metal-organic materials (MOFs)3 has rarely been studied. This approach can improve energy and charge transfer interactions by constraining their interaction and minimizing nonradiative energy transfer. Additionally, the formation of D-A pairs as dimers or a polymeric phase without altering the CT interactions can be controlled; band gap tunability is also possible. We hypothesize that confining D-A pairs within a porous network will also enhance the exciton lifetime compared to its dimer state in a crystal or in solution. In 2014, we reported an example of successful confinement of dihexyl-sexithiophene (acceptor) and [6,6]-phenyl-C61-butyric acid methyl ester (donor) molecules within the pores of MOF-177.4 In the present work, we focused on different sets of D-A pairs to provide direct structural insights, such as the location within the pore, host-guest interactions, and guest-guest orientation. For this purpose, we dissolved naphthalene-TCNQ or pyrene-TCNQ in dichloromethane (DCM) at a 1:1 ratio and soaked MOF-177 crystals in the solution for 3 days. UV-Vis spectroscopy reveals the difference in the absorption bands of the isolated molecules vs. D-A pairs in MOF pores. To confirm the presence of guest species inside the MOF and to determine the donor vs. acceptor ratio we obtained nuclear magnetic resonance (NMR) spectra. Interestingly, our preliminary results confirm that both naphthalene-TCNQ and pyrene-TCNQ pairs were accommodated inside the MOF but in different stoichiometric ratios. We also collected single crystal X-ray diffraction of the MOF crystals after being soaked after infiltration with D-A pairs. Structural refinement is underway to determine their position and interactions. Our approach provides new mechanistic insights and also produces new benchmark materials with long exciton lifetimes, which can be utilized to advance current photonic technologies. References Abou Taka, J. E. Reynolds Iii, N. C. Cole-Filipiak, M. Shivanna, C. J. Yu, P. L. Feng, et al. Phys. Chem. Chem. Phys. 2023, 25, 27065.Sun, Y. Wang, F. Yang, X. Zhang and W. Hu. Adv. Mater. 2019, 31, 1902328.Shivanna, Q.-Y. Yang, A. Bajpai, E. Patyk-Kazmierczak and M. J. Zaworotko, Nat. Commun. 2018, 9, 3080.K. Leong, M. E. Foster, B. M. Wong, E. D. Spoerke, D. Van Gough, J. C. Deaton, et al. J. Mat. Chem. A 2014, 2, 3389.

Optical performance and luminescence properties of Dy3+-doped LaMgB5O10 phosphors

Despite significant advancements in borate-based phosphors, improving luminescent efficiency and thermal stability, particularly at high temperatures, remains a persistent challenge. In this study, Dy3+-doped LaMgB5O10 (LMBO) phosphors were synthesized and characterized for their photoluminescent properties to address these issues. Under 344 nm excitation, the Dy3+-activated LMBO phosphors exhibited strong luminescence with characteristic peaks at 482 nm (blue), 578 nm (yellow), and 663 nm (red), corresponding to specific Dy3+ transitions. Optimal luminescence was achieved at a doping level of 2 wt% Dy3+, beyond which quenching effects reduced emission intensity. The critical quenching distance (Rc) was estimated at 24.66 Å, indicating predominant non-radiative energy transfer. Moreover, thermal quenching was reduced, with the activation energy for thermal quenching determined to be 0.1975 eV, demonstrating that the material can maintain reasonable luminescence efficiency at elevated temperatures. Time-resolved photoluminescence spectroscopy revealed multi-exponential decay behavior, indicating the presence of multiple decay processes. The average luminescence lifetimes were calculated as 632 µs for the 2 wt% Dy3+ sample and 539 µs for the 3 wt% Dy3+ sample, with a clear concentration quenching effect observed at higher dopant levels. Colorimetric analysis in the CIE 1931 color space revealed a shift toward yellow with increasing Dy3+ concentration, achieving a correlated color temperature (CCT) of 6595 K at 2 wt% Dy3+. This shift supports the material’s potential for photonic and lighting applications. These findings highlight a significant advancement in addressing the thermal stability issue in phosphor materials, making Dy3+-doped LMBO phosphors promising candidates for advanced photonic technologies.

Photoluminescence of Tetra(benzimidazole)phenylethene Derivatives and Their Carbene Metallacycles in Aggregates and Langmuir-Blodgett Films.

Molecular structure, external stimuli, and environmental factors all have a strong effect on the internal molecular rotation and vibration of aggregate-induced emission (AIE) luminogens. Here, we report the AIE effect for several newly synthesized amphiphilic tetra(benzimidazole)phenylethene (TBiPE) derivatives and their binuclear N-heterocyclic carbene silver (NHC-Ag) metallacycles in solutions, aggregates, and Langmuir-Blodgett (LB) films. Monolayer behaviors and microscopic images indicate that introducing alkyl chains and binuclear NHC-Ag metallacycles can facilitate the formation of a well-defined insoluble monomolecular layer at the air-water interface. Absorption and luminescence spectral features suggest that both the TBiPEs' cyclization structure and binuclear NHC-Ag metallacycles can provide additional driving forces to restrict the internal molecular motion of the tetraphenylethene (TPE) unit, thus enhancing the AIE effects. Further, external stimuli and environmental factors such as poor solvent addition and LB film deposition also play important roles in the photoluminescent intensity, maximum wavelength, and lifetime. These internal and external factors can result in around 30-40 nm blue-shift for the maximum luminescence wavelength and 2-3 times shorter for the luminescent lifetime. These phenomena can be attributed to the reason that the nonradiative energy transfer efficiency is weakened because of the enhanced hydrophobic interaction and metal-carbene coordination as well as the closely packed arrangement of AIEgens in the LB films; consequently, the radiation energy transfer efficiency increased.

2D Titanium Carbide MXene and Single-Molecule Fluorescence: Distance-Dependent Nonradiative Energy Transfer and Leaflet-Resolved Dye Sensing in Lipid Bilayers.

Despite their growing popularity, many fundamental properties and applications of MXene materials remain underexplored. Here, the nonradiative energy transfer properties of 2D titanium carbide MXene are investigatedand their application in single-molecule biosensing is explored for the first time. DNA origami positioners are used for single dye placement immobilized by a specific chemistry based on glycine-MXene interactions, allowing precise control of their orientation on the surface. Each DNA origami structure carries a single dye molecule at predetermined heights. Single-molecule fluorescence confocal microscopy reveals that energy transfer of an organic emitter (ATTO 542) on transparent thin films made of spincast Ti3C2Tx flakes follows a cubic distance dependence, where 50% of energy transfer efficiency is reached at 2.7nm (d0). MXenes are applied as short-distance spectroscopic nanorulers, determining z distances of dye-labeled supported lipid bilayers fused on MXene's hydrophilic surface. Hydration layer (2.1nm) and lipid bilayer thickness (4.5nm) values that agree with the literature are obtained. These results highlight titanium carbide MXenes as promising substrates for single-molecule biosensing of ultrathin assemblies, owing to their sensitivity near the interface, a distance regime that is typically inaccessible to other energy transfer tools.

Exploring the viability of thermally robust β-BaB2O4: Dy3+ through FIR based polynomial approach for advanced temperature sensing and WLED applications

In this present work, we have explored the optical, structural, and thermal sensing properties of novel β-BaB2O4: xDy3+ (x = 1, 2, 3, 4, and 5 mol%) phosphors prepared using the solid-state reaction method. The optimization of the phosphors was achieved by using the characteristic emission spectra of Dy³⁺ ions. A thorough investigation was conducted into the various mechanisms contributing to concentration quenching, including cross-relaxation pathways, multipole-multipole interactions, and non-radiative energy transfer processes. Using the diffused reflectance spectra, significant parameters including optical band gap, nephelauxetic ratio, bonding parameter, and refractive index were evaluated. Temperature-dependent optical properties revealed a very high quenching temperature of 492.7 K. Using the florescent intensity ratio (FIR) with polynomial fit from 2nd to 5th order, the highest absolute sensitivity was obtained as 0.0472 K−1 at 483 K, and the highest relative sensitivity of 0.3922 % K−1 at 303 . Finally, the optimized phosphor exhibited exceptional thermal stability up to 500˚C with nearly 1 wt% of loss.

Spectroscopic Properties of TmF3-Doped CaF2 Crystals.

In this study, we report the growth and comprehensive spectroscopic analysis of TmF3-doped CaF2 crystals, grown using the vertical Bridgman method. The optical absorption and photoluminescence properties of both trivalent (Tm3+) and divalent (Tm2+) thulium ions were investigated. Optical absorption spectra in the UV-VIS-NIR range reveal characteristic transitions of Tm3+ ions, as well as weaker absorption bands corresponding to Tm2+ ions. The Judd-Ofelt (JO) formalism was applied to determine the intensity parameters Ω2, Ω4, and Ω6, which were used to calculate radiative transition probabilities, branching ratios, and radiative lifetimes for the Tm3+ ions. The emission spectra showed concentration-dependent quenching effects, with significant emissions observed for the concentration of 0.1 mol% TmF3 under excitation at 260 nm and 353 nm for Tm3+ ions and at 305 nm for Tm2+ ions. A new UV emission associated with divalent Thulium is reported. The results indicate that higher TmF3 concentrations lead to increased non-radiative energy transfer, which reduces luminescence efficiency. These findings contribute to the understanding of the optical behavior of Tm-doped fluoride crystals, with implications for their application in laser technologies and radiation dosimetry.

Carbon Dots and Their Films with Narrow Full Width at Half Maximum Orange Emission.

To obtain carbon dots (CDs) with narrow full width at half maximum (FWHM) and long-wavelength emission, carbon sources with high conjugate sizes and abundant functional groups can be employed to synthesize CDs. In this study, orange-emissive carbon dots (OCDs) were synthesized with phloroglucinol and rhodamine B as precursors. When the molar ratio of them was 30:1, and ethanol was served as the solvent, OCDs with optimized emission wavelength at approximately 580 nm, an FWHM of 30 nm, and a quantum yield (QY) of 27.31% were obtained. Subsequently, the OCDs were incorporated into polyvinyl alcohol (PVA) to fabricate solid-state OCD/PVA fluorescent films, which exhibited an FWHM of 47 nm. The PVA matrix facilitated the dispersion of OCDs, thereby suppressing non-radiative energy transfer among the OCDs and enhancing luminescence efficiency. Consequently, compared with OCDs, the OCD/PVA film exhibited significant luminescent enhancement, and the QY of the composite film was increased to 84.74%. Moreover, OCD/PVA film showed good transmittance and thermal stability. This research offers a solid theoretical and experimental foundation for the potential applications of CDs in the field of solid-state lighting.

Dysprosium ion concentration variations and their comprehensive influence on the physical, structural and optical properties of multi-component borate glasses for luminescence tailoring

A set of Zinc Strontium Lithium Fluoroborate (ZSLFB) glasses with different concentrations of Dysprosium ions (Dy3+) was created using the melt quench technique. The presence of non-crystallinity and various functional groups have been confirmed via X-Ray Diffraction (XRD) and Infrared Fourier Transform FT-IR measurements, respectively. The band gap values obtained from Tauc plot were utilised to analyse the optical characteristics. The photoluminescence (PL) emission spectra display three well-defined intensity peaks at wavelengths of 481, 574, and 664 nm. The intensity of peaks exhibits an ascending trend until a concentration of 0.5 mol% of Dy3+ ions is reached, after which it decreases. The PL intensity maintains up to 82 % at 200° C to room temperature, showing excellent thermal stability. The Judd Ofelt (J-O) parameter values pursue the Ω2 > Ω6 > Ω4 pattern, which shows its asymptotic nature. The CIE coordinates were assessed and determined to fall inside the white region. The interaction in the non-radiative energy transfer process was elucidated by utilizing the Dexter theory and Inokuti-Hiryama (I-H) model.

Singlet oxygen generation by nanoassemblies containing porphyrin macrocycles: Steric and screening effects, energy transfer and competing processes

In this semi-review paper, we discuss some principal aspects that should be taken into account upon quantitative analysis of the interaction with molecular oxygen O2 and the singlet oxygen (1O2 or [Formula: see text] generation by various tetrapyrrolic photosensitizers (including monomers, chemical dimers, triads, pentads and organic-inorganic nanoassemblies). In all cases, the direct experimental measurements of 1O2 emission at [Formula: see text] = 1.27 μ need to be corrected to the solvent influence (refractive indexes, molecular polarizability) on the rate constant of the radiative transition [Formula: see text] in a 1O2 molecule. For porphyrin and chlorin chemical dimers, T1 states quenching by O2 followed by 1O2 generation depends on donor-acceptor interactions between the dimer halves, and extra-ligation effects as well as the spacer flexibility. In the case of self-assembled triads and pentads containing Zn-porphyrin dimers and pyridyl substituted porphyrin free bases (H2P) as extra-ligands, quenching rate constants of H2P T1 states by O2 are smaller compared to those found for individual monomeric H2P molecules which is explained by the spatial screening influence of a strongly quenched Zn-porphyrin dimer in multiporphyrin complexes. Finally, at 293 K for nanoassemblies of two types (semiconductor quantum dots CdSe/ZnS + coordinative linked tetra-pyridyl porphyrins, and semiconductor negatively charged quantum dots AgInS/ZnS + positively charged porphyrin molecules) it was quantitatively shown that non-radiative energy transfer FRET quantum dot [Formula: see text] porphyrin (competing with electron tunneling under conditions of quantum confinement) is only responsible for the singlet oxygen 1O2 generation by nanoassemblies.

Synthesis of a BODIPY-quinoline dyad probe and studies of its biophysical interactions with fibrinogen/HSA by spectral and computational methods

A new BODIPY-based quinoline dyad probe (Bdq) was synthesized and its binding affinity with fibrinogen (Fib) and human serum albumin (HSA) was examined using steady-state/three-dimensional (3D) fluorescence and UV–vis absorption as well as molecular docking method. Fluorescence titration assays indicated that protein intrinsic emission was quenched by Bdq with a combined (static and dynamic) mechanism to form a non-fluorescent complex. 3D spectra showed that the two proteins undergo conformational changes when they interact with Bdq. Based on Förster’s non-radiative energy transfer; r, binding distances were found as 3.64/3.47 nm for Fib/HSA. The negative values of both ΔH (−62.27 kJ/mol) and ΔS (−83.03 J/mol K) parameters pointed out van der Waals forces/hydrogen bonds with Fib and also positive values of both ΔH (240.0 kJ/mol) and ΔS (920.0 J/molK) showed hydrophobic interactions with HSA of Bdq. Molecular docking also gave consistent results supporting the experimental binding types.

Maximizing Upconversion Luminescence of Co-Doped CaF₂:Yb, Er Nanoparticles at Low Laser Power for Efficient Cellular Imaging.

Upconversion nanoparticles (UCNPs) are well-reported for bioimaging. However, their applications are limited by low luminescence intensity. To enhance the intensity, often the UCNPs are coated with macromolecules or excited with high laser power, which is detrimental to their long-term biological applications. Herein, we report a novel approach to prepare co-doped CaF2:Yb3+ (20%), Er3+ with varying concentrations of Er (2%, 2.5%, 3%, and 5%) at ambient temperature with minimal surfactant and high-pressure homogenization. Strong luminescence and effective red emission of the UCNPs were seen even at low power and without functionalization. X-ray diffraction (XRD) of UCNPs revealed the formation of highly crystalline, single-phase cubic fluorite-type nanostructures, and transmission electron microscopy (TEM) showed co-doped UCNPs are of ~12 nm. The successful doping of Yb and Er was evident from TEM-energy dispersive X-ray analysis (TEM-EDAX) and X-ray photoelectron spectroscopy (XPS) studies. Photoluminescence studies of UCNPs revealed the effect of phonon coupling between host lattice (CaF2), sensitizer (Yb3+), and activator (Er3+). They exhibited tunable upconversion luminescence (UCL) under irradiation of near-infrared (NIR) light (980 nm) at low laser powers (0.28-0.7 W). The UCL properties increased until 3% doping of Er3+ ions, after which quenching of UCL was observed with higher Er3+ ion concentration, probably due to non-radiative energy transfer and cross-relaxation between Yb3+-Er3+ and Er3+-Er3+ ions. The decay studies aligned with the above observation and showed the dependence of UCL on Er3+ concentration. Further, the UCNPs exhibited strong red emission under irradiation of 980 nm light and retained their red luminescence upon internalization into cancer cell lines, as evident from confocal microscopic imaging. The present study demonstrated an effective approach to designing UCNPs with tunable luminescence properties and their capability for cellular imaging under low laser power.

Blue and white light emissions and energy transfer in Tm3+ and Dy3+/Tm3+ doped lithium-aluminum-zinc phosphate glasses

Lithium-aluminum-zinc phosphate glasses doped with thulium and dysprosium ions are characterized by using spectroscopy techniques. The Judd-Ofelt parameters were evaluated to calculate the radiative parameters of thulium 1D23F4 and 1G43H6 visible transitions and 3H43F4 near infrared transition, which shows the highest optical amplification parameters. Upon 356 nm excitation, the Tm3+ doped phosphate glass emits blue light with CIE1931 chromaticity coordinates x = 0.1540 and y = 0.0283 and color purity around 96.8%. With excitations at 347 and 350 nm, the Dy3+/Tm3+ doped phosphate glass emits neutral and cold white light with correlated color temperature values of 4716 and 6628 K, respectively. The dysprosium emission decay time in the codoped glass is shorter than that in the Dy3+ single-doped glass, indicating a non-radiative energy transfer from Dy3+ to Tm3+. The dominant electrical interaction involved in the energy transfer, following the model Inokuti-Hirayama, is of dipole-dipole type. The energy transfer probability and efficiency are 769.0 s-1 and 0.53, respectively. Tm3+ doped and Dy3+/Tm3+co-doped lithium-aluminum-zinc phosphate glasses could be appropriate for blue and neutral/cold white light-emitting device applications.