Journal of Luminescence最新文献

The efficient design of dual-sensing mechanisms for fluorescent probes holds significant implications for real-time monitoring of acetylcholinesterase (AChE) under oxidative stress. In this study, we employed density functional theory (DFT) and time-dependent density functional theory (TD-DFT) to investigate the fluorescence detection mechanisms of 2-(2-hydroxyphenyl)benzothiazole derivatives SNCN-AE and SNC-AE. We proposed a fluorescence detection method based on the mechanisms of excited-state intramolecular proton transfer (ESIPT) and photo-induced electron transfer (PeT). Computational results indicate that the fluorescence quenching of SNCN-AE and SNC-AE results from the typical PeT process initiated by the dimethyl carbamate ester moiety. Upon reaction with the AChE, the electron donor is replaced by the hydroxyl group, and the PeT is suppressed. The redshift of emission wavelength arises from the ESIPT process rather than the ICT mechanism, as evidenced by the absence of charge transfer phenomena in the computed frontier molecular orbitals. This study provides a novel insight for the further development of fluorescence probes in the field of biomedicine, based on the PeT-ESIPT mechanism regulation.

The appearance of the ultraviolet Bi³⁺-related emission band in the thermally stimulated luminescence (TSL) spectrum is observed around 465 K after selective irradiation of the YAlO₃:Bi perovskite in the Bi³⁺-related absorption bands. The excitation spectrum of the TSL glow curve peak at 465 K, activation energies of its creation by photons of different energies, and the dependence of the TSL peak intensity on the irradiation duration are measured. The origin of the optically created electron centers and the mechanisms of photostimulated creation of the electron and hole centers under irradiation in the Bi³⁺-related absorption bands of YAlO₃:Bi are discussed. The TSL glow curve peak at 465 K is suggested to appear as a result of electrons release from the electron centers intrinsic to the YAlO₃ lattice and their recombination with the hole Bi⁴⁺ centers. The same processes are shown to take place in the X-ray-irradiated YAlO₃:Bi perovskite. The obtained results are important for possible applications of the investigated material in thermoluminescent dosimetry.

Luminescence properties of strontium fluoride transparent ceramics with various TbF₃ amounts (0.1, 0.5, and 1 %) were investigated. Scintillation peaks derived from the electronic transitions between 4f levels in Tb³⁺ were observed. The observed scintillation decay times of approximately 8.3 ms were typical for the electronic transitions in Tb³⁺. Furthermore, the Tb-doped strontium fluoride transparent ceramics showed thermoluminescence and optically stimulated luminescence (OSL) with Tb³⁺ serving as the recombination center. The most intense thermoluminescence signal was detected from the 0.1 % Tb-doped transparent ceramic within the range of 0.01–100 mGy. OSL stimulated by 600 nm light of the same material was the most intense, and its lowest detectable limit was about 100 mGy.

Despite the appreciable high color-purity green-light of chiral Tb³⁺-complexes, it remains a great challenge to enable their both high quantum efficiency and large circularly polarized light (CPL) activity. Herein, through the self-assemble of the chiral Salen-type bis-Schiff-base ligand (S,S)-H₂L or (R,R)-H₂L with Zn(OAc)₂·2H₂O and Ln (NO₃)₃·6H₂O (Ln = La, Tb, Gd), two series of chiral Zn(II)-Ln (III)-heterobinuclear enantiomers [Zn ((S,S)-L)Ln (μ₁-OAc)(μ₂-NO₃)₂] (Ln = La, 1; Tb, 2; Gd, 3) or [Zn ((R,R)-L)Ln (μ₁-OAc)(μ₂-NO₃)₂] (Ln = La, 4; Tb, 5; Gd, 6) were afforded, respectively. Photophysical study shows that the destabilized ³π-π* energy level upon Zn²⁺ coordination, is confirmed to effectively sensitize of the Tb³⁺-centered green-light for the two chiral complexes [Zn ((S,S)-L)Tb (μ₁-OAc)(μ₂-NO₃)₂] (2) and [Zn ((R,R)-L)Tb (μ₁-OAc)(μ₂-NO₃)₂] (5). The merits of efficient (${\Phi }_{\text{Tb}}^L$ = 5.6–6.2 %) Tb³⁺-centered green-light and strong CPL activity (|g_PL| = 0.03, ⁵D₄→⁷F₃ transition), engender chiral Zn(II)-Tb(III)-Salen complexes like 2 and 5 a new platform to ideal chiral organo-Tb³⁺ candidates.

ZIF-8 (zinc-methylimidazolate framework-8) has shown promising applications as a fluorescence sensing platform, particularly in fluorescence quenching sensors for various biological and chemical analyses and detections. However, the impact of the morphology of ZIF-8 crystals on their performance of biomolecule detection, especially DNA detection, remains to be explored. In this study, six types of ZIF-8 crystals with different morphology (cubic, rough octahedral, flakes, rhombic, dodecahedral, and hexapod) are successfully synthesized by incorporating different concentrations of the surfactant/end-capping agent, namely cetyltrimethylammonium bromide (CTAB) and/or tris(hydroxymethyl)aminomethane (TRIS). These crystals are characterized in terms of morphology, crystal structure, specific surface area, and electrostatic adsorption capacity. Subsequently, these morphologically different ZIF-8 crystals are combined with fluorophore carboxyfluorescein (FAM)-labeled single-stranded DNA (ss-DNA) to form FAM-DNA@ZIF-8 biosensor. Then, their fluorescence quenching efficiency is characterized by using the fluorescence spectroscopy. The measurement results show that, due to its higher external specific surface area and zeta potential thereby higher electrostatic adsorption capacity, the cubic ZIF-8 crystal can effectively capture more FAM-DNA molecules through the electrostatic adsorption and achieve high fluorescence quenching efficiency via the fluorescence resonance energy transfer mechanism. Thus, the fluorescence quenching efficiency of the cubic FAM-DNA@ZIF-8 reaches up to 98.1 %. Finally, the cubic FAM-DNA@ZIF-8 biosensor is used to detect the complementary target HIV-1 DNA via the fluorescence recovery. The experimental results show that the fluorescence recovery efficiency of the FAM-DNA@ZIF-8 reaches up to 40.8 upon the addition of complementary target ssDNA, significantly higher than the recovery efficiency when non-complementary target DNA is introduced. Also, both fluorescence quenching efficiency and recovery efficiency of the cubic FAM-DNA@ZIF-8 are much higher than those of the reported biosensors based on ZIF-8 crystals with non-optimal morphology. Additionally, the fluorescence recovery sensitivity of the biosensor is 0.536/(nM⋅mL), with a detection limit as low as 1.37 nM. In addition, its detection performance remains almost unchanged after ten days of storage. These findings provide valuable insights for optimizing ZIF-8-based DNA biosensor.

Optical scatterer additives play a critical role in enhancing the light conversion efficiency and uniformity of quantum dot-converted light-emitting diodes (Qc-LEDs). This study investigates the impact of optical characteristics and morphology of nanoscatterer on the light conversion and extraction efficiency of Qc-LEDs. Various metal oxides and boron nitride nanoparticles and nanoplates with different diffraction index were selected to carry out the study. Finite-Difference Time-Domain (FDTD) simulation was employed to evaluate the scattering effect of various nanosphere and nanoplate scatterers on the optical performance of the Qc-LEDs. The simulation results revealed that the hybrid nanoscatterer integrates the forward-scattering from the nanosphere and backward-scattering of blue light from the nanoplate. Spectral analysis was conducted to examine the optical performance of Qc-LEDs with varying combinations and concentrations of nanoscatterers. TiO₂ nanoparticles and Al₂O₃ nanoplates were found to be the best combination for maximal light conversion and extraction efficiency within Qc-LEDs. The results indicate an optimal light efficiency is obtained with the optimal ratio of 1:2:2 for quantum dots, TiO₂ nanoparticles, and Al₂O₃ nanoplates. These findings reveal the relationship between optical properties, morphology, and light conversion efficiency in Qc-LEDs, highlighting the advantages of the hybrid nanoscatterers for improving optical performance of Qc-LEDs.

Investigation of the signal enhancement of Nd³⁺ codoped TeO₂-ZnO pedestal waveguides, at 1064 nm, due to Au nanoparticles deposited over the core is presented for the first time. Nd³⁺ doped TeO₂-ZnO thin film was obtained by RF Magnetron Sputtering deposition. The resulting core with 500 nm height and widths in the 4–40 μm range, exhibited low roughness average in all area measured (0.48 ± 0.04) nm. Minimum propagation losses of 2.2 dB/cm were observed for waveguide width of 40 μm whereas an increase took place for smaller ones. Scanning electron microscopy (SEM) allowed the waveguide structure inspection and transmission electronic microscopy (TEM) the Au nanoparticles evaluation. The results showed that the Au nanoparticles contributed up to 75 % of relative gain enhancement, under 808 nm excitation. This increase was due to the local field growth in the proximity of the nanoparticles that enhances the density of excited Nd³⁺. The internal gain that considers the propagation losses reached positive values for larger core widths (above 8 μm).

The present study opens possibilities for optical amplifiers with low propagation losses based on different metal-dielectric composites, as well as other waveguide-based devices.

Extensive studies have been conducted on hybrid metal halides due to their application in radiation detection, solid-state lighting, and solar cells. Here, we present an environmentally friendly zero-dimensional halide, (C₉H₁₅N₃)ZnBr₄, which crystallizes in the P2₁/c space group. This compound is highly thermally stable, and doping Mn²⁺ results in a bright green light emission, with an impressive internal quantum efficiency of 52.9 % and an external quantum efficiency of 45.9 % for (C₉H₁₅N₃)Mn_0.3Zn_0.7Br₄. Combining spectroscopic analysis with first-principles density functional theory (DFT), it is concluded that the high external quantum efficiency arises from efficient energy transfer from the organic component to the [MnBr₄]^2-. Notably, the (C₉H₁₅N₃)Mn_0.3Zn_0.7Br₄ luminescence intensity maintains 50 % of its room temperature level even at 400 K. Moreover, these doped powders display exceptional scintillation performance, higher than Bi₄Ge₃O₁₂. Finally, the radioluminescence intensity of (C₉H₁₅N₃)Mn_0.3Zn_0.7Br₄@polydimethylsiloxane flexible films is about three times that of Bi₄Ge₃O₁₂. These features position Mn:(C₉H₁₅N₃)ZnBr₄ as an ideal material for X-ray detection and an efficient green photoluminescent material.

Increasing the spin-orbit coupling (SOC) constant by introducing heteroatoms is crucial approach for achieving efficient pure organic room-temperature phosphorescent (RTP). This research focused on the molecules 3,3″-Di(9H-carbazol-9-yl)-1,1':3′,1″-terphenyl (DCzTp) and 2,6-Bis[3-(9H-carbazol-9-yl)phenyl]pyridine (DCzPPy) using transient absorption spectroscopy experiments. For DCzTp, the femtosecond spectroscopy revealed an excited state absorption (ESA) signal at 630 nm, which reached a maximum within 1.3 ps, followed by decay of the ESA signal and appearance of triplet-triplet absorption (TTA) signal at 405 nm. An isosbestic point at 465 nm indicated the presence of intersystem crossing (ISC). In nanosecond spectroscopy, the TTA signal reached its maximum within 23 ns, and then the triplet state lifetime (τ_TTA) decayed within 1.9 μs. DCzPPy exhibited faster ISC lifetime (τ_ISC = 5.5 ns) and longer τ_TTA (4.9 μs) compared to DCzTp. Theoretical simulations demonstrated that DCzTp transitions from the lowest singlet excited state (S₁) to the lowest triplet excited state, while DCzPPy transitions from S₁ to the higher triplet excited state (T₂). Notably, due to the heteroatom effect, the SOC constant of DCzPPy (0.27 cm⁻¹) was greater than that of DCzTp (0.23 cm⁻¹), leading to a faster τ_ISC (5.5 ns vs. 11.4 ns). Additionally, DCzPPy exhibited an additional triplet state internal conversion process (1.1 μs), leading to a longer τ_TTA (4.9 μs vs. 1.9 μs). This research provides valuable insights into how heteroatoms enhance RTP efficiency in pure organic molecules.

Herein, a series of Er³⁺ self-sensitized NaYS₂ phosphors are synthesized by the solid-gas reaction method for a novel upconversion luminescence thermometer. Er³⁺ possesses abundant excited state energy levels in the near-infrared region, enabling efficient upconversion luminescence by absorbing different near-infrared wavelength light. Compared to 980 nm excitation, the emission intensity is enhanced by nearly an order of magnitude under 1532 nm excitation, which can be attributed to the larger absorption cross-section of ⁴I_13/2 and stronger absorption efficiency for Er³⁺. Based on the luminescence intensity ratio technique, the optical thermometry behaviors of NaYS₂:Er³⁺ under different wavelength excitation are evaluated by employing the thermally coupled energy levels of ²H_11/2/⁴S_3/2. It can be deduced that the excitation wavelength has no significant effect on the temperature sensing parameters. Compared to other typical upconversion luminescence thermometers, NaYS₂:Er³⁺ thermometer exhibits not only excellent sensitivity performance but also high upconversion luminescence efficiency, which is expected to be applied in wide-temperature-range and highly-sensitive temperature sensing.