Sensitive Luminescence Research Articles

Sensitive ratiometric sensor for Al(III) detection in water samples using luminescence or eye-vision

A facile, quick, and sensitive ratiometric luminescence sensor is designed for detection aluminum ions in water samples using luminescence or eye-vision. This approach relies on the emission change of the europium(III) complex with 3-(2-naphthoyl)-1,1,1,-trifluoro acetone (3-NTA) after interaction with various concentration of aluminum ions. The addition of aluminum ions suppressed the Eu(III) emission at 615 nm under 333 nm excitation, while simultaneously enhancing the ligand emission at 480 nm. Optimum detection was obtained in methanol. The quantification of aluminum ions using ratiometric method was determined by plotting the luminescence ratio (F480nm/F615nm) versus aluminum ions concentration. The calibration plot was obtained within the range 0.1–100 µM with LOD = 0.27 µM. Additionally, the concentration of aluminum ions can be estimated semi-quantitatively by visually observing the luminescence colour change of the probe from red to light green and then to dark green after being excited by a UV lamp with 365 nm. As far as we are aware, this is the first luminescent lanthanide complex-based ratiometric probe for the detection of aluminum ions. The probe showed remarkable aluminum ions selectivity relative to that of other metal ions. The suggested sensor was used effectively to identify aluminum ions in water samples with good results.Graphical

Solid-State Luminescence Turn-On Sensing Using MOF-Confined Reporter-Spacer-Receptor Architectures Facilitated by Quencher Displacement.

The reporter-spacer-receptor (RSR) approach is prevalent to develop molecular turn-on sensors. However, the fluorescent RSR sensors barely operate in solid state, which hinders their fabrication into devices for practical applications. Herein, we present a novel strategy to achieve solid-state luminescence turn-on sensing by assembling RSR architectures within MOF frameworks. Unlike the regular RSR systems, the framework-confined fluorophore and receptor are well arranged and separated even in the solid state. This concept is illustrated by a multicomponent MOF (Fc@NU-1000), which contains organic linkers with a highly luminescent pyrene core as the reporter, Zr6 nodes with unsaturated sites as the receptor, and the incorporated Fc molecules as the quencher. The separate incorporation of pyrene core and Fc in the multicomponent MOF favors an efficient pseudointramolecular photoinduced electron transfer (PET) process, resulting in significant luminescence quenching. Interestingly, such PET process can be blocked via the quencher displacement initiated by the phosphate analyte, therefore recovering the solid-state luminescence of MOF microcrystals. We found that Fc@NU-1000 is shown as a sensitive solid-state luminescence turn-on probe for phosphate with the naked-eye response at a low content. What's more, this study is the first example of confining a quencher displacement-based RSR system in the MOF framework for solid-state luminescence turn-on sensing, thus also providing new opportunities for MOF materials to develop luminescence turn-on sensors.

An advanced organic molecular probe for multimodal fluorescence imaging of cellular lipid droplets

Lipid droplets (LDs) are critical cellular organelles associated with various physiological processes in eukaryotic cells. To visualize LDs and research their complex physiological functions, various fluorescence imaging models including the confocal imaging, the lambda scan imaging and the stimulated emission depletion (STED) super-resolution imaging have been successfully employed in recent years. However, since different fluorescence imaging models have different requirements for fluorescent probes, it is very challenging to employ single fluorescent probe for multimodal fluorescence imaging. Herein, an advanced organic fluorescent probe Lipi-DSBOMe has been sophisticatedly developed for purpose. Featuring with the advantages of high staining selectivity towards LDs, polarity sensitive luminescence, high photostability and low STED saturation intensity, this fluorescent probe is well suited for multimodal fluorescence imaging. For instance, employed with this probe for three-dimensional (3D) confocal imaging to quantitatively determine the change of number of LDs under the oleic acid stimulation, lambda scan imaging to precisely measure the polarity of LDs in different types of cells, and STED imaging to measure the size of LDs with the state-of-the-art resolution (42 nm). In overall, employing this single fluorescent probe for multimodal fluorescence imaging has allowed to provide abundant information about LDs, thus effectively promoting the LDs biology studies.

Probing the Cr3+ luminescence sensitization in β-Ga2O3 with ion-beam-induced luminescence and thermoluminescence

Ion-beam-induced luminescence (IBIL) measurements were performed in Cr-doped β-Ga2O3 using both protons and helium ions, showing a strong enhancement of the Cr3+ luminescence upon ion irradiation. Theoretical modelling of the IBIL intensity curves as a function of the fluence allowed estimating the effective cross-sections associated with the defect-induced IBIL enhancement and quenching processes. The results suggest that sensitizing the Cr3+ luminescence is more efficient for H+ than for He+ irradiation. Thermoluminescence (TL) studies were performed in the pristine sample, with no TL signal being observed in the spectral region corresponding to the Cr3+ emission. In agreement with the IBIL study, upon ion irradiation (with either protons or helium ions), this TL emission is activated. Moreover, it can be quenched by annealing at 923 K for 10 s, thus revealing the role played by the defects induced by the irradiation. These results show that the irradiation-induced defects play a major role in the activation of the Cr3+ luminescence, a fact that can be exploited for radiation sensing and dosimetry.

Metformin mitigates radiation toxicity exerting antioxidant and genoprotective properties.

The antidiabetic drug metformin (MF) exhibits redox-modulating effects in various pathologies associated with oxidative stress and mitigates ionizing radiation-induced toxicity, but the underlying mechanisms remain to be elucidated. Thus, we studied some radiomitigatory effects of MF and explored the possible mechanisms behind them. Highly sensitive luminescence methods and non-competitive enzyme-linked immunosorbent assay (ELISA) were used in in vitro studies, and in vivo the damage to bone marrow cells and its repair were assessed by the micronucleus test. In a solution, MF at concentrations exceeding 0.1µM effectively intercepts •OH upon X-ray-irradiation, but does not react directly with H2O2. MF accelerates the decomposition of H2O2 catalyzed by copper ions. MF does not affect the radiation-induced formation of H2O2 in the solution of bovine gamma-globulin (BGG), but has a modulating effect on the generation of H2O2 in the solution of bovine serum albumin (BSA). MF at 0.05-1mM decreases the radiation-induced formation of 8-oxoguanine in a DNA solution depending on the concentration of MF with a maximum at 0.25mM. MF at doses of 3mg/kg body weight (bw) and 30mg/kg bw administered to mice after irradiation, but not before irradiation, reduces the frequency of micronucleus formation in polychromatophilic erythrocytes of mouse red bone marrow. Our work has shown that the radiomitigatory properties of MF are mediated by antioxidant mechanisms of action, possibly including its ability to chelate polyvalent metal ions.

Impact of chiral ligands on photophysical and electro-optical properties of β-diketonate europium complexes in circularly polarized OLEDs.

Luminescent lanthanide complexes exhibiting chiroptical properties are attracting attention for their application in chiral optoelectronics and photonics, thanks to their unique optical properties, allied to intraconfigurational f-f transitions, which are generally electric-dipole-forbidden and can be magnetic dipole-allowed, which in an appropriate environment can lead to high dissymmetry factors and strong luminescence, in the presence of an antenna ligand. However, because luminescence and chiroptical activity are governed by different selection rules, their successful application in commonly used technologies is still an expectation. Recently, we showed that europium complexes bearing β-diketonates acting as luminescence sensitizers, and chiral bis(oxazolinyl) pyridine derivatives as the chirality inducer, reasonably perform in circularly polarized (CP) organic light-emitting devices (OLEDs). Indeed, europium β-diketonate complexes are an interesting molecular starting point, given their strong luminescence and their established use in conventional (i.e., nonpolarized) OLEDs. In this context, it is interesting to investigate in detail the impact of the ancillary chiral ligand on complex emission properties and the performances of corresponding CP-OLEDs. Here we show that, by incorporating the chiral compound as emitter in the architecture of solution processed electroluminescent devices, CP emission is retained, and the efficiency of the device is comparable to reference unpolarized OLED. The observed remarkable dissymmetry values strengthen the position of chiral lanthanide-OLEDs as CP-emitting devices.

Synthesis and characterization of the new carbacylamidophosphate based rare earth tetrakis-complexes NEt4[LnL4]. Effect of the ligand nitro group on luminescence of Eu3+ and Tb3+.

O,O′-dimethyl-N-(3-nitrobenzoyl)amidophosphate (HL) was synthesized, structurally characterized, tested as ligand to obtain lanthanide complexes NEt4[LnL4] (Ln = La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Er3+, Y3+) and as a sensitizer of Eu3+ and Tb3+ luminescence. It was shown that besides of typical for carbacylamidophosphates intermolecular contacts, the electrostatic interactions N∙∙∙O of the length 2.936 Å exist in the crystal of NEt4[EuL4] and influence on both the crystal packing and the lanthanide polyhedron shape. In the structure of the complex anion, two pairs of symmetry-related ligands differ in configuration (syn- or anti-) of nitro groups with respect to the carbonyl groups. The obtained complexes were found to be thermally stable to near 200 °C. Luminescent studies have shown that excitation energy is dissipated, which prevents ligands from efficient luminescence sensitization of europium and terbium.

Modulating the Extent of Anisotropic Cuprophilicity via High Pressure with Piezochromic Luminescence Sensitization.

Metallophilicity has been widely studied as a fundamental supramolecular interaction. However, the extent and directionality thereof remain controversial. A major obstacle lies in the difficulty to separately control the geometry and chemical composition. Herein, we address this challenge by modulating metallophilicity with mechanical pressure. Using a multinuclear Cu(I) complex as model system, we report anomalous anisotropies of (supra)molecular structures, vibrations, and interaction energies upon isotropic compression as well as concomitant (essentially turn-on) piezochromic luminescence enhancement with ∼103 modulation. The in situ characterizations indicate opposite behaviors of contact distances and cuprophilic interactions for intermolecular vs intramolecular Cu-Cu pairs under pressure. Theoretical calculations break down the attractive and repulsive forces associated with cuprophilicity, its spontaneous 4p-3d hybridization origin, and direction-dependent interaction strength. The use of isotropic mechanical force reveals the intrinsic anisotropy of metallophilicity in multinuclear systems.

Boosting organic room-temperature phosphorescence performance through joint luminescence sensitization

Boosting organic room-temperature phosphorescence performance through luminescence sensitization involving multi-step energy transfer.

Chemiluminescence resonance energy transfer-based multistage nucleic acid amplification circuits for MiRNA detection with low background.

Chemiluminescence resonance energy transfer (CRET)-based assays have shown great potential in biosensing due to their negligible background autofluorescence, yet are still limited by their low sensitivity and short half-life luminescence. Herein, a multistage CRET-based DNA circuit was constructed with amplified luminescence signals for accurate miRNA detection and fixed reactive oxygen species (ROS) signals for cell imaging. The DNA circuit is designed through an ingenious programmable catalytic hairpin assembly (CHA), hybridization chain reaction (HCR), and the use of DNAzyme to realize target-triggered precise regulation of distance between the donor and acceptor for CRET-mediated excitation of photosensitizers. In detail, the analyte catalyzes the hybridization of CHA reactants, which leads to the assembly of multiple HCR-mediated DNAzyme nanowires. Subsequently, DNAzymes catalyze the oxidation of luminol by H2O2, and the adjacent photosensitizer chlorin e6 (Ce6) anchored on the DNA nanostructure is stimulated by the CRET process, resulting in the amplified long-wavelength luminescence and the generation of single oxygen signals through further energy transfer to oxygen. The biomarker miRNA can be detected with great sensitivity by integrating the recognition module into a universal platform. Furthermore, the DNA circuit enables CRET-mediated intracellular miRNA imaging, by detecting singlet oxygen signals through a ROS probe. The significant amplification effect is attributed to the robust multiple recognition of the target and the guaranteed transduction of the CRET signal through programmable engineering of DNA nanostructures. The CRET-based DNA circuit achieves amplified long-wavelength luminescence for accurate miRNA detection with low background and ROS-mediated signal fixation for cell imaging, making it a promising candidate for early diagnosis and theranostics.

A Tb and Ag co-doped borate compound forms a high sensitive X-ray, gamma-ray and neutron luminescence dosimeter

Thermal and optical stimulations of neutron-sensitive CaB6O10:Tb3+,Ag+ led to two recombination pathways.

A New Method for the Synthesis of Layered Europium Hydroxide Using Propylene Oxide as the Precipitating Agent

A new method for the synthesis of layered europium basic chloride in up to 90% yield was developed. The method is based on hydrolysis of europium chloride in the presence of propylene oxide. The effect of reaction temperature on the yield and composition of the products of europium chloride hydrolysis in the presence of propylene oxide was analyzed. The obtained layered europium basic chloride had pronounced anion exchange properties. The possibility of intercalation of the isonicotinate anion into a layered rare earth hydroxide was demonstrated for the first time. The intercalation of the benzoate or isonicotinate anions into layered europium hydroxide led to luminescence sensitization and decrease in the Eu3+ local symmetry.

Synthesis, characterization, luminescence properties and deciphering the role of a terpyridyl-imidazole based ligand in the dissimilar luminescence sensitization of ternary lanthanide(III) tris-(β-diketonate) complexes.

We designed four ternary lanthanide tris-(β-diketonate) complexes of the form [Ln(tta)3(tpy-HImzphen)], where Ln = LaIII, EuIII, SmIII and TbIII; tta = (2-theonyltrifluoroacetonate) and tpy-HImzphen = 2-(4-[2,2':6',2'']terpyridin-4'-yl-phenyl)-1H-phenanthro[9,10-d]imidazole. All the complexes have been thoroughly characterized by standard analytical tools and spectroscopic techniques including single crystal X-ray diffraction. In situ generation of the complexes was also monitored via absorption and emission spectroscopy upon incremental addition of the respective lanthanide precursor {Ln(tta)3(H2O)2} to the dichloromethane solution of the terpyridyl-imidazole ligand. The photophysical behaviors of all the complexes were thoroughly investigated via absorption and both steady-state and time-resolved emission spectroscopic techniques. The emission spectral measurements were carried out at both room temperature and 77 K to understand the deactivation dynamics of the excited states and elucidate the distinctive luminescence responses from the four lanthanide metal ions owing to the introduction of the terpyridyl-based ancillary ligand.

A butterfly shaped Eu4(OH)2 cluster-based luminescent metal-organic framework with Lewis basic triazole sites demonstrating turn off sensing in the presence of organic amines.

The effective detection of organic amines is particularly important for environmental protection and human health. Herein, according to hard and soft acid base theory, a novel three-dimensional (3D) butterfly shaped Eu4(OH)2 cluster-based metal-organic framework with Lewis basic triazole sites, {[Eu4(taip)4(ox)(OH)2(H2O)4]·3H2O}n (1) (H2taip = 5-(1,2,4-triazol-1-yl) isophthalic acid, H2ox = oxalic acid), was successfully synthesized under solvothermal conditions, and was characterized by single crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, infrared spectroscopy and thermogravimetric analysis. Structural analysis reveals that compound 1 is a 3D net constructed from butterfly shaped Eu4(OH)2 clusters and contains isosceles triangular channels with dimensions of 8.84 × 8.84 × 8.63 Å3, which shows an unprecedented 8-connected topology with a Schläfli symbol {36·418·53·6}. Fluorescence experiments of compound 1 show sensitive luminescence quenching responses to organic amines such as diethylamine (DEA), trimethylamine (TMA), triethylamine (TEA), ethylenediamine (EDA) and aniline, and the quenching constants (KSV) decrease in the following order: EDA > DEA > TMA > TEA > aniline. The fluorescence quenching responses may be attributed to the energy gap between the LUMO energy values of H2taip and organic amines, which hinders the transfer of excited state energy to the emission state of Eu3+ and results in luminescence quenching. The fluorescence lifetimes of compound 1 in ethanol and organic anilines indicate that the fluorescence recognition process of organic amines was static.

Designing dual-emission phosphors for temperature warning indication and dual-mode luminescence thermometry.

Color tunable phosphors of Mn4+ and Tb3+ co-doped double-perovskite SrGdLiTeO6 (SGLT) were synthesized in this work. The crystal parameters and photoluminescence performances were investigated in detail. By taking advantage of the different thermal quenching strengths between Mn4+ and Tb3+ ions, the emission color of SGLT:0.7%Mn4+/1%Tb3+ changed from red to green, which could be used for high-temperature temperature warning indication. Moreover, according to the luminescence intensity ratio (LIR) technique, wide temperature-range optical thermometry was developed and further, the maximum relative sensitivity (SR1) value of the SGLT:0.7%Mn4+/5%Tb3+ phosphor was determined to be 1.49% K-1 at 560 K. On the other hand, the sensing properties were also analyzed based on the temperature-dependent lifetime method. The most interesting thing is that the maximum SR2 value reached 1.88% K-1 at 573 K. This work proved that the Mn4+ and Tb3+ co-doped double-perovskite SrGdLiTeO6 could be potentially used in temperature warning indication and high sensitivity luminescence thermometry.

Luminescence and temperature-dependent sensitivity of Yb3+/Er3+ doped glass ceramics containing NaGd(MoO4)2 nanocrystals

Yb3+/Er3+ doped NaGd(MoO4)2 glass ceramics (GCs) were manufactured by melting quenching and subsequent controllable crystallization method, and the structure, transmissivity, up-conversion luminescence and temperature sensitive characteristics were studied. The results show that NaGd(MoO4)2 nanocrystals are embedded in the precursor glass (PG). The crystallization temperature and soaking time directly affect the crystallinity of the glass. Enhanced up-conversion luminescence in the GC sample is clearly observed. According to thermal coupling emission states, the maximum relative sensitivity (Sr-max) of 1.32 % K−1 and absolute sensitivity (Sa-max) of 1.90 % K−1 between 297 K and 437 K are acquired in the GC700-2h sample. This finding reveals that the obtained GC materials have great potential in optical temperature measurement.

Simple synthesis of dual-emission CsPbBr3@EuBTC composite for latent fingerprints and optical anti-counterfeiting applications

As an emerging optical material, all-inorganic perovskite quantum dots (QDs) have been successfully applied in some fields. However, inherent ionic properties of perovskite QDs lead to poor stability of water and heat which severely hinders the further industrial applications. Therefore, the incorporation of Metal-Organic Framework (MOF) into QDs to obtain CsPbX 3 @MOF composite is developing to improve the stability of all-inorganic perovskite QDs. In this work, a simple and fast method was developed to synthesize a CsPbBr 3 @EuBTC composite. The water stability and thermal stability of the CsPbBr 3 @EuBTC composite have been improved compared to pure CsPbBr 3 QDs. Simultaneously, luminescent properties and promising latent fingerprints and optical anti-counterfeiting applications of the CsPbBr 3 @EuBTC composite are further explored. Under fluorescent interference, it still shows excellent luminescence sensitivity and anti-interference ability. The CsPbBr 3 @EuBTC composite displays dual-mode luminescence as excited under the 365 nm or 254 nm ultraviolet (UV) excitation wavelength. Adjusting the ratio of CsPbBr 3 QDs to EuBTC in the CsPbBr 3 @EuBTC composite can also achieve multi-color luminescence. Therefore, it is expected that CsPbBr 3 @EuBTC can be applied to latent fingerprints and multi-mode optical anti-counterfeiting materials.

Molecular architecture, characterization, and applications of homoleptic heteronuclear 3d/4f metals’ complexes derived from bi-compartmental Schiff-base

A series of homoleptic heterotrinuclear 3d/4f metal complexes (2-6) of general formula [Zn2Ln(salopn)2(NO3)3H2O].CH3CN.H2O; where Ln = La (2), Nd (3), Sm (4), Gd (5) and Dy (6); have been synthesized by using tetradentate bi-compartmental Schiff base ligand, [2-((E)-(2-((E)-2-hydroxybenzylideneamino)phenylimino)methyl)phenol], and Zn(salopn) precursor (1). The unequivocal evidence of their structural motifs is obtained by characterizing the compounds through FT-IR spectroscopic, and single crystal XRD data, besides the elemental analyses. The trinuclear complex 6 shows that the ligand attached to the metals’ centers, Zn(II) and Dy(III) through N, O and O, O sites respectively. The zinc center is pentacoordinated having distorted square pyramidal geometry and to which Zn-O and Zn-N bond lengths lie in range 2.006-2.035 Å and 2.044-2.060 Å respectively. The dysprosium center is octa-coordinated which is attached to four oxygen atoms from salopn−2 and four oxygens from bidentate nitrate moieties, where Dy-O bond length is in range 2.292-2.517 Å. The photoluminescence (PL) data described that the heteronuclear complexes show characteristic luminescence properties and sensitization across the bi-compartmental ligand. The magnetic parameters for (2-6) are determined and their room temperature χm T and µeff values are found in range 0.18-15.12 emu.mole−1.K and 1.20-10.96 µB respectively that describe the paramagnetic nature.

Recent Development in Sensitizers for Lanthanide-Doped Upconversion Luminescence.

The attractive features of lanthanide-doped upconversion luminescence (UCL), such as high photostability, nonphotobleaching or photoblinking, and large anti-Stokes shift, have shown great potentials in life science, information technology, and energy materials. Therefore, UCL modulation is highly demanded toward expected emission wavelength, lifetime, and relative intensity in order to satisfy stringent requirements raised from a wide variety of areas. Unfortunately, the majority of efforts have been devoted to either simple codoping of multiple activators or variation of hosts, while very little attention has been paid to the critical role that sensitizers have been playing. In fact, different sensitizers possess different excitation wavelengths and different energy transfer pathways (to different activators), which will lead to different UCL features. Thus, rational design of sensitizers shall provide extra opportunities for UCL tuning, particularly from the excitation side. In this review, we specifically focus on advances in sensitizers, including the current status, working mechanisms, design principles, as well as future challenges and endeavor directions.

A high-nuclearity Cd(II)-Tb(III) nanocage for the rapid and quantitative time-resolved luminescence detection of guanosine-5-monophoshpate and RNA

One 32-metal Cd(II)-Tb(III) nanocage 1 was obtained using a flexible Schiff base ligand. The addition of guanosine-5-monophosphate (GMP) and RNA of human pancreas cancer results in the Tb(III) luminescence (5D4 → 7Fn transitions, n = 6, 5, 4 and 3), which is dominated by the static enhancement model. 1 exhibits highly sensitive time-resolved luminescence (TRL) detection to GMP and RNA with a delay time of 500 μs, and the corresponding linear fitting equations are (I-I0)/I0 = 14502·CGMP + 856 and (I-I0)/I0 = 2421·CRNA + 1926, respectively. The limits of detection to GMP and RNA are 0.021 μM and 0.71 ng/μL, respectively, and 1 can be used to determine the concentrations of GMP and RNA accurately. 1 displays rapid and stable luminescence response to the analytes, with the response times less than five seconds and no changes for the lanthanide emission over one week.