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Lanthanide luminescence is dominated by quenching by high-energy oscillators in the chemical environment. The rate of non-radiative energy transfer to a single H2O molecule coordinated to a Eu3+ ion exceeds the usual rates of emission by an order of magnitude. We know these rates, but the details of these energy transfer processes are yet to be established. In this work, we study the quenching rates of [Eu(D2O)9]3+ and [Eu(DOTA)(D2O)]− in H2O/D2O mixtures by sequentially exchanging the deuterons with protons. Flash freezing the solutions allows us to identify species with various D/H contents in solution and thus to quantify the energy transfer processes to individual OH-oscillators. This is not possible in solution due to fast exchange in the ensembles present at room temperature. We conclude that the energy transfer processes are accurately described, predicted, and simulated using a step-wise addition of the rates of quenching by each O–H oscillator. This documents the sequential increase in the rate of the energy transfer processes in the quenching of lanthanide luminescence, and further provides a methodology to identify isotopic impurities in deuterated lanthanide systems in solution. [ABSTRACT FROM AUTHOR]

A series of Tb3+-doped Sr2YTaO6 double perovskite phosphors (SYT:Tb3+) were synthesized using a conventional solid-state reaction method. A strong green emission was observed in the SYT:Tb3+ phosphors, and the optimal doping concentration of Tb3+ was confirmed to be 5 mol%. The electric dipole-dipole interaction was ascribed to be the main mechanism for the luminescence concentration quenching. Analysis of the concentration-dependent fluorescence decay confirmed that the self-generated quenching model holds for the dynamic process of Tb3+ decays in SYT. Furthermore, the internal quantum efficiencies, non-radiative transition rates, and energy transfer rates of the 5D4 level for the SYT:Tb3+ samples were estimated, respectively. The luminescence thermal stability of the sample was also evaluated based on the Arrhenius model. The chromaticity shift of the SYT:5 mol% Tb3+ phosphor was examined to be 0.013 when the sample temperature was increased from 303 to 483 K, thus indicating excellent chromaticity shifting resistance under high temperature conditions. Moreover, the Judd-Ofelt parameters were calculated from the emission spectra of SYT:Tb3+ to be Ω2 = 0.29 × 10-20, Ω4 = 0.45 × 10-20, and &@937;6 = 0.72 × 10-20 cm², respectively. The fluorescence branching ratios and radiative transition rates for the 5D4 level were calculated based on the obtained Judd-Ofelt parameters. Finally, a white light-emitting diode (LED) prototype was assembled using a 310 nm LED chip combined with a prepared green SYT:Tb3+ phosphor and two other commercial blue and red phosphors. The obtained warm white light exhibits good chromaticity coordinates (0.32, 0.32) and a high color rendering index of 96.1. Based on the above results, it can be known that the prepared SYT:Tb3+ phosphors have a potential application as green emitting phosphors in white LEDs. [ABSTRACT FROM AUTHOR]

The accurate and rapid detection of antibiotics and heavy-metal-based toxic oxo-anions in water media employing coordination polymers (CPs) as luminescent probes has attracted a lot of attention. Three new Cd(II)-based ternary CPs derived from first-presented L ligands, including [Cd(DCTP)(L)(OH)]n (1), [Cd(TBTA)(L)(OH)]n (2), and [Cd(NPHT)(L)(H2O)]n (3) (L = 2-((1H-imidazol-1-yl)methyl)-5,6-dimethyl-1H-benzo[d]imidazole, H2DCTP = 2,5-dichloroterephthalic acid, H2TBTA = tetrabromoterephthalic acid and H2NPHT = 3-nitrophthalic acid), were successfully assembled and characterized. 1 and 2 show 2D hcb layers, which can be further extended into a 3D supramolecular framework via classic hydrogen bonding interactions. 3 features a 1D double chain that ultimately spreads into a 2D network through weak hydrogen bonding interactions. With the advantages of high stability and excellent luminescent properties, the three CPs display high sensitivity, selectivity, and good anti-interference for the sensing of pefloxacin (PEF) and Cr2O72− ions (LOD values toward PEF: 3.82 × 10−7 mol L−1 for 1, 4.06 × 10−7 mol L−1 for 2, and 1.36 × 10−8 mol L−1 for 3, and toward Cr2O72− ions: 5.97 × 10−7 mol L−1 for 1, 5.87 × 10−7 mol L−1 for 2, and 8.21 × 10−8 mol L−1 for 3). These CPs are the first examples of bifunctional luminescent sensors to detect PEF and Cr2O72− in aqueous solutions. The luminescence quenching mechanisms are explored in detail. [ABSTRACT FROM AUTHOR]

Thermal quenching is the core challenge that hinders the application of luminescent materials. Herein, a synergistic mechanism involving energy transfer and energy gap modulation is proposed based on the local crystal field regulation around sensitizers. The substitution of coordination cation V5+/P5+ weakens the crystal field strength of the sensitizer Bi3+, and the weakening of crystal field splitting causes an increase in the 3P1 energy level, thus increasing its energy gap. Compared with the YVO4:Bi3+,Eu3+ phosphor, the thermal stability of the YV0.25P0.75O4:Bi3+,Eu3+ phosphor is significantly improved, and the relative emission intensity of Eu3+ continuously increases with heating and reaches 1.24 times the original intensity at 523 K and does not show a decreasing trend in the studied temperature range. The anti-thermal quenching performance is mainly attributed to the increasing thermal quenching activation energy (ΔE) of the sensitizer by energy gap modulation, which enhances the energy transfer to compensate thermal quenching. Based on the thermal quenching characteristics of the materials, an optical thermometer is designed. The maximum relative sensitivity (Sr) and absolute sensitivity (Sa) are as high as 1.74% K−1 and 0.59 K−1, respectively, and the minimum temperature resolution reaches 0.288 K. The synergistic effect between energy gap modulation of the sensitizer and energy transfer enables the regulation of thermal quenching. Thus, this study provides a new strategy for exploiting high-performance luminescent materials. [ABSTRACT FROM AUTHOR]

Herein, a series of Y2W3O12:10%Yb3+/x%RE3+ (RE = Er/Ho/Tm) phosphors is prepared via a solid-state reaction. The upconversion and downshift luminescence properties of the phosphors were investigated under an excitation of 980 nm. The bright blue light emission from Tm3+ ion and the green and red light emissions from Ho3+(Er3+) ions were observed. The near-infrared light intensity of NIR-I (Tm3+, ∼850 nm), NIR-II (Er3+: ∼1550 nm; Tm3+: ∼1783 nm) and NIR-III (Ho3+: ∼2050 nm) were analyzed. In particular, the dramatic thermal enhancement phenomenon in visible and NIR regions was exhibited by the Y2W3O12:10%Yb3+/x%RE3+ (RE = Er/Ho/Tm) phosphors. Among them, the green light intensity of Er3+ ions increased 26.77 times, from 303 to 573 K. The NIR-II emission band (∼1783 nm) intensity of Tm3+ ions at 533 K increased 168.7 times compared to that at 313 K. The possible thermal enhancement mechanism is illustrated by the negative thermal expansion (NTE) and Frenkel defect of the Y2W3O12 host. Finally, the optical temperature sensing performances of Y2W3O12:10%Yb3+/x%RE3+ (RE = Er/Ho/Tm) samples are investigated according to the luminescence intensity dependence relationship on temperature. The maximum value of SR reached 4.24% K−1 at 353 K for Y2W3O12:10%Yb3+/0.6%Ho3+ phosphor. The results indicate that the Y2W3O12:10%Yb3+/x%RE3+ (RE = Er/Ho/Tm) phosphors possess anti-thermal quenching properties and are suitable for developing optical temperature sensors. [ABSTRACT FROM AUTHOR]

Upconversion luminescence (UCL) is a fluorescence process where two or more lower-energy photons convert into a higher-energy photon. Lanthanide (Ln3+)-doped UCL materials often suffer from weak luminescence, especially when directly synthesized by a hydrothermal (HT) process due to the existing hydroxyl group and undesirable arrangement of dopants within host lattices which quench luminescence and limit energy transfer. Therefore, additional heat treatment processes are required to enhance their UCL emission, even though direct hydrothermal synthesis without further heat treatment has the advantages of low energy consumption, fast synthesis, and wide applicability to generate UCL materials. In this study, via a HT process without annealing, we have produced Yb3+ and Er3+ co-doped SrMoO4 submicron spindles with a strong green UCL emission which can be seen with the naked eye, which HT produced oxide-based UCL materials often fail to demonstrate. We have investigated different HT synthesis conditions, such as temperature, time, pH and dopant composition, which control the nucleation, growth, lattice structure arrangement, and ultimately their UCL properties through XRD, SEM, EDS and UCL measurements. The bright green UCL from the SrMoO4:Yb,Er submicron spindles is further enhanced by post-synthesis annealing within a molten NaNO3/KNO3 system to prevent particle size growth. The green UCL intensity from the annealed SrMoO4:Yb,Er submicron spindles surpasses samples produced by the solid-state method and is comparable to that from the commercial NaYF4:Yb,Er sample. We have further studied the temperature-dependent luminescence of both the HT-prepared and molten-salt annealed SrMoO4:Yb,Er submicron spindle samples. The strong UCL from our SrMoO4:Yb,Er submicron spindles could warrant their candidacy for bioimaging and anticounterfeiting applications. [ABSTRACT FROM AUTHOR]

It is challenging to explore novel-structure lanthanide coordination polymers (Ln-CPs) for sensing environmental pollutants. Herein, we designed and synthesized an organic bridging linker 3-(carboxymethoxy)-1-(carboxymethyl) pyrazole-4-carboxylic acid (H3ccpc), and then successfully prepared and characterized a novel Ln-CP, namely [Tb2(ccpc)2(H2O)6]·1.5H2O (ccpcTb). Structural analysis indicates that ccpcTb exhibits a two-dimensional structure, in which Tb ions are in an eight-coordinated environment. The photoluminescence performance of ccpcTb was discussed in detail. The ccpcTb displays bright green luminescence and behaves as a multi-responsive luminescent sensor toward Fe3+ ions, Cr2O72− ions and 2,4,6-trinitrophenol with high selectivity and low detection limits. Furthermore, the possible luminescence sensing mechanisms have been addressed in detail. The luminescence quenching mechanism of sensing Fe3+ and Cr2O72− is attributed to the energy competitive absorption, while that of sensing TNP is due to the synergistic effect of energy competitive absorption and photo-induced electron transfer. [ABSTRACT FROM AUTHOR]

Photochromic materials have been found to be promising for a broad range of applications. However, it remains a great challenge to develop new photochromic materials. In this work, a dihydroanthracene-based photochromic organic molecule 9,10-bis(di(pyridine-4-yl)methylene)-9,10-dihydroanthracene (L) was developed as a functional ligand to construct a LMOF-based sensor material [Cd2L(HBTC)2·2H2O·2i-PrOH]n (1) (LMOF = luminescent metal–organic framework; H3BTC = benzene-1,3,5-tricarboxylic acid; i-PrOH = isopropanol). 1 is constructed using a 6-connected [Cd2(COO)2]2+ cluster, a 4-connected L unit and a HBTC double-bridge and exhibits a two-dimensional (2-D) (4,6)-connected architecture. 1 has good water and thermal stability. Before and after photochromism, this LMOF exhibits different luminescence properties, which results in dual-response and highly selective sensing properties. 1 can detect TNP with high sensitivity and selectivity in aqueous media by luminescence quenching effects. More importantly, 1′ (1 after photochromism) shows ultrahigh sensing sensitivity and selectivity towards MnO4− (the second highest Ksv of 4.08 × 105 M−1). Furthermore, 1′ can identify MnO4− in the presence of a similar strong oxidizing anion Cr2O72−. In addition, quenching sensing mechanisms are discussed in detail. This work will contribute to the development of highly efficient dual-response sensors. [ABSTRACT FROM AUTHOR]

A Cd(II)-based metal–organic framework (MOF), [Cd(PDA)(L)2] (PDA = 1,4-phenylenediacetate and L = 2,4,5-tri-4-pyridyl-1H-imidazole), 1, was synthesized by a solvothermal method and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The single-crystal X-ray studies showed that the connectivity among Cd2+ ions, PDA and 2,4,5-tri-4-pyridyl-1H-imidazole ligands forms two-dimensional structures. The two-dimensional structures are arranged in an AAA....fashion to form a three-dimensional packing arrangement. Compound 1 showed selective and efficient sorption of the large anionic dye remazol brilliant blue R (RBBR) in aqueous medium, whereas it exhibited low sorption towards orange G (OG), methyl orange (MO), methylene blue (MB) and rhodamine B (RhB). Compound 1 also exhibited photoluminescence-based sensing behaviors towards Fe3+, Cr3+ and Al3+ ions in aqueous medium based on the luminescence quenching effect. However, photoluminescence studies in the presence of other common metal ions such as Cd2+, Cu2+, Mg2+, Ca2+, Co2+, K+, Mn2+, Pb2+, Zn2+, and Na+ in aqueous medium showed a negligible turn-on effect. The limits of detection for Fe3+, Cr3+, and Al3+ ions were 75, 257 and 107 ppb, respectively. Compound 1 also showed comparable gas sorption capacity towards CO2 (64.5 cm3 g−1), N2 (72.25 cm3 g−1) and H2 (45.30 cm3 g−1) at 1 bar. [ABSTRACT FROM AUTHOR]

A novel radio-photoluminescence material featuring fluorochromic responses toward UV or X-ray irradiation has been obtained. Such a unique monomer- to excimer-based luminescence transition allows for dosimetry of ionizing radiation in a ratiometric manner. Rather than quenching the luminescence, the radiation-induced radical species of Th-105 boost the excimer emission, rendering it as a rare material possessing radical-excimers. [ABSTRACT FROM AUTHOR]

We have synthesized a co-condensed hollow ethane-bipyridine periodic mesoporous organosilica (HEt-bpy-PMO) as a host material to anchor lanthanides for the purpose of developing a multifunctional chemical sensor. The host material was grafted with lanthanide chloride salts or complexes. The luminescence properties of the developed series of hybrid materials were studied in detail in the solid-state and after dispersing in water. The Eu3+ or Tb3+ singly incorporated materials were investigated for their use as ion sensors, showing ions selectivity towards Cu2+, Co2+ and Fe3+. Additionally, the Eu3+ or Tb3+ incorporated materials showed obvious luminescence quenching behavior towards acetone compared to other organic solvents, indicating excellent acetone sensing selectivity. [ABSTRACT FROM AUTHOR]

An anomalous solvent-induced luminescence quenching of NH2-MIL-53(Fe) in D2O is reported. Contrary to conventional understanding, the quenching is originated from the inhibition of charge transfer by hydrogen bonding between NH2-MIL-53(Fe) and D2O, rather than protonation or high-frequency vibrations of solvent molecules. This enables accurate quantitative detection towards specific volume fractions of D2O in H2O. [ABSTRACT FROM AUTHOR]

Under solvothermal conditions, one new CdII coordination polymer [Cd(bbimc)(ata)]n (1)] based on carbazole ligand 3,6-bis(1H-benzo[d]imidazol-1-yl)-9-methyl-9H-carbazole (bbimc) and 2-aminoterephthalic acid ligand (H2ata) was synthesized. Single-crystal structural determination revealed that 1 takes a two-dimensional (2D) structure with an sql topology. In particular, 1 shows good thermal (413 °C) and excellent acid/base stability in aqueous solutions with pH values of 1–13. Furthermore, 1 could selectively detect Hg2+, Fe3+, and antibiotics (TC: tetracycline; CTC: chlortetracycline) in aqueous solutions with high selectivity and sensitivity through a turn-off effect, and the detection limits are 0.246 μM (Hg2+), 0.342 μM (Fe3+), 0.208 μM (TC), and 0.307 μM (CTC). Moreover, the detection mechanism analysis by experiment and theoretical calculation revealed that competitive absorption (CA) and photoinduced electron transfer (PET) are largely responsible for sensing Fe3+ and the two antibiotics (TC, CTC). However, the weak interaction between Hg2+ and –NH2 of the framework structure contributes to partial luminescence quenching. [ABSTRACT FROM AUTHOR]

The early diagnosis and real-time prognosis of cardiovascular diseases (CVDs) at the bedside are important. However, real-time detection of myocardial infarction involves the use of large-scale instrumentation and long test times. Herein, a simple, rapid and sensitive lateral flow immunochromatographic strip (LFIS) based on Yb/Er co-doped NaYF4 upconversion nanoparticles (UCNPs) was demonstrated for use in the detection of myocardial infarction. First, through heavy Yb/Er doping and an inert NaYF4 shell coating on the nanoparticles, the surface-related luminescence quenching effect of UCNPs was eliminated to enhance the upconversion luminescence. Second, through uniform coating of a SiO2 layer on the UCNPs, the biological affinity was improved to couple UCNPs and antibody proteins. Finally, through modification and activation with a specific antibody protein (serum amyloid A (SAA)), the UCNPs exhibited intense upconversion luminescence and high specificity when applied as a lateral flow immunochromatographic strip (LFIS). The developed UC-LFIS was highly sensitive (0.1 μg mL−1) and specific for detecting SAA in only 10 μL of serum. The UC-LFIS holds great potential for the early diagnosis and prognosis of CVDs. [ABSTRACT FROM AUTHOR]

The development of luminescent metal–organic frameworks for effective sensing and monitoring of environmental pollutants is of great significance for human health and environmental protection. In this work, a novel water-stable ZnII-based luminescent coordination polymer, namely {[Zn(BBDF)(ATP)]·2DMF·3H2O}n ((BBDF = 2,7-bis(1H-benzimidazol-1-yl)-9,9-dimethyl-9H-fluorene) and H2ATP = 2-aminoterephthalic acid), was designed and obtained using the mixed-ligand method. Structural analysis indicated that 1 presents a two-fold interpenetrated two-dimensional layer structure with one dimensional (1D) channels along the a axis. Intriguingly, the uncoordinated –NH2 group was danged onto the pore walls of 1. Remarkably, compound 1 shows good aqueous stability at different pH values of 3–13 and exhibits a fluorescence turn-off sensing behavior for Hg2+, Cr2O72−, CrO42−, and antibiotics (NFZ, NFT) in aqueous solution with high selectivity and sensitivity. The limits of detection (LOD) are 0.12 μM (Hg2+), 0.17 μM (Cr2O72−), 0.21 μM (CrO42−), 0.098 μM (NFZ), and 0.14 μM (NFT). The luminescence quenching mechanism analysis by experiment and theoretical calculation revealed that the competitive absorption and the photoinduced electron transfer process are largely responsible for the sensing of the two antibiotics, while the weak interaction contributes to the selective luminescence quenching for Hg2+. [ABSTRACT FROM AUTHOR]

Bimodal imaging probes that combine magnetic resonance imaging (MRI) and photoluminescence imaging are quite appealing since they can supply both anatomical and molecular information to effectively ameliorate the accuracy of detection. In this study, an activatable nanoprobe, [Eu(BTD)3(DPBT)]@MnO2, for bimodal time-gated luminescence imaging (TGLI) and MRI has been constructed by anchoring visible-light-excitable Eu3+ complexes on lamellar MnO2 nanosheets. Due to the luminescence quenching effect and non-magnetic resonance (MR) activity of MnO2 nanosheets, the developed nanoprobe presents quite weak TGL and MR signals. After exposure to H2O2 or GSH, accompanied by the transformation from MnO2 to Mn2+, the nanoprobe exhibits rapid, sensitive, and selective "turn-on" responses towards GSH and H2O2 in TGL and MR detection modes. Furthermore, the nanoprobe displays high stability, low cytotoxicity, good biocompatibility and water dispersion. Given the high contents of GSH and H2O2 in cancer cells, the nanoprobe was used for the identification of cancer cells by TGLI of intracellular GSH and H2O2, as well as for the tracing of tumor cells in tumor-bearing mice by tumor-targeting in vivo MRI and TGLI of tumor tissues. The research outcomes proved the potential of [Eu(BTD)3(DPBT)]@MnO2 as a useful nanoprobe for the tracing and accurate detection of cancer cells in vitro and in vivo via bimodal TGLI and MRI. [ABSTRACT FROM AUTHOR]

Five new ZnII/CdII coordination polymers (CPs) based on a flexible bis(imidazole) ligand 9,10-bis((2-methyl-1H-imidazol-1-yl)methyl)anthracene (bmima) with three different aromatic carboxylic acid ligands have been synthesized under solvothermal conditions: {[Cd(bmima)0.5(atp)(H2O)]·DMF·0.5H2O} (CP 1), {[Zn(bmima)(atp)]·DMF} (CP 2), {[Cd(bmima)(bpdc)]·2DMF} (CP 3), and {[M(bmima)0.5(oda)]·DMF·H2O} (M = Zn for CP 4 and Cd for CP 5), (H2atp = 2-aminoterephthalic acid; H2bpdc = [1,1′-biphenyl]-4,4′-dicarboxylic acid and H2oda = 4,4′-oxydibenzoic acid). CP 1 displays a 3,4-connected TiSc topology 3D framework with vertex symbols of {42·6·102·12}{42·6}. CP 2 and CP 3 both feature 2D layer structures with a five-fold interpenetration framework for CP 3. CP 4 and CP 5 both show a 3D "pillar-layer" structure with pcu α-Po topology. The structural differences of the five CPs may be due to the diverse coordination modes of dicarboxylate ligands and the conformation of flexible N-donor ligands. Moreover, CP 1 and CP 3 are two good fluorescent sensors for the detection of Fe3+, Cr2O72− and TNP. The mechanism of the two sensors shows that the fluorescent sensing process toward Fe3+ and Cr2O72− is mainly attributed to the competitive absorption process, while both competitive absorption and the more efficient FRET mechanism for TNP, respectively, which indicates that CP 1 and CP 3 can serve as two fluorescence sensors to sensitively and selectively detect the presence of Fe3+ and Cr2O72− in water. [ABSTRACT FROM AUTHOR]

Luminescence concentration quenching exists widely in lanthanide-doped luminescent nanomaterials, and significantly hinders their emission intensity. In this work, we report the concentration-quenching-free properties of the 406 nm emission in Pr3+-doped nanoscintillators, which is attributed to the large energy gap between the 1S0 and 1I6 states (ΔE = ∼25 000 cm−1) of Pr3+ ions, preventing the concentration quenching effects caused by both cross-relaxation and energy migration to surface quenchers. This work provides further understanding about the concentration quenching effect of lanthanide-doped luminescent nanomaterials and a new perspective for avoiding detrimental concentration quenching. In addition, we also demonstrate the potential use of Pr3+-doped nanoscintillators as anti-counterfeiting materials. [ABSTRACT FROM AUTHOR]

Optically-active luminescent materials based on lanthanoid ions attract significant attention due to their unique spectroscopic properties and the possibility of application as chemical sensors. Five isostructural lanthanoid metal organic frameworks, namely {[Pr(3,4-PDA)(Glu)0.5(H2O)2]CH3CN}(1) and [Ln(3,4-PDA)(Glu)0.5(H2O)2]: Ln = Nd (2), Sm (3), Eu (4), and Tb (5) (where 3,4-PDA = pyridine-3,4-dicarboxylic acid, Glu = glutaric acid), synthesized via the solvothermal method are reported. These lanthanoid metal–organic frameworks were characterized by FTIR, single-crystal X-ray diffraction, powder X-ray diffraction, BET, Hirshfeld surface analysis, DFT calculations, electronic spectroscopy, and photoluminescence techniques. MOFs 1–5 show porous two-dimensional (2D) structures. The luminescence properties of MOFs 4 and 5 demonstrated the range of sensing capabilities for some toxic heavy metals. However, MOFs 4 and 5 are highly sensitive for the detection of Pb2+, exhibiting the most effective luminescence quenching with the lowest detectable change in the signal occurring at ∼0.014 and ∼0.013 ppm of Pb2+ with MOFs 4 and 5, respectively, at room temperature in minutes. The MOF-based luminescence sensors designed in this paper demonstrate a successful and feasible strategy to use pyridine-3,4-dicarboxylic acid-based ligand as an antenna, which can efficiently sensitize Eu3+ and Tb3+ emission. MOFs 4 and 5 show great potential in the application of environmental detection of Pb2+ in water. [ABSTRACT FROM AUTHOR]

Hierarchically structured-lanthanide (LnIII)-doped β-NaGdF4 nanoparticles emitting by upconversion (UC), downconversion (DC) and/or downshifting (DS) are currently investigated for potential applications as anti-counterfeiting agents or in energy conversion. Yet, the role of doping concentration, excitation pump power density (Pexc), and LnIII–LnIII separation on the LnIII-to-LnIII energy transfer (ET), luminescence quenching, and emission color tunability need to be further elucidated to boost their luminescence. In light of that, herein, these issues are discussed in nanostructured β-NaGdF4:TbIII,TmIII,YbIII core@shell nanoparticles emitting by UC, DS, and DC. In the NaGdy−xTm0.015Yb0.20TbxF4@NaYF4 compositions, larger TbIII amounts induce stronger TbIII UC while for Pexc lower than 20 W cm−2, both cooperative sensitization upconversion (CSU) and energy transfer upconversion (ETU) mechanisms may occur. On the other hand, for Pexc larger than 50 W cm−2, energy migration upconversion (EMU) dominates the UC. By separating TbIII from TmIII and YbIII in core@shell@NaGdF4 architectures, only the CSU and ETU mechanisms occur, while for Pexc densities larger than 40 W cm−2, saturation of upconversion takes place. Upon 488 nm excitation, TbIII DS and YbIII DC emissions are noticed as well. Thus, this study helps to understand how the proper design of hierarchically structured nanoparticles can control the LnIII-to-LnIII ET mechanisms while their versatile excitation and multi-emission are interesting features for use as anti-counterfeiting agents or in energy conversion. [ABSTRACT FROM AUTHOR]

Detection of Fe(III) and Cu(II) in water is highly desirable because their abnormal levels can cause serious harm to human health and environmental safety. In this work, a ratiometric luminescence sensing platform based on lanthanide-based silica nanoparticles was constructed for the detection of Fe3+ and Cu2+ ions. The terbium-silica nanoparticles (named SiO2@Tb) with dual-emission signals were successfully prepared by grafting Tb3+ ions onto trimellitic anhydride (TMA) functionalized silica nanospheres. It can serve as a ratiometric fluorescent probe for the detection of Fe3+ and Cu2+ ions in water with the green emission of Tb3+ ions as a response signal and the blue emission of silica nanospheres as the reference signal. Significantly, an easy-to-differentiate color change for visual detection was also realized. SiO2@Tb shows high sensitivity even in very low concentration regions towards the sensing of Fe3+ and Cu2+ with low detection limits of 0.75 μM and 0.91 μM, respectively. Moreover, the mechanism for the luminescence quenching of SiO2@Tb was systematically investigated, and was attributed to the synergetic effect of the absorption competition quenching (ACQ) mechanism and cation exchange. This study demonstrates that SiO2@Tb can be employed as a promising fluorescent probe for the detection of Fe3+ and Cu2+ ions, and the combination of lanthanide ions with silica nanoparticles is an effective strategy to construct a ratiometric fluorescent sensing platform for the determination of analytes in environmental detection. [ABSTRACT FROM AUTHOR]

To settle the problem of phosphors with unsatisfactory luminescence efficiency and serious thermal quenching, Eu2+-activated Sr8Si4O12Cl8 cyan-emitting phosphors were designed. Excited at 387 nm, a dazzling cyan emission located at 492 nm is observed in the resultant phosphors and its maximum intensity is obtained when the Eu2+ content is 4 mol%. Moreover, the zero-thermal quenching luminescence, even when the temperature is 503 K, the integrated emission intensity still maintains 106% of its starting value at 303 K, is realized in resultant phosphors because of the efficient energy transfer from defect levels to Eu2+, which is confirmed by the thermoluminescence spectrum. The electroluminescence spectrum of the packaged white light-emitting diode (white-LED) is detected and it is found to possess a high color rendering index (91.0), low correlated color temperature (4875 K) and a superior luminous efficiency (68.7 lm W−1), implying that the developed phosphors can be adopted as cyan-emitting components to fulfill the cyan gap and realize a full spectrum white-LED. Furthermore, the cathodoluminescence (CL) performance of samples is also studied, in which its CL emission intensity is greatly impacted by the accelerating voltage and the filament current. Additionally, using the synthesized phosphors, various types of patterns are designed for use in information encryption. These achievements reveal that the Eu2+-activated Sr8Si4O12Cl8 phosphors are multifunctional cyan-emitting candidates for full spectrum white-LED, field-emission display and anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An imidazole-substituted nitronyl nitroxide radical NIT-Ph-3-(1-Im) was coordinated with Ln(hfac)3·2H2O to obtain five new one-dimensional lanthanide-nitronyl nitroxide radical complexes [Ln(hfac)3(NIT-Ph-3-(1-Im))]n (Ln = Gd 1, Tb 2, Dy 3, Ho 4, Yb 5; hfac = hexafluoroacetylacetonate; NIT-Ph-3-(1-Im) = 2-(3-(1-imidazole))-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide). The functionalized radical ligand NIT-Ph-3-(1-Im) acts as a bridge ligand to link two Ln(III) ions through a "head-to-tail" mode, leading to a one-dimensional chain. Variable temperature magnetization shows that the antiferromagnetic interactions dominate in complex 1. Magnetic studies reveal that slow magnetization relaxations occur in complexes 2 and 3. Furthermore, complex 2 exhibits an excellent application as a luminescence sensor for detecting Fe3+ cations and Cr2O72− anions with high sensitivity and selectivity according to luminescence quenching effects. [ABSTRACT FROM AUTHOR]

The design and application of functional metal–organic frameworks are very important and meaningful. Herein, based on a V-shape carboxylic acid ligand, a rigid nitrogen heterocyclic ligand with a triazole group, and Zn(NO3)2·6H2O, a 3D luminescent Zn-MOF [Zn2(OBA)2(L1)·3DMF·4H2O]n (compound 1; H2OBA = 4,4′-oxybis(benzoic acid), L1 = 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole) with a pillared-layer structure, has been synthesized under solvothermal conditions. Two independent skeletons penetrate each other, forming a 2-fold interpenetrated structure. As an excellent chemical sensor, compound 1 can detect Fe3+ and Cr2O72− by luminescence quenching with high selectivity and sensitivity. The limits of detection of compound 1 are 0.58 μM for Fe3+ and 1.37 μM for Cr2O72−, respectively. Meanwhile, compound 1 can serve as a host to encapsulate Eu3+/Tb3+ ions, realizing the tunable luminescence emission of Eu3+/Tb3+-doped samples. Furthermore, the Eu3+/Tb3+-co-doped compound 1 obtained by soaking the as-synthesized MOF into Ln3+ ion solution (total 25 mM; Eu3+ : Tb3+ = 2 : 3, molar ratio) exhibits white-light emission with ideal Commission International de I'Eclairage coordinates of (0.32, 0.33), a moderate correlated color temperature value of 6180 K, and an absolute quantum yield of 25.3%. These results indicate that compound 1 has promising applications in ion sensing and white-light emission. [ABSTRACT FROM AUTHOR]

Anion- and temperature responsive behaviors of three luminescent Ru(II)-terpyridine complexes are utilized here to demonstrate multiple Boolean (BL) and fuzzy logic (FL) operations. Taking advantage of the imidazole NH protons, anion-promoted alteration of the photophysical characteristics of the complexes was thoroughly investigated via absorption, and emission spectral and lifetime measurements. In their free state, the complexes display luminescence representing the "on-state", whereas quenching of luminescence is observed with anions demonstrating the "off-state". Likewise, lowering of temperature induces a substantial increase of luminescence and lifetime demonstrating the "on-state", while the increase of temperature induces a significant decrease of emission intensity and lifetime indicating the "off-state" and the process is reversible in both cases. The complexes thus can act as anion- and temperature-responsive molecular switches. The spectral signatures of the complexes under the influence of anions and temperature were employed to mimic multiple BL and FL functions. Performing very detailed sensing studies by varying the analyte concentration within a wide domain is very tedious, time-consuming and expensive. In order to overcome the lacuna, we implemented machine learning and soft computing tools such as artificial neural networks (ANNs), fuzzy-logic and adaptive neuro-fuzzy inference system (ANFIS) to predict the experimental anion sensing data of the complexes. [ABSTRACT FROM AUTHOR]

Two coordination polymers, namely {[Cd3(TIYM)2(5-SASS)2(H2O)2]·H2O}n (1) and {[Zn2(TIYM)(5-SASS)(μ2-OH)]·5H2O}n (2), were assembled using a mixed ligand strategy with the semi-rigid linker tetrakis(imidazol-1-ylmethyl)methane (TIYM) and 5-sulfoisophthalic acid sodium salt (5-SASS). Luminescence studies reveal that compounds 1 and 2 show strong fluorescence and exhibit efficient luminescence quenching in detecting UO22+ cations, Cr2O72−/CrO42− anions, and the NFT antibiotic in aqueous media, and can thus serve as promising sensors. The detection limits of compounds 1–2 are 1.96 × 10−4/1.36 × 10−4 M for UO22+ cations, 6.53 × 10−5/5.41 × 10−5 M for Cr2O72− anions, 2.29 × 10−4/1.04 × 10−4 M for CrO42− anions, and 5.62 × 10−5/4.74 × 10−5 M for the NFT antibiotic, respectively, indicating that the two CPs are promising multi-functional luminescent sensors. Additionally, the possible mechanisms for luminescence quenching have been investigated using spectral overlap experiments and DFT calculations. [ABSTRACT FROM AUTHOR]

We report the use of optofluidic hollow-core photonic crystal fibres as microreactors for Stern–Volmer (SV) luminescence quenching analysis of visible-light photocatalytic reactions. This technology enables measurements on nanolitre volumes and paves the way for automated SV analyses in continuous flow that minimise catalyst and reagent usage. The method is showcased using a recently developed photoredox-catalysed α-C–H alkylation reaction of unprotected primary alkylamines. [ABSTRACT FROM AUTHOR]

A new gadolinium(III)-based coordination polymer (CP), [Gd(3,5-pydc)1.5(CO2)0.5(H2O)4]·3H2O (1, where 3,5-pydc = 3,5-pyridinedicarboxylate), has been successfully synthesized using a slow diffusion method at room temperature. Single-crystal X-ray diffraction study of 1 confirmed its one-dimensional ladder-like structure. The Gd3+ ions are in a distorted tricapped trigonal prismatic geometry. Two types of 3,5-pydc ligands are present in the structures: in one case, the pyridine nitrogen remains vacant, whereas in the other case, the pyridine nitrogen is coordinated with CO2 to form zwitterionic carbamate. The phase purity of 1 has been confirmed by powder X-ray diffraction, thermogravimetric analysis and IR spectroscopic studies. The aqueous dispersion of compound 1 exhibits weak luminescence emission at 385 nm upon excitation at 270 nm. To explore the ligand-sensitized metal-centred luminescence, we have prepared a composite by mixing the CP with Tb3+ ions (Tb@1). The formation of the composite has been confirmed by IR spectroscopic studies in the solid state. The composite showed excellent ligand-sensitized metal-centred luminescence. We have utilized this luminescence property for the sensing of anions in aqueous media. The composite shows luminescence quenching behaviour in the presence of Cr2O72−, CrO42−, and NO2−, with high sensitivity, and their limits of detection are 147 ppb, 142 ppb and 20 ppb, respectively. Selectivity experiments show that the detection of these three anions is highly selective in the presence of other common anions. Detailed experimental studies suggest that the preferable interaction of the three anions with the Tb3+ ions inside the composite and the reduction of the excitation energy are probably responsible for the quenching behaviour. [ABSTRACT FROM AUTHOR]

It is necessary to decrease the application cost of luminescent Ln-MOF sensors to develop multiple functionalities. The ingenious design of ligands and the rational doping of Ln3+ ions are the main approaches to endowing Ln-MOFs with more functionalities. "V" shaped ligands can cause diamond pore channels commonly. "O＝C–NH" groups as hydrogen bonding sites not only can participate in supramolecular self-assembly but also can achieve molecular recognition. Based on the above considerations, a "V" shaped ligand, H2L, with a suitable triplet state and "O＝C–NH" groups was designed and synthesized firstly. And the Ln-MOFs (Ln = Eu, Gd, Tb) were obtained by solvothermal reactions. Single crystal X-ray diffraction showed that Ln-MOFs had two types of diamond pore channels where "O＝C–NH" groups adhered to the surface. "O＝C–NH" groups not only played an important role in the stacking process of 2D coordinated layers but also can reduce the non-radiative transition resulting from molecular vibration. The Eu-MOF and Tb-MOF not only can emit strong "f–f" transitions characteristic of luminescence but also can detect o-phenylenediamine (OPD) and p-phenylenediamine (PPD) by luminescence quenching. Besides, EuxTb1−x-MOFs (x = 0.02, 0.05, 0.1) were synthesized and can be used as ratio luminescence thermometers whose maximum relative sensitivities were 1.19% K−1 at 400 K. It is pointed out specifically that the relationship between the relative sensitivities and the Eu3+ content was studied. What's more, our work not only developed a series of Ln-MOF luminescent sensors by designing functional ligands and doping Ln3+ rationally but also provided valuable knowledge for the following work. [ABSTRACT FROM AUTHOR]

The designing of luminescent metal–organic frameworks (LMOFs) as sensors for the detection of molecules and ions constitutes an active area of research. Four different three-dimensional (3D) unusual LMOFs, namely, {[Zn(3-pda)(TA)]·H2O}n (1), {[Zn(4-pda)(TA)]·2H2O}n (2), [Cd(3-pda)(TA)]n (3), and {[Cd2(4-pda)2(TA)2]·(4-fpia)·H2O}n (4) (3-pda = 1,4-bis(3-pyridylcarboxylamide)benzene, 4-pda = 1,4-bis(4-pyridylcarboxylamide)benzene, 4-fpia = N-(4-formylamino-phenyl)-isonicotinamide, and TA = terephthalic acid) were successfully synthesized by a hydrothermal method and characterized by single-crystal X-ray diffraction. Under solvothermal conditions, a structurally transformational 3D 3-fold interpenetrated porous MOF, [Cd2(4-pda)2(TA)2(DMF)]n (4a), was obtained, which could be further transformed to isostructural [Cu2(4-pda)2(TA)2(DMF)]n (4b) by single-crystal to single-crystal (SCSC) transformation. The effect of N-donor ligands, metal ions and solvents on the structure of MOFs is discussed in detail. A series of luminescence recognition tests proved that complexes 1–4 can be used as luminescent sensors for detecting certain metal cations, oxyanions, and toxic organic solvents in an aqueous environment. Furthermore, the luminescence quenching mechanism and structure–function relationship were studied systematically. [ABSTRACT FROM AUTHOR]

Synergistic assembly of uranyl centres and luminescent 2,6-bis(pyrazol-1-yl)pyridine-4-carboxylates (bppCOOH) gives rise to a uranyl coordination polymer, namely U-bppCOO, which exhibits a luminescence quenching response toward UV or X-ray irradiation doses. Notably, the photosensitivity of U-bppCOO has been significantly enhanced via metal–ligand assembly compared with that of the naked bppCOOH ligand. [ABSTRACT FROM AUTHOR]

Excessive use of tetracycline (TC) exacerbates environmental pollution and seriously threatens human health. Therefore, it is of great significance to explore an effective approach for detecting TC. In this work, a water-stable and ratiometric luminescent sensor based on a dual-emitting Eu-based metal–organic framework (Eu-TCPE, H4TCPE = tetrakis(4-carboxyphenyl)ethylene) was established through a solvothermal method. Benefiting from the luminescence quenching behavior of H4TCPE linkers through the inner filter effect (IFE) and the enhanced fluorescence emission of Eu3+via the antenna effect, supported by the results of UV-vis absorption spectra and density functional theory (DFT) calculations, the Eu-TCPE sensor exhibited a fast and selective response towards TC detection with a low detection limit of 14 nM in a linear range of 0–50 µM. Application of the Eu-TCPE sensor in real samples of tap water and milk was also investigated. Furthermore, a test-strip-based sensor with the Eu-TCPE probe fixed on the surface was developed for the real-time selective detection of TC in aqueous solution, and the fluorescence color changes of the test strip under UV-light excitation can be captured using the portable online analyzer of a smartphone-color detector App, which showed a handheld platform for the rapid and visual detection of TC in practical applications. [ABSTRACT FROM AUTHOR]

In this work, a single particle imaging method based on the total internal reflection (TIR) imaging platform for the sensing and cell imaging of nitrite (NO2−) in the near-infrared region using cyanine dye-assembled composite upconversion nanoparticles (UCNPs) was developed. The NaYF4:Yb,Tm@NaGdF4 UCNPs were synthesized as energy donors, and the cyanine dye IR-798 was prepared as an energy acceptor. Since the absorption spectrum of the cyanine dye IR-798 and the luminescence spectrum of upconversion nanoparticles overlapped effectively, IR-798 quenched the luminescence of the UCNPs. When NO2− was added to the cyanine dye-assembled composite upconversion nanoparticle system, NO2− destroyed the conjugate structure of IR-798, so that the luminous intensity of UCNPs could be restored. Based on the mechanism, a quantitative image analysis with high sensitivity, low sample usage, and fast response time using the TIR single particle imaging platform was developed to determine the content of nitrite in human serum samples. In addition, the UCNPs-IR-798 probe was applied to image the exogenous NO2− content in HeLa living cells based on the single particle imaging platform. [ABSTRACT FROM AUTHOR]

An efficient synthesis of polymethine dyes carrying thiobarbituric and a carboxylic acid moiety has been developed. Such compounds play a key role in many photometric detections and quantifications of enzyme activities. In such tests, the metabolite of the enzyme activities is transformed into a b-dicarbonyl derivative. In the present study, this compound was prepared from furfural through organic synthesis. Its in situ transformation with thiobarbituric acid derivatives yields the target compounds on a gram-scale (0.4 to 0.6 g). A combined experimental and theoretical study of the photophysical properties of the synthesized compounds was carried out. Absorption and emission spectroscopy measurements highlighted a slight solvatochromism effect. The luminescence was quenched by molecular oxygen, indicating the partial triplet multiplicity character of the lowest excited state. Density Functional Theory (DFT) calculations have been applied for the evaluation of favoured conformations for these new compounds and the study of their optical properties. Within the Franck Condon principle, the vibrationally resolved electronic one-photon absorption spectrum has been simulated. This simulation shows the presence of a major band followed by a vibronic sideband, typical of organic chromophores in solution. The performed computational study revealed that the transition from the ground to the first excited electronic state has a p-p* character. Finally, TD-DFT energy level diagram calculations highlighted the presence of triplet states very close to the first singlet excited one, suggesting probable access to the triplet-excited state. [ABSTRACT FROM AUTHOR]

A potential luminescent sensor, based on porous metal organic framework (MOF) for the detection of metal ions (Al3+, Fe3+ or Cr3+) and nitro explosive, 2,4,6-tri-nitrophenol (TNP) has been identified. The cadmium(II) containing mixed-linker MOF viz. {[Cd(L1)(L2)](DMA)}n (L1 = 2-amino-1,4-benzenedicarboxylate, L2 = 4,40- azopyridine and DMA = N,N-dimethylacetamide) has been prepared employing the solvothermal method using L1 and L2 in DMA medium. Single crystal X-ray diffraction analysis revealed {[Cd(L1)(L2)](DMA)}n is crystallized in orthorhombic system with space group Cmca. {[Cd(L1 )(L2)](DMA)}n features an interpenetrated 3D framework structure consist of pendant Lewis basic --NH2 groups directed towards the pores. Thermogravimetric analysis revealed that the desolvated framework compound is stable up to 350 1C under nitrogen atmosphere. Furthermore, porosity of the desolvated {[Cd(L1)(L2)](DMA)}n has been investigated through N2, H2 and CO2 adsorption studies as well as sorption of water vapour. {[Cd(L1 )(L2)](DMA)}n exhibits superior selective turn on sensing towards tri-positive metal ions (Al3+, Fe3+, Cr3+) and luminescence quenching behavior towards nitroaromatics with high selectivity. [ABSTRACT FROM AUTHOR]

Two porous complexes, namely, {[H2N(Me)2]2[Zn5(L)2(OH)2]·3DMF·4H2O}n (1), and {[H2N(Me)2]4[Cu3(L)2(H2O)2]·4DMF·3H2O}n (2) were solvothermally constructed based on a symmetrical V-shaped rigid multicarboxylic acid ligand H5L (H5L = 3,5-di(2′,5′-dicarboxylphenyl)benzoic acid). Complexes 1 and 2 display 3D frameworks with various metal clusters. Complex 1 is a 3D porous framework with a (4,8)-connected topology featuring a 1D pore structure in the a-axis direction with a penta-nuclear cluster [Zn5(μ2-COO)6(μ1-COO)4(μ3-O)2]. By contrast, 2 displays a 3D (3,4)-connected net based on binuclear [Cu2(COO)4] paddlewheel SBUs. Complex 1 reveals solid-state luminescent properties at ambient temperature, and the maximum emission peak was observed at ∼443 nm (λex = 339 nm). Meanwhile, 1 shows high selectivity and sensitivity not only for Fe3+ cations but also for Cr2O72− anions via the luminescence quenching effect with a low detection limit, which thus could be a potential crystalline material for detecting these substances. The mechanisms of the quenching effect and sensing properties of 1 were discussed in detail. [ABSTRACT FROM AUTHOR]

Four Zn(II)-based coordination polymers (CPs), [Zn(4-tkpvb)(FB)2] (CP1), [Zn(4-tkpvb)(CB)2] (CP2), [Zn(4-tkpvb)(BB)2] (CP3) and [Zn(4-tkpvb)(NTP)]n (CP4), were prepared from solvothermal reactions of Zn(NO3)2·6H2O with 1,2,4,5-tetrakis((E)-2-(pyridin-4-yl)vinyl)benzene (4-tkpvb) in the presence of 3-fluorobenzoic acid (HFB), 3-chlorobenzoic acid (HCB), 3-bromobenzoic acid (HBB) and nitroterephthalic acid (H2NTP). These four compounds were structurally characterized by IR, elemental analysis, powder X-ray diffraction and single-crystal X-ray diffraction. CP1–CP3 have similar one-dimensional (1D) zigzag chain structures assembled by 4-tkpvb connecting the [ZnL2] (L = FB, CB, BB) units. CP4 displays an unusual 6-fold interpenetrating three-dimensional (3D) net with a 'dia' topology formed by linking the 2D [Zn(NTP)(4-tkpvb)]n layers via 4-tkpvb ligands. CP1–CP4 all exhibited luminescence emission in the solid state. The representative CP3 exhibited good water stability in the pH range from 3 to 13. It was revealed to be an intriguing luminescent probe for CrO42− anions in H2O by a selective fluorescence quenching method or Fe3+ ions in H2O by selective fluorescence enhancement. The detection limit was 0.679 ppm for CrO42− or 0.429 ppm for Fe3+. The emission quenching process may be ascribed to the overlap between the absorption band of the CrO42− anion and those of the excitation and/or emission bands of CP3, while the emission enhancement mechanism was likely due to the weak interaction between Fe3+ and the uncoordinated pyridyl group in CP3. [ABSTRACT FROM AUTHOR]

Simple synthetic modulation based on uranyl acetate and phenanthroline has resulted in two uranyl clusters (1 and 2) with different topologies and nuclearities. Notably, the dimeric complex exhibits distinct luminescence quenching upon UV and X-ray irradiation with detection limits of 4.30 × 10−6 J and 0.32 Gy, respectively. To advance the practical application, 1 was further fabricated with polyvinylidene fluoride into a flexible strip as a UV and X-ray indicator. [ABSTRACT FROM AUTHOR]

Highly selective sensing of Fe3+ is very important due to its great effect on biological systems. A novel ligand [1,1′:4′,1′′:4′′,1′′′:4′′′,1′′′′-quinquephenyl]-2,2′′,2′′′′,5′′-tetracarboxylic acid (H4qptca) was designed and successfully obtained for the first time via three steps in high total yields according to the absorption spectrum of Fe3+. The europium(III)-based metal–organic framework derived from H4qptca, {[Eu(qptca)1/2(H2qptca)1/2(H2O)2]·DMF}n (referred to as SLX-1), was then synthesized and used as a water-stable and highly selective luminescent sensor for Fe3+ in aqueous solution with a comparable detection limit using Ln-MOF probes (6.45 μM) through the antenna effect of SLX-1. Furthermore, the luminescence quenching mechanism was also proposed as a competitive absorption mechanism. [ABSTRACT FROM AUTHOR]

Carbon dots have promising prospects for analytical and monitoring purposes, but are greatly hindered by the aggregation-induced luminescence quenching owing to the π–π interaction or the non-radiation-excited radical complex formation. Herein hydrothermally prepared orange-yellow fluorescent carbon dots (O-CDs) show an aggregation-induced fluorescence enhancement (AIFE) with Cu2+ owing to the complexation of Cu(II) and the O-CDs. Cu2+ was then sensitively and selectively detected in the linear range from 0.02 to 30 μM with the detection limit of 14 nM, making the detection of Cu2+ in fresh water and E. coli lysate successful, showing that the as-prepared O-CDs could be well applied to the environmental monitoring of heavy metals. [ABSTRACT FROM AUTHOR]

The development of metal complex-based aggregation-induced emission (AIE) active materials is of great importance and a challenging task. We have designed and successfully synthesized a new bis-heteroleptic ruthenium(II) polypyridine complex, Ru-1, of a thiophenol substituted 1,10-phenanthroline based ligand (L1). The solution structure of Ru-1 was fully characterized by 1D (1H, 13C) and 2D (1H-1H COSY, 1H-13C HSQC, and 1H-13C HMBC) NMR spectroscopy, and ESI-MS. Ru-1 shows aggregation-induced emission (AIE) enhancement in water and highly dense polyethylene glycol (PEG) media supported by DLS, SEM, and TEM studies. The complex, Ru-1, is weakly luminescent in acetonitrile, and a very bright luminescence of Ru-1 in the weakly soluble water and highly dense PEG media arises due to the formation of nanoaggregates and the restricted intramolecular motion (RIM). The probe in aqueous acetonitrile solution (7 : 3; v/v) is able to selectively and sensitively detect picric acid (PA) over other competitive nitroaromatic compounds through luminescence quenching. The limit of detection (LOD) signifies that Ru-1 is capable of detecting picric acid at the micromolar level. Theoretical calculations were carried out to assign electronic transitions in Ru-1, both the ground and excited states. Furthermore, a paper strip kit with Ru-1 has been constructed for the practical application and in-field detection of picric acid without any interference of other nitroaromatic analytes. [ABSTRACT FROM AUTHOR]

High-performance fluorescence sensors combining convenience, low cost and high sensitivity are prospective for water pollution and human health. Luminescent metal–organic frameworks (LMOFs) as sensors can meet these criteria for high efficient detection of toxic metal ions. Herein, a new LMOF LCU-109 has been fabricated by Sharpless in situ tetrazole synthesis system assisted by polycarboxylic O-donor ligand. It showed a 2D binodal (3,6)-connected kgd structure with multiple N and O dual-functional sites for detecting guest metal ions. As expected, LCU-109 can be highly sensitive and selectively detect trace amounts of Fe3+ and Cu2+ ions in an aqueous solution by the luminescence quenching mechanism. Notably, the detection limits (LODs) of Fe3+ and Cu2+ ions are 0.0043 and 0.0028 ppm, respectively, in water, which are significantly lower than the minimum standards stipulated for drinking water by the World Health Organization (WHO) (0.3/2.0 ppm) and U.S. Environmental Protection Agency (USEPA) (0.3/1.2 ppm). Moreover, LCU-109 also shows excellent luminescent sensing activities for Fe3+ and Cu2+ ions in simulated HEPES biological system and actual river water with low LODs of 0.034/0.019 ppm and 0.0756/0.107 ppm, respectively, which is also lower than the standard of WHO and USEPA. Moreover, convenient and real-time naked eye detection effects are provided by the exquisitely made LCU-109 fluorescent test papers. Importantly, combining density functional theory (DFT) calculations with a variety of experiments, the fluorescence quenching mechanism for energy competitive absorption and weak interaction is further revealed. [ABSTRACT FROM AUTHOR]

Two new mononuclear complexes based on the anion 3-cyano-4-dicyanomethylene-5-oxo-4,5-dihydro-1H-pyrrol-2-olate (C8HN4O2− = HA−) and Mn2+ or Zn2+ cations, namely [Mn(HA)2(H2O)4]·2H2O (1) and [Zn(HA)2(H2O)4] (2), were synthesized and characterized by single-crystal X-ray diffraction and photoluminescence spectroscopy. Complexes 1 and 2 crystallize in the triclinic space group P1¯. Units [M(HA)2(H2O)4] (M = Mn, Zn) are the basic building blocks in both 1 and 2 crystal structures. The metal cation, located on an inversion center, is bound to two nitrogen atoms of two HA− and four water oxygen atoms. Units [M(HA)2(H2O)4] are connected by π–π stacking interactions between anions HA− and by hydrogen bonds to form a 3D crystal structure. Complexes 1 and 2 are isostructural with previously reported complexes [Cd(HA)2(H2O)4]·2H2O and [Cu(HA)2(H2O)4], respectively. A comparison between the luminescence properties of isostructural complexes confirms that the incompletely filled 3d subshell (3d5, 3d9) of a divalent metal cation is a key factor leading to the total luminescence quenching of anion HA− upon complexation with metal cations. Salts M(HA)2 (M = Mn, Cd, Cu, or Zn) adsorbed on cellulose paper display thermo-sensitive luminescence. The luminescence is due to HA− anions. The intensity of the luminescence peak reversibly decreases by 6–7 times upon heating from 27 up to 123 °C. [ABSTRACT FROM AUTHOR]

A novel two-dimensional coordination polymer with a negatively charged framework named {[(CH3)2NH2][Zn2(L)2]·DMF}n (1) was solvothermally synthesized via the assembly of Zn(II) ions with the organic ligand H3L (2-(3,5-dicarboxylphenyl)-6-carboxyl-benzimidazole). 1 was characterized by IR spectroscopy, thermogravimetry, single-crystal, and powder X-ray diffraction methods. 1 possesses a 1D rectangle channel decorated by abundant uncoordinated imidazole N atoms and carboxylate O atoms, and is a better CO2 adsorbent and promising CO2/CH4 selective material, suggesting potential application in gas separation. Moreover, 1 can also serve as a multi-responsive sensing material for detecting nitrobenzene (NB) and Cr2O72−via a luminescence quenching effect with a low detection limit, and the mechanisms of the quenching effect and sensing properties of 1 are discussed in detail. [ABSTRACT FROM AUTHOR]

A CB[6]-based supramolecular assembly: [Zn(QDS)2]·(CB[6])2 (1) (CB[6] = cucurbit[6]uril, HQDS = 8-hydroxy-5-quinolinesulfonic acid hydrate) has been synthesized under solvothermal conditions. Luminescence measurement reveals that 1 can serve as a fast and recyclable luminescence sensor for 2,4,6-trinitrophenol (TNP) and 4-nitrophenol (4-NP) organic explosives, as well as oxytetracycline (OTC) and tetracycline (TC) antibiotic detection in water solution through luminescence quenching with a low limit of detection (LOD) at parts per billion (ppb) levels. Simultaneously, 1 also can be used in real samples with satisfactory results. These results indicate that 1 can be applied as a multifunctional luminescent sensor in various potential applications. [ABSTRACT FROM AUTHOR]

Platinum(II) complexes are the most commonly used anticancer drugs and potential optical materials, but the detectability of Pt(II) complex-based probes is seldom reported. In our previous work, a tetradentate Pt(II) complex Pt-CHO was utilised as a 'turn-off' probe to detect ClO− and image cancer cells. However, the recognition mechanism has not been completely clarified and there are still doubts. In this work, three Pt(II) complexes, Pt-H, Pt-CHO and Pt-COOH, were developed to elucidate the mechanism of this class of complexes and refine their property studies. As a result, the UV–visible absorption and luminescence emission experiments, as well as the mass spectrum, proved that the oxidation of Pt(II) to Pt(IV) was the real reason for luminescence quenching, which has nothing to do with aldehyde groups. This first reported mechanism introduces a new type of ClO− probe based on Pt(II) complexes, thereby expanding the application fields of platinum complexes. Moreover, the quantum yield measurements, the effect of biomolecules and reversibility were studied to improve the properties of the probes. Theoretical calculations were used to gain an in-depth understanding of optical characteristics and related mechanisms. The cell imaging of RAW264.7 cells under endogenous ClO− proved the potential of the probes in bioimaging. [ABSTRACT FROM AUTHOR]

A new family of isostructural 3d-4f heterometallic metal--organic frameworks (HMOFs), [Zn3EuxTb2-x(TZI)4(DMA)5(H2O)3]·4DMA [x = 0 (1), 0.3 (2), 0.6 (3), 0.9 (4), 1 (5), 1.2 (6), 1.5 (7), 1.8 (8), 2 (9)], has been synthesized using the 5-(4-(tetrazol-5-yl) phenyl)isophthalic acid (H3TZI) ligand, LnIII ions and ZnII ions under solvothermal conditions. All HMOFs exhibit a (3,3,4,5,5)-connected 6³·6³(4²·6²·8²)(4·65·8) (4·66·83) topology, which features three different types of motifs: one is a mononuclear ZnII ion and the other two motifs are binuclear [Zn(COO)3Ln] clusters. The adsorption experiments indicate that Zn3Tb2 (1) could efficiently remove almost all I2 from cyclohexane solution after 12 h and also showed better adsorption towards neutral red (NR) dye (adsorption: only the Zn3Tb2 (1) was taken as one representative). Simultaneously, the luminescence sensing showed that Zn3Tb2 (1) and Zn3Eu2 (9) have excellent response and sensitivity towards pollutants such as Fe3+ ions and 2,4,6-trinitrophenol (TNP) with high selectivity and a fairly low limit of detection through luminescence quenching effect. Moreover, seven trimetallic-doped HMOFs 2-8 analogues of Zn3Ln2 (single) HMOFs were designed and prepared, showing different changes of luminescent color. More interestingly, Zn3Eu1.5Tb0.5 (7) with white-light emission was fabricated by doping relative concentrations of Eu3+ and Tb3+ ions. To the best of our knowledge, Zn3Eu1.5Tb0.5 (7) represents a novel kind of heterometallic Zn3Ln2 HMOFs with white-light emission. It could be deduced that the excellent characteristics, namely strong typical luminescence emission of ZnII and LnIII ions, microporous channels, active open metal sites (tetra-coordinated ZnII--metal sites), and uncoordinated carboxylate O atoms and uncoordinated tetrazolate N atoms, made the above HMOFs an ideal platform for adsorption, luminescence sensing, and white-light emission. More significantly, these HMOFs are the first reported Zn-Ln heterometallic materials with the H3TZI ligand. [ABSTRACT FROM AUTHOR]

On the basis of the 3-(pyrazin-2-yl)-1H-pyrazole-5-carboxylic acid (H2L) ligand, four new polymers [Cu2(L2−)2] (1), [Zn3(L2−)2(H2O)4Cl2]n (2), [Pb(HL−)Cl]n (3), and {[Ni(L2−)(H2O)]·(H2O)}n (4) have been synthesized under solvothermal conditions. Polymer 1 possesses a discrete (0D) binuclear structure, which is further formed into a three-dimensional (3D) supramolecular structure by hydrogen bonding and π⋯π stacking interactions. Polymers 2 and 3 display one-dimensional (1D) infinite chain structures, which further extend into 3D supramolecular structures through hydrogen bonding interactions. Polymer 4 features two-dimensional (2D) layers which can form a 3D supramolecular architecture via interlayer hydrogen bonds. The ligand in the four polymers adopts different coordination modes for constructing versatile structures. Moreover, luminescence sensing study shows that polymer 2 is a promising luminescent sensor for the detection of Cu2+, Co2+ and Fe3+via drastic luminescence quenching in aqueous solution with high efficiency. The quenching constants KSV for Cu2+, Co2+ and Fe3+ are 6.35 × 103 M−1, 8.70 × 103 M−1 and 1.62 × 104 M−1, respectively. What's more, 1–4 with electrochemical luminescence (ECL) properties show high intensity in N,N-dimethylformamide (DMF) solution and high thermal stability. [ABSTRACT FROM AUTHOR]