Selective Luminescent Probe Research Articles

Heterometal–organic frameworks as highly sensitive and highly selective luminescent probes to detect Cu2+, H2PO4− ions and CTC in aqueous solutions

Heterometal–organic frameworks as highly sensitive and highly selective luminescent probes to detect Cu2+, H2PO4− ions and CTC in aqueous solutions

Eu-MOF-based highly sensitive and selective luminescence probe for trace, in situ and visual detection of flunitrazepam

Flunitrazepam, as an emerging new psychoactive substance classified as a third-generation drug that is more harmful and camouflaged, is gradually proliferating globally. Maliciously used as a criminal tool in homicide and rape cases, it has already caused serious harm to public safety and social stability. Owing to its special molecular structure, low concentration level and rapid metabolic process in the human body, accurate detection of flunitrazepam remains a major challenge, especially for real sample and on-site detection. In this paper, a lanthanide MOF (Eu-MOF) based on bi-ligand was constructed as a luminescence probe and used for the first time to detect trace amounts of flunitrazepam. The ’antenna effect’ promotes strong luminescence of Eu-MOF, while the lower LUMO orbital energy level of flunitrazepam allows it to accept electrons from the electron donor leading to quenching of Eu-MOF luminescence. The probe has a high sensitivity and can detect flunitrazepam in the range of 0–800 μM with a detection limit as low as 73 nM. Moreover, flunitrazepam was detected in urine from real samples as well as in a variety of beverages to further validate its accuracy and practicality. The reported Eu-MOF represents one of the pioneering luminescence probes for the detection of flunitrazepam, which offers great promise for the on-site or on-line analysis of flunitrazepam.

A pyridyl-benzimidazole based ruthenium(II) complex as optical sensor: Targeted cyanide detection and live cell imaging applications

An extreme toxicity of cyanide (CN−) ion in diverse environmental media has encouraged significant attention for scheming well-organised molecular probes for its selective and sensitive detection. Keeping in mind, we present here a monometallic Ru(II) complex (Ru-1) based on 2-(pyridin-2-yl)-1H-benzo[d]imidazole moiety acting as a highly selective luminescent probe for CN− recognition in pure water. Besides, Ru-1 also acted as an efficient sensor for F−, AcO− and H2PO4− ions along with CN− when acetonitrile was chosen as solvent system. The binding constant (Kb) and detection limit (LoD) for CN− have been depicted as 3.05 × 106 M−1 and 12.8 nM, respectively, in water. The close proximity of N-H site with Ru(II) centre along with its remarkable acidity were identified as mainly responsible for the high selectivity of Ru-1 toward CN− in water. Job’s plot and DFT analyses were carried out to support the anion binding mechanism. Furthermore, the time-resolved fluorescence (TRF) spectroscopy was performed to assess the cyanide-induced emission lifetime change of Ru-1 in aqueous medium. In order to investigate applied potential, the probe Ru-1 was notably developed into paper-based strips that could readily detect CN− ion in mM range via naked eye under 365 nm light illumination, and also adequately employed to detect CN− in human breast cancer MCF-7 cell lines and natural food sources (such as apple seeds and sprouting potatoes).

A Switch-On Affinity-Based Iridium(III) Conjugate Probe for Imaging Mitochondrial Glutathione S-Transferase in Breast Cancer Cells.

Glutathione S-transferase is heterogeneously expressed in breast cancer cells and is therefore emerging as a potential diagnostic biomarker for studying the heterogeneity of breast cancers. However, available fluorescent probes for GSTs depend heavily on GSTs-catalyzed glutathione (GSH) nucleophilic substitution reactions, making them susceptible to interference by the high concentration of nucleophilic species in the cellular environment. Moreover, the functions of subcellular GSTs are generally overlooked due to the lack of suitable luminescence probes. Herein, we report a highly selective affinity-based luminescence probe 1 for GST in breast cancer cells through tethering a GST inhibitor, ethacrynic acid, to an iridium(III) complex. Compared to activity-based probes which require the use of GSH, this probe could image GST-pi in the mitochondria by directly adducting to GST-pi (or potentially GST-pi/GS) in living cells. Probe 1 possesses desirable photophysical properties including a lifetime of 911 ns, a Stokes shift of 343 nm, and high photostability. The "turn on" luminescence mode of the probe enables highly selective detection of the GST with a limit of detection of 1.01 μM, while its long emission lifetime allows sensitive detection in organic dye-spiked autofluorescence samples by a time-resolved mode. The probe was further applied to specifically and quantitatively visualize MDA-MB-231 cells via specific binding to mitochondrial GST, and could differentiate breast cell lines based on their expression levels of GST. To the best of our knowledge, this probe is the first affinity-based iridium(III) imaging probe for the subcellular GST. Our work provides a valuable tool for unmasking the diverse roles of a subcellular GST in living systems, as well as for studying the heterogeneity of breast cancers.

Slow magnetic relaxation and selective luminescent probe in a 2p–3d–4f heterotrispin chain

Three types of radical–3d/3d–4f heterotrispin complexes have been obtained. The Tb derivative reveals slow magnetic relaxation and a selective luminescent probe coexisting in a molecular entity.

Dinuclear Lanthanide Compound as a Promising Luminescent Probe for Al3+ Ions.

Luminescent probes have wide applications in biological system analysis and environmental science. Here, one novel luminescent dinuclear europium compound with a crown ether analogous ligand was synthesized through a solvent-thermal reaction. Through transformation, upon the addition of Al3+ ions to the N,N'-dimethyl formamide solution of the europium compound, the luminescent intensity of the characteristic emission of Eu3+ decreased, and a new emission peak appeared at 346 nm and increased rapidly. The luminescent investigation indicated that it could act as a highly sensitive and selective luminescent probe for Al3+ ions. Moreover, mass spectrometry and single-crystal X-ray diffraction confirmed the formation of a new more stable trinuclear aluminium compound during the sensing process.

A sensitive and selective fluorescent probe for nitrobenzene based on Europium(III) post-functionalized Al(III)-based MOF

A post-functionalized Eu 3+ @MIL-121 MOF was prepared through a facile hydrothermal approach and developed as a highly selective luminescent probe for detecting NB in aqueous solution. • A new MOF Eu 3+ @MIL-121 is designed and prepared. • A novel fluorescent strategy is proposed to specifically identify nitrobenzene in nitro-aromatic interferents in aqueous solution. • A new MOF fluorescent probe with the lower LOD for nitrobenzene compared to previous literature. Nitrobenzene (NB) is a substance with potential and possible hazards, which is widely used in industry field. In the current study, Europium(III) post-functionalized Al(III)-based metal–organic framework (Eu 3+ @MIL-121) was synthesized and utilized as an independently luminescent probe for the purpose of sensing NB. The red luminescence of Eu(III) could be quenched by NB through a process called fluorescence resonance energy transfer (FRET), and thus it could be used as a fluorescence off switch for NB, leading to its recognition. Eu 3+ @MIL-121 has its advantages of high sensitivity, selectivity, fast response time and wide response window. Compared with other MOFs, Eu 3+ @MIL-121 can specifically detect NB in aqueous solution, avoid secondary contamination by organic solvents, and has excellent linear range and LOD (limit of detection). Under the optimal conditions, the newly constructed Eu 3+ @MIL-121 fluorescent probe showed a satisfactory linear detection range of 0.005 to 20.000 μM, with a detection limit of 1.56 nM. Furthermore, the probe has been successfully applied to detect NB in real water samples.

Cover Feature:Efficient Synthesis of Yellow‐Green Carbon Quantum Dots as a Sensitive Fluorescent Probe of Folic Acid (Chem. Asian J. 15/2022)

Bright yellow-green carbon quantum dots (YGCDs) were efficiently synthesized by a one-step hydrothermal method, and the absolute quantum yield of YGCDs reaches a high level in a short time compared with that using commonly reported solvothermal methods. The obtained carbon quantum dots could be used as a selective luminescent probe of folic acid in the range of 2.0 × 10-8 mol/l to 1.0 × 10-5 mol/l. This work is part of a special collection at Chemistry – An Asian Journal celebrating the 100th anniversary of Shanghai University (1922-2022), which commemorates the wonderful development process of the chemistry discipline of Shanghai University. More information on this study can be found in the Research Article by Bao-Li An, Jiaqiang Xu et al.

Ratiometric fluorometric and colorimetric dual-mode sensing of glucose based on gold-platinum bimetallic nanoclusters

The synthesis of highly sensitive and selective luminescent probes provides a vital and efficient approach for diagnosing and preventing clinical diseases. In this work, gold-platinum bimetallic nanoclusters (Au − PtNCs-GMP) were synthesized with guanosine monophosphate (GMP) as the capping agent, which possessed strong fluorescent emission at 418 nm, and also exhibited great peroxidase-like mimetic activity. Glucose can be catalyzed to generate H2O2 by glucose oxidase, in the presence of H2O2, o-phenylenediamine (OPD) regarded as a representative non-fluorescent substance was catalyzed by Au-PtNCs-GMP and produced fluorescent 2,3-diaminophenazine (DAP) with an emission wavelength of 560 nm. Furthermore, the colorless OPD was oxidized to yellow DAP with UV–vis absorption peak at 420 nm. The generation of DAP can efficiently quench the fluorescence signal of Au-PtNCs-GMP at 418 nm on account of inner filter effect (IFE). The decrease of Au-PtNCs-GMP fluorescence and the increase of DAP fluorescence made it possible to detect glucose via ratiometric fluorometric intensity. Thus, a ratiometric fluorescent and colorimetric dual-mode sensing was achieved for glucose detection. The linear ranges of ratiometric fluorescence method and colorimetric method toward glucose were in the range of 0.01–0.4 mM and 0.05–0.4 mM, with the low limits of detection (LOD) of 7 μM and 11 μM, respectively. In addition, this dual-mode sensing method can be used for detecting glucose concentration in real biological samples with satisfying results, which provided a valuable and reliable strategy for glucose-related detections.

A selective luminescent probe to monitor cellular ATP: Potential application for in vivo imaging in zebrafish embryo

Adenosine 5′-triphosphate (ATP) is the major energy currency of living cells and its efficient real-time monitoring in vivo has increased the demand for the development of fluorescent chemosensors. For the prompt detection of ATP in submolar range, we have developed an easily accessible colorimetric and fluorescence probe 4-(Di-p-tolylphosphoryl)-7-hydroxychroman-2-one (DPC). The selective nature of DPC towards ATP has been confirmed through UV–vis, fluorescence titration, NMR titration as well as computational studies. Coupled with high mitochondrial membrane potential and ATP levels, the chemosensor DPC shows intense blue fluorescence signal at intracellular compartments in murine splenocytes and A549 human lung cancer cells. Moreover, using live zebrafish (Danio rerio)embryos with high energetic demands, we have successfully achieved fluorescence imaging of ATP at distinct sites in vivo(neural tube, myotome or embryonic muscle tissue, somite boundaries and tail regions) followed by estimation of endogenous ATP level from embryo extract. Collectively, our designed probe demonstrates excellent cellular permeability, sensitivity and specificity for intracellular ATP, and may provide valuable insights in the research of ATP-regulated biological processes in living cells or organisms.

A luminescent ATCUN peptide variant with enhanced properties for copper(II) sensing in biological media

The measurement of labile CuII in biological samples is fundamental for understanding Cu metabolism and has been emerging as a promising diagnostic marker for Cu-related pathologies such as Wilson's and Alzheimer's diseases. The use of fluorescent chelators may be useful to circumvent separation steps employed by current methods. For this purpose, we recently designed a selective and suited-affinity turn-off luminescent probe based on a peptide bearing the CuII-binding Xxx-Zzz-His (Amino-Terminal CuII- and NiII-binding, ATCUN) motif and a TbIII-DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) complex. Here, we present an analogue probe bearing the ATCUN motif variant Xxx-His-His. This probe showed much faster response in biologically-relevant media and higher stability than the previous motif at low pH. These features could be beneficial to the measurement of dynamic CuII fluctuations and the application in slightly acidic media, such as urine.

A water-stable pyridine bisphosphonate-based metal–organic framework as a selective and sensitive luminescent probe for Cr(VI) ions and acetone

A rare photoluminescent nitroxide pyridine bisphosphonate-based metal–organic framework, [Eu4(L)3(H2O)6]n (1) [H4L = 2,6-bis(phosphonomethyl)pyridine 1-oxide], was prepared under hydrothermal conditions and has a 3D supramolecular structure built from phosphonate linkers bridging Eu3+. It was characterized by single-crystal X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), thermogravimetric analyses (TGAs), etc. The luminescence spectra of 1 show the strong characteristic luminescence of Eu3+ ions, and 1 shows high water stability, thermal stability, and chemical stability. Furthermore, luminescence studies have shown that 1 can be used as a fluorescent probe for detecting trace amounts of Cr(VI) ions and acetone in water samples with excellent sensitivity, great selectivity, and reproducibility. The detection limits are as low as 0.61 μM, 0.63 μM, and 0.0066 vol% for Cr2O7 2-, CrO4 2-, and acetone, respectively. The fluorescence quenching of 1 by Cr(VI) ions and acetone may be due to spectral overlap and absorption competition. This is the first example of a Eu-based pyridine phosphonate fluorescence sensor for simultaneous detection of Cr(VI) ions and acetone.

Incorporation of thiazolothiazole fluorophores into a MOF structure: A highly luminescent Zn(II)-based MOF as a selective and reversible sensor for Cr2O72− and MnO4− anions

A highly luminescent ZnII-MOF, [Zn2 (TzTz)2(BDC)2]·2DMF, TzTz ​= ​2,5-di (4-pyridyl)thiazolo [ (Liu et al., 2019; Shen et al., 2018) [4,5]-d]thiazole and BDC ​= ​terephthalic acid), has been solvothermally assembled and fully characterized by single crystal X-ray crystallography, elemental analysis, FT-IR spectroscopy and X-ray diffraction (XRD). This transition-metal based luminescent MOF exhibits strong blue emission while capable as a selective sensor for detection of anions. Only trace amounts of fluorescent MOF can act as a highly selective and recyclable luminescent probe for the quantitative detection of CrVI and MnVII (Cr2O72−, MnO4−) anions in aqueous solutions with large quenching constants (9 ​× ​107 ​M−1 and 4.8 ​× ​103 ​M−1 for Cr2O72−and MnO4−) via an energy-transfer mechanism. The first sensing study of a TzTz-functionalized MOF material demonstrates the highest sensing ability among the previously reported fluorescent MOFs with detection limits for Cr2O72− and MnO4− ions in drinking water as low as 4 ​μM (100 ​ppb).

Cd-Based Metal-Organic Framework Containing Uncoordinated Carbonyl Groups as Lanthanide Postsynthetic Modification Sites and Chemical Sensing of Diphenyl Phosphate as a Flame-Retardant Biomarker.

With the judicious selection of an appropriate semirigid polycarboxylate, 2,5-bis(3',5'-dicarboxylphenyl)benzoic acid (H5bdba), and an inorganic metal ion, a novel anionic framework, {[NH2(CH3)2]2·[Cd3.5(bdba)(Hbdba)(H2O)1.5]}n (Cd-MOF), has been synthesized solvothermally. Single-crystal measurement results show that the prepared Cd-MOF features a three-dimensional structure containing two types of one-dimensional channels, and as we expected, there exist accessible uncoordinated -COOH groups on Hbdba pointing toward the rhombus channels. Powder X-ray diffraction and thermogravimetric analysis measurements were performed for the thermal and chemical stability analysis of Cd-MOF. In addition, the lanthanide(III)-functionalized hybrids, Ln(III)@Cd-MOF, were initially prepared by coordinated postsynthetic modification to incorporate luminescent Ln(III) ions into the structure. The luminescence properties of the hybrids are studied, and the results show notable and specialized fluorescent sensitization of Cd-MOF to Tb(III) ions. Moreover, the Tb(III)@Cd-MOF hybrid with outstanding fluorescence properties was developed as a highly sensitive and selective luminescent probe for the biomarker diphenyl phosphate (DPP) based on multiquenching effects. Tb(III)@Cd-MOF is the first case to realize the detection of urinary DPP through lanthanide metal-organic framework fluorescence spectrometry and shows practical detection potential.

New luminescent Zn(II) compound as a highly selective and sensitive luminescence probe for the detection of Fe3+ in aqueous solution

A new Zn(II) metal–organic framework, namely [Zn3(3-atrz)2(4-atrz)2(SO4)2]n (1 3-atrz = 3-amino-1,2,4-triazole, 4-atrz = 4-amino-1,2,4-triazole), has been solvothermally synthesized via the reactions of ZnSO4·7H2O and two different kinds of isomorphic aminotriazole ligands (3-atrz and 4-atrz). Single crystal X-ray diffraction analysis revealed that compound 1 features a trinuclear [Zn3(3-atrz)2(4-atrz)2(SO4)2] subunits based 3D framework with 6-connected pcu topology. In the 3D framework of 1, 3-atrz ligand displays a μ 3-κN1, κN2, κN3 coordination mode and 4-atrz ligand displays a μ 2-κN1, κN2 coordination mode. The luminescent properties investigation indicated that compound 1 shows strong luminescence at room temperature and high selectivity and sensitivity for Fe3+ ion in aqueous solution.

An Eu(III)-functionalized Sr-based metal-organic framework for fluorometric determination of Cr(III) and Cr(VI) ions.

An Eu(III)-functionalized strontium-organic framework (Eu3+@Sr-MOF) was synthesized by encapsulating Eu3+ ions into the pores of Sr-MOF via postsynthetic modification (PSM) and fully characterized by XRD, SEM, EDS, FTIR, and TGA. The luminescent properties of Eu3+@Sr-MOF were measured and investigated in detail, which demonstrated that Eu3+@Sr-MOF not only possessed excellent water and chemical stabilities in a wide pH range (5-10) but also displayed red luminescence with excitation/emission maxima at 332/617nm. The Eu3+@Sr-MOF can be considered as a highly selective and sensitive recyclable luminescence probe for sensing Cr(III) and Cr(VI) based on strong luminescence quenching effects; itcan be recycled at least five times. The luminescence probe for Cr3+, CrO42-, and Cr2O72- shows low detection limits (0.15μM, 0.17μM, and 0.13μM, respectively), relatively broad linear ranges (0.6-150μM, 0.1-200μM and 0.4-180μM, respectively), and high quenching constants KSV. Thesignals can be observed by the naked eye under UV light of 365nm. The method was applied to the determination of total Cr in environmental water samples. Graphical abstract.

Water Stable Zn(II) Metal-Organic Framework as a Selective and Sensitive Luminescent Probe for Fe(III) and Chromate Ions.

Sensing and monitoring toxic contaminants like Fe3+, CrO42-, and Cr2O72- ions in water is very important due to their harmful effects on biological and environmental systems. Enhanced hydrolytic stability, sensitivity, and selectivity, in addition to their excellent luminescence properties, are important attributes of metal-organic framework (MOF)-based sensors for sensing applications. In this work, the water stable Zn-MOF [Zn2(tpeb)(bpdc)2] (where tpeb = 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene and bpdc = biphenyl-4,4'-dicarboxylic acid) was synthesized and characterized. The framework retains its crystallinity and structural integrity in harsh acidic and basic conditions (pH 4-11). Most interestingly, the Zn-MOF demonstrates a strong blue luminescence in water that can be quenched selectively only by contaminants like Fe3+, CrO42-, and Cr2O72- ions. Higher Ksv values and low detection limits in selective luminescence quenching confirm the superior sensing performance, which is comparable to those of contemporary materials. Furthermore, in all cases, quenching efficiency remains unaltered in the presence of interfering ions, even after the compound is used in multiple cycles, which makes this MOF an attractive, reliable, and recyclable luminescent sensor material. The luminescence quenching mechanism is based on the competitive absorption and weak interactions. It is worth noting that most of the reported MOF-based sensors used for the separate sensing of Fe(III) and chromate ions are used in organic media due to their poor hydrolytic stabilities. Reports on the dual sensing of Fe(III) and chromate ions, which are also in aqueous media, are rare. Based on these results, Zn-MOF can be considered as a suitable candidate for advanced practical applications for the efficient sensing of Fe(III) and chromate ions in water.

Metal–organic framework-5 as a novel phosphorescent probe for the highly selective and sensitive detection of Pb(II) in mussels

Lead ion (Pb(II)) has emerged as a major mussel pollutant in recent decades, thus the development of sensors capable of detecting Pb(II) is of considerable interest. In this work, a novel, rapid, and “turn-on” phosphorescent sensor was developed to monitor Pb(II) using metal-organic framework-5 (MOF-5, Zn4O(TPA)3, TPA: terephthalic acid) as a highly selective and sensitive luminescent probe. A mechanism describing the leaching of Zn(II) from Zn4O complexes and self-assembly of TPA after Pb(II) coordination is proposed for the MOF-5-Pb(II) system. Using enhanced phosphorescence, the sensor displays a wide linear detection range of 0.01−10 μmol/L and a low detection limit of 2 nmol/L for the determination of Pb(II). Moreover, it is noteworthy that when immobilized in a polyethylene glycol (PEG) film, the MOF-5 probe exhibited a visually distinct color change at 1.0 μmol/L Pb(II) under 365 nm UV light. From these results, a test strip was prepared for semi-quantitative analysis of Pb(II) content. Finally, the proposed phosphorescent sensor was successfully utilized to detect Pb(II) content in mussel. This study demonstrates the first MOF-based “turn-on” phosphorescent sensor for monitoring Pb(II), from which future high-performance phosphorescent sensors to determine food pollutants may be developed.

A mechanical stability enhanced luminescence lanthanide MOF test strip encapsulated with polymer net for detecting picric acid and macrodantin.

The improper use of organic explosives and antibiotics have brought serious threats to the public health and the environmental safety, exploiting cost-effective and handy luminescent sensors with water stability and high selectivity in monitoring and detecting these hazardous substances are of utmost importance. Herein, we developed a simple yet powerful luminescent test strip sensor in a facile way. As for fabricating this test strip, the filter paper used for filtering lanthanide MOF (Ln-MOF) of [Tb(HIP)(H2O)5]·(H2O)·(HIP)1/2 (Tb-HIP, where HIP is 5-hydroxyisophthalate) powders was firstly recycled, and encapsulated with poly(methyl methacrylate) (PMMA) polymer net. The as-fabricated Tb-HIP test strips exhibit enhanced mechanical stability than the un-encapsulated ones, and show characteristic green emission of Tb3+. These test strips can behave as promising highly selective luminescent probes for picric acid (PA) and macrodantin (MDT) even existence of relevant potentially competing analytes. The detection limit for PA is 0.26μM, and for MDT is 0.21μM. In addition, the sensors can be successfully applied to detect PA in the river water samples as well as MDT in serum samples with satisfactory results. More importantly, the Tb-HIP test strips are highly efficient, recyclable luminescence sensors to detect PA and MDT.

A Water-Stable Uranyl Organic Framework as a Highly Selective and Sensitive Bifunctional Luminescent Probe for Fe3+ and Tetracycline Hydrochloride.

A new coordination polymer (H2 bpy)0.5 ⋅[(UO2 )1.5 (ipa)2 (H2 O)] (1) (H2 ipa=isophthalic acid, bpy=4,4'-bipyridine) was synthesized by hydrothermal condition. It was characterized by IR spectroscopy, elemental analysis, TG-DTA analysis, and powder X-ray diffraction. Analysis of single-crystal X-ray diffraction results showed that the title compound exhibited a double chain bridged by the different uranyl ions and ipa2- ligands. Through the hydrogen bond interactions and π⋅⋅⋅π stacking interactions, the double chains were assembled into the three-dimensional supramolecular framework. Furthermore, the compound can be used as a promising bifunctional luminescence sensor for detecting and identifying Fe3+ and tetracycline hydrochloride antibiotic molecules with high selectivity and sensitivity in aqueous solutions. Moreover, the luminescent sensing mechanisms for different analytes were proposed. Moreover, the electronic properties of title compound were explored by density functional theory (DFT) calculations. The sensor system has been successfully applied for the detection of Fe3+ and tetracycline hydrochloride with high recovery percentages and low relative standard deviation in real river water samples.