Europium Luminescence Used for Logic Gate and Ions Sensing with Enoxacin As the Antenna

Lanthanide MOFs based portable fluorescence sensing platform: Quantitative and visual detection of ciprofloxacin and Al3

In the current context of water environmental monitoring and pollution control, there's a crucial need for rapid and simple methods to detect multi-pollutant. We herein report an easy one-step hydrothermal synthesis method to produce Eu-based metal-organic frameworks (Eu MOFs), which was used as a fluorescent probe to detect the aquatic environmental pollutants of ciprofloxacin (CIP) and aluminum ions (Al3+). This fluorescent sensor enabled the cascade detection of CIP and Al3+ through fluorescence enhancement and ratio fluorescence response, respectively. The introduction of CIP significantly turned on the characteristic fluorescence of Eu MOFs at 595 nm and 616 nm through the "antenna effect". Based on this, the sensor enables quantitative detection of CIP within a linear range of 0-120 μM with a LOD as low as 50.421 nM. In the presence of Al3+, the fluorescence emission of Eu MOFs-CIP was sharply turned off due to strong Al3+ coordination with CIP, while the blue fluorescence emission of CIP was remarkably enhanced. And thus allowing ratio fluorescence quantitative detection of Al3+ (LOD = 2.681 μM). The introduction of CIP and Al3+ in cascade resulted in distinct fluorescence color changes from colorless to red and eventually to blue, exhibiting pronounced fluorescence characteristics. This observable phenomenon enables the visual detection of CIP and Al3+ in both aqueous phase and paper test strips. By combining the analysis of fluorescence chromaticity with the use of a smartphone, the fluorescence color of test papers allows for simple quantitative determination, which provides a convenient and accessible approach for quantifying CIP and Al3+ in water environments.

A portable and intelligent logic detector for simultaneous and in-situ detection of Al3+ and fluoride in groundwater

To develop a convenient and intelligent detector for simultaneous and in-situ detection of Al³⁺ and F^- in groundwater, a novel organic probe called RBP has been prepared. With the increase of Al³⁺, RBP showed a significant fluorescence enhancement at 588 nm, and the detection limit was 0.130 mg/L. After combining with fluorescent internal standard CDs, the fluorescence of RBP-Al-CDs at 588 nm was quenched due to the replace of F^- for Al³⁺, while the CDs at 460 nm remained unchanged, and the detection limit was 0.0186 mg/L. For convenient and intelligent detection, an RBP-based logic detector has been developed for simultaneous detection of Al³⁺ and F^-. Within the ultra-trace, low concentration, and high concentration range of Al³⁺ and F^-, the logic detector can achieve rapid feedback on their concentration levels ("U", "L" and "H") through different output modes of the signal lamps. The development of logical detector is of great significance for studying the in-situ chemical behavior of Al³⁺ and F^- and for daily household detection.

Multi-color fluorescence sensing platform for visual determination of norfloxacin based on a terbium (Ш) functionalized covalent organic framework

Sensitive and visual determination of fluoroquinolone antibiotics (FQs) is of great significance since their abuse and inappropriate handling can be problematic. Herein, we propose a lanthanide covalent organic framework fluorescence sensing system (Tb@COF-Ru) with visualization capability to determine the FQs level, where Tb@COF was employed as the sensing probe, while the red-emitting Ru(bpy)₃²⁺ serves as a constant red fluorescent background. With increasing norfloxacin concentration, the green fluorescence of Tb³⁺ is gradually enhanced, finally realizing the multicolor fluorescence change from red to green. With a smartphone for RGB analysis, visual monitoring and quantitative analysis were realized without any sophisticated instrument. Limits of detection for the fluorescence quantitative and visual mode for norfloxacin were 0.33 nM and 7.3 μM, respectively. This method was rapid (1 min) and visualized, providing a simple analysis of various food matrices (honey, milk, egg and beef) and water samples for trace FQs.

A versatile logic detector and fluorescent film based on Eu-based MOF for swift detection of formaldehyde in solutions and gas phase

Due to the huge threat of formaldehyde (FA) on human beings, the development of chemical sensors for swift detection of FA in solutions and gas phase is highly anticipated. In this paper, a versatile logic detector and a portable fluorescent film based on small-scaled Eu-based MOF were applied successfully to detect FA in solutions and gas phase, respectively. For FA in aqueous solution, the design of logic detector will efficiently identify FA in different concentration ranges: when the FA concentration are 0-500 ppb, 500-1000 ppb and >1000 ppb, the output signals of logic detector are the concentration level of FA ("L", "H" and "VH"), and accompanied by red, purple and blue signal lamps to remind, respectively. For FA in the air, the color of rigid film sensor will gradually change from red to blue with the increase of FA under UV lamp, and the detection limit of gaseous FA is 11.8 ppb. Through the preparation of logic devices and fluorescent films, Eu-based MOF realized swift detection of FA in solutions and gas phase, which will be very helpful to improve the human response level to FA from different emission sources.

A versatile molecular logic system based on Eu(III) coordination polymer film electrodes combined with multiple properties of NADH

Herein, a new type of lanthanide coordination polymer film made up of europium (Eu(iii)) and poly(N-methacryloylglycine) (Eu(iii)-PMAG) was prepared on an ITO electrode surface driven by the coordination between N-methacryloylglycine (MAG) and Eu(iii) through a single-step polymerization process. The fluorescence signal of Eu(iii)-PMAG films at 617 nm originating from Eu(iii) could be well retained in the buffer solution but was regulated by the concentration of Cu(ii) and the complexing agent EDTA. The switching of fluorescence by Cu(ii) was attributed to the inhibition of the "antenna effect" between Eu(iii) and the MAG ligand in the films. The coexistence of reduced β-nicotinamide adenine dinucleotide (NADH) in the solution can apparently quench the fluorescence of Eu(iii)-PMAG films through the internal filtration effect of UV absorbance overlapping the excitation wavelength, but itself exhibiting a fluorescence emission at 468 nm. In addition, the electrocatalytic oxidation of NADH with the help of the ferrocenedicarboxylic acid (FcDA) probe demonstrated a cyclic voltammetry (CV) signal at 0.45 V (vs. SCE). Based on various reversible stimulus-responsive behaviours, a 4-input/10-output logic network was built using Cu(ii), EDTA, NADH and FcDA as inputs and the signals of fluorescence from Eu(iii)-PMAG (617 nm) and NADH (468 nm), the CV response from FcDA and the UV-vis absorbance from the Cu(ii)-EDTA complex as outputs. Meanwhile, 6 different functional logic devices were constructed based on the same versatile platform, including a 2-to-1 encoder, a 1-to-2 decoder, a 1-to-2 demultiplexer, a parity checker, a transfer gate and a reprogrammable 3-input/2-output keypad lock. Combined with the new type of lanthanide coordination polymer film, NADH played central roles in designing sophisticated computing systems with its fluorescence, UV and electrocatalytic properties. This work might provide a novel avenue to develop intelligent multi-analyte sensing and information processing at the molecular level based on one single platform.

The SPE-assisted europium (III) based complex fluorometric assay for the highly selective and sensitive detection of manganese (II) in water

Detection of trace manganese (Ⅱ) ion (Mn²⁺) is crucial to water safety. Here, commercially available PS-DVB microspheres were sulfonated and then filled into the SPE column in order to separate Mn²⁺ from complex matrices. Meanwhile, europium (III) complex was prepared with a simple "one pot" method, and its fluorescence intensity was quenched gradually with the increase of Mn²⁺ concentration. Europium (III) complex combined with home-made SPE column was utilized for highly selective and sensitive measurement of Mn²⁺. The detectable concentrations of Mn²⁺ can be low as 0.2 μM, which was less than the drinking water guidelines. Consequently, this new method is promising to assess the content of Mn²⁺ rapidly and accurately in real-world water samples.

One-step fabrication of a boric acid-functionalized lanthanide metal–organic framework as a ratiometric fluorescence sensor for the selective recognition of dopamine

A boric acid-functionalized Eu-MOF ratiometric fluorescence sensor was prepared for the selective recognition of dopamine.

A selective colorimetric sensing strategy for cysteine based on an indicator-displacement mechanism

Rapid determination of cysteine in aqueous solution is important for the diagnosis and treatment of some diseases.

Dicarbohydrazide based chemosensors for copper and cyanide ions via a displacement approach

Ligands attached to pyridine dicarbohydrazide were synthesized and characterized using NMR, FT-IR, elemental analysis, UV-visible spectroscopy, mass spectrophotometry, emission spectra and single crystal X-ray diffraction, and were assessed for their ability to sense copper and cyanide ions.

Carbon dots with red emission as a fluorescent and colorimeteric dual-readout probe for the detection of chromium(vi) and cysteine and its logic gate operation

A schematic illustration for assaying Cr(vi) and Cys activity by CDs with both fluorescent and colorimetric readouts.

Carbon nano-dots as a fluorescent and colorimetric dual-readout probe for the detection of arginine and Cu2+ and its logic gate operation

A new visual fluorescent probe based on carbon nano-dots (CNDs) has been facilely synthesized via one step microwave-assisted pyrolysis and utilized for sequential detection of arginine (Arg) and Cu²⁺ by fluorescent and colorimetric dual-readout assay. The fluorescence of CNDs can be effectively quenched by Arg, and recovered upon addition of Cu²⁺ due to the competitive binding of Arg and Cu²⁺ that leads Arg to escape from the surface of CNDs. The probe displayed high sensitivity and selectivity toward Arg and Cu²⁺ over other analytes with a low detection limit of 0.26 μM and 0.17 μM, respectively. Meanwhile, the CNDs can also give dual responsive signals of a visible color change (yellow-pink-light yellow). According to this phenomenon, an "AND" logic gate based on the novel CNDs has been constructed. More importantly, the probe was also extended to cellular imaging. The proposed method was simple with ease of operation, which demonstrated great potential in bio-sensing, disease diagnosis or environmental monitoring.

Boric-Acid-Functional Lanthanide Metal-Organic Frameworks for Selective Ratiometric Fluorescence Detection of Fluoride Ions

Here, we report that boric acid is used to tune the optical properties of lanthanide metal-organic frameworks (LMOFs) for dual-fluorescence emission and improves the selectivity of LMOFs for the determination of F^- ions. The LMOFs are prepared with 5-boronoisophthalic acid (5-bop) and Eu³⁺ ions as the precursors. Emission mechanism study indicates that 5-bop is excited with UV photons to produce its triplet state, which then excites Eu³⁺ ions for their red emission. This is the general story of the antenna effect, but electron-deficient boric acid decreases the energy transfer efficiency from the triplet state of 5-bop to Eu³⁺ ions, so dual emission from both 5-bop and Eu³⁺ ions is efficiently excited at the single excitation of 275 nm. Moreover, boric acid is used to identify fluoride specifically as a free accessible site. The ratiometric fluorescent detection of F^- ions is validated with the dual emission at single excitation. The LMOFs are very monodisperse, so the determination of aqueous F^- ions is easily achieved with high selectivity and a low detection limit (2 μM). For the first time, we reveal that rational selection of functional ligands can improve the sensing efficiency of LMOFs through tuning their optical property and enhancing the selectivity toward targets.

Water-stable Eu-MOF fluorescent sensors for trivalent metal ions and nitrobenzene

We have synthesized two functionalized Eu-MOFs and found that the MOFs are promising luminescent probes for selectively sensing metal ions (Fe³⁺and Cr³⁺) and nitrobenzene.