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A highly selective turn-on fluorescent and naked-eye colourimetric dual-channel probe for cyanide anions (CNˉ) has been designed and characterized. In the mixed solution (DMSO / H2O, 9:1, v / v), only CNˉ could cause an increase in the UV absorption intensity and the corresponding fluorescence intensity increased, and other anions had no significant effect on the probe. After treatment with cyanide in the probe solution, the solution showed a noticeable colour change, from light yellow to purple. Moreover, a fluorescence spectrophotometer can be used to observe that the fluorescence intensity of the solution is significantly enhanced. The response of the colourimetric and fluorescent dual-channel probe to CNˉ was attributed to nucleophilic addition, and the mechanism was determined by 1H NMR spectroscopy. In addition, this probe was used to detect CNˉ in actual water samples, including river water, drinking water, and tap water. The spiked CNˉ recovery rate is very high (97.2%-100.06%), and analytical precision is also very high (RSD

Based on tetraphenylethylene as the skeleton, two novel salamo-type fluorescent probes (TPES1 = 2-hydroxy-1-naphthaldehyde O-(3-(((-2-hydroxy-5-(1,2,2-triphenylvinyl)benzylidene)amino)oxy)propyl) oxime and TPES2 = bis(2-hydroxy-1-naphthaldehyde O-(3-(((2-hydroxy-5-(1,2,2-triphenylvinyl)benzylidene)amino)oxy)propyl) dioxime) were designed and synthesized. Through the colorimetric and fluorescence dual-channel modes, cyanide ions could be specifically recognized by the two probe molecules. Interestingly, the probes TPES1 and TPES2 exhibited completely different spectral behaviors during the recognition process. Of the two, the TPES1 molecule is a ratio-type fluorescent probe, and double fluorescence emission peaks appeared during the titration process. The reason for this phenomenon is due to the rotation of the C–C single bond in tetraphenylethylene, causing the solution system to contain molecules in two states. On the other hand, the TPES2 molecule is a fluorescence-enhanced probe that has undergone two reaction processes of deprotonation and addition reaction successively, causing the fluorescence intensity to increase continuously. Theoretical calculations indicated that the configuration of probe TPES1 is reversed after interacting with cyanide ions (CN−). By calculating the minimum detection limits of TPES1 and TPES2 to CN−, the LOD values were 8.56 × 10−8 M and 5.37 × 10−8 M, respectively. In addition, probe-based test strips have been prepared for quick and simple detection of cyanide ions.

A simple Schiff base fluorescent probe (SW) composed of oxime and salicylaldehyde units was designed and synthesized. The probe has high selectivity and sensitivity for Zn2+ ion in mixed solvent (DMSO/H2O, V/V = 9:1). The fluorescence has obvious redshift phenomenon and visible color change. The stoichiometric ratio of the probe to Zn2+ ion was confirmed to be 1:2 (mole) by 1H NMR, MS analysis and job curves. And the detection limit of fluorescence response of the SW to Zn2+ is down to 2.53 × 10–8 mol/L. At the same time, the probe SW can be applied to the test paper detection of Zn2+ ions under 365 nm UV light and the detection of Zn2+ ions in actual water samples.

A novel strategy for microRNAs (miRNAs) detection has been developed utilizing duplex-specific nuclease-assisted signal amplification (DSNSA) and guanine-rich DNA-enhanced fluorescence of DNA-templated silver nanoclusters (AgNCs). The combination between target miRNA, DSNSA, and AgNCs is achieved by the unique design of DNA sequences. Target miRNA opens the hairpin structure of the Hairpin DNA probe (HP) by hybridizing with the HP and initiates the duplex-specific nuclease-assisted signal amplification (DSNSA) reaction. The DSNSA reaction generates the release of the guanine-rich DNA sequence, which can turn on the fluorescence of the dark AgNCs by hybridizing with the DNA template of the dark AgNCs. The fluorescence intensity of AgNCs corresponds to the dosage of the target miRNA. This is measured at 630 nm by exciting at 560 nm. The constructed method exhibits a low detection limit (~8.3 fmol), a great dynamic range of more than three orders of magnitude, and excellent selectivity. Moreover, it has a good performance for miR-21 detection in complex biological samples. A novel strategy for microRNAs (miRNAs) detection has been developed utilizing duplex-specific nuclease-assisted signal amplification (DSNSA) and guanine-rich DNA-enhanced fluorescence of DNA-templated silver nanoclusters (AgNCs).

A new salamo-type fluorescence probe H2L was synthesized by a series of reactions and corroborated by single-crystal X-ray crystallography and 1H NMR spectra. Fluorescence of Co2+ selectively response showed “off” when cations were sequentially detected. The LOD of H2L to Co2+ was calculated to be 3.73 × 10-7 M in DMF/water (9:1, v/v) solution system. Meanwhile, the single crystal of the Co2+ complex with H2L was obtained by solvent evaporation. The structure of the complex [Co3(L)2(MeOH)2(μ-OAc)2]·2MeOH was validated by single-crystal X-ray diffraction, IR, and elemental analyses, and the mechanism of recognition of Co2+ by H2L was got. Density functional theory (DFT) and Hirshfeld surface analyses were investigated to further understand the experimental results observed.

An unprecedented dinuclear CuII complex, [Cu2(L2)2], derived from a salamo-like chelating ligand H2L2, was produced by the cleavage of a newly synthesized, half-salamo-like ligand HL1 (2-[O-(1-ethyloxyamide)]oxime-3,5-dichloro-phenol). This was synthesized and characterized by elemental analyses, IR, UV&ndash, Vis and fluorescent spectra, single crystal X-ray diffraction analysis, and Hirshfeld surface analysis. X-ray crystallographic analysis indicated that the two CuII (Cu1 and Cu2) ions bore different (N2O3 and N2O2) coordination environments, the penta-coordinated Cu1 ion possessed a slightly twisted tetragonal pyramid geometry with the &tau, value &tau, = 0.004, and the tetra-coordinated Cu2 ion showed a slightly twisted square planar geometry. Interestingly, one oxime oxygen atom participated in the coordination reported previously. Moreover, an infinite two-dimensional layered supramolecular network was formed. Compared with HL1, the CuII complex possessed the characteristic of fluorescence quenching.

A bissalamo-coumarin-based chemical sensor H4L was designed and synthesized. It was found that the sensor molecule can selectively recognize Cr3+ and Al3+. In a buffer solution system, its complex L − Cr3+ is highly sensitive to the detection of S2− anion, and the sensor H4L can recognize Cr3+ at an acceptable physiological pH. Within the range, L − Cr3+ can recognize S2− anions with high selectivity and sensitivity. The detection limit for the sensor molecule H4L to recognize Cr3+ is 4.87 × 10-7 M, and the quenching constant with Cr3+ is 2.406 × 106 M-1. It was calculated that the detection limit of L − Cr3+ as a sensor was 8.23 × 10-7 M, and the binding constant with S2- anion was 1.44 × 106 M-1. The possible recognition mechanisms were discussed by UV, fluorescence titration, ESI-mass spectrometry and Job curve. In addition, S2− in different water samples was detected and the recovery was good.

A novel Schiff-base oxime sensor H2L with the ONON chelating moieties was designed and synthesized based on condensation reaction. Different methods such as elemental analyses, FT-IR, 1H and 13C NMR were fully utilized in characterizing the structure of sensor H2L. The UV–vis spectra of the Zn2+ complex exhibit four clear isosbestic points which may be assigned to the ONON moieties binding to Zn2+. Sensor H2L operates on the CHEF and PET mechanisms, and the tendency of Zn2+ to strongly enhance fluorescence of sensor H2L was explored. Fluorescence measurements show that sensor H2L has excellent fluorescent selectivity for Zn2+ over many other metal ions based on intramolecular charge-transfer, and the results demonstrate that the binding between sensor H2L and Zn2+ is chemically reversible. The crystal structure of the Zn2+ complex has been characterized by X-ray crystallography.

Two novel mono- and heptanuclear Ni(II) complexes, [Ni(HL1)2(EtOH)2]·2EtOH (1) and [Ni7(L2)3(μ3-OMe)2(μ3-OH)6(MeOH)6] (2), have been synthesized by the reaction of Ni(II) acetate with H2L1 and H2L2, respectively. In the Ni(II) complex 1, the ligand H2L1 was partially deprotonated, only NO donor atoms of one salicylidene moiety of the (HL1)− unit coordinate to Ni(II) atom. While all the three H2L2 ligands in the Ni(II) complex 2 were completely deprotonated. The seven Ni(II) atoms are all hexa-coordinated, and have two coordination environments. The fluorescence properties of the ligands, the Ni(II) complexes 1 and 2 have been discussed.

A highly selective fluorescent sensor H4L based on a bis(salamo)-type compound with two N2O2 chelating moieties as ionophore was successfully developed. Sensor H4L was found to have excellent selectivity for B4O72− over many other anions (Br−, CI−, CN−, CO32−, HCO3−, H2PO4−, HSO4−, NO3−, OAc−, S2O3−, SCN−, SO42−, Hcy (homocysteine) and H2O2), and it exhibited an approximately 150-fold enhancement of the fluorescence response to B4O72− in Tris-HCl buffer (DMF/H2O = 9:1, v/v, pH = 7) solutions. Significantly, its fluorescence intensity was enhanced in a linear fashion with increasing concentrations of B4O72−. The detection limit of sensor H4L towards B4O72− was 8.61 × 10−7 M. The test strips could conveniently, efficiently and simply detect B4O72− ions in Tris-HCl buffer (DMF/H2O = 9:1, v/v, pH = 7) solutions. Furthermore, sensor H4L showed excellent membrane permeability in living cells, and it was successfully used to monitor intracellular B4O72− by confocal luminescence imaging.

Base on the principle of fluorescence, a method for the analysis of carbamate pesticide residues in vegetables by fluorescence has been investigated. The optimum wavelength and the dose of the agents were optimized by a series of experimental design. Thus, 1 mL of HAc-NaAc buffer, 1 mL SDBS and 1 mL neutral red were the optimal test procedure used for the determination. And then the experiments showed that the regression equation of standard curve of the method was y=91.5242x-0.6143, with correlation coefficient R2=0.9970. This method was efficient for the simple, fast, and reliable to determination of the methmyl in vegetables.

A rare homotrinuclear CuII salamo-based complex [Cu3(L)2(μ-OAc)2(H2O)2]·2CHCl3·5H2O was prepared through the reaction of a non-symmetric salamo-based ligand H2L and Cu(OAc)2·H2O, and validated by elemental analyses, UV-Visible absorption, fluorescence and infrared spectra, molecular simulation and single-crystal X-ray analysis techniques. It is shown that three CuII atoms and two wholly deprotonated ligand (L)2− moieties form together a trinuclear 3:2 (M:L) complex with two coordination water molecules and two bi-dentate briging μ-acetate groups (μ-OAc−). Besides, the Hirshfeld surface analysis of the CuII complex was investigated. Compared with other ligands, the fluorescent strength of the CuII complex was evidently lowered, showing that the CuII ions possess fluorescent quenching effect.

A new naphthalenediol-based bis(salamo)-type fluorescent probe H4L for Zn2+ and CN- was reported. Probe H4L showed a highly selective fluorescence enhancement toward Zn2+ over other metal ions including Cd2+, and obtained the L-Zn2+complex can only detect CN- in various anions. Their recognition mechanisms were explained by Job plots, fluorescent and UV-vis titrations, and theoretical calculations. The L-Zn2+complex has been synthesized and structurally characterized using Hirshfeld surface analysis, elemental analyses, IR, UV-Vis and fluorescent spectra. Additionally, the relay probe with the wide adaptability of pH range and excellent stability showed highly selectivity for CN- recognition.

A new Cu(II) complex with asymmetric Salamo-type ligand (H2L, 4-bromo-6′-ethoxy-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol) has been synthesized and characterized structurally. The X-ray crystal structure of the Cu(II) complex shows it to be a binuclear complex, in which each Cu(II) atom is in a distorted square-pyramidal geometry. The Cu(II) complex crystallizes in the monoclinic system, space group P21/c, with unit cell parameters a = 14.7109(1), b = 8.6254(7), c = 30.124(3) A, β = 100.7400(1), and Z = 4. The Cu(II) complex consists of two Cu(II) atoms, and two L2– units, and each Cu(II) complex molecule links four other molecules into an infinite 2D-layer supramolecular structure. Meanwhile, the Cu(II) complex exhibits emission with the maximum emission wavelength λmax = 443 nm when excited at λex = 340 nm.

The supramolecular interaction between cucurbit[7]uril (CB[7]) as the host and the anti-cancer drug methotrexate (MTX) as the guest was studied using fluorescence spectroscopy, UV-visible absorption spectroscopy, 1H NMR, 2D NOESY, and theoretical calculations. The experimental results confirmed the formation of 1:2 inclusion complex with CB[7] and indicated a simple and sensitive competitive method for the fluorescence detection of MTX. It was found that the fluorescence intensities of CB[7]-palmatine, CB[7]-berberine and CB[7]-coptisine were quenched linearly upon the addition of MTX. The linear ranges obtained in the detection of MTX were 0.1-15μgmL-1, 0.2-15μgmL-1, and 0.4-15μgmL-1 with detection limits of 0.03μgmL-1, 0.06μgmL-1, and 0.13μgmL-1, respectively. This method can be used for the determination of MTX in biological fluids. These results suggested that cucurbit[7]uril is a promising drug carrier for targeted MTX delivery and monitoring, with improved efficacy and reduced toxicity in normal tissues.

A novel azine derivative colorimetric and fluorescent dual-channel probe salicylaldehyde hydrazine-3,5-dibromosalicylaldehyde ( 1 ) has been designed, synthesized and characterized. The probe 1 is confirmed to have especial selectivity and good sensitivity on detecting CN − via UV–vis absorption and fluorescence spectrum in aqueous solution (H 2 O/DMSO, 1:4, v/v). This colorimetric and fluorescent dual-channel probe response to CN − owed to the deprotonation process and established the mechanism by using 1 H NMR spectroscopy. Further researches showed that the detection limit of the probe 1 to CN − anions is 8.01 × 10 − 9 M, significantly lower than the maximum level 1.9 × 10 − 6 M in potable water from WHO guidelines.

A simple and effective strategy for designing a ratiometric fluorescent nanosensor is described in this work. A carbon dots (CDs) based dual-emission nanosensor for Bisphenol A (BPA) was prepared by coating CDs on the surface of dye-doped silica nanoparticles. The fluorescence of dual-emission silica nanoparticles was quenched in hydrochloric acid by potassium bromate (KBrO3) oxidation; BPA inhibited KBrO3 oxidation, resulting in the ratiometric fluorescence response of dual-emission silica nanoparticles. Several important parameters affecting the performance of the nanosensor were investigated and optimized. The detection limit of this nanosensor was 0.80 ng mL− 1 with a linear range from 10 to 500 ng mL− 1. This was applied successfully to determine BPA in the leached solution of different plastic products with satisfactory results.

[Zn4(L1)2(OAc)2(CH3CH2OH)2] and [CuL2(H2O)] with new asymmetric Salamo-type ligands have been synthesized and characterized. There are two coordination geometries (trigonal bipyramidal and square pyramidal) in the Zn(ΙΙ) complex, and the Cu(II) complex has square-pyramidal geometry. A self-assembling continual zigzag chain is formed by intermolecular hydrogen bonds in the Cu(II) complex. The self-assembling array of the Zn(II) complex is linked by intermolecular C–H⋯O and C–H⋯π interactions. Blue emissions of the Zn(II) and Cu(II) complexes in DMF solution are exhibited by fluorescence.

The insecticide cartap (CP) is non-fluorescent in aqueous solutions. This property makes its determination through direct fluorescent method difficult. In acidic medium and at room temperature, palmatine (PAL) can react with cucurbit[7]uril (CB[7]) to form stable complexes, and the fluorescence intensity of the complex is greatly enhanced. Significant quenching of the fluorescence intensity of the CB[7]-PAL complex was observed with the addition of cartap. Based on the significant quenching of the supramolecular complex fluorescence intensity, a new spectrofluorimetric method with high sensitivity and selectivity was developed to determine cartap in aqueous solution. The fluorescence quenching values (ΔF) showed good linear relationship with cartap concentrations from 0.009 to 2.4 μg mL−1 with a detection limit 0.0029 μg mL−1. The proposed method had been successfully applied to the determination of cartap residues in grain and vegetable with recoveries of 87.4-103%. In addition, the association constants of the complexes formed between the host and the guest were determined. The competing reaction and the supramolecular interaction mechanisms between the cartap and PAL as they fight for occupancy of the CB[7] cavity were studied using spectrofluorimetry, 1H NMR and molecular modeling calculations.

A new mononuclear Zn(II) complex, [ZnL(HOAc)] (1) (H2L = 6,6’-diethoxy-2,2’-[1,2-ethylenedioxybis(nitrilomethylidyne)]diphenol), was synthesized by reaction of H2L and Zn(II) acetate under solvothermal conditions. Complex 1 acts as a metallohost possessing a pentadentate O5 donor. Complex 1 molecules bonded to one Sr(II) or Ba(II) form two new hetero-trinuclear complexes, [(ZnL)2M(OAc)2] (M = Sr (2), Ba (3)). In 2 and 3, Zn(II) ions are five-coordinate, but the Sr(II) or Ba(II) ion is ten-coordinate by four μ-phenolic oxygens from two L2- units, four oxygens from four ethoxy groups and two oxygens from two μ-acetato ligands. Furthermore, 1, 2 and 3 exhibit blue emissions with the maximum emission wavelengths λmax = 477, 500 and 471 nm when excited at 360 nm.

A complexation of non-fluorescent phenformin hydrochloride (PFH) with cucurbit [7]uril (CB [7]) in aqueous solution was investigated using the fluorescent probe of palmatine (PAL) coupled with CB [7]. The fluorescent probe of CB [7]-PAL exhibited strong fluorescence in aqueous solution, which was quenched gradually with the increase of PFH. This effect is observed because when PFH was added to the host-guest system of CB [7]-PAL, PFH and PAL competed to occupy the CB [7] cavity. Portions of the PAL molecule were expelled from the CB [7] cavity owing to the introduction of PFH. Based on the significant quenching of the supramolecular complex fluorescence intensity, a fluorescence method of high sensitivity and selectivity was developed to determine PFH with good precision and accuracy for the first time. The linear range of the method was 0.005-1.9 μg mL(-1) with a detection limit of 0.003 μg mL(-1). In this work, association constants (K) of PFH with CB [7] were also determined. KCB [7]-PFH=(2.52±0.05)×10(5) L mol(-1). The ability of PFH to bind with CB [7] is stronger than that of PAL. The results of a density functional theory calculation authenticated that the moiety of PFH was embedded in the hydrophobic cavity of CB [7] tightly, and the nitrogen atom is located in the vicinity of a carbonyl-laced portal in the energy-minimized structure. The molecular modelling of the interaction between PFH and CB [7] was also confirmed by (1)H NMR spectra (Bruker 600 MHz).

A simple and sensitive high performance liquid chromatography-fluorescence detector (HPLC-FLD) method was developed for simultaneous determination of palmatine (PAL) and berberine (BRH). The method is based on the enhancement of the fluorescence of PAL and BRH in aqueous solution in the presence of cucurbit[7]uril (CB[7]). The chromatographic resolution of PAL and BRH was performed on a SymmetryShieldTM RP 18 column with CB[7] as the mobile phase additive. The composition of the mobile phase was (50/50, v/v) absolute methanol/0.05% (v/v) triethylammonium acetate buffer (pH 4.1) with 1.25 × 10−4 M CB[7] at a flow-rate of 0.5 mL · min−1. The linear ranges of PAL and BRH were 3–230 and 2–220 ng · mL−1, with the regression equations of Y = 594248 + 7.56 × 104X (R = 0.9993), Y = 811028 + 6.32 × 104X (R = 0.9995), respectively. The limits of detection for PAL and BRH were 1 and 0.7 ng · mL−1, respectively, with fluorescence detection at an excitation wavelength of 347 nm and an emission wavelength of 495 nm. Th...

In the presence of cucurbit[7]uril (CB[7]), the CB[7] could react with palmatine, which served as a sensitive fluorescence probe, to form host-guest stable complexes and the fluorescence intensity of the complexes was greatly enhanced. The fluorescence intensity decreased linearly with an increasing number of L-cystine in the inclusion system. The experimental results show that there exists a competition between L-cystine and palmatine for the CB[7] hydrophobic cavity and L-cystine occupies the space of CB[7] cavity, leading palmatine molecules to be forced to reside in the aqueous environment. Based on the fluorescence quenching of the CB[7]/palmatine complexes resulting from complex formation between CB[7] and L-cystine, a spectrofluorimetric method for the determination of L-cystine in aqueous solution in the presence of CB[7] was developed. The linear relationship between the corresponding values of the fluorescence quenching ΔF and L-cystine concentration was obtained in the range of 6.0 to 1.5×103 ng·mL−1, with a correlation coefficient (r) of 0.9996. The detection limit was 2.0 ng·mL−1. The application of the present method to the determination of L-cystine in tablets gave satisfactory results. This paper also discussed the mechanism of the fluorescence indicator probe.

Amantadine hydrochloride (AMA) and rimantadine hydrochloride (RIM) are non-fluorescent in aqueous solutions. This property makes their determination through direct fluorescent method difficult. The competing reactions and the supramolecular interaction mechanisms between the two drugs and coptisine (COP) as they fight for occupancy of the cucurbit[7]uril (CB[7]) cavity, were studied using spectrofluorimetry, (1)H NMR, and molecular modeling calculations. Based on the significant quenching of the supramolecular complex fluorescence intensity, a fluorescent probe method of high sensitivity and selectivity was developed to determine AMA or RIM in their pharmaceutical dosage forms and in urine samples with good precision and accuracy. The linear range of the method was from 0.0040 to 1.0 μg mL(-1) with a detection limit ranging from 0.0012 to 0.0013 μg mL(-1). This shows that the proposed method has promising potential for therapeutic monitoring and pharmacokinetics and for clinical application.

A validated, simple, and sensitive fluorescence quenching method for the determination of ranitidine, nizatidine, and cimetidine in tablets and biological fluids is presented. This is the first single fluorescence method reported for the analysis of all three H(2) antagonists. The competitive reaction between the investigated drug and the palmatine probe for the occupancy of the cucurbit[7]uril (CB[7]) cavity was studied using spectrofluorometry. CB[7] was found to react with the probe to form a stable complex. The fluorescence intensity of the complex was also enhanced greatly. However, the addition of the drug dramatically quenched the fluorescence intensity of the complex. Accordingly, a new fluorescence quenching method for the determination of the studied drugs was established. The different experimental parameters affecting the fluorescence quenching intensity were studied carefully. At optimum reaction conditions, the rectilinear calibration graphs between the fluorescence quenching values (ΔF) and the medicament concentration were obtained in the concentration range of 0.04-1.9 μg mL(-1) for the investigated drugs. The limits of detection ranged from 0.013 to 0.030 μg mL(-1) at 495 nm using an excitation wavelength of 343 nm. The proposed method can be used for the determination of the three H(2) antagonists in raw materials, dosage forms and biological fluids.