A fluorescent sensor with high selectivity and sensitivity for potassium in water

This communication describes a new optical sensor suitable for practical measurement of extracellular (serum or whole blood) potassium. The sensor responds rapidly and reversibly to changes in potassium concentrations typical of whole blood samples. No interferences from clinical concentrations of calcium or pH are observed, and the sodium interference is very minor. Excitation and emission occur in the visible light region. This new potassium sensor is currently used in the Roche OPTI CCA, a commercially available whole blood analyzer.     

A ratiometric fluorescent sensor for Ag(I) with high selectivity and sensitivity

A bicyclic cycloadduct 1 bearing a pyrenyl moiety has been synthesized and investigated as a ratiometric fluorescent sensor for AgI. In an aqueous ethanol solution of 1, the presence of silver ion induces the formation of a 1:2 metal-ligand complex, which exhibits a strong intensity enhancement of the pyrene excimer emission at the expense of the emission of monomeric pyrene.     

An off-on fluorescent sensor with high selectivity and sensitivity for Fe(III)

A new fluorescent derivative (1) containing coumarin exhibits Fe(III)-selective strong yellow-green fluorescence in ethanol. This compound could be used as an “off-on” chemosensor and allow the detection of Fe³⁺ by monitoring changes in absorption and fluorescence spectra. Upon addition of Fe³⁺, an overall emission change of 125-fold was observed. High selectivity and sensitivity were observed over other metal ions, mainly due to the spirolactam ring-opening power of Fe³⁺. The detection limit was as low as 5.6?ppb. Photo-induced electron transfer, coupled with intramolecular charge transfer are proposed to account for the observed spectral response.     

KCN sensor: unique chromogenic and 'turn-on' fluorescent chemodosimeter: rapid response and high selectivity

An indole conjugated coumarin 1 for KCN chemodosimeter has been prepared and displayed considerable dual changes in both absorption (blue-shift) and emission (turn-on) bands exclusively for KCN. DFT/TDDFT calculations support that the fluorescence enhancement of 1-KCN is mainly due to blocking of the ICT process.     

Stable fluorescent gold nanoparticles for detection of Cu2+ with good sensitivity and selectivity

A simple and one-pot method for the synthesis of water-soluble, red-emitting, highly fluorescent gold nanoparticles has been reported using 11-mercaptoundecanoic acid (11-MUA) as the protecting group. We found that the fluorescent gold nanoparticles could selectively detect copper ions in aqueous solution, with a limit of detection of about 87 nM.     

A fluorescent probe for zinc ions based on N-methyltetraphenylporphine with high selectivity

N-methyl-alpha,beta,gamma,delta-tetraphenylporphine (NMTPPH) has been used to detect trace amount of zinc ions in ethanol-water solution by fluorescence spectroscopy. The fluorescent probe undergoes a fluorescent emission intensity enhancement upon binding to zinc ions in EtOH/H(2)O (1:1, v/v) solution. The fluorescence enhancement of NMTPPH is attributed to the 1:1 complex formation between NMTPPH and Zn(II) which has been utilized as the basis for the selective detection of Zn(II). The linear response range covers a concentration range of Zn(II) from 5.0x10(-7) to 1.0x10(-5)mol/L and the detection limit is 1.5x10(-7)mol/L. The fluorescent probe exhibits high selectivity over other common metal ions except for Cu(II).     

A fluorescent sensor based on quinazoline ketone derivatives for selectivity of Fe3+

In this work, we provided a fluorescent sensor based on a compound containing fluorophore quinazoline ketone for detecting metal ions. 2-Methyl-4(3 H)-quinazoline thione was synthesised as a fluorescent probe for tervalent ferric ion (Fe³⁺) detection. Fluorescent determination of 2-methyl-4(3 H)-quinazoline thione indicated its maximum emission wavelength of 306.5 nm. The fluorescence interference and titration experiments have shown that the compound has a high selective fluorescence response to Fe³⁺. With an increase in the Fe³⁺ ion concentration, the fluorescence emission strength gradually weakened, and a slight red shift appeared. With Job’s method, 2-methyl-4(3 H)-quinazoline thione was proved to form a 1:2 complex with Fe³⁺. The results revealed that 2-methyl-4(3 H)-quinazoline thione could be used as a fluorescent probe for the recognition of Fe³⁺ with high selectivity.     

Probing disaccharide selectivity with modular fluorescent sensors

Six modular photoinduced electron transfer (PET) sensors bearing two phenylboronic acid receptors have been evaluated as fluorescent disaccharide sensors. The length of linker separating the two boronic acid moieties was varied and the sensors’ interaction with disaccharides assessed via fluorescence spectroscopy. It was shown that saccharide selectivity was influenced by the choice of linker length. Diboronic acid sensors 3_n also displayed significant specificity for the disaccharides linked to the carbon on the 3rd or 6th position (as numbered from the anomeric centre) over those linked at the 4th position.     

Development of a novel fluorescent sensor to detect a specific range of pH

A novel fluorescent sensor for monitoring the change of pH was developed, based on a structure containing two hydroxyl groups that are sequentially deprotonated as the pH is increased: the first deprotonation increases the fluorescence intensity and the second decreases it. Compared with most reported pH sensors that can detect only whether or not the pH is below or above a specific value, our sensor could detect a specific range of pH (centered on pH 8–9) that should be useful for the study of biological microenvironment.     

Significant improved selectivity of a fluorescent sensor for Al3+ made from a fluorinated rhodamine B Schiff base

Research on Chemical Intermediates - Two rhodamine B-based Schiff bases (RBF, RBC) with different substituent groups (–F and –COOH) have been synthesized. In order to study the sensing...     

Single-fluorophore-based fluorescent probes enable dual-channel detection of Ag and Hg with high selectivity and sensitivity

A new type of fluorescent probe capable of detecting Ag⁺ and Hg²⁺ in two independent channels was developed in the present work. Specifically, in CH₃CN–MOPS mixed solvents with CH₃CN/MOPS ratio (v/v) of 15/85, this type of probe fluoresced weakly, and the addition of Ag⁺ remarkably induced fluorescence enhancement of the probe. In CH₃CN–MOPS mixed solvents with the percentage of CH₃CN increased up to 65%, the probe was highly fluorescent and addition of Hg²⁺ dramatically induced the fluorescence quenching. Thus, using such single-fluorophore-based probe and tuning the polarity of the mixed solvent, Ag⁺, and Hg²⁺ can be detected in independent channels with high selectivity and sensitivity. As a result, the mutual interference usually encountered in most cases of Ag⁺ and Hg²⁺ sensing owing to the similar fluorescence response that these two ions induced, can be effectively circumvented by using the probes developed herein.     

A turn-on and reversible fluorescence sensor with high affinity to Zn in aqueous solution

A new simple receptor 1 based on aminosalicylimine was prepared. It exhibited an ‘off–on fluorescence type’ mode with high sensitivity in the presence of Zn²⁺. In particular, this chemosensor could clearly distinguish Zn²⁺ from Cd²⁺. Also, it could be a reusable chemosensor because the addition of EDTA quenched the fluorescence of the Zn²⁺-2·1 complex. Furthermore, receptor 1 had a sufficiently low detection limit (68 nM) in aqueous solutions, which implies that 1 could sense the nanomolar concentration of Zn²⁺. Therefore, this sensor has the ability to be a practical system for the monitoring of Zn²⁺ concentrations in aqueous samples.     

A molecularly imprinted photonic polymer sensor with high selectivity for tetracyclines analysis in food

A molecularly imprinted photonic polymer (MIPP) sensor for respective detection of tetracycline, oxytetracycline and chlortetracycline is developed based on the combination of a colloidal crystal templating method and a molecular imprinting technique. Colloidal crystal templates are prepared from monodisperse polystyrene colloids. The molecularly imprinted polymer, which is embodied in the colloidal crystal templates, is synthesized with acrylic acid and acrylamide as monomers, N,N'-methylene bisacrylamide as a cross-linker and tetracyclines (TCs) as imprinting template molecules. After removal of the colloidal crystal template and the molecularly imprinted template, the resulted MIPP consists of a three-dimensional, highly ordered and interconnected macroporous array with a thin hydrogel wall, where nanocavities complementary to analytes in shape and binding sites are distributed. The response of MIPP to TCs stimulants in aqueous solution is detected through a readable Bragg diffraction red-shift, which is due to the lattice change of MIPP structures responding to their rebinding to the target TCs molecules. A linear relationship was found between the Δλ and the concentration of TCs in the range from 0.04 μM to 0.24 μM. With this sensory system, direct and selective detection of TCs has been achieved without using label techniques and expensive instruments. The developed method has been applied successfully to detect tetracycline in milk and honey samples.     

A simple dual-channel sensor for detecting cyanide in water with high selectivity and sensitivity

Taking advantage of the special nucleophilicity of cyanide, a new simple colorimetric chemosensor has been synthesised. This allows a deprotonation reaction to monitoring the cyanide. With the addition of CN^? to the chemosensor aqueous solution, which could induce a change in the solution colour from yellowish to deep yellow, while no colour change could be observed in the presence of other hackneyed anions, by which CN^? can be distinguished from other anions immediate with the naked eye. At the same time, a fluorescence quenching was implemented upon adding cyanide into the chemosensor aqueous solution. The absorption spectra detection limits of the chemosensor for cyanide was 5.35 × 10^?8 M and the fluorescence spectra detection limit was 2.63 × 10^?8 M. The cyanide test strips based on the chemosensor could serve as a convenient cyanide test kits. Furthermore, the chemosensor was successfully applied to detect cyanide in sprouting potatoes.