Acylhydrazone Functionalized Triphenylamine-Based Fluorescent Probe for Cu2+: Tunable Structures of Conjugated Bridge and Its Practical Application

Novel fluorescent probes were constructed for the convenient and rapid analysis of Cu2+ ions, taking advantages of the the triphenylamine backbone as chromophore and acylhydrazone group as the Cu2+ recognition site. Especially, probe T2 could act as a dual-channel probe towards Cu2+ through both fluorescent and colorimetric method. Through the fluorescent method, the detection limit of probe T2 was calculated to be as low as 90 nmol/L and there was a good linear relationship between the intensity change and the concentration of Cu2+ ions. By virtue of the two-phase liquid-liquid extraction method, probe T2 could be successfully applied in practical extraction and separation of Cu2+. Furthermore, by applying a "turn-off-turn-on" circle, compound T2 could act as a sensitive probe towards S2- anions through the indirect approach and the detection limit of complex T2-Cu2+ for S2- anion was found to be 110 nmol/L.

Simultaneous Observation of Visible Upconversion and Near-Infrared Downconversion in SrF2:Nd3+/Yb3+/Er3+ Nanocrystals and Their Application for Detecting Metal Ions under Dual-Wavelength Excitation

In this work, a sequence of Nd3+, Yb3+, and Er3+ tridoped SrF2 nanocrystals (NCs) is synthesized by a hydrothermal method. Both the efficient near-infrared downconversion luminescence (DCL) and visible upconversion luminescence (UCL) of the Er3+ and Nd3+ ions are simultaneously observed and systematically demonstrated under dual-wavelength excitation (808 and 980 nm continuous-wave lasers). Subsequently, the SrF2:Nd3+/Yb3+/Er3+ (15/4/0.2 mol %) NCs with the strongest luminescence were utilized for detecting the metal ion concentrations under 808 nm excitation. The results reveal that both the UCL and DCL gradually decrease as the metal ion concentrations increase, and high sensitivity is obtained for Cu2+ ions with a detection limit of 0.22 nM (∼650 nm) and 0.63 nM (∼976 nm). In addition, these SrF2:Nd3+/Yb3+/Er3+ NCs are further demonstrated to achieve a solid-state display under 980 nm excitation, exhibiting obvious "red" and "green" patterns by varying the doping rare earth ion concentrations.

The Schiff Base Probe With J-aggregation Induced Emission for Selective Detection of Cu2

Here, three Schiff bases 3a-c, differing by the substitutions (-H, -Cl, and -N(CH₃)₂) on the phenyl ring, have been designed and synthesized via the reaction of ortho-aminophenol with benzaldehyde, 2,4-dichlorobenzaldehyde and para-dimethylamine benzaldehyde in 1:1 molar ratio with favourable yields of 89-92%, respectively. Their structural characterizations were studied by FT-IR, NMR, MALDI-MS and elemental analysis. The fluorescence behaviours of compounds 3a and 3b exhibited a severe aggregation caused quenching (ACQ) effect in EtOH/water system. On the contrary, compound 3c had an obvious J-aggregation induced emission (AIE) feature in EtOH/water mixture (v/v = 1:1), and exhibited excellent sensitivity and anti-interference towards Cu²⁺ with the limit of detection (LOD) of 1.35 × 10^-8 M. Job's plot analysis and MS spectroscopic study revealed the 2:1 complexation of probe 3c and Cu²⁺. In addition, probe 3c was successfully applied to the determination of Cu²⁺ in real aqueous samples.

Nitrogen-doped carbon quantum dots for fluorescence detection of Cu2+ and electrochemical monitoring of bisphenol A

Nitrogen-doped carbon dots were applied in the fluorescence detection of Cu²⁺ and electrochemical detection of BPA.

Introduction

Primordial life forms on earth comprised oxygen-sensitive organisms: the anaerobic fermenters and cyanobacteria, which released oxygen as a metabolic by-product, causing the oxygen levels in the atmosphere to rise Benzie (Eur J Nutr 39:53–61, 2000 [1]), Halliwell (Free Radic Res 31:261–272, 1999 [2]).

A benzo-15-crown-5-modifying ratiometric-absorption and fluorescent OFF-ON chemosensor for Cu(2.)

One new benzo-15-crown-5-modifying fluorene Schiff base (FBC), together with the CN-linked fluorene-3,4-dimethoxybenzene (FBDMO) and fluorene-benzene (FB) references, has been designed and facilely synthesized. The binding of Cu(2+) with nitrogen atom of CN moiety in these three compounds can inhibit the photo-induced electronic transition process and induce the ratiometric-absorption and fluorescent OFF-ON response to Cu(2+). Whereas the employment of benzo-15-crown-5 moiety in FBC as additional binding platform for Cu(2+) not only amplifies the fluorescent enhancement of FBCvia preventing the isomerization of CN moiety, but also endows this compound high selectivity and rapid response towards Cu(2+) over the references FB and FBDMO. These results render FBC highly sensitive ratiometric-absorption and fluorescent OFF-ON detecting potential for Cu(2+) with the detection limit of 3.91 × 10(-6) M.

Dimethyl yellow-based colorimetric chemosensors for “naked eye” detection of Cr3+ in aqueous media via test papers

New dimethyl yellow-based dipodal receptors as colorimetric probes were designed and synthesised for selectively sensing Cr³⁺ in a “naked eye” output manner via test papers.

A “turn-on” fluorescent probe for the detection of Cu2+ in living cells based on a signaling mechanism of NN isomerization

A “turn-on” probe A based on coumarin with a mechanism of NN isomerization was developed for detecting Cu²⁺ in living cells.

Novel anthracene- and pyridine-containing Schiff base probe for selective “off–on” fluorescent determination of Cu2+ ions towards live cell application

A simple anthracene-based AP probe was synthesized to detect Cu²⁺ ions, via the photoinduced electron transfer mechanism, in live cells.

A novel pyrazole biscoumarin based chemosensors for the selective detection of Cu(2+) and Zn(2+) ions

A novel chemosensor based on pyrazole biscoumarin molecule "4-hydroxy-3-((4-hydroxy-2-oxo-2H-chromen-3-yl)(1,3-diphenyl-1H-pyrazol-4-yl)methyl)-2H-chromen-2-one" (PBC) was synthesized by a simple method. The chemosensing properties of PBC towards transition metal ions like Cu(2+) and Zn(2+) by naked eye, UV-Visible and fluorescence spectroscopic methods were described. The PBC solution with Cu(2+) and Zn(2+) ion showed brown and blue colour respectively. The UV-Visible spectra of PBC with Cu(2+) and Zn(2+) ions exposed their corresponding absorption maxima. Further, the Job's plot method confirmed the 1:1 and 2:1 stoichiometry of the complex formation between the PBC with Cu(2+) and Zn(2+) ions respectively. The fluorescence enhancement of PBC on binding with Cu(2+) and Zn(2+) is due to the inhibition of photo induced electron transfer mechanism.

Fluorescence detection of Fe(3+) ions in aqueous solution and living cells based on a high selectivity and sensitivity chemosensor

Although ferric ion (Fe(3+)) performs critical roles in diverse biochemical processes in living systems, its physiological and pathophysiological functions have not been fully explored due to the lack of methods for quantification of Fe(3+) ions in biological system. In this work, a highly sensitive and selective fluorescence chemosensor, L, was developed for the detection of Fe(3+) ions in aqueous solution and in living cells. L was facile synthesized by one step reaction and well characterized by NMR, API-ES, FT-IR, and elementary analysis. The prepared chemosensor displayed excellent selectivity for Fe(3+) ions detection over a wide range of tested metal ions. In the present of Fe(3+) ions, the strong green fluorescence of L was substantially quenched. The 1:1 stoichiometry of the complexation was confirmed by a Job's plot. The association constant (Ka) of L with Fe(3+) was evaluated using the Benesi-Hildebrand method and was found to be 1.36×10(4) M(-1). The MTT assay determined that L exhibits low cytotoxicity toward living cells. Confocal imaging and flow cytometry studies showed that L is readily interiorized by MDA-MB-231 cells through an energy-dependent pathway and could be used to detect of Fe(3+) ions in living cells.

Optical sensor: a promising strategy for environmental and biomedical monitoring of ionic species

In this review, we cover the recent developments in fluorogenic and chromogenic sensors for Cu²⁺, Fe²⁺/Fe³⁺, Zn²⁺and Hg²⁺.

1,8-Naphthyridine-based molecular clips for off–on fluorescence sensing of Zn2+ in living cells

New 1,8-naphthyridine-based clip-like receptor as “off–on” fluorescent probe was designed and synthesised for selectively sensing Zn²⁺ in living cells.

Highly sensitive and selective chemosensors for Cu2+and Al3+based on photoinduced electron transfer (PET) mechanism

Two new fluorescent PET chemosensors were synthesised from an acridine core. The sensors can be used to monitor Cu²⁺and Al³⁺in CH₃CN. The detection limits for7a–Cu²⁺and7b–Al³⁺were calculated to be 2.8 × 10⁻⁷M and 5.8 × 10⁻⁷M, respectively.

Selectively sensing first-row transition metal ions through fluorescence enhancement

Fluorescence signaling systems that give enhancement in the presence of first-row transition metal ions are discussed.

Conjugation-induced fluorescence labelling of mesoporous silica nanoparticles for the sensitive and selective detection of copper ions in aqueous solution

A newly developed fluorescent “on–off” chemosensor presents high selectivity towards Cu²⁺ with detection limit as low as 0.28 μM.