A colorimetric chemosensor for Cu²⁺ ion detection based on an iridium(III) complex

A Reversible Fluorescent Chemosensor for the Selective Detection of Cu2+ and CN- ions by Displacement Approach

A novel fluorescence chemosensor BDP (2-(1-(benzothiazol-2-yl)-5-(4-(diphenylamino)phenyl)-4,5-dihydro-1H-pyrazol-3-yl)phenol) has been synthesized and its sensing behavior has been screened towards various cations by absorption, emission and mass spectroscopic techniques. The probe BDP detects Cu2+ ions preferentially over other metal ions, and the resulting BDP-Cu2+ ensemble acts as a secondary sensor for cyanide anion detection over other anions. The fluorescence intensity of the probe BDP is quenched when it comes into contact with Cu2+ ions, but it is increased reversibly when it comes into contact with cyanide anion, according to spectroscopic measurements. Along with this, optical studies indicate that the sensor BDP has capability to sense Cu2+ and CN- ions selectively over other examined competitive ions with the LOD of 2.57×10-8 M and 2.98×10-8 M respectively. The detection limit of Cu2+ ions is lower than the WHO recommended Cu2+ ions concentration (31.5 µM) in drinking water. On the basis of "on-off-on" fluorescence change of the probe BDP upon interaction with Cu2+ and CN- ions, a possible mechanism for this selective sensing behavior was presented and IMPLICATION logic gate was successfully designed. Furthermore, cell imaging investigations were used to investigate the probe BDP's biological applicability.

Multicolor Emissive Phosphorescent Iridium(III) Complexes Containing L-Alanine Ligands: Photophysical and Electrochemical Properties, DFT Calculations, and Selective Recognition of Cu(II) Ions

Three novel Ir(III) complexes, (ppy)₂Ir(L-alanine) (Ir1) (ppy = 2-phenylpyridine), (F₄ppy)₂Ir(L-alanine) (Ir2) (F₄ppy = 2-(4-fluorophenyl)pyridine), and (F_2,4,5ppy)₂Ir(L-alanine) (Ir3) (F_2,4,5ppy = 2-(2,4,5-trifluorophenyl)pyridine), based on simple L-alanine as ancillary ligands were synthesized and investigated. Due to the introduction of fluorine substituents on the cyclometalated ligands, complexes Ir1-Ir3 exhibited yellow to sky-blue emissions (λ_em = 464-509 nm) in acetonitrile solution. The photoluminescence quantum yields (PLQYs) of Ir1-Ir3 ranged from 0.48-0.69, of which Ir3 with sky-blue luminescence had the highest PLQY of 0.69. The electrochemical study and density functional theory (DFT) calculations show that the highest occupied molecular orbital (HOMOs) energy of Ir1-Ir3 are stabilized by the introduction of fluorine substituents on the cyclometalated ligands, while L-alanine ancillary ligand has little contribution to HOMOs and lowest unoccupied molecular orbitals (LUMOs). Moreover, Ir1-Ir3 presented an excellent response to Cu²⁺ with a high selectivity, strong anti-interference ability, and short response time. Such a detection was based on significant phosphorescence quenching of their emissions, showing the potential application in chemosensors for Cu²⁺.

Verbascoside extracted from Clerodendrum inerme: A natural monomer for the fabrication of a sensitive electrochemical Cu(II) sensor

Verbascoside is isolated from the whole plants of the Verbenaceae family and demonstrates significant levels of bioactivity. In this work, we report on the isolation of verbascoside, a phenolic glycoside, from the stems of Clerodendrum inerme collected in Vietnam and verify its structure by comparing its spectroscopic data with those reported in the literature. Verbascoside is then applied as a monomer for the electrochemical deposition of a layer of polyverbascoside onto glassy carbon electrodes toward Cu2+ sensing. Electrochemical results demonstrate that the polyverbascoside-modified glassy carbon electrode is highly selective for Cu2+ ions compared to other evaluated ions including Ni2+ and Co2+. The developed sensor can detect Cu2+ in a concentration range from 0 to 175 μM with a sensitivity of 0.372 µA µM−1 and a limit of detection of 50 nM Cu2+ ions.

In Situ Preconcentration and Quantification of Cu2+ via Chelating Polymer-Wrapped Multiwalled Carbon Nanotubes

Trace analysis of heavy metals in complex, environmentally relevant matrices remains a significant challenge for electrochemical sensors employing stripping voltammetry-based detection schemes. We present an alternative method capable of selectively preconcentrating Cu²⁺ ions at the electrode surface using chelating polymer-wrapped multiwalled carbon nanotubes (MWCNTs). An electrochemical sensor consisting of poly-4-vinyl pyridine (P4VP)-wrapped MWCNTs anchored to a poly(ethylene terephthalate) (PET)-modified gold electrode (r = 1.5 mm) was designed, produced, and evaluated. The P4VP is shown to form a strong association with Cu²⁺ ions, permitting preconcentration adjacent to the electrode surface for interrogation via cyclic voltammetry. The sensor exhibited a detection limit of 0.5 ppm with a linear range of 1.1-13.8 ppm (16.6-216 μM) and a relative standard deviation (RSD) of 4.9% at the Environmental Protection Agency (EPA) limit of 1.3 ppm. Evaluation in tap water, lake water, ocean water, and deionized water rendered similar results, highlighting the generalizability of the presented preconcentration strategy. The advantages of electrochemical analysis paired with polymeric chelation represent an effective platform for the design and deployment of heavy metal sensors for continuous monitoring of natural waters.

PAA Modified Upconversion Nanoparticles for Highly Selective and Sensitive Detection of Cu2+ Ions

Detection of the Cu²⁺ ions is crucial because of its environmental and biological implications. The fluorescent-based organic sensors are not suitable for Cu²⁺ detection due to their short penetration depth caused by the UV/visible excitation source. Therefore, we have demonstrated a highly sensitive and selective near-infrared (NIR) excitable poly(acrylic acid) (PAA) coated upconversion nanoparticles (UCNPs) based sensor for Cu²⁺ detection. We construct the PAA modified Na(Yb, Nd)F₄@Na(Yb, Gd)F₄:Tm@NaGdF₄ core-shell-shell structured UCNPs based sensor via a co-precipitation route. The upconversion emission intensity of the PAA-UCNPs decreases linearly with the increase in the Cu²⁺ concentration from 0.125 to 3.125 μM due to the copper carboxylate complex formation between Cu²⁺ and PAA-UCNPs. The calculated detection limit of the PAA-UCNPs based sensor is 0.1 μM. The PAA-UCNPs based sensor is very sensitive and selective toward detecting the Cu²⁺ ions, even when the Cu²⁺ co-exist with other metal ions. The EDTA addition has significantly reversed the upconversion emission quenching by forming the EDTA-Cu²⁺ complex based on their greater affinity toward the Cu²⁺. Therefore, the PAA-UCNPs based sensor can be a promising candidate for Cu²⁺ detection because of their higher sensitivity and selectivity under 980 nm NIR excitation.

Novel Quinoline-Based Thiazole Derivatives for Selective Detection of Fe3+, Fe2+, and Cu2+ Ions

New quinoline-based thiazole derivatives QPT and QBT were synthesized and characterized by various spectroscopic and single-crystal X-ray crystallographic studies. The metal-sensing properties of the probes were further examined by absorption and fluorescence spectrometry. The fluorescence intensity of QPT and QBT was remarkably quenched during the addition of Fe³⁺, Fe²⁺, and Cu²⁺ ions in THF/H₂O (1:1) at pH = 7.4 in HEPES buffer, while the addition of other metal ions did not affect the fluorescence intensity of the ligands. The detection ability of the probes QPT and QBT was further investigated by titration with various equivalents of metal ions, optimized pH ranges for detection, and reversibility with Na₂EDTA for biological applications.

Ultrasensitive Colorimetric and Ratiometric Detection of Cu2+: Acid-Base Properties, Complexation, and Binding Studies

Herein, we report the synthesis and characterization of a chemosensor, 5-(diethylamino)-2-(2,3-dihydro-1H-perimidin-2-yl)phenol (HL), synthesized from a condensation between 4-(diethylamino)salicylaldehyde and 1,8-diaminonaphthalene. Upon investigation of the sensing properties of HL, it was found that this sensor may be employed for simple yet efficient detection of Cu2+ in aqueous methanol solutions. The selective and ratiometric response to Cu2+ yielded an outstandingly low limit of detection of 3.7 nM by spectrophotometry and is also useful as a naked-eye sensor from 2.5 μM. The system was studied by spectrophotometric pH titrations to determine Cu2+ binding constants and complex speciation. Binding of Cu2+ to HL occurs in 1:1 stoichiometry, in good agreement with high-resolution electrospray ionization mass spectrometry (ESI-HRMS) results, Cu2+ titrations, and Job's plot experiments, while the coordination geometry was tentatively assigned as square pyramidal by spectroscopic studies.

Coordination mode-induced isomeric cyclometalated [Ir(tpy)(nbi)Cl](PF6) complexes: distinct luminescence, self-assembly and cellular imaging behaviors

Two isomeric Ir(iii) complexes Ir-O and Ir-R arising from the different coordination mode of a naphthalene-containing ligand, show distinct luminescence, self-assembly ability and cellular imaging behaviors.

Nanomolar-level selective dual channel sensing of Cu2+and CN−from an aqueous medium by an opto-electronic chemoreceptor

A novel chromogenic and fluorogenic chemoreceptor exhibiting a proclivity towards Cu²⁺and CN⁻, with applications in bioimaging and molecular electronics, was developed.

A selective distance-based paper analytical device for copper(II) determination using a porphyrin derivative

Meso-tetrakis(1,2-dimethylpyrazolium-4-yl)porphyrin sulfonate (TDMPzP), a water-soluble porphyrin derivative, was synthesized and used as a colorimetric reagent for Cu²⁺ detection on a microfluidic paper-based analytical device (µPAD) using distance-based quantification. TDMPzP showed a high selectivity for Cu²⁺ detection in aqueous solutions. When Cu²⁺ was added to the TDMPzP under acidic conditions, a color change from green to a pink was observed by the naked eye. Under optimized conditions, the application of this system to a distance-based μPAD exhibited good analytical response. The presence of common metal ions (Al³⁺, Fe³⁺, Mg²⁺, Co²⁺, Mn²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Sn²⁺, and Ni²⁺) did not interfere with Cu²⁺ detection within reasonable tolerance ratios. The lowest concentration of copper that could be measured was 1mgL^-1 (1ppm) which meets the requirements for drinking water contamination regulations from the US Environmental Protection Agency (EPA) and World Health Organization (WHO) guidelines for drinking water. Real drinking water samples were analyzed to confirm the practical application of this system and the results showed good agreement with ICP-MS data. This distance-based µPAD based on TDMPzP for Cu²⁺ detection is convenient and effective for real-time drinking water analysis.

Cyclometalated Ir(iii) complexes containing quinoline–benzimidazole-based N^N ancillary ligands: structural and luminescence modulation by varying the substituent groups or the protonation/deprotonation state of imidazole units

Four Ir(iii) complexes have been prepared, showing structural and luminescence modulation upon varying their substituent groups or protonation/deprotonation state.

Cyclometalated Ir(iii) complexes based on 2-(2,4-difluorophenyl)-pyridine and 2,2′-(2-phenyl-1H-imidazole-4,5-diyl)dipyridine: acid/base-induced structural transformation and luminescence switching, and photocatalytic activity for hydrogen evolution

1·PF₆and2show luminescence switching behaviors, and serve as photosensitizers for H₂evolution.

A hybrid magnetic core–shell fibrous silica nanocomposite for a chemosensor-based highly effective fluorescent detection of Cu(ii)

Herein, a novel hybrid magnetic core–shell fibrous silica nanocomposite (RhB–Fe₃O₄/MnO₂/SiO₂/KCC-1) probe-based chemosensor was designed and its behaviour towards Cu(ii) metal ion was investigated using a fluorescence spectrometer.

Heteroleptic Ir(iii) and Pt(ii) complexes based on 2-(2,4-difluorophenyl)-pyridine and bisthienylethene BrLH: the influence of the metal center on structures, luminescence and photochromism

Based on bisthienylethene BrLH, [Ir(dfppy)₂(BrL)]·3CH₃OH (1) and [Pt(dfppy)(BrL)]·CH₃OH (2) have been prepared. The two complexes are significantly different in structure, luminescence and photochromic behavior, due to their different metal centers.

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⁺.

A highly selective chemosensor for naked-eye sensing of nanomolar Cu(ii) in an aqueous medium

A colorimetric chemosensor was developed for the sensitive detection and quantification of Cu²⁺with a short response time in an aqueous medium.

A visual volumetric hydrogel sensor enables quantitative and sensitive detection of copper ions

A volumetric sensor design enables the precise naked-eye readout of hydrogel volume changes for quantitative and sensitive detection of copper ions.