A novel donor–acceptor receptor for selective detection of Pb2+and Fe3+ ions

Bis(thiophen-2-yl-methylene) Benzene-1, 4-Diamine as Fluorescent Probe for the Detection of Fe3+ in Aqueous Samples

A Schiff base bis(thiophen-2-yl-methylene)benzene-1, 4-diamine (L) was synthesized and used for selective and sensitive detection of Fe³⁺. L exhibited enhanced fluorescence response at excitation of 365 nm and emission wavelength of 440 nm for Fe³⁺. The formation of a 1:1 complex between L and Fe³⁺ was suggested by Job's plot by fluorescence titration and from optimized structures using Density functional theory (DFT). The fluorescence intensity was directly proportional to concentration of Fe³⁺ (R² = 0.999) with the detection limit of 3.8 × 10^-7 M and the binding constant of 1.20 × 10⁴ M^-1 at pH = 6.0. The probe was used to detect Fe³⁺ in different water samples with the percentage recovery of 99.7-103%. The interference of the other cations are < 5%.

Amino Appended Coumarin Composites for Pb2+ Capturing in Aqueous Medium

The C1-C3 receptors were synthesized by using coumarin and amines viz., 1-butylpiperazine (1), cis-myrtanylamine (2), and 3-methyldiphenyl amine (3) at room temperature without using harsh conditions. All the probes show beautiful and strong binding with Pb²⁺ ions among all the tested essential elements of human body. The binding is clearly seen and confirmed in UV-visible, NMR and HPLC studies. Also, all the substituted amines (1-3) are well known bioactives viz., piperazine as anthelmintic, cis-myrtanyl use for cannabinoid receptor (CB2) antagonists, 3-methyldiphenyl is used in probes for selective detection of explosive nitroaromatic compounds further increases their sensitivity for use as Pb²⁺ sensor. As they are already well in use for research on human body metabolomics their future introduction as sensors in the human body for lead toxicity is highly favourable.

Studies of the labile lead pool using a rhodamine-based fluorescent probe

Lead is a heavy metal which has long been known to have toxic effects on the body. However, much remains to be learnt about the labile lead pool and cellular uptake of lead. We report here RPb1 that undergoes a 100-fold increase in fluorescence emission in the presence of Pb2+, and which can be applied to study the labile lead pool within cells. We demonstrate the capacity of RPb1 for investigating labile lead pool in DLD-1 cells and changes in labile lead during differentiation of K562 cells.

Tetraphenylethylene AIEgen bearing thiophenylbipyridine receptor for selective detection of copper(ii) ion

A new tetraphenylethylene (TPE) AIEgen appended with a thiophenylbipyridine moiety exhibits sensitivity and selectivity towards copper ions via a PET “turn on–turn off” mechanism.

A nanoneedle-based reactional wettability variation sensor array for on-site detection of metal ions with a smartphone

An enhancement of the reactional wettability variation (RWV) sensing strategy is achieved based on the wettability switch of a nanoneedle surface. The sensor unit is formed by coating hydrophobic azoimidazole compounds, as the responder compounds onto the originally hydrophilic surface of cobalt hydroxide nanoneedles. The complexation reaction between metal ions and azoimidazole ligands etches the hydrophobic coating and switches the surface wettability, making the surface hydrophilic again. This switch is revealed by a decrease in the static contact angle (CA) and an increase in the sliding angle of the surface. The reactivity is tuned by the derivatization and conformational manipulation of the azoimidazole compounds. A sensor array composed of six as-tuned sensor units is constructed to distinguish among the species and concentrations of Fe³⁺, Ni²⁺ and La³⁺ at a low limit of 10^-6 M using the chemometric method of principal component analysis (PCA). In addition, a new on-site detection strategy is developed based on PCA of the sliding angle, which can be measured conveniently and swiftly with a smartphone app and a commercially available setup. The application of the general RWV strategy is envisioned to open new possibilities for on-site detection.

A pyrene based fluorescent turn-on chemosensor: aggregation-induced emission enhancement and application towards Fe3+ and Fe2+ recognition

A pyrene-based probe bearing benzothiazole ionophore (Py-BTZ) was synthesised as a "turn-on" fluorescent chemosensor for the detection of Fe³⁺ and Fe²⁺ ions in CH₃CN : H₂O (1 : 1, v/v) solvent mixes. The chemosensor showed optical as well as colorimetric changes towards Fe³⁺ and Fe²⁺ ions along with a remarkable enhancement in fluorescence emission. The detection limit of Py-BTZ towards Fe³⁺ and Fe²⁺ ions was found to be 2.61 μM and 2.06 μM, respectively. The binding of Py-BTZ with Fe³⁺ and Fe²⁺ was determined by using FT-IR experiments. Interestingly, Py-BTZ shows aggregation induced emission enhancement (AIEE) properties in polar solvent mixes such as CH₃CN : H₂O (1 : 1, v/v).

Highly selective and sensitive fluorogenic ferric probes based on aggregation-enhanced emission with -SiMe3 substituted polybenzene

In this study, thiophene was linked to polybenzene to generate novel fluorescent probes, namely 3,4-diphenyl-2,5-di(2-thienyl)phenyl-trimethylsilane (DPTB-TMS) with a -SiMe₃ substituent and 3,4-diphenyl-2,5-di(2-thienyl)phenyl (DPTB) without the -SiMe₃ substituent, respectively. Both of the two compounds exhibit aggregation-enhanced emission (AEE) properties in tetrahydrofuran/water mixtures due to restricted intramolecular rotation of the peripheral groups, which make the two compounds good candidates for the detection of Fe³⁺ ions in aqueous-based solutions. The fluorescence intensity of the two compounds decreases immediately and obviously upon addition of a trace amount of Fe³⁺, and decreases continuously as the amount of Fe³⁺ increases. The fluorescence was quenched to 92% of its initial intensity when the amount of Fe³⁺ ions reached 6μmol for DPTB-TMS and to 80% for DPTB in the systems, indicating that the compound with the -SiMe₃ group is a more effective probe. The detection limit was found to be 1.17μM (65ppb). The detection mechanism is proposed to be static quenching. DPTB-TMS is highly efficient for the detection of ferric ions even in the presence of other metal ions. In addition, the method is also successfully applied to the detection of ferric ions in water, blood serum, or solid films. This indicates that these polybenzene compounds can be applied as low-cost, high selectivity, and high efficiency Fe³⁺ probes in water or in clinical applications.

A highly sensitive and selective chemosensor for Pb2+ based on quinoline–coumarin

In this study, a highly sensitive and selective fluorescent chemosensor, ethyl(E)-2-((2-((2-(7-(diethylamino)-2-oxo-2H-chromene-3-carbonyl)hydrazono)methyl)quinolin-8-yl)oxy)acetate (1), was synthesized and characterized by ¹H NMR, ¹³C NMR and ESI-MS. Sensor 1 showed an “on–off” fluorescence response to Pb²⁺ with a 1 : 1 binding stoichiometry in CH₃CN/HEPES buffer medium (9 : 1 v/v). The detection limit of sensor 1 to Pb²⁺ was determined to be 0.5 μM, and the stable pH range for Pb²⁺ detection was from 4 to 8.

A highly sensitive and selective fluorescent chemosensor 1 was synthesized and used for naked eye detection of Pb²⁺.

Green synthesis of carbon dots originated from Lycii Fructus for effective fluorescent sensing of ferric ion and multicolor cell imaging

Green, economical and effective method was developed for synthesis of fluorescent carbon dots (CDs), using one-pot hydrothermal treatment of Lycii Fructus. Optical and structural properties of the CDs have been extensively studied by UV-visible and fluorescence spectroscopic, x-ray diffraction (XRD) techniques, transmission electron microscopy (TEM) and high resolution TEM (HRTEM). Surface functionality and composition of CDs has been illustrated by Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS) spectra and elemental analysis. The fabricated CDs possess stable fluorescent properties. The fluorescent quantum yield of the CDs can reach 17.2%. The prepared CDs emitted a broad fluorescence between 415 and 545nm and their fluorescence was tuned by changing excitation wavelength. Meanwhile, the fluorescence intensity of the CDs could be significantly quenched by Fe³⁺ (turn-off). The CDs exhibit captivating sensitivity and selectivity toward Fe³⁺ with a linear range from 0 to 30μM and a detection limit of 21nM. The prepared CDs were successfully applied to the determination of Fe³⁺ in the urine samples, the water samples from the from the Yellow River and living HeLa (Henrietta Lacks) cells. Moreover, the low-toxicity and excellent biocompatibility of the CDs were evaluated through MTT assay on HeLa cells. The CDs were also employed as fluorescent probes for multicolor imaging of HeLa cells successfully.

A new macrocyclic ligand as a turn-on fluorescent chemosensor for the recognition of Pb2+ions

The chemosensor L has a detection limit of 9.63 nM for Pb²⁺in an acetonitrile/H₂O (9 : 1, v/v) mixture.

Substitutional group dependent colori/fluorimetric sensing of Mn(2+), Fe(3+) and Zn(2+) ions by simple Schiff base chemosensor

Schiff base is one of the easiest synthesizable chemosensor and exhibit strong coordination with metal ions; the property that has been vastly exploited for metal ions sensing. Simple Schiff base chemosensors (1a-d and 2a-d) were synthesized and demonstrated substitutional group dependent colorimetric sensing of metal ions. Chemosensor without (1a, 2a) and OCH3 substitution (1b, 2b) did not show any significant colour change for metal ions. However, a highly selective colorimetric change (colourless to pink) for Mn(2+) ions (10(-6)M) was observed with diethylamine substituted 1c, 2c. Hydroxyl substitution (1d, 2d) leads to selective colorimetric sensing (colourless to orange) of Fe(3+) ions (10(-6)M). PVA thin films of 2c/2d were fabricated and demonstrated selective colorimetric sensing of Mn(2+) and Fe(3+) ions. The practical applicability of the synthesized chemosensors were also demonstrated by performing selective colorimetric sensing of Mn(2+) and Fe(3+) ions in real samples such as tap, ground, pond and river water. Effect of substitution on the fluorescence selectivity of Zn(2+) has also been investigated.