A fluorescent and colorimetric chemosensor for selective detection of aluminum in aqueous solution

Low cost, high sensitivity detection of waterborne Al3+ cations and F- anions via the fluorescence response of a morin derivative dye

Morin dye is known as a cheap and readily available selective 'off → on' fluorescent sensitiser when immobilised in a phase transfer membrane for the detection of Al³⁺ ions. Here, a morin derivative, NaMSA, which readily dissolves in water with good long-term stability is used in conjunction with a fibre optic transducer with lock-in detection to detect Al³⁺ in drinking water below the potability limit. The combination of a water soluble dye and the fibre optic transducer require neither membrane preparation nor a fluorescence spectrometer yet still display a high figure-of- merit. The known ability to recover morin-based Al³⁺ cation sensors selectively by exposure to fluoride (F^-) anions is further developed enabling a complementary sensing of either fluoride anions, or aluminium cations, using the same dye with a sub-micromolar limit-of-detection for both ions. The sensor performance parameters compare favourably to prior reports on both aqueous aluminium and fluoride ion sensing.

Selective monitoring ATP using a fluorogenic Al(III)-probe complex in aqueous medium

A simple commercially available probe 8-hydroxyjulolidine-9-aldehyde (HJ) has been developed as a turn-on fluorescent probe specifically for Al³⁺ and characterized systemically. The probe HJ for Al³⁺ ion exhibits strong green fluorescence under ultraviolet light. The HJ acted as an OFF-ON-OFF type fluorescent probe for Al³⁺ and ATP in nearly 100% aqueous media. The 1:1 binding stoichiometry between probe and Al³⁺ has been established from Job's plot and HRMS studies. The limit of detection for Al³⁺ ion is found to be 5.75 × 10^-8 M. The large association constant between HJ and Al³⁺ ion is 1.05 × 10⁵ M^-1. Detailed insights of probe-metal interaction mechanisms have been studied by the density functional theory (DFT) as well as the time dependent-DFT (TDDFT) calculations. Moreover, benefiting from the water solubility and biocompatibility of the probe HJ and its HJ-Al³⁺ complex, they have also been successfully applied to detect Al³⁺ and ATP by bioimaging in onion epidermal cells and adult zebrafish respectively.

Antipyrine based Schiff's base as a reversible fluorescence turn "off-on-off" chemosensor for sequential recognition of Al3+ and F- ions: A theoretical and experimental perspective

A Schiff's base probe (L) based on antipyrine has been intended, synthesized and assessed as a turn "off-on-off" probe for successive recognition of Al³⁺ and F^-. The probe L act out as a turn "on" fluorescence probe towards Al³⁺ in methanol at pH 6 which turned "off" by F^- at 433 nm. The 1:1 binding stoichiometry of L + Al³⁺ complex was revealed by Job's plot and approved by ESI-HRMS data. The binding constant and limit of detection of probe L for Al³⁺ were found to be 2.951 × 10⁷ M^-1 and 0.61 × 10^-7 M respectively, which is lesser than the acceptable limit (0.74 × 10^-7 M) in drinking water. The proposed binding sites and the mode of interaction of probe L was studied and validated by ¹H NMR titration and ²⁷Al NMR spectroscopic studies. To get detailed vision into binding mechanism and optimized structure of receptor L and L + Al³⁺, L + Al³⁺ + F^- complex, theoretical calculations using DFT/DND and TDDFT method were performed. Furthermore, probe L can mimic INHIBIT logic function using Al³⁺ and F^- being logic inputs and examining the fluorescence maxima at 433 nm as output.

A novel colorimetric-fluorescent probe for Al3+ and the resultant complex for F- and its applications in cell imaging

A novel quinoline-based Schiff-base probe QL had been synthesized, which could sequentially monitor Al³⁺ and F^- in MeOH-H₂O solution (v/v = 8/1, 0.01 M, HEPES buffer, pH = 7.3). The probe QL expressed a high selective and sensitive "OFF-ON-OFF" fluorescent response for Al³⁺ and F^- (excitation at 460 nm and emission at 530 nm) accompanying visible color changed, which was ascribed to intramolecular charge transfer (ICT) process and chelation-enhanced fluorescence (CHEF) mechanism. The binding stoichiometry of QL with Al³⁺ was 2:1 counting on Job's plot and HRMS, while F^- could pull Al³⁺ to depart from the complexation 2QL-Al³⁺ and released free QL. The limit of detections of probe QL for Al³⁺ and F^- ions were calculated to be 0.10 μM and 0.50 μM. The ¹H NMR experiments and density functional theory (DFT) calculations were carried out to further prove the binding mode between QL and Al³⁺. Furthermore, fluorescence imaging studies demonstrated that the probe QL was low cytotoxicity and could be applied to detect Al³⁺ and F^- in living PC12cells.

Novel polysiloxane-based rhodamine B fluorescent probe for selectively detection of Al3+ and its application in living-cell and zebrafish imaging

Polysiloxanes have excellent stability and biological relevance and are suitable for biological research. However, there were few polysiloxane-based fluorescent probes for bioimaging. This report successfully designed a new polysiloxane-based polymer fluorescent probe (RB-1) for the first time as a "turn-on" fluorescent probe response to Al³⁺ ion with highly sensitive and selectivity. Importantly, this probe could also apply both in cell and zebrafish imaging, indicating the huge application development prospects of polysiloxane-based fluorescent probes in future.

Selective Interactions of Al(III) with Plasmonic AgNPs by Colorimetric, Kinetic, and Thermodynamic Studies

In this paper, we report a simple, novel, and highly selective plasmonic nanoparticles (NPs)-based colorimetric nanoprobe for the detection of Al(III) ions in aqueous solution. 5-Hydroxy indole-2-carboxylic acid (5H-I2CA) was utilized as a reducing as well as capping agent for the preparation of silver nanoparticles (5H-I2CA@AgNPs). The interaction between Al(III) and AgNPs was determined by UV-vis absorption spectroscopy, high-resolution transmission electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, and dynamic light scattering techniques. The absorption values (A 452-410) of the 5H-I2CA@AgNPs solution exhibited a linear correlation with Al(III) ion concentrations within the linear range of 0.1-50 nM. An outstanding selectivity toward Al(III) was demonstrated by the proposed nanoprobe in the presence of interfering cations. Kinetics was used to study the selectivity of nanoprobe, which indicated second-order kinetics, and the rate constant was very high. The activation energies of Al(III) were found to be the lowest compared to those of other interfering ions. The results of kinetics and thermodynamic study of Al(III) were compared to those of four other competing ions. The thermodynamic data reveal that the interaction best suited for Al(III) ion compared to other metal ions (Al(III) > Co(II) > Hg(II) > Cr(III) ≅ Cr(VI)). The lower detection limit of the proposed nanoprobe for Al(III) is 1 nM. The present method also holds practical applicability for real water samples.

Mentha-Stabilized Silver Nanoparticles for High-Performance Colorimetric Detection of Al(III) in Aqueous Systems

The present paper reports a facile and selective colorimetric method for the detection of potential environmental and health hazardous metal ions using green synthesized silver nanoparticles (AgNPs). Here the organic functional groups present in the plant extract (Mentha arvensis) are used as reductants and stabilizers in the synthesis of AgNPs. They also provide a suitable binding site to the (Al(III)) analyte in the detection mechanism. The leaf extract of Mentha arvensis was used to synthesize AgNPs at room-temperature and at 80 °C. The AgNPs synthesized at 80 °C exhibit excellent selective colorimetric detection of Al(III). The as-synthesized AgNPs have been characterized, and the synthesis, stabilization of NPs and detection mechanism has also been illustrated by using UV-vis, XPS, FTIR, TEM, EDX, SEM, AAS, and TGA analytical tools and techniques. The selectivity of detection probe was supported by the reaction between probe and metal ions followed first-order kinetics having the highest value of the regression coefficient (R² = 0.99) for Al(III) and the analysis of thermodynamic parameters. The prepared sensor showed a lower limit of detection (LOD) of 1 nM (S/N = 3.2) in real water samples. The proposed method can be successfully utilized for the detection of Al(III) from both drinking and real water samples at the nanomolar level.

A highly selective and sensitive fluorescent chemosensor and its application for rapid on-site detection of Al3

In this paper, a simple naphthalene-based derivative (HL) has been designed and synthesized as a Al³⁺-selective fluorescent chemosensor based on the PET mechanism. HL exhibited high selectivity and sensitivity towards Al³⁺ over other commonly coexisting metal ions in ethanol with a detection limit of 2.72nM. The 1:1 binding stoichiometry of the complex (HL-Al³⁺) was determined from the Job's plot based on fluorescence titrations and the ESI-MS spectrum data. Moreover, the binding site of HL with Al³⁺ was assured by the ¹H NMR titration experiment. The binding constant (Ka) of the complex (HL-Al³⁺) was calculated to be 5.06×10⁴M^-1 according to the Benesi-Hildebrand equation. In addition, the recognizing process of HL towards Al³⁺ was chemically reversible by adding Na₂EDTA. Importantly, HL could directly and rapidly detect aluminum ion through the filter paper without resorting to additional instrumental analysis.

Mixed polymeric micelles as a multifunctional visual thermosensor for the rapid analysis of mixed metal ions with Al3+ and Fe3+

A novel type of responsive mixed double hydrophilic block copolymer (DHBC)-based multifunctional visual thermosensor for the detection of Al³⁺ and Fe³⁺ was designed and synthesized based on reversible addition fragmentation chain transfer (RAFT) polymerization.

Design and application of a fluorogenic receptor for selective sensing of cations, small neutral molecules, and anions

An unprecedented single multi-analyte fluorogenic receptor, a sodium salt of N-(methyl-2-thiophenyl)-tyrosine (NaHTyrthio), is reported for the selective sensing of cations (Cu²⁺), small neutral molecules (nitrobenzene and aniline) and anions (F⁻) by variable spectral responses.

Naphthol-based fluorescent sensors for aluminium ion and application to bioimaging

Three naphthol Schiff base-type fluorescent sensors, 1,3-Bis(2-hydroxy-1-naphthylideneamino)propane (L1), 1,3-Bis(1-naphthylideneamino)-2-hydroxypropane (L2) and 1,3-Bis(2-hydroxy-1-naphthylideneamino)-2-hydroxypropane (L3), have been synthesized. Their recognition abilities for Al(3+) are studied by fluorescence spectra. Coordination with Al(3+) inhibited the CN isomerization of Schiff base which intensely increase the fluorescence of L1-L3. Possessing a suitable space coordination structure, L3 is a best selective probe for Al(3+) over other metal ions in MeOH-HEPES buffer (3/7, V/V, pH=6.6, 25°C, λem=435nm). A turn-on ratio over 140-fold is triggered with the addition of 1.0 equiv. Al(3+) to L3. The binding constant Ka of L3-Al(3+) is found to be 1.01×10(6.5)M(-1) in a 1:1 complex mode. The detection limit for Al(3+) is 0.05μM. Theoretical calculations have also been included in support of the configuration of the L3-Al(3+) complex. Importantly, the probe L3 has been successfully used for fluorescence imaging in colon cancer SW480 cells.

A highly selective colorimetric and fluorescent turn-on chemosensor for Al(3+) based on naphthalimide derivative

A new chemosensor L based on the naphthalimide moiety was synthesized and characterized. L exhibited the high selectivity and sensitivity for Al(3+) in CH3OH, along with colorimetric and fluorometric dual-signaling responses based on the joint contribution of the ICT and CHEF processes. A 1:1 stoichiometry for the L-Al(3+) complex was formed with an association constant of 7.6×10(4)M(-1), and the limit of detection for Al(3+) was determined as 6.9μM. In addition, L was successfully applied to the determination of Al(3+) in real water samples.

Fluorescent sensor for Al3+ ion in partially aqueous media using julolidine based probe

A novel chemosensor was synthesised and used as a selective fluorescent sensor for aluminium ions.

Highly sensitive and selective colorimetric and off-on fluorescent reversible chemosensors for Al³⁺ based on the rhodamine fluorophore

A series of rhodamine derivatives L1-L3 have been prepared and characterized by IR, 1H-NMR, 13C-NMR and ESI-MS. These compounds exhibited selective and sensitive "turn-on" fluorescent and colorimetric responses to Al3+ in methanol. Upon the addition of Al(III), the spiro ring was opened and a metal-probe complex was formed in a 1:1 stoichiometry, as was further confirmed by ESI-MS spectroscopy. The chemo-dosimeters L1-L3 exhibited good binding constants and low detection limits towards Al(III). We also successfully demonstrate the reversibility of the metal to ligand complexation (opened ring to spirolactam ring).

A novel turn-on Schiff-base fluorescent sensor for aluminum(iii) ions in living cells

Quinoline Schiff base L exhibits a more than 38-fold fluorescence enhancement after addition of Al³⁺ ions at an excitation wavelength of 373 nm, and shows a high selectivity for Al³⁺ over other metal ions.

Selective and sensitive turn-on chemosensor for Al(iii) ions applicable in living organisms: nanomolar detection in aqueous medium

A new crystallographically characterized non-cytotoxic CHEF based highly sensitive Al(iii) ion selective chemosensor (L) is useful to detect the Al(iii) ions' distribution in A549 cell lines and also able to sense Al(iii) ions in tea extract.

FRET based ‘red-switch’ for Al3+ over ESIPT based ‘green-switch’ for Zn2+: dual channel detection with live-cell imaging on a dyad platform

Our designed chemosensor, rhodamine-HBT-dyad (RHD), selectively detects two biologically important ions (Al³⁺ and Zn²⁺) at two different wavelengths (red and green, respectively) through FRET and ESIPT in vitro and in vivo.

A new coumarin-based chromogenic chemosensor for the detection of dual analytes Al3+ and F−

A simple and easy-to-make colorimetric sensor for Al³⁺ and F⁻ was designed and synthesized.

A single chemosensor for multiple analytes: fluorogenic detection of Zn2+ and OAc− ions in aqueous solution, and an application to bioimaging

A single fluorescent chemosensor 1 for multiple analytes (Zn²⁺ and OAc⁻) has been developed and it can monitor Zn²⁺ ions in living cells.