Synergistic integration of a rhodamine-labelled tripeptide into AIE-active fluorogenic probe: Enabling nanomolar detection of Al3+ ions through test strips, thin films, and Arduino-assisted optosensing platform

Peptide-fluorophore conjugates (PFCs) have been expeditiously utilized for metal ion recognition owing to their distinctive characteristics. Selective detection and quantification of aluminum is essential to minimize health and environmental risks. Herein, we report the synthesis and characterization of a new chemoprobe with aggregation-induced emission characteristics by chemically conjugating rhodamine-B fluorophore with a tripeptide. The probe revealed β-sheet secondary conformation in both solid and solution states, as confirmed by FT-IR, PXRD, and CD experiments. AIE characteristics of the probe in water-MeCN mixtures revealed the formation of spherically shaped nanoaggregates with an average size of 353 ± 7 nm, as confirmed by SEM, TEM, and DLS studies. The probe exhibited a large stokes shift (175 nm) and displayed selective colorimetric and fluorometric responses towards Al3+ ions with an extremely low detection limit (51 nm) and a fast response time (≤15 s). Comparative NMR studies confirmed the cleavage of spirolactam ring upon aluminum binding. The probe's practicality was enhanced through integration into test strips and thin films, allowing solid-phase detection of Al3+ ions. Furthermore, an RGB-Arduino enabled optosensing device has been developed to enable instant quantifiable analysis of aluminum concentrations in real-time conditions.

Recent developments in the creation of a single molecular sensing tool for ternary iron (III), chromium (III), aluminium (III) ionic species: A review

Rational design of a molecular sensing tool is an important topic in molecular recognition, signalling, and optoelectronics that has piqued the interest of chemists, biologists, and environmental scientists. Approximately 150 years have passed since the beginning of the fluorescent chemosensor sector. Due to the paramagnetic properties of Cr3+ and Al3+ , it is tough to prepare a photoluminescence plug-in detector. Most dye-based Al3+ sensors must be utilized in organic or mixed solvents for robust hydration of Al3+ in water. The sophisticated molecular design of sensors, conversely, allows for the detection of these metal ions in aqueous medium. The design of chemosensors using various fluorophores and their mechanisms of action have been thoroughly discussed. A literature survey covering the design of chemosensors and their mechanisms of action have been thoroughly discussed covering the period 2010-2022 and that was carried out including innovative and exemplary activities from numerous groups throughout the world that have significantly contributed to this sector. The most important advantages of these probes are their aqueous solubility and quick response with outstanding selectivity and sensitivity for temporal distribution with high fidelity of metals in living cells.

Ratiometric fluorescent sensing for phosphate based on Eu/Ce/UiO-66-(COOH)2 nanoprobe

The sensing of phosphate anion (PO₄^3-) is an important subject for human health and environmental monitoring. Herein, a unique ratiometric fluorescent nanoprobe based on postsynthetic modification of metal-organic frameworks (MOF) UiO-66-(COOH)₂ with Eu³⁺ and Ce³⁺ ions toward PO₄^3- was proposed (designated as Eu/Ce/Uio-66-(COOH)₂). The Eu/Ce/Uio-66-(COOH)₂ nanoprobe exhibits three emission peaks at 377 nm, 509 nm, and 621 nm with the single excitation wavelength at 250 nm, respectively. The strong coordinating interaction between Ce³⁺ and O atoms in the PO₄^3- group can result in the fluorescence quenching at 377 nm, while the fluorescence of 621 nm almost remains unchanged. Such a useful phenomenon is exploited for the construction of a ratiometric fluorescence platform for the detection of PO₄^3-. The assay exhibited a good linear response in the 0.3-20 μM concentration range with the detection limit of 0.247 μM. In addition, this ratiometric fluorescent sensing method not only can be applied to read out PO₄^3- concentration in real water samples, but also shows higher sensitivity, easier preparation and sensing procedures than other detection strategies.

Development of Rhodamine 6G-Based Fluorescent Chemosensors for Al3+-Ion Detection: Effect of Ring Strain and Substituent in Enhancing Its Sensing Performance

Four rhodamine 6G-based chemosensors (H 3 L1-H 3 L4) are designed for selective detection of Al3+ ion. They are characterized using various spectroscopic techniques and X-ray crystallography. All absorption and emission spectral studies have been performed in 10 mM N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid (HEPES) buffer solution at pH 7.4 in H2O/MeOH (9:1, v/v) at 25 °C. In absorption spectra, chemosensors exhibit an intense band around 530 nm in the presence of Al3+ ion. Chemosensors (H 3 L1-H 3 L4) are nonfluorescent when excited around 490 nm. The presence of Al3+ ion enhances the emission intensity (555 nm) many times. The formation of complexes 1-4 is established with the aid of different spectroscopic techniques. The limit of detection value obtained in the nanomolar range confirms the high sensitivity of the probes toward Al3+ ion. It has been observed that the presence of aliphatic spacers in the diamine part and different halogen substituents in the salicylaldehyde part strongly influences the selectivity of the chemosensors toward Al3+ ion. The propensity of the chemosensors to identify intracellular Al3+ ions in triple-negative human breast cancer cell line MDA-MB-468 by fluorescence imaging is also examined in this study.

A smart chemosensor: Discriminative multidetection and various logic operations in aqueous solution at biological pH

A novel rhodamine-pyrazole based molecular probe was designed and easily synthesized. The probe could to detect several analytes in aqueous solution at biological pH (HEPES, pH = 7.2). Several heavy metal cations, including Cu²⁺, Fe³⁺, Al³⁺, Hg²⁺ and Ni²⁺ were detected discriminately by the probe. Also, the novel compound exhibited a good sensory selectivity towards S₂O₅^2- by both absorption and emission spectra. Moreover, probe/Cu²⁺ complex could to detect several anions, including F^-, CN^-, S^2-, CH₃COO^-, CO₃^2- and NO₂^-. Furthermore, the probe exhibited a high potential to work as a molecular system able to perform a number of logical operations such as AND, NAND, NOR and INHIBIT logic gates.

A chemosensoring molecular lab for various analytes and its ability to execute a molecular logical digital comparator

We reported here the unique ability of a Rhodamine 6G-based probe (3) to detect discriminately several targets, including H⁺, HO^-, Cu²⁺, Hg²⁺, Fe³⁺, Co²⁺, Cd²⁺, Zn²⁺, Sn²⁺, Ni²⁺, Al³⁺, Pb²⁺, Ce³⁺and Ag⁺, by unambiguously colorimetric and fluorimetric outcomes. In aqueous solutions, the presence of proton induced the ring-opening of rhodamine moiety but the presence of hydroxide induced the conversion of 2-hydroxyphenyl hydrazone moiety from the non-fluorescent benzenoid form into the fluorescent quinoid form. The probe could to distinguish between different cations in DMF and to work like an artificial tongue at molecular level. Several logic gates including OR, INHIBIT and TRANSFER, were performed by the probe. Moreover, the probe is able to execute three INHIBIT logic gates by two inputs, which was exploited to execute a digital molecular comparator.

A Specific Turn-On Fluorescent Sensing for Ultrasensitive and Selective Detection of Phosphate in Environmental Samples Based on Antenna Effect-Improved FRET by Surfactant

Phosphate is not only an important indicator for aquatic ecosystems, but also plays vital roles in biosystems. A new strategy for ultrasensitive and selective detection of phosphate is fabricated based on a new insight found in this paper, in which a lower concentration of surfactant sodium dodecylbenzenesulfonate (SDBS) can greatly induce fluorescence resonance energy transfer (FRET) from ciprofloxacin (CIP) to Eu³⁺ in the CIP-Eu³⁺ complex. Surfactant SDBS does not act as a sensitizer for enhancing the fluorescence intensity of the system, but acts as a sensitizer of FRET and makes the native fluorescence of CIP quenched completely (switch off). Eu³⁺ ions can coordinate with the oxygen-donor atoms of phosphate, which weakens FRET from CIP to Eu³⁺ and results in the fluorescence recovery of CIP (turn on). The multicomplex of the CIP-Eu³⁺-phosphate has more sensitive fluorescent response than that of the reported coordination nanoparticle-based fluorescent probes. The LOD (S/N = 3) of this sensing system can attain 4.3 nM. The possible interferential substances existing in environmental samples, such as 17 common metal ions, 11 anions, and fulvic acid investigated, do not interfere with the phosphate detection. This sensing system has been successfully applied for phosphate detection in environmental samples such as wastewater, surface water, and atmospheric particulates. This work not only develops a fluorescent probe for the phosphate detection, but also provides a new strategy for designing fluorescent probes based on FRET or coordination nanoparticles.

An ampyrone based azo dye as pH-responsive and chemo-reversible colorimetric fluorescent probe for Al3+ in semi-aqueous medium: implication towards logic gate analysis

A novel ampyrone based azo dye, 4-((6-hydroxybenzo[d][1,3]dioxol-5-yl)diazenyl)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (1), was synthesized by coupling sesamol and 4-amino antipyrine (ampyrone).

Facile synthesis of a water-soluble fluorescence sensor for Al3+ in aqueous solution and on paper substrate

In this study, a facile water-soluble fluorescence sensor 2-((2-hydroxybenzylidene)-amino)-2-(hydroxymethyl)propane-1,3-diol (ST) was synthesized via one-step reaction, and its fluorescence sensing performance for Al³⁺ both in aqueous solution and on paper substrate was evaluated. The results showed that ST exhibited an specific fluorescence "turn-on" response to Al³⁺ over other cations in aqueous solution as well as on the test paper. The limit of detection was found to be 3.2×10^-7M, which revealed that the obtained Schiff-base based fluorescence chemosensor ST possessed a great potential for the rapid, quantitative and qualitative detection of Al³⁺.

Europium-based infinite coordination polymer nanospheres as an effective fluorescence probe for phosphate sensing

Uniform europium-based infinite coordination polymer nanospheres have been successfully fabricated as an effective fluorescence probe for phosphate sensing.

Potentiometric sensing of aqueous phosphate by competition assays using ion-exchanger doped-polymeric membrane electrodes as transducers

Using Zn(2+)-BPMP or Cu(2+)-BPMP as a receptor and o-mercaptophenol as an indicator, potentiometric sensing of aqueous phosphate by competition assays was achieved. With attractive features of portability, low cost and resistance to interference from turbidity and color, this sensor was successfully used for phosphate detection in biological and water samples.

Selective chromo-fluorogenic detection of trivalent cations in aqueous environments using a dehydration reaction

Trivalent cations induced a dehydration reaction of a chemodosimeter in water that is coupled with colour and emission changes.

A highly selective fluorescent sensor for Al3+ and the use of the resulting complex as a secondary sensor for PPi in aqueous media: its applicability in live cell imaging

An “off–on–off” reversible fluorescent sensor has been developed for sequential detection of Al³⁺ and PPi in aqueous media, and has further been applied to live cell imaging.

A differentially selective molecular probe for detection of trivalent ions (Al3+, Cr3+and Fe3+) upon single excitation in mixed aqueous medium

A chemosensor was developed which could selectively detect and differentiate trivalent metal ions (Al³⁺, Cr³⁺and Fe³⁺) upon single excitation at two different wavelengths in aqueous medium.

An easy and accessible water-soluble sensor for the distinctive fluorescence detection of Zn2+ and Al3+ ions

A water-soluble fluorescence sensor was facilely synthesized and it can be used for the distinctive fluorescence detection of Zn²⁺ and Al³⁺ ions.

Binding site-driven sensing properties of a quinazoline derivative with metal cations

A quinazoline derivative showed high sensitivity and selectivity for Al³⁺, Cr³⁺ and Fe³⁺ ions in methanol solution.