Rhodamine-Based Fluorescent Probe for Al3+ through Time-Dependent PET–CHEF–FRET Processes and Its Cell Staining Application

Design and Synthesis of Nanosensor Based on CdSe Quantum Dots Functionalized with 8-Hydroxyquinoline: a Fluorescent Sensor for Detection of Al3+ in Aqueous Solution

A novel nanosensor based on CdSe quantum dots (QDs) capped with 8-hydroxyqunoline (HQ) was developed for Al³⁺ ions determination in aqueous solutions. The method is based on the fluorescence enhancement of the HQ functionalized QDs in the presence of Al³⁺ ions, due to the strong interaction between Al³⁺ and HQ. Prepared nanosensor exhibited an acceptable selectivity and sensitivity for Al³⁺ ions in the presence of other metal ions. Plot of Log(I/I₀) against Log[Al³⁺] shows a good linearity in the range of 0.02-3.0 mM, and the method could be used for detection of Al³⁺ ions concentration in aqueous solutions.

Exploring the Scope of Photo-Induced Electron Transfer-Chelation-Enhanced Fluorescence-Fluorescence Resonance Energy Transfer Processes for Recognition and Discrimination of Zn2+, Cd2+, Hg2+, and Al3+ in a Ratiometric Manner: Application to Sea Fish Analysis

A rhodamine-based smart probe (RHES) has been developed for trace-level detection and discrimination of multiple cations, viz. Al³⁺, Zn²⁺, Cd²⁺, and Hg²⁺ in a ratiometric manner involving photo-induced electron transfer-chelation-enhanced fluorescence-fluorescence resonance energy transfer processes. The method being very fast and highly selective allows their bare eye visualization at a physiological pH. The optimized geometry and spectral properties of RHES and its cation adducts have been analyzed by time-dependent density functional theory calculations. RHES detects as low as 1.5 × 10^-9 M Al³⁺, 1.2 × 10^-9 M Zn²⁺, 6.7 × 10^-9 M Cd²⁺, and 1.7 × 10^-10 M Hg²⁺, whereas the respective association constants are 1.33 × 10⁵ M^-1, 2.11 × 10⁴ M^-1, 1.35 × 10⁵ M^-1, and 4.09 × 10⁵ M^-1. The other common ions do not interfere. The probe is useful for intracellular imaging of Zn²⁺, Cd²⁺, and Hg²⁺ in squamous epithelial cells. RHES is useful for the determination of the ions in sea fish and real samples.

A highly selective and sensitive turn-on probe for aluminum(III) based on quinoline Schiff's base and its cell imaging

A reversible Schiff's base fluorescence probe for Al³⁺, (3,5-dichloro-2- hydroxybenzylidene) quinoline-2-carbohydrazide (QC), based on quinoline derivative has been designed, synthesized and evaluated. The QC exhibited a high sensitivity and selectivity toward Al³⁺ in EtOH-H₂O (v/v=1:9, pH=6) by forming a 1:1 complex with Al³⁺ and the detection limit of QC for Al³⁺ was as low as 0.012μM. Furthermore, these results displayed that the binding of QCAl³⁺ was broken by F^-, so this system could be used to monitor F^- in the future. The enhancement fluorescence of the QC could be attributed to the inhibition of PET and ESIPT and the emergency of CHEF process induced by Al³⁺. More importantly, QC was not only successfully used for the determination of trace Al³⁺ in the tap water and the human blood serum, but was valid for fluorescence imaging of Al³⁺ in the Hela cells.

Tailoring the Fluorescence of AIE-Active Metal-Organic Frameworks for Aqueous Sensing of Metal Ions

A hydroxyl-functionalized ligand was designed for the construction of metal-organic framework (MOF) materials with the aggregation-induced emission (AIE) feature, in which the fluorescence can be deliberately tailored: quenching the fluorescence to an "off" state by the decoration with heterocyclic auxiliary ligand 4,4'-bypyridine (Bpy) in the framework as a quenching agent and triggering the enhanced fluorescence to an "on" state by removal of Bpy through the metal competitive coordination substitution strategy. Our study shows that the occurrence of exciton migration between the AIE linker and conjugated auxiliary ligand Bpy causes fluorescence quenching. Time-dependent density functional theory was employed to understand the photoinduced electron transfer process and explain the origins of fluorescence quenching. Using this strategy, the prepared MOF material can perform as a fluorescence "off-on" probe for highly sensitive detection of Al³⁺ in aqueous media. The hydroxyl group plays a crucial role in sensing as it can selectively chelate Al³⁺, which is directly related to the dissociation of nonfluorescent MOF and consequent activation of the AIE process.

Dihydroindeno[1,2-b]pyrroles: new Al3+selective off–on chemosensors for bio-imaging in living HepG2 cells

An approach for the expeditious synthesis of a new Al³⁺-selective turn-on dihydroindeno[1,2-b]pyrrole probe under environmentally benevolent conditions and its bio-imaging studies on HepG2 cell.

Hydrazinopyrimidine derived novel Al3+ chemosensor: molecular logic gate and biological applications

For the first time, a hydrazinopyrimidine based chemosensor has been designed for sensing Al³⁺ through CHEF-PET-ESIPT fluorescence mechanisms and by building an ‘INHIBIT’ molecular logic gate.

A novel chemosensor based on rhodamine and azobenzene moieties for selective detection of Al3+ ions

Both rhodamine and azobenzene moieties have been conjugated to prepare a novel chemosensor for the detection of Al³⁺ through CHEF-PET and the spirolactam ring opening mechanism.

A two-pocket Schiff-base molecule as a chemosensor for Al3+

A new Schiff-base molecule with two binding pockets acts as a selective fluorescent chemosensor for Al³⁺.

Fluorescent detection of multiple ions by two related chemosensors: structural elucidations and logic gate applications

Two related chemosensors L1 and L2 display selective detection of multiple ions (Cu²⁺, Al³⁺, Cd²⁺ and S²⁻) as a result of minor variation of functional groups at a remote arene ring.

FRET based selective and ratiometric detection of Al(iii) with live-cell imaging

A cell permeable FRET based platform for dual mode ‘naked-eye’in vitroandin vivodetection of Al³⁺over other common ions (including trivalent ions).

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.

Exploration of Energy Modulations in Novel RhB-TPE-Based Bichromophoric Materials via Interactions of Cu(2+) Ion under Various Semiaqueous and Micellar Conditions

Novel bichromophoric materials TR-A and TR-B consisting of an entirely new combination of TPE and RhB units were developed to explore the optimum conditions of energy modulations via pH variation and Cu(2+) interaction at various water contents of CH3CN. Interestingly, TR-A and TR-B, at 60 and 70% water contents, respectively, favored the optimum Cu(2+)-mediated energy modulations from TPE to RhB and thus achieve the brightest orange emissions of free RhB with complete disappearance of aggregation-induced emission (AIE) from TPE. Furthermore, various micellar conditions of triton-X-100, SDS, and CTAB were employed to adjust energy modulations of TR-A and TR-B at high water contents (at 80 and 90%, respectively). The incorporation of RhB into triton-X-100 micellar cavities disrupted AIE from TPE; thus, none of the energy modulations from TPE to RhB occurred even in the presence of Cu(2+) ion. Interestingly, the micellar conditions of anionic surfactant (SDS) favored the increased local concentration of Cu(2+) ions in the vicinity of scavangable RhB and facilitated the generation of noncyclic free RhB in situ via bright-orange emissions.

5-Hydroxymethylfurfural modified rhodamine B dual-function derivative: Highly sensitive and selective optical detection of pH and Cu(2+)

A dual-function optical chemosensor (RBF) was designed and easily synthesized by condensation reaction of 5-Hydroxymethylfurfural and rhodamine B hydrazide. RBF exhibited highly sensitive, highly selective and quick response to acidic pH. The fluorescence intensity of RBF exhibited a more than 41-fold increase within the pH range from 7.50 to 3.73 with a pKa value of 5.02, which could be successfully applied to monitor intracellular pH in living PC12 cells and HeLa cells. Additionally, the spectroscopy of UV-Vis and EDTA-adding experiments indicated that RBF was a highly selective and reversible colorimetric chemosensor for Cu(2+) in Tris-HCl (10mM, pH=7.2) aqueous buffer solution as well as other metal ions had no obvious interference. Moreover, RBF has been successfully applied to detect Cu(2+) in real water samples.

A multi-addressable diarylethene for the selective detection of Al3+ and the construction of a logic circuit

A multi-addressable diarylethene was designed and synthesized, which not only acted as a fluorescent sensor for Al³⁺ with high selectivity, but was also used to construct a combinational logic circuit.

A robust fluorescent chemosensor for aluminium ion detection based on a Schiff base ligand with an azo arm and application in a molecular logic gate

A new azo based chemosensor for detection of Al³⁺ ion has been reported. The sensor has been well characterized using different techniques like single crystal X-ray, NMR, IR, UV etc. Detection limit of the chemosensor was found to be 6.93 nM.

A rhodamine-based sensor for Hg2+ and resultant complex as a fluorescence sensor for I−

A rhodamine-based sensor displays a quick response for Hg²⁺. The resulting complex can act as a reversible fluorescence sensor for I⁻.

Rhodamine B-based ordered mesoporous organosilicas for the selective detection and adsorption of Al(iii)

A novel “Off–On” solid chemosensor for Al³⁺ was constructed by combining ordered mesoporous silica with a rhodamine B derivative.

Green synthesis of highly fluorescent AuNCs with red emission and their special sensing behavior for Al3+

Facile methods were fabricated for preparation of highly fluorescent AuNCs with red emission using l-cysteine.

Solvent-dependent fluorescent-colorimetric probe for dual monitoring of Al3+ and Cu2+ in aqueous solution: an application to bio-imaging

A solvent-dependent reversible fluorescent-colorimetric bis-iminopyridyl Schiff base receptor (N¹E,N⁴E)-N¹,N⁴-bis(quinolin-4-ylmethylene)benzene-1,4-diamine (L) has been developed for the first time for sensitive and selective determination of Al³⁺ and Cu²⁺ in aqueous solution.

Fluorescent chemosensors manipulated by dual/triple interplaying sensing mechanisms

This review highlights the design strategies and response processes of the fluorescent chemosensors with dual/triple interplaying sensing mechanisms.

A sandwich-type zinc complex from a rhodamine dye based ligand: a potential fluorescent chemosensor for acetate in human blood plasma and a molecular logic gate with INHIBIT function

Zn-R1 exhibits reversible binding with acetate yielding different optical and fluorescence outputs on alternate addition of zinc and acetate ions.

A Highly Selective Fluorescent Sensor for Al3+ based on an Aza-18-Crown-6 Derivative

A new fluorescent sensor derived from 2,5-diphenyl-furan and aza-18-crown-6 has been synthesised. It can selectively bind Al3+ in aqeuous ethanol solution with fluorescence enhancement.

A dual functional probe for "turn-on" fluorescence response of Pb(2+) and colorimetric detection of Cu(2+) based on a rhodamine derivative in aqueous media

A dual functional probe L based on rhodamine was devised and synthesized. Probe L can sense Pb(2+) and Cu(2+) in aqueous solution through two approaches: a significant fluorescence enhancement caused by Pb(2+) and a visible color change from colorless to orchid induced by Cu(2+). Competitive experiments showed that probe L had high fluorescence sensitivity for Pb(2+) and excellent colorimetric selectivity for Cu(2+) over many environmentally relevant ions. The mechanisms of L for sensing Pb(2+) and Cu(2+) have been well demonstrated by ESI-MS, (1)H NMR titration, IR, the crystal structure of L-Pb(2+) and density functional theory calculation of L-Cu(2+). In addition, fluorescence image detection of Pb(2+) in living cells displayed an enhanced fluorescence effect.

A highly selective turn-on fluorescent probe for Al(III) based on coumarin and its application in vivo

In this study, a turn-on coumarin-based fluorescent probe, 7-hydroxy-6-[(2-hydroxy-naphthalen-1-ylmethylene)-amino]-4-methyl-chroman-2-one (CN), was developed for detecting Al(3+) in aqueous systems. The binding ratio of CN-Al(3+) complexes was determined from the Job plot and ESI-MS data to be 1 : 1. The binding constant (Ka) of Al(3+) binding to CN was calculated to be 9.55 × 10(4) M(-1) from a Benesi-Hildebrand plot and the detection limit was evaluated to be as low as 0.10 μM (LOD = 3σ/slope). CN could be used as an effective fluorescent probe for detecting Al(3+) in living HeLa cells. Moreover, CN could also be applied in the in vivo detection of Al(3+) in zebrafish.

A highly selective fluorescent probe for Al(3+) based on quinoline derivative

A novel Schiff base fluorescent probe, 1-phenyl-3-methyl-5-hydroxypyrazole-4-carbaldehyde (2'-methylquinoline-4'-formyl) hydrazone (PMHCH), for selective detection of Al(3+) has been designed and synthesized. Upon addition of various metal ions, the receptor only shows 286-fold enhancement of fluorescence intensity which might be attributed to a 1:1 stoichiometry between PMHCH and Al(3+) and the photo-induced electron transfer progress in the present of Al(3+) at 505n m. More importantly, the detection limit of PMHCH for Al(3+) could reach at 10(-7) M level.

A new fluorescent probe for Al(3+) based on rhodamine 6G and its application to bioimaging

A water-soluble rhodamine-based derivative (L) has been rationally designed for selective recognition of Al(3+) in aqueous medium with good sensitivity. The addition of Al(3+) to the aqueous solution of L induces a remarkable fluorescence enhancement along with obvious color change detected by the naked eye, due to the ring-opening mechanism of the rhodamine spirolactam, which has been proved by single crystal diffraction analyses directly. The recognizing behavior has been investigated both experimentally and computationally. Furthermore, the fluorescent probe can also be used as a bioimaging reagent for detection of Al(3+) in living cells.

Nanomolar fluorogenic detection of Al(III) by a series of Schiff bases in an aqueous system and their application in cell imaging

Three positional isomers of a Schiff base containing -OH as end groups have been synthesized and evaluated for selective Al(III) detection due to inhibition of ESIPT, PET and activation of CHEF in 70% aqueous medium. Devoid of any conventional fluorophore, these sensors have nanomolar detection limits with high quantum yields and naked eye sensing of Al(III). Moreover, these probes have been demonstrated to enable the Al(III) detection in live human HeLa cells and rat C6 glioma cells using a confocal microscope.

A new pyrazoline-based fluorescent sensor for Al3+ in aqueous solution

A new pyrazoline-based fluorescent sensor was synthesized and the structure was confirmed by single crystal X-ray diffraction. The sensor responds to Al(3+) with high selectivity among a series of cations in aqueous methanol. This sensor forms a 1:1 complex with Al(3+) and displays fluorescent quenching.

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 polynuclear hetero atom containing molecular organic scaffold to detect Al3+ ion through a fluorescence turn-on response

A simple polynuclear hetero atom (N and O) containing molecular organic scaffold/probe, 3 has been designed and synthesized and explored as a potential chemosensor to detect Al³⁺ (22 nM; ∼0.6 ppb) ion in a HEPES buffer.

Three N-stabilized rhodamine-based fluorescent probes for Al3+via Al3+-promoted hydrolysis of Schiff bases

New fluorescent probes L1–L3 displayed high sensitivity toward Al³⁺.

A highly selective fluorescent probe for in vitro and in vivo detection of Hg2+

In this paper, a simple fluorescent probe, rhodamine B derivatives (RS), was designed and prepared for sensitive detection of Hg²⁺ in CH₃CN/H₂O (5/5, v/v).

Fluorescence sensing and intracellular imaging of Al3+ions by using naphthalene based sulfonamide chemosensor: structure, computation and biological studies

Naphthyl appended sulfonamide Schiff base (HL), an antimicrobial nontoxic agent, serves as a fluorogenic sensor to Al³⁺, LOD 33.2 nM and is used for living cell imaging.

Sn(ii) induced concentration dependent dynamic to static excimer conversion of a conjugated naphthalene derivative

The colorimetric and fluorescence recognition of Sn²⁺ has been achieved using a naphthalene appended diformyl-p-cresol derivative (L). The dynamic excimer, observed up to 50 μM Sn²⁺, gradually converts to a static type above 50 μM Sn²⁺. DFT calculations support the experimental findings.

ESIPT and CHEF based highly sensitive and selective ratiometric sensor for Al3+ with imaging in human blood cells

We have synthesised a probe for the fluorescence ratiometric detection of Al³⁺. This probe can be used to image Al³⁺ in living cells.