A ratiometric fluorescent chemosensor for Al in aqueous solution based on aggregation-induced emission and its application in live-cell imaging

A ratiometric fluorescent chemosensor 1 was developed for the detection of Al³⁺ in aqueous solution based on aggregation-induced emmision (AIE). The chemosensor showed the fluorescence of its aggregated state and Al³⁺-chelated soluble state in the absence and in the presence of Al³⁺, respectively, and resulted in a fluorescence ratio (I₄₆₁/I₅₃₇) response to Al³⁺ in neutral aqueous solution at a detection limit as low as 0.29 μmol L⁻¹. The method was also highly selective to Al³⁺ over other physiological relevant metal ions investigated in this study. Taking advantage of its AIE characteristics, the chemosensor was successfully applied on test papers for simple and rapid detection of Al³⁺. Moreover, the application of 1 for the imaging of Al³⁺ in living cells by ratiometric fluorescence changes was also achieved.     

A biacylhydrazone-based chemosensor for fluorescence ‘turn-on’ detection of Al3+ with high selectivity and sensitivity

A simple Al³⁺ fluorescent chemosensor (1) based on diacylhydrazone has been designed and synthesized by the condensation reaction of 2-hydroxy naphthaldehyde and metaphthalic hydrazide. The chemosensor 1 displays a specific and sensitive response to Al³⁺ over other cations in DMSO solution. Upon the addition of DMSO solution of Al³⁺, the sensor 1 shows an immediate fluorescence ‘turn-on’ response and emitting strong blue emission with visible color change from colorless to green. The fluorescence quantum yield enhanced from 7.24% to 48.68%. Meanwhile, the fluorescence and UV absorption spectra detection limits of the chemosensor 1 for Al³⁺ were 2.0 × 10^?7 M and 5.6 × 10^?7 M respectively, indicating the high sensitivity of 1 to Al³⁺. Furthermore, test strips based on 1 were fabricated, which could be used as a convenient test kit for the detection of Al³⁺ and an efficient Al³⁺ controlled fluorescent security display materials.     

A new rhodamine-based dual chemosensor for Al and Cu

A new rhodamine B derivative bearing a hydrazone group has been designed and prepared. The synthesized colorimetric and fluorescent molecular chemosensor can be used as a dual probe, selectively detecting Al³⁺ and Cu²⁺ in acetonitrile solution by monitoring changes in the absorption and fluorescence spectral patterns. The results show that Al³⁺ ions can induce a greater fluorescence enhancement, while the addition of Cu²⁺ ions induces a strong UV–vis absorption enhancement with weak fluorescence. The limits of detection of Cu²⁺ and Al³⁺ were estimated to be 2.9 × 10⁻⁷ M and 8.3 × 10⁻⁹ M, respectively.     

A ‘turn-on’ fluorescent chemosensor based on rhodamine-N-(3-aminopropyl)-imidazole for detection of Al ions

A novel N-(3-aminopropyl)-imidazole-appended rhodamine-based fluorescent chemosensor was synthesized. The sensing behavior and selectivity of the synthesized chemosensor toward metal cations were studied by UV/vis and fluorescence spectroscopy. The chemosensor recognized Al³⁺ ions by a significantly enhanced fluorescence and a visible color change due to opening of the spirolactam ring triggered by the addition of Al³⁺ ions.     

Perimedine-linked rhodamine dye in visual sensing of Al3+, Fe3+ and Fe2+ ions in aqueous organic medium under different experimental conditions

ABSTRACT

Perimedine labelled rhodamine dye 1 has been designed and synthesised. Metal ion binding studies of 1 have been performed in CH₃CN/H₂O (3:1, v/v, 10 mM Tris-HCl buffer, pH = 6.90). Compound 1 senses multiple metal ions such as Al³⁺, Fe³⁺ and Fe²⁺ by exhibiting turn on fluorescence and colour change (colourless to pink) under different experimental conditions. Concentration variation distinguishes Al³⁺ from Fe³⁺ ion. At low concentration (c = 1 x 10^?4 M), only Al³⁺ ion can exhibit turn on fluorescence with sharp colour change. Sensing of Fe²⁺ ion through turn on fluorescence and colour change has been possible via in situ oxidation by following Fenton’s reaction.     

Study on the synthesis of novel fluorescent macrocyclic sensors and their sensitive properties for Cu2+ and Fe3+ in aqueous solution

In this work, we synthesised and characterised three novel fluorescence macrocyclic sensors containing optically active dansyl groups. The studies for the interaction of the synthesised compounds with various mental ions (Li⁺, Na⁺, K⁺, Ag⁺, Mg²⁺, Ca²⁺, Ba²⁺, Pb²⁺, Zn²⁺, Co²⁺, Cd²⁺, Hg²⁺, Ni²⁺, Cu²⁺, Mn²⁺, Cr³⁺, Al³⁺, Fe³⁺) were performed by fluorescence titration, Job’s plot, ESI-MS and DFT calculations. The results showed that the sensors 1a–1c displayed selective recognition for Cu²⁺ and Fe³⁺ ions and formed stoichiometry 1:1 complex through PET mechanism in DMSO/H₂O solution (1:1, v/v, pH 7.4 of HEPES). The binding constant (K) and detection limit were calculated.     

Electrically induced fluorescence Fe sensing behavior of nanostructured Tiron doped polypyrrole

Nanostructured polypyrrole (PPy) film doped with Tiron was electrodeposited from aqueous solution on the surface of transparent electrode and used for sensitive, selective and rapid electrically controlled fluorescence detection of Fe³⁺ in aqueous media. The fluorescence intensity of PPy-Tiron film decreases linearly in the presence of Fe³⁺ by applying negative potential over a concentration range from 5.0 × 10⁻⁸ to 1.0 × 10⁻⁶ mol L⁻¹, with a relatively fast response time of less than 30 s at pH 7.4. The detection is not affected by the coexistence of other competitive metal ions such as Al³⁺, Ce³⁺, Tl³⁺, La³⁺, Bi³⁺, Cr²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺. The proposed electro-fluorescence sensor has a potential application to the determination of Fe³⁺ in environmental and biological systems. The fluorescent thin film sensor was also used as a novel probe for Fe³⁺/Fe²⁺ speciation in aqueous solution.     

Linear Schiff-base fluorescence probe with aggregation-induced emission characteristics for Al detection and its application in live cell imaging

A simple Schiff-base derivative with salicylaldehyde moieties as fluorescent probe 1 was reported by aggregation-induced emission (AIE) characterization for the detection of metal ions. Spectral analysis revealed that probe 1 was highly selective and sensitive to Al³⁺. The probe 1 was also subject to minimal interference from other common competitive metal ions. The detection limit of Al³⁺ was 0.4 μM, which is considerably lower than the World Health Organization standard (7.41 μM), and the acceptable level of Al³⁺ (1.85 μM) in drinking water. The Job's plot and the results of ¹H-NMR and FT-IR analyses indicated that the binding stoichiometry ratio of probe 1 to Al³⁺ was 1:2. Probe 1 demonstrated a fluorescence-enhanced response upon binding with Al³⁺ based on AIE characterization. This response was due to the restricted molecular rotation and increased rigidity of the molecular assembly. Probe 1 exhibited good biocompatibility, and Al³⁺ was detected in live cells. Therefore, probe 1 is a promising fluorescence probe for Al³⁺ detection in the environment.     

Photo-Physical Properties of a New Norfloxacin-Containing Polymer for Protons and Fe3+ Sensing

A novel norlfoxacin-containing fluorescent polymer was synthesized via copolymerization of two derivatives of norfloxacin and methylmetacrylate (MMA). It could emit blue fluorescence in both the solution and film states. Fluorescence characteristics of the polymer as a function of pH were investigated in aqueous solution. The polymer solution showed weaker fluorescence between pH 5-9. When the pH of the solution was higher than 9 or lower than 5, stronger fluorescence could be seen. Responses of metal cations (Mn^{2 +}, Fe^{3 +}, Co^{2 +}, Ni^{2 +}, Cu^{2 +} and Zn^{2 +}) to the fluorescence intensity of this polymer were obtained that only Fe^{3 +} could quench efficiently the fluorescence intensity of the polymer in solution and film state. The results suggested the possibility that this newly synthesized compound might work as a polymeric sensor responding to water polluted by protons and Fe^{3 +}.     

Carbazole-based Schiff base: A sensitive fluorescent ‘turn-on’ chemosensor for recognition of Al(III) ions in aqueous-alcohol media

Carbazole-based Schiff base chemosensor was synthesized in one-pot synthesis using 2-hydroxy-1-naphtaldehyde for fluorescent sensing of Al³⁺ ions. Characterization of the ligand (L) was revealed through spectroscopic and physicochemical techniques. The fluorescence emission responses of L to various metal ions and anions were investigated. The chelation was studied by UV–vis, ¹H NMR, LC-MS/MS, fluorescence titration and Job’s plot analysis. Bathochromic shift resulted from charge transfer from L to electrophilic Al³⁺ ion was observed in the chelation of L with Al³⁺. The potentiality of L to be a distinguished probe to detect Al³⁺ ions was due to a chelation enhanced fluorescence (CHEF) effect, concomitant with noticeable fluorescent enhancement. A significant fluorescence enhancement at 533 nm was observed in ethanol–water (1:1, v/v) solution upon addition of Al³⁺ along with a distinct color change from yellow to white. Non-fluorescent ligand exposed highly sensitive turn-on fluorescent sensor behavior for selectively sensing Al³⁺ ions via 1:1 (ligand:metal) stoichiometry. The ligand’s specificity in the existence of other tested metal ions and anions indicated no observation in color change. The ligand-Al³⁺ complex formation was reversible upon addition of chelating agent EDTA. The ligand interacted with Al³⁺ ions with an association constant of K_a = 5 × 10⁴ M^?1. The limit of detection (LOD) was found to be 2.59 × 10^-7 M. The synthesized Schiff base could efficiently detect Al³⁺ ions as a fluorescent sensor.     

Photo-physical aspects of BODIPY-coumarin conjugated sensor and detection of Al3+ in MCF-7 cell

ABSTRACT

BODIPY azine bearing chemosensor R1 has been synthesised for selective detection of Al³⁺with visual colour change from red-purple to purple and photo-physical studies were explained through Förster Resonance Energy Transfer (FRET) mechanism. Chemosensor showed good sensing capability with high binding constant and lower Limit of Detection (LOD) towards Al³⁺. Cell viability and fluorescence microscopic experiments illustrated about the cytocompatibily of the sensor in presence of Al³⁺ in living cells (MCF-7).     

New regioisomeric naphthol–thiazole based ‘turn-on’ fluorescent chemosensor for Al

Two new reactive and highly selective turn-on fluorescent chemosensors based on the position of ring annulation of the naphthalene–thiazole moiety for aluminum ions in ethanol, were synthesized and investigated. It was found that sensors 2 and 4 exhibited a remarkable enhancement of emission upon complexation with Al³⁺. A TD-B3LYP/6-31G(d,p) calculation was performed to characterize the nature of the fluorescence behavior of sensors 2 and 4 upon Al³⁺ complexation. The mechanism of fluorescence was based on the cation promoted hydrolysis of ester and subsequent complexation. The combination of experimental and computational analyses provides a more complete understanding of the molecular level origin of these types of unique photophysical properties.     

Etodolac:β-cyclodextrin inclusion complex as a novel fluorescent chemosensor probe for Ba2+

The inclusion complex of etodolac (ETD) with β-CD was investigated by UV-visible and fluorescence spectroscopy. The chemosensory ability of ETD:β-CD complex for various metal cations was investigated thoroughly, and we found that the emission of the complex showed a drastic increase in the intensity for Ba²⁺. Competitive experiments of ETD:β-CD complex with Ba²⁺ showed that no significant variation was found in the fluorescence intensity of the ETD:β-CD/Ba²⁺ complex upon adding other cations, such as Na⁺, Ag⁺, Hg²⁺, Cd²⁺, Al³⁺, Cr³⁺, Fe³⁺, Se⁴⁺, and Ti⁴⁺. The linearity range, limit of detection (LOD), and limit of quantitation (LOQ) were determined from the selectivity and sensitivity studies.     

Enhancement of the Up-conversion Luminescence of 12CaO · 7Al2O3:Tm3+/Yb3+ Doped with Alkaline Earth Metal Ions

12CaO?·?7Al₂O₃ doped with lanthanide is characterized by remarkable and technologically important up-conversion emission. However, the low up-conversion efficiency still remains the main limitation for practical applications. To improve the efficiency, bivalent alkaline earth ions (Mg²⁺, Sr²⁺, Ba²⁺)-tridoped Tm³⁺/Yb³⁺/12CaO?·?7Al₂O₃ were synthesized through a high-temperature solid-state reaction. The up-conversion luminescence properties of the samples were investigated by X-ray diffraction, fluorescence spectral measurement pump power, and fluorescence decay curves. The luminescence intensity of samples was significantly enhanced by bivalent alkaline earth ions. 12CaO?·?7Al₂O₃ doped with Sr²⁺ ions has stronger effects on up-conversion enhancement, which is better than Mg²⁺ and Ba²⁺. The up-conversion emission intensity was enhanced by 318 times and the red emission intensity by 218 times with 10?mol% Sr²⁺ ion. Additionally, the blue and red up-conversion emission peaks at 475 and 650?nm corresponding to energy transitions of ¹G₄ → ³H₆ and ¹G₄ → ³F₄, ³F₂ → ³H₆ were characterized using steady-state rate equations.     

Strong visible up-conversion emissions and thermometric applications of Er<Superscript>3+</Superscript>–Yb<Superscript>3+</Superscript> codoped Al<Subscript>2</Subscript>O<Subscript>3</Subscript> prepared by the sol–gel method

The Er³⁺–Yb³⁺ codoped Al₂O₃ has been prepared by the sol–gel method using the aluminium isopropoxide [Al(OC₃H₇)₃]-derived Al₂O₃ sols with addition of the erbium nitrate [Er(NO₃)₃ · 5H₂O] and ytterbium nitrate [Yb(NO₃)₃ · 5H₂O]. The phase structure, including only two crystalline types of doped Al₂O₃ phases, θ and γ, was obtained for the 1 mol% Er³⁺ and 5 mol% Yb³⁺ codoped Al₂O₃ at the sintering temperature of 1,273 K. By a 978 nm semiconductor laser diodes excitation, the visible up-conversion emissions centered at about 523, 545, and 660 nm were obtained. The temperature dependence of the green up-conversion emissions was studied over a wide temperature range of 300–825 K, and the reasonable agreement between the calculated temperature by the fluorescence intensity ratio (FIR) theory and the measured temperature proved that Er³⁺–Yb³⁺ codoped Al₂O₃ plays an important role in the application of high temperature sensor.     

Fluorescence sensor using a molecularly imprinted polymer as a recognition receptor for the detection of aluminium ions in aqueous media

This paper describes the investigation of a molecularly imprinted polymer (MIP) as a sensing receptor for Al³⁺ ion detection by using an optical approach. Al³⁺ ion was adopted as the template molecule and 8-hydroxyquinoline sulfonic acid ligand as the fluorescence tag. The polymer was synthesised using acrylamide as monomer, 2-hydroxyethyl methacrylate as co-monomer and ethylene glycol dimethracylate as cross-linker. The free radical polymerisation was performed in methanol and initiated by 2,2′-azobisisobutyronitrile at 70 °C. The imprinted polymer was fluorometrically characterised using a fibre optic attachment in a self-designed flow-cell. NaF was used to leach the Al³⁺ ion from the MIP. The optimum pH for the rebinding of Al³⁺ ion with the leached polymer was found to be pH 5 and the fluorescence response was found to be stable within the buffer strength range of 0.05–0.10 M. The fluorescence intensity during Al³⁺ ion rebinding was inversely dependent on temperature, and a low interference response (<3%) toward metal ions except for Cu²⁺ and Zn²⁺ ions was observed. The polymer rebinding repeatability study conducted over 9 cycles with Al³⁺ ion (0.8×10⁻⁴ M) was found to give an RSD value of 2.82% with a standard deviation of 0.53. The dynamic range of the system was found to be linear up to 1.0×10⁻⁴ M Al³⁺ ion with a limit of detection of 3.62 μM.     

Luminescent properties of Sr<Subscript>3</Subscript>Al<Subscript>2</Subscript>O<Subscript>6</Subscript>: Eu,Pr prepared by sol–gel method

A new red-emitting long afterglow Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphor was synthesized by sol–gel methods using Sr(NO₃)₂, Al(NO₃)₃·9H₂O, Eu(NO₃)₃ and Pr(NO₃)₃ as raw materials. The crystalline structure of the phosphor powders were characterized by X-ray diffraction. Luminescent properties of the phosphor powders were analyzed by the fluorescence spectrophotometer. Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphor powders with single Sr₃Al₂O₆ phase were prepared at 1200 °C for 2 h in the reducing atmosphere. Pr³⁺ doped made the light intensity and the light-lasting time of Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphors improved. The emission peaks of the Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphor powders lay at 612 nm with the excitation of 472 nm and the longest afterglow time could last for about 15 min at Pr³⁺ content of 0.06.     

Non-random cation distribution in hexagonal Al0.5Ga0.5PO4

Based on powder X-ray diffraction and ³¹P Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) investigations of mixed phosphate Al_0.5Ga_0.5PO₄, prepared by co-precipitation method followed by annealing at 900 °C for 24 h, it is shown that Al_0.5Ga_0.5PO₄ phase crystallizes in hexagonal form with lattice parameter a=0.491(2) and c=1.106(4) nm. This hexagonal phase of Al_0.5Ga_0.5PO₄ is similar to that of pure GaPO₄. The ³¹P MAS NMR spectrum of the mixed phosphate sample consists of five peaks with systematic variation of their chemical shift values and is arising due to existence of P structural units having varying number of the Al³⁺/Ga³⁺ cations as the next nearest neighbors in the solid solution. Based on the intensity analysis of the component NMR spectra of Al_0.5Ga_0.5PO₄, it is inferred that the distribution of Al³⁺ and Ga³⁺ cations is non-random for the hexagonal Al_0.5Ga_0.5PO₄ sample although XRD patterns showed a well-defined solid solution formation.     

A selective fluorescent probe for La and Y based on calix[6]arene

A new fluorescent probe based on calix[6]arene functionalized with three naphthoic acid groups was synthesized and showed selective fluorescence enhancement in the presence of La³⁺ and Y³⁺. In addition, the fluorescence enhancement behaviors depended on the pH values of the solution.