Investigation of the spectral properties of a squarylium near-infrared dye and its complexation with Fe(III) and Co(II) ions

Highly selective silica-based fluorescent nanosensor for ferric ion (Fe3+) detection in aqueous media

A highly selective fluorescence nanosensor was built based on the functionalized SBA-15 mesoporous silica with Dinitrophenylhydrazine (DNPH). The interaction of fabricated nanosensor was studied with metals ions in aqueous media. Under optimum conditions (time 5min, pH7, sensor dose 0.02g dispersed in 1L), SBA-15-DNPH was highly selective toward the Fe³⁺ ion in the presence of the different groups of interfering metal ions. The detection limit and linear concentration range of the nanosensor were 39×10^-6M and 5×10^-5-375×10^-5M; respectively. The efficiency of nanosensor was independent on the pH range studied (6-9), which indicated that SBA-15-DNPH is a promising candidate for sensing and identification of Fe³⁺ ion in the environmental and other real matrix samples. SBA-15-DNPH showed good performance for Fe³⁺ ion detection and quantification in real samples.

Diphenylether based derivatives as Fe(iii) chemosensors: spectrofluorimetry, electrochemical and theoretical studies

Differential pulse voltammetric studies on DPE-I and DPE-II indicating selective response to Fe³⁺, supported by DFT studies using Gaussian software.

A highly selective fluorescent sensor for Fe3+ based on covalently immobilized derivative of naphthalimide

In this paper, the fabrication and analytical characteristics of fluorescence-based ferric ion-sensing glass slides were described. To fabricate the sensor, a naphthalimide derivative (compound 1) with a terminal double bond was synthesized and copolymerized with 2-hydroxyethyl methacrylate (HEMA) on the activated surface of glass slides by UV irradiation. Upon the addition of Fe(3+) in 0.05 mol/L Tris/HCl (pH 6.02) at 25 °C, the fluorescence intensity of the resulting optical sensor decrease, which has been utilized as the basis for the selective detection of Fe(3+). The sensor can be applied to the quantification of Fe(3+) with a linear range covering form 1.0×10(-5) to 1.0×10(-3) M and a detection limit of 4.5×10(-6) M. The experiment results show that the response behavior of the sensor to Fe(3+) is pH-independent in medium condition (pH 5.00-8.00) and exhibits high selectivity for Fe(3+) over a large number of cations such as alkali, alkaline earth and transitional metal ions. Moreover, satisfactory reproducibility, reversibility and a rapid response were realized. The sensing membrane was found to have a lifetime at least 2 months. The accuracy and the precision of the method were evaluated by the analysis of the standard reference material, iron in water (1.0 mol/L HNO3). The developed sensor is applied for the determination of iron in pharmaceutical preparation samples with satisfactory results.

An efficient and selective flourescent chemical sensor based on 5-(8-hydroxy-2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane as a new fluoroionophore for determination of iron(III) ions. A novel probe for iron speciation

A novel fluorescent chemical sensor for the highly sensitive and selective determination of Fe(3+) ions in aqueous solutions is prepared. The iron sensing system was prepared by incorporating 5-(8-hydroxy-2-quinolinylmethyl)-2,8-dithia-5-aza-2,6-pyridinophane (L) as a neutral Fe(3+)-selective fluoroionophore in the plasticized PVC membrane containing sodium tetraphenylborate as a liphophilic anionic additive. The response of the sensor is based on the strong fluorescence quenching of L by Fe(3+) ions. At pH 5.5, the proposed sensor displays a calibration curve over a wide concentration range from 6.0 × 10(-4) to 1.0 × 10(-7) M, with a relatively fast response time of less than 2 min. In addition to a high stability and reproducibility, the sensor shows a unique selectivity toward Fe(3+) ion with respect to common coexisting cations. The proposed fluorescence optode was applied to the determination of iron(III) content of straw of rice, spinach and different water samples. The fluorescent sensor was also used as a novel probe for Fe(3+)/Fe(2+) speciation in aqueous solution.

Investigating noncovalent squarylium dye–protein interactions by capillary electrophoresis–frontal analysis

Noncovalent interactions between fluorescent probe molecules and protein analyte molecules, which typically occur with great speed and minimal sample handling, form the basis of many high sensitivity analytical techniques. Understanding the nature of these interactions and the composition of the resulting complexes represents an important area of study that can be facilitated by capillary electrophoresis (CE). Specifically, we will present how frontal analysis (FA) and Hummel-Dreyer (HD) methods can be implemented with CE to determine association constants and stoichiometries of noncovalent complexes of the red luminescent squarylium dye Red-1c with bovine serum albumin (BSA) and beta-lactoglobulin A. By adjusting solution conditions, such as pH or ionic strength, it is possible to selectively modify the binding process. As such, conditions for optimal selectivity for labeling reactions can be established by capillary electrophoresis-frontal analysis (CE-FA) investigations.