Salicylic acid doped silica nanoparticles as a fluorescent nanosensor for the detection of Fe3+ in aqueous solution

A novel organic-inorganic hybrid nanosensor (SASP) was prepared by a one-step sol-gel method and characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, N2 adsorption-desorption, fluorescence spectroscopy, etc. The nanosensor showed almost 3-fold fluorescence emission quenching upon excitation with a 293 nm wavelength in the presence of 20 μM Fe3+ ions. The presence of 18 other metal ions had no observable effect on the sensitivity and selectivity of the nanosensor. A fluorescence analysis method based on the SASP for the selective detection of Fe3+ was established under optimal conditions. The results showed that there was a linear relationship between the log luminescence value and the concentration of Fe3+ over the range of 2.0 × 10-7-9.0 × 10-5 mol L-1 with a detection limit (3σ) of 2.5 × 10-8 mol L-1. Furthermore, the proposed method was successfully applied for the determination of trace Fe3+ in fetal bovine serum without the interference of other molecules and ions. Good recovery (96.5-104.5%) and a relative standard deviation of less than 8.6% were obtained from serum samples spiked with four levels of Fe3+. Additionally, the nanosensor showed a good reversibility; the fluorescence could be switched "off" and "on" in two ways, by adjusting the pH of the solution and adding metal chelating agent EDTA.

Applications of surface functionalized Fe3O4 NPs-based detection methods in food safety

Food safety has always been an issue of great concern to people. The development of rapid, sensitive and specific detection technology of food pollutants is one of the hot issues in food science field. The rapid development of functionalized Fe₃O₄ nanoparticles (NPs) provides unprecedented opportunities and technical support for the innovation of food safety detection. The surface functionalized Fe₃O₄ NPs, which combine superparamagnetic with nanoscale feature, have become an excellent tool for food quality and safety detection. This review highlights the mechanism, principles, and applications of surface functionalized Fe₃O₄ NPs-based detection technique in the agrifood industry. Then the relevant characteristics, functional roles and general mechanisms of nanomaterial-based detection of various endogenous components and exogenous pollutants in foods are discussed in detail. Ultimately, this review is expected to promote the optimization of functionalized Fe₃O₄ NPs and provide direction for the diversity of signal recognition and the sustainability of detection methods.

Nano γ-Fe2O3-Quinuclidine-Based Catalyst as a Recyclable Organic Base for the Diastereoselective Synthesis of Trans-2,3-Dihydrofuro[3,2-C]Coumarins

A nano γ-Fe2O3-quinuclidine-based catalyst as a new, magnetically recyclable heterogeneous organic base was synthesised and used in the efficient synthesis of a series of 11 trans-3-aroyl-2-(4-halobenzoyl)-2,3-dihydro-4H-furo[3,2-c]chromen-4-ones by the reaction of N-(2-(4-halobenzoyl)-2-oxoethyl)pyridinium bromide with 4-hydroxycoumarin and an aryl glyoxal. The catalyst was easily isolated from the reaction mixture using a magnetic bar and reused at least 10 times without significant decrease in its activity.

1,3,4-Thiadiazol derivative functionalized-Fe3O4@SiO2 nanocomposites as a fluorescent probe for detection of Hg2+ in water samples

5-Amino-1,3,4-thiadiazole-2-thiol was used to synthesize a novel fluorescent functionalizing group on a Fe₃O₄@SiO₂ magnetic nanocomposite surface for detection of heavy metal ions in water samples. The prepared probe was characterized by using X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and a vibrating sample magnetometer. Among various tested ions, the new nanocomposite responded to Hg²⁺ ions with an intense fluorescence “turn-off”. The limit of detection of the probe shows that it is sensitive to the minimum Hg²⁺ concentration of 48.7 nM. Theoretical calculations were done for estimating binding energies of the three possible bonding modes and the visualized molecular orbitals were presented.

VBYT-Fe₃O₄@SiO₂ fluorescent probe was designed for sensitive detection of mercury in water samples.

Solvent-dependent "turn-on" fluorescence chemosensor for Mg(2+) based on combination of C=N isomerization and inhibition of ESIPT mechanisms

A fluorescent chemosensor (L) for Mg(2+) has been synthesized and characterized, which exhibits turn-on fluorescence response for Mg(2+) only in alcohol solvent (methanol or ethanol) with high sensitivity and selectivity. But in both nonpolar and polar solvents (cyclohexane, DCM, DMSO or MeCN), L showed negligible fluorescent response for Mg(2+). In order to discover the unique phenomenon, optical measurements, liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and a high performance liquid chromatography with a fluorescence detector (HPLC-FLD) of L and L with Mg(2+) ions in solvents were studied. In alcohol solvent, [L+alcohol molecule] was formed and the mechanism aspect of L concerning the remarkable fluorescence response for Mg(2+) has been discussed.

Hg2+-induced deprotonation of an anthracene-based chemosensor: set–reset flip-flop at the molecular level using Hg2+ and I− ions

A simple chemosensor 1 shows a “turn-off” sensing of Hg²⁺ ions, whereas the in situ formed Hg²⁺ complex can be used for “turn-on” sensing with I⁻ ions. These fluorescence changes have been used for the construction of a set–reset flip-flop circuit.

Biosynthesis of Fe, Pd, and Fe–Pd bimetallic nanoparticles and their application as recyclable catalysts for [3 + 2] cycloaddition reaction: a comparative approach

The Fe–Pd bimetallic nanoparticles exhibit strong catalytic activity compared to their respective monometallic nanoparticles.

A new pyrene-based Schiff-base: a selective colorimetric and fluorescent chemosensor for detection of Cu(II) and Fe(III)

A new receptor 1 was prepared, for the detection of Cu2+ and Fe3+ in solutions as a colorimetric and fluorescent sensor, respectively. Receptor 1 shows highly selective and sensitive recognition toward Cu2+ and Fe3+ by naked eye UV-Vis and fluorescent color changes in aqueous solution (DMSO/H2O=8/2, v/v), respectively. The sensitivity toward Cu2+ or Fe3+ was not interfered with by the presence of other metal ions such as Mg2+, Cd2+, Ag+, Zn2+, Ni2+, Co2+, Mn2+, Cr3+, Ca2+, Na+, Pb2+, K+, Fe2+, Li+ and Hg2+ ions. Receptor 1 can be used for semi-quantitative recognition of Cu2+ ions at ppm level. The fluorescence microscopy experiments showed that the receptor is efficient for detection of Fe3+ in vitro, developing a good image of the biological organelles.

Coordinating ligand functionalized AgNPs for colorimetric sensing: effect of subtle structural and conformational change of ligand on the selectivity

Metal coordinating C₂-symmetric phenolic chelating ligands (1–3) were used to prepare surface functionalized AgNPs for selective colorimetric sensing of metal cations and anions.