Magneto-Fluorescent Hybrid Sensor CaCO3-Fe3O4-AgInS2/ZnS for the Detection of Heavy Metal Ions in Aqueous Media

Fluorescence sensing and adsorption kinetics of Gd-doped AgInS2 I-III-VI quantum dots - A case study of Ag+ ions interactions

The poor fluorescence properties of magneto-fluorescent paramagnetic-ion (Gd, Mn, or Co) doped I-III-VI quantum dots (QDs) at higher paramagnetic-ion doping concentrations have limited their use in magnetic-driven water-based applications. This work presents, for the first time, the use of stable magneto-fluorescent Gd-doped AgInS2 QDs at high Gd mole ratios of 16, 20, and 30 for the fluorescence detection and adsorption of Ag+ ions in water environments. The effect of pH, initial concentration, contact time, and adsorbent dosage were systematically evaluated. The AgInS2 QDs with the least Gd mole ratio (16) exhibited the best fluorescence characteristics (LOD = 0.88, R2 = 0.9549) while all materials showed good adsorption properties under optimized conditions (pH of 2, initial concentration of 30 ppm, contact time of 10 min and adsorbent dosage of 0.02 g) and a pseudo 2nd order reaction was followed. The adsorption mechanism was proposed to be a combination of ion-exchange, electrostatic interaction, complexation, and diffusion processes. Application in environmental wastewater samples revealed complete removal of Ag + ions alongside Ti2+ Pb2+, Ni2+, Cr3+, and Zn2+ ions.

Synthesis and Computational Study of an Optical Fluorescent Sensor for Selective Detection of Ni2+ Ions

The presence of an abnormal amount of Ni2+ in the human body causes various health issues. Therefore, this work aimed to synthesize the curcumin-based fluorescence-on sensor P [2,6-bis((E)-4-chlorobenzylidene)-cyclohexan-1-one] that was capable of selectively responding to Ni2+ ions in aqueous solution. The structure of P was confirmed by 1H NMR and Fourier transform infrared (FTIR) spectroscopy. The Ni2+ ion sensing was based on the fluorescence enhancement of the fluorophore (P) in neutral aqueous medium. The response of the P-based sensor was highly selective toward Ni2+ ions, whereas the possible interferences from other metal cations were negligible. P had a fast response; it was selective and had a sensitive detection limit (LOD = 2 × 10-10 M) toward Ni2+ ions in neutral medium with a high association constant (K) value of 3.6 × 105 M-2 for the complex formation between the P and Ni2+ ions. Job's plot and DFT calculations proved that the binding stoichiometry of P for Ni2+ was 2:1. P was recovered using EDTA as a chelating agent after being employed as a fluorescent sensor. These characteristics ensured the potential use of P as a new class of chemosensor for environmental applications.

Magnetic Fluorescent Quantum Dots Nanocomposites in Food Contaminants Analysis: Current Challenges and Opportunities

The presence of food contaminants can cause foodborne illnesses, posing a severe threat to human health. Therefore, a rapid, sensitive, and convenient method for monitoring food contaminants is eagerly needed. The complex matrix interferences of food samples and poor performance of existing sensing probes bring significant challenges to improving detection performances. Nanocomposites with multifunctional features provide a solution to these problems. The combination of the superior characteristics of magnetic nanoparticles (MNPs) and quantum dots (QDs) to fabricate magnetic fluorescent quantum dots (MNPs@QDs) nanocomposites are regarded as an ideal multifunctional probe for food contaminants analysis. The high-efficiency pretreatment and rapid fluorescence detection are concurrently integrated into one sensing platform using MNPs@QDs nanocomposites. In this review, the contemporary synthetic strategies to fabricate MNPs@QDs, including hetero-crystalline growth, template embedding, layer-by-layer assembly, microemulsion technique, and one-pot method, are described in detail, and their advantages and limitations are discussed. The recent advances of MNPs@QDs nanocomposites in detecting metal ions, foodborne pathogens, toxins, pesticides, antibiotics, and illegal additives are comprehensively introduced from the perspectives of modes and detection performances. The review ends with current challenges and opportunities in practical applications and prospects in food contaminants analysis, aiming to promote the enthusiasm for multifunctional sensing platform research.

Highly Sensitive and Selective Fluorescence "Turn-On" Detection of Pb (II) Based on Fe3O4@Au-FITC Nanocomposite

New nanocomposites, Fe₃O₄@Au-FITC, were prepared and explored to develop a fluorescent detection of Pb²⁺. The Fe₃O₄@AuNPs-FITC nanocomposites could be etched by Pb²⁺ in the presence of Na₂S₂O₃, leading to fluorescence recovery of FITC quenched by Fe₃O₄@Au nanocomposites. With the increase of Pb²⁺ concentration, the fluorescence recovery of Fe₃O₄@AuNPs-FITC increased gradually. Under optimized conditions, a detection limit of 5.2 nmol/L of Pb²⁺ with a linear range of 0.02-2.0 µmol/L were obtained. The assay demonstrated negligible response to common metal ions. Recoveries of 98.2-106.4% were obtained when this fluorescent method was applied in detecting Pb²⁺ spiked in a lake-water sample. The above results demonstrated the high potential of ion-induced nanomaterial etching in developing robust fluorescent assays.