A single optical sensor with high sensitivity for detection of Fe 3+ and CN − ions

Spiroindeno-pyridineindoles (SIPIs) as new visible colorimetric pH indicators

Some new, highly selective, and sensitive colorimetric pH indicators, spiro[4H-indeno-[1,2-b]pyridine-4,3'-[3H]indoles] (SIPIs) in aqueous solution were developed. SIPIs were synthesized via a one-pot four-component condensation of isatin derivatives, β-diketones 1,3-indandione, and ammonium acetate using FSi-PrNH-BuSO₃H as a nanocatalyst in EtOH. According to the experimental evaluations, it was found that SIPI derivatives are pH indicators for naked-eye detection of OH- ion with intense color changes from orange to purple in the pH range of 10.3-12.

A Turn-On Fluorescent Chemosensor for Cyanide Ion Detection in Real Water Samples

We have designed and synthesized a novel simple colorimetric fluorescent probe with aggregation-induced emission (AIE) properties. Probe 5-(4-(diphenylamine)phenyl) thiophen-2-formaldehyde W exhibited a turn-on fluorescent response to cyanide ion (CN−), which induces distinct visual color changes. Probe W exhibited a highly selective and sensitive ratiometric fluorescence response for the detection of CN− over a wide pH range (4–11) and in the presence of common interferents. The linear detection of CN− over the concentration range of 4.00–38.00 µM (R2 = 0.9916, RSD = 0.02) was monitored by UV-Vis absorption spectrometry (UV-Vis) with the limit of detection determined to be 0.48 µM. The linear detection of CN− over the concentration range of 8.00–38.00 µM was examined by fluorescence spectrophotometry (R2 = 0.99086, RSD = 0.031), and the detection limit was found to be 68.00 nM. The sensing mechanisms were confirmed by 1H NMR spectroscopic titrations, X-ray crystallographic analysis, and HRMS. Importantly, probe W was found to show rapid response, high selectivity, and sensitivity for cyanide anions in real water samples, over the range of 100.17∼100.86% in artificial lake water and 100.54∼101.64% in running water by UV-Vis absorption spectrometry, and over the range of 99.42∼100.71% in artificial lake water and 100.59∼101.17% in running water by fluorescence spectrophotometry. Importantly, this work provides a simple and effective approach which uses an economically cheap and uncomplicated synthetic route for the selective, sensitive, and quantitative detection of CN− ions in systems relevant to the environment and health.

FRET probe for selective and sensitive detection of vitamin A by cadmium free quantum dots (ZnS)

Vitamin A as a powerful antioxidant plays an important role in human body functions including bone remodeling regulation, healthy immune system and cell growth reproduction. An accurate determination of vitamin A is taken into consideration because of its importance for human health. In this paper, we reported a fluorescence resonance energy transfer (FRET) probe, MPS-capped ZnS QDs, for sensitive and selective detection of vitamin A. The colloidal MPS-capped ZnS QDs were prepared from Zinc acetate and sodium sulfide by employing 3-mercaptopropyltrimethoxysilane (MPS) molecules as the stabilizer or capping agent at the pH condition of 10. The synthesized MPS-capped ZnS QDs were characterized by means of FT-IR, UV-Vis, DLS, and TEM techniques. The sensing behavior of MPS-capped ZnS QDs for selective and sensitive detection of vitamin A, vitamin B₂, vitamin B₆, vitamin E, vitamin K, vitamin H, vitamin D₃ and vitamin C was investigated using fluorescence spectroscopy. The detection mechanism involves photoinduced charge transfer from the surface of ZnS QDs to Vitamin resulting in the fluorescence quenching of ZnS QDs followed by nonradiative fluorescence resonance energy transfer. An excellent selectivity was observed for vitamin A versus other tested species. A linear relationship was observed between the fluorescence intensity of MPS-capped ZnS QDs and the concentration of vitamin A in the range of 3.33-36.66 μM with detection limit of 1.062 μM.

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.

A novel colorimetric and "turn-on" fluorimetric chemosensor for selective recognition of CN- ions based on asymmetric azine derivatives in aqueous media

A novel chemosensor 2-((Z)-(((E)-quinolin-2-ylmethylene)hydrazono)methyl)phenol PX has been successfully designed and synthesized, which showed both colorimetric and "turn-on" fluorescence responses for CN^- in DMSO/H₂O (3:2, v/v; pH=7.20) solution. The sensor could respond effectively to the stimulation of CN^- ions via deprotonation and sensing mechanism of intramolecular charge transfer (ICT). Moreover, the sensor PX was successfully utilized to detect CN^- in bitter almond, and the detection limit on fluorescence response of PX towards CN^- was down to 4.5×10^-7M. Test strips containing PX were also prepared, which could act as a practical colorimetric tool to detect CN^- in aqueous media.

A novel dual-channel chemosensor for CN- using asymmetric double-azine derivatives in aqueous media and its application in bitter almond

In this paper, we have designed and synthesized a novel sensor L1 based on asymmetric double-azine derivatives, which showed both "naked eye" recognition and fluorescence responses for CN^- in DMSO/H₂O (v/v=4:1, pH=7.20) solution. This simple sensor L1 could distinguish CN^- from coexisting anions via the way of deprotonation and sensing mechanism of intramolecular charge transfer (ICT), and the minimum detection limit on fluorescence response of the sensor L1 towards CN^- was down to 9.47×10^-7M. Moreover, we have successfully utilized the sensor L1 to detect CN^- in bitter almond. Test strips containing L1 were also prepared, which could act as a practical colorimetric tool to detect CN^- in aqueous media.

A novel dual-channel chemosensor for CN− based on rhodamine B hydrazide derivatives and its application in bitter almond

We successfully designed and synthesized a novel chemosensor PW bearing rhodamine B hydrazide and 8-formyl-7-hydroxyl-4-methylcoumarin, which displayed both colorimetric and “turn-on” fluorescence responses for CN⁻ in DMSO/H₂O (1 : 1, v/v, pH = 7.20) solution.