3-Hydroxy-2-naphthoic hydrazide as a probe for fluorescent detection of cyanide and aluminium ions in organic and aquo-organic media and its application in food and pharmaceutical samples

Multi-Spectroscopic and TD-DFT Studies on Chromogenic and Fluorogenic Detection of Cyanide in an Aqueous Solution

Different spectroscopic techniques and Density Functional Theory (DFT)/Time-Dependent Density Functional Theory (TDDFT) calculations have been employed to investigate the dual channel CN- detection behaviour of the developed chemo-dosimeter (AK3). The CN- with AK3 reaction triggered a colour change from pale yellow to colourless and enhanced fluorescence. UV-Vis, fluorescence, 1H & 13C NMR and mass techniques coupled with theoretical calculations (Mulliken charges, dihedral angles) revealed that the CN- sensing process mechanism involves deprotonation of the N-H group followed by nucleophilic addition reaction. Detailed TD-DFT calculations showed that the relaxation of excited electrons from LUMO and to two different ground states is responsible for the weak/moderate fluorescence of AK3. Nucleophilic addition of CN- to the C-atom of the CH = CH bridge terminated the π-conjugation between donor and acceptor regions, reduced the coplanarity, decreased the ICT transition and consequently enhanced the fluorescence of the probe. The practical utility of the probe was demonstrated by detecting cyanide in food materials and determining CN- in environmental water samples.

A pyridine modified naphthol hydrazone Schiff base chemosensor for Al3+ via intramolecular charge transfer process

A pyridine modified naphthol hydrazone Schiff base chemosensor, NaPy, was prepared in a two-step process to detect aluminum ion (Al³⁺) in different samples. The probe shows a turn-off emission response towards Al³⁺ at a 1:1 binding stoichiometry via intramolecular charge transfer (ICT) mechanism, as validated by density functional theory (DFT) calculations and a series of spectroscopic measurements. The response time is slightly over one minute with a limit of detection (LOD) value of 0.164 µM, demonstrating the great sensitivity of the probe. It is also found that NaPy exhibits high selectivity towards Al³⁺ and resists interference from seventeen other cations. Application investigations in paper strips, water samples and HeLa cells suggest that NaPy can be used as an efficient probe for sensing Al³⁺ in real environmental samples and biosystems.

N-doped carbon nanomaterials as fluorescent pH and metal ion sensors for imaging

Herein we describe the facile synthesis of new N-doped carbon nanoparticles (CNPs) obtained from 1,10-phenanthroline by the solvothermal method. Characterization of CNPs were carried out with transmission electron microscope (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectra (FTIR), UV-vis absorption spectra, and luminescence spectra. CNPs were pH sensitive and exploited as fluorescent chemosensors and imaging agents for Al(III) and Zn(II) ions in real-life samples. Remarkably, we show that CNPs can be used for the detection of Al(III) and Zn(II) ions in water samples. Accordingly, the results indicate that CNPs are highly effective in detecting Zn(II) content of cosmetic creams. We also demonstrated that the CNPs could be used for in vitro imaging of Al(III) and Zn(II) in Human Larynx Squamous Cell Carcinoma (Hep-2). Finally, Al(III) imaging in Angelica Officinalis root tissue was also achieved successfully. The CNPs are promising as luminescent multianalyte (pH, Al(III) and Zn(II)) sensors.

A highly selective and sensitive ratiometric fluorescent probe for quantitative detection of Al(III) in different natural matrices

Highly selective and sensitive assay of Al(III) using ratiometric fluorescence enhancement is reported in an aqueous solution. The probe (named as RS5) exhibits a red-shift of 54 nm upon binding with Al(III) ion. The significant enhancement response of RS5 at 481 nm is attributed to the formation of a 1:1 complex between the probe and Al(III), wherein RS5 acts as a tridentate NNN-donor ligand. The complexation process is ascertained by 1H, 13C and 27Al NMR and HR-MS spectral techniques. The binding constant of the complex is determined to be 1.3x105 M-1. The ratiometric change in fluorescence upon complexation with Al(III) is ascribed to increase in intramolecular charge transfer (ICT) transition along with chelation enhanced fluorescence (CHEF) processes. The probe can be applied for monitoring Al(III) in a pH range of 6 - 8. The limit of detection (LOD) of RS5 for the examination of Al(III) is found to be 0.3 µM. With an aim to understand the sensing behaviour of RS5, the optical properties of the probe and its Al(III) complex are investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The probe is successfully employed for the determination of Al(III), with very high recovery percentages, in natural matrices like deep well water, tap water, drinking water, pond water, river water, bovine serum albumin (BSA) solution and blood serum.

A benzaldehyde-indole fused chromophore-based fluorescent probe for double-response to cyanide and hypochlorite in living cells

With the rapid development of various industries, cyanide (CN-) and hypochlorite (ClO-) have a tremendously adverse effect on the health of humans and animals. In this study, a fluorescent probe HHTB based on a benzaldehyde-indole fused chromophore was designed to detect cyanide and hypochlorite simultaneously. The synthesized probe was found to have strong anti-interference ability. In addition, the designed probe could respond rapidly to ClO- in just 80 s, while the color changed visibly from red to colorless. Moreover, the response time to CN- was longer (about 160 s), with the apparent color change from red to light red. The ratiometric and colorimetric absorbance variation of HHTB was due to the nucleophilic attack of CN- on the indole C[double bond, length as m-dash]N functional group and the strong oxidization of ClO- which destroyed the C[double bond, length as m-dash]C bonds and the conjugation systems. Furthermore, the probe HHTB responding to ClO- and CN- presented high sensitivity, as the calculated detection limits were 1.18 nM and 1.40 nM, respectively. The probe was also found to have low biological toxicity and was used in living cells successfully. Therefore, it has good application prospect in the field of cell imaging and biomedicine. The binding mechanism of HHTB-CN and the reaction mechanism of HHTB and ClO- were further elucidated by a series of experiments.