Li Zhang,Hetong Qi,Yuexiang Wang,Lifen Yang,Ping Yu,Lanqun Mao
This study demonstrates a rapid visualization assay for on-spot sensing of alcohol content as well as for discriminating methanol-containing beverages with solvent stimuli-responsive supramolecular ionic material (SIM). The SIM is synthesized by ionic self-assembling of imidazolium-based dication C10(mim)2 and dianionic 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) in water and shows water stability, a solvent stimuli-responsive property, and adaptive encapsulation capability. The rationale for the visualization assay demonstrated here is based on the combined utilization of the unique properties of SIM, including its water stability, ethanol stimuli-responsive feature, and adaptive encapsulation capability toward optically active rhodamine 6G (Rh6G); the addition of ethanol into a stable aqueous dispersion of Rh6G-encapsulated SIM (Rh6G-SIM) destructs the Rh6G-SIM structure, resulting in the release of Rh6G from SIM into the solvent. Alcohol content can thus be visualized with the naked eyes through the color change of the dispersion caused by the addition of ethanol. Alcohol content can also be quantified by measuring the fluorescence line of Rh6G released from Rh6G-SIM on a thin-layer chromatography (TLC) plate in response to alcoholic beverages. By fixing the diffusion distance of the mobile phase, the fluorescence line of Rh6G shows a linear relationship with alcohol content (vol %) within a concentration range from 15% to 40%. We utilized this visualization assay for on-spot visualizing of the alcohol contents of three Chinese commercial spirits and discriminating methanol-containing counterfeit beverages. We found that addition of a trace amount of methanol leads to a large increase of the length of Rh6G on TLC plates, which provides a method to identify methanol adulterated beverages with labeled ethanol content. This study provides a simple yet effective assay for alcohol content sensing and methanol differentiation.
A PBA/Rh6G ratiometric sensing platform was constructed by simple fluorophore mixing. • The system enabled sensitive Ag + detection with a LOD of 6.8 × 10 −14 mol L −1 . • Ratiometric readout improved repeatability and enabled reliable analysis of real water samples. The sensitive and accurate detection of silver ions (Ag + ) is of considerable significance for environmental monitoring and health risk assessment. To address the susceptibility of single-channel fluorescence detection to variations in probe concentration, excitation intensity, and sample matrix effects, a dual-channel ratiometric fluorescence sensing system for Ag + detection was constructed by directly mixing 1-pyrenebutyric acid (PBA) and rhodamine 6G (Rh6G). In this system, PBA served as the Ag + -responsive unit and exhibited a characteristic emission at approximately 400 nm under excitation at 328 nm, with its fluorescence intensity decreasing as the total Ag + concentration increased. Rh6G provided a relatively stable reference signal at approximately 578 nm, and the fluorescence intensity ratio I 400 /I 578 was used as the ratiometric response parameter. Suitable conditions for dual-channel detection were established by systematically optimizing the concentrations of PBA and Rh6G, the DMSO volume fraction, pH, and reaction time. The results showed a good linear relationship between the ratiometric fluorescence signal and the logarithm of the total Ag + concentration (R 2 = 0.992), with a detection limit as low as 6.8 × 10 −14 mol L −1 . Preliminary analysis of spiked campus lake water samples yielded recoveries ranging from 95% to 105%. Without requiring complex nanomaterial synthesis or multistep surface functionalization, this method provides a simple strategy for constructing ratiometric fluorescence sensing systems for Ag + detection. Download: Download high-res image (310KB) Download: Download full-size image
Siyang Deng,Junmei Liu,Dong Han,Xinting Yang,Huan Liu,Chunhui Zhang,Christophe Blecker
A novel ratiometric fluorescent nanoprobe (Rh6G@UIO-66-NH 2 ) was fabricated for efficient nitrite (NO 2 – ) detection in the present study. When NO 2 – was introduced, it interacted with the amino groups on the surface of Rh6G@UIO-66-NH 2 , forming diazonium salts that led to the quenching of blue fluorescence. With this strategy, a good linear relationship between NO 2 – concentration and the fluorescent intensity ratio of the nanoprobe in the range of 1–100 μM was established, with a detection limit of 0.021 μM. This dual-readout nanosensor was applied to analyze the concentration of NO 2 – in real meat samples, achieving satisfactory recovery rates of 94.72–104.52%, highlighting the practical potential of this method. Furthermore, a portable Gel/Rh6G@UIO-66-NH 2 hydrogel test kit was constructed for on-spot dual-mode detection of NO 2 – . This kit allows for convenient colorimetric analysis and fluorometric detection when used in conjunction with a smartphone. All the photos taken with the portable kit was converted into digital information using ImageJ software. It provides colorimetric and fluorescent visual detection of NO 2 – over a range of 0.1–1.5 mM, achieving a direct quantitative tool for NO 2 – identification. This methodology presents a promising strategy for NO 2 – detection and expands the application prospects for on-spot monitoring of food safety assessment.
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