Tetraphenylethene-Based Fluorescent Chemosensor with Mechanochromic and Aggregation-Induced Emission (AIE) Properties for the Selective and Sensitive Detection of Hg2+ and Ag+ Ions in Aqueous Media: Application to Environmental Analysis.

It is critical to design a novel and simple bifunctional sensor for the selective and sensitive detection of ions in an aqueous media in environmental samples. As a result, in this study, tetraphenylethene hydrazinecarbothioamide (TPE-PVA), known as probe 1, was successfully synthesized and characterized as having impressive photophysical phenomena such as aggregation-induced emission (AIE) and mechanochromic properties by applying mechanical force to the solid of probe 1. The emission of the solid of probe 1 changed from turquoise blue to lemon yellow after grinding, from lemon yellow to parakeet green after annealing at 160 °C, and to arctic blue after fuming with DCM. Such characteristics could lead to a variety of applications in several fields. The probe was implemented and demonstrated remarkable selectivity and sensitivity toward mercury(II) and silver(I) ions by substantially switching off emission over other cations. Following an extensive photophysical analysis, it was discovered that detection limits (LOD) as low as 0.18344 and 0.2384 µg mL-1 for Hg2+ and Ag+, respectively, are possible with a quantum yield (Φ) of 2.26. Probe 1 was also explored as a Hg2+ and Ag+ paper strip-based sensor and kit for practical use. The binding mechanisms of probe 1 (TPE-PVA) with Hg2+ and Ag+ were confirmed by 1H NMR titration. These results could lead to the development of reliable onsite Hg2+ and Ag+ fluorescent probes in the future.

Sawmill waste derived carbon dots as a fluorescent probe for synthetic dyes in soft drinks.

Herein, for the first time the carbon dots (CDs) were synthesized by reflux method from sawmill waste material. We also represent a novel strategy based on fluorescent CDs for determination of ponceau 4R and allura red dyes in soft drinks. Interestingly, both the dyes were sensitive and showed effective fluorescence quenching of the CDs owing to the interaction between them. The analytical applicability of CDs were evaluated for detection of both the dyes with a good linear relationship between the concentration range of 0.0 to 3.0 µg mL-1 and having detection limit 0.45 and 0.47 µg mL-1 for allura red and ponceau 4R dyes respectively. Meanwhile, the potential application of this novel fluorescent probe for dyes determination in real samples was validated in different soft drink samples with good accuracy and precision. Thus, these findings provides new insights for the potential risk assessment of both the dyes. Moreover, CDs acted as an excellent fluorescent material in cellular imaging owing to their cellular uptake and localization.

Carbon Nanodots Derived from Kitchen Waste Biomass as a Growth Accelerator for Fenugreek Plant.

Herein, we report the utilization of kitchen waste biomass as a source of carbonaceous material for carbon nanodots synthesis and its application as a plant growth regulator in agricultural crops. The water soluble carbon dots (CDs) were synthesized by pyrolysis of kitchen derived waste tea residue (WTR) and used in the field of agriculture nanotechnology. Herein, we have explored the effect of different concentrations of WTR-CDs (10, 30 and 50 mg/L) on growth of FG with respect to various plant growth parameters. It was observed that the WTR-CDs has positive effect on all plant growth parameters investigated and also assist for micronutrient uptake which is confirmed by AAS and zeta potential measurement. UV light, Fluorescence spectroscopy, and confocal fluorescence microscopy examination were employed for the understanding of uptake and transport route of WTR-CDs in FG plant through absorption of WTR-CDs by root as well as seed coat along with water. Therefore, the growth of FG was a significant increase in quality of the plant which appears to be effective and no serious side effects were seen during the study.

Nitrogen-doped carbon dot threads as a "turn-off" fluorescent probe for permanganate ions and its hydrogel hybrid as a naked eye sensor for gold(III) ions.

Highly fluorescent nitrogen-doped carbon dot (NCD) threads were synthesized via simple pyrolysis of citric acid, p-hydroxybenzoic acid, and ammonia. The NCDs show excitation-independent behavior with maximum excitation and emission wavelengths of 350 nm and 435 nm, respectively. The developed probe was used as a turn-off fluorescent sensor for the selective and sensitive determination of permanganate ions in aqueous media. The probe's hydrogel hybrid displayed a beautiful purple color demonstrating its potential as a naked eye sensor for gold detection. The ratiometric sensor exhibited excellent selectivity towards permanganate ions over 27 other ions with a linear range of 510 nM to 2 µM, a detection limit of 170 nM, and a linear regression value (R2) of 0.9944. Similarly, the linear range and limit of detection for gold ions was 3.89-20 µM and 1.285 µM, respectively. The synthesized NCDs were also used as a fluorescent ink as well as a naked eye marker in association with a gold solution demonstrating its potential forensic and anti-counterfeiting applications. Graphical abstract.