Receptor-free phenothiazine derivative as fluorescent probe for picric acid: Investigation of the inner filter effect channel

Tryptanthrin incorporated spiropiperidine derivative as a fluorescent chemosensor for picric acid detection

The photophysical properties of a previously synthesized tryptanthrin incorporated spiropiperidine molecule (CTSP) is described. Studies revealed that the fluorescence of the compound gets significantly quenched by addition of picric acid (PA). The selectivity, anti-interference and quenching mechanistic studies are also described. The quenching mechanism was largely attributed to photo-induced electron transfer (PET) process facilitated by a strong electrostatic interaction between the protonated NH2 group of CTSP and PA. Additionally, pH variations significantly influenced the quenching efficiency, with the highest response observed at neutral pH. These findings demonstrate that CTSP is a promising candidate for PA detection, with potential applications in environmental monitoring and security fields.

A fluorescent nonconjugated zwitterionic polymer dot: hydrothermal synthesis and application in the nano-molar sensing of 2,4,6-trinitrophenol

Developing nonconjugated polymer dot-based sensors with high quantum yield for a targeted application is a challenging research field. Herein, we report the synthesis of a zwitterionic polymer dot (PD PAMAM 2.5, average diameter 12 nm), which contains a poly(aminoamide) core and amine and acid groups on the surface. The molecular structure and functionalities of the polymer dot were carefully established using various spectroscopic techniques, including NMR, FTIR, and XPS. The polymer dot revealed greenish blue/aqua emission (λmax = 470 nm) with a quantum yield of 28%. The mechanism for the synthesis of polymer dot with respect to its structure and fluorescence property was examined using a combination of techniques, including NMR, zeta potential and fluorescence spectrometry. The application of the fluorescent polymer dot for the selective detection of 2,4,6-trinitrophenol was studied in detail. The limit of detection was determined to be 0.77 nM, which was the best value among the current state-of-the-art. Furthermore, application of the polymer dot in real life scenarios was demonstrated using real life wastewater samples and a paper-based strip-test method.

Nitrogen-doped carbon quantum dots from pumpkin for the sensing of nifuratel and temperature

Herein, nitrogen doped carbon quantum dots (N-CQDs) were synthesized using a hydrothermal strategy. The raw materials for the preparation of N-CQDs were sourced from pumpkin and melamine. The N-CQDs suggested fascinating water solubility, favorable UV and salt resistance stability. The fluorescence quantum yield of N-CQDs was carried out to be 16.7 %. The prepared N-CQDs suggested good optical features and favorable blue fluorescence under a UV lamp (365 nm). The as-prepared N-CQDs could be employed as rapid, sensitive and promising fluorescence nanoprobes to detect nifuratel because of static quenching and inter filter effect. For nifuratel detection, the linear range of 0.5-100 μM and detection limit of 0.074 μM were obtained. Furthermore, N-CQDs were subsequently applied to determine nifuratel in river water and Yili milk samples with acceptable experiment results. Significantly, N-CQDs suggested evident temperature-sensitive characteristics and were employed as fluorescent temperature sensing nanoprobes.

Metal-organic frame material encapsulated Rhodamine 6G: A highly sensitive fluorescence sensing platform for the detection of picric acid contaminants in water

As a water pollutant with excellent solubility, 2,4,6-trinitrophenol (also known as picric acid, PA) poses a potential threat to the natural environment and human health, so it is crucial important to detect PA in water. In this study, a novel composite material (MIL-53(Al)@R6G) was successfully synthesized by encapsulating Rhodamine 6G into a metal-organic frame material, which was used for fluorescence detection of picric acid (PA) in water. The composite exhibits bright yellow fluorescence emission with a fluorescence quantum yield of 58.23 %. In the process of PA detection, the composite has excellent selectivity and anti-interference performance, and PA can significantly quench the fluorescence intensity of MIL-53(Al)@R6G. MIL-53(Al)@R6G has the advantages of fast detection time (20 s), wide linear range (1-100 µM) and low detection limit (4.8 nM). In addition, MIL-53(Al)@R6G has demonstrated its potential for the detection of PA in environmental water samples with satisfactory results.

Revealing the high efficiency of fluorescence quenching of rhodamine B by triangular silver nanodisks due to the inner filter effect mechanism

Performing effective fluorescence quenching based on a metal nanomaterial is essential to construct fluorescence sensors. Silver nanomaterials are well known as an excellent candidate for an absorber in fluorescence sensing systems. Herein, we investigated the fluorescence quenching of rhodamine B (RhB) in the presence of triangular silver nanodisks in which perfect overlap between the absorption of the absorber and the fluorescence of the fluorophore was observed. The fluorescence quenching mechanism of RhB was investigated under various excitation wavelengths, together with measurement of the fluorescence lifetime. The quenching efficiency of RhB was proportional to the wavelength excitation. Remarkably, the highest efficiency of fluorescence quenching of RhB was achieved (∼60%). The quenching mechanism was investigated and revealed to be mostly due to the inner filter effect (IFE) mechanism, without the contribution of energy transfer. This result shows a completely different story from most previous studies based on silver nanoparticles, where energy transfer was reported to play a significant role.

A phenothiazine-functionalized pyridine-based AIEE-active molecule: a versatile molecular probe for highly sensitive detection of hypochlorite and picric acid

In this study, we designed and synthesized a novel compound (PTH-AB-PY) based on phenothiazine and pyridine moieties with aggregation-induced emission enhancement (AIEE) properties. The compound has shown exceptional selectivity and sensitivity towards ClO- ions with an impressive detection limit of 6.86 × 10-4 M. Its remarkable sensitivity arises from its effective inhibition of the photoinduced electron transfer (PET) mechanism. Job's plot analysis and high-resolution mass spectrometry (HR-MS) confirmed the 1 : 1 binding ratio between the compound and ClO-. The synthesized compound also exhibits higher sensitivity and fluorescence quenching towards the explosive species (picric acid), with a detection limit of around 1.44 × 10-6 M. Furthermore, our work was carried out for real-time water sample analysis to check ClO- and picric acid detection and high recovery rates (94 to 99%) were achieved. These findings highlight the potential of PTH-AB-PY as a promising molecular probe for ClO- ions and picric acid detection with various analytical and environmental applications.