Fluorescence Detection of Metals and Nitro Aromatic Compounds Based on Tetrastyrene Derivatives

An extensive experimental and DFT studies on highly selective detection of nitrobenzene through deferasirox based new fluorescent sensor

A deferasirox based substituted triazole amine sensor TAD has been synthesized for the highly selective detection of nitrobenzene in real samples. Sensor TAD exhibited selective quenching response against nitrobenzene among the other nitroaromatic compounds (NACs). Photoinduced electron transfer (PET) process was devised as plausible sensing mechanisms which was supported via UV-visible and fluorescence spectroscopy, 1H NMR titration experiment, density functional theory (DFT) analysis and Job's plot. Non-covalent interaction (NCI) analysis and Bader's quantum theory of atoms in molecules (QTAIM) analysis were performed to investigate the presence of non-covalent interactions and symmetry perturbation theory (SAPT0) was performed for energy decomposition and quantitative analysis of interaction energies between sensor TAD and NB. Furthermore, sensor TAD was practically applied for the identification of NB in real samples.

Tetraphenylethene-Based Cross-Linked Conjugated Polymer Nanoparticles for Efficient Detection of 2,4,6-Trinitrophenol in Aqueous Phase

The cross-linked conjugated polymer poly(tetraphenylethene-co-biphenyl) (PTPEBP) nanoparticles were prepared by Suzuki-miniemulsion polymerization. The structure, morphology, and pore characteristics of PTPEBP nanoparticles were characterized by FTIR, NMR, SEM, and nitrogen adsorption and desorption measurements. PTPEBP presents a spherical nanoparticle morphology with a particle size of 56 nm; the specific surface area is 69.1 m2/g, and the distribution of the pore size is centered at about 2.5 nm. Due to the introduction of the tetraphenylethene unit, the fluorescence quantum yield of the PTPEBP nanoparticles reaches 8.14% in aqueous dispersion. Combining the porosity and nanoparticle morphology, the fluorescence sensing detection toward nitroaromatic explosives in the pure aqueous phase has been realized. The Stern-Volmer quenching constant for 2,4,6-trinitrophenol (TNP) detection is 2.50 × 104 M-1, the limit of detection is 1.07 μM, and the limit of quantification is 3.57 μM. Importantly, the detection effect of PTPEBP nanoparticles toward TNP did not change significantly after adding other nitroaromatic compounds, indicating that the anti-interference and selectivity for TNP detection in aqueous media is remarkable. In addition, the spike recovery test demonstrates the potential of PTPEBP nanoparticles for detecting TNP in natural environmental water samples.

AIEE active J-aggregates of naphthalimide based fluorescent probe for detection of Nitrobenzene: Combined experimental and theoretical approaches for Non-covalent interaction analysis

A new naphthalimide-based fluorescent probe NS with exceptional J-aggregates based aggregation-induced emission enhancement (AIEE) properties was rationally synthesized through a single-step imidation reaction. Probe NS exhibited excellent AIEE properties in aqueous media through the formation of J-aggregates with remarkable red-shift. The AIEE active probe NS was used for selective and sensitive detection of nitrobenzene (NB) based on fluorescence quenching response. Formation of J-aggregates was assessed through fluorescence titration. These J-aggregates contributed significantly to produce favorable interaction between probe NS and NB. The highly selective fluorescence detection of NB was accredited to the adjustable smaller size of NB that can easily penetrate into interstitial spaces of probe molecules. Ability of sensor to detect NB in solid state was also accomplished through solid state fluorescence spectroscopy. Nature of interaction and sensitivity of probe NS for NB has also been investigated through ¹H NMR titration and density functional theory (DFT) including non-covalent interaction (NCI), quantum theory of atom in molecule (QTAIM), electron density differences (EDD), frontier molecular orbitals (FMO) and density of states (DOS) analysis. Advantageously, probe exhibited colorimetric and vapor phase detection of NB. Moreover, probe was quite sensitive for the trace detection of NB in real samples.

Ultrasonic assisted preparation of ultrafine Pd supported on NiFe-layered double hydroxides for p-nitrophenol degradation

NiFe-layered double hydroxide (NiFe-LDH)-loaded ultrafine Pd nanocatalysts (Pd/NiFe-LDHs) were prepared by a facile ultrasonic-assisted in situ reduction technology without any stabilizing agents or reducing agents. Pd/NiFe-LDHs were characterized by FT-IR, XRD, XPS, and TEM. PdNPs are uniformly dispersed on NiFe-LDHs with a particle size distribution of 0.77-2.06 nm and an average particle size of 1.43 nm. Hydroxyl groups in Fe-OH and Ni-OH were dissociated into hydrogen radicals (·H) excited by ultrasound, and ·H reduced Pd²⁺ to ultrafine PdNPs. Then, Pd was coordinated with O in Ni-O and Fe-O, which improved the stability of the catalysts. Pd/NiFe-LDHs completely degraded 4-NP in 5 min, and the TOF value was 597.66 h^-1, which was 16.7 times that of commercial Pd/C. The 4-NP conversion rate remained at 98.75% over Pd/NiFe-LDHs after 10 consecutive catalytic cycles. In addition, the catalyst also has high catalytic activity for the reduction of Congo red, methylene blue, and methyl orange by NaBH₄.

Aggregation-Induced Emission of Quinoline Based Fluorescent and Colorimetric Sensors for Rapid Detection of Fe3+ and 4-Nitrophenol in Aqueous Medium

New quinoline based fluorescent sensors 4 and 5 were rationally synthesized that exhibited excellent aggregation induced emission (AIE) in an aqueous medium. High fluorescence emission of sensors was accompanied by a noticeable redshift in their absorption and emission spectra that corresponds to the formation of J-aggregates. An AIE feature of sensors 4 and 5 was used for selective detection of Fe³⁺ and 4-NP in an aqueous medium that is attributed to the involvement of intermolecular charge transfer (ICT). The interaction mechanism of sensors with Fe³⁺ and 4-NP was investigated through ¹H NMR titration, Jobs plots, dynamic light scattering (DLS), and DFT analysis. The fluorescence quenching response of sensors 4 and 5 displayed distinguished linear behavior with the concentrations of Fe³⁺ and limits of detection (LOD) were calculated to be 15 and 10 nM, respectively. Further, LOD of sensors 4 and 5 for 4-NP (7.3 and 4.1 nM, respectively) was very low compared to previously reported sensors. Moreover, sensors' coated test strips were fabricated for solid-supported detection of Fe³⁺ and 4-NP. Sensors were successfully applied for the detection and quantification of Fe³⁺ and 4-NP in real water samples. Additionally, sensors were used for the determination of trace amounts of Fe³⁺ in the human serum sample.

Chitosan-bodipy macromolecular fluorescent probes prepared by click reactions for highly sensitive and selective recognition of 2,4-dinitrophenylhydrazine

Chitosan-based probes were prepared and they could identify 2,4-dinitrophenylhydrazine (DNH). CC bonds formed in a click reaction act as recognizing sites for DNH.

Four imidazole derivative AIEE luminophores: sensitive detection of NAC explosives

Four imidazole sensors with aggregation-induced emission enhancement (AIEE) properties were used for the sensitive detection of NAC explosives.