Turn-on, photostable, nontoxic and specific, iron(II) sensor

A combined experimental and theoretical approach for doxycycline sensing using simple fluorescent probe with distinct fluorescence change in wide range of interferences

Overuse of doxycycline (DOXY) can cause serious problems to human health, environment and food quality. So, it is essential to develop a new sensing methodology that is both sensitive and selective for the quantitative detection of DOXY. In our current research, we synthesized a simple fluorescent probe 4,4'-bis(benzyloxy)-1,1'-biphenyl (BBP) for the highly selective detection of doxycycline by through fluorescence spectroscopy. The probe BBP displayed ultra-sensitivity towards doxycycline due to Forster resonance energy transfer (FRET). Fluorescence spectroscopy, density functional theory (DFT), 1H NMR titration, UV-Vis, and Job's plot were used to confirm the sensing mechanism. The charge transfer between the probe and analyte was further examined qualitatively by electron density differences (EDD) and quantitively by natural bond orbital (NBO) analyses. Whereas the non-covalent nature of probe BBP towards DOXY was verified by theoretical non-covalent interaction (NCI) analysis as along with Bader's quantum theory of atoms in molecules (QTAIM) analysis. Furthermore, probe BBP was also practically employed for the detection of doxycycline in fish samples, pharmaceutical wastewater and blood samples.

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.

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.

Nanocomposite Based on HA/PVTMS/Cl2FeH8O4 as a Gas and Temperature Sensor

In this paper, a novel nanocrystalline composite material of hydroxyapatite (HA)/polyvinyltrimethoxysilane (PVTMS)/iron(II)chloride tetrahydrate (Cl₂FeH₈-O₄) with hexagonal structure is proposed for the fabrication of a gas/temperature sensor. Taking into account the sensitivity of HA to high temperatures, to prevent the collapse and breakdown of bonds and the leakage of volatiles without damaging the composite structure, a freeze-drying machine is designed and fabricated. X-ray diffraction, FTIR, SEM, EDAX, TEM, absorption and photoluminescence analyses of composite are studied. XRD is used to confirm the material structure and the crystallite size of the composite is calculated by the Monshi-Scherrer method, and a value of 81.60 ± 0.06 nm is obtained. The influence of the oxygen environment on the absorption and photoluminescence measurements of the composite and the influence of vaporized ethanol, N₂ and CO on the SiO₂/composite/Ag sensor device are investigated. The sensor with a 30 nm-thick layer of composite shows the highest response to vaporized ethanol, N₂ and ambient CO. Overall, the composite and sensor exhibit a good selectivity to oxygen, vaporized ethanol, N₂ and CO environments.

Fluorescein based fluorescent and colorimetric sensors for sensitive detection of TNP explosive in aqueous medium: Application of logic gate

Rapid detection of 2,4,6-trinitrophenol (TNP) in real samples has recently attained considerable attention from the perspective of national security, human health, and environmental safety. In this context, cost-effective and convenient detection of TNP explosive was accomplished through two new fluorescein based sensors F2 and F3. Sensors displayed effective fluorescence quenching response towards TNP in the aqueous medium. Highly sensitive fluorescence detection of TNP explosive (detection limit, 0.73 (F2) and 1.7 nM (F3)) was governed by ground-state charge transfer complex formation, facilitated by favorable H-bonding between sensor and TNP explosive. Fluorescence quenching mechanism for the detection of TNP explosive was investigated through UV-Visible absorption, dynamic light scattering (DLS), density functional theory (DFT) calculations, the Benesi-Hildebrand, and Job's plots. Advantageously, sensors displayed selective and immediate colorimetric recognition of TNP explosive. Importantly, sensors exhibited quick response time towards TNP even in the presence of potential interferences that make them highly suitable for practical applications. Sensors were successfully applied for fluorescent and colorimetric detection of TNP explosive in industrial water samples and fabrication of logic gates. Further, convenient contact mode and instant surface sensing of TNP explosive were achieved through the fabrication of fluorescent strips and explosive responsive test kits.