Fluorescent film sensors based on SAMs of pyrene derivatives for detecting nitroaromatics in aqueous solutions

Photophysical and Fluorescence Nitroaromatic Sensing Properties of Methylated Derivative of a Pamoic Acid Ester

Rapid and selective detection of nitroaromatic explosives is very important for public safety, life, and environmental health. Current instrumental techniques suffer from high cost and poor site used. In order to investigate fluorescence sensing of nitroaromatics, we prepare a new small fluorescence probe derived from pamoic acid. This study covers the synthesis of Pamoic acid based [diisopropyl 4,4'-methylenebis(3-methoxy-2-naphthoate)] (2) material and characterization of its structure. The methylation of Pamoic acid ester, which we have successfully synthesized in our previous studies, was carried out in this study. Determination of the photophysical and fluorescent nitroaromatic detection properties of the compound forms the basis of the study. Structural characterization of the synthesized compound [diisopropyl 4,4'-methylenebis(3-methoxy-2-naphthoate)] (2) was characterized using spectroscopic methods. In addition, Molecular structure of the synthesized compound was determined by single crystal X-ray diffraction studies. In the final step, compounds [diisopropyl 4,4'-methylenebis(3-hydroxy-2-naphthoate)] (1) and [diisopropyl 4,4'-methylenebis(3-methoxy-2-naphthoate)] (2) were tested as fluorescent probes for the detection of some nitroaromatic explosives. It is seen that Nitrobenzene provides the best quenching effect on the compound [diisopropyl 4,4'-methylenebis(3-hydroxy-2-naphthoate)] (1) containing the -OH group, with lowest the limit of detection (LOD) value. It was observed that Picric acid provided the best quenching effect with lowest the limit of detection (LOD) value in the compound [diisopropyl 4,4'-methylenebis(3-methoxy-2-naphthoate)] (2) obtained by methylation of the -OH group in the compound [diisopropyl 4,4'-methylenebis(3-hydroxy-2-naphthoate)] (1).

Silicon-based fluorescent platforms for copper(ii) detection in water

The potential of silicon-based fluorescent platforms for the detection of trace toxic metal ions was investigated in an aqueous environment. To this aim, silicon chips were first functionalized with amino groups, and fluorescein organic dyes, used as sensing molecules, were then covalently linked to the surface via formation of thiourea groups. The obtained hybrid heterostructures exhibited high sensitivity and selectivity towards copper(ii), a limit of detection compatible with the recommended upper limits for copper in drinking water, and good reversibility using a standard metal–chelating agent. The fluorophore–analyte interaction mechanism at the basis of the reported fluorescence quenching, as well as the potential of performance improvement, were also studied. The herein presented sensing architecture allows, in principle, tailoring of the selectivity towards other metal ions by proper fluorophore selection, and provides a favorable outlook for integration of fluorescent chemosensors with silicon photonics technology.

Covalent linkage of fluorescein to silanized silicon chips yields solid-state platforms for detection of copper(ii) in water. This architecture represents a step forward towards the fabrication of sensors for remote water analysis applications.

Ab initio study on the excited states of pyrene and its derivatives using multi-reference perturbation theory methods

The excited states of phenyl-substituted pyrene derivatives were calculated using multi-reference perturbation theory methods.

Selective and sensitive detection of picric acid based on a water-soluble fluorescent probe

A pyrene-based probe has been applied for the fluorescent detection of picric acid in aqueous media and on test strips.

Fundamental Study of Electrospun Pyrene-Polyethersulfone Nanofibers Using Mixed Solvents for Sensitive and Selective Explosives Detection in Aqueous Solution

Fluorescent pyrene-polyethersulfone (Py-PES) nanofibers were prepared through electrospinning technique using mixed solvents. The effects of mixed solvent ratio and polymer/fluorophore concentrations on electrospun nanofiber's morphology and its sensing performance were systematically investigated and optimized. The Py-PES nanofibers prepared under optimized conditions were further applied for highly sensitive detection of explosives, such as picric acid (PA), 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) in aqueous phase with limits of detection (S/N = 3) of 23, 160, 400, and 980 nM, respectively. The Stern-Volmer (S-V) plot for Py excimer fluorescence quenching by PA shows two linear regions at low (0-1 μM) and high concentration range (>1 μM) with a quenching constant of 1.263 × 10(6) M(-1) and 5.08 × 10(4) M(-1), respectively. On the contrary, S-V plots for Py excimer fluorescence quenching by TNT, DNT, and RDX display an overall linearity in the entire tested concentration range. The fluorescence quenching by PA can be attributed to the fact that both photoinduced electron transfer and energy transfer are involved in the quenching process. In addition, pyrene monomer fluorescence is also quenched and exhibits different trends for different explosives. Fluorescence lifetime studies have revealed a dominant static quenching mechanism of the current fluorescent sensors for explosives in aqueous solution. Selectivity study demonstrates that common interferents have an insignificant effect on the emission intensity of the fluorescent nanofibers in aqueous phase, while reusability study indicates that the fluorescent nanofibers can be regenerated. Spiked real river water sample was also tested, and negligible matrix effect on explosives detection was observed. This research provides new insights into the development of fluorescent explosive sensor with high performance.

Curcumin-cysteine and curcumin-tryptophan conjugate as fluorescence turn on sensors for picric Acid in aqueous media

Rapid detection of picric acid in real sample is of outmost importance from the perspective of health, safety, and environment. In this study, a very simple and cost-effective detection of picric acid is accomplished by developing a couple of biobased conjugates curcumin-cysteine (CC) and curcumin-tryptophan (CT), which undergo efficient fluorescence turn on toward picric acid in aqueous media. Both the probes experience about 26.5-fold fluorescence enhancements at 70 nM concentration of the analyte. Here, the fluorescence turn on process is governed by the aggregation induced emission, which is induced from the electrostatic interaction between the conjugates with picric acid. The detection limit of CC and CT are about 13.51 and 13.54 nM of picric acid, respectively. Importantly, both the probes exhibit high selectivity and low interference of other analogues toward the detection of picric acid. In addition, the probes are highly photostable, show low response time and are practically applicable for sensing picric acid in real environmental samples, which is the ultimate goal of this work.

Coupling paper-based microfluidics and lab on a chip technologies for confirmatory analysis of trinitro aromatic explosives

A new microfluidic paper-based analytical device (μPAD) in conjunction with confirmation by a lab on chip analysis was developed for detection of three trinitro aromatic explosives. Potassium hydroxide was deposited on the μPADs (0.5 μL, 1.5 M), creating a color change reaction when explosives are present, with detection limits of approximately 7.5 ± 1.0 ng for TNB, 12.5 ± 2.0 ng for TNT and 15.0 ± 2.0 ng for tetryl. For confirmatory analysis, positive μPADs were sampled using a 5 mm hole-punch, followed by extraction of explosives from the punched chad in 30 s using 20 μL borate/SDS buffer. The extractions had efficiencies of 96.5 ± 1.7%. The extracted explosives were then analyzed with the Agilent 2100 Bioanalyzer lab on a chip device with minimum detectable amounts of 3.8 ± 0.1 ng for TNB, 7.0 ± 0.9 ng for TNT, and 4.7 ± 0.2 ng for tetryl. A simulated in-field scenario demonstrated the feasibility of coupling the μPAD technique with the lab on a chip device to detect and identify 1 μg of explosives distributed on a surface of 100 cm(2).

A nitroaromatic fluorescence sensor from a novel tripyrenyl truxene

A new fluorescent sensor for 2-nitrophenol and picric acid is successfully synthesized from truxene and ethynyl pyrene.

A portable explosive detector based on fluorescence quenching of pyrene deposited on coloured wax-printed μPADs

A new technique for the detection of explosives has been developed based on fluorescence quenching of pyrene on paper-based analytical devices (μPADs). Wax barriers were generated (150 °C, 5 min) using ten different colours. Magenta was found as the most suitable wax colour for the generation of the hydrophobic barriers with a nominal width of 120 μm resulting in fully functioning hydrophobic barriers. One microliter of 0.5 mg mL(-1) pyrene dissolved in an 80:20 methanol-water solution was deposited on the hydrophobic circle (5 mm diameter) to produce the active microchip device. Under ultra-violet (UV) illumination, ten different organic explosives were detected using the μPAD, with limits of detection ranging from 100-600 ppm. A prototype of a portable battery operated instrument using a 3 W power UV light-emitting-diode (LED) (365 nm) and a photodiode sensor was also built and evaluated for the successful automatic detection of explosives and potential application for field-based screening.