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Ultrasensitive fluorescent detection of nitroexplosives by dihydro-oxoisobenzofuranyl-phthalazinone engendered from Cd(II) catalyzed cyclization of azinodimethylidyne-benzoic acid
Abstract
Chemical explosive detection through a feasible, straightforward and efficient technique is essential for human life safety. A Schiff base 2,2′-(azinodimethylidyne)-bis-benzoic Acid (2) was synthesized, characterized and inducibly cyclized to form...
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Picric acid, due to its low pKa value, possesses distinct physicochemical features from all other nitroaromatic derivatives, enabling the design of fluorescent probes for its sensitive and selective detection. The electrostatic interactions between the positive charge on the fluorescent probe, which arises due to protonation or the presence of a quaternary nitrogen, and the picrate anion increase the proximity between the fluorescent probe and the analyte, thus increasing the efficiency of the electron or energy transfer processes. This provides a salient feature for the design of fluorescent probes for the selective detection of picric acid over other nitroaromatic compounds. Here, the literature on the use of fluorescent small organic molecules for the selective detection of picric acid based on electrostatic interactions between positively charged/protonated fluorophores and their ability to selectively detect picric acid has been discussed. The fluorescent probes have been classified into three broad categories – neutral fluorophores, which are selectively protonated by picric acid; positively charged probes, which exhibit electrostatic interactions with the picrate anion; and metal complexes with protonatable sites. This comprehensive review will prove a benchmark for the future design of fluorescent probes for picric acid.
Apart from national security and military purposes, it is also of great importance to detect picric acid (PA) in aqueous solution for pollution control. Herein, we report a gold nanoparticle (AuNP)-based sensor for detection of PA in aqueous condition, based on metal-enhanced fluorescence (MEF) of poly(allylamine)hydrochloride (PAH). Notable enhancement in fluorescence intensity is observed when PAH is incubated with [email protected]2 nanoparticles, where silica shell controls the distance between gold core and PAH. Almost ∼ 280 fold enhancement is recorded when PAH is incubated with ∼ 45 nm diameter Au nanoparticles. A significant reduction in excited state lifetime followed the enhancement in fluorescence intensity, identifying the mechanism to be primarily obtained from the intrinsic radiative decay rate enhancement of PAH. The MEF sensor shows excellent selectivity for detection of PA in water, among similar electron deficient compounds via fluorescence quenching. The detection limit of the sensor is calculated to be 79 nM, in the linear range. Detection of PA is demonstrated in simulated water samples, where matrix effects are taken into account to assess the efficacy of the sensor.
A heterocycle compound, C 16 H 10 N 2 O 3 , has been synthesized by the reaction of hydrazine hydrate, 2-carboxybenzaldehyde and magnesium chloride hexahydrate in CH 3 CH 2 OH-water (v: v= 1: 1) solution. The crystal structure of (S)-2-(3-oxo-1, 3- dihydroisobenzofuran-1-yl) phthalazin-1(2H)-one has been determined by X-ray single crystal diffraction analysis. The result shows that the (S)-2-(3-oxo-1, 3- dihydroisobenzofuran-1-yl) phthalazin-1(2H)-one belongs to triclinic, space group P -1 with a = 7.2049(8) Å, b = 8.0215(9) Å, c = 10.9938(14) Å, a = 81.120(10)°, β = 85.939(10)°, γ =88.934(9)°, V = 626.17(13) Å ³ , Z = 2, Dc = 1.476 mg·m ⁻³ , μ = 0.104 mm ⁻¹ , F (000)=288, and final R 1 =0.0935, ωR 2 = 0.1018. The title compound molecules form 3D network structure by the interaction of aza-heterocycle and oxa-heterocycle of (S)-2-(3-oxo-1, 3-dihydroisobenzofuran-1-yl) phthalazin-1(2H)-one molecules.
A calix[4]arene conjugate possessing a tetrapyrenyl moiety at its upper rim (R) is designed as a receptor for sensing trinitrophenol (TNP). To understand the role of the calix[4]arene platform and that of pyrenyl moieties in R, two other control molecules were synthesized. These are as follows: the one possessing a tetraphenyl moiety in place of tetrapyrenyl (R
1
) and the other one is a p-pyrenyl-hydroxy benzene (R
2
) that is devoid of the calix[4]arene platform. The R shows high sensitivity toward TNP in tetrahydrofuran (THF) over eleven other nitroaromatic compounds (NACs) studied by exhibiting large fluorescence enhancement and hence is selective to TNP over the other NACs studied. However, the control molecules R
1
and R
2
showed only marginal fluorescence enhancement, supporting the need of a calixarene platform and the presence of a tetrapyrenyl moiety in the receptor system for the selective sensing of TNP. Further, R
1
and R
2
are not suitable for sensing, since these exhibit similar fluorescence response over several NACs studied. The binding of TNP by R has been addressed by fluorescence titration and isothermal titration calorimetry. The nature of the complexation of TNP by R has been revealed by the computational calculations, wherein the data showed the entrapment of TNP by two adjacent pyrene moieties via π-π stacking interactions. Such host-guest complexation is expected to restrict the mobility of the pyrene moieties present in R. The reduction of the flexibility of the pyrenyl moieties of R upon TNP binding is evidenced by the 1H NMR spectral study, wherein this acts as an additional evidence for the complexation. In the present study, the sensing of TNP by R has been shown in THF solution, on the surface of silica gel and the cellulose paper to result in lowest detection limits (LODs) of 1.5, 3.5, and 6.5 μM, respectively. Even the solid mixture of R and TNP showed LOD of 2.1 μmol. Since R is expected to show supramolecular aggregation that is dependent on the guest species, the corresponding details were probed by microscopy techniques, using scanning electron microscopy, atomic force microscopy, and transmission electron microscopy methods, and significant changes in the aggregation of R upon interaction with TNP were found. Such aggregation is responsible for the observed fluorescence enhancement. Thus, the tetrapyrenyl calix[4]arene conjugate (R) acts as a sensitive and robust platform for selective detection of TNP from a mixture of nitroaromatic compounds (NACs) wherein the fluorescence intensities can be imaged and managed by a cellular phone.
An optical sensing gadget using fluorescence of carbon dots (CDs) was developed to realize the in-field detection of 2,4,6-trinitrophenol (TNP) in tap water and lake water samples. Fluorescent CDs were prepared through a one-step hydrothermal synthetic route. The fluorescence spectra demonstrated that the CDs could specifically discriminate TNP from other nitroaromatic explosives in an aqueous medium. The fluorescence of the CDs was quenched linearly with the concentration of TNP in the range from 1 to 100 μM, with a detection limit of 0.48 μM (3σ/k). The detection mechanism was ascribed to the synergistic effect of the inner filter effect and electron transfer. In addition, a portable sensing gadget based on a high-precision RGB color sensor and a micro control unit was developed. With use of the sensing gadget and the CDs, TNP detection in tap water and lake water samples was realized. Importantly, the portable sensing gadget combined with highly stable, low-toxicity, and sensitive CDs might have great potential for application in extensive in-field sensing situations.
Picric acid (PA) as an environmental pollutant and high explosive, has recently received considerable attention. In this paper, a novel fluorescent and colorimetric chemo-probe (L) for the highly selective and sensitive detection of picric acid has been revealed. The probe was facilely constructed using rhodamine B, ethylenediamine and 4-(9H-carbazol-9-yl)benzoyl chloride. Significant fluorescence changes based on an intramolecular fluorescence resonance energy transfer (FRET) effect followed by a distinct color change from colorless to pink were observed after addition of picric acid to the probe solution. Selectivity measurements revealed that the as-synthesized probe exhibited high selectivity toward PA in the presence or absence of other analytes. The experimental titration results suggested that the as-synthesized probe is an effective tool for detection of PA with a nanomolar scale detection limit (820 nM) and could also serve as a “naked-eye” indicator for PA detection.
A new three-dimensional metal–organic framework (MOF) sensor with molecular formula (C2H6NH2)2[Tb2(ptptc)2(DMF)(H2O)]·DMF·6H2O (complex 1) has been constructed from terphenyl-3,3′,5,5′-tetracarboxylic acid (H4ptptc) and terbium nitrate under solvothermal conditions. The structure of complex 1 was characterized by single-crystal X-ray diffraction analysis (XRD), elemental analysis, IR spectroscopy and thermogravimetric (TG) analysis, and the purity was further confirmed by powder X-ray diffraction (PXRD) analysis. XRD analysis reveals that complex 1 crystallizes in a triclinic system P space group and consists of a three-dimensional anionic network which has one-dimensional channels. Fluorescence titration experiments showed that complex 1 displayed real-time, highly selective and sensitive fluorescence quenching behavior towards picric acid with a nanomolar scale experimental detection limit (100 nM). Recycling titration experiments suggested that the as-synthesized probe has good reversibility and can be used for at least five cycles in fluorescence titration experiments without obvious fluorescence intensity reduction or framework structure destruction. Furthermore, the high selectivity and sensitivity as well as good recyclability of complex 1 make it a potential fluorescent sensor for picric acid.
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants generated primarily during the incomplete combustion of organic materials (e.g. coal, oil, petrol, and wood). Emissions from anthropogenic activities predominate; nevertheless, some PAHs in the environment originate from natural sources such as open burning, natural losses or seepage of petroleum or coal deposits, and volcanic activities. Major anthropogenic sources of PAHs include residential heating, coal gasification and liquefying plants, carbon black, coal-tar pitch and asphalt production, coke and aluminum production, catalytic cracking towers and related activities in petroleum refineries as well as and motor vehicle exhaust. PAHs are found in the ambient air in gas-phase and as sorbet to aerosols. Atmospheric partitioning of PAH compounds between the particulate and the gaseous phases strongly influences their fate and transport in the atmosphere and the way they enter into the human body. The removal of PAHs from the atmosphere by dry and wet deposition processes are strongly influenced by their gas/particle partitioning. Atmospheric deposition is a major source for PAHs in soil.
Many PAHs have toxic, mutagenic and/or carcinogenic properties. PAHs are highly lipid soluble and thus readily absorbed from the gastrointestinal tract of mammals. They are rapidly distributed in a wide variety of tissues with a marked tendency for localization in body fat. Metabolism of PAHs occurs via the cytochrome P450-mediated mixed function oxidase system with oxidation or hydroxylation as the first step.
Several different remediation technologies have been tested in efforts to remove these environmental contaminants. Among them, bioremediation is showing particular promise as a safe and cost-effective option. In spite of their xenobiotic properties, a variety of genera of gram-positive and -negative bacteria, fungi and algae have been isolated and characterized for their ability to utilize PAHs.
The aim of this review is to discuss PAHs impact on the environmental and the magnitude of the human health risks posed by such substances. They also contain important information on concentrations, burdens and fate of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere. The main anthropogenic sources of PAHs and their effect on the concentrations of these compounds in air are discussed. The fate of PAHs in the air, their persistence and the main mechanisms of their losses are presented. Health hazards associated with PAH air pollution are stressed.
A series of core-shell porous aromatic frameworks (PAFs) are synthesized for selective detection of nitro-explosives. The conjugated core-shell PAFs possess large surface areas, which can facilitate the pre-concentration of a targeted analyte, leading to superior sensitivity. The tunable LUMO energy levels of these core-shell PAFs make them selectively detect high explosive TNT and TNP from other competing nitro compounds. Moreover, vapor phase detection of nitro aromatics using PPC-PPyS-PAF-2 exhibits a two dimensional fluorescence signal response toward different nitro aromatics. The power to accurately recognize nitro aromatic explosives in the fluorescent 2D map highlights the core-shell PAFs as very promising materials for nitro explosive sensing. This journal is
Porous organic polymers allow the integration of various π-units into robust porous π-networks, but they are usually synthesized as unprocessable solids with poor light-emitting performance as a result of aggregation-related excitation dissipation. Herein, we report a general strategy for the synthesis of highly emissive photofunctional porous polymer films on the basis of a complementary scheme for the structural design of aggregation-induced-emissive π-systems. We developed a high-throughput and facile method for the direct synthesis of large-area porous thin films at the liquid-electrode interface. The approach enables the preparation of microporous films within only a few seconds or minutes and allows precise control over their thickness with sub-nanometer precision. By virtue of rapid photoinduced electron transfer, the thin films can detect explosives with enhanced sensitivity to low parts-per-million levels in a selective manner.
© 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
The key types of low-molecular-mass chemosensors for the detection of nitroaromatic compounds representing energetic substances (explosives) are analyzed. The coordination and chemical properties of these chemosensors and structural features of their complexes with nitroaromatic compounds are considered. The causes and methods for attaining high selectivity of recognition are demonstrated. The primary attention is paid to the use of low-molecular-mass chemosensors for visual detection of explosives of this class by colorimetric and photometric methods. Examples of using photo- and chemiluminescence for this purpose are described. A separate section is devoted to electrochemical methods of detection of nitroaromatic compounds. Data published from 2000 to 2014 are mainly covered. The bibliography includes 245 references.
Tuning fluorescence properties and frontier orbital energy levels of hyperbranched conjugated polymer nanoparticles (HCPN-NMe) by the facile introduction of terminal N,N-dimethylaniline groups via an intramolecular charge transfer (ICT) process between the nanoparticle core and the terminal groups was demonstrated for the first time. Compared with the similar hyperbranched conjugated polymer nanoparticles with terminal benzene groups (HCPN-H), a large Stokes shift and remarkable fluorescence solvatochromism were observed for HCPN-NMe. Based on the environmental-sensitive ICT emission, HCPN-NMe can be used as a fluorescence sensor for the detection of water in THF with enhanced sensitivity.
Highly fluorescent, multifunctional and thermoreversible conformational switching (1) has been designed and developed by embedding two imidazo[1,2-c]quinazoline (IQ) units in the pyridyl scaffold. The origin of the conformational and optical switching of 1 to 1' has been established by various studies and by developing a model compound.
A novel fluorescent film was fabricated by doping the aggregates of hexaphenylsilole (HPS) into a chitosan film. It was demonstrated that the fluorescence emission of the film is stable, sensitive and highly selective to the presence of picric acid (PA). The detection limit for PA is about 2.1 × 10−8 mol/L. Introduction of 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), nitrobenzene (NB), phenol, benzene, toluene, methanol, ethanol, and zinc nitrate (Zn(NO3)2) had little effect upon the fluorescence emission of the film. The selectivity of the film was attributed to the specific electrostatic association effect of the protonated substrate film to picrate anion and the screening effect of the film to the interferents. The network structure of the substrate film is also favourable for the stabilization of the fluorescence emission of the hybrid film, by preventing the further aggregation of silole aggregates. Fluorescence lifetime measurements revealed that the quenching is static in nature. Furthermore, the quenching process is fully reversible. Considering the simplicity of the preparation and the outstanding performance of the hybrid film, it is anticipated that it could be developed into a real-life PA sensor.
New concave host molecules show strong noncovalent binding of hydroxybenzene derivatives by an induced fit mechanism (Ka up to 3.4 × 106 dm3 mol–1).
Due to rising threats of terrorism, pollution, timely and rapid detection of 2,4,6-trinitrophenol (TNP) and 2,4,6-trinitrotoluene (TNT) explosives has earned paramount significance. Herein, easily synthesized fluorenone sensor 3 was found selective towards the detection of TNP with a limit of detection (LOD) value of 0.5 nM. The fluorescence detection of TNP was achieved through the electrostatic interaction between sensor and TNP. Moreover, sensors 4 and 5 were rationally synthesized for selective nanoscale detection of TNT (LODs; 5.0 nM (4) and 7.0 nM (5)) through fluorescence emission enhancement response. Selective detection of TNT was accomplished through blockage of ICT and ESIPT in sensors. Sensing mechanisms were supported by ¹H NMR titration, Job’s plots, computational methodologies, and DLS analysis. Interestingly, sensor 3 also showed selective colorimetric response towards TNP while sensors 4 and 5 displayed selective colorimetric detection of TNT explosive. Explosive responsive test kits were also prepared for on-site detection of TNP by sensor 3 and TNT by sensors 4 and 5. Moreover, sensors 3, 4, and 5 were successfully applied in the analysis of industrial effluents for the rapid detection of explosives.
In this paper, polyvinylpyrrolidone-templated copper nanoclusters (PVP–CuNCs) were synthesised using a hydrothermal method. Through the electrostatic interaction between PVP–CuNCs and rhodamine 6G, a dual-emission ratiometric fluorescent probe was constructed, and two well-separated emission peaks appeared at 420 nm and 570 nm. The selective detection of rutin and picric acid was achieved by fitting the relationship between the ratiometric fluorescence intensity (F420/F570) and the concentration of the target detection substance. The limits of detection of rutin and picric acid were 0.84 μM and 0.27 μM, respectively. The synthesised material has high stability and successfully allows the determination of rutin content in drugs and picric acid content in water samples with satisfactory recoveries.
Owing to the escalating threat of criminal activities and pollution aroused by 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenol (TNP), development of a proficient sensor for the detection of these explosives is highly demanded. Herein, a water-soluble ionic liquid-tagged fluorescent probe, 1-ethyl-3-(3-formyl-4-hydroxybenzyl)-1H-benzimidazol-3-ium chloride (EB-IL) has been designed and synthesized for the detection of TNT and TNP in 100 % aqueous medium. The EB-IL fluorescent probe displayed strong cyan-blue fluorescence at 500 nm which gets quenched upon the addition of TNT/TNP over other concomitant nitro-compounds. The distinct binding response of EB-IL towards TNT could be due to the formation of hydrogen bonding between the acidic proton of benzimidazolium (C2–H) and nitro group of TNT. Meanwhile, the selective binding of TNP with EB-IL could be due to the exchange of counter Cl⁻ anion of EB-IL with picrate anion. The fluorescence quenching of EB-IL by TNT could be attributed to the resonance energy transfer (RET) and that of TNP is ascribed to the anion-exchange process. The developed sensor is extremely selective and sensitive towards TNT and TNP with high quenching constants of 1.94 × 10⁵ M⁻¹ and 2.32 × 10⁶ M⁻¹ and shows a lower detection limit of 159 nM and 282 nM, respectively.
Easy and fast detection of aquatic pollutants is highly desirable to avoid water contamination. This work is focused on the fluorescence detection of picric acid in water using sol–gel ceria nanoparticles synthesized in the presence of fenugreek extract. The nanostructure and material morphology of cubic phase fluorite ceria are analyzed using X-ray diffraction, Fourier Transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Optical studies indicated its strong absorbance and intense photoluminescence emission. Sensing of picric acid is performed here by investigating the fluorescence quenching of the nanoparticle dispersion. Ceria showed a linear concentration range of 0.33–41.6 µM with a lower detection limit of 0.33 µM picric acid. The strong binding interaction between the nanoceria and picric acid is indicated from the high Stern–Volmer constant. The CeO2 nanoparticles are selective to picric acid with other phenolic compounds and also found to be sensitive to picric acid in real water samples.
Nitroaromatic effluents are common wastes generated from different industrial activities. These wastes can cause various environmental problems due to their toxicity on living organisms and difficulties to decompose either chemically or biologically. However, picric acid (2,4,6-trinitrophenol, TNP) could be used as a sole carbon, nitrogen, and energy source by a few bacterial cells. In this study, a bacterial strain isolated from the Red Sea, Jeddah, Saudi Arabia, has been shown to utilize picric acid as a sole carbon and nitrogen source at a relatively high concentration. The growth medium altered from yellow into the orange-red color (hydride-Meisenheimer complex) after 48 h of incubation as detected using High-Performance Liquid Chromatography (HPLC). The stoichiometric release of 0.285 mol of nitrite showed strong evidence that the picric acid was completely mineralized. Molecular identification using 16S rRNA analysis indicated that the isolated strain is Enterococcus thailandicus RF1 (Genbank Accession No. MN960654). This strain is capable of utilizing TNP aerobically at pH 7.0 and 30 °C with nitrite release. Furthermore, Enterococcus thailandicus RF1 cells were immobilized by adsorption on polyurethane foam and TNP degradation was enhanced and increased to 1.12-folds of free cells. The immobilized cells were found to be used efficiently for bioremediation of TNP from wastewaters.
A sensitive and selective detection of 2,4,6-trinitrophenol (TNP) is of great importance for the national security and pollution control. Herein, we report a novel 2,7-carbazole and tetraphenylsilane based polymer PCzSi, and applied it for nitroaromatics sensing. PCzSi shows a deep-blue photoluminescence (PL) emission peaking at 410 nm with a high glass transition temperature and good thermal stability. During the PL titration experiments, the polymer exhibited an obvious PL quenching phenomenon, with different extent towards different nitroaromatic analytes. Remarkably, a selective detection of TNP was realized using our polymer sensor, and the KSV value towards TNP is two orders of magnitude higher than 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitrobenzene (TNB). The sensing mechanism was further discussed to clarify the selectivity towards TNP based on the analysis of UV-vis absorption, excitation and PL spectra and cyclic voltammogram results. In addition, the paper strips were fabricated to detect both TNP solution and vapor, which demonstrates a good potential of our polymer for practical and on-site application as a solid PL sensor of TNP.
The simple and rapid detection of chemical explosives is important for life safety and social stability, and correlative explorations of new material or system have attracted more and more attention. Two kinds of pyrene-based polymers (PyM and PyP) were prepared by Heck-coupling reaction in this work. The obtained fluorescent materials exhibited excellent fluorescence properties and showed high selectivity and sensitivity for the detection of trinitrophenol (TNP). Furthermore, a portable paper sensor based on this material for fast detection of TNP was explored. The obtained fluorescent materials were further applied in cell imaging. The construction strategy of fluorescent materials involved in this paper expands a new perspective for the design of fluorescent probes for detecting nitroaromatic compounds.
The sensitive and selective detection of nitroexplosive molecules thorough a simple methodology has received a significant field of research affecting global security and public safety. In the present study, the synthesis of anthracene-based chalcone (S1) was conducted using a simple condensation method. S1 was found to exhibit unique properties, such as aggregation-induced emission in solution and mechanochromic behavior in solid state. A fluorescent aggregate was applied to sense electron-deficient picric acid (PA) and 2,4-dinitrophenol (2,4-DNP) in an aqueous solution. Notably, the developed test strip-based sensor (S1) could be used to effectively detect PA and 2,4-DNP, which were visualized by the naked eye. Photophysical analysis revealed the occurrence of an electron transfer from electron-rich S1 to the electron-deficient nitro compounds, which was confirmed using density functional theory and ¹H-nuclear magnetic resonance studies. In addition, the observed results confirmed the simple synthesis of S1 as a promising material for the development of test strip-based sensor devices for the detection of toxic and explosive aromatic nitro molecules.
The detection of o-nitrophenol in the environment is of great significance to environmental protection. In this paper, the fluorescence sensor of CsPbBr3@SHFW was synthesized by ultrasonic assisted which was using the perovskite quantum dots as the fluorescence source and super hydrophobic porous organic polymer framework (SHFW) as the protective layer. Then CsPbBr3@SHFW was used to detect o-nitrophenol in dichloromethane. Under the optimum conditions, the detection limit of CsPbBr3@SHFW was 7.69×10-3 µM, and the linear range was 0-280 µM. It was also proved that the fluorescence quenching of this work is electron transfer. This work provided help for the construction of stable perovskite quantum dot sensor and the application of perovskite quantum dot sensor in the field of fluorescence detection.
In this study, we presented a water-soluble fluorescent probe (HBN) for 2,4,6-trinitrophenol (TNP) detection by introducing a quaternary ammonium group. Probe HBN exhibited significant fluorescence quenching toward 2,4,6-trinitrophenol via electrostatic and charge transfer interactions. The obtained results demonstrated that probe HBN could rapidly (< 30 s) and selectively detect 2,4,6-trinitrophenol over other nitroaromatic compounds and relevant ions with a low detection limit of 57 nM. The excellent sensing properties of probe HBN enable its applications in visual detection of 2,4,6-trinitrophenol by a paper test system and monitoring 2,4,6-trinitrophenol in environmental water systems.
In this communication, a bluish-green fluorescent histidine was synthesized by direct heating of an aqueous solution of histidine at 70°C for 48 h and characterized by various techniques like FT-IR, UV–Vis,fluorescence, FESEM and DLS. Then, the sensing ability of the fluorescent histidine was applied towards nitroaromatic compounds in pure aqueous medium. The fluorescence of fluorescent histidine at 450 nm was selectively quenched upon addition of picric acid (PA) and para-nitrophenol (PNP) through energy transfer mechanism among the other tested nitroaromatic compounds. With the proposed sensor, the PA and PNP can be estimated down to 27.16 × 10⁻⁷ M and 35.26 × 10−7M, respectively without any interference from other tested nitroaromatic compounds. Finally, the practical utility of the developed sensor was applied for the detection of PA and PNP in real environmental samples.
Metal organic frameworks (MOFs) have been hotly concerned due to their unique structure and properties. A new highly fluorescent MOF was developed via post-synthesis of UIO-66-NH 2 through an efficient click reaction with 1-ethynylpyrene for the 2,4,6-trinitrophenol (PA) detection which named UIO-66-Py. It exhibited a significantly enhanced fluorescence intensity than UIO-66-NH 2 and showed excellent selectivity and sensitivity for sensing PA in solution via the fluorescence quenching mechanism. The UIO-66-Py showed an 85% fluorescence quenching efficiency with 0.203 mM PA and the detection limit was 4.5 × 10 ⁻⁷ M. The excellent selectivity of the probe was ascribed to the hydrogen bond interaction between UIO-66-Py and PA as evidenced by FT-IR. The hydrogen bond interaction promoted the photo-induced electron transfer (PET) between UIO-66-Py and PA which leading to the better selectivity of UIO-66-Py for PA detection over TNT. This post-synthetic modification idea provided a strategy for the development of MOFs with multifunctional sensing.
A simple, rapid and low cost sensing method for the fluorescent detection of TNP in 100% aqueous media was successfully developed based on a commercial probe. Under the non-covalent interactions between TNP with probe, a ratiometric output signal was achieved, which can be applied in real samples test.
Phthalazin-1(2H)-one is a diazaheterobicycle found in a wide variety of synthetic molecules relevant to several branches of chemistry, including medicinal chemistry. The versatility of phthalazinone core in drug discovery has promoted the search for new synthetic methods to get access to differently substituted and functionalized derivatives. This review highlights the latest advances in synthesis of phthalazinone derivatives that have relevance to drug discovery processes, analyzing modifications of classical methodologies based on [4 + 2] two-component cyclocondensations as well as novel multicomponent approaches, mostly based on a [3 + 2+1] three-component strategy and very attractive not only because of its synthetic efficiency but also in the matter of environmental compatibility.
A series of 2‐arylbenzothiazoles has been designed and synthesized as chromogenic and fluorescent probes for the detection of picric acid (PA) over other nitro analytes. A straightforward condensation of a variety of aryl nitriles with 2‐aminobenzenethiol under metal‐ and base‐free conditions afforded the corresponding products in 26–98% yields. All 2‐arylbenzothiazoles could efficiently sense PA at micromolar levels. The highly sensitive compound 2‐(4‐((2‐methyl‐1H‐imidazol‐1‐yl)methyl)phenyl)benzo[d]thiazole (3c) showed 95% fluorescence quenching on addition of 1.0 eq of PA which can be attributed to hydrogen bonding and ground state charge transfer complex formation with a detection limit of 19.0 μM. The high sensitivity of 3 c for PA detection was also established by test strips experiment. The sensing mechanism was explored by ¹H NMR titrations and Job's plot.
In this paper, the synthesis and spectral properties of a fluorescent probe Nph-An for TNP detection has been introduced and its sensing mechanism has been studied with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. For TNP detection in aqueous solution the probe shows high sensitivity, selectivity and efficiency. The theoretical results demonstrate that the excited-state intermolecular hydrogen bonding (H–B) plays an important role for the TNP detection. In the excited state, the intermolecular H–B between Nph-An and TNP is strengthened, and thus strongly facilitates the nonirradiative PET process to induce the fluorescence quenching. Whereas, the probe Nph-An emits strong fluorescence because of the intramolecular charge transfer (ICT) properties, which is confirmed by the solvatochromism effect. The calculated absorption spectra of Nph-An and Nph-An + TNP agree well with the experimental values and theoretical analysis provides a detailed and clear explanation of the sensing mechanism.
A Zinc(II) coordination polymer {[Zn3(mtrb)3(btc)2]•3H2O}n (1) was synthesized and characterized (mtrb = 1,3-bis(1,2,4-triazole-4-ylmethyl)benzene, btc = 1,3,5-benzenetricarboxylate). 1 shows an unusual (3,4,4)-coordinated self-catenated 3D network with the point symbol of {63}2{62.82.102}{64.82}2. 1 is the first luminescent sensor for detection of 2-amino-4-nitrophenol (ANP). 1 is also a good luminescence sensor for detection of TNP, 2,4-DNP, 4-NP, ANP and 2-NP in MeOH, especially for TNP. The order of detection efficiency is TNP > 2,4-DNP > 4-NP > ANP > 2-NP. 1 also exhibits high sensitive and selective luminescence sensor for detection of Fe3+, Cr2O72- and CrO42- in aqueous solution. Our experiments showed that the presence of interfering ions did not make any significant effect to in the sensing the Fe3+, Cr2O72- or CrO42- ion. The detection limits for TNP, ANP, Fe3+, Cr2O72- and CrO42- are 0.22 M, 4.12 M, 1.78 M, 2.83 M, and 4.52 M, respectively. The luminescence sensor is stable and can be recycled for detection at least five times. The possible quenching mechanisms were discussed. 1 is also an effective photocatalyst for degradation of methylene blue (MB) under visible or UV light irradiation.
We have designed and developed three single-molecule fluorescent probes differing in the number of amino groups. 5-((4,6-diamino-1,3,5-triazin-2-yl)amino)isophthalic acid (H2ATAIA, 1), 5-((4-amino-6-methoxy-1,3,5-triazin-2-yl)amino)isophthalic acid (H2AMTAIA, 2) and 5-((4,6-dimethoxy-1,3,5-triazin-2-yl)amino)isophthalic acid (H2DMTAIA, 3), from cheap and readily available starting materials via simple procedures in high yields for demonstrating their application in highly selective and ultrafast sensing of 2,4,6-trinitrophenol (TNP) in water (slurry mode). Probes 1-3 have been characterized by various analytical techniques, such as melting point, FTIR, UV-vis and NMR (1H and 13C) spectroscopy and high resolution mass spectrometry (HRMS). It is quite evident that the effect of an amino group is more prominent compared to a methoxy group towards the selective detection of TNP over other potentially interfering nitro compounds. The detection limit for the diamino derivative was found to be 120 ppb compared to those with one amino or no amino group (0.8 ppm and 1.2 ppm, respectively). We also report the ideal real time detection of TNP through contact mode or instant spot via paper strips. Spectral overlap, time-resolved fluorescence studies, quantum yield, Stern-Volmer plots, field emission scanning electron microscopy (FESEM) and DFT calculations have been used to establish their mechanism of action. Furthermore, competitive nitro-analyte tests demonstrate that the selectivity for TNP is more in 1 compared to 2 and 3. To the best on our knowledge, we have demonstrated for the first time molecular decoding of TNP based on the dual read-out identification scheme constructed from life-time and quantum yield. These probes have been found to be highly photostable in presence of acidic TNP as well as recyclable without much loss of sensitivity up to five cycles. These results vividly depict that these are excellent candidates for environmental monitoring.
A covalent triazine-based framework with tetraphenylthiophene backbone (TTPT) was prepared by the AlCl3 catalyzed Friedel-Crafts reaction of commercially available materials 2,4,6-trichloro-1,3,5-triazine with tetraphenylthiophene in dichloromethane. This is the first report about the tetraphenylthiophene-based covalent triazine-based framework, which belongs to nitrogen-rich conjugated microporous polymer. The surface area of TTPT was 315.5 m2 g−1. Taking advantages of its large surface area and strong fluorescence, TTPT showed very fast responses and high sensitivity, selectivity to sensing o-nitrophenol, with an SV constant of 6.20×103 L mol−1. The limit of detection (LOD) was 2.18×10-9 mol L-1. Furthermore, TTPT displayed efficient, reversible adsorption of radioactive I2 in vapor (up to 1.77 g g-1) and in solution.
A novel hybrid fluorophore (FHPY) has been synthesized based on condensation reaction of two standard fluorescent hydrophobic-hydrophilic molecules viz. pyrene and fluorescein with an objective to tune the aggregation induced emission (AIE) along with morphology. Owing to distinct photophysical properties of pyrene and fluorescein, the hybrid FHPY dramatically exhibits the flourescence change from colourless to yellow-green via blue colour upon varying the volume fraction of water (poor solvent) in methanol (good solvent). FHPY has not been only exhibited AIE, but also outstanding quantum yield (F) 97% at 70% water fraction in methanol (70:30, v/v). We attribute the reason behind tuning of AIE and quantum yield to the opening of lactam ring of fluorescein as well as the amassing of hydrophobic pyrene at certain water fraction. The mechanism involved in AIE has been well supported by a detailed UV-vis, fluorescence, lifetime, SEM, AFM, DFT, PXRD and 1H NMR experiments. In addition, FHPY served as good candidate for live cell imaging process of HeLa cells.
A new type of chemosensor-based approach to the detection of 2,4,6-trinitrophenol (TNP) is described in this paper. Two hexahomotrioxacalix[3]arene-based chemosensors 1 and 2 were synthesized through click chemistry, which exhibited high binding affinity and selectivity toward TNP as evidenced by UV-vis and fluorescence spectroscopy studies. 1H NMR titration analysis verified that CH⋯O hydrogen bonding is demonstrated as the mode of interaction, which possibly facilitates effective charge-transfer.
This study reports the synthesis and photophysical properties of a star-shaped, novel, fluoranthene-tetraphenylethene (TFPE) conjugated luminogen, which exhibits aggregation-induced blue-shifted emission (AIBSE). The bulky fluoranthene units at the periphery prevent intramolecular rotation (IMR) of phenyl rings and induces a blueshift with enhanced emission. The AIBSE phenomenon was investigated by solvatochromic and temperature-dependent emission studies. Nanoaggregates of TFPE, formed by varying the water/THF ratio, were investigated by SEM and TEM and correlated with optical properties. The TFPE conjugate was found to be a promising fluorescent probe towards the detection of nitroaromatic compounds (NACs), especially for 2,4,6-trinitrophenol (PA) with high sensitivity and a high Stern-Volmer quenching constant. The study reveals that nanoaggregates of TFPE formed at 30 and 70 % water in THF showed unprecedented sensitivity with detection limits of 0.8 and 0.5 ppb, respectively. The nanoaggregates formed at water fractions of 30 and 70 % exhibit high Stern-Volmer constants (Ksv =79 998 and 51 120 m(-1) , respectively) towards PA. Fluorescence quenching is ascribed to photoinduced electron transfer between TFPE and NACs with a static quenching mechanism. Test strips coated with TFPE luminogen demonstrate fast and ultra-low-level detection of PA for real-time field analysis.
TPE-based oxacalixarenes were synthesized by one-pot condensation. Their AIE properties and self-assembled structures in the solid state can be tuned effectively by utilization different building blocks in the synthetic process. Moreover, the oxacalixarene 1a can be assembled into nanoparticles in THF/water and can be used as a detector for nitroaromatic explosives, such as TNP.
A novel and sensitive fluorescence sensor has been designed by click chemistry. Based on the obvious and selective fluorescence quenching of anthryl calix[4]arene, a sensitive and robust platform were developed for visual detection of picric acid (TNP) in the mixture of nitro aromatics. The computational calculations revealed the formation of host-guest complex driven by pi-pi stacking interactions.
Rapid and sensitive detection of nitroaromatic explosives have attracted considerable attention due to their serious harm to our world. In this work, two porous luminescent covalent-organic polymers (COP-401 and COP-301) have been synthesized through copolymerization of double ligands. Results indicate that the two COPs with high thermal stability show significant luminescence quenching effects for nitroaromatic explosives. In particular, the two COPs exhibit not only high sensitivity (about 1 ppm) for nitoraromatic explosives, but also extremely high selectivity for 2,4,6-Trinitrophenol (PA), which suggests that they are promising luminescent probe for highly sensitive and selective detection of nitroaromatic explosives, especially for PA.
Four imidazoanthraquinone derivatives (2a-d) were synthesized and characterized and their coordination behavior against selected anions and cations tested. Acetonitrile solutions of probes showed charge-transfer absorptions in the 407-465 nm range. The four probes emitted in the 533-571 nm interval. The recognition ability of 2a-d was evaluated in the presence of F(-), Cl(-), Br(-), I(-), OCN(-), BzO(-), ClO4(-), AcO(-), HSO4(-), H2PO4(-), and CN(-). Only F(-), AcO(-), and H2PO4(-) induced a new red-shifted absorption band that was attributed to a deprotonation process involving the amine moiety of the imidazole ring. Moreover, upon increasing quantities of F(-), AcO(-), and H2PO4(-), moderate quenching was induced in the emission of 2a-d together with the appearance of a new red-shifted band. The UV-visible and emission behavior of the four probes in the presence of Cu(2+), Co(2+), Mg(2+), Fe(3+), Ba(2+), Fe(2+), Ni(2+), Ca(2+), Zn(2+), Pb(2+), Cd(2+), Cr(3+), Al(3+), K(+), and Li(+) was also assessed. Only addition of Fe(3+), Cr(3+), and Al(3+) caused a new blue-shifted band in 2a-d that was ascribed to a preferential coordination with the acceptor part of the probes. Moreover, an important quenching of the emission was observed which was ascribed to the interaction between these trivalent cations and 2a-d.
“ United we stand, divided we fall .”–Aesop.
Aggregation‐induced emission (AIE) refers to a photophysical phenomenon shown by a group of luminogenic materials that are non‐emissive when they are dissolved in good solvents as molecules but become highly luminescent when they are clustered in poor solvents or solid state as aggregates. In this Review we summarize the recent progresses made in the area of AIE research. We conduct mechanistic analyses of the AIE processes, unify the restriction of intramolecular motions (RIM) as the main cause for the AIE effects, and derive RIM‐based molecular engineering strategies for the design of new AIE luminogens (AIEgens). Typical examples of the newly developed AIEgens and their high‐tech applications as optoelectronic materials, chemical sensors and biomedical probes are presented and discussed.
Molecularly imprinted polymers (MIPs) with trinitrophenol (TNP) as dummy template molecule capped CdTe quantum dots (QDs) were prepared by using 3-aminopropyltriethoxy silane (APTES) as functional monomer and tetraethoxysilane (TEOS) as cross-linker, through seed growth method via a sol-gel process, i.e., DMIP@QDs, for sensing of 2,4,6-trinitrotoluene (TNT) based on electron transfer induced fluorescence quenching. With the presence and increase of TNT in sample solutions, a Meisenheimer complex was formed between TNT and the primary amino groups on the surface of QDs, then the energy of QDs transfered to the complex, resulting in the quenching of QDs and thus decreasing the fluorescence intensity, by which the TNT could be sensed optically. The DMIP@QDs generated a significantly reduced fluorescent intensity within less than 10 min upon binding TNT. The fluorescence quenching fractions of the sensor presented a satisfactory linearity with TNT concentrations in the range of 0.8-30 μM, and its limit of detection could reach 0.28 μM. The sensor exhibited distinguished selectivity and high binding affinity to TNT over its possibly competing molecules of 2,4-dinitrophenol (DNP), 4-nitrophenol (4-NP), phenol and dinitrotoluene (DNT), due to more nitro groups in TNT and thereby stronger electron-withdrawing ability as well as its high similarity in shape and volume to TNP. The sensor had been successfully applied to determine the TNT in soil samples, and the average recoveries of the TNT at three spiking levels ranged from 90.3% to 97.8% with relative standard deviations below 5.12%. The results provided an effective way to develop sensors for rapid recognition and determination of hazardous materials from complex matrices.