Showing papers on "Fluorene published in 2020"
TL;DR: Overall, this study offers a developed adsorbent that has the advantage of being recyclable, low cost, biodegradable and biocompatible for effectively removing PAHs from aqueous solution.
44 citations
TL;DR: In this article, the authors showed that the performance of fluorene-type polymer photocatalysts for hydrogen production from water in the presence of a sacrificial hole scavenger is significantly improved by the incorporation of heteroatoms into the bridge-head.
Abstract: The photocatalytic performance of fluorene-type polymer photocatalysts for hydrogen production from water in the presence of a sacrificial hole scavenger is significantly improved by the incorporation of heteroatoms into the bridge-head. This improvement can be explained by a combination of factors, including changes in thermodynamic driving-force, particle size, dispersibility under photocatalytic conditions, and light absorption, all of which vary as a function of the heteroatom incorporated.
44 citations
TL;DR: The stainless steel mesh, in the form of the disk, was coated with graphene oxide and poly(dimethylsiloxane) (GO-PDMS) by sol–gel technique to achieve fast isolation and preconcentration of polycyclic aromatic hydrocarbons (PAHs) from real water samples.
Abstract: The stainless steel mesh, in the form of the disk, was coated with graphene oxide and poly(dimethylsiloxane) (GO-PDMS) by sol–gel technique. The coated stainless steel meshes are loaded in the mini-column as solid-phase extraction cartridge for the fast isolation and preconcentration of polycyclic aromatic hydrocarbons (PAHs) from real water samples. The extracted PAHs (naphthalene, acenaphthene, acenaphthylene, anthracene, benz[a]anthracene, fluorene, and pyrene) were quantified by gas chromatography-mass spectrometry. The operation parameters affecting the extraction efficiency including sample volume, desorption conditions, and ionic strength were investigated. At optimized conditions, the linearity of this method is obtained from 0.001 to 20 ng mL−1 with 0.2 to 1.0 pg mL−1 limit of detection. For 5 replicates at 3 spiking levels (0.1, 1, and 10 ng mL−1), the relative standard deviations between 4.0 and 6.3% were achieved. The absolute extraction recovery varied from 89.1 to 94.7%. The enrichment factors were in the range of 2227–2367. The method has been employed in the determination of PAHs in the real water samples including well water, tap water, river water, and wastewater. Relative recoveries are between 95.2 and 100.9%.
40 citations
TL;DR: In this paper, a high-efficiency host material for single-layer phosphorescent organic light-emitting diodes (SL-PhOLEDs) is reported, which is constructed on the association of an electron-rich phenylacridine unit connected by a spiro carbon atom to an electrondeficient 2,7-bis(diphenylphosphineoxide)-fluorene.
Abstract: Herein, a high-efficiency host material for single-layer phosphorescent organic light-emitting diodes (SL-PhOLEDs) is reported. This host material is synthesized via an efficient approach and is constructed on the association of an electron-rich phenylacridine unit connected by a spiro carbon atom to an electron-deficient 2,7-bis(diphenylphosphineoxide)-fluorene. In addition to a high ET value and adequate highest occupied molecular orbital/lowest unoccupied molecular orbital energy levels, the key point in this molecular design is the suitable balance between hole and electron mobilities, which leads to a high-performance blue SL-PhOLED with an external quantum efficiency of 17.6% (current efficiency = 37.8 cd A−1 and power efficiency = 37.1 lm W−1) and a low Von of 2.5 V. This performance shows that the molecular design of the present host fulfills the criteria required for high-efficiency SL-PhOLEDs. The present performance is one of the highest reported to date for blue SL-PhOLEDs and more importantly shows the potential of such a molecular design to reach very high-performance single-layer devices.
39 citations
TL;DR: In this article, a series of molecular dibenzo[b,d]thiophene sulfone and fluorene oligomers were used as well-defined model systems to probe the relationship between photocatalytic activity and structural features such as chain length and planarity.
Abstract: Most organic semiconductor photocatalysts for solar fuels production are linear polymers or polymeric networks with a broad distribution of molecular weights. Here, we study a series of molecular dibenzo[b,d]thiophene sulfone and fluorene oligomers as well-defined model systems to probe the relationship between photocatalytic activity and structural features such as chain length and planarity. The hydrogen evolution rate was found to vary significantly with bridge head atom, chain length, and backbone twisting. A trimer (S3) of only three repeat units has excellent activity for proton reduction with an EQE of 8.8% at 420 nm, approaching the activity of its polymer analogue and demonstrating that high molar masses are not a prerequisite for good activity. The dynamics of long-lived electrons generated under illumination in the S3 oligomer are very similar to the corresponding polymer, both under transient and quasi-continuous irradiation conditions.
35 citations
TL;DR: A tailor-designed novel fluorene-based organic phosphor with efficient spin-orbit coupling activated by bromine, aromatic carbonyl, and spiro-annulated phenyl moieties is reported for OLED devices incorporating metal-free organic phosphors.
Abstract: Metal-free organic phosphorescent materials are promising alternatives to the organometallic counterparts predominantly adopted in organic light-emitting diodes due to their low cost, chemical stability, and large molecular design window. However, only a few reports on OLED devices incorporating metal-free organic phosphors have been presented due to the lack of understanding on material properties, device physics, and device fabrication processes. Here, we report a tailor-designed novel fluorene-based organic phosphor with efficient spin–orbit coupling activated by bromine, aromatic carbonyl, and spiro-annulated phenyl moieties. Photoluminescence quantum yield of 24.0% was achieved when doped in optically inert amorphous polymer hosts. Effects of OLED host materials on the phosphor were investigated in terms of color purity, suppression of exciplex emission, and restraint of molecular motion. Bright green phosphorescence emission (1430 cd/m2 at 100 mA/cm2) was realized with 2.5% maximum external quantum ...
28 citations
TL;DR: Based on the structural diversity and the superior luminescence properties of 4,4-(9,9-dimethyl-9H-fluorene-2,7-diyl) dibenzoic acid (H2DLDA), a series of new lanthanide coordination compounds [Ln(DLDA)(DMF)(H2O)(COO)]n (Sm (1), Eu (2), Ce (3), Nd (4), Gd (5)) were successfully prepared by the reaction of H 2DLDA, which is a
27 citations
TL;DR: In this article, three simple donor (D)-π-D triphenylamine-based hole transporting materials with biphenyl, fluorine or carbazole derivative as π-linker are prepared by facile process.
27 citations
TL;DR: A series of comb-shaped fluorene-based poly (arylene ether sulfone nitrile) (CFPESN-x) was synthesized as anion exchange membranes (AEMs).
24 citations
TL;DR: The Al-doped mesoporous crystalline material-41 composite was prepared and applied as fiber coating material of headspace solid-phase microextraction (HS-SPME) for extraction of polycyclic aromatic hydrocarbons (PAHs) from human urine with reasonable recoveries.
24 citations
TL;DR: A novel Pd(0)-catalyzed [4+1] spiroannulation of simple o-iodobiaryls with bromonaphthols for the one-step construction of [4,5]-spirofluorenes in high yields with excellent functional group tolerance.
Abstract: Rapid assembly of fluorene-based spirocycles represents a highly significant but challenging task in organic synthesis. Reported herein is a novel Pd(0)-catalyzed [4+1] spiroannulation of simple o-iodobiaryls with bromonaphthols for the one-step construction of [4,5]-spirofluorenes in high yields with excellent functional group tolerance. Noteworthily, these valuable fluorene-based coumarin skeletons can enrich the database of C-coumarins and exhibit excellent spectroscopic properties.
TL;DR: The PAH sorption results indicated that the adsorption mechanism is based on PAH hydrophobicity, and π-π electron-donor-acceptor interaction with surfactant.
TL;DR: The results suggest that the heterogeneous photochemical reaction of NO2 on FL and FL/Na2SO4 can be an important source of HONO in the urban environment and indoor atmosphere and should be considered in photochemical models.
Abstract: The polycyclic aromatic hydrocarbons (PAHs) as constituents of urban grime and indoor surfaces can impact the photochemical conversion of nitrogen dioxide (NO2) to nitrous acid (HONO) thereby impac...
TL;DR: In this paper, a novel donor (D)-spiroacceptor (A) emitter, namely 10-phenyl-10H-spiro[acridine-9,9′-fluorene]-2′,4′,7′-tricarbonitrile (SAF-3CN), was synthesized for high efficiency, yellowish green third-generation thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs).
Abstract: A novel donor (D)–spiro-acceptor (A) emitter, namely 10-phenyl-10H-spiro[acridine-9,9′-fluorene]-2′,4′,7′-tricarbonitrile (SAF-3CN), was synthesized for high efficiency, yellowish green third-generation thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs). The CN-modulation of the fluorene was adopted for the modification of the singlet state with minor modifications of the triplet state. Compared to the reference material 10-phenyl-10H-spiro[acridine-9,9′-fluorene]-2′,7′-dicarbonitrile (ACRFLCN), the electron-withdrawing –CN substituent on the C4 site of the fluorene results in a sufficiently small singlet–triplet energy gap (ΔEST) and obvious TADF characteristics of SAF-3CN in the doped films. Encouragingly, the device performance achieves an external quantum efficiency (EQE) of 19.4% and small roll-off, which is better than that of ACRFLCN and closer to the best performance in this system.
TL;DR: In this article, a bis(phenyl)fluorene-based PIM (Cardo-PIM-1) based on 9,9-bis(3,4-dihydroxyphenyl) fluorene (BDPF), 2,3,5,6-tetrafluoroterephthalonitrile (TFTPN) and spirocyclic 5,5′,6,6′-Tetramethylspirobisindane (TTSBI) were prepared vis dibenzodioxane polymer
Abstract: Polymers of intrinsic microporosity (PIM) as one of potential next generation membrane materials for gas separation has attracted great interests due to its ultra-permeable characteristics. Herein, a novel bis(phenyl)fluorene-based PIMs (Cardo-PIM-1) based on 9,9-bis(3,4-dihydroxyphenyl) fluorene (BDPF), 2,3,5,6-tetrafluoroterephthalonitrile (TFTPN) and spirocyclic 5,5′,6,6′-tetrahydroxy-3,3′,3,3′-tetramethylspirobisindane (TTSBI) were prepared vis dibenzodioxane polymerization reaction, and then the functionalized multi-walled carbon nanotubes (f-MWCNTs) were incorporated into Cardo-PIM-1 to fabricate mixed matrix membranes (MMMs) with solution mixing method for CO2 separation. The structure analysis indicated that the MWCNTs were cut into short ropes and the amino groups were incorporated into the nanotubes surface after treated with acid mixtures followed by ethylenediamine modification. FTIR spectroscopy and nuclear magnetic resonance (NMR) measurement confirmed the formation of Cardo-PIM-1 macromolecule. BET and positron annihilation lifetime spectroscopy (PALS) analysis exhibited that Cardo-PIM-1 contained larger pore-size distribution and fractional free volume (FFV), and preferential CO2 adsorption capacity over N2 compared with that of PIM-1. This work investigated the structure of polymer as well as the effect of nanofillers in the gas separation performance. High CO2 permeability of 2.9 × 104 Barrer with a desirable CO2/N2 separation factor of 24.2 was achieved using the MMMs with 7.5 wt% f-MWCNTs loading, which were among the best performance for CO2 separation. The Cardo-PIM-1/f-MWCNTs MMMs will provide a promising alternative in industrial flue gas separation and CO2 capture process.
TL;DR: It is shown that an available force field such as ReaxFF and its parameterization can be transferable to simulate new systems without specific re-parameterization, provided that this model is validated against reference methods or data.
Abstract: We investigate the interaction of polyfluorene and fluorene/carbazole copolymers bearing various functional groups and side chains with small to large diameter—from 1.7 nm to 9 nm—carbon nanotubes (CNTs) in vacuo. We use variable-charge molecular dynamics simulations based on the reactive force field ReaxFF. We show that non-covalent functionalization of nanotubes, driven by π − π interactions, is effective for all the polymers studied, thanks to their conjugated backbone and regardless of the presence of specific functional groups. The geometry at equilibrium of these polymer/CNT hybrids is analyzed in detail at the scale of each fluorene or carbazole unit. The role of both the functional groups and the alkyl chain length is analyzed in detail. Adsorption of the polymers on the nanotube sidewalls is shown to be either complete—with the whole chain physisorbed—or partial—due to intrachain coiling or interchain repulsion—depending on the initial geometry, number of polymers, and nanotube diameter. Energetic arguments supplement the described geometric features. Both energetic and geometric adsorption features are derived here for the first time for large diameter carbon nanotubes (up to 9 nm) and fluorene/carbazole copolymers having up to 30 monomers and bearing different functional groups. The force field ReaxFF and its available parameterization used for the simulations are validated, thanks to a benchmark and review on higher-level quantum calculations—for simple π − π interacting compounds made up of polycyclic aromatic molecules adsorbed on a graphene sheet or bilayer graphene. Although it is shown that the influence of the nanotube chirality on the adsorption pattern and binding strength cannot be discussed with our method, we highlight that an available force field such as ReaxFF and its parameterization can be transferable to simulate new systems without specific re-parameterization, provided that this model is validated against reference methods or data. This methodology proves to be a valuable tool for optimal polymer design for nanotube functionalization at no re-parameterization cost and could be adapted to simulate and assist the design of other types of molecular systems.
TL;DR: In this article, a possible sequence of steps leading to some of the observed compounds in aqueous solution as well as in the gas phase is proposed, and the reaction pathways initiated by excited triplet state of FL (3 FL*) are supported by theoretical calculations of the reaction Gibbs energies.
Abstract: Polycyclic aromatic hydrocarbons and dimethyl sulfoxide (DMSO) are ubiquitous at the sea surface. Photochemistry at the air-sea interface is a potentially important source of volatile organic compounds, but the relevant chemical processes are currently not well known. When aqueous solutions containing a mixture of fluorene (FL) and DMSO are irradiated with actinic radiation, a large suite of unsaturated high molecular weight compounds appear in the aqueous phase; a broad variety of saturated and unsaturated oxygenated multifunctional compounds are also observed in the gas phase, most of which are more toxic than FL. A possible sequence of steps leading to some of the observed compounds in aqueous solution as well as in the gas phase is proposed. The reaction pathways initiated by excited triplet state of FL (3 FL*) are supported by theoretical calculations of the reaction Gibbs energies. The formation of organosulfur compounds has been observed to occur in the gas and the aqueous phases initiated by the reaction between 3 FL* and DMSO. The aforementioned photosensitized chemistry at the water surface can have an important impact on the formation of secondary organic aerosol in marine boundary layer as polycyclic aromatic hydrocarbons and DMSO enriched at the water surface are ubiquitous.
TL;DR: In this article, the photophysical properties of o-carborane-containing heterocyclic compounds were investigated and compared with each other, and the results showed that all compounds were AIE luminogens with tunable fluorescence colors from blue to yellow emissions (λem = 465-570 nm).
Abstract: o-Carborane was used to alter the electronic states of π-conjugated organic aryls and was demonstrated as an effective optical and electronic control unit to tune the photophysical properties, endowing the molecules with certain luminescence properties and modifying the HOMO and LUMO energies for electron transfer. We introduced fluorene and its heteroanalogs (carbazole, dibenzofuran and dibenzothiophene), four types of substitutes with different electron-rich or electron-deficient heteroatoms, to the two carbon atoms of o-carborane to synthesize CDC, CDN, CDO and CDSvia a modified nickel-catalyzed cross-coupling reaction. The photophysical properties of o-carborane-containing heterocyclic compounds were investigated and compared with each other. The results showed that all compounds were AIE luminogens with tunable fluorescence colors from blue to yellow emissions (λem = 465–570 nm) and possessed excellent emission quantum efficiencies in the solid state (ΦF > 70%). Among the four o-carborane-containing heterocyclic compounds, the ground state structures confirmed by crystallographic measurements provided a close correlation of the structure and electronic properties between the π-conjugated organic aryl groups and o-carborane. Besides, the heteroatoms controlled and altered the electronic interaction between aryls and o-carborane due to the different electron-rich or electron-deficient attributes. The HOMO and LUMO energies were estimated by DFT calculations. The excited states were calculated by TD-DFT and correlated with the corresponding absorption and emission spectra to systematically elucidate the electronic perturbation. This work not only demonstrates an efficient strategy for constructing o-carborane-containing heterocyclic AIE luminogens but also indicates that they are promising as advanced optoelectronic materials.
TL;DR: In this article, the aggregation-induced emission effect of compound 1 was investigated by the systematic research of photoluminescence spectroscopy, and the results indicated that luminogen 1 displayed obvious aggregationinduced yellow light-emitting phenomenon.
TL;DR: In this article, a photo-initiating system for the metal-free preparation of conjugated microporous polymers (CMPs) was reported, in which irradiation of solutions containing an electroactive monomer, possessing both carbazole and fluorene units, 9,9′-(9,9-dihexyl-9H-fluorene-2,7-diyl)bis- 9H-carbazole (CFD), and the iodonium salt (Ph2I+PF6-) as the oxidizing agent resulted
Abstract: A new photoinitiating system for the metal-free preparation of conjugated microporous polymers (CMPs) is reported. In this approach, irradiation of solutions containing an electroactive monomer, possessing both carbazole and fluorene units, 9,9′-(9,9-dihexyl-9H-fluorene-2,7-diyl)bis-9H-carbazole (CFD), and the iodonium salt (Ph2I+PF6–) as the oxidizing agent resulted in the formation of CMPs. Photoinduced step-growth polymerization proceeded through the successive electron transfer between the excited CFD and iodonium salt, proton release, and coupling reactions. The polymers formed were characterized by FT-IR and 1H NMR analyses. The electrochemical and optical properties of CMPs before and after the dedoping process were evaluated by cyclic voltammetry, differential pulse voltammetry, and UV–vis absorption and photoluminescence techniques. The porous structure of the obtained polymers was confirmed by atomic force microscopy and scanning electron microscopy studies.
TL;DR: The synthesis and study of the first examples of cycl ofluorenes possessing five constituting fluorene units are reported, highlighting the key role played by the ring size in the cyclofluorene family.
Abstract: For the last ten years, ring-shaped π-conjugated macrocycles possessing radially directed π-orbitals have been subject to intense research. The electronic properties of these rings are deeply dependent on their size. However, most studies involve the flagship family of nanorings: the cyclo-para-phenylenes. We report herein the synthesis and study of the first examples of cyclofluorenes possessing five constituting fluorene units. The structural, optical and electrochemical properties were elucidated by X-ray crystallography, UV-vis absorption and fluorescence spectroscopy, and cyclic voltammetry. By comparison with a shorter analogue, we show how the electronic properties of [5]-cyclofluorenes are drastically different from those of [4]-cyclofluorenes, highlighting the key role played by the ring size in the cyclofluorene family.
TL;DR: In this article, the role of pressure (0.1-4.0 MPa) and temperature (600 oC-900 °C) in flash pyrolysis of palm kernel shell (PKS) was investigated.
Abstract: This study reports the role of pressure (0.1-4.0 MPa) and temperature (600 oC-900 °C) in flash pyrolysis of palm kernel shell (PKS). The main objective was to study the extent to which pressure affects the mechanism of pyrolysis reactions to enhance the selective production of target products. Higher pressures and temperatures selectively promoted the generation of polycyclic aromatic hydrocarbon (PAHs) and H2 gas. Bio-oil samples generated at lower temperatures and pressures were mainly composed of phenolics. Increasing pressure and temperature favored the selective formation of phenanthrene, fluoranthene, pyrene, fluoranthene, and fluorene, which reached 96.17 area%. Elevated temperatures and pressures enhanced hydrogen transfer into light gaseous phase. The yield of H2 peaked at 40.82 gH2/kg.PKS at 900 ⁰C and 2.0 MPa. The results obtained in this study implied that the pyrolysis of biomass at elevated pressures is an effective method for poly-generation of hydrogen gas and chemical feedstock, in partic...
TL;DR: The sp3 C-H alkylation of 9H-fluorene using alcohol and Ru-catalyst via borrowing hydrogen concept has been described, allowing primary and secondary alcohols to be employed as non-hazardous and greener alkylating agents with the formation of environmentally benign water as a by-product.
Abstract: The sp3 C-H alkylation of 9H-fluorene using alcohol and a Ru catalyst via the borrowing hydrogen concept has been described. This reaction was catalyzed by the [Ru(p-cymene)Cl2]2 complex (3 mol %) and exhibited a broad reaction scope with different alcohols, allowing primary and secondary alcohols to be employed as nonhazardous and greener alkylating agents with the formation of environmentally benign water as a byproduct. A variety of 9H-fluorene underwent selective and exclusive mono-C9-alkylation with primary alcohols in good to excellent isolated yield (26 examples, 50-92% yield), whereas this reaction with secondary alcohols in the absence of any external oxidants furnished the tetrasubstituted alkene as the major product. Furthermore, a base-mediated C-H hydroxylation of the synthesized 9H-fluorene derivatives afforded 9H-hydroxy-functionalized quaternary fluorene derivatives in excellent yield.
TL;DR: The results showed that the Cl radical initiated reaction of fluorene mainly produces 9-fluorene radical that has significant potential to form secondary pollutants with more persistent toxic properties and increase the environmental risks of fluroene.
TL;DR: A series of biarylaminofluorene-based systems with donor-π-donor structure have been designed and synthesized in order to study the dependence on the π-conjugated bridge length of the intervalence charge-transfer transitions (IV-CT) and of the electronic coupling between the redox centers.
TL;DR: In this article, a donor-acceptor-donor (D-A-D) structure was used to synthesize solution-processable organic semiconductors for top-contact/bottom-gate organic thin-film transistors (OTFTs).
TL;DR: The late-stage oxidation of benzothiophene-fused indacenes and dicyclopentanaphthalenes to their corresponding sulfone derivatives is reported, and it is found that while such modifications increase the HOMO-LUMO energy gap to a small degree, other properties such as HOMo and LumO energy levels, molecule paratropicity, and singlet-triplet energy gaps are influenced to a greater degree.
Abstract: The ability to alter optoelectronic and magnetic properties of molecules at a late stage in their preparation is in general a nontrivial feat. Here, we report the late-stage oxidation of benzothiop...
TL;DR: Two sets of conjugated polymers with anthraquinone groups as pendant acceptors were designed and synthesized and show distinct TADF characteristics, confirmed by transient photoluminescence spectra and theoretical calculations.
Abstract: Two sets of conjugated polymers with anthraquinone groups as pendant acceptors were designed and synthesized. The acceptor is tethered to an diphenylamine group via a phenylene bridge, constructing a thermally activated delayed fluorescence (TADF) unit, which is embedded into the polymer backbone through its donor fragment, while the backbone is composed of dibenzothiophene-S, S-dioxide and 2, 7-fluorene or 2, 7-carbazole groups. The polymers show distinct TADF characteristics, confirmed by transient photoluminescence spectra and theoretical calculations. The carbazole-based polymers exhibit shorter delay lifetimes and lower energy emission relative to the fluorene-based polymers. The non-doped organic light-emitting diodes fabricated via solution processing approach produce efficient red emissions with the wavelengths of 625-646 nm. The carbazole containing polymer with 2% molar content of the TADF unit exhibits the best maximum external quantum efficiency of 13.6% and saturated red electroluminescence with the Commission Internationale de l'Eclairage coordinates of (0.62, 0.37).
TL;DR: This work has shown direct access to functionalized fluorene and fluorenone derivatives through benzannulation of 1-indanylidene-malononitrile with Morita-Baylis-Hillman carbonates with metal-free carbonates.
TL;DR: A series of highly emissive π-conjugated A-alt-B type copolymers (P1-P3) with a 1,2,3-triazole moiety was synthesized via Suzuki polymerization as mentioned in this paper.
Abstract: A series of highly emissive π-conjugated A-alt-B type copolymers (P1–P3) appended with a 1,2,3-triazole moiety was synthesized via Suzuki polymerization. The well-defined and soluble π-conjugated copolymers were characterized via multinuclear NMR spectroscopy and tetradetector GPC studies, showing a molecular weight (Mn) in the range of 16.4–20.1 kDa with a polydispersity index in the range of 1.25–1.42. The synthesized emissive π-conjugated polymer probes were explored as fluorescent chemosensors for nitroaromatic compounds (NACs) in solution, vapor and contact mode. Detailed photophysical and sensing studies were performed to understand the polymer–NAC interaction, inducing the selective fluorescence quenching of the π-conjugated polymer probes through the photoinduced electron transfer (PET) mechanism. All the polymeric probes (P1–P3) were highly reversible in nature with NACs, and thus could be reused multiple times. The limit of detection of the probes towards nitroaromatics was found to be in the range of 120–200 ppb with a high association constant in the order of 104 M−1. Furthermore, test paper kits were also fabricated, which allowed the trace detection of picric acid by the naked eye, making it a practical means for the quick, easy and inexpensive on-site detection of NAC-based explosives.