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1.
Content S Trogler WC Sailor MJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(12):2205-2213
The detection of nitroaromatic molecules in air by the quenching of the photoluminescence of porous silicon (porous Si) films has been explored. Detection is achieved by monitoring the photoluminescence (PL) of a nanocrystalline porous Si film on exposure to the analyte of interest in a flowing air stream. The photoluminescence is quenched on exposure to the nitroaromatic, presumably by an electron-transfer mechanism. Detection limits of 500 parts-per-billion (ppb), 2 ppb, and 1 ppb were observed for nitrobenzene, 2.4-dinitrotoluene (DNT), and 2,4,6-trinitrotoluene (TNT), respectively (exposure times of 5 min for each, in air). Specificity for detection is achieved by catalytic oxidation of the nitroaromatic compound. A platinum oxide (PtO2) or palladium oxide (PdO) catalyst at 250 degrees C. placed in the carrier gas line upstream of the porous Si detector, causes oxidation of all the nitroaromatic compounds studied. The catalyst does not oxidize benzene vapor, and control experiments show no difference in the extent of PL quenching by benzene with or without an upstream catalyst. The PL quenching by NO2, released in the catalytic oxidation of nitroaromatic compounds, is less efficient than the quenching of the intact nitroaromatic compound. This provides a means to discriminate nitro-containing molecules from other organic species. 相似文献
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Bruins EE Bauer TS den Bok HW Duif CP van Hoek WC de Lange DJ Misiejuk A Papandreou Z Sichtermann EP Tjon JA Willering HW Yeomans DM Reike H Durek D Frommberger F Gothe R Jakob D Kranefeld G Kunz C Leiendecker N Pfeiffer G Putsch H Reichelt T Schoch B Wacker D Wehrmeister D Wilhelm M Jans E Konijn J de Vries R Furget C Voutier E Arenhövel H 《Physical review letters》1995,75(1):21-24
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Toal SJ Jones KA Magde D Trogler WC 《Journal of the American Chemical Society》2005,127(33):11661-11665
Colloidal suspensions of 3-aminopropylmethyl(tetraphenyl)silole nanoparticles can be used as selective chemosensors for carcinogenic chromium(VI) analyte. Methylhydrosilole is functionalized by hydrosilation of allylamine, and the colloid is prepared by the rapid addition of water to a THF solution of the silole. The method of detection is through electron-transfer quenching of the fluorescence of the silole colloid (lambda(em) = 485 nm at 360 nm excitation) by the analytes, with hundred parts per billion detection limits. Stern-Volmer plots are linear up to 10 ppm in the case of chromium, but exhibit saturation behavior near 5-10 ppm for arsenic. Dynamic light scattering experiments and AFM measurements show the particle sizes to be around 100 nm in diameter and dependent on solvent composition, with a particle size dispersity of +/-25%. The fluorescence lifetimes of the silole in solution and colloid are approximately 31 ps and approximately 4.3 ns, respectively, while the silole has a lifetime of 6 ns in the bulk solid. A minimum volume fraction of 80% water is necessary to precipitate the colloid from THF, and the luminescence continues to rise with higher water fractions. Colloids in a pH 7 phosphate-buffered suspension show both higher sensitivity and greater selectivity (100-fold) for CrO4(2-) detection than for other oxoanion interferents, NO3-, NO2-, SO4(2-), and ClO4-. 相似文献
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Sohn H Sailor MJ Magde D Trogler WC 《Journal of the American Chemical Society》2003,125(13):3821-3830
The synthesis, spectroscopic characterization, and fluorescence quenching efficiency of polymers and copolymers containing tetraphenylsilole or tetraphenylgermole with Si-Si, Ge-Ge, and Si-Ge backbones are reported. Poly(tetraphenyl)germole, 2, was synthesized from the reduction of dichloro(tetraphenyl)germole with 2 equivs of Li. Silole-germole alternating copolymer 3 was synthesized by coupling dilithium salts of tetraphenylsilole dianion with dichloro(tetraphenyl)germole. Other tetraphenylmetallole-silane copolymers, 4-12, were synthesized through the Wurtz-type coupling of the dilithium salts of the tetraphenylmetallole dianion and corresponding dichloro(dialkyl)silanes. The molecular weights (M(w)) of these metallole-silane copolymers are in the range of 4000 approximately 6000. Detection of nitroaromatic molecules, such as nitrobenzene (NB), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), and picric acid (PA), has been explored. A linear Stern-Volmer relationship was observed for the first three analytes, but not for picric acid. Fluorescence spectra of polymetalloles or metallole-silane copolymers obtained in either toluene solutions or thin polymer films displayed no shift in the maximum of the emission wavelength. This suggests that the polymetalloles or metallole-silanes exhibit neither pi-stacking of polymer chains nor excimer formation. Fluorescence lifetimes of polymetalloles and metallole-silanes were measured both in the presence and absence of TNT, and tau(o)/tau is invariant. This requires that photoluminescence quenching occurs by a static mechanism. 相似文献
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Jason C. Sanchez Antonio G. DiPasquale Anthony A. Mrse William C. Trogler 《Analytical and bioanalytical chemistry》2009,395(2):387-392
The high sensitivity of silole- and silafluorene-containing polymers for detecting organic nitro, nitrate, and nitramine explosives
cannot be solely attributed to favorable analyte–polymer hydrophobic interactions and amplified fluorescence quenching due
to delocalization along the polymer chain. The Lewis acidity of silicon in conjugated poly(silafluorene-vinylene)s is shown
to be important. This was established by examining the 29Si NMR chemical shifts (Δ) for the model trimer fragment of the polymer CH3–silafluorene–(trans-C2H2)–silafluorene–(trans-C2H2)–silafluorene–CH3. The peripheral and central silicon resonances are up-field from a TMS reference at −9.50 and −18.9 ppm, respectively. Both
resonances shift down-field in the presence of donor analytes and the observed shifts (0 to 1 ppm) correlate with the basicity
of a variety of added Lewis bases, including TNT. The most basic analyte studied was acetonitrile and an association constant
(K
a) of 0.12 M−1 was calculated its binding to the peripheral silicon centers using the Scatchard method. Spin-lattice relaxation times (T
1) of 5.86(3) and 4.83(4) s were measured for the methyl protons of acetonitrile in benzene-d
6 at 20 °C in the absence and presence of the silafluorene trimer, respectively. The significant change in T
1 values further supports a binding event between acetonitrile and the silafluorene trimer. These studies as well as significant
changes and shifts observed in the characteristic UV–Vis absorption of the silafluorene group support an important role for
the Lewis acid character of Si in polymer sensors that incorporate strained silacycles. The nitro groups of high explosives
may act as weak Lewis-base donors to silacycles. This provides a donor–acceptor interaction that may be crucial for orienting
the explosive analyte in the polymer film to provide an efficient pathway for inner-sphere electron transfer during the electron-transfer
quenching process.
Figure
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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P B Zmolek H Sohn P K Gantzel W C Trogler 《Journal of the American Chemical Society》2001,123(6):1199-1207
Broad band solar or 300--400 nm irradiation (Hg--Xe arc source) of liquid-phase carbon disulfide produces a new carbon--sulfur polymer with the approximate (n = 1.04--1.05) stoichiometry (CS(n))(x). The polymer, from here on called (CS)(x), forms as a approximately 200 nm thick transparent golden membrane as measured by SEM and AFM techniques. IR spectra for this polymer show some similarities with those obtained for the gas-phase photopolymerized (CS(2))(x) and the high-pressure-phase polymer of CS(2), called Bridgman's Black. The observed FT-IR absorptions of (CS)(x) include prominent features at 1431 (s, br), 1298 (m), 1250 (ms), and 1070 cm(-1) (m). In contrast to previous proposals for (CS(2))(x), (13)C labeling and model compound studies of alpha-(C(3)S(5))R(2) and beta-(C(3)S(5))R(2) (R = methyl or benzoyl) suggest that the absorption at 1431 cm(-1) and those at 1298 and 1250 cm(-1) are indicative of carbon--carbon double bonds and carbon--carbon single bonds, respectively. The molecular structure of alpha-(C(3)S(5))(C(O)C(6)H(5))(2), determined at -84 degrees C, belongs to space group P1, with a = 7.486(5) A, b = 13.335(11) A, c = 17.830(13) A, alpha = 105.60(6) degrees, beta = 95.32(6) degrees, gamma = 90.46(6) degrees, Z = 4, V = 1706(2) A(3), R = 0.0785, and R(w) = 0.2323. With use of electron and chemical ionization mass spectrometry, C(4)S(6) and C(6)S(7) were identified as the dominant soluble molecular side-products derived from a putative ethylenedithione (S==C==C==S) precursor. Atomic force microscopy (AFM) provided surface topology information for the thin film (CS)(x) and revealed features that suggested the bulk material is formed from small polymer spheres 20--50 nm in size. Both (CS(2))(x) and (CS)(x) are extensively cross-linked through disulfide linkages and both materials show strong EPR resonances (g > 2.006) indicative of sulfur-centered radicals from incomplete cross-linking. A polymerization mechanism based on the intermediacy of S(2)C=CS(2) is proposed. 相似文献
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Royer JE Zhang C Kummel AC Trogler WC 《Langmuir : the ACS journal of surfaces and colloids》2012,28(14):6192-6200
Air-stable organic thin-film transistor (OTFT) sensors fabricated using spin-cast films of 5,9,14,18,23,27,32,36-octabutoxy-2,3-naphthalocyanine (OBNc) demonstrated improved chemical vapor sensitivity and selectivity relative to vacuum-deposited phthalocyanine (H(2)Pc) OTFTs. UV-vis spectroscopy data show that annealed spin-cast OBNc films exhibit a red-shift in the OBNc Q-band λ(max) which is generally diagnostic of improved π-orbital overlap in phthalocyanine ring systems. Annealed OBNc OTFTs have mobilities of 0.06 cm(2) V(-1) s(-1), low threshold voltages (|V(th)| < 1 V), and on/off ratios greater than 10(6). These air-stable device parameters are utilized for sensing modalities which enhance the sensitivity and selectivity of OBNc OTFTs relative to H(2)Pc OTFTs. While both sensors exhibit mobility decreases for all analytes, only OBNc OTFTs exhibit V(th) changes for highly polar/nonpolar analytes. The observed mobility decreases for both sensors are consistent with electron donation trends via hydrogen bonding by basic analytes. In contrast, V(th) changes for OBNc sensors appear to correlate with the analyte's octanol-water partition coefficient, consistent with polar molecules stabilizing charge in the organic semiconductor film. The analyte induced V(th) changes for OBNc OTFTs can be employed to develop selective multiparameter sensors which can sense analyte stabilized fixed charge in the film. 相似文献
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