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41.
Jukka Hassinen Jussi Kauppila Jarkko Leiro Anni Määttänen Petri Ihalainen Jouko Peltonen Jukka Lukkari 《Analytical and bioanalytical chemistry》2013,405(11):3611-3617
The fabrication concept for a low-cost sensor device using reduced graphene oxide (rGO) as the sensing material on a porous paper substrate is presented. The sensors were characterized using conductivity and capacitance measurements, atomic force microscopy and X-ray photoelectron spectroscopy. The effects of different reducing agents, graphene oxide (GO) flake size and film thickness were studied. The sensor was sensitive to NO2, and devices based on a thin (10-nm) hydrazine-reduced GO layer had the best sensitivity, reaching a 70 % reduction in resistance after 10 min of exposure to 10 ppm NO2. The sensitivity was high enough for the detection of sub-parts per million levels of NO2. Desorption of gas molecules, i.e. the recovery of the sensor, could be accelerated by UV irradiation. The structure and preparation of the sensor are simple and up-scalable, allowing their fabrication in bulk quantities, and the fabrication concept can be applied to other materials, too. Figure
Low‐cost reduced graphene oxide based conductometric nitrogen dioxide sensitive sensor on paper 相似文献
42.
Tapio Saarinen Sanna Haavisto Anni Sorvari Juha Salmela Jukka Seppälä 《Cellulose (London, England)》2014,21(3):1261-1275
Rheology of microfibrillated cellulose (MFC) water suspensions was characterized with a rotational rheometer, augmented with optical coherence tomography (OCT). To the best of the authors’ knowledge, this is the first time the behavior of MFC in the rheometer gap was characterized by this real-time imaging method. Two concentrations, 0.5 and 1 wt% were used, the latter also with 10?3 and 10?2 M NaCl. The aim was to follow the structure of the suspensions in a rotational rheometer during the measurements and observe wall depletion and other factors that can interfere with the rheological results. The stepped flow measurements were performed using a transparent cylindrical measuring system and combining the optical information to rheological parameters. OCT allows imaging in radial direction from the outer geometry boundary to the inner geometry boundary making both the shear rate profile and the structure of the suspension visible through the rheometer gap. Yield stress and maximum wall stress were determined by start-up of steady shear and logarithmic stress ramp methods and they both reflected in the stepped flow measurements. Above yield stress, floc size was inversely proportional to shear rate. Below the yield stress, flocs adhered to each other and the observed apparent constant shear stress was controlled by flow in the depleted boundary layer. With higher ionic strength (10?2 M NaCl), the combination of yield stress and wall depletion favored the formation of vertical, cylindrical, rotating floc structures (rollers) coupled with a thicker water layer originating at the suspension—inner cylinder boundary at low shear rates. 相似文献
43.
De Giorgi M Vasanelli A Rinaldi R Anni M Lomascolo M Antonaci S Passaseo A Cingolani R Taurino A Catalano M Di Fabrizio E 《Micron (Oxford, England : 1993)》2000,31(3):245-251
We show how the electronic states of quantum wires and quantum dots can be evaluated exactly starting from the profile of the nanostructure observed by transmission electron microscopy, scanning tunneling microscopy and atomic force microscopy. The calculated quantization energies reproduce the energy position of the luminescence resonances in the optical spectra of different samples, without fitting parameters. 相似文献
44.
Lijue Chen Anni Feng Maoning Wang Junyang Liu Wenjing Hong Xuefeng Guo Dong Xiang 《中国科学:化学(英文版)》2018,61(11):1368-1384
Benefiting from the development of molecular electronics and molecular plasmonics, the interplay of light and electronic transport in molecular junctions has attracted growing interest among researchers in both fields, leading to a new research direction of “single-molecule optoelectronics”. Here, we review the latest developments of photo-modulated charge transport, electroluminescence and Raman spectroscopy from single-molecule junctions, and suggest future directions for single-molecule optoelectronics. 相似文献
45.
Mehdi Jafari Jamnani Bjarte Holmelid Anni Vedeler Hoda Houshiar Parsian Heidi Lie Andersen Torgils Fossen 《Molecules (Basel, Switzerland)》2023,28(1)
For several millennia, leaves of Echium amoenum Fisch. & C. A. Mey., an important Iranian medicinal plant with nutritional value as nutraceutical, have been used as tea for the treatment of several conditions, including inflammation. The nutritional value of intake of E. amoenum tea has mainly been correlated to its rich content of mainly water-soluble antioxidants. Although the entire plant is utilized, only natural products of the flowers have previously been thoroughly investigated. The rare natural products bis(3-(3,4-dihydroxyphenyl)-1-methoxy-1-oxopropan-2-yl)-1-(3,4-dihydroxyphenyl)-6,7-dihydroxy-1,2-dihydronaphthalene-2,3-dicarboxylate, 4-Oxy-(E)-caffeoyl-2,3-dihydroxybutanoic acid methyl ester and 4-Oxy-(Z)-caffeoyl-2,3-dihydroxybutanoic acid methyl ester, in addition to the widely distributed compounds rosmarinic acid methyl ester and (E)-caffeic acid, were purified and characterized from leaves of Echium amoenum. The structures were determined by a combination of several 2D NMR spectroscopic techniques, circular dichroism spectroscopy and high-resolution mass spectrometry. The fact that bis(3-(3,4-dihydroxyphenyl)-1-methoxy-1-oxopropan-2-yl)-1-(3,4-dihydroxyphenyl)-6,7-dihydroxy-1,2-dihydronaphthalene-2,3-dicarboxylate belongs to a rare group of natural products which have previously been patented for their significant anti-inflammatory activity may rationalize the traditional treatment of inflammations with E. amoenum. 相似文献
46.
Rate constants have been measured at 296 ± 2 K for the gas‐phase reactions of camphor with OH radicals, NO3 radicals, and O3. Using relative rate methods, the rate constants for the OH radical and NO3 radical reactions were (4.6 ± 1.2) × 10−12 cm3 molecule−1 s−1 and <3 × 10−16 cm3 molecule−1 s−1, respectively, where the indicated error in the OH radical reaction rate constant includes the estimated overall uncertainty in the rate constant for the reference compound. An upper limit to the rate constant for the O3 reaction of <7 × 10−20 cm3 molecule−1 s−1 was also determined. The dominant tropospheric loss process for camphor is calculated to be by reaction with the OH radical. Acetone was identified and quantified as a product of the OH radical reaction by gas chromatography, with a formation yield of 0.29 ± 0.04. In situ atmospheric pressure ionization tandem mass spectrometry (API‐MS) analyses indicated the formation of additional products of molecular weight 166 (dicarbonyl), 182 (hydroxydicarbonyl), 186, 187, 213 (carbonyl‐nitrate), 229 (hydroxycarbonyl‐nitrate), and 243. A reaction mechanism leading to the formation of acetone is presented, as are pathways for the formation of several of the additional products observed by API‐MS. © 2000 John Wiley and Sons, Inc. Int J Chem Kinet 33: 56–63, 2001 相似文献
47.
Asger W. Nørgaard Anni Vibenholt Mario Benassi Per Axel Clausen Peder Wolkoff 《Journal of the American Society for Mass Spectrometry》2013,24(7):1090-1096
Limonene and its ozone-initiated reaction products were investigated in situ by low temperature plasma (LTP) ionization quadrupole time-of-flight (QTOF) mass spectrometry. Helium was used as discharge gas and the protruding plasma generated ~850 ppb ozone in front of the glass tube by reaction with the ambient oxygen. Limonene applied to filter paper was placed in front of the LTP afterglow and the MS inlet. Instantly, a wide range of reaction products appeared, ranging from m/z 139 to ca. 1000 in the positive mode and m/z 115 to ca. 600 in the negative mode. Key monomeric oxidation products including levulinic acid, 4-acetyl-1-methylcyclohexene, limonene oxide, 3-isopropenyl-6-oxo-heptanal, and the secondary ozonide of limonene could be identified by collision-induced dissociation. Oligomeric products ranged from the nonoxidized dimer of limonene (C20H30) and up to the hexamer with 10 oxygen atoms (C60H90O10). The use of LTP for in situ ozonolysis and ionization represents a new and versatile approach for the assessment of ozone-initiated terpene chemistry. Figure
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50.
Anni M Della Sala F Raganato MF Fabiano E Lattante S Cingolani R Gigli G Barbarella G Favaretto L Görling A 《The journal of physical chemistry. B》2005,109(12):6004-6011
The intramolecular radiative and nonradiative relaxation processes of three thiophene-S,S-dioxide derivatives with different molecular rigidity are investigated in different solutions and in inert matrix. We show that the fluorescence quantum efficiency and the relaxation dynamics are strongly dependent on the environment viscosity, whereas they are almost independent of the environment polarity. We demonstrate that this strong dependence is due to an environment dependent nonradiative decay rate, whereas no relevant variations of the radiative decay rate are observed. We demonstrate that the dipole coupling with the solvent does not provide an efficient nonradiative decay channel and that the S(n) - S(1) vibrational relaxation is very efficient in all of the molecules and for all of the investigated environments. Moreover first-principles time-dependent density-functional theory calculations in the correct, i.e., excited-state, molecular conformation, suggest that significant contributions of intersystem crossing to the triplet manifold can be excluded. We then conclude that the main nonradiative process determining the fluorescence quantum efficiency of this class of molecules is S(1) - S(0) internal conversion (IC). An explanation for the IC rate dependence in terms of the environment viscosity, molecular rigidity, S(1) - S(0) energy-gap, and molecular volume is presented. 相似文献