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101.
Sicre C  Cid MM 《Organic letters》2005,7(25):5737-5739
[chemical reaction: see text]. A stereoselective total synthesis of the visual pigment A2E has been achieved with use of palladium-catalyzed cross-coupling reactions in all key steps: a regioselective Suzuki or Negishi coupling of 2,4-dibromopyridine, a Sonogashira reaction, and a double Stille cross-coupling to complete the bispolyenyl skeleton.  相似文献   
102.
1‐Boraphenalenes have been synthesized by reaction of BBr3 with 1‐(aryl‐ethynyl)naphthalenes, 1‐ethynylnaphthalene, and 1‐(pent‐1‐yn‐1‐yl)naphthalene and they can be selectively functionalized at boron or carbon to form bench‐stable products. All of these 1‐boraphenalenes have LUMOs localized on the planar C12B core that are closely comparable in character to isoelectronic phenalenyl cations. In contrast to the comparable LUMOs, the aromatic stabilization of the C5B ring in 1‐boraphenalenes is dramatically lower than the C6 rings in phenalenyl cations. This is due to the occupied orbitals of π symmetry being less delocalised in the 1‐boraphenalenes.  相似文献   
103.
An intramolecular 1,2‐boryl‐anion migration from boron to carbon has been achieved by selective activation of the π system in [(vinyl)B2Pin2)]? using “soft” BR3 electrophiles (BR3=BPh3 or 9‐aryl‐BBN). The soft character is key to ensure 1,2‐migration proceeds instead of oxygen coordination/B?O activation. The BR3‐induced 1,2‐boryl‐anion migration represents a triple borylation of a vinyl Grignard reagent using only B2Pin2 and BR3 and forms differentially protected 1,1,2‐triborylated alkanes. Notably, by increasing the steric bulk at the β position of the vinyl Grignard reagent used to activate B2Pin2, 1,2‐boryl‐anion migration can be suppressed in favor of intermolecular {BPin}? transfer to BPh3, thus enabling simple access to unsymmetrical sp2?sp3 diboranes.  相似文献   
104.
Thermal decomposition of various synthetic manganese oxides (MnO, Mn3O4, Mn2O3, MnOOH) and a natural manganese dioxide (MnO2) from Gabon was studied with the help of termogravimetry in inert, oxidizing and reducing atmospheres. The compounds were characterized by XRD and electrochemical activity was tested by cyclic voltammetry using a carbon paste electrode. The natural manganese dioxide showed the best oxidizing and reducing capacity, confirmed by the lower temperatures of the transitions, the extent of the reactions and electrochemical performance in cyclic voltammograms.  相似文献   
105.
Silicic acid produces marked expansion in dipalmitoyl lecithin films and in mixed cholesterol-dipalmitoyl lecithin films with more than 50 % phospholipid. In the presence of silicic acid, these films no longer exhibit a transition region between the liquid-expanded and liquid-condensed states. Mixed cholesterol-dilauroyl lecithin.films are also expanded by silicic acid. In the absence of silicic acid, the addition of cholesterol produces greater condensation in dilauroyl lecithin films than in films of dipalmitoyl lecithin, but the reverse is the case if the substrate contains silicic acid. These results have been interpreted in terms of a possible electrostatic interaction between negatively charged dissociated silicate ions and the positively charged trimethyl ammonium group of the choline fragment.  相似文献   
106.
Limit of accuracy for the fluorescence lifetime (FL) temperature-sensing method performed and marked that at lower temperature (< 400 K) it works well but for higher temperatures FL method does not found suitable. The non-radiative relaxation rate is noted to vary with increase in the temperature.  相似文献   
107.
108.
To enable detailed studies of interactions between nanoparticles and their environment and the correlations between various nanoparticle properties, one must go beyond ensemble averages and toward single-particle measurements. However, current methodologies for the single-nanoparticle analysis of charge and size either lack the flexibility to study dynamic processes on the single-particle level or are highly specific and require complex microfluidic devices. In addition, accurate measurements of the electrophoretic mobility (or zeta-potential) based on the optical detection of single nanoparticles remain challenging due to the low photon budget, the required sampling frequency, and the fact that electroosmosis in typical microfluidic devices must be analyzed carefully. In this study, a method is investigated to accurately characterize the electrophoretic mobility of individual nanoparticles and estimate their size by simultaneously analyzing the electrokinetic- and Brownian motion in a simple microfluidic channel. Fast laser scanning excitation and sensitive detection of fluorescent photons enable single-nanoparticle velocimetry experiments in an oscillating electric field at high frame rates.  相似文献   
109.
We report measurements of the nonlinear refractive index, n(2), of nickel oxide nanoparticles (NPs) in toluene at 532 nm. The measurements were performed using the Z-scan technique with 80 ps laser pulses at 7 Hz. Large values of n(2) in the range of 10(-13)-10(-12) cm(2)/W were measured, and negligible two-photon absorption coefficient was estimated for colloids having NP filling fractions in the range of 10(-8)-10(-7).  相似文献   
110.
Cid CC  Riu J  Maroto A  Rius FX 《The Analyst》2008,133(8):1001-1004
We report a new type of ion-sensitive field effect transistor (ISFET). This type of ISFET incorporates a new architecture, containing a network of single-walled carbon nanotubes (SWCNTs) as the transduction layer, making an external reference electrode unnecessary. To show an example of its application, the SWCNT-based ISFET is able to detect at least 10(-8) M of potassium in water using an ion-selective membrane containing valinomycin.  相似文献   
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