L'analyse quantitative par la spectrographie raman

The authors have studied the application of the gerlach-rollwagen-coheur method, based on the measurement of the width of spectral lines, to quantitative Raman spectrographic analysis.Results obtained on binary mixtures of carbon tetrachloride-cyclohexne and ortho-paraxylene indicate that this method is quicker and a little more precise than the one based on measuring the intensities of the rays. Moreover, the width of the bands is, within the limits examined, independent of the exposure time.However, the presence of an intense continuous background on the spectrum, has the effect of greatly reducing the precision of the method; the method of ratio intensities corrects, for this continuous background but this necessitates a sensitivity standardisation of the photographic plate not only in the normal range of exposure but also in that of under-exposure.     

Sur les valeurs moyennes des fonctions

Sans résumé     

Time-dependent internal Quantum Efficiency and diffusion Modulation Transfer Function of N/P photodiodes

The minority carrier continuity equation has been solved with the Green’s function approach in a N/P photodiode under the low-level injection assumption. The analytical solution obtained with this approach depends on the three spatial coordinates and on time. The diffusion and the collection of the excess minority carriers have been studied during the transitional period corresponding to very short integration times. The internal Quantum Efficiency and the diffusion Modulation Transfer Function have been calculated according to time. The simulations showed that they evolve with time until their steady-state values. When the integration time is very short, this evolution has to be taken into account for the estimation of the sensitivity of a photodiode and the contrast on an image of a sensor based on several adjacent N/P-type photodiodes.     

Bis‐clickable Mesoporous Silica Nanoparticles: Straightforward Preparation of Light‐Actuated Nanomachines for Controlled Drug Delivery with Active Targeting

Bis(clickable) mesoporous silica nanospheres (ca. 100 nm) were obtained by the co‐condensation of TEOS with variable amounts (2–5 % each) of two clickable organosilanes in the presence of CTAB. Such nanoparticles could be easily functionalized with two independent functions using the copper‐catalyzed alkyne‐azide cycloaddition (CuAAC) reaction to transform them into nanomachines bearing cancer cell targeting ligands with the ability to deliver drugs on‐demand. The active targeting was made possible after anchoring folic acid by CuAAC click reaction, whereas the controlled delivery was performed by clicked azobenzene fragments. Indeed, the azobenzene groups are able to obstruct the pores of the nanoparticles in the dark whereas upon irradiation in the UV or in the blue range, their trans‐to‐cis photoisomerization provokes disorder in the pores, enabling the delivery of the cargo molecules. The on‐command delivery was proven in solution by dye release experiments, and in vitro by doxorubicin delivery. The added value of the folic acid ligand was clearly evidenced by the difference of cell killing induced by doxorubicin‐loaded nanoparticles under blue irradiation, depending on whether the particles featured the clicked folic acid ligand or not.     

Gas phase double-resonance IR/UV spectroscopy of an alanine dipeptide analogue using a non-covalently bound UV-tag: observation of a folded peptide conformation in the Ac-Ala-NH2–toluene complex

Structural Chemistry - The conformation-selective IR spectroscopy of the alanine dipeptide analogue Ac-Ala-NH2, a molecule deprived of a UV chromophore, has been obtained by laser double-resonance...     

Mechanism of Polyvinyl Chloride) Stabilization by Studies with Model Compounds

4-Chloro-2-hexene can be considered a model compound for the chlorinated allylic structure appearing in PVC chains after dehydrochlorination. This model compound was used to elucidate the mechanism of reaction of primary or secondary stabilizers.     

Visualization of arborescent architecture of polystyrenes prepared by raft‐based initiator‐monomer polymerization using atomic force microscopy

This article presents the utilization of “molecular amplification” to visualize the molecular architecture of “arborescent” (tree‐like) polystyrenes (arbPSs) using atomic force microscopy (AFM). arbPSs with M_n > 80,000 g/mol were synthesized via initiator‐monomer‐type (inimer) RAFT polymerization of styrene mediated by 4‐vinylbenzyl dithiobenzoate in bulk. These arbPS were then used as macrochain transfer agents for polymerization of vinylbenzyl chloride (VBCl) to give arborescent poly(styrene‐block‐vinylbenzyl chloride) (arbPS‐b‐VBCl). Poly(styryl) diphenylethyl lithium (M_n = 11,000 g/mol) was then grafted onto the VBCl units of the arbPS‐b‐VBCl. The M_n of the amplified arbPSs increased over >10 million g/mol, exceeding the exclusion limit of our size exclusion chromatography equipment. AFM confirmed the proposed branches on branches architecture in the samples, together with lesser branched species. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012