No abstract

Syntheses of push-pull substituted non-symmetric bis(thienyl) ethenes (BTEs) possessing a central perfluorocyclopentene core are described. The substituent effects of anisole, phenole, and phenolate as well as pyridine, pyridinium, and N-methylpyridinium substituents, joined through their 3-or 4-positions to the central BTE core, respectively, cover the range from very strongly electron-donating [σ(4-phenolate) = À 1.00] to extremely strongly electron-withdrawing [σ(pyridinium-4-yl) = + 2.57] in the title mesomeric betaines. The different isomers possessing 4-yl/4-yl, 4-yl/3-yl and 3-yl/3-yl substituents represent different combinations of conjugated and cross-conju-gated partial structures and cause different spectroscopic properties. In addition, through-space conjugation between the 2-and 2'-position of the thiophenes can be observed which circumvents the charge-separation of through-bond crossconjugation. The BTE possessing the push-pull chromophore consisting of 3-anisole and 4-pyridinium substituents (24) displays the best extinction coefficients within the series of compounds described here (ɛ = 33.8/15.7 L/mol • cm), while the mesomeric betaine possessing an N-methylpyridinium-4-yl and a 4-phenolate substituent (29) displays considerable bathochromic shifts to λ max = 724 nm in its closed form.

Nowadays, cold plasma techniques like dielectric barrier discharge (DBD) plasmas have attracted considerable interest in view of high deoxidation efficiencies as well as relative simplicity of setups. Although DBD plasma deoxidation of copper has been mainly studied in Ar/H2 mixtures, there is no information on reduction performance of such methods in other protective atmospheres. In this study, the reduction of natively oxidized copper surfaces using a DBD plasma in an Ar/SiH4 atmosphere at 100 hPa and 20 °C was investigated. The influence of a silane gas on the deoxidation performance was studied by varying the SiH4 concentration from 0.0 to 0.5 vol%. An addition of a SiH4 gas to an Ar atmosphere results in the increase of the deoxidation effect of a DBD plasma, so almost all Cu2O was reduced after 10 s of treatment in 0.1 vol% silane. Surface morphology analysis showed formation of particles after Ar/SiH4 plasma treatments that can be cleaned from the surfaces by wiping. Additionally, characterization of the plasma phase indicated the presence of SiH* radicals that likely play a role in the deoxidation effect. Moreover, an elimination of residual oxygen and nitrogen species in Ar by addition of SiH4 was observed.

In recent years, fluorescence microscopy has been revolutionized. Reversible switching of fluorophores has enabled circumventing the limits imposed by diffraction. Thus, resolution down to the molecular scale became possible. However, to the best of our knowledge, the application of the principles underlying superresolution fluorescence microscopy to reflection microscopy has not been experimentally demonstrated. Here, we present the first evidence that this is indeed possible. A layer of photochromic molecules referred to as the absorbance modulation layer (AML) is applied to a sample under investigation. The AML-coated sample is then sequentially illuminated with a one-dimensional (1D) focal intensity distribution (similar to the transverse laser mode TEM01) at wavelength λ 1 = 325 nm to create a subwavelength aperture within the AML, followed by illumination with a Gaussian focal spot at λ 2 = 633 nm for high-resolution imaging. Using this method, called absorbance modulation imaging (AMI) in reflection, we demonstrate a 2.4-fold resolution enhancement over the diffraction limit for a numerical aperture (NA) of 0.65 and wavelength (λ) of 633 nm.

Plasma in hydrogen-containing atmospheres is an efficient method for the reduction of iron oxides. Although a vast number of approaches were performed for the reduction of bulk Fe oxides with thermal hydrogen plasmas, there is almost no information about the non-thermal plasma reduction efficiency in the atmospheric pressure range. In the current article we present the reduction of natively oxidized iron surfaces applying a dielectric barrier discharge plasma in an Ar/H2 atmosphere at 1000 hPa. By varying the surface temperature from 25 to 300 °C, we studied the plasma reduction efficiency, which was then compared with a thermal method. Whereas plasma treatments at 25 °C and 100 °C did not result in the significant reduction of iron oxidized species, experiments at 200 °C and 300 °C yielded a reduction of approximately 88% and 91% of initial oxidized components already after 10 s, respectively. Moreover, we observed an increase in the efficiency with a plasma-thermal reduction in comparison to a thermal method, which was attributed to the presence of atomic hydrogen in the plasma phase. Analysis of morphology revealed the formation of Fe–C structures on surfaces after thermal and plasma-thermal treatments at 200 °C and 300 °C that may be connected with the diffusion of bulk contaminations to the deoxidized surface and reactions between the reduced Fe with plasma-activated adventitious carbon. Conclusively, the plasma was characterized by analyzing the reactive species and the electron temperatures.