Organic Base-Facilitated Thiol-Thioalkyne Reaction with Exclusive Regio- and Stereoselectivity.

Here, we report the regiospecific hydrothiolation of electron-rich thioalkynes with exclusive stereoselectivity facilitated by an organic base, which could proceed exceedingly fast under ambient atmosphere and room temperature, affording ß trans addition products in up to nearly quantitative yields. The dual nature of the sulfur atom in attracting and donating electrons is supposed to be pivotal in determining the regio- and stereoselectivity. This system tolerates a wide range of thiols and thioalkynes and shows great potential in polymer synthesis.

Microenvironment Created by SnSe2 Vapor and Pre-Selenization to Stabilize the Surface and Back Contact in Kesterite Solar Cells.

The ambient air-processed preparation of kesterite Cu2 ZnSn(S,Se)4 (CZTSSe) thin film is highly promising for the fabrication of low-cost and eco-friendly solar cells. However, the Sn volatilization loss and formation of a thick Mo(S,Se)2 interfacial layer during the traditional selenization process pose challenges for fabricating high-efficiency CZTSSe solar cells. Here, CZTS precursors prepared by a sol-gel process in ambient air are selenized and assisted with SnSe2 vapor via one- and two-step selenization to prepare a CZTSSe absorber on a Mo film and, subsequently, solar cells. For one-step selenization, the thickness of the fine grain and Mo(S,Se)2 layers near the back contact can be significantly reduced with increasing SnSe2 vapor partial pressure in the mixed selenization atmosphere, while the device efficiency is only 7.97% due to the severe interface recombination. For two-step selenization, the desired morphology and stoichiometry of the absorber can be achieved through the assistance of Sn-poor precursors selenized with high SnSe2 vapor partial pressure to regulate the Sn content in CZTSSe, yielding the highest efficiency of 10.85%. This study improves the understanding of the key role of the microenvironment during film growth towards the production of high-efficiency thin film solar cells and other photoelectronic devices.

Application of far-infrared spectroscopy to the structural identification of protein materials.

Although far-infrared (IR) spectroscopy has been shown to be a powerful tool to determine peptide structure and to detect structural transitions in peptides, it has been overlooked in the characterization of proteins. Herein, we used far-IR spectroscopy to monitor the structure of four abundant non-bioactive proteins, namely, soybean protein isolate (SPI), pea protein isolate (PPI) and two types of silk fibroins (SFs), domestic Bombyx mori and wild Antheraea pernyi. The two globular proteins SPI and PPI result in broad and weak far-IR bands (between 50 and 700 cm-1), in agreement with those of some other bioactive globular proteins previously studied (lysozyme, myoglobin, hemoglobin, etc.) that generally only have random amino acid sequences. Interestingly, the two SFs, which are characterized by a structure composed of highly repetitive motifs, show several sharp far-IR characteristic absorption peaks. Moreover, some of these characteristic peaks (such as the peaks at 260 and 428 cm-1 in B. mori, and the peaks at 245 and 448 cm-1 in A. pernyi) are sensitive to conformational changes; hence, they can be directly used to monitor conformational transitions in SFs. Furthermore, since SF absorption bands clearly differ from those of globular proteins and different SFs even show distinct adsorption bands, far-IR spectroscopy can be applied to distinguish and determine the specific SF component within protein blends.

Direct Observation of Native Silk Fibroin Conformation in Silk Gland of Bombyx mori Silkworm.

To understand the natural silk spinning mechanism, synchrotron Fourier transform infrared (S-FTIR) microspectroscopy was employed in this study to monitor the conformation changes of silk protein in the silk gland of Bombyx mori silkworm. The ultrahigh brightness of S-FTIR microspectroscopy allowed the imaging of the silk gland with micrometer-scale spatial resolution. Herein, tissue sections of a silk gland, including cross-section slices and longitudinal-section slices, were characterized. The results obtained clearly confirm that the conformation of the silk fibroin changes gradually along the silk gland from the tail to the spinneret. In the middle silk gland, silk fibroin mainly contains random coil/helix conformation. When it comes to the spinneret through the anterior silk gland, the content of ß-sheet increases, but the content of random coil/helix instead reduces gradually. Further, the ß-sheet distribution in the cross-section of the anterior silk gland was imaged using S-FTIR mapping technique. The results show that the structural distribution of the silk fibroin in cross-section is uniform without significant shell-core structure, which implies that the primary driving force to induce the conformation transition of silk fibroin from random coil/helix to ß-sheet during the spinning process is elongational flow of silk fibroin in the silk gland and not the shear force between the silk fibroin and the lumen wall of silk gland. These direct pieces of evidence of silk fibroin structure in the silk gland would definitely promote a deeper understanding of the natural spinning process.