Nickel-Catalyzed Three-Component Unsymmetrical Bis-Allylation of Alkynes with Alkenes: A Density Functional Theory Study.

Density functional theory (DFT) characterizations were employed to resolve the structural and energetic aspects and product selectivities along the mechanistic reaction paths of the nickel-catalyzed three-component unsymmetrical bis-allylation of alkynes with alkenes. Our putative mechanism initiated with the in situ generation of the active catalytic species [Ni(0)L2] (L = NHC) from its precursors [Ni(COD)2, NHC·HCl] to activate the alkyne and alkene substrates to form the final skipped trienes. This proceeds via the following five sequential steps: oxidative addition (OA), ß-F elimination, ring-opening complexation, C-B cleavage and reductive elimination (RE). Both the OA and RE steps (with respective free energy barriers of 24.2 and 24.8 kcal·mol-1) contribute to the observed reaction rates, with the former being the selectivity-controlling step of the entire chemical transformation. Electrophilic/nucleophilic properties of selected substrates were accurately predicted through dual descriptors (based on Hirshfeld charges), with the chemo- and regio-selectivities being reasonably predicted and explained. Further distortion/interaction and interaction region indicator (IRI) analyses for key stationary points along reaction profiles indicate that the participation of the third component olefin (allylboronate) and tBuOK additive played a crucial role in facilitating the reaction and regenerating the active catalyst, ensuring smooth formation of the skipped triene product under a favorably low dosage of the Ni(COD)2 catalyst (5 mol%).

Palladium-Catalyzed Sequential Cross-Coupling/Annulation of ortho-Vinyl Bromobenzene with Aryl Bromide: Bimetallic Pathway versus Pd(II)-Pd(IV) Pathway: A DFT Investigation.

The palladium-catalyzed sequential cross-coupling/annulation of ortho-vinyl bromobenzenes with aryl bromides generating phenanthrenes was characterized by density functional theory (DFT). The Pd(II)-Pd(IV) pathway (Path V) is shown to be less probable than the bimetallic pathway (Path I), the latter proceeding via the following six steps: oxidative addition, vinyl-C(sp2)-H activation, Pd(II)-Pd(II) transmetalation, C-C coupling, aryl-C(sp2)-H activation, and reductive elimination. The aryl-C(sp2)-H activation process acts as the rate-determining step (RDS) of the entire chemical transformation, with an activation free energy barrier of ca. 27.4-28.8 kcal·mol-1, in good agreement with the corresponding experimental data (phenanthrenes' yields of ca. 65-90% at 130 °C after 5 h of reaction). The K2CO3 additive effectively reduces the activation free energy barrier of the RDS through direct participation in the reaction while preferentially modulating the charge distributions and increasing the stability of corresponding intermediates and complexes along the reaction path. Furthermore, bonding and electronic structure analyses of the key structures indicate that the chemo- and regioselectivities of the reaction are strongly influenced by both electronic effects and steric hindrance.

Liquid-Metal Molecular Scissors.

Molecules are the smallest units of matter that can exist independently, relatively stable, maintaining their physical and chemical activities. The key factors that dominate the structures and properties of molecules include atomic species, alignment commands, and chemical bonds. Herein, we reported a generalized effect in which liquid metals can directly cut off oxygen-containing groups in molecular matter at room temperature, allowing the remaining groups to recombine to form functional materials. Thus, we propose basic liquid-metal scissors for molecular directional clipping and functional transformations. As a proof of concept, we demonstrate the capabilities of liquid-metal scissors and reveal that the gallium on the surface of liquid metals directly extracts oxygen atoms from H2O or CH3OH molecules to form oxides. After clipping, the remaining hydrogen atoms from the H2O molecules recombine to form H2, while the remaining fragments of CH3OH produce H2, carbon materials, and carboxylates. This finding refreshes our basic understanding of chemistry and should lead to the development of straightforward molecular weaving techniques, which can help to overcome the limitations of molecular substances with single purposes. It also opens a universal route for realizing future innovations in molecular chemical engineering, life sciences, energy and environment research, and biomedicine.

Anchored Cu single atoms on porous g-C3N4 for superior photocatalytic H2 evolution from water splitting.

One of the most promising strategies for producing hydrogen is photocatalytic water splitting, in which the photocatalyst is a key component. Among many semiconductor photocatalysts, g-C3N4 has attracted great attention due to its narrow band gap, excellent stability and low cost. However, practical application is limited by its poor intrinsic activity. In this work, a high-performance porous g-C3N4 (PCN) photocatalyst with anchored Cu single atoms (CuSAs) was synthesized by a one-step co-heating approach. The obtained Cu1.5-PCN displays an excellent hydrogen evolution rate (HER) of 2142.4 µmol h-1 g-1 under visible light (=420 nm), which is around 15 and 109 times higher than those of PCN and bulk g-C3N4, respectively. In addition, it also shows good stability during H2 evolution. The results of experimental research and DFT simulations indicate that the single Cu ions formed bonds with the N-ring and these remain stable. Meanwhile, the special electronic structure of the Cu-N charge bridge extends the light absorption band to the visible-light region (380-700 nm). This high-performance and low-cost photocatalyst has great potential in solar energy conversion.

Surface Optics and Color Effects of Liquid Metal Materials.

Liquid metals (LMs) are emerging as new functional materials with rather unique physical or chemical behaviors. They are generally safe and nontoxic, have high boiling points, reflectivities, good thermal and electrical conductivities, flexibility, fluidity, self-healing capability and remain in liquid state at room temperature. However, the further applications of LMs are limited by their single-color physical appearance, such as working in the situations with imposed stringent requirements for color and aesthetics. Recently, the color and fluorescence functionalization of LMs have overcome many conventional technical bottlenecks and opened significant potential for emerging applications in numerous fields owing to their rich colors and unique liquid structure. In this review, the recent developments in the optical properties, color and fluorescence effects of LMs are comprehensively investigated. The synthesis, structures, properties, chromogenic mechanisms, and potential photoelectric applications of colorful LMs are systematically analyzed and compared. The effectiveness and characteristics of colorful LMs induced by coating, mixing, compounding, surface modification, external stimuli are provided, aiming to establish a potential system for the synthesis and practices of colorful LMs. Finally, the challenges and prospects in the field have also been identified and explained to preferably guide further scientific and technical research in the coming time.

New Strategy and Excellent Fluorescence Property of Unique Core-Shell Structure Based on Liquid Metals/Metal Halides.

The further applications of liquid metals (LMs) are limited by their common shortcoming of silver-white physical appearance, which deviates from the impose stringent requirements for color and aesthetics. Herein, a concept is proposed for constructing fluorescent core-shell structures based on the components and properties of LMs, and metal halides. The metal halides endow LMs with polychromatic and stable fluorescence characteristics. As a proof-of-concept, LMs-Al obtained by mixing of LMs with aluminum (Al) is reported. The surface of LMs-Al is transformed directly from Al to a multi-phase metal halide of K3 AlCl6 with double perovskites structure, via redox reactions with KCl + HCl solution in a natural environment. The formation of core-shell structure from the K3 AlCl6 and LMs is achieved, and the shell with different phases can emit a cyan light by the superimposition of the polychromatic spectrum. Furthermore, the LMs can be directly converted into a fluorescent shell without affecting their original features. In particular, the luminescence properties of shells can be regulated by the components in LMs. This study provides a new direction for research in spontaneous interfacial modification and fluorescent functionalization of LMs and promises potential applications, such as lighting and displays, anti-counterfeiting measures, sensing, and chameleon robots.

Unique Surface Fluorescence Induced from the Core-Shell Structure of Gallium-Based Liquid Metals Prepared by Thermal Oxidation Processing.

Liquid metals (LMs) have emerged as promising functional materials that combine the properties of both liquid and metal. These characteristics enabled them to find applications in many fields. However, the LMs usually can only display a silver-white physical appearance, which limits their further applications in the fields with the imposition of stringent requirements for color and aesthetics. Herein, we report that the surface of LMs was transformed directly from metal to fluorescent semiconductor layer by an example of eutectic GaInSn (eGaInSn) induced by thermal oxidation. Specifically, a core-shell structure is formed from the fluorescent layer and the LMs. The shell endows the LMs with fluorescence without affecting their interior fluidity and conductivity. In particular, the formation process as well as the degree of crystallization, phase transformation, and light emission of the fluorescent oxide shell on the surface of LMs is regulated by the component content. A thorough analysis of surface morphology, composition, structure, and properties of the fluorescent shell suggests that the Ga2O3 layer is formed on the surface of gallium-based LMs after their immersion in deionized water. Subsequently, thermal oxidation results in the formation of the ß-Ga2O3 shell on the surface of liquid metals. Importantly, abundant oxygen vacancies (VO) in ß-Ga2O3 as the donors and the gallium vacancies (VGa), gallium-oxygen vacancy pairs (VO-VGa), defect energy levels, and intrinsic defects as the acceptors enabled the light emission. The fluorescent LMs have promising potential for flexible lighting and displays, anticounterfeiting measures, sensing, and chameleon robots.

Unique and Excellent Paintable Liquid Metal for Fluorescent Displays.

A liquid metal (LM) generally has excellent electrical conductivity, thermal conductivity, flexibility, fluidity, and reflectivity. Innovative electronics using a LM to paint colorful fluorescent patterns may be applied to many important fields. Herein we propose, for the first time, the use of a LM to paint fluorescent patterns in the field of natural science. An LM containing a main-group metal (Ga50.25Bi8.28In28.2Sn13.27) is used to paint a uniform alloy film on a ceramic substrate. The painting is not restricted by any curved surface, shape, or size, which therefore gives the LM diverse adaptability. We have adopted the strategy of "painting-annealing-dealloying" through which LM can easily be diffused and doped into the substrate to produce various defects. Defects, my themselves or through their interactions, can produce different colors of emitted light. The primary fluorescence colors, such as purple, yellow, blue, and white, have been painted with the LM. Importantly, the brightness and color coordinates can be adjusted by changing the LM composition or annealing temperature, and intricate, delicate, colorful fluorescence patterns can be produced. Due to the unique painting form, colorful fluorescence, high stability, corrosion resistance, and low cost of the technique used for the LM, it can be used for displays, lighting panels, flexible electronic circuits, anticounterfeiting devices, and sensors.

Novel Strategy for Organic Cocrystals of n-Type and p-Type Organic Semiconductors with Advanced Optoelectronic Properties.

Cocrystallization has been applied widely for material synthesis. Recently cocrystal of organic molecules has been developing rapidly, taking the advantages of the flexibility and self-assembly of organic molecules. Here we report an experimental study of a cocrystal of copper-phthalocyanines and fluorinated ones. We have grown the samples via the vapor-phase deposition of the mixture with different mass ratios from 1:13.5 to 6:1. As suggested by our scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy, new crystal structures and morphologies through our novel strategy for the cocrystallization of these molecules have been found. Our work will provide a solid foundation to systematically synthesize the cocrystal of phthalocyanine molecules with new crystal structures, thus providing the opportunity to advance material properties.

Enhancement of astaxanthin production from Haematococcus pluvialis mutants by three-stage mutagenesis breeding.

Haematococcus pluvialis was modified for higher astaxanthin production compatible with the superiorities of high biomass and high activity by three-stage mutagenesis breeding. UV irradiation mutants named UV11-4 made an increase on cell dry weight, but showed a longer growth circle than the wild type. On the basis of UV mutants, ethyl methane sulphonate (EMS) mutants E2-5 cut down the latent phase, brought forward and extended the logarithmic phase. The inhibitor diphenylamine (DPA) was employed to screen high-yield astaxanthin producer by the color change of colonies from green to red on solid medium. Via the contravariant cultivation, proliferation and transformation, the mutant DPA12-2 possessed an 1.7-fold astaxanthin production compared to the wild type, reaching 47.21±3.30mg/g dry cells.

[Study on the Properties of the Pc-Si Films Prepared by Magnetron Co-Sputtering at Low Temperature].

The polycrystalline silicon thin films play an important role in the field of electronics. In the paper, α-SiAl composite membranes on glass substrates was prepared by magnetron co-sputtering. The contents of Al radicals encapsulated-in the α-Si film can be adjusted by changing the Al to Si sputtering power ratios. The as-prepared α-Si films were converted into polycrystalline films by using a rapid thermal annealing (RTP) at low temperature of 350 degrees C for 10 minutes in N2 atmosphere. An X-ray diffractometer, and Raman scattering and UV-Visible-NIR Spectrometers were used to characterize the properties of the Pc-Si films. The influences of Al content on the properties of the Pc-Si films were studied. The results showed that the polycrystalline silicon films were obtained from α-SiAl composite films which were prepared by magnetron co-sputtering at a low temperature following by a rapid thermal annealing. The grain size and the degree of crystallization of the Pc-Si films increased with the increase of Al content, while the optical band gap was reduced. The nc-Si films were prepared when the Al to Si sputtering power ratio was 0.1. And a higher Crystallization rate (≥ 85%) of polycrystalline silicon films were obtained when the ratio was 0.3. The band gaps of the polycrystalline silicon films can be controlled by changing the aluminum content in the films.

Enhancement of cell biomass and cell activity of astaxanthin-rich Haematococcus pluvialis.

Fed-batch culture and the transformation conditions of Haematococcus pluvialis in a 5L photobioreactor were investigated. Methods of feeding model, low temperature at night and proper feeding time were used to increase both cell biomass and cell activity. Dry cell weight of 1.87 g/L which was 2.0-fold of batch culture and the specific growth rate of 0.43 d(-1) suggested the superduper results of these methods to increase the dry cell weight in the short cultivation time. Furthermore, mixed lights of blue and white (ratio of 3:1) at 7000 xl were used to expedite the morphologic changes of H. pluvialis from green cells to red cyst cells with the yield of 91.8±2.53 mg/L.

[Spectral Characteristics of Si Quantum Dots Embedded in SiN(x) Thin Films Prepared by Magnetron Co-Sputtering].

The silicon-rich SiN(x) films were fabricated on Si(100) substrate and quartz substrate at different substrate temperatures varying from room temperature to 400 degrees C by bipolar pulse ane RF magnetron co-sputtering deposition technique. After deposition, the films were annealed in a nitrogen atmosphere by rapid photothermal annealing at 1050 degrees C for 3 minutes. This thermal step allows the formation of the silicon quantum dots. Fourier transform infrared spectroscopy, Raman spectroscopy, grazing incidence X-ray diffraction and photoluminescence spectroscopy were used to analyze the bonding configurations, microstructures and luminescence properties of the films. The experimental results showed that: silicon-rich Si-N bonds were found in Fourier transform infrared spectra, suggesting that the silicon-rich SiN, films were successfully prepared; when the substrate temperature was not lower than 200 degrees C, the Raman spectra of the films showed the transverse optical mode of Si-Si vibration, while the significant diffraction peaks of Si(111) and Si(311) were shown in grazing incidence X-ray diffraction spectra, confirming the formation of silicon quantum dots; our work indicated that there was an optimal substrate temperature (300 degrees C), which could significantly increase the amount and the crystalline volume fraction of silicon quantum dots; three visible photoluminescence bands can be obtained for both 30 degrees C sample and 400 degrees C sample, and in combination with Raman results, the emission peaks were reasonably explained by using the quantum confinement effect and radiative recombination defect state of Si nanocrystals; the average size of the silicon quantum dots is 3.5 and 3.4 nm for the 300 degrees C sample and 400 degrees C sample, respectively. These results are useful for optimizing the fabrication parameters of silicon quantum dots embedded in SiN. thin films and have valuable implications for silicon based photoelectric device applications.

[Research on the phase and optical properties of nc-Si films prepared by low temperature aluminum induced crystallization].

In the present paper, nanocrystalline silicon thin films on glass substrates were prepared by rapid thermal annealing (RTA) of RF magnetron sputtered system and alpha-Si/Al films at a low temperature in Nz atmosphere. Optical metallographic microscope, confocal optical microscopy, X-ray diffractometer, Raman scattering and UV-Vis-NIR spectrometers were used to characterize the surface morphology and the phase and optical properties of nc-Si films. The influence of annealing process on the nc-Si films properties was studied. The results showed that nc-Si films were obtained after aluminum induced crystallization of the alpha-Si/Al films at 300 degrees C, withthe crystallization rate 15.56% and the grain size 1.75 nm. The surface uniformity and lattice distortion of nc-Si films reduced, while grain size, degree of crystallization and the optical band gap of the films increased with increasing annealing temperature from 300 to 400 degrees C. As the annealing temperature increased from 400 to 500 degrees C, although the degree of crystallization and grain size increased, the tendencies of all other characteristics were opposite. On the contrary, the surface uniformity and the lattice distortion increased, but the optical band gap of nc-Si films reduced. The optical properties of the resulting films were confirmed by the absorption model of nc-Si thin films, where the tendency of band gap changes is in consistent with the optical modeling.