Generation of 287 W, 5.5 ps pulses at 78 MHz repetition rate from a cryogenically cooled Yb:YAG amplifier seeded by a fiber chirped-pulse amplification system

We generate linearly polarized, 287 W average-power, 5.5 ps pulses using a cryogenically cooled Yb:YAG amplifier at a repetition rate of 78 MHz. An optical-to-optical efficiency of 41% is obtained at 700 W pump power. A 6 W, 0.4 nm bandwidth picosecond seed source at 1029 nm wavelength is constructed using a chirped-pulse fiber amplification chain based on chirped volume Bragg gratings. The combination of a fiber amplifier system and a cryogenically cooled Yb:YAG amplifier results in good spatial beam quality at large average power. Low nonlinear phase accumulation as small as 5.1 x 10(-3) rad in the bulk Yb:YAG amplifier supports power scalability to a > 10 kW level without being affected by self-phase modulation. This amplification system is well suited for pumping high-power high-repetition-rate optical parametric chirped-pulse amplifiers.     

Growth mechanism and optoelectronic properties of nanocrystalline In2O3 films prepared by chemical spray pyrolysis of metal-organic precursor

Thin films of indium oxide, In₂O₃, were deposited by chemical spray pyrolysis technique, using aqueous alcoholic solutions of indium acetylacetonate (In-acac) precursor, on glass substrates kept at temperatures between 300 and 500 °C. The structural, optical, and electrical properties have been investigated as a function of deposition temperature, precursor concentration, carrier gas pressure, and substrate-to-nozzle distance. X-ray diffraction studies showed that the formation of nanocrystalline In₂O₃ films is preferentially oriented along (2 2 2) plane. The surface morphological modifications with substrate temperature were observed using scanning electron and atomic force microscopic studies. Optical transmittance behavior of the films in the visible and IR region was strongly affected by the deposition parameters. The optical band gap values observed are between 3.53 and 3.68 eV. The long wavelength limit of refractive index is 1.83. The Hall mobility is found to vary from 23 to 37 cm²/V s and carrier density is found nearly constant at about 10²⁰ cm⁻³.     

Macromolecular salen catalyst with largely enhanced catalytic activity

A dinuclear copper(II) Schiff-base complex was immobilized in a poly(acrylate) matrix by emulsion polymerization. The spheric microbeads were used for aerobic catalytic oxidation of 3,5-di-tert-butylcatechol into 3,5-di-tert-butylquinone in methanol at ambient temperature to study the contribution of the macromolecular matrix to the overall rate acceleration of the reaction. The polymeric catalyst catalyzes the oxidation about 1 order of magnitude faster (kcat/knon = 470,000) than its low molecular weight analogue (kcat/knon = 60,000).     

Magnesium indium oxide (MgIn2O4) spinel thin films: chemical spray pyrolysis (CSP) growth and materials characterizations

MgIn(2)O(4), which has an inverse spinel structure, has been adopted as the transparent material in optoelectronic device fabrication due to its high optical transparency and electrical conductivity. Such a technologically important material was prepared by the spray pyrolysis technique. Precursors prepared for the cationic ratio Mg/In=0.5 were thermally sprayed onto glass substrates at 400 and 450 degrees C. We report herein the preparation and characterization of the films by X-ray diffraction (XRD), energy-dispersive absorption X-ray spectroscopy (EDAX), and atomic force microscopy (AFM). The XRD results showed the single phase formation of the material that revealed the presence of Mg(2+) and In(3+) in the inverse spinel-related structure. The FTIR and EDAX results further confirmed that the nanocrystalline films were mainly composed of magnesium, indium, and oxygen, in agreement with XRD analysis. We surmised from the AFM micrographs that the atoms have enough diffusion activation energy to occupy the correct site in the crystal lattice. For the 423-nm-thick magnesium indium oxide films grown at 400 degrees C, the electrical conductivity was 5.63x10(-6) Scm(-1) and the average optical transmittance was 63% in the visible range (400-700 nm). Similar MgIn(2)O(4) films deposited at 450 degrees C have a conductivity value of 1.5x10(-5) Scm(-1) and an average transmittance of 75%. Hall coefficient observations showed n-type electrical conductivity and high electron carrier concentration of 2.7x10(19) cm(-3).     

Ethene-1,1-disulfonyl Difluoride (EDSF) for SuFEx Click Chemistry: Synthesis of SuFExable 1,1-Bissulfonylfluoride Substituted Cyclobutene Hubs

We present the synthesis of 1,1-bis(fluorosulfonyl)-2-(pyridin-1-ium-1-yl)ethan-1-ide, a bench-stable precursor to ethene-1,1-disulfonyl difluoride (EDSF). The novel SuFEx reagent, EDSF, is demonstrated in the preparation of 26 unique 1,1-bissulfonylfluoride substituted cyclobutenes via a cycloaddition reaction. The regioselective click cycloaddition reaction is rapid, straightforward, and highly efficient, enabling the generation of highly functionalized 4-membered ring (4MR) carbocycles. These carbocycles are valuable structural motifs found in numerous bioactive natural products and pharmaceutically relevant small molecules. Additionally, we showcase diversification of the novel cyclobutene cores through selective Cs₂CO₃-activated SuFEx click chemistry between a single S−F group and an aryl alcohol, yielding the corresponding sulfonate ester products with high efficiency. Finally, density functional theory calculations offer mechanistic insights about the reaction pathway.     

Using thermally activated hydrotalcite for the uptake of phosphate from aqueous media

Hydrotalcites of formula Mg₆A₁₂(OH)₁₆(PO₄)·4H₂O formed by intercalation with the phosphate anion as a function of pH show variation in the d-spacing attributed to the size of the hydrated anion in the interlayer. The value changes from 11.91 Å for pH 9.3, to 7.88 Å at pH 12.5. No crystalline hydrotalcites with phosphate in the interlayer were formed at pH 9.3. Thermal decomposition identifies three steps namely dehydration, dehydroxylation and some loss of carbonate during the thermal treatment. The addition of a thermally activated ZnAl-HT to a phosphate solution resulted in the uptake of the phosphate and the reformation of the hydrotalcite. The technology has the potential for water purification through anion removal.     

The growing applications of click chemistry

Click chemistry, the subject of this tutorial review, is a modular synthetic approach towards the assembly of new molecular entities. This powerful strategy relies mainly upon the construction of carbon-heteroatom bonds using spring-loaded reactants. Its growing number of applications are found in nearly all areas of modern chemistry from drug discovery to materials science. The copper(I)-catalysed 1,2,3-triazole forming reaction between azides and terminal alkynes has become the gold standard of click chemistry due to its reliability, specificity and biocompatibility.