Surface modification of high-nuclearity lanthanide clusters: two tetramers constructed by cage-shaped [Dy26] clusters and isonicotinate linkers

By incorporation of NO3- ligands with trigonal planar geometry as surface modifiers into the lanthanide cluster core backbone to remarkably improve the dimension of cluster cores, two novel lanthanide cluster compounds, Dy30I(micro3-OH)24(micro3-O)6(NO3)9(IN)41(OH)3(H2O)38 (1) and Dy104I4(micro3-OH)80(micro3-O)24(NO3)36(IN)125(OH)19(H2O)167 (2) (HIN = isonicotinic acid), have been obtained under hydrothermal conditions. Single-crystal X-ray diffraction shows that in both cluster compounds, the block blocks of [Dy26(micro3-OH)20(micro3-O)6(NO3)9I]36+, [Dy26], are the largest cage-shaped lanthanide cluster cores known. Compound 1 is the first tetramer based on the linkage of two different types of high-nuclearity lanthanide clusters and IN ligands, while compound 2 represents the first tetramer constructed by [Dy26] clusters and IN linkers.     

Restoration of atmospheric turbulence degraded images

A blind image deconvolution algorithm in the frequency domain is proposed which uses the edge-preserving method and generic bandwidth of optical system. Generic bandwidth of optical system is analyzed. With the benefits of bandwidth and edge-preserving method as compelling constraints, the algorithm cannot only suppress noise effectively but also restrict the bandwidth of point-spread function (PSF), so high-quality result can be obtained. The new algorithm is superior in handling unregistered channels. The performance of this approach is investigated with simulated data. As shown in our investigation, the algorithm can significantly alleviate the artifacts produced by the deconvolution process.     

Reversible Phase Transfer of Luminescent ZnO Quantum Dots between Polar and Nonpolar Media

A facile and reversible phase‐transfer protocol for luminescent ZnO quantum dots (QDs) between methanol and hexane is presented. Oleylamine together with acetic acid trigger this reversible phase‐transfer process, during which the structure and optical properties of the ZnO QDs are well‐protected. ZnO QDs with a diameter of approximately 5 nm emit yellow light at 525 nm, while those with a diameter of approximately 4 nm emit green light at 510 nm. The positions of the emission peaks remain unchanged during the presented phase‐transfer process. The Pearson’s hard and soft (Lewis) acid and base principle, together with the principle that similar substances are more likely to be dissolved by each other, describes the current reversible phase‐transfer process. Herein, we circumvent the time‐consuming work required to synthesize ZnO QDs in different environments, making it possible to combine the advantages of ZnO QDs dispersed in polar and nonpolar solvents.     

Visualization of nanosecond laser-induced dewetting,ablation and crystallization processes in thin silicon films

In the present work, nanosecond pulsed laser crystallization, dewetting and ablation of thin amorphous silicon films are investigated by time-resolved imaging. Laser pulses of 532 nm wavelength and 7 ns temporal width are irradiated on silicon film. Below the dewetting threshold, crystallization process happens after 400 ns laser irradiation in the spot central region. With the increasing of laser fluence, it is observed that the dewetting process does not conclude until 300 ns after the laser irradiation, forming droplet-like particles in the spot central region. At higher laser intensities, ablative material removal occurs in the spot center. Cylindrical rims are formed in the peripheral dewetting zone due to solidification of transported matter at about 500 ns following the laser pulse exposure.     

Phytophenol Dimerization Reaction: From Basic Rules to Diastereoselectivity and Beyond

Phytophenol dimerization, which is a radical-mediated coupling reaction, plays a critical role in many fields, including lignin biosynthesis. To understand the reaction, 2,2-diphenyl-1-picrylhydrazyl radical was used to initiate a series of phytophenol dimerization reactions in methanol. The products were identified using ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC-ESI-Q-TOF-MS/MS) analysis in situ. The identified products mainly included biphenols, magnolol, honokiol, gingerol 6,6′-dimers, 3,6-dimethoxylcatechol β,β′ dimer, euphorbetin, bis-eugenol, dehydrodiisoeugenol, trans-ε-viniferin, (+) pinoresinol, and (−) pinoresinol. Structure–function relationship analysis allowed four basic rules to be defined: meta-excluded, C–C bonding domination, ortho-diOH co-activation, and exocyclic C=C involvement. The exocyclic C=C involvement, however, required conjugation with the phenolic core and the para-site of the -OH group, to yield a furan-fused dimer with two chiral centers. Computational chemistry indicated that the entire process was completed via a radical coupling reaction and an intramolecular conjugate addition reaction. Similar results were also found for the horseradish peroxidase (HRP)-catalyzed coniferyl alcohol dimerization, which produced (+) and (−) pinoresinols (but no (−) epipinoresinol), suggesting that the HRP-catalyzed process was essentially an exocyclic C=C-involved phytophenol dimerization reaction. The reaction was highly diastereoselective. This was attributed to the intramolecular reaction, which prohibited Re-attack. The four basic rules and diastereoselectivity can explain and even predict the main products in various chemical and biological events, especially oxidase-catalyzed lignin cyclization.