Immersion of charged nanoparticles in a salt solution/air interface

Electrostatic interactions strongly affect the immersion depth of nanoparticles into an interface. We prove this statement by measuring the diffusion constant of charged nanoparticles at a sodium chloride solution/air interface. Interfacial diffusion of nanoparticles slows down with increasing ionic strength of the sodium chloride solution. Hydrodynamic calculations are used to estimate the immersion depth from the diffusion constant, suggesting that nanoparticles with a carboxylate surface are only slightly immersed into a bare air/water interface. With increasing molarities of sodium chloride, the immersion depth increases to complete immersion for a 10(-2) molar solution. Our experiments show that the location of nanoparticles at interfaces is determined by an intricate interplay between the electrostatic properties of the solution/air interface, the solution/solid interface, and the classical contact angle.     

Unprecedented dithiolation of enals via their NHC-catalysed umpolung reaction with organic disulfides

A novel one-pot N-heterocyclic carbene (NHC)-catalysed dithiolation of α,β-unsaturated aldehydes (enals) with organic disulfides is reported. The protocol involves homoenolate reactivity of enals, where the homoenolate attacks on the disulfide as a d(3) nucleophile followed by thioesterification to afford β-aryl/alkylsulfanyl thioesters with complete atom economy.     

Bromodimethylsulfonium bromide (BDMS)-catalyzed multicomponent synthesis of 3-aminoalkylated indoles

Bromodimethylsulfonium bromide (BDMS)-catalyzed three-component coupling reaction between indoles, aldehydes, and N-alkylanilines is reported to access substituted 3-aminoalkylated indoles at room temperature in high yields (82-96%) within 1.5-3.5 h. The salient features of this protocol are the simplicity of the procedure, the ready accessibility of the catalyst, its cost effectiveness, and higher yields in relatively short reaction times.     

Anisotropic magnetic properties and superzone gap formation in CeGe single crystal

Single crystals of CeGe and its non-magnetic analog LaGe have been grown by the Czochralski method. The CeGe compound crystallizes in the orthorhombic FeB-type crystal structure with the space group Pnma (#62). The anisotropic magnetic properties have been investigated for well oriented single crystals by measuring the magnetic susceptibility, electrical resistivity and heat capacity. It has been found that CeGe orders antiferromagnetically at 10.5?K. Both transport and magnetic studies have revealed large anisotropy, reflecting the orthorhombic crystal structure. The magnetization data at 1.8?K reveal metamagnetic transitions along the [010] direction at 4.8 and 6.4?T and along the [100] direction at a critical field of 10.7?T, while the magnetization along the [001] direction increases linearly without any anomaly up to a field of 16?T. From the magnetic susceptibility and the magnetization measurements it has been found that the [010] direction is the easy axis of magnetization. The electrical resistivity along the three crystallographic directions exhibits an upturn at T(N), indicating superzone gap formation below T(N) in this compound. We have performed crystal electric field analysis on the magnetic susceptibility and the heat capacity data and found that the ground state is a doublet, and the energies of splitting from the ground state to the first and second excited doublet states were estimated to be 39 and 111?K, respectively.     

Germanium microsphere high-Q resonator

In this Letter, the fabrication and characterization of a microsphere resonator from the semiconductor germanium is demonstrated. Whispering gallery modes are excited in a 46 μm diameter germanium microsphere resonator using evanescent coupling from a tapered silica optical fiber with a waist diameter of 2 μm. Resonances with Q factors as high as 3.8×10(4) at wavelengths near 2 μm are observed. Because of their ultrahigh optical nonlinearities and extremely broad transparency window, germanium microsphere resonators offer the potential for optical processing devices, in particular at long wavelengths, such as around 2 μm.