Preparation of new hybrid organic/inorganic polymeric chiral stationary phases for ligand-exchange chromatography

Three new hybrid organic/inorganic polymeric ligand-exchange chiral stationary phases were developed by radical chain transfer reaction and surface grafting on silica gel, and successfully used for the enantioseparations of DL-amino acids and DL-hydroxyl adds. The resolutions were achieved by using water containing 2.0 × 10^-4 mol/L of CuAc2 as a mobile phase, column temperature of 40 ℃, flow rate of 1.0 mL/min and detection at UV 254 nm. The elution order of D-isomer before L-isomer was observed for all DL-amino acids resolved except DL-Pro.

A chiral stationary phase with special hydrophobic framework for ligand-exchange chromatography

A novel chiral stationary phase （CSP1） for ligand-exchange chromatography （CLEC） was prepared by firstly using dimethylchlorosilane as an endcapping reagent for decreasing residual silanol group on the surface of silica gel, and then introducing L-Pro as a chiral selector and hydrophobic octyl group to the silica gel surface simultaneously. The enantioseparations of 14 DL-amino acids on CSP1 were achieved with the enantioselectivity α ranging from 1.09 to 2.44 and the resolution Rs being between 0.8 and 6.3. The chromatographic performances of CSP1 with the bonded phase （CSP2） prepared using reference method were compared. The results showed that the column efficiency and resolution Rs of chiral stationary phase could be improved by using the above modifying method.

Fast synthesis of dopamine-coated Fe_3O_4 nanoparticles through ligand-exchange method

A fast approach was described for the synthesis of water-dispersible monodisperse dopamine-coated Fe304 nanoparticles （DA- Fe304） with uniform size and shape via ligand-exchange of oleic acid on Fe304 using only 2 min. The prepared DA-Fe304 nanoparticles were characterized by transmission electron microscopy, Fourier transform infrared spectrometry, and vibrating sample magnetometer. The results indicated that the resulting DA-Fe304 nanoparticles had an average diameter of about 19.2 nm. The magnetic saturation value of the prepared DA-Fe304 nanoparticles was determined to be 72.87 emu/g, which indicating a well- established superparamagnetic property.

Investigation of Mixed Chiral Selectors of Different Metal Ion-L-Alanine Complex and β-Cyclodextrin on the Chiral Separation of Dansyl Amino Acids with Capillary Electrophoresis

Chiral separation of dansyl amino acids by capillary electrophoresis using mixed selectors of Mn(II)- L -alanine complex and β -cyclodextrin ( β -CD) was studied. Resolution was considerably superior to that obtained by using either Mn(II)- L -alanine complex or β -CD alone. The effects of separation parameters,such as pH value of buffer solution,capillary temperature,the concentration of Mn(II)- L -alanine complex,the types of CD and ligand on the migration times and resolutions were investigated. Six different transition metal complexes, Cu(II), Zn(II),Co(II),Ni(II),Hg(II) and Cd(II)- L -alanine complexes have been employed and compared with Mn(II) complex. Differences in retention and selectivity were found. The substitution of Cu(II),Zn(II),Co(II) and Ni(II) for Mn(II) resulted in a better chiral resolution while Hg(II) and Cd(II) showed poorer resolution abilities. The chiral separation mechanism was also discussed briefly.

Preparation and ζ-potential characterization of highly dispersible phosphate—functionalized magnetite nanoparticles

By the combination of high-temperature organometallic synthesis and phase transfer through complete ligand-exchange withmixed phosphate, highly water-dispersible Fe3O4nanoparticles with narrow size distribution are obtained, which show appli-cable response to magnetic field. IR and -potential characterization of this system provides insights into ligand structures onparticle surface.

Generalized assembly of sandwich-like 0D/2D/0D heterostructures with highly exposed surfaces toward superior electrochemical performances

Heterostructures composed of two-dimensional(2D)nanosheets and zero-dimensional(0D)nanoparticles(NPs)have attracted increasing attention because of the synergy arising from the coupling interactions between the two mixed-dimensional components.Despite recent advances,it remains a challenge to fabricate 2D/0D heterostructures with clean and accessible surfaces,which is highly desirable for the diversity of catalytic,sensing,and energy storage applications.Herein,we report a generalized methodology that enables the facile assembly of sandwich-like 0D/2D/0D heterostructures with facilitated mass-transport channels and exposed surface active sites.A ligand-exchange strategy with HBF4 is employed to strip off the surface-coating ligands of colloidal NPs,rendering them positively charged and dispersible in polar solvents.This allows subsequent electrostatic assembly of NPs with oppositely charged 2D nanosheets to afford sandwich-like 0D/2D/0D heterostructures.The barely covered surfaces and the advantageous architectures of such sandwich-like 0D/2D/0D heterostructures induce the desired synergistic effect,making them particularly suitable for electrochemical energy storage and conversion.We demonstrate this by employing MXene/NiFe_(2)O_(4) and MXene/Fe3O4 heterostructures for high-performance electrocatalytic oxygen evolution and supercapacitors,respectively.

THE SYNTHESIS OF CROSS-LINKED POLYSTYRENE RESINS GRAFTED BY L-PROLINE THROUGH HYDROPHILIC SPACERS

L-proline was linked onto cross-linked polystyrene to give chiral chelating resin (1). The copper (Ⅱ) chelate of resin (1) was used as the chiral stationary phase for the chromatographic resolution of DL-amino acids. However, the hydrophobicity of polystyrene causes an amino acid to transfer slowly during chromatographic process so