Xiao-Min Lin

In situ visualization of self-assembly of charged gold nanoparticles.

Self-assembly of Au nanoparticles (NPs) coated with positively charged cetyltrimethylammonium ions (CTA(+)) and negatively charged citrate ions in aqueous liquid cell was investigated by in situ transmission electron microscopy (TEM). Under electron illumination in TEM, the hydrated electrons will reduce the overall positive charges of the CTA(+) covered Au NPs and decrease the repulsive electrostatic forces among NPs, leading to assembly of individual NPs into one-dimensional structures. On the contrary, the negatively charged Au NPs coated with citrate ions are steady in liquid cell regardless of electron beam intensity.

Electrooxidative Tandem Cyclization of Activated Alkynes with Sulfinic Acids To Access Sulfonated Indenones

An electrooxidative direct arylsulfonlylation of ynones with sulfinic acids via a radical tandem cyclization strategy has been developed for the construction of sulfonated indenones under oxidant-free conditions. This method provides a simple and efficient approach to prepare various sulfonylindenones in good to excellent yields, demonstrating the tremendous prospect of utilizing electrocatalysis in oxidative coupling. Notably, this reaction could be easily scaled up with good efficiency.

THERMAL BLOOMING EFFECT ON PARTICLE SIZING WITH PHOTON CORRELATION SPECTROSCOPY

Photon correlation spectroscopy autocorrelation spectra were measured for gold nanocrystal superlattice colloids under several intensities of an incident laser beam. Thermal blooming in the colloid shifted the correlation spectra toward smaller times. A second cumulant term in the fitting curve proved effective to correct for the thermal blooming effect to yield the correct particle size.

Binary Transition Metal Oxide Hollow Nanoparticles for Oxygen Evolution Reaction

Low-cost transition metal oxides are actively explored as alternative materials to precious metal-based electrocatalysts for the challenging multistep oxygen evolution reaction (OER). We utilized the Kirkendall effect allowing the formation of hollow polycrystalline, highly disordered nanoparticles (NPs) to synthesize highly active binary metal oxide OER electrocatalysts in alkali media. Two synthetic strategies were applied to achieve compositional control in binary transition metal oxide hollow NPs. The first strategy is capitalized on the oxidation of transition-metal NP seeds in the presence of other transition-metal cations. Oxidation of Fe NPs treated with Ni (+2) cations allowed the synthesis of hollow oxide NPs with a 1-4.7 Ni-to-Fe ratio via an oxidation-induced doping mechanism. Hollow Fe-Ni oxide NPs also reached a current density of 10 mA/cm2 at 0.30 V overpotential. The second strategy is based on the direct oxidation of iron-cobalt alloy NPs which allows the synthesis of hollow Fe xCo100- x-oxide NPs where x can be tuned in the range between 36 and 100. Hollow Fe36Co64-oxide NPs also revealed the current density of 10 mA/cm2 at 0.30 V overpotential in 0.1 M KOH.

Low Pressure Flow Chemistry of CuAAC Click Reaction Catalyzed by Nanoporous AuCu Membrane

Click chemistry has been widely used in bioconjugation, polymer synthesis, and the development of new anticancer drugs. Here, we report a nanoporous membrane made of AuCu alloy nanowires, which can effectively catalyze copper(I)-catalyzed 1,3-dipolar cycloaddition between azide and terminal alkyne (CuAAC) in flow condition with pressure less than one bar. Comparison studies of the nanowires before and after the reaction using X-ray photoelectron spectroscopy reveal Cu(0) and Cu(I) are main species that promote the reaction. This simple strategy can be used to synthesize a variety of compounds with triazole linkage and extended to gram level chemical production.