Enabling Complete Ligand Exchange on the Surface of Gold Nanocrystals through the Deposition and Then Etching of Silver.

We report an indirect method for the effective replacement of ligands on the surface of Au nanocrystals with different morphologies. The method involves the deposition of an ultrathin layer of Ag to remove a strong capping agent such as cetyltrimethylammonium chloride (CTAC), followed by selective etching of the Ag layer in the presence of citrate ions as a stabilizer. Using multiple characterization techniques, we confirm that the surface of the Au nanocrystals is covered by citrate ions after the indirect ligand exchange process, and there is essentially no aggregation during the entire process.

In Situ Atomic-Level Tracking of Heterogeneous Nucleation in Nanocrystal Growth with an Isocyanide Molecular Probe.

We report the use of 2,6-dimethylphenyl isocyanide (2,6-DMPI) as a spectroscopic probe to study the heterogeneous nucleation and deposition of Pd on Ag nanocubes under different conditions by surface-enhanced Raman scattering. As a major advantage, the spectroscopic analysis can be performed in situ and in real time with the nanoparticles still suspended in the reaction solution. The success of this method relies on the distinctive stretching frequencies (ν) of the isocyanide group in 2,6-DMPI when it binds to Ag and Pd atoms through σ donation and π-back-donation, respectively.

Enriching Silver Nanocrystals with a Second Noble Metal.

Noble-metal nanocrystals have received considerable interests owing to their fascinating properties and promising applications in areas including plasmonics, catalysis, sensing, imaging, and medicine. As demonstrated by ample examples, the performance of nanocrystals in these and related applications can be augmented by switching from monometallic to bimetallic systems. The inclusion of a second metal can enhance the properties and greatly expand the application landscape by bringing in new capabilities.

Ag@Au Concave Cuboctahedra: A Unique Probe for Monitoring Au-Catalyzed Reduction and Oxidation Reactions by Surface-Enhanced Raman Spectroscopy.

We report a facile synthesis of Ag@Au concave cuboctahedra by titrating aqueous HAuCl4 into a suspension of Ag cuboctahedra in the presence of ascorbic acid (AA), NaOH, and poly(vinylpyrrolidone) (PVP) at room temperature. Initially, the Au atoms derived from the reduction of Au(3+) by AA are conformally deposited on the entire surface of a Ag cuboctahedron. Upon the formation of a complete Au shell, however, the subsequently formed Au atoms are preferentially deposited onto the Au{100} facets, resulting in the formation of a Ag@Au cuboctahedron with concave structures at the sites of {111} facets.

[Efficacy analysis of endoscopic submucosal dissection for the early cancer and precancerous lesions in the remnant stomach].

Objective: To determine the feasibility and efficacy of endoscopic submucosal dissection(ESD) in treating early gastric cancer(EGC) and precancerous lesions in the remnant stomach of patients after gastrectomy.

Methods: Clinical data of 36 patients with EGC and precancerous lesions in remnant stomach undergoing ESD in Endoscopy Center of Zhongshan Hospital from January 2008 to December 2013 were retrospectively analyzed. Operative, postoperative conditions and long-term follow-up of these patients were evaluated.