RESUMEN
Precisely controlling the selectivity of nanocatalysts has always been a hot topic in heterogeneous catalysis but remains difficult owing to their complex and inhomogeneous catalytic sites. Herein, an effective strategy to regulate the chemoselectivity of Pd nanocatalysts for selective hydrogenation reactions by inserting single-atom Zn into Pd nanoparticles is reported. Taking advantage of the tannic acid coating-confinement strategy, small-sized Pd nanoparticles with inserted single-atom Zn are obtained on the O-doped carbon-coated alumina. Compared with the pure Pd nanocatalyst, the Pd nanocatalyst with single-atom Zn insertion exhibits prominent selectivity for the hydrogenation of p-iodonitrobenzene to afford the hydrodeiodination product instead of nitro hydrogenation ones. Further computational studies reveal that the single-atom Zn on Pd nanoparticles strengthens the adsorption of the nitro group to avoid its reduction and increases the d-band center of Pd atoms to facilitate the reduction of the iodo group, which leads to enhanced selectivity. This work provides new guidelines to tune the selectivity of nanocatalysts with guest single-atom sites.
RESUMEN
OBJECTIVE: To investigate the relationship between the hepatitis B virus (HBV) infection in pregnant women and intrauterine infection in local region. METHODS: The markers of hepatitis B (HBVM) were determined by time-resolved fluoroimmunoassay and HBV-DNA were determined by FQ-PCR. RESULTS: A total of 1262 pregnant women were examined the HBVM, 2.6%, 38.2%, 0.9%, 22.6%, 23.1% subjects were identified HBsAg, HBsAb, HBeAg, HBeAb, HBcAb positive respectively. In 33 cases of serum HBsAg-positive pregnant women, HBV-DNA were observed in most of 11 cases of pregnant women with HBeAg-positive and intrauterine infection rates were 6/11. In contrast, 22 cases of pregnant women with HBeAg negative, HBV-DNA were detected lowly-loaded and intrauterine infection rates were 2/22 (P < 0.01). Intrauterine infection rates of HBV in pregnant women with HBsAg-positive were 24.2% (8/33). CONCLUSION: HBV infective rates in pregnant women in the local region were low. Pregnant women with serum HBeAg positive and HBV-DNA high-loaded were prone to intrauterine infection.
