Enhanced stability of nitrogen-doped carbon-supported palladium catalyst for oxidative carbonylation of phenol

Enhancing the stability of supported noble metal catalysts emerges is a major challenge in both science and industry.Herein,a heterogeneous Pd catalyst(Pd/NCF)was prepared by supporting Pd ultrafine metal nanoparticles(NPs)on nitrogen-doped carbon;synthesized by using F127 as a stabilizer,as well as chitosan as a carbon and nitrogen source.The Pd/NCF catalyst was efficient and recyclable for oxidative carbonylation of phenol to diphenyl carbonate,exhibiting higher stability than Pd/NC prepared without F127 addition.The hydrogen bond between chitosan(CTS)and F127 was enhanced by F127,which anchored the N in the free amino group,increasing the N content of the carbon material and ensuring that the support could provide sufficient N sites for the deposition of Pd NPs.This process helped to improve metal dispersion.The increased metal-support interaction,which limits the leaching and coarsening of Pd NPs,improves the stability of the Pd/NCF catalyst.Furthermore,density functional theory calculations indicated that pyridine N stabilized the Pd^(2+)species,significantly inhibiting the loss of Pd^(2+)in Pd/NCF during the reaction process.This work provides a promising avenue towards enhancing the stability of nitrogen-doped carbon-supported metal catalysts.

Polymeric complex micelle loaded with axially substituted silicon(Ⅳ) phthalocyanine

A novel axially substituted silicon（IV） phthalocyanine, namely di-pyridyloxy axially substituted silicon（IV） phthalocyanine 2 was synthesized and characterized by UV/vis, IR, elemental analysis, MS as well as IH NMR spectroscopy. Hydrophobic 2 was encapsulated by amphiphilic triblock copolymer poly[N^e-（benzyloxycarbonyl-lysine]-poly（ethylene glycol）-poly [N^e-（benzyl oxycarbonyl） （PLL（Z）-b-PEG-b-PLL（Z）） to form hydrophobic 2-loaded polymeric complex micelle （PIC） （2-loaded P/C）. Atom force microscopy （AFM） image showed that 2-loaded PIC formed a spherical nanocarrier with approximately 35-50 nm in diameter. The fluorescence intensity and lifetime of 2-loaded PIC was significantly enhanced bv the incorporation 2 into PIC nanocarrier.

Micelle or polymersome formation by PCL-PEG-PCL copolymers as drug delivery systems

Polye-caprolactone）-b-poly（ethylene glycol）-b-poly（e-caprolactone）（PCL-b-PEG-b-PCL,PCEC） triblock copolymers have been widely investigated in last several decades.Here,by altering the weight ratio of monomers in ring-opening polymerization,a series of PCEC triblock copolymers with varying hydrophobicity were synthesized,which were characterized by FTIR,1 H NMR,GPC and DSC.When PCEC copolymers with different weight ratios of PCL/PEG were dispersed in different aqueous solutions,they could self-assemble and form two distinctive nanoparticular structures：micelles or polymersomes.We then chose paclitaxel（PTX） as the model drug and encapsulate PTX into PCEC polymeric micelles and polymersomes.The physicochemical characterizations of the nanoparticles such as morphology,the size and distribution,zeta potential,drug loading content,and encapsulation efficiency were also performed.Our results showed that polymeric micelles or polymersomes from PCEC both displayed narrow size distributions and could achieve high drug loading efficiencies.In vitro cellular uptake results suggested that Nile Red loaded polymeric micelles or polymersomes displayed more internalization after 24 h incubation than those after 4 h incubation.These findings suggest that polymeric micelles and polymersomes based on PCL-b-PEG-b-PCL copolymers have great potential to effectively delivery hydrophobic drugs.