Disintegration or redispersion of supported sintered gold nanoparticles （Au NPs） in the presence of alkyl halide can give catalyst regeneration or redispersion of sintered Au catalysts. The selectivity of alkyl hali...Disintegration or redispersion of supported sintered gold nanoparticles （Au NPs） in the presence of alkyl halide can give catalyst regeneration or redispersion of sintered Au catalysts. The selectivity of alkyl halides, temperature and size distributions were investigated to elucidate the redispersion of Au NPs during halide-induced decomposition. This study proved that the alkyl halide induced the redispersion of sintered Au NPs which depended on the R-X （X = I, Br, CI） bond dissociation energy （BDE） and thus provided a simple descriptor for the regeneration of inactive supported Au cata- lysts. A correlation between the BDE of R-X and dispersion efficiency was established. The tendency for disintegration and redispersion followed the R-X BDE of the alkyl halide. Compared to alkyl chlorides and bromides, iodides were more efficient for redispersing sintered Au NPs. As a descriptor, the BDE of R-I played a crucial role in particle redispersion. These findings provided in- sights into the mechanism of organic halide-induced Au NP disintegration and the effect of the hal- ide type on the redispersion of sintered catalysts.展开更多
A Cu2O/SiC heterogeneous catalyst was prepared via a two‐step liquid‐phase method using diethyleneglycol as both the solvent and the reducing agent.The catalyst was characterized using X‐raydiffraction,X‐ray photo...A Cu2O/SiC heterogeneous catalyst was prepared via a two‐step liquid‐phase method using diethyleneglycol as both the solvent and the reducing agent.The catalyst was characterized using X‐raydiffraction,X‐ray photoelectron spectroscopy,scanning electron microscopy(SEM),transmissionelectron microscopy(TEM),and H2temperature‐programmed reduction.All the results indicatethat Cu is present on the SiC support primarily as Cu2O.The SEM and TEM results show that cubicCu2O nanoparticles are uniformly dispersed on theβ‐SiC surface.The reaction conditions,namelythe temperature,reaction time,and amounts of base and catalyst used,for the Ullmann‐type C–Ocross‐coupling reaction were optimized.A model reaction was performed using iodobenzene(14.0mmol)and phenol(14.0mmol)with Cu2O/SiC(5wt%Cu)as the catalyst,Cs2CO3(1.0equiv.)as thebase,and tetrahydrofuran as the solvent at150°C for3h;a yield of97%was obtained and theturnover frequency(TOF)was1136h?1.The Cu2O/SiC catalyst has a broad substrate scope and canbe used in Ullmann‐type C–O cross‐coupling reactions of aryl halides and phenols bearing a varietyof different substituents.The catalyst also showed high activity in the Ullmann‐type C–Scross‐coupling of thiophenol with iodobenzene and substituted iodobenzenes;a TOF of1186h?1was achieved.The recyclability of the Cu2O/SiC catalyst in the O‐arylation of phenol with iodobenzenewas investigated under the optimum conditions.The yield decreased from97%to64%afterfive cycles.The main reason for the decrease in the catalyst activity is loss of the active component,i.e.,Cu2O.展开更多
In this paper, we produce porous silicon （PSi） by electrochemical etching, and it is the first time to evaluate the performance of label-free porous silicon biosensor for detection of variable domain of heavy chain ...In this paper, we produce porous silicon （PSi） by electrochemical etching, and it is the first time to evaluate the performance of label-free porous silicon biosensor for detection of variable domain of heavy chain of heavy-chain antibody （VHH）. The binding of hen egg white lysozyme （HEWL） and VHH causes a red shift in the reflection spectrum of the biosensor. The red shift is proportional to the VHH concenlration in the range from 14 gg.ml-I to 30 pg.ml~ with a detection limit of 0.648 ng.ml~. The research is useful for the development of label-free biosensor applied in the rapid and sensitive determination of small molecules.展开更多
文摘Disintegration or redispersion of supported sintered gold nanoparticles （Au NPs） in the presence of alkyl halide can give catalyst regeneration or redispersion of sintered Au catalysts. The selectivity of alkyl halides, temperature and size distributions were investigated to elucidate the redispersion of Au NPs during halide-induced decomposition. This study proved that the alkyl halide induced the redispersion of sintered Au NPs which depended on the R-X （X = I, Br, CI） bond dissociation energy （BDE） and thus provided a simple descriptor for the regeneration of inactive supported Au cata- lysts. A correlation between the BDE of R-X and dispersion efficiency was established. The tendency for disintegration and redispersion followed the R-X BDE of the alkyl halide. Compared to alkyl chlorides and bromides, iodides were more efficient for redispersing sintered Au NPs. As a descriptor, the BDE of R-I played a crucial role in particle redispersion. These findings provided in- sights into the mechanism of organic halide-induced Au NP disintegration and the effect of the hal- ide type on the redispersion of sintered catalysts.
基金supported by the National Natural Science Foundation of China (21203233,21473232,21403270)Youth Innovation Promotion Association,CAS (2013115)~~
文摘A Cu2O/SiC heterogeneous catalyst was prepared via a two‐step liquid‐phase method using diethyleneglycol as both the solvent and the reducing agent.The catalyst was characterized using X‐raydiffraction,X‐ray photoelectron spectroscopy,scanning electron microscopy(SEM),transmissionelectron microscopy(TEM),and H2temperature‐programmed reduction.All the results indicatethat Cu is present on the SiC support primarily as Cu2O.The SEM and TEM results show that cubicCu2O nanoparticles are uniformly dispersed on theβ‐SiC surface.The reaction conditions,namelythe temperature,reaction time,and amounts of base and catalyst used,for the Ullmann‐type C–Ocross‐coupling reaction were optimized.A model reaction was performed using iodobenzene(14.0mmol)and phenol(14.0mmol)with Cu2O/SiC(5wt%Cu)as the catalyst,Cs2CO3(1.0equiv.)as thebase,and tetrahydrofuran as the solvent at150°C for3h;a yield of97%was obtained and theturnover frequency(TOF)was1136h?1.The Cu2O/SiC catalyst has a broad substrate scope and canbe used in Ullmann‐type C–O cross‐coupling reactions of aryl halides and phenols bearing a varietyof different substituents.The catalyst also showed high activity in the Ullmann‐type C–Scross‐coupling of thiophenol with iodobenzene and substituted iodobenzenes;a TOF of1186h?1was achieved.The recyclability of the Cu2O/SiC catalyst in the O‐arylation of phenol with iodobenzenewas investigated under the optimum conditions.The yield decreased from97%to64%afterfive cycles.The main reason for the decrease in the catalyst activity is loss of the active component,i.e.,Cu2O.
基金supported by the National Natural Science Foundation of China (No.60968002)
文摘In this paper, we produce porous silicon （PSi） by electrochemical etching, and it is the first time to evaluate the performance of label-free porous silicon biosensor for detection of variable domain of heavy chain of heavy-chain antibody （VHH）. The binding of hen egg white lysozyme （HEWL） and VHH causes a red shift in the reflection spectrum of the biosensor. The red shift is proportional to the VHH concenlration in the range from 14 gg.ml-I to 30 pg.ml~ with a detection limit of 0.648 ng.ml~. The research is useful for the development of label-free biosensor applied in the rapid and sensitive determination of small molecules.
