We developed a general and effective strategy to afford rod-like [Au25(SPh)5(PPh3)10X2]X2 (X = Cl/Br) nanoclusters, capped by conjugated delocalized pπ electron mediated ligands. The detailed atomic structure of thes...We developed a general and effective strategy to afford rod-like [Au25(SPh)5(PPh3)10X2]X2 (X = Cl/Br) nanoclusters, capped by conjugated delocalized pπ electron mediated ligands. The detailed atomic structure of these materials was resolved by synchrotron radiation X-ray diffraction (SRXRD) combined with electrospray ionization mass spectrometry (ESI-MS) and UV–vis analyses. The Au17(SR)3(PPh3)6X2minimum asymmetric unit, with exposed Au atoms at the center, can serve as an important model to understand the transformation of homogold nanoclusters into alloy nanoclusters. The conjugated delocalized pπ electrons of the thiolate ligands can effectively tune the electronic properties of the Au25 kernel, as qualitatively evidenced by the energy gaps measured by UV–vis experiments and density functional theory (DFT) calculations. The delocalized electrons distinctly flow to the orbitals of the Au25 kernel via the S atoms of the aromatic thiolates. The ESI-MS analysis indicates that Au3 clusters are formed during the etching reactions, which provide an opportunity to gain insight into the intriguing conversion pathway of the Aun(PPh3)mXy precursor to the final Au25 nanorods. Finally, the thiophenol-protected Au25 nanorods, immobilized on activated carbon, show good catalytic activity in the aerobic oxidation of glucose to gluconic acid (74% glucose conversion and 100% selectivity for gluconic acid), much higher than that of the aliphatic Au25 analogue. The Au25(SPh)5(PPh3)10X2 catalyst yields a turnover frequency (TOF) of 13.5 s^–1, higher than that of commercial catalysts such as Pd/activated carbon (AC) and Pd-Bi/AC. The insight obtained from this study will support the development and design of efficient nanogold catalysts for special oxidation reactions.展开更多
The catalytic properties of two nanocluster catalysts with atomically precisely known structures,icosahedral two-shelled Au25(SC2H4Ph) 18 nanospheres and biicosahedral Au25(PPh3) 10(SC2H4Ph) 5Cl2 nanorods,were compare...The catalytic properties of two nanocluster catalysts with atomically precisely known structures,icosahedral two-shelled Au25(SC2H4Ph) 18 nanospheres and biicosahedral Au25(PPh3) 10(SC2H4Ph) 5Cl2 nanorods,were compared. Their catalytic performance in the two reactions of the selective oxidation of styrene and chemoselective hydrogenation of α,β-unsaturated benzalacetone was investigated. The catalytic activities of icosahedral Au25(SC2H4Ph) 18 nanospheres were superior to those of the bi-icosahedral Au25(PPh3) 10(SC2H4Ph) 5Cl2 nanorods for both reactions. The better catalytic performance of the Au25(SC2H4Ph) 18 nanospheres can be attributed to their unique core-shell(Au13/Au12) geometric structure that has an open exterior atomic shell and to their electronic structure with an electron-rich Au13 core and an electron-deficient Au12 shell.展开更多
Well-defined gold nanoclusters with average size less than 2 nm have emerged as a new and novel catalyst. The gold nanocluster loaded on the oxide surface usually aggregates to larger particles at high temperature （...Well-defined gold nanoclusters with average size less than 2 nm have emerged as a new and novel catalyst. The gold nanocluster loaded on the oxide surface usually aggregates to larger particles at high temperature （〉 300℃）, which is caused by the removal of the surface ligands. We herein pre-sent a novel method to prepare Au25cluster catalyst （-1.3 nm） with high thermal stability （up to 400℃）. Au25@Si02 is synthesized via a co-hydrolyzing reaction of Au2s[SC3H6Si（OCH3）3118 and tet-raethyl orthosilicate, and then it is treated at different temperature （e.g., 200, 300, 400℃） in air to remove the organic ligands. Au25@SiO2 is well characterized by transmission electron microscopy, ultraviolet-visible spectroscopy and diffuse reflectance UV-vis spectroscopy. Further, the Au2s@SiO2 catalysts are investigated in the hydrogenation ofp-nitrophenol into p-aminophenol.展开更多
We report the controlled growth of Au25（SR）18 and Au38（SR）24 （where R = CH2CH2Ph） nanoclusters of molecular purity via size-focusing from the same crude product that contains a distribution of nanoclusters. In t...We report the controlled growth of Au25（SR）18 and Au38（SR）24 （where R = CH2CH2Ph） nanoclusters of molecular purity via size-focusing from the same crude product that contains a distribution of nanoclusters. In this method, gold salt was first mixed with tetraoctylammonium bromide （TOAB）, and then reacted with excess thiol to form Au（I）-SR polymers in THF （as opposed to toluene in previous work）, followed by NaBH4 reduction. The resultant crude product contains polydisperse nanoclusters and was then used as the common starting material for controlled growth of Au25（SR）18 and Au38（SR）24, respectively. In Route I, Au25（SR）18 nanoclusters of molecular purify were produced from the crude product alter 6 h aging at room temperature. In Route II, the crude product was isolated and further subjected to thermal thiol etching in a toluene solution containing excess thiol, and one obtained pure Au38（SR）24 nanoclusters, instead of Au25（SR）Is. This work not only provides a robust and simple method to prepare both Au25（SR）18 and Au3s（SR）24 nanoclusters, but also reveals that these two nanoclusters require different environments for the size-focusing growth process.展开更多
基金We thank the financial support by the National Natural Science Foundation of China (No. 21701168), Liaoning Natural Science Foundation (No. 20170540897),open project Foundation of State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University (No. 201709)Shanxi Province Hundred Talent ProjectBL14B and BL17B beamline of National Facility for Protein Science in Shanghai, Shanghai Synchrotron Radiation Facility for providing the beam time.
文摘We developed a general and effective strategy to afford rod-like [Au25(SPh)5(PPh3)10X2]X2 (X = Cl/Br) nanoclusters, capped by conjugated delocalized pπ electron mediated ligands. The detailed atomic structure of these materials was resolved by synchrotron radiation X-ray diffraction (SRXRD) combined with electrospray ionization mass spectrometry (ESI-MS) and UV–vis analyses. The Au17(SR)3(PPh3)6X2minimum asymmetric unit, with exposed Au atoms at the center, can serve as an important model to understand the transformation of homogold nanoclusters into alloy nanoclusters. The conjugated delocalized pπ electrons of the thiolate ligands can effectively tune the electronic properties of the Au25 kernel, as qualitatively evidenced by the energy gaps measured by UV–vis experiments and density functional theory (DFT) calculations. The delocalized electrons distinctly flow to the orbitals of the Au25 kernel via the S atoms of the aromatic thiolates. The ESI-MS analysis indicates that Au3 clusters are formed during the etching reactions, which provide an opportunity to gain insight into the intriguing conversion pathway of the Aun(PPh3)mXy precursor to the final Au25 nanorods. Finally, the thiophenol-protected Au25 nanorods, immobilized on activated carbon, show good catalytic activity in the aerobic oxidation of glucose to gluconic acid (74% glucose conversion and 100% selectivity for gluconic acid), much higher than that of the aliphatic Au25 analogue. The Au25(SPh)5(PPh3)10X2 catalyst yields a turnover frequency (TOF) of 13.5 s^–1, higher than that of commercial catalysts such as Pd/activated carbon (AC) and Pd-Bi/AC. The insight obtained from this study will support the development and design of efficient nanogold catalysts for special oxidation reactions.
文摘The catalytic properties of two nanocluster catalysts with atomically precisely known structures,icosahedral two-shelled Au25(SC2H4Ph) 18 nanospheres and biicosahedral Au25(PPh3) 10(SC2H4Ph) 5Cl2 nanorods,were compared. Their catalytic performance in the two reactions of the selective oxidation of styrene and chemoselective hydrogenation of α,β-unsaturated benzalacetone was investigated. The catalytic activities of icosahedral Au25(SC2H4Ph) 18 nanospheres were superior to those of the bi-icosahedral Au25(PPh3) 10(SC2H4Ph) 5Cl2 nanorods for both reactions. The better catalytic performance of the Au25(SC2H4Ph) 18 nanospheres can be attributed to their unique core-shell(Au13/Au12) geometric structure that has an open exterior atomic shell and to their electronic structure with an electron-rich Au13 core and an electron-deficient Au12 shell.
基金supported by the National Natural Science Foundation of China (21273231, 21422308)Dalian Excellent Youth Foundation (2014J11JH126) (FW)the Starting Funds of “Thousand Youth Talents Plan” (GL)~~
文摘Well-defined gold nanoclusters with average size less than 2 nm have emerged as a new and novel catalyst. The gold nanocluster loaded on the oxide surface usually aggregates to larger particles at high temperature （〉 300℃）, which is caused by the removal of the surface ligands. We herein pre-sent a novel method to prepare Au25cluster catalyst （-1.3 nm） with high thermal stability （up to 400℃）. Au25@Si02 is synthesized via a co-hydrolyzing reaction of Au2s[SC3H6Si（OCH3）3118 and tet-raethyl orthosilicate, and then it is treated at different temperature （e.g., 200, 300, 400℃） in air to remove the organic ligands. Au25@SiO2 is well characterized by transmission electron microscopy, ultraviolet-visible spectroscopy and diffuse reflectance UV-vis spectroscopy. Further, the Au2s@SiO2 catalysts are investigated in the hydrogenation ofp-nitrophenol into p-aminophenol.
基金supported by the Air Force Office of Scientific Research under AFOSR Award (FA9550-11-1-9999, FA9550-11-1-0147)the Camille Dreyfus Teacher-Scholar Awards Programsupport by the China Scholarship Council (CSC)
文摘We report the controlled growth of Au25（SR）18 and Au38（SR）24 （where R = CH2CH2Ph） nanoclusters of molecular purity via size-focusing from the same crude product that contains a distribution of nanoclusters. In this method, gold salt was first mixed with tetraoctylammonium bromide （TOAB）, and then reacted with excess thiol to form Au（I）-SR polymers in THF （as opposed to toluene in previous work）, followed by NaBH4 reduction. The resultant crude product contains polydisperse nanoclusters and was then used as the common starting material for controlled growth of Au25（SR）18 and Au38（SR）24, respectively. In Route I, Au25（SR）18 nanoclusters of molecular purify were produced from the crude product alter 6 h aging at room temperature. In Route II, the crude product was isolated and further subjected to thermal thiol etching in a toluene solution containing excess thiol, and one obtained pure Au38（SR）24 nanoclusters, instead of Au25（SR）Is. This work not only provides a robust and simple method to prepare both Au25（SR）18 and Au3s（SR）24 nanoclusters, but also reveals that these two nanoclusters require different environments for the size-focusing growth process.
