Piperidine absorbs CO2 and H2O in air to form a molecular complex： piperidium-l-piperidinecarboxylate-H2O. The structure of the complex was characterized by X-ray single crystal diffraction. The crystal structure was...Piperidine absorbs CO2 and H2O in air to form a molecular complex： piperidium-l-piperidinecarboxylate-H2O. The structure of the complex was characterized by X-ray single crystal diffraction. The crystal structure was determined to be triclinic, space group P1^-with a=0.648 6（8） nm, b=0.809 200） nm, c= 1.357 1（16） nm, a=96.96706）°, β =102.506（15）°,γ=104.202 05）°, Z=2. The complex is stabilized via five hydrogen bonds between the three components, N-O electrostatic interaction and O-O interaction （electron transfer） betweenl-piperidinecarboxylate and H2O. Due to electron transference of carbamate ion, the oxygen atom in water molecule is strongly negatively charged and the O-H bond is considerably shorter than that of the free molecule of water. The formation of the molecular complex is a reversible process and will decompose upon heating. The mechanism of formation and stabilization is further investigated herein.展开更多
Recent progress in the research of atomically-precise metal nanoclusters has identified a series of exceptionally stable nanoclusters with specific chemical compositions. Structural determination on such "magic s...Recent progress in the research of atomically-precise metal nanoclusters has identified a series of exceptionally stable nanoclusters with specific chemical compositions. Structural determination on such "magic size" nanoclusters revealed a variety of unique structures such as decahedron, icosahedron, as well as hexagonal close packing(hcp) and body-centered cubic(bcc) packing arrangements in gold nanoclusters, which are largely different from the face-centered cubic(fcc) structure in conventional gold nanoparticles. The characteristic geometrical structures enable the nanoclusters to exhibit interesting properties, and these properties are in close correlation with their atomic structures according to the recent studies. Experimental and theoretical analyses have been applied in the structural identification aiming to clarify the universal principle in the structural evolution of nanoclusters. In this mini-review, we summarize recent studies on periodic structural evolution of fcc-based gold nanoclusters protected by thiolates. A series of nanoclusters exhibit one-dimensional growth along the [001] direction in a layer-by-layer manner from Au_(23)(TBBT)_(20) to Au_(36)(TBBT)_(24),Au_(44)(TBBT)_(28), and to Au_(52)(TBBT)_(32)(TBBT: 4-tert-butylbenzenethiolate). The optical properties of these nanoclusters also evolve periodically based on steady-state and ultrafast spectroscopy. In addition, two-dimensional growth from Au_(44)(TBBT)_(28) toward both [100] and [010] directions leads to the Au_(92)(TBBT)_(44) nanocluster, and the recently reported Au_(52)(PET)_(32)(PET: 2-phenylethanethiol) also follows this growth pattern with partial removal of the layer. Theoretical predictions of relevant fcc nanoclusters include Au_(60)(SCH_3)_(36), Au_(68)(SCH_3)_(40), Au_(76)(SCH_3)_(44), etc, for the continuation of 1 D growth pattern, as well as Au_(68)(SR)_(38)mediating the 2 D growth pattern from Au_(44)(TBBT)_(28) to Au_(92)(TBBT)_(44). Overall, this mini-review provides guidelines on the rules of structural evolution of fcc gold nanoclusters based on 1 D, 2 D and 3 D growth patterns.展开更多
Piperidine absorbs CO2 and H2O contents in air to form a molecular complex： piperidium-1-piperidinecarboxylate-H2O. The structure of the complex was characterized by FT-IR and NMR. The complex is stabilized via five ...Piperidine absorbs CO2 and H2O contents in air to form a molecular complex： piperidium-1-piperidinecarboxylate-H2O. The structure of the complex was characterized by FT-IR and NMR. The complex is stabilized via five hydrogen bonds between the three components, N…O electrostatic interaction and O…O interaction （electron transfer） betweenl-piperidinecarboxylate and H2O. Through electron transfer from the carbamate ion, the oxygen atom in water molecule is strongly negatively charged and the O-H bond is considerably shorter than that of free water molecule. The formation of the molecular complex is a reversible process and will decompose upon heating. The mechanism of formation and stabilization is further investigated herein.展开更多
Inorganic nanoparticles(NPs)are being intensely pursued in current nanoscience research.However,fundamental research is hampered by the imprecisions of nanoparticles.Some of the major issues are as follows.(1)Polydisp...Inorganic nanoparticles(NPs)are being intensely pursued in current nanoscience research.However,fundamental research is hampered by the imprecisions of nanoparticles.Some of the major issues are as follows.(1)Polydispersity:Even highly monodisperse NPs still have a standard deviation of 5%and they vary from one to another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supported by Carnegie Mellon University （CMU） the Air Force Office of Scientific Research （AFOSR） and the National Institute for Occupational Safety and Health （NIOSH） USA supported by the National Science Foundation-Research Experiences for Undergraduates USA （NSF grant DMR #1005076）
基金Supported by Project of Education Department of Liaoning Province(20040084)
文摘Piperidine absorbs CO2 and H2O in air to form a molecular complex： piperidium-l-piperidinecarboxylate-H2O. The structure of the complex was characterized by X-ray single crystal diffraction. The crystal structure was determined to be triclinic, space group P1^-with a=0.648 6（8） nm, b=0.809 200） nm, c= 1.357 1（16） nm, a=96.96706）°, β =102.506（15）°,γ=104.202 05）°, Z=2. The complex is stabilized via five hydrogen bonds between the three components, N-O electrostatic interaction and O-O interaction （electron transfer） betweenl-piperidinecarboxylate and H2O. Due to electron transference of carbamate ion, the oxygen atom in water molecule is strongly negatively charged and the O-H bond is considerably shorter than that of the free molecule of water. The formation of the molecular complex is a reversible process and will decompose upon heating. The mechanism of formation and stabilization is further investigated herein.
基金The project was supported by the Air Force Office of Scientific Research (FA9550-15-1-0154) and the U.S. National Science Foundation (DMREF-0903225).
文摘Recent progress in the research of atomically-precise metal nanoclusters has identified a series of exceptionally stable nanoclusters with specific chemical compositions. Structural determination on such "magic size" nanoclusters revealed a variety of unique structures such as decahedron, icosahedron, as well as hexagonal close packing(hcp) and body-centered cubic(bcc) packing arrangements in gold nanoclusters, which are largely different from the face-centered cubic(fcc) structure in conventional gold nanoparticles. The characteristic geometrical structures enable the nanoclusters to exhibit interesting properties, and these properties are in close correlation with their atomic structures according to the recent studies. Experimental and theoretical analyses have been applied in the structural identification aiming to clarify the universal principle in the structural evolution of nanoclusters. In this mini-review, we summarize recent studies on periodic structural evolution of fcc-based gold nanoclusters protected by thiolates. A series of nanoclusters exhibit one-dimensional growth along the [001] direction in a layer-by-layer manner from Au_(23)(TBBT)_(20) to Au_(36)(TBBT)_(24),Au_(44)(TBBT)_(28), and to Au_(52)(TBBT)_(32)(TBBT: 4-tert-butylbenzenethiolate). The optical properties of these nanoclusters also evolve periodically based on steady-state and ultrafast spectroscopy. In addition, two-dimensional growth from Au_(44)(TBBT)_(28) toward both [100] and [010] directions leads to the Au_(92)(TBBT)_(44) nanocluster, and the recently reported Au_(52)(PET)_(32)(PET: 2-phenylethanethiol) also follows this growth pattern with partial removal of the layer. Theoretical predictions of relevant fcc nanoclusters include Au_(60)(SCH_3)_(36), Au_(68)(SCH_3)_(40), Au_(76)(SCH_3)_(44), etc, for the continuation of 1 D growth pattern, as well as Au_(68)(SR)_(38)mediating the 2 D growth pattern from Au_(44)(TBBT)_(28) to Au_(92)(TBBT)_(44). Overall, this mini-review provides guidelines on the rules of structural evolution of fcc gold nanoclusters based on 1 D, 2 D and 3 D growth patterns.
基金Supported by Project of Education Department of Liaoning Province (20040084)
文摘Piperidine absorbs CO2 and H2O contents in air to form a molecular complex： piperidium-1-piperidinecarboxylate-H2O. The structure of the complex was characterized by FT-IR and NMR. The complex is stabilized via five hydrogen bonds between the three components, N…O electrostatic interaction and O…O interaction （electron transfer） betweenl-piperidinecarboxylate and H2O. Through electron transfer from the carbamate ion, the oxygen atom in water molecule is strongly negatively charged and the O-H bond is considerably shorter than that of free water molecule. The formation of the molecular complex is a reversible process and will decompose upon heating. The mechanism of formation and stabilization is further investigated herein.
文摘Inorganic nanoparticles(NPs)are being intensely pursued in current nanoscience research.However,fundamental research is hampered by the imprecisions of nanoparticles.Some of the major issues are as follows.(1)Polydispersity:Even highly monodisperse NPs still have a standard deviation of 5%and they vary from one to another
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.
