Colloidal nanoparticles are being intensely pursued in current nanoscience research. Nanochemists are often frustrated by the well-known fact that no two nanoparticles are the same, which precludes the deep understanding of many fundamental properties of colloidal nanoparticles in which the total structures (core plus surface) must be known. Therefore, controlling nanoparticles with atomic precision and solving their total structures have long been major dreams for nanochemists. Recently, these goals are partially fulfilled in the case of gold nanoparticles, at least in the ultrasmall size regime (1–3 nm in diameter, often called nanoclusters). This review summarizes the major progress in the field, including the principles that permit atomically precise synthesis, new types of atomic structures, and unique physical and chemical properties of atomically precise nanoparticles, as well as exciting opportunities for nanochemists to understand very fundamental science of colloidal nanoparticles (such as the s...

Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

The field of chiral inorganic nanostructures is rapidly expanding. It started from the observation of strong circular dichroism during the synthesis of individual nanoparticles (NPs) and their assemblies and expanded to sophisticated synthetic protocols involving nanostructures from metals, semiconductors, ceramics, and nanocarbons. Besides the well-established chirality transfer from bioorganic molecules, other methods to impart handedness to nanoscale matter specific to inorganic materials were discovered, including three-dimentional lithography, multiphoton chirality transfer, polarization effects in nanoscale assemblies, and others. Multiple chiral geometries were observed with characteristic scales from angstroms to microns. Uniquely high values of chiral anisotropy factors that spurred the development of the field and differentiate it from chiral structures studied before, are now well understood; they originate from strong resonances of incident electromagnetic waves with plasmonic and excitonic st...

Chiral Inorganic Nanostructures

Publications Financial Statement pursuant to rule 154-ter paragraph 1 of Legislative Decree No. 58/1998 Annual Report Annual Report on Form 20-F for the Securities and Exchange Commission Fact Book (in Italian and English) Eni in 2011 (in English) Interim Consolidated Report as of June 30 pursuant to rule 154-ter paragraph 2 of Legislative Decree No. 58/1998 Corporate Governance Report pursuant to rule 123-bis of Legislative Decree No. 58/1998 (in Italian and English) Remuneration Report pursuant to rule 123-ter of Legislative Decree No. 58/1998 (in Italian and English)

Annual Report 2011 -個人別教育研究報告-

The chemistry of gold

Ligand-protected gold clusters: the structure, synthesis and applications

Organic thiols are known to react with gold surface to form self-assembled monolayers (SAMs), which can be used to produce materials with highly attractive properties. Although the structure of various SAMs is widely investigated, some aspects of their formation still represent a matter of debate. One of these aspects is the mechanism of S–H bond dissociation in thiols upon interaction with gold. This work presents a new suggestion for this mechanism on the basis of DFT study of methanethiol interaction with a single gold atom and a Au20 cluster. The reaction path of dissociation is found to be qualitatively independent of the model employed. However, the highest activation barrier of S–H bond dissociation on the single gold atom (12.9 kcal/mol) is considerably lower than that on the Au20 cluster (28.9 kcal/mol), which can be attributed to the higher extent of gold unsaturation. The energy barrier of S–H cleavage decreases by 4.6 kcal/mol in the presence of the second methanethiol molecule at the same ads...

Theoretical prediction of S-H bond rupture in methanethiol upon interaction with gold.

The morphology and charged state of gold clusters play a crucial role in heterogeneous catalysis. The selection and optimization of theoretical approaches are necessary for the investigation of act...

A Structural and Stability Evaluation of Au12 from an Isolated Cluster to the Deposited Material

The reactions of methane with the gold complexes [Au(OH)]−, [Au(OCH3)4]−, [Au(O(CO)2O2]− and [Au(O2CH)2]+, [AuI(acac)], [AuIII(acac)2]+ (acac-acetylacetonato) were studied using the DFT/PBE method with the SBK basis set. High activation barriers were obtained for the electrophilic substitution in [Au(OH)]−, [Au(OCH3)4]−, [Au(O(CO)2O)2]-and [AuIII(acac)2]+ complexes, which excludes the possibility that these reactions might proceed under mild conditions. The reactions of the [Au(HCO2)2]+ and [AuI(acac)] complexes with methane have rather low energy barriers and proceed through the formation of an intermediate complex. The alternative mechanism of methane oxidation with a gold complex in the presence of oxygen is simulated.

Gold complexes with

The spin-crossing mechanism of oxygen dissociation on Ag20 and monodoped Ag19Au clusters was investigated via spin-polarized scalar-relativistic DFT calculations using the PBE, TPSSh, M06L, mPBE, BLYP, OLYP, and B3LYP functionals. In particular, the singlet and triplet O–O bond rupture pathways at vertex-edge and facet-edge sites on the tetrahedral clusters were studied. The calculations reveal that for the Ag20O2 and Ag19AuO2 complexes, the spin inversion from the triplet to singlet state occurs during the last step, which involves O–O bond rupture through a singlet transition state (TS). When spin crossing during oxygen dissociation on the clusters is considered, the activation energies decrease by 10–29 kJ mol−1; however, they are still high due to the magic nature of the clusters and high vertical spin excitation energies. For these silver clusters, size effects based on the relationship between the TS structure and oxidation activation energy were predicted.

D. A. Pichugina

Papers

Ligand-protected gold clusters: the structure, synthesis and applications

Theoretical prediction of S-H bond rupture in methanethiol upon interaction with gold.

A Structural and Stability Evaluation of Au12 from an Isolated Cluster to the Deposited Material

Gold complexes with

Spin and structural features of oxygen dissociation on tetrahedral Ag20 and Ag19Au clusters.