陽性電荷状態と,金ナノクラスターの可能なポリモルフィズム 減少したセリアの上で
Changjun Zhang1, Angelos Michaelides, David A King
1Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Journal of the American Chemical Society
|January 28, 2010
まとめ
この研究は,密度関数理論を用いてセリウム二酸化物 (CeO2) 表面上の小さな金 (Au) ナノクラスターの新しい構造と側面を明らかにしています. これらの発見は,触媒作用に不可欠な原子レベルの詳細についての洞察を提供します.
科学分野:
- マテリアルサイエンス 材料科学
- 表面科学とは,地表科学である.
- コンピューティング・ケミストリー
背景:
- 金 (Au) のセリウム二酸化物 (CeO2) への触媒性能は,Auクラスターの原子構造に依存する.
- CeO2上の小さなAuクラスターの詳細な原子レベルの理解は,依然として限られている.
研究 の 目的:
- 縮小されたCeO2{111}表面上の小さな金ナノクラスターの核化と構造特性を調査する.
- これらのナノクラスターの幾何学的および電子的特性を計算的方法を使用して探求する.
主な方法:
- 密度関数理論 (DFT) の計算が採用されました.
- 縮小されたCeO2{111}表面に金原子 (Au11まで) のシミュレートされた連続堆積.
- 核形成パターン,クラスター幾何学,ファセット,電子構造の分析.
主要な成果:
- 小型のAuナノクラスターの面中心の立方体 (fcc) 幾何学とともに,新しい六角形の密集型 (hcp) 構造を特定しました.
- fcc の {111}/{100} と hcp クラスタの {1011}/{0001} を含む多様な側面が観察されました.
- 二酸化セリウムの表面と接触した金原子が正電荷を示すことを発見した.
結論:
- CeO2上の小さな金ナノクラスターは,散発型のfccアレンジメントを超えてユニークな構造的多様性を表しています.
- インタフェースの電子電荷分布は,加熱活性が強化される可能性を示唆しています.
- これらの原子規模の洞察は,高度なAu/CeO2触媒の設計に不可欠です.
関連する概念動画
03:27Ions and Ionic Charges
In ordinary chemical reactions, the nucleus — which contains the protons and neutrons of each atom and thus identifies the element — remains unchanged. Electrons, however, can be added to atoms by transfer from other atoms, lost by transfer to other atoms, or shared with other atoms. The transfer and sharing of electrons among atoms govern the chemistry of the elements. During the formation of some compounds, atoms gain or lose electrons to form electrically charged particles called ions.
02:48Ionic Bonding and Electron Transfer
Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence shell, and an anion (a negative ion) forms when a neutral atom gains one or more electrons in its valence shell. Compounds composed of ions are called ionic compounds (or salts), and their constituent ions are held together by ionic bonds: electrostatic forces of attraction between oppositely charged cations and anions.
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
01:19Complexation Equilibria: The Chelate Effect
In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
01:09Colloidal precipitates
The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...