纳米材料表面化学作用之电子结构原理

The Electronic Principle of Nanomaterial Surface Chemistry

在电子结构层面揭示纳米材料表面化学作用的物理与化学机制、共性规律与普适原理是纳米材料相关领域基础研究的科学目标,然而由于缺乏成熟的研究策略和系统性理论认知框架,相关概念与原理体系长期不完善,导致纳米化学领域的理论认识远落后于实验探索。本文基于作者近年研究成果,介绍基于表面价轨道竞争重构机制的纳米材料表面化学作用在电子结构层面的概念与理论认知体系;基于表面化学吸附电子态与纳米材料能带态间的竞争作用与相互影响模型,对纳米材料表面化学领域中的一些基本共性科学问题给出自洽解答。其一,阐明了纳米材料表面活性与稳定性的对立统一辩证关系的物理根源在于波函数的归一化原理。其二,揭示出尺寸减小普遍增强纳米材料表面化学活性的物理根源有两种机制:一是削弱对表面价原子轨道的束缚强度,二是放大缺陷等其他结构参数的影响效果。其三、建立纳米尺度协同化学吸附(NCC)模型,揭示出配体覆盖度调控纳米材料能带电子态及物理与化学性质的电子结构层面机制与共性规律。其四、揭示纳米材料尺寸(r)、比表面积(S/V)、表面配体及覆盖度(θ)在纳米表面化学作用中电子结构状态变化角度发挥作用的物理意义。

Revealing the intrinsic electronic principles driving the surface chemistry of nanomaterials is a central goal in nanoscience;however,the concepts and theoretical frameworks have long remained incomplete and unsystematic.This review systematically introduces a theoretical framework to reveal the interaction mechanisms and trends of surface ligands with nanomaterials at the electronic level,on the basis of competitive orbital redistribution in chemisorption and a concept of orbital potential,the characteristic electronic attribute directly determining surface reactivity.Based on the competitive interactions between surface coordination bonds and bulk energy bands,this theoretical framework can provide coherent answers to these key scientific issues.(1)The opposite and uniform relation of surface activity and stability in nanomaterials originates from the normalization principle of wavefunctions.(2)The physical nature of enhanced surface activity by size reduction lies in two mechanisms:weakening the constrain strength to surface valence atomic orbitals by nanomaterial energy bands,and amplifying the effects of other structural parameters like defects.(3)Nanoscale cooperative chemisorption(NCC)model generally reveals the electronic-level mechanisms and common rules how ligand coverage regulates the energy band states and physical/chemical properties of nanomaterials.(4)The roles and interaction mechanisms of nanomaterial size(r),specific surface area(S/V),surface ligands,and ligand coverage(θ)in nanomaterial surface chemical reactions are elucidated.