目的 Ag/SiO2复合材料在抗菌、涂层领域应用广泛,但其界面结合弱、Ag⁺释放不可控、易氧化团聚等问题制约了实际应用。目前对Ag与不同SiO2表面终端的结合机制,以及羟基化对界面稳定性的影响尚不清楚。本研究通过理论计算,揭示界面键合特性与羟基化的关系,为优化材料性能提供理论依据。方法 基于第一性原理计算构建了Ag(111)面与3种不同终端结构的SiO2(001)面（Si端、O端、Si-O端）的界面模型。通过表面能计算评估各终端结构的相对稳定性,采用黏附功、电荷密度差、态密度分布和Bader电荷分析等方法,定量表征界面结合强度、电荷转移特性和化学键本质。特别考察了水分子吸附解离引起的表面羟基化对界面性能的影响。结果 SiO2(001)各终端表面稳定性存在显著差异,Si端表面最稳定（表面能1.37~4.67 J/m2）,O表面活性最高（表面能2.39~5.72 J/m2）。Ag(111)/SiO2(001)-O端界面因形成强极性Ag—O共价键,表现出最高的界面结合强度（黏附功3.17 J/m2）,明显优于Si端（1.23 J/m2）和Si-O端（1.16 J/m2）界面。表面羟基化导致界面结合强度大幅降低（黏附功降至0.33 J/m2）,电子结构分析表明羟基化使界面电荷转移量减少约50%,显著削弱界面稳定性。结论 本研究表明Ag/SiO2界面稳定性受表面终端原子类型和羟基化程度的共同影响：O终端界面结合最强,而羟基化会严重损害界面性能。这些发现为优化Ag/SiO2复合材料提供了重要指导。
Abstract
Ag/SiO2 composites are widely used in antimicrobial and coating applications, but their practical use is limited by issues such as weak interfacial bonding, uncontrolled release of Ag+, and susceptibility to oxidation and agglomeration. Currently, the bonding mechanisms between Ag and different SiO2 surface terminations, as well as the impact of hydroxylation on interfacial stability, remain unclear. Based on this, the work aims to employ the first-principles calculations to systematically investigate the interfacial stability of Ag/SiO2 and the regulatory effects of hydroxylation, providing a solid theoretical foundation for the design and application of high-performance composite materials. With the Ag(111) and SiO2(001) crystal planes as the core study objects, interface models with three different surface structures were constructed: Si-terminated (containing two-coordinated Si), O-terminated (containing two one-coordinated O atoms), and Si-O-terminated (containing one one-coordinated Si and one one-coordinated O atom). Surface energy calculations revealed significant differences in the stability of the three SiO2(001) terminations. The Si-terminated surface had the lowest surface energy, ranging from 1.37-4.67 J/m2, exhibiting optimal thermodynamic stability and reaching convergence at 16 layers. The O-terminated surface had the highest surface energy, ranging from 2.39-5.72 J/m2, showing the strongest chemical reactivity and stabilizing at 17 layers. The Si-O-terminated surface had a fixed surface energy of 2.45 J/m2, achieving convergence at 18 layers, with its stability lying between the Si-terminated and O-terminated surfaces.
Interfacial stability analysis showed that under the same lattice mismatch rate (2.45%), the Ag(111)/SiO2(001)-O interface exhibited the highest work of adhesion, reaching 3.17 J/m2, which was significantly better than the Si-terminated (1.23 J/m2) and Si-O-terminated (1.16 J/m2) interfaces. Electronic structure analysis further revealed the underlying mechanisms of this difference. In the O-terminated interface, strong hybridization occurred between the p-orbitals of O atoms and the d-orbitals of Ag atoms, forming strong polar covalent Ag-O bonds. This interface showed the highest charge transfer, extensive electron cloud overlap, and robust bonding. In contrast, the Si-terminated interface exhibited weak charge accumulation between Ag and Si atoms, resulting in weaker Ag-Si bonding. The Si-O-terminated interface, due to the synergistic Si-O effects on the stoichiometric surface, reduced the activity of O atoms, and competitive charge transfer effects lowered bonding efficiency, leading to poorer interfacial stability.
Studies on the hydroxylation effect revealed that the dissociation adsorption energy of water molecules on the SiO2(001)-Si-O surface was ‒2.68 eV, enabling the formation of stable hydroxyl (—OH) groups. During adsorption, electrons transferred from the H atoms of water molecules and the Si atoms of the SiO2 surface to adjacent O atoms. After an interface was constructed between the hydroxylated SiO2 surface and Ag, the work of adhesion sharply decreased to 0.33 J/m2, and the charge transfer of Ag atoms was reduced by approximately 50% (from ‒0.16e - ‒0.08e). According to the relationship between work of adhesion and contact angle, hydroxylation significantly impaired interfacial wettability. This phenomenon arose because the polar repulsion of hydroxyl groups hindered interfacial charge transfer and disrupted the original bonding structure, thereby substantially weakening the interfacial bonding strength. Additionally, while hydroxylation improved the thermodynamic stability of the SiO2 surface to some extent, its detrimental effect on the overall performance of the Ag/SiO2 interface was more pronounced, necessitating close attention during the fabrication and service of composite materials.
This study systematically reveals the core regulatory mechanisms of Ag/SiO2 interfacial stability at the atomic and electronic scales, confirming that interfacial performance is jointly determined by the SiO2 surface termination type and the degree of hydroxylation. The O-terminated structure enables strong interfacial bonding between Ag and SiO2, whereas surface hydroxylation severely deteriorates interfacial bonding strength and wettability. The findings provide an important theoretical basis for precisely regulating the SiO2 surface termination structure, optimizing fabrication processes to suppress hydroxylation, and thereby enhancing the interfacial bonding strength, service stability, and functional reliability of Ag/SiO2 composite materials.
关键词
第一性原理计算 /
Ag/SiO2界面 /
黏附功 /
电子结构 /
SiO2羟基化
Key words
first-principles calculations /
Ag/SiO2 interface /
adhesion work /
electronic structure /
SiO2 hydroxylation
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基金
河北白沙烟草有限责任公司保定卷烟厂科技项目（HBZY-BY2024A003）
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