First-Principles Insights into the Interface Chemistry between 4-Aminothiophenol and Zinc Phosphide (Zn₃P₂) Nanoparticles

Accurate prediction of the structures, stabilities, and electronic structures of hybrid inorganic/organic systems is an essential prerequisite for tuning their electronic properties and functions. Herein, the interface chemistry between the 4-aminothiophenol (4ATP) molecule and the (001), (101), and (110) surfaces of zinc phosphide (Zn₃P₂) has been investigated by means of first-principles density functional theory calculation with a correction for van der Waals interactions. In particular, the atomic-level insights into the fundamental aspects of the 4ATP adsorption, including the lowest-energy adsorption configurations, binding energetics, structural parameters, and electronic properties are presented and discussed. The 4ATP molecule is demonstrated to bind most strongly onto the least stable Zn₃P₂(001) surface (E_ads = -1.91 eV) and least strongly onto the most stable Zn₃P₂(101) surface (E_ads = -1.21 eV). Partial density of states analysis shows that the adsorption of 4ATP on the Zn₃P₂ surfaces is characterized by strong hybridization between the molecule's sulfur and nitrogen p-orbitals and the d-orbitals of the interacting surface Zn ions, which gave rise to electron density accumulation around the centers of the newly formed Zn-S and Zn-N chemical bonds. The thermodynamic crystal morphology of the nonfunctionalized and 4ATP-functionalized Zn₃P₂ nanoparticles was obtained using Wulff construction based on the calculated surface energies. The stronger binding of the 4ATP molecule onto the less stable (001) and (110) surfaces in preference to the most stable (101) facet resulted in the modulation of the Zn₃P₂ nanocrystal shape, with the reactive (001) and (110) surfaces becoming more pronounced in the equilibrium morphology.