Diameter- and Length-controlled Synthesis of Ultrathin ZnS Nanowires and Their Size-Dependent UV Absorption Properties, Photocatalytical Activities and Band-Edge Energy Levels.

Guanjie Xing,Xiaohong Li,Simeng Hao,Xiaoli Liu,Yunchao Li,Louzhen Fan

doi:10.3390/nano9020220

Abstract

Benefiting from their ultra-small diameters and highly structural anisotropies, ultrathin semiconductor nanowires (USNWs) are well-known for their fascinating physical/chemical properties, as well as their promising applications in various fields. However, until now, it remains a challenge to synthesize high-quality USNWs with well-controlled diameters and lengths, let alone the exploration of their size-dependent properties and applications. To solve such a challenge, we report herein a ligand-induced low-temperature precursor thermolysis route for the controlled preparation of ultrathin ZnS nanowires, which is based on the oriented assembly of the in-situ formed ZnS clusters/tiny particles. Optimized synthetic conditions allowed the synthesis of ZnS nanowires with a diameter down to 1.0 nm and a length approaching 330 nm. The as-prepared ultrathin ZnS nanowires were then intensively examined by morphological, spectroscopic and electrochemical analytical means to explore their size-dependent optical absorption properties, photocatalytic activities and band-edge energy levels, as well as their underlying growth mechanism. Notably, these USNWs, especially for the thinnest nanowires, were identified to possess an excellent performance in both the selective absorption of ultraviolet (UV) light and photocatalytic degradation of dyes, thus enabling them to serve as longpass ultraviolet filters and high-efficiency photocatalysts, respectively. For the ultrathin ZnS nanowires with a diameter of 1.0 nm, it was also interesting to observe that their exciton absorption peak positions were kept almost unchanged during the continuous extension of their lengths, which has not been reported previously.

Highlights

Ultrathin semiconductor nanowires (USNWs) typically refer to the semiconductor nanowires with diameter well below their exciton Bohr radius, especially for those with an ultra-small diameter [1,2]
The challenge lies in the lack of effective means to control the nanowire diameters into a magic size range during their growths, quite a few methods, like the vapor–liquid–solid (VLS) [12,13], template-assisted deposition (TAD) [14, 15], and solution–liquid–solid (SLS) method [16,17] have been developed for preparing regular semiconductor nanowires
According to the above consideration, Scheme 1, we designed a low-temperature single-source precursor thermolysis route to prepare ultrathin ZnS nanowires; reactive zinc ethylanthate (Zn(exan)2) was chosen as the precursor for its easy decomposition at low temperature; alkylamines of different chain lengths were served as the reaction solvents and the capping ligands simultaneously because of their activation effect and selective binding ability; rapid and a large volume of precursor injection was adopted to intentionally separate the nucleation and growth process by enhancing the temperature difference between them

Summary

Introduction

Ultrathin semiconductor nanowires (USNWs) typically refer to the semiconductor nanowires with diameter well below their exciton Bohr radius, especially for those with an ultra-small diameter (less than 2.0 nm) [1,2]. The challenge lies in the lack of effective means to control the nanowire diameters into a magic size range during their growths, quite a few methods, like the vapor–liquid–solid (VLS) [12,13], template-assisted deposition (TAD) [14, 15], and solution–liquid–solid (SLS) method [16,17] have been developed for preparing regular semiconductor nanowires This difficult situation stems from the fact that these methods typically require high reaction temperatures (SLS ≥ 270 ◦C, VLS ≥ 400 ◦C) and specific-sized catalyst particles (from several nm to tens of nm), or physical temples with specific-sized pores (≥ 20 nm) to accomplish the synthesis.

Methods

Results

Conclusion