Inter-diffusion of Cu2+ ions into CuS nanocrystals confines the microwave absorption properties. Issue 41 (4th October 2018)

• Record Type: Journal Article
• Authors: Gu, Jiani; Xie, Yi; Chen, Wenhui; Hu, Chao; Qiao, Fen; Xu, Zhiyuan; Liu, Xiaoqing; Zhao, Xiujian; Zhang, Gaoke
• Is Part Of: CrystEngComm. Volume 20:Issue 41(2018)
• Page Start: 6565
• Page End: 6572
• Publication Date: 2018-10-04
• Subjects: Crystals -- Periodicals; Crystal growth -- Periodicals; Crystallography -- Periodicals; Cristaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Cristallographie -- Périodiques; 548
• DOI: 10.1039/c8ce01435c
• Languages: English
• ISSNs: 1466-8033

Abstract

Abstract : The inter-diffusion of Cu 2+ cations into CuS nanocrystals generates CuS@Cu2− x S core–shell and Cu2 S NCs in the presence of ascorbic acid (AA) at varying precursor Cu 2+ : Cu + molar ratios. The inter-diffusion process has a confining effect on the microwave absorption properties. Abstract : We report inter-diffusion of as-synthesized covellite CuS nanocrystals (NCs) with Cu 2+ cations at room temperature in the presence of a mild reducing agent ( i.e., ascorbic acid). Unlike the previously-reported incorporation of Cu + or Cu 2+ ions with CuS that generates homogenous Cu2− x S NCs, the controlled diffusion of Cu 2+ ions into the CuS NCs allows the formation of a unique CuS@Cu2− x S core–shell-like nanostructure as the intermediate and Cu2 S NCs in the presence of excess Cu 2+ ions. The CuS@Cu2− x S core–shell nanostructure can evolve into homogenous Cu2− x S NCs by further cation diffusion from the Cu2− x S shell toward the center ( i.e. the CuS core) under E-beam irradiation during TEM test or when the core–shell NCs are stored in toluene for some time ( e.g. four weeks). Notably, the CuS/paraffin composite with filler loading of 50 wt% and thickness of 1.95 mm displays a minimum reflection loss (RL) of −54.84 dB at 12.6 GHz. By adjusting the thickness in the range of 1–5 mm, the effective absorption bandwidth (below −10 dB, 90% microwave absorption) could reach 15 GHz (3–18 GHz). In particular, the diffusion of Cu 2+ into CuS NCs leads to dampening of the NIR plasmon absorbance and a decrease in free carrier ( i.e., hole) density and conductivity, which accounts for the confinement effect on the microwave absorption properties of the resulting samples.