title: Single-crystal γ-MnS nanowires conformally coated with carbon.
abstract: We report for the first time the fabrication of single-crystal metastable manganese sulfide nanowires (γ-MnS NWs) conformally coated with graphitic carbon via chemical vapor deposition technique using a single-step route. Advanced spectroscopy and electron microscopy techniques were applied to elucidate the composition and structure of these NWs at the nanoscale, including Raman, XRD, SEM, HRTEM, EELS, EDS, and SAED. No evidence of α-MnS and β-MnS allotropes was found. The γ-MnS/C NWs have hexagonal cross-section and high aspect ratio (∼1000) on a large scale. The mechanical properties of individual γ-MnS/C NWs were examined via in situ uniaxial compression tests in a TEM-AFM. The results show that γ-MnS/C NWs are brittle with a Young's modulus of 65 GPa. The growth mechanism proposed suggests that the bottom-up fabrication of γ-MnS/C NWs is governed by vapor-liquid-solid mechanism catalyzed by bimetallic Au-Ni nanoparticles. The electrochemical performance of γ-MnS/C NWs as an anode material in lithium-ion batteries indicates that they outperform the cycling stability of stable micro-sized α-MnS, with an initial capacity of 1036 mAh g(-1) and a reversible capacity exceeding 503 mAh g(-1) after 25 cycles. This research advances the integration of carbon materials and metal sulfide nanostructures, bringing forth new avenues for potential miniaturization strategies to fabricate 1D core/shell heterostructures with intriguing bifunctional properties that can be used as building blocks in nanodevices.
authors.affiliation: Institute for Functional Nanomaterials, University of Puerto Rico , San Juan, Puerto Rico 00931, United States.
authors.forename: Juan
authors.initials: J
authors.lastname: Beltran-Huarac
authors.forename: Oscar
authors.initials: O
authors.lastname: Resto
authors.forename: Jennifer
authors.initials: J
authors.lastname: Carpena-Nuñez
authors.forename: Wojciech M
authors.initials: WM
authors.lastname: Jadwisienczak
authors.forename: Luis F
authors.initials: LF
authors.lastname: Fonseca
authors.forename: Brad R
authors.initials: BR
authors.lastname: Weiner
authors.forename: Gerardo
authors.initials: G
authors.lastname: Morell