Multispectroscopic Approach to Graphite-Encapsulated Metal Nanoparticles

Abstract:

Graphite-encapsulated Nickel nanoparticles exhibit remarkable potential for various applications due to their combined metallic and graphitic properties. However, evaluating the quality of the carbon shells using Raman spectroscopy as widely recognized tool is challenging, primarily due to spectral variance caused by flake heterogeneity and increasing graphene layer thickness.

To address this, we designed a full-factorial experiment by varying two key parameters: the initial thickness of the nickel seeding film and the carbon deposition duration. Comprehensive surface characterization techniques, including SEM, EDS, XPS, and AFM, were employed to assess encapsulation efficiency and morphology, revealing strong correlations between input parameters and shell properties.

For deeper structural analysis, we applied Raman spectroscopy, UV-Vis-nIR transmission, and Transient Absorption Spectroscopy (TAS), extracting 107 metrics from the spectral data. Statistical methods, such as Correlation Analysis and Principal Component Analysis (PCA), were used to identify meaningful relationships and uncover the most relevant structural metrics, including promising candidates from less prominent Raman bands.

Our findings demonstrate inter-metric correlations that enable the interchangeable use of spectroscopic techniques, offering a robust framework for analyzing heterogeneous graphitic nanostructures. This study advances the understanding of graphitic shell properties and facilitates their optimized design for targeted applications.

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