Zamudio-Ojeda A, Guevara-Martínez S J, Rodríguez-Zavala J G, Guirado-López R A
University Center of Exact Sciences and Engineering, University of Guadalajara, Blvd. Marcelino García Barragán 1421, 44430, Guadalajara, Jalisco, Mexico.
University Center of Los Lagos, Department of Exact Sciences and Technology, University of Guadalajara, Enrique Díaz de León, 1144, Lagos de Moreno, Jalisco, Mexico.
Phys Chem Chem Phys. 2025 Jul 2;27(26):14113-14127. doi: 10.1039/d4cp04884a.
We present extensive density functional theory (DFT) calculations dedicated to analyze the stability and Raman response of ZnO-covered C fullerenes. The zinc oxide coating does not wet the carbon surface but instead prefers to assemble into small (ZnO) clusters of different sizes, leading to the formation of a highly nonuniform ZnO overlayer. There is a notable charge transfer within our hybrid C/metal-oxide material, occurring in both C → ZnO and ZnO → C directions, depending on the structure of the ZnO coating. This phenomenon is expected to modify the electronic properties of the fullerene compounds. The presence of the metal oxide overlayer considerably enhances the Raman signals associated to the C molecule. Most interestingly, CO adsorption on ZnO-covered C leads to enhancement factors (EF) for the intensity of the Raman active C-O stretching vibration as large as 5500. This value is considerably greater than that found in free-standing ZnO clusters, clearly defining our considered carbon nanostructures as ultrasensitive sensors for this toxic molecular species. The CO molecule interacts strongly with the Zn adatoms and, by analyzing different local atomic environments, hot spots on the ZnO surface have been identified. The here-reported CO recognition by our C-supported ZnO material, based only in the chemical contribution to the Raman intensity variations reveals, for the first time, the existence of the fullerene-enhanced Raman scattering (FERS) effect. We believe that CO sensing based in Raman spectroscopy measurements are complementary to previous studies where, upon CO adsorption, changes in the electrical resistance of zinc oxide/nanocarbon samples are mostly analyzed. Our theoretical predictions define additional applications for hybrid C/ZnO nanostructures through the appearance of the FERS effect.
我们展示了广泛的密度泛函理论（DFT）计算，致力于分析氧化锌覆盖的碳富勒烯的稳定性和拉曼响应。氧化锌涂层不会润湿碳表面，而是倾向于组装成不同尺寸的小（ZnO）团簇，导致形成高度不均匀的氧化锌覆盖层。在我们的混合碳/金属氧化物材料中存在显著的电荷转移，根据氧化锌涂层的结构，电荷在C→ZnO和ZnO→C两个方向上转移。这种现象预计会改变富勒烯化合物的电子性质。金属氧化物覆盖层的存在显著增强了与C分子相关的拉曼信号。最有趣的是，CO吸附在氧化锌覆盖的C上会导致拉曼活性C - O伸缩振动强度的增强因子（EF）高达5500。这个值远大于在独立的氧化锌团簇中发现的值，明确地将我们所考虑的碳纳米结构定义为对这种有毒分子物种的超灵敏传感器。CO分子与锌吸附原子强烈相互作用，通过分析不同的局部原子环境，已确定了氧化锌表面的热点。我们的碳负载氧化锌材料对CO的识别仅基于对拉曼强度变化的化学贡献，首次揭示了富勒烯增强拉曼散射（FERS）效应的存在。我们认为基于拉曼光谱测量的CO传感与先前的研究互补，在先前的研究中，主要分析了CO吸附后氧化锌/纳米碳样品电阻的变化。我们的理论预测通过FERS效应的出现定义了混合碳/氧化锌纳米结构的其他应用。
