Few-Layered MoS2 Nanoparticles Covering Anatase TiO2 Nanosheets: Comparison between Ex Situ and In Situ Synthesis Approaches

Rosangela Santalucia,Tiziano Vacca,Domenica Scarano,Federico Cesano,Francesco Pellegrino,Gianmario Martra

doi:10.3390/app11010143

Abstract

MoS2/TiO2 nanostructures made of MoS2 nanoparticles covering TiO2 nanosheets have been synthesized, either via ex situ or in situ approaches. The morphology and structure of the MoS2/TiO2 hybrid nanostructures have been investigated and imaged by means of X-ray diffraction (XRD) analysis and high-resolution transmission electron microscopy (HRTEM), while the vibrational and optical properties have been investigated by Raman, Fourier-transform infrared (FTIR), and UV−visible (UV–vis) spectroscopies. Different stacking levels and MoS2 nanosheets distribution on TiO2 nanosheets have been carefully evaluated from HRTEM images. Surface sites on the main exposed faces of both materials have been established by means of in situ FTIR spectra of CO probe molecule adsorption. The results of the ex situ and in situ approaches are compared to underline the role of the synthesis processes affecting the morphology and structure of MoS2 nanosheets, such as curvature, surface defects, and stacking order. It will be shown that as a result of the in situ approach, the reactivity of the TiO2 nanosheets and hence, in turn, the MoS2–TiO2 nanosheets interaction are modified.

Highlights

Heterostructures of different dimensionality have been investigated in the past because of their novel properties and challenging applications, including clean energy and new energy-related technologies, photocatalysis [1,2], electrocatalysis [3], solar cells [4], energy conversion and storage [1,5], up to research studies in biomedical fields [6,7,8]
2D−2D van der Waals heterostructures made of distinct 2DLMs and superlattices [8] play a considerable role in controlling and manipulating the generation, confinement, and transport of charge carriers, excitons, photons, and phonons within the atomic interfaces, giving chances for the design of unique and challenging devices [9,10,11]
TiO2 nanosheets have been obtained via a solvothermal procedure, which we briefly summarize because many papers have already reported on this subject [35,37]

Summary

Introduction

Heterostructures of different dimensionality have been investigated in the past because of their novel properties and challenging applications, including clean energy and new energy-related technologies, photocatalysis [1,2], electrocatalysis [3], solar cells [4], energy conversion and storage [1,5], up to research studies in biomedical fields [6,7,8]. Many efforts have been focused on the combination of two-dimensional layered materials (2DLMs) with zerodimensional ones (0D), such as plasmonic nanoparticles and quantum dots, and with monodimensional (1D) nanostructures, such as nanowires and nanoribbons, introducing a new way of nanoscale material integration and enabling the development of many extraordinary electronic devices In this regard, 2D−2D van der Waals heterostructures made of distinct 2DLMs and superlattices [8] play a considerable role in controlling and manipulating the generation, confinement, and transport of charge carriers, excitons, photons, and phonons within the atomic interfaces, giving chances for the design of unique and challenging devices [9,10,11].

Methods

Results

Conclusion