In-situ Characterization Techniques for Nanomaterials

This chapter lays out experimental evidence from the field of liquid cell electron microscopy, related concepts from radiation chemistry, and models explaining particle growth, diffusion, and electron charging during experiments. We present an overview of main results regarding particle growth, observation of low contrast systems such as proteins, and in-operando experiments using nonaqueous solutions.

In-Situ and time-resolved X-ray scattering and diffraction is dedicated to yielding the change of structural information as the materials are processed or grown in a controlled environment. In this chapter, we introduce the use of in situ and time-resolved X-ray techniques to understand molecular packing, crystal orientation, and phase transformation during the synthesis and processing of functional organic semiconductors, organic nanowires, and hybrid perovskite materials.

During the past two decades, nanomaterials have had an enormous diversity of applications in different industrial fields and fundamental research. Some of these nanomaterials are specifically engineered to exhibit unique optical, electrical, or other physical or chemical characteristics. Owing to these attributes, the products containing various engineered nanoparticles (NP) cover large segments of the market from clothing to electronics and healthcare products [1]. The rapid development of nanotechnologies, their industrial applications, and related nanosafety concerns demand sensitive analytical methods for the identification and analysis of nanoparticles (NPs) in very different media [2]. In the same time, there are serious concerns on possible toxicity of nanoparticles for humans and environment [3]. Engineered NPs (ENPs) have to be analyzed not only during their production, in pure and concentrated form, but also at trace concentrations in environment, drinking water and food, healthcare and pharmacological products, biological fluids, etc. Ideally, such a technique should provide a possibility to detect NPs at the level of single particles and deliver information on their concentration, core and surface chemical composition, size, and shape [2–4].

Localized surface plasmon resonance (LSPR) spectroscopy of metallic nanoparticles (NPs) is a powerful technique for chemical and biological sensing experiments. LSPR is responsible for the electromagnetic field enhancement that leads to surface-enhanced Raman scattering (SERS) and other surface-enhanced spectroscopic processes [1].

X-ray absorption spectroscopy (XAS) is a powerful technique to study the unoccupied states and the local structure around an excited species of atoms from an element present in a material. Recently, in situ XAS is being used to study catalytic transformations, synthesis of nanoparticles and thin films, kinetics of potential battery materials, etc. Such studies can explain the mechanisms associated with the formation of chemical species during various types of reactions. In this chapter, we shall describe how XAS has proved to be a powerful characterization tool for nanomaterials with potential applications by determining the variation in interatomic distances, coordination numbers, and the type of neighboring atoms within the first few coordination shells of the atom of interest in nanoparticles.

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In situ characterization of topological insulator nanomaterials using several, complementary surface analysis techniques enables to investigate topological surface states without exposing the samples to ambient conditions. Adsorbants from exposure to air and other ex situ contaminations result in notable changes in the bulk and surface state properties of topological insulators. In this chapter, we describe recent developments in the in situ characterization of topological insulator nanomaterials. Extensive studies on individual samples are made possible by connecting the deposition chamber to a large number of surface analysis tools and by using a vacuum suitcase technology which allows sample transfer in ultra-high vacuum conditions between vacuum systems worldwide.

Life in the twenty-first century is dependent on an unlimited variety of advanced hybrid materials – among them, nanomaterials (NMs). The design of these NMs mostly depends on the current necessities of the society, the availability of resources, and the investment required for an appropriate scale-up production. Thus, regarding the preparation of novel NMs, it is mandatory for the evaluation of their properties in order to satisfy the desired applications with high performance. In this chapter, we discuss different techniques that offer the possibility of the in situ characterization of NMs and nanocomposite materials (NCs), in terms of their chemical composition, spatial distribution, and optical and electrochemical features, without modifying the material itself.

Thickness Shear Mode (TSM) sensors and, in particular, Quartz Crystal Resonator (QCR) sensors are very efficient systems because of their elevated accuracy, sensitivity, and biofunctionalization capacity. They are highly reliable when measuring deposited samples, both for gaseous and liquid media. Moreover, they can be used for real time monitoring and their manufacturing cost is relatively low. These characteristics explain the many possible applications of QCR sensors as biosensors. In this chapter, recent remarkable applications of QCRs in different contexts are described. Applications of these sensors range from medical an environmental monitoring applications, to mixed applications with other techniques such as Atomic Force Microscopy (AFM), Surface Plasmon Resonance (SPR) or electrochemical in order to improve the sensor system response.

Quartz crystal microbalance (QCM) or quartz microbalance (QMB) as an in situ precise method for mass control allows vast research of many processes of hetero-phasic mass transfer.

In the last century, progress in electrochemistry and electrocatalysis was very spectacular due to the remarkable evolution in surface science, chemistry, and physics. Electrochemical study of perfect smooth or bulk materials was the usual way to understand the interaction between the surfaces of such materials with their close environment. Therefore, any modification of the surface structure or composition provides change in the material behavior and the nature of the adsorbed species or near. Usually, the modification of smooth surface consists in the increase of its roughness factor through the deposition of sublayer or layer of metal particles. The deposition can be done on a well-defined surface (model electrode with a known crystallographic structure) [1]. Then, surface modification becomes a way of creating new active sites to enhance the reactivity of molecules. The development of nanoscale materials has changed the approach of studying and identifying active sites in heterogeneous catalysis, and particularly in electrocatalysis. Indeed, electrocatalysis uses the surface of a material, which is submitted to an electrode potential, as the reaction site. Therefore, the material structure, morphology and its composition are the key parameters to control the electrochemical process [2]. The nature of the active site depends on these parameters. Furthermore, the assessment of the nature of the active site before, during, and after the electrocatalytic reaction becomes a huge challenge. Thereby, electrochemical tools like cyclic voltammetry, underpotential deposition of a monolayer of a species [3–5], the specific adsorption of species or molecule, and CO stripping [6] were the first approaches. It is the basic measurement of the electrons flow through the surface per unit of time during the reaction at the surface. Therefore, the electric current per area unit represents the charge transfer reaction that occurs at a metal-solution interface. Since the middle of the last century, an increase in the development of several in situ spectroscopic techniques was observed due to the need of understanding the structure of the interface between electrodes and solutions. Indeed, coupling the electrochemistry measurements to other techniques such as Fourier Transform Infrared Spectroscopy (FTIRS), X-Ray Diffraction (XRD) [7, 8], Transmission Electron Microscopy (TEM) [9], Scanning Tunneling Microscopy (STM) [10], Surface-Enhanced Raman Scattering (SERS) [11] becomes a suitable approach to assess in real time at the electrified interface electrode-solution; some relevant data on electrocatalysts structure, morphology, composition, and stability of materials; and on the reaction intermediates and products. The identification of the surface state in addition to that of adsorbed species, intermediates, and products of the reaction process have permitted to determine a mechanistic pathway which is essential for enhancing the material performance and selectivity. It appears obvious that the identification of surface state of a nanomaterial under realistic electrochemical reaction conditions represents a noble scientific breakthrough. In the present chapter, for the first time some techniques coupled with electrochemistry able to characterize nanomaterials as electrodes will be extensively addressed. This chapter will also show the progress in in situ electrochemical approaches. One motivated approach is to be able to characterize electrochemically and experimentally the surface of the nanoparticle. Therefore, in the first part of the chapter, an example of a pure electrochemical tool, which permits to probe the nanoelectrocatalyst surface, is discussed. Although the progress in nanotechnology increases rapidly, various tools have been developed in electrochemistry for understanding the reaction pathway, intermediates, and products formation.