Surface characterization of nanomaterials and nanoparticles: Important needs and challenging opportunities

TLDR

Nanomaterial studies frequently suffer from inadequate characterization, leading to uncertain data value and challenges in reproducibly synthesizing and maintaining material properties. The review aims to assess how surface and interface characterization methods can address nanomaterial synthesis challenges and track property changes. The authors discuss using traditional surface‑sensitive techniques (XPS, AES, SPM, SIMS) and emerging methods (NMR, sum‑frequency generation, LEIS) to extract detailed surface and interface information, often enhanced by advanced data analysis. Despite limited accessibility, these techniques prove valuable for targeted questions, as illustrated by examples in nanomaterial research.

Abstract

This review examines characterization challenges inherently associated with understanding nanomaterials and the roles surface and interface characterization methods can play in meeting some of the challenges. In parts of the research community, there is growing recognition that studies and published reports on the properties and behaviors of nanomaterials often have reported inadequate or incomplete characterization. As a consequence, the true value of the data in these reports is, at best, uncertain. With the increasing importance of nanomaterials in fundamental research and technological applications,it is desirable that researchers from the wide variety of disciplines involved recognize the nature of these often unexpected challenges associated with reproducible synthesis and characterization of nanomaterials, including the difficulties of maintaining desired materials properties during handling and processing due to their dynamic nature. It is equally valuable for researchers to understand how characterization approaches (surface and otherwise) can help to minimize synthesis surprises and to determine how (and how quickly) materials and properties change in different environments. Appropriate application of traditional surface sensitive analysis methods (including x-ray photoelectron and Auger electron spectroscopies, scanning probe microscopy, and secondary ion mass spectroscopy) can provide information that helps address several of the analysis needs. In many circumstances, extensions of traditional data analysis can provide considerably more information than normally obtained from the data collected. Less common or evolving methods with surface selectivity (e.g., some variations of nuclear magnetic resonance, sum frequency generation, and low and medium energy ion scattering) can provide information about surfaces or interfaces in working environments (operando or in situ) or information not provided by more traditional methods. Although these methods may require instrumentation or expertise not generally available, they can be particularly useful in addressing specific questions, and examples of their use in nanomaterial research are presented.