Bioanalytically relevant functional groups and characterization methods: Electrochemical methods (blue), optical assays (yellow), other analytical techniques (green).
Source: BAM division Biophotonics
Surface-functionalized nanomaterials, i.e., small particles with a diameter below 100 nanometers that contain specific functional groups on their surface, are rapidly gaining industrial and economic importance for many technologies of the twenty-first century. For example, nanomaterials find use in the life sciences, e.g., as sensor materials or for drug delivery applications, in opto-electronic devices, solid-state lighting, photovoltaics, and in anti-counterfeit tags for security applications as well as increasingly in consumer products. For all these purposes, a wide variety of nanomaterials of different sizes, shapes, compositions, and surface properties are used. The surface chemistry significantly determines the characteristics and functional properties of nanomaterials, such as their physicochemical properties, processability, and performance. In addition, surface chemistry can also influence the impact of the nanomaterial on human health and the environment. For this reason, analytical methods for the quantitative characterization of surface functional groups are crucial to the fabrication, application, and safety of nanomaterials. In this work various analytical methods commonly used to quantify functional groups on nanomaterials were compared with respect to their advantages, disadvantages, and application ranges so that readers and the public can learn what laboratory methods are readily available, cost-effective, and best suited. The methods reviewed include electrochemical titration methods, dye-based optical assays, and instrumental analysis techniques such as infrared (IR) spectroscopy and thermal analysis techniques, as well as more elaborate methods such as nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), and X-ray photoelectron spectroscopy (XPS). In our review, we classified these analytical techniques in terms of signal generation (e.g., the need for a fluorescent reporter dye to obtain a fluorescence signal), the type of functional group to be measured, and the need for expensive instrumentation. In addition, we evaluated these analytical methods regarding their suitability for quality control in nanomaterial synthesis and functionalization, as well as their challenges and limitations. Our comparative work can now help manufacturers and users of functionalized nanomaterials to make decisions about what analytical methods they can use for measuring and controlling the quality of their products containing functionalized nanomaterials.
Analyzing the surface of functional nanomaterials — how to quantify the total and derivatizable number of functional groups and ligands
Daniel Geißler, Nithiya Nirmalananthan-Budau, Lena Scholtz, Isabella Tavernaro, Ute Resch-Genger
published in Microchimica Acta, Vol. 188, issue 10, no. 321, pages 1 - 28, 2021
BAM Division Biophotonics