NSF Award
2438038
The ability to precisely separate and characterize nanoscale objects, such as molecules, inorganic particles, and biological particles (e.g., exosomes), is crucial in fields like analytical chemistry, environmental science, and medical diagnostics. Chromatography is a key method used for these purposes. As such, it remains a vibrant academic and industrial research and development field. In fact, the chromatography industry generates approximately $9 billion in net global revenue, which is expected to grow by 7% annually over the next decade. Liquid chromatography separates the nanoscale objects (solutes), which are dissolved in a liquid, by passing the solute-laden fluid over the separation medium. The interactions between the solutes and the separation medium govern the effectiveness of the separation. Despite the economic and scientific importance of chromatographic separations, a detailed understanding of the dynamic interactions between solutes and the separation medium at a microscopic level has not been established, hindering progress toward developing more robust and effective techniques. This knowledge gap exists primarily because few experimental techniques can reliably observe these interactions in situ at the interfacial layer. This research project brings together an international team of scientists from the U.S. and Germany to address this gap. The team will use their newly developed, state-of-the-art instruments to directly observe the chromatographic steps at the fundamental, single-particle level during the separation process. Graduate students will gain valuable technical and professional experience through this international collaboration. <br/><br/>Liquid chromatography is an important separation technique. Its wide-ranging applications include chemical purification, pharmaceutical analysis and production, and environmental monitoring, among others. Furthermore, it is foundational in understanding complex biological systems, developing new materials, and optimizing chemical processes. The basic principle of liquid chromatography involves partitioning components between a stationary phase and a mobile phase, with differential interactions leading to their separation based on relative retention times. The general view of the underlying principle is that smaller flexible molecular species are segregated by their retention in the porous environment of the solid substrate. This notion that entropic and enthalpic contributions can be separated in a purely size-exclusion process or by affinity chromatography is now being challenged by the development of liquid chromatography for hybrid nanomaterials with inorganic hard cores and functional soft organic shells. New studies reveal a complex interplay of entropic and enthalpic interactions, the latter resulting from the hybrid materials’ functional shells. Unfortunately, a comprehensive microscopic picture of this interplay cannot be developed because of the limited experimental techniques capable of in situ observations at the interfacial layers governing the chromatographic process. This project aims to shed new light on the interfacial layer dynamics that occur during the chromatographic separation of nanomaterials. Recent advancements in nanomaterials synthesis and functionalization, high-resolution three-dimensional (3D) fluorescence microscopy, and boundary layer thermofluidic manipulation enable this project. The enthalpic contributions will be controlled by synthesizing functional quantum dots (QDs) and modifying the stationary phase of the chromatography column with complementary DNA strands. The 3D dynamics of the functionalized QDs will be explored in situ with unprecedented spatial (10 nanometers) and temporal resolution (10 microseconds). The dynamics and enthalpic interaction of functionalized QDs will be further investigated with complementary planar interfaces by controlling thermo-osmotic flows induced directly at the liquid-solid interface. The results are expected to lead to a new fundamental understanding of chromatography that will considerably improve performance and trigger the development of more efficient or selective separation methods based on novel osmotic flows in microfluidic environments.<br/><br/>This project was awarded through the “Measurements of Interfacial Systems at Scale with In-situ and Operando aNalysis (NSF-DFG MISSION)" opportunity, a collaborative solicitation that involves the National Science Foundation and Deutsche Forschungsgemeinschaft (DFG).<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
