Professors Xavier Roy and Latha Venkataraman of Columbia University are supported by the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program of the Division of Chemistry to generate self-assembled monolayers of carbene molecules on metallic surfaces, and to investigate the structure electronic properties and stability of the resulting self-assembled monolayers. Coating metallic surfaces with molecules having tunable properties imparts the surface with special functionalities suitable for a variety of practical applications, including sensing, nanoelectronics, nanofabrication and electrochemistry. The usefulness of traditional self-assembled monolayers made with thiol chemical groups on gold surfaces is limited due to the poor chemical, electrochemical and thermal stability of the metal surface coating. This research on carbene monolayers has the potential to significantly improve the stability, tunability and metal compatibility of molecular monolayers on surfaces, thus positively impacting their potential practical applications. The project integrates research with educational and outreach activities. Graduate and undergraduate students from diverse backgrounds are involved in the research; research topics are integrated in Chemistry and Applied Physics curricula; and middle-school minority students from Central Harlem in New York are exposed to nanoscience concepts. In addition, the students involved in the research are provided with an international research opportunity through collaboration with international groups in Italy and the Czech Republic.
In this research project the research team study the formation, stability, structure and electronic properties of self-assembled carbene monolayers on metallic surfaces through an interdisciplinary effort that includes chemical synthesis, x-ray spectroscopy, electrochemical characterization, electron transport measurements and theory. Carbenes are promising candidates for creating thermally and chemically ultra-stable self-assembled monolayers. Being exceptionally strong sigma-donors with unusual electronic structures, carbenes bind much more strongly to metal surfaces than traditional thiols, thus opening the door to novel applications as tunable platforms for (bio)sensing, lab-on-a-chip, electrochemistry, electrocatalysis and nanoelectromechanical systems. Carbenes could also potentially passivate nanoelectrodes and modify metal work functions while serving as novel ligands. Despite these promises and the vast scientific literature on metal-carbene complexes, the assembly and conformation of carbenes on surfaces is poorly understood, and the electronic structure and properties of the resulting monolayers are largely unknown. To address this knowledge gap, this research project focuses on three research objectives: (1) Designing and synthesizing carbene monolayers with varying electronic and steric characteristics, (2) Probing the structure and electronic coupling of carbene monolayers to metal surfaces using x-ray spectroscopy and scanning tunneling microscopy, and (3) Developing room temperature and solution-based methods to prepare carbene monolayers on metal surfaces, and characterizing the structure and electronic coupling using electrochemical and scanning probe techniques.
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.
