GOALI: Manufacturing of Two-Dimensional MXene Nanosheets by Salt Solution Etching and Their Solution-based Layer-by-Layer Assembly into Heterostructures

MXenes是一个广泛的二维（2D）陶瓷纳米片家族，具有广泛的成分多样性和可定制性，可用于广泛的实际应用，包括储能，催化，电磁干扰屏蔽，传感器，复合材料和电池。然而，MXenes在先进制造方面的挑战阻碍了其广泛生产和使用。制造方面的挑战包括(i)除了钛铝碳化物之外的MAX相合成困难，（ii）在合成中使用有害酸，（iii）缺乏化学稳定性，特别是在水或潮湿环境中，以及（iv）在功能薄膜和涂层中的粘附性和控制。这项学术与工业联络资助机会（GOALI）奖支持基础研究，以提供应对这些挑战所需的知识。该项目涉及新的合成和加工途径，使新的MXene组合物的可扩展纳米制造成为可能，同时防止降解，以及在功能涂层中控制MXene的逐层组装的新方法。特别强调的是涂层组装的特点，如可调谐的光电性能。此外，教育目标还包括(1)与GOALI行业合作伙伴一起指导本科生和研究生，以及(2)通过以2D纳米材料为重点的课程改进、联合产学研研讨会和K-12外展来吸引更广泛的社区。应对MXene纳米片先进制造挑战的技术方法包括合成、蚀刻和组装方面的实验进展。该项目利用熔融盐溶液等替代蚀刻剂进行一步无hf合成下一代MXene，重点研究蚀刻剂类型和蚀刻条件如何影响MXene的收率、质量和抗化学降解的稳定性。该项目的另一个目标是创建含有这些下一代MXenes的逐层组装的异质结构功能涂层。该目标的重点是将MXene的水基溶液组装成独特的异质结构涂层，该涂层包含各种MXene类型的精确堆叠区域，有或没有聚合物。聚合物和MXene交替块的保形涂层的制造允许定制光电特性，从而导致诸如肖特基结，布拉格反射器和光学滤光器等应用。此外，GOALI项目还与Lynntech合作，在MXene生产和先进制造的可扩展性方面增加了专业知识。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

MXenes are a broad family of two-dimensional (2D) ceramic nanosheets with a wide compositional diversity and tailorability of properties for a broad range of practical applications, including energy storage, catalysis, electromagnetic interference shielding, sensors, composites, and batteries. However, challenges in the advanced manufacturing of MXenes prevent widespread production and use. Manufacturing challenges include (i) difficulties in synthesizing MAX phases beyond titanium aluminum carbide, (ii) the use of hazardous acids in the synthesis, (iii) a lack of chemical stability, particularly in aqueous or humid environments, and (iv) adhesion and control in functional films and coatings. This Grant Opportunity for Academic Liaison with Industry (GOALI) award supports fundamental research to provide the knowledge needed to meet these challenges. This project involves new synthesis and processing avenues that enable the scalable nanomanufacturing of new MXene compositions while preventing degradation and new methods of controlled layer-by-layer assembly of MXenes in functional coatings. A special emphasis is placed on coating assembly features such as tunable optoelectronic properties. Additionally, education objectives include (1) mentoring undergraduate and graduate students alongside the GOALI industry partner, and (2) engaging the broader community via 2D nanomaterial-focused curriculum enhancements, a joint industry-government-academic workshop, and K-12 outreach.The technical approach to meeting the challenges with advanced manufacturing of MXene nanosheets includes experimental advances in their synthesis, etching, and assembly. In one objective, this project utilizes alternative etchants such as molten salt solutions for one-step HF-free synthesis of next-generation MXenes with a focus on how etchant type and etching conditions affect MXene yield, quality, and stability against chemical degradation. In another objective, this project creates layer-by-layer-assembled heterostructured functional coatings containing these next-generation MXenes. The focus of this objective is on the water-based solution assembly of MXenes into unique heterostructured coatings that contain precisely stacked regions of various MXene types with or without polymers. The manufacture of conformal coatings with alternating blocks of polymer and MXene allows for tailored optoelectronic properties leading to applications such as Shottky junctions, Bragg reflectors, and optical filters. In addition, this GOALI project has a partnership with Lynntech for added expertise in scalability of MXene production and advanced manufacturing.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.