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Title of the thesis: Mesostructure engineering in MXene-based nanocomposites for broadband modulation: from microwave to infrared

Thesis defender: Xiaodan Hong
Opponent: Professor Chong Min Koo, Sungkyunkwan University, Republic of Korea 
Custos: Aalto Distinguished Professor Olli Ikkala, Aalto University School of Science

From smartphones to aerospace systems, our modern world relies heavily on advanced electronics. However, this progress introduces a major hidden challenge: electromagnetic interference (EMI), which disrupts neighboring electronics and degrades performance. To safeguard this technology, developing ultra-thin, highly efficient shielding materials is paramount. 

MXenes—a revolutionary family of 2D nanomaterials discovered in the wake of Nobel-prize-winning graphene—have emerged as a leading candidate for this role. Yet, their practical application has been bottlenecked by inherent instabilities; they degrade rapidly in air and water, aggregate easily, and remain difficult to manufacture on an industrial scale. 

This doctoral thesis directly addresses these challenges by engineering MXenes at the molecular level. The study demonstrates that specific high-permittivity organic solvents drastically suppress material oxidation, while the introduction of lignin—a sustainable byproduct of the wood pulping industry—acts as a "smart wrapper" to prevent aggregation. This amphiphilic additive broadens solvent compatibility and enables sub-nanometer precision in controlling the material's internal structure, which was accurately mapped using a newly developed, facile X-ray scattering method. 

The core breakthrough lies in the successful fabrication of ultra-thin, freestanding films and coatings that boast outstanding EMI shielding performance while maintaining exceptional long-term stability. By establishing a clear playbook on how microscopic alignment dictates macroscopic traits, this thesis bridges a critical gap in materials science—elevating MXenes from a delicate laboratory curiosity to a robust, scalable platform for advanced manufacturing. 

The applications for these stabilized MXene architectures are vast. They can be seamlessly integrated into 5G/6G networks, wearable electronics, and aerospace components. Beyond passive EMI shielding, these versatile materials can be customized for active electromagnetic wave absorption or infrared light modulation for advanced thermal management. 

Ultimately, the insights from this thesis prove that nano-engineering paired with sustainable, bio-derived components can overcome the intrinsic flaws of 2D materials. By providing a stable, scalable, and structurally precise framework for multi-functional thin films, this work paves the way for smaller, safer, and more reliable electronic devices in our interconnected future.

Keywords: MXene, colloidal stability, mesostructure, broadband modulation 

Thesis available for public display 7 days prior to the defence at .