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1. Chemistry & Photochemistry on Interfaces

   Flinn, L; Kanaththage, M; Wozniak, N; Rubasinghege, G; Navea, J G (July 2025, American Chemical Society)

   When we think of a chemical process, we typically envision it occurring in the bulk phase of a system, leaving the interface overlooked. However, the chemistry at the surface can be significantly different from what happens in the bulk. As we scale down—considering water droplets in a cloud, mineral dust particles in the atmosphere, or the surface of a crystal exposed to reactive gases—the surface area becomes much more prominent than the bulk. Conversely, when considering larger systems, like the oceans or a planet's surface, it becomes evident that interfaces play a crucial role in chemical processes. Chemistry at surfaces and interfaces is pervasive, impacting many scientific fields. Surface chemistry and photochemistry are essential for understanding and controlling the processes at these interfaces. These disciplines are key to natural phenomena and technological advancements by revealing how molecules interact and transform at boundaries. Surface chemistry uncovers the unique behaviors of surface atoms and molecules, which experience unbalanced forces and higher free energies compared to their counterparts in the bulk. This distinctive reactivity drives adsorption, surface tension, and heterogeneous catalysis. In this primer, the authors explore the fundamental phenomena and core concepts shaping chemistry and photochemistry at interfaces. Each chapter examines a specific aspect of interface chemistry; however, reading the entire primer is recommended to gain a thorough understanding of the material. Whether you're a student beginning research in this area or seeking a deeper understanding of these complex dynamics, we hope this primer is a valuable resource for your future work. 

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2. Active colloids on fluid interfaces

   https://doi.org/10.1016/j.cocis.2022.101629  

   Deng, Jiayi; Molaei, Mehdi; Chisholm, Nicholas G.; Yao, Tianyi; Read, Alismari; Stebe, Kathleen J. (October 2022, Current Opinion in Colloid & Interface Science)
3. Energy landscapes on polymerized liquid crystal interfaces

   https://doi.org/10.1039/d3sm00356f  

   Hendley, Rachel S.; Jumai’an, Eugenie; Fuster, Hector A.; Abbott, Nicholas L.; Bevan, Michael A. (June 2023, Soft Matter)

   We measure and model monolayers of concentrated diffusing colloidal probes interacting with polymerized liquid crystal (PLC) planar surfaces. At topological defects in local nematic director profiles at PLC surfaces, we observe time-averaged two-dimensional particle density profiles of diffusing colloidal probes that closely correlate with spatial variations in PLC optical properties. An inverse Monte Carlo analysis of particle concentration profiles yields two-dimensional PLC interfacial energy landscapes on the kT -scale, which is the inherent scale of many interfacial phenomena ( e.g. , self-assembly, adsorption, diffusion). Energy landscapes are modelled as the superposition of macromolecular repulsion and van der Waals attraction based on an anisotropic dielectric function obtained from the liquid crystal birefringence. Modelled van der Waals landscapes capture most net energy landscape variations and correlate well with experimental PLC director profiles around defects. Some energy landscape variations near PLC defects indicate either additional local repulsive interactions or possibly the need for more rigorous van der Waals models with complete spectral data. These findings demonstrate direct, sensitive measurements of kT -scale van der Waals energy landscapes at PLC interfacial defects and suggest the ability to design interfacial anisotropic materials and van der Waals energy landscapes for colloidal assembly. 

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4. Adhesive anti-fibrotic interfaces on diverse organs

   https://doi.org/10.1038/s41586-024-07426-9  

   Wu, Jingjing; Deng, Jue; Theocharidis, Georgios; Sarrafian, Tiffany L; Griffiths, Leigh G; Bronson, Roderick T; Veves, Aristidis; Chen, Jianzhu; Yuk, Hyunwoo; Zhao, Xuanhe (June 2024, Nature)

   Abstract Implanted biomaterials and devices face compromised functionality and efficacy in the long term owing to foreign body reactions and subsequent formation of fibrous capsules at the implant–tissue interfaces^1–4. Here we demonstrate that an adhesive implant–tissue interface can mitigate fibrous capsule formation in diverse animal models, including rats, mice, humanized mice and pigs, by reducing the level of infiltration of inflammatory cells into the adhesive implant–tissue interface compared to the non-adhesive implant–tissue interface. Histological analysis shows that the adhesive implant–tissue interface does not form observable fibrous capsules on diverse organs, including the abdominal wall, colon, stomach, lung and heart, over 12 weeks in vivo. In vitro protein adsorption, multiplex Luminex assays, quantitative PCR, immunofluorescence analysis and RNA sequencing are additionally carried out to validate the hypothesis. We further demonstrate long-term bidirectional electrical communication enabled by implantable electrodes with an adhesive interface over 12 weeks in a rat model in vivo. These findings may offer a promising strategy for long-term anti-fibrotic implant–tissue interfaces. 

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5. In situ investigation of water on MXene interfaces

   https://doi.org/10.1073/pnas.2108325118  

   Zaman, Wahid; Matsumoto, Ray A.; Thompson, Matthew W.; Liu, Yu-Hsuan; Bootwala, Yousuf; Dixit, Marm B.; Nemsak, Slavomir; Crumlin, Ethan; Hatzell, Marta C.; Cummings, Peter T.; et al (November 2021, Proceedings of the National Academy of Sciences)

   A continuum of water populations can exist in nanoscale layered materials, which impacts transport phenomena relevant for separation, adsorption, and charge storage processes. Quantification and direct interrogation of water structure and organization are important in order to design materials with molecular-level control for emerging energy and water applications. Through combining molecular simulations with ambient-pressure X-ray photoelectron spectroscopy, X-ray diffraction, and diffuse reflectance infrared Fourier transform spectroscopy, we directly probe hydration mechanisms at confined and nonconfined regions in nanolayered transition-metal carbide materials. Hydrophobic (K + ) cations decrease water mobility within the confined interlayer and accelerate water removal at nonconfined surfaces. Hydrophilic cations (Li + ) increase water mobility within the confined interlayer and decrease water-removal rates at nonconfined surfaces. Solutes, rather than the surface terminating groups, are shown to be more impactful on the kinetics of water adsorption and desorption. Calculations from grand canonical molecular dynamics demonstrate that hydrophilic cations (Li + ) actively aid in water adsorption at MXene interfaces. In contrast, hydrophobic cations (K + ) weakly interact with water, leading to higher degrees of water ordering (orientation) and faster removal at elevated temperatures. 

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