CAS: Solution Routes Towards Metastable Functional Chalcogenides

硫系材料，即含硫、硒或碲的无机材料，广泛应用于各种领域。开发具有更好的磁性和热电特性的新型硫系材料对于可再生能源收集、能量转换和存储以及信息和数据存储等领域的进步至关重要。在该项目中，由NSF材料研究部固态与材料化学项目支持，Kovnir教授和他的研究小组通过开发新的合成技术来提高溶剂热合成能力，以及硫系功能材料的可持续合成方法。新的合成方法稳定了亚稳态功能材料，具有传统高温固态合成无法实现的前所未有的成分、结构碎片和性能。此外，研究人员还制备了独特的混合材料层状结构，这种材料包含多种不同的材料成分。大的层间分离使得过渡金属-硫族化合物层可以进行软化学修饰，稳定了前所未有的亚稳硫族化合物。作为该奖项的一部分，教育工作的重点是向公众传播科学和化学，并教育Kovnir教授小组的学生有效地进行这种传播。Kovnir教授小组的研究生和本科生在当地K-12学校和得梅因科学中心从事激动人心的教育化学演示，以培养公众对STEM的兴趣。目前的溶剂热合成仅限于一个狭窄的温度窗口，这是由室温附近反应的缓慢动力学或容器稳定性和高温端反应性决定的。在这个由NSF材料研究部固态和材料化学项目支持的项目中，对当前溶剂热合成能力的两个扩展是在接近室温下进行反应的可持续活化硒前驱体的开发，以及高温范围内的加压二氧化硅安瓿和熔盐。所开发的合成技术的合理组合允许合成各种硫族化合物，包括手性杂化化合物和亚稳掺杂和取代的全无机硫族化合物。系统地研究了这些化合物的反应机理和构效关系，揭示了控制这些化合物的磁性、热电性和超导性的因素。这种新方法产生了具有独特性能的亚稳态功能材料。除了为参与项目的学生提供全面的材料化学教育外，教育工作的重点是向公众传播科学和化学，并教育学生有效地进行这种传播。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。

Non-technical SummaryChalcogenide materials, i.e. inorganic materials containing sulfur, selenium or tellurium, are widely used in various applications. Development of novel chalcogenide materials with improved magnetic and thermoelectric characteristics is crucial for the advances in renewable energy harvesting, energy conversion and storage, and information and data storage, among others. In this project, supported by the Solid State and Materials Chemistry program in NSF’s Division of Materials Research, Prof. Kovnir and his research group study approaches to enhancing the solvothermal synthetic capabilities by developing novel synthetic techniques, and the sustainable synthesis of chalcogenide functional materials. The new synthesis methods stabilize metastable functional materials with unprecedented composition, structural fragments, and properties which are not attainable by traditional high-temperature solid state syntheses. Additionally, the researchers prepare unique layered structures of hybrid materials, materials that contain more than one distinct material component. The large interlayer separation makes transition metal-chalcogen layers accessible for soft chemistry modification, stabilizing unprecedented metastable chalcogenides. As part of this award, educational efforts focus on communicating science and chemistry to the public and educating students in Prof. Kovnir’s group to be effective in such communication. Graduate and undergraduate students in Prof. Kovnir’s group are engaged in exciting yet educational chemistry demonstrations at local K-12 schools, and Des Moines Science Center to foster the interest of the general public in STEM.Technical SummaryCurrent solvothermal synthesis is limited to a narrow temperature window dictated by slow kinetics of the reaction near room temperature, or container stability and reactivity at the high-temperature end. In this project, supported by the Solid State and Materials Chemistry program in NSF’s Division of Materials Research, two expansions for the capabilities of current solvothermal synthesis are the development of sustainable activated selenium precursor to perform reaction at near room temperature, and pressurized silica ampoules and molten salts for the high temperature range. A rational combination of the developed synthetic techniques allows for the synthesis of various chalcogenide materials, including chiral hybrid compounds and metastable doped and substituted all-inorganic chalcogenides. Systematic investigations of the reaction mechanisms and structure-property relationships for the produced compounds are carried out to reveal the factors controlling magnetic, thermoelectric, and superconducting properties in these compounds. The new approach produces metastable functional materials with unique properties. Educational efforts are focused on communicating science and chemistry to the public and also educating students to be effective in such communication, in addition to providing a comprehensive materials chemistry education for the students involved in the project.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.