CAS: Solution Routes Towards Metastable Functional Chalcogenides

非技术概述硫化物材料，即含硫、硒或碲的无机材料，在各种应用中得到广泛应用。开发具有改进的磁特性和热电特性的新型硫系材料对可再生能源收集、能量转换和存储以及信息和数据存储等方面的进展至关重要。在NSF材料研究部固态和材料化学项目的支持下，Kovnir教授和他的研究小组研究了通过开发新的合成技术来增强溶剂热合成能力的方法，以及硫系功能材料的可持续合成。新的合成方法稳定了亚稳态功能材料，具有前所未有的组成、结构碎片和传统高温固相合成无法获得的性能。此外，研究人员还准备了独特的混杂材料分层结构，这种材料含有不止一种不同的材料成分。较大的层间分离使过渡金属-硫化物层易于进行软化学修饰，从而稳定了前所未有的亚稳定硫化物。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，并教育科夫尼尔教授所在小组的学生在这种交流中发挥作用。Kovnir教授小组的研究生和本科生在当地的K-12学校和得梅因科学中心从事令人兴奋的但具有教育意义的化学演示，以培养公众对STEM的兴趣。技术摘要目前的溶剂热合成仅限于狭窄的温度窗口，受室温附近反应的缓慢动力学或高温端容器稳定性和反应性的影响。在该项目中，在NSF材料研究部固态和材料化学计划的支持下，目前溶剂热合成能力的两个扩展是开发可持续活化的硒前驱体，以在接近室温的情况下进行反应，以及在高温范围内开发加压二氧化硅安瓶和熔盐。合理地结合已开发的合成技术可以合成各种硫系材料，包括手性杂化化合物和亚稳态掺杂和取代的全无机硫系化合物。对所合成化合物的反应机理和结构-性质关系进行了系统的研究，揭示了控制这些化合物的磁性、热电和超导性质的因素。这种新方法可以生产出具有独特性能的亚稳态功能材料。除了为参与该项目的学生提供全面的材料化学教育外，教育努力的重点是向公众传播科学和化学，并教育学生在这种交流中有效。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.