Two-Dimensional and Magic Size Layers of Metal Thiolates: Synthesis and Nanocalorimetry Characterization

技术概述：PI提议在材料研究部固态和材料化学项目的支持下合成和表征极薄的银硫酸盐（AgSR）层。晶体可以形成各种形状和大小，但有些晶体比其他晶体更特殊。这些特殊尺寸，通常被称为幻数尺寸，在材料化学和物理学中引起了极大的兴趣，因为它们通常是材料独特的潜在特性的证据。AgSR是一种有趣的聚合物，因为它以堆叠的扁平双层形式生长。PI设想，层状AgSR将成为一种新型的上层结构自组装模型，可用于物理、化学、生物和微电子技术领域的各种新材料应用。PI最近开发了一种新的合成方法，使用金属纳米颗粒产生大的AgSR晶体血小板。这些晶体的直径为1微米，高度可达30层厚，表面接近原子平面（Langmuir 2009）。本提案的一个主要目标是利用AgSR的不同寻常的平面属性，并扩展这一新的合成路径，以生产基本最小厚度的晶体，单层二维AgSR晶体。这种单层晶体是自下而上自组装合成的最终起点。2004年石墨烯的发现打破了传统观点，即这些薄晶体不可能存在，部分原因是由于熔化温度降低（与尺寸有关的熔化）而固有的不稳定性。这项提议的一个主要目标是测量这些一层晶体的熔化程度，这是迄今为止从未做过的。这一目标将通过纳米热法来实现。这些结构可以用来研究热力学和尺寸相关的熔化现象，单层控制晶体尺寸是不可能的，除非簇束。除了液晶和亚稳相的形成外，PI还建议使用NanoDSC研究该系统的尺寸效应。非技术总结：这项工作的科学影响将是在微电子工业应用中产生新的合成方法的发展。此外，在热分析中开发的新的表征技术将极大地扩展我们在非常小的尺寸尺度上探测材料特性的科学能力，这对纳米技术的进步是有用的。这项研究的广泛影响将包括纳米技术领域研究生的教育和培训以及新合成方法的发展。学生将接受教育和培训，使用微电子技术制造MEMs器件，并使用自组装合成方法。几乎所有接受PI培训的学生目前都在微电子行业工作。除了正式的期刊文章，这项工作的传播将以PI和研究生和本科生的会议演讲的形式进行，以及在专门的热分析会议上的纳米热学短期课程。通过进一步发展合成方法和纳米odsc技术的能力，这项工作将增加该国基础科学和技术的制造和仪器基础设施。预计将在热分析领域与西班牙和加拿大的研究小组以及美国的其他研究小组开展科学合作。

TECHNICAL SUMMARY: The PI proposes to synthesize and characterize extremely thin layers of Ag thiolate (AgSR) with the support from the Solid State and Materials Chemistry program in the Division of Materials Research. Crystals form in a variety of shapes and sizes but some crystals are more special than others. These special sizes, often referred to as Magic Number Sizes, are of great interest in materials chemistry and physics because often they are evidence of unique underlying properties of the material. AgSR is an interesting polymer in that it grows as stacked flat bilayers. The PI envisions lamellar AgSR to be a new model building block for bottom-up self assembly of superstructures that can be used in a variety of new material applications in physics, chemistry, biology and microelectronic technologies. The PI recently developed a new synthesis method using nanoparticles of metal which generates large AgSR crystal platelets. These crystals have diameters of 1 micron and heights of up to ~30 layers thick with nearly atomically flat surfaces (Langmuir 2009). One major objective in this proposal is to exploit the unusual planar attributes of AgSR and to extend this new synthesis path to produce crystals of the fundamental minimum thickness, one-layer two-dimensional AgSR crystals. This one-layer crystal is the ultimate starting point for bottom-up self-assembly synthesis. Discovery in 2004 of graphene has defied the conventional wisdom that these thin crystals could not exist because of an inherent instability in part due to reduced melting temperature (size-dependent melting). A major objective of this proposal is to measure the melting of these 1-layer crystals which to date has never been done. This goal will be accomplished using Nanocalorimetry. These structures can be used to study thermodynamics and size-dependent melting phenomenon with single-layer control of crystal size which has been implausible except for cluster beams. The PI proposes to study size-effects in this system using NanoDSC in addition to the formation of liquid crystal and metastable phases.NON-TECHNICAL SUMMARY: The scientific impact of this work will be in the development of generating new synthesis methods for applications in the microelectronics industry. Furthermore the new characterization techniques developed in thermal analysis will greatly expand our scientific ability to probe material properties at a very small size scale which is useful for advancement in Nanotechnology. The broad impact of this research will include the education and training of graduate students in the field of nanotechnology and the development of new synthesis methods. The students will be educated and trained in fabrication of MEMs devices using microelectronic techniques and in using self-assembly synthesis methods. Almost all of the students who have been trained by the PI are currently working in the microelectronics industry. In addition to formal journal articles, the dissemination of this work will be in the form of conference talks given by both the PI and graduate and undergraduate students along with Nanocalorimetry short courses in specialized Thermal Analysis conferences. By further developing the capabilities of the synthesis methods and NanoDSC technique, this work will add to the fabrication and instrumentation infrastructure of the country for basic science as well as for technology. Scientific collaborations are expected to be developed in the area of Thermal Analysis with groups in Spain and Canada as well as other research groups in the United States.