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

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

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.