Local Atomic-level Thermodynamic Probe for Nanoscience of 2D Membranes: Synthesis, NMR and Nanocalorimetry Study

1. 非技术总结通过这个奖项，由NSF材料研究部的固态和材料化学计划资助，PI为纳米科学界开发了一种新的表征方法。这种新方法对超薄膜材料的研究特别有用，因此可能在健康方面（了解生物膜）以及其对纳米电子工业的有用性方面服务于国家利益，纳米电子工业在传统和先进设备中使用极小纳米尺寸的材料（例如硅和石墨烯）。目前，这些设备既用于国防组件，也用于下一代手机等商业设备。这项新技术被称为“局部原子级热力学探针”，它使用核磁共振技术，这种技术在性质上类似于医院经常用于诊断人体内特征的流行MRI医疗仪器，并将其与纳米量热法相结合，纳米量热法是一种相当新颖的技术，可以测量材料特性，例如只有几个原子厚的膜层的熔化温度。在该项目的“更广泛影响”活动中，最突出的是旨在增加美洲原住民对科学界教育和研究的参与。为了实现这一目标，外展工作的重点是在蒙大拿州布朗宁的当地社区学院提供为期两天的暑期科学营，这里是美洲土著黑脚部落的家园。夏令营的主题是使用专注于能源相关项目的实践实验。活动将包括：（1）使用电压表进行电气测量;（2）组装用于LED照明的风力涡轮机;（3）组装利用太阳能的成套工具;（4）动手安装热量计/太阳能/仪表，利用太阳能加热水。该夏令营将教育60名高中生。该项目的另一个更广泛的影响是国家仪器基础设施的增强与nanocalorimetry技术的发明，这有助于保持国家的领导作用，在纳米热分析领域，通过解决目前的差距，在纳米技术领域的先进分析技术的广度。 2. 技术总结通过这个奖项，由NSF材料研究部的固态和材料化学计划资助，PI为纳米科学界开发了一种新的表征方法。该工具是一个局部原子级热力学探针，包括将NMR和纳米量热法与新的建模方法（唯象热力学模型，DFT，MD和Monte Carlo）相结合。该项目需要合成一套特殊的AgSCn-X 2D膜，作为开发新技术的基础材料系统。二维（2D）膜材料表现出在自然界中普遍存在的非凡性质。它们存在于活细胞和纳米电子学中。例如，石墨烯具有非常高的电子迁移率和零带隙，而生物膜形成所有活细胞的外层结构。当膜的厚度接近临界纳米尺寸范围时，物理性质发生异常变化，例如，尺寸对生物细胞系统中脂质膜的熔化具有巨大影响。即使是几度的温度变化对人体来说也是至关重要的，因为人体的生存温度范围很窄。测量单层膜（~2 nm）的热力学熔融特性并获得其熔点和焓值只是最近才使用新的纳米量热技术完成的。最新的发现集中在烷基链中少于7个碳的超薄膜上。在这里，吉布斯-汤普森尺寸依赖模型在本体和离散尺寸之间的过渡处的临界链长处破裂。在这种小尺寸范围内，当膜的厚度接近其极限时，纳米量热法和热分析法的缺点变得明显。在这个小的链长下，熔点飙升50 K，熔融焓增加~ 400%。纳米量热法没有深度感知;它只产生平均热力学值。另一方面，NMR可以区分一个原子与另一个原子。NMR具有通过监测化学位移来测量单个（类型）原子的局部化学环境的独特能力。结合这两种技术产生了一个强大的工具，纳米科学的调查。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

1. NON-TECHNICAL SUMMARYThrough this award, funded by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, the PI develops a new characterization method for the nanoscience community. This new method is especially useful for research in ultra-thin membrane material and therefore might serve national interests in terms of health (understanding biological membranes) as well as by its usefulness for the nanoelectronics industry, which uses material (e.g. silicon and graphene) at extremely small nanometer size in both conventional as well as advanced devices. Currently, these devices are used in both national defense components as well as commercial devices such as next generation cell phones. The new technique is called "Local Atomic-Level Thermodynamic Probe" and it uses nuclear magnetic resonance, a technique which is similar in nature to the popular MRI medical instrument often used in hospitals to diagnose features within the human body, and combines it with nanocalorimetry, a rather novel technique that can measure materials properties such as melting temperatures of membrane layers that are only a few atoms thick. Most prominent among the Broader Impacts activities of this project is the aim to increase the Native American participation in education and research within the scientific community. To achieve this, outreach efforts focus on offering two-day sessions of a Summer Science Camp at the local community college in Browning, MT, the home of the Native American Blackfeet tribe. The theme of the camp uses hands-on experiments focusing on energy related projects. Activities will include (1) the use of voltmeter for electrical measurements; (2) assembly of Wind Turbine for LED lighting; (3) assembling kits that utilize solar energy; (4) hands-on calorimetry/solar/meter setup for heating water from solar energy. The camp will educate 60 high/middle school students. Another Broader Impact of this project is the enhancement of National Instrumentation Infrastructure with the invention of the nanocalorimetry technique which helps sustain the country's leadership role in the field of nanoscale thermal analysis by addressing a current gap in the breadth of advanced analytical techniques in the field of nanotechnology. 2. TECHNICAL SUMMARYThrough this award, funded by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, the PI develops a new characterization method for the Nanoscience Community. This tool is a local atomic-level thermodynamic probe and consists of combining NMR and nanocalorimetry with new modeling methods (phenomenological thermodynamic models, DFT, MD and Monte Carlo). The project requires the synthesis of a special set of AgSCn-X 2D membranes, which act as the base material system for the development of the new technique. Two-dimensional (2D) membrane materials exhibit extraordinary properties that are universal in nature. They occur in living cells as well as in nanoelectronics. For example, graphene has remarkably high electron mobility and zero band gap while biological membranes form the outer layer structures of all living cells. Extraordinary changes in physical properties occur as the thickness of the membrane approaches the critical nanometer size range, e.g. size has a huge effect on the melting of lipid membranes in biological cell systems. Even changes of few degrees in temperature are critical in human body where the survival temperatures span over a very narrow range. Measuring the thermodynamic melting properties of single-layer membranes (~2 nm) and obtaining values for their melting point and enthalpy were only recently accomplished with the use of new nanocalorimetry technology. The latest discovery focuses on ultra-thin membranes with less than 7 carbons in the alkyl chains. Here the Gibbs-Thompson size-dependent model breaks down at a critical chain length at the transition between bulk and discrete sizes. In this small size regime, the shortcomings of nanocalorimetry and thermoanalysis become apparent when the thickness of membranes approaches their ultimate limit. At this small chain length, the melting point soars by 50 K and the melting enthalpy increases by ~400%. Nanocalorimetry has no depth perception; it only yields average thermodynamic values. NMR, on the other hand, can distinguish one atom from another. NMR has the unique capability to measure the local chemical environment of individual (type) atoms by monitoring the chemical shift. Combining these two techniques produces a powerful tool for Nanoscience investigations.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.