The mechanism of fumarate photoreduction on zinc sulfide nanoparticles

硫化锌纳米颗粒富马酸盐光还原机理

• 批准号: 1324791
• 负责人: Jillian Banfield
• 金额: $ 39.97万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1324791&HistoricalAwards=false
• 关键词: mechanism; fumarate; photoreduction; zinc; sulfide

(1) Technical Abstract Light-driven redox interactions between semiconducting sulfide minerals and organic molecules may have initiated the abiotic carbon chemistry needed for the appearance of life on Earth. In particular, the tricarboxylic acid (TCA) cycle has been proposed as a primordial metabolism for emerging organisms. Testing this proposal requires knowledge of the products and mechanisms of candidate mineral-organic reactions. We will determine the rates, mechanism, and intermediate species in one light-driven reaction from the TCA cycle. Specifically, we will study the two-electron reduction of fumarate to succinate on colloidal zinc sulfide (ZnS) surfaces, using time-resolved transient optical and infrared absorption spectroscopy and Fourier transform electron paramagnetic resonance spectroscopy to probe reaction progress from the subnanosecond to the microsecond timescales. These complementary techniques will allow correlating the temporal evolution of the charge distribution in the semiconductor and the breaking and formation of bonds in the organic reactant. This research will contribute new constraints on the geochemical conditions of the early Earth that could have permitted the establishment of a prebiotic carbon cycle driven by solar energy.(2) Broader significance and importanceThe absorption of light by metal sulfide minerals can initiate photochemical reactions between the mineral surface and adsorbed organic molecules. This kind of semiconductor photochemistry must have been occurring under the conditions known to exist in the early Earth and it is speculated that they played an important role in synthesis of complex organic molecules required for the development of life. One particular reaction that transforms one small organic acid molecule, fumarate, into another, succinate, occurs readily on the surface of zinc sulfide (ZnS) particles under ultraviolet (UV) illumination. In this process, the surface transfers two electrons to fumarate, which also acquires two protons from water, to form two new carbon-hydrogen bonds. The precise pathway of the reaction, including the ordering of electron and proton transfer steps, is currently unknown. In particular, we hypothesize that the binding of fumarate to the ZnS surface stabilizes the intermediate chemical species and enables this relatively complex redox reaction to proceed without forming side products. In our proposed research, we plan on using time-resolved spectroscopic techniques to capture chemical signatures of the different intermediate species and thereby determine the reaction pathway. By subsequently investigating how the reaction pathway and rate changes in response to changing ZnS or solution chemistry, we expect to be able to determine the role of the sulfide surface in influencing this reaction. This work will put constraints on the geo chemical conditions of the early Earth that could have permitted solar-driven, abiotic organic reactions. This work has implications not only for understanding the origins of life, but also the development of materials for solar energy applications based upon Earth-abundant elements. This work also addresses fundamental science at the basis of mineral-biomolecule interactions, which may provide further insights into topics in medical geology.

（1）半导体硫化物矿物质和有机分子之间的技术抽象驱动的氧化还原相互作用可能已经引发了地球上生命出现所需的非生物碳化学。特别是，已经提出了三羧酸（TCA）周期作为新兴生物的原始代谢。测试该建议需要了解候选矿物有机反应的产物和机制。我们将在一个从TCA循环的一个光驱动反应中确定速率，机制和中间物种。具体而言，我们将研究使用时间分辨的瞬态光学和红外吸收光谱和傅立叶转化电子顺式谐振光谱镜头，以探测从纳米秒近无秒时代calseconscalseconscalsecalseconscore的进展。这些互补技术将允许将半导体中电荷分布的时间演变以及有机反应物中键的断裂和形成。这项研究将对早期地球的地球化学条件产生新的限制，该限制可能允许建立由太阳能驱动的益生元碳循环。（2）金属硫化物矿物质对光吸收的较广泛的意义可以启动矿物表面和矿物质表面和辅助有机分子之间的光化学反应。这种半导体光化学一定是在地球早期已知存在的条件下发生的，据推测，它们在综合生命发展所需的复杂有机分子中起着重要作用。一种特殊的反应将一个小有机酸分子（富马酸盐）转化为另一种有机酸分子，很容易出现在硫化锌（Zns）颗粒的表面下，紫外线（UV）照明下。在此过程中，表面将两个电子传输到富马酸盐，这些电子也从水中获取了两个质子，形成了两个新的碳氢键。目前尚不清楚反应的精确途径，包括电子和质子转移步骤的顺序。特别是，我们假设富马酸与Zns表面的结合稳定了中间的化学物种，并使这种相对复杂的氧化还原反应在不形成副产物的情况下进行。在我们提出的研究中，我们计划使用时间分辨的光谱技术来捕获不同中间物种的化学特征，从而确定反应途径。随后，通过研究反应途径和速率如何响应变化的锌或溶液化学，我们希望能够确定硫化物表面在影响该反应中的作用。这项工作将对早期地球的地理化学条件施加限制，这可以允许太阳能驱动的非生物有机反应。 这项工作不仅对理解生命的起源有影响，而且还具有基于地球丰富元素的太阳能应用的开发。 这项工作还涉及基础科学，基于矿物生物分子的相互作用，这可能会进一步了解医学地质学中的主题。