Department of Electrical & Computer Engineering, Iowa State University, Ames, Iowa 50011, United States.
Microelectronics Research Center, Iowa State University, Ames, Iowa 50011, United States.
ACS Appl Mater Interfaces. 2022 Jun 8;14(22):25949-25961. doi: 10.1021/acsami.2c01988. Epub 2022 May 31.
Nitrogen management through monitoring of crop nitrate status can improve agricultural productivity, profitability, and environmental performance. Current plant nitrate test methods require expensive instruments, time-intensive labor, and trained personnel. Frequent monitoring of nitrate levels of the stalks in living plants can help to better understand the nitrogen cycle and the physiological responses to environmental variations. Although existing enzymatic electrochemical sensors provide high selectivity, they suffer from short shelf life, high cost, low-temperature storage requirement, and potential degradation over time. To overcome these issues, an artificial enzyme (vitamin B12 or VB12) and a two-dimensional material (graphene oxide or GO) are introduced into a conventional photoresist (SU8) to form a bioresin SU8-GO-VB12 that can be patterned with photolithography and laser-pyrolyzed into a carbon-based nanocomposite C-GO-VB12. The electrocatalytic activity of the cobalt factor in VB12, the surface enhancement properties of GO, and the porous feature of pyrolytic carbon are synergized through design to provide C-GO-VB12 with a superior ability to detect nitrate ions through redox reactions. In addition, laser writing-based selective pyrolysis allows applying thermal energy to target only SU8-GO-VB12 for selective pyrolysis of the bioresin into C-GO-VB12, thus reducing the total energy input and avoiding the thermal influence on the materials and structures in other areas of the substrate. The C-GO-VB12 nitrate sensor demonstrates a year-long shelf lifetime, high selectivity, and a wide dynamic range that enables a direct nitrate test for the extracted sap of maize stalk. For monitoring of the nitrate level and dynamic changes in living maize plants, a microelectromechanical system-based needle sensor is formed with C-GO-VB12. The needle sensor allows direct insertion into the plant for measurement of nitrate ions under different growth environments over time. The needle sensor represents a new method for monitoring nitrate dynamics with no need for sample preparation, thus making a significant impact in plant sciences.
通过监测作物硝酸盐状况进行氮素管理可以提高农业生产力、盈利能力和环境绩效。当前的植物硝酸盐测试方法需要昂贵的仪器、耗时的劳动力和经过培训的人员。频繁监测活体植物茎中的硝酸盐水平有助于更好地了解氮循环和对环境变化的生理反应。尽管现有的酶电化学传感器具有高选择性，但它们存在保质期短、成本高、低温储存要求以及随着时间的推移潜在降解等问题。为了克服这些问题，将人工酶（维生素 B12 或 VB12）和二维材料（氧化石墨烯或 GO）引入到常规光致抗蚀剂（SU8）中，形成可以通过光刻和激光热解形成碳基纳米复合材料 C-GO-VB12 的生物树脂 SU8-GO-VB12。VB12 中的钴因子的电催化活性、GO 的表面增强特性和热解碳的多孔特性通过设计协同作用，为 C-GO-VB12 提供了通过氧化还原反应检测硝酸盐离子的卓越能力。此外，基于激光写入的选择性热解允许仅将热能施加到 SU8-GO-VB12 上，以选择性地将生物树脂热解为 C-GO-VB12，从而减少总能量输入并避免对基底其他区域的材料和结构的热影响。C-GO-VB12 硝酸盐传感器具有长达一年的保质期、高选择性和宽动态范围，可直接对玉米茎提取的汁液进行硝酸盐测试。为了监测活体玉米植物中的硝酸盐水平和动态变化，使用 C-GO-VB12 形成基于微机电系统的针传感器。针传感器允许直接插入植物中，以在不同的生长环境下随时间测量硝酸盐离子。针传感器代表了一种无需样品制备即可监测硝酸盐动态的新方法，因此在植物科学领域产生了重大影响。
