Agricultural and Biological Engineering Department, Institute of Food and Agricultural Sciences , University of Florida , Gainesville , Florida 32611 , United States.
Ames Laboratory , Ames , Iowa 50011 , United States.
ACS Appl Mater Interfaces. 2018 Nov 14;10(45):39124-39133. doi: 10.1021/acsami.8b10991. Epub 2018 Nov 1.
Flexible graphene electronics are rapidly gaining interest, but their widespread implementation has been impeded by challenges with ink preparation, ink printing, and postprint annealing processes. Laser-induced graphene (LIG) promises a facile alternative by creating flexible graphene electronics on polyimide substrates through the one-step laser writing fabrication method. Herein, we demonstrate the use of LIG, created with a low-cost UV laser, for electrochemical ion-selective sensing of plant-available nitrogen (i.e., both ammonium and nitrate ions: NH and NO) in soil samples. The laser used to create the LIG was operated at distinct pulse widths (10, 20, 30, 40, and 50 ms) to maximize the LIG electrochemical reactivity. Results illustrated that a laser pulse width of 20 ms led to a high percentage of sp carbon (77%) and optimal peak oxidation current of 120 μA during cyclic voltammetry of ferro/ferricyanide. Therefore, LIG electrodes created with a 20 ms pulse width were consequently functionalized with distinct ionophores specific to NH (nonactin) or NO (tridodecylmethylammonium nitrate) within poly(vinyl chloride)-based membranes to create distinct solid contact ion-selective electrodes (SC-ISEs) for NH and NO ion sensing, respectively. The LIG SC-ISEs displayed near Nernstian sensitivities of 51.7 ± 7.8 mV/dec (NH) and -54.8 ± 2.5 mV/dec (NO), detection limits of 28.2 ± 25.0 μM (NH) and 20.6 ± 14.8 μM (NO), low long-term drift of 0.93 mV/h (NH sensors) and -5.3 μV/h (NO sensors), and linear sensing ranges of 10-10 M for both sensors. Moreover, soil slurry sensing was performed, and recovery percentages of 96% and 95% were obtained for added NH and NO, respectively. These results, combined with a facile fabrication that does not require metallic nanoparticle decoration, make these LIG electrochemical sensors appealing for a wide range of in-field or point-of-service applications for soil health management.
柔性石墨烯电子产品正在迅速受到关注，但由于墨水制备、墨水打印和后印刷退火工艺的挑战，其广泛应用受到了阻碍。激光诱导石墨烯（LIG）通过一步激光书写制造方法在聚酰亚胺基板上制造柔性石墨烯电子产品，提供了一种简单的替代方法。在此，我们展示了使用低成本 UV 激光创建的 LIG 用于电化学离子选择性检测土壤样品中的植物可用氮（即铵和硝酸盐离子：NH 和 NO）。用于创建 LIG 的激光以不同的脉冲宽度（10、20、30、40 和 50 ms）运行，以最大限度地提高 LIG 的电化学反应性。结果表明，激光脉冲宽度为 20 ms 导致 sp 碳的百分比达到 77%，并且在亚铁/铁氰化物的循环伏安法中氧化峰电流达到 120 μA。因此，具有 20 ms 脉冲宽度的 LIG 电极随后用特定于 NH（非他霉素）或 NO（三癸基甲基硝酸铵）的不同离子载体功能化，在基于聚氯乙烯的膜内创建用于 NH 和 NO 离子感应的不同固态接触离子选择性电极（SC-ISE），分别。LIG SC-ISE 表现出接近 Nernst 灵敏度的 51.7 ± 7.8 mV/dec（NH）和-54.8 ± 2.5 mV/dec（NO），检测限为 28.2 ± 25.0 μM（NH）和 20.6 ± 14.8 μM（NO），低长期漂移为 0.93 mV/h（NH 传感器）和-5.3 μV/h（NO 传感器），两种传感器的线性感应范围均为 10-10 M。此外，进行了土壤悬浮液感应，添加的 NH 和 NO 的回收率分别为 96%和 95%。这些结果，再加上简单的制造工艺，不需要金属纳米粒子修饰，使这些 LIG 电化学传感器在广泛的现场或服务点应用中对土壤健康管理具有吸引力。
