The Institute of Scientific and Industrial Research, Osaka University , 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
Advanced Technology R&D Center, Mitsubishi Electric Corporation , 8-1-1 Tsukaguchi-Honmachi, Amagasaki, Hyogo 661-8661, Japan.
ACS Sens. 2018 Jan 26;3(1):200-204. doi: 10.1021/acssensors.7b00851. Epub 2018 Jan 16.
We have combined a graphene field-effect transistor (GFET) and a surface acoustic wave (SAW) sensor on a LiTaO substrate to create a graphene surface acoustic wave (GSAW) sensor. When a SAW propagates in graphene, an acoustoelectric current (I) flows between two attached electrodes. This current has unique electrical characteristics, having both positive and negative peak values with respect to the electrolyte-gate voltage (V) in solution. We found that I is controlled by V and the amplitude of the SAW. It was also confirmed that the GSAW sensor detects changes of electrical charge in solution like conventional GFET sensors. Furthermore, the detection of amino-group-modified microbeads was performed by employing a GSAW sensor in a phthalate buffer solution at pH 4.1. The hole current peak shifted to the lower left in the I-V characteristics. The left shift was caused by charge detection by the GFET and can be explained by an increase of amino groups that have positive charges at pH 4.1. In contrast, the downward shift is thought to be due to a reduction in the amplitude of the propagating SAW because of an increase in the mass loading of microbeads. This mass loading was detected by the SAW sensor. Thus, we have demonstrated that the GSAW sensor is a transducer capable of the simultaneous detection of charge and mass, which indicates that it is an attractive platform for highly sensitive and multifunctional solution sensing.
我们在 LiTaO 衬底上结合了石墨烯场效应晶体管 (GFET) 和表面声波 (SAW) 传感器，制造出了石墨烯表面声波 (GSAW) 传感器。当 SAW 在石墨烯中传播时，两个附着的电极之间会产生电流（I）。该电流具有独特的电学特性，其大小与溶液中的电解质门电压（V）有关，既有正值也有负值。我们发现，I 受 V 和 SAW 幅度的控制。同时也证实了 GSAW 传感器像传统的 GFET 传感器一样，能够检测溶液中的电荷变化。此外，我们还在 pH 值为 4.1 的邻苯二甲酸缓冲溶液中，使用 GSAW 传感器对氨基修饰的微球进行了检测。在 I-V 特性中，电流峰值向左下方移动。这种左移是由 GFET 检测到的电荷引起的，其原因可以解释为在 pH 值为 4.1 时，带正电荷的氨基数量增加。相反，向下的移动则被认为是由于传播的 SAW 幅度减小，因为微球的质量加载增加了。该质量加载可以通过 SAW 传感器检测到。因此，我们已经证明，GSAW 传感器是一种能够同时检测电荷和质量的传感器，这表明它是一种非常有吸引力的用于高灵敏度多功能溶液感应的平台。
