Opt Express. 2022 Apr 11;30(8):12268-12277. doi: 10.1364/OE.452416.
Quantitative detection of neurotransmitters in aqueous environment is crucial for the early diagnosis of many neurological disorders. Terahertz waves, as a non-contact and non-labeling tool, have demonstrated large potentials in quantitative biosensing. Although the detection of trace-amount analyte has been achieved with terahertz metamaterials in the recent decades, most studies have been focused on dried samples. Here, a hexagonal asymmetric metamaterial sensor was designed and fabricated for aqueous solution sensing with terahertz waves in the reflection geometry. An absorption enhancement of 43 was determined from the simulation. Dilute adrenaline solutions ranging from 30 µM to 0.6 mM were measured on our sensor using a commercial terahertz time-domain spectroscopy system, and the effective absorption was found to be linearly correlated with the concentration (R= 0.81). Furthermore, we found that as the concentration becomes higher (>0.6 mM), a non-linear relationship starts to take place, which confirmed the previous theory on the extended solvation shell that can be probed on the picosecond scale. Our sensor, without the need of high-power and stable terahertz sources, has enabled the detection of subtle absorption changes induced by the solvation dynamics.
在水相环境中定量检测神经递质对于许多神经疾病的早期诊断至关重要。太赫兹波作为一种非接触式和非标记工具，在定量生物传感中显示出巨大的潜力。尽管在过去几十年中，已经使用太赫兹超材料实现了痕量分析物的检测，但大多数研究都集中在干燥样品上。在这里，我们设计并制作了一个六边形不对称超材料传感器，用于在反射几何形状下用太赫兹波进行水溶液传感。从模拟中确定了 43 的吸收增强。使用商业太赫兹时域光谱系统，在我们的传感器上测量了浓度范围从 30 µM 到 0.6 mM 的稀肾上腺素溶液，发现有效吸收与浓度呈线性相关（R= 0.81）。此外，我们发现，随着浓度的增加（>0.6 mM），开始出现非线性关系，这证实了关于可以在皮秒尺度上探测到的扩展溶剂化壳的先前理论。我们的传感器，不需要高功率和稳定的太赫兹源，已经能够检测到溶剂化动力学引起的细微吸收变化。
