一种新发现的伴生谐振模式及其对石英晶体微天平响应的影响

The resonant frequency of thickness shear mode (TSM) in a quartz crystal microbalance (QCM) decreases linearly with the increase in surface mass loading. Hence, QCM is an important tool to detect in real time the mass change in nanogram level. When QCM is operated in liquid phase, the changes in liquid properties (including viscosity, density, conductivity and dielectric constant) and other factors result in additional frequency shifts, which invalidate the Sauerbrey equation. Eliminating the interference from the non-mass effects is the prerequisite for ensuring the reliability of surface mass detection. After the research and development for nearly 60 years, the response theory and measuring technique of QCM seems to be mature. However, our group reports recently an unfound associated high frequency resonance (HFR) model for QCM, with the intensity 2 orders of magnitude higher than that of the fundamental peak in liquid phase. The HFR model exhibits obvious impact on the response of TSM, especially for overtones nearby. It is very possible that the interaction between HFR and TSM is one of the reasons to cause the baseline drift and abnormal responses of QCM overtones. In this project，we will investigate the response characteristics of the HFR and the interaction between TSM and HFR peaks. We will explore the strategy to suppress the unfavourable influence of HFR on TSM to improve the stability of QCM and the reliability in mass detection. By estimating a new calibration method with multi-model and multi-parameters for QCM, the applicability of HFR in chemical and biological sensors will be exploited. This project is innovative and academic in improving the QCM sensing theory, which is helpful to exhibits good applicability of QCM method.

石英晶体微天平(QCM)厚度剪切模式(TSM)的谐振频率随表面质量增加而线性下降，能实时检测纳克级质量变化。当QCM在液相中使用时，如何消除非质量效应(如溶液粘度、密度、电导率、介电常数，以及其它因素等所致的频率变化)的干扰，是保障其质量测定可靠性的前提。虽然经过近60年的研究与开发，QCM的响应理论与测量技术趋于成熟，但近期本课题组发现在高频率区竟然还隐藏着一个比基频峰更强的伴生谐振峰(HFR),它对QCM的谐振行为存在不容忽略的影响，可能是造成QCM基频基线漂移与倍频峰异常响应的原因之一，乃至主因。本项目将研究所发现的HFR的响应特性,它与QCM的TSM谐振峰之间的相互作用，建立基于双模式的分析方法，探讨抑制HFR的措施以提高QCM质量测定信息的可靠性，尝试利用HFR的频率变化中所包含的信息进行化学与生物传感，其研究成果将有助于完善QCM传感理论，颇具创新性、学术价值和应用前景。

根据计划任务书所设定的基本框架，围绕石英晶体微天平(QCM)、响应特性、伴生谐振、生物分析、电化学传感等关键词，进行了一系列探索性的研究。首先对所发现的QCM中存在的一种高频伴生谐振(HFR)现象进行了系统深入的研究，通过阻抗测定和理论分析，确定了HFR起源与QCM电极引线的分布电感与QCM的静态电容之间的LC谐振，其谐振频率随电极引线长度、溶液介电常数、电导率、液层厚度的增加而下降，对QCM传感电极上的质量负载、溶液粘度、密度本身的变化不敏感，随着HFR谐振峰与QCM的基频、倍频谐振峰的间距减小，相互影响程度增加，是造成QCM倍频谐振峰异常变化的主要原因。当HFR谐振峰与QCM的倍频谐振峰重叠时产生共振，致使二者的谐振峰扭曲变形，QCM的倍频谐振峰强度可提高2个数量级，频率变化幅度达到180 kHz，QCM基频的谐振频率随HFR谐振峰频率下降呈现出加速下降的变化趋势，根据HFR谐振频率与QCM的基频、倍频谐振频率之间的关联性，可以扣除HFR谐振频率变化所引起的QCM附加频率变化，提高QCM响应的选择性和稳定性，研究结果表明，QCM研究文献中的“姚-周”公式，QCM的谐振频率随溶液电导率、介电常数增加而下降的结论，实际上是来自HFR谐振频率下降所引起的QCM附加频率下降，QCM的谐振频率对纯粹的溶液电导率、介电常数变化无响应。联用QCM的基频、倍频、HFR谐振频率的综合信息，可以更可靠地监测固/液界面的传质过程中的质量变化。在拓展研究中，提出了差分型分子印迹传感策略，将分子印迹传感器的抗干扰能力提高一个多数量级。所研制的简易电化学发光仪的灵敏度比CCD型电化学发光光谱仪高2个数量级，所发的基于智能手机的便携测定装置，可应用于环境分析的现场检测。所取得的研究成果已经在 Anal. Chem.、Biosens. Bioelectron.、Sens. Actuators B、ACS Sensors、J. Hazard. Mater.、Nanoscale、Electrochem. Acta、Anal. Chim. Acta、 Microchim. Acta、Analyst、Talanta、Microchem. J.等SCI 期刊上发表论文34 篇，等SCI 期刊上发表论文33 篇，获授权国家发明专利4项，授权实用新型专利3项。