基于双面金属波导的乙酸溶液检测方法

Detection Method of Acetic Acid Solution Based on Double-Sided Metal Waveguide

传统的物质浓度的检测方法主要是基于吸收光度法,其中包括分光光度计、气相或液相色谱法等,虽然这几种方法的测量灵敏度较高,但是由于其测试的过程较复杂,测试设备体积过大且耗时较长。因此研究一种测量溶液折射率微小变化的便捷方法。主要利用双面金属包覆波导的高阶模特性,从而实现了测量的高灵敏度。通过使用一种双金属包层波导结构,以待测样品作为其导波层,两层金属薄膜作为其包层。醋酸溶液和溴甲酚绿在波导引导层中消光系数的微小变化会导致反射光谱中光强度的显著变化。利用双面金属包覆波导的衰减全反射(attenuated total reflection)曲线对波导结构的灵敏响应从而实现了物质的痕量检测。理论模拟和实验结果均表明,该方法对乙酸的检测限可低至1.3 nm,与表面等离子体场增强共振散射(SP-RLS)方法相比,其性能提高了16倍,与火焰原子吸收光谱法和荧光光谱法相比,分别提高了4倍。该方法是一种耗时短、需样少、稳定性高、便捷且廉价的一种溶液浓度实时检测技术,为以后的化工生产流程提供了一种有效的检测路线。

The traditional detection methods of substance concentration are mainly based on absorption spectrophotometry, including spectrophotometer, gas phase or liquid chromatography, etc. Although these methods have high sensitivity, due to the complex testing process, testing equipment is too large and time-consuming. Therefore, a convenient method for measuring small changes in refractive index of solution is investigated. We mainly use the high order model of the double-sided metal clad waveguide to achieve the high sensitivity of measurement. We proposed a bimetallic clad waveguide structure, the sample to be tested was used as its guide layer, and two metal films were used as its cladding layer. A tiny change of extinction coeffient in the waveguide guiding layer where the acetic acid solution and bromocresol green can lead to a significant change of light intensity in the reflection spectrum. Trace detection of substances was achieved by using the Attenuated Total Reflection curves of the double-sided metal-clad waveguides in response to the waveguides structure. Both theoretical simulation and experimental results showed that using this method, the detection limit of acetic acid can be as low as 1.3 nm, which was 16 times higher than the surface plasma field enhanced resonance scattering(SP-RLS) method, and four times higher than flame atomic absorption spectrometry and fluorescence spectrometry, respectively. This method is a real-time detection technology of solution concentration which is short in time, requires less samples, has high stability, is convenient and cheap, and provides an effective detection route for the chemical production process in the future.