介孔TiO_2薄膜光波导共振传感器对苯并(a)芘的探测灵敏度

采用溶胶-凝胶分子模板法在覆金的玻璃基底上制备了厚度约为295 nm的介孔TiO_2薄膜,再经表面化学修饰形成表面疏水的光波导共振(OWR)传感芯片,用于探测水中苯并(a)芘。利用Kretschmann棱镜耦合结构观测到OWR芯片在可见-近红外波段只有一个共振波谷,基于相位匹配条件确定了该共振波谷对应于二级横磁导模(TM2);进一步利用Fresnel理论并结合Bruggeman介电常数近似方程对实验测得的导模共振波长进行拟合,得出介孔TiO_2薄膜的多孔度约为0.4;利用疏水介孔TiO_2薄膜OWR传感芯片对水中苯并(a)芘小分子进行了原位和离位探测,结果表明离位探测灵敏度比原位探测高2倍多,其最低检测限约为100 nmol·L~(-1);对比实验指出OWR传感芯片的多孔结构和疏水化处理都有助于提高芯片对苯并(a)芘的探测灵敏度。研究表明这种介孔TiO_2薄膜OWR传感芯片具有良好的稳定性,可重复利用。

Detection Sensitivity to Benzo[a]pyrene of Nanoporous TiO2 Thin-Film Waveguide Resonance Sensor

Nanoporous TiO₂ (NPT) films with a thickness of about 295 nm were prepared through the sol-gel copolymer-templating approach on a 40-nm-thick gold film sputtered on a glass substrate for optical waveguide resonance (OWR) sensing. Using the prism-coupled Kretschmann configuration, a single resonance dip was observed in the wavelength range from visible to near infrared, which was attributed to the second order transverse magnetic mode of the OWR chip based on the phase-match condition. By using a combination of Fresnel theory and Bruggeman equation to fit the measured resonance dip, the porosity of NPT films was determined to be about 0.4. After hydrophobilization of the NPT films, the OWR chips were used for both in-situ and ex-situ detections of benzoa]pyrene (BaP) in water. The experimental results indicate that the ex-situ detection sensitivity to BaP is 2 times higher than the in-situ detection sensitivity. The lowest concentration of BaP detectable with the hydrophobilized OWR chip is ca. 100 nmol·L^-1. The experimental comparisons reveal that both the nanoporous structure and hydrophobilization of the OWR chip enable to enhance the sensor's sensitivity to BaP. The work demonstrated that the NPT thin-film OWR sensing chips are stable and robust with good reusability.