Development of Environental Optical Sensing Devices by a Combination of Photonic Crystals and Nano-Probes

• Main Authors: Hsu, Shu-Kang, 徐樹剛
• Other Authors: Chang, Sue-min
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/hc8hjv

博士 === 國立交通大學 === 環境工程系所 === 105 === Environmental sensors are developed for demands of efficient analysis of pollutants in order to well control environmental quality, identify scope of contamination areas, and evaluate treatment performance. In the regard, they have to be capable of identifying targets rapidly and selectively in complex matrix. Optical sensors, due to the advantages of multi-signals, rapid response, and non-contact detection, are popular in various environmental monitoring and sensing applications. However, the chemicals and optical components used for optical sensors are expensive, thus constraining the growth in the market. Photonic crystals (PCs) are periodically structured dielectric media with specific photonic bandgaps. The light with the energy underlying the bandgap cannot propagate through the structure. This unique optical property can be applied in sensing systems in terms of translating stimuli events into optical signals or amplifying optical signals of sensing probes. In this study, we combined photonic crystals with nano-probes to develop two photonic-crystal-based sensing systems for detection of bisphenol A (BPA) and Cu2+ ions, in which photonic crystals were used as a signal transducer and an amplifier, respectively. BPA, being considered as one of environmental hormones, is commonly used for manufacturing plastic products. In this study, a silicon-based molecularly imprinted polymers (MIPs) with good selectivity for BPA was fabricated, and it was also constructed as an inverse opal film (IOF) by using a polystyrene microsphere opal as the template. The reflection wavelength of inverse opal film will be shifted after BPA adsorption due the overall refractive index of MIPs changed. Compared with the analog compound of 4-tert-Butyl phenol (4-BP), the imprinting factor (α) and selectivity coefficient (β) of the BPA silicon-based MIPs prepared in this study were 10.5 and 3.94, respectively. The MIP-IOF sensor responded BPA molecules within 10 minutes and had a signal linearity (r2 = 0.974) in the concentration range of 1 - 100 mg / L. Copper is widely used as a conductive material in the manufacturing industries. Because of the serious impact of Cu2+ ions on the ecosystem and human health, the discharge of Cu species should be monitored in the effluent of wastewater treatment plants. In this study, thiol-capped CdS/ZnS quantum dots (QDs) were used as fluorescence probes for Cu2+ ions determination. Three types of ligands, including L-cysteine (LC), mercaptosuccinic acid (MSA), and thioglycolic acid (TGA), were used as capping agents for stabilizing and functionalizing the QDs. They have well performance, high recovery (81.7-114.5 %), high precision (relative standard deviation=0.36-4.56 %), for detection of Cu2+ ions in the field samples, even though it contained Ca2+, Mg2+, Na+, K+ and NH4+ ions, which were 300-16,600 times higher in concentrations than the target. A cholesteric liquid crystal (CLC), which is one-dimensional PCs, and an aluminium mirror were further introduced into the system to enhance the fluorescence of TGA-capped CdS/ZnS QDs for Cu2+ ions determination. The intensities of enhanced-fluorescence were 7.5-10.3 times higher than the original values. The results clearly show that the low cost optical systems are sensitive and reliable for environmental sensing.