Balderas-Valadez Ruth Fabiola, Schürmann Robin, Pacholski Claudia
Institute of Chemistry, University of Potsdam, Potsdam, Germany.
Front Chem. 2019 Sep 4;7:593. doi: 10.3389/fchem.2019.00593. eCollection 2019.
Sensors composed of a porous silicon monolayer covered with a film of nanostructured gold layer, which provide two optical signal transduction methods, are fabricated and thoroughly characterized concerning their sensing performance. For this purpose, silicon substrates were electrochemically etched in order to obtain porous silicon monolayers, which were subsequently immersed in gold salt solution facilitating the formation of a porous gold nanoparticle layer on top of the porous silicon. The deposition process was monitored by reflectance spectroscopy, and the appearance of a dip in the interference pattern of the porous silicon layer was observed. This dip can be assigned to the absorption of light by the deposited gold nanostructures leading to localized surface plasmon resonance. The bulk sensitivity of these sensors was determined by recording reflectance spectra in media having different refractive indices and compared to sensors exclusively based on porous silicon or gold nanostructures. A thorough analysis of resulting shifts of the different optical signals in the reflectance spectra on the wavelength scale indicated that the optical response of the porous silicon sensor is not influenced by the presence of a gold nanostructure on top. Moreover, the adsorption of thiol-terminated polystyrene to the sensor surface was solely detected by changes in the position of the dip in the reflectance spectrum, which is assigned to localized surface plasmon resonance in the gold nanostructures. The interference pattern resulting from the porous silicon layer is not shifted to longer wavelengths by the adsorption indicating the independence of the optical response of the two nanostructures, namely porous silicon and nanostructured gold layer, to refractive index changes and pointing to the successful realization of two sensors in one spot.
制备了由覆盖有纳米结构金层薄膜的多孔硅单层组成的传感器，该传感器提供了两种光信号转导方法，并对其传感性能进行了全面表征。为此，对硅衬底进行电化学蚀刻以获得多孔硅单层，随后将其浸入金盐溶液中，促进在多孔硅顶部形成多孔金纳米颗粒层。通过反射光谱监测沉积过程，并观察到多孔硅层干涉图案中出现一个凹陷。这个凹陷可归因于沉积的金纳米结构对光的吸收，从而导致局部表面等离子体共振。通过记录在具有不同折射率的介质中的反射光谱来确定这些传感器的整体灵敏度，并与仅基于多孔硅或金纳米结构的传感器进行比较。对反射光谱中不同光信号在波长尺度上的变化进行的全面分析表明，多孔硅传感器的光学响应不受顶部金纳米结构的影响。此外，仅通过反射光谱中凹陷位置的变化检测到硫醇封端的聚苯乙烯吸附到传感器表面，该凹陷归因于金纳米结构中的局部表面等离子体共振。多孔硅层产生的干涉图案不会因吸附而向更长波长移动，这表明两种纳米结构（即多孔硅和纳米结构金层）的光学响应与折射率变化无关，并且表明在一个位置成功实现了两个传感器。
