SPR sensor functionalized with zinc oxide and its detection of gaseous formaldehyde
Abstract
<p indent="0mm">The surface plasmon resonance (SPR) refractive index (RI) sensor, developed on the basis of the extreme sensitivity of the surface plasmon resonance condition (resonance wavelength, resonance angle, etc.) to the surface RI, has been frequently used in physics, chemistry, biomedicine, and other fields. SPR characteristics, such as resonance wavelength and resonance angle, depend highly on the surface RI. However, the object of sensing is primarily confined to the solution system. This restriction is due to several factors, including: (1) the change in gas concentration and other parameters has a negligible impact on the RI of the sensor surface, thus demanding a sensor chip with higher sensitivity; (2) the transmission of the sensing gas requires a further combination of the sensor chip with a stable flow device; (3) specific detection of gaseous molecules also requires specific modification to the surface of the sensor chip. In the present work, we report a design of an SPR RI optofluidic sensing system of gaseous formaldehyde, in which zinc oxide nanoparticles operate as the functional recognition layer. Following the surface modification with zinc oxide nanoparticles, the ultra-sensitive, self-made SPR refractive sensor chip is tightly sealed with a gas flow device for <italic>in situ</italic>, real-time gas transmission and sensing. The findings demonstrate that the detection system can precisely measure the concentration of formaldehyde gas by shifting the positions of the SPR spectral peaks. Furthermore, zinc oxide nanoparticles effectively enhanced the sensor’s ability to detect formaldehyde gas and tripled its sensitivity. This portable real-time and <italic>in situ</italic> gas sensor will play an essential role in the sensing and detection of more gaseous molecules.</p>
