Nanoplasmonic NO₂ Sensor with a Sub-10 Parts per Billion Limit of Detection in Urban Air

Abstract

Urban air pollution is a critical health problem in cities all around the world. Therefore, spatially highly resolved real-time monitoring of airborne pollutants, in general, and of nitrogen dioxide, NO 2 , in particular, is of utmost importance. However, highly accurate but fixed and bulky measurement stations or satellites are used for this purpose to date. This defines a need for miniaturized NO 2 sensor solutions with detection limits in the low parts per billion range to finally enable indicative air quality monitoring at low cost that facilitates detection of highly local emission peaks and enables the implementation of direct local actions like traffic control, to immediately reduce local emissions. To address this challenge, we present a nanoplasmonic NO 2 sensor based on arrays of Au nanoparticles coated with a thin layer of polycrystalline WO 3 , which displays a spectral redshift in the localized surface plasmon resonance in response to NO 2 . Sensor performance is characterized under (i) idealized laboratory conditions, (ii) conditions simulating humid urban air, and (iii) an outdoor field test in a miniaturized device benchmarked against a commercial NO 2 sensor approved according to European and American standards. The limit of detection of the plasmonic solution is below 10 ppb in all conditions. The observed plasmonic response is attributed to a combination of charge transfer between the WO 3 layer and the plasmonic Au nanoparticles, WO 3 layer volume expansion, and changes in WO 3 permittivity. The obtained results highlight the viability of nanoplasmonic gas sensors, in general, and their potential for practical application in indicative urban air monitoring, in particular.

Bulk-Processed Plasmonic Plastic Nanocomposite Materials for Optical Hydrogen Detection

“…Well-established examples are H 2 -absorbing Pd or (surface) oxidizing Al and Cu nanoparticles. In indirect sensing, these two functions are separated in space and executed by two different materials where one of them is a (inert and usually Au or Ag) plasmonic nanoparticle probe and the second one is a closely adjacent sensing material that undergoes chemical change. ,− Depending on the targeted sensing function and environment, nanoparticle size and shape can be rationally selected to steer both the spectral position of the plasmonic resonance and the abundance of specific surface sites that control the surface chemistry . Furthermore, their composition can be manipulated at the atomic level by forming nanoalloys with the purpose of engineering both optical − and chemical ,, properties.…”

“…Over the years, such systems have proven an ideal platform for the realization of a wide range of technologies, including plasmonic sensors, photocatalysts, photovoltaic devices, plasmonic lasers, and optical metamaterials . In particular, sensors, in their most prominent application area of the life sciences, have been implemented in a plethora of designs geared toward the detection of biological analytes with point-of-care diagnostics, affordable test kits, and single-molecule detection being some core concepts that have driven this development. − Similarly, plasmonic sensor platforms in a multitude of surface-based designs have been developed for measuring contaminations in water and food, as well as for detecting gaseous species, where the detection of H 2 is the most widely explored and developed application ,− and where other gaseous species, such as NO 2 , − CO, and CO 2 , have been successfully targeted as well. For an overview of existing H 2 sensor technologies and their corresponding strengths and weaknesses, we refer to our recent review of this topic …”

Plasmonic Nanostructure Lattices for High‐Performance Sensing

“…[ 169 ] By taking advantage of the charge transfer between Au NPs and WO 3 as well as the volume expansion of WO 3 induced index modification, high sensitivity detection with LOD below 10 ppb was achieved. [ 169 ]…”

Environmental formaldehyde sensing at room temperature by smartphone-assisted and wearable plasmonic nanohybrids

“…0.1–10 vol% for H 2 ) and sometimes strong interaction with the corresponding nanoparticle surfaces ( e.g. H 2 and Pd clusters form Pd x H y 4 ) yielding sufficient sensitivity 5 and selectivity.…”

“…0.1-10 vol% for H 2 ) and sometimes strong interaction with the corresponding nanoparticle surfaces (e.g. H 2 and Pd clusters form Pd x H y 4 ) yielding sufficient sensitivity 5 and selectivity. Yet, the sensing of volatile organic compounds (VOC) by LSRP remains challenging and less established, despite their high relevance for environmental monitoring, 6 non-invasive medical diagnostics 7 or food quality assessment.…”