Enrichment-enhanced photoacoustic spectroscopy based on vertical graphene

This manuscript proposes a method to improve the gas detection sensitivity of the photoacoustic spectroscopy (PAS) by the enrichment of the concentration of a gas species based on vertical graphene (VG). This is accomplished by exploiting the characteristics of vertical graphene grown on Ni foam to adsorb gas molecules and subsequently desorb them at high temperatures. After the adsorption by the VG material, the enrichment cell is heated to 150 ℃; then the enriched gas is collected and passed into the PAS cell. A DFB-QCL laser tuned at 5263 nm was used as the excitation light source of the PAS sensor for NO detection. The experimental results showed that at a gas pressure of 760 torr and with a signal integration time of 1 s, the ultimate detection limit of traditional photoacoustic spectroscopy for NO gas is 14 ppb, while that of enrichment-enhanced photoacoustic spectroscopy is 1.3 ppb, proving that this method can increase the sensitivity of one order of magnitude. •First demonstration of sample enrichment systems for optical gas sensing.•Gas sample enrichment exploiting vertical graphene (VG) grown on a Nichel foam.•Record PAS-based NO detection limit of 1.3 ppb was achieved for a 1 s integration time.•More than one order of magnitude in sensitivity using the enrichment phase.