Fabrication of a SERS-encoded microfluidic paper-based analytical chip for the point-of-assay of wastewater

Abstract

New environmental problems have arisen due to the production of numerous toxic materials with the development of industrial technologies. Although various technologies have been developed to solve these critical problems, the results were not satisfactory. Therefore, this study introduces a label-free, paper-based biosensing strip sensor to directly analyze the components of wastewater on site. Raman spectroscopy was used for fingerprinting the chemically-vibrational responses of the wastewater. In order to enhance the low signal intensity of the Raman results, the surface-enhanced Raman scattering (SERS) effect was implemented by using gold nanoparticles (AuNPs). Dense and uniform AuNPs were synthesized and distributed onto paper by a power-free successive ionic layer absorption and reaction (SILAR) method. The biosensing ability of the SERS paper strip showed a sensitivity of 10–10 M and an enhancement factor of 2.8 × 107 for rhodamine 6G. Two organic toxic drugs were selected to mimic wastewater. It was demonstrated that the SERS paper strip was sensitive to concentrations of 10–9 M and 10-5 M with correlation coefficients of 0.85 and 0.99 for 4-aminobenzoic acid and pyrocatechol, respectively. Therefore, the proposed SERS-encoded gold paper analytical strip has the potential to be used for the point-of-assay of wastewater.