Role of polyelectrolyte multilayers over gold film for selective creatinine detection using Raman spectroscopy

Highlights: • Nanostructured polyelectrolyte mulilayer films coated on Au film was used as SERS substrate for creatinine detection. • Type of top polyelectrolyte plays a crucial role for selective detection of creatinine molecule. • 30 bilayers of PAA/PAH bilayer coated Au film substrate exibits the highest creatinine detection. • This SERS substrate shows high selectivity to creatinine detection. • Low detection limit of creatinine detection in surine was about 1.47 µM. Development of nano-roughened surface-enhanced Raman scattering (SERS) substrates is still of great interest for applications in SERS sensor with good sensitivity, selectivity, and uniformity. In this work, nanostructured polyelectrolyte films coated Au film is designed as a SERS substrate for label-free and selective creatinine detection. Two-component multilayer films are fabricated by layer-by-layer (LbL) deposition of polyacrylic acid (PAA) and polyallylamine hydrochloride (PAH). The SERS sensing behaviors including electric field enhancement, sensitivity, and selectivity strongly influence by morphology and types of polyelectrolyte. The dense polyelectrolyte nanostructured film over Au substrate (30 PAA/PAH bilayers) possesses the strongest SERS hotspots. The PAH outermost layer exhibits the highest creatinine signal comparing to other selected polyelectrolytes. This creatinine signal could amplify by free vibration of creatinine on PAH. This substrate exhibited good performance for creatinine detection in pH 5 to 7-buffered solutions. By performing creatinine analysis in artificial urine, good sensitivity with wide linear response (1 µM to 10 mM) and low detection limit of 1.47 µM was found. Moreover, this substrate has high selectivity for creatinine detection compared to interferences. With the contribution of both plasmonic Au film and polyelectrolyte multilayers, these findings underscore the guideline for creating selective SERS substrate for creatinine detection.