Thermal annealing-boosted photoinduced electron transfer efficiency of g-C3N4/Au NPs hybrids for promoting SERS detection of uric acids

Abstract

As for the ultrasensitive diagnosis of biomolecules via surface-enhanced Raman scattering spectroscopy (SERS), the primary requirement is to effectively enhance the activity of nano-substrates. Herein, we report an interesting strategy for further boosting SERS activity by thermal annealing treatment of as-prepared hybrid substrates. Initially, highly dense and monodisperse plasmonic Au nanoparticles (NPs) were loaded on two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets. By adopting uric acids (UAs) as probe biomolecules, the g-C3N4/Au NPs with appropriate ~2.1% Au compositions exhibit much higher Raman signals than that of the hybrids with other Au contents. Besides the enhancement by routinely controlling hybrid components, the further maximizing SERS activity with a ~2.6-fold improvement than the original one can be obtained by thermal annealing of g-C3N4/Au NPs at 350 ℃ condition. It enables the thermal modified g-C3N4/Au NPs to be applied for highly sensitive monitoring of UAs in artificial urine. The corresponding detection limit is achieved at the ultralow level of 10−11 M, which is nearly two orders of magnitude better than that of the unannealed sample. It should be attributed to the stronger synergistic coupling effect by thermal annealing treatment that gives rise to the higher-efficiency photoinduced electron transfer (PIET) between g-C3N4 supports and plasmonic Au NPs. The present work provides a new opportunity for further promoting the SERS activity of prefabricating nano-substrates, holding great potential for practical monitoring of ultra-trace biomolecules in the near future.