Crystal-amorphous Ni(OH)2 nanocages as SERS substrate with conspicuous defects-induced charge-transfer resonance for ultrasensitive detection of MicroRNA 155

Herein, an innovative Ni(OH) 2 nanocages (Ni(OH) 2 NCs) with crystal-amorphous structure were fabricated as surface-enhanced Raman scattering (SERS) substrate, which realized excellent SERS enhancement by the significant defects-induced charge transfer resonance and was applied to the construction of SERS biosensor for ultrasensitive microRNA 155 (miRNA 155) detection. The surface oxygen vacancy (Ovs) and defective phases endowed Ni(OH) 2 NCs the increased charge carrier density and preponderant energy-level matching with signal molecules methylene blue (MB), thereby inducing the remarkable charge transfer resonance via the augment of electron transition probability for improving the SERS effect of Ni(OH) 2 NCs. Impressively, the SERS performance of Ni(OH) 2 NCs was stronger than that of amorphous Ni(OH) 2 nanocages (a-Ni(OH) 2 NCs), ascribing to the abundant Ovs and high degree of charge transfer ( ρ CT ) in Ni(OH) 2 NCs. Furthermore, the limited target miRNA 155 was transformed into the plentiful MB molecules by employing the target-related cleavage amplification reaction and hybridization chain reaction (HCR), thus achieving an enhanced SERS intensity for detecting target miRNA 155 based on Ni(OH) 2 NCs substrate and obtaining a low detection limit of 30 aM. This strategy developed candidate materials for the practical applications of SERS technology and provided a promising method to disease diagnosis. • An innovative Ni(OH) 2 nanocages (Ni(OH) 2 NCs) with crystal-amorphous structure were fabricated as surface-enhanced Raman scattering (SERS) substrate. • Defects-induced charge-transfer resonance improves the SERS sensitivity of Ni(OH) 2 NCs. • The biosensor based on the Ni(OH) 2 NCs substrate and DNA amplification strategy achieves a low detection limit of 30 aM for target microRNA 155.