Fig. 7: SERS properties of the δ-Mo₂N MLHSs.

a SERS spectra of R6G with different concentrations obtained on the γ-Mo₂N MLHS substrate. b Raman EFs with R₁ and R₂ at different concentrations of the γ-Mo₂N MLHSs. The error bars are based on the standard deviations of ten measurements at each concentration. The data has been normalized to the integration time. c SERS spectra of 2,4-DCP obtained in the γ-Mo₂N MLHSs. d High stability of the γ-Mo₂N MLHSs. LOD limit of detection, PB phosphate buffer, NS normal saline. e Coupling matching between excitation light, SPR of substrate, and probe molecule. f Schematic diagram of the multiple-reflection effect of the γ-Mo₂N MLHSs. g SEM image of the γ-Mo₂N MLHSs adsorbed PS nanospheres from 1000 μg mL^–1 suspension. h SEM image of the γ-Mo₂N MLHSs adsorbed PS nanospheres from 10 μg mL^–1 suspension. i SERS spectra of PS nanospheres with different concentrations obtained on the γ-Mo₂N MLHS substrate. Excitation wavelength: 532 nm, laser power: 0.6 mW, integration time: 2 s for 10⁻⁹ M, 5 s for 10⁻¹⁰ M, 15 s for 10⁻¹¹ M R6G, 3 s for 10⁻⁹ M, 7 s for 10⁻¹⁰ M, 18 s for 10⁻¹¹ M 2,4-DCP, 1 s for 50–1000 μg mL⁻¹, 3 s for 25 μg mL⁻¹, 7 s for 10 μg mL⁻¹ PS spheres. Source data are provided as a Source Data file.