Fig. 1. Synthesis model of silver nanotrees and SEM characterization of silver nanotrees at different reaction times. (a) Reaction between AgNO₃ dissolved in HF and ethylene glycol, leading to the formation of silver nanoparticles that subsequently deposit on silicon wafer; (b) growth of silver nanoparticles into silver nanotrees on the silicon wafer; (c) 15 min; (d) 20 min; (e) 25 min; (f) 30 min; (g) 35 min

Fig. 2. SERS substrate of silver nanotrees characterized by EDS. (a) SEM image for EDS analysis; (b) EDS analysis of elemental types on the surface of silver nanotrees substrates; (c) silver element distribution; (d) silicon element distribution

Fig. 3. Particle size statistics and UV visible absorption spectrogram of silver nanotrees. (a) Model of silver nanotrees; (b) particle size statistics of silver nanotrees; (c) model for UV visible absorption spectroscopy analysis; (d) improved model for UV visible absorption spectroscopy analysis based on SEM images; (e) UV visible absorption spectral result of silver nanotrees

Fig. 4. Numerical analysis of electromagnetic fields. (a) Silver nanotrees secondary branch crystal structure; (b) electric field simulation of the silver nanotrees secondary branch crystal in the xy-plane; (c) silver nanotrees tertiary branch crystal structure; (d) electric field simulation of the silver nanotrees tertiary branch crystal in the xy-plane

Fig. 5. Raman testing results of dendritic silver SERS substrates prepared at different reaction times for R6G from 10^-9 mol/L to 10^-12 mol/L and the relationship between reaction time and detection performance of silver nanotrees SERS substrates. (a) 15 min; (b) 20 min; (c) 25 min; (d) 30 min; (e) 35 min; (f) variation of Raman characteristic peak intensity with reaction time at 611 cm^-1 in 10^-9 mol/L R6G solution detected by silver nanotrees SERS substrates

Fig. 6. Detection limits experiments. (a) Detection limits of dendritic silver nanotrees SERS substrates prepared at different reaction times; (b) Raman signal intensity of characteristic peak located at 611 cm^-1

Fig. 7. Homogeneity experiments and Raman testing results for multi-molecule. (a) Mapping testing results of silver nanotrees SERS substrates for R6G at 10^-10 mol/L; (b) RSD values corresponding to three characteristic peaks located at 611, 770, 1650 cm^-1; (c) Raman testing results for multi-molecule testing with concentrations of 10^-10 mol/L R6G, 10^-8 mol/L CV and 10^-6 mol/L MG on SERS substrates

Fig. 8. Stability testing and repeatable preparation testing of dendritic silver SERS substrates. (a) Raman testing results of the substrates stored in air every other week; (b) Raman testing results of the substrates stored in a vacuum every other week; (c) the signal intensity of 611 cm^-1 Raman characteristic peak with storage time in the vacuum and in the air; (d) Raman detection results of 10^-10 mol/L R6G solution on three groups of silver nanotrees SERS substrates