Fig. 1

Characterization of Nb@IC-NPs. a TEM imaging of Nb@IC-NPs; b Size distribution of Nb@IC-NPs; c UV absorption spectrum of Nb@IC-NPs to NTR; d Fluorescence emission spectrum of Nb@IC-NPs to NTR; e UV absorption spectrum showing a concentration-dependent response of Nb@IC-NPs to NTR; f Fluorescence emission spectrum showing a concentration-dependent response of Nb@IC-NPs to NTR; g Photoacoustic signal showing a concentration-dependent response of Nb@IC-NPs to NTR; h Fluorescence signal change of Nb@IC-NPs in response to NTR under different PH; i Effect of different active substances on Nb@IC-NPs’ fluorescence signal. Comparison between two groups were performed by unpaired t test. Comparisons among multiple groups were performed by one-way ANOVA with Tukey’s post hoc test. Comparison among groups at different time points was performed using repeated measures ANOVA with Bonferroni’s post hoc test. p < 0.05 indicated the difference was statistically significant