Figure 4: (a) Normalized and offset Raman spectra of Au@Ag-4MPy nanoparticles in varying pH-buffered solutions. (b) In vitro (closed circle) calibration curve of Au@Ag-4MPy nanosensors and in vivo (open circle) calibration curves of Au@Ag-4MPy-DNP nanosensors inside RBL-2H3 cells in pH-buffered media containing nigericin. -axis represents ratio of integration of peak centered at 1580 cm−1 versus the additive integration of both the peak centered around 1580 cm−1 and 1612 cm−1. Vertical error bars are dependent on approximately 100 pixels per image, repeated five times.