Fig. 1. Electron microscopic image of Au NPs

Fig. 2. Raman spectral curves of six drug solutions

Fig. 3. Principal components analysis score plot of samples

Fig. 4. Principal component feature explained variance contribution ratio

Fig. 5. Comparison of accuracy of different dimensionality reduction methods in testing set
(a): PCA; (b): Variance Threshold; (c): GA; (d): Mutual Information