Fig. 1. TEM image and absorption spectrum of nanocolloids of different sizes or shapes
(a): Gold nanospheres; (b): Gold nanorods; (c): Silver nanocubes;(d): Gold nanostar; (e): Silver triangle; (f): Gold nanocages

Fig. 2. Synthesis of gold nanocrystals

Fig. 3. (a) Raman spectra on fresh citrus fruits. Curve Ⅰ, clean peel; curve Ⅱ, contaminated with methyl parathion; Curve Ⅲ, contaminated orange surface modified by Au/SiO₂ nanoparticles; Curve Ⅳ, methyl parathionpowder; (b) Schematic of the SHINERS experiment

Fig. 4. Silver particles coated with polyethylene microspheres modified cysteamine or mercaptopropionic acid for detection of pesticides with different charges in seawater

Fig. 5. Diagram of the device for in-fiber optofluidic SERS detection. Inset: end-face of the MHF without modifying Ag NPs

Fig. 6. Schematic diagram of detection of acephate in rice using by D-SERS and AuNRs-cys combined with multivariant methods

Fig. 7. Scatter plot of first two principle component score obtained by KPCA with σ of 1 000 (a), 5 000 (b), 8 000 (c) and 10 000 (d)
PC1: The first principle component; PC2: The second principle component

Fig. 8. Predicted error of the optimal model built using SVR and KPCA with σ of 8 000