Fig. 1. (a) Gold/silver nanocrystal doping causing glass to have bright colors (lycurgus cup, manufactured in ancient Rome in the 4th century AD); (b) the absorption spectrum of gold nanoparticle-doped glass, the illustration shows the pattern of gold nanoparticles precipitated in glass by femtosecond laser; (c) free electrons in spherical particles oscillate under the action of light field; (d) distribution of electric field enhancement near the surface of silver nanoparticles with different shapes

Fig. 2. (a) Photoluminescence of gold and copper under excitation by a 488 nm argon ion laser, the excitation light is incident at an oblique angle of 10° and collected perpendicular to the surface^[16]; (b) energy band diagram of the interband transition between the d-band and the sp-band (conduction band) in noble metals^[16]; (c) photoluminescence spectrum (black line) of a gold nanorod single particle under 785 nm laser excitation and dark field scattering spectrum (black circle) under white light excitation, the insets correspond to the polarization-dependent (top) and excitation power-dependent (bottom) photoluminescence intensities of nanorod single particle excitation light, respectively^[24]

Fig. 3. (a) Normalized PL excited by a 532 nm laser (solid lines) and dark-field scattering (dotted lines) spectra of silver nanorods with different aspect ratios; (b) normalized PL excited by a 633 nm laser (solid lines) and dark-field scattering (dotted lines) spectra of silver nanorods with different aspect ratios; (c) ratio spectrum of photoluminescence and dark field scattering under 532 nm laser excitation; (d) ratio spectrum of photoluminescence and dark field scattering under 633 nm laser excitation; (e) simplified band diagram of silver, showing the interband transition, intraband transition, and electronic Raman process^[20]

Fig. 4. (a)(b) Anti-Stokes SERS spectra from 60 K (blue) to 410 K (red) in 25 K steps displayed on linear scale and log scale; (c) band diagram of Au around the L point; (d) origin of anti-Stokes scattering background produced by ILS from the thermally excited electrons above the Fermi level (shaded red)^[18]

Fig. 5. (a) Anti-Stocks emission of a single nanorod at different irradiation powers, the inset shows the extracted temperature at each power (blue dots) and a linear extrapolation of the data to 0 μW excitation power, the value obtained for room temperature is 293 K, while the measured value is 296 K; (b) calibration-free temperature measurement, extracted temperatures from the anti-Stocks-luminescence emission of an individual nanorod at different excitation powers and at different sample temperatures, the dashed lines are fits with the same slope for the three temperatures, the squares in the inset plot show the local temperature of the sample obtained by extrapolating the temperature at zero excitation power as a function of the water temperature, the red line represents the expected curve if both temperatures are identical^[28]

Fig. 6. (a) The SEM image of widely-dispersed individual plasmonic nanodisks on the quartz substrate, the inset shows the atomic force microscopy (AFM) image of an individual nanodisk; (b) Raman spectra for a representative nanodisk under laser illumination as a function of laser power, the green line is the background spectrum for quartz collected at an area adjacent to the nanodisk; (c) Raman spectral data and fitting results obtained by normalizing the spectra collected at a laser power of 5 mW; (d) the temperature of the nanodisk extracted as a function of laser power^[37]

Fig. 7. The comparison in photostability between AuNRs and RB^[39]

Fig. 8. (a)(b) PL images of gold nanocubes in QGY cells and 293T cells^［42］

Fig. 9. (a) Luminescence spectra of the same GND for different gap distances (20‒31 nm), the increasing gap size results in a shift of the emission band to shorter wavelengths, which is saturating for larger gaps; (b) spectral position of the emission maximum as a function of the gap distance of three consecutive measurements, an increase of the gap leads to a blueshift of the emission maximum from 687 to 677 nm; (c) phase shift obtained for three consecutive measurements for the same gap sizes as in Fig. 9(b); (d) normalized spectral shift (blue circles and line) and phase shift (red circles and line) over the given gap range^［43］