Integrating sphere

The formed particles were observed by field-emission scanning electron microscopy (FESEM, FEI Helios NanoLab G3 UC, ThermoFisher Scientific). An accelerating voltage of 5 kV was used. The EDX spectra recording was also realized by FESEM with a JSM-6700F from JEOL Ltd using a silicon drift detector (SDD) XFlash 5130 from Bruker Nano. In the JSM-6700F, the energy of the exciting electrons was set to 10 keV and the accumulation live time was 200 s in all cases. To prevent charging effects in the SEM, a 5 nm thick carbon layer is deposited on the sample before analysis.
For optical characterization of the mixed particles after laser treatment as well as after the etching procedure, the transmission spectra were determined using a spectrometer (H2000, Ocean Optics) setup with a coupled fiber (wavelength range of 200–1100 nm) under transmitted illumination with a halogen-lamp (400–900 nm emission and illumination diameter 2 mm) and with a UV-vis spectrometer with an integrating sphere of PerkinElmer in the same spectral range (illumination area 1 × 2 mm²). All raw spectra are corrected by the background and light source signal.
The resonance spectra of single pure Au and Ag NPs were calculated depending on different diameters in the wavelength range of 350 to 900 nm using the open source software Mie-Plot (https://www.philiplaven.com/mieplot.htm).

Before transfer to light with an incident intensity of 61 µE m⁻² s⁻¹, dark-arrested cultures in small flasks were covered with colour filters (Lee Filters, UK): Blood Red (#789), Marius Red (#787), Primary Green (#139), Moonlight Blue (#183) and Special Medium Blue (#363). For the flow cytometry and qPCR experiments, a reduced set of filters was used, consisting of Blood Red, Primary Green and Special Medium Blue (Table 1). The transmittance spectrum of each filter (Supplementary Fig. S2) was measured using a Lambda-650S spectrophotometer equipped with an integrating sphere (PerkinElmer). To reduce the potential confounding effect of light intensity on the spectral composition experiments, an approximate correction was made to compensate for the transmittance in the spectral range of each colour filter. The objective was to provide approximately the same incident light intensity, in the wavelength range of the colour filter, for the colour filter treatment versus the control receiving the full spectrum (Supplementary Fig. S3). The approximate correction was made by changing the illumination to compensate for the transmittance at the wavelength of maximum transmittance of each colour filter. Dark and light controls were included by covering flasks with aluminum foil or leaving them uncovered. All experiments were carried out in triplicate.