Usb2000 spectrophotometer

Reflectance measurements were completed in a home-made sample holder using a USB2000 + spectrophotometer, a HL-2000-FHSA tungsten light source, and a R400-7-VISNIR optical fiber reflectance probe, all from Ocean Optics (Dunedin, FL). The spectra were recorded using Ocean Optics Spectra Suite Spectroscopy Software over a wavelength range of 350–1025 nm. Measurements were performed in the sample holder that leads to careful sample positioning, test stability, and precise temperature control.

A Hitachi H-7650 transmission electron microscope (TEM, Japan) with an accelerating voltage of 200 kV was utilized to obtain TEM images. X-Ray Photoelectron Spectroscopy (XPS) was performed on a Kratos AXIS Ultra spectrometer equipped with a monochromated Al Kα (hν = 1486.6 eV) X-ray source (Kratos Analytical, Manchester, UK). Nicolet Magna 750 FTIR Spectrometer and Nic-Plan FTIR Microscope (Nicolet, USA) with pure KBr as the background was applied to record Fourier transform infrared (FTIR) spectra (400–4000 cm⁻¹). The microgel samples for TEM, XPS and FTIR characterization were prepared using the procedure described below for generating AgNPs in the etalons with two modifications. First, to obtain sufficient sample for analysis we didn't wash the slide after microgel painting, which yielded a thick microgel layer for AgNP generation. Second, the etalon's top Au layer was not deposited on the microgels, which allowed for their easy removal from the surface while avoiding potential contamination. Reflectance measurements were conducted using a USB2000+ spectrophotometer, an HL-2000-FHSA tungsten light source, and an R400-7-VISNIR optical fiber reflectance probe, all from Ocean Optics (Dunedin, FL). The spectra were recorded using Ocean Optics Spectra Suite spectroscopy software over a wavelength range of 400–1000 nm.

The spectral reflectance of petals was measured with a USB2000 spectrophotometer (Ocean Optics, Inc., Ostfildern, Germany) and illumination was provided by a DH-2000-BAL light-source (Ocean Optics, Inc., Ostfildern, Germany), both connected via coaxial fiber cable (QR400–7-UV-VIS, Ocean Optics, Inc., Dunedin, FL, USA). Reflectance was measured relative to a standard white reference tile (Diffuse Reflectance Standard, Spectralon®, labsphere). All reflectance measurements were taken in a constant angle of 90° towards the upper surface of each petal, and the distance between the probe tip and the sample surface was kept constant (5 mm) (cf. Fig. 4a).

We measured the spectral intensity profile (in µW cm^–2 nm^–1) of our light stimuli with a calibrated USB2000+ spectrophotometer (Ocean Optics). We then transformed the stimulus intensity into rod-effective photons cm^–2 s^–1 by converting the spectrum to photons cm^–2 s^–1 nm^–1, and integrating it with the normalized spectrum of rod sensitivity^{53 (link)}. In addition, for comparison we report stimulus intensity in equivalents of photoisomerizations per rod and second (R* rod^–1 s^–1), assuming dark-adapted rods, by multiplying the photon flux with the effective collection area of rods (0.5 µm²)^{54 (link)}. The results for a stimulus intensity of “30” range from 2 × 10⁸ rod-effective photons cm^–2 s^–1 (1 R* rod^–1 s^–1, ND8) to 2 × 10¹⁵ photons cm^–2 s^–1 (10⁷ R* rod^–1 s^–1, ND1), see Fig. 2b, c. Note that the intensity values given as R* rod^–1 s^–1 (isomerizations events s^–1 rod^–1) serves for only comparison. It truly reflects photoisomerizations only at low intensities; at high backgrounds, bleaching adaptation leads to a much lower effective rate of isomerizations.