Hr2000

Rice pellets were analyzed using a LIBS system equipped with a 1064 nm Q-switched Nd:YAG laser (Quantel, Big Sky Ultra 50, Bozeman, USA) operating at 50 mJ maximum power energy with a pulse duration that is less than 8 ns, lens for laser focalization with focal distance of 10 cm, and an optical fiber bundle to lead plasma emissions to four spectrometers (Ocean Optics HR2000+, Dunedin, USA), which feature the spectral resolution of 0.1 nm FWHM (full width at half maximum) and cover a spectral range from 200 to 600 nm. The instrumental fixed integration time was 1 ms and the Q-Switch delay was set to 2.5 μs. Additionally, a spark discharge device, previously proposed by Vieira et al. [25 (link)] was coupled to the LIBS system to increase the sensitivity of the measures. The output discharge was set to 4.5 kV. The OOLIBS software from Ocean Optics, USA, was used to control the instrument and for data acquisition.
For analysis, rice pellets were placed in LIBS’s sample holder, which was moved in x and y directions relative to each laser pulse with a pulse duration of 20 ns, providing spectra acquisitions corresponding to fifty pulses spread on the pellets’ surface. The interaction laser sample provided a spot diameter of around 300 μm and irradiance in the focal point around 6.2 GW cm⁻². In addition, a video camera inside the sampling chamber was used for monitoring the analysis.

All optical transmission profiles shown in Fig. 6A were measured with a spectrometer (HR2000+, Ocean Insight, Orlando, USA). One hundred transmission measurements of each optical component were averaged and then smoothed across wavelengths by rolling window averaging with a window of ≈19 nm width. The values in the ranges 400 to 419 nm and 681 to 700 nm were ignored after smoothing to avoid unwanted border effects.

Scanning electron microscopic (SEM) images are taken with a ZEISS Auriga SEM/FIB Crossbeam System. Optical images are captured by a microscope MC-D800U(C). The LED emission spectra are measured with a spectrometer (HR2000 + , Ocean Optics). Current–voltage characteristics are recorded by a Keithley 2400 source meter. LED irradiances and external quantum efficiencies are measured using a spectroradiometer with an integrating sphere (LabSphere Inc.). The angular-dependent emission profiles are measured by a standard Si photodetector (DET36A, Thorlabs) with the device mounted on a goniometer. The probe’s mechanical properties are measured with dynamic mechanical analysis (DMA Q800, TA Instruments). For in vitro tests, micro-LED probes are implanted into the brain phantom. The brain phantom is made of agarose (0.5% w/v), hemoglobin (0.2% w/v), and intralipid (1% w/v) mixed in phosphate buffer solutions (98.3% w/v). After stirring, the mixed liquid is heated to boiling and then naturally cooled to room temperature, forming the gels.

Before eye opening at 14 days of age, B6 mice were randomly assigned to one of three visual environment groups: normal white light (n = 24), quasi-monochromatic red light (peak wavelength = 629 nm, n = 25), or quasi-monochromatic blue light (peak wavelength = 452 nm, n = 17). The mothers were kept in these cages for two or three days to enable the baby mice to nurse. Illumination was provided by light emitting diode (LED) tubes installed on the walls and ceiling of the cages to obtain a luminance of 275 ± 30 lux. Refraction and axial dimensions of all mice were measured every 2 weeks between 4 and 10 weeks of age. The emission characteristics of the LEDs were determined with a high-resolution spectrometer (HR 2000; Ocean Optics, Dunedin, FL, USA) (Fig. 1).Figure 1

Spectral emission curves for the three types of LEDs used for mice rearing. The white light emitting LEDs had a broad emission spectrum (400–760 nm) with a high peak at 443 nm and a lower broad peak at 575 nm. The spectrum of the blue-emitting LEDs ranged from 410 to 510 nm with a sharp peak at 452 nm. The spectrum of the red-emitting LEDs spanned from 585 to 660 nm with a major peak at 629 nm.

For pure absorber 10-nm AuNPs, absorbance of different concentration from 1 fold to 30 fold was collected on a UV-Vis spectrometer (Ocean Optics, Model: HR2000 + CG) with a standard 10 mm × 10 mm × 45 mm cuvette. The absorbance A at 532 nm and the molar concentration of AuNPs (aq) c showed a linear relationship, expressed as A = 4.18 × 10⁴ c, which agrees well with the Lambert-Beer law.