Lambda 650

The sheet resistances were measured using a sheet resistance meter (FPP-40K, DASOL ENG) and were obtained by measuring nine points on the substrate and determining the mean value and the standard deviation. The absorption spectra were measured by using an ultraviolet-visible spectrometer (Lambda 650S, Perkin Elmer). The surface chemical compositions were measured by using XPS (XPS-Theta Probe, Thermo Fisher Scientific Co.). The structure and the chemical composition were investigated by using SEM (NOVA NANOSEM 450, FEI), TEM, and EDS (JEM-2100F, JEOL).

The sheet resistances were measured by using a sheet resistance meter (FPP-40K, DASOL ENG) and were obtained by measuring nine points on the substrate and determining the mean value and the standard deviation. The transmittance spectra were measured by using a UV-visible spectrometer (Lambda 650 S, Perkin Elmer). The structural properties were investigated by using SEM (NOVA NANOSEM 450, FEI) while the surface chemical compositions were measured by using XPS (XPS-Theta Probe, Thermo Fisher Scientific Co.).

After extraction, the absorption spectra of retinal in the supernatant were recorded with a Lambda 650 S UV-visible spectrometer (Perkin Elmer, Uberlingen, Germany) at 25 °C in the range of 250–500 nm using a quartz cuvette with 10 mm path length (Quartz Suprasil, Hellma Analytics, Müllheim, Germany). The band maximum of the retinal is at 380–400 nm. The results obtained from the skin probes from PRN-loaded MN, PRN and conv. RAL were compared with the untreated skin areas, which served as control. The amount of recovered retinal in epidermis and dermis from all formulations was calculated using the standard reference curve prepared of retinal standards.

UV-VIS-NIR light transmittance and reflectance at wavelengths of 300–2500 nm were measured using a UV-visible spectrometer with an integrating sphere (Lambda 650 S, Perkin Elmer), and IR light transmittance and reflectance in the wavelengths of 2.5–25 μm region were measured using a Fourier transform infrared spectrometer (Nicolet 6700, Thermo Scientific). All samples had a thickness of 50 μm unless otherwise mentioned. The haze in visible light was calculated by dividing the diffuse transmittance by the total transmittance^{66 (link)}. The diffuse and total transmittances were measured according to the ASTM D1003 method. To quantify the mechanical properties of the metamaterials, tensile tests were performed using a universal testing machine with a 100 N load cell at a speed of 0.1 mm/min. Dogbone-shaped specimens were prepared according to the ASTM D 412 standard. To evaluate the moisture-impermeable properties of the metamaterials, the water vapor transmission rate was measured using a permeation testing system (Permatran-W 3/33 MA, Mocon) at room temperature and at a relative humidity of 100% according to the ASTM F1249 method.

The electrical measurements were performed using a semiconductor analyzer system (4200, Keithley), an oscilloscope (TDS 2024 C, Tektronix) and a waveform generator (33220 A, Agilent) in an atmospheric environment at room temperature. In the electrical measurements, all of the bias voltages were applied to the top Al electrodes while keeping the bottom Al electrodes grounded. SEM image was obtained by using Nova Nano SEM 230 system. The absorption spectra of the films were characterized by using an UV–Vis spectrophotometer (Lambda 650 S, Perkin Elmer). The UPS measurements were performed in an analysis chamber using a He discharge lamp (XPS-Theta Probe, Thermo Fisher Scientific). The resolution of the measurements was 50 meV.