Optistat dn 5 ln2

Photoluminescence (PL) spectra and PL intensity decreases were collected on a FLS920 fluorimeter (Edinburgh Instruments, Edinburgh, Scotland) in air, and in a vacuum (pressure 1Pa) ensured by the cryostat Optistat DN-V LN2 (Oxford Instruments, Oxford, UK), Oxford Instruments. An integrating sphere method was used for the determination of quantum yields of luminescence for both thin films and solutions. All measurements were carried out at room temperature.
To evaluate the dose of UV energy received over the surface of a sample, the intensity of monochromatic light was measured with a high-precision radiometer RM22 (Opsytec Dr. Gröbel, Ettlingen, Germany) equipped with the UV-A sensor. The size of the irradiated area was calculated from a digital image of graph paper with a visible ray trace. A UV fluorescent marker was used for the visualization of the light beam spot. The calculated powers of the radiating monochromatic light with a wavelength of 340 nm depending on the slit size are shown in Table 1.

Photoluminescence (PL) spectra were collected with an FLS920 fluorimeter (Edinburgh Instruments, Edinburgh, Scotland) in helium at various temperatures, provided by the cryostat Optistat DN-V LN2 (Oxford Instruments, Oxford, UK), Oxford Instruments. Thin films on QG substrates were analyzed during cooling down from RT to 77 K (controlled by liquid nitrogen), followed by heating up to 353 K. Emission spectra were collected as follows: (1) immediately after film preparation (labeled fresh); (2) during film cooling at particular temperatures; (3) after cooling at RT (labeled after cooling); (4) during heating at certain temperatures; (5) after spontaneous cooling down to RT (labeled after heating); (6) after 24 h in the cryostat chamber without opening (labeled after 24 h).