The far-ultraviolet C (UVC) light has been used recently as an alternative disinfection system to deactivate the novel coronaviruses that cause coronavirus disease (COVID-19) without introducing any health damage to humans. We investigate that the far-UVC light from far-UVC excimer lamps (BEST 20 Watt) is a promising candidate for a far-UVC disinfection system to prevent human-to-human transmission of COVID-19. The optical characterization of far-UVC excimer lamps was examined. The maximum irradiance of the far-UVC excimer lamps is 219 nm, which is known to have antimicrobial capabilities on microorganisms, including coronaviruses. We propose a design of a disinfection chamber system based on eight 219 nm far-UVC excimer lamps which are attached vertically about 35 cm to each other, and the irradiation angle was installed at the angle of approximately 120° in order to optimize the irradiation of far-UVC light to a human body. For microorganism inactivation at a distance of around 10 cm from the human body, 219 nm far-UVC excimer lamps requires less than 5 s of irradiation time and the required intensity of 840 mW/cm2 at a low dose of 3000 mJ/cm2. We recommend that our proposed disinfection chamber can be used for humans and applied in public areas to decrease the spread of COVID-19 without any adverse health effect.
We fabricate the phenyl-substituted poly(p-phenylene vinylene) copolymer (super yellow, SY-PPV)-based polymer light-emitting diodes (PLEDs) with different device architectures to modulate the injection of opposite charge carriers and investigate the corresponding magnetoconductance (MC) responses. At the first glance, we find that all PLEDs exhibit the positive MC responses. By applying the mathematical analysis to fit the curves with two empirical equations of a non-Lorentzian and a Lorentzian function, we are able to extract the hidden negative MC component from the positive MC curve. We attribute the growth of the negative MC component to the reduced interaction of the triplet excitons with charges to generate the free charge carriers as modulated by the applied magnetic field, known as the triplet exciton-charge reaction, by analyzing MC responses for PLEDs of the charge-unbalanced and hole-blocking device configurations. The negative MC component causes the broadening of the line shape in MC curves.
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