Attenuation Of Ultraviolet Light Research Articles

Bioinspired, vertically stacked, and perovskite nanocrystal-enhanced CMOS imaging sensors for resolving UV spectral signatures.

Imaging and identifying target signatures and biomedical markers in the ultraviolet (UV) spectrum is broadly important to medical imaging, military target tracking, remote sensing, and industrial automation. However, current silicon-based imaging sensors are fundamentally limited because of the rapid absorption and attenuation of UV light, hindering their ability to resolve UV spectral signatures. Here, we present a bioinspired imaging sensor capable of wavelength-resolved imaging in the UV range. Inspired by the UV-sensitive visual system of the Papilio xuthus butterfly, the sensor monolithically combines vertically stacked photodiodes and perovskite nanocrystals. This imaging design combines two complementary UV detection mechanisms: The nanocrystal layer converts a portion of UV signals into visible fluorescence, detected by the photodiode array, while the remaining UV light is detected by the top photodiode. Our label-free UV fluorescence imaging data from aromatic amino acids and cancer/normal cells enables real-time differentiation of these biomedical materials with 99% confidence.

Fluorescence imaging analysis of depth‐dependent degradation in photovoltaic laminates: insights to the failure

AbstractAccurate evaluation of the reliability of photovoltaic (PV) packaging materials is critically important for the long‐term safe operation of modules. However, the complexity of the laminated systems due to their multilayered and multicomponent structures and diverse aging mechanisms makes a thorough system evaluation very challenging, especially when the degradation is non‐uniform through the thickness. In such a case, neither surface nor bulk measurements can present a clear picture of the degradation profile. In this study, fluorescence imaging was developed to visualize the degradation depth‐profiles of an aged laminated PV system. A glass/ethylene vinyl acetate (EVA) encapsulant/poly(ethylene terephthalate) (PET)‐PET‐EVA (PPE) backsheet laminate was weathered with the glass‐side facing an ultraviolet (UV) light source for 3840 h. Cross‐sectional fluorescence images revealed a non‐uniform distribution of degradation species across the thickness of the EVA encapsulant, providing greater insight into the mechanisms of degradation, which are unavailable by traditional bulk‐based methods. In addition, strong fluorescence emissions were observed from the two thin adhesive layers of the aged backsheet, indicating severe degradation of the adhesives and a potential for interlayer delamination. This method is further confirmed with other microscale characterization techniques. The changes in optical (yellowness index), chemical (oxidation, UV absorber concentration), mechanical (Derjaguin‐Muller‐Toporov modulus), and thermal (melting enthalpy) properties of the EVA encapsulant were found to be related to fluorescence profiles, following the attenuation of UV light. This study highlights that fluorescence imaging is a spatially‐resolved and sensitive method for rapid failure assessment and in‐depth mechanism study for complex PV‐laminated system.

Effect of light attenuation on polymerization of ceramic suspensions for stereolithography

Weak bonding strength between interlayers can seriously affect the quality of ceramic parts manufactured by stereolithography. Therefore, the possibility of using chemical bonds to strengthen the adhesion within these parts and the extent to which may be effective are of interest. Thus, a multi-exposure model was built to illustrate the state of this interface. The secondary conversion of a cured layer defined as conversion rate increment caused by decayed ultraviolet (UV) light in a subsequent exposure was selected to represent the extent of a chemical bond. The level of UV light attenuation occurred when travelling through a suspension layer was determined using the Attenuation Law. When decayed light illuminated a cured layer, it underwent further photopolymerization, which was detected by temperature change. The secondary conversion was affected by parameters including the incident energy dose and the propagating length. Optimization of these parameters helped to achieve higher chemical bond ratio.

Effect of different coagulants on the ultraviolet light intensity attenuation

Abstract The effect of different coagulants added to deionized water on ultraviolet (UV) light intensity at the wavelength of 253.7 nm was investigated in this study. It was demonstrated that iron salts had a greater negative effect on the UV transmittance (UVT) of the solution, but aluminum salts had little effect on the UVT of the solution except polyaluminium chloride (PAC). Polyferric sulfate (PFS) and PAC, as highly effective inorganic-polymer coagulants, had a greater negative effect on the UVT of the solution than the related metal salts. UV light attenuation of iron salts and aluminum salts existing in the solution were in good agreement with the Lambert-Beer law, except PAC and PFS. The UV absorption coefficients of different coagulants were obtained and compared below: PFS>FeCl3>Fe2(SO4)3>FeSO4>PAC>AlCl3>Al2(SO4)3. If the coagulation pretreatment with PFS was added before UV disinfection of water, it would lead to stronger UV light attenuation than that with PAC. It means that more UV light can ...

The state of nano‐sized titanium dioxide (TiO2) may affect sunscreen performance

In the past several years, there has been a trend in the sunscreen/cosmetics industry to replace micron-sized titanium dioxide (TiO(2)) particles with nanoscale materials. The increased use of nanoscale TiO(2) has resulted in questions about these and other nanoproducts. This study examines the effects of using nanoscale TiO(2) on ultraviolet (UV) attenuation in simple to complex sunscreen formulations. UV light attenuation, product stability, and potential damage to the skin barrier were examined with both nanoscale and microscale TiO(2) particles. Results indicate that none of the formulations decreased the barrier function of the skin and the best UV attenuation occurs when the TiO(2) particles are stabilized with a coating and evenly distributed such as with non-agglomerated coated nanoscale materials. This indicates that nanoscale TiO(2) may have better efficacy while lacking toxicity.

Observations of ultraviolet light reflection and transmission by first‐year sea ice

As part of a comprehensive program investigating the electromagnetic properties of sea ice, measurements were made of the optical properties of young ice and first‐year sea ice at ultraviolet wavelengths. Young sea ice observations were made in a specially designed sea ice pond at the Cold Regions Research and Engineering Laboratory (Hanover, NH), while first‐year sea ice was examined in the Chukchi Sea and Beaufort Sea near Barrow, Alaska. The results indicated that, in general, albedo increased with increasing wavelength from 305 to 380 nm, with values for first‐year ice in the 0.4 to 0.6 range. Transmittance through bare first‐year ice was roughly 0.5 to 2 percent. Extinction coefficients for bare sea ice were between 2 and 4 m−1 and decreased with increasing wavelength. The presence of a snow cover had a profound impact on ultraviolet light levels under sea ice, with even a thin (0.1‐m‐thick) snow cover reducing transmitted ultraviolet light by more than an order of magnitude. Observed transmittances indicated that the attenuation of ultraviolet light by sea ice and snow was greater than that of the photosynthetically active radiation.

An erase model in double poly-Si gate n-channel FAMOS devices

The existence of a poly-Si control gate in an n-channel FAMOS makes the erase characteristics due to ultraviolet light (UVL) illumination different from those of conventional p-channel FAMOS's without control gates. The difference in erasing times between these two types of FAMOS has been explained by the attenuation of UVL in the control gate. However, it was clarified experimentally and analytically in n-channel FAMOS that UVL is propagated horizontally in an optical guide formed between the control gate and substrate and is then absorbed by the floating poly-Si gate. The absorbed UVL intensity in the floating gate through the proposed optical guide is calculated to be 109times stronger than that transmitted directly through the control gate whose thickness and absorption coefficient are assumed to be 3500 A and 106cm-1, respectively. The proposed optical guide model is supported in experiments that erase time does not depend on the thickness of the control gate (2400- and 3600-A devices are compared) and erase time in a device whose optical guides are open only on one side and the other side is covered by the control gate is about 2 times longer than that in a device which has two optical guides open on both sides.

Errata*: Horizontal Attenuation of Ultraviolet Light by the Lower Atmosphere

Errata*: Horizontal Attenuation of Ultraviolet Light by the Lower Atmosphere

The Attenuation of Ultra-Violet Light by the Lower Atmosphere

Measurements were made with a quartz mercury lamp, a quartz spectrograph and a recording densitometer of the attenuation of ultra-violet light from 3000 to 2050A by the atmosphere at sea level. For wave-lengths from 5000 to 3000A the absorption was too slight to be observed at distances up to 400 meters; for wave-lengths below 2800A there was pronounced absorption above that attributable to molecular scattering. The absorption was the same day and night, was unaffected by changes in the humidity, but increased with haze. The thicknesses of clear air necessary to reduce the light to ${10}^{\ensuremath{-}2}$ were about 22, 5, 0.57 and 0.20 km for 2800, 2500, 2200 and 2050A, respectively. The absorption in the lower atmosphere around 2800 to 2900A was not sufficient to account for the sharp cessation of the solar spectrum in this region. This result is in keeping with the fact that the ultra-violet limit of the solar spectrum is due to ozone in the high atmosphere. The absorption in the lower atmosphere at 2200 to 2050A, a spectrum region where ozone is relatively transparent, is great enough to prevent sunlight of these wave-lengths from penetrating to sea level.