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Effect of UV wavelength on humic acid degradation and disinfection by-product formation during the UV/chlorine process
摘要： The efficiency of the ultraviolet (UV)/chlorine process strongly depends on UV wavelength because chlorine photolysis and its subsequent radical formation are highly wavelength-dependent. This study compared the degradation of humic acid (HA) during the UV/chlorine process by low pressure mercury lamp (LPUV, 254 nm) and ultraviolet light-emitting diode (UV-LED, 275 and 310 nm). The results indicated that HA degradation followed the pseudo-first-order kinetics, and the fluence-based degradation rate constants (kobs) were significantly affected by UV wavelength and solution pH. HA degradation decreased greatly with increasing solution pH during the UV/chlorine process at 254 nm, while the opposite trend was observed at 275 and 310 nm. In the meantime, kobs decreased in the order of 275 nm > 254 nm > 310 nm at pH > 7.0. The changes of chlorine molar absorption coefficients at different UV wavelengths resulted in the variation of chlorine photodecay rates (kobs, chlorine), and the synergistic effects of kobs, chlorine and chlorine quantum yields (Φchlorine) affected HA reduction. The formation of disinfection by-products (DBPs) during the UV/chlorine process was also evaluated. A significant suppression on DBP formation and DBP-associated calculated theoretical cytotoxicity were observed at 275 nm high UV fluence and alkaline pHs. These findings in this study demonstrate that UV wavelength at 275 nm is more suitable for HA degradation by the UV/chlorine advanced oxidation process in practical applications.
关键词： Disinfection by-products,Ultraviolet light-emitting diode (UV-LED),UV/chlorine,Humic acid,Toxicity,UV wavelength
更新于2025-11-19 16:46:39
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Ultraviolet light-related DNA damage mutation signature distinguishes cutaneous from mucosal or other origin for head and neck squamous cell carcinoma of unknown primary site
摘要： Background: Head and neck squamous cell carcinoma of unknown primary site (HNSCCUP) is a diagnostic challenge. Identification of an ultraviolet (UV) light-related DNA damage signature using next-generation sequencing (NGS) can classify the primary site of origin as cutaneous. Methods: A 62-year-old male was seen with 2 months of left neck swelling. He was a lifetime nonsmoker but had a history of cutaneous squamous cell carcinoma (SCC) of the left helix. He was also found to have left hilar adenopathy. He had a p16-negative HNSCCUP on fine needle aspiration (FNA) biopsy of the left neck. Results: NGS of the FNA specimen revealed a high number of somatic mutations that were mostly C to T transitions, indicating a UV mutation signature and confirming the diagnosis of cutaneous SCC. Conclusions: Identification of a UV DNA damage signature with NGS distinguishes HNSCCUP of cutaneous vs mucosal or other squamous cell carcinoma origin.
关键词： unknown primary squamous cell carcinoma of head and neck,cutaneous tumor mutation burden,next-generation sequencing,ultraviolet light-related DNA damage signature,skin cancer
更新于2025-09-23 15:23:52
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Development of mercury-free ultraviolet light emitting devices
摘要： We developed rare-earth doped phosphors for mercury-free narrowband ultraviolet light sources. The narrowband emission is a typical feature of the intra-orbital electron transition in the rare-earth Gd3+ ion. Al1-xGdxN epitaxial films were grown by using an ultra-pure reactive sputtering technique performed under molecular-beam epitaxial quality. A narrowband luminescence line from Gd3+ ions has been observed at 318 nm. We fabricated field-emission devices using Al1-xGdxN thin films and investigated detailed device characteristics. Furthermore, recently, we have successfully developed bright fluorescent lamps with an ultraviolet phosphor containing Gd3+ ions.
关键词： mercury free,ultraviolet,light source,rare-earth
更新于2025-09-23 15:21:21
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Polymers and Electromagnetic Radiation || Front Matter
摘要： This book concentrates on the interaction of electromagnetic waves with polymers and deals only exceptionally with particle radiation. Electromagnetic waves comprise a very broad range of frequencies that extends over more than 20 orders of magnitude from the radiofrequency region up to the region of hard c-rays emitted from radionuclides or being part of the cosmic rays.
关键词： microwave,radiofrequency,visible light,infrared radiation,gamma rays,polymers,electromagnetic waves,interaction,X-rays,ultraviolet light
更新于2025-09-23 15:21:01
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Graphene-assisted molecular beam epitaxy of AlN for AlGaN deep-ultraviolet light-emitting diodes
摘要： We report on the van der Waals epitaxy of high-quality single-crystalline AlN and the demonstration of AlGaN tunnel junction deep-ultraviolet light-emitting diodes directly on graphene, which were achieved by using plasma-assisted molecular beam epitaxy. It is observed that the substrate/template beneath graphene plays a critical role in governing the initial AlN nucleation. In situ reflection high energy electron diffraction and detailed scanning transmission electron microscopy studies confirm the epitaxial registry of the AlN epilayer with the underlying template. Detailed studies further suggest that the large-scale parallel epitaxial relationship for the AlN epilayer grown on graphene with the underlying template is driven by the strong surface electrostatic potential of AlN. The realization of high-quality AlN by van der Waals epitaxy is further confirmed through the demonstration of AlGaN deep-ultraviolet light-emitting diodes operating at 260 nm, which exhibit a maximum external quantum efficiency of 4% for an unpackaged device. This work provides a viable path for the van der Waals epitaxy of ultra-wide bandgap semiconductors, providing a path to achieve high performance deep-ultraviolet photonic and optoelectronic devices that were previously difficult.
关键词： AlGaN,AlN,molecular beam epitaxy,deep-ultraviolet,light-emitting diodes,van der Waals epitaxy
更新于2025-09-23 15:21:01
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Counter-intuitive junction temperature behavior in AlGaN-based deep-ultraviolet light-emitting diodes
摘要： The junction temperature, one of the major parameters that strongly affect the performance of light-emitting diodes (LEDs), increases during operation because of the power dissipated as heat within an LED device. Therefore, LED devices with poor characteristics are expected to have higher junction temperatures for the same driving conditions. In this study, an observation contrary to this expectation is presented: a deep-ultraviolet LED device with superior electrical characteristics shows a higher junction temperature at the same input electrical power than a device with poor characteristics. A simple equivalent circuit comprising a diode, a series resistor, and shunt components is employed to elucidate this counter-intuitive observation by considering the possible heat sources inside the LED device. It is found that the junction temperature is mainly dominated by the power dissipated at the diode instead of the other possible heat sources including the Joule heating effect of the resistive components.
关键词： junction temperature,Joule heating,AlGaN-based deep-ultraviolet light-emitting diodes,power dissipation,equivalent circuit
更新于2025-09-23 15:21:01
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Vacuum Arc Plasma Heated by Sub-Terahertz Radiation as a Source of Extreme Ultraviolet Light
摘要： This paper presents the results of the ?rst experimental studies of the interaction of a powerful sub-terahertz radiation with expanding highly inhomogeneous plasma of vacuum arc discharge. The tantalum plasma of a vacuum arc discharge additionally heated by the focused sub-terahertz radiation of a gyrotron, the radiation power is up to 250 kW, and the wavelength is 1.2 mm. Characteristics of the light emission in the extreme ultraviolet range are presented.
关键词： gyrotron,vacuum arc plasma,Extreme ultraviolet light,sub-terahertz radiation
更新于2025-09-23 15:21:01
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Enhanced Optical Output of Near-Ultraviolet Light-Emitting Diodes by a Monolayer of Nanospheres
摘要： The optical output of near-ultraviolet (NUV) light-emitting diodes (LEDs) was improved by including a monolayer of hexagonal close-packed polystyrene (PS) nanospheres. PS nanospheres with different sizes were deposited on the indium tin oxide layer of the NUV LEDs. The electroluminescence results showed that the light extraction efficiency of the NUV LEDs was increased by the inclusion of PS nanospheres, and the maximum optical output enhancement was obtained when the size of the nanospheres was close to the light wavelength. The largest enhancement of the optical output of 1.27-fold was obtained at an injection current of 100 mA. The enhanced optical output was attributed to part of the incident light beyond the critical angle being extracted when the exit surface of the NUV LEDs had a PS nanosphere monolayer. This method may serve as a low-cost and effective approach to raise the efficiency of NUV LEDs.
关键词： polystyrene nanospheres,optical output enhancement,near-ultraviolet,light-emitting diodes,light extraction efficiency
更新于2025-09-23 15:19:57
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Polarization-engineered AlGaN last quantum barrier for efficient deep-ultraviolet light-emitting diodes
摘要： The AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) has been identified as a prospective mercury-free UV source. However, the observation of severe electron overflow and low hole injection efficiency in the conventional DUV LED deteriorates the device performance, attributing to the downward band bending as a result of the strong polarization-induced electric fields between the last quantum barrier (LQB) and the electron blocking layer (EBL). In this study, a composition-graded AlGaN layer with linearly increasing of Al composition from 0.5 to 0.65 is proposed to act as the LQB, replacing the conventional flat LQB to reduce the effective barrier height for hole injection while improving the electron blocking ability. Hence, a considerable enhancement of the output power can be obtained. Moreover, further investigations show that the thickness of graded LQB determine the band bending in the LQB and thus significantly suppress the electron leakage, eventually leading to a boosted output power. The thorough investigation on the LQB could pave the way towards the realization of efficient DUV LEDs of the future.
关键词： electron blocking layer,ultraviolet light-emitting diodes,light output power,polarization field,graded last quantum barrier
更新于2025-09-23 15:19:57
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Light Extraction Efficiency Optimization of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes
摘要： Using finite-difference time-domain method, the light extraction efficiency (LEE) of AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) is investigated. Simulation results show that compared to flat sapphire substrate, the nano-patterned sapphire substrate (NPSS) expands the extraction angles of top surface and sidewalls. As a result, the LEE of transverse-magnetic (TM) polarized light is improved significantly. Roughening on the backside of n-AlGaN surface significantly enhances the LEE of top surface of thin-film flip-chip DUV LEDs. However, the LEE of sidewalls of thin-film flip-chip DUV LEDs is greatly weakened. For bare DUV LED, the LEE of flip-chip LED on NPSS is estimated to be about 15%, which is around 50% higher than that of thin-film flip-chip DUV LED with roughening on the backside of n-AlGaN surface.
关键词： AlGaN,nano-patterned sapphire substrate,light-emitting diodes,deep-ultraviolet,light extraction efficiency
更新于2025-09-23 15:19:57