- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
A novel upper-room UVC-LED irradiation system for disinfection of indoor bioaerosols under different operating and airflow conditions
摘要： The potential of inactivating indoor bacteria aerosols using a novel rotating ultraviolet-C (UVC) light-emitting-diode (LED) system was investigated. The system was installed in the upper level of the full scale chamber and its effectiveness against aerosolized E. coli, S. marcescens, and S. epidermidis under well-mixed and stationary scenario were initially tested. The estimated susceptibility values were 1.068, 1.148, and 0.156 m2/J for E. coli, S. marcescens, and S. epidermidis, respectively. Three additional scenarios of experiments were conducted, in which E. coli was aerosolized into the test chamber and then allowed to decay under (i) poorly-mixed condition with stationary system, (ii) well-mixed with rotating system, and (iii) poorly-mixed conditions with rotating system. Our results showed no significant difference between the performance of stationary and rotating UR-UVGI-LED systems under a well-mixed condition. While the performance of the stationary UR-UVGI-LED system under a poorly-mixed condition decreased by 52.90–79.38% compared to a well-mixed condition, rotating the UR-UVGI-LED system under a poorly-mixed condition, compared to the stationary system, enhanced its performance by 22.36–49.86%. Thus, our proposed rotating irradiation offers great potential for application in environments where bioaerosols are unevenly distributed in a built environment.
关键词： Upper-room UVGI,Disinfection bioaerosols,IAQ,UVC,LED
更新于2025-09-23 15:19:57
-
Photonics integrated circuits using Al<sub>x</sub>Ga<sub>1-x</sub>N based UVC light-emitting diodes, photodetectors and waveguides
摘要： We report on a study of UVC photonics integrated circuit (PIC) consisting of monolithically integrated AlxGa1-xN multiple quantum wells (MQWs) based light-emitting diodes, detectors and channel waveguides on sapphire substrates. The waveguide stack consisted of a 1.5 μm thick n-Al0.65Ga0.35N waveguide over an AlN (3.5 μm thick) clad layer. Using the integrated devices, we measured that approximately 80% of the guided-light was confined in the n+-Al0.65Ga0.35N layer, estimated the multi-mode ridge waveguide losses to be 23 cm-1 at λemission~280 nm. We also estimated the multi-mode ridge waveguide losses to be 23 cm-1 at λemission~280 nm. We also measured that approximately 80% of the guided-light was confined in the n+-Al0.65Ga0.35N layer, 7% in the underlying AlN cladding and the remaining 13% in the double-side polished sapphire substrate.
关键词： AlGaN LED,Atomic Layer Deposition,UVC Waveguides,Waveguide Loss,AlGaN Detector,Photonic Integrated Circuit,high Al composition
更新于2025-09-16 10:30:52
-
Design of AlGaN-based quantum structures for low threshold UVC lasers
摘要： The influence of the polarization field on the emission properties of the AlGaN-based quantum structures grown on AlN substrates was investigated as a function of well width, barrier width, and barrier height. A thin AlGaN well and a thin AlN barrier design reduced the polarization field to ～0.5 MV/cm, resulting in an ultralow laser threshold of 3 kW/cm2 in an optically pumped configuration. These experimental results were used to validate the simulation. In the next step, a structure with Al0.7Ga0.3N barriers was designed to support carrier injection with a minimal loss in optical performance. This structure showed a threshold of 7 kW/cm2 under optical pumping and an estimated threshold current of 8 kA/cm2 for the electric injection.
关键词： UVC lasers,AlGaN,quantum structures,laser threshold,polarization field
更新于2025-09-12 10:27:22
-
Internal quantum efficiencies of AlGaN quantum dots grown by molecular beam epitaxy and emitting in the UVA to UVC ranges
摘要： AlyGa1?yN quantum dots (QDs) have been grown by molecular beam epitaxy on AlxGa1?xN (0001) using a 2-dimensional–3-dimensional growth mode transition that leads to the formation of QDs. QDs have been grown for Al compositions y varying between 10% and 40%. The influence of the active region design [composition y, QD height, and bandgap difference (ΔEg) between the AlxGa1?xN cladding layer and the AlyGa1?yN QDs] is discussed based on microscopy, continuous wave photoluminescence (PL), and time-resolved PL (TRPL) measurements. In particular, increasing y leads to a shift of the QD emission toward shorter wavelengths, allowing covering a spectral range in the UV from 332 nm (UVA) to 276 nm (UVC) at room temperature (RT). The low-temperature (LT) internal quantum efficiency of the QD ensembles was estimated from TRPL experiments at 8 K and values between 11% and 66% were deduced. The highest internal quantum efficiency (IQE)-LT is found for the QDs with higher Al content y. Then, the PL spectrally integrated intensity ratios between RT and LT were measured to estimate the IQE of the samples at RT. The PL ratio is higher for larger ΔEg, for QDs with y of 0.1 or 0.2, and high PL intensity ratios up to 30% were also measured for QDs with larger y of 0.3 and 0.4. RT IQE values between 5% and 20% are deduced for AlyGa1?yN QDs emitting in the 276–308 nm range.
关键词： AlGaN,internal quantum efficiency,UVC,quantum dots,molecular beam epitaxy,time-resolved photoluminescence,photoluminescence,UVA
更新于2025-09-12 10:27:22
-
Determination of Sapphire Off‐Cut and its Influence on the Morphology and Local Defect Distribution in Epitaxially Laterally Overgrown AlN for Optically Pumped UVC Lasers
摘要： In this paper a systematic study of the morphology and local defect distribution in epitaxial laterally overgrown (ELO) AlN on c-plane sapphire substrates with different off-cut angles is presented. Precise measurements of the off-cut angle, using a combination of optical alignment and X-ray diffraction with an accuracy of ±5° for the off-cut direction and ±0.015° for the off-cut angle were performed. For ELO AlN growth a transition from step flow growth at a < 0.14° with height undulations on the surface to step bunching with step heights up to 20 nm for a > 0.14° was observed. Furthermore, the terraces of the step bunched surface exhibit curved steps. An analysis of the local defect distribution by scanning transmission electron microscopy and a comparison with atomic force microscopy reveals a bunching of defects in line with the ELO pattern and a roughening of step edges in highly defective regions. In addition, a reduction of the threshold excitation power density for optically pumped UVC lasers with smooth surface morphologies was observed.
关键词： AlN,off-cut,optically pumped laser,sapphire,UVC,ELO
更新于2025-09-11 14:15:04
-
Effects of UVB and UVC irradiation on cariogenic bacteria in vitro
摘要： The aim of this study was to evaluate the bactericidal effect of ultraviolet (UV) light at 265-nm (UVC) and 310-nm (UVB) wavelengths from a newly developed UV light-emitting diode (LED) device against cariogenic bacteria in vitro. Suspensions of Streptococcus mutans (S. mutans) and Streptococcus sobrinus were directly irradiated by UVB or UVC for 2.5 min or 5 min. Numbers of colonies were counted and calculated as colony forming units (CFU) per milliliter. Fluorescence microscopy (FM) and optical density measurements at 490 nm (OD490) were also taken after irradiation. In addition, the bactericidal effects of irradiation against S. mutans under 0.5 mm-thick dentin were compared using culture tests and OD490 measurements. Direct UV-LED irradiation with both UVB and UVC showed strong bactericidal effects. UVB showed superior bactericidal effect through 0.5-mm-thick dentin than did UVC, especially after demineralization. These results suggest that UVB irradiation could be utilized for the prevention and management of dental caries.
关键词： UVB,UVC,Demineralized dentin,Streptococcus sobrinus,Streptococcus mutans,UV-LED
更新于2025-09-10 09:29:36
-
Mechanisms underlying the protective effects of blueberry extract against ultraviolet radiation in a skin cell co-culture system
摘要： Ultraviolet radiation induces skin damage, inflammation, and aging. To explore the protective effects of blueberry extract (BE) against ultraviolet-C (UV-C) radiation, we analysed human skin keratinocyte (HaCaT) and human foreskin fibroblast (HFF) cells alone or in a co-culture, treated or not with BE, after exposure to UV-C. Surprisingly, MMP-1 was significantly up-regulated in HFF cells and in the co-cultured cell group in response to UV-C irradiation (8 mJ/cm2), but not in HaCaT cells. As expected, BE had a significantly protective effects; it decreased DNA fragmentation and inhibited MMP-1 and inflammatory factors expression in response to UV-C radiation. In addition, BE reduced the accumulation of proteins (MMP-1, c-fos, and c-jnu) in the MAPK (mitogen-activated protein kinase) pathway after UV-C radiation. Taken together, these results showed that BE exerted a protective effect against UV-C irradiation, and modulated MMP-1 production through MAPK signalling by direct and indirect pathways in HaCaT and HFF cells.
关键词： UVC,MAPK signals,Anti-ultraviolet,Co-culture models,Blueberry extracts
更新于2025-09-09 09:28:46