| 1. |
- Zhang, Qinghua, et al.
(författare)
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Quantitative assessments of retinal macular structure among rural-dwelling older adults in China : a population-based, cross-sectional, optical coherence tomography study
- 2024
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Ingår i: BMJ Open. - 2044-6055. ; 14:2
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Tidskriftsartikel (refereegranskat)abstract
- ObjectivesTo quantitatively assess and compare retinal macular structures of rural-dwelling older adults in China using two different optical coherence tomography (OCT) scanners and to examine their associations with demographic, lifestyle, clinical and ocular factors.Design, setting and participants This population-based, cross-sectional study included 971 participants (age ≥60 years) derived from the Multimodal Interventions to Delay Dementia and Disability in Rural China study. We collected data on demographics, lifestyle factors, clinical conditions (eg, cardiovascular disease (CVD)) and ocular factors (eg, visual acuity and spherical equivalent). We used two models of spectral-domain OCT to measure macular parameters in nine Early Treatment Diabetic Retinopathy Study subfields. Data were analysed using the multiple general linear models.Results Spectralis OCT demonstrated higher macular thickness but a lower macular volume than Primus 200 OCT (p<0.05). Nasal quadrant of the inner and outer subfields was the thickest, followed by superior quadrant. Adjusting for multiple potential confounding variables, older age was significantly correlated with lower average inner and outer macular thicknesses and overall macular volume. Men had higher macular parameters than women. The presence of CVD was correlated with lower central macular thickness (β=−6.83; 95% CI: −13.08 to −0.58; p=0.032). Middle school or above was associated with higher average inner macular thickness (β=7.85; 95% CI: 1.14 to 14.55; p=0.022) and higher spherical equivalent was correlated with lower average inner macular thickness (β=−1.78; 95% CI: −3.50 to −0.07; p=0.042).Conclusions Macular thickness and volume assessed by Spectralis and Primus 200 OCT scanners differ. Older age and female sex are associated with lower macular thickness and volume. Macular parameters are associated with education, CVD and spherical equivalent.Trial registeration number MIND-China study (ChiCTR1800017758).
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| 2. |
- Gu, Enyao, et al.
(författare)
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A real-time Raman spectroscopy study of the dynamics of laser-thinning of MoS2 flakes to monolayers
- 2017
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Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 7:12
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Tidskriftsartikel (refereegranskat)abstract
- Transition metal dichalcogenides (TMDCs) in monolayer form have attracted a great deal of attention for electronic and optical applications. Compared to mechanical exfoliation and chemical synthesis, laser thinning is a novel and unique “on-demand” approach to fabricate monolayers or pattern desired shapes with high controllability and reproducibility. Its successful demonstration motivates a further exploration of the dynamic behaviour of this local thinning process. Here, we present an in-situ study of void formation by laser irradiation with the assistance of temporal Raman evolution. In the analysis of time-dependent Raman intensity, an empirical formula relating void size to laser power and exposure time is established. Void in thinner MoS2 flakes grows faster than in thicker ones as a result of reduced sublimation temperature in the two-dimensional (2D) materials. Our study provides useful insights into the laser-thinning dynamics of 2D TMDCs and guidelines for an effective control over the void formation.
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| 3. |
- Zhang, Youwei, et al.
(författare)
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Competing Mechanisms for Photocurrent Induced at the Monolayer-Multilayer Graphene Junction
- 2018
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Ingår i: Small. - : WILEY-V C H VERLAG GMBH. - 1613-6810 .- 1613-6829. ; 14:24
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Tidskriftsartikel (refereegranskat)abstract
- Graphene is characterized by demonstrated unique properties for potential novel applications in photodetection operated in the frequency range from ultraviolet to terahertz. To date, detailed work on identifying the origin of photoresponse in graphene is still ongoing. Here, scanning photocurrent microscopy to explore the nature of photocurrent generated at the monolayer-multilayer graphene junction is employed. It is found that the contributing photocurrent mechanism relies on the mismatch of the Dirac points between the monolayer and multilayer graphene. For overlapping Dirac points, only photothermoelectric effect (PTE) is observed at the junction. When they do not coincide, a different photocurrent due to photovoltaic effect (PVE) appears and becomes more pronounced with larger separation of the Dirac points. While only PTE is reported for a monolayer-bilayer graphene junction in the literature, this work confirms the coexistence of PTE and PVE, thereby extending the understanding of photocurrent in graphene-based heterojunctions.
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| 4. |
- Zhang, Youwei, et al.
(författare)
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Extending the Spectral Responsivity of MoS2 Phototransistors by Incorporating Up-Conversion Microcrystals
- 2018
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Ingår i: Advanced Optical Materials. - : Wiley. - 2162-7568 .- 2195-1071. ; 6:21
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Tidskriftsartikel (refereegranskat)abstract
- Layered 2D semiconductors are characterized by unique photoelectric properties and, therefore, constitute a new class of basic building block for next‐generation optoelectronics. However, their wide bandgaps limit the spectral responsivity to a narrow range. Here, a facile approach is demonstrated by integrating β‐NaYF4:Yb3+, Er3+ up‐conversion microcrystals (UCMCs) with monolayer‐MoS2 phototransistors to break this bandgap‐imposed barrier and to drastically extend the responsivity range. In essence, the UCMCs up‐convert a near‐infrared excitation at 980 nm to visible light of photons with energy matching the large bandgap (i.e., 1.8 eV) of monolayer‐MoS2, thereby activating the phototransistor with remarkable photocurrent and minimum interference. This approach leads to preservation of the excellent electrical merits of monolayer‐MoS2 and simultaneous retention of its low dark current and high photoresponsivity to the above‐bandgap lights. Significantly, an enhancement by over 1000 times is achieved for both responsivity and specific detectivity at 980 nm excitation. Moreover, the rate of response is kept identical to that when the MoS2 phototransistor is excited by a visible light. Therefore, integrating with UCMCs can enable the emerging 2D semiconductors of wide bandgap to respond to infrared excitations with high efficacy and without sacrificing their performance in the visible region.
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