Two-dimensional (2D) layered materials provide a promising alternative solution for overcoming the scaling limits in conventional Si-based devices. However, practical applications of 2D materials are ...facing crucial bottlenecks, particularly that arising from the instability under ambient condition. The studies of degradation mechanisms and protecting strategies for overcoming the ambient instability of 2D materials have attracted extensive research attentions, both experimentally and theoretically. This review attempts to provide an overview on the recent progress of the encapsulation strategies for 2D materials. The encapsulation strategies of mechanical transfer, polymer capping, atomic layer deposition, in-situ oxidation, and surface functionalization are systematically discussed for improving the ambient stability of 2D materials. In addition, the current advances in air-stable and high-performance 2D materials-based field effect transistors (FETs) and photodetectors assisted by the encapsulation strategies are outlined. Furthermore, the future directions of encapsulation techniques of 2D materials for FETs and photodetectors applications are suggested.
Two-dimensional materials’ ambient instability poses a considerable challenge to their practical application in electronics and optoelectronics. Encapsulation provides a powerful strategy for achieving air-stable and high-performance 2D-based device Display omitted .
As an emerging group III−VI semiconductor two-dimensional (2D) material, gallium selenide (GaSe) has attracted much attention due to its excellent optical and electrical properties. In this work, ...high-quality epitaxial growth of few-layer GaSe nanoflakes with different thickness is achieved via chemical vapor deposition (CVD) method. Due to the non-centrosymmetric structure, the grown GaSe nanoflakes exhibits excellent second harmonic generation (SHG). In addition, the constructed GaSe nanoflake-based photodetector exhibits stable and fast response under visible light excitation, with a rise time of 6 ms and decay time of 10 ms. These achievements clearly demonstrate the possibility of using GaSe nanoflake in the applications of nonlinear optics and (opto)-electronics.
Reduced nicotinamide adenine dinucleotide (NADH) plays a crucial role in many biochemical reactions in human metabolism. In this work, a flow-mediated skin fluorescence (FMSF)–post-occlusion reactive ...hyperaemia (PORH) system was developed for noninvasive and in vivo measurement of NADH fluorescence and its real-time dynamical changes in human skin tissue. The real-time dynamical changes of NADH fluorescence were analyzed with the changes of skin blood flow measured by laser speckle contrast imaging (LSCI) experiments simultaneously with FMSF-PORH measurements, which suggests that the dynamical changes of NADH fluorescence would be mainly correlated with the intrinsic changes of NADH level in the skin tissue. In addition, Monte Carlo simulations were applied to understand the impact of optical property changes on the dynamical changes of NADH fluorescence during the PORH process, which further supports that the dynamical changes of NADH fluorescence measured in our system would be intrinsic changes of NADH level in the skin tissue.
Phosphorite is a nonrenewable strategic resource, a convenient and rapid method of phosphorite grade identification and classification is important to improve phosphate utilization. In this study, ...Raman spectroscopy has been combined with principal component analysis and hierarchical clustering analysis (PCA-HCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) models for an investigation of different grade phosphorite samples. Both the PCA-HCA and OPLS-DA models showed that different grade phosphorite samples can be clearly distinguished by statistically analyzing the Raman spectra after smoothing, baseline correction, and first derivation. In addition, the S-line study on the OPLS-DA model clearly demonstrated that the symmetrical stretching vibrational mode of phosphate near 960 cm−1 had a much more significant contribution than other vibrational modes for the differentiation of different grade phosphorite samples.
Two-dimensional (2D) β-In2S3 with a natural defective structure is a promising semiconductor for electronic and optoelectronic applications. Herein, oxidation of 2D β-In2S3 is investigated by ...photoluminescence, Raman scattering, and X-ray photoelectron spectroscopy studies for understanding its optoelectronic properties. Our results show that the intrinsic structural defects of sulfur vacancies induce the oxidation of β-In2S3, which can act as active sites to adsorb oxygen in air. Oxygen atoms react with indium atoms to form an inner layer of In2S3-3xO3x and outer layer of In2O3, resulting in intriguing optical properties over the exposure time to air. Moreover, the energy level diagram based on the defect-mediated oxidation process is presented. Additionally, the effect of oxidation under ambient air on β-In2S3 based photodetector and field effect transistor is investigated. Our study provides an in-depth understanding of the oxidation process of 2D β-In2S3 and paves a fundamental step for its potential applications in future electronics and optoelectronics.
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•Defects can act as active sites for molecule adsorption in air to induce oxidation.•β-In2S3 is a typical natural defective crystal.•Photoluminescence of two-dimensional β-In2S3 varies as the exposure time to air.•Performance of photoresponsivity degrades while mobility increases after oxidation.
•The chemical vapor deposition method realizes the controllable preparation of uniform γ-In2Se3 nanosheets.•Growing γ-In2Se3 nanosheets on SiO2/Si substrates can avoid potential contamination and ...damage during the transfer process.•The prepared γ-In2Se3 based photodetector has a stable broadband optical response.
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Two-dimensional (2D) In2Se3 with excellent optical and electrical properties has great application potential for flexible devices, photodetectors, and phase change memories. Here, we report the successes of growing In2Se3 nanosheets on SiO2/Si substrates by chemical vapor deposition (CVD) and fabricating broadband photodetector based on In2Se3. The Raman spectroscopy and transmission electron microscopy studies indicate that our 2D In2Se3 is in γ-phase. Our 2D γ-In2Se3 photodetector shows a broadband response range from near ultraviolet (350 nm) to infrared (1000 nm). The stable broadband response provides opportunities for the application of 2D γ-In2Se3-based devices and also a reference for the preparation and application of other 2D materials.
With the rise of two-dimensional (2D) materials, layered metal thiophosphates (MPS3), as an important branch, have attracted much attention because of their excellent physical and chemical ...properties. Cadmium phosphorus trisulfide (CdPS3), as a promising photocatalyst, can be used for hydrogen evolution and organic degradation. Herein, high-quality 2D CdPS3 few layers are obtained by exfoliating bulk CdPS3 crystal. The optical properties of the as-obtained CdPS3 few layers show good light-harvesting ability, endowing it with excellent photocatalytic hydrogen evolution performance (10.88 mmol g−1 h−1) and high organic degradation performance (more than 92% within 30 min) under Xe lamp irradiation. This research provides opportunities for the preparation and application of other 2D MPS3 type materials in the field of photocatalysis.
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•CdPS3 few layers can be exfoliated from bulk crystals by a facile method.•CdPS3 few layers have highly efficient photocatalytic performance.•CdPS3 few layers have excellent Rh B degradation performance.
In order to reduce the influence of scattering and absorption on tissue fluorescence spectra, after tissue fluorescence and diffuse reflectance in different tissue optical properties were simulated ...by the Monte Carlo method, a tissue intrinsic fluorescence recovering algorithm making use of diffuse reflectance spectrum was developed. The empirical parameters in the tissue intrinsic fluorescence recovering algorithm were coded as a particle in the solution domain, the classification performance was defined as the fitness, and then a particle swarm optimization (PSO) algorithm was established for empirical parameters optimization. The skin autofluorescence and diffuse reflectance spectra of 327 subjects were collected in Anhui Provincial Hospital. The skin intrinsic autofluorescence spectra were recovered by using the empirical approach and the integration area of the spectra were calculated as fluorescence intensity. Receiver operating characteristic (ROC) analysis for fluorescence intensity was applied to evaluate the classification performance in type 2 diabetes screening. In addition, a support vector machine (SVM) method was implemented to improve the performance of the classification. The results showed that the sensitivity and specificity were 32% and 76% respectively, and the area under the curve was 0.54 before recovering, while the sensitivity and specificity were 72% and 86% respectively, and the area under the curve was 0.86 after recovering. Furthermore, the sensitivity and specificity increased to 83% and 86% respectively when using linear SVM while 84% and 88%, respectively, when using nonlinear SVM. The results indicate that using the tissue fluorescence spectrum recovery algorithm based on PSO can improve the application of tissue fluorescence spectroscopy effectively.
Abstract
Preventing aggregation of amyloid beta (Aβ) peptides is a promising strategy for the treatment of Alzheimer’s disease (AD), and gold nanoparticles have previously been explored as a ...potential anti-Aβ therapeutics. Here we design and prepare 3.3 nm L- and D-glutathione stabilized gold nanoparticles (denoted as L3.3 and D3.3, respectively). Both chiral nanoparticles are able to inhibit aggregation of Aβ42 and cross the blood-brain barrier (BBB) following intravenous administration without noticeable toxicity. D3.3 possesses a larger binding affinity to Aβ42 and higher brain biodistribution compared with its enantiomer L3.3, giving rise to stronger inhibition of Aβ42 fibrillation and better rescue of behavioral impairments in AD model mice. This conjugation of a small nanoparticle with chiral recognition moiety provides a potential therapeutic approach for AD.
The consolidation of municipal districts is a momentous change in administrative divisions, which are formulated by municipal governments to optimize the layout of urban functions and coordinate ...regional development. How the consolidation of municipal districts affects property values in relevant areas has yet to be empirically tested. Using resold property transaction micro-data, this study empirically explores the impact of the consolidation of Jing'an and Zhabei districts in Shanghai on the property values via boundary difference-in-difference estimation. Empirical results show that, during the sample period, i) the overall property values in the consolidated region increased by 1.6% after the consolidation, ii) the consolidation increased property values by 4.8% in the less developed Zhabei but had no significant impact on the property values in the more developed Jing'an, and iii) the consolidation had an expanding impact on the property values in Zhabei district over time.
•The effect of district consolidation, a momentous change in administrative division, on property values has seldomly studied.•We explore the response of property values to a district consolidation case in Shanghai by boundary difference-in-difference.•The consolidation causes a rise in property values by 1.6% in the consolidated two districts.•The impact of consolidation on property values in the more developed Jing'an is insignificant.•The property values in less-developed Zhabei have increased by 4.8% since the consolidation is reported.
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