Comparative Study of Structural and Electronic Properties of Cu-based Multinary Semiconductors

We present a systematic and comparative study of the structural and electronic properties of Cu-based ternary and quaternary semiconductors using first-principles electronic structure approaches. The important role that Cu d electrons play in determining their properties is illustrated by comparing results calculated with different exchange correlation energy functionals. We show that systematic improvement of the calculated anion displacement can be achieved by using the Heyd-Scuseria-Ernzerhof (HSE06) functional compared with the Perdew-Burke-Ernzerhof (PBE) functional. Quasiparticle band structures are then calculated within the G0W0 approximation using the crystal structures optimized within the HSE06 functional and starting from the PBE+U mean-field solution. Both the calculated quasiparticle band gaps and their systematic variation with chemical constituents agree very well with experiments. We also predict that the quasiparticle band gaps of the prototypical semiconductor Cu2ZnSnS4 in the kesterite (KS) phase is 1.65 eV and that of the stannite (ST) phase is 1.40 eV. These results are also consistent with available experimental values which vary from 1.45 to 1.6 eV.Comment: 21 pages, 8 figures, 2 table

Holographic Grating Enhancement of TI/PMMA Polymers in the Dark Diffusion Process

The dark diffusion enhancement process (DDEP) caused by photopolymerization during the pre-exposure of TI/PMMA (titanocene dispersed methyl methacrylate matrix) polymers was theoretically analyzed and experimentally investigated, revealing the holographic grating enhancement of TI/PMMA polymers in the post-exposure process without additional operations. The diffusion of photo-initiators and photoproducts dominated the grating enhancement process after exposure. We adopted two pre-exposure methods, long-time (second level) and short-time (millisecond level) laser exposure, at 532 nm, to investigate the DDEP during the post-exposure process. A five-fold enhancement in grating strength was achieved in consecutive long-time pre-exposures, while a two-fold grating development was examined after short-time exposure. Additionally, the exposure durations and repetition rates influenced the grating increment of the DDEP. This study provided a basis for the feasibility of holographic application in TI/PMMA photopolymers via the dark diffusion effect

Dual nonlinearity Controlling of Mode and Dispersion Properties in Graphene-Dielectric Plasmonic Waveguide

Abstract We study the mode and dispersion properties of graphene-dielectric nonlinear plasmonic waveguide considering the dual nonlinearity of dielectric and graphene. For TM polarization, the mode distribution, the permittivity distribution, and dispersion relation were obtained by numerically solving the Maxwell equations. Compared with the case considering only the nonlinearity of dielectric, the initial field intensity to excite plasmon modes reduces obviously when introducing the dual nonlinearity. In addition, the influence of dual nonlinearity on dispersion relation is discussed, and we find that the graphene’s nonlinearity affects strongly the dispersion properties. The introduction of dual nonlinearity leads to the decrease of the initial field intensity, which has potential application in all-optical switches with low threshold

LSPR Tunable Ag@PDMS SERS Substrate for High Sensitivity and Uniformity Detection of Dye Molecules

At present, the use of efficient and cost-effective methods to construct plasmonic surface-enhanced Raman scattering (SERS) substrates of high sensitivity, uniformity and reproducibility is still crucial to satisfy the practical application of SERS technology. In this paper, a localized surface plasmonic resonance (LSPR) tunable flexible Ag@PDMS substrate was successfully constructed by the low-cost bio-template-stripping method and magnetron sputtering technology. The theory proves that the local electromagnetic field enhancement and “hot spot” distribution is adjustable by modifying the size of the optical cavity unit in the periodicity nanocavity array structure. Experimentally, using rhodamine 6G (R6G) as the target analyte, the SERS performance of optimal Ag@PDMS substrate (Ag film thickness for 315 nm) was researched in detail, which the minimum detection limit was 10−11 M and the enhancement factor was calculated as 8.03 × 108, indicating its high sensitivity. The relative standard deviation (RSD) was calculated as 10.38%, showing that the prepared substrate had excellent electromagnetic field enhancement uniformity. At last, the trace detection of Crystal violet (CV, LOD = 10−9 M) and the simultaneous detection of three common dyes (R6G, CV and Methylene blue (MB) mixture) were also realized. This result suggests that the SERS substrate has a good application prospect in the quantitative and qualitative detection of dye molecules

Advances in Monitoring Soil Nutrients by Near Infrared Spectroscopy

International audienceSoil nutrients play an important role in crop growth, and traditional monitoring methods are still the first choice for high precision measurement. However, it is necessary to have a quicker and simpler way to improve the efficiency of soil nutrient monitoring because of its long monitoring time, pollution and high labor cost. Near infrared spectroscopy has become the focus of its research because of its rapid and pollution-free advantages. At present, using near infrared spectroscopy to distinguish soil types, soil heavy metal pollution technology has become increasingly mature, but the soil nutrients, such as monitoring of soil organic matter, available phosphorus, available potassium, available nitrogen is still in the research stage. This paper reviews the recent research results of soil nutrients in near infrared spectrum monitoring technology based on collation, summary and key technology of common data processing method, and analysis the advantages and disadvantages of different detection methods for soil nutrient direction of near infrared spectroscopy technology put forward suggestions to further research

Holographic stability and storage capacity on bulk green-light sensitive TI/PMMA materials

An emerging cationic photo-initiator titanocene (TI) dispersed poly (methyl methacrylate) (PMMA) photopolymer was fabricated by an optimized three-step thermo-polymerization method with excellent holographic performances. Materials with different thicknesses (1-3 mm) were prepared and characterized experimentally. The influences of material thickness changes on holographic properties have been investigated in detail. We achieved the response time of 4.98s in 1mm TI/PMMAs, while the cumulative gratings strength of 6.88 and single grating diffraction efficiency of 74% in 3 mm ones. Furthermore, gratings recorded in materials were examined with controlling experimental conditions in a green-light two-beam coupling interference system, under different polarization directions, ambient temperatures and intersection angles, respectively. A better holographic recording condition was proposed. Meanwhile, the influence on recording surroundings for TI/PMMA were analyzed. This work can provide a basis to depict the holographic storage capacity and stability in TI/PMMA polymers

Design and Realization of E-Marketing System for Fresh Agricultural Products

This paper firstly introduced the PHP + Oracle database development technology. Based on B/S structure, using MVC (Model View Controller) framework development mode, and in line with actual demands of fresh agricultural products for e-marketing in Shanghai, it designed and expected to realize e-marketing system for fresh agricultural products in B2B2C mode. It made an in-depth analysis from system demands, design of functional modules, design of database, and relevant technologies for system realization