Assessing the optical properties of chalcogenide glasses and fibres: towards the development of new light sources

Owing to their properties of mid-infrared (MIR) transparency, high refractive index, low phonon energy, high optical non-linearity, and an ability to dope them with rare-earth element ions, chalcogenide glasses are a promising candidate for planar photonic integrated circuits, and narrow- and broad-band fibre-based laser sources and amplifiers for the MIR. Although much research effort has been paid to the development and characterisation of chalcogenide glasses for photonics, relatively little refractive index dispersion data are presently available at MIR wavelengths. Therefore, the aim of this Project is to assess the optical properties, especially refractive index, material dispersion and thermo-optic coefficient, of the chalcogenide glasses and fibres (As40Se60, Ge16As24Se15.5Te44.5, Ge20Sb10Se70 and Ge20Sb10Se67S3 at. % (atomic %)) fabricated for developing MIR light source and fibre-sensing. As a well-know technique to determine the refractive index with a high accuracy, the minimum deviation method is applied to determine the refractive index of the chalcogenide glasses investigated in this Project. The errors in each part of the minimum deviation measurement using our experimental setup are analysed using a commercial LAF850322 right-angled prism. The refractive indices of different chalcogenide glass prisms are then successfully measured at wavelengths of ~1500 nm, 3100 nm, 3800 nm and 6450 nm with a standard deviation of less than 0.001 refractive index unit (RIU)) using different light sources. The results obtained are taken as the benchmark values for the techniques developed later. After analysing in the literature the refractive index change with changing composition of Ge-As-Se-Te, an interpolation modelling scheme for estimating the refractive index of GexAsz-xSe100-z-yTey within the range of 10≤x≤25, 40≤y≤50 and 30≤z≤40 is set up with an error of less than 0.22 %. To investigate a suitable refractive index model to describe the refractive index dispersion of chalcogenide glasses in the MIR region, several refractive index models (the Cauchy and Sellmeier models) are applied to fit the refractive index data points of the Ge16As24Se15.5Te44.5 at. %, As40Se60 at. %, Ge10As23.4Se66.6 at. %, Ge16.5As16Ga3Se64.5 at. % and Pr3+ doped Ge16As21Ga1Se62 at. % glasses made in-house, obtained using spectroscopic ellipsometry at MIR wavelengths. A two-term Sellmeier model, with one resonant optical bandgap electronic absorption and one resonant MIR fundamental vibrational absorption, is verified to be unique and sufficient to describe the refractive index dispersion of the chalcogenide glasses within their transparent windows. The numerical aperture of a step-index fibre based on an As40Se60 at. % core and Ge10As23.4Se66.6 at. % cladding and a step-index fibre based on the Ge16As24Se15.5Te44.5 at. % and Ge10As23.4Se66.6 at. % glass pair is respectively calculated to be larger than 0.97 and 1.86 over the wavelength range from 0.5 to 30 µm. The two-term Sellmeier fits to the measured refractive index data are also used to calculate material dispersion characteristics for these compositions. The well-known method presented by Swanepoel can be used to determine the refractive index dispersion of thin films over the wavelength range from 0.7 to 2 µm from wavelength values at maxima and minima, only, of the transmission interference fringes. In order to extend this method into the MIR spectral region (measurements described are over the wavelength range from 2 to 25 µm), the method is improved by using a two-term Sellmeier model instead of the Cauchy model as the dispersive equation. The refractive index dispersion of hot-pressed chalcogenide thin films is determined by the improved method with a standard deviation of less than 0.002. The accuracy of the method is shown to be within 0.4% with of a benchmark refractive index value obtained from prism measurements at a wavelength of 3.1 µm. The refractive indices of other compositions investigated in this Project were also determined using this method. A simple technique is proposed to determine the small refractive index contrast of a low numerical aperture (NA) glass pair. A core fibre (Ge20Sb10Se70 at. %) is hot-pressed together with a cladding fibre (Ge20Sb10Se67S3 at. %) to form a two-composition thin film with the advantages of the two glasses having the same thermal history and post-fibre processing. The refractive index contrast can be simply determined with an error of less than ±0.002 only using their FTIR (Fourier transform infrared) transmission spectra. Moreover, a 3 at. % substitution of S for Se in the Ge-Sb-Se glass system is shown to blue-shift the visible (VIS) optical bandgap, the MIR fundamental vibrational absorption bands, the zero dispersion wavelength and lower the refractive index. In this Project, the effect of temperature on the optical properties of chalcogenide glasses, including their transparent windows, impurity and multiphonon absorptions, refractive index, zero dispersion wavelengths and thermo-optic coefficients of the chalcogenide glasses is investigated. In order to obtain the continuous thermo-optic coefficient of a chalcogenide glass at MIR wavelengths, the FTIR continuous dn/dT method is proposed based on the FTIR transmission spectra at upper and lower temperatures. It is shown that this method can successfully determine the thermo-optic coefficients of the chalcogenide glass thin films (Ge16As24Se15.5Te44.5 at. % and As40Se60 at. %) over the wavelength range from 2 to 20 µm with an error of less than ±7.5 ppm (parts per million) /ºC. The proposed method is shown to provide a much lower error than the minimum deviation method and the improved Swanepoel method. In summary, some techniques are successfully developed to obtain the refractive index, material dispersion data and thermo-optic coefficients for bulk chalcogenide glasses and chalcogenide glass thin films in the MIR region in this Project. These data are useful for the design of step-index fibres for new MIR light sources and fibre-sensing

Determining the continuous thermo-optic coefficients of chalcogenide glass thin films in the MIR region using FTIR transmission spectra

A new method (FTIR continuous dn / dT method, n is refractive index and T temperature) for measuring the continuous thermo-optic coefficients of thin transparent films in the mid-infrared (MIR) spectral region is introduced. The technique is based on Fourier transform infrared (FTIR) transmission spectra measured at different temperatures. It is shown that this method can successfully determine the thermo-optic coefficient of chalcogenide glass thin films (of batch compositions Ge20Sb10Se70 at. % (atomic %) and Ge16As24Se15.5Te44.5 at. %) over the wavelength range from 2 to 25 µm. The measurement precision error is less than ±11.5 ppm / ºC over the wavelength range from 6 to 20 µm. The precision is much better than that provided by the prism minimum deviation method or an improved Swanepoel method

Primerjalna študija genetske raznovrstnosti talnih bakterij in gliv v različnih sukcesijah vegetacije na krasu v provinci Guizhou, Kitajska

To study the soil genetic diversity of bacteria and fungi in different vegetation successions (grassland, shrubbery, primary forest and secondary forest) from the karst area, the Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) technology was applied. The results showed that: (1) the diversity of bacterial communities and the fungal communities in karst area were higher than non karst area in each vegetation succession. Compared with the survey from bacterial (the Shannon index was 2.97 in primary forest, 2.91 in secondary forest, 3.18 in shrubbery, 3.14 in grassland and 2.68 in non karst), fungal diversity between karst areas (the Shannon index was 3.56 in primary forest, 3.78 in secondary forest, 3.73 in shrubbery and 3.70 in grassland) and non karst areas (the Shannon index was 3.08) was more evident, which may be related to the alterations of the composition of plant community and the source of carbon in soil with the vegetation succession of karst ecosystem; (2) The comparation of bacterial diversity index and the richness comprehensively evaluated as follows: shrubbery > grassland > primary forest > nsecondary forest. The diversity index and the richness of fungal communities was as follows: secondary forest > shrubbery > grassland > primary forest. The results suggest that the fungal communities have been greatly changed via vegetation successions, but the diversity index and the richness of the bacterial communities have not been seriously affected. The results provide scientific basis for understanding karst surface ecosystem, which contributes to the future aim of protecting the karst from desertification.Za proučevanje genetske pestrosti talnih bakterij in gliv v različnih sukcesijah vegetacije (travišče, grmičevje, primarni gozd in sekundarni gozd) na krasu je bila uporabljena tehnologija verižne reakcije s polimerazo-denaturirajoča gradientna gelska elektroforeza (PCR-DGGE). Rezultati raziskave so pokazali, da: (1) je bila v vsaki sukcesiji vegetacije pestrost bakterijskih in glivnih združb na kraškem območju višja kot na nekraškem. V primerjavi z bakterijsko raznovrstnostjo (Shannonov indeks je bil 2,97 v primarnem gozdu, 2,91 v sekundarnem gozdu, 3,18 v tleh grmičevja, 3,14 v tleh travišč in 2,68 v nekraškem območju) je bila raznovrstnost gliv med kraškimi območji (Shannonov indeks je bil v primarnem gozdu 3,56, 3,78 v sekundarnem gozdu, 3,73 v tleh grmičevja in 3,70 v tleh travišč) in nekraškimi (Shannonov indeks je bil 3,08) jasneje izražena. To je lahko povezano s spremembami v sestavi rastlinske združbe in vira ogljika v tleh glede na stanje sukcesije v vegetaciji kraškega ekosistema. (2) Primerjava kazalnikov bakterijske raznovrstnosti in abundance je bila celostno ovrednotena in sledi takole: grmičevje > travišče > primarni gozd > sekundarni gozd. Kazalnika raznovrstnosti in abundance glivnih združb kažeta sledeči trend: sekundarni gozd > grmičevje > travišče > primarni gozd. Rezultati izkazujejo, da so se glivne združbe precej spremenile zaradi sukcesije v vegetaciji, vendar pa na drugi strani ni bilo bistvenega vpliva na kazalnika bakterijske raznovrstnosti in abundance. Rezultati med drugim dajejo tudi znanstveno podlago za razumevanje delovanja kraškega površinskega ekosistema, kar ključno prispeva k cilju zaščite krasa pred dezertifikacijo (širjenjem puščav)

Assessing the optical properties of chalcogenide glasses and fibres: towards the development of new light sources

Owing to their properties of mid-infrared (MIR) transparency, high refractive index, low phonon energy, high optical non-linearity, and an ability to dope them with rare-earth element ions, chalcogenide glasses are a promising candidate for planar photonic integrated circuits, and narrow- and broad-band fibre-based laser sources and amplifiers for the MIR. Although much research effort has been paid to the development and characterisation of chalcogenide glasses for photonics, relatively little refractive index dispersion data are presently available at MIR wavelengths. Therefore, the aim of this Project is to assess the optical properties, especially refractive index, material dispersion and thermo-optic coefficient, of the chalcogenide glasses and fibres (As40Se60, Ge16As24Se15.5Te44.5, Ge20Sb10Se70 and Ge20Sb10Se67S3 at. % (atomic %)) fabricated for developing MIR light source and fibre-sensing. As a well-know technique to determine the refractive index with a high accuracy, the minimum deviation method is applied to determine the refractive index of the chalcogenide glasses investigated in this Project. The errors in each part of the minimum deviation measurement using our experimental setup are analysed using a commercial LAF850322 right-angled prism. The refractive indices of different chalcogenide glass prisms are then successfully measured at wavelengths of ~1500 nm, 3100 nm, 3800 nm and 6450 nm with a standard deviation of less than 0.001 refractive index unit (RIU)) using different light sources. The results obtained are taken as the benchmark values for the techniques developed later. After analysing in the literature the refractive index change with changing composition of Ge-As-Se-Te, an interpolation modelling scheme for estimating the refractive index of GexAsz-xSe100-z-yTey within the range of 10≤x≤25, 40≤y≤50 and 30≤z≤40 is set up with an error of less than 0.22 %. To investigate a suitable refractive index model to describe the refractive index dispersion of chalcogenide glasses in the MIR region, several refractive index models (the Cauchy and Sellmeier models) are applied to fit the refractive index data points of the Ge16As24Se15.5Te44.5 at. %, As40Se60 at. %, Ge10As23.4Se66.6 at. %, Ge16.5As16Ga3Se64.5 at. % and Pr3+ doped Ge16As21Ga1Se62 at. % glasses made in-house, obtained using spectroscopic ellipsometry at MIR wavelengths. A two-term Sellmeier model, with one resonant optical bandgap electronic absorption and one resonant MIR fundamental vibrational absorption, is verified to be unique and sufficient to describe the refractive index dispersion of the chalcogenide glasses within their transparent windows. The numerical aperture of a step-index fibre based on an As40Se60 at. % core and Ge10As23.4Se66.6 at. % cladding and a step-index fibre based on the Ge16As24Se15.5Te44.5 at. % and Ge10As23.4Se66.6 at. % glass pair is respectively calculated to be larger than 0.97 and 1.86 over the wavelength range from 0.5 to 30 µm. The two-term Sellmeier fits to the measured refractive index data are also used to calculate material dispersion characteristics for these compositions. The well-known method presented by Swanepoel can be used to determine the refractive index dispersion of thin films over the wavelength range from 0.7 to 2 µm from wavelength values at maxima and minima, only, of the transmission interference fringes. In order to extend this method into the MIR spectral region (measurements described are over the wavelength range from 2 to 25 µm), the method is improved by using a two-term Sellmeier model instead of the Cauchy model as the dispersive equation. The refractive index dispersion of hot-pressed chalcogenide thin films is determined by the improved method with a standard deviation of less than 0.002. The accuracy of the method is shown to be within 0.4% with of a benchmark refractive index value obtained from prism measurements at a wavelength of 3.1 µm. The refractive indices of other compositions investigated in this Project were also determined using this method. A simple technique is proposed to determine the small refractive index contrast of a low numerical aperture (NA) glass pair. A core fibre (Ge20Sb10Se70 at. %) is hot-pressed together with a cladding fibre (Ge20Sb10Se67S3 at. %) to form a two-composition thin film with the advantages of the two glasses having the same thermal history and post-fibre processing. The refractive index contrast can be simply determined with an error of less than ±0.002 only using their FTIR (Fourier transform infrared) transmission spectra. Moreover, a 3 at. % substitution of S for Se in the Ge-Sb-Se glass system is shown to blue-shift the visible (VIS) optical bandgap, the MIR fundamental vibrational absorption bands, the zero dispersion wavelength and lower the refractive index. In this Project, the effect of temperature on the optical properties of chalcogenide glasses, including their transparent windows, impurity and multiphonon absorptions, refractive index, zero dispersion wavelengths and thermo-optic coefficients of the chalcogenide glasses is investigated. In order to obtain the continuous thermo-optic coefficient of a chalcogenide glass at MIR wavelengths, the FTIR continuous dn/dT method is proposed based on the FTIR transmission spectra at upper and lower temperatures. It is shown that this method can successfully determine the thermo-optic coefficients of the chalcogenide glass thin films (Ge16As24Se15.5Te44.5 at. % and As40Se60 at. %) over the wavelength range from 2 to 20 µm with an error of less than ±7.5 ppm (parts per million) /ºC. The proposed method is shown to provide a much lower error than the minimum deviation method and the improved Swanepoel method. In summary, some techniques are successfully developed to obtain the refractive index, material dispersion data and thermo-optic coefficients for bulk chalcogenide glasses and chalcogenide glass thin films in the MIR region in this Project. These data are useful for the design of step-index fibres for new MIR light sources and fibre-sensing

Research status, trends, and mechanisms of biochar adsorption for wastewater treatment: a scientometric review

Abstract In the last decade, biochar application research has emerged as a hot topic in water treatment studies, which made biochar adsorption one of the primary wastewater treatment strategies. This paper presents a global bibliometric analysis of 2673 publications from the Web of Science database, spanning 2011–2022. For a comprehensive understanding of the research status and trends in biochar adsorption for wastewater treatment, the advanced quantitative and visual analysis tools (i.e., CiteSpace and ArcGIS) were employed. The results showed that China emerged as the leading country with the most published articles. The key research area is on the magnetic adsorption of biochar in wastewater. The articles summarized in the review demonstrated unequivocally that biochar can treat a wide range of wastewater even though the adsorption mechanisms of biochar on heavy metals, inorganic salts and organic pollutants in wastewater are not entirely consistent. The review further analyzes the factors affecting the performance of biochar in adsorbing pollutants from wastewater and the improvement measures of biochar functional characteristics, proposing the future research directions focusing on the improvement of the adsorption capacity of biochar products. The information synthesis and discussion would provide valuable insights on the historical, current, and future trends in biochar research, beneficial to solve the practical problems of water pollution and improve the quality of the environment

Wheat Germ-Derived Peptide Alleviates Dextran Sulfate Sodium-Induced Colitis in Mice

This study explores the protective properties and potential mechanisms of wheat-germ-derived peptide APEPEPAF (APE) against ulcerative colitis. Colitis mice induced by dextran sulfate sodium (DSS) were used as the animal model. The results showed that the APE peptide could alleviate colitis symptoms including weight loss, colon shortening, and histopathological changes. This peptide attenuated the generation of inflammatory cytokines by inhibiting the phosphorylation of protein kinase PKCζ (Thr410) and NF-κB transcriptional activity in DSS-induced mice, suggesting that APE ameliorates colitis inflammation by regulating the PKCζ/NF-κB signaling pathway. APE also preserved the barrier function of the colon by dose-dependently promoting the expression of tight junction proteins (claudin-1, zonula occluded-1, and occludin). In addition, APE significantly decreased the abundance of Bacteroides and increased the abundance of Dubosiella and Lachnospiraceae_UCG-006 to improve the intestinal flora imbalance in DSS-induced colitis mice. Therefore, wheat germ peptide APE can be used as a novel agent and dietary supplement to treat ulcerative colitis.

Intra-bronchial epithelial Shp2 depletion exert little effects on OVA-induced inflammation and TH2 and TH17 polarization.

<p>Twenty-four hours after the last challenge, the cellular profiles (A) were analyzed, and total cell numbers (B) were counted in BALF of mice. (C) IL-4, IL-17 and foxp3 mRNA were measured in the lung tissues of the mice. (D) Ratios of TH2 (stained by FITC-CD4 and APC-IL-4) and TH17 (stained by FITC-CD4 and PE-IL-17A) in the lung homogenates. (n = 5 mice/group, in two separate experiments). Results were expressed as mean ± SEM. ^n.s.<i>p</i> >0.05. PBS_ave: average value of three PBS subgroups, including <i>CC10-rtTA /Shp2</i>^<i>f/f</i>:DOX (toxicity control, TC), <i>CC10-rtTA/(tetO)7-Cre/Shp2</i>^<i>f/f</i>:H₂O (Shp2^F/F), and <i>CC10-rtTA/(tetO)7-Cre/Shp2</i>^<i>f/f</i>:DOX (Shp2^△/△). ^n.s.<i>p>0</i>.<i>05</i>. Eos: Eosinophil, Neu: Neutrophil, Lym: Lymphocyte, Macro: Macrophage.</p