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Te-based glasses are ideal material for life detection and infrared-sensing applications because of their excellent far-infrared properties. In this study, the influence of Ag- and AgI- doped Te-based glasses were discussed. Thermal and optical properties of the prepared glasses were evaluated using X-ray diffraction, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Results show that these glass samples have good amorphous state and thermal stability. However, Ge–Ga–Te–Ag and Ge–Ga–Te–AgI glass systems exhibit completely different in optical properties. With an increase of Ag content, the absorption cut-off edge of Ge–Ga–Te–Ag glass system has a red shift. On the contrary, a blue shift appears in Ge–Ga–Te–AgI glass system with an increase of AgI content. Moreover, the transmittance of Ge–Ga–Te–Ag glass system deteriorates while that of Ge–Ga–Te–AgI glass system ameliorates. All glass samples have wide infrared transmission windows and the far-infrared cut-off wavelengths of these glasses are beyond 25 μm. The main absorption peaks of these glasses are eliminated through a purifying method. [ABSTRACT FROM AUTHOR]

CO 2 molecule, one of the main molecules to create new life, should be probed accurately to detect the existence of life in exoplanets. The primary signature of CO 2 molecule is approximately 15 μm, and traditional S- and Se-based glass fibers are unsuitable. Thus, Te-based glass is the only ideal candidate glass for far-infrared detection. In this study, a new kind of Te-based chalcohalide glass system was discovered with relatively stable and large optical band gap. A traditional melt-quenching method was adopted to prepare a series of (Ge 15 Ga 10 Te 75 ) 100− x (CsBr) x chalcogenide glass samples. Experiment results indicate that the glass-forming ability and thermal properties of glass samples were improved when CsBr was added in the host of Ge–Ga–Te glass. Ge–Ga–Te glass could remarkably dissolve CsBr content as much as 85 at.%, which is the highest halide content in all reports for Te-based chalcohalide glasses. Moreover, Δ T values of these glass samples were all above 100 °C. The glass sample (Ge 15 Ga 10 Te 75 ) 65 (CsBr) 35 with Δ T of 119 °C was the largest, which was 7 °C larger than that of Ge 15 Ga 10 Te 75 host glass. The infrared transmission spectra of these glasses show that the far-infrared cut-off wavelengths of (Ge 15 Ga 10 Te 75 ) 100− x (CsBr) x chalcogenide glasses were all beyond 25 μm. In conclusion, (Ge 15 Ga 10 Te 75 ) 100− x (CsBr) x chalcogenide glasses are potential materials for far-infrared optical application. [ABSTRACT FROM AUTHOR]

In this study, a novel Te-based glass system was investigated. Some properties of Ge–Ga–Te–NaI chalcogenide glasses such as physical, thermal and optical transmitting were discussed. XRD patterns show this glass system with best amorphous state can dissolve content of NaI as much as 35 at.%. The lowest cut-off wavelength of glass samples is 1645 nm which is the smallest wavelength among the reported Te-based glasses doping with halide. DSC curves indicate that all glass samples have good thermal stabilities (Δ T > 100 °C) and the highest Δ T value corresponding to (Ge 15 Ga 10 Te 75 ) 85 (NaI) 15 glass is 120 °C which is 8 °C greater than that of Ge–Ga–Te host glass. The infrared spectra manifest Ge–Ga–Te–NaI chalcogenide glass system has a wide infrared transmission window between 1.6 μm and 20 μm. Consequently, Ge–Ga–Te–NaI glasses can be a candidate material for far infrared optic imaging and bio-sensing applications. [ABSTRACT FROM AUTHOR]

Chalcogenide glasses of the GeSbSeI ( x = 0, 5, 10, 15, 20 at.%) system were prepared. This study was performed to examine some Ge-Sb-Se-I glass physical and optical properties, the structural evolution of the glass network, and the optical properties of the infrared glass fibers based on our previous studies. The variation process of the glass physical properties, such as transition temperature, glass density, and refractive index, was investigated from the glass of GeSbSe to the GeSbSeI glass series. The structural evolutions of these glasses were examined by Raman spectroscopy. The GeSbSeI composition was selected for the preparation of the IR fiber. The GeSbSeI glass was purified through distillation, and the intensity of the impurity absorption peaks caused by Ge-O, HO, and Se-H was reduced or eliminated in the purified glasses. Then, GeSbSeI chalcogenide glass fiber for mid-infrared transmission was fabricated using high-purity materials. The transmission loss of the GeSbSeI fiber was greatly reduced compared with that of the GeSbSe glass fiber. The lowest losses obtained were 3.5 dB/m at 3.3 μm for GeSbSeI fiber, which was remarkably improved compared with 48 dB/m of the unpurified GeSbSe fiber. [ABSTRACT FROM AUTHOR]

The enantioselective hydrolysis of ortho-chloromandelonitrile with nitrilase is one of the most attractive approaches to prepare ( R)- ortho-chloromandelic acid. To date, efforts to develop this nitrilase-mediated process were plagued by either insufficient eep (enantiomeric excess of product) or low activity due to the steric hindrance from the ortho-substituted substrate. To improve the nitrilase potential for producing ( R)- ortho-chloromandelic acid, an enhancement of both activity and enantioselectivity towards sterically hindered nitriles would be highly desirable. Molecular docking of the ( R)- ortho-chloromandelonitrile into the active site of wild-type 2A6 nitrilase (nitA) allowed the identification of proximal nitA active site residues. Several residues (52, 132, 189 and 190) were selected as targets for single and double point mutation to improve nitA activity and enantioselectivity towards ortho-chloromandelonitrile. Targeted mutagenesis yielded several nitA variants with superior activity and enantioselectivity. The best mutant T132A/F189T exhibited a 4.37-fold higher specific activity (7.39 U/mg) towards ortho-chloromandelonitrile than the wild-type nitA. More importantly, the enantioselectivity ( E) was improved from 17.34 to >200, resulting in a highly enantiopure product. Molecular docking experiments further support the enhanced activity and enantioselectivity shown experimentally and the structural effects of this amino acid substitution on the active site of nitA are provided. The amino acids at sites 189 and 132 determine the activity and enantioselectivity towards ortho-chloromandelonitrile. With mutant T132A/F189T as a catalyst, a maximum of 450 mM of ( R)- ortho-chloromandelic acid was produced with a 90% conversion and >99% eep within 3 h. This is the first time that a high productivity of ( R)- ortho-chloromandelic acid of up to 671.76 g L−1 d−1 using a nitrilase-mediated approach is reported. The engineered T132A/F189T variant represents a promising and competitive biocatalyst for practical application in synthesizing ( R)- ortho-chloromandelic acid. [ABSTRACT FROM AUTHOR]

A high precision multi-node clock network for multiple users was built following the precise frequency transmission and time synchronization of 120 km fiber. The network topology adopts a simple star-shaped network structure. The clock signal of a hydrogen maser (synchronized with UTC) was recovered from a 120 km telecommunication fiber link and then was distributed to 4 sub-stations. The fractional frequency instability of all substations is in the level of 10-15 in a second and the clock offset instability is in sub-ps in root-mean-square average. [ABSTRACT FROM AUTHOR]

Decreasing glass network defects and improving optical transmittance are essential work for material researchers. We studied the function of halogen iodine (I) acting as a glass network modifier in Ge–Sb–Se-based chalcogenide glass system. A systematic series of Ge 20 Sb 5 Se 75− x I x ( x = 0, 5, 10, 15, 20 at.%) infrared (IR) chalcohalide glasses were investigated to decrease the weak absorption tail (WAT) and improve the mid-IR transparency. The mechanisms of the halogen I affecting the physical, thermal, and optical properties of Se-based chalcogenide glasses were reported. The structural evolutions of these glasses were also revealed by Raman spectroscopy and camera imaging. The progressive substitution of I for Se increased the optical bandgap. The WAT and scatting loss significantly decreased corresponding to the progressive decrease in structural defects caused by dangling bands and structure defects in the original Ge 20 Sb 5 Se 75 glass. The achieved maximum IR transparency of Ge–Sb–Se–I glasses can reach up to 80% with an effective transmission window between 0.94 μm and 17 μm, whereas the absorption coefficient decreased to 0.029 cm −1 at 10.16 μm. Thus, these materials are promising candidates for developing low-loss IR fibers. [ABSTRACT FROM AUTHOR]

The theoretical analysis and experimental preparation of a hollow-core Bragg fiber based on chalcogenide glasses are demonstrated. The fiber has potential applications in bio-sensing and IR energy transmission. Two chalcogenide glasses with, respectively, high and low refractive indexes are investigated in detail for the fabrication of hollow-core Bragg fibers. The most appropriate structure is selected; this structure is composed of four concentric rings and a center air hole . Its band gap for the Bragg fiber is analyzed by the plane wave method. The chalcogenide glasses GeSbSI and GeSbSe are chosen to extrude the robust multi-material glass preform with a specialized punch and glass container. The glass preform is simultaneously protected with a polyetherimide polymer. The hollow-core Bragg fibers are finally obtained after glass preform extrusion, fiber preform fabrication, and fiber drawing. Results showed that the fiber has a transparency window from 2.5 to 14 μm, including a low-loss transmission window from 10.5 to 12 μm. The location of this low-loss transmission window matches the predicted photonic band gap in the simulation. [ABSTRACT FROM AUTHOR]