Cryogenic lithium-niobate-on-insulator optical filter.

Photonic integrated circuits have garnered significant attention and experienced rapid development in recent years. To provide fundamental building blocks for scalable optical classical and quantum information processing, one important direction is to develop cryogenic compatible photonic integrated devices. Here, we prepare one optical filter on a lithium-niobate-on-insulator (LNOI) platform based on a multimode waveguide grating and verify its availability at temperature from 295 to 7 K. We find that the integrated optical filter still shows good quality under cryogenic conditions, and the shift of the working wavelength at different temperatures is well explained by the index variation of the material. These results advance LNOI integrated optical devices in applications under cryogenic conditions.

Thermo-alkaline pretreatment of excess sludge: Effects of temperature on volatile fatty acids accumulation and microbial community.

In order to explore the role of thermal-alkaline pretreatment temperatures (TAPT) in sludge fermentation and the microbial characteristics, five groups (100, 120, 140, 160 °C and control group) were set up and the results showed that the increasing TAPT promoted the dissolution of soluble chemical oxygen demand (SCOD) and VFAs, but had slight influence on the release of NH4+-N and PO43--P. What's more, when it was 120 °C, the SCOD dissolution was comparable to that at 160 °C. Overall, 120 °C was the optimal condition, corresponding to the fact that the maximum release of SCOD was 8788.74 mg/L (2.63 times of the control group), the maximum dissolution of VFAs was 4596 mg/L (about 1.28 times of the control group). The trend of C/N was not significant. High-throughput sequencing showed that Firmicutes and Actinobacteriota were enriched with the temperature increasing, while Proteobacteria and Chloroflexi did not change significantly. Firmicutes was in a stable dominant position. Temperature conditions brought about significant changes in microbial interspecific interaction. Carbohydrate and amino acids had the highest metabolic abundance, especially at 120 °C group. The change rule of amino acid metabolism was similar to that of lipid metabolism, and the abundance of energy metabolism gradually increased with temperature. The protein metabolism was greatly affected by temperature. This study revealed the effect of microbial mechanism of TAPT on the sludge acid production efficiency.

High-performance lithium-niobate-on-insulator optical filter based on multimode waveguide gratings.

A high-performance optical filter is proposed and realized with multimode waveguide grating (MWG) and two-mode multiplexers on the x-cut lithium-niobate-on-insulator (LNOI) platform for the first time, to the best of our knowledge. The present optical filter is designed appropriately to avoid material anisotropy as well as mode hybridness, and has a low excess loss of 0.05 dB and a high sidelobe suppression ratio (SLSR) of 32 dB in theory with Gaussian apodization. The fabricated filters show a box-like response with 1-dB bandwidth of 6-23 nm, excess loss of ∼0.15 dB, sidelobe suppression ratio of >26 dB. The device performance is further improved with a sidelobe suppression ratio as high as 48 dB and a low excess loss of ∼0.25 dB by cascading two identical MWGs.

Zirconium Complexes with Bulkier Amine Bis(phenolate) Ligands and Their Catalytic Properties for Ethylene (Co)polymerization.

A series of new zirconium complexes bearing bulkier amine bis(phenolate) tetradentate ligands, Me2NCH2CH2N{CH2(2-O-3-R-5-tBu-C6H2)}2ZrCl2 [R = CPhMe2 (1); CMePh2 (2); CPh3 (3); Ph (4); 3,5-Me2C6H3 (5); 3,5-tBu2C6H3 (6); 4-tBuC6H4 (7)], were synthesized and characterized by 1H nuclear magnetic resonance (NMR), 13C NMR, and elemental analyses. The molecular structures of complexes 1 and 3 were determined by single-crystal X-ray diffraction analysis. The X-ray crystallography analysis reveals that these complexes display a slightly distorted octahedral geometry around their metal centers. Upon activation with methylaluminoxane (MAO), dry-MAO, MAO/butylated hydroxytoluene (BHT), or AliBu3/CPh3B(C6F5)4, these zirconium complexes exhibit high catalytic activity for ethylene polymerization [up to 1.07 × 107 g PE (mol Zr)-1 h-1] and ethylene/1-hexene copolymerization [up to 2.78 × 107 g polymer (mol Zr)-1 h-1], affording (co)polymers with moderate to high molecular weights and good comonomer incorporations. The zirconium complexes with bulkier R groups show higher catalytic activities and longer lifetimes and produce polymers with higher molecular weights, while the zirconium complexes with aryls as R groups demonstrate relatively good comonomer incorporation ability for the copolymerization reactions. These catalytic systems also show moderate catalytic activities for the polymerization reactions of propylene, 1-hexene, and 1-decene. Upon activation with MAO, the zirconium complexes also show moderate catalytic activities for the copolymerization reaction of ethylene with 3-buten-1-ol (treated with 1 equiv of AliBu3), affording copolymers with the incorporation of 3-buten-1-ol up to 1.05%.

Titanium and zirconium complexes bearing new tridentate [OSO] bisphenolato-based ligands: synthesis, characterization and catalytic properties for alkene polymerization.

A number of new sulfur-bridged tridentate [OSO] bisphenolato-based ligand precursors S(2-CH2-4-tBu-6-R-C6H2OH)2 [R = CMe3 (H2L1), CMe2Ph (H2L2), CMePh2 (H2L3), CPh3 (H2L4), and C(p-Tol)3 (H2L5)] were synthesized by reactions of Na2S·9H2O with 2 eq. of the corresponding 2-(bromomethyl)-4-(tert-butyl)-6-R-phenol. Their neutral titanium complexes [S(2-CH2-4-tBu-6-R-C6H2O)2]TiCl2 [R = CMe3 (1), CMe2Ph (2), CMePh2 (3), CPh3 (4), and C(p-Tol)3 (5)] were synthesized in high yields by direct HCl-elimination reactions of TiCl4 with the corresponding ligand precursors in toluene. Ionic titanium complexes [NHEt3][S(2-CH2-4-tBu-6-R-C6H2O)2TiCl3] [R = CMe3 (6), CMePh2 (7)] and [NH2Et2][S(2-CH2-4-tBu-6-R-C6H2O)2TiCl3] [R = CMe3 (8) and CMePh2 (9)] were obtained in high yields from the reactions of TiCl4 with the corresponding ligand precursors in the presence of 2 eq. of triethylamine or diethylamine. Neutral zirconium complexes [S(2-CH2-4-tBu-6-R-C6H2O)2]ZrCl2(THF) [R = CMe2Ph (10·THF), and CMePh2 (11·THF)] were synthesized by reactions of ZrCl4 with 1 eq. of the dilithium salt of the corresponding ligand precursors Li2L in THF. The new titanium and zirconium complexes were characterized by 1H and 13C NMR, IR and elemental analyses. The molecular structures of complexes 4, 6 and 10·THF were determined by single-crystal X-ray diffraction analysis. The X-ray crystallography analysis reveals that titanium complex 4 has a five-coordinating environment surrounding the central metal atom, while the titanium complex 6 and the THF-solvated zirconium complex 10·THF possess a six-coordinating pseudo-octahedral environment around the central metal atom. Upon activation with MAO or AliBu3/Ph3CB(C6F5)4, all these titanium and zirconium complexes exhibit moderate to high catalytic activities for ethylene polymerization and ethylene/1-hexene copolymerization with moderate to high comonomer incorporation, and the ionic titanium complexes 6, 7, 8 and 9 show lower catalytic activity than their corresponding neutral complexes under similar conditions.

Highly active self-immobilized FI-Zr catalysts in a PCP framework for ethylene polymerization.

A series of zirconium-based porous coordination polymers (PCPs) containing FI catalysts in the frameworks have been developed and studied as catalysts for ethylene polymerization. These PCPs exhibit good catalytic activities and long life times, producing polyethylenes with high molecular weights and bimodal molecular weight distribution in the form of particles.