Three-Dimensional Bimetallic Ammonium K-Eu Nitrate with a Rare (6,6)-Connected Ion Topology Exhibiting Structural Phase Transition and Photoluminescence Properties.

A K-Eu bimetallic ammonium metal-nitrate three-dimensional (3D) framework incorporating R-N-methyl-3-hydroxyquinuclidine, (RM3HQ)2KEu(NO3)6 (RM3HQ = R-N-methyl-3-hydroxyquinuclidine, 1), was characterized and reported. Distinguishing from the former hybrid rare-earth double perovskites, 1 adopts a mixed corner- and face-sharing K+/Eu3+-centered polyhedral connectivity to form a 3D inorganic framework, showing a rare (6, 6)-connected ion topology with a 66 framework. Notably, 1 exhibits clear phase transition, and the switchable thermodynamic behavior is confirmed by variable-temperature dielectric measurements and second-harmonic generation response. Moreover, 1 also shows photoluminescence properties. The activator Eu3+ plays a crucial role in this process, leading to a significant narrow emission at 592 nm with a photoluminescence quantum yield (PLQY) of 20.76%. The fluorescence lifetime (FLT) of 1 is 4.32 ms. This finding enriches the bimetallic hybrid system for potential electronic and/or luminescence applications.

Gas-Liquid Interface Route to Hybrid Copper Bromine Perovskite Single-Crystal Membrane with Dielectric Transitions and Ferromagnetic Exchanges.

Single-crystal membranes (SCMs) show great promise in the fields of sensors, light-emitting diodes, and photodetection. However, the growth of a large-area single-crystal membranes is challenging. We report a new organic-inorganic SCMs [HCMA]2CuBr4 (HCMA = cyclohexanemethylamine) crystallized at the gas-liquid interface. It also has low-temperature ferromagnetic order, high-temperature dielectric anomalies, and narrow band gap indirect semiconductor properties. Specifically, the reversible phase transition of the compound occurs at 350/341 K on cooling/heating and exhibits dielectric anomalies and stable switching performance near the phase transition temperature. The ferromagnetic exchange interaction in the inorganic octahedra and the organic layer enables ferromagnetic ordering at low-temperature 10 K. Finally, the single crystal exhibits an indirect semiconducting property with a narrow band gap of 0.99 eV. Such rich multichannel physical properties make it a potential application in photodetection, information storage and sensors.

Modulation of the Acetone/Butanol Ratio during Fermentation of Corn Stover-Derived Hydrolysate by Clostridium beijerinckii Strain NCIMB 8052.

Producing biobutanol from lignocellulosic biomass has shown promise to ultimately reduce greenhouse gases and alleviate the global energy crisis. However, because of the recalcitrance of a lignocellulosic biomass, a pretreatment of the substrate is needed which in many cases releases soluble lignin compounds (SLCs), which inhibit growth of butanol-producing clostridia. In this study, we found that SLCs changed the acetone/butanol ratio (A/B ratio) during butanol fermentation. The typical A/B molar ratio during Clostridium beijerinckii NCIMB 8052 batch fermentation with glucose as the carbon source is about 0.5. In the present study, the A/B molar ratio during batch fermentation with a lignocellulosic hydrolysate as the carbon source was 0.95 at the end of fermentation. Structural and redox potential changes of the SLCs were characterized before and after fermentation by using gas chromatography/mass spectrometry and electrochemical analyses, which indicated that some exogenous SLCs were involved in distributing electron flow to C. beijerinckii, leading to modulation of the redox balance. This was further demonstrated by the NADH/NAD+ ratio and trxB gene expression profile assays at the onset of solventogenic growth. As a result, the A/B ratio of end products changed significantly during C. beijerinckii fermentation using corn stover-derived hydrolysate as the carbon source compared to glucose as the carbon source. These results revealed that SLCs not only inhibited cell growth but also modulated the A/B ratio during C. beijerinckii butanol fermentation.IMPORTANCE Bioconversion of lignocellulosic feedstocks to butanol involves pretreatment, during which hundreds of soluble lignin compounds (SLCs) form. Most of these SLCs inhibit growth of solvent-producing clostridia. However, the mechanism by which these compounds modulate electron flow in clostridia remains elusive. In this study, the results revealed that SLCs changed redox balance by producing oxidative stress and modulating electron flow as electron donors. Production of H2 and acetone was stimulated, while butanol production remained unchanged, which led to a high A/B ratio during C. beijerinckii fermentation using corn stover-derived hydrolysate as the carbon source. These observations provide insight into utilizing C. beijerinckii to produce butanol from a lignocellulosic biomass.

Tuning the luminescent properties of a three-dimensional perovskite ferroelectric (Me-Hdabco)CsI3via Sn(II) doping.

As promising functional materials, organic-inorganic hybrid metal halide perovskites have attracted significant interest because of their excellent photovoltaic performance. However, although considerable efforts have been made, three-dimensional (3D) metal halide perovskites beyond lead halides have been rarely reported. Herein, a new 3D organic-inorganic hybrid ferroelectric material (Me-Hdabco)CsI3 (1, Me-Hdabco = N-methyl-1,4-diazoniabicyclo[2.2.2]octane) was synthesized and characterized. 1 underwent a ferroelectric to paraelectric phase transition at Tc = 441 K, which was investigated by differential scanning calorimetry (DSC), dielectric measurements, and variable temperature structural analyses. Moreover, 1 shows a clear ferroelectric domain switching recorded by piezoelectric force microscopy. More interestingly, the pristine colorless crystal of 1 has no photoluminescence properties, while 10% Sn(II):(Me-Hdabco)CsI3 shows intense photoluminescence with a quantum yield of 8.90% under UV excitation. This finding will open up a new avenue to probe organic-inorganic hybrid multifunctional materials integrated ferroelectric and photoluminescence.

Synthesis, dielectric, magnetic, and photoluminescence properties of two new hybrid rare-earth double perovskites.

Two new organic-inorganic hybrid double perovskites (R3HQ)4CsSm(NO3)8 (1) (R3HQ = (R)-(-)-3-quinuclidinol) and (R3HQ)4CsEu(NO3)8 (2) were synthesized and characterized. Compounds 1 and 2 exhibit obvious phase transitions at 379 and 375 K, respectively, confirmed by differential scanning calorimetry (DSC) and variable temperature powder X-ray diffraction. The rapid switching between high- and low-dielectric states makes it a typical dielectric material with a switchable dielectric constant for thermal stimulus response. Furthermore, 1 and 2 show attractive photoluminescence and paramagnetic behavior, and the fluorescence quantum yield of 2 reached 14.6%. These results show that compounds 1 and 2 can be used as excellent candidates for multifunctional intelligent materials, which also provides a new way for development of multifunctional materials.

[Influence of Carbonization Temperature on Bacterial Community of the Biological Carbon Electrode Based on High-throughput Sequencing Technology].

Microbial diversity of anodic biofilm in bioelectrochemical systems with hemp rod carbonized at 1000 and 1800℃ as anode was investigated using Solexa high-throughput sequencing technology. The results showed that a total of 4231 and 5263 optimized 16S rRNA gene sequences were gained from the electrode biofilm on the hemp rod carbonized at 1000 and 1800℃, respectively. At the level of 97% similarity, 1187 and 1338 OTUs were obtained for electrode biofilm carbonized at 1000 and 1800℃, respectively. The result of α diversity analysis showed that microbial diversity increased with decreasing carbonization temperature. Dominant phylum for both biofilms were Proteobacteria, Firmicutes and Bacteroidetes, which accounted for 66%, 10% and 9%, respectively for 1000℃, while 71%, 7% and 9%, respectively for 1800℃. Beside the coexisting phylum, some unique species were also discovered, demonstrating that carbonization temperature did not only influence the electrode structure, but also affected the microbial community structure.

[Comparative Analysis of the Bacterial Community on Anodic Biofilms in Sediment Microbial Fuel Cell Under Open and Closed Circuits].

To investigate the differences in microbial community of anodic biofilms under open and closed circuits, sediment microbial fuel cell (SMFCs) reactors connecting with a 5 kΩ external resistance and open circuit during the start-up period were operated individually. Anodic biofilms were collected and analyzed using Solexa high-throughput sequencing technology. A total of 3936 and 3930 operational taxonomic units (OTUs) were obtained from the anodic biofilms under open and closed circuits, respectively. After 97% similarity merging, 1581 and 1551 OTUs were finally determined from open and close circuit biofilms, respectively. The analysis of α diversity showed that bacterial diversity of anodic biofilm under open circuit was higher than that under closed circuit. The dominant bacterial were Proteobacteria, Firmicutes and Bacteroidetes for both open and closed circuits. They accounted for 59.79%, 12.54% and 9.02% under open circuit biofilm respectively; and these values were 63.02%, 10.01% and 3.60% in the closed circuit biofilm respectively, and Geobacter accounted for 16.55% in the closed circuit biofilm. The present study demonstrated that the electron transfer process during start-up period affected the microbial community structure of the anodic biofilms.

In situ probing the effect of potentials on the microenvironment of heterotrophic denitrification biofilm with microelectrodes.

Bio-electrochemical reactor provides a promising technology to remove nitrogen contaminants in water. In this study, a heterotrophic biofilm for denitrification process was developed, and stable total nitrogen removal efficiencies (>80%) were achieved. Fluorescence in situ hybridization showed that genes norB mainly transcribed in inner biofilm while genes nosZ showed similar transcription activities in the entire biofilm. The microelectrodes of pH and nitrous oxide (N2O) were applied to profile the microenvironment of denitrification biofilm. In all measurements, the microenvironment pH decreased as a function of biofilm depth. The highest N2O concentration of 90 µM in biofilm was detected when the bulk solution pH was 7.3, and an applied potential of -0.2V did not decrease the yield of N2O in biofilm at pH 7.3. Nevertheless, pH 9.5 or an applied potential of -0.4V seemed not to suppress the yield of N2O in biofilm.