Ultra-sensitive H2S sensor based on sunflower-like In-doped ZnO with enriched oxygen vacancies.

Metal oxide sensors face the challenge of high response and fast recovery at low operating temperatures for the detection of toxic and flammable hydrogen sulfide (H2S) gases. Herein, novel In-doped ZnO with a sunflower-like structure and tunable surface properties was rationally synthesized. The substitutional In atom in the ZnO crystal can dramatically enhance the concentration of oxygen vacancies (Ov), the In-ZnO sites are responsible for fast recovery, and the formation of sub-stable sulfide intermediates gives rise to the high response towards H2S. As a result, the response of the optimized 4In-ZnO sensor is 3538.36 to 50 ppm H2S at a low operating temperature of 110 °C, which is 106 times higher than that of pristine ZnO. Moreover, the response time and recovery time to 50 ppm H2S are 100 s and 27 s, respectively, with high selectivity and stability. First-principles calculations revealed that 4In-ZnO with rich Ov exhibited higher adsorption energy for the H2S molecule than pristine ZnO, resulting in effortless H2S detection. Our work lays the foundation for the rational design of highly sensitive gas sensors through precise doping of atoms in oxygen-rich vacancies in semiconductor materials.

Multifunctional DyIII Enantiomeric Pairs Showing Enhanced Photoluminescences and Third-Harmonic Generation Responses through the Coordination Role of Homochiral Tridentate N,N,N-Pincer Ligands.

By utilizing Dy(hfac)3(H2O)2 to react with enantiomerically pure tridentate N,N,N-pincer ligands, namely (-)/(+)-2,6-bis(4',5'-pinene-2'-pyridyl)pyridine (LR and LS), respectively, homochiral DyIII enantiomeric pairs formulated as Dy(hfac)3LR/Dy(hfac)3LS (R-1/S-1) (hfac- = hexafluoroacetylacetonate) were achieved and structurally characterized. Meanwhile, their magnetic, photoluminescent (PL), and chiroptical properties were probed. The PL test results indicate that the precursor Dy(hfac)3(H2O)2 only shows very weak emission, while R-1 exhibits characteristic DyIII f-f transition emission bands at room temperature. Furthermore, the nonlinear optical responses of Dy(hfac)3(H2O)2, LR/LS, and R-1/S-1 were investigated in detail based on crystalline samples. The results reveal that LR and LS present the coexistence of second- and third-harmonic generation (SHG and THG) responses with more intense signals for SHG responses; and Dy(hfac)3(H2O)2 merely displays weak THG responses, while R-1 and S-1 also only exhibit THG responses. However, the THG intensities of R-1 and S-1 are more than six times larger than that of Dy(hfac)3(H2O)2 under the identical measurement conditions. These results demonstrate that introducing homochiral N,N,N-pincer ligands to replace two H2O molecules of Dy(hfac)3(H2O)2 results in significant improvements of both PL performances and THG responses of resultant R-1/S-1 enantiomers. R-1 and S-1 integrate PL, THG, and chiral optical activity in one molecule, suggesting their multifunctional merits. In particular, a convenient method is introduced to simultaneously test THG and SHG responses of molecular materials based on crystalline samples in this work.

Advances in Doped ZnO Nanostructures for Gas Sensor.

Gas sensors based on metal oxides semiconductor (MOS) have attracted extensive attention from both academic and industry. ZnO, as a typical MOS, exhibits potential applications in toxic gas detection, owning to its wide band gap, n-type transport characteristic and excellent electrical performance. Meanwhile, doping is an effective way to improve the sensing performance of ZnO materials. In this review, the effects of different types of doping on morphology, crystal structure, band gap and depletion layer of ZnO materials are comprehensively discussed. Theoretical analysis on the strategies for enhancing the sensing properties of ZnO is also provided. This review puts forward the reasonable insight for designing efficient n-type ZnO-based semiconductor oxide sensing materials.

Highly enhanced photocatalytic H2 evolution of Cu2O microcube by coupling with TiO2 nanoparticles.

A Cu2O/TiO2 p-n heterojunction composite was created via a facile, controllable, one-pot hydrothermal method based on cubic Cu2O and TiO2 nanoparticles in the presence of dioctyl sulfosuccinate sodium salt (AOT) surfactant. The TiO2 nanoparticles with an average edge length of ∼10.1 nm were uniformly distributed on the crystal surface of a Cu2O cube {100}. The photocatalytic performance of the composite was effectively tuned by controlling the amount of TiO2. The Cu2O/TiO2 (60 wt%, labeled as CT-60) exhibits the highest enhanced photocatalytic activity in hydrogen production with H2 evolution of 3002.5 µmol g-1. The yield remained around 92.6% after three cycles. Hydrogen production of the CT-60 is 103 and 8.5 fold higher than the cubic Cu2O and TiO2 nanoparticles, respectively. The improvement in photocatalytic performance could be attributed to the formation of p-n heterojunction. Furthermore, the interface effect of Cu2O and TiO2 caused a broader absorbance in the visible-light region and the lower recombination of photogenerated electron-hole pairs. It is believed that the Cu2O/TiO2 p-n heterojunction composites could provide an alternative method to design highly efficient photocatalysts for solar energy.

Double-platelet Pd@ZnO microcrystals for NO2 chemical sensors: their facile synthesis and DFT investigation.

Double-platelet, single-platelet and spherical ZnO microcrystals were fabricated via a facile and controllable hydrothermal method. The morphology of the ZnO microcrystals and the exposure ratio of the (001) crystal surface were regulated by adjusting the pH of the solution. The ZnO microcrystals were modified with Pd nanoparticle loading by simple calcining, and the interaction of Pd nanoparticles (NPs) on the ZnO crystal surface increased its oxygen vacancy content. A micro-amount (0.05 wt%) of Pd NP-doped ZnO double-platelets (D-ZnO-0.05) enhanced the gas sensing of the sensor to 3.5 times that of pure double-platelet ZnO. The gas sensing results indicate that D-ZnO-0.05 exhibits a high response (71.2 for NO2 with 25 ppm), fast response/recovery (25 s/21 s), and superior long-term stability (remained at around 95.5% after 35 days). The enhancement in the gas sensing could be attributed to the catalysis of Pd NPs and the increase in the number of oxygen vacancies as a result of Pd loading. The band structure of D-ZnO-0.05 could be effectively tuned by introducing Pd nanoparticles, as shown in density functional theory (DFT) calculations. The Pd dopant and oxygen vacancies reduce the band gap of the ZnO(001) crystal materials, resulting in excellent sensor performance. It is believed that the D-ZnO-0.05 microcrystals could provide inspiration for crystal growth studies and high NO2 gas sensing.

Metal-Organic Framework Supported on Processable Polymer Matrix by In Situ Copolymerization for Enhanced Iron(III) Detection.

Metal-organic frameworks (MOFs) represent a promising class of porous materials. However, MOFs show poor processability that impedes their full potential in applications. This work develops a composite strategy to skillfully load MOFs on a polymer plate to afford processability for these powder materials. A predesigned mesoporous MOF with active -NH2 groups around the pore walls was prepared and its copolymerization with the -NCO groups of macromonomers (polyurethane acrylate) could be facilely induced by an initiator under mild conditions. Notably, the target MOF-polymer composite is transparent, elastic, and shows enhanced Fe3+ detection compared with that of the individual MOF functional component. This result can be ascribed to the synergistic effect of the composite with newly formed chemical bonds between the MOF particle and polymer matrix.

Lanthanide-organic coordination frameworks showing new 5-connected network topology and 3D ordered array of single-molecular magnet behavior in the Dy case.

Five isostructural lanthanide-organic coordination frameworks with a unique 3-D 5-connected (4(7).6(3))(4(3).6(5).8(2)) network, namely, [Ln(phen)(L)]n (Ln = Dy for 1, Gd for 2, Ho for 3, Er for 4, and Tb for 5), have been prepared based on bridging 5-hydroxyisophthalic acid (H3L) and chelating 1,10-phenanthroline (phen) coligand. Significantly, the Dy(III) complex 1 is an organized array of single-molecular magnets (SMMs), with frequency-dependent out-of-phase ac susceptibility signals and magnetization hysteresis at 4 K. Further analysis of the magnetic results can reveal that the SMM behavior of 1 should arise from the smaller ferromagnetic interaction between the Dy(III) ions. Complex 1 was also characterized by X-ray absorption spectra, which give the clear X-ray magnetic circular dichroism signal.

Versatile mesoporous DyIII coordination framework for highly efficient trapping of diverse pollutants.

This work presents a mesoporous Dy(III) metal-organic framework with two types of void cages (diameters: 4.4 and 2.8 nm), which can efficiently adsorb a variety of chemical pollutants, including toxic metals, iodine, and formaldehyde.

Pd Decoration with Synergistic High Oxygen Mobility Boosts Hydrogen Sensing Performance at Low Working Temperature on WO3 Nanosheet.

Pd-based materials have received remarkable attention and exhibit excellent H2 sensing performance due to their superior hydrogen storage and catalysis behavior. However, the synergistic effects originated from the decoration of Pd on a metal oxide support to boost the sensing performance are ambiguous, and the deep investigation of metal support interaction (MSI) on the H2 sensing mechanism is still unclear. Here, the model material of Pd nanoparticle-decorated WO3 nanosheet is synthesized, and individual fine structures can be achieved by treating it at different temperatures. Notably, the Pd-WO3-300 materials display superior H2 sensing performance at a low working temperature (110 °C), with a superior sensing response (Ra/Rg = 40.63 to 10 ppm), high sensing selectivity, and anti-interference ability. DFT calculations and detailed structural investigations confirm that the moderate MSI facilitates the generation of high mobility surface O2- (ad) species and a proper ratio of surface Pd0-Pd2+ species, which can significantly boost the desorption of intermediate PdHx species at low temperatures and contribute to enhanced sensing performance. Our work illustrates the effect of MSI on sensing performance and provides insight into the design of advanced sensing materials.

Modulation of homochiral Dy(III) complexes: single-molecule magnets with ferroelectric properties.

Homochiral Dy(III) complexes: by changing the ligand-to-metal ratio, enantiomeric pairs of a Dy(III) complex of different nuclearity could be obtained. The mono- and dinuclear complexes exhibit characteristics of single-molecule magnets and different slow magnetic relaxation processes. In addition, the dinuclear complexes exhibit ferroelectric behavior, thus representing the first chiral polynuclear lanthanide-based single-molecule magnets with ferroelectric properties.

The effects of Clostridium butyricum on Ira rabbit growth performance, cecal microbiota and plasma metabolome.

Clostridium butyricum (C. butyricum) can provide many benefits for animals' growth performance and gut health. In this study, we investigated the effects of C. butyricum on the growth performance, cecal microbiota, and plasma metabolome in Ira rabbits. A total of 216 Ira rabbits at 32 days of age were randomly assigned to four treatments supplemented with basal diets containing 0 (CG), 200 (LC), 400 (MC), and 600 mg/kg (HC) C. butyricum for 35 days, respectively. In comparison with the CG group, C. butyricum supplementation significantly improved the average daily gain (ADG) and feed conversion rate (FCR) at 53 and 67 days of age (P < 0.05) and digestibilities of crude protein (CP) and crude fiber (CF) at 67 days of age (P < 0.05). The cellulase activity in the HC group was higher respectively by 50.14 and 90.13% at 53 and 67 days of age, than those in the CG groups (P < 0.05). Moreover, at 67 days of age, the diet supplemented with C. butyricum significantly increased the relative abundance of Verrucomicrobia at the phylum level (P < 0.05). Meanwhile, the concentrations of different metabolites, such as amino acids and purine, were significantly altered by C. butyricum (P < 0.05). In addition, 10 different genera were highly correlated with 52 different metabolites at 53-day-old and 6 different genera were highly correlated with 18 different metabolites at 67-day-old Ira rabbits. These findings indicated that the C. butyricum supplementation could significantly improve the growth performance by modifying the cecal microbiota structure and plasma metabolome of weaned Ira rabbits.

Recent advances in Cu2O-based composites for photocatalysis: a review.

Cu2O-based composites for photocatalysis have been extensively explored owing to their promising application in solving environmental and energy problems. At present, the research on photocatalysis is focused on improving the photocatalytic performance of materials. It has been reported that adjusting the morphology and size of Cu2O can effectively improve its photocatalytic property. However, photocorrosion is still an inevitable problem, which hinders the application of Cu2O in photocatalysis. The strategies of constructing heterogeneous nanostructures and ion doping can significantly improve the light stability, light absorption capacity and separation efficiency of electron-hole pairs. Cu2O-based composites exhibit superior performances in degrading organic matter, producing hydrogen, reducing CO2 and sterilization. Therefore, the construction of multi-materials will be one of the future directions in their photocatalytic application. This review summarizes the recent strategies for enhancing the photocatalytic activity of Cu2O by analyzing different Cu2O-based photocatalysts, and the charge transfer pathway is further discussed in detail. Finally, several opportunities and challenges in the field of photocatalysis are illustrated.

From infinite one-dimensional helix to discrete Cu(II)15 cluster along with in situ S(N)2 ring-cleavage of cis-epoxysuccinic acid: pH-controlled assemblies, crystal structures, and properties.

Two Cu(II) coordination complexes {[Cu(ces)(H(2)O)(2)](H(2)O)(0.5)}(n) (1) and [Cu(15)(dhs)(6)(OH)(6)(H(2)O)(10)](H(2)O)(20) (2) have been synthesized from cis-epoxysuccinic acid (cis-H(2)ces) and Cu(II) perchlorate under different pH conditions (ces = cis-epoxysuccinate and dhs = 2,3-dihydroxysuccinate), and fully characterized by IR spectra, elemental analyses, as well as single crystal and powder X-ray diffraction techniques. Notably, when the reaction was performed at pH above about 7.4, a one-dimensional (1-D) helical chain complex 1 is formed, whereas a neutral isolated Cu(15) nanocluster 2 is generated when the pH value is decreased to the range of about 6.6-7.3, being concomitant with in situ S(N)2 ring-cleavage reaction of cis-H(2)ces to form (2S,3S)- and (2R,3R)-H(4)dhs. Further, extended supramolecular architectures are constructed via secondary interactions in both structures. The magnetic properties of 1 and 2 have also been studied in detail, showing that 1 is an antiferromagnetic helical chain of S = 1/2 spins and 2 possesses an S = 3/2 spin ground state.

Ultrathin agaric-like ZnO with Pd dopant for aniline sensor and DFT investigation.

Aniline detection is of great importance in many industries, but most of the aniline sensors suffers from tedious and time consuming process. Herein, we present an efficient aniline sensor based on Pd decorated ZnO nanomaterials. Ultrathin ZnO nanosheets were synthesized by a facile one-step hydrothermal method. The nanosheets were corrugated into a unique agaric morphology, endorsing the nanomaterials with high surface area that is ideal for gas sensing applications. The obtained ZnO nanosheets were then uniformly decorated with uniform Pd nanoparticles (Pd NPs) around 5 nm in diameter. Gas sensing experiment on the ZnO decorate with different amount of Pd nanoparticles were systematically evaluated. The sample decorated with 0.3 % Pd NPs (Pd-ZnO-0.3) exhibited the highest sensitivity to aniline, which is about two orders higher than that of the pure ZnO nanosheet. The gas sensor based on Pd-ZnO-0.3 has a detection limit to aniline down to 0.5 ppm, with very short response and recovery times of 29 s and 23 s, respectively to 100 ppm aniline. First-principles DFT study was employed to provide the sensing mechanism. The improved sensing performance could be attributed to the increasing adsorbed oxygen and tunable band alignment for Pd-ZnO materials. This work provides new insights to the design strategy of Pd-decorated ZnO nanomaterials for high performance gas sensors.

catena-Poly[[chloridomercury(II)]-µ-1,4-diaza-bicyclo-[2.2.2]octane-κN:N'-[chlorido-mercury(II)]-di-µ-chlorido].

In the title coordination polymer, [Hg(2)Cl(4)(C(6)H(12)N(2))](n), each Hg(II) center within the chain is four-coordinated by one terminal Cl atom, two bridging µ(2)-Cl atoms, and one N-atom donor from a µ(2)-1,4-diaza-bicyclo-[2.2.2]octane (µ(2)-daco) ligand in a distorted tetra-hedral geometry. The daco ligand acts as an end-to-end bridging ligand and bridges adjacent Hg(II) centers, forming a chain running along [001]. Weak C-H⋯Cl hydrogen-bonding inter-actions link the chains into a three-dimensional network. Comparison of the structural differences with previous findings suggests that the space between the two N donors, as well as the skeletal rigidity in N-heterocyclic linear ligands, may play an important role in the construction of such supra-molecular networks.

Diaqua-bis[5-(2-pyrid-yl)tetra-zolato-κN,N]iron(II).

The title complex, [Fe(C(6)H(4)N(5))(2)(H(2)O)(2)], was synthesized by the reaction of ferrous sulfate with 5-(2-pyrid-yl)-2H-tetra-zole (HL). The Fe(II) atom, located on a crystallographic center of inversion, is coordinated by four N-atom donors from two planar trans-related deprotonated L ligands and two O atoms from two axial water mol-ecules in a distorted octa-hedral geometry. The Fe(II) mononuclear units are further connected by inter-molecular O-H⋯N and C-H⋯O hydrogen-bonding inter-actions, forming a three-dimensional framework.

Poly[[diaqua-bis(µ(2)-4,4'-bipyridine)-manganese(II)] bis-[2-(2-carboxy-phenyl-di-sulfanyl)benzoate]].

The title complex, {[Mn(C(10)H(8)N(2))(2)(H(2)O)(2)](C(14)H(9)O(4)S(2))(2)}(n), contains an octa-hedrally coordinated Mn(II) cation and 2-(2-carboxy-phenyl-disulfan-yl)benzoate anions. The Mn(II) center is situated on a crystallographic center of inversion and is coordinated by four 4,4'-bipyridine (4,4'-bipy) ligands and two water mol-ecules. The 4,4'-bipy ligands act as bridging ligands, producing a fishing-net-like two-dimensional framework. In the crystal structure, this positively charged framework is charge balanced by 2-(2-carboxy-phenyl-disulfan-yl)benzoate anions that form a separate anionic two-dimensional framework via inter-molecular O-H⋯O hydrogen bonds and C-H⋯π stacking inter-actions. Additional inter-molecular O-H⋯O hydrogen bonds link the cationic and anionic frameworks to form the three-dimensional crystal structure.

catena-Poly[[dichloridomercury(II)]-micro-1-(2-pyridylmethyl)-1H-benzotriazole]: the effect of different metal centers on the self-assembly of coordination complexes.

To further investigate the relationship between the structures of benzotriazol-1-yl-based pyridyl ligands and their complexes, a new linear one-dimensional Hg(II) coordination polymer, [HgCl(2)(C(12)H(10)N(4))](n), with the 1-(2-pyridylmethyl)-1H-benzotriazole (L) ligand was obtained through the reaction of L with HgCl(2). In this complex, each Hg(II) center within the one-dimensional chain is coordinated by two chloride anions as well as by one pyridine and one benzotriazole N-atom donor of two distinct L ligands in a distorted tetrahedral geometry, forming a linear one-dimensional chain running along the [010] direction. Weak C-H...pi and pi-pi stacking interactions link the one-dimensional motifs to generate an overall two-dimensional network parallel to the (100) plane. Comparison of the structural differences with previous findings suggests that the presence of different metal centers may plays an important role in the construction of such supramolecular frameworks.

Bis[µ-2-(3-pyridylmeth-yl)-2H-benzo-triazole]bis-[nitratosilver(I)].

In the title centrosymmetric binuclear Ag(I) complex, [Ag(2)(NO(3))(2)(C(12)H(10)N(4))(2)], each Ag(I) center is coordinated by one pyridine and one benzotriazole N-donor atom of two inversion-related 2-(3-pyridylmeth-yl)-2H-benzotriazole (L) ligands, and an O atom of a coordinated NO(3) (-) anion in a distorted T-shaped geometry. This forms a unique box-like cyclic dimer with an intra-molecular non-bonding Ag⋯Ag separation of 6.327 (2) Å. Weak inter-molecular Ag⋯O(nitrate) inter-actions [2.728 (4) and 2.646 (3) Å] link the binuclear units, forming a two-dimensional network parallel to (100). Inter-molecular C-H⋯O hydrogen-bonding inter-actions, involving the L ligands and the coordinated NO(3) (-) anions, link the sheets, forming a three-dimensional framework.

[Study on the application of absorption spectrum to the treatment of landfill leachate by membrane technology].

Molecular weight (MW) distributions of organics in the Bei Shenshu landfill leachate and their permeation from membranes were determined and studied by absorption spectrum, and the removal rates of organics with various molecular weight were measured. A new FTIR preparation method of wastewater sample used in the determination of landfill leachate was proposed in the present paper. The results showed that the aromatics in landfill leachate were mainly related to the organics with MW < 2 500, whereas the distribution of total organics was dispersal comparatively. The removal rates of various humic compounds and oils in landfill leachate were estimated in accordance with the change in FTIR absorbance of permeation from membranes at three characteristic wave numbers 2 930, 2 960 and 3 030 cm(-1), indicating that the defined membrane treatment process can removed organics with relevant MW fractions effectively.