Geological Borehole Video Image Stitching Method Based on Local Homography Matrix Offset Optimization.

Due to the influence of the shooting environment and inherent image characteristics, there is a large amount of interference in the process of image stitching a geological borehole video. To accurately match the acquired image sequences in the inner part of a borehole, this paper presents a new method of stitching an unfolded borehole image, which uses the image generated from the video to construct a large-scale panorama. Firstly, the speeded-up robust feathers (SURF) algorithm is used to extract the image feature points and complete the rough matching. Then, the M-estimator sample consensus (MSAC) algorithm is introduced to remove the mismatched point pairs and obtain the homography matrix. Subsequently, we propose a local homography matrix offset optimization (LHOO) algorithm to obtain the optimal offset. Finally, the above process is cycled frame by frame, and the image sequence is continuously stitched to complete the construction of a cylindrical borehole panorama. The experimental results show that compared with those of the SIFT, Harris, ORB and SURF algorithms, the matching accuracy of our algorithm has been greatly improved. The final test is carried out on 225 consecutive video frames, and the panorama has a good visual effect, and the average time of each frame is 100 ms, which basically meets the requirements of the project.

An Efficient LiDAR Point Cloud Map Coding Scheme Based on Segmentation and Frame-Inserting Network.

In this article, we present an efficient coding scheme for LiDAR point cloud maps. As a point cloud map consists of numerous single scans spliced together, by recording the time stamp and quaternion matrix of each scan during map building, we cast the point cloud map compression into the point cloud sequence compression problem. The coding architecture includes two techniques: intra-coding and inter-coding. For intra-frames, a segmentation-based intra-prediction technique is developed. For inter-frames, an interpolation-based inter-frame coding network is explored to remove temporal redundancy by generating virtual point clouds based on the decoded frames. We only need to code the difference between the original LiDAR data and the intra/inter-predicted point cloud data. The point cloud map can be reconstructed according to the decoded point cloud sequence and quaternion matrices. Experiments on the KITTI dataset show that the proposed coding scheme can largely eliminate the temporal and spatial redundancies. The point cloud map can be encoded to 1/24 of its original size with 2 mm-level precision. Our algorithm also obtains better coding performance compared with the octree and Google Draco algorithms.

Adaptive Fixed-Time Neural Networks Control for Pure-Feedback Non-Affine Nonlinear Systems with State Constraints.

A new fixed-time adaptive neural network control strategy is designed for pure-feedback non-affine nonlinear systems with state constraints according to the feedback signal of the error system. Based on the adaptive backstepping technology, the Lyapunov function is designed for each subsystem. The neural network is used to identify the unknown parameters of the system in a fixed-time, and the designed control strategy makes the output signal of the system track the expected signal in a fixed-time. Through the stability analysis, it is proved that the tracking error converges in a fixed-time, and the design of the upper bound of the setting time of the error system only needs to modify the parameters and adaptive law of the controlled system controller, which does not depend on the initial conditions.

Bimetallic MOFs-derived coral-like Ag-Mo2C/C interwoven nanorods for amperometric detection of hydrogen peroxide.

Coral-like Ag-Mo2C/C-I and blocky Ag-Mo2C/C-II composites were obtained from one-step in situ calcination of [Ag(HL)3(Mo8O26)]n·nH2O [L: N-(pyridin-3-ylmethyl) pyridine-2-amine] under N2/H2 and N2 atmospheres, respectively. The coral-like morphology of Ag-Mo2C/C-I is composed of interwoven nanorods embedded with small particles, and the nano-aggregate of Ag-Mo2C/C-II is formed by cross-linkage of irregular nanoparticles. The above composites are decorated on glassy carbon electrode (GCE) drop by drop to generate two enzyme-free electrochemical sensors (Ag-Mo2C/C/GCE) for amperometric detection of H2O2. In particular, the coral-like Ag-Mo2C/C-I/GCE sensor possesses rapid response (1.2 s), high sensitivity (466.2 µA·mM-1·cm-2), and low detection limit (25 nM) towards trace H2O2 and has wide linear range (0.08 µM~4.67 mM) and good stability. All these sensing performances are superior to Ag-Mo2C/C-II/GCE, indicating that the calcining atmosphere has an important influence on microstructure and electrochemical properties. The excellent electrochemical H2O2 sensing performance of Ag-Mo2C/C-I/GCE sensor is mainly attributed to the synergism of unique microstructure, platinum-like electron structure of Mo2C, strong interaction between Mo and Ag, as well as the increased active sites and conductivity caused by co-doped Ag and carbon. Furthermore, this sensor has been successfully applied to the detection of H2O2 in human serum sample, contact lens solution, and commercial disinfector, demonstrating the potential in related fields of environment and biology. Graphical abstract.

Ladder chain Cd-based polymer as a highly effective adsorbent for removal of Congo red.

Developing of high effective and fast-rate adsorbent materials has been recently attracted intensive attentions all over the world due to organic dye polluted water treatment. However, few studies have been reported on the ultrahigh-capacity and fast-rate removal of Congo red. In this work, a new stable Cd-based coordination polymer exhibits excellent adsorption performance towards Congo Red. This ladder chain [Cd4(H2L)4(H2O)8(NDS)]n·3n(NDS) (I) (H2L = N1,N2-bis(pyridin-3-ylmethyl) ethane-1,2-diamine, 1,5-H2NDS = 1,5-naphthalene disulfonic acid) has been successfully synthesized by the hydrothermal reaction. At room temperature, the experimental adsorption capacity of coordination polymer (I) towards Congo red can reach up to 16,880 mg g-1 in 20 min (pH = 2.0-3.2), and its higher capacity and faster rate are all better than those in reported inorganic and metal-organic frameworks absorbents. The adsorption process is spontaneous and endothermic reaction, and fits well with the second-order kinetics, Langmuir and Scatchard isotherm adsorption models. The excellent adsorption performance of (I) towards Congo red is related to the strong electrostatic, various hydrogen bonding and π-π stacking interactions under acidic conditions.

Phosphorus-Doped Carbon Nitride Tubes with a Layered Micro-nanostructure for Enhanced Visible-Light Photocatalytic Hydrogen Evolution.

Phosphorus-doped hexagonal tubular carbon nitride (P-TCN) with the layered stacking structure was obtained from a hexagonal rod-like single crystal supramolecular precursor (monoclinic, C2/m). The production process of P-TCN involves two steps: 1) the precursor was prepared by self-assembly of melamine with cyanuric acid from in situ hydrolysis of melamine under phosphorous acid-assisted hydrothermal conditions; 2) the pyrolysis was initiated at the center of precursor under heating, thus giving the hexagonal P-TCN. The tubular structure favors the enhancement of light scattering and active sites. Meanwhile, the introduction of phosphorus leads to a narrow band gap and increased electric conductivity. Thus, the P-TCN exhibited a high hydrogen evolution rate of 67 µmol h(-1) (0.1 g catalyst, λ >420 nm) in the presence of sacrificial agents, and an apparent quantum efficiency of 5.68 % at 420 nm, which is better than most of bulk g-C3 N4 reported.

Convergent modulation of singlet and triplet excited states of phosphine-oxide hosts through the management of molecular structure and functional-group linkages for low-voltage-driven electrophosphorescence.

The controllable tuning of the excited states in a series of phosphine-oxide hosts (DPExPOCzn) was realized through introducing carbazolyl and diphenylphosphine-oxide (DPPO) moieties to adjust the frontier molecular orbitals, molecular rigidity, and the location of the triplet excited states by suppressing the intramolecular interplay of the combined multi-insulating and meso linkage. On increasing the number of substituents, simultaneous lowering of the first singlet energy levels (S(1)) and raising of the first triplet energy levels (T(1), about 3.0 eV) were achieved. The former change was mainly due to the contribution of the carbazolyl group to the HOMOs and the extended conjugation. The latter change was due to an enhanced molecular rigidity and the shift of the T(1) states from the diphenylether group to the carbazolyl moieties. This kind of convergent modulation of excited states not only facilitates the exothermic energy transfer to the dopants in phosphorescent organic light-emitting diodes (PHOLEDs), but also realizes the fine-tuning of electrical properties to achieve the balanced carrier injection and transportation in the emitting layers. As the result, the favorable performance of blue-light-emitting PHOLEDs was demonstrated, including much-lower driving voltages of 2.6 V for onset and 3.0 V at 100 cd m(-2), as well as a remarkably improved E.Q.E. of 12.6%.

Well-designed strategy to construct helical silver(I) coordination polymers from flexible unsymmetrical bis(pyridyl) ligands: syntheses, structures, and properties.

In this Article, self-assembly of AgX (X = NO3(-) and ClO4(-)) salts and four flexible unsymmetrical bis(pyridyl) ligands, namely, N-(pyridin-2-ylmethyl)pyridin-3-amine (L1), N-(pyridin-3-ylmethyl)pyridin-2-amine (L2), N-(pyridin-4-ylmethyl)pyridin-2-amine (L3), and N-(pyridin-4-ylmethyl)pyridin-3-amine (L4), results in the formation of eight helical silver(I) coordination polymers, [Ag(L)(NO3)]n [L = L1 (1), L2 (2), L3 (3), L4 (4)] and [Ag(L)(ClO4)]n [L = L1 (5), L2 (6), L3 (7), L4 (8)], which have been characterized by elemental analysis, IR, TG, PL, and powder and single-crystal X-ray diffraction. The alternating one-dimensional (1-D) left- and right-handed helical chains are included in achiral complexes 1-3 and 5-8. By contrast, the ligand L4 only alternately bridges Ag(I) cation to form the 1-D right-handed helical chain in complex 4. The pitches of these helical chains locate in the range 5.694(5)-17.016(6) Å. Meanwhile, the present four unsymmetrical bis(pyridyl) ligands in the eight complexes present diverse cis-trans and trans-trans conformation and facilitate the construction of helical structures. Moreover, the solid-state luminescent emission intensities of the perchlorate-containing complexes are stronger than those of nitrate-containing complexes at room temperature.

Short-axis substitution approach selectively optimizes electrical properties of dibenzothiophene-based phosphine oxide hosts.

Two dibenzothiophene (DBT)-based phosphine oxide hosts, named 4-diphenylphosphoryl dibenzothiophene (DBTSPO) and 4,6-bis(diphenylphosphoryl) dibenzothiophene (DBTDPO), were prepared by short-axis substitution with the aim to selectively adjust electrical properties. The combined effects of short-axis substitution and the involvement of electron-donating S atom in conjugation effectively suppress the influence of electron-withdrawing diphenylphosphine oxide (DPPO) moieties on the frontier molecular orbitals and the optical properties. Therefore, DBTSPO and DBTDPO have the nearly same hole injection ability and the excited energy levels, while more electron-transporting DPPOs and the symmetrical configuration endow DBTDPO with enhanced electron-injecting/transporting ability. As the result, on the basis of this short-axis substitution effect, the selective adjustment of electrical properties was successfully realized. With the high first triplet energy level (T(1)) of 2.90 eV, the suitable energy levels of the highest occupied molecular orbital and the lowest unoccupied molecular orbital of -6.05 and -2.50 eV and the improved carrier-transporting ability, DBTDPO supported its blue- and white-emitting phosphorescent organic light-emitting diodes as the best low-voltage-driving devices reported so far with the lowest driving voltages of 2.4 V for onset and <3.2 V at 1000 cd m(-2) (for indoor lighting) accompanied with the high efficiencies of >30 lm W(-1) and excellent efficiency stability.

catena-Poly[[silver(I)-µ-2-[(pyrazin-2-yl-κ(2)N(1):N(4))amino-meth-yl]phenol] nitrate].

The Ag(I) atom in the polycationic salt, {[Ag(C(11)H(11)N(3)O)]NO(3)}(n), shows a linear coordination [N-Ag-N = 175.0 (2)°]; the polymeric nature arises from bridging by the pyrazine portion of the ligand, resulting in chains extending parallel to [100]. The NO(3) (-) counter-ions surround the polymeric chain and inter-act only weakly with it [Ag⋯O = 2.701 (4) and 2.810 (5) Å]. Adjacent chains are linked into a three-dimensional network by O-H⋯O and N-H⋯O hydrogen bonds.

Ammonium diamminesilver(I) bis-(5-chloro-2-hy-droxy-benzene-sulfonate) trihydrate.

The reaction of silver nitrate with 5-chloro-2-hy-droxy-benzene-sulfonic acid in the presence of ammonia yielded the title salt, (NH(4))[Ag(NH(3))(2)](C(6)H(4)ClO(4)S)(2)·3H(2)O. The Ag(I) ion shows linear coordination [N-Ag-N = 175.2 (1) °]. The ammonium and diamminesilver cations, the benzene-sulfonate anion and the lattice water mol-ecules inter-act through an intricate network of N-H⋯O and O-H⋯O hydrogen bonds to form a three-dimensional network.

Porous Cr2O3 Architecture Assembled by Nano-Sized Cylinders/Ellipsoids for Enhanced Sensing to Trace H2S Gas.

How to achieve high sensing of Cr2O3-based sensors for harmful inorganic gases is still a challenge. To this end, Cr2O3 nanomaterials assembled from different building blocks were simply prepared by chromium salt immersion and air calcination with waste scallion roots as the biomass template. The hierarchical architecture calcined at 600 °C is constructed from nanocylinders and nanoellipsoids (named as Cr2O3-600), and also possesses multistage pore distribution for target gas accessibility. Interestingly, the synergism of two shapes of nanocrystals enables the Cr2O3-based sensor to realize highly sensitive detection of trace H2S gas. At 170 °C, Cr2O3-600 exhibits a high response of 42.8 to 100 ppm H2S gas, which is 3.45 times larger than that of Cr2O3-500 assembled from nanocylinders. Meanwhile, this sensor has a low detection limit of 1.0 ppb (S = 1.4), good selectivity, stability, and moisture resistance. These results show that the combination of nanosized cylinders/ellipsoids together with exposed (104) facet can effectively improve the sensing performance of the p-type Cr2O3 material. In addition, the Cr2O3-600 sensor shows satisfactory results for actual monitoring of the corruption process of fresh chicken.

A new phosphine oxide host based on ortho-disubstituted dibenzofuran for efficient electrophosphorescence: towards high triplet state excited levels and excellent thermal, morphological and efficiency stability.

An efficient host for blue and green electrophosphorescence, 4,6-bis(diphenylphosphoryl)dibenzofuran (o-DBFDPO), with the structure of a short-axis-substituted dibenzofuran was designed and synthesised. It appears that the greater density of the diphenylphosphine oxide (DPPO) moieties in the short-axis substitution configuration effectively restrains the intermolecular interactions, because only very weak π-π stacking interactions could be observed, with a centroid-to-centroid distance of 3.960 Å. The improved thermal stability of o-DBFDPO was corroborated by its very high glass transition temperature (T(g)) of 191 °C, which is the result of the symmetric disubstitution structure. Photophysical investigation showed o-DBFDPO to be superior to the monosubstituted derivative, with a longer lifetime (1.95 ns) and a higher photoluminescent quantum efficiency (61 %). The lower first singlet state excited level (3.63 eV) of o-DBFDPO demonstrates the stronger polarisation effect attributable to the greater number of DPPO moieties. Simultaneously, an extremely high first triplet state excited level (T(1)) of 3.16 eV is observed, demonstrating the tiny influence of short-axis substitution on T(1). The improved carrier injection ability, which contributed to low driving voltages of blue- and green-emitting phosphorescent organic light-emitting diodes (PHOLEDs), was further confirmed by Gaussian calculation. Furthermore, the better thermal and morphological properties of o-DBFDPO and the matched frontier molecular orbital (FMO) levels in the devices significantly reduced efficiency roll-offs. Efficient blue and green electrophosphorescence based on the o-DBFDPO host was demonstrated.

Planar tetranuclear Dy(III) single-molecule magnet and its Sm(III), Gd(III), and Tb(III) analogues encapsulated by salen-type and ß-diketonate ligands.

The syntheses, structures, and magnetic properties are reported for four new lanthanide clusters [Sm(4)(µ(3)-OH)(2)L(2)(acac)(6)]·4H(2)O (1), [Gd(4)(µ(3)-OH)(2)L(2)(acac)(6)]·4CH(3)CN (2), and [Ln(4)(µ(3)-OH)(2)L(2)(acac)(6)]·2H(2)L·2CH(3)CN (3, Ln = Tb; 4, Ln = Dy) supported by salen-type (H(2)L = N,N'-bis(salicylidene)-1,2-cyclohexanediamine) and ß-diketonate (acac = acetylacetonate) ligands. The four clusters were confirmed to be essentially isomorphous by infrared spectroscopy and single-crystal X-ray diffraction. Their crystal structures reveal that the salen-type ligand provides a suitable tetradentate coordination pocket (N(2)O(2)) to encapsulate lanthanide(III) ions. Moreover, the planar Ln(4) core is bridged by two µ(3)-hydroxide, four phenoxide, and two ketonate oxygen atoms. Magnetic properties of all four compounds have been investigated using dc and ac susceptibility measurements. For 4, the static and dynamic data indicate that the Dy(4) complex exhibits slow relaxation of the magnetization below 5 K associated with single-molecule magnet behavior.

New family of silver(I) complexes based on hydroxyl and carboxyl groups decorated arenesulfonic acid: syntheses, structures, and luminescent properties.

Self-assembly of silver(I) salts and three ortho-hydroxyl and carboxyl groups decorated arenesulfonic acids affords the formation of nine silver(I)-sulfonates, (NH(4))·[Ag(HL1)(NH(3))(H(2)O)] (1), {(NH(4))·[Ag(3)(HL1)(2)(NH(3))(H(2)O)]}(n) (2), [Ag(2)(HL1)(H(2)O)(2)](n) (3), [Ag(2)(HL2)(NH(3))(2)]·H(2)O (4), [Ag(H(2)L2)(H(2)O)](n) (5), [Ag(2)(HL2)](n) (6), [Ag(3)(L3)(NH(3))(3)](n) (7), [Ag(2)(HL3)](n) (8), and [Ag(6)(L3)(2)(H(2)O)(3)](n) (9) (H(3)L1 = 2-hydroxyl-3-carboxyl-5-bromobenzenesulfonic acid, H(3)L2 = 2-hydroxyl-4-carboxylbenzenesulfonic acid, H(3)L3 = 2-hydroxyl-5-carboxylbenzenesulfonic acid), which are characterized by elemental analysis, IR, TGA, PL, and single-crystal X-ray diffraction. Complex 1 is 3-D supramolecular network extended by [Ag(HL1)(NH(3))(H(2)O)](-) anions and NH(4)(+) cations. Complex 2 exhibits 3-D host-guest framework which encapsulates ammonium cations as guests. Complex 3 presents 2-D layer structure constructed from 1-D tape of sulfonate-bridged Ag1 dimers linked by [(Ag2)(2)(COO)(2)] binuclear units. Complex 4 exhibits 3-D hydrogen-bonding host-guest network which encapsulates water molecules as guests. Complex 5 shows 3-D hybrid framework constructed from organic linker bridged 1-D Ag-O-S chains while complex 6 is 3-D pillared layered framework with the inorganic substructure constructing from the Ag2 polyhedral chains interlinked by Ag1 dimers and sulfonate tetrahedra. The hybrid 3-D framework of complex 7 is formed by L3(-) trianions bridging short trisilver(I) sticks and silver(I) chains. Complex 8 also presents 3-D pillared layered framework, and the inorganic layer substructure is formed by the sulfonate tetrahedrons bridging [(Ag1O(4))(2)(Ag2O(5))(2)](∞) motifs. Complex 9 represents the first silver-based metal-polyhedral framework containing four kinds of coordination spheres with low coordination numbers. The structural diversities and evolutions can be attributed to the synthetic methods, different ligands and coordination modes of the three functional groups, that is, sulfonate, hydroxyl and carboxyl groups. The luminescent properties of the nine complexes have also been investigated at room temperature, especially, complex 1 presents excellent blue luminescence and can sensitize Tb(III) ion to exhibit characteristic green emission.

A rational design of layered metal-organic framework towards high-performance adsorption of hazardous organic dye.

Water pollution originating from organic dyes is endangering the survival and development of society; however, adsorbents with high capacity (>5000 mg g-1) for the fast removal (≤30 min) of Congo Red (CR) in aqueous solution have been not reported to date. In the present work, an acid-base stably layered MOF, [Cd(H2L)(BS)2]n·2nH2O (L-MOF-1, H2L = N1,N2-bis(pyridin-3-ylmethyl)ethane-1,2-diamine, BS = benzenesulfonate), was hydrothermally prepared. L-MOF-1 exhibited high-performance adsorption of CR in aqueous solution at room temperature. The experimental adsorption capacity of the L-MOF-1 adsorbent towards CR reached up to about 12 000 mg g-1 in 20 min in the pH range of 2.2-4.7, which is the best adsorbent with the highest capacity and fastest adsorption of CR to date. The spontaneous adsorption process can be described by the pseudo-second-order kinetic and Langmuir isotherm models. Meanwhile, the L-MOF-1 absorbent possessed a highly positive zeta potential in acid condition (even at pH = 2.2, zeta potential = 36.2 mV). Its good adsorption performance mainly originates from its strong electrostatic attraction with CR in acidic condition, together with diverse hydrogen bonds and ππ stacking interactions. Furthermore, the L-MOF-1 absorbent exhibited good selectivity and could be reused five times through simply washing, where its adsorption efficiency was hardly affected. Therefore, L-MOF-1 is a potential absorbent for effectively removing CR from dye wastewater.

Novel neuron-network-like Cu-MoO2/C composite derived from bimetallic organic framework for highly efficient detection of hydrogen peroxide.

Fabrication of non-enzymatic electrochemical sensors based on metal oxides with low valence-state for nanomolar detection of H2O2 has been a great challenge. In this work, a novel neuron-network-like Cu-MoO2/C hierarchical structure was simply prepared by in-situ pyrolysis of 3D bimetallic-organic framework [Cu(Mo2O7)L]n [L: N-(pyridin-3-ylmethyl)pyridine-2-amine] crystals. Meanwhile, the MoO2/C nano-aggregates were also obtained by liquid phase copper etching. Subsequently, two non-enzymatic electrochemical sensors were fabricated by simple drop-coating of the above two materials on the surface of glassy carbon electrode (GCE). Electrochemical measurements indicate that the Cu-MoO2/C/GCE possesses highly efficient electrocatalytic H2O2 property during wider linear range of 0.24 µM-3.27 mM. At room temperature, the Cu-MoO2/C composite displays higher sensitivity (233.4 µA mM-1 cm-2) and lower limit of detection (LOD = 85 nM), which are 1 and 2.5 times larger than those of MoO2/C material, respectively. Such excellent ability for trace H2O2 detection mainly originates from the synergism of neuron-network-like structure, enhanced electrical conductivity and increased active sites caused by low valence-state MoO2 and co-doping of Cu and carbon, and even the interaction between Cu and Mo. In addition, the H2O2 detection in spiked human serum and commercially real samples indicates that the Cu-MoO2/C/GCE sensor has certain potential application in the fields of environment and biology.

Potential Anti-Tumor Drug: Co-Crystal 5-Fluorouracil-nicotinamide.

5-Fluorouracil-nicotinamide (5-FU-NCM), a co-crystal with a 2D layer structure formed by hydrogen bonds, was synthesized by solvent evaporation and liquid phase-assisted grinding at room temperature. Compared to 5-FU alone, the results of solubility, oil-water partition coefficient, anti-tumor effect in vivo and vitro, acute toxicity, and pharmacokinetic parameters indicate that the co-crystal is a potential anti-tumor drug.

Cd(ii) coordination polymers constructed from bis(pyridyl) ligands with an asymmetric spacer in chelating mode and diverse organic dicarboxylates: syntheses, structural evolutions and properties.

Self-assembly of diverse Cd(ii) metal salts, four organic dicarboxylic acids, and two flexible bis(pyridyl) ligands leads to the formation of thirteen complexes, namely, [Cd(L1)(C4H4O4)]n (1), [Cd(L2)(C4H4O4)0.5]n·nOH·8nH2O (2), [Cd(L1)(C4H2O4)]n (3), [Cd(L1)(C4H2O4)]n (4), [Cd2(L2)(C4H2O4)2(H2O)2]n·nH2O (5), [Cd2(L1)(m-BDC)2(H2O)2]n (6), [Cd2(L2)(m-BDC)2(H2O)2]n (7), [Cd3(L1)2(p-BDC)3(H2O)4]n·2nH2O (8), [Cd(L2)(p-BDC)0.5Cl]n (9), [Cd(L2)(p-BDC)0.5(H2O)]n·n(ClO4)·nH2O (10), [Cd3(L2)2(p-BDC)(SO4)2(H2O)6]n·4nH2O (11), [Cd(L2)(p-BDC)]n·nH2O (12) and [Cd(L2)(p-BDC)]n·nMeOH (13) (L1 = N,N'-bis(pyridin-4-ylmethyl)propane-1,2-diamine, L2 = N,N'-bis(pyridin-3-ylmethyl)propane-1,2-diamine, m-BDC2- = m-benzene dicarboxylate dianion, p-BDC2- = p-benzene dicarboxylate dianion), which have been characterized by elemental analysis, IR, TG, PL, and powder and single-crystal X-ray diffraction. The influence of different Cd(ii) salts on the structure variations and properties has also been investigated. Complexes 1 and 3 present a (4,4) layer motif accomplished by the interconnection of adjacent Cd(ii) cations through L1 molecules and trans-conformational succinates or fumarates. In contrast, the cis-conformational succinates in complex 2 only afford the formation of a chain structure. The L1 and L2 molecules in complexes 4 and 5 adopt the same coordination and join adjacent Cd(ii) cations together with fumarates, giving rise to different 3D networks with vma and irl topologies. The same coordination mode of L1 and L2 in complexes 6-8 joins adjacent Cd(ii) cations together with aromatic dicarboxylates, leading to different (63)(65·8), 2-periodic (6·3) and (4·4) layer motifs. The L2 molecules in complexes 9-13 present different coordination modes and join adjacent Cd(ii) cations together with p-BDC2- dianions to form diverse (6·3) layer motifs, and different 3D networks with cds and eca topologies. Therefore, the diverse coordination modes of the bis(pyridyl) ligand and the feature of different organic dicarboxylate anions can effectively influence the topological structures of these complexes. Luminescence investigation reveals that the emission maximum of these complexes varies from 403 to 433 nm in the solid state at room temperature.

Enhanced H2S gas-sensing performance of Zn2SnO4 hierarchical quasi-microspheres constructed from nanosheets and octahedra.

Most of the reported ternary oxides based sensors have not been realized to detect ppb-level H2S till now. In this work, Zn2SnO4 hierarchical quasi-microspheres were prepared through a facile surfactant-free hydrothermal method followed by calcination in air atmosphere. The quasi-microspheres are composed of nanosheets with the thickness of 100 nm and octahedra with the average size of 0.63 µm, respectively. The sensor fabricated from such Zn2SnO4 hierarchical quasi-microspheres shows excellent selective response to H2S at 133 °C with the lowest detection limit of 1 ppb. The gas response exhibits good linear relationship in the concentration range of 1-1000 ppb. Such outstanding H2S sensing property might be attributed to its porous structure, the synergistic effect of the two typical building blocks and the surface adsorbed oxygen, and the possible sensing mechanism is also discussed.