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.

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.

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.

Coral-like CoMoO4 hierarchical structure uniformly encapsulated by graphene-like N-doped carbon network as an anode for high-performance lithium-ion batteries.

Encapsulation of metal oxide anode material with hierarchical structure in graphene-like high conductivity carbon network is conducive to improving the lithium storage performance of the anode material. However, it is very challenging to rational synthesizing anode materials with such structure. Herein, a mesoporous spiny coral-like CoMoO4 (SCL-CMO) self-assembled from the mesoporous nanorods made of nanoparticles is prepared by a simple one-step solvothermal method. The layered coral-like CoMoO4@N-doped Carbon (LCL-CMO@NC) composite is synthesized by polymerization of DA on the surface of SCL-CMO at room temperature and the subsequent sintering treatment. This LCL-CMO@NC composite perfectly combines the comprehensive advantages of the spiny coral-like hierarchical architecture and the N-doped graphene-like carbon coating, which not only effectively improve the electron and Li+ ion transport dynamics and accommodate the large volume changes, but also prevent hierarchical structure aggregation and pulverization during cycle process. Therefore, LCL-CMO@NC composite exhibits superior electrochemical kinetics and stability. The reversible specific capacity remained 1321.6 and 132 mA h g-1 after 900 and 10,000 cycles at 0.4 and 5 A g-1, respectively.

Large-Scale Synthesis of Hierarchically Porous ZnO Hollow Tubule for Fast Response to ppb-Level H2S Gas.

Response and recovery time to toxic and inflammable hydrogen sulfide (H2S) gas are important indexes for metal oxide sensors in real-time environmental monitoring. However, large-scale production of ZnO-based sensing materials for fast response to ppb-level H2S has been rarely reported. In this work, hierarchically porous hexagonal ZnO hollow tubule was simply fabricated by zinc salt impregnation and subsequently calcination using absorbent cotton as the template. The influence of calcination temperature on the corresponding morphology and sensing properties is also explored. The hollow tubules calcined at 600 °C are constructed from abundant cross-linked nanoparticles (∼20 nm). Its Brunauer-Emmett-Teller surface area is 31 m2·g-1 and the meso- and macroporous sizes are centered at 35 and 115 nm, respectively. The sensor with a lower detection limit of 10 ppb exhibits a fast response speed of 29 s toward the 50 ppb H2S rather than those of the reported intrinsic and doped ZnO-based sensing materials. Furthermore, the sensor shows a wide linear range (10-1000 ppb), good reproducibility, and stability. Such excellent trace ppb-level H2S performances are mainly related to the inherent characteristics of hierarchically porous hollow tubular structure and the surface-adsorbed oxygen control type mechanism.

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.

Poly[(µ(2)-4,4'-bipyridine-κN:N')(µ(2)-2,2-dimeth-yl-cyclo-pentane-1,3-dicarboxyl-ato-κO,O:O,O)cadmium].

In the title polymeric compound, [Cd(C(9)H(12)O(4))(C(10)H(8)N(2))](n), the Cd(II) atom is located on a twofold rotation axis and is coordinated by two 4,4'-bipyridine ligands and two 2,2-dimethyl-cyclo-pentane-1,3-dicarboxyl-ate ions. The carboxyl-ate ion and the N-heterocycle both function as bridges to link adjacent Cd(II) atoms to result in the formation of a layer structure parallel to (010). The mid-point of the central C-C bond of the 4,4'-bipyridine ligand is located on an inversion center. In the crystal, the carboxyl-ate ion is disordered over a twofold rotation axis in respect of its methyl group and the cyclo-pentane ring.

A three-dimensional lead(II) coordination polymer: poly[aqua-mu-imidazole-4,5-dicarboxylato-lead(II)].

In the title coordination polymer, [Pb(C5H2N2O4)(H2O)](n), the Pb(II) atom is seven-coordinated by one N atom and five O atoms from four individual imidazole-4,5-dicarboxylate (HIDC2-) groups and one water molecule. It is interesting to note that the HIDC2- group serves as a bridging ligand to link the Pb(II) atoms into a three-dimensional microporous open-framework.

Poly[[bis(pyridin-3-ol)manganese(II)]-di-mu-pyridin-3-olato].

In the title complex, [Mn(C5H4NO)2(C5H5NO)2]n or [Mn(mu-3-PyO)2(3-PyOH)2]n (3-PyO- is the pyridin-3-olate anion and 3-PyOH is pyridin-3-ol), the Mn(II) atom lies on an inversion centre and has octahedral geometry, defined by two N atoms and two deprotonated exocyclic O atoms of symmetry-related pyridin-3-olate ligands [Mn-N = 2.3559 (14) A and Mn-O = 2.1703 (11) A], as well as two N atoms of terminal 3-PyOH ligands [Mn-N = 2.3482 (13) A]. The Mn(II) atoms are bridged by the deprotonated pyridin-3-olate anion into a layer structure, generating sheets in the (-101) plane. These sheets are linked by O-H...O hydrogen bonds. There are also pi-pi and C-H...pi interactions in the crystal structure.