Metal Oxide Gas Sensors: Sensitivity and Influencing Factors

Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above

Porous hierarchical TiO2/MoS2/RGO nanoflowers as anode material for sodium ion batteries with high capacity and stability

To enhance the reversible capacity and cycle stability of MoS2 as anode materials for sodium ion batteries (SIBs), we constructed a hybrid architecture composed of MoS2 and TiO2 nanosheets, linking with reduced graphene oxide (RGO) to another TiO2/MoS2 to form a nanoflower structure. Owing to layered RGO coupled with TiO2/MoS2 hybrid, such a composite offered interconnected conductive channels to short shuttle path of Na+ ions and favorable transport kinetics under charge/discharge cycling. Moreover, this unique structure showed a porous and hierarchical architecture, which not only buffered volume changes but also provided more electrochemical active sites during insertion/deintercalation processes of Na ions. Outstanding electrochemical performances were identified by the component matching effect among TiO2, MoS2 and RGO with a three-dimensional (3D) interconnected network, exhibiting a good reversible capacity of 616 mA h g-1 after 100 cycles at 0.1 A g-1, an excellent rate capability of 250 mA h g-1 even at 5A g-1 and a long cycling stability of 460 mA h g-1 with a capacity fluctuation of 0.03% per cycle within 350 cycles at 1 A g-1

Research on ecological compensation of urban residual space to promote social integration

The continuous urbanization leads to a large number of land lost farmers pouring into the city, and the social integration of these people has become an important research topic of urban renewal. By means of field exploration and in-depth visit, this paper investigates and collates the data of some typical urban residual spaces where new industrial workers live, and finds that these spaces have common spatial characteristics, such as single spatial level, poor ecological environment and lack of landscape facilities. Then, by using statistical analysis and structural model, the comparative analysis of different types of space, and finds that the use of ecological compensation regulation can form a reasonable spatial layout, high-quality ecological effects and rich service facilities, so as to improve the spatial quality of urban residual space and provide highquality space environment for new industrial workers, Promote social integration, social integration of workers in new industries

Application of bismuth sulfide based nanomaterials in cancer diagnosis and treatment

Cancer is still the leading disease threatening human life and health at present. With the development of nanotechnology, multifunctional nanomaterials integrated with different diagnostic and therapeutic functions have become the most active field in nano-research. Among them, Bi2S3-based nanomaterials have attracted great attention in the biomedical field due to their special photothermal effect and biocompatibility. In this review, we systematically summarize the synthetic strategies and their physical-chemical properties of Bi2S3-based nanomaterials. Then we outline the recent research progress in the diagnosis and treatment of cancer, which are highlighted and discussed in detail. In addition, the safety and biodistribution of Bi2S3-based nanomaterials are emphasized and discussed. It is believed that the emerging Bi2S3-based nanomaterials may realize the practical applications via unremitting efforts of scientific researchers in the near future

Application of bismuth sulfide based nanomaterials in cancer diagnosis and treatment

Cancer is a complicated disease with a significant degree of heterogeneity, despite having made impressive advances in the field of cancer treatment, cancer remains a major threat to human life and health. The complexity of cancer on the genetic and phenotypic planes defines its clinical diversity and the difficulty of treatment. The increasing incidence of integrative types as well as individual types of cancer with the passage of time has prompted the development of novel cancer treatment strategies. Current treatment protocols are based on correcting gene mis-expression, blocking nutrient delivery to the tumor, or destroying the cancer cells. Often, surgery cannot completely eliminate all cancer cells in the body, leaving the cancer at risk of recurrence and high mortality. Chemotherapy and radiotherapy have serious side effects on normal tissue cells in the body while killing cancer cells, and these approaches are still unsatisfactory due to insufficient specificity and dose limitations. The development of novel drugs with specific targeted therapies or site-specific delivery systems to deliver therapeutic agents can greatly avoid the toxicity to healthy tissues caused by non-specificity. The preparation of nanomaterials is the most important basic technology in nanotechnology research, as well as a prerequisite for nanoapplication technology and nano-industrialization, which has been the key focus of nanotechnology researchers’ attention and research. With the development of nanotechnology, multifunctional nanomaterials, which integrate various diagnostic and therapeutic functions, have become the most active field in nanoscale research, and have been applied in the fields of early screening of tumors, identification of tumor biomarkers, targeted release of chemotherapeutic drugs and development of novel therapies. After decades of development, biomedical nanomaterials have been applied to cancer diagnosis, tumor imaging, drug loading, tumor therapy, etc. They have excellent biocompatibility and biodistribution, with advantages unmatched over traditional therapeutic methods. Among them, Bi2S3 based nanomaterials have attracted great attention in the biomedical field due to their special photothermal effect and biocompatibility, etc. The authors summarize the preparation methods of Bi2S3 based nanomaterials with different morphological dimensions reported in the literature, as well as effective strategies for constructing different heterogeneous structures. Currently, Bi2S3 based nanomaterials have been widely used in cancer diagnosis. The main strategy is the combination of various functionalized probe-loaded Bi2S3 with various imaging methods to determine tumor boundaries, histological analysis and 3D stereoscopic imaging detection. Meanwhile, due to its superior photothermal conversion efficiency and X-ray attenuation coefficient, Bi2S3 based nanomaterials have been widely used in a range of fields such as photothermal therapy, photodynamic therapy, radio sensitization therapy, immunotherapy and chemotherapy by means of rational modifications and loading. Since individual imaging modalities cannot provide complete information about the tumor treatment, Bi2S3 based nanomaterials with multimodal imaging capabilities can enable real-time monitoring of tumors and real-time observation of therapeutic agent metabolism, providing guidance for tumor treatment. In addition, a mono-therapeutic approach is often unable to completely inhibit and kill tumors, so Bi2S3 based nanomaterials integrating multiple therapeutic approaches can not only reduce the dose of chemotherapeutic drugs, but also cause serious damage to tumor cells and inhibit the metastasis of cancer cells, which greatly reduces the possibility of tumor recurrence and is of great significance for a favorable prognosis of tumor treatment. Finally, the authors highlight and discuss the biosafety and biodistribution of Bi2S3 based nanomaterials, as well as summarize methods to improve the biocompatibility of nanoparticles, providing indicative clues for further biosafety applications of Bi2S3 based nanomaterials

Rare Earth Partition Characteristics and Sedimentary Diagenetic Response in Layered Argillaceous Limestone: Taking the Shale of Upper Es4 in the Nx55 Well Area as an Example

Taking the layered argillaceous limestone in the upper Es4 in the Dongying Sag as the research object, the geochemical analysis of major, trace, and rare earth elements (REEs) established the response relationship between REE distribution characteristics and sedimentary diagenesis. The average values of total light REE (ΣLREE)/total heavy REE (ΣHREE) of micrite calcite and argillaceous laminae are 6.75 and 4.06, respectively. The LREEs and HREEs are differentiated, consistent with the distribution pattern of REEs in the crust. Th and U elements are more enriched in the sediments in the lacustrine sedimentary environment than in the diagenetic calcite veins. In primary sediments (argillaceous clay and micrite calcite laminae), LREEs are more enriched, HREEs are depleted, and Eu shows positive anomaly-enrichment characteristics. The LREEs and HREEs of the sparry calcite veins are lower than those of the original sediment argillaceous clay and micrite calcite, showing characteristics of a negative anomaly depletion. Sparry calcite veins originate from diagenetic fluid crystallization and precipitation and have the characteristics of low Th and U, evident positive anomalies of Sr and Eu, and substantial depletion of La. The distribution patterns of REEs within the four components of the laminated argillaceous sparry limestone reflect the order of REE distribution from primary sediment laminae (argillaceous clay and micrite calcite) to diagenetic laminae (calcite veins). Compared with the North American shale, the four components of the contact surface between the argillaceous and bright crystalline laminae, the micrite calcite, the calcite veins, and the argillaceous laminae all showed weak negative δCe anomalies and positive δEu anomalies. The fractionation degree between LREEs and HREEs reflected by La/Smcn and Gd/Ybcn is in descending order: the interface between the argillaceous lamina and sparry calcite lamina, micritic calcite, calcite vein, and argillaceous lamina. The argillaceous laminar material has the characteristics of basalt REEs, indicating that the terrestrial debris and argillaceous lacustrine shale in the upper Es4 member of the Niuzhuang subsag are primarily derived from the basic extrusive rocks of the Qingtuozi bulge. REE differentiation is most noticeable at the interface between the argillaceous lamina and calcite vein, proving the directionality of REE differentiation from the original sedimentary lamina to the diagenetic lamina. Shale in the study area is primarily deposited below the redox interface of water at a certain depth, and the deposition rate is stable and slow, providing good conditions for preserving organic matter

Synergy between nanozymes and natural enzymes on the hybrid MoS2 nanosheets/graphite microfiber for enhanced voltammetric determination of hydrogen peroxide

A biosensor for hydrogen peroxide (H2O2) has been developed based on the use of MoS2 nanosheets and graphite that are assembled to form a microfiber hybrid structure. The MoS2 nanosheets are synthesized in situ on a graphite microfiber. The chemical composition and surface morphology of the microfiber hybrid structure has been characterized. The microfiber is shown to display peroxidase-mimicking activity. In the next step, horseradish peroxidase, methylene blue, and chitosan are co-immobilized on the microfiber electrode. The use of MoS2 nanosheets warrants high electrochemical activity of immobilized enzyme on the electrode surface. The modified microfiber electrode, best operated at a voltage of − 0.3 V (vs. Ag/AgCl), can be used to sense H2O2 with a linear response in the 0.1 to 90 μM concentration range and with a determination limit of 30 nM (at S/N = 3). The good response is attributed to the synergistic enhancement of the synthetic nanozymes (few-layered MoS2 nanosheets) and immobilized natural horseradish peroxidase (HRP). [Figure not available: see fulltext.] © 2020, Springer-Verlag GmbH Austria, part of Springer Nature