Recognition of Significant Multi-Element Geochemical Signatures of Lower Soil on Hainan Island, China: Implications for Thermal Mineral Water Exploration

As an important geothermal resource, thermal mineral water has high resource efficiency and thermal energy efficiency. The aim of this study was to delineate prospective areas of thermal mineral water based on potential thermal mineral water sites and faults. Linear regression was used to process the temperature of 22 known thermal mineral water sites as dependent variables, and 54 indices of the lower soil of multipurpose regional geochemical surveys as independent variables, in the area of intermediate-acid intrusive rocks and sediment degeneration rocks on Hainan Island. Published data were quoted from the National Multi-Purpose Regional Geochemical Survey (Hainan Province, China). According to the regressive modelling of 2197 lower soil samples, 547 potential thermal mineral water sites were delineated after considering 4 factors—geological background, regional structure, interval of dependent variable’s predictive temperature, and boundary of independent variable’s contents—which were compared against 22 known thermal mineral water sites to choose the 2197 lower soil samples, based on the choice of prospective sites of thermal mineral water on Hainan Island. The results showed that the proportion of A1-level sites that were >70 °C constituted 11% of all A1-level prospective sites, reflecting the superiority of east–west or north–east directional regional faults in controlling the distribution of thermal mineral water. This study shows the indications of the multipurpose regional geochemical survey with regards to thermal mineral water, which is one of the most important tourist resources of Hainan Island

Recognition of Significant Multi-Element Geochemical Signatures of Lower Soil on Hainan Island, China: Implications for Thermal Mineral Water Exploration

As an important geothermal resource, thermal mineral water has high resource efficiency and thermal energy efficiency. The aim of this study was to delineate prospective areas of thermal mineral water based on potential thermal mineral water sites and faults. Linear regression was used to process the temperature of 22 known thermal mineral water sites as dependent variables, and 54 indices of the lower soil of multipurpose regional geochemical surveys as independent variables, in the area of intermediate-acid intrusive rocks and sediment degeneration rocks on Hainan Island. Published data were quoted from the National Multi-Purpose Regional Geochemical Survey (Hainan Province, China). According to the regressive modelling of 2197 lower soil samples, 547 potential thermal mineral water sites were delineated after considering 4 factors—geological background, regional structure, interval of dependent variable’s predictive temperature, and boundary of independent variable’s contents—which were compared against 22 known thermal mineral water sites to choose the 2197 lower soil samples, based on the choice of prospective sites of thermal mineral water on Hainan Island. The results showed that the proportion of A1-level sites that were >70 °C constituted 11% of all A1-level prospective sites, reflecting the superiority of east–west or north–east directional regional faults in controlling the distribution of thermal mineral water. This study shows the indications of the multipurpose regional geochemical survey with regards to thermal mineral water, which is one of the most important tourist resources of Hainan Island

Covalent Entrapment of Cobalt–Iron Sulfides in N‑Doped Mesoporous Carbon: Extraordinary Bifunctional Electrocatalysts for Oxygen Reduction and Evolution Reactions

To alleviate the kinetic barriers associated with ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) in electrochemical systems, efficient nonprecious electrocatalysts are urgently required. Here we report a facile soft-template mediated approach for fabrication of nanostructured cobalt–iron double sulfides that are covalently entrapped in nitrogen-doped mesoporous graphitic carbon (Co_0.5Fe_0.5S@N-MC). Notably, with a positive half-wave potential (0.808 V) and a high diffusion-limiting current density, the composite material delivers unprecedentedly striking ORR electrocatalytic activity among recently reported nonprecious late transition metal chalcogenide materials in alkaline medium. Various characterization techniques, including X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, are conducted to elucidate the correlation between structural features and catalytic activities of the composite. Moderate substitution and well-dispersion of iron in bimetallic sulfide composites are believed to have positive effect on the adsorption and activation of oxygen-containing species, thus leading to conspicuous ORR and OER catalytic enhancement compared to their monometallic counterparts. Besides, the covalent bridge between active sulfide particles and mesoporous carbon shells provides facile pathways for electron and mass transport. Beneficially, the intimate coupling interaction renders prolonged electrocatalytic performances to the composite. Our results may possibly lend a new impetus to the rational design of bi- or multimetallic sulfides encapsulated in porous carbon with improved performance for electrocatalysis and energy storage applications

Copper-Nitrogen-Coordinated Carbon Dots: Transformable Phototheranostics from Precise PTT/PDT to Post-Treatment Imaging-Guided PDT for Residual Tumor Cells

Phototheranostics has attracted considerable attention in the fields of cancer diagnosis and treatment. However, the complete eradication of solid tumors using traditional phototheranostics is difficult because of the limited depth and range of laser irradiation. New phototheranostics enabling precise phototherapy and post-treatment imaging-guided programmed therapy for residual tumors is urgently required. Accordingly, this study developed a novel transformable phototheranostics by assembling hyaluronic acid (HA) with copper-nitrogen-coordinated carbon dots (CDs). In this transformable nanoplatform, named copper-nitrogen-CDs@HA, the HA component enables the specific targeting of cluster determinant (CD) 44-overexpressing tumor cells. In the tumor cells, redox glutathione converts Cu(II) (cupric ions) into Cu(I) (cuprous ions), which confers the novel transformable functionality to phototheranostics. Both in vitro and in vivo results reveal that the near-infrared-light-photoactivated CuII-N-CDs@HA could target CD44-overexpressing tumor cells for precise synergistic photothermal therapy and photodynamic therapy. This study is the first to observe that CuII-N-CDs@HA could escape from lysosomes and be transformed in situ into CuI-N-CDs@HA in tumor cells, with the d9 electronic configuration of Cu(II) changing to the d10 electronic configuration of Cu(I), which turns on their fluorescence and turns off their photothermal properties. This transformable phototheranostics could be used for post-treatment imaging-guided photodynamic therapy on residual tumor cells. Thus, the rationally designed copper-nitrogen-coordinated CDs offer a simple in situ transformation strategy for using multiple-stimulus-responsive precise phototheranostics in post-treatment monitoring of residual tumor cells and imaging-guided programmed therapy