Axs d8 focus

The chemical bonds of the specimens were determined by AXS D8-Focus from Bruker, Rheinstetten, Germany, and FTIR-8000S from Seiko, Tokyo, Japan. The microstructures of LiB-AC grout were investigated by Scanning Electron Microscopy (SEM, COXEM EM-30Plus, Daejeon, Republic of Korea). All specimens of microstructure analyzed were crushed into pieces using the stone body after the mechanical test, then stored in alcohol and dried at 60 °C for 24 h before microstructure analysis.

The pH of drip waters was measured in situ with a multiparameter water quality detector (HACH, Loveland, CO, United States). Temperature, humidity, and the concentration of carbon dioxide for cave air from entrance to the innermost were detected in field. pH of solid samples was measured with a UB-7 pH meter (Denver Instrument) in the laboratory. The concentrations of dissolved major anions and cations were analyzed using an ICS-900 ion chromatograph (Thermo Fisher, USA). The mineral phases of weathered rocks and sediments were analyzed by X-ray diffraction (XRD, Bruker AXS D8-Focus, Germany).

The mineralogical composition of the samples was determined by the combination of XRD and Raman spectroscopy. XRD was conducted using a Bruker X-Ray diffractometer (AXS D8-Focus), scanning samples in the 2 ϴ-diffraction angle from 5° to 70°, with a scanning step size of 0.01°, at 40 kV and 40 mA with a Cu X-ray source (Cu Kα1,2, λ = 1.54056 Å). Near Infrared (NIR; from 10,000 to 4,000 cm⁻¹) spectra were collected at 4 cm⁻¹ resolution with a Nicolet iS50FTIR spectrometer using the diffuse reflection (DRIFTS) attachment, a DTGS-KBr detector, and a XT-KBr beamsplitter. Raman spectroscopy was performed with a Horiba JobinYvon Hri550 connected to a Charge Coupled Device (CCD) with 1024 × 256 pixels cooled to 203 K for thermal-noise reduction. Before work, the Raman spectrometer was prepared with four diffraction gratings of 600, 1200, 1800 and 2400 grooves/mm that provide a wide range of intensity signal/resolution ratio. Sample excitation was done by an intensity-modulated (0–200 mW) non-polarized Nd:YAG solid state laser with a wavelength of 532 nm. The spectrometer was connected through fiber optics to a B&W Tek microscope with a 20X objective (Microbeam S. A.), which gives a spot size of 105 µm. When using a 1200 grooves/mm diffraction grating and 198 µm aperture of slit entrance, the resolution is better than 5 cm⁻¹.

CDS-PMo₁₂@PVP_x(x = 0 ~ 1) NPs were synthesized according to the previously described approach with some modifications [25 (link)]. Detailed procedures are given in the experimental part of the SI. The morphology of the CDS-PMo₁₂@PVP_x(x = 0 ~ 1) NPs was observed with transmission electron microscopy (biology TEM, Tecnai G2 spirit Biotwin operated at 120 kV; Talos F200X G2 operated at 200 kV). The crystalline structure was recorded by X-ray diffractometer (XRD) (Bruker AXS D8 Focus), using Cu Ka radiation (λ = 1.54056 A). Fourier transform infrared (FT-IR) spectra were acquired from a Nicolet 50 FT-IR spectrometer (Thermo Fisher Scientific, Waltham, MA, USA), ranging from 400 to 4000 cm⁻¹. The UV–Vis absorption spectra were measured on UV 2600 UV–Vis spectrophotometer. The nanoparticles distribution characteristics and zeta-potential were measured using a particle size analyzer (Malvern, Nano ZS, Japan). Fluorescence measurements were performed on a Jobin Yvon Horiba Fluoromax-3 spectrophotometer.

The mineral phases of the precipitates were detected via X-ray diffraction (XRD) (Bruker AXS D8-Focus, Germany) using Cu-Kα radiation. The peaks of the minerals were detected from 3 to 70° (2𝜃) with a step size of 0.01° and scan speed of 10°/min. The XRD spectra were analyzed using the Jade 6.5 software. The percentages of the minerals in the precipitates were calculated by the Software of Xpowder 12. The mole percentage of Mg²⁺ in dolomite was calculated based on the empirical equation of Goldsmith et al. (1961) and Zhang et al. (2010) (link). XRD analysis was conducted at the School of Material and Chemical Engineering at the China University of Geoscience (Wuhan).
The morphology and elements of the precipitates were determined by scanning electron microscopy (SEM, FEI Quanta 450 FEG, United States) with an X-ray Energy Dispersive Spectrometer (EDS, SDD Inca X-Max 50, Britain). Dried precipitates were adhered onto SEM stubs with double-sided conductive tapes, followed by coating with Pt for image observation. The accelerating voltages of the SEM and EDS were 15 and 20 kV, respectively. SEM analysis was done at the State Key Laboratory of Geobiology and Environmental Geology at the China University of Geoscience (Wuhan).