ABSTRACT
Li7La3Zr2O12 (LLZO) garnet is one kind of solid electrolyte drawing extensive attention due to its good ionic conductivity, safety, and stability toward lithium metal anodes. However, the stability problem during synthesis and storage results in high interfacial resistance and prevents it from practical applications. We synthesized air-stable dual-doped Li6.05La3Ga0.3Zr1.95Nb0.05O12 ((Ga, Nb)-LLZO) cubic-phase garnets with ionic conductivity of 9.28 × 10-3 S cm-1. The impurity-phase species formation on the garnet pellets after air exposure was investigated. LiOH and Li2CO3 can be observed on the garnet pellets by Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) once the garnets are exposed to humid air or come in contact with water. The (Ga, Nb)-LLZO garnet is found to form less LiOH and Li2CO3, which can be further reduced or removed after drying treatment. To confirm the stability of the garnet, an electrochemical test of the Li//Li symmetric cell was also performed in comparison with previously reported garnets (Li7La2.75Ca0.25Zr1.75Nb0.25O12, (Ca, Nb)-LLZO). The dual-doped (Ga, Nb)-LLZO showed less polarized and stable plating/stripping behavior than (Ca, Nb)-LLZO. Through Rietveld refinement of XRD patterns of prepared materials, dopant Ga was found to preferably occupy the Li site and Nb takes the Zr site, while dopant Ca mainly substituted La in the reference sample. The inherited properties of the dopants in (Ga, Nb)-LLZO and their structural synergy explain the greatly improved air stability and reduced interfacial resistance. This may open a new direction to realize garnet-based solid electrolytes with lower interfacial resistance and superior air stability.
ABSTRACT
Deoxynivalenol (DON) is one of the trichothecene mycotoxin, a frequent contaminant of pig feed. Surface-enhanced Raman spectroscopy (SERS) is a fast and ultrasensitive analytical tool for point-of-need applications to identify molecular fingerprint structures at low concentrations. However, the use of SERS for analyte detection with flexible and robust structures is still challenging. Herein, we have developed core-shell silver nanocubes coated with polydopamine (Ag NCs@PDA) SERS substrate for the quantitative detection of deoxynivalenol in pig feed. The Ag NCs@PDA substrate with ultrathin (1.6 nm) PDA shell thickness enhances the absorption of DON via hydrogen bonding and π-π stacking interactions, as well as improves the stability of the substrate. The results of the SERS showed a high analytical enhancement factor (AEF) of 1.82 × 107 and a detection limit (LOD) as low as femtomolar range (0.82 fM). The LOD of the Ag NCs@PDA substrate for DON detection is 1.8 times lower than the bare Ag NCs. Furthermore, the Ag NCs@PDA substrate is stable which retains 88.24% of the original Raman intensity after storage for three months. The obtained results demonstrate that the Ag NCs@PDA substrates can realize label-free detection of deoxynivalenol mycotoxin with high sensitivity, reproducibility, and stability. Our work proposes a low-cost method for the designing of the SERS sensing device, and has great potential to be applied in food safety, biomedical sciences, and environmental monitoring.
