RESUMO
The success and continued expansion of research on metal-oxo clusters owe largely to their structural richness and wide range of functions. However, while most of them known to date are negatively charged polyoxometalates, there is only a handful of cationic ones, much less functional ones. Here, we show an all-inorganic hydroxyiodide [H10.7Sb32.1O44][H2.1Sb2.1I8O6][Sb0.76I6]2·25H2O (HSbOI), forming a face-centered cubic structure with cationic Sb32O44 clusters and two types of anionic clusters in its interstitial spaces. Although it is submicrometer in size, electron diffraction tomography of HSbOI allowed the construction of the initial structural model, followed by powder Rietveld refinement to reach the final structure. The cationic cluster is characterized by the presence of acidic protons on its surface due to substantial Sb3+ deficiencies, which enables HSbOI to serve as an excellent solid acid catalyst. These results open up a frontier for the exploration and functionalization of cationic metal-oxo clusters containing heavy main group elements.
RESUMO
Microbially induced calcite precipitation (MICP) has been shown to mitigate sand erosion; however, few studies have applied MICP on loess soils. In this study, polyacrylamide (PAM) was added to the cementation solution, and combined MICP-PAM treatment was applied to improve the surface erosion resistance of loess-slopes. The freeze-thaw (FT) durability of MICP-PAM treated loess slopes was also studied. The obtained results showed that MICP-PAM treatment improved erosion resistance and addition of 1.5 g/L PAM achieved the best erosion control and highest surface strength. The high erosion resistance of MICP-PAM treated slopes could be attributed to the stable spatial structure of precipitation, and PAM addition conveyed stronger resistance to tension or shear force. With increasing number of FT cycles, the surface strength of MICP-PAM treated loess slopes decreased; however, slopes subjected to 12 FT cycles still only lost little soil. In MICP-PAM treated loess slopes, cracks and pores evolved with increasing number of FT cycles. With increasing number of FT cycles, porosity and fractal dimension increased, pore ellipticity decreased slightly, and the percentage of various pores changed slightly. The number of FT cycles had less effect on MICP-PAM treated loess slopes than on untreated slopes. MICP-PAM treatment significantly mitigated surface erosion of loess-slopes and improved FT weathering resistance, thus presenting promising potential for application in the field. In addition, based on the linear correlations between surface strength and rainfall-erosion resistance, surface strength could be measured to evaluate the rainfall-erosion resistance for MICP-PAM treated slopes in practical engineering applications.
Assuntos
Polímeros , Solo , Carbonato de CálcioRESUMO
Vitamin C (VC) and folic acid (FA) are the important nutrient and antioxidant in human body. In order to improve their stability, their co-loaded liposomes (VCFA-Lip) and chitosan-coated liposomes (CS-VCFA-Lip) are prepared and characterised. The mean particle size of VCFA-Lip and CS-VCFA-Lip is 138 nm and 249 nm, respectively. The encapsulation efficiencies of both drugs for CS-VCFA-Lip are much higher than those for VCFA-Lip. Furthermore, the experimental results show that the antioxidant activity of CS-VCFA-Lip is higher than that of VCFA-Lip. Moreover, the storage stability study reveals that the chitosan coating can efficiently improve the physical stability of VCFA-Lip. These results indicate that stability of VC and FA can be greatly improved after being wrapped by liposomes. In addition, the performance of CS-VCFA-Lip is better than VCFA-Lip, indicating CS-VCFA-Lip can be applied as a promising delivery system for the antioxidant defence system to the food industry and cosmetic industry.
