RESUMO
A mild hydrothermal method was employed to successfully synthesize two new sulfate fluorides, namely, AYSO4F2 (A = K, Rb). They are isomorphic, and both contain [YO4F4] polyhedra and [SO4] tetrahedra in the structure. Theoretical calculations and experimental tests show that AYSO4F2 (A = K, Rb) have large band gaps (7.79 and 7.82 eV) and moderate birefringence (0.015 and 0.02 @ 546.1 nm), with significantly enhanced birefringence and band gaps as compared to that of the single alkali metal sulfates A2SO4 (A = K, Rb). Furthermore, theoretical calculations show that [YO4F4] polyhedra are the main reason for the band gap and birefringence enhancement. This work contributes to the advancement of structural chemistry in the field of rare-earth sulfates, offering a novel approach for the design of sulfates characterized by large birefringence.
RESUMO
Zero-order waveplates are widely used in the manufacture of laser polarizer waves, which are important in polarimetry and the laser industry. However, there are still challenges in designing deep-ultraviolet (DUV) waveplate materials that satisfy large band gaps and small optical anisotropy simultaneously. Herein, three cases of aluminum sulfate fluorides: Na2AlSO4F3, Li4NH4Al(SO4)2F4, and Li6K3Al(SO4)4F4, with novel [AlSO4F3] layers or isolated [AlS2O8F4] trimers were designed and synthesized by the rational assembly of [AlO2F4] and [SO4] groups through a hydrothermal method. Experiments and theoretical calculations imply that these three possess short cutoff edges (λ < 200 nm) and small birefringence (0.0014-0.0076 @ 1064 nm), which fulfils the prerequisite for potential DUV zero-order waveplate materials. This work extends the exploration of DUV zero-order waveplate materials to the aluminum sulfate fluoride systems.
RESUMO
The combination of π-conjugated groups [NO3] and Cl-centered polyhedra generates a new birefringent crystal with a perovskite-related framework, KRb2(NO3)2Cl, which is the first alkali metal nitrate chloride synthesized by a mild hydrothermal method. It crystallizes in the orthorhombic space group pbam (no. 55). In addition, KRb2(NO3)2Cl crystals with dimensions up to 7 × 1.5 × 1 mm3 were grown. Notably, KRb2(NO3)2Cl has a short UV cut-off edge (below 228 nm) and a significantly enhanced birefringence (Δn = 0.084 at 1064 nm). Theoretical calculations indicate that the birefringence enhancement mainly derives from π-conjugated [NO3] plane triangles.
RESUMO
PURPOSE: To compare the ocular trauma score (OTS) and the paediatric penetrating ocular trauma score (POTS) as prognostic model for visual outcome in paediatric traumatic cataract cases after penetrating eye injuries. METHODS: All children younger than 16 years with unilateral traumatic cataract following penetrating trauma between 2007 and 2012 were retrospectively reviewed. Univariate chi-square analysis was conducted to identify the variables associated with profound visual loss. The area under the receiver-operating characteristic curves (AUROC) was used to assess the predictive ability of the two models. RESULTS: The study group comprised 65 boys and 37 girls. The variables associated with profound visual loss were: a relative afferent papillary defect (RAPD) (P<0.001), poor initial vision (P=0.01), vitreous haemorrhage (P<0.001), retinal detachment (P<0.001), posterior penetrating site (P<0.001), hyphema (P<0.001), no intraocular len implantation (P<0.001) and endophthalmitis (P=0.001). OTS could not be calculated in 21 patients (20.6%) without clinical data on initial visual acuity and RAPD. For the patients with complete clinical data, POTS was similar to OTS in predicting poor vision (AUROC 0.904 vs 0.924) and in predicting good vision (AUROC 0.766 vs 0.736). For all the samples, POTS was a robust predictor of poor vision (AUROC 0.910) and had a moderate ability to predict good vision (AUROC 0.764). CONCLUSION: OTS has high ability to predict visual outcome for paediatric traumatic cataract following penetrating ocular trauma. POTS is also a reliable prognostic model for very young child without initial vision or RAPD, but is only for penetrating eye injuries.
