Two-Dimensional Tin Selenide Nanostructures for Flexible All-Solid-State Supercapacitors

Due to their unique electronic and optoelectronic properties, tin selenide nanostructures show great promise for applications in energy storage and photovoltaic devices. Despite the great progress that has been achieved, the phase-controlled synthesis of two-dimensional (2D) tin selenide nanostructures remains a challenge, and their use in supercapacitors has not been explored. In this paper, 2D tin selenide nanostructures, including pure SnSe₂ nanodisks (NDs), mixed-phase SnSe–SnSe₂ NDs, and pure SnSe nanosheets (NSs), have been synthesized by reacting SnCl₂ and trioctylphosphine (TOP)-Se with borane-<i>tert</i>-butylamine complex (BTBC) and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1<i>H</i>)-pyrimidinone. Utilizing the interplay of TOP and BTBC and changing only the amount of BTBC, the phase-controlled synthesis of 2D tin selenide nanostructures is realized for the first time. Phase-dependent pseudocapacitive behavior is observed for the resulting 2D nanostructures. The specific capacitances of pure SnSe₂ NDs (168 F g^–1) and SnSe NSs (228 F g^–1) are much higher than those of other reported materials (<i>e.g</i>., graphene-Mn₃O₄ nanorods and TiN mesoporous spheres); thus, these tin selenide materials were used to fabricate flexible, all-solid-state supercapacitors. Devices fabricated with these two tin selenide materials exhibited high areal capacitances, good cycling stabilities, excellent flexibilities, and desirable mechanical stabilities, which were comparable to or better than those reported recently for other solid-state devices based on graphene and 3D GeSe₂ nanostructures. Additionally, the rate capability of the SnSe₂ NDs device was much better than that of the SnSe NS device, indicating that SnSe₂ NDs are promising active materials for use in high-performance, flexible, all-solid-state supercapacitors

The odds ratios for breast cancer risk by plasma 25(OH)D concentration.

*<p>The OR was adjusted by age, age at first birth, age at menarche, use of contraceptive, menopausal status, first-degree relatives’ history of breast cancer and season of blood collection.</p

Characteristics of the studies included in the meta-analysis of blood 25(OH)D and breast cancer risk.

*<p>Abbreviations: OR, odds ratio; 95% CI, 95% confidence interval; BMI, body mass index; HRT, hormone replacement therapy; PTH, parathyroid hormone; WHI, women’s health initiative.</p>#<p>Odds ratio for the highest versus lowest category of blood 25(OH)D level.</p

Forest plot of the highest quantile versus lowest quantile blood 25(OH)D level and breast cancer risk.

<p>Forest plot of the highest quantile versus lowest quantile blood 25(OH)D level and breast cancer risk.</p

Working flow chart for selection of studies included in meta-analysis.

<p>Working flow chart for selection of studies included in meta-analysis.</p

The baseline characters for the participants in the study.

<p>The baseline characters for the participants in the study.</p