Iron Intercalation in Covalent-Organic Frameworks: A Promising Approach for Semiconductors

Covalent-organic frameworks (COFs) are intriguing platforms for designing functional molecular materials. Here, we present a computational study based on van der Waals dispersion-corrected hybrid density functional theory (DFT-D) to design boroxine-linked and triazine-linked COFs intercalated with Fe. Keeping the original $P-6m2$ symmetry of the pristine COF (COF-Fe-0), we have computationally designed seven new COFs by intercalating Fe atoms between two organic layers. The equilibrium structures and electronic properties of both the pristine and Fe-intercalated COF materials are investigated here. We predict that the electronic properties of COFs can be fine tuned by adding Fe atoms between two organic layers in their structures. Our calculations show that these new intercalated-COFs are promising semiconductors. The effect of Fe atoms on the electronic band structures and density of states (DOSs) has also been investigated using the aforementioned DFT-D method. The contribution of the $d$-subshell electron density of the Fe atoms plays an important role in improving the semiconductor properties of these new materials. These intercalated-COFs provide a new strategy to create semi-conducting materials within a rigid porous network in a highly controlled and predictable manner.Comment: 39 pages. arXiv admin note: text overlap with arXiv:1703.0261

Physiological Correlates of Volunteering

We review research on physiological correlates of volunteering, a neglected but promising research field. Some of these correlates seem to be causal factors influencing volunteering. Volunteers tend to have better physical health, both self-reported and expert-assessed, better mental health, and perform better on cognitive tasks. Research thus far has rarely examined neurological, neurochemical, hormonal, and genetic correlates of volunteering to any significant extent, especially controlling for other factors as potential confounds. Evolutionary theory and behavioral genetic research suggest the importance of such physiological factors in humans. Basically, many aspects of social relationships and social activities have effects on health (e.g., Newman and Roberts 2013; Uchino 2004), as the widely used biopsychosocial (BPS) model suggests (Institute of Medicine 2001). Studies of formal volunteering (FV), charitable giving, and altruistic behavior suggest that physiological characteristics are related to volunteering, including specific genes (such as oxytocin receptor [OXTR] genes, Arginine vasopressin receptor [AVPR] genes, dopamine D4 receptor [DRD4] genes, and 5-HTTLPR). We recommend that future research on physiological factors be extended to non-Western populations, focusing specifically on volunteering, and differentiating between different forms and types of volunteering and civic participation

Birnessite: A Layered Manganese Oxide To Capture Sunlight for Water-Splitting Catalysis

We show a comprehensive study on the structure and electronic properties of a layered manganese oxide commonly known as birnessite. We present the effects of substituting different intercalated cations (Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Zn²⁺, B³⁺, Al³⁺, Ga³⁺, Sc³⁺, and Y³⁺) and the role of waters in the intercalated layer. The importance of the Jahn–Teller effect and ordering of the Mn³⁺ centers due to cation intercalation are addressed to explain the ability to tune the indirect band gap (<i>E</i>_gⁱ) from 2.63 to ∼2.20 eV and the direct band gap (<i>E</i>_g^d) from 3.09 to ∼2.50 eV. By aligning the structures’ bands, we noted that structures with Sr, Ca, B, and Al have potential for usage in water splitting, and anhydrous B-birnessite is predicted to have a suitable direct band gap for light capturing. Furthermore, we also demonstrate how the effects of cations in the bulk differ from the behavior on single layer surfaces. More specifically, we show that an indirect to direct band transition is observed when we separate the bulk into a single layer oxide. This study shows a new strategy for tuning the band gap of layered materials to capture light which may couple to its intrinsic water-splitting catalytic properties, thus resembling photosynthesis

Media 1: High-repetition-rate three-dimensional OH imaging using scanned planar laser-induced fluorescence system for multiphase combustion

Originally published in Applied Optics on 20 January 2014 (ao-53-3-316

Media 2: High-repetition-rate three-dimensional OH imaging using scanned planar laser-induced fluorescence system for multiphase combustion

Originally published in Applied Optics on 20 January 2014 (ao-53-3-316