RESUMO
Chemical functionalization is a powerful approach to tailor the physical and chemical properties of two-dimensional (2D) materials, increase their processability and stability, tune their functionalities and, even, create new 2D materials. This is typically achieved through post-synthetic functionalization by anchoring molecules on the surface of an exfoliated 2D crystal, but it inevitably alters the long-range structural order of the material. Here we present a pre-synthetic approach that allows the isolation of crystalline, robust and magnetic functionalized monolayers of coordination polymers. A series of five isostructural layered magnetic coordination polymers based on Fe(II) centres and different benzimidazole derivatives (bearing a Cl, H, CH3, Br or NH2 side group) were first prepared. On mechanical exfoliation, 2D materials are obtained that retain their long-range structural order and exhibit good mechanical and magnetic properties. This combination, together with the possibility to functionalize their surface at will, makes them good candidates to explore magnetism in the 2D limit and to fabricate mechanical resonators for selective gas sensing.
RESUMO
The system Bi(2(n + 2))Mo(n)O(6(n + 1)) is described within the superspace formalism. Two superspace models are proposed for the different members of this family, depending on the parity of the parameter n. The superspace model for the odd members is constructed through the embedding of the cationic distribution of the member with n = 3, and the modification of a superspace model previously proposed for the compound Bi(2)MoO(6). However, this model cannot be applied to the even members of the family. Performing the appropriate transformations, a suitable superspace model for the even members is obtained. The atomic structure of the different compounds of the family have been refined through the Rietveld method combining synchrotron X-ray and neutron powder diffraction data.
RESUMO
The structure of the monoclinic phase of the compound InAl(1 - x)Ti(x)O(3 + x/2) with x = 0.701 (1) has been analyzed within the (3 + 1)-dimensional superspace formalism. Two different models were refined describing the structure as an incommensurate modulated layer and modulated composite, respectively. Both models include the same composition-structure relation. In the composite approach it is derived from the mismatching between the two subsystems. In the incommensurate modulated system, it is derived from a closeness condition between O atomic domains. The distribution and coordination of the cations is discussed and compared with previously proposed models for similar compounds.
RESUMO
There is evidence of the increasing economic losses from extreme natural events during the last decades. These facts, thought to be triggered by environmental changes coupled with inefficient management and policies, highlight particularly exposed and vulnerable regions worldwide. Argentina faces several challenges associated with global environmental change and climate variability, especially related to water resources management including extreme floods and droughts. At the same time, the country's production capacity (i.e. natural resource-based commodities) and future development opportunities are closely tied to the sustainable development of its natural resource endowments. Given that vulnerability is registered not only by exposure to hazards (perturbations and stresses), but also resides in the sensitivity and resilience of the system experiencing such hazards, Argentina will need to improve its water management capacities to reduce its vulnerability to climate variability and change. This paper presents the basic components of the vulnerability analysis and suggests how it can be used to define efficient water management options.
