Polarization Controlled Assembly of Ultrathin Thiorphan Nanostructures on ZnO Surface Facets.

Despite the importance of thiorphan as a small molecule with vital biological roles, its interactions with zinc oxide (ZnO) nanomaterials that are prospective in drug delivery and theranostic applications have not yet been sufficiently explored. Here the impact of surface polarity of different ZnO facets on thiorphan adsorption is studied both experimentally by atomic force microscopy (AFM) and angle resolved X-ray photoelectron spectroscopy (XPS) and theoretically by force field molecular dynamics (FFMD) and density functional tight binding simulations (DFTB). Polar ZnO surfaces cause the formation of thiorphan nanodots, where the size of the nanodots depends on the direction of dipoles: small (4 nm) nanodots are formed on Zn-face ZnO, while large (25 nm) nanodots are formed on O-face ZnO. Nonpolar ZnO surfaces cause self-assembly into layered nanoislands with characteristic 4 nm layer thickness, which subsequently merge into rigid nanolayers. The self-assembly is shown to be controlled solely by the effect of surface dipole electric field orientation and magnitude, whereas effects of surface chemistry or solution are negligible. The results thus also show a way for controlling the assembly of thiorphan and other molecular nanomaterials for diverse applications.

Strong Structural and Electronic Binding of Bovine Serum Albumin to ZnO via Specific Amino Acid Residues and Zinc Atoms.

ZnO biointerfaces with serum albumin have attracted noticeable attention due to the increasing interest in developing ZnO-based materials for biomedical applications. ZnO surface morphology and chemistry are expected to play a critical role on the structural, optical, and electronic properties of albumin-ZnO complexes. Yet there are still large gaps in the understanding of these biological interfaces. Herein we comprehensively elucidate the interactions at such interfaces by using atomic force microscopy and nanoshaving experiments to determine roughness, thickness, and adhesion properties of BSA layers adsorbed on the most typical polar and non-polar ZnO single-crystal facets. These experiments are corroborated by force field (FF) and density-functional tight-binding (DFTB) calculations on ZnO-BSA interfaces. We show that BSA adsorbs on all the studied ZnO surfaces while interactions of BSA with ZnO are found to be considerably affected by the atomic surface structure of ZnO. BSA layers on the (0001‾) surface have the highest roughness and thickness, hinting at a specific upright BSA arrangement. BSA layers on (101‾0) surface have the strongest binding, which is well correlated with DFTB simulations showing atomic rearrangement and bonding between specific amino acids (AAs) and ZnO. Besides the structural properties, the ZnO interaction with these AAs also controls the charge transfer and HOMO-LUMO energy positions in the BSA-ZnO complexes. This ZnO facet-specific protein binding and related structural and electronic effects can be useful for improving the design and functionality of ZnO-based materials and devices.

Corrigendum to "Designing of smart tourism organization (STO) for tourism management: A case study of tourism organizations of South Khorasan province, Iran" [Heliyon Volume 5, Issue 6, June 2019, Article e01850].

[This corrects the article DOI: 10.1016/j.heliyon.2019.e01850.].

Designing of smart tourism organization (STO) for tourism management: A case study of tourism organizations of South Khorasan province, Iran.

The present study uses a review of the literature and the views of tourism and management professors and experts in order to the identification of organizational intelligence elements in tourism management (STO) for the first time. The census method was used to determine the research sample and the Delphi technique was used to design the questionnaire. Construct divergence was then used to determine the validity and reliability of the questionnaire. The final results indicated that providing e-services for tourists had the greatest impact on the development of STO (loading factor: 0.677). Moreover, New Tourism Marketing Methods (NTMM) had the least effect on the development of STO (loading factor: 0.431). Overall, the most important achievement of the present research is introducing the concept of STO in tourism management.