We report on the structural and electronic properties in the heterostructure of graphene/silicon/Ir(111). A (√19 × √19)R23.41° superstructure is confirmed by low energy electron diffraction and scanning tunneling microscopy and its formation is ascribed to silicon intercalation at the interface between the graphene and the Ir(111) substrate. The dI/dV measurements indicate that the interaction between graphene and Ir is effectively decoupled after silicon intercalation. Raman spectroscopy also reveals the vibrational states of graphene, G peak and 2D peak, which further demonstrates that the silicon-buffered graphene behaves more like intrinsic graphene.
Hydrogen atoms bonded within molecular cavities often undergo tunneling or thermal-transfer processes that play major roles in diverse physical phenomena. Such transfers may or may not entail intermediate states. The existence of such fleeting states is typically determined by indirect means, while their direct visualization has not been achieved, largely because their concentrations under equilibrium conditions are negligible. Here we use density-functional-theory calculations and scanning-tunneling-microscopy (STM) image simulations to predict that, under specially designed nonequilibrium conditions of voltage-enhanced high transfer rates, the cis-intermediate of the two-hydrogen transfer process in metal-free naphthalocyanine molecules adsorbed on Ag(111) surfaces would be visualizable in a composite image of double-C morphology. As guided by the theoretical predictions, at adjusted scanning temperature and bias, STM experiments achieve a direct visualization of the cis-intermediate. This work demonstrates a practical way to directly visualize elusive intermediates, which enhances understanding of the quantum dynamics of hydrogen atoms.
Here we report the thermo-controllable self-assembled structures of single-layer 4, 4''-diamino-p-terphenyl (DAT) molecules on Au (110), which are investigated by scanning tunneling microscopy (STM) combined with density functional theory (DFT) based calculations. With the deposition of monolayer DAT molecules on Au (110) and subsequent annealing at 100 °C, all DAT molecules adsorb on a (1 × 5) reconstructed surface with a ladder-like structure. After annealing the sample at about 200 °C, STM images show three distinct domains, including DAT molecules on a (1 × 3) reconstructed surface, dehydrogenated molecules with two hydrogen atoms detached from one amino group (−2H-DAT) on a (1 × 5) reconstructed surface and dehydrogenated molecules with four hydrogen atoms detached from two amino groups (–4H-DAT) on a (1 × 3) reconstructed surface through N–Au bonds. Furthermore, after annealing the sample to 350 °C, STM image shows only one self-assembled structure with −4H-DAT molecules on a (1 × 3) reconstructed surface. Relative STM simulations of different self-assembled structures show excellent agreements with the experimental STM images at different annealing temperatures. Further DFT calculations on the dehydrogenation process of DAT molecule prove that the dehydrogenation barrier on a (1 × 5) reconstructed surface is lower than that on (1 × 3) one, which demonstrate the experimental results that the formation temperature of a (1 × 3) reconstructed surface is higher than that of a (1 × 5) one.
Structures of self-assembled films play essential roles in the performance of potential organic molecular electronics; therefore, detailed knowledge of molecular adsorption and structural evolution is fundamental for the implementation of molecular electronics. Here, we systematically investigated the initial adsorption and structure evolution of metal-free naphthalocyanine (H2Nc) on the Ag(111) surface from dimers to ordered self-assembled structures in the submonolayer range. H2Nc molecules deposited on Ag(111) at 100 K accumulate into clusters dominated by dimers. Subsequent sample annealing induces the emergence of two ordered self-assembled structures, denoted by Sl and Sll. Molecule-resolved scanning tunneling microscopy images confirm that structure Sl is more stable with six rotation domains lying in two chiralities. Deviations of the lattice parameters from a threefold symmetry indicate non-neglectable intermolecular interactions in self-assembled patterns. Combined with density functional theory calculations, orientations of the two inner hydrogens of H2Nc in the self-assembled film are revealed.
Background : The association of DLG5 R30Q with IBD has been replicated in several populations, but is not statistically significant in others. We studied the incidence of DLG5 alleles in a population of IBD patients from Pennsylvania. Methods : DLG5 R30Q (rs1248696) and G1066G (rs1248634) were analyzed with PCR-based RFLP methods in a total of 521 subjects, that included 105 individuals with IBD and 139 without IBD from a familial IBD registry, 107 with sporadic IBD, and 170 unrelated healthy controls. R30Q was further analyzed with SNPlex™ Genotyping System in 473 samples. Results : RFLP genotyping data showed that, DLG5 R30Q was significantly associated with IBD overall ( p =0.006), and separately with CD ( p =0.009) and UC ( p =0.024). The association of R30Q with IBD was entirely due to a male-associated effect (male vs female p =0.015 vs 0.241 (IBD), p =0.024 vs 0.190 (CD), and p =0.019 vs 0.575 (UC)). The frequency of the A allele carriage was elevated in both affected and unaffected members in the familial IBD cohort compared to healthy controls ( p =0.037). In the family pedigrees, we observed differences in the expression of IBD in individuals carrying the A allele between families. Conclusions : In the studied population, DLG5 R30Q was associated with all forms of IBD. An elevated presence of the R30Q variant was observed in all members of a familial IBD registry. This association of the R30Q variant with IBD was male-specific.
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