Two-dimensional materials draw further attention because of their superior properties applicable in novel technologies. We have calculated the optical properties of α and β allotropes of antimonene monolayers. The dielectric matrix has been calculated within the random phase approximation (RPA) using density functional theory. We have calculated dielectric function, absorption coefficient, refractive index, electronic energy loss spectroscopy and optical reflectivity in the energy range between 0 and 21 eV. Our simulations predict that absorption process starts in the infrared, but peaks in the ultraviolet. Refractive indices are 2.3 (α-Sb) and 1.5 (β-Sb) at the zero energy limit and scale up to 3.6 in the ultraviolet. Reflection rises up to 86% at the UV energies, where antimonene behaves like a metal regarding the incident electromagnetic radiation. Our calculations show that antimonene is appropriate as a material for the microelectronic and optoelectronics nanodevices and solar cell applications, as well as new optical applications using various light emission, detection, modulation and manipulation functions.

The first step in the activation of the classical complement pathway, by immune complexes, involves the binding of the globular heads of C1q to the Fc regions of aggregated IgG or IgM. Located C-terminal to the collagen region, each globular head is composed of the C-terminal halves of one A (ghA), one B (ghB), and one C chain (ghC). To dissect their structural and functional autonomy, we have expressed ghA, ghB, and ghC in Escherichia coli as soluble proteins linked to maltose-binding protein (MBP). The affinity-purified fusion proteins (MBP-ghA, -ghB, and -ghC) bound differentially to heat-aggregated IgG and IgM, and also to three known C1q-binding peptides, derived from HIV-1, HTLV-I, and β-amyloid. In the ELISAs, the MBP-ghA bound to heat-aggregated IgG and IgM as well as to the HIV-1 gp41 peptide; the MBP-ghB bound preferentially to IgG rather than IgM, in addition to binding β-amyloid peptide, whereas the MBP-ghC showed a preference for IgM and the HTLV-I gp21 peptide. Both MBP-ghA and MBP-ghB also inhibited C1q-dependent hemolysis of IgG- and IgM-sensitized sheep erythrocytes. However, for IgM-coated erythrocytes, MBP-ghC was a better inhibitor of C1q than MBP-ghB. The recombinant forms of ghA, ghB, and ghC also bound specifically to apoptotic PBMCs. We conclude that the C1q globular head region is likely to have a modular organization, being composed of three structurally and functionally independent modules, which retains multivalency in the form of a heterotrimer. The heterotrimeric organization thus offers functional flexibility and versatility to the whole C1q molecule.

No abstract

Titanium dioxide nanocrystals were prepared by the wet chemical method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman scattering (RS) and photoluminescence techniques. The XRD pattern shows the formation of single phase anatase structure of average sizes ∼7 nm (sample A) and ∼15 nm (sample B) for two samples. Additionally, TEM and RS were used to confirm the anatase crystal structure for both samples. The PL spectra show that the intensity of the sample A is more than that of sample B, which has been attributed to defect(s) and particle size variation. A modified phonon confinement model incorporating particle size distribution function and averaged dispersion curves for two most dispersive phonon branch ( -X direction) have been used to interpret the size effect in Raman spectra. The obtained Raman peak shift and full width at half-maximum agree well with the experimental data. Our observations suggest that the phonon confinement effects are responsible for a significant shift and broadening for the Raman peaks.

Two dimensional monolayer nanostructures for water splitting solar photocatalyst are drawing more attention due to their extraordinary properties. Using the first principles calculations we have systematically investigate the structural, electronic and vibrational properties of the corresponding HfS 2 monolayer in both phases of hexagonal (1H) and trigonal (1T). The most stable adsorption configurations and adsorption energies are calculated. The adsorption energy of H 2 O on the substrate is 646.53 kJ/mol for 1H-phase and 621.65 kJ/mol for 1T-phase of HfS 2 . It shows that H 2 O molecule has higher interaction with the HfS 2 substrate. The calculated redox potentials of H 2 O splitting are properly astride by the valence and conduction bands suggesting monolayer of 1H and 1T-HfS 2 shows same characteristic as a photocatalyst for water splitting.Further we have also calculated obtained optical band gap for 1H and 1T phases of HfS 2 is 2.60 eV and 3.10 eV, respectively. We have also calculated Raman spectrum signatures of the monolayer 1H and 1T-phase of in -plane vibrational mode of the Hf and S atoms (E 1g ) and the out-of-plane vibrational mode of S atoms (A 1g and A 2u ). Our works suggest a lot more research and attention in this field needed for their practical application as a visible light active photocatalysts.

The physical properties of two-dimensional (2D) lead halide based hybrid perovskites are quite exciting and challenging. Further, the role of organic cations in 2D perovskites is still in a debate. We investigated layered (CH 3 (CH 2 ) 3 NH 3 ) 2 (CH 3 NH 3 )Pb 2 I 7 2D Ruddlesden−Popper (2DRP) phase (M1) and 2D derivative of CH 3 NH 3 PbI 3 (M2) using density functional theory. The spin orbit coupling mediates the significantly large Rashba splitting energy of 328.5 meV for M2, which is higher than earlier 2D hybrid perovskites. At the picosecond time scale, the dynamical Rashba effect was observed due to organic and inorganic cation dynamics. Two step absorption suggests an indirect optical gap of 2.38 and 2.15 eV for M1 and M2, respectively and solar performance depicts excellent power conversion efficiency of 14.92% and 19.75% for M1 and M2, respectively. For the first time, we explored the thermoelectric properties of 2D hybrid perovskites and perceived high power factor for p-type doping in M2. Our findings suggest that these novel 2D perovskites have the potential to be used in solar and heat energy harvesting.

The optical and vibrational properties of nanocrystalline thin films of MoS 2, comprised of a mixture of edge terminated vertically aligned (ETVA) and (001)-oriented regions, on large insulating substrates are reported. From high resolution transmission electron microscopy (HRTEM), the average size of ETVA nanocrystals were ~5 nm and each nanocrystal consisted of only 3 to 5 monolayers of MoS 2 . The films were highly transparent (~80%) but the percent of transmittance decreased as the energy of the incident light approached to the band gap.Additionally, weak excitonic peaks were observed both in the absorption and transmission spectra. The room temperature Raman study showed that both the E 1 2g and A 1g modes were significantly broader, and a few additional Raman modes were observed when compared to bulk MoS 2 . The broadening of the A 1g mode was analyzed using the phonon-confinement model and the calculated particle size was in good agreement with TEM observations. Moreover, the temperature coefficient of the A 1g mode was estimated from the temperature dependent Raman studies.

Si based group V binary compounds have shown better thermoelectric performance at room temperature in addition with ultrahigh carrier mobilities.