Stability and the electronic and optical properties of two-dimensional iridium trihalides with promising applications in photocatalytic water splitting.

Based on density functional theory (DFT) calculations, we systematically investigate the structural stabilities, mechanical, electronic, and optical properties of an unexplored kind of two-dimensional (2D) material IrX3 (X = Cl, Br, I) monolayers. Calculations reveal that IrX3 monolayers have low cleavage energies, making them feasible to be extracted from their 3D layered bulk counterparts, and possess excellent energetic, dynamical, mechanical, and thermodynamic stabilities. The calculated band gaps fall in the range from 1.796 to 2.410 eV, with the conduction band (CB) edge and valence band (VB) edge straddling between the redox potentials of water. Analysis of optical properties shows that the monolayers exhibit large exciton binding energies and good optical absorption in the visible-light and ultraviolet regions. The van der Waals (vdW) heterostructures IrCl3:IrBr3 and IrBr3:IrI3 have type-II band alignment with enhanced charge separation, narrower band gap, and better visible light absorption, suggesting that the heterostructures hold promising applications in photocatalytic water splitting.

Fourier transform IR and Fourier transform Raman spectroscopy studies of metallothionein-III: amide I band assignments and secondary structural comparison with metallothioneins-I and -II.

The secondary structures of porcine brain Cu(4)Zn(3)-metallothionein (MT)-III and Cd(5)Zn(2)MT-I, Cd(5)Zn(2)MT-II, and Zn(7)MT-I from rabbit livers in the solid state are investigated by Fourier transform IR spectroscopy (FTIR) and Fourier transform Raman spectroscopy (FT-Raman). The Cu(4)Zn(3)MT-III contains 26-28% beta-turns and half-turns, 13-14% 3(10)-helices, 47-49% random coils, and 11-12% beta-extended chains. The structural comparison of porcine brain Cu(4)Zn(3)MT-III with rabbit liver Cd(5)Zn(2)MT-I (II) and Zn(7)MT-I shows that the contents of the random coil structure are obviously increased. The results indicate that the insert of an acidic hexapeptide in the alpha domain of Cu(4)Zn(3)MT-III possibly forms an alpha helix. However, because the bands assigned to the alpha-helix and random coil structures are overlapped in the spectra, the content of random coil structures in Cu(4)Zn(3)MT-III is therefore higher than those in Cd(5)Zn(2)MT-I, Cd(5)Zn(2)MT-II, and Zn(7)MT-I.