In the search of novel photocatalysts to increase the effect of visible light in photocatalysis, g-C3N4 (CN) has become a shining star. Rare earth metals have been used as dopant material to reinforce the photocatalytic activity of CN due to their unique electron configuration recently. In this present study, the pure and different amounts of Ho-doped g-C3N4 (HoCN) photocatalysts were successfully synthesized using urea as a precursor by the one-pot method. Morphological, structural, optical, and vibrational properties of the synthesized photocatalysts were characterized by SEM, EDX, XRD, TGA, XPS, FTIR, PL, TRPL, Raman, DRS, and BET analyses. In addition, theoretical calculations using density functional theory (DFT) were meticulously carried out to delve the changes in the structural and electronic structure of CN with holmium doping. According to calculations, the chemical potential, electrophilicity, and chemical softness are higher for HoCN, while HOMO–LUMO gap, dipole moment, and the chemical hardness are lower for the pure one. Thus, holmium doping becomes desirable with low chemical hardness which indicates more effectivity and smaller HOMO–LUMO gap designate high chemical reactivity. To determine the photocatalytic efficiency of the pure and doped CN photocatalysts, the degradation of methylene blue (MB) was monitored under visible light. The results indicate that holmium doping has improved the photocatalytic activities of CN samples. Most strikingly, this improvement is noticeable for the 0.2 mmol doped CN sample that showed two times better photocatalytic activity than the pure one.

•Kinetic energy changes film properties significantly at low coverages.•Films grown with helium carrier gas have larger grain size.•Thick PFP films have similar IR spectra on different substrates.•On different substrates monolayer films have significantly different IR spectra.•For both monolayer and thick films Davydov splitting was observed.

We studied vibrational properties and the effect of beam kinetic energy on perfluoropentacene (PFP) thin films grown by supersonic molecular beam deposition (SMBD) technique on gold surfaces. Though similar growth mechanism was observed for different beam kinetic energies, in the case of low coverage (less than 1 monolayer) films and for low deposition rates significant differences were observed in the properties of films grown by using helium and argon carrier gasses with the former case resulting in higher average grain size. For multilayer films however there were no significant differences between helium and argon grown films. Vibrational properties were investigated by using Infrared Scattering-type Scanning Nearfield Optical Microscopy (s-SNOM) on clean and m-carborane-1-thiol (M1) coated template-stripped gold (TSAu) substrates. For both substrates thick PFP films (15 nm) had similar spectra whereas there were significant differences in the spectra of thin films (1 nm) due to PFP-substrate interactions. Davydov splitting of the IR modes were observed for both 1 nm and 15 nm films indicating similar molecular arrangements in both type of films.

The structure and function of self-assembled monolayers (SAMs) at the nanoscale are determined by the steric and electronic effects of their building blocks. Carboranethiol molecules form pristine monolayers that provide tunable two-dimensional systems to probe lateral and interfacial interactions. Additional omega-functionality, such as carboxyl groups, can be introduced to change the properties of the exposed surfaces. Here, two geometrically similar isomeric m-carborane analogues of m-mercaptobenzoic acid, 1-COOH-7-SH-1,7-C2B10H10 and racem-1-COOH-9-SH-1,7-C2B10H10, are characterized and their SAMs on Au{111} are examined. The latter isomer belongs to the rare group of chiral cage molecules and becomes, to our knowledge, the first example assembled on Au{111}. Although different in symmetry, molecules of both isomers assemble into similar hexagonal surface patterns. The nearest-neighbor spacing of 8.4 +/- 0.4 angstrom is larger than that of non-carboxylated isomers, consistent with the increased steric demands of the carboxyl groups. Computational modeling reproduced this spacing and suggests a tilt relative to the surface normal. However, tilt domains are not observed experimentally, suggesting the presence of strong lateral interactions. Analyses of the influence of the functional groups through the pseudo-aromatic m-carborane skeleton showed that the thiol group attached to either carbon or boron atoms increases the carboxyl group acidity in solution. In contrast, the acidity of the exposed carboxyl group in the SAMs decreases upon surface attachment; computational analyses suggest that the driving force of this shift is the dielectric of the environment in the monolayer as a result of confined intermolecular interactions, proximity to the Au surface, and partial desolvation.

We studied the effect of chemical properties of substrates on the structural properties of perfluoropentacene (PFP) thin films grown by the supersonic molecular beam deposition technique. To this end, we have used m-carborane-1-thiol, template-stripped gold, and mica substrate surfaces and investigated the PFP film properties as a function of film thickness and molecular flux (deposition rate). On all three substrates, the PFP molecules adsorb in standing-up orientation in the first layer and overlayers. However, with an increasing hydrophobicity of the substrate, the mean grain size in the first layer increases. Bulk-like PFP films with needle-shaped grains grow on top of the first (wetting) layer on all the substrates, with smaller and taller grains on gold and larger and wider grains on mica surfaces.

Carboranethiol self-assembled monolayers on metal surfaces have been shown to be very convenient systems for surface engineering. Here we have studied pure and mixed self-assembled monolayers (SAMs) of three different carboranethiol (CT) isomers on gold surfaces. The isomers were chosen with dipole moments pointing parallel to (m-1-carboranethiol, M1), out of (m-9-carboranethiol, M9) and into (1-carboranethiol, 01) the surface plane, in order to investigate the effect of dipole moment orientation on the film properties. In addition, influence of the substrate surface morphology on the film properties was also studied by using flame annealed (FA) and template stripped (TS) gold surfaces. Contact angle measurements indicate that in M1/M9 and M1/01 mixed SAMs, M1 is the dominant species on the surface even for low M1 ratio in the growth solution. Whereas for 01/M9 mixed SAMs no clear evidence could be observed indicating dominance of one of the species over the other one. Though contact angle values were lower and hysteresis values were higher for SAMs grown on TS gold surfaces, the trends in the behavior of the contact angles with changing mixing ratio were identical for SAMs grown on both substrates. Atomic force microscopy images of the SAMs on TS gold surfaces indicate that the films have similar morphological properties regardless of mixing ratio. (C) 2017 Elsevier B.V. All rights reserved.