Six representative isotope-labeled samples of titanium dioxide were synthesized: Ti(16)O(2), Ti(17)O(2) and Ti(18)O(2), each in anatase and rutile forms. Their Raman scattering was analyzed at temperatures down to 5 K. Spectral assignment was supported by numerical simulation using DFT calculations. The combination of experimental and theoretical Raman frequencies with the corresponding isotopic shifts allowed us to address various still-open questions about the second-order Raman scattering in rutile, and the analysis of overlapping features in the anatase spectrum.

Tweaking the properties of carbon nanotubes is a prerequisite for their practical applications.Here we demonstrate fine-tuning the electronic properties of single-wall carbon nanotubes via filling with ferrocene molecules. The evolution of the bonding and charge transfer within the tube is demonstrated via chemical reaction of the ferrocene filler ending up as secondary inner tube. The charge transfer nature is interpreted well within density functional theory. This work gives the first direct observation of a fine-tuned continuous amphoteric doping of single-wall carbon nanotubes.

(18)O-isotope labelled titania (anatase, rutile) was synthesized. The products were characterized by Raman spectra together with their quantum chemical modelling. The interaction with carbon dioxide was investigated using high-resolution FTIR spectroscopy, and the oxygen isotope exchange at the Ti(18)O(2)/C(16)O(2) interface was elucidated.

Recent nuclear-magnetic-resonance measurements on isotope engineered double walled carbon nanotubes ͑DWCNTs͒ surprisingly suggest a uniformly metallic character of all nanotubes, which can only be explained by the interaction between the layers. Here we study the intershell interaction in DWCNTs by densityfunctional theory and the intermolecular Hückel model. Both methods find charge transfer between the inner and outer tubes. We find that the charge transfer between the walls is on the order of 0.001 e − / atom and that the inner tube is always negatively charged. We also observe orbital mixing between the states of the layers. We find that these two effects combined can in some cases lead to a semiconductor-to-metal transition of the double walled tube, but not necessarily in all cases. We extend our study to multiwalled nanotubes as well, with up to six layers in total. We find similar behavior as in the case of DWCNTs: electrons tend to be transferred from the outermost layer toward the innermost one. We find a notable peculiarity in the charge transfer when the ͑5,0͒ tube is present as the innermost tube; we attribute this to themixing in such small diameter tubes.

We review the key aspects of Raman spectroscopy of graphite and graphene, focusing on the double resonant Raman modes such as the D, D Ã (also known as G' or 2D), and D' bands. We discuss the practical significance of Raman spectroscopy for the study of single-and multi-layer graphene.

Two‐dimensional heterostructures are generally extremely sensitive to perturbations due to the large surface–volume ratio. A widely used non‐destructive experimental technique to characterize these perturbations is the Raman spectroscopy. However, vibrational frequencies of monolayer MoS2 is proven to be non‐sensitive to perturbations such as strain and doping. In order to characterize the effect of these perturbations to the spectra we compute the frequencies and Raman intensities of monolayer MoS2 on the ab initio level. In agreement with previous experimental works, we show that the frequencies of the Raman active peaks (A1′ and E′) are rather non‐sensitive to strain or doping. On the other hand, we demonstrate that the intensity ratio depends strongly on the strain − thus it can be used as a supplementary method to characterize strain in the samples.

Single-walled carbon nanotubes (CoMoCat) have been enriched with (6,5) tubes via density-gradient ultracentrifugation. Thin solid films of quasi-isolated nanotubes were fabricated from a solution of sorted nanotubes by vacuum filtration and extraction with water. Optical spectroscopy in the vis−NIR region and Raman spectroscopy were used to characterize these materials. The experimental studies were supported by a theoretical analysis of the electronic and vibrational structure of selected (n,m) tubes by using density functional theory. Besides the most abundant tubes (6,5), the experimental and theoretical data for tubes (6,4), (7,3), (7,5), (8,3), and (9,1) are also discussed. A detailed investigation by in situ Raman spectroelectrochemistry was focused on the effects of electrochemical p-/n-doping. The experimental analysis of the intensities and frequencies of the radial breathing mode and the tangential displacement modes were correlated with the theoretically calculated optical transition energies and Raman frequencies. It was demonstrated that electrochemical charging is a useful tool for the study of doping effects on the electronic structure of carbon nanotubes.

Spin orbit interaction can be strongly boosted when a heavy element is embedded into an inversion asymmetric crystal field. A simple structure to realize this concept in a 2D crystal contains three atomic layers, a middle one built up from heavy elements generating strong atomic spin-orbit interaction and two neighboring atomic layers with different electron negativity. BiTeI is a promising candidate for such a 2D crystal, since it contains heavy Bi layer between Te and I layers. Recently the bulk form of BiTeI attracted considerable attention due to its giant Rashba interaction, however, 2D form of this crystal was not yet created. In this work we report the first exfoliation of single layer BiTeI using a recently developed exfoliation technique on stripped gold. Our combined scanning probe studies and first principles calculations show that SL BiTeI flakes with sizes of 100 µm were achieved which are stable at ambient conditions. The giant Rashba splitting and spin-momentum locking of this new member of 2D crystals open the way towards novel spintronic applications and synthetic topological heterostructures.