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Graphene nanoribbons are prepared inside boron nitride nanotubes by liquid phase encapsulation and subsequent annealing of 1,2,4‐trichlorobenzene. The product is imaged with high‐resolution transmission electron microscopy, and characterized by optical absorption and Raman spectroscopy. Carbon‐containing material is detected inside the boron nitride nanotubes with energy‐dispersive X‐ray spectroscopy (EDS) and scanning transmission electron microscopy (STEM). The observed structures twist under the electron beam and the characteristic features of nanoribbons appear in the Raman spectra. [ABSTRACT FROM AUTHOR]

Hybrid materials composed of single walled carbon nanotubes (SWCNTs) as hollow containers and small molecules as fillers possess intriguing physical and chemical properties. Infrared spectroscopy is a useful method in most cases to characterize hybrid systems; however, regardless of the type of small molecule encapsulated in the SWCNT, the IR spectrum of the hybrid system remains silent. The possible explanation involves the highly polarizable [ABSTRACT FROM AUTHOR]

Scattering-type scanning near-field optical microscopy (s-SNOM) is becoming a premier method for the nanoscale optical investigation of materials well beyond the diffraction limit. A number of popular numerical methods exist to predict the near-field contrast for axisymmetric configurations of scatterers on a surface in the quasi-electrostatic approximation. Here, a fully electrodynamic approach is given for the calculation of near-field contrast of several scatterers in arbitrary configuration, based on the generalized Mie scattering method. Examples for the potential of this new approach are given by showing the coupling of hyperbolic phonon polaritons in hexagonal boron nitride (hBN) layers and showing enhanced scattering in core-shell systems. In general, this method enables the numerical calculation of the near-field contrast in a variety of strongly resonant scatterers and is able to accurately recreate spatial near-field maps. [ABSTRACT FROM AUTHOR]

Potassium addition to mixed‐halide perovskites is found to be a promising way to overcome their major stability issue, the segregation of the mixed phase to iodide and bromide‐rich regions. To fully exploit the potential of potassium addition, it is essential to achieve a better understanding of its working mechanism, and understand the limitations of the stabilization it provides. Photoluminescence emission spectra of MAPb(Br0.6I0.4)3 films are studied upon addition of KBr and KI under nitrogen and air atmosphere. The halide exchange between the added potassium salts and the perovskite is demonstrated. It is shown that the potassium addition does not passivate the surface, and it is therefore prone to oxygen and water absorption. The significant contribution of the adsorbed water to the prevention of halide segregation is discussed, which should be taken into account when the stability of the mixed‐halide films is evaluated under ambient conditions. [ABSTRACT FROM AUTHOR]

Amorphous calcium carbonate (ACC) is a precursor material that plays a key role in polymorph selection and crystallization of carbonates. It is involved in the formation of the cryogenic carbonate ikaite (CaCO3·6H2O), but the role of ACC during the transformation of this room-temperature-metastable material is poorly understood. We report the occurrence of two ACC types that differ in their mode of formation, morphology, particle size, water content and stability. ACC precipitated in solution below 5 °C, referred to as ACC (I), is amorphous, forms as ∼100 nm sized spheres, and contains 1.12 mol adsorbed and 0.26 mol chemically bonded water. Aging of ACC (I) for 25 min under cold conditions forms euhedral ikaite, whereas calcite forms within 10 min at room temperature. Our findings suggest that ACC (I) is the same precursor phase for both crystalline forms and their selection can be controlled by temperature alone. Rapid dehydration of ikaite by organic solvents and vacuum pumping at room temperature and by increasing the temperature from 5 to 30 °C within 1 min forms amorphous carbonate, referred to as ACC (II). ACC (II) consists of micron-sized, porous grains that preserve the ikaite grain morphology and contains 0.42 mol physically adsorbed and 0.35 mol chemically bonded water. Temperature-dependent investigations performed between 25 and 350 °C indicate that ACC (I) is more stable than ACC (II) despite its higher water content. At 300–350 °C ACC (I) can be dehydrated to an amorphous material containing 0.03 mol water, which crystallizes to calcite without a transitional anhydrous phase. The different ACC types can be attractive for materials science applications. The finding of an amorphous phase during the ikaite → calcite transition suggests the alteration of the original geochemical signal and thus has implications for interpreting paleoclimatological data. [ABSTRACT FROM AUTHOR]

Scattering type scanning near-field optical microscopy (s-SNOM) is an effective tool for the nanoscale examination of nano-objects. In this paper, we present a modified device setup that enables spectroscopic measurements with a tunable laser, even without an FTIR (Fourier Transform Infrared) spectroscopy add-on. We demonstrate the effectiveness of this setup by measurements on boron nitride nanotubes (BNNTs). In far-field absorption measurements, BNNTs have a characteristic peak around 1375 cm−1 due to a phonon polariton mode. This peak is also visible in near-field measurements along with several other peaks that are not present in the far-field spectrum. As these peaks are caused by local defects, their spatial distribution reveals the defect structure of individual nanotubes. [ABSTRACT FROM AUTHOR]

One of the most challenging tasks in nanotube research is to identify the different electronic types of nanotubes for device fabrication. The implementation of standard spectroscopy techniques at the single-tube level has remained a great task due to small nanotube signal and low spatial resolution. Scattering-type scanning near-field optical microscopy (s-SNOM) yields information on the optical characteristics of the sample with high spatial resolution. We have already demonstrated that this method is able to distinguish between different electronic types of carbon nanotube bundles based on their optical properties in the infrared region. Now we applied the same method to characterize individual horizontally aligned single-walled carbon nanotubes (SWCNTs). [ABSTRACT FROM AUTHOR]

We demonstrate that scattering-type near-field optical microscopy (s-SNOM) at infrared frequencies can be effectively used to distinguish between carbon nanotube (CNT) bundles based on their electrical properties. Samples from separated metallic and semiconductor nanotubes and their mixtures were investigated using infrared lasers under near-field conditions. In this frequency range, the difference in the free-carrier concentration between metallic and semiconducting tubes is expected to influence the properties of the scattered light. The remarkable difference in the optical phase images proves that this is indeed the case: the metallic and semiconducting bundles are unambiguously identifiable in the sample, even in case of 5 nm diameter bundles. The measurements agree qualitatively with our calculations based on the extended finite dipole model using the known optical functions of the constituting nanotubes. [ABSTRACT FROM AUTHOR]

Reductive hydrogenation was applied to two types of single-walled carbon nanotubes with different diameter range. Alkali metal intercalation, followed by reaction with methanol, led to hydrogenated products. Both yield and selectivity of this reaction showed strong dependence on diameter, contrary to expectation based on simple curvature effects. The observed yield, as detected by thermogravimetry–mass spectrometry and 1 H NMR, is drastically reduced in small-diameter tubes where the alkali dopant does not reach the inside of the bundles. Wide range optical transmission measurements were employed to determine the selectivity and indicate that besides higher yield, lower diameter selectivity occurs above a critical diameter. [ABSTRACT FROM AUTHOR]

Abstract: Depth profile of electrodeposited Fe–Co–Ni alloys was measured using secondary neutral mass spectrometry with the reverse sputtering direction. A spontaneous near-substrate composition modulation was found for each sample studied. The initial deposit is very rich in Fe, which decays due to the depletion of the electrolyte in the vicinity of the cathode surface. The near-substrate modulation pattern can be elucidated by taking into account the mutual deposition preference of the iron-group metals and the mass transport of the ions in the solution. The composition fluctuations of Fe and Co at distances larger than 100nm from the substrate are strictly correlated. Composition fluctuations beyond the near-substrate zone are attributed to the instability of the depleted electrolyte layer in the vicinity of the cathode. A critical analysis of earlier depth profile data for electrodeposited Fe–Co–Ni samples is also given. [Copyright &y& Elsevier]

The frequency axis of Fig. 3 is corrected. [ABSTRACT FROM AUTHOR]