Atomic force and shear force based tip-enhanced Raman spectroscopy and imaging

Underlying near-field optibal effects on the nanoscale have stimulated the development of apertureless vibrational spectroscopy and imaging with ultrahigh spatial resolution. We demonstrate tip-enhanced Raman spectra of single-walled carbon nanotubes (SWCNTs), recorded with a scanning near-field optical spectrometer using both atomic force (AF) and shear force (SF) feedback lock-in regulation, and critically discuss the advantages and drawbacks of both operation modes. For accurate calculation of the enhancement factor obtained, we have analysed the tip shape and diameter by means of scanning electron and transmission electron microscopy (SEM and TEM). In our experiments we reproducibly attain diameter-corrected and area-corrected enhancement factors of up to ~10 4 and 10 5, respectively, estimated as the linear ratio of near- and far-field intensities, and we are able to demonstrate near-field Raman imaging if SWCNTs with spatial resolution better than 50 nm

Tip-enhanced Raman spectroscopy and imaging : Nanoscopic imaging of single-walled carbon nanotubes

A possibility to not only visualize but to locally probe a chemical structure, composition, conformational state and stresses on the nanoscale has stimulated the development of apertureless near-field vibrational spectroscopy and imaging with ultrahigh spatial resolution laying beyond the diffraction limit [1–3]. It has become possible due to the delocalization of evanescent waves (near-field) existing in the proximity of nano-sized objects with a sharp metal probe

Cables of BN-insulated B-C-N nanotubes

BN-covered and insulated multiwalled semiconducting B-C-N nanotubes (NT), assembled in long ropes were produced and electrically tested. The atomic structure and chemical composition of ropes were analyzed by high-resolution transmission and energy-filtered electron microscopy. Individual ropes displayed perfect insulating performance of BN-rich outer layers and excellent field emission.</p

Structure, transport and field-emission properties of compound nanotubes: CNx vs. BNCx (x < 0.1)

Transport and field-emission properties of assynthesized CNx and BNCx (x x nanotubes displayed well-defined metallic behavior and low resistivities of ∼ 10-100 kΩ or less at room temperature, whereas those made of BNCx nanotubes exhibited semiconducting properties and high resistivities of ∼ 50-300 MΩ. Both types of ropes revealed good field-emission properties with emitting currents per rope reaching ∼ 4 μA (CNx) and ∼ 2 μA (BNCx), albeit the latter ropes severely deteriorated during the field emission. Macrofilms made of randomly oriented CNx or BNCx nanotubes displayed low and similar turn-on fields of ∼ 2-3 V/μm. 3 mA/cm2 (BNCx) and 5.5 mA/cm2 (CNx) current densities were reached at 5.5 V/μm macroscopic fields. At a current density of 0.2-0.4 mA/cm2 both types of compound nanotubes exhibited equally good emission stability over tens of minutes; by contrast, on increasing the current density to 0.2-0.4 A/cm2, only CNx films continued to emit steadily, while the field emission from BNCx nanotube films was prone to fast degradation within several tens of seconds, likely due to arcing and/or resistive heating.</p

Influence of the electrolyte’s pH on the properties of electrochemically deposited hydroxyapatite coating on additively manufactured Ti64 alloy

Properties of the hydroxyapatite obtained by electrochemical assisted deposition (ED) are dependenton several factors including deposition temperature, electrolyte pH and concentrations, appliedpotential. All of these factors directly influence the morphology, stoichiometry, crystallinity,electrochemical behaviour, and particularly the coating thickness. Coating structure together withsurface micro- and nano-scale topography significantly influence early stages of the implant biointegration.The aim of this study is to analyse the effect of pH modification on the morphology,corrosion behaviour and in vitro bioactivity and in vivo biocompatibility of hydroxyapatite preparedby ED on the additively manufactured Ti64 samples. The coatings prepared in the electrolytes withpH = 6 have predominantly needle like morphology with the dimensions in the nanometric scale(~30 nm). Samples coated at pH = 6 demonstrated higher protection efficiency against the corrosiveattack as compared to the ones coated at pH = 5 (~93% against 89%). The in vitro bioactivity resultsindicated that both coatings have a greater capacity of biomineralization, compared to the uncoatedTi64. Somehow, the coating deposited at pH = 6 exhibited good corrosion behaviour and highbiomineralization ability. In vivo subcutaneous implantation of the coated samples into the white rats for up to 21 days with following histological studies showed no serious inflammatory process