Carbon nanotube-tipped endoscope for in situ intracellular surface-enhanced Raman spectroscopy

Gold nanoparticle-decorated carbon nanotubes (CNTs) are used to study intracellular environments in situ using surface-enhanced Raman spectroscopy (SERS). CNTs are decorated with gold nanoparticles and assembled onto the tips of pulled glass capillaries to form a SERS-enabled endoscope. The sub-micrometer size and high mechanical strength of the endoscope make it possible to penetrate the cell membrane for intracellular probing and remain positioned inside during lengthy SERS measurements without causing damage to the cell. Using the SERS-enabled endoscope, DNA and other biomolecules are detected in situ within the nucleus of a single human cervical carcinoma cell in a minimally invasive manner. The SERS-enabled endoscopes exhibit high selectivity and sensitivity for detecting trace amounts of analytes (≈1 pM) in biofluid environments, highlighting their capabilities as label-free, biological sensors for real-time in situ cellular diagnostics, biological detection, and pharmaceutical research.     

Phase transformations in materials studied by micro-Raman spectroscopy of indentations

 Phase transformations occurring in materials under high pressures are important for a wide range of problems in materials science and solid-state physics. Most of the results in this area have been obtained using various sophisticated high-pressure cells. We studied solid-state phase transformations and amorphisation under high non-hydrostatic pressures in very simple experiments using a combination of hardness indentation tests with micro-Raman spectroscopy. Amorphisation of diamond, that did not occur under hydrostatic loading, has been observed. Shearing and distortion of cubic diamond structure above 100 GPa resulted not only in its amorphisation, but also in the formation of threefold coordinated carbon. A carbon film that was squeezed between a SiC substrate and diamond indenter lost its graphitic structure and produced a Raman band typical of diamond-like carbon (DLC). Even for such a well-studied material as Si, principally new data have been obtained. High spatial resolution of the method allowed us to show that the Raman spectrum that was previously ascribed to a metastable Si-III phase originates from two different high-pressure phases of Si. Up to five different phases of Si were found within a single impression. Studies of reversible transformations that occur upon unloading or heating of samples by the laser beam have also been carried out. Amorphisation and/or phase transformations have been observed for some other materials, such as SiC, quartz, Ge, GaAs and other. The combination of indentation tests with micro-Raman spectroscopy provides a powerful and fast tool for in-situ and ex-situ monitoring of pressure-induced phase transformations in materials. Received: 2 January 1997 / Accepted: March 1997     

Specific Features of Glass Damage and Fracture Resistance under the Rockwell Indenter Scratching of the Specimen Surface until the Edge Chipping Appearance

Strength of Materials - The paper presents the experimental results of investigations using different types of glass by the Rockwell indenter scratching of the specimen surface till its edge...     

Mechanical properties of epoxy composites with high contents of nanodiamond

Mechanical properties and thermal conductivity of composites made of nanodiamond with epoxy polymer binder have been studied in a wide range of nanodiamond concentrations (0-25 vol.%). In contrast to composites with a low content of nanodiamond, where only small to moderate improvements in mechanical properties were reported before, the composites with 25 vol.% nanodiamond showed an unprecedented increase in Young’s modulus (up to 470%) and hardness (up to 300%) as compared to neat epoxy. A significant increase in scratch resistance and thermal conductivity of the composites were observed as well. The improved thermal conductivity of the composites with high contents of nanodiamond is explained by direct contacts between single diamond nanoparticles forming an interconnected network held together by a polymer binder.     

Multifunctional carbon-nanotube cellular endoscopes

Glass micropipettes, atomic force microscope tips and nanoneedles can be used to interrogate cells, but these devices either have conical geometries that can damage cells during penetration or are incapable of continuous fluid handling. Here, we report a carbon-nanotube-based endoscope for interrogating cells, transporting fluids and performing optical and electrochemical diagnostics at the single organelle level. The endoscope, which is made by placing a multiwalled carbon nanotube (length, 50-60?μm) at the tip of a glass pipette, can probe the intracellular environment with a spatial resolution of ～100?nm and can also access organelles without disrupting the cell. When the nanotube is filled with magnetic nanoparticles, the endoscope can be remotely manoeuvered to transport nanoparticles and attolitre volumes of fluids to and from precise locations. Because they are mounted on conventional glass micropipettes, the endoscopes readily fit standard instruments, creating a broad range of opportunities for minimally invasive intracellular probing, drug delivery and single-cell surgery.     

Mechanical property characterization of a 9 mol% Ce-TZP ceramic material — I. Flexural response

Investigations were carried out on four tetragonal zirconia polycrystalline (TZP) ceramics of differing grain size containing 9 mol% CeO₂. Precision flexural tests on these materials were conducted to determine the elastic modulus, the non-linear deflection and the associated acoustic emission during such testing. The deformation was characterized in terms of the number and size of the transformation bands that developed during the non-linear response. The finest grained material initially exhibited permanent set without the presence of such bands, whereas all the coarser grained materials showed a linear relationship between the summation of the band widths and the residual deflection. The acoustic emission and plastic strain behaviour are discussed in terms of the number and size of the stress induced phase transformation bands.