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1.
Nanoscale Res Lett ; 5(3): 539-544, 2010 Feb 04.
Article in English | MEDLINE | ID: mdl-20672089

ABSTRACT

Dense, vertically aligned multiwall carbon nanotubes were synthesized on TiN electrode layers for infrared sensing applications. Microwave plasma-enhanced chemical vapor deposition and Ni catalyst were used for the nanotubes synthesis. The resultant nanotubes were characterized by SEM, AFM, and TEM. Since the length of the nanotubes influences sensor characteristics, we study in details the effects of changing Ni and TiN thickness on the physical properties of the nanotubes. In this paper, we report the observation of a threshold Ni thickness of about 4 nm, when the average CNT growth rate switches from an increasing to a decreasing function of increasing Ni thickness, for a process temperature of 700 degrees C. This behavior is likely related to a transition in the growth mode from a predominantly "base growth" to that of a "tip growth." For Ni layer greater than 9 nm the growth rate, as well as the CNT diameter, variations become insignificant. We have also observed that a TiN barrier layer appears to favor the growth of thinner CNTs compared to a SiO(2) layer.

2.
Small ; 5(9): 996-1006, 2009 May.
Article in English | MEDLINE | ID: mdl-19360718

ABSTRACT

The human body is an intricate biochemical-mechanical system, with an exceedingly precise hierarchical organization in which all components work together in harmony across a wide range of dimensions. Many fundamental biological processes take place at surfaces and interfaces (e.g., cell-matrix interactions), and these occur on the nanoscale. For this reason, current health-related research is actively following a biomimetic approach in learning how to create new biocompatible materials with nanostructured features. The ultimate aim is to reproduce and enhance the natural nanoscale elements present in the human body and to thereby develop new materials with improved biological activities. Progress in this area requires a multidisciplinary effort at the interface of biology, physics, and chemistry. In this Review, the major techniques that have been adopted to yield novel nanostructured versions of familiar biomaterials, focusing particularly on metals, are presented and the way in which nanometric surface cues can beneficially guide biological processes, exerting influence on cellular behavior, is illustrated.


Subject(s)
Biocompatible Materials/chemistry , Crystallization/methods , Metals/chemistry , Nanostructures/chemistry , Nanostructures/ultrastructure , Nanotechnology/methods , Prostheses and Implants , Macromolecular Substances/chemistry , Materials Testing , Molecular Conformation , Particle Size , Surface Properties
3.
J Chem Phys ; 128(14): 144705, 2008 Apr 14.
Article in English | MEDLINE | ID: mdl-18412469

ABSTRACT

Surface modification of titanium and its alloys is of great importance for their practical application as biomedical implants. We have studied and compared assembly of dodecylphosphoric acid on commercial polished and on nanostructured titanium disks. The latter were produced by chemical etching that created nanoscale pits of typical size of about 20 nm. Enhanced hydrophobicity and high molecular density were obtained after functionalization of the nanotextured substrate. Aging tests showed a lifetime of the organic films of about one month in phosphate buffer. The samples were characterized by means of infrared spectroscopy, contact angle measurements, ellipsometry, and atomic force and scanning tunneling microscopies.


Subject(s)
Alkanes/chemistry , Crystallization/methods , Membranes, Artificial , Nanostructures/chemistry , Nanostructures/ultrastructure , Phosphoric Acids/chemistry , Titanium/chemistry , Adsorption , Particle Size , Surface Properties
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