Positional control of catalyst nanoparticles for the synthesis of high density carbon nanofiber arrays

Abstract

Precise arrangement of nanoscale elements within larger systems, is essential to controlling higher order functionality and tailoring nanophase material properties. Here, we present findings on growth conditions for vertically aligned carbon nanofibers that enable synthesis of high density arrays and individual rows of nanofibers, which could be used to form barriers for restricting molecular transport, that have regular spacings and few defects. Growth through plasma-enhanced chemical vapor deposition was initiated from precisely formed nickel catalyst dots of varying diameter and spacing that were patterned through electron beam lithography. Nanofiber growth conditions, including power, precursor gas ratio, growth temperature and pressure were varied to optimize fiber uniformity and minimize defects that result from formation and migration of catalyst particles prior to growth. It was determined that both catalyst dot diameter and initial plasma power have a considerable influence on the number and severity of defects, while growth temperature, gas ratio (C 2 H 2 :NH 3 ) and pressure can be varied within a considerable range to fine-tune nanofiber morphology.

Fabrication of nanoporous membranes for tuning microbial interactions and biochemical reactions

“…Such membranes have been made using self-assembled nanowires, 4 colloidal selfassemblies, 5 amorphous silicon (a-Si) to porous nanocrystalline silicon (pnc_Si) crystallization, 6 and vertically aligned carbon nanofibers. [7][8][9][10][11] These membranes still rely on restricting transport with implementation of tortuous paths that molecules must take to pass through the membrane. The distribution of effective pore size depends on the thickness of the membrane.…”

Development and fabrication of nanoporous silicon-based bioreactors within a microfluidic chip

“…Figure 5 demonstrates that vessels are defect free and have a functional pore size, and size distribution between 100nm and 350nm. In previous work we examined the use of patterned carbon nanofiber membranes for similar separations, but found that defect density resulting from the nanofiber growth resulted in “leaky” membrane structures 25, 26 . In addition to being free of defects, the deterministic nature of the structures used here help make modeling and simulation of these systems more tractable.…”

“…In previous work we examined the use of patterned carbon nanofiber membranes for similar separations, but found that defect density resulting from the nanofiber growth resulted in ''leaky'' membrane structures. 25,26 In addition to being free of defects, the deterministic nature of the structures used here helps to make modeling and simulation of these systems more tractable. This basic demonstration helps illustrate the potential utility in using the reaction vessels to exclude molecules or functionalized particles based on size.…”

Spatial tracking of individual fluid dispersed particles via Raman spectroscopy

“…Dispersions of nanoparticles are becoming a ubiquitous element of everyday life, and are the subject of intensive scientific investigation. Applications have been developed spanning the breadth of: pharmaceuticals such as cancer treatment 1 and drug delivery systems 2 ; antibacterial and anti-fouling coating materials 3 ; improved cosmetics formulations 3 ; stronger construction materials 4 ; and numerous other technologies 5 – 10 , representing a huge expenditure of human resources and effort. Furthermore, nanoparticles of scientific interest are not uniquely synthetic.…”