Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
Hollow Cathode Type Glow Discharge for Starch Modification
Ritchie Eanes* and Sümeyra Bayır
Department of Chemistry, Izmir Institute of Technology, Izmir 35430, Turkey
Abstract— A home-built hollow cathode type dc glow discharge instrument modified with a special glass holder is
used to effect possible surface and bulk modification of starch films. Specifically built for the study of the cross-linking of
starch by plasma treatment, this device makes use of a hollow cathode arrangement towards enhanced plasma interactions.
There is much interest in biodegradable polymers and in
this regard much work has focused on the cross-linking of
starch [see 1 and the references therein]. Although probably
more often considered as a part of food science, starch, in its
crosslinked or modified form, has found uses in non-food
applications including those in the biomedical,
pharmaceutical, and wastewater fields as mentioned by Ayoub
and Rizvi in their review [2]. There are several methods
available for the modification of starch; however, some of
these methods require the use of rather exotic or potentially
harmful crosslinking reagents [see 3 and references therein].
Zou et al. have described their modification of starch
using a glow discharge plasma [3]. In their design, a starch
slurry sample was placed in the positive column of their glow
discharge device, between the anode and cathode. They
concluded that a highly crosslinked starch could be obtained
by using the glow discharge plasma in place of a more
traditional chemical crosslinking reagent [3]. More recently,
Bastos et al. have described the production of hydrophobic
starch films by plasma treatment where the sample was placed
directly on the cathode of a radio-frequency (rf) glow
discharge apparatus [4].
The glow discharge is a useful medium for sputterdeposition
[5] as well as analytical spectroscopies [6]. Under
vacuum, gas is introduced into the region between an anode
and cathode. This gas can be of the relatively "non-reactive"
or "reactive" variety. Quite often argon, helium, or a
combination of these two gases is used, especially for
analytical glow discharge applications. More traditionally,
both the anode and cathode are flat. However, especially for
analytical glow discharge spectroscopy, the hollow-cathode
design has gained interest due to the increased electron density
of this electrode geometry. Also present in the plasma are
ions of the discharge gas as well as the cathode. However,
depending on the cathode material, the degree of sputtering of
the cathode can be kept to a minimum [6].
In our dc glow discharge configuration, the cathode is large
enough to contain a small sample that is immersed in the
plasma by means of a glass L-shaped holder. By using
holders of varying lengths, the sample can be placed at
different positions within the glow discharge. Likewise, the
cathode is attached to a probe that also allows adjustment in
the position of the hollow cathode. This movable probe
design is a modified form of the pin-type analytical glow
discharge direct insertion probe of Duckworth and Marcus [7].
Other adjustable parameters include discharge voltage,
discharge gas type, and pressure. By modifying these
parameters, the shape and contents of the plasma can be varied
as well as their degree of interaction with the sample.
This work was partially supported by IYTE BAP project
2003 IYTE 02. N.R.E. is gratefully acknowledged for
financial support. We thank Polat Bulanık for his glass
blowing expertise and Prof. Dr. Tamerkan Özgen for the high
voltage power supply and vacuum pump.
Figure 1. Simple schematic of the hollow cathode glow discharge arrangement
with the glass L-shaped sample holder immersed in the plasma.
Figure 2. View through the UV transparent window of the inside of the hollow
cathode glow discharge in operation without the glass sample holder in place.
*Corresponding author: ritchieeanes@iyte.edu.tr
[1] N. Reddy and Y. Yang. Food Chemistry. 118, 702-711 (2010).
[2] A. S. Ayoub and S.S.H. Rizvi. J. Plastic Film & Sheeting. 25, 25-45
(2009).
[3] J.-J. Zou, C-J. Liu, and B. Eliasson. Carbohydrate Polymers. 55, 23-26
(2004).
[4] D.C. Bastos, A.E.F. Santos, M.L.V.J. da Silva, and R.A. Simão.
Ultramicroscopy. 109, 1089-1093 (2009).
[5] B. Chapman. Glow Discharge Processes. John Wiley & Sons, New York:
1980.
[6] R. K. Marcus and J.A.C. Broekaert, Eds. Glow Discharge Plasmas in
Analytical Spectroscopy. John Wiley & Sons, Chichester: 2003.
[7] R. K. Marcus, Ed. Glow Discharge Spectroscopies. Plenum Press, New
York: 1993, p. 309.
6th Nanoscience and Nanotechnology Conference, zmir, 2010 413