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# Eric Mock <ericmock@uiuc.edu>
# requesting 2 days, at minimum=2 days
# beamline 33ID, Structure of Anisotropic Nanoparticles
# instrument 33ID-D SRUSAXS
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# top:/home/www/beamtime-requests/req00897.txt
# UNICAT Member Beam Time Request  #897
# created Tue Dec 06 22:00:40 CST 2005
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apsrun:
	2006-01

beamline:
	33ID

collaboration:
	Yes

contact:
	ericmock@uiuc.edu

days:
	2

description:
	Anisotropic colloid particles are encountered in numerous applications, including coatings, impact modifiers, and photonic crystals.  Here we are interested in controlling the anisotropy of nanoparticles with the goal of building novel microstructures to enhance macroscopic properties.

Previously, we performed side bounce ultra-small angle x-ray scattering (SBUSAXS) on polystyrene spherical and dumbbell shaped nanoparticles.  These particles were suspended in glycerol, and to obtain form factors, the scattering intensity was measured as a function of the scattering vector, Q, for dilute suspensions (volume fractions of 0.05).  It was seen that the shape of the dumbbell particles reduces the maxima and minima present in the spherical particle form factor plot, indicating that difference in anisotropy of the samples is significant enough to be observed with SBUSAXS.  After obtaining form factors for the two batches of particles, experiments were performed on more concentrated suspensions (volume fractions of 0.35) to obtain structure factors.  From the plots of these structure factors as a function of Q, it was apparent that the spacing between the first and second peak of the dumbbell particles is larger than for the spherical particles.  Some iridescence was observed in these samples, suggesting that the particles were beginning to order.  This suggests, the dumbbell particles and spheres order into different configurations.

In order to further explore the ordered structures of dumbbells and spheres, we would like to perform experiments on more concentrated suspensions of these particles (volume fractions of 0.55) where suspensions of both particles are expected to be highly ordered.  Likewise, we have synthesized uniform particles that have small and moderate sized bumps so that they are between spheres and dumbbells in appearance, and we would like to perform experiments on concentrated suspensions of these particles to see if structure changes as anisotropy is changed.

equipment_required:
	

experiment:
	Structure of Anisotropic Nanoparticles

foreign_nationals:
	

hazards:
	The experiments themselves will simply require an aluminum sample cell with Kapton windows (we have both of these in our lab at the University of Illinois) under ambient conditions, and thus there are no hazards associated with the actual experiment.  In order to keep the samples at a constant ionic strength, solutions of glycerol and potassium chloride are prepared.  While only a small amount of potassium chloride is used (enough to give the glycerol solutions an ionic strenght of 1E-4 molar) potassium chloride is a toxic substance, and thus care should be taken when using it (i.e. personal protective equipment should be worn and contact with the skin should be minimized).

instrument:
	33ID-D SRUSAXS

instrument_other:
	

minimumdays:
	2

name:
	Eric Mock

nonmembers:
	

submit:
	Submit

unacceptable_dates:
	

z34ID_details:
	


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