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Experimental details
Briefly, pure Sn02 sols were prepared starting from commercially available anhydrous tin
(IV) chloride SnCl4 (ACROS Organics), deionized water, propanol (C3H7OH, Fisher Scientifics), and insopropanol (2-C3H7OH,
Fischer Scientifics) in the following molar ratio: SnCl4:H2O: C3H7OH2-C3H7OH:1:9:9:6. Following the above recipe, the following
chemical reactions occurs,
SnCl4+nH20=Sn(OH)nCl4-n=nHCl,(n=1,2,3,4) (I)
Commercially available poly (ethylene oxide)
(PEO) [-CH2CH2O-]n (molecular weight 900,000, Aldrich) and chloroform CHCl3 (Sigma) were mixed at the ration of 100mg PEO/10mL
CHCl3 and were magnet-stirred before a homogenous solution was formed. The solution was mixed with liquid dimethyldineodecanoate
tin C22H4404Sn at a volume ratio of 2:1, and the mixture was again magnet-stirred until it finally became a homogenous precursor
solution with appropriate viscosity. The precursor solution was prepared at room temperature.
Electrospinning was conducted
also at room temperature in a homemade setup. The DC power supply was an ES30-0.IP model HV power supply manufactured by Gamma
High Voltage Research; the plastic pipette was, in fact, a 5 ml syringe, with a 16G11/2 hypodermic needle, whose tip was filed
flat. The pipette was tilted appropriately so that a small drop was maintained at the capillary tip due to the surface tension
of the solution. The collection screen was a grounded large aluminium foil pasted flatly onto the vertical panel of a paperboard
box at a horizontal distance of 15 cm from the tip. The potential difference between the tip and the grounded screen was 15
kV with an average electrical field of 1 x 105Vm-1. the substrates, held on the screen by adhesive tape, were oxidized (150
nm) single crystal silicon wafers. The whole set-up was placed in a ventilation hood. Single crystal silicon wafers with an
oxidized surface layer of 150 nm in thickness were used as substrates. Depositions were performed for several seconds and
several hours so as to obtain single precursor fibers and dense fiber mats, respectively. The as-deposited single fiber and
mat samples were dried at 80oC for one hour in the air using a hotplate. Using a resistive furnace equipped with a Sentry
2.0 Digital Temperature Controller made by Paragon Industries, Inc., the dried samples were sintered in the air for two hours
at 400, 500, 600, 700 and 8000C, respectively.
The sintered single fiber and mat samples were observed under a JORL JSM-6360
scanning electron microscope (SEM) operated in secondary electron mode under the accelerating voltage of 3.0 and 20kV, respectively.
A Digital Instruments Dimension 3000NS-III Scanning probe microscopy (SPM), operated in tapping mode, was used to record the
height and amplitude images of the fibers at data files. Offline image processing software was used to obtain the apparent
average cross-section profile. The sintered mat samples were characterized by x-ray diffraction (XRD), Raman scattering and
x-ray photoelectron spectroscopy (XPD). XRD was conducted using a Siemens D5000 X-ray diffractometer with the incident x-ray
source of Cu K radiation and a graphite monochromator. It was operated at the tube voltage and current of 45kV and 40mA, respectively,
and the angular scanning rate of 20C/min. Raman micro-scattering was conducted using a Jovin-Yvon ISA T64000 Raman microscope/microspectrometer
with Argon laser (wavelenghth = 514.532nm) as the incident light sourct. Perkin-Elmer Corporation conducted XPS using a PHI
5600 ESCA System, with its Mg K radiation source operated at 14kV and 400W and a Model 10-410 monochromator.
Conclusions
Micro- and nano-fibres of tin oxide (Sn02) in the rutile structure were synthesized from precursors of poly(ethylene
oxide) (molecular weight 900,00), chloroform and dimethyldineo-decanoate tin using electrospinning and metallorganic decomposition
techniques. Scanning electron microscopy, x-ray diffraction, and Raman microspectrometery characterizations showed that the
synthesized fibers are composed of the rutile phase of Sn02. Electrical conducting properties require further study.
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