Fabrication of free-standing ordered fluorescent polymer nanofibres by
electrospinning
J.R.Y. Stevenson,1 S. Lattante,2 P. André,1,3 M. Anni2 and G. A. Turnbull1
1
Organic Semiconductor Centre, SUPA, School of Physics and Astronomy,
University of St Andrews, St Andrews, KY16 9SS, UK
Dipartimento di Matematica e Fisica “Ennio de Giorgi”, Università del Salento, Via
2
per Arnesano 73100, Lecce, Italy
3
RIKEN, Wako, Saitama 351-0198, Japan
Supplementary Information
The effect of solution concentration and electrospinning voltage on fibre thickness
Nanofibres were deposited for solutions of concentrations 10% to 25% and the results are shown in
table S1. No fibres were deposited for solutions of 5% and 30% concentrations; in these cases the
solution viscosity was outside the range that would support a stable jet and only droplets were emitted
from the tip.
We found that an increase in both the applied voltage and in the solution concentration (from 10% to
25%), yields an increase in average fibre diameter from 290 ± 50 nm (10%, 17 kV) to 1200 ± 200 nm
(25%, 26 kV). The 25% solution shows a large increase in the diameter compared to the other
concentrations because this solution was much more viscous. Upon evaporation from an equivalent
volume there will be a higher mass of material left behind and therefore a thicker fibre. In addition the
viscosity increases with concentration, resulting in a reduced mobility of polymer chains to rearrange
into thinner fibres.1, 2 Furthermore at the higher concentrations the solvent will evaporate off sooner,
resulting in a more mechanically resistant jet. The increase in diameter with voltage has been seen in
studies on other materials and was attributed to an increased draw of solution from the tip. 3 The 15%
solution gave reasonably low fibre diameter (380 ± 70 nm at 20 kV) and was relatively insensitive to
spinning conditions and so was subsequently selected for deposition with the parallel plate setup
(results in tables S2, S3).
Concentration
10%
15%
20%
25%
Voltage (Kv)
17
20
26
17
20
26
17
20
26
17
20
26
Mean
thickness (nm)
Median
thickness (nm)
Standard
deviation (nm)
290
-
390
-
380
430
400
460
-
830
510
1200
300
-
380
-
380
430
400
430
-
790
400
1200
50
-
90
-
70
90
50
130
-
190
120
200
Table S1. The measured thickness of random fibre samples. A dash indicates no fibres were obtained
for those parameters.
Separation
0.7 cm
1 cm
2 cm
4 cm
Voltage (Kv)
17
20
26
17
20
26
17
20
26
17
20
26
Mean thickness
(nm)
Median
thickness (nm)
-
510
710
440
670
690
-
540
-
-
680
-
-
510
680
450
680
690
-
520
-
-
660
-
Standard
deviation (nm)
-
90
160
50
100
130
-
120
-
-
120
-
Table S2. Measured diameters of aligned fibres. A dash indicates no fibres were obtained for those
parameters.
Concentration
10%
15%
20%
25%
Plate
(cm)
0.7
separation
0.7 (suspended)
1.0
2.0
4.0
Voltage (kV)
17
20
26
17
20
26
17
20
26
17
20
26
Voltage (kV)
Order parameter
0.004
0.007
0.054
0.019
0.051
0.011
0.063
0.030
0.058
Order parameter
17
20
26
20
17
20
26
17
20
26
17
20
26
0.33
0.35
0.56
0.09
0.28
0.28
0.23
0.12
-
Table S3. The order parameter measured for each sample. A dash indicates no fibres were produced
for that configuration. “0.7 (suspended)” refers to the order parameter of the suspended free-standing
fibre sample. Aligned samples with lower order parameters were due to relatively poor quality and
less dense samples being produced at the given electrospinning settings (1cm separation, 17kV and
4cm separation).
Calculated transverse field distributions for the experimental configuration in fig. 1(b)
Figure S1. (i) to (v): x-component of electric field in a series of horizontal (x-y) planes at heights 5,
45, 85, 125, 165 mm below the needle tip (tip to collector plate separation is 170 mm). (vi) The ycomponent of the electric field for the plane 165 mm below the tip. The square seen in each image is a
representation of the 10 cm x 10 cm top plate. Electric field in units of V/m with positive field
directed in the positive x or y directions.
Full set of plate modelling images
FIG. S2. (a), (b), (c), (d) x-component (horizontal) of the electric field in the x-z plane, around the
parallel collection plates (shown in outline) for plate separations of (a) 0.7 cm, (b) 1 cm, (c) 2 cm and
(d) 4 cm.
FIG. S3. (a), (b), (c), (d) z-component (vertical) of the electric field in the x-z plane, around the
parallel collection plates (shown in outline) for plate separations of (a) 0.7 cm, (b) 1 cm, (c) 2 cm and
(d) 4 cm.
Emissive properties of the nanofibres
FIG. S4. (a) Fluorescence image taken of the ordered fibres excited at 540 nm, (b) photoluminescence
excitation (PLE) and photoluminescence spectra for suspended fibres and rhodamine B in toluene
solution. PLE was recorded at an emission wavelength of 650 nm, and emission scans for an
excitation wavelength of 520 nm.
References
1.
B. Cramariuc, R. Cramariuc, R. Scarlet, L. R. Manea, I. G. Lupu and O. Cramariuc, J
Electrostat. 71, 189 (2013).
2.
J. F. Zheng, A. H. He, J. X. Li, J. A. Xu and C. C. Han, Polymer 47, 7095 (2006).
3.
P. Heikkilä and A. Harlin, Eur. Polym. J. 44, 3067 (2008).