Photon Factory Activity Report 2014 #32 (2015) B

BL-27A/2013G714

X-ray absorption spectroscopy of ultraviolet-irradiated polyacetylene derivative
Hiromi Ikeura-SEKIGUCHI*1, Tetsuhiro SEKIGUCHI2
Research Institute for Measurement and Analytical Instrumentation (RIMA),
National Metrology Institute of Japan (NMIJ),
National Institute of Advanced Industrial Science and Technology (AIST),
Tsukuba, Ibaraki 305-8568, Japan
2
Japan Atomic Energy Agency (JAEA), Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan
1

2 Experiment
Experiments were performed at beamline BL-27A withenergy resolution of 0.9 eV. The XAS spectra weremeasured using monitoring sample drain current near theS K-edge (2465–2505 eV). Such energies were chosen toexcite the S 1s core electron to unoccupied orbitals ofPATAC-Me. PATAC-Me films were fabricated on
silicon substrate by drop-casting from dilute solution (1.5mg /g). All spectra were recorded at room temperature in
the vacuum conditions. The XAS spectra werenormalized to the incident X-ray flux measured by Al thinfilm. Photo-reaction process was measured with
irradiation of UV light using a100 W arc Hg lamp.
3 Results and Discussion
Figure 1 shows the S K-edge XAS spectra of PATACMe films at θ = 55 (magic angle) in various irradiation
time of Hg lamp. A linear pre-edge was removed for eachspectrum and the data were normalized by the height ofthe edge jump. There are one strong feature and three
weak features in the XAS of PATAC-Me. The mostintense peak 1 can be assigned mainly to S 1s → σ*(S–C)
and partly to S 1s → π*(C=C) unoccupied states. The
deference in both peak positions is 1 eV or less. Thus, it
is difficult to be separated from one another by peakfitting method in the present energy resolution. A weakpeak 2 can be attributed to S 1s →σ*(C–S) unoccupiedstate. The broad, higher-energy peaks 3 and 4 correspondto shape resonance states of σ*(C–C) and σ*(C=C),
respectively. Only the intensity of the peak 1 decreases
with increasing exposure time of UV irradiation. In

contrast, two new peaks A near peak 2 and B near peak 3
appeared, and increase with increasing exposure time ofUV irradiation. It has been known that the sulfur K-edge
XAS allows a determination of sulfur chemicals such as
thiol, disulfide, sulfoxide and sulfone groups. The peaks
A and B observed at  2476.8 eV and  2481.2 eV
typically imply sulfone and sulfonate, respectively [3].

A B
1 2 3

4120minIntensity (arb. units)

1 Introduction
Poly(bis-alkylthioacetylene) (PATAC) [1-2] is one of
the trans-PA derivatives, which is easily soluble inhalogenated hydrocarbons and aromatic solvents. PATAC
can be doped by only an ultraviolet (UV) / laser
irradiation to become permanently conducting materials
from initially insulating materials and produce micropattering of electrically conducting wires for integrated
circuit designs. The electrical conductivity in PATAC is
supposed to relate with the formation of a π-conjugatedcarbon chains linked by sulfur. However, there is little
spectroscopic data about photoreaction products formed
in UV-irradiated PATAC. In order to investigate thereaction process of poly[bis(methylthio)acetylene](PATAC-Me), especially to clarify the production ofsulfur compound by UV irradiation, we used sulfur Kedge X-ray absorption spectroscopy (XAS).

60min
30min
15min
0min

UV
2470 2480 2490 2500
Photon Energy (eV)Fig. 1: XAS spectra of UV-irradiated PATAC-Mefilm near the S K-edge.
References[1] H.K. Roth et al., Synth. Met. 37, 151 (1990).
[2] H.K. Roth, et al., Synth. Met. 101, 832 (1999).
[3] A. Manceau and K.L. Nagy, Geochim. Cosmochim.
Acta, 99, 206 (2012).
*ikeura-sekiguchi@aist.go.jp