Design, synthesis, and biological evaluation of 1-substituted -2-aryl imidazoles targeting tubulin polymerization as potential anticancer agents

Article abstract of DOI:10.1016/j.ejmech.2019.111732

A series of novel 1-substituted-2-aryl imidazoles (SAI) were designed and synthesized based on our previously reported ABI (2-Aryl-4-Benzoyl Imidazole) analogs and on the structure of combretastatin A-4 (CA-4). These compounds showed potent antiproliferat

Full text of DOI:10.1016/j.ejmech.2019.111732

JournaloftheEuropeanCeramicSociety39(2019)4307–4312
Contents lists available at ScienceDirect
Journal of the European Ceramic Society
journal homepage: www.elsevier.com/locate/jeurceramsoc
Original Article
Irradiation damage in xenon-irradiated α-Al2O3 before and after annealing
⁎
Bingsheng Lia,b, , Huiping Liub, Long Kangb, Tongmin Zhangb, Lijun Xub, Anli Xiongc
a State Key Laboratory for Environment-friendly Energy Materials, Southwest University of Science and Technology, Mianyang, Sichuan, 621010, China
b Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu, 730000, China
c Fundamental Science on Nuclear Wastes and Environmental Safety Laboratory, Southwest University of Science and Technology, Mianyang, Sichuan, 621010, China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Alumina
Irradiation damage
Microstructure
Raman spectroscopy
The irradiation damage build-up of α-Al2O3 under Xe20+ ion irradiation has been investigated by a combination
of Raman spectroscopy and transmission electron microscopy. α-Al2O3 crystalline was irradiated with 5 MeV
Xe20+ ions to fluences of 1 × 1014 cm−2, 5 × 1014 cm−2, 1 × 1015 cm−2 and 5 × 1015 cm−2 at room tem-
perature. No amorphous phase was formed under the experimental condition. The Raman intensities of feature
peaks of Al2O3 decrease after Xe ion irradiation. The interstitial-type dislocation loops with Burgers vectors of
b = 1/3 < 10-11 > on the {10-10} and (0001) habit planes were found. The formation of basal and prism
dislocation loops is related to the lattice damage and position. After annealing, the Raman intensities of feature
peaks of Al2O3 increases with annealing temperature. With annealing at 1500℃ for 30 min, lattice defects were
completely annealed out in the near surface region. Meanwhile, long dislocations and facet cavities on long
dislocations were found in the Xe deposition region. Some lattice defects beyond the projected region were found
due to the diffusion toward deep region during thermal annealing.
1. Introduction
have investigated radiation effects on α-Al2O3 irradiated with H2+ ions
at room temperature, 400℃, 650℃ and 800℃ [6]. Bubbles were found
Due to the advanced physicochemical stability, high electrical re-
sistivity and high chemical inertness, alumina (Al2O3) is regarded as
one of the important candidate ceramics materials used in fusion re-
actors, i.e., the window for a microwave heating system, an insulating
material, optical windows and tritium permeation barriers [1,2].
Therefore, the effects of irradiation on α-Al2O3 have been studied in
decades. The microstructural evolution of α-Al2O3 during neutron or
ion irradiation has been widely studied. Neutron irradiation can induce
the formation of interstitial dislocation loops with Burgers vectors of
b = 1/3 < 10-11 > on both {10-10} and (0001) habit planes [3].
Yamada et al. have investigated microstructure of α-Al2O3 pre-
implanted with H, He, C and irradiated with Ar+ ions at 260-810℃ and
assumed the dislocation loops with (0001) and {1–100} habit planes
[4]. The number density of loops on the (0001) habit plane was higher
than that on the {1–100} planes. In addition, the influence of pre-im-
planted H, He and C on cavity distribution is not significant [4]. Zinkle
and Pells have investigated microstructure of α-Al2O3 irradiated with
Ar+ at 200 and 300 K. They found dislocation loops and network dis-
locations formed in α-Al2O3 under irradiation at 300 K. The values of
step-height swelling are 4.5%, 3.5% and 2.8% after Ar+ irradiation to a
dose of 10 dpa at 200 K, 300 K and 900 K, respectively [5]. Furuno et al.
in the sample irradiated at room temperature. Below 400℃, dislocation
loops and bubbles were homogeneously distributed. Above 650℃,
bubbles are preferential to nucleate with the dislocation loops. Chen
et al. have investigated microstructure of He-implanted α-Al2O3 after
annealing. The majority loops with interstitial-type have habit planes of
{10-10} and (0001). Furthermore, the loops had a round shape on
(0001) plane while some loops had a rectangular shape on {10-10}
planes. Bubbles associated with loops were formed after annealing at
1000℃ [7]. The threshold dose for amorphization in α-Al2O3 is related
to the irradiation temperature and ion species. Below 80 K, it needs a
dose of 3–6 displacements per atom (dpa), while it needs over 100 dpa
with implanted ion levels of on the order of 50 at.% during irradiation
at room temperature [8,9].
Alumina can be also used in fission reactors, such as inert fuel host
and rector components. Xenon is regarded as a major inert gas fission
product, and it is worth studying xenon behavior in α-Al2O3. Up to now,
xenon ion irradiation effects on α-Al2O3 have been less reported [10].
In this paper, we report the microstructure of lattice disorder in α-Al2O3
under xenon ion irradiations. The interstitial-type dislocation loops
were investigated by conventional transmission electron microscopy
and high resolution transmission electron microscopy. The type of Xe-
⁎ Corresponding author at: State Key Laboratory for Environment-friendly Energy Materials, Southwest University of Science and Technology, Mianyang, Sichuan,
621010, China.
E-mail address: libingshengmvp@163.com (B. Li).
https://doi.org/10.1016/j.jeurceramsoc.2019.05.035
Received 17 March 2019; Received in revised form 17 May 2019; Accepted 20 May 2019
Availableonline24May2019
0955-2219/©2019ElsevierLtd.Allrightsreserved.

B. Li, et al.
JournaloftheEuropeanCeramicSociety39(2019)4307–4312
irradiation induced dislocation loops is related to the level of lattice
damage and depth distribution. Most of lattice defects were recovered
upon annealing at 1500℃ for 30 min.
2. Experimental process
In the present study, the material is < 0001 > oriented α-Al2O3
single-crystal wafers, which were obtained from MIT Company with a
dimension of 10 × 10 × 0.5 mm3. Xe20+ ions with an energy of 5 MeV
were supplied by 320 kV High-voltage Platform in the Institute of
Modern Physics, Chinese Academy of Sciences. The irradiation fluences
were
1 × 1014 cm−2
,
5 × 1014 cm−2
,
1 × 1015 cm−2
and
5 × 1015 cm−2. The beam flux during irradiation was of the order of
1011 ions cm-2s-1 and the irradiation temperature was room tempera-
ture. Beam scanning was employed to achieve a uniform irradiation
with an area of 15 × 15 mm2. The irradiation damage in dpa and
concentration were simulated by SRIM-2008 quick cascade simulations
using the displacement energies of O = 50 eV, Al =20 eV, and density
of 3.98 g/cm3) [11]. Isochronal annealing was performed for 30 min
under argon gas flow over the temperature range from 900℃ to 1500℃.
Micro-Raman spectroscopy (μ-RS) was employed to research the
evolution of chemical bonds. μ-RS was performed using a Horiba Jobin
Yvon HR-800 spectrometer at room temperature. The excitation wa-
velength was 532 nm from the Ar+ laser and the laser spot was about
1 μm. The microstructure of the Xe irradiation-induced damage was
studied by cross-sectional transmission electron microscopy (XTEM)
and high resolution TEM (HRTEM) using a Tecnai G20 operated at
200 kV with a point resolution of 0.19 nm. The preparation process of
the XTEM sample was mechanical thinning and then Ar+ ion milling
[12,13]. The sample was observed near the [11–20] direction. The
micrograph conditions were bright field (BF) and weak-beam dark field
(WBDF). The distribution of defects under WBDF was counted with an
uncertainty of about + 20%. The thickness of the foils was determined
by electron energy loss spectrum (EELS).
Fig. 2. XTEM bright field micrograph of Al2O3 irradiated with 5 MeV Xe20+
ions to a fluence of 5 × 1015 He+/cm2 at RT, superposed the distribution of
damage and helium deposition of the Xe irradiated GaN simulated by SRIM-
2008. Electron diffraction pattern taken from the damaged layer and micro-
graph taken from the tail of the damage layer are shown as insets.
present experimental condition, the mode corresponding to A1g at
648 cm-1 is not observed, while an extra band with peak at 478 cm-1 is
observed. After Xe20+ ion irradiation, the background intensity in-
creases due to the Rayleigh scattering from the defects induced by
Xe20+ irradiation. The strong luminescence induces the raising baseline
of spectrum. Furthermore, the intensities of Raman scattering peaks
decrease with increasing the fluence. It is attributed to the increase of
optical absorption induced by Xe20+ irradiation-induced defects. It
should be noted that the Raman scattering peaks of Al2O3 can be still
clearly observed in the sample irradiated with the maximum fluence. It
indicates that the crystalline structure is remained under the present
experimental condition.
The simulated profiles of the damage and xenon deposition of Al2O3
irradiated with 5 MeV Xe20+ ions with a fluence of 5 × 1015/cm2 su-
perposed a XTEM view of the Xe20+ irradiated sample, as shown in
Fig. 2. The electron diffraction pattern demonstrates the single crystal
structure in the irradiation region, consistent with the result of Raman
spectra. According to SRIM simulation, the mean projected region Rp is
approximately 1130 nm with a straggling of ΔRp is approximately
350 nm. The maximum damage is approximately 8 dpa. Dense black
contrasts arising from Xe irradiation-induced dislocation loops, stacking
faults and strain were observed. The damaged layer ranges from surface
to a depth of 1650 nm and the irradiation damage is more serious at
depths ranging from 1350 to 1650 nm. It is clearly shown that the
SRIM-predicted Xe distribution and damage profiles are much shal-
lower than that shown by the contrasted features in the XTEM image.
Large discrepancies in the ion range between SRIM and experimental
value is due to overestimation of electronic stopping power of the
medium mass ions. Zhang et al. investigated Au+ ion irradiation in GaN
and argued a deviation of about 25% between the SRIM-predicted value
and experimental value [15]. According to the defect contrast shown in
Fig. 2, the damage peak appears located at a depth of 1500 nm, while
the maximum Xe deposition is located at a depth of 1050 nm predicted
by SRIM. There is a deviation of about 23%, consistent with Au+ ion
irradiation in GaN.
3. Results and discussion
3.1. As-implanted state
The Raman spectra of the α-Al2O3 samples before and after irra-
diated by 5 MeV Xe20+ to fluences of 1 × 1014 cm−2, 5 × 1014 cm−2
,
1 × 1015 cm−2 and 5 × 1015 cm−2 are illustrated in Fig. 1. The virgin
Al2O3 normally known as corundum with Rc space group, presents
seven Raman active phonon modes, 2A1g+5Eg (418 cm-1 and 648 cm-1
arise from A1g (internal); 378 cm-1, 432 cm-1, 451 cm-1, 755 cm-1 arise
from Eg (external); 578 cm-1 arises from Eg (internal)) [14]. In the
Fig. 3 presents weak beam dark field images of the damaged layer
for the Xe20+ irradiated Al2O3 at room temperature. The images were
taken along the [11–20] zone axis. High densities of bright contrasts
correlated to point defect clusters, dislocation loops, stacking faults and
strains were observed. Rel-rod-streaks in the (0001) plane were pre-
sented in the electron diffraction pattern, as shown in the inset of
Fig. 3(a). It indicates a very high density of dislocation loops located in
the basal plane. Image taken under g = 1–104 condition, many dis-
location loops exhibited edge-on contrast. It can be clearly visible some
dislocation loops parallel to the basal plane but others perpendicular to
Fig. 1. Raman scattering spectra of Al2O3 before and after irradiated with
5 MeV Xe20+ to fluences of 1 × 1014 cm−2, 5 × 1014 cm−2, 1 × 1015 cm−2 and
5 × 1015 cm−2 at RT.
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JournaloftheEuropeanCeramicSociety39(2019)4307–4312
Fig. 3. XTEM weak beam dark field micrographs of Al2O3 irradiated with 5 MeV Xe20+ to a fluence of 5 × 1015 cm−2 at RT. (A) g = (1–104), (B) g = (-3300) and (C)
g = (-1102). The bottom six images (A1 to C2) show the magnified images as marked in figures (A, B and C) respectively.
the implanted surface. More importantly, the majority of observed
dislocation loops lying on the prism {1–100} habit planes are located in
the near surface region, as shown in Fig. 3(A1). However, the observed
dislocation loops lying on the basal (0001) plane are located in the deep
region, as shown in Fig. 3(A2). Image taken under g = 3–300 condition,
a high density of point defect clusters and dislocation loops were ob-
served in the damaged layer, as shown in Fig. 3(B). In the near surface
region, the lattice defects exhibited large and bright contrasts compared
to the lattice defects located in the deep region. It indicates that the
sizes of observed lattice defects are larger in the near surface region
than that in the deep region. Image taken under g = -1102 condition,
the defect contrast is similar to the case of g = 1–104.
The size distributions of the lattice defects for two different dif-
fraction factors are plotted in Fig. 4. Under g = 1–104, as shown in
Fig. 4(a), the observed dislocation loops perpendicular to the implanted
surface have a mean size of 8.11 nm and a number density of 3.7 +
0.7 × 1022 cm−3. The observed dislocation loops parallel to the basal
plane have a mean size of 13.37 nm and a number density of 5.8 +
1.2 × 1022 cm−3. The dislocation loops on the basal plane are little
larger than the dislocation loops on the prism planes. Under g = 3–300,
as shown in Fig. 4(b), in the near surface region, the observed point
defect clusters and dislocation loops have a mean size of 3.77 nm and a
number density of 7.3 + 1.5 × 1022 cm−3. In the deep region, the
observed point defect clusters and dislocation loops have a mean size of
3.13 nm and a number density of 1.4 + 0.3 × 1023 cm−3. In the deep
region, the number density of observed lattice defects is larger than that
in the near surface region. There are two reasons that can account for it.
One reason is that the surface acts as a strong sink for implantation-
induced lattice defects, leading to the decrease in the number density of
lattice defects in the near surface region. The other reason is that im-
purity due to Xe deposition can reduce the mobility of lattice defects,
and thereby suppress the recombination of interstitials and vacancies,
resulting in the increase in the number density of lattice defects in the
Xe deposition region.
HRTEM was carried out to investigate atomic structure of disloca-
tion loops on the prism planes and on the basal plane. The [11–20] zone
axis was chosen for the HRTEM observation. Fig. 5(a) shows a typical
morphology of one basal dislocation loop located at between two prism
dislocation loops. Lattice fringes are clearly visible and partial regions
of lattice fringes are wavy due to lattice disorder. Fig. 5(b) shows
Fourier-filtered HRTEM image and interstitial-type dislocation loops on
the (1–100) plane and (0006) plane were clearly visible. Pyramidal
dislocations as well as their corresponding stacking faults were noted.
The Burgers vectors of the pyramidal dislocation loops were b = 1/
3[1–101], as shown in Fig. 5(c). The b = 1/3[1–101] can be regarded
via the following reaction: 1/3[1–100] + 1/3[0001] →1/3[1–101].
Partial zone containing observed basal dislocation loop and prism dis-
location loops was magnified, as shown in Fig. 5(d). Interstitial-type
basal dislocation loops on the (0006) plane and interstitial-type prism
dislocation loops on the (1–100) plane were visible. Fourier-filtered
HRTEM image of Fig. 5(d) presents that the interstitial-type dislocation
loops have Burgers vectors of b = 1/3[1–101]. In addition, the signal
intensities of different lattice atoms of the basal dislocation loop on the
(1–104) plane and the prism dislocation loop on the (1-10-2) plane
Fig. 4. Dislocation loop-size distributions for 5 MeV Xe20+ ion-irradiated Al2O3 at RT observed under g = (1–104) and g = (3–300).
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JournaloftheEuropeanCeramicSociety39(2019)4307–4312
Fig. 5. HRTEM micrograph in the damaged layer, (a) showing the pyramidal plane dislocation loop and basal plane dislocation loop; (b) Fourier-filtered (0002)
diffraction HRTEM image showing the pyramidal plane dislocation loops, prismatic plane dislocation loops and basal plane dislocation loops; (c) and (d) the
magnified micrograph of the interstitial-type prismatic plane dislocation loop and basal dislocation loop as marked in figure (a) and (b) respectively; (e) and (f) the
signal intensity of the analyzed atoms as indicated by one line across the prismatic plane dislocation loop and basal dislocation loop respectively.
were measured. One can clearly see that the signal intensities are quite
low and signal peaks broadened for some lattice atoms. It indicates that
the lattice atoms of the (1–104) and (1-10-2) planes occur shift under
the formation of the basal dislocation loop and the prism dislocation
loop, respectively.
Ions or neutron irradiation into alumina, irradiation induced the
formation of interstitial dislocation loops with Burgers vectors of
b = 1/3 < 0001 > lying on the (0001) plane and Burgers vectors of
b = 1/3 < 1-100 > plane on the {1–100} planes [7]. With increasing
irradiation, these loops nucleate a shear partial dislocation with a
Burgers vectors of b = 1/3 < 10-11 > lying on both the (0001) and
{1–100} planes. In the present study, the formation of prism dislocation
loops and basal dislocation loops is related to lattice damage and po-
sition. Near the maximum damage layer, only basal dislocation loops
were observed. Xe20+ ion irradiation produces dense Frenkel pairs, and
interstitials are preferential to agglomerate on the basal plane. There-
fore, basal dislocation loops are easy to nucleate in the maximum da-
mage region. However, Xe impurity can reduce the mobility of inter-
Fig. 6. Raman scattering spectra of Al2O3 before and after irradiated with
5 MeV Xe20+ to a fluence of 5 × 1015 cm−2 at RT followed by annealing at
900℃, 1200℃ and 1500℃ for 30 min.
stitials, resulting in the sizes of basal dislocation loops that are too small
to be found. Near the maximum damage region, one can see the basal
dislocation loops with a high density and small sizes as compared to the
case of away the maximum damage region. In the near surface region,
surface acting as a sink for interstitials become significant. In this case,
interstitials are preferential to migrate toward the sample surface,
which can promote the nucleation of prism dislocation loops. In con-
trast to the ion-implanted GaN that the density of basal dislocation
loops is far more than that of prism dislocation loops. It is related to a
huge energy barrier for defect migration in GaN has been predicted by
MD calculations [16], which can explain why it is hard to observe prism
dislocation loops in GaN.
annealed at 1500℃ has been carried out.
Fig. 7 presents the over-viewed micrograph of the Xe-irradiated α-
Al2O3 after 1500℃ annealing. There is an obvious damaged band lo-
cated at depths ranging from 920 nm to about 1800 nm. The defect-
denuded layer in the near surface region was clearly visible. It indicates
dense lattice defects located in the near surface region that acting as a
defect sink were annealed out during annealing at 1500℃. In the da-
maged band, the distributions of lattice defects and cavities are het-
erogeneous. In the middle of the damaged layer corresponding to the
region between the damage peak and the maximum Xe deposition,
isolated long dislocations with over 100 nm length were clearly ob-
served, as shown in Fig. 7(b). In the vicinity of these long dislocations,
no contrast was visible. It indicates that the long dislocations act as sink
for lattice defects, leading to the annihilation of basal dislocation loops.
In general, the binding energy per atom in a cluster increases with
cluster size, so small clusters decompose to form large clusters at ele-
vated temperature [17–21]. It is reasonable to state that basal dis-
location loops would be disappeared, instead of long dislocations with
increasing annealing time. In addition, Fig. 7(d) presents that the many
faceted cavities prefer to grow on the long dislocations, because va-
cancies in the vicinity of long dislocation aggregate easily and lead to
3.2. After annealing
Fig. 6 shows the Raman spectra of 5 MeV Xe20+ ions with the flu-
ence of 5 × 1015/cm2 irradiated α-Al2O3 after annealing at 900℃,
1200℃ and 1500℃ for 30 min. The intensities of Raman scattering
peaks increase, while the background intensity decreases with increase
in the annealing temperature, in particular, for the case of annealing at
1500℃ that the baseline is almost the same with the un-irradiated
sample. It indicates that the lattice defects were significantly annealed
out during annealing at 1500℃. In order to verify this argument, a
detailed TEM analysis of the sample irradiated at this fluence and then
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JournaloftheEuropeanCeramicSociety39(2019)4307–4312
Fig. 7. XTEM bright field micrograph of Al2O3 irradiated with 5 MeV Xe20+ ions to a fluence of 5 × 1015 He+/cm2 at RT followed by annealing at 1500℃ for 30 min.
(a) an over-viewed image of the damage distribution; (b) bright field image and (c) weak beam dark field with g = (-2110) image of the dislocation lines and
dislocation loops in the damaged layer; (d) under-focused view of cavities in the damaged layer; (e) the magnified micrograph showing basal and prism dislocation
loops at the lower boundary of the damaged layer; (f) the magnified micrograph showing the cavity as marked in figure (d). The direction of the sample surface was
noted.
faceted cavity formation due to the different free energies along the
different crystal orientations [22–25]. The HRTEM micrograph presents
the lattice fringes that are heavily disordered and only short-distance
orders are visible on the cavity plane, as shown in Fig. 7(f). It indicates
that the cavity exhibited over-pressurized state due to containing a very
high density of Xe atoms. At the upper boundary of the damaged band,
only basal dislocation loops were observed and some basal dislocation
loops are of ˜ 30 nm in diameter. Furthermore, cavities are smaller with
a higher density in this region than that of the middle of the damaged
band. However, at the lower boundary of the damaged band, very few
of cavities close to the long dislocations were observed. Basal disloca-
tion loops and prism dislocation loops were observed simultaneously.
Some prism dislocation loops are of ˜ 200 nm in diameter, as shown in
Fig. 7(e). It can be seen that some basal dislocation loops attach with
these large prism dislocation loops. Fig. 7(b) and (c) show that a narrow
distribution of basal dislocation loops and a tail distribution of prism
dislocation loops were visible, indicating that interstitials migrate to-
ward deep region and accumulate in the {10-10} planes, but not (0001)
plane during the thermal annealing. It is the same case with the prism
dislocation loops that are easily formed in the near surface region
during Xe20+ ion irradiation at RT. The phenomenon of lattice defects
migration toward deep region has been observed in Si and MgO
[26,27], but not in SiC and ZrO2 [28,29]. It is related to a huge energy
barrier for defect migration in SiC and ZrO2.
4. Conclusions
The damage processes formed in α-Al2O3 under Xe20+ ion irradia-
tion at RT and after thermal annealing were investigated by coupling
the Raman spectroscopy and TEM. The intensities of Raman scattering
decreases with increasing the fluence and no amorphous phase is
formed upon Xe irradiation to 8 dpa. The interstitial-type dislocation
loops with Burgers vectors of b = 1/3 < 10-11 > on the {10-10} and
(0001) habit planes were found. The lattice atoms of the (1–104) and
(1-10-2) planes occur shift under the formation of the basal dislocation
loop and the prism dislocation loop, respectively. Furthermore, the
prism dislocation loops are easily formed in the near surface region and
the basal dislocation loops are easily formed near the damage peak.
After annealing at 1500℃ for 30 min, the recovery of lattice defects
is significant. Prism dislocation loops formed in the near surface region
are completely annealed out. In the damage peak, long dislocations and
large facetted cavities formed on the long dislocations are observed.
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JournaloftheEuropeanCeramicSociety39(2019)4307–4312
Facetted cavities contain a very high density of Xe atoms. Many prism
dislocation loops, but no cavities, migrate toward deep region.
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Acknowledgements
The work was supported by National Nature Science Foundation of
China (Grant Nos.11475229, U1832133) and the Doctor Research
Foundation of Southwest University of Science and Technology (Grant
No. 18zx7141). The authors appreciate the Laboratory of 320 kV High-
voltage Platform in Institute of Modern Physics, CAS for Xenon irra-
diation and Dr. Xu Lijun for TEM observation.
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