Tian et al. Nanoscale Research Letters(2019) 14:269
https://doi.org/10.1186/s11671-019-3103-y

NANO EXPRESS

Open Access

One-Drop Self-Assembly of Ultra-Fine
Second-Order Organic Nonlinear Optical
Crystal Nanowires
Tian Tian1 , Bin Cai1,2*, Qingqing Cheng1, Cheng Fan1, Yanyan Wang1, Gongjie Xu1, Fuxing Gu1, Feng Liao1,
Okihiro Sugihara2, Eiji Hase3 and Takeshi Yasui3

Abstract
In this study, we propose a one-drop self-assembly method, which proved capable of successfully preparing 4-N, Ndimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) single-crystalline nanowires (NWs). The apparent roughnessof the DAST NWs was determined to be less than 100 pm by using a high-resolution atomic force microscope,
indicating their ultrafine quality. The DAST NWs also exhibited excellent nonlinear optical properties, including twophoton excited fluorescence and second harmonic generation, which could enable the production of low-cost,
low-power-consumption wideband wavelength conversion devices. Thus, the described method may provide a
new avenue for organic NW fabrication.
Keywords: Nanowires, DAST, Nonlinear, Self-assembly

Introduction
Second-order organic nonlinear optical (NLO) materials
have ultra-fast electro-optic response times as well asvery large bandwidths and NLO coefficients, andtherefore, have been intensively researched for a wide
range of applications related to electrical/optical signaltransduction, optical switching, phased-array radar,analogue/digital conversion, terahertz signal generation,and digital signal processing [1, 2]. Organic ionic 4-N, Ndimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST)
crystals are recognized as benchmark organic NLO crystals
due to their electro-optic coefficients γ11 = 55 ± 80pm/
V at 1315 nm , high-NLO susceptibilities χ(2)(−2ω, ω, ω) =580 ± 30pm/V at 1535 nm, and low-dielectric constants(5.2, 103–105 kHz) [3, 4] and consequently are researched
intensively [5–9]. However, the applications of DAST crystals are limited due to their deficient quality and the difficulty of fabricating DAST crystal optical waveguides using
the traditional “top-down” approach. Meanwhile, self* Correspondence: bullcai@usst.edu.cn
1
Shanghai Key Lab of Modern Optical System, Ministry of Education,
University of Shanghai for Science and Technology, Shanghai 200093, China
2
Graduate School of Engineering, Utsunomiya University, Utsunomiya
321-8585, Japan
Full list of author information is available at the end of the article

assembly, a bottom-up technique, is becoming a powerful
method for fabricating micro/nanoscale one-dimensional(1D) structures and is promising for the production of miniaturized integrated electronic, optoelectronic, and photonic
devices [10–12]. For organic materials, the self-assembly driving forces can originate from interactions suchas coordination bonding, aromatic π−π stacking,hydrogen bonding, Van der Waals forces, and electrostatic interactions [13–15]. Although many organic
materials have been successfully employed tosynthesize second harmonic generation (SHG) active
1D crystalline nanostructures, their second-order susceptibilities are still far lower than those of organic
NLO crystals with large dipole moments [16]. In thisstudy, we develop an environmentally friendly onedrop self-assembling method for DAST NWs fabrication. We separate crystal seeds preparation andgrowth process by substrate-supported rapid evaporation crystallization (SSREC) [17, 18] and saturated
vapor cultivation respectively. In this way, we caneasily obtain ultra-fine single-crystalline DAST NWs
with good NLO properties.

© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made.

Tian et al. Nanoscale Research Letters(2019) 14:269

Methods
The DAST powder (Daiichi Pure Chem. Co. Ltd.),methanol (99.9%, Surper Dry, with molecular sieves,water ≦ 30 ppm, J&K Seal), and the surfactant (cetyltrimethylammonium bromide, CTAB, TCI) were used directly without further purification.
Preparation

Firstly, 30 mg of DAST powder and 10 mg of the surfactant were dissolved in 5 mL of methanol. Next, 100 μLof this DAST-CTAB methanol solution was diluted with
10 mL of methanol (DAST concentration of approximately 0.146 mM, ) and stirred for 0.5 h to obtain ahomogeneous solution (for more details, see Additional
file 1: Figure S1).
Characterization

The DAST NW morphology was studied using an optical microscope (Imager.A2m, Zeiss), BTEM (Tecnai
G2 SpiritBiotwin), SEM (Nanolab600i, Helios, Quanta200, Fei), and AFM (MultiMode8, Bruker). The UV-Vis
spectra were obtained using a fiber spectrometer (Nova,
Idea Optics). The crystal structure of the NW was examined using XRD (D/Max 2550 V, Rigaku). The two-photon excited fluorescence (TPEF) was excited using a1064 nm cw laser (MIL-III-1064-1W, CNI), the images
were obtained using an optical microscope (DS-RI2,
Nikon), and the emission spectrum was measured using
the fiber spectrometer.
The second harmonic generation (SHG) polarization
dependence of the DAST NCs was measured using ahomemade SHG microscope. A 1250-nm femtosecond
laser (Insight DeepSee, Spectra-Physics) with a wavelength of 1250 nm, the repetition rate of 80 MHz, and apulse width of 130 fs were employed as the light source(for more details, see Additional file 1: Figure S1).

Results and Discussion
A schematic of the one-drop self-assembly method isshown in Fig. 1a. First, the hydrophilic substrate wasplaced on a hot plate and heated to 80 °C. Then, 100 μLof the 0.146 mM DAST-CTAB methanol solution was
dropped onto the heated hydrophilic substrate andheated continuously for 20 s. As the methanol solvent
spread and evaporated, the DAST nano/microcrystals(NC/MCs, orange color) were rapidly deposited on thesubstrate shown in step 1, Fig. 1a. In step 2, the substrate was placed into a culture dish and sealed with approximately 0.1 mL of methanol solvent for the wetcultivation process. After ~ 3 h of cultivation at room
temperature, the DAST NWs (green color) were obtained in step 3. The morphological evolution of the
DAST crystals is shown in Fig. 1b–f. The DAST crystals
as-deposited appear as micro-flakelets with a relatively

Page 2 of 8high density, and no wires can be observable as shownin Fig. 1b. And then after 40 min of cultivation in the atmosphere of saturated methanol vapor pressure, at room
temperature, the shorter DAST rods begin to appear,
shown in Fig. 1c.The slice-shaped crystals are smaller
than the crystals in Fig. 1b. Furthermore, after 2.5 h ofcultivation, some longer DAST crystal wires show up,
see Fig. 1e. The DAST wires have uniform widths generally with several hundred micrometers long; some ofthem could even be longer than 1 mm. There is a microscope image of the DAST wires with the polarizer rotated by 90° in Fig. 1f. The entire tilted wires appear tohave been changed from their maximized anisotropy birefringence (brightest) states to their minimal (extinguished) states. This alteration implies that the single
crystalline structures of the fabricated DAST wires arehighly uniform. Meanwhile, large DAST crystal particles
no longer appear, and instead, small crystal dots are visible. Furthermore, the crystal dot density near the DAST
wires is obviously lower than the density further away.
Thus, we expect that the DAST wire formation
process was as follows. After the SSREC process, small
DAST crystals were deposited on the substrate. Whenthey were put into the methanol atmosphere, the DAST
crystals absorbed the methanol and partially dissolved
into it, resulting in NC/MCs surrounded by a DAST-saturated methanol solution. The self-assembling driven
force could originate from the huge dipole moments of
NC/MCs [19–21]. For instance, an MC with 0.35-micron diameter may have a dipole moment magnitude aslarge as ~ 4.5 x 104 D. Meanwhile, the methanol solution
acts as a lubricant and can facilitate the motion of the
DAST NC/MCs. Due to the electrostatic interaction andthe lubrication provided by the methanol solution, theDAST NC/MCs undergo self-assembly, yielding DAST
NWs. As an evidence, a biology transmission electron
microscope (BTEM) image of an unfinished DAST NW
is shown in Fig. 1d, plenty of NCs gathered in the NW
can be confirmed. As the DAST NWs grow, they continually absorb the nearby DAST solution via the capillary effect. Consequently, as is evident from Fig. 1d, e,
the residual crystal dot density near the wires is lower
than that further away.
An X-ray diffraction (XRD) pattern of DAST NWs ispresented in Fig. 2a. By referring to the crystal cell parameters of bulk DAST crystals (monoclinic Cc spacegroup, point group m, a = 10.365 Å, b = 11.322 Å, α =β = 90°, and γ = 92.24°) [4], the diffractive peaks near 10°,20°, and 30° corresponding to the [002], [004], and [006]
faces of the DAST crystals, respectively. It means thatDAST NWs grown on the substrate have the [001]orientation with the a- and b-axes along the film plane.
The morphologies of the DAST NWs were further studied using an SEM. An SEM image from the [001]Tian et al. Nanoscale Research Letters(2019) 14:269

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Fig. 1 a The schematic of the one-drop self-assembly method. b The fluorescence image of DAST crystal after the SSREC process. c After 40 minof cultivation in a methanol atmosphere. d The BTEM image of unfinished DAST NW. e After 2.5 h of cultivation in a methanol atmosphere. f
After 2.5 h of cultivation in a methanol atmosphere with the cross-polarizer rotated by 90°

perspective is shown in Fig. 2b. Based on the characteristics of bulk DAST crystal growth, the [111], [-111], [1–11], and [110] end faces can be identified easily (seeFig. 2). The single-crystalline DAST NW has a belt-likemorphology, with a typical width of 1.5 ± 0.5 μm andthickness of 0.8 ± 0.4 μm. According to the NW’s crystal
orientation, the alignment of the DAST molecules in the
NW can be depicted as in Fig. 2c, the tosylate anions
have been removed for clarity. For the DAST, bulky
crystal directly grows from saturated DAST solution, thegrowth speed along the crystallographic a-axis is thefastest, in other words, in the [100] direction [22]; however, in the case of self-assembly, the [110] direction haspriority. Thus, there is a different mechanism drive the

NW fabrication. We expect that the NW formation begins with DAST NC/MC self-assembly due to the electrostatic force. For a four-molecule model, the dipole
moments along the a-, b-, and c-axes in a DAST crystal
lattice are 158.2 D, 141.2 D, and 121.0 D, respectively[18]. The growth along the c-axis was limited due to theconfiguration of the present experiment, so the NWs
could only grow along the direction of the vector sum of
the dipole moments of the a- and b-axes. Since the dipole moments along the a- and b-axes are similar, the[110] direction become preferred NW growth direction.
To investigate the internal quality of the DAST
NWs, we used an electron beam to cut an NW,
whose cross-section was shown in Fig. 2d. The whiteTian et al. Nanoscale Research Letters(2019) 14:269

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Fig. 2 a The XRD pattern of DAST NWs. b SEM image of a DAST NW from the [001] perspective, where, based on the typical characteristics ofbulk crystal growth, the [-111], [111], [1-11], and [110] faces can be identified. c DAST molecular alignment in the NW, where the tosylate anions
have been omitted for clarity. d The cross-section of a DAST NW cut by a focused ion beam. e AFM image of a DAST NW. e The surface
roughness of a DAST NW, as determined using an AFM

dots on the NW are silver nanoparticles that were deposited to increase the conductivity of the NW. The
roughness of the cut cross-section is similar to asgrown DAST crystals, and no defect can be detected
at this scale. We further investigated the DAST NWmorphology by using a high-resolution atomic force
microscope (AFM) to obtain the surface information
directly without disturbing the metallic silver nanoparticles. As shown in Fig. 2e, the NW has a clear
belt configuration with the [001] face as the flat top
surface, which is consistent with the SEM results. By
zooming in on the top surface of the DAST NW
using the AFM, we obtained the morphology of a1000 x 1000 nm2 region of the [001] face, which ispresented in Fig. 2f. According to the results, an average roughness of DAST NW is about ~ 85 pm, whichis even smaller than that of a graphene monolayer on
a SiO2 substrate [23]; thus, an ultra-flat DAST NW
crystal was realized. For a low-loss optical waveguide,

its surface roughness must be less than 10 nm. Obviously, our DAST NWs were of much higher quality
than required.
The UV-Vis absorption spectrum of the DAST NWs is
compared with those of the bulk crystal, NC, and solution states in Fig. 3a. Due to the unique 1D conformation of the NW, its absorption spectrum (black line) is
obviously different from those of the other states. In
methanol solution, an absorption peak at ~ 476 nm [8,17] is originated from the π-conjugation system of
DAST cation. Upon crystallization, due to the electronictransition of the π-π conjugated system of the cation,
the absorption band will expand toward hypsochromic
and bathochromic shifts (i.e., blue and red shifts, respectively). The bathochromic shift originates from the
J-aggregation of the chromophore cations along the aaxis of the crystal in a head-to-tail stacking mode, while
the hypsochromic shift originates from the H-aggregation in a face-to-face stacking mode [24, 25]. The NCs

Tian et al. Nanoscale Research Letters(2019) 14:269

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Fig. 3 a Absorption spectra of DAST NWs, NCs, and bulk crystals and fluorescence spectra of DAST NWs and bulk crystals excited by a 407 nm
laser. b Fluorescence images of DAST MCs (top left), a DAST NW (center), and the DAST NW at different polarization angles (bottom). c Opticalsetup for TPEF measurements. d Top view of a DAST NW with 1064 nm laser input. e TPEF image of a DAST NW upon irradiation by the 1064 nm
cw laser. f TPEF spectra of the DAST NW at different input laser intensities, where the inset shows the logarithm of the TPEF intensity as afunction of the logarithm of the input laser intensity

exhibit only a slight expansion in the blue and red directions, as indicated by the red line in Fig. 3a with an absorption peak at ~ 512 nm, which reflects the size
limitations of the two aggregation directions. In the bulk
crystal case, the J- and H-aggregation lengths are significantly expanded, so the bulk crystal spectrum has thebroadest absorption band, which extends from 350 nm
to 750 nm, with an absorption peak at ~ 550 nm, as
shown by the blue line in Fig. 3a.
In contrast, the DAST NWs, due to their well-structured 1D conformation, have an absorption band from~ 380 nm to 600 nm, as indicated by the black line in
Fig. 3a. They exhibit only a slight extension in the red
direction and more significant extension in the blue direction. In other words, the NW growth does notproceed along the a-axis (J-aggregation direction), whichis consistent with the NW morphology results. Owing to
the 1D structure of the NWs, the H-aggregation isgreatly enhanced, causing the NWs to exhibit similar absorption on the blue side. The fluorescence spectrum of
the DAST NWs was also different from bulky DAST
crystals. The spectra of DAST bulk crystals and NWs
are depicted in Fig. 3a in pink and green, respectively.
Since shortening the J-aggregation lengths of chromophores will cause the blue-shifted of the fluorescence
spectrum [26], the DAST NWs have a spectrum more

hypsochromic than that of the bulk crystals. In contrast,
the cut-off wavelength on the short-wavelength side of
the DAST NW spectrum is blue-shifted by ~ 30 nm.
There is a new peak at ~ 730 nm, which may originate
from the Fabre-Perot resonance [27] of the DAST NWs’linear structures. The fluorescence microscopy images inFig. 3b confirm these differences.
DAST crystals with size on the order of micrometers are
depicted in the upper left and appear orange upon irradiation by blue light. However, the DAST NW emits yellowgreen light when irradiating under the same conditions. Besides, the end of the NW is distinctly brighter than its body,which implies that the NW confines light well; in otherwords, the fluorescent light was confined and enhanced bythis waveguide structure [27]. The fluorescence also exhibits very strong polarity, as illustrated at the bottom of
Fig. 3b, which shows polarized microscope images of a single NW rotated at various angles. Clearly, the fluorescenceis altered as the rotation angle changed, which illustrates
that DAST NW has strong polarized property.
We launched a 1064-nm continuous wave (cw) laser
into a DAST NW through a home-made taper fiber toobserve its propagation characteristics. The pump light
was launched using a butt-coupling technique [26] withthe setup illustrated in Fig. 3c. A top view of the propagation is shown in Fig. 3d. Since the DAST NW has ultra-

Tian et al. Nanoscale Research Letters(2019) 14:269

fine crystal quality, there is no distinct scattering from its
side walls. We could not evaluate the propagation loss because it is difficult for the NW’s cut-back to change thepropagation distances. The NW exhibited fluorescenceeven when it was irradiated by the 1064 nm cw laser. A
fluorescent image of the DAST NW is presented in Fig. 3e,
which emits yellow-green light which is very similar towhen irradiated with blue light. We can easily confirm the1064 nm laser propagation path since the NW absorbs thelaser light and emits fluorescence. The 1064 nm laser lightand the fluorescent light are well confined in the NW structure, as evidenced by the fact that the end of the NW isbrighter than its side walls. The fluorescence intensity increases as the laser input increases, as shown in Fig. 3f. The
dependence of the two-photon excited fluorescence (TPEF)
intensity (ITPEF) on the excitation intensity (IExcitation) was
analyzed by taking the logarithm (lg) of each quantity. The
plot of lg IExcitation vs. lg ITPEF appears in the inset of Fig. 3f,
where the slope k of the fitting line is 1.84, near 2, it demonstrates the quadratic of the TPEF dependence on the excitation intensity in this measurement range. Notably, the
TPEF signals were collected from the top of the NW, which
was perpendicular to the light propagation direction. Alongthe propagation direction, the spectrum could be significantly different due to the resonance in the waveguide. The
SHG signal was not observable using this setup for the following reasons: the exciting laser was launched from theend of the NW; the SHG signal collected from the top of awell-confined waveguide structure [26] is weak; the phase ismismatched in an as-grown DAST NW; the strong TPEF

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masked the SHG signal; and the SHG signal was in the
crystal absorption band.
The crystalline features of the DAST NW were further
investigated by performing SHG microscopy; the setup
is shown in Fig. 4a. The SHG responses as functions of
the incident laser polarization angle were collected. The
inset of Fig. 4a presents a typical polar plot, where thered dots indicate the experimental data. The intensitiesof the parallel and vertical SHG components, Ix and Iy,
respectively, can be written as
I 2ω
x ¼ A cos4α þ B cos2α þ C (1)
and
K
I 2ω
y ¼ 2 ð− cos4α þ 1Þ (2)Where α is the angle between the laser polarization andthe long axis of the NW; A, B, and C are parameters related
to the material; and K is a constant merging various parameter [28]. The solid lines in the inset of Fig. 4a represents thetheoretical fits obtained using Eqs. (1) and (2). The observed
SHG response has a two-lobe pattern, indicating that theanisotropy of the SHG is attributable to the intrinsic orientation of the DAST crystal. Since the SHG signal is emitted
laterally from the NW [29], it is difficult to evaluate the second-order susceptibility tensors in the NW for this setup.
A DAST NW SHG image with a field size of 170x170μm is shown in Fig. 4b where the colors represent the
NW orientation angles of the crystals. The DAST NWs
and MCs are distributed throughout the depicted area.
Both the NWs and the crystals emit SHG signals, whichindicate that both have SHG active crystal structuresand similar NLO properties. The SHG signals from theFig. 4 a The SHG microscopy setup, where L is a lens, OL is an objective lens, DM is a dichroic mirror, GM is a galvanometer mirror, P is apolarizer, HWP is a half-wavelength polarizer, QWP is a quarter-wavelength polarizer, BPF is a band-pass filter, and PMT is a photomultiplier tube.
The inset is a typical plot of the SHG intensity of a NW as a function of the incident laser polarization angle, where the red dots indicate theexperimental data, and the solid blue lines represent theoretical fits. b SHG image of DAST NWs and their orientation angles, the field size is 170
x 170 μm

Tian et al. Nanoscale Research Letters(2019) 14:269

NWs are relatively uniform, which indicates the highquality of the NWs.

Conclusions
In this study, we demonstrated a one-drop self-assembling method for the DAST NWs preparation. TheDAST NWs have SHG active crystal structure with verystrong TPEF. The DAST NWs were observed to be single-crystalline, to have few defects, and to be well-faceted with ultra-fine surface roughness of 85 pm, which
is highly beneficial for integrated device fabrication.
Moreover, the method is highly efficient, the material requirement can be lower to microgram level (only 6 μg isneeded in our fabrication process); thus, it is very ecofriendly.

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5.

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7.

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12.

Additional Files
Additional file 1: Figure S1. DAST NWs preparation. (DOC 2375 kb)
Abbreviations
AFM: Atomic force microscope; BTEM: Biology transmission electron
microscope; CTAB: Cetyl trimethyl ammonium bromide; DAST: 4-N, Ndimethylamino-4′-N′-methyl-stilbazolium tosylate; MCs: Microcrystals;
NCs: Nanocrystals; NLO: Nonlinear optical; NWs: Nanowires; SEM: Scanelectron microscope; SHG: Second harmonic generation; SSREC: Substratesupported rapid evaporation crystallization; TPEF: Two-photon excited
fluorescence; XRD: X-ray diffraction
Authors’ Contributions
BC conceived the experiments. TT fabricated the DAST NWs and conducted
the fluorescence observations and XRD experiment. QC and TT performed
the SEM measurements. YW and GX made the AFM measurements. FG, FL,
and TT conducted the TPEF experiment. OS, EH, and TY performed the SHG
experiment. BC wrote the manuscript in collaboration with all of the otherauthors.

13.

14.

15.
16.

17.

18.

Funding
This work was supported by the National Natural Science Foundation ofChina under grant no. 61377111 and NICT International Exchange Program.

19.

Availability of Data and Materials
All the data are fully available without restrictions.

20.

Competing Interests
The authors declare that they have no competing interests.

21.

Author details
1
Shanghai Key Lab of Modern Optical System, Ministry of Education,
University of Shanghai for Science and Technology, Shanghai 200093, China.
2
Graduate School of Engineering, Utsunomiya University, Utsunomiya
321-8585, Japan. 3Department of Mechanical Engineering, University ofTokushima, Tokushima, Japan.

22.
23.
24.

Received: 20 March 2019 Accepted: 25 July 201925.
References
1. Shi YQ, Zhang C, Zhang H, James HB, Larry RD, Bruce HR, William HS (2000)
Low (sub-1-volt) halfwave voltage polymeric electro-optic modulators
achieved by controlling chromophore shape. Science 288:119–122
2. Dalton LR, Sullivan PA, Bale DH (2010) Electric field poled organic electrooptic materials: state of the art and future prospects. Chem Rev 110:25–55
3. Jazbinsek M, Mutter L, Gunter P (2008) Photonic applications with theorganic nonlinear optical crystal DAST. IEEE J Sel Top Quant 14:1298–1311

26.

27.

Marder SR, Perry JW, Yakymyshyn CP (1994) Organic salts with large secondorder optical nonlinearities. Chem Mater 6:1137–1147
Katayama I, Akai R, Bito M, Shimosato H, Miyamoto K, Ito H, Ashida M (2010)
Ultrabroadband Terahertz generation using 4-N, N-dimethylamino-4 ′ -N ′4′-N′-methyl-stilbazoliumtosylate single crystals. Appl Phys Lett 97:021105
Kaino T, Cai B, Takayama K (2002) Fabrication of DAST channel opticalwaveguide. Adv Funct Mater 12:599–603
Fan SZ, Qi F, Notake T, Nawata K, Matsukawa T, Takida Y, Minamide H (2014)
Diffraction-limited real-time Terahertz imaging by optical frequency upconversion in a DAST crystal. Appl Phys Lett 104:101106
Zheng ML, Chen WQ, Fujita K, Duan XM, Kawata S (2010) Dendrimer
adjusted nanocrystals of DAST: organic crystal with enhanced nonlinear
optical properties. Nanoscale 2:913–916
Tonouchi M (2007) Cutting-edge Terahertz technology. Nat Photonics 1:97–
105
Meijer EW, Schenning APHJ (2002) Chemistry: material marriage inelectronics. Nature 419:353–354
Hoeben FJM, Jonkheijm P, Meijer EW, Schenning APHJ (2005) About
supramolecular assemblies of π-conjugated systems. Chem Rev 105:1491–
1546
Yamamoto Y, Fukushima T, Suna Y, Ishii N, Saeki A, Seki S, Tagawa S,
Taniguchi M, Kawai T, Aida T (2006) Photoconductive coaxial nanotubes ofmolecularly connected electron donor and acceptor layers. Science 314:
1761–1764
Zhang XJ, Jie JS, Deng W, Shang QX, Wang JC, Wang H, Chen XF, Zhang
XH (2016) Alignment patterning of ordered small-molecule organic
semiconductor micro-/nanocrystals for device applications. Adv Mater 28:
2475–2503
Zang L, Che Y, Moore JS (2008) One-dimensional Self-assembly of Planar πconjugated molecules: Adaptable building blocks for organic nanodevices.
Accounts Chem Res 411:1596–1608
Koepf M, Cherioux F, Wytko JA, Weiss J (2012) 1D and 3D surface-assisted
self-organization. coordin. Chem Rev 256:2872–2892
Rosenne S, Grinvald E, Shirman E, Neeman L, Dutta S, Bar-Elli O, Ben-Zvi R,
Oksenberg E, Milko P, Kalchenko V, Weissman H, Oron D, Rybtchinski B(2015) Self-assembled organic nanocrystals with strong nonlinear opticalresponse. Nano Lett 15:7232–7237
Tian T, Cai B, Sugihara O (2016) DAST single-nanometer crystal preparation
using a substrate-supported rapid evaporation crystallization method.
Nanoscale 8:18882–18886
Tian T, Cai B, Ye TM, Cheng QQ, Zhan P, Xu GJ, Zhang L, Sugihara O (2017)
One-minute self-assembly of millimetre-long DAST crystalline microbelts via
substrate-supported rapid evaporation crystallization. RSC Adv 7:31691–
31695
Oikawa H, Fujita S, Kasai H, Okada S, Tripathy SK, Nakanishi H (2000)
Electric field-induced orientation of organic microcrystals with large
dipole moment in dispersion liquid. Colloid Surf A-Physicochem Eng
Asp 169:251–258
Chiang HC, Iimori T, Onodera T, Oikawa H, Ohta N (2012) Gigantic electric
dipole moment of organic microcrystals evaluated in dispersion liquid withpolarized electroabsorption spectra. J Phys Chem C 116:8230–8235
Zhang XJ, Zhang XH, Zou ZK, Lee CS, Lee ST (2007) Single-crystal
nanoribbons, nanotubes, and nanowires from intramolecular charge-transferorganic molecules. J Am Chem Soc 129:3527–3532
Ruiz B, Jazbinsek M, Gunter P (2008) Crystal growth of DAST. Cryst Growth
Des 8:4173–4184
Lui CH, Liu L, Mak KF, George WF (2009) Ultraflat graphene. Nature 462:339–341
Macchi R, Cariati E, Marinotto D, Roberto D, Tordin E, Ugo R, Bozio R,
Cozzuol M, Pedron D, Mattei G (2010) Stable SHG from in situ grownoriented nanocrystals of [(E)-N, N-dimethylamino-N'-methylstilbazolium][ptoluenesulfonate] in a PMMA film. J Mater Chem 20:1885–1890
Miniewicz A, Palewska K, Sznitko L, Lipinski J (2011) Single-and two-photon
excited fluorescence in organic nonlinear optical single crystal 3-(1,1dicyanoethenyl)-1-phenyl-4,5-dihydro-1 h-pyrazole. J Phys Chem A 115:
10689–10697
Gu FX, Zhang L, Wu GQ, Zhu YB, Zeng HP (2014) Sub-bandgap transverse
frequency conversion in semiconductor nano-waveguides. Nanoscale 6:
12371–12376
Zhang XL, Feng JS (2013) Spectral engineering by flexible tunings of
optical Tamm states and; Fabry-Perot cavity resonance. Optics Letters
38:4382–4385

Tian et al. Nanoscale Research Letters(2019) 14:269

28. Gusachenko I, Latour G¨e, Claire M, Klein S (2010) Polarization-resolved
second harmonic microscopy in anisotropic thick tissues. Opt Express 18:
19339–19352
29. Liu WW, Wang K, Liu Z, Shen GZ, Lu PX (2013) Laterally emitted surface
second harmonic generation in a single ZnTe nanowire. Nano Lett 13:4224–
4229

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