www.acsami.org

Research Article

Rational Strategy for Space-Conﬁned Seeded Growth of ZnO
Nanowires in Meter-Long Microtubes
Ryoma Kamei, Takuro Hosomi, Eisuke Kanao, Masaki Kanai, Kazuki Nagashima, Tsunaki Takahashi,
Guozhu Zhang, Takao Yasui, Jun Terao, Koji Otsuka, Yoshinobu Baba, Takuya Kubo,
and Takeshi Yanagida*

Downloaded via UNIV OF TOKYO on April 14, 2021 at 08:25:26 (UTC).
See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

Cite This: ACS Appl. Mater. Interfaces 2021, 13, 16812−16819

ACCESS

Metrics & More

Read Onlinesı Supporting Information*

Article Recommendations

ABSTRACT: Seeded crystal growths of nanostructures within
conﬁned spaces oﬀer an interesting approach to design chemical
reaction spaces with tailored inner surface properties. However,such crystal growth within conﬁned spaces tends to be inherently
diﬃcult as the length increases as a result of conﬁnement eﬀects.
Here, we demonstrate a space-conﬁned seeded growth of ZnO
nanowires within meter-long microtubes of 100 μm inner diameterwith the aspect ratio of up to 10 000, which had been unattainable
to previous methods of seeded crystal growths. ZnO nanowires
could be grown via seeded hydrothermal crystal growth for
relatively short microtubes below the length of 40 mm, while any
ZnO nanostructures were not observable at all for longer
microtubes above 60 mm with the aspect ratio of 600. Microstructural and mass spectrometric analysis revealed that a
conventional seed layer formation using zinc acetate is unfeasible within the conﬁned space of long microtubes as a result of theformation of detrimental residual Zn complex compounds. To overcome this space-conﬁned issue, a ﬂow-assisted seed layer
formation is proposed. This ﬂow-assisted method enables growth of spatially uniform ZnO nanowires via removing residualcompounds even for 1 m long microtubes with the aspect ratio of up to 10 000. Finally, the applicably of ZnO-nanowire-decorated
long microtubes for liquid-phase separations was demonstrated.
KEYWORDS: ZnO nanowires, conﬁned space, crystal growth, microtubes, liquid-phase separation, capillary column, hydrothermal method■

INTRODUCTION
Designing inner surface chemical properties of conﬁned spaces
is an important research subject to create novel chemical
events.1−6 Clearly, the inner surface characteristics dominantly
determine the chemical interaction to target molecules withinspaces. Among various surface modiﬁcation methods on innersurfaces of conﬁned spaces, a seeded crystal growth method of
inorganic solid nanostructures oﬀers a unique approach.7−18
This is because inorganic solid surface modiﬁcations arethermally robust, which diﬀers from conventional organic
molecule surface modiﬁcations.7−18 Furthermore, the seeded
crystal growth enables the spatial design of the position ofnanostructures within conﬁned spaces via positioning theseeds, which are hardly attainable to other surface modiﬁcation
methods.8,13 For example, Yin et al. have demonstrated such
space-conﬁned seeded growth of black silver nanostructures forsolar steam generation.19 Yin et al. also reported an interesting
approach using space-conﬁned seeded growth of Cu nanorods
with strong surface plasmon resonance for photothermal
actuation.20 Furthermore, they have extended to shapedeformable space of anisotropic seeded growth of Ag
nanoplates.21 Thus, space-conﬁned seeded growths oﬀer a© 2021 American Chemical Society

versatile tool to design various devices. However, such seeded
crystal growth within conﬁned spaces inherently tends to be
diﬃcult as the aspect ratio of conﬁned spaces increases as aresult of conﬁnement eﬀects.22,23 Because a longer conﬁned
space increases the probability of the interaction between
molecules and inner surfaces (e.g., a longer capillary column ingeneral is preferred for liquid-phase separations),24 developinga rational methodology to enable a seeded crystal growth ofnanostructures within conﬁned spaces is required.
Here, we report a space-conﬁned seeded growth of ZnO
nanowires within meter-long microtubes of 100 μm diameterwith the aspect ratio of up to 10 000. ZnO nanowires weregrown via seeded hydrothermal crystal growth for relatively
short microtubes below the length of 40 mm, while any ZnO
Received: December 23, 2020
Accepted: March 17, 2021
Published: March 30, 2021

16812

https://doi.org/10.1021/acsami.0c22709
ACS Appl. Mater. Interfaces 2021, 13, 16812−16819

ACS Applied Materials & Interfaces

www.acsami.org

Research Article

Figure 1. (a) Schematic of two-step experimental procedures for a seeded crystal growth of hydrothermal ZnO nanowires within a microtube, (b)SEM images of a ZnO-nanowire-decorated microtube when varying the length, and (c) relationship between the microtube length and the ZnO
nanowire density at the center of the microtube.

Figure 2. (a) Schematic of experiments to examine a water solubility of formed ZnO seed layers within a microtube and (b) eﬀect of the microtube
length on EDS spectra (Zn Lα) of inner surfaces of ZnO-decorated microtubes when performing a seed layer formation and a water rinse
treatment.

provides ultralow-pressure analysis, such as in LC. Herein, we
anticipate that the strong intermolecular interactions based on
the ZnO nanowires contribute for the liquid-phase separation.

nanostructures were not observable at all for longer microtubes. Microstructural and mass spectrometric analysis
revealed that a conventional seed layer formation using zincacetate is impossible within the conﬁned space for long
microtubes. To overcome this space-conﬁned issue, a ﬂowassisted seed layer formation is proposed. This ﬂow-assisted
method enables us to grow spatially uniform ZnO nanowires
even for 1 m long microtubes with the aspect ratio of up to
10 000. Finally, we investigated a possibility of using the
nanowire microtubes as a separation medium in liquid
chromatography (LC). In general, particle-packed or monolithic columns are employed in liquid-phase separations.25−28
Open tubular columns can be used only in gas chromatography
and microﬂuidics29,30 because the molecular diﬀusion is notenough in liquid-phase separations. The achievement of aneﬀective liquid-phase separation with an open tubular column■

RESULTS AND DISCUSSION
Figure 1a illustrates the ﬂowchart of a series of experiments toperform a seeded crystal growth of hydrothermal ZnOnanostructures within microtubes (inner diameter of 100μm). This experimental procedure consists of two steps: theﬁrst step is a formation of the ZnO seed layer within amicrotube using zinc acetate, and the second step is aformation of ZnO nanowires on the fabricated seed layers
using zinc nitrate. The other detailed experimental conditions
employed can be seen in the Methods section.31−37 Figure 1b
shows the eﬀect of the microtube length on scanning electron
microscopy (SEM) images of inner surfaces at the center
16813

https://doi.org/10.1021/acsami.0c22709
ACS Appl. Mater. Interfaces 2021, 13, 16812−16819

ACS Applied Materials & Interfaces

www.acsami.org

Research Article

Figure 3. (a) Schematic of experiments to analyze volatile components from microtubes with diﬀerent lengths after the seed layer formation
process, (b) GC−MS data of m/z 60 for the microtube lengths of 20 and 100 mm, and (c) possible reaction scheme within a microtube to explain
the length dependence upon the seed layer formation process.

position of the microtube. The microtube length was varied
from 20 to 120 mm. We estimated the nanowire density fromthe SEM images, as shown in Figure 1c. As clearly seen in theimages and estimated data, ZnO nanowires could be grown via
seeded hydrothermal crystal growth for relatively shortmicrotubes below the length of 40 mm, while any ZnOnanostructures were not observable at all for longer microtubes. The geometrical sizes of fabricated ZnO nanowires are
typically 200−300 nm in diameter and 2−3 μm in height.
Although these data are at the center position of the
microtube, the spatial uniformity of the presence of nanowires(L = 20 and 40 mm) or the absence of nanostructures (L =60−120 mm) was consistently observed for all microtubes.
Thus, these experimental results highlight the limitation of
conventional seeded hydrothermal crystal growth of ZnO
nanowires within long microtubes.
Next, we question what causes the above observed length
limitation of seeded hydrothermal crystal growth of ZnO
nanowires for microtubes. The most plausible mechanism isbased on the conﬁnement eﬀect within microtubes, whichmight alter the chemical reaction pathways during seed layer
formation and/or nanowire formation. First, we examine sucha conﬁnement eﬀect on ZnO seed layer formations using zincacetate (step 1 in Figure 1a). To investigate such an eﬀect, westudy whether the fabricated ZnO seed layer is soluble or not
in water. This is because such water-soluble substances nolonger play a role as seed layers for hydrothermal ZnO
nanowires in aqueous solution of reactants in the hydrothermal
growth. As illustrated in Figure 2a, we examine such an eﬀect
by preforming a rinse with water after ZnO seed layer
formations. Figure 2b shows energy-dispersive X-ray spectroscopy (EDS) data to reveal the presence of zinc compounds
after water rinse treatments when varying the length of
microtubes (20 and 100 mm). Clearly, there is a diﬀerence
between the two samples on the presence of ZnO seed layers.
For the capillary column with the length of 20 mm, thepresence of Zn-related compounds was conﬁrmed. On theother hand, any Zn-related compounds were not observable forthe microtube with the length of 100 mm. Thus, these results
imply that altering a water solubility of zinc-related compounds

consisting of the seed layer is responsible for the observed
experimental trend on the microtube length dependence inpanels b and c of Figure 1.
Although there is a correlation between nanowire formationsin Figure 1 and the seed layer formation process in Figure 2,
we still have no experimental evidence to explain how a seedlayer formation using zinc acetate is altered by increasing the
microtube length. Therefore, we analyze volatile components
from microtubes with diﬀerent lengths after the seed layer
formation process, as illustrated in Figure 3a. Gas chromatography−mass spectrometry (GC−MS) was used for the
analysis. Figure 3b shows the comparison between microtubes
with diﬀerent lengths (20 and 100 mm) on the GC−MS data.
As seen in the chromatogram data, a signiﬁcant peak at 15.2
min was observed (monitored at m/z 60) only for the longer
microtube (100 mm) but not for the shorter microtube (20mm). The mass fragment pattern of the peak reveals that thecompound can be assigned to N-(2-hydroxyethyl)acetamide,
which must be closely related to the inherent diﬀerence
between microtubes with diﬀerent lengths on the seed layer
formation process. On the basis of this observed compound,Figure 3c illustrates a model to explain the plausible diﬀerent
chemical reaction schemes when varying the length of
microtubes. First, a condensation of ethanolamine and acetate
gives N-(2-hydroxyethyl)acetamide, which coordinates with
Zn2+ to yield the water-soluble complex. The complex candehydrate into ZnO and N-(2-hydroxyethyl)acetamide. The
reaction is considered to be reversible. If the microtube is shortenough, the amide is immediately eliminated from the system
as a gas and ZnO is continuously generated according to Le
Chatelier’s principle. On the other hand, in the case of thelonger microtubes (>60 mm), a poor exchange of the outerand inner atmosphere prevents removal of N-(2hydroxyethyl)acetamide. Remaining N-(2-hydroxyethyl)acetamide promotes the backward reaction to the soluble
Zn2+ complex and prevents ZnO growth. Thus, these mass
spectrometric data revealed that a conventional seed layer
formation using zinc acetate is impossible within the conﬁned
space for long microtubes as a result of detrimental residual N16814

https://doi.org/10.1021/acsami.0c22709
ACS Appl. Mater. Interfaces 2021, 13, 16812−16819

ACS Applied Materials & Interfaces

www.acsami.org

Research Article

Figure 4. (a) Schematic of the proposed ﬂow-assisted method to enhance a seed layer formation process for longer microtubes, (b) eﬀect of the
ﬂow-assisted method on nanowire density data at the center of the microtube, which is extracted from SEM images, (c) optical image of the 1 m
microtube, where ZnO nanowires are uniformly grown, and SEM images of the inner surface at the marked positions (A, B, and C) of the 1 m
microtube with the inner diameter of 100 μm, (d) measured data of the nanowire length at various positions in the capillary column, and (e)measured data of the nanowire diameter at various positions in the capillary column.

Supporting Information). Thus, the newly proposed ﬂowassisted method enables one to overcome the limitation ofseeded crystal growth of hydrothermal ZnO nanowires insidehighly conﬁned long microtubes with high aspect ratios.
Finally, we examine the applicability of fabricated long
microtubes with ZnO nanowires uniformly grown on the innersurface for liquid-phase separations, as illustrated in Figure 5a.
We prepared microtubes with ZnO nanowires on the insidewall (L = 130 and 300 mm) and compared the retention
behavior of aromatic compounds to a bare microtube having
functional groups and −SiOH based on the fused silica by
nanoﬂow liquid chromatography (nano-LC) system, separately(Figure 5a). Signiﬁcant diﬀerences in the retention behavior ofeach solute on the nanowire array column were conﬁrmed,
although not on the bare microtube. This result clearly
indicated that the heteroatoms in the solutes reversiblyinteracted with ZnO nanowires. In particular, the longer
microtube (L = 300 mm) retained the solutes more stronger
than the shorter microtube (L = 130 mm), and more clear
diﬀerences in the retention time of each solute were conﬁrmed.
The molecular retention behaviors are maintained in repeatedexperiments (Table S1 of the Supporting Information) without
signiﬁcant changes in their nanowire morphologies (Figure S2of the Supporting Information). These strong retentions on thelonger microtube were achieved as a result of the increase of(2-hydroxyethyl)acetamide and resultant Zn complex compounds.
Next, we propose a rational strategy to overcome the above
limitation of conventional seeded crystal growth of ZnO
nanowires for long microtubes. On the basis of the above
reaction schemes within conﬁned spaces, it is necessary to
remove the detrimental residual product N-(2-hydroxyethyl)acetamide during the ZnO seed layer formation process. Thus,
we apply the air ﬂow process to remove the compounds, wherea small amount of air is introduced a few times into themicrotube during the heating process for ZnO seed layer
formation, as illustrated in Figure 4a. Figure 4b shows the SEM
images of inner surfaces at the center position of the column
when varying the length of microtubes from 20 to 1000 mm by
performing the above ﬂow-assisted seed layer formation
process. The nanowire density data extracted from the SEM
images are shown in Figure 4c. As clearly seen in the images,
this newly proposed ﬂow-assisted method enables us to growspatially uniform ZnO nanowires even for longer microtubes(up to 1000 mm) with the aspect ratio of up to 10 000, as
shown in SEM images of Figure 4c. Both the diameter andlength of the nanowires are relatively uniform throughout the
microtubes (panels d and e of Figure 4). It should also be
noted that an appropriate concentration of Zn(NO3)2 is
important for the uniform ZnO growth (Figure S1 of the16815

https://doi.org/10.1021/acsami.0c22709
ACS Appl. Mater. Interfaces 2021, 13, 16812−16819

ACS Applied Materials & Interfaces

www.acsami.org

Research Article

Figure 5. (a) Chromatograms of sample solutes in each microtube. Green plots show acetophenone; blue plots show benzyl alcohol; and red plotsshow benzyl amine. A comparison of the retention time in each microtube is also shown when varying the microtube length. Conditions:microtube, without nanowires (300 mm × 100 μm inner diameter) and with nanowires (125 mm × 100 μm and 300 mm × 100 μm innerdiameter); ﬂow rate, 5.0 μL min−1; mobile phase, n-hexane; ultraviolet (UV) detection, 254 nm; and temperature, 25.0 °C. (b) Comparison
between the ZnO nanowire microtubes and conventional monolithic columns on the retention time. (c) Comparison between the ZnO nanowire
microtube, bare microtube, and monolithic capillary column on the internal pressures required for experiments.

provide separation media with high eﬃciency and low backpressures for LC.

the chance of interactions with ZnO nanowires in proportion
to the microtube length. Furthermore, we compared theretention behavior to a typical silica-based monolithic column(monolith column). Monolithic columns are generally used in
LC for a high-throughput separation as a result of the threedimensional skeleton with micrometer-sized throughpores.44,45 We anticipated that the polar interactions should
be worked between surface −SiOH and polar functionalgroups in the solutes. Interestingly, the order of elution wascompletely diﬀerent between the monolith column and the
ZnO-nanowire-decorated microtube (Figure 5b). To be more
precise, the order of elution was acetophenone, benzyl alcohol,and benzyl amine on the nanowire column, while the order of
elution was benzyl amine, acetophenone, and benzyl alcoholon the monolith column. This result clearly indicated thatthese microtubes possess completely diﬀerent separation
mechanisms. Although precisely describing such diﬀerent
separation mechanisms on the order of elution is diﬃcult,the preferential hydrogen bond for the silica monolith column
may more strongly interact with more strongly polarizedalcohols rather than others, while the Lewis acidity of the Znsite on the m plane of ZnO nanowires might enhance theinteraction to the amine group. Furthermore, it is noted that
the ZnO nanowire microtube shows less than one-tenth of theback pressure of the monolith column under the same ﬂow rate
conditions, which is almost the same as that of the baremicrotube (Figure 5c). Brieﬂy, a high-speed separation in thehigh ﬂow rate range could be carried out on nanowire
microtubes and not on silica monolithic columns. This
extremely lower back pressure was due to the lower packing
rate of the stationary phase in nanowire microtubes than inmonolithic columns. The open tubular column with ultrathinlayered ZnO nanowires eﬀectively contributed in liquid-phaseseparations. Thus, the fabricated ZnO-nanowire-decorated
microtubes by the ﬂow-assisted method have the potential to■

CONCLUSION
We report a space-conﬁned seeded growth of ZnO nanowires
within a 1 m long microtube of 100 μm diameter with the
aspect ratio of up to 10 000. ZnO nanowires were grown via
seeded hydrothermal crystal growth for relatively shortmicrotubes below the length of 40 mm, while any ZnOnanostructures were not observable at all for long microtubes
above the aspect ratio of 600. Microstructural and mass
spectrometric analysis revealed that a conventional seed layer
formation using zinc acetate is impossible within the conﬁned
space for long microtubes. To overcome this space-conﬁned
issue, a ﬂow-assisted seed layer formation is proposed. This
ﬂow-assisted method enables the growth of spatially uniform
ZnO nanowires even for a 1 m long microtube with the aspectratio of up to 10 000. Finally, the applicably of ZnO-nanowiredecorated long microtubes was demonstrated for liquid-phaseseparations.

■

METHODS

Preparation of ZnO-Nanowire-Decorated Microtubes andTheir Characterizations. ZnO-nanowire-decorated microtubes inthis study were fabricated via a seed-assisted hydrothermal method,which consisted of two steps, including a seed layer formation37 and ananowire formation.28−34 The ﬁrst seed layer formation process was
performed using zinc acetate Zn(OAc)2 in ethanolamine/EtOH
solution. The seed solution was injected into a ﬂexible fused silica
capillary column with the inner diameter of 100 μm and the outer
diameter of 375 μm (Molex 1068150023). Then, the column was
annealed at 150 °C for 1 h to crystallize the ZnO seed layer. After thisseed layer formation process, the ZnO nanowire formation process
was performed.31−43 The growth solution was prepared at room
temperature by dissolving in deionized (DI) water zinc nitratehexahydrate Zn(NO3)2·6H2O (99.0% pure, Wako), hexamethylene16816

https://doi.org/10.1021/acsami.0c22709
ACS Appl. Mater. Interfaces 2021, 13, 16812−16819

ACS Applied Materials & Interfaces

www.acsami.org

tetramine (HMTA) (CH2)6N4 (99.0% pure, Wako), and polyethylenimine (PEI) [−CH2CH2NH−]n with an average molecularweight of 1800 (50 wt % in H2O, Aldrich); the ratio of Zn(NO3)2/
HMTA/PEI = 1:1:0.1. Zn(NO3)2 is 25 mM; HMTA is 25 mM; andPEI is 2.5 mM.46 The pH value of the solution was measured before
nanowire growth. A growth temperature of 75 °C was maintained
during the whole growth process for 5 h. The morphology of the ZnOnanostructures within microtubes was characterized by ﬁeld emission
scanning electron microscopy with energy-dispersive X-ray spectroscopy (FESEM−EDS, JEOL JSM-7610F, 30 kV). The length data ofnanowires were estimated from the cross-sectional SEM images. The
desorbed gas species from columns were analyzed by GC−MS (GCMS-QP 2020, Shimadzu, Japan) with an OPTIC-4 inlet temperature
control system.
Preparation of a Monolithic Column. The monolithic column
was prepared following the protocols in the previous report.47−49 Abare capillary column (2−3 m in length) was treated with a 1.0 M
aqueous sodium hydroxide solution at 40 °C for 3 h. Then, thecolumn was washed with water and acetone and then dried.
Tetramethyl orthosilicate (TMOS, 56 mL) was added to a solutionof polyethylene glycol (PEG, 11.9 g) and urea (9.0 g) in 0.01 M acetic
acid (100 mL), and the mixture was stirred at 0 °C for 30 min. The
column was ﬁlled with the resultant homogeneous solution and stoodstill at 30 °C overnight for the reaction. Then, the temperature wasincreased, and the prepared monolithic column was treated at 120 °C
for 3 h to form mesopores with ammonia generated by the hydrolysis
of urea, followed by rinsing with water and methanol. After drying, aheat treatment was carried out at 330 °C for 25 h, resulting in thedecomposition of the organic moieties inside the column.
Nano-LC Analysis. The samples were analyzed with nano-LC.
The nano-LC system consisted of LC-Mikros (Shimadzu, Kyoto,
Japan) as a pump, MU701 (GL Sciences, Tokyo, Japan) as an UV
detector, CHEMINERT (Valco Instruments, Houston, TX, U.S.A.) asa sample injector, and CTO-20AC (Shimadzu, Kyoto, Japan) as acolumn oven. The mobile phase was n-hexane. n-Hexane waspurchased from Nacalai Tesque (Kyoto, Japan). Acetophenone,
benzyl alcohol, and benzyl amine were purchased Tokyo Chemical
Industry (Tokyo, Japan).

■Tokyo 113-8654, Japan; Precursory Research for Embryonic
Science and Technology (PRESTO), Japan Science andTechnology Agency (JST), Kawaguchi, Saitama 332-0012,
Japan; orcid.org/0000-0002-5649-6696
Eisuke Kanao − Graduate School of Pharmaceutical Sciences,
Kyoto University, Kyoto 606-8501, Japan; National
Institutes of Biomedical Innovation, Health and Nutrition,
Ibaraki, Osaka 567-0085, Japan
Masaki Kanai − Department of Applied Chemistry, Graduate
School of Engineering, The University of Tokyo, Tokyo 1138654, Japan; Institute for Materials Chemistry andEngineering, Kyushu University, Kasuga, Fukuoka 816-8580,
Japan
Kazuki Nagashima − Department of Applied Chemistry,
Graduate School of Engineering, The University of Tokyo,
Tokyo 113-8654, Japan; Precursory Research for Embryonic
Science and Technology (PRESTO), Japan Science andTechnology Agency (JST), Kawaguchi, Saitama 332-0012,
Japan; orcid.org/0000-0003-0180-816X
Tsunaki Takahashi − Department of Applied Chemistry,
Graduate School of Engineering, The University of Tokyo,
Tokyo 113-8654, Japan; Precursory Research for Embryonic
Science and Technology (PRESTO), Japan Science andTechnology Agency (JST), Kawaguchi, Saitama 332-0012,
Japan; orcid.org/0000-0002-2840-8038
Guozhu Zhang − Department of Applied Chemistry, Graduate
School of Engineering, The University of Tokyo, Tokyo 1138654, Japan
Takao Yasui − Precursory Research for Embryonic Science andTechnology (PRESTO), Japan Science and Technology
Agency (JST), Kawaguchi, Saitama 332-0012, Japan;
Graduate School of Engineering, Nagoya University, Nagoya
464-8603, Japan; orcid.org/0000-0003-0333-3559
Jun Terao − Department of Basic Science, Graduate School of
Art and Sciences, The University of Tokyo, Tokyo 153-8902,
Japan; orcid.org/0000-0003-1867-791X
Koji Otsuka − Graduate School of Engineering, Kyoto
University, Kyoto 615-8510, Japan; orcid.org/00000003-1088-0569
Yoshinobu Baba − Graduate School of Engineering, Nagoya
University, Nagoya 464-8603, Japan
Takuya Kubo − Graduate School of Engineering, Kyoto
University, Kyoto 615-8510, Japan; orcid.org/00000002-9274-3295

ASSOCIATED CONTENT

sı Supporting Information*

The Supporting Information is available free of charge athttps://pubs.acs.org/doi/10.1021/acsami.0c22709.

■

Research Article

Results of Zn2+-concentration-dependent growth experiments (Figure S1), repeatability of the nanowire arraytube as chromatography columns (Table S1), andchemical corrosion test of the ZnO nanowire arraywith a chromatography condition (Figure S2) (PDF)

Complete contact information is available at:https://pubs.acs.org/10.1021/acsami.0c22709

AUTHOR INFORMATION

Notes

Corresponding Author

Takeshi Yanagida − Department of Applied Chemistry,
Graduate School of Engineering, The University of Tokyo,
Tokyo 113-8654, Japan; Institute for Materials Chemistry
and Engineering, Kyushu University, Kasuga, Fukuoka 8168580, Japan; orcid.org/0000-0003-4837-5701;
Email: yanagida@g.ecc.u-tokyo.ac.jp

The authors declare no competing ﬁnancial interest.

■

ACKNOWLEDGMENTS
This work was supported by Grants-in-Aid for ScientiﬁcResearch (KAKENHI; Grants JP17H04927, JP18H01831,
JP18H05243, and JP18KK0112) PRESTO, JST, Japan(Grant JPMJPR19T8), Core Research for Evolutional Scienceand Technology (CREST), JST, Japan (Grant
JPJSBP120187207) and JST Mirai R&D, and Chinese
Academy of Sciences (CAS)−Japan Society for the Promotionof Science (JSPS) Joint Research Projects(JPJSBP120187207). This work was performed under the
Cooperative Research Program of “Network Joint ResearchCenter for Materials and Devices”, “Dynamic Alliance for

Authors

Ryoma Kamei − Department of Applied Chemistry, Graduate
School of Engineering, The University of Tokyo, Tokyo 1138654, Japan; Institute for Materials Chemistry andEngineering, Kyushu University, Kasuga, Fukuoka 816-8580,
Japan
Takuro Hosomi − Department of Applied Chemistry,
Graduate School of Engineering, The University of Tokyo,
16817

https://doi.org/10.1021/acsami.0c22709
ACS Appl. Mater. Interfaces 2021, 13, 16812−16819

ACS Applied Materials & Interfaces

www.acsami.org

Open Innovation Bridging Human, Environment and Materials”, and the MEXT Project of “Integrated ResearchConsortium on Chemical Sciences”.

(18) Zhao, D.; Wu, Z.; Yu, J.; Wang, H.; Li, Y.; Duan, Y. Highly
Sensitive Microfluidic Detection of Carcinoembryonic Antigen via a
Synergetic Fluorescence Enhancement Strategy Based on the Micro/
Nanostructure Optimization of ZnO Nanorod Arrays and In Situ ZIF8 Coating. Chem. Eng. J. 2020, 383, 123230.
(19) Chen, J.; Feng, J.; Li, Z.; Xu, P.; Wang, X.; Yin, W.; Wang, M.;
Ge, X.; Yin, Y. Space-Confined Seeded Growth of Black Silver
Nanostructures for Solar Steam Generation. Nano Lett. 2019, 19,
400−407.
(20) Chen, J.; Feng, J.; Yang, F.; Aleisa, R.; Zhang, Q.; Yin, Y. SpaceConfined Seeded Growth of Cu Nanorods with Strong Surface
Plasmon Resonance for Photothermal Actuation. Angew. Chem., Int.
Ed. 2019, 58, 9275−9281.
(21) Chen, J.; Bai, Y.; Feng, J.; Yang, F.; Xu, P.; Wang, Z.; Zhang,Q.; Yin, Y. Anisotropic Seeded Growth of Ag Nanoplates Confined in
Shape-Deformable Spaces. Angew. Chem., Int. Ed. 2021, 60, 4117−
4124.
(22) Mouarrawis, V.; Plessius, R.; van der Vlugt, J. I.; Reek, J. N. H.
Confinement Effects in Catalysis Using Well-Defined Materials andCages. Front. Chem. 2018, 6, 623.
(23) Wu, S. M.; Yang, X. Y.; Janiak, C. Confinement Effects in
Zeolite-Confined Noble Metals. Angew. Chem., Int. Ed. 2019, 58,
12340−12354.
(24) Lam, S. C.; Sanz Rodriguez, E.; Haddad, P. R.; Paull, B. Recent
Advances in Open Tubular Capillary Liquid Chromatography. Analyst
2019, 144, 3464−3482.
(25) Tranchida, P. Q.; Mondello, L. Current-day Employment of theMicro-Bore Open-Tubular Capillary Column in the Gas Chromatography Field. J. Chromatogr. A 2012, 1261, 23−36.
(26) Lee, J.; Lim, S. H. Development of Open-Tubular-Type Micro
Gas Chromatography Column with Bump Structures. Sensors 2019,19, 3706.
(27) Li, M. W. H.; She, J. Y.; Zhu, H. B.; Li, Z. Q.; Fan, X. D.
Microfabricated Porous Layer Open Tubular (PLOT) Column. Lab
Chip 2019, 19, 3979−3987.
(28) Galietti, M. R.; Peulon-Agasse, V.; Cardinael, P.; Fogwill, M.
O.; Besner, S.; Gritti, F. G. Turbulent Supercritical Fluid
Chromatography in Open-Tubular Columns for High-Throughput
Separations. Anal. Chem. 2020, 92, 7409−7412.
(29) Jandera, P.; Hajek, T.; Stankova, M. Monolithic and Core-Shell
Columns in Comprehensive Two-Dimensional HPLC: A Review.
Anal. Bioanal. Chem. 2015, 407, 139−151.
(30) Ma, S. J.; Li, Y.; Ma, C.; Wang, Y.; Ou, J. J.; Ye, M. L.
Challenges and Advances in the Fabrication of Monolithic Bioseparation Materials and their Applications in Proteomics Research.
Adv. Mater. 2019, 31, 1902023.
(31) He, Y.; Yanagida, T.; Nagashima, K.; Zhuge, F. W.; Meng, G.;
Xu, B.; Klamchuen, A.; Rahong, S.; Kanai, M.; Li, X.; Suzuki, M.; Kai,S.; Kawai, T. Crystal-Plane Dependence of Critical Concentration for
Nucleation on Hydrothermal ZnO Nanowires. J. Phys. Chem. C 2013,
117, 1197−1203.
(32) Nakamura, K.; Takahashi, T.; Kanai, M.; Zhang, G.; Hosomi,T.; Seki, T.; Nagashima, K.; Shibata, N.; Yanagida, T. Redox-Inactive
CO2 Determines Atmospheric Stability of Electrical Properties of
ZnO Nanowire Devices through Room-Temperature Surface
Reaction. ACS Appl. Mater. Interfaces 2019, 11, 40260−40266.
(33) Sakai, D.; Nagashima, K.; Yoshida, H.; Kanai, M.; He, Y.;
Zhang, G.; Zhao, X.; Takahashi, T.; Yasui, T.; Hosomi, T.; Uchida, Y.;
Takeda, S.; Baba, Y.; Yanagida, T. Substantial Narrowing on the
Width of “Concentration Window” of Hydrothermal ZnO Nanowires
via Ammonia Addition. Sci. Rep. 2019, 9, 14160.
(34) Wang, C.; Hosomi, T.; Nagashima, K.; Takahashi, T.; Zhang,G.; Kanai, M.; Zeng, H.; Mizukami, W.; Shioya, N.; Shimoaka, T.;
Tamaoka, T.; Yoshida, H.; Takeda, S.; Yasui, T.; Baba, Y.; Aoki, Y.;
Terao, J.; Hasegawa, T.; Yanagida, T. Rational Method of Monitoring
Molecular Transformations on Metal-Oxide Nanowire Surfaces. Nano
Lett. 2019, 19, 2443−2449.
(35) Wang, C.; Hosomi, T.; Nagashima, K.; Takahashi, T.; Zhang,G.; Kanai, M.; Yoshida, H.; Yanagida, T. Phosphonic Acid Modified■

REFERENCES(1) Daiguji, H.; Yang, P.; Majumdar, A. Ion Transport in
Nanofluidic Channels. Nano Lett. 2004, 4, 137−142.
(2) Green, Y.; Eshel, R.; Park, S.; Yossifon, G. Interplay between
Nanochannel and Microchannel Resistances. Nano Lett. 2016, 16,2744−2748.
(3) Wang, M.; Cheng, B.; Yang, Y.; Liu, H.; Huang, G.; Han, L.; Li,
F.; Xu, F. Microchannel Stiffness and Confinement Jointly Induce theMesenchymal-Amoeboid Transition of Cancer Cell Migration. Nano
Lett. 2019, 19, 5949−5958.
(4) Ostler, D.; Kannam, S. K.; Frascoli, F.; Daivis, P. J.; Todd, B. D.
Efficiency of Electropumping in Nanochannels. Nano Lett. 2020, 20,
3396−3402.
(5) Kitao, T.; Nagasaka, Y.; Karasawa, M.; Eguchi, T.; Kimizuka, N.;
Ishii, K.; Yamada, T.; Uemura, T. Transcription of Chirality from
Metal-Organic Framework to Polythiophene. J. Am. Chem. Soc. 2019,
141, 19565−19569.
(6) Daiguji, H. Ion Transport in Nanofluidic Channels. Chem. Soc.
Rev. 2010, 39, 901−911.
(7) Hu, W.; Lu, Z.; Liu, Y.; Chen, T.; Zhou, X.; Li, C. M. A Portable
Flow-through Fluorescent Immunoassay Lab-on-a-Chip Device using
ZnO Nanorod-Decorated Glass Capillaries. Lab Chip 2013, 13,
1797−1802.
(8) Yasui, T.; Rahong, S.; Motoyama, K.; Yanagida, T.; Wu, Q.; Kaji,N.; Kanai, M.; Doi, K.; Nagashima, K.; Tokeshi, M.; Taniguchi, M.;
Kawano, S.; Kawai, T.; Baba, Y. DNA Manipulation and Separation in
Sublithographic-Scale Nanowire Array. ACS Nano 2013, 7, 3029−
3035.
(9) Rahong, S.; Yasui, T.; Yanagida, T.; Nagashima, K.; Kanai, M.;
Klamchuen, A.; Meng, G.; He, Y.; Zhuge, F. W.; Kaji, N.; Kawai, T.;
Baba, Y. Ultrafast and Wide Range Analysis of DNA Molecules Using
Rigid Network Structure of Solid Nanowires. Sci. Rep. 2015, 4, 5252.
(10) Wang, G.; Shi, G.; Wang, H.; Zhang, Q.; Li, Y. In Situ
Functionalization of Stable 3D Nest-Like Networks in Confined
Channels for Microfluidic Enrichment and Detection. Adv. Funct.
Mater. 2014, 24, 1017−1026.
(11) Hu, W.; Liu, Y.; Chen, T.; Liu, Y.; Li, C. M. Hybrid ZnONanorod-Polymer Brush Hierarchically Nanostructured Substrate for
Sensitive Antibody Microarrays. Adv. Mater. 2015, 27, 181−185.
(12) Rahong, S.; Yasui, T.; Yanagida, T.; Nagashima, K.; Kanai, M.;
Meng, G.; He, Y.; Zhuge, F. W.; Kaji, N.; Kawai, T.; Baba, Y. ThreeDimensional Nanowire Structures for Ultra-Fast Separation of DNA,
Protein and RNA Molecules. Sci. Rep. 2015, 5, 10584.
(13) Wang, G.; Li, K.; Purcell, F.; Zhao, D.; Zhang, W.; He, Z.; Tan,
S.; Tang, Z.; Wang, H.; Reichmanis, E. Three-Dimensional Clustered
Nanostructures for Microfluidic Surface-Enhanced Raman Detection.
ACS Appl. Mater. Interfaces 2016, 8, 24974−24981.
(14) Yasui, T.; Yanagida, T.; Ito, S.; Konakade, Y.; Takeshita, D.;
Naganawa, T.; Nagashima, K.; Shimada, T.; Kaji, N.; Nakamura, Y.;
Thiodorus, I. A.; He, Y.; Rahong, S.; Kanai, M.; Yukawa, H.; Ochiya,T.; Kawai, T.; Baba, Y. Unveiling Massive Numbers of Cancer-Related
Urinary-Micro RNA Candidates via Nanowires. Sci. Adv. 2017, 3,
No. e1701133.
(15) Wu, Z.; Zhao, D.; Hou, C.; Liu, L.; Chen, J.; Huang, H.; Zhang,Q.; Duan, Y.; Li, Y.; Wang, H. Enhanced Immunofluorescence
Detection of a Protein Marker using a PAA Modified ZnO Nanorod
Array-Based Microfluidic Device. Nanoscale 2018, 10, 17663−17670.
(16) Guo, L.; Shi, Y.; Liu, X.; Han, Z.; Zhao, Z.; Chen, Y.; Xie, W.;
Li, X. Enhanced Fluorescence Detection of Proteins using ZnONanowires Integrated Inside Microfluidic Chips. Biosens. Bioelectron.
2018, 99, 368−374.
(17) Luo, H.; Leprince-Wang, Y.; Jing, G. Tunable Growth of ZnO
Nanostructures on the Inner Wall of Capillary Tubes. J. Phys. Chem. C
2019, 123, 7408−7415.
16818

Research Article

https://doi.org/10.1021/acsami.0c22709
ACS Appl. Mater. Interfaces 2021, 13, 16812−16819

ACS Applied Materials & Interfaces■

www.acsami.org

ZnO Nanowire Sensors: Directing Reaction Pathway of Volatile
Carbonyl Compounds. ACS Appl. Mater. Interfaces 2020, 12, 44265−
44272.
(36) Zhao, X.; Nagashima, K.; Zhang, G.; Hosomi, T.; Yoshida, H.;
Akihiro, Y.; Kanai, M.; Mizukami, W.; Zhu, Z.; Takahashi, T.; Suzuki,
M.; Samransuksamer, B.; Meng, G.; Yasui, T.; Aoki, Y.; Baba, Y.;
Yanagida, T. Synthesis of Monodispersedly Sized ZnO Nanowires
from Randomly Sized Seeds. Nano Lett. 2020, 20, 599−605.
(37) Liu, J.; Nagashima, K.; Yamashita, H.; Mizukami, W.; Uzuhashi,J.; Hosomi, T.; Kanai, M.; Zhao, X.; Miura, Y.; Zhang, G.; Takahashi,T.; Suzuki, M.; Sakai, D.; Samransuksamer, B.; He, Y.; Ohkubo, T.;
Yasui, T.; Aoki, Y.; Ho, J. C.; Baba, Y.; Yanagida, T. Face-Selective
Tungstate Ions Drive Zinc Oxide Nanowire Growth Direction andDopant Incorporation. Commu. Mater. 2020, 1, 58.
(38) Zeng, H.; Takahashi, T.; Zhang, G.; Hosomi, T.; Kanai, M.;
Seki, T.; Nagashima, K.; Shibata, N.; Yanagida, T. Oxygen-Induced
Reversible Sn-dopant Deactivation between Indium Tin Oxide andSingle-Crystalline Oxide Nanowire Leading to Interfacial Switching.
ACS Appl. Mater. Interfaces 2020, 12, 52929−52936.
(39) Liu, Q.; Yasui, T.; Nagashima, K.; Yanagida, T.; Hara, M.;
Horiuchi, M.; Zhu, Z.; Takahashi, H.; Shimada, T.; Arima, A.; Baba,
Y. Ammonia-induced Seed Layer Transformations in A Hydrothermal
Growth Process of Zinc Oxide Nanowires. J. Phys. Chem. C 2020, 124,
20563−20568.
(40) Akihiro, Y.; Nagashima, K.; Hosomi, T.; Kanai, M.; Anzai, H.;
Takahashi, T.; Zhang, G.; Yasui, T.; Baba, Y.; Yanagida, T. WaterOrganic Cosolvent Effect on Nucleation of Solution-Synthesized ZnO
Nanowires. ACS Omega 2019, 4, 8299−8304.
(41) Koga, H.; Nagashima, K.; Huang, Y.; Zhang, G.; Wang, C.;
Takahashi, T.; Inoue, A.; Yan, H.; Kanai, M.; He, Y.; Uetani, K.; Nogi,
M.; Yanagida, T. Paper-Based Disposable Molecular Sensor
Constructed from Oxide Nanowires, Cellulose Nanofibers, andPencil-Drawn Electrodes. ACS Appl. Mater. Interfaces 2019, 11,15044−15050.
(42) Zeng, H.; Zhang, G.; Nagashima, K.; Takahashi, T.; Hosomi,T.; Yanagida, T. Metal−Oxide Nanowire Molecular Sensors andTheir Promises. Chemosensors 2021, 9, 41.
(43) Musa, M.; Yasui, T.; Nagashima, K.; Horiuchi, M.; Zhu, Z.; Liu,
Q.; Shimada, T.; Arima, A.; Yanagida, T.; Baba, Y. ZnO/SiO2 Core/
Shell Nanowires for Capturing CpG Rich Single-Stranded DNAs.
Anal. Methods 2021, 13, 337−344.
(44) Motokawa, M.; Kobayashi, H.; Ishizuka, N.; Minakuchi, H.;
Nakanishi, K.; Jinnai, H.; Hosoya, K.; Ikegami, T.; Tanaka, N.
Monolithic Silica Columns with Various Skeleton Sizes and ThroughPore Sizes for Capillary Liquid Chromatography. J. Chromatogr. A
2002, 961, 53−63.
(45) Tanaka, N.; Kobayashi, H.; Nakanishi, K.; Minakuchi, H.;
Ishizuka, N. Peer Reviewed: Monolithic LC Columns. Anal. Chem.
2001, 73, 420 A−429 A.
(46) Greene, L. E.; Law, M.; Tan, D. H.; Montano, M.; Goldberger,
J.; Somorjai, G.; Yang, P. General Route to Vertical ZnO Nanowire
Arrays Using Textured ZnO Seeds. Nano Lett. 2005, 5, 1231−1236.
(47) Kubo, T.; Murakami, Y.; Tsuzuki, M.; Kobayashi, H.; Naito, T.;
Sano, T.; Yan, M.; Otsuka, K. Unique Separation Behavior of a C60
Fullerene-Bonded Silica Monolith Prepared by an Effective Thermal
Coupling Agent. Chem. - Eur. J. 2015, 21, 18095−18098.
(48) Kanao, E.; Kubo, T.; Naito, T.; Sano, T.; Yan, M.; Tanaka, N.;
Otsuka, K. Tunable Liquid Chromatographic Separation of H/DIsotopologues Enabled by Aromatic π Interactions. Anal. Chem. 2020,
92, 4065−4072.
(49) Kanao, E.; Morinaga, T.; Kubo, T.; Naito, T.; Matsumoto, T.;
Sano, T.; Maki, H.; Yan, M.; Otsuka, K. Separation of HalogenatedBenzenes Enabled by Investigation of Halogen−π Interactions with
Carbon Materials. Chem. Sci. 2020, 11, 409−418.

Research Article

NOTE ADDED AFTER ASAP PUBLICATIONThis paper was published on the Web on March 30, 2021. The
y-axes for panels d and e in Figure 4 were updated, and thecorrected version was reposted on April 14, 2021.

16819

https://doi.org/10.1021/acsami.0c22709
ACS Appl. Mater. Interfaces 2021, 13, 16812−16819