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ArticleMaximizing Conversion of Surface Click Reactions for Versatile
Molecular Modiﬁcation on Metal Oxide Nanowires
Rimon Yamaguchi, Takuro Hosomi,* Masaya Otani, Kazuki Nagashima, Tsunaki Takahashi,
Guozhu Zhang, Masaki Kanai, Hiroshi Masai, Jun Terao, and Takeshi Yanagida*

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ABSTRACT: Click reactions (e.g., Huisgen cycloaddition) on metal oxide nanostructuresoﬀer a versatile and robust surface molecular modiﬁcation for various applications because
they form strong covalent bonds in a wide range of molecular substrates. This study
reports a rational strategy to maximize the conversion rate of surface click reactions on
single-crystalline ZnO nanowires by monitoring the reaction progress. p-Polarized
multiple-angle incidence resolution spectrometry (pMAIRS) and Fourier-transformed
infrared (FT-IR) spectroscopy were employed to monitor the reaction progress of an
azide-terminated self-assembled monolayer (SAM) on single-crystalline ZnO nanowires.
Although various reaction parameters including the concentration of Cu(I) catalysts,
triazolyl ligands, solvents, and target alkynes were systematically examined for the surface click reactions, 10−30% of terminal azide
on the nanowire surface remained unreacted. Temperature-dependent FT-IR measurements revealed that such unreacted residual
azides deteriorate the thermal stability of the nanowire molecular layer. To overcome this observed conversion limitation of click
reactions on nanostructure surfaces, we considered the steric hindrance around the closely packed SAM reaction points, thenexperimented with dispersing the azide moiety into a methyl-terminated SAM. The mixed-SAM method signiﬁcantly improved theazide conversion rate to almost 100%. This reaction method enables the construction of spatially patterned molecular surface
modiﬁcations on metal oxide nanowire arrays without detrimental unreacted azide groups.

■

py4,6,13,15,19−21 are particularly useful because of the wide
range of detectable functional groups. However, despite thesuperiority of IR spectroscopy, a comprehensive study on asingle metal oxide nanostructured surfaces, exhaustively
covering orientations and conformations of the molecularlayers, steric environments around the reaction sites, eﬀects ofcatalytic systems, optimized conditions to maximize conversions of the reaction sites, and the range of available
substrates has not been investigated.
We recently reported that single crystal metal oxide
nanowire arrays provide favorable surface for IR measurements.22,23 A single-crystal metal oxide nanowire array consistof large amount of thin single crystals (diameters: 10−100 nm)
perpendicularly grown on a ﬂat substrate, which is favorable toinvestigate surface molecular quantities, conﬁgurations, andorientations by IR. We conducted time-dependent monitoringof the surface Huisgen reaction on a ZnO nanowire array andexamined the eﬀects of solution composition, additional
ligands, and species of substrates. As a result, we found that

INTRODUCTION
Surface molecular modiﬁcations on metal oxide nanostructures
have proven useful and exhibit potential to tailor physical andchemical properties for various applications, including electric,
catalytic, and sensory devices.1−5 The modifying organic
compounds possess ﬁne tunability and designability at themolecular level, qualities not attainable with bulk metaloxides.2 Among various methodologies for such surface
molecular modiﬁcations on metal oxide nanostructures, click
reaction-based methods are particularly promising because of
the strong covalent bonds formed and the wide range of usable
compounds.2−10 It has been reported that various functional
molecules can be introduced via Huisgen cycloaddition withterminal azide or alkynyl groups on the top of self-assembled
monolayers (SAMs).11−15 This two-step surface molecular
modiﬁcation is complicated and diﬀerent from conventional
solution processes.15 It is because ﬁxations of reaction points(e.g., azide) on the surface increase their planar densities andlimit their degree of freedom of translational motions, which
can signiﬁcantly aﬀect their reactivities.16,17 Therefore, theHuisgen cycloaddition reactivities on surfaces need to bemonitored and investigated independently from those in thesolutions. Some techniques to observe molecular changes like
cyclic voltammetry,13,15,18 or X-ray photoelectron spectroscopy3,13,19,20 have successfully employed to monitor surface click
reactions. Among them, infrared (IR) spectrosco© 2021 American Chemical Society

Received: January 12, 2021
Revised: April 1, 2021
Published: April 23, 2021

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ArticleFigure 1. Conformational and spatial environments of terminal azide of the SAM on the ZnO nanowire arrays: (a) Scheme images of the alkyl
conformation of the azide-terminated SAM on the ZnO nanowires; (b) pMAIRS spectrum of alkyl region (3000−2800 cm−1) of azide-terminated
SAM on the ZnO nanowire array (OP: out-of-plane signal, IP: in-plane signal); (c) FT-IR spectrum of azide region (2200−2050 cm−1) and (d)phosphonic acid region (1300−800 cm−1) of azide-terminated SAM on the ZnO nanowire array.

Figure 2. Thermal resistance of azide group on a SAM: temperature-dependent FT-IR spectra of (12-azidododecyl)phosphonic acid in the regionof alkyl (a) and azide (b); (c) residual ratio of alkyl or azide calculated from IR peak area plotted against temperature.

nanowire surface. The P−O−H bands at 1000−920 cm−1 arealmost absent, suggesting that the organic moieties stack on
the ZnO surface via P−O−Zn bonds formed by dehydrative
condensation between phosphonic acid and ZnO.24,25 The
binding structure is considered to be dominantly tridentate
because only a small PO absorption (around 1200−1250cm−1) is observed.24 These characteristics are similar to thoseof methyl-terminated phosphonic acids on ZnO.24,26,27 On theother hand, the behaviors of the alkyl chains of the (12azidodocecyl)phosphonic acid SAM are quite diﬀerent fromthose of methyl-terminated SAMs. Figure 1b shows the ppolarized multiple-angle incidence resolution spectrometry(pMAIRS) spectra of the SAM alkyl region (OP: out-of-planesignal, IP: in-plane signal). Wavenumbers of the characteristic
alkyl peaks (νas(CH2): 2922 cm−1, νs(CH2): 2852 cm−1)
suggest that the SAM has a gauche-rich conformation, unlike
typical methyl-terminated n-alkyl SAMs, which have transzigzag-dominated conformations. The average tilt angle wascalculated to be almost perpendicular (86°) against the(1) to obtain stable SAMs, high terminal azide conversion ispreferable because of the thermal vulnerability of azides; (2)azide conversion rates do not reach 100% on completely azideterminated SAMs even under optimized conditions; and (3)the use of mixed SAMs is eﬀective in achieving stoichiometricazide conversion on the metal oxide nanowires. Based on theseﬁndings, we developed reaction conditions applicable to a wide
range of target molecules on nanowire arrays.

■

RESULTS AND DISCUSSIONFirst, we evaluated the structural properties of the azideterminated SAMs on ZnO nanowires (Figure S1), because thesteric and electric environment of the reaction points
signiﬁcantly aﬀect the reaction progress (Figure 1). Figure
1c,d show the Fourier-transformed infrared (FT-IR) spectrumof a ZnO nanowire array functionalized with (12azidodocecyl)phosphonic acid. The sharp azide absorption(at 2103 cm−1) and the broad P−O absorption (centered at1080 cm−1) conﬁrm the presence of the substrate on the5173

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ArticleFigure 3. Scheme and spectroscopic trace of Huisgen cycloaddition on ZnO nanowires: (a) reaction scheme; (b) FT-IR spectral changes in theazide and imide regions, which show azide decrease and imide appearance via Huisgen cycloaddition; (c) azide conversion and imide yield of the
Huisgen cycloaddition plotted against reaction time. The conversion and the yield are calculated against the initial azide amount on the SAM.

consumed by the reaction. Instead, the imide peak (1735cm−1) appeared after the reaction, showing the successful
introduction of the imide moiety. Figure 2c shows theconversion rate of azide and yield of imide plotted against
the reaction time (see Figure S2 for the raw spectra). These
two values are consistent with each other, suggesting that thereaction proceeds without signiﬁcant side reactions in thattime. Interestingly, the reaction rate and azide conversion rate
immediately saturated at a moderate yield, in contrast to
typical Huisgen reaction behaviors in solution phases.31 Such
immediate saturations of conversion rates are also observed in
the aliphatic or aromatic alkynes (Figure S3). Therefore, we
next examined whether the conditions of the reaction can
improve this limitation.
The conditions, concentrations, catalysts, ligands, andsolvents of this reaction were screened. Conditions of eachentry are shown in Table 1. First, both Cu(I) ions and ligands
are necessary to this reaction. Almost no reaction proceeded
without catalyst (entry 2) and without ligand (entry 3). The
issue may be that Cu(I), which is thought to be an active
species in the Huisgen reaction, is unstable even in thepresence of sodium ascorbate.32 In other words, thecomparably slow solid−liquid reaction rate may reﬂect the
instability of the active species. Therefore, we next investigatedthe eﬀect of ligands, because certain kinds of diamine-type
ligands are well known to be eﬀective in stabilizing Cu(I)species by chelate eﬀects.33 The addition of (triazolylmethyl)amine ligands improved the reaction progress (entries 4−7). In
particular, (triazolylmethyl)amine, which has more than two
triazolyl moieties (BBTA and TBTA), showed a signiﬁcanteﬀect, in contrast to the ineﬀectiveness of the MBTA. These
trends also support the importance of the chelate eﬀect of
BBTA and TBTA for stabilization of Cu(I) species. Although
BBTA yields higher yield than TBTA in the 3 mM condition,
signiﬁcantly decreased yield was observed in the lower
concentration (0.3 mM) condition (entry 7). The changes ofthe solutions are also not eﬀective to improve the yield andconversion (entries 8 and 9; see Figures S4 and S5 for detailed
spectral changes). Therefore, we next examined the scope ofthe substrates under the reaction conditions because changes
in the steric or electric structures of substrates may improve

nanowire major axis by the ratio of OP and IP signal
intensities,28 indicating interfered alkyl chain orientations.
These results suggest that the terminal azides make alkyl chain
packing disordered (Figure 1a). It can be caused by theintermolecular azide-azide interactions19 or steric hinderancesby the terminal azides, which is relatively freely rotational andhas larger rotational diameters compared with alkyl moieties.
From these observations, the reaction points on the azideterminated SAM are considered to exist in a spatially proximate
environment.
We next examined the stability of the azide-terminated SAM,
because the azide group is known for thermal instability
derived from decomposition into N2.29 Such decompositions
may lead to unintentional changes in the properties of themolecular-modiﬁed nanowires. To evaluate the thermal
resistance of the azide group, we collected temperaturedependent FT-IR spectra of the azide-terminated SAM on
ZnO nanowires (Figure 2). We observed that the alkyl peaks
tolerated heat until the temperature reached approximately 250°C, then gradually decreased between 250 and 300 °C. This
result is consistent with previous stability research on simple
alkyl monolayers.30 In contrast, the azide absorption essentiallydisappears at approximately 200 °C, presumably as the azide
undergoes thermal decomposition into N2. Therefore, it can besaid that residual azides can make the resultant molecular
modiﬁcations instable by their unintentional decompositions.
It will be especially problematic in some electric devices which
are sensitive to the existence of polar functional groups likeazides. In other words, full conversion of surface azides in thesubsequent Huisgen cycloaddition reactions is crucial toachieve long-term, thermally robust monolayer surfaces.
To trace surface azide conversions, we conducted in situ FTIR measurements during the Huisgen cycloaddition between
the azide-terminated SAM and an alkyne in the presence of
CuSO4, sodium ascorbate, and tris(benzyltriazolylmethyl)amine (TBTA). N-(2-Propynyl)phthalimide (1a) was chosen
as the model substrate because of its FT-IR traceability derived
from the imide moiety (Figure 3a). Figure 3b shows the FT-IR
spectra of the SAM-modiﬁed ZnO nanowire before and after
Huisgen cycloaddition for 10 min. The disappearance of theazide peak (2103 cm−1) shows that the azide moiety is5174

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Articlemolecules can be considered well-dispersed in the dodecyl
phosphonic acid SAM, and the azide moieties in the mixed
SAM can be considered isolated. The wavenumber of vs(CH2)ﬁrst decreases with decrease of terminal azides ratio, and thensaturates at the ratio is approximately 0.5 (Figure S10). Thisdata suggests the uniform azide dispersion in the mixed SAM
because the wavenumber of vs(CH2) should decrease linearly if
azide- and proton-terminated molecules form separated
domains in the mixed SAM. The wavenumber of Figure 4
shows the transformed azide ratio against the initial azide
amount (red line), and imide-functionalized ratio (blue line)
for all phosphonic acids. The imide-functionalized ratio
decreases by increase in the ratio of n-dodecyl phosphonicacid because reaction points (azide) in the SAM decreases. As
can be seen, an increase in the ratio of n-dodecyl phosphonicacid causes a corresponding increase in the conversion. The
azide conversion rate reaches almost 100% before the imidefunctionalized ratio initiate signiﬁcant decrease (>60%). Thisphenomenon strongly supports our hypothesis that the reacted
molecules interfere the reactions of neighboring azides. These
results clearly demonstrate the eﬀectiveness of our new
approach to eliminating residual azides from surface chemicalfunctionalization by the Huisgen reaction.

Table 1. Entries of Reaction Conditions■

CONCLUSIONSIn summary, we have successfully monitored surface Huisgenreactions between azide-terminated self-assembled monolayers
and various alkynes by utilizing a combination of metal oxide
nanowires and FT-IR spectroscopy. The time-dependent FTIR spectrum showed that relatively concentrated Cu(I)catalysts (3.0 mM) and appropriate ligands are needed toobtain good conversion of the surface azides. At the same time,even under optimized conditions, the surface azides were notfully converted, in contrast to those in the solution. We foundthat this limitation is related to the proximity of surface azides
on the SAM. We developed a mixed-SAM method to decrease
the surface density of the reaction points and successfully
improved the azide conversion rate to achieve almost
stoichiometric conversion. These results demonstrate theeﬀectiveness of our approach to providing stable azide-freeinterfaces by controlling the steric environment around thesurface reaction points.

the azide conversion dramatically. We tested 16 kinds ofalkynes (1a−1p), which contain a wide variety of alkynes withvarious sizes and functional groups. The spectral changes foreach alkyne are shown in Figures S6−S8, and calculated azide
conversions are summarized in Table 2. As can be seen in
Table 2, these substrates show moderate conversion rates,
excepting 1i, which have carboxylic acid moiety. The low
conversion of 1i is considered to be a salt formation withTBTA to prevent the coordination ability to Cu(I). Repeatedmeasurements (5 times) for a model substrate (1e) shows astandard error = 2.1%, indicating that our system has suﬃcient
repeatability. From the above-mentioned entries, it can be said
that the reaction conditions can be applicable to a wide rangeof substrates. However, even in the case of most reactive
alkynes, the conversion rate saturates before 100%. In order toachieve full conversion of surface azides, another approach isstill required.
Therefore, we developed a surface Huisgen reaction systemthat can realize almost 100% conversion of surface azide. We
hypothesized that the limitation of the azide conversion
described above are results of the close proximity of theterminal azides on the SAM. Once the triazole products areformed on the SAM surface, they are expected to act as sterichindrances which prevent copper-alkyne complexes fromaccessing the adjacent azides because each azide group isplaced near to cause disordering of the alkyl chains asmentioned in Figure 1. This assumption is also supported by
the negative relationships between the sizes of alkynes andazide conversion rates (Figure S9). Based on this assumption,
we utilized the mixed-SAM method, which disperses (12azidododecyl)phosphonic acid throughout a methyl-terminated dodecyl phosphonic acid (i.e., n-dodecyl phosphonicacid) SAM. Previous studies have shown the eﬀectiveness ofthe mixed-SAM method.29 Because the alkyl chain length inthese two phosphonic acids is the same, the azide-terminated■

EXPERIMENTAL SECTION

Growth of ZnO Nanowires. ZnO nanowire arrays on Si (100)wafers were grown using the hydrothermal method. First, a 5 nm Ti
buﬀer layer was sputtered onto the Si substrate (2 cm × 2.5 cm), andthen a 100 nm ZnO ﬁlm was sputtered on as the seed layer. Zinc
nitrate hexahydrate (25 mM, Zn(NO3)2·6H2O, 99.0%), 25 mM
hexamethylenetetramine (HMTA, (CH2)6N4, 99.0%), and 2.5 mMpolyethyleneimine (PEI, Mw 1800, 50 wt % in H2O) were dissolved
sequentially in deionized (DI) water (200 mL). The pre-prepared
substrate was dipped into the solution and maintained at 80 °C for 24
h. After growth, the samples were rinsed with DI water and dried
under N2 ﬂow. Then the as-grown ZnO nanowires were annealed at
400 °C in air for 1 h.
Characterization of ZnO Nanowires Morphology. Scanningelectron microscope (SEM) images were acquired using a JEOL JSM7610F instrument. The SEM images (Figure S1) conﬁrm that thegrown ZnO nanowires exhibit hexagonal columnar structures(diameter of ∼100 nm), which indicates that the ZnO nanowires
have a single wurtzite structure with the prism (10−10) plane as themain face.
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ArticleTable 2. Scope of Alkynesaa
The common reaction condition for all alkynes is shown on the table. See the Supporting Information for the raw data of the IR spectral change ofeach alkyne. bResults of 5-min reaction.

Figure 4. Eﬀect of mixed-SAM on the azide reaction eﬃciency. (a) Click reaction on the pure azide-terminated SAM. (b) Click reaction on amixed-SAM surface in which azide-terminated phosphonic acids are dispersed in methyl-terminated phosphonic acids. (c) Transformed N3 ratio
for initial N3 amount on the SAM (red marks), and ratio of imide-functionalized molecules for all phosphonic acid molecules (blue marks) plottedagainst ratio of N3 terminated phosphonic acid in the mixed-SAM.
Synthesis of (12-Azidododecyl)Phosphonic Acid. (12azidododecyl)phosphonic acid was synthesized by a two-step reaction
from 12-dibromododecane according to the literature procedure.34
Modiﬁcation of (12-Azidododecyl)Phosphonic Acid SAM on
ZnO Nanowires. Modiﬁcation solutions (1.0 mM) were prepared bydissolving (12-azidododecyl)phosphonic acid in tetrahydrofuran atroom temperature. The annealed ZnO nanowire array was dipped
into the solution (10 mL) for 30 min at room temperature. Then, thesamples were washed several times with tetrahydrofuran and dried
under N2 ﬂow.
Huisgen Cycloaddition on SAM-Modiﬁed ZnO Nanowires. A
reaction mixture for surface Huisgen cycloaddition was prepared by5176

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Authors

dissolving 3.0 mM each of copper(II) sulfate (CuSO4, Wako, 97.5%),
ligand (MBTA, BBTA, or TBTA), and sodium ascorbate into 20 mLof DMSO/H2O (9/1), followed by addition of 3.0 mM of substratealkyne. The SAM-modiﬁed ZnO nanowire array was dipped into thesolution (10 mL) at room temperature for a given time. The samples
were washed several times with tetrahydrofuran before the FT-IR andpMAIRS measurements.
FT-IR and pMAIRS Analysis of the Molecular Modiﬁcation.
The FT-IR and pMAIRS spectra of the surface molecules on the ZnO
nanowires were recorded at room temperature on a Thermo Fisher
Scientiﬁc Nicolet iS50 FT-IR spectrometer equipped with a mercury−cadmium−telluride (MCT) detector. 300 scans were accumulated toobtain each spectrum. For each pMAIRS measurement, a series ofeight single-beam sample measurements were carried out at angles ofincidence from 9 to 44° at 5° steps and with a resolution of 4 cm−1.
The test room was always purged with dry air. After collection of thesample data, the OP and IP spectra were automatically calculated withthe pMAIRS software (Thermo Fisher Scientiﬁc). The theoreticaldetails of the IR pMAIRS analysis can be found in the literature.35−37
FT-IR and pMAIRS spectra for a bare ZnO was used as the
background spectrum for the other measurements. Conversions of
Huisgen cycloaddition were calculated as the ratio IR peak area
against initial azide peak area. The each azide peak area was calibrated
by the peak area of asymmetric vibration band of −CH2. Yields ofHuisgen cycloaddition were also calculated as the ratio IR peak area
against initial azide peak area, after collecting IR calibration curve of
1a by using known amount of 1a solution drops with known
concentrations.
Temperature-Dependent FT-IR Analyses on the SAMModiﬁed ZnO Nanowires. (12-azidodecyl)phosphonic acid-modiﬁed ZnO nanowires were placed in an electric furnace. The
temperature in the furnace was increased linearly to a determined
temperature (50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325,
or 350 °C) for 30 min. After the temperature reached to thedetermined value, the furnace temperature was kept at thattemperature for 10 min. Then, the furnace temperature was allowed
to cool down to room temperature. The FT-IR measurements were
performed according to the procedure described above. The
percentage of remaining azide was calculated as the azide peak ratio
of after/before heating.

■Rimon Yamaguchi − Department of Applied Chemistry,
Graduate School of Engineering, The University of Tokyo,
Tokyo 113-8656, Japan; Institute for Materials Chemistry
and Engineering, Kyushu University, Kasuga, Fukuoka 8168580, Japan
Masaya Otani − Department of Basic Science, Graduate
School of Art and Sciences, The University of Tokyo, Tokyo
153-8902, Japan
Kazuki Nagashima − Department of Applied Chemistry,
Graduate School of Engineering, The University of Tokyo,
Tokyo 113-8656, Japan; Japan Science and Technology
Agency (JST), PRESTO, 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 113-8656, Japan; Japan Science and Technology
Agency (JST), PRESTO, 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 1138656, Japan
Masaki Kanai − Institute for Materials Chemistry andEngineering, Kyushu University, Kasuga, Fukuoka 816-8580,
Japan
Hiroshi Masai − Department of Basic Science, Graduate
School of Art and Sciences, The University of Tokyo, Tokyo
153-8902, Japan
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
Complete contact information is available at:https://pubs.acs.org/10.1021/acs.langmuir.1c00106
Author Contributions

Sample fabrication, spectroscopic measurements, and sensor
evaluations were performed by R.Y. Characterizations of the
nanowire and molecular functionalization states by theobtained data were conducted by R.Y., T.H., K.N., T.T., andT.Y. (12-azidododecyl)phosphonic acid was synthesized by
M.O., H.M., and J.T. The surface reaction behaviors werediscussed by R.Y., T.H., K.N., T.T., G.Z., M.K., M.O., H.M.,
J.T., and T.Y. This manuscript was written by T.H. and T.Y.,
while R.Y., K.N., T.T., G.Z., M.K., M.O., H.M., and J.T.
contributed improvements. All the authors contributed to themanuscript preparation and approved the ﬁnal version of themanuscript.

ASSOCIATED CONTENT

sı Supporting Information*

The Supporting Information is available free of charge athttps://pubs.acs.org/doi/10.1021/acs.langmuir.1c00106.
SEM images of ZnO nanowires; FT-IR spectral changes
during Huisgen cycloadditions in various solvents; FTIR spectra for the Huisgen cycloadditions with various
alkynes (PDF)■

ArticleAUTHOR INFORMATION

Notes

The authors declare no competing ﬁnancial interest.

Corresponding Authors■

Takuro Hosomi − Department of Applied Chemistry,
Graduate School of Engineering, The University of Tokyo,
Tokyo 113-8656, Japan; Japan Science and Technology
Agency (JST), PRESTO, Kawaguchi, Saitama 332-0012,
Japan; orcid.org/0000-0002-5649-6696; Phone: +81-35841-3840; Email: t-hosomi@g.ecc.u-tokyo.ac.jp
Takeshi Yanagida − Department of Applied Chemistry,
Graduate School of Engineering, The University of Tokyo,
Tokyo 113-8656, Japan; Institute for Materials Chemistry
and Engineering, Kyushu University, Kasuga, Fukuoka 8168580, Japan; orcid.org/0000-0003-4837-5701;
Phone: +81-3-5841-3862; Email: yanagida@g.ecc.utokyo.ac.jp

ACKNOWLEDGMENTS
This work was supported by KAKENHI (Grant Nos.
JP20H02, JP18H01831, JP18H05243, and JP18KK0112).
T.H. was supported by JST PRESTO, Japan (Grant No.
JPMJPR19T8). T.H., K.N., T.T., and T.Y. were supported by
JST CREST, Japan (Grant No. JPMJCR19I2), JST Mirai
R&D. T.Y. and K.N. were supported by the CAS-JSPS Joint
Research Projects (Grant No. JPJSBP120187207). This work
was performed under the Cooperative Research Program of
the Network Joint Research Center for Materials and Devices,
the Dynamic Alliance for Open Innovation Bridging Human,
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Environment and Materials, and the MEXT project “Integrated
Research Consortium on Chemical Sciences”.

■

Article(19) Al-Hajj, N.; Mousli, Y.; Miche, A.; Humblot, V.; Hunel, J.;
Heuzé, K.; Buffeteau, T.; Genin, E.; Vellutini, L. Influence of theGrafting Process on the Orientation and the Reactivity of AzideTerminated Monolayers onto Silica Surface. Appl. Surf. Sci. 2020, 527,
No. 146778.
(20) Bishop, L. M.; Yeager, J. C.; Chen, X.; Wheeler, J. N.; Torelli,
M. D.; Benson, M. C.; Burke, S. D.; Pedersen, J. A.; Hamers, R. J. A
Citric Acid-Derived Ligand for Modular Functionalization of Metal
Oxide Surfaces via “Click” Chemistry. Langmuir 2012, 28, 1322−
1329.
(21) Henriksson, A.; Friedbacher, G.; Hoffmann, H. Surface
Modification of Silicon Nanowires via Copper-Free Click Chemistry.
Langmuir 2011, 27, 7345−7348.
(22) 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.
(23) Wang, C.; Hosomi, T.; Nagashima, K.; Takahashi, T.; Zhang,G.; Kanai, M.; Yoshida, H.; Yanagida, T. Phosphonic Acid Modified
ZnO Nanowire Sensors: Directing Reaction Pathway of Volatile
Carbonyl Compounds. ACS Appl. Mater. Interfaces 2020, 12, 44265−
44272.
(24) Hotchkiss, P. J.; Malicki, M.; Giordano, A. J.; Armstrong, N. R.;
Marder, S. R. Characterization of Phosphonic Acid Binding to Zinc
Oxide. J. Mater. Chem. 2011, 21, 3107−3112.
(25) Schulmeyer, T.; Paniagua, S. A.; Veneman, P. A.; Jones, S. C.;
Hotchkiss, P. J.; Mudalige, A.; Pemberton, J. E.; Marder, S. R.;
Armstrong, N. R. Modification of BaTiO3 Thin Films: Adjustment of
the Effective Surface Work Function. J. Mater. Chem. 2007, 17, 4563−
4570.
(26) Timpel, M.; Nardi, M. V.; Krause, S.; Ligorio, G.;
Christodoulou, C.; Pasquali, L.; Giglia, A.; Frisch, J.; Wegner, B.;
Moras, P.; Koch, N. Surface Modification of ZnO(0001)−Zn with
Phosphonate-Based Self-Assembled Monolayers: Binding Modes,
Orientation, and Work Function. Chem. Mater. 2014, 26, 5042−5050.
(27) Quiñones, R.; Shoup, D.; Behnke, G.; Peck, C.; Agarwal, S.;
Gupta, R. K.; Fagan, J. W.; Mueller, K. T.; Iuliucci, R. J.; Wang, Q.
Study of Perfluorophosphonic Acid Surface Modifications on Zinc
Oxide Nanoparticles. Materials 2017, 10, No. 1363.
(28) Hasegawa, T.; Iiduka, Y.; Kakuda, H.; Okada, T. Analysis of
Structurally Heterogeneous Langmuir-Blodgett Films of Folded/
Unfolded Long-Chain Molecules by Infrared Multiple-Angle Incidence Resolution Spectroscopy. Anal. Chem. 2006, 78, 6121−6125.
(29) Yoffe, A. D. Thermal Decomposition and Explosion of Azides.
Proc. R. Soc. A 1951, 208, 188−199.
(30) Valiokas, R.; Ö stblom, M.; Svedhem, S.; Svensson, S. C. T.;
Liedberg, B. Thermal Stability of Self-Assembled Monolayers:
Influence of Lateral Hydrogen Bonding. J. Phys. Chem. B 2002, 106,
10401−10409.
(31) Moses, J. E.; Moorhouse, A. D. The Growing Applications ofClick Chemistry. Chem. Soc. Rev. 2007, 36, 1249−1262.
(32) Hein, J. E.; Fokin, V. V. Copper-Catalyzed Azide-Alkyne
Cycloaddition (CuAAC) and beyond: New Reactivity of Copper(I)Acetylides. Chem. Soc. Rev. 2010, 39, 1302−1315.
(33) Chan, T. R.; Hilgraf, R.; Sharpless, K. B.; Fokin, V. V.
Polytriazoles as Copper(I)-Stabilizing Ligands in Catalysis. Org. Lett.
2004, 6, 2853−2855.
(34) Toulemon, D.; Pichon, B. P.; Leuvrey, C.; Zafeiratos, S.;
Papaefthimiou, V.; Cattoën, X.; Bégin-Colin, S. Fast Assembling ofMagnetic Iron Oxide Nanoparticles by Microwave-Assisted Copper(I) Catalyzed Alkyne−Azide Cycloaddition (CuAAC). Chem. Mater.
2013, 25, 2849−2854.
(35) Hasegawa, T. A Novel Measurement Technique of Pure Outof-Plane Vibrational Modes in Thin Films on a Nonmetallic Material
with No Polarizer. J. Phys. Chem. B 2002, 106, 4112−4115.
(36) Itoh, Y.; Kasuya, A.; Hasegawa, T. Analytical Understanding ofMultiple-Angle Incidence Resolution Spectrometry Based on a

REFERENCES(1) Schoenbaum, C. A.; Schwartz, D. K.; Medlin, J. W. Controlling
the Surface Environment of Heterogeneous Catalysts Using SelfAssembled Monolayers. Acc. Chem. Res. 2014, 47, 1438−1445.
(2) Vutti, S.; Schoffelen, S.; Bolinsson, J.; Buch-Månson, N.; Bovet,
N.; Nygård, J.; Martinez, K. L.; Meldal, M. Click Chemistry MediatedFunctionalization of Vertical Nanowires for Biological Applications.
Chem. − Eur. J. 2016, 22, 496−500.
(3) He, C.; Abraham, B.; Fan, H.; Harmer, R.; Li, Z.; Galoppini, E.;
Gundlach, L.; Teplyakov, A. V. Morphology-Preserving Sensitizationof ZnO Nanorod Surfaces via Click-Chemistry. J. Phys. Chem. Lett.
2018, 9, 768−772.
(4) Kantheti, S.; Narayan, R.; Raju, K. V. Pyrene-Anchored ZnO
Nanoparticles through Click Reaction for the Development of
Antimicrobial and Fluorescent Polyurethane Nanocomposite. Polym.
Int. 2015, 64, 267−274.
(5) Haensch, C.; Hoeppener, S.; Schubert, U. S. Chemical
Modification of Self-Assembled Silane Based Monolayers by Surface
Reactions. Chem. Soc. Rev. 2010, 39, 2323−2334.
(6) Shah, S.; Benson, M. C.; Bishop, L. M.; Huhn, A. M.; Ruther, R.
E.; Yeager, J. C.; Tan, Y.; Louis, K. M.; Hamers, R. J. Chemically
Assembled Heterojunctions of SnO2 Nanorods with TiO2 Nanoparticles via “Click” Chemistry. J. Mater. Chem. 2012, 22, 11561−
11567.
(7) Mehlich, J.; Ravoo, B. J. Click Chemistry by Microcontact
Printing on Self-Assembled Monolayers: A Structure-Reactivity Studyby Fluorescence Microscopy. Org. Biomol. Chem. 2011, 9, 4108−
4115.
(8) Rozkiewicz, D. I.; Gierlich, J.; Burley, G. A.; Gutsmiedl, K.;
Carell, T.; Ravoo, B. J.; Reinhoudt, D. N. Transfer Printing of DNA
by “Click” Chemistry. ChemBioChem 2007, 8, 1997−2002.
(9) Michel, O.; Ravoo, B. J. Carbohydrate Microarrays byMicrocontact “Click” Chemistry. Langmuir 2008, 24, 12116−12118.
(10) Godula, K.; Rabuka, D.; Nam, K. T.; Bertozzi, C. R. Synthesis
and Microcontact Printing of Dual End-Functionalized Mucin-like
Glycopolymers for Microarray Applications. Angew. Chem., Int. Ed.
2009, 48, 4973−4976.
(11) Poonthiyil, V.; Lindhorst, T. K.; Golovko, V. B.; Fairbanks, A. J.
Recent Applications of Click Chemistry for the Functionalization ofGold Nanoparticles and Their Conversion to Glyco-Gold Nanoparticles. Beilstein J. Org. Chem. 2018, 14, 11−24.
(12) Amblard, F.; Cho, J. H.; Schinazi, R. F. Cu(I)-Catalyzed
Huisgen Azide−Alkyne 1,3-Dipolar Cycloaddition Reaction in
Nucleoside, Nucleotide, and Oligonucleotide Chemistry. Chem. Rev.
2009, 109, 4207−4220.
(13) Bandyopadhyay, S.; Mukherjee, S.; Dey, A. Modular Synthesis,
Spectroscopic Characterization and in Situ Functionalization Using“Click” Chemistry of Azide Terminated Amide Containing SelfAssembled Monolayers. RSC Adv. 2013, 3, 17174−17187.
(14) Xi, W.; Scott, T. F.; Kloxin, C. J.; Bowman, C. N. Click
Chemistry in Materials Science. Adv. Funct. Mater. 2014, 24, 2572−
2590.
(15) Collman, J. P.; Devaraj, N. K.; Eberspacher, T. P. A.; Chidsey,
C. E. D. Mixed Azide-Terminated Monolayers: A Platform for
Modifying Electrode Surfaces. Langmuir 2006, 22, 2457−2464.
(16) Fryxell, G. E.; Rieke, P. C.; Wood, L. L.; Engelhard, M. H.;
Williford, R. E.; Graff, G. L.; Campbell, A. A.; Wiacek, R. J.; Lee, L.;
Halverson, A. Nucleophilic Displacements in Mixed Self-Assembled
Monolayers. Langmuir 1996, 12, 5064−5075.
(17) Deckert, A. A.; Lesko, J.; Todaro, S.; Doyle, M.; Delaney, C.
Kinetics and Mechanism of Substitution Reactions between
Myoglobin and Activated Self-Assembled Monolayers Investigated
Using Surface Plasmon Resonance. Langmuir 2002, 18, 8156−8160.
(18) Choi, I. S.; Chi, Y. S. Surface Reactions On Demand:
Electrochemical Control of SAM-Based Reactions. Angew. Chem., Int.
Ed. 2006, 45, 4894−4897.
5178

https://doi.org/10.1021/acs.langmuir.1c00106
Langmuir 2021, 37, 5172−5179

Langmuirpubs.acs.org/Langmuir

ArticleClassical Electromagnetic Theory. J. Phys. Chem. A 2009, 113, 7810−
7817.
(37) Shioya, N.; Shimoaka, T.; Murdey, R.; Hasegawa, T. Accurate
Molecular Orientation Analysis Using Infrared P-Polarized MultipleAngle Incidence Resolution Spectrometry (PMAIRS) Considering theRefractive Index of the Thin Film Sample. Appl. Spectrosc. 2017, 71,
1242−1248.

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Langmuir 2021, 37, 5172−5179