Spreading of benquitrione droplets on superhydrophobic leaves through pillar[5]arene-based host-guest chemistry

Article abstract of DOI:10.1039/d0cc02187c

Spreading of agricultural sprays on plant surfaces is a significant task as it helps decrease pesticide usage and thereby reduces the risk of environmental pollution. Here, we report a method of increasing the spreading of herbicide benquitrione droplets

Full text of DOI:10.1039/d0cc02187c

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DOI: 10.1039/D0CC02187C
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Spreading of Benquitrione Droplets on Superhydrophobic Leaves
through Pillar[5]arene-based Host-guest Chemistry
Qianqian Song+, Longcan Mei, Xujie Zhang, Pingping Xu, Manivannan Kalavathi Dhinakaran,
Haibing Li * and Guangfu Yang*
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Spreading of agricultural sprays on plant surfaces is a significant Pillar[n]arene, as a new type of host molecule with electron rich
task, since it helps decrease pesticide usage and thereby reduces cavity, has molecular recognitive specificity and reversibility
21-24
the risk of environmental pollution. Here, we report a method of through host-guest interaction.
As a novel herbicide
increasing the spreading of herbicide benquitrione droplets on discovered by ourselves, benquitrione (BEN) 25 shows excellent
superhydrophobic surfaces through its selective dynamic self- activity of herbicidal against wide range of weeds at small
assembly with amino pillar[5]arene. Supramolecular interaction dosage with high safety to sorghum, maize and wheat. Its active
such as host-guest interaction was utilized for complete diffusion of target has been proved to be 4-hydroxyphenyl-pyruvate
benquitrione over hydrophobic plant surface, further molecular dioxygenase (HPPD). In order to improve the spreading of
dynamics simulations were used to verify that AP5A improved the benquitrione on plant leaves, we designed water-soluble amino
spreading of benquitrione droplets on superhydrophobic pillar[5]arene (AP5A) which can form effective supramolecular
interfaces. Moreover, complexation of benquitrione didn’t affect interaction with benquitrione, and improve the spreading of
its biological activity. The present work provides a new method for herbicides on superhydrophobic surfaces (Scheme 1).
improving the utilization rate of pesticides and reducing pesticide
use.
In the process of using pesticides, the common problems such
as high dosage and low effective utilization not only leads to a
larger wastage of pesticides, but also accumulates pesticides in
non-target location, resulting in environmental pollution, even
it may cause death to human being and other organisms.1-4
Hence, how to improve the biological utilization rate of
pesticides is a big challenge that pesticide chemists have to face.
5-7
The key of improving the bio-utilization of pesticides is the
8-9
spreading of pesticide on leave surface.
Then, there is a
problem about the diffusion of pesticides on the surface of
leaves. It was well known that, due to influence of surface
micro-structure and hydrophobic chemical composition of the
leaves, plant leaves exhibit superhydrophobic state, making the
spreading of pesticide droplets on the surface of the leaves as
more difficult. 10-13 In order to solve this problem, scientist have Scheme 1 Schematic illustration for improving the spreading of
pesticide benquitrione droplets on superhydrophobic leaves by
AP5A.
made great efforts to conclude that droplet diffusion can be
promoted by reducing surface tension under static conditions,
14-17
whereas, how to promote the dynamic diffusion of
Three water-soluble pillar[n]arenes were successfully
pesticide droplet is rarely reported. Then it is found that weak
prepared in quantitative yield (Figure S1, S2, S3), and the
18
intermolecular interaction such as electrostatic interaction,
hydrogen bonding interaction
identity of the compound was confirmed by 1H NMR (Figure S4,
19-20
and host-guest interaction
39-40
S5, S6), which consistent with literatures.
First, UV-Vis
can improve the dynamic diffusion behavior of droplets.
analysis of benquitrione and its different host molecules was
carried out to the interaction of the herbicide benquitrione with
host molecules. After the addition of AP5A to the benquitrione
solution, the absorptive peaks were amplified through the test
of ultraviolet spectrum at 217 nm (Figure S7). However, for
other hosts, the peak at 217 nm disappears. Moreover, The
a. Key Laboratory of Pesticide and Chemical Biology (CCNU), Ministry of Education,
College of Chemistry, Central China Normal University, Wuhan 430079, P. R.
China. E-mail: gfyang@mail.ccnu.edu.cn; lhbing@mail.ccnu.edu.cn
† These authors contributed equally to this work.
‡ Electronic Supplementary Information (ESI) available. See DOI: 10.1039/x0xx000x
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absorption peak of AP5A at 298 nm red shifted with the BEN to AP5A is less than the binding energy of BEN to other
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DOI: 10.1039/D0CC02187C
dropping of BEN, and the deviation of AP5A was larger than that hosts, indicating that the complex of BEN and AP5A is more
of CP5A and P5A, Through applying the data obtained from UV- stable. These results indicate that BEN selectively binds to AP5A.
35
Vis titration in Benesi-Hildebrand equation, it was identified
that the 1/(A-Ao) and 1/[benquitrione] have a good linear
relationship. The ratio of linear intercept to slope obtained by
linear fitting shows that the association constant of
benquitrione and AP5A determined by ultraviolet continuous
titration is 1.75 × 104 M-1, which is greater than benquitrione
and CP5A, P5A (Figure S7). Meanwhile, from the Job plot (Figure
S8) it was identified that higher absorbance at 298 nm was
attained, upon reaching the mole fraction of 0.5, this indicates
that host-guest complexation is in the ratio of 1 : 1. And the
strong interaction between AP5A and benquitrione was found
1
by H NMR titration (Figure 1B, S10). The chemical shifts of
hydrogen on the benzene ring of AP5A shift to a higher field
with the drop addition of BEN, while the chemical shifts of
hydrogen on the benzene ring of CP5A and P5A hardly change.
The results show that the interaction between AP5A and
benquitrione is the most stable by comparing the binding
constants KaAP5A+BEN (5.18 × 102 M-1) > KaCP5A+BEN (1.05 × 102 M-
1) > KaP5A+BEN (7.78 × 10 M-1) > KaMER+BEN (4.96 × 10 M-1), and the
1
Fig. 2 A) H NMR (CD3OD, 600 MHz, 298 K) of BEN , AP5A and
signal of AP5A downfield shifting at 7.30 ppm was observed, this
corresponds to the interaction of hydrogen atom in benzene
ring with AP5A, indicating that herbicide benquitrione partially
enters into the cavity of AP5A.
BEN + AP5A; B) A diagram of gauss simulation of the interaction
between BEN and AP5A.
In order to study the diffusion of the BEN + AP5A complex over
the
superhydrophobic
surfaces,
biomimetic
silicon
interface(Figure S11a) was chosen as the superhydrophobic
surface (Figure S22). 10-13 Contact angle of pure water droplets
at the interface of silicon was measured to be 150.9 ± 1.0o
(Figure S11b). Contact angle for droplets of BEN, BEN + CP5A,
BEN BEN + AP5A (complex), BEN + P5A and BEN + Mercapto-
ethylamine (MER) over the silicon were measured and given in
Figure 3A. Higher contact angle was observed for BEN (148.9 ±
1.0o) and BEN + 1, 4-diallyloxy benzene (140.6 ± 1.5o), indicates
that the these droplets were stable. While droplets of BEN +
AP5A was rapidly spreading than BEN + CP5A (95.4 ± 2.0o) and
BEN + P5A (100.6 ± 1.2o), thus the contact angle was 89.7 ± 2.0o.
However, the BEN complex was completely spreading on the
superhydrophobic surface, through the dynamic process of the
droplets, it is found that the BEN droplets after adding MEN
almost remain the same for a period of time, and the BEN
droplets after adding AP5A and P5A have slight changes, and
the droplets spread immediately after adding AP5A, this
indicates that spreading of BEN droplets can be significant
promoted on the biomimetic superhydrophobic surfaces by
AP5A. To further demonstrate that self-assembled complex can
facilitate BEN spreading on the superhydrophobic surfaces,
Fig. 1 A) The chemical structures of the tested hosts and guest;
B)The binding constant of BEN after adding CP5A, AP5A, P5A
and MER.
In order to study the binding sites of BEN with AP5A, partial
1H NMR of AP5A, BEN and BEN + AP5A mixture was given in
figure 2A, it was observed that signals of protons Ha, Hb and Hc
underwent downfield shifts of 0.024 ppm, 0.038 ppm and 0.038
ppm respectively, while protons Hd and He of AP5A underwent
downfield shift of 0.054 ppm and 0.078 ppm respectively, which
are consistent with the reference for strong interaction. 26-27 In
addition, the binding of BEN to AP5A was also examined by
gaussian 03 simulation (Figure S9, 2B).41 The binding energy of
additional evidence is provided by measuring dynamic
30-34
spreading area.
follows:
The formula for calculating area is as
2
2
S(푡) = 휋(푉 3/휑 3(cos 휃(푡))) ∅(푐표푠 휃(푡)) = (휋/3)(
(2 ― 3푐표푠 휃(푡) + 푐표푠 휃(푡))/( 1 ― 푐표푠 휃(푡) 3))
,
3
3
2
(
)
.
The
spreading area of BEN droplets was measured to be 0.7 mm2,
but upon addition of AP5A the spreading area of BEN droplets
have reached 3.5 mm2, the growth rate of contact angle is 41.9%
2 | J. Name., 2012, 00, 1-3
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(Figure 3B). While, the spreading area of BEN + CP5A droplets double-layer stretching of liquid surface reduces surface
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and BEN + P5A droplets have reached 2.8 mm2 and 2.1 mm2, the tension, thereby inhibiting liquid surface contraction and
DOI: 10.1039/D0CC02187C
growth rate of contact angle is 16.9% and 16.1% increment. In promoting droplet spreading. In order to further verify the
order to prove that the cavity effect of AP5A leads to the correctness of the mechanism, finite element computations
spreading of droplets. In addition BEN + MER mixture showed, were performed using molecular dynamics simulation (MDS). 35-
36
the spreading area of 0.9 mm2, the growth rate of contact angle
The calculation of the contact angles of water droplets
is 15.2% (Figure 3B), this also indicates that the spreading of containing BEN/ BEN + AP5A molecules was carried out with
BEN droplets can be promoted remarkably by AP5A alone molecular dynamics simulation. The electrostatic interactions
(Figure S12). The spreading area of benquitrione + AP5A were computed by using the particle mesh Ewald (PME)
complex increases rapidly with the increasing in the strategy. 37-38 The total potential energy between two atoms i
concentration and reaches maximum at 2.0 × 10-4 mol/L, and and j with a distance of 푖푗 is the sum of Lennard-Jones potential
푟
퐸푖푗 = 4휀푖푗
푖푗, Where 푖푗 is the depth of
푘푒
then it's stable (Figure S13 and S25).
and the Coulombic pairwise potential:
12
6
(
)
(
)
]
[
휎푖푗/푟푖푗 ― 휎푖푗/푟푖푗 + 푘푒푞푖푞푗/푟
휀
the potential well, σ is the zero-crossing distance,
is the
Coulomb constant and q is the charge of an atom. We
performed simulations with trilayer graphene monolayers as
the hydrophobic substrate. The carbon atoms were fixed at the
lattice positions with a carbon-carbon distance of 0.142 nm and
an interlayer distance of 0.34 nm. The TIP3P water model was
employed to describe water-water interactions. The contact
angle θ of water droplet can be computed according to the
Young’s equation:
훾푙푣 푐표푠휃 = 훾푠푣 ― 훾푠푙
(1)
훾
, 푠푣 and 푠푙 are LV, SV and SL interfacial tensions,
훾
푙푣
훾
Where
respectively. In the case of the low vapor density fluid of water
and the superhydrophobic surface of graphene, the
훾
훾
.
푠푙
contribution of 푠푣 to the contact angle is much lower than
∆γ =
Thus, the transformation of eq. 1 can be shown as below:
훾푙푣 ― 훾푠푙 = 훾푙푣 (1 + cos 휃), ∆γ
is the difference in interfacial
훾
tension between a system characterized by
where water
푙푣
Fig. 3 A) The change of the contact angle of BEN, BEN + CP5A,
BEN + AP5A, BEN + P5A and BEN + MER with 30 s on
superhydrophobic silicon surface; B) Drop spreading areas of
droplets of BEN, BEN + CP5A, BEN + AP5A, BEN + P5A and BEN
+ MER on superhydrophobic silicon surface.
barely interacts with a substrate and a system with the
훾
interfacial tension
where water interacts with a carbon-
푠푙
based substrate. Furthermore, the quantity is the difference in
the excess interfacial Gibbs free energy between a carbon-
based surface and an inactive surface.
A mechanism was proposed to explain the spreading of
pesticide BEN promoted by AP5A. Upon addition of AP5A into
herbicide BEN solution, AP5A encapsulate BEN into its cavity
through its efficient recognition and self-assemble into vesicles
(Figure 4A and Figure S14). Once, the droplet contacts with the
superhydrophobic surfaces, the complex adsorbs from the
liquid-vapor (LV) surface to the three-phase contact line (CL)
surface quickly. The molecular complementation can be
obtained on the solid-liquid (SL) surface in time by the
disintegration of vesicles for maintaining the molecular balance
between LV and SL, which leads to the formation of bilayers.
AP5A's long direct connection is free from the outside and
strong hydrogen bonding between the two layers of -NH2
promotes the spreading of droplets by stretching the liquid
surface and inhibiting shrinkage. In the figure 4B, it was shown
that surface tension of the solution decreases significantly and
finally tends to be stable due to addition of AP5A. However, the
surface tension of the pesticide BEN droplets is larger, which
inhibit its diffusion over hydropobic surface. Upon addition of
AP5A, dynamic surface tension decreases until saturation is
attained with the increase of concentration, this indicates that
AΔγ
The gibbs free energy change
can be the sum of an
enthalpy contribution and an entropy contribution:
(
AΔγ = A 훾 ― 훾
푙푣 푠푙
)
AΔγ = ΔH ― TΔS
. According to
, we can
ΔH ΔS
cos 휃
. As given in
deduce the relationship between
,
and
Figure 4C, we observed that this double layer continued to grow
and continued to spreading. At 1000 ps, there is a significant
difference in the spreading of the complex droplets against the
BEN droplets, where all of the complex molecules are adsorbed
at LV or SL interface around the water molecules. The pesticide
droplets carrying AP5A are typically expanded and have a fully
wet final state. The results show that the spreading rate of
pesticide BEN droplets is accelerated after adding AP5A, which
is consistent with the experimental results.
Apply the method to the surface of the bamboo and cotton
leaves. The surface structure of bamboo and cotton leaves was
characterized by SEM (Figure S23) and contact angle is 127.2 ±
1.0o, 88.6 ± 2.0o. The spreading area of BEN droplets over the
bamboo leaves was almost obviously unchanged after 60 s, but
the droplets of complex showed complete spreading over the
time period of 60 s in the figure S24a and figure S15. After the
addition of AP5A, the BEN droplets were spreading and the
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spreading area was increased by 1.4 times. Meanwhile, in case
of cotton leaf, the spreading area of BEN droplet remained
unchanged upto 30 s, but rapid and maximum spreading area
was attained with complex droplets (Figure S24b, S17). After
the addition of AP5A, the BEN droplets were spreading and the
spreading area was increased by 1.3 times (Figure S18). The
above studies have showed that addition of AP5A could
improve the spreading of BEN on different hydrophobic plant
surface. It is also necessary to study the influence of AP5A over
the activity of BEN. The inhibitory effect of BEN + AP5A complex
on AtHPPD was slightly enhanced compared with BEN (Figure
S19). Moreover, in living tests revealed that the spraying of BEN
and BEN + AP5A on the grass, causes yellowing of both the
groups within 24 h of administration and death of both the
DOI: 10.1039/D0CC02187C
Interests.
Notes and references
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basic research and operation of MOE.
Conflicts of interest
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