Subscriber access provided by the University of Exeter
Article
Synthesis of (Hexaconazole-Zinc/Aluminium-Layered Double Hydroxide Nanocomposite) Fungicide Nanodelivery System for Controlling Ganoderma Disease in Oil Palm Isshadiba Mustafa, Mohd Zobir Hussein, Bullo Saifullah, Abu Seman Idris, Nur Hailini Zainol Hilmi, and Sharida Fakurazi J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.7b04222 • Publication Date (Web): 28 Dec 2017 Downloaded from http://pubs.acs.org on December 29, 2017
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Journal of Agricultural and Food Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 30
Journal of Agricultural and Food Chemistry
1
Synthesis of (Hexaconazole-Zinc/Aluminium-Layered Double Hydroxide Nanocomposite)
2
Fungicide Nanodelivery System for Controlling Ganoderma Disease in Oil Palm
3 4
Isshadiba F. Mustafa1, Mohd Zobir Hussein1*, Bullo Saifullah1, Abu Seman Idris2, Nur
5
Hailini Z. Hilmi2 and Sharida Fakurazi3,4
6 1
7 8
Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia 2
9
Malaysian Palm Oil Board (MPOB), No.6, Persiaran Institusi, Bandar Baru Bangi, 43000,
10
Kajang, Selangor, Malaysia 3
11 12 13
Materials Synthesis and Characterization Laboratory, Institute of Advanced Technology,
Laboratory of Vaccine and Immunotherapeutics, Institute of Bioscience (IBS), Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
4
Department of Human Anatomy, Faculty of Medicine and Health Sciences, Universiti Putra
14
Malaysia, 43400 UPM Serdang, Selangor, Malaysia
15
Corresponding author:
[email protected] 16 17 18 19 20 21 22 23 24 25
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
26
Abstract: Fungicide, namely hexaconazole was successfully intercalated into the
27
intergalleries of zinc/aluminium-layered double hydroxide (ZALDH) using ion exchange
28
method. Due to the intercalation of hexaconazole, the basal spacing of the ZALDH was
29
increased from 8.7 Å in ZALDH to 29.45 Ǻ in hexaconazole-intercalated ZALDH
30
(HZALDH). The intercalation of hexaconazole into the interlayer of the nanocomposite was
31
confirmed using the Fourier-transform infrared (FTIR) study. This supramolecular chemistry
32
intercalation process enhanced the thermal stability of the hexaconazole moiety. The
33
fungicide loading was estimated to be 51.8 %. The nanodelivery system also shows better
34
inhibition towards the Ganoderma boninense growth than the counterpart, free hexaconazole.
35
The results from this work have a great potential to be further explored for combating basal
36
stem rot (BSR) disease in oil palm plantation.
37 38
Keywords: Nanocomposite, layered double hydroxide, hexaconazole, nanodelivery,
39
agronanochemical.
40 41 42 43 44 45 46 47 48 49
ACS Paragon Plus Environment
Page 2 of 30
Page 3 of 30
Journal of Agricultural and Food Chemistry
50
1. Introduction
51 52
Ganoderma boninense is a wood-rotting fungus that has caused basal stem rot (BSR)
53
disease in oil palm. This disease is one of the critical issue causing low yields in the oil palm
54
industry in Malaysia.
55
In controlling the BSR disease, the fungicides such as hexaconazole and dazomet were
56
used. However, it was reported that the use of the fungicides had increased soil acidity since
57
the residue of hexaconazole fungicide in the soil sample was found to be at the double
58
recommended dosage1. There is currently no effective way to ensure that the fungicides was
59
only released at the fungal site instead of going downward in soil profile through leaching. In
60
this work, a fungicide controlled release formulation was designed and synthesized in
61
controlling the release of fungicides and subsequently reduce the acidity problem.
62
Lately, many researchers were attracted on layered double hydroxides or also called
63
hydrotalcite-like compounds. LDHs are a group of inorganic nanolayers with structurally
64
positively charged layers and interlayer balancing anions. This inorganic nanolayer also
65
known as anionic clay, with formula (MII
66
referring to divalent while MIII is trivalent cations and An- represents the anions which are able
67
to balance the electro-neutrality of the positive charged layers2. The superior properties of
68
LDH such as its biocompatibility, its ability to act as removal agents of pesticides, slow
69
release system and low toxicity makes it suitable to be used for various agriculture
70
applications 3.
1-x
MIII
x
[OH]2 ).(Ax/nn-).yH2O in which MII is
71
It was reported that hexaconazole was intercalated into Mg/Al-LDH exhibited a
72
potential pesticide controlled release4, but currently, no study on antifungal potential towards
73
Ganoderma boninense by using Zn/Al LDH as a carrier. In this work, hexaconazole was
74
accommodated in intergalleries of Zn/Al-LDH (ZALDH) so that the release of fungicide can
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
75
be occurred in a sustained manner. The use of Zn/Al-LDH is hoped to have beneficial effect
76
as Zn is an essential element for plant.
77
Here we discuss our work on the intercalation of hexaconazole into the interlamellae of
78
ZALDH to form a nanocomposite of hexaconazole-ZALDH 2D layered structure and
79
subsequently study its physico-chemical and phytotoxicity properties. Hexaconazole was
80
selected in this work because it is widely introduced as a preventive treatment and prolonging
81
the productive life of infected palms5.
82
2. Materials and methods
83 84
2.1 Materials
85 86
Hexaconazole, with 95 % pure (Changzhou, China) was used as received. All chemical
87
reagents involved were obtained from Sigma-Aldrich. All experiments were conducted using
88
deionized water.
89 90
2.2 Method
91 92
2.2.1
Synthesis of Zn/Al-NO3-LDH
93 94
The salts of Zn(NO3)2 and Al(NO3)3 were dissolved in 250 mL deionised water with a
95
molar ratio of 2:1. After 15 minutes, the NaOH solution with concentration of 2 M, was
96
dropped slowly to the mixture until the solution was achieved to pH 7-7.5 with vigorous
97
stirring under nitrogen environment. Then, the sample was kept into an oil bath at 70 °C for
98
18 h, washed three times with deionised water and centrifuged 6. After drying in an oven for
ACS Paragon Plus Environment
Page 4 of 30
Page 5 of 30
Journal of Agricultural and Food Chemistry
99
two days, the sample obtained was labeled as ZALDH.
100 101
2.2.2 Synthesis of hexaconazole micelle
102 103
An amount of 1.223 g of anionic surfactant, sodium dodecylbenzenesulfonate was
104
dispersed into 250 mL deionised water, 100 mL acetone solution containing 0.2 mol
105
fungicide, hexaconazole was mixed with the surfactant and stirred at 40-45 °C. The fungicide
106
micelle was obtained once the acetone was fully evaporated 7.
107 108
2.2.3 Synthesis of Zn/Al-hexaconazole by the ion-exchanged method
109 110
About 0.5 g ZALDH was added into a 250 mL solution containing approximately 150
111
mL, 0.2 M hexaconazole micelle. Then, the mixture was stirred at 75 ºC for 72 h. After that,
112
the sample was obtained after centrifugation process using deionised water and acetone. The
113
fungicide-LDHs, labeled as HZALDH nanocomposite was obtained after drying at 70 ºC in an
114
oven for about 72 h.
115 116
2.3
Characterizations
117 118
Powder X-ray diffraction (PXRD) pattern was recorded using a Shidmadzu
119
diffractometer, with 2-60° in range, by a CuKα radiation source (λ=1.5405 Å) driven at 40 kV
120
and 30 mA. The FTIR spectra were obtained using a Perkin-Elmer 1725X spectrophotometer
121
by ATR technique with wavelength of 400-4000 cm-1. Thermogravimetric analyses (TGA)
122
was carried out using a Mettler Toledo instrument with 50 mL/min nitrogen flow and 10
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
123
⁰C/min heating rate, between 25-1000 ⁰C. The surface morphology of the nanocomposite was
124
studied using a scanning electron microscope (SEM), JEOL JSM – 6400 model. A Perkin
125
Elmer ultraviolet-visible spectrophotometer (Lambda 35) was used in determination of
126
controlled release property. The high-performance liquid chromatography (HPLC), equipped
127
with Sykam S3250 UV/Vis detector was used to determine the percentage of the
128
hexaconazole loading.
129 130
2.4
Measurements of release amount of hexaconazole from HZALDH
131 132
The release of fungicide from HZALDH nanocomposite was conducted in a pH 5.5
133
(soil pH) of phosphate-buffered solution. HZALDH nanocomposite (10 mg) was put into 20
134
mL phosphate buffer solution. At preset interval times, the sample was taken (2-3 mL) and
135
replaced with new solution. After the aliquot was filtered, the fungicide content was
136
determined at the maximum wavelength of 202 nm using an ultraviolet-visible
137
spectrophotometer.
138 139
2.5
Loading amount of hexaconazole in HZALDH
140 141
HPLC analysis of the hexaconazole fungicide in the HZALDH nanocomposite was
142
carried out using the method as previously described elsewhere8. Two mobile phases were
143
used, namely acetonitrile and 0.1 % orthophosphoric acid. The isocratic mobile phase of
144
acetonitrile and orthophosphoric acid was fixed at a ratio of 75:25, with a flow rate of 1
145
mL/min. It was shown that the retention time was 2.9 minutes. A calibration curve was
146
obtained by running a standard at different concentrations of hexaconazole (0, 50, 100, 150,
147
and 200 ppm), resulted in a good R2 value of 0.98. Approximately, 10 mg of the HZALDH
ACS Paragon Plus Environment
Page 6 of 30
Page 7 of 30
Journal of Agricultural and Food Chemistry
148
was dissolved in 50 mL (5 mL of 1 molar HCl and the remaining volume was composed of
149
the mobile phase) and standard hexaconazole solutions were also prepared in the same way.
150
The percentage loading of hexaconazole in HZALDH nanocomposite was calculated to be
151
51.8 %.
152 153
2.6
Assessment of antifungal activity
154 155
2.6.1 Culture of Ganoderma boninense
156 157
Pathogenic G. boninense culture (PER71) was obtained from the Malaysian Palm Oil
158
Board (MPOB), Bangi, Malaysia. The culture was maintained in Petri dishes (diameter 10
159
mm) on potato dextose agar (PDA) media (Oxoid, Thermo Scientific) (pH 5.5) and incubated
160
at 28 ± 2 °C prior to further usage.
161 162
2.6.2 Determination of antifungal activity of the nanocomposites against G. boninense
163 164
The antifungal activity of the nanocomposites was tested for their antibiosis properties
165
through poison food agar assay. Mycelial discs (5 mm) of 7 days old fungal culture were sub-
166
cultured in the middle of PDA agar plates containing different concentrations of
167
nanocomposites. The PDA has been previously prepared by incorporating the desired
168
concentration of fungicide, i.e. 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1.0, 5.0 and 10.0 ppm into
169
sterilized PDA. The inoculated plates were sealed and incubated at 28 ± 2 °C for 7 days.
170
The growth of G. boninense in the agar plate was measured through the radius growth
171
and the measurements were taken throughout the 7 days. Using the Equation 19, the
172
percentage inhibition of radical growth (PIRG) was calculated;
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
PIRG = (R1 – R2) / R1 x 100
173
(1)
174
where R1 is the radius growth of G. boninense in a control plate and R2 is the radius growth of
175
G. boninense in the fungicides treated plate.
176 177
2.6.3 Statistical analysis
178 179
All data are presented as mean ± standard deviation for 5 independent tests. The
180
comparison of values obtained was analyzed using a Minitab 16 statistical analysis software
181
(Minitab Inc., State College, PA, USA) by one way and two way analysis of variance
182
(ANOVA) followed by the Tukey’s test. The significant value was considered when p-value
183
is less than 0.05.
184
3.
Results and Discussion
185 186
3.1 Powder x ray diffraction analysis
187 188
The XRD patterns of HZALDH nanocomposite, prepared using ion exchange method
189
was shown in Figure 1(A). Based on the figure, pure ZALDH has a basal spacing of 8.7 Ǻ,
190
consistent with a monolayer of nitrate as the counter anion. This is because the brucite-like
191
layer has a thickness of 4.8 Ǻ and the remaining 3.9 Ǻ corresponds to a monolayer of the the
192
nitrate anion 10. The resulting nanocomposite has expanded from 8.7 to 28.9 Ǻ, which indicate
193
that the newly exchanged anion, hexaconazole has been intercalated into the intergalleries of
194
ZALDH to replace nitrate. It was obviously seen that the hexaconazole has higher affinity to
195
be intercalated into the LDH intergalleries compared to the nitrate, due to its higher
196
concentration or bigger size11.
ACS Paragon Plus Environment
Page 8 of 30
Page 9 of 30
Journal of Agricultural and Food Chemistry
197
The results showed that the preparation using 0.2 M HZALDH displayed a sharp,
198
symmetric, high crystallinity, showing the pure product has been obtained with no left over
199
adsorbed Zn(NO3)2 and Al2(NO3)3. After several optimisations using various concentrations
200
of hexaconazole micelle, this sample was then chosen for further studies. A slow scan PXRD
201
of the sample, HZALDH exhibits 8 harmonics; 29.45, 14.83, 9.65, 7.30, 5.84, 4.96, 4.25, and
202
3.67 Ǻ as shown in Figure 1D, which producing an average basal spacing of 29.42 Ǻ. This
203
value was determined by dividing sum of reflections (nxd) with the total number of
204
reflections. This value was then used to predict the plausible arrangement of hexaconazole in
205
the intergallery of HZALDH nanocomposite.
206 207
3.2 Spatial orientation of the hexaconazole moiety in the ZALDH interlayers.
208 209
Figure 2 (A) and (B) show the three dimensional molecular size of hexaconazole and
210
sodium dodecylbenzesulfonate (SDBS) using a Chemoffice software. The x, y and z axes of
211
hexaconazole and SDBS were calculated and were found to be 10 Å, 8 Å, 5 Å and 24 Å, 6 Å,
212
4 Å, respectively. Based on the XRD pattern, HZALDH nanocomposite synthesized at 0.2 M
213
hexaconazole has a mean of basal spacing (d) with value of 29.42 Å. Therefore by subtracting
214
the layer thickness of the ZALDH layer which is 4.8 Å, a value of 24.62 Å was obtained.
215
Therefore, 24.62 Å is a space that can be allocated for the spatial orientation of hexaconazole
216
molecule in the interlayer of ZALDH. The plausible arrangement of hexaconazole is found
217
to be oriented in a biomolecular vertical form along with sodium dodecylbenzene sulfonate
218
and water molecules, as shown in Figure 2 (C)12.
219 220
3.3 Fourier-transform infrared analysis
221
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
222
The presence of hexaconazole moiety in the ZALDH nanolayers has been confirmed
223
by the FTIR spectroscopy (see Fig. 3). The hydroxyl group of the LDH layers and the nitrate
224
anion stretching vibration can be seen at 3440 and 1378 cm-1 as shown in infrared spectrum of
225
ZALDH (Fig. 3B). The 1638 cm-1 band was due to H-OH bending vibration. Fig. 3A shows
226
that the hexaconazole displays a band at 3217 cm-1, which represents hydroxyl group
227
vibrational mode. The C=C and C-H stretching from the aromatic ring were detected at 1431
228
and 847 cm-1. FTIR spectra of HZALDH nanocomposite (Fig. 3C) shows the characteristic
229
bands of hexaconazole alone with slightly shift in the wavenumber position, which indicates
230
the incorporation of hexaconazole into the ZALDH intergalleries.
231
After the intercalation of hexaconazole, the 1601 cm-1 band has been formed, which
232
indicates that C=N stretching from hexaconazole molecule has present. The band assigned to
233
the nitrate anions (1378 cm-1) was absent in this resulting nanocomposite, which strongly
234
support that the NO3- anions have been replaced by the fungicide moiety, hexaconazole. The
235
existence of hexaconazole in the new nanodelivery system and sulfonate ions can be observed
236
at 2956 and 687 cm-1 13.
237 238
3.4 Thermal Studies
239 240
Fig. 4 illustrates the TGA/DTG thermograms of free hexaconazole, ZALDH and
241
HZALDH nanocomposite. . For hexaconazole, the thermogram (Fig. 4A) shows a sharp peak
242
at 283 °C with 100 % weight loss, due to complete combustion of hexaconazole moiety. In
243
Fig.4B, ZALDH shows four stages of weight loss, observed at 108, 244, 310 and 510 °C, with
244
percentage loss of 7.0, 16.7, 4.0 and 5.5 %, respectively. The first one was associated with
245
loss of water molecule. The second one is due to strongly held water molecules and the third
246
and fourth weight losses are almost completed at 510 °C, which referring to dehydroxylation
ACS Paragon Plus Environment
Page 10 of 30
Page 11 of 30
247
Journal of Agricultural and Food Chemistry
of brucite-like layers and removal of the interlayer anions14.
248
Due to the intercalation of hexaconazole into the interlayer of ZALDH (Fig. 4C),
249
TGA/DTG curves show five thermal events at 90, 229, 322, 425 and 888 °C with weight
250
losses of 6.9, 8.3, 10.9, 30.3 and 6.9 %, respectively. The first and the second stage of weight
251
losses are the same as that for ZALDH, which is due to the removal of adsorbed water and
252
dehydroxylation of the hydroxyl layer, respectively. The third stage at 322 °C is a result of the
253
organic moiety decomposition in the interlayer of the nanohybrid, leaving only a relatively
254
less volatile metal oxide15. The weight loss was increased to 30.3 % at 425 °C in HZALDH
255
nanocomposite because of the hexaconazole anions combustion. The last stage of weight loss
256
that occurred at around 888 °C was due to the formation of the spinel (ZnAl2O4) phase16. This
257
was presumably due to the high electrostatic force in the molecule as the thermal
258
decomposition affected by the substituents on the ligand17.
259
It was obviously seen that the thermal stability of HZALDH nanocomposite was
260
greatly increased after the intercalation which is at 425 °C compared to 283 °C (for the free
261
hexaconazole). The result had shown that ZALDH has a potential to be used as a carrier to
262
store fungicide with good thermal stability.
263 264
3.5 Surface morphology
265 266
Figs. 5 (A) and (B) show the field emission scanning electron micrograph, showing
267
the surface morphology of HZALDH at 50,000x and 100,000x magnifications, respectively.
268
The HZALDH nanocomposite shows agglomerated non uniform granule structure, similar to
269
the other nanocomposites previously prepared by other works18.
270 271
3.6 Release behavior of hexaconazole from HZALDH nanocomposite
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
272 273
The release behaviors of both pure hexaconazole and HZALDH nanocomposite
274
were studied in PBS solution at pH 5.5 as shown in Fig. 6. The release behavior of pure
275
hexaconazole was very fast for the first 420 min, and become slower thereafter, before it
276
achieved 100 % complete release in 2000 min. The rapid release of the hexaconazole from the
277
nanocomposite was observed initially, then followed with a slower one thereafter and finally
278
the sustained release was achieved at 62 % after 3000 min. It is obviously seen that the
279
hexaconazole released from the nanocomposite was slower than the release of free
280
hexaconazole. This indicates that the nanocomposite served a role as a fungicide controlled
281
release system. The electrostatic interaction between the positively charged ZALDH
282
nanolayers and the negatively charged hexaconazole anions have influences the release
283
property of hexaconazole from its HZALDH interlayers.
284 285
3.7 Release kinetics of hexaconazole from the nanocomposite
286 287
The release kinetics of the hexaconazole from HZALDH nanocomposite was
288
analyzed using the pseudo-first order Eq. (2)19, pseudo-second order Eq. (3)20, Hixon-Crowell
289
Eq. (4)21, Higuchi Eq. (5)22, and Korsmeyer Peppas model Eq. (6)23. The equations are given
290
below;
291 292
ln (qe-qt) = ln qe-kt
(2)
293
t/qt = 1/kqe2 + t/qe
(3)
294
qo 1/3 – qt 1/3 = kt
(4)
295
qt = k(t)0.5
(5)
296
qt = ktn
(6)
ACS Paragon Plus Environment
Page 12 of 30
Page 13 of 30
Journal of Agricultural and Food Chemistry
297 298
where qo, qe and qt are the initial amount of anions, equilibrium release amount and release
299
amount at time t, respectively with k is the corresponding release rate constant.
300
Fig. 7 displays the five kinetic models used to fit the release data of hexaconazole from
301
nanocomposite. The parameters such as the rate constant, k and the correlation coefficient
302
value, R2 obtained from the five models are shown in Table 2. As shown in results above, the
303
best fitted of the release of hexaconazole from the pure phase, ZALDH inorganic host is the
304
pseudo-second order kinetic model.
305 306
3.8 Antifungal activity of the nanocomposite against the G. boninense
307 308
The antifungal activity of free hexaconazole, ZALDH and HZALDH sample of different
309
concentrations (0.001 to 10 ppm) towards G. Boninense were tested and are represented in
310
Fig. 8 (A to D) with the error bar as standard deviation. The inhibition zone of G. boninense
311
by the samples are also illustrated in Fig. 8 (E). (Based on Fig. 8(A) and 8(C), it can be seen
312
that the HZALDH is fully inhibited the G. boninense growth at lower concentration, 0.1 ppm,
313
compared to hexaconazole alone, which is at 0.5 ppm. On the other hand, for the ZALDH
314
(Fig. 8B), the radial growth of G. boninense steadily increased to the seventh days, which
315
shows that it gives no effect on inhibition towards the G. boninense growth. This study also
316
revealed that the as-synthesized nanocomposite exhibited significant anti-fungal activity as
317
shown in Fig. 8(D).
318
As a result of using probit analysis of Sigma Plot 10.0, the half maximal effective
319
concentration, EC50 was obtained. The value of EC50 for hexaconazole, ZALDH and
320
HZALDH was found to be 0.05, 2.03 and 0.03 ppm, respectively. These findings indicate that
321
the resulting nanodelivery system of hexaconazole developed in this work is more effective in
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
322
combating G. boninense compared to its counterpart, the free hexaconazole as indicated by
323
the lower EC50 value, 0.03 compared to 0.05 ppm, respectively.
324
Table 3 and Table 4 represent the significant effects of pure hexaconazole, ZALDH,
325
HZALDH concentrations under one – way ANOVA and the interaction between the treatment
326
and concentration towards the growth of Ganoderma boninense under two-way ANOVA,
327
respectively. The mean and standard deviation of different concentrations of pure
328
hexaconazole and HZALDH are significant, while for the ZALDH, it is insignificant to
329
growth as shown in Table 3. In comparing both factors of treatment and concentration, the
330
treatment give highly significant effect towards the growth, about seven times compared to
331
concentration, as shown in Table 4.
332
This finding has showed that zinc/aluminium layered double hydroxide can be used
333
as a nanocarrier for a fungicide, hexaconazole in developing new environmental-friendly
334
agronanochemicals.
335
Acknowledgement
336 337
This project was supported by the Universiti Putra Malaysia and the Ministry of Higher
338
Education of Malaysia (UPM-MOHE) grants under the NANOMITE vot no. 9443100 and
339
5526300. The G. boninense studies were accomplished at the Malaysian Palm Oil Board
340
(MPOB) laboratory and facilities.
341
References
342
1.
343
344
Maznah Z, Halimah M, Ismail S, Idris AS. Dissipation of the fungicide hexaconazole in oil palm plantation. Environ Sci Pollut Res Int. August 2015.
2.
Touloupakis E, Margelou A, Ghanotakis DF. Intercalation of the herbicide atrazine in
ACS Paragon Plus Environment
Page 14 of 30
Page 15 of 30
Journal of Agricultural and Food Chemistry
345
layered double hydroxides for controlled-release applications. Pest Manag Sci. 2011,
346
67, 837-841.
347
3.
348
349
Morais R, Aquino LA De. Revisão De Literatura Layered Double Hydroxides : Nanomaterials for Applications in Agriculture. 2011, 1,1-13.
4.
Zhenlan Q, Heng Y, Bin Z, Wanguo H. Synthesis and release behavior of bactericides
350
intercalated Mg-Al layered double hydroxides. Colloids Surfaces A Physicochem Eng
351
Asp. 2009, 348,164-169.
352
5.
Idris, A S And Maizatul Sm. Prolonging The Productive Life Of Ganoderma-Infected
353
Oil Palm With Dazomet, Mpob Information Series No. 616, Mpob Ts No. 108. 2pp.
354
2012, 2-4.
355
6.
Saifullah B, Hussein MZ, Hussein-Al-Ali SH, Arulselvan P, Fakurazi S.
356
Antituberculosis nanodelivery system with controlled-release properties based on para-
357
amino salicylate-zinc aluminum-layered double-hydroxide nanocomposites. Drug
358
Design , Development and Therapy. 2013, 7, 1365-1375.
359
7.
360
361
camptothecin. 2004, 95, 501-514.
8.
362
363
Tyner KM, Schiffman SR, Giannelis EP. Nanobiohybrids as delivery vehicles for
Extraction S. Simultaneous Extraction and Detection of Six Fungicide Residues in Mango Fruit Followed by New Validated HPLC-UV Method. 2013, 1, 80-84.
9.
Skidmore Bam, Dickinson Ch. Colony Interactions And Hyphal Interference Between
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
364
365
Septoria Nodorum And Phylloplane Fungi. Trans Br Mycol Soc. 1976, 66, 57-64.
10.
366
367
Touloupakis E, Margelou A, Ghanotakis DF. Intercalation of the herbicide atrazine in layered double hydroxides for controlled-release applications. 2011, 837-841.
11.
Sheikh Mohd Ghazali SAI, Hussein MZ, Sarijo SH. 3,4-Dichlorophenoxyacetate
368
interleaved into anionic clay for controlled release formulation of a new
369
environmentally friendly agrochemical. Nanoscale Res Lett. 2013, 8, 362.
370
12.
Saifullah B, Arulselvan P. Development of a highly biocompatible antituberculosis
371
nanodelivery formulation based on para-aminosalicylic acid—zinc layered hydroxide
372
nanocomposites. Sci World Journal. 2014.
373
13.
374
375
Xu ZP, Braterman PS. High affinity of dodecylbenzene sulfonate for layered double hydroxide and resulting morphological changes. J Mater Chem. 2002, 13(2), 268-273.
14.
Barahuie F, Hussein MZ, Gani SA, Fakurazi S, Zainal Z. Synthesis of protocatechuic
376
acid-zinc/aluminium-layered double hydroxide nanocomposite as an anticancer
377
nanodelivery system. J Solid State Chem. 2015, 221, 21-31.
378
15.
Hussein MZ, Hashim N, Yahaya AH, Zainal Z. Synthesis of Dichlorprop-Zn/Al-
379
hydrotalcite Nanohybrid and its Controlled Release Property. Sains Malaysiana. 2011,
380
40(8), 887-896.
381 382
16.
Cheng X, Huang X, Wang X, Sun D. Influence of calcination on the adsorptive removal of phosphate by Zn – Al layered double hydroxides from excess sludge liquor.
ACS Paragon Plus Environment
Page 16 of 30
Page 17 of 30
Journal of Agricultural and Food Chemistry
383
384
J Hazard Mater. 2010, 177(1-3), 516-523.
17.
385
386
Lalia-Kantouri M. Factors Influencing The Thermal Decomposition Of Transition Metal Complexes With 2-Oh-Aryloximes Under Nitrogen. 2005, 82, 791-796.
18.
Zobir M, Yahaya AH, Zainal Z, et al. Nanocomposite-based controlled release
387
formulation of an herbicide, 2,4-dichlorophenoxyacetate incapsulated in zinc –
388
aluminium-layered
389
formulation of an herbicide. 2005, 6996.
390
19.
double
hydroxide
Nanocomposite-based
controlled
release
Dong L, Li Y, Hou W, Liu S. Journal of Solid State Chemistry Synthesis and release
391
behavior of composites of camptothecin and layered double hydroxide. J Solid State
392
Chem. 2010, 183, 1811-1816.
393
20.
394
395
equation and the sorbate intraparticle diffusivity. 2013, 1055-1064.
21.
396
397
Ramteke KH, Dighe PA, Kharat AR, Patil S V. Review Article Mathematical Models of Drug Dissolution : A Review. 2014, 3(5), 388-396.
22.
398
399
Plazinski W, Dziuba J. Modeling of sorption kinetics : the pseudo-second order
Singhvi G, Singh M. Review : In-Vitro Drug Release Characterization Models. 2011, II(I).
23.
Nguyen TX, Huang L, Liu L, Elamin M. Electronic Supplementary Information ( ESI )
400
Chitosan-coated nano-liposomes for the oral delivery of berberine hydrochloride. 2014,
401
1-4.
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
402
ACS Paragon Plus Environment
Page 18 of 30
Page 19 of 30
Journal of Agricultural and Food Chemistry
Fig. 1. PXRD patterns of free hexaconazole (A), ZALDH (B) and HZALDH nanocomposite (C) and the slow scan with a dwell time of 0.5°/min (D) and from the 8 reflections, the average value of the interlamellae (nxd) was found to be 29.42 Å.
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
Page 20 of 30
C
A
B
Carbon
Nitrogen
Sulphur
Chlorine
Hydrogen
Oxygen
Fig. 2. Three–dimensional structure of hexaconazole (A), sodium dodecylbenzenesulfonate (B) and plausible arrangement of hexaconazole and sodium dodecylbenzenesulfonate in the intergallery of HZALDH nanocomposite (C)
ACS Paragon Plus Environment
Page 21 of 30
Journal of Agricultural and Food Chemistry
Fig. 3. Fourier transformed infrared (FTIR) spectra of free hexaconazole (A), ZALDH (B) and HZALDH (C).
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
A
a
B B
C
Fig. 4. TGA/DTG thermograms of hexaconazole (A), ZALDH (B) and HZALDH nanocomposite (C).
ACS Paragon Plus Environment
Page 22 of 30
Page 23 of 30
Journal of Agricultural and Food Chemistry
A
B
Fig. 5. Field emission scanning electron micrographs of HZALDH nanocomposites (A and B) at 50,000x and 100,000x magnifications.
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
Page 24 of 30
Table 1. The thermal properties of pure hexaconazole, ZALDH and HZALDH nanocomposite.
Sample name
T1-T2
Ts (⁰C )
∆m (mg)
Weight loss (%)
Pure hexaconazole
160-328
283
8.34
100
34-160
108
0.40
7.0
160-285
244
1.57
16.7
285-355
310
0.33
4.0
355-560
510
0.45
5.5
30-146
90
0.58
6.9
146-265
229
0.77
8.3
265-361
322
1.07
10.9
361-587
425
3.08
30.3
778-994
888
0.41
6.9
ZALDH
HZALDH
ACS Paragon Plus Environment
Page 25 of 30
Journal of Agricultural and Food Chemistry
Fig. 6. Release profiles of hexaconazole from pure hexaconazole and HZALDH nanocomposite at pH 5.5.
ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
Fig. 7. Fitting the release data of hexaconazole from nanocomposite using the pseudo-first order, pseudo-second order kinetics, Higuchi, Hixon-Crowell and Korsmeyer Peppas models.
ACS Paragon Plus Environment
Page 26 of 30
Page 27 of 30
Journal of Agricultural and Food Chemistry
Table 2. Rate constant and correlation coefficient (R2) value of the release data of hexaconazole from the nanocomposite using pseudo-first order, pseudo-second order, Higuchi model, Hixon-Crowell and Korsmeyer Peppas kinetic models.
Sample
HZALDH
C
Saturation release (%) 62
R2 Pseudofirst order 0.9166
Korsmeyer -Peppas model 0.8101
Pseudo-second order Higuchi model 0.8743
HixonCrowell model 0.7227
D
ACS Paragon Plus Environment
R2
0.9975
Rate constant, k (mg/min) 1.54x10-2
Journal of Agricultural and Food Chemistry
Page 28 of 30
E
I
II
III
IV
Fig. 8. The growth curves of G. Boninense treated with hexaconazole (A), ZALDH (B), HZALDH (C) for seven days and the percentage of inhibition radical growth (PIRG) against concentration (ppm) of free hexaconazole, HZALDH and the control after 7 days (D) where *p >0.05 and **p