Evaluation of Controlled-Release Property and Phytotoxicity Effect of

Subscriber access provided by UNIV LAVAL

Article

Evaluation of Controlled Release Property and Phytotoxicity Effect of Insect Pheromone-Zinc Layered Hydroxide Nanohybrid Intercalated with Hexenoic Acid Rozita Ahmad, Mohd Zobir Hussein, Wan Rasidah Wan Abdul Kadir, Siti Halimah Sarijo, and Yun Hin Taufiq-Yap J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.5b03102 • Publication Date (Web): 26 Oct 2015 Downloaded from http://pubs.acs.org on November 18, 2015

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 36

Journal of Agricultural and Food Chemistry

Evaluation of Controlled-Release Property and Phytotoxicity Effect of Insect Pheromone-Zinc Layered Hydroxide Nanohybrid Intercalated with Hexenoic Acid Rozita Ahmad1,2, Mohd Zobir Hussein1*, Wan Rasidah Wan Abdul Kadir 2, Siti Halimah Sarijo3 & Taufiq-Yap Yun Hin4

1

Materials Synthesis and Characterisation Laboratory (MSCL), Institute of Advanced Technology (ITMA), Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia ; E-Mail: [email protected]

2

Forest Biotechnology Division, Forest Research Institute Malaysia (FRIM), 52109 Kepong, Selangor, Malaysia; E-Mail: [email protected] ;[email protected]

3

Faculty of Applied Science, Universiti Teknologi MARA (UiTM), 40540 Shah Alam, Malaysia; E-Mail:[email protected]

4

Chemistry Department, Faculty of Science, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia; E-Mail:[email protected]

*

Corresponding author: E-Mail: [email protected]; Address: Materials Synthesis and Characterisation Laboratory (MSCL), Institute of Advanced Technology (ITMA), Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor Tel:+6-03-8946-8092; Fax:+6-03-8943-5380

1

ACS Paragon Plus Environment


Page 2 of 36

1

Abstract

2

A controlled release formulation for insect pheromone, hexenoic acid (HE) was successfully

3

developed using zinc-layered hydroxide (ZLH) as host material through a simple co-precipitation

4

technique, resulted in the formation of inorganic-organic nanolayered material with sustained

5

release properties. The release of HE from its nanohybrid was found to occur in a controlled

6

manner, governed by pseudo-second order kinetics model. The maximum amount of HE released

7

from the nanocomposite into solutions at pH 4, 6.5 and and 8 was found to be 84, 73 and 83%

8

for 1100 mins, respectively. The hexenoate-zinc layered hydroxide nanomaterial, (HEN), was

9

found to be non-toxic for plant when green beans and wheat seeds were successfully germinated

10

in all HEN concentrations tested in the experiment, with higher percentage of seed germination

11

and higher radical seed growth as compared to its counter anion, HE. ZLH can be a promising

12

carrier for insect pheromone towards a new generation of environmentally-safe pesticide

13

nanomaterial for crop protection.

14

Keywords: hexenoic acid, zinc layered hydroxide nanohybrid, insect pheromone, controlled

15

release, phytotoxicity

2


Page 3 of 36

16


1. Introduction

17

Research on nanotechnology for agricultural applications has gained high interest due to

18

major concern on the use of chemical pesticides in crop production. Excessive use of

19

agrochemicals are usually not fully utilized by plants as most of them are lost through leaching in

20

soil 1-2. Direct application of pesticide onto the plant through spraying will contaminate the crop,

21

leaving harmful chemical residue which enter through direct pathway into human food chain 3.

22

It also causes environmental pollution in ecosystem and pose problem to human health. The use

23

of pheromone in orchard for insect control has proved successful and could become a potential

24

biopesticide 4-5. However, the application of pheromone is not effective under field condition as

25

most of the chemical is volatile and easily affected by environmental factors which include

26

temperature, sunlight, wind and rainfall6. A controlled release formulation hence is required to

27

provide precise delivery target and releasing the active chemicals in smaller amounts and thus

28

help to reduce the chemical safe level 3.

29

A number of controlled released carrier in nanopesticide research have been widely

30

studies to provide an environmentally-safe, non-pesticide product. This include polymer-based

31

nanoformulations comprising of polysaccharide materials such as starch6,7, alginates8,

32

chitosan9,10, polyethylene glycol11 and polyester substance

33

from natural materials are also in used which consisted of neem oil13 and garlic essential oil 14.

34

The list extended to other forms as well, which govern to nanospheres15, nanogels16 and

35

nanofibers17,18.

12

. Plant protection products derived

36

Research on inorganic-organic nanomaterial namely layered double hydroxide (LDH)

37

and layered hydroxide salt (LHS) nanocomposites has grow rapidly, due to their unique structure

38

as ion exchanger and their tailor-made behavior resulted to various potential applications. Early 3



Page 4 of 36

39

work on LDH as catalysts19, catalyst precursor20 then the research proceeded to polymer21,22,

40

flame retardant for smoke suppression23,24,corrosion inhibitor25, extended as controlled release

41

formulation for drugs26,27, agrochemicals28 and removal of toxic substances in environmental

42

applications29,30. Nanolayered structure material of layered inorganic-organic nanocomposite can

43

be formed by encapsulation of an organic moiety into an inorganic interlayer spacings of LDH

44

and LHS which acted as host. The brucite-like structure of both LDH and LHS provide an ion

45

exchange platform for many chemical types: nitrates, sulphates and organic acids. High

46

positively charged densities of LDH and LHS can accomodate the anionic organic compound

47

within the interlayer spaces to compensate the positively charged, and consequently form high

48

stability material.

49

LDH is represented by the general formula, [M2+1-xM3+x(OH)2]x+(Am-)x/m.nH2O, while

50

LHS is given by the general formula, M2+(OH)2-x(An-)x/n.mH2O, where M2+ and M3+ is the

51

divalent and the trivalent metallic cation, respectively. In both layered hydroxide structure, Am- is

52

the interlayered anion that balance the positive charge layers. Thus, LDH and LHS nanomaterial

53

are represented by a positively charged brucite-like inorganic layers with anions and water

54

molecules existing between the interlayers 31-32.

55

ZLH is a type of LHS, comprised of one type of divalent metal cation in which only zinc

56

and hydroxyl represent

the inorganic layers. ZLH is comprised of layers of octahedral

57

coordinated zinc cations, in which 1/4 of them are displaced leaving an empty octahedral site

58

forming cationic centers tetrahedrically coordinated to the top and bottom of the octahedral

59

sheet. Water molecules occupy the apexes and the nitrate counter ions are free between the

60

interlayers. Due to its higher charge densities and possess larger interspacing than LDH, ZLH

61

can become host for higher number of guest anion of different sizes33. This makes it potential to 4


Page 5 of 36


62

be use as carrier and slow release delivery system for many chemical agents in various

63

applications such as drugs

64

absorber 39,40 , catalyst 41, DNA42, food preservatives 43, pharmaceutical and nutracuetical agents

65

44

34,35

, anti-corrosion agent36, herbicides37, dye industry

38

, sunscreen

.

66

Meditarranean fruit flies, (Ceratitis capitata) is categorized as agricultural pests as they

67

attack both unripe and ripe fruits. This causes problem in the quality of food supply and effect

68

agriculture yield. In this study, hexenoic acid, a pheromone for this pest is being used as guest

69

with ZLH as host for the formulation of host-guest nanocomposite with controlled release

70

properties. To our knowledge, the use of ZLH as controlled release carrier for insect pheromone

71

has not yet been reported in the open literature. Here, we discussed our work on the intercalation

72

of trans-2-hexenoic acid (HE), C6H10O6, a short chain carboxylic anion into the interlayer of

73

ZLH by simple co-precipitation method. A new organic-inorganic ZLH-HE nanohybrid

74

compound was synthesized by direct reaction of ZnO with HE under aqueous environment

75

followed by precipitation with alkaline solution, and subsequently evaluated its control released

76

behavior and phytotoxicity effect.

77

ZLH as the encapsulated host material for active chemicals can provide beneficial input

78

to the environment. It can be used as zinc source for soil supplement which is an advantage to

79

the soil as most soil around the world is deficient in zinc. It is an essential micronutrient for plant

80

development and obtain most of its nutrient from soil in which they grow

81

test of ZLH-HE nanohybrid carried out on two types of seed shows higher percentage of

82

germination and longer radical seed length compared to its counterpart chemical, HE. This

83

indicates that the synthesized nanolayered structure material is not toxic to plant and intended

45

. The phytotoxicity

5



Page 6 of 36

84

towards a new generation of green, environmentally-safe pesticide nanomaterial for insect

85

control and crop protection.

86 87

2. Experimental

88

2.1 Synthesis of Materials

89

All chemicals used in this experiment were obtained from various chemical supplier and

90

applied without any further purification. All solutions were prepared using deionized water.

91

Trans-2-hexenoic acid nanohybrid (HEN) was synthesized by co-precipitation method using

92

ZnO as starting material. About 0.20 g of ZnO was firstly suspended into 100 mL deionized

93

water stirred for 15 minutes. Hexenoic acid solution of various concentrations; 0.1M, 0.2M,

94

0.3M and 0.4M were each prepared by dissolving respective amount of HE in 40 mL ethanol and

95

adjusted to 100 mL volume in a volumetric flask with deionized water. Each of the HE solution

96

was then added dropwise into ZnO suspension with constant stirring, producing a clear mixed

97

solution at the end of the process. pH of the solution was adjusted to 7.9 with 0.5 M NaOH

98

aqueous solution to obtain white precipitate. The slurry solution was vigorously stirred via a

99

magnetic stirrer for 3 h and the aging process was further continued in an oil bath shaker for 18 h

100

at 70 oC. The obtained product was centrifuged, thoroughly washed with deionized water to

101

wash away any contaminants and then dried in an oven at 70 oC. The obtained material was then

102

powdered for further use and characterizations.

103

2.2 Characterization

104

Powder X-ray diffraction patterns of nanohybrids were obtained at 2–60o on a Shimadzu

105

diffractometer, XRD-6000 using CuKα radiation (λ =1.5418 Å) and dwell time of 4 degrees per

106

minute. Surface characterization of the synthesized product was carried out using a nitrogen gas 6


Page 7 of 36


107

adsorption method at 77 K on a Micromeritries ASAP 2000. The sample was degassed in an

108

evacuated heated chamber at 100 oC overnight. Surface morphology of the synthesized

109

nanohybrid was captured on a field emission scanning electron microscope (FESEM), model

110

JOEL JSM-7600F. The dried sample was dispersed on a conductive carbon adhesive tape surface

111

which was attached to a FESEM stub, and then gold coated. Internal morphology of ZLH-HE

112

nanohybrids was observed using a Hitachi H-7100 transmission electron microscope (TEM) at

113

magnifications, 30 – 200 k. A drop of the nanohybrid – 20% v/v ethanol dispersion was placed

114

onto a 300 mesh Fomvar copper grid and air dried, overnight in a dessicator. The average

115

diameter and particle size distribution (PSD) of the nanohybrid was measured using dynamic

116

light scattering (DLS) photon-cross correlation spectroscopy (PCCS). The sample was dispersed

117

in 20% v/v ethanol prior to analysis.

118

2.3 Kinetic Release Study

119

The release of hexenoic acid from the nanohybrid host into different media were

120

accomplished using distilled water at pHs=4, 6.5 and 8 by adding 2 mg of the nanohybrid into

121

3.5 mL of the solution. The pH solution in distilled water was obtained by adjusting its pH using

122

HCl or NaOH and pH values were measured using a pH meter. The accumulated amount of

123

hexenoic acid released into the solution was measured at preset time at 207 nm using a Perkin

124

Elmer UV-Visible spectrophotometer, Lamda 35. The cumulative release pattern was fitted to

125

first, pseudo-second order kinetics and parabolic diffusion models.

126

2.4 Phytotoxicity Test

127

The pytotoxicity test for ZLH-HE nanohybrid was carried out on two types of seed using

128

a method adopted by Keeling 46. The nanohybrid material of different weight, 0.01g, 0.1g and 1g

129

and 100 mL distilled water were mixed respectively and shake using an orbital shaker for 1 h. 7



Page 8 of 36

130

The mixture was filtered through Whatman filter paper no. 1. 3 mL of the filtered solution was

131

pipetted on a petry dish which was placed with a filter paper Whatman no. 1 containing 15 seeds

132

of green beans and wheat. The petry dish was covered to avoid loss through evaporation. The

133

petry dishes were then incubated at 28 oC in an incubator for 48 h. Various types of controls

134

which consisted of distilled water, ZnO and HE were carried out to determine their effect on

135

plant. A series of concentration of 0.01g/100 mL, 0.1g/100mL and 1g/100mL of HE and ZnO

136

respectively, were also prepared as in HEN, and then tested on the two seeds.

137 138 139 140

3.

Results and Discussion

3.1 Powder X-ray Diffraction Analysis

141

The PXRD patterns of the unbound chemical, HE and ZLH-HE nanolayered structure

142

materials prepared at various concentrations of HE, 0.1 – 0.4 mol/L using 0.2g of ZnO are

143

potrayed in Fig. 1. The Powder X-ray diffraction pattern of ZnO reflects five sharp peaks

144

between 30 – 60o region, correspond to reflections of 100, 002, 101, 102 and 110 lattice planes

145

which indicate high crystallinity which represents a distinctive pattern of metal oxide. The

146

PXRD pattern of the counterpart anion, HE (Fig. 1) shows some reflection peaks, which

147

demonstrates the crystalline nature of this chemical.

148

The produced nanolayered structure material synthesized at various concentrations of HE

149

(Fig. 1) with fixed amount of 0.2g ZnO, show reflection peaks diffracted at lower 2θ angle with

150

increase in the basal d-spacing, is evidence that inclusion of the anion, HE inside the interlayer

151

spacing of ZLH. The resulting nanolayered material prepared from 0.1 M HE, shows the

152

presence of ZnO phase, which indicate incomplete reaction, while the nanohybrids synthesized at

153

concentrations 0.2 and 0.3 mol/L HE show disappearance of ZnO characteristic peaks. The 8


Page 9 of 36


154

expansion basal spacing of nanohybrid material synthesized at 0.2 and 0.3 mol/L HE is 24.6 Å

155

and 23.4Å, respectively and disappearance of ZnO peak indicate that successful intercalation of

156

the organic anion between the inorganic ZLH interlayer has taken place. However, comparing

157

both 0.2 mol/L and 0.3 mol/L HE together, the nanolayered structure material obtained using 0.3

158

mol/L HE, shows a symmetric peak with reflection up to three separate harmonics at 2θ angle

159

of 3.76o, 7.50o and 12.45o with respective d-basal spacing values of 23.5 Å, 11.8 Å and 7.1 Å

160

as shown in the slow scan PXRD patterns (Fig.1b). This indicate the formation of a well ordered

161

2D layered structure of the nanocomposite. Hence, the nanolayered structure material obtained

162

from 0.3 mol/L HE was selected for further characterizations and labeled as HEN.

163

The formation of nanolayered structure material of ZLH-HE from direct reaction of ZnO

164

in an hydrated environment of HE, is reported to follow the ‘dissociation-deposition’

165

mecahanism process31,47. The hydrolysis of ZnO in an aqueous environment takes place to form

166

Zn(OH)2 on the surface of solid particles. Further reaction lead to the dissociation of Zn(OH)2

167

in the HE solution, releasing Zn2+. The released Zn2+ then reacted with hydroxyls, HE anions

168

and H2O in the solution to obtain nanolayered ZLH-HE material. The process is repeated until all

169

the ZnO phase and the Zn(OH)2 phase has completely changed to the layered material. The

170

mechanism of the process is given below:

171

ZnO + H2O

Zn(OH)2

(1)

172

Zn(OH)2

Zn2+ + 2OH-

(2)

173

Zn2+ + 2OH- + HE- + H2O

174

Zn2+(OH)2-x (HEm-)x/m .nH2O

(3)

3.2 Surface Properties

175

The adsorption-desorption isotherms of nitrogen gas on ZnO and its nanolayered material,

176

HEN is depicted in Fig. 2a. Based on the IUPAC classification, both ZnO and HEN potrayed a 9



Page 10 of 36

177

similar pattern of adsorption-desorption isotherms with Type IV indicating mesopore and/or

178

nonporous types of material. The adsorption for ZnO showed that it started from a slow uptake

179

at low relative pressure in the range of 0.0 – 0.9, followed by a rapid increase in adsorption of the

180

adsorbent of > 0.9, reaching its optimum uptake of nitrogen gas at 33 cm3/g. Similarly, the

181

nanolayered material, HEN gave a slow adsorption increment at low relative pressure in the

182

range of 0.0 – 0.8 and then a quick rise of the adsorbate at a relative pressure of more than 0.8,

183

approaching saturated uptake of 26 cm3/g. The effect of surface properties of the produced

184

nanolayered structure material upon successful intercalation of organic anion, HE into the

185

interlayer space of zinc layered hydroxide was evaluated by measuring the surface area and pore

186

size distribution and the data are summarized in Table 1.

187

The surface area of ZnO and HEN analysed by the Brunauer, Emmet and Teller (BET)

188

method shows a reduce in the surface area of HEN with a value of 4 m2/g, compare to ZnO with

189

a value of 6 m2/g. The same trend was also observed for the formation of other nanohybrids

190

reported for 2,4,5 –trichlorophenoxyacetic acid and ellagic acid as guest anions into LDH and

191

ZLH35,48.

192

property48. It is believed that the nature of the guest anion used could also contribute to the

193

decrease in surface area. As mentioned in the earlier discussion, the counter anion, HE has a

194

combination of amorphous and crystallinity structure, which might affect the formation of the

195

produced nanolayered material. The intercalation of HE into the ZLH resulting the formation of

196

HEN has resulted in the increase in size pore. The BET average diameter pore of HEN was

197

found to be higher than ZnO, with values of 297 Å and 64 Å respectively.

The microstructure of the material used was reported to influence the surface

198

The desorption pore size distributon of ZnO and HEN was determined by Barret-Joyner-

199

Halenda (BJH) procedure and the plot is displayed in Fig. 2b. The pore size distribution pattern 10


Page 11 of 36


200

of ZnO shows the tallest peak at 18 Å along with two other scattering peaks. While HEN shows

201

trend of pore size distribution adsorption similar to ZnO with the highest peak around 12 Å. The

202

intercalation of HE into the interlayer ZLH had changed the pore size and pore volume of the

203

obtained nanolayered material HEN higher than its host. The BJH pore diameter and volume

204

was increased from 111 Å (ZnO) to 121 Å (HEN) and 0.01 cm3g-1 (ZnO) and 0.03 (HEN),

205

respectively.

206

3.3 Morphology and Particle Size Distribution of Intercalated Compound

207

The surface morphology of ZnO and HEN captured on FESEM are presented in Fig. 3a

208

and 3b respectively. The morphology of zinc oxide exhibited non-uniform granular structure

209

with no specific shapes while HEN showed multilayer of non-uniform broad and flat shapes and

210

sizes. This shows that the transformation of ZnO into an intercalated compound resulted changes

211

in the surface morphology.

212

Internal microstructure image of ZnO and HEN examined on TEM are shown in Fig. 4a

213

and 4b respectively. It is observed that ZnO has granular shape and this corresponds nicely with

214

FESEM image (Fig. 3a). On the other hand, HEN exhibited non-uniform shape, overlapping

215

each other. The particle size distribution (PSD) of ZnO and HEN on TEM images were measured

216

using UTHSCSA image tool software. The PSD was found to be 31 to 157 nm for ZnO and 23 to

217

87 nm for HEN. The average PSD of ZnO and HEN was estimated to be 108 + 32 nm and 49 +

218

15 nm respectively. High standard deviation is attributed to the non uniform shapes and irregular

219

sizes for both ZnO and HEN.

220

The PSD of ZnO and HEN (Fig. 5a and 5b) were also carried out using DLS (dynamic

221

light scattering) measurement, however the results were not in good agreement with TEM 11



Page 12 of 36

222

measurement. The TEM result is more meaningful due to its direct observation. In addition, the

223

tendency of both ZnO and HEN to re-agglomerate during the DLS analysis cannot be ruled out.

224

Summary of the results of particle size distribution from TEM and DLS are given in Table 2.

225

3.4 Release Behavior of HE into Distilled Water at Various pHs

226

A series of distilled water at various pH were prepared to study the effect of different

227

pHs on the release behavior of HE from the interlayer spacing of the nanolayered material, HEN.

228

The release profiles of HE from the organic-inorganic layer of its nanomaterial, HEN into pH 4,

229

6.5 and 8 are depicted in Fig. 6. All the release profiles show a broad curve indicating a constant

230

release of the anion from the nanomaterial into the solution at various pHs. Generally, the

231

percentage anion release was observed to increase constantly in the range of 800 mins from the

232

starting time of dispersion of the nanomaterial in the pH solution, followed by a slower release

233

before attaining equilibrium rate after 1100 mins.

234

A high amount of anion release was observed in the first 200 mins with percentage

235

release recorded to be 34, 26 and 36% in distilled water at pH 4, 6.5 and 8, respectively. This is

236

due to the “burst effect” which is caused by the high release of anions that are weakly adsorbed

237

on the external surface of layered ZLH

238

anion release has increased up to 26, 18 and 23% to obtain the accumulated release of 60, 44

239

and 59% for pH 4, 6.5 and 8, respectively. The following 400 to 800 mins, the rate of HE release

240

into pH 4, 6.5 and 8 has increases in the range of 18 to 20% to produce a total amount of anion

241

release of 80, 64 and 77%, respectively. It was observed that the release of HE into pH 4 and 8

242

are faster than at pH 6.5. This is due to the partial dissolution of ZLH occurred with the collapsed

243

of nanolayered structure and the releasing of pheromone anions to the environment48,51-53. This

244

indicate that ZLH is not stable at high and low pHs48,54 which causes the interlamallae layer to

48-50

. Within the ranges of 200 to 400 mins, the rate of

12


Page 13 of 36


245

dissolve and affect the composition amount of HE from the nanomaterial. Pan et al55 reported

246

release of drug (doxifluridine) at high pH with release of 60% at pH 6.8 and 72% at pH 7.4 from

247

Mg/AL layered hydroxides.

248

While at pH 6.5, ZLH is more stable and the release of HE is slower as compared to pH 4

249

and 8. The release could be related to the diffusion of anion from the interlayer as suggested by

250

Gao et al.56 that the deintercalation of intercalated anion, vitamin C in deionized water followed

251

the diffusion mechanism whereby the rate of drug diffusion is controlled by the rigidity of the

252

layers and the diffusion pathlength. After diffusion, the release of HE anions were proceeded to

253

anion exchange process. Gao et al.56 reported 36% of vitamin C was released into deionized

254

water from its MgAl intercalated compound. In this study, at pH 6.5 medium, HE could be ion

255

exchange with carbonate anion from the dissolution of carbon dioxide from atmosphere in

256

distilled water

257

chlorine anion from HCl solution for preparation of pH 4 solution51. Excess OH- in pH 8 medium

258

might contribute to the ion exchange process of HE.

57

. The ion exchange process of HE in pH 4 medium could be related to the

259

However, 800 mins and beyond, a slower release process of HE was observed at the rate

260

of 2 to 5%. This could be attributed to the release of HE ions from deeper interlayer sites 52 and

261

ion exchanged with anions in the solution and later proceeded through diffusion within the

262

interlayer space53. The saturated amount of HE released into solutions of pH 4, 6.5 and and 8 was

263

achieved at 84, 73 and 83%, at 1139, 1159 and 1143 mins, respectively. It was found that HE

264

molecules did not be fully released to 100%, could be attributed that the anions were strongly

265

held to positive charge of host resulting the reduced diffusion from the interlayer into medium

266

solution

58

and some remains entrapped inside the inorganic layered host. At equilibrium stage,

13



Page 14 of 36

267

the interlayer anions cannot be exchanged completely and the intercalated anions would be

268

released continously in a slow manner51.

269

3.5 Release Kinetics of HE from HEN

270

In order to understand the release mechanism of HE from the nanolayered material, HEN

271

into different pHs solution, the release data were fitted into various kinetic models. The highest

272

correlation coefficient values were used to determine the best kinetic models that governs the

273

kinetic release. The three kinetic equation as given below were used in this work;

274

Pseudo-first order

:

In (qe-qt) = In qe – k1t

(4)

275

Pseudo-second order

:

t/qt = 1/k2qe2 + t/qe

(5)

276

Parabolic diffusion

:

(1-Mt/Mo)/t = k t-0.5 + b

(6)

277

where qe, qt represents the equilibrium release amount and release amount of anion at any time

278

respectively, t and k is the apparent release-rate constant respectively while Mt and Mo

279

correspond to the chemical content remaining in the ZLH at zero time and release time, t,

280

respectively.

281

The plots for all the fitting are given in Fig. 7 and the parameters obtained are

282

summarized in Table 3. It was found that the psuedo-second order model offers a more

283

satisfactory description of the kinetics release of HE from its nanohybrid, HEN compared to

284

other kinetic models use in this work. The highest correlation coeffiecient, R2 were obtained

285

from psuedo-second order model equation with value of 0.9357, 0.9692 and 0.9833 for release of

286

HE into pH 4, 6.5 and 8 solution respectively. The t1/2 value, which represented the time taken

287

for HE concentration to be half of its accumulated release and the release rate values, k of HE

288

into different pH media were calculated and tabulated in Table 3. t1/2 and k values of HE are

289

250 minutes and 1.81x 10-5 g/mg.min (pH 4), 301 minutes and 1.24x 10-5 g/mg.min (pH 6.5), 14


Page 15 of 36


290

235 minutes and 2.69 x 10-5 g/mg.min (pH 8). This corresponds to the maximum accumulated

291

values of 84, 73 and 83% HE in pH 4, 6.5 and 8, respectively which strongly indicates that the

292

release of HE from HEN into pH 6.5 is slower compare to pH. 4 and 8. HE release from HEN

293

into pH 6.5 solution has the lowest k rate which delivers small amount of HE at longer duration

294

time. The release of hexenoic acid from its interlamellae of its organic-inorganic nanohybrid at

295

various pHs was found to be in a controlled manner governed by the pseudo-second order kinetic

296

model. The amount of HE released at pH 4 and 8 is higher than pH 6.5 with the order of pH 4 =

297

8 > 6.5.

298

3.5 Phytotoxicity Test

299

In order to investigate the toxicity of HEN to plant, a phytotoxicity test

of

the

300

nanolayered material was tested using two seed types i.e. green beans and wheat seeds

301

germinated on distilled water and series of concentrations of 0.01g/100 mL, 0.1g/100mL and

302

1g/100mL of ZnO, HE and HEN, respectively. The results of seed germination are shown in Fig.

303

8 and Table 4. In Table 4, it can be seen that the percentage seed germination of green beans on

304

untreated sample i.e. distilled water alone was recorded to be the lowest percentage of 91% when

305

compared to the other chemical treatments. The percentage seed germination of green beans

306

exposed to ZnO extract solution increased to 93, 96 and 98% with increment to ZnO

307

concentration of 0.01g/100 mL, 0.1g/100mL and 1g/100mL, respectively. This could be

308

attributed to the availability of Zn from ZnO which is required for plant development. For free

309

anion, HE, at 0.01g/100 mL, 0.1g/100mL concentration the percentage seed germination was 98

310

and 96% respectively. However, at 1g/100mL HE, green beans failed to germinate, which

311

indicate that it is not suitable and toxic for seed germination at high concentration. This is in

312

contrast with nanolayered material, HEN that seed germination of green beans was successful 15



Page 16 of 36

313

in all the concentrations tested. HEN shows high percentage of green beans germination of

314

98% at 0.01g/100 mL, 0.1g/100mL and slightly reduced to 96% at 1g/100 mL concentration. The

315

seed germination result demonstrated that the nanolayered material, HEN is not toxic to plant

316

under our experimental conditions.

317

Wheat seeds gave slightly different response compared to green beans. In distilled water,

318

wheat seeds recorded 82% of germination and the percentage increased to 84 and 87 % when it

319

was treated with 0.1g/100mL and 1g/100mL ZnO, respectively. On the other hand, the

320

germination of wheat seed was found to survive at 0.01g/100 mL HE with 89% but at higher

321

concentration of HE, no wheat seed was found to be germinated. For HEN, wheat seeds were

322

successfully germinated at all concentrations with recorded values of 73% (0.1g/100 mL), 78%

323

(0.1g/100 mL) and 82% (1g/100 mL) for seed germination respectively. This shows that when

324

HE is converted into nanolayered structure material of HEN, the phytotoxicity of HEN on both

325

green beans and wheat seeds was found non-toxic to plant and safe for seed germination. HE

326

from the nanohybrid could be released to surroundings in a sustained manner when in contact

327

with anions of higher affinity such as carbonate in air. The release of small amount of HE from

328

its nanohybrid to surroundings did not toxicate the seed germination as compared to its free

329

anion, HE. Partial dissolution of Zn from the collapsed of ZLH interlayer structure during the

330

anion exchange are used up and increases the seed germination.

331

Radical seed length for both seeds on untreated sample and at different chemical

332

treatments were measured to determine the effect of HE, HEN and ZnO on the radical seed

333

growth and the results are depicted in Fig. 9 and Table 5. Fig. 9 shows that the radical seed

334

length of both green beans and wheat seeds gave higher values for all the chemical treatments

335

when compared to untreated sample, distilled water. The radical seed growth for both seeds 16


Page 17 of 36


336

increases as the amount of ZnO increased. As expected, this is due to the effect of ZnO as zinc

337

source as an essential micronutrient for plant development which has important effect on the

338

radical seed growth.

339

The radical seed length of both seeds germinated on free anion, HE recorded lower

340

values than its nanomaterial, HEN as shown in Table 5. HEN recorded higher radical seed length

341

for green beans measuring at 31.2 mm (0.01g/100 mL) and 27.1mm (0.1g/100 mL) than its

342

counterpart, HE with values of 25.9 mm (0.01g/100 mL) and 20.7 mm (0.1g/100 mL). While

343

radical seed length for wheat seed recorded 10.6 mm (0.01 g/100mL HEN) compared to 7.9 mm

344

(0.01g/100 mL HE). This could be due to the effect of ZLH that enhance the properties of HEN

345

and also contribute Zn source as important micronutrient for plant development. This further

346

indicates that the nanolayered material, HEN influence and improve the radical seed growth

347

compare to its free anion, HE. The controlled release properties of the nanohybrid could

348

contribute to the occurred situation. HE anion is released slowly from its nanohybrid to the

349

surroundings and used by seed for further development. This study suggests the possibility of

350

zinc layered hydroxide as a promising encapsulate material for insect pheromone with controlled

351

release capabilities for the generation of environmentally-safe pesticide for crop protection.

352

Abbreviations

353

ZLH = zinc layered hydroxide ; ZnO = zinc oxide; LHS = layered hydroxide salt;

354

HE = hexenoic acid (C6H10O6); HEN = hexenoic acid nanohybrid; NaOH = sodium hydroxide;

355

FESEM = field emission scanning electron microscope; TEM = transmission electron

356

microscope; PSD = particle size distribution ; DLS = dynamic light scattering (DLS); PCCS =

357

photon-cross correlation spectroscopy.

358 17



Page 18 of 36

359

Acknowledgement

360

Funding for this research was provided by the Ministry of Higher Education (MOHE) under the

361

Grant No. FRGS/1/11/SG/UPM/01/2 (vot. No. 5524165) is greatly appreciated. The authors

362

gratefully acknowledged FRIM for sponsor for RA in her MSC program.

363 364

References

365

1. Vijiandran, J.R.; Xaviar, A.; Ho, S.H.; Zaharah, A.R. Leaching losses of nutrients and

366

performances of oil palm in marine clay soils. In Wan Rasidah, K. et al Eds. Proceedings of

367

Soil Science Conference of Malaysia. 2012, 68-71.

368

2. Stephenson, G.R.Pesticide use and world food production:risks and benefits. In Coats, J.R.

369

;Yamamoto H., Eds. Environment fate and effects of pesticides. ACS Symposium series.

370

Washington, 2003, 853, 261-270.

371 372

3. Ahmed, A. Novel utilizations of conventional agrochemicals by controlled release formulations. Mat.Sc.and Eng.1996, C4, 83-98.

373

4. Final report of the sub-group of the advisory committee on pesticides of alternatives to

374

conventional pest control techniques in the UK:A scoping study of the potential for their

375

wider use. ACP. 2003

376 377

5. Mansoor, A.S.; Nasreen, M.; Ahmed, A.B. Use of sex pheromones and light traps for monitoring the population of adult moths of control bollworms. J. Agri. 2012, 27(3),435-442.

378

6. Petroski, R.J.; Tellez M.R.;Behle, R.W. Semiochemicals in pest and weed control: An

379

introduction. ACS symposium series; American Chemical Society. Washington, DC. 2005.

380

7. Jana, T.; Roy,B.C.;Maiti, S. Biodegradeable Film. 6. Modification of the film for control

381

release of insecticides. Eur. Poly. J. 2001,37,861-864. 18


Page 19 of 36

382 383


8. Yosha, I.; Shani, A.;Magdassi, S. Slow release of pheromone to the atmosphere from gelatinalginate beads. J.Agr. Food Chem. 2008,56,8045-8049.

384

9. Hwang, I.C.; Kim, T.H.; Bang, S.H.; Kim, K.S.; Kwon, H.R.;Seo, M.J.; Youn, Y.N.; Park

385

H.J.; Yasunaga-Aoki, C.; Yu, Y.M.; Insecticidal effect of controlled release formulations of

386

etofenprox based on nano-bio technique. J. of Fac.Agr. Kyushu Univ. 2011,56,33-40.

387 388

10. Li, M.; Huang, Q.; Wu, Y. A novel chitosan-poly(lactide) copolymer and its submicron particles as imidacloprid carriers. Pest Mgt. Sc. 2011,67,831-836.

389

11. Loha, K.M.; Shakil, N.A.; Kumar, J.; Singh, M.K.; Srivasta, C. Bio-efficacy evaluation of

390

nanoformulation of β-cyfluthrin against Callosobruchus maculatus (Coleoptera:Bruchidae).

391

J.Env. Sc. Health. Part b-Pesticides Food Cont. Agric. Waste. 2012, 47, 687-691.

392 393

12. Melanie, K.; Thilo, H. Nanopesticide research: Current trends and future priorities. Env. Int. 2014, 63, 224-235.

394

13. Anjali, C.H.; Sharma, Y.; Mukherjee, A.; Chandrasekaran, N. Neem oil (Azadirachta indica)

395

nanoemulsion as potent larvicidal agent against Culex quinquefasciatus. Pest Man. Sci. 2012,

396

68(2),158-163.

397

14. Yang, F.L.; Li, X.G.; Zhu, C.L.; Lei, C.L. Structural characterization of nanoparticles loaded

398

with garlic essential oil and their insecticidal activity against T.castaneum (Herbst)

399

(Coleoptera:Tenebrionidae). J.Agrc. Food Chem. 2009, 57(21),10156-10162.

400

15. Mingming, A.; Yuncong, Z.; Shun, H.; Deguang, L.; Pingliang, L.; Jianqiang, L. Preparation

401

and characterization of 1-naphthylacetic acid-silica conjugated nanospheres for enhancement

402

of controlled-released performance. Nanotech. 2013,24(3):035601-035608.

403 404

16. Bhagat, D.; Samantha, S.K.; Bhattacharya, S. Efficient management of fruit pests by pheromone nanogels. Sci Rep 2013;3.http://dx.doi.org/10.1038/srep01294. 19



Page 20 of 36

405

17. Xiang, C.; Taylor, A.G.; Hinestroza, J. P.; Frey, M.W. Controlled release non ionic

406

compounds from poy(lactic acid)/cellulose nanocrystal nanocomposite fibers.J Appl Polym

407

Sci 2013,127(1),79-86.

408 409 410 411 412 413

18. Hellman, C.; Greiner, A.; Wendorff, J.H. Design of pheromone releasing nanofibers for plant protection. Polym. Adv. Technol. 2011, 22(4), 407-413. 19. Cavani, F.; Trifiro, F.; Vaccari, A. Hydrotalcite-type anionic clays:preparation, properties and applications. Catalysis Today. 1991, 11:173-301. 20. Kayuga, W.; Hassan, ;Z., Jones, W.Catalytic properties of layered double hydroxides and their calcined derivatives. Inor. Chem. 1996, 35:5970-5974.

414

21. Jiao, F.P.; Chen, X.Q.; Fu, Z.D.; Hu, Y.H.; Wang, Y.H. Intercalation of Mg-Al layered double

415

hydroxides by (+)-dibenzoyl-d-tartaric acid: preparation and characterization. J.Mol.Struct.

416

2009, 921:328-332.

417

22. Kovanda, F.; Jindová, E.; Douśová, B.; Kolouśek, D.; Pleśtil, J.; Sedláková, Z.Layered double

418

hydroxides intercalated with organic anions and their application in preparation of

419

ldh/polymer nanocomposites. Acta geodynamica et geomaterialla 2009, 6, No.1(153):111-

420

119.

421

23. Manzi-Nshuti, C. ; Hossenlopp, J.M.; Wilkie, W.A. Fire retardency of melamine and zinc

422

layered double hudroxide in poly(methyl methacrylate). Poly Degrad. and Stability. 2008,

423

93:1855-1863.

424

24. Xu, S.; Zhang, L.; Lin, X.; Li, R.; Zhang, F.; Layered double hydroxides used as flame

425

retardant for engineering plastic acrylonitrile-butadiene-styrene (ABS). J. Phy. and Chem.

426

2012, 73:1514-1517.

20


Page 21 of 36


427

25. Hang, T.T.X.; Truc, T.A.; Duong, N.T.; Vu, P.G.; Hoang, T. Preparation and characterization

428

of nanocontainers of corrosion inhibitor based on layered double hydroxides. Appl. Clay Sc.

429

2012, 67-68:18-25.

430 431

26. Zhi, P.X.; Lu, G.Q.M.; Layered double hydroxide nanomaterials as potential cellular drug delivery agents. Pure Appl. Chem. 2006, 78(9): 1771-1779.

432

27. Qina, L.; Xuea, M.; Wanga,M.; Zhua, R.; Wanga, S.; Sunb, J. The in vitro and in vivo anti-

433

tumor effect of layered double hydroxides nanoparticles as delivery for podophylliotoxin Int.

434

J. Pharm. 2010, 388;223-230.

435 436

28. Cardoso, L.P.; Celis, R.; Cornejo, J.; Valim, J.B. Layered double hydroxides as supports for the slow release of acid herbicides. J.Agric. Food Chem. 2006, 54:5968-5975.

437

29. Xu, Y.; Zhang, J.;Zhou, J.; Chen, C.; Liu, Q. ; Qian, G.; Xu, Z.P. CN and heavy metal

438

removal through formation of layered double hydroxides from mixed CN-containing

439

electroplating wastewaters and pickle acid liquor. Chem. Eng. J. 2013, 215-216:411-417.

440

30. Lu, H.; Zhu, Z.; Zhang, H.; Qiu, Y. Simultaneous removal of arsenate and antimore in

441

simulated and practical water samples by adsorption onto Zn/Fe layered double hydroxide.

442

Chem. Eng. J. 2015, 276:365-375.

443

31. Hussein, M.Z.; Hashim, N.; Yahya, A.; Zainal, Z. Synthesis and characterization of [4-(2,4-

444

dichlorophenoxybutyrate)-zinc layered hydroxide] nanohybrid. Solid State Sc. 2010,12,770-

445

775.

446 447

32. Asayo, K.; Fujihara, S. Layered single metal hydroxide/ethylene glycol as a new class of hybrid material. Inorg Chem. 2006, 45,415-418.

21



Page 22 of 36

448

33. Hussein, M.Z.; Abd. Rahman,N.S.S.; Sarijo, S.H.; Zainal, Z. Herbicide-intercalated zinc

449

layered hydroxide for a dual-guest controlled release formulation. Int. J. Mol. Sci. 2012,

450

13,7328-7342.

451

34. Yang, J.H.; Han, Y.S.; Park, M.; Park, T.; Hwang, S.J.; Choy, J.H. New inorgan-based drug

452

delivery system of indole-3 acetic acid-layered metal hydroxide nanohybrids with controlled

453

release rate. Chem Mater. 2007, 19:2679-2685.

454

35. Hussein, M.Z.; Ali,,S.H.A.; Zainal, Z.; Hakim, M.N. Development of antipropoliferative

455

nanohybrid compound with controlled release property using ellagic acid as the active agent.

456

Int. J. Nanomed. 2011, .,1373-1383.

457

36. Rocca, E.; Caillet, C.; Mesbah, A.; Francois, M.; Steinmetz, J. Intercalation in zinc-layered

458

hydroxide: Zinc hydroxyheptanoate used as protective material on zinc. Chem.Mater.2006,

459

18:6186-6193.

460

37. Hussein, M.Z.; Nazaruddin, N.F.; Sarijo S.H.; Yarmo, M.A.Synthesis of a layered organic-

461

inorganic nanohybrid of 4-chlorophenoxyacetate-zinc layered hydroxide with sustained

462

release properties. J. Nanomat. 2012 Article ID 860352.9 pages. Doi:10.1155/2012/860352.

463

38. Marangoni, R.; Ramos, L.P.; Wypych, F. New multifunctional materials obtained by the

464

intercalation of anionic dyes into layered hydroxide nitrate followed by dispersion into

465

Poly(vinyl alcohol) (PVA). J. Colloid Interface Sci. 2009, 330:303-309.

466 467

39. Cursino, A.C.T.; Gardolinski, J.; Wypych, F. Intercalation of anionic organic ultraviolet ray absorbers into layered zinc hydroxide nitrate. J Colloid Interface Sc. 2010, 347(1),49-55.

468

40. Mohsin, S.M.N.; Hussein, M.Z.; Sarijo, S.H.; Fakurazi, S.; Aruselvan, P. Synthesis of

469

(cinnamate-zinc layered hydroxide) intercalation compound for sunscreen application. Chem

470

Cent. J. 2013,7(26), 1-12. 22


Page 23 of 36


471

41. Kim, T.W.; Hwang, S-J.; Park,Y.; Choi,W.; Choy, J-H.Chemical bonding character and

472

physicochemical properties of mesoporous zinc oxide-layered titanate nanocomposites. J.Phy.

473

Chem.C. 2007,111,1658-1664.

474

42. Choy, J.H.; Kwak, S.Y.; Park, J.S.; Jeong, Y.J.; Porter, J. Intercalative nanohybrids of

475

nucleoside monophosphates and DNA in layered metal hydroxide. J. Am.Chem.Soc.1999,

476

121(6),1399-1400.

477

43. Bashi, A.M,.; Khadim, A.A.; Hashim, A.S. Characterizations of synthesized nanohybrid octyl

478

gallate with ZNO LHS and determined its anti microbial activities. Chem. & Mater. Res.

479

2014, 6(9), 7-15.

480

44. Hwang, S.H.; Han, Y.S.; Choy, J.H. Intercalation of functional organic molecules with

481

pharmaceutical, cosmecuetical and nuetraceutical functions into layered double hydroxides

482

and zinc basic salts. Bul.-Kor. Chem. Soc. 2001,22(9), 1019-1022.

483 484 485 486 487 488

45. Fageri,N.K.; Baligar,V.C.; Clark, R.B. Micronutrients in crop production. Adv.Agron. 2002, 77,185-268. 46. Keeling, A.A.; Paton, I.K.; Mullet, J.A.J. Germination and growth of plants in media containing unstable refuse-derived compost. Soil Biol. Boichem. 1994, 26(6), 767-772. 47. Degan, A.; Kosec, M. Effect of pH and impurities on the surface charge of zinc oxide in aqueous solution. J. Eur. Ceram. Soc. 2000, 20,667-673.

489

48. Sarijo, S.H.; Hussein, M.Z.; Yahya, A.; Zainal, Z. Effect of incoming and outgoing

490

exchangeable anions on the release kinetics of phenoxyherbicides nanohybrids. J. Haz. Mat .

491

2010, 182, 563-569.

23



Page 24 of 36

492

49. Biswick, T.; Park, D-H.; Shul, Y-G.; Choy, J-H. P-coumaric acid basic salt nanohybrid for

493

controlled release and sustained antioxidant activity. J. Phy. Chem. of Solids.2010, 71:647-

494

649.

495

50. Romain, M.S.; Holgado, M.J.; Salinas, B; Rives,V. Drug release from layered double

496

hyfroxides and from polylactic acid (PLA) nanocomposites. Appl. Clay Sc. 2013 (71) 1-7.

497

51. Xia, S-J; Ni, Z-M.; Xu, Q.; Hu, B-X.; Hu, J. Layered double hydroxides as supports for

498

intercalation and sustained release of antihypertensive drugs. J. Solid State Chem. 2008 ,

499

181:2610-2619.

500

52. Lima, E.; Flores, J.; Cruz, A.s.; Leyva-Gomez, G.; Krotzsh, E. Controlled release of ferulic

501

acid from a hybrid hydrtalcite and its application as an antioxidant for human fibroblasts.

502

Microporous and Mesoporous Mat. 2013, 181:1-7.

503

53. Costantino, U.; Ambrogi, V.; Nocchetti, M.; Perioli, L. Hydrotalcite-like compounds:

504

versatile layered host molecular anions with biological activity. Microporous and Mesoporous

505

Mat. 2008, 107:149-160.

506

54. Nabipour, H.; Sadr, M.H. Controlled release of diclofenac, an anti-inflammatory drug by

507

nanocomposting with layered zinc hydroxide. J. Porous Mater. 2015. 8pp.doi:

508

10.1007/s10934-015-99310-0.

509

55. Pan, D.; Zhang, H.; Duan, X. A novel organic-inorganic microhybrids containing anticancer

510

doxifluridine and layered double hydroxides:structure and controlled release properties.

511

Chem.Eng.Sci. 2010, 65:3762-3771.

512

56. Gao, X; Lei, L.; O’Hare, D.; Xie, J.; Gao, P.; Chang, T. Intercalation and controlled release

513

properties of vitamin C intercalated layered double hydroxide. J. Solid State Chem. 2013,

514

203:174-180. 24


Page 25 of 36


515

57. Hussein. M.Z.; Yahaya, A.; Zainal, Z.; Kian, L.H. Nanocomposite-based controlled release

516

formulation of an herbicide, 2,4-dichlorophenoxyacetate incapsulated in zinc-aluminium-

517

layered double hydroxide. Sc.Tech.Adv.Mater. 2005, 4pp. doi:10.1016/j.stam.2005.09.004.

518

58. Rives, V.; Arco, M.D.; Martin, C. Intercalation of drugs in layered double hydroxides and

519

their controlled release: A review. Appl. Clay Sc. 2014, 88-89:239-269.

25



0.4 M HEN

Page 26 of 36

20000 23.5 Å

23.47 Å 0.3 M HEN

24.64 Å

15000

0.2 M HEN 0.1 M HEN

10000 0.3M HEN

5000

ZNO

11.8 Å

HE 7.1 Å 20

40

60

Fig.1a PXRD patterns of HE, ZnO and HEN nanohybrids prepared at different concentrations of HE.

0

5

10

15

20

Fig.1b Slow scan of PXRD patterns of HEN nanohybrid prepared at 0.3 mol/L HE.

Abbreviations: ZnO, zinc oxide; HE, hexenoic acd; HEN, hexenoic acid nanohybrid (o = ZnO phase, peak from left to right is for 100, 002, 101, 101 reflections)

Trans-2-hexenoic acid

26


Page 27 of 36


40

1.8 1.6

2a

2b

ZnO

ZnO

1.4

30

P o r e V o lu m e (c m 3 /g )

V o lu m e a b s o r b e d a t S T P ( c m 3 /g )

35

25 20

HEN 15 10

1.2 1.0 0.8 0.6

HEN 0.4

5

0.2 0 0.0

0.2

0.4

0.6

0.8

Relative pressure (P/Po)

1.0

0.0 10

100

1000

Pore diameter (Å)

520 and HEN (a) and Barret-Joyner-Halenda method Fig.2 Adsorption-desorption isotherms for zinc oxide pore size distribution for zinc oxide and HEN (b). Abbreviations: ZnO, zinc oxide;HEN, hexenoic acid nanohybrid

27



3a

Page 28 of 36

3b

Fig. 3 FESEM micrograph of (a) ZnO and (b) HEN at 50,000 x magnification

4a

4b

Fig. 4 TEM micrograph of (a) ZnO and (b) HEN

28


Page 29 of 36


15

10

1.0

1.0

5a

0.8

8

5b 0.8

10

6 0.6

0.6 4

5

0.4

0.4 0.2

2 0.2

0 0.0

0 0

1000

2000

3000

0.0

4000

0

1000

2000

3000

Fig. 5 Particle size distribution studied using DLS for (a) ZnO and (b) HEN

100

pH 8 pH 6.5 pH 4

% Anion Release

80

60

40

20

0 0

200

400

600

800

1000

1200

1400

Time(min) Fig. 6 Release profiles of hexenoic acid (HE) from its nanohybrid (HEN) interlayers into distilled water at pH=4, 6.5 and 8.


29


A (Pseudo-first order)

Page 30 of 36

B (Pseudo-second order)

C (Parabolic diffusion)

18

1.0

pH 4 2 R =0.9130

12

t/qt

1.0

10 8

pH 4 R =0.9357

6 0.5

2

4

0.8

1-(M t/M o)

14

1-(Mt – Mo)

1.5

16

t/qt

Log(q –qt) lo g(q e-qet)

2.0

0.6

pH 4 2 R =0.8856

0.4

0.2

2 0.0

0 200

400

600

800

1000

1200

1400

0.0 0

200

400

Time (min)

1000

1200

1400

0

5

10

15

20

t

E (Pseudo-second order) 1.0

Equation

y = a + b*x

Weight

No Weighting

t/q t

t/qt

1 -(M t/M o )

15

10

0.5

5

0.0

0

40

0.96844

Adj. R-Square

1.0

35

6.09721

Residual Sum of Squares

1.5

30

pH 6.5 2 R =0.9692

0.5

F (Parabolic diffusion)

20

pH 6.5 2 R =0.9536

25

t^0.5

Time (min)

D (Pseudo-first order)

Log(q e–qt) lo g (q e -q t)

800

Time(min)

Time (min)

2.0

600

1-(Mt – Mo)

0

0.8

Value

Standard Error

1-(Mt/Mo)

Intercept

-0.05864

0.00302

1-(Mt/Mo)

Slope

0.03081

1.11508E-4

0.6

0.4

pH 6.5 R =0.9684 2

0.2

0.0

0

200

400

600

800

1000

1200

1400

0

0

200

Time(min)

800

1000

1200

pH 8 2 R =0.9411

1-(Mt – Mo)

10

0.8

8

0.6

6

0.4

4

0.2

1 -(M t/M o )

t/qt

t/q t

1.0

pH 8 2 R =0.9833

2 800

Time(min)

1000

Time (min)

1200

35

40

1400

0.6

0.4

pH 8 R =0.9111 2

0.2

0.0 600

30

0.8

12

400

25

1.0

14

1.2

200

20

16

1.4

0

15

I (Parabolic diffusion)

18

1.6

10

t^0.5 t0.5

H (Pseudo-second order)

2.0 1.8

5

1400

Time (min)

G (Pseudo-first order)

lo g (q e -q t)

600

Time(min)

Time (min)

Log(qe–qt)

400

0.0

0 0

200

400

600

800

1000

1200

1400

TimeTime(min) (min)

0

5

10

15

20

t

25

30

0.5 t^0.5

30 Fig. 7 Fitting the data of hexenoic acid released from its nanohybrid into distilled water at different pHs using first, pseudosecond order and parabolic diffusion models at pH4 (A-C), 6.5 (D-E) and 8 (G-I).


35

40

Page 31 of 36


Fig. 8 Phytotoxicity of green beans and wheat seeds in distilled water (water), zinc oxide (ZnO), hexenoic acid nanohybrid (HEN) and hexenoic acid (HE) at 0.01, 0.1 and 1.0 g/100mL concentration. The data were presented as mean + S.D.(n=90).

31



Page 32 of 36

Fig. 9 Radical seed growth of green beans and wheat seeds in distilled water (water), zinc oxide (ZnO), hexenoic acid nanohybrid (HEN) and hexenoic acid (HE) at 0.01, 0.1 and 1.0 g/100mL concentration . The results are given as mean + S.D. (n = 90)

32


Page 33 of 36


Table 1. Surface properties of ZnO and HEN Material

BET surface area (m2g-1)

BET BJH average pore desorption pore volume (cm3g-1) diameter (Å)

BJH average pore diameter (Å)

ZNO

6

0.01

64

111

HEN

4

0.03

297

121

Table 2 Particle size distribution (PSD) of ZnO and HEN analysed from DLS and TEM Mean diameter (nm)

Method

Sample

TEM

DLS

ZnO

108 + 32

579 + 12

HEN

49 + 15

257 + 3

33



Page 34 of 36

Table 3. Parameters derived from the fitting of the data obtained from the release of HE from HEN into distilled water at pH 4, 6.5 and 8. pH

Saturation

Correlation coefficient ,R

Release (%)

Pseudofirst order

Pseudosecond order

2

Pseudo-second order

Parabolic diffusion

Rate constant, k (g/mg.h) x 10-5

t1/2 (min)

4

84

0.9130

0.9357

0.8856

1.81

250

6.5

73

0.9536

0.9692

0.9684

1.24

301

8

83

0.9411

0.9833

0.9111

2.69

235

Table 4. Mean values of percentage seed germination of green beans and wheat seeds in distilled water (water), zinc oxide (ZnO), hexenoic acid nanohybrid (HEN) and hexenoic acid (HE) at different concentrations. Seed germination (%) Conc. g/100mL

Green beans Water

0

ZnO

HEN

Wheat seed HE

Water

ZnO

HEN

HE

91.11+0.47

-

-

-

82.22+0.55

-

-

-

0.01

-

93.33+0.82

97.78+0.47

97.78+0.77

-

80.00+0.82

73.33+0.94

88.89+0.85

0.10

-

95.56+0.47

97.78+0.65

95.56+0.47

-

84.44+0.65

77.78+0.45

0

1.00

-

97.78+0.55

95.56+0.72

0

-

86.67+0.75

82.22+0.65

0

34


Page 35 of 36


Table 5. Mean value of radical seed length of green beans and wheat seeds in distilled water (water), zinc oxide (ZnO), hexenoic acid nanohybrid (HEN) and hexenoic acid (HE) at different levels of concentration solution. (n=90). Radical seed length (mm) Conc. g/100mL

Green beans

Water 0

ZnO

Wheat seed

HEN

HE

Water

ZnO

HEN

HE

13.33+0.47

-

-

-

6.63+0.87

-

-

-

0.01

-

28.65+0.88

31.22+0.56

25.9

-

9.34+0.69

10.65+0.49

7.93+0.75

0.10

-

33.55+0.54

27.35+0.78

20.7

-

10.22+0.78

15.67+0.85

0

1.00

-

35.25+0.79

22.22+0.85

0

-

13.15+0.94

12.28+0.77

0

35



Page 36 of 36

TOC GRAPHIC

ZLH (host) ZnO

Release media

Co-precipitation

+

Dissolution of host and diffusion of anion

ZLH (host)

Hexenoic Acid

Release of guest hexenoate from ZLH host into release media

ZLH (host)

100

Green beans seeds

) 35 m m ( 30 h t 25 g n el 20 d ee s 15 la ci d10 a R5

HEN

ZnO

HE

pH 8 pH 6.5 pH 4

80

% Anion Release

40

Water

Wheat seeds

60

40

20

0 0

0 0

0.01

0.1

1

0

0.01

0.1

200

400

600

800

1000

1200

Time(min)

1

Concentration (g/100 mL)

14 12

t/q t

10 8 6 4 2

40

40

35

35

ZnO 30 25 20

HEN 15 10 5

1.8 1.6

25 20 15

200

400

600

800

1000

1200

Time(min)

1.0 0.8

HEN

0.6

HEN 0.2

5 0.0

1400 0

10

0 0.0

0.2

0.4

0.6

0.8

1.0


Pseudo-second kinetic model

1.2

0.4

10

0 0

ZnO

ZnO

1.4

30

P o r e V o lu m e (c m 3 /g )

V olum e a bs orbe d at S T P (c m 3 /g)

16

V olum e a bs orbe d at S T P (c m 3 /g)

18

0.0

0.2

100

0.4

0.6 Pore diameter 0.8 (Å)

Adsorption-desorption Isotherm (BET) & BJH for ZnO and HEN


1000

1.0


36

1400

Evaluation of Controlled-Release Property and Phytotoxicity Effect of

Recommend Documents