SYNTHESIS AND CHARACTERIZATIONS OF COPPER NANOPARTICLES MATERIAL

- Investigating the influence of the parameters in the synthesis to the shape, size and distribution of copper nanoparticles forming such as reaction temperature, concentration of reduci

MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY

SCIENCE AND TECHNOLOGY

GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY

DOCTORAL THESIS ABSTRACTS’ INORGANIC CHEMISTRY

Ho Chi Minh City – 2016

The work was completed at:

Laboratory nano Lac Hong University, Laboratory of nano University of Natural Sciences, Institute for Materials Science Applications, Vietnam Academy of Science and Technology

Scientific guidance:

1 Assoc Prof Dr Nguyen Thi Phuong Phong

2 Dr Nguyen Thi Kim Phuong

At , ………, 2016

Can learn dissertation at the library:

National Library of Vietnam,

Library of Vietnam Academy of Science and Technology

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INTRODUCTION

In recent years, metal nanoparticles have attracted the attention of scientists due to their special properties that differ distinctly from the corresponding bulk materials by surface area to volume ratio and small size of them The ability to synthesize metal nanoparticles with different shapes and sizes is important to explore their applications in electronics, catalysis, sensors, optical and biological devices As most of these applications were governed by silver, gold and platinum However, the high cost constraint

of these metals restricted their applications in high volume production Presently, copper nanoparticles provided a good alternative of silver, gold and platinum nanoparticles because of their lower cost and catalytic activity, novel electronic, optical and magnetic properties or have antibacterial and antifungal properties Compared to other metal nanoparticles materials, the synthesis of copper nanoparticles are more difficult because of surface easy oxidizing of copper Therefore, the synthesis of copper nanoparticles with high purity would be a prerequisite for many application areas such as electricity - electronics, optics, catalysis, chemistry, biology

Up to now, several methods have been developed for the preparation of copper nanoparticles, such

as electron irradiation, the plasma process, chemical reduction method, in situ methods, two-step reduction method, thermal decomposition, electro-chemical reduction, reduction with ultrasound, microwave heating, supercritical methods,

Methods for the preparation of copper nanoparticles often common aim is to create nanoparticles at small sizes, high-stability for maximize applications However, a large number of published on synthetic

of copper nanoparticles still has many disadvantages, such as long time or high temperatures to complete the reaction, copper salts were chemically reduced in organic solvents under strict conditions, complex equipment systems, using capping agents not guarantee for the stability of the copper nanoparticles colloidal solutions Moreover, in the most recent published works, one of the most important applications

of the copper nanoparticles was tested for antibacterial to treat and kill drug-resistant microorganisms The results showed that copper nanoparticles colloidal solutions shown bactericidal activity with various gram (-), gram (+) cause disease in humans and animals Antifungal activity has not been mentioned much, only published work of Sahar M Ouda (2014) showed results in resistance against two strains of

plant pathogenic fungi on Botrytis cinerea is Alternaria alternate and Botrytis cinerea

On this basis, to overcome the disadvantages of synthetic copper nanoparticles with traditional chemical reaction system The content of the thesis is performed primarily with the synthesis of copper nanoparticles from the basic reaction systems including precursor, protection and reducing agent The limitations of these reaction system will be improved by the synthesis of the new systems that is a combination of two or three protections The combination of protective substances include protection of large molecular weight (PVA) and the protection of small molecular weight (trisodium citrate, ascorbic acid, CTAB) will make new rules of the synergistic effect in order to control the size and ensure the

stability of copper nanoparticles The thesis also clarified the physicochemical and biological characteristics of copper nanoparticles materials forming

The main contents of the thesis :

- Synthesis of the copper nanoparticles colloidal solutions by chemical reduction method with various precursors including copper oxalate, CuCl2, CuSO4, Cu(NO3)2 with hydrazine hydrate reducing agent, NaBH4; solvent glycerin and water, PVA and PVP protection, dispersants and protective agents: includingtrisodium citrate, ascorbic acid, CTAB

- Investigating the influence of the parameters in the synthesis to the shape, size and distribution of copper nanoparticles forming such as reaction temperature, concentration of reducing agent, the ratio of precursors and capping agent, solution pH

- Investigating the effect of the protective agent PVA, PVP, dispersants trisodium citrate, ascorbic acid protect auxiliaries, CTAB surfactant to the size and distribution of copper nanoparticles forming

- Investigating the specific physicochemical properties of copper nanoparticles forming by the modern analytical methods such as UV-Vis spectrum, X-ray diffraction (XRD), transmission electron microscopy (TEM)

- Investigating the antifungal activity and high killing ability against Corticium salmonicolor of the

copper nanoparticles colloidal solutions in the laboratory

Meaning of science and practice of the thesis

The thesis provides the basis for the study a systematic process of synthetic copper nanoparticles material overview domestic and foreignresearches

The results of the thesis will make clarify the rules of relationship between the size of copper nanoparticles forming with their specialcharacteristic is surface plasmon resonance via UV-Vis spectrum

By using a various of precursors, reducing agents, protective agents, the synthesis was performed with the survey parameters which control the size of copper nanoparticles forming, from that explore best bioavailability of the copper nanoparticles colloidal solutions This is also the scientific basis for subsequent applied research

The layout of the thesis:

The thesis has 128 pages with 8 tables, 108 figures Besides the introduction (3 pages), conclusions (2 pages), list of publications (2 pages) and references is updated to 2015 (9 pages), Annex (11 pages) The thesis is divided into 3 chapters as follows:

Chapter 1 : Overview 28 pages

Chapter 2 : Experimental 10 pages

Chapter 3 : Results and discussions 74 Pages

New contributions of the thesis

1 The first time thesis presented a systematic synthesis of the copper nanoparticles colloidal solutions base on chemical process with various precursors including copper oxalate, CuCl2, CuSO4,

Using thermal analysis DTA-TG to determine temperature ranges that CuC2O4 changes volume, creating the basis for the synthesis of copper nanoparticles from copper oxalate precursors

Using UV-Vis to determine the optical properties, the shift plasmon absorption peaks of copper nanoparticles Predicting the size of copper nanoparticle forming

Using X-ray diffraction (XRD) to determine the crystal structure, the purity of the copper nanoparticles

Using TEM to determine the morphology, size, combined with IT3 software to performparticle size distribution of copper nanoparticles

Using invitro testing method and spray directly method for testing antifungal activity and high

killing ability against C salmonicolor

3 RESULTS AND DISCUSSION 3.1 Synthesis of copper nanoparticles from copper oxalate precursors

3.1.2 Investigating the influence of the parameters on the size of copper nanoparticles

only occurs at temperatures of 270 °C Thus, with the result obtained, it can be concluded that the reaction formed copper nanopaticles occurs in both thermal reduction and chemical reduction mechanism with glycerin acts as both solvent and reduction.

- Curve (c): Samples were prepared at temperature of 230 oC, UV-Vis results showed that there was only the absorbance peak at 584 nm wavelength; do not appears absorbance peak of copper oxalate Thus, the reduction of copper oxalate has occurred almost completely

Copper nanoparticles were synthesized at 240 °C with unchanged reaction conditions Figure 3.6 and 3.7 are TEM images and particle size distributions of copper nanoparticles were synthesized at temperature of 230 °C and 240 °C At temperatures of 230 °C, the copper nanoparticles were created in spherical, had average diameter in range of 12 ± 3.6 nm (Figure 3.6) At temperature of 240 °C, copper nanoparticles have spherical with the average size in range of 29.6 ± 4.2 nm (Figure 3.7)

3.1.2.2 Effect of ratio CuC 2 O 4 /PVP

Table 3.1: Data and results of the copper nanoparticles were synthesized via ratio CuC2O4/PVP

Samples ratio (%)

CuC2O4/PVP

PVP (g) CuC2O4 (g)

Temperature (oC)

Absorbance peak (nm)

Average size via TEM (nm) K1 1

0.2

0.002

230

580 5.5 ± 2.3 K2 3 0.006 585 …

Figure 3.6: TEM and particle size distribution of CuPNs were synthesized at 230 oC)

Figure 3.6: TEM and particle size distribution of CuPNs were synthesized at 240 oC)

Figure 3.5: UV-Vis spectra of (a) copper

oxalate, (b) CuNPs + copper oxalate (220

°C, (c) and CuNPs (230 oC)

The results of TEM images in Figure 3.11 to Figure 3.13 show that, at concentration 1 % of CuC2O4

compared to PVP, copper nanoparticles were created mostly in spherical and distributed with the average size was 5.5 ± 2.3 nm (Figure 3.11) When concentration of CuC2O4 increase to 5 % (Figure 3.12) and 9

% (Figure 3.13) compared to PVP, copper nanoparticles forming were distributed in a wide range and agglomerated, with the average size 36 ± 5 nm and 68 ± 6.3 nm, respectively These results were consistent entirely compared to the shift position of maximum absorance peaks of copper nanoparticles in the UV-Vis spectrum from 580 to 600 nm

3.1.2.3 Effect of pH

Initial solution has neutral pH values, to investigate the influence of solution pH to the formation of copper nanoparticles colloidal solutions, the reaction solution was controlled pH by NaOH 0.1 M All samples were prepared with the same condition such as CuC2O4/PVP = 5 %, the reaction time was 2 minutes Preliminary experiments showed that when the solution pH of the mixture increases, the reaction

to form copper nanoparticles occurs at lower temperatures (140 °C)

Observe the change of color in the solution pH adjustment process as well as the actual reaction occured, the synthesis mechanism was changed and can be explained as follows: when adding NaOH to the mixture along with mixing, the mixture of copper oxalate in glycerol changed the color from light blue to dark blue, this could be the formation of complex [Cu(OH)4]2+, this complex could be bonded with PVP at the position of nitrogen and oxygen in a chain of molecule PVP Thus, potential redox (ECu2+/Cu) changed and made the ΔG value of reaction was more negative, therefor the temperature of the reaction in the case of high solution pH ( 8) will be lower (140 °C) compared to the reaction occurs at neutral solution pH (230 oC)

Figure 3.11: TEM image and particle

size distribution of CuNPs were

synthesized in the weight ratio

CuC2O4 /PVP = 1 %

Figure 3.12: TEM image and particle size distribution of CuNPs were synthesized in the weight ratio CuC2O4 /PVP = 5 %

Figure 3.13: TEM image and particle size distribution of CuNPs were synthesized in the weight ratio CuC2O4 /PVP = 9 %

Table 3.2: Data and results of the copper nanoparticles were synthesized via solution pH

Samples pH

Value

Ratio (%) CuC2O4/PVP

Temperature (oC)

Absorbance peak (nm)

Average size via TEM (nm) Particle shapeK3 7

5

230 592 36 ± 5 spherical D1 8

140

596 … D2 9 600 77 ± 5.3 spherical, polygon D3 10 601 82 ± 4.2 spherical, polygon D4 11 601 …

D5 12 600 96 ± 5.6 spherical, cubic,

triangle, rod

The results were summarized in Table 3.2 shows that, when the pH value increases in 8 ÷ 12, the copper nanoparticles had phenomenon of surface plasmon resonance corresponding to maximum absorbance peaks at wavelengths 596; 600; 601; 601; 600 nm, respectively TEM images showed that, when the solution pH increases, the size of copper nanoparticles forming also increases Specific, the average size of the copper nanoparticles at pH = 9, pH = 10, pH = 12 in range of 77 ± 5.3 nm (Figure 3.16), 82 nm ± 4.2 (Figure 3.17), 96 ± 5.6 nm (Figure 3.18), respectively In particular, copper nanoparticles were formed not only spherical but also cubic, triangle, rod, polygon

3.2 Synthesis of copper nanoparticles from copper salt precursors

3.2.1 Synthesis of copper nanoparticles from copper nitrate precursors

3.2.1.1 Effect of the concentration of reducing agent

Figure 3.22 to Figure 3.24 were TEM images and the particles size distribution of copper nanoparticles were synthesized at different concentrations of reducing agent Figure 3.22 shows that, at

HH concentration 0.1 M, the copper nanoparticles forming had smallest average size (14 ± 9 nm) However, the particle size distribution was created in the wide range from 6 ÷ 47 nm, mostly in spherical and combined of smaller particle size When increases HH concentrations from 0.2 to 0.5 M, the copper nanoparticles were created in spherical and monodisperse with average size 25 ± 5 nm (Figure 3.23) and

67 ± 9 nm (Figure 3.24) respectively

Figure 3.17: TEM image and particle size distribution of CuNPs were synthesized at solution pH = 10

Figure 3.18: TEM image and particle size distribution of CuNPs were synthesized at solution pH = 12

Figure 3.16: TEM image and particle

size distribution of CuNPs were

synthesized at solution pH = 9

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3.2.1.2 Effect of temperature

Figure 3.27 to 3.29 were TEM images and particle size distribution of the copper nanoparticles were synthesized at different temperatures At temperatures of 110 °C (Figure 3.27), the copper nanoparticles were created in spherical, monodisperse with average size of 17 ± 4 nm As the temperatures were higher, at 130 °C (Figure 3.28) and 150 °C (Figure 3.29) the copper nanoparticles forming had larger size, in a wide range with the average size 33 ± 5 nm and 50 ± 20 nm respectively

3.2.1.3 Effect of ratio Cu(NO3 ) 2 /PVP

Figure 3.33: TEM image and particle size distribution of CuNPs were synthesized with ratio of Cu(NO3)2/PVP

= 3 %

Figure 3.27: TEM image and particle

size distribution of CuNPs were

synthesized at 110 oC

Figure 3.29: TEM image and particle size distribution of CuNPs were synthesized at 150 oC

Figure 3.28: TEM image and particle size distribution of CuNPs were synthesized at 130 oC

Figure 3.22: TEM image and particle

size distribution of CuNPs were

synthesized at HH concentration 0.1 M

Figure 3.23: TEM image and particle size distribution of CuNPs were synthesized at HH concentration 0.2 M

Figure 3.24: TEM image and particle size distribution of CuNPs were synthesized at HH concentration 0.5 M

Figure 3.32: TEM image and particle

size distribution of CuNPs were

synthesized with ratio of Cu(NO3)2/PVP

= 1 %

Figure 3.33: TEM image and particle size distribution of CuNPs were synthesized with ratio of Cu(NO3)2/PVP

= 7 %

The results of TEM images from Figure 3:32 to 3:34 shows, as ratio of Cu(NO3)2/PVP was 1 %, the copper nanoparticles were formed mainly in spherical, monodisperse in range of 5 ± 3 nm (Figure 3.32) When the ratio of Cu(NO3)2/PVP increased to 3% and 7%, the copper nanoparticles were formed still in spherical and had diameter with average size of 15 ± 5 nm (Figure 3:33) and 22 ± 5 nm (Figure 3:34) respectively, the copper nanoparticles were agglomerated

 Summary and general discussion about the results of copper nanoparticles were synthesized

from copper oxalate and copper nitrate precursors when using only PVP as protective agent:

Table 3.4: Summary the results of copper nanoparticles were synthesized from copper oxalate and copper

Copper nitrate Glycerol

Hydrazine hydrate

Synthetic

conditions

Temp (oC)

Concentrations of reducing agents

Ratio Copper oxalate/ PVP

Temp (oC)

Concentrations

of reducing agents HH (M)

Ratio Copper nitrate/ PVP

210 ÷

240 … 1 ÷ 15% 110 ÷

160 01 ÷ 0,5 1 ÷ 9% Results of UV-

Ratio Copper oxalate/ PVP Temp

Concentrations

of reducing agents

Ratio Copper nitrate/ PVP

- At the best conditions, copper nanosparticles formming had the smallest average size (2.3 ± 5.5

nm from copper oxalate precursor and 5 ± 3 nm from copper nitrate precursor) However, these results were achieved by using with small amount of precursor (ratio precursor/protectant = 1 %), corresponding

to low concentration of copper nanoparticles were obtained in this procedure

Thus, it can be concluded that the copper nanoparticles were produced by using PVP (Mw: 1,000,000 g/mol) as a protective agent The steric stabilisation of copper nanoparticles were achieved in this procedure However, because of the large size of polymer molecules so it is difficult to coat all

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surfaces of the copper nanoparticles in order to protect them from their collision as the large amount of copper nanoparticles were formed Therefore, to control the copper nanoparticles in smaller size, with larger concentration then protective agents must have the ability of electrostatic stabilisation and steric stabilization simultaneously To solve this problem, in the next content of the thesis, copper nanoparticles

were produced by using trisodium citrate as second protective agents

With the results of the thesis has presented, the rules of the change size of copper nanoparticles according to the survey have been published with two articles in the Journal of Science and Technology 52 (1C), 2014 The rule of the change size with temperature, the result of XRD analysis were discussed in the article "Synergistic effect of citrate dispersant polymers on controlling size and capping growth of ultrafine copper nanoparticles" in the journal international Journal of Experimental Nanoscience, Vol 10, No 8, 2015 (IF: 0981)

3.2.1.4 Investigating the synthesis of copper nanoparticles in the present of trisodium citrate

a Effect of the amount of trisodium citrate

Figure 3.37 is UV-Vis spectra of copper nanoparticles were synthesized by amount of trisodium citrate The results showed that the position of the peak absorption were shifted by using trisodium citrate dispersant Specifically, UV–Vis absorbance of copper colloidal solution were prepared without trisodium citrate had absorbance peak at 584 nm wavelength (the curve M3), samples have trisodium citrate with low concentrations (trisodium citrate/Cu(NO3)2 = 0.1; 0.25) in which the UV–Vis absorbance of copper colloidal solution had absorption peaks at a wavelength of 574 and 568 nm respectively (the curve M2, M1) The samples (trisodium citrate/Cu(NO3)2 = 0.5; 0.75; 1.0; 1.25 ; 1.5) had the absorption peaks in the wavelength range from 562 to 563 nm Thus, it can be concluded that the size of copper nanoparticles were prepared in the presence of trisodium citrate smaller than copper nanoparticles were prepared without trisodium citrate The size of copper nanoparticles had stable and the smallest size which were synthesized by using ratio of trisodium citrate/Cu(NO3)2 ≥ 0.5

Figure 3.38 and 3.39 are TEM images of the copper nanoparticles colloidal solution were prepared

by using ratio of trisodium citrate/Cu(NO3)2 = 0.5 and 1.0 The results showed that copper nano particles

Figure 3.37: UV-Vis spectra of copper

nanoparticles were synthesized by

amount of trisodium citrate

Figure 3.38: TEM image and particle size distribution of CuNPs were synthesized by ratio of trisodium/Cu(NO3)2 = 0,5

Figure 3.39: TEM image and particle size distribution of CuNPs were synthesized by ratio of trisodium/Cu(NO3)2 = 1,0

generated mainly in the spherical, with narrow distribution, the average size of copper nanoparticles are 4

± 2 and 3 ± 2 nm respectively

b Effect of ratio Cu(NO 3 ) 2 /PVP in the presence of trisodium citrate

The copper nanoparticles colloidal solution were synthesized in the presence of trisodium citrate, the results of the UV-Vis analysis were shown in figure 3.41 The results shown that, the increase in the ratio of Cu(NO3)2/PVP, the intensity of absorbance peak also increased However, the shift of the maximum absorbance peak changed in narrow wavelength Specifically, when the ratio of Cu(NO3)2/PVP increased from 1 to 13 %, the position of the maximum absorbance peak was displayed at the wavelength from 562 to 564 nm As the ratio of Cu(NO3)2/ PVP increased to 14 and 15

%, the position of maximum absorbance peak shifted to longer wavelengths (two the tallest peaks) at 566 and 568 nm respectively These signals indicated that the larger of the particles were prepared by using the ratio of Cu(NO3)2/PVP greater than 13 %

Figure 3.42, 3.38 and 3.43 are TEM images of copper nanoparticles colloidal solutions which were prepared by using the ratio of Cu(NO3)2/PVP = 5 %, 7 % and 9 % in the presence of trisodium citrate The results shown that, with the ratio of Cu(NO3)2/PVP = 5 %, the copper nanoparticles were generated mainly in the spherical, with narrow distribution, its diameter appears in a range of the average size of 4 ±

1 nm (Figure 3.42) Copper nanoparticles were created with similar results by using the ratio of Cu(NO3)2/PVP = 7 % and 9 %, its diameter appears in a range of the average size of 4 ± 2 nm (Figure 3.38 ) and 3 ± 2 nm (Figure 3.43) respectively These results fited perfectly with the results of UV-Vis analysis in Figure 3.41 This study will be the basis for the syntheis of copper nanoparticles with narrow distribution, small size and high performance

3.2.2 Synthesis of copper nanoparticles from copper cloride precursors

3.2.2.1 The basis on the synthesis of copper nanoparticles from copper chloride precursors

Based on the results from the synthesis of copper nanoparticles from copper nitrate salt, this study will focus on the synthesis of copper nanopaticles colloidal solution from copper chloride sprecursor The process was performed according to the synthesis of copper nitrate precursor, the parameters of the investigating will be prepared with the reaction agents including copper chloride precursor, hydrazine

Figure 3.41: UV–Vis spectra of copper

nanoparticles were synthesized by using

ratio of Cu(NO3)2/PVP from 1 to 15 %

Figure 3.42: TEM image and particle size distribution of CuNPs were synthesized by using ratio of Cu(NO 3 ) 2 /PVP = 5 %

Figure 3.43: TEM image and particle size distribution of CuNPs were synthesized by using ratio of Cu(NO3)2/PVP = 9 %

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hydrate reducing agent, protective agent PVP (MW = 58,000 g/mol), solvent glycerol, trisodium citrate dispersant agent The best parameters were used to synthesize copper nanoparticles colloidal solution by using PVA (Mw = 60,000 g/mol) as protective agent The results from these investigating will be collated with the result of the synthesis copper nanoparticles from copper nitrate precursors From that, the rules

of the synergistic effect of large molecular weights (PVP, PVA) and small molecular weight (trisodium citrate) will be made clearly, the best system protection for the synthesis of copper nanoparticles from this conclution will be clarified

3.2.2.2 investigating of parameters on the size of copper nanoparticles

According to the results of Xiao-Feng Tang [13], Mustafa BICER [16], Mohammad Vaseem [18], ZHANG Qiu-li [21] as they synthesized copper nanoparticles by chemical reduction method with the different of reaction agents (table 1.1) or in the study with copper xalate and copper nitrate precursors of the thesis The parameters such as temperature or concentration of the reducing agent has strong influence

on the size and distribution of the copper nanoparticles forming However, the relationship between the size, the distribution of particles with the parameters of the synthesis in various reaction systems still need to clarify In this study, the effect of various parameters on the size and distribution of copper nanoparticles will be clarified when the protective polymer (PVP, PVA) and trisodium citrate were used together

a Effect of temperature

Figure 3:45 is UV-Vis spectra of copper nanoparticles colloidal solution which were synthesized at different temperatures The results shown that, when the temperature increased from 100 to 160 °C, the position of the maximum absorbance peak unchanged or changed very little The absorbance peak appeared at the wavelength from 562 to 564 nm These results predicted that the size of copper nanoparticles forming changed a little when temperature were controlled from 100 to 160 °C In addition,

in the range of wavelength 400 ÷ 500 nm does not appear strange peaks, which may be concluded that the copper nanoparticles were created by protected surface, not oxidized, the product has high purity and do not has Cu2O On other hand, compared to the the results of the investigating according to the temperature from copper nitrate It could be confirmed the role of trisodium citrate as dispersant agent to controll the

Figure 3.45: UV–Vis spectra of copper

nanoparticles were synthesized from copper

chloride at diffirent temp from 100 to 160 oC

Hình 3.47: UV–Vis spectra of copper nanoparticles were synthesized with various of reducing agent concentration hydrazinezin hydrate from 0,1 to 0,7M