Summary of environmental technique doctoral thesis: Synthesis of silver, copper, iron nanoparticles and their applications in controlling cyanobacterial blooms in the fresh water body

The objectives of the thesis: Research, fabricate and determine the characteristic of three nanomaterials (silver, copper and iron) and evaluate the ability to inhibit the cyanobacteria of nanomaterials in fresh water bodies.

TRAN THI THU HUONG

SYNTHESIS OF SILVER, COPPER, IRON

NANOPARTICLES AND THEIR APPLICATIONS IN CONTROLLING CYANOBACTERIAL IN THE FRESH

AND TRAINING SCIENCE AND TECHNOLOGY

GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY

-and Technology, Vietnam Academy of Science -and Technology

Scientific Supervisor 1: Assoc Prof Dr Duong Thi Thuy

Scientific Supervisor 2: Dr Ha Phuong Thu

This thesis can be found at:

- The library of the Graduate University of Science and Technology

- National Library of Viet Nam

INTRODUCTION OF THESIS

1 The necessary of the thesis

In recent years, pollution of soil, water and air has become a serious problem not only in Vietnam but also in many parts of the world in which the water pollution is more serious problem

"Water blooming" is the development of microalgae outbreak, especially cyanobacteria in fresh water bodies and often cause the harmful effects on the environment such as: the water turbidity and

pH are increase, the levels of dissolved oxygen is reduce due to the respiration or degradation of algae biomass and especially, the fact that most cyanobacteria produce the toxicity high The preventing and minimizing the development of cyanobacteria is an important environmental issue that need to pay the attention The many methods have been used such as: chemistry, mechanics, biology, etc., but they are ineffective and expensive, affecting ecosystem and conducting is difficult, especially in large water bodies Therefore, the search and development of new effective solutions without secondary pollution and friendly with the environment are increasingly focused research Nanotechnology is the technology relating to the synthesis and application of materials with nanometer sizes (nm) At nanoscale, the material has many advantage features such as: size is smaller than 100 nm, larger surface to volume ratio, crystalline structure, high reactivity potential, creating the effect of resonance Plasmon surface; high adhesion potential and the nanomaterial was applied in various fields such as: medical, cosmetics, electronics, chemical catalyst, environment For the above reasons, the thesis is proposed as:

“Synthesis of silver, copper, iron nanoparticles and their applications in controlling cyanobacterial blooms in the fresh water body” was selected to researched

2 The objectives of the thesis

Research, fabricate and determine the characteristic of three nanomaterials (silver, copper and iron) and evaluate the ability to inhibit the cyanobacteria of nanomaterials in fresh water bodies

3 The main contents of the thesis

- Fabricate and determine the characteristic of three nanomaterials: silver, copper and iron

- Investigate the ability to inhibit and prevent cyanobacteria of three nanomaterials

- Assess the safety of materials and their application

- Experimental application of materials at laboratory-scale with the Tien lake water sample

5 The structure of the thesis

The thesis is composed of 149 pages, 10 tables, 62 figures, 219 references The thesis consists of three parts: Introduction (3 pages); chapter 1: Literature review (42 pages); chapter 2: Methodology (16 pages); chapter 3: Resutl and discussion (59 pages); Conclusion and recommendation (2 pages)

CHAPTER 1 LITERATURE REVIEW

1.1 Introduction of nanomaterial

1.2 Introduction of Cyanobacteria and Eutrophication

1.3 Introduction of the methods to treat the toxic algae contamination

CHAPTER 2 METHODOLOGY 2.1 The research subjects

2.2 The equipment is used in study

2.3 The methods for synthesis of materials

2.3.1 Synthesis of silver nanomaterial by chemical reduction method

The silver nanomaterial was synthesized by chemical reduction method, ion Ag+ in the silver salt solution is reducted to Ag0 by the reducing agent NaBH4

2.3.2 Synthesis of copper nanomaterial by chemical reduction method

The copper nanomaterial was synthesized by chemical reduction method, ion Cu2+ in the copper salt solution is reduced to

Cu0 by the reducing agent NaBH4

2.3.3 Synthesis of iron magnetic (Fe 3 O 4 ) nanomaterial by simultaneously precipitation method

The iron magnetic (Fe3O4) nanomaterial was synthesized by simultaneously precipitation method of Fe2+ and Fe3+ salts by NH4OH

2.4 The methods for determining the characteristic of material structure

The morphology of the three nanomaterials is determined by a number of methods such as: TEM, SEM, IR, XRD, UV-VIS, EDX

2.5 The experimental setup methods

The experimental setup methods such as: culture of algae, selection of nanomaterials, evaluation of the material toxicity, the evaluation of the influence of nanomaterial sizes and the safety of nanomaterials on microalgae and the experiment with the Tien lake water sample were setup

2.6 The methods of evaluating the effect of nanomaterials on the growth of microalgae

To evaluate the effect of nanomaterials on the growth of microalgae, the following methods such as: OD, chlorophyll a, cell density, the methods for analysis of some environmental quality indicators (NH4+, PO43-) and SEM, TEM were used

2.7 The method of statistical analysis

CHAPTER 3 RESUTL AND DISCUSSION

3.1 Synthesis of nanomaterial

3.1.1 Synthesis of silver nanomaterial by chemical reduction method

The UV-VIS spectrophotometer (Fig 3.1) showed that the nanosilver colloid was absorbed at the wavelengths about 400 nm and the synthesized efficiency of silver nanoparticles was maximum achieved at a ratio 1:2 TEM images (Figure 3.2) showed that silver nanoparticle size was less than 20 nm

Figure 3.1 The UV-VIS spectra

of nanosilver colloid depends on

the NaBH4/Ag+ concentration

ratios

Figure 3.2 The TEM images of

nanosilver colloid depends on the BH4-/Ag+ concentration ratio

3.1.1.2 Effect of stabilizer concentration chitosan

The UV-VIS measurements in Figure 3.4 showed that the nanosilver colloid is absorbed at the wavelengths 402-411 nm The TEM image of the silver nanoparticles depends on the concentration of chitosan shown in Figure 3.5 The optimum chitosan concentration of nanosilver colloid fabricating was chosen

as 300 mg/L

Figure 3.4 The UV-VIS spectra

of nanosilver colloid depends on

chitosan concentrations

Figure 3.5 The TEM images

of nanosilver colloid depends

on the chitosan concentrations

3.1.1.3 Effect of citric acid concentration

The UV-VIS measurements in Figure 3.7 showed that the nanosilver colloid is absorbed at the wavelengths 402-411 nm At the rate of [Citric]/[Ag+] = 3.0 the silver nanoparticles obtained were of the most uniform, small size and less than 20 nm, the TEM measurement is shown in Figure 3.8

Figure 3.7 The UV-VIS

spectra of nanosilver colloid

depends on acid concentration

Figure 3.8 The TEM images of

nanosilver colloid depends on the [Citric]/[Ag+] concentration

Figure 3.9 The HR-TEM of nanosilver colloid was tested at

optimal ratio The structure of silver nanoparticle at the optimum ratio indicates that they have a typical hexagon crystal structure of metallic nanoparticles The HR-TEM images in Figure 3.9 showed that the crystals has got Fcc (Face-centered cubic) structure The silver nanomaterial at the conditions such as: the ratio of NaBH4/Ag+ is 1/4, the [Citric]/[Ag +] is 3.0 and a concentration of chitosan stabilizer is 300 mg/L were synthesized to experimented the effect of material on the growth of the studied subjects in the thesis

3.1.2 Synthesis of copper nanomaterial by chemical reduction method

The results in Figure 3.10 show that, in the XRD spectrum appears the three peak with the intensity match for the standard spectra of the copper metal at the side (111), (200), (220) corresponding to angle 2θ = 43.3; 50.4 and 74.00

belong to the Bravais network in the fcc structure of the copper metal

Figure 3.10 The XRD pattern

of CuNPs were tested in

NaBH4/Cu2+ concentration

Figure 3.11 The SEM images

of CuNPs in NaBH4/Cu2+ ratio The SEM measurements (Fig 3.11) of the material were performed to determine the distribution of the copper particles and

the TEM measurement for determine the size of copper nanoparticles (Fig 3.12)

Figure 3.12 The TEM images

of CuNPs in NaBH4/Cu2+ ratio

To respone the objective of this thesis, the M3 sample (NaBH4/Cu2+ ratio is 2: 1) was chosen as the representative sample

XRD spectrum in Figure 3.13 showed that the of copper nanoparticles presents the characteristic peaks of copper nanomaterial The characteristic peaks on the schematic have the sharpness intensity and the wide range of the absorption peak relatively narrow In addition, the XRD spectrum of the material also shows the characteristic peaks of CuO, Cu2O crystals

The SEM (Fig 3.14) measurement results showed that, the copper nanoparticles form of the unequal size distribution when the concentration of Cu0 increases At concentrations of Cu0 is 2g/L, the copper nanoparticles are distributed rather uniformly with the size at 20-40 nm When the concentration of Cu0 increases to 3; 4g/L, the synthesized copper particles will clump together and form of the particle sizes >50 nm; at Cu0 concentration is 6, 7 g/L,

the nanoparticles distributed unevenly and match for the TEM

measurement (Fig 3.15)

Figure 3.14 The SEM image of

copper nanomaterial was tested at

Cu0 concentration

Figure 3.15 The TEM image

of copper nanomaterial was tested at Cu0 concentration

01-085-1326 (C) - Copper - Cu - Y: 16.13 % - d x by: 1 - WL: 1.5406 - Cubic - a 3.61500 - b 3.61500 - c 3.61500 - alpha 90.000 - beta 90.000 - gamma 90.000 - Face-centered - Fm-3m (225) - 4 - 47.2416 - I/Ic PDF 8.9 - F4

Figure 3.16 The detail characteristics of the N1 copper

nanomaterials sample: (a) SEM image, (b) TEM image, (c) XRD

spectrum The structure of copper nanomaterial at selected ratio showed

that, the formed copper nanoparticles have the rather

homogeneous surface (SEM image, Fig 3.16a), the uniformly size

in the range of 30 - 40 nm (TEM image, Fig 3.16b) and have the

Fcc structure with diffraction peaks of the netface (111), (200) and

(220) corresponding to angle 2θ = 43.3; 50.4 and 74.00

with high intensity (XRD spectrum, Fig 3.16c) This material sample is

suitable with the objective of the thesis and were choosen for

3.1.3 Synthesis of magnetic solution nanomaterial by precipitation method

co-3.1.3.1 Effect of the CMC stabilizer concentration

The tested result of morphological, size and the dispersion of material in the ratio of CMC stabilizer and precursor (Fe3O4) respectively were 1/1; 2/1; 3/1; 4/1 and 1/2 by the SEM and methods shown in Figure 3.17 and 3.18 The SEM result showed that the concentration of CMC in the solution is high, the ferromagnetic nanoparticles are unevenly and the particle size is big, the accumulation of nanoparticles is easy to occur At the rate

of CMC/Fe3O4 is 2/1, the obtained ferromagnetic nanoparticles are uniformly sized and less 20 nm

Figure 3.17 The SEM image of

magnetic solution nanostructure

tested in ratios of CMC/Fe3O4

Figure 3.18 The TEM image of

magnetic solution nanostructure

tested in ratios of CMC/Fe3O4 The TEM results showed that the nanoparticle size varies considerably when the CMC concentrations changed When the Fe3O4/CMC is 2:1, the obtained nanoparticles were the smallest, most uniform and less than 20nm within the superparamagnetic size range Therefore, the material sample has a Fe3O4/CMC ratio of 2:1 (encoded sample is FC21) selected to tested for the further factors

3.1.3.2 The result of infrared measurement of the material

Figure 3.19 The infrared spectrum

of Fe3O4 (a), CMC (b), FC21 (c) and

spectrum of three samples (d)

Figure 3.20 The

magnetization hysteresis

result of material FC21

The observation in Figure 3.19 showed that the IR spectrum of ferromagnetic nanoparticles have peaks similar with CMC and Fe3O4, this proves that the structure of CMC is not broken by the material synthesis conditions Therefore, the co-precipitation method for synthesis of material is suitable for purity as well as efficiency

3.1.3.3 The magnetization hysteresis result of material

The result of saturate magnetization hysteresis measurement in Figure 3.20 showed that ferromagnetic nanoparticles are in the form of superparamagnetic The saturate magnetization of Fe3O4 and FC21 is 68 emu/g and 49 emu/g, corresponding to the content

of magnetic phase of the material The result proves that the surface interaction of the magnetic phase with the polymer decreased the saturate magnetization and suitable with the results

of the TEM analysis

3.2 Evaluating the ability of growth inhibition and prevent microalgae by synthesized nanomaterials

3.2.1 Study on the selection of concentrations of three types of nanomaterials

Table 3.1 The screening results of removal M aeruginosa KG

cyanobacteria of fabricated nanomaterials

No Samples Experimental

concentration (mg/L)

The growth inhibition of cyanobacteria

Figure 3.21 Effect of nanomaterials on growth of cyanobacteria M

aeruginosa KG after for 7 days

The concentration screening tests were conducted to rapidly

assess inhibition effect to M aeruginosa KG for 7 days The

results in Table 3.1 and Figure 3.21 showed that the two silver and copper nanomaterials inhibited the growth and development of

cyanobacteria M aeruginosa KG after 6 days (Table 3.1 and Fig

3.21a, b), whereas that the ferromagnetic nanomaterial were not

effective against M aeruginosa KG (Table 3.1 and Fig 3.21c)

3.2.2 Effect of silver nanoparticles on growth and development

of cyanobacteria M aeruginosa KG and green algae C vulgaris

3.2.2.1 Effect of silver nanoparticles on growth and development

cyanobacteria M aeruginosa KG as measured by the concentration

of supplementary material into the culture medium that affected 50% of the individuals (EC50) was 0.0075 mg/L

Figure 3.22 Effect of silver

nanomaterial on growth of the

cyanobacteria M aeruginosa

KG after 10 days was

measured by (OD) (a),

chlorophyll a (b)

Figure 3.23 Effect of silver

nanomaterial was measured by the cell density (a) and the growth inhibition efficiency on

cyanobacteria M aeruginosa

KG (b)

The cell density and chlorophyll a showed that, the cell density and biomass in the control sample increased from the first day (D0) (110,741 ± 6,317 cells/mL and 1.98 ± 0.06 μg/L, respectively) to the end of experiment (D10) (5,475, 556 ± 541,274 cells/mL and 23.4 ± 2.96 μg/L, respectively) (Fig 3.23a) All five tested concentration

ranges are toxic to cyanobacteria M aeruginosa KG The growth

inhibition efficiency (Fig 3.23b) > 75% appears in only 4 tested concentrations from 0.01; 0.05; 0.1 and 1 ppm

The SEM image result of cell surface structure after 48h exposed

to silver nanoparticles at the concentration of 1 ppm is shown in Figures 3.24a (the control sample) and 3.24b (the sample exposed to the concentration of 1ppm silver nanoparticles) In the control sample,

the morphological of cyanobacteria M aeruginosa KG cells

maintained a round and had a spherical shape with a smooth exterior surface (Fig 3.24a) In the experimental sample, the cells were changed to with a distorted and shrunk cell after exposure to silver nanoparticles (Fig 3.24b) It is said that the silver nanoparticles have significantly altered the morphology of the cell

Figure 3.24 Scanning Electron

Microscopy (SEM) micrograph of

on the cell surface of M aeruginosa KG The EDX result in Figure

3.25 showed that the silver nanoparticles appear on the surface of

the cyanobacteria M aeruginosa KG with 0.37% Ag by weight The TEM image in the control sample (Fig 3.26a), the M

aeruginosa KG ultrastructure image had clearly cell wall and the

organelle lie neatly in the cell When exposed to silver nanoparticles at a concentration of 1ppm after 48 hours, the cyanobacteria cells were destroyed (Fig 3.26b) It is proved that the silver nanoparticles was affected to structure of the cyanobacteria