Production of antibacterial glass using nano silver

THE JOINT ACADEMIC PROGRAM OF EXECUTIVE MASTER IN SCIENCES AND MANAGEMENT OF THE LIÈGE UNIVERSITY OF HOCHIMIMH CITY PRODUCTION OF ANTIBACTERIAL GLASS USING NANO SILVER Major: EXECUTIVE M

THE JOINT ACADEMIC PROGRAM OF EXECUTIVE MASTER IN SCIENCES AND MANAGEMENT OF THE

LIÈGE

UNIVERSITY OF HOCHIMIMH CITY

PRODUCTION OF ANTIBACTERIAL GLASS USING NANO SILVER

Major: EXECUTIVE MASTER IN SCIENCES AND MANAGEMENT OF THE ENVIRONMENT

MASTER ’ S THESIS

HOCHIMINHCITY, 2022

Theproject was completed at TheIndustrial University of Hochiminh City

Supervisor’s name: Associate Prof Le Hung Anh

(Write full name and signature)

The thesis was taken at The Industrial University of Hochiminh City date 17 February, 2023

Committee members (name):

1 Associate Prof.Nguyen Thanh Binh - Committee Chair

2 Dr Nguyen Thi ThanhTrue - Commissioner

3 Dr Nguyen Thi Ngoc - Secretary

(Write full name and signature)

COMMITTEE CHAIR DEAN OF INSTITUTE OF ENVIRONMENTAL

SCIENCE, ENGINEERING AND MANAGEMENT

POS TS LÊ HỪNG ANH

In order to complete this graduation thesis report, I have received a lot of help,guidance and inputfrom many people First ofall, Iwould like to express my sincere thanks to my instructor - lecturer ofHo Chi MinhCity University ofIndustry - Assoc

Dr.Le Hung Anhand Dr.Pham Trung Kien -lecturerat Ho Chi Minh CityUniversity

of Technology, duringthe past time, he has guided me very enthusiastically Thanks

to the guidance of the teacher, I know how to study, work and research topics scientifically and effectively And thanks to the dedicated guidance and guidance ofthe teacher, I have gained a lotof knowledge, so that I can complete this graduationthesis report

Sincere thanks to the laboratory staff, of the Institute of Science, Technology and EnvironmentManagement and the Faculty of Materials Technology for creating thebest conditions for equipment and tools duringthe experiment period

At the sametime, Iwouldliketo express mythanks tothe previous classmates of theenvironment, thewedsite management boards for documents onthe environment for creating conditions for the team to learn and investigate and survey to get thecompleted dataproject plan

Although I have tried to complete the report as much as possible, it inevitably hasshortcomings, Ihope to receivevaluable contributions from teachers andprofessors

Nanosilver (AgNPs) has good bactericidal ability to create a clean environment,minimizing the possibility of spreading diseases from glass and porcelain surfaces Thesubjectcoveredthenano silver layer onthe glasssurface by dipping andspinningcoating technique.Throughthe methods: FT-IR(assessment ofphysical andchemicalcharacteristics ofsolution), thereby determining coconut oil is a good solvent, andthe ratio of resinate and coconut oil 1:20 (with 1 gram of solid resinate: 20 ml ofcoconut oil) selected as the optimal ratio to cover silver resintae with glass XRD (identifying the product to be nano silver), SEM(determining the size of the particleafter calcination), EDX (determining the composition of glass material aftercalcination withAg +ions), ƯV-VIS (measuring the transmittance of materials after silvernanoparticles) a defined topic on the glass surface exists a layer ofnanosilver,the size of the nanoparticles is relatively evenly distributed on the surface of coated glass and the glass sample aftercoating has uvresistance is quitegood In addition,the antibacterial test with five types of bacteria causing hospital infections isEscherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella Typhimurium, Bacillus cereus,the silver-coated glass for silver has very good results.All samplesinfluenced the growth of bacteria, with the two types of Escherichia coli Pseudomonas aeruginosa giving completeresistance

Since then, the thesis has had high applicability to reality and is the foundation forsome economic sectors in general andthe hospital environment in particular

TABLE OF CONTENTS LIST OF TABLE V LIST OF FIGURES V

LIST OF ABBREVIATIONS vi

CHAPTER 1: INTRODUCTION 1

1.1 The necessity of the topic 1

1.2 Objectives of the study 2

1.3 Object ofresearch - Scope of research 2

1.3.1 Research subjects 2

1.3.2 Research scope 2

1.4 Research content 3

1.5 Scientific and practical meanings 3

1.6 Novelty of the topic 4

CHAPTER 2 OVERVIEW 5

2.1 Introduction of silver nanomaterials 5

2.1.1 Silvernano concept 5

2.1.2 The characteristics of nano silver 6

2.1.3 Antiseptic mechanism of nano silver 6

2.1.4 Methods of synthesizing nano silver 7

2.1.5 Application of nano silver , 10

2.2 Overviewof coconut oil 13

2.2.1 General introduction about coconut oil 13

2.2.2 Coconutoil productiontechnology 14

2.2.3 Application 17

2.3 Methods of creating films 18

2.3.1 Physical method 18

2.3.2 Chemical method (Sol- gel) 21

CHAPTER 3: MATERIALS AND METHODS 28

3.1 Materials and tools 28

3.2 The researchmethodology 30

3.3 Test design 31

CHAPTER 4: RESULTS AND DISCUSSION 38

4.1 Determine the viscosity of a silverresinate mixture - coconut oil 38

4.2 Determination of silver content in silver resinate mixture 39

4.2.1 Determined by FTIR method 39

4.2.2 Determined by XRDmethod 40

4.3 Determination of silver size and elemental composition in coated and calcined glass samples 42

4.3.1 Determined by XRD method 42

4.3.2 Observe the surface of SEM glass 42

4.3.3 Analysis of elemental composition of EDX glass 44

4.4 Evaluate the results of silver nano coatingon glass by uv - VISmethod 44

4.5 Assess the antibacterialproperties of nano-silver on representativebacteria types 45

4.6 General discussion 48

CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS 50

Conclusion 50

Request 51

REFERENCES 52

LIST OF TABLE

Table 2.1 Numberof silver atoms ina unit ofvolume 5

Table 3.1: Chemicals used inresearch 28

Table 3.2: Instrumentsused in the process of research 29

Table 3.3: Equipment in the researchprocess 30

Table 4.1: Results of viscosity measurement 38

Table 4.2: Antibacterial test results of glass (spin coating, dip coating) 46

LIST OF FIGURES Figure 2.1 silver element (Ag) 5

Figure 2.2 Antiseptic mechanism of nano silver 6

Figure 2.3: Application ofsilver nano in household products 11

Figure 2.4: Application of silvernano in agriculture 12

Figure 2.5: Nano Silver water filtercore 12

Figure 2.6: Application ofsilver nano in textiles 13

Figure 2.7: Coconut essential oil 14

Figure 2.9: Technology diagram of coconutoilproduction by hot pressing hot pressingmethod 16

Figure 2.10 Diagramof coconutoilproduction technology by centrifugal method 17

Figure 2.11: Principle of method of evaporation 19

Figure 2.12: Principle ofsputtering process 20

Figure 2.13: Evolution of Sol - gel process 23

Figure 2.14: Some methods of Sol - gel membrane coating 23

Figure 2.15: Dip - coating process 24

Figure 2.16: Steps of the Spin - coatingprocess 25

Figure 3.1: Process diagram of manufacturing antibacterial glass 32

Figure 3.2 Chart of experimental assessment ofresults 35

Figure 4.1: FT-IR spectrum of (a) NaOH IM; (b) coconut oil, (c)AgNO3 and (d) silverresinate 40

Figure 4.2: XRD result of Silver resinate sample after drying 105°C/18h 41

Figure 4.3: XRD result of Silver Resinate sample after heating 500°C/3h 41

Figure 4.4: XRD spectrum of (a) uncoated glass sample; (b) sample of dip coated glass, calcined at 500°C/3 hours; and(c) Spinning coated glass sample, calcined at 500oC/3 hours 42

Figure 4.5: SEMimages of dipped and spin coated glass samples at different magnifications 43

Figure 4.6: Results of EDX surface dip coatedglasses 44

Figure 4.7: Results of EDX spin coating glasssurfaces 44Figure 4.8: Results of transmission of two glass samples 45

LIST OF ABBREVIATIONS

FT-IR Fourrier Transformation Insfrared

X-XDR X-ray diffraction

SEM Scanning Electron Microscope

EDX Energy-dispersive X-ray spectroscopy

UV-VIS Ultraviolet-Visible spectrophotometer

CHAPTER 1: INTRODUCTION

1.1 The necessity of the topic

Silver is the oldest known natural antibacterial agent Silver and its compounds exhibit toxicityto bacteria, viruses, algae and fungi Silver does not show toxicity to humans,non-toxic, non-irritant Scientific facthasprovedthatsilverions can destroy more than 650 strains of microorganisms, 260 types of harmful germs that causedisease and also gram-negative and positive bacteria Silverinhibits the metabolism

of respiration and the transport of substances through microbial cell membranes Silver has the ability to destroy the enzyme thattransports the nutrients of bacterialcells, weakens membranes, cellwallsand cytoplasm, disrupts metabolism, leading to bacterial destruction

Silver Nanohasthe potential to be applied in many fields such as agriculture, industryand health to create many new and high quality products, bringing socio-economicefficiency The application of nano silver in health, life and manufacturing will also help protect human health, minimize environmental pollution and developproduction In medical use, silver nano solution is used: Covering artificial bone details, treating respiratory tract infections, treating urogenital infections, bandages for wounds such as bums, necrotic ulcers

From the advantages of nano silver as well as the usefulness, the difference of themethod to create silver resinate from coconut oil is extremelynecessary with the goal

of going beyond creating an environmentally friendly product Users can take advantage of availableraw materials in Vietnam at low cost Withthe goal of creating

a sterile environment forhospitals, and food processing facilities researching silvernano-coated glass materials with coconut oil solvents A type of organic substancevery popular in Vietnam

1.2 Objectives of the study

- To be accomplished with the support ofthe following laboratories:

- Solid waste research and intensive research laboratory of the Institute of Science,Technology and Environment Management, Industrial University of Ho Chi Minh City (12 Nguyen Van Bao, Ward 4, GoVap District, Ho Chi Minh City)

- Silicate laboratory ofHo Chi Minh City Universityof Technology (268 Ly Thuong Kiet, Ward 14, District 10, Ho Chi Minh City)

- Centerfor BioScience and Biotechnology at VNUHCM-University of Science (227 Nguyen Van Cu, Ward 4, District 5, Ho Chi Minh City)

> Scale

- Laboratory

- Glass: blue glass.

- Solvents: coconut oil

- Bacteria: Antibacterial test with 5 representative strains of bacteria (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella Typhimurium,Bacillus cereus)

> Research period

From December 2018 to August 2019

1.4 Research content

- Manufacturing coconut oil soap and silver Resinate coating

- Coatingnano silver onglass

- Assessing antibacterial ability

1.5 Scientific and practical meanings

- The introduction of nano silver-coated glass with high bactericidal ability, will help improve public health

- Inthe future, this bactericidal glass material may be an alternative material such assmartphone screens, glasses

1.6 Novelty of the topic

Current methods of nano silver coating are using expensive imported solvents Therefore, we seethe novelty of thistopic in theuse ofcoconut oil solvent is a natural material, popular in Vietnam and affordable

CHAPTER 2 OVERVIEW

2.1 Introduction of silver nanomaterials

2.1.1 Silver nano concept

Silver nanoparticles are particles with a size of Inm silver to lOOnm Althoughoften described as silver, some are made up of a large percentage of silver oxides due to the large proportion of surface silver atoms compared to theữ large number Many shapes of commonly used nanoparticles, such as spherical, octagonal, andthin silvernanoparticles are also verycommon [33]

Electron configurationofsilver: ls22s22p63s23p63d104s24p64d105s1

+ Atomic radius Ag: 0,288 nm

+ Atomic radius silver ion: 0,23 nm

Table 2.1 Number of silver atoms in a unit of volume

2.1.2 The characteristics of nano silver

Nano silver material has a surface area greaterthan bulk materials so it can releasemoreAg+ ions, so silvernanoparticles have better antibacterial properties

Silver nanoparticles have the phenomenon of surface Plasmon resonance Thisphenomenon makes the solution containing silver nanoparticles have differentcolors depending on the concentration and size of nanoparticles

High chemical stability, not change under the effect oflight and oxidizing agents reducingtheusual

-Stabilityathigh temperatures [4]

2.1.3 Antiseptic mechanism of nano silver

Antibacterial properties of nano-silver are explained by several mechanisms:

Figure 2.2 Antiseptic mechanism of nano silver

The first mechanism (Figure 2.2A): Inhibiting the transport process of Na+and Ca2+ ions across the cellmembrane, preventing metabolism

The second mechanism (Figure 2.2B): Break down cell membranes,oxidizing the protoplasm of bacterial cells, protoplasm destroyed by oxygendissolved inwater with a catalyticrole of Silver

The third mechanism (Figure 2.2C): Indirect effects on DNA molecules by increasing the number of freeradicalsthatreducethe activity ofactive oxy gen­containing compounds, disrupt oxidation as well as phosphorylation inbacterial cells.

The fourth mechanism (Figure 2.2D): Disabling enzyme containing -SH Sunphohydril group and - COOH, disrupting osmotic pressureequilibrium, orcomplexing with nucleic acids resulting in changes in the DNA structure ofmicrobial cells, (direct impact on DNAstructure) [39]

> Advantages of nano silver over antibiotics

Silver nano kills bacteria immediately by degenerating and oxidizing mechanisms

So bacteria are not resistant to silver Human cells in tissues should not be affected

by this process

Unlike antibiotics absorbed in the bactericidalprocess, nano silver acts as a catalyst without being absorbed

Another property that enhances silver's effectiveness in human mechanisms is that it

is in the form of small metal particles different from the silver ions often convertedinto silver chloride in the stomach or blood vessels Silver chloride dissolves verylittle and is much less effectivethanmetal silveror silver ions Only silver metal can survive with HC1 in the stomach while retaining activity in blood vessels and bodytissues This is significant because accordingto the EPA (Environmental ProtectionAgency), a person can only use 350 eg / dose daily if more will be poisoned withsilver Ifusing 1-2teaspoons/day (20 ppm) is equivalent to 100-200 eg day (lowerthan EPA's recommendation on the amount of silver supplied in American water sources), it willhave avery effective preventive effect, good This can ensure usersuse nano silver as a dietary supplement as well as in drinking water without being poisoned [40]

2.1.4 Methods of synthesizing nano silver

> Chemical reduction method

In this method, using chemical agents remove silver-ion to form metallic silver andthen theyagglomerate to formmetallic silver nanoparticles Nanoparticles formed bythis method are sized from 10 nm to 100 nm.

Basic principles of this method:

Ag+ + X nAg° + nano Ag

In this method, Ag+ ion under the impact of X reducing agent will create atomAg°,and then these atoms cohere together to form nano-sized silver particles The chemical agents (X) as NaNĩỈ4, sodium citrate creating stability ofmanufacturing nano silver Besides, other agents such as: hydrogen, hydrogen peroxide, hydroxyllammine, hydrazine, acid ascorbic and its derivative, EDTA, and monosaccharidealso can remove Ag+ to Ag°, however, the stability isn’t as good as the two aboveagents

Each chemical will have a reduction method forpreparing silver nanoparticles, such

as citrate reduction method with citrate agent, EDTA reduction method for EDTA agent each method has a specific mechanism of that method for specific reducing agent

The choice of a suitable chemical depends on the economy, the requirements of thepreparation process as well as the quality of the nanoparticlesbecauseeach chemicalwill create a different particle size Also, each chemical that also forthe sustainability

of the solution of Ag nanoparticles of different and ability to make nano silver nanoparticle solution created by these chemicals depends on the applications you need, therefore, thepreparation of silver nanoparticles bythe chemical method should

be carefully selected

> Physical reduction method

This is the method of usingphysical agents such as electronics, and electronicwavessuch as uv rays, lasers, and gamma [18], to reduce silver ions to form silver nanoparticles Under the influence ofphysicalagents, there aremany transformations

of solvents and additives in solventsto produce chemical radicals that reduce silver ions intometals so that they can form particles nano silver.

The physical method of synthesizing silvernanoparticles has many advantages suchas: it is possible to synthesize colloidal silver nanoparticles in large quantities, creating silver nanoparticles of small size from 4-10 nm However, this methodrequires expensive equipment

> Physical and chemical reduction method

This is the intermediate method between chemistry and physics The principle is to use electrolysis method combined with ultrasound to create nanoparticles.Conventional the electrolysis can only create thin metal films Before the formation

of the membrane, the metal atoms after electrochemical will create nanoparticlesattached to the negative electrode At this time, when an ultrasonic pulse is synchronized with the electrolyte pulse, the metal nanoparticles leave the electrodeand enter the solution [42]

> Biological elimination method

Biological methods use agents such as bacteria and virusescapable of reducing silver ions to formmetallic silver atoms [42] Under the effect of microorganisms, the silverion virus will be converted into silvernanoparticles

Ag+ vsv Ago

-►

Factors include fungi such as Verticillium and Fusarium oxysporum This method is simple and environmentally friendly However, the disadvantage of this method isthat silver nanoparticles create a relatively large size compared to othermethods

> The method of using microwaves

A microwave is a heating device, that provides steady heat and uniform heating Using microwave conduct deionizing Ag+ to Ag° according to polyol process to formsilver nanoparticles [38] In this method, silver salt and mellow reducing agenthave

the effect of helping to remove Ag+ about Ag° such as: C2H5OH, C2Hs(OH)2,C3H5(OH)3,HCHO as well as stabilizingsilver nanoparticles when it forms Under the effect of microwaves, polar molecules such as Ag+ molecules and reducing auxiliaries will heat up very quickly, heat will be supplied to the entire solution due

tothe object that the silver reductionprocess will take place more quickly and moremellow than other methods

Microwave heating is method that has many advantages compared to other basic methods Because heating on a flat area will have locations where the temperature on the surface will be far different fromthe inside of the solution,and heating onsurfaceswill easily lead to the temperature at the wall of the device The heating is much higherthan the average temperature of the solution, hl contrast, microwave heating

is provided throughoutthe heating device, andthe temperature of the solution andthedevice walls are almost the same This is the critical factor for creating uniformlysized silver nanoparticles and is much smaller than conventional heating methods

2.1.5 Application of nano silver

Silver nano is put into use for antibacterial and bacterial growth A study by theODENSE medical university showed that silver nano does not have a strong interaction with the human body nor is it a toxic agent Therefore nano silver does not affecthuman health and is considered harmless

Nano silveristhe agent that contributesto cleaningtheenvironment, not toxins inthehuman body

Currently, there are many types of silver nano products on the market, such asbactericidal nano-silver refrigerators, nano silver masks, nano silver-coated milk bottles, silver nano silver toothpaste, etc (Figure 2.3) These products have shownthe wide application of nano silver inpractice

Figure 2.3: Application of silver nano in household products

Silvernano also has applications in catalysis with a large surface area and surfaceenergy When catalyzed, silver nanoparticles are coated on a lattice-like flat silica.They work to keep silver nanoparticles attached to the carrier At the same timeincreases the durability, increases the catalyst, and extends the operatingtime ofthecatalyst For example, silver nanocatalysts are used in the oxidation of organic compounds, converting ethylene into ethylene oxide for the reduction of nitro compounds, as an additive to improve the NO and co handling capacity of FCCcatalyst, catalyst in dyereactionwithNaBFU

For agriculture, the nano silver product lines used for agriculture are based on thetypical properties of nano silver such as (super antibacterial, bactericidal, fungi, strong viruses - fast - natural - safe and no loss when cleaning, the antibacterial ability works throughout the life of the product) with the main ingredient is molecularsilver combined with herbal ingredients, safety additives for use: and kill99.99% of the bacteria, viruses and fungi that cause disease in trees - breeding animals, creating a clean living environment, increasing resistance for subjects without affecting, causing no side effects on crops, cattle, poultry, shrimp, fish, aquatic products, etc products ensure standards on food safety and hygiene (Figure2.4)

Figure 2.4: Application of silver nano in agriculture

Typically, water treatment uses chemical agents such as chlorine, its derivatives,idod Physical agents: uvrays, radiation, Using silver nanoparticles in this field

is also a new dữection and promises great potentials At present, silver-containing

PƯis used to create water filters with high bactericidalproperties (Figure 2.5) [35]

Figure 2.5: Nano Silver water filter core

In addition, nano silver is now used in textiles In the long run, the textile industry uses CuSO4 and ZnSƠ4 compounds in cloth to create clean products with bactericidal properties However, the above factors do not meet the basicrequirements So nano silver with bactericidal properties of 98-99% is thought of.Currently, silver nano has been introduced into the fibers of the textile industry,

applied in products with high antiseptic properties: medical clothing, gloves andproductsto avoidodors (Figure 2.6).

Figure 2.6: Application of silver nano in textiles 2.2 Overview of coconut oil

2.2.1 General introduction about coconut oil

We all know that coconutis used in many life such as beverages, spices for cakes,making dishes more flavorful In addition, the use of coconut oil is coconutextract also contributes to helping our body become healthy, beautiful, full of life,

in addition to the gentle fragrance of coconut oil will also bring US a sense ofrelaxation

Coconut oil (Figure 2.7) is an edible oil extracted from copra In the tropics,coconut oil is an important source of fat in people's meals Coconut oil is used in many areas such as food, medicine, and industry Coconut oil provides a verystable source of heat so coconutoil is suitable for high temperature cookingsuch as frying

or frying Due to its stability, coconut oil is less oxidized, and because of its high saturatedfatcontent, itcan be storedfor upto 2 years

Talking about the beauty of coconut oil, includingthe abilitysuch as skin care, haircare, weight loss or oral bleaching, anti-cancer, bleaching, besides coconut oil is also usedas a whole cosmetic materials [36]

Figure 2.7: Coconut essential oil 2.2.2 Coconut oil production technology

down the heat to make coconut milk simmer and stir well Stir until coconut milk becomes lumpy, the water evaporates and the clear colored coconut oil appears tofloat Put coconut oil in a bowl, let itcool andsediment settles, then pour the oil intothe jar for use and storage.

Not economically efficient

2.2.2.2 Hot drying — hot pressing technology

The way to make coconutoil by hot drying - hot pressingtechnology is shownin thefollowing diagram (Figure 2.9):

Figure 2.9: Technology diagram of coconut oil production by hot pressing - hot

Improved than traditionalmethods

Can produce in large quantities

> Disadvantages

- The product is not considered to be pure coconut oil due to the high temperature drying and pressing process, so it does not retain the aroma and whiteness of fresh coconut(coconut oil after pressing willbe opaquewhite)

2.2.2.3 Method of centrifugation

The way to make coconutoilby centrifugal method is showninthefollowing diagram (Figure 2.10)

Figure 2.10 Diagram of coconut oil production technology by centrifugal

method

Similar to the process of making coconut milk in the traditional method Coconut milk is put into the first coconutoil centrifuge to separatethe two types of insoluble liquid, water and coconut oil in coconutmilk We will get coconut oil, but coconutoil also contains many impurities Therefore, continue to put it into a second coconut oil centrifugeto make itclear and filter the impuritiesmixed in coconut oil The final product will be pure coconutoilwith animpurity levelwithin the allowed limit

> Advantages

Copra meal is processed with the lowest temperature compared to the

existing methods, so the scent and essence arekept completely

Can produce large quantities

2.2.3 Application

- Prevent heart attack and high blood pressure: the saturated fats in coconut oil not only increase HDL cholesterol but also convert bad LDT cholesterol into goodcholesterol Increased HDL cholesterol reduces the risk suffer from cardiovascular disease and high bloodpressure

- Cure urinary tract infections and kidney infections: coconut oil has natural anti­inflammatory, and antibacterial properties by breaking down the lipid layer ofbacteria and killing them They help heal urinary tractinfections (UTIs), and kidney infections and protectthe liver

- Preventing and treating cancer: Coconut oil has antibacterial properties that help eradicate H pylori (helicobacter pylori), reduce the risk of stomach cancer, prevent cancer from developing

- Strengthen the immune system: Coconut oil contains lauric acid with antibacterial and antifungal properties and creates an adverse environment for viruses This helps

prevent many diseases due to the overgrowth of bad bacteria, fungi, viruses and parasites in the body.

- Improve memory and brain function: Coconut oil contains fatty acids thatare easily absorbed in the body and brain without using insulin This helps brain cells workbetter, improving memory problems in older adults

- Improve skin problems: coconut oil has anti-inflammatory properties inside,antioxidant, moisturizing outside Coconut oil is great solution for all skin types, helping to improve and treat many skin conditions (such as eczema, dandruff,dermatitis, psoriasis )

2.3 Methods of creating films

2.3.1 Physical method

2.3.1.1 Vacuum evaporation method

Thermal evaporation, also known as vacuum evaporation, is a technique for creating nano films by evaporating materials that need to be created in a high vacuumenvironment and condensing on the substrate, heated or not heated) [44]

> Principle of the method

The mainpart of the evaporators is a high vacuum evacuation chamber (size 10-5 - 10-6 Torr) thanks to vacuum pumps (diffusion or molecular pumps ) A resistor boat is used (usually made ofrefractory materials and has little interaction with thematerial, such as tungsten, tantalum, platinum, etc.)to meltthe source materials, andthen continue to burn, so that the material evaporates

Evaporation material will condense onto the mountsmounted above Sometimes thesubstrate is also heated (depending on the purpose of creating crystal films oramorphous ) to control the deposition process ofmaterials on the film The filmthicknessis usually determined directly during fabrication by quartz modifiers Whenthe membrane evaporates, it willstick to the element placed next tothe substrate, the

substrate, the variable frequency of the variable will be proportionalto the thickness

of themembrane attachedto the variable (Figure 2.11) [44]

Figure 2.11: Principle of method of evaporation

> Advantages and disadvantages of themethod

The advantage ofthis method is that it is simple andeasy to create a compound film because when evaporating the material, the entire compound or alloy will be evaporated, so the created film has a fairly close meeting with the composition ofthe object, raw material (especially alloys)

The important disadvantage is that it is not possible to create films that are too thin

At the same time, the fabrication of multilayer films is very difficult with thismethod

Recently, people have improved this method such as using an electron beam to fly,and improving the wall surrounding the burning source (hot wall method) However, the ratio ofusing the evaporation method in the thin film technique is getting less andless [44]

2.3.1.2 Cathode sputtering method

Sputtering (Cathode Sputtering) is a technique of manufacturing thin films based onthe principle of kinetic energy transmission by using rare air ions such as Ar, Xe,

He, accelerated under the electric field, in order to bombard the surface of thematerial from the material cover, this kinetic energy drives these atoms towards thesubstrateand deposits on the substrate [44]

> Sputtering processprinciple

This method is basedon a dynamic drive process Thesource materialis made up oftarget plates and is placed at the electrode (usually the cathode), in a highly vacuumed chamber and loaded with ionized rare gases, accelerating and moving towards the target at high speed, the magnitude and bombarding the surface ofthetarget, transmitting kinetic energy to the atoms at the target surface Thedynamically charged atoms fly toward the substrate and settle on the substrate.These atoms are called sputtered atoms Thus, the mechanism of sputtering is collision and momentumexchange Normally, atoms are sputtered when the baseof the sample has an energy of about l-2eV, this energy is large enough for thedeposition atoms to automaticallyarrange and attach to the base of the sample more firmly than the flying method, heat The thickness of the film layer depends on thesputtering time (Figure 2.12) [44]

Đế (Si )

Figure 2.12: Principle of sputtering process

> Advantages and disadvantages of sputtering

Applicable to many different materials: conductive or non-conductive materials, materials with high melting point or low saturated vapor pressure

Easy to make multi-layer films easily by creating many separate beer At the same time, this method is cheap, and easy to implement, so it is easy to deploy on an industrial scale

The adhesion of the filmon the substrate is very high because the atoms that deposit

onthe membrane have a relatively high kinetic energy (abouta few eV) compared to the method of evaporation

The film produces a low surface roughness and is close to that of the beer, which is much more accurate than the vacuumevaporationmethod

Because the substances have different sputtering performance, the control ofingredients withcombination beerbecomes complicated The ability to produce verythin films with high precision of sputtering method is not high Moreover, it is notpossible to create a single crystal membrane

The energy efficiency of sputtering is low: most of the bombardment energy of theions is converted into heatto heatthe beer (so beer needs to be cooled well)

2.3.2 Chemical method (Sol - gel)

2.3.2.1 The basic concepts

> Precursor

Precusor is the initial element to create colloidal particles It is made up of metallic

or nonmetallic components, surrounded by different ligands Precursors can beinorganic metals or organic metals

The general formula ofprecursor: M(OR)x

With: M: metal; R: ankyl group has the formula CnH2n +1

Depending on the materials to be studied, M may be Si, Ti, Al or organic metalssuchas Tetramethoxy silane (TMOS), Tetraehoxysilan (TEOS) [12]

2.3.2.2 Change the process Sol - gel

The process of coatingby Sol-gel method consists of 4 steps and is shown in Figure 2.13:

- Step 1: The desired colloidal particles from precursor suspension moleculesdispersed into a liquid to form a Sol system

- Step 2: Deposition of Sol solution creates coatings on the substrate by spraying, dipping androtating

- Step 3: The particles in the Sol system are polymerized through the removal ofstabilizing components and creatingagel system in the state ofa continuous network

- Step 4: Finally, the pyrolysis process of the remaining organic and inorganic components creates a crystalline or amorphous membrane

sintering - - ► Glass

Figure 2.13: Evolution of Sol - gel process

In terms of chemical mechanism: Sol-gel process is formed with two main types

of reaction: hydrolysis reaction and condensation reaction including alcohol condensation and water condensation reaction

2.3.2.3 Sol - gel coating methods

The prerequisite for the Sol - gel coatingprocess is: The laboratory must be clean,the filtered film coating solution and the glass substrate and some equipment must

be cleaned Some methods of Sol - gel coating are: Dip coating (dip - coating), rotary coating (spin - coating), spraycoating (spray - coating), rolling coating (roll - eating), capillary- coating [36]

Dip - coating

Thin films

Figure 2.14: Some methods of Sol - gel membrane coating

> Method of dipping (dip - coating)

This is a method used a lot in the Department ofApplied Physics at the University

of Natural Sciences The glass used to cover the membrane is brought down and completely immersed in the liquid at a certain speed under the control oftemperature and atmospheric pressure The membrane is then pulled up at the samevelocity (Figure 2.15)

cupping

Figure 2.15: Dip - coating process

+Dipthe base into the coating solution

+ Formsa wet filmwhenpulling up the sole

+ Gelprocess occurs bysolvent evaporation

Filmthickness: calculated by Laudau-Levich equation:

ơỉvỷ 3

h=0’4xr^>’/P)With:

h: Film thickness

T|: Viscosity ofliquid

^LV: Pressure atthe surface of the gas liquid

: Density, specificgravity of liquid

g: weight

v: membrane pulling speed