WO2022055459A2

WO2022055459A2 - Method of producing metal particles having metal oxide nanostructures for antimicrobial applications

Info

Publication number: WO2022055459A2
Application number: PCT/TR2021/050911
Authority: WO
Inventors: Abdulcabbar YAVUZ
Original assignee: Gaziantep Universitesi Rektorlugu
Priority date: 2020-09-09
Filing date: 2021-09-09
Publication date: 2022-03-17
Also published as: WO2022055459A3; TR202014290A2

Abstract

The invention relates to a method for producing micro-sized metal powder particles having nanostructures on their surfaces for use on surfaces of in materials such as dye, cement, fabric, plaster and paper where antimicrobial (antibacterial or antifungal) properties are desired. More specifically, the invention is a method of producing an antibacterial additive suitable for use in surface coating materials, comprising the process step of subjecting micro- sized particles made from at least one kind of metal to a heat treatment at a temperature lower than the melting temperature of the metal used and adding the resultant particles into the materials used on surfaces.

Description

METHOD OF PRODUCING METAL PARTICLES HAVING METAL OXIDE NANOSTRUCTURES FOR ANTIMICROBIAL APPLICATIONS

Subject Matter of the Invention

The invention relates to a method comprising producing microsized powder particles having nanostructures on their surfaces for use on surfaces of materials such as dye, cement, fabric, plaster and paper desired to be antimicrobial (antibacterial or antifungal) , and adding them to the surface binder material in certain proportions.

Known State of the Art

Metal and metal oxide-based nanoparticles can be obtained by different methods. These methods include hydrothermal (solvothermal) , hydrogen reduction, gas condensation technique, electrolysis, chemical vapor deposition, sol-gel, spray pyrolysis and mechanical etching methods. These methods generally require a liquid medium or a pressure (or vacuum) medium. There are various studies in the literature on obtaining nanomaterials, but the production of materials with homogeneous nanostructures in a cheap and easy way is laborious. Here, there is a need to obtain particles with homogeneous nanostructures in a more practical and economical way .

Nano-sized materials may have different magnetic, optical, electrical properties with respect to their base materials. Therefore, nanomaterials open new doors for the production of materials with different properties. Accordingly, there have been efforts to develop different nanomaterials in recent years . It is desirable for materials used in high amounts such as dye , cement and polymer to have multi functional properties . For example , thermochromical ( changing colors at di f ferent temperatures ) or antimicrobial dyes are produced . However, it is laborious to obtain additives that result in multi functional properties . Nanoparticles to be added into dye , cement , plaster or polymer material lose their active properties over time .

In particular, in order to give antibacterial properties to surface coating areas , surface coatings and fabric materials comprising nano-si zed materials should be developed .

One of the biggest problems with nano-si zed materials is the agglomeration of particles . In order to prevent agglomeration, nanoparticles are generally taken into a liquid and a surfactant ( surface active agent ) is added to the liquid . The use of surfactants causes both financial and time losses . Therefore , there is a need to develop a method for solving the agglomeration problem without the need to use a surfactant .

In the known state of the art , there are documents describing the methods developed to produce antibacterial nanostructures .

Patent document US2012201759A1 is a patent document relating to the thermal oxidation of metals such as copper and iron, and the formation of nanowires on metal particles . More speci fically, said document describes particles having a metal oxide outer layer and metal oxide nanowires on this layer . In the document , a mixture is obtained from particles having a si ze below and above a certain threshold value , and the mixture is subj ected to oxidation at a given temperature for a given period. In the document, there is an emphasis on copper and iron particles, but it is stated that said method is applicable to various metals such as zinc, aluminum, titanium, etc. The invention of the document also provides a method for controlling growth of nanowires on metal particles. Said method is based on determining an initial particle size with respect to a threshold value for nanowire growth, and subjecting the particles to oxidation at a certain temperature for a certain time until the desired size is obtained. However, antibacterial use of the resultant particles is not mentioned in this document.

The article titled "Synthesis of cupric oxide nanowires in spherical surface by thermal oxidation method" by Xuyang Li, Jianbo Liang, Naoki Kishi and Tetsuo Soga (Materials Letters 96 (2013) 192-194) discloses the synthesis of copper (II) Oxide (CuO) nanowires on spherical surface by thermal oxidation. In said document, CuO nanowires are obtained by heating 5 pm copper powder with high purity (99.9%) at temperatures in the range of 300°C - 700°C. Said method generally includes the process steps of spreading the copper powder on a high temperature resistant quartz glass substrate; positioning the quartz glass substrate in the center of a quartz tube, positioning the quartz tube in the middle of a horizontal tube furnace; introducing nitrogen gas into the quartz tube until the determined temperatures ( 300 °C-400 °C- 500°C-600°C-700°C) ; when the determined temperatures are reached, replacing the nitrogen gas with air; and cooling the samples to room temperature under nitrogen gas. However, the use of the resultant particles obtained in antimicrobial applications is not pointed out in this document.

The article titled "Metal Oxide Nanowires by Thermal Oxidation

Reaction Technique" relates to obtaining metal oxide nanowires by thermal oxidation technique. Said document mentions that metal oxide nanostructures have many application areas, and does not specifically refer to copper and zinc oxide. The document mentions that the thermal oxidation technique is easy and cheap. There are studies in the art on the synthesis of zinc oxide and copper oxide nanowires under different conditions (temperature, time, catalyst and gas flow, etc.) . (Supab Choopun, Niyom Hongsith and Ekasiddh Wongrat (2010) . Metal-Oxide Nanowires by Thermal Oxidation Reaction Technique, Nanowires, Paola Prete (Ed.) , ISBN: 978-953-7619-79-4)

In the article titled "Structural, Morphological and Antibacterial Characterization of CuO Nanowires", copper oxide nanowires are obtained by subjecting them to heat treatment on copper plate/foil [M. Azam, S. Solaymani, M. Amini, N. B. Nezafat, M. Ghoranneviss . Structural, morphological and antibacterial characterization of CuO nanowires. Silicon. 10 (2018) 1427-1431] . In said publication, it has been shown that copper foil can be used in antibacterial applications thanks to the copper oxide nanowires obtained by heating on its surface, but the use of micro-sized particles with nanostructures obtained by heating on surfaces for antimicrobial (antibacterial or antifungal) purposes is not mentioned.

In the documents of the art, no method or use has been described for the use of metal oxide nanoparticles in surface coating materials for antibacterial purposes. Therefore, this need in the art continues to exist. Apart from this, there is no information on the solution to the agglomeration problem, and the need to eliminate the agglomeration problem without the use of surface active substance (surfactant) continues to exist . Detailed Description of the Invention

The invention relates to the production of micro-si zed metal powder particles having nanostructures on their surfaces for use on surfaces ( in materials such as dye , cement , fabric, plaster and paper ) where antimicrobial ( antibacterial or anti fungal ) properties are desired . In this invention, the method of producing a surface coating material with antibacterial additives is described .

The invention has been developed for the use of particles with these antimicrobial properties in surface coating materials such as dye, cement , plaster or polymer .

The invention is based on the principle of subj ecting the micro-si zed metal particles (powders ) to heat treatment , thereby forming nano-si zed structures on their surface .

The invention, in general , is a method of producing an antibacterial additive suitable for use in surface coating materials , comprising the process step of subj ecting microsi zed particles made from at least one kind o f metal to a heat treatment at a temperature lower than the melting temperature of the metal used .

Partial oxidation of microparticles is provided by applying heat treatment . In other words , it is provided that the surface of the metal microparticles is oxidi zed and nanostructures are formed on the surface region of these particles .

In an embodiment of the invention, the metal particles are in powder form . In an embodiment of the invention, the metal particle used comprises at least one of following metals: copper, titanium, cobalt, gold, manganese, zinc, aluminum, silver and cerium.

In an embodiment of the invention, an alloy comprising at least two of the following metals as the metal particles is used: zinc, copper, titanium, cobalt, gold, manganese, aluminum, silver and cerium.

In an embodiment of the invention, the temperature during heat treatment is lower than the melting temperature of the metal used. For example, there may be both copper (I) oxide and unoxidized copper on the surface of copper particles subjected to heat treatment at 200 °C.

In an embodiment of the invention, when micro-sized particles are made from copper, these particles are subjected to heat treatment from 200 °C to 400 °C.

In an embodiment of the invention, micro-sized copper particles are subjected to heat treatment from 100 °C to 1000 °C to obtain nanostructures that are copper oxides.

In an embodiment of the invention, when micro-sized particles are made from zinc, these particles are subjected to heat treatment from 100 °C to 418 °C.

In an embodiment of the invention, the size of more than half of the metal particles ranges from 1 micrometer to 1 millimeter .

In an embodiment of the invention, the size of the metal particles ranges from 1 micrometer to 50 micrometers. In an embodiment of the invention, the size of the metal particles ranges from 50 micrometers to 200 micrometers.

In an embodiment of the invention, the size of the metal particles ranges from 200 micrometers to 600 micrometers.

In an embodiment of the invention, mixing is performed during heat treatment (oxidation) . In an embodiment of the invention, the heating process is performed in open or closed systems.

In an embodiment of the invention, the amount of oxygen delivered to the medium during heat treatment is adjusted.

Preferably, the gas medium may be different from oxygen for different surface morphologies. Depending on the surface structure, hydrogen, nitrogen, argon and/or carbon dioxide gases may be added.

In an embodiment of the invention, depending on the surface structure, different proportions of hydrogen, nitrogen, argon and/or carbon dioxide gases are added together with oxygen to the gas medium on which the heat treatment is to be performed.

In an embodiment of the invention, different micro-sized powders are subjected to heat treatment in the same medium. In this case, different micro-sized powders can be heated in the same medium to obtain their oxide forms on the surfaces of the particles, and they can be used together.

In an embodiment of the invention, heat treatment is carried out in the same medium after mixing different metal powders. In an embodiment of the invention, the alloyed metal powders before heat treatment are used by heating at di f ferent temperatures .

The heating times and temperatures of the powder particles may vary with respect to the targeted surface morphology and topography .

In an embodiment of the invention, shapes of the metal particles used are di f ferent from each other . Examples of shapes include cylindrical , spherical , amorphous round, needle-like , angled, cubical , leaf-like , and sponge-like shapes . An embodiment of the invention comprises at least one of these shapes .

Nanostructures in the additive obtained by the invention are in the shapes of nanoparticles , nanocrystals , nanobars , nanotubes or nanowires , or a mixture thereof . The factors af fecting the formation of these shapes are the temperature applied, the amount of gas in the medium, and the substances heated . These shapes are formed during heat treatment .

The use of an additive having the nanostructures obtained by the method of the invention for antibacterial purposes is also within the scope of protection of the invention . In an embodiment of the invention, there is a process step of taking the additive with nanostructures into a liquid and then adding it to the surface coating material (matrix phase ) or directly adding it to the surface coating material by spraying method .

In an embodiment of the invention, the additive may be added to the base material (matrix phase ) before , during, or after the production of the material . In an embodiment of the invention, after particles with microstructures are added to the surface coating material , heating process is performed during which antibacterial additives are obtained .

The surface coating material containing the particles obtained by the method of the invention is also within the scope of protection of the invention . These microparticles having nanostructures are located on at least a part of the surface region of the surface coating material . The purpose of this is to ensure that these particles show their antibacterial properties upon contact with air . I f they are located inside the material and do not have any contact with air, they may not actively show their antibacterial properties .

The invention confers antibacterial properties to surface coating materials used in high amounts such as dye , cement , plaster and polymer in response to the need for these materials to have multi functional properties . The nanoparticles obtained by the method of the invention are added to various surface coating materials to show antibacterial properties . Examples of these materials include cement , concrete , plaster, dye , sawdust for chipboard construction, and polymer and paper for composite additives .

Thanks to the invention, the production process of particles with nanostructures is facilitated and the production costs are reduced . Microparticles are oxidi zed by heat treatment and nanostructures are formed thereon . Depending on the medium conditions ( time , temperature , pressure , gas in the medium) and duration, nano-si zed particles can be obtained on microsi zed metal powders in a controlled manner . The agglomeration problem, one of the biggest problems with nano-si zed materials , is also solved with the method of the invention . In the invention, particles with nano structures can easily be mixed without the need for a surfactant into the base material as nano structures are located on microsi zed metal powders , and no agglomeration problem occurs .

The nanostructures obtained by the invention have a more homogeneous structure since they are grown with temperature on micro-si zed powders . Therefore , by having a more homogeneous structure than the nanostructures obtained in the liquid medium, it provides a solution to the problem of achieving homogeneity, which is another problem in the art .

The metal oxide particles obtained by this method can be used for a long time due to their high corrosion resistance . The reason why the particles within the scope of the invention have high corrosion resistance is that as they have already been oxidi zed, it is unlikely that their surfaces will be oxidi zed again after long term use . Further oxidation of these particles , which have already been oxidi zed during the process , will not af fect the surface topography signi ficantly .

Within the scope of this invention, both copper and zinc powders were heated and it is understood from color changing that the structures of resultant products changed . In order to see these changes , scanning electron microscopy ( SEM) , X- ray di f fraction (XRD) and X-Ray Photoelectron Spectrometry (XPS ) results of copper particles are given here .

The nanoscale morphology (magni fied 100 000 times ) of the oxidi zed form of copper as a result of heating was obtained using SEM . SEM images of unheated copper and heated copper are shown in Figure 1. The surface morphologies of unheated copper (Figure la) and copper heated at 200°C (Figure lb) , 300°C (Figure 2c) and 400°C (Figure Id) over 60 minutes are different. The surface area of the unheated copper (Figure la) is smaller compared to that of the heated copper (Figure lb, Figure 1c and Figure Id) . The effect of thermal treatment (thermal oxidation) is clearly seen in Figure 1. After one hour of heat treatment on copper in a muffle furnace of 200 °C, particles of generally 20 to 50 nm are formed on the copper surface. When the copper is heated at 300°C, the surface morphology of the oxidized copper has changed. (Figure 1c) . The nanoparticles observed on the copper surface at 200°C (Figure lb) were agglomerated more at 300°C (Figure 1) . When the oven temperature was increased to 400°C, the nanofibers were grown on the copper surface. Thus, these coppers with nanostructures can be used in desired applications. The copper microparticles to be used in order to have nanostructures may be of different shapes and sizes as shown in the SEM image with 500 times magnification in Figure le.

X-ray diffraction is used to analyze the crystalline structure of materials. In Figure 2, X-ray diffraction results of unheated copper (top line) and X-ray diffraction results of coppers heated at 200 °C (second line from the top) , 300 °C (third line from the top) and annealed at 400 °C (bottom line) for one hour are given for 2° to 80°. The three copper peaks observed at 43°, 50° and 74° respectively can be indexed to FCC coppers (111) , (200) and (220) respectively according to JCPDS 04-0836 [Y.T. Prabhu, K.V. Rao, V.S. Sai, T. Pavani, A facile biosynthesis of copper nanoparticles: a micro- structural and antibacterial activity investigation, J. Saudi Chem. Soc. 21 (2017) 180-185] . The fact that these three peaks are also seen in the XRD results of annealed coppers shows that fine copper oxide is formed on the copper. According to the XRD result of the copper annealed at 300 °C for 60 minutes (the third line from the top in Figure 2) , a new peak has emerged at 38 °C, which belongs to the cuprite ( copper-oxide mineral) (Cu₂O) (111) . [Kouti, M., and L. Matouri . "Fabrication of nanosized cuprous oxide using fehling's solution." (2010) : 73-78.] . Therefore, copper heated at 300 °C is in the form of copper (I) oxide.

The two new XRD peaks seen at 37° and 39° on the bottom line in Figure 2 show that the copper heated at 400 °C is in the form of copper (II) oxide. [D. Collins, T. Luxton, N. Kumar, S. Shah, V.K. Walker, V. Shah, Assessing the impact of copper and zinc oxide nanoparticles on soil: a field study, PLoS One. 7 (2012) e42663.] (JCPDS card no: 801268) [P.K. Raul, S. Senapati, A.K. Sahoo, I.M. Umlong, R.R. Devi, A. J. Thakur, V. Veer, CuO nanorods: a potential and efficient adsorbent in water purification, Rsc Adv. 4 (2014) 40580-40587.] . Copper (I) oxide formation from copper by thermal oxidation is as follows : 4Cu + O₂ - > 2CU₂O.

Copper (II) oxide can be produced by annealing at a high temperature (typically around 550°C) in the air with the following reaction [L.D.L.S. Valladares, D.H. Salinas, A.B. Dominguez, D.A. Najarro, S.I. Khondaker, T. Mitrelias, C.H.W. Barnes, J. A. Aguiar, Y. Majima, Crystallization and electrical resistivity of Cu₂O and CuO obtained by thermal oxidation of Cu thin films on SiO₂/Si substrates, Thin Solid Films. 520 (2012) 6368-6374.] : 2Cu + O₂ 2CuO

Therefore, copper heated at 300°C and 400°C is in the form of Cu₂O and CuO, respectively, which means that heating at a higher temperature can result in a greater oxidation step (excess oxidation) of the copper. In these studies, it is shown that copper has nano protrusions when heated at a high temperature and that these are in the form of oxides of copper .

Figure 3 shows the XPS results of the particles heated at 200 °C, 300 °C and 400 °C for one hour. According to these results, copper, copper (I) oxide and copper (II) oxide are present in the resultant particles. [L. Haiyue, J. Xie, P. Liu, B. Dai. Effect of Cu⁺/Cu²⁺ ratio on the catalytic behavior of anhydrous nieuwland catalyst during dimerization of acetylene, Catalysts. 6 (2016) 120.]

In summary, the invention is a method of producing a surface coating material with antibacterial additives, comprising the process step of

- subjecting micro-sized particles made from at least one kind of metal to heat treatment at a temperature lower than the melting temperature of the metal (s) used to obtain an antibacterial additive with nanostructures, and adding this substance to the surface coating material or

- adding micro-sized particles made from at least one kind of metal to the surface coating material and then subjecting them to heat treatment at a temperature lower than the melting temperature of the metal (s) used.

A surface coating material obtained by this method is also within the scope of protection of the invention. Description of the Figures

Figure-la SEM Image of Unheated Copper

Figure-lb SEM Image of Copper Heated at 200 ° C for 60 Minutes

Figure-lc SEM Image of Copper Heated at 300 ° C for 60 Minutes

Figure-Id SEM Image of Copper Annealed at 400 ° C for 60 Minutes

Figure-le Micro-si zed SEM Image of Unheated Copper Particles

Figure-2 X-Ray Di f fraction Results of Unheated, Heated Coppers

Figure-3 XPS Results of Unheated Copper, and Coppers Heated at 200 ° C, 300 ° C and 400 ° C for 60 Minutes

Claims

CLAIMS A method of producing a surface coating material with antibacterial additives comprises the steps of

- obtaining an antibacterial additive with nanostructures by subjecting micro-sized particles made from at least one kind of metal to heat treatment at a temperature lower than a melting temperature of the metal/metals and adding this additive to the surface coating material or

- adding micro-sized particles made from at least one kind of metal to the surface coating material and then subjecting them to heat treatment at a temperature lower than a melting temperature of the metal/metals. The method according to claim 1, wherein the metal particles comprises at least one of the following metals: copper, titanium, cobalt, gold, manganese, zinc, aluminum, silver and cerium. The method according to claim 2, wherein the micro-sized particles are subjected to heat treatment from 200 °C to 400 °C when these particles are made from copper. The method according to claim 2, wherein the micro-sized copper particles are subjected to heat treatment from 100 °C to 1000 °C to obtain copper oxide nanostructures. The method according to claim 2, wherein the micro-sized particles are subjected to heat treatment from 100 °C to 418 °C when these particles are made from zinc. The method according to claim 1, wherein as the metal particles, an alloy comprising at least two of the following metals is used: zinc, copper, titanium, cobalt, gold, manganese, aluminum, silver and cerium. The method according to claim 1 or 2, wherein the size of more than half of the metal particles ranges from 1 micrometer to 1 millimeter. The method according to claim 7, wherein the size of the metal particles ranges from 1 micrometer to 50 micrometers. The method according to claim 7, wherein the size of the metal particles ranges from 50 micrometers to 200 micrometers . The method according to claim 7, wherein the size of the metal particles ranges from 200 micrometers to 600 micrometers . The method according to claim 1, wherein mixing is performed during heat treatment (oxidation) . The method according to claim 1, wherein the heat treatment is performed in open or closed systems. The method according to claim 1, wherein oxygen is delivered during the heat treatment by adjusting its amount. The method according to claim 13, wherein different proportions of hydrogen, nitrogen, argon and/or carbon dioxide gases are added together with the oxygen. The method according to claim 1, wherein depending on the surface structure, hydrogen, nitrogen, argon and/or carbon dioxide gases are added to the gas medium in which the heat treatment is to be performed. The method according to claim 1, wherein the shapes of the metal particles are different from each other. The method according to claim 1, wherein the metal particles comprise at least one of cylindrical, spherical, amorphous round, needle-like, angled, cubical, leaf-like, and spongelike shapes. The method according to claim 1, wherein the additive with the resultant nanostructures is in the form of nanoparticles, nanocrystals, nanobars, nanotubes or nanowires, or a mixture thereof. The method according to claim 1, wherein it comprises the steps of

- taking the additive into a liquid and then adding it to the surface coating material; or

- directly adding it to the surface coating material by spraying method. The method according to claim 19, wherein the additive is added to the surface coating material before, during or after the production of the material. A surface coating material according to any one of claims 1 to 19. The surface coating material of claim 21, wherein the additives are present in at least one part of the surface region .

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