STUDY ON THE SYNTHESIS OF COLLOIDAL SILVER ANTIMICROBIAL SUBSTANCE

Transcription

1 VAEC-AR 7--3 STUDY ON THE SYNTHESIS OF COLLOIDAL SILVER NANOPARTICLES BY γ-irradiation FOR USING AS AN ANTIMICROBIAL SUBSTANCE Dang Van Phu (), Bui Duy Du (), Nguyen Trieu (), Vo Thi Kim Lang () Doan Thi The () and Nguyen Quoc Hien () () Research and Development Center for Radiation technology, VAEC, Vietnam. () Institute of Applied Material Science, Vietnam National Institute for Science and Technology ABSTRACT: Colloidal silver nanoparticles of different sizes less than nm were synthesized by γ Co-6 irradiation of Ag + in solution containing polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP) as stabilizer. The saturated conversion dose (D) of Ag + to Ag and particle size (d) depended on Ag + concentration from to 5 mm were found out to be as: D (kgy) = -.4[Ag + ] [Ag + ] + 3.6, d (nm) =.9[Ag + ] +.59[Ag + ] for PVA g/ml and D (kgy) = -.5[Ag + ] +.558[Ag + ] , d (nm) = -.6[Ag + ] [Ag + ] for PVP g/ml. Colloidal silver nanoparticles showed the maximal absorption peak at λ max ~ 4-4 nm. The size and size distribution of silver nanoparticles were characterized by transmission electron microscopy (TEM). The silver nanoparticle size of approximate nm showed highly antimicrobial effect against E.coli and S.aureus.. Introduction In recent years, nanoscience and nanotechnology have attracted considerable interest. Metal nanoparticles with the size of. to nm show unique properties []. Silver nanoparticles for instance shows higher antibacterial effect of, to 6, time compared to Ag + ions []. At present many kind of products containing silver nanoparticles have been already commercialized [3]. A number of synthetic methods have been reported for preparation of silver nanoparticles, such as chemical, photochemical, electrochemical, sonochemical, radiolytic reduction [4, 5]. Compared to other methods, the radiation method provides several advantages such as i) process is carried out at room temperature ii) reducing agents are uniformly distributed in the solution iii) silver nanoparticles can be obtained in highly pure and stable state [5-7]. The mechanism of the radiation method was based on the highly active species occurred due to radiolysed process of water [6]. H O e - aq, H, OH, H 3 O +,.. () The solvated electrons and H atoms are powerful reducing agents so that they easily reduce Ag + ions to the zero-valent state (Ag ). Ag + + e - aq (H ) Ag o + e Ag ( H - aq + ) Ag Ag + n+ Ag n+ () OH radical formed during irradiation is strongly oxidative agent which must be converted into reducing agent by reacting with alcohol [8]: RCH OH (R CHOH) + OH R CHOH (R COH) + H O (3) R CHOH (R COH) + Ag + n+ Ag o n + + RCHO (R CO) + H + (4) The Annual Report for 7, VAEC 5

2 VAEC-AR 7--3 Silver atoms which aggregate to silver clusters and these clusters agglomerate with other nearby to form larger particles [6, 8]. To prevent agglomeration of silver clusters, polymers such as PVA, PVP were used as stabilizer [4,9]. In Vietnam the product of colloidal silver nanoparticles has been approved by the Ministry of Health for medical and household utilization as antibactericidal substance []. In this work, study to preparation of colloidal silver nanoparticles by γ Co-6 irradiation and to use as antimicrobial substance in medicine and in environment.. EXPERIMENTAL.. Chemicals: Silver nitrate was obtained from Shanghai Chemical Co., Absolute ethanol was a product of Vietnam. Polyvinyl alcohol (PVA) with molecular weight M w = 8 4 Da was purchased from Kuraray, Japan. Polyvinyl pyrrolidone: PVP K9 (M w = 6 Da) and PVP K3 (M w = 5 4 Da) were obtained from BASF, Germany. Pure water for chromatography was used throughout in this study. Two bacterial strains namely E.coli ATCC and S.aureus ATCC were supplied by University of Medicine and Pharmacy, Ho Chi Minh City... Methods... Preparation of colloidal silver nanoparticles by γ-ray irradiation: The solutions containing PVA, PVP, ethanol and Ag + with different concentration from to 5 mm in glass tubes, which were deaerated by bubbling with nitrogen. The γ-ray irradiation was carried out on a Co-6 source with dose rate of.5 kgy/h, at VINAGAMMA center, HCM City and gamma cell with dose rate of.7kgy/h.... Characterization: Absorption spectra of silver nanoparticles solution which was diluted by water to.mm calculated as Ag + concentration were taken on an Uv-vis spectrophotometer model UV-4PC, Shimadzu, Japan. The size of the silver nanoparticles was measured using a transmission electron microscope (TEM) model JEM, JEOL, Japan operated at an accelerating voltage of 8kV. The size and size distribution of silver nanoparticles were statistically processed using Photoshop CS, Version Investigation of antibacterial effect: Colloidal silver nanoparticles were diluted to: (Ref.), 5,, and 5 ppm in liquid medium containing of 6 CFU/ml of E.coli and S.aureus. After contact time of 3 min. determined the survival number of bacteria in samples. It was calculated as follows: Antibacterial effect (%) = -N t /N Where N and N t are the reference and survival number of bacteria in samples respectively. 3. Results and discussion 3.. PVA stabilizer It was observed from Fig. that the optical density increased with decreasing Ag + concentration [Ag + ]. The maximum absorption wavelengths (λ max ) for the colloidal silver nanoparticles solution varied from 4 to 4 nm. 6 The Annual Report for 7, VAEC

3 VAEC-AR mm 5mM mm mm 3mM 5mM Dose, kgy Wavelength, nm Fig. : The relationship of optical density of colloidal silver nanoparticles and dose Table : The dependence of [Ag + ] and average sizes (d) of colloidal silver (PVA g, Ethanol ml/ml) [Ag + ], mm 5 5 d, nm 8.5 ± ±.6. ±.7.7 ± ±.3 The saturated conversion dose (D) varied from 4 to 36 kgy for Ag + concentration from to 5 mm and it was fitted as: D (kgy) =.4 [Ag + ] [Ag + ] (R =.9799) The d of silver nanoparticles was calculated to be as: d (nm) =.6[Ag + ] +.36[Ag + ] (R =.9736). Results indicated the Ag nanoparticles size to be in the range of 9-9 nm for the Ag + concentration from to 5 mm. d, nm A B Frequency, % d:.7 ± d, nm PVA conc., g/ml PVA % Fig. : The relationship of PVA conc. with d of colloidal silver nanoparticles mm Ag + The Annual Report for 7, VAEC 7

4 VAEC-AR 7--3 Fig. A showed the effect of PVA concentration on the size of Ag nanoparticles. It indicated that with the PVA concentration of g/ml are excellently selected. Fig. B showed a typical TEM image and size distribution of Ag nanoparticles from the sample of mm Ag +. It indicated that the Ag nanoparticles have spherical shape and Gaussian size distribution. 3.. PVP stabilizer mm mm 5mM mm mm 5mM - mm - mm - 5mM - mm - mm - 5mM Dose, kgy Wavelength, nm Fig. 3: The relationship of optical density of colloidal silver nanoparticles and doses Table : The dependence of [Ag + ] on d of (PVP g, ethanol ml/ml) [Ag + ], mm 5 5 d, nm 5. ± ±. 9.5 ±.8.8 ±.. ±.8.3 ±.4 Table 3: Effect of PVP molecular weight (MW) on colloidal silver nanoparticles PVP- K9 M w = 6 Da PVP- K3 M w = 5 4 Da [Ag + ] (mm) D (kgy) d (nm) E λ max. E λ max ± ± ± ± ± ±.9 8 The Annual Report for 7, VAEC

5 VAEC-AR 7--3 PVP K9 with high M W showed good stabilization effect compared to that of K3 low M W, particularly the size of silver nanoparticles was smaller in PVP K9. The saturated conversion dose (D) varied from 8 to 48 kgy for Ag + concentration from to 5 mm and it was fitted as: D (kgy) =.4 [Ag + ] [Ag + ] (R =.9799). The d of silver nanoparticles was calculated to be as: d (nm) =.6[Ag + ] +.36[Ag + ] (R =.9736). Results indicated the Ag nanoparticles size to be in the range of 5 nm to nm Antibacterial effect of silver nanoparticles 3 3 Frequency, % 5 Ag + mm d:. ± d, 8 E.coli P 8 S.aureus P Log(CFU/ml) 6 4 P 6 4 P 5 5 [Ag-nano], ppm Fig. 4: Effect of silver nanoparticles on bacterial growth Results in Fig. 4 indicated that silver nanoparticles with the size of 7.3 nm (P) and.8 nm (P) showed inhibition effect against E.coli and S.aureus more than 9% at ppm and concentration dependence. The bactericidal property of silver nanoparticles was more effective against E.coli than S.aureus. 4. Conclusions Colloidal silver nanoparticles were synthesized by gamma Co-6 irradiation of Ag + concentration from to 5 mm using PVA and PVP as stabilizer. Maximum absorption wavelengths (λ max ) of silver nanoparticles were from 4 nm to 4 nm. The saturated conversion dose obtained from 4-36 kgy for PVA and from 8-48 kgy for PVP. The suitable concentration of stabilizer was g/ml and high molecular weight exhibited good stabilization effect. The average size of silver nanoparticles was in the range of 9-9 nm for PVA and 5- nm for PVP. 5 5 [Ag-nano], ppm The Annual Report for 7, VAEC 9

6 VAEC-AR 7--3 Silver nanoparticles with the size of about nm showed strongly inhibition effect against E.coli and S.aureus. REFERENCES []. K.A. Bogle, S.D. Dhole, V.N. Bhoraskar, Silver nanoparticles: Synthesis and size control by electron irradiation, Nanotechnology, 7, pp.34-38, 6. []. [3]. S. Silver, L.T. Phung, G. Silver, Silver as biocide in burn and wound dressings and bacterial resistance to silver compounds, J. Ind. Microbiol. Biotechnol, 33, pp , 6. [4]. Z. Zhang, B. Zhao, L. Hu, PVP protective mechanism of ultrafine silver powder synthesized by chemical reduction processes, J. Solid State Chem.,, pp.5-, 996. [5]. T. Li, H.G. Park, S.H. Choi, γ-irradiation-induced preparation of Ag and Au nanoparticles and their characterizations, Mater. Chem. Phys., 5, pp.35-33, 7. [6]. D. Meisel, Radiation effects on nanoparticles, IAEA-TECHDOC-438, pp.5-36, 5. [7]. M. Kumar, L. Varshney, S. Francis, Radiolysis formation of Ag clusters in aqueous polyvinyl alcohol solution and hydrogel matrix, Radiat. Phys. Chem., 73, pp.-7, 5. [8]. B.D. Du, D.V. Phu, N. Trieu, N.Q. Hien, Synthesis of colloidal silver nanoparticles by γ-irradiation methods, J. Chem. Appl., (in Vietnamese), 3(63), pp.4-43, 7. [9]. K.S. Chou, C.Y. Ren, Synthesis of nanosized silver nanoparticles by chemical reduction method, Marter. Chem. Phys., 64, pp.4-46,. []. Ministry of Health, Permit No: 9/6/QĐ-BYT. PAPERS PUBLISHED IN RELATION TO THE PROJECT:. Nghiên cứu chế tạo bạc nano bằng phương pháp chiếu xạ, Tạp chí Hóa học và Ứng dụng, Số 3(63), Tr.4-43, 7.. Synthesis of silver nanoparticles by γ-ray irradiation using PVA as stabilizer, Tạp chí Hóa học, Số ĐB(45), Tr.36-4, Nghiên cứu chế tạo keo bạc nano bằng phương pháp chiếu xạ gamma Co-6 dùng PVP/chitosan làm chất ổn định, Hội nghị KH&CN Hạt nhân toàn quốc lần thứ 7, Đà Nẵng, 8/7. 4. Hiệu ứng ức chế vi khuẩn hiếu khí trong nước cắm hoa của keo bạc nano chế tạo bằng phương pháp chiếu xạ, Hội nghị KH&CN Hạt nhân toàn quốc lần thứ 7, Đà Nẵng, 8/7. 5. Preparation of colloidal silver nanoparticles in poly (N-vinylpyrolidone) by γ- Irradiation, Hội thảo Quốc tế lần thứ về Công nghệ nano và ứng dụng, Vũng Tàu, /7. The Annual Report for 7, VAEC