Open Access

Irradiation of silver and agar/silver nanoparticles with argon, oxygen glow discharge plasma, and mercury lamp

  • Mahmoud M Ahmad1Email author,
  • Essam A Abdel-Wahab1,
  • A A El-Maaref1,
  • Mohammed Rawway2 and
  • Essam R Shaaban1
SpringerPlus20143:443

https://doi.org/10.1186/2193-1801-3-443

Received: 26 February 2014

Accepted: 23 July 2014

Published: 19 August 2014

Abstract

The irradiation effect of argon, oxygen glow discharge plasma, and mercury lamp on silver and agar/silver nanoparticle samples is studied. The irradiation time dependence of the synthesized silver and agar/silver nanoparticle absorption spectra and their antibacterial effect are studied and compared. In the agar/silver nanoparticle sample, as the irradiation time of argon glow discharge plasma or mercury lamp increases, the peak intensity and the full width at half maximum, FWHM, of the surface plasmon resonance absorption band is increased, however a decrease of the peak intensity with oxygen glow plasma has been observed. In the silver nanoparticle sample, as the irradiation time of argon, oxygen glow discharge plasma or mercury lamp increases, the peak intensity of the surface plasmon resonance absorption band is increased, however, there is no significant change in the FWHM of the surface plasmon resonance absorption band. The SEM results for both samples showed nanoparticle formation with mean size about 50 nm and 40 nm respectively. Throughout the irradiation time with the argon, oxygen glow discharge plasma or mercury lamp, the antibacterial activity of several kinds of Gram-positive and Gram-negative bacteria has been examined.

Keywords

Silver nanoparticlesGlow discharge plasmaUV light irradiationAntibacterial activity

Introduction

Due to their unique properties, metal nanoparticles are attracted a great interest of experimental and theoretical investigations (Amoruso et al. 2005; Link and El-Sayed 2000; Richardson et al. 2009; Shalaev 2002). Controlling of metalic nanoparticles geometry has found special interset since this allows tuning optical properties that are not present in bulk materials (Ahmadi et al. 1996). The tunability of the plasmon position and its charachterstics such as Full width at half maximum (FWHM), and peak intensity makes the nanoparticles attractive for several applications (Cobley et al. 2009; McFarland and Van Duyne 2003). The mainpulation of nanoparticles can be achieved with laser, UV-light as well as with plasma sources (Hou et al. 2013; Mafune et al. 2000; Zhen et al. 2013). In principle, irradiation with a given light source excites and heats nanoparticles of certain sizes or/and shapes and leads to diffusion and evaporation of surface atoms. Thus, tuning the plasmon position and its charachterstics of the nanoparticles can be accomplished. In the present experiment, silver and agar/silver nanoparticles were prepared using chemical reduction method (Pillai and Kamat 2004). The prepared samples have been irradiated with argon, oxygen glow discharge plasma sources, and mercury lamp at different time periods. Spectrophotometric measurements were carried out to follow the irradiation process and to characterize the optical properties of the resultant silver and agar/silver nanoparticles. Finally, the resultant nanoparticles samples have been examined for antibacterial activity against various types of Gram-positive and Gram-negative bacteria, which are necessary in order to fully evaluate its possible use as a new bactericidal material.

Methods

Synthesis

The silver nanoparticle samples have been prepared by using chemical reduction method. All solutions of reacting materials have been prepared in distilled water. Silver nitrate AgNO3 and trisodium citrate C2 H5O7Na3 of analytical grade purity were used as starting materials without further purification. In the present procedure 150 mL of 1 mM AgNO3 was heated to boiling and 15 mL of 1% trisodium citrate was added drop by drop to the solution until its color change to pale yellow. Then it was removed from the heating plate and stirred until cooled to room temperature and it kept in dark place. The agar/Silver nanoparticles sample has been prepared by adding 0.1 gm of agar powder to 10 mL of silver nanoparticles solution and stirred for two minutes at room temperature.

For SEM analysis, samples are prepared by depositing a drop of colloidal solution on a carbon coated copper SEM holder and drying at room temperature. Absorption spectra were recorded at room temperature using Jasco-670 double beam spectrometer.

Discharge plasma setup and Irradiation procedures

In order to setup argon, oxygen glow discharge plasma sources, two copper circular plane electrodes are used. The two electrodes are centered in the reaction chamber axes. The gas has injected into the reaction chamber through the side flange. The reaction chamber was evacuated up to 10−3 mmHg before the gas inlet. The gas pressure has controlled using vacuum system and gauges to 0.11 mmHg and kept constant during the measurement procedure. The discharge voltages of the argon and oxygen plasma were 248 and 358 volt respectively. More details of the plasma source setup can be found in (Shaaban et al. 2013). Figure 1 shows a schematic diagram of the discharge plasma setup. The strong emission spectral lines of argon, oxygen glow discharge plasma sources and mercury light source are listed in Table 1 (Reader et al. 1996; Bacławski and Musielok 2008).
Figure 1

Schematic diagram of an electric discharge cell. Where E is two copper circular plane electrodes (0.2 cm thickness and 5 cm diameter), C is the reaction chamber (cylindrical Pyrex glass of 7 cm diameter and 15 cm length with 2 cm gap spacing, VS is the vacuum system, VG is the vacuum gauge, H is the sample holder, and B is cuvette place holder.

Table 1

The strongest emission lines in nm of argon, oxygen glow discharge plasma sources and mercury light source (Bacławski and Musielok 2008 ; Reader et al. 1996 )

Oxygen lines (nm) O I

Mercury lines (nm) Hg I

Argon lines (nm) Ar I

777.337

253.652

696.543

645.499

296.728

706.722

725.436

302.150

714.704

615.727

313.155

727.294

715.670

334.148

738.398

926.387

365.015

750.387

948.289

404.656

763.511

949.794

407.783

772.376

950.560

435.833

794.818

949.271

546.074

826.452

948.743

576.960

842.465

 

579.066

852.144

  

866.794

  

912.297

  

922.450

Six samples of the same volume 3 mL of silver and agar/silver nanoparticles have been irradiated with argon, oxygen glow discharge plasma sources, and mercury lamp at different time periods. Spectrophotometric measurements were carried out to follow the irradiation process and to characterize the optical properties of the resultant silver and agar/silver nanoparticles.

Antibacterial procedures

The disc diffusion assay method was used to study the antibacterial activity of the synthesized nanoparticle samples (NCCLS 1993). All the glassware, media and reagents used were sterilized in an autoclave at 121°C for 20 min.

The antibacterial activity of nanoparticle samples was evaluated against some of Gram positive (Bacillus cereus, Bacillus subtilis, Micrococcus roseus, Staphylococcus aureus and Streptococcus sp.) and Gram negative bacteria (E.coli, Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa and Serratia marcescens). Bacterial suspension was prepared by growing a single colony overnight in nutrient broth and by adjusting the turbidity to 0.5 McFarland standards (Kora et al. 2009).

Media plates were inoculated with this bacterial suspension. The sterile filter-paper disks (Whatman filter paper no.1) of 6 mm were impregnated with nanoparticle samples solution and placed on the surface of the media inoculated with bacterial species. These plates were incubated at 37°C for 24 h and the zone of inhibition (ZOI) was measured.

Results and discussions

SEM analysis has been performed in order to observe morphology of the synthesized samples. Figures 2 and 3 show SEM images and the corresponding size distributions of silver and agar/silver nanoparticle samples respectively. From SEM images the silver and agar/silver nanoparticles are spherically shaped with mean size about 50 nm and 40 nm respectively. The effect of agar powder on the synthesized silver nanoparticles states as controller of nucleation as well as stabilizer.
Figure 2

SEM image and particle size histogram of silver nanoparticles.

Figure 3

SEM image and particle size histogram of agar/silver nanoparticles.

Measurements of UV–vis spectrophotometer show the expected surface plasmon resonance SPR peak of silver nanoparticles. In the UV–vis spectra a single strong peak with a maximum around 424 nm is observed of silver nanoparticle samples, which corresponds to the typical SPR of conducting electrons of the surface of silver nanoparticles. In agar/silver nanoparticle samples a single strong peak with a maximum around 428 nm has been detected. This shift of peak position of the SPR band between the two samples is due to the sensitivity of SPR to the shape, size, and interaction of the particle with the medium and local refractive index.

It is observed that, there are no peaks located around 335 and 560 nm, which indicate to the complete absence of nanoparticle aggregation (Mohan et al. 2007; Kora et al. 2009).

Figures 4, 5, and 6 show the absorption spectrum of silver nanoparticle samples irradiated with argon, oxygen, and mercury lamp at different time intervals respectively. It is shown that, in the case of silver nanoparticle sample as the irradiation time of argon, oxygen glow discharge plasma or mercury lamp increases, the peak intensity of the SPR absorption band is increased. However, there is no significant change of the FWHM at the SPR absorption band.
Figure 4

UV–vis absorbance spectra of silver nanoparticle sample before and after irradiation with argon plasma at different time periods.

Figure 5

UV–vis absorbance spectra of silver nanoparticle sample before and after irradiation with oxygen plasma at different time periods.

Figure 6

UV–vis absorbance spectra of silver nanoparticle sample before and after irradiation with mercury lamp at different time periods.

Figures 7, 8, and 9 show the absorption spectrum of agar/silver nanoparticle samples irradiated with argon, oxygen, and mercury lamp at different time intervals respectively. It is shown that for agar/silver nanoparticle sample as the irradiation time of argon glow discharge plasma or mercury lamp increases, the peak intensity and the FWHM of the SPR absorption band are increased. However a decrease of the peak intensity with oxygen glow discharge plasma is observed and the FWHM remains constant.
Figure 7

UV–vis absorbance spectra of agar/silver sample before and after irradiation with argon plasma at different time periods.

Figure 8

UV–vis absorbance spectra of agar/silver nanoparticle sample before and after irradiation with mercury lamp at different time periods.

Figure 9

UV–vis absorbance spectra of agar/silver nanoparticle sample before and after irradiation with oxygen plasma at different time periods.

Variation of SPR peak position of silver and agar/silver nanoparticle samples after irradiation with argon, oxygen plasma and mercury lamp have been plotted in Figures 10, 11, and 12 respectively. It is shown that, the SPR peak position remains constant in the case of silver nanoparticle sample irradiated with argon plasma, however a stepwise increment is observed in the case of agar/silver nanoparticle sample.
Figure 10

Variation of SPR peak position of silver and agar/silver samples after irradiation with argon plasma.

Figure 11

Variation of SPR peak position of silver and agar/silver samples after irradiation with oxygen plasma.

Figure 12

Variation of SPR peak position of silver and agar/silver samples after irradiation with mercury lamp.

When both samples are irradiated with oxygen plasma, the SPR peak position remains constant.

It is observed that, the SPR peak position is increased for agar/silver nanoparticle sample after irradiation with mercury lamp. However there is no significant change of SPR peak position of silver nanoparticle sample.

Figures 13, 14, and 15 show the variation of the FWHM of silver and agar/silver nanoparticle samples after irradiation with argon, oxygen plasma and mercury lamp respectively. It is observed that, there is no change of FWHM for silver nanoparticle sample irradiated with argon plasma however the FWHM is increased rapidly for agar/silver nanoparticle sample. In the case of oxygen plasma irradiation the FWHM remains constant for both samples.
Figure 13

Variation of FWHM of silver and agar/silver samples after irradiation with argon plasma.

Figure 14

Variation of FWHM of silver and agar/silver samples after irradiation with oxygen plasma.

Figure 15

Variation of FWHM of silver and agar/silver samples after irradiation with mercury lamp.

After irradiation with mercury lamp the FWHM increases rapidly for silver nanoparticle sample; however there is a hysterics behavior of agar/silver nanoparticle sample.

The above results are discussed in terms of a mechanism in which, agar consists of a mixture of agarose and agaropectin. It is composed of alternating 1,3-linked d-galactose and 1,4-linked 3,6 anhydro-l galactose units (Labropoulos et al. 2002). It has the ability to form reversible gels simply by cooling a hot aqueous solution.

It is well known that, polysaccharide contains of hydroxyl, acetyl, carbonyl and carboxylic functional groups. This disaccharide can be substituted by sulfate esters and methoxyl, and may also carry pyruvic acid residues (Duckworth and Yaphe 1971). The type, amount, and location of these substitutes strongly affect the physical properties of the gel and therefore, its functionality (Freile-Pelegrin and Murano 2005).

Based on these facts, it can be inferred that both hydroxyl and carbonyl groups of agar are involved in the synthesis of agar/silver nanoparticle sample and effectively help in capping the surface of nanoparticles. The variations in the shape and peak position of the hydroxyl and carboxylate groups using FTIR have been reported (Guerrero et al. 2014). Also silver nanoparticles can synthesized using another polysaccharide i.e. gum Acacia (Mohan et al. 2007), gum kondagogu (Kora et al. 2010) and gum Arabia (Gils et al. 2010).

Throughout the irradiation time with the argon, oxygen glow discharge plasma or mercury lamp, the antibacterial activity of several kinds of bacteria has been examined. Table 2 shows diameter of bacterial inhibition (clear zone) in mm. Bacterial strains number 1, 2, 5, 9 and 10 are Gram-positive bacteria while bacterial strains number 3, 4, 6, 7 and 8 are Gram-negative bacteria.
Table 2

Diameter of bacterial inhibition zone (clear zone) in mm

Sample name

Untreated silver NP (A)

Untreated agar/silver NP (B)

Treated (A) with argon plasma for 180 min

Treated (B) with argon plasma for 180 min

Treated (A) with oxygen plasma for 150 min

Treated (B) with oxygen plasma for 150 min

Treated (B) with mercury lamp at for 40 min

Treated (A) with mercury lamp for 15 min

Treated (B) with mercury lamp for 15 min

No.

Bacteria name

1

Bacillus cereus

8

8

10

9

8

8

8

8

8

2

Bacillus subtilis

9

10

9

9

8

8

8

8

8

3

E. coli

11

14

12

13

11

11

10

11

11

4

Klebsiella pneumoniae

15

10

10

10

10

10

10

12

10

5

Micrococcus roseus

16

11

10

10

11

10

10

11

10

6

Proteus vulgaris

11

8

9

15

9

9

8

8

8

7

Pseudomonas aeruginosa

12

11

14

12

16

14

12

14

12

8

Serratia marcescens

9

10

9

9

9

9

9

10

9

9

Staphylococcus aureus

17

15

12

11

12

12

11

12

10

10

Streptococcus sp.

15

18

13

13

17

14

13

14

12

Conclusions

In summary, the irradiation effects of argon, oxygen glow discharge plasma, and mercury lamp on silver and silver/agar nanoparticle samples are studied and compared. The tunability of the SPR position and its characteristics such as FWHM and peak intensity has been investigated. Therefore, the choice of suitable light source leads to controlling the SPR characteristics.

In the present process, glow discharge plasma and mercury lamp irradiation could have high potentials to enhance photochemical reduction method. The irradiation procedure is simple and reproducible and it can be operated at different glow discharge plasma conditions.

The virgin and treated nanoparticles samples exhibited strong antibacterial activity against both the Gram-positive and Gram-negative bacteria. Therefore, the resulting silver and agar/silver nanoparticles samples with antibacterial activity could have high potentials for many applications such as an antibacterial food packaging and a biomedical application such as wound dressings. However, actual applications of antibacterial nanoparticles require further studies focused on the potential health-hazard of such nanoparticles included products.

Declarations

Authors’ Affiliations

(1)
Physics Department, Faculty of science, Al-Azhar University-Assuit branch
(2)
Botany and Microbiology Department, Faculty of science, Al-Azhar University-Assuit branch

References

  1. Ahmadi TS, Wang ZL, Green TC, Hengleinet A, El-Sayedal MA: Shape-controlled synthesis of colloidal platinum nanoparticles. Science 1996, 272(5270):1924-1925. doi:10.1126/science.272.5270.1924 View ArticleGoogle Scholar
  2. Amoruso S, Ausanio G, Bruzzese R, Vitiello M, Wang X: Femtosecond laser pulse irradiation of solid targets as a general route to nanoparticle formation in a vacuum. Phys Rev B 2005, 71(3):033406-033410. doi:10.1103/PhysRevB.71.033406View ArticleGoogle Scholar
  3. Bacławski A, Musielok J: Transition probabilities for some infrared O I spectral lines—Application for determining excitation temperatures in low temperature plasmas. Spectrochim Acta B 2008, 63: 1315-1319. doi:10.1016/j.sab.2008.10.019 View ArticleGoogle Scholar
  4. Cobley CM, Skrabalak SE, Campbell DJ, Xia Y: Shape-controlled synthesis of silver nanoparticles for plasmonic and sensing applications. Plasmonics 2009, 4(2):171-179. doi:10.1007/s11468-009-9088-0View ArticleGoogle Scholar
  5. Duckworth M, Yaphe W: The structure of agar: Part I: Fractionation of a complex mixture of polysaccharides. Carbohydr Res 1971, 16(1):189-197. doi:10.1016/S0008-6215(00)86113-3View ArticleGoogle Scholar
  6. Freile-Pelegrin Y, Murano E: Agars from three species of Gracilaria (Rhodophyta) from Yucatan Peninsula. Bioresour Technol 2005, 96(3):295-302. doi:10.1016/j.biortech.2004.04.010View ArticleGoogle Scholar
  7. Gils PS, Ray D, Sahoo PK: Designing of silver nanoparticles in gum arabic based semi-IPN hydrogel. Int J Biol Macromol 2010, 46(2):237-244. doi:10.1016/j.ijbiomac.2009.12.014View ArticleGoogle Scholar
  8. Guerrero P, Etxabide A, Leceta I, Peñalba M, de la Caba K: Extraction of agar from Gelidium sesquipedale (Rodhopyta) and surface characterization of agar based films. Carbohydr Polym 2014, 99: 491-498. doi:10.1016/j.carbpol.2013.08.049View ArticleGoogle Scholar
  9. Hou W-C, Stuart B, Howes R, Zepp RG: Sunlight-driven reduction of silver ions by natural organic matter: formation and transformation of silver nanoparticles. Environ Sci Tech 2013, 47(14):7713-7721. doi:10.1021/es400802wView ArticleGoogle Scholar
  10. Kora AJ, Manjusha R, Arunachalam J: Superior bactericidal activity of SDS capped silver nanoparticles: synthesis and characterization. Mater Sci Eng 2009, C29(7):2104-2109. doi:10.1016/j.msec.2009.04.010View ArticleGoogle Scholar
  11. Kora AJ, Sashidhar RB, Arunachalam J: Gum kondagogu (Cochlospermum gossypium): A template for the green synthesis and stabilization of silver nanoparticles with antibacterial application. Carbohydr Polymer 2010, 82(3):670-679. doi:10.1016/j.carbpol.2010.05.034View ArticleGoogle Scholar
  12. Labropoulos KC, Niesz DE, Danforth SC, Kevrekidis PG: Dynamic rheology of agar gels: theory and experiments. Part I. Development of a rheological model. Carbohydr Polymer 2002, 50(4):393-406. doi:10.1016/S0144-8617(02)00084-XView ArticleGoogle Scholar
  13. Link S, El-Sayed MA: Shape and size dependence of radiative, non-radiative and photothermal properties of gold nanocrystals. Int Rev Phys Chem 2000, 19(3):409-453. doi:10.1080/01442350050034180View ArticleGoogle Scholar
  14. Mafune F, J-y K, Takeda Y, Tamotsu K: Formation and size control of silver nanoparticles by laser ablation in aqueous solution. J Phys Chem B 2000, 104(39):9111-9117. doi:10.1021/jp001336yView ArticleGoogle Scholar
  15. McFarland AD, Van Duyne RP: Single silver nanoparticles as real-time optical sensors with zeptomole sensitivity. Nano Lett 2003, 3(8):1057-1062. doi:10.1021/jp001336y 10.1021/nl034372sView ArticleGoogle Scholar
  16. Mohan YM, Raju KM, Sambasivudu K, Satyendra S: Preparation of acacia stabilized silver nanoparticles: A green approach. J Appl Polymer Sci 2007, 106(5):3375-3381. doi:10.1002/app.26979View ArticleGoogle Scholar
  17. NCCLS: National Committee for Clinical Laboratery Standards: Performance standard for antimicrobial Disc susceptibility Tests. Approved Standard NCCLS Publication, Villanova, PA, USA; 1993.Google Scholar
  18. Pillai ZS, Kamat PV: What factors control the size and shape of silver nanoparticles in the citrate ion reduction method? J Phys Chem B 2004, 108(3):945-951. doi:10.1021/jp037018rView ArticleGoogle Scholar
  19. Reader J, Sansonetti CJ, Bridges JM: Irradiances of spectral lines in mercury pencil lamps. Appl Optic 1996, 35(1):78-83. doi:10.1364/AO.35.000078View ArticleGoogle Scholar
  20. Richardson HH, Carlson MT, Tandler PJ, Pedro H, Alexander OG: Experimental and theoretical studies of light-to-heat conversion and collective heating effects in metal nanoparticle solutions. Nano Lett 2009, 9(3):1139-1146. doi:10.1021/nl8036905View ArticleGoogle Scholar
  21. Shaaban ER, Abdel-Wahab EA, Ahmad M: Optical characterization of As–S thin films induced by plasma immersion O − ion implantation. Phys Scr 2013, 88(1):015703. doi:10.1088/0031-8949/88/01/015703View ArticleGoogle Scholar
  22. Shalaev VM: Optical properties of nanostructured random media, vol 82. Topics in Applied Physics, Springer Verlag, Berlin; 2002. doi:10.1007/3-540-44948-5View ArticleGoogle Scholar
  23. Zhen SJ, Zhang ZY, Li N, Zhang ZD, Wang J, Li CM, Zhan L, Zhuang HL, Huang CZ: UV light-induced self-assembly of gold nanocrystals into chains and networks in a solution of silver nitrate. Nanotechnology 2013, 24(5):055601. doi:10.1088/0957-4484/24/5/055601View ArticleGoogle Scholar

Copyright

© Ahmad et al.; licensee Springer. 2014

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.