Synthesis of silver nanoparticles using plant extracts

Transcription

1 Mex. J. Mat. Sci. Eng. xxxx (2017) x-y Synthesis of silver nanoparticles using plant extracts J. Luis López-Miranda 1,*, R. Esparza 2, and G. Rosas 3 1 Instituto de Investigaciones Metalúrgicas, UMSNH, Santiago Tapia # 403, Col. Centro, Morelia Michoacán, México 2 Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Boulevard Juriquilla 3001, Santiago de Querétaro, Querétaro, C.P , México. Abstract. In this work, we report the green synthesis of silver nanoparticles using two plant extracts: Conyza filaginoides and Ficus carica. The Uv-vis spectra show a plasmon resonance band typical of the silver nanoparticles. As the Conyza filaginoides extract volume increases, the size of the nanoparticles decreases. Whereas when the Ficus carica extract was used, the best result was obtained with 4ml. The X-ray diffraction confirmed the presence of silver with an fcc structure. TEM analysis showed spherical nanoparticles with size ranges of 5 to 30nm. In addition, HRTEM images confirmed that the nanoparticles obtained have an fcc structure type. Finally, the FTIR spectra showed that the phenolic compounds of both plants involved in the synthesis of silver nanoparticles. Keywords: Silver nanoparticles; Green synthesis; plant extracts. Introduction The metal nanoparticles have attracted particular interest in recent years. Their unique properties are entirely different from their counterparts large [1-3]. In particular, the silver nanoparticles have potential applications in the area of electronics, catalyst, cosmetic and biomedicine [4-7]. However, its use in medicine is limited due to the synthesis processes employees, among which chemical reduction. This process involves the use of toxic agents, which are also expensive [8, 9]. An alternative to this problem is the use of green synthesis in which organisms such as fruits, algae, fungi and plant extracts are used [10-13]. They provide the reducing and stabilizing agents to carry out the synthesis of nanoparticles. Among the organisms, the use of plant extracts is the most used because it is an inexpensive, simple and reproducible method [14]. Several plants have been employed for the synthesis of silver nanoparticles: Plectranthus amboinicus [15], Ficus benghalensis [16], Dalbergia spinosa [17], Boswellia Serrata [18], Ceropegia thwaitesii [19]. Among the plants with Article history: Received ; Accepted ; Available online. medicinal properties are Conyza filaginoides and Ficus carica. The Ficus carica leaves have been used against throat diseases, antitussive, emollient, emmenagogue, and resolvent [20]. Konyalioglu et al have demonstrated their antioxidant capacity [21]. The Ficus carica leaves contain flavonoids and phenolic compounds that can act as the reducer agents and stabilizer agents. On the other hand, there are a few studies on the chemical composition of Conyza filaginoides. The leaves extract of Conyza filaginoides has been used for the treatment of cramps, diarrhea, dysentery, stomach pain and liver pain. Therefore, this work shows the results of the synthesis of silver nanoparticles using leaves extracts of Conyza filaginoides and Ficus carica. Methodology or experimental section The synthesis method described below has some advantages over conventional chemical methods. For example, this method is simple, inexpensive, reproducible, and environmentally friendly. AgNO3 crystals analytical grade was used as precursor salt and purchased from Meyer. AgNO3 was used in aqueous solution at 5mM ISSN:

2 concentration using distilled water. The Conyza filaginoides and Ficus carica leaves were collected from Zacapu Michoacan, Mexico. The leaves were washed with distilled water and then dried in the shade for ten days. After that, the leaves were milled to obtain fine powders. Subsequently, 2 g of powders were mixed in a beaker with 100 ml distilled water and heated at 80 C for 30 min, with magnetic stirring. Finally, the extract was filtered with Whatman filter paper # 41. The nanoparticles synthesis reaction consisted of the mix of 10 ml of AgNO3 solution with the plant extract. The extract amount was varied using 2, 3, 4 and 5 ml and consequently changing the precursor salt-reducing agent relationship. In all cases, the reactions were carried out at room temperature and without magnetic agitation. The silver nanoparticles were characterized by several techniques. UV-Vis spectroscopy using a Beckman DU-20 spectrophotometer was used to monitored the reaction solution 1 hour after mixing. Transmission electron microscopy made in a microscope Phillips Tecnai F20 operating at a voltage of 200 KeV provided with a field emission filament; the points resolution is 0.21 nm. The technique of high-resolution (HRTEM) was used to analyze the crystallographic phases. The X-ray diffraction analysis was conducted using a SIEMENS D5000 diffractometer with a CuKα radiation ( Å), in an angular range of Finally, the FT-IR spectroscopy analysis was performed using a Bruker Tensor 27 equipment with a resolution of 4 cm -1. indicating a decrease of the nanoparticles size [23]. Moreover, the intensity of the band increases as the amount extract increases. This behavior suggests the formation of a higher concentration of silver nanoparticles. Therefore, the use of 5ml of Conyza filaginoides extract showed the best result. This behavior is similar to the reported in other works [15, 16]. On the other hand, the Fig. 1b shows the UV-vis results when the Ficus carica extract was used. In this case, an SPR is centered at 425nm for 2ml of extract. The intensity of the band increases for 3ml and 4ml. However, the SPR intensities of 4ml and 5ml are very similar. Besides, the SPR shifts to the right as the volume extract increases, indicating the growth of the nanoparticle size [23]. Therefore, the use of 4ml of Ficus carica extract shows the best results about the concentration and size of the silver nanoparticles obtained. Results and discussion The UV-vis spectroscopy is a simple technique useful to corroborate the formation of nanoparticles. The silver nanoparticles show a typical Surface Plasmon Resonance (SPR) localized in the range of nm [22]. The Fig. 1a shows the UV-vis spectra of the silver nanoparticles obtained with different volume of Conyza filaginoides extract. As can be appreciated, an SPR at 450nm appears when 2ml of Conyza filaginoides was employed. For 3ml of volume extract, the SPR shift to the left at 437nm, ISSN:

3 Figure 1. UV-vis spectra of the silver nanoparticles using leaves extract of a) Conyza filaginoides and b) Ficus carica. The Fig. 2 shows the results of transmission electron microscopy. The Fig 2a is a representative micrograph of the silver nanoparticles obtained with 5ml of Conyza filaginoides leaves extract. As can be observed, there are a high concentration of silver nanoparticles, most of them with spherical morphology. The range size is between 10-30nm. Moreover, the Fig. 2b is a micrograph of HRTEM showing the lattice planes whose distance is 0.23nm corresponding to the (111) plane of the face-centered cubic silver. On the other hand, the Fig. 2c is the micrograph of the silver nanoparticles synthesized with 4ml of Ficus carica extract. It is observed a high concentration of the nanoparticles with spherical morphology and size of 10-18nm. In this case, the characteristics of the nanoparticles are more homogeneous. These results are better than the obtained by Aldebasi et al [24]. They synthesized silver nanoparticles with this plant. However, in their work, they used an extract with a higher concentration. Their results indicated the synthesis of silver nanoparticles with a broad size range (5 to 40 nm), several morphologies, and some agglomerates of nanoparticles. Finally, the Fig. 2d is an HRTEM micrograph showing the interplanar distance that corresponds to the (111) plane. The differences in size and morphology between the nanoparticles obtained with each plant extract are due the different chemical compounds acting as reducing and stabilizing agents for the synthesis of the nanoparticles. It can be concluded that the Conyza filaginoides leaves extract has a lower concentration of stabilizing agents than the Ficus carica extract. Therefore, the nanoparticles synthesized with Conyza filaginoides leaves extract have a higher size and irregular shapes. Figure 2. TEM analysis of the silver nanoparticles synthesized with leaves extract of a-c) Conyza filaginoides and b) Ficus carica. Fig. 3 shows the X-Ray diffraction patterns of the silver nanoparticles obtained with extracts of Conyza filaginoides and Ficus carica. In both diffractograms is appreciated the four mean reflections of the silver face cubic centered. The peaks appear at 38º, 44º, 64º and 77º corresponding to the planes (111), (200), (220) and (311), respectively. The Scherer equation was used to determine the crystal size of both patterns. The crystal size measured was 24nm and 15nmfor the silver nanoparticles synthesized with leaves extract of Conyza filaginoides and Ficus carica, respectively. These results confirmed the structure of the nanoparticles obtained. On the other hand, the unindexed peaks correspond to organic compounds surrounding and stabilizing the nanoparticles formed, as have been reported previously [25, 26]. ISSN:

4 Figure 3. X-Ray analysis of the silver nanoparticles synthesized with leaves extracts of a) Conyza filaginoides and b) Ficus carica. The FT-IR analysis was carried out to determine the functional groups involved in the synthesis of the silver nanoparticles. The Fig 4a shows the results of the silver nanoparticles synthesis using Conyza filaginoides. The leaves spectra show six bands; the band at 3230 cm -1 corresponding to O-H bond of the phenolic groups. The C-H group appears at 2970 cm -1. The band at 1600 cm -1 corresponds to aromatic compounds. N-H bond of the amide compounds is centered at 1370 cm -1. The peak at 1255 cm -1 assigned to N-H group from the amides and the band at 1068 cm -1 attributed to C-OH bond of aromatic compounds. Finally, the band at 823 cm - 1 assigned to C-H bond. In the spectra of the silver nanoparticles, the bands corresponding to the phenolic compounds are observed, i.e., the O-H, C-H, C=C and CO-H bonds. The FT-IR analysis of the silver nanoparticles synthesized using Ficus carica is shown in the Fig. 4b. The results are similar to the obtained with Conyza filaginoides. The same bands are observed with slight differences in intensity and position. Thus, it can be concluded that the phenolic compounds such as flavonoids have an important role in the synthesis of silver nanoparticles. This kind of compounds provide the electrons to reduce Ag + in Ag 0. Moreover, the flavonoids act as stabilizers, capping the nanoparticles, avoiding excessive and uncontrolled growth of nanoparticles. Figure 4. FT-IR analysis of the synthesis of silver nanoparticles using a) Conyza filaginoides and b) Ficus carica leaves extract (solid line correspond to leaves spectra and dot lines correspond to nanoparticles spectra). Summary The leaves extracts of Conyza filaginoides and Ficus carica showed capacity for the reduction of Ag ions to Ag metallic. Furthermore, both plants have in their composition the compounds to stabilize the nanoparticles synthesized. According to UV-vis analysis the silver nanoparticles showed a surface plasmon resonance around nm. The increase of the volume extract leads to a higher concentration of silver nanoparticles formed. The XRD technique confirmed the presence silver with the fcc structure. According to Scherrer equation, the crystal sizes were 24nm and 15nm for the nanoparticles synthesized with Conyza filaginoides and Ficus carica, ISSN:

5 respectively. TEM observations showed spherical nanoparticles. The size range of 10 to 30 nm were obtained in the nanoparticles synthesized with Conyza filaginoides leaves extract. Whereas, a size of 10-18nm was observed with Ficus carica extract. The role of phenolic compounds from the plants in the synthesis of silver nanoparticles was demonstrated by FT-IR spectroscopy. These results lead to a new, simple, economical, and free of toxic substances method for the metallic nanoparticles synthesis. References [1] B. Ajitha, Y. Ashok Kumar Reddy, P.S. Reddy, Biomolecular Spectroscopy, vol. 128, pp , [2] V. K. Sharma, R. A. Yngard, Y. Lin, Advances in Colloid and Interface Science, vol. 145, pp , [3] K. Roy, C. K. Sarkar, C. K. Ghosh, Applied Nanoscience, vol. 5, pp , [4] P. R. RathiSre, M. Reka, R. Poovazhagi, M. Arul Kumar, K. Murugesan, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, vol. 135 pp , 2015 [5] V. Kathiravan, S. Ravi, S. Ashokkumar, S. Velmurugan, K. Elumalai, C. P. Khatiwada, Biomolecular Spectroscopy, vol. 139 pp , 2015 [6] R. Mata, J. R. Nakkala, S. R. Sadras, Materials Science and Engineering C, vol. 51, pp , 2015 [7] D. I. Gittins, D. Bethell, R. J. Nichols, D. J. Schiffrin, Journal of Materials Chemistry, vol. 10, pp , [8] K. Rajarama, D. C. Aiswarya, P. Sureshkumar, Materials Letters, vol. 138, pp , [9] Y. Mo, Y. Tang, S. Wang, J. Lin, H. Zhang, D. Luo, Materials Letters, vol. 144 pp , [10] M. R. Bindhu, M. Umadevi, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, vol. 135, pp , [11] S. Patra, S. Mukherjee, A. K. Barui, A. Ganguly, B. Sreedhar, C. R. Patra, Materials Science and Engineering C, vol. 53, pp , [12] A. Syed, S. Saraswati, G. C. Kundu, A. Ahmad, Biomolecular Spectroscopy, vol. 114, pp , [13] M. Yousefzadi, Z. Rahimi, V. Ghafori, Materials Letters, vol. 137, pp. 1-4, [14] A. K. Mittal, Y. Chisti, U. C. Banerjee, Biotechnology advances, vol. 31, pp , [15] B. Ajitha, Y. A. K. Reddy, P. S. Reddy, Biomolecular Spectroscopy, vol. 128, pp , [16] A. Saxena, R. M. Tripathi, F. Zafar, P. Singh, Materials Letters, vol. 67, pp , [17] N. Muniyappan, N. S. Nagarajan, Process Biochemistry, vol. 49, pp , [18] A. J. Kora, R. B. Sashidhar, J. Arunachalam. Process Biochemistry, vol. 47, pp , [19] A. Saxena, R. M. Tripathi, F. Zafar, P. Singh, Materials Letters, vol. 67, pp , [20] P. Guarrera, Fitoterapia, vol. 74, pp , [21] S. Konyalioglu, H. Saglam, B. Kivcak, Pharmaceutical Biology, vol. 43, pp , [22] M. Jeyaraj, M. Rajesh, R. Arun, D. M. Ali, G. Sathishkumar, G. Sivanandhan, G. K. Dev, M. Manickavasagam, K. Premkumar, N. Thajuddin, A. Ganapathi, Colloid Surface B, vol. 102, pp , [23] K. L. Kelly, E. Coronado, L. L. Zhao, G. C. Schatz, Journal of Physical Chemistry B, vol. 107, pp , [24] Y. H. Aldebasi, S. M. Aly, R. Khateef, H. Khadri, African Journal of Biotechnology, vol. 13, pp , [25] K. Rajaram, D. C. Aiswarya, P. Sureshkumar, Materials Letters, vol. 138, pp , ISSN:

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