Phytosynthesis of Au, Ag and Au–Ag bimetallic nanoparticles using aqueous extract and dried leaf of Anacardium occidentale

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Abstract

Present study reports a green chemistry approach for the biosynthesis of Au, Ag, Au–Ag alloy and Au core–Ag shell nanoparticles using the aqueous extract and dried powder of Anacardium occidentale leaf. The effects of quantity of extract/powder, temperature and pH on the formation of nanoparticles are studied. The nanoparticles are characterized using UV–vis and FTIR spectroscopies, XRD, HRTEM and SAED analyses. XRD studies show that the particles are crystalline in the cubic phase. The formation of Au core–Ag shell nanoparticles is evidenced by the dark core and light shell images in TEM and is supported by the appearance of two SPR bands in the UV–vis spectrum. FTIR spectra of the leaf powder before and after the bioreduction of nanoparticles are used to identify possible functional groups responsible for the reduction and capping of nanoparticles. Water soluble biomolecules like polyols and proteins are expected to bring about the bio-reduction.

Highlights

► Metallic NPs are synthesized for the first time using Anacardium occidentale. ► Both leaf extract and powder are used for the biosynthesis. ► Formation of Au core–Ag shell bimetallic nanoparticles is reported. ► The possible bio-molecule responsible for reduction and stabilization is suggested. ► The method is a simple, efficient and environment-friendly approach.

Introduction

A naturally motivated investigational practice for the biosynthesis of metal nanoparticles is now established as an emerging area of nanoscience research and development. As nature make optimum use of materials and space, many inorganic materials are produced in biological systems [1]. Similar to such natural processes, plants [2], [3], [4], [5], fungi [6], and bacteria [7] are found to be of great success for the synthesis of metal nanoparticles [8].

The advances in the field of biotechnology and nanotechnology owes to the tremendous improvement in human life. In recent years, an increasing percentage of nanomaterials are emerging and making advancement in different fields. Unlike the bulk counterparts, nanoparticulate materials exhibit very interesting electrical, optical, magnetic and chemical properties [9]. Nanoparticles of noble metals are widely applied in common products like soaps, cosmetics, toothpaste, shampoos and medicines which make their synthesis vital [10]. Nanoparticle synthesis is usually carried out by various physical and chemical methods like laser ablation, pyrolysis, lithography, chemical vapour deposition, sol–gel technique and electro-deposition which are very expensive and hazardous. Therefore scientists are looking forward for greener methods [11], [12]. In the present study, we report the green synthesis of gold and silver nanoparticles using both leaf extract and powder of Anacardium occidentale. These metal nanoparticles have received attention due to their unique and tunable SPR and shape and size-dependent properties [13]. They find applications in scientific and technological fields like drug delivery [14], tissue/tumor imaging [15], photothermal therapy [15], catalysis [16], [17], optoelectronics [18], water purification [19], SERS detection [20], [21], and biosensing [22], [23]. Silver nanoparticles have found to posses anti-fungal, anti-bacterial, anti-inflammatory, anti-viral, anti-angiogenesis, and anti-platelet activity and cytotoxicity against cancer cells which makes them vital [24], [25], [26], [27].

In recent years, synthesis of both Au and Ag NPs has been reported using the extracts of Chenopodium album [1], Coleus amboinicus Lour [13], Cinnamomum camphora [28], Sorbus aucuparia [29], Hibiscus rosa sinensis [30], Ocimum sanctum [31], Azadirachta indica [32] and Camellia sinensis [33]. There are also reports of using extracts of fruits like papaya [34], tansy [35], peer [36], lemon [37] and gooseberry [38] in the green synthesis of these nanoparticles. Shankar et al. [32] have shown that Au core–Ag shell NPs in solution can be synthesized using Neem leaf extracts. The Ag NPs prepared using Pelargonium graveolens leaves were found to be stabilized by an enzymatic process [39]. Importantly Huang et al. [28] have reported the synthesis of Au and Ag NPs by novel sundried biomass of Camphora leaf. Recently Ankamwar [40] has demonstrated the synthesis of stable Au NPs of size range 10–35 nm using Terminalia catappa leaf extract. Their group have also reported the synthesis of Au NPs using Indian goose berry fruit extract [38] and their phase transfer in to organic solution using a cationic surfactant. The transmetallation reaction between hydrophobised Ag NPs and hydrophobised chloroaurate ions in chloroform resulted in the formation of hollow-Au shells. A rapid synthesis of gold NPs having a mixture of plate and spherical structures using Magnolia kobus and Diopyros kaki leaf extracts were investigated by Song et al. [10]. Torresdey et al. [41] have reported the synthesis of Au and Ag NP within live Alfalfa plants. Wang et al. [42] used Skullcup herb for the extracellular synthesis of gold NPs. Chandran et al. had observed the formation of crystalline gold nano triangles using Aloe vera extract [43]. Ghodake et al. [36] have successfully biosynthesized triangular and hexagonal nanoplates, elegantly assembled with gold NPs using Peer fruit extract. Earlier reports from our lab include the green synthesis of Ag and Au NPs using Honey [44], H. rosa sinensis [30], O. sanctum [31], Mangifera indica [45], [46] and Murraya Koenigii [47]. Au–Ag alloy nanoparticles were also synthesized using edible Mushroom extract [48]. In biosynthesis, plants are preferred to micro-organisms, as it does not involve any tedious process of maintaining cell cultures [15]. Beyond that, the seasonal effects of plants and variation boiling time can be eliminated by using dried biomass of plant material which can be used at any time anywhere.

A. occidentale (Fig. 1) belonging to Anacardiaceae family, has great economic and medicinal value [49], [50]. It is commonly called Cashew and is a multipurpose tree whose leaves, stem and bark extracts are used extensively for the treatment of diarrhea, hypertension, dysentery, toothache, sore gums, colonic pain etc. It has also been reported to possess anti-diabetic, anti-bacterial, anti-inflammatory and anti-ulcerogenic properties [51], [52], [53]. India is the second largest producer of cashew nuts and it is widely cultivated in India. But the other parts of the plant have not been exploited. In this paper, rapid biosynthesis of Au, Ag and Au–Ag bimetallic NPs using cashew leaf extract and powder has been investigated which is an easiest, cost efficient, non-toxic, eco-friendly and efficient method for exploiting cashew leaves.

Section snippets

Materials and methods

Fresh A. occidentale leaves were collected from rural areas of Thiruvananthapuram, India. Fresh leaves were washed thoroughly with de-ionized water. 10 g of the homogenized leaves were stirred with 100 ml de-ionized H2O for 5 min and filtered to get the extract. For the preparation of leaf powder, the leaves were dried for two weeks, grounded and sieved to get fine powder. AgNO3 and HAuCl4 were procured from Sigma–Aldrich chemicals. All glasswares were cleaned with aqua regia and rinsed several

Characterization

The optical absorption spectra of the synthesized nanoparticles were observed by UV-2450 Shimadzu UV spectrometer. HRTEM images and electron diffraction patterns were obtained with a JEOL 3010 and Philips CM 200 transmission electron microscope. FTIR spectra of dried gold and silver nanoparticles, native and treated leaf power were recorded with an IR Pestige-21 Shimadzu spectrometer. X-ray diffraction pattern of dried nanoparticle powder were obtained using XPERT-PRO diffractometer using Cu Kα

UV–vis spectral studies

The optical absorption spectrum of metal nanoparticles is sensitive to several factors like particle size, shape, particle–particle interaction with the medium and local refractive index [54]. Fig. 2a and b show the UV–vis spectra of Au NPs prepared using leaf extract and dried leaf powder with SPR band around 529 nm and 526 nm respectively. The appearance of red color was due to the excitation of surface Plasmon vibrations which is absent in bulk material [55], [56]. From Fig. 2a, it is seen

Conclusion

Biosynthesis of gold and silver nanoparticles using cashew leaf powder and extract were investigated. The amount of plant material was found to play a critical role in the size dispersity of NPs. It is found that lower amounts of plant material were sufficient to bring about reduction. Use of leaf powder is advantageous over leaf extract as it eliminates the seasonal effects and its concentration can be optimized. Similarly leaf powder is found to be useable at any time at any place. Au NPs

Acknowledgements

Sheny D S thanks the UGC for the Junior Research Fellowship. The authors are pleased to acknowledge Prof. T. Pradeep, DST unit of Nanoscience, IIT Madras and SAIF, IIT Bombay for TEM measurements.

References (76)

  • A.D. Dwivedi et al.

    Colloids Surf. A

    (2010)
  • A.R. Binupriya et al.

    J. Hazard. Mater.

    (2010)
  • J.Y. Song et al.

    Process Biochem.

    (2009)
  • K.B. Narayanan et al.

    Mater. Charact.

    (2010)
  • F.K. Alanazi et al.

    Saudi Pharm. J.

    (2010)
  • T. Pradeep et al.

    Thin Solid Films

    (2009)
  • D. Philip et al.

    Spectrochim. Acta A

    (2008)
  • B. Zheng et al.

    Talanta

    (2010)
  • M. Sathishkumar et al.

    Colloids Surf. B

    (2009)
  • K. Kalishwaralal et al.

    Colloids Surf. B

    (2010)
  • S.P Dubey et al.

    Colloids Surf. B

    (2010)
  • D. Philip

    Phys. E

    (2010)
  • S.S. Shankar et al.

    J. Colloid Interface Sci.

    (2004)
  • S.P. Dubey et al.

    Process Biochem.

    (2010)
  • G.S. Ghodake et al.

    Colloids Surf. B

    (2010)
  • T.C. Prathna et al.

    Colloids Surf. B

    (2011)
  • Y. Wang et al.

    Colloids Surf. B

    (2009)
  • D. Philip

    Spectrochim. Acta A

    (2010)
  • D. Philip

    Spectrochim. Acta A

    (2011)
  • D. Philip

    Spectrochim. Acta A

    (2010)
  • D. Philip et al.

    Spectrochim. Acta A

    (2011)
  • D. Philip

    Spectrochim. Acta A

    (2009)
  • J.G.S. Maia et al.

    J. Food Compos. Anal.

    (2000)
  • D. Inbakandan et al.

    Colloids Surf. B

    (2010)
  • D. Philip

    Spectrochim. Acta A

    (2008)
  • S.L. Smitha et al.

    Spectrochim. Acta A

    (2008)
  • K.B. Narayanan et al.

    Mater. Lett.

    (2008)
  • E. Filippo et al.

    J. Non-Cryst. Solids

    (2010)
  • S.L. Smitha et al.

    Spectrochim. Acta A

    (2009)
  • H. Bar et al.

    Colloids Surf.

    (2009)
  • D. Zheng et al.

    Sens. Actuators

    (2010)
  • N. Ahmad et al.

    Colloids Surf.

    (2010)
  • H. Schulz et al.

    Vib. Spectrosc.

    (2007)
  • L. Castro et al.

    Chem. Eng. J.

    (2010)
  • A. Bankar et al.

    Colloids Surf. B

    (2010)
  • R.K. Das et al.

    Mater. Lett.

    (2010)
  • N. Ahmad et al.

    Biotechnol. Res. Int.

    (2011)
  • R. Sarkar et al.

    Nanomater. Biostruct.

    (2010)
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