Elsevier

Applied Surface Science

Volume 366, 15 March 2016, Pages 275-283
Applied Surface Science

Spectrophotometric evaluation of surface morphology dependent catalytic activity of biosynthesized silver and gold nanoparticles using UV–vis spectra: A comparative kinetic study

https://doi.org/10.1016/j.apsusc.2016.01.093Get rights and content

Highlights

  • The biosynthesized silver nanoparticles were stable for 6 months and used as effective SERS active substrate.

  • They are effective catalyst in the chemical reduction of 4-nitrophenol to 4-aminophenol.

  • Comparative catalytic efficiency of both silver and gold nanoparticles was studied spectrophotometrically.

  • Our results demonstrate surface morphology dependent catalytic activity of both nanoparticles.

Abstract

The development of eco-friendly and cost-effective synthetic protocol for the preparation of nanomaterials, especially metal nanoparticles is an emerging area of research in nanotechnology. These metal nanoparticles, especially silver can play a crucial role in various catalytic reactions. The biosynthesized silver nanoparticles described here was very stable up to 6 months and can be further exploited as an effective catalyst in the chemical reduction of 4-nitrophenol to 4-aminophenol. The silver nanoparticles were utilized as an efficient surface-enhanced Raman scattering (SERS) active substrate using Rhodamine 6G as Raman probe molecule. We have also carried out systematic comparative studies on the catalytic efficiency of both silver and gold nanoparticles using UV–vis spectra to monitor the above reaction spectrophotometrically. We find that the reaction follows pseudo-first order kinetics and the catalytic activity can be explained by a simple model based on Langmuir–Hinshelwood mechanism for heterogeneous catalysis. We also find that silver nanoparticles are more efficient as a catalyst compare to gold nanoparticles in the reduction of 4-nitrophenol to 4-aminophenol, which can be explained by the morphology of the nanoparticles as determined by transmission electron microscopy.

Introduction

Metal nanoparticles are of great importance due to their remarkable physical and chemical properties as well as their potential applications in optics, electronics, sensing, catalysis, biodiagnostics and surface-enhanced Raman scattering (SERS) [1], [2], [3], [4], [5]. The various properties of metal nanoparticles can be tuned by controlling their shapes and sizes. Silver nanoparticles are of tremendous interest to researchers due to their excellent optical, electrical, catalytic and antibacterial properties [6], [7], [8], [9]. The antibacterial activities of silver ions and salts have studied since early days and they can be utilized to control the bacterial growth in various applications such as prosthese, catheters, burn wounds, etc. [10], [11]. Silver nanoparticles can also exhibit excellent catalytic activity due to its high surface area to volume ratio and high surface energy making them extremely reactive. Therefore, silver nanoparticles of various sizes and shapes can be used as an effective catalyst in various catalytic reactions including chemical, electrochemical and photochemical [12], [13], [14].

Therefore, developing new and novel synthetic protocol for the preparation of silver nanoparticles is very important in nanotechnological research with special emphasis on the controlling of their sizes and shapes. The most common method for the synthesis of silver nanoparticles is the chemical reduction of silver salts by reducing agents in the presence of different stabilizing agents such as polymers and surfactants. However, the chemical reduction method is highly tedious, expensive and non-eco-friendly due to the use of toxic and harmful chemicals.

The natural constituents of the environment, especially the secondary metabolites present in the plant and fruit extracts as well as in micro-organisms such as bacteria and fungi can be a possible sources of reducing and stabilizing agents to synthesize metal nanoparticles. The biosynthesis of metal nanoparticles can provide a cost effective eco-friendly alternative to the most commonly used chemical routes due to its biocompatibility, simplicity and low cost. Several groups have used plant and fruit extracts to synthesize both silver and gold nanoparticles of various sizes and shapes [15], [16], [17], [18], [19], [20]. In this article, we have reported the synthesis of silver nanoparticles using the plant extract of Piper betle. The synthesized silver nanoparticles were characterized by UV–vis spectroscopy, X-ray diffraction (XRD), Fourier-transform infra-red (FTIR) spectroscopy and transmission electron microscopy (TEM). We have used the biosynthesized silver nanoparticles as effective surface-enhanced Raman scattering (SERS) active substrate. We have also carried out a systematic comparative studies on the catalytic activity of as synthesized silver nanoparticles along with the gold nanoparticles synthesized by the same plant extract to study the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4 at 0–4 °C. It is important to mention here that 4-AP is an important intermediate in the synthesis of various analgesic and antipyretic drugs like paracetamol, acetaniline, phenacetin, etc. As 4-NP is used as a common precursor, the conversion of 4-NP to 4-AP is of great importance to study further. Metal nanoparticles such as gold and silver can exhibit catalytic activity towards this reaction.

The catalytic activities of gold and silver nanoparticles were studied using UV–vis spectra and the reaction was monitored spectrophotometrically varying the nanoparticles concentrations. We find that reaction has a pseudo-first order rate constant of 2.18 × 10−3 s−1 and corresponding activity parameter of 436 s−1 g−1 in the presence of 0.5 × 10−5 g of silver nanoparticles as the whole reaction completed within 85 min.

Section snippets

Materials and methods

All chemicals used in our studies were of analytical grade and used without further purification. All aqueous solutions were prepared with de-ionized water (DI). Sodium borohydride (NaBH4) (Sigma–Aldrich) solution was freshly prepared in ice cold water. 4-NP (Sigma–Aldrich) was purified by repeated crystallization in petroleum ether and ethyl acetate.

Results and discussion

The bio-reduction of Ag+ ions to Ag0 was monitored by UV–vis spectroscopy. Fig. 1(A) shows the UV–vis spectra of the biosynthesized Ag nanoparticles along with Piper betle broth (curve 1). A strong surface-plasmon resonance band (SPR) at 434 nm is clearly seen in curve 2 and arises due to the excitation of localized surface-plasmon oscillations of conduction electrons in silver nanoparticles whereas, the SPR band typically observed for silver nanoparticles is totally absent in the broth of the

Conclusions

We have synthesized silver nanoparticles using Bombay Piper betle plant extract as the source for reducing and stabilizing agents at room temperature. The biosynthesized silver nanoparticles were characterized by UV–vis spectroscopy, XRD, FTIR spectroscopy and TEM studies. We have also reported SERS measurements of R6G molecules adsorbed on these biosynthesized silver nanoparticles. The SERS results suggest that silver nanoparticles can be used as an efficient SERS active substrate. We have

Acknowledgements

BA thanks the Board of College and University Development (BCUD), (BCUD, Finance/2013-14/1776/dated: 20/01/2014) University of Pune for provision of financial support and UKS would like to thank Indian National Science Academy (INSA), New Delhi, India for INSA Visiting Scientist Fellowship (SP/VF-9/2014-15/273/01 April, 2014) under the supervision of BA at Bio-inspired Materials Science Laboratory, Department of Chemistry, Savitribai Phule Pune University, Ganeshkind, Pune-411007, India. UKS

References (36)

  • W. Fritzsche et al.

    Nanostruct. Mater.

    (1998)
  • Q. Zhou et al.

    Thin Solid Films

    (2008)
  • G. Gosheger

    Biomaterials

    (2004)
  • P. Liu et al.

    Appl. Surf. Sci.

    (2009)
  • K.L. Niraimathi et al.

    Colloid Surf. B

    (2013)
  • K.Y. Lee et al.

    J. Colloid Interface Sci.

    (2007)
  • N. Pradhan et al.

    Colloids Surf. A

    (2002)
  • I.O. Sosa et al.

    J. Phys. Chem. B

    (2003)
  • A. Roucoux et al.

    Chem. Rev.

    (2002)
  • N.L. Rosi et al.

    Chem. Rev.

    (2005)
  • C.J. Orendorff et al.

    Anal. Chem.

    (2005)
  • Z.Q. Tian et al.

    Annu. Rev. Phys. Chem.

    (2004)
  • L.T. Chen et al.

    J. Appl. Polym. Sci.

    (1995)
  • Q.L. Feng et al.

    J. Mater. Sci. Lett.

    (1999)
  • U. Samuel et al.

    Int. J. Antimicrob.

    (2004)
  • Q. Lu et al.

    Nat. Commun.

    (2014)
  • X. Chen et al.

    Green Chem.

    (2010)
  • B. Ankamwar et al.

    Digest. J. Nano Biostruct.

    (2012)
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