A Simple and Green Method for Synthesis of Ag and Au Nanoparticles using Biopolymers and Sugars as Reducing Agent
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A Simple and Green Method for Synthesis of Ag and Au Nanoparticles using Biopolymers and Sugars as Reducing Agent Germán Ayala1, Luci Cristina de Oliveira Vercik1, Thiago Antônio Villa Menezes1 and Andrés Vercik1. 1
Basic Sciences Department ZAB/FZEA, University of São Paulo, Av. Duque de Caxias Norte 225, 13635-000, Pirassununga, SP, Brazil.
ABSTRACT In this work we study the effect of different reducing agent (chitosan, starch and sugars) on to synthesis of silver (AgNPs) and gold (AuNPs) nanoparticles by reduction of silver nitrate (AgNO3) and chloroauric acid (HAuCl4), respectively. The plasmon absorption peak between 419 - 434 nm, measured using a UV-Vis spectrophotometer indicates the existence of AgNPs, this reaction was favored by the increase of temperature with optimal results at 90°C. Synthesis of AuNPs was only obtained using chitosan as reducing agent, the use of solutions of starch and sugars allows the reduction of the gold salt present in the chloroauric acid, however the low pH of the solutions creates thermodynamic instabilities for the AuNP synthesis, due to low repulsive force for colloid stability.
1. INTRODUCTION Metal nanoparticles have been studied over time because of their electrical, chemical, magnetic, optical, electronic and thermal properties, which render several important applications in areas of nanoscience and technology [1-5]. The properties of nanoparticles are based on the size, shape and surface morphology [1]. Silver nanoparticles (AgNPs) also presents applications in medicine and food packaging due their antimicrobial activity, which has already been evaluated for E. coli, B. cereus, B. subtilis, S. aureus, P. aeruginosa [6-9]. Gold nanoparticles (AuNPs) are used in the immobilization of enzymes (in biosensor) for the detection of pathogens, virus and bacteria and others applications in biomedical science such as controlled drug delivery [10-13], and theragnostics [14]. Conventional methods for producing nanoparticles involve the use of organic solvents and toxic reducing agents that generate an environmental risk [15]. The partial or total elimination of waste along with sustainable processes is known as green chemistry, which employs nontoxic chemical and renewable materials [1, 15]. Different works have addressed the green synthesis of Ag, Au and Pt nanoparticles using chitosan, starch, sugars, latex of Jatropha curcas and natural hydrocolloid of gum kondagogu, reporting the production of nanoparticles between 1-40 nm [1-5, 8, 9, 15-19].
The synthesis of nanoparticles using sugar as reducing agent usually requires long times or high temperatures for processing [4]. Sugars, as well as starch, are very cheap, nontoxicity, bio-friendly and do not need the use of organic solvents [1, 3]. Green synthesis can produced nontoxic nanoparticles that are stable under in vivo conditions for potential applications in nanomedicine and food technology [17, 20]. The objective of the this study is to compare a simple method of synthesis of Ag and Au nanoparticles utilizing chitosan as
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