SYNTHESIS OF SILVER NANO PARTICLES USING ALOE VERA

SYNTHESIS OF SILVER NANO PARTICLES USING ALOE VERA 

ABSTRACT

Silver nanoparticles (AgNPs) were synthesized using Aloe vera leaf extract as both reducing and stabilizing agents via microwave irradiation method. The effects of the microwave exposure time and the amount of AgNO3 solution on the mean particle size and concentration of the synthesized AgNPs solution were investigated using response surface methodology. The synthesized AgNPs were characterized by transmission electron microscopy, UV-Vis spectroscopy, and dynamic light scattering. Well-dispersed and spherically fabricated AgNPs with mean particle size (46 nm) and maximum concentration (64 ppm) and zeta potential (+15.5 mV), were obtained at optimal synthesis conditions, using 9 ml of AgNO3 (1 mm) and 0.1 ml of Aloe vera extract during microwave exposure time of 360 s. The antibacterial activity of the synthesized AgNPs was tested using Escherichia coli and Staphylococcus aureus bacteria and the obtained results indicated their significant inhibitory effects against these two Gramnegative

and Gram-positive bacteria.

 CHAPTER ONE

1.0 INTRODUCTION

The term nanoparticle is used to describe a particle with size in the range of 1–100nm (Yehia and Al-Sheikh 2014). They tend to react differently than larger particles of the same composition because of their large surface area, thus allowing them to be used in novel applications (Abou et al. 2010). Moreover, they serve as the fundamental building block of nanotechnology (Vahabi et al. 2011). 

Nowadays there is a wide application of nanoparticles in diverse fields including catalysis, energy, chemistry and medicine (Yehia and Al-Sheikh 2014). Nanotechnology approaches to control disease in human and plants have recently been increasing greatly and the unique physicochemical properties of nano-sized metal particles make them successful in biology and medicine (Jo et al. 2012). The current understanding of potential risks associated with the release of these materials in the environment for human and animal health is still insufficient (Wang et al. 2012). However, very recently Narayanan and Park 2014). There are numerous methods for synthesis of silver nanoparticles, but, mostly used chemical methods, including toxic chemicals and mostly non-polar solvent.

Therefore, there is tremendous need for the development of clean and biocompatible as well as cost effective and sustainable method for synthesizing silver nanoparticles.

According to Bansal et al. (2011) biological synthesis of silver nanoparticles is the novel approach. Many previous researchers highlighted the green synthesis of silver nanoparticles (Vahabi et al. 2011; Mondal et al. 2014; Sukirtha et al. 2012; Huang et al. 2007). Green synthesis of silver nanoparticle has some advantages towards the reduction of metal ions and their stability.

1.1 LITERATURE REVIEW

Verano-Braga et al. (2014) reported that the toxicity of AgNPs depends upon both dosage and particle size. Metal nanoparticles show large surface to volume ratio and exhibit antimicrobial properties due to their ability to interact with cellular membranes through disruption of cell wall structure (Ahmad et al. 2013; Trop et al. 2006). Especially silver has long been known for its strong toxicity against a wide range of microorganisms including bacteria and fungi Narayanan and Sakthivel 2010). Due to the presence of a myriad of biomolecules in plant metabolites possessing bioreduction and biostabilization ability, the exploration of such molecules could facilitate control over size and morphology of metal nanoparticles (Narayanan and Park 2014). They reported that ‘rapid and green’ method for the synthesis of silver metal nanoparticles (SNPs) using important medicinal plant Aloe vera and possible mechanism on the basis of the role played by the phytochemical constituents present in the plant extract. Aloe vera contains several groups of chemical constituents such as steroidal lactones, alkaloids, flavonoids and tannin.

The plant system, therefore, was selected for fabrication of silver nanoparticles and its antifungal activity against Rhizopus sp. And Aspergillus sp. (Katok et. al. Katok el al. have reported that as diameter of AgNPs is reduced below 32 nm, mercury (II) is reduced from water onto AgNPs. Esmaielzadeh Kandjani el al. have purposed ZnO/Ag nanoarrays, another nanostructured system, to remove Hg (II) due to its high selectivity because of the unique way in which mercury interacts with Ag nanoparticles. Because mercury is one of the most toxic heavy metals and concerns the threats to environment and human, other nanostructed systems have been proposed.

(Chudasama el al., 2010). Chemical reduction of silver ions using sodium borohydride (Zhang el al., 2000, hydrazine (Taleb, Petit & Pileni, 1997), ascorbic acid (Lee el., 2004), trisodium citrate (Sun, Mayers, & Xia, 2003), and polyos (Sun & Xia, 2002) were reported and are considered well-established methods. Although chemicals routes are effective, these method may suffer from toxicity due to the chemicals reagents used in these methods are hazardous to the environment (Nabikhan et al., 2010). To avoid the toxicity of chemicals, green synthesis was developed (Sharma, Yngard & Lin, 2009). This methods of biosynthesis of metal nanoparticles has been proposed as a cost effective and environmental friendly way of fabricating these materials.

1.2 AIMS AND OBJECTIVES 

The aims of this research work is to explore the synthesis of silver nanoparticles using aloe vera, through the following objectives:

To evaluate the potentials of aloe vera extract as a green reducer and the stabilizer for the synthesis of silver nanoparticles (AgNPs).

To analyze the ultraviolent radiation (UV) of the synthesized silver nanoparticle.

To optimize the synthesis process based on microwave irradiation to fabricate silver nanoparticles (AgNPs) with smaller particle size and the higher concentration and the stability.

CHAPTER TWO

2.0 MATERIALS AND METHODS

2.1 MATERIALS

2.1.1 Reagent 

Sodium hydroxide NaOH

 Silver nitrate AgN03

2.1.2 Apparatus 

S/N

Tools

Manufacturer

1.

250ml conical flask

Pyrex England

2.

500ml beaker

Pyrex England

3.

Funnel

Pyrex England

4.

Filter paper

Whatman No.1

5.

Magnetic stirrer

Pyrex England

6.

UV Spectrometer

Pyrex England

7.

PH meter

Pyrex England

8.

Weighing machine

Pyrex England

9.

Measuring cylinder

Pyrex England

10.

Reagent bottles 

Pyrex England

2.2 METHODS 

2.3 DEFINATION OF ALOE VERA

Aloe vera (aloe vera barbadensis miller) is succulent plant used in alternative medicine. With a total of 420 various plant species of aloe vera, it has been popular in Indian medicine for treatment of many conditions. For centuries, the plant has gained immense popularity for its beauty, health, skin care, and medical properties.

The name aloe vera was derived from the Arabic word “Alloeh”, meaning a “shining bitter substance” and vera came from Latin word “vera” meaning “true”. For years, aloe vera has been widely used in several culture – Egypt, Greece, Mexico, India, China, and Japan. The plant belongs to the Asphodelaceae (Liliaceae) family that thrives in dry regions in Asia, Europe, America, and Africa.

2.4 PREPARATION OF ALOE VERA EXTRACT

Fresh leaves of aloe vera were washed with distilled water to remove any impurity and the cut it into small pieces.

Measure 50Kg using weighing machine and putted it into 500ml beaker.

Heat it for 1 hour using heating machine after that the mixture was cooled and filtered using filter paper, and the filtered extract was stored at 40C.

2.5 SILVER NANOPARTICLES (AgNAPS)

Silver nanoparticles are nanoparticles of silver of between 1nm and 100nm in size. While frequently described as being ‘silver’ some are composed of a large percentage of silver oxide due to their large ration of surface to bulk silver atoms. Numerous shapes of nanoparticles can be constructed depending on the application at hand. Commonly used silver nanoparticles are spherical, but diamond, octagonal, and thin sheets are also common.

2.6 SYNTHESIS OF SILVER NANOPARTICLES 

20ml of aloe vera extract and 10ml of silver nitrate with the PH6 and heat for 20 minutes.

30ml of aloe vera extract and 20ml of silver nitrate with PH8 and heat for 30 minutes.

40ml of aloe vera extract and 30ml of silver nitrate with PH9 and heat for 40 minutes. 

50ml of aloe vera extract and 40ml of silver nitrate with PH10 and heat for 50 minutes.

CHAPTER THREE

3.0 RESULTS AND DISCUSSION

UV–Visible spectra analysis and colour change The colour of synthesised AgNPs clearly changes to red- dish brown within 72 h of incubation at room temperature (Fig. 1) and corresponding UV–Visible absorption spec- trum of AgNPs was recorded in Fig. 3.1. The spectra of AgNPs showed maximum absorption at 450 nm to the surface plasmon resonance of the formed silver nanoparticles. The colour change was due to the excitation of SPR in the production of silver nanoparticles (Narayanan and Sakthivel 2008; Xiaoming et al. 2009). Previous report from Huang et al. (2007) on C. camphora show that silver nanoparticles may grow in a process involving rapid bio- reduction and that they strongly influence the SPR in the water extract. This is accordance with the results obtained from bioreduction of silver nanoparticles using Spirulina Platensis, which showed that a SPR silver band occurred at 400–480 nm (Narayanan and Sakthivel 2008; Kasthuri et al. 2009).

Concentration 

PH

Absorption 

Wavelength 

20ml of aloe vera extract and 10ml of silver nitrate 

PH6

1.5

300nm

30ml of aloe vera extract and 20ml of silver nitrate 

PH8

0.2

350nm

40ml of aloe vera extract and 30ml of silver nitrate 

PH9

0.8

400nm

50ml of aloe vera extract and 40ml of silver nitrate 

PH10

0.5

450nm

Figure 3.1: UV–Visible spectra of silver nanoparticles

Figure 3.2: Change of colour after 72 h a. only AgNO3 solution, b. 5 % Aloe vera extract and c. 3 mM AgNO3 + 5 % Aloe vera extract

CHAPTER FOUR

4.1 CONCLUSION

In the present study, we focused on green synthesis of silver nanoparticles using aqueous leaf extract of Aloe vera. The physical property of synthesized nanoparticle was characterized using relevant technique. The data represented in our study contributed to a novel and unique virgin area of nano-materials as an alternative UV for future. With little uncovered mechanism in the current study, there is a wide scope for detailed investigation in the future for the application of AgNPs in the field of Agriculture for controlling the pathogen.

4.2 RECOMMENDATION

This methods of synthesis of AgNO3 nanoparticles has been proposed as a cost effective and environmental friendly way of fabricating materials.

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