Green Synthesis of Gold and Silver Nanoparticles from Plant Extracts

Cassandra Dyal,1 Nguyen Nguyen,1 Jodi Hadden,1Linfeng Gou,2 Tan, Li,2 Catherine J. Murphy,2 Will

Lynch,1 Delana Nivens1

1Department of Chemistry and Physics, Armstrong Atlantic State University, 11935 Abercorn St., Savannah, GA 314192Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208

Abstract

The synthesis of metal and semiconductor nanoparticles is an expanding research area due to the potential applications for the development of novel technologies. Generally, nanoparticles are prepared by a variety of chemical methods which are not environmentally friendly. We report a rapid and convenient method to reductively prepare gold and silver nanoparticles from auric chloride and silver nitrate respectively. In this report we use aqueous extracts from plants indigenous to southeastern Georgia, namely the Southern Live Oak (Quercus virginiana), Southern Magnolia (Magnoliagrandiflora), Kudzu (Pueraria lobata) and Loblolly Pine (Pinus taeda). The extracts template the reductive preparation of both gold and silver nanoparticles which are found to be < 100 nm in size. The synthesis and characterization, including FT-IR, TGA and TEM analysis of these particles will be described.

Purpose

Identify “green” pathways to produce nanoparticles using regionally (south Georgia)significant resources

Presently, minimal information on using environmentally benign chemicals for particle synthesis

Prepare aqueous extract – broth prepared by boiling 20 grams of plant leaf mass in 100 mL distilled water for 5 minutes followed by filtering. Broth stored in refrigerator at 4ºC.

Use extracts from:Quercus virginiana – Southern Live OakMagnolia grandiflora – Southern MagnoliaPueraria lobata – KudzuPinus taeda – Loblolly Pine

Add 5 mLs of extract with 100 mLs of 1 mM AgNO3 or AuCl3 heated to 75ºC. Maintain this temperature for the entire reaction (different plant extracts require different times to complete the reaction)

Monitor the UV-Vis spectrum of the particle formation (exciton band near 430 nmfor silver and 550 nm for gold

Centrifuge product, wash 3 x with di water and perform FT-IR, TGA and TEM analysis

Experimental

Gold Nanoparticles

Ag Nanoparticle Formation

Live Oak MagnoliaUV-Vis Spectra of the Formation of Silver Nanoparticles Using Live Oak Leaf Broth

0

0.5

1

1.5

2

2.5

200 300 400 500 600

Wavelength (nm)

Ab

so

rban

ce

Au Nanoparticle Formation

Live Oak Magnolia

0

0.5

1

1.5

300 400 500 600 700Wavelength (nm)

Ab

so

rba

nc

e

Ag/Au Nanoparticle Formation – Other Plants

Pine (Cold)Pine (Hot)Kudzu

Au Nanoparticle Formation – Temperature Dependence

Gold Nanoparticles Formation Rate

-0.50000

0.00000

0.50000

1.00000

1.50000

2.00000

0 4 8 12 16 20

Time (min)

Abs

orba

nc(A

u)

40 60 23 80 70

Au Nanoparticle Formation – Concentration Dependence

Gold Nanoparticles Formation Rate

0.00

0.50

0 4 8 12 16 20

Time (min)

Abs

orba

nc (A

U)

Room Temp. Room Temp. 2x Extract

“Green” Nanoparticle IR Analysis Ag – Live Oak

76

77

78

79

80

400140024003400

Wavenumber (cm-1)

% T

29173351

3186

1613

1355

1044

Wavenumber (cm-1) Functional group Biomolecule1044 Alkane, C-O stretch Lipids 1613 Amide Amino acids2917 Alkane C-H stretch Lipids 3186 Hydroxyl group Sugars 3351 N-H amines Amino acids

“Green” Nanoparticle IR Analysis Au – Magnolia

15

25

35

45

55

5001000150020002500300035004000

1627cm-11450 cm-1

1141 cm-1

2931 cm-1

3502cm-1

Wavenumber (cm-1) Functional group Biomolecule 1141 C-O,C-N or CC Stretch Lipids, Amino acids ,Sugars1450 CH, OH bend Lipids, Sugars 1627 Amide Amino acids 2931 Alkane C-H stretch Lipids 3520 N-H amines Amino acids

TGA Analysis

40

60

80

100

100 250 400 550 700 850 1000

Temperature (oC)

Wei

ght %

70

80

90

100

100 250 400 550 700 850 1000

Temperature (oC)

Weigh

t %

Scan Rate = 20 °C/min

Live oak loss-28%

Magnolia Loss 57%

Gold - Magnolia

Gold Live Oak

TGA Analysis

55

70

85

100

100 250 400 550 700 850 1000

Temperature (oC)

Weig

ht

%

Silver, Magnolia

Loss of 44%

Scan Rate = 40 °C/min

Conclusions

1. Green methods for NP preparation are being developed

2. Pine and Live oak extracts seem to be the fastest for the preparation of both gold and silver nanoparticles while Kudzu is the slowest.

3. Rate of reaction is dependent upon T and [ Mn+ ]

4. IR indicates biomolecule capping agent present

5. Sizes are typically on the order of 20 nm by TEM imaging.

6. Some interesting triangle shaped nanoparticles are seen in the gold nanoparticles

Acknowledgements

•National Science Foundation Division of Undergraduate Education: Nanotechnology in Undergraduate Education Grant CHE/NUE 0303994

•National Science Foundation Course Curriculum and Improvement Grant DUE/CCLI - 9952343

•USG Matching Grant

•AASU College of Arts and Sciences, Department of Chemistry and Physics

•AASU Research and Scholarship Grant / Gignilliat Scholarship