Controlling the Absorption of Gold Nanoparticles via Green Synthesis
Using Sargassum crassifolium Extract
Angeline F. Maceda1,a, Johnny Jim S. Ouano1,3,b, Mar Christian O. Que4,
Blessie A. Basilia4, Melchor J. Potestas1,2,c, Arnold C. Alguno1,2,d
1Materials Science Laboratory, Department of Physics
2Premier Research Institute for Science and Mathematics (PRISM), Mindanao State University –
Iligan Institute of Technology, Bonifacio Avenue, 9200 Iligan City, Philippines
3Physics Department, Mindanao State University, Marawi City, 9700, Philippines
4Department of Science and Technology Industrial Technology Development Institute, Bicutan,
Taguig City, 1631, Philippines
Keywords: Gold nanoparticles, bioreduction, green synthesis, Sargassum crassifolium, Surface
Abstract. This work controls the absorption of gold nanoparticles (GNPs) via green synthesis
utilizing Sargassum crassifolium extract. The amount of seaweed extract acts as both reducing
(from Au+ to Au0) and capping agent. The S. crassifolium extract is mainly composed of
biomolecules such as protein and phenolic compounds which are responsible for the synthesis of
GNPs. The synthesized GNPs were characterized using UV-Visible spectroscopy, Fourier
Transform Infrared (FTIR) spectroscopy and Transmission Electron Microscopy (TEM). UV-Vis
spectra revealed peaks around 505 nm to 544 nm which corresponds to the Surface Plasmon
Resonance (SPR) of GNPs. FTIR spectroscopy analysis showed peak at 825 cm-1 and 1144 cm-1
which corresponds to the signature peaks of GNPs. Polydisperse GNPs with varied sizes (between
5 nm to 300 nm) were further confirmed by TEM analysis.
Nanotechnology has become one of the most promising fields of research in modern materials
science nowadays. It develops therapeutic nanoparticles for biomedical and pharmaceutical
applications. From its bulk properties, nanoparticles can display completely new and enhanced
properties based on size, shape, density and morphology [1,2]. One of the most interesting areas in
nanotechnology is the synthesis of gold nanoparticles (GNPs) with well-defined properties. These
unique and tunable properties of GNPs include Surface Plasmon Resonance (SPR), biocompatibility
and easy surface modification . For biological and medical purposes, GNPs are preferred
compare to other metal nanoparticles because of its low-toxicity and easy conjugation to
As the revolution of nanotechnology continue to unfold, it is very essential to utilize
environment-friendly and non-hazardous methods in the production of GNPs. Most of the
conventional methods for GNPs fabrication involve toxic chemicals, expensive techniques or
inefficient consumption of energy and resources . In addition, there were reports that existing
synthetic processes lead to the presence of toxic chemical species adsorbed on the surface of GNPs
that may have adverse effects in medical applications . The unfavorable effects of synthetic
methods in producing GNPs lead scientists to explore alternative technique such as green synthesis
using bacteria, fungi, plants and seaweeds. Green synthesis offers safe, environment-friendly,
inexpensive and compatibility for biomedical applications as it lessens the utilization of toxic
A number of researchers have worked on the synthesis of GNPs using plant species. They
explored lemon grass (Cymbopagon flexuosus), cinnamon (Cinnamomum camphora), wheat
Key Engineering Materials Submitted: 2018-01-28
ISSN: 1662-9795, Vol. 765, pp 44-48 Accepted: 2018-02-06
doi:10.4028/www.scientific.net/KEM.765.44 Online: 2018-03-26
© 2018 Trans Tech Publications, Switzerland
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans
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(Triticum aestivum), oat (Avena sativa) and green tea (Camellia sinesis) [8-11]. Their works
revealed that polyols such as terpenoids, polysaccharides and flavone compounds participate in the
reduction process . Recently, extracts from seaweeds have gained much favorable attention in
the synthesis of GNPs because it contains more compounds needed in the bioreduction and
stabilization process . Seaweeds offer advantages in the synthesis of GNPs due to its high metal
uptake capacity and rapid bioreduction . There were several reports utilizing Sargassum
polycystum, Turbinaria conoides, Stoechospermum marginatum and Padina pavonica extracts for
the formation of GNPs [15-18]. These reports have shown successfully synthesized GNPs that
stabilizes over a short time with polydisperse sizes. However, to the best of our knowledge, the
brown seaweed Sargassum crassifolium was not yet utilized in the synthesis of GNPs. S.
crassifolium is very abundant in the Philippines and its extract contains more phytochemical
compounds that might trigger bioreduction and stabilization of GNPs. In this work, we are going to
utilize S. crassifolium extract for the synthesis of GNPs. Varied amounts of S. crassifolium extract
were employed to control the absorption peak of the synthesized GNPs.
Materials and Methods
Chemicals and collections of brown seaweed
Analytical grade of chloroauric acid (HAuCl4) used in this work was purchased from Sigma-aldrich.
The brown seaweed Sargassum crassifolium was collected from the Municipality of Initao,
Misamis Oriental, Philippines.
Preparation of seaweed extract
The collected brown seaweed was washed thoroughly with tap water to remove epiphytes that may
have lived in the fronds. The clean seaweed was subsequently washed with distilled water for
several times and air dried for a week. It was then kept in an oven overnight at 60◦C to remove the
remaining moisture. The dried seaweed was then pulverized in an analytical mill to obtain a very
fine powder. The seaweed extract was formulated by adding 10 g of seaweed powder to 100 ml of
deionized water and stored for 24 hours. The resulting extract was filtered thoroughly using
Whattman filter paper 1 until no insoluble material appeared in the seaweed extract.
Synthesis of gold nanoparticles
Aqueous solution (1mM) of chloroauric acid was prepared and used for the synthesis of gold
nanoparticles. Four samples were prepared with constant volume of chloroauric acid while varying
the amount of seaweed extract from 1 mL, 10mL, 20 mL and 40 mL. The samples were stored for
24 hours to allow the complete reduction of metal ions. Bioreduction was further monitored by
visual observation through the change in color of the solution.
Characterization of gold nanoparticles
The reduction of Au+ to Au0 was observed by measuring the absorbance in the UV-Visible spectrum
at different amount of brown seaweed extract. UV-Visible spectral analysis has been monitored
using Perkin Elmer Lambda 35 spectrophotometer at a resolution ranging from 400 to 750 nm. The
samples were then freeze dried to obtain dry powder. The dried powder was mixed with KBr
powder and pressed into pellet for measurement. Background correction was made using a blank
KBr pellet. The pellet was analyzed using FTIR (Perkin Elmer Spectrum 100) to identify the
functional groups in the S. crassifolium extract responsible for the reduction of gold ions to
nanoparticles. Transmission Electron Microscopy (TEM) was carried out using JEOL JEM-2100F
to identify the shape and size distribution of the synthesized gold nanoparticles.
Results and Discussion
The UV-Vis spectra of the synthesized GNPs utilizing varied amount of S. crassifolium extracts are
shown in Figure 1. The absorption peak around 505 nm to 544 nm corresponds to the SPR of the
synthesized GNPs. These observed absorption peaks are similar to the previous works using
different seaweed species reported elsewhere [15-18]. As shown in the inset image found in Figure
1, the absorption peak of the SPR can be tailored depending on the amount of S. crassifolium
Key Engineering Materials Vol. 765 45
extract. It is observed that increasing the amount of S. crassifolium extract will exhibit a blue shift
(to lower wavelength) in the absorption peak. This blue shift may be attributed to the increasing
nucleation centers available in the bioreductant that may result to the decrease in particle size.
Fig. 1. The absorption spectra of synthesized gold nanoparticles. Inset image is the absorption peak of the synthesized
GNPs at different volume of S. crassifolium extract.
FTIR spectra of the synthesized GNPS using different amount of S. crassifolium extract is shown
in Figure 2. It is observed that peaks at 825 cm-1 and 1144 cm-1 are the signature peaks of the
synthesized GNPs. These peaks are absent for the spectrum corresponds to S. crassifolium extract
alone. This revealed that successful formation of GNPs took place. The band at 3400 cm-1
corresponds to OH- stretching which indicates the presence of mostly alcohol and phenols in the
seaweed extract meanwhile the stretching in 2947 cm-1 is due to the carboxylic acid. On the other
hand, the peaks at 1630 cm-1 and 1420 cm-1 are due to the presence of amines. In 1255 cm-1 there is
a peak that corresponds to C-O stretching of carboxylic groups whereas 1088 cm-1 and 1044 cm-1
correspond to C-N stretching or the vibrations of amines in proteins while 880 cm-1 is assigned to S-
O stretching of sulfonates.
Fig. 2. FTIR spectra of the synthesized GNPs with varied amount of S. crassifolium extract. The FTIR spectrum of S.
crassifolium extract only is shown for reference.
The TEM image of the synthesized GNPs is shown in Figure 3. Polydisperse growth of GNPs is
observed. Several shapes such as sphere, rod-like, triangle, hexagon and colloids are present. Size
distribution varied from 5 nm to 300 nm. Different sizes and shapes of the GNPs maybe attributed
to the different compounds found in S. crassifolium extract that maybe responsible for the reduction
and stabilization of GNPs. These polydisperse GNPs were previously reported by other authors
utilizing different plant extracts [8-11,15-18].
46 Advanced Materials Research VII
Fig. 3. TEM images of the synthesized GNPs. (a) lower magnification (b) higher magnification.
The green synthesis technique is performed for the preparation of GNPs utilizing different amount
of S. crassifolium extract which acts both as reducing and capping agent. The formation of GNPs
(from Au+ to Au0) is confirmed by the observation of Surface Plasmon Resonance at around 505 nm
to 544 nm in the UV-Vis spectra. Increased amount of seaweed extract, resulted a shift in the
absorption peak to lower wavelength which gave the optimum nanoparticle size at 505 nm. FTIR
spectra analysis revealed that GNPs are successfully synthesized. The TEM image revealed the
formation of polydisperse GNPs. Finally, the utilization of Sargassum crassifolium extract for the
synthesis of GNPs promotes a potential alternative that offers a facile, safe, environment-friendly
and low-cost method.
One of the authors (AFM) is grateful to Department of Science and Technology - Accelerated
Science and Technology Human Resource Development Program (DOST-ASTHRDP) for the
scholarship grant. The Department of Science and Technology – Philippine Council for Industry,
Energy and Emerging Technology Research and Development (DOST-PCIEERD) is also
acknowledge for the equipment used in this study.
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