ISSN 0974-3618
(Print) www.rjptonline.org
0974-360X (Online)
RESEARCH ARTICLE
Seaweed (Sargassum wightii Greville) assisted green synthesis of palladium nanoparticles
B.S. Naveen Prasad1*,
TVN. Padmesh2, V.
Ganesh Kumar3 and K. Govindaraju3
1Department of Chemical Engineering,
Sathyabama University, Chennai-600 119
2Department of Chemical Engineering,
Manipal International University, Malaysia
3Nanoscience Division, Centre for Ocean
Research, Sathyabama University, Chennai – 600 119
*Corresponding Author E-mail:
bsnaveenprasad@gmail.com
Biosynthetic processes for palladium
nanoparticles would be more useful if nanoparticles were produced using plants
or their extracts or seaweeds and in a controlled manner according to their
size, dispersity and shape, however reduction of palladium chloride using plant
extracts or marine alga has not been explored much. Aqueous extract of Sargassum wightii has been used for the
bioreduction of Pd2+ to Pd0. The absence of absorbance
band above 300 nm revealed the complete reduction of Pd2+ ions.
Using Fourier transform infrared spectroscopy (FTIR functional groups involved
in the synthesis were identified. Morphology of palladium nanoparticles in the
colloidal solutions were analyzed using Scanning Electron Microscopy (SEM) and
their size distribution were also investigated using HR-TEM.
KEYWORDS: Sargassum
wightii; green
synthesis; palladium nanoparticles; SEM; HR-TEM
INTRODUCTION:
Metal nanoparticles can be synthesized by
chemical, electrochemical or sonochemical methods 1,2. Greener
synthesis of metal nanoparticles helps to replace the hazardous chemicals that
cause toxicity, minimizes harmful pollution to the environment when debris such
as surfactants/dispersants released by the large scale industries and lead to
an eco-friendly environment3.
Among noble metals, palladium nanoparticles derive considerable
attention due to their optical, electrical and catalytic properties. Palladium
recovery by biosorption was also attempted using various biosorbents such as
bacteria, moss4. The problems with these biosorbents include a low
adsorption and desorption capacity and the cost-factor for maintaining aseptic
conditions. Alga such as S. platensis, which has the ability to inhibit
HIV-1 replication in humans, has been explored in the synthesis of bimetallic
nanoparticles5.
To utilize and optimize chemical or
physical properties of nano-sized metal particles, a large spectrum of research
has been focused to control the size and shape, which is crucial in tuning
their physical, chemical and optical properties 6-8. Palladium nanoparticles have been heavily
studied in a wide range of catalytic applications including hydrogenations,
oxidations, carbon–carbon bond formation, and electrochemical reactions in fuel
cells9.
Seaweeds constitute commercially important
marine renewable resources which provide considerable development in the area
drug development against cancer, microbial infections and inflammations10.
Sargassum species are tropical and sub-tropical brown macroalgae
(seaweed) of shallow marine meadow. These are nutritious and rich source of
bioactive compounds such as vitamins, carotenoids, dietary fibers, proteins,
and minerals 11. In the present investigation, a rapid biosynthesis
of palladium nanoparticles using pharmacological potent seaweed Sargassum
wightii has been studied in detail.
MATERIALS AND METHODS:
Materials
Palladium chloride (PdCl2) was
purchased from SRL Pvt. Ltd., India and used as received. All other reagents used were of
analytical grade with maximum purity. Fresh Sargassum wightii seaweed
was collected from Mandapam (Latitude 9.2800° N, Longitude 79.1200° E),
Rameshwaram, East Coast of India. Seaweed were cleaned with double distilled
water, shade dried, and ground to powder and stored for further studies.
Synthesis of palladium nanoparticles
Seaweed extract was prepared by adding 1g
of dried Sargassum wightii powder to 20 mL of distilled water and placed
in an orbital shaker for 24 h. After 24 h, the extract was filtered and stored
for further experiments. For the synthesis of PdNPs, about 100 mL of seaweed
extract was mixed with 1 mL PdCl2 (1M) and incubated at
room temperature for 5 days.
Characterization
of PdNPs
The reaction mixture was monitored for the
formation of PdNPs at different time intervals by an UV-Vis spectrophotometer
(Schimadzu-UV1800). Fourier Transform Infrared Spectra (FTIR) was carried out
by KBr pellet method using Perkin Elmer Spectrum ONE at a range of 4000 cm-1
to 450 cm-1 before and after the reduction reaction. Scanning
electron microscopy (SEM) analysis was carried out to study the morphology of
PdNPs using HITACHI-S3400N equipment. The sample was prepared by drop coating
the PdNPs onto a carbon tape mounted on an aluminum stub, dried in a controlled
environment and the images were captured. Transmission Electron Microscopy
(TEM) analysis was carried out to know the exact size and morphology of the
PdNPs. It was done by drop coating the PdNPs onto a carbon coated TEM grid, air
dried and the images were photographed using JEOL 3010.
RESULTS AND
DISCUSSION:
Performance and applicability of
synthesized palladium nanoparticles were based on the size, shape, surface
morphology, composition and structure. It was observed that the reduction of
the Pd2+ ions during exposure to Sargassum wightii may be
easily followed by UV–vis spectroscopy. Bioreduction of Pd2+ ions to
Pd0 with the S.wightii were identified using UV- vis
spectrophotometer. The appearance of blackish brown colour indicates the
formation of PdNPs. The peak at 285 nm indicates the presence of Pd2+
ions and the gradual disappearance of the peak with time showed the complete
formation of PdNPs (Fig.1). The absence of absorbance band above 300 nm
revealed the complete reduction of the initial Pd2+ ions.
Figure 1. UV-vis
spectra of PdNPs synthesized using seaweed Sargassum wightii
As shown in Figure 2, FTIR measurements
were carried out to identify the possible functional groups responsible for the
reduction and efficient stabilizing of the PdNPs. FTIR spectrum of Sargassum
wightii synthesized PdNPs (Fig 2) shows peaks at 3436 cm-1
(hydroxyl), 1639 cm-1 (carboxylic acid), 1097 cm-1 (amine)
and 789 cm-1 (alkyl halides). From the results of FTIR spectra, it
is clear that the hydroxyl group (3436 cm-1) responsible for capping
and carboxylic acid functional group is responsible for reduction form Pd2+
ions to Pd0.
Figure 2. FT-IR spectra of the Sargassum wightii
synthesized PdNPs
The morphology of the palladium
nanoparticles in the colloidal solution and their distribution was analysed by
scanning electron microscope. Figure 3 shows SEM images clearly indicate the
morphology of palladium nanoparticles which shows well dispersed and spherical
shaped particles of size 5-37 nm. The
morphology and size of PdNPs in the colloidal solutions and their size
distribution was investigated by TEM. A TEM image infers PdNPs formed were in
different sizes, ranging from small sphere to large spheres and the
nanoparticles were in the range of 5 -37 nm as shown in Figure 4.
Figure 3. SEM
image of the Sargassum wightii synthesized PdNPs
Figure 4. TEM image of the Sargassum
wightii synthesized PdNPs
CONCLUSIONS:
In the present study, synthesis of PdNPs
was carried out by using seaweed Sargassum wightii at room temperature
in 5 days. Biosynthesized PdNPs were different sizes, ranging from polydisperse
small sphere to large spheres with an approximate size of 5-37 nm. The results
provide green approach synthesis method for PdNPs than other conventional
methods. These synthesis methods will be of greater benefit in scaling up PdNPs
for applications in biomedical and engineering sector.
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