1) The document reports on an experiment to synthesize star-like gold nanoparticles (SGNs) and measure the effect of stirring time on particle size and size distribution. Chloroauric acid and hydroquinone were stirred in water at room temperature for up to 40 minutes to produce SGNs.
2) Samples taken every 10 minutes were analyzed using UV-vis spectroscopy, zeta potential measurements, and transmission electron microscopy (TEM). UV-vis showed no change in average size with stirring. Zeta potential increased with longer stirring, indicating improved stability.
3) TEM analysis found that stirring for 30 minutes increased particle diameter by about 10 nm and decreased the size distribution by 3.5 nm,
Perchlorates on Mars enhance the bacteriocidal effects of UV lightSérgio Sacani
Perchlorates have been identified on the surface of Mars. This has prompted speculation of what
their influence would be on habitability. We show that when irradiated with a simulated Martian UV
flux, perchlorates become bacteriocidal. At concentrations associated with Martian surface regolith,
vegetative cells of Bacillus subtilis in Martian analogue environments lost viability within minutes.
Two other components of the Martian surface, iron oxides and hydrogen peroxide, act in synergy with
irradiated perchlorates to cause a 10.8-fold increase in cell death when compared to cells exposed to
UV radiation after 60 seconds of exposure. These data show that the combined effects of at least three
components of the Martian surface, activated by surface photochemistry, render the present-day
surface more uninhabitable than previously thought, and demonstrate the low probability of survival of
biological contaminants released from robotic and human exploration missions.
Biofabrication of Silver Nanoparticles Using the Aqueous Extract of Weaver An...BRNSS Publication Hub
Environment has created creative and well-designed ways for developing nanomaterials having intriguing properties. Nanotechnology is having hope to open new avenues to combat and avert diseases using atomic-level fabrication of materials. Herein, we demonstrate the fabrication of silver nanoparticles using aqueous extract of weaver ant’s (Oecophylla smaragdina) nest and its characterization using valuable techniques such as ultraviolet-visible spectroscopy, X-ray diffraction analysis, scanning electron microscopy analysis, Fourier-transform infrared spectroscopy, and atomic force microscopy analysis. Cytotoxicity of newly synthesized silver nanoparticles was analyzed using the Vero cells. By analyzing the results critically, it is hypothesized that synthesis and stabilization of silver nanoparticles were achieved using the molecules present in the aqueous extract of O. smaragdina nest.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Perchlorates on Mars enhance the bacteriocidal effects of UV lightSérgio Sacani
Perchlorates have been identified on the surface of Mars. This has prompted speculation of what
their influence would be on habitability. We show that when irradiated with a simulated Martian UV
flux, perchlorates become bacteriocidal. At concentrations associated with Martian surface regolith,
vegetative cells of Bacillus subtilis in Martian analogue environments lost viability within minutes.
Two other components of the Martian surface, iron oxides and hydrogen peroxide, act in synergy with
irradiated perchlorates to cause a 10.8-fold increase in cell death when compared to cells exposed to
UV radiation after 60 seconds of exposure. These data show that the combined effects of at least three
components of the Martian surface, activated by surface photochemistry, render the present-day
surface more uninhabitable than previously thought, and demonstrate the low probability of survival of
biological contaminants released from robotic and human exploration missions.
Biofabrication of Silver Nanoparticles Using the Aqueous Extract of Weaver An...BRNSS Publication Hub
Environment has created creative and well-designed ways for developing nanomaterials having intriguing properties. Nanotechnology is having hope to open new avenues to combat and avert diseases using atomic-level fabrication of materials. Herein, we demonstrate the fabrication of silver nanoparticles using aqueous extract of weaver ant’s (Oecophylla smaragdina) nest and its characterization using valuable techniques such as ultraviolet-visible spectroscopy, X-ray diffraction analysis, scanning electron microscopy analysis, Fourier-transform infrared spectroscopy, and atomic force microscopy analysis. Cytotoxicity of newly synthesized silver nanoparticles was analyzed using the Vero cells. By analyzing the results critically, it is hypothesized that synthesis and stabilization of silver nanoparticles were achieved using the molecules present in the aqueous extract of O. smaragdina nest.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Gel matrix dependence on the dose response properties and diffusion phenomena...inventionjournals
Fricke-gel dosimeters proved to be suitable tools to perform 3D radiotherapy pre-treatment dosimetry. The tissue equivalent gel matrix helpsto preserve the spatial information of the dose. Several gel matrices proved to be suitable for dosimetric purposes. The influence of the gel matrices on both system dose response and diffusion processwasinvestigated. Three gel matrices were considered: Gelatinfrom porcine skin, Agaroseand polyvinyl alcohol (PVA) cross-linked with glutaraldehyde(GTA). In these systems, Xylenol-Orange (XO), an iron(III)chelator, forms red-colored complexeswith Fe3+ that eases the optical determination of the dose. However, the dose evaluationresults to be affectedbydifferent XO-Fe3+ complexes that absorb at different wavelengths. In particular,this phenomenon influences the dose response, the calibration curveand the dose threshold.Therefore, a deeper study of the XO-Fe3+ speciation mechanism could lead to a more accurate evaluation of the dose. A novel procedure, based on a laser-beam irradiation, was implemented for the diffusion process evaluation. The diffusion coefficients were calculated for the three gel matrices tested. PVAmatrix proved to highly limit the diffusion with respect to the other matrices. Further investigations are needed to verify the influence of XO-Fe3+complexeson the diffusion phenomenon.
Synthesis and Characterization of Novel Nanomaterials for SERS Biomedical/Env...Necla YÜCEL
In this study, a simple green method was employed to synthesize functionalized silver nanoparticles (Ag NPs) as surface-enhanced Raman scattering (SERS) substrate for detection of dopamine (DA). In this method, polyethylene glycol (PEG) was functionalized on silver nanoparticles to prepare the uniform and controlled size of nanoparticles (NPs). The optical and structural properties of functionalized nanoparticles were characterized. The Raman spectra of the prepared PEG-Ag SERS substrate clearly indicated an enhancement in the SERS signal of dopamine. The developed functionalized SERS substrate can be potentially used as a sensitive SERS substrate for detection of various neurotransmitters for biomedical application.
Air- and water-stable halide perovskite nanocrystals protected with nearly-mo...Pawan Kumar
Halide perovskites are exciting candidates for broad-spectrum photocatalysts but have the problem of ambient stability. Protective shells of oxides and polymers around halide perovskite nano- and micro-crystals provide a measure of chemical and photochemical resilience but the photocatalytic performance of perovskites is compromised due to low electron mobility in amorphous oxide or polymer shells and rapid charge carrier recombination on the surface. Herein an in situ surface passivation and stabilization of CsPbBr3 nanocrystals was achieved using monolayered graphenic carbon nitride (CNM). Extensive characterization of carbon nitride protected CsPbBr3 nanocrystals (CNMBr) indicated spherical CsPbBr3 nanoparticles encased in a few nm thick g-C3N4 sheets facilitating better charge separation via percolation/tunneling of charges on conductive 2D nanosheets. The CNMBr core-shell nanocrystals demonstrated enhanced photoelectrochemical water splitting performance and photocurrent reaching up to 1.55 mA cm−2. The CNMBr catalyst was successfully deployed for CO2 photoreduction giving carbon monoxide and methane as the reaction products.
Green Synthesis of Calcium Oxide Nanoparticles and Its ApplicationsIJERA Editor
Green synthesis of metal oxide nanoparticles is gaining considerable interest due to the use of environmentally friendly reactants and room temperature synthesis. This is the most preferred method of preparation as it makes use of pollution free chemicals and encourages the use of non-toxic solvents such as water and plants extracts. The present study is proposed with an objective to synthesize CaO nanoparticles by the eco-friendly green synthesis using environmentally benign papaya leaf extract and Green Tea extract. The obtained CaO nanoparticles have been characterized by UV- Vis, Fourier Transform Infrared (FTIR) X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) studies. The antibacterial and photocatalytic activity of the calcium oxide nanoparticles were also analysed.
In this work, the synthetic Hydroxyapatite (HAP)
was studied using different preparation routes to
decrease the crystal size and was studied the
temperature effect on the nano-sized hydroxyapatite
crystallization. X-ray diffraction (XRD) analysis
indicated the all samples were composed by a
crystalline HAP phase and another amorphous part.
Austin Biomolecules: open access is a peer reviewed, scholarly journal dedicated to publish articles covering all areas of Biomolecules.
The journal aims to promote latest information and provide a forum for doctors, researchers, physicians, and healthcare professionals to find most recent advances in the areas of Biomolecules. Austin Biomolecules: open access accepts research articles, reviews, mini reviews, case reports and rapid communications covering all aspects of Biomolecules.
Austin Biomolecules: open access strongly supports the scientific up gradation and fortification in related scientific research community by enhancing access to peer reviewed scientific literary works. Austin Publishing Group also brings universally peer reviewed journals under one roof thereby promoting knowledge sharing, mutual promotion of multidisciplinary science.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Gel matrix dependence on the dose response properties and diffusion phenomena...inventionjournals
Fricke-gel dosimeters proved to be suitable tools to perform 3D radiotherapy pre-treatment dosimetry. The tissue equivalent gel matrix helpsto preserve the spatial information of the dose. Several gel matrices proved to be suitable for dosimetric purposes. The influence of the gel matrices on both system dose response and diffusion processwasinvestigated. Three gel matrices were considered: Gelatinfrom porcine skin, Agaroseand polyvinyl alcohol (PVA) cross-linked with glutaraldehyde(GTA). In these systems, Xylenol-Orange (XO), an iron(III)chelator, forms red-colored complexeswith Fe3+ that eases the optical determination of the dose. However, the dose evaluationresults to be affectedbydifferent XO-Fe3+ complexes that absorb at different wavelengths. In particular,this phenomenon influences the dose response, the calibration curveand the dose threshold.Therefore, a deeper study of the XO-Fe3+ speciation mechanism could lead to a more accurate evaluation of the dose. A novel procedure, based on a laser-beam irradiation, was implemented for the diffusion process evaluation. The diffusion coefficients were calculated for the three gel matrices tested. PVAmatrix proved to highly limit the diffusion with respect to the other matrices. Further investigations are needed to verify the influence of XO-Fe3+complexeson the diffusion phenomenon.
Synthesis and Characterization of Novel Nanomaterials for SERS Biomedical/Env...Necla YÜCEL
In this study, a simple green method was employed to synthesize functionalized silver nanoparticles (Ag NPs) as surface-enhanced Raman scattering (SERS) substrate for detection of dopamine (DA). In this method, polyethylene glycol (PEG) was functionalized on silver nanoparticles to prepare the uniform and controlled size of nanoparticles (NPs). The optical and structural properties of functionalized nanoparticles were characterized. The Raman spectra of the prepared PEG-Ag SERS substrate clearly indicated an enhancement in the SERS signal of dopamine. The developed functionalized SERS substrate can be potentially used as a sensitive SERS substrate for detection of various neurotransmitters for biomedical application.
Air- and water-stable halide perovskite nanocrystals protected with nearly-mo...Pawan Kumar
Halide perovskites are exciting candidates for broad-spectrum photocatalysts but have the problem of ambient stability. Protective shells of oxides and polymers around halide perovskite nano- and micro-crystals provide a measure of chemical and photochemical resilience but the photocatalytic performance of perovskites is compromised due to low electron mobility in amorphous oxide or polymer shells and rapid charge carrier recombination on the surface. Herein an in situ surface passivation and stabilization of CsPbBr3 nanocrystals was achieved using monolayered graphenic carbon nitride (CNM). Extensive characterization of carbon nitride protected CsPbBr3 nanocrystals (CNMBr) indicated spherical CsPbBr3 nanoparticles encased in a few nm thick g-C3N4 sheets facilitating better charge separation via percolation/tunneling of charges on conductive 2D nanosheets. The CNMBr core-shell nanocrystals demonstrated enhanced photoelectrochemical water splitting performance and photocurrent reaching up to 1.55 mA cm−2. The CNMBr catalyst was successfully deployed for CO2 photoreduction giving carbon monoxide and methane as the reaction products.
Green Synthesis of Calcium Oxide Nanoparticles and Its ApplicationsIJERA Editor
Green synthesis of metal oxide nanoparticles is gaining considerable interest due to the use of environmentally friendly reactants and room temperature synthesis. This is the most preferred method of preparation as it makes use of pollution free chemicals and encourages the use of non-toxic solvents such as water and plants extracts. The present study is proposed with an objective to synthesize CaO nanoparticles by the eco-friendly green synthesis using environmentally benign papaya leaf extract and Green Tea extract. The obtained CaO nanoparticles have been characterized by UV- Vis, Fourier Transform Infrared (FTIR) X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) studies. The antibacterial and photocatalytic activity of the calcium oxide nanoparticles were also analysed.
In this work, the synthetic Hydroxyapatite (HAP)
was studied using different preparation routes to
decrease the crystal size and was studied the
temperature effect on the nano-sized hydroxyapatite
crystallization. X-ray diffraction (XRD) analysis
indicated the all samples were composed by a
crystalline HAP phase and another amorphous part.
Austin Biomolecules: open access is a peer reviewed, scholarly journal dedicated to publish articles covering all areas of Biomolecules.
The journal aims to promote latest information and provide a forum for doctors, researchers, physicians, and healthcare professionals to find most recent advances in the areas of Biomolecules. Austin Biomolecules: open access accepts research articles, reviews, mini reviews, case reports and rapid communications covering all aspects of Biomolecules.
Austin Biomolecules: open access strongly supports the scientific up gradation and fortification in related scientific research community by enhancing access to peer reviewed scientific literary works. Austin Publishing Group also brings universally peer reviewed journals under one roof thereby promoting knowledge sharing, mutual promotion of multidisciplinary science.
The effects of zinc oxide nanoparticles on differentiation of human mesenchym...Nanomedicine Journal (NMJ)
Abstract
Objective(s):
The mesenchymal stem cells (MSCs) have been introduced as appropriate cells for tissue engineering and medical applications. Some studies have shown that topography of materials especially physical surface characteristics and particles size could enhance adhesion and proliferation of osteoblasts. In the present research, we studied the distinction effect of 30 and 60 μg/ml of zinc oxide (ZnO) on differentiation of human mesenchymal stem cells to osteoblast.
Materials and Methods:
After the third passage, human bone marrow mesenchymal stem cells were exposed to 30 and 60 μg/ml of ZnO nanoparticles having a size of 30 nm. The control group has received no ZnO nanoparticles. On day 15 of incubation for monitoring the cellular differentiation, alizarin red staining and RT-PCR assays were performed to evaluate the level of osteopontin, osteocalsin and alkaline phosphatase genes expression.
Results:
In the group receiving 30 μg/ml of ZnO nanoparticles, the expression of osteogenic markers such as alkaline phosphatase, osteocalcin and osteopontin genes were significantly higher than both control and the group receiving 60 μg/ml ZnO nanoparticle. These data also confirmed by alizarin red staining.
Conclusion:
It seems the process of differentiation of MSCs affected by ZnO nanoparticles is dependent on dose as well as on the size of ZnO.
Greener cum chemical synthesis and characterization of Mg doped ZnS nanoparti...IJERA Editor
In the present investigations, high-quality Mg doped ZnS nanoparticles were synthesized by Greener cum
chemical process with the assistance of polyvinyl pyrrolidone (PVP) with two different Mg concentrations.
Doping of Mg metal in nanoparticles were found to be a good technique for tuning the band gap of ZnS
nanoparticles. Simultaneously, Mg doping also inhibited the growth of particle size and it decreased from 33.2
nm to 18.3 nm with the increase in doping concentration from 0% to 5%. Band gap was found to rise from 3.12
eV to 3.38 eV and photoluminescence studies exposed that visible Photoluminescence (PL) emission was
improved with doping concentration. The nanoparticles have been characterized by Field Emission Scanning
Electron Microscopy (FESEM), X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy,
Ultra Violet visible (UV–vis) spectroscopy, and Energy Dispersive X-ray Analysis (EDAX).
Synthesis, Characterization of ZnS nanoparticles by Coprecipitation method us...IOSR Journals
ZnS nanoparticles are prepared by coprecipitation method using various capping agents like PVP (polyvinylpyrrolidone), PVA (polyvinylalcohol) and PEG-4000 (polyethyleneglycol). These are characterized by UV-Visible spectra, X-ray diffraction (XRD) studies, Fourier Transform Infra-red spectra (FTIR) and Transmission electron microscopy (TEM). UV-Visible absorption spectra are used to find the optical band gap and the values obtained have been found to be in the range of 3.80-4.00eV. The particle size of nanoparticles calculated from XRD pattern has been in the range of 2-4 nm. It is also observed that the particle size of nanoparticle is affected by the nature of capping agent. Photo catalytic degradation of xylenol orange (XO) by the nanoparticles shows that these act as photo catalysts under sunlight irradiation. The XO dye was degraded more than 87.24, 83.42 and 73.05% in the presence of PEG-4000, PVA and PVP capped ZnS nanoparticles in 120, 150 and 180 min. respectively. The kinetics of catalyzed by synthesized ZnS nanoparticles with XO dye follows pseudo-first order kinetics with reasonable apparent rate constants.
A Comparison of Microsecond vs. Millisecond Dwell Times on Particle Number Co...PerkinElmer, Inc.
With the growing popularity of nanomaterials in a wide variety of products and processes, the need to measure and characterize these materials has also grown. For metallic or metal-containing engineered nanoparticles (NPs), single particle ICP-MS (SP-ICP-MS) has been developed and is growing in popularity due to its ability to rapidly detect and characterize a large number of particles, determine particle size and size distributions, the particle number concentration in a sample, and the elemental mass concentration of both dissolved and particulate species. SP-ICP-MS has been applied to a wide variety of sample types1-5, demonstrating its versatility.
Carbohydrate Research 405 (2015) 55–65Contents lists availab.docxwendolynhalbert
Carbohydrate Research 405 (2015) 55–65
Contents lists available at ScienceDirect
Carbohydrate Research
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c a r r e s
Electrochemical synthesis of nanostructured gold film for the study
of carbohydrate–lectin interactions using localized surface plasmon
resonance spectroscopy
http://dx.doi.org/10.1016/j.carres.2014.08.019
0008-6215/� 2014 Elsevier Ltd. All rights reserved.
⇑ Corresponding author. Tel.: +1 (314) 516 5346; fax: +1 (314) 516 5342.
E-mail address: [email protected] (K.J. Stine).
Jay K. Bhattarai a,b, Abeera Sharma a,b, Kohki Fujikawa a, Alexei V. Demchenko a, Keith J. Stine a,b,⇑
a Department of Chemistry and Biochemistry, University of Missouri—St. Louis, One University Boulevard, St. Louis, MO 63121, United States
b Center for Nanoscience, University of Missouri—St. Louis, One University Boulevard, St. Louis, MO 63121, United States
a r t i c l e i n f o a b s t r a c t
Article history:
Received 30 April 2014
Received in revised form 15 July 2014
Accepted 30 August 2014
Available online 16 September 2014
Keywords:
Lectin
Mannose
Monolayer
Plasmon
Gold
Localized surface plasmon resonance (LSPR) spectroscopy is a label-free chemical and biological molec-
ular sensing technique whose sensitivity depends upon development of nanostructured transducers.
Herein, we report an electrodeposition method for fabricating nanostructured gold films (NGFs) that
can be used as transducers in LSPR spectroscopy. The NGF was prepared by electrodepositing gold from
potassium dicyanoaurate solution onto a flat gold surface using two sequential controlled potential steps.
Imaging by scanning electron microscopy reveals a morphology consisting of randomly configured block-
like nanostructures. The bulk refractive index sensitivity of the prepared NGF is 100 ± 2 nm RIU�1 and the
initial peak in the reflectance spectrum is at 518 ± 1 nm under N2(g). The figure of merit is 1.7. In addition,
we have studied the interaction between carbohydrate (mannose) and lectin (Concanavalin A) on the
NGF surface using LSPR spectroscopy by measuring the interaction of 8-mercaptooctyl-a-D-mannopyran-
oside (aMan-C8-SH) with Concanavalin A by first immobilizing aMan-C8-SH in mixed SAMs with 3,6-
dioxa-8-mercaptooctanol (TEG-SH) on the NGF surface. The interaction of Con A with the mixed SAMs
is confirmed using electrochemical impedance spectroscopy. Finally, the NGF surface was regenerated
to its original sensitivity by removing the SAM and the bound biomolecules. The results from these exper-
iments contribute toward the development of inexpensive LSPR based sensors that could be useful for
studying glycan–protein interactions and other bioanalytical purposes.
� 2014 Elsevier Ltd. All rights reserved.
1. Introduction
Localized surface plasmon resonance (LSPR) spectroscopy based
on the development of noble metal nanostructures with tunable
and responsive plasmonic behavior has become of b ...
Effect of cold atmospheric pressure plasma needle on DNAiosrjce
Non-thermal argon plasma needle at atmospheric pressure was constructed. The experimental setup
was based on a simple and low cost electric components that generate a sufficiently high electric field at the
electrodes to ionize various gases which flow at atmospheric pressure. A high AC power supply was used with
1.1Kv and 19.57KHz. Non-thermal atmospheric pressure plasma has much potential for medical applications.
The atmospheric pressure plasma needle contains almost equal amounts of positive and negative charges. In
this research we focused on the possible biomedical application of the atmospheric pressure plasma needle,
where we used plasma ignited in Argon (Ar) gas flow to cause strand breaks in DNA. However, the mechanism
by which plasma destroys DNA is not yet understood. In this study we investigated the effects of exposure time
and distance between the plasma source and the DNA sample. In this study we found that plasma does indeed
alter DNA. We came to this conclusion through qualitative interpretations using a standard gel electrophoresis
technique on DNA samples treated with the atmospheric pressure plasma needle.
Analysis Of Carbon Nanotubes And Quantum Dots In A Photovoltaic DeviceM. Faisal Halim
Analysis of Carbon Nanotubes and Quantum Dots in a Photovoltaic Device
A poster prepared by Francis and me; presented by Francis. I modified on of the photographs used, in this copy.
Multiplexed immunoassay based on micromotors and microscale tags
cme320_lab04
1. STONY BROOK UNIVERSITY
COLLEGE OF ENGINEERING AND APPLIED SCIENCES
Chemical and Molecular Engineering Program
Chemical Engineering Laboratory II:
CME 320
Gold Nanoparticles
By
Marcin Kielkiewicz
Team Members: Jennifer Imbrogno & Kathryn Margaret Caducio
Instructor: Tatsiana Mironava
Submitted to:
Prof. Miriam Rafailovich and Dr. Pinkas-Sarafova
Submitted: May 6, 2015
2. Marcin Kielkiewicz 108225444 CME 320 Hydrogels April 15, 2015
Abstract
The goal of this experiment was to synthesize Star-Like Gold Nanoparticles (SGNs) and measure
the effect stirring of the reaction mixture had on the eventual size and size distribution of SGNs produced.
Chloroauric acid was reduced by hydroquinone in water to produce SGNs; the reaction was conducted and
room temperature and the mixture was stirred for forty minutes. Five samples were extracted from the
reaction mixture every ten minutes, starting at t = 0 minutes and ending when t = 40 minutes. The samples
were first analyzed with UV-Vis spectroscopy,which revealed a common peak absorption between 637 nm
– 642 nm indicating a constant SGN diameter of approximately one hundred nanometers. Further testing
with ζ-potential equipment showed that stirring time improved the stability of the colloidal dispersion.
Every additional ten minutes of stirring increased the ζ-potential by approximately four millivolts until the
final ten minutes, in which the increase was only one millivolt. It appeared that stirring quickly establishes
a permanent stationary layer of fluid around the SGNs which is unaffectedby prolonged storage.Transition
electron microscopy (TEM) gave insight as to the actual SGNs diameter and size distribution. Only three
samples were successfully tested, however from those results it was shown that stirring for ten minutes
produced no noticeable effect on particle size or particle size distribution. However, stirring for thirty
minutes increased the nanoparticle diameter by approximately ten nanometers and narrowed the size
distribution by approximately three and a half nanometers. From these results we recommend that future
synthetic procedures include a thirty minute stirring window in order to improve colloidal stability and
narrow down the size distribution of the SGNs produced. Additional tests must be completed using the
TEM to determine whether the process can be further optimized.
Introduction
Gold nanoparticles (AuNPs) are sub-
micrometer sized nanoparticles that have unique
optical and electronic properties that are unlike
those of the bulk material.1
AuNPs are subject to
ongoing research with a wide range of
applications, including X-ray imaging,2
photocatalysis,3
cancer therapy,4
among others in
the fields of materials science and medicine.
There are several reasons why AuNPs
have received significant attention from the
scientific community. First off, they are easily
synthesized and stabilized. Second, they provide
an exceptionally high surface to volume ratio.
Third, they are biocompatible when appropriate
ligands are affixed to them. Fourth, the ability to
modify the size and shape of AuNPs allows for
the optimization of many properties, such as
plasmon resonance absorption, conductivity,
fluorescence, and redox properties.5
There are severaltypes of AuNPs,one of
them being Star-Like Gold Nanoparticles
(SGNs), which have been proposed as reliable
nanostructures for Surface Enhanced Raman
Spectroscopy (SERS).6
To provide some
background, this technique measuresthe inelastic
scattering of photons as they are reflected off of a
layer of molecules adsorbed on the surface of a
nanoparticle. Because SGNs have protruding
“hooks” from their surface, they are well suited
for this application because various proteins and
enzymes can be easily adsorbed onto their
surface.7
SGNs have been previously synthesized
by the reduction of chloroauric acid by
hydroquinone in aqueous solution, followed by
stabilization of the nanoparticles by sodium
citrate.8
The goal of our experiment was to
synthesize SGNs utilizing the reagents listed
above and study the effect of stirring time on
particle size and particle size distribution. In our
3. Marcin Kielkiewicz 108225444 CME 320 Hydrogels April 15, 2015
experimental procedure hydroquinone and
chloroauric acid were stirred at room temperature
for forty minutes. A1-2 mL sample wasextracted
from the reaction vessel every ten minutes
starting at t = 0 min. Samples were analyzed
using UV-Vis spectroscopy, ζ-potential, and
transition electron microscopy (TEM) to
determine whether stirring time affected the size
distribution of the particles. Using the data
obtained we sought to determine the optimal
stirring time that would produce SGNs with the
most narrow size distribution.
Methods and Materials
The SGNs synthesis was carried out in a
fume hood with proper ventilation. Latex gloves
were worn throughout the experiment as some
reactants/reagents were corrosive. 40 mL ± 1 mL
of deionized (DI) water was added to a 250 mL
glass beaker. The glass beaker was positioned on
a magnetic stirrer, and a magnetic stir rod was
added to the beaker. Stirring was started without
reagents at moderate speed and no heating
element was used. 200 μL of chloroauric acid
(30%, HAuCl4, aqueous) was added to the beaker
using a micropipette. Next, 400 μL of
hydroquinone (11
𝑚𝑔
𝑚𝐿
, p-C6H4(OH)2, aqueous)
was added to the beaker using a micropipette.
After the two reagents were mixed the solution
immediately turned pale blue. A 1-2 mL sample
was extracted after no more than one minute after
the addition of hydroquinone. This sample was
stored in a scintillation flask and labeled t = 0
min. Four more samples of similar volume were
extractedfrom the beakerafterten, twenty, thirty,
and forty minutes. No visible changes in color of
the solution were noticed during this time period.
Time intervals were determined using a smart
phone stopwatch. All samples were stored in
separate scintillation flasks and stabilized with
sodium citrate as well.
After one week in storage the samples
were subject to analysis by UV-Vis spectroscopy
[Thermo Scientific, UV Insight]. A scan of each
sample was conducted from 400 nm to 750 nm in
1 nm increments. The test was conducted to see
determine whether stirring time affected the size
of SGNs. It has been documented that the peak
absorption in the UV-Vis spectra corresponds to
the average diameter of the SGNs. To clarify with
an example, SGNs with diameters of
approximately 50 nm appear red in color, while
those with diameters of approximately 100 nm
appearblue. However,given a mixture of the two,
UV-Vis will indicate a single absorption peak
instead of two distinct peaks.9
The phenomena
that causes AuNPs of different size to have
unique absorption properties is known as surface
plasmon resonance. Electromagnetic radiation
induces a dipole on the surface of the metal that
oscillates with the frequency of the light;10
in turn
the electron cloud is of the AuNP is also
oscillating with a specific frequency, which is
dependent on both the shape and size the AuNPs,
since changing either parameter alters the
geometry of the electron cloud. By illuminating
the metal surface with light that has a frequency
equal to that of oscillations within the electron
cloud (resonance frequency), the energy of the
harmonic oscillations will increase. A plasmon is
the term used to describe the smallest unit of
electron density oscillation.11
On the same day the samples were
subject to UV-Vis analysis, the ζ-potential of all
five samples was also measured [NanoBrook
Omni, Brookhaven Instruments]. The ζ-potential
test measured the electric potential between the
stationary fluid layer at the surface of the SGNs
and the mobile plane of molecules surrounding
the stationary plane.12
The test was used to
determine the stability of the colloidal
distribution of SGNs in water. The magnitude of
the ζ-potential indicated the degree of
electrostatic repulsion between adjacent particles
4. Marcin Kielkiewicz 108225444 CME 320 Hydrogels April 15, 2015
in a dispersion. Hence colloids with high ζ-
potential were electrically stabilized while
colloids with low ζ-potential would tend to
coagulate or flocculate.13
After two weeks in storage the samples
were analyzed using TEM [SBU Research and
Development Park]. The previous week a droplet
of each SGN sample was administered onto a
copper support mesh and dried to remove
moisture (which would otherwise vaporize in the
TEM and disrupt imaging). At least five images
of SGN clusters were taken of each sample on
each mesh grid, and the diameter of one hundred
distinguishable nanoparticles was measured
using ImageJ software. Because the SGNs were
not spherical, the diameter was of each was
obtained in a random direction without the use of
a common axes. For each sample set,the average
diameter and the population standard deviation
were obtained using Eq. 1 and 2, respectively.
[Equation 1] xavg =
1
𝑁
∑ 𝑥𝑁
𝑖=1 i
[Equation 2] σ = √
1
𝑁
∑ (𝑥𝑁
𝑖=1 i - xavg)2
Eachsample setwascomparedto another
one using the Student’s t-Test.The parametersfor
the test were unequal variance, independent
samples, equal sample size, and two-tailed
analysis. The null hypothesis was as follows:
Two sets of data (A and B), with sample means
xavgA and xavgB, were both part of the same
population, so that their populations were equal.
The t-value was calculated using Eq. 3.
[Equation 3]
t = (xavgA - xavgB) ÷ (sxAsxB√
2
𝑁
)
Data and Data Analysis
Selected UV-Vis spectra data are shown
in Table 1. The UV-Vis spectra from the sample
t = 0 min is shown in Fig. 1. The UV-Vis spectra
of the other samples were omitted in this report
because they appeared identical to one in Fig. 1,
hence they would’ve been redundant. In Table 1
the peak absorbance wavelength for the first two
samples was 642 nm. This indicating that the
average size of the molecules was not affected by
stirring over this time interval. However,afterten
minutes the peak absorption wavelength
decreased slightly relative to those two values,
indicating that the overall average diameter of the
SGNs decreased. However,this conclusion may
be skewed, because the change in wavelength
absorbance was minute and only one UV-Vis
spectra was taken of each sample. Overall, we
concluded that the average size of the molecules
did not change significantly over the forty
minutes of stirring and was largely unaffected by
it. The data was able to confirm that the size of
the molecules was approximately one hundred
nanometers for all the samples, since a blue
colored AuNP solution corresponds to
nanoparticles of that size.
Sample # Absorbance Wavelength
(nm)
t = 0 min 0.15714 642
t = 10 min 0.154929 642
t = 20 min 0.223036 639
t = 30 min 0.154096 640
t = 40 min 0.154282 637
Table 1. UV-Vis spectra data.
Figure 1. UV-Vis spectra of the sample, t = 0 min. From 400
nm to 750 nm, plotted with 1 nm increments.
5. Marcin Kielkiewicz 108225444 CME 320 Hydrogels April 15, 2015
The results of the ζ-potential test
indicated that stirring time increased the stability
of the SGNs. The average ζ-potential for each
sample and the corresponding standard deviation
are shown in Table 2. It is clear from the data that
ζ-potential increased from t= 0 min to t = 40 min.
From the UV-Vis analysis the consensus was that
the size of the SGNs is relatively constant,
therefore a change in particle size cannot be the
reason behind the increase in ζ-potential. A
possibility was that stirring rapidly saturated the
stationary layer of fluid around the SGNs with
both water and sodium citrate. The increase in ζ-
potential appeared to taper off between thirty and
forty minutes, indicating that the stationary layer
may have been close to reaching its saturation
point at around that time. Further research must
be done to support this theory, and an assumption
has to be made that states that interchange
between the bulk fluid and the stationary layer is
almost nonexistent throughout the week spent in
storage, otherwise the samples would have the
same ζ-potential. Regardless of the reason, the
test confirms that stirring longer stirring time
produces more stable colloidal SGNs solutions.
TEM provided the most useful
information in this experiment. Images of SGNs
clusters were obtained and then analyzed using
ImageJ software. The data is shown in Table 3.
The data from Table 3 were then analyzed using
the Student’s t-Test; the results are shown in
Table 4. Unfortunately, for samples t = 20 min
and t = 40 min, the copper mesh grids were
damaged prior to being inserted into the TEM,
and no SGN clusters were detectedon either grid.
For the remaining samples, it was evident that
stirring increased the diameter of the SGNs and
decreased the size distribution (the standard
deviation decreased). Between t = 0 min and t =
10 min, there was no meaningful change in size
distribution or nanoparticle size. This result is
supported by the t-Test, which indicated there
wasa 51% probability that the SGNs from sample
t = 0 min and t = 10 min belonged to the same
population. From this information we drew the
conclusion that stirring for the first ten minutes
had no effect on the SGNs. On the other hand,
between the first two samples and t = 30 min,
there was a noticeable change in diameter and
size distribution. Between t = 10 min/t = 0 min
and t = 30 min, the diameter increased by over
seven nanometers and the size distribution was
narrowed down by three and a half nanometers.
The t-Test indicated that the probability either
sample t = 0 min or t = 10 min being part of the
same population as t = 30 min was below 10%,
therefore unlikely according to Dr. Rafailovich,
meaning that stirring had a meaningful effect on
size distribution and particle diameter. We
concluded from the data that stirring the solution
for thirty minutes improved the size distribution,
however it increased also SGNs diameter.
However,because the data for samples t =20 min
and t = 40 min are missing, we recommend the
TEM test be repeated to obtain the missing data
because it could lead to an improved
optimization.
As proof of the successful synthesis of
SGNs, a TEM image from the sample t = 10 min
is shown in Fig. 2.
Table 2. Select data from the ζ-potential test.
Sample # ζ-potential
(mV)
σ (mV)
t = 0 min -3.27 0.42
t = 10 min -7.55 5.82
t = 20 min -10.92 2.53
t = 30 min -15.37 3.56
t = 40 min -16.88 2.77
Sample # Avg.
Diameter
(nm)
σ (nm)
t = 0 min 90.0 29.1
t = 10 min 92.8 29.2
t = 20 min No data No data
t = 30 min 100.1 25.6
t = 40 min No data No data
Table 3. Average diameter and population standard
deviation of the data obtained from ImageJ software
after analyzing TEMimages.
6. Marcin Kielkiewicz 108225444 CME 320 Hydrogels April 15, 2015
Conclusion
In this experiment we successfully synthesized SGNs and measured the effect stirring time of the
reaction mixture had on the size and size distribution of SGNs. UV-Vis analysis confirmed the existence of
SGNs with diameters of approximately one hundred nanometers; size was not noticeably affected by
stirring, given that the peak absorption remained between 637 nm – 642 nm. ζ-potential testing showed that
stirring time improved the stability of colloidal nanoparticle solutions and that they were less likely to
coagulate, even if stored at room temperature for a week. TEM gave insight as to the actual SGNs diameter
and size distribution. After analyzing the three samples, it was shown that stirring for ten minutes produced
no noticeable effect on particle size or particle size distribution. However, stirring for thirty minutes
increased the nanoparticle diameter by approximately ten nanometers and narrowed the size distribution by
approximately three and a half nanometers. From these results we recommend that future production cycles
of SGNs be conducted with a thirty minute stirring period, as it will both improve colloidal stability and
narrow down the size distribution.
Table 4. Student’s t-Test results.
Two samples being
compared
t-test result (*100%)
t = 0 min and t = 10
min
51%
t = 10 min and t= 30
min
6%
t = 0 min and t = 30
min
1%
Figure 2. A magnified image of SGNs from the sample t =
10 min obtained from the TEM.
7. Marcin Kielkiewicz 108225444 CME 320 Hydrogels April 15, 2015
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