Though much research has been conducted for nanoparticles, naturally occurring nanoparticles have not yet been well explored for their diverse properties and potential applications. This paper reports the optical absorption and scattering properties of nanoparticles secreted by English ivy. Both experimental and theoretical studies have been conducted. Strong ultraviolet extinction and excellent visible transparency are observed, compared to the inorganic TiO2 and ZnO nanoparticles at similar concentrations. The contributions of absorption and scattering to the total extinction are quantified by simulation of the Mie scattering theory

AP Popov

B Herzog

BG Zanetti-Ramos

C Neinhuis

CB Coulter

CM Hoo

DG Rabus

DR Lide

GP Dransfield

GT Wei

K Hirakawa

Lijin Xia

LP Biro

M Daimon

M Jahanshahi

Mingjun Zhang

MJ Zhang

Quanshui Li

R Dunford

S Schauder

T Asahi

V Monnier

W Hong

WG Wamer

Zhili Zhang

English

PubMed

Crossref

Ultraviolet Extinction and Visible Transparency by Ivy Nanoparticles

Springer - Publisher Connector

NANO EXPRESS
Ultraviolet Extinction and Visible Transparency
by Ivy Nanoparticles
Quanshui Li • Lijin Xia • Zhili Zhang •
Mingjun Zhang
Received: 6 May 2010 / Accepted: 3 June 2010 / Published online: 16 June 2010
 The Author(s) 2010. This article is published with open access at Springerlink.com
Abstract Though much research has been conducted for
nanoparticles, naturally occurring nanoparticles have not
yet been well explored for their diverse properties and
potential applications. This paper reports the optical
absorption and scattering properties of nanoparticles
secreted by English ivy. Both experimental and theoretical
studies have been conducted. Strong ultraviolet extinction
and excellent visible transparency are observed, compared
to the inorganic TiO2 and ZnO nanoparticles at similar
concentrations. The contributions of absorption and scat-
tering to the total extinction are quantified by simulation of
the Mie scattering theory.
Keywords Ivy nanoparticle  Optical absorption 
Light scattering
Introduction
Optical properties of naturally occurring organic nano-
particles have not been well explored. Their potential
applications are largely unknown. This may be due to two
reasons. First, research in the field of natural organic
nanoparticles is new to material science. Although natural
nanostructures with biological functions have been found
for many years [1, 2], natural organic nanoparticles have
not been investigated for material properties such as
mechanical and optical properties until recent years [3].
Second, most attention is attached to artificial organic
nanoparticles [4, 5]. These nanoparticles formed of
organic molecules and polymers offer variable optical
properties due to the abundant alternative components.
However, in the case of biological applications, organic
nanoparticles formed in nature are also a promising
alternative due to their compatibility and non-toxicity.
Natural nanoparticles can be used as the functional
materials just as the artificial nanoparticles. Optical
absorption and light scattering are the two main optical
properties that induce the extinction effect. Optical
absorption and light scattering of materials have many
applications. Nanoparticles with ultraviolet extinction
properties have the potential to be used in sunscreen. The
ingredients of modern sunscreens usually contain organic
compounds [6], inorganic nanoparticles [7] and organic
nanoparticles [8]. The inorganic nanoparticles (such as
ZnO and TiO2) and organic nanoparticles can reflect,
absorb and scatter the solar light. Though inorganic
nanoparticles have been widely used in cosmetic products,
there are still concerns about the toxicity of these inor-
ganic materials. TiO2 has been reported to induce DNA
[9, 10] and RNA [11] damage through the process of
chemical oxidation. Considering these situations, if nature-
derived harmless organic nanoparticles have strong ultra-
violet absorption, they will be a potential promising
alternative for sunscreen. In this paper, we reported the
optical absorption and light scattering of ivy nanoparticles.
These nanoparticles were isolated by two approaches, size
exclusion chromatography and filtration. Optical absorp-
tion and light scattering properties of these samples were
characterized. The advantages of these nanoparticles in
their application to sunscreen compared to inorganic
nanoparticles were also demonstrated.
Q. Li  L. Xia  Z. Zhang (&)  M. Zhang
Department of Mechanical, Aerospace and Biomedical
Engineering, University of Tennessee, Knoxville,
TN 37996, USA
e-mail: zzhang24@utk.edu
123
Nanoscale Res Lett (2010) 5:1487–1491
DOI 10.1007/s11671-010-9666-2
Experiments
Fresh-grown rootlets of English ivy were collected around
the University of Tennessee, Knoxville Campus, before
attaching themselves to solid surfaces. The collected
rootlets were meshed using tweezers in 5-ml clean tube
containing 500ll of 20-nm-filtered water after washing
them three times with ddH2O. The solution was then cen-
trifuged at 3000 RPM for 5 min, and the supernatant was
collected. Two-thirds of the solution was dialyzed over-
night at 4 degrees with ddH2O through a cellulose mem-
brane (Sigma–Aldrich, D9277) allowing free pass of
chemicals less than 12,500 Daltons. Size exclusion chro-
matography and high-performance liquid chromatography
(SEC–HPLC) was used to isolate the nanoparticles from
the solution. This technology can separate the nanoparticles
in solution based on their sizes [12]. The Varian HPLC
system consists of three components including Varian
Prostar 210, the Varian Prostar 335 detector and the Varian
Prostar 430 autosampler. Next, 200 ll of dialysis solution
was loaded to the column (PhenomenexBIOSEP-SEC-
S3000 column with an attached Security Guard cartridge
system). The running speed of the mobile phase was set to
0.5 ml/min, and the back pressure of the column was 580
psi. Samples were collected depending on the retention
time. These samples we investigated in this study were
named SEC-1, SEC-2 and SEC-3 with the time sequence.
Filtration was another method used to reveal the optical
properties of ivy nanoparticles. The dialyzed solution was
filtered through the Millipore membrane (220-nm Nylon
filters). This solution was marked as D220D1. Half of this
solution was filtered again through 20-nm filters. The fil-
tered solution was marked as D20D1. Furthermore, a
portion of each solution was diluted into 1/3 concentra-
tions. The diluted solutions were named D220D2 and
D20D2, respectively. The non-dialysis solutions were also
prepared and named ND220 and ND20, respectively.
The morphologies of the ivy nanoparticles were
observed by Agilent 5500 atomic force microscope (Agi-
lent Technologies, Santa Clara, CA). The instrument was
operated at room temperature (20C) using PicoviewTM in
AC mode, which means little or no contact between the tip
and the sample.
Dynamic light scattering (DLS) measurements were
performed by a Brookhaven Instruments BI-200SM goni-
ometer equipped with a PCI BI-9000AT digital correlator.
The operating wavelength is 633 nm. The detector is
located at the scattering angle of 908.
The ultraviolet and visible (UV–Vis) extinction
(absorption and scattering) spectra were measured by the
Thermo Scientific Evolution 600 UV-Visible spectropho-
tometers. The optical length of the quartz cuvette is
10 mm.
Results and Discussion
Dry ivy nanoparticles were first imaged using an AFM, as
shown in Fig. 1. The average diameter of ivy nanoparticles
is 68.3 nm. This value is similar to that of the previous
measurements [3]. The sizes of nanoparticles are not uni-
form in AFM image. Furthermore, size distributions of the
ivy nanoparticles were observed in the samples of SEC-1,
SEC-2, D220D1 and ND220 by dynamic light scattering
(DLS) measurement. No size distribution was found in the
sample of SEC-3. This effect is believed to be due to the
low concentration of ivy nanoparticles in SEC-3. The
nanoparticles in solutions are the polydisperse system. The
sizes of nanoparticles display the large ranges from tens of
nanometers to several hundred nanoparticles. The average
diameters of particles are 117.4 nm for SEC-1, 131.6 nm
for SEC-2, 97.8 nm for D220D1 and 112.3 nm for ND220.
It is worth to note, in principle, DLS gives the hydrody-
namic sizes of the particles. The hydrodynamic sizes are
usually greater than the sizes of dry particles obtained by
AFM [13, 14]. This is due to the polydispersity of the
nanoparticles [14]. Large particles scatter a significant
amount of light so that the diameters given by DLS
intensity distributions will be greater than that obtained by
AFM even if there are only a few large particles [14]
Fig. 2.
The extinction spectra of samples from the SEC tech-
nology and the filtration are shown in Fig. 3a and b,
respectively. The extinction spectra of ivy nanoparticles
using the filtration method are obtained by subtracting the
extinction spectra of samples filtered using 20-nm filters
Fig. 1 The morphologies of ivy nanoparticles observed by AFM
1488 Nanoscale Res Lett (2010) 5:1487–1491
123
from those filtered by 220-nm filters. For example, the
curve in Fig. 3b with the symbol of high concentration
denotes the difference between the extinction spectra found
in D220D1 and D20D1. The spectrum characteristics of
those samples from the SEC technology and the filtration
are approximately consistent. These phenomena including
the DLS results mean that the SEC and the filtration are the
effective direct and indirect methods to investigate the
optical properties of ivy nanoparticles. These nanoparticles
display strong ultraviolet and weak visible light extinction
and, interestingly, a sharp transition edge from the ultra-
violet to the visible range. A significant extinction band
and a shoulder can be found around the wavelengths of
280 nm and 325 nm for all the samples, respectively.
To illustrate the content of the solution, the original
spectra are shown before subtraction in Fig. 4. The
extinction band and the shoulder are at the same positions
not only for the samples filtered through the 220-nm filters
but also the ones filtered through the 20-nm filters. This
similarity implies that the components in the solutions are
similar to that of the ivy nanoparticles. In addition, the non-
dialysis samples show differences when compared to the
dialysis samples in the original absorption spectra in Fig. 4.
This may be due to the dialysis process in which some
protein or other molecules less than 12,500 Daltons are
filtered out. The ingredients of ivy nanoparticles have been
analyzed by this research team. Proteins have been con-
firmed as the dominant compounds of the ivy nanoparticles
[15]. The absorption peak at the wavelength of 280 nm is
the characteristic for many proteins [16]. In general, three
of the amino acid side chains (Trp, Tyr and Phe) contribute
significantly to the UV absorption of a protein at 280 nm.
Those amino acids are believed to form ivy nanoparticles,
but the actual types of proteins and amino acids are still
under investigation. Furthermore, the concentration of ivy
nanoparticles in the sample of high concentration
(D220D1-D20D1) was measured to be 4.92 lg/ml by the
Bradford protein assay [17].
Scattering (just as the Tyndall effects shown in DLS
experiments) also makes considerable contribution to the
total extinction besides the absorption. Herein, we simu-
lated extinction behaviors of the ivy nanoparticles by the
Mie scattering theory with the help of the software MieTab
8.38 [18, 19]. While the refractive index of most organic
compounds is between 1.3 and 1.73 [20], the refractive
index of ivy nanoparticle was set to 1.5. The refractive
index of water from 280 nm to 400 nm was from the
reported data [21]. The extinction coefficients were
Fig. 2 Size distributions of ivy nanoparticles in water (SEC-1 and D220D1) obtained by dynamic light scattering
Fig. 3 UV–Vis extinction
spectra of ivy nanoparticles in
the samples prepared by a size
exclusion chromatography
technology and b the filtration.
High concentration (Low
concentration, Non-dialysis)
represents the difference
between the extinction spectra
found in D220D1 (D220D2,
ND220) and D20D1 (D20D2,
ND20)
Nanoscale Res Lett (2010) 5:1487–1491 1489
123
adjusted to fit the experimental results. The fitting curve of
the total extinction, scattering and absorption curves are
shown in Fig. 5. From these results, the scattering effect is
found to contribute to the extinction, although this contri-
bution is much smaller than that of the absorption. The
absorption and scattering make ivy nanoparticles display
strong ultraviolet extinction behavior. This behavior offers
some potential applications such as sunscreen.
The characteristics of extinction spectra of ivy nano-
particle make a great advantage in the sunscreen applica-
tion for blocking the ultraviolet light and maintaining the
high visible transparence. Ivy nanoparticles can use their
optical absorption and scattering properties to eliminate the
ultraviolet light, just as inorganic nanoparticles such as
ZnO and TiO2 do in sunscreen [7]. In order to illustrate the
relative ultraviolet–visible extinction characteristics, solutions
of ZnO nanoparticles (NanoAmor, 99.9%, 90–200 nm) and
TiO2 nanoparticles (NanoAmor, Rutile, 99%, 50 nm) were
adjusted to be the same extinction value as SEC-2 at
280 nm. This wavelength is the beginning of UV-B (280–
320 nm). Sunscreens protect from both UV-B and UV-A
(320–400 nm) irradiation. In Fig. 6a, the ivy nanoparticles
display a sharper edge from the ultraviolet range to the
visible range. Herein, the concentrations of TiO2 and ZnO
suspensions are 23 lg/ml and 100 lg/ml, respectively.
After this, the extinction spectra of the above TiO2 and
ZnO suspensions were roughly converted to the spectra
with the concentration of 4.92 lg/ml, as shown in Fig. 6b.
The ivy nanoparticles (high concentration) exhibit a much
stronger ultraviolet absorption and sharper decrease near
the visible range. Due to the non-toxicity and strong
extinction property, ivy nanoparticles are a promising
material for sunscreen application.
Natural or biological nanoparticles have not been
investigated in detail for their material properties. In this
study, we investigate these type nanoparticles as the
functional materials just like usual inorganic and organic
nanoparticles. The ivy nanoparticles are not monodisperse
in solutions. This effect is due to the biological process of
the nanoparticle formation. Nanoparticles from the original
tiny ones to the mature ones all exit in the rootlets of ivy.
The SEC technology isolated the nanoparticles from the
mixed solutions including molecules, but it did not give us
uniform size of nanoparticles. The effective methods to
obtain the monodisperse ivy nanoparticles are in the future
investigation. The modifications of ivy nanoparticles to
improve the optical properties are expected. Recently, in
order to increase refractive index of organic polymers,
Fig. 4 Original extinction spectra of the filtered samples
Fig. 5 Fitting curves considering scattering and absorption extinc-
tion. Experimental result is from the curve of high concentration in
Fig. 3b
Fig. 6 Comparison of the UV–
Vis extinction spectra of TiO2,
ZnO nanoparticles and ivy
nanoparticles. a the relative
UV–Vis extinction
characteristics with the same
extinction value at 280 nm.
b the extinction behaviors at the
same concentration
(4.92 lg/ml)
1490 Nanoscale Res Lett (2010) 5:1487–1491
123
surface modification methods, such as deep UV modifica-
tion and ion-beam implantation, have been reported [22,
23]. If similar modifications are applied to ivy nanoparti-
cles, the refractive index mismatch between ivy nanopar-
ticles and the medium will become larger. This effect can
increase the light scattering of ivy nanoparticles and, fur-
thermore, benefit the extinction.
Conclusions
In conclusion, ivy nanoparticles have been isolated by the
SEC technology and the filtration methods. Optical
absorption and scattering properties of these nanoparticles
have been characterized. The extinction spectra of the ivy
nanoparticles display strong ultraviolet and weak visible
extinction with a sharp transition edge. Compared to
inorganic nanoparticles, ivy nanoparticles can be used in
ultraviolet protection due to their optical properties and
harmless nature.
Acknowledgments This work was support by the University of
Tennessee. We also thank the help of Dr. Scott Lenaghan, Dr. Ziling
Xue, Dr. Bin Zhao, Mr. Royce Dansby-Sparks and Mr. Xueguang
Jiang on the absorption and DLS measurement.
Open Access This article is distributed under the terms of the
Creative Commons Attribution Noncommercial License which per-
mits any noncommercial use, distribution, and reproduction in any
medium, provided the original author(s) and source are credited.
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Abstract Though much research has been conducted for nanoparticles, naturally occurring nanoparticles have not yet been well explored for their diverse properties and potential applications. This paper reports the optical absorption and scattering properties of nanoparticles secreted by English ivy. Both experimental and theoretical studies have been conducted. Strong ultraviolet extinction and excellent visible transparency are observed, compared to the inorganic TiO2 and ZnO nanoparticles at similar concentrations. The contributions of absorption and scattering to the total extinction are quantified by simulation of the Mie scattering theory.</p

Li Quanshui

Xia Lijin

Zhang Zhili

Zhang Mingjun

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Ultraviolet Extinction and Visible Transparency by Ivy Nanoparticles

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