RESEARCH ARTICLE
Copyright © 2011 American Scientific Publishers
All rights reserved
Printed in the United States of America
Journal of
Nanoscience and Nanotechnology
Vol. 11, 1–6, 2011
Vanadium Oxide Nanoparticles as
Optical Sensors of Cysteine
W. Celestino-Santos
1
, A. G. Bezerra, Jr.
2
, A. B. Cezar
1
, N. Mattoso
1
, and W. H. Schreiner
1 ∗
1
Departamento de Física, Universidade Federal do Paraná, Centro Politécnico,
Jardim das Américas, 81531-880, Curitiba, Paraná, Brazil
2
Departamento Acadêmico de Física, Universidade Tecnológica Federal do Paraná,
Avenida Sete de Setembro, 3165, Centro, 80230-010, Curitiba, Paraná, Brazil
We report on the synthesis of vanadium oxide nanoparticles using the laser ablation in solution
technique. The particles were characterized by dynamic light scattering-DLS, transmission elec-
tron microscopy-TEM, X-ray diffraction-XRD, X-ray photoelectron spectroscopy-XPS and UV-Vis
optical spectroscopy. The oxide nanoparticles are mainly composed of tetragonal V
2
O
5
, a semicon-
ductor with a 2.2 eV band gap. The interaction of the nanoparticles with cysteine, a very impor-
tant aminoacid present in proteins, was studied. Upon reaction with cysteine, the bandgap of the
nanoparticles shifts to the ultraviolet region at 2.87 eV. This color change from yellow to transpar-
ent can be used for selective cysteine sensing. Additionally, the intervalence band of the optical
absorption spectra shows capability for cysteine sensing in the M range.
Keywords:
1. INTRODUCTION
Vanadium oxides have many properties which have been
used in several different areas of applications. For the
Physicist, vanadium oxides present a wealth of interest-
ing features. The phase diagram of the vanadium-oxygen
system shows some twenty oxides with many different
structures.
1
Several of these oxides present metal-insulator
or semiconductor-insulator transitions, with peculiar elec-
tronic, magnetic and structural behavior, which are only
partially understood. Thermochromic behavior has been
reported for VO
2
2
and vanadium oxides are also consid-
ered as materials for solar energy harvesting
3
as well as
for electrochromic applications.
4
For the Chemist, vana-
dium oxides are important for their catalytical applications
in many industries. These catalytic properties are based
on two aspects: vanadium oxides have a variety of oxida-
tion states, ranging from 2
+
to 5
+
, and a great variabil-
ity of oxygen coordination geometries. For the Biologist,
vanadium and vanadium oxides have important action in
proteins and biological materials. This has applications in
medicine for the treatment of cancer tumors.
Vanadium oxide nanoparticles have been produced in
several ways. Laser pyrolysis,
5
pulsed laser deposition
(PLD),
6
sol–gel,
7 8
chemical vapor deposition (CVD)
∗
Author to whom correspondence should be addressed.
and sputtering,
9
co-implantation
10
and microwave plasma
decomposition
11
have been used as synthesis routes.
Laser ablation synthesis in solution, LASiS, emerged in
the last years as an alternative to the traditional techniques
for nanoparticle production.
12
Nanoparticles are formed
during the abrupt collapse of the plasma generated by a
laser pulse with a target located in a liquid. The control of
nanoparticle size is one of the major problems associated
to LASiS. The nanoparticles can be obtained in water or
solvents without stabilizing molecules. Probably, LASiS is
one of the easiest routes for nanoparticle production.
Here we report on the LASiS production of vanadium
oxide nanoparticles in water, their characterization and
their interaction with cysteine. Cysteine is one of the
20 aminoacids found in proteins. Cysteine has a thiol
sidechain and is the main representative of thiols in Biol-
ogy. The functionalization of noble metals with cysteine
has been repeatedly studied (see e.g. Ref. [13] and refer-
ences therein).
2. EXPERIMENTAL DETAILS
A Q-switched Quantronix Model 117 Nd:YAG laser, oper-
ating at 300 Hz and delivering 150 ns pulses at 1064 nm
was used in the experiments. The laser beam was focused
with a 50 mm lens on a vanadium target, Williams
Advanced Materials 2N7, producing a 40 m spotsize.
J. Nanosci. Nanotechnol. 2011, Vol. 11, No. xx 1533-4880/2011/11/001/006 doi:10.1166/jnn.2011.4194 1