b2815 Tissue Engineering and Nanotheranostics “9.61x6.69”
160 Tissue Engineering and Nanotheranostics
incident light at the nanoscale.2,24,25 As the electric field of nanoparti
cle depends on its size, shape, structure and surrounding environ
ment,5,19,26 its plasmon property, corresponding with its LSPR, the
wavelength of the exciting light are tunable. Today, advances in col
loidal synthesis methods enable nanoparticle with tunable shape,27,28
such as nanosphere, nanorods, nanostars, varied sizes29–32 and there
fore wide range of applications in catalysis, optics, chemical and bio
logical sensing, and medical therapeutics to be obtained.
During the last two decades, to acquire nanoparticle with certain
plasmonic property and strong LSPR effect, considerable effort has
been focused on improving the methods of synthesizing and organ
izing nanoparticles with certain shape, structure, solubility, stability,
and functionality. Although numerous preparative methods have been
reported, these methods generally can be divided into two approaches,
“topdown”33–37 (physical manipulation) and “bottomup” (chemical
transformation). In the following section, I would like to briefly
introduce several popular methods of synthesizing and modifying
plasmonic nanoparticles from these approaches.
3.1. Bottom-Up Approach (Chemical Methods)
Bottomup approach, mainly based on chemical methods by reducing
metalsalt in the presence of surface stabilizers,38,39 provides us a serial
of metal nanoparticles with controllable size, morphology, coupled
structure and plasmonic property. We will briefly introduce some
chemical methods to synthesize gold nanoparticle (AuNP) and silver
nanoparticle (AgNP), which show strong LSPR effect and are widely
applied in biosensor and bioimaging.
3.1.1. Gold nanoparticles
Among the conventional methods of AuNPs synthesis by reduction
of gold (III) derivatives, the most popular method is reducing
HAuCl 4 with citrate in water, which was proposed by Turkevitch in
1951.^40 In this method, citric acid acts as both reducing and stabiliz
ing agents and provides AuNPs with diameters of 20 nm. G. Frens’
