PD Research Report for the 2017 year
Name（Research group）Beata Wrzosek（Ozaki Research Group, Graduate School of Science and Technology）
Research ThemeSERS blinking on anisotropic nanoparticles
Research Period
1.09.2017-30.11.2017
Research Results
The aim of the project was to study SERS blinking on anisotropic Ag nanoparticles. The whole work
was divided on few steps:
1)
2)
3)
4)
5)

Synthesis of anisotropic Ag nanoparticles
UV-Vis and SEM/TEM study, calculation of shape distribution
Check if SERS blinking is possible on them
Analysis of results
Preparation of result for comparison with results of SERS blinking on spherical NP

1) Synthesis of anisotropic Ag nanoparticles
The anisotropic nanoparticle was synthesized in seed mediated growth methods. The first step
was the synthesis of small spherical nanoparticles – seeds, as follow:

The next step was carried out with using of additional substrate: capping agent:

The chosen capping agent was cyclodextrine.
2) UV-Vis and SEM/TEM study, calculation of shape distribution
In the results of optimized condition of synthesis about 40 of colloid solution of Ag was obtained,
differed in clarity and colors – from orange, through red, pink, violet, blue to green. The UV-Vis
spectra of all of them were recorded to find out the position of the LSPR bands (Fig. 1). For thechosen 4 solution the TEM imagines were collected to get information about shape and size ofnanoparticles. The shape distribution of shapes was calculated from amount of 250-550 number ofnanoparticules for every of sample (Fig. 2). The general conclusion is that the amount of the small
spherical NP is almost the same in every solution, the nanorods amount decrease and triangle andbigger circular and polygonal plates amount increase with LSPR band shifting to the higher nm.
Some of this tendency seems to be a little broken in case of the two middle solutions, what isadditional interesting effect.
3) Check if SERS blinking is possible on them
For SERS blinking experiments the sample was prepare as follow: on a clean glass drop of 0.1 ml
anisotropic NP (blue) + 0.1 ml 3,3’-diethylthiacyanine iodine salt (λ max 424 nm) dye was put anddried with compressed air duster, a drop of 1 M NaCl was dropped on this, and covered withanother glass.
Before SERS blinking experiments also LSPR Dark Field images were collected for theprepared sample, which proved small contribution of scattering in the LSPR bands.

Fig. 1 UV-Vis spectra of chosen Ag NP solutions.

Fig. 2 Shape distribution of NP

As the SERS blinking turn out to be possible to observe, the complex of films has beenrecorded, differed in condition showed in the table:

Fig. 3 Example for fitting the probability distribution
in time with a new equation

After time profile analysis the set of data was collected – probability coefficient of bright anddark state and the truncation time for dark state were calculated, the histograms of its distribution aresummarized and are ready to be compared with the results obtained for spherical nanoparticles by drKitahama.
During analysis of dark states of anisotropic NP different than for spherical NP dependents wasobserved. My proposition for a new analysis of SERS blinking equation is:curve fitting for different cases of anisotropic NP (Fig. 3).

The additional parameter D allow better

The results obtained in this project will be described and published in international journal incooperation with dr Yasutaka Kitahama and professor Yukihiro Ozaki.