We are a group of seven students from Tháder secondary school in

Orihuela (Alicante, Spain) who have decided to carry out this project so that we

might get to visit CERN’s facilities and have the opportunity to work with the

greatest experts in Physics.

Our group, which is led by our teacher Jesús Carnicer, likes to think we

have a great scientific spirit and we are so excited at the chance that CERN is

giving us to achieve our dream. It is not only the possibility of going to these

facilities, but also of knowing that we could realise something that many

teenagers dream of. Every day we are resigned to looking at how the biggest

problems in science have been solved, but for the first time we could be able to

contemplate them first hand and participate in their resolution. We are being

given the chance to make Science, and we do not intend to waste it without a

fight.

Travelling to Geneva and being able to use the particle accelerator would

be an unforgettable experience for us, with which we could show our abilities as

promising young scientists and furthermore, acquire knowledge that we will be

able to use in our future as scientists.

PROPOSED PROBLEM:In what way will the behaviour of alpha particles or protons colliding against either a thin plate of gold or gold nanoparticles differ depending on the speed of these particles?

Firstly, we propose to reproduce the experiment performed by Rutherford

in 1909, in which he collided alpha particles against thin plates of gold,

repeating it at the accelerator, if possible with alpha particles or otherwise

“A BEAM LINE FOR SCHOOL”

replacing them with protons. Secondly, we want to extend this experiment using

a new material as a target that was not available for Rutherford, gold

nanoparticles. Finally, we also are interested to know what will happen to the

beam of particles (alpha or protons) when it collides with gold and with gold

nanoparticles.

HYPOTHESIS: When the protons collide with the target (Au) with a small amount of energy, about the order of 6 MeV (approximately that which Rutherford used), the results will be different for the sheet of gold compared to the nanoparticles.

Because the orbital of the nanoparticles of gold is slightly different from

that for the particles of the plate, the impact parameter will be different and,

consequently, the angle of dispersion. In any case, we expect greater angles of

dispersion for alpha particles than for protons.

In contrast, when we use high energy alpha particles and protons, nuclear reactions will take place in the nucleus of the target producing the same number and types of particles.

EXPERIMENTAL DESIGN:Technical requirements of the accelerator:

1. Sinctillator Counter (Scint) – This detector is the fundamental piece of

equipment for our project. With it, we intend to measure the tiny angles at

which the particles scatter.

2. Delay Wire Chamber (DWC) - Used to check whether the trajectory of

the particles is rectilinear after crossing the gold sheet (reproducing

Rutherford's experiment).

3. Cherenkov Counter – To determine what kind of particles we get after

bombarding the gold (only in the two experiments that use high energies.

4. Halo Counter – The objective of this detector is to measure the larger

angles at which some particles will be deviated and the number of

particles with a high level of deviation (reproducing Rutherford's

experiment).

5. Absorbers – For two of the four proposed experiments (those that use a

small amount of energy), we intend to use this material to reduce the

energy of the beam even more. We would like to place the Absorber in

front of the gold plate as long as it won't interfere with our main objective.

6. MNP17 – As we know both the initial momentum that we give the beam

and the momentum of the particles produced after the collision (thanks to

this detector), we can determine the interaction between the beam and

the gold plate.

Synthesis of the Gold Nanoparticles:Our team, Los Salvadores del gato de Schrödinger (The Saviours of

Schrödinger's Cat), is supported by the Institute of Molecular Science at

Valencia University, Spain, with the researcher from this institute, Gonzalo

Abellán, who from September will work as a Marie Curie Fellow with Prof. Dr.

Andreas Hirsch in Erlangen-Nuremberg Institut für Organische Chemie II, who

has taught us how to synthesise gold nanoparticles by a seed growth strategy

kinetically controlled by reduction of tetrachloroauric acid (HAuCl4 using the

method developed by the group of Victor Puntes Landmuir, 2011, 27 (17) pp

11098-11105.

By this method we obtain aqueous dispersions of colloidal gold

nanoparticles of controlled size, monodisperse and quasi-spherical.

Experimental procedure:We begin with a sodium citrate solution in distilled water which it is

heated up while being shaken vigorously. When the mixture

starts to boil, we add the HAuCl4. The resulting particles (ca. 10

nm, ca. 3.1012 Nps/mL) are coated with negatively charged

citrate ions, so they remain well suspended in H2O.

In a second step, we can increase the size of the nanoparticles in a

controlled way, avoiding the formation of new growth seeds:

Immediately after synthesising the NPs of Au and in

the same flask, the reaction cools down

and we sequentially inject the sodium

citrate and the HAuCl4. In the end, we

obtain the NPs, the size of which can be

modulated by repeating this last addition up to 14 times,

getting a range of sizes from approximately 20nm to

180nm. If the water of the solution is evaporated, we can

obtain a dust of gold nanoparticles.

Therefore, we can have for the experiment a suspension of nanoparticles

either in water or in dust.

Having completed our experiment, it is worth mentioning that working in

such a large team supposed an added difficulty, but something that was solved

easily if we take into account the fun that we have found in every little detail,

from when we chose the group’s name to making the video that accompanies

this project; spending untold hours in the laboratory was also made enjoyable

by performing experiments that are normally forbidden, playing with helium

balloons and computer games behind the teacher's back.

Electronic microscopy image showing

quasi spherical Au nanoparticles

obtained. The scale bar represents

50nm

Histogram showing the size distribution

of the Au nanoparticles. The analysis of

more than 400NPs yields an average

size of 16.3 (±2.1) nm.gg

UV-vis Absorption spectrum of Au.

It is obvious that the work and effort that we have put into this project is

no small thing. Nevertheless, whatever the final result may be, we already

consider the mere fact of having worked together as a team, in addition to what

we have learned about nanoscience and how particle accelerators work (which

was more difficult than we expected), to be a personal and collective triumph

that we are and will be proud of in the future.

BIBLIOGRAPHY:

Tipler P. A. y Mosca G., 1997, Physics for scientists and engineers.

Puentes, V. 2011. Landmuir, 2011, 27 (17) pp 11098-11105.

web: i-cpan.es

Authors: “Los Salvadores del Gato de Schrödinger” (IES Tháder – Alicante - Spain)

Students: Abel Lidón Gloria Llor María Marco Cristina Moreno Cristian Pérez Paula Riquelme Guillermo Rocamora

Teachers: Rocío Espinosa Jesús Carnicer

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Special Thanks: Gonzalo Abellán: investigator who taught us how to

synthesize gold nanoparticles Alex Watkins: Video Narrator

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