7/23/2019 NANOCIENCE english

1/2

NANOCIENCE

NAME: Christian Castro

DATE: 03/12/2015

CHARACTERIZATION OF GOLD AND SILVER NANOPARTICLES USING

UV-VIS SPECTROMETRY

There are mainly two ways to obtain nanoparticles: bottom to top and top to bottom. In

the first case there are three major staes: red!ction" n!cleation and stabili#ation. This

process is applicable for preparin both old and sil$er nanoparticles.

%efore of the synthesis of nanoparticles it&s necessary to obtain metal ions" in the case

of sil$er this can be done by placin it in the presence of hydroen" prod!cin '1

chared ions" and in the case of old ions enerated" will ha$e a '3 chare. (nce these

ions enerated" the chare sho!ld be red!ced to 0" to achie$e this" we can !se red!cin

aents from di$erse so!rces" for instance synthetic compo!nds or fla$onoids from plant

e)tracts" which pro$ide the necessary electrons to red!ce the metals. This red!ctiondoesn&t show a sinificant chane in the ions si#e" for instance sil$er si#e is 0.2* nm

when it has '1 chare and this si#e remains wen it has 0 chare.

The ne)t step in the process is n!cleation" in which ions witho!t chares are atherin

rad!ally with the time" increasin the si#e of the nanoparticle that has a direct

infl!ence on some of its properties" incl!din opticals li+e the s!rface plasmon

resonance" which indicates that the chane in color of the nanoparticles is proportional

to the sol$ent cooncentration" the nanoparticles form or dimensions. ,or instance at a

macro le$el sil$er has a characteristic white color" while their nanoparticles dependin

on their si#e $ary in color from yellows to browns" this $ariation is d!e to its lambda

ma) can be fo!nd between 3-0-0 nm. (n the other hand the old at the macro le$el

has a characteristic yellow color" b!t as nanoparticles their colors can rane from p!rple

to bl!e" or in terms of lambda ma) from 52050 nm.

!e to the s!rface plasmon resonance e)plained abo$e" it is possible to estimate the si#e

of the nanoparticles !sin is spectroscopy" obtainin an bs $s. 4a$elenth raph"

which will show a sinle pea+ between 3-0-0 nm if we are in the presence of sil$er

nanoparticles and between 52050 if the nanoparticles are old. ,!rthermor this

analysis can ser$e to predict the shape of the nanoparticles" for instance if the

nanoparticles are sphericals the raph only show a sinle pea+ d!e to the !nic s!rface

present in a sphere" while if the form is c!bic the raph show three pea+s" each

7/23/2019 NANOCIENCE english

2/2

correspondin to the particle orientation that this may ha$e at the time of liht

incidence.