GUARNIM-NOS AMB QUÍMICA
Potser us preguntareu per què serveixen aquests
bastonets. De fet, es tracta de poder reproduir amb les vostres
mans un fenomen meravellós que es dóna a la naturalesa i
que té lloc en molts boscos i selves d’arreu del món.
A Europa on els mascles de lluerna ( cuques de llum) no brillen les
femelles intenten atreure’ls lluint contínuament, mitjançant una reacció molt
semblant a la següent.
En canvi, en algunes zones del Sudest Asiàtic i a Sudamèrica, les femelles
emeten llampades quimioluminiscents en resposta a un senyal lluminós i
periòdic emès per un mascle volador.
Al caient de la tarda, bassals, arbres, i fins i tot manglars sencers habitats
per colònies enormes d’aquests insectes emeten llampades de llum verda. Els
senyals aparentment aleatoris i independents, al principi, acaben sincronitzantse totalment quan la foscor esdevé la reina de la nit, i es produeix un fenomen
espectacular que es pot veure a quilòmetres de distància.
Mitjançant aquest comportament les cuques de llum poden aconseguir:
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¾
¾
¾
Augmentar l’atractiu de la femella
Il·luminar el terreny per desplaçar-se
Foragitar els depredadors
Enganyar les preses per menjar-se-les
Com que nosaltres som humans i no lluernes, tenim la sort, gràcies a la
química, de poder escollir la possibilitat que més ens interessi.
Sincronitzem els nostres senyals !!!
Procediment:
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•
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Tanqueu el ulls
Formuleu un desig
Quan us avisem obriu els ulls i torceu els tres bastonets
Uniu-los amb els tres manigets
Pengeu-vos-ho al coll
Feu senyals quimioluminiscents segons el vostre propòsit
Per ampliar coneixements
A continuació teniu el nom del colorant que es combina amb el luminol per
aconseguir diversos colors:
¾ Bastó blau→ Luminol + 9,10-difenilantracè
¾ Bastó groc→ Luminol + 1-clor-9,10-bis(feniletil)antracè. Àlies
“Rubren”
¾ Bastó verd→ Luminol + 9,10-bis(fenimetil)antracè
¾ Bastó vermell→ Luminol + Clorur de dietil (o-carboxifenil)-6(difenilamina)-3H-xanten-3-iledina). Àlies “Rodamina B”
I desprès diem que els científics són poc romàntics!
BONES FESTES CUQUES DE LLUM !!
us desitja
el Seminari de Física i Química
Desembre 2011
http://www.sonoscop.net/jmb/lucy/sinnombresinmemoria.pdf
Jose Manuel Berenguer (Lucy . sin nombre y sin menoria: reflejos de un manglar profundo)
http://chemistry.about.com/library/weekly/aa031703a.htm
There are several chemiluminescent chemical
reactions, but the luminol and oxalate
reactions are most commonly used for light
sticks and glow sticks. American Cyanamid's
Cyalume light sticks are based on the reaction
of bis(2,4,5-trichlorophenyl-6carbopentoxyphenyl)oxalate (CPPO) with
hydrogen peroxide. The fluorophors (FLR) in
this reaction are the chemicals that provide
the color of the light stick.
A similar reaction occurs with bis(2,4,6trichlorophenyl)oxlate (TCPO) with hydrogen
peroxide:
These are some fluorescent dyes that may be
added to light sticks to release colored light:
Blue
9,10-diphenylanthracene
Green
9,10-bis(phenylethynyl)anthracene
Yellow
1-chloro-9,10-bis(phenylethynyl)anthracene
Rubrene
Orange
5,12-bis(phenylethynyl)-naphthacene
Rhodamine 6G
Red
Rhodamine B
Although red fluorophors such as Rhodamine B are available, red-emitting light sticks tend not to
use them in the oxalate reaction. The red fluorophors are not very stable when stored with the
other chemicals in the light sticks. Instead, a fluorescent red pigment is molded into the plastic
tube that encases the light stick chemicals. The red-emitting pigment absorbs the light from the
high yield (bright) yellow reaction and re-emits it as red. This results in a red light stick that is
approximately twice as bright as it would have been had the light stick used the red fluorophor in
the solution.
http://chemistry.about.com/od/howthingsworkfaqs/a/howlightsticks.htm
How Do Lightsticks Work?.....
What is a Lightstick and How Does it Operate?
What's Involved?
There are three components of a lightstick. There need to be two chemicals that interact to release
energy and also a fluorescent dye to accept this energy and convert it into light. Although there is more
than one recipe for a lightstick, a common commercial lightstick uses a solution of hydrogen peroxide
that is kept separate from a solution of a phenyl oxalate ester together with a fluorescent dye. The color
of the fluorescent dye is what determines the resulting color of the lightstick when the chemical
solutions are mixed. The basic premise of the reaction is that the reaction between the two chemicals
releases enough energy to excite the electrons in the fluorescent dye. This causes the electrons to jump
to a higher energy level and then fall back down and release light.
Specifically, the chemical reaction works like this: The hydrogen peroxide oxidizes the phenyl oxalate
ester, to form phenol and an unstable peroxyacid ester. The unstable peroxyacid ester decomposes,
resulting in phenol and a cyclic peroxy compound. The cyclic peroxy compound decomposes to carbon
dioxide. This decomposition reaction releases the energy that excites the dye.