Sinteza i karakterizacija elektrolitičkog kupatila za pozlatu na bazi kompleksa zlata sa merkaptotriazolom
Syntesis and characterization of a gilding bath based on gold complex with mercaptotriazole
Author
Dimitrijević, Silvana B.
Mentor
Rajčić-Vujasinović, Mirjana
Committee members
Alagić, Slađana
Stević, Zoran

Jančić-Heinemann, Radmila

Trujić, Vlastimir
Metadata
Show full item recordAbstract
Elektrolit na bazi kompleksa zlata sa merkaptotriazolom sintetizovan je u širokoj oblasti
pH vrednosti od kisele do alkalne (pH=2-12). Nakon sinteze elektrolita urađena je
detaljna karakterizacija kompleksa u tečnom i čvrstom stanju u celom opsegu stabilnosti
kompleksa.
Fizičko-hemijska karakterizacija elektrolita urađena je najpre primenom Ultraljubičaste-
Vidljive (UV-vis) spektroskopije i Atomske Emisione Spektrometrije sa indukovano
spregnutom plazmom (AAS- ICP). UV-vis spektri elektrolita na pH vrednostima dva i
sedam pokazali su pikove na talasnim dužinama koje su vrlo bliske talasnim dužinama
pikova za merkaptotriazol, što može ukazati na to da su na ovim pH vrednostima veze
Au-MT elektrolitu uspostavljene u najmanjoj meri. UV - vis spektrometrija Au-MT
elektrolita na pH 9 pokazala je pik na 272,0 nm što može da ukaže na to da je jedino na
ovoj pH vrednosti uspostavljena veza između Au i MT. Pojava pika pri vrednost od
272,0 nm koja je bliska vrednostima koje se mogu naći u lite...raturi za druge necijanidne
elektrolite (sulfiti, tiosulfati i tiousulfati-sulfiti) može da ukaže na to da je veza između
Au i MT ostvarena preko atoma sumpora.
AAS - ICP analiza je potvrdila predviđene koncentracije zlata u elektrolitu uz
maksimalno odstupanje od 0,01 g/dm3.
Uporedna toksikološka ispitivanja elektrolita na bazi kompleksa zlata sa
merkaptotriazolom (pH=2, 4, 7, 9 i 12) i klasičnog cijanidnog elektrolita (pH=9),
urađena metodom "in vitro" na kulturi ćelija humane leukemije K562 su pokazala da je
toksičnost organskog kompleksa zlata pri pH vrednostima od: pH=4, 7 i 12 manja u
odnosu na alkalni cijanidni elektrolit a nešto veća na pH=2, dok su na pH=9 ove
vrednosti približno iste.
Elektrohemijska karakterizacija kompleksa zlata sa merkaptotriazolom urađena je
merenjem potencijala otvorenog kola, metodom ciklične voltametrije i snimanjem
polarizacionih krivih uz praćenje pH vrednosti i provodljivosti elektrolta pre i posle
elektrohemijskih eksperimenta. Ova ispitivanja su vršena u periodu od 12 meseci pri
različitim pH vrednostima 2, 4, 7, 9 i 12 i optimalnoj koncentraciji zlata u elektrolitu od
2,5 g/dm3 i u periodu od četiri meseca pri optimalnoj pH vrednosti od 9 i
koncentracijama zlata u elektrolitu od 1,5; 2,0; 2,5; 3,0 i 3,5 g/dm3. Na elektrolitima čija
je pH=4, 7 i 12 prvi vidljivi znakovi raspadanja kompleksa su se pojavili nakon tri
meseca od sinteze. Elektrohemijske karakteristike kompleksa zlata sa
merkaptotriazolom čija je pH vrednost dva i devet su ostale nepromenjene u periodu od
godinu dana. Na ovim elektrolitima nisu zapažene nikakve vizuelne promene u periodu
od 12 meseci.
Ispitivanje uticaja organskog kompleksa zlata sa merkaptotriazolom na fotoosetljive
slojeve koji se koriste pri izradi štampanih ploča urađeno je na prethodno pripremljenim
štampanim pločama sa razvijenom mrežom i sa ivicama - linijama na koje je nanešen
lak. Fotoosetljivi slojevi na pločicama otporni su na dejstvo elektrolita pri pH
vrednostima od 2, 7 i 9. Pri pH=4 prve vizuelne promene se zapažaju nakon 150 s dok
se na pH=12 prve promene pojavljuju već nakon 30 s. Sa mikrofotografija površina
pločica se takođe može videti da su fotoosetljivi slojevi pločica najotporniji na dejstvo
elektrolita na pH=2 i pH=9. Pri pH=9 fotoosetljivi slojevi na pločicama otporni su na
dejstvo elektrolita pri svim koncentracijama zlata u opsegu od 1,5 do 3,5 g/dm3.
Sintetizovani rastvori kompleksa zlata sa merkaptotriazolom uparavani su na sobnoj
temperaturi do suva u cilju dobijanja i karakterizacije nagrađenog jedinjenja u
kristalnom obliku. Optička mikroskopija ovih kristala, pokazala je da se kristali dobijeni
pri različitim pH vrednostima međusobno razlikuju po boji, krupnoći i homogenosti.
Najhomogeniji (po boji i krupnoći) i najsitniji kristali su dobijeni iz elektrolita na pH=9.
Najvažnije otkriće IC/Raman spektroskopije je da je Raman spektroskopija obezbedila
definitivnu potvrdu o uspostavljenoj vezi jona metala i atoma sumpora. Takođe, ove
tehnike su ukazale na to da atom azota u prstenu nagrađenog jedinjenja Au-MT, ostaje
protonovan, što ne ide u prilog prvobitnoj pretpostavci proistekloj iz analize UVspektara,
da je na pH=9 moguća koordinacija ne samo atoma sumpora, već i atoma
azota sa zlatom.
Metoda masene spektrometrije ukazala je na prisustvo molekula velikih masa koji mogu
da odgovaraju kombinacijama Au-2MT, Au-2MT-Gly, pa se čak ni kombinacija Au-
2MT-2Gly ne može u potpunosti isključiti u konačnoj formulaciji strukture nastalog
jedinjenja. Takođe su zapaženi pikovi koji ukazuju na prisustvo trovalentnog zlata.
Međutim, maseni spektar čvrstog uzorka otkriva i pojavu pika na m/z koji odgovara
masi atoma zlata, to jest može da ukaže na prisustvo jednovalentnog zlata. Ipak, ovaj
pik je mnogo slabijeg intenziteta. Jedan od dominantnih pikova kod svih masenih
spektara dobijenih za uzorke na pH=2, 4 i 7, je pik na m/z 201, koji može da potiče od
dva molekula merkaptotriazola (2MT), što dodatno sugeriše mogućnost formiranja
disulfidnog mosta između ova dva molekula.
X-ray difraktogram za kristale kompleksa zlata sa merkaptotriazolom dobijene iz
elektrolita na pH=9, ne pokazuje poklapanje sa karticama nijednog poznatog jedinjenja
zlata, što takođe potvrđuje pretpostavke da je sintetizovano novo jedinjenje.
Uporedna karakterizacija elektrohemijski staloženih dekorativnih prevlaka zlata
dobijenih iz sveže sintetisnog elektrolita, iz elektrolita nakon stajanja od godinu dana,
kao i prevlaka dobijenih iz elektolita dobijenog rastvaranjem kristala zlatomerkaptotriazola
(spoljni izgled, debljina, hrapavost, mikrotvrdoća po Knoopu i
elektronska mikroskopija - SEM sa EDS-om) pokazala je da su prevlake dobijene iz sva
tri elektrolita sjajne sa dobrom adhezijom. Najmanja hrapavost je izmerena za prevlaku
dobijenu iz svežeg elektrolita a najveća za prevlaku dobijenu iz elektrolta dobijenog
rastvaranjem kristala. U pogledu mikrotvrdoće ne postoje značajne razlike.
An electrolyte based on gold complex with mercaptotriazole was synthesized in a wide
pH range from acid to alkaline (pH=2-12). After synthesis of the electrolyte, detailed
characterization of the complex in liquid and solid state in the whole range of its
stability was performed.
Physico-chemical characterization of the electrolyte was performed, firstly by
Ultraviolet-visible spectroscopy (UV-vis) and by atomic asorption spectroscopy with
inductively coupled plasma (AAS-ICP). UV- spectra of Au-MT electrolyte at pH=2
and 7 show absorbtion peaks at wavelenghts which are very close to the wavelenght of
apsorption peak of mercaptotriazole, which may indicate that in these solutions,
chemical bonds Au-MT was the weakest. UV- spectra of Au-MT electrolyte at pH=9
shows an absorption peak at 272.0 nm, which may suggest that the bond between MT
and Au has only realised in this particular case. The appearance of the peak as the value
of 272.0 nm is close to the literature data for the other non...-cyanide electrolytes
(sulphite, thiosulphate and thiosulphate-sulphite), it may be assumed that the
coordination of Au to MT at pH 9 is realized through the sulphur atom.
AAS-ICP analysis confirmed the projected gold concentrations in the electrolyte with a
maximum deviation of 0.01 g/dm3.
For a comparative toxicity study of electrolyte based on the mercaptotriazole gold
complex (pH=2, 4, 7, 9 and 12) and the classic alkaline cyanide electrolyte (pH=9), "in
vitro" method was applied. For cytotoxicity testing, the culture of K562 cells of human
leukemia was used. Results show that the toxicity of organic complex of gold at pH
values of 4, 7 and 12 is lower than alkaline cyanide electrolyte but higher at pH=2,
while at pH=9 the relative cell viability is almost equal.
Electrochemical characterization of gold complex based on mercaptotriazole was
performed by: the open circuit potential measurment, cycling voltametry method and
recording the polarization curves, with pH values and conductivity of the electrolyte
measurment before and after each electrochemical experiment. These tests were
performed for a period of 12 months at different pH values: 2, 4, 7, 9 and 12 at optimal
concentration of gold in the electrolyte of 2,5 g/dm3 and in the period of four mounths at
optimal pH value of 9 and at the concentrations of gold in the electrolyte of 1,5; 2,0;
2,5; 3,0 and 3,5 g/dm3. For electrolytes with pH= 4, 7 and 12 the first visible signs of
decomposition of the complex appeared three months after synthesis. Electrochemical
characteristics of gold complex with mercaptotriazole at pH value of two and nine
remained unchanged for a period of one year. In that period any visual changes on these
electrolytes did not appear too these electrolytes.
Study of the effect of organic gold complex with mercaptotriazole on photoresist layers
used in the manufacture of printed circuit boards, was performed on previously prepared
PCB with developed net and lacquered edges - lines. The photoresist layers on the
boards are resistant to the effects of electrolyte at pH values of 2, 7 and 9. At pH=4 the
first visual changes are observed after 150 s while at pH=12 the first changes appeared
after only 30 seconds. From tiles surfaces micrographs it can also be seen that the
photoresist layers of tiles most resistant to the effects of electrolyte pH=2 and pH=9. At
pH=9 photoresist layers of tiles are resistant to the influence of electrolyte at all
concentrations of gold in the range of 1.5 to 3.5 g/dm3.
Synthesized solutions of gold complex based on mercaptotriazole are vaporized at room
temperature to dry in order to obtain and characterize Au-MT in the crystalline form.
Optical microscopy showed that the crystals obtained from solutions of different pH
values are different in color, size and homogeneity. The most homogeneous (according
to size and color) and the smallest crystals were obtained from the electrolyte with
pH=9.
The most important finding of IC/Raman spectroscopy analysis is that the Raman
spectroscopy has provided a definitive confirmation of bond established between metal
ion and sulphur atom. Also, both techniques indicated that the nitrogen atom in the ring
of obtained Au-MT compound, remains protonated at pH = 9, which does not support
an assumption formulated from the analysis of UV-spectra, that MT molekules at this
pH may interact with the metal ion not only through the sulphur, but also through the
nitrogen atom.
Mass spectrometry indicated the presence of high weight molecule that can match
combinations of Au-2MT and 2MT-Au-Gly. Even the combination of 2MT-Au-2Gly
could not be completely excluded in the final formulation of the structure of the
resulting compound. The peaks indicating the presence of Au (III) were also noticed.
Additionally, the mass spectra of solid sample reveal a peak at m/z corresponding to the
mass of a gold atom, which may indicate the presence of Au (I). However, this peak is
of very weak intensity. One of the major peaks in all mass spectra obtained for the
samples at pH = 2, 4 and 7, is the peak at m/z 201, which may originate from a fragment
corresponding to the mass of two molecules of mercaptotriazole (2MT); this further
suggests the possibility of formation of a disulfide „bridge“ between these two
molecules.
In available data bases no compound was found that match with the X-ray difractogram
of crystals of the gold mercaptotriazole complex obtained from the electrolyte of pH =
9. It confirms the assumption that a new compound was synthesized.
Comparative characterization of electrochemically deposited gold decorative coatings
obtained from the freshly synthesized electrolyte, then from the electrolyte after a year,
and coatings obtained from the electrolyte obtained by dissolving crystals of goldmercaptotriazole
(external appearance, thickness, surface roughness, the Knoop
microhardness and electron microscopy - SEM with EDS) showed that the coatings
obtained from all the three electrolytes are bright and with good adhesion. The smallest
roughness was measured for the coatings obtained from fresh electrolyte and the
greatest for the coatings obtained from electrolyte obtained by dissolving crystals. In
terms of hardness there are no significant differences.