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Theoretical model to study the effect of concentration on the absorption spectrum of crystal violet in methanol using asymmetric double sigmoid

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  • Mustansiriyah University

Abstract and Figures

Crystal violet is a dye laser that changes the color of its solutions depending on the type of solvent. In this research we have dissolved the crystal violet in methanol and got the solution with the color violet. Then we have varied the concentration ratio to 1×10-5 , 1.5×10-5 , 2×10-5 , 2.5×10-5 and 3×10-5 mol/liter. The absorption spectrum for such concentrations is taken and the highest peak absorption obtained at 578 nm. We determined the bandwidth for absorption spectrum; it was constant for all concentrations at almost 126582 cm-1. Also, the molar extinction coeffi cient and oscillator strength are calculated, the results showed these coeffi cients decreasing with increasing concentration. We have estimated a theoretical mathematical model that simulates the behavior of absorption spectrum of crystal violet in methanol, by fi nding the best fi tting of the absorption spectrum for different concentrations using " table curve, 2D software ". The best function was for " Asymmetric Double Sigmoid ". Then we tested this theoretical function for three arbitrary concentrations and found that the theoretical results match experimental results.
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Theoretical model to study the effect of concentration
on the absorption spectrum of crystal violet
in methanol using asymmetric double sigmoid
ISRAA F. ALSHARUEE (*)
SUMMARY. – Crystal violet is a dye laser that changes the color of its solutions depending on
the type of solvent. In this research we have dissolved the crystal violet in methanol and got the
solution with the color violet. Then we have varied the concentration ratio to 1×10-5, 1.5×10-5,
2×10-5, 2.5×10-5 and 3×10-5 mol/liter. The absorption spectrum for such concentrations is taken
and the highest peak absorption obtained at 578 nm. We determined the bandwidth for absorption
spectrum; it was constant for all concentrations at almost 126582 cm-1. Also, the molar extinction
coeffi cient and oscillator strength are calculated, the results showed these coeffi cients decreasing
with increasing concentration. We have estimated a theoretical mathematical model that simulates
the behavior of absorption spectrum of crystal violet in methanol, by fi nding the best fi tting of
the absorption spectrum for different concentrations using “table curve, 2D software”. The best
function was for “Asymmetric Double Sigmoid”. Then we tested this theoretical function for three
arbitrary concentrations and found that the theoretical results match experimental results.
Key word: Absorption spectrum, dye laser, crystal violet, theoretical model, molar extinc-
tion coeffi cient.
1. Introduction
The behavior of the triphenylmethane (TPM) dye in aqueous solutions con-
taining polyoxyethylene nonionic surfactants was investigated using absorption
and fl uorescence spectroscopic techniques, triphenylmethane (TPM) dyes are an
important class of commercial dyes that have potential applications in the textile
industry as sensitizers for photoconductivity (1-5). The TPM dyes are character-
(*) Al-Mustansiriyah Univ., College of Science, Physics Dep., Iraq; e-mail: i81f54@yahoo.
com
ATTI DELLA “FONDAZIONE GIORGIO RONCHI” ANNO LXVII, 2012 - N. 1
DYE LASERS
Israa F. Alsharuee
6
ized by their intense colors, which include vivid reds, blues, greens and violets. Due
to the wide range of applications, the TPM dyes are often found in wastewaters
and some of these dyes have been found to be carcinogenic and genotoxic (6,7).
The photophysics and photochemistry of dyes in general are of considerable
interest in the appreciation of various phenomena such as fl uorescence, phospho-
rescence, long range and short range excitation energy transfer and other modes
of quenching, as probes for liquid structure in mixed solvents and various relax-
ation processes in solution (8). Crystal violet or Gentian violet is a triarylmethane
dye, it has antibacterial, antifungal, and anthelmintic properties and was formerly
important as a topical antiseptic. The name “gentian violet” was originally used
for a mixture of methyl pararosaniline dyes (methyl violet) but is now often con-
sidered a synonym for crystal violet. The name refers to its colour, being like that
of the petals of a gentian fl ower; it is not made from gentians or from violets (9).
The different colours are a result of the different charged states of the dye
molecule. In the yellow form all three nitrogen atoms carry a positive charge, two
of which are protonated, while the green colour corresponds to a form of the
dye with two of the nitrogen atoms positively charged. At neutral pH both extra
protons are lost to the solution leaving only one of the nitrogen atoms positive
charged (10). The visible absorption spectrum of crystal violet in solution ap-
pears to be composed of two bands, whose origin was interpreted based on the
existence of two isomers or two ground states (11,12). Photostability of organic
dyes depends strongly on the nature of the solvent used (13,14), among other
factors. Photodegradation of the dye molecule and subsequent reactions of the
degraded products amongst themselves, or with the solvent molecules, is a com-
plex phenomenon. Solvent purity is known to appreciably affect the process of
photodegradation (15).
2. Experimental part
The crystal violet of the dye laser we used, is a powder with violet to grey
colour, the molecular weight is 407.979 g/mol and the molecular formula is
C16H12N3O5Cl. We prepare the dye solution of these concentrations according
to the relation:
[1] m = C × V × M
where
m: weight of the dye needed to obtain the desired concentration (in gm).
C: the concentration needed for the preparation (in mol/liter).
V: the volume of solvent (methanol) to be added to the dye (in liter)
M: the molecular weight of the dye used.
Theoretical model to study the effect of concentration … 7
Absorption spectrum emitted from crystal violet solution in ethanoal was
recorded by “UV visible spectrophotometer EL04113001, 100 conc, CARY”. Fit-
ting curves for absorption spectrum were taken by the program “Table Curve 2D
version 5.01”.
3. Results and discussion
3.1 Practical results
Absorption spectrum for different concentrations of crystal violet in methanol
(namely 1×10–5, 1.5×10–5, 2×10–5, 2.5×10–5 and 3×10–5 mol/liter) is shown in Fig. 1.
FIG. 1
Absorption spectrum of crystal violet in methanol at different concentration.
We can see that the intensity of absorption spectrum decreases with decreas-
ing concentration and that the wavelength of maximum of absorption was 578 nm
in the range 576-578 nm. But at concentration 2.5×10–5 mol/liter, we observed the
exceptional result that the intensity of absorption spectrum at this concentration
should be less.
The bandwidth Δν1/2 in cm–1 of the absorption spectra was calculated by
measuring the full width at half maximum of absorbance. The molar extinction
coeffi cient ε(λ) (in M–1cm–1) at the peak wavelength of the absorption spectra was
calculated using the relation (16):
[2]
where:
A: the absorbance at the peak wavelength of the absorption spectra.
L: the path length of the dye solution medium (in cm).
C: the molar concentration of dye (in moles/liter).
ε(λ)=A
CL
Israa F. Alsharuee
8
The oscillator strength f was calculated by using the relation,
[3]
Table 1 refers to the values of molar extinction coeffi cient ε(λ) and oscillator
strength f according to Eqs.[2] and [3].
f=4.33×1033ε(λ)Δν1/2
Table 1
Optical absorption parameters of crystal violet in methanol.
C (mol/liter) Ε(λ) (liter/mol cm) f (liter/mol cm2)
1×10-5 1.221×10+5 6.692×10-25
1.5×10-5 1.295×10+5 7.097×10-25
2×10-5 0.797×10+5 4.368×10-25
2.5×10-5 0.456×10+5 2.488×10-25
3×10-5 0.787×10+5 4.313×10-25
The value of bandwidth for all the absorption spectra in Fig. 1 turns out
to be the same and equal to 126582 cm–1. This explains the fact that the width
of spectrum for all concentrations is similar and independent of the variation of
concentration, which is a property of material. In addition, from Fig. 2 and 3)
the molar extinction coeffi cient and the oscillator strength are seen to decrease
with increasing concentration except for the values 1.5×10–5 and 3×10–5 mol/liter.
These cases contrast with Beer’s law that states molar extinction coeffi cient is con-
stant and the absorbance is proportional to concentration for a given substance
dissolved in a given solute and measured at a given wavelength.
FIG. 2
Relation between the concentration and molar extinction coeffi cient
for crystal violet in methanol.
Theoretical model to study the effect of concentration … 9
3.2Modeling Results
The fi tting curves for all practical results for crystal violet in methanol in dif-
ferent concentration 1×10–5, 1.5×10–5, 2×10–5, 2.5×10–5 and 3×10–5 mol/liter are
illustrated in Fig. 4, where we used Asymmetric Double Sigmoid (ADS) function
for these fi tting processes.
This ADS equation is given as follows:
[4]
The parameters a, b, c, d, and e of Eq.[4] are shown in Table 2 for each
concentration.
Table 2
The parameters of Asymmetric Double Sigmoid equation.
Parameter C=1×10–5
mol/liter
C=1.5×10–5
mol/liter
C=2×10–5
mol/liter
C=2.5×10–5
mol/liter
C=3×10–5
mol/liter
r20.9983608 0.99795967 0.99779647 0.99788573 0.99786525
a 1.3330876 2.109711 1.7439588 1.2343391 2.5969369
b 562.77829 563.63735 564.23034 563.75996 564.00317
c 76.975585 75.765536 74.371247 76.108724 74.822127
d 17.942069 18.261153 18.233103 17.897166 18.330481
e 8.9119315 8.4925916 8.511416 8.3906474 8.4317565
FIG. 3
Relation between the concentration and oscillator strength
for crystal violet in methanol.
y=a
1+exp xb+c/2
d
11
1+exp xbc/2
e
Israa F. Alsharuee
10
Here r2 represents the difference between the experimental and theoretical
values (coeffi cient of determination); note that fi t improves when the r² values ap-
proach 1. The variations of each parameter with concentration are plotted in Figs.
5-9. The fi tting curve for each spectrum was taken, the fi tting equation being illus-
trated above the curve. We used different fi tting equations for these parameters.
(a)
(c)
(e)
FIG. 4
Fitting curve for absorption spectrum of crystal violet in methanol:
(a) 1×10-5; (b) 1.5×10-5; (c) 2×10-5; (d) 2.5×10-5; (e) 3×10-5 mol/liter.
(b)
(d)
Theoretical model to study the effect of concentration … 11
FIG. 5
The relation between a-parameter
and concentration.
FIG. 7
The relation between c-parameter
and concentration.
FIG. 6
The relation between b-parameter
and concentration.
FIG. 8
The relation between d-parameter
and concentration.
tting = equation
y = −3.090+2.372e+11x2−8.689e+13x2.5+8.165e+15x3
tting = equation
y=83.842−3.148e+11x2+1.093e+14x2.5−9.798e+15x3
tting = equation
y = 341938.94+7.047e+8x2ln x−341378.71ex
tting = equation
y=16.073+9.613e+10x2−3.471e+13x2.5+3.215e+15x3
tting = equation
y=7.782+8.132e−7/x1.5−1.302e−9lnx/x2−1.745e−8/x3
FIG. 9
The relation between e-parameter and concentration.
Israa F. Alsharuee
12
With the benefi t of the fi tting equation above, we calculate the fi nal param-
eters for the purpose of fi nding the estimated theoretical equation for absorption
spectrum of crystal violet in methanol. We take three test concentrations to ver-
ify this equation. First:, for the concentration 1.7×10–5 mol/liter, the theoretical
equation was as follows:
[5]
Second, for the concentration 2.2×10–5 mol/liter, the theoretical equation
was given as follows:
[6]
Third, for the concentration 2.7×10–5 mol/liter, the theoretical equation was
given as follows:
[7]
Then, the theoretical absorption spectrum for these three test concentra-
tions were plotted in Fig. 10. These theoretical absorption spectra of crystal violet
in methanol give us the ability of drawing the absorption spectrum of this dye in
any concentration. The value of absorbance does not increase proportionally with
the increase in the value of concentration, but differs from the concentration to
another. It follows the general equation to Asymmetric Double Sigmoid function,
which is the best equation describing the behavior of crystal violet in methanol.
y=2.061915
1+exp x563.80021+74.999 / 2
18.298
×
×11
1+exp x563.8002174.999 / 2
8.484
y=1.43964
1+exp x564.08567+75.34549 / 2
18.04997
×
×11
1+exp x564.08567 75.34540 / 2
8.46061
y=1.45933
1+exp x564.04590 +75.64461/ 2
17.97381
×
×11
1+exp x564.04590 75.64461/ 2
8.43676
Theoretical model to study the effect of concentration … 13
FIG. 10
Theoretical absorption spectrum of crystal violet in methanol.
4. Conclusions
Of all the above, we can arrive, from the study of the effect of absorbance
spectra of the crystal violet in methanol, at the following conclusions: the band-
width of all absorption spectra for any concentration is constant and about 126582
cm-1; the molar extinction coeffi cient and the oscillator strength are decreasing
with increasing concentration; a theoretical model for behavior of dye lasers crys-
tal violet in methanol has been predicted from absorption spectra, and we found
Asymmetric Double Sigmoid function to be the best fi tting equation to determine
the theoretical model. Such a function showed a signifi cant match in the behavior
with the experimental results for dye under research.
REFERENCES
(1) DUXBURY D.-F., The photochemistry and photophysics of triphenylmethane dyes in solids
and liquid media., Chem. Rev., 93, 381-443 (1993).
(2) DUXBURY D.-F., The sensitized fading of o-triphenylmethane dyes in polymer fi lms, Dye
Pigment, 25, 179-204 (1994).
(3) SARKAR M., PODDAR S., Studies on the interaction of surfactants with cationic dyes by
absorption spectroscopy, J. Colloid Interface Sci., 221, 181-185 (2000).
(4) DE S., GIRIGOSWAMI A., MANDAL S., Enhanced fl uorescence of triphenylmethane dyes in
aqueous surfactant solutions at supramicellar concentrations. Effect of added electrolyte, Spectro-
chim. Acta, A58, 2547-2555 (2002).
(5) DE SANTANA H., DAM Z., CORIO P., EL HABER F., LOUARN G., Preparation and characteri-
zation of Sersactive substrates: A study of the crystal violet adsorption on Ag nano particles, Quim.
Nova, 29, 194-199 (2006).
(6) PEARCE C.-I., LLOYD J.R., GUTHRIE J.T., The removal of colour from textile waste water
using whole bacteria cells, Rev. Dye Pigment, A58, 179-196 (2003).
Israa F. Alsharuee
14
(7) SRIVASTAVA S., SINHA R., ROY D., Toxicological effects of malachite green, Aquat. Toxi-
colog.,66, 319-329 (2004).
(8) ROHATGI-MUKHERJEE K.K., Some aspects of photophysics of dyes and self aggregation
phenomenon in solution, Ind. J. of Chemistry, 31A, 500-511 (1992).
(9) THETNER D., Triphenylmethane and related dyes, in: Kirk-Othmer Encyclopedia of
Chemical Technology, (Wiley, 2000).
(10) ADAK A., BANDYOPADHYAY M., PAL A., Removal of crystal violet dye from wastewater
by surfactant-modifi ed alumina, Sep. Purif. Technol., 44, 139-144 (2005).
(11) CLARK F.T., DRICKAMER H.G., High-pressure study of triphenylmethane dyes in polyme-
ric and aqueous media, J. Phys. Chem., 90 (4), 589-592 (1986).
(12) MARUYAMA Y., ISHIKAWA M., SATOZONO H., Femtosecond Isomerization of Crystal
Violet in Alcohols, J. Am. Chem. Soc., 118, 6257-6263 (1996).
(13) MIALOCQ J.C., HEBERT P., ARMAND X., BONNEAU R., Photophysical and Photochemical
Properties of Rhodamine 6G in Alcoholic and Aqueous Sodium Dodecylsulphate Micellar Solu-
tions, J.P. Morand, J. Photochem. Photobiol A: Chem., 56, 323-338 (1991).
(14) SINHA S., RAY A.K., KUNDU S., SASIKUMAR S., NAIR S.K.S., DASGUPTA K., Photo-stability
of laser dye solutions under Copper-vapour-laser excitation, Appl. Phys., B72, 617-621 (2001).
(15) TALLMAN C., TENNANT R., In: High Power Dye Lasers, ed. by F.B. Duarte (Springer,
Berlin, Heidelberg, 1991).
(16) Lange’s Handbook of Chemistry, 14th ed., Dean J.A. Ed. (McGraw-Hill Inc., New
York, 1992).
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The photochemistry and photophysics of triphenylmethane dyes in solids and liquid media
DUXBURY D.-F., The photochemistry and photophysics of triphenylmethane dyes in solids and liquid media., Chem. Rev., 93, 381-443 (1993).
Preparation and characterization of Sersactive substrates: A study of the crystal violet adsorption on Ag nano particles
  • H De Santana
  • Z Dam
  • P Corio
  • El Haber F
  • G Louarn
DE SANTANA H., DAM Z., CORIO P., EL HABER F., LOUARN G., Preparation and characterization of Sersactive substrates: A study of the crystal violet adsorption on Ag nano particles, Quim. Nova, 29, 194-199 (2006).