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Inspect the Influence of Solvents, Magnesia and Alumina
Nanoparticles on Rhodamine 6G Laser Dye Spectroscopic
Properties
Fairooz F. Kareem, Asrar Abdulmunem Saeed, Mahasin F. Hadi Al- Kadhemy
Physics Department, College of Science, Mustansiriyah University, Baghdad, Iraq.
Email Address:
cenderlla78@yahoo.com (Fairooz), dr.asrar@uomustansiriyah.edu.iq (Asrar), dr.mahasin@uomustansiriyah.edu.iq
(Mahasin)
Received:
4
Aug 2021, Revised: 9 Aug 2021, Accepted: 25 Aug 2021, Online: 17 Sep 2021
Abstract
Some photophysical properties of Rhodamine 6G(Rh6G) dye are being explored in various solvents such as
Distilled Water, Dimethyl sulfoxide (DMSO), Chloroform, and Dichloroethane at various concentrations (1×10-
4 - 1×10-6) M. At room temperature, all samples were served. The links between several parameters that
describe the strength of optical transitions in atoms and molecules are examined. Also, by discussing how
(concentration, solvent) affect the dye's absorption and fluorescence spectra, this paper displays a variety of
opinions. The results demonstrated that the absorption spectrum peak of Rhodamine 6G relied on the type of
solvent, it displays a band about 525 nm in both Distilled Water and Dichloroethane. Furthermore, red shift
about 5 nm in Chloroform. Also, shift the absorption spectra to red in DMSO about 15 nanometres. increasing
solvent polarity will shift the gain curve toward longer wavelength. It is known that π→π* bands show a red
shift in the solvents of increasing polarity. In general, the gain of the medium increases with an increase in
polarity. The fluorescence spectrum shows red shift till the concentration 1×10-5 M then show blue shift in
Distilled Water, DMSO and Chloroform, while Dichloroethane exhibit red shift till 0.5×10-5 M then blue shift.
The transition is π→π*, since the oscillator strength value is less than 1. The best value of fluorescence quantum
yield is 0.98 in DMSO at the concentration 1×10-6 M. The maximum value of radiative lifetime is 9.79 n sec at
the concentration0.5×10-5 M in Dichloroethane. The best value of fluorescence lifetime in Chloroform about
5.54 n sec at the concentration 0.5×10-5M. Adding metal oxide nanoparticles (MgO & Al2O3) led to enhance
the absorption spectral intensity, but decrease fluorescence spectral intensity. The value of oscillator strength ƒ
is more than 1 which mean its strong transition. The best value of fluorescence quantum yield is 0.51 in the mix
of nanoparticles. The maximum value of radiative life time calculated to be found 1.47n sec in the mix of
nanoparticles. The best value of the fluorescence life time is 0.74 n sec in the mix of nanoparticles.
Keywords: Rhodamine6G, Absorption spectrum, Fluorescence spectrum, MgO NPs, Al2O3 NPs
1. Introduction
Rhodamine 6G (Rh6G) is derivative of the
xanthene dyes which are among the oldest and most commonly used of all synthetic
dyestuffs[1]. Rh6G is used in numerous
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Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1696
applications such as petroleum products
dyeing, paper printing, forensic
technology, colour photography, cosmetic
products, laser technology, optical
conversion, solar cells, diode, signal
amplification in optics, optical
communications , optoelectronics and as
an active medium for dye lasers [2]. Ionic
dyes self-associate to varying degrees in
solutions, depending on a variety of
conditions such as dye concentration, dye
structure, temperature, pH, and solvent,
among others, resulting in a deviation from
Beer's law [3]. When it comes to defining
physical qualities and potential, the solvent
in which the dye is dissolved is play an
important role. In moderate to higher
polarity solvents, the properties like
Stokes’ shifts, fluorescence quantum
yields, fluorescence lifetimes, radiative
and nonradiative rate constants follow
more or less linear correlation with the
solvent polarity [4].
Metal oxide nanoparticles attracted
attention due to their increased use in
various fields such as cosmetics,
electronics, material sciences, catalysis,
environment, energy and Biomedicine[5].
Magnesium Oxide(MgO) nanoparticles
have interesting applications in
microelectronics, diagnostics, and
biomolecular detection [6]. In the field of
catalysis, the unique structure of
Aluminium Oxide (Al2O3) is employed as
a foundation for active phases coated with
other materials. [7]. Presence of the
metallic structures in the vicinity of the
fluorophore can alter the optical properties
of the fluorophore. There have been some
attempts to show both quenching and
enhancement of the fluorescence intensity
of fluorophore can be introduced by
NPs[8]. Kumar et al. (2014)[9] studied
both quenching and enhancement of the
fluorescence intensity of Rh6G with
different dye concentrations, ranging from
3 to 300 µM, in presence of 15 nm
diameter Au NPs. For lower dye
concentrations, fluorescence quenching
and for higher concentrations, fluorescence
enhancement was occurred. Thus,
fluorescence intensity of the fluorophore in
the presence of metal NPs exhibit non-
monotonic behaviour. Fluorescence
quenching of Rh6G in Au nanocomposite
polymers was investigated by Karthikeyan
(2010), and found that the fluorescence
decay rate of Rh6G changes because of the
presence of AuNPs, and this change
depends on the particle size[10].
In this study, concentration effects in the
absorption and fluorescence spectra of
Rh6G were explored using a series of four
distinct organic solvents (distilled Water,
DMSO, Chloroform, and Dichloroethane),
In addition, the effect of adding MgO and
Al2O3 NPs to the photophysical properties
of Rhodamine water solution (because NPs
only dissolve in water) in different amount
of masses of NPs. were considered.
2. Theoretical Part
The intensity of light absorption at a
wavelength λ by an absorbing medium is
characterized by the absorbance A(λ) or
the transmittance T (λ), defined as[11].
(1)
Where Iₒ and I are the light intensities of
the beams entering and leaving the
absorbing medium, respectively. In many
cases, the absorbance of a sample follows
the Beer–Lambert Law[11].
(2)
Where ԑ(λ) is the molar absorption
coefficient, expresses the ability of a
molecule to absorb light in a given solvent
(commonly expressed in L mol-1 cm-1), C
is the concentration (in M) of absorbing
species and L is the absorption path length
(thickness of the absorbing medium) (in
cm). In the classical theory, molecular
absorption of light can be described by
considering the molecule as an oscillating
Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1697
dipole, which allows us to introduce a
quantity called the oscillator strength (ƒ),
which is directly related to the integral of
the absorption band as follows [12]:
(3)
Where m and e are the mass and the
charge of an electron, respectively, Cₒ is
the speed of light, n is the index of
refraction, Na is Avogadro’ s number and
is the wavenumber (in cm-1). The
oscillator strength is a ratio that compares
the strength of the transition with that of a
bound electron behaving as a 3D harmonic
oscillator. For strong molecular transitions,
ƒ values are close to 1 (sometimes they
even slightly exceed this value). For weak
transitions, ƒ values can be several orders
of magnitude lower than 1, and as low as
10 -8. For n → π * transitions, the values of
ε are in the order of a few hundred or less
and those of ƒ are no greater than ∼ 10 − 3.
For π → π * transitions, the values of ε and
ƒ are in principle much higher (except for
symmetry - forbidden transitions). ƒ is
close to 1 for some compounds, which
corresponds to values of ε that are of the
order of 105. ƒ is a dimensionless
quantity[11].
The fluorescence quantum yield( is the
ratio of the number of emitted photons
(over the whole duration of the decay) to
the number of absorbed photons [11].
(4)
Where: number of photons emitted and
absorbed is the area integration under the
fluorescence and absorption spectrum,
respectively.
The radiative lifetime , has been
related to the extinction coefficient using a
variety of formulas, Bowen and Woks'
method is the easiest to utilize. [11]:
(5)
Where ʃԑ ( is the area under the
curve of molecular extinction coefficient
plotted against wave number. is the
wave number of the maximum of the
absorption band, Then, the fluorescence
life time ( ) is obtained by using the
following equation [11].
(6)
The Stokes shift ( is the term used to
describe the difference in the wavelength
at which a molecule emits light is relative
to the wavelength at which the molecule
was excited [14].
(7)
This important parameter can provide
information on the excited states for
instance, when the dipole moment of a
fluorescent molecule is higher in the
excited state than in the ground state, the
Stokes shift increases with solvent polarity
[15].
The Full Width of Half Maximum
(FWHM) calculated by knowing the half
intensity of absorption or fluorescence
spectra and determines the half width of
spectra by slipping toward the x-axis
which represent the wavelength in
nanometre [16]. The FWHM is the
function of the possibility of tunable in the
active medium laser.
3. Experimental Work
Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1698
3.1. Materials
The Rh6G (C28H31N2O3Cl, molecular
weight 479.02 g·mol−1) from Sigma-
Aldrich. The solvents namely Distilled
Water (H2O), polarity (10.2)[17],
Dimethyl sulfoxide(C7H6OS), with
polarity (7.2)[17], Chloroform (CHCl3),
polarity (4.1)[17] and
Dichloroethane(C2H4Cl2), polarity (3.5)[17]
were supplied with 99% purity in terms of
mass percentage. Magnesium Oxide
(MgO) with an average diameter of 40 nm,
and purity of 99.9% from Intelligent
Materials Pvt.Ltd. While, Alumina Oxide
(Al2O3), with an average diameter of (20-
30) nm, purity of 99.9% from China.
3.2. Preparation of Samples and
Equipment’s measurements
Rhodamine 6G dye solution of primary
concentration of (1× 10-2) M were
prepared by dissolving the appropriate
amount of this dye (weighted by Mattler
balance of 0.1mg sensitivity) in each
solvent. The amount of dye, m, (in g) was
calculated using the following equation (6)
[18].
(8)
Where Mw is the molecular weight of dye
(g/mole), V is the volume of the solvent
(ml), and C is dye concentration (M). The
concentration of dye was then diluted to
get concentrations in the range of (1× 10-2)
M to (1× 10-6) M according to eq. (9) [19].
(9)
where, C1 is the high concentration, V1 is
the volume before dilution, C2 is the low
concentration, and V2 is the total volume
after dilution. It has been noticed that the
prepared solutions have a good
homogeneity. The absorption spectra of
Rh6G were recorded using a UV-Visible
spectrophotometer (T70/T80) and the
fluorescence emission spectrum for all
samples was recorded by using
(SHIMATDZU RF-5301pc).
Variety of Nano (MgO & Al2O3) amount
of masses were investigated for dye
solution. All the samples were prepared
using a hot plate magnetic stirrer until the
(MgO & Al2O3) nanoparticles diffuse
homogeneously through the Rh6G distilled
water solution. All the samples were kept
in a dark place so as to avoid any
possibility of photo-bleaching or fading of
dye. The samples were used immediately
after preparation. All the figures done with
Origin Pro 2019b.
4. Results and Discussions
The absorption spectra of Rh6G laser dye
in different solvents (Distilled water,
DMSO, Chloroform and Dichloroethane)
at various concentrations (1×10-4, 0.5×10-4,
1×10-5, 0.5×10-5 and 1×10-6) M illustrated
in the fig. (1). Also, table (1) display the
photophysical parameters for Rh6G in
different solvents with different
concentrations. The maximum absorption
and fluorescence wavelength (λmax) for
standard Rh6G in Methanol is (528 nm)
and (551nm) respectively[20].
Fig. (1a) showed Rh6G dissolved in
Distilled water. The maximum absorption
wavelength (λmax) at (525nm), that is a
good agreement with [21], with shoulder
peak at (495 nm) appears clearly at the
concentration (0.5×10-5) M, which it rises
with increase the concentration. Also,
increase the intensity of absorption respect
to concentration. Decrease FWHM for
absorption spectrum with increase the
concentration from 35.88 nm in the
concentration 1×10-6 M to be 26.68nm at
the concentration 1×10-4 M with note an
increase in the FWHM at the concentration
0.5×10-4 M to be 58.52 nm then it
decreases again.
It can be noticed increase the intensity of
absorption with increase the concentration
in fig.(1b) which is related to Rh6G
Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1699
dissolved in DMSO. The maximum
absorption (λmax) is (540nm), The result is
close to research [22] with shoulder peak
at (515nm), which it rises with increase the
concentration. DMSO which it less
polarity than Distilled Water show red
shift about 15nm. Increase FWHM for
absorption spectrum with increase the
concentration, where it is 33.53 nm at the
concentration 1×10-6 M, till reach 62.6 nm
at the concentration 0.5×10-4M, then it
decreases to be 35 nm at the concentration
1×10-4 M.
Fig.(1c) showed the absorption spectra of
Rh6G dissolved in Chloroform, Where the
maximum absorption (λmax) at (530nm).
This result has well agreement with [23]
and shoulder peak at (495 nm), which it
rises with increase the concentration. The
spectrum exhibit about 10 nanometres red
shift than Distilled Water. Also, increase
the intensity of absorption with respect to
concentration. Decrease FWHM for
absorption spectrum with increasing the
concentration from 42.58 nm at the
concentration 1×10-6 M to 21.97 nm at the
concentration 1×10-4M.
Fig.(1d) showed maximum absorption
(λmax) of Rh6G dissolved in
Dichloroethane at (525nm), that has a
good agreement with [24] and shoulder
peak at (510 nm) which it rises with
increase the concentration. Also, increase
the intensity of absorption with respect to
concentration. increase FWHM for
absorption spectrum with increasing the
concentration. where it is 38.83 nm at the
concentration 1×10-6 M then become
39.71nm at 1×10-4 M.
From fig. (1) it is clearly concluded that
the absorption intensity increased as the
Rh6G concentration increased. This is in
agreement with Beer–Lambert’s law [25].
When comparison Rh6G solution among
polarity solvents (Distilled Water, DMSO,
Chloroform and Dichloroethane), it will be
observed that the maximum absorption
wavelength increasing from (525) nm in
Dichloroethane to be (540) nm in DMSO.
In a majority, increasing solvent polarity
will shift the gain curve toward longer
wavelength [26]. It is known that π→π*
bands show a red shift in the solvents of
increasing polarity. In general, the gain of
the medium increases with an increase in
polarity [27].
a
Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1700
b
c
d
Figure (1) absorption spectra of Rh6G in: a) Distilled water, b) DMSO, c) Chloroform d) Dichloroethane
at various concentrations
Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1701
The fluorescence spectra of Rh6G laser
dye in different solvents (Distilled Water,
DMSO, Chloroform, Dichloroethane) at
various concentrations (1×10-4, 0.5×10-4,
1×10-5, 0.5×10-5 and 1×10-6) M illustrated
in fig. (2). Figure(2a) showed the
fluorescence spectra of Rh6G dissolved in
Distilled Water. The maximum
fluorescence (λmax) is 552 nm in the
concentration 1×10-6 M to be 564 nm in
the concentration 1×10-4 M that’s mean
there’s red shift about 12 nm. FWHM
increase from 22.36 nm to 34.2 nm at the
concentration 0.5×10-5 M then it decreases
from 32.96 nm at the concentration 1×10-5
M to be finally 27.46 nm at the
concentration 1×10-4 M.
Fig.(2b) display the fluorescence spectra of
Rh6G dissolved in DMSO. The maximum
fluorescence wavelength (λmax) increase
with increase the concentration, from
(564nm) at the concentration (1×10-6) M
till (576nm) at the concentration (1×10-4)
M, this result has well agreement with
research [28].It observed there is a shift
about 12 nm to red. FWHM for
fluorescence spectrum decease with
increase the concentration from 31 nm at
the concentration 1×10-6 M to be 25.85 nm
at the concentration 1×10-4 M.
From fig.(2c) which is related to the
fluorescence spectra of Rh6G dissolved in
Chloroform. It observed increasing
maximum fluorescence with increasing the
concentration from 550 nm in (1×10-6) M
to be 568 nm in (1×10-4) M. Noticeable red
shift about 18 nm with increasing
concentration. Also, FWHM increase from
14.99 nm to 32.76 nm at the concentration
0.5×10-5 M then it decreases from 30.32
nm at the concentration 1×10-5 M to be
finally 26.04 nm at the concentration 1×10-
4 M.
Fig.(2d) showed the fluorescence spectra
of Rh6G dissolved in Dichloroethane. The
maximum fluorescence (λmax) was
(544nm) at (1×10-6) M, which is identical
to results obtained researchers in reference
[24]and become increasing with increase
the concentration to be (567) nm at the
concentration (1×10-4) M. Red shift about
23 nm when increasing the concentration.
The fluorescence intensity increases with
increasing concentrations until 0.5×10-5 M
then it will be decreases respect to
concentration. FWHM for fluorescence
spectrum decreases with an increase in
concentration from 32.89 nm at the
concentration 1×10-6 M to be 26.69 nm at
the concentration 1×10-4 M.
The fluorescence intensity of Figs.
(2a,2b,2c) which is related to the solvents
namely Distilled Water, DMSO and
Chloroform respectively display increases
with concentrations till 1×10-5 M then it
decreases with increase the concentration.
Moreover, the fluorescence intensity of
fig.(2d) which is belong to Rh6G dissolved
in Dichloroethane increases with
increasing concentrations until 0.5×10-5 M
then it will be decreases respect to
concentration.
Figure (2) shows a decrease in
fluorescence intensity accompanied by a
blue-shift. This can be related to the
phenomenon of re-absorption and re-
emission, which ultimately reduces
fluorescence emission [13].
Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1702
500 550 600 650
0
200
400
600
800
Intensity (a.u)
Wavelength (nm)
1*10-4 M
0.5*10-4 M
1*10-5 M
0.5*10-5 M
1*10-6 M
500 550 600 650
0
100
200
300
400
500
600
700
Intensity (a.u)
Wavelength (nm)
1*10-4 M
0.5*10-4 M
1*10-5 M
0.5*10-5 M
1*10-6 M
500 550 600 650
0
100
200
300
400
500
600
700
Intensity(a.u)
Wavelength(nm)
1*10-4 M
0.5*10-4 M
1*10-5 M
0.5*10-5 M
1*10-6 M
500 550 600 650
0
100
200
300
400
500
600
700
800
900
Intensity(a.u)
Wavelength(nm)
1*10-4 M
0.5*10-4 M
1*10-5 M
0.5*10-5 M
1*10-6 M
Figure (2) fluorescence spectra of Rh6G in: a) Distilled water, b) DMSO, c) Chloroform d) Dichloroethane
a
b
c
d
Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1703
Table (1): Table (1) Photophysical Parameters for Rh6G in different Solvents with Different
Concentrations.
The quantum yield closely depends on the
environment of the fluorescing molecule
and on processes like internal conversion,
intersystem crossing and solute– solute
interaction. These parameters strongly
depend on the excitation source, solvent
characteristics and concentration of the
dye. Table (1) clearly reveals a decrease in
fluorescence quantum yield at higher
concentrations. This is a direct indication
Solvent
C(M)
λabsmax
(nm)
IAbsmax
FWH
M
(nm)
λfluomax
(nm)
Ifluo max
FWHM
(nm)
Stocks
shift
(cm-1)
ƒ
ՓF
FM
(n
sec)
F
(n sec)
Distilled Water
1*10-4
525
2.64
26.68
564
53.887
27.46
1317.1
0.51
0.005
3.13
0.01
0.5*10-4
525
2.46
58.52
561
210.58
28.63
1222.3
0.36
0.06
4.76
0.28
1*10-5
525
0.75
35.47
554
789.167
32.96
997.07
0.41
0.81
4.17
3.37
0.5*10-5
525
0.338
35.2
553
553.011
34.2
964.4
0.37
0.88
4.68
4.11
1*10-6
525
0.04
35.88
552
65.883
22.36
931.6
0.25
0.05
6.79
0.33
DMSO
1*10-4
540
2.57
35
576
59.907
25.85
1157.4
0.93
0.002
1.27
0.0025
0.5*10-4
540
2.508
62.6
575
114.53
25.23
1127.2
0.33
0.03
3.99
0.11
1*10-5
540
2.32
38.4
567
628.196
28.09
881.8
0.88
0.30
1.52
0.45
0.5*10-5
540
0.594
33.72
566
583.626
29.74
850.6
0.57
0.85
2.37
2.01
1*10-6
540
0.27
33.53
564
323.244
31.00
788.0
0.66
0.98
2.04
1.99
Chloroform
1*10-4
530
2.46
21.97
568
55.628
26.04
1262.2
0.80
0.02
1.57
0.03
0.5*10-4
530
2.42
21.89
565
167.612
26.47
1168.8
0.81
0.08
1.77
0.14
1*10-5
530
1.24
36.99
558
670.338
30.32
946.7
0.66
0.63
2.14
1.34
0.5*10-5
530
0.76
38.59
556
538.419
32.76
882.3
0.21
0.87
6.37
5.54
1*10-6
530
0.14
42.58
550
152.572
14.99
784.7
0.43
0.54
3.19
1.72
Dichloroethane
1*10-4
525
2.49
39.71
567
55.951
26.69
1410.9
0.10
0.22
0.13
0.02
0.5*10-4
525
2.46
37.01
562
118.891
27.53
1254.0
0.19
0.06
7.18
0.43
1*10-5
525
0.56
29.17
551
838.797
31.87
898.7
0.24
0.72
5.70
4.1
0.5*10-5
525
0.16
28.44
547
873.943
32.17
766.0
0.14
0.49
9.79
4.79
1*10-6
525
0.06
28.83
544
358.818
32.89
665.2
0.30
0.50
4.53
2.26
Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1704
of the fact that non-radiative processes
become significant at higher
concentrations, which contribute to
enhanced thermal lensing [29]. The
fluorescence quantum yield ( can be
calculated from eq. (4). The best value is
(0.98) in DMSO at the concentration
(1×10-6) M, their values not exceed than 1
and varied with change concentration and
solvents for Rh6G dye. While the value of
the fluorescence quantum yield is 0.05 in
the Distilled Water, 0.54 in Chloroform
and 0.50 in Dichloroethane at the same
concentration (1×10-6) M. These values
demonstrated less value comparing with
DMSO fluorescence quantum yield.
According to absorption spectra for all
samples, the radiative lifetime
calculated from eq. (5). Generally, the
maximum value is (9.79) nsec for
concentration (0.5×10-5) M in
Dichloroethane. Their values differ
according to concentrations and solvents.
From these two parameters and as stated
by eq. (6), the fluorescence lifetime ( )
planned as in table (1). Its well known the
fluorescence lifetime is a measure of the
time a fluorophore spends in the excited
state before returning to the ground state
by emitting a photon[11]. So, the best
value is in Chloroform, especially at the
concentration (0.5×10-5) M to be (5.54) n
sec.
The oscillator strength calculated by using
the equation (3). with all values less
than1, resulting in a kind of transition π
→π *.
Figure (3a) shows absorption and
fluorescence spectra for Rh6G in distilled
water at the best concentration (1×10-5) M,
that deal with Beer-Lambert law. The
maximum absorption wavelength (λabs)
was 525 nm, and the fluorescence
wavelength (λfluo) was 554 nm. This result
well agreement with [30].
Figure (3b) shows absorption and
fluorescence spectra for Rh6G in DMSO at
the best concentration (0.5×10-5) M. The
maximum absorption wavelength (λabs)
was 540 nm, and the fluorescence
wavelength (λfluo) was 566 nm. Figure (3c)
shows absorption and fluorescence spectra
for Rh6G in Chloroform at the best
concentration (0.5×10-5) M. The maximum
absorption wavelength (λabs) was 530 nm,
and the fluorescence wavelength (λfluo)
was 556 nm.
Figure (3d) shows absorption and
fluorescence spectra for Rh6G in
Dichloroethane at the best concentration
(1×10-5) M. The maximum absorption
wavelength (λabs) was 525 nm, and the
fluorescence wavelength (λfluo) was 551
nm.
It can be noted from fig. (3) that the stocks
shift increase with increase the
concentration in all Rh6G dye solution.
Also, the fluorescence spectrum is
typically a mirror image of the absorption
spectrum resulting from the ground to first
excited state transition. Furthermore, all
peaks are symmetric.
Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1705
400 450 500 550 600 650 700
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8 Abs.
Fluo.
Wavelength(nm)
Absorbance(a.u)
0
200
400
600
800
Intensity(a.u)
400 500 600 700
0.0
0.1
0.2
0.3
0.4
0.5
0.6 Abs.
Fluo.
Wavelength (nm)
Absorbance (a.u)
0
100
200
300
400
500
600
Intensity (a.u)
400 450 500 550 600 650 700
0.0
0.1
0.2
0.3
0.4
0.5
0.6 Abs.
fluo
Wavelength (nm)
Absorbance (a.u)
0
200
400
600
800
1000
Intensity (a.u)
400 450 500 550 600 650 700
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8 Abs.
Fluo.
Wavelength (nm)
Absorbance (a.u)
0
100
200
300
400
500
600
Intensity (a.u)
Figure (3) Absorption and fluorescence spectra of Rh6G in: a) Distilled water, b) DMSO, c) Chloroform d)
Dichloroethane at best concentration
c
d
b
a
Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1706
The best concentration of Rh6G dissolved
in water that obey Beer Lambert law is
(1×10-5) M Therefore, it mixed with (MgO
& Al2O3) nanoparticles to study the effect
of these NPs on spectroscopic properties of
Rh6G dye solution. Fig. (4) displays the
absorption spectra of Rh6G with different
amounts of (MgO & Al2O3) nanoparticles.
The maximum absorption wavelength
(525) nm at all amounts of NPs. when
adding NPs to Rh6G aqueous solution,
there are an increase in MgO and Al2O3
intensity from 0.75 in Rh6G only to be
1.89 and 1.92 in MgO and Al2O3,
respectively. Noted that decreases in
intensity of mix (MgO & Al2O3). It can be
observed that adding NPs led to increase
the absorption intensity, whereas the
maximum absorption wavelength till
constant at the same peak.
FWHM for absorption spectrum increasing
with increase concentration in the case of
adding Alumina nanoparticles, Whereas
FWHM decreasing in both of Magnesia
nanoparticles or the mix of Magnesia and
Alumina nanoparticles.
400 450 500 550 600
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Absorbance (a.u)
Wavelength (nm)
1×10-5 Rh6G
1×10-5 Rh6G+0.004 MgO
1×10-5 Rh6G+0.004 Al2O3
1×10-5 Rh6G+0.002 Al2O3+0.002MgO
Fig. 4. Absorption spectra of Rh6G with different amount of masses of (MgO & Al2O3) nanoparticles.
Fig. (5) and table (2) display the
fluorescence spectra of Rh6G with
different amounts of (MgO & Al2O3)
nanoparticles. The maximum fluorescence
wavelength (555) nm in all amounts of
nanoparticles. While it 554 nm in Rh6G
aqueous solution. Deceasing in the
intensity when adding MgO NPs or Al2O3
NPs or mix of MgO & Al2O3 nanoparticles
to Rh6G aqueous solution. It can be noted
that adding NPs led to decrease the
fluorescence intensity with increase
amount masses of NPs, while the
maximum fluorescence peak still constant.
FWHM for fluorescence spectra increased
when adding Alumina nanoparticles. It is
decreasing in both of Magnesia
nanoparticles or the mix of Magnesia and
Alumina nanoparticles.
Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1706
400 450 500 550 600 650 700
0
200
400
600
800
Intensity(a.u)
Wavelength (nm)
1*10-5 M Rh6G
1*10-5 Rh6G+0.004 MgO
1*10-5 Rh6G+0.004 Al2O3
1*10-5 Rh6G+0.002MgO+0.002 Al2O3
Fig. 5. Fluorescence Spectra of Rh6G with different amounts of (MgO & Al2O3) nanoparticles
Table (2) shows that increasing (MgO &
Al2O3) amounts led to enhancement of
absorption spectral intensity, while
decrease (quenching) fluorescence spectral
intensity. The value of oscillator strength
is more than 1 which mean its strong
transition. The best value of fluorescence
quantum yield is 0.51 in the mix of
nanoparticles. The maximum value of
radiative life time calculated to be found
1.47 nm in the mix of nanoparticles. The
best value of the fluorescence life time is
0.74 nm in the mix of nanoparticles.
Table (2) Spectral Information for Rh6G Aqueous Solution with Addition of Nanoparticles
5. Conclusions
The effects of solvents and concentrations
on the absorption and fluorescence spectra
of Rhodamine 6G are investigated in this
paper. The intensity and wavelength of the
Rhodamine 6G dye's absorption spectra
peak is affected by the solvent utilized.
There is 15 nanometres red shift in DMSO
and red shift about 5 nanometres in
Chloroform which is less polarity than
DMSO. While it remains constant in
Distilled Water and Dichloroethane. With
increasing concentration, the absorption
spectra of Rhodamine 6G dye solutions
shift towards the long wave length (red
shift). increasing solvent polarity will shift
Rh6G
1×10-5
M
Amount of
MgO(g)NPs
Amount
of Al2O3
NPs
λabs
max
(nm)
Iabs
FWHM
(nm)
λfluo
max
(nm)
IFluo
FWHM
(nm)
ƒ
ΦF
FM
(nsec)
F
(nsec)
0
0
525
0.75
35
554
789.16
32.96
0.41
0.81
4.17
3.37
0.004
0
525
1.89
58.30
555
649.9
31.83
1.26
0.42
1.38
0.57
0
0.004
525
1.92
83.65
555
717.44
33.12
1.65
0.25
1.05
0.26
0.002
0.002
525
1.68
56.31
555
735.34
31.55
1.18
0.51
1.47
0.74
Kareem, F. F. et al. Journal of Global Scientific Research (ISSN: 2523-9376) 2021/ 6 (9) 1708
the gain curve toward longer wavelength.
It is known that π→π* bands show a red
shift in the solvents of increasing polarity.
In general, the gain of the medium
increases with an increase in polarity. The
fluorescence spectra of Rhodamine 6G dye
solutions shift towards the short
wavelength (blue shift) with increasing
concentration. Oscillator strength is less
than 1(without adding NPs), so the
transition is π→π*. Stokes shift increasing
with increasing concentrations and the
fluorescence spectrum is typically a mirror
image of the absorption spectrum. The best
value of fluorescence quantum yield in
DMSO about 0.98 at the
concentration1×10-6 M. The maximum
value of radiative life time calculated to be
found 9.79 nm in Dichloroethane at the
concentration0.5×10-5 M. The fluorescence
life time calculated and found that the best
value is 5.54 nm at the concentration
0.5×10-5 M in Chloroform. Adding
nanoparticles to the Rh6G dye solution
enhance the physical properties of the
absorption spectra. Furthermore, the
addition of NPs to the Rh6G result in
quench the fluorescence spectra.
The value of oscillator strength is more
than 1 which mean its strong transition.
The best value of fluorescence quantum
yield is 0.51 in the mix of nanoparticles.
The maximum value of radiative life time
calculated to be found 1.47 in the mix of
nanoparticles. The best value of the
fluorescence life time is 0.74 in the mix of
nanoparticles.
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