luminescence as a result of formation of IA aggregates. The quenching of luminescence
through the formation of dimers or more highly aggregated species is well known [12].
Maximum fluorescence intensity of Astra Phloxine is observed at an excitation
wavelength of 540 nm, which corresponds to the maximum absorbance in the spectrum
of the dye, while the maximum in the emission spectrum is located at a wavelength of
557 nm (Fig. 2). The addition of 12-MPC to the Astra Phloxine solution leads to the
quenching of dye luminescence. At the same time, an intensive band appears at the
same emission wavelength as that of excitation: 540 nm. The appearance of such a
band was also observed by Motomizu and co-workers during the formation of IAs of
12-MPC with Malachite Green and Rhodamine B [18] and was attributed to the
scattering of the excited light by aggregates of the IA formed. The number of molecules
of IA in the aggregate was roughly estimated in the same study to be 4.3 × 10
7
.
Figure 2. The RLS spectra of AP (1); ІА AP-Мо(VI) (2); ІА АP-12-МPC (3)
and absorption spectra of АP (4), АP+12-МPC (5).
С
AP
= 2.0 10
-6
mol L
-1
(1-3), С
AP
= 4,0 10
-6
mol L
-1
(4,5); С
P(V)
= 1,0 10
-7
mol L
-1
(3),
C
P(V)
= 8,010
-7
mol L
-1
(5), C
Mo(VI)
= 0,0028 mol L
-1
, C
H
= 0,2 mol L
-1
, l = 5 сm (4,5)
Resonance Rayleigh light scattering (RLS) method is a new analytical technique
developed in 1990s [19, 20] It has been widely applied in the study of
biomacromolecules such as nucleic acids, proteins, drugs, organic compounds and
inorganic substances because of the high sensitivity and simplicity. The enhanced RLS
signals can be simply obtained by simultaneously scanning the excitation and emission
monochromators of a common spectrofluorometer with λ
ex
=λ
em
. RLS is a scattering-
absorption-rescattering process produced by the resonance of scattering and absorption
when the wavelength of Rayleigh scattering is located at or is close to its molecular
absorption band [20]. It can be seen from comparison of the RLS spectra with
absorption spectra (Fig. 2) that the RLS spectra of the complexes were located in the
300
400
500
600
700
0
200
400
600
800
1000
λ, nm
0,0
0,5
1,0
1,5
2,0
2,5
1
2
5
I
RRS
(
arbi
tra
ry
u
ni
ts)
Abs
orba
nc
e
3
4
- 1420 -