2-Hydroxyacetophenone and ethylenediamine condensed Schiff base: Fluorescent sensor for Al3+ and PO43?, biological cell imaging and INHIBIT logic gate

Article abstract of DOI:10.1016/j.ica.2017.03.003

The condensation product of 2-hydroxyacetophenone and ethylene diamine (L) acts as fluorescent sensor for Al³⁺ by “off-on” mode over the metal ions – Na⁺, K⁺, Ca²⁺, Mn²⁺, Fe²⁺, Fe³⁺

Full text of DOI:10.1016/j.ica.2017.03.003

Accepted Manuscript
2-Hydroxyacetophenone and ethylenediamine condensed Schiff base: Fluores-
cent sensor for Al3+ and PO4 3-, biological cell imaging and INHIBIT logic gate
Diganta Kumar Das, Jutika Kumar, Ananya Bhowmick, Pradip Kr.
Bhattacharyya, Sofia Banu
PII:
S0020-1693(16)30662-4
http://dx.doi.org/10.1016/j.ica.2017.03.003
ICA 17463
DOI:
Reference:
Inorganica Chimica Acta
To appear in:
Received Date:
Revised Date:
Accepted Date:
7 October 2016
27 February 2017
2 March 2017
Please cite this article as: D.K. Das, J. Kumar, A. Bhowmick, P.K. Bhattacharyya, S. Banu, 2-Hydroxyacetophenone
and ethylenediamine condensed Schiff base: Fluorescent sensor for Al3+ and PO4 3-, biological cell imaging and
INHIBIT logic gate, Inorganica Chimica Acta (2017), doi: http://dx.doi.org/10.1016/j.ica.2017.03.003
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2-Hydroxyacetophenone and ethylenediamine condensed Schiff base:
Fluorescent sensor for Al3+ and PO43-, biological cell imaging and
INHIBIT logic gate
Diganta Kumar Das1*, Jutika Kumar1, Ananya Bhowmick2, Pradip Kr.
Bhattacharyya3, Sofia Banu2
1Department of Chemistry, Gauhati University, Guwahati-781 014, Assam, India
2Department of Bio-engineering and Technology, Institute of Science and Technology, Gauhati University,
Guwahati-781 014, Assam, India
2Department of Chemistry, Arya Vidyapeeth College, Guwahati-781 016, Assam, India
digantakdas@gmail.com
1

A B S T R A C T
The condensation product of 2-Hydroxyacetophenone and ethylene diamine (L) acts as fluorescent sensor
for Al3+ by “off-on” mode over the metal ions –Na+, K+, Ca2+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+,
Pb2+, Cd2+, Hg2+ and Ag+. The interaction of L with Al3+ results bright blue fluorescence under UV
radiation and the fluorescence intensity enhances by ca. 40 times. The 1:1 interaction between L and
Al3+has been established from spectroscopic data as well as from DFT calculations. Snapping of photo
induced electron transfer (PET) prevailed in L, due to interaction with Al3+, is responsible for the
fluorescence intensity enhancement. The detection limit and binding constant of L towards Al3+ is 10-5 M
and 105.14 M-1 respectively. L is applicable for determination of Al3+ in bovine serum albumin and for live
cell imaging. The Al3+:L complex acts as PO43- ion sensor by fluorescent “on-off” mode over the anions –
-
-
2-
F-, Br-, I-, NO3 , HF2 , SCN-, CH3COO- and HCO3 .L is found to exhibit INHIBIT logic gate behaviour
with PO43- and Al3+ as inputs.
Key words: Fluorescence; Aluminium; Sensor; Cell imaging, Phospahte; Logic gate
2

1. Introduction
8% of the total mass of the earth’s crust is Aluminium (Al) which is higher than any other metal
ion [1]. Modern life, in various forms (e.g. light alloys, pharmaceuticals, water purification instruments,
house hold utensils etc.) depends on Al [2]. While Al in atomic form is normally not harmful, its
conversion into Al3+due to the environmental acidification is extremely harmful. When Al3+ enters human
body through plants it causes Alzheimer’s disease, Parkinsonism dementia, osteoporosis, colic and rickets
[3]. There is report that Al3+can also damage plant roots [4]. According to World Health Organization
(WHO) Al3+ is one of the prime food pollutants and in drinking water its concentration be limited to 200
µg L-1 (7.41 µM) [5]. WHO recommended tolerable weekly dietary human intake of Al3+ is 7.0 mg kg−1
body weight [6]. Detection of Al3+ in water is of environmental, biological and human health importance.
At present, different detection methods, like atomic absorption and emission, spectrophotometry,
electrochemiluminscence and electrochemical methods are known for detection of Al3+ ion [7-10]. But
due to the expensive instrumentations, requirement of highly-trained operators and complicated pre-
treatment makes these methods difficult for routine monitoring and applications.
Simple Schiff base ligands have gained recent interest as fluorescent sensors for metal ions
including Al3+ due to their relatively easy one step synthesis [11–13]. Recently reported Schiff bases
which act as “off-on” fluorescent sensor for Al3+ are based on – thiazole and salicylaldehyde [14]; 2-
hydroxyethylether-2-nitrophenol and salicylaldehyde [15], 8-hydroxyjulolidine-9-carboxaldehyde and
benzohydrazide [16]; 2-hydroxyaniline and 2 hydroxybenzaldehyde [17]; salicylhydrazide and ortho-
phthalaldehyde [18]; salicylaldehyde and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene [19]; thiophene-2-
carboxylic acid hydrazide [20]; 8-hydroxyquinoline-7-carbal- dehyde and 4-aminopyrine [21]; 2-methyl
quinoline-4-carboxylic hydrazide and 8-formyl-7-hydroxyl-4-methyl coumarin [22]; perylenebisimide
and di(2-(salicylideneamino))ethylamine [23]; 4-aminoantipyrine and salicylaldehyde, 4-aminoantipyrine
and 2-hydroxy-1-naphthaldehydeantipyridine [24]; Rhodamine ethylenediamine and 1,8-naphthalic
anhydride [25] etc.
3-
Excess phosphate ion (PO4 ) in water leads to increased algal growth, eutrophication, and reduced
water quality [26]. The excess of phosphate in human body results in kidney failure, while its deficiency
3-
leads to hyperthyroidism [27]. Fluorescent sensors are known for PO4 which adopted different
3-
approaches - PO4 was reacted with molybdate under acidic conditions to produce molybdophosphate
which forms non-fluorescent complex with Rhodamine 6G [28]; Azodiimine based “off-on” sensor
3

3-
involving ESPT [29]; Pyrene appended benzimidazolium-based simple cleft [30]; competition of PO4
with tannic acid-stabilized Cu nanoclusters for Eu3+ binding [31]; carbon dots [32]; 9-Anthraldehyde
nanoparticles in aqueous suspension [33]; combined effect of metal-organic frameworks and ZnO
quantum dot [34]; organic ligands coated Ag nanoparticles to quench fluorescence by Cu2+/Fe3+ and
3-
regain it by PO4 [35]; supramolecular interaction of 1,3,5-triethylbenzene core with PO4 [36] etc. Dual
3-
fluorescent sensor for Al3+ and PO4 is rare and only rhodamine B based sensor was developed to detect
3-
3-
Al3+ by “off-on” mode and the resulting complex could detect PO4 by “on-off” mode [37]. Schiff base
type isophthaloyl salicylaldehyde hydrazine moiety selectively detected Al3+ and PPi with “off-on” mode
at two different wavelengths in aqueous solution and exhibited INHIBIT and EXOR gates [38]. Other
Al3+ based fluorescent molecular switches are also recently reported [39, 40].
In present day, density functional theory (DFT) has become an effective tool for determining
molecular structures, interaction energy and other electronic properties of molecules [41-46]. Herein we
have employed DFT method to ascertain the binding pattern in the Al3+:L complex. The geometry has
been optimized using 6-31+G(d) basis set, with Becke three-parameter exchange and Lee, Yang and Parr
correlation functional, B3LYP [47] and has been confirmed by the absence of imaginary frequency.
In this paper, we report that the sensor obtained from the condensation product of 2-
Hydroxyacetophenone and ethylene diamine detects Al3+ by fluorescence “on” mode and shows bright
blue fluorescence under UV radiation. The binding stoichiometry, binding constant and detection limit of
the sensor towards Al3+has been established from spectroscopic data and DFT calculations. The sensor is
applicable for Al3+ in BSA as well as in live cell imaging. PO42- detection in presence of other anions by
the sensor: Al3+ complex is also reported.
Scheme 1: Chemical structure of L and DFT optimised structure of L in more stable trans form
4

2. Experimental
2.1 Chemicals and experimental techniques
All the chemicals were purchased from Merck and except Pb(NO3)2, AgNO3, CaCl2 the other
metal salts are sulphates. The metal salts were recrystallized from double distilled water before use.
Solutions of L(5.0×10-4 M) and metal salts (10-2 M) were prepared in 1:1 (v/v) CH3OH:H2O.
UV/Visible spectra were recorded in a Shimadzu UV 1800 spectrophotometer using 1 cm path
1
length quartz cuvette. H NMR spectra were recorded in a BrukerUltrashield 300 MHz spectrometer
using CDCl3 as solvent and the chemical shifts were reported in δ values (ppm) relative to
tetramethylsilane (TMS). Fluorescence spectra were recorded in Hitachi 2500 spectrophotometer using
quartz cuvette of 1 cm path length. The FT-IR spectra were recorded in a Perkin Elmer RXI spectrometer.
High resolution mass (HRMS) spectra were recorded on an Agilent spectrometer using HPLC methanol
as the solvent.
2.2 Synthesis and characterisations of the sensor, L
L (2-[2-(E)-(2-hydroxyphenyl)ethylidene]aminoethyl)-ethanimidoyl] phen) was synthesized based
on the reported procedure [48]. A solution of 2- hydroxyacetophenone (6 mL, 0.05 m mol) was prepared
in 50 mL absolute ethanol. Ethylenediamine (3.38 mL, 0.05 m mol) was added to this solution drop wise.
The reaction mixture was refluxed for 3 hours. Yellow coloured precipitate was obtained which was
filtered, recrystallized from ethanol and then dried under vacuum (melting point 199.8oC, yield 90%).
ESI-MS:[M]+ m/z, 296.49 (C18N2H20O2, 100% abundance); FT-IR (KBr): 1610.56 cm-1 (νC=N), 3446 cm-
1
(νO-H), 1292.31 cm-1 (νO-H, bending), 2931.80cm-1 (νC-H, aliphatic) and 1508.33 (νC=C, aromatic).
13
1HNMR (CDCl3, δ ppm, TMS): 2.396 (s, 6H), 3.994 (s, 4H), 6.774-7.545 (m, 8H). C NMR: (CDCl3, δ
ppm, TMS): 173.53, 163.39, 132.66,129.13, 119.42, 118.21, 117.31, 49.80, 15.06
2.3 Biological cell imaging studies
Rat L6 myoblasts were grown in DMEM medium supplemented with 10% Fetal Bovine Serum
(FBS), 1 % penicillin–streptomycin and maintained at 37 °C in a humidified atmosphere with 5% CO2.
For in vitro imaging study the cells were seeded in a 6 well (35 mm) culture dish with a seeding density
of 3×105 cells per dish. After reaching 60% confluence, cells were washed with PBS and incubated in
serum free media which was supplemented with Al2(SO4)3 (100 µM) for 40 hours. Cells were then
5

observed under a fluorescence microscope using a 20× objective with excitation and emission filters of
370 nm and 465 nm respectively. The images were taken through an attached CCD camera. Al3+ treated
cells were then washed with PBS and further incubated with L (50 µM) for 3 hours and observed under
fluorescence microscope.
3. Results and discussion
3.1 Fluorescence detection of Al3+ by L
Insert Figure 1 Here
L (5×10-4 M) in 1:1 (v/v) CH3OH:H2O showed weak fluorescence emission in the range 380 nm
to 700 nm when excited with 370 nm photons. The addition of Al3+ to the solution of L was found to
increase the fluorescence intensity with associated red shift (Fig. 1, Scheme 2). The final fluorescence
peak was observed at λmax=464 nm when Al3+:L concentration ratio became 1:1. Fig. 1B shows the plot
of I/Io versus Al3+ concentration where I is fluorescence intensity at a particular concentration of Al3+ and
Io is the fluorescence intensity of L at zero Al3+ concentration. The I/Io value gradually increased and
became ca. 40 when the concentration ratio of Al3+ and L reached 1:1, further addition of Al3+ did not
change the I/Io value.
Scheme 2: L (left) and L+Al3+(right) in 1:1 (v/v) 1:1 (v/v) CH3OH:H2O under UV light of 365 nm
6

Similar fluorescent spectral titrations were performed with metal ions – Na+, K+, Ca2+, Cr3+, Mn2+,
Fe2+, Fe3+, Cu2+, Co2+, Ni2+, Zn2+, Cd2+, Hg2+, Pb2+, Mg2+ and Ag+ but no appreciable change in
fluorescence characteristics of L was observed. The effect of different metal ions on the relative
fluorescence intensity (I/Io) of L has been shown in Fig. 2 through bar diagram. From the diagram it is
clear that L can clearly distinguish Al3+ over the other metal ions. Here Io and I are the fluorescence
intensities of L at zero and at one equivalent concentration of other metal ion respectively in the solution.
Insert Figure 2 Here
Insert Figure 3 Here
The selectivity of L towards Al3+ in the presence of other metal ions has been done. For this
purpose fluorescence intensity of L in presence of one equivalent of a metal ion Na+, K+, Ca2+, Cr3+,
Mn2+, Fe2+, Fe3+, Cu2+, Co2+, Ni2+, Zn2+, Cd2+, Hg2+, Pb2+, Mg2+ and Ag+ was recorded. Then one
equivalent of Al3+ was added to the solution already containing one equivalent metal ion and the
fluorescence intensity was observed after 5 minutes of standing. The fluorescence intensity was enhanced
with the almost same I/I0 ratio that was observed when only Al3+ ion was present (Fig. 3).
The interaction between L and Al3+ was also confirmed by UV-Visible spectroscopy. The UV-
Visible spectra of 5×10-4 M Lin 1:1 (v/v) CH3OH:H2O has been recorded at different added concentration
of Al3+ (Fig. 4). Absorption maxima for L in 1:1 (v/v) CH3OH:H2O were observed at λmax 386 nm, 327
nm and 276 nm (sh). With the addition of Al3+ the absorbance peak at 386 nm and 327 nm gradually
shifted by 10 nm towards lower wavelength that is blue shift occurred with a decrease in absorbance.
Insert Figure 4 Here
The fluorescence data have been used to determine the binding stoichiometry and binding constant
between L and Al3+ through the plot of log[(Io–I)/(I–Ifinal)] versus log[Al3+]28,29 (Fig. 5). Io, I and Ifinal are
the fluorescence intensities of L in absence of Al3+,at an intermediate concentration of Al3+ and at one
equivalent concentration of Al3+ respectively. The slope of the plot was found to be 1.18 indicating that
oneAl3+ binds to one L and the binding constant (β) was found as logβ = 5.14.The detection limit was
determined from the (I-I0) versus log[Al3+] plot and was found to be 10-5 M.74
Insert Figure 5 Here
7

The Al3+ induced fluorescence “off–on” behavior of L could be explained on the basis of the
photoinduced electron transfer (PET) mechanism. In L the PET occurs from the lone pair electron density
on immine N atoms to the phenyl rings. Binding of Al3+ to the N atoms of L snaps this PET process
leading to fluorescence enhancement.
scheme 2: (A) PET from N lone pair to the benzene rings and (B) Snapping of PET due to binding
of L with Al3+ through N lone pairs electrons
In order to substantiate the PET mechanism and hence the involvement of N lone pair electron
density for bond formation with Al3+ we recorded, in solution, the FT-IR and HRMS of the Al3+:L
complex. Before recording the FT-IR spectrum or HRMS the completeness of complex formation was
checked by recording the fluorescence spectra, which showed ca. 40 times increase in fluorescence
intensity. The observed significant change in the FT-IR spectrum recorded was that the 1610 cm−1 peak of
L due to νC=N shifted to 1653 cm−1. The HRMS spectrum of the Al3+:L complex showed molecular ion
peak at 324 which confirms the formation of the complex.
3.2 Reversibility of L towards Al3+
Insert Figure 6 Here
The fluorescence intensity enhancement of L on interaction with Al3+ was found to be reversible.
When the strong metal ion chelator disodium salt of ethylenediaminetetraacetate (Na2EDTA) was added
gradually to a 1:1 mixture of Al3+:L the already enhanced fluorescence intensity of the solution was found
to decrease till it reaches the original fluorescence intensity of L. Fig. 6 shows the effect of EDTA2- on
the fluorescence spectra of Al3+L. The Al3+ of the complex was removed by EDTA2- through chelation
leaving free L and hence fluorescence intensity was lowered.
8

3.3 DFT Calculations
The structure of L as well as L:Al3+was optimised using 6-31+G(d) basis set, with Becke three-
parameter exchange and Lee, Yang and Parr correlation functional, B3LYP75and was confirmed by the
absence of imaginary frequency. In case of L two orientations were possible, one trans and the other cis
with the former being more stable (Fig. 7). However, in the L:Al3+ complex the two N of L are at the cis
positions which is (in gas phase) 0.94 kcal/mol more stable compared to the corresponding trans complex
(Fig. 8). The calculated values of different bond lengths and bond angles are included in Table 1 which
supports that the complex acquired a distorted planar structure.
Insert Figure 7 Here
Insert Figure 8 Here
As the complex formation is taking place in solvent phase (1:1 methane-water) we further
observed the effect of the solvent phase on the structure of the complexes. For this purpose we optimized
the gas phase structure in solvent phase (in methanol and water) using the same level of theory. It is
interesting to note that the solvent phases do not impart any significant impact on the structures (the bond
lengths are varied by ~0.02 Ǻ and bond angles by 1º-2º only), Supplement table 1.
3.4 Determination of Al3+ in bovine serum albumin
Insert Figure 9 Here
The sensor L was successfully utilized for the determination of Al3+ in aqueous solution of bovine
serum albumin (BSA). Fig. 9A shows the fluorescence intensity enhancement for L in BSA medium upon
interaction with Al3+. Fig. 9B, inset shows the plot of I/Io as a function of Al3+ concentration. An
enhancement in fluorescence intensity of ca. 34 times has been observed at 1:1 concentration ratio of L
and Al3+. This value is comparable to the I/Io value of 40 in case of water. The same experiment was
repeated with biologically relevant fluorescence excitation at 410 nm. A gradual increase in fluorescence
intensity with increasing Al3+ concentration was observed (Fig. 9B) at this excitation too. Thus L is
applicable for determination of Al3+ in aqueous solution of BSA.
9

3.5 Living biological cell imaging studies
Insert Figure 10 Here
Figure 10 shows the fluorescence sensing ability of L to detect Al3+ in live Rat L6 myoblasts cells.
Panel [A] shows the fluorescent microscopic image of live Rat L6 myoblasts cells in PBS, panel [B]
shows the fluorescent microscopic image of live Rat L6 myoblasts cells incubated with L in PBS, panel
[C] shows the fluorescent microscopic image of live Rat L6 myoblasts cells incubated with Al3+ in PBS.
No fluorescent spot was observed in these panels. When both L and Al3+were incubated with live Rat L6
myoblasts cellsin PBS bright circular spots were observed as shown in panel [D] of Fig. 10. This clearly
proves that our developed sensor L is applicable for Al3+ detection in live biological cells.
Reversibility of Al3+ and L interaction with respect to Na2EDTA was also performed in cells. The
bright spots shown in panel D was found to gradually fade with the addition of Na2EDTA and finally
disappear at 1:1 concentration ratio of Al3+ and Na2EDTA (Panel E, Fig. 10).
3.6 Fluorescent “on-off” sensing of PO43- by Al3+L complex
Insert Figure 11 Here
The fluorescent Al3+L complex in 1:1 v/v CH3OH:H2O was tested for anion sensing and found to
3-
show positive result towards PO4 ion by fluorescent “on-off” mode. Fig. 11 shows that with increasing
3-
PO4 anion concentration the fluorescence intensity of L:Al3+ complex deceases and becomes minimum
3-
when PO4 anion concentration becomes three equivalents. Similar fluorescence titration with anions –
2-
-
2-
-
HPO4 , H2PO4 , HCO3 , NO3 , F-, Cl-, Br-, I-, SCN-, H2F- and CH3COO- resulted insignificant change in
fluorescence intensity of the Al3+L complex in 1:1 v/vCH3OH:H2O. Fig. 12 depicts the I/Io values of
3-
Al3+L complex through bars in 1:1 v/v CH3OH:H2O on interaction with these anions together with PO4
2-
-
anion. From this figure it is clear that the Al3+L complex can distinguish PO43- anion over HCO3 , NO3 ,
F-, Cl-, Br-, I-, SCN-, H2F- and CH3COO- by fluorescence “off-on” mode.
Insert Figure 12 Here
Insert Figure 13 Here
10

Selectivity of Al3+L complex towards PO43- anion in presence of another anion was also judged by
3-
recording fluorescence spectra of Al3+L complex in presence of PO4 anion and another anion. Fig. 13
3-
3-
compares through bars the I/Io values of Al3+L + PO4 anion and Al3+L + PO4 anion + another anion.
The comparable height of the bars in both the cases confirms that Al3+L complex is selective towards
PO43- anion even in presence of another anion.
3.7 INHIBIT logic gate behaviour of L
Insert Figure 14 Here
Based on the two different fluorescence emission states “on” or “off’, the sensor L has been
analysed with a molecular logic gate considering the two inputs PO43− and Al3+ as input “a” and input “b”
respectively. Input value “1” means presence and input “0” means absence of the input. Similarly out put
“1” means presence and “0” means absence of fluorescence when L interacts with the input. The logic
truth table has been illustrated in Fig. 14. Only the addition of Al3+led to fluorescence emission of L
which is not observed when both Al3+ and PO43- are present leading to an INHIBIT (INH) logic gate.
4. Conclusion
In summary, we have reported a new fluorescent sensor for Al3+ by fluorescent “on” mode
which is highly selective over the metal ions - Na+, K+, Ca2+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+,
Pb2+, Cd2+, Hg2+ and Ag+. The detection limit and binding constant of the sensor towards Al3+ is 10-5 M
3-
and 105.14 M-1 respectively. The sensor:Al3+ complex acts as sensor for PO4 ion by fluorescent “off”
-
-
2-
mode and is selective over anions - F-, Br-, I-, NO3 , HF2 , SCN-, CH3COO- and HCO3 . The sensor has
been applied for fluorescent detection of Al3+ in live Rat L6 myoblasts cells and in bovine serum albumin.
The sensor has been found to act as INHIBIT logic gates for Al3+ and PO43- ion as input.
Acknowledgement
The authors thank UGC, New Delhi and DST, New Delhi for financial assistance to the
department under DSA and FIST-II programme, respectively. INFLIBNET (UGC) is thanked for
literature survey help and IIT-Guwahati is thanked for HRMS data.
11

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13

[47] A.D. Becke, J. Chem. Phys., 98 (1993) 5648.
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14

Fig. 1- Fluorescence emission spectra of L (50 µM) in 1:1 (v/v) CH3OH-H2O upon addition of 0, 5, 10,
15, 20, 25, 30, 35, 45 and 50 µM Al3+ (λem 464 nm, λex 370 nm). Inset: Plot of I/Io versus Al3+
concentration.
15

Fig. 2 Bar diagram showing the effect of different metal ions on I/Io values of Lin1:1 (v/v) CH3OH-H2O.
.
16

Fig. 3 I/Io response of L in the presence of (i) Al3+(grey bars); (ii) Al3+ in presence of another metal ion
(black bars) in 1:1 (v/v) CH3OH-H2O. Similar heights of black and grey bars confirm selectivity of L
towards Al3+over another metal ion.
17

Fig. 4- Change in the UV/Visible spectra of L (50 µM) as a function of added Al3+ (5-50 µM) in 1:1 (v/v)
CH3OH-H2O.
18

Fig. 5- Plot of log[(Io–I)/(I–Ifinal)] versus log[Al3+] for L and Al3+ interaction in 1:1 (v/v) CH3OH-H2O.
19

Fig. 6: Decrease in fluorescence intensity of Al3+L complex with the addition of EDTA2- in 1:1 (v/v)
CH3OH-H2O.
20

A
B
Fig. 7: DFT optimised structure of L when- N atoms are trans [A] and N atoms are cis [B].
21

Fig. 8: DFT optimised structure of Al3+L complex obtained at B3LYP/6-31G(d,p) level of theory
22

20
15
10
5
0
450
500
550
600
650
700
Wavelength (nm)
Fig. 9: Fluorescence emission spectra of L (50 µM) at different added concentration of Al3+in- [A] BSA-H2O
medium (λem: 464 nm, λex: 370 nm. Inset: Plot of fluorescence intensity versus Al3+ concentration in BSA-
H2O medium. [B] BSA-H2O medium (λem: 480 nm, λex: 410 nm. Inset: Plot of fluorescence intensity versus
Al3+ concentration in BSA-H2O medium.
23

3-
PO4
Fig. 10: Effect of PO43- ion on the fluorescence spectra of Al3+L complex in 1:1 (v/v) CH3OH-H2O.
24

I/I0
Fig. 11: Effect of different anions on the I/Io value of Al3+L complex in 1:1 (v/v) CH3OH-H2O. Compared
to other anions the fluorescence quenching effect of PO43- anion is distinguishably different.
25

Fig. 12: I/Io values of Al3+L complex in presence of PO43- alone (grey bars) and in presence of PO43- and
another anion (black bars). The similar heights of bars indicate that Al3+L complex is selective towards
PO43- in presence of other anions.
26

A
B
C
D
E
Fig. 13: Fluorescent microscope images of live Rat L6 myoblasts cells (A), cells in presence of L
(B), cells in presence of Al3+ (C), cells in presence of L and Al3+ (D), cells in presence of
L, Al3+ and Na2EDTA (E).
27

Input
3-
PO4
Input 2
Output
Al3+
0
0
0
1
1
0
1
0
0
1
0
1
Fig. 14: Truth table for two input (PO43- and Al3+) INHIBIT logic gate.
28

29