Polyoxy-Derivatized Perylenediimide as Selective Fluorescent Ag (I) Chemosensor

Article abstract of DOI:10.1007/s10895-016-1927-8

Recent investigations indicated that same concentrations of the ionic silver have harmful effects on aquatic life, bacteria and human cells. Herein we report chemosensory properties of N,N^′-Bis(4-{2-[2-(2-methoxyethoxy)ethoxy] eth- oxy}phenyl)

Full text of DOI:10.1007/s10895-016-1927-8

J Fluoresc
DOI 10.1007/s10895-016-1927-8
ORIGINAL ARTICLE
Polyoxy-Derivatized Perylenediimide as Selective
Fluorescent Ag (I) Chemosensor
Merve Zeyrek Ongun1 & Kadriye Ertekin2 & Said Nadeem3,4 & Ozgül Birel3
Received: 19 July 2016 /Accepted: 26 August 2016
#
Springer Science+Business Media New York 2016
Abstract Recent investigations indicated that same concen-
trations of the ionic silver have harmful effects on aquatic life,
bacteria and human cells. Herein we report chemosensory
properties of N,N′-Bis(4-{2-[2-(2-methoxyethoxy)ethoxy] eth-
oxy}phenyl) -3,4:9,10-perylene tetracarboxydiimide
(PERKAT) towards ionic silver. The dye doped sensing agents
were prepared utilizing ethyl cellulose (EC) and poly
(methylmethacrylate) (PMMA) and then forwarded to
electrospinning to prepare sensing fibers or mats. The
PERKAT exhibited bright emission in embedded forms in
EC or in the solvents of N,N-Dimethylformamide (DMF),
Dichloromethane (DCM), Tetrahydrofurane (THF) and in
the mixture of DCM/ethanol. The PERKAT exhibited selec-
tive and linear response for ionic silver in the concentration
range of 10−10 – 10−5 M Ag (I) at pH 5.5. Detection limits
were found to be 2.6 × 10−10 and 4.3 × 10−11 M, in solution
phase studies and PERKAT doped sensing films, respectively.
Cross sensitivity of the PERKAT towards pH and some metal
ions was also studied. There were no response for the Li+,
Al3+, Cr3+,Mn2+, Sn2+, Hg+, Hg2+, Fe2+ and Fe3+ in buffered
solutions. To the best of our knowledge, this is the first study
investigating silver sensing abilities of the PERKAT.
.
.
Keywords Polyoxy perylenediimide Electrospinning Ag
.
.
(I) Fluorescence Sensor
Introduction
Contamination of the fresh waters with ionic silver has be-
come a matter of concern due to the increasing use of silver
in industry medicine and technology. Different forms of silver
are found in functional products for water purification, bio-
films, dental treatment water, wound healing bandages, pool
water, integrated into textile for medicinal benefits, in washing
machines and refrigerators and numerous others. This inten-
sive interest towards silver arises from its antibacterial effi-
ciency. Today exposure to silver compounds is widespread
owing to the intensive use of soluble silver formulations. On
the other hand the Environmental Protection Agency (EPA)
limits concentrations of the Ag(I) lower than 1.6 nM for aquat-
ic life and microorganisms, and to 0.9 mM in drinking water
[1]. Consequently, analysis of trace amounts of ionic silver is
very important. Atomic absorption spectrometry, inductively
coupled plasma-atomic emission spectrometry, voltammetry
potentiometric applications and spectrofluorimetry have been
utilized for detection of Ag(I) in a variety of moieties includ-
ing biological and environmental samples. Among them
fluorescence-based detection methods generally possess ad-
vantages of selectivity, sensitivity, and simplicity as compared
to the other analytical techniques. The fluorescent based sens-
ing approaches utilize fluorescent dyes and ionophores or their
integrated form, fluoroionophores. Up to now a number of
fluorescent chemosensors for silver ion have been designed
Na+, K+, Ca2+, Ba2+, Mg2+, NH4 , Ni2+, Co2+, Cu2+,Pb2+,
+
* Kadriye Ertekin
kadriye.ertekin@deu.edu.tr
1
Chemistry Technology Program, Izmir Vocational School,
University of Dokuz Eylul, 35160 Izmir, Turkey
2
Faculty of Sciences, Department of Chemistry, University of Dokuz
Eylul, 35160 Izmir, Turkey
3
Faculty of Sciences, Department of Chemistry, Mugla Sıtkı Koçman
University, Kötekli, 48121 Mugla, Turkey
4
Department of Medicinal and Aromatic Plants, Köyceyiz Vocational
School, Mugla Sıtkı Koçman University, Koyceyiz,
48000 Muğla, Turkey

J Fluoresc
and tested successfully [2–9]. Most of these studies have been
performed in the solution phase. Obviously, studies performed
in liquid phase provided valuable information for researchers.
Nevertheless, the integration of sensing ionophores with solid
state components is necessary for better detection limits.
Previous studies on the determination of Ag + ions are com-
pared in detail in Table 1 in terms of the sensing material,
analysis media, working range, detection limit, and selectivity.
According to the numbers, studies performed in solid state
present better detection limits (7, 10–13).
Here we have successfully combined the solid state mate-
rials with optical sensing technology for silver detection at
sub-nanomolar levels utilizing the electrospun fiber materials.
In this study, matrix materials of poly (methyl methacrylate)
(PMMA) and ethyl cellulose (EC) were used to produce silver
sensing mats. The fluorescent probe: N,N′-Bis(4-{2-[2-(2-
methoxyethoxy)ethoxy]ethoxy}phenyl)-3,4:9,10-perylene
tetracarboxydiimide (PERKAT) was chosen as the indicator
due to the strong absorbance, bright luminescence, large
Stoke’s shift and excellent photostability.
−OCH2–CH2OCH3), 3.63–3.61 (16H, −OCH2CH2O–), 3.5
(8H, −CH2OCH3), 3.33 (12H, −OCH3), C64H74N2O20.
The polymers of ethyl cellulose (with an ethoxy content of
46 %) and poly (methyl methacrylate) were purchased from
Acros and Aldrich companies, respectively. The plasticizer,
dioctyl phthalate (DOP) was supplied from Aldrich. The ionic
liquid, 1-butyl-3-methylimidazolium tetrafluoroborate
(BMIMBF4) and potassium tetrakis-(4-chlorophenyl) borate
were supplied from Fluka. All of the solvents and other
chemicals (AAS standards or nitrate salts of the Li+, Na+,
+
K+, Ca2+, Ba2+, Mg2+, NH4 , Ni2+, Co2+, Cu2+ Pb2+, Al3+,
,
Cr3+,Mn2+, Sn2+, Hg+, Hg2+, Fe2+ and Fe3+ ) were of analyt-
ical grade and purchased from Merck, Fluka, and Riedel, re-
spectively. Aqueous solutions were prepared with freshly de-
ionized ultra pure water (specific resistance >18 MΏ cm,
pH 5.5) from a Millipore reagent grade water system.
AgNO3 was used for the calibration studies.
Preparation of Sensing Composites and Electrospun
Nanofibers
The electrospun fibers were characterized using scanning
electron microscopy (SEM) and their average diameters were
evaluated. To our knowledge this is the first attempt using the
PERKAT as the fluoroionophore-along with electrospinning
approach for silver sensing at sub-nanomolar levels.
In this study, electrospinning was chosen to fabricate the sens-
ing materials. Conditions of the electrospinning were opti-
mized in order to form bead-free PMMA or EC based contin-
uous fibers by varying the concentrations of plasticizer,
PMMA or EC and Room Temperature Ionic Liquids
(RTILs) in the composites. The sensing composites were pre-
pared by mixing 240 mg of polymer (PMMA or EC), 192 mg
of plasticizer (DOP), 48 mg of ionic liquid and 3 mg of
PERKAT in 2.0 mL of DCM:EtOH (25:75). IL-free forms
were also prepared for comparison. Then, the viscous solution
was taken in a plastic syringe and an electric potential of
27 kV was applied between the needle of the syringe and
the substrate coated with an aluminum foil. The distance be-
tween the needle and the electrode was 10 cm while the diam-
eter of the needle was 0.40 mm. Flow rate of the solution was
maintained at 0.5 mL/h programming the syringe pump.
The concentration of RTIL was varied from 0.0 up to
50.0 % w/w (0.0, 5.0, 10.0, 20.0, 40.0, and 50.0 w/w), with
respect to the content of PMMA or EC. It was found that the
presence of the optimum amount of RTILs in the PMMA
solutions facilitates the electrospinning of bead-free fibers
from the lower polymer concentrations. This behavior can
be attributed to the ionic conductivity and proper viscosity
of the RTIL doped precursor polymer solutions. Schematic
structure of the electrospinning apparatus has been Publisher
earlier [9] Fig. 2 reveals SEM images of EC and PMMA based
electrospun membranes under various magnifications.
Silver Sensing Ionophore and Used Chemicals
Synthesis of N,N′-Bis(4-{2-[2-(2-Methoxyethoxy)Ethoxy]
Ethoxy}Phenyl)-3,4:9,10-Perylene Tetracarboxydiimide
(PERKAT)
PERKAT was synthesized in our labs according to the reported
procedure [13, 14]. Perylene diimide utilized here bears
polyoxyethylene substituent groups. Polyoxyethylene chains
enhance solubility of the molecule and improve compatibility
of the dye with non-ionic polymeric matrices. A short summary
of the followed synthetic procedure is given here [14] Perylene-
3,4:9,10-tetracarboxylic dianhydride (0.69 mmol), 1 3,4-
di{2-[2-(2 methoxyethoxy) ethoxy] ethoxy}aniline (5 mmol)
and imidazole (5 g) were heated at 140 °C for 4.5 h under Ar
atmosphere. Then HCl (200 mL 2 N) was added into the reac-
tion solution and the resulting mixture was stirred for 1 h at
room temperature. Then extracted with CHCl3. The organic
phase evaporated under vacuum and crude product was puri-
fied by column chromatography. The schematic structure of the
employed fluoroionophore is shown in Fig. 1.
(CH2Cl2: MeOH, 10:1). FT–IR (cm−1): 2922, 2867, 1704
and 1663 (imide group), 1595, 1512, 1455, 1404, 1361,
1299,1255, 1178, 1124. 1H NMR (CDCl3; δ, ppm): 8.68–
8.59 (q, 8H, ArH (perylene)), 7.20–7.02 (6H, ArH),4.15
(8H, ArOCH2–), 3.84 (8H, ArOCH2CH2–), 3.7 (8H,
While, the EC based cocktails exhibiting a micro scale
porous structure, the PMMA based ones were in fiber forms.
In both cases, the empty spaces of the holes within the net-
work structures allow diffusion of ionic silver into the plasti-
cized matrix. It was observed that the electrospun membranes

J Fluoresc

J Fluoresc
substrate. The diameters of the fibers varied between 1.2 μm
and 146 nm (See Fig. 2). This type of fibrous-structure of the
electrospun membrane provided higher surface area than that
of the conventional continuous thin films. Further increase of
the surface area may be achieved by changing the conditions
of the electrospinning process such as solvent composition,
viscosity, concentration, temperature, humidity and working
distance, which results in either smaller diameter fibers or
increased porosity at the fiber surface.
Apparatus
UV-vis spectra were recorded by using a Shimadzu 2101 UV-
visible spectrophotometer. Emission spectra were recorded
using a Varian Cary Eclipse or FLS920 instrument from
Edinburg Instruments. Lifetime measurements were recorded
by a Time Correlated Single Photon Counting TCSPC) sys-
tem (Edinburgh Instruments (UK). The instrument was
equipped with a Standard15W Xe lamp and laser or a micro-
second flash lamp for steady- state and lifetime measurements,
respectively. During measurements, the Instrument Response
Function (IRF) was obtained from a non-fluorescing suspen-
sion of a colloidal silica (LUDOX30%, Sigma Aldrich) in
water, held in 10 mm path length quartz cell and was consid-
ered to be wavelength independent. All lifetimes were fit to a
χ2 value of less than1.1and with residuals trace symmetrically
distributed around the zero axes. All of the measurements
were performed at room temperature.
F i g .
1
S t r u c t u r e o f t h e N , N ′ - B i s ( 4 - { 2 - [ 2 - ( 2 -
methoxyethoxy)ethoxy]ethoxy}phenyl)-3,4:9,10-perylene
tetracarboxydiimide (PERKAT)
made up of PMMA exhibited 3D network like structure with a
random fiber orientation that was evenly distributed on the
Fig. 2 SEM images of EC and
PMMA based electrospun
membranes under various
magnifications

J Fluoresc
Spectral Characterization of the Fluoroionophore
We investigated effect of the acidic and alkaline species
o n e m i s s i o n p e r f o r m a n c e o f P E R K AT. We
spectrofluorimetrically titrated 10−5 M solution of the
Absorption, excitation and emission spectra of the
PERKAT were recorded in the solvents of DMF, DCM,
THF, and in mixture of toluene/ethanol 80:20 (v/v), re-
spectively. In all of the solvents the dye exhibited two
distinct absorption maxima with high molar extinction
coefficients, around 490 and 526 nm, respectively (See
Fig. 3). The dye exhibited highest absorption efficiency
in DMF. Absorption maxima observed in the visible side
of the spectrum located between 487 and 530 nm corre-
sponds to π– π* singlet transitions reported for the
perylenediimide.
PERKAT (in DCM) with non-aqueous HClO4 (10−3
M
in dioxane) and strong quaternary ammonium base;
tetrabutylammonium hydoxide (10−3 M in 2-propanol).
We recorded a high sensitivity both in the acidic and basic
regions during titrations. However when encapsulated in
EC matrix along with ionic liquid BMIMBF4, the acid-
base sensitivity of the PERKAT diminished significantly.
Figure 4 I and II reveals acid-base response of the EC
encapsulated PERKAT towards strong acids and bases,
respectively.
Spectral data of the dye were shown in Table 2. Upon
excitation around 485 nm, the dye displayed emission maxima
at 532, 532, 525, and 539 nm in the solvents of DMF, DCM,
THF and DCM:EtOH, respectively. As can be seen from
Table 2, the dye can be excited around 485 nm or further
wavelengths in the solvents. However when encapsulated in
polymeric matrices the excitation maximum shifts to shorter
wavelengths, 340 or 349 nm for EC and PMMA, respectively.
The highest and lowest Stoke’s shift values of 50 and 36 nm
were observed in EC and in PMMA, respectively. Due to the
higher Stoke’s shift, the EC matrix was chosen for further
sensing studies.
Even in encapsulated forms; the dye is still sensitive to
strong acidity around pH 1.0. However at higher pH values
of 3.0, this effect is not significant and can be overcome uti-
lizing the calibration standards in the buffered solutions. The
encapsulated forms of the PERKATalong with the ionic liquid
exhibited both short and long term stability with respect to the
IL-free forms. The tuned sensitivity and long term stability of
the PERKAT in EC can be attributed to the intrinsic buffering
effect of the ionic liquid. The BMIMBF4 acts like a buffer
system by neutralizing the acidic species due to the formation
of weak Lewis acid–base complexes between proton and an-
ionic side of the RTIL. Formation of such a buffer-like system
tunes the sensitivity of the sensor and enhances the long-term
stability of the indicator since it slowly acts as a sink for acidic
species in the ambient air. Similar effects of the RTILs have
been observed in our previous studies [15, 16].
Cross Sensitivity towards Acidic or Alkaline Species
In most cases the calibration standards are either in acidic
form or should be acidified to prevent the precipitation of
the ion under investigation. Therefore, cross sensitivity of
the chromoionophore towards pH should be questioned.
For further metal ion sensing studies we employed buffered
solutions keeping the acidity constant at pH 5.5. The effect of
pH on the complexation of PERKAT with Ag (I) ions was
investigated between pH 2.5 and 7.0 at fixed metal ion con-
centration of 10−5 mol L−1. The relative signal change; (I0 − I)/
I0 produced by the Ag (I) ions was high and stable around
pH 5.5. Distribution of the chemical species in the working
conditions was theoretically checked with chemical equilibri-
um software programme (Visual MINTEQ). At pH 5.5 abun-
dance of the acetate (CH3COO−(aq)) acetic acid
CH3COOH(aq) and Ag+(aq) were 36.4 %, 66.6 % and
100.0 %, respectively. Due to the excellent solubility of silver,
the acetic acid/acetate buffered solutions of pH 5.5 were cho-
sen as working moiety further studies.
Silver Uptake into the Mats and Fluorescence Based
Response
When doped into the EC matrices along with the anionic ad-
ditive, potassium tetrakis-(4-chlorophenyl) borate, the
PERKAT dye becomes a Ag (I) selective probe. In this sys-
tem, silver ions are selectively extracted into the porous films
(mats) by the anionic additive meanwhile potassium ions dif-
fuse from the membrane into the aqueous phase due to the
Fig. 3 Absorption spectra of the PERKAT in different solvents a) DMF
b) DCM c) DCM:EtOH (20:80) d) THF

J Fluoresc
Table 2 Absorption and emission based spectral data of the dye acquired in different moieties
Matrix
λ1
λ 2
εmax (λ1
εmax (λ2
abs)
(Excitation wavelength)
λmax
(Emission wavelength)
λmax
Stoke’s shift
Δλ(nm)
abs
abs
abs)
ex
em
DMF
490
490
487
495
526
526
521
530
12,060
9120
8240
9340
17,560
13,400
6900
485
485
478
491
340
349
535
532
525
539
390
385
50
47
47
48
50
36
DCM
THF
DCM:EtOH
EC
10,200
PMMA
mechanism of ion-exchange. Physical aspect of the response
mechanism of PERKAT dye can be explained by the follow-
ing ion-exchange pathway shown in Eq. (1).
Figures 5 and 6 show the change in fluorescence spectra of
solution and electrospun materials as a function of different
concentrations of silver ions. Upon exposure to Ag (I) ions, both
the solution and EC based electrospun materials exhibited sim-
ilar fluorescence signal change in direction of fluorescence
quenching. Signal drops observed at the emission maxima of
534 nm or 572 nm can be followed as the analytical signal for
the concentration range of 10−9–10−3 M in solution phase. In EC
PERKATðorgÞ ðpinkÞ þ 2KþðorgÞ þ 2TpCIPB−
ðorgÞ
þ
þ 2AgþðaqÞ↔PERKATAg2
ðorgÞ ðcolorlessÞ
ð1Þ
þ 2TpCIPB−ðorgÞ þ 2Kþ
ðaqÞ
Fig. 4 I: Acid base sensitivity of
PERKAT encapsulated in EC in
the pH range of 1.0–7.0. II: pH
range of 7.0–11.0. Buffer
solutions were prepared with
0.01 M CH3COOH, 0.01 NaOH,
0.01 M NaH2PO4, and 0.01 M
BES at desired pH

J Fluoresc
Fig. 5 Fluorescence response of
the (a) Ag-free solution in DCM-
EtOH, (b) 10−9 M, (c) 10−8 M, (d)
10−7 M, (e) 10−6 M, (f) 10−5 M,
(g) 10−4 M, (h) 10−3 M Ag (I).
Inset: calibration plot for the
concentration range of 10−9 to
10−3 M Ag (I)
based forms the signal quenching at 390 nm is very stable and
repeatable. The working range shifted to lower concentrations,
combined quenching both by collisions (dynamic quenching)
and by complex formation (static quenching) with the same
quencher [17]. In case of dynamic quenching the collisions
between the quencher and the fluorophore affect only the excit-
ed state of the fluorophore, no changes in the absorption or
excitation spectrum are expected. On the contrary, the formation
of ground-state complex in static quenching will perturb the
absorption spectra of the fluorophore.
Thus, a careful examination of the absorption spectrum
would be helpful to distinguish static and dynamic quenching.
Figure 7 depicts the absorption spectrum of PERKAT dye in
the absence and presence of Ag (I) ions (See spectrum Ba^ and
Bb^). Dramatic changes observed in the absorption integral
upon exposure to ionic silver reveal formation of a non-
fluorescent complex with Ag (I) in the ground state. When
the linear shape of the fluorescence intensity based response
data were evaluated together, the quenching mechanism be-
tween PERKAT and Ag (I) can be concluded as Bstatic^
quenching. Measurement of fluorescence lifetimes also
and exhibited a more liner response between10−10 -10−5
M
Ag(I) when the dye was embedded in the EC (See Figs. 5 and
6). The calibration curves were plotted by taking the mean
values of four different solutions (n = 4) of the same medium.
Detection limits in solution and PERKAT doped sensing
films were found to be 2.6 × 10−10 and 4.3 × 10−11 M, respec-
tively (The LOD values have been calculated utilizing concen-
tration of the metal ion giving a signal equal to average of the
blank signal (for n = 20) plus three standard deviations). The
data given in Table 1 indicate that, the LOD associated with the
proposed sensing material for Ag(I) ion is undoubtedly superior
with respect to that of most of other silver probes. The intensity
decrease is known to be due to the quenching of the PERKAT
by Ag (I) ions. In many instances the fluorophore can be
quenched both by collisions and by complex formation. The
intensity based data (I0/I) or (I0 − I)/I0 exhibiting an upward-
concave curvature towards the y-axis is the evidence of
Fig. 6 Excitation–emission
based response of the dye-doped
EC based electrospun mats to Ag
(I) ions at pH 5.5. (a) Ag-free
buffer, (b) 10−10 M, (c) 10−9 M,
(d) 10−8 M, (e) 10−7 M, (f)
10−6 M, (g) 10−5 M Ag (I). Inset:
calibration plot for the
concentration range of 10–10 to
10–5 M Ag (I)

J Fluoresc
Fig. 7 Absorption spectra of the PERKAT in DCM: EtOH (20:80) a:
Ag(I) free b: Ag (I) containing moieties
supported our findings. Figure 8 compares decay curves of the
Ag (I)-free and Ag (I) containing solutions of the PERKAT.
Bi-exponential decay times of 2.15 0.1 (7.2 %) and
13.4 0.1 (92.8 %) nanoseconds were measured for the Ag-
free forms. The decay times of 2.14 0.1 (7.3 %) and
13.6 0.1 (92.7 %) nanoseconds reported for Ag containing
forms can be concluded as the evidence of static quenching.
The method of continuous variation (Job’s method) was
used to determine the stoichiometry of the binding and a 1:2
complex formation of PERKAT: 2Ag+ was suggested,
consistent with Job’s plot analysis (See Fig. 9).
Fig. 9 Job’s plot based on the absorption intensity of PERKAT-Ag(I) at
486 nm in DCM:EtOH solution (20:80 v/v), [PERKAT +
Ag(I)] = 100 μmol L−1
Selectivity
Calcium, magnesium, potassium and sodium, which are the
most abundant ions in natural water samples as well as phys-
iologically relevant species and could be potential interferents
for determination of the Ag (I). In chemosensing based ap-
proaches, affinity of chromoionophores for the above
Fig. 10 Response of EC based fibers for the 10−3 M concentrations of
metal ions at pH 5.5. II: Response of the same composition towards
conventional anions and proton
Fig. 8 Decay curves of PERKAT in DCM: EtOH (20:80) in the absence
and presence of the ionic silver

J Fluoresc
mentioned metal ions is still a problem. In order to reveal the
selectivity of the proposed method on ionic silver, the influ-
ence of a number of cations were investigated.
Ag (I) containing CH3COOH/CH3COO−buffer (10−3 M) and
slightly acidic 0.1 M EDTA solutions, alternatively.
Approximately100% regeneration performance was succeeded
with 0.1 M thiourea. However due to the toxicity considerations,
for further regeneration treatments 0.01 M CH3COOH/
CH3COO− buffered EDTA solutions (at pH: 4.5) were preferred.
The average response and regeneration times for EC based struc-
tures were measured as 3.5 and 7.5 min (n = 15). Between the 1st
and 15th cycles, the level of reproducibility achieved was quite
good and exhibited a SD of 309.5 6.7 and RSD% 2.2 for upper
signal level, respectively (see Fig. 11). Figure 11 also reveals
short term stability of the encapsulated forms of PERKAT. We
have demonstrated that the BIMIMBF4 doped sensor fibers and
mesoprorous slides exhibited a stable and reproducible response
for silver measurements for a large concentration range. The
sensing composites were left in the lab atmosphere in a
dessicator and long term stabilities were tested within certain
time intervals, during 8 months. There was no significant signal
drift or instability in their response to oxygen even after
14 months. Our long term stability tests are still in progress.
Tests were performed in presence of 10−3 M of Li+, Na+, K+,
+
Ca2+, Ba2+, Mg2+, NH4 , Ni2+, Co2+, Cu2+,Pb2+, Al3+
,
Cr3+,Mn2+, Sn2+, Hg+, Hg2+, Fe2+ and Fe3+ ions in acetic
acid/acetate buffered separete solutions at pH 5.5. From
Fig. 10-I, it can be concluded that, the sensing membranes are
capable of determining Ag (I) with a high selectivity over other
ions. The fluorescence was dramatically quenched in the pres-
ence of Ag + at 390 nm exhibiting an I0/I ratio of 41. The inter-
ference effects of the anions of F-, Cl−, Br−, NO3− , NO2− ,SO4
2−
PO43− and proton were also tested. The sensing agents exhibited
negligible signal changes when exposed to all of the conventional
anions at pH 5.5 (See Fig. 10-II). Only very high concentrations
of proton caused a considerable signal change which can be
overcome using buffered solutions under test conditions.
Response Time, Regeneration and Stability
The sensor exhibited a very fast but non-reversible response
towards 10−4 M of Ag (I) in solution phase studies. The response
time (τ 90) was less than 30 s. However, in solid state the re-
sponse was fully reversible and only a slight drift (1.89 %) on the
upper signal level has been observed after 15 cycles. Response
Conclusion
Herein we report sensing properties of N,N′-Bis(4-{2-[2-(2-
methoxyethoxy)ethoxy] eth- oxy}phenyl) -3,4:9,10-perylene
tetracarboxydiimide (PERKAT) towards ionic silver as well as
other potential interferants. In this work, we performed coupling
of polymeric electrospun materials with fluorescence-based
measurement technique without scattering and other side ef-
fects. We performed to measure the Ag (I) concentrations as
low as 10−11 M exploiting the dye along with solid state mate-
rials. Our sensing approach resulted with large linear working
ranges extending to 10−11–10−5 mol L−1 Ag (I). Utilization of
the ionic liquid within the matrix enhanced the long term stabil-
ity of the molecule considerably. Further efforts will focus on
exploring new sensing materials and polymer compositions,
controlling the size of the electrospun membranes, and optimiz-
ing the sensitivities for the detection of a variety of analytes.
and regeneration experiments were carried out utilizing 10−4
M
Acknowledgments Funding this research was provided by Scientific
Research Funds of Dokuz Eylul University and the Scientific and
Technological Research Council of Turkey (TUBITAK).
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J Fluoresc
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