Sensor potential of 1,8-naphthalimide and its dyeing ability of cotton fabric

Article abstract of DOI:10.1016/j.dyepig.2013.01.019

A new 4-(2-N,N-dimethylamino)ethylamino-N-2-hydroxyethyl-1,8-naphthalimide has been synthesized. The photophysical characteristics have been determined in aqueous and acetonitrile solutions. The influence of metal cations (Ni ²⁺, Zn²⁺, and Cu²) and protons on the fluorescence intensity has been studied to evaluate the capacities of the newly synthesized 1,8-naphthalimide as a fluorescence sensor. The 1,8- naphthalimide dye has been chemically bonded to a cotton textile fabric in order to obtain a heterogeneous fluorescent sensor for detecting of metal cations and protons.

Full text of DOI:10.1016/j.dyepig.2013.01.019

Dyes and Pigments 98 (2013) 64e70
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Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Sensor potential of 1,8-naphthalimide and its dyeing ability of cotton fabric
,
b
a
Desislava Staneva a , Ivo Grabchev , Rosica Betcheva
*
a University of Chemical Technology and Metallurgy, 1756 Sofia, Bulgaria
b Sofia University “St. Kliment Ohridski”, Faculty of Medicine, 1407 Sofia, Bulgaria
a r t i c l e i n f o
a b s t r a c t
Article history:
A new 4-(2-N,N-dimethylamino)ethylamino-N-2-hydroxyethyl-1,8-naphthalimide has been synthesized.
The photophysical characteristics have been determined in aqueous and acetonitrile solutions. The in-
fluence of metal cations (Ni2þ, Zn2þ, and Cu2) and protons on the fluorescence intensity has been studied
to evaluate the capacities of the newly synthesized 1,8-naphthalimide as a fluorescence sensor. The 1,8-
naphthalimide dye has been chemically bonded to a cotton textile fabric in order to obtain a heteroge-
neous fluorescent sensor for detecting of metal cations and protons.
Received 10 December 2012
Received in revised form
22 January 2013
Accepted 27 January 2013
Available online 8 February 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
1,8-Naphthalimide
Sensors
Textile
Dyeing
Metal cations
Fluorescence
1. Introduction
has also been used to design fluorescent molecular probes sensitive
to variations of pH or metal ions concentrations [9e15].
In the recent years the development of new materials which can
detect and react to external stimuli providing important informa-
tion on chemical, biological, medical and physical change occurring
in the environment have been studied intensively [1].
In this paper we present the synthesis and properties of a new 4-
(2-N,N-dimethylamino)ethylamino-N-(2-hydroxyethyl)-1,8-
naphthalimide designed to act as a fluorescence sensor. The influ-
ence of biologically important metal cations and protons on the
fluorescence intensity of acetonitrile and aqueous solutions has
been discussed with regard to its potential application as a detector
for these ions. The dyeing of cellulose textile fibers with the new 1,8-
naphtalimide under different conditions has also been investigated.
Textile materials have some specific physicomechanical prop-
erties making them favored matrixes for immobilizing different
substances. They are particularly suitable for the design of che-
mosensors or biosensors indicating biological functions and when
they should be constantly worn by an individual without ham-
pering their daily routine. The advantages of textile materials are
their large specific surface, the good mechanical and exploitation
properties (flexibility, softness, strength, lightness, ability to per-
meate gases) [2e5]. The large contact surface of textiles in general
enables efficient contact with the detected substances compared to
other polymer materials used for the same purpose.
Derivatives of 1,8-naphthalimide have been extensively studied
owing to their interesting photophysical and biological properties
and the wide range of their applications in different chemical and
biochemical areas [6e8]. Amongst the fluorescent compounds
utilized as sensors 1,8-naphthalimide derivatives have emerged as
quite appropriate for the purpose. The 1.8-naphthalimides moiety
2. Experimental
2.1. Materials and methods
Bleached and unmercerized cotton fabrics were used through-
out the work. Cotton fabric with a surface weight of about 140 g/m2
has been used. Chloroacetyl chloride, 4-nitro-1,8-naphthalic an-
hydride, 2-hydroxyethylamine and N,N-dimethylaminoethylendi-
amine were used without further purification as obtained from
(Aldrich). Cu(NO3)2$3H2O, Ni(NO3)2$6H2O, and Zn(NO3)2$4H2O,
used as source for metal cations.
2.1.1. Synthesis of 4-nitro-N-(2-hydroxyethyl)-1,8-naphthalimide
4-Nitro-1,8-naphthalic anhydride (2.43 g, 0.01 mol) was reacted
with 2-hydroxyethylamine (0.61 mL, 0.01 mol) in 2-methoxyethanol
* Corresponding author. Tel.: þ359 2 8163 265.
E-mail addresses: grabchev@mail.bg, i.grabchev@chem.uni-sofia.bg (I. Grabchev).
0143-7208/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.dyepig.2013.01.019

D. Staneva et al. / Dyes and Pigments 98 (2013) 64e70
65
(60 mL) for 3 h at 100 ꢀC. Aftercooling the precipitate was filtered off,
washed with water, and then dried in vacuum at 40 ꢀC. Yield: 86%.
FT-IR (KBr) cmꢁ1: 3456, 2940, 1700, 1662, 1567, 1457, 1373, 1342,
1236, 1000, 931, 779. 1H NMR (DMSO, 250 MHz) ppm: 3.62 (m., 2H,
CH2CH2OH); 4.13 (t. 2H, J ¼ 6.4 Hz, NCH2CH2OH); 4.82 (t., 1H,
J ¼ 6.1 Hz, CH2CH2OH); 8.05 (dd.,1H, J ¼ 7.5 Hz, 8.5 Hz, ArH-4); 8.5e
8.7 (m., 4H, ArH).
13C NMR (DMSO, 62 MHz) ppm: 42.2, 57.6, 122.7, 122.8, 124.3,
126.7, 128.3, 128.7, 129.5, 130.1, 131.6, 149.0, 162.2, 163.0.
Analysis: C14H10N2O5 (286.14 g molꢁ1): Calc. (%): C-58.74, H 3.50,
N 9.79. Found (%): C-58.49, H 3.58, N 9.64.
Scheme 1. Synthesis of 4-(2-N,N-dimethylamino)ethylamino-N-(2-hydroxyethyl)-1,8-
naphthalimide.
2.1.2. Synthesis of 4-(2-N,N-dimethylamino)ethylamino-N-(2-
hydroxyethyl)-1,8-naphthalimide (NI)
using a dual 5 mm probe head. The measurements were carried out
in DMSO-d6 solution at ambient temperature. The chemical shift
was referenced to tetramethylsilane (TMS). Thin layer chromato-
graphic (TLC) analysis of the dyes was followed on silica gel (Fluka
F60 254 20 ꢂ 20; 0.2 mm) using the solvent system n-heptane/
acetone (1:1) as an eluent.
4-Nitro-N-(2-hydroxyethyl)-1,8-naphthalimide (1.43 g, 0.005mol)
was reacted with N,N-dimethylaminoethylendiamine (0.55 mL,
0.0005 mol) in N,N-dimethylformamide (60 mL) for 24 h at room
temperature. After that the liquor was added to the 600 mL of water.
The precipitate was collected by filtration, washed with water, and
then dried in vacuum at 40 ꢀC. Yield: 94%.
3. Results and discussion
M.p. 93e95 ꢀC.
FT-IR (KBr) cmꢁ1: 3383, 3064, 2964, 2881, 1676, 1637, 1567, 1469,
1388, 1342, 1248, 1024, 775.
4-Nitro-1,8-naphthalic anhydride, was reacted at an equimolar
ratio with 2-hydroxyethylamine for 3 h in 2-methoxyethanol at
100 ꢀC until 4-nitro-N-(2-hydroxyethyl)-1,8-naphthalimide was
obtained. The final 4-(2-N,N-dimethylamino)ethylamino-N-(2-
hydroxyethyl)-1,8-naphthalimide (NI) was obtained in good yield
by nucleophilic substitution of the nitro group in 4-nitro-N-(2-
hydroxyethyl)-1,8-naphthalimide with N,N-dimethylethylendi-
amine in DMF solution at room temperature according to Scheme 1.
In this case the electron accepting carbonyl groups of the 1,8-
naphthalimide molecule favors the nucleophilic substitution re-
actions wherein the nitro group is displaced by the aliphatic N,N-
dimethylaminoethylamino group.
1H NMR (DMSO, 250 MHz) ppm: 2.86 (s., 6H, CH3); 3.43 (t. 2H,
J ¼ 5.9 Hz, CH2N(CH3)2); 3.56 (t., 2H, J ¼ 6.7 Hz, CH2CH2OH); 3.78 (q.,
2H, J ¼ 5.6 Hz, NHCH2CH2N(CH3)2); 4.07 (t., 2H, J ¼ 6.7 Hz,
NCH2CH2OH); 6.84 (d.,1H, J ¼ 8.6 Hz, ArH-2); 7.62 (dd.,1H, J ¼ 7.5 Hz,
8.2 Hz, ArH-4); 8.06 (t., 1H, J ¼ 5.1 Hz, NHCH2CH2N(CH3)2); 8.19 (d.,
1H, J ¼ 8.5 Hz, ArH-1); 8.35 (d., 1H, J ¼ 7.2 Hz, ArH-3); 8.85 (d., 1H,
J ¼ 8.5 Hz, ArH-5).
13C NMR (DMSO, 62 MHz) ppm: 37.8, 41.4, 42.2, 54.4, 57.9, 104.2,
108.8, 120.4, 121.8, 124.4, 129.1, 129.2, 130.6, 133.9, 149.8, 163.0,
163.8.
Analysis: C18H21N2O3 (313.18 g molꢁ1): Calc. (%): C-69.01, H 6.71,
N 8.95. Found (%): C-68.76, H 6.62, N 8.89.
3.1. Photophysical properties of NI
2.2. Analysis
The photophysical properties of 4-substituted-1,8-naphthali-
mides depend mainly on the polarization of the naphthalimide
molecule. Upon irradiation the polarization occurs resulting from
the donor substituents at a C-4 position and the carbonyl groups
from the imide structure of the chromophoric system. In general
the derivatives with amino groups are yellow in color and emit
a green fluorescence. Table 1 presents the spectral characteristics of
the NI under study in acetonitrile and water solution at two dif-
ferent pH values: the absorption (lA) and fluorescence (lF) maxima,
UVeVis spectrophotometric investigations were performed
using “Thermo Spectronic Unicam UV 500” spectrophotometer at
concentrations of 1 ꢂ 10ꢁ5 mol lꢁ1. The fluorescence spectra were
taken on a “Cary Eclipse” spectrophotometer at concentrations of
1 ꢂ 10ꢁ5 mol lꢁ1. IR analysis of compounds and both treated and
untreated cotton was carried out using the Infrared Fourier trans-
form spectrometer (IRAffinity-1 “Shimadzu”) with the diffuse-
reflectance attachment (MIRacle Attenuated Total Reflectance
Attachment). The color characteristics of the fabrics were deter-
mined on a Texflach ACS/DATACOLOR with spectrophotometer
Spectraflash 600 using D65 illuminant and 10ꢀobserver.
the extinction coefficient (log
yield of fluorescence (FF).
3 ), Stokes shift (nAenF), and quantum
In acetonitrile and aqueous solutions the NI exhibits yellowe
green color with absorption maxima lA ¼ 430e432 nm. The fluo-
rescence maxima is situated at lF ¼ 520e540 nm. From the data in
Table 1 it is seen that in alkaline aqueous medium (pH ¼ 10)
a batochromic shift has been observed of the fluorescence max-
imum compared to the acidic environment (pH ¼ 5). An example of
the absorption and fluorescence spectra of the NI in aqueous so-
lution is shown in Fig. 1. As seen the fluorescence spectra has
a fluorescence band with a single maximum, without vibrational
The quantum fluorescence yield has been calculated on the basis
of the results obtained from the absorption and fluorescence
spectra using Equation (1):
2
Su Ast nDu
Sst Au
FF
¼
Fst
(1)
2
nDst
where Fst is the quantum yield of the reference, Ast and Au repre-
sent the absorbance of the reference and the sample, respectively,
Sst and Su are the integrals of the emission of the reference and the
sample respectively, and nDst and nDu are the refractive index of the
reference and the sample, respectively. Fluorescein was used as
reference (Fst ¼ 0.85) [16] All spectra in organic solvents were
recorded using 1 cm path length synthetic quartz glass cells. The
NMR spectra were obtained on a Bruker DRX-250 spectrometer,
operating at 250.13 and 62.90 MHz for 1H and 13C, respectively
Table 1
Photophysical properties of NI in acetonitrile and aqueous solutions.
lA nm
3
mol lꢁ1 cmꢁ1
lF nm
n
AenF cmꢁ1
FF
CH3CN
432
432
430
10 430
16 400
14 600
520
530
540
3917
4280
4668
0.011
0.883
0.071
H2O at pH ¼ 5.0
H2O at pH ¼ 10.2

66
D. Staneva et al. / Dyes and Pigments 98 (2013) 64e70
1,0
0,8
0,6
0,4
0,2
0,0
Scheme 2. Schematic presentation of coordination of NI with metal cations (M2þ).
400
500
600
3.2. Influence of biologically important metal cations on the
fluorescence intensity of NI
Wavelength / nm
Fig. 1. Normalized absorption and fluorescence spectra of NI in aqueous solution at
pH ¼ 7.0.
We stated in our previous papers that in organic solvents some
transition metal cations can quench or the enhance fluorescence
intensity of the 1,8-naphthalimide [19e21]. Their fluorescent
characteristics have been studied in different media viewing their
practical application as fluorescent sensors able to detect metal
ions.
In this work the ability of a NI to detect metal cations has been
tested in acetonitrile and water solutions by monitoring the
changes in their absorption and fluorescent spectra in the presence
of tree biologically important metal cations (Cu2þ, Zn2þ and Ni2þ).
The influence of these metal cations and their concentration upon
the fluorescence intensity has been investigated spectrophoto-
metrically with regard to its application as photoinduced electron
transfer (PET) sensors for these cations.
Also for the practical applications the investigation in water is
very important. In this case, the fluorescence intensity (fluo-
rescence quantum yields) is of particular importance in the absence
of the metal cations.
The influence of the metal cations on the fluorescence intensity
of NI alone has been measured in both acetonitrile and buffered
structure. The fluorescence curve is an approximate mirror image
of the absorption one. This is an indication of the prevailing fluo-
rescence emission and of the unchanged molecular structure of the
1,8-naphthalimide fluorophore in the exited state.
In all cases the extinction coefficients
3
are higher than
10,000 mol lꢁ1 cmꢁ1, indicating that the long-wavelength band of
the absorption spectra is a band of charge transfer/CT/, electron
transfer on S0 / S1 transition. The Stokes shift is a parameter which
indicates the difference in the properties and structure of the dyes
between the ground state S0 and the first exited state S1. The Stokes
shift values are in the 3917e4668 cmꢁ1 region, which is in accord-
ance with our previous investigations on the 1,8-naphthalimide
derivatives [17,18]. The fluorescence efficiency of NI is estimated
by measuring its quantumyield FF on the basis of the absorption and
fluorescence spectra. As seen from the data in Table 1, the NI studied
has low quantum yield FF ¼ 0.011e0.071 at polar solvents as ace-
tonitrile and alkali water solution. In an acidic environment (pH ¼ 5)
the fluorescence intensity dramatically increases (FF ¼ 0.883).
40
32
24
16
8
70
60
- water
50
- acetonitrile
40
30
20
10
0
450
500
550
600
650
700
Wavelength / nm
0
Zn2+
Ni2+
Cu2+
none
Fig. 3. Fluorescence spectra of NI in aqueous solution (pH ¼ 7.0) at various concen-
trations of Cu2þ cations. The concentrations of Cu2þ cations are in order of increasing
intensity from 0 to 1 ꢂ 10ꢁ4 mol lꢁ1. The concentration of NI is 1 ꢂ 10ꢁ5 mol lꢁ1. The
inset displays the relationship between the fluorescence intensity and cation
concentration.
Fig. 2. Fluorescence enhancement factor (FE) of NI (c ¼ 1 ꢂ 10ꢁ5 mol lꢁ1) in the
presence of different metal cations (c ¼ 5 ꢂ 10ꢁ5 mol lꢁ1) in acetonitrile and aqueous
(pH ¼ 7.0) solutions.

D. Staneva et al. / Dyes and Pigments 98 (2013) 64e70
67
Table 2
1.0
Photophysical characteristics of NI in acetonitrile in the presence of metal cations
(see text).
lA nm
lF nm
n
AenF cmꢁ1
FF
0.8
0.6
0.4
0.2
0.0
CH3CN
Cu2þ
Zn2þ
Ni2þ
432
432
432
430
520
511
509
511
3917
3578
3502
3686
0.011
0.793
0.727
0.589
water (pH ¼ 7.0) solutions. A dramatic enhancement in the fluo-
rescence intensity in presence of the guest metal cations has been
observed in acetonitrile. The influence of the metal cations on the
fluorescence enhancement (FE) is presented in Fig. 2. The FE ¼ I/Io
has been determined from the ratio of maximum fluorescence in-
tensity I (after addition of metal cations) and fluorescence intensity
Io (before metal cations addition). Upon the addition of metal cat-
ions the enhancements of fluorescence emission is determined by
the nature of the cations added. The highest values have been
observed in the presence of Cu2þ cations (FE ¼ 66.5).
4
6
8
10
pH
Fig. 4. pH dependence of fluorescence intensity of NI.
Similar results have been obtained in aqueous solution, but the
FE values are less than in acetonitrile solution. Probably in this case
the water molecules coordinate the metal cations before their
ability to coordinate with the diamine receptor fragment.
In both cases the effect of metal cations on the fluorescence
intensity of NI can be ranked as follows:
The data collected in Tables 2 and 3 evidence no change in the
absorption maxima in comparison with the NI free from the metal
ions. In both cases the metal cations induce a hypsochromic shift of
the fluorescence maxima (DlF ¼ 9e11 nm) indicating a possible the
interaction between the NI and metal cations. The results also show
the high increase in the fluorescence caused by the presence of
metal cations. In acetonitrile solution the quantum yields
Cu2þ > Zn2þ > Ni2þ
In the absence of metal cations, NI emits a very weak fluo-
rescence emission which can be attributed to an efficient PET
process that takes place between the photoexcited 1,8-
naphthalimide and the lone-pair electrons of the free amine at
the substituent at C-4 position. In the presence of metal cations, the
lone-pair electron of the free tertiary amine quencher is engaged in
coordination with metal cations (Scheme 2). Accordingly, when
a metal cation engages the lone electron pair of the receptor ni-
trogen atom in coordination, it reduces the donor potential and
consequently leads to a deceleration or a complete “switching off”
of the electron transfer. The result is a fluorescence emissive
complex and the fluorescence of the system is “switched on”
(Scheme 2).
The typical change in the fluorescence intensity of NI induced by
Cu2þ is plotted in Fig. 3. As seen the addition of Cu2þ leads to an
increase in the fluorescence intensityof NI solution (c ¼ 10ꢁ5 mol lꢁ1),
thought it depends on the concentration. Above the concentration of
10ꢁ5 mol lꢁ1 the change in fluorescence intensity is insignificant.
Cu2þ cations induce a hypsochromic shift DlF ¼ 11 nm of the fluo-
rescence maximum (lF ¼ 531 nm) which indicates that the switch
might bind metal cations to the nitrogen atoms from the receptor via
chelation [22].
(
FF ¼ 0.58e0.79) increase after adding of metal ions with con-
centration 10ꢁ5 mol lꢁ1, if compared to those of the ions free so-
lution (FF ¼ 0.01). The highest quantum yield values have been
obtained in the presence of Cu2þ cations (FF ¼ 0.79). We suppose
the higher quantum yield in the case to be on account of the better
coordination ability of Cu2þ cations as well as on the stabilization of
the coplanar system of the complex formed. The spectrum of the NI
complex with metal cations has a Stokes shift smaller than that of
the spectrum of NI alone, which indicates the stabilized planarity of
the chromophoric structure after the complexation. In this case the
non-radiative emission during the transition from S1 to the ground
state S0 is smaller and leads to higher fluorescence quantum yields.
Similar results have been obtained in water solution, but the FE
values are less than in acetonitrile solution. Probably in this case the
water molecules attack metal cations before their ability to coor-
dinate with the receptor fragment (Fig. 2).
3.3. Effect of pH on the spectral properties of NI
It was of great interest to investigate the influence of pH on the
fluorescence intensity of the 1,8-naphthalimide under study. The
fluorescence intensity NI was investigated in a pH range of 3.2e
11.0. The fluorescence intensity against pH is plotted in Fig. 4 and
a sigmoidal dependence has been established. NI exhibit high
sensitivity to the presence of protons due to the protonation of the
distal tertiary nitrogen atoms [NHCH2CH2N(CH3)2] of the C-4sub-
stituents. At pH values up to 7.0 NI does not change its fluorescence
intensity. At pH >7 a drastic decrease of the fluorescence intensity
has been observed, and finally at pH ¼ 10.2 the curve again pla-
teaus. In the acidic medium the protonation of the distal tertiary
The basic photophysical characteristics obtained for NI in ace-
tonitrile and aqueous solutions in the presence of metal cations
under study are presented in Tables 2 and 3: absorption (lA) and
fluorescence (lF) maxima, Stokes shift (nAenF) and quantum (FF)
yield of fluorescence.
Table 3
Photophysical characteristics of NI in aqueous solution in the presence of metal
cations (see text).
lA nm
lF nm
n
AenF cmꢁ1
FF
H2O at pH ¼ 7.0
430
428
430
429
541
530
529
530
4771
4496
4352
4442
0.711
0.864
0.812
0.792
Cu2þ
Zn2þ
Ni2þ
Scheme 3. Modification of cellulose with chloroacetyl chloride.

68
D. Staneva et al. / Dyes and Pigments 98 (2013) 64e70
Table 4
CIELab color coordinates of cotton fabrics dyed at pH ¼ 5, pH ¼ 8 and pH ¼ 10.
100
90
80
70
60
L*
a*
b*
at pH ¼ 5
at pH ¼ 8
95.17
94.5
95.09
ꢁ21.65
ꢁ21.84
ꢁ21.95
63.92
70.65
63.65
νС=О
1749 сm-1
νC-Cl
789 cm-1
at pH ¼ 10
νC-O-C
1197 cm-1
2
chlorine atoms. Acyl chloride easily forms esters and amines
by nucleophilic substitution reactions with alcohols or amines
respectively.
For this purpose cotton fabric was modified with 10% (v/v)
chloroacetyl chloride (ClCOCH2Cl) in DMF solution at 60 ꢀC for 2 h
[24,25]. Thus the cellulose macromolecules have obtained active
chlorine atoms, which can react with hydroxyl reactive groups from
NI. The use of chloroacetyl chloride for the modification of cotton
fabric is illustrated in Scheme 3.
1
2000
1600
1200
cm-1
800
IR spectra of the modified and none treated cotton fabrics with
chloroacetyl chloride are plotted and are compared in Fig. 5. There
is an appearance of new bands in the modified fabric which are
characteristic of the ester carbonyl band at 1749 cmꢁ1 (C]O ester
group) at 1197 cmꢁ1 (CeO ester group) and 789 cmꢁ1 (CeCl bond).
Fig. 5. Infrared spectra of cotton fabrics before (1) and after acylation with chloroacetyl
chloride (2).
nitrogen atoms of the C-4 substituent stops the PET process and the
fluorescence increases. The fluorescence intensity at pH ¼ 7 is
fourteen times higher than that at pH ¼ 10.2.
3.4.2. Dyeing of modified cotton fabrics
The pH dependence of fluorescence intensity has been calcu-
lated according to Equation (2).
The aim of this work is to find the conditions of dyeing in which
NI reacts with the functional groups of the cotton fabrics, so that the
sensor fragment responsible for the photoinduced electron is free.
In acidic media the hydroxyl group from NI is protonated, and in
an alkaline media it is deprotonated, while at pH z 8 (pKa ¼ 8.51)
there is balance between two forms. The dyeing of cotton fabric has
been conducted at pH ¼ 5, 8 and 10 and the concentration of NI
0.5 owf% by mass of fiber at 25 ꢀC for 80 min. The dyeing process
has been followed spectrophotometrically. At pH 5 the process
takes place gradually with maximum extraction of the dye 60% and
at pH ¼ 10, this percentage increased up to 90%, the fastest and the
largest percentage of exhaustion/fixation occurs at pH 8 as seen
from Fig. 6.
pH ꢁ pKa ¼ logðIFmax ꢁ IFÞ=ðIF ꢁ IFminÞ
The calculated pKa ¼ 8.51.
(2)
3.4. Dyeing of cellulose textile fabrics by NI
3.4.1. Chemical modification of cellulose textile fabrics by
chloroacetyl chloride
As demonstrated NI has properties that make it suitable for
detection of protons and metal cations in solution. Of interest was
the immobilization of NI on the textile matrix. The NI does not have
any affinity for the cotton fabric. One approach is to modify the dye
with reactive groups and the other is to modify the matrix by
introducing new functional groups capable of reacting readily with
the hydroxyl group from the NI and to form a covalent bond [23]. In
this work we have modified the cotton fabric with chloroacetyl
chloride. It is a bifunctional compound having two different active
Thus fluorescent cotton fabrics were received with intense
yellow-green color. Their CIELab colorimetric parameters are pre-
sented in Table 4. A small difference has been observed at L*, a* and
b* coordinates of the dyed cotton fabric at pH 8.
3.4.3. Functional characteristics of dyed cotton fabric
The photophysical characteristics of dyed cotton fabric have
been investigated with regard for its potential for heterogeneous
100
%
50000
80
40000
2
1
60
30000
40
20000
10000
0
pH=8
pH=10
pH=5
20
0
0
20
40
60
80
350
400
450
500
550
600
650
Time, min
Wavelength, nm
Fig. 6. NI dye bath exhaustion from the modified cotton fabric dyeing at pH ¼ 5,
pH ¼ 8 and pH ¼ 10 and 25 ꢀC.
Fig. 7. Excitation and fluorescence spectra of dyed cotton fabrics with NI at pH ¼ 5,
lfyt 1 ¼ 410 nm, lfyt 2 ¼ 467 nm and lem ¼ 520 nm).
(

D. Staneva et al. / Dyes and Pigments 98 (2013) 64e70
69
reflectance (
D
R% at
l
¼ 530 nm) after and before the addition of
70
60
50
40
30
20
10
0
metal cations and are presented in Fig. 9. This reflection increase is
cause by the fluorescence emission of the fabric. This confirms the
statement that after dyeing the sensor fragment responsible for PET
effect remain free for the metal ion detection. The immobilized on
the textile matrix 1,8-naphthalimide dye as distinguished from its
R (%)
pH 3,17
pH 3,89
pH 4,85
pH 5,90
pH 7,30
pH 7,93
pH 8,97
pH 9,87
pH 10,70
water solution shows selectivity to Zn2þ ions compared to Cu2þ
Probably in this case important role play the cotton fabric matrix.
.
4. Conclusion
The synthesis of a new 4-(2-N,N-dimethylamino)ethylamino-N-
2-hydroxyethil-1,8-naphthalimide has been described and its
functional properties have been investigated. The modification of
cotton fabric by chloroacetyl chloride has been studied by IR
spectroscopy. The cotton fabrics thus modified has been dyed with
the new 1,8-naphthalimide dye. That resulted in a new textile
material with promising properties as a heterogeneous fluo-
rescence sensor of biologically important metal cations (Zn2þ and
Cu2) and protons in aqueous media.
400
450
500
550
600
650
700
Wavenumber, nm
Fig. 8. pH influence on the reflectance R% of the cotton fabric dyed at pH ¼ 5.
fluorescence sensor of biologically important metal cations (Zn2þ
and Cu2) and protons in aqueous media.
Acknowledgment
Excitation fluorescence spectra of the dyed cotton are shown in
Fig. 7. As can be seen the excitation spectrum has two well pro-
nounced maxima. The maximum at 467 nm is with higher intensity
compared to the first maximum at 410 nm. The fluorescence
spectrum obtained with excitation at 467 nm is more intensive
compared to that obtained at 410 nm without change in the fluo-
rescence maximum (lF ¼ 520 nm). Fluorescence spectra of dyed
cotton fabrics at pH ¼ 5, 8 and 10 have well pronounced maxima at
516e520 nm. This fact indicates that during the dyeing of cotton
fabrics, there are no structural changes in the chromophore system
of NI which maintaining its fluorescent characteristics.
The Authors wish to thank for the financial support of the
University of Chemical Technology and Metallurgy.
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