From Smart Materials to Chromic Textiles
263
further improvement of this modification and dyeing methodologies may be essential
to offer commercially usable photochromic textile products.
Long-lasting phosphorescent materials have been applied in various commercial products due to their ability to continue emit light for a longer period of time
after excitation. This is usually beneficial to be used in directional safety signs,
toys, protective clothing, and other applications where the phenomenon of glow
in the dark presents amusement, ornamental and/or safety characteristics [52, 60].
Long-lasting phosphorescent products are composed of a carrier in combination
with a photoluminescent synthetic pigment phosphor which can be easily excited
by a certain wavelength of light of an external source. The photoluminescent pigment can then slowly discharge the stored light energy after the removal of the
external light source. Long-persistence phosphorescent lanthanide-doped pigments
have been used in producing various commercial merchandises, such as ornamental
decorations, indicators, clothing, guide signs, switches and toys [52, 60–62]. Longpersistent phosphorescent materials are generally consists of crystals and traps. The
crystals are photoluminescent collective elements which can be charged via excitation by an external light source. The energy traps are characterized by their high
capacity to store this light energy for a long period of time [63]. After excitation, the
crystals continue to discharge light and glow in the dark as time proceeds. This is
supported by the traps, such as divalent europium and trivalent dysprosium, which
extend the time period for light emission. There are various pigment phosphors
that have been available for use in affording long-lasting photoluminescence, such
as the red emission by Y 2 O 2 S:Mg
2+ /Ti
4+ , green emission by SrAl 2 O 4 :Eu
2+ /Dy
3+ ,
and blue emission CaAl 2 O 4 :Eu
2+ /Nd
3+ [64–66]. These long-lasting photoluminescent inorganic pigments are characterized by high stability to chemicals, light and
heat, as well as being non-toxic, recyclable, non-radioactive, reversible, bright, long
period of phosphorescence time that could be higher than ten hours and high quantum efficiency [67]. Strontium aluminate phosphor has been applied to introduce
photochromic and fluorescence functionalities for both textile and paper cellulosic
fibers while maintaining their pristine characteristics, such as appearance, handle and
mechanical properties. Immobilizing the inorganic Strontium aluminate phosphor at
low total content value in an aqueous binder onto on cotton fabric via screen printing
was reported recently by Khattab et al. to introduce light-responsive clothing with
improved color-exchange performance and colorant stability [68]. The photochromic
knitted cotton were firstly dyed conventionally with Reactive Red AEF to introduce
a dark red background followed by screen printing with an aqueous paste containing
strontium aluminate pigment, binder, diammonium phosphate, synthetic thickener
and ammonium hydroxide. The printed cotton was dried under ambient conditions
and then exposed to thermofixation at 160 °C. This approach was characterized by
fast and simple application, easy to handle and low cost affording photochromic cotton fabric of high durability without affecting its aesthetic features, such as comfort
and handling. The color switching of cotton fabric was from red to greenish yellow (Fig. 6). It exhibited excellent fatigue resistance, satisfactory colorfastness, high
reversibility, and photo- and thermal stability [68].
263
further improvement of this modification and dyeing methodologies may be essential
to offer commercially usable photochromic textile products.
Long-lasting phosphorescent materials have been applied in various commercial products due to their ability to continue emit light for a longer period of time
after excitation. This is usually beneficial to be used in directional safety signs,
toys, protective clothing, and other applications where the phenomenon of glow
in the dark presents amusement, ornamental and/or safety characteristics [52, 60].
Long-lasting phosphorescent products are composed of a carrier in combination
with a photoluminescent synthetic pigment phosphor which can be easily excited
by a certain wavelength of light of an external source. The photoluminescent pigment can then slowly discharge the stored light energy after the removal of the
external light source. Long-persistence phosphorescent lanthanide-doped pigments
have been used in producing various commercial merchandises, such as ornamental
decorations, indicators, clothing, guide signs, switches and toys [52, 60–62]. Longpersistent phosphorescent materials are generally consists of crystals and traps. The
crystals are photoluminescent collective elements which can be charged via excitation by an external light source. The energy traps are characterized by their high
capacity to store this light energy for a long period of time [63]. After excitation, the
crystals continue to discharge light and glow in the dark as time proceeds. This is
supported by the traps, such as divalent europium and trivalent dysprosium, which
extend the time period for light emission. There are various pigment phosphors
that have been available for use in affording long-lasting photoluminescence, such
as the red emission by Y 2 O 2 S:Mg
2+ /Ti
4+ , green emission by SrAl 2 O 4 :Eu
2+ /Dy
3+ ,
and blue emission CaAl 2 O 4 :Eu
2+ /Nd
3+ [64–66]. These long-lasting photoluminescent inorganic pigments are characterized by high stability to chemicals, light and
heat, as well as being non-toxic, recyclable, non-radioactive, reversible, bright, long
period of phosphorescence time that could be higher than ten hours and high quantum efficiency [67]. Strontium aluminate phosphor has been applied to introduce
photochromic and fluorescence functionalities for both textile and paper cellulosic
fibers while maintaining their pristine characteristics, such as appearance, handle and
mechanical properties. Immobilizing the inorganic Strontium aluminate phosphor at
low total content value in an aqueous binder onto on cotton fabric via screen printing
was reported recently by Khattab et al. to introduce light-responsive clothing with
improved color-exchange performance and colorant stability [68]. The photochromic
knitted cotton were firstly dyed conventionally with Reactive Red AEF to introduce
a dark red background followed by screen printing with an aqueous paste containing
strontium aluminate pigment, binder, diammonium phosphate, synthetic thickener
and ammonium hydroxide. The printed cotton was dried under ambient conditions
and then exposed to thermofixation at 160 °C. This approach was characterized by
fast and simple application, easy to handle and low cost affording photochromic cotton fabric of high durability without affecting its aesthetic features, such as comfort
and handling. The color switching of cotton fabric was from red to greenish yellow (Fig. 6). It exhibited excellent fatigue resistance, satisfactory colorfastness, high
reversibility, and photo- and thermal stability [68].