Functional finishing of fibrous substrates coated with AG-deposited TiO2 nanoparticles.
Vrinceanu, Narcisa ; Coman, Diana ; Popovici, Eveline 等
Abstract: This research aimed at the development of nano-structural
fibrous composites with optimal dispersion containing Ag deposited
Ti[O.sub.2] nano-particles, providing enhanced barrier properties.
Firstly, the study was focused on the synthesis of Ag-deposited
Ti[O.sub.2] particles formed by a chemical reduction method, the
morphology and microstructure of Ag-deposited Ti[O.sub.2] particles have
been determined. Secondly, the characterization of the nanoscale
finished surfaces has been performed using a co-assisted system: surface
area measurements (adsorption/desorption isotherms, surface area
measurement and pore size distribution). The structural properties of
these as-prepared nanocomposites were characterized with scanning
electron microscopy (SEM) and X-ray diffraction (XRD), showing that
Ag-deposited Ti[O.sub.2] nanoparticles were deposited on the surface of
studied textile. Due to the uniformity distribution of Ag deposited
Ti[O.sub.2] nano-particles onto the surface of supports, our results
could be considered a preliminary step towards a safe methodology of
nano-particles incorporation into selected fibrous substrates with
multifunctionality, such as: self-cleaning performance, UV protection,
photocatalyti, water stability etc.
Key words: fibrous substrates, nanotechnology, Ag-deposited
Ti[O.sub.2], nanoparticles, functionalization, finishing fibrous
substrates, nanotechnology, finishing
1. INTRODUCTION
Innovative materials, including textiles for specific applications,
have to satisfy consumers' growing demands (Tsuji, 2002). It is
extremely important, even compulsory that a material should perform
several functions, due to various applications, wearing and also
economic aspects.
There are some nanoparticles of metal-oxides: titanium
(Ti[O.sub.2]) and zinc (ZnO) belonging to a group of compounds with
photo-catalytic properties, which are able to absorb UV radiation. There
are researches involving metal deposition (Esumi, 1998) and much
attention has been paid to doping the material with transition and noble
metals such as Pd, Pt (Esumi, 1998), Rh, Au, and Ag (Innocezi, 2000). In
this work, silver nanoparticles were deposited on the surface of
Ti[O.sub.2] particles by using a chemical reduction method (Shirai,
1999). In the formation process of silver nanoparticles by the chemical
reduction method, there are several factors that influence in a great
extent the preparing of nano-sized silver powder. Important parameters,
such as the molar concentration ratio of R ([AgN[O.sub.3]][reducing
agent]), the dispersant concentration, and the feed rate of reactant,
affect the properties of the silver nanoparticles obtained by this
method (Andrzejewska, 2004; Jesionowski, 2001). The main aim of these
research works was the development of nano-scaled textile composites
with barrier properties.
In the first stage, the works focused on:
--a method for the synthesis of Ag--deposited Ti[O.sub.2]
nanoparticles by using a chemical reduction method;
--a methodology of nano-particles incorporation into selected
fibrous substrates.
2. EXPERIMENTAL
Materials and methods. Nanoparticle preparation/Synthesis of
Ag-deposited Ti[O.sub.2] nanoparticles. In all experiments the
Ti[O.sub.2] nanoparticles used were synthesized. The ageing of
Ti[O.sub.2] suspensions lasted for 30 min in an ultrasonic bath, to
which were added the required quantities of silver nitrate (AgN[O.sub.3]
(99.99%), Aldrich) with SDS (sodium dodecyl sulfate (C[H.sub.3][(C[H.sub.2]).sub.11] OS[O.sub.3]Na (99%), Aldrich) such that
the desired Ag/Ti atomic concentration ratio was obtained. After mixing,
Ag-deposited Ti[O.sub.2] suspensions were prepared by feeding in
hydrazine hydrate ([N.sub.2][H.sub.4] X [H.sub.2]O (98%), Aldrich)
aqueous solution. In this experiment, hydrazine hydrate and sodium
dodecyl sulfate played the role of reducing agent and dispersant,
respectively.
2.1. Nanoscaled finishing of linen fabrics with Ag-deposited
Ti[O.sub.2] particles
For the experimental purpose small fine-medium weight 100% linen
woven fabrics were used. Linen fabrics were washed and dried, before
being used. The dimensions of samples were of 4 x 12 [cm.sup.2]. The
application of Ag-deposited Ti[O.sub.2] particles on linen has been
performed using pad-dry-cure method. For the successive treatment of
fabrics with colloidal silver, the solution was agitated continuously.
The linen samples were immersed in the solution (150 mL) containing
Ag-deposited Ti[O.sub.2] particles, for 5 min, then squeezed to 100% wet
pick up with laboratory padder at constant pressure. A subsequently
immersion for 5 min in 2 g/L of sodium lauryl sulfate has been performed
to remove unbound nanoparticles. To completely take out all the soap
solution, the fabric was rinsed at least 10 times. The drying took place
at 70[degrees]C for 3 min, followed by curing at 150[degrees]C for 2
min.
2.2. Characterization of Ag-deposited Ti[O.sub.2] nanoparticles
SEM photographs were used to observe the distribution of silver
deposited on the Ti[O.sub.2] surface. As shown in Fig. 1, a small amount
of silver particles with a size of 5 nm was deposited on the surface of
the Ti[O.sub.2] particles. It can be confirmed that silver particles
were deposited on the surface of the individual Ti[O.sub.2]
crystallites.
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
The particle size and the size distribution of Ag-deposited
Ti[O.sub.2] nanoparticles were observed using a Nova High Speed Gas
Sorption Analyser. Both reference and tested samples show a type-IV
isotherm, which is representative of mesoporous solids (Fig 2 and Fig.
3). The specific surface area of the Ag/Ti[O.sub.2] composite is 176
[m.sup.2]/g, by means of Brunauer--Emmett--Teller (BET) method. The pore
diameter of the Ag/Ti[O.sub.2] is 6.22 nm (estimated using the
desorption branch of the isotherm) with very narrow pore size
distribution.
The Ti[O.sub.2] possesses virtually identical average pore diameter
(5 nm) and specific surface area (189 [m.sup.2]/g), considering a
typical uncertainty of 5% for BET surface area measurements. The
addition of Ag causes a slight decrease, from 0.261 to 0.007
[cm.sup.3]/g, in the pore volume of Ti[O.sub.2].
Fig. 4 shows the X-ray diffraction patterns of Ag-deposited
Ti[O.sub.2] powders Ti[O.sub.2]/AgN[O.sub.3] for 2[theta] diffraction
angles between 5[degrees] and 70[degrees]. The XRD pattern of TiO2 shows
five primary peaks at: 25,4[degrees], 38,14[degrees], 48,14[degrees],
54,7[degrees] and 63,04[degrees], which can be assigned to different
diffraction planes of anatase TiO2.
As shown in Fig. 4, the most intense (101) peak was observed at 29
= 25.34[degrees], meaning the interference-free reflection of the
typical tetragonal anatase structure. Results reveal that the addition
of silver did not significantly affect the crystal size. The XRD
patterns of silver deposited TiO2 samples almost coincide with that of
pure TiO2 showing no diffraction peaks due to silver deposition thus
suggesting that the silver are merely placed on the surface of the
crystals.
[FIGURE 4 OMITTED]
These results show that the deposition of Ag particles does not
significantly change the textural properties of Ti[O.sub.2], properly
due to the small amount of Ag loaded. Thus, most of the pore channels in
Ti[O.sub.2] film are open, although a small portion of the channels may
be filled with the Ag particles. Such open mesoporous architecture with
large surface area and 3D connected pore-system is an important
consideration in catalyst design because it can improve the molecular
transport of reactants and products.
These results are the consequence of the presence of Ag particles
and their interaction with Ti[O.sub.2] particles. Summarizing, the high
dispersion of silver nanoparticles is thoroughly achieved by
encapsulation in the pore channels of ordered mesoporous Ti[O.sub.2]
film. The Ag particles are well confined in the pore channels and the
particle size can be controlled to below 5 nm. Such porous architecture
and dimensions are desirable features for catalytic and photocatalytic
applications.
3. CONCLUSION AND PERSPECTIVES
This study revealed the silver deposited Ti[O.sub.2] nanoparticles
synthesis by a chemical reduction method and the nanoscaled finishing
with Ag-deposited Ti[O.sub.2] powders onto fabrics. The main aim of
these research works was the development of appropriate nano-structural
textile composites with barrier properties. The research had two phases:
(1) a methodology for the synthesis of Ag--deposited Ti[O.sub.2]
nanoparticles by using a chemical reduction method and (2) the
methodology of nano-particles incorporation into selected fibrous
substrates. The characterization of Ag-deposited Ti[O.sub.2]
nanoparticles suggested that such porous architecture and dimensions are
desirable features for providing a high multifunctionality:
photocatalytic applications, photoprotective, self-cleaning of
nano-structural textile composites. Our future research will be focused
towards potential barrier properties of this type of nano-scaled textile
composites obtained, as well as their photocatalytic activity.
4. ACKNOWLEDGEMENTS
This work was supported by the Research Contract within POSDRU
No./89/1.5/S/49944 Project.
5. REFERENCES
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Tab. 1. Textural properties
Sample S, [m.sup.2]/g Vp, cc/g Pore
diameter, nm
Ti[O.sub.2] 189 0.423 5
Ti[O.sub.2]/Ag 176.301 0.261 6.22
Linen + Ti[O.sub.2]/Ag 31.542 0.007 7.78