**3. Results and conclusions of additives**

*Waste in Textile and Leather Sectors*

**2.2 Characterization of the additives**

purity), measured in a range between 400 and 4000 cm<sup>−</sup><sup>1</sup>

Two hundred scans were collected at a resolution of 4 cm<sup>−</sup><sup>1</sup>

**2.3 Assessment of the antifungal activity of the additives**

and the standard deviation was determined.

electron microscopy (SEM) was used to obtain different micrographs of the additives, in Philips 505 equipment (Holland), using a voltage of 15 kV. Samples were supported on graphite and metallized with a sputtered gold film. The micrographs were obtained with an ADDAII acquisition device (Soft Imaging System). Transmission electron microscopy (TEM) was performed with a JEOL microscope (100 CX) (Japan), with an accelerating voltage of 100 kV. Samples were prepared by their suspension in ethanol and placing an aliquot over carbon-coated copper grids, allowing the samples to dry in a desiccator for 30 min at room temperature. X-ray mapping was acquired by using a Talos F200X HR-TEM microscope operating at 200 kV equipped with a SuperX EDS spectrometer (composed of 4 EDS SDD

*Aspergillus* sp., *Chaetomium globosum*, and *Cladosporium* sp. fungi were selected to evaluate the antifungal activity of the solids, based on their cellulolytic ability in agar plate assays. *Aspergillus* sp. and *Cladosporium* sp. were previously isolated from biodeteriorated fabrics by conventional microbiological techniques, whereas *C. globosum* was selected from the CIDEPINT culture collection [30]. From subcultures growing in Petri dishes, inoculums of cited fungi were obtained using a solution of 0.85% p/v NaCl and 0.005% p/v Tween 20, being the concentration of the suspension adjusted to 106 spores/mL employing a Neubauer chamber. The composition of the culture medium used was 1.5 g agar (Parafarm), 1 g dextrose (Anedra, analytical reagent), 0.5 g proteose peptone (OXOID), 0.1 g KH2PO4 (Anedra, analytical reagent), 0.05 g MgSO4.7H2O (Anedra, analytical reagent), and distilled water (Laboratory). Two different silver concentrations were selected to carry out the agar plate assays, 60 and 120 ppm. The Petri dishes were inoculated in the center with 20 mL of spore suspension of each fungus per triplicate and incubated at 28°C for 10 days. With the obtained results, the inhibition percentage (I%) was calculated according to Eq. [31]: inhibition % = [(C − E)/C] × 100, where C and E correspond to the average diameter of each fungus in the control plate and on the plate with the tested solids, respectively. Three measurements of the fungal growth diameter were made in each plate,

The acidic properties of the solids were evaluated by potentiometric titration with *n*-butylamine, in a Metrohm 794 Basic Titrino titrator (Switzerland) with a double-junction electrode. First, 0.025 g of sample was suspended in 45 mL of acetonitrile and stirred for 540 s, and second, 0.025 mL/min of an *n*-butylamine solution in acetonitrile (0.025 N) was added, while stirring constantly. The textural properties of the additives, such as the specific surface area (SBET), the pore volume, and pore size, were determined by adsorption/desorption in Micromeritics Accusorb 2100 equipment (USA), using N2 as absorbable gas at 77 K. Before the measurement, each sample was degassed at 100°C for 12 h and under 30 mmHg. The X-ray diffraction (XRD) diagrams were obtained in Philips (Holland) PW-1390 (channel control) and PW-1394 (motor control) equipment coupled to a scanning graphical recorder, using Cu Kα (α = 1.5417 Å) radiation, Ni filter, 20 mA and 40 kV in the voltage source, a 5–60 *2θ* scanning angle range, a scanning rate of 2°/min, and 2000 counts/s for the amplitude of the vertical scale. Fourier transform infrared spectroscopy (FT-IR) spectra were obtained using Bruker Vertex 70 equipment (Germany) and pellets of the sample in KBr (Aldrich, 99 wt% FT-IR

at room temperature.

and averaged. Scanning

**4**

detectors).

**Figure 1** shows the synthesized samples of silica with different concentrations of carbon whose images were obtained digitally. If we look at **Figure 1**, the SB sample is the one obtained with ammonium hydroxide and is taken as a control sample (it does not contain carbon), while the other images provide a light gray to dark gray coloration for higher carbon contents. For the three cases presented, the granulometry is similar when they are already dry, it is not significant compared to the SB, and only the S3B has larger granules.

The determination of the structure of the synthesized silicas was carried out by XRD. Thus the amorphous character of the synthesized materials that have only wide peaks in the 15–30° 2θ interval was confirmed and the band located around 23° 2θ was observed, which is the typical structure of this type of silica. The acid properties of the silicas measured through the potentiometric titration with *n*-butylamine were studied, which allows the evaluation of the number of acid sites and their acid strength. To interpret the results obtained, it is known that the initial electrode potential (Ei) indicates the maximum acid strength of the surface sites and the values (meq/g solid) where the plateau is reached indicate the total number of acidic sites [32]. The acid strength of surface sites can be classified according to the following ranges: very strong sites Ei > 100 mV; strong sites 0 < Ei <100 mV; weak sites −100 < Ei <0 mV, and very weak sites Ei < −100 mV, respectively [30]. It is important to clarify that this technique only indicates the trend of mass acidity of the synthesized samples. Bulk carbon has an Ei value of 37.1 mV, while silica without carbon has an Ei of 157.9 mV. It is interesting to note that the potentiometric curves have a similar shape to each other, with continuous and relatively rapid decrease in potential, which would indicate that their acidic sites are very few, regardless of the change in the amount of carbon they contain, this could that compounds that impurity carbon tend to be basic in nature. In any case, the potentiometric curves have a strong parallel with the behavior of pure silica and not of bulk carbon.

The FT-IR spectrum of the SB silica shows characteristic bands at 3748 and 3473 cm<sup>−</sup><sup>1</sup> assigned to the interactions between the hydroxyl groups on the silica surface and the water presented in the surrounding atmosphere. These bands can be related to the presence of isolated groups (Si▬OH) and OH stretch bands, caused by hydrogen-bound water molecules (HOH.. H) and surface silanol groups, hydrogenbound to water molecular (SiO▬H....H2O). The other characteristic bands that confirm the hydrophilic character of the silica are located at 968 and 1883 cm<sup>−</sup><sup>1</sup> and are directly related to the Si▬O interaction of the silanol groups. At 1640 cm<sup>−</sup><sup>1</sup> , an intense band associated with the adsorption of water on the surface of the sample is also observed due to its hydrophilic nature. Bands in the range 1200–1000 cm<sup>−</sup><sup>1</sup> and 800 cm<sup>−</sup><sup>1</sup> were also detected. These interactions can be related to antisymmetric and

**Figure 1.** *Digital images of silicas.*

symmetric vibration between Si▬O▬Si with a minimum of 1076 cm<sup>−</sup><sup>1</sup> and 801 cm<sup>−</sup><sup>1</sup> , respectively. The vibration mode that appears at 1231 cm<sup>−</sup><sup>1</sup> can be assigned to the symmetric deformation of C-H in CH2 groups, corresponding to the residual nonhydrolyzed alkoxy groups (▬OC2H5) in the silica xerogel. The characteristic interaction band was observed at 1381 cm<sup>−</sup><sup>1</sup> , which may be related to the C▬H interaction of the ethyl radicals on the silica surface. These radicals can be formed as a product of condensation reactions between Si(OH)4 and Si(OC2H5)4. Carbon-containing samples show similarity to pure silica [33].

The immobilization of antimicrobial agents within multiple materials obtained by sol-gel has recently been investigated. For example, Copello et al. [34] studied the incorporation of dodecyl-di (aminoethyl) glycine in a matrix of SiO2-xerogel for use as an antimicrobial in glasses, and Marini et al. [35] incorporated quaternary ammonium salts in an organic and inorganic hybrid coating for plastics. This methodology offers the possibility of obtaining materials of different porosity, as well as allowing the introduction of metals and other molecules through a simple impregnation, dissolution, or suspension of the metal precursors in the gel [36, 37]. In particular, several investigations are found in the literature on the use of immobilized Ag in materials obtained by sol-gel [38, 39]. Generally, materials impregnated with Ag consist of Ag ions integrated in inert ceramic, zeolite, or vitreous matrices. The sol-gel method became an effective procedure for linking organic and inorganic molecules in the same matrix and offers a unique opportunity to incorporate metal components into an organically modified inorganic matrix. The methods are entrapment, electrostatic interaction, adsorption, and covalent bonding.

The samples with Ag included are SBAg, without C, and 4% Ag that possess an Ei of 113.5 mV and S3BAg, with 10% C, and 4% Ag that showed an Ei of 67.7 mV. This could be due to the electrons of the ammonium groups that would be induced to OH more acids and may result in a redox reaction of Ag1+ to Ag0 . The potentiometric curves of SBAg and S3BAg are similar to the previous samples without Ag. The area under the curves is more open, indicating a greater amount of acid sites. The adsorption/desorption isotherms of N2 corresponding to samples obtained using ammonium hydroxide as a catalyst could be included in Langmuir type II, characteristics of low porous solids, with meso- and macroporosity. Point B is where the coverage of the monolayer is complete and multilayer adsorption is about to begin. This kind of isotherm is a characteristic of nonporous solids or macroporous adsorbents. For the SBAg and S3BAg samples, the isotherms are similar which would indicate that the dopants (Ag and C) do not influence the basic hydrolysis that prevails in the synthesis of these samples. Regarding the FT-IR spectra, the samples show a shift, with respect to the SBAg. The bands are at 1182, 1094, 860, 674, and 464 cm<sup>−</sup><sup>1</sup> , but they are not substantial so that it can induce the variation of links in the siliceous network.

In the case of using ammonium hydroxide, in SEM (**Figure 2**), it can be seen that the particles of laminar morphology of the silica with acid hydrolysis become rounded. This generates a sharp decrease in the specific area and is independent of the dopants included, both in the SBAg and in the S3BAg, respectively.

It should not be forgotten when discussing this point that the sol is defined as a stable suspension of colloidal solid particles in a liquid [40]. For the existence of the sun, the colloidal particles that form it, denser than the surrounding liquid, must be small enough not to precipitate, being suspended by the repulsion of weak forces, such as those of van der Waals, or by surface charges that keep them in suspension. To meet these requirements, the particles must have sizes between 1 and 100 nm, which corresponds to the existence of 103–109 atoms per particle [41]. In the case of TEM (**Figure 3**), the rounded forms of silica and the superficial presence of Ag particles in both samples can be distinguished.

**7**

*Antimicrobial Fabrics Impregnated with Ag Particles Included in Silica Matrices*

Babapour et al. [42] studied the inclusion of silver in a siliceous matrix through the sol-gel method and analyzed the materials by X-ray photoelectronic spectroscopy, to elucidate the chemical state of the silver nanoparticles on the surface. They observed that at 100°C, the silver particles have a high tendency to accumulate on the surface, but, at higher temperatures, they diffuse from the surface to the matrix. Also, they found that in dry samples (in air at 100°C) more than 90% of the con-

*TEM micrographics of samples: (A) SBAg (100,000×), (B) SBAg (270,000×), (C) S3Ag (100,000×), and* 

the materials thermally at 200°C, the silver particles oxidize, presenting an increase

the results being independent of the concentration of silver in the siliceous matrix.

To obtain the biodeteriorated fabric, source of the strains used in this work, samples of 100% cotton (plain weave fabric), 5 cm × 5 cm in size, previously moistened with distilled water, were exposed to accelerate the process of biodeterioration. They remained for 30 days in an indoor environment, under conditions of high relative humidity. It should be noted that this type of fabric is used in the hospital field as stretchers and oxygen tube covers, sheets, both (shirt and pants), etc. At the end of the exposure time of the samples, they were surficially decontaminated to orient the isolation to the fungal species that were growing in the fabric. According to the observations made, the isolates that presented the highest cellulolytic activity (halo ≥0.4 cm) were found to be used as bioindicators: *Aspergillus*

(metallic) state. However, after treating

and Ag2+, which continues to grow up to 400°C,

*DOI: http://dx.doi.org/10.5772/intechopen.91631*

*SEM micrographics of samples: (A) SBAg and (B) S3Ag (5000×).*

**Figure 2.**

**Figure 3.**

*(D) S3Ag (270,000×).*

centration of Ag on the surface is in the Ag0

**4.1 Insulation of fungi from biodeteriorated fabrics**

in the surface concentration of Ag+

**4. Antimicrobial fabrics**

*Antimicrobial Fabrics Impregnated with Ag Particles Included in Silica Matrices DOI: http://dx.doi.org/10.5772/intechopen.91631*

#### **Figure 2.**

*Waste in Textile and Leather Sectors*

tion band was observed at 1381 cm<sup>−</sup><sup>1</sup>

1094, 860, 674, and 464 cm<sup>−</sup><sup>1</sup>

variation of links in the siliceous network.

particles in both samples can be distinguished.

samples show similarity to pure silica [33].

symmetric vibration between Si▬O▬Si with a minimum of 1076 cm<sup>−</sup><sup>1</sup>

entrapment, electrostatic interaction, adsorption, and covalent bonding. The samples with Ag included are SBAg, without C, and 4% Ag that possess an Ei of 113.5 mV and S3BAg, with 10% C, and 4% Ag that showed an Ei of 67.7 mV. This could be due to the electrons of the ammonium groups that would be induced to OH more acids and may result in a redox reaction of Ag1+ to Ag0

The potentiometric curves of SBAg and S3BAg are similar to the previous samples without Ag. The area under the curves is more open, indicating a greater amount of acid sites. The adsorption/desorption isotherms of N2 corresponding to samples obtained using ammonium hydroxide as a catalyst could be included in Langmuir type II, characteristics of low porous solids, with meso- and macroporosity. Point B is where the coverage of the monolayer is complete and multilayer adsorption is about to begin. This kind of isotherm is a characteristic of nonporous solids or macroporous adsorbents. For the SBAg and S3BAg samples, the isotherms are similar which would indicate that the dopants (Ag and C) do not influence the basic hydrolysis that prevails in the synthesis of these samples. Regarding the FT-IR spectra, the samples show a shift, with respect to the SBAg. The bands are at 1182,

In the case of using ammonium hydroxide, in SEM (**Figure 2**), it can be seen that the particles of laminar morphology of the silica with acid hydrolysis become rounded. This generates a sharp decrease in the specific area and is independent of

It should not be forgotten when discussing this point that the sol is defined as a stable suspension of colloidal solid particles in a liquid [40]. For the existence of the sun, the colloidal particles that form it, denser than the surrounding liquid, must be small enough not to precipitate, being suspended by the repulsion of weak forces, such as those of van der Waals, or by surface charges that keep them in suspension. To meet these requirements, the particles must have sizes between 1 and 100 nm, which corresponds to the existence of 103–109 atoms per particle [41]. In the case of TEM (**Figure 3**), the rounded forms of silica and the superficial presence of Ag

the dopants included, both in the SBAg and in the S3BAg, respectively.

, but they are not substantial so that it can induce the

symmetric deformation of C-H in CH2 groups, corresponding to the residual nonhydrolyzed alkoxy groups (▬OC2H5) in the silica xerogel. The characteristic interac-

of the ethyl radicals on the silica surface. These radicals can be formed as a product of condensation reactions between Si(OH)4 and Si(OC2H5)4. Carbon-containing

The immobilization of antimicrobial agents within multiple materials obtained by sol-gel has recently been investigated. For example, Copello et al. [34] studied the incorporation of dodecyl-di (aminoethyl) glycine in a matrix of SiO2-xerogel for use as an antimicrobial in glasses, and Marini et al. [35] incorporated quaternary ammonium salts in an organic and inorganic hybrid coating for plastics. This methodology offers the possibility of obtaining materials of different porosity, as well as allowing the introduction of metals and other molecules through a simple impregnation, dissolution, or suspension of the metal precursors in the gel [36, 37]. In particular, several investigations are found in the literature on the use of immobilized Ag in materials obtained by sol-gel [38, 39]. Generally, materials impregnated with Ag consist of Ag ions integrated in inert ceramic, zeolite, or vitreous matrices. The sol-gel method became an effective procedure for linking organic and inorganic molecules in the same matrix and offers a unique opportunity to incorporate metal components into an organically modified inorganic matrix. The methods are

respectively. The vibration mode that appears at 1231 cm<sup>−</sup><sup>1</sup>

and 801 cm<sup>−</sup><sup>1</sup>

.

can be assigned to the

, which may be related to the C▬H interaction

,

**6**

*SEM micrographics of samples: (A) SBAg and (B) S3Ag (5000×).*

**Figure 3.** *TEM micrographics of samples: (A) SBAg (100,000×), (B) SBAg (270,000×), (C) S3Ag (100,000×), and (D) S3Ag (270,000×).*

Babapour et al. [42] studied the inclusion of silver in a siliceous matrix through the sol-gel method and analyzed the materials by X-ray photoelectronic spectroscopy, to elucidate the chemical state of the silver nanoparticles on the surface. They observed that at 100°C, the silver particles have a high tendency to accumulate on the surface, but, at higher temperatures, they diffuse from the surface to the matrix. Also, they found that in dry samples (in air at 100°C) more than 90% of the concentration of Ag on the surface is in the Ag0 (metallic) state. However, after treating the materials thermally at 200°C, the silver particles oxidize, presenting an increase in the surface concentration of Ag+ and Ag2+, which continues to grow up to 400°C, the results being independent of the concentration of silver in the siliceous matrix.
