*2.2. Methods*

#### 2.2.1. Essential Oil Extraction

Hydro-distillation was used to extract essential oils. The plant material (mashed cinnamon barks/cloves) was laid out with water, boiled and then concentrated by an evaporator with heat at low pressure. The essential oil was transferred through the steam toward a condenser where the oil was separated from the cooled steam using a separatory funnel and collected in a receiving container.

#### 2.2.2. Microcapsule Preparation

Chitosan–essential oil microcapsules were prepared by coacervation technique as described in the literature with some modifications [19]. Chitosan solution was prepared by dissolving 1 g of chitosan in 100 mL of 1% (*v*/*v*) aqueous acetic acid solution. The resulting system was left under magnetic agitation for 3 h. Chitosan was used to form the wall membrane of microcapsules.

An amount of 20 mL of a mixture of cinnamon and clove essential oil (1:1 *v*/*v*) was added to the prepared chitosan solution. Then, 0.1 mL of surfactant (Tween 20) was added to the system.

To form an oil–water emulsion, the system was emulsified at a speed rate of 900 rpm using an Ultra-Turrax (IKA, Staufen, Germany). Coacervation was induced by adding the obtained emulsion to a solution (250 mL) containing sodium hydroxide (0.2 M) and ethanol (4/1). The stirring speed was reduced to 400 rpm. The microcapsules were washed with ultrapure water and collected by decantation.

#### 2.2.3. Green Grafting of the Microcapsules

A green binding agen<sup>t</sup> (citric acid) was used to attach the shell material based on chitosan to the cellulosic fibers through ester bonds. The padding drying method was applied as reported in previous studies, with a few rectifications.

The cotton samples were immersed in an aqueous solution (pH = 5) containing 100 <sup>g</sup>·L−<sup>1</sup> of the microcapsule emulsion, 30 <sup>g</sup>·L−<sup>1</sup> of citric acid and 2 <sup>g</sup>·L−<sup>1</sup> of monosodium phosphate (a catalyst). The system was heated at 50 ◦C for 5 min. Finally, samples were washed with ultrapure water and padded to obtain a wet pickup percentage of 80%. Drying was carried out at 90 ◦C for 5 min and thermocondensation at 120 ◦C for 5 min.

#### *2.3. FTIR Analysis*

In order to evidence the crosslinking of microcapsules on cotton fabrics, Attenuated Total Reflectance-Fourier Transformed Infrared (ATR-FTIR) spectra were recorded using a spectrophotometer (ATR-FTIR, Perkin Elmer, Waltham, MA, USA). The spectra were collected in transmittance mode with a spectral resolution of 32 scans and 4 cm<sup>−</sup><sup>1</sup> over the range of 4000–400 cm<sup>−</sup>1.

#### *2.4. GC-MS Analysis*

Extracted oils were analysed by Gas Chromatography/Mass Spectrometry (GC/MS) provided with HP-5MS fused −5% phenyl methyl siloxane capillary column (30 m, 0.25 mm, 0.25 μm) (Agilent Technologies, Santa Clara, CA, USA) and interfaced with a PerkinElmer Turbo mass spectrometer (Software version 4.1) (PerkinElmer, Inc., Waltham, MA, USA). The column operation conditions were adjusted in the following manner: the sample solution injected was 1 μL, the carrier gas (helium) was adjusted at 1.0 mL/min, the injector was set at 250, the ion source temperature was regulated at 200 ◦C, the split ratio was 100:1, the electron impact ionization was of 70 eV and the interface line temperature was set at 300 ◦C. The operating temperature started at 110 ◦C, then was gradually raised to 180 ◦C with a gradient of 4 ◦C/min, then 220 ◦C with a gradient of 2 ◦C/min, and reached 300 ◦C at a gradient of 20 ◦C/min.

#### *2.5. Optical Microscopy*

In order to confirm that essential oils were successfully microencapsulated, an optical microscope (Leica DM 500, Leica Microsystems, Heerbrugg, Switzerland) was employed.

The optical microscope is equipped with a digital camera controlled by analysis software and different objectives. Microscopy technique was also considered to control the size and size distribution of microcapsules.

#### 2.5.1. Scanning Electron Microscopy

Morphological analysis was performed using a high-resolution scanning electron microscope (FEIQ250, Thermo-Fisher ESEM, Waltham, MA, USA). The cotton samples were coated with a conductive gold layer (a thin layer) by vapor deposition. Imaging parameters were regulated at low working voltages (5–10 kV) to save the original state of the textile material.

#### 2.5.2. Mechanical Properties

Tensile strength tests were conducted using a dynamometer (Lloyd LR 5 K, Lloyd Instruments Ltd., Largo, FL, USA). Samples were cut to a gauge length of 75 mm, and tests were performed as stated by NF EN ISO 13934-2 standards using a load cell of 5 kN and an extension speed of 50 mm·min−1.

#### 2.5.3. Surface Wettability

The contact angle aspects were recorded using a Drop Shape Analyzer (DSA25, Kruss, Germany). A droplet of 2 μL of ultra-pure water was placed on the fabric surface immobilized on the stage. For each sample, the test was repeated three times in different places.

#### 2.5.4. Washing Durability

To evaluate the washing durability, a domestic washing cycle was conducted as described in our previous publication [20]. A qualitative evaluation of the microcapsules crosslinking was realized based on optical microscope photographs.

#### *2.6. Antibacterial Activity*

The agar diffusion method was applied to evaluate essential oil activity. The cell density was adjusted to approximately 10<sup>6</sup> CFU/mL. An amount of 100 mL of the inoculi was spread over each petri dish containing the nutrient agar (Mueller–Hinton Agar). A paper filter disc (5 mm) impregnated with 20 μL/disc of the essential oils (cinnamon oil, cloves oil and oil mixture 50/50) was placed on the surface of the petri dishes, which were then incubated at 37 ◦C for 24 h. Each test was repeated twice.

The same method was applied to evaluate the activity of treated textiles against bacteria. All the tests were performed using the strains *Staphylococcus aureus* (ATCC 25923) and *Escherichia coli* (ATCC 8739). An autoclave was used, before experiments, for instruments and fabrics sterilization by heated steam at 120 ◦C for 20 min.

#### **3. Results and Discussion**

#### *3.1. Essential Oil Extraction and Characterization*

The hydro-distillation of the barks of Ceylon *cinnamon* and cloves of *Syzygium aromaticum* produced essential oils in yields of 1.8% and 10.5%, *<sup>v</sup>*/*<sup>w</sup>*, respectively, based on fresh weight.

The phytochemical composition of the two extracted oils was determined using a gas chromatograph coupled with a mass selective detector.

The composition of clove and cinnamon essential oils were found to be diverse. The major active constituents of clove essential oil were eugenol (83.55%) and phenol, 2-methoxy-4-(2-propenyl)-, acetate (14.92%), while the main active constituents of cinnamon essential oil were cinnamaldheyde (28.37%) and cinnamyl acetate (22.63%).

#### *3.2. Morphology and Size of Microcapsules*

Figure 1a shows an optical photograph of essential oil-loaded microcapsules. Figure 1b shows the optical microscopy of a microcapsule on the cellulosic fiber surface. The prepared microcapsules clearly show regular and spherical structures without fragments.

Figure 1b evidences the crosslinking of microcapsules on the fabric surface conserving their spherical shape. Figure 1c shows the cellulosic fiber, after a cycle of domestic washing, on which we can clearly identify an attached microcapsule.

Finally, Figure 1d shows the SEM images, at different magnifications, of a ruptured microcapsule after lightly rubbing the fabric. The crushed microcapsule presents a rough shell wall.

**Figure 1.** Optical photographs of (**a**) microcapsule solution, (**b**) microcapsules on the surface of the cellulosic fiber, (**c**) microcapsules on the surface of the cellulosic fiber after washing and (**d**) SEM images of ruptured microcapsule at different magnifications (the inset in **d**) is the ruptured microcapsule at 1000× magnification).

The microcapsule size distribution was evaluated by optical microscopy. The size of 80 microcapsules was determined. Figure 2 shows the size distribution of prepared microcapsules is between 12 and 48 μm, and the mean diameter is 22 μm. It was reported that the non-uniformity of size distribution is due to the stirring process. The water– oil emulsion flows rapidly around the agitator. The microcapsules with larger size are formed far away from the agitator, while small microcapsules are formed near the agitator [21]. In addition, the agglomeration of the oil phase enhances the non-uniformity of the microcapsules' size [22].

**Figure 2.** Microcapsule size distribution.

#### *3.3. ATR-FTIR Results*

In order to evaluate the success of the attachment of microcapsules on the surface of the cellulosic fibers through the citric acid, the control fabric (untreated cotton) and the treated fabric were characterized by ATR-FTIR (Figure 3).

 **Figure 3.** FTIR spectra of untreated cotton fabric and cotton fabric treated with microcapsules.

The FTIR spectra show prominent peaks of cellulose. The stretching vibration of the hydroxyl group gives a wide peak at 3300 cm<sup>−</sup>1. The band at 2890 cm<sup>−</sup><sup>1</sup> is characteristic of CH stretching vibration. Typical bands observed in the region of 1650–898 cm<sup>−</sup><sup>1</sup> are assigned to cellulose. The characteristic peaks of –CH2 and –CH, –OH and C–O bonds in cellulose gives the bands at 1428, 1368, 1317, 1061 and 895 cm<sup>−</sup><sup>1</sup> [20].

The appearance of a new peak at 1730 cm<sup>−</sup><sup>1</sup> was revealed on the spectrum of the treated cotton fabric. This peak is not present in the untreated sample spectrum and it corresponds to C=O ester stretching, which evidences the successful interaction between the chitosan (the wall of microcapsules) and cellulosic fibers through ester bond formation.

In addition, the small intensity of the peak at 1645 cm<sup>−</sup><sup>1</sup> is attributed to the NH group bending vibration, resulting from the chemical reaction between the NH2 groups of chitosan in the microcapsule walls and the COOH groups of the acid.

The ATR-FTIR results are in agreemen<sup>t</sup> with optical microscopy and SEM photographs of treated samples where the attached microcapsules were clearly seen (Figure 1).

#### *3.4. Mechanical Properties*

Maximum breaking load and extension were the characteristic parameters considered to evaluate mechanical properties. The two parameters were extracted from the load versus extension curves. As shown in Table 1, the maximum breaking load of untreated fabric is lower than that of the treated one. This result is due to the fact that the grafting process was conducted under acidic conditions (pH = 5). Highly acidic mediums are known to reduce the mechanical properties of cellulose by affecting its crystalline structure. The reduction rates depend on the pH value. High acidic pH values result in an important reduction in mechanical properties.

The extension indicates the percentage of strain at maximum applied force. High extension values evidence a stretch behavior of the textile substrate. Microcapsule grafting slightly reduced the stretch rate of the fabric. However, this reduction is not considered sufficient to affect the textile properties.


