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Abstract

A novel series of bioactive polymer nanocomposites was recently created using the polycondensation method in conjunction with ultrasonic radiation. These nanocomposites comprise multi-wall carbon nanotubes and polyazomethine, which is based on the pyrazole moiety with various derivatives. The polyazomethine polymer was supplemented with a 2% concentration of multi-wall carbon nanotubes. The produced polymer nanocomposites were identified by Fourier-transform infrared spectroscopy and characterized by common characterization tools including X-ray diffraction, Scanning electron microscopy, and Transmission electron microscopy. The thermal stability was measured by thermogravimetric analysis and differential thermal gravimetry. The results of the X-ray diffraction patterns indicate that the multi-wall carbon nanotubes are really in the polymer matrix. The thermal analysis of these polymer nanocomposites shows high thermal stability. The agar diffusion technique was used to assess the antibacterial properties of the freshly synthesized polymer nanocomposites against various bacterial and fungal species. The chosen bacteria and fungi were susceptible to varying degrees of antimicrobial and antifungal activity in the polymer nanocomposites that were evaluated. Moreover, the antibacterial properties of the fabricated Polymer nanocomposites were assessed through colony forming units against Escherichia coli bacteria and showed good effectiveness of all tested polymer nanocomposites. All samples showed an effect on bacterial growth after 12 h by 22%–35%. After 24 h, the percent inhibition of E. coli in the presence of the prepared polymer nanocomposites was highest; it showed 45%–60%.

Keywords

Antimicrobial performance polyazomethine nanocomposites pyrazole moiety carbon nanotubes

Introduction

Research into polymer nanocomposites is one of the most exciting fields in the scientific community right now. Many people are interested in low-dimensional carbon nanomaterials such as graphene, carbon nanotubes (CNTs), and fullerene because of their remarkable electrical, optical, mechanical, and chemical capabilities. Sensing, energy storage, optoelectronics, biology, and medicine are just a few of the many fields that benefit from these sp2 hybridized carbon-based materials’ many uses.^1–9 Particularly intriguing are polymer-based nanocomposites that combine polymer with carbon nanotubes (CNTs). The extraordinary improvement that they bring to the functional properties of polymers opens up a whole new universe of opportunities for their application in a wide variety of sectors. The excellent physical, chemical, and service features of carbon nanotubes (CNTs) are significantly influenced by the distribution and disentanglement of CNTs inside the polymer matrix.¹⁰ The current spike in popularity of carbon-based nanomaterials (CNMs) can be attributed to the antibacterial capabilities that were discovered in these materials.^11,12 The exceptional insoluble nature of carbon nanoparticles (CNMs) and their high level of chemical resistance are two of the most significant advantages of these materials. Due to the fact that the concentration of these antibacterial chemicals does not change over the course of time, it is anticipated that there would be no decline in activity. In the same way that a rolled-up sheet of graphene is similar to a carbon nanotube (CNT), hemi fullerenes are typically used to close their ends. Single-wall carbon nanotubes, also known as SWCNTs, typically have a diameter that is only a few nanometers in size. The outside diameter of Multi-Wall Carbon Nanotubes (MWCNTs) can reach up to 100 nm, and they are made up of concentrated single-walled carbon nanotubes (SWCNTs). However, polyazomethines are a kind of π-conjugated polymer that stands in opposition to this. As a result of the existence of HC = N, these polymers are one of a kind; they have the ability to complex and protonate. In the year 1923, Adams and his colleagues were the first to successfully synthesize polyazomethine.¹³ Polymer science is fascinated by this material because of its nonlinear optical, electrical, optoelectronic, and liquid crystalline properties.^14–19 Additionally, this material is quite stable in terms of temperature. Their extraordinary qualities make it possible for them to be utilized in a variety of contexts.^{11,12,20–26} Consequently, a novel class of pyrazole-based nanocomposites containing azomethine linkages and multiwalled carbon nanotubes PAZm/Py/MWCNTs have been created using the polycondensation method and ultrasonic aid. In addition to FT-IR spectroscopy for material identification, standard characterization methods including XRD, SEM, and TEM were used to evaluate the synthesized polymer nanocomposites. Also covered were thermal analyses, such as TGA and DTG, of PAZm/Py/MWCNTs nanocomposites. The antibacterial properties of the freshly synthesized nanocomposites were tested on several types of bacteria and fungus. Additionally, Escherichia coli was used to test the antibacterial characteristics, and the percentage of decrease was determined after 12 and 24 h.

Experimental

Chemicals, solvents, and reagents

Substituted aniline derivatives (4-nitroaniline, p-toluidine, 2-chloroaniline) were purchased from (Sigma-Aldrich) and used as starting materials for the synthesis of monomers. Sodium nitrite (NaNO₂), malononitrile (CH₂(CN)₂), sodium acetate (C₂H₃NaO₂), and hydrazine hydrate were purchased from (BHD) and used directly as it was received. Glacial acetic acid CH₃CO₂H (99%) from Sigma-Aldrich was used as a catalyst. Terephthalaldehyde purchased from NANO TECH Co. LTD Egypt. Concentrated hydrochloric acid (HCl) was received from (Merck), as a solvent with (% pure) was used for dissolving substituted aniline derivatives. Ethanol absolute (99.9% pure) provided by (Merck) was used as solvent in the monomers, polymer nanocomposites fabrication. Multi-walled carbon nanotube (CNTs) was supplied by NANO TECH Co. LTD Egypt (99% purity) and used to fabricate polymers nanocomposites. All of the chemicals and solvents mentioned were used without any more purification because they were all highly pure.

Preparation of monomers

The monomers were synthesized according to the following general procedure as in a previous study.^27–29

In a suitable beaker, 0.01 mol of substituted aniline derivatives 1(a, b, c) were mixed with 10 mL concentrated hydrochloric acid (HCl) to dissolve, then the solutions were left to cool to 0–5°C in an ice bath. In another beaker, 0.01 mol of sodium nitrite (NaNO₂) was dissolved in 3 mL of water. To form the diazonium salts of aniline derivatives the sodium nitrite solution was added dropwise to the solutions of aniline hydrochloride derivatives with continuous stirring (in an ice bath). In the presence of 0.01 mol of sodium acetate, the clear solutions of substituted diazonium salts were then added dropwise to solutions of 0.01 mol of malononitrile in 20 mL of ethanol. The solutions were stirred for a further 4 h in an ice bath, then colored. The solid products were collected and washed with cold water and crystallized from ethanol to give the derivatives 4(a, b, c). The latter derivatives were cyclized as follows: To a solution of derivatives 4(a-c) (0.01 mol) in ethanol (30 mL), hydrazine hydrate (0.5 g, 0.01 mol) was added and the whole solutions were refluxed for 5 h. After the reactions were completed through investigation with TLC test, the solid precipitated products were collected with filtration and crystallized from ethanol to afford the diaminopyrazole derivatives 5(a-c).

4-((4-Nitrophenyl) diazenyl)-1H-pyrazole-3,5-diamine (a)

The monomer (a) was prepared using the aniline derivative (4-nitroaniline) in the same way as the previous preparation, yielding (60%) as a reddish-brown, m. p. 255°C–256°C. FT-IR: 3399-3390 cm⁻¹ and 3371-3330 cm⁻¹due to two NH₂ (3-NH₂ and 5-NH₂), 3235-3208 cm⁻¹ due to NH group, 1633 cm⁻¹ (C = N), 3082 cm⁻¹ (=C-H aromatic), 1460 cm⁻¹ (N = N), 1600 cm⁻¹ and 1465 cm⁻¹ (C = C), 1518 cm⁻¹ and 1321 cm⁻¹ (NO₂).

4-(p-tolyldiazenyl)-1H-pyrazole-3,5-diamine (b)

The monomer (c) was prepared using the aniline derivative (p-toluidine) in the same way as the previous preparation, yielding (88%) as yellow crystals, m. p. 243°C–245°C. FT-IR: 3399-3390 cm⁻¹ and 3371-3330 cm⁻¹due to two NH₂ (3-NH₂ and 5-NH₂) groups, at 3235-3208 cm⁻¹ due to NH group, 1610 cm⁻¹ (C = N), 3080-3010 cm⁻¹ (=C-H aromatic), 1460 cm⁻¹ (N = N), 1559 cm⁻¹ and 1494 cm⁻¹ (C = C), 2913 cm⁻¹ (C-H aliphatic).

4-((2-Chlorophenyl) diazenyl)-1H-pyrazole-3,5-diamine (c)

The monomer (e) was prepared using the aniline derivative (2-chloroaniline) in the same way as the previous preparation, yielding (90%) as yellow crystals, m. p. 267°C–270°C. FT-IR: 3400-3100 cm⁻¹ [NH, NH₂ (3-NH₂ and 5-NH₂)], 1607 cm⁻¹ (C = N), 3050-3010 cm⁻¹ (=C-H aromatic), 1544 cm⁻¹ and 1458 cm⁻¹ (C = C). 1460 cm⁻¹ (N = N), 750 cm⁻¹ (C-Cl).

Fabrication of PAZm/Py/MWCNTs_a-c nanocomposites

The PAZm/Py/MWCNTs_a-c nanocomposites were prepared via the polycondensation technique with the assistance of ultrasonics throughout the following general procedures: 1 mol of diaminopyrazole derivatives (a, b & c) and 2% loading MWCNT were dissolved in a suitable amount of ethanol using an ultrasonicator for 10 min at 60°C. Then 1 mol of terephthalaldehyde was added in the presence of a few drops of glacial acetic acid as a catalyst to activate the polymerization process. In a three-necked flask equipped with a condenser inside a system saturated with dry nitrogen, inlet and outlet, the previous reaction mixture was heated under a magnetic stirrer for 8 h at 70°C–80°C. Then, by filtration, the polymer precipitated was isolated, and washed with hot ethanol and left to dry at room temperature. Table 1 illustates the suggested abbrivations for the fabricated polymer nanocomposites, MWCNT percent loading and the reaction components in each case.

Table 1.

Polymer nanocomposites codes, MWCNT % loading and reaction mixture.

Code	MWCNT (%)	Reaction mixture
PAZm/Py/MWCNTs_a	2	4-((4-nitrophenyl) diazenyl)-1H-pyrazole-3,5-diamine + terephthalaldehyde
PAZm/Py/MWCNTs_b	2	4-(p-tolyldiazenyl)-1H-pyrazole-3,5-diamine + terephthalaldehyde
PAZm/Py/MWCNTs_c	2	4-((2-chlorophenyl) diazenyl)-1H-pyrazole-3,5-diamine + terephthalaldehyde

PAZm/Py/MWCNTs_a

PAZm/Py/MWCNTs_a was fabricated in the presence of 1 mol (0.308 g) of monomer a with 1 mol (0.1676 g) of terephthalaldehyde by adding 2% (0.0079 g) MWCNTs as the same procedure previously discussed. FT-IR: 1633 cm⁻¹ (C = N), 2887 cm⁻¹ (=C-H stretching of aliphatic), 3268 cm⁻¹ (N-H of pyrazole), 1499 cm⁻¹ and 1588 cm⁻¹ (C = C of the aromatic), 1564 cm⁻¹ and 1322 cm⁻¹ (NO₂), 3049 cm⁻¹ (C-H stretching of aromatic). The typical peak for MWCNTs is 1564 cm⁻¹.³⁰

PAZm/Py/MWCNTs_b

PAZm/Py/MWCNTs_b was fabricated in the presence of 1 mol (0.154 g) of monomer b with 1 mol (0.095 g) of terephthalaldehyde by adding 2% (0.0037 g) MWCNTs as the same procedure previously discussed. FT-IR: 1629 cm⁻¹ (C = N), 2870 cm⁻¹ (=C-H stretching of aliphatic), 3259 cm⁻¹ (N-H of pyrazole), 1497 cm⁻¹ and 1603 cm⁻¹ (C = C of the aromatic), 3040 cm⁻¹ (C-H stretching of aromatic), 2935 cm⁻¹ (C-H aliphatic).

PAZm/Py/MWCNTs_c

PAZm/Py/MWCNTs_c was fabricated in the presence of 1 mol (0.19 g) of monomer c with 1 mol (0.11 g) of terephthalaldehyde by adding 2% (0.0047 g) MWCNTs as the same procedure previously discussed. FT-IR: 1632 cm⁻¹ (C = N), 2828 cm⁻¹ (=C-H stretching of aliphatic), 3273 cm⁻¹ (N-H of pyrazole), 1514 cm⁻¹ and 1602 cm⁻¹ (C = C of the aromatic), 3050 cm⁻¹ (C-H stretching of aromatic), 737 cm⁻¹ (C-Cl).

Antimicrobial activity

The antimicrobial activities of the newly fabricated PAZm/Py/MWCNTs_a-c nanocomposites were evaluated using the agar diffusion method with different bacterial species and fungi, including the Staphylococcus aureus (ATCC 29213) and Bacillus Cereus (ATCC 14579) as selected Gram-positive bacteria strains, (E. coli (ATCC 35218) and Serratia marcescens (ATCC 21074) as selected Gram-negative bacteria strains, and Aspergillus flavus (ATCC 9643) and Candida albicans (ATCC 76615) as selected fungi. The method used to determine the antimicrobial effect of the new nanocomposites has been described in the previous literature.³¹ In brief, a 90 mm Petri dish was filled with 25 mL of Muller-Hinton agar; 200 μL of bacterial cultures were autoclaved for 25 min and then spread on the surface of the agar plates using sterile swabs. The targeted materials were cut into 6 mm diameter disk specimens. The discs were washed with distilled water and disinfected at 120°C/20 min. The discs were then placed on the surface of the media. Finally, the Petri dishes were incubated at 30°C for 24–48 h.

As a control for antibacterial and antifungal activity, respectively, chloramphenicol and clotrimazole were utilized. The size of the growth inhibition zone was measured, and the results are given later in Table 2.

Table 2.

Antifungal and antibacterial activities of PAZm/Py/MWCNTs_a-c nanocomposites against the selected fungi and bacteria.

Code	Fungal and bacterial species/Inhibition zone (mm)
Code	A. flavus	C. albicans	S. marcescens	E. coli	S. aureus	B. subtilis
PAZm/Py/MWCNTs_a	10 (±0.2)	12 (±0.5)	11 (±0.3)	13 (±0.3)	6 (±0.3)	5 (±0.2)
PAZm/Py/MWCNTs_b	5 (±0.3)	6 (±0.1)	9 (±0.6)	10 (±0.1)	1 (±0.1)	1 (±0.2)
PAZm/Py/MWCNTs_c	8 (±0.4)	10 (±0.2)	11 (±0.4)	13 (±0.5)	2 (±0.2)	3 (±0.3)

Clotrimazole and Chloramphenicol were used as control for antifungal and antibacterial activities respectively.

Bacterial cell culturing

For evaluation of the antibacterial activities, E. coli O157:H7 was used as a model, which was provided by National Research Center, Cairo. Bacterial cells were grown for antibacterial test on nutrient agar (Sigma-Aldrich-70148) containing 1 g/L meat extract, 5 g/L peptones, 2 g/L yeast extract, 2 g/L sodium chloride and 15 g/L agar in distilled water. Nutrient agar medium plates were prepared, sterilized and solidified. After solidification bacterial cultures were swabbed on these plates.

Antibacterial assessment

Antibacterial activities of the fabricated PAZm/Py/MWCNTs_a-c nanocomposites were assessed through colony forming units (CFU) count method.³² About 0.1 g/mL of samples were added to each of the test tubes containing 9 mL of liquid medium (Nutrient Broth). Then 1 mL of E. coli O157:H7 was added to 9 mL of tube containing liquid medium and incubated at 30°C for 24 h. The samples were serially diluted and then spread over nutrient agar. For the determination of colonies, samples were taken at two different timings (12 h and 24 h) and the number of colonies were counted using colony counter. The experiment was repeated three times and the results obtained have been listed in Table 3 (please check later).

Table 3.

Growth conditions and percent of inhibition of E. coli in the presence of PAZm/Py/MWCNTs_a-c nanocomposites.

Material used (Cfu/ml)	Incubation time (h)		Reduction (%)
Material used (Cfu/ml)	12 (h)	24 (h)	12 (h)	24 (h)
Control	0 × 10⁶	0 × 10⁶	0	0
PAZm/Py/MWCNTs_a	60 × 10⁶	85 × 10⁶	35	60
PAZm/Py/MWCNTs_b	62 × 10⁶	84 × 10⁶	22	45
PAZm/Py/MWCNTs_c	60 × 10⁶	92 × 10⁶	25	50

Characterization method

Fourier Transform Infrared (FT-IR) spectrophotometer technique is used to analyze the functional groups present in final products, the (Perkin Elmer Precisely Spectrum 100) was used to record the infrared spectra. Each spectrum was in the 400–4000 cm⁻¹ wavenumber range. The X-ray Diffraction (XRD) is a technique used to determine whether a material is crystalline or amorphous. The XRD of polymer nanocomposites was recorded using (XRD) D8 ADVANCE in the range 2θ between 5° and 80° at 40 kV voltage and 40 mA using Cu-Kα radiation. Scanning Electron Microscope (JSM-7610FPlus Schottky Field Emission) was used to know Surface morphology of PAZm/Py/MWCNTs. TEM micrographs of polymer nanocomposites were taken using the JEM-F200 Multi-Purpose Electron Microscope at magnification of 25x magnification and voltage of 100 kV. The thermal behavior of all PAZm/Py/MWCNTs was evaluated by a Thermo-Gravimetric Analysis (TGA) and derivative thermal gravimetric (DTG) using a Shimadzu TG-50H thermal analyzer at temperatures rising from air temp to 800°C and heating rate of 10°C/min.

Results and discussion

Chemistry part

The monomers 4-((4-nitrophenyl) diazenyl)-1H-pyrazole-3,5-diamine (a), 4-(p-tolyldiazenyl)-1H-pyrazole-3,5-diamine (b), and 4-((2-chlorophenyl) diazenyl)-1H-pyrazole-3,5-diamine (c) were prepared demonstrated in Figure 1 and characterized by FT-IR spectral analysis as clarified in the experimental section. Furthermore, the melting points of these monomers were measured, and the results were consistent with those found in the literature.^27,29

Figure 1.

Synthesis of monomers.

PAZm/Py/MWCNTs_a-c nanocomposites containing polyazomethine and 2% of multi-walled carbon nanotubes were fabricated by polymerization procedures depending fundamentally on the polycondensation process. The fabrication process is based chiefly on diaminopyrazole derivatives and terephthalaldehyde in the presence of a 2% loading of MWCNT. The synthetic route for synthesizing the PAZm/Py/MWCNTs_a-c nanocomposites is demonstrated in Figure 2.

Figure 2.

Synthetic route for synthesizing the PAZm/Py/MWCNTs_a-c.

Identification and characterization of PAZm/Py/MWCNTs_a-c composites

The chemical structures of these nanocomposites were gained using an FT-IR spectrophotometer in the wavenumber range of 4000–400 cm⁻¹ as presented in the experimental section. The physical interaction between neat polyazomethine and its MWCNT type fabricated products is confirmed using FT-IR data. Figure 3(a) shows the FT-IR spectra of monomer(a), terephthalaldehyde and PAZm/Py/MWCNTs_a which confirm the absence of terephthalaldehyde CHO bond in the PAZm/Py/MWCNTs_a composite and the formation of the azomethine linkage (HC = N). Such observation illustrates an excellent interaction for the polymerization process, Whereas, Figure 3(b) shows the FT-IR spectra of PAZm/Py/MWCNTs_a-c composites. The spectra displayed absorption bands at around 1628-1633 cm⁻¹, indicating the formation of an azomethine bond in PAZm/Py/MWCNTs_a-c. Furthermore, a peak of nearly 3257-3273 cm⁻¹ is allocated to the N-H bond. The typical peak for MWCNTs is 1564 cm⁻¹.³⁰

Figure 3.

(a) FT-IR spectra of monomer (a) terephthalaldehyde and PAZm/Py/MWCNTs_a. (b) FT-IR spectra of PAZm/Py/MWCNTs_a-c composites.

The X-ray diffraction patterns of the PAZm/Py/MWCNTs_a-c nanocomposites were analyzed using an X-ray diffractometer (D8 ADVANCE) throughout the 2θ range of 5° to 80°. Figure 4 demonstrates that the nanocomposites exhibit a combination of crystalline behavior and the amorphous nature of the polymers. In addition, the XRD nanocomposites exhibited many signal peaks, the most significant peak appeared at 2θ = 13.9°. The polymer chains in the PAZ/MWCNT nanocomposites effectively insert themselves between the layers of the carbon nanotubes, resulting in a substantial decrease in the crystalline structure of the polymer. This is in conformity with the results of a previous study.³³ The MWCNTs present a diffraction peak of about 26.13° (002) related to graphite planes as a feature of carbon-based materials.³⁴ The results indicate that the MWCNTs are really in the polymer matrix. No other peaks indicating the presence of impurities were found in PAZm/Py/MWCNTs_a-c composite materials.

Figure 4.

XRD diffraction of PAZm/Py/MWCNTs_a-c.

TGA and DTG were used to examine the thermal behavior of PAZm/Py/MWCNTs_a-c at a heating rate of 10°C/min under nitrogen atmosphere from room temperatures up to 800°C. Fig. 5 (a) shows the TGA curves of all nanocomposites. It is clear from the curves that PAZm/Py/MWCNTs_a-c are decomposed in three main steps; the first step starts at 38.43°C, 39.45°C, and 39.69°C and ends at 285°C, 209.69°C, and 283°C for PAZm/Py/MWCNTs_a-c, respectively. Small weight losses are observed in the first step, which is attributed to the loss of moisture and entrapped solvents, which might lose a small weight in the range of 7%–14%. They overlap between the second and third steps, starting at around 361°C and going up to 798°C. The degradation mostly returns to PAZm, which is the main backbone for such composite materials. Depending on the nature of these composite materials, scission of N = CH bonds occurs, resulting in the liberation of free shorter chains, which eventually results in the formation of char as the end product.^35,36 T₁₀, T₂₀, T₃₀, T₄₀ and T₅₀ values are listed in Table 4 which are referring to the temperatures for various % weight losses at 10%, 20%, 30%, 40% and 50%. As a result, the information in Table 4 shows the 10% weight loss of sample occur at temperatures were in the range of 270°C–347°C, that indicates that the thermal stabilities of these materials. The T₅₀ value is one of the most important criteria for determining a polymer’s relative thermal stability. The T₅₀ values of the PAZm/Py/MWCNTs_a-c were discovered after the examination of the data. They were in the 558°C–577°C range. PAZm/Py/MWCNTs_a shows the highest thermal stability of all fabricated products. The weight loss of the PAZm/Py/MWCNTs (a, b, and c) at 800°C was 71%, 69%, and 74%, respectively, which indicates the thermal stability of these polymers. The maximum decomposition temperature of composites (CDT_max) is where the maximum rate of weight loss is observed.^37–39 As shown in Figure 5(b) The CDT_max values are in the range of 298.61°C–356.73°C.

Table 4.

Thermal properties of PAZm/Py/MWCNTs_a-c.

Materials	CDT_max^a (°C)	Temperature (°C) for different percentage decompositions^b
Materials	CDT_max^a (°C)	T₁₀	T₂₀	T₃₀	T₄₀	T₅₀
PAZm/Py/MWCNTs_a	356.73	347	361	366	464	577
PAZm/Py/MWCNTs_b	349.18	337	339	341	380	558
PAZm/Py/MWCNTs_c	298.61	270	294	366	472	565

^aThe values were determined from DTG curves.

^bThe values were determined by TGA at 10°C per min heating rate.

Figure 5.

(a) TGA thermograms of PAZm/Py/MWCNTs_a-c. (b) DTG curves of PAZm/Py/MWCNTs_a-c.

Scanning electron microscopy SEM (JSM-7610FPlus Schottky Field Emission) was used to investigate the morphological properties of the fabricated materials, as shown in Figure 6. SEM images for PAZm/Py/MWCNTs_a as chosen example are given in Figure 6 at different magnifications, it shows clear morphological evidence for the composites’ expected formation. Coral reefs with mini holes in the form of porous spongy shapes can be seen on the polyazomethine surface with an aggregation of MWCNTs on the polymer surface. The other two samples PAZm/Py/MWCNTs_b and PAZm/Py/MWCNTs_c might show similar observation with significant variation caused by the different polarity of the produces due to the different groups attached to the polymer’s main chains 4-methyl and 2-chloro derivatives respectively rather than 4-nitro, for the first derivative. The thin component of the composites was also imaged using Transmission Electron Microscopy TEM (JEM-F200 Multi-purpose) to gain a better understanding of MWCNT diffusion. The TEM images of the PAZm/Py/MWCNTs_a composite are shown in Figure 7. TEM images indicate that the immersed MWCNTs are distinctly seen in their nanotube form with a uniform distribution in the presence of some agglomeration.

Figure 6.

SEM images of PAZm/Py/MWCNTs_a (a,b,c) at magnifications (x = 24,000, 30,000 and 60,000.

Figure 7.

TEM images of PAZm/Py/MWCNTs_a composite material.

Antimicrobial activities

The diffusion method was used to determine the antibacterial activities of the newly fabricated PAZm/Py/MWCNTs_a-c nanocomposites were evaluated against different bacterial species and fungi , including S. aureus and Bacillus Cereus as selected Gram-positive bacteria strains, E. coli and S. marcescens as selected Gram-negative bacteria strains, and A. flavus and C. albicans as selected fungi. As a control for antibacterial and antifungal activity, chloramphenicol and clotrimazole were utilized respectively. All antimicrobial results have been illustrated in Figure 8. The area of inhibition was introduced in mm and the antibacterial and antifungal activities were shown in Table 2. All the tested compounds possessed variable antibacterial activity, in which compound PAZm/Py/MWCNTs_a was found to have the strongest inhibitory effect against the selected bacteria, while compound PAZm/Py/MWCNTs_b had the weakest inhibitory effect against the same bacteria. Furthermore, all synthesized polymer nanocomposites showed antifungal activity against A. flavus and C. albicans.

Figure 8.

Antifungal and antibacterial activities diagram of PAZm/Py/MWCNTs_a-c nanocomposites against the selected (a) fungi and (b) Gram-positive, Gram-negative bacteria.

The count method was used to determine the biological properties of PAZm/Py/MWCNTs_a-c nanocomposites against E. coli as a selected Gram-negative bacteria through colony forming units (CFU).³² Table 3 and Figure 9 provide illustrations of the results of the possibility of E. coli O157:H7 cell growth after treatment with PAZm/Py/MWCNTs_a-c. Generally, the antibacterial activity of PAZm/Py/MWCNTs_a-c nanocomposites was investigated against E. coli and showed good effectiveness of all tested polymer nanocomposites. The PAZm/Py/MWCNTs_a, PAZm/Py/MWCNTs_b, and PAZm/Py/MWCNTs_c nanocomposites showed an effect on bacterial growth after 12 h by 35%, 22%, and 25%, respectively. After 24 h, the percent of inhibition of E. coli in the presence of the PAZm/Py/MWCNTs_a-c nanocomposites were highest; it showed 60%, 45%, and 50% for PAZm/Py/MWCNTs_a, PAZm/Py/MWCNTs_b, and PAZm/Py/MWCNTs_c respectively. The CFU values/mL are 60 × 10⁶–62 × 10⁶ for nanocomposites after 12 h. After 24 h, PAZm/Py/MWCNTs_a-c show CFU values/mL in the range of 84 × 10⁶–92 × 10⁶.

Figure 9.

Reduction percentage of E. coli after contact with PAZm/Py/MWCNTs_a-c nanocomposites for 12 and 24 h.

Conclusion

The researcher team has successfully produced aromatic polyazomethine nanocomposites PAZm/Py/MWCNTs_a-c using the polycondensation process with ultrasonic assistance based on the pyrazole moiety. The polymer nanocomposites that were created were detected using infrared spectroscopy and studied using standard characterization techniques such as XRD, TGA, SEM, and TEM. The X-ray diffraction patterns confirm the presence of MWCNTs within the polymer matrix. The PAZm/Py/MWCNTs (a, b, and c) had weight losses of 71%, 69%, and 74% at 800°C, respectively, demonstrating the thermal resilience of these polymers. The PAZm/Py/MWCNTs_a exhibits the highest thermal stability among all the manufactured items. The scanning electron microscopy (SEM) pictures of PAZm/Py/MWCNTs_a reveal the presence of porous spongy structures resembling coral reefs, together with small holes on the polyazomethine surface. Additionally, there is an accumulation of multi-walled carbon nanotubes (MWCNTs) on the polymer surface. Additionally, the submerged MWCNTs are clearly visible in their nanotube shape in the TEM pictures. We tested the newly synthesized PAZm/Py/MWCNTs_a-c nanocomposites against various bacterial and fungal species to find out how effective they were as antibacterial agents using the diffusion method. The antibacterial activity of the studied compounds was diverse; however, compound PAZm/Py/MWCNTs_a exhibited the most potent inhibitory effect against the chosen bacteria, whereas compound PAZm/Py/MWCNTs_b exhibited the least. Also, when tested against A. flavus and C. albicans, every single one of the manufactured polymer nanocomposites exhibited antifungal properties. All of the polymer nanocomposites examined showed good efficacy when evaluated for antibacterial activity against E. coli, including PAZm/Py/MWCNTs_a-c.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication publication of this article: This research work was funded by Institutional Fund Projects under grant no. (IFPDP-297-22). The authors gratefully acknowledge the technical and financial support provided by the Ministry of Education and King Abdulaziz University, DSR, Jeddah, Saudi Arabia.

ORCID iD

Mahmoud A. Hussein

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Synthesis,and antimicrobial activity of polyazomethine-pyrazole/multi-walled carbon nanotubes nanocomposite materials

Abstract

Keywords

Introduction

Experimental

Chemicals, solvents, and reagents

Preparation of monomers

4-((4-Nitrophenyl) diazenyl)-1H-pyrazole-3,5-diamine (a)

4-(p-tolyldiazenyl)-1H-pyrazole-3,5-diamine (b)

4-((2-Chlorophenyl) diazenyl)-1H-pyrazole-3,5-diamine (c)

Fabrication of PAZm/Py/MWCNTsa-c nanocomposites

PAZm/Py/MWCNTsa

PAZm/Py/MWCNTsb

PAZm/Py/MWCNTsc

Antimicrobial activity

Bacterial cell culturing

Antibacterial assessment

Characterization method

Results and discussion

Chemistry part

Identification and characterization of PAZm/Py/MWCNTsa-c composites

Antimicrobial activities

Conclusion

Footnotes

Declaration of conflicting interests

Funding

ORCID iD

References

Fabrication of PAZm/Py/MWCNTs_a-c nanocomposites

PAZm/Py/MWCNTs_a

PAZm/Py/MWCNTs_b

PAZm/Py/MWCNTs_c

Identification and characterization of PAZm/Py/MWCNTs_a-c composites