Synthesis of silver-PMMA nanocomposite film

BACKGROUND

1. Field

The disclosure of the present patent application relates to polymer/metal nanoparticle composites, and particularly to the synthesis of a silver-PMMA nanocomposite film wherein the silver nanoparticles are synthesized using green chemistry, the resulting nanocomposite having antibacterial properties suitable for water purification and other applications.

2. Description of the Related Art

Nanomaterials are some of the most studied materials of the past century, giving birth to a new branch of science known as "nanotechnology." Nanomaterials can be prepared from bulk amounts of material, but the small size and shape of the resulting nanoparticles is an entirely different chemical action profile compared to the "parent" bulk material.

The much smaller size of nanomaterials helps them to penetrate particular cellular sites, while their additional surface area facilitates increased adsorption and targeted delivery of the substance. Nanomaterials frequently are found to exist in volcanic dust, mineral composites, and in anthropogenic waste materials, such as coal combustion, diesel exhaust, and welding fumes. Engineered nanomaterials manufactured with nanoscale dimensions are generally grouped into distinct types, including carbon, metals, metal oxides, dendrimers and composites.

Silver nanoparticles (AgNPs) have been shown to form composites with polymers, such as polyvinyl alcohol, polypyrrole, polyvinylidene fluoride, chitosan, and cellulose. The formation of polymer-silver nanocomposites requires that the size of the nanoparticles in the polymer matrix be controllable, and that their distribution within the polymer matrix be uniform.

Nanomaterials can be synthesized by different methods, including chemical, physical, and biological methods. Some chemical and physical methods have resulted in or contributed to environmental contamination, since the chemical procedures involved can generate a large amount of hazardous byproducts. Thus, there is a need to continue to develop new "green" synthesis procedures for nanoparticles that are clean, safe, ecofriendly, and nontoxic, without the use of high pressure, energy, temperature, and toxic chemicals. The biological methods include synthesis of nanomaterials from the extracts of plant, bacterial, and fungal species, among other procedures.

Thus, the synthesis of a silver-PMMA nanocomposite film solving the aforementioned problems is desired.

SUMMARY

The synthesis of a silver-PMMA nanocomposite film includes mixing an aqueous extract of Trigonella foenum-graecum (also known as Helba and fenugreek) seeds with an aqueous solution of silver nitrate, thereby reducing the silver ions to silver metal nanoparticles. A solution of the silver nanoparticles is added to a solution of PMMA [poly (methyl methacrylate)] in N'N-dimethylformamide (DMF) with stirring at 90.degree. C. A light brown solution of silver colloids develops, which is cast in a glass plate and the DMF is evaporated at room temperature, leaving a silver-PMMA nanocomposite film. Testing on water shows the silver-PMMA nanocomposite film prevents or inhibits growth of microbes, suggesting use as an antimicrobial or antibacterial agent, e.g., in water purification.

These and other features of the present disclosure will become readily apparent upon further review of the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an X-ray powder diffraction (XRD) plot of pure PMMA [poly (methyl methacrylate)] polymer.

FIG. 1B is an XRD plot of a silver-PMMA nanocomposite film synthesized as described herein.

FIG. 2 is a composite plot of TGA (thermogravimetric analysis) thermograms for pure PMMA polymer (line 1) and a silver-PMMA nanocomposite film synthesized as described herein (line 2).

FIG. 3 is a photograph of plated microorganism activity assays comparing treated and untreated tap water samples.

FIG. 4A is a TEM (transmission electron microscopy) micrograph of silver nanoparticles prepared using Helba extract, the scale bar corresponding to 100 nm.

FIG. 4B shows the size distribution curve of the silver nanoparticles prepared using Helba extract, determined by DLS (dynamic light scattering), the average size being 83.01 nm.

Similar reference characters denote corresponding features consistently throughout the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The synthesis of a silver-PMMA nanocomposite film using Trigonella foenum-graecum aqueous extract to synthesize the silver nanoparticles and subsequent synthesis of the polymer nanocomposite film, and analysis of the antimicrobial activity of the nanocomposite, is set forth below.

Seeds from fenugreek, or Helba (Trigonella foenum-graecum) are washed and dried, and then soaked in boiled distilled water overnight. The aqueous extract is then filtered, and combined filtrates are used as a precursor for preparing the nanoparticles.

The nanoparticles are prepared by treating the combined filtrates with an aqueous solution of silver nitrate (AgNO.sub.3). The aqueous silver nitrate solution is first formed by dissolving silver nitrate in distilled water, with vigorous stirring and at 80.degree. C., for 5 minutes. The extract is then added to the silver nitrate solution, and the nanoparticle solution is incubated at room temperature until it is used.

To form the nanocomposite film, PMMA is dissolved in DMF (dimethyl formamide), and then the silver nanoparticle solution is added, and stirred for one hour. The resulting solution is cast on a glass plate. The DMF is allowed to evaporate at room temperature, resulting in the nanocomposite film. Once dried, the nanocomposite film is removed from the glass plate.

The nanocomposite film demonstrates higher thermal stability than pure PMMA. The nanocomposite also demonstrates substantial antibacterial activity, as measured by comparing tap water treated with the nanocomposite material with untreated tap water.

Example 1

Preparation of Greener Helba AgNPs/PMMA Nanocomposite Film

We obtained Trigonella foenum-graecum (Helba) seeds from a local market in Saudi Arabia. We washed and dried 3 g of the seeds, and then soaked them in 90 ml of boiled, distilled water overnight, to prepare a Helba extract. The Helba extract was filtered, and the filtrate was immediately used for preparation of the nanoparticles solution. The filtrate was treated with an aqueous solution of silver nitrate (AgNO.sub.3), which was first prepared as follows.

We dissolved 1 mmol/ml of silver nitrate (AgNO.sub.3, analytical grade, obtained from Techno Pharmchem, India) in 50 ml of distilled water, with vigorous stirring at 80.degree. C. for 5 minutes. Then the Helba extract filtrate was added to the silver nitrate solution. The colloidal solution changed in color from colorless to brown, as noted by visual observation, confirming reduction of the silver ions and the formation of the greener AgNPs. Then, the resulting nanoparticle solution was incubated at room temperature until it was used.

We obtained PMMA from SABIC Company, in Saudi Arabia. We dissolved 6 g of the PMMA in dimethylformamide (DMF) obtained from R & M Marketing, in Essex, UK. A freshly prepared solution of the greener silver nanoparticles was added to the PMMA solution. The addition was carried out in a hood under constant stirring at 90.degree. C. The mixture was stirred for 1 hour in order to complete the reaction.

The resulting solution was light brown, due to the formation of silver colloids. The solution was then cast on a glass plate. The DMF was evaporated at room temperature, resulting in the nanocomposite film. Once dry, the film was removed from the glass plate.

We used transmission electron microscopy (TEM) using a JEM-1011 transmission electron microscope, obtained from JEOL, in Japan, to characterize the size, shape, and morphology of the synthesized nanoparticles, using accelerating voltage of 100 KV. See FIG. 4A. X-ray diffraction (XRD) was performed on a Bruker D8 Discover, to examine and compare the greener AgNPs/PMMA nanocomposite and PMMA films. See FIGS. 1A and 1B. The average particle size of the silver nanoparticles was estimated to be 83.01 nm.

TGA (thermogravimetric analysis) thermograms were carried out on a Mettler Toledo TGA/DSC 1, providing comparison between the greener AgNPs/PMMA nanocomposite and PMMA films. See FIG. 2. About 4 mg of dried film in each sample was used for the TGA comparison. TGA thermograms were obtained through a range of 0-800.degree. C., under nitrogen air flow, at a rate of 10.degree. C./min. The distinct graphs were plotted with weight (percentage) loss against temperature.

Example 2

Microbiological Testing

To treat the tap water with the greener nanocomposite film, a 1.times.1 cm square of the film was soaked in 50 ml tap water in a glass Erlenmeyer flask for 48 hours. Then, the treated water was tested for microorganism activity.

To prepare 250 ml general purpose nutrient agar medium, we dissolved 7 g of the agar medium in 250 ml of distilled water. To prepare 250 ml Eosin methylene blue (EMB) agar medium for the isolation of coliforms and E. coli, we dissolved 12.87 g of the agar medium in 250 ml of distilled water. For Mueller Hinton agar (MHA) medium, we dissolved 9.5 g of the agar medium in 250 ml of distilled water. Each of these was subsequently autoclaved, and, for testing, we added 100 .mu.l tap water (untreated or treated), mixed thoroughly, and poured each medium mixture into a petri dish. The plates were then incubated at 37.degree. C. for 24-48 hours.

In each instance, the treated sample exhibited no microorganism growth, in stark contrast to the tap water control. See FIG. 3.

As noted above, TGA was performed comparing the AgNPs/PMMA nanocomposites and pure PMMA. See FIG. 2. The weighed samples were heated at a rate of 10.degree. C./min, from room temperature to 800.degree. C., which is in the middle of the boiling point of the solvent and the degradation temperature of the polymer. FIG. 2 demonstrates two particular phases over the temperature range. The underlying weight reduction was figured to be around 20% and 5% for PMMA and Ag/PMMA, respectively, for the range of room temperature up to 300.degree. C. The weight reduction for this range of temperature is credited to low sub-atomic weight oligomers, loss of dampness, and leftover dissolvables in this scope of temperatures.

The second weight reduction demonstrates the corruption at over 360.degree. C. of the pure PMMA, which totally disintegrates at 400.degree. C., while the Ag/PMMA nanocomposite portion disintegrates over 800.degree. C. This second significant weight reduction was ascribed to basic deterioration of the polymer.

The weight reduction of Ag/PMMA nanoparticles and pure PMMA is organized in FIG. 2. The TGA investigation of Ag/PMMA nanocomposite indicates a decomposition profile beginning at 400.degree. C. and proceeding until over 800.degree. C. This demonstrates that the high thermal stability of the polymer is enhanced because of the presence of Ag as a nano-filler.

Thus, the greener Helba AgNPs/PMMA nanocomposite demonstrates higher thermal stability than the PMMA polymer alone, along with significant antibacterial activity. There was no visible growth of microbes in the treated water samples. Thus, these AgNPs provide a promising potential use in water purification, water containers, filters, water and wastewater treatment, and various associated industrial and commercial applications.

It is to be understood that the synthesis of a silver-PMMA nanocomposite film is not limited to the specific embodiments described above, but encompasses any and all embodiments within the scope of the generic language of the following claims enabled by the embodiments described herein, or otherwise shown in the drawings or described above in terms sufficient to enable one of ordinary skill in the art to make and use the claimed subject matter.