Keywords: copper nanoparticles, plant extract, biological synthesis

However, copper nanoparticles have major limitations, which include rapid oxidation on exposure to air. Copper oxidizes to CuO and Cu2O, and converts to Cu2+ during preparation and storage, so it is difficult to synthesize copper nanoparticles in an ambient environment. Therefore, alternative pathways have been developed to synthesize metal nanoparticles in the presence of polymers (eg, polyvinylpyrrolidone, polyethylene glycol, and chitosan) and surfactants (cetyl trimethyl ammonium bromide) as stabilizers, and to form coatings on the surface of nanoparticles. Recently, plant extracts have been used to stabilize nanoparticles in green synthesis. In general, quite a number of nanoparticles are prepared using polymer dispersions.– A number of techniques can be used to prepare copper nanoparticles, including thermal reduction, a capping agent method, sonochemical reduction, metal vapor synthesis, microemulsion techniques, laser irradiation, and induced radiation.

T1 - Study of the synthesis of copper nanoparticles

Copper nanoparticle - Wikipedia

A copper nanoparticle is a copper based particle 1 to 100 nm in size

NanoSight was founded in 2004 by Dr Bob Carr and John Knowles after Carr discovered a technology which allows particles so small they were below the normal optical microscope limit to be seen, sized and counted in less than a minute for a fraction of the cost of electron microscopes.

Synthesis of Copper Nanoparticles

Antibacterial have been widely used in the textile industry, water disinfection, medicine and food packaging. Organic compounds used for disinfection have some drawbacks, including toxicity to the human body, therefore, the interest in inorganic disinfectants such as metal oxide nanoparticles (NPs) is increasing (). Antibacterial activities of nanoparticles depend on two main factors, including physico of NPs and type of bacteria (). An important factor that can influence the tolerance of bacteria against NPs is the rate of bacterial growth. Fast growing bacteria are more susceptible to NPs than slow-growing bacteria (). It is possible that the tolerance property of slow-growing bacteria is related to the expression of stress-response genes (). Therefore, antibacterial effects highly depend on the particular strain. The exact mechanisms of NPs toxicity against various bacteria are not fully understood. It is believed that NPs are able to attach to the membrane of bacteria by electrostatic interaction and disrupt the integrity of the bacterial membrane (). The toxicity of NPs depends on the combination of several factors such as temperature, aeration, pH, concentration of NPs and concentration of bacteria. The , high aeration and low pH decrease the agglomeration and increase the toxicity (). In this study, synthesis of copper nanoparticles was approached by a single-precursor route via controlling the growth temperature and Cu-NPs effects on the growth rate of were investigated.

The scheme of synthesizing albumin-polymer-based nanoparticles. Figure adapted with permission from [].
T1 - Synthesis and characterization of metal-dielectric composites with copper nanoparticles embedded in a glass matrix

Copper Nanoparticles: Synthetic Strategies, Properties …

Growth studies with optical density (OD) measurements were used to evaluate the antimicrobial activity in a quantitative manner. Prior to incubation with the nanoparticles, the bacteria were cultured overnight in 5 mL of Luria-Bertani broth and the yeast was cultured in potato dextrose broth. The microbial culture suspension was adjusted to an OD600 of 1.0 as determined spectrophotometrically. The overnight cultures were diluted 105 to approximately 104 colony-forming units per mL using sterile broth for further investigation. The chitosan-copper nanoparticles were suspended in sterilized distilled water (Millipore) to give a final concentration of 2.5 mg in each well, and the suspension was distributed uniformly on the surface of six-well sterile tissue culture plates (Nalge Nunc International, Roskilde, Denmark). To examine microbial growth and to determine growth behavior in the presence of the chitosan-copper nanoparticles, 100 μL of the microbial culture suspensions were added to each well supplemented with the nanoparticle compounds. Cultures of nanoparticle-free medium under the same growth conditions were used as a control. To avoid potential optical interference caused by the light-scattering properties of the nanoparticles during determination of OD in the growing cultures, the same Luria-Bertani broth medium without microorganisms but containing the same concentration of nanoparticles cultured under the same conditions was used as the blank control. These plates, as well as the negative and the positive control plates, were incubated overnight in a Certomat SII incubation shaker at 37°C and in a humid atmosphere to minimize evaporation from each well. Following incubation of the test microorganisms with the nanoparticles overnight, the OD of the cultures in each well was determined spectrophotometrically. The corresponding number of colony-forming units was determined and the percentage inhibition was calculated as follows:

Copper nanoparticles stabilized by reduced graphene …

The antibacterial properties of the as-synthesized chitosan-copper nanoparticles were evaluated by a qualitative method against the aforementioned microorganisms using the agar disk diffusion method as described previously. Gram-positive and Gram-negative bacteria were cultured on LB agar medium (Fluka) while yeast was cultured on potato dextrose agar (Becton Dickinson Difco, Franklin Lakes, NJ, USA). Briefly, 20 mL of liquid Mueller Hinton agar (pH 7.3 ± 0.2 at 25°C) was poured onto disposable sterilized Petri dishes and allowed to solidify. The surfaces of the solidified agar plates were allowed to dry in the incubator prior to streaking of microorganisms onto the surface of the agar plates. Next, 100 μL of the microbial culture suspension in broth containing approximately 106 colony-forming units per mL as measured spectrophotometrically was streaked over the dried surface of the agar plate and spread uniformly using a sterilized glass rod and allowed to dry before applying the loaded disks. The chitosan-copper nanoparticle compounds were suspended in sterilized distilled water, and blank sterilized Whatman No 1 filter paper disks were loaded with the suspension. The loaded disks were applied carefully to the surface of the seeded agar plates using sterile forceps. The experiment was carried out in triplicate and the diameters of the zones of inhibition were measured after 24 hours of incubation at 37°C. Standard antimicrobial agents including nystatin (for yeast, 100 mg/mL), ampicillin (for Gram-negative bacteria, 100 mg/mL), and streptomycin (Gram-positive bacteria, 100 mg/mL) were used as controls.

Copper Oxide (CuO) Nanoparticles - Properties, Applications

As mentioned earlier, the effects of chitosan on the stability and antimicrobial properties of the synthesized chitosan-copper nanoparticles were evaluated. Prior to susceptibility testing, the synthesized nanoparticles were subjected to different methods of characterization to determine their purity. Samples containing various amounts of dispersant (0.05, 0.1, 0.2, or 0.5 wt%) differed with regard to the color of the nanoparticles obtained, ie, from light brown to deep red. This may be indicative of particle stability, as evidenced by the characterization methods. Nevertheless, the samples containing various chitosan concentrations did not display any significant difference in color throughout the different stages of the reaction. The green coloration of the chitosan-copper complex, obtained by addition of sodium hydroxide, did not differ over the 0.05–0.5 wt% range. A different pattern was observed for particle sizes and antimicrobial properties, with slight variation in susceptibility of the 0.2 wt% and 0.5 wt% nanoparticles.