Silver nanoparticles: Green synthesis and their antimicrobial activities
Introduction
The application of nanoscale materials and structures, usually ranging from 1 to 100 nanometers (nm), is an emerging area of nanoscience and nanotechnology. Nanomaterials may provide solutions to technological and environmental challenges in the areas of solar energy conversion, catalysis, medicine, and water treatment [1], [2]. This increasing demand must be accompanied by “green” synthesis methods. In the global efforts to reduce generated hazardous waste, “green” chemistry and chemical processes are progressively integrating with modern developments in science and industry. Implementation of these sustainable processes should adopt the 12 fundamental principles of green chemistry [3], [4], [5], [6], [7]. These principles are geared to guide in minimizing the use of unsafe products and maximizing the efficiency of chemical processes. Hence, any synthetic route or chemical process should address these principles by using environmentally benign solvents and nontoxic chemicals [3].
Nanomaterials often show unique and considerably changed physical, chemical and biological properties compared to their macro scaled counterparts [8]. Synthesis of noble metal nanoparticles for applications such as catalysis, electronics, optics, environmental, and biotechnology is an area of constant interest [9], [10], [11], [12], [13], [14], [15]. Gold, silver, and copper have been used mostly for the synthesis of stable dispersions of nanoparticles, which are useful in areas such as photography, catalysis, biological labeling, photonics, optoelectronics and surface-enhanced Raman scattering (SERS) detection [16], [17]. Additionally, metal nanoparticles have a surface plasmon resonance absorption in the UV–Visible region. The surface plasmon band arises from the coherent existence of free electrons in the conduction band due to the small particle size [18], [19]. The band shift is dependent on the particle size, chemical surrounding, adsorbed species on the surface, and dielectric constant [20]. A unique characteristic of these synthesized metal particles is that a change in the absorbance or wavelength gives a measure of the particle size, shape, and interparticle properties [20], [21]. Moreover, functionalized, biocompatible and inert nanomaterials have potential applications in cancer diagnosis and therapy [22], [23], [24], [25], [26]. The target delivery of anticancer drugs has been done using nanomaterials [22]. With the use of fluorescent and magnetic nanocrystals, the detection and monitoring of tumor biomakers have been demonstrated [24], [25].
Generally, metal nanoparticles can be prepared and stabilized by physical and chemical methods; the chemical approach, such as chemical reduction, electrochemical techniques, and photochemical reduction is most widely used [27], [28]. Studies have shown that the size, morphology, stability and properties (chemical and physical) of the metal nanoparticles are strongly influenced by the experimental conditions, the kinetics of interaction of metal ions with reducing agents, and adsorption processes of stabilizing agent with metal nanoparticles [21], [22]. Hence, the design of a synthesis method in which the size, morphology, stability and properties are controlled has become a major field of interest [29].
Section snippets
Silver nanoparticles
Silver is widely known as a catalyst for the oxidation of methanol to formaldehyde and ethylene to ethylene oxide [30]. In the United States, more than 4 × 106 tons of silver were consumed in 2000. Colloidal silver is of particular interest because of distinctive properties, such as good conductivity, chemical stability, catalytic and antibacterial activity [31]. For example, silver colloids are useful substrates for surface enhanced spectroscopy (SERS), since it partly requires an electrically
Polysaccharide method
In this method, Ag NPs are prepared using water as an environmentally benign solvent and polysaccharides as a capping agent, or in some cases polysaccharides serve as both a reducing and a capping agent. For instance, synthesis of starch-Ag NPs was carried out with starch as a capping agent and β-d-glucose as a reducing agent in a gently heated system [7]. The starch in the solution mixture avoids use of relatively toxic organic solvents [56]. Additionally, the binding interactions between
Ag NPs and their incorporation into other materials
The unique properties of Ag NPs have been extended into a broader range of applications. Incorporation of Ag NPs with other materials is an attractive method of increasing compatibility for specific applications.
Antimicrobial activities
Silver is known for its antimicrobial properties and has been used for years in the medical field for antimicrobial applications and even has shown to prevent HIV binding to host cells [178], [183], [184], [185], [186]. Additionally, silver has been used in water and air filtration to eliminate microorganisms [187], [188], [189].
Human Health
Nanoparticles may have different effects on human health relative to bulk material from which they are produced [15]. Increase in biological activity of nanoparticles can be beneficial, detrimental or both. Many nanoparticles are small enough to have an access to skin, lungs, and brain [15], [231], [232]. Currently, no sufficient information is available on the adverse effects of nanoparticles on human health [233], but studies are forthcoming to address this subject [234], [235], [236], [237],
Concluding remarks
Several synthetic methods for Ag NPs using inexpensive and nontoxic compounds under water environments were summarized and experimental approaches under different conditions were given to control the morphology of the Ag particles. Rapid and green synthetic methods using extracts of bio-organisms have shown a great potential in Ag NP synthesis. However, understanding the mechanism by which biomolecules of these organisms are involved in synthesis is lacking. A progress in this area will give
Acknowledgment
We wish to thank three anonymous reviewers for their useful comments that greatly improved this paper.
References (260)
- et al.
J Colloid Interface Sci
(2001) - et al.
Mater Chem Phys
(2005) - et al.
Appl Catal A
(1999) - et al.
Mater Chem Phys
(2005) Radiat Phys Chem
(2003)- et al.
J Colloid Interface Sci
(1999) - et al.
Mater Chem Phys
(2000) - et al.
J Colloid Interface Sci
(2003) - et al.
J Petrol Sci Eng
(2005) - et al.
Carbohydr Res
(2004)
Carbohydr Res
Mat Chem Phys
Mater Chem Phys
Mater Chem Phys
Radiat Phys Chem
Radiat Phys Chem
Food Chem
Plant Sci
Chem Rev
ACSNano
Green Chemistry: Theory and Practice
Science
Science
Nature
J Am Chem Soc
Nano Lett
Langmuir
J Environ Sci Health A
J Environ Sci Health A
J Environ Sci Health A
J Environ Sci Health A
Environ Sci Technol
Green Chem
Phys Chem Chem Phys
Anal Chem
Chem Rev
J Am Chem Soc
Langmuir
Nature
Nature
Adv Drug Deliv Rev
Nat Biotechnol
Nat Biotechnol
Dig J Nanomater Biostruct
Acc Chem Res
Science
Chem Rev
Angew Chem Int Ed
Chem-Eur J
J Phys Chem
Cited by (3260)
Synthesis and characterization of zinc basic salt–loaded PVA-PEI polymeric composite for antimicrobial activity and triboelectric nanogenerator applications
2024, Sensors and Actuators A: PhysicalFacile synthesis and surface characterization of silver metal nanoparticles using Acorus calamus and its applications
2024, Inorganic Chemistry CommunicationsCancerous cell viability affected by synergism between electric pulses and a low dose of silver nanoparticle: An adaptive neuro-fuzzy inference system
2024, Medicine in Novel Technology and Devices