Silver nanoparticles applications

Ahamed, M., AlSalhi, M.S., Siddiqui, M.K.J., 2010. Silver nanoparticle applications and human health. Clin. Chim. Acta 411, 1841—1848. 

In this chapter, we discuss first how the silver clusters relate to silver atoms and silver nanoparticles. Then we overview the formation of fluorescent silver clusters in aqueous solution, using silver salts as precursors and various scaffolds as stabilizers. Finally we discuss applications of silver clusters in fluorescent labeling of biological tissues, and their use as fluorescent probes for sensing of molecules. 

In 2007, Dickson et al. found that it is possible to stain fixed cells with fluorescent silver clusters instead of silver nanoparticles by tuning the staining conditions [57]. The new approach consists of staining fixed cells with a low concentrated silver nitrate solution 20-100 mM, within 20 h at ambient conditions, and reducing the silver by photoactivation, with the result of small silver clusters that present a broad emission band between 500 and 700 nm (Fig. 8a-d). The discovery that fluorescent silver clusters can be generated by photoactivation of cells fed with silver salt, opens up new paths for the application of silver clusters in biological systems. 

Wei G, Wang L, Liu Z, Song Y, Sun L, Yang T, Li Z (2005) DNA-network-templated self-assembly of silver nanoparticles and their application in surface-enhanced raman scattering. J Phys Chem B 109 23941-23947... 

Lochner, N., Wirth, M., Pittner, F., Gabor, F., Preparation, characterization and application of artificial Caco-2 cell surfaces in the silver nanoparticle enhanced fluorescence technique. J Control Release 89, 249-259 (2003). 

Vigneshwaran et al. (2006) s mthesized stable silver nanoparticles by using soluble starch as both the reducing and stabilizing agents. The use of environmentally benign and renewable materials like soluble starch offers numerous benefits of eco-friendliness and compatibility for pharmaceutical and biomedical applications. 

Despite the pronounced antimicrobial effect, silver ions have only limited usefulness as an antimiaobial agent in applications such as medicine, clothing, and household products. This is due to their rapid binding to or inactivating by components of the medium. This limitation can be overcome by using as an antimicrobial agent, silver nanoparticles, which continuously release Ag ions in sufficient concentration [16]. 

Silver nanoparticles synthesized by a cost-effective three-stage electrochemical technique have demonstrated great promise as antimicrobial agents. Nanosilver was less effective against E. coli, S. aureus, B. subtilis and P. phoeniceum compared to silver ions. However silver nanoparticles have prolonged bactericidal effect as a result of continuous release of Ag ions in sufficient concentration and thus nanoparticles can be more suitable in some bactericidal applications. The synthesized silver nanoparticles added to water paints or cotton fabrics have demonstrated a pronounced antibacterial/antifungal effect, despite the fact that they tend to agglomerate into clusters up to 200 nm. 

In applications where self-polishing is not possible, the combination of a microbe-repelling surface and a release system seems to be desirable. One example of a design for such a surface is shown in Fig. 8. The depicted coating is based on a hydrophilic polymer network that contains polyethyleneimine crosslinkers, which are capable of selectively taking up silver ions and acting as a template for silver nanoparticles [90], This reloadable co-network was surface-modified with PEG,... 

The electrodeposition of silver from chloroaluminate ionic liquids has been studied by several authors [45-47], Katayama et al. [48] reported that the room-temperature ionic liquid l-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]BF4) is applicable as an alternative electroplating bath for silver. The ionic liquid [EMIM]BF4 is superior to the chloroaluminate systems since the electrodeposition of silver can be performed without contamination of aluminum. Electrodeposition of silver in the ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) and l-butyl-3-methylimidazoliumhexafluorophosphate was also reported [49], Recently we showed that isolated silver nanoparticles can be deposited on the surface of the ionic liquid Tbutyl-3-methylimidazolium trifluoromethylsulfonate ([BMIMJTfO) by electrochemical reduction with free electrons from low-temperature plasma [50] (see Chapter 10). This unusual reaction represents a novel electrochemical process, leading to the reproducible growth of nanoscale materials. In our experience silver is quite easy to deposit in many air- and water-stable ionic liquids. 

Silver nanoparticles have also been prepared in aqueous solution using Capsicum annum L. extract. It is thought in this example that Ag(i) is reduced to Ag(0) by proteins within the natural extract and that these proteins also act to stabilize the particles. The size of the nanoparticles was found to increase with reaction time 5 h, 10 2 nm 9 h, 25 3 nm 13 h, 40 5 nm. It should be noted that gold and silver nanoparticles have potential pharmaceutical and biomedical applications, and it is therefore highly desirable to use natural stabilizing agents (starch, glucose or plant extracts) and biocompatible solvents such as water. 

Muthu, P., Gryczynski, I., Gryczynski, Z., Talent, J., Akopova 1., Jain, K., Borejdo, J. (2008). Decreasing photobleaching by silver nanoparticles on metal surfaces application to muscle myofibrils. J. Biomed Opt. 13 014023. 

Metal nanoparticles have attracted considerable interest due to their properties and applications related to size effects, which can be appropriately studied in the framework of nanophotonics [1]. Metal nanoparticles such as silver, gold and copper can scatter light elastically with remarkable efficiency because of a collective resonance of the conduction electrons in the metal (i.e., the Dipole Plasmon Resonance or Localized Surface Plasmon Resonance). Plasmonics is quickly becoming a dominant science-based technology for the twenty-first century, with enormous potential in the fields of optical computing, novel optical devices, and more recently, biological and medical research [2]. In particular, silver nanoparticles have attracted particular interest due to their applications in fluorescence enhancement [3-5]. 

Size-tunable and water-soluble silver nanoparticles have been successfully synthesized with the assistance of glutathione. The optical properties of surface-modifiable silver nanoparticles depend on their size and the surface modification. Silver nanoparticles with an average diameter of 6 run effectively suppress the proliferation of human leukemia cells in the dose- and time-dependent manners, suggesting their promising application in cancer therapy [13]. 

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