Nanoparticle-based biocides

Typical SAMs, such as alkanethiols reacted with gold and alkylsilanes reacted with silica, have been studied extensively, as demonstrated by numerous reports in the literature/ Studies of the properties of n-alkanoic acids reacted with oxidized aluminium and alkyl phosphonic acids with tantalum oxide ° surfaces can also be found in the literature. However, although some information is available in the literature on the behaviour of phosphonic acid SAMs, which are one of the important classes of self-assembling organic molecules on a range of metal oxide surfaces, there is not much information reported on phosphonate SAMs on Cu in the public domain. SAMs can be formed on various surfaces such as nickel oxide, copper oxide, iron oxide, etc. 

Nickel is a key component in the electronics industry, where it is utilized in diodes, wires and switches and as an important alloying constituent in many biomaterials. In spite of the spontaneous formation of a nickel oxide layer under ambient conditions, the use of nickel can cause corrosion-related issnes. 

In electronic applications, the corrosion of the surface leads to reduced performance and device lifetime. In biomedical applications, corrosion leads to Ni ion release into the body and nickel toxicity. Therefore, forming an organic thin film on nickel oxide may serve as an effective barrier to conosioa This is in large part due to the flexibihty that SAMs offer they form stracturally well-defined films on the solid surface and they can be deposited by a nnmber of easy techniques such as immersing the substrate in solution, aerosol spraying and vapour deposition. Currently, immersion coating is the most popular and widely studied method for monolayer formation.  

SAMs of allgrlphosphonic acids (butylphosphonic acid, octylphosphonic acid, undecylphosphonic acid and octadecylphosphonic acid) on native niekel oxide allow substrates to be functionalized easily. Monolayer formation has been investigated by diffuse reflectance Fourier transform infrared spectroscopy, non-contact mode atomic force microscopy, contact angle measurements and matrix-assisted laser desorption ionization mass spectrometry. Cyclic voltammetry and electrochemical impedance spectroscopy studies showed that the monolayer increased surface resistance to oxidation. 

Formation of SAMs on Cu substrates has attracted attention for both fundamental and apphed research, e.g. corrosion inhibition of Cu used in microelectronic device fabrication. Cu is destined to replace A1 alloy as the principal very-large 

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Silver-based biocides are also gaining a share in plastics markets, especially in Japan, where silver ions supported in inorganic matrix/substrates (such as zeolites or alumina-silica), are often used in hospital settings. Silver-nanoparticle-coated PU foams have been shown to be effective antibacterial water filters [46]. 

Copper at low concentrations below 2 mg Cu" /kg serve as a co-factor for metalloproteinase and enzymes, hence, it has potent apphcation of antimicrobial properties. Environmental Protection Agency (EPA) of the United States approved the registration of copper based alloys on the claim that they reduce microbial infections and confirmed the antimicrobial efficacy ((http // www.epa.gov/pesticides/factsheets/copper-alloy-products.htm). Nano-sized ZnO particles have biocidal activity and several advantages over the silver nanoparticles. They have low cost, white appearance, high versatility, and doping ability with several inorganic carriers and UV blocking property. 

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