Nanoparticles act as an intermediate between phases and atoms which thermodynamics describe from completely opposite positions – for phases, only internal energy matters, while for atoms – only external energy does. For nanoparticles, both energies are relevant. Therefore, abovementioned unique properties of nanoparticles are caused by two factors: surface (high surface-to-bulk atoms ratio) and quantum-sized effects. The latter are especially significant when dimensions of solid nanoparticles are comparable with correlation radius of a physical phenomenon (free path length of electrons and phonons, size of magnetic domain or excitons etc.). Very high ratio of surface atoms to bulk ones: for nanoparticles which size is close to 3 nm, the ratio is about 50%, and for particles which size varies between 1.5 and 2 nm, this ratio is almost 80% (!). This results in their greatly enhanced catalytic activity for chemical and biochemical reactions. You can find more details in the book chapter:

Chapter 1. Nanoanalytics: Definitions, Classification, History, and ...

Nanoparticles act as an intermediate between phases and atoms which thermodynamics describe from completely opposite positions – for phases, only internal energy matters, while for atoms – only external energy does. For nanoparticles, both energies are relevant. Therefore, abovementioned unique properties of nanoparticles are caused by two factors: surface (high surface-to-bulk atoms ratio) and quantum-sized effects. The latter are especially significant when dimensions of solid nanoparticles are comparable with correlation radius of a physical phenomenon (free path length of electrons and phonons, size of magnetic domain or excitons etc.). Very high ratio of surface atoms to bulk ones: for nanoparticles which size is close to 3 nm, the ratio is about 50%, and for particles which size varies between 1.5 and 2 nm, this ratio is almost 80% (!). This results in their greatly enhanced catalytic activity for chemical and biochemical reactions. You can find more details in the book chapter:

Chapter 1. Nanoanalytics: Definitions, Classification, History, and ...

The identity of the particles, regardless their size, is totally different from that of ions, thus, it is not correct to consider the ions as "the particles in their smallest size".

As you know, the structure of the ions and the particles are different that is why their properties, behavior, and identification are different.

Explanation from Shtykov is a good detail for nanoparticles and Desher answer States the non Comparabilities between the two. For more understanding the nanoparticles in specific and nanosize in general I suggest to see the following power point presentation

"Solid Surface and Nanoscale materials Structure" M. S. Omar Presentation · July 2016 with 156 Reads DOI: 10.13140/RG.2.2.31947.59684 Charmo, University of Charmo, University of Salahaddin, DOI:10.13140/RG.2.2.31947.59684

We consume ions of Na + and ions of Mg +, and not nanoparticles of Na and Mg. What in this case are considered better ? There are other examples. You probably wanted to ask something else. What is the relationship between ions and nanoparticles? When you get a phase (a piece of copper 1 mol) from copper ions by a half-reaction reduction, you must go through the path Cu + -> Cu (atom) -> Cu (cluster) -> Cu nanoparticles) -> Cu (phase). There are methods for obtaining these substances and they are needed for various technologies. In an aqueous solution from ions, twins (Cu+ Cl_)and tees (Cl-Cu2+Cl- ) can arise.

Thanks yuri for the giving relevant information and thanks everybody for the valuable information..

Abhimanyu,

It sounds like you are talking about the formation of colloidal particles from salt solutions by electrolysis such as for creating silver colloids.

In applications such as nasal sprays, topical antiviral formulations etc, colloidal particles are preferable for a number of reasons. They diffuse much more slowly than free ions which means they remain in the location you want them to be. They act like a large reservoir of concentrated silver ions. In the case of nasal/throat sprays, they will impact and remain on the mucous membranes whereas as simple salt solutions will either just be inhaled then exhaled or will drain very quickly into the stomach.

I hope this gives you some ideas.

John.

Thanks john for the relevant information.. could you please elaborate or give reference of some article where such nanoparticles has been used for depot therapy for different purpose...

I don't fully understand "where such nanoparticles has been used for depot therapy for different purpose". Can you explain a bit more?

actually I also want to know the same thing as you mentioned in your earlier answer that they diffuse much more slowly than free ions which means they remain in the location you want them to be. it means that nanoparticles may be choice of depot therapy due to its slow release and localized action. actually I have extrapolated your view... it may be that I have misunderstood your opinion..

In the context of something like delivering particles to the nose or the lung, there is an additional factor that plays a key role in getting the particles to deposit in the correct region in the first place. It relates to the size of the particles - more specifically the aerodynamic size. Whether you are inhaling particles from a medical device or from exhaust, the particles are entrained in an airstream. When that airstream passes along a bend such as the throat or in the nostrils, the smaller/lighter particles will stay entrained in the air whereas larger particles will maintain their trajectory due to momentum and hit whatever the surface happens to be. Typically, particles of say 3-5um are most preferable for delivery to the middle lung. Historically, such particles have been made simply by milling large particles (micronizing). There is now a lot of interest in making appropriately sized particles from nanoparticle composites. One reason is that the final particles can be made to be porous. Because it is the aerodynamic size that matters, larger less dense particles behave the same as smaller more dense ones and they are easier to process.

Generally, the surface that the particles deposit on in the airway is mucous. Nanoparticles (and large assemblies of them) will become quite immobilized and, hopefully, will remain in the same general location while it dissolves (or whatever it needs to do). For a simple solution, where the material deposits is driven more by the size of the droplets being inhaled. There are too many different kinds of device to generate a suitable aerosol of droplets/particles to describe here. A solution depositing on mucous maybe able to diffuse faster across it to get to the tissue beyond but, of course, the molecule you are trying to deposit needs to be soluble. Most drugs are "poorly adsorbed, low solubility" and so nanoparticles are important because of the ability to control the nature of the interface between the particle and the liquid.

John.

that's right john...definitely particle size is an important factor in bioavailability of drugs. also in the case of oral delivery, definite size particles are taken through M cells of small intestine especially size having size less then 5 um are taken through M cells and delivered to wandering macrophages which ultimately reaches the systemic circulation..

Single nanopaarticles can produce hundreds of ions

In photocatalysis, there is also another effect: the plasmon excitation which allows catalysts like TiO2 to become very active under Visible excitation when mixed with Ag and/or Au nanoparticles.

Think of this (iron just for example): the agglomerated Iron nanpoarticles ar smaller in size relative to iron metal (the bulk material we deal with in labs) but larger compared to the Iron atom itself.

Whats there in size? it is not smaller better or bigger is not active. Nano-particles are particles and not ions. Both species are different principally in their existence. (Eg Ag+ ions is not same as Ag nanoparticles (NPs) chemically.

But more to size its band gap which plays role in catalysis, the orientation of facets exposed from different shape of NPs needs a consideration when correlation is made for its activity.