Size of nanostructure is one of the key factors, but I'm curious to know the exact chemistry of ligand. Some ligands yields Fluorescent clusters, but some are not. What should be the major aspects of ligand for designing fluorescent nanoclusters?
First I prefer to define nanoclusters from nanoparticles as the small particles with diameter less than 2 nm. However, there is no clear demarcation, nanoparticles exhibit plasmonics due to collective oscillations of electrons.
The fluorescence mechanism of the nanoclusters is poorly understood. There are at least two mechanism suggested:
1. Intrinsic quantization of metal core due to small size. i.e electronic energy states are discretized.
2. And there is formation of surface states governed by the chemical interaction between the metal core or encapsulating matrix. Some kind of new electronic states, which supports electronic transition such as absorption and fluorescence.
Fluorescence of nanoparticles depends on their metal core (as we know naoparticles have two different building block: one is metal core and other is capping motifs, which is combination of metal and ligands, to protect the core). If metal core is small enough as like Ag32/Ag15 they can fluorescent.
Yeah, I know this, metals like Au,Ag and Cu show fluorescence if they have smaller NPs (NCs) with a suitable ligand, as far as I know the ligand with rich electron pairs gives good fluorescence. But this is not true always, also the color of the fluorescence is different even we are using same ligand.
@halasya , Tyndall effect is not there in bigger NPs? or changing the ligand will change Tyndall effect? come on, ans only if you know
As you said about ligands, Ligand is important to form metal core. For an example if small chain water soluble thiol ligands are used as capping ligand, then they form series of nps. whereas it is easy to synthesized single sized nps from aromatic thiol ligands like p-MBA for Ag44 or Au102, but they are not fluroscent due to big metal core. If ligand is small then it will form bigger nps, whereas if ligand is bigger it can form fluroscent nps e.g., Ag32 or Ag15 with glutathione. I hope this can help. Mr. Abbas, you also think about Mr. Halasya's suggestion. Tyndall effect can explain about any light scattering properties of particles though.
Wonderful that we can learn from questions that leads Zaker's answer . have a wonderful New Year 2017.
First I prefer to define nanoclusters from nanoparticles as the small particles with diameter less than 2 nm. However, there is no clear demarcation, nanoparticles exhibit plasmonics due to collective oscillations of electrons.
The fluorescence mechanism of the nanoclusters is poorly understood. There are at least two mechanism suggested:
1. Intrinsic quantization of metal core due to small size. i.e electronic energy states are discretized.
2. And there is formation of surface states governed by the chemical interaction between the metal core or encapsulating matrix. Some kind of new electronic states, which supports electronic transition such as absorption and fluorescence.
Thanks @Puskal Kunwar ,
I used broader term to convey my question to massive audience, you are right about definition of NCs. Quantum confinement is really one of major factor, but many times we see even NCs of same sizes, some show fluorescence and some don't. The next important parameter is ligand. A ligand rich of lone pairs etc.
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructured Materials
- Nanoparticles