If I'm not mistaken you want to explore a presence of two resonance for Au NRs (transverse and longitudinal) to distinguish them from other types of Au NPs. It may work to a certain extent but in practice it will be limited by practical considerations.

Let's say that you measure two samples with Uv-Vis-NIR. One gives you two peaks (say, somewhere around 510 nm and around 750 nm) and the other just one (say, around 520 nm OR 750 nm). You can say that the first solution likely contains Au NRs while the second one some OTHER type of Au NPs. Ans this may be almost correct if ideal conditions could be applied to most particle synthesis procedures.

The problem is that in some (don't want to say in most) protocols of synthesis of targeted Au NP shapes there is a certain uncontrolled and undesired fraction of Au NPs with other shapes. Obviously, this fraction can be seen in spectroscopy measurements by manifesting plasmon resonance features in a spectral range that is different from the expected one. The interpretation of such spectra in terms of a binary (YES/NO) answer to the question "Nanorods?" may be problematic.

So, it may work for protocols that are known to produce only a particular single shape of Au NPs. However, there are always times when something goes wrong in the lab.. Since you can't know a priori that it was or wasn't a case, I'd recommend always follow up with other characterization techniques (TEM, SEM, etc.)

Hope it helps,

Serge         

If I'm not mistaken you want to explore a presence of two resonance for Au NRs (transverse and longitudinal) to distinguish them from other types of Au NPs. It may work to a certain extent but in practice it will be limited by practical considerations.

Let's say that you measure two samples with Uv-Vis-NIR. One gives you two peaks (say, somewhere around 510 nm and around 750 nm) and the other just one (say, around 520 nm OR 750 nm). You can say that the first solution likely contains Au NRs while the second one some OTHER type of Au NPs. Ans this may be almost correct if ideal conditions could be applied to most particle synthesis procedures.

The problem is that in some (don't want to say in most) protocols of synthesis of targeted Au NP shapes there is a certain uncontrolled and undesired fraction of Au NPs with other shapes. Obviously, this fraction can be seen in spectroscopy measurements by manifesting plasmon resonance features in a spectral range that is different from the expected one. The interpretation of such spectra in terms of a binary (YES/NO) answer to the question "Nanorods?" may be problematic.

So, it may work for protocols that are known to produce only a particular single shape of Au NPs. However, there are always times when something goes wrong in the lab.. Since you can't know a priori that it was or wasn't a case, I'd recommend always follow up with other characterization techniques (TEM, SEM, etc.)

Hope it helps,

Serge         

thank you Serge sir for your valuable suggestion..

You can use polarization-resolved extinction microscopy. All you need is a wide-field transmission microscope with a polarizer, which can be turned in a few steps between 0 and 90 deg. Then you can measure the extinction cross-section of individual gold nanoparticles deposited on a coverslip, as as function of polarization. This way, you can estimate the size and elongation of each individual particle, and use it to analyse the ensemble. See the work done by my colleagues: http://langsrv.astro.cf.ac.uk/Crosssection/PayneAPL13.pdf

Thank you very much George...ill surely look into polarization-resolved extintion microscopy and keep you posted.