For small silver nanoparticles UV spectrum depends on size!

What is the difference between Ag (ionized) and Ag(net charge) in UV Spectroscopy spectrum ?

Spherical Ag nanoparticles with diameter smaller than about 100 nm show a plasmonic resonance in the UV-Vis spectra, centred between 400 and 470-500 nm depending on the size and, to somewhat extent, also on the surrounding (liquid) medium - Mie theory. For example, 10 nm nanoparticles in water resonate at about 400-410 nm. Larger particles will show a red-shift. You must also take into the due account the dominant shape of nanoparticles. If you have a significant population of disk-shaped, or other non-spherically-shaped, nanoparticles, you may expect peaked contribution at wavelengths even larger than 500 nm.

As a rule, increasing the nanoparticle size, or occurring aggregation of nanoparticles, will cause a sensible broadening of the plasmonic band towards larger wavelengths.

Purely ionic silver may show a contribution in the near UV range, around 300 nm wavelength.

I have pick around 411.5-412nm and 200-300nm.

If your peak is narrow I guess you got spherical nanoparticles in the 10-20 nm diameter range. The low wavelength peak may be indicative of some ionic silver remaining, but before saying anything more you should be sure that the spectral analysis procedure you followed did not modyfy the lineshape (background elimination may cause strange and unrealistic contribution in the UV range)

Please see my articles; " Hydroxy propyl cellulose capped silver nanoparticles produced by simple dialysis process" and "Synthesis, characterization and mechanical properties of nylon–silver composite nanofibers prepared by electrospinning"

They are already uploaded in RG.

Best Regards

Lijo

What is the main peak in the XRD spectrum of the silver nanoparticles?

So, can i say that, any peak after 400nm upto 500nm, given the situation tat Silver nitrate was used., the peak would represent Silver nanoparticle?

But, the size of the synthesized particle will determine the exact position of the peak?

Also,

I got a peak at jus after 405 and with different biological process, i got peaks at 426nm, 423nm, ,, Can this be Nanoparticles or differing sizes?

If so, then i also have a peak before 400nm,, to be exact, 397nm. What could this be?

Thanks in Advance

yes.I have a peack around 300nm(narrow)and 420 nm.

Thanks sachindri

 Hello everybody,

I know it´s a bit late but I would like to make a question about the UV-VIS spectrum of silver nanoparticles. I started a project to synthesize silver nanoparticles in the plant extracts and I have two peaks in my spectrum, one narrow at 300nm and another wide at 400 nm. What I understood in your comments is that the peak at 300 nm is because of the silver that didn´t react and the peak at 400 nm is because of the silver nanoparticles so, my question is: Should the peak at 300 nm decrease with the time and the peak at 400 nm increase? Moreover, What does it mean to have a wide peak at 400 nm and a narrow peak at 300 nm?

Kind regards

María Iglesias

i just did an experiment yesterday and found a peak at 390nm, but i then agglomerated the particles and i had a right/red shift by 10nm, does this make sense?

The absorbance also shifted down and im not sure if this should be happening

Regards

Alpha

Hallo Alpha Ubisi.

It would be better having some more info about your samples, as for example the nanopartcle synthesis method you used, the solvent in which your nanoparticles are suspended, the presence of other components and by-products. Shifting of the absorption peak to about 400 nm may be indicative of a somewhat marked nanoparticle growth, but if aggregation occurs you should face a larger shift plus a wide broadening of the peak towards larger wavelengths, and an overall lowering of the spectrum. Also precipitation may occur that would reduce the absorption intensity as well. I suggest you to keep monitoring your original sample and see if absorption is further red-shifting and perhaps broadening. That would be evidence of instability and aggregation. On the other side, if your spectra are stable and keep showing a 400 nm peak, that would suggest completion of a slow nanoparticle synthesis in a stable suspension

Hi Ramin,you must have the basic idea of spectrophotometery that absorption depends on sizes ,shape ,fabrication,state of agglomeration or aggregation of nanoparticles,but in more simply your range varies with the size ,uv ranges mean small size NP's (200-380nm),larger NP's contributes visible (400-780nm),largest NP's absorb above 780nm( IR region).hope it will helps you

I got peak from 390 nm to 470 nm based on the extract used for nanoparticles syn thesis

Dear RG's peak near 390 nm indicate small nanoparticles(1 to 5 nm) that mostly collect few more Ag atoms from the system and become larger (10 to below 100 nm) which causes red shift more or less 470 nm, if peak raised above this range indicate aggregation or even precipitation(this is silver now not Ag-Nanoparticles),you can avoid this using suitable surfactant or capping agent.

If peak give blue shift below 390 nm it means your system have some others participants (impurities,organic species,solvent etc) causing blue shift according to my personal experience.

Hope you will get better idea 

Regard 

Muhammad imran khattak 

What is the absorption of silver nitrate alone?

What is the absorption of silver nitrate+PVP alone?

How do I find that The reaction is complete?

The silver nitrate peaks sometimes start around 300 nm when every you are performing UV-Vis Spectroscopy. Most times it comes around 380 to 450 nm but the appearance of a sharp peak around 420 nm indicates the synthesis of silver nanoparticles which you can confirm their characteristic features using SEM, TEM, EDX, XRD, TEM, HRTEM.

Hey ,Giuseppe. Yesterday I did synthesis of silver nanoparticles.One of my silver nanoparticle uv peak at 534nm and onther one is at 404 nm.Are these uv peaks ok for silver nanoparticles..and could you please tell me the shapes of silver nps at both peaks..

the peak for silver nanoparticles comes around 420 nm if its smaller in size and the absorption values is high it also tells that the particles are smaller in size and have small width, presence of other peaks near 450-470 nm may be due to larger particles but they are in the range of 100-200 nm further shift in the curve above 470 nm indicates precipitation and hence no nanoparticles can be said to form if the peaks are above the range of 480 nm or so.

Most likely from 420-450 nm.

Silver nitrate usually show peak at 220 nm

420nm

Normally AgNPs will peak at ~420 nm, however, it would rely on the size and shape that is often found to alter depending on the surrounding environment and its interaction with the AgNPs. Here is a recent study that might give you more insight:

Article Biosynthetic Conversion of Ag + to highly Stable Ag 0 Nanopa...

what is the exact temperature to synthesize AgNP without aggregation.

Absorption peak of silver nanoparticles is at about 400 nm.

Depending upon size and morphology, Ag Np absorb in range 380-470 nm. Smaller the wavelength of absorption smaller is the size and vice versa. Absorption at 460 nm means particles are big but still in nano range but absorption above 470 nm cues aggregation and precipitation then it is just silver.

Good answer from Mudasir Dar

But there are a few clarifications.

In some cases peak at long-wave region may be caused by interaction of stabilizer with nanoparticle surface. For example, for small (~ 5 nm) AgNPs stabilized by polyacrylates we observed peak at ~500-540 nm ( https://doi.org/10.1007/s00396-019-04488-4)

At the same time AgNPs with non-spherical shape may demonstrate two-peak spectrum, see https://doi.org/10.1070/RC2008v077n03ABEH003751 for example.

Best wishes,

Liliya

Dear Muhammad Ismail

As for AgNO3. I was found the article that demonstrate a peak at ~300 nm for AgNO3. See https://doi.org/10.1007/s00339-011-6499-5

With kind regards,

Liliya

Ag NPs colloidal solution have a characteristic peak at about 390-420 nm using UV-Vis spectrophotometer. The intensity of the peak is proportional to the concentration of the Ag NPs of the measured solution.

What should be done when the absorption is more than 1 during the study in UV spectrum of silver nanoparticles?