Based on your protocol, how would you expect silver nanoparticles to form? you have a silver salt and a capping agent, but no reducing agent to reduce Ag+ to metallic silver. what is the colour of your UV-Vis samples? round silver nanoparticles in water should exhibit a plasmon peak around 400 nm (and at higher wavelengths depending on their size) but if you have a very complex sample, with different components that absorb in various regions of the visible spectrum, then i think it is unlikely you'd be able to distinguish the silver nanoparticles from everything else.

Hi,

I can see the effort that you have making for your experiment, let me tell you something, it seems that you have succeed the synthesis  by assistance of the bacteria, please try to dilute your samples when you carried out your UV-Vis and try to look for every 90mn of your cultures it gives you the increases of the obtained NPs because after 24h the concentration can be high and the absorbance will be cumulative and you will not be able to study the difference between your samples. I have joint for you a paper that you can identify AgNPs using UV-Vis (it is 430nm +/-10nm)

http://esatjournals.net/ijret/2014v03/i05/IJRET20140305158.pdf

UV-Vis spectra does not give you the AgNPs demonstration. As Teodora Miclaus said, you have a capping agent (PVP) and a precursor agent (silver nitrate), but a reducing agent is usually required. You need some complemetary techniques to ensure the AgNPs formation, such as TEM microscopy or XRD. 

Hi,

i agree with Dr. Hidouri , it's best idea, you must try to dilute your samples.

Regards.

Dear Sayedur Rahman, it is definitely you are doing very nice job in the field. What do you what to characterize by UV-Vis? You can use the alternative methods to identify your nanoparticles like light scattering (esp. dynamic light scattering) and TEM to give the clear picture of your products  based on size and/or shape.

From UV-Vis spectra you can observe the dispersity ranges of your products, which is clearly seen in your presented spectra. Read some comments from

https://www.researchgate.net/post/How_can_I_calculate_the_size_of_AuNPs_by_UV-Spectra2?tpr_view=PReFSldLeetghAUR0ReDmsVdAf18Q0O8qV5O_1

Dear Rahman

I saw your UV-Vis spectrum.

(a) In this spectra you cant identified Ag(0) Absorption spectra clearly, but there is silver Nps spectra in aggregated form.

for conformation of Ag (0) formation, you must do absorption spectra for : 

1) endophyte solution

2) endophyte solution and PVP

3) endophyte solution and AgNO3

4) PVP + AgnO3

5) endophyte solution and PVP + AgnO3

Then you compression all spectra, if you got some change in abs spectra in rage 390 to 500 nm, this range for Ag(0).

(b) 2nd thing also you do XRD ( 2-80 degree ) after that

(c) TEM, it may be despersed NPs and Aggregated NPs 

(d) By colour change also give some idea for formation of Ag(0). (yellow or red)

.

Dear, Md. Sayedur

the procedure you applied to systhesize Ag Nps is correct. here PVP will act as a reducing as well as stabilizing agent. according to my knowledge you can identify the formation of Ag Nps by observing the color of the solution. it will gradually turned from colorless to yellow and finally brown color solution which indicate the presence of Ag Nps. if you measure the absorbency of this solution it will definitely give a strong absortion peak in between 390-430 nm which is the characteristic absorption peak for Ag Nps depending on the shape of the Ag Nps. from your UV diagrams it can be concluded that Ag NPs is formed but may be in lower ratio. but i suggest you to prepare Ag Nps only by using bacteria alone not by using PVP. 

Best of luck. hope my ans will satisfy you. have a nice day.

In my opinion, the nanoparticles were formed in day 1 (probably you have large size dispersion) and then aggregate inday 2 and 3, in all samples. To obtain more risolved spectra, you have to diluite your suspensions.

Best wishes.

Hi Sayedur Rahman,

As far as I know, Ag nanoparticles (spherical, uniform) typically have clear and sharp absorption peak around 420 nm ( can be slightly blue/red shift depending on the size) This is correspond to their plasmon resonance.

From your protocol, it seems you used bacteria to synthesize the Ag NPs. This is one of the alternative. Otherwise, you can use also reducing agent like NaBH4.

Your UV-Vis absorption spectras show peaks around 420nm. I think you obtain the Ag NPs. The broad peak at wavelength

I prepared silver nanoparticles with PVP addition and there is a sharp peak usually between 400-410 nm

Although PVP could be used as stabilizing agent, I think it is more pertinent when it is necessary to have directional growth of silver seed. PVP helps to passivate faces while leaving faces for growth. That's why people commonly use it for nanowire synthesis.

I would suggest to use Alcalyamine and cationic surfactant for silver nanoparticle synthesis.  

Try to do sampling at interval of 18 hrs,22 hrs 24 hrs and so on. 

If you can do DLS(Average particle size analyzer) or NanoSight (exact particle size analyzer) for your study that will be much useful.

Otherwise go for SEM.

UV visible will not give you  exact idea about how much aggregation of NPs has occurred.

Hi,

       Silver nanoparticles shows a clear and sharp peak 400to 420 nm, your data does not shows these clear peaks . see the image attached.

 Silver nano particle has UV- Vis band  at 408 nm 

According to your images attached, nanoparticle synthesis is better on 3rd day. But noise overcomes the presence of silver nanoparticles. Impurities may present and interfere with the peaks. sharp curve can be obtained only in fresh samples. Refrigerate them after proper time interval of incubation if u cant take the reading immediately. Dilution may also be required. Consider these while synthesizing AgNPs. Go for XRD studies where you can get the peak of silver exactly showing the presence of AgNPs

From the images it is clear that your sample is concentrated. Before taking spectra dilute your sample so that its absorption should come less than 2. As soon as the growth starts the color of solution changes from light brown to brown. Take spectra after span of 1 hr.

Remember the dilution factor.

I hope this will help.

I think in your image there is hardly any indication of presence of silver nanoparticles. As suggested by other I also suggest you first dilute your sample so that absorbance value of colloidal solution less than 1 and then check the peak if you find any clear peak in the range of 400-450 then you can think about formation of silver nanoparticles. If your particles sizes are found to be small then you will find peak around 400-420 nm and if the it is larger then peak max red shifted.

All the best.

I add 0.1 from crude cellulase to 9.9 ml silver nitrare , the solution be ok after 10 min >>>the color change .. however after 2 h I found something in solution ( see the picture ) 

what is the reason ? and what is this ? 

anothe Q: 

what the blank can i use when i check nanoparticle by UV-VIS spectro? 

there is a colour change due to AgNP synthesis (dark brown). this can be confirmed by peak formation at 400 - 450 nm. The particles may have been formed even before 24 hours.

I'm doing this research about silver nanoparticles. I use exopolysacharide from Bacillus subtilis as reducing and stabilizing agent. uv vis spectra analysis in my research shows that peak around at 320-345 nm. what i going to do about my research? i'm very confused.

Dear Dwi,

This peak is not in the spectrum range for silver nanoparticles. May be you need to do electron microscopy or DLS to see if the silver nanoparticles is already formed or not. 

Dear Md. Sayedur if color of the solution changed to redish brown and it shows a UV absorbance at 420 nm then you can confirm that Ag NPs are formed in your reaction mixture. Though some times absorbance spectra may vary from 390 nm to 450 nm also. I am attaching one of my publication with this answer so that this answer becomes relevant to you. Best of luck.   

Dear Mohamed Shaalan

I've done analysis with SEM and the result shows the silver  particles size around 80-100 nm.

Dilute the solution about 5 times of your current solution then take the UV-vis spectra. If the color of your solution is orange/brown then it is the indication for the silver nanoparticle formation.

Dear Akreama Aki

I've diluted until 3 times before take to the Uv-Vis Spectra. But, in analysis with SEM, the result shows that there are agglomeration form in particles. Maybe, this is affecting my uv-vis spectra analysis.

Recently I used photo treatment under sunlight ( 85 - 95 k lux) with a 2% extracellar filtrate to 1 mM of AgNO3 solution. AgNPs formation was confirmed within 15 minutes. There I used no PVP as fixing material. Therefore, promising results from photo treatment!

Dear Sir

First it seems there are agglomeration of AgNO3.  

Dear Sir

First it seems there are agglomeration of AgNO3.  

It seems you have agglomeration

Dear all,

I want to synthesize silver nanoparticles. 

I got the UV-Vis spectrum as attached in the file.

Does anyone please help me to identify the formation of AgNPs in the solution media?

Thanks!

Dear Mr Huu

Please  It seem you got silver nanoparticles because  the band is between  370 – 385 nm . How ever you dont  have monodisperse particles. Please change the pH, concentraion and the temperature,. Also see

https://www.researchgate.net/publication/282176556

: https://www.researchgate.net/publication/282249006

Good Luck 

Ahmed Moosa

Article Green Synthesis of Silver Nanoparticles using Spent Tea Leav...

Article Process Parameters for Green Synthesis of Silver Nanoparticl...

The silver nitrate peaks sometimes start around 300 nm whenever 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 .

Moreover, when you have peaks like these within these ranges you have to dilute your synthesized nanoparticle very well.

This kind of sharp peak will be there at around 420 nm if nanoparticles are being formed, although this graph shows that there are larger particles too in this due to which there are peaks between 450-470 nm causing the red shift.

Hi, here are some general tips for making silver nanoparticles.

First is to make sure all glassware/ containers used are super clean. For glassware I would do Aqua Regia for 20 minutes then rinse 30 times with city water, 32 times with distilled water, and 17 times with deionized water.

Second, make sure the AgNO3 doesn't decompose since it is light sensitive. I would prevent light from hitting the solution (eg use electrical tape or tin foil on containers).

Good luck!

Concentration of AgNO3 is very low. Used upto 10 mM.

Use dilute concentration of your nanoparticles in cuvette

Yes the uploaded spectra show very noisy peak

Dear Ismail,

No doubt, that you have synthesized the silver nanoparticles. But you UV-spectra seems very noisy which could be avoided by diluting your parent AgNPs solution.

After dilution you may find the UV-spectra in the wavelength range of 400-500 nm.

Very hardly you will find the UV-spectra below 400 nm because it is observed only when the particles are very small (~10 nm or lesser than that).

Use diluted solution

Surface plasmon resonance occurs at 420-450nm as indicative of silver Nanoparticles formation

• diluting the AgNp solution will remove noise.

Surface plasmon resonance(SPR) occurs at 400-480 nm as indicates of Ag-NPs formation.

I prepared copper/starch nanocomposite using medicinal plant as a reducing agent. How I prepare a composite solution for uv-vis measurment or which solvent is exactly dissolve my sample?

It is obvious that your particles have aggregated because the uv spectrum is hasn‘t had one peak I have found that this article might be helpful

https://nanocomposix.com/pages/silver-nanoparticles-optical-properties#target

You got AgNPs but you need dilution of your AgNPs solution.

https://www.researchgate.net/project/Green-Synthesis-of-Silver-Nanoparticles-using-Spent-Tea-Leaves-Extract-with-Atomic-Force-Microscopy

dear Md. Sayedur Rahman

i think you should record a spectra for a solution that contain every thing you use except silver nitrate as baseline

so many peaks in your records will disappear

and one peak which indicate the formation of silver nanoparticles will appear clearly in the range 390- 500 nm

Dilute it you will get clear peak..try it..

Agree. Dilution will decrease the noise

you all are correct and spoken well given adequate answers to the question...one more question, what would u say if you see a peak at 262nm and not 420nm?

you can get further info here

https://www.nature.com/articles/srep45154/figures/2

thanks

The UV-Vis spectrum shows distinguishable surface plasmonic resonance (SPR) absorption peaks at about 430 nm for the samples containing different amount of silver salt. The SPR peaks indicate the existence of silver nanoparticles.

I totally agree with Mehrdad Khatami

Please see

UV-Vis peak of AgNPs is 370 – 385 nm . The SPR peak is shifted toward the shorter wavelength with a decrease in the absorbance due to increasing in destabilization of the particles. Furthermore a decreased absorbance may be due to increased particle aggregation and precipitation.

please see

https://www.researchgate.net/publication/282249006

Open-source UV-Vis Spectroscopy Library for Nanomaterials,

https://www.instanano.com/2021/01/uv-vis-open-source-reference-liberary.html

l agree with the answer of Mehrdad Khatami.

390-470nm

How to dissolve silver nanoparticles for proper reading in uv Vis spectrum .