You carried out TGA in which atmosphere? Nitrogen or Air or Oxygen...

If Nitrogen, there is a chance of formation of Pt-Nitride or Pt-C-Nitride.. analyze the residue

Thank you so much for your kind help..

I used Nitrogen for the sample gas and Air for the balance gas...

Oh I forgot to tell that the sample result color after using this TGA is metallic silver.. The former sample color is black..

So, you're saying that there's some chemical reaction between Pt precursor and NH2-G4-PAMAM dendrimer to form such Pt-Nitride or Pt-C-Nitride at such high temperature?

OK.. residue is metallic silver.. so may be its pure Pt..

But, since you are using aminated PAMAM, there's a distinct possibility of formation of Pt Nitrides.. Test the residue by XPS, this will give definitive answer.

Thank you very much, Mr Vadahanambi, I really appreciate your concern in this matter..

Wait... if Pt reacts with N2 mas should increase. But you used oxygen as balance. maybe resideu formed from dendrimer was burned and the mass decreased. Try TG-MS if available-you find what gas, if any/ leaves TGA system at tha 800C or above.

I don't think the Pt is affected. Manufacturers sell Pt pans for TGA specifically because of their stability for high temp TGA. As Jacek points out any reaction to form Pt derivatives should increase the weight not decrease. What type of pan did you use for the experiment?

Chris, you are right. All we know that Pt is a noble metal and it is so hard to turn it to Pt compound. Therefore I again point oxidation of residual material formed from the dendrimer accompanied by the weight loss.

Jacob, if you are able to measure what gas is released at above 800C you possibly may guess reason of the loss. Carriyng out TG in different atmospheres also can be helful. Jacek

I do not think the weight loss is resulted from the reaction relative to Pt. It is likely caused by the decompose of the polymer itself.

Revising all the informations exchanged so far, I belevie during the TGA analysis just the organic part has been removed/degraded/broken. Why do not you perform the same experiment on the G4-PAMAM dendrimer without Pt NPs and copare the two thermograms (with and without Pt MPs)?

I think with that most of your doubts would be cleared.

At the 800C and nitrogen, the compound was decomposed and form the carboneous material. For the Pt, it maybe turn to the Pt particles. Please, take the XRD to confirm the Pt FCC structure. The XPS is also helpful to interpret the oxidation state of Pt in the material. You can see the Pt paritlces by the TEM or STEM observation.

I will support the idea of the platinum oxidation and the decomposition of the dendrimer, if you think that Pt is a noble metal and it will not react in bulk it is ok, but if you think of Pt NPs, then the surface will be very active and the oxidation can take place at this conditions.

@Mr. Przepiórski : Thank you very much for your help.. maybe I should discuss with my professor that it comes from the residue of decomposed dendrimers..

weight loss of Pt-encapsulated G4-PAMAM dendrimer results should be compared with pure G4-PAMAM dendrimer. If possible you post the TGA data for G4-PAMAM.

@Mr. Patridge : Thank you very much for your help..

Ooo I just realized, yes I use platinum pan for holding my samples.. But, the platinum in my samples is a nanoparticle, which before TGA is encapsulated by G4-PAMAM-dendrimer, that's why when the dendrimer decomposes (until 400 C), i suspected the platinum (later at 800 C) reacted or transformed from black color to metallic silver color..

@Mr. Liu : Thanks so much for your help..

But, the decomposition of polymer happens between 150 to 400 C (the second peak from the derivative weight line)..

@Mr. Pal : Thank you so much for your help..

I've already done only the dendrimer itself and turns out that decomposition only ends at 400 C (as the majority of organic matters will decomposes at 500 C tops)..

@Mr. Arellano : Thank you so much for your concern..

Sorry for my bad english.. What I meant was what you said, but apparently I put it in a wrong writing.. (Hahaha ^^!)..

Yes, I will consider the residue decomposition around that temperature..

@Mr. Pak : Thank you very much for your suggestion..

Yes, I would certainly try to confirm the after-TGA samples with XRD, XPS, and TEM..

@Ms. Redón : Thank you so much for your comment..

In my case, the Pt is a NP and encapsulated by dendrimer, but after the dendrimer is burned around 400 C, I suspected that Pt would reacted or oxidised just like you said..

Fan did you noticed your TGA result still showing weight loss below 1000 C, so that we have to go down lower than which showed 20 % of the compound is still un degradable. Form your datas 20 % residual indicates not only Platinum metal, but also some carbonized materials of your dendrimers and if any halogen may presences. Upto 300 C trace out the moisture lost of your G4 material, which reflects in derivative curves indicates both physic and chemisorped water loss. Can you able to see the sharp melting peak region near 600 C, it has established that starting stage of degrade your polymer of amido group trace till 900 C. if you want to conform it you know the quantity of dendrimers weight kept in the sample holder compared to major weight loss in your TGA contributes from 50 to 20 % weight loss = 30 %. That 30 % multiplied in to molecular weight of your G4 dendrimer. The results suppose to be match we assign it loss due to denderimenrs. Fine your TGA trace till 1000 C and I felt your nano incorporate in ppm level it dosent show any structural changes in platinum residual in TGA. The stable structure of platinum I guess FCC up to 1700 C, but I am not sure. May 800 C before possible to form platinum oxide, but their identification through the weight loss is tedious.

@Jacob....

Discussion with Professor should be the first step. Its known that many Professors will be chasing "research funds" or busy in some mundane administrative tasks, but still, try to get hold of your Professor and discuss your data. :) RG can't replace teachers. All the best in your research..

Hai first u calculate % of pt loaded in the dendrimer. Also there is possibility of impurities, if the pt is encapsulate inside the pamam dendrimer by electro chemical or electro reduction method. so, first u ensure that % of dendrimer , pt and other impurities present in the sample. Based on that u can exactly conclude u r result. also consider pt melting point at 1768 C. till u have 20% sample in the pan. May be it is Pt

By comparing TGA curve of pure G4-PAMAM and TGA curve of the nanocomposite in the range of 0-1000 oC, you can find the reason of the loss weight at 800 oC. Because after 800 oC, the loss weight is not constant and TGA analysis should be done to 1000 oC.

I agree with Palanirajan, first you should work out weight percentages - it seems from the decomposition up to 400 that you only have around 40% dendrimer - this seems very little. Did you do this in air or nitrogen?

One intriguing possibility is that Pt has been known to catalyse the formation of carbon nanotubes at temperatures as low as 450 oC in a CVD setup. 800 oC is a bit high for air, but nanotubes are certainly stable enough to decompose around 800 in nitrogen, so perhaps you have converted your dendrimer to CNTs using the carbon from the dendrimer as a carbon source.

I suggest the 20% remaining is Pt.

I am not sure that remaining 20 % is Pt. Can we see the weight loss not come into base line, it still degrading so its not platinum or conform it some reffernce anything mentioned pt degradation happened starting at 800 C itself. Still I dont know what is the usage we tracing out platinum in TGA. We have to go beyond 1000 C only we can assume what kind this, but cant assure the residue due to regarding this. In Tga sample holder pt/alumina pan contains 5- 10 mg for sample analysis, and fan used the total range 5 to 10 ppm in total G4. As per the TGA results absence of base line curve we assure to say it remain 20 % is not only the platinum. From TGA results fan could claim feature only about thermal stability of the polymer encapsulation. I feel Mr. rui comment CNT that we tried once, but dont know Fan have such Chemical vopor deposition facilities and surity to workout. Fan its just openion of RG followers, not for teaching, your practical experience might be help you. All the best and thank Jele and kamal ....

@Mr. Kumar & Mr. Mohandes : This is why I thought at above 800C shouldn't be the dendrimer decomposition..

@ Mr. Kumar, Mr. Mohandes, Mr Kraus, Mr Haran : Thank you for your comments & suggestions.. But, from the above line graph of dendrimer, I think we can clearly see that above 800C is not related to dendrimer & its decomposed products, can't we?

Can I say this is related to Pt particle, since the sample after TGA has metallic silver color..

@ Mr. Vadahanambi : Thank you for your comment, but I have already discussed with my professor and she also wonders about what happens above 800C.. That's why I ask for some suggestion here..

oh fan this is only for dentrimers you Know, for encapsulation and their generation of dendrimers you may added additional solvents which may not perfectly eliminates after that synthesis. From that complete melt of Dendremers at 600 C compared with above the tga shows 50 % of your residual compound. is it you 50 % additions of Pt in dendrimers. it is difficult too go beyond 1000 C. May the composition of your polymer matrix change by addition methanol and show some impurities. in dendrimers alone again the base line not be obtained its still go down the decomposition it is suceptible to cut further datas in XL values. han you said sample changed colour to metallic silver, its full of un decomposed organic mater i feel it thats why your first TGA goes still down. Some time science is to be argument like this and I feel better use this TGA for your additional information’s, try to concentrate the formaldehyde decompositions of your better results 

Yes, Mr. Haran, theoretically I calculated in the sample preparation that dendrimers (after drying the water) should be 52% in the dried samples.. the problem is on the Pt nanoparticles.. since Pt complexes are reduced to Pt nanoparticles with the help of dendrimer as the capping agent and sodium borohydride as the reducing agent, I only how many miligrams of Pt nanoparticles can be produced but I cannot measure the percentage to which I should refer to.

The percentage details of all prepared substances (after drying):

- G4-PAMAM dendrimer (amine terminated) = 52.5%.

- Na2PtCl6 (platinum precursor) = 26.5%.

- NaBH4 (reducing agent) = 17.8%.

- NaOH = 3.2%

Yes, I think I should discuss with my professor to consider this as additional information.

It's using the weight percentages..

Han yah you tel all these composition fan, see the Pt composition is 26 percent, and calculate the amount of Pt in Na2ptCl6 is still lower (2:1:6 for Na:Pt:Cl) composition. Your PAMAM highly intract with Na salts resulting your spectra showed the higher % content reffered with Dendrimers alone. Note the residues of the following compositions and the weight % of Na in Platinum precosor of 26 % and reducing agent of NaBH4 17 % and NaOH in3.2 %, B in 17 .8 % and Cl of Na2PtCl6, where is these impurities (Na, B, Cl ion). It is showed in residual in TGA. yes offcourse borohydrates good reducing agents but you previously synthesized nano particles that incorporate in G4 is helps you for the reactions not obtained the results in TGA. Find out in TEM or in chemical complex colour visuvalisation. Carry on :)..

Hari is right, with this new information your salts (B, Na, Cl) if not well washed out will contribute to the final mass. As a rough calculation, if the Pt precursor was 26%(by weight) of the preparation, it should give you a theoretical maximum of around 11% of your TGA weight loss, so the rest making up the 20% left at 1000oC would likely be inorganic.

This still does not explain the 800oC weight loss. I suggest you could heat a sample to around 700, where the dendrimer will have decomposed, and then take it out and do some analysis on the material left in the pan. You could certainly get some info from TEM or SEM (EDX). If you do the same with the sample at 1000oC you will be able to determine what is there at 700 that decomposes at 800.

Yah, Mr. Rui suggested one more additional information which is very important in your study Fan. Kept your sample in Muffle furnance upto 600 C for 7 h for complete elimination of dendrimers in Pt encapsulated G4. Then it will subjecte again in TGA that we can assing to reduction of further any functionalized groups. Acctually it is common practice in hetrogenious catalyst and valuble one.