Thermogravimetric analysis (TGA) using air  can be a cheap, useful technique to complement Raman. It can give you some idea of purity (for example amorphous carbon vs carbon nanotubes, and any amounts of residual catalyst)

However I agree with the answer you're given above. You really need a range of different analytical techniques to get a full picture.

Raman spectroscopy can tell you whether you have any single wall CNTs there, and can  also give you some information about their diameter, but isn't a quantitative method (so it won't tell you how much is SWNT, how much is MWNT etc)

In TGA, _as long as your sample does not have a lot of residual catalyst in it_ , with a slow ramp rate (or a dynamic TGA program) you should get separate oxidation events for SWNTs and MWNTs, and this will give you quantitative information about the ratio.

Hi Lega 

Above two answers are already dragged the  line of your question. I just want add something more. How about to use Raman and Nitrogen adsorption?

1. From Raman you could get the RBM peak for CNTs and the splinting of the g band. It will confirm the defect as well as the wall numbers.  

2. Nitrogen adsorption will give you characteristic BET surface area of CNT as well as the pore size and isotherm pattern. 

Hope so it will help

Cheers 

Try FTIR

Raman spectroscopy is The tool of choice for the investigation of carbon nanomaterials! It is also fast and non-destructive.

Raman and FTIR  spectroscopy are your options.

Simplest and best characterization of nanotubes whether  single wall or multiwall  is HRTEM. No other characterization is required after doing this.  If you can not afford this, use FESEM initially. When you get the fiberous structure in your sample, try to do one of two samples for TEM for confirmation. 

Raman spectroscopy is the simplest and cheaper characterization technique you can employ to perform a quick and non-destructive analysis of your samples. Moreover, with Raman spectroscopy you can analyze your samples in powder form without worrying about preparation of the sample for the analysis.

In literature there are so many papers that will help you out in the identification and analysis of the peaks you will obtain.

All the best

Paola

Hey Legha,

I hope you are doing good research work,

Simple and conventional techniques for the Carbon Nanotubes characterization  are as follows:

1. UV Spectroscopy

2. Fourier Transform Infrared Spectroscopy

3. XRD

4. TGA/DTA

5. Raman Spectroscopy

6. Electron Microscopy

Apart from the above-mentioned characterization techniques, the other techniques are more expensive.

All the best for your upcoming research

Since you plan to change the pressure and type of gases, you will have a change in the SWCNT diameter and concentration SWCNT.

Raman spectroscopy is used to determine SWCNT diameters. To determine the concentration of SWCNT use UV-viz-NIR spectroscopy. Read the article Nano Lett. 3, 309-314 (2003) and similar

Try for TEM and Raman. 

I think you first need to be sure that your synthesis procedure would lead to synthesis of carbon nanotube. Therefore, you need to carry out XRD and Raman tests. The next experiments depend on your purpose. If you want to focus on the functional groups, acidity, content of oxygent and so on, you can use a simple PZC experiment to have an insight of your acidity. Then you can use simple titration method to determine quantitativelly and qualitativelly the functional groups on your sample. PZC and titration methods are easy to do and you can do them in lab by yourself and you need only a pH meter.

If you want to study the textural properties, you need to do BET and TEM.

If you are trying to detect a certain functional group or you want to dope an element on your sample or if you want to know the elemens on the surface of your sample, I recommend to do FTIR and XPS.

Hope you find it useful.

TEM and Raman characterization techniques are enough to confirm the CNT whether SWCNT or MWCNT. 

Raman spectroscopy is a powerful, simplest, reliable, cheapest and confirmation of carbon nanotubes (CNTs) technigue. From Raman you could get the RBM peak for CNTs and the spliting of the g band. It will confirm the defect as well as the wall numbers.

It seems like most people suggested Raman spectroscopy. I do agree with this completely... Specially for CNTs, its easy, non-destructive, quick and can tell you a lot of properties in details. And making a systematic study would be very easy.

Since you can not change experimental parameters of the process like pressure, type of gases, etc, to study their effect on the characteristics of synthesized CNTs. I think Raman spectrocopy is the best one techniques for faster, easiest and non-destructive test for CNTs. If you get for peaks of G and D bands then it make sure that your synthesized sample is CNTs.

It depends on what aspects do you want to investigate:

Dispersion Test:

Shows the solubility of Carbon nanotubes (CNTs) It can be performed by adding CNTs to a solution and sonicated for several seconds to minutes and then record the sedimentation rate after specific time.

Fourier-transform infrared spectroscopy (FTIR): Give you the information about functional groups that attached to the surface of CNTs.

RAMAN: It can show the ratio of D (Defect) and G (Graphitic) bands. You can compare different structure of CNTs and understand the effect of different procedure or functionalization on the structure of them. Moreover, these bands and the location of them can be as the identification that we have a CNTs which can be useful when you synthesize CNTs or purchase from a company and you need to proof that your material is CNTs.

X-ray powder diffraction (XRD): It shows the crystallinity structure of CNTs and graphitic peak around 26 is the strongest and sharpest peak mostly in your graph. This test can be used for understanding of crystallinity of CNTs and how different processes changed the SP2 structure of CNTs.

Thermogravimetric Analysis (TGA): Thermogravimetric Analysis is a technique in which the mass of a substance is monitored as a function of temperature or time as the sample specimen is subjected to a controlled temperature program in a controlled atmosphere. You can use for different applications:

• To reverse engineer a product
• To compare two (2) similar products
• To ensure product safety
• Identify a counterfeit product
• To enhance product formulation processes
• Identify safe operating temperatures in various gases
• To determine carbon content

Differential Scanning Calorimetry (DSC): Differential Scanning Calorimetry, or DSC, is a thermal analysis technique that looks at how a material’s heat capacity (Cp) is changed by temperature.

Thermomechanical Analysis (TMA): Thermomechanical Analysis (TMA) provides valuable information on the dimensional properties of a wide range of materials used alone or in combination with other thermal analysis techniques such as, differential scanning calorimetry (DSC), thermogravimetric analysis (TMA) , dynamic mechanical analysis (DMA), or thermal conductivity. TMA provides a large amount of valuable information on solids and other materials that is difficult to obtain by other analytical techniques. TMA offers a higher degree of sensitivity compared to DSC for the detection of the glass transition temperature of highly filled or highly cross-linked materials, such as composites.

Dynamic Mechanical Analysis (DMA): It is a technique that is widely used to characterize a material’s properties as a function of temperature, time, frequency, stress, atmosphere or a combination of these parameters. Dynamic Mechanical Analysis, otherwise known as DMA, is a technique where a small deformation is applied to a sample in a cyclic manner. This allows the materials response to stress, temperature, frequency and other values to be studied. The term is also used to refer to the analyzer that performs the test. DMA is also called DMTA for Dynamic Mechanical Thermal Analysis.

Scanning Electron Microscopy (SEM): A scanning electron microscope (SEM), like a transmission electron microscope, consists of an electron optical column, a vacuum system, electronics, and software. The column is considerably shorter because the only lenses needed are those above the specimen used to focus the electrons into a fine spot on the specimen surface. The specimen chamber, however, is larger because the SEM technique does not impose any restriction on specimen size other than chamber size. The electrons in the beam interact with the sample, producing various signals that can be used to obtain information about the surface topography and composition.

Transmission electron microscopy (TEM): The TEM operates on the same basic principles as the light microscope but uses electrons instead of light. Because the wavelength of electrons is much smaller than that of light, the optimal resolution attainable for TEM images is many orders of magnitude better than that from a light microscope. Thus, TEMs can reveal the finest details of internal structure - in some cases as small as individual atoms.

There are so many other tests that you can use for investigating CNTs.

Try Raman spectroscopy with near-infrared laser line. Good luck.

The main problem between CNTs and other carbons is the fibrous shape. SEM is the cheapest and best method. It gives idea about the fibrous shape of carbon nanotubes.

I agree with Saeidi point, therefore, I suggest that before Raman spectroscopy or other techniques, you can first test the wetting properties of the prepared samples (CNTs are known to be super-hydrophobic).

The best way is HRSEM

Hi there,

If CNTs is powder and you want to study the influence of CNTs on the mechanical properties of any soft materials such as polymer, you have to test Tensile strength of the composite. Since the price of this test between $10-25.

Or, you can dispersed CNTs in Epoxy polymer (very cheap material) and test the Impact strength by Charpy apparatus (the test price about $5-10), as where this brittle composite shows a clear improvement in impact absorption property. After that, you go with SEM test using the cross section of the broken samples (from the first or second test) for the pure samples and the CNTs/polymer sample composite. I did that when I was student, it worked.

Majid Ahmadpouri Legha

Cheapest route is to look at them. It's free.

If they're not black then they're unlikely to be CNT's.

Seriously, you need to think about critical quality attributes (CQA's) and product performance indicators (PPI's) rather than a set of numbers from any technique. 'Characterization' is meaningless otherwise.

https://www.materials-talks.com/blog/2014/02/06/characterization-is-a-number-42-not-a-goal/

Just like Alan said, carbon nanotubes are extremely black, so first of all they must be one of the blackest materials you have ever seen.

However, an essential technique is the RAMAN to evaluate and certify whether they are nanotubes.

Article Structural Characterization of CVD Custom-Synthesized Carbon...

Check our recent paper, we have characterized our synthesized CNTs with the best methods.

Dear Legha,

I think Raman spectroscopy is easiest technique to characterize CNTs.

Good luck!