I am working on single-walled carbon nanotube (SWNT) samples and observed an unexpected deviation in the XRD patterns. The (002) peak, which usually appears around 2θ ≈ 26° (interlayer spacing ~0.34 nm), is instead found at approximately 23° in my samples (see attached XRD plot).
Attached: XRD pattern showing the (002) peak shifted to ~23° in SWNTs
The SWNTs are [pristine / acid-treated / oxidized / functionalized — please select the one matching your process]. The measurements were performed using Cu Kα radiation (λ = 1.5406 Å) within a 10–60° 2θ range, with a step size of 0.02°.
I would like to understand what could cause this shift of the (002) reflection towards lower angles:
- Interlayer expansion due to oxidation, doping, or functionalization?
- Turbostratic disorder or defects introduced during synthesis?
- Tube–tube interactions or bundle morphology?
- Possible influence of sample preparation and residual strain?
Any references, experimental insights, or similar observations from other researchers would be greatly appreciated.
Thank you for your contributions!
Hello, Possible causes of your case are:
- Poor bundle packing or loose aggregation of nanotubes
- Functional groups (e.g., –OH, –COOH) inserted between tubes, expanding the intertube distance
- Amorphous carbon contamination or residual surfactants from purification/dispersal processes
- Poor Crystallinity or Disorder
- Presence of Other Carbon Phases
In particular, amorphous carbon often shows broad humps centered between 2θ ≈ 20–23°.
To check this difference, you need to do the below tests:
1. Check TEM or HRTEM to examine bundling and intertube distances.
2. Perform Raman spectroscopy to evaluate disorder (D-band intensity) and tube structure.
3. Thermal treatment or annealing may help restore tighter packing and reduce amorphous content.
Hello,
Thank you very much for your valuable response.
I will take the necessary action based on this response.
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