Single-walled carbon nanotubes are more complicated to buy than multi-walled. SWCNT material varies along at least four axes — purity (60% to 99%+), length (short to ultra-long), functionalization (pristine, COOH, OH, NH2), and bundling (single-walled vs single-walled / double-walled mixed). The differences across those axes affect price by an order of magnitude and affect application performance by even more. Picking the right SWCNT for a transparent conductive film is a totally different decision than picking SWCNT for a polymer composite or a biosensor. This guide walks through how to make the call, with specific recommendations by application and the trade-offs at each tier.
The Quick Answer by Application
If your application is…
- Transparent conductive films (TCF), high-conductivity printed electronics, RF and microwave devices, single-tube spectroscopy → 99% purity, ultra-long. The flagship grade. The long aspect ratio + minimal junction resistance is what makes TCF work; anything less and the sheet conductivity collapses.
- General academic research, ink formulation, biosensor substrates, hybrid composite material development, electrochemistry, photovoltaic R&D → 95% purity (id=7757) or 90% SW-DW (id=154). The research-grade tier. Reproducible, defensible in published methods, broadly cited.
- Bulk polymer composites, EMI shielding, conductive coatings for paint or fabric, cost-sensitive composite reinforcement → 60% SW-DW (id=161). Cheapest SWCNT tier. Adequate for percolation work where purity isn't the limit.
- Biosensor functionalization, drug-delivery scaffolds, DNA/protein attachment, surface-chemistry-controlled electrode work → functionalized variants — pre-attached COOH, OH, or NH2 groups in the purity tier matched to your application.
- Polymer matrix inks, sprayable composites, dispersion-limited processing → short variants (1-4 nm length). Easier to disperse, less tangling during sonication, suitable for inkjet and spray-coat workflows.
Side-by-Side Comparison — Pristine Purity Tiers
| Spec | 60% SW-DW | 90% SW-DW | 95% SWCNT | 99% Ultra-Long |
|---|---|---|---|---|
| Purity | 60% | 90% | 95% | 99% |
| Length | Standard + Short variant | Standard | Standard | Ultra-long (flagship spec) |
| Tube structure | SW + DW mixed | SW + DW mixed | SWCNT (predominantly single-walled) | SW + DW mixed |
| Functionalization options | DIY only (or buy 99% functionalized variants) | COOH, OH, NH2 (general SW-DW variants) | DIY or use general SW-DW functionalized variants | COOH-99 (id=152) |
| Price tier | $ (lowest) | $$ | $$$ | $$$$ (premium) |
| Best for | Bulk composite percolation, EMI shielding, cost-driven applications | General research, ink formulation, hybrid material work | Defined-SWCNT research where SW vs DW matters, biosensors, electronics | TCF, RF / microwave, high-conductivity printed electronics, premium R&D |
| Product page | SW-DW 60% (id=161) | SW-DW 90% (id=154) | SWCNT 95% (id=7757) | SW-DW 99% Ultra-Long (id=148) |
The Four Purity Tiers — Detail
60% SW-DW — the cost tier
SW-DW 60% (id=161): CVD-synthesized, minimally post-processed. Mixed single-walled and double-walled tube population. The other 40% is amorphous carbon plus residual catalyst metals plus DWCNT fraction. Use it for bulk composite percolation, conductive coatings for paint or fabric, EMI shielding applications where impurity load doesn't affect performance. Don't use it for single-tube spectroscopy, biosensors, electronics that depend on defined surface chemistry, or any application where SW vs DW distinction matters.
Short variant available: Short SW-DW 60% (id=163) — for ink and dispersion work where aspect ratio matters less than processability.
90% SW-DW — the workhorse research tier
SW-DW 90% (id=154): CVD synthesized with post-purification to research grade. Mixed SW + DW population. Cleaner than 60% by a meaningful margin; the 10% impurity is largely amorphous carbon with minimal catalyst residue. Use it for general academic research, ink formulation, hybrid material development (SWCNT/polymer, SWCNT/graphene, SWCNT/metal oxide), electrochemistry, photovoltaic R&D, sensor substrate prep. Don't use it for single-tube spectroscopy, applications requiring defined SWCNT-only composition, or premium electronics where ultra-long aspect ratio matters.
95% SWCNT — the defined-single-walled research tier
SWCNT 95% (id=7757): research-grade material specifically purified to predominantly single-walled composition (vs the SW-DW mixed populations at 60% and 90%). The distinction matters when your application sensitivity to tube structure (electronic band gap, chirality distribution, single-tube vs double-tube optoelectronic properties) is high. Use it for defined-SWCNT research, biosensor electrode work, electronics applications that depend on single-tube band-structure properties, electrochemistry where DWCNT contamination would skew results. Don't use it for bulk composite work where you're paying for purification you don't need.
99% SW-DW Ultra-Long — the flagship premium tier
SW-DW 99% Ultra-Long (id=148): the highest purity grade plus the longest tube length in the SWCNT catalog. Recently upgraded with a new ultra-long spec for transparent-conductive-film and RF/microwave applications where junction resistance between tubes dominates performance. Long tubes = fewer tube-to-tube contacts per unit area = lower sheet resistance for the same coverage. Use it for TCF for touchscreens and flexible displays, transparent EMI shielding, high-conductivity printed electronics, RF / microwave electronics, supercap electrodes where the conductivity matters more than the surface area, photovoltaic transparent electrodes, premium SWCNT research where reproducibility and lowest possible impurity load are essential. Don't use it for applications where 90% or 95% would have worked — you're paying the premium for ultra-long aspect ratio and 99% purity that doesn't affect your application.
Pre-functionalized 99% variant available: COOH-99 (id=152) for ultra-pure carboxylated SWCNT work.
Length — Standard vs Short Variants
Most Cheap Tubes SWCNT ship in standard length (typical 5-30 μm for the SWCNT material). For applications where dispersion is the bottleneck (ink formulation, sprayable composites, polymer matrix mixing under shear), short variants (1-4 nm) are easier to disperse, less likely to tangle during sonication, and produce more uniform composite microstructure. Short SWCNT pay for processability with reduced aspect ratio, which lowers electrical percolation efficiency — the trade-off is application-dependent.
- Short pristine variants: Short SW-DW 60% (id=163), Short SW-DW (id=157) (general grade)
- Short functionalized: Short COOH SW-DW 1-4 nm (id=231), Short OH SW-DW 1-4 nm (id=217)
Functionalization Options
Pre-functionalized SWCNT variants save you the in-house surface chemistry workflow when your application needs COOH, OH, or NH2 groups attached to the SWCNT sidewall. Available across the SWCNT catalog:
- COOH SW-DW (id=156) — standard grade carboxylated SWCNT, general research
- COOH-99 SW-DW (id=152) — ultra-pure carboxylated for premium R&D
- OH SW-DW (id=155) — hydroxyl-functionalized SWCNT for hydrophilic dispersion + bioconjugation
- NH2 SW-DW (id=182) — amine-functionalized for protein attachment, drug delivery, biosensor coupling
- Short variants (1-4 nm): Short COOH SW-DW (id=231), Short OH SW-DW (id=217)
The COOH and OH functionalization is degree-controlled in production; if you need a specific degree-of-functionalization for your application, contact us for custom specifications.
Specialty Products
- Thin Walled Carbon Nanotubes (id=379) — specialty grade between SWCNT and DWCNT, with controlled wall thickness for applications requiring intermediate electronic and mechanical properties.
Common Mistakes Researchers Make
- Buying 99% Ultra-Long SWCNT for a polymer composite filler. The ultra-long aspect ratio doesn't help you in a sheared polymer composite; the tubes break during processing anyway, and you're paying the premium for a property you can't preserve. 60% or 90% is the right tier.
- Buying 60% SW-DW for biosensor work. The 40% impurity (including DWCNT fraction) will scramble your defined-surface chemistry. Spend the extra and buy 95% or functionalized variants.
- Not specifying the SW vs DW composition in published methods. Reviewers will ask. The 95% SWCNT product is “predominantly single-walled” by design; SW-DW products are mixed. Pick deliberately and cite explicitly.
- DIY-functionalizing 99% SWCNT when COOH-99 (id=152) ships pre-functionalized. Pre-functionalized variants save you the surface chemistry workflow and give consistent batch-to-batch degree of functionalization — buy the pre-functionalized SKU unless you need a specialty chemistry we don't offer.
- Ignoring length when ink formulation is the bottleneck. Short SWCNT variants (1-4 nm) disperse dramatically better than standard length and avoid the tangling that limits inkjet and spray-coat workflows. The aspect-ratio trade-off is small relative to the processing benefit.
Browse the SWCNT Catalog
60% SW-DW SWCNT
Bulk composites, EMI shielding, conductive coatings, cost-sensitive percolation work.
SW-DW 60% →90% SW-DW SWCNT
General academic research, ink formulation, hybrid material work, electrochemistry, PV R&D.
SW-DW 90% →95% SWCNT
Defined-SWCNT research, biosensors, electronics where SW vs DW matters.
SWCNT 95% →99% SW-DW Ultra-Long
TCF, RF / microwave, high-conductivity printed electronics, premium R&D.
SW-DW 99% →Or Browse by Category
All single-walled and double-walled carbon nanotubes, plus functionalized variants and specialty products.
All SWCNT → Functionalized CNTs →Frequently Asked Questions
What's the difference between SWCNT, SW-DW, and DWCNT?
Single-walled carbon nanotubes (SWCNT) are individual tubes formed from a single rolled graphene sheet. Double-walled (DWCNT) have two concentric tubes. SW-DW mixed products contain both populations because CVD synthesis without specialized chirality purification produces both. The 95% SWCNT product is predominantly single-walled by design; the 60%, 90%, and 99% products are SW-DW mixed. The distinction matters when your application is sensitive to band-structure properties or single-tube optoelectronics.
How do I pick between 60%, 90%, 95%, and 99% purity?
Match purity to what your measurement or application is sensitive to. For bulk percolation, EMI shielding, or composite mechanical reinforcement: 60% is fine. For general academic research and ink formulation: 90% SW-DW is the workhorse. For applications where SW vs DW distinction matters or where electronic band-structure properties are central: 95% SWCNT (predominantly single-walled by design). For TCF, RF and microwave electronics, premium high-conductivity work: 99% Ultra-Long.
Why does the 99% product have the “Ultra-Long” tag?
Long SWCNT have fewer tube-to-tube junction contacts per unit area than short SWCNT. For applications like transparent conductive films, RF and microwave devices, and high-conductivity printed electronics, junction resistance between tubes dominates the overall sheet conductivity. Ultra-long tubes produce dramatically lower sheet resistance at the same coverage density. The 99% Ultra-Long product is specifically engineered for those applications.
What about Short SWCNT variants?
Short SWCNT (1-4 nm) sacrifice aspect ratio for processability. Easier to disperse, less tangling during sonication, more uniform composite microstructure. The trade-off is reduced electrical percolation efficiency. Use short variants when dispersion is the bottleneck (inkjet, spray-coat, polymer matrix mixing under shear). Use standard length when percolation efficiency matters more than processability.
Are functionalized SWCNT pre-attached or do I DIY-functionalize?
Cheap Tubes ships pre-functionalized SWCNT variants in COOH, OH, and NH2 forms — no DIY needed for standard chemistry. Pre-functionalized variants include COOH SW-DW (id=156), OH SW-DW (id=155), NH2 SW-DW (id=182), COOH-99 SW-DW (id=152), Short COOH SW-DW (id=231), Short OH SW-DW (id=217). DIY-functionalize only if you need specialty chemistry (PEG, biotin, custom ligands) we don't offer pre-attached.
How do I cite Cheap Tubes SWCNT in a paper?
Cite the specific product (e.g., “Single Walled-Double Walled Carbon Nanotubes 99 Ultra-Long, Cheap Tubes Inc., Grafton, VT, USA”) along with the purity, length, and functionalization (if any). Use cheaptubes.com URLs in your bibliography if your journal accepts URL references. Reproducibility downstream depends on other researchers being able to source the same material.