Selective carboxylation <i>versus</i> layer-by-layer unsheathing of multi-walled carbon nanotubes: new insights from the reaction with boiling nitrating mixture

Kolanowska, Anna; Wąsik, Patrycja; Zięba, Wojciech; Terzyk, Artur P.; Boncel, Sławomir

doi:10.1039/c9ra08300f

Cited by 16 publications

(20 citation statements)

References 27 publications

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“…Moreover, the functionalization must be strictly monitored both qualitatively and quantitatively. The effect was also recently confirmed and further studied by Kolanowska et al [54]. As the authors demonstrated for progressively functionalized and quenched MWCNTs over the oxidation under harsh conditions (boiling in nitrating mixture of concentrated H 2 SO 4 and concentrated HNO 3 , v/v = 3/1), inter alia by counting the nanotube walls, titration of COOH groups, and quantitative TGA for the products, nanotubes could indeed be identified as alternatively functionalized and non-functionalized.…”

Section: Introductionsupporting

confidence: 55%

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Electrophoretic Deposition of Layer-by-Layer Unsheathed Carbon Nanotubes—A Step Towards Steerable Surface Roughness and Wettability

Korczeniewski

Zięba

et al. 2020

Materials

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It is well known that carbon nanotube (CNT) oxidation (usually with concentrated HNO3) is a major step before the electrophoretic deposition (EPD). However, the recent discovery of the “onion effect” proves that multiwalled carbon nanotubes are not only oxidized, but a simultaneous unsheathing process occurs. We present the first report concerning the influence of unsheathing on the properties of the thus-formed CNT surface layer. In our study we examine how the process of gradual oxidation/unsheathing of a series of multiwalled carbon nanotubes (MWCNTs) influences the morphology of the surface formed via EPD. Taking a series of well-characterized and gradually oxidized/unsheathing Nanocyl™ MWCNTs and performing EPD on a carbon fiber surface, we analyzed the morphology and wettability of the CNT surfaces. Our results show that the water contact angle could be gradually changed in a wide range (125–163°) and the major property determining its value was the diameter of aggregates formed before the deposition process in the solvent. Based on the obtained results we determined the parameters having a crucial influence on the morphology of created layers. Our results shed new light on the deposition mechanism and enable the preparation of surfaces with steerable roughness and wettability.

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Section: Introductionsupporting

confidence: 55%

“…This so-called "onion effect" was confirmed by our groups for different oxidizing agents and different CNTs. Additionally, the kinetics of the unsheathing process was determined [54].…”

Section: Introductionmentioning

confidence: 99%

Electrophoretic Deposition of Layer-by-Layer Unsheathed Carbon Nanotubes—A Step Towards Steerable Surface Roughness and Wettability

Korczeniewski

Zięba

et al. 2020

Materials

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“…Furthermore, prolonged oxidation not necessarily increases the amount of the oxygen functional groups on CNTs surface due to the so-called onion effect leading to rapid decomposition of oxidized CNTs walls after achieving a particular level of oxidation. 27 To exclude varying dimensions connected with the oxidation process, we accomplished the introduction of "second generation" OFGs on oxidized MWCNTs through a nondestructive process -[2+1] nitrene cycloaddition ( Figure 1D). For this purpose, two different types of Fe@MWCNTs were chosen -in-house prepared, large diameter, "our" MWCNT O with high iron loading and commercially available Nanocyl 7000 TM MWCNT (MWCNT N ) with a small diameter ( Table 2).…”

Section: Introductionmentioning

confidence: 99%

“…Oxidation can introduce only a limited number of protic functional groups, due to the so-called onion effect on the MWCNT surface. 27 The second generation of hydroxyl and carboxyl groups was introduced, aside from already existing ones, directly to sp 2 MWCNT skeleton, in a single step through [2+1]-cycloaddition of nitrenes generated in situ from 4-azidosalicylic acid containing both hydroxyl and carboxylic groups. 8,[33][34][35] The reaction led to degrees of functionalization of 17.4% for oMWCNT O -Sal and 12.2% for oMWCNT N -Sal in reference to the starting oMWCNTs.…”

Section: Introduction Of Second-generation Ofgs -[2+1] Nitrene Cycloamentioning

confidence: 99%

<p>Oxygen Functional Groups on MWCNT Surface as Critical Factor Boosting T2 Relaxation Rate of Water Protons: Towards Improved CNT-Based Contrast Agents</p>

Tomczyk¹,

Boncel²,

Herman³

et al. 2020

IJN

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Purpose: Salicyl (Sal)-among other oxygen functionalities-multi-walled carbon nanotubes (MWCNTs) and their nanohybrids are investigated as promising contrast agents (CA) in magnetic resonance imaging (MRI) or drug delivery platforms, due to their unique properties. The preliminary results and the literature reports were the motivation to endow high r 2 relaxivities, excellent dispersibility in water, and biocompatibility to superparamagnetic MWCNTs nanohybrids. It was hypothesized that these goals could be achieved by, not described in the literature yet, two-stage oxygen functionalization of MWCNTs. Results: Two structurally different MWCNT materials differing in diameters (44 and 12 nm) and the iron content (4.7% and 0.5%) are studied toward the functionalization effect on the T 2 relaxometric properties. MWCNT oxidation is typically the first step of functionalization resulting in "first generation" oxygen functional groups (OFGs) on the surface. Until now, the impact of OFGs on the relaxivity of MWCNT was not truly recognized, but this study sheds light on this issue. By follow-up functionalization of oxidized MWCNT with 4-azidosalicylic acid through [2+1] cycloaddition of the corresponding nitrene, "second generation" of oxygen functional groups is grafted onto the nanohybrid, ie, Sal functionality. Conclusion: The introduced OFGs are responsible for an almost 30% increase in the relaxivity, which leads to remarkable r 2 relaxivity of 951 mM −1 s −1 (419 (mg/mL) −1 s −1), the unprecedented value reported to date for this class of CAs. Also, the resulting nanohybrids express low cytotoxicity and superb diffusion after subcutaneous injection to a mouse.

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“…[88] (CC BY-NC 4.0) are more acidic than the respective base, and the ratios of the amounts of the different oxygen-containing FG can then be calculated directly from the base consumption. Boehm titration has been utilized to characterize the FG on different kinds of CNT [106][107][108] as well as on other carbon-based materials like ozone-treated nanodiamonds, carbon NP derived from organic resin, graphite-decorated MnFe 2 O 4 nanocomposites, and natural char nano-and microparticles [109][110][111][112]. To evaluate and standardize Boehm titration regarding accuracy, robustness, repeatability, and precision, Schönherr et al investigated the FG on oxidized multi-walled CNT using different reaction bases, treatment times, and amounts of carbon material [105,113].…”

Section: Boehm Titrationmentioning

confidence: 99%

Analyzing the surface of functional nanomaterials—how to quantify the total and derivatizable number of functional groups and ligands

et al. 2021

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Functional nanomaterials (NM) of different size, shape, chemical composition, and surface chemistry are of increasing relevance for many key technologies of the twenty-first century. This includes polymer and silica or silica-coated nanoparticles (NP) with covalently bound surface groups, semiconductor quantum dots (QD), metal and metal oxide NP, and lanthanide-based NP with coordinatively or electrostatically bound ligands, as well as surface-coated nanostructures like micellar encapsulated NP. The surface chemistry can significantly affect the physicochemical properties of NM, their charge, their processability and performance, as well as their impact on human health and the environment. Thus, analytical methods for the characterization of NM surface chemistry regarding chemical identification, quantification, and accessibility of functional groups (FG) and surface ligands bearing such FG are of increasing importance for quality control of NM synthesis up to nanosafety. Here, we provide an overview of analytical methods for FG analysis and quantification with special emphasis on bioanalytically relevant FG broadly utilized for the covalent attachment of biomolecules like proteins, peptides, and oligonucleotides and address method- and material-related challenges and limitations. Analytical techniques reviewed include electrochemical titration methods, optical assays, nuclear magnetic resonance and vibrational spectroscopy, as well as X-ray based and thermal analysis methods, covering the last 5–10 years. Criteria for method classification and evaluation include the need for a signal-generating label, provision of either the total or derivatizable number of FG, need for expensive instrumentation, and suitability for process and production control during NM synthesis and functionalization. Graphical abstract

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Selective carboxylation versus layer-by-layer unsheathing of multi-walled carbon nanotubes: new insights from the reaction with boiling nitrating mixture

Abstract: Treatment of multi-walled carbon nanotubes (MWCNTs) with a boiling nitrating mixture proceeds via two interrelated phenomena, i.e. periodic-like carboxylation and layer-by-layer desheathing, and overall, it can be controlled by kinetics of the process.

Cited by 16 publications

References 27 publications

Electrophoretic Deposition of Layer-by-Layer Unsheathed Carbon Nanotubes—A Step Towards Steerable Surface Roughness and Wettability

Electrophoretic Deposition of Layer-by-Layer Unsheathed Carbon Nanotubes—A Step Towards Steerable Surface Roughness and Wettability

<p>Oxygen Functional Groups on MWCNT Surface as Critical Factor Boosting T2 Relaxation Rate of Water Protons: Towards Improved CNT-Based Contrast Agents</p>

Analyzing the surface of functional nanomaterials—how to quantify the total and derivatizable number of functional groups and ligands

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