Determination of the Surface Coverage of Exfoliated Carbon Nanotubes by Surfactant Molecules in Aqueous Solution

Grossiord, Nadia; Schoot, Ppam Paul van der; Meuldijk, J.; Koning, CE Cor

doi:10.1021/la062684f

Cited by 97 publications

(75 citation statements)

References 61 publications

(112 reference statements)

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“…162 Our observations of low absorption and fluorescence intensities at both low and high surfactant concentrations can be understood in the context of this interpretation. For example, the fluorescence decrease at high surfactant concentrations most likely results from the presence of residual bundles, which quench fluorescence, in the suspensions.…”

Section: Recommended Sample Preparation Conditionsmentioning

confidence: 70%

Photophysics of Individual Single-Walled Carbon Nanotubes

2008

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Single-walled carbon nanotubes (SWNTs) are cylindrical graphitic molecules that have remained at the forefront of nanomaterials research since 1991, largely due to their exceptional and unusual mechanical, electrical, and optical properties. The motivation for understanding how nanotubes interact with light (i.e., SWNT photophysics) is both fundamental and applied. Individual nanotubes may someday be used as superior near-infrared fluorophores, biological tags and sensors, and components for ultrahigh-speed optical communications systems. Establishing an understanding of basic nanotube photophysics is intrinsically significant and should enable the rapid development of such innovations. Unlike conventional molecules, carbon nanotubes are synthesized as heterogeneous samples, composed of molecules with different diameters, chiralities, and lengths. Because a nanotube can be either metallic or semiconducting depending on its particular molecular structure, SWNT samples are also mixtures of conductors and semiconductors. Early progress in understanding the optical characteristics of SWNTs was limited because nanotubes aggregate when synthesized, causing a mixing of the energy states of different nanotube structures. Recently, significant improvements in sample preparation have made it possible to isolate individual nanotubes, enabling many advances in characterizing their optical properties. In this Account, single-molecule confocal microscopy and spectroscopy were implemented to study the fluorescence from individual nanotubes. Single-molecule measurements naturally circumvent the difficulties associated with SWNT sample inhomogeneities. Intrinsic SWNT photoluminescence has a simple narrow Lorentzian line shape and a polarization dependence, as expected for a one-dimensional system. Although the local environment heavily influences the optical transition wavelength and intensity, single nanotubes are exceptionally photostable. In fact, they have the unique characteristic that their single molecule fluorescence intensity remains constant over time; SWNTs do not “blink” or photobleach under ambient conditions. In addition, transient absorption spectroscopy was used to examine the relaxation dynamics of photoexcited nanotubes and to elucidate the nature of the SWNT excited state. For metallic SWNTs, very fast initial recovery times (300–500 fs) corresponded to excited-state relaxation. For semiconducting SWNTs, an additional slower decay component was observed (50–100 ps) that corresponded to electron–hole recombination. As the excitation intensity was increased, multiple electron–hole pairs were generated in the SWNT; however, these e−h pairs annihilated each other completely in under 3 ps. Studying the dynamics of this annihilation process revealed the lifetimes for one, two, and three e−h pairs, which further confirmed that the photoexcitation of SWNTs produces not free electrons but rather one-dimensional bound electron–hole pairs (i.e., excitons). In summary, nanotube photophysics is a rapidly developing area o...

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Section: Recommended Sample Preparation Conditionsmentioning

confidence: 70%

Photophysics of Individual Single-Walled Carbon Nanotubes

2008

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“…Therefore, ultraviolet-visible near infrared absorbance will be highest only for maximally exfoliated CNTs. 37 If dispersed CNTs reaggregate over the course of an experiment, absorbance values will gradually decrease affecting the accuracy of the experiment. It has previously been demonstrated that single-walled CNTs show the highest solubility in organic solvents such as DCB, and in order to maximize dispersability of CNTs, we chose this solvent for our ultraviolet-visible near infrared absorption experiments.…”

Section: Dispersion In Dcbmentioning

confidence: 99%

Pharmaceutical characterization of solid and dispersed carbon nanotubes as nanoexcipients

Földvári¹,

Иванова²,

Loureiro³

et al. 2012

IJN

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Background: Carbon nanotubes (CNTs) are novel materials with considerable potential in many areas related to nanomedicine. However, a major limitation in the development of CNT-based therapeutic nanomaterials is a lack of reliable and reproducible data describing their chemical and structural composition. Knowledge of properties including purity, structural quality, dispersion state, and concentration are essential before CNTs see widespread use in in vitro and in vivo experiments. In this work, we describe the characterization of several commercially available and two in-house-produced CNT samples and discuss the physicochemical profiles that will support their use in nanomedicine. Methods: Eighteen single-walled and multi-walled CNT raw materials were characterized using established analytical techniques. Solid CNT powders were analyzed for purity and structural quality using thermogravimetric analysis and Raman spectroscopy. Extinction coefficients for each CNT sample were determined by ultraviolet-visible near infrared absorption spectroscopy. Standard curves for each CNT sample were generated in the 0-5 µg/mL concentration range for dispersions prepared in 1,2-dichlorobenzene. Results: Raman spectroscopy and thermogravimetric analysis results demonstrated that CNT purity and overall quality differed substantially between samples and manufacturer sources, and were not always in agreement with purity levels claimed by suppliers. Absorbance values for individual dispersions were found to have significant variation between individual single-walled CNTs and multi-walled CNTs and sources supplying the same type of CNT. Significant differences (P , 0.01) in extinction coefficients were observed between and within single-walled CNTs (24.9-53.1 mL·cm ). The results described here suggest a considerable role for impurities and structural inhomogeneities within individual CNT preparations and the resulting spectroscopic properties of their dispersions. Conclusion: Raw CNT materials require thorough analytical workup before they can be used as nanoexcipients. This applies especially to the determination of CNT purity, structure, and concentration. The results presented here clearly demonstrate that extinction coefficients must be determined for individual CNT preparations prior to their use.

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“…Sabe-se que concentrações acima da cmc não apresentam um aumento significativo de moléculas de surfactante na interface ar-líquido e não têm qualquer influência sobre a tensão superficial, que permanece constante, somente contribuindo para a formação de mais micelas em solução. 19,20 A Figura 1 apresenta a tensão superficial versus concentração de SDS na presença de 0,20 mg mL -1 de CNT. O gráfico de tensão superficial de SDS sem o CNT (Figura 1S, material suplementar) apresentou um mínimo, possivelmente devido à presença de dodecanol, 21 e o valor encontrado de cmc aparente para o SDS foi de 6,2 mmol L -1 , diferente do encontrado na literatura pela mesma técnica para o SDS puro.…”

Section: Tensão Superficialunclassified

“…20 Quando a tensão superficial foi realizada na presença de 0,20 mg mL -1 de CNT (Figura 1), não apresentou um mínimo, sugerindo que o dodecanol pode ter sido adsorvido na parede do nanotubo por interação hidrofóbica. O valor encontrado para a concentração de agregação crítica (cac) foi de 7,0 mmol L -1 , este aumento (comparado à cmc aparente) se deve ao fato de algumas moléculas de surfactante adsorverem hidrofobicamente à parede dos nanotubos de carbono 25 que estão em solução, levando à diminuição da tensão interfacial CNT-água.…”

Section: Tensão Superficialunclassified

Estudo das dispersões aquosas de nanotubos de carbono utilizando diferentes surfactantes

2013

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Recebido em 7/12/11; aceito em 9/8/12; publicado na web em 27/11/12 STUDY OF AQUEOUS DISPERSIONS OF CARBON NANOTUBES USING DIFFERENT SURFACTANTS. The dispersion of carbon nanotubes in water for their utilization in nanoscale devices is a challenging task. Comparative studies on interaction and dispersion of multi-wall carbon nanotubes (MWNT) using two different surfactants (sodium dodecyl sulfate, SDS, and polyoxyethylenesorbitanmonooleate, Tween 80) are presented. The interaction between carbon nanotubes and surfactants was studied by tensiometry, conductivimetry, and fluorimetry. The dispersions of MWNT in surfactants were characterized using a UV-vis spectrophotometer. For effective dispersion, the minimum weight ratio of MWNT to surfactant was 1:41 and 1:3 for SDS and Tween 80, respectively.Keywords: carbon nanotube; surfactant; dispersion. INTRODUÇÃOOs nanotubos de carbono (CNTs) foram observados pela primeira vez por Iijima, 1 em 1991, e desde então têm recebido muita atenção devido às suas propriedades físicas exclusivas.2,3 Os CNTs exibem excelentes propriedades mecânica, elétrica, magnética e térmica, diâmetro de escala nanométrica, bem como razão de aspecto alta (~1000) em comparação com os silicatos lamelares (~200), que os tornam um elemento ideal de reforço para compósitos de polímeros. 3,4 Em diversas das suas importantes aplicações, os CNTs somente apresentam suas propriedades únicas se estiverem em uma dispersão altamente homogênea.5 No entanto, CNTs são pouco solúveis na maioria dos solventes. Devido à forte atração de van der Waals, eles exibem uma tendência a se agregarem e formarem grandes agregados de difícil dispersão. 6 No intuito de obter dispersões homogêneas, duas alternativas diferentes estão atualmente sendo utilizadas para dispersar os nanotubos de carbono, por exemplo, métodos mecânicos (físicos) ou métodos químicos. O uso de métodos mecânicos, como ultrassonicação e agitação com alta taxa de cisalhamento, permite a separação dos nanotubos uns dos outros. Além destes métodos fragmentarem os nanotubos durante o processo, causando a diminuição da razão de aspecto, também são métodos ineficientes e consomem tempo e energia elevados. Os métodos químicos usam surfactantes ou modificações químicas para alterar a energia de superfície dos CNTs, melhorando as características de molhabilidade e adesividade, e aumentam a estabilidade da dispersão no solvente. A funcionalização covalente inclui a ligação de diferentes grupos funcionais nas paredes dos nanotubos de carbono. No entanto, funcionalizações químicas agressivas causam um aumento nos defeitos nas paredes laterais, o que pode alterar as propriedades mecânicas e elétricas dos CNTs. geralmente é necessária uma alta concentração de surfactantes para se obter dispersões estáveis de CNTs, que é inconveniente devido ao alto custo dos surfactantes, seus impactos ambientais e por restringir o uso destas suspensões em materiais compósitos. 9Considerando a relevância dos surfactantes nas dispersões de CNTs, o objetivo do presente estudo foi comp...

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Determination of the Surface Coverage of Exfoliated Carbon Nanotubes by Surfactant Molecules in Aqueous Solution

Cited by 97 publications

References 61 publications

Photophysics of Individual Single-Walled Carbon Nanotubes

Photophysics of Individual Single-Walled Carbon Nanotubes

Pharmaceutical characterization of solid and dispersed carbon nanotubes as nanoexcipients

Estudo das dispersões aquosas de nanotubos de carbono utilizando diferentes surfactantes

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