All About CTAB Capped Gold Nanoparticles

Definition, Properties, Applications, Storage and Handling

Background, Properties and Applications

CTAB-coated gold nanoparticles have been extensively studied for various applications due to their unique properties. These nanoparticles have been utilized in fields such as colorimetric detection of bacteria (Verma et al., 2014), cellular uptake and cytotoxicity studies (Alkilany et al., 2009), optical properties of star-shaped gold nanoparticles (Nehl et al., 2006), self-assembly patterns (Sau & Murphy, 2005), and in vitro toxicity assessments (Gong et al., 2014). The CTAB coating on gold nanoparticles plays a crucial role in their stability, surface charge, and interactions with biological systems.

Studies have shown that the CTAB coating can be modified to change the surface charge of the nanoparticles, affecting their cellular uptake and cytotoxicity (Alkilany et al., 2009). Additionally, the CTAB coating has been used to stabilize gold nanorods and facilitate their organization onto surfaces (Gole & Murphy, 2005). The coating can also be modified to enable silica-coating, which is essential for applications like controlled drug delivery Li et al. (2017) and hydrophobation (Pastoriza‐Santos et al., 2006).

Furthermore, the CTAB coating on gold nanoparticles has been investigated for its role in skin penetration (Fang et al., 2017), photothermal tumor ablation (Freitas et al., 2013), and as a stabilizing agent for various shapes of gold nanoparticles (Rostro-Kohanloo et al., 2009). The unique properties of CTAB-coated gold nanoparticles make them promising candidates for a wide range of applications, from biosensing to nanomedicine.

In conclusion, CTAB-coated gold nanoparticles have shown great potential in various fields due to their tunable properties, ease of functionalization, and biocompatibility. Further research is warranted to explore the full range of applications and to optimize the synthesis and surface modifications of these nanoparticles for specific uses.

Storage and Handling

CTAB is a positively charged adsorbed ligand that exists as a micelle in concentrations greater than 1mM. The micelle is crucial for nanoparticle stability and if diluted, a minimum of 1mM is necessary to maintain colloidal stability. Like all gold nanoparticles, it is most important to not freeze and not contaminate. CTAB capped gold nanoparticles have less of a requirement for refrigeration as the CTAB itself is a natural disinfectant. If refrigerated, CTAB crystals may form. These can be easily and reversibly dissolved by raising the temperature to 4 to 5 degrees C above room temperature.

Solvents at very low concentrations will disrupt CTAB micelles and should be avoided.

CTAB micelles are not resistant to salt concentrations greater than 10mM and should be avoided.

Replacing CTAB on Gold Nanoparticles

Replacing CTAB on gold nanoparticles is a crucial step in enhancing their biocompatibility and modulating their properties. Several studies have investigated different methods and effects of replacing CTAB on gold nanoparticles. Alkilany et al. (2010) demonstrated the use of a large concentration gradient to replace CTAB molecules on the surfaces of gold nanorods, aiming to improve their biocompatibility. Wang et al. (2021) highlighted how chemical reducing agents can not only reduce mercury ions but also replace CTAB molecules on gold nanorods. Kalipillai et al. (2022) discussed the replacement of the CTAB layer with alkane thiols for long-term stability. Li et al. (2020) verified the structure of CTAB on gold nanoparticles and its replacement with a polymerizable surfactant. Guerrero‐Martínez et al. (2009) showed that replacing CTAB during nanorod synthesis leads to the production of monodisperse nanorods with unique optical properties.

Moreover, Plowman et al. (2015) compared the electron transfer properties of gold nanoparticles capped with citrate or CTAB. Deviprasada & Sinha (2023) replaced CTAB with 11-mercaptoundecanoic acid to study nanoparticle stability. Cheng et al. (2003) supported the experimental scheme with previous studies on TOAB-capped gold nanoparticles. Indrasekara et al. (2014) emphasized the complexity of replacing CTAB with other capping agents and the need for a thorough understanding of the process. Additionally, Schmutzler et al. (2019) discussed the assumption of CTAB forming bilayers for stabilizing seed particles.

In summary, the replacement of CTAB on gold nanoparticles is a critical process that can significantly impact their properties, stability, and biocompatibility. Various studies have explored different methods and effects of replacing CTAB, highlighting the importance of understanding the mechanisms and implications of such replacements for tailored nanoparticle applications.

Go here for Nanopartz Gold Nanorods




Background, Properties and Applications

Alkilany, A., Nagaria, P., Hexel, C., Shaw, T., Murphy, C., & Wyatt, M. (2009). Cellular uptake and cytotoxicity of gold nanorods: molecular origin of cytotoxicity and surface effects. Small, 5(6), 701-708.

Fang, H., Jin, X., Liu, Q., Zhou, Q., & Jiang, G. (2017). Epidermal penetration of gold nanoparticles and its underlying mechanism based on human reconstructed 3d episkin model. Acs Applied Materials & Interfaces, 9(49), 42577-42588.

Freitas, L., Zanelatto, L., Mantovani, M., Silva, P., Ceccini, R., Grecco, C., … & Plepis, A. (2013). in vivophotothermal tumour ablation using gold nanorods. Laser Physics, 23(6), 066003.

Gole, A. and Murphy, C. (2005). Polyelectrolyte-coated gold nanorods:  synthesis, characterization and immobilization. Chemistry of Materials, 17(6), 1325-1330.

Gong, T., Goh, D., Olivo, M., & Yong, K. (2014). In vitro toxicity and bioimaging studies of gold nanorods formulations coated with biofunctional thiol-peg molecules and pluronic block copolymers. Beilstein Journal of Nanotechnology, 5, 546-553.

Li, Y., Li, N., Pan, W., Yu, Z., Yang, L., & Tang, B. (2017). Hollow mesoporous silica nanoparticles with tunable structures for controlled drug delivery. Acs Applied Materials & Interfaces, 9(3), 2123-2129. Nehl, C., Liao, H., & Hafner, J. (2006). Optical properties of star-shaped gold nanoparticles. Nano Letters, 6(4), 683-688.

Pastoriza‐Santos, I., Pérez-Juste, a., & Liz‐Marzán, L. (2006). Silica-coating and hydrophobation of ctab-stabilized gold nanorods. Chemistry of Materials, 18(10), 2465-2467.

Rostro-Kohanloo, B., Bickford, L., Payne, C., Day, E., Anderson, L., Zhong, M., … & Hafner, J. (2009). The stabilization and targeting of surfactant-synthesized gold nanorods. Nanotechnology, 20(43), 434005.

Sau, T. and Murphy, C. (2005). Self-assembly patterns formed upon solvent evaporation of aqueous cetyltrimethylammonium bromide-coated gold nanoparticles of various shapes. Langmuir, 21(7), 2923-2929.

Verma, M., Chen, P., Jones, L., & Gu, F. (2014). Branching and size of ctab-coated gold nanostars control the colorimetric detection of bacteria. RSC Advances, 4(21), 10660-10668.

Replacing CTAB on Gold Nanoparticles

Alkilany, A., Nagaria, P., Wyatt, M., & Murphy, C. (2010). Cation exchange on the surface of gold nanorods with a polymerizable surfactant: polymerization, stability, and toxicity evaluation. Langmuir, 26(12), 9328-9333.

Cheng, W., Dong, S., & Wang, E. (2003). Synthesis and self-assembly of cetyltrimethylammonium bromide-capped gold nanoparticles. Langmuir, 19(22), 9434-9439.

Deviprasada, P. and Sinha, R. (2023). Highly stable 11-mua capped gold nanobipyramid for refractive index sensing. Journal of Biomedical Photonics & Engineering, 010308.

Guerrero‐Martínez, A., Pérez‐Juste, J., Carbó‐Argibay, E., Tardajos, G., & Liz‐Marzán, L. (2009). Gemini‐surfactant‐directed self‐assembly of monodisperse gold nanorods into standing superlattices. Angewandte Chemie, 121(50), 9648-9652.

Indrasekara, A., Wadams, R., & Fabris, L. (2014). Ligand exchange on gold nanorods: going back to the future. Particle & Particle Systems Characterization, 31(8), 819-838.

Kalipillai, P., Raghuram, E., Bandyopadhyay, S., & Mani, E. (2022). Self-assembly of a ctab surfactant on gold nanoparticles: a united-atom molecular dynamics study. Physical Chemistry Chemical Physics, 24(46), 28353-28361.

Li, R., Wang, Z., Gu, X., Chen, C., & Zhang, Y. (2020). Study on the assembly structure variation of cetyltrimethylammonium bromide on the surface of gold nanoparticles. Acs Omega, 5(10), 4943-4952.

Plowman, B., Tschulik, K., Young, N., & Compton, R. (2015). Capping agent promoted oxidation of gold nanoparticles: cetyl trimethylammonium bromide. Physical Chemistry Chemical Physics, 17(39), 26054-26058.

Schmutzler, T., Schindler, T., Zech, T., Lages, S., Thoma, M., Appavou, M., … & Unruh, T. (2019). n-hexanol enhances the cetyltrimethylammonium bromide stabilization of small gold nanoparticles and promotes the growth of gold nanorods. Acs Applied Nano Materials, 2(5), 3206-3219.

Wang, N., Cao, P., Ma, H., & Lin, M. (2021). How stabilizers and reducing agents affect the formation of nanogold amalgams. Langmuir, 37(25), 7681-7688.