Radiation-induced grafting of carbon nanotubes on HPLC silica microspheres: theoretical and practical aspects

Abstract

Multi-walled carbon nanotubes (MWCNTs) were grafted for the first time by γ-radiation onto silica microspheres in the presence of polybutadiene (PB) as the linking agent, obtaining a novel hybrid material with chromatographic properties, with an alternative approach to the existing procedures. The synthesis involves the one-pot γ-radiation-induced grafting of MWCNTs onto silica microspheres in the presence of PB as a linking agent. PB also serves as a coating layer of the silica particles, to which MWCNTs are anchored through stable chemical bonds formed via radical chain reaction with the polymer. The product (MWCNT-PB-modified silica) resulted in MWCNT bundles interlaying the silica particles which acted as a support and as a spacer. This new material highlights the unquestionable properties of CNTs also when grafted in a composite, thus allowing the disposition of a more robust material whose properties are still related to the nanotube structure. The grafting was confirmed by Raman spectroscopy. The surface area, determined by BET isotherms, resulted in 132 m(2) g(-1), about 34% lower than that of pure silica, pointing to the cross-linking effect of PB in the silica matrix. The evaluation of MWCNT-PB-modified silica as a LC stationary phase was performed by separation of aromatics, with satisfactory resolution and reproducibility, while structural selectivity was proved by isomer separation. A good resolution was obtained also for acid/basic compounds as barbiturates. A comparison with a commercial C18 sorbent highlighted the advantage in using the CNT column for separating aromatic hydrocarbons. Control experiments on the PB-coated silica column proved the key role of MWCNTs in the chromatographic performance.

Multifunctionalized Carbon Nanotubes Polymer Composites: Properties and Applications

“…The polybutadiene composites using CNTs show higher enhancement in the electrical properties that can interrelate within the framework of percolation theory (Zhou et al 2005). The electrical percolation for polybutadiene often observed in the greater CNTs content around between 2 and 14 wt% (Speltini et al 2013). The application range of polybutadiene once suitably reinforced with CNTs can extend to a variety of products such as sensors/actuators, materials with electromagnetic shielding properties, vapor and infrared sensor, and capacitors.…”

Tuning retention and selectivity in reversed-phase liquid chromatography by using functionalized multi-walled carbon nanotubes

“…MWCNTs were purified by HCl treatment as earlier reported (Merli et al 2011;Speltini et al, 2010); the purified MWCNTs were grafted onto the silica particles by gamma radiation following the procedure previously described (Speltini et al, 2013b), to obtain MWCNT-PB-silica (CNT content 5 wt%).…”

“…In this context, differently from the common chromatographic reversed-phases that can be regarded as mono-modal separation media, nanostructured carbon materials showed special selectivity (Speltini et al, 2013a). The good sorption properties of CNTs have been exploited to prepare a number of chromatographic stationary phases for both gas chromatography (GC) (Hussain et al, 2011;Merli et al, 2010;Saridara and Mitra, 2005;Speltini et al, 2010Speltini et al, , 2012 and liquid chromatography (LC) (André et al, 2012;Chambers et al, 2011;Merli et al, 2015;Speltini et al, 2013b), as recently reviewed (Speltini et al, 2013a;Zhang and Qiu, 2015). The analytical application of these carbon nanomaterials in the field of separation science does not cover the chromatographic technique only, but also includes sample preparation, in particular with regard to solidphase extraction (SPE) and solid-phase micro-extraction (SPME) (Herrera-Herrera et al, 2012;SocasRodríguez et al, 2014).…”

“…Recently, a novel method entailing gamma radiation has been proposed to anchor MWCNTs onto silica (Speltini et al, 2013b), and the procedure turned out to be simple, mild, one-pot and maintaining the CNT pristine structure. Being the adsorption affinity of such composite strictly related to the MWCNTs properties, that stationary phase resulted as a double-purpose material, suitable for chromatographic applications, and at the same time a valid tool to study the intermolecular interactions of aromatics with the nanotubes (Merli et al, 2015).…”

“…These were prepared starting from pristine MWCNTs (purified from the metallic fraction) by derivatization with 2,2'-(ethylenedioxy)diethylamine, and their functionalization degree was determined by thermogravimetric analysis (TGA). Derivatized MWCNTs were immobilized by gamma radiation onto the silica support in presence of polybutadiene (PB) which has the sole function of linking agent (Speltini et al, 2013b). The hybrid material (MWCNT-R-NH 2 -PB-silica) was characterized by scanning electron microscopy (SEM), Brunauer, Emmett and Teller (BET) isotherms and attenuated total 5 reflectance Fourier transform infrared spectroscopy (ATR FT-IR) measurements, and the batch-to-batch reproducibility was investigated.…”