Colloids and Surfaces B: Biointerfaces 152 (2017) 12–17 Contents lists available at ScienceDirect Colloids and Surfaces B: Biointerfaces jo ur nal ho me p ag e: www.elsevier.com/locate/colsurfb Protocols Hybrid nano-composites made of ss-DNA/wrapped carbon nanotubes and titania Martina Romio, Camillo La Mesa ∗ Dept. of Chemistry, La Sapienza University, P.le A. Moro 5, 00185, Rome, Italy a r t i c l e i n f o Article history: Received 15 July 2016 Received in revised form 25 November 2016 Accepted 8 December 2016 Available online 24 December 2016 Keywords: Multi-walled carbon nanotubes ss-DNA DNA-MWCNT adducts Titania nano-particles Surfactant-assisted adsorption Titania binding onto DNA-MWCNT adducts a b s t r a c t Multi-walled carbon nanotubes, MWCNTs, are stabilized thanks to the surface wrapping of single-strand DNA, ss-DNA; the resulting adducts are kinetically and thermodynamically stable Such entities build up nano-hybrids with titania, TiO 2 , nano-particles, in presence of surfactant as an adjuvant. The conditions leading to TiO 2 adsorption onto ss-DNA/CNTs were investigated, by optimizing the concentration of adducts, nano-particles (NPs), and of the cationic surfactant (CTAB). Controlling the working conditions makes possible to get homogeneously organized hybrids. Characterization by DLS, electro-phoretic mobility, SEM and AFM clarified the surfactant-assisted association modes between adducts and CTAB-functionalized TiO 2 . Nano-particles’ clustering onto DNA- wrapped adducts gives hybrids trough electrostatic interactions. Surface coverage by TiO 2 is significant and homogeneous. It is expected that the reported hybrids can be useful for applications in heterogeneous catalysis. © 2016 Published by Elsevier B.V. 1. Introduction Because of their outstanding physical and chemical proper- ties carbon nanotubes, CNTs, play a key role in applied research since over twenty years [1–3]. They are relevant in materials sci- ences, surface coverage, heterogeneous catalysis, energy storage and biomedical applications [4–7]. The above facts hold true despite drawbacks met in the stabilization of their dispersions [8–10]. To circumvent these disadvantages, hindering possible applications, and to avoid the use of toxic solvents, efforts focus on the stabiliza- tion in aqueous-based media. Accordingly, covalent, [11,12] or non covalent [13–17], stabilization procedures were proposed. Among stabilizers considered to date, single-stranded DNA received much attention [18–21]. Dispersions of ss-DNA/CNTs are kinetically and thermodynamically stable. It is possible, thus, to disperse sig- nificant CNTs amounts (some wt%). Consider that the maximum quantity effectively dispersible in the original form is orders of mag- nitude lower. Many properties of such adducts were investigated in detail, and the regions of existence of the different phases they form were defined [22,23]. New research fields may take advantage from the behav- ior of the above adducts. Along this line, the manuscript uses ∗ Corresponding author. E-mail address: camillo.lamesa@uniroma1.it (C.L. Mesa). ss-DNA/MWCNTs (Multi-Walled Carbon Nanotubes) as templates for mono-dimensional nano-particles assembly [24]. The pro- cedure deals with electrostatic interactions and replaces the non-specific ones reported so far [25]. It is possible, for instance, to get nano-hybrids, NHs, by mixing ss-DNA/MWCNTs and nano- particles, NPs, in due ratios. We report on the preparation of NHs made of ss-DNA/MWCNTs and titania, TiO 2 . NPs were functional- ized and characterized before mixing them, to form the hybrids. The preparation procedures and the control of intermediate adducts formed accordingly are described. A physico-chemical and mor- phological characterization of the hybrids were also performed and the optimal working conditions leading to the desired products were determined. The manuscript gives information on the procedures and control of forces leading to assembly. We described how TiO 2 adsorbs onto ss-DNA/MWCNTs and controlled these processes by DLS, electro- phoretic mobility, SEM and AFM in a step-by-step strategy. Data analysis gives information on each stage, and on final NHs, as well. We attempted to solve problems related with the self-assembly of colloids differing in nature, size, shape, surface coverage and charge density. The results showed that the formation of stable hybrids is possible if binding of CTAB-covered TiO 2 is controlled by their net charge. Binding requires a careful modulation of surface charge density for effective interactions to occur. Taking into account that CNTs are surface-functionalized by DNA, the interactions are electrostatic in nature. Aqueous TiO 2 is http://dx.doi.org/10.1016/j.colsurfb.2016.12.011 0927-7765/© 2016 Published by Elsevier B.V.