<p> Electronic Supplementary Material An aptasensor for voltammetric and impedimetric determination of cocaine based on a glassy carbon electrode modified with platinum nanoparticles and using rutin as a redox probe</p><p>Mahmoud Roushani*, Faezeh Shahdost-fard</p><p>Department of Chemistry, Ilam University, Ilam, Iran E-mail address: [email protected] (M. Roushani). …An aptasensor for cocaine detection based on a nanocomposite</p><p>Synthesis of PtNPs</p><p>Controlling of reaction condition parameters for synthesis of NPs is a key factor. Stabilizer agent, concentration, time, pH and reaction temperature affects on the shape and size of NPs.</p><p>Based on the developed method, due to the fact that PtNPs should be coupled with the 5′-NH2-3′-</p><p>SH2-terminated aptamer via covalent bonds between the thiol and PtNPs, size of the synthesis NP should be appropriate. As reported in literature with decreasing the size of PtNPs, the binding energy between the S atom and PtNPs will be increased [1]. Because the very strong Pt-S covalent bond restricts Pt surface diffusion, thus PtNPs cannot coalesce into the larger atoms [2]. So, in order to achieve this objective, PtNPs with small size were prepared and the strong coupling between thiol-terminated aptamers and Pt atoms is one of the advantages of the present study. PtNPs were synthesized according to the reported procedure [3]. Briefly, a glycol solution of NaOH (0.5 M, 50 mL) was added into vigorously stirred 50 mL glycol solution of K2PtCl6 (1.0 g). To take away organic by compound and water, the obtained transparent yellow platinum hydroxide or oxide colloidal solution was heated at 160 °C under an atmosphere of N 2 (3 h). Then, a transparent dark-brown homogenous solution of platinum metal NPs (Pt: 3.76 g L-1 glycol, 19.3 mmol L-1) was obtained. The resulted colloidal solution have not any precipitate and remain stable for several months. The structure and morphology of prepared PtNPs were investigated be means of HRTEM and EDAX.</p><p>2 Fig. 1S SEM images of MWCNTs/IL/Chit nanocomposite. …An aptasensor for cocaine detection based on a nanocomposite</p><p>Fig. 2S (a and b) HRTEM photographs of the prepared PtNPs. (c) EDAX of the PtNPs and (d) TEM-SAED electron diffraction pattern of the PtNPs.</p><p>4 Fig. 3S Effect of incubation time on aptasensor response. 45 min is optimum time. …An aptasensor for cocaine detection based on a nanocomposite</p><p>References:</p><p>[1] Yang GW, Gao GY, Zhao GY, Li HL (2007) Effective adhesion of Pt nanoparticles on thiolated multi–walled carbon nanotubes and their use for fabricating electrocatalysts. Carbon 45(15):3036– 3041</p><p>[2] Yong TK, Tadaoki M (2006) Oxidation treatment of carbon nanotubes: an essential process in nanocomposite with RuO2 for supercapacitor electrode materials. J Catal 238(1):394–401</p><p>[3] Wang Y, Ren J, Deng K, Gui L, Tang Y (2000) Preparation of tractable platinum, rhodium, and ruthenium nanoclusters with small particle size in organic media. Chem Mater 12(6):1622–1627</p><p>6</p>