Facile synthesis of polymer and carbon spheres decorated with highly dispersed metal nanoparticles

Transcription

1 Electronic Supplementary Material (ESI) for ChemComm. This journal is The Royal Society of Chemistry 1 Facile synthesis of polymer and carbon spheres decorated with highly dispersed metal nanoparticles Nilantha P. Wickramaratne and Mietek Jaroniec* Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio,, USA EXPERIMENTAL Synthesis of cysteine-stabilized polymer spheres. Cysteine-stabilized polymer spheres (PS) were synthesized using a slightly modified recipe reported in our previous work. 3 In a typical experiment, an aqueous-alcoholic solution was prepared by mixing 8 ml of ethanol and 1 ml of distilled water under refluxing conditions at 7 o C. Subsequently,.6 ml of 8 wt% ammonia and 1. g of cysteine were added under continuous stirring for 1 hour. Then, 1. g of resorcinol was added and stirred for another 3 minutes. Next, 1. ml of 37 wt% formaldehyde was slowly added and stirred for h under reflux conditions. Finally, the reaction mixture was transferred to a closed polypropylene bottle, which was placed in an oven at 1 o C for h under static conditions. The solid product (cysteine-stabilized PS) was obtained by centrifugation and washing several times with water. Finally, this product was dispersed in 1 ml of water and freeze-dried. Synthesis of polymer spheres decorated with metal nanoparticles. To decorate PS with metal nanoparticles,.1 g of cysteine-stabilized PS was dispersed in 1 ml of various metal salts (1 mm) and stirred for hours. Next, these metal-containing polymeric spheres were centrifuged and freeze-dried as described in the aforementioned section. The resulting polymeric spheres were labeled as PS-x and PS-x** in the case of metal-polymer composites obtained using 1 mm and mm solutions of metal salts, respectively; symbol x denotes metal, whereas CS refers to carbon spheres. In order to obtain CS, polymeric spheres were subjected to thermal treatment at 6 o C (carbonization) in flowing nitrogen in a tube furnace using a heating rate of o C/min up to 6 o C and dwell for h. The resulting carbon spheres were labeled as CS-x and CS-x* in the case of metal-carbon composites carbonized at 6 o C and 8 o C, respectively; symbol x denotes metal. Measurements and Characterization. Transmission electron microscopy (TEM) imaging was carried out using a FEI Tecnai FST/STEM instrument operated at kev. The preparation of samples for TEM analysis involved their sonication in ethanol for to 5 min and deposition on a mesh lacey carbon coated copper grid. 1

2 The X-ray diffraction (XRD) measurements were recorded for the carbonized samples using a PANanalytical, Inc. X Pert Pro (MPD) Multi-Purpose Diffractometer with Cu Kα radiation (1.56 Å) at an operating voltage of 5 kv. Nitrogen adsorption isotherms were measured at -196 C on ASAP 1 volumetric adsorption analyzer manufactured by Micromeritics (Norcross, GA, USA) using nitrogen of % purity. Before adsorption measurements, each sample was degassed under vacuum for at least h at C. The specific surface area of the samples was calculated using the Brunauer-Emmett-Teller (BET) method within the relative pressure range of.5-.. Pore size distributions were calculated using the BJH algorithm for cylindrical pores according to the KJS method. Thermogravimetric analysis (TGA) was performed on a TA instrument TGA Q5 thermogravimetric analyzer using a high resolution mode. The curves were recorded in flowing air with a heating rate of 1 o C/min from 3 to 8 o C. Two types of plots were obtained from the TGA data: (1) weight loss % vs. temperature; this plot is used to obtain the residue amount, and () derivate weight % vs. temperature; this plot is used to estimate the decomposition temperatures of organic components in the samples studied. Table S1. Surface area in m /g calculated from N adsorption isotherms using BET equation and residue % obtained from the TGA profiles. Sample CS CS-Ru CS-Ag CS-Mn CS-Gd CS-Fe CS-Au Surface area (m /g) Residue % <

3 PS Gd PS Gd PS Gd PS Fe CS Fe CS Mn CS Fe* CS Fe* CS Fe* PS Au CS Au CS Au Fig. S1 TEM images of the metal-containing PS and CS studied. 3

4 A B C Fig. S. The TEM and EDX spectra of PS-Fe (A), PS-Ru (B), and PS-Gd (C).

5 -Derivative weight (%/ o C) 3 Temperature (oc) 6 8 Temperature ( o C) A PS-Ag (h) PS-Ag (h) PS-Ag** Weight (%) -Derivative weight (%/ o C) Temperature (oc) 6 8 Temperature ( o C) B CS-Fe CS-Fe* Weight (%) Fig. S3. TG and differential weight change (DTG, inset) profiles for the PS-Ag (A) and CS-Fe series of carbons. 5

6 -Derivative weight (%/ o C) PS-Au PS-Ag PS-Ru PS-Fe A 3 Temperature (oc) 16 -Derivative weight (%/ o C) CS-Au CS-Ag CS-Ru CS-Fe 3 B Temperature ( o C) Fig. S. Differential weight change (DTG) profiles for the metal-containing PS (A) and CS (B). Note that the oxidation temperatures of carbon can vary due to the metal present in the carbon sample. For example, it has been shown that the presence of K, Na, etc. can catalyze the oxidation of carbon in oxygen-containing atmosphere at elevated temperatures (Ogura, M.; Morozumi, K.; Elangovan, S. P.; Tanada, H.; Ando, H.; Okubo, T. Applied Catalysis B, Environmental 8, 77, 9-99). 6

7 PS-Ag CS-Ag Intensity (arb.units) CS-Ru = Ru, = RuS CS-Au 6 8 / degree Fig. S5. Wide angle XRD patterns for selected metal-containing polymer and carbon spheres studied. Volume Adsorbed (cm 3 STPg -1 ) 5 CS CS-Ru CS-Ag CS-Mn CS-Gd 3 CS-Fe CS-Au Relative Pressure Fig. S6. N adsorption isotherms for the metal-containing carbon spheres studied. 7