Functional Hollow Carbon Nanospheres by Latex Templating Robin J. White,* Klaus Tauer, Markus Antonietti, and Maria-Magdalena Titirici Max-Planck-Institut fu ¨r Kolloid- und Grenzflaechenforschung, MPI Campus Golm, Am Muehlenberg, 14476 Golm, 14424 Potsdam, Germany Received August 26, 2010; E-mail: robin.white@mpikg.mpg.de Abstract: A facile and sustainable synthesis of hollow carbon- aceous nanospheres is presented, offering a scalable and multifunctional route to the generation of useful nanocontainers, which critically possess the stability not offered by polymeric equivalents and functionality not afforded by other nanocarbons. Carbonization temperature provides a subtle but elegant mech- anism to control structure and thereby hydrophobicity, nanopar- titioning, and permeation between the inner and outer space. Future nanotechnology depends importantly on the ability to synthesize new nanomaterials possessing distinct structural and functional features. 1 In this context hollow nanospheres are unique materials and have attracted much research and industrial interest, due to their special shape, low density, and large void space fraction. Hollow nanospheres are “processable Voids”, possessing excellent flow performance and high surface area, where the high internal volume provides a unique storage space or artificial reaction “cell”. 2 Applications of such hollow “bodies or pores” are diverse; they can be utilized as delivery/protection devices for a wide range of biologically/pharmaceutically important moieties (e.g., drugs, 3 contrast imaging agents, 4 and DNA 5 ), are attractive candidates for the heterogenization and structure direction of catalysts (e.g., in fuel cells), 6,7 and find use as templates 8 and adsorbents/detoxifi- cation media. 9 In the context of the aforementioned applications, immense research interest has recently focused on the production of new high value hollow carbon-based nanomaterials, arising due to anticipated enhanced mechanical and electronic application per- formance. Current 2D and 3D carbon nanomaterials possess highly curved condensed aromatic/graphitic wall structuring and include nanotubes, 10 fullerenes, 10b,11 onions, 12 and nanocones. 13 These materials are however typically prepared in low yield, using expensive high vacuum techniques such as laser vaporization, 14 resistive heating, 15 or arc discharge methods, 16 with the products often lacking size or structure homogeneity, and hence are difficult to isolate and purify. 17 Furthermore, catalysts are often employed to access these materials at lower graphitization temperatures. 18 Here, we will focus on derivatives of hollow (graphitic) carbon nanospheres (HCS), owing to their proposed good electric con- ductivity, outstanding thermal stability, low density, and oxidation resistance at moderate temperature. In addition, we will describe control of additional, application relevant properties (e.g., surface functionality/degree of aromatic condensation (Vis-a `-Vis surface polarity)). Our group has previously exploited the hydrothermal carbon- ization (HTC) of a carbohydrate-based biomass under mild aqueous conditions for the production of a variety of useful functional carbonaceous nanomaterials, 19 including hollow micrometer-sized inorganic spheres, 20 and also the first versions of hollow but still weakly controlled HCS. 21 Given the techno- logical importance of HCS, we decided to investigate the use of inexpensive renewable carbohydrate precursors (e.g., D- glucose) in combination with polymer latex templates, in the production of HCS via HTC, thus providing a simple multifac- eted economical synthetic route which offers material property control in terms of surface chemistry/polarity, nanosphere size and shell thickness (Scheme 1). Homodisperse latex nanoparticles have been exploited previously for the synthesis of a wide range of hollow (inorganic) sphere materials. 2b,22 Latex nanoparticles can be readily prepared at a selectable size with a narrow size distribution allowing in principle subtle control of the hollow carbon nanosphere size over a wide range of diameters (e.g., below 150 nm). In this investigation hydroxyl terminated polystyrene latex (PSL) nanoparticles were selected as a suitable hydrogen bonding surface for the initial adsorption of HTC decomposition products, while the presence of sodium dodecyl sulfate (SDS) inhibits particle precipitation and association during the process. This approach also negates hazardous reagent use during the template extraction while the synthetic step is performed under relatively benign HTC conditions. An aqueous dispersion of PSL of the desired size (e.g., D ) 100 nm) is mixed with D-glucose acting as the carbon precursor (Scheme 1; Supporting Information). Our approach however is not limited to this model monomer, and in principle a broad variety of plant biomass-based products can be employed. 23 The system is then heated at 180 °C for 20 h. After reaction, the carbonaceous product can be filtered off, followed by washing with excess H 2 O and drying under vacuum. To remove the polymer template and to graphitize the carbonaceous shell, the composite material is then heated to the desired temperature above the template decomposition point (e.g., >500 °C; Figure 1S Supporting Information) The Scheme 1. Synthetic Strategy for the Synthesis Carbohydrate-Derived Hollow Carbonaceous Nanospheres Published on Web 11/18/2010 10.1021/ja107697s  2010 American Chemical Society 17360 9 J. AM. CHEM. SOC. 2010, 132, 17360–17363