Mendeleev Commun., 2015, 25, 358–360 – 358 – Mendeleev Communications © 2015 Mendeleev Communications. Published by ELSEVIER B.V. on behalf of the N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences. Porous nanocomposites based on polysaccharides are widely used in cosmetic and medical fields and for the production of carbon materials, catalytic supports etc. 1 Cellulose is of special interest because the modification of this natural polymer with metal nanoparticles (NPs) gives special magnetic, catalytic and antibacterial properties to the material. 1,2 For example, cellulose modified with Ag NPs exhibits high antibacterial properties. 3 Methods for modifying cellulose with metal NPs are based on metal recovery from precursors, such as metal salts, metal complexes and other metal compounds introduced into the polymer. 4 As a rule, polymers modified with metals require an additional cleaning procedures to remove the decomposition products of the complex, the reducing agent, surfactants or other compounds used in the synthesis of metal NPs. Metal-vapor synthesis (MVS) is free of these disadvantages and affords mono- and bimetallic NPs 5 and materials based on them. 6 Metal NPs synthesized by MVS are in the non-oxidized form, the formation of materials occurs at temperatures up to 300 K, which allow the polymer to avoid degradation. The formation of porous polymer structure promotes effective stabilization and more uniform distribution of NPs in polymer surface layers. For instance, porous cellulose can be produced by direct dissolving cellulose in an aqueous alkali followed by precipitation and freeze drying. 7 The XRD patterns of MCC [Figure 1(a)] and Au/powder MCC † [Figure 1(b)] show peaks characteristic of native cellulose 10 Mesoporic material from microcrystalline cellulose with gold nanoparticles: a new approach to metal-carrying polysaccharides Alexander Yu. Vasil’kov,* a Margarita S. Rubina, a Albina A. Gallyamova, b Alexander V. Naumkin, a Michael I. Buzin a and Galina P. Murav’eva b a A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow, Russian Federation. Fax: +7 499 135 9380; e-mail: alexandervasilkov@yandex.ru b Department of Chemistry, M. V. Lomonosov Moscow State University, 119991 Moscow, Russian Federation 09.014 DOI: 10.1016/j.mencom.2015. The mesoporic hybrid material was prepared from microcrystalline cellulose modified with gold nanoparticles by metal-vapor synthesis. † Metal-carrying polymer composite was prepared by the impregnation of microcrystalline cellulose (MCC) (Avicel PH-101; degree of poly- merization, 180; Sigma Aldrich) with an Au organosol in Pr i OH which was distilled from molecular sieves (4 Å) and degassed in a vacuum by freezing–thawing cycles. The organosol was prepared by MVS according to a procedure described elsewhere. 8 Gold (99.99%) was evaporated by resistively heating a tungsten rod (d = 1.5 mm) at a residual pressure of 10 –2 Pa. In a typical experiment, the metal and Pr i OH vapor were condensed on liquid nitrogen-cooled walls of a 5-l reactor. Next, the deposit was melted, and the resulting metal organosol was infiltrated into MCC in an evacuated Schlenk vessel. The excess organosol was removed, and the support was dried in a vacuum of 1 Pa at 90 °C for 1 h. At the final stage, the powder of MCC containing gold nanoparticles was obtained (Au/powder MCC). All manipulations were performed in a pure Ar atmosphere. The sol-gel technology 9 combined with freeze-drying was used for preparing cellulose with porous structure. Firstly, Au/powder MCC was mixed with water and kept for 2 h at 5 °C to allow fiber swelling. Then, the blend was cooled at –6 °C, and aqueous alkali precooled at –6 °C was added. For preparing a 100-ml solution, 5 g of MCC in 60 ml of water and 7.6 g of NaOH in 40 ml of water were taken. Mixing was performed at –6 °C for 2 h with a stirring rate of 1000 rpm. After 2 h, the solution was poured into cylindrical molds, in which gelation occurred at 60 °C for 2 h. Then, the cylindrical blocks of MCC with gold nanoparticles were washed with water to remove NaOH. The regenerated block was cooled to –12 °C in a refrigerator and subjected to freeze-drying in a vacuum at 1 Pa and at room temperature. Finally, porous structure of MCC with gold nanoparticles (Au/porous MCC) was obtained. The Au concentration in the sample was determined on a VRA 30 X-ray fluorescent analyzer (Germany) using the Au La line. The X-ray diffractometry (XRD) of the samples was performed in reflection mode (Stoe Stad P, Germany) with CuKa radiation ( l = = 0.15406 nm) in the range of 2q = 5–40°. The crystallite sizes were estimated with full-width half-maximum of respective diffraction peaks. The XPS measurements were performed with Quantera SXM (Physical Electronics, USA) using an Al Ka X-ray source (1486.6 eV). The spectra were measured at room temperature and the pressure in the sample analysis chamber was ~5×10 –8 Pa. The binding energy scale was calibrated against the peaks of Au 4f 7/2 (84.0 eV), Ag 3d 5/2 (368.3 eV) and Cu 2p 3/2 (932.7 eV). Thermogravimetric analysis (TGA) and dynamic thermogravimetric analysis (DTA) were carried out on a DerivatographC (MOM, Hungary) at a scan rate of 10 K min –1 from room temperature to 800 °C in air and argon atmospheres, respectively. Nitrogen physisorption measurements at 77 K were performed on a Gemini VII 2390 (V1, 02 t) instrument (Micrometrics, USA). Before the analysis the samples were degassed at 300 °C for 12 h in a vacuum to remove the adsorbed species. The Brunauer–Emmett–Teller (BET) and Barrett–Jyner–Halenda (BJH) analyses were done by the standard software. Specific surface areas were calculated by the BET model for a relative vapor pressure of 0.2. The total pore volume and pore radius distribution were calculated by the BJH model for a relative vapor pressure of 0.95. 5 10 15 20 25 30 35 40 45 50 0 20 40 60 80 110 020 110 Au (200) Au (111) Au (200) 110 Intensity (arbitrary units) 2q/deg 110 200 400 Au (111) (c) (b) (a) XRD patterns: ( Figure 1 a) Au/porous MCC, (b) Au/powder MCC and (c) MCC.