Supporting information file 1

Characterization of SiO2-Cu2O

The SiO2-Cu2O was characterized by FTIR, thermogravimetric analysis (TGA), X-ray diffractometry (XRD), X-ray photoelectronspectroscopy(XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic absorption spectroscopic analysis (AAS). In FTIR spectra, the activated silica showed absorption peaks at 459, 800, 964, 1344, 1384, 1400, 1598, 2341, 2362, 2856, 2929 cm-1 and wide absorption bands are observed at 1078 and 3396 cm-1 (Fig 1).For SiO2-Cu2O, an additional peak was observed at 669 cm-1 which corresponded to Cu2O (Fig 2).

Fig. 1 FTIR spectra of activated silica.

Fig. 2 FTIR spectra of SiO2-Cu2O.

Further, the stability of the SiO2-Cu2O was determined by thermal analysis (TGA) (Fig 3).. The curve showed an initial weight loss up to 116 oC which may be due to the loss of residual water trapped onto the surface of silica and then slight weight loss occur upto 325 oC, which may be due to the loss of unreacted glucose or components of Fehling solution followed by continuous weight loss upto 648 oC. This indicates that catalyst is stable upto 325 oC and hence it is safe to carry out the reaction at 100 oC.

Fig. 3 TGA of SiO2-Cu2O.

The powdered XRD diffraction patterns for SiO2-Cu2O showed the peaks which were indexed on the basis of crystallographic data for the known structure of silica. In addition, reflection patterns were found in XRD pattern corresponding to 2θ= 36.3o and 42.2o which were attributed to Cu2O and there is no peak corresponding to 2θ= 38.7o,which rules out the possibility of formation of CuO (Fig 4).

Fig. 4 XRD pattern of SiO2-Cu2O.

Further, the oxidation state of copper in SiO2-Cu2O was determined by the measurements of binding energies using XPS. The spectrum of Cu2p3/2 photoelectrons is shown in Fig 5. The intense and broad peak at 933 eV corresponds to Cu (I) which is in accordance with the literature values [23-24].

Fig. 5XPS spectra of SiO2-Cu2O.

The amount of copper loaded onto the surface of silica was determined by AAS analysis. The catalyst was stirred in dil. HNO3 and then subjected to AAS analysis. It was found that SiO2-Cu2O contained 0.0158 g of Cu per gram of catalyst. The microstructure and morphology of SiO2-Cu2O was studied using Scanning Electron Microscope (SEM) andtransmission electron microscopy (TEM). SEM image of SiO2-Cu2O indicated that it is a fine homogenous powder with porous structure (Fig. 6).

(a) 500 X (b) 3,500 X

Fig. 6SEM images of SiO2-Cu2O.

The TEM micrographs of the catalyst showed that copper is uniformly distributed onto the surface of silica (Fig. 7). The mean diameter was found to be 7 nm. Further, no bulk aggregation of the metal occurred indicating that Cu was finally dispersed onto the surface of silica.

(a)

(b)

Fig. 7 TEM images of SiO2-Cu2O.