Photocatalytic activity of silica-silver nanocomposites to degrade aromaticcompounds.

- Electronic Supporting Information -

Photocatalytic activity of silica-silver nanocomposites to degrade aromatic compounds.

G. Romolini^ǂ M. Gambucci, D. Ricciarelli, L. Tarpani, G. Zampini^* L. Latterini^*.

Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy.

ǂ Present address: Chem & Tech, Molecular Imaging and Photonics, KULeuven, Celestijnenlaan 200 F, B- 3001 Leuven, Belgium.

*Corresponding authors. GZ giulia.zampini87@gmail.com; LL loredana.latterini@unipg.it Tel.: +39 075 5855583; Fax: +39 075 5855598

Table of contents

- FTIR spectra of SiO2 NPs and NH2-SiO2 NPs 2

- Size distribution of SiO2 NPs and NH2-SiO2 NPs 2-3

- TEM image and size distribution of Ag-NPs 3

- Extinction spectra of Ag NPs in water before and after the contact with NH2-SiO2 NPs 4 - Extinction spectra NPs suspension at time 0 and after 72 hours 4

- Fluorescence spectra of 9ACA 5

- Normalized absorption and fluorescence spectra of 9ACA 5

- Kinetics analysis of 9ACA photodegradation under irradiation with indoor light lamp 6

- Absorption spectra of DPBF solution 6

- Absorption spectra of DPBF solution exposed to different irradiation times 7 - Absorption spectra of DPBF solution in the presence of Rose Bengal 7

- Emission spectra of Hg and fluorescent lamp 8

Determination of the quantum efficiency of reactive oxygen species formation 9

Figure S1. IR spectra of SiO2 NPs and SiO2-NH2 NPs.

Figure S2. TEM size distribution of SiO2 NPs, counting approximately 100 nanoparticles. The

Figure S3. TEM size distribution of NH2-SiO2 NPs, counting approximately 100 nanoparticles. The average diameter obtained is 123 nm ( = 9).

Figure S4. TEM image (scale bar 100 nm) and size distribution of Ag NPs counting approximately 400 nanoparticles. From the analysis of the size distribution, it has been derived an average diameter of 10 nm ( = 3 nm).

Figure S5. Extinction spectra of Ag NPs in water before (black line) and after (red line) the contact procedure with NH2-SiO2 NPs. The different intensity of the plasmonic band has been used to quantify the amount of silver colloids adsorbed onto silica surface.

Figure S6. Extinction spectra of an aqueous Ag-SiO2 NPs suspension (0.5 mg/mL) at time 0 (black line) and after 72 hours (red line).

Figure S7. Examples of 9ACA emission spectra (exc = 363 nm) collected after different time of irradiation at 313 nm in the absence (a) and in the presence of SiO2 NPs (b), NH2-SiO2 NPs (c) and Ag-SiO2 NPs (d). The emission spectrum at time 0 is reported in bold black line, whereas that at time 120 minutes in red line.

Figure S8. Normalized absorption (blue line) and fluorescence spectra (exc = 363 nm, red line) of an aqueous solution of 9ACA.

Figure S9. Kinetics analysis of 9ACA photodegradation under common indoor light irradiation (FL), using various silica nanocomposites: SiO2 (red circle), NH2-SiO2 (blue triangle) and Ag-SiO2

(magenta triangle). As reference, it is reported 9ACA photodegradation in absence of silica nanocomposites (black square). The dotted lines are the fittings of the kinetic data.

Figure S10. Absorption spectra of DPBF solution, stored in dark for different time, in the absence (a) and in the presence (b) of Ag-SiO2 NPs.

Figure S11. Absorption spectra of DPBF solution exposed to different time of FL irradiation, in the absence of the photocatalyst.

Figure S12. DPBF absorption spectra (a) and decay (b) of Rose Bengal (RB) at 410 nm upon irradiation with common indoor light irradiation source (FL), used as standard for the calculation of ROS production efficiency.

Figure S13. Emission spectrum of a high-pressure Hg lamp used for the experiments. The emission lines at 313 nm or 405 nm were selected through interferential filters, whose band-pass width is depicted, to obtain monochromatic light.

Figure S14. Emission spectrum of a fluorescent lamp used in the experiments.

Figure S15. Emission intensity of 9ACA under 313 nm (black squares) or 405 nm (red circles) irradiation in the presence of AgNP.

Determination of the quantum efficiency of reactive oxygen species formation

The photoinduced quantum efficiency of ROS formation has been determined through a widely used ROS trap, 1.3-diphenylisobenzofuran (DPBF), whose absorption is centered at 410 nm. The time evolution of DPBF concentration, as consequence of DPBF oxidation upon reaction with the formed ROS, has been determined through spectrophotometric data.

The kinetic analysis of the spectrophotometric data has been carried out upon applying the steady state approximation to ROS, through the following equation:

ln

(

)

where [DPBF]0 and [DPBF]t are the DPBF concentrations at the beginning and at different irradiation times (t) respectively, and kobs is the pseudo-first order rate constant for DPBF photo- induced oxidation. kobs has been determined by the linear correlation of ln

[

/A_t⁴¹⁰

]

time, where A_t⁴¹⁰ and A₀⁴¹⁰ are the absorbance values at 410 nm recorded at different irradiation times and before irradiation, respectively.

The values of DPBF photo-oxidation rates, determined in the presence of the sample under investigation ( k_obs^x ) or in the presence of the standard ( k_obs^s ), enabled the determination of

ROS formation quantum efficiency ( Φ_ROS^x ), according to Equation below reported [35]. Rose Bengal in ethanol was used as standard.

∫

350nm 700nm

|¿^x|

350

∫

|¿^s|

¿ Φ_ROS^x =Φ_ROS^s ∙k_obs^x

k_obs^s ∙¿

|¿^s|

¿ and ^|¿^x|

¿ are the absorbance values of the standard and the sample under investigation, respectively, integrated into the UV-VIS range.

Since DPBF spectrophotometric spectrum has been corrected for the spectra of the colloids (SiO2

NPs, NH2-SiO2 NPs or Ag-SiO2 NPs.

The solvent used was ethanol.