Porous Silicon for Photosensitized Formation of Singlet Oxygen in Water and in Simulated Body Fluid: Two Methods of Modification by Undecylenic Acid
| Autor: | Jarno Salonen, María Balaguer, Ester Pastor, Vesa-Pekka Lehto, Eugenia Matveeva, Vladimir S. Chirvony, Leszek Bychto |
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| Rok vydání: | 2009 |
| Předmět: |
Luminescence
Materials science Aqueous solution Biomedical Engineering Chemical modification Bioengineering General Chemistry Condensed Matter Physics Porous silicon Photochemistry Surface Modification Silicon Nanoparticles Undecylenic acid Semiconductor Photosensitizer medicine Surface modification Aqueous Suspension General Materials Science Chemical binding Surface states medicine.drug |
| Zdroj: | RiuNet. Repositorio Institucional de la Universitat Politécnica de Valéncia instname |
| ISSN: | 1533-4880 |
| Popis: | Initially H-terminated and therefore hydrophobic surface of electrochemically prepared luminescent porous silicon (PSi) powder was transformed to the hydrophilic one by means of surface modification by undecylenic acid. Physical adsorption of undecylenic acid as a non-ionic surfactant and its chemical binding through C[triple bond]C bond opening and Si-C bond formation were applied as two different methods of PSi surface modification, physical and chemical modification, respectively. Luminescence of aqueous suspensions of the both types of modified PSi powders in merely water and in simulated body fluid physiological electrolyte was measured as a function of time. Many-fold (up to 20 times) building-up of the luminescence intensity was observed for PSi aqueous suspensions during the first few days, the growth was followed by a slower (a week and more) luminescence intensity decay. As it is evidenced by FTIR spectra and SEM images, the effect of the luminescence growth and decay of PSi suspension in water can be in part attributed to the PSi surface oxidation accompanied by its dissolution and de-aggregation of large PSi particles. It is concluded also from the experiments on PSi luminescence reversible quenching by O2 that SiO-related surface states with the excitation energy about 2.2 eV are formed during water-assisted oxidation of Si nanocrystal surface. An appearance of a large number of such surface states can be also responsible for the observed PSi luminescence building-up. |
| Databáze: | OpenAIRE |
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