Structure, electronic levels, and ionic interactions of 1 nanometer silicon particles

Silicon nanocrystal;Vibrational spectroscopy;Fluorescence;Metal ion complex

Mantey, Kevin A.

关键词: Silicon nanocrystal;    Vibrational spectroscopy;    Fluorescence;    Metal ion complex;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/26172/Mantey_Kevin.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Silicon particles are created via anodic or platinum catalyzed etching of bulksilicon. A peroxide and HF etchant provides uniform surface termination, andresults in discrete stable sizes for particles below 3 nm in size. The smallestof these are 1 nm silicon particles, which is amenable torst principles quan-tum calculations of the structure, electronic levels, and ionic interactions.The vibrational modes of several candidate structures of the 1 nm particlesare calculated at the Hartree-Fock level, and compared to previously acquiredRaman spectra to determine the structure. The vibrational modes are alsocompared to the vibrational structure in low temperature photo-luminescenceto indicate surface reconstruction bonds play a role in the uorescence. Theuorescence mechanism is explored further with calculations of the excitedstate potential energy surface using time dependent density functional theory,which show radiative traps accessible via direct excitation at the band edgeof the ground state geometry. The self-trapped excitons proposed by Lannooet al. [1, 2] are found to be unstable for the Si29H24 structure, with theouter-well leading to non-radiative recombination via conical intersection ofthe excited state with the ground state. Absorption measurements indicatethe silicon nanoparticles may form charge complexes with iron ions in aque-ous solutions. Calculations including solvation e ects provide a proposedstructure for the complex, with a binding energy of 0.49 eV. The bindingmechanism is quite general and suggests many other ions could form chargecomplexes with the silicon particles in aqueous solutions, potentially leadingto new applications.