the effect of oh groups on the optical and structural properties of tio 2 nanoparticles sami...
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![Page 1: The effect of OH groups on the optical and structural properties of TiO 2 nanoparticles Sami Auvinen, Olga Miroshnichenko, Matti Alatalo, Lappeenranta](https://reader036.vdocument.in/reader036/viewer/2022062407/56649e7b5503460f94b7cd83/html5/thumbnails/1.jpg)
The effect of OH groups on the optical and structural properties of
TiO2 nanoparticles
Sami Auvinen, Olga Miroshnichenko, Matti Alatalo,
Lappeenranta University of Technology
![Page 2: The effect of OH groups on the optical and structural properties of TiO 2 nanoparticles Sami Auvinen, Olga Miroshnichenko, Matti Alatalo, Lappeenranta](https://reader036.vdocument.in/reader036/viewer/2022062407/56649e7b5503460f94b7cd83/html5/thumbnails/2.jpg)
Motivation
Manufacturing methods are based on hydrolysis from different solutions
Many applications of titanium dioxide take place in aqueous environment
Source: Flickr
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Computational details
A B
• DFT, TDDFT
• Real space grid
• Non-periodic boundary conditions
• PBE
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Breaking or stretching Ti-Ti and Ti-O bonds =>
● Lower number of bonds in relaxed structures,● Increasing of average dimensions of clusters,
but the average length of bonds does not change much
Structural effects
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Electronic properties
DOS for bare A- (a) and B- (b) structures. HOMO and LUMO levels are plotted with vertical dashed lines.
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Electronic properties
DOS for bare B- (a) and B- with one OH (b) structures. HOMO and LUMO levels are plotted with vertical dashed lines. In (b) HOMO and LUMO levels are almost identical.
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Electronic properties
DOS for bare A- (a), A- with one OH (b), A- with 6 OH (c), and A- with 16 OH (d) structures. HOMO and LUMO levels are plotted with vertical dashed lines. In (b) and (d) HOMO and LUMO levels are almost identical. 8
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Optical properties
Total photoabsorption spectra for bare A-structure, A-structure with one OH-group, with 6 OH-groups, and with 16 OH-groups.
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Optical properties
Total averaged refractive index function for bare A-structure, A-structure with one OH-group, with 6 OH-groups, and with 16 OH-groups.
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Conclusions
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• OH groups alter the structure of the particles, breaking and streching the near surface Ti-Ti and Ti-O bonds
• Adsorbed OH groups cause enhancement of the intensity of the DOS of particles at the lower part of the valence band and at the upper part of the conduction band
• The same trend with increasing absorption at low and higher energies can be seen in photoabsorption spectra and RIFs of the nanoparticles
=> The effects of the surrounding media have to be taken into consideration when considering the computationally modeled absorption properties of the small TiO2 nanoparticles