Chapter 10
Hetero- and Under-Coordination
Coupling
Abstract A combination of the hetero- and under-coordination forms a promising means of mediating the bonding and electronic dynamics and properties of a
substance as the hetero- and under-coordination enhance each other on the charge
entrapment and polarization. However, at a critical size, polarization may compensate or override quantum entrapment because of the polarization screens and splits
the interatomic potentials.
Highlights
• Hetero- and under-coordination enhances each other on the CL shift and valence
states.
• The enhanced polarization screens and splits the interatomic potential and offsets
the CLS.
• The joint effect mediates the band gap, electroaffinity, carrier life, and work
function.
• Coordination engineering forms powerful means of modulating materials performance.
10.1 Ti(0001) Skin and TiO 2 Nanocrystals
10.1.1 Photoactivity of Defected TiO 2
The photoactivity of the nanoscaled or the highly defected TiO 2 has received much
attention owing to its tunable band gap and work function [1–6]. The heterocoordinated bulk TiO 2 is only active under UV irradiation exciting electrons to
overcome the band gap of 3.2 eV for the anatase and 3.0 eV for the rutile phase
[7, 8]. Although the defected, or undercoordinated TiO 2 that contains the Ti
3+ ions
or oxygen vacancies absorbs visible light [9, 10], the mechanism for the defect modulation of the band gap, affinity, carrier life, and work function is very important for
devising materials having derived functions.
© The Editor(s) (if applicable) and The Author(s), under exclusive license
to Springer Nature Singapore Pte Ltd. 2020
C. Q. Sun, Electron and Phonon Spectrometrics,
https://doi.org/10.1007/978-981-15-3176-7_10
205
Hetero- and Under-Coordination
Coupling
Abstract A combination of the hetero- and under-coordination forms a promising means of mediating the bonding and electronic dynamics and properties of a
substance as the hetero- and under-coordination enhance each other on the charge
entrapment and polarization. However, at a critical size, polarization may compensate or override quantum entrapment because of the polarization screens and splits
the interatomic potentials.
Highlights
• Hetero- and under-coordination enhances each other on the CL shift and valence
states.
• The enhanced polarization screens and splits the interatomic potential and offsets
the CLS.
• The joint effect mediates the band gap, electroaffinity, carrier life, and work
function.
• Coordination engineering forms powerful means of modulating materials performance.
10.1 Ti(0001) Skin and TiO 2 Nanocrystals
10.1.1 Photoactivity of Defected TiO 2
The photoactivity of the nanoscaled or the highly defected TiO 2 has received much
attention owing to its tunable band gap and work function [1–6]. The heterocoordinated bulk TiO 2 is only active under UV irradiation exciting electrons to
overcome the band gap of 3.2 eV for the anatase and 3.0 eV for the rutile phase
[7, 8]. Although the defected, or undercoordinated TiO 2 that contains the Ti
3+ ions
or oxygen vacancies absorbs visible light [9, 10], the mechanism for the defect modulation of the band gap, affinity, carrier life, and work function is very important for
devising materials having derived functions.
© The Editor(s) (if applicable) and The Author(s), under exclusive license
to Springer Nature Singapore Pte Ltd. 2020
C. Q. Sun, Electron and Phonon Spectrometrics,
https://doi.org/10.1007/978-981-15-3176-7_10
205