Facile tailoring of photoluminescence properties of surface-modified TiO2 nanocrystals

Surface modification of metal oxide nanomaterials is one of the promising techniques for tailoring its optoelectronic properties. In this paper, a novel method has been reported for controlling the optical band gap, generation of trapping states and inhibiting the charge carrier's recombination rate in TiO2 nanocrystals (NCs). It has been achieved through the surface modification of TiO2 NCs using organic ligands such as formamide (FA) and polyethylene glycol (PEG). Investigations reveal that the luminescence properties have also been tuned exhibiting efficient visible light-harvesting photocatalytic activity. All these have been attributed to the interaction between ligands (PEG) and TiO2 forming deep electronic states associated to C-C and C-O bonds which facilitate blue and green wavelength emissions. On the other hand, FA plays an important role as capping ligand and nitriding agent generating shallow and deep trapping states endowed with visible emission at higher wavelength. Furthermore, nitrogen doped functionalized TiO2 NCs (N-TiO2) using urea are prepared solvothermally at temperature as low as 150 C and pressure higher than 1 atm. Under that conditions, well defined N-TiO2 anatase phase NCs show a band gap of 2.3 eV and exhibit slow electron hole recombination which have been discussed with an emphasis in view of surface modification.

Automated summary

This paper reports a novel method of surface modification of TiO2 nanocrystals (NCs) using organic ligands, which can control the optical band gap, generation of trapping states, and inhibiting charge carrier recombination rate. The luminescence properties of TiO2 NCs have been tuned by interacting with ligands such as PEG and FA, leading to efficient visible light-harvesting photocatalytic activity. Furthermore, N-TiO2 NCs with nitrogen doping and functionalization using urea have been synthesized solvothermally at low temperature and high pressure, exhibiting a narrow band gap and slow electron-hole recombination, which can be attributed to surface modification.