Comparing defect-assisted interfacial charge transfer in CdS/PSA and CdS/TiO2NTAs nanoheterojunctions for enhanced photodegradation and biosensing

Abstract

Firstly, oxygen vacancy defects are intentionally introduced in the preparation process of TiO2 nanotube arrays (TiO2-NTAs) and porous silicon arrays (PSA) films through the anodic oxidation method after annealing treatment, as expected. Then, CdS/TiO2-NTAs and CdS/PSA heterostructures are successfully fabricated using the electrodeposition method, incorporating abundant surface vacancy defects. The crafted CdS/TiO2-NTAs nanoheterojunctions presented elevated photoelectrochemical (PEC) performances and sensing activities compared with that of CdS/PSA, validating by photodegradation and PEC biosensing tests, which mainly ascribed to the synergistic effect between the promoted carriers separation efficiency and boosted surface active sites induced by vacancies defects. Furthermore, a comparative and comprehensive interfacial charge transfer mechanism and qualitative dynamic processes for CdS/TiO2-NTAs and CdS/PSA type-II nanoheterojunctions are proposed, revealing an enlarged staggered band offset between CdS and TiO2-NTAs. The evaluation of this band offset was conducted using nanosecond time-resolved transient photoluminescence and steady photoluminescence spectra, respectively. Following this scheme, the photodegradation rate for CdS/TiO2-NTAs nanocomplex toward degradation of MO was 92.8% and 1.06 times than that of CdS/PSA; while the PEC biosensing performance for CdS/TiO2-NTAs showed a detection range 0 – 600 μM and limit of detection of 2.3 μM, with a sensitivity of 456 mA cm−2 M−1.

Keywords

• Type-II nanoheterostructure
• Defect states
• Charge transfer
• Photoelectrochemical photodegradation and biosensing performance