Effects of K⁺, Mg²⁺, Ca²⁺, Zn²⁺, La³⁺, Cr³⁺, Ce³⁺, Ce⁴⁺, and Mo⁵⁺ Doping on the Adsorption Performance and Optical Properties of Sodium Titanate Nanotubes

Abstract

Metal-doped titanate nanotubes (TNTs) were synthesized using a simple ion-exchange method. Cations with different valencies (Mg2+, Ca2+, Zn2+, K+, Cr3+, Ce3+, Ce4+, Mo5+, and La3+) were used to assess their effects on the adsorption performance and optical properties of the prepared nanotubes. All samples were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDXS), and elemental mapping, and the optical properties were analyzed using photoluminescence (PL) spectroscopy. The adsorption performance of the prepared doped titanate nanotubes was tested against methylene blue (MB) as a model cation dye. The results revealed that all samples except Ce(IV)-TNT showed high removal efficiencies but at different equilibrium times. Mg-TNT, Zn-TNT, and K-TNT showed higher MB removal percentages (97%) after 45 min, while Ca-TNT, Cr-TNT, Ce(III)-TNT, Mo-TNT, La-TNT, and Na-TNT showed removal efficiencies of 95, 84, 95, 96, 94, and 96% after 65, 1200, 120, 300, 180, and 105 min, respectively. The titanate nanotubes were recycled by photocatalytic degradation of the adsorbed dye molecules. The band gaps, valence band, and conduction band were calculated and compared for the potential photocatalytic water splitting application.

Tuning the band gap of M-doped titanate nanotubes (M = Fe, Co, Ni, and Cu): an experimental and theoretical study

“…These results showed that the semiconductor band gaps could be modified in the range of 2.02–2.8 eV. 19 Additionally, Tang et al reported a comparative study of Ti-NT doped with various metal cations (Cu 2+ , Co 2+ , Ni 2+ , Fe 2+ , and Mn 2+ ). Nevertheless, the band gap energy was only slightly modified from 3.43 (Ti-NT) to 3.18 eV (Fe–Ti-NT).…”

“…14,18 In this regard, the inuence of different metal cations on the Ti-NT optical properties has been studied previously. 9,[19][20][21][22] Lee and Zaki studied the inuence of cations with different valences (Mg 2+ , Ca 2+ , Zn 2+ , K + , Cr 3+ , Ce 3+ , Ce 4+ , Mo 5+ , and La 3+ ). These results showed that the semiconductor band gaps could be modied in the range of 2.02-2.8 eV.…”

Application of Titanate Nanotubes for Photocatalytic Decontamination in Water: Challenges and Prospects

“…This ion-exchange doping method is also applicable for modification of Na-TNTs by various metal cations with different valences (e.g., K + , Mg 2+ , Ca 2+ , Zn 2+ , La 3+ , Cr 3+ , Ce 3+ , Ce 4+ , and Mo 5+ ), and the narrowed band gaps of metal-TNTs (2.02–2.80 eV) will enhance their potential application as photocatalysts under visible or solar light irradiation. The nonmetal doped TNTs (e.g., N-doped TNTs) also exhibit a narrower band gap but better visible-light response, as new linkages such as Ti–O–N, Ti–N–O, and N–Ti–O are formed, resulting in the efficient charge transfer and promoted photocatalytic ability. ,,, …”

“…Summary on band gap structures of TNT-based photocatalysts (information is obtained from the literature; ,,− ,,,,, photocatalysts with no CB and VB data reported are not listed here).…”

Electronic Structures and Electrical Properties of Cr2+-, Cu2+-, Ni2+-, and Zn2+-Doped Sodium Titanate Nanotubes

“…Copper sulfate heptahydrate, chromium acetate, nickel acetate, and zinc sulfate heptahydrate were mixed with Na-TNTs to produce Cu-TNTs, Cr-TNTs, Ni-TNTs, and Zn-TNTs, respectively. The simple sonochemical method used here is the main technique implemented for preparing doped samples, 17 where the mixtures were exposed to ultrasonication with a probe sonicator (20 kHz, pulsed mode with 9.9 s on and 3 s off) for 15 min. To remove unreacted sodium salts, the obtained samples were then washed several times with bidistilled water.…”