Intrinsic peroxidase-like activity and enhanced photo-Fenton reactivity of iron-substituted polyoxometallate nanostructures

Abstract

Heteropolyacids (HPAs) are a class of polyoxometallates (POMs) with oxygen-rich surfaces. Herein, we have developed an Fe-containing heteropolyacid by cation-exchange and employed KFePW12O40 nanostructures for Fenton, photo-Fenton and enzyme-mimetic reactions. The as-prepared KFePW12O40 catalyst exhibits efficient degradation of Rhodamine B (RhB) via the photo-Fenton reaction. As an enzyme-mimetic, this material can effectively oxidize TMB and dopamine. The obtained nanomaterials were characterized via SEM, TEM, XPS, BET surface area, TGA, UV-Vis spectroscopy, FT-IR, and XRD techniques. The photocatalyst has a relatively large surface area of 38 m2 g-1, and the Keggin structure of phosphotungstic ions is kept intact during the preparation. The RhB dye pollutants can be efficiently bleached and degraded up to about 80% within a one hour photo-Fenton reaction under visible light irradiation. Our results indicate that the KFePW12O40 nanomaterial can effectively mimic the enzyme cascade reaction of horseradish peroxidase (HRP). It also has a high affinity toward 3,3',5,5'-tetramethylbenzidine (TMB) for oxidation and henceforth, it has been used for the colorimetric assay of dopamine and H2O2. Overall, our study suggests that KFePW12O40 can be used for the efficient degradation of environmental pollutants. The KFePW12O40 catalyst is stable and can be easily separated from the reaction system for reuse without an obvious loss of activity.

Keggin‐type Heteropolyacids‐Catalyzed Selective Hydrothermal Oxidation of Microalgae for Low Nitrogen Biofuel Production

“…X‐ray photoelectron spectroscopy (XPS) of HPAs synthesized are shown in Figure 2. The peaks at 135 eV and 134 eV are corresponding to P 2p1/2 and P 2p3/2, indicating that P(V) is existed in the HPAs [36] . The Mo 3d spectrum is deconvoluted into 2 doublets at 232.6 eV and 233.45 eV, which are contributing to Mo 6+ in MoO 3 existed in the keggin anion and more electropositive surrounded Mo 6+ , respectively [37] .…”

“…The peaks at 135 eV and 134 eV are corresponding to P 2p1/2 and P 2p3/2, indicating that P(V) is existed in the HPAs. [36] The Mo 3d spectrum is deconvoluted into 2 doublets at 232.6 eV and 233.45 eV, which are contributing to Mo 6 + in MoO 3 existed in the keggin anion and more electropositive surrounded Mo 6 + , respectively. [37] The broad peak between 515 and 521 eV assigned to V 2p3/2 of all samples is deconvoluted to V 5 + and V 4 + species at 517.8 � 0.1 and 516 � 0.1 eV, respectively.…”

“…V 5 + is the dominate unit of Keggin structure with existence of less V 4 + due to the redox equilibrium at the surface of catalyst. [36] The broad and asymmetric O 1s spectrum is deconvoluted into two peaks. The main component peak at 531.25 eV is assigned to the presence of lattice oxygen bounded to phosphorus and metals, while the weak peak at 532.3 eV may be due to surface adsorbed H 2 O.…”

“…The broad peak between 515 and 521 eV assigned to V 2p3/2 of all samples is deconvoluted to V 5+ and V 4+ species at 517.8±0.1 and 516±0.1 eV, respectively. V 5+ is the dominate unit of Keggin structure with existence of less V 4+ due to the redox equilibrium at the surface of catalyst [36] . The broad and asymmetric O 1s spectrum is deconvoluted into two peaks.…”

Perylene diimide‐modified magnetic γ‐Fe2O3/CeO2 nanoparticles as peroxidase mimics for highly sensitive colorimetric detection of Vitamin C

“…the holes on the value band (VB) of γ-Fe 2 O 3 and CeO 2 were injected into the VB of CeO 2 and PDI, respectively, to oxidize H 2 O 2 producing •OH radicals; iii. The slowly dissolved Fe 3+ ions on the surface of γ-Fe 2 O 3 were reduced by photogenerated electrons from PDI, and the obtained Fe 2+ ions could [2] Fe 3 O 4 nanofibers 0.45 18.7 -- [11] NiFe-LDHNS 0.50 2.40 -- [49] KFePW 12 O 40 0.346 165 3.70 6.90 [50] also catalyze H 2 O 2 to be •OH radicals. The obtained •OH radicals would react with colorless TMB, producing blue ox-TMB that could be reduced by VC to be TMB again.…”