Pyrocatalysis—The DCF assay as a pH-robust tool to determine the oxidation capability of thermally excited pyroelectric powders

Abstract

Pyrocatalysis uses thermally excited pyroelectric materials for the generation of reactive oxygen species in water. This unique feature allows it to harvest energy in the form of natural temperature gradients or waste heat from industrial processes in order to degrade organic pollutants at low costs. Its further development into an advanced oxidation process for water remediation is dependent on the availability of pH-robust and nonspecific redox assays for the determination of its oxidation capability. Nevertheless, previous studies neglected the influence of pH changes and they were focused mainly on the degradation of one organic compound or specific chemical dosimetries. In this study, a pH-robust and nonspecific reaction protocol of the dichlorofluorescein assay was established for the investigation of the oxidation capability of the pyrocatalytic process. This reaction protocol was tested on three pyroelectric powders (LiNbO 3 , LiTaO 3 , BaTiO 3) in different amounts and it overcomes major constraints of a previously used dichlorodihydrofluorescein diacetate-based reaction protocol. Instead of its diacetate, dichlorodihydrofluorescein was used as fluorogenic probe and its concentration was drastically reduced to 1 μM. For the first time, these changes enable the determination and comparison of the oxidation capability independently of pH-rising processes, which are present for all investigated pyroelectric powders up to a pH of 11. Additionally, the precision of the dichlorofluorescein assay was drastically increased and the determination and consideration of autoxidation processes was enabled. Of all three pyroelectric powders, BaTiO 3 exhibited the highest oxidation capability with a linear increase with respect to the powder amount.

Pyrocatalytic oxidation – strong size-dependent poling effect on catalytic activity of pyroelectric BaTiO3 nano- and microparticles

“…This result corresponds to results of our previous study with BT200 (1.2 nM DCF per mg mL À1 BT200). 37 Wu et al and Qian et al on the other hand found that the pyrocatalytic degradation of rhodamine B with BiFeO 3 and ZnO powders reached a plateau for a low b of 1 mg mL À1 . 41,42 For the piezocatalytic degradation of RhB and Acid Orange 7 with sonicated suspensions of K 0.5 Na 0.5 NbO 3 and Pb(Zr 0.52 Ti 0.48 )O 3 , an optimum and a plateau was reached at higher b values of 4 mg mL À1 and 12.5 mg L À1 .…”

“…35 The DCHF-based reaction protocol was introduced by Carthcart et al and further modified in a previous study (Scheme S1, ESI †). 36,37 This method was proven pH-and cationindependent over a wide range; it offers a high precision and enables the determination and consideration of autoxidation processes. A DCHF reaction solution was prepared by dissolving DCHF-DA in methanol (140 mL per mg DCHF-DA) and adding 0.01 M NaOH (570 mL per mg DCHF-DA) to trigger a complete deesterification of DCHF-DA to DCHF within 30 min.…”

Accelerated pyro-catalytic hydrogen production enabled by plasmonic local heating of Au on pyroelectric BaTiO3 nanoparticles

“…Pyro-catalysis refers to the catalysis triggered by temperature fluctuation induced pyroelectric surface charges in pyroelectric materials 1 , 2 , which is a self-powered catalysis technique by harvesting waste energy from the environment. Recently, pyro-catalysis has attracted increasing attention in clean energy production and reactive oxygen species (ROS) generation 3 – 9 . Xie et al reported the coupling between pyroelectric effect and electro-chemical process, where pyroelectric polyvinylidene fluoride and lead zirconate titanate (PZT-5H) polycrystalline ceramic thin films were used as a voltage source to electrolyze water 3 .…”

“…Xiao et al presented pyro-catalytic CO 2 reduction by using bismuth tungstate nanoplates, where 55.0 μmol g −1 methanol production was achieved after 20 thermal cycles between 15 and 70 °C 5 . The pyroelectric induced surface charges are also capable of generating ROS, such as, hydroxyl (•OH), superoxide (•O 2 − ), singlet oxygen ( 1 O 2 ), and hydrogen peroxide (H 2 O 2 ) 6 – 9 . The pyro-catalytic generated ROS can be further used for disinfection and dye treatment.…”