Synthesis of Refractory Metal Carbides on Carbon Fibers in Molten Salts and Their Electrocatalytic Properties

Coatings of TaC and NbC and Mo2C crystals on carbon fibers were obtained by currentless transfer in molten salts. Investigation of electrocatalytic properties of these compositions in the reaction of the hydrogen peroxide decomposition was carried out. It was determined that the hydrogen peroxide decomposition reaction has a zero order for all refractory metal carbides. Using the values of the rate constants at different temperatures the activation energies for the reaction of the hydrogen peroxide decomposition on refractory metal carbides were calculated using the Arrhenius equation. It has been established that coating of NbC on carbon fibers has a higher electrocatalytical properties in comparison with other carbides. The electrocatalytic properties of NbC/C, TaC/C and Mo2C/C composites were studied also by cyclic voltammetry.

Innovative Method of Utilising Hydrogen Peroxide for Source Water Management of Cyanobacteria

The treatment and control of cyanobacterial blooms using copper-based algaecides in water reservoirs has historically been used, however, due to the adverse impact of copper on the environment, water authorities have been researching and studying new and innovative ways to control cyanobacterial blooms. Hydrogen peroxide has been investigated as an environmentally friendly alternative and this research aims to determine the impact of water quality on its effectiveness based on the decay characteristics in different water samples. Natural water samples from South Australian reservoirs were used to evaluate hydrogen peroxide decomposition and provide a better strategy for water operators in using it as an algaecide. Our experiments show the dependency of hydrogen peroxide decomposition not only on water quality but also on the initial hydrogen peroxide dose. A higher initial hydrogen peroxide dose can trigger the increase of pH, leading to increased consumption of hydrogen peroxide. In addition, the hydrogen peroxide decomposition is significantly accelerated with the rise of copper concentration in water samples. Moreover, it is found that UV light can also affect the decomposition rate of hydrogen peroxide. The hydrogen peroxide decay is more significant under UV light for the samples with lower hydrogen peroxide concentrations. Our study also shows the impact of DOC on hydrogen peroxide decomposition is not substantial. The study also presents a modelling method to optimise hydrogen peroxide application based on water quality characteristics. Our findings can provide knowledge for the water industry to produce a suitable model which can be used to optimise the application of hydrogen peroxide for the control of cyanobacteria.

Intratumoral synthesis of nano-metalchelate for tumor catalytic therapy by ligand field-enhanced coordination

The iron gall ink-triggered chemical corrosion of hand-written documents is a big threat to Western cultural heritages, which was demonstrated to result from the iron gall (GA-Fe) chelate-promoted reactive oxygen species generation. Such a phenomenon has inspired us to apply the pro-oxidative mechanism of GA-Fe to anticancer therapy. In this work, we construct a composite cancer nanomedicine by loading gallate into a Fe-engineered mesoporous silica nanocarrier, which can degrade in acidic tumor to release the doped Fe3+ and the loaded gallate, forming GA-Fe nanocomplex in situ. The nanocomplex with a highly reductive ligand field can promote oxygen reduction reactions generating hydrogen peroxide. Moreover, the resultant two-electron oxidation form of GA-Fe is an excellent Fenton-like agent that can catalyze hydrogen peroxide decomposition into hydroxyl radical, finally triggering severe oxidative damage to tumors. Such a therapeutic approach by intratumoral synthesis of GA-Fe nano-metalchelate may be instructive to future anticancer researches.

Efficacy and Safety of Bleaching Gels According to Application Protocol

SUMMARY Objectives: This study evaluated bleaching efficacy, enamel microhardness, and roughness of highly concentrated hydrogen peroxide (HP) gels (35%–40%) using different application protocols. Gel decomposition and pH alteration were also analyzed. Methods and Materials: Bovine enamel/dentin specimens were divided into groups according to the bleaching gel—Pola Office Plus (POP–SDI, 37.5% HP), Opalescence Boost (OPB–Ultradent, 40% HP), Whiteness HP (WHP–FGM, 35% HP)— and application protocol—single application (SA) and multiple application (MA) during the in-office session. Deionized water was used in control group (no bleaching). Thus, seven final groups were obtained (n=15/group). Color (CIE L*a*b*), surface microhardness (SMH), and roughness (Ra) were assessed before/after treatments. The pH of gels was measured, and HP concentration was determined with potassium permanganate titration method in different times. Data were submitted to analysis of variance and Tukey tests (5%). Results: All gels presented similar and clinically acceptable bleaching efficacy (ΔE>2.7) for both SA and MA, as well as no significant differences for SMH and Ra comparing the two protocols in the same gel. Peroxide decomposition significantly increased with time, but final gel concentrations were still high after 45 minutes (32.29% POP; 38.45% OPB; and 32.74% WHP). The pH decreased over time (initial - after 45 min) for WHP (6.83±0.07 - 5.81±0.06), but minimal alterations were observed for POP (8.09±0.09 - 7.88±0.07) and OPB (7.82±0.11 - 7.87±0.07). Conclusions: Peroxide decomposition was very low for all gels tested, and pH remained stable for POP and OPB gels. Bleaching protocol did not influence whitening efficacy and hazardous effects over enamel, thus potentially there was no clinical significance. Therefore, for the products tested, there is no evidence for recommending the gel change during the bleaching session.