Dissolution of Manganese Oxides of Various Compositions in Sulfuric Acid Solutions Studied by Kinetic Methods

Godunov, E. B.; Изотов, А. Д.; Горичев, И. Г.

doi:10.1134/s002016851801003x

Cited by 11 publications

(9 citation statements)

References 8 publications

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Section: Resultsmentioning

confidence: 99%

“…The similarity of Mn 2+ release from all NP formulations in acidic media was surprising, as Godunov et al [ 42 ] have shown that Mn 3 O 4 dissolves incompletely in dilute acidic conditions due to the formation of Mn 2+ ions as well as MnO 2 , whereas MnO dissolves completely. Their study also demonstrated that MnO dissolves at a faster rate than Mn 3 O 4 in concentrated acidic solutions, but both compounds completely dissociate [ 42 ]. The similarity of our Mn 2+ controlled release curves between NP formulations could indicate that the slower anticipated Mn 2+ release from MnO/Mn 3 O 4 NP mixtures could be counteracted by their smaller NP diameter with increased surface area.…”

Section: Resultsmentioning

confidence: 99%

“…The other MnO NP formulations (S5 Fig) showed similar controlled release curves with no significant differences between Mn 3 O 4 /MnO NP mixtures and MnO only. The total Mn 2+ amount released at each temperature condition and pH are shown in S2 Table. The similarity of Mn 2+ release from all NP formulations in acidic media was surprising, as Godunov et al [42] have shown that Mn 3 O 4 dissolves incompletely in dilute acidic conditions due to the formation of Mn 2+ ions as well as MnO 2 , whereas MnO dissolves completely. Their study also demonstrated that MnO dissolves at a faster rate than Mn 3 O 4 in concentrated acidic solutions, but both compounds completely dissociate [42].…”

Section: Mn 2+ Release Rate From Mno Nps Is Maximum At Ph 5 and Unaffmentioning

confidence: 99%

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Tuning the size and composition of manganese oxide nanoparticles through varying temperature ramp and aging time

et al. 2020

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Manganese oxide (MnO) nanoparticles (NPs) can serve as robust pH-sensitive contrast agents for magnetic resonance imaging (MRI) due to Mn 2+ release at low pH, which generates a~30 fold change in T 1 relaxivity. Strategies to control NP size, composition, and Mn 2+ dissolution rates are essential to improve diagnostic performance of pH-responsive MnO NPs. We are the first to demonstrate that MnO NP size and composition can be tuned by the temperature ramping rate and aging time used during thermal decomposition of manganese (II) acetylacetonate. Two different temperature ramping rates (10˚C/min and 20˚C/min) were applied to reach 300˚C and NPs were aged at that temperature for 5, 15, or 30 min. A faster ramping rate and shorter aging time produced the smallest NPs of~23 nm. Shorter aging times created a mixture of MnO and Mn 3 O 4 NPs, whereas longer aging times formed MnO. Our results indicate that a 20˚C/min ramp rate with an aging time of 30 min was the ideal temperature condition to form the smallest pure MnO NPs of~32 nm. However, Mn 2+ dissolution rates at low pH were unaffected by synthesis conditions. Although Mn 2+ production was high at pH 5 mimicking endosomes inside cells, minimal Mn 2+ was released at pH 6.5 and 7.4, which mimic the tumor extracellular space and blood, respectively. To further elucidate the effects of NP composition and size on Mn 2+ release and MRI contrast, the ideal MnO NP formulation (~32 nm) was compared with smaller MnO and Mn 3 O 4 NPs. Small MnO NPs produced the highest amount of Mn 2+ at acidic pH with maximum T 1 MRI signal; Mn 3 O 4 NPs generated the lowest MRI signal. MnO NPs encapsulated within poly (lactide-co-glycolide) (PLGA) retained significantly higher Mn 2+ release and MRI signal compared to PLGA Mn 3 O 4 NPs. Therefore, MnO instead of Mn 3 O 4 should be targeted intracellularly to maximize MRI contrast.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Mn 2+ Release Rate From Mno Nps Is Maximum At Ph 5 and Unaffmentioning

confidence: 99%

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Tuning the size and composition of manganese oxide nanoparticles through varying temperature ramp and aging time

et al. 2020

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“…For MnO, in acidic environments, it directly dissociates into Mn 2+ as shown by eq . Meanwhile, Mn 2 O 3 and Mn 3 O 4 dissociate into MnO 2 and Mn 2+ as per eqs and , resulting in incomplete dissolution of the metal oxides; MnO degrades at a faster rate in acidic solutions compared to Mn 3 O 4 , which degrades more quickly than Mn 2 O 3 . Thus, to complete dissolution, Mn 2 O 3 and Mn 3 O 4 follow eqs and after primary dissolution.…”

Section: Resultsmentioning

confidence: 94%

Caveat Emptor: Commercialized Manganese Oxide Nanoparticles Exhibit Unintended Properties

Martinez de la Torre,

Freshwater,

Looney-Sanders

et al. 2023

ACS Omega

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Nano-encapsulated manganese oxide (NEMO) particles are noteworthy contrast agents for magnetic resonance imaging (MRI) due to their bright, pH-switchable signal (“OFF” to “ON” at low pH), high metal loading, and targeting capability for increased specificity. For the first time, we performed a head-to-head comparison of NEMO particles from In-house and commercialized sources (US Nano vs Nanoshel) to assess their potential as bright T1 MRI contrast agents. Manganese oxide nanocrystals (MnO, Mn2O3, and Mn3O4) were systematically evaluated for size, chemistry, release of manganese ions, and MRI signal pre- and post-encapsulation within poly(lactic-co-glycolic acid) (PLGA). Suprisingly, a majority of the commercialized formulations were not as advertised by displaying unintended sizes, morphologies, chemistry, dissolution profiles, and/or MRI signal that precludes in vivo use. US Nano’s Mn3O4 and Mn2O3 nanocrystals contained impurities that impacted Mn ion release as well as micron-sized rodlike structures. Nanoshel’s MnO and Mn2O3 nanoparticles had very large hydrodynamic sizes (>600 nm). In-house MnO and Nanoshel’s Mn3O4 nanoparticles demonstrated the best characteristics with brighter T1 MRI signals, small hydrodynamic sizes, and high encapsulation efficiencies. Our findings highlight that researchers must confirm the properties of purchased nanomaterials before utilizing them in desired applications, as their experimental success may be impacted.

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“…- formation of a thinner coating with rod-like morphology [55]. The morphological difference of the two coatings may also result from the higher ionic conductivity of the strongly acidic bath (i.e., 179.3 mS cm -1 for 0.5 M H2SO4, vs 24.5 mS cm -1 for 0.05 M H2SO4), which leads to higher current during the anodic deposition of the MnxOy, and thus significantly reduced deposition time (i.e., 42 s) compared to the less acidic bath (i.e., 74 s) (Figure S3).…”

Section: Characterization Of the Ti/tio2 Nta-mnxoy Electrodesmentioning

confidence: 99%

Manganese oxide coated TiO2 nanotube-based electrode for efficient and selective electrocatalytic sulfide oxidation to colloidal sulfur

Sergienko

Radjenović

2021

Applied Catalysis B: Environmental

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Dissolution of Manganese Oxides of Various Compositions in Sulfuric Acid Solutions Studied by Kinetic Methods

Cited by 11 publications

References 8 publications

Tuning the size and composition of manganese oxide nanoparticles through varying temperature ramp and aging time

Tuning the size and composition of manganese oxide nanoparticles through varying temperature ramp and aging time

Caveat Emptor: Commercialized Manganese Oxide Nanoparticles Exhibit Unintended Properties

Manganese oxide coated TiO2 nanotube-based electrode for efficient and selective electrocatalytic sulfide oxidation to colloidal sulfur

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