Biogenic and Synthetic MnO 2 Nanoparticles

Size and Growth Probed with Absorption and Raman Spectroscopies and Dynamic Light Scattering

Alexandra V. Soldatova, Gurusamy Balakrishnan, Oyeyemi F. Oyerinde, Christine A. Romano, Bradley Tebo, Thomas G. Spiro

Research output: Contribution to journalArticle

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Abstract

MnO 2 nanoparticles, similar to those found in soils and sediments, have been characterized via their UV-visible and Raman spectra, combined with dynamic light scattering and reactivity measurements. Synthetic colloids were prepared by thiosulfate reduction of permanganate, their sizes controlled with adsorbates acting as capping agents: bicarbonate, phosphate, and pyrophosphate. Biogenic colloids, products of the manganese oxidase, Mnx, were similarly characterized. The band-gap energies of the colloids were found to increase with decreasing hydrodynamic diameter, D h , and were proportional to 1/D h 2 , as predicted from quantum confinement theory. The intensity ratio of the two prominent Mn-O stretching Raman bands also varied with particle size, consistent with the ratio of edge to bulk Mn atoms. Reactivity of the synthetic colloids toward reduction by Mn 2+ , in the presence of pyrophosphate to trap the Mn 3+ product, was proportional to the surface to volume ratio, but showed surprising complexity. There was also a remnant unreactive fraction, likely attributable to Mn(III)-induced surface passivation. The band gap was similar for biogenic and synthetic colloids of similar size, but decreased when the enzyme solution contained pyrophosphate, which traps the intermediate Mn(III) and slows MnO 2 growth. The band gap/size correlation was used to analyze the growth of the enzymatically produced MnO 2 oxides.

Original languageEnglish (US)
Pages (from-to)4185-4197
Number of pages13
JournalEnvironmental Science and Technology
Volume53
Issue number8
DOIs
StatePublished - Apr 16 2019

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Colloids
Raman spectroscopy
light scattering
Dynamic light scattering
atomic absorption spectroscopy
colloid
Absorption spectroscopy
Nanoparticles
Energy gap
Thiosulfates
Quantum confinement
thiosulfate
capping
Adsorbates
Manganese
Bicarbonates
bicarbonate
Passivation
Oxides
Stretching

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

Cite this

Biogenic and Synthetic MnO 2 Nanoparticles : Size and Growth Probed with Absorption and Raman Spectroscopies and Dynamic Light Scattering. / Soldatova, Alexandra V.; Balakrishnan, Gurusamy; Oyerinde, Oyeyemi F.; Romano, Christine A.; Tebo, Bradley; Spiro, Thomas G.

In: Environmental Science and Technology, Vol. 53, No. 8, 16.04.2019, p. 4185-4197.

Research output: Contribution to journalArticle

Soldatova, Alexandra V. ; Balakrishnan, Gurusamy ; Oyerinde, Oyeyemi F. ; Romano, Christine A. ; Tebo, Bradley ; Spiro, Thomas G. / Biogenic and Synthetic MnO 2 Nanoparticles : Size and Growth Probed with Absorption and Raman Spectroscopies and Dynamic Light Scattering. In: Environmental Science and Technology. 2019 ; Vol. 53, No. 8. pp. 4185-4197.
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