Paramagnetic Resonance of Mn2+ in Glasses and Compounds of the Lithium Borate System

Griscom, D. L.; Griscom, R. E.

doi:10.1063/1.1712288

Cited by 192 publications

(61 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This hyperfine coupling constant indicates that the Mn ions are in cubic ZnS lattice sites, and this result confirms that the dopants are indeed located inside the core/shell nanocrystals. [31][32][33] In addition, the Mn-doped nanocrystal sample before pyridine treatment shows a nearly identical EPR spectrum (grey line in Figure 1 D) to that of the sample after pyridine treatment (black line in Figure 1 D). Moreover, ICP measurements show that these two samples have a nearly identical doping level of 0.36 % (Figure 1 E).…”

Section: Resultsmentioning

confidence: 75%

Radial‐Position‐Controlled Doping of CdS/ZnS Core/Shell Nanocrystals: Surface Effects and Position‐Dependent Properties

Yang

Chen

Angerhofer

et al. 2009

Chemistry A European J

108

View full text Add to dashboard Cite

Energy transfer in doped semiconductor nanocrystals: Mn-doped CdS/ZnS nanocrystals show interesting photoluminescence and EPR properties that are strongly dependent on the radial position of Mn dopants inside nanocrystals (see graphic). Furthermore, the results suggest a two-step mechanism for the energy transfer inside the doped nanocrystals.This paper reports a study of the surface effects and position-dependent properties of Mn-doped CdS/ZnS core/shell nanocrystals, which were prepared by using a three-step synthesis method. The Mn-doping level of these nanocrystals was determined by a combination of electron paramagnetic resonance spectroscopy and inductively coupled plasma atomic emission spectroscopy. These nanocrystals were further characterized by using transmission electron microscopy and fluorescence spectroscopy. First, we found that injecting a large excess of zinc stearate at the end of nanocrystal synthesis can sufficiently eliminate the surface-trap states from the doped CdS/ZnS core/shell nanocrystals and enhance their photoluminescence (PL) quantum yield (QY). Second, our results demonstrate that the Mn-PL QY is determined by the product of the efficiency of energy transfer from an exciton inside the CdS core to a Mn ion (Phi(ET)) and the efficiency of the emission from the Mn ion (Phi(Mn)). Third, Phi(Mn) strongly depends on the radial position of Mn ions in the doped core/shell nanocrystals. The position-dependent changes of Phi(Mn) nearly perfectly correlate to those of the linewidth of Mn EPR peaks: the higher the Phi(Mn), the narrower the linewidth of the Mn EPR peak. Fourth, the results demonstrate that Phi(ET) depends on the Mn-doping level as well as the inverse sixth power of the distance between a Mn ion and the center of its host nanocrystal. Accordingly, we propose a two-step mechanism for the energy transfer: 1) the energy transfer from an exciton inside the CdS core to a bound exciton around a Mn center, which is the rate-determining step and follows the Förster mechanism, and 2) the energy transfer from the bound exciton to the Mn center, which might follow a mechanism such as dark exciton (triplet exciton) or Auger transfer.

show abstract

Section: Resultsmentioning

confidence: 75%

Radial‐Position‐Controlled Doping of CdS/ZnS Core/Shell Nanocrystals: Surface Effects and Position‐Dependent Properties

Yang

Chen

Angerhofer

et al. 2009

Chemistry A European J

108

View full text Add to dashboard Cite

show abstract

“…Signals around g ϭ 4.8 that have Mn 2ϩ hyperfine have previously been attributed to a "forbidden" M s ϭ Ϯ2 transition (38). This transition is often seen in Mn 2ϩ complexes that have a large zero field splitting (33,39,40). In the acetone carboxylase spectrum, there is also a shoulder at g ϭ 2.3 (3000 G) accompanied by a large broad peak centered at g ϭ 1.5 (4550 G).…”

Section: Correlation Of Acetone-dependent Growth With Increased Intramentioning

confidence: 99%

Bacterial Acetone Carboxylase Is a Manganese-dependent Metalloenzyme

Boyd

Ellsworth²,

Ensign

2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

Bacterial acetone carboxylase catalyzes the ATP-dependent carboxylation of acetone to acetoacetate with the concomitant production of AMP and two inorganic phosphates. The importance of manganese in Rhodobacter capsulatus acetone carboxylase has been established through a combination of physiological, biochemical, and spectroscopic studies. Depletion of manganese from the R. capsulatus growth medium resulted in inhibition of acetone-dependent but not malate-dependent cell growth. Under normal growth conditions (0.5 M Mn 2؉ in medium), growth with acetone as the carbon source resulted in a 4-fold increase in intracellular protein-bound manganese over malate-grown cells and the appearance of a Mn 2؉ EPR signal centered at g ‫؍‬ 2 that was absent in malate-grown cells. Acetone carboxylase purified from cells grown with 50 M Mn 2؉ had a 1.6-fold higher specific activity and 1.9-fold higher manganese content than cells grown with 0.5 M Mn 2؉ , consistently yielding a stoichiometry of 1.9 manganese/␣ 2 ␤ 2 ␥ 2 multimer, or 0.95 manganese/␣␤␥ protomer. Manganese in acetone carboxylase was tightly bound and not removed upon dialysis against various metal ion chelators. The addition of acetone to malate-grown cells grown in medium depleted of manganese resulted in the high level synthesis of acetone carboxylase (15-20% soluble protein), which, upon purification, exhibited 7% of the activity and 6% of the manganese content of the enzyme purified from acetone-grown cells. EPR analysis of purified acetone carboxylase indicates the presence of a mononuclear Mn 2؉ center, with possible spin coupling of two mononuclear sites. The addition of Mg⅐ATP or Mg⅐AMP resulted in EPR spectral changes, whereas the addition of acetone, CO 2 , inorganic phosphate, and acetoacetate did not perturb the EPR. These studies demonstrate that manganese is essential for acetone carboxylation and suggest a role for manganese in nucleotide binding and activation.Acetone is a toxic molecule that is produced biologically by the fermentative metabolism of certain anaerobic bacteria and from ketone body breakdown in mammals (1, 2). In addition to producing acetone, mammals and microorganisms also metabolize acetone, producing acetoacetate or acetol (1-hydroxyacetone) from the carboxylation or hydroxylation, respectively, of acetone (3-12). Despite more than 60 years of research on the subject and direct evidence for enzymatic conversion of acetone to acetoacetate and acetol, the physiological significance of acetone metabolism in mammals remains unclear (2, 13). The role of acetone metabolism in bacteria is more clearly defined, in that a variety of aerobic and anaerobic bacteria are able to grow using acetone as their primary source of carbon and energy (14).Despite some early evidence suggesting that acetol is an intermediate in aerobic acetone metabolism by some bacteria (4,6,15), it now appears that carboxylation of acetone to acetoacetate is the primary, if not only, reaction by which both aerobic and anaerobic bacteria initiate acetone catabolism ...

show abstract

“…Electron paramagnetic resonance (EPR) studies of transition metal ions in oxide glasses is of scientific interest and gives information concerning the state of the ligands, the glass structure, nature of bonding, and site symmetry around metal ion [1][2][3][4]. The electron paramagnetic resonance (EPR) spectroscopic technique was first applied to glassy materials by Sands [1].…”

Section: Introductionmentioning

confidence: 99%

EPR and Optical Absorption Spectral Investigations of Cu²⁺ in Bi₂O₃-ZnO-B₂O₃-Li₂O Glasses

Bale

Rahman

2012

ISRN Spectroscopy

View full text Add to dashboard Cite

O glasses were made by introducing Cu 2+ as spin probe. The EPR spectra of Cu 2+ in all the glass samples recorded in the X-band frequency have similar spectral features. The variation in glass composition influences the spin Hamiltonian parameters calculated from the spectra. The spin Hamiltonian parameters indicate that the Cu 2+ ions are coordinated with six ligand atoms in a distorted octahedron elongated along one of the axes and the ground state of the Cu 2+ is d x 2 −y 2 orbital. The optical absorption spectra exhibited a broad band corresponding to d-d transition bands of Cu 2+ ion. The values of bonding parameters indicate a covalent nature for the in-plane σ bonding and pure ionic nature for the in-plane and out-of-plane π bonding. The theoretical optical basicity parameter values were evaluated, and it was observed that the value of Γ σ increases whereas Γ π decreases with the increase in optical basicity.

show abstract

Paramagnetic Resonance of Mn2+ in Glasses and Compounds of the Lithium Borate System

Cited by 192 publications

References 23 publications

Radial‐Position‐Controlled Doping of CdS/ZnS Core/Shell Nanocrystals: Surface Effects and Position‐Dependent Properties

Radial‐Position‐Controlled Doping of CdS/ZnS Core/Shell Nanocrystals: Surface Effects and Position‐Dependent Properties

Bacterial Acetone Carboxylase Is a Manganese-dependent Metalloenzyme

EPR and Optical Absorption Spectral Investigations of Cu²⁺ in Bi₂O₃-ZnO-B₂O₃-Li₂O Glasses

Contact Info

Product

Resources

About

Paramagnetic Resonance of Mn2+ in Glasses and Compounds of the Lithium Borate System

Cited by 192 publications

References 23 publications

Radial‐Position‐Controlled Doping of CdS/ZnS Core/Shell Nanocrystals: Surface Effects and Position‐Dependent Properties

Radial‐Position‐Controlled Doping of CdS/ZnS Core/Shell Nanocrystals: Surface Effects and Position‐Dependent Properties

Bacterial Acetone Carboxylase Is a Manganese-dependent Metalloenzyme

EPR and Optical Absorption Spectral Investigations of Cu2+ in Bi2O3-ZnO-B2O3-Li2O Glasses

Contact Info

Product

Resources

About

EPR and Optical Absorption Spectral Investigations of Cu²⁺ in Bi₂O₃-ZnO-B₂O₃-Li₂O Glasses