Generation of paramagnetic centres in crystalline quartz by ultraviolet irradiation

Leyderman, Alexander; Weil, John A.; Williams, James

doi:10.1016/0022-3697(85)90121-0

Cited by 10 publications

(3 citation statements)

References 12 publications

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“…Correction for the Quartz Background. Point defects in crystalline quartz have long been known to be precursors to electron and hole centers and have been extensively studied as such. , Indeed, trapped atomic hydrogen along with other species has been found to act as paramagnetic centers in crystalline quartz. − In our system, the quartz background becomes significant at doses of 50 kGy and higher. It was necessary, therefore, to correct the sample EPR spectrum for the quartz background at each dose point.…”

Section: Methodsmentioning

confidence: 87%

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What Is the Initial Chemical Precursor of DNA Strand Breaks Generated by Direct-Type Effects?

Purkayastha

Bernhard

2004

J. Phys. Chem. B

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The present study tests the hypothesis that the majority of DNA strand breaks produced by directtype effects are due to sugar free radical precursors and that these radicals are produced by direct ionization of the sugar-phosphate backbone or by hole transfer to the sugar from tightly bound water. Well-defined crystalline DNA samples of d(CGCG) 2 , d(CGCACG:GCGTGC), d(GTGCGCAC) 2 , and d((GCACGCGTGC) 2 were irradiated at 4 K, and their free radical dose response determined from 0 to 1800 kGy. A model is proposed that effectively describes the dose response curves. It includes the following parameters: the free radical concentration at saturation C max , the free radical yields G b and G s , and the destruction constants k b and k s . The subscripts b and s refer to base-centered and sugar-centered radicals, respectively. In each of these systems, the free radical concentration exhibits a remarkable resistance to dose saturation up to at least 1500 kGy. As predicted, G b > G s , the G b /G s ratio varying between 4 and 12. Likewise, k b > k s , the k b /k s ratio varying between 28 and 81. The lower cross-section for destruction of the sugar-centered radicals is consistent with the expectation that they are relatively radiation resistant. G b /G is between 0.81 and 0.92, indicating that at low doses the bases trap out 80-90% of the total free radical population. The remaining 10-20% are located on the sugar. At high dose, a larger fraction of the radicals are trapped on the backbone as seen from the ratio C mxS /C mxB , which ranges from 3.5 to 8. This unusually late onset of dose saturation closely parallels that observed for strand break products in earlier studies. There is, therefore, a good correlation between the dose response profiles of sugar-trapped radicals and strand breaks. These observations strongly support the hypothesis that sugar radicals are precursors to the majority of strand breaks produced by the direct-type effect in DNA.

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Section: Methodsmentioning

confidence: 87%

“…30,31 Indeed, trapped atomic hydrogen along with other species has been found to act as paramagnetic centers in crystalline quartz. [30][31][32][33] In our system, the quartz background becomes significant at doses of 50 kGy and higher. It was necessary, therefore, to correct the sample EPR spectrum for the quartz background at each dose point.…”

Section: Samplementioning

confidence: 99%

What Is the Initial Chemical Precursor of DNA Strand Breaks Generated by Direct-Type Effects?

Purkayastha

Bernhard

2004

J. Phys. Chem. B

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“…The peak position strongly depends on the size of the ion cluster and the peak maximum is shifted to smaller wavelengths with increasing silver ion cluster size m. Furthermore it seems to be probable that other effects play an important role as well. Leyderman et al [37] describe alumina complexes that act as HC after irradiation, especially if either Na, Li or H are part of the complex. Reference [38] states that these alumina related hole centers (Al-HC) cause an optical absorption at λ = 620 nm in soda lime glass.…”

Section: Uv-vis Spectroscopy After Exposure Processmentioning

confidence: 99%

Fabrication of 3D microchannels for tissue engineering in photosensitive glass using NIR femtosecond laser radiation

Brokmann¹,

Milde²,

Rädlein³

et al. 2019

Biomedical Glasses

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The biocompatibility of photosensitive glasses allows various biomedical applications; one is the field of tissue engineering and more precisely microengineered tissue-on-a-chip platforms to study the tissue microenvironment and disease modelling. Three dimensional architectures of adapted components are required for modern materials. A photosensitive lithiumalumosilicate glass FS21 was investigated regarding the interaction with a Ti:Sapphire laser systemto build three dimensional buried channels inside the glass. Femtosecond laser radiation with a wavelength of 800 nm and pulse duration of 140 fs was used to modify the glass structure. Subsurface channel geometries were achieved by a subsequent thermal treatment and were formed into capillaries using wet chemical etching of the exposed and crystallised channels. Contrary to ultraviolet (UV) exposure, spectral optical investigations showed that fs laser exposure caused various radiation induced defects in the base glass coupled with the generation of photoelectrons for the photochemical modification of silver ions. We observed an outgassing of different species coming from raw materials of the original glass batch during the glass crystallisation process. Etch rate ratios differ between 1:25 and 1:45 and are dependent on: stoichiometric deviation between surface and bulk, crystal size and distribution and exchange of the etching agent in narrow capillaries.

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A Review of the EPR Spectroscopy of the Point Defects in α-Quartz: The Decade 1982–1992

Weil

1993

The Physics and Chemistry of SiO2 and the Si-SiO2 Interface 2

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Generation of paramagnetic centres in crystalline quartz by ultraviolet irradiation

Cited by 10 publications

References 12 publications

What Is the Initial Chemical Precursor of DNA Strand Breaks Generated by Direct-Type Effects?

What Is the Initial Chemical Precursor of DNA Strand Breaks Generated by Direct-Type Effects?

Fabrication of 3D microchannels for tissue engineering in photosensitive glass using NIR femtosecond laser radiation

A Review of the EPR Spectroscopy of the Point Defects in α-Quartz: The Decade 1982–1992

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