Room-Temperature Luminescence from Kaolin Induced by Organic Amines

Origins Life Evol Biosphere

1985

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The postulated roles of clays and other minerals in chemical evolution and the origin of life are reconsidered in terms of the interaction of these minerals with penetrating sources of energy such as ionizing radiation and mechanical stress. This interaction, including such facets as excitation, degradation, storage, and transfer, is considered here with regard to its profound potential for altering the capabilities of minerals to serve both as substrates for prebiological chemistry and as inorganic prototypic life forms. The interaction of minerals and energy in relationship to surface chemistry is discussed in terms of the spectroscopic properties of minerals, the interaction of energy with condensed phases, some commonly accepted concepts of heterogeneous catalysis in the absence of electronic energy inputs, and some commonly accepted and novel means by which surface activity might be enhanced in the presence of energy inputs. An estimation is made of the potential contribution of two poorly characterized prebiotic energy sources, natural radioactive decay and triboelectric energy. These estimates place a conservative lower limit on their prebiotic abundance. Also some special properties of these energy sources, relative to solar energy, are pointed out which might give them particular suitability for driving reactions occurring under geological conditions. Skeletal support for this broadly defined framework of demonstrated and potential relationships between minerals, electronic excitation, and surface reactivity, as applied to chemical evolution, is provided from the results of our studies on 1/1 clays. We have discovered and partially characterized a number of novel luminescent properties of these clays, that indicate energy storage and transfer processes in clays. These luminescent properties are interpreted in relationship to the electron spin resonance phenomena, to provide a basis for estimating the potential significance of energy storage and transduction in monitoring or driving clay surface chemistry. Consideration of the electronic structure of abundant minerals in terms of band theory and localized defect centers provides a predictive theoretical framework from which to rationalize the capacity of these materials to store and transduce energy. The bulk crystal is seen as a collecting antenna for electronic energy, with the defect centers serving as storage sites. The clay properties produced by isomorphic substitution appear to be intimately associated with all of the life-mimetic chemical processes that have been attributed to clays.(ABSTRACT TRUNCATED AT 400 WORDS)

Section: Iiic Summary Of Recent Research On Photophysical Processes mentioning

confidence: 99%

“…The wavelength distribution of the delayed burst of light induced by hydrazine has been measured using a rapid, multiple-scanning spectrophotofluorometer, (Coyne et al, 1984). At low resolution (-,~ 12 nm), it shows a single slightly asymmetric broad peak with a maximum at 365 nm.…”

Section: Hydrazine-induced Luminescence In Relationship To Dehydratiomentioning

confidence: 99%

A possible energetic role of mineral surfaces in chemical evolution

Origins Life Evol Biosphere

1985

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“…One of the principal photophysical properties of clay minerals is the capacity for electronic energy storage as evidenced by (1) thermal luminescence (TL) (Seigel et aL, 1968;Nishita and Hamilton, 1975;and Lemons and McAtee, 1983); (2) electron spin resonance (ESR); and (3) a variety of room-temperature luminescent phenomena related to dehydration, shock, and shearing which have been recently discovered and partially characterized (Coyne et al, 1981a(Coyne et al, , 1981bLahav et aL, 1982;Coyne et al, 1983Coyne et al, , 1984Lahav and Coyne, 1985;Coyne, 1985). This stored energy may alter surface reaction mechanisms and rates.…”

Section: Introductionmentioning

confidence: 99%

Effect of Adsorbed Iron on Thermoluminescence and Electron Spin Resonance Spectra of Ca-Fe-Exchanged Montmorillonite

Banin

1986

Clays and clay miner.

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Abstract-The electron spin resonance (ESR) spectra and the natural and gamma-induced thermoluminescence (TL) glow curves of a series of variably cation-exchanged Fe-Ca-clays prepared from SWy-1 montmoriUonite were examined. The ESR signal (g = 2) intensity associated with the surface Fe was found to increase linearly with surface Fe content up to a nominal concentration of 50% exchangeable Fe. At > 50% exchangeable Fe, no appreciable increase in the signal was noted. The TL intensity decreased linearly with increasing surface Fe up to 50% nominal exchangeable Fe. At > 50%, the signal was not appreciably further diminished. The natural TL showed only a high-temperature peak, but irradiation produced an additional low-temperature peak. One month after gamma-irradiation, the integrated TL signal was still 10-100 times higher than that from the non-irradiated material. Thus, (1) surface iron clusters may form above a certain critical Fe concentration; (2) the Fe clusters are probably less effective in quenching TL than are single Fe atoms, implying interaction between surface Fe and the stored energy content of the material; and (3) the electronic energy stored in the material as the result of gamma-irradiation is only slowly dissipated.

“…Dehydration-induced luminescence is one of several novel luminescence effects first reported by the authors (Coyne et al, 1980(Coyne et al, , 1981(Coyne et al, , 1983(Coyne et al, , 1984Lahav et al, 1982). The only other luminescence from kaolin to have been reported is thermoluminescence, first described by Seigel et al in 1966.…”

Section: Introductionmentioning

confidence: 93%

Characterization of Dehydration-Induced Luminescence of Kaolinite

Lahav

Lawless

1985

Clays and clay miner.

Abstract--Dehydration-induced luminescence (DIL), the emission of light from a clay paste upon dehydration, was characterized experimentally for a colloidal kaolinite. The relationship between total photon count of the emitted light and film thickness is linear up to a thickness of 30/~m. The photon emission was obtained over a critical range of water contents (25-60%) of the oven-dry clay, and the kinetics of photon emission was presumed to be closely associated with the kinetics of film dehydration. Whether drying proceeded throughout the bulk or via a moving front was undetermined, but in either mode it was preceded by the formation of a thin dry film at the interface with the atmosphere. Grinding of the kaolinite for several minutes by mortar and pestle before paste preparation resulted in an overall increase of photon emission compared to unground kaolinite and in the formation of more than one emission peak, as well as a prolongation of the light emission. This effect on the kinetics of light emittance was observed for about two months after the application of the mechanical stress and suggests a means of detecting the mechanical stress history of a clay.An estimate was made of the spectral characteristics of the emitted light using optical filters and by incorporating tryptophan and salicylic acid into the kaolinite paste where they acted as fluorescent probes. The latter technique shifted the frequency of the light emitted by the kaolinite from the ultraviolet to the visible range where it was less effectively reabsorbed. The first method showed that the wavelengths of 97% of the emitted light was <460 nm and that 75% of the light had wavelengths <410 nm. The second method showed that the total intensity of DIL increased in the presence of fluorescence molecules, suggesting that the emittance was in the ultraviolet range.