Thermoluminescence from spinach leaf without excitation by any radiation or external stimuli: Stimulatory role of thermal fluctuations

This article argues that the sources of glow seen by the thermoluminescence (TL) technique may be from largely in vivo biological nanoparticles with property of quantum confinement that entails trapping of energy and delayed emission, not solely due to the charges that undergo recombination. TL in spinach leaf, following prolonged period of idling in dark at ambient temperatures but without any excitation, has been observed. Occasional loss of stringent control of heating rate revealed that fluctuations generated complex TL structures. Following the trails of this observation we discovered that ripples larger than ′1°C gave rise to multiple small bands and spikes which were missing when the rate was controlled within ′ 1°C, both with or without excitation by light. The results do not warrant the application of Randall and Wilkins' theory to interpret TL from photosynthetic materials.