Photoluminescence and thermally stimulated luminescence characteristics of rice flour

Abstract

The present paper reports the photoluminescence (PL) and the thermoluminescence (TL) characteristics of rice flour. This study is undertaken to consider storage of rice at low temperature and irradiation for disinfection. From the Indian market a few varieties of rice was bought. All the samples of rice was ground using an agate motor and pestle. Thereafter, the powder was sieved to the size of 140 μm using appropriate sieves. When comparing the PL characteristics of the different rice powders studied, it is interesting to note that the PL emission wavelength (around 445 nm) is nearly same for all the rice varieties studied even though the excitation wave length is different. TL characteristics are studied in the temperature range 77–230 K as well as 300–700 K. TL is recorded for the virgin samples and also on irradiation of the same by exposing it to X-ray at 77 K, beta at 300 K and gamma at 77 K. The two varieties are given an X-ray dose of 1 kGy. The TL is recorded for 200 mg rice powder. The TL displayed for the as-received 1 kGy X- ray dose peak is around 160 K with a broad shoulder around 120 K. Basmati variety is given a gamma dose of 12.5 kGy and the TL and TL emission is recorded. It is seen that a well-defined low-temperature TL peak around 119 K and a hump around 145 K are observed in the sample. The TL emission is around 430 nm.The TL peak observed in most of the rice samples above room temperature is around 558 K.