Abstract: By means of varying addition rate of the reactants in a double jet precipitation,the growth of nano-sized silver iodobromide particles in an aqueous fish gelatin solution was observed by TEM.The relationship of the average size (d) and size distribution (±σ) of the silver iodobromide nanoparticles with the addition rate (R) of the reactants was discovered.Increasing R values, values decreases linearly in a region of R values from 1.3 to 8.0 mmol/min,but no significant change of σ values was observed except for one or two data.Thiourea dioxide was used as chemical sensitizer to improve the photographic properties of the nanoparticles silver iodobromide emulsion.The results showed that photographic sensitivity increased by increasing the amount of thiourea dioxide or prolonging the sensitizing time.Improvement in low-intensity reciprocity law failure due to thiourea dioxide sensitization was also found.Besides,photosensitive response of thiourea dioxide sensitized emulsion to color temperature of light source at exposure was indicated.

Key words: nano-sized silver halide particles, particle growth, thiourea dioxide sensitization, photosensitivity, fish gelatin