Synthesis and characterization of silver/alanine nanocomposites for radiation detection in medical applications: the influence of particle size on the detection properties

Abstract

Silver/alanine nanocomposites with varying mass percentage of silver have been produced. The size of the silver nanoparticles seems to drive the formation of the nanocomposite, yielding a homogeneous dispersion of the silver nanoparticles in the alanine matrix or flocs of silver nanoparticles segregated from the alanine crystals. The alanine crystalline orientation is modified according to the particle size of the silver nanoparticles. Concerning a mass percentage of silver below 0.1%, the nanocomposites are homogeneous, and there is no particle aggregation. As the mass percentage of silver is increased, the system becomes unstable, and there is particle flocculation with subsequent segregation of the alanine crystals. The nanocomposites have been analyzed by transmission electron microscopy (TEM), UV-Vis absorption spectroscopy, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy and they have been tested as radiation detectors by means of electron spin resonance (ESR) spectroscopy in order to detect the paramagnetic centers created by the radiation. In fact, the sensitivity of the radiation detectors is optimized in the case of systems containing small particles (30 nm) that are well dispersed in the alanine matrix. As the agglomeration increases, particle growth (up to 1.5 mm) and segregation diminish the sensitivity. In conclusion, nanostructured materials can be used for optimization of alanine sensitivity, by taking into account the influence of the particles size of the silver nanoparticles on the detection properties of the alanine radiation detectors, thus contributing to the construction of small-sized detectors.

Potential application of metal nanoparticles for dosimetric systems: Concepts and perspectives

“…In other words, the size of the gold nanoparticles in the composites bearing gold, does not vary (~5 nm), whereas the size of silver nanoparticles in the silver/alanine composites rises with increasing silver content. Furthermore, TEM images revealed that large silver particles become segregated from the alanine matrix 9,42 .…”

“…3) 41 . For the case of silver nanocomposites, the DEF as calculated by ESR dosimetry was shown to be sensitive to nanoparticle concentration, size, and position in the alanine composites 9,41 . In this case, optimum DEF occurs for silver nanoparticles smaller than 30 nm homogeneously distributed in the sensitive medium.…”

“…In this case, optimum DEF occurs for silver nanoparticles smaller than 30 nm homogeneously distributed in the sensitive medium. As the percentage of silver mass increases, aggregation, growth, and segregation of the particles diminish the DEF, probably due to self-absorption of dose by the silver nanoparticles 9,41,43 . Figure 2 shows that the peak-to-peak amplitude of the alanine spectrum is larger for sample containing a percentage of silver mass of 0.05% as compared with the sample containing a percentage of silver mass of 1%, which is unexpected according to the Bragg rule for composite materials 9,41,44 .…”

“…Silver nanoparticles were produced as reported elsewhere 9 . In this synthesis, a 2 mmol L -1 AgNO3 aqueous solution was added to a freshly prepared 4 mmol L -1 NaBH4 aqueous solution.…”

“…It is possible to conduct radiation dosimetry by many techniques such as thermoluminescence (TL) 1-2 , optically stimulated luminescence(OSL) [3][4] , electron spin resonance (ESR) spectroscopy [5][6][7][8][9] , and radioluminescence (RL) [10][11] , among others. Because fulfilling each specific treatment and/or diagnosis modality, such as radiotherapy [12][13] , radiology [14][15] , and personal dosimetry 16 , is desirable, the search for new materials with improved properties has been intense.…”