Abstracts Book - IMRC 2018

• SD6-P008
THERMODYNAMICS OF THE SILICA NANOPARTICLE SYNTHESIS
FOR IMPROVING EFFICIENCY IN REACTION MEDIA.
Carlos Alfonso Luna Mayo 1 , Jose Miguel Reyes Zarate 1 , Andrea Acevedo 2 , Cecilia Salinas 1 , Erick
Flores Romero 1,3 , Juan Carlos Cheang Wong 1
1 Instituto de Física - Universidad Nacional Autónoma de México, Fisica Experimental, Mexico.
2 Instituto de Ciencias Físicas, UNAM, Fisica Experimental, Mexico. 3 Consejo Nacional de Ciencia
y Tecnologia - CONACYT, Catedras CONACyT, Mexico.
The synthesis of silica nanoparticles TEOS precursor has many drawbacks
because it is highly sensitive to environmental conditions. Humidity and
temperature are influential factors for the adequate formation of monodisperse
silica particles. The knowledge of the thermodynamical properties of the
synthesis reaction would help to setup the laboratory conditions favoring a
greater efficiency in the formation of the silica particles. For the silica synthesis,
the Stöbers method uses ethanol as a solvent mixed with a low concentration
of TEOS, then a solution of ammonium hydroxide and distilled water is dripped,
and the reaction continues at room temperature under magnetic stirring. This
provides a basic medium for the hydrolysis of the precursor. Once the synthesis
finished, a monolayer of silica particles is deposited by spin-coating on highpurity
Si substrates. In this work the initial temperature of the reagents was
controlled, so that the increase in the recorded temperature is mostly due to the
energy released by the system and not due to a thermal equilibrium between
the TEOS solution and the basic solution. The temperature was monitored after
each 1 mL addition of the solution and after each 0.5 minutes once the drip
finished, for 1.5 hours. This procedure allows us to record the temperature
behavior at each stage of the reaction, i.e., during the hydrolysis (drip) as well as
during the condensation (continuous stirring). The size and shape of the
deposited silica particles were studied by SEM.
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of tetraethoxysilane (TEOS) and an infrared study of its thermal
decomposition. Journal de Physique IV Colloque, 1993, 03 (C3), pp.C3-75-C3-82.
E.R. Pohl, F.D. Osterholtz, Molecular characterization of composite interfaces
Eds. H Ishida and G Kumar, Plenum, New York, 1985, pp 157.
D.J. Belton, O. Deschaume, C.C Perry, An overview of the fundamentals of the
chemistry of silica with relevance to biosilicification and technological