In this paper we present a new theory to re-examine the immobilization technique of dye doped sol-gel films, define the strength and types of possible bonds between the immobilized molecule and sol-gel glass, and show that the immobilized molecule is not free inside the pores as was previously thought. Immobilizing three different pH sensitive dyes with different size and functional groups inside the same sol-gel films revealed important information about the nature of the interaction between the doped molecule and the sol-gel matrix. The samples were characterized by means of ultraviolet-visible spectrophotometer (UV-VIS), thermal gravimetric analysis (TGA), mercury porosimetry (MP), nuclear magnetic resonance spectroscopy ((29)Si NMR) and field-emission environmental scanning electron microscopy (ESEM-FEG). It was found that the doped molecule itself has a great effect on the strength and types of the bonds. A number of factors were identified, such as number and types of the functional groups, overall charge, size, pK(a) and number of the silanol groups which surround the immobilized molecule. These results were confirmed by the successful immobilization of bromocresol green (BCG) after a completely polymerized sol-gel was made. The sol-gel consisted of 50% tetraethoxysilane (TEOS) and 50% methyltriethoxysilane (MTEOS) (w/w). Moreover, the effect of the immobilized molecule on the structure of the sol-gel was studied by means of a leaky waveguide (LW) mode for doped films made before and after polymerization of the sol-gel.
Wi n d mill C e ntr e f or Ultr as o ni c E n gi n e eri n g, El e ctr o ni c & El e ctri c al E n gi n e eri n g D e pt., Bi o a c o usti cs Gr o u p, U ni v ersit y of Str at h cl y d e Gl as g o w, S c otl a n d, U nit e d Ki n g d o m Ol u w as e u n. o m o ni yi @str at h. a c. u k
Sugar casting is a simple and cost-effective direct method of generating polymer foams. By incorporating grains directly into mixtures of polymer and piezoelectric nanoparticles it is possible to create highly compliant materials with excellent piezoelectric properties. In this work, we use the sugar casting method in combination with spin coating to prepare a highly sensitive and flexible 0-3 piezoelectric polymer thin film membranes with a layer thickness of 20 to 190 µm. Porosities and elasticity are tuned by simply adjusting the sugar/polymer mass ratio. The expected outcome of this research was improvements to the piezoelectric voltage, the g 33 measure, due to the increased compliance of the material, however iezoelectric composite membranes with high concentrations of PMN-PT also demonstrated gains in piezoelectric coupling, the d 33 measure, when cast with high volume fractions of sugar. A remarkably high d 33 coefficient of 69 pm/V was measured using the laser vibrometer technique. These innovative materials were developed as broadband ultrasonic sensors for partial discharge detection in undersea cables, however they have potential uses in energy scavenging platforms, biosensors, and acoustic actuators, among others.
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