Bioapplicable, nanostructured and nanocomposite materials for catalytic and biosensor applications
Authors:   , Patel Alpa C. , Wei Yen 
Published: July 2021

Novel, nanostructured porous nanocomposites and bioapplicable materials have been successfully developed for catalytic, sensor and reinforcement applications. Nonsurfactant templated method of pore formation and electrospinning of nanofibers are the two main technologies that have been employed separately and together, to develop novel and potentially commercialize-able products. The porous composite products thus developed take the form of fine particles and nanofiber mats. For the first time, porous silver nanoparticle/silica composites were synthesized using a simple method of silver nitrate reduction. The glucose template present inside the mesoporous silica material reduces silver nitrate to silver nanoparticles. The particles thus formed are lodged inside the porous silica matrix. The synthesis procedure is very simple, economical, and the samples produced have good catalytic properties. Organic/inorganic hybrid nanofiber mats were fabricated for the first time using the electrospinning technology. The fiber mats have high surface area and good mechanical properties. These fibers mats are then used in reinforcement applications, by utilizing them as fillers in dental materials. The mechanical properties of dental materials thus produced is seen to improve dramatically with the addition of just a small amount of fiber sample. An in-situ method was used to produce silver and gold nanoparticles inside porous silica nanofibers via electrospinning. Metal salts used to produce the nanoparticles are mixed with silica and polymer precursors and spun into fibers. The fibers are then heat-treated to reduce the metal salt into metal nanoparticles. The factors affecting the size and distribution of the nanoparticles inside the porous fibers were studied. The fibers thus produced were then tested for catalytic activity. Horseradish peroxidase (HRP) enzyme was also encapsulated in porous silica nanofibers via electrospinning. The fibers showed significant enhancement in enzyme activity, which was three orders of magnitude greater than that of the non-templated, conventional microporous silica materials. The factors affecting the enzyme activity, like pH, temperature, etc., was also studied. The response time of the encapsulated enzymes to the external reagents was ~ 2 to 3 seconds, showing high efficiency of the fibers to sensor applications. Finally, the encapsulation and alignment of quantum dots in silica nanofibers for sensor and telecommunication applications was attempted. MnO2 and several enzymes encapsulated porous silica samples were also synthesized for universities and companies as part of the ongoing collaborative research work for various catalytic applications. All the above-mentioned products have high surface area, maintain high enzyme activity, and protect the enzymes and nanoparticles from high temperatures, pH fluctuations and strong chemicals. The morphology, size, porosity, composition of the developed products were studied in detail, via infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectroscopy, etc. Inexpensive raw materials, convenient synthesis method, distinctive structure and physical-chemical properties make the developed products greatly suitable for a wide range of potential applications.