Nanoparticles composites for catalysis and sensing

Zusammenfassung

Catalysis is usually divided into three branches: heterogeneous, homogeneous and enzyme pathway reflecting the catalytic conditions in a designed and optimum temperature, pressure for major applications. Traditionally, heterogeneous metal nanocatalysts normally obtained via the reduction of the precursor directly over the supports. Although they can achieve the nanoscale nanoparticles (NPs) on the surface or inside supports, it is one challenge to get the define size, composition and morphology of nanostructure. Recently, we in our group have further developed the approach to design the nanocatalysts with controlled morphologies by simple ''dipping catalysts'' with cellulose filter papers, where synthesis of defined nanocatalysts is one of key steps before the preparing the ''dipping catalysts''. ¿Dipping catalyst¿ based on the cellulose filter papers exhibiting the high surface area where nanopaticles can be dispersed well have been utilized for one universal approach to design the high stability, high efficiency heterogeneous catalysts. In this approach, the filter papers as the substrate are dipped into the nanoparticles ink for several seconds, drawn out quickly and dried by the hair drier. The heterogeneous catalysts can be obtained in a large scale and even stable into the volatile solvent, such as chloroform. Metal-organic frameworks (MOFs), one novel mesoporous materials with adjustable permanent porosity and specific surface area, supported the nanoparticles for the drug delivery, gas sensing, optical and catalyst applications. Nanoparticles exhibiting the higher surface energy and large surface area leading to thermodynamically unstable and often accompanied loss of the catalytic property because of the surface contamination, nanoparticle aggregation. Combining the nanoparticles with MOFs can prohibit the NPs aggregation and also integration both functionality. The difference of lattice mismatch between the MOFs and the nanocrystals, lead to difficulty in growing the MOFs on the surface of the nanocrystals. Embed the NPs into the MOFs also needs challenge the stability of NPs in the high polarity solvent. Therefore, synthesis of nanoparticles is imperious task applied to the heterogeneous nanocatalysts. One of the challenge is that obtain the nanoparticles in high concentration without the aggregation. Compared to prepare the nanoparticles in the aqueous solution, synthesis of the nanoparticles in the organic phase not only get the smaller size of the nanoparticles, but also it is prohibited the nanoparticles from aggregation even if in higher concentration. However, one limitation in the organic phase is that decomposition of the metal precursor is higher and reaction conditions is strict, such as N2. Hybrid NPs is very hot and challenge to the scientists because the excellent property compared to the single nanoparticles. Strain effect and electron communication via the nanointerfaces between the nanodomains are usually regarded as the most important mechanism to modify the electron, magnetic, optical property of the hybrid NPs. Lattice mismatch is one obstacle to obtain the hybrid NPs, however, the scientists recently has achieved the hybrid NPs through the seed mediated growth approach. In order to achieve this goal, we have carried out the synthesis of hybrid nanoparticles through the seed mediated growth approach; subsequently, Pd NPs doped the cellulose filter papers are prepared and evaluated by the Suzuki-cross coupling reaction, the conversion of the nitrophenol to aminophenol, etc organic reaction; and then, Au NPs assembled on the filter papers are applied to in-situ monitor the chemical reaction on the surface of the heterogeneous catalysts; Finally, we have examined the optical property of the novel platform that plasmonic NPs @ metal-organic frameworks (MOFs) and monitor the molecular diffusion property through SERS.