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Ag nanoparticles synthesized on n and p-type Si were shown to exhibit charge-selective surface-enhanced Raman scattering and fluorescence quenching. As revealed by electric force microscopy, the polarity and magnitude of the nanoparticle charge is controllable with the metal-semiconductor Fermi level difference and nanoparticle size. It is inferred that the Fermi level alignment is dominantly contributed by the charge-induced nanoparticle voltage. Nanoparticle charging also accounts for self-inhibition of coalescence during chemical reduction, allowing strong plasmon hybridization.

The present work demonstrates a high biomass content (i.e., up to 90% by weight) and moldable material by controlled covalent cross-linking of lignocellulosic particles by a thermoset through epoxide-hydroxyl reactions. As an example for lignocellulosic biomass, Eastern redcedar was employed. Using scanning fluorescence microscopy and vibrational spectroscopy, macroscopic to molecular scale interactions of the thermoset with the lignocellulose have been revealed. Impregnation of the polymer resin into the biomass cellular network by capillary action as well as applied pressure results in a self-organizing structure in the form of thermoset microrods in a matrix of lignocellulose. We also infer permeation of the thermoset into the cell walls from the reaction of epoxides with the hydroxyls of the lignin. Compression tests reveal, at 30% thermoset content, thermoset-cross-linked lignocellulose has superior mechanical properties over a commercial wood plastic composite while comparable stiffness and strength to bulk epoxy and wood, respectively. The failure mechanism is understood to be crack propagation along the particle-thermoset interface and/or interparticle thermoset network.

This study investigates the effect of graphene nanoplatelets on the microstructure and mechanical properties of silicon carbide (SiC). Graphene nanoplatelets are dispersed in a liquid preceramic polymer by ball milling. Pyrolysis of the graphene nanoplatelet-preceramic polymer slurry results in near-stoichiometric SiC-graphene nanoplatelet powder. This method leads to improved dispersion of graphene in the SiC matrix as compared to conventional mechanical blending of dry powders and thereby significantly influences the resulting mechanical properties. Subsequently, spark plasma sintering (SPS) is used to consolidate dense bulk SiC-graphene composites with varying graphene content up to a maximum of 5 wt%. X-ray diffraction (XRD) investigation reveal that inclusion of graphene restricts grain growth of SiC matrix during SPS processing. Fracture toughness of SiC-graphene composite is increased by 40 % with the inclusion of 2 wt% graphene nanoplatelets. However, for higher graphene content the change in fracture toughness is limited. Improvement in fracture toughness is due to crack bridging reinforcing mechanism provided by the graphene platelets. Finally, Raman spectroscopy is used to understand the effect of SPS processing on integrity of graphene nanoplatelets.