Sustainable Biocomposites for Structural Applications with Environmental Affinity.

In this work, we report a facile preparation of biocomposites using a chitosan matrix that is reinforced with morphed graphene in amounts from 1 to 5 wt % C. The composites are processed by milling and conventional sintering. The morphed graphene additions show clear improvements in mechanical properties, having a direct correlation with temperature in particular for 180 °C. Higher temperatures are detrimental to chitosan and the properties drop because chitosan degrades. Mechanical properties in the composite such as yield strength and compressive strength increase between 40 and 50% with respect to the pure chitosan samples. The Young's modulus presents a drop of approximately 10%, but the fracture toughness increases up to 3.5 fold. The properties of our sustainable composites are comparable to those seen in polymers such as polyethylene, polypropylene, nylon, and poly(methyl methacrylate), among other commodity or single use plastics. The enhancement in the mechanical properties is attributed to the morphed graphene embedded chitosan matrix that generates a network of intergranular "anchors" that hold the chitosan crystals in place, preventing failure. The composites can be molded into near-net-shape products, machined, or shaped using various methods including laser lithography. These studies demonstrate the feasibility of fabricating biocomposites with different architectures and sizes for disposable structural components. Both chitosan and the composites are compostable and biodegradable with the potential to sustain plant growth when discarded. In addition, morphed graphene and chitosan are produced from byproducts or waste, which may result in a negative carbon footprint on the environment.

Electroless Deposition of Pb Monolayer: A New Process and Application to Surface Selective Atomic Layer Deposition.

The present work demonstrates an electroless (e-less) deposition of Pb monolayer on Au and Cu surface whose morphology and properties resemble its underpotentially deposited counterpart. Our results and analysis show that the e-less Pb monolayer deposition is a surface selective, surface controlled, self-terminating process. Results also show that the electroless Pb monolayer deposition is enabling a phenomenon for new deposition method called "electroless atomic layer deposition" (e-less ALD). Here, the e-less Pb monolayer serves as reducing agent and sacrificial material in surface limited redox replacement reaction with noble metal ions such as Pt n+, i.e., Pt deposition. The e-less ALD is highly selective to the metal substrates at which Pb forms the e-less monolayer. The full e-less ALD cycle leads to an overall deposition of a controlled amount of the noble metal. Repetition of the two-step e-less ALD cycle an arbitrary number of times leads to formation of a highly compact, smooth, and conformal noble metal thin film with applications spanning from catalyst synthesis to semiconductor technology. The process is designed for (but not limited to) aqueous solutions that can be easily scaled up to any size and shape of the substrate, deeming its wide applications.