Xiaofei Duan

Molecular Organization of the Nanoscale Surface Structures of the Dragonfly Hemianax papuensis Wing Epicuticle

The molecular organization of the epicuticle (the outermost layer) of insect wings is vital in the formation of the nanoscale surface patterns that are responsible for bestowing remarkable functional properties. Using a combination of spectroscopic and chromatographic techniques, including Synchrotron-sourced Fourier-transform infrared microspectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS) depth profiling and gas chromatography-mass spectrometry (GCMS), we have identified the chemical components that constitute the nanoscale structures on the surface of the wings of the dragonfly, Hemianax papuensis. The major components were identified to be fatty acids, predominantly hexadecanoic acid and octadecanoic acid, and n-alkanes with even numbered carbon chains ranging from C14 to C30. The data obtained from XPS depth profiling, in conjunction with that obtained from GCMS analyses, enabled the location of particular classes of compounds to different regions within the epicuticle. Hexadecanoic acid was found to be a major component of the outer region of the epicuticle, which forms the surface nanostructures, and was also detected in deeper layers along with octadecanoic acid. Aliphatic compounds were detected throughout the epicuticle, and these appeared to form a third discrete layer that was separate from both the inner and outer epicuticles, which has never previously been reported.

Non-covalently modified graphene supported ultrafine nanoparticles of palladium for hydrogen gas sensing

A facile aqueous based method of decorating p-phosphonic acid calix[8]arene functionalized graphene with well-dispersed ultrafine palladium nanoparticles (∼2 nm) has been developed. The electrocatalytic Pd-NP–graphene nano-composite has been incorporated into a functional hydrogen sensing device using a simple drop casting technique on interdigitated electrodes.

Biogenic production of palladium nanocrystals using microalgae and their immobilization on chitosan nanofibers for catalytic applications

Spherical palladium nanocrystals were generated from aqueous Na2[PdCl4] via photosynthetic reactions within green microalgae (Chlorella vulgaris). Electrospun chitosan mats were effective for immobilizing these biogenic nanocrystals, as a material for recycling as a catalyst for the Mizoroki–Heck cross-coupling reaction. This photosynthetically-driven metal transformation system can serve as a good candidate for an environmentally-friendly method for the synthesis of metal nanocatalysts.

Facile synthesis of electrochemically active Pt nanoparticle decorated carbon nano onions

Well dispersed platinum nanoparticles 1–5 nm (average 2 nm) in diameter on carbon nano onions (CNOs) are accessible using a simple and scalable one-step batch method. This technique involves pre-treatment of acid digested CNOs with H2PtCl6 prior to reduction using hydrogen at ambient conditions, with the composite material being electrochemically active. The effect of different Pt loading, surface treatment, and the processing temperature on the dispersion of platinum nanoparticles on the CNOs has been studied in detail.

Unzipping oyster shell

A novel technique to extract nacre tablets (bricks) from molluskan shells using ‘soft energy’ ionic liquid based dissolution of the organic material (mortar) between the tablets rather than using high energy and potentially tablet-damaging ball milling processing has been developed. The tablets isolated from this ‘unzipping’ of the shell in the ionic liquid n-butyl-3-methylimidazolium hexafluorophosphate were structurally characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). High resolution AFM combined with in situ SEM shows nanoparticles of calcium carbonate approximately 4–5 nm in diameter present at the interface between multiple tablets of pearl nacre where there is incomplete dissolution of the mortar in the ionic liquid.

Transparent Aluminium Oxide Coatings of Polymer Brushes

A novel method for the preparation of transparent Al2O3 coatings of polymers is presented. An environmental-friendly sol-gel method is employed, which implies mild conditions and low costs. A thermoresponsive brush is chosen as a model surface. X-ray photoelectron spectroscopy is used to characterize the samples during the conversion of the precursor Al(OH)3 into oxide and to prove the mildness of the protocol. The study evidences a relation between lateral homogeneity of alumina and the wettability of the polymer surface by the precursor solution, while morphology and elasticity are dominated by the polymer properties. The study of the swelling behavior of the underneath brush reveals the absence of water uptake, proving the impermeability of the alumina layer. The broad chemical and structural variety of polymers, combined with the robustness of transparent alumina films, makes these composites promising as biomedical implants, protective sheets and components for electric and optical devices.

Transmission electron microscopy determination of quantum dot profile

Investigation of the morphology of buried and unburied In/sub x/Ga/sub 1-x/As/GaAs quantum dots (QDs) has been carried out using cross-section transmission microscopy and the [001] on-zone bright-field technique with image simulation. The study shows that both the buried and unburied QDs are lens-shaped.