By embedding “dilute” gold nanoparticles in single polystyrene thin films as “markers”, we probe the local viscosity of the free surface at temperatures far above the glass transition temperature (Tg). The techniq...
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By embedding “dilute” gold nanoparticles in single polystyrene thin films as “markers”, we probe the local viscosity of the free surface at temperatures far above the glass transition temperature (Tg). The technique used was x-ray photon correlation spectroscopy with resonance-enhanced x-ray scattering. The results clearly showed the surface viscosity is about 30% lower than the rest of the film. We found that this reduction is strongly associated with chain entanglements at the free surface rather than the reduction in Tg.
We developed an optical tweezers directed approach that allows synthesis of different oligonucleotide on an array of controlled pore glass (CPG) beads in parallel in a two-stream laminar flow microreactor and obtained...
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We developed an optical tweezers directed approach that allows synthesis of different oligonucleotide on an array of controlled pore glass (CPG) beads in parallel in a two-stream laminar flow microreactor and obtained one oligo sequence per bead. This reactor has been shown to effectively facilitate CPG bead loading and confinement, maintain liquid/ liquid (inert liquid/reagent) interface and withstand the reagents and solvents present in the modified phosphoramidite chemistry. The optical tweezers allows us to externally manipulate the CPG beads inside the channel without having to modify the microfluidic device itself. The parallel synthesis of several different oligonucleotides in a single synthetic run was demonstrated.
The reconstruction and evaporation at graphene nanoribbon (GNR) edges are investigated by tight-binding molecular-dynamics simulations and ab initio calculations. It is observed that reconstruction through the formati...
The reconstruction and evaporation at graphene nanoribbon (GNR) edges are investigated by tight-binding molecular-dynamics simulations and ab initio calculations. It is observed that reconstruction through the formation of pentagon-heptagon pairs can take place quickly along the zigzag edge and it is energetically favorable. At very high temperatures, the armchair edge is found to change into a zigzag edge structure, which further accelerates the evaporation of carbon atoms and leads to the formation of carbon linear chains. The evaporation of carbon atoms from both the zigzag and armchair edges is preceded by the formation of heptagon rings, which serve as a gateway for carbon atoms to escape. In the simulation for a GNR armchair-zigzag-armchair junction, carbon atoms are evaporated row by row from the outermost row of the zigzag edge while the armchair edge remains nearly intact. These results can be applied to nanoelectronic devices fabrication through the temperature-controlled edge structure of GNR.
Functional nanoparticles often contain ligands including targeting molecules, fluorophores, and/or active moieties such as drugs. Characterizing the number of these ligands bound to each particle and the distribution ...
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This study examined the structural evolution of ultrathin Hf1−xZrxO2 composite films with various mixing ratios (x=0,0.1,0.3,0.5,0.7,0.9,1) prepared by atomic layer deposition using x-ray photoelectron spectroscopy (X...
This study examined the structural evolution of ultrathin Hf1−xZrxO2 composite films with various mixing ratios (x=0,0.1,0.3,0.5,0.7,0.9,1) prepared by atomic layer deposition using x-ray photoelectron spectroscopy (XPS), x-ray absorption spectroscopy (XAS), and x-ray absorption fine structure (XAFS) analysis. As the relative Zr concentration (x) was increased, the composite films underwent a martensitic transition from monoclinic to tetragonal crystal structures near x=0.5–0.7. Zr K- and Hf L3-edge XAFS revealed a change in the local structures near the Zr and Hf atoms with changes in the crystal structure. At a low Zr content (x≤0.5), the next-nearest-neighbor coordination in the monoclinic (m) local structure showed significant structural disorder due to diverse structural reconstruction from the tetragonal (t) local structure. Combined XPS and O K-edge XAS studies revealed a decrease in the conduction-band (CB) edge energy with increasing x, whereas the valence-band edge energies were invariant. The evolution in the CB structures was analyzed using the concept of metal-ion crystal fields in the t and m cluster models.
Devices for continuous glucose monitoring (CGM) are currently a major focus of research in the area of diabetes management. It is envisioned that such devices will have the ability to alert a diabetes patient (or the ...
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Polymers are receiving considerable attention as components in novel optical systems because of the tailored functionality, easy manufacturing, and relatively low cost. The processing of layered polymeric systems by c...
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