Simultaneous Writing and Erasing Using Probe Lithography Synchronized Erasing and Deposition (PLiSED).

Simultaneous writing and erasing of two and three molecules in one single step at the microscale using Polymeric Lithography Editor (PLE) probes is demonstrated. Simultaneous writing and erasing of three molecules was accomplished by rastering a nanoporous probe that was loaded with rhodamine B and fluorescein over a quinine-coated glass substrate. The solvated quinine molecules were erased and transported into the probe matrix, whereas both rhodamine and fluorescein molecules were simultaneously deposited and aligned with the path of the erased quinine on the substrate. The simultaneous writing and erasing of molecules is referred to as PLiSED. The writing and erasing speed can be easily tuned by adjusting the probe speed to as large as 10,000 µm2/s. The microscale patterns on the orders of square millimeter area were fabricated by erasing fluorescein with an efficiency (ηe) > 95% while simultaneously depositing rhodamine molecules at the erased spots. The roles of the probe porosity, transport medium, and kinetics of solvation for editing were also investigated─the presence of a transport medium at the probe-substrate interface is required for the transport of the molecules into and out of the probe. The physical and mechanical properties of the polymeric probes influenced molecular editing. Young's modulus values of the hydrated hydrogels composed of varying monomer/cross-linker ratios were estimated using atomic force microscopy. Probes with the highest observed erasing capacity were used for further experiments to investigate the effects of relative humidity and erasing time on editing. Careful control over experimental conditions provided high-quality editing of microscale patterns at high editing speed. Combining erasing and deposition of multiple molecules in one single step offers a unique opportunity to significantly improve the efficiency and the accuracy of lithographic editing at the microscale. PLiSED enables rapid on-site lithographic rectification and has considerable application values in high-quality lithography and solid surface modification.

Ethane adsorption on aggregates of dahlia-like nanohorns: experiments and computer simulations.

This is a report on a study of the adsorption characteristics of ethane on aggregates of unopened dahlia-like carbon nanohorns. This sorbent presents two main groups of adsorption sites: the outside surface of individual nanohorns and deep, interstitial spaces between neighbouring nanohorns towards the interior of the aggregates. We have explored the equilibrium properties of the adsorbed ethane films by determining the adsorption isotherms and isosteric heat of adsorption. Computer simulations performed on different model structures indicate that the majority of ethane adsorption occurs on the outer region of the aggregates, near the ends of the nanohorns. We have also measured the kinetics of adsorption of ethane on this sorbent. The measurements and simulations were conducted along several isotherms spanning the range between 120 K and 220 K.

Sorption Kinetics on Open Carbon Nanohorn Aggregates: The Effect of Molecular Diameter.

We present the results of a study of the kinetics of adsorption on aggregates of open carbon nanohorns using argon and CF4 sorbates. We measured the equilibration times for each value of the sorbent loading along eight adsorption isotherms (four isotherms for each sorbate species). We found that: the equilibration times decrease as the sorbent loading (and the equilibrium pressure of the coexisting gas) increases, for a given temperature; and, that, for a given value of the sorbent loading, the equilibration times decrease with increasing temperature. When considering the effect of scaling of the temperatures by the respective critical temperatures we found that, at the same scaled temperature and at comparable loadings, the equilibration times for CF4 were longer than those for argon. We discuss a possible explanation for this result.