Thermal treatment affects aptamers' structural profiles.

Using anion-exchange high performance liquid chromatography under non-denaturing conditions, the conformational flexibility of adenosine-, ampicillin-, and quinine aptamers were studied. It was found that all three aptamers showed more than one species when not subjected to thermal anneal. Addition of ligand to untreated aptamers did not significantly change the structural distribution. Upon heating followed by slow cooling, however, all three aptamers were found to exist virtually solely in one structure, presumably the partial hairpin species. It was also found that sonication of quinine aptamer, but not adenosine and ampicillin aptamer, led to its elution off HPLC as virtually a single species. These changes in conformational distribution as a result of thermal anneal or sonication were further confirmed by UV/vis and circular dichroism spectroscopy, as well as melt curves. The findings provided basis for future optimization of aptamer selection and preparation, where thermal anneal can help optimize selection efficiency and improve the consistency in the interpretation of results.

Performance Improvement and Characterization of Spray-Coated Organic Photodetectors.

Low dark current organic photodetectors (OPDs) with a conventional structure consisting of poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as active layer have been fabricated by spray-coating. Tuning the thickness of active layer and thermal annealing process for the spray-coated OPDs results in a remarkable performance with a low dark current density ( Jd) of 2.90 × 10-8 A/cm2 at reverse bias of 1 V. The impact of thermal annealing on the performance of sprayed OPDs is also investigated by the impedance analysis for mechanistic understanding. Our results demonstrate that the optimization of PCBM cluster and interfacial contact between the active layer and the metal electrode tailored by thermal annealing, respectively, could effectively reduce the Jd and increase the sensitivity of sprayed OPDs. The control of PCBM cluster is more important than the interfacial contact between the layers for improving Jd. In addition, structural characterization of the active layer studied by synchrotron small-angle X-ray scattering technique reveals why the spray-coated process can achieve the lowest dark current due to the favorable structure.

Fabrication of oriented wrinkles on polydopamine/polystyrene bilayer films.

Wrinkles exist widely in nature and our life. In this paper, wrinkles on polydopamine (PDA)/polystyrene (PS) bilayer films were formed by thermal annealing due to the different thermal coefficients of expansion of each layer. The factors that influenced the dimensions of wrinkles were studied. We found that oriented wrinkles could be formed if the bilayer films were patterned with micro-grooves, and the degree of the orientation depended on the thickness of the PDA and the dimensions of the grooves. Combined with the strong adhesion, biocompatibility and reactivity of PDA, the oriented wrinkles on PDA/PS patterned bilayers may find potential application in diffraction gratings, optical sensors and microfluidic devices.

Suppressing Segregation in Highly Phosphorus Doped Silicon Monolayers.

Sharply defined dopant profiles and low resistivity are highly desired qualities in the microelectronic industry, and more recently, in the development of an all epitaxial Si:P based quantum computer. In this work, we use thin (monolayers thick) room temperature grown silicon layers, so-called locking layers, to limit dopant segregation in highly phosphorus doped silicon monolayers. We present secondary ion mass spectroscopy and atom probe tomography measurements that demonstrate the effectiveness of locking layers in suppressing P segregation. Scanning tunneling micrographs of the surface of the locking layer show that the growth is epitaxial, despite the low growth temperature, while magnetotransport measurements reveal a 50% decrease in the active carrier density. We show that applying a finely tuned rapid thermal anneal can restore the active carrier density to 3.4 × 10(14) cm(-2) while maintaining ultra sharp dopant profiles. In particular, 75% of the initial deposited P is confined in a layer with a full width at half-maximum thickness of 1.0 nm and a peak P concentration of 1.2 × 10(21) cm(-3) (2.5 atom %).