Enhancing the photoluminescence of peptide-coated nanocrystals with shell composition and UV irradiation

The composition and structure of inorganic shells grown over CdSe semiconductor nanocrystal dots and rods were optimized to yield enhanced photoluminescence properties after ligand exchange followed by coating with phytochelatin-related peptides. We show that, in addition to the peptides imparting superior colloidal properties and providing biofunctionality in a single-step reaction, the improved shells and pretreatment with UV irradiation resulted in high quantum yields for the nanocrystals in water. Moreover, peptide coating caused a noticeable red-shift in the absorption and emission spectra for one of the tested shells, suggesting that exciton-molecular orbital (X-MO) coupling might take place in these hybrid inorganic-organic composite materials.     

convergence of the reconstruction formula for the potential function

It is known that the potential function of the Sturm-Liouville problem can be reconstructed from the nodal data by a pointwise limit. We show that this convergence is in fact .

     

Temperature dependence of energy gaps in some II–VI compounds

The Brooks-Yu theory is applied to the calculation of the temperature dependence of the energy band gaps in some II–VI compounds. The theory is applied in the framework of the empirical pseudo-potential method, and utilizes a recent lattice dynamical calculation of the Debye-Waller factors. The temperature dependence of several critical-point band gaps are determined and compared with a vailable experimental data. In general, reasonable agreement is obtained. The interesting case of HgTe, which exhibits an anomalous positive temperature coefficient of the fundamental band gap, is also discussed.     

Electron spin resonance of manganous ions in frozen methanol solution

An analysis of the electron spin resonance of Mn²⁺ in frozen methanol is presented. The broadened, asymmetric lineshape is shown to be due to inhomogeneous broadening caused by combined second - and third-order effects of randomly distributed zero-field splittings in the range of 80-150 G.     

Threshold behavior of multiple photon dissociation of SF6

Multiple photon dissociation of SF₆ by a short pulse of a CO₂ laser has been investigated by simultaneous measurements of the average number of photons absorbed per molecule 〈n〉 and chemiluminescence intensities which result from the dissociated F atoms. A criterion for the dissociation threshold which is independent of laser wavelength is found to be 〈n〉 = 16 ± 3 photons per molecule. A thermal distribution of the excited molecules is shown to be inconsistent with the behavior just above threshold.     

Influences of the interfacial state between Co and a Si substrate on the magnetic properties of Co/Si(1 1 1) films

Morphology and magnetic properties of Co/Si(1 1 1) interfaces have been investigated using scanning tunneling microscope and surface magneto-optic Kerr effect techniques. As deposited at room temperature for Co/Si(1 1 1), defects have been observed with shapes of dark patches and bright islands on the surface with different Co coverage. The defect formation causes a rough interface. For subsequently deposited Co layers, the interfacial state between Co and the Si substrate results in the appearance of both the longitudinal and polar Kerr loops. After annealing treatments, interdiffusion of Co atoms and Si(1 1 1) substrate occurs as revealed by Auger electron spectroscopy. Scanning tunneling microscope images show the formation of Si clusters with average diameter of 10 nm at high temperatures. The disappearance of ferromagnetism of the films occurs due to the structural and compositional changes.     

Interaction between 3-(p-tolylamino)-1,5-azulenequinone and the deoxyguanosine residue in various oligonucleotides upon photolysis.

Eight single-stranded oligodeoxyribonucleotides 32P-labeled at the 5'-end were synthesized; they were annealed with the complementary oligodeoxyribonucleotides to form the corresponding double-stranded helices. These duplexes possessed standard Watson-Crick base pairs, locally perturbed sites of a base mismatch, or a bulge. Further, 5'-32P-labeled oligodeoxyribonucleotides with a hairpin loop were also synthesized. Cleavage of these single- and double-stranded oligodexyribonucleotides selectively at the deoxyguanosine residue was accomplished by use of 3-(p-tolylamino)-1,5-azulenequinone 1 upon irradiation with 350 nm UV light. The single strands were cleaved more efficiently than the double-helices. For the helices containing a deoxyguanosine residue at a bulge, at a hairpin loop or toward the end, the cleaving efficiency was increased. Computation results indicate that two possibilities exist for agent 1 to form two "Watson-Crick type" hydrogen bonds with guanine in single-stranded oligodeoxyribonucleotides; yet, only one possibility exists in duplexes.