Highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) tuning is an important consideration in the development of organic-based semiconducting materials. A study of the specific effects and overall trends for the HOMO-LUMO tuning of a diverse series of 9-fluorenones by means of extended conjugation and substituent effects is described. Trends were explored in a range of compounds, beginning with structures having highly electron-withdrawing substituents and progressing to structures having highly electron-donating substituents. Compounds with an incremental increase in conjugation were also examined. Electrochemical and optical measurements were used to calculate the HOMO-LUMO levels and HOMO-LUMO bandgap (HLG) for each structure. Results from both methods were compared and correlated with the differences in molecular structure. Increasing the electron-donating character of the substituents was observed to decrease the HLG and increase the energy levels of the HOMO and the LUMO, whereas an increase in the electron-withdrawing character produced the opposite results. Increasing conjugation decreased the HLG, increased the HOMO energy level, but decreased the LUMO energy level. Spectroscopic evidence of substituent influence on the carbonyl suggests that substituents directly impact the HLG by influencing the availability of nonbonding electrons within the carbonyl, which impacts the probability of an nπ* transition. The data presented not only elaborate on the HOMO -LUMO tuning of 9-fluorenone systems but also enable the consideration of 9-fluorenones as analogous models for HOMO-LUMO tuning in other more complex polyaromatic systems such as bifluorenylidenes. These trends may provide insight into developing materials with specifically tuned HLGs and HOMO-LUMO levels for a variety of applications.

Continuous films of silver(II) oxide (Ago) have been electrodeposited directly from aqueous solutions of 50 mM silver acetate/25 mM sodium acetate onto 430 stainless steel, polycrystalline platinum, and indium-tin oxide-coated glass. Current efficiencies for the electrodeposition process ranged from 62 to 95% and were a function of the applied current density. X-ray diffraction of the electrodeposited films reveals a [010] texture when the thickness is greater than 1 tim. Freshly ground films or powders exhibit only reflections consistent with the monoclinic Ago structure. Rietveld analysis confirms the ground films are single-phase Ago with a P 21/c space group. The films were imaged and film thickness was measured by atomic force microscopy. Thermogravimetric analysis shows that the films begin to decompose in air above 130°C, with an abrupt weight loss between 180 and 200°C. The total weight loss of 6.4 to 6.5% corresponds to thermal decomposition of Ago to Ag2O with loss of oxygen. A direct optical bandgap of 1.1 eV was measured. The black Ago films absorb strongly in the near infrared and throughout the visible region. The four-point resistivity of the Ago films was 12 1 11 cm.

Nanometer-scale layered structures based on thallium(III) oxide were electrodeposited in a beaker at room temperature by pulsing the applied potential during deposition. The conducting metal oxide samples were superlattices, with layers as thin as 6.7 nanometers. The defect chemistry was a function of the applied overpotential: High overpotentials favored oxygen vacancies, whereas low overpotentials favored cation interstitials. The transition from one defect chemistry to another in this nonequilibrium process occurred in the same potential range (100 to 120 millivolts) in which the rate of the back electron transfer reaction became significant. The epitaxial structures have the high carrier density and low electronic dimensionality of high transition temperature superconductors.

The objective of this study was to develop interactive lecture demonstrations (ILD) based on conceptual-change learning theory. Experimental instruction was designed for an introductory chemistry course for nonmajors to address misconceptions related to mole ratios and limiting reagents. Students were asked a series of questions related to two chemical demonstrations via an electronic keypad system. Questions asked during the demonstrations included conceptual items, particulate items, and traditional textbook-style calculations. Results indicate that use of the ILDs decreased students' misconceptions and that they were a positive addition to the course. Students' understanding was determined via a pretest and posttest that included multiple-choice and free-response questions. Students showed significant improvement on the multiple-choice items after instruction. Evaluation of free-response items via a rubric indicated that participants understanding of stoichiometry increased. A large majority of student evaluations suggested that the interactive system had a positive effect on their learning.

The conducting oxy salt Ag(Ag3O4I2NO3 has been electrodeposited onto highly oriented conducting oxides of T1203 and Pb,TlbO,. T1203 was grown in a [loo] texture while the mixed oxide Pb,TlbOc was grown with two different thickness-dependent textures of [110] and [210]. The orientation of the Ag(Ag304),N03 crystals with respect to the substrate surface was determined by X-ray diffraction. The face-centered-cubic Ag( &$4) 2NO3 crystals deposited on body-centered-cubic n 2 O 3 and face-centered-cubic Pb,TlbO, followed the orientation of these prelayers. However, Ag(Ag3O4I2NO3 electrodeposited onto polycrystalline 430 stainless steel had a nearly random orientation. The lattice mismatch is 6.6% between T1203 and Ag-(Ag304)2N03, and it is 7.8% between Ag(Ag304)2N03 and the doubled unit cell edge length of Pb,T1boc. It was also found that Pb,TlbOc undergoes a transition from a body-centered-cubic to a face-centered-cubic Bravais lattice at a lead content (determined on a metals-only basis) of greater than 40 atom %. IntroductionThe occurrence of the silver oxy salt Ag(Ag3O4),N03 has been known for quite some It is one of a series of compounds Ag(Ag304)2X where X = NO3-, ClOL, F-,6 HF2-, and BFQ.~ The material can be electrodeposited from AgN03 solutions by the following anode half-reaction: