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A fast and simple method is proposed for producing homogeneous silvered nanostructures on a glass surface as potential substrates for fluorescence enhancement assays. It is demonstrated that the Au core-Ag shell nanostructures on glass surfaces are promising substrates for fluorescence enhancement with outstanding macroscopic homogeneity.

A study focusing on the ability to utilize isotopic analysis of Pb used in small arms projectiles from varying geographic origin was undertaken using the GV Instruments Isoprobe multicollector inductively coupled plasma mass spectrometer. With the exception of two classes of ammunition, these samples were able to be distinguished from one another. Also, following rigorous normalization and mass bias correction, these data were compared to data collected by geochemists in localities corresponding to projectile manufacture. This comparison was successful when projectiles in certain economically isolated countries were analyzed. Pb isotopic analysis with MC--ICPMS is shown to be useful as a tool for distinguishing between ammunition of various manufacturing origins.

Electrolyte concentration affects the rate of ion-exchange by changing the equilibrium loading of the methyl viologen dications (MV(super 2+)) in zeolite Y. For lower electrolyte concentrations, more MV(super 2+) ions are retained in the zeolite at equilibrium causing a lowering of the ion-exchange rate.

The use of a scientifically operated charge-coupled device (CCD) for the detection and quantitation of aflatoxins on a high-performance thin-layer chromatographic (HPTLC) plate was investigated. A nebulizer-based sample application system was utilized to quantitatively transfer the sample onto the HPTLC plate without disturbing the sorbent layer. Fluorescence excitation of the aflatoxins was accomplished with an ultraviolet transilluminator, which caused the analytes of interest to emit in the blue-green portion of the visible spectrum. The dynamic range, sensitivity, accuracy, and precision of the system were evaluated. Detection limits of the aflatoxins were determined to be in the low picogram range. The existence of aflatoxins in peanut butter samples was analyzed both quantitatively and qualitatively by using multidimensional TLC. The capabilities of the system for performing real-time monitoring of the separation process were also investigated.

The photochemical rearrangement of a variety of selected ketone analogs with a simple dimethylallenyl moiety is investigated. The systems used in the study are the allenic analogs of 4,4-diphenylcyclohexenone and a similar counterpart of 4,4-diphenyl-2,5-cyclohexadienone. Results show that the photochemical rearrangement of the allenic systems analogs of cyclohexenones and cyclohexadienones exhbit phenyl migration rather than the type A rearrangement.

The complex chronoamperometry (CA) of partially silver ion exchange Ag3.1Na2.59Y was explained by considering the crossing of silver cations to the electrode solution interface as a diffusion-controlled reaction followed by a feeding chemical step. The separation of the zeolite particle into volume elements depended on the link between the large and small channels in the zeolite Y. It was discovered that the accurate measurement of intrazeolite diffusion coefficients was only possible in the event that the actual equilibrium cation locations were known.

Electrochemical studies of thickness shear mode (TSM) acoustic wave oscillators coated with zeolites are described. The results indicate that the silver deposit formed via the reduction of silver ions originally within the zeolite phase mechanically couples the zeolite film to underlying substrate.

The article focuses on teaching strategies for nanochemistry in the undergraduate curriculum, with focus on the Madelung constants (MC) of nanocrystals. It is stated that MC refers to the electrostatic energy per ion per unit charge for a bulk material that has been normalized to the closest distance between an anion and a cation. It discusses a method for introducing size-dependent phenomena based on lectures during the first semesters of undergraduate chemistry. Calculations of the lattice energies of binary ionic solids are explained.

This paper describes electrochemical studies of thickness shear mode (TSM) acoustic wave oscillators coated with zeolites. The frequency response of gold on AT-cut 9 MHz quartz oscillators of silver-ion-exchanged zeolite-modified electrodes (ZMEs) under an electrochemical bias is interpreted. This is achieved using a combination of cyclic voltammetry, double-potential-step chronocoulometry (DPSC), and the frequency and resistance responses of the quartz crystal oscillators. Three ZMEs were investigated including fully exchanged Ag12A plus partially exchanged Ag6.4A and Ag3.5A. In all cases, the frequency response of the quartz crystal nanobalance (QCN) could only be interpreted when motional resistance changes were considered. This determines the importance of energy storage and energy dissipation of the shear wave produced by the oscillator in the zeolite film, which was affected by the deposition of silver at the zeolite−electrode−solution interface. The silver deposit formed via the reduction of silver ions originally within the zeolite phase mechanically couples the zeolite film to the underlying substrate. The resistance changes occurring during redox are thus linked to an inner interfacial slip between the zeolite film and the underlying oscillating surface. The data presented are consistent with an extrazeolite redox mechanism. [ABSTRACT FROM AUTHOR]

Doped ceria-based metal oxides are widely used as supports and stand-alone catalysts in reactions where CO 2 is involved. Thus, it is important to understand how to tailor their CO 2 adsorption behavior. In this work, steering the CO 2 activation behavior of Ce-La-Cu-O ternary oxide surfaces through the combined effect of chemical and mechanical strain was thoroughly examined using both experimental and ab initio modeling approaches. Doping with aliovalent metal cations (La 3+ or La 3+ /Cu 2+ ) and post-synthetic ball milling were considered as the origin of the chemical and mechanical strain of CeO 2 , respectively. Experimentally, microwave-assisted reflux-prepared Ce-La-Cu-O ternary oxides were imposed into mechanical forces to tune the structure, redox ability, defects, and CO 2 surface adsorption properties; the latter were used as key descriptors. The purpose was to decouple the combined effect of the chemical strain (ε C ) and mechanical strain (ε M ) on the modification of the Ce-La-Cu-O surface reactivity toward CO 2 activation. During the ab initio calculations, the stability (energy of formation, E O v f ) of different configurations of oxygen vacant sites (O v ) was assessed under biaxial tensile strain (ε > 0) and compressive strain (ε < 0), whereas the CO 2 -philicity of the surface was assessed at different levels of the imposed mechanical strain. The E O v f values were found to decrease with increasing tensile strain. The Ce-La-Cu-O(111) surface exhibited the lowest E O v f values for the single subsurface sites, implying that O v may occur spontaneously upon Cu addition. The mobility of the surface and bulk oxygen anions in the lattice contributing to the O v population was measured using 16 O/ 18 O transient isothermal isotopic exchange experiments; the maximum in the dynamic rate of 16 O 18 O formation, R max ( 16 O 18 O), was 13.1 and 8.5 μmol g -1 s -1 for pristine (chemically strained) and dry ball-milled (chemically and mechanically strained) oxides, respectively. The CO 2 activation pathway (redox vs associative) was experimentally probed using in situ diffuse reflectance infrared Fourier transform spectroscopy. It was demonstrated that the mechanical strain increased up to 6 times the CO 2 adsorption sites, though reducing their thermal stability. This result supports the mechanical actuation of the "carbonate"-bound species; the latter was in agreement with the density functional theory (DFT)-calculated C-O bond lengths and O-C-O angles. Ab initio studies shed light on the CO 2 adsorption energy ( E ads ), suggesting a covalent bonding which is enhanced in the presence of doping and under tensile strain. Bader charge analysis probed the adsorbate/surface charge distribution and illustrated that CO 2 interacts with the dual sites (acidic and basic ones) on the surface, leading to the formation of bidentate carbonate species. Density of states (DOS) studies revealed a significant E g drop in the presence of double O v and compressive strain, a finding with design implications in covalent type of interactions. To bridge this study with industrially important catalytic applications, Ni-supported catalysts were prepared using pristine and ball-milled oxides and evaluated for the dry reforming of methane reaction. Ball milling was found to induce modification of the metal-support interface and Ni catalyst reducibility, thus leading to an increase in the CH 4 and CO 2 conversions. This study opens new possibilities to manipulate the CO 2 activation for a portfolio of heterogeneous reactions.

CO elimination through oxidation over highly active and cost-effective catalysts is a way forward for many processes of industrial and environmental importance. In this study, doped CeO 2 with transition metals (TM = Cu, Co, Mn, Fe, Ni, Zr, and Zn) at a level of 20 at. % was tested for CO oxidation. The oxides were prepared using microwave-assisted sol-gel synthesis to improve catalyst's performance for the reaction of interest. The effect of heteroatoms on the physicochemical properties (structure, morphology, porosity, and reducibility) of the binary oxides M-Ce-O was meticulously investigated and correlated to their CO oxidation activity. It was found that the catalytic activity (per gram basis or TOF, s -1 ) follows the order Cu-Ce-O > Ce-Co-O > Ni-Ce-O > Mn-Ce-O > Fe-Ce-O > Ce-Zn-O > CeO 2 . Participation of mobile lattice oxygen species in the CO/O 2 reaction does occur, the extent of which is heteroatom-dependent. For that, state-of-the-art transient isotopic 18 O-labeled experiments involving 16 O/ 18 O exchange followed by step-gas CO/Ar or CO/O 2 /Ar switches were used to quantify the contribution of lattice oxygen to the reaction. SSITKA-DRIFTS studies probed the formation of carbonates while validating the Mars-van Krevelen (MvK) mechanism. Scanning transmission electron microscopy-high-angle annular dark field imaging coupled with energy-dispersive spectroscopy proved that the elemental composition of dopants in the individual nanoparticle of ceria is less than their composition at a larger scale, allowing the assessment of the doping efficacy. Despite the similar structural features of the catalysts, a clear difference in the O lattice mobility was also found as well as its participation (as expressed with the α descriptor) in the reaction, following the order α Cu > α Co > α Mn > α Zn . Kinetic studies showed that it is rather the pre-exponential (entropic) factor and not the lowering of activation energy that justifies the order of activity of the solids. DFT calculations showed that the adsorption of CO on the Cu-doped CeO 2 surface is more favorable (-16.63 eV), followed by Co, Mn, Zn (-14.46, -4.90, and -4.24 eV, respectively), and pure CeO 2 (-0.63 eV). Also, copper compensates almost three times more charge (0.37 e - ) compared to Co and Mn, ca. 0.13 e - and 0.10 e - , respectively, corroborating for its tendency to be reduced. Surface analysis (X-ray photoelectron spectroscopy), apart from the oxidation state of the elements, revealed a heteroatom-ceria surface interaction (O a species) of different extents and of different populations of O a species.