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Engineering cell-derived nanovesicles with active-targeting ligands is an important strategy to enhance the targeting efficiency. However, the enhanced binding capability to targeting cells also leads to the binding with nontarget cells that share the same biomarkers. DNA-based logic gate is a kind of molecular system that responds to chemical inputs by generating output signals, and the relationship between the input and the output is based on a certain logic. Thus, the DNA-based logic gate could provide a new approach to improve the delivery efficiency of the nanovesicle. In this work, we developed a DNA logic-gated module that coupled two tumor cell-targeting factors (e.g., low pH and a tumor cell biomarker) in a Boolean manner. Immobilization of this module on the surface of the nanovesicle enables the nanovesicle to sense tumor cell-targeting factors and regard these cues as inputs AND logic gate. With the guide of DNA-based logic gate, gold carbon dots (GCDs) encapsulated within nanovesicles were delivered into target cells, and then the intracellular redox status variation was reflected by fluorescence change of GCDs. Overall, we developed DNA logic-gated nanovesicles that contract different targeting factors into a unique tag for target cells. This facile functionalization strategy can pave the way for constructing smart nanovesicles and would broaden their application in the field of precision medicine and personalized treatment.

Cerium oxide (ceria, CeO2) is a technologically important material for energy conversion applications. Its activities strongly depend on redox states and oxygen vacancy concentration. Understanding the functionality of chemical active species and behavior of oxygen vacancy during operation, especially in high-temperature solid-state electrochemical cells, is the key to advance future material design. Herein, the structure evolution of ceria is spatially resolved using bulk-sensitive operando X-ray diffraction and spectroscopy techniques. During water electrolysis, ceria undergoes reduction, and its oxygen non-stoichiometry shows a dependence on the electrochemical current. Cerium local bonding environments vary concurrently to accommodate oxygen vacancy formation, resulting in changes in Ce-O coordination number and Ce3+/Ce4+ redox couple. When reduced enough, a crystallographic phase transition occurs from α to an α' phase with more oxygen vacancies. Nevertheless, the transition behavior is intriguingly different from the one predicted in the standard phase diagram of ceria. This paper demonstrates a feasible means to control oxygen non-stoichiometry in ceria via electrochemical potential. It also sheds light on the mechanism of phase transitions induced by electrochemical potential. For electrochemical systems, effects from a large-scale electrical environment should be taken into consideration, besides effective oxygen partial pressure and temperature.

In this contribution, we present an industrial example on how tailored operando spectroscopic methodologies provide the insights needed for the development of new catalytic technologies and support their global utilization. We describe the use of operando spectroscopic methods to investigate how the CO oxidation performance of catalysts is impacted by NOx, H2, temperature, and moisture, as well as the catalyst support. This operando spectroscopic analysis provides mechanistic insights into the current diesel oxidation catalyst (DOC) system and shines light on the material and process development efforts on future DOC catalysts for low-temperature emission control to meet the new regulations. This investigation has shown that at cold-start temperatures, the nitrate growth can occupy the precious metal–alumina support interfacial sites that are critical for O2 dissociation and/or oxygen transfer and hinder CO conversion. Introduction of hydrogen on the catalyst surface can inhibit the nitrate growth, which in turn keeps these critical interfacial sites open.

Fluid Catalytic Cracking (FCC) has maintained its crucial role in refining decades after its initial introduction owing to the flexibility it has as a process as well as the developments in its key enabler, the FCC catalyst. Boron-based technology (BBT) for passivation of contaminant metals in FCC catalysts represents one such development. In this contribution we describe Fourier Transform Infrared Spectroscopy (FTIR) characterization of boron-containing catalysts to identify the phase and structural information of boron. We demonstrate that FTIR can serve as a sensitive method to differentiate boron trioxide and borate structures with a detection limit at the 1000 ppm level. The FTIR analysis validates that the boron in the FCC catalysts studied are in the form of small borate units and confirms that the final FCC catalyst product contains no detectable isolated boron trioxide phase. Since boron trioxide is regulated in some parts of the world, this novel FTIR methodology can be highly beneficial for further FCC catalyst development and its industrial application at refineries around the world. This new method can also be applied on systems beyond catalysts, since the characterization of boron-containing materials is needed for a wide range of other applications in the fields of glass, ceramics, semiconductors, agriculture, and pharmaceuticals.

Fluid Catalytic Cracking (FCC) is a crucial refining process supplying majority of gasoline used worldwide as well as other key building blocks for chemical industry. Nickel, a contaminant in crude oil, deposits on FCC catalysts and induces unwanted dehydrogenation reactions, inhibiting the FCC unit from reaching optimal operation. We describe a new spectroscopic methodology to characterize the impact of boron interaction on nickel in FCC catalysts through a trend analysis of CO DRIFTS for FCC catalysts from boron-based technology. Results obtained by the new method provide direct spectroscopic evidence of boron effect on nickel passivation by decreasing reducibility of nickel.

Spatially resolved ambient pressure X-ray photoelectron spectroscopy has been used to measure and visualize regions of electrochemical activity, local surface potential losses, overpotentials, and oxidation state changes on single sided ceria/yttria-stabilized zirconia (YSZ)/Pt solid oxide electrochemical cells. When hydrogen electro-oxidation (negative applied bias) or water electrolysis (positive applied bias) is promoted on the ceria electrocatalyst, the Ce3+/Ce4+ ratios shift away from equilibrium values and thereby demarcate electrochemically active regions on the ceria electrode. In addition to the ceria oxidation state shifts, inactive surface impurities with high photoelectron cross sections, such as Si, can provide local markers of activity through chemical and surface potential mappings under various electrochemical conditions. Localized removal of chemically active carbonaceous surface impurities also reveals regions of electrochemical oxidation activity on the ceria electrode. Finally, we show...

Ambient pressure X-ray photoelectron spectroscopy was used to detect rigid shifts in photoelectron kinetic energies and material chemical states for operating solid oxide electrochemical cells. The kinetic energy shifts directly correspond to the surface electric potentials and therefore can be used to detect the local potentials / potential losses for operating cells. The ceria valence state changes under applied biases relative to equilibrium conditions (at open circuit voltage) reveal the electrochemically active regions ~150 μm away from the current collectors for ceria thin film electrodes. The results provide fundamental mechanistic information about the active length scales in ceria electrodes, the surface reaction kinetics, charge transport, as well as activities for oxidation and electrolysis on operating solid oxide electrochemical cells.

Thin-film GDC (Ce0.8Gd0.2O2-x 300 nm thick) electrodes with porous Ni or Au metal overlayers (300 nm thick) were sputter-deposited on polycrystalline YSZ substrates and tested in single-chamber cells. With a back-side Pt-counter electrode, the electrochemical cells were characterized by linear-sweep voltammetry and impedance spectroscopy between 650 to 750 ºC in mixtures of H2/H2O/Ar diluent. To complement the electro-chemical tests, ambient-pressure XPS at the Advanced Light Source was performed on active cells in H2/H2O mixtures to measure surface potential and oxidation states. The GDC electrodes showed lower resistance to H2O electrolysis than H2 oxidation with Ni and Au overlayers. XPS measurements indicated large overpotentials across the YSZ/GDC interface particularly for H2 oxidation on the GDC electrode. Increasing PH2/PH2O (up to 10) resulted in higher rates for not only H2 oxidation, but also H2O electrolysis, suggesting that H2O electrolysis activity is enhanced by increased reduction of the GDC surface.

Ambient pressure X-ray photoelectron spectroscopy (XPS) is used to measure near-surface oxidation states and local electric potentials of thin-film ceria electrodes operating in solid oxide electrochemical cells for H2O electrolysis and H2 oxidation. Ceria electrodes which are 300 nm thick are deposited on YSZ electrolyte supports with porous Pt counter electrodes for single-chamber tests in H2/H2O mixtures. Between 635 and 740 °C, equilibrium (zero-bias) near-surface oxidation states between 70 and 85% Ce3+ confirm increased surface reducibility relative to bulk ceria. Positive cell biases drive H2O electrolysis on ceria and further increase the percentage of Ce3+ on the surface over 100 μm from an Au current collector, signifying broad regions of electrochemical activity due to mixed ionic-electronic conductivity of ceria. Negative biases to drive H2 oxidation decrease the percentage of Ce3+ from equilibrium values but with higher electrode impedances relative to H2O electrolysis. Additional tests indic...

Undoped ceria with its facile redox at high-temperatures has potential as an effective material for electrolysis. This study explores the electrochemical performance of thin-film ceria electrodes for H2O electrolysis at 700 °C. The electrochemical characterization is complemented by in situ XPS measurements, which show that the highly reduced ceria surface increases in degree of reduction with electrolysis voltage. Results also show that H2O electrolysis is enhanced with increased H2 partial pressure. Analysis of electrochemical impedance spectra and voltammetric measurements show that the electrolysis reactions depend strongly on H2 pressure. These trends, which are not readily explained by simple surface kinetic models, do indicate that increased ceria surface reduction by the presence of H2 product enhances activity for H2O electrolysis. The results were used to create a microkinetic model to assess surface and subsurface processes in ceria for H2O electrolysis.

Heterogeneous films of ordered CeO(2)/Ni concentric nanostructures have been fabricated through template-assisted electrodeposition. The free-standing films of Ni metal (8 mum thickness) contain ordered arrays of ceria tubes (200 nm OD, 100 nm ID). Ni/CeO(2) coaxial nanotubes were also obtained by tuning experimental conditions. The interfacial contact area within the 3-dimensional oxide nanotube/nickel matrix is approximately 100 times greater than 2-dimensional thin films of nickel and ceria of the same area. The use of the film as an anode electrocatalyst/current collector is demonstrated in a solid oxide fuel cell.

Single chamber electrochemical cells were fabricated by patterning working and counter electrodes of Ni and Pt on single-crystal Y2O3-stabilized ZrO2. Cells were characterized in mixed atmospheres of H2 and H2O at ratios of 1:1 and 1:20 at nominally 923 K and 67 Pa total pressure. Potential sweep and impedance measurements were conducted simultaneously with ambient-pressure x-ray photoelectron spectroscopy (APXPS), which is a unique synchrotron-based probe designed for in-situ chemical characterization of surfaces using photoemission at gas pressures large enough to achieve realistic densities of faradic current. Electrochemically induced oxidation of Ni was observed under anodic polarization and could be reversed by applying a cathodic bias. The thin-film microstructure could also be manipulated electrochemically in that pores exposing underlying electrolyte would open through the Ni film after polarization. Application of APXPS to resolve fundamental details of high-temperature electrochemical process in-situ is discussed.

Magnetoresistance properties of Ni nanocontacts in the ballistic quantum regime are investigated in situ for several orientations between applied magnetic field and current direction. The symmetry properties of the magnetoresistance curves are similar to anisotropy magnetoresistance effects, even if the shape of the contact is modified. A change of conductance under magnetic field has a magnitude between 0.2e 2 /h and e 2 /h, varying little with the absolute conductance values ranging between e 2 /h and 100e 2 /h. We discuss possible mechanical artifacts to our magnetoresistance curves, showing that the shear of the substrate might contribute to conductance changes. However, replacing the metal used as substrate does not modify our observations.

Semiconductor selenides of MSe (M = Cd, Hg) nanocrystalline powders were synthesized through the reactions between metal chlorides and sodium selenosulfate in the ammoniacal aqueous solution at room temperature for 6–10 h. The samples were characterized by x-ray powder diffraction, transmission electron microscopy, electron diffraction, x-ray photoelectron spectroscopy, and elemental analysis. The average diameters of CdSe and HgSe nanocrystallites are 4 and 8 nm, respectively. The storage and an interesting phase transition under hydrothermal conditions have been presented. The absorption spectrum of the as-prepared samples exhibits obvious blue shift due to the size confinement.

Magnetoresistance properties of Ni nanocontacts in the ballistic quantum regime are investigated in situ during closure and opening of electrochemically grown planar electrodes. The magnitude of conductance change when sweeping the magnetic field is of the order of the quantum conductance e2/h for conductance values spanning 1–100 quanta. The relative orientation of electric current and applied magnetic field changes the magnetoresistance sign, with symmetry properties reminiscent of bulk anisotropy magnetoresistance. Ex situ investigations of samples of higher conductance values, of the order of 1000 quanta, unambiguously show the analogy with bulk anisotropy magnetoresistance.

Metal/organic self-assembled monolayer/metal junctions were investigated for junction areas 10-2 to 102 μm2. Several types and thickness of monolayers are investigated, and magnetic electrodes were made. Electroless deposition was used to make the top metal without disrupting the organic film. This deposition is activated with Pd clusters obtained by evaporation or by chemical reduction of a Pd-based catalyst. This method allows us to obtain a high yield of junctions that are not electrically shorted and are mechanically and electrically stable over a wide temperature range. Low-temperatures investigations reveal strong non-linearity in the IV curves and an increase of resistance with decreasing temperature. Zero bias anomalies observed at low temperatures are attributed to a Coulomb blockade associated with the Pd clusters.