Polypyrrole (PPy)/CuBi₂O₄ nanosheets (NSs) were prepared by an in situ polymerization process and the NS-modified glassy carbon electrode (GCE) for electrochemical determination of benzoic acid was studied. The structure, morphology, and functional groups of the PPy/CuBi₂O₄-NSs were analyzed by X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, and Fourier transform infrared spectroscopy. The obtained NSs contain a tetragonal CuBi₂O₄ phase, and nanoscale PPy particles attach to the surface of the NSs. The electrochemical responses of the PPy/CuBi₂O₄-NS-modified GCE in 0.1 M KCl solution with benzoic acid were investigated by the cyclic voltammetry (CV) and electrochemical impedance spectroscopy. An irreversible CV peak is located at −0.84 V on the PPy/CuBi₂O₄-NS-modified GCE in 2 mM benzoic acid and 0.1 M KCl solution. The intensities of the CV peaks show linear variation with increasing the scan rate and concentration of benzoic acid. The linear range is 0.001−2 mM with a detection limit of 0.52 μM. The PPy/CuBi₂O₄-NS-modified GCE shows high stability and reproducibility. The prepared PPy/CuBi₂O₄-NSs have great promise in the electrochemical detection of benzoic acid.

For understanding complex reactions in the electrodes of lithium-air batteries (LABs), time-of-flight secondary ion mass spectrometry (ToF-SIMS) is one of the most powerful methods because ToF-SIMS provides molecular information including organic and organic-inorganic complex materials. Although ToF-SIMS has been used to characterize various lithium-ion battery electrodes, low-mass peaks, less than 100 Da, were mainly focused for obtaining the distribution images and depth profiles. Nonetheless, high-mass peaks are important for identifying the products and reactions that cause battery aging. The selection of the mass peaks specific to a particular sample among similar samples, such as a particular electrode and control electrodes, is generally very difficult by manual analysis because the ToF-SIMS spectra contain more than hundreds of mass peaks. This renders the detailed evaluation by TOF-SIMS for improved LABs challenging. Herein, we demonstrate that by applying a sparse autoencoder to the ToF-SIMS data of air electrodes containing a redox mediator that suppressed aging, it was possible to distinguish specific mass peaks corresponding to the electrodes with the redox mediator, initial electrodes before aging, and aged electrodes. The results indicate that the intensity of the mass peaks originating directly from the electrolyte material increases when the residual products on the air electrode are removed by the redox mediator. The analysis presented herein can be utilized to monitor the aging and degradation of these next-generation batteries.

We have developed the method of preparing sodium and potassium ion-selective electrodes in double-barrel glass pipettes at the size of 1 μm. Stable and precise fabrication parameters were found for producing a double-barrel 1 μm pipette, and the produced double-barrel micropipettes were used in this study. The ionophores comprising of crown ethers of 12-crown-4 for sodium ions and 15-crown-5 for potassium ions were respectively doped in poly(vinyl chloride) films in the divided double-barrel glass pipette. The obtained selectivity coefficients and selectivity ratios are compared with the previous studies. The developed ion-selective dual-micropipettes can be applied for local ion-selective measurements such as living cells.

We fabricate α-terthiophene single-molecule junctions (SMJs) and characterize their conductive states by the simultaneous measurements of surface-enhanced Raman scattering (SERS) and electronic conductance. The α-terthiophene SMJ showed broad conductance distribution due to the different portions of the multiple aromatic rings connected to the electrodes. SERS spectra obtained by the simultaneous measurement showed the vibrational energy of the C−C stretching mode depends on the conductance. The Raman spectra calculated by the density-functional theory (DFT) explain the tendency of the vibrational energy shift for typical junction structures. Therefore, the SERS measurement and DFT calculation have revealed that conductance modulation originates from the change in the connecting point of the α-terthiophene SMJ. These findings provide efficient information for building molecule-based circuits and lead to molecule-based potentiometry with aromatic rings.

Real-time X-ray photoemission spectroscopy was used to characterize the SiO₂ surface, and SiO₂/Si interface after irradiating n-Si(001) with a 0.06-eV supersonic O₂ molecular beam. Molecularly-adsorbed O₂ was observed not only during the Si surface oxidation process but also during the SiO₂/Si interface oxidation process, suggesting that trapping-mediated adsorption occurs both at SiO₂/Si interface and on the Si surface. We found an excellent linear correlation between the interface oxidation rate and the amount of molecularly-adsorbed O₂, indicating that at room temperature, the double-step oxidation loop exclusively proceeds through P_b1-paul formation and minority carrier trapping. The offset of the linear correlation indicates the presence of ins-paul on the SiO₂ surface, which has nothing to do with the double-step oxidation loop because point defect generation is not affected by the volume expansion of ins-paul oxidation in the flexible SiO₂ network.

Silicon nanowires (SiNWs) fabricated by metal-assisted chemical etching (MACE) of highly doped silicon are promising thermoelectric materials because of their high conductivity and porosity. However, it is difficult to fabricate long SiNWs using highly doped silicon with doping concentrations higher than 10¹⁹ cm⁻³. In this study, we fabricated SiNWs up to 44 μm in length using highly doped silicon with a doping concentration of 10²⁰ cm⁻³, analyzed the etching characteristics in SiNWs length and the morphology, and investigated the thermal conductivity. The phenomenon of continuous loss of SiNWs was found, which is a unique phenomenon indicating the presence of loss SiNWs throughout the whole etching process and difficulty of forming long SiNWs with highly doped silicon. On the other hand, the thermal conductivity results showed that the lowest thermal conductivity of the samples reached 2.98 W m⁻¹ K⁻¹, and the mean diameters of pores in these samples were 5−10 nm. Thus, the SiNWs using highly doped silicon is a potential material for thermoelectric device.

A surface treatment using atomic hydrogen annealing (AHA) of aluminum oxide (alumina, Al₂O₃) has been investigated. In AHA, high-density atomic hydrogen is generated on a heated tungsten surface by catalytic cracking reaction. Sintered alumina and thermal sprayed alumina coating surfaces were subjected to AHA. The different behavior in the decrement of carbon and OH groups observed by X-ray photoelectron spectroscopy on the surface of AHA-treated sintered alumina and sprayed alumina was assumed to affect the observed different behavior in the changes of water contact angle by AHA. The difference is thought to be attributed to the different crystal structure of alumina. The chemical reactions of atomic hydrogen with carbon contamination, hydroxyl groups, and adsorbed H₂O molecules were also discussed.

The possibility of growing multicomponent epitaxial films of a semiconductor solid solution of molecular substitution (Si₂)_1−y−z(GaP)_y(ZnSe)_z on Si and GaP substrates by liquid-phase epitaxy is shown. The distribution profiles of the atoms of the solid solution components Ga, P, Zn, Se, and Si over the thickness of the epitaxial film have been determined. The current-voltage (I−V) characteristics of p-Si-n-(Si₂)_1−y−z(GaP)_y(ZnSe)_z heterostructures have been studied. A temperature-independent I−V characteristic has been found, the existence of which is explained on the basis of a theory considering the possibility of "blurring" of the impurity level. By comparing the theoretical and experimental results, the half-width of the blurring band for the energy levels of atoms of Si₂ and GaP molecules was determined, which had values equal to 0.146 and 0.34 eV, respectively.

Silver nanoparticles (Ag NPs) can be produced from various approaches including physical, chemical, and biological approaches. However, green synthesis methods are simple, efficient, and eco-friendly methods and provide relatively more stable nanoparticles. In the current investigation, Ag NPs have been synthesized utilizing Citrullus colocynthis fruit extract as a reducing, capping, and stabilizing agent. Then, Ag NPs were characterized through various classification methods to investigate their size, purity, stability, degree of crystallinity, structure, and optical properties. The impact of different parameters including concentration of AgNO₃, pH, and reaction temperature on the biosynthesized Ag NPs and corresponding surface plasmon resonance (SPR) behavior were investigated intensively. This study showed that increasing pH values cause tightening the SPR peaks, and therefore, obtaining monodisperse NPs. On the other hand, increasing the reaction temperature increased the band gap of NPs and, thus, reduced the size of NPs. However, the agglomeration state and later the stability of the biosynthesized Ag NPs are increasing with increasing the AgNO₃ concentration. This investigation, exceptional and unique, confirms that reaction pH, the reaction temperature, and the precursor concentration play important roles in the formation process of NPs. Through selective combination of these trio, one can produce Ag NPs with desired structural, morphological, and optical properties which can be suitable for different applications.

Graphene prepared on an atomically flat Cu(111) surface by chemical vapor deposition (CVD) process was investigated by noncontact atomic force microscopy (NCAFM) and Kelvin probe force microscopy (KPFM) under ultra-high-vacuum (UHV) conditions to exclude extrinsic effects from the atmosphere. Through NCAFM observations, the growth of characteristic layered structures of graphene was recognized. Individual layers were approximately 0.33 nm thick, in agreement with that of graphene. Meanwhile, KPFM measurements revealed that the work function varied with the number of graphene layers on the Cu(111) surface, and the work function for the monolayer was determined to be approximately 4.23 eV. Specifically, the work function obtained from the top layer of stacked graphene sheets increased monotonically depending on the number of stacking layers, reaching 4.8 eV with seven layers, which is similar to that of graphite (4.6 eV). In contrast, characteristic changes in the contrast of the NCAFM image depended on the applied bias voltage between the NCAFM cantilever and observed sample surface, which reflected the two-dimensional features of electronic structures of graphene.

Novel directed motion of an atomic lattice on a substrate with impurity-like disorder is studied using numerical simulations based on an extended Frenkel-Kontorova model. The directed motion of the lattice is caused by the spatiotemporal modulation of natural length between atoms. Even in the presence of surface disorder due to impurities the directed motion occurs when the strength of impurity potential is smaller than a certain value. For strong impurity potential cases, however, the effect of impurities is dominant for the behaviors of the atomic lattice, and then no directed motion occurs. Using a scaling analysis based on a impurity pinning theory, the physical nature of the directed motion of atomic lattices in the disordered interfacial system is clarified.