This research utilizes anatase TiO2 incorporated with lithium salt via a simple wet physical method to surface-modified the commercial graphite to form the lithium titanate/graphite composite coated with an amorphous carbon layer on its surface (the double core–shell structure) to enhance its surface conductivity. This double core–shell structure provides a stable specific capacity about 280 mAh/g under the high current density, 2.25 A/g with 15% capacity retention decay. Its intercalation potential is below 1 V that is much lower than that of 1.55 V, the intercalation potential of spinel Li4Ti5O12, to make higher power and energy density for a full cell.

Direct electrical measurement of single grain boundaries is performed for ZnO-based multilayer ceramic varistors with fine grains of 2 µm, using a nano-prober. The effect of ZnO grains on non-linearity is shown to be significant. The microstructure is comprised at least two non-linear types as good- and bad-junctions. The numerical ratio of good to bad is estimated to be about one (non-linearity exponent α max ≥ 10) to two (<10), which is independent of microstructural development as grain growth. The grain control of twinning as well as crystal orientation and donor concentration is considered effective in the further improvement.

Lateral memristors consisting of planar Ag electrodes (with sub-micrometer separation) supported on thin films of amorphous zinc-tin-oxide have been characterized. After an initial filament-forming process, each device exhibited volatile, resistive switching. In the low resistance state, the transport mechanism and conductance depended on prior activity and on the imposed current limit, mimicking biologic synaptic plasticity. Microscopic observations performed on each device revealed nanoscale filaments between the electrodes. These filaments were subject to Rayleigh instability and exhibited relaxation times determined by their effective radii. The relaxation times and on:off resistance ratios suggest suitability for threshold switching selector devices.

We investigate the two-photon absorption characteristics of hemicyanine dyes that exhibit a one-photon absorption at around 500 nm. The dyes exhibited two-photon-induced fluorescence upon irradiation with an Yb-doped femtosecond fiber laser operating at 1030 nm. Among the dyes, 4-[4-[4-(dimethylamino)phenyl]-1,3-butadienyl]-1-ethyl-pyridinium perchlorate exhibited the most efficient two-photon-induced fluorescence at 1030 nm. Since these dyes possess cationic moiety, the dyes accumulated in the mitochondria of a living cell. Two-photon images of mitochondria were obtained by staining living HEK293 cells with these dyes. When 4-[4-[4-(dimethylamino)phenyl]-1,3-butadienyl]-1-ethyl-pyridinium perchlorate was employed, a two-photon-induced fluorescence image could be obtained even when a 3 mW fiber laser beam was used as the excitation source.

We present the first characterization of strongly scale-dependent charge transport of a unique, hierarchical complex topology: an interconnected random network of silicon quantum dots (QDs) and nanowires. We show that this specific topology has different charge transport characteristics on the nanoscale and the microscale: photogenerated charge carriers tend to be confined inside the QDs and externally injected charge carriers flow preferably along the nanowires. The former enables expression of quantum confinement properties, and the latter mainly contributes to the good electrical conduction on the microscale. Our findings strongly suggest that this multifunctionality can be controlled and used in photovoltaic device applications.

Oligodepsipeptides (ODPs) with alternating amide and ester bonds prepared by ring-opening polymerization of morpholine-2,5-dione derivatives are promising matrices for drug delivery systems and building blocks for multifunctional biomaterials. Here, we elucidate the behavior of three telechelic ODPs and one multiblock copolymer containing ODP blocks at the air–water interface. Surprisingly, whereas the oligomers and multiblock copolymers crystallize in bulk, no crystallization is observed at the air–water interface. Furthermore, polarization modulation infrared reflection absorption spectroscopy is used to elucidate hydrogen bonding and secondary structures in ODP monolayers. The results will direct the development of the next ODP-based biomaterial generation with tailored properties for highly sophisticated applications.

ZnO-based oxides are promising for thermoelectric energy generation at elevated temperatures. We study electrical transport properties of Ni-doped ZnO applying the density functional theory, indicating increase of the electrical conductivity (σ) and decrease of the Seebeck coefficient (S) due to Ni-doping, in full accordance with experimental results. We calculate the temperature-dependent σ and S applying the Boltzmann transport theory, approximating the electron relaxation time, τe. Good agreement with experimental data is obtained considering both temperature and energy dependence of τe. This yields explicit expressions for τe and provides us with powerful predictive tool assessing electronic transport in ZnO.

A quantitative correlation between R-line luminescence at around 1.37 µm and {311} defect nature, size and concentration has been undertaken in silicon, following keV Si-implantation and subsequent annealing using photoluminescence spectroscopy and plan-view transmission electron microscopy. The formation and evolution of the rod-like defects were found to be dependent on annealing time at a temperature of 700 °C, but there was no simple correlation found between the density and size of those defects and the R-line intensity. In particular, whereas the presence of {311} defects is essential for observing R-line luminescence, both very small {311} defects at short annealing times and fully developed {311} defects at long annealing times do not contribute to such luminescence. We provide possible explanations for this behavior and suggest that the local (strain) environment around defects, the dopant level and impurities in the silicon substrate may all play a role in determining R-line intensity.

Plasma electrolysis (PE) is a combination of electrolysis and plasma discharge. Previous studies indicated that PE usually created porous surface with irregular morphology as a result of the plasma–cathode interaction that was dominated by physical reactions. This paper demonstrated that highly ordered textured silicon surfaces could be created using PE. This abnormal anisotropic etching phenomenon implied that the chemical reactions were decoupled from the physical processes and the physical reactions were suppressed. Raman spectra confirmed that the textured silicon surface created by PE conserved the crystalline structure. Therefore, PE may lead to new process regimes for surface engineering.

Epitaxial Ba2YNbO6 (BYNO) films were deposited on textured NiW substrates via pulsed laser deposition. The films have dense and smooth surface structure, and more importantly, significantly improved out-of-plane texture, compared with the NiW substrate texture. Transmission electron microscopy study confirms the c-axis tilting of BYNO film and formation of misfit dislocations at NiW/BYNO interface, suggesting that the improved texture should be attributed to the tilted epitaxy via biased dislocation mechanism. YBa2Cu3O7−δ films deposited on BYNO single-buffered NiW substrates show further texture improvement, high superconducting transition temperature of ~91 K, and critical current density of 1.8 MA/cm2 at 77 K, self-field.

Solubilizing alkyl chains play a crucial role in the design of semiconducting polymers because they define the materials solubility and processability as well as both the crystallinity and solid-state microstructure. In this paper, we present a scarcely explored design approach by attaching the alkyl side chains on one side (cis-) or on both sides (trans-) of the conjugated backbone. We further investigate the effects of this structural modification on the solid-state properties of the polymers and on the charge-carrier mobilities in organic thin-film transistors.

Perovskite solar cells have evolved significantly since their inception. However, stability is still a major concern. We fabricated devices using a glass/ITO/PEDOT:PSS/MAPbI3/PCBM/Ag device configuration. Devices fabricated using the Pb-acetate precursors showed an efficiency of 13%. This work reports the effect of adding excess lead to the precursor and its impact on the light-induced degradation of efficiency. It is found that 5% excess lead is best for devices regarding the performance and stability and devices retained greater than 50% of the initial efficiency after 2 h of prolonged irradiation. We attribute this phenomenon to the formation of PbI2 which induces passivation in the grain-boundaries.

A bimodal mixture of silver nanoparticles consisting of spheres and triangular nanoplates was synthesized from silver nitrate (AgNO3) and polyvinylpyrrolidone with the aid of a microwave reactor system, reducing total reaction time from days to minutes; a specific shape-directing reagent was not used. It is known that freshly prepared solutions of AgNO3 contain a high population of Ag3+, while aged solutions contain fewer trimers. We propose that the product ratios of spheroidal to triangular particles are proportional to the relative population of trimers in solution prior to initiation of the microwave reaction.

Engineering of thermoelectric materials requires an understanding of thermal conduction by lattice and electronic degrees of freedom. Filled skutterudites denote a large family of materials suitable for thermoelectric applications where reduced lattice thermal conduction attributed to localized low-frequency vibrations (rattling) of filler cations inside large cages of the structure. In this work, a multi-wavelength method of exploiting x-ray dynamical diffraction in single crystals of CeFe4P12 is presented and applied to resolve the atomic amplitudes of vibrations. The results suggest that the vibrational dynamics of the whole filler-cage system is the actual active mechanism behind the optimization of thermoelectric properties.

A novel method for the in situ thermomechanical test of micro/nanoscale samples at high temperature is presented. During the in situ test, the stage is resistively heated while the temperature is measured by a cofabricated temperature sensor. For experimental demonstration of the thermomechanical testing method, we fabricate the Micro-Electro-Mechanical Systems (MEMS) stage using silicon carbide (SiC) and carry out in situ uniaxial tests for single-crystal silicon (SCS) microsamples at temperatures from room temperature to 400 °C. We recover the known elastic modulus of SCS within 1% error in this temperature range.

Temperature-memory technology was utilized to generate flat substrates with a programmable stiffness pattern from cross-linked poly(ethylene-co-vinyl acetate) substrates with cylindrical microstructures. Programmed substrates were obtained by vertical compression at temperatures in the range from 60 to 100 °C and subsequent cooling, whereby a flat substrate was achieved by compression at 72 °C, as documented by scanning electron microscopy and atomic force microscopy (AFM). AFM nanoindentation experiments revealed that all programmed substrates exhibited the targeted stiffness pattern. The presented technology for generating polymeric substrates with programmable stiffness pattern should be attractive for applications such as touchpads, optical storage, or cell instructive substrates.

Research into pyrolysis-based recycling of sheet molding compounds (SMCs) to recover glass fiber for reuse has indicated significant pre-existing tensile strength damage in the shredded recycling input materials. This loss in mechanical durability inherently hurts the value proposition of recycled glass fiber by limiting reuse of the fiber for reinforcement. In this study, the mechanical properties of glass fibers at each step in the first lifecycle of an SMC material are measured to assess the extent of cumulating fiber damage prior to recycling and identify potential causes of this degradation to maximum fiber tensile performance.

A hydrothermal method was developed to synthesize Ag–Pt nanoparticles with controlled surface composition where formaldehyde (HCHO) was utilized as a directing agent. Transmission electron microscopy and powder x-ray diffraction characterizations showed no change in bulk composition and phases as well as the size and morphology of as-made bimetallic nanocrystals. X-ray photoelectron spectroscopy study revealed, however, the enrichment of Pt on the surface as the amount of HCHO used increased. This chemically driven change in surface composition represents a nontraditional approach in the control of synthesis of bimetallic nanoparticle catalysts. A close relationship between catalytic performance and surface composition of these Ag–Pt nanocrystals was observed for electrochemical oxidation of formic acid.

We analyze the effect of functionalization in the surface of zinc oxide crystal structure by 3-mercaptopropionic acid. X-ray powder diffraction data and extended x-ray absorption fine structure studies confirms a wurtzite structure. However, the morphology of the surface seems to be reduced and shows a film-like surface as demonstrated by x-ray absorption near edge structure and scanning electron microscopy. As a result of surface functionalization, the energy levels of the semiconductor were shifted toward reductive potentials (by 50 mV) as determined by diffuse reflectance and cyclic voltammetry.

In the current manuscript we discuss the response of dynamic metallogels that display reversion to the liquid state when exposed to phosphines. The metallogels are formed through the condensation of formaldehyde and poly(alkyloxide)amines in polar aprotic solvents. The gel formation can be catalyzed with trivalent metals (Al(III and Fe(III)) with concomitant enhanced dynamism (gelation/degelation). When various phosphines are introduced, the metallogel is irreversibly liquefied. This process adds a new vector for controlling the bulk properties of this class of materials. Here, we explore the mechanism in detail for the reaction of tris(carboxyethyl)phosphine with N,N,N-triethoxylethyl-1,3,5-hexahydro-1,3,5-triazine (HEHT, 1) a stable derivative of the active hexahydrotriazine (HT) core in dimethylformamide in the presence or absence of Al(III). Additionally, density functional theory is used on the model N,N,N-trimethyl system (MHT, 2) to estimate reaction parameters and predict nuclear magnetic resonance spectra.