Structural and band alignment properties of atomic layer Al₂O₃ oxide film deposited on crystallographically oriented epitaxial Ge grown in-situ on (100), (110), and (111)A GaAs substrates using two separate molecular beam epitaxy chambers were investigated using cross-sectional transmission microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). High-resolution triple axis x-ray measurement demonstrated pseudomorphic and high-quality Ge epitaxial layer on crystallographically oriented GaAs substrates. The cross-sectional TEM exhibited a sharp interface between the Ge epilayer and each orientation of the GaAs substrate as well as the Al₂O₃ film and the Ge epilayer. The extracted valence band offset, ΔE_v, values of Al₂O₃ relative to (100), (110), and (111) Ge orientations using XPS measurement were 3.17 eV, 3.34 eV, and 3.10 eV, respectively. Using XPS data, variations in ΔE_v related to the crystallographic orientation were $\Delta E_V\left(110\right)\text{Ge}>\Delta E_V\left(100\right)\text{Ge}\ge \Delta E_V\left(111\right)\text{Ge}$ and the conduction band offset, ΔE_c, related to the crystallographic orientation was $\Delta E_c\left(111\right)\text{Ge}>\Delta E_c\left(110\right)\text{Ge}>\Delta E_c\left(100\right)\text{Ge}$ using the measured ΔE_v, bandgap of Al₂O₃ in each orientation, and well-known Ge bandgap of 0.67 eV. These band offset parameters are important for future application of Ge-based p- and n-channel metal-oxide field-effect transistor design.

It is one of the most important needs to develop renewable, scalable and multifunctional methods for the fabrication of 3D carbon architectures. Even though a lot of methods have been developed to create porous and mechanically stable 3D scaffolds, the fabrication and control over the synthesis of such architectures still remain a challenge. Here, we used Magnetospirillum magneticum (AMB-1) bacteria as a bio-template to fabricate light-weight 3D solid structure of carbon nanotubes (CNTs) with interconnected porosity. The resulting porous scaffold showed good mechanical stability and large surface area because of the excellent pore interconnection and high porosity. Steered molecular dynamics simulations were used to quantify the interactions between nanotubes and AMB-1 via the cell surface protein MSP-1 and flagellin. The 3D CNTs-AMB1 nanocomposite scaffold is further demonstrated as a potential substrate for electrodes in supercapacitor applications.

Novel approaches to boost quantum dot solar cell (QDSC) efficiencies are in demand. Herein, three strategies are used: (i) a hydrothermally synthesized TiO₂–multiwalled carbon nanotube (MWCNT) composite instead of conventional TiO₂, (ii) a counter electrode (CE) that has not been applied to QDSCs until now, namely, tin sulfide (SnS) nanoparticles (NPs) coated over a conductive carbon (C)-fabric, and (iii) a quasi-solid-state gel electrolyte composed of S²⁻, an inert polymer and TiO₂ nanoparticles as opposed to a polysulfide solution based hole transport layer. MWCNTs by virtue of their high electrical conductivity and suitably positioned Fermi level (below the conduction bands of TiO₂ and PbS) allow fast photogenerated electron injection into the external circuit, and this is confirmed by a higher efficiency of 6.3% achieved for a TiO₂–MWCNT/PbS/ZnS based (champion) cell, compared to the corresponding TiO₂/PbS/ZnS based cell (4.45%). Nanoscale current map analysis of TiO₂ and TiO₂–MWCNTs reveals the presence of narrowly spaced highly conducting domains in the latter, which equips it with an average current carrying capability greater by a few orders of magnitude. Electron transport and recombination resistances are lower and higher respectively for the TiO₂–MWCNT/PbS/ZnS cell relative to the TiO₂/PbS/ZnS cell, thus leading to a high performance cell. The efficacy of SnS/C-fabric as a CE is confirmed from the higher efficiency achieved in cells with this CE compared to the C-fabric based cells. Lower charge transfer and diffusional resistances, slower photovoltage decay, high electrical conductance and lower redox potential impart high catalytic activity to the SnS/C-fabric assembly for sulfide reduction and thus endow the TiO₂–MWCNT/PbS/ZnS cell with a high open circuit voltage (0.9 V) and a large short circuit current density (∼20 mA cm⁻²). This study attempts to unravel how simple strategies can amplify QDSC performances.

It is known that different diseases have characteristic biomarkers that are secreted very early on, even before the symptoms have developed. Before any kind of therapeutic approach can be used, it is necessary that such biomarkers be detected at a minimum concentration in the bodily fluids. Here, we report the fabrication of an interdigitated sensing device integrated with polyvinyl alcohol (PVA) nanofibers and carbon nanotubes (CNT) for the detection of an inflammatory biomarker, C-reactive protein (CRP). The limit of detection (LOD) was achieved in a range of 100 ng mL⁻¹ and 1 fg mL⁻¹ in both phosphate buffered saline (PBS) and human serum (hs). Furthermore, a significant change in the electrochemical impedance from 45% to 70% (hs) and 38% to 60% (PBS) over the loading range of CRP was achieved. The finite element analysis indicates that a non-redox charge transduction at the solid/liquid interface on the electrode surface is responsible for the enhanced sensitivity. Furthermore, the fabricated biosensor consists of a large electro-active surface area, along with better charge transfer characteristics that enabled improved specific binding with CRP. This was determined both experimentally and from the simulated electrochemical impedance of the PVA nanofiber patterned gold electrode.