Low-cost fabrication technologies for nanostructures: state-of-the-art and potential.

In the last decade, some low-cost nanofabrication technologies used in several disciplines of nanotechnology have demonstrated promising results in terms of versatility and scalability for producing innovative nanostructures. While conventional nanofabrication technologies such as photolithography are and will be an important part of nanofabrication, some low-cost nanofabrication technologies have demonstrated outstanding capabilities for large-scale production, providing high throughputs with acceptable resolution and broad versatility. Some of these nanotechnological approaches are reviewed in this article, providing information about the fundamentals, limitations and potential future developments towards nanofabrication processes capable of producing a broad range of nanostructures. Furthermore, in many cases, these low-cost nanofabrication approaches can be combined with traditional nanofabrication technologies. This combination is considered a promising way of generating innovative nanostructures suitable for a broad range of applications such as in opto-electronics, nano-electronics, photonics, sensing, biotechnology or medicine.

Evidence of additional excitation energy transfer pathways in the phycobiliprotein antenna system of Acaryochloris marina.

To improve the energy conversion efficiency of solar organic cells, the clue may lie in the development of devices inspired by an efficient light harvesting mechanism of some aquatic photosynthetic microorganisms that are adapted to low light intensity. Consequently, we investigated the pathways of excitation energy transfer (EET) from successive light harvesting pigments to the low energy level inside the phycobiliprotein antenna system of Acaryochloris marina, a cyanobacterium, using a time resolved absorption difference spectroscopy with a resolution time of 200 fs. The objective was to understand the actual biochemical process and pathways that determine the EET mechanism. Anisotropy of the EET pathway was calculated from the absorption change trace in order to determine the contribution of excitonic coupling. The results reveal a new electron energy relaxation pathway of 14 ps inside the phycocyanin component, which runs from phycocyanin to the terminal emitter. The bleaching of the 660 nm band suggests a broader absorption of the terminal emitter between 660 nm and 675 nm. Further, there are trimer depolarization kinetics of 450 fs and 500 fs in high and low ionic strength, respectively, which arise from the relaxation of the ß84 and α84 in adjacent monomers of phycocyanin. Under conditions of low ionic strength buffer solution, the evolution of the kinetic amplitude during the depolarization of the trimer is suggestive of trimer conservation within the phycocyanin hexamer. The anisotropy values were 0.38 and 0.40 in high and in low ionic strength, respectively, indicating that there is no excitonic delocalization in the high energy level of phycocyanin hexamers.

Electron states in a silicon nanowire in the presence of surface potential and field.

In this paper, the energy states of electrons in a silicon nanowire are analytically calculated in the presence of a surface potential and an electric field, as in a nanowire field-effect transistor. The calculations are done for both partial and complete volume inversion and accumulation biasing conditions. Computations are performed for the <100> and <110> orientations of the silicon nanowire. The results show the effects of the surface potential, the electric field and the transverse dimensions of the nanowire on the electron energies and wavefunctions. Depending on the combinations of the surface potential and electric field, the energy level can increase, decrease or remain constant as the thickness of the nanowire increases. It is also observed that higher surface potentials can significantly change the energy states due to the increase of volume inversion/accumulation.

Electrochemical growth of high-aspect ratio nanostructured silver chloride on silver and its application to miniaturized reference electrodes.

The sensitivity of many biological and chemical sensors is critically dependent on the stability of the potential of the reference electrode being used. The stability of a reference electrode's potential is highly influenced by the properties of its surface. In this paper, for the first time, the formation of nanosheets of silver chloride on silver wire is observed and controlled using high anodic constant potential (>0.5 V) and pulsed electrodeposition. The resulting nanostructured morphology substantially improves the electrode's potential stability in comparison with the conventional globular surface structure. The increased stability is attributed to the increase in the surface area of the silver chloride produced by the nanosheet formation.

Finite-Element Modelling of Biotransistors.

Current research efforts in biosensor design attempt to integrate biochemical assays with semiconductor substrates and microfluidic assemblies to realize fully integrated lab-on-chip devices. The DNA biotransistor (BioFET) is an example of such a device. The process of chemical modification of the FET and attachment of linker and probe molecules is a statistical process that can result in variations in the sensed signal between different BioFET cells in an array. In order to quantify these and other variations and assess their importance in the design, complete physical simulation of the device is necessary. Here, we perform a mean-field finite-element modelling of a short channel, two-dimensional BioFET device. We compare the results of this model with one-dimensional calculation results to show important differences, illustrating the importance of the molecular structure, placement and conformation of DNA in determining the output signal.

Case studies of the ischemic foot and management with bypass surgery.

Four case studies are presented to demonstrate the interdisciplinary approach used in management of the ischemic foot. In each case, bypass surgery was used to increase vascularity to the affected limb. This surgical aggressive approach, medical management combined with local wound care, provided a satisfying clinical outcome.

Design and simulated performance of a CARS spectrometer for dynamic temperature measurements using electronic heterodyning.

A new design for generating CARS signals and for the detection and processing of these signals is presented and evaluated. The design is based on electronic heterodyning of the CARS spectrum of nitrogen at two selected narrowband frequencies, ratioing the resulting signal strengths, and comparing this ratio with a theoretically derived temperature scale. A reference cell is incorporated into the design for system calibration and for accurate temperature measurements. The spectrometer is found capable of measuring temperature in the submillisecond time scale with an accuracy of 10% in the 1000-2000 K temperature range. A typical result using the Hg(x)Cd(1-x) Te photomixer for T = 1500 K,DeltaT = 50 K is a SNR of 21 dB and a data collection rate of 300 Hz.