COSMOS

Metal Nanoparticle Blended Bulk Heterojunction Organic Solar Cells: Performance Enhancement or Degeneration?

Watching atoms and electrons move: freeze-frame snapshots of ultrafast phenomena

Nanoelectronics: High performance nano-switches

Nanomaterials: "Superheated" Water that can Corrode Diamonds

An Emerging New Age in Biological Microscopy

A major goal of molecular biology is to correlate molecular structure with function. Since most enzymes and biological catalysts are proteins, the focus for correlating 'form' with 'function' has been entirely on protein macromolecular structure. It is obvious that any understanding of protein function must come through an understanding protein dynamics. Furthermore, all of the regulatory reactions are through changes in dynamics brought about by post-translational modifications, the most important of which is phosphorylation. This review highlights the important role of covalent phosphorylation and noncovalent phosphates in regulating allosteric effects and function through a study of protein dynamics. Mass spectrometry is a relatively new and increasingly important tool for describing protein dynamics. All examples described in this review have been studied by amide hydrogen/deuterium exchange mass spectrometry.

The high-resolution Fourier transform infrared absorption spectrum of the ν₂ + ν₁₂ combination band of normal ethylene (¹²C₂H₄) in the 3050–3105 cm^-1 region was recorded at a resolution of 0.0063 cm^-1 and at an ambient temperature of 296 K. Upper state rovibrational analysis was carried out using a standard Watson's Hamiltonian in asymmetric reduction in I^r representation. The band center, rotational constants and centrifugal distortion constants up to quartic terms of the upper ν₂ + ν₁₂ = 1 state were determined from the final fit that included 102 infrared transitions. The root-mean-square deviation of the fit was 0.000729 cm^-1.

The usage of chemically-amplified, negative tone SU-8 photoresist is numerous, spanning industrial, scientific and medical fields. Hence, in this study, some preliminary studies were conducted to understand the dosage and heat treatment requirements of the SU-8 photoresist essential for pattern generation using X-ray lithography. In this work, using Synchrotron as the X-ray source, SU-8 photoresist was characterized for X-ray lithography in terms of its process parameters such as X-ray exposure dose, post exposure bake (PEB) time and temperature for various photoresist thicknesses which is considered worthwhile in view of applications of SU-8 for the fabrication of very high aspect ratio micro structures. The process parameters were varied and the resultant cross linking of the molecular chains of the photoresist was accurately monitored using a Fourier Transform Infra-Red (FTIR) spectrometer and the results are discussed. The infrared absorption peak at 914 cm^-1 in the spectrum of the SU-8 photoresist was found to be a useful indicator for the completion of cross linking in the SU-8 photoresist. Results show that the cross linking of the SU-8 photoresist is at a higher rate from 0 J/cm³ to 30 J/cm³ after which the peak almost saturates regardless of the PEB time. It is a good evidence for the validation of dosage requirement of SU-8 photoresist for effective completion of cross linking, which in turn is a requirement for efficient fabrication of micro and nano structures. An analogous behavior was also observed between the extent of cross linking and the PEB time and temperature. The rate of cross linking declines after a certain period of PEB time regardless of PEB temperature. The obtained results also show a definite relation between variation of the absorbance area of the peak at 914 cm^-1 and the X-ray exposure dose.

The mineralogical properties of black nephrite jade from Western Australia are studied by Fourier transform infrared (FTIR) spectroscopy using both transmission and specular reflectance techniques in the 4000–400 cm^-1 wavenumber region. The infrared absorption peaks in the 3700–3600 cm^-1 region which are due to the O–H stretching mode provides a quantitative analysis of the Fe/(Fe+Mg) ratio in the mineral composition of jade samples. The Fe/(Fe+Mg) percentage in black nephrite is found to be higher than that in green nephrite, but comparable to that of actinolite (iron-rich nephrite). This implies that the mineralogy of black nephrite is closer to actinolite than tremolite. The jade is also characterized using Raman spectroscopy in the 1200–200 cm^-1 region. Results from FTIR and Raman spectroscopic data of black nephrite jade are compared with those of green nephrite jade from New Zealand and jadeite jade from Myanmar. Black nephrite appears to have a slightly different chemical composition from green nephrite. Spectra from FTIR and Raman spectroscopic techniques were found to be useful in differentiating black nephrite, green nephrite, and green jadeite jades. Furthermore, data on refractive index, specific gravity, and hardness of black nephrite jade are measured and compared with those of green nephrite and of jadeite jade.

This paper reports the tailoring of acceptor defects in oxygen rich ZnO thin films at different post-deposition annealing temperatures (500–800°C) and Mn doping concentrations. The XRD spectra exhibited the nanocrystalline nature of ZnO thin films along with inconsistent variation in lattice parameters suggesting the temperature-dependent activation of structural defects. Photoluminescence emission spectra revealed the temperature dependent variation in deep level emissions (DLE) with the presence of acceptors as dominating defects. The concentration of native defects was estimated to be increased with temperature while a reverse trend was observed for those with increasing doping concentration. A consistent decrease in DLE spectra, with increasing Mn content, revealed the quenching of structural defects in the optical band gap of ZnO favorable for good quality thin films with enhanced optical transparency.

The way in which biological cells function is of prime importance, and the determination of such knowledge is highly dependent on probes that can extract information from within the cell. Probing deep inside the cell at high resolutions however is not easy: optical microscopy is limited by fundamental diffraction limits, electron microscopy is not able to maintain spatial resolutions inside a whole cell without slicing the cell into thin sections, and many other new and novel high resolution techniques such as atomic force microscopy (AFM) and near field scanning optical microscopy (NSOM) are essentially surface probes. In this paper we show that microscopy using fast ions has the potential to extract information from inside whole cells in a unique way. This novel fast ion probe utilises the unique characteristic of MeV ion beams, which is the ability to pass through a whole cell while maintaining high spatial resolutions.

This paper first addresses the fundamental difference between several types of charged particle probes, more specifically focused beams of electrons and fast ions, as they penetrate organic material. Simulations show that whereas electrons scatter as they penetrate the sample, ions travel in a straight path and therefore maintain spatial resolutions. Also described is a preliminary experiment in which a whole cell is scanned using a low energy (45 keV) helium ion microscope, and the results compared to images obtained using a focused beam of fast (1.2 MeV) helium ions. The results demonstrate the complementarity between imaging using low energy ions, which essentially produce a high resolution image of the cell surface, and high energy ions, which produce an image of the cell interior. The characteristics of the fast ion probe appear to be ideally suited for imaging gold nanoparticles in whole cells. Using scanning transmission ion microscopy (STIM) to image the cell interior, forward scattering transmission ion microscopy (FSTIM) to improve the contrast of the gold nanoparticles, and Rutherford Backscattering Spectrometry (RBS) to determine the depth of the gold nanoparticles in the cell, a 3D visualization of the nanoparticles within the cell can be constructed. Finally a new technique, proton induced fluorescence (PIF), is tested on a cell stained with DAPI, a cell-nucleic acid stain that exhibits a 20-fold increase in fluorescence when binding to DNA. The results indicate that the technique of PIF, although still at an early stage of development, has high potential since there does not seem to be any physical barrier to develop simultaneous structural and fluorescence imaging at sub 10 nm resolutions.