Microwire array for giant magneto-impedance detection of magnetic particles for biosensor prototype

A new giant magneto-impedance (GMI) biosensor prototype based on a glass-coated microwires array is reported. The optimal measurement conditions and the influence of a liquid suspension of commercially available polymer-based magnetic microparticles on the magneto-impedance (MI) response of the array were studied. The relative change in MI response enlarges as the number of the active microwires increases. The highest variation of 35% was found for 10 active microwires, for a current intensity of 10 mA. Some possible applications of the biosensor prototype are outlined.     

Coherent and diffusional motion of a chemisorbed atom

Experiments indicate that there are two extreme types of motion of an atom on a solid surface. One is characterized by an average velocity and has a mean square displacement proportion to the square of the time (we call this coherent). The other (called purely diffusional) is characterized by a diffusion coefficient and has a mean square displacement proportional to time. We present a simple stochastic model to explain the microscopic origin of these two extreme types of motion. In the case in which both types of motion coexist, the motion becomes diffusional for times longer than an intrinsic time depending on the intensity of the thermal fluctuations of the atom—lattice coupling.     

A new geometry for field enhancement in surface-enhanced spectroscopy

We present calculations that indicate that for well-chosen materials a system consisting of a small sphere (diameter ?400 Å) suspended above a planar surface, is a good laser intensity amplifier and an interesting candidate for surface-enhanced spectroscopy. Use of SiC and doped InSb extends the frequency range of surface-enhanced spectroscopy to the infrared (≈200 to ≈1100 cm^?1).     

Preface: special topic section on photochemistry at surfaces

This Special Topic Section on Photochemistry at Surfaces contains invited essays by several leading scientists in the field. These essays present personal perspectives on the field and provide an overview of promising areas for future research on photo-initiated processes at surfaces using advanced experimental techniques. The authors focus on fundamental aspects of the field, which also has significant future applications in photovoltaic solar cells and photocatalytic water splitting.     

Swelling and drug release properties of acrylamide/carboxymethyl cellulose networks formed by gamma irradiation

Hydrogels based on acrylamide monomer (AM) and different ratios (5–20 wt%) of carboxymethyl cellulose (CMC) were synthesized by gamma irradiation. The hydrogels were characterized in terms of gel content, swelling and drug release characters. The effect of temperature and pH on the degree of swelling was also studied. The results showed that the gel fraction of AM/CMC hydrogels decreases greatly with increasing the contents of CMC in the initial feeding solution. The kinetic study showed that the swelling of all the hydrogels tends to reach the equilibrium state after 5 h. However, the swelling of AM/CMC hydrogels was greater than the hydrogel based on pure AM. On the other hand, it was found that the swelling of all the hydrogels changes within the temperature range 30–40 °C and within the pH range 4–8. The AM/CMC hydrogels was evaluated for the possible use in drug delivery systems. In this respect, the release properties of methylene blue indicator, as a drug model, was investigated. It was found that the percentage release from the hydrogels increase with time to reach ～80% after 3 h at pH of 2 compared to ～100% at pH of 8.     

Composite polarizability and the construction of an invariant function of refraction and mass density for solutions

Re-examination of dynamical ionic polarizabilities in water solutions leads to the formulation of a solution function r(c), which combines the indices of refraction and mass densities of solutions. We show that this function should be independent of ionic concentration if the composite polarizabilities of hydrated solute clusters are constant. Using existing experimental data for a number of aqueous salt and organic solutions, we find that the r(c) function is either constant or varies linearly with concentration, in most cases with negligible slope. We use this function to compare ionic polarizabilities of crystals and aqueous solutions and to highlight how solute polarizabilities at infinite dilution scale with the electronic valence shell of cations and anions. The proposed r(c) function can be used generally to verify the consistency of experimental measurements and of simulation results, and it provides a test of assumptions in current theories of ionic polarizabilities.     

Pinning mass-selected Agn clusters on the TiO2(110)-1x1 surface via deposition at high kinetic energy

We present the first scanning tunneling microscopy (STM) study of the deposition of mass-selected silver clusters (Ag(n),n=1, 2, 3) on a rutile TiO(2)(110)-1x1 surface at room temperature under hard-landing conditions. Under hard-landing conditions, only small features are observed on the surface in all cases without sintering or surface damage. This suggests that the high impact energy of the clusters mainly dissipates as thermal energy in the substrate, resulting in the recovery of any initial impact-induced surface damage and the formation of bound clusters on the surface near the impact point. STM images indicate that Ag(1) binds on the bridging oxygen rows twice as often as on the Ti rows. Density-functional Theory (DFT) calculations are consistent with Ag(1) binding at either bridging oxygen vacancies or with two adjacent bridging oxygen atoms in the same bridging oxygen row. STM images of Ag(2) and Ag(3) depositions indicate almost exclusive binding centered on the Ti-atom rows. DFT calculations suggest that the Ag(2) and Ag(3) clusters are bound between two bridging oxygen rows, which is consistent with the STM observations.