The paper presents a comparative study of the photoluminescence (PL) and Raman scattering spectra of core-shell CdSe/ZnS quantum dots (QDs) in nonconjugated states and after the conjugation to the anti-human papilloma virus (HPV), HPV 16-E7, antibodies. All optical measurements are performed on the dried droplets of the original solution of nonconjugated and bioconjugated QDs located on the Si substrate. CdSe/ZnS QDs with emission at 655 nm have been used. PL spectra of nonconjugated QDs are characterized by one Gaussian shape PL band related to the exciton emission in the CdSe core. PL spectra of bioconjugated QDs have changed essentially: the core PL band shifts into the high energy spectral range (“blue” sift) and becomes asymmetric. A set of physical reasons has been proposed for the “blue” shift explanation of the core PL band in bioconjugated QDs. The variation of PL spectra versus excitation light intensities has been studied to analyses the exciton emission via excited states in QDs. Finally the PL spectrum transformation for the core emission in bioconjugated QDs has been attributed to the electronic quantum confined effects stimulated by the electric charges of bioconjugated antibodies.

Bio-conjugated CdSe/ZnS core/shell quantum dots (QDs) attract essential scientific interest due to their possible nano-medicine applications, including selective highlighting of affected tissues and targeted drug delivery to the certain type of cells. The paper is focused on the theoretical description of the blue shift observed in the luminescence spectra of CdSe/ZnS QDs upon their bio-conjugation with the anti-interleukin-10 antibodies. We propose a model that describes the ground state of the exciton confined in a quantum dot and explaining the bio-conjugation phenomenon by the change of the effective confinement volume.

Cadmium sulfide nanoparticles were synthesized by a microwave-assisted route in aqueous dispersion. The cadmium sulfide nanoparticles showed an average diameter around 5 nm and a cubic phase corresponding to hawleyite. The aqueous dispersions of the nanoparticles were characterized by UV-Vis spectroscopy, luminescence analysis, transmission electron microscopy and X-ray diffraction. The addition of sodium hydroxide solutions at different concentrations causes a red-shift in the wavelength of the first excitonic absorption peak of the cadmium sulfide nanoparticles, indicating a reduction of the band gap energy. Besides, the intensity of the luminescence of the nanoparticle dispersions was increased. However, there is a threshold concentration of the hydroxide ion above which the precipitation of the cadmium sulfide nanoparticles occurs.

The effect of bio-conjugation of CdSe/ZnS core-shell quantum dots (QDs) with Interleukin 10 (IL-10) antibodies on the aging of photoluminescence (PL) spectra of the QDs was investigated. The aging occurred upon storage of QDs for about 2 years or thermal annealing at 190 oC for up to 12 hours at atmospheric ambience and consisted in “blue” shifting the PL band position, increasing a PL band half-width and decreasing the PL intensity. The bio-conjugation is found to promote PL aging. The aging upon storage is attributed to the oxidation that decreases the QD core dimension, while the aging upon thermal annealing can be due to both oxidation and alloying of CdSe core and ZnS shell.

Colloidal β-In2S3 quantum dots stabilized in water by a number of polymers or sodium polyphosphate and mercaptoacetate were synthesized. An increase in the stabilizer content was found to result in a decrease in the average dot size from 20–30 to 5–10 nm and formation of a narrow absorption band centered at 290 nm. The position and spectral width of the band were found to be independent on stabilizer concentration, synthesis temperature and molar In:S ratio. The band was assumed to belong to a molecular cluster smaller than 1 nm which is a precursor for formation of larger regular indium sulfide quantum dots.

Thermal stability of the luminescent properties of CdSe and CdSe/ZnS quantum dots (QDs) in polymer films of gelatin and polyvinyl alcohol (PVA) is studied. Thermal annealing of the films at the air ambience at 100 °C is found to result in two effects in the photoluminescence (PL) spectra: (i) an enhancement of the PL intensity and (ii) a red spectral shift of the PL bands. The first effect is observed in both QDs-gelatin and QDs-PVA composites, while the second one - in the QDs-gelatin only. The passivation of CdSe QDs with ZnS shell reduces the effects. The enhancement of the PL intensity is supposed to be due to the decrease of nonradiative defect density. The red shift is explained by dissociation of coordination bonds between surface Cd atoms and amino-groups of gelatin. This dissociation decreases the PL intensity too. This effect competes with the effect of PL enhancement and is supposed to be responsible for non-monotonous dependence of the PL intensity versus annealing time in the QDs-gelatin composite.

We systematically study the Cherenkov optical emission by a nonrelativistic modulated source crossing 3D dispersive metamaterial. It is found that the interference of the field produced by the modulated source with the periodic plasmonic-polariton excitations leads to the specific interaction in the frequency range where the dispersive refractive index of a metamaterial is negative. Such resonance considerably modifies the spatial structure of the Cherenkov fieldand the reversed Cherenkov emission. In our study parameters of metamaterial and modulated source are fixed while the frequency spectrum of the plasmonic excitations is formed due to the fields interplay in the frequency domain.

The transmission and reflection properties of a meta-stack composed of a periodic AB arrangement of an air(A)/metamaterial(B) bilayer is presented, with the multi layered system embedded between two semi-infinite layers of the A material. For oblique incidence, a finite projection along the growth direction of the electric or magnetic field of the incident wave associated with the TM or TE modes, respectively, leads to a coupling of the photon modes with the bulk electric or magnetic metamaterial plasmons, in each layer of the meta-stack. This field-matter coupling gives rise to plasmon-polariton modes and signatures of electric or magnetic longitudinal bulk-plasmon polariton modes in the transmission, as well as in the reflection properties of the meta-stack, by means of a plasmon-polariton gap. Such features survive even in the case of a single bilayer and experimental observation should be, therefore, easily achieved.

Magnetic properties at nano-scale provide a whole spectrum of new phenomena that can be beneficial for spintronic devices characterized with ultra-short response time, high sensitivity to magnetic field and miniature size. The properties and stability of a magnetic system can be enhanced by creating ordered arrays of ferromagnetic nano-particles. Here we report a considerable reduction of coercitivity for a magnetic array using triangular, square and hexagonal particle arrangement. The reduction of coercitivity can be explained by fine-tuning of dipole-dipole interaction between magnetic particles, which is to large degree influenced by the number of nearest neighbors and distance between the particles.

Two-photon pumping of excited exciton states in semiconductor quantum wells is a tool for realization of ultra-compact terahertz (THz) lasers based on stimulated optical transition between excited 2p and ground 1s exciton state. We show that the probability of two-photon absorption by a 2p-exciton is strongly dependent on the polarization of both photons. Variation of the threshold power for THz lasing by a factor of 5 is predicted by switching from linear to circular pumping. We calculate the polarization dependence of the THz emission and identify photon polarization configurations for achieving maximum THz photon generation quantum efficiency.

An exhaustive analysis of the frequency-dependent series resistance associated with the on-chip interconnects is presented. This analysis allows the identification of the regions where the resistance curves present different trending due to variations in the current distribution. Furthermore, it is explained the apparent discrepancy of experimental curves with the well-known square-root-of-frequency models for the resistance considering the skin-effect. Measurement results up to 40 GHz show that models involving terms proportional to the square root of frequency are valid provided that the section of the interconnect where the current is flowing is appropriately represented.

In this paper we present an ac-magneto-transport study of a two-dimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime, for frequencies in the range [100Hz, 1MHz]. We present an approach to understand admittance measurements based in the Landauer-Buttiker formalism for QHE edge channels and taking into account the capacitance and the topology of the cables connected to the contacts used in the measurements. Our model predicts an universal behavior with the a-dimensional parameter RHCω where RH is the 2 wires resistance of the 2DEG, C the capacitance cables and the angular frequency, in agreement with experiments. For a specific configuration, we measure the electrochemical capacitance of the quantum Hall edge channels as predicted by Christen and Büttiker.

Papers in the Appendix were published in electronic format as Volume 1534

http://journals.cambridge.org/issue_MRS Online Proceedings Library/OPL1534no-1