A Compact Surface Plasmonics Polariton Quantum Entanglement Device

Plasmonics - Large-scale quantum integrated circuit requires its basic component at nanoscale beyond the diffraction limit. To obtain nanodimensional quantum operation, we introduce two surface...     

Phenomenon of Quantum Entanglement in a System Composed of Two Minimal Protocells

The quantum mechanical self-assembly of two separate photoactive supramolecular systems with different photosynthetic centers was investigated by means of density functional theory methods. Quantum entangled energy transitions from one subsystem to the other and the assembly of logically controlled artificial minimal protocells were modeled. The systems studied were based on different photoactive sensitizer molecules covalently bonded to a non-canonical oxo-guanine::cytosine supramolecule with the precursor of a fatty acid (pFA) molecule attached via Van der Waals forces, all surrounded by water molecules. The electron correlation interactions responsible for the weak hydrogen and Van der Waals chemical bonds increased due to the addition of polar water solvent molecules. The distances between the separated sensitizer, nucleotide, pFA, and water molecules are comparable to Van der Waals and hydrogen bonding radii. As a result, the overall system becomes compressed, resulting in photo-excited electron tunneling from the sensitizer (bis(4-diphenylamine-2-phenyl)-squarine or 1,4-bis(N,N-dimethylamino)naphthalene) to the pFA molecules. Absorption spectra as well as electron transfer trajectories associated with the different excited states were calculated using time dependent density functional theory methods. The results allow separation of the quantum entangled photosynthetic transitions within the same minimal protocell and with the neighboring minimal protocell. The transferred electron is used to cleave a “waste” organic molecule resulting in the formation of the desired product. A two variable, quantum entangled AND logic gate was proposed, consisting of two input photoactive sensitizer molecules and one output (pFA molecule). It is proposed that a similar process might be applied for the destruction of tumor cancer cells or to yield building blocks in artificial cells.     

Entanglement of Two Quantum Dots with Azimuthal Angle Difference in Plasmonic Waveguide System

We investigate the properties of entanglement between two quantum dots (QDs) with an azimuthal angle difference in two different plasmonic waveguide systems where a cavity coupled to the QDs is included or not. The real space formalism and the concurrence are used in solving the eigenvalue equation and calculating the entanglement, respectively. We analyze the influence of azimuthal angle difference on the entanglement and propose several effective ways to achieve high entanglement by adjusting the detuning, the QD-cavity coupling strength, and so on. Moreover, comparing the entanglement in the two models, we demonstrate that the addition of cavity can improve the entanglement of two QDs.

     

Refractometric Sensing with Silicon Quantum Dots Coupled to a Microsphere

Quantum dots (QDs) coupled to an optical microsphere can be used as fluorescent refractometric sensors. The QD emission couples to the whispering gallery resonances of the microsphere, leading to sharp, periodic maxima in the fluorescence spectrum. Silicon QDs (Si-QDs) are especially attractive fluorophores because of their low toxicity and ease of handling. In this work, a thin layer of Si-QDs was coated onto the surface of a microsphere made by melting the end of a tapered optical fiber. Refractometric sensing experiments were conducted using two methods. First, the sphere was immersed directly into a cuvette containing methanol–water mixtures. Second, the sphere was inserted into a silica capillary and the solutions were pumped through the capillary channel. The latter method enables microfluidic operation, which is otherwise difficult to achieve with a microsphere. In both geometries, high-visibility (V?=?0.83) modes were observed with Q factors up to 1,700. Using standard signal processing methods applied to the whispering gallery mode (WGM) spectrum, sensorgram-type measurements were conducted using single Si-QD-coated microspheres. The WGM resonances shifted as a function of the refractive index of the analyte solution, giving sensitivities ranging from ~30 to 100 nm/refractive index unit (RIU) for different microspheres and a detection limit on the order of 10^?4 RIU.     

Nanocrystal technology, drug delivery and clinical applications

Nanotechnology will affect our lives tremendously over the next decade in very different fields, including medicine and pharmacy. Transfer of materials into the nanodimension changes their physical properties which were used in pharmaceutics to develop a new innovative formulation principle for poorly soluble drugs: the drug nanocrystals. The drug nanocrystals do not belong to the future; the first products are already on the market. The industrially relevant production technologies, pearl milling and high pressure homogenization, are reviewed. The physics behind the drug nanocrystals and changes of their physical properties are discussed. The marketed products are presented and the special physical effects ofnanocrystals explained which are utilized in each market product. Examples of products in the development pipelines (clinical phases) are presented and the benefits for in vivo administration of drug nanocrystals are summarized in an overview.     

Molecular Entanglement and Electrospinnability of Biopolymers

Electrospinning is a fascinating technique to fabricate micro- to nano-scale fibers from a wide variety of materials. For biopolymers, molecular entanglement of the constituent polymers in the spinning dope was found to be an essential prerequisite for successful electrospinning. Rheology is a powerful tool to probe the molecular conformation and interaction of biopolymers. In this report, we demonstrate the protocol for utilizing rheology to evaluate the electrospinnability of two biopolymers, starch and pullulan, from their dimethyl sulfoxide (DMSO)/water dispersions. Well-formed starch and pullulan fibers with average diameters in the submicron to micron range were obtained. Electrospinnability was evaluated by visual and microscopic observation of the fibers formed. By correlating the rheological properties of the dispersions to their electrospinnability, we demonstrate that molecular conformation, molecular entanglement, and shear viscosity all affect electrospinning. Rheology is not only useful in solvent system selection and process optimization, but also in understanding the mechanism of fiber formation on a molecular level.     

Coherent Control of Two-Dimensional Optical Absorption in a Quantum Dot Nanostructure

We investigate the two-dimensional (2D) optical absorption spectrum in a semiconductor quantum dot nanostructure driven by two orthogonal standing-wave lasers. It is found that, due to the position-dependent quantum interference effect, the 2D optical absorption spectrum can be easily controlled via adjusting the system parameters. Thus, our scheme may provide some technological applications in solid-state optoelectronics.     

Control of apple blue mould disease with Torulaspora delbrueckii in combination with Silicon

In this study, Torulaspora delbrueckii alone and in combination with silicon were evaluated for the control of apple blue mould disease caused by Penicillium expansum. In vitro, the antagonistic effects of T. delbrueckii in controlling mycelial growth of P. expansum on potato-dextrose-agar (PDA) in dual cultures, and the growth of P. expansum alone with cell-free metabolites and volatile components of T. delbrueckii were assayed. In vitro, to evaluate the direct effect of silicon on mycelial growth of pathogen, silicon at different concentrations (0.2, 0.4, 0.6, 1 and 2% (wt./vol.)) was added to PDA medium. Silicon at 0.6% (wt./vol.) and above concentrations completely inhibited the mycelial growth of P. expansum. However, it had no significant effect on population dynamics of yeast in vitro and in apple wounds. In vivo, silicon at 0.2 and 1% (wt./vol.) in combination with antagonistic yeast (1 × 10⁸ cell/ml) was a more effective approach to reduce the lesion diameter of blue mould decay of apples than the application of silicon or T. delbrueckii alone at 20 and 4°C, respectively.     

Plasmonic Control of Spontaneous Emission of Quantum Dots in Sub-Wavelength Photonic Templates

Finite difference time domain (FDTD) simulations were performed on two different plasmonic sub-wavelength photonic templates embedded with CdSe quantum dots. Tunable loading of these templates with plasmonic nano antenna allowed control of the emission from the embedded quantum dots. We discuss how large loading of nano antenna can effectively control the optical density of states for the quantum dots leading to enhancement of their radiative decay rates as observed in experiments. On the other hand, at low level of loading, while FDTD fails to capture the observed enhancement of decay rates in experiment, an alternative mechanism is suggested to exist in such cases. Thus, subtle interplay of multiple mechanisms engineered by appropriate placement and loading of plasmonic nano antenna in such templates is demonstrated as an effective method to control optical density of states and hence spontaneous emission of embedded quantum dots.     

Electron Spin Resonance in ATP and RNA

Cu⁺⁺, Mn⁺⁺, and Fe⁺⁺⁺ account for the electron spin resonances observed in certain samples of ATP and RNA. The copper ion seems more loosely bound to these substances than either iron or manganese. A striking similarity is observed between the manganese spectra in manganese RNA, ATP, and ADP suggesting that the binding sites are similar in the three compounds. The similarity of the e.s.r. spectra of iron ATP and of iron and manganese RNA, except for hyperfine spectrum (hfs) in the latter, suggests that the two ions bind similarly in the two compounds. A detailed interpretation of the spectra is lacking however and these conclusions can only be tentative. When manganese TPP and ATP are heated or pH changed the e.s.r. alters indicating a change in the environment of the ion. The sharp 6 line manganese spectrum in both TPP and ATP at pH 1 suggests an almost “free” ion at this pH in the sense of an almost isotropic average environment.     

Spin trapping artifacts in DMSO

Spin-trapping experiments in alkaline aqueous dimethyl sulfoxide (DMSO) solution using sodium 3,5-dibromo-4-nitrosobenzenesulfonate (DBNBS) yielded a strong signal of the sulfur trioxide anion radical adduct. This radical adduct is identical to that obtained by the oxidation of sulfite with horseradish peroxidase/hydrogen peroxide and subsequent spin trapping with DBNBS. This radical adduct is very stable, and satellite peaks of the natural abundance 13C and 33S could be obtained. Apparently, under alkaline conditions DMSO decomposes in air to form the sulfur trioxide anion radical. A comparison with a recent publication shows that this DMSO-derived radical adduct has been misassigned as a uniquely stable spin adduct of superoxide (Ozawa and Hanaki (1986) Biochem. Biophys. Res. Commun. 136, 657-664).     

Dark-Bright Exciton Splitting Dominates Low-Temperature Diffusion in Halide Perovskite Nanocrystal Assemblies

Semiconductor nanocrystals can replace conventional bulk materials completely in displays and light-emitting diodes. Exciton transport dominates over charge carrier transport for materials with high exciton binding energies and long ligands, such as halide perovskite nanocrystal films. Here, how beneficial superlattices – nearly perfect 3D assemblies of nanocrystals - are to exciton transport is investigated. Surprisingly, the high degree of order is not as crucial as the individual nanocrystal size, which strongly influences the splitting of the excitonic manifold into bright and dark states. At very low temperatures, the energetic splitting is larger for the smallest nanocrystals, and dark levels with low oscillator strength effectively trap excitons inside individual nanocrystals, suppressing diffusion. The effect is reversed at elevated temperatures, and the larger nanocrystal size becomes detrimental to exciton transport due to enhanced exciton trapping and dissociation. The results reveal that the nanocrystal size must be strongly accounted for in design strategies of future optoelectronic applications.