Circadian adaptation in offshore shift workers returning to day life at home

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Optical properties of ZnO deposited by atomic layer deposition (ALD) on Si nanowires

International audienceIn this work, we report proof-of-concept results on the synthesis of Si core/ ZnO shell nanowires (SiNWs/ZnO) by combining nanosphere lithography (NSL), metal assisted chemical etching (MACE) and atomic layer deposition (ALD). The structural properties of the SiNWs/ZnO nanostructures prepared were investigated by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopies. The X-ray diffraction analysis revealed that all samples have a hexagonal wurtzite structure. The grain sizes are found to be in the range of 7-14 nm. The optical properties of the samples were investigated using reflectance and photoluminescence spectroscopy. The study of photoluminescence (PL) spectra of SiNWs/ZnO samples showed the domination of defect emission bands, pointing to deviations of the stoichiometry of the prepared 3D ZnO nanostructures. Reduction of the PL intensity of the SiNWs/ZnO with the increase of SiNWs etching time was observed, depicting an advanced light scattering with the increase of the nanowire length. These results open up new prospects for the design of electronic and sensing devices

Interaction mechanism between TiO2 nanostructures and bovine leukemia virus proteins in photoluminescence-based immunosensors

In this research a mechanism of interaction between a semiconducting TiO2 layer and bovine leukemia virus protein gp51, applied in the design of photoluminescence-based immunosensors, is proposed and discussed. Protein gp51 was adsorbed on the surface of a nanostructured TiO2 thin film, formed on glass substrates (TiO2/glass). A photoluminescence (PL) peak shift from 517 nm to 499 nm was observed after modification of the TiO2/glass by adsorbed gp51 (gp51/TiO2/glass). After incubation of the gp51/TiO2/ glass in a solution containing anti-gp51, a new structure (anti-gp51/gp51/TiO2/glass) was formed and the PL peak shifted backwards from 499 nm to 516 nm. The above-mentioned PL shifts are attributed to the variations in the self-trapped exciton energy level, which were induced by the changes of electrostatic interaction between the adsorbed gp51 and the negatively charged TiO2 surface. The strength of the electric field affecting the photoluminescence centers, was determined from variations between the PLspectra of TiO2/glass, gp51/TiO2/glass and anti-gp51/gp51/TiO2/glass. The principle of how these electric field variations are induced has been predicted. The highlighted origin of the changes in the photoluminescence spectra of TiO2 after its protein modification reveals an understanding of the interaction mechanism between TiO2 and proteins that is the key issue responsible for biosensor performance

Photoactivation of luminescence in CdS nanocrystals

This paper presents the results of the research on the luminescence of cadmium sulfide nanocrystals (NCs) synthesized by colloid chemistry in a gelatinous matrix. The photostimulation of the short-wavelength emission band with λmax = 480 nm has been detected. It is shown that the determining factor of the photostimulation effect is the adsorption of the water molecules on the surface of NC. The observed effect is explained by the recombination mechanism that is responsible for the short-wavelength emission band

THE AMMONIA VAPORS INFLUENCE ON THE ELECTRICAL CHARACTERISTICS OF NANOSIZED TIN DIOXIDE FILMS OBTAINED USING A POLYMER

In the presented paper the effect of ammonia vapors on the electrical properties of nanosized tin dioxide films obtained using polymers was investigated to assess the possibility of their use as an ammonia sensor’s sensitive element at room temperature. Ammonia vapor leads to a decrease in the conductivity of the studied SnO2 films. This is due to the fact that the adsorbed ammonia molecules increase the height of the intergranular potential barriers, and the surface shut-off bend of the energy bands. The main role in this is played by the processes of physical adsorption of ammonia molecules. The sensitivity of the films to ammonia vapor is in the range of 0.35-0.63 and reaches a maximum at a voltage of 300 V. The processes of adsorption and desorption take place in two stages and are reversible, as evidenced by the calculated time constants of adsorption and desorption.В представленной работе исследовано влияние паров аммиака на электрические свойства наноразмерных пленок диоксида олова, полученных с использованием полимеров, с целью оценки возможности их использования в качестве чувствительного элемента датчика аммиака при комнатной температуре. Пары аммиака приводят к снижению проводимости исследованных пленок SnO2. Это связано с тем, что адсорбированные молекулы аммиака увеличивают высоту межзеренных потенциальных барьеров и поверхностный запирающий изгиб энергетических зон. Основную роль в этом играют процессы физической адсорбции молекул аммиака. Чувствительность пленок к парам аммиака находится в диапазоне 0,35-0,63 и достигает максимума при напряжении 300 В. Процессы адсорбции и десорбции протекают в две стадии и являются обратимыми, о чем свидетельствуют рассчитанные постоянные времени адсорбции и десорбции.У представленій роботі досліджено вплив аміаку на електричні властивості нанорозмірних плівок діоксиду олова, отриманих із використанням полімерів, з метою оцінки їх можливості використання в якості чутливого елемента датчика аміаку при кімнатній температурі. Пари аміаку призводять до зменшення провідності плівок SnO2. Це пов'язано з тим, що адсорбовані молекули аміаку збільшують висоту міжзеренних потенційних бар’єрів та поверхневий вигин енергетичних зон. Основну роль у цьому відтворюють процеси фізичної адсорбції молекули аміаку. Чутливість плівок до пари аміаку знаходиться в діапазоні 0,35-0,63 і досягає максимуму при напрузі 300 В. Процеси адсорбції та десорбції протікають у дві стадії і є зворотними, про що свідчать розраховані сталі часу адсорбції та десорбції

Application of ZnO Nanorods Based Whispering Gallery Mode Resonator in Optical Immunosensors

In this research a whispering gallery mode (WGM) resonator based on vertically oriented ZnO nanorods, which were formed on silicon surface (silicon/ZnO-NRs), has been applied in the design of optical immunosensor that was dedicated for the determination of grapevine virus A-type (GVA) proteins. Vertically oriented ZnO-NRs were grown on silicon substrates by atmospheric pressure metal organic chemical vapor deposition (APMOCVD) and the silicon/ZnO-NRs structures formed were characterized by structural and optical methods. Optical characterization demonstrates that silicon/ZnO-NRs-based structures can act as whispering gallery mode (WGM) resonator where quasi-whispering gallery modes (quasi-WGMs) are generated. These quasi-WGMs were experimentally observed in the visible and infrared ranges of the photoluminescence spectra. In order to design an immuno-sensing system the anti-GVA antibodies were immobilized on the surface of silicon/ZnO-NRs and in this way silicon/ZnO-NRs/anti-GVA structure was formed. The immobilization of anti-GVA antibodies and then the interaction of silicon/ZnO-NRs/anti-GVA structure with GVA proteins (GVA-antigens) resulted in an opposite shifts of the WGMs peaks in the visible range of the photoluminescence spectra observed as a defect-related photoluminescence emission of ZnO-NRs. Here designed silicon/ZnO-NRs/anti-GVA immuno-sensing structure demonstrates the sensitivity towards GVA-antigens in the concentration range of 1-200 ng/ml. Bioanalytical applicability of the silicon/ZnO-NRs-based structures in the WGMs registration mode is discussed.Funding Agencies|Ukrainian-Lithuanian Research project "Application of hybrid nanostructures which are based on TiO2 or ZnO and modified by biomolecules, in optoelectronic sensors" Lithuanian Research Council [P-LU-18-53]; Swedish Research Council (VR) Marie Sklodowska Curie International Grant [2015-00679]; AForsk [14-517]</p

Optical biosensors based on ZnO nanostructures: advantages and perspectives. A review

This review article highlights the application of beneficial physico-chemical properties of ZnO nanostructures for the detection of wide range of biological compounds. As the medical diagnostics require accurate, fast and inexpensive biosensors, the advantages inherent optical methods of detection are considered. The crucial points of the immobilization process, responsible for biosensor performance (biomolecule adsorption, surface properties, surface defects role, surface functionalization etc.) along with the interaction mechanism between biomolecules and ZnO are disclosed. The latest achievements in surface plasmon resonance (SPR), surface enhanced Raman spectroscopy (SERS) and photoluminescence based biosensors along with novel trends in the development of ZnO biosensor platform are presented. (c) 2016 Elsevier B.V. All rights reserved.Funding Agencies|EC [318520]</p