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Fiber-optic sensors find numerous applications in science and industry, but their full potential is limited because of the risk of damaging the measurement head, in particular, due to the vulnerability of unprotected tips of the fiber to mechanical damage and aggressive chemical agents. In this paper, we report the first use of a new nanocrystalline diamond structure in a fiber-optic measurement head as a protective coating of the fiber tip. The nanocrystalline sheet structures, produced with the use of Microwave Plasma Assisted Chemical Vapor Deposition System (MW PA CVD), were characterized by Scanning Electron Microscopy (SEM) and successfully transferred from the deposition substrate onto the surface of the tip of a single-mode fiber sensor head. A Fabry-Perot sensing interferometer for distance measurement comprising that fiber was built. The measurement results were compared with numerical modeling. High values of achieved correlation coefficients (R2 > 0.99) between a linear model and distance measurements data indicate that the diamond sheet does not affect the correct operation of the sensor while extending its potential scope of applications.

The intercalation of layered compounds opens up a vast space of new host-guest hybrids, providing new routes for tuning the properties of materials. Here, it is shown that uniform and continuous layers of copper can be intercalated within the van der Waals gap of bulk MoS

Studies of nanoscale superconducting structures have revealed various physical phenomena and led to the development of a wide range of applications. Most of these studies concentrated on one- and two-dimensional structures due to the lack of approaches for creation of fully engineered three-dimensional (3D) nanostructures. Here, we present a ‘bottom-up’ method to create 3D superconducting nanostructures with prescribed multiscale organization using DNA-based self-assembly methods. We assemble 3D DNA superlattices from octahedral DNA frames with incorporated nanoparticles, through connecting frames at their vertices, which result in cubic superlattices with a 48 nm unit cell. The superconductive superlattice is formed by converting a DNA superlattice first into highly-structured 3D silica scaffold, to turn it from a soft and liquid-environment dependent macromolecular construction into a solid structure, following by its coating with superconducting niobium (Nb). Through low-temperature electrical characterization we demonstrate that this process creates 3D arrays of Josephson junctions. This approach may be utilized in development of a variety of applications such as 3D Superconducting Quantum interference Devices (SQUIDs) for measurement of the magnetic field vector, highly sensitive Superconducting Quantum Interference Filters (SQIFs), and parametric amplifiers for quantum information systems., Fabrication of superconducting 3D nanoarchitectures, using standard nanofabrication methods, is challenging. Here, the authors demonstrate the fabrication of a nanostructured 3D superconducting array of Josephson junctions, exploiting self-assembled DNA origami lattices as a template.

The authors want to acknowledge the financial support of the Polish National Science Centre under Grant No. 2017/25/N/ST7/01610, the Polish National Agency for Academic Exchange NAWA under Bilateral exchange of scientists between France and Poland PHC Polonium PPN/BFR/2019/1/00005/U/00001, Polish National Agency for Academic Exchange under Iwanowska Programme PPN/IWA/2018/1/00026/U/00001, Polish National Agency for Academic Exchange under Iwanowska Programme PPN/IWA/2018/1/00058/U/00001, and DS Programs of Faculty of Electronics, Telecommunications and Informatics of Gdańsk University of Technology. KD thanks the UK Engineering and Physical Sciences Research Council for funding (Grant EP/P030017/1). Fiber optic sensors are widely used in environmental, biological and chemical sensing. Due to the demanding environmental conditions in which they can be used, there is a risk of damaging the sensor measurement head placed in the measuring field. Sensors using nanolayers deposited upon the fiber structure are particularly vulnerable to damage. A thin film placed on the surface of the fiber end-face can be prone to mechanical damage or deteriorate due to unwanted chemical reactions with the surrounding agent. In this paper, we investigated a sensor structure formed with a Zinc Oxide (ZnO) coating, deposited by Atomic Layer Deposition (ALD) on the tip of a single-mode fiber. A nanocrystalline diamond sheet (NDS) attached over the ZnO is described. The diamond structure was synthesized in a Microwave Plasma Assisted Chemical Vapor Deposition System. The deposition processes of the nanomaterials, the procedure of attaching NDS to the fiber end-face covered with ZnO, and the results of optical measurements are presented. Publisher PDF

Similarly to other transition metal sulfides, nickel sulfide nanocrystals can be potentially used for functional device applications. However, controlling morphology and stoichiometry to target specific applications is a synthesis challenge. In this work we developed a rapid, one-step, chemical vapor deposition synthesis of nickel sulfide dendritic nanostructures with fractal geometry. Microtome-EDS compositional analysis of the mature crystal indicates a trend of decreasing sulfur and increasing nickel concentration towards the tip of the mature crystals. Following thorough investigation of these nanocrystals at different stages of their nucleation and growth by means of XRD, HR-SEM, HR-TEM, and Raman spectroscopy, we suggest possible kinetic mechanisms for the crystal formation and development. This work contributes to the understanding of growth mechanisms of dendritic structures with complex morphology.

Due to the global problem with plastic contaminating the environment, with bisphenol A (BPA) being one of the highest demand, effective monitoring and purification of the pollutants are required. The electrochemical methods constitute a good solution but, due to polymerization of electrochemical oxidation bisphenol A products and their adsorption to the surfaces, measurement head elements are clogged by the formed film. In this research, we propose a nanocrystalline diamond sheet protection for securing elements in direct contact with bisphenol A during electrochemical processes. The solution was presented on the example of a zinc oxide (ZnO) coating deposited on a fiber-optic end-face by Atomic Layer Deposition. Series of optical and electrochemical measurements were performed in a dedicated hybrid setup. The results show that ZnO can be modified during the electrochemistry leading to the drastic change of its properties. Such degradation did not show in case of nanocrystalline diamond sheet-protected sample proving the solution’s effectiveness, giving a possibility of re-using the measurement element and prolonging its lifespan.

Focused ion beam (FIB) is an extremely valuable tool in nanopatterning and nanofabrication for potentially high-resolution patterning, especially when refers to He ion beam microscopy. The work presented here demonstrates an 'out-of-the-box' method of writing using FIB, which enables creating very large matrices, up to the beam-shift limitation, in short times and with high accuracy unachievable by any other writing technique. The new method allows combining different shapes in nanometric dimensions and high resolutions for wide ranges.

In this paper, we studied the influence of LiAlO2 coatings of 0.5, 1 and 2 nm thickness prepared by Atomic Layer Deposition onto LiNi0.8Co0.15Al0.05O2 electrodes, on their electrochemical behavior at 30 and 60 degrees C. It was demonstrated that upon cycling, 2 nm LiAlO2 coated electrodes displayed similar to 3 times lower capacity fading and lower voltage hysteresis comparing to bare electrodes. We established a correlation among the thickness of the LiAlO2 coating and parameters of the self-discharge processes at 30 and 60 degrees C. Significant results on the elevated temperature cycling and aging of bare and LiAlO2 coated electrodes at 4.3 V were obtained and analyzed for the first time. By analyzing of X-ray diffraction patterns of bare and 2 nm coated LiNi0.8Co0.15Al0.05O2 electrodes after cycling, we concluded that cycled materials preserved their original structure described by R-3m space group and no additional phases were detected. (c) The Author(s) 2017. Published by ECS. All rights reserved.

The intercalation of layered compounds opens up a vast space of new host-guest hybrids, providing new routes for tuning the properties of materials. Here, it is shown that uniform and continuous layers of copper can be intercalated within the van der Waals gap of bulk MoS2 resulting in a unique Cu-MoS2 hybrid. The new Cu-MoS2 hybrid, which remains semiconducting, possesses a unique plasmon resonance at an energy of ≈1eV, giving rise to enhanced optoelectronic activity. Compared with high-performance MoS2 photodetectors, copper-enhanced devices are superior in their spectral response, which extends into the infrared, and also in their total responsivity, which exceeds 104 A W-1 . The Cu-MoS2 hybrids hold promise for supplanting current night-vision technology with compact, advanced multicolor night vision.

The repeatability of the Raman scattering (RS) spectra was analyzed in monolayer and bilayer CVD-grown graphene films. Position and width of the two main RS lines (G-line and 2D-line) together with their intensity ratio I2D/IG were measured in samples where graphene film was supported by a SiO2/Si substrate and where the film was suspended over pits in the substrate. The results are presented as histograms averaged by a Gaussian with the width W, considered as a measure of non-repeatability. Relatively large fluctuations in the I2D/IG value and linewidth were observed upon repeated measurements at the same point both in supported and suspended samples. The RS measurements in crystalline graphite and mechanically exfoliated graphene deposited on hexagonal boron nitride showed higher repeatability which means that increased W in CVD-grown films reflects the sensitivity of RS processes in these films to changes in charge and deformation. In bilayer CVD samples, the values of W are higher due to additional fluctuations in the twist angle between two misoriented layers. The average position of the RS lines is shifted in opposite directions and makes it possible to distinguish between bilayer and monolayer films, despite the similarity in the RS spectra.

Utilizing self-assembled DNA structures in the development of nanoelectronic circuits requires transforming the DNA strands into highly conducting wires. Toward this end, we investigate the use of DNA self-assembled nanowires as templates for the deposition of a superconducting material. Nanowires formed by the deposition of superconducting NbN exhibit thermally activated and quantum phase slips as well as exceptionally large negative magnetoresistance. The latter effect can be utilized to suppress a significant part of the low temperature resistance caused by the quantum phase slips.

We synthesized millimeter-tall, dense carpets of crystalline CNTs on nonpolished copper substrates with a thin Al2O3 (below 10 nm) underlayer and Fe (1.2 nm) layer as a catalyst using chemical vapor deposition (CVD). Preheating of the hydrocarbon precursor gases and in-situ formation of controlled amounts of water vapor were critical process parameters. High-resolution microscopy showed that the CNTs were crystalline with lengths up to a millimeter. Electrical conduction between the CNTs and the copper substrate was demonstrated using multiple methods (probe station, electrodeposition, and hydrolysis of water). Through TEM characterizations of cross sections, we demonstrated that copper diffusion into the alumina layer during the thermal process was the key to explain the observed electrical conductivity. Additionally, the high electrical conductivity of a thermally processed sample compared to the insulating behavior of a pristine sample confirmed the mechanistic hypothesis. Adsorption isotherm measureme...

Here we demonstrate an approach to enhance the growth of vertically aligned carbon nanotubes (CNTs) by including a catalyst reservoir underneath the thin-film alumina catalyst underlayer. This reservoir led to enhanced CNT growth due to the migration of catalytic material from below the underlayer up to the surface through alumina pinholes during processing. This led to the formation of large Fe particles, which in turn influenced the morphology evolution of the catalytic iron surface layer through Ostwald ripening. With inclusion of this catalyst reservoir, we observed CNT growth up to 100% taller than that observed without the catalyst reservoir consistently across a wide range of annealing and growth durations. Imaging studies of catalyst layers both for different annealing times and for different alumina support layer thicknesses demonstrate that the surface exposure of metal from the reservoir leads to an active population of smaller catalyst particles upon annealing as opposed to a bimodal catalyst size distribution that appears without inclusion of a reservoir. Overall, the mechanism for growth enhancement we present here demonstrates a new route to engineering efficient catalyst structures to overcome the limitations of CNT growth processes.

In this work, the kinetics of 15 and 25 nm gold nanoparticle (AuNP) precipitation on silanized SiO 2 /Si surfaces were studied. The NP coverage as well as distribution on the substrates was explored. It was found that at the beginning of the process, the 25 nm AuNPs precipitate faster than their 15 nm counterparts. However, early saturation and low final surface coverage by these NPs were observed. The 15 nm AuNPs, exhibited higher (∼40%) surface coverage and precipitation saturation only after longer treatment times. This makes small NPs a promising candidate for catalyzing the deposition of ultra-thin metallic films on insulating substrates. In addition, it has been demonstrated for the first time that NPs, independently of their size, precipitate with a certain regularity and order. Using high-resolution scanning electron microscopy (HRSEM) it was observed that NPs are organized in pairs, and in each pair they are located at 50–60 nm from each other and under certain angle.

A critical limitation imposed on all imaging systems is to achieve an optimal balance between optical resolution and bandwidth. The optical system determines and affects the relations between temporal information, spatial bandwidth, and resolution, so the resulting signal may differ for each wavelength. This is of significant importance for hyperspectral imaging in particular, because it extracts both spatial and temporal wavelength information. We present a dispersive device that can be used for hyperspectral imaging hypercube image measurements. We utilize the Vernier effect by integrating two silicon slabs that act together as a modified Fabry–Perot filter. The transition between wavelength bands is achieved by heating, utilizing the thermo-optic effect. Importantly, we show that red-shifting with concatenated slabs requires less heating than with a single slab. With the presented technique, a wide effective free spectral range of up to 90 nm around a central wavelength of 1550 nm was achieved along with 20-nm full-width-at-half-maximum resolution. With the same configuration, observing a narrower 0.7-nm free spectral range bandwidth, a fine spectrum resolution of 0.07 nm was obtained. Such variety covers most of the spatial and temporal standard limitations of current hyperspectral imaging requirements.

The light transmission through metallic films with different types of nano-structures was studied both theoretically and experimentally. It is shown that the positions of the surface plasmon resonances depend on nano-structural details. Those can be changed from sample to sample or in given sample by applying an external dc electric or magnetic field. The dependence of transmission spectrum on the shape of holes (inclusions) and external fields can be used for manipulation of the light transmission, as well as the polarization of the transmitted light and other optical properties, by external field. Two complementary situations are considered: a metal film with dielectric holes and a dielectric film with metallic islands. A new analytical asymptotic approach for calculation of the optical properties of such plasmonic systems is developed.

Surface-enhanced Raman spectroscopy (SERS) has been used to characterize three isomeric pyridine compounds adsorbed to silver colloids. The three structural isomers, which all adsorb in the carboxylate form, to the silver colloids, bind in two different geometries to the silver surface. The differences in the binding geometry correlate with Raman resonance shifts and intensity enhancements that can be probed by SERS. For picolinic acid, the ortho isomer, we observed blue shifts of many of the SERS peaks attributed to the pyridine ring in comparison to the normal Raman vibrations of the non-adsorbed crystalline material. For this molecule, steric hindrance between the carboxylate and nitrogen groups causes the pyridine ring and the carboxylate group to tilt from the flat geometry, and hence both groups can form σ bonding to the silver surface. On the other hand, nicotinic and isonicotinic acid, the meta and para isomers (respectively), that have less steric hindrance, adsorb to the silver colloids with the pyridine ring in a flat geometry, where only the carboxylate functional group tilts in order to bind coordinatively to the silver colloids. In this case, π bonding between the pyridine ring and the metal colloids causes small red shifts between the Raman and SERS peaks.

Narrow gated Raman spectroscopy is used to detect Raman signals of explosives, which are usually screened by their intrinsic or background luminescence. It was found that the Raman/luminescence ratio is improved by 2–10 times with gate width of 500 ps compared to the 10 ns gate. It enables in certain cases to combine the luminescence suppression by gating with higher identification ability of Raman signals achievable with green excitation.

Surface-enhanced Raman scattering (SERS) spectroscopy has been used to characterize multilayers of three isomeric aromatic compounds adsorbed on silver nanoclusters. The three structural isomers, all of which adsorb in the carboxylate form onto the silver nanoclusters, bind in two different geometries to the silver surface. Different molecular configurations correlate to differences in bonding strength of these molecules to the silver surface, which can be probed by SERS. For ortho-hydroxybenzoic acid (salicylic acid), we observed red shifts of major SERS peaks in comparison to the normal Raman vibrations of nonadsorbed crystalline material. For this molecule the steric hindrance between the adjacent carboxylate and hydroxyl groups causes the carboxylate group to rotate from the common flat geometry of benzene substituents on surfaces and bond directly through one of the oxygen atoms to the surface. In this case, strong coordinative bonding between the carboxylate group and the metal surface causes the red shifts in the SERS peaks. For para-, and meta-hydroxybenzoic acid, the steric hindrance is less likely since the two functional groups are not at adjacent positions, and therefore these molecules adsorb on the silver surface in a totally flat geometry. For these molecules, in contrast to the ortho isomer, the CO2 interacts with the surface through an extended π bond, and these molecules are physically adsorbed in the common flat position. Therefore, for the meta and para substituents, we do not observe significant red shifts in the SERS spectrum. Copyright © 2009 John Wiley & Sons, Ltd.

Surface enhanced Raman spectroscopy (SERS) has been used to characterize multilayers of three different aromatic compounds in the proximity of silver nanoclusters. SERS of mercapto benzoic acid (MBA), which adsorbs onto the silver nanoclusters through the sulfur moiety, exhibits frequency shifts in comparison to the Raman spectrum of crystalline MBA. Conversely, benzoic acid and benzophenone that adsorb through the oxygen species lack these frequency shifts, and show only a typical SERS enhancement. We employed X-ray photoelectron spectroscopy (XPS), to probe the nature of the binding between the silver and the three different aromatic compounds. Thereafter, we assigned the major Raman peaks of all three molecules to specific molecular vibrations. Overall, this enables us to determine the origin of the observed shifts in the SERS spectrum of MBA and similar molecules.

The Raman cross-section dependence on excitation energy in spectral range 620–248 nm have been investigated for UN, TATP, RDX, TNT, and PETN explosives. For all investigated explosive materials, significant pre-resonance enhancement in the UV spectral range has been revealed. Normalized Raman scattering signals are 100–200 times stronger with UV excitation at 248 nm compared to visible excitation at 532 nm. Thus the gated Raman technique with UV excitation has significant advantages compared to IR–VIS excitation for the remote detection of explosives. Certain of the observed Raman lines exhibit deviations from classical λ −4 dependence of Raman cross-section and may totally disappear with UV excitation. The possible explanation for this may be that numerous electronic transitions contribute to the molecular polarizability. These contributions could be of opposite sign and lead to partial cancellation of certain transitions. Another possible reason could be that this is a result of the stronger UV absorption that reduces the sampling volume and therefore the number of scatterers that produce the Raman signal.

Presented here are measurements at 77 K of I–V curves of reinforced BSCCO tapes in a perpendicular field regime of 0–700 G, and I–V curves of Ricor-made pancakes in self-field. The difference between the I–V characteristics of tapes and pancakes is discussed and explained by traveling across field different I–V curves of the tapes. We estimate the critical current of coils, based on the magnetic field dependence of the critical current in BSCCO tapes. The current distribution in the tape is assumed to be homogeneous, or non-homogeneous distribution opposing the local critical current density resulting from the magnetic field distribution in the tape. Applying our computational methods to the measured pancakes, results in a 90% (homogeneous current distribution) and 98% match (field-dependent current distribution) with the measured pancakes critical current. 2003 Elsevier B.V. All rights reserved.

The light transmission through metallic films with different types of nano-structures was studied both theoretically and experimentally. It is shown, analytically, numerically and experimentally, that the positions of the surface plasmon resonances depend on the nano-structural details. Those can be changed from sample to sample or in given sample by applying an external dc electric or magnetic field. The dependence of transmission spectrum on the shape of holes (inclusions) and external fields can be used for manipulation of the light transmission, as well as the polarization of the transmitted light and other optical properties, by external field. Two complementary situations are considered: a metal film with dielectric holes and a dielectric film with metallic islands. In the case of metallic islands, we propose two ways of controlling plasmon resonance frequency: changing the aspect ratio of the elliptical (or rectangular) islands and changing their mutual distances. For this case a new analytical asymptotic approach for calculating the optical properties of such plasmonic systems is developed. The results of our analytical and numerical studies are in good qualitative agreement with experiment.

The absorption spectrum of a dielectric film with periodic array of metallic islands of different shapes and different mutual distances was studied analytically, numerically, and experimentally. We show that the positions of the surface plasmon resonances depend on the nano-structural details. We propose two ways of controlling plasmon resonance frequency: changing the aspect ratio of the elliptical or rectangular islands and changing their mutual distances. A new analytical asymptotic approach for calculating the optical properties of such plasmonic systems is developed. The results of our analytical and numerical studies are in good qualitative agreement with experiment.

Effects of size, morphology, and composition of gold and silver nanoparticles on surface plasmon resonance (SPR) and surface enhanced Raman spectroscopy (SERS) are studied with the purpose of optimizing SERS substrates. Various gold and silver films made by evaporation and subsequent annealing give different morphologies and compositions of nanoparticles and thus different position of the SPR peak. SERS measurements of 4-mercaptobenzoic acid obtained from these films reveal that the proximity of the SPR peak to the exciting laser wavelength is not the only factor leading to the highest Raman enhancement. Silver nanoparticles evaporated on top of larger gold nanoparticles show higher SERS than gold-silver alloyed nanoparticles, in spite of the fact that the SPR peak of alloyed nanoparticles is narrower and closer to the excitation wavelength. The highest Raman enhancement was obtained for substrates with a two-peak particle size distribution for excitation wavelengths close to the SPR.

The magnetic moment and relaxation rates in Bi2Sr2CaCu2O8+δ crystals exhibit remarkable dependence on the sample size in the vicinity of the vortex order–disorder phase transition line. Specifically, we find that: (1) the magnitude of the normalized magnetic moment increases as the sample size decreases, (2) the relaxation rate increases with the sample size, and (3) the difference between the relaxation rates in samples of different size, decreases with temperature and field. These phenomena are attributed to dynamic coexistence of quasi-ordered and metastable disordered vortex states in the samples, in the temperature and field range near the vortex phase transition.