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Highly ordered porous anodic alumina (PAA) with interpore distances ( D c ) tunable in the range of 250–400 nm have been fabricated in a two-step anodization. In the first step a modified hard anodization (HA) was developed, which allowed for extension of the maximal anodizing voltage up to 220 V, giving rise to larger pores intervals than usually attained in HA (∼300 nm). The HA process was carried out in 0.3 M ethanol-free (group I) and ethanol-modulated (group II) oxalic acid electrolytes. It was observed that ethanol worsens the hexagonal arrangement of Al concavities and strongly affects the D c performance with respect to applied voltages. The Al nano-concave arrays prepared in the modified HA were subsequently used in the second anodization, performed in 0.1 M phosphoric acid solution. The geometrical features and regularity of Al concavities were directly transferred to porous anodic alumina (PAA). An excellent long-range ordering of pores was achieved when the guidance effect of regular hexagonal Al concaves prepared in ethanol-free electrolyte was reinforced by the self-ordering conditions prevailing in 0.1 M phosphoric acid solution at voltages close to 195 V.

Anodization of AA1050 foil in 0.3 M oxalic acid at 50 V was performed and nanoporous alumina was formed. Four various approaches of electrochemical barrier layer thinning with varied voltage steps were applied to optimize the experimental conditions. Scanning electron microscopy was employed to investigate the bottoms of the anodic alumina after electrochemical barrier layer thinning. Values of the barrier layer thickness derived from Bode plots extrapolations confirmed the FE-SEM observations. For the most suitable barrier layer the thinning procedure was applied to successfully form nickel nanowires via pulse electrodeposition.

Direct, acid (HCl) initiated sol-gel polycondensation of resorcinol with pyrrole-2-carboxaldehyde or its derivative N-methyl-2-pyrrolecarboxaldehyde yields thermosetting phenolic organic gels with N-content of up to 8.4 wt %. After carbonization, sturdy monoliths of N-doped carbon xerogels with N-content of up to 8 wt % are produced. The morphology and porosity of the doped carbons can be tuned by the solvent composition and the amount of polymerization catalyst used. An increase in carbonization temperature from 600 to 1000 °C strongly affects the carbon gels' microporosity, resulting in a decrease in N2 adsorption capacity, but a significant increase in H2 adsorption capacity (at -196 °C). The growing H2 sorption capacity with the decreasing specific surface area (measured by N2) is related to the gradual shrinkage of the carbon xerogel matrix and narrowing of the small micropores. In addition, it is demonstrated that pyridine-based heterocyclic aldehydes, that is, 2- or 4-pyridinecarboxaldehyde, condensate with resorcinol in basic conditions (KOH, NH4OH). However, in this case, monoliths cannot be produced and powders/rigid solid precipitates are obtained instead. If NH4OH is used as a sol-gel polycondensation catalyst, N-doped foams are obtained as a final carbonaceous product.

Technical purity aluminum (AA1050) was subjected to a cold rolling process up to 80% of thickness reduction. So prepared samples were anodized in 0.3 M oxalic acid at the voltage ranging from 20 to 60 V. On one hand, no significant changes in current density, or thickness of the formed oxide were noticed. On the other hand, a cold deformation of aluminum before the self-organized two step anodization caused formation of additional pores, among the hexagonal ones (anodization at 30 V of aluminum rolled to the thickness reduction of 80%). Moreover, cold rolling of aluminum before anodization caused interpore distance decrease (30 V) or increase (50–60 V), with relevant pore density increase and decrease. Additionally, fast Fourier transform based quantitative arrangement analysis revealed that rolling of aluminum prior to the anodization spoils the pore ordering. The results show clearly that substrate also plays an important role in the self-organized anodization.

For several decades the plasmonic behavior of materials has been almost exclusively studied in visible region. Emerging applications require, however, the development of efficient materials operating in UV range. In UV nanoplasmonics aluminum (Al) can play a leading role due to its advantageous electronic properties. Yet, there is still lack of reproducible method to obtain Al nanostructures with desired parameters. Al nanoconcaves can provide a way to overcome these limitations. Here, two different periodicities of the Al nanoconcaves arrays were analyzed. It was observed that the Al concaves can dramatically reduce the optical reflectivity as compared to flat, unstructured Al. At the same time pronounced reflectivity dips were discernible, which were ascribed to (0,1) plasmonic mode. The positions of the dips were at around 250 nm and 350 nm for Al concaves with interpores distance ( D c ) of 246.3 nm and 456.7 nm, respectively. The refractive index sensitivity (RIS) was: ∼191 nm/RIU for the Al concaves with D c = 246.3 nm, and ∼291 nm/RIU for the Al nanoconcaves arrays with D c = 456.7 nm.

UV plasmonics is of particular interest because of large variety of applications, where the higher energy plasmon resonances would advance scientific achievements, including surface-enhanced Raman scattering (SERS) with UV excitation, ultrasensitive label-free detection of important biomolecules absorbing light in the UV, or the possibility for exerting control over photochemical reactions. Despite its potential, UV plasmonics is still in its infancy, mostly due to difficulties in fabrication of reproducible nanostructured materials operating in this high energy range. Here, we present a simple electrochemical method to fabricate regular arrays of aluminum concaves demonstrating plasmonic properties in UV/violet region. The method enables the preparation of concaves with well-controlled geometrical parameters such as interpore distance ( D c ), and therefore, well controllable plasmon resonances. Moreover, the patterning is suitable for large scale production. The UV/violet properties of Al concaves can be further fine-tuned by Ag and Cu metals. The refractive index sensitivity (RIS) increases after the metals deposition as compared to RIS of pure Al nanohole arrays. The highest RIS of 404 nm/RIU was obtained for Cu coated Al nanoconcaves with the D c = 460.8 nm, which is similar or better than the RIS values previously reported for other nanohole arrays, operating in visible/near IR range.

Anodic aluminum oxide was formed in 0,3 M oxalic acid at various content of glycerol (from 0 to 100 vol. %), at voltage range from 20 to 60 V (30 °C, 1 h long steps). Due to the influence of viscosity on the ionic mobility, current density, as well as on the thickness of the grown oxide, current density and thickness of the grown oxide were found to be linear functions of the inversed viscosity. Quantitative FE-SEM images analyses revealed surprising relation: interpore distance increases with the viscosity (logarithmic function). Additionally, pore diameter, porosity and pores density were also influenced by viscosity of the electrolyte. We have found that viscosity of the electrolyte, one of the most important factors in electrochemistry, has significant influence on the anodic alumina formation.

Anodic aluminum oxide has been formed in 0.3 M oxalic acid with various additions of glycerol (0–100% vol. of glycerol) at voltage range from 20 to 60 V at 30 °C. It was found that properties of the electrolytes, as well as the voltage have strong influence on the type of formed oxide (porous, or non-porous barrier type oxide) and its arrangement. Quantitative arrangement analysis of the nanoporous oxide has been performed with the use of fast Fourier transforms of the FE-SEM images. The obtained data were confronted with criterion number estimated from the operating conditions and electrolytes properties. It was found that the best arrangement of the nanopores is when the criterion number is close to the literature data for other, aqueous electrolytes.

C. The resulting nanoporous alumina surfaces were characterized by high resolution scanning electron microscopy, and the images were quantitatively analysed by means of an innovative approach based on fast Fourier transform. The influence of operating anodization voltage and electrolyte temperature on nanopores geometry (pore diameter, interpore distance, porosity, pores density) and arrangement has been studied in details and compared to literature data and theoretical calculations. It was found that independently from the temperature, the best arrangement of the nanopores is for anodic aluminum oxide formed at voltages ranging from 40 to 50 V. Moreover, it was found that pore diameter and interpore distance increase linearly with voltage, what is in line with the literature data. Keywords: nanopores, anodization, self-organization, fast fourier transform.INTRODUCTIONAnodic aluminum oxide (AAO) is a nanostructured material formed with electrochemical oxidation of alu-minum foil. It consists of parallel, hexagonally arranged nanopores

Poorly arranged nanopores focus attention of the researchers due to the many fundamental aspects. Thus, quantitative arrangement analysis of non-ideally arranged pores is demanded. In the paper, radial average fast Fourier transform based arrangement analysis of the nanopores has been reported. This arrangement analysis tool has been applied in the quantification of arrangement of anodic alumina formed in 0.3 M chromic acid at voltage ranging from 20 to 50 V and temperature ranging from 20 to 50 °C. Presented approach, in contrary to typically applied methods, is based on the radial average of the fast Fourier transform (FFT). Averaged regularity ratio, estimated with the use of the reported tool, gives more repeatable results with smaller spread. Thus, reliable dependencies between operating conditions and the averaged regularity ratio can be also obtained for poorly arranged pores. It was found that the greater the voltage and temperature, the better nanopores arrangement.

The research on the development of solid state catalyst is presented. In this study, the catalytic activity and catalytic stability tests of the Ni3Al thin intermetallic foils in methanol decomposition were investigated. The catalytic activity of Ni3Al started above 300 °C, and reached a maximum of methanol conversion (94%) at 500 °C. Carbon deposit formed during the catalytic tests was analyzed in details by SEM, BET, XRD, and Raman spectroscopy. It was found that the carbon deposit consists of well crystallized, curved multi-walled carbon nanotubes, and amorphous carbon, perhaps in the form of nanofibers, without single-walled carbon nanotubes. Despite the presence of various forms of carbon on the Ni3Al surface, the catalyst provides a good catalytic stability: even after 17 h of the reaction, the methanol conversion is 90%. At the ends of the obtained nanotubes/nanofibers one can see Ni nanoparticles. Moreover, it has been proven that the Ni nanoparticles are situated inside the carbon nanofibers/nanotubes, as well. The mechanism of the carbon deposit growth on Ni3Al thin foils was proposed.

The photoluminescence (PL) properties of tin oxide nanostructures are investigated. Three samples of different morphology, induced by deposition process and various geometrical features of nanoporous anodic aluminum oxide (AAO) substrate, are analyzed. X-ray photoelectronic spectroscopy (XPS) analysis reveals the presence of two forms of tin oxide on the surface of all studied samples: SnO and SnO 2 . The former form is typical for reduced surface with bridging oxygen atoms and every other row of in-plane oxygen atoms removed. The oxygen defects give rise to a strong emission in visible region. Two intense PL peaks are observed centered at about 540 (band I) and 620 (band II) nm. The origin of these bands was ascribed to the recombination of electrons from the conduction band (band I) and shallow traps levels (band II) to the surface oxygen vacancy levels. Upon deposition of Au nanoparticles on the top of tin oxide nanostructures the emission at 540 and 620 nm disappears and a new band (band III) occurs in the range >760 nm. The PL mechanism operating in the studied systems is discussed. The tin oxide/Au nanocomposites can be used as efficient multi-band light emitters in a wide (from visible to near infrared) wavelength range.

A simple method of fabrication of anodic aluminum oxide at low voltages (from 5 to 15 V) in 0.3 M oxalic acid is presented. To overcome the issues concerning the anode's burning, a high velocity stirring was applied. It allowed to achieve nanopores with ultra-small diameters (even 12 nm), interpore distance (even 31 nm) and tremendously high pore densities (up to 980 pores per 1 µm 2 ) with simultaneous high porosity (up to 38%). Moreover, the presented approach (no modifier added to the electrolyte) resulted in the AAO with relatively well arranged ultra-small nanopores.

Anodic aluminum oxide (AAO) is typically applied as a template for nanofabrication. It was found that during anodization the anions of electrolytes are being incorporated into the nanopore walls giving rise to an emission in the UV/VIS range. In this paper, incorporation of copper-EDTA chelate ions was studied. The anodization of all studied samples was carried out in 0.02 M CuSO 4 +0.02 M EDTA in 2 wt% sulfuric acid, which has provided suitable conditions for self-organized two-step process of AAO growth. Nanoporous alumina was formed and studied with Scanning Electron Microscopy. Chemical composition analysis of the anodic alumina revealed that the greater the oxide growth rate, the more copper is being incorporated. The photoluminescence studies confirmed the presence of copper in the AAO pore walls.

In this work the quality, arrangement, composition, and regularity of nanoporous AAO formed on the low-purity (AA1050) and high-purity aluminum during two-step anodization in a mixture of sulfuric acid solution (0.3 M), water and glycol (3:2, v/v), at various voltages (15, 20, 25, 30, 35 V) and at temperature of −1 °C, are investigated. The electrochemical conditions have allowed to obtain pores with the size ranging from 30 to 50 nm, which are much larger than those usually obtained by anodization in a pure sulfuric acid solution (

A non-agglomerated submicron-sized titanium carbide powder has been synthesised in a simple combustion process with titanium tetrachloride and hexachloroethane as reactants, and with magnesium as a reducing agent. X-ray analysis of the purified product revealed that only the cubic titanium carbide phase is present. High-resolution transmission electron microscopy showed that TiC particles are coated with low-ordered carbon film on the surface. To remove free carbon, a melting process with calcium metal was used.

Pyrolysis of organic xerogels accompanied by catalytic graphitization and followed by selective-combustion purification was used to produce porous graphitic carbons. Organic gels impregnated with iron(III) chloride or nickel(II) acetate were obtained through polymerization of resorcinol and furfural. During the pyrolysis stage graphitization of the gel matrix occurs, which in turn develops mesoporosity of the obtained carbons. The evolution of the carbon into graphitic structures is strongly dependent on the concentrations of the transition metal. Pyrolysis leads to monoliths of carbon xerogel characterized by substantially enhanced mesoporosity resulting in specific surface areas up to 400 m2/g. Removal of the amorphous carbon by selective-combustion purification reduces the xerogels' mesoporosity, occasionally causing loss of their mechanical strength. The graphitized carbon xerogels were investigated by means of SEM, XRD, Raman scattering, TG–DTA and N2 physisorption. Through this procedure well graphitized carbonaceous materials can be obtained as bulk pieces.

Formation of the nanoporous alumina on the surface of Ni3Al intermetallic alloy has been studied in details and compared with anodization of aluminum. Successful self-organized anodization of this alloy was performed in 0.3 M citric acid at voltages ranging from 2.0 to 12.0 V using a typical two-electrode cell. Current density records revealed different mechanism of the porous oxide growth when compared to the mechanism pertinent for the anodization of aluminum. Electrochemical impedance spectroscopy experiments confirmed the differences in anodic oxide growth. Surface and cross-sections of the Ni3Al intermetallic alloy with anodic oxide were observed with field-emission scanning electron microscope and characterized with appropriate software. Nanoporous oxide growth rate was estimated from cross-sectional FE-SEM images. The lowest growth rate of 0.14 μm/h was found for the anodization at 0 °C and 2.0 V. The highest one – 2.29 μm/h – was noticed for 10.0 V and 30 °C. Pore diameter was ranging from 18.9 nm (2.0 V, 0 °C) to 32.0 nm (12.0 V, 0 °C). Interpore distance of the nanoporous alumina was ranging from 56.6 nm (2.0 V, 0 °C) to 177.9 nm (12.0 V, 30 °C). Pore density (number of pore occupying given area) was decreasing with anodizing voltage increase from 394.5 pores/μm2 (2.0 V, 0 °C) to 94.9 pores/μm2 (12.0 V, 0 °C). All the geometrical features of the anodic alumina formed by two-step self-organized anodization of Ni3Al intermetallic alloy are depending on the operating conditions.

Anodization of Ni3Al alloy is of interest in the field of industrial manufacturing, thanks to the formation of protective oxide layer on the materials working in corrosive environments and high temperatures. However, homogeneous surface treatment is paramount for technological applications of this material. The anodization conditions have to be set outside the ranges of corrosion and burning, which is the electric field enhanced anodic dissolution of the metal. In order to check against occurrence of these events, proper quantitative means for assessing the surface quality have to be developed and established. We approached this task by advanced analysis of scanning electron microscope images of anodized Ni3Al plates. The anodization was carried out in 0.3 M citric acid at two temperatures of 0 and 30°C and at voltages in the range of 2 12 V. Different figures can be used to characterize the quality of the surface, in terms of uniformity. Here, the concept of regularity ratio spread is used for the first time on surfaces of technological interest. Additionally, the Minkowski parameters have been calculated and their meaning is discussed.

We will present details of optical properties of silver nanoparticles in titanium dioxide host (Ag-TiO 2 ) plasmonic absorbers. These nanocomposites were fabricated using electron beam physical vapour deposition technique. Components were deposited sequentially. We varied several parameters of the structures and fabrication process including silver and TiO 2 layer thickness, number of layers, deposition temperature and post fabrication annealing. Utilizing the semicontinuous nature of thin silver films we achieved structures with broadband absorption spanning across visible and near infrared. The level and spectral width of absorption can be tuned by design. Such composites could be used as efficient absorbers in sunlight to heat conversion applications.

The anodization of aluminum in 0.3 M chromic acid is studied. The influence of operating conditions (like anodizing voltage and electrolyte's temperature) on the nanoporous anodic aluminum oxide geometry (including pore diameter, interpore distance, the oxide layer thickness and pores density) is thoroughly investigated. The results revealed typical correlations of the anodic alumina nanopore geometry with operating conditions, such as linear increase of pore diameter and interpore distance with anodizing voltage. The anodic aluminum oxide is characterized by a low pores arrangement, as determined by Fast Fourier transforms analyses of the FE-SEM images, which translates into a high concentration of oxygen vacancies. Moreover, an optimal experimental condition where chromate ions are being successfully incorporated into the anodic alumina walls, have been determined: the higher oxide growth rate the more chromate ions are being trapped. The trapped chromate ions and a high concentration of oxygen vacancies make the anodic aluminum oxide a promising luminescent material.

The anodized alumina oxide (AAO) pattern-transferred Pd nanotubes occluded by Mg nanoparticles were easily manufactured by the use of vacuum evaporation technique at room temperature. The nanostructures were subjected to the H2 absorption at ambient conditions. The material can absorb H2 very fast (the equilibration between the hydrogen gas and within the material at each target pressure occurs in a time shorter than 110 s) reaching approximately 1 wt.% of H2 at only 0.4 kPa of H2 pressure. At 100 kPa the system absorbs up to 2 wt.% of H2 at room temperature. After hydrogenation a drastic change in the structure and morphology of the nanostructures, as an effect of the metal lattice expansion in all three dimensions, was observed which was characterized by the appearance of a regular array of columns with a substantial increase in volume as compared to the nanostructures before hydrogenation. The application of the system in a potential hydrogen sensing device is envisaged.

The influence of different morphology of the thin films deposited on the non-porous glass and nano-porous anodic aluminum oxide (AAO) substrates on the hydrogen absorption at room temperature was studied. A well-known sandwich-like Pd/Mg/Pd film was investigated. It is observed that the film deposited on the porous AAO template demonstrates a better hydrogen absorption in the H 2 pressure range 10–600 mbar with respect to the same film supported by the non-porous glass substrate. Moreover, the layer grown on the AAO, owing to its specific morphology inherited from the nano-porous substrate, has revealed its resistance toward stress accumulation caused by the lattice expansion, showing no buckle-to-crack network formation upon the hydrogen uptake. This interesting feature is expected to improve the cycling properties and structural stability of the system, and may help to investigate better the interaction of the H 2 with metal.

The anti-reflective properties of amorphous silicon (a-Si) films deposited directly on Al nanoconcave arrays with various interpore distances ( D c ) were studied. The Al anodized at 195 V ( D c =456.7 nm) and covered by a 277-nm a-Si layer demonstrated the best light- trapping efficiency. It absorbed up to ~86% of incident light. Average reflectivity under AM1.5 solar spectrum is strongly correlated to height alteration at the a-Si front surface. Further optimization found that D c and film thickness of 450–500 nm and 250–300 nm, respectively, take full advantage of the excellent optical properties of this simple, low cost material suitable for large scale production.

The transverse 1H relaxivities of aqueous colloidal solutions of dextran coated Dy2O3 nanoparticles of different sizes were investigated at magnetic field strengths (B) between 7 and 17.6 T. The particle size with the maximum relaxivity (r2) appears to vary between 70 nm at 7 T (r2 approximately = 190 s(-1) mM(-1)) and 60 nm at 17.6 T (r2 approximately = 675 s(-1) mM(-1)). A small difference between r2 and r2* was observed, which was ascribed to the effect of the dextran coating. The value of r2 is proportional to B2 up to 12 T after which it saturates. Independent magnetization measurements on these particles at room temperature at magnetic field strengths up to 30 T, however, show a typical paramagnetic behavior with a magnetization of the particle that is proportional to the field strength. The saturation in the curve of r2 as a function of B2 was tentatively explained by the presence of an extremely fast relaxing component of the signal at high field strengths, which is not observable on the NMR time scale. The results of this study can be exploited for the rational design of MRI contrast agents, based on lanthanide oxide particles, with high efficiencies at magnetic field strengths of more than 1.5 T.

There is a growing necessity of reducing greenhouse gases emissions to the atmosphere. A renewable energy system based on the use of electricity and hydrogen as energy carriers does not result in harmful pollutants being released to the natural environment. Hydrogen and fuels cells satisfy all requirements for an environmentally friendly vehicle. However, on-board hydrogen storage remains a key problem. It still remains to understand better the mechanisms involved in the interaction of hydrogen with matter. The search of an optimal storage material is a complicated process, were an interplay of many variables need to be considered.

A ternary Mg2COH5 hydride was synthesized using a novel method that relies on a relatively short mechanical milling time (1 h) of a 2:1 MgH2-Co powder mixture followed by sintering at a sufficiently high hydrogen pressure (>85 bar) and heating from RT to 500 degrees C. The ternary hydride forms in less than 2.5 h (including the milling time) with a yield of similar to 90% at similar to 300 degrees C. The mechanisms of formation and decomposition of ternary Mg2COH5 were studied in detail using an in situ synchrotron radiation powder X-ray diffraction (SR-PXD). The obtained experimental results are supported by morphological and microstructural investigations performed using SEM and high-resolution STEM. Additionally, thermal effects occurring during the desorption reaction were studied using DSC. The morphology of as-prepared ternary Mg2COH5 is characterized by the presence of porous particles with various shapes and sizes, which, in fact, are a type of nanocomposite consisting mainly of nanocrystallites with a size of similar to 5 nm. Mg2COH5 decomposes at approximately 300 degrees C to elemental Mg and Co. Additionally, at approximately 400 degrees C, MgCo is formed as precipitates inserted into the Mg Co matrix. During the rehydrogenation of the decomposed residues, prior to the formation of Mg2COH5, MgH2 appears, which confirms its key role in the synthesis of the ternary Mg2COH5. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. (Less)

A series of zeolite-type silicates containing stoichiometric amounts of Ln(3+) ions in the framework (Ln-AV-9 materials), with composition (Na(4)K(2))(Ln(2)Si(16)O(38)).10H(2)O (Ln = Nd, Sm, Eu, Tb, Gd, Dy) has recently been synthesized and characterized. They form paramagnetic microparticles, which as aqueous suspensions have negligible water (1)H longitudinal relaxivities (r(1)) for all Ln(3+) ions studied and quite large transverse relaxivities (r(2)). In this work we further analysed the size distribution of the Ln-AV-9 particles and their r(2)* and r(2) relaxivities. The r(2)* relaxivity effects are explained by the static dephasing regime (SDR) theory. The r(2) relaxivities appear to be strongly dependent on the interval between two consecutive refocusing pulses (tau(CP)) in the train of 180 degrees pulses applied. For long tau(CP) values, the r(2) of the systems saturates at a value, which is always an order of magnitude smaller than r(2)*. These features are explained by a crude model, which takes into account the residual diffusion effect in the static dephasing regime. The large microparticles, although not efficient in T(1) relaxation, are quite effective in enhancing T(2) relaxation, particularly at high magnetic fields. The r(2)* values and the saturation values for r(2) were found to increase linearly with B(0) and mu(0)(2). The largest transversal relaxation rate enhancements were observed for Dy-AV-9 with a saturation value of r(2) of 60 s(-1) mM(-1) and a r(2)* value of 566 s(-1) mM(-1) at 9.4 T and 298 K.

Aqueous suspensions of paramagnetic lanthanide oxide nanoparticles have been studied by NMR relaxometry. The observed R * 2 relaxivities are explained by the static dephasing regime (SDR) theory. The corresponding R 2 relaxivities are considerably smaller and are strongly dependent on the interval between the two refocusing pulses. The experimental data are rationalized by assuming the value of the diffusion correlation time, τ D , to be very long in a layer with adsorbed xanthan on the particle's surface. In this layer, the refocusing pulses are fully effective and R 2 ≈ 0. Outside this layer, the diffusion model for weakly magnetized particles was applied. From the fit of the experimental relaxation data with this model, both the particle radii (r p ) and the radii of the spheres, within which the refocusing pulses are fully effective (r diff ), were estimated. The values of r p obtained are in agreement with those determined by dynamic light scattering. Because the value of r diff depends on the external magnetic field B and on the magnetic moment of the lanthanide of interest (μ eff 2 ), the R 2 relaxivity was found to be proportional to B and to μ eff 2 .

The results of a (1)H nuclear magnetic relaxation dispersion (NMRD) and EPR study on aqueous suspensions of Gd(3+)-loaded NaY nanozeolites and AlTUD-1 mesoporous material are described. Upon increase of the Si/Al ratio from 1.7 to 4.0 in the Gd(3+)-loaded zeolites, the relaxation rate per mM Gd(3+) (r1) at 40 MHz and 25 degrees C increases from 14 to 27 s(-)1 mM(-1). The NMRD and EPR data were fitted with a previously developed two-step model that considers the system as a concentrated aqueous solution of Gd(3+) in the interior of the zeolite that is in exchange with the bulk water outside the zeolite. The results show that the observed increase in relaxivity can mainly be attributed to the residence lifetime of the water protons in the interior of the material, which decreased from 0.3 to 0.2 micros, upon the increase of the Si/Al ratio. This can be explained by the decreased interaction of water with the zeolite walls as a result of the increased hydrophobicity. The importance of the exchange rate of water between the inside and the outside of the material was further demonstrated by the relatively high relaxivity (33 s(-1) mM(-1) at 40 MHz, 25 degrees C) observed for a suspension of the Gd(3+)-loaded mesoporous material AlTUD-1. Unfortunately, Gd(3+) leaches rather easily from that material, but not from the Gd(3+)-loaded NaY zeolites, which may have potential as contrast agents for magnetic resonance imaging.

Luminescent properties of ZnO nanorods covered with Ag nanoparticles are examined. Nanorods were synthesized on AAO templates using Atomic Layer Deposition (ALD) technique. Two types of the samples were prepared with different arrangement of ZnO nanorods and doping conditions. Nanorods of the second type were codoped with Al, to stimulate defect-related emissions. The ZnO material fills heterogeneously the interior of the AAO nanopores and has hexagonal, wurtzite structure. Both types of structures exhibit a broad defect-related emission at about 440 nm, most probably related to recombination at zinc interstitial (Zni) defects. This emission in samples with a random distribution of ZnO:Al nanorods and finer Ag nanoparticles is enhanced by factor of ∼2.5 upon Ag deposition. The so-obtained material is interesting from the point of view of its application in blue range emitting diodes.