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Micro- and nanoscale corrosion and etching at are important in several fields, from the fabrication of sensors and membranes to investigations of the properties of micro- and nanocomposites [...]

The mid-infrared region (MIR) is crucial for many applications in security and industry, in chemical and biomolecular sensing, since it contains strong characteristic vibrational transitions of many important molecules and gases (e.g. CO2, CH4, CO). Despite its great potential, the optical systems operating in this spectral domain are still under development. The situation is caused mainly by the lack of inexpensive and adequate optical materials which show no absorption in the MIR. In this work, we present an easy and affordable way to develop 1D photonic crystals (PCs) based on porous anodic alumina for MIR region. The porous PCs were produced by the pulse anodization of aluminum using charge-controlled mode. The first order photonic stopbands (λ 1) were located within ca. 3.5–6.5 μm. Annealing of the material at 1100 °C for an hour has allowed to recover the wavelength range from around 5.8 to 7.5 μm owing to the decomposition of the absorption centers (oxalate anions) present in the anodic oxide framework while maintaining the PC structural stability. The spectral position and the shape of the resonances were regulated by the charge passing under high (U H) and low (U L) voltage pulses, porosity of the corresponding d H and d L segments, and dura tion of the process (t tot). The thickness of the d H and d L layers was proportional to the charge passing under respective pulses, with the proportionality coefficient increasing with the applied voltage. Despite the constant charge (2500 mC cm−2) applied during the anodization, the thickness of anodic alumina (d) increased with applied voltage (10–60 V) and anodizing temperature (5 °C–30 °C). This behavior was ascribed to the different kinetics of the anodic alumina formation prompted by the variable electrochemical conditions. The photonic material can be used in portable nondispersive gas sensors as an enhancement layer operating up to around 9 μm.

The production of self-organized porous anodic alumina (PAA) with large intepore intervals (D c > 380 nm) is still under development. The PAA is very interesting for application in optics and photonics where a large-scale periodicity corresponding to visible or infrared light is required. However, the process remains challenging because it usually involves anodization under high voltages that is prone to instabilities and breakdown events. The basic problem relies on harnessing the electrochemical conditions to find a balance between various phenomena that occur during transformation from aluminum to porous alumina. The overall process is quite complicated but it is believed that regularity of pore formation is governed mainly by an equilibrated counter-ion (Al3+ and electrolyte anions A−) exchange at the electrolyte/oxide interface. Accordingly, a new concept of PAA growth is proposed which takes into account three basic elements of field-enhanced dissolution, plastic flow, and electro-convective models. The results on recent achievements in the high-voltage anodization is discussed focusing on the strategies that led to the self-ordering growth of PAA with large D c . It is hoped that the review will contribute to better designing of anodization parameters to produce the ordered porous material with desired morphology.

The influence of arsenazo-I additive on electrochemical anodizing of pure aluminum foil in malonic acid was studied. Aluminum dissolution increased with increasing arsenazo-I concentration. The addition of arsenazo-I also led to an increase in the volume expansion factor up to 2.3 due to the incorporation of organic compounds and an increased number of hydroxyl groups in the porous aluminum oxide film. At a current density of 15 mA·cm−2 and an arsenazo-I concentration 3.5 g·L−1, the carbon content in the anodic alumina of 49 at. % was achieved. An increase in the current density and concentration of arsenazo-I caused the formation of an arsenic-containing compound with the formula Na1,5Al2(OH)4,5(AsO4)3·7H2O in the porous aluminum oxide film phase. These film modifications cause a higher number of defects and, thus, increase the ionic conductivity, leading to a reduced electric field in galvanostatic anodizing tests. A self-adjusting growth mechanism, which leads to a higher degree of self-ordering in the arsenazo-free electrolyte, is not operative under the same conditions when arsenazo-I is added. Instead, a dielectric breakdown mechanism was observed, which caused the disordered porous aluminum oxide film structure.

A robust and reliable method for fabricating porous anodic alumina (PAA)-based distributed Bragg reflectors (DBRs), operating in mid-infrared (MIR) spectral region, is presented. The method relies on application of high (UH) and low (UL) voltage pulse sequence repeated in cycles. PAA-based DBR consists of alternating high-(dH) and low-porosity (dL) layers translated directly into periodically varied refractive index. Two anodization modes were used: time- and charge density-controlled mode. The former generated dH + dL pairs with non-uniform thickness (∆d) and effective refractive index (∆neff). It is supposed, that owing to a compensation effect between the ∆d and ∆neff, the photonic stopbands (PSBs) were symmetrical and intensive (transmittance close to zero). Under the charge density-controlled mode dH + dL pairs of uniform thickness were formed. However, the remaining ∆neff provided an asymmetrical broadening of PSBs. Furthermore, it is demonstrated that the spectral position of the PSBs can be precisely tuned in the 3500–5500 nm range by changing duration of voltage pulses, the amount of charge passing under subsequent UH and UL pulses, and by pore broadening after the electrochemical synthesis. The material can be considered to be used as one-dimensional transparent photonic crystal heat mirrors for solar thermal applications.

Zinc oxide (ZnO) has been regarded as one of the most promising candidate for efficient UV light emitted devices owing to its unique optical properties, such as direct wide band-gap and a large exciton binding energy. In many optoelectronical applications, reducing the size of the semiconductor down to nanometer scale is necessary. However, in ZnO nanostructures the UV emission can be drastically weakened owing to high surface-to-volume ratio, crystal imperfections, or unintentional defects. These factors induce competitive processes to the near-band-edge (NBE) excitonic recombination in the UV region, including defect-related radiative recombination, resulted in the emission in the visible part of the spectrum, or other quenching processes, resulted in dissipation of excitation energy in the form of non-radiative recombination. Therefore, for future applications a strategy is needed to limit the quenching processes and to optimize the NBE emission of the ZnO nanomaterials. In this review article, the most effective approaches to achieve this goal are summarized and discussed.

Surface-enhanced Raman spectroscopy (SERS) is a very promising analytical technique for the detection and identification of trace amounts of analytes. Among the many substrates used in SERS of great interest are nanostructures fabricated using physical methods, such as semicontinuous metal films obtained via electron beam physical vapor deposition. In these studies, we investigate the influence of morphology of semicontinuous silver films on their SERS properties. The morphologies studied ranged from isolated particles through percolated films to almost continuous films. We found that films below the percolation threshold (transition from dielectric-like to metal-like) made of isolated silver structures provided the largest SERS enhancement of 4-aminothiophenol (4-ATP) analyte signals. The substrate closest to the percolation threshold has the SERS signal about four times lower than the highest signal sample.

Electropolished copper foil was passivated in aqueous solution of 1.0 M NaOH at negative potential range vs. silver chloride electrode at room temperature. The passivations were performed at −50, −100, −150, and −200 mV for 1, 5 or 15 h. The resulting nano-needle layers were characterized by X-ray photoelectron spectroscopy and band gaps derived from UV–Vis spectroscopy evidencing coincidence of Cu(OH)2, CuO and Cu2O phases. Scanning Electron Microscopy revealed that the diameter of nanoneedles was not influenced by the passivation potential, however, the nanoneedles diameter was decreasing with extension of the passivation time (the smallest diameter obtained was 60 ± 17 nm). Additionally, the as-prepared oxide nano-needles were found to be polycrystalline, without any post treatments. All together, chemical compositionand physical properties (band gap) show that the inner part of the grown nano-needles is rather made of Cu2O, while outer part, there where the passivation reaction takes place, is made of CuO and Cu(OH)2.

Carbide-derived carbons (CDCs) are synthesized from TiC micropowder via gas phase bromination at the temperature range of 350–1150 °C. The resultant carbon materials demonstrate high specific surface areas and micropore volumes of up to 1745 m2 g−1 and 0.64 cm3 g−1 respectively. Successful bromination of TiC in a wide temperature range permitted the first in-depth comparative study of CDCs produced by Br2 and Cl2 thermochemical extraction. Although minor, some structural differences between TiC-CDCs obtained via bromination and chlorination reactions are observed. It is concluded that it is not the size of halogen and evolving titanium halide molecules but the reactivity of the halogen that affects the microporosity of TiC-CDCs. The structural similarity of materials obtained via Br2 and Cl2 extraction proves that the extractive step does not determine the final structure of CDCs. Cryogenic high-pressure hydrogen storage studies show that the maximum excess hydrogen uptake of TiC-CDCs strongly correlates to the volume of micropores below 1.75 nm in size.

A multi-variant process of cold rolling to different reductions of thickness (0–50%) and subsequent heating under different temperature was applied to Al substrates. Next, a comprehensive analysis of the influence of various microstructural, structural, and mechanical parameters of the Al substrates on the nanopore growth in anodic aluminum oxide (AAO), was performed. As an effect, new evidences concerning an important role of Al substrate state on the AAO growth were provided. The obtained results unambiguously show that the number of dislocations is the only parameter responsible for the regular pore formation is the AAO. Since the dislocation density is greatly reduced solely after recrystallization process, a significant reduction of the percentage of defects in AAO occurs only when Al substrate is annealed at the recrystallization temperature (483 °C), independent of percent cold work. All microstructural (elongation, circularity, and size of grains) or structural (texture, lattice strain) parameters are irrelevant for the pore formation, until the number of dislocations in the Al substrate remains high. Therefore, before anodization Al substrate should be annealed, at least for 1 h, under the temperature ≥ recrystallization temperature, not lower. Stress-relief anneal at temperature

Porous anodic alumina (PAA) photonic crystals with a photonic stop-band (PSB) placed in the mid-infrared (MIR) spectral region represent a promising approach for increasing of gas sensors sensitivity. An onion-like layered distribution of anionic impurities is a hallmark of PAA, and its presence is generally considered to demarcate the boundary between transparent and opaque ranges in the infrared spectral region. Here, we study the effect of annealing in the temperature range of 450 °C–1 100 °C on the structural stability and optical properties in photonic crystals based on PAA fabricated by pulse anodization in oxalic acid. Pulse sequences were selected in a way to obtain photonic crystals of different periodic structures with a PSB located in visible and MIR spectral regions. The first photonic crystal was composed of layers with gradually changing porosity, whereas the second photonic crystal consisted of a sequentially repeated double-layer unit with an abrupt change in porosity. We investigated the response of alumina with rationally designed porosities and different arrangements of porous layers for high-temperature treatment. The microstructure (scanning electron microscopy), phase composition (x-ray diffraction), and optical properties (optical spectroscopy) were analysed to track possible changes after annealing. Both photonic crystals demonstrated an excellent structural stability after 24 h annealing up to 950 °C. At the same time, the evaporation of the anionic impurities from PAA walls caused a shift of the PSB towards the shorter wavelengths. Furthermore, the annealing at 1 100 °C induced a high transparency (up to 90%) of alumina in MIR spectral region. It was shown thus that properly selected electrochemical and annealing conditions enable the fabrication of porous photonic crystals with the high transparency spanning the spectral range up to around 10 μm.

The outstanding properties of carbon materials doped with p-block elements are usually attributed directly to the presence of certain foreign atoms. By using the example of selenium-doped carbon gels, we hereby postulate that in many cases the properties of doped carbon materials are not determined by the presence of the heteroatom itself, but rather by how the element affects the carbon structure during high-temperature synthesis. Se-doped microporous carbogels were obtained via sol-gel polycondensation of resorcinol and 2-formylselenophene followed by pyrolysis at 600–1200 °C. Pyrolysis temperatures above 800 °C result in a decrease in the Se-content accompanied by a distinct increase in ultramicroporosity. A comparative analysis of oxygen-, sulfur- and selenium-doped carbogels shows that chalcogens increase the porosity of carbonaceous materials via the high-temperature oxidation of carbon to corresponding dichalcogenides (CO2, CS2 or CSe2), but their oxidative power diminishes with increasing atomic mass. Consequently, S and Se are more selective carbon oxidants.

In this work, the influence of a wide range anodizing temperature (5&ndash, 30 &deg, C) on the growth and optical properties of PAA-based distributed Bragg reflector (DBR) was studied. It was demonstrated that above 10 &deg, C both structural and photonic properties of the DBRs strongly deteriorates: the photonic stop bands (PSBs) decay, broaden, and split, which is accompanied by the red shift of the PSBs. However, at 30 &deg, C, new bands in transmission spectra appear including one strong and symmetric peak in the mid-infrared (MIR) spectral region. The PSB in the MIR region is further improved by a small modification of the pulse sequence which smoothen and sharpen the interfaces between consecutive low and high refractive index layers. This is a first report on PAA-based DBR with a good quality PSB in MIR. Moreover, it was shown that in designing good quality DBRs a steady current recovery after subsequent application of high potential (UH) pulses is more important than large contrast between low and high potential pulses (UH-UL contrast). Smaller UH-UL contrast helps to better control the current evolution during pulse anodization. Furthermore, the lower PSB intensity owing to the smaller UH-UL contrast can be partially compensated by the higher anodizing temperature.

A synergistic effect of surface plasmons (SPs) and surface passivation on ZnO thin film optical performance was studied. The ZnO thin film of thickness of ca. 40 nm was deposited on Al concave arrays with a period (Dc) of about 125, 252, and 340 nm. Next, the Al2O3 coating thickness was tested with respect to UV light enhancement. About 20-fold enhancement of the UV emission was achieved upon simultaneous application of Al concave array with Dc ≈ 340 nm and 10 nm thick Al2O3 coating. Moreover, it was found that the Al concave array with Dc of ca. 125 nm does not sustain the SP resonance in UV region.

Self-aligned and equal-space SnO2 nanotubes (NTs) with external diameters ranging from ca. 124 to ca. 325 nm and wall thickness of around 30 nm were synthesized by AAO template-assisted atomic layer deposition. The bulk and surface structure of the SnO2 nanostructures were studied in detail by XRD and XPS techniques, respectively. The SnO2 NTs were polycrystalline with an average crystallite size of ca. 3 nm. The structure analysis has revealed that the SnO2 NTs are composed of the rutile-type SnO2. The SnO2 nanotube arrays with the smaller external diameters emitted green light centered at around 520 nm. The emission was ascribed to the radiative recombination between electrons trapped in shallow donor levels and holes at the intrinsic surface states, associated with the oxygen deficient sites near surface region. The PL intensity diminished with the nanotube diameter and spacing. With increasing external diameter of the SnO2 nanotubes and decreasing the distance between the neighboring nanotubes, the emission become progressively weaker. The results demonstrate that the structure, morphology and arrangement of SnO2 nanotubes play an important role in their luminescent properties.

A range of heteroatom-doped carbon gels was studied to identify factors determining the efficiency of oxidative and adsorptive degradation/removal of phenolic compounds from aqueous solutions. Carbon xerogels were obtained via pyrolysis of resorcinol-heterocyclic aldehyde thermosetting resins. By utilizing either nitrogen-, sulfur- or oxygen-bearing heterocycles and impregnating the resins with FeCl3, carbons doped with the selected heteroatoms (N, S, O) and Fe could be obtained. This synthetic approach allows precise control of the doped element(s) amount and type. The efficiency of the chlorophenol removal process was correlated with the texture of the obtained carbon gels (for adsorptive removal), the pH of an aqueous solution and the H2O2 concentration (for oxidative degradation). The coexistence of iron and nitrogen within porous carbons enhances their catalytic properties towards oxidative decomposition of organic compounds via H2O2 activation, while the adsorption capacity for chlorophenols is directly correlated with microporosity and specific surface area values. The extensive mesoporosity and graphitic structure of the Fe and N co doped carbons result in efficient oxidative decomposition of the model organic pollutants. Sulfur doping prevented Fe-assisted graphitization during pyrolysis yielding disordered and highly microporous S and Fe co doped materials. The extent of oxidative degradation of chlorophenols decreased with an increasing number of Cl atoms in the phenolic ring. This report shows that Fe and N co doped carbons (the so-called Fe N C pyrolyzed materials) are more active heterogeneous catalysts for oxidative (chloro)phenol degradation than their nitrogen- and/or iron-free counterparts, showing the importance of simultaneous coexistence of both elements (Fe and N) in the carbon scaffold.

In this work, highly ordered porous anodic alumina (PAA) with tapered pore structure and interpore distance (Dc) in the range of 550 nm to 650 nm were fabricated. To produce hexagonal close-packed pore structure a two-step process, combining anodization in etidronic acid electrolyte in the first step and high-concentration, high-temperature anodization in citric acid electrolyte in the second step, was applied. The Al pre-patterned surface obtained in the first anodization was used to produce regular tapered pore arrays by subsequent and alternating anodization in 20 wt.% citric acid solution and pore wall etching in 10 wt.% phosphoric acid solution. The height of the tapered pores was ranging between 2.5 μm and 8.0 μm for the PAA with Dc= 550 nm and Dc= 650 nm, respectively. The geometry of the obtained graded structure can be used for a production of efficient antireflective coatings operating in IR spectral region.

(Co)polycondensation of resorcinol and heterocyclic aldehydes yields heteroaromatic porous polymers. Carbonization of such polymers results in N-doped, S-doped, N/S-co-doped or undoped carbon gels depending on the starting composition of reactants. If the (co)polycondensation is initiated with FeCl3, Fe-containing carbon gels are obtained. Depending on the nature of the heteroatom doping (solely N or S, both N and S or no heteroatom) the Fe-containing carbon gels exhibit distinct structural properties. While the presence of sulfur hinders Fe-driven graphitization, yielding carbons with high specific surface area (SSA), N-doping exhibits the contrary effect, resulting in highly graphitic structures with low SSAs. More importantly, increasing the Fe content in the N/S-co-doped carbons results in remarkable increases in microporosity, yielding materials with SSA of up to 1240 m2g-1. The Fe-containing carbon gels are considered non-precious metal catalysts for the oxygen reduction reaction. It is demonstrated that in the case of Fe/N/C/S type catalysts, the interaction between S, C and Fe (at the pyrolysis stage) results in the enhancement of microporosity, where S acts as a soft oxidant toward carbon, while Fe recaptures the sulfur- and carbon-containing pyrolytic gases. The incidental deposition of pyrolytic gases contributes significantly to the final structure of the catalysts.

Self-aligned and equal-spaced zinc oxide (ZnO) nanotube arrays were fabricated with anodic aluminum oxide (AAO)-assisted growth and the ALD technique. The near band-edge (NBE) emission was strongly affected by the nanotube's geometrical parameters, such as a packing density and thickness of the nanotube walls. The NBE emission was further enhanced with Al2O3 coating. The effect was analyzed by X-ray photoelectron spectroscopy (XPS) and ascribed to the surface defect passivation and a ZnAl2O4 spinel formation. The NBE emission enhancement was greater in ZnO nanotubes with thicker walls. A smaller UV enhancement factor was explained by less uniform and integral Al2O3 coverage of the ZnO nanotubes with thinner walls; this, possibly induced a variation of the Al2O3 refractive index along the nanotubes. As a result, the optical conditions at the ZnO/Al2O3/air interfaces was changed and the light extraction efficiency was reduced in the latter samples.

Highly ordered, conical-pore anodic alumina (AAO) membranes with interpore distance (D c ) between ca. 530 and 620 nm and thickness ranging between 2.4 and 7.8 μm, were produced. In the fabrication process aluminum surface was first pre-patterned by the anodization in etidronic acid solution. Then, the regular arrays of Al concaves were used as nucleation sites to grow AAO during the second anodization, which was carried out in highly concentrated citric acid solution (20 wt%) and at relatively high temperature (33–35 °C). The conical pore shape was engineered by a multistep process combining anodization in the citric acid electrolyte and the subsequent chemical pore broadening in phosphoric acid solution. The morphological analyses has revealed that the geometrical parameters of the Al concaves were successfully transferred to the AAO membranes. Furthermore, FTIR spectra analysis confirmed that the electrolyte species, such as phosphonate and citric ions, are being embedded into the AAO framework during the anodization. The graded-index structure formed in AAO can be used for a production of antireflective coatings operating in a broad spectral range.

Atomic layer deposition (ALD), a gas-phase thin film deposition technique based on repeated, self-terminating gas-solid reactions, has become the method of choice in semiconductor manufacturing and many other technological areas for depositing thin conformal inorganic material layers for various applications. ALD has been discovered and developed independently, at least twice, under different names: atomic layer epitaxy (ALE) and molecular layering. ALE, dating back to 1974 in Finland, has been commonly known as the origin of ALD, while work done since the 1960s in the Soviet Union under the name "molecular layering" (and sometimes other names) has remained much less known. The virtual project on the history of ALD (VPHA) is a volunteer-based effort with open participation, set up to make the early days of ALD more transparent. In VPHA, started in July 2013, the target is to list, read and comment on all early ALD academic and patent literature up to 1986. VPHA has resulted in two essays and several presentations at international conferences. This paper, based on a poster presentation at the 16th International Conference on Atomic Layer Deposition in Dublin, Ireland, 2016, presents a recommended reading list of early ALD publications, created collectively by the VPHA participants through voting. The list contains 22 publications from Finland, Japan, Soviet Union, United Kingdom, and United States. Up to now, a balanced overview regarding the early history of ALD has been missing; the current list is an attempt to remedy this deficiency.

The structural and optical evolution of the ZnS thin films prepared by atomic layer deposition (ALD) from the diethylzinc (DEZ) and 1,5-pentanedithiol (PDT) as zinc and sulfur precursors was studied. A deposited ZnS layer (of about 60 nm) is amorphous, with a significant S excess. After annealing, the stoichiometry improved for annealing temperatures &ge, 400 &deg, C and annealing time &ge, 2 h, and 1:1 stoichiometry was obtained when annealed at 500 &deg, C for 4 h. ZnS crystallized into small crystallites (1&ndash, 7 nm) with cubic sphalerite structure, which remained stable under the applied annealing conditions. The size of the crystallites (D) tended to decrease with annealing temperature, in agreement with the EDS data (decreased content of both S and Zn with annealing temperature), the D for samples annealed at 600 &deg, C (for the time &le, 2 h) was always the smallest. Both reflectivity and ellipsometric spectra showed characteristics typical for quantum confinement (distinct dips/peaks in UV spectral region). It can thus be concluded that the amorphous ZnS layer obtained at a relatively low temperature (150 &deg, C) from organic S precursor transformed into the layers built of small ZnS nanocrystals of cubic structure after annealing at a temperature range of 300&ndash, 600 &deg, C under Ar atmosphere.

Three types of niobia nanostructured films (so-called native, planarized, and column-like) were formed on glass substrates by porous alumina assisted anodizing in a 0.2 M aqueous solution of oxalic acid in a potentiostatic mode at a 53 V and then reanodizing in an electrolyte containing 0.5 M boric acid and 0.05 M sodium tetraborate in a potentiodynamic mode by raising the voltage to 230 V, and chemical post-processing. Anodic behaviors, morphology, and optical properties of the films have been investigated. The interference pattern of native film served as the basis for calculating the effective refractive index which varies within 1.75–1.54 in the wavelength range 190–1100 nm. Refractive index spectral characteristics made it possible to distinguish a number of absorbance bands of the native film. Based on the analysis of literature data, the identified oxide absorbance bands were assigned. The effective refractive index of native film was also calculated using the effective-medium models, and was in the range of 1.63–1.68. The reflectance spectra of all films show peaks in short- and long-wave regions. The presence of these peaks is due to the periodically varying refractive index in the layers of films in two dimensions. FDTD simulation was carried out and the morphology of a potential 2-D photonic crystal with 92% (wavelength 462 nm) reflectance, based on the third type of films, was proposed.

The influence of various pre-anodization voltage (Vs) on pore self-ordering process in anodic alumina (AAO) produced by hard anodization (HA) was investigated. It was demonstrated that the Vs has substantial effect on the pore arrangement in the AAO. Moreover, the results revealed that the pre-anodization under the mild condition is not necessary to form a long-range ordered AAO. When the HA process starts at relatively high Vs, only a small change of voltage and current during the second anodization stage is sufficient to rearrange the pores into the close-packed hexagonal structure. Excellent pore ordering was achieved when the samples were pre-anodized at 120 V.

Surface plasmons (SPs) supported by Al nano-concave arrays with increasing interpore distance (D c ) were used to enhance the ultraviolet light emission from ZnO thin films. Two sets of samples were prepared: in the first set the thin ZnO films were deposited directly on Al nanoconcaves (the Al/ZnO samples) and in the second set a 10 nm − Al 2 O 3 spacer was placed between the textured Al and the ZnO films (the Al/Al 2 O 3 -ALD/ZnO samples). In the Al/ZnO samples the enhancement was limited by a nonradiative energy dissipation due to the Ohmic loss in the Al metal. However, for the ZnO layer deposited directly on Al nanopits synthesized at 150 V (D c = 333 ± 18 nm), the largest 9-fold enhancement was obtained by achieving the best energy fit between the near band-edge (NBE) emission from ZnO and the λ (0,1) SPP resonance mode. In the Al/Al 2 O 3 -ALD/ZnO samples the amplification of the UV emission was smaller than in the Al/ZnO samples due to a big energy mismatch between the NBE emission and the λ (0,1) plasmonic mode. The results obtained in this work indicate that better tuning of the NBE − λ (0,1) SPP resonance mode coupling is possible through a proper modification of geometrical parameters in the Al/Al 2 O 3 -ALD/ZnO system such as Al nano-concave spacing and the thickness of the corresponding layer. This approach will reduce the negative influence of the non-radiative plasmonic modes and most likely will lead to further enhancement of the SP-modulated UV emission from ZnO thin films.

Aluminum was anodized in mixtures of aqueous sulfuric and chromic acid in different ratios, with overall concentration of 1.0 M. It was found that the logarithm of current density (and consequently, oxide growth rate) is a square function of the anodizing voltage. Moreover, the barrier layer thickness at the pores bottom was found to increase exponentially with the voltage, and increased as well with the fraction of chromic acid in the electrolyte. Additionally, interpore distance of anodic aluminum oxide, formed at the same voltage, was found to increase exponentially with the molar fraction of the chromic acid. Altogether, the high impact of the composition of the electrolyte on the morphological features of the nanoporous arrays is revealed.

Recent research concerning heteroatom-doped carbon materials reveals strong evidence of the superior electrochemical performance of S, N-dually doped carbons over their mono- or multidoped counterparts enriched with different elements. Herein sulfur and nitrogen co-doped carbon gels produced via sol–gel copolycondensation of a mixture of S- and N-containing heterocyclic aldehydes with resorcinol are presented and examined for the first time. The characteristics of the carbonaceous materials can be tuned by means of the initial ratio of the aldehydes (control of the S and N content, control of the texture), sol–gel synthesis conditions (control of morphology) and carbonization conditions (control of texture, amount of doped heteroatoms, their chemical state and the structure of the carbon framework). The S, N-co-doped carbon gels obtained are characterized by specific surface areas of up to 570 m 2 /g, maximal S and N content of up to 14 and 9 wt%, respectively, and a peculiar correlation between the amount of S- and N-doping, carbonization temperature and the development of micro- and ultramicroporosity.

The influence of ethylene glycol (EG) on the morphology of anodic alumina fabricated during hard anodization (HA) was analyzed. A transformation from continuous nano-porous film to separated alumina nano-tubes was induced upon addition of EG to a 0.3 M oxalic acid solution. Moreover, while anodization under constant voltage in a 1:1 v / v EG:H 2 O acidic solution resulted in distinct current density ( i a ) reduction in reference with the i a registered for the HA in an EG-free solution, the anodization in a 1:4 v / v EG:H 2 O mixture was often accompanied by a sudden i a increase and irregular current oscillations. In the latter case mostly the alumina nanotubes with wall thickness variation were produced. In general, the separation phenomena was explained by extensive incorporation of soluble C 2 O 4 2 − and COO − ions into the oxide framework leading to an enhanced oxide dissolution rate and preferred cleavages along the cell boundaries. The current oscillation and the production of nanotubes with an altered diameter were ascribed to a higher value of e el ∙ e ox / η ratio (where e el and e ox are the dielectric coefficient of electrolyte and the formed anodic oxide, respectively, and η is the dynamic viscosity of the solvent) as compared to the value relevant for more viscous solvent.

Nanoporous anodic aluminum oxide was formed in sulfuric acid with addition of indigo carmine. During anodizing, the organic dye was incorporated into the porous oxide walls. X-ray photoelectron spectroscopy revealed the presence of nitrogen and sulfur in the anodic aluminum oxide. Two types of incorporated sulfur were found: belonging to the sulfate anions SO42 − of the electrolyte and belonging to the C-SO3− side groups of the indigo carmine. Raman spectroscopy confirmed the incorporation and showed that the inorganic–organic hybrid material inherited optical properties from the indigo carmine. Typical modes from pyrrolidone rings, unique for indigo carmine in the investigated system (650 and 1585 cm− 1), were found to be the strongest for the greatest anodizing voltages used. Despite the indigo carmine incorporation, the morphology of the oxide is still nanoporous and its geometry is still tuned by the voltage applied during aluminum anodization. This work presents an inexpensive and facile approach to doping an inorganic oxide material with organic compounds.

The chemical dissolution&mdash, in 0.1 M solutions of phosphoric, malonic, citric, sulfosalicylic, and tartaric acids and 0.6 M solutions of sulfuric, oxalic, malonic, phosphoric, tartaric, and citric acids&mdash, of aluminum (Al) and its barrier anodic oxide, with thicknesses of 240 and 350 nm, produced during the anodization of Al deposited on a sitall substrate and Al foil, respectively, in a 1% citric acid aqueous solution, was investigated. Signs of chemical dissolution for 0.1 M phosphoric acid solution and 0.6 M concentrations of all the listed solutions were found. It was shown that the dissolution rate and the nature of its change depend on the acid nature, the state of the sample surface, and the classification of the electrolytes according to their degrees of aggressiveness with respect to aluminum.

Infrared (IR) spectroscopy is a powerful technique to characterize the chemical structure and dynamics of various types of samples. However, the signal-to-noise-ratio drops rapidly when the sample thickness gets much smaller than penetration depth, which is proportional to wavelength. This poses serious problems in analysis of thin films. In this work, an approach is demonstrated to overcome these problems. It is shown that a standard IR spectroscopy can be successfully employed to study the structure and composition of films as thin as 20 nm, when the layers were grown on porous substrates with a well-developed surface area. In contrast to IR spectra of the films deposited on flat Si substrates, the IR spectra of the same films but deposited on porous ceramic support show distinct bands that enabled reliable chemical analysis. The analysis of Zn-S ultrathin films synthesized by atomic layer deposition (ALD) from diethylzinc (DEZ) and 1,5-pentanedithiol (PDT) as precursors of Zn and S, respectively, served as proof of concept. However, the approach presented in this study can be applied to analysis of any ultrathin film deposited on target substrate and simultaneously on porous support, where the latter sample would be a reference sample dedicated for IR analysis of this film.