One-dimensional photonic crystals (PhCs) based on anodic titanium oxide (ATO) exhibit a periodic modulation of porosity, enabling the formation of photonic band gaps (PBGs) that control light propagation through the structure. While ATO PhCs produced by titanium anodizing are initially amorphous, achieving crystallinity is essential for advanced applications in photocatalysis and solar energy conversion. However, the required annealing process induces an undesired shift in the PBG position. Here, we propose an anodizing regime based on voltage variation as a function of optical path length, enabling the controlled synthesis of anatase PhCs with a desired PBG position in the visible and near-infrared range with accuracy above 94%. Furthermore, we investigate the influence of the PBG position on the photocatalytic degradation rate of methylene blue. The proposed synthesis procedure enables the fabrication of anatase PhCs with the desired PBG position and number of periods suitable for nanophotonic and photocatalytic applications.

Superconducting electronics is a rapidly growing field in micro- and nanoelectronics. Various planar structures, such as Josephson junctions, exhibit intriguing phenomena with potential applications in spin-based and quantum devices. However, the integration density of these thin-film digital components is still lower than that of semiconductor elements. The nanometer-scale miniaturization of Josephson junctions can be achieved by using a new approach, such as nanowire-based geometry. This article reports an automated electrochemical method for producing segmented Au/Ni/Au nanowires with diameters less than 100 nm. The potentiostatic electrodeposition of metals from different baths using coulometric control leads to the formation of segments with narrow length distributions and well-defined boundaries. The ability to fabricate coarse-grained gold segments and single-crystal ferromagnetic nickel layers as thin as 7 nm has been demonstrated. For a nanowire-based Nb/Au/Ni/Au/Nb hybrid structure with planar Nb electrodes and a 7-nm-thick Ni segment, a critical current of 0.6 mu A at 1.2 K has been detected. The low-temperature transport properties are described by an effective resistance model, in which the Ni ferromagnetic layer exhibits ballistic electron transport. The fabricated structures represent the first example of miniature SFS Josephson junctions based on individual segmented nanowires that demonstrate proximity-induced superconducting behavior. These findings pave the way for designing compact, F-containing digital devices for superconducting nanoelectronics and spintronics.

The aggregation-induced emission (AIE) effect opens up new opportunities and prospects for the development of organic light-emitting materials. By exploiting the intrinsic ability of boron-dipyrromethenes (BODIPYs) to form aggregates, we rationally designed water-soluble AIE-active dyes derived from BODIPY fluorophores by their modification with azamacrocyclic units. The most AIE-active cyclen-BODIPY derivatives 5a and 8a showed high fluorescence quantum yields and they were found to be sensitive to water content, viscosity, pH, and temperature with a "turn-on" fluorescence response. The DLS and SEM results showed that these compounds exist as nanoscale aggregates in aqueous solutions. A possible molecular arrangement of dye 5a in aggregates was rationalized using TD-DFT calculations. The biologically relevant metal ions, such as Li+, K+, Na+, and Mg2+, have no pronounced effect on absorption and emission spectra of the dyes 5a and 8a. In vitro confocal microscopy studies in HeLa cells demonstrated that dyes 5a and 8a successfully permeated the cell membrane and selectively labeled lysosomes. These findings suggest that cyclen-BODIPY derivatives hold promise for investigating lysosomal dynamics and function in living cells via fluorescence imaging.

Cyclic anodizing is an advanced method for synthesis of periodic porous structures, such as photonic crystals, heterostructures, and optical microcavities (OMs). These structures have a wide range of applications in sensing, nanophotonics, and lasing. However, OMs based on anodic titanium oxide (ATO) have not been synthesized to date. Here, optical microcavities based on anodic titanium oxide (ATO) have been prepared for the first time by cyclic anodizing of titanium with a voltage versus charge modulation using a phase shift of pi after half the number of cycles to form a defect in the periodic modulation of an effective refractive index of the ATO. The structure and optical properties of ATO OMs were studied by scanning electron microscopy and optical spectroscopy. The wavelength position of resonance bands of ATO OMs is in the range of 390-1640 nm and is defined by a charge density per anodizing cycle. The quality factor of the fabricated OMs is up to 16.2, which exceeds the best value reported for ATO-based photonic crystals in the literature.

In this study, we successfully obtained for the first time a luminescent organic-based thermometer that exhibits high reproducibility, stability, and functionality up to 400 degrees C. Our approach involved the selection of novel highly emissive and thermally stable MOFs KEu(btec)(H2O) and dehydrated KTb(btec), btec = benzene-1,2,4,5-tetracarboxylate, along with the highly thermally stable copolyimide P84 = 80% methylphenylene-diamine + 20% methylene as the matrix; luminescence lifetime was selected as a temperature-dependent parameter due to its versatility in diverse environmental conditions. Synthesis peculiarities were studied for various lanthanide benzene-1,2,4,5-tetracarboxylates, and the crystal structures of KEu(btec)(H2O) and KTb(btec) were determined by Rietveld refinement from powder X-ray diffraction data.

One-dimensional photonic crystals (1D PCs) based on porous anodic aluminium oxide (AAO) are promising for light manipulation and sensing. As -prepared AAO, being amorphous material, suffers degradation in acidic and alkaline media. It is commonly known that the chemical stability of AAO increases drastically after thermal treatment. Here, the effect of annealing up to 1200 degrees C on the morphology and the optical properties of AAO PCs is studied. The two-step crystallization of asprepared AAO at 860 and 1190 degrees C leads to a two-step blue shift of the central wavelength of photonic band gap (PBG) and the decrease in PBG depth, whereas the Qfactor of the PBG enhances. The observed changes in optical transmittance spectra of PCs are mainly attributed to the increase in pore diameter, the formation of crystalline particles of alumina polymorphs, and the removal of impurities. Annealed AAO PCs demonstrate much higher stability of optical parameters during exposure in acidic media compared to the as -prepared ones. Thermal treatment at 600 degrees C results in 30% decrease in the rate of the PBG shift during chemical etching. Furthermore, AAO crystallization into a mixture of low -temperature alumina polymorphs at 860 degrees C leads in a negligible change in transmittance spectra even after chemical etching in 1 M HCl for 75 h. The excellent stability achieved for the annealed AAO PCs in aggressive media proves the perspectives of their application as the optical sensors with long-term stability.

A combination of the unique porous structure and physical and chemical properties of anodic aluminum oxide (AAO) makes it widely used in cutting-edge areas of materials science and nanotechnology. Selenic acid electrolyte provides the ability to obtain AAO with low porosity and high optical transparency and thus is promising for the preparation of AAO photonic crystals (PhCs). Here, we show the influence of crystallographic orientation of Al on the electrochemical oxidation rate in 1 M H2SeO4 as well as on the growth rate, porosity, and the effective refractive index of AAO. The cyclic anodization regime is used to prepare AAO PhCs with photonic band gaps, their wavelength positions are used to measure the AAO growth rate. At an anodization voltage of 40-45 V, the growth rate varies by up to 22.6% with crystallographic orientation of Al grains, causing the stained glass effect, which can be seen with the naked eye.

Photonic crystal heterostructures (PhCHs) have emerged as a promising tool to control light propagation with high precision. Anodization techniques are widely used to prepare PhCHs based on porous silicon and valve metal oxides. These techniques rely on oscillating anodization voltage or current to modulate the effective refractive index along the normal to the porous film surface, thereby creating photonic band gaps (PBGs) in PhCHs. However, anodization regimes described in the literature lack direct control over the optical path length (L) of prepared photonic structures, which is essential for fine-tuning the optical properties of PhCHs. In this work we present an anodization method for the preparation of PhCHs based on anodic aluminum oxide (AAO). The proposed anodizing regime accounts for chromatic dispersion of the refractive index and dispersion of L of the porous AAO film, providing direct control over the L of the prepared PhCHs. The potential of this approach was demonstrated by preparing PhCHs with up to 21 PBGs in the wavelength range from 250 to 1050 nm. Furthermore, we showcase a promising practical application of PhCHs by encoding 10-letter words and storing 47 bits of data using AAO photonic barcodes. The developed anodizing approach opens up avenues for designing and fabricating PhCHs with enhanced optical properties and potential applications in optical communication, data storage, and sensing.

Photonic crystals (PCs) consisting of a periodic arrangement of holes in dielectric media have found success in light manipulation and sensing. Among them, three-dimensional (3D) PCs are in high demand due to their unique properties originating from multiple photonic band gaps (PBGs) and even full ones. Here, 3D PCs based on porous anodic aluminum oxide (AAO) were fabricated for the first time. Our approach involves prepatterning of the aluminum surface by a focused ion beam to form a hexagonal array of pore nuclei. Subsequent anodization in 1 M H3PO3 using a sine wave profile of voltage provides AAO with a defect-free in-plane porous structure and out-of-plane porosity modulation. The ability to tune the position, width, and depth of the PBGs is demonstrated. The combination of the flexibility of the proposed approach with the unique properties of AAO extends the range of practical applications of 3D PCs far beyond the current achievements.

The slowing down of the group velocity of light at the edges of the photonic band gap is one of the important optical effects observed in photonic crystals. In particular, the “slow light” effect is used in photocatalysis to increase the photocatalytic activity of semiconductors. In this work, anatase photonic crystals with different spectral positions of the photonic band gap (390–1283 nm, measured in water) were obtained. It is shown that if one of the photonic band gaps is located near the absorption edge of the semiconductor (410 nm), photonic crystal exhibits high photocatalytic activity in the photodegradation of methylene blue. At the same time, the photocatalytic activity of anatase photonic crystal increases by 30% when the photonic band gap of the third order rather than the first order is located near the absorption edge of the semiconductor.

Electrochemical oxidation of aluminium in acidic electrolyte solutions, also known as anodizing, is a widely used process for the finishing of pure aluminium and its alloys. The resulting anodic aluminium oxide (AAO) porous films play a significant role in modern science and technology. One of the most exciting features of AAO is the self-organization of pores into two-dimensional hexagonal patterns under specific anodizing conditions. The combination of a hexagonal arrangement of pores and precise control over pore diameter, interpore distance, and film thickness gives rise to a wide range of potential applications from decorative coatings to quantum technologies. This review discusses the kinetic approach to the guided search for anodizing conditions that lead to the formation of highly ordered porous structures, as well as recent data on how the crystallographic orientation of the aluminium substrate affects the growth rate and structure of AAO.

Catalytic combustion-type gas sensors are widely used in industry and everyday life for detecting flammable gases. However, high power consumption is one of the main drawbacks of the catalytic sensors. Replacing the platinum wire heating element with a thin-film microheater can significantly reduce power consumption, but maintaining high sensitivity and long-term stability of such devices is a challenge. Here we developed microheater-type catalytic hydrogen sensors based on porous anodic aluminium oxide served simultaneously as a substrate for platinum microheater and as a carrier for a catalyst. The fabricated sensors have a high sensitivity of 76 mV/vol. % hydrogen. The deviation of the sensory response during continuous operation for 14 days is less than 4%. The relative humidity of the ambient atmosphere does not affect the sensor response. The low sensor response time (0.4 s) makes it possible to use the pulsed power supply mode to reduce the power consumption to 3.2 mW without sacrificing the measurement accuracy. Thus, the performance of the developed catalytic hydrogen sensors promotes the high competitiveness in the market and the prospects for industrial applications.

One of the possible ways to enhance photocatalytic activity is the use of photonic band gap (PBG) materials. Anodic titania photonic crystals (PhCs) are promising PBG structures, whose structure can be tuned easily by anodizing conditions. However, the effect of various doping approaches on the photocatalytic activity of anodic titania PhCs has never been studied before. Here anodic titania PhCs were synthesized by cycling anodizing of titanium with voltage versus charge density modulation followed by annealing at 450 degrees C in air. The PhCs were post-treated by electrochemical reduction in 0.1 M Na2SO4, annealing in H2/Ar mixture or NH3. The phase composition and structure of titania PhCs were studied by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy. Photocatalytic activity of PhCs in the degradation of the methylene blue dye decreases after electrochemical reduction and annealing in NH3, whereas the annealing in H2/Ar at 600 degrees C for 2 h leads to an increase in the degradation rate constant by 60%.

Anodic titanium oxide (ATO) one-dimensional photonic crystals (PhCs) are materials with uniaxial periodic modulation of porosity. A periodic change of an effective refractive index caused by porosity modulation results in the formation of photonic band gaps (PBGs). The non-uniform dissolution of ATO cell walls during the fabrication process hampers the obtaining of a strict optical periodicity of ATO PhCs. Recently it was found that the dissolution of ATO cell walls is accelerated by anodic polarization. However, the main factor controlling the accelerated dissolution of ATO cell walls during anodizing remains unclear. In this study, the correlation between ATO PhC porosity and the charge density is discussed. The dependencies of the spectral photonic band gap (PBG) position and PBG reflectance on the charge density are studied experimentally. The findings open a pathway to the synthesis of ATO PhCs with flawless optical periodicity and high PBG reflectance.

Anodic titanium oxide photonic crystals (ATO PhCs) are promising for optical sensing and photocatalysis due to their photonic band gaps (PBGs). The ability to control the spectral position and width of the PBG are essential for application of ATO PhCs. Anodizing charge density has recently been reported to be a main factor affecting the porosity and hence the effective refractive index (n(eff)) and PBG position of ATO PhCs. In this paper, we propose a method for accurate determining the dependence of n(eff) of ATO PhCs on the etching charge density varying in a wide range. The method is based on an analysis of the spectral positions of PBGs in photonic heterostructures. The obtained dependence was used for the synthesis of the ATO PhCs with desired PBG positions in a wide wavelength range (400-1500 nm) by the periodic voltage modulation on optical path length. The deviation of the experimental PBG position from the specified one does not exceed 10 %. The prepared PhCs possess similar to 100 % reflectance in the PBG region.

Graphene materials currently open new perspectives to electrochemical systems, providing high electron transfer rates, electrochemical stability in a wide potential range, and ability to control these properties, for instance, by introducing impurity atoms. One of the most important electrochemical characteristics of the graphene is the heterogeneous electron transfer rate (or electrochemical activity). However, contradictory results have been presented on the electrochemical activity of graphene, and how structural defects, the number of graphene layers, and the graphene substrate alter its activity. We found here that the question of an electron transfer regime on graphene, which is disputable and rarely considered, is critically important in understanding its electrochemical activity. We provide an evidence of different electron transfer regimes for O 2 /O 2 − and ferrocenium/ferrocene redox on the graphene electrode, that result in different structure-activity relationships. Our results contribute to further understanding of the graphene electrochemistry.

Anodization of aluminum with a pre-patterned surface is a promising approach for preparing anodic aluminum oxide (AAO) films with defect-free pore arrangement. Although pronounced effects of crystallographic orientation of Al on the AAO structure have been demonstrated, all current studies on the anodization of pre-patterned aluminum consider the substrate as an isotropic medium and, thus, do not consider the azimuthal orientation of the pattern relative to the basis vectors of the Al unit cell. Here, we investigate the interplay between the azimuthal alignment of the pore nuclei array and the crystallographic orientation of aluminum. Al(100) and Al(111) single-crystal substrates were pre-patterned by a Ga focused ion beam and then anodized under self-ordering conditions. The thickness-dependent degree of pore ordering in AAO was quantified using statistical analysis of scanning electron microscopy images. The observed trends demonstrate that the preferred azimuthal orientation of pore nuclei rows coincides with the <110> directions in the Al unit cell, which is favorable for creating AAO with a high degree of pore ordering. In the case of an unspecified azimuthal orientation of the pore nuclei array, crystallography-affected disorder within the AAO structure occurs with increasing film thickness. Our findings have important implications for preparing defect-free porous films over 100 µm in thickness that are crucial for a variety of AAO applications, e.g., creating metamaterials and 2D/3D photonic crystals.

The anodizing of aluminium under oscillating conditions is a versatile and reproducible method for the preparation of one-dimensional photonic crystals (PhCs). Many anodizing parameters have been optimised to improve the optical properties of anodic aluminium oxide (AAO) PhCs. However, the influence of the crystallographic orientation of an Al substrate on the characteristics of AAO PhCs has not been considered yet. Here, the effect of Al substrate crystallography on the properties of AAO PhCs is investigated. It is experimentally demonstrated that the cyclic anodizing of coarse-grained aluminium foils produces a mosaic of photonic crystals. The crystallographic orientation of Al grains affects the electrochemical oxidation rate of Al, the growth rate of AAO, and the wavelength position of the photonic band gap.

We have studied the effect of anodizing voltage on the optical properties and structure of anodic titanium oxide films before and after annealing. Annealing at temperatures in the range 400–550°C has been shown to cause crystallization of initially amorphous anodic titanium oxide in the anatase phase, accompanied by an increase in porosity, pore diameter, and the refractive index of cell walls and a decrease in film thickness and average nanotube center-to-center distance.

The self-ordered anodic aluminium oxide (AAO) structure consists of micron-scale domains-defect-free areas with a hexagonal arrangement of pores. A substantial increase in domain size is possible solely by pre-patterning the aluminium surface in the form of a defect-free hexagonal array of concaves, which guide the pore growth during subsequent anodization. Among the numerous pre-patterning techniques, direct etching by focused gallium ion beam (Ga FIB) allows the preparation of AAO with a custom-made geometry through precise control of the irradiation positions, beam energy, and ion dosage. The main drawback of the FIB approach includes gallium contamination of the aluminium surface. Here, we propose a multi-step anodizing procedure to prevent gallium incorporation into the aluminium substrate. The suggested approach successfully covers a wide range of AAO interpore distances from 100 to 500 nm. In particular, anodization of FIB pre-patterned aluminium in 0.1 M phosphoric acid at 195 V to prepare AAO with the interpore distance of about 500 nm was demonstrated for the first time. The quantification of the degree of pore ordering reveals the fraction of pores in hexagonal coordination above 96% and the in-plane mosaicity below 3° over an area of about 1000μm2. Large-scale defect-free AAO structures are promising for creating photonic crystals and hyperbolic metamaterials with distinct functional properties.