Chemical Etching Method Research Articles

An approach for 3-D distribution measurement of tritium in tungsten by chemical etching and imaging plate technique

Measurement of tritium distribution details both on surface and in bulk of tungsten is of great importance for studies on the retention properties of plasma facing materials (PFMs) in magnetic fusion reactors. An attempt was made to determine the tritium 3-D distribution in tungsten sample through layer by layer chemical etching method (LLCE) and imaging plate technique (IP). As chemical etching method has been rarely employed for tritium measurement in tungsten, the influence of key experimental parameters were evaluated. And the tritium 3-D distribution in a tungsten sample was obtained by LLCE and IP. It is found that LLCE is a promising and reliable method for tritium depth profile measurement. The relative error of tritium content in each layer is approximately 5.2% when the thickness of erosion layer is 0.4 μm. Combined with IP technique, the detailed 3-D distribution could be obtained and it is clearly indicated that tritium is unevenly distributed on the radial section of this sample. In addition, the good agreement of tritium depth profile by LLCE and IP shows the reliability of this approach.

Enhanced fiber mounting and etching technique for optimized optical power transmission at critical cladding thickness for fiber-sensing application

Optical fibers offer various applications to cater to industrial needs, from power and data transmission to environmental sensing. Different sensing mechanisms of optical fibers depend on modifications made to the fiber itself primarily in the cladding and core sections. Different types of optical fiber sensors may require thinning of the cladding to allow propagated light to interact closer to the environmental stimuli. Chemical etching is commonly used for the de-cladding of a fiber, and there are many ways to execute this method. A conventional method of chemical etching is typically used for cladding removal. This paper reports and discusses the effectiveness of enhanced techniques for improvement towards conventional chemical etching methods with the assistance of a makeshift fiber holder. The fiber holder allows the fiber to be oriented well, allowing for smoother etching and thus conserving its mechanical structure. Thickness reduction is seen to be more consistent when the enhanced technique is employed, and the fiber takes a longer time (∼45 min) to break. This allows etching of the cladding close to the core, which is more manageable for the user if very thin cladding is required. A fiber etched without any holder tends to break earlier (∼35 min) than expected with a rather wide error margin. The lower coefficient of determination, R 2 values (95%) of the thickness reduction from conventional etching shows irregular thickness along the fibers. Optical power also fluctuates between 30–35 dBm for the conventional method, while the mounted fiber technique maintains stable optical power at 50 dBm during etching. Therefore, it is concluded that proper fiber horizontal fiber orientation during etching has a significant effect on the fiber strength due to the smooth cladding removal around the corecore while minimizing any permanent power loss to or the occurrence of fluctuations in the fiber. This smooth and efficient etching technique allows the production of enhanced fiber sensors with minimal structural or power defects.

An efficient method for enhancing adhesion and uniformity of Al2O3 coatings on nickel micro-foam used in micropacked beds

• An efficient coating method to overcome the capillary force was proposed. • The pore size on substrate surface can be controlled by the pretreatment conditions. • Correlation was proposed with excellent practicality for predicting the pore size. • Squeezing of Al 2 O 3 particles in the pores can improve the adhesion of coatings. Methods of coating Al 2 O 3 on nickel micro-foam were compared and screened, aiming to overcome the capillary force and prepare the micro-foam monolithic catalyst coatings. The surface of micro-foam substrate was pretreated by a chemical etching method to improve the adhesion of the coatings on the substrate. The results showed that the slurry circulation at 162 ml·min −1 was evaluated as the optimal method. The pore size on the substrate surface can be controlled by changing the pretreatment conditions. An empirical correlation was also proposed, showing an excellent practicality for predicting the pore size. The adhesion of the coatings with substrate pretreatment was significantly better than that without substrate pretreatment. The minimum value of mass loss after ultrasonic vibration was 3.9%. This mainly attributes to the squeezing of Al 2 O 3 particles in the pores of substrate surface. The coatings on nickel micro-foam are hopefully used in micropacked beds for catalytic reactions.

RHEED analysis of the oxidized M′2M″xXyene sheets by ablated plasma thrust method in pulsed laser deposition chamber

M′2M″xXyene (M′ and M″ are the early transitional metals and X is carbide with x = 1 for y = 2 and x = 2 for y = 3) are the ordered double transitional metal layered carbides derived from their parent MAX phases M′2M″xAlXyene by a wet chemical etching method. Their oxides are predicted to have topological properties for which they should be annealed at around 800 °C in an oxygen background. This paper includes the new ablated plasma thrust method for the ionization and adsorption of oxygen on the M′2M″xXyene substrate in the pulsed laser deposition chamber. We have found that the background pressure has a negative effect and the substrate temperature has a positive effect on plume expansion. The density profile of the background gas is highly affected by deposition temperature. Similarly, it is found that the density of plasma generated by longer wavelengths is not affected significantly due to the inverse bremsstrahlung process. A shorter wavelength produces the bremsstrahlung process as photoionization takes place. At a certain time (200 ns), the pressure of background gas and plasma pressure are equal (snow-plogh effect) so that all the wavelengths then produce electrons (highest for shorter wavelengths), thereby increasing its density. The energy necessary for the oxidation of the substrate is provided by the energy of the ablated species. The adsorption is assured by the reflective high electron energy diffraction technique, and it is found that the ambient gas pressures p = 0.1 mbar and 0.2 mbar are appropriate for the adsorption process. The obtained M′2M″xXyene oxides can be used for their topological test.

Experimental study of nucleate pool boiling heat transfer on microporous structured by chemical etching method

Cooling of high heat flux devices and electronics devices with a high heat dissipation system uses Boiling Heat Transfer (BHT). In this paper, a pool boiling heat transfer experiments conducted on saturated distilled water for a bare and microstructured copper surface prepared through chemical etching at atmospheric pressure. A two-step chemical etching process is used for the fabrication of copper microstructure. In the first step, HNO3 and CTAB are used, and in the second step, NaOH and (NH4)2S2O8 are used. This practice comes up with simple management of various surface properties that influence critical heat flux (CHF) and boiling heat transfer coefficient (BHTC) like porosity, roughness, contact angle, etc. These properties are examined with the help of required equipment and are found better. The result of the experiment shows a significant enhancement for BHTC. The maximum BHTC is 82.7 kW/m2K, which is a 60 % increment compared to the bare copper surface. The enhancement of BHTC is due to the microstructure formed on the copper surface through chemical etching. Because of this microstructure, surface properties like roughness, surface wettability are improved in favor of boiling heat transfer performance. But due to the hydrophobic nature, chemically etched surfaces show less CHF than the bare copper surface. For repeatability performance, the surfaces' heat transfer coefficient shows a 4.8 % deviation after a four times repeated test.

The Emission Mechanism of Gold Nanoclusters Capped with 11-Mercaptoundecanoic Acid, and the Detection of Methanol in Adulterated Wine Model.

The absorption and emission mechanisms of gold nanoclusters (AuNCs) have yet to be understood. In this article, 11-Mercaptoundecanoic acid (MUA) capped AuNCs (AuNC@MUA) were synthesized using the chemical etching method. Compared with MUA, AuNC@MUA had three obvious absorption peaks at 280 nm, 360 nm, and 390 nm; its photoluminescence excitation (PLE) peak and photoluminescence (PL) peak were located at 285 nm and 600 nm, respectively. The AuNC@MUA was hardly emissive when 360 nm and 390 nm were chosen as excitation wavelengths. The extremely large stokes-shift (>300 nm), and the mismatch between the excitation peaks and absorption peaks of AuNC@MUA, make it a particularly suitable model for studying the emission mechanism. When the ligands were partially removed by a small amount of sodium hypochlorite (NaClO) solution, the absorption peak showed a remarkable rise at 288 nm and declines at 360 nm and 390 nm. These experimental results illustrated that the absorption peak at 288 nm was mainly from metal-to-metal charge transfer (MMCT), while the absorption peaks at 360 nm and 390 nm were mainly from ligand-to-metal charge transfer (LMCT). The PLE peak coincided with the former absorption peak, which implied that the emission of the AuNC@MUA was originally from MMCT. It was also interesting that the emission mechanism could be switched to LMCT from MMCT by decreasing the size of the nanoclusters using 16-mercaptohexadecanoic acid (MHA), which possesses a stronger etching ability. Moreover, due to the different PL intensities of AuNC@MUA in methanol, ethanol, and water, it has been successfully applied in detecting methanol in adulterated wine models (methanol-ethanol-water mixtures).

Enhanced efficiency of silicon micro-pyramids/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate/gold nanoparticles hybrid solar cells

The hybrid solar cells have been receiving great attention as a promising candidate for the next generation of energy-harvesting devices. In this study, we present some results on the fabrication and characterization of n-type silicon micro-pyramid (SiMPs)/poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) hybrid solar cells. SiMPs were prepared by a chemical etching method and their influence on the performance of the hybrid solar cells was investigated. The obtained results showed that the micro-pyramidal structures could provide an adequate generation of charge carriers by relatively low reflectance. The hybrid solar cell using SiMPs showed a power conversion efficiency (PCE) to be 5.24% which improves about 40% compared to that of the planar Si solar cell (3.68%). Besides, the effect of AuNP concentrations on the performance of the hybrid solar cell was also investigated. The maximum PCE was measured to be 7.55% with a device containing 0.5 wt% AuNP concentration, which is 44% higher compared to that of the solar cells without AuNPs. The enhancement is attributed to the increase in electrical conductivity and localized surface plasmon resonance of the PEDOT:PSS coating layer due to the addition of the AuNPs.

A facile approach to enhancing the UV blocking properties of layered double hydroxides and potential application in asphalt

Defect-structured ZnaMgbAlc layered double hydroxides (d-ZnaMgbAlc-LDHs) with varying Mg/Zn ratios have been prepared by modifying the surface of ZnaMgbAlc-LDHs through a chemical etching method. The ultraviolet (UV) blocking properties of d-ZnaMgbAlc-LDHs were significantly improved, and d-Zn4Al2-LDH was added into asphalt to explore the potential anti–UV-aging application in asphalt. Research results show that 3 wt% of d-Zn4Al2-LDH could significantly improve the anti–UV-aging ability of asphalt, resulting from oxygen vacancy defects produced on the surface of d-Zn4Al2-LDH. Specifically, these oxygen defect vacancies can adsorb the free radicals generated during the asphalt aging process; therefore, it blocked the fragmentation of the macromolecule chain in asphalt and postponed the aging process.

Plasma-induced chemical etching generating Ni3S2 for formaldehyde detection

In this paper, Ni3S2 nanosheet (NS) was generated by chemical etching with sodium sulfide directly on the nickel foam (NF), which was induced by dielectric barrier discharge plasma in liquid. Compared with other chemical etching methods of nickel-based nanomaterials, this method was not only rapid (40 min) and mild (at room temperature and atmospheric pressure), but also showed consistent stability and good reproducibility. The Ni3S2 NS/NF electrode showed excellent performance in the electrochemical detection of formaldehyde under alkaline conditions. It had a good linear relationship with the concentration of formaldehyde in the range of 0.002-5.45 mmol/L (R2 = 0.9957) and the limit of detection (LOD) was 1.23 µmol/L (S/N = 3). The sensitivity was 1286.9 µA L mmol‒1 cm‒2, and the response time was about 5 s. The plasma-induced chemical etching strategy provides a simple and stable electrode preparation method, which has great application prospects in nonenzymatic electrochemical sensors.

High-Order Vector Bessel-Gauss Beams for Laser Micromachining of Transparent Materials

Here, we present thorough research into high-order vector Bessel-Gauss beams from a theoretical perspective, with experimental realization and application to transparent-material laser micromachining. Efficient, stable, high-quality, and power-vector Bessel-Gauss beam generation using two geometric-phase-based optical elements, a high-order $S$-wave plate and an axicon in combination with simple optical elements, such as lenses, wave plates, and polarizers, is demonstrated. Ultrashort pulse-vector Bessel-Gauss beams are used to induce modifications in the glass, creating three-dimensional tubular structures of type I and type II modification in D263T glass. Furthermore, samples containing tubular modifications are tested for etch selectivity in the femtosecond-laser-induced chemical-etching method with KOH solution by etching throughout channels.

Effect of graphene oxide concentration on the properties of silicon nanoholes/poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate)/graphene oxide hybrid solar cell

We present herein some results on the fabrication and characterisation of n-type silicon nanoholes (SiNH)/poly(3,4-ethylene dioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) containing different graphene oxide (GO) hybrid solar cells. SiNH prepared by a chemical etching method showed a relatively low reflectance below 10% in the incident wavelength range of 300–1000 nm. The effect of GO concentrations on the performance of the hybrid solar cell was also investigated. The solar cell containing 0.5 wt% GO concentration had a maximum power conversion efficiency (PCE) of 9.07%, a V oc of 0.519 V, a J sc of 26.85 mA cm−2 and an FF of 65%, which is about 20% improvement compared to the device without GO (7.53%). The enhancement is attributed to the increase in electrical conductivity of the PEDOT:PSS coating layer due to the addition of the GO.

Convolutional neural network for sapphire ingots defect detection and classification

Optical homogeneity detection can be brought into play for quality control of sapphire substrate, sapphire mobile phone screen, and sapphire window material. By detecting the optical homogeneity of the sapphire crystal, the crystal lattice distortion inside the crystal can be evaluated non-destructively and intuitively. However, due to the small birefringence coefficient of sapphire crystals, it is difficult to detect the optical homogeneity of sapphire ingots through the conventional setup. In this work, we detected the optical homogeneity of the sapphire ingot using the Focused Polarization Interference (FPI) method also known as Conoscopic Birefringence Interferometry. The main principle of this technique is that the stress induced by the lattice distortion may cause the variation of the crystal birefringence which leads to the formation of the polarization interference patterns. To quantitatively evaluate the pattern deformation, we used pattern recognition technique. However, the main issue in pattern recognition and notably images classification problems is image feature extraction and image encoding. To solve the above problem, here we showed and compared different approaches: Bag of features, ResNet-50, AlexNet, VGG16, and GoogleNet pre-trained convolutional neural network (CNN) models. The reliability, practicality, and verification of the proposed models, in this work, is according to the detection measures use accuracy, confusion matrix, and Area Under the Curve (AUC). The Bag of features model achieved the classification accuracy of 94.3%, while the ResNet-50 pre-trained convolutional neural network achieved 97.6%. The findings show that ResNet-50 is capable of correctly classifying the samples from the datasets with high true fraction value and low false positive followed by AlexNet as compare to other models like VGG16 and GoogleNet. Finally, the proposed models have been in contrast with the well-known chemical etching method. The results showed that the time required to etch one sample using chemical etching is about 10 h, while by using the proposed models, we can detect and classify the whole dataset within 80 min and 27 s. The proposed pre-trained convolutional neural network models based on sapphire crystal defects classification would potentially serve as a new tool for predicting the quality inspection-based on crystal growth technology. • Optical homogeneity detection can be used for quality control of sapphire substrate. • The small birefringence coefficient of sapphire crystals. • It is difficult to detect the optical homogeneity of sapphire ingots through the conventional setup. • Focused Polarization Interference (FPI) method, so-called Conoscopic Birefringence Interferometry is used. • Pre-trained convolutional neural network (CNN) models evaluate and classify the patterns deformations.

Fabrication of inverted pyramid structure for high-efficiency silicon solar cells using metal assisted chemical etching method with CuSO4 etchant

Inverted pyramid texture is used to improve the performance of single crystalline silicon (sc-Si) solar cell due to its excellent light-trapping properties. In this paper, inverted pyramid structures are fabricated on large area sc-Si wafers by metal assisted chemical etching method using CuSO 4 instead of Cu(NO 3 ) 2 . Three groups of solar cells were fabricated with textured structures prepared by CuSO 4, Cu(NO 3 ) 2 and NaOH respectively. The surface microstructure, average reflectivity, surface recombination and auger recombination, internal quantum efficiency and external quantum efficiency of the sc-Si solar cells were studied in detail. The results show that CuSO 4 can prepare uniform inverted pyramid structures on silicon substrate by reducing the generation of bubbles and promoting the deposition copper nano-particles on the surface of sc-Si wafer, and thus improve the properties of solar cells. More importantly, the chemical reaction mechanism for etching silicon wafer with CuSO 4 and Cu(NO 3 ) 2 during the texturing process was compared and analyzed. Finally, the average efficiency of large-area sc-Si PERC solar cells fabricated by CuSO 4 was 22.63%, which was 0.60% absolutely higher than that of Cu(NO 3 ) 2 , and 1.56% higher than normal pyramid group.

Computational Study of Novel Semiconducting Sc2CT2 (T = F, Cl, Br) MXenes for Visible-Light Photocatalytic Water Splitting

Seeking candidate photocatalysts for photocatalytic water splitting, via visible light, is of great interest and importance. In this study, we have comprehensively explored the crystal structures, electronic properties, and optical absorbance of two-dimensional (2D) Sc2CT2 (T = F, Cl, Br) MXenes and their corresponding photocatalytic water splitting, under the visible-light region, by first-principles calculations. Herein, we have proposed that 2D Sc2CT2 MXenes can be fabricated from their layered bulk compounds, alternatively to the traditional chemical etching method. Creatively, we proposed Sc2CT2 (T = F, Br) as new materials; the band edge alignments of Sc2CF2 can be tuned to meet the water redox potentials at pH = 8.0. It is highlighted that Sc2CF2 shows outstanding optical spectra harvested under visible-light wavelength regions, and efficient separation of photo-induced electrons and holes in different zones. These present results provide eloquent evidence and open a new door on the photocatalysis applications of such novel semiconducting MXenes.

Study of metal-assisted chemical etching of silicon as an alternative to dry etching for the development of vertical comb-drives

Metal-assisted chemical etching (MaCEtch) has recently emerged as a promising technique to etch anisotropic nano- and microstructures in silicon by metal catalysts. It is an economical wet chemical etching method, which can be a good alternative to deep-reactive ion etching (DRIE) process in terms of verticality and etch depth. In the present study, gold is used as a metal catalyst and deposited using physical vapour deposition. It has already been demonstrated that (100) p-type Si wafer can be etched with vertical and smooth side walls. Effects of varying concentrations of etchant constituents and various other parameters, that is, porosity of deposited Au, surface contaminants, oxide formation, metal catalyst, etching time, role of surface tension of additives on the etch depth and surface defects are studied and discussed in detail. By increasing the hydrofluoric acid (HF) concentration from 7.5 M to 10 M, lateral etching is reduced and the microstructure’s width is increased from 17 µm to 18 µm. Porous defects are suppressed by decreasing the hydrogen peroxide (H2O2) concentration from 1.5 M to 1 M. On increasing the etching time from 30 min to 60 min, the microstructures are over-etched laterally. Smoother side walls are fabricated by using the low-surface-tension additive ethanol. The maximum etch depth of 2.6 µm is achieved for Au catalyst in 30 min. The results are encouraging and useful for the development of vertical comb-drives and Micro-Electro-Mechanical Systems (MEMS).

Chemical Etching of Silicon Assisted by Graphene Oxide in an HF-HNO3 Solution and Its Catalytic Mechanism.

Chemical etching of silicon assisted by various types of carbon materials is drawing much attention for the fabrication of silicon micro/nanostructures. We developed a method of chemical etching of silicon that utilizes graphene oxide (GO) sheets to promote the etching reaction in a hydrofluoric acid-nitric acid (HF-HNO3) etchant. By using an optimized composition of the HF-HNO3 etchant, the etching rate under the GO sheets was 100 times faster than that of our HF-H2O2 system used in a previous report. Kinetic analyses showed that the activation energy of the etching reaction was almost the same at both the bare silicon and GO-covered areas. We propose that adsorption sites for the reactant in the GO sheets enhance the reaction frequency, leading to a deeper etching in the GO areas than the bare areas. Furthermore, GO sheets with more defects were found to have higher catalytic activities. This suggests that defects in the GO sheets function as adsorption sites for the reactant, thereby enhancing the etching rate under the sheets.

A Comparative Study of Cytotoxicity of PPG and PEG Surface-Modified 2-D Ti3C2 MXene Flakes on Human Cancer Cells and Their Photothermal Response.

The MXenes are a novel family of 2-D materials with promising biomedical activity, however, their anticancer potential is still largely unexplored. In this study, a comparative cytotoxicity investigation of Ti3C2 MXenes with polypropylene glycol (PPG), and polyethylene glycol (PEG) surface-modified 2-D Ti3C2 MXene flakes has been conducted towards normal and cancerous human cell lines. The wet chemical etching method was used to synthesize MXene followed by a simple chemical mixing method for surface modification of Ti3C2 MXene with PPG and PEG molecules. SEM and XRD analyses were performed to examine surface morphology and elemental composition, respectively. FTIR and UV-vis spectroscopy were used to confirm surface modification and light absorption, respectively. The cell lines used to study the cytotoxicity of MXene and surface-modified MXenes in this study were normal (HaCaT and MCF-10A) and cancerous (MCF-7 and A375) cells. These cell lines were also used as controls (without exposure to study material and irradiation) to measure their baseline cell viability under the same lab environment. The surface-modified MXenes exhibited a sharp reduction in cell viability towards both normal (HaCaT and MCF-10A) and cancerous (MCF-7 and A375) cells but cytotoxicity was more pronounced towards cancerous cell lines. This may be due to the difference in cell metabolism and the occurrence of high pre-existing levels of reactive oxygen species (ROS) within cancerous cells. The highest toxicity towards both normal and cancerous cell lines was observed with PEGylated MXenes followed by PPGylated and bare MXenes. The normal cell’s viability was barely above 70% threshold with 250 mg/L PEGylated MXene concentration whereas PPGylated and bare MXene were less toxic towards normal cells, even at 500 mg/L concentration. Moreover, the toxicity was found to be directly related to the type of cell lines. In general, the HaCaT cell line exhibited the lowest toxicity while toxicity was highest in the case of the A375 cell line. The photothermal studies revealed high photo response for PEGylated MXene followed by PPGylated and bare MXenes. However, the PPGylated MXene’s lower cytotoxicity towards normal cells while comparable toxicity towards malignant cells as compared to PEGylated MXenes makes the former a relatively safe and effective anticancer agent.

Magnetically separable NiFe2O4/Ag3VO4/Ag2VO2PO4 direct Z‐scheme heterostructure with enhanced visible‐light photoactivity

AbstractBACKGROUNDThe occurrence of organic contaminants in surface water has drawn great concern in recent years. The construction of a heterostructure has been shown to improve photoactivity by boosting the separation of photogenerated charge carriers. In this work, magnetically separable NiFe2O4/Ag3VO4/Ag2VO2PO4 (NFO/AVO/AVPO) heterojunction photocatalysts were synthesized via a chemical etching method in ammonia solution of different concentrations, using NFO/AVPO as the source material. The magnetic NFO/AVO/AVPO not only endows magnetic recoverability using an external magnetic field, but also possesses a heterojunction, boosting the separation of photoinduced charges.RESULTSCompared with NFO, AVPO and NFO/AVPO, NFO/AVO/AVPO composites as synthesized show improved visible‐light photoactivities. At the optimum concentration (0.15 mol L−1) of ammonia solution, the NFO/AVO/AVPO shows 8.5 and 10.7 times improved photodegradation efficiency for methylene blue and imidacloprid than that of pristine NFO/AVPO, respectively. Due to the presence of magnetic NiFe2O4, the NFO/AVO/AVPO can be magnetically separated easily from the photoreaction system using a magnet. The improved photoactivity can be attributed to the formation of a direct Z‐scheme heterojunction, which boosts the separation of photoinduced electron–hole pairs.CONCLUSIONThis work not only opens up a new method to fabricate heterojunction photocatalysts, but also paves the way for designing advanced magnetically separable photocatalysts with improved photoactivity. © 2021 Society of Chemical Industry (SCI).

Increasing reliability of forensic analysis while research on destroyed relief marking with magneto-optical devices

While research on destroyed relief marking of metal objects using the magneto-optical method, visualization of (invisible) fields of internal stress in the VIN plate area is performed and then a forensic analysis of obtained instrumental data is carried out (indirect organoleptic observation of the visualization results); thus, forensic analysis reliability of results directly depends on sensitivity of instruments and informativeness of instrumental data.
 The main quantitative characteristic in this case is probability of correct signal recognition (contours of marking signs) against the background of noise (structural noise of investigated surface and the noise of the visualization method itself) determined by the signal-to-noise ratio.
 This article presents results of a comparative experimental assessment of signal-to-noise ratio and probability of correct signal recognition while restoringthe destroyed relief markings for two complexes of magneto-optical imaging – models of 2006 and 2018.
 This article purpose is a quantitative and qualitative comparative assessment of results of visualization of internal stresses in areas of completely removed relief marking of metal objects. The results of successful practical research obtained by forensic experts from different countries make it possible to assess effectiveness and prospects of using the magneto-optical imaging method.
 In a new modification of the magneto-optical complex:
 
 signal level is 4.35 dB higher (contrast of reconstructed marking signs);
 2.71 dB lower noise level (surface relief/texture and magnetic copying noise);• probability of correct character recognition is P> 0.995 (increased by 14.9%).
 
 Technical improvements in implementation of magneto-optical visualization method made it possible to expand the range of materials for research objects(magnetic and electrically conductive materials were investigated).
 The high efficiency of method for restoring marking is illustrated by results of forensic examinations for materials with a low level of residual stresses (aluminum alloy, low-carbon steel) which chemical etching method did not give results for.
 The use of new modification allows examining the rust layer, up to cases of corrosion to the entire depth of marks.
 Considering non-destructive nature of magneto-optical researches, possibility of their repeated repetition without losing object properties, this method (in accordance with the order of application of types of studies) deserves more attention for application.

Ultrathin Silicon Nanowires for Optical and Electrical Nitrogen Dioxide Detection.

The ever-stronger attention paid to enhancing safety in the workplace has led to novel sensor development and improvement. Despite the technological progress, nanostructured sensors are not being commercially transferred due to expensive and non-microelectronic compatible materials and processing approaches. In this paper, the realization of a cost-effective sensor based on ultrathin silicon nanowires (Si NWs) for the detection of nitrogen dioxide (NO2) is reported. A modification of the metal-assisted chemical etching method allows light-emitting silicon nanowires to be obtained through a fast, low-cost, and industrially compatible approach. NO2 is a well-known dangerous gas that, even with a small concentration of 3 ppm, represents a serious hazard for human health. We exploit the particular optical and electrical properties of these Si NWs to reveal low NO2 concentrations through their photoluminescence (PL) and resistance variations reaching 2 ppm of NO2. Indeed, these Si NWs offer a fast response and reversibility with both electrical and optical transductions. Despite the macro contacts affecting the electrical transduction, the sensing performances are of high interest for further developments. These promising performances coupled with the scalable Si NW synthesis could unfold opportunities for smaller sized and better performing sensors reaching the market for environmental monitoring.