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Here, we propose a novel approach to the classification of blue ballpoint pen inks based on a combination of selective extraction of coloring components from a paper carrier, digital color analysis (DCA) of the remaining traces, and hierarchical cluster analysis of DCA results. Since most documents of high importance are still produced in hard copies, the proposed method, being highly time- and cost-efficient, could be a significant contribution to forensic science in the field of authenticating handwritten documents. Several commonly used solvents were applied in parallel as extractants to the replicate strokes produced by each pen. It turned out to be possible to limit the number of extractants required for an unambiguous classification to three. We have shown that the optimal descriptor for agglomerative clustering is the colorimetric distance between the original and extracted ink traces in the RGB color space. Five separate clusters of inks that are independent of sample storage temperature were obtained from a set of 16 different pens. This conclusion was further confirmed by the analysis of principal components. The developed DCA-based data processing pipeline outperformed the clustering based on the data of high-performance liquid chromatography in terms of versatility providing a more informative analysis with respect to the inks based on the phthalocyanine dyes.

In this work, we proposed a rapid single-stage laser-induced fabrication of bimetallic micro-patterns on an oxide glass surface using deep eutectic solvents (DESs) consisting of choline chloride, citric acid along with nickel, copper and cobalt acetates as metallization solutions. The resulting bimetallic micropatterns were tested as working electrodes for non-enzymatic determination of dopamine. The linear range for dopamine detection was found to be 1–500 µM, with a sensitivity of 340.4 µA mM−1 and 615.2 µA mM−1 and a detection limit of 0.36 µM and 0.51 µM for Ni-Cu and Ni-Co sensor, respectively. For the first time, bimetallic Ni-Cu and Ni-Co structures have been obtained from DESs for high-performance dopamine detection with great potential for further application in non-enzymatic sensing and biosensing.

The precise control of nanostructure and surface atomic arrangement can be used to tune the electrocatalytic properties of materials and improve their performance. Unfortunately, the long-term structural stability of electrocatalysts with complex nanoscale morphology, a necessary requirement for industrial implementation, often remains elusive. Here we study how electrochemical and complex current behaviours affect the nanoscale object and its structural stability during electrocatalysis. We find that metal electromigration can drive structural transformation during electrolysis to minimize current crowding in nanoscale geometric constrictions. This electrical phenomenon, acting in combination with electrochemically induced atomic migration, can result in specific structural transformations of the catalyst, with the extent and rate depending on the material, geometry and reaction. Using a series of nanostructure examples, we establish a general framework for evaluating the structural transformations in cathodic metal nanocatalysts and explain specific qualitative trends. In conjunction with catalyst design rules, this mechanistic framework will facilitate the development of nanostructured electrocatalysts with sufficient stability for sustainable applications. The structural stability of electrocatalysts with complex nanoscale morphology, a requirement for their industrial implementation, often remains elusive. Now, a combination of electrical and electrochemical effects is shown to drive specific structural transformations of the catalyst during electrolysis.

Fabrication of the conductive copper structures on the surface of various dielectric materials is quite important in many fields of science. There are a lot of chemical and physical methods and approaches that can be used for this purpose. Recently, we demonstrated the possibility of performing laser-assisted deposition of copper using deep eutectic solvents (DESs). The use of DESs instead of aqueous solutions allowed increasing the deposition rate by more than 100 times. In this work, for the first time, the influence of different chemical parameters, such as nature of deep eutectic solvent and concentration of copper, as well as physical parameters, including the intensity of laser radiation and the scanning speed, on the process of copper deposition was investigated. We experimentally showed and confirmed theoretically that the use of citric and tartaric acids such as DES components provides conditions for the formation of copper micropatterns with predefined characteristics.

In this work, we reported in situ laser-induced synthesis of sensor-active copper‑silver microcomposite. This bimetallic microelectrode exhibits highly developed surface area and good electrical conductivity, and can be successfully used for glucose and alanine sensing demonstrating decent sensitivity (31,000 μА cm−2 mМ−1 for d -glucose and 11,177 μА cm−2 mМ−1 for l -alanine) and low limit of detection (2.8 μM for d -glucose and 0.83 μM for l -alanine). High sensor activity and good electrochemical characteristics of the synthesized material can be associated with the eutectic type of the Cu-Ag system. The implemented technique is quite useful for fabrication of new promising small size sensors for enzymeless determination of different biological analytes.

We investigated the influence of morphology of Ni microstructures modified with Au and Pt on their cell biocompatibility and electrocatalytic activity toward non-enzymatic glucose detection. Synthesis and modification were carried out using a simple and inexpensive approach based on the method of laser-induced deposition of metal microstructures from a solution on the surface of various dielectrics. Morphological analysis of the fabricated materials demonstrated that the surface of the Ni electrode has a hierarchical structure with large-scale 10 μm pores and small-scale 10 nm irregularities. In turn, the Ni-Pt surface has large-scale cavities, small-scale pores (1-1.5 μm), and a few tens of nanometer particles opposite to Ni-Au that reveals no obvious hierarchical structure. These observations were supported by impedance spectroscopy confirming the hierarchy of the surface topography of Ni and Ni-Pt structures. We tested the biocompatibility of the fabricated Ni-based electrodes with the HeLa cells. It was shown that the Ni-Au electrode has a much better cell adhesion than Ni-Pt with a more complex morphology. On the contrary, porous Ni and Ni-Pt electrodes with a more developed surface area than that of Ni-Au have better catalytic performance toward enzymeless glucose sensing, revealing greater sensitivity, selectivity, and stability. In this regard, modification of Ni with Pt led to the most prominent results providing rather good glucose detection limits (0.14 and 0.19 μA) and linear ranges (10-300 and 300-1500 μA) as well as the highest sensitivities of 18,570 and 2929 μA mM-1 cm-2. We also proposed some ideas to clarify the observed behavior and explain the influence of morphology of the fabricated electrodes on their electrocatalytic activity and biocompatibility.

We report here a simple and cost-effective technique for classification of the samples of writing inks based on their digital color analysis (DCA). The dynamics of artificial aging of writing inks under UV irradiation was studied by means of DCA for the first time. The color of ballpoint pen marks was recorded over time using an ordinary consumer DSLR camera. The inks were classified according to the parameters of their color degradation curves with precision superior to conventional Raman scattering method, which serves as a proof-of-concept of the proposed approach. The reported approach has broad prospects for implementation by criminalists for document investigation when document forgery is suspected. The proposed technique can be of interest not only in the field of forensic science but also for those who deal with dyes and dye-containing materials and their degradation over time as well as for the study of any processes, the evolution of which is reflected in a color change.

In the current study, the method of Selective Surface Activation Induced by Laser (SSAIL) was used for the fabrication of metallic and bimetallic structures based on copper and gold on the surface of glass and glass-ceramics. It was shown that the fabricated electrodes are suitable for non-enzymatic detection of biologically essential analytes such as glucose. The implemented approach allows performing high-rate metallization of various dielectrics. Voltammetric methods were applied to evaluate the electrocatalytic activity of the obtained structures, which were used as working electrodes. The most promising results were revealed by copper–gold electrode structures manufactured on glass-ceramics. For these structures, sensitivity towards glucose sensing was 3060 μA mM−1 cm−2. The linear range of glucose detection varied between 0.3 and 1000 μM. Besides, the manufactured electrodes exhibited high selectivity and long-term stability.

We synthesized highly-developed bimetallic micro-and nanostructures applicable for non-enzymatic sensing of biologically important analyte. In this regard, for the fabrication of sensor-active small size electrodes, we use a simple and cheap approach based on in situ laser-induced deposition of metals on the surface of glass-ceramics substrate, whereas investigation of electrochemical and electrocatalytic properties was studied using cyclic voltammetry and amperometry

A simple approach for in situ laser-induced modification of iridium-based materials to increase their electrocatalytic activity towards enzyme-free glucose sensing was proposed. For this purpose, we deposited gold and platinum separately and as a mixture on the surface of pre-synthesized iridium microstructures upon laser irradiation at a wavelength of 532 nm. Then, we carried out the comparative investigation of their morphology, elemental and phase composition as well as their electrochemical properties. The best morphology and, as a result, the highest sensitivity (~9960 &micro, A/mM cm2) with respect to non-enzymatic determination of D-glucose were demonstrated by iridium-gold-platinum microstructures also showing low limit of detection (~0.12 &micro, M), a wide linear range (0.5 &micro, M&ndash, 1 mM) along with good selectivity, reproducibility and stability.

Plasmonic metal nanostructures with complex morphologies provide an important route to tunable optical responses and local electric field enhancement at the nanoscale for a variety of applications including sensing, imaging, and catalysis. Here we report a high-concentration synthesis of gold core-cage nanoparticles with a tethered and structurally aligned octahedral core and examine their plasmonic and catalytic properties. The obtained nanostructures exhibit a double band extinction in the visible-near infrared range and a large area electric field enhancement due to the unique structural features, as demonstrated using finite difference time domain (FDTD) simulations and confirmed experimentally using surface enhanced Raman scattering (SERS) tests. In addition, the obtained structures had a photoelectrochemical response useful for catalyzing the CO2 electroreduction reaction. Our work demonstrates the next generation of complex plasmonic nanostructures attainable via bottom-up synthesis and offers a variety of potential applications ranging from sensing to catalysis.

In the current paper, in situ laser-induced synthesis of gas sensing microcomposites based on molybdenum and its oxides is discussed. The influence of pH of the solutions used for deposition and optical characteristics of a dielectric substrate on electrical conductivity and sensor properties of the synthesized microdeposits is also studied. It was shown that the phase distribution in the obtained materials is consistent with temperature level in the thermal zones of the laser beam focused on the surface of a dielectric substrate of different type. In turn, highly developed surface area of these microsensors is directly responsible for their high sensitivity, short response time, and low temperature of regeneration with respect to hydrogen sulfide and ammonia. Indeed, the highest sensitivity was observed for detection of small concentration (≤50 ppm) of hydrogen sulfide at temperatures of 300–350 °C, whereas at temperatures of 300 °C or less, the deposited molybdenum-containing microstructures are applicable for the ammonia sensing. Thus, this work demonstrates that the method of laser-induced metal deposition is a promising and perspective approach for fabrication of new effective standalone micro-sized gas sensors.

We carried out highly rapid laser-assisted deposition of conductive nickel microstructures on the surface of oxide glass from a deep eutectic solvent (DES). The implementation of deep eutectic solvents may significantly simplify the experimental procedure and drastically increase the deposition rate by more than 150 times in opposite to those observed for laser deposition from the aqueous solutions. It was shown that these structures exhibit promising electrocatalytic performance toward enzyme-free dopamine and acetaminophen sensing, including good sensitivity, low limit of detection and broad linear ranges.

The conditions for synthesis of conductive copper and nickel microstructures using laser-induced deposition technique were determined and electrocatalytic activity of these materials towards D-glucose was investigated. It was found out that formation of these conductive electrodes upon laser irradiation occurs only in solutions containing OH- coordinating ligands. Coordination via other functional groups (including carboxyl and amino) does not lead to synthesis of conductive structures. Topology and composition of copper and nickel deposits were observed using scanning electron microscopy and EDX analysis, respectively. The electrochemical properties of the synthesized structures were studied using cyclic voltamperometry and amperometry. The studied materials display linear dependencies of the Faraday current vs. concentration between 2 µM and 1.1 mM for nickel and 0.25 mM and 3 mM for copper.

We report one-step synthesis of carbon-based microstructures on the surface of polyimide by using the 2D direct laser writing technique. It was shown that the properties of obtained conductive structures can be tuned by varying the conditions of the laser synthesis (scanning speed, laser power). The fabricated materials exhibited high electrochemical activity towards d-glucose measured by cyclic voltammetry analysis (limit of detection—0.564 μM and 6.31 μM for different linear ranges). Comparatively high sensing activity of the synthesized structures makes them promising materials for flexible non-enzymatic biosensing devices.

In this work we study the influence of l-(+)-КNaC4H4O6 × 4H2O (KNaT) and l-H2C4H4O6 (H2T) on the complexation processes occurring during in situ laser-induced catalytic destruction of the organic components of the aqueous solutions with formation of the unsaturated hydrocarbons. For that purpose, ATR-FTIR, Raman, IR, and NIR spectroscopy as well as quantum chemical calculations were implemented. It was observed that hydration of T2− anion via carboxylate groups is stronger than that via hydroxyl groups. We also established the changes in the spectral characteristics of the absorption bands corresponding to vibrations of T2−, HT−, and H2T, at solid state-liquid and acid-salt transitions, depending on concentration of the solution components and the [OH−]/[H2T] ratio. Finally, it was shown that ethylene is a main product of the catalytic destruction of the copper tartrate complexes.

In this work, we propose the promising approach that provides conditions for laser-induced ex situ synthesis of Raney-like copper-based nanostructured catalysts. Their catalytic activity and selectivity were investigated in Cu-catalyzed acetylene homo-coupling, Pd/Cu-catalyzed the Sonogashira cross-coupling and Cu-catalyzed azide-alkyne cycloaddition (CAAC). It was found that the growth of particles generated within the focus of the laser beam can last even if laser irradiation is off and can be controlled by adding phenanthroline to the reaction mixture as the stabilizing ligand or by increasing its temperature and concentration. Particle size of the synthesized copper-based catalysts significantly affects the reaction selectivity. Thus, it is possible to manage the course of the catalytic reaction towards formation of either homo-coupling or cross-coupling products by changing the size of the catalytically active copper-containing particles produced during laser-induced synthesis.

In this paper, we propose a fast and simple approach for the fabrication of the electrocatalytically active ruthenium-containing microstructures using a laser-induced metal deposition technique. The results of scanning electron microscopy and electrical impedance spectroscopy (EIS) demonstrate that the fabricated ruthenium-based microelectrode had a highly developed surface composed of 10 &mu, m pores and 10 nm zigzag cracks. The fabricated material exhibited excellent electrochemical properties toward non-enzymatic dopamine sensing, including high sensitivity (858.5 and 509.1 &mu, A mM&minus, 1 cm&minus, 2), a low detection limit (0.13 and 0.15 &mu, M), as well as good selectivity and stability.

We report one-step in situ laser-induced synthesis of the conductive copper microstructures doped with iron, zinc, nickel, and cobalt with highly developed surface area. It was observed that the presence of chlorides of the aforementioned metals in the solutions used in our experiments increases the deposition rate and the amount of copper in the resulting deposits; it also leads to the deposit miniaturization. The laser deposition from solutions containing cobalt (II) chloride of concentration more than 0.003 M results in fabrication of copper microelectrode with better electrochemical properties than those deposited from solutions containing chlorides of other metals of the same concentration. Moreover, copper microelectrode doped with cobalt has demonstrated good reproducibility and long-run stability as well as sensitivity and selectivity towards determination of hydrogen peroxide (limit of detection-0.2 μM) and d -glucose (limit of detection-2.2 μM). Thus, in this article we have shown the opportunity to manufacture two-phase microcomposite materials with good electrical conductivity and electrochemical characteristics using in situ laser-induced metal deposition technique. These materials might be quite useful in development of new perspective sensors for non-enzymatic detection of such important analytes as hydrogen peroxide and glucose.

The method of laser-induced metal deposition from solution was applied in the continuous in situ laser generation of metal copper catalysts for model organic synthesis reactions. The gas phase products producing during laser-induced copper deposition were analyzed by mass spectrometry whereas solutions used for the copper deposition were investigated before and after laser irradiation using chromato-mass spectrometry and NMR spectroscopy. It was found out that the catalysis of the studied organic reactions by metal catalysts generated during laser deposition process occurs only upon laser irradiation of the reaction mixture.

The simple and cheap method for fabrication of micro-sized electrochemical electrodes was proposed. The porous copper microstructures synthesized by laser-induced metal deposition technique were used as an indicator electrode, whereas a bulk polycrystalline copper with similar geometric parameters was used as an etalon electrode. The electrochemical properties of these electrodes were studied by cyclic voltammetry and impedance spectroscopy. The surface of the deposited copper structures was investigated by X-ray photoelectron spectroscopy and atomic force microscopy. An analytical response of the fabricated copper electrode is 15 times higher than those observed for a pure bulk copper. A study of sensory characteristics for hydrogen peroxide and d-glucose detection showed that the value of Faraday current at the fabricated copper electrode is 2–2.5 orders of magnitude higher than for etalon one.

The synthesis of conductive gold and copper-gold microstructures with high developed surface based on the method of laser-induced metal deposition from solution was developed. The topology and crystallization phase of these structures were observed by means of scanning electron microscopy and X-ray diffraction, respectively. The electrochemical properties of the synthesized materials were investigated using cyclic voltamperometry and amperometry. According to the obtained results, it was found out that copper-gold microstructures demonstrate a linear dependence of Faraday current vs. concentration from 0.025 to 5µM for D-glucose and from 0.025 to 10µM for hydrogen peroxide. In turn, gold deposit exhibits a linear dependence of Faraday current vs. concentration from 0.025 to 50µM for D-glucose and from 0.025 to 1µM for hydrogen peroxide. Moreover, the synthesized materials reveal low detection limits (0.025µM) with respect to the aforementioned analytes, which is quite promising for their potential application in design and fabrication of new non-enzymatic biosensors.

Nanostructured nickel deposits can be applied in hydrogenation reactions catalysis and electrochemical systems development. Laser-induced liquid-phase metal deposition allows creating microscaled nickel structures with a developed surface. In this paper a possibility of abandoning technologically imperfect plating solutions containing various reducing agents such as hypophosphite, boron hydride is shown. Deposition was conducted from solutions only containing nickel salt and various organic ligands which allow avoiding phosphorus and boron codeposition. Influence of ligand nature, ligand concentration and solution pH on laser deposition results was studied. Obtained deposits were researched using SEM, EDX, XRD methods.