One-Stage Femtosecond Laser-Assisted Deposition of Gold Micropatterns on Dielectric Substrate

In this study, a simple one-stage laser-assisted metallization technique based on laser-induced backside wet etching and laser-induced chemical liquid-phase deposition is proposed. It allows for the fabrication of gold micropatterns inside the laser-written trace on a glass substrate. The reduction and deposition of gold inside and outside the laser-ablated channel were confirmed. The presence of Au nanoparticles on the surface of the laser-written micropattern is revealed by atomic force microscopy. The specific resistivity of the gold trace formed by ultrafast light-assisted metal micropatterning on a dielectric glass substrate is estimated as 0.04 ± 0.02 mΩ·cm. The obtained results empower the method of the selective laser-assisted deposition of metals on dielectrics and are of interest for the development of microelectronic components and catalysts, heaters, and sensors for lab-on-a-chip devices.

Robust metallic micropatterns fabricated on quartz glass surfaces by femtosecond laser-induced selective metallization

Quartz glass has a wide range of application and commercial value due to its high light transmittance and stable chemical and physical properties. However, due to the difference in the characteristics of the material itself, the adhesion between the metal micropattern and the glass material is limited. This is one of the main things that affect the application of glass surface metallization in the industry. In this paper, micropatterns on the surface of quartz glass are fabricated by a femtosecond laser-induced backside dry etching (fs-LIBDE) method to generate the layered composite structure and the simultaneous seed layer in a single-step. This is achieved by using fs-LIBDE technology with metal base materials (Stainless steel, Al, Cu, Zr-based amorphous alloys, and W) with different ablation thresholds, where atomically dispersed high threshold non-precious metals ions are gathered across the microgrooves. On account of the strong anchor effect caused by the layered composite structures and the solid catalytic effect that is down to the seed layer, copper micropatterns with high bonding strength and high quality, can be directly prepared in these areas through a chemical plating process. After 20-min of sonication in water, no peeling is observed under repeated 3M scotch tape tests and the surface was polished with sandpapers. The prepared copper micropatterns are 18 µm wide and have a resistivity of 1.96 µΩ·cm (1.67 µΩ·cm for pure copper). These copper micropatterns with low resistivity has been proven to be used for the glass heating device and the transparent atomizing device, which could be potential options for various microsystems.

Laser-Assisted Surface Modification of Ni Microstructures with Au and Pt toward Cell Biocompatibility and High Enzyme-Free Glucose Sensing

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.

High rate fabrication of copper and copper-gold electrodes by laser-induced selective electroless plating for enzyme-free glucose sensing

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.

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.

Copper and Nickel Microsensors Produced by Selective Laser Reductive Sintering for Non-Enzymatic Glucose Detection

In this work, the method of selective laser reductive sintering was used to fabricate the sensor-active copper and nickel microstructures on the surface of glass-ceramics suitable for non-enzymatic detection of glucose. The calculated sensitivities for these microsensors are 1110 and 2080 μA mM⁻¹·cm⁻² for copper and nickel, respectively. Linear regime of enzymeless glucose sensing is provided between 0.003 and 3 mM for copper and between 0.01 and 3 mM for nickel. Limits of glucose detection for these manufactured micropatterns are equal to 0.91 and 2.1 µM for copper and nickel, respectively. In addition, the fabricated materials demonstrate rather good selectivity, long-term stability and reproducibility.

Laser-Induced Synthesis of Composite Materials Based on Iridium, Gold and Platinum for Non-Enzymatic Glucose Sensing

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 µA/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 µM), a wide linear range (0.5 µM–1 mM) along with good selectivity, reproducibility and stability.

Deposition of Durable Micro Copper Patterns into Glass by Combining Laser-Induced Backside Wet Etching and Laser-Induced Chemical Liquid Phase Deposition Methods

Glass is a well-known non-conductive material that has many useful properties, and considerable research has been conducted into making circuits on glass. Many deposition techniques have been studied, and laser-induced chemical liquid phase deposition (LCLD) is a well-known and cost-effective method for rapid prototyping of copper deposition on glass. However, the deposition results from the LCLD method on the surface of glass, which shows an issue in its detachment from the substrates because of the relatively low adhesion between deposited copper and the nontreated glass surface. This problem undermines the usability of deposited glass in industrial applications. In this study, the laser-induced backside wet etching (LIBWE) method was performed as a preceding process to fabricate microchannels, which were filled with copper by LCLD. Additional durable copper wire was produced as a result of the enhanced adhesion between the glass and the deposited copper. The adhesion was enhanced by a rough surface and metal layer, which are characteristics of LIBWE machining. Furthermore, the proposed method is expected to broaden the use of deposited glass in industrial applications, such as in stacked or covered multilayer structures with built-in copper wires, because the inserted copper can be physically protected by the microstructures.

Glass/Au Composite Membranes with Gold Nanoparticles Synthesized inside Pores for Selective Ion Transport

Nanocomposite membranes have been actively developed in the last decade. The involvement of nanostructures can improve the permeability, selectivity, and anti-fouling properties of a membrane for improved filtration processes. In this work, we propose a novel type of ion-selective Glass/Au composite membrane based on porous glass (PG), which combines the advantages of porous media and promising selective properties. The latter are achieved by depositing gold nanoparticles into the membrane pores by the laser-induced liquid phase chemical deposition technique. Inside the pores, gold nanoparticles with an average diameter 25 nm were formed, which was confirmed by optical and microscopic studies. To study the transport and selective properties of the PG/Au composite membrane, the potentiometric method was applied. The uniform potential model was used to determine the surface charge from the experimental data. It was found that the formation of gold nanoparticles inside membrane pores leads to an increase in the surface charge from −2.75 mC/m² to −5.42 mC/m². The methods proposed in this work allow the creation of a whole family of composite materials based on porous glasses. In this case, conceptually, the synthesis of these materials will differ only in the selection of initial precursors.

The laser writing of highly conductive and anti-oxidative copper structures in liquid

Flexible conductive structures are essential for the fabrication of commercial integrated electronic devices. Developing efficient processes for manufacturing these structures with high conductivity and stability is significant. Based on a modifiable cost-effective Cu-based ionic liquid precursor, here we present an in situ laser patterning technique to manufacture flexible electrodes. The fabricated Cu structure has excellent conductivity, approximately comparable to bulk Cu, while its oxidation resistance could be further enhanced through introducing an additional carbon source to form a Cu@C microstructure. The chemical and electrical stabilities are evaluated. This method provides a possible bottom-up route for manufacturing microelectronic devices in one step, as we demonstrated through a flexible heater.

High rate laser deposition of conductive copper microstructures from deep eutectic solvents

In this communication, the phenomenon of the laser chemical deposition of copper using deep eutectic solvents (DESs) on a dielectric substrate has been shown for the first time. The use of eutectic solvents made it possible to greatly simplify the procedure of metal deposition and increase the deposition rate by more than 150 times compared to the use of aqueous solutions.

In situ laser-induced codeposition of copper and different metals for fabrication of microcomposite sensor-active materials

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.

Solvent Effects on Nonradiative Relaxation Dynamics of Low-Energy Ligand-Field Excited States: A CuCl42- Complex

Nonradiative relaxation dynamics of CuCl₄^2- complexes photoexcited into the highest-energy ligand-field electronic state (²A₁) is studied in acetonitrile, dichloromethane, and chloroform solvents, as well as in acetonitrile-water and in acetonitrile-deuterated water mixtures. Due to ultrafast internal conversion, this excited state directly converts to the electronic ground state in dichloromethane and chloroform. The nonradiative relaxation constant is similar in anhydrous acetonitrile. Addition of water to acetonitrile solutions efficiently quenches the excited ligand-field ²A₁ state. The quenching is proposed to be due to the diffusion-controlled formation of an electronically excited pentacoordinated [CuCl₄H₂O]^2- encounter complex or a short-lived exciplex of similar structure, in which the electronic excitation energy transfers into the O-H stretch of the coordinated H₂O molecule. This is followed by the dissociation of the pentacoordinated species, resulting in the reformation of the ground-state CuCl₄^2- and free H₂O molecules.

Non-enzymatic sensors based on in situ laser-induced synthesis of copper-gold and gold nano-sized microstructures

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.

Ultrafast Photochemistry of Copper(II) Monochlorocomplexes in Methanol and Acetonitrile by Broadband Deep-UV-to-Near-IR Femtosecond Transient Absorption Spectroscopy

Photochemistry of copper(II) monochlorocomplexes in methanol and acetonitrile solutions is studied by UV-pump/broadband deep-UV-to-near-IR probe femtosecond transient absorption spectroscopy. Upon 255 and 266 nm excitation, the complexes in acetonitrile and methanol, respectively, are promoted to the excited ligand-to-metal charge transfer (LMCT) state, which has a short (sub-250 fs) lifetime. From the LMCT state, the complexes decay via internal conversion to lower-lying ligand field (LF) d-d excited states or the vibrationally hot ground electronic state. A minor fraction of the excited complexes relaxes to the LF electronic excited states, which are relatively long-lived with lifetimes >1 ns. Also, in methanol solutions, about 3% of the LMCT-excited copper(II) monochlorocomplexes dissociate forming copper(I) solvatocomplexes and chlorine atoms, which then further react forming long-lived photoproducts. In acetonitrile, about 50% of the LMCT-excited copper(II) monochlorocomplexes dissociate forming radical and ionic products in a ratio of 3:2. Another minor process observed following excitation only in methanol solutions is the re-equilibration between several forms of the copper(II) ground-state complexes present in solutions. This re-equilibration occurs on a time scale from sub-nanoseconds to nanoseconds.