Raimonds Meija

University of Latvia | LU · Institute of Chemical Physics

This work presents the synthesis of novel copper oxide–multiwalled carbon nanotube (CuO–MWCNT) hybrid nanostructured composites and a systematic study of their thermoelectric performance at near-room temperatures as a function of MWCNT wt% in the composite. The CuO–MWCNT hybrid nanostructured composites were synthesized by thermal oxidation of a th...

Bi 2 Se 3 , MXenes, and SWCNTs are promising potential alternatives to replace the conventional graphite in the anodes of lithium-ion batteries (LIBs) and enhance their performance. However, all these materials have drawbacks,...

This work is devoted to the development of epoxy-encapsulated zinc oxide-multiwalled carbon nanotubes (ZnO–MWCNT) hybrid nanostructured composites and the investigation of their thermoelectric performance in relation to the content of MWCNTs in the composite. For the preparation of nanocomposites, self-assembling Zn nanostructured networks were coa...

This study focuses on the surface engineering of binder‐free anodes composed of Bi, Se, Cu, and carbon nanotubes to enhance lithium‐ion batteries. The anodes synthesized in this study showed promising electrochemical properties. However, issues with cycle stability, operational speed, and solid electrolyte interface (SEI) formation affected their o...

Electrochemical impedance spectroscopy was applied for studying copper oxide (CuO) nanowire networks assembled between metallic microelectrodes by dielectrophoresis. The influence of relative humidity (RH) on electrical characteristics of the CuO nanowire-based system was assessed by measurements of the impedance Z . A slight increase of Z with inc...

The changes in global energy trends and the high demand for secondary power sources, have led to a renewed interest in aqueous lithium-ion batteries. The selection of a suitable anode for aqueous media is a difficult task because many anode materials have poor cycling performance due to side reactions with water or dissolved oxygen. An effective me...

In recent years, aqueous rechargeable lithium-ion batteries (ARLIBs) have attracted at- tention as an alternative technology for electrical storage. One of the perspective battery anode materials for application in ARLIBs is Bi2Se3, which has already shown good perspectives in the application of conventional lithium-ion batteries (LIBs) that use or...

Arrays of aligned carbon nanotubes (CNTs) are anisotropic nanomaterials possessing a high length-to-diameter aspect ratio, channels passing through the array, and mechanical strength along with flexibility. The arrays are produced in one step using aerosol-assisted catalytic chemical vapor deposition (CCVD), where a mixture of carbon and metal sour...

Bi2Se3 thin films are widely studied as topological insulators and as prospective materials for thermoelectric and sensor applications. Storage of films under ambient conditions, especially at different humidities, may influence the physical properties of thin films. In the present work, electrochemical impedance spectroscopy is used to investigate...

Due to their layered structure and high theoretical capacity, bismuth chalcogenides have been proposed as anodes in organic electrolyte Li- and Na-ion batteries. On the other hand, their electrochemical properties in aqueous systems have not been reported. Here, the electrochemical performance of Bi2Se3 thin films in 1 M NaNO3 aqueous electrolyte i...

Nanoelectromechanical (NEM) switches are potential candidates for memory and logic devices for low standby-current and harsh environment applications. Cryogenic operation of these devices would allow to use them, e.g., in space probes and in conjunction with quantum computers. Herein, it is demonstrated that cryogenic application requirements such...

Dielectrophoresis is used to assemble nanowires between metallic electrodes to form scalable functional interconnects. The dielectrophoresis parameters are investigated for semiconductor copper oxide (CuO) nanowires that are desirable for energy conversion and storage, gas sensors and nanoelectromechanical systems. Experimental yields of multiple-...

Environmental pollution with contaminants of emerging concern (CECs) is a worldwide problem that is receiving increasing attention. Although these substances have been released in the aquatic environment for a long time, wastewater treatment plants are still incapable of removing emerging contaminants completely. Consequently, trace metals, metallo...

Electrostatically actuated nanoelectromechanical (NEM) switches hold promise for operation with sharply defined ON/OFF states, high ON/OFF current ratio, low OFF state power consumption, and a compact design. The present challenge for the development of nanoelectromechanical system (NEMS) technology is fabrication of single nanowire based NEM switc...

Size distribution, Young’s moduli and electrical resistivity are investigated for CuO nanowires synthesized by different thermal oxidation methods. Oxidation in dry and wet air were applied for synthesis both with and without an external electrical field. An increased yield of high aspect ratio nanowires with diameters below 100 nm is achieved by c...

In the present work, a catalyst-free physical vapour deposition method is used to synthesize high yield of Bi2Se3 nanoribbons. By replacing standard glass or quartz substrates with aluminium covered with ultrathin porous anodized aluminium oxide (AAO), the number of synthesized nanoribbons per unit area can be increased by 20–100 times. The mechani...

Germanium tin (GeSn) has been proposed as a promising material for electronic and optical applications due to the formation of a direct band-gap at a Sn content >7 at%. Furthermore, the ability to manipulate the properties of GeSn at the nanoscale will further permit the realisation of advanced mechanical devices. Here we report for the first time...

Electrostatically actuated nanobeam-based electromechanical switches have shown promise for versatile novel applications, such as low power devices. However, their widespread use is restricted due to poor reliability resulting from high jump-in voltages. This article reports a new method for lowering the jump-in voltage by inducing mechanical oscil...

In the Duchy of Courland and Semigallia, corresponding to the southern and western parts of present-day Latvia, an iron industry based on blast-furnace technology, mainly using local bog iron ore, existed in the 17th and 18th centuries. Transfer of knowledge and skill through the recruitment of specialists from other countries of Europe was crucial...

The formation conditions of limonite, often iron-oxide and hydroxide containing mineraloids can be related to the crystallisation process of iron oxides minerals in weathering crust sedimentation. Iron oxides (goethite, hematite) and their various admixtures form lithification compounds. The research involved the analysis of limonite concretions an...

Spherical-shape cryoconite holes, carrying dark coloured material, occur on glacier surfaces and have been studied worldwide. Here, we focus on fine-grained mineral material of the cryoconite holes from the Greenland ice sheet, which is related to the ablation zone of the Russell Glacier, southwest Greenland. Since in this area, quartz is abundant...

This review summarizes relevant research in the field of electrostatically actuated nanobeam-based nanoelectromechanical (NEM) switches. The main switch architectures and structural elements are briefly described and compared. Investigation methods that allow for exploring coupled electromechanical interactions as well as studies of mechanically or...

Electrical properties of Bi 2 S 3 nanowires grown using a single source precursor in anodic aluminum oxide templates are sensitive to the relative humidity in an inert gas environment. Dynamic sensing dependency is obtained and shows presence of spontaneous resistance switching effect between low and high relative humidity states. Employing the the...

The western ablation zone of the Greenland ice sheet is darker than the surrounding ice, because a higher amount of fine-grained particles, known as a cryoconite, occur. To date, biotic cryoconite components have gained a lot of attention, in contrast with mineral components, which have been studied to a limited extent. In this study, fine-grained...

It is assumed that close to the margins of ice-sheets, glacial, fluvial and aeolian processes overlap, and combined with weathering processes, produce numer- ous sediments, in which quartz is a common mineral. Quartz grains, if available, may serve as a powerful tool in determining the depositional history, transportation mode and postdepositional...

We report a strong tangential component of the reaction force at electrode to nanowire adhesive contact which was previously established using electrostatic attraction. The reaction force tangential component absolute value was found to be comparable to or even bigger than the corresponding normal component. This effect is important for understandi...

An electrostatically induced resonance behaviour of individual topological insulator Bi₂Se₃ nanoribbons grown by a catalyst free vapour-solid synthesis was studied in-situ by scanning electron microscopy. It was demonstrated that the relation between the resonant frequencies of vibrations in orthogonal planes can be applied to...

Carbon-based three-dimensional aerographite networks, built from interconnected hollow tubular tetrapods of multilayer graphene, are ultra-lightweight materials recently discovered and ideal for advanced multifunctional applications. In order to predict the bulk mechanical behaviour of networks it is very important to understand the mechanics of th...

Supplementary Figures, Supplementary Notes and Supplementary References

Second type of in situ experiment showing the formation of a buckling-hinge in a single AG tube clamped between two gold tips.

FEM simulation corresponding to the experiment shown in Supplementary Video 4

FEM simulation corresponding to the experiment shown in Supplementary Video 1

FEM simulation of tetrapod test in compression with sliding boundary conditions.

First type of in situ experiment showing the formation of a buckling-hinge at the central joint of a tetrapod with three arms fixed at a substrate and one being bent by an AFM cantilever. This video was used as basis for the curves shown in figures 2 and 3 in the main text.

FEM simulation of tetrapod test in compression with fixed boundary conditions.

FEM simulation of tetrapod test in tension with fixed boundary conditions.

FEM simulation of tetrapod test in tension with sliding boundary conditions.

In modern glacial environment ice acts as a weathering agent, triggering rock disintegration and preferentially producing quartz grains (Schwamborn et al., 2012). These grains are considered as recording the history and processes to which they have been exposed during sediment transportation and after deposition (Konopinski et al., 2012). In this s...

In this work, stoichiometric separate bismuth selenide (Bi2Se3) nanoplates and continuous Bi2Se3 coatings are synthesized on graphene substrate by catalyst-free vapor–solid deposition method. The orientation of synthesized nanoplates relative to the substrate surface varies from heteroepitaxial (planar) to oriented under different angles (non-plana...

In this study we address the mechanical properties of Sb2S3 nanowires and determine their Young's modulus using in situ electric-field-induced mechanical resonance and static bending tests on individual Sb2S3 nanowires with cross-sectional areas ranging from 1.1·10(4) nm(2) to 7.8·10(4) nm(2). Mutually orthogonal resonances are observed and their o...

Bismuth sulfide (Bi2S3) nanowires were grown in porous aluminium oxide template and a selective chemical etching was applied to transfer the nanowires to a solution. Well aligned nanowire arrays were assembled on pre-patterned silicon substrates employing dielectrophoresis. Electron beam lithography was used to connect aligned individual nanowires...

We present an investigation of contact properties of a germanium (Ge) nanowire based nanoelectromechanical (NEM) switch in its ON state. The contact stiffness in the ON state was evaluated by detecting the nanowire's resonance frequency. It was found that the resonance frequency increases when electric current flows through the nanowire/counter ele...

Alkylresorcinols (ARs) are phytochemicals mainly associated with rye/wheat bran. Plasma ARs and their plasma and urine metabolites are considered as biomarkers for whole-grain rye/wheat intake. However ARs metabolite day and night variations have not been studied in prostate cancer patients yet. We investigated ARs metabolites 3, 5-dihydroxy-benzoi...

We present a systematic study of membrane structure (pore diameter and arrangement) in anodized aluminum oxide (AAO) layers obtained by anodization voltages 8–20 V in sulfuric and 15–40 V in oxalic acid electrolyte solutions. Anodization of bulk aluminum in sulfuric acid at 10 V potential was found to be optimal for production or ultrathin freestan...

Recently, several research groups presented bistable two-terminal nanoelectromechanical switches based on individual single-clamped active element. All presented devices had one input electrode. Similar devices having two or more input electrodes have not been yet investigated. In this work we present the two-input bistable controlled nanoelectrome...

A unique two-source controlled nanoelectromechanical switch has been assembled from individual, single-clamped Ge nanowires. The switching behaviour was achieved by superimposing the control signals of specific frequencies to the electrostatic potential of the output terminals, eliminating the need for an additional gate electrode. Using an in situ...

Recently, nanoelectromechanical systems (NEMS) have attracted much attention due to their unique properties and possible applications that differ greatly from those of microelectromechanical systems. NEMS operating frequencies may achieve giga- and terahertz levels and their power consumption and heat capacity is extremely low. Moreover, integratio...