Synthesis and studying of reduced few-layered graphene coatings in gas sensor applications

In this work reduced few-layered graphene (rFLG) nanoparticles were synthesized using electrochemical pulse exfoliation method from waste graphite crucibles. The regular change in voltage polarity in the synthesis process ensures both the separation of graphite in layers and the reduction of graphene oxide. A method for synthesizing free-standing rFLG and nitrocellulose (NC) composite film has been developed involving creation of rFLG-NC ink that can be deposited on various substrates. It has been observed that a successful synthesis of a free-standing composite coating is possible with the mass ratio of rFLG:NC at least 9:1 of which resistivity is on the order of approximate 10 ohm-centimetres in dependence from temperature and surrounding atmosphere. Sensor electrode was prepared by simple dip-coating method and the response to humidity, organic solvent vapours and nitrogen containing gases was measured and conclusion made that rFLG-NC coating is sensitive to many kinds of gases (cross-sensitive) what may result in false detecting or can be used to multi-sensor chips for artificial olfaction devices.Latvian Council of Science 2018-1/0194; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Electro-catalytic and photo-catalytic reformation of CO2–reactions and efficiencies processes (Review)

Energy harvesting with lowest environmental impact is one of key elements for cleaner future. Photocatalytic as well as electrocatalytic CO2 reformation processes are considered as prominent methods. Thus, extensive research of CO2 reformation is being done to find the right materials that holds crucial qualities. For photocatalysis that includes pronounced separation of light-generated opposite sign charge carriers, sensitivity to visible light, high quantum yield. In electrocatalysis high CO2 adsorption, chemical stability, multielectron reaction catalysts are necessary. Additionally, materials participating in the reaction process must be provided with charge carriers at proper reduction and oxidation potentials. To meet the set goal of lowering environmental impact and lower CO2 amounts exhausted into the atmosphere by human activities, it is necessary to find right technology for capturing, storing, and reusing carbon dioxide. Various technologies and materials in different levels of readiness are available and under development, such as CuO loaded TiO2 nanotubes for photocatalytic reformation or electrocatalytic reduction on copper. Not only the proof of concept is necessary but estimation and more importantly determination of the efficiency of both electro and photo catalytic reformation of CO2. In this work review of reactions and efficiency of both processes based on existing established technological methods is done.Horizon 2020 Research and Innovation Program 768789; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Cladding-Pumped Er/Yb-Co-Doped Fiber Amplifier for Multi-Channel Operation

The Institute of Solid State Physics, University of Latvia, as a Center of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2. We express our gratitude to rer. nat. Nicoletta Haarlammert from Fraunhofer Institute for Applied Optics and Precision Engineering IOF for the refractive index measurements of ytterbium/erbium-co-doped fibers. This work is supported by the European Regional Development Fund project No. 1.1.1.1/18/A/068.Cladding-pumped erbium (Er3+)/ytterbium (Yb3+)-co-doped fiber amplifiers are more advantageous at high output powers. However, this amplification technique also has potential in telecom-related applications. These types of amplifiers have complex properties, especially when considering gain profile and a pump conversion efficiency. Such metrics depend on the doped fiber profile, absorption/emission spectra, and the input signal power. In this context, we design, build and characterize an inhouse prototype of cladding-pumped Er3+/Yb3+-co-doped fiber amplifier (EYDFA). Our goal is to identify the EYDFA configuration (a co-doped fiber length, pump power, input signal power) suitable for signal amplification in a multichannel fiber-optic transmission system with a dense wavelength allocation across the C-band (1530–1565 nm). Our approach involves experimentally determining the Er3+/Yb3+-co-doped fiber’s parameters to be used in a simulation setup to decide on an initial EYDFA configuration before moving to a laboratory setup. An experimental EYDFA prototype is tested under different conditions using a 48-channel dense wavelength division multiplexing (DWDM, 100 GHz) system to evaluate the absolute gain and gain uniformity. The obtained results allow the cladding pump amplifier’s suitability for wideband signal amplification to be assessed. The developed prototype provides > 21 dB of gain with a 12 dB ripple within 1534–1565 nm. Furthermore, we show that the gain profile can be partially flattened out by using longer EYDF spans. This enhances signal amplification in the upper C-band in exchange for a weaker amplification in the lower C-band, which can be marginally improved with higher pump powers. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.ERDF project No. 1.1.1.1/18/A/068; the Institute of Solid State Physics, University of Latvia, as a Center of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

FIBRE OPTICAL COUPLER SIMULATION BY COMSOL MULTIPHYSICS SOFTWARE

Funding: The research has been supported by the European Regional Development Fund project No.1.1.1.1/18/A/068. The Institute of Solid State Physics, University of Latvia as a Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.The paper presents a simulation model developed for a special optical coupler intended for coupling radiation from signal and pump sources used for the realization of cladding-pumped doped fibre amplifiers. The model is developed in COMSOL Multiphysics and used to assess the pumping efficiency for different side pumping angles and different numbers of electromagnetic modes. The obtained results show that the highest pumping efficiency, above 75 %, is achieved for 5–14 modes when two fibres representing the pump source and the signal source form a 10-degree angle between their central axes. The search for the optimal number of modes corresponds to the development trend in optical coupler technology where the multimode pumping by light-emitting diode (LED) replaces the classical scheme with a single-mode pumping by a laser diode (LD). © 2022 Sciendo. All rights reserved. --//-- This is an open access article Elsts E., Supe A., Spolitis S., Zakis K., Olonkins S., Udalcovs A., Murnieks R., Senkans U., Prigunovs D., Gegere L., Draguns K., Lukosevics I., Ozolins O., Grube J., Bobrovs V. FIBRE OPTICAL COUPLER SIMULATION BY COMSOL MULTIPHYSICS SOFTWARE (2022) Latvian Journal of Physics and Technical Sciences, 59 (5), pp. 3 - 14, DOI: 10.2478/lpts-2022-0036 published under the CC BY-NC-ND 4.0 licence.ERDF No.1.1.1.1/18/A/068; The Institute of Solid State Physics, University of Latvia as a Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

Electrochemical exfoliation-streamline method for synthesis of nitrogen doped graphene

The authors gratefully acknowledge financial support from the Latvian Council of Science, Project LZP FLPP No. LZP-2018/1 0194, and the Institute of Solid State Physics, University of Latvia that as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2026-2017-TeamingPhase2 under Grant Agreement No. 739508, Project CAMART2.Graphene was discovered in the early 21st century, but has already proven itself in many applications – energy, medicine, electronics, food and sports, and more. Functionalization of nanostructured carbon materials with both non-metallic and metallic atoms is possible in various ways, imparting enhanced or new properties to the starting material, even catalytic activity. A method of electrochemical exfoliation was used to obtain the graphene sheets and simultaneously functionalize them with nitrogen. To ensure N-doping the process is done in a NaN3 electrolyte solution which provides less quantity of oxygen groups that tend to block defect sites on the graphene, compared with such solvents as NaNO2. Two graphite electrodes are inserted into the electrolyte and a pulse power of 0–10V is applied. The solution containing the obtained material is filtered through a 0.1 µm filter and dried. The material is characterized using SEM, XRD and XPS. In the XPS characterization graphene oxide is used as a reference material.Latvian Council of Science, Project LZP FLPP No. LZP-2018/1 0194; the Institute of Solid State Physics, University of Latvia that as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2026-2017-TeamingPhase2 under Grant Agreement No. 739508, Project CAMART2