Luka Pirker

The Czech Academy of Sciences | AVCR

This review delves into the intricacies of the interfaces formed between two-dimensional (2D) materials and metals, exploring a realm rich with fundamental insights and promising applications. Historically, our understanding of 2D materials emanated from studies employing dielectric substrates or suspended samples. However, integrating metals in th...

Several biopersistent high aspect ratio nanomaterials show pronounced pathogenic effects, from chronic lung inflammation and fibrosis to cancer. For example, asbestos fibers are classified as carcinogens, whereas the carcinogenicity of highly inflammatory multi-wall carbon nanotubes (MWCNTs), and TiO2 nanomaterials is still being evaluated. The exa...

In this work, we demonstrate selected optimization changes in the simple design of filtration masks to increase particle removal efficiency (PRE) and filter quality factor by combining experiments and numerical modeling. In particular, we focus on single-layer filters fabricated from uniform thickness fibers and double-layer filters consisting of a...

The optoelectronic properties of two-dimensional (2D) atomically thin transition metal di-chalcogenides (TMDCs) are predominantly governed by excitons and their interaction with lattice and various physical fields. Therefore, it is essential to understand the role played by excitons in the light-matter interaction processes. We introduce sulphur is...

Pollutants and infectious diseases can spread through air with airborne droplets and aerosols. A respiratory mask can decrease the amount of pollutants we inhale and it can protect us from airborne diseases. With the onset of the COVID-19 pandemic, masks became an everyday item used by a lot of people around the world. As most of them are for a sin...

Molybdenum disulfide nanoribbons and nanotubes are quasi‐one dimensional semiconductors with strong spin‐orbit interaction, a nanomaterial highly promising for quantum electronic applications. Here, we demonstrate that a bismuth semimetal layer between the contact metal and this nanomaterial strongly improves the properties of the contacts. Two‐poi...

Transition metal dichalcogenide (TMDC) nanotubes complement the field of low‐dimensional materials with their quasi‐1D morphology and a wide set of intriguing properties. By introducing different transition metals into the crystal structure, their properties can be tailored for specific purpose and applications. Herein, the characterization and a s...

Molybdenum disulfide nanoribbons and nanotubes are near-one dimensional semiconductors with strong spin-orbit interaction, a nanomaterial highly promising for quantum electronic applications. Here, we demonstrate that a bismuth semimetal layer between the contact metal and this nanomaterial strongly improves the properties of the contacts. Two-poin...

Fireworks pollute the local atmosphere with various air pollutants, which can pose a health hazard for the local population. Mass and number concentrations of aerosols were measured before, during, and after the 2016/2017 New Year event in Ljubljana, Slovenia. Our findings highlight the negative impact of fireworks on the environment. First, both t...

There exists a lack of aerosol absorption measurement techniques with low uncertainties and without artefacts. We have developed the two-wavelength Photothermal Aerosol Absorption Monitor (PTAAM-2λ), which measures the aerosol absorption coefficient at 532 and 1064 nm. Here we describe its design, calibration and mode of operation and evaluate its...

Four distinct tungsten suboxide (WO 3-x ) nanomaterials were synthesized via chemical vapour transport reaction and the role of their crystal structures on the optical properties was studied. These materials grow either as thin, quasi-2D crystals with the W n O 3n-1 formula (in shape of platelets or nanotiles), or as nanowires (W 5 O 14 , W 18 O 49...

While WO3 is one of the most studied metal-oxides in bulk, it is increasingly gaining interest as a two-dimensional (2D) material as it exhibits different behaviour compared to bulk. In addition, many substoichiometric WO3–x (0≤x≤1) phases exist both in bulk and 2D form. These Magneli phases have different physical and chemical properties than thei...

Because the SARS-CoV-2 virus primarily spreads through droplets and aerosols, a protective box could provide adequate protection by shielding medical professionals during the intubation and extubation procedures from generated droplets and aerosols. In this study, size- and time-dependent aerosol concentrations were measured inside and outside the...

WnO3n−1 nanotiles, with multiple stoichiometries within one nanotile, were synthesized via the chemical vapour transport method. They grow along the [010] crystallographic axis, with the thickness ranging from a few tens to a few hundreds of nm, with the lateral size up to several µm. Distinct surface corrugations, up to a few 10 nm deep appear dur...

The objective of this study was to explore the possible use of a new combination of two excipients, i.e., nanocrystalline cellulose (NCC) and macroporous silica (MS), as matrix materials for the compounding of dry emulsion systems and the effects these two excipients have on the characteristics of dry emulsion powders produced by the spray drying p...

The metallic-associated adverse local tissue reactions (ALTR) and events accompanying worn-broken implant materials are still poorly understood on the subcellular and molecular level. Current immunohistochemical techniques lack spatial resolution and chemical sensitivity to investigate causal relations between material and biological response on su...

A one-step method for plasma synthesis of nitrogen-doped carbon nanomesh is presented. The method involves a molten polymer, which is a source of carbon, and inductively coupled nitrogen plasma, which is a source of highly reactive nitrogen species. The method enables the deposition of the nanocarbon layer at a rate of almost 0.1 µm/s. The deposite...

During the Covid-19 pandemic, face masks have become our daily companions. Masks were used for protection as early as antiquity. For example, the Romans knew that masks made of animals' bladders protected wearers from poisonous particles while working in mines. Over the centuries, masks have been used for other purposes as well but it was only in t...

Size- and time-dependent particle removal efficiency (PRE) of different protective respiratory masks were determined using a standard aerosol powder with the size of particles in the range of an uncoated SARS-CoV-2 virus and small respiratory droplets. Number concentration of particles was measured by a scanning mobility particle sizer. Respiratory...

Ionizing radiation has been identified as an option for sterilization of disposable filtering facepiece respirators in situations where the production of the respirators cannot keep up with demand. Gamma radiation and high energy electrons penetrate deeply into the material and can be used to sterilize large batches of masks within a short time per...

Quasi-two-dimensional tungsten oxide structures, which nucleate by epitaxial growth on the W19O55 nanowires (NW) and grow as thin platelets, were identified. Both the nanowires and the platelets accommodate oxygen deficiency by formation of crystallographic shear planes. Stoichiometric phases, W18O53 (WO2.944), W17O50 (WO2.941), W16O47 (WO2.938), W...

Single crystalline tungsten oxides in a form of W5O14 and W18O49 nanowires were synthesized by iodine transport method. The morphology, work functions and field emission properties of these nanowires were investigated. Work functions of the W5O14 (4.20 - 4.34 eV) and W18O49 (4.55 - 4.57 eV) nanowires (NWs) have been measured by Kelvin probe force m...

Transition metal dichalcogenides such as MoS2 and WS2 are low-dimensional semiconductor materials. MoS2 and WS2 nanotubes and flakes were grown by a chemical transport reaction under a temperature gradient. I2 was used as a transport agent for previously synthesized MoS2 and WS2, respectively. These multilayered nanotubes are indirect bandgap semic...

Use of pyrotechnic articles is a common, though forbidden practice at football matches. While the fans, especially the members of the ultras groups, view pyrotechnic displays as a part of their culture, these devices can be dangerous for the public. In addition to the risks of burning, hand flares and similar items release toxic combustion by-produ...

We use an electron holographic method to determine the charge distribution along a quasi-one-dimensional W5O14nanowire during in situ field emission in a transmission electron microscope. The results show that the continuous charge distribution along the nanowire is not linear, but that there is an additional accumulation of charge at its apex. An...

This works investigates the in-situ formation of MoS2 and WS2 tribofilms by the synergy between transition metal oxide nanoparticles and conventional sulphur-containing anti-wear and extreme pressure additives. The formation of these low friction tribofilms can be obtained under reciprocating sliding contact and under extreme pressure conditions, a...

We demonstrate low‐temperature transport spectroscopy measurements on a quantum dot lithographically defined in a multiwall MoS2 nanotube. At T = 300 mK, clear Coulomb blockade is observed, with charging energies in the range of 1 meV. In single electron tunneling, discrete conductance resonances are visible at finite bias. Additionally, a magnetic...

We demonstrate low-temperature transport spectroscopy measurements on a quantum dot lithographically defined in a multiwall MoS2 nanotube. At T = 300 mK, clear Coulomb blockade is observed, with charging energies in the range of 1 meV. In single electron tunneling, discrete conductance resonances are visible at finite bias. Additionally, a magnetic...

We demonstrate low-temperature transport spectroscopy measurements on a quantum dot lithographically defined in a multiwall $\mathrm{MoS}_2$ nanotube. At T=300mK, clear Coulomb blockade is observed, with charging energies in the range of 1meV. In single electron tunneling, discrete conductance resonances are visible at finite bias. Additionally, a...

The W5O14 (O/W=2.8) nanowires are metallic oxides with specific resistivity of 25 μΩcm and diameters bellow 100 nm [1]. They were synthesized by iodine transport method using nickel as a growth promoter and WO3 as source of tungsten and oxygen. The field emission characteristics of single nanowires [2] and the films composed of these nanowires have...

Despite being a recognized health hazard, burning incense remains in widespread use. A number of studies have investigated the emissions of air pollulants from incense burning, but less attention has been given to particle decay following incense burning. We have studied the elemental composition and indoor emission characteristics of incense stick...

MoS2 nanoparticles are typically obtained by high temperature sulfurization of organic and inorganic precursors in S rich atmosphere and have excellent friction reduction properties. We present a novel approach for making the sulfurization unnecessary of MoO3 nanotubes during the synthesis process for friction and wear reduction applications while...

Laser ablation and modification using bursts of picosecond pulses and a tightly focused laser beam are used to manufacture structures in the bulk silicon. We demonstrate precise control of the surface crystallinity as well as the structure depth and topography of the processed areas, achieving homogeneous surface properties. The control is achieved...