Mantas Simenas

Vilnius University · Faculty of Physics

The S100 family consists of calcium binding proteins that are largely known for their contribution to the neuroinflammatory processes. They are associated with various cardiac and neurological functions as well as related diseases. A few S100 proteins can form unspecific or amyloid aggregates in neuropathologies and thus play a part in dementia pat...

Membrane proteins are integral to numerous cellular processes, yet their conformational dynamics in native environments remains difficult to study. This study introduces a nanodelivery method using nanodiscs to transport spin-labeled membrane proteins into the membranes of living cells, enabling direct in-cell double electron–electron resonance (DE...

Synthesis via dehalogenative coupling due to thermal annealing is one of the most common routes of growing metal-organic and covalent polymer networks on the catalytic metal surfaces. We present a...

Flavin mononucleotide (FMN) is a ubiquitous blue-light pigment due to its ability to drive one- and two-electron transfer reactions. In both light-oxygen-voltage (LOV) domains of phototropin from the green algae Chlamydomonas reinhardtii, FMN is noncovalently bound. In the LOV1 cysteine-to-serine mutant (C57S), light-induced electron transfer from...

Hybrid methylammonium (MA) lead halide perovskites have emerged as materials exhibiting excellent photovoltaic performance related to their rich structural and dynamic properties. Here, we use multifrequency (X-, Q-, and W-band)...

Recently, hybrid double-perovskite structures have attracted attention due to their versatile multifunctional properties originating from the variety of different constituent units in these materials. Here, we report the synthesis and comprehensive multitechnique characterization of a novel hybrid double-perovskite formate-based material [CH3CH2NH3...

Lead halide perovskites are extensively investigated as efficient solution-processable materials for photovoltaic applications. The greatest stability and performance of these compounds are achieved by mixing different ions at all three sites of the APbX3 structure. Despite the extensive use of mixed lead halide perovskites in photovoltaic devices,...

Multivalent ligands hold promise for enhancing avidity and selectivity to simultaneously target multimeric proteins, as well as potentially modulating receptor signaling in pharmaceutical applications. Essential for these manipulations are nanosized scaffolds that precisely control ligand display patterns, which can be achieved by using polyproline...

Ytterbium-doped cesium lead halide perovskites exhibit unusual down-conversion with quantum efficiencies exceeding 100%. This phenomenon has been attributed to the quantum-cutting (QC) when a perovskite exciton is converted into two...

The pulse electron paramagnetic resonance (EPR) is widely used in different branches of material and life sciences, including promising applications in quantum information processing and quantum sensing. Here, we study the effect of the high polarizability of KTaO3 and SrTiO3 quantum paraelectrics on local electric and magnetic field components of...

Hybrid organic–inorganic lead halide perovskites are promising candidates for next-generation solar cells, light-emitting diodes, photodetectors, and lasers. The structural, dynamic, and phase-transition properties play a key role in the performance of these materials. In this work, we use a multitechnique experimental (thermal, X-ray diffraction,...

Following the success of cryogenic EPR signal preamplification at X-band, we present a Q-band EPR cryoprobe compatible with a standard EPR resonator. The probehead is equipped with a cryogenic ultra low-noise microwave amplifier and its protection circuit that are placed close to the sample in the same cryostat. Our cryoprobe maintains the same fun...

At low temperature, methyl groups act as hindered quantum rotors exhibiting rotational quantum tunneling, which is highly sensitive to a local methyl group environment. Recently, we observed this effect using pulsed electron paramagnetic resonance (EPR) in two dimethylammonium-containing hybrid perovskites doped with paramagnetic Mn2+ ions. Here, w...

Rare-earth doped crystals have long coherence times and the potential to provide quantum interfaces between microwave and optical photons. Such applications benefit from a high cooperativity between the spin ensemble and a microwave cavity—this motivates an increase in the rare-earth ion concentration which in turn impacts the spin coherence lifeti...

Inspired by the success of NMR cryoprobes, we recently reported a leap in X-band EPR sensitivity by equipping an ordinary EPR probehead with a cryogenic low-noise microwave amplifier placed closed to the sample in the same cryostat [Šimėnas et al. J. Magn. Reson. 322, 106876 (2021)]. Here, we explore, theoretically and experimentally, a more genera...

As in conventional computing, memories for quantum information benefit from high storage density and, crucially, random access, or the ability to read from or write to an arbitrarily chosen register. However, achieving such random access with quantum memories in a dense, hardware-efficient manner remains a challenge. Here we introduce a protocol us...

Mixing molecular cations in hybrid lead halide perovskites is a highly effective approach to enhance the stability and performance of optoelectronic devices based on these compounds. In this work, we prepare and study novel mixed 3D methylammonium (MA)-ethylammonium (EA) MA1-x EA x PbI3 (x < 0.4) hybrid perovskites. We use a suite of different tech...

Inspired by the success of NMR cryoprobes, we recently reported a leap in X-band EPR sensitivity by equipping an ordinary EPR probehead with a cryogenic low-noise microwave amplifier placed closed to the sample in the same cryostat [Šimėnas et al. J. Magn. Reson. 322, 106876 (2021)]. Here, we explore, theoretically and experimentally, a more genera...

Impurity spins in crystal matrices are promising components in quantum technologies, particularly if they can maintain their spin properties when close to surfaces and material interfaces. Here, we investigate an attractive candidate for microwave-domain applications, the spins of group-VI Te+125 donors implanted into natural Si at depths as shallo...

Mixing of molecular cations in hybrid lead halide perovskites is a highly effective approach to enhance stability and performance of the optoelectronic devices based on these compounds. In this work, we prepare and study novel mixed methylammonium (MA)-ethylammonium (EA) MA1-xEAxPbI3 (x < 0.4) hybrid perovskites. We use a suite of different techniq...

Rare-earth doped crystals have long coherence times and the potential to provide quantum interfaces between microwave and optical photons. Such applications benefit from a high cooperativity between the spin ensemble and a microwave cavity -- this motivates an increase in the rare earth ion concentration which in turn impacts the spin coherence lif...

A proper understanding of structural phase transitions and cation dynamics in hybrid lead halide perovskites is important for further enhancement of the photovoltaic properties of these materials. Here, we propose a model describing the FA cation ordering in FAPbX3 (X = Br, I) hybrid perovskites. Our model is based on the available structural infor...

Given the need to process anodes and composites based on nano-YSZ in reducing atmosphere or in air containing carbon atmospheres for the fabrication of solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs), we have studied the effect of the exposure to CO+N2/H2 or CO2+air mixtures during sintering of YSZ green pellets, prepared...

We propose a lattice model describing the ordering of 1,6-dibromo-3,8-diiodopyrene (Br2I2Py) molecules on the Au(111) surface into two-dimensional structures and correlated one dimensional rows. Our model employs three (intact, singly and doubly deiodinated) types of Br2I2Py molecules and mimics the situation which occurs with increasing temperatur...

Hybrid organic–inorganic perovskites (HOIPs) constitute unique coordination polymers with a huge potential of transforming modern materials chemistry due to their wide applications, mainly in electronics, optoelectronics and photovoltaics. Yearly, thousands of works on HOIPs are published in various fields of science, technology and industry. Many...

Photosynthesis and respiration rely upon a proton gradient to produce ATP. In photosynthesis, the Respiratory Complex I homologue, Photosynthetic Complex I (PS-CI) is proposed to couple ferredoxin oxidation and plastoquinone reduction to proton pumping across thylakoid membranes. However, little is known about the PS-CI molecular mechanism and atte...

Impurity spins in crystal matrices are promising components in quantum technologies, particularly if they can maintain their spin properties when close to surfaces and material interfaces. Here, we investigate an attractive candidate for microwave-domain applications, the spins of group-VI $^{125}$Te$^+$ donors implanted into natural Si at depths o...

The organic components in metal-organic frameworks (MOFs) are unique: they are embedded in a crystalline lattice, yet, as they are separated from each other by tunable free space, a large variety of dynamic behavior can emerge. These rotational dynamics of the organic linkers are especially important due to their influence over properties such as g...

p>We use a multi-technique approach to determine the phase diagram and molecular cation dynamics of mixed methylammonium-formamidinium MA1-xFAxPbBr3 (0 ≤ x ≤ 1) hybrid perovskites. The calorimetric, ultrasonic and X-ray diffraction experiments show a substantial suppression of the structural phase transitions and stabilization of the cubic phase up...

In this work, we compare the dielectric properties of single-crystal and pelletized perovskite-like formamidinium-templated inorganic-organic hybrid [NH2CHNH2][Mn(HCOO)3] (FAMn) at ambient pressure. Furthermore, we report pressure-dependent dielectric measurements of pelletized FAMn allowing us to determine the equation of state, as well as changes...

We propose a model and determine the formation conditions of the deprotonated dimeric structure, which is known to substitute the honeycomb (HON) phase in a trimeric acid (TMA) molecular assembly subjected to temperature or electric field effect. The model demonstrates that the dimeric phase occurs in a system of singly deprotonated molecules (depr...

Quantum memories capable of faithfully storing and recalling quantum states on-demand are powerful ingredients in bulding quantum networks [arXiv:0806.4195] and quantum information processors [arXiv:1109.3743]. As in conventional computing, key attributes of such memories are high storage density and, crucially, random access, or the ability to rea...

Photosynthesis and respiration rely upon a proton gradient to produce ATP. In photosynthesis, the Respiratory Complex I homologue, Photosynthetic Complex I (PS CI) is proposed to couple ferredoxin oxidation and plastoquinone reduction to proton pumping across thylakoid membranes, and is fundamental to bioenergetics in photosynthetic bacteria and so...

In ferroelectrics, the effects of acceptor doping on electrical and electromechanical properties, often referred to as the “hardening” effects, are commonly related to domain-wall pinning mechanisms mediated by acceptor–oxygen-vacancy defect complexes. In contrast, hardening effects in relaxor ferroelectric materials are complicated by the nano-pol...

In this contribution, more evidence is provided to support the presence of low-temperature anomaly in CsPbBr 3 single crystals.

Ensembles of bismuth-donor spins in silicon are promising storage elements for microwave quantum memories due to their long coherence times, which exceed seconds. The operation of an efficient quantum memory requires the achievement of critical coupling between the spin ensemble and a suitable high-quality factor resonator—this in turn requires a t...

Three-dimensional methylhydrazinium (CH3NH2NH2⁺, MHy⁺) lead halides, related to the famous methylammonium (CH3NH3⁺, MA⁺) and formamidinium (CH(NH2)2⁺, FA) perovskites, are attractive optoelectronic materials crystallizing in polar structures. In this work, temperature-dependent ¹H and ²⁰⁷Pb magic-angle spinning (MAS) NMR, Raman as well as high-pres...

Inspired by the considerable success of cryogenically cooled NMR cryoprobes, we present an upgraded X-band EPR probehead, equipped with a cryogenic low-noise preamplifier. Our setup suppresses source noise, can handle the high microwave powers typical in X-band pulsed EPR, and is compatible with the convenient resonator coupling and sample access f...

The rich dielectric properties of hybrid formate frameworks are tightly related to the dipolar dynamics and phase transitions of these compounds. A complete understanding of such phenomena requires experiments performed under non-standard conditions. Herein, we report high-pressure dielectric properties of anisotropic single crystal of 1,4-diaminob...

Cation engineering provides a route to control the structure and properties of hybrid halide perovskites, which has resulted in the highest performance solar cells based on mixtures of Cs, methylammonium, and formamidinium. Here, we present a multi-technique experimental and theoretical study of structural phase transitions, structural phases and d...

The organic components in metal-organic frameworks (MOFs) enjoy a unique situation: they are embedded in a crystalline lattice, yet, as they are separated from each other by tunable free space, a large variety of dynamic behavior can emerge. These rotational dynamics of the organic linkers are especially important due to their influence over proper...

Ensembles of bismuth donor spins in silicon are promising storage elements for microwave quantum memories due to their long coherence times which exceed seconds. Operating an efficient quantum memory requires achieving critical coupling between the spin ensemble and a suitable high-quality factor resonator -- this in turn requires a thorough unders...

Cesium–lead–bromide (CsPbBr3) is the simplest all inorganic halide perovskite. It serves as a reference material for understanding the exceptional solar cell properties of the organic–inorganic hybrid halide perovskites and is itself discussed as an alternative absorber material. Broadband dielectric spectroscopy has proven to yield an in depth und...

Methyl groups are ubiquitous in synthetic materials and biomolecules. At sufficiently low temperature, they behave as quantum rotors and populate only the rotational ground state. In a symmetric potential, the three localized substates are degenerate and become mixed by the tunnel overlap to delocalized states separated by the tunnel splitting ν t...

The nearest neighbor model is proposed to explain the occurrence of the metal-assisted pinwheel structures of deprotonated trimesic acid molecules on Ag(111). The main bonding interactions of molecules in these structures are estimated by the density functional theory calculations. The determined interaction energies are further used as a starting...

We present an X- and Q-band continuous wave (CW) and pulse electron paramagnetic resonance (EPR) study of a manganese doped [NH4][Zn(HCOO)3] hybrid framework, which exhibits a ferroelectric structural phase transition at 190 K. The CW EPR spectra obtained at different temperatures exhibit clear changes at the phase transition temperature. This sugg...

We present a dielectric spectroscopy study of dipolar dynamics in the hydrated UiO-66(Zr) type metal-organic frameworks (MOFs) functionalized with −NH2 and −F groups. Experiments are performed in a broad temperature and frequency ranges allowing us to probe several dipolar relaxations. For both samples at temperature below 220 K, we observe confine...

Formation of noncentrosymmetric three-dimensional (3D) lead halide perovskites has been a widely sought after goal since polar structure opens up new vistas to properties of these materials, e.g. improved charge separation for photovoltaics arising from ferroelectric order. Here, we report growth and unique properties of a new highly distorted 3D p...

We present X- and Q-band continuous wave (CW) and pulse electron paramagnetic resonance (EPR) study of manganese doped [NH4][Zn(HCOO)3] hybrid framework, which exhibits a ferroelectric structural phase transition at 190 K. The CW EPR spectra obtained at different temperature exhibit clear changes at the phase transition temperature. This suggests a...

The conductivity and percolation concentration of the composite material filled with randomly distributed carbon nanotubes were simulated as a function of the mechanical deformation. Nanotubes were modelled as the hard-core ellipsoids of revolution with high aspect ratio. The evident anisotropy was observed in the percolation threshold and conducti...

At the present time, the formation of titanium monoxide (TiOx) two dimensional (2D) species with distinct composition, size, shape, and a significantly reduced bandgap (Eg) value compared to TiO2 is of great scientific and practical importance. This paper describes our findings investigating Ti surface oxidation for the formation of TiOx films poss...

The formation of ordered molecular structures on surfaces is determined by the balance between molecule-molecule and molecule-substrate interactions. Whether the aggregation process is guided by non-covalent forces or on-surface reactions, a deeper understanding of these interactions is pivotal to formulating a priori predictions of the final struc...

Dimethylammonium zinc formate[(CH3)2NH2][Zn(HCOO)3] (DMAZn) treated as a model dense metal-organic framework is a compound being intensively studied in the last decade. It undergoes a first order order-disorder structural phase transition at T0~166 K, considered as the improper ferroelectric one. The complex mechanism of this phase transition is at...

We present a theoretical model of the methylhydrazinium CH3NH2NH2⁺ molecular cation ordering in perovskite [CH3NH2NH2][M(HCOO)3] (M = Mn, Mg, Fe and Zn) formate frameworks, which exhibit two structural phase transitions. The proposed model is constructed by analyzing the available structural information and mapping the molecular cation states on a...

We report the synthesis and dielectric characterization of novel polyvinylidene fluoride-trifluoroethylene P(VDF-TrFE) composite films containing [(CH3)2NH2][Mg(HCOO)3] (DMAMg) and [NH4][Zn(HCOO)3] (AmZn) dense metal-organic frameworks (MOFs). The optical camera and Raman microscopies are used to map the distribution of the MOF fillers in the prepa...

The indications of peculiar multiferroic behavior of dimethylammonium metal-formate perovskite frameworks raised important questions about the origin of the structural phase transition, structural phases and dipolar dynamics in these compounds. Here we provide answers on some of these phenomena by presenting a comprehensive experimental and theoret...

We present a combined study of [(CH3)2NH2][Cd(N3)3] hybrid perovskite dense metal-organic framework by IR, Raman, continuous-wave electron paramagnetic resonance (CW EPR), phase-transition-induced current and dielectric measurements. The Raman and IR study has shown that the phase transition observed near 175 K is associated with a pronounced narro...

Investigating two-dimensional (2D) self-assembled structures of biological monomers governed by intermolecular interactions is a prerequisite to understand the self-assembly of more complex biomolecular systems. 5,6-dihydroxyindole carboxylic acid (DHICA) is one of the building blocks of eumelanin - an irregular heteropolymer and the most common fo...

We have synthesised and characterised a novel organic-inorganic hybrid crystal, [(CH3)2NH2]2KCr(CN)6. The thermal DSC, TMA, DTG and DTA analyses indicate two solid-to-solid structural phase transitions (PTs). According to the X-ray diffraction experiments, the first PT at 220 K is isostructural, since it does not involve a change of the space group...

We report temperature-dependent X-ray diffraction, thermal, dielectric, electron paramagnetic resonance (EPR), Raman and IR studies of [(C3H7)4N][Cd(N(CN)2)3] ([TPrA][Cd(dca)3]) exhibiting a rich sequence of temperature-induced phase transitions occurring at T3 = 386 K, T2 = 362 K, T1 = 241 K and T0 = 228 K. The X-ray diffraction study confirms the...

Self-assembly of trimesic acid (TMA) molecules into the honeycomb structure with filled pores and resulting host-guest chemistry are studied by the density functional theory (DFT) and Monte Carlo (MC) simulations. The DFT calculations demonstrate that a guest TMA molecule prefers a non-central position in a relaxed hexagonal pore formed of six TMA...

Remarkable gas adsorption properties of zeolitic imidazolate frameworks (ZIFs) are believed to be tightly related to a flexible nature of organic linkers in these compounds. We present a low-frequency dielectric spectroscopy study of dynamic effects in ZIF-90 hybrid compound. Experiments of dehydrated framework reveal slow motion of imidazolate-2-c...

Sodium-ion batteries (SIBs) are potential cost-effective solutions for stationary energy storage applications. Unavailability of suitable anode materials, however, is one of the important barriers to the maturity of SIBs. Here, we report a Na2+xTi4O9/C composite as a promising anode candidate for SIBs with high capacity and cycling stability. This...

Here we report the dynamics of organic cations as guest molecules in a perovskite host-framework. The molecular motion of CH3NH3+ (MAFe), (CH3)2NH2+ (DMAFe) and (CH3)3NH+ (TrMAFe) in the cage formed by KFe(CN)63- units was studied using combination of experimental methods: (i) thermal analysis, (ii) dielectric and electric studies, (iii) optical ob...

Metal–organic frameworks (MOFs), in which framework is formed of metal centers coupled by organic molecules, exhibit inherent porosity and crystallinity. Although these systems have been examined for vast potential applications, the multiferroic properties in MOFs still remain poorly understood. One of the approaches to get insight into the ferroic...

The ability of catecholamines to undergo oxidative self-polymerization enables an attractive preparation route of coatings for biotechnology and biomedicine applications. However, efforts toward developing a complete understanding of the mechanism that underpin polymerization have been hindered by the multiple catechol crosslinking reaction pathway...

Diluted magnetic oxides attracted a great interest in the last years as materials for spintronics and magnetoelectric devices. We propose in the present paper such a magnetoelectric ceramic system for an application as miniaturized resonator antenna in GHz range. BaTi1-xFexO3-x/2 (0 ≤ x ≤ 0.02) polycrystalline ceramics have been produced by solid s...

The use of renewable but intermittent energy sources, such as solar and wind energy, means that it is necessary to store this energy for later use. Hence, a shift towards renewable sources of energy requires the development and use of efficient and inexpensive large-scale energy storage devices. Whereas portable electronics conventionally utilize l...

We present a combined differential scanning calorimetry (DSC), infrared (IR), Raman, electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) study of dimethylammonium zinc formate frameworks [(CH3)2NH2][Zn(HCOO)3] containing ¹⁴N and ¹⁵N nitrogen isotopes. The DSC reveals very small differences in the phase transition temperatures...

We report a continuous-wave (CW) and pulse electron paramagnetic resonance (EPR) as well as pulse electron nuclear double resonance (ENDOR) study of Cu²⁺ doped [(CH3)2NH2][Zn(HCOO)3] hybrid perovskite which exhibits a structural phase transition. The multifrequency (X, Q and W-band) CW EPR measurements allow to study the temperature evolution of th...

We present a study of the q-orientational statistical model for self-assembly of symmetric triangular molecules of trimesic acid in two dimensions. Density functional theory is used to estimate the pair interactions of two such molecules located at the ground-state (dimeric H-bond) distance for q² different mutual orientations of these molecules. T...

We present a theoretical modeling of the point defect screening by the CH3NH3⁺ dipoles in CH3NH3PbX3 (X = I, Br, Cl) perovskites. The organic sublattice of these materials is believed to be related to the exceptional performance of the perovskite solar cells. Our work is based on a statistical model with the short-range and dipolar interactions bet...

We present a pulse electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) study of a manganese doped [(CH3)2NH2][Zn(HCOO)3] dense metal-organic framework which exhibits a structural phase transition at 163 K. The echo-detected field sweep Mn²⁺ EPR spectrum of the low-temperature phase is in a perfect agreement with the...

The high power conversion efficiency of the hybrid CH3NH3PbX3 (where X = I, Br, Cl) solar cells is believed to be tightly related to the dynamics and arrangement of the methylammonium cations. In this Letter, we propose a statistical phase transition model which accurately describes the ordering of the CH3NH3⁺ cations and the whole phase transition...