Nature-Inspired Photocatalytic Hydrogen Production with a Flavin Photosensitizer.

Green hydrogen, by definition, must be produced with renewable energy sources without using fossil fuels. To transform the energy system, we need a fully sustainable production of green and renewable energy as well as the introduction of such "solar fuels" to tackle the chemical storage aspect of renewable energies. Conventional electrolysis of water splitting into oxygen and hydrogen gases is a clean and nonfossil method, but the use of massive noble-metal electrodes makes it expensive. Direct photocatalytic hydrogen evolution in water is an ideal approach, but an industrial scale is not available yet. In this paper, we intend to introduce flavins as metal-free organic photosensitizers for photoinduced reduction processes. Specifically, a flavin photosensitizer was employed for the photocatalytic evolution of hydrogen gas in aqueous media. The ratio of photosensitizer to cocatalyst concentration has been found to affect the efficiency of the hydrogen evolution reaction. Since flavins are nature-inspired molecules (like vitamin B2) with easily tunable properties through structure modification, this family of compounds opens the door for new possibilities in sustainable green hydrogen production.

Fluorescent Rotary Switches: Four- vs Three-Substituted Phthalimide Boron Difluoride Schiff Base Complexes.

The influence of the substitution pattern in phthalimide boron difluoride Schiff base complexes as fluorescent molecular rotors has been investigated. Due to their ground-state zwitterionic structures, they have exhibited negative solvatochromism in absorption and blue-green emission with moderate to satisfactory photoluminescence quantum yields in solution. Ground-state and excited-state theoretical calculations and time-resolved emission spectroscopy revealed that the excited-state rotation is triggered by planar-induced charge transfer, resulting in switched emission toward the green region. Fluorescence lifetime measurements and species-associated emission spectra exhibited two emitting excited species in equilibrium via a planar transition-state barrier. The substitution pattern models showed different behavior in solid-state mechanochromic switching and were analyzed by subcell unit packing obtained from X-ray structure data. We have attempted to gain in-depth insight into the fluorescence mechanism and photoluminescence properties associated with the substitution pattern of the phthalimide motif in order to understand the structure-property-function relationship.

Suicides in the Region of Northern Slovakia: A Retrospective, Single-centre Autopsy Observational Study over a 10-year Period.

Suicidal behavior is multifaceted and encompasses various factors. Among these, alcohol dependence and acute alcohol intoxication stand out as significant risk factors for suicide. The retrospective study aimed to record the development of suicide, also in connection with alcohol consumption, in the catchment area of the Department of Forensic Medicine and Pathological Anatomy of the Health Care Surveillance Authority in Martin, Slovak Republic, in the years 2009-2019.

Spectroscopic behavior differences between lumazine and alloxazine in the DMSO-water mixture.

The absorption and emission spectra were investigated for lumazine, alloxazine and their cyanated or fluorinated derivatives, respectively. The spectroscopic properties were modulated by varying water concentration in dimethyl sulfoxide (DMSO). Some intriguing experimental results were found for the samples containing 65 % of water and 35% of DMSO. This finding is consistent with previously published molecular dynamics (MD) simulations confirming the concept of the 'local bulk' model. In this case, a notable decrease in absorption and emission intensities was registered, even larger than the water quenching observed in other cases. The changes in midrange DMSO concentrations could be explained by the formation of local solvents structures as predicted by MD, specifically the formation of DMSO·2H2O dimers. Experimentally, the cyano-substituted lumazine has shown a remarkable sensitivity to DMSO concentration. The spectroscopic measurements were interpreted using the density functional theory where the implicit DMSO solvent model was combined with explicit water molecules. Together with its enhanced water solubility, the cyanated lumazine derivate could be used for non-destructive DMSO detection in vitro for applications such as drug uptake monitoring, since DMSO is often used in pharmaceutical practice.

High-Pressure Depolymerization of Poly(lactic acid) (PLA) and Poly(3-hydroxybutyrate) (PHB) Using Bio-Based Solvents: A Way to Produce Alkyl Esters Which Can Be Modified to Polymerizable Monomers.

The polyesters poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) used in various applications such as food packaging or 3D printing were depolymerized by biobased aliphatic alcohols-methanol and ethanol with the presence of para-toluenesulphonic acid (p-TSA) as a catalyst at a temperature of 151 °C. It was found that the fastest depolymerization is reached using methanol as anucleophile for the reaction with PLA, resulting in the value of reaction rate constant (k) of 0.0425 min-1 and the yield of methyl lactate of 93.8% after 120 min. On the other hand, the value of constant k for the depolymerization of PHB in the presence of ethanol reached 0.0064 min-1 and the yield of ethyl 3-hydroxybutyrate was of 76.0% after 240 min. A kinetics study of depolymerization was performed via LC-MS analysis of alkyl esters of lactic acid and 3-hydroxybutanoic acid. The structure confirmation of the products was performed via FT-IR, MS, 1H NMR, and 13C NMR. Synthesized alkyl lactates and 3-hydroxybutyrates were modified into polymerizable molecules using methacrylic anhydride as a reactant and potassium 2-ethylhexanoate as a catalyst at a temperature of 80 °C. All alkyl esters were methacrylated for 24 h, guaranteeing the quantitative yield (which in all cases reached values equal to or of more than 98%). The methacrylation rate constants (k') were calculated to compare the reaction kinetics of each alkyl ester. It was found that lactates reach afaster rate of reaction than 3-hydroxybutyrates. The value of k' for themethacrylated methyl lactate reached 0.0885 dm3/(mol·min). Opposite to this result, methacrylated ethyl 3-hydroxybutyrate's constant k' was 0.0075 dm3/(mol·min). The reaction rate study was conducted by the GC-FID method and the structures were confirmed via FT-IR, MS, 1H NMR, and 13C NMR.

Experimental and Numerical Analysis of High-Temperature Superconducting Tapes Modified by Composite Thermal Stabilization Subjected to Thermomechanical Loading.

The strain behavior of SiC/Stycast 2850 FT composites under thermomechanical loading using a finite element analysis (FEA) was studied. These composites can serve as thermal stabilizers of high-temperature superconducting (HTS) tapes during limitation event in resistive superconducting fault current limiter (R-SCFCL) applications. For this purpose, the thermomechanical properties of four composite systems with different filler content were studied experimentally. The FEA was calculated using an ANSYS software and it delivered useful information about the strain distribution in the composite coating, as well as in particular layers of the modified HTS tapes. The tapes were subjected to bending over a 25 cm core, cooled in a liquid nitrogen (LN2) bath, and finally, quenched from this temperature to various temperatures up to 150 °C for a very short time, simulating real limitation conditions. The outputs from simulations were also correlated with the experiments. The most promising of all investigated systems was SB11-SiC20 composite in form of 100 µm thick coating, withstanding a temperature change from LN2 up to 120 °C.

Forgotten in time: The state of legislation, recovery, identification, and repatriation of World War I and II soldiers in Slovakia.

Recovery, identification, and burial of casualties from World War I and II is still a topic of interest in many countries. In Slovakia, recent discoveries of such remains are usually accidental. Unfortunately, in many cases the remains are disrupted and without any material culture present, rendering the identification of the victim almost impossible. Majority of accidental skeletal remains are analyzed by legal medical doctors at forensic medicine departments spread across ten regional workplaces around the country. The aim of the paper is to point out the problems with recovery and identification of World War I and World War II remains in Slovakia.

Suicidal electrocution: a report of three unusual cases.

Electricity is a modern technology that can be used as method of suicide. Authors presents three cases of suicidal electrocution. The first case is a 55-year-old man who wrapped his chest and arms with electrically active wires connected to a timer. In second case, a 69-year-old man constructed electric mechanism from a disassembled extension cord. The last case describes a 53-year-old woman who was found dead in a water-filled bathtub.

Singlet Fission in Thin Solid Films of Bis(thienyl)diketopyrrolopyrroles.

The singlet fission (SF) process discovered in bis(thienyl)diketopyrrolopyrroles (TDPPs) can boost their potential for photovoltaics (PV). The crystal structures of TDPP analogs carrying n-hexyl, n-butyl, or 2-(adamant-1-yl)ethyl substituents are similar, but contain increasingly slipped stacked neighbor molecules. The observed SF rate constants, kSF , (7±4), (9±3) and (5.6±1.9) ns-1 for thin films of the three compounds, respectively, are roughly equal, but the triplet quantum yields vary strongly: (120±40), (160±40) and (70±16), respectively. The recent molecular pair model reproduces the near equality of all three kSF at the crystal geometries and identifies all possible pair arrangements in which SF is predicted to be faster, by up to two orders of magnitude. However, it is also clear that the presently non-existent ability to predict the rates of processes competing with SF is pivotal for providing a guide for efforts to optimize the materials for PV.

Tunable Properties of Nature-Inspired N,N'-Alkylated Riboflavin Semiconductors.

A series of novel soluble nature-inspired flavin derivatives substituted with short butyl and bulky ethyl-adamantyl alkyl groups was prepared via simple and straightforward synthetic approach with moderate to good yields. The comprehensive characterization of the materials, to assess their application potential, has demonstrated that the modification of the conjugated flavin core enables delicate tuning of the absorption and emission properties, optical bandgap, frontier molecular orbital energies, melting points, and thermal stability. Moreover, the thin films prepared thereof exhibit smooth and homogeneous morphology with generally high stability over time.

Synthesis conditions influencing formation of MAPbBr3 perovskite nanoparticles prepared by the ligand-assisted precipitation method.

This work reports on an optimized procedure to synthesize methylammonium bromide perovskite nanoparticles. The ligand-assisted precipitation synthetic pathway for preparing nanoparticles is a cost-effective and promising method due to its ease of scalability, affordable equipment requirements and convenient operational temperatures. Nevertheless, there are several parameters that influence the resulting optical properties of the final nanomaterials. Here, the influence of the choice of solvent system, capping agents, temperature during precipitation and ratios of precursor chemicals is described, among other factors. Moreover, the colloidal stability and stability of the precursor solution is studied. All of the above-mentioned parameters were observed to strongly affect the resulting optical properties of the colloidal solutions. Various solvents, dispersion media, and selection of capping agents affected the formation of the perovskite structure, and thus qualitative and quantitative optimization of the synthetic procedure conditions resulted in nanoparticles of different dimensions and optical properties. The emission maxima of the nanoparticles were in the 508-519 nm range due to quantum confinement, as confirmed by transmission electron microscopy. This detailed study allows the selection of the best optimal conditions when using the ligand-assisted precipitation method as a powerful tool to fine-tune nanostructured perovskite features targeted for specific applications.

Anti-Stokes photoluminescence study on a methylammonium lead bromide nanoparticle film.

Photon cooling via anti-Stokes photoluminescence (ASPL) is a promising approach to realize all-solid-state cryo-refrigeration by photoexcitation. Photoluminescence quantum yields close to 100% and a strong coupling between phonons and excited states are required to achieve net cooling. We have studied the anti-Stokes photoluminescence of thin films of methylammonium lead bromide nanoparticles. We found that the anti-Stokes photoluminescence is thermally activated with an activation energy of ∼80 meV. At room temperature the ASPL up-conversion efficiency is ∼60% and it depends linearly on the excitation intensity. Our results suggest that upon further optimization of their optical properties, the investigated particles could be promising candidates for the demonstration of photon cooling in thin solid films.

Composite Heat Sink Material for Superconducting Tape in Fault Current Limiter Applications.

We enhanced the performance of superconducting tapes during quenching by coating the tapes with various composites, with regards to the application of such coated systems in superconducting fault current limiters. In composition of the coating, we varied the type of epoxy matrix, the content of ceramic filler particles and the use of reinforcement in order to optimize the thermal and the mechanical stability of the coated tapes. By this way modified superconducting tapes were able to reduce the maximum temperature 170 °C of not modified superconducting tape to 55 °C during the quench with electric field up to 130 V m-1.

Microwave-Assisted Preparation of Organo-Lead Halide Perovskite Single Crystals.

The efficiency of organo-lead halide perovskite-based optoelectronic devices is dramatically lower for amorphous materials compared to highly crystalline ones. Therefore, it is challenging to optimize and scale up the production of large-sized single crystals of perovskite materials. Here, we describe a novel and original approach to preparing lead halide perovskite single crystals by applying microwave radiation during the crystallization. The microwave radiation primarily causes precise heating control in the whole volume and avoids temperature fluctuations. Moreover, this facile microwave-assisted method of preparation is highly reproducible and fully automated, it and can be applied for various different perovskite structures. In addition, this cost-effective method is expected to be easily scalable because of its versatility and low energy consumption. The crystallization process has low heat losses; therefore, only a low microwave reactor power of 8-15 W during the temperature changes and of less than 1 W during the temperature holding is needed.

Autoerotic deaths: report of two unusual cases.

Autoerotic death is a rare but recurring phenomenon in forensic medicine. This article presents two cases of unusual autoerotic death with signs of autoerotic asphyxia. Although the first case appeared to be asphyxia, the autopsy confirmed natural cause of death during solitary sexual activity of 69-year-old man found with exposed and bandaged genitals. The other case was asphyxiation utilizing a plastic bag and multiple panties wrapped around the head of 18-year-old man disguised in women´s dress.

Can Sub-zero Treatment at -75 °C Bring Any Benefits to Tools Manufacturing?

: Vanadis 6 ledeburitic tool steel was subjected to sub-zero treatment at -75 °C for different durations, and for different subsequent tempering regimes. The impact of these treatments on the microstructure, hardness variations, and toughness characteristics of the steel was investigated. The obtained results infer that the retained austenite amount was reduced to one fourth by sub-zero treatment (SZT), and the population density of add-on carbides was increased by factor of three to seven, depending on the duration of SZT. Tempering always reduced the population density of these particles. A hardness increased by 30-60 HV10 was recorded after sub-zero treatment but tempering to the secondary hardness peak induced much more significant hardness decrease than what was established in conventionally quenched steel. The flexural strength was not negatively influenced by sub-zero treatment at -75 °C while the fracture toughness tests gave worse values of this quantity, except the case of steel tempered to the secondary hardness peak.

Cyclic Peptide Stabilized Lead Halide Perovskite Nanoparticles.

Combining the unique properties of peptides as versatile tools for nano- and biotechnology with lead halide perovskite nanoparticles can bring exceptional opportunities for the development of optoelectronics, photonics, and bioelectronics. As a first step towards this challenge sub 10 nm methylammonium lead bromide perovskite colloidal nanoparticles have been synthetizes using commercial cyclic peptide Cyclo(RGDFK), containing 5 amino acids, as a surface stabilizer. Perovskite nanoparticles passivated with Cyclo(RGDFK) possess charge transfer from the perovskite core to the peptide shell, resulting in lower photoluminescence quantum yields, which however opens a path for the application where charge transfer is favorable.

Density of bulk trap states of hybrid lead halide perovskite single crystals: temperature modulated space-charge-limited-currents.

Temperature-modulated space-charge-limited-current spectroscopy (TMSCLC) is applied to quantitatively evaluate the density of trap states in the band-gap with high energy resolution of semiconducting hybrid lead halide perovskite single crystals. Interestingly multicomponent deep trap states were observed in the pure perovskite crystals, which assumingly caused by the formation of nanodomains due to the presence of the mobile species in the perovskites.

Wheelchair-Assisted Ligature Strangulation: An Unusual Suicide by a Quadriparetic.

Multiple sclerosis, currently incurable and potentially profoundly disabling demyelinating central nervous system disease, is associated with higher occurrence of suicide as affected individuals are prone to major depression and psychosis. Despite progressively incapacitating neurologic impairment, well-staffed institutions, and limited repertoire of methods of suicide, which prevents patients from purposefully ending their lives, suicide-determined patients typically commit suicide resulting from a medication overdose, sharp force traumata, self-neglect, or deliberate starvation. Here we describe a successful suicide committed by a 39-year-old wheelchair-bound, institutionalized, quadriparetic male patient with a diagnosis of multiple sclerosis with secondary progressive clinical course who utilized his motorized wheelchair to terminate his life. He tied a rope between his neck and wall bars and then propelled the wheelchair forwardly. The acceleration of the wheelchair resulted in ligature self-strangulation. This case report, with a review of the literature, is noteworthy for the rareness of the wheelchair-related fatality combined with an unusual, if not entirely unseen, suicidal mechanism in severely disabled adult.

Glycolated Thiophene-Tetrafluorophenylene Copolymers for Bioelectronic Applications: Synthesis by Direct Heteroarylation Polymerisation.

A series of copolymers containing a glycolated 1,4-dithienyl-2,3,5,6-tetrafluorophenylene unit copolymerized with thiophene, bithiophene, thienothiophene and 1,2,4,5-tetrafluorobenzene comonomer units were designed and synthesised by direct heteroarylation polymerisation. The optical, electrochemical, electrochromic and solid-state structural properties of the copolymers were investigated. The copolymers exhibit stable redox properties in organic solvents and promising redox properties in thin film configuration with an aqueous electrolyte. Finally, the potential of the copolymers as active materials in organic electrochemical transistors (OECTs) was assessed, and promising performance was shown as an accumulation-mode OECT material with a peak transconductance of 0.17 mS and a good on/off ratio of 105 for the thiophene copolymer.