Effect of Ag modification on TiO2 and melem/g-C3N4 composite on photocatalytic performances

Here, the comparison of two different semiconductor materials is demonstrated, TiO₂ and melem/g-C₃N₄ composites-modified with balls of approximately 5 nm Ag nanoparticles (NPs) as photocatalysts for the degradation of the model dye acid orange 7 (AO7). The melem molecule synthesized here is one of a series of organic compounds consisting of triazine ring compounds with a structure similar to that of melam and melamine. The photodegradation process of AO7 was carried out to examine all powder materials as a potential photocatalyst. Additionally, two different lamps of wavelengths 368 nm (UV light) and 420 nm (VIS light) were applied to compare the photodegradation tests. A new synthesis route for the acquisition of Ag NPs (Ag content 0.5, 1.0 and 2.5 wt%), based on a wet and low temperature method without the use of reducing reagents was proposed. The best photocatalytic performances under UV and VIS light were obtained for both, TiO₂ and melem/g-C₃N₄ materials (new synthesis route) modified with a very low Ag content-0.5 wt%. The photodegradation activities using UV lamp (3 h, 368 nm irradiation) for samples with 0.5 wt% of Ag: TiO₂ and melem/g-C₃N₄, in excess of 95 and 94%, respectively, were achieved. The highest photoactive materials melem/g-C₃N₄ with 0.5 and 1 wt% Ag revealed 98% of activity under the VIS lamp after 3 h long irradiation. Our work demonstrates a novel, environmentally acceptable, and cost-effective chemical strategy for preparation of photocatalysts suitable for degradation of organic contaminants in wastewater treatment.

Empirical relationship between the number of review and research articles

In this contribution, an empirical relationship between the number of review and research articles published per year was searched. The simple idea based on proportionality (linearity) between the numbers of both kinds of articles was expressed in terms of a quadratic relationship, in which the quadratic member can reflect negative or positive deviations from the assumed linearity. The quadratic relationship was able to describe beginning periods of research fields as well as their mature phases and to detect the unpredictably high number of review articles. It was verified by the articles published in 20 various research fields taken from the Web of Science during different time spans.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11192-023-04654-0.

Graphitic Carbon Nitride as a Platform for the Synthesis of Silver Nanoclusters

Graphitic carbon nitride (CN) synthetized by the thermal polycondensation of melamine at 550 °C for 4 h was further exfoliated by heating at 500 °C for 3 h. Silver cations were adsorbed on the exfoliated graphitic carbon nitride (CNE) and then reduced by sodium borohydride forming silver nanoclusters (NCs) with a size of less than 1 nm. The NCs were located on the CNE surface and did not change the CNE properties except for its pore size distribution and thereby specific surface area (SSA). The Ag NCs were able to collect the photoinduced electrons of CNE and thus reduce their recombination with the holes. It was also documented by the increase in the CNE photocatalytic activity in terms of the degradation of antibiotic Ofloxacin. This study demonstrates the ability of CNE to serve as a platform for a simple and fast synthesis of Ag NCs without any stabilizing compounds.

In and Al Schottky Contacts Comparison on P-Type Chlorine-Doped CdTe

The performance of the CdTe radiation detectors heavily relies on the method of contact preparation. A convenient research method addressing this problem is the laser-induced transient current technique. In this paper, we compare the performance of two CdTe crystals which underwent different metallization processes. We showed that appropriately designed Au/Al contacts induce much less bulk polarization than commercial Pt/In electrodes under the same working conditions and can thus provide a convenient alternative to the industry standard. The comparison was based on the monitoring of the time-dependent sensor polarization measuring transient currents excited by above-bandgap laser illumination complemented by the Am 241 gamma spectroscopy. The theoretical analysis of current waveforms and radiation spectra enabled us to determine the charge carrier mobility, mobility-lifetime products of electrons and holes, and temporal and bias dependence of the space charge formation.

Tailoring the stoichiometry of C3N4 nanosheets under electron beam irradiation

Two-dimensional polymeric graphitic carbon nitride (g-C3N4) is a low-cost material with versatile properties that can be enhanced by the introduction of dopant atoms and by changing the degree of polymerization/stoichiometry, which offers significant benefits for numerous applications. Herein, we investigate the stability of g-C3N4 under electron beam irradiation inside a transmission electron microscope operating at different electron acceleration voltages. Our findings indicate that the degradation of g-C3N4 occurs with N species preferentially removed over C species. However, the precise nitrogen group from which N is removed from g-C3N4 (C-N-C, [double bond, length as m-dash]NH or -NH2) is unclear. Moreover, the rate of degradation increases with decreasing electron acceleration voltage, suggesting that inelastic scattering events (radiolysis) dominate over elastic events (knock-on damage). The rate of degradation by removing N atoms is also sensitive to the current density. Hence, we demonstrate that both the electron acceleration voltage and the current density are parameters with which one can use to control the stoichiometry. Moreover, as N species were preferentially removed, the d-spacing of the carbon nitride structure increased. These findings provide a deeper understanding of g-C3N4.

Deciphering the effect of traps on electronic charge transport properties of methylammonium lead tribromide perovskite

Halide perovskites have undergone remarkable developments as highly efficient optoelectronic materials for a variety of applications. Several studies indicated the critical role of defects on the performance of perovskite devices. However, the parameters of defects and their interplay with free charge carriers remain unclear. In this study, we explored the dynamics of free holes in methylammonium lead tribromide (MAPbBr₃) single crystals using the time-of-flight (ToF) current spectroscopy. By combining ToF spectroscopy and Monte Carlo simulation, three energy states were detected in the bandgap of MAPbBr₃ In addition, we found the trapping and detrapping rates of free holes ranging from a few microseconds to hundreds of microseconds. Contrary to previous studies, we revealed a strong detrapping activity of traps. We showed that these traps substantially affect the transport properties of MAPbBr₃, including mobility and mobility-lifetime product. Our results provide an insight on charge transport properties of perovskite semiconductors.

Graphitic Carbon Nitride for Photocatalytic Air Treatment

Graphitic carbon nitride (g-C₃N₄) is a conjugated polymer, which recently drew a lot of attention as a metal-free and UV and visible light responsive photocatalyst in the field of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability and earth-abundant nature. In the present work, bulk g-C₃N₄ was synthesized by thermal decomposition of melamine. This material was further exfoliated by thermal treatment. S-doped samples were prepared from thiourea or further treatment of exfoliated g-C₃N₄ by mesylchloride. Synthesized materials were applied for photocatalytic removal of air pollutants (acetaldehyde and NO_x) according to the ISO 22197 and ISO 22197-1 methodology. The efficiency of acetaldehyde removal under UV irradiation was negligible for all g-C₃N₄ samples. This can be explained by the fact that g-C₃N₄ under irradiation does not directly form hydroxyl radicals, which are the primary oxidation species in acetaldehyde oxidation. It was proved by electron paramagnetic resonance (EPR) spectroscopy that the dominant species formed on the irradiated surface of g-C₃N₄ was the superoxide radical. Its production was responsible for a very high NO_x removal efficiency not only under UV irradiation (which was comparable with that of TiO₂), but also under visible irradiation.

Post-Synthetic Derivatization of Graphitic Carbon Nitride with Methanesulfonyl Chloride: Synthesis, Characterization and Photocatalysis

Bulk graphitic carbon nitride (CN) was synthetized by heating of melamine at 550 °C, and the exfoliated CN (ExCN) was prepared by heating of CN at 500 °C. Sulfur-doped CN was synthesized by heating of thiourea (S-CN) and by a novel procedure based on the post-synthetic derivatization of CN with methanesulfonyl (CH₃SO₂⁻) chloride (Mes-CN and Mes-ExCN). The obtained nanomaterials were investigated by common characterization methods and their photocatalytic activity was tested by means of the decomposition of acetic orange 7 (AO7) under ultraviolet A (UVA) irradiation. The content of sulfur in the modified CN decreased in the sequence of Mes-ExCN > Mes-CN > S-CN. The absorption of light decreased in the opposite manner, but no influence on the band gap energies was observed. The methanesulfonyl (mesyl) groups connected to primary and secondary amine groups were confirmed by high resolution mass spectrometry (HRMS). The photocatalytic activity decreased in the sequence of Mes-ExCN > ExCN > CN ≈ Mes-CN > S-CN. The highest activity of Mes-ExCN and ExCN was explained by the highest amounts of adsorbed Acetic Orange 7 (AO7). In addition, in the case of Mes-ExCN, chloride ions incorporated in the CN lattice enhanced the photocatalytic activity as well.

Charge Sharing in (CdZn)Te Pixel Detector Characterized by Laser-Induced Transient Currents

Performance of the (CdZn)Te pixelated detectors heavily relies on the quality of the underlying material. Modern laser-induced transient current technique addresses this problem as a convenient tool for characterizing the associated charge distribution. In this paper, we investigated the charge sharing phenomenon in (CdZn)Te pixel detector as a function of the charge collected on adjacent pixels. The current transients were generated in the defined 4 mm² spots using 660 nm laser illumination. Waveforms measured on the pixel of interest and its surroundings were used to build the maps of the collected charge at different biases. The detailed study of the maps allowed us to distinguish the charge sharing region, the region with a defect, and the finest part in terms of the performance part of the pixelated anode. We observed the principal inhomogeneity complicating the assignment of the illuminated spot to the nearest pixel.

Photocatalytic Degradation of Selected Pharmaceuticals Using g-C3N4 and TiO2 Nanomaterials

Exfoliated graphitic carbon nitride (g-C₃N₄) and two commercially available nanomaterials from titanium dioxide (P25 and CG300) were tested for the photocatalytic degradation of paracetamol (PAR), ibuprofen (IBU), and diclofenac (DIC). Prior to photocatalytic experiments, the nanomaterials were characterized by common methods, such as X-ray diffraction (XRD), UV–VIS diffuse reflectance spectroscopy (DRS), Fourier transformed infrared spectroscopy in attenuated total reflection mode (FTIR–ATR), transmission electron microscopy (TEM), physisorption of nitrogen, and dynamic vapor adsorption (DVS) of water. The sizes and specific surface area (SSA) of the TiO₂ nanoparticles were 6 nm and 300 m²·g⁻¹ for CG300 and 21 nm and 50 m²·g⁻¹ for P25. The SSA of g-C₃N₄ was 140 m²·g⁻¹. All photocatalytic experiments were performed under UV (368 nm), as well as VIS (446 nm) irradiation. TiO₂ P25 was the most active photocatalyst under UV irradiation and g-C₃N₄ was the most active one under VIS irradiation. Photodegradation yields were evaluated by means of high performance liquid chromatography (HPLC) and reaction intermediates were identified using gas chromatography with mass detection (GC–MS). Paracetamol and ibuprofen were totally removed but the intermediates of diclofenac were observed even after 6 h of irradiation. Some intermediates, such as carbazole-1-acetic acid, 2,6-dichloraniline, and hydroxylated derivates of diclofenac were identified. This study showed that g-C₃N₄ is a promising photocatalyst for the degradation of pharmaceuticals in an aqueous environment, under visible light.

Photocatalytic decomposition of N2O over g-C3N4/WO3 photocatalysts

Although the nitrous oxide belongs among three of the most contributing greenhouse gases to global warming, it is quite neglected by photocatalytic society. The g-C₃N₄ and WO₃ composites were therefore tested for the photocatalytic decomposition of N₂O for the first time. The pure photocatalysts were prepared by simple calcination of precursors, and the composites were prepared by mixing of suspension of pure components in water followed by calcination. The structural (X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy), textural (N₂ physisorption), and optical properties (diffuse reflectance spectroscopy, photoluminescence spectroscopy, photoelectrochemical measurements) of all composites were correlated with photocatalytic activity. The experimental results and results from characterization techniques confirmed creation of Z-scheme in the WO₃/g-C₃N₄ composites, which was confirmed by hydroxyl radicals' trapping measurements. The photocatalytic decomposition of N₂O was carried out in the presence of UVA light (peak intensity at 365 nm) and the 1:2 WO₃/g-C₃N₄ composite was the most active one, but the photocatalytic activity was just negligibly higher than that of pure WO₃. This is caused by relatively weak interaction between WO₃ and g-C₃N₄ which was revealed from XPS.

[Stalking of psychiatrists and psychotherapists : Results of an online survey]

BACKGROUND

Currently, there are clear indications that due to their exposed occupational position psychiatrists and psychotherapists are at a higher risk than the general public to become the victim of stalking by patients.

OBJECTIVES

This study investigated the frequency of stalking and its psychosocial impact among psychiatrists and psychotherapists in the Federal Republic of Germany.

METHODS

Analysis of an online survey among members of the German Association for Psychiatry, Psychotherapy and Psychosomatics (DGPPN) from 23 September 2015 until 22 October 2015.

RESULTS

Of the respondents 26.5% reported having been the victim of stalking. In more than a third of the reported cases the stalking was described as severely or very severely debilitating. The majority of the perpetrators suffered from psychotic or personality disorders. Male victims were significantly more frequently stalked by a female perpetrator. Approximately 1 in 10 stalking victims continued the treatment of the perpetrator. The majority of the stalking victims did not obtain substantial support from their employer.

CONSLUSION

The phenomenon of stalking within therapeutic relationships needs to be incorporated into the medical and psychotherapeutic professional training, e. g. by implementing specialized training courses and the systematic integration of this topic into clinical supervision. The institutional dealing with stalking by patients needs to optimized, e. g. by promptly transferring treatment of patients who stalk to other professionals and, where required, providing assistance in reporting stalking incidents to the police.

Intracellular Monitoring of AS1411 Aptamer by Time-Resolved Microspectrofluorimetry and Fluorescence Imaging

Time-resolved microspectrofluorimetry and fluorescence microscopy imaging-two complementary fluorescence techniques-provide important information about the intracellular distribution, level of uptake and binding/interactions inside living cell of the labeled molecule of interest. They were employed to monitor the "fate" of AS1411 aptamer labeled by ATTO 425 in human living cells. Confocal microspectrofluorimeter adapted for time-resolved intracellular fluorescence measurements by using a phase-modulation principle with homodyne data acquisition was employed to obtain emission spectra and to determine fluorescence lifetimes in U-87 MG tumor brain cells and Hs68 non-tumor foreskin cells. Acquired spectra from both the intracellular space and the reference solutions were treated to observe the aptamer localization and its interaction with biological structures inside the living cell. The emission spectra and the maximum emission wavelengths coming from the cells are practically identical, however significant lifetime lengthening was observed for tumor cell line in comparison to non-tumor one.

Capillary isotachophoresis for separation of silver nanoparticles according to size

Capillary isotachophoresis was used for the separation of Ag nanoparticles stabilized by gelatin according to their size.

Distance-wise pathway discovery from protein-protein interaction networks weighted by semantic similarity

Reconstruction of signaling pathways is crucial for understanding cellular mechanisms. A pathway is represented as a path of a signaling cascade involving a series of proteins to perform a particular function. Since a protein pair involved in signaling and response have a strong interaction, putative pathways can be detected from protein-protein interaction (PPI) networks. However, predicting directed pathways from the undirected genome-wide PPI networks has been challenging. We present a novel computational algorithm to efficiently predict signaling pathways from PPI networks given a starting protein and an ending protein. Our approach integrates topological analysis of PPI networks and semantic analysis of PPIs using Gene Ontology data. An advanced semantic similarity measure is used for weighting each interacting protein pair. Our distance-wise algorithm iteratively selects an adjacent protein from a PPI network to build a pathway based on a distance condition. On each iteration, the strength of a hypothetical path passing through a candidate edge is estimated by a local heuristic. We evaluate the performance by comparing the resultant paths to known signaling pathways on yeast. The results show that our approach has higher accuracy and efficiency than previous methods.

Stabilization of ZnS Nanoparticles in Micellar Dispersion of Cetyltrimethylammonium Bromide

ZnS nanoparticles were precipitated in micellar dispersions of cetyltrimethylammonium bromide (CTAB). ZnS nanoparticles and cetyltrimethylammonium (CTA+) ions formed positively charged ZnS-CTA micelles with the mode zeta potential of 35 mV. The ZnS-CTA micelles were simulated by molecular modelling that confirmed the formation of positive CTA+ bilayers on the ZnS surface. The large agglomerates of the ZnS-CTA micelles were observed by the dynamic light scattering (DLS) method and electron transmission microscopy (TEM). The size of the ZnS nanoparticles of about 5 nm was estimated from their band-gap energy obtained from UV spectra and electron transmission micrographs. The relationship between zeta potentials (ξ) and hydrodynamic sizes (d) was found as ξ = 641/d - 5.9.

Single-crystal sapphire tubes as economical probes for optical pyrometry in harsh environments

One-end-sealed single-crystal sapphire tubes are presented as a simple, robust, and economical alternative for bulky lightpipe probes. Thermal radiation from a blackbody cavity created at the inner surface of the sealed end is gathered by a simple lens-based collecting system and transmitted via optical fiber to the remote detection unit. Simplicity and applicability of the concept are demonstrated by the combination of commercially available sapphire tubes with a common optical pyrometer. Radiation thermometers with sapphire tubes as invasive probes can be useful for applications requiring immunity to electromagnetic interference, resistance to harsh environments, simple replacement in the case of failure, and enhanced mechanical firmness, enabling wider range probe positioning inside the medium of interest.

Time-resolved microspectrofluorometry and fluorescence imaging techniques: study of porphyrin-mediated cellular uptake of oligonucleotides

Time-resolved confocal microspectrofluorometry and fluorescence microscopy imaging were applied to monitor the cellular uptake of fluorescent-labeled oligonucleotides (ONs) delivered by a porphyrin molecule. The fate of porphyrin-ON complexes inside living cells has also been monitored. Due to intrinsic fluorescence of the porphyrin and sensitivity of its characteristics to microenvironment, multicomponent analysis of time-resolved fluorescence provides unique information about stability of the porphyrin-ON complexes, ON interactions with their target sequences, and ON and porphyrin distributions after delivery inside the cells. Time-resolved confocal microspectrofluorometry indeed delivers additional information compared with fluorescence confocal microscopy imaging widely employed to study ON uptake.

Study of cetyltrimethylammonium and cetylpyridinium adsorption on montmorillonite

Adsorption of cetyltrimethylammonium (CTA) and cetylpyridinium (CP) onto Na-rich montmorillonite (MMT) was studied. For this purpose, the adsorption isotherms of CTA and CP, along with desorption curves of metal cations (Na+, K+, Ca2+, Mg2+), were obtained by means of capillary isotachophoresis and atomic absorption spectrometry. Infrared, X-ray diffraction pattern, specific surface area, porosity, and moisture adsorption measurements of montmorillonite revealed that CTA and CP were adsorbed in monolayer arrangements. CTA is assumed to be attached to the negatively charged MMT surface mainly by electrostatic forces. On the other hand, CP, adsorbed in higher amounts, can be additionally bound via other interactions of pyridinium rings, such as induced and pi-pi interactions. By the surfactant adsorption, the montmorillonite surface became hydrophobic and its micro- and mesopores were significantly diminished. Using scanning electron microscopy, aggregation of such organically modified MMT particles was observed.

Cellular uptake of phosphorothioate oligonucleotide facilitated by cationic porphyrin: a microfluorescence study

Cationic 5,10,15,20-tetrakis (1-methyl-4-pyridyl) porphyrin was tested as a delivery agent for oligonucleotides. By using fluorescence microimaging, it has been shown that complexation of the porphyrin to the phosphorothioate analog of dT(15) labeled by rhodamine enabled its nonendocytic penetration into the cell and regular distribution in the cytoplasm and preferentially into the nucleus. Time-resolved microfluorescence spectroscopy revealed that the oligonucleotide integrity was kept. A small fraction of the porphyrin molecules seems to undergo change of the binding mode after internalization, probably due to duplex formation between the oligonucleotide and its cellular target sequences, or due to dissociation of the porphyrin from the oligonucleotide and subsequent interactions in the cellular environment.

Intracellular uptake of modified oligonucleotide studied by two fluorescence techniques

Interaction, i.e., cellular uptake and intracellular distribution, of synthetic modified antisense oligonucleotide with the B16 melanoma cell line was studied using cationic polyene antibiotic, amphotericin B 3-dimethylaminopropyl amide, as a carrier vector. The antisense oligonucleotide--dT(15) oligomer analogue containing isopolar, nonisosteric, phosphonate-based internucleotide linkages 3'-O-P-CH(2)-O-5'--was labeled with fluorescent tetramethylrhodamine marker. The oligonucleotide itinerancy across the cell membrane and its distribution inside the cell was visualized using fluorescence microimaging. During the first several hours a strong preference staining of the cell nucleus was found. Fluorescence lifetime measurements from the intracellular environment (confocal laser microspectrofluorimeter, frequency domain phase/modulation technique in 1 to 200 MHz frequency region) yielded two spectral components of 4.9 and 1.4 ns lifetime, respectively. While the former component correlates with the previously characterized effect of the fluorophore binding to biomolecular targets in membranes and/or cytoplasm, the latter component is newly observed and its possible origin is discussed.

Spectral decomposition of intracellular complex fluorescence using multiple-wavelength phase modulation lifetime determination: technical approach and preliminary applications

Lifetime-based spectral decomposition using a frequency-domain phase/modulation technique is developed on a microspectrofluorimeter prototype. In a fluorescent mixture with strongly overlapping components, such measurements enable us to not only obtain excited state lifetimes of each fluorescent component but also determine the specific spectral contribution of each species without the use of any model spectra. Examples of such applications are first given for complex mixtures of highly overlapping fluorescent components in solution. Preliminary results concerning cellular applications are also reported. This allows us to follow the cellular uptake and intracellular stability of fluorescent labeled modified oligonucleotides in the context of antisense strategy studies. Indeed, the intracellular signal from the fluorescent label bound to oligonucleotides can be distinguished from those of the free label by its specific excited state lifetime.

Structural features of two distinct molecular complexes of copper(II) cationic porphyrin and deoxyribonucleotides

The associations of the water-soluble cationic copper(II)-5,10,15,20-meso-tetrakis(4-N-methylpyridyl) porphyrin (CuP) with d(pT)9 oligothymidylate and its building blocks deoxythymidine (dT) and deoxythymidine 5'-monophosphate (dTMP) were investigated by spectrophotometric titration [absorption, nanosecond transient resonance Raman (ns-RR) and picosecond time-resolved resonance Raman (ps-TR3) spectroscopies] to elucidate the structural requirements for the CuP exciplex formation in molecular complexes with unchained mononucleotides. In the d(pT)9 a factor analysis and global fit of the CuP absorption spectra revealed the formation of a single spectral species attributable to a 1 : 1 CuP. d(pT)9 complex throughout a wide range of d(pT)9/CuP ratios (0-10). Using ps-TR3 spectroscopy, the CuP. d(pT)9 complex was shown to be fully responsible for exciplex formation. In contrast, CuP mixed with dTMP ([dTMP]/[CuP] < 3000) yielded two spectroscopically distinct types of molecular complexes with 1 : 1 (CuP. dTMP) and 1 : 2 (CuP. (dTMP)2) (or even higher for [dTMP]/[CuP] > 3000) stoichiometry, the latter being spectroscopically identical to the CuP. d(pT)9 and providing a microenvironment favorable for exciplex formation to the same extent as the oligothymidylate. On the other hand, the 1 : 1 CuP. dTMP complex (prevailing for [dTMP]/[CuP] < 100) yielded no exciplex features. Similar behavior was observed for the CuP complexed with dT. To explain the difference in the ability of the CuP. dTMP and CuP. (dTMP)2 species to form the exciplex, two types of molecular complexes were suggested and discussed, differing in the orientation of the thymine planes with respect to the porphyrin macrocycle.

Simultaneous determination of Fe(II) and Fe(III) in waters by capillary isotachophoresis

An ITP method for the simultaneous determination of Fe(II) and Fe(III) in waters, based on separation of their EDTA and fluoride complexes, respectively, was developed. The leading electrolyte used consists of chlorides, La(III) as co-counter ion and is buffered with beta-alanine to pH = 3.5. The terminating electrolyte contains caproic acid and L-histidine (pH = 4.5). The method was validated and tested with samples of artificial, ground and treated water with good results, comparable to those obtained by other analytical techniques. Fe(II) and Fe(III) up to 20 mg/L were measured with an RSD = 1.4-1.5% and detection and determination limits of 0.8-0.9 and 3.0-3.5 mg/L, respectively. The ITP method can be recommended for routine utilization in hydroanalytical laboratories.