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We investigated temperature (T) and excitation density dependent ultrafast near-infrared (NIR) transient reflectivity dynamics in the charge density wave (CDW) phases of bulk layered 1T-VSe2 using NIR and visible excitations. The data reveal fingerprints of conventional non-adiabatic CDW collective dynamics with rather fast electronic order parameter dynamics showing sub-picosecond suppression and recovery. The slower T-dependent 100-ps dynamics indicates rather isotropic heat transport dominated by the lattice degrees of freedom. [ABSTRACT FROM AUTHOR]

Protein structures evolved through a complex interplay of cooperative interactions, and it is still very challenging to design new protein folds de novo. Here we present a strategy to design self-assembling polypeptide nanostructured polyhedra based on mod

The spinel-structure CuIr2S4 compound displays a rather unusual orbitally-driven three-dimensional Peierls-like insulator–metal transition. The low-T symmetry-broken insulating state is especially interesting due to the existence of a metastable irradiation-induced disordered weakly conducting state. Here we study intense femtosecond optical pulse irradiation effects by means of the all-optical ultrafast multi-pulse time-resolved spectroscopy. We show that the structural coherence of the low-T broken symmetry state is strongly suppressed on a sub-picosecond timescale above a threshold excitation fluence resulting in a structurally inhomogeneous transient state which persists for several-tens of picoseconds before reverting to the low-T disordered weakly conducting state. The electronic order shows a transient gap filling at a significantly lower fluence threshold. The data suggest that the photoinduced-transition dynamics to the high-T metallic phase is governed by first-order-transition nucleation kinetics that prevents the complete ultrafast structural transition even when the absorbed energy significantly exceeds the equilibrium enthalpy difference to the high-T metallic phase. [ABSTRACT FROM AUTHOR]

The spinel-structure CuIr2S4 compound displays a rather unusual orbitally-driven three-dimensional Peierls-like insulator–metal transition. The low-T symmetry-broken insulating state is especially interesting due to the existence of a metastable irradiation-induced disordered weakly conducting state. Here we study intense femtosecond optical pulse irradiation effects by means of the all-optical ultrafast multi-pulse time-resolved spectroscopy. We show that the structural coherence of the low-T broken symmetry state is strongly suppressed on a sub-picosecond timescale above a threshold excitation fluence resulting in a structurally inhomogeneous transient state which persists for several-tens of picoseconds before reverting to the low-T disordered weakly conducting state. The electronic order shows a transient gap filling at a significantly lower fluence threshold. The data suggest that the photoinduced-transition dynamics to the high-T metallic phase is governed by first-order-transition nucleation kinetics that prevents the complete ultrafast structural transition even when the absorbed energy significantly exceeds the equilibrium enthalpy difference to the high-T metallic phase. [ABSTRACT FROM AUTHOR]

The accurate and rapid identification of explosives and their toxic by-products is an important aspect of safety protocols, forensic investigations and pollution studies. Herein, surface-enhanced Raman scattering (SERS) is used to detect different explosive molecules using an improved substrate design by controllable oxidation of the tungsten surface and deposition of Au layers. The resulting furrow-like morphology formed at the intersection of the tungsten Wulff facets increases nanoroughness and improves the SERS response by over 300 % compared to the untreated surface. The substrate showed excellent reproducibility with a relative standard deviation of less than 15 % and a signal recovery of over 95 % after ultrafast Ar/O 2 plasma cleanings. The detection limit for the "dried on a surface" measurement case was better than 10 -8 M using the moving scanning regime and an acquisition time of 10 s, while for the "water droplets on a surface" scenario the LoD is 10 -7 , which is up to 2 orders of magnitude better than the UV-Vis spectroscopy method. The substrates were successfully used to classify the molecular fingerprints of HMX, Tetryl, TNB and TNT, demonstrating the efficiency of a sensor for label-free SERS screening in the practice of monitoring traces of explosives in the water medium., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

In this work, nanocomposites based on titanium dioxide and reduced graphene oxide (TiO 2 @rGO) with different weight percentages of rGO (4, 8, and 16 wt%) were prepared by the hydrothermal/solvothermal synthesis method and thermally treated at 300 °C. The prepared nanocomposites were explored for the removal of methylene blue dye (MB) in the presence of simulated solar illumination as well as natural sunlight. The structural, morphological, chemical, and optical properties of the as-synthesized TiO 2 @rGO nanocomposites were characterized. The obtained results of the graphene-based nanocomposite materials indicated the existence of interactions between TiO 2 and rGO, i.e., the Ti-O-C bond, which confirmed the successful integration of both components to form the TiO 2 @rGO nanocomposites. The addition of rGO increased the specific surface area, decreased the band gap energy, and increased the photocatalytic degradation efficiency of MB from water compared to TiO 2 nanoparticles. The results of photocatalytic activity indicated that the amount of rGO in the prepared TiO 2 @rGO nanocomposites played a significant role in the application of different photocatalytic parameters, including the initial dye concentration, catalyst concentration, water environment, and illumination source. Our studies show that the reinforcement of the nanocomposite with 8 wt% of rGO allowed us to obtain the maximum photocatalytic decomposition performance of MB (10 mg·L -1 ) with a removal percentage of 99.20 after 2 h. Additionally, the obtained results show that the prepared TiO 2 @rGO_8 wt% nanocomposite can be used in three consecutive cycles while maintaining photocatalytic activity over 90%.

The formation of giant hailstones is a rare weather event that has devastating consequences in inhabited areas. This hazard has been occurring more frequently and with greater size of hailstones in recent years, and thus needs to be better understood. While the generally accepted mechanism is thought to be a process similar to the formation of smaller hailstones but with exceptional duration and stronger updrafts, recent evidence suggests that biotic and abiotic factors also influence the growth of these unusually large ice chunks. In this study, we improved these findings by determining the distribution of a wide variety of these factors throughout the hail volume and expanding the search to include new particles that are common in the environment and are of anthropogenic origin. We melted the concentric layers of several giant hailstones that fell to the ground over a small region in Slovenia in 2019. The samples, up to 13 cm in diameter, were analyzed for biotic and abiotic constituents that could have influenced their formation. Using 16S rRNA-based metagenomics approaches, we identified a highly diverse bacterial community, and by using scanning electron microscopy and Raman spectroscopy, we found natural and synthetic fibers concentrated in the cores of the giant hailstones. For the first time, we were able to detect the existence of microplastic fibers in giant hailstones and determine the changes in the distribution of sand within the volume of the samples. Our results suggest that changes in the composition of hail layers and their great diversity are important factors that should be considered in research. It also appears that anthropogenic microfiber pollutants were a significant factor in the formation of the giant hailstones analyzed in this study., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

It is shown that surface-enhanced Raman spectroscopy (SERS) can identify bacteria based on their genomic DNA composition, acting as a "sample-distinguishing marker". Successful spectral differentiation of bacterial species was accomplished with nanogold aggregates synthesized through single-step plasma reduction of the ionic gold-containing vapored precursor. A high enhancement factor (EF = 10 7 ) in truncated coupled plasmonic particulates allowed SERS-probing at nanogram sample quantities. Simulations confirmed the occurrence of the strongest electric field confinement within nanometric gaps between gold dimers/chains from where the molecular fingerprints of bacterial DNA fragments gained photon scattering enhancement. The most prominent Raman modes linked to fundamental base-pair molecular vibrations were deconvoluted and used to proceed with nitrogenous base content estimation. The genomic composition (percentage of guanine-cytosine and adenine-thymine) was successfully validated by third-generation sequencing using nanopore technology, further proving that the SERS technique can be employed to swiftly specify bioentities by the discriminative principal-component statistical approach.

Mechanical energy harvesting using piezoelectric nanogenerators (PNGs) offers an attractive solution for driving low-power portable devices and self-powered electronic systems. Here, we designed an eco-friendly and flexible piezocomposite nanogenerator (c-PNG) based on H 2 (Zr 0.1 Ti 0.9 ) 3 O 7 nanowires (HZTO-nw) and Ba 0.85 Ca 0.15 Zr 0.10 Ti 0.90 O 3 multipods (BCZT-mp) as fillers and polylactic acid (PLA) as a biodegradable polymer matrix. The effects of the applied stress amplitude, frequency and pressing duration on the electric outputs in the piezocomposite nanogenerator (c-PNG) device were investigated by simultaneous recording of the mechanical input and the electrical outputs. The fabricated c-PNG shows a maximum output voltage, current and volumetric power density of 11.5 V, 0.6 μA and 9.2 mW cm -3 , respectively, under cyclic finger imparting. A high-pressure sensitivity of 0.86 V kPa -1 (equivalent to 3.6 V N -1 ) and fast response time of 45 ms were obtained in the dynamic pressure sensing. Besides this, the c-PNG demonstrates high-stability and durability of the electrical outputs for around three months, and can drive commercial electronics (charging capacitor, glowing light-emitting diodes and powering a calculator). Multi-physics simulations indicate that the presence of BCZT-mp is crucial in enhancing the piezoelectric response of the c-PNG. Accordingly, this work reveals that combining 1D and 3D fillers in a polymer composite-based PNG could be beneficial in improving the mechanical energy harvesting performances in flexible piezoelectric nanogenerators for application in electronic skin and wearable devices., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The design of lead-free ceramics for piezoelectric energy harvesting applications has become a hot topic. Among these materials, Ba 0.85 Ca 0.15 Zr 0.10 Ti 0.90 O 3 (BCZT) and BaTi 0.89 Sn 0.11 O 3 (BTSn) are considered as potential candidates due to their enhanced piezoelectric properties. Here, the structural, electrical, piezoelectric and piezoelectric energy harvesting properties of the (1 - x )Ba 0.85 Ca 0.15 Zr 0.10 Ti 0.90 O 3 - x BaTi 0.89 Sn 0.11 O 3 ( x BTSn, x = 0.2, 0.4 and 0.6) system are investigated. A systematic study of the structural properties of the x BTSn samples was carried out using X-ray diffraction, Raman spectroscopy, and dielectric measurements. The addition of BTSn allows a successive phase transition, which broadens the application temperature range. The enhanced piezoelectric energy harvesting properties were found in the 0.2BTSn ceramic, where the large-signal and small-signal piezoelectric coefficients, piezoelectric voltage and the piezoelectric figure of merit reached 245 pm V -1 , 228 pC N -1 , 16.2 mV m N -1 and 3.7 pm 2 N -1 , respectively. Consequently, the combination of BCZT and BTSn could provide suitable lead-free materials with enhanced piezoelectric energy harvesting performances.

High specific surface area makes carbon nanofibres suitable for catalyst support. Here we report on optimization of carbon nanofibre (CNF) growth on molybdenum carbide nanowires (MoCNW) by direct carburization of Mo 6 S 2 I 8 nanowire bundles. Typical CNFs obtained by this method are several hundreds of nanometres long at a diameter of 10-20 nm. We show that nanofibre growth does not depend on the initial morphology of the nanowires: nanofibres grow on individual bundles of MoCNW, on dense networks of nanowires deposited on silicon substrate, and on free-standing nanowire foils. We find that carbon nanofibres remain firmly attached to the nanowires even if they are modified into Mo 2 C and further into Mo S 2 nanowires. The method thus enables production of a novel hybrid material composed of Mo S 2 nanowires densely covered with carbon nanofibres. We have additionally shown that the obtained CNFs can easily be self-decorated with platinum nanoparticles with diameters of several nanometres directly from water solution at room temperature without reducing agents. Such efficient synthesis and decoration process yield hybrid platinum/CNF/molybdenum-based NW materials, which are a promising material for a wide range of possible future applications, including sensitive sensorics and improved catalysis., Competing Interests: The authors declare no competing interests., (© 2020 The Authors.)

To improve functionalization of MoSI cluster polymers we have studied the effects of adsorption doping on the electrical transport, bundling, and optical absorption spectra. Doping results both in enhanced conductivity and aggregated bundles in dispersion. The different electronic properties of different bundle diameters can be ascribed to self-doping during the synthesis. Furthermore, doping shifts the characteristic absorption peaks and transfers oscillator strength to lower energies. Femtosecond optical spectroscopy shows that the spectral signature of adsorption and self-doping indeed originates from the population of electronic levels that are empty or absent in the undoped sample. The large spectral shifts and long lifetimes of photoinduced charges suggest efficient localization.

Protein structures evolved through a complex interplay of cooperative interactions, and it is still very challenging to design new protein folds de novo. Here we present a strategy to design self-assembling polypeptide nanostructured polyhedra based on modularization using orthogonal dimerizing segments. We designed and experimentally demonstrated the formation of the tetrahedron that self-assembles from a single polypeptide chain comprising 12 concatenated coiled coil-forming segments separated by flexible peptide hinges. The path of the polypeptide chain is guided by a defined order of segments that traverse each of the six edges of the tetrahedron exactly twice, forming coiled-coil dimers with their corresponding partners. The coincidence of the polypeptide termini in the same vertex is demonstrated by reconstituting a split fluorescent protein in the polypeptide with the correct tetrahedral topology. Polypeptides with a deleted or scrambled segment order fail to self-assemble correctly. This design platform provides a foundation for constructing new topological polypeptide folds based on the set of orthogonal interacting polypeptide segments.

Joule heating of bundles of Mo(6)S(3)I(6) nanowires, in real time, was studied using in situ TEM probing. TEM imaging, electron diffraction, and conductivity measurements showed a complete transformation of Mo(6)S(3)I(6) into Mo via thermal decomposition. The resulting Mo nanowires had a conductivity that was 2-3 orders higher than the starting material. The conductivity increased even further, up to 1.8 x 10(6) S m( - 1), when the Mo nanowires went through annealing phases. These results suggest that Joule heating might be a general way to transform or anneal nanowires, pointing to applications such as metal nanowire fabrication, novel memory elements based on material transformation, or in situ improvement of field emitters.

One-dimensional nanostructures based on the Mo-S-I system have recently aroused a lot of interest as a viable alternative to the ubiquitous carbon nanotube due to their uniform structure and electronic properties for a given composition. Previous research on the Mo(6)S(3)I(6) and Mo(6)S(4.5)I(4.5) stoichiometries has also shown them to be soluble in common solvents like water, acetone or isopropyl alcohol, and to debundle on dilution. Here, the solubility, debundling and composition of Mo(6)S(2)I(8) nanowires are presented. They were found to be most soluble in dimethylformamide, which retained 47 wt% of a 0.08 gl(-1) nanowire (NW) material dispersion as thin NW bundles after one week. Dispersions of 0.8 gl(-1) and 5 gl(-1) even retained 54 wt% and 66 wt%, respectively. However the NW material was completely insoluble in water, and the surface energy of Mo(6)S(2)I(8) NWs was deduced as 67 mJ m(-2), higher than for other Mo-S-I NWs. UV-vis-NIR spectroscopy showed nanowire peaks familiar from Mo(6)S(3)I(6) and Mo(6)S(4.5)I(4.5) spectra around 1.8 and 2.8 eV, as well as unforeseen ultraviolet peaks at 3.5 and 4.4 eV. These chemical differences suggest an alternate, more strongly bonded structure to that seen for Mo(6)S(3)I(6) and Mo(6)S(4.5)I(4.5) NWs. Films deposited from a range of concentrations were investigated using atomic force microscopy (AFM) to determine bundle diameter distributions. The average diameter and the spread in diameters were found to decrease somewhat with decreasing concentration. However extrapolation gave a finite bundle size at infinite dilution, and an extension of the existing debundling model is proposed to take this into account. To confirm the nominal stoichiometry of Mo(6)S(2)I(8), which does not follow the generic Mo(6)S(x)I(9-x) formula of previous stoichiometries, EDX was carried out. The composition of nanowire bundles was found to be Mo(6)S(2.3)I(8.6), supporting the nominal composition.

We investigate for the first time the topological characteristics of large molecular-scale inorganic networks self-assembled in solution using the unique sulfur-bonding chemistry of conducting MoSI molecular wires and gold nanoparticles (GNPs). The network self-assembly is shown to display power-law distribution of graph edges, indicating an intrinsic tendency to self-organize into scale-invariant critical state, without any external control parameter. We discuss the electronic transport properties of such networks particularly with regard to the possibility of data processing.

We report on a new highly reproducible route to recognitive self-assembly of molecular-scale circuits using sulfur-terminated subnanometer diameter Mo6S9-xIx (MoSIx) molecular nanowires. We demonstrate solution-processed attachment of MoSIx connecting leads to gold nanoparticles (GNPs). We also show that naked nanowires have the potential to bind thiolated proteins such as green fluorescent protein directly, thus providing a universal construct to which almost any protein could be attached. We further demonstrate three-terminal branched circuits with GNPs, opening a self-assembly route to multiscale complex molecular-scale architectures at the single-molecule level.