Search Results (122)

There is considerable interest in broadband nanomaterials, particularly transparent semiconductor oxides, within both fundamental research and technological applications. Historically, it has been considered that the variation in dopant concentration during the synthesis of semiconductor materials is a crucial factor in activating and/or modulating the optical and structural properties, particularly the bandgap and the parameters of the unit cell, of semiconductor oxides. Recently, tin oxide has emerged as a key material due to its excellent structural properties, optical transparency, and various promising applications in optoelectronics. This study utilized the ultrasonic spray pyrolysis technique to synthesize aluminum-doped tin oxide (ATO) thin films on quartz and polished single-crystal silicon substrates. The impact of varying aluminum doping levels (0, 2, 5, and 10 at. %) on morphology and structural and optical properties was examined. The ATO thin films were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmittance spectroscopy. SEM images demonstrated a slight reduction in the size of ATO nanoparticles as the aluminum doping concentration increased. XRD analysis revealed a tetragonal crystalline structure with the space group P42/mnm, and a shift in the XRD peaks to higher angles was noted with increasing aluminum content, indicating a decrease in the crystalline lattice parameters of ATO. The transmittance of the ATO films varied between 75% and 85%. By employing the transmittance spectra and the established Tauc formula the optical bandgap values of ATO films were calculated, showing an increase in the bandgap with higher doping levels. These findings were thoroughly analyzed and discussed; additionally, an effort was made to clarify the contradictory analyses present in the literature and to identify a doping range that avoids the onset of a secondary phase. Full article

Both tungsten trioxide (WO₃) nanosheet arrays and tungsten trioxide/zinc oxide (WO₃/ZnO) nanocomposites were grown on fluorine-doped tin oxide (FTO) coated glass slides using a hydrothermal method to develop a visible-light-driven photocatalyst with easy reusability. Field emission scanning electron microscopy (FE-SEM) observations confirmed the formation of irregular oxide nanosheet arrays on the FTO surfaces. X-ray diffraction (XRD) analysis revealed the presence of hexagonal WO₃ and wurtzite ZnO crystal phases. UV-Vis diffuse reflectance spectroscopy showed that integrating ZnO nanostructures with WO₃ nanosheets resulted in a blue shift of the absorption edge and a reduced absorption capacity in the visible-light region. Photoluminescence (PL) spectra indicated that the WO 0.5/ZnO 2.0 sample exhibited the lowest electron-hole recombination rate among the WO₃/ZnO nanocomposite sample. Photocatalytic degradation tests demonstrated that all WO₃/ZnO nanocomposite samples had higher photodegradation rates for a 10 ppm methylene blue (MB) aqueous solution under visible-light irradiation compared to pristine WO₃ nanosheet arrays. Among them, the WO 0.5/ZnO 2.0 sample showed the highest photocatalytic efficiency. Furthermore, it exhibited excellent recyclability and high photodegradation stability over three cycles. Full article

Diorganotin(IV) compounds of types RR′Sn(SeCH₂CH₂pz)₂ [R = R′ = ⁿBu (2), Ph (3); R = 2-(Me₂NCH₂)C₆H₄, R′ = Me (4), ⁿBu (5), Ph (6)], and RR′SnX(SeCH₂CH₂pz) [R = 2-(Me₂NCH₂)C₆H₄, R′ = ⁿBu, X = Cl (7), R′ = Me, X = SCN (9)], as well as [2-(Me₂NCH₂)C₆H₄](Me)Sn(NCS)₂ (8), and the tin(II) Sn(SeCH₂CH₂pz)₂ (10) (pz = pyrazole), were prepared by salt metathesis reactions between the appropriate diorganotin(IV) dichloride or dipseudohalide and Na[SeCH₂CH₂pz], with the latter freshly prepared from (pzCH₂CH₂)₂Se₂ (1). The solution behaviour of these compounds was investigated by multinuclear NMR (¹H, ¹³C, ⁷⁷Se, ¹¹⁹Sn), and the NMR spectra showed the existence of the Se–Sn bonds in solution. Compounds 4 and 5 showed decomposition in a solution of chlorinated solvents with the formation of selenium bridged dimeric species of type {[2-(Me₂NCH₂)C₆H₄](R’)Se}₂ [R′ = Me (4-a), ⁿBu (5-a)], as the single-crystal X-ray diffraction studies revealed, in contrast with compound 9, for which a monomeric structure was observed with the desired composition. The solid state structures of 4-a, 5-a, 8, and 9 revealed N→Sn intramolecular coordination of the nitrogen atom in the pendant CH₂NMe₂ arm. The NMR spectra suggested such a coordination at room temperature only for compound 7. Full article

Today, flexible and lightweight electronics are regarded as a viable alternative to conventional rigid and heavy devices in various application fields. In the optoelectronic area, organic semiconductors offer advantages such as high absorption coefficients, low processing temperatures, mechanical flexibility and compatibility with plastic substrates, while inorganic nanostructures provide good electronic properties and high thermal stability. Thus, composite films with enhanced properties can be achieved by inserting inorganic nanostructures within organic layers. In this research work, CuS nanoparticles were prepared by wet chemical precipitation and then added to an organic mixture containing poly(3-hexylthiophene) (P3HT) and N,N-bis-(1-dodecyl)perylene-3,4,9,10 tetracarboxylic diimide (AMC14), a chemically synthesized semiconductor, for fabricating hybrid composite films by matrix assisted pulsed laser evaporation (MAPLE) on indium tin oxide/poly(ethylene terephthalate) (ITO/PET) flexible substrates. A comparative assessment of the morphological, compositional, optical and electrical properties of the composite (P3HT:AMC14:CuS) and organic (P3HT:AMC14) layers was performed to evaluate their applicability in the photovoltaic cells. The transmission and emission spectra of the composite films are dominated by the optical features of AMC14, a perylene diimide derivative compound used as acceptor. In the case of devices based on MAPLE deposited composite layer fabricated on ITO/PET substrates, the electrical measurements carried under illumination revealed an improvement in the open circuit voltage parameter emphasizing their potential applications in the flexible device area. Full article

Mössbauer spectroscopy can be advantageous for studying catalysts. In particular, its use in in situ studies can provide unique access to structural features. However, special attention must be paid to the interpretation of data, since in most studies, the samples are not perfectly homogeneous. Balance and compromise should be found between the refinement of evaluations by extracting and interpreting data from spectra, while also considering the presence of possible inhomogeneities in samples. In this review, examples of studies on two types of catalysts are presented, from which, despite possible inhomogeneities, clear statements can be derived. The first example pertains to selected iron-containing microporous zeolites (with ⁵⁷Fe Mössbauer spectroscopy), from which unique information is collected on the coordination of iron ions. The second example is related to studies on supported PtSn alloy particles (with ¹¹⁹Sn probe nuclei), from which reversible modifications of the tin component due to interactions with the reaction partners are revealed. Full article

Data on spectral line widths and shifts broadened by interactions with charged particles, for 44 lines in the spectrum of ionized tin, for collisions with electrons and H II and HeII ions, are presented as online available tables. We obtained them by employing the semiclassical perturbation theory for temperatures, T, within the 5000–100,000 K range, and for a grid of perturber densities from 10¹⁴ cm⁻³ to 10²⁰ cm⁻³. The presented Stark broadening data are of interest for the analysis and synthesis of ionized tin lines in the spectra of hot and dense stars, such as, for example, for white dwarfs and hot subwarfs, and for the modelling of their atmospheres. They are also useful for the diagnostics of laser-induced plasmas for high-order harmonics generation in ablated materials. Full article

Nb-Sn, V-Sn mixed-metal oxides and Nb-Si, V-Si metal oxide–silicas were successfully synthesized through a “soft” templating method, in which appropriate amounts of metal salts (either niobium(V) chloride, or vanadium(IV) oxide sulfate hydrate or tin(II) chloride dihydrate) or tetraethyl orthosilicate (TEOS) were mixed with hexadecyltrimethylammonium chloride (HDTA) or sodium dodecyl sulfate (SDS) solutions to obtain a new series of mesoporous oxides, followed by calcination at different temperatures. As-obtained samples were characterized by SEM, TEM, XRD, and UV-Vis spectra techniques. The photocatalytic activities of the samples were evaluated by degradation of methyl orange II (MO) under simulated sunlight irradiation. The effects of metal species and calcination temperature on the physicochemical characteristic and photocatalytic activity of the samples were investigated in detail. The results indicated that, compared to pure oxides, mixed-metal oxide showed superior photocatalytic performance for the degradation of MO. A maximum photocatalytic discoloration rate of 97.3% (with MO initial concentration of 0.6·10⁻⁴ mol/dm³) was achieved in 300 min with the NbSiOx material, which was much higher than that of Degussa P25 under the same conditions. Additionally, the samples were tested in the photochemical oxidation process, i.e., advanced oxidation processes (AOPs) to treat the commercial non-ionic surfactant: propylene oxide ethylene oxide polymer mono(nonylphenyl) ether (N8P7, PCC Rokita). A maximum of 99.9% photochemical degradation was achieved in 30 min with the NbSiOx material. Full article

Palladium phthalocyanine (PdPc) and palladium phthalocyanine integrated with tin–zinc oxide (PdPc:SnZnO) were prepared using a simple chemical approach, and their structural and morphological properties were identified using X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscopy, and transmission electron microscopy techniques. The PdPc:SnZnO nanohybrid revealed a polycrystalline structure combining n-type metal oxide SnZnO nanoparticles with p-type organic PdPc molecules. The surface morphology exhibited wrinkled nanofibers decorated with tiny spheres and had a large aspect ratio. The thin film revealed significant optical absorption within the ultraviolet and visible spectra, with narrow band gaps measured at 1.52 eV and 2.60 eV. The electronic characteristics of Al/n-Si/PdPc/Ag and Al/n-Si/PdPc:SnZnO/Ag Schottky diodes were investigated using the current–voltage dependence in both the dark conditions and under illumination. The photodiodes displayed non-ideal behavior with an ideality factor greater than unity. The hybrid diode showed considerably high rectification ratio of 899, quite a low potential barrier, substantial specific photodetectivity, and high enough quantum efficiency, found to be influenced by dopant atoms and the unique topological architecture of the nanohybrid. The capacitance/conductance–voltage dependence measurements revealed the influence of alternative current signals on trapped centers at the interface state, leading to an increase in charge carrier density. Full article

In this study, chemical deposition was used to synthesize structures of Ga₂O₃ -NW/SiO₂/Si (NW—nanowire) at 348 K and SnO₂-NW/SiO₂/Si at 323 K in track templates SiO₂/Si (either n- or p-type). The resulting crystalline nanowires were δ-Ga₂O₃ and orthorhombic SnO₂. Computer modeling of the delta phase of gallium oxide yielded a lattice parameter of a = 9.287 Å, which closely matched the experimental range of 9.83–10.03 Å. The bandgap is indirect with an Eg = 5.5 eV. The photoluminescence spectra of both nanostructures exhibited a complex band when excited by light with λ = 5.16 eV, dominated by luminescence from vacancy-type defects. The current–voltage characteristics of δ-Ga₂O₃ NW/SiO₂/Si-p showed one-way conductivity. This structure could be advantageous in devices where a reverse current is undesirable. The p-n junction with a complex structure was formed. This junction consists of a polycrystalline nanowire base exhibiting n-type conductivity and a monocrystalline Si substrate with p-type conductivity. The I–V characteristics of SnO₂-NW/SiO₂/Si suggested near-metallic conductivity due to the presence of metallic tin. Full article

Metal oxide core–shell fibrous nanostructures are promising gas-sensitive materials for the detection of a wide variety of both reducing and oxidizing gases. In these structures, two dissimilar materials with different work functions are brought into contact to form a coaxial heterojunction. The influence of the shell material on the transportation of the electric charge carriers along these structures is still not very well understood. This is due to homo-, hetero- and metal/semiconductor junctions, which make it difficult to investigate the electric charge transfer using direct current methods. However, in order to improve the gas-sensing properties of these complex structures, it is necessary to first establish a good understanding of the electric charge transfer in ambient air. In this article, we present an impedance spectroscopy study of networked SnO₂/Ga₂O₃ core–shell nanobelts in ambient air. Tin dioxide nanobelts were grown directly on interdigitated gold electrodes, using the thermal sublimation method, via the vapor–liquid–solid (VLS) mechanism. Two forms of a gallium oxide shell of varying thickness were prepared via halide vapor-phase epitaxy (HVPE), and the impedance spectra were measured at 189–768 °C. The bulk resistance of the core–shell nanobelts was found to be reduced due to the formation of an electron accumulation layer in the SnO₂ core. At temperatures above 530 °C, the thermal reduction of SnO₂ and the associated decrease in its work function caused electrons to flow from the accumulation layer into the Ga₂O₃ shell, which resulted in an increase in bulk resistance. The junction resistance of said core–shell nanostructures was comparable to that of SnO₂ nanobelts, as both structures are likely connected through existing SnO₂/SnO₂ homojunctions comprising thin amorphous layers. Full article

Phononic or acoustic bandgap materials have often been made using a polymer matrix with metal inclusions such as tin and steel, which have high densities compared to the matrix material. Acoustic bandgaps are observed when waves are not transmitted at certain frequencies. These have been applied in cavity resonators, acoustic waveguides, and more. This paper introduces a concept of using cement as the surrounding matrix and carbon nanotubes as the core inclusions to develop phononic materials. The exhibition of a bandgap makes it possible for the cementitious phononic material to be used as a sensor for cement cracking and defects in oil well bores. This paper discusses ways to optimize the characteristics of the carbon nanotube core to develop gaps in transmission spectra. It shows the behavior of the cementitious material with changing filling fraction, location of core cells, and surrounding defects, creating a pathway for paradigm-shifting non-destructive sensing technologies. Full article

Polyalcohol liquefaction can be performed by acid or base catalysis, producing polyols with different properties. This study compared the mechanical properties of foams produced using polyols from liquefied Cytisus scoparius obtained by acid and base catalysis and using two different foam catalysts. The differences were monitored using FTIR analysis. Acid-catalyzed liquefaction yielded 95.1%, with the resultant polyol having an OH index of 1081 mg KOH/g, while base catalysis yielded 82.5%, with a similar OH index of 1070 mg KOH/g. Generally, compressive strength with dibutyltin dilaurate (DBTDL) ranged from 16 to 31 kPa (acid-liquefied polyol) and 12 to 21 kPa (base-liquefied polyol), while with stannous octoate (TIN), it ranged from 17 to 42 kPa (acid) and 29 to 68 kPa (base). Increasing water content generally decreased the compressive modulus and strength of the foams. Higher water content led to a higher absorption at 1670 cm⁻¹ in the FTIR spectrum due to the formation of urea. Higher isocyanate indices generally improved compressive strength, but high amounts led to unreacted isocyanate that could be seen by a higher absorption at 2265 cm⁻¹ and 3290 cm⁻¹. DBTL was shown to be the best foam catalyst due to higher trimer conversion seen in the spectra by a higher absorption at 1410 cm⁻¹. Acid- and base-derived polyols lead to different polyurethane foams with different FTIR spectra, particularly with a higher absorption at 1670 cm⁻¹ for foams from acid-derived liquefaction. Full article

In this study, we explored the manipulation of optical properties in the terahertz (THz) frequency band of radio-frequency (RF) sputtered indium tin oxide (ITO) thin films on highly resistive silicon substrate by rapid thermal annealing (RTA). The optical constants of as-deposited and RTA-processed ITO films annealed at 400 °C, 600 °C and 800 °C are determined in the frequency range of 0.2 to 1.0 THz. The transmittance can be changed from ~27% for as-deposited to ~10% and ~39% for ITO films heat-treated at different annealing temperatures (T_a’s). Such variations of optical properties in the far infrared for the samples under study are correlated with their mobility and carrier concentration, which are extracted from Drude–Smith modeling of THz conductivity with plasma frequency, scattering time and the c-parameters as fitting parameters. Resistivities of the films are in the range of 10⁻³ to 10⁻⁴ Ω-cm, confirming that annealed ITO films can potentially be used as transparent conducting electrodes for photonic devices operating at THz frequencies. The highest mobility, μ = 47 cm²/V∙s, with carrier concentration, N_c = 1.31 × 10²¹ cm⁻³, was observed for ITO films annealed at T_a = 600 °C. The scattering times of the samples were in the range of 8–21 fs, with c-values of −0.63 to −0.87, indicating strong backscattering of the carriers, mainly by grain boundaries in the polycrystalline film. To better understand the nature of these films, we have also characterized the surface morphology, microscopic structural properties and chemical composition of as-deposited and RTA-processed ITO thin films. For comparison, we have summarized the optical properties of ITO films sputtered onto fused silica substrates, as-deposited and RTA-annealed, in the visible transparency window of 400–800 nm. The optical bandgaps of the ITO thin films were evaluated with a Tauc plot from the absorption spectra. Full article

Titanium nitride (TiN) is a candidate material for several plasmonic applications, and pulsed laser ablation in liquids (PLAL) represents a rapid, scalable, and environmentally friendly approach for the large-scale production of nanomaterials with customized properties. In this work, the nanosecond PLAL process is developed, and we provide a concise understanding of the process parameters, such as the solvent and the laser fluence and pulse wavelength, to the size and structure of the produced TiN nanoparticles (NPs). TiN films of a 0.6 μm thickness developed by direct-current (DC) magnetron sputtering were used as the ablation targets. All laser process parameters lead to the fabrication of spherical NPs, while the laser pulse fluence was used to control the NPs’ size. High laser pulse fluence values result in larger TiN NPs (diameter around 42 nm for 5 mJ and 25 nm for 1 mJ), as measured from scanning electron microscopy (SEM). On the other hand, the wavelength of the laser pulse does not affect the mean size of the TiN NPs (24, 26, and 25 nm for 355, 532, and 1064 nm wavelengths, respectively). However, the wavelength plays a vital role in the quality of the produced TiN NPs. Shorter wavelengths result in NPs with fewer defects, as indicated by Raman spectra and XPS analysis. The solvent type also significantly affects the size of the NPs. In aqueous solutions, strong oxidation of the NPs is evident, while organic solvents such as acetone, carbides, and oxides cover the TiN NPs. Full article

A series of TiN/ITO composite films with various thickness of ITO buffer layer were fabricated in this study. The enhancement of optical properties was realized in the composite thin films. The absorption spectra showed that absorption intensity in the near-infrared region was obviously enhanced with the increase of ITO thickness due to the coupling of surface plasma between TiN and ITO. The epsilon-near-zero wavelength of this composite can be tuned from 935 nm to 1895 nm by varying the thickness of ITO thin films. The nonlinear optical property investigated by Z-scan technique showed that the nonlinear absorption coefficient (β = 3.03 × 10⁻⁴ cm/W) for the composite was about 14.02 times greater than that of single-layer TiN films. The theoretical calculations performed by finite difference time domain were in good agreement with those of the experiments. Full article