Trigonal Research Articles

Photocatalytic performance of pristine NiO and Ni6MnO8 nanopowders in degradation of Rose Bengal dye.

Effective tuning of bandgap of transition metal oxides is a promising approach in improving their photocatalytic activity towards organic pollutant removal from water. The present paper describes synthesis of nickel oxide and Ni6MnO8 nanopowders by simple hydrothermal technique. During the synthesis of nickel oxide by hydrothermal process, addition of Mn source resulted in the formation of Ni6MnO8. X-ray diffraction analysis has confirmed the formation of nickel oxide and Ni6MnO8 both having cubic structures. The average crystallite size decreases from 20 to 12nm on increasing Mn source concentration during the synthesis of nickel oxide. Rectangular, hexagonal, and triangular faceted structures are revealed from the scanning electron microscopic images. HRTEM also indicated formation of cubical shaped structure with average sizes of 32 and 21nm for pristine NiO and Ni6MnO8 nanopowders. In the case of Ni6MnO8 nanopowder, inter-connected cubes are seen. Modification in Ni6MnO8 nanopowder is found to display multiple optical band gaps at 1.21, 1.82, and 2.65eV. The formation of Ni6MnO8 phase was further confirmed by XPS studies due to the presence of + 4 oxidation state of Mn. The photocatalytic properties of synthesized nickel oxide and Ni6MnO8 nanopowders are measured by using Rose Bengal dye under UV illumination. Enhancement in the photocatalytic activity is noticed in the case of Ni6MnO8 nanopowder as compared to nickel oxide nanopowder. Nearly 90% dye degradation is observed on utilizing Ni6MnO8 nanopowder.

Multiphase Coexistence in an Ionic Liquid: 1-Decyl-3-methylimidazolium Nitrate.

Complicated phase transitions were observed in a single-component 1-decyl-3-methylimidazolium nitrate ([C10mim][NO3]) ionic liquid (IL) using Raman spectroscopy and synchrotron small- and wide-angle X-ray scattering (SWAXS). Time-resolved synchrotron SWAXS could distinguish the phase transitions depending upon the cooling rate. Low-Q peaks representing a few kinds of layered structures were decomposed. Multiphase coexistence was observed in [C10mim][NO3] at specific cooling rates (8-9 K/min). Ionic liquid crystals (ILCs), hybrid-layered crystals, and hexagonal close-packed structures coexisted simultaneously. At the cooling rate region, the reentrant phase transition of the ILC phase upon heating was observed.

Dimension-Dependent Nonlinear Optical Properties of Stanene Nanosheets.

Stanene (Sn)-based materials, with a graphene-like hexagonal structure, are now attracting considerable interest for potential applications in photoelectricity. However, the nonlinear optical properties of stanene remain largely unexplored. In this work, we prepared different sizes of stanene by liquid phase exfoliation and differential centrifugation methods, including two-dimensional (2D) Sn nanosheets (NSs) and zero-dimensional (0D) Sn nanodots (NDs). Z-scan measurements reveal that 2D Sn NSs exhibited high saturable absorption behavior, while the 0D Sn NDs led to reverse saturable absorption. Femtosecond ultrafast transient absorption spectra revealed that the reverse saturable absorption of Sn NDs is derived from a stronger excited state absorption and faster exciton relaxation dynamics. This research expands the potential applications of stanene in laser shielding and other ultrafast photonics technologies.

Investigation of structural, optical, dielectric, and electrical properties of NaMn4(PO4)3 (NMP) with fillowite-type structure

We synthesized sodium tetra manganese phosphate, NaMn4(PO4)3, by a solid-state method at a temperature of 900 °C for a duration of 10 h. The application of Rietveld analysis to the PXRD patterns revealed that the sample synthesized show the small amount of the secondary phase (Mn2P2O7). The NaMn4(PO4)3 compound belongs to the trigonal system, namely the R-3 space group. The powder's morphology was examined using scanning electron microscopy (SEM), which revealed an average grain size of approximately 7 μm. The powder underwent elemental analysis using energy dispersive X-ray spectroscopy (EDS), which confirmed the uniformity of the sample. Raman and Fourier transform infrared (FTIR) spectroscopies reveal the distinctive spectral peaks associated with P-O bonds in the (PO4)3- functional group. The optical bandgap energy of 1.57 eV was calculated using the diffuse reflectance technique with the Kubelka-Munk function and Tauc's relation. The chromatic coordinates of NaMn₄(PO₄)₃ suggest that the sample can generate blue-purple light, rendering it appropriate as a red phosphor in white light-emitting diodes (LEDs). Integrating this red emission with blue and green light from additional LED components might enhance the overall color quality and efficiency of white light generation. The dielectric properties of NMP exhibited characteristics that were consistent with ionic conductivity. The Nyquist plot displayed a conspicuous semicircle, indicating the presence of a dominant singular process, most probably linked to the bulk grain. The material demonstrates a significant degree of conductivity, with a measured value of around 3.72 × 10–4 S·cm-1 at a temperature of 300 °C.

Neutron Radiation Effects on the Performance of the CdSe Thin Film for Photodetector Applications

Cadmium Selenide CdSe thin films were deposited on (7.5×1.3×0.1 cm3) glass substrates and (1×1 cm2) p-type silicon substrates using pulsed laser deposition technique (Nd: YAG laser beam with 80 mJ energy, λ = 1064 nm). Then, they were annealed at 300 °C for 1 h to get diodes as visible light detectors. Some of these samples (diodes) were exposed to different intervals (5, 7, 9, 12) days of neutron radiation using (241Am -10Be) source with a flux of 3×105 n/cm2.s and energy of 5.71 MeV. For comparison purposes, the other diodes were kept without any irradiation The morphological and electrical properties of these samples were studied by XRD, FE-SEM and I-V measurements. Results have shown all these thin films exhibit a hexagonal structure. However, there is a slight shift in the preferred orientation (100) for the irradiated films. Also, there was a new (102 - SiO2) peak that appeared in the irradiated thin film pattern. The crystallite size of pristine and (5, 7, 9, 12) days irradiated CdSe thin films were (26.9, 18.3, 24.9, 20.3 and 24.5) nm respectively, whereas, the mean particle size of the pristine film was 37 nm whereas for the irradiated films 53, 64, 73 and 92 nm. Results also show that the band gap of these samples increased from 2.17 eV for pristine thin films to 2.3, 2.48, 2.25, and 2.3 eV for the irradiated thin films. On the other hand, the results of I-V characteristics show the dark/light current. The current under illumination increases when exposed to small values of neutron radiation then it decreases with higher values of exposure. In contrast, the dark current decreases significantly with the irradiation. The effect of the irradiation was clear on the response/recovery period for all devices. Nevertheless, it was more profound in the response/recovery time of pristine devices. Also, the photo-responsivity of the pristine device was larger than the other devices and it was decreased with increasing absorbed doses. HIGHLIGHTS Hexagonal Structure: All CdSe thin films (both pristine and irradiated) exhibit a hexagonal structure, with a slight shift in orientation due to neutron irradiation. Neutron Radiation Impact: Neutron radiation causes a significant shift in crystallite size, decreasing the size for irradiated films. Additionally, a new (102 SiO2) peak emerges in irradiated samples, indicating radiation-induced changes. Band Gap Increase: The optical band gap of the CdSe films increased with neutron irradiation, starting from 2.17 eV in pristine films to values as high as 2.48 eV after irradiation. Morphological Changes: Irradiated films showed increased grain sizes, with neutron exposure leading to the enlargement of mean particle sizes from 37 nm in pristine samples to 92 nm in the most heavily irradiated samples. Electrical Behavior: Neutron irradiation impacted the photodetectors' electrical properties. The light current initially increased with small neutron doses but decreased with higher doses, while dark current consistently decreased after irradiation. GRAPHICAL ABSTRACT

Pressure-Induced Structural Phase Transitions and Photoluminescence Properties of Micro/Nanocrystals HoF3.

HoF3 crystals of varying sizes and morphologies were synthesized by controlling the amount of water. As the water content gradually decreased, the size of the crystals reduced, transforming from microcrystals to approximately 100 nm nanocrystals with unique morphologies. At room temperature, the pressure-induced phase transitions, and photoluminescence (PL) properties of HoF3 micro/nanocrystals are studied using in situ high-pressure PL technique. The PL spectra show that the HoF3 micro/nanocrystals exhibit two structural phase transformations at 5 (6 GPa for NCs) and 12 GPa. Nanoparticles have higher fluorescence intensity, which initially increases and then decreases with changes in pressure. Based on first-principles calculations, HoF3 transforms from an orthorhombic structure to a hexagonal structure during the phase transition, with the coordination number of holmium atoms increasing from 9 to 11. The high-pressure Raman spectra on lattice modes also confirmed the existence of the two phase transitions. This work not only provides precise structural changes but also facilitates the understanding of two typical structures of rare-earth trifluoride (REF3), which may play an important role in the application of the RE family.

Revealing Intrinsic Functionalization, Structure, and Photo-Thermal Oxidation in Hexagonal Antimonene.

Antimonene is one of the more exciting members of the post-graphene family with promising applications in optoelectronics, energy storage and conversion, catalysis, sensing or biomedicine. Efforts have been focused on developing a large-scale production route, and indeed, through a colloidal approach, high-quality few-layers antimonene (FLA) hexagons have been recently obtained. However, their oxidation behavior remains unexplored, as well as their interface, inner structure, and photothermal properties. Herein, it is revealed that the hexagons have an intrinsic surface functionalization with alkyl thiols that protects the core of the hexagonal flake against oxidation, and displayed inner defects related to the crystal formation during synthesis, as confirmed by cross-sectional scanning transmission electron microscopy energy dispersive X-ray spectroscopy (STEM-EDX) and temperature-dependent X-ray photoelectron spectroscopy (XPS) and selected area electron diffraction (SAED) analysis. A comprehensive study of temperature and laser power-dependent Raman spectroscopy on varying FLA hexagon thicknesses is carried out. Thinner flakes (<20nm) exhibited a blueshift and intensity decrease, contrasting with thicker ones resembling typical exfoliated flakes with a redshift. This work addresses a literature gap, providing insights into hexagonal FLA structure and characterization, and highlighting the influence of surface functional groups on oxidation behavior. Additionally, it emphasizes the potential of antimonene hexagons as building blocks for 2D heterostructures, including combinations with antimonene oxides and other 2D materials.

Advancing Graphene Imaging for Clear Identification of Lattice Defects: The Application of Revolve Sphere Levelling to Scanning Tunnelling Microscopy Images.

Application of revolve sphere levelling (RSL) as a practical and effective image processing tool for enhancing scanning tunnelling microscopy (STM) images of graphene atomic lattices is presented. Low-cost, ambient, and non-invasive STM methods overcome limitations of traditional imaging methods like scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) that can introduce or alter defects in graphene. Utilizing high-quality graphene synthesized via Paragraf's patented Metal-Organic Chemical Vapor Deposition (MOCVD) method, RSL, which is easily implemented via the Gwyddion software package, effectively highlights the hexagonal lattice structure and specific defect structures. This provides clarity of the atomic structure that traditional methods struggle to achieve. This research emphasizes the utility of RSL in materials science for defect identification in graphene, and points to future research in optimizing RSL for a broader range of defects and applications in other 2D materials.

High-pressure synthesis and characterizations of a new ternary Ce-based compound Ce3TiAs5

We report the structure and properties of a new Ce-based compound Ce3TiAs5synthesized under high-pressure and high-temperature conditions. It crystallizes in a hexagonal Hf5Sn3Cu-anti type structure with zig-zag like Ce chains along thecaxis. This compound is metallic and undergoes a magnetic phase transition atTN= 13 K. A metamagnetic transition occurs at ∼0.7 T. The Sommerfeld coefficient for the compound is determined to be about 215 mJ/(Ce-mol*K2), demonstrating a heavy Fermion behavior. The resistivity is featured with two humps, which arises from the synergistic effect of crystal electric field and magnetic scattering. The magnetic ordering temperatureTNgradually increases in the sequence of Ce3TiPn5with Pn = Bi, Sb, and As, which implies that the Ruderman-Kittel-Kasuya-Yosida interaction should be still predominant in Ce3TiAs5.

Quaternion and Biquaternion Representations of Proper and Improper Transformations in Non-Cartesian Reference Systems

Quaternion and biquaternion symmetry transformations have been applied to non-Cartesian reference systems of direct and reciprocal crystal lattices. The transformations performed directly in the sets of crystal reference axes simplify the calculations, eliminate the need for orthogonalization, permit the use of crystallographic vectors for defining the directions of rotations and perform the computations directly in the crystal coordinates. The applications of the general quaternion transformations are envisioned for physical, chemical, crystallographic and engineering applications. The general quaternion multiplication rules for any symmetry-unrestricted lattices have been derived for the triclinic crystallographic system and have been applied to the biquaternion representations of all point-group symmetry elements, including the crystallographic hexagonal system. Cayley multiplication matrices for point-groups, based on the biquaternion symbols of proper and improper symmetry elements, have been exemplified.

Plasmonic ZnO-Au Nanocomposites: A Synergistic Approach to Enhanced Photocatalytic Activity through Nonthermal Plasma-Assisted Synthesis

A novel and efficient method for synthesizing Au-decorated ZnO nanoparticles (NPs) with enhanced photocatalytic activity is presented. The synthesis involves a two-step process: hydrothermal preparation of ZnO NPs followed by nonthermal plasma-assisted deposition of Au nanoparticles on their surface. Comprehensive characterization of the ZnO and ZnO–Au NPs was carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Optical properties were evaluated via UV-Vis absorption and fluorescence measurements. The synthesized ZnO NPs displayed a hexagonal wurtzite structure, and the successful deposition of Au NPs was confirmed by TEM and XPS analysis, along with Raman and fluorescence data showing the quenching effect caused by Au. The incorporation of Au nanoparticles led to the appearance of localized surface plasmon resonance (LSPR) at 540 nm, enhancing visible light absorption and improving photocatalytic performance. Notably, the methylene blue (MB) degradation efficiency increased from 78% with pure ZnO NPs to 91.6% with ZnO–Au NPs under UV-Vis irradiation, demonstrating superior photocatalytic activity. This study introduces a simple and scalable method for synthesizing plasmonic ZnO-Au hybrid nanomaterials using plasma technology and highlights the critical role of Au NPs in enhancing photocatalytic performance by reducing electron–hole recombination.

Graphite–Phosphate Composites: Structure and Voltammetric Investigations

The utilization of lithium-ion batteries (LIBs) is increasing sharply with the increasing use of mobile phones, laptops, tablets, and electric vehicles worldwide. Technologies are required for the recycling and recovery of spent LIBs. In the context of the circular economy, it is urgent to search for new methods to recycle waste graphite that comes from the retired electrode of LIBs. The conversion of waste graphite into other products, such as new electrodes, in the field of energy devices is attractive because it reduces resource waste and processing costs, as well as preventing environmental pollution. In this paper, new electrode materials were prepared using waste anode graphite originating from a spent mobile phone battery with an xBT·0.1C12H22O11·(0.9-x)(NH4)2HPO4 composition, where x = 0–50 weight% BT from the anodic active mass of the spent phone battery (labeled as BT), using the melt quenching method. Analysis of the diffractograms shows the graphite crystalline phase with a hexagonal structure in all prepared samples. The particle sizes decrease by adding a higher BT amount in the composites. The average band gap is 1.32 eV (±0.3 eV). A higher disorder degree in the host network is the main factor responsible for lower band gap values. The prepared composites were tested as electrodes in an LIB or a fuel cell, achieving an excellent electrochemical performance. The voltammetric studies indicate that doping with 50% BT is the most suitable for applications as electrodes in LIBs and fuel cells.

Nanosized Eu3+-Doped NaY9Si6O26 Oxyapatite Phosphor: A Comprehensive Insight into Its Hydrothermal Synthesis and Structural, Morphological, Electronic, and Optical Properties.

Detailed analysis covered the optical and structural properties of Eu3+-doped NaY9Si6O26 oxyapatite phosphors, which were obtained via hydrothermal synthesis. X-ray diffraction patterns of NaY9Si6O26:xEu3+ (x = 0, 1, 5, 7, 10 mol% Eu3+) samples proved a single-phase hexagonal structure (P63/m (176) space group). Differential thermal analysis showed an exothermic peak at 995 °C attributed to the amorphous to crystalline transformation of NaY9Si6O26. Electron microscopy showed agglomerates composed of round-shaped nanoparticles ~53 nm in size. Room temperature photoluminescent emission spectra consisted of emission bands in the visible spectral region corresponding to 5D0 → 7FJ (J = 0, 1, 2, 3, 4) f-f transitions of Eu3+. Lifetime measurements showed that the Eu3+ concentration had no substantial effect on the rather long 5D0-level lifetime. The Eu3+ energy levels in the structure were determined using room-temperature excitation/emission spectra. Using the 7F1 manifold, the Nv-crystal field strength parameter was calculated to be 1442.65 cm-1. Structural, electronic, and optical properties were calculated to determine the band gap value, density of states, and index of refraction. The calculated direct band gap value was 4.665 eV (local density approximation) and 3.765 eV (general gradient approximation). Finally, the complete Judd-Ofelt analysis performed on all samples confirmed the experimental findings.

X‐ray–induced multicolor long afterglow and photostimulated luminescence from Pr3+‐doped Sr3(PO4)2

AbstractIn this paper, X‐ray–induced multicolor long afterglow and photostimulated luminescence from Sr3(PO4)2: Pr3+ was reported. The Rietveld refinement results have confirmed the as‐prepared sample was pure Sr3(PO4)2 phase with hexagonal crystal system. And Sr3(PO4)2: Pr3+ showed an excellent X‐ray–induced long afterglow luminescent performance. Under the excitation of X‐ray, the sample showed multicolor long afterglow luminescence from UVC to red region located at 268, 359, 466, 548, 604.3 and 685 nm, which can be ascribed to 4f5d‐3H4, 4f5d‐ 1D2, 4f5d‐3P0, 3P0→3H5 and 1D2→3H4, respectively. And the strongest afterglow emission intensity appeared at 468 nm. Furthermore, only 30 s X‐ray irradiation can induce 12 h afterglow emission, which afterglow emission intensity of 468 nm still reached 3.71 × 104 cps and was about 37.1 times stronger than the background intensity. In particular, the relation between 268 nm afterglow emission intensity and 468 nm afterglow emission intensity showed good linearity. And the UVC afterglow emission can be easily “observed” via the visible afterglow light. Furthermore, Sr3(PO4)2: Pr3+ possessed an excellent photostimulated luminescence (PSL) under the excitation of 980 nm NIR laser and the PSL intensity of the 12 circle still arrived at 1.26 × 105 cps, which was about 37.1 times stronger than the afterglow emission intensity after 5 h decay. All these results showed that the as‐prepared Sr3(PO4)2: Pr3+ phosphor was an excellent X‐ray–induced long afterglow luminescence phosphor, which possessed large potential applications in the medical field.

Low-cost fabrication methods of ZnO nanorods and their physical and photoelectrochemical properties for optoelectronic applications

Zinc Oxide (ZnO) nanorods have great potential in several applications including gas sensors, light-emitting diodes, and solar cells because of their unique properties. Here, three low cost and ecofriendly techniques were used to produce ZnO nanorods on FTO substrates: hydrothermal, chemical bath deposition (CBD), and electrochemical deposition (ECD). This study explores the impact of such methods on the optical, structural, electrical, morphological, and photoelectrochemical properties of nanorods using various measurements. XRD analysis confirmed the hexagonal wurtzite structure of ZnO nanorods in all three methods, with hydrothermal showing a preferred orientation (002) and CBD and ECD samples showing multiple growth directions, with average particle sizes of 31 nm, 34 nm, and 33 nm, respectively. Raman spectra revealed hexagonal Wurtzite structure of ZnO, with hydrothermal method exhibiting higher E2 (high) peak at 438 cm−1 than CBD and ECD methods. SEM results revealed hexagonal ZnO nanorods became more regular and thicker for the hydrothermal method, while CBD and ECD led to less uniform with voids. UV-vis spectra showed absorption lines between 390 nm and 360 nm. Optical bandgap energies were calculated as 3.32 eV, 3.22 eV, and 3.23 eV for hydrothermal, CBD, and ECD samples, respectively. PL spectra revealed UV emission band with a small intensity peak around 389 nm and visible emission peaks at 580 nm. Temperature dependent PL measurements for ZnO nanorods indicated that the intensities ratio between bound exciton and free exciton decreases with temperature increases for the three methods. Photocurrent measurements revealed ZnO nanorod films as n-type semiconductors, with photocurrent values of 2.25 µA, 0.28 µA, and 0.3 µA for hydrothermal, CBD, and ECD samples, and photosensitivity values of 8.01, 2.79, and 3.56 respectively. Our results suggest that the hydrothermal method is the most effective approach for fabricating high-quality ZnO nanorods for optoelectronic applications.

Zinc oxide-based sensor prepared by modified sol–gel route for detection of low concentrations of ethanol, methanol, acetone, and formaldehyde

Abstract We4 4 We received the acceptance date as 26 September 2024. Could you please update it to reflect this exact date for our project, instead of 1 October 2024? This is very important for our project funding. successfully synthesized zinc oxide (ZnO) nanoparticles using the sol–gel method, followed by their application onto alumina substrates for sensor testing. Comprehensive characterization of the nanomaterials was carried out utilizing XRD, SEM, TEM, UV–VIS-IR, and Photoluminescence (PL) techniques. The nanoparticles displayed a hexagonal wurtzite crystal structure, typical of ZnO. UV–Vis-IR spectroscopy revealed significant absorption in the UV region, with the band gap energy calculated to be 3.22 eV. PL spectra indicated the presence of various defects, such as oxygen vacancies and zinc interstitials, within the ZnO structure. SEM analysis of the deposited film surface showed spherical agglomerates, confirming the nanoscale dimensions, while energy-dispersive x-ray spectroscopy spectra affirmed the high purity of the ZnO films, rich in Zn and O elements. Sensor tests demonstrated the ZnO sensor’s high sensitivity to low concentrations of volatile organic compounds such as ethanol, formaldehyde, methanol, and acetone. Notably, at an operational temperature of 300 °C, the sensor exhibited a remarkable response to 5 ppm of each gas, with the following response and response/recovery times: for methanol, 11.47 and 36 s/57 s; for acetone, 11.54 and 25 s/52 s; for formaldehyde, 0.79 and 53 s/58 s; and for ethanol, 3.88 and 9 s/59 s.

Physical and electrochemical performance of Mn-doped zinc oxide electrode material for asymmetric supercapacitor

Manganese-doped zinc oxide has emerged as a promising material for high-performance supercapacitors (SCs) due to its enhanced electrochemical properties, including improved charge storage capacity and cycling stability. Pristine Zinc oxide (ZO) and Manganese (Mn) doped (2 wt % and 4 wt %) zinc oxide (hereby labeled: ZO, 2MZO, and 4MZO) derivatives have been synthesized via an aqueous sol-gel-based co-precipitation method. The physical characterizations of synthesized samples have been performed using TGA, XRD, FESEM, and BET. The XRD has confirmed the phase pure hexagonal wurtzite structure synthesis of ZO, 2MZO, and 4MZO samples. The FE-SEM images revealed that synthesized material had shown the mixed morphology as polyhedral particles, rods, and flakes in the nano region. Mn-doped has increased specific surface by 132 % compared to bare ZO. The electrochemical characterization techniques, including CV, GCD, and EIS, have been used to access electrochemical parameters using an aqueous 4 M KOH electrolyte. A detailed CV analysis was also carried out to investigate the capacitive contribution of the material in cycling. The electrochemical characterization techniques (CV, GCD, and EIS) have been performed to access electrochemical parameters using an aqueous 4 M KOH electrolyte. The 4MZO electrode material has shown an enhancement in specific capacitance (164.28 Fg-1) compared to pristine ZO (42.83 Fg-1). The EIS study revealed that the 4MZO has the lowest internal impedance 0.30 Ω compared to 0.70 Ω, and 2.60 Ω for 2MZO and ZO, respectively.

Tunable mechanical properties of the 3D anticircular-curve transversal-isotropic auxetic structure

This work studies a three-dimensional anticircular-curve transversal-isotropic auxetic structure (3D-ATAS) with tunable Poisson’s ratio (υ) and tunable Young’s modulus (E) on the basis of hexagonal symmetry in the transverse plane using the anti-deformation method by the design of inclined rods as circular-curve rods in the opposite direction of the deformation (under compressive loading). By using the energy method, expressions of υ and E of 3D-ATAS are acquired, and based on the periodic boundary conditions, υ and E of 3D-ATAS are parametrically researched through numerical simulation and uniaxial compression experiments. The effects of anticircular-curve rod thickness t, anticircular-curve rod width b, and anticircular-curve cross-section angle θ to υ and E of 3D-ATAS are investigated. The tunable ranges of υ and E of 3D-ATAS are predicted, and the wide range of E is attained. Compared with the 3D circular-curve transversal-isotropic auxetic structure, E of 3D-ATAS is significantly enhanced in different directions, and the maximum enhanced up to 10 times. In the same way, both υ and E of 3D-ATAS are transversal-isotropic.

3D bi-directional auxetic square metastructure with programmable thermal expansion and Poisson's ratio

Multifunctional integration research on metastructures has become the current development trend and hotspot, especially satellite platforms and hypersonic aircraft in the aerospace field. A 3D bi-directional auxetic square metastructure (BASM) with the programmable coefficient of thermal expansion (CTE) and Poisson's ratio (PR) is designed through the combination of re-entrant hexagonal structures and bi-material triangles. Specimens in the form of the 1*2 array are designed and fabricated through 3D printing. The correctness of the results of finite element analysis (FEA) of the BASM is verified by uniaxial compression experiments. Additionally, FEA is adopted to investigate the effective mechanical properties of the BASM with the form of the 2*3 array, and deformation mechanisms are further explored. Results indicate that the CTE, PR, and stiffness of the BASM depend on material combinations and geometric parameters. Under thermal and mechanical loads, the BASM achieves bi-directional regulation of the CTE and PR, encompassing both axial and circumferential deformations. Notably, the deformation mechanisms and critical conditions of the BASM are explored under the thermo-mechanical load. A novel strategy for programming the PR of the BASM is proposed in addition to changing the geometric parameters and the material combinations.

Phyto-mediated synthesis of ZnO nanoparticles and their sunlight-driven photocatalytic degradation of cationic and anionic dyes

Abstract In this study, zinc oxide-based nanocatalysts were biosynthesized using Ocimum basilicum (OB) and Olea africana (OA) leaf aqueous extracts, termed OB-ZnO and OA-ZnO, as a simple, affordable, and environmentally friendly approach. Their characteristics and efficacy in photodegrading cationic dyes (crystal violet and methylene blue) and anionic dyes (methyl orange and naphthol blue black) were investigated. The catalyst’s properties were analyzed using various techniques, including Fourier transform infrared, X-ray diffraction, photoluminescence, thermogravimetric analysis, UV-Vis, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller. Analysis revealed pure products having a hexagonal wurtzite structure, crystallite sizes of 15.04 and 21.46 nm, surface areas of 23.65 and 7.97 m2/g, particle sizes of 35 and 170 nm with spherical (uniform) and oval-like (non-uniform) shapes, and optical bandgaps of 3.15 and 3.05 eV, respectively. Photocatalytic applications under sunlight indicated excellent activity of both catalysts against targeted cationic and anionic dyes. Most notably, even though OA-ZnO has a lower surface area than OB-ZnO, it demonstrated greater efficiency. The variation in effectiveness is explained by the lower bandgap value of OA-ZnO and its ability to reduce electron–hole recombination due to its larger crystal size, which accelerates the degradation process. Additionally, both catalysts exhibited high stability after being used four times.