Search Results (198)

Under normal conditions, the novel zinc blende beryllium oxide (zb BeO) exhibits in a metastable crystalline phase, which is less stable than its wurtzite counterpart. Ultrathin zb BeO epifilms have recently gained significant interest to create a wide range of advanced high-resolution, high-frequency, flexible, transparent, nano-electronic and nanophotonic modules. BeO-based ultraviolet photodetectors and biosensors are playing important roles in providing safety and efficiency to nuclear reactors for their optimum operations. In thermal management, BeO epifilms have also been used for many high-tech devices including medical equipment. Phonon characteristics of zb BeO at ambient and high-pressure P ≠ 0 GPa are required in the development of electronics that demand enhanced heat dissipation for improving heat sink performance to lower the operating temperature. Here, we have reported methodical simulations to comprehend P-dependent structural, phonon and thermodynamical properties by using a realistic rigid-ion model (RIM). Unlike zb ZnO, the study of the Grüneisen parameter γ(T) and thermal expansion coefficient α(T) in zb BeO has revealed atypical behavior. Possible reasons for such peculiar trends are attributed to the combined effect of the short bond length and strong localization of electron charge close to the small core size Be atom in BeO. Results of RIM calculations are compared/contrasted against the limited experimental and first-principle data. Full article

This study investigates the effects of NaCl activation on the structural and chemical properties of kaolin for the adsorption of Zn²⁺ from solution. Kaolin was treated with NaCl solution at varying concentrations (0.5, 1.0, 2.0, and 4.0 M), and ultrasonication was used as a means of agitation. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and dynamic light scattering (DLS) were employed to characterize the physical and chemical effects of the NaCl activation and its subsequent influence on the kaolin’s heavy metal removal efficiency. The kaolin activated with 0.5 M NaCl solution yielded the optimal performance with a 13% increase in Zn²⁺ removal compared to the unmodified clay. The adsorption data best matched the pseudo-second-order kinetic model and the Langmuir isotherm. This indicates a monolayer adsorption on a homogeneous surface, with chemisorption as the dominant adsorption mechanism. Thermodynamic analysis also revealed that the adsorption process was endothermic and spontaneous. Furthermore, NaCl activation slightly enhanced the microstructural properties of the kaolin and moderated the surface charge, creating a more favorable electrostatic environment for improved heavy metal ion adsorption. The findings further highlight the potential of NaCl activation to introduce exchangeable Na⁺ onto the kaolin surface in a pH-neutral environment and promise a clean, mechanistically clear, and practical route for ion exchange with heavy metals such as Zn²⁺. Full article

LiTaO₃ crystals doped with Cr³⁺ and Nd³⁺ ions are promising for developing active nonlinear laser media. In this work, the defect structure of LiTaO₃ crystals, including those doped with Cr³⁺ and Nd³⁺, is examined. X-ray patterns of all six investigated LiTaO₃:Cr:Nd crystals are identical and correspond to a highly perfect structure. Using optical microscopy, the presence of defects of various shapes, microinhomogeneities, and lacunae was revealed. The optical absorption and Raman scattering spectra of a series of nonlinear, optical, double-doped LiTaO₃:Cr³⁺:Nd³⁺ (0.06 ≤ [Cr³⁺] ≤ 0.2; 0.2 ≤ [Nd³⁺] ≤ 0.45 wt%) crystals showed that at concentrations of doping Cr³⁺ ions less than 0.09 wt% and Nd³⁺ ions less than 0.25 wt%, the crystal structure is characterized by a low level of defects, and the optical transmission spectra characterized by narrow lines corresponding to electron transitions in Nd³⁺ ions. In this case, for the radiative transition in the cation sublattice, the existence of three nonequivalent neodymium centers is observed, and for the radiative transition, two nonequivalent centers are observed. IR absorption spectroscopy in the OH⁻-stretching vibration range revealed two main spectral regions: 3463–3465 cm⁻¹, associated with stoichiometry changes, and 3486–3490 cm⁻¹, linked to complex defects such as (V^-_Li)-OH and (Ta⁴⁺_Li)-OH. A distinct low-intensity line at ~3504 cm⁻¹ was observed only in doped crystals, attributed to (Nd²⁺_Li)-OH defects that significantly distort the oxygen-octahedral clusters due to the larger ionic radius of Nd³⁺ compared to Ta⁵⁺. In contrast, Cr-related defects cause only minor distortions. The Klauer method indicated that the highest concentration of OH⁻-groups occurs in the LiTaO₃:Cr³⁺ (0.09 wt%):Nd³⁺ (0.25 wt%) crystal, where multiple complex defects are present. Full article

The detection of Fe²⁺ in environmental water sources is critical due to its biological relevance and potential toxicity at elevated levels. Herein, we report a plasmon-driven catalytic sensing nanoplatform based on p-aminothiophenol (pATP)-functionalized silver nanoparticles (AgNPs) for the selective and sensitive detection of Fe²⁺. The nanoplatform exploits the inhibition of the plasmon-driven catalytic conversion of pATP to 4,4-dimercaptoazobenzene (DMAB), monitored via surface-enhanced Raman scattering (SERS) spectroscopy. The catalytic efficiency was quantified by the intensity ratio between the formed DMAB-specific Raman band and the common aromatic ring vibration band of pATP and DMAB. This ratio decreased proportionally with increasing Fe²⁺ concentration over a range of 100 µM to 1.5 mM, with a calculated limit of detection of 39.7 µM. High selectivity was demonstrated against common metal ions, and excellent recovery rates (96.6–99.4%) were obtained in real water samples. Mechanistic insights, supported by chronopotentiometric measurements under light irradiation, revealed a competitive oxidation pathway in which Fe²⁺ preferentially consumes plasmon-generated hot holes over pATP. This mechanism clarifies the observed catalytic inhibition and supports the design of redox-responsive SERS sensors. The platform offers a rapid, low-cost, and portable solution for Fe²⁺ monitoring and holds promise for broader applications in detecting other redox-active analytes in complex environmental matrices. Full article

Both ZnO and BeO semiconductors crystallize in the hexagonal wurtzite (wz), cubic rock salt (rs), and zinc-blende (zb) phases, depending upon their growth conditions. Low-dimensional heterostructures ZnO/Be_xZn_1-xO and Be_xZn_1-xO ternary alloy-based devices have recently gained substantial interest to design/improve the operations of highly efficient and flexible nano- and micro-electronics. Attempts are being made to engineer different electronic devices to cover light emission over a wide range of wavelengths to meet the growing industrial needs in photonics, energy harvesting, and biomedical applications. For zb materials, both experimental and theoretical studies of lattice dynamics ${\mathsf{\omega }}_{\mathrm{j}}\left(\overrightarrow{\mathrm{q}}\right)$ have played crucial roles for understanding their optical and electronic properties. Except for zb ZnO, inelastic neutron scattering measurement of ${\mathsf{\omega }}_{\mathrm{j}}\left(\overrightarrow{\mathrm{q}}\right)$ for BeO is still lacking. For the Be_xZn_1-xO ternary alloys, no experimental and/or theoretical studies exist for comprehending their structural, vibrational, and thermodynamical traits (e.g., Debye temperature ${\mathsf{\Theta }}_{\mathrm{D}}\left(\mathrm{T}\right);$ specific heat ${\mathrm{C}}_{\mathrm{v}}\left(\mathrm{T}\right))$. By adopting a realistic rigid-ion model, we have meticulously simulated the results of lattice dynamics, and thermodynamic properties for both the binary zb ZnO, BeO and ternary Be_xZn_1-xO alloys. The theoretical results are compared/contrasted against the limited experimental data and/or ab initio calculations. We strongly feel that the phonon/thermodynamic features reported here will encourage spectroscopists to perform similar measurements and check our theoretical conjectures. Full article

The increasing prevalence of antimicrobial resistance alongside the pharmacological limitations and adverse effects associated with conventional antibiotics necessitates the development of novel and efficacious antimicrobial agents. In this study, magnetic iron oxide nanoparticles (MIONPs) were synthesized via a chemical co-precipitation method. Activated carbon (AC) derived from Hibiscus esculentus (HE) fruit was coated onto the nanoparticle surfaces to fabricate MIONPs/HEAC nanocomposites. To augment their antimicrobial properties, silver ions were chemically reduced and deposited onto the MIONPs/HEAC surface, yielding MIONPs/HEAC@Ag nanocomposites. Comprehensive characterization of the synthesized nanocomposites was performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), dynamic light scattering (DLS), and zeta potential analysis. DLS measurements indicated average particle sizes of approximately 122 nm and 164 nm for MIONPs/HEAC and MIONPs/HEAC@Ag, respectively. Saturation magnetization values were determined to be 73.6 emu/g for MIONPs and 65.5 emu/g for MIONPs/HEAC. Antibacterial assays demonstrated that MIONPs/HEAC@Ag exhibited significant inhibitory effects against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923, with inhibition zone diameters of 11.50 mm and 13.00 mm, respectively. In contrast, uncoated MIONPs/HEAC showed negligible antibacterial activity against both bacterial strains. These findings indicate that MIONPs/HEAC@Ag nanocomposites possess considerable potential as antimicrobial agents for biomedical applications, particularly in addressing infections caused by antibiotic-resistant bacteria. Full article

To probe the properties of single atoms is a challenging task, especially from the experimental standpoint, due to sensitivity limits. Nevertheless, it is sometimes possible to achieve this by making corresponding choices and adjustments to the experimental technique and sample under investigation. In the present case, the absolute value of the electronic charge the Fe atoms acquire when they are adsorbed on the surface of aluminum oxide α-Al₂O₃(0001) was measured by a set of surface-sensitive techniques: low-energy ion scattering (LEIS), Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and work function (WF) measurements, in combination with density functional theory (DFT) calculations. The main focus was the submonolayer coverage of Fe atoms in situ deposited on the well-ordered stoichiometric α-Al₂O₃(0001) 7 nm thick film formed on a Mo(110) crystal face. An analysis of the evolution of the Fe LVV Auger triplet upon variation of the Fe coverage shows that there is electronic charge transfer from Fe to alumina and that its value gradually decreases as the Fe coverage grows. The same trend is also predicted by the DFT results. Extrapolation of the experimental Fe charge value versus coverage plot yields an estimated value of a single Fe atom adsorbed on α-Al₂O₃(0001) of 0.98e (electron charge units), which is in reasonable agreement with the calculated value (+1.15e). The knowledge of this value and the possibility of its adjustment may be important points for the development and tuning of modern sub-nanometer-scale technologies of diverse applied relevance and can contribute to a more complete justification and selection of the corresponding theoretical models. Full article

Coordination polymers are attractive materials for various fields of practical application. The high degree of freedom of choice of metal ions and organic ligands plays a critical role in functional diversification. In the present study, we report the liquid–liquid interfacial synthesis of a 2D bis(terpyridine)copper(II) polymer thin film, Cu-tpy. The synthesized Cu-tpy was characterized by various microscopic observations such as TEM, SEM, and AFM, and spectroscopic measurements such as XPS, Raman spectroscopy, SEM/EDS, and UV–Vis spectroscopy. Synchrotron-radiated X-ray scattering confirmed that Cu-tpy was oriented crystalline films. Moreover, Cu-tpy showed electrochemical micro-supercapacitor behavior in the solid-state owing to its ionic nature. This study expands the potential of bis(terpyridine)metal(II) polymers as electro-functional materials. Full article

Surface-enhanced Raman scattering (SERS) spectroscopy is an ultra-sensitive analytical method with the powerful signal-molecule detection capability. Coupling with the polydimethylsiloxane (PDMS) material, SERS can be enabled on a polymeric substrate for fast-developing bio-compatible sensing applications. However, due to PDMS’s high viscosity, conventional PDMS-SERS substrates are typically thick and stiff, limiting their freedom for engineering flexible micro/nano functioning devices. To address this issue, we propose to adopt a low viscosity decamethylcyclopentasiloxane (D5) solvent as a diluent solution. Via controlling the mixture ratio of D5 and PDMS and the spin-coating speed for deposition, this method resulted in a film of a well-defined thickness from sub-millimeter down to a 100 nm scale. Furthermore, thanks to the unsaturated Si-H chemical bonds in the PDMS curing agent, the PDMS film could effectively reduce the $A{g}^{+}$ ions to Ag nanoparticles (NPs) directly bonding onto the substrate surface uniformly. Via adjusting the size and density of the AgNPs through reaction temperature and time, strong SERS was achieved and verified using R6G with the detection limit down to 0.1 ppm, attributed to the AgNPs’ plasmonic enhancement effect. Full article

The process of recycling lithium-ion batteries is drawing global attention due to a shortage of critical raw materials (CRMs), a sustainable and environmentally friendly approach that meets the needs of many industries. Characterization is an important step in the recycling of black mass resulting from the processing of a lithium-ion battery at the beginning and the end of the processes because of the complexity of the feed material and to evaluate the process. This research proposes a beneficiation flowchart for the further separation of graphite particles from metal oxides based on the characterization results by combining scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), laser-induced breakdown spectroscopy, laser scattering particle size distribution analysis, X-ray fluorescence (XRF), X-ray diffraction analysis (XRD), inductively coupled plasma–optical emission spectroscopy (ICP-OES), and thermogravimetry–differential thermal analysis (TG/DTA). Based on these characterization results, it is suggested that black mass with coarser particle size (0.2–1 mm) goes to the liberation process for beneficiation of the Al and Cu and black mass with a size range of 0.053–0.2 mm goes to the froth flotation for beneficiation of the Mn, Ni, Fe, and Co. Finally, a black mass with a size range of <0.053 mm goes through the froth flotation after the agglomeration process. Full article

We report the first synthesis of zwitterionic thiacalixarenes featuring imidazolium and sulfonate groups on the upper rim and alkyl (butyl or octyl) fragments on the lower rim of the platform. Despite their amphiphilic structure, these macrocycles exhibit limited water solubility. However, dynamic light scattering detected the formation of associates for derivatives with octyl moieties at a concentration of 0.1 mM. To develop stable materials for aqueous environments and to investigate the functionality of zwitterionic sulfonate-imidazolium groups along with the thiacalixarene platform, mixed organo-organic systems based on polydiacetylene polymer were created. Characterization of the modified polydiacetylene systems through various analytical methods revealed a significant colorimetric response to lead ions in aqueous media, surpassing that of the unmodified polydiacetylene polymer. Additionally, the modified polymers demonstrated efficacy in purifying aqueous media from lead ions, as evidenced by anodic stripping voltammetry (ASV) and microwave plasma atomic emission spectroscopy (MP AES). Full article

Understanding cellular interaction with nanomaterials represents a subject of great interest for the validation of new diagnostic and therapeutic tools. A full characterization of a designed product includes the evaluation of its impact on specific biological systems, including the study of cell behavior as a response to that particular interaction. Copper and copper-based nanoparticles (CuO NPs) have emerged as valuable building blocks for various biomedical applications such as antibacterial and disinfecting agents for infectious diseases, and the evaluation of the metabolism of food, including the iron required for proteins and enzymes or as drug delivery systems in cancer therapy. In this study, the biological impact of manganese-doped crystalline copper oxide (CuO:Mn) nano-platelets on human normal BJ fibroblasts and human A375 skin melanoma was assessed. The particles were synthesized at room temperature via the hydrothermal method. A complete physicochemical characterization of the materials was performed by employing various techniques including X-ray diffraction, electron microscopy, X-Ray photoelectron spectroscopy, and dynamic light scattering. Morphological investigations revealed a flat structure with nearly straight edges, with sizes spanning in the nanometer range. XRD analysis confirmed the formation of the CuO phase with good crystallinity, while XPS provided insights into the Mn doping. The findings indicate that nano-platelets interact with cells actively by mediating essential molecular processes. The exogenous manganese triggers increased MnSOD production in mitochondria, compensating ROS produced by external stress factors (Cu²⁺ ions), and mimics the endogenous SODs production, which compensates internal ROS production as it normally results from cell biochemistry. The effect is differentiated in normal cells compared to malignant cells and deserves investigation. Full article

The colloidal long-storage stability of nanosized drugs is a crucial factor for pharmacology, as they require much time for robust estimation. The application of bioavailable magnetic nanosuspensions in theranostics is limited by incomplete information about their colloidal stability in the internal media of human organisms. A method for the accelerated temperature stress “aging” of magnetic nanosized suspensions is proposed for the rapid assessment and prediction of the colloidal stability over time of nanosized iron oxide suspensions stabilized by albumin HSA. Colloidal stability is assessed using dynamic light scattering (DLS), fluorescence spectroscopy, electrophoresis, and ion monitoring methods during short- and long-term storage. Rapid assessment is achieved by short high-temperature (70 °C) processing of carboxymethyl-dextran-coated nanosol in the presence of albumin. The role of albumin in the sustained stability of superparamagnetic iron oxide particles (SPIONs) was studied under conditions mimicking blood plasma (pH = 7.4) and endolysosomal cell compartments (pH = 5.5). According to the fluorescence quenching and DLS data, colloidal stability is ensured by the formation of an HSA corona on carboxymethyl-dextran-coated SPIONs and their process of clustering. In the presence of albumin, the colloidal stability of nanoparticles is shown to increase from 80 to 121 days at a storage temperature of 8 °C The prognostic shelf life of magnetic nanosol is estimated by calculating the Van’t Hoff’s relation for the rate of chemical reactions. The validity of using the Van’t Hoff’s rule is confirmed by the agreement of the calculated activation energy at 8 °C and 70 °C. The developed method of the accelerated aging of nanoparticles can not only be employed for the estimation of the shelf life of magnetic nanoparticles coated with HSA in vitro but also for assessing the stability of SPIONs applied in vivo. Full article

In this research, Hall effect experiments and optical fittings were mainly conducted to elucidate the effect of hydrogen annealing on the electronic properties of polycrystalline Al-doped Zinc Oxide thin films by distinguishing the scattering by ion impurities and the scattering by grain boundaries. By comparing the carrier density and those mobilities of H₂-annealed samples with Ar-annealed samples, the effect of H₂ annealing was highlighted. AZO thin films were prepared on the quartz glass substrate at R.T. by an RF magnetron sputtering method, and the carrier density was controlled by changing the number of Al chips on the Zn target. After fabricating them, they were post-annealed in hydrogen or argon gas. Optical fitting was based on the Drude model using the experimental data of Near-Infrared spectroscopy, and the mobility at grain boundaries was analyzed by Seto’s theory. Other optical and crystalline properties were also checked by SEM, EDX, XRD and profilometer. It is indicated that the H₂ annealing would improve both carrier density and mobility. The analysis referring to Seto’s theory implied that the improvement of mobility was caused by the carrier generation from introduced hydrogen atoms both at the grain boundary and its intragrain region. Furthermore, the effect of H₂ annealing is relatively pronounced especially in low-doped region, which implies that Al and H have some interaction in AZO thin film. The interaction between Al and H in AZO thin film is still not confirmed, but this result implied that this interaction negatively affects the mobility at grain boundary. Full article

Zinc oxide (ZnO) has recently gained considerable attention due to its exceptional properties, including higher electron mobility, good thermal conductivity, high breakdown voltage, and a relatively large exciton-binding energy. These characteristics helped engineers to develop low dimensional heterostructures (LDHs)-based advanced flexible/transparent nanoelectronics, which were then integrated into thermal management systems. Coefficients of thermal expansion $\mathsf{\alpha }\left(\mathrm{T}\right),$ phonon dispersions ${\mathsf{\omega }}_{\mathrm{j}}(\overrightarrow{\mathrm{q}})$, and Grüneisen parameters ${\mathsf{\gamma }}_{\mathrm{j}}\left(\overrightarrow{\mathrm{q}}\right)$ can play important roles in evaluating the suitability of materials in such devices. By adopting a realistic rigid-ion model in the quasi-harmonic approximation, this work aims to report the results of a methodical study to comprehend the structural, lattice dynamical, and thermodynamic behavior of zinc-blende (zb) ZnO. Systematic calculations of ${\mathsf{\omega }}_{\mathrm{j}}(\overrightarrow{\mathrm{q}})$, ${\mathsf{\gamma }}_{\mathrm{j}}\left(\overrightarrow{\mathrm{q}}\right),$ and $\mathsf{\alpha }\left(\mathrm{T}\right)$ have indicated negative thermal expansion (NTE) at low T. Soft transverse acoustic shear mode gammas ${\mathsf{\gamma }}_{\mathrm{T}\mathrm{A}}$ at critical points offered major contributions to NTE. Our results of ${\mathsf{\omega }}_{\mathrm{j}}(\overrightarrow{\mathrm{q}})$ at ambient pressure compare reasonably well with Raman scattering spectroscopy measurements and first-principles calculations. By adjusting the layers of materials with positive and negative thermal expansion, it is possible to create LDHs with near-zero $\mathsf{\alpha }\left(\mathrm{T}\right)$. Such a nanostructure might experience a minimal dimensional change with T fluctuations, making it ideal for devices where precise dimensional stability is crucial. Full article