Zinc Aluminum Research Articles

Bandgap engineering—Influence of the evolution of (Zn/Mg)Al2O4:Cr3+ spinel phosphors on the photoluminescence properties

AbstractAs a luminescent center ion in materials for deep red and near‐infrared light, Cr3+ has been extensively studied in octahedral host materials. In this study, using zinc aluminate (ZnAl2O4) and magnesium aluminate (MgAl2O4) spinels with abundant octahedra as substrates, a series of Zn1−xMgxAl2O4:0.5%Cr3+ (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) fluorescent powders were first prepared via a high‐temperature solid‐state method. The influence of different Mg/Zn ratios on (Zn/Mg)Al2O4:0.5%Cr3+ optical properties was thoroughly explored. Experimental results show that an increase in the Mg/Zn ratio reduces the crystal field strength (Dq) and leads to distortion of the [AlO6] octahedra, resulting in broadening of the photoluminescence emission spectrum. Furthermore, the addition of Mg gradually reduces the formation of inverse spinel. An appropriate Mg/Zn ratio can improve luminescent intensity and quantum efficiency. In summary, this paper, through bandgap engineering by adjusting the Mg/Zn ratio, provides a detailed account of the changes in optical properties and the underlying mechanisms during the transition from ZnAl2O4:0.5%Cr3+ to MgAl2O4:0.5%Cr3+ spinels. It offers valuable insights for further research on the practical applications of Cr3+ in areas such as lighting displays and bioimaging.

Preparation of a Solid-Phase Compound from an Aluminum–Zinc Alloy under Conditions of Low-Temperature Superplasticity

Preparation of a Solid-Phase Compound from an Aluminum–Zinc Alloy under Conditions of Low-Temperature Superplasticity

Glycerol carbonate synthesis via Zn(OBu)2/AlCl2(OBu) initiated-glycerolysis of urea

Glycerol carbonate (4-hydroxymethyl-1,3-dioxolane-2-one) was efficiently synthesized from glycerolysis of urea initiated by Zn(OBu)2/Al(OBu)Cl2. The zinc-aluminum complex mixture was prepared from zinc chloride (ZnCl2) and aluminum tri-sec-butylate (Al(OBu)3. The complex successfully initiated the urea glycerolysis in 1 : 1 ​mol ratio of glycerol to urea to produce glycerol carbonate up to 85% and selectivity up to 97% at 150 ​°C and 1 ​atm of N2 for 4 ​h in the absence of solvents. Isocyanate was observed as a key intermediate in this reaction. A kinetic study showed the reaction likely followed pseudo first-order kinetics with estimated activation energy (Ea) of 38 ​kJ/mol. Density-functional theory calculations with MN15-L functional described the formation of glycerol carbonate as spontaneous with the Gibbs free energy of −28.41 ​kJ ​mol−1.

Effect of adding silver on photocatalytic properties of ZnAl2O4 nanopowder synthesized using microemulsion and polyacrylamide gel methods for recycled water

In recent decades, water purification and removal of organic pollutants such as organic dyes have been among the most important issues. Photocatalyst is one of the most effective methods for recycled water to eliminate organic pollutants and break them down into safe compounds. One of the most significant factors for determining the efficiency of photocatalyst nanoparticles is the utilization of new synthesis methods. Microemulsion and polyacrylamide gel methods are the two methods that were used for the synthesis of zinc aluminate nanoparticles for this study. The powders obtained from these two synthesis methods were characterized using the X-ray diffraction (XRD) technique, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and ultraviolet–visible spectroscopy (UV–Vis) which were utilized as photocatalysts in the photocatalytic degradation reaction of methylene blue (MB). The results demonstrated that the nanoparticles synthesized in both methods were of single-phase zinc aluminate with a spinel structure. The crystallite size obtained for zinc aluminate synthesized using the microemulsion method was 21.7 nm, whereas, in the polyacrylamide gel method, it was 26.3 nm. Microscopic images represented smaller and more uniform particle sizes in the nanoparticles obtained by the microemulsion method. The band gap energy of zinc aluminate nanoparticles obtained using microemulsion and polyacrylamide gel methods was 4.15 and 3.82 eV, respectively. Similarly, the results of MB removal showed that zinc aluminate nanoparticles synthesized using the microemulsion method and polyacrylamide gel, respectively, were 100% and 71% after 120 min. In the second phase of this study, silver nanoparticles were added to zinc aluminate nanoparticles during the synthesis process. X-ray diffraction showed that silver nanoparticles are formed metallically next to zinc aluminate. Moreover, the addition of silver decreased the crystallite size and slightly increased the band gap energy of zinc aluminate. The results of MB dye degradation tests in the presence of ZnAl2O4–Ag nanocomposites showed that the kinetics of dye degradation increased when the silver increased up to 5 wt%. Finally, the mechanism studied on dye degradation using scavenger agents showed that the main agents of dye degradation are the superoxide radical and the holes created in the valence band. It was consistently confirmed by examining the valence and conduction band potentials and also by comparing these potentials with those responsible for producing superoxide and hydroxyl radicals.

An experimental investigation of the effects of blending camphor oil infused with jack fruit biodiesel and nanoparticles on the performance, combustion, and exhaust emissions of a compression ignition engine

Growing urbanisation, higher standards of living, and population growth are all factors that will drive up global energy demand. The direct injection of jack fruit biodiesel in compression ignition engine to result in indigent performance and to overcome the addition of nanoparticles of zinc oxide, cerium oxide, and aluminium oxide to biodiesel-camphor blends is the focus of this research. The fuels’ soluble were tested at a temperature range of 30 °C, 50 °C, and 100 °C. One was picked to simulate a diesel engine's performance, combustion, and emissions. Equal parts of zinc oxide, cerium oxide, and aluminium oxide (100 ppm each) were included into the mixture. The inclusion of nanoparticles in the fuel increases its calorific value. Nanoparticles as catalysts enhanced brake-specific fuel consumption by 3.6%, 13.5%, and 17.5% for zinc oxide (ZnO), cerium oxide, (CeO2) and aluminium oxide (Al2O3) compared to diesel at full load. ZnO, CeO2, and Al2O3 nanofuels improved brake thermal efficiency by 15.3%, 10.8%, and 4% at higher loads than BD10C10 at full load. Max heat release increased 10.64%, 9.36%, and 8.8% for ZnO, CeO2, and Al2O3 nanofuels. Carbon monoxide, hydrocarbons, nitrogen oxides, and smoke emissions were reduced when nano-fluid was added in diesel. Directions for using Nano-assisted renewable fuel sources to reduce fossil fuel use as a novel approach in the present study.

Behavior of Zn5Al hot-dip galvanized steel members under fire exposure

PurposeBased on the known positive effects of conventional hot-dip galvanizing under fire exposure and indicative results on zinc–aluminum coatings from smallscale tests, a series of tests were conducted on zinc-5% aluminum galvanized test specimens under fire loads to verify the previous positive findings under largescale boundary conditions.Design/methodology/approachThe emissivity of zinc-5% aluminum galvanized surfaces applied to steel specimens was determined experimentally under real fire loads and laboratory thermal loads in accordance with the normative specifications of the standard fire curve. Both large and smallscale specimens were used in this study. The steel grade and surface conditions of the specimens were varied for both test scenarios.FindingsLargescale tests on specimens with typical steel construction dimensions under fire loads showed that the surface emissivity of zinc-5% aluminum galvanized steel was significantly lower than that of the conventionally galvanized steel. Only minor influences from the weathering of the specimens and steel chemistry were observed. These results agree well with those obtained from smallscale tests. The design values of zinc-5% aluminum melt (Zn5Al) required for the structural fire design were proposed based on the obtained results.Originality/valueThe novel tests presented in this study are the first ones to study the behavior of zinc-5% aluminum galvanized largescale steel construction components under the influence of real fire exposure and their positive effect on the emissivity of steel components galvanized by this method. The results provide valuable insights and information on the behavior in the case of fire and the associated savings potential for steel construction.

Eliminating surface cracks in metal film-polymer substrate for reliable flexible piezoelectric devices

In a flexible piezoelectric-metal-polymer device, the occurrence of surface cracks in metal-polymer interface may cause unstable metal connections, unreliable piezoelectric yield, poor passivation behaviour and metal electrode delamination. In this study, the properties of polydimethylsiloxane (PDMS) polymer substrate are optimised, and the sputter-deposition of aluminium (Al) and molybdenum (Mo) metal film layer is controlled to eradicate cracks and promote only surface wrinkles on large area metal-polymer interface. The PDMS substrate thickness of ∼123.8 µm, 20:1 prepolymer base to curing agent weight ratio, 50 °C PDMS curing temperature and 30 min of Al sputtering time have been discovered to produce crack-free wrinkle-only Al thin film layer on PDMS substrate. The Al thin film is 100 % conductive over large area and adhere well on PDMS with 0 % of Al removal. The grown zinc oxide (ZnO) and aluminium nitride (AlN) piezoelectric layer on the improved Al-PDMS are of good crystal quality, generating low leakage current and decent piezoelectric voltage. The attained crack-free wrinkled-only metal film-polymer substrate interface is vital for flexible piezoelectric-metal-polymer device to perform well as an acoustic sensor, energy harvester, or even as an insulation/buffer layer in stretchable electronics.

Peristaltic transport of hybrid nanofluid under the effects of thermal radiation through asymmetric curved geometry: a numerical approach

ABSTRACT Magnetohydrodynamics (MHD) has various applications in the field of medicine, particularly in drug delivery and hyperthermia treatment for cancer therapy to the affected area via peristaltic phenomena. Further elaboration is required to optimize the delivery method of hybrid nanoparticles with aluminum oxide and zinc oxide to the target area via the esophagus to get the best-desired results. Keeping the importance of MHD in mind, the present problem highlights the characteristics of Magnetohydrodynamics (MHD) peristaltic transport by incorporating the properties of nanoparticles of aluminum and zinc oxides when suspended in water through an asymmetric curved conduit. The governing equations are mathematically modeled under consideration of Hall current, viscous dissipation, ohmic heating, thermal radiation, and heat sink/source effects. The influence of magnetic field, velocity, and thermal slips is also considered. Negligible Reynolds number and long-wavelength approximations are used to overcome the complexity of the system. To compute the numerical solutions of the simplified nonlinear system, two different techniques are utilized via MATLAB and Mathematica. The outcomes of the different flow parameters on the hybrid nanofluid’s velocity, trapping phenomena, temperature distribution, heat transfer rates, and pressure gradient are analyzed through tables and graphs.

Interaction of Glass Powder with Al Powder and Zinc Oxide in Aluminum Paste

By analyzing the interaction of different glass powders with Al powder and Zinc oxide, the effect of the wetting property of glass powders on the surface morphology of aluminum paste and the adhesion between aluminum paste and Zinc oxide substrate is discussed. The effect of wetting property for different glass powders on Al and Zinc oxide is analyzed by a high-temperature contact angle tester, and the contact angle-temperature and extension radius-temperature curves are determined during the wetting process of the glass powders. The microstructure of the cross-section of the glass powders and of the substrate, and the surface morphology of the aluminum pastes are analyzed by a scanning electron microscope. Adhesion between the aluminum paste and the Zinc oxide substrate is analyzed by a vertical tensile strength meter. The results show that the wetting property of glass powder is an important factor affecting the adhesion and surface morphology of the paste, and it plays a role in preventing excessive oxidation of aluminum paste during sintering at high temperatures.

Using RAM method for optimal selection of flame retardant nanocomposite material fabrication solution

This study aimed to optimize the selection of manufacturing solutions for flame retardant nanocomposite materials based on polyvinyl chloride (PVC). A total of eight different options were considered. The first option utilized PVC as the base material, and the subsequent options were carried out by adding specific amounts of reinforcing agents, including aluminum hydroxide (ATH) and zinc borate (ZB). The seven following options were denoted by their respective symbols: 5ATH/PVC, 10ATH/PVC, 15ATH/PVC, 5ZB/PVC, 10ZB/PVC, 15ZB/PVC, and 5ATH/5ZB/PVC. The number preceding the symbol of the reinforcing agent represents the percentage of the reinforcing agent added to the PVC material. For example, 5ATH/PVC signifies the addition of 5% of ATH reinforcing agent to the PVC material. To evaluate each option, five different indices were employed. The weight for each index was determined using four different methods, including the Equal method, Entropy method, MEREC method, and LOPCOW method. The RAM method was used to select the best option. The combination of the RAM method and the four weight determination methods generated four different datasets of option rankings. In all four of these datasets, the best and worst options consistently matched. The results indicated that the 15ATH/PVC option was deemed the best, while the pure PVC option was the worst.

Design, synthesis, and thermal stability of rare earth luminescent materials

As a new generation of luminescent materials, aluminate rare earth materials have the characteristics of long luminescent time, adjustable wavelength and high brightness. Aluminate rare earth luminescent materials were prepared by high temperature solid-state method, and the luminescent properties of the luminescent materials were studied. Firstly, the author synthesized magnesium aluminate, calcium aluminates, and zinc aluminate matrix by combustion method. Then aluminate rare earth luminescent materials were prepared by high temperature solid phase method through raw material distribution, raw material mixing, drying, calcination, and post-treatment. Finally, a fluorescence spectrophotometer was used to measure the excitation and emission spectra of the prepared sample material. The research results indicate that the excitation wavelength does not affect the relationship between the emission wavelength and light intensity, the emission spectra of MgAl2O4:Tb3+ and CaAl2O4:Tb3+ exhibit narrowband transition emission states; When the mass fraction of rare earth factor Eu3+ in the activator is 6% and the temperature is 1300?C, the emission peak intensity of the luminescent material reaches its maximum value, and the luminescence intensity is the best.

An on-site and portable electrochemical sensing platform based on spinel zinc ferrite nanoparticles for the quality control of paracetamol in pharmaceutical samples.

In this study, crystalline spinel zinc ferrite nanoparticles (ZnFe2O4 NPs) were successfully prepared and proposed as a high-performance electrode material for the construction of an electrochemical sensing platform for the detection of paracetamol (PCM). By modifying a screen-printed carbon electrode (SPE) with ZnFe2O4 NPs, the electrochemical characteristics of the ZnFe2O4/SPE and the electrochemical oxidation of PCM were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and differential pulse voltammetry (DPV) methods. The calculated electrochemical kinetic parameters from these techniques including electrochemically active surface area (ECSA), peak-to-peak separation (ΔEp), charge transfer resistance (Rct), standard heterogeneous electron-transfer rate constants (k0), electron transfer coefficient (α), catalytic rate constant (kcat), adsorption capacity (Γ), and diffusion coefficient (D) proved that the as-synthesized ZnFe2O4 NPs have rapid electron/mass transfer characteristics, intrinsic electrocatalytic activity, and facilitate the adsorption-diffusion of PCM molecules towards the modified electrode surface. As expected, the ZnFe2O4/SPE offered excellent analytical performance towards sensing of PCM with a detection limit of 0.29 μM, a wide linear range of 0.5-400 μM, and high electrochemical sensitivity of 1.1 μA μM-1 cm-2. Moreover, the proposed ZnFe2O4-based electrochemical nanosensor also exhibited good repeatability, high anti-interference ability, and practical feasibility toward PCM sensing in a pharmaceutical tablet. Based on these observations, the designed electrochemical platform not only provides a high-performance nanosensor for the rapid and highly efficient detection of PCM but also opens a new avenue for routine quality control analysis of pharmaceutical formulations.

Influence of Si contents on the microstructure and corrosion resistance of the Zn−Al−Mg−Si alloys

Hot dip galvanized products are widely used in various aspects of production and life due to their excellent corrosion resistance. Some studies have added a fourth trace alloying element to the zinc aluminum magnesium coating to form a quaternary alloy for better performance. This article prepared two different types of Zn−Al−Mg alloy ingots with trace amounts of Si added by induction melting, consisting of Zn1Al1Mg0.01Si and Zn1Al1Mg0.05Si, and solidified them in a heating furnace with argon gas protection atmosphere. The precipitation process of Zn1Al1Mg(0.01,0.05)Si alloy components under non equilibrium and equilibrium solidification conditions was calculated. The initial crystalline phase of the alloy and the initial solidification temperature were predicted through phase diagram calculations. The microstructure and phase types of the alloy were analyzed using scanning electron microscopy (SEM) and field emission scanning electron microscopy (FE-SEM). The electrochemical Tafel curves of Zn1Al1Mg(0.01,0.05)Si with different Si contents showed that the Zn1Al1Mg0.05Si has the highest corrosion potential and Zn1Al1Mg0.01Si has the lowest corrosion current which means the 1Al1Mg0.01Si alloy possesses the highest corrosion resistance. The Nyqust curves and bode curves also showed that the practical impedance of 1Al1Mg0.01Si alloy is higher than that of 1Al1Mg0.05Si. Moreover, electron probe X-ray micro-analyzer(EPMA) reveals the distribution of Si elements in the Zn1Al1Mg(0.01,0.05)Si. At present, there is little research on the microstructure and properties of quaternary alloys containing silicon. Therefore, studying the influence of silicon content on the microstructure and properties of alloys is of great significance.

Toxicity of Metal Oxide Nanoparticles: Looking through the Lens of Toxicogenomics.

The impact of solubility on the toxicity of metal oxide nanoparticles (MONPs) requires further exploration to ascertain the impact of the dissolved and particulate species on response. In this study, FE1 mouse lung epithelial cells were exposed for 2-48 h to 4 MONPs of varying solubility: zinc oxide, nickel oxide, aluminum oxide, and titanium dioxide, in addition to microparticle analogues and metal chloride equivalents. Previously published data from FE1 cells exposed for 2-48 h to copper oxide and copper chloride were examined in the context of exposures in the present study. Viability was assessed using Trypan Blue staining and transcriptomic responses via microarray analysis. Results indicate material solubility is not the sole property governing MONP toxicity. Transcriptional signaling through the 'HIF-1α Signaling' pathway describes the response to hypoxia, which also includes genes associated with processes such as oxidative stress and unfolded protein responses and represents a conserved response across all MONPs tested. The number of differentially expressed genes (DEGs) in this pathway correlated with apical toxicity, and a panel of the top ten ranked DEGs was constructed (Hmox1, Hspa1a, Hspa1b, Mmp10, Adm, Serpine1, Slc2a1, Egln1, Rasd1, Hk2), highlighting mechanistic differences among tested MONPs. The HIF-1α pathway is proposed as a biomarker of MONP exposure and toxicity that can help prioritize MONPs for further evaluation and guide specific testing strategies.

Microwaves assisted deconstruction of HDPE waste into structured carbon and hydrogen fuel using Al2O3-(Ni, Zn, Mg)Fe2O4 composite catalysts

Plastic waste management is becoming an issue of global concern due to the excessive consumption of plastics with one-time use. The decomposition of plastic into valuable products by catalytic pyrolysis has gained significant attention as a promising method of valorizing plastic waste. This paper demonstrates the microwave-assisted decomposition of plastic waste materials for carbon nanotubes (CNTs) and high H2 production using magnetic-based catalysts via in-situ exsolution. Magnetic-based catalysts, namely Al2O3-NiFe2O4, Al2O3-ZnFe2O4, and Al2O3-MgFe2O4 were prepared using aluminum oxide, iron nitrate, zinc nitrate, and magnesium nitrate. CNTs and H2 were produced from the decomposition of wasted HDPE using the prepared catalysts. The Al2O3-NiFe2O4 catalyst showed better formation of CNTs and gas due to its low dielectric loss factor. The high surface area and magnetic-support interaction also promoted the catalytic activity of the catalyst. The oil byproduct mainly contained C8-C16 compounds, showing better selectivity for small molecules in the tested process. Conclusively, Al2O3-NiFe2O4 produced CNTs with good structural properties and fewer impurities than Al2O3-ZnFe2O4 and Al2O3-MgFe2O4 composites. The Al2O3-NiFe2O4 catalyst showed 90% hydrogen composition in evolved gases. In all cases, almost 90% of the hydrogen evolved from the feedstock within the first 2 min of the processing time.

Analysis of Different Piezoelectric Materials on the Film Bulk Acoustic Wave Resonator

The performance of film bulk acoustic wave resonators (FBAR) is greatly dependent on the choice of piezoelectric materials. Different piezoelectric materials have distinct properties that can impact the performance of FBAR. Hence, this work presents the analysis of three different piezoelectric materials which are aluminum nitride (AlN), scandium aluminum nitride (ScAlN) and zinc oxide (ZnO) on the performance of FBARs working at resonance frequencies of 6 GHz until 10 GHz. The one-dimensional (1-D) modelling is implemented to characterize the effects of these materials on the quality (Q) factor, electromechanical coupling coefficient (k2eff) and bandwidth (BW). It is determined that employing ScAlN in FBAR results in the highest Q factor, ranges from 628 to 1047 while maintaining a relatively compact area (25 µm × 25 µm) and thickness (430 nm to 720 nm). However, ScAlN yields the narrowest BW, measuring 0.11 GHz at 6 GHz, as opposed to AlN and ZnO, which exhibit broader bandwidths of 0.16 GHz and 0.23 GHz, respectively.

Multiple hydrogen bonds enable high strength and anti-swelling cellulose-based ionic conductive hydrogels for flexible sensors

Although ionic conductive hydrogels (ICHs) have been widely utilized to fabricate excellent flexible sensors, traditional ICHs are generally easy to swell, resulting in the inevitable failure of flexible sensors. Herein, a facile and effective strategy is employed to impart ICHs with excellent mechanical properties, satisfying anti-swelling property, favorable anti-freezing property, and high ion-conductivity simultaneously, that is to construct multiple hydrogen bonds (H-bonds) through directly dissolving cellulose in salt solutions, avoiding the tedious preparation process of traditional ICHs as well. Notably, the cellulose is directly dissolved in the solution containing zinc ions (Zn2+) and aluminum ions (Al3+), and then acrylic acid (AA) and acrylamide (AAm) are copolymerized in it. Multiple H-bonds are formed among the abundant − OH groups, −NH2 groups, and − COOH groups belonging to cellulose, AAm, and AA, respectively. As a result, the improved anti-swelling ability (88.03 %) and compressive performance (24.11 MPa) of the resultant Ion-C-P(AA-co-AAm) hydrogel are achieved. Besides, excellent conductivity (48.39 mS/cm) and frost resistance are provided by generous Zn2+ and Al3+. Moreover, Ion-C-P(AA-co-AAm) hydrogel exhibits favorable sensitivity in monitoring human activities and can output stable electrical signals in a low-temperature environment, showing a great potential application for flexible sensors.

Facile Synthesis of Spinel Zinc Aluminate Using Biofuel For Effective Photocatalytic Dye Degradation And Electrochemical Sensor Studies

Zinc aluminate nanomaterial provide a potential candidate for photocatalytic and sensor applications. Using biofuel (banana peel powder), zinc aluminate was synthesized by SCM (solution combustion method) in the current study. The properties of the phase structures, chemical composition, morphologies, and photocatalytic sensors were characterized by utilizing powder X-ray diffraction, scanning electron microscope, CH analyzer, UV-Visible spectroscopy, and photocatalytic reactor. Indigo Carmine (IC) dye degradation under UV light was used to assess the photocatalytic activity. The results showed that zinc aluminate makes a superior photocatalyst for degrading organic dyes like indigo carmine. In a potassium hydroxide electrolyte medium, zinc aluminate was also an effective substance for paracetamol and lead metal sensing. The results confirm that the novel material could be used for various industrial applications.

Immunogenicity of different nanoparticle adjuvants containing recombinant RBD coronavirus antigen in animal model.

Ongoing mutations of SARS-CoV-2 present challenges for vaccine development, promising renewed global efforts to create more effective vaccines against coronavirus disease (COVID-19). One approach is to target highly immunogenic viral proteins, such as the spike receptor binding domain (RBD), which can stimulate the production of potent neutralizing antibodies. This study aimed to design and test a subunit vaccine candidate based on the RBD. Bioinformatics analysis identified antigenic regions of the RBD for recombinant protein design. In silico analysis identified the RBD region as a feasible target for designing a recombinant vaccine. Bioinformatics tools predicted the stability and antigenicity of epitopes, and a 3D model of the RBD-angiotensin-converting enzyme 2 complex was constructed using molecular docking and codon optimization. The resulting construct was cloned into the pET-28a (+) vector and successfully expressed in Escherichia coli BL21DE3. As evidenced by sodium dodecyl-polyacrylamide gel electrophoresis and Western blotting analyses, the affinity purification of RBD antigens produced high-quality products. Mice were immunized with the RBD antigen alone or combined with aluminum hydroxide (AlOH), calcium phosphate (CaP), or zinc oxide (ZnO) nanoparticles (NPs) as adjuvants. Enzyme-linked immunosorbent assay assays were used to evaluate immune responses in mice. In-silico analysis confirmed the stability and antigenicity of the designed protein structure. RBD with CaP NPs generated the highest immunoglobulin G titer compared to AlOH and ZnO after three doses, indicating its effectiveness as a vaccine platform. In conclusion, the recombinant RBD antigen administered with CaP adjuvant NPs induces potent humoral immunity in mice, supporting further vaccine development. These results contribute to ongoing efforts to develop more effective COVID-19 vaccines.

Formic Acid Gas Sensors Based on Electrolytically Exfoliated Graphene-loaded Flame-Made Spinel Zn2SnO4 Composites

In this w ork, effective gas-sensing material were prepared by combining spinel zinc stannate (Zn2SnO4) nanoparticles synthesized by flame spray pyrolysis and graphene produced by the electrolytic exfoliation for volatile organic acids (VOAs) detection. The effect of graphene content in the range of 0.2–5 wt% on formic acid (HCOOH)-sensing performance of Zn2SnO4 nanoparticles was evaluated. Structural, physical, and chemical properties were investigated using X-ray diffraction, Raman spectroscopy, BET-surface analysis, energy dispersive X-ray spectroscopy, and electron microscopy. From the gas-sensing test towards 0.005-0.1 vol% HCOOH in dry air at 200-400°C, the graphene-loaded Zn2SnO4 sensor with the optimal graphene content of 0.5 wt% displayed the highest response of ~4970 towards HCOOH at the optimal temperature of 300°C. Moreover, it showed high HCOOH selectivity against several other VOAs, volatile organic compounds, and environmental gases. Therefore, graphene-loaded spinel Zn2SnO4 sensors could be attractive choices for selective HCOOH detection and useful for food science and industrial applications.