X-ray Photoelectron Microscopy Research Articles

Novel bioelectrode for sweat lactate sensor based on platinum nanoparticles/reduced graphene oxide modified carbonized silk cocoon

Silk cocoons were used as a bioelectrode for the wearable electrochemical sensors of sweat lactate via carbonization and the in situ electrodeposition of platinum nanoparticles (PtNPs) and reduced graphene oxide (rGO), followed by lactate oxidase immobilization. Scanning electron microscopy, atomic force microscopy, and x-ray photoelectron microscopy confirmed that PtNPs/rGO were deposited on the carbonized silk cocoon surfaces, characterized via the physical and chemical alterations of silk cocoons. The electrocatalytic activity of PtNPs and the high surface area and functionality of rGO enhanced the electrochemical sensitivity of the sensor in lactate detection. This biosensor detected sweat lactate selectively in a range of 0–25 mM with a limit of detection of 0.07 mM, which is sufficient to distinguish between normal individuals and muscle fatigue-prone patients at a cut-off sweat lactate level of 12.5 mM. This biosensor was applied for sweat lactate detection and validated through laser desorption–ionization mass spectrometry with satisfactory results. This bioelectrode exhibits cytocompatibility with non-irritation and non-allergy to human skin, highlighting its application as a wearable lactate biosensor for self-monitoring of muscle fatigue.

Rapid assembly of mixed thiols for toll-like receptor-based electrochemical pathogen sensing.

Herein, we describe a rapid and facile fabrication of electrochemical sensors utilizing two different toll-like receptor (TLR) proteins as biorecognition elements to detect bacterial pathogen associated molecular patterns (PAMPs). Using potential-assisted self-assembly, binary mixtures of 11-mercaptoundecanoic acid (MUA) and 6-mercapto-1-hexanol (MCH), or MUA and an in-house synthesized zwitterionic sulfobetaine thiol (DPS) were assembled on a gold working electrode within 5 minutes, which is >200 times shorter than other TLR sensors' preparation time. Electrochemical methods and X-ray photoelectron microscopy were used to characterize the SAM layers. SAMs composed of the betaine terminated thiol exhibited superior resistance to nonspecific interactions, and were used to develop the TLR sensors. Biosensors containing two individually immobilized TLRs (TLR4 and TLR9) were fabricated on separate MUA-DPS SAM modified Au electrodes (MUA-DPS/Au) and tested for their response towards their respective PAMPs. The changes to electron transfer resistance in EIS of the TLR4/MUA-DPS/Au sensor showed a detection limit of 4 ng mL-1 for E. coli 0157:H7 endotoxin (lipopolysaccharide, LPS) and a dynamic range of up to 1000 ng mL-1. The TLR4-based sensor showed negligible response when tested with LPS spiked human plasma samples, showing no interference from the plasma matrix. The TLR9/MUA-DPS/Au sensor responded linearly up to 350 μg mL-1 bacterial DNA, with a detection limit of 7 μg mL-1. The rapid assembly of the TLR sensors, excellent antifouling properties of the mixed SAM assembly, small size and ease of operation of EIS hold great promise for the development of a portable and automated broad-spectrum pathogen detection and classification tool.

Engineering the S-scheme heterojunction between NiFeAl - LDH and BiOCOOH nanoflower by constructing an interfacial electric field for efficient degradation of levofloxacin under visible light

The antibiotic levofloxacin (LVF), utilized across the world during the COVID-19 pandemic, presents a notable concern in environmental safety owing to its deposition in water bodies. This work reports the engineering of S-scheme heterojunction, NiFeAl LDH coupled with BiOCOOH nanoflower by constructing an interfacial electric field for efficient degradation of LVF under visible light. The scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis reveal the uniform decoration of NiFeAl LDH flakes over flowers like BiOCOOH and the high crystallinity is confirmed with SAED pattern distribution. The construction of an interfacial electric field was confirmed by X-ray photoelectron microscope (XPS) analysis. The X-ray diffraction (XRD), XPS, and Raman spectroscopy studies were conducted to confirm the purity and chemical bonding nature of the BiOCOOH-NiFeAl LDH nanocatalyst (NFB NCs). The band gap of materials was calculated to be 3.38 and 2.03 eV for BiOCOOH and NiFeAl LDH respectively. The NFB NCs showed remarkable performance of 95.2 % than its pristine BiOCOOH (35.4 %) and NiFeAl LDH (18 %). ESR and scavenging studies identified the major involvement of •OH, O2•- and h+ in the process. The intermediates formed during the degradation were examined by using GC–MS and a possible degradation pathway was proposed. Furthermore, the toxicity analysis using the ECOSAR program demonstrates NFB NCs safety level for extensive wastewater treatment. The stability of the NCs over six cycles and magnetic removal properties showcased their potential for large-scale wastewater treatment applications. This comprehensive study highlights the importance of LDH in advancing photocatalytic materials for environmental remediation and paves a way for manufacturing innovation.

Tailoring the composition of a non-noble, Cubic Shaped MnSn(OH)6 Bi-functional electrocatalysts for methanol and urea oxidation reactions in alkaline solutions

A systematic study of the effect of Sn-precursor concentration on the composition of (MnSn(OH)6) is carried out, and the samples' structural, morphological, and electrochemical variations are investigated. Four different SnCl2·5H2O precursor concentrations (5, 10, 20, and 40 mM) are varied to synthesize MnSn(OH)6 electrocatalysts, denoted as MS-1, MS-2, MS-3, and MS-4, respectively, using a hydrothermal method. All four samples' crystal structure and chemical states are identified using X-ray diffraction analysis and X-ray photoelectron microscopy. Morphological studies are carried out using scanning electron and transmission electron microscopy studies. The electrocatalytic performance and the stability of the synthesized samples are evaluated using cyclic voltammetry and chronoamperometry. Among the samples, MS-3, which has an optimized ratio of Mn/Sn, displayed the highest current density values of 80.3 mA g−1 and 84.7 mA g−1 at a higher potential of 0.7 V for the urea oxidation reaction in the presence of 0.33 M urea + 1.0 M KOH and for the methanol oxidation reaction in the presence of 0.5 M methanol + 1.0 M KOH, respectively. This intrinsic activity of MS-3 samples is due to its more significant electrochemically active surface area value of 208 mF cm−2, primarily because of the dominance of Mn3+ on the surface. Furthermore, MS-3 displayed reduced overpotential, as evidenced by the onset potential of 1.45 (V vs RHE) @ 10 mA cm−2, indicating enhanced electrocatalytic performance. These findings highlight the importance of tuning the Mn/Sn metal ratio to design and develop cost-effective non-precious electrocatalysts for urea and methanol oxidation reactions.

A facile green synthesis of gold nanoparticles using Canthium parviflorum extract sustainable and energy efficient photocatalytic degradation of organic pollutants for environmental remediation

Organic dye and nitrophenol pollution from textiles and other industries present a substantial risk to people and aquatic life. One of the most essential remediation techniques is photocatalysis, which uses the strength of visible light to decolorize water. The present study reports Canthium Parviflorum (CNP) leaf extract utilization as an effective bio-reductant for green synthesis of Au NPs. A simple, eco-friendly process with low reaction time and temperature was adopted to synthesize CNP extract-mediated Au-NPs (CNP-AuNPs). The prepared AuNPs characterization involving X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS) surface area analysis, ultraviolet–visible spectroscopy (UV–Vis). XRD results showed that the cubic-structured AuNPs had a crystallite size of 14.12 nm. Assessment of organic dyes performance in degrading brilliant green (BTG) and amido black 10B (AMB) under visible light irradiation highlights an impressive 83.25% and 86% degradation efficiency within 120 min, accompanied by a kinetic rate constant dyes was found to be 0.0828 min⁻1, BTG, and 0.0123 min⁻1, Furthermore, the reduction of 4-nitrophenol by NaBH4 using CNP-AuNPs as a catalyst demonstrated good catalytic performance and rapid degradation at 89.4%. and rate constant 0.099 min−1 followed pseudo-first-order. The LC-MS analysis identified various intermediates during the degradation of the CR dye. Radical trapping experiments suggest that photogenerated free electrons and hydroxyl radicals are crucial for degrading the amido black 10B dye The AuNPs influenced the significant factors responsible for the photocatalytic activity, such as the increase in range of absorbance, increased e− and h+ pair separation, improvement in the charge transfer process, and active site formation, which significantly enhanced the process of degradation. We found that the CNP-AuNPs could effectively remove dyes and nitrophenol from industrial wastewater.

Synergistic effects and electrocatalytic insight of single-phase hexagonal structure as low-temperature solid oxide fuel cell cathode

Enhancing the electrocatalytic activity of the electrode materials, specifically oxygen reduction reaction (ORR), at lower operating temperatures (<600 °C) is the prime rank to realize the commercialization of solid oxide fuel cells (SOFCs) research. Herein, a new hexagonal structure-based cathode material was developed with the co-doping of Gd2O3 and Cr2O3 of parent SrFe12O19 oxide, respectively. At 550‒475 °C, Sr0.90Gd0.10Fe11.90Cr0.10O19 (SFO-10) cathode sample leading to the large peak power density (PPD) of 395 mW/cm2, has appropriate surface oxygen defects (Oβ) up to 17%, as verified by X-ray photoelectron microscopy (XPS). Theoretical calculations reveal that the co-doping of Gd and Cr oxides creates lattice disorder at the hexagonal lattice, which decreases the energy barrier for ion transport and enhances the electrocatalytic characteristics of ORR. Consequently, the SFO-10 cathode shows a favorable ORR activity with the least lower polarization resistance (ASR) at 550 °C with gadolinium-doped ceria (GDC) electrolyte. This work provides a self-assembled single-phase hexagonal cathode to accelerate the low-temperature hindrance of SOFC technology.

Characterizing oxidation, thickness, and composition of metallic glass thin films with combined electron probe microanalysis and X-ray photoelectron spectroscopy

Metallic glass thin films (MGTFs) are a recently developed class of alloy coatings with potential applications ranging from biomedical devices to electrical components. Their tribological performance in service conditions is dictated by MGTF bulk composition but can be limited by the native oxide surface that inevitably forms upon exposure to atmosphere. Surface oxidation, thickness, and composition of ZrCuNiAl MGTFs were characterized using a combination of X-ray photoelectron microscopy (XPS) and electron probe microanalysis (EPMA). MGTF samples with nominal thicknesses of 50, 500, and 1500 nm were sputtered onto Si and SiN wafer substrates within a high vacuum deposition chamber and their amorphicity was confirmed by X-ray diffraction. XPS depth profiling identified the thin film composition and showed that the surface oxide was dominated by a mixed layer of mostly ZrO2, a little oxidized Al, and some metallic Zr. EPMA X-ray intensities were acquired as a function of beam energy to excite characteristic X-rays from different depths of the MGTFs and reconstructed using open-source thin film analysis software BadgerFilm, to determine the composition and thickness of sample layers. EPMA results constrain the composition to be Zr54Cu29Al10Ni7 within 0.7 at. % variation and total thicknesses to be 49, 470, and 1546 nm. Using the oxide composition identified from XPS depth profiling as an input for BadgerFilm analysis, EPMA results indicate the surface oxidation layer on each of the thin film samples was 6.5 ± 1.1 nm thick and uniform across a 0.25 mm region of the film.

Unveiling nano-scale chemical inhomogeneity in surface oxide films formed on V- and N-containing martensite stainless steel by synchrotron X-ray photoelectron emission spectroscopy/microscopy and microscopic X-ray absorption spectroscopy

Nano-scale chemical inhomogeneity in surface oxide films formed on a V- and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron- based hard X-ray Photoelectron emission spectroscopy (HAXPES) and microscopy (HAXPEEM) as well as microscopic X-ray absorption spectroscopy (µ-XAS) techniques. The results reveal the inhomogeneity in the oxide films on the micron-sized Cr2N- and VN-type particles, while the inhomogeneity on the martensite matrix phase exists due to localised formation of nano-sized tempering nitride particles at 600 °C. The oxide film formed on Cr2N-type particles is rich in Cr2O3 compared with that on the martensite matrix and VN-type particles. With the increase of tempering temperature, Cr2O3 formation is faster for the oxidation of Cr in the martensite matrix than the oxidation of Cr nitride-rich particles.

Facile Synthesis and Electrochemical Analysis of Zn-Doped V2O5 Anode Materials for High-Rate Li Storage

The surging demand for Li rechargeable batteries with high energy densities and rapid rate capability has propelled research on materials that can replace the conventional anode materials like graphite. Vanadium pentoxides (V2O5) have emerged as promising anode candidates owing to their excellent rate capability. Specifically, V2O5 allows the electrochemical prelithiation process, in which three Li-ions can be inserted to form Li3V2O5, followed by reversible insertion and extraction of two Li-ions. Nevertheless, the unsatisfactory Li-ion diffusion coefficients and electrical conductivities of these materials remain major drawbacks. Here, we propose a Zn-doped V2O5 anode, fabricated using a two-step sol–gel method, for high-rate Li-ion batteries. Zn was incorporated into V2O5 to enhance the Li-ion transport kinetics through the electrode. The crystal structure (orthorhombic) of Zn-doped V2O5 was identified by X-ray diffraction analysis, and the Zn doping was confirmed by X-ray photoelectron microscopy. The effect of Zn doping was thoroughly examined using various analytical methods, such as cyclic voltammetry and galvanostatic intermittent titration technique. The Zn-doped V2O5 electrode exhibited remarkable cycling durability, enduring for 1000 cycles, while retaining an enhanced capacity, even under a high rate of 2C.

Cobalt concentration effect on the Structural, Magnetic and Optical properties of Zn1-xCoxSe Nanoparticles

Cobalt doped Zinc selenide (Zn1-xCoxSe where x = 0.00,0.03, 0.05, 0.07, 0.09, 0.1, 0.15) nanoparticles are synthesized using co-precipitation method. For studying structural properties of prepared samples, nanoparticles are characterized by XRD (X-ray diffraction),SEM (Scanning Electron Microscope) with EDX (Energy Dispersive X-ray Diffractometer), HRTEM (High resolution transmission electron microscope),Elemental composition confirmed by EDX (Energy Dispersive X-ray Diffractometer), Inductively coupled plasma (ICP) spectroscopy test and XPS (X-ray photoelectron microscope). XRD study confirms that prepared samples are crystalline in nature and size is appeared in nanometer range with cubic structure. Optical investigation is done by UV–visible spectra and PL spectra at room temperature which indicates change in energy band gap as doping of cobalt increases in host material due to quantum confinement which shows the altered optical properties due to doping of transition metal in host material. FTIR (Fourier transform infra-red) spectroscopy reports presence of different functional groups in nanoparticles and thermal stability is confirmed by TG/DTA(Thermogravimetric) analysis. Magnetic analysis by using ESR (electron spin resonance) and VSM (Vibrating Sample Magnetometer) confirms presence of ferromagnetic coupling in cobalt doped zinc selenide nanoparticles which make these nanoparticles suitable for using in different devices e.g. in magnetic storage devices, magnetic imaging, magneto-optics and sensors etc. Combined semiconducting and magnetic nature of these Co doped ZnSe nanoparticles make them useful in spintronics, magnetic storage devices etc applications.

Fabrication and characterization of binary composite MgO/CuO nanostructures for the efficient photocatalytic ability to eliminate organic contaminants: A detailed spectroscopic analysis

Design and eco-friendly fabrication of affordable and sustainable materials for the treatment of wastewater consisting of dyes, antibiotics, and other harmful substances has always been demanding. Untreated wastewater being released from industries imposes serious threats to our ecosystem, seeking convenient approaches to diminish this alarming issue. Here in this work, we synthesized MgO/CuO nanocomposites from a plant extract of Ammi visnaga L. and then employed these nanocomposites for the treatment of organic dye (methylene blue). We characterized the synthesized nanocomposites by dynamic light scattering (DLS), zeta potential, scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and X-ray photoelectron microscopy (XPS). DLS presented information about the explicit size of nanocomposites, while the surface charge was examined by zeta potential. XRD provided detailed information about the crystalline behavior and the information regarding surface morphology and size was extracted by SEM, TEM, and AFM. Moreover, the fabricated nanocomposites were used as a photocatalyst in the treatment of methylene blue. The overall catalytic reaction took an hour to complete, and the value of percentage degradation was 98 %. Substantially, a detailed account of the kinetics, rate of reaction, and mechanism is also fostered in the context. The presented study can assist scientists and researchers around the world to reproduce the results and use them to apply them on a broader scale.

Synthesis of stannite Cu2CoSnS4 and its use as photocatalyst for degradation of pollutants

We report the synthesis of p-type stannite Cu2CoSnS4 (CCTS) powder by direct fusion, and its use as a photocatalyst for the degradation of methylene blue (MB) under solar irradiation. Structural analysis by X-ray diffraction and Raman spectroscopy revealed that the prepared powder is polycrystalline and has preferential orientation along the (112) plane, characteristic of the stannite phase. Scanning electron microscopy (SEM) images show agglomerated nanoparticles. Compositional analysis by energy dispersive spectroscopy shows that the composition of the prepared CCTS powder approaches the theoretical 2:1:1:4 stoichiometry. The oxidation state of the constituent elements in CCTS powder were investigated by X-ray photoelectron microscopy (XPS), which reveals that the valence states of the constituent elements present in the CCTS sample are: Cu+, Co2+, Sn4+and S2−. Optical analysis through diffusion reflectance and photoluminescence (PL) spectroscopy were used to estimate the bandgap, which was found to be about 1.4 eV. Upon visible light illumination, CCTS powder exhibits an excellent photocatalytic performance. The apparent reaction rate constant k found to be k = 13.10−3 min−1, which suggests that the p-type stannite CCTS powder would be a promising candidate of photocatalyst for the degradation of MB in aqueous solution.

Characterization of Surface Modifications in Oxygen Plasma-Treated Teflon AF1600.

We explore the surface properties of Teflon AF1600 films treated by oxygen plasma with various procedure parameters. Contact angle (CA) measurements, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron microscopy (XPS) are employed to investigate the wetting behavior, surface topography, and chemical composition, respectively. While the etched thickness reveals a linear relationship to the applied plasma energy, the surface presents various wetting properties and topographies depending on the plasma energy: low advancing and zero receding CA (1 kJ), super high advancing and zero receding CA (2-3 kJ), and super high advancing and high receding CA (≥4.5 kJ) for the wetting behaviors; pillar-like (≤6 kJ) and fiber-like (>6 kJ) nanoscaled structures for the topographies. The results of XPS analysis reveal slight changes in the presence of O- and F-components (<4%) after oxygen plasma treatment. Furthermore, we discuss the applicability of the Wenzel and Cassie-Baxter equations and employ the Friction-Adsorption (FA) model, where no wetting state and structure-related parameters are needed, to describe the CAs on the plasma-treated surfaces. Additionally, we conduct electrowetting experiments on the treated surfaces and find that the experimental results of the advancing CA are in good agreement with the predictions of the FA model.

One-Step Non-Contact Additive LIFT Printing of Silver Interconnectors for Flexible Printed Circuits

The single-pass one-step method for printing conductive silver tracks on a glass surface, using the laser-induced forward transfer (LIFT) technique, was proposed, providing a unique opportunity for high-throughput printing of surface micro- and nanostructures with high electrical conductivity and positioning accuracy. This method was developed via our multi-parametric research, resulting in the selection of the optimal material, laser irradiation, and transfer conditions. Optical, scanning and transmission electron, and atomic force microscopy methods, as well as X-ray diffraction, were used to characterize the surface structure and phase state of the printed structures, while energy-dispersive X-ray and X-ray photoelectron microscopy were employed for their chemical microanalysis. Depending on the laser irradiation parameters, the specific electrical conductivity of the printed tracks varied from 0.18 to 83 kS/cm, approaching that of donor magnetron-sputtered films. This single-pass one-step method significantly facilitates fast, large-scale, on-demand local laser printing of metallic (sub)microcomponents of microelectronic devices.

Fe3O4-CdO Nanocomposite for Organic Dye Photocatalytic Degradation: Synthesis and Characterization

In this study, pure CdO nanoparticles, magnetic Fe3O4 nanoparticles, and Fe3O4-CdO nanocomposites were prepared via a solution combustion method using cetyltrimethylammonium bromide (CTAB) as a template. These prepared nanomaterial samples were characterized by X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron microscopy (XPS), transmittance electron microscopy (TEM), and scanning electron microscopy (SEM) analysis. XRD patterns confirmed the purity and the crystalline nature of the prepared samples. FTIR and Raman spectra observed the metal-oxygen (M-O) bond formation. UV-vis DRS studies were performed to investigate the optical properties and the bandgap energy determination. The surface morphology and the size of the pure CdO nanoparticles, magnetic Fe3O4, and nanocomposites of Fe3O4-CdO were determined via TEM and SEM analysis. Under optimum experimental conditions, the Fe3O4-CdO nanocomposites were applied for photocatalytic activity against Methylene blue dye. Under visible light irradiation, Fe3O4-CdO nanostructures showed an efficient photocatalytic degradation of 92% against Methylene blue organic dye and showed excellent stability for multiple cycles of reuse.

Effect of annealing environment on the electrochemical performance of biosynthesized V2O5@C thin films

In the present work, the V2O5 thin films were prepared on flexible stainless steel mesh (FSSM) substrate using Bengal gram bean extract (BGBE) as a medium by reflux condensation method for its use as an electrode for supercapacitor application. The bio-molecules present in BGBE were in-situ converted into carbonaceous material after the annealing process. A systematic study of the influence of the annealing environment was investigated by heating the as-prepared V2O5 thin films in two different annealing atmospheres viz nitrogen and air. The annealing of the as-prepared V2O5 thin films under N2 atmosphere (V2O5-N) produces more carbonaceous material when compared to V2O5 thin films annealed in air atmosphere (V2O5-A). Interestingly, annealing in air atmosphere completely oxidizes the biomass, while annealing in nitrogen leaves traces of carbonaceous matrix in the thin film. This improves the conductivity and electrical properties of the material and its advantage is taken in fabricating supercapacitor devices. The obtained V2O5-N and V2O5-A thin films were characterized using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Raman, and X-ray Photoelectron Microscopy (XPS). Moreover, the electrochemical performance of V2O5-N and V2O5-A was investigated. The V2O5-N electrode exhibited a specific capacitance (Csp) of 633.3 F g−1 with an energy density (ED) of 87.9 wh kg−1 at 2 mA cm−2 current density and good cycles stability with capacitive retention of 86.2 % over the 10,000 continuous GCD cycles which is higher than the V2O5-A. A flexible symmetric solid state (SSC) device was assembled using V2O5-N electrodes with PVA-LiClO4 gel electrolyte. The device exhibited a Csp of 82.6 F g−1 with an ED of 22.4 wh kg−1 at 1 mA cm−2 current density. In summary, the V2O5-N demonstrated significantly improved electrochemical performance than the V2O5-A electrode and is supported with the appropriate data.

Superparamagnetic titanate nanocomposites obtained from a polymorphic mixture of titanium dioxide

The n-type titanate heterojunction with p-type transition metal oxides reduces the recombination effect (e−/h+) and improves the magnetic, electronic, and luminescent properties. Based on these related properties, the synthesis of nanocomposite sodium-cobalt titanate nanotube and iron oxide (Co-NaTiNT@FeO) was performed using titanium dioxide (polymorphic mixture: brookite, anatase and rutile), cobalt nitrate hexahydrate and iron oxide (FeO). The synthesized materials were characterised by X-ray diffraction (XRD), Raman and infrared (IR) spectroscopies, thermogravimetry and differential (TG-dTG), transmission electron microscopy (TEM) and scanning (SEM), X-ray photoelectron spectroscopy (XPS), adsorption/desorption of N2 by Brunauer-Emmett-Teller (BET) method, Ultraviolet–Visible (UV–Vis) by diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and vibrating sample magnetometer (VSM). The results revealed the presence of Co2+ ions in the lamellar region of the nanotubes, in addition to verifying that there was no collapse of the nanotubes before and after the anchoring of the FeO nanoparticles. Using the XPS technique, the presence of 2.49 wt% of Fe (2p), as well as 1.55 wt% of Co (2p), was identified; these elements favoured the band gap reduction from 3.61 to 2.66 eV compared to sodium titanate nanotube (NaTiNT); in addition, they favoured the emergence of emissions associated with the red, yellow, and orange colours, described through PL. The surface area of the composite changed from 197.00 to 210.46 m2 g−1, possibly due to the homogeneous presence of anchored superparamagnetic FeO nanoparticles. Finally, the results were consistent with the proposal for the synthesis of Co-NaTiNT@FeO, which had improvements in its properties, especially its magnetic properties.

In Situ Fabrication and Characterization of g-C3N4 onto Cellulose Nanofibers and Selective Separation of Heavy Metal Ions.

Graphitic carbon nitride nanosheets were synthesized onto cellulose nanofiber surfaces utilizing an eco-friendly salt melt approach. The fabricated material CNF@C3N4 selectively removes Ni(II) and Cu(II) from electroplating wastewater samples. The immobilization of g-C3N4 on solid substrates eases handling of nanomaterial in a flow-through approach and mitigates sorbent loss during column operations. Characterization techniques such as scanning electron microscopy, tunneling electron microscopy, and X-ray photoelectron microscopy were employed to analyze the surface morphology and chemical bonding within the synthesized material. Selective Cu(II) and Ni(II) sorption predominantly arises from the soft-soft interaction between metal ions and associated nitrogen groups. An inner-sphere surface complexation mechanism effectively elucidated the interaction dynamics between the metal and CNF@C3N4. Experimental findings demonstrated satisfactory separation of Ni(II) and Cu(II) ions, with the extraction of 340.0 and 385.0 mg g-1 of material, respectively. Additionally, the devised technique was executed for the preconcentration and quantification of trace metals ions in water samples with a detection limit and limit of quantification of 0.06 and 0.20 μg L-1, respectively.

Guanidinium-Functionalized Polymer Dielectrics for Triboelectric Bacterial Detection.

Development of rapid detection strategies that target potentially pathogenic bacteria has gained increasing attention due to the increasing awareness for better health and safety. In this study, we evaluate an intrinsically antimicrobial polymer, 2Gdm, which is a poly(norbornene)-based functional polymer featuring guanidinium groups as side chains, for bacterial detection by the means of triboelectric nanogenerators (TENGs) and triboelectric nanosensors (TENSs). Attachment of bacteria to the sensing layer is anticipated to alter the overall triboelectric properties of the underlying polymer layer. The positively charged guanidinium functional groups can interact with the negatively charged phospholipid bilayer of bacteria and lead to bacterial death, which can then be detected by optical microscopy, X-ray photoelectron microscopy, and more advanced self-powered sensing techniques such as TENGs and TENSs. The double bonds present along the poly(norbornene) backbone allow for thermally induced cross-linking to obtain X-2Gdm and thus rendering materials remain stable in water. By monitoring the change in voltage output after immersion in various concentrations of Gram-negative Escherichia coli (E. coli) and Gram-positive Streptococcus pneumoniae (S. pneumoniae), we have demonstrated the utility of X-2Gdm as a new polymer dielectric for autonomous bacterial detection. As the bacterial concentration increases, the amount of adsorbed bacteria also increases, resulting in a decrease in the surface potential of the X-2Gdm thin film; this reduction in surface potential can cause a decrease in the triboelectric output for both TENGs and TENSs, which serves as a key working mechanism for facile bacterial detection. TENG and TENS systems are capable of detecting E. coli and S. pneumoniae within a range of 4 × 105 to 4 × 108 CFU/mL with a limit of detection of 106 CFU/mL. This report highlights the promising prospects of employing TENGs and TENSs as innovative sensing technologies for rapid bacterial detection by leveraging the electrostatic interactions between bacterial cell membranes and cationic groups present on polymer surfaces.

Co-Free Heteroatom-Doped P2-Type Layered Oxide Cathodes: Advancing High Power Sodium-Ion Battery Technology

Sodium-ion battery technology has been blooming as an indigenous solution to stationary storage applications, triggering the cultivation of a cutting-edge alternative to the archaic lithium-ion (Li-ion) batteries due to high abundance, inexpensiveness, sustainability, safety and similar redox chemistry as of Li-ion technology 1. Although Na-ion batteries are propitious however, challenges such as long-term stability, high energy density, high specific capacity have impeded the practical application 2. The stepping stone for a successful Na-ion battery lies in the cathode, thus researchers have focused on development of layered oxide cathode. These are classified into P2, P3, O3 phases, depending on the environment of Na (prismatic or octahedral) and the stacking sequence of the anionic layers 3. P2-type Na0.67Ni0.33Mn0.65O2 (NMNO) cathodes offer high theoretical capacity, environmental friendliness, air-moisture stability, facile synthesis, and direct sodium-ion diffusion. However, there are still some setbacks, such as limited reversible capacity, rapid capacity decay, sluggish Na-ion kinetics, cracking and exfoliation in the crystallites 4. In order to overcome the challenges faced by sodium-ion batteries, researchers have employed several strategies such as inert or active cation substitution, limiting the cut-off voltage, surface modification, preparation of mixed-phase materials, sodium compensation additives, selection of binder, and choice of electrolyte 5. One of the most effective strategies is the doping of electrochemically inactive transition metals in layered transition metal oxide cathodes. However, a better understanding of the parameters that govern the stability of these cathodes are still necessary.By exploring the various factors that impact the stability of layered transition metal oxide cathodes, we propose a novel approach to synthesize a durable P2-type Na0.67Ni0.33Mn0.65Nb0.02O2 (NMNNbO) electrode with robust hexagonal crystallites through a quick, energy-efficient and cost-effective microwave-irradiated synthesis technique. Previous studies have utilized modified Pechini or conventional solid-state routes for inactive transition metal doping, which can be expensive, time-consuming and energy-intensive 6. This leads to an efficient cathode material with higher capacity and improved rate capability, which could be produced on a commercial scale at a lower cost due to the reduced synthesis time. A comprehensive investigation of the cathode material through X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron microscopy (XPS), reveals its superior electrochemical performance, stability, and durability. Through the use of advanced in-situ and ex-situ characterization techniques, the mechanism of Na-ion insertion and extraction, phase transition, and crack formation have been elucidated. Additionally, first-principle calculations using density functional theory (DFT) have been employed to gain a deeper understanding on the role of Nb in the cathode material. Electrochemical characterization was done against Na-metal in a half-cell format utilizing the electrolyte, 1 M NaPF6 in ethylene carbonate and propylene carbonate (1:1). The practicality of the material has also been validated through the evaluation of a full-cell performance against pre-sodiated hard carbon anode. A deeper understanding of the parameters affecting the electrochemical performance, can accelerate the development of high power and durable sodium-ion batteries, making them a more viable option for energy storage applications.