High-resolution Microscopy Techniques Research Articles

Emerging Technologies for the Discovery of Novel Diversity in Cyanobacteria and Algae and the Elucidation of Their Valuable Metabolites

Until recently, the study of cyanobacteria and microalgae has been hampered by the need to cultivate these organisms to gain insight into their cytomorphology, life cycle and molecular biology. However, various microbial species characterized by thick sheaths of exopolymeric substances were difficult to isolate in culture due to their associated symbiotic bacteria. Other microbes evaded culture. Such challenges have now been overcome by the development of metagenomic techniques that allow direct DNA sequencing from environmental samples, as well as high resolution microscopy techniques that permit direct imaging of environmental samples. The sampling of understudied taxa from extreme environments and of toxic species has been facilitated by specialized robotic equipment. Single-cell sequencing has allowed for the proper characterization of microalgal species and their response to environmental changes. Various strains of cyanobacteria, microalgae and macroalgae have gained renewed interest for their high-value metabolites. This paper provides an overview of the emerging technologies and explains how they are being used to identify such strains and their products for industrial application. Advances in genetic engineering and CRISPR technology have facilitated the production of strains that are more amenable to culture, metabolite extraction, scale-up and application in biorefinery approaches. Emerging analytical techniques are discussed, with the advent of multiomics and its application in this field.

Photo-induced synthesis of star poly(DL-Lactide)-templated Au and Ag nanoparticles and evaluation of their catalytic performance

In this report, photochemical synthesis of monodispersed gold (Au) and silver (Ag) nanoparticles (NPs) was reported using cholic acid functionalized star poly(DL-lactide) (CA-(PDLLA)) as a capping and reducing agent. CA-(PDLLA) was synthesized by ring-opening polymerization (ROP) of DL-lactide with a feed ratio of 1:120 (cholic acid: DL-lactide). The molecular weight of CA-(PDLLA) was measured by using the gel permeation chromatography (GPC) technique. The thermal properties of the polymer and its nanocomposite materials were studied by thermogravimetric analysis (TGA). The optical properties of Ag and Au NPs were studied by UV–visible absorption spectroscopy. Morphological studies and size of the polymer-nanocomposites were assessed by using field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) techniques. The percentage composition of Au and Ag present in the polymer-nanocomposites was calculated using energy-dispersive X-ray spectroscopic (EDX) analysis. Finally, the synthesized polymer-metal nanocomposites were used as heterogeneous catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as a model reaction and the apparent rate constant (kapp) values of CA-(PDLLA)-AuNPs and CA-(PDLLA)-AgNPs were found to be 5.76 × 10−4 s−1 and 19.7 × 10−4 s−1, respectively.

Graphitic carbon nitride (g–C3N4)-based electrochemical sensors for the determination of antiviral drug acyclovir

Acyclovir (ACR) is an antiviral drug used to treat chickenpox, shingles, and herpes infections in various parts of the body, including infants. It shortens illness duration and reduces symptoms, but may cause kidney damage and allergic reactions in some individuals. It may also be beneficial for those with compromised immune systems. ACR, despite its positive attributes, can cause kidney damage and allergic reactions in some individuals, requiring careful observation and monitoring. ACR was detected electrochemically in this work using graphitic carbon nitride (g-C3N4), which was effectively synthesized. Energy dispersive X-ray (EDX), X-ray diffraction (XRD), Raman, Fourier-transform infrared (FT-IR), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HR-TEM) techniques were used to characterize the synthesized g-C3N4. To monitor ACR, g-C3N4 combined with pure carbon paste (g-C3N4/CPE) was used in voltammetric techniques. The sensor's ability to detect the ACR via g-C3N4 was investigated utilizing the amperometric i-t curve method. Electrochemical impedance spectroscopy (EIS) was used to examine the electrochemical characteristics of various electrodes. The Rct of the bare glassy carbon electrode (GCE), the bare CPE, and the g-C3N4/CPE were, respectively, 12770Ω, 3794Ω, and 3114Ω. From 10 μM to 80 μM ACR concentration, the current response rose linearly. The constructed sensor had an exceptional detection limit of 3.52 nM. By introducing 100 μM concentrations of a variety of common interferents to the ACR solution during the measurement, it was possible to evaluate the impact of several foreign interferents on the outcomes at the g-C3N4. The electrochemical behavior of ACR was investigated in respect to several electrokinetic variables. The mechanism of potential electrochemical oxidation was demonstrated. The developed g-C3N4/CPE effectively identified ACR quantitatively in samples of human blood serum and urine.

The histomorphological and stereological assessment of rat dorsal root ganglion tissues after various types of sciatic nerve injury.

Peripheral nerve injuries lead to significant changes in the dorsal root ganglia, where the cell bodies of the damaged axons are located. The sensory neurons and the surrounding satellite cells rearrange the composition of the intracellular organelles to enhance their plasticity for adaptation to changing conditions and response to injury. Meanwhile, satellite cells acquire phagocytic properties and work with macrophages to eliminate degenerated neurons. These structural and functional changes are not identical in all injury types. Understanding the cellular response, which varies according to the type of injury involved, is essential in determining the optimal method of treatment. In this research, we investigated the numerical and morphological changes in primary sensory neurons and satellite cells in the dorsal root ganglion 30days following chronic compression, crush, and transection injuries using stereology, high-resolution light microscopy, immunohistochemistry, and behavioral analysis techniques. Electron microscopic methods were employed to evaluate fine structural alterations in cells. Stereological evaluations revealed no statistically significant difference in terms of mean sensory neuron numbers (p > 0.05), although a significant decrease was observed in sensory neuron volumes in the transection and crush injury groups (p < 0.05). Active caspase-3 immunopositivity increased in the injury groups compared to the sham group (p < 0.05). While crush injury led to desensitization, chronic compression injury caused thermal hyperalgesia. Macrophage infiltrations were observed in all injury types. Electron microscopic results revealed that the chromatolysis response was triggered in the sensory neuron bodies from the transection injury group. An increase in organelle density was observed in the perikaryon of sensory neurons after crush-type injury. This indicates the presence of a more active regeneration process in crush-type injury than in other types. The effect of chronic compression injury is more devastating than that of crush-type injury, and the edema caused by compression significantly inhibits the regeneration process.

The composition of the dental pellicle: an updated literature review.

The dental pellicle is a thin layer of up to several hundred nm in thickness, covering the tooth surface. It is known to protect the teeth from acid attacks through its selective permeability and it is involved in the remineralization process of the teeth. It functions also as binding site and source of nutrients for bacteria and conditioning biofilm (foundation) for dental plaque formation. For this updated literature review, the PubMed database was searched for the dental pellicle and its composition. The dental pellicle has been analyzed in the past years with various state-of-the art analytic techniques such as high-resolution microscopic techniques (e.g., scanning electron microscopy, atomic force microscopy), spectrophotometry, mass spectrometry, affinity chromatography, enzyme-linked immunosorbent assays (ELISA), and blotting-techniques (e.g., western blot). It consists of several different amino acids, proteins, and proteolytic protein fragments. Some studies also investigated other compounds of the pellicle, mainly fatty acids, and carbohydrates. The dental pellicle is composed mainly of different proteins, but also fatty acids, and carbohydrates. Analysis with state-of-the-art analytical techniques have uncovered mainly acidic proline-rich proteins, amylase, cystatin, immunoglobulins, lysozyme, and mucins as main proteins of the dental pellicle. The pellicle has protective properties for the teeth. Further research is necessary to gain more knowledge about the role of the pellicle in the tooth remineralization process.

Plasmon-Enhanced Perovskite Solar Cells Based on Inkjet-Printed Au Nanoparticles Embedded into TiO2 Microdot Arrays.

The exceptional property of plasmonic materials to localize light into sub-wavelength regimes has significant importance in various applications, especially in photovoltaics. In this study, we report the localized surface plasmon-enhanced perovskite solar cell (PSC) performance of plasmonic gold nanoparticles (AuNPs) embedded into a titanium oxide (TiO2) microdot array (MDA), which was deposited using the inkjet printing technique. The X-ray (XRD) analysis of MAPI (methyl ammonium lead iodide) perovskite films deposited on glass substrates with and without MDA revealed no destructive effect of MDA on the perovskite structure. Moreover, a 12% increase in the crystallite size of perovskite with MDA was registered. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) techniques revealed the morphology of the TiO2_MDA and TiO2-AuNPs_MDA. The finite-difference time-domain (FDTD) simulation was employed to evaluate the absorption cross-sections and local field enhancement of AuNPs in the TiO2 and TiO2/MAPI surrounding media. Reflectance UV-Vis spectra of the samples comprising glass/TiO2 ETL/TiO2_MDA (ETL-an electron transport layer) with and without AuNPs in TiO2_MDA were studied, and the band gap (Eg) values of MAPI have been calculated using the Kubelka-Munk equation. The MDA introduction did not influence the band gap value, which remained at ~1.6 eV for all the samples. The photovoltaic performance of the fabricated PSC with and without MDA and the corresponding key parameters of the solar cells have also been studied and discussed in detail. The findings indicated a significant power conversion efficiency improvement of over 47% in the PSCs with the introduction of the TiO2-AuNPs_MDA on the ETL/MAPI interface compared to the reference device. Our study demonstrates the significant enhancement achieved in halide PSC by utilizing AuNPs within a TiO2_MDA. This approach holds great promise for advancing the efficiency and performance of photovoltaic devices.

Effect of Nano Quaternary Ni1-xZnxFe2-2xMn2xO4 on the Structural, Optical and Dielectric Characteristics of Poly(Methyl Methacrylate)/Polyethylene Oxide Blends

Poly(methyl methacrylate)/polyethylene oxide (PMMA/PEO)/Ni1-xZnxFe2-2xMn2xO4 blends of various composition were formed using coprecipitation and casting techniques. X-ray diffraction (XRD) analysis was performed on the blends and fillers. High-resolution transmission electron microscopy technique revealed that the fillers had a crystallite size of 15–25 nm. The impact of Ni1-xZnxFe2-2xMn2xO4 loading on the light absorbance, transmission, reflectance, refractive index and extinction coefficient and the dielectric constant, energy loss functions, and optical conductivity of PMMA/PEO blend was examined. The absorbance of the PMMA/PEO blend increased irregularly as it was loaded with the nanocomposite samples, and it peaked at x = 0.25. The transmittance reduced to a minimum value (28–58%) as the blend was doped with x=0.25. The PMMA/PEO blended polymer’s direct and indirect band gaps were 5.02 and 4.74 eV, respectively. As the blend was loaded with NiFe2O4 alone, they reached their minimum values (direct/indirect: 4.94/4.66 eV). Depending on the amounts of Zn and Mn ions in the NiFe2O4 doped PMMA/PEO blends, the various blends displayed a blue-violet color on their chromaticity diagram. The electrical dielectric constant, electric modulus, ac conductivity and energy density of the different blends depended on the amount of Zn and Mn ions added in the NiFe2O4 matrix.

Robust Switchable Polarization and Coupled Electronic Characteristics of Magnesium-Doped Zinc Oxide.

Ferroelectrics possess a spontaneous polarization that is switchable by an electric field and is critical for the development of low-energy nanoelectronics and neuromorphic applications. However, apart from a few recent developments, the realization of switchable polarization in metal oxides with simpler structures has been a major challenge. Here, we demonstrate the presence of robust switchable polarization at the level of a single nanocrystallite in magnesium-doped zinc oxide thin films with polar wurtzite crystal structures. Using a combination of high-resolution scanning probe microscopy and spectroscopic techniques, voltage control of the polarization and the coupled electronic transport behavior revealing a giant resistance change of approximately 10000% is unveiled. Time- and frequency-resolved nanoscale measurements provide key insights into the polarization phenomenon and a 9-fold increase in the effective longitudinal piezoelectric coefficient. Our work thus constitutes a crucial step toward validating nanoscale ferroelectricity in polar wurtzites for use in advanced nanoelectronics and memory applications.

(Keynote) Aerogel-Derived Nickel-Iron Oxide Catalysts for Oxygen Evolution Reaction in Alkaline Media

Low-temperature alkaline water electrolyzers, both liquid alkaline and—more recently—anion exchange membrane (AEM) ones, represent an attractive path towards large-scale generation of green hydrogen, possibly without relying on precious metals, otherwise required by the competing proton exchange membrane (PEM) electrolyzer technology. Of the two alkaline systems, the AEM electrolyzer offers an additional benefit of not needing highly concentrated alkaline solutions and, upon further development, possibly not requiring any electrolyte at all. The ultimate success of the AEM technology will depend though on progress in the development of several key materials: alkaline exchange membranes, electrode ionomers, and platinum group metal-free (PGM-free) electrocatalysts for the anode and the cathode. It will also depend on successful integration of the developed materials into a complete device, aiming especially at well-performing catalyst/membrane and catalyst/ionomer interfaces that are free of significant charge and mass transport losses.The focus of this work has been on NiFe oxide electrocatalysts for oxygen evolution reaction (OER) for alkaline media in low temperature electrolyzers. The catalysts have been derived from aerogels heat-treated at different temperatures. Depending on the synthesis temperature the catalysts have shown dissimilar OER activities and morphologies, required different activation procedures and incurred diverse structural changes during testing. In addition to extensive performance evaluation in a three-electrode electrochemical cell and a small electrolyzer, the catalysts have undergone wide-ranging physicochemical characterization with the purpose of identifying causes of the differences in their activity and performance durability. Characterization involved among others high-resolution scanning microscopic techniques and electron and X-ray spectroscopy methods (e.g., EELS, XPS, EXAFS/XANES).Of special interest in this research has been the development and optimization of catalyst activation approaches, both in-situ (in an operating cell) and ex-situ. The effect of ionomer type on catalyst performance and overall performance of NiFe catalysts in electrolyzer-type electrodes has been studied, too, and will be summarized in this presentation. Acknowledgement This work has been performed as part of catalyst development efforts in Electrocatalysis Consortium (ElectroCat), funded by U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE) via Hydrogen and Fuel Cell Technologies Office (HFTO).

Synaptic expression of TAR-DNA-binding protein 43 in the mouse spinal cord determined using super-resolution microscopy.

Amyotrophic Lateral Sclerosis (ALS) is characterised by a loss of motor neurons in the brain and spinal cord that is preceded by early-stage changes in synapses that may be associated with TAR-DNA-Binding Protein 43 (TDP-43) pathology. Cellular inclusions of hyperphosphorylated TDP-43 (pTDP-43) are a key hallmark of neurodegenerative diseases such ALS. However, there has been little characterisation of the synaptic expression of TDP-43 inside subpopulations of spinal cord synapses. This study utilises a range of high-resolution and super-resolution microscopy techniques with immunolabelling, as well as an aptamer-based TDP-43 labelling strategy visualised with single-molecule localisation microscopy, to characterise and quantify the presence of pTDP-43 in populations of excitatory synapses near where motor neurons reside in the lateral ventral horn of the mouse lumbar spinal cord. We observe that TDP-43 is expressed in approximately half of spinal cord synapses as nanoscale clusters. Synaptic TDP-43 clusters are found most abundantly at synapses associated with VGLUT1-positive presynaptic terminals, compared to VGLUT2-associated synapses. Our nanoscopy techniques showed no difference in the subsynaptic expression of pTDP-43 in the ALS mouse model, SOD1G93a, compared to healthy controls, despite prominent structural deficits in VGLUT1-associated synapses in SOD1G93a mice. This research characterises the basic synaptic expression of TDP-43 with nanoscale precision and provides a framework with which to investigate the potential relationship between TDP-43 pathology and synaptic pathology in neurodegenerative diseases.

The atomic structure and mechanisms of formation of some geometrically incompatible interfaces within cubic B2 austenite – monoclinic B19′ martensite shape memory alloy microstructures

Microstructures of aged nickel‑titanium‑hafnium shape memory alloys (SMAs) Ni50.3Ti41.2Hf8.5 and Ni50.3Ti43.7Hf6 (at.%) are examined using high-resolution transmission electron microscopy (HRTEM) techniques. Characterizations of the structures of austenite-martensite, martensite-martensite, and martensite-precipitate interfaces provide new insights into cubic B2 austenite–monoclinic B19′ martensite phase transformation and martensite reorientation mechanisms. Specifically, in the absence of external load, theoretically unfavorable (001) compound martensite twins nucleate at H-phase precipitate interfaces. At the interface of these twins and the austenite matrix, a zig-zag-rise structure follows an extension of superdislocation theory previously developed to explain analogous zig-zag structured interfaces in non-shape-memory martensitic alloys. Additionally, 〈011〉 type II martensite twins that are theoretically favorable to form were also observed within the austenite matrices. However, instead of forming defect-free habit planes accommodated by elastic strains as predicted by theory, misfit dislocations worked in cooperation with elastic strain fields to accommodate atomic misfits between the austenite and martensite phases, and the elastic strain fields were smaller at the interfaces. Finally, the atomic scale thermoelastic mechanism of <011> type II twins reorienting to form (001) compound twins within the martensite is proposed in a manner consistent with direct observations of such interfaces. In total, connections with previous work on other binary and ternary NiTi base alloys show that these new mechanistic understandings generalize to other B2 - B19′ SMAs that should not perform well according to the elasticity-based Phenomenological Theory of Martensite Crystallography, yet still exhibit robust cyclic thermomechanical performances due to transformation-plasticity interactions.

Structural properties, bandgap, and complex dielectric function in Bi2Te3 thermoelectric by Valence Electron Energy Loss Spectroscopy (VEELS) analysis

This article describes the results and discussion performed to analyze the bandgap, optoelectronic properties, and complex dielectric function of Bi2Te3 thermoelectric material, using Valence Electron Energy Loss Spectroscopy. A key aspect of the report presented in this article is that the properties described above have not been analyzed and reported using the Valence Electron Energy Loss Spectroscopy technique. The material’s structure was analyzed using Rietveld and High-Resolution Transmission Electron Microscopy techniques. The band gap obtained value is 0.91 eV by Valence Electron Energy Loss Spectroscopy. Whereas, values obtained by other techniques are between 0.26 and 0.92 eV for Bi2Te3. The real part (ε1) and imaginary part (ε2) of the complex dielectric function (ε * ) were measured. For ε1, the principal peak at 1.03 eV and a second peak at 1.4 eV were observed. Furthermore, the optical dielectric constant is 8.6 for (ε0 = 0 eV), which is related to electronic contributions and is given by the refractive index squared (n2).

High-temperature graphitization characteristics of vitrinite and inertinite

In order to explore the graphitization characteristic differences between vitrinite and inertinite in coal, this study conducted high-temperature thermal simulation experiments (at five temperature points: 1800°C, 2100°C, 2400°C, 2700°C, and 3000°C) using inertinite-rich and vitrinite-rich samples as graphitization precursors. The quantitative comparison for the evolution characteristics of their graphite lattice was carried out using high-resolution transmission electron microscopy (HRTEM), X-ray diffractometer (XRD), and Raman spectroscopy (Raman) techniques. HRTEM revealed that an evident increase in carbon layer numbers and degree of extension was observed with increasing treatment temperature, XRD showed the variation of lattice parameters (d002/La/Lc) with temperature, Raman data revealed the variation of lattice defects (R2/R3) with temperature. It was discussed about the differences of graphite lattice construction processes between inertinite and vitrinite, throughout the entire temperature range of the experiment, the d002 spacing of inertinite was always smaller than that of vitrinite, indicating a higher degree of graphitization. vitrinite exhibited a uniform and smooth evolution state throughout the entire heating process, while inertinite exhibited an “inert” state between 1800°C and 2100°C (d002 values stagnated near at 0.3440 nm). With increasing simulated temperature, the defect level (R2 and R3) of vitrinite rapidly decreased below that of inertinite, throughout the entire temperature range, vitrinite demonstrated superior defect healing ability in terms of both rate and capability compared to inertinite. Under high-temperature thermal simulation, the three-dimensional lattice construction and defect elimination of vitrinite exhibited synchronous evolution characteristics. On the other hand, the formation of the graphite lattice in inertinite showed an evolutionary trend of “first three-dimensional lattice construction, followed by gradual defect elimination”.

Evaluation of synthesis time in the growth of vertical-aligned MWCNTs by spray pyrolysis

Multi-Wall Carbon Nanotubes (MWCNTs) were analyzed on crystalline silicon substrates (type P) under optimal temperature conditions, using different synthesis times (2, 3, 4, 5, 10, 20, 30, 60, 120, and 180 min) in order to examine the effect on the structural quality and length of the CNTs produced by ultrasonic spray pyrolysis, using pure toluene and ferrocene as precursor solutions under argon flow. Structural, optical, and morphological differences of the MWCNTs grown were analyzed. Raman spectroscopy evidenced the MWCNTs' high quality, noted by the ID/IG (from 0.41 to 0.68) and I2D/IG intensity ratios around 0.75. Morphological differences of the MWCNTs grow evaluated by Field Emission Scanning Electron Microscopy (FE-SEM); the micrographs examined the thickness of CNTs' layers. High-Resolution Transmission Electron Microscopy (HRTEM) technique was used to determine the diameters of CNTs, which were found from 15 to 140 nm. X-Ray Diffraction (XRD) showed two characteristic peaks around 26° and 44°, which corroborated that the MWCNTs were well-graphitized. The influence of the time in these CNTs demonstrated that the final length of these nanotubes could easily reach micrometers. The alienation was better as time increased, and the graphitization extent is good in most cases compared to other more expensive synthesis methods.

Nano-refinement of the face-centered cubic Zr(Fe,Cr)2 secondary phase particles in Zircaloy-4 alloy via localized-shearing/bending-driven fracture under high-temperature compression

Nanoparticles are extensively introduced to improve the mechanical, physical, and chemical properties of alloys. In the present study, the underlying nano-refinement mechanisms of face-centered cubic Zr(Fe, Cr)2 secondary phase particles (SPPs) that precipitated in Zircaloy-4 alloy under high-temperature compression were investigated in detail by utilizing high-resolution transmission electron microscopy (HRTEM) and conventional TEM techniques. The frequently observed Zr(Fe, Cr)2 SPPs were incoherent with the matrix and exhibited brittle fracture behaviors without measurable plasticity. HRTEM observations revealed two mechanisms underlying the nano-refinement of incoherent micro-sized SPPs via localized shear fracture on {112¯}SPP and nanoprecipitate-assisted bending fracture, respectively. The latter was, for the first time, found to occur when the movements of large SPPs were blocked by nanometer-sized SPP during alloy deformation. Accordingly, two force models were proposed to visualize their potential nano-refinement processes. The knowledge attained from this study sheds new light on the deformation behaviors of Zr(Fe, Cr)2 SPPs and their associated size refinement mechanisms under high-temperature compression, and is expected to greatly benefit the process optimization of zirconium alloys to achieve precipitate nano-refinement.

Optical Properties of Cationic Perylenediimide Nanowires in Aqueous Medium: Experimental and Computational Studies

Cationic perylenediimide derivative, namely N,N’-di(2-(trimethylammoniumiodide)ethylene) perylenediimide (TAIPDI), has been synthesized and characterized in an aqueous medium by using dynamic light scattering (DLS), X-ray diffraction (XRD), fourier-transform infrared (FTIR), scanning electron microscope (SEM), and high-resolution transmission electron microscopy (HRTEM) techniques. The optical absorption and fluorescence spectra of TAIPDI revealed the formation of aggregated TAIPDI nanowires in water, but not in organic solvents. In order to control the aggregation behavior, the optical properties of TAIPDI have been examined in different aqueous media, namely cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). Furthermore, the utilization of the examined TAIPDI for constructing supramolecular donor–acceptor dyad has been achieved by combining the electron accepting TAIPDI with the electron donating 4,4’–bis (2-sulfostyryl)-biphenyl disodium salt (BSSBP). The formed supramolecular dyad TAIPDI-BSSBP through the ionic and electrostatic π-π interactions have been well examined by various spectroscopic techniques, e.g., steady-state absorption and fluorescence, cyclic voltammetry, and time-correlated single-photon counting (TCSPC), and first principle computational chemistry methods. Experimental results suggested the occurring of intra-supramolecular electron transfer from BSSBP to TAIPDI with rate constant and efficiency of 4.76 × 109 s−1 and 0.95, respectively. The ease of construction, absorption in the UV–Visible region, and fast electron transfer process render the supramolecular TAIPDI-BSSBP complex as a donor–acceptor material for optoelectronic devices.

Nanocomposites with ZrO2@S-Doped g-C3N4 as an Enhanced Binder-Free Sensor: Synthesis and Characterization.

This study describes new electrocatalyst materials that can detect and reduce environmental pollutants. The synthesis and characterization of semiconductor nanocomposites (NCs) made from active ZrO2@S-doped g-C3N4 is presented. Electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) measurements were used to examine electron transfer characteristics of the synthesized samples. Using X-ray diffraction (XRD) and high-resolution scanning electron microscopy (HR-SEM) techniques, inclusion of monoclinic ZrO2 on flower-shaped S-doped-g-C3N4 was visualized. High-resolution X-ray photoelectron spectroscopy (XPS) revealed successful doping of ZrO2 into the lattice of S-doped g-C3N4. The electron transport mechanism between the electrolyte and the fluorine tin-oxide electrode (FTOE) was enhanced by the synergistic interaction between ZrO2 and S-doped g-C3N4 as co-modifiers. Development of a platform with improved conductivity based on an FTOE modified with ZrO2@S-doped g-C3N4 NCs resulted in an ideal platform for the detection of 4-nitrophenol (4-NP) in water. The electrocatalytic activity of the modified electrode was evaluated through determination of 4-NP by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) under optimum conditions (pH 5). ZrO2@S-doped g-C3N4 (20%)/FTOE exhibited good electrocatalytic activity with a linear range from 10 to 100 μM and a low limit of detection (LOD) of 6.65 μM. Typical p-type semiconductor ZrO2@S-doped g-C3N4 NCs significantly impact the superior detection of 4-NP due to its size, shape, optical properties, specific surface area and effective separation of electron-hole pairs. We conclude that the superior electrochemical sensor behavior of the ZrO2@S-doped g-C3N4 (20%)/FTOE surfaces results from the synergistic interaction between S-doped g-C3N4 and ZrO2 surfaces that produce an active NC interface.

Pd–Ni–P metallic glass nanoparticles for nonenzymatic glucose sensing

Metallic glass nanoparticles hold great promise as nonenzymatic glucose sensors due to their rich low-coordinated active sites and high biocompatibility. However, their non-periodic atomic structure and unclear structure-property relationship pose significant challenges for realizing and optimizing their sensing performance. In this work, Pd–Ni–P metallic glass nanoparticles with variable compositions were successfully prepared as nonenzymatic glucose sensors via a laser-evaporated inert-gas condensation method. The electrochemical tests show that the sensor based on Pd41·25Ni41·25P17.5 nanoparticles shows a wide linear detection range (0.003–1.31 ​mM), high sensitivity (516 ​μA ​mM−1 ​cm−2), and high stability (∼97.8% current retention after 1000 cycles). Local structural investigations using synchrotron pair distribution function and high-resolution microscopic techniques reveal a strong structural correlation within short-to medium-range orders in the Pd41·25Ni41·25P17.5 nanoparticles, which can be well retained after electrochemical cycling. These atomic-scale structural characteristics might be responsible for the high sensing performance. This study demonstrates the high applicability of Pd–Ni–P metallic glass nanoparticles as sensitive and stable non-enzymatic glucose sensors.

Uncovering the cytotoxic effects of air pollution with multi-modal imaging of in vitro respiratory models.

Annually, an estimated seven million deaths are linked to exposure to airborne pollutants. Despite extensive epidemiological evidence supporting clear associations between poor air quality and a range of short- and long-term health effects, there are considerable gaps in our understanding of the specific mechanisms by which pollutant exposure induces adverse biological responses at the cellular and tissue levels. The development of more complex, predictive, in vitro respiratory models, including two- and three-dimensional cell cultures, spheroids, organoids and tissue cultures, along with more realistic aerosol exposure systems, offers new opportunities to investigate the cytotoxic effects of airborne particulates under controlled laboratory conditions. Parallel advances in high-resolution microscopy have resulted in a range of in vitro imaging tools capable of visualizing and analysing biological systems across unprecedented scales of length, time and complexity. This article considers state-of-the-art in vitro respiratory models and aerosol exposure systems and how they can be interrogated using high-resolution microscopy techniques to investigate cell-pollutant interactions, from the uptake and trafficking of particles to structural and functional modification of subcellular organelles and cells. These data can provide a mechanistic basis from which to advance our understanding of the health effects of airborne particulate pollution and develop improved mitigation measures.

Biosensor for Multimodal Characterization of an Essential ABC Transporter for Next-Generation Antibiotic Research.

As the threat of antibiotic resistance increases, there is a particular focus on developing antimicrobials against pathogenic bacteria whose multidrug resistance is especially entrenched and concerning. One such target for novel antimicrobials is the ATP-binding cassette (ABC) transporter MsbA that is present in the plasma membrane of Gram-negative pathogenic bacteria where it is fundamental to the survival of these bacteria. Supported lipid bilayers (SLBs) are useful in monitoring membrane protein structure and function since they can be integrated with a variety of optical, biochemical, and electrochemical techniques. Here, we form SLBs containing Escherichia coli MsbA and use atomic force microscopy (AFM) and structured illumination microscopy (SIM) as high-resolution microscopy techniques to study the integrity of the SLBs and incorporated MsbA proteins. We then integrate these SLBs on microelectrode arrays (MEA) based on the conducting polymer poly(3,4-ethylenedioxy-thiophene) poly(styrene sulfonate) (PEDOT:PSS) using electrochemical impedance spectroscopy (EIS) to monitor ion flow through MsbA proteins in response to ATP hydrolysis. These EIS measurements can be correlated with the biochemical detection of MsbA-ATPase activity. To show the potential of this SLB approach, we observe not only the activity of wild-type MsbA but also the activity of two previously characterized mutants along with quinoline-based MsbA inhibitor G907 to show that EIS systems can detect changes in ABC transporter activity. Our work combines a multitude of techniques to thoroughly investigate MsbA in lipid bilayers as well as the effects of potential inhibitors of this protein. We envisage that this platform will facilitate the development of next-generation antimicrobials that inhibit MsbA or other essential membrane transporters in microorganisms.