Graphite-Mediated Microwave-Exfoliated Graphene Fluoride as Supercapacitor Electrodes.

A graphite-mediated microwave-based strategy was used for solid-state exfoliation of graphite fluoride in a few seconds, followed by a simple yet efficient separation to obtain exfoliated materials based on the density difference between graphite and graphene fluoride in solvent. The microwave-exfoliated graphene fluoride was a few layers thick and electrically conductive. The electrochemical testing of pouch-cell supercapacitors assembled by using the exfoliated graphene fluoride electrodes and a novel microemulsion-based electrolyte showed reasonable performance with typical electrical double-layer capacitance behavior and good rate capability (gravimetric specific capacitance: 3.2 F g-1 at 500 mA g-1 and 3.1 F g-1 at 5000 mA g-1). The BET specific surface areas of the as-exfoliated graphene fluoride are ~60-80 m2 g-1, which could be increased by activation using this simple yet versatile microwave-based method for further improvements on the electrochemical performance.

Unraveling the multivalent aluminium-ion redox mechanism in 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA).

Rechargeable Aluminium-organic batteries are an exciting emerging energy storage technology owing to their low cost and promising high performance, thanks to the ability to allow multiple-electron redox chemistry and multivalent Al-ion intercalation. In this work, we use a combination of Density Functional Theory (DFT) calculations and experimental methods to examine the mechanism behind the charge-discharge reaction of the organic dye 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) in the 1,3-ethylmethylimidazolium (EMIm+) chloroaluminate electrolyte. We conclude that, contrary to previous reports claiming the intercalation of trivalent Al3+, the actual ionic species involved in the redox reaction is the divalent AlCl2+. While a less-than-ideal scenario, this mechanism still allows a theoretical transfer of four electrons per formula unit, corresponding to a remarkable specific capacity of 273 mA h g-1. However, the poor reversibility of the reaction and low cycle life of the PTCDA-based cathode, due to its solubility in the electrolyte, make it an unlikely candidate for a commercial application.

Novel devices for isolation and detection of bacterial and mammalian extracellular vesicles.

Extracellular vesicles are spherical nanoparticles inherently released by almost all cell types. They acquire the cell's membrane and cytoplasmic characteristics offering abundant identical units that can be captured to recognize the cell of origin. The abundance of vital cell information and multifunctional roles in cellular processes has rendered them attention, particularly as promising biomarkers for disease diagnosis and use in potential drug delivery systems. This review provides insights into standard approaches towards cultivation and isolation of mammalian and bacterial extracellular vesicles. We assess gaps in conventional separation and detection technologies while also tracking developments in ongoing research. The review focuses on highlighting alternative state-of-the-art microfluidic devices that offer avenues for fast, cost-effective, precision-oriented capture and sensing of extracellular vesicles. Combining different detection technologies on an integrated "lab-on-a-chip" system has the prospective to provide customizable opportunities for clinical use of extracellular vesicles in disease diagnostics and therapeutic applications.

Corrigendum: Electrospun, Oriented, Ferromagnetic Ni 1-x Fe x Nanofibers.

[This corrects the article DOI: 10.3389/fchem.2020.00047.].

Photometric Sensing of Active Chlorine, Total Chlorine, and pH on a Microfluidic Chip for Online Swimming Pool Monitoring.

A microfluidic sensor was studied for the photometric detection of active chlorine, total chlorine, and pH in swimming pool samples. The sensor consisted of a four-layer borosilicate glass chip, containing a microchannel network and a 2.2 mm path length, 1.7 mL optical cell. The chip was optimised to measure the bleaching of methyl orange and spectral changes in phenol red for quantitative chlorine (active and total) and pH measurements that were suited to swimming pool monitoring. Reagent consumption (60 mL per measurement) was minimised to allow for maintenance-free operation over a nominal summer season (3 months) with minimal waste. The chip was tested using samples from 12 domestic, public, and commercial swimming pools (indoor and outdoor), with results that compare favourably with commercial products (test strips and the N,N'-diethyl-p-phenylenediamine (DPD) method), precision pH electrodes, and iodometric titration.

Electrospun, Oriented, Ferromagnetic Ni 1-x Fe x Nanofibers.

Electrospinning has been used to fabricate ferromagnetic Ni0.47Fe0.53 nanofiber mats that were composed of individual, orientated Ni0.47Fe0.53 nanofibers. The key steps were processing a polyvinylpyrrolidone nanofiber template containing ferric nitrate and nickel acetate metal precursors in Ar at 300°C and then 95% Ar: 5% H2 at 600°C. The Ni0.47Fe0.53 fibers were nanostructured and contained Ni0.47Fe0.53 nanocrystals with average diameters of ~14 nm. The Ni0.47Fe0.53 ferromagnetic mats had a high saturation magnetic moment per formula unit that was comparable to those reported in other studies of nanostructured Ni1-x Fe x . There is a small spin-disordered fraction that is typically seen in nanoscale ferromagnets and is likely to be caused by the surface of the nanofibers. There was an additional magnetic contribution that could possibly stem from a small Fe1-z Ni z O phase fraction surrounding the fibers. The coercivity was found to be enhanced when compared with the bulk material.

Highly efficient electrocatalytic hydrogen evolution promoted by O-Mo-C interfaces of ultrafine ß-Mo2C nanostructures.

Optimizing interfacial contacts and thus electron transfer phenomena in heterogeneous electrocatalysts is an effective approach for enhancing electrocatalytic performance. Herein, we successfully synthesized ultrafine ß-Mo2C nanoparticles confined within hollow capsules of nitrogen-doped porous carbon (ß-Mo2C@NPCC) and found that the surface layer of molybdenum atoms was further oxidized to a single Mo-O surface layer, thus producing intimate O-Mo-C interfaces. An arsenal of complementary technologies, including XPS, atomic-resolution HAADF-STEM, and XAS analysis clearly reveals the existence of O-Mo-C interfaces for these surface-engineered ultrafine nanostructures. The ß-Mo2C@NPCC electrocatalyst exhibited excellent electrocatalytic activity for the hydrogen evolution reaction (HER) in water. Theoretical studies indicate that the highly accessible ultrathin O-Mo-C interfaces serving as the active sites are crucial to the HER performance and underpinned the outstanding electrocatalytic performance of ß-Mo2C@NPCC. This proof-of-concept study opens a new avenue for the fabrication of highly efficient catalysts for HER and other applications, whilst further demonstrating the importance of exposed interfaces and interfacial contacts in efficient electrocatalysis.

Glucose Sensor Using Redox Active Oligonucleotide-Templated Silver Nanoclusters.

Redox active, photoluminescent silver nanoclusters templated with oligonucleotides were developed for glucose sensing. The silver nanoclusters had a photoluminescent emission at 610 nm that reversibly changed to 530 nm upon oxidation. The reversible emission change was measured with photoluminescent spectroscopy and used to detect H2O2, which is a by-product of the reaction of glucose with glucose oxidase. The ratio of the un-oxidised emission peak (610 nm) and the oxidised analogue (530 nm) was used to measure glucose concentrations up to 20 mM, well within glucose levels found in blood. Also, the reversibility of this system enables the silver nanoclusters to be reused.

Copper Metallopolymer Catalyst for the Electrocatalytic Hydrogen Evolution Reaction (HER).

Conjugated polymers with stabilizing coordination units for single-site catalytic centers are excellent candidates to minimize the use of expensive noble metal electrode materials. In this study, conjugated metallopolymer, POS[Cu], was synthesized and fully characterized by means of spectroscopical, electrochemical, and photophysical methods. The copper metallopolymer was found to be highly active for the electrocatalytic hydrogen generation (HER) in an aqueous solution at pH 7.4 and overpotentials at 300 mV vs. reversible hydrogen electrode (RHE). Compared to the platinum electrode, the obtained overpotential is only 100 mV higher. The photoelectrochemical tests revealed that the complexation of the conjugated polymer POS turned its intrinsically electron-accepting (p-type) properties into an electron-donor (n-type) with photocurrent responses ten times higher than the organic photoelectrode.

An In Vitro Investigation of Cytotoxic Effects of InP/Zns Quantum Dots with Different Surface Chemistries.

Indium phosphide quantum dots (QDs) passivated with zinc sulphide in a core/shell architecture (InP/ZnS) with different surface chemistries were introduced to RAW 264.7 murine "macrophage-like" cells to understand their potential toxicities. The InP/ZnS quantum dots were conjugated with an oligonucleotide, a carboxylic acid, or an amino-polyethylene glycol ligand, and cell viability and cell proliferation were investigated via a metabolic assay. Membrane integrity was measured through the production of lactate dehydrogenase. Fluorescence microscopy showed cellular uptake. All quantum dots exhibited cytotoxic behaviour less than that observed from cadmium- or lead-based quantum dots; however, this behaviour was sensitive to the ligands used. In particular, the amino-polyethylene glycol conjugated quantum dots proved to possess the highest cytotoxicity examined here. This provides quantitative evidence that aqueous InP/ZnS quantum dots can offer a safer alternative for bioimaging or in therapeutic applications.

Improved uniaxial dielectric properties in aligned diisopropylammonium bromide (DIPAB) doped poly(vinylidene difluoride) (PVDF) nanofibers.

Diisopropylammonium bromide (DIPAB) doped poly(vinylidene difluoride) (PVDF) nanofibers (5, 10 and 24 wt% DIPAB doping) with improved and tunable dielectric properties were synthesised via electrospinning. DIPAB nanoparticles were grown in situ during the nanofiber formation. X-Ray diffraction (XRD) patterns and Fourier transform infrared spectroscopy (FTIR) proved that electrospinning of DIPAB doped PVDF solutions led to the formation of a highly electro-active ß-phase in the nanofibers. Electrospinning in the presence of DIPAB inside PVDF led to very well aligned nanofibers with preferred (001) orientation that further enhanced the effective dipole moments in the nanofiber structures. The dielectric properties of the composite nanofibers were significantly enhanced due to the improved orientation, ionic and interfacial polarisation upon the applied electrospinning process, ionic nature of DIPAB and the interface between the PVDF nanofibers and equally dispersed DIPAB nanoparticles inside them, respectively. The relative dielectric constant of the PVDF nanofibers was improved from 8.5 to 102.5 when nanofibers were doped with 5% of DIPAB. Incorporating DIPAB in PVDF nanofibers has been shown to be an effective way to improve the structural and dielectric properties of PVDF.

Rapid synthesis of defective and composition-controlled metal chalcogenide nanosheets by supercritical hydrothermal processing.

This study presents a simple one-pot synthesis method to achieve few-layered and defective Mo(S,Se)2 and (Mo,W)S2 by using supercritical water with organic reducing agents from simple and less-toxic precursors. This synthesis process is expected to be suitable for preparing other various kinds of TMD solid solutions.

Acetamide: a low-cost alternative to alkyl imidazolium chlorides for aluminium-ion batteries.

We propose a new electrolyte for rechargeable aluminium-ion batteries based on a room-temperature eutectic mixture of acetamide and aluminium chloride. When diluted with dichloromethane, the electrolyte shows similar cycling performance to the more traditional 1-ethyl-3-methylimidazolium chloride-based electrolytes for a fraction of the cost.

Cadmium-Free Quantum Dots as Fluorescent Labels for Exosomes.

Quantum dots are attractive alternatives to organic fluorophores for the purposes of fluorescent labeling and the detection of biomarkers. They can also be made to specifically target a protein of interest by conjugating biomolecules, such as antibodies. However, the majority of the fluorescent labeling using quantum dots is done using toxic materials such as cadmium or lead due to the well-established synthetic processes for these quantum dots. Here, we demonstrate the use of indium phosphide quantum dots with a zinc sulfide shell for the purposes of labeling and the detection of exosomes derived from the THP-1 cell line (monocyte cell line). Exosomes are nano-sized vesicles that have the potential to be used as biomarkers due to their involvement in complex cell processes. However, the lack of standardized methodology around the detection and analysis of exosomes has made it difficult to detect these membrane-containing vesicles. We targeted a protein that is known to exist on the surface of the exosomes (CD63) using a CD63 antibody. The antibody was conjugated to the quantum dots that were first made water-soluble using a ligand-exchange method. The conjugation was done using carbodiimide coupling, and was confirmed using a range of different methods such as dynamic light scattering, surface plasmon resonance, fluorescent microscopy, and Fourier transform infrared spectroscopy. The conjugation of the quantum dot antibody to the exosomes was further confirmed using similar methods. This demonstrates the potential for the use of a non-toxic conjugate to target nano-sized biomarkers that could be further used for the detection of different diseases.

Unraveling aminophosphine redox mechanisms for glovebox-free InP quantum dot syntheses.

The synthesis of colloidal indium phosphide quantum dots (InP QDs) has always been plagued by difficulties arising from limited P3- sources. Being effectively restricted to the highly pyrophoric tris(trimethylsilyl) phosphine (TMS3P) creates complications for the average chemist and presents a significant risk for industrially scaled reactions. The adaptation of tris(dialkylamino) phosphines for these syntheses has garnered attention, as these new phosphines are much safer and can generate nanoparticles with competitive photoluminescence properties to those from (TMS)3P routes. Until now, the reaction mechanics of this precursor were elusive due to many experimental optimizations, such as the inclusion of a high concentration of zinc salts, being atypical of previous InP syntheses. Herein, we utilize density functional theory calculations to outline a logical reaction mechanism. The aminophosphine precursor is found to require activation by a zinc halide before undergoing a disproportionation reaction to self-reduce this P(iii) material to a P(-iii) source. We use this understanding to adapt this precursor for a two-pot nanoparticle synthesis in a noncoordinating solvent outside of glovebox conditions. This allowed us to generate spherical InP/ZnS nanoparticles possessing fluorescence quantum yields >55% and lifetimes as fast as 48 ns, with tunable emission according to varying zinc halide acidity. The development of high quality and efficient InP QDs with this safer aminophosphine in simple Schlenk environments will enable a broader range of researchers to synthesize these nontoxic materials for a variety of high-value applications.

General Synthetic Strategy for Libraries of Supported Multicomponent Metal Nanoparticles.

Nanoparticles comprising three or more different metals are challenging to prepare. General methods that tackle this challenge are highly sought after as multicomponent metal nanoparticles display favorable properties in applications such as catalysis, biomedicine, and imaging. Herein, we report a practical and versatile approach for the synthesis of nanoparticles composed of up to four different metals. This method relies on the thermal decomposition of nanostructured composite materials assembled from platinum nanoparticles, a metal-organic framework (ZIF-8), and a tannic acid coordination polymer. The controlled integration of multiple metal cations (Ni, Co, Cu, Mn, Fe, and/or Tb) into the tannic acid shell of the precursor material dictates the composition of the final multicomponent metal nanoparticles. Upon thermolysis, the platinum nanoparticles seed the growth of the multicomponent metal nanoparticles via coalescence with the metallic constituents of the tannic acid coordination polymer. The nanoparticles are supported in the walls of hollow nitrogen-doped porous carbon capsules created by the decomposition of the organic components of the precursor. The capsules prevent sintering and detachment of the nanoparticles, and their porosity allows for efficient mass transport. To demonstrate the utility of producing a broad library of supported multicomponent metal nanoparticles, we tested their electrocatalytic performance toward the hydrogen evolution reaction and oxygen evolution reaction. We discovered functional relationships between the composition of the nanoparticles and their electrochemical activity and identified the PtNiCu and PtNiCuFe nanoparticles as particularly efficient catalysts. This highlights how to generate diverse libraries of multicomponent metal nanoparticles that can be synthesized and subsequently screened to identify high-performance materials for target applications.

"Exosomics"-A Review of Biophysics, Biology and Biochemistry of Exosomes With a Focus on Human Breast Milk.

Exosomes are biomolecular nanostructures released from cells. They carry specific biomolecular information and are mainly researched for their exquisite properties as a biomarker source and delivery system. We introduce exosomes in the context of other extracellular vesicles, describe their biophysical isolation and characterisation and discuss their biochemical profiling. Motivated by our interest in early-life nutrition and health, and corresponding studies enrolling lactating mothers and their infants, we zoom into exosomes derived from human breast milk. We argue that these should be more extensively studied at proteomic and micronutrient profiling level, because breast milk exosomes provide a more specific window into breast milk quality from an immunological (proteomics) and nutritional (micronutrient) perspective. Such enhanced breast milk exosome profiling would thereby complement and enrich the more classical whole breast milk analysis and is expected to deliver more functional insights than the rather descriptive analysis of human milk, or larger fractions thereof, such as milk fat globule membrane. We substantiate our arguments by a bioinformatic analysis of two published proteomic data sets of human breast milk exosomes.

Electrospun Composites of Polycaprolactone and Porous Silicon Nanoparticles for the Tunable Delivery of Small Therapeutic Molecules.

This report describes the use of an electrospun composite of poly(ε-caprolactone) (PCL) fibers and porous silicon (pSi) nanoparticles (NPs) as an effective system for the tunable delivery of camptothecin (CPT), a small therapeutic molecule. Both materials are biodegradable, abundant, low-cost, and most importantly, have no known cytotoxic effects. The composites were treated with and without sodium hydroxide (NaOH) to investigate the wettability of the porous network for drug release and cell viability measurements. CPT release and subsequent cell viability was also investigated. We observed that the cell death rate was not only affected by the addition of our CPT carrier, pSi, but also by increasing the rate of dissolution via treatment with NaOH. This is the first example of loading pSi NPs as a therapeutics nanocarrier into electronspun PCL fibers and this system opens up new possibilities for the delivery of molecular therapeutics.

Demonstration of the lack of cytotoxicity of unmodified and folic acid modified graphene oxide quantum dots, and their application to fluorescence lifetime imaging of HaCaT cells.

The authors describe the synthesis of water-soluble and fluorescent graphene oxide quantum dots via acid exfoliation of graphite nanoparticles. The resultant graphene oxide quantum dots (GoQDs) were then modified with folic acid. Folic acid receptors are overexpressed in cancer cells and hence can bind to functionalized graphene oxide quantum dots. On excitation at 305 nm, the GoQDs display green fluorescence with a peak wavelength at ~520 nm. The modified GoQDs are non-toxic to macrophage cells even after prolonged exposure and high concentrations. Fluorescence lifetime imaging and multiphoton microscopy was used (in combination) to image HeCaT cells exposed to GoQDs, resulting in a superior method for bioimaging. Graphical abstract Schematic representation of graphene oxide quantum dots, folic acid modified graphene oxide quantum dots (red), and the use of fluorescence lifetime to discriminate against green auto-fluorescence of HeCaT cells.

Conducting Copper(I/II)-Metallopolymer for the Electrocatalytic Oxygen Reduction Reaction (ORR) with High Kinetic Current Density.

The oxygen reduction reaction (ORR) is still the most research-intensive aspect of a fuel cell. The sluggish kinetics of the electrocatalysts toward the ORR requires large amounts of platinum to be used as cathode material, which calls for alternatives to replace or minimize the amount of the noble metals used. This study describes the synthesis and complete characterization of a copper metallopolymer (Cu MP) based on a conducting polymer (CP) and single-site catalytic centers for the electrocatalytic ORR. The copper (II) catalyst, embedded in a redox-active and conducting polymeric environment, was pursued as a potential candidate to replace noble metals in fuel cell applications. Performance studies at a rotating disk electrode (RDE) showed that the metallopolymer exhibited a direct four-electron reduction at potentials between -150 and -350 mV vs. the reversible hydrogen electrode (RHE) and high kinetic current densities of over 22.62 mA/cm². The kinetic current densities obtained at the Cu MP electrode outperformed most of the reported state-of-the art electrocatalysts toward the ORR. Further analysis of the Cu/CP hybrid revealed the copper being largely reduced to the oxidation state +I.