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A modified glassy carbon electrode (GCE) was developed based on a synthesized graphene oxide (GO) gold nanorod (AuNR) decorated composite (GO/AuNR) for sensitive electrochemical sensing of uric acid (UA). The electrochemical performance of GO/AuNR/GCE for UA detection was investigated employing the differential pulse voltammetry (DPV) technique. Central composite design (CCD) was applied to obtain the optimum composition of the GO and AuNR composite, which provide the highest possible UA oxidation peak current. The optimum composition was obtained at a GO concentration of 5 mg mL

A bio-derived polyester has been crosslinked into flexible films for solid polymer electrolyte applications in Li+-ion batteries, with ionic conductivity around 10−5 S cm−1 at 60 °C, high Li+ transference number (0.84), and hydrolytic degradability.

This review throws light on the development and emerging electrocatalytic applications of potentially important 2D material MXene with specific references to oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER).

Conductive polymeric microneedle (MN) arrays as biointerface materials show promise for the minimally invasive monitoring of analytes in biodevices and wearables. There is increasing interest in microneedles as electrodes for biosensing, but efforts have been limited to metallic substrates, which lack biological stability and are associated with high manufacturing costs and laborious fabrication methods, which create translational barriers. In this work, additive manufacturing, which provides the user with design flexibility and upscale manufacturing, is employed to fabricate acrylic-based microneedle devices. These microneedle devices are used as platforms to produce intrinsically-conductive, polymer-based surfaces based on polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). These entirely polymer-based solid microneedle arrays act as dry conductive electrodes while omitting the requirement of a metallic seed layer. Two distinct coating methods of 3D-printed solid microneedles, in situ polymerization and drop casting, enable conductive functionality. The microneedle arrays penetrate ex vivo porcine skin grafts without compromising conductivity or microneedle morphology and demonstrate coating durability over multiple penetration cycles. The non-cytotoxic nature of the conductive microneedles is evaluated using human fibroblast cells. The proposed fabrication strategy offers a compelling approach to manufacturing polymer-based conductive microneedle surfaces that can be further exploited as platforms for biosensing.

A blue light mediated photochemical process using solid graphitic carbon nitride (g-C3N4) in ambient air/isopropanol vapour is suggested to be linked to “nanophase” water inclusions and is shown to produce...

A highly selective electrochemical sensor based on a molecularly imprinted polymer (MIP) to be developed for uric acid detection in the presence of dopamine as an interference molecule was demonstrated in this study. This non-enzymatic uric acid sensor was developed by electropolymerizing poly-pyrrole onto a composite of electrochemically reduced graphene oxide (ErGO) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) on a glassy carbon electrode (GCE) to give MIP/ErGO/PEDOT:PSS electrodes. The structural properties, surface morphology, and electrochemical interface of this fabricated uric acid sensor was then characterized using infrared spectroscopy, scanning electron microscopy, atomic force microscopy, and electrochemical impedance spectroscopy. This fabricated non-enzymatic electrochemical sensor (MIP/ErGO/PEDOT:PSS modified GCE) also showed excellent analytical performance at the optimum ratio of monomer/template concentration and optimized electropolymerization conditions, for example in the low concentration range of 0.1-100 μM with a detection limit of 0.05 μM towards uric acid detection in the presence of dopamine. Furthermore, this fabricated uric acid sensor also exhibited good reproducibility and stability for uric acid measurements in the presence of dopamine for 5 consecutive days. In addition, this sensor demonstrates highly selective detection of uric acid in the presence of several interfering species such as dopamine, urea, glucose, magnesium ions, and ascorbic acid. This fabricated uric acid sensor ultimately showed satisfactory uric acid measurement in samples of human urine and is expected to be used in early-stage disease diagnosis.

In order to prevent the microwave leakage and mutual interference, more and more microwave absorbing devices are added into the design of electronic products to ensure its routine operation. In this work, we have successfully prepared MoS2/TiO2/Ti3C2Tx hierarchical composites by one-pot hydrothermal method and focused on the relationship between structures and electromagnetic absorbing properties. Supported by comprehensive characterizations, MoS2 nanosheets were proved to be anchored on the surface and interlayer of Ti3C2Tx through a hydrothermal process. Additionally, TiO2 nanoparticles were obtained in situ. Due to these hierarchical structures, the MoS2/TiO2/Ti3C2Tx composites showed greatly enhanced microwave absorbing performance. The MoS2/TiO2/Ti3C2Tx composites exhibit a maximum reflection loss value of −33.5 dB at 10.24 GHz and the effective absorption bandwidth covers 3.1 GHz (13.9–17 GHz) at the thickness of 1.0 mm, implying the features of wide frequency and light weight. This work in the hierarchical structure of MoS2/TiO2/Ti3C2Tx composites opens a promising door to the exploration of constructing extraordinary electromagnetic wave absorbents.

Commercial resin microbeads are widely applied in ion exchange and extraction. Here, a single anion-selective and phosphate binding resin microbead (FerrIX™) is mounted into an epoxy membrane and investigated by 4-electrode membrane voltammetry and membrane impedance spectroscopy. Anion transport properties are observed to dominate associated with three distinct potential domains: (I) a low bias ohmic potential domain (dominant at high electrolyte concentration), (II) a concentration polarisation potential domain, and (III) an over-limiting potential domain. Voltammetric responses show transient diffusion-migration features at higher scan rates and quasi-steady state features at lower scan rates. Inherent microbead conductivity is shown to be linked to two resistive elements, electrolyte concentration dependent and independent, in series. The effects of phosphate binding are revealed as transient pattern in impedance spectroscopy data. Preliminary data suggest phosphate concentration-dependent peak features in the imaginary impedance versus frequency plot due to phosphate binding into the microbead. Graphical abstract

Ionic rectifier membranes or devices generate uni-directional ion transport to convert an alternating current (AC) ion current input into stored energy or direct current (DC) in the form of ion/salt gradients. Electrochemical experiments 80 years ago were conducted on biological membrane rectifier systems, but today a plethora of artificial ionic rectifier types has been developed and electroanalytical tools are employed to explore mechanisms and performance. This overview focuses on microscale ionic rectifiers with a comparison to nano- and macroscale ionic rectifiers. The potential is surveyed for applications in electrochemical analysis, desalination, energy harvesting, electrochemical synthesis, and in selective ion extraction.

Here we report the development of a new scalable and transferable plasma assisted atomic layer deposition (PEALD) process for the production of uniform, conformal and pinhole free NiO with sub-nanometre control on a commercial ALD reactor. In this work we use the readily available nickel precursor nickelocene in conjunction with O2 plasma as a co-reagent (100 W) over a temperature range of 75–325 °C. An optimised growth per cycle of 0.036 nm was obtained at 250 °C with uniform thickness and coverage on scale-up to and including an 6 inch Si wafer (with a 200 nm thermal SiO2 top layer). The bulk characteristics of the NiO thin films were comprehensively interrogated by PXRD, Raman spectroscopy, UV-vis spectroscopy and XPS. The new NiO process was subsequently used to fabricate a 3D nanostructured NiO/TiO2/FTO heterojunction by depositing 20 nm of NiO onto pre-fashioned TiO2 nanorods at 250 °C for application in the photo-electrolysis of water in a photoelectrochemical cell (PEC). The NiO/TiO2 3D array was shown to possess a peak current of 0.38 mA cm−2 at 1.23 VRHE when stimulated with a one sun lamp.

Microporous polymer materials based on molecularly “stiff” structures provide intrinsic microporosity, typical micropore sizes of 0.5 nm to 1.5 nm, and the ability to bind guest species. The polyamine PIM-EA-TB contains abundant tertiary amine sites to interact via hydrogen bonding to guest species in micropores. Here, quercetin and catechin are demonstrated to bind and accumulate into PIM-EA-TB. Voltammetric data suggest apparent Langmuirian binding constants for catechin of 550 (± 50) × 103 M-1 in acidic solution at pH 2 (PIM-EA-TB is protonated) and 130 (± 13) × 103 M-1 in neutral solution at pH 6 (PIM-EA-TB is not protonated). The binding capacity is typically 1:1 (guest : host polymer repeat unit), but higher loadings are readily achieved by host/guest co-deposition from tetrahydrofuran solution. In the rigid polymer environment, bound ortho-quinol guest species exhibit 2-electron 2-proton redox transformation to the corresponding quinones, but only in a thin mono-layer film close to the electrode surface. Release of guest molecules occurs depending on the level of loading and on the type of guest either spontaneously or with electrochemical stimuli.

Graphitic carbon nitride (g-C

Photo-generated high-energy surface states can help to produce chlorine in aqueous environments. Here, aligned rutile (TiO2) nanocrystal arrays are grown onto fluorine-doped tin oxide (FTO) substrates and activated either by hydrothermal Sr/Ba surface doping and/or by vacuum-annealing. With vacuum-annealing, highly photoactive films are obtained with photocurrents of typically 8 mA cm−2 at 1.0 V vs. SCE in 1 M KCl (LED illumination with λ = 385 nm and approx. 100 mW cm−2). Photoelectrochemical chlorine production is demonstrated at proof-of-concept scale in 4 M NaCl and suggested to be linked mainly to the production of Ti(III) surface species by vacuum-annealing, as detected by post-catalysis XPS, rather than to Sr/Ba doping at the rutile surface. The vacuum-annealing treatment is proposed to beneficially affect (i) bulk semiconductor TiO2 nanocrystal properties and electron harvesting, (ii) surface TiO2 reactivity towards chloride adsorption and oxidation, and (iii) FTO substrate performance.

Nicked-based metal–organic framework-derived carbon (Ni/MOFDC) and its acid-treated counterpart (AT-Ni/MOFDC) have been prepared as supports for palladium nanoparticle electrocatalysts (Pd/Ni/MOFDC...

In this work, 2D-layered Ti3C2/TiO2 hybrids derived from Ti3C2 MXenes were calcined at different temperature for 2 h with a ramping rate of 5 °C/min to adjust the electromagnetic wave absorption performance, and the static dielectric properties of the Ti3C2 and anatase TiO2 were studied by density functional theory calculations to illustrate the contribution to dielectric loss of TiO2 and Ti3C2 MXenes. The 2D-layered Ti3C2/TiO2 Hybrids exhibit a minimum reflection loss of −40.07 dB at 19.2 GHz with a relative thin thickness of 1.1 mm, and the effective bandwidth with reflection loss less than −10 dB reaches more than 3.6 GHz. The calculated results display higher e ' and e ' ' of Ti3C2 MXenes than that of anatase TiO2 in the measured range of frequency, which is in accordance with the experiments. The 2D-layered Ti3C2/TiO2 hybrids are expected to exhibit the enhanced electromagnetic wave absorption performance thanks to the appropriate complex permittivity, matching impendence and high dielectric loss.

The transformation of solar energy into chemical energy stored as hydrogen fuel underlies the water splitting process into O2 and H2 in photo-electrochemical (PEC) cells. This a potentially promising technology to generate renewable and clean energy. To make this technology commercially viable, the engineering of appropriate low-cost and robust photo-electrode materials and substrates is needed. In this study, we introduce BiVO4-photoelectrodes grown on conductive bulk SnO2–Sb2O5 ceramics acting as porous substrate. For these photoelectrodes, the value of photocurrent density of 1.1 mA/cm2 was achieved in 0.1 M NaOH electrolyte at 1.23 V vs. RHE (reversible hydrogen electrode) under LED light (λ = 455 nm). This PEC performance of these BiVO4 photoelectrodes is reached in spite of using a simple and low-cost deposition technique, where the BiVO4-precursor is delivered to the bulk porous ceramic substrate as a nebulized aerosol in air-flow at room temperature. The high porosity of the ceramic substrate permits some permeation of the aerogel into the pores to a depth of several micrometers to provide a 3D-growth of the BiVO4-coating on conductive SnO2 grains. The film thickness of the BiVO4 on individual grains is approximately 100 nm. This construction of the photoelectrode leads to an effective interface with good absorption of solar radiation and good electron harvesting. The bulk ceramics assure favorable conditions for electron collection and charge transport, which results in a good PEC performance with this type of photoanode.

Hydrogen permeation through a pure palladium film (25 μm thickness, optically dense) is employed to trigger electron transfer (hydrogen-driven) reactions at the external palladium | aqueous electrolyte interface of a two-compartment electrochemical cell. Two systems are investigated to demonstrate feasibility for (i) indirect hydrogen-mediated silver electrodeposition with externally applied potential and (ii) indirect hydrogen-mediated silver electrodeposition driven by external formic acid decomposition. In both cases, porous metal deposits form as observed by optical and electron microscopies. Processes are self-limited as metal deposition blocks the palladium surface and thereby slows down further hydrogen permeation. The proposed methods could be employed for a wider range of metals, and they could provide an alternative (non-electrochemical or indirect) procedure for metal removal or metal recovery processes or for indirect metal sensing.

Voltammetric analysis is often dependent on pH and on the addition of buffer reagents to optimise the analytical procedure. This approach is not always possible for in situ analytical measurements, for example when studying biological fluids or ingredients in food. Therefore, a method is proposed herein, which employs a working electrode to do both, that is, to locally modulate the pH value and to measure the analytical response. As a model system, thiamine (vitamin B1) is detected in aqueous KCl with a pH modulation brought about with negative potentials applied to the working electrode. Interferences from ascorbic acid and uric acid are considered. Exploratory data are presented and methods for improving the detection limit are suggested. Their potential for applications in electroanalysis (and in a broader range of processes) is discussed and the detection of thiamine in rice is demonstrated.

The availability of end-user products, including lifesaving medicines and protection materials, from the pharmaceutical, agrochemical, dye, polymer and corrosion industries mainly relies on sustainable catalytic efficiency towards the reduction of nitroaromatics. The recovery of catalysts from the reaction mixture requires additional instrumentation; therefore, dip-catalyst platforms have been developed in the modern research era. Nitroarene reduction is evaluated by a model reaction involving the conversion of 4-nitrophenol to aminophenol by sodium borohydride in the presence of a test catalyst. The dissolved oxygen is a critical feature in the model catalytic reaction because it causes reduced induction time, slower kinetics, reversible reactions, side product formation and catalyst passivation/restructuring. Here, the role of dissolved oxygen in the model reaction, catalyzed by a developed silver-anchored textile (as a ‘dip-catalyst’), is investigated with UV-Vis and in situ dissolved oxygen measurements. The studies show that the depletion rate of dissolved oxygen increases with [NaBH4] and the area of the catalyst also contribute to the increase in the apparent rate constant. The apparent rate constant increases from 1.85 × 10−3 to 0.0435 s−1 with the decreasing contribution of dissolved oxygen concentration from 12.21 ppm to 0.45 ppm. The developed catalyst shows the reduction of 4-nitrophenol towards 4-aminophenol; however, the production rate is slow, even in the presence of excess dissolved oxygen. The effect of dissolved oxygen on the apparent rate constant on the micromolar scale is highly significant; however, this effect decreased to a minimum or negligible contribution on the millimolar scale. Further, the catalyst reduced 10 nitroarenes and retained 95% of its catalytic efficiency after ten cycles on the millimolar scale.

This work demonstrates the chemical synthesis of two-dimensional nanoflakes of mesoporous nickel/nickel (II) hydroxide (Ni/Ni(OH)2-NFs) using double templates of surfactant self-assembled thin-film and foam of hydrogen bubbles produced by sodium borohydride reducing agent. Physicochemical characterizations show the formation of amorphous mesoporous 2D nanoflakes with a Ni/Ni(OH)2 structure and a high specific surface area (165 m2/g). Electrochemical studies show that the electrocatalytic activity of Ni/Ni(OH)2 nanoflakes towards methanol oxidation in alkaline solution is significantly enhanced in comparison with that of parent bare-Ni(OH)2 deposited from surfactant-free solution. Cyclic voltammetry shows that the methanol oxidation mass activity of Ni/Ni(OH)2-NFs reaches 545 A/cm2 gcat at 0.6 V vs. Ag/AgCl, which is more than five times higher than that of bare-Ni(OH)2. Moreover, Ni/Ni(OH)2-NFs reveal less charge transfer resistance (10.4 Ω), stable oxidation current density (625 A/cm2 gcat at 0.7 V vs. Ag/AgCl), and resistance to the adsorption of reaction intermediates and products during three hours of constant-potential methanol oxidation electrolysis in alkaline solution. The high-performance electrocatalytic activity of Ni/Ni(OH)2 nanoflakes is mainly derived from efficient charge transfer due to the high specific surface area of the 2D mesoporous architecture of the nanoflakes, as well as the mass transport of methanol to Ni2+/Ni3+ active sites throughout the catalyst layer.

The concept of a reversible polymer displacement sensor mechanism for electrochemical glucose monitoring is demonstrated. A pyrene-derivatised boronic acid chemo-receptor for glucose is adsorbed onto a graphene foam electrode. Spontaneous oxidative polymerisation of nordihydroguaiaretic acid (NHG) onto the graphene foam electrode leads to a redox active film (poly-NHG) covalently attached to the boronic acid receptors. Oxidation of poly-NHG frees the boronic acid receptors to interact with glucose from the solution phase, which is detected due to competitive binding when reduced poly-NHG re-binds to the boronic acid functional groups. The sensor shows the anticipated boronic acid selectivity of fructose > glucose. The ratio of charges under the voltammetric peaks for poly-NHG unbound and bound is employed for glucose sensing with an approximately linear analytical range from 1 to 50 mM glucose in aqueous pH 7 buffer. The new methodology is shown to give apparent saccharide – boronic acid binding constants and to work in human serum. Therefore, in the future it could be developed further for glucose monitoring.

Bacteriophage material (M13, wild-type) deposited as a film onto a poly-ethylene-terephthalate (PET) substrate (6 m thick with a 20 m diameter laser-drilled microhole) has been investigated for ion conductivity and ionic current rectification effects for potential applications in membranes. The M13 aggregate membrane forms under acidic conditions (in aqueous 10 mM acids) and behaves like a microporous anion conductor with micropores defined by the packing of cylindrical virus particles. Asymmetric deposition on the PET film substrate in conjunction with semi-permeability leads to anionic diode behaviour. Typical rectification ratio values are around 10 (determined at +/-1V) in aqueous 10 mM acids. Cationic guest species (aqueous Cu2+, Co2+, Ag+) consistently lead to a rectification minimum at 0.5 mM guest concentration. In contrast, anionic guest species (indigo carmine) lead to a similar rectification minimum already at 5 M concentration. The behaviour is proposed to be associated with cation exclusion effects on transport.

We report the use of the alkaline-earth (Ae) metal-catalyzed dehydrocoupling of silanes and amines for the synthesis of ferrocene-containing polycarbosilazanes. The barium complex [Ba(N(SiMe 3) 2) 2·(THF) 2] catalyzed the dehydrocoupling of the hydrosilane FeCp(CpSiPhH 2) (1) with 1,4-(H 2NCH 2) 2C 6H 4 under mild conditions to give a polycarbosilazane with pendant ferrocene groups. The polymer could be readily cross-linked by the addition of phenylsilane to the unquenched reaction mixture. Well-defined polycarbosilazanes with ferrocene in the main chain were also obtained from the dehydrocoupling of hydrosilanes Fe(Cp(SiPhH 2)) 2 (3) and Fe(Cp(SiMe 2H)) 2 (IX) with 1,4-(H(Me)NCH 2) 2C 6H 4 and 1,4-(H 2NCH 2) 2C 6H 4, respectively. Crystalline monomeric analogues, FeCp(Cp(SiPh(NHBn) 2)) (2, Bn = CH 2(C 6H 5)), and Fe(Cp(SiPh(NHBn) 2)) 2 (4), were also obtained via the dehydrocoupling benzylamine with 1 and 3, respectively. The barium-catalyzed dehydrocoupling of diaminoferrocene with Ph 2SiH 2 or Ph(Rc)SiH 2 (6, Rc = (C 5H 4)Ru(C 5H 5)) did not result in polymer, but instead in the formation of the silazane-bridged ansa-[3]ferrocenophanes (Fe(ν-C 5H 4NH) 2SiPh 2) (5) and (Fe(ν-C 5H 4NH) 2SiPh(Rc)) (7), respectively. Both polymeric and molecular products were electrochemically investigated, and the polymers proved to be promising precursors to magnetic iron-containing ceramics in yields of up to 64%.

Photoelectrochemical water splitting using solar energy is a highly promising technology to produce hydrogen as an environmentally friendly and renewable fuel with high-energy density. This approach requires the development of appropriate photoelectrode materials and substrates, which are low-cost and applicable for the fabrication of large area electrodes. In this work, hematite photoelectrodes are grown by aerosol assisted chemical vapour deposition (AA-CVD) onto highly-conductive and bulk porous SnO2 (Sb-doped) ceramic substrates. For such photoelectrodes, the photocurrent density of 2.8 mA cm-2 is achieved in aqueous 0.1 M NaOH under blue LED illumination (λ = 455 nm; 198 mW cm-2) at 1.23 V vs. RHE (reversible hydrogen electrode). This relatively good photoelectrochemical performance of the photoelectrode is achieved despite the simple fabrication process. Good performance is suggested to be related to the three-dimensional morphology of the porous ceramic substrate resulting in excellent light-driven charge carrier harvesting. The porosity of the ceramic substrate allows growth of the photoactive layer (SnO2-grains covered by hematite) to a depth of some micrometers, whereas the thickness of Fe2O3-coating on individual grains is only about 100–150 nm. This architecture of the photoactive layer assures a good light absorption and it creates favourable conditions for charge separation and transport.

We demonstrate that ionic current rectification effects are observed with a film of negatively charged carbon nanofibers (CNFs) deposited as a film or mat onto a 10 μm diameter microhole in poly-ethylene-terephthalate (PET). CNFs are synthesized by using a chemical vapor deposition (CVD) method, followed by oxidation with hydrogen peroxide to introduce carboxyl moieties (providing negative surface charges). CNFs are characterized with transmission electron microscopy, scanning electron microscopy, elemental analysis, and zeta potential measurements. When drop-dried asymmetrically onto a 10 μm diameter cylindrical channel on a 6 μm thick PET substrate and placed as a membrane between two electrolyte compartments, ionic current rectification is observed. Effects of pH, ionic strength, and nature of electrolyte are investigated. Bipolar reactivity of iodide is demonstrated. Potential for future applications in water purification are discussed.

Here we exploit the high surface area and ability of wild bacteriophage particles to form self-assembled structures. Utilization of these particles for modifying electrodes with carbon nanofibres (CNF) leads to the generation of a novel hybrid material with highly developed surface and thus an electrode with an extended active area, which is desirable when preparing new sensing platforms. This report helps filling gaps in the current knowledge about bacteriophage-nano-material interactions. The wild bacteriophage-carbon nanofibre interactions were thoroughly characterized by microscopy techniques and zeta potential measurements. Our results show that the electroactive surface area is better developed when the bacteriophages are added to the CNF-based electrodes, compared to the case of only the bare electrode, or an electrode modified only with CNFs. The electrocatalytic response towards the oxidation of the thiol biomarker l -cysteine was evaluated with cyclic voltammetry. The results show that the response of the electrode is improved if bacteriophages are used for CNF-based electrode modification.

Thermogalvanic systems represent a means to convert a temperature gradient into electricity, using only redox chemistry. However, the kinetics of electron transfer and physical mass transport of the redox couples are known limitations. In this study we present self-contained gelled thermogalvanic cells (or thermocells) containing the ferricyanide/ferrocyanide redox couple, which additionally have gold nanoparticles either immobilised at the gel/electrode interface, or distributed throughout the entire gel. Both methods of introducing the gold nanoparticles result in an apparent electrocatalytic improvement, as demonstrated by significant decreases in the electron transfer resistance. However, when used as thermogalvanic cells, only minor improvements were observed in power generation, and relatively rapid dissolution of the gold nanoparticles was observed, to yield passivating gold analogues of Prussian blue. Therefore successful preparation and short-term improvements have been demonstrated, but are offset by long-term stability issues. The relatively surprising instability of the generally inert gold nanoparticles in the presence of ferricyanide/ferrocyanide, particularly under thermogalvanic conditions, is of particular note. Keywords: Thermoelectrochemistry, Thermogalvanic cells, Gold nanoparticles

Cation transport through nanochannels in graphene oxide can be rectified to give ionic diode devices for future applications, for example, in desalination. A film of graphene oxide is applied to a 6 μm thick poly(ethylene terephthalate) substrate with a 20 μm diameter microhole and immersed in aqueous HCl solution. Strong diode effects are observed even at high ionic strength (0.5 M). Switching between open and closed states, microhole size effects, and time-dependent phenomena are explained on the basis of a simplified theoretical model focusing on the field-driven transport within the microhole region. In aqueous NaCl, competition between Na + transport and field-driven heterolytic water splitting is observed but shown to be significant only at low ionic strength. Therefore, nanostructured graphene oxide is demonstrated to exhibit close to ideal behavior for future application in ionic diode desalination of seawater.

Advances in materials science have accelerated the development of diagnostic tools with the last decade witnessing the development of enzyme-free sensors, owing to the improved stability, low cost and simple fabrication of component materials. However, the specificity of non-enzymatic sensors for certain analytes still represents a challenging task, for example the determination of cholesterol level in blood is vital due to its medical relevance. In this work, a reagent displacement assay for cholesterol sensing in serum samples was developed. It is based on coating of a glassy carbon electrode with a polymer of intrinsic microporosity (PIM) that forms a host-guest complex with methylene blue (MB). In the presence of cholesterol, the MB electroactive probe was displaced due to the stronger association of cholesterol guest to the PIM host. The decrease in the oxidative current was proportional to the cholesterol concentration achieving a detection limit of approximately 0.1 nM. Moreover, to further assist the experimental studies, comprehensive theoretical calculations are also performed by using density functional theory (DFT) calculations. Graphical abstract: [Figure not available: see fulltext.].

In order to prevent the microwave leakage and mutual interference, more and more microwave absorbing devices are added into the design of electronic products to ensure its routine operation. In this work, we have successfully prepared MoS2/TiO2/Ti3C2Tx hierarchical composites by one-pot hydrothermal method and focused on the relationship between structures and electromagnetic absorbing properties. Supported by comprehensive characterizations, MoS2 nanosheets were proved to be anchored on the surface and interlayer of Ti3C2Tx through a hydrothermal process. Additionally, TiO2 nanoparticles were obtained in situ. Due to these hierarchical structures, the MoS2/TiO2/Ti3C2Tx composites showed greatly enhanced microwave absorbing performance. The MoS2/TiO2/Ti3C2Tx composites exhibit a maximum reflection loss value of −33.5 dB at 10.24 GHz and the effective absorption bandwidth covers 3.1 GHz (13.9–17 GHz) at the thickness of 1.0 mm, implying the features of wide frequency and light weight. This work in the hierarchical structure MoS2/TiO2/Ti3C2Tx composites opens a promising door to the exploration of constructing extraordinary electromagnetic wave absorbents.

A new heterotrinuclear (d-f-d) complex [Eu(btfa)31c] (btfa = 4,4,4-trifluoro-1-phenyl-1,3-butanedione and 1c = [(Ph)(Et3P)2Pt-C[triple bond, length as m-dash]C-R-C[triple bond, length as m-dash]C-Pt(Et3P)2(Ph)] (R = 2,2'-bipyridine-5,5'-diyl) has been synthesized by utilizing the N,N-donor sites of the organometallic chromophore. The complex was characterized by analytical and spectroscopic methods. Photophysical properties of the complex were analysed in detail using both steady-state and time-resolved emission and excitation spectroscopy. The optical absorption spectrum of the complex is dominated by the spin allowed π-π* transitions of the btfa and 1c units in the UV-visible region (200-418 nm) and thus is excitable over a wide range of wavelengths across the UV into the visible region of the electromagnetic spectrum. The complex displays typical red Eu(iii) emission when excited at 345 nm. However, it also shows green emission when excited at 464 nm and, thus could be an interesting candidate for full colour display applications. The change in the colour could be a result of the high value of the energy back-transfer rate (6.73 × 105 s-1) from the triplet state of the organometallic chromophore to the 5D1 state of Eu(iii). Judd-Ofelt (J-O) intensity parameters (Ω2 and Ω4), radiative (AR), non-radiative (AR) decay rates and intrinsic quantum yield (Q) have been calculated.

Films of titanate nanosheets (approx. 1.8-nm layer thickness and 200-nm size) having a lamellar structure can form electrolyte-filled semi-permeable channels containing tetrabutylammonium cations. By evaporation of a colloidal solution, persistent deposits are readily formed with approx. 10-μm thickness on a 6-μm-thick poly(ethylene-terephthalate) (PET) substrate with a 20-μm diameter microhole. When immersed in aqueous solution, the titanate nanosheets exhibit a p.z.c. of − 37 mV, consistent with the formation of a cation conducting (semi-permeable) deposit. With a sufficiently low ionic strength in the aqueous electrolyte, ionic current rectification is observed (cationic diode behaviour). Currents can be dissected into (i) electrolyte cation transport, (ii) electrolyte anion transport and (iii) water heterolysis causing additional proton transport. For all types of electrolyte cations, a water heterolysis mechanism is observed. For Ca2+ and Mg2+ions, water heterolysis causes ion current blocking, presumably due to localised hydroxide-induced precipitation processes. Aqueous NBu4+ is shown to ‘invert’ the diode effect (from cationic to anionic diode). Potential for applications in desalination and/or ion sensing are discussed.

Porous carbon nanohybrids are promising materials as high-performance electrodes for both sensing and energy conversion applications. This is mainly due to their high specific surface area and specific physicochemical properties. Here, new porous nanohybrid materials are developed based on exfoliated MoS

An "indirect" photo-electrochemical sensor is presented for the measurement of a mixture of analytes including reducing sugars (e.g. glucose, fructose) and non-reducing sugars (e.g. sucrose, trehalose). Its innovation relies on the use of a palladium film creating a two-compartment cell to separate the electrochemical and the photocatalytic processes. In this original way, the electrochemical detection is separated from the potential complex matrix of the analyte (i.e. colloids, salts, additives, etc.). Hydrogen is generated in the photocatalytic compartment by a Pt@g-C3N4 photocatalyst embedded into a hydrogen capture material composed of a polymer of intrinsic microporosity (PIM-1). The immobilised photocatalyst is deposited onto a thin palladium membrane, which allows rapid pure hydrogen diffusion, which is then monitored by chronopotentiometry (zero current) response in the electrochemical compartment. The concept is demonstrated herein for the analysis of sugar content in commercial soft drinks. There is no requirement for the analyte to be conducting with electrolyte or buffered. In this way, samples (biological or not) can be simply monitored by their exposition to blue LED light, opening the door to additional energy conversion and waste-to-energy applications.

An "indirect" photo-electrochemical sensor is presented for the measurement of a mixture of analytes including reducing sugars (e.g. glucose, fructose) and non-reducing sugars (e.g. sucrose, trehalose). Its innovation relies on the use of a palladium film creating a two-compartment cell to separate the electrochemical and the photocatalytic processes. In this original way, the electrochemical detection is separated from the potential complex matrix of the analyte (i.e. colloids, salts, additives, etc.). Hydrogen is generated in the photocatalytic compartment by a Pt@g-C

Polymers of intrinsic microporosity (PIMs) provide high surface area materials (typically 1000 m2 g-1 apparent BET surface area) that are processable from organic solvents to give glassy films or composite coatings. Multi-functionality for sensing with these materials is achieved (i) based on the polymer backbone itself being fluorescent or chemically active or (ii) based on guest species (chromophores, nano-catalysts, nano-photo-catalysts, etc.) that are readily embedded into PIMs and accessible through micropores in the polymer host. The ease of forming uniform microporous films or composite films is linked to molecular rigidity and highlighted here for sensing/electroanalytical applications.

Heteroaryl incorporated acetylide-functionalized pyridinyl ligands (L1-L6) with the general formula Py-C≡C-Ar (Py = pyridine and Ar = thiophene-2-yl, 2,2' -bithiophene]-5-yl, 2,2' :5',2″ -terthiophene]-5-yl, thieno[2,3- b]thiophen-2-yl, quinoline-5-yl, benzo[c][1,2,5]thiadiazole-5-yl) have been synthesized by Pd(0)/Cu(I)-catalyzed cross-coupling reaction of 4-ethynylpyridine and the respective heteroaryl halide. Ligands L1-L6 were isolated in respectable yields and characterized by microanalysis, IR spectroscopy, 1H NMR spectroscopy, and ESI-MS mass spectrometry. A series of dinuclear Cu(I) complexes 1-10 have been synthesized by reacting L1-L6 with CuI and triphenylphosphine (PPh3) (R1) or with an anchored phosphine derivative, 4-(diphenylphosphino) benzoic acid (R2)/2-(diphenylphosphino)benzenesulfonic acid (R3), in a stoichiometric ratio. The complexes are soluble in common organic solvents and have been characterized by analytical, spectroscopic, and computational methods. Single-crystal X-ray structure analysis confirmed rhomboid dimeric structures for complexes 1, 2, 4, and 5, and a polymeric structure for 6. Complexes 1-6 showed oxidation potential responses close to 0.9 V vs Fc0/+, which were chemically irreversible and are likely to be associated with multiple steps and core oxidation. Preliminary photovoltaic (PV) results of these new materials indicated moderate power conversion efficiency (PCE) in the range of 0.15-1.56% in dye-sensitized solar cells (DSSCs). The highest PCE was achieved with complex 10 bearing the sulfonic acid anchoring functionality.

Nafion offers microporous channels of typically 1–4-nm diameter for cation exchange. Recently, it has been shown that these cation exchanger properties can be inverted to allow anion binding by pre-filling the hydrophilic channel structure. Here, pre-filling is performed with hydrous iron oxide and sensitivity towards anionic phosphate and arsenate analytes is investigated. After a period of phosphate/arsenate accumulation, the voltammetric response in aqueous 1 M NaNO3 is obtained based on the Fe(III/II) redox process. The position of the peak at distinct potentials clearly reveals the presence of either phosphate or arsenate, presumably present in the form of FePO4 and FeAsO4. In the presence of mixtures of phosphate and arsenate, a competition of FePO4 versus FeAsO4 nucleation (within the Nafion microporous host) is suggested to result in a switch of phosphate detection at higher concentrations (ca. > 500 μM, solubility controlled) towards arsenate detection at lower concentrations (ca.