Explore the vast range of titles available.

Photoinduced electron transfer (PET) is a phenomenon whereby the absorption of light by a chemical species provides an energetic driving force for an electron-transfer reaction 1 – 4 . This mechanism is relevant in many areas of chemistry, including the study of natural and artificial photosynthesis, photovoltaics and photosensitive materials. In recent years, research in the area of photoredox catalysis has enabled the use of PET for the catalytic generation of both neutral and charged organic free-radical species. These technologies have enabled previously inaccessible chemical transformations and have been widely used in both academic and industrial settings. Such reactions are often catalysed by visible-light-absorbing organic molecules or transition-metal complexes of ruthenium, iridium, chromium or copper 5 , 6 . Although various closed-shell organic molecules have been shown to behave as competent electron-transfer catalysts in photoredox reactions, there are only limited reports of PET reactions involving neutral organic radicals as excited-state donors or acceptors. This is unsurprising because the lifetimes of doublet excited states of neutral organic radicals are typically several orders of magnitude shorter than the singlet lifetimes of known transition-metal photoredox catalysts 7 – 11 . Here we document the discovery, characterization and reactivity of a neutral acridine radical with a maximum excited-state oxidation potential of −3.36 volts versus a saturated calomel electrode, which is similarly reducing to elemental lithium, making this radical one of the most potent chemical reductants reported 12 . Spectroscopic, computational and chemical studies indicate that the formation of a twisted intramolecular charge-transfer species enables the population of higher-energy doublet excited states, leading to the observed potent photoreducing behaviour. We demonstrate that this catalytically generated PET catalyst facilitates several chemical reactions that typically require alkali metal reductants and can be used in other organic transformations that require dissolving metal reductants. Photoexcited acridine radical catalysts are found to have redox potentials more reducing than lithium, which is attributed to the population of higher-energy doublet excited states via a twisted intramolecular charge-transfer species.

In this paper, we present the first highly porous gold (h-PG) microneedles-based second-generation biosensor for minimally invasive monitoring of glucose in artificial interstitial fluid (ISF). A highly porous microneedles-based electrode was prepared by a simple electrochemical self-templating method that involves two steps, gold electrodeposition and hydrogen bubbling at the electrode, which were realized by applying a potential of −2 V versus a saturated calomel electrode (SCE). The highly porous gold surface of the microneedles was modified by immobilization of 6-(ferrocenyl)hexanethiol (FcSH) as a redox mediator and subsequently by immobilization of a flavin adenine dinucleotide glucose dehydrogenase (FAD-GDH) enzyme using a drop-casting method. The microneedles-based FcSH/FAD-GDH biosensor allows for the detection of glucose in artificial interstitial fluid with an extended linear range (0.1–10 mM), high sensitivity (50.86 µA cm−2 mM−1), stability (20% signal loss after 30 days), selectivity (only ascorbic acid showed a response about 10% of glucose signal), and a short response time (3 s). These properties were favourably compared to other microneedles-based glucose biosensors reported in the literature. Finally, the microneedle-arrays-based second-generation biosensor for glucose detection was tested in artificial interstitial fluid opportunely spiked with different concentrations of glucose (simulating healthy physiological conditions while fasting and after lunch) and by placing the electrode into a simulated chitosan/agarose hydrogel skin model embedded in the artificial ISF (continuous glucose monitoring). The obtained current signals had a lag-time of about 2 min compared to the experiments in solution, but they fit perfectly into the linearity range of the biosensor (0.1–10 mM). These promising results show that the proposed h-PG microneedles-based sensor could be used as a wearable, disposable, user-friendly, and automated diagnostic tool for diabetes patients.

A self-assembled periodic superlattice material was obtained by integrating positively charged semiconductive sheets of a Zn-NiAl layered double hydroxide (LDH) and negatively charged layers of reduced graphene oxide (rGO). The material was used to modify a glassy carbon electrode which then is shown to be a viable sensor for the diagnostic parameters dopamine (DA), uric acid (UA) and ascorbic acid (AA). The modified GCE displays excellent electrocatalytic activity towards these biomolecules. This is assumed to be due to the synergistic effects of (a) excellent interfacial electrical conductivity that is imparted by direct neighboring of conductive rGO to semiconductive channels of LDHs, (b) the superb intercalation feature of LDHs, and (c) the enlarged surface with an enormous number of active sites. The biosensor revealed outstanding electrochemical performances in terms of selectivity, sensitivity, and wide linear ranges. Typically operated at working potentials of −0.10, +0.13 and + 0.27 V vs. saturated calomel electrode, the lower detection limits for AA, DA and UA are 13.5 nM, 0.1 nM, and 0.9 nM, respectively, at a signal-to-noise ratio of 3. The sensor was applied to real-time tracking of dopamine efflux from live human nerve cells. Graphical abstract Schematic of the preparation of a superlattice self-assembled material by integrating positively charged semiconductive sheets of Zn-NiAl layered double hydroxide (LDH) with negatively charged reduced graphene oxide (rGO) layers. It was applied to simultaneous electrochemical detection of dopamine (DA), uric acid and ascorbic acid.

Visible-light-absorbing semiconductor nanocrystals have shown great promise as photocatalysts for promoting photoredox chemistry. However, their utilization in organic synthesis remains considerably limited compared to small molecule photosensitizers. Recently, the generation of hot electrons from quantum-confined systems has emerged as a powerful means of photoreduction, yet the efficiencies remain limited under mild conditions. In this study, we present an efficient hot-electron generation system facilitated by the spin-exchange Auger process in Mn 2+ -doped CdS/ZnS quantum dots. These hot electrons can be effectively utilized in a wide range of organic reactions, such as the Birch reduction and reductive cleavage of C-Cl, C-Br, C-I, C-O, C-C, and N-S bonds. Notably, these reactions accommodate substrate reduction potentials as low as −3.4 V versus the saturated calomel electrode. Through two-photon excitation, we achieve the generation of a “super” photoreductant using visible-light irradiation power that is only 1% of that previously reported for molecular and quantum dot systems. By modulating the intensity of light output, the spin-exchange Auger process enables the on/off generation of hot electrons, allowing for programmable assembly-point cross-coupling cascades. Our findings demonstrate the potential of quantum-confined semiconductors in facilitating challenging organic transformations that were unattainable with molecular photocatalysts. The authors present an efficient hot-electron generation system facilitated by the spin-exchange Auger process in Mn2 + -doped CdS/ZnS quantum dots. These hot electrons can be used in a wide range of organic reactions, such as the Birch reduction and reductive cleavage of C-Cl, C-Br, C-I, C-O, C-C, and N-S bonds.

The aim of this work was to prepare poly(3,4-ethylenedioxythiophene) electrodes from an electrolyte containing graphene oxide and sodium dodecyl sulfate or poly(4-styrenesulfonate) solutions. The synthesis was also carried out without the presence of graphene oxide. Two different electrode supports were used, glassy carbon and a thin layer of graphene oxide pre-deposited on glassy carbon. All poly(3,4-ethylenedioxythiophene) layers were synthesised by applying 1.0 V vs. saturated calomel electrode for 300 s. After synthesis, the electrode with graphene oxide support was additionally polarised at − 1.4 V vs. saturated calomel electrode in 0.1 mol dm −3 potassium chloride solution for 600 s to obtain reduced graphene oxide. In this way, electrodes with reduced graphene oxide were prepared. The prepared electrodes were used to assemble symmetric supercapacitors, which were tested by cyclic voltammetry and electrochemical impedance spectroscopy. The stability of the supercapacitors was determined by charging/discharging at constant current during 1000 cycles, maintaining the capacitance between 72% and 95%. The highest specific capacitance and energy values were 74.67 F g⁻ 1 and 5.60 W h kg⁻ 1 , respectively. The presence of graphene oxide in the synthesis solution or as support decreased the synthesis rate and resulted in a more compact layer with a lower specific capacitance value. However, the successful reduction of graphene oxide significantly improved the capacitive properties, making this electrode suitable for high-energy applications. Graphical abstract

The corrosion behavior of CoCrCu 0.1 FeMoNi high entropy alloy (HEA) in 0.5 mol/L NaOH solution was investigated using X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, potentiodynamic polarization measurement, and electrochemical impedance spectroscopy. The results showed that the microstructure of this HEA displayed a dendritic morphology along with inter-dendritic regions. At the applied potential of –0.3, 0, and 0.1 V vs . saturated calomel electrode (SCE), no significant damage to the surface of the alloy was observed. At the applied potentials of 0.15 and 0.2 V vs . SCE, selective detachment and tearing of the microstructure on the alloy surface were observed, attributed to micro-galvanic corrosion. HEA demonstrates typical spontaneous passivation behavior and exhibits capacitance at all five applied potentials. The energy dispersive spectroscopy results indicate significant elemental segregation within HEA, with a decrease in the content of Cr 2 O 3 in the passive film as the applied potential increases. Consequently, the protective efficacy of the passive film over the substrate in 0.5 mol/L NaOH solution was compromised.

A pyrolytic method is described for preparation of ultrafine Fe 3 C nanoparticles incorporated into N-doped graphitic carbon nanosheets (Fe 3 C@NGCSs). Iron phthalocyanine and graphitic carbon nitride (g-C 3 N 4 ) are used as starting materials. The hybrid nanocomposite was placed on a glassy carbon electrode (GCE) and then applied to simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and xanthine (XA). Figures of merits are as follows: for AA, the linear response range covers the 54.0–5491.0 μM range, the lower detection limit is 16.7 μM, and the best working voltage (vs. the saturated calomel electrode (SCE)) is 0.05 V. The respective data for DA are 1.2–120.8 μM, 0.34 μM and 0.19 V (vs. SCE). For UA, the respective data are 4.8–263.0 μM, 1.4 μM and 0.32 V (vs. SCE), and for XA the data are 4.8–361.0 μM, 1.5 μM and 0.71 V (vs. SCE). The method was successfully applied to their simultaneous determination in spiked serum samples. Graphical abstract Ultrafine Fe 3 C nanoparticles embedded in N-doped graphitic carbon sheets for simultaneous determination of ascorbic acid, dopamine, uric acid and xanthine.

Gold-catalysed oxidative coupling reactions often require strong oxidants because of the high redox potential of Au(i)/Au(iii) (1.41 V versus the saturated calomel electrode), resulting in poor reaction economy and functional group compatibility. Here we report a dinuclear gold-catalysed C(sp2)–C(sp) coupling reaction between structurally diverse alkynes and arylhydrazines under electrochemical conditions. This approach provides a practical oxidative C–C coupling reaction that avoids the use of synthetic oxidants and instead produces H2. This method exhibits excellent functional group compatibility towards compounds such as alcohols, amines, sulfides and electron-rich arenes, which possess functional groups sensitive to oxidizing agents. This synthetic robustness is further shown by the successful late-stage modification of different kinds of alkynes tethered to biomolecules such as amino acids, peptides, nucleotides and saccharides. Mechanistic studies suggest a first aryl radical oxidative addition step with Au(i), followed by anodic oxidation to generate the highly electrophilic Ar–Au(iii) species for subsequent σ-activation of alkynes.The development of gold catalysis is restricted by its high redox potential, and the introduction of strong oxidants to overcome this is accompanied by poor functional group compatibility. Here electrochemical oxidation is used to control gold valence changes, showing excellent compatibility with a wide range of active functional groups and bio-additives.

The anodic oxidation of glucose in a neutral medium is a target electrocatalytic reaction for non-enzymatic glucose sensors and continuous glucose monitoring systems that are vital for diabetes patients. In respect to this reaction, the prospects of three kinds of platinum electrocatalysts were compared, namely, Pt electrodeposited from a neutral phosphate-based Roseleur electrolyte, colloidal surfactant-free Pt prepared by the Lottermoser method (1901) and commercial platinum on carbon powder widely used in catalysis. Regarding electrodeposited Pt electrocatalysts, the effect of the electrodeposition potential on their morphology and activity in glucose oxidation, which was studied in a NaCl-based phosphate-buffered saline (pH 7.40), was also investigated. To estimate and compare real surface area of Pt in all the samples, underpotential deposition of hydrogen was analyzed. Special attention was focused on the quantitative glucose determination in a physiological concentration range (e.g., 1–30 mM) at potentials of negligible oxygen reduction as well as on the long-term stability of glucose oxidation currents. For the most promising electrodeposited Pt sample with a 0.18 mg Pt   cm geo - 2 loading the glucose oxidation current of ca. 40.5 μA  cm geo - 2 at +0.4 V vs. saturated calomel electrode in the 7 mM solution was observed. The linear concentration dependence in the physiological glucose range (3–30 mM) with the sensitivity of ca. 21.4 μA mM −0.5   cm geo - 2 at 25 °C was achieved. Finally, glucose selectivity of platinum with regard to fructose, galactose, xylose, ribose, urea, lactic acid, acetone, ascorbic acid and paracetamol was examined. Graphical abstract

Herein, a simple electrochemical process was proposed for the electrochemical modification of a graphite rod electrode (GrE) with a zinc hydroxide thin film. Two sequential steps were enough for the modification of the graphite rod using chronoamperometry technique. In the first step, the metallic zinc film was electrochemically deposited on GrE surface at pH 4.5, by reducing Zn 2+ on GrE at − 1.78 V vs. saturated calomel electrode (SCE) for only 210 s forming GrE@ZnNPs. In the second step, the electrode previously coated with a metallic zinc film was oxidized in buffer solution at pH 7, at 0.1 V vs. SCE for 360 s to form GrE@Zn(OH) 2 NPs. X-ray diffraction, optical microscope and interferometric microscope were used to confirm and identify the obtaining of the desired layer (Zn and Zn(OH) 2 nanoparticles (NPs) thin layer). Then, several electrochemical techniques were used before and after the modification in order to study the electrochemical properties of the bare and modified electrodes. These analyses are based on the comparison of open-circuit potentials, polarization resistances of fast electrochemical systems ( R p ), potentiodynamic polarizations (Tafel curves) and electrochemical impedances.