Electron Transfer Reactions Research Articles

A reasoned general explanation about the concepts of diffusion and reaction layers

The understanding of the implication of the transport of matter is fundamental in the teaching of heterogeneous charge transfers, which are the central element of the electrochemical science and technologies. Thus, even in the absence of intrinsic kinetic complications, the overall rate of such events is frequently conditioned by the mass transport and also by the occurrence of homogeneous coupled chemical reactions. Upon comprehending and accounting for these two effects, the emergent and widely used concepts of the diffusion and reaction layers will be discussed and disentangled under potential-controlled conditions. First, some basic concepts about the transport of charged species in solution are recalled, in order to establish the experimental conditions under which diffusion-only transport can be considered. Under these premises, a fast electron transfer will be considered to introduce the concept of “diffusion layer”, discussing its relationship with the time of the experiment and with the characteristics of the diffusive field that is strongly influenced by the geometry and size of the electrode considered. Next, fast electron transfer reactions “conditioned” by homogeneous chemical reactions undergone by the reactant and/or the product of the redox couple will be analysed. A historical introduction to the concept of “reaction layer” is carried out, pointing out its value in processes with chemical regeneration of the electroactive species and its non-negligible interplay with the mode of diffusion.

Long-Time Oxygen and Superoxide Localization in Arabidopsis thaliana Cryptochrome.

Cryptochromes are proteins that are highly conserved across species and in many instances bind the flavin adenine dinucleotide (FAD) cofactor within their photolyase-homology region (PHR) domain. The FAD cofactor has multiple redox states that help catalyze reactions, and absorbs photons at about 450 nm, a feature linked to the light-related functions of cryptochrome proteins. Reactive oxygen species (ROS) are produced from redox reactions involving molecular oxygen and are involved in a myriad of biological processes. Superoxide O2•- is an exemplary ROS that may be formed through electron transfer from FAD to O2, generating an electron radical pair. Although the formation of a superoxide-FAD radical pair has been speculated, it is still unclear if the required process steps could be realized in cryptochrome. Here, we present results from molecular dynamics (MD) simulations of oxygen interacting with the PHR domain of Arabidopsis thaliana cryptochrome 1 (AtCRY1). Using MD simulation trajectories, oxygen binding locations are characterized through both the O2-FAD intermolecular distance and the local protein environment. Oxygen unbinding times are characterized through replica simulations of the bound oxygen. Simulations reveal that oxygen molecules can localize at certain sites within the cryptochrome protein for tens of nanoseconds, and superoxide molecules can localize for significantly longer. This relatively long-duration molecule binding suggests the possibility of an electron-transfer reaction leading to superoxide formation. Estimates of electron-transfer rates using the Marcus theory are performed for the identified potential binding sites. Molecular oxygen binding results are compared with recent results demonstrating long-time oxygen binding within the electron-transfer flavoprotein (ETF), another FAD binding protein.

Effect of pH on UV/H2O2-mediated removal of single, mixed and halogenated parabens from water

Adjusting pH values in aqueous environments can significantly improve the efficiency by which parabens and halo-parabens are removed. In this study, 20 neutral and deprotonated species were selected as models to investigate their pH-dependent removal mechanisms and kinetics by a UV/H2O2 process using density functional theory (DFT). Compared to neutral species, deprotonated species exhibit higher reactivity to HO• due to their high electron cloud density. H atom abstraction (HAA) reactions on the substitution groups are the most favorable pathways for neutral species, while radical adduct formation (RAF) reactions are the most favorable for deprotonated species. Single electron transfer (SET) reactions can be neglected for neutral species, while these reactions become a viable route for deprotonated molecules. The total reaction rate constants range from 1.63 × 109 to 3.74 × 1010 M− 1 s− 1 at pH 7.0, confirming the experimental results. Neutral and weakly alkaline conditions are favorable for the degradation of MeP and halo-parabens in the UV/H2O2 process. The order of removal efficiency at optimum pH is dihalo-parabens > mono-halo-parabens ≈ F, F-MeP > MeP. Furthermore, the transformation products must undergo oxidative degradation due to their high toxicity. Our findings provide new insights into the removal of parabens and their halogenated derivatives from wastewater.

Zinc Tetrapyrrole Coordinated to Imidazole Functionalized Tetracyanobutadiene or Cyclohexa-2,5-diene-1,4-diylidene-expanded-tetracyanobutadiene Conjugates: Dark vs. Light-Induced Electron Transfer.

Using the popular metal-ligand axial coordination self-assembly approach, donor-acceptor conjugates have been constructed using zinc tetrapyrroles (porphyrin (ZnP), phthalocyanine (ZnPc), and naphthalocyanine (ZnNc)) as electron donors and imidazole functionalized tetracyanobutadiene (Im-TCBD) and cyclohexa-2,5-diene-1,4-diylidene-expanded-tetracyanobutadiene (Im-DCNQ) as electron acceptors. The newly formed donor-acceptor conjugates were fully characterized by a suite of physicochemical methods, including absorption and emission, electrochemistry, and computational methods. The measured binding constants for the 1 : 1 complexes were in the order of 104 -105 M-1 in o-dichlorobenzene. Free-energy calculations and the energy level diagrams revealed the high exergonicity for the excited state electron transfer reactions. However, in the case of the ZnNc:Im-DCNQ complex, owing to the facile oxidation of ZnNc and facile reduction of Im-DCNQ, slow electron transfer was witnessed in the dark without the aid of light. Systematic transient pump-probe studies were performed to secure evidence of excited state charge separation and gather their kinetic parameters. The rate of charge separation was as high as 1011 s-1 suggesting efficient processes. These findings show that the present self-assembly approach could be utilized to build donor-acceptor constructs with powerful electron acceptors, TCBD and DCNQ, to witness ground and excited state charge transfer, fundamental events required in energy harvesting, and building optoelectronic devices.

Nuclear-Electronic Orbital Quantum Mechanical/Molecular Mechanical Real-Time Dynamics.

Simulating the nuclear-electronic quantum dynamics of large-scale molecular systems in the condensed phase is key for studying biologically and chemically important processes such as proton transfer and proton-coupled electron transfer reactions. Herein, the real-time nuclear-electronic orbital time-dependent density functional theory (RT-NEO-TDDFT) approach is combined with a hybrid quantum mechanical/molecular mechanical (QM/MM) strategy to enable the accurate description of coupled nuclear-electronic quantum dynamics in the presence of heterogeneous environments such as solvent or proteins. The densities of the electrons and quantum protons are propagated in real time, while the other nuclei are propagated classically on the instantaneous electron-proton vibronic surface. This approach is applied to phenol bound to lysozyme, intramolecular proton transfer in malonaldehyde, and nonequilibrium excited-state intramolecular proton transfer in o-hydroxybenzaldehyde. These examples illustrate that the RT-NEO-TDDFT framework, coupled with an atomistic representation of the environment, allows the simulation of condensed-phase systems that exhibit significant nuclear quantum effects.

Differences in the degradation behavior of disinfection by-products in UV/PDS and UV/H2O2 processes and the effect of their chemical properties

In this work, sixteen typical chlorinated and brominated aromatic disinfection by-products (DBPs) were selected as examples to investigate their different degradation mechanisms initiated by HO• and SO4•-. Addition reactions were the main mode of degradation of DBPs by HO•, while SO4•- dominated H-abstraction reactions and single electron transfer reactions. Chlorinated compounds had higher reactivity than brominated compounds. Furthermore, substituents with stronger electron-donating effects promoted the electrophilic reaction of DBPs with the two radicals. In addition, we developed a model based on the chemical properties LUMO, fmax−, and hardness for predicting the average reaction energy barriers for the initial reactions of DBPs with HO• and SO4•-. The model had good predictive performance for the difficulty of degradation of different DPBs by HO• and SO4•-, with R2 values of 0.85 and 0.87, respectively. Through the degradation efficiency simulation, we found that longer reaction times, higher oxidant concentrations and lower pollutant concentrations were more favorable for the removal of DBPs. The UV/PDS process showed better degradation of DBPs than the UV/H2O2 process. In addition, most degradation products of DBPs exhibited less toxicity to aquatic organisms than their parent compounds. This study provided theoretical guidance for the degradation and removal of other aromatic DBPs at the molecular level.

Characterizing the multi-dimensional reaction dynamics of dihalomethanes using XUV-induced Coulomb explosion imaging.

Site-selective probing of iodine 4d orbitals at 13.1nm was used to characterize the photolysis of CH2I2 and CH2BrI initiated at 202.5nm. Time-dependent fragment ion momenta were recorded using Coulomb explosion imaging mass spectrometry and used to determine the structural dynamics of the dissociating molecules. Correlations between these fragment momenta, as well as the onset times of electron transfer reactions between them, indicate that each molecule can undergo neutral three-body photolysis. For CH2I2, the structural evolution of the neutral molecule was simultaneously characterized along the C-I and I-C-I coordinates, demonstrating the sensitivity of these measurements to nuclear motion along multiple degrees of freedom.

Doping of molecular semiconductors through proton-coupled electron transfer.

The chemical doping of molecular semiconductors is based on electron-transfer reactions between the semiconductor and dopant molecules; here, the redox potential of the dopant is key to control the Fermi level of the semiconductor1,2. The tunability and reproducibility of chemical doping are limited by the availability of dopant materials and the effects of impurities such as water. Here we focused on proton-coupled electron-transfer (PCET) reactions, which are widely used in biochemical processes3,4; their redox potentials depend on an easily handled parameter, that is, proton activity. We immersed p-type organic semiconductor thin films in aqueous solutions with PCET-based redox pairs and hydrophobic molecular ions. Synergistic reactions of PCET and ion intercalation resulted in efficient chemical doping of crystalline organic semiconductor thin films under ambient conditions. In accordance with the Nernst equation, the Fermi levels of the semiconductors were controlled reproducibly with a high degree of precision-a thermal energy of about 25 millielectronvolts at room temperature and over a few hundred millielectronvolts around the band edge. A reference-electrode-free, resistive pH sensor based on this method is also proposed. A connection between semiconductor doping and proton activity, a widely used parameter in chemical and biochemical processes, may help create a platform for ambient semiconductor processes and biomolecular electronics.

An electrochlorination process integrating enhanced oxidation of phosphonate to orthophosphate and elimination: Verification of matrix chloridion-induced oxidation mechanism

Phosphonate used as scale inhibitor is a non-negligible eutrophic contaminant in corresponding polluted waters. Besides, its conversion to orthophosphate (ortho-P) is a precondition for realizing bioavailable phosphorus recovery. Due to the feeble degradation efficiency with less than 30 % from classical Fenton commonly used in industrial wastewater treatment and itself vulnerable to strong inhibition interference of matrix chloride ions, we proposed an electrochemical approach to transform the native salt in the solution into oxidizing substances, sort of achieving beneficial utilization of matrix waste, and enhanced the ortho-P conversion rate of 1-Hydroxyethane-1,1-diphosphonic acid (HEDP) to 89.2 % (± 3.6 %). In electrochlorination system, it was found that HEDP rapidly complexed with Fe(II) and then coordinated in-situ Fe(III) to release free HEDP via intramolecular metal-ligand electron transfer reaction. The subsequent degradation mainly rooted in the oxidation of pivotal reactive species HClO, FeIVO2+ and 1O2, causing C-P and CC bonds to fracture in sequence. Eventually the organically bound phosphorus of HEDP was recovered as ortho-P. This study acquainted the audiences with the rare mechanism of chloridion-triggered HEDP degradation under electrochemical way, as well as offered a feasible technology for synchronous transformation of organically bound phosphorus to ortho-P and elimination from phosphonates.

The varied roles of pilA-N, omcE, omcS, omcT, and omcZ in extracellular electron transfer by Geobacter sulfurreducens.

Geobacter sulfurreducens mediates extracellular electron transfer (EET) reactions with different substrates, such as solid-phase Fe(III)-containing minerals, anodes and the cells of Geobacter metallireducens. To compare their roles in EET, the pilA-N, omcE, omcS, omcT and omcZ genes of G. sulfurreducens were systematically deleted. All mutants showed impaired and varied ability to form biofilms on nonconductive surface. Deletion of omcE also impaired bacterial ability to reduce ferrihydrite, but its impacts on the ability for anode reduction and the co-culture of G. metallireducens-G. sulfurreducens were minimal. The mutant without omcS showed diminished ability to reduce ferrihydrite and to form the co-culture, but was able to regain its ability to reduce anodes. Deletion of omcT, omcZ or pilA-N alone impaired bacterial ability to reduce ferrihydrite and anodes and to form the co-culture. Deletion of all tested genes abolished bacterial ability to reduce ferrihydrite and anodes. Triple-deletion of all omcS, omcT and omcZ abolished the ability of G. sulfurreducens to co-culture with G. metallireducens. However, deletion of only omcZ or pilA-N or both omcS and omcT abolished the ability of G. sulfurreducens without hydrogenase gene hybL to co-culture with G. metallireducens, which show their indispensable roles in direct electron transfer from G. metallireducens to G. sulfurreducens. Thus, the roles of pilA-N, omcE, omcS, omcT and omcZ for G. sulfurreducens in EET vary substantially, which also suggest that possession of PilA-N and multiple cytochromes of different structures enables G. sulfurreducens to mediate EET reactions efficiently with substrates of different properties.

Facilitating Proton Coupled Electron Transfer Reaction through the Interfacial Micro Electric Field with Fe─N4 ─C in FeMOFs Glass.

The proton-coupled electron transfer(PCET) reaction plays a crucial role in the chemical transformation process andhas become one of the most concerned elementary reactions. However, the complex kinetics of PCET reaction, which requires the simultaneous transfer of protons and electrons, leads to the dilemma that thermodynamics and kinetics cannot bebalanced and restricts its further development. In this, an interface micro-electric field (IMEF) basedon Fe─N4 in FeMOFs (Fe-Based Metal-Organic Frameworks) glass is designed tosynchronize proton/electron interface behavior for the first time to realizeefficient PCET reaction and optimize reaction thermodynamics and kinetics. The IMEF facilitates the separation of photogenerated electrons and holes, and accelerates Fe(III)/Fe(II) cycle. Driven by near-surface electric field force, the protons near surfacemigrate to Fe sites and participate in Fe(IV)═O formation and reaction, lowering the reaction energy barrier. Based on the interface regulation ofIMEF, a high-efficiency PCET reaction is realized, and kinetic reactionrate constant of photocatalytic oxidation of emerging contaminants is increasedby 3.7times. This study highlights a strategy for IMEFs to modulate PEC Treactions for a wide range of potential applications, including environmental and ecological applications.

Exploring oxidative stress pathways in Geobacter sulfurreducens: the redox network between MacA peroxidase and triheme periplasmic cytochromes.

The recent reclassification of the strict anaerobe Geobacter sulfurreducens bacterium as aerotolerant brought attention for oxidative stress protection pathways. Although the electron transfer pathways for oxygen detoxification are not well established, evidence was obtained for the formation of a redox complex between the periplasmic triheme cytochrome PpcA and the diheme cytochrome peroxidase MacA. In the latter, the reduction of the high-potential heme triggers a conformational change that displaces the axial histidine of the low-potential heme with peroxidase activity. More recently, a possible involvement of the triheme periplasmic cytochrome family (PpcA-E) in the protection from oxidative stress in G. sulfurreducens was suggested. To evaluate this hypothesis, we investigated the electron transfer reaction and the biomolecular interaction between each PpcA-E cytochrome and MacA. Using a newly developed method that relies on the different NMR spectral signatures of the heme proteins, we directly monitored the electron transfer reaction from reduced PpcA-E cytochromes to oxidized MacA. The results obtained showed a complete electron transfer from the cytochromes to the high-potential heme of MacA. This highlights PpcA-E cytochromes' efficient role in providing the necessary reducing power to mitigate oxidative stress situations, hence contributing to a better knowledge of oxidative stress protection pathways in G. sulfurreducens.

Flavin mononucleotide in visible light photoinitiating systems for multiple-photocrosslinking and photoencapsulation strategies

Visible light-induced photocrosslinking techniques have attracted significant attention for their flexibility, controllability, safety, and energy conservation, especially in tissue engineering and biofabrication, compared to UV photocrosslinking. Despite these advantages, current photoinitiators are constrained by various challenges, including inadequate photoinitiation efficiency, low biocompatibility, poor water solubility, and limited compatibility with diverse crosslinking systems. Here, a water-soluble derivative of riboflavin, flavin mononucleotide (FMN−), was used to assess its potential as an initiator in multiple-photocrosslinking systems, including radical photopolymerization, dityrosine, and ditryptophan coupling crosslinking, under blue light irradiation. Blue light irradiation facilitated an efficient electron transfer reaction between FMN− and persulfate, owing to their suitable spectral compatibility and photoactivity. The resulting oxidizing free radicals and excited triplet state of FMN− served as initiating active species for the multiple-photocrosslinking reactions. The combination of FMN− and potassium persulfate (KPS) exhibited exceptional photoinitiation efficiency for various biomaterials, including silk fibroin, gelatin, poly(ethylene glycol) diacrylate, and carboxymethyl cellulose modified with amino acids. Furthermore, the cytocompatibility of the FMN−/KPS photoinitiator was demonstrated by the survival rates of 3T3-LI fibroblasts encapsulated in it, which exceeded 95 % when compared to a commercial initiator. Statement of significanceBy introducing persulfate, the photoinitiation efficiency of flavin mononucleotide was significantly improved. The application scenarios of flavin mononucleotide and persulfate combinations were also greatly extended, including radical photopolymerization, dityrosine, diphenylalanine, and ditryptophan coupling crosslinking. Among them, the coupling crosslinking of amino acids (di-phenylalanine, and di-tryptophan) modified carboxymethyl cellulose, to our knowledge, was first reported. The excellent cytocompatibility of cell encapsulation further proved that the combinations of flavin mononucleotide and persulfate have great potential in tissue engineering.

Contribution Factors of the First Kind Calculated for the Marcus Electron-Transfer Rate and Their Applications.

In this study, we applied the concept of the "contribution factor of the first kind (CFFK)" to the original electron-transfer (ET) rate theory proposed by Marcus. Mathematical derivations provided simple and convenient formulas for estimating the relative contributions of ten physical and chemical parameters involved in the Marcus ET rate formula: (1) the maximum strength of the electronic coupling energy between two molecules, (2) the exponential decay rate of the electronic coupling energy versus the distance between both molecules, (3) the distance between both molecules, (4) the equilibrium distance between both molecules, (5) the Gibbs free energy, (6) reorganization free energy in the prefactor of the Marcus ET rate equation, (7) reorganization free energy in the denominator of the exponential term, (8) reorganization free energy in the argument of the exponential term, (9) Boltzmann constant times absolute temperature in the prefactor of the rate equation, and (10) Boltzmann constant times absolute temperature in the denominator of the exponential term. We applied our theories to (i) ET reactions at bacterial photosynthesis reaction centers, PSI and PSII, and soluble ferredoxins (Fd); (ii) intraprotein ET reactions for designed azurin mutants; and (iii) ET reactions in flavodoxin (Fld). The formulas and calculations suggest that the theory behind the CFFK is useful for quantitatively identifying major and minor physical and chemical factors and corresponding trade-offs, all of which affect the magnitude of the Marcus ET rate.

The ultrasensitive detection of p-nitrophenol using a simple activated carbon electrode modified with electrodeposited bismuth dendrites

Bismuth dendrites were electrodeposited onto an activated glassy carbon electrode and the resulting modified electrode was employed in the electrochemical detection of para-nitrophenol, an aromatic aquatic pollutant. The carbon electrode was activated by cycling between − 2.0 and 2.0 V vs. SCE to create active sites that can promote the electron transfer reaction. Bismuth dendrites were subsequently deposited at a potential of − 1.0 V vs. SCE for 400 s. A near 5-fold increase in the peak current associated with the conversion of para-nitrophenol (100 μM) to para-hydroxyaminophenol was obtained on activating the glassy carbon electrode. A more impressive 7-fold increase in the peak current was achieved on decorating the activated glassy carbon with bismuth dendrites. Calibration curves with linear regions from 1.6 to 170 μM and between 0.005 and 1.6 μM para-nitrophenol were obtained to give a LOD value of 0.18 nM and a sensitivity of 29.4 μA μM−1 cm−2 for the lower concentration range. Good repeatability, reproducibility and selectivity were achieved, while recovery values between 96.5 and 106.7 % were obtained in water samples. In addition, the bismuth dendrites were easily regenerated through an oxidation step at 0.6 V vs. SCE followed by a 400 s electrodeposition period in 1.0 mM Bi(III).

A specific purple–blue color reaction between tryptophan and tyrosine in concentrated acidic medium

Electron transfer between tryptophan (Trp) and tyrosine (Tyr) is often accompanied with transient emission of visible blue-purple light, which is very common in numerous laser-induced photolysis experiments. However, recent experiments have shown that in the absence of pulse radiolysis, by mixing Trp and Tyr in concentrated aqueous hydrochloric acid can also produce a blue–purple color as it was observed in photolysis experiments. Unexpectedly, this color is quite stable in strong acid media (it can be kept at room temperature for at least a week). It is proposed that after initial formation of Trp radical products (TrpH▪+/Trp▪) by the solvent radical oxidation, charge-transfer complexes were generated via electron transfer reactions between Trp radical products and phenol of Tyr or their directly hole-trapping mechanism, which exhibit a blue-purple color. In this work, HPLC analysis and density functional calculations show that there are loosely reversible associations in the charge-transfer complexes which can be stabilized by strong hydrogen bonding. A Trp radicals signal was observed but the intensity was not so strong as expected. This color reaction exhibits high selectivity towards Trp and Tyr, and thus it can be a convenient method for naked-eye identifying the coexistence of these two amino acids or protein modifications of related to them.

Degradation of 17β-estradiol and antifouling properties of magnéli phase Ti4O7 reactive electrochemical membrane in the presence of fulvic acid

This study systematically investigated the electrooxidation of 17β-estradiol (E2) and inhibition of formation of fulvic acid (FA) aggregation in reactive electrochemical membrane (REM) made of Ti4O7. Our results indicate that aggregated FA in the membrane could retard the breakthrough rate of E2, while the interception for E2 was significantly alleviated for treated FA due to its structural change during REM electrooxidation. The electrooxidation removal efficiency of E2 during REM operation increased with the decrease of permeate flow rates due to the longer residence time within REM, and 95.90 ± 0.92% removal was reached at 20 mA cm−2 with the permeate flow rate of 7.5 mL min−1. FA inhibited the electrooxidation of E2 accompanied by the generation of specific intermediate products. Our results involving designed experiments and molecular simulation calculation indicated that direct electron transfer (DET) reaction induced polymer generation, and the generation of hydroxylation and ring-opening products was initiated by the reaction with hydroxyl radicals (•OH). Permeate flux analysis and excitation-emission matrix characterization indicated that significant antifouling performance of REM was mainly attributed to the structural change of FA during REM treatment. These results revealed the potential roles of natural organic matter in Ti4O7 REM treatment of organic contaminants that greatly promoted the development of REM operation application.

Semiempirical Approach to the Fukui Function Analysis of Uric Acid under Different pH Conditions.

Analytic Fukui functions calculated at a first-principles level are combined with experimental pKa values and the calculation of tautomerization energies to obtain the effective regioselectivity of uric acid toward electron-transfer reactions under different pH conditions. Second-order electron binding energies are also computed to determine which of the tautomers is more likely to participate in the electron transfer. A comparison of vertical and adiabatic proton detachment energies allows us to conclude that tautomerization is not mediating deprotonation and that two monoanionic species are of comparable relevance. The main difference between these monoanionic species is the ring that has been deprotonated. Both monoanionic species are produced from a single neutral tautomer and mainly produce a single dianionic tautomer. As a method for the analysis of systems affected by pH such as uric acid, we propose to plot condensed Fukui functions versus pH, allowing us to draw the effect of pH on the regioselectivity of electron transfer in a single image.

Highly sensitive and selective electrochemical sensor for simultaneous determination of gallic acid, theophylline and caffeine using poly(l-proline) decorated carbon nanotubes in biological and food samples

In this work, a novel, simple and reproducible poly(l-proline)/functionalized multi-walled carbon nanotube composite on glassy carbon electrode (poly(PRO)-MWCNTs/GCE) was developed as an electrochemical sensor for the simultaneous determination of gallic acid (GA), theophylline (TP) and caffeine (CAF) by differential pulse voltammetry (DPV).The sensing platform was optimized by experimental design and response surface methodology, using various factors affecting polymerization and detection, such as electropolymerization time and potential, and pH, respectively. As a result, the dispersion conditions were the mixing of 1.78 mg MWCNTs with 1.00 mL l-proline solution to 4.14 mg mL−1 (in SDBS 0.5%), followed by 21 min of sonication with electropolymerization by 16 cyclic scans. In addition, the final analysis was performed at a pH of 3.00 and prior accumulation at 0.350 V for 40 s.The electrochemical behavior of GA, TP and CAF on the optimized sensor was investigated. As a result, the electrode preserves and synergistically combines the properties of each modifier. This new electrochemical sensor showed superior electrocatalytic properties for the oxidation of GA, TP and CAF, which significantly improved the sensitivity of the three compounds.Under the optimized experimental conditions, the detection limits achieved by S/N were 0.03, 0.04 and 0.11 μmol L−1 for GA, TP and CAF, respectively. The analysis of real samples was successfully performed in human breast milk, tea, infusion of yerba mate, coffee, Coca-Cola zero and energy drink, showing good recoveries, ranged between 87 and 108%. The proposed sensor also showed good selectivity, repeatability and reproducibility, indicating feasibility and reliability.This is the first time that the l-proline monomer is used as a dispersant for MWCNTs and as a precursor for the in-situ polymerization of the proline polymer. Previously, the electropolymerizations were carried out with the monomer in solution rather than as an exfoliant of MWCNTs, where the polymer is electrosynthesized between MWCNTs rather than on them. In this way, the large specific surface area and strong adsorption ability of the nanomaterial are enhanced, and the ability to promote electron transfer reaction is increased, which provides enough effective reaction sites.

Synthesis and Prospects of Holey Two‐dimensional Platinum‐group Metals in Electrocatalysis

AbstractAdvanced electrocatalysts can enable the widespread implementation of clean energy technologies. This paper reviews an emerging class of electrocatalytic materials comprising holey two‐dimensional free‐standing Pt‐group metal (h‐2D‐PGM) nanosheets, which are categorically challenging to synthesize but inherently rich in all the qualities necessary to counter the kinetic and thermodynamic challenges of an electrochemical conversion process with high catalytic efficiency and stability. Although the 2D anisotropic growth of typical nonlayered metal crystals has succeeded and partly improved their atom‐utilization efficiency, regularly distributed in‐planar porosity can further optimize three critical factors that govern efficient electrocatalysis process: mass diffusion, electron transfer, and surface reactivity. However, producing such advanced morphological features within h‐2D‐PGMs is difficult unless they are specially engineered using approaches such as templating or kinetic ramification during 2D growth or controlled etching of preformed 2D‐PGM solids. Therefore, this review highlighting the successful fabrication of various porous PGM nanosheets and their electrocatalytic benefits involving smart nanoscale features could inspire next‐generation scientific and technological innovations toward securing a sustainable energy future.