Generation Of Radical Species Research Articles

Dichloramine Hydrolysis in Membrane Desalination Permeate: Mechanistic Insights and Implications for Oxidative Capacity in Potable Reuse Applications.

Dichloramine (NHCl2) naturally exists in reverse osmosis (RO) permeate due to its application as an antifouling chemical in membrane-based potable reuse treatment. This study investigated mechanisms of background NHCl2 hydrolysis associated with the generation of oxidative radical species in RO permeate, established a kinetic model to predict the oxidative capacity, and examined its removal efficiency on trace organic contaminants in potable reuse. Results showed that NHCl2 hydrolysis generated transient peroxynitrite (ONOO-) and subsequently dissociated into hydroxyl radical (HO•). The maximal HO• exposure was observed at an RO permeate pH of 8.4, higher than that from typical ultraviolet (UV)-based advanced oxidation processes. The HO• exposure during NHCl2 hydrolysis also peaked at a NH2Cl-to-NHCl2 molar ratio of 1:1. The oxidative capacity rapidly degraded 1,4-dioxane, carbamazepine, atenolol, and sulfamethoxazole in RO permeate. Furthermore, background elevated carbonate in fresh RO permeate can convert HO• to carbonate radical (CO3•-). Aeration of the RO permeate removed total carbonate, significantly increased HO• exposure, and enhanced the degradation kinetics of trace organic contaminants. The kinetic model of NHCl2 hydrolysis predicted well the degradation of contaminants in RO permeate. This study provides new mechanistic insights into NHCl2 hydrolysis that contributes to the oxidative degradation of trace organic contaminants in potable reuse systems.

Peroxymonosulfate-activated photocatalytic degradation of norfloxacin via a dual Z-scheme g-C3N5/BiVO4/CoFe − LDH heterojunction: Operation and mechanistic insights

The design of novel dual Z-scheme heterojunction plays a significant path in eradicating organic contaminants via enriched charge carrier separation. Herein, a wet chemical method was used to synthesize ternary g-C3N5/BiVO4/CoFe–LDH (CBCF) nanocomposites, and their corresponding abilities were characterized as follows: crystal phases, optical properties, surface morphologies, and compositions. The g-C3N5/BiVO4/CoFe–LDH-30% (CBCF-3) sample optimized the removal efficiency of norfloxacin (NOR) by up to 95.3% through peroxymonosulfate (PMS) activation in a visible light medium. The combined effects from the Vis/PMS/CBCF-3 catalytic system led to 7-times higher degradation efficiency than visible light only system. This improved performance was attributed to the generation of reactive radical species because of higher PMS utilization and an effective Z-charge transfer process from well-oriented band structures. Moreover, scavenging tests and electron spin resonance analysis revealed the production of active radical and non-radical species, namely •OH, SO4•−, •O2−, and 1O2. Based on the appropriate experimental analysis, the expected NOR degradation mechanism and possible pathways were proposed. Then, the toxicity evaluation results revealed that the intermediate products may not have an adverse effect on the aquatic ecosystems. This research study provides a positive outcome for wastewater remediation using enriched dual Z-scheme mechanism.

Hypervalent Sulfur Derivatives as Sulfenylating Reagents: Visible-Light-Mediated Direct Thiolation of Activated C(sp2)-H Bonds with Dihalosulfuranes.

In contrast to hypervalent iodine compounds, the chemistry of their sulfur analogues has been considerably less explored. Herein, we report the direct C-H bond thiolation of electron-rich heterocycles, arenes, and 1,3-dicarbonyls by dichlorosulfuranes under mild conditions. Mechanistic studies and density functional theory calculations suggest the radical chain mechanism of the disclosed transformation. The key to success is attributed to a strikingly low S-Cl bond dissociation energy, which enables the generation of radical species upon exposure to daylight.

Pseudocannabinoid H4CBD Reduces Cardiac Damage Indicator 4HNE in OLETF (Otsuka Long Evans Tokushima Fatty) Rats

Cardiovascular disease (CVD) is a leading cause of death globally and MetS is an associated precursor of CVD. Of the 6 known cluster factor conditions of MetS, obesity, and poor glucose tolerance are known to contribute to high lipid peroxidation, which can contribute to the generation of damaging free radical species and a pro-oxidant system. Cannabidiol (CBD) is a known antioxidant and a growing understanding of CBD analogs and pseudocannabinoids, like H4CBD, implicate similar antioxidant effects. However, little is known about the effects of CBD analogs on MetS-associated cardiac tissue damage. To better understand these effects during extreme metabolic dysfunction, 41-weeks-old animals were assigned into three groups, (n=8/group): (1) one-lean-strain control, Long Evans Tokushima Otsuka (LETO), (2) untreated OLETF, and (3) OLETF + H4CBD (200 mg/kg/day x 4 weeks). Our hypothesis focuses on the prospect that ongoing treatment with H4CBD in a MetS model using Otsuka Long-Evans Tokushima Fatty (OLETF) rats will reduce indicators of lipid peroxidation including 4-hydroxynonenal (4HNE), a toxic end product of lipid peroxidation. After the 4-week treatment, cardiac tissue was analyzed for 4-hydroxynonenal (4HNE) protein expression. We found that H4CBD decreased cardiac 4HNE protein expression in treated OLETF rats by 68% (p<0.05) compared to OLETF control, which indicates H4CBD attenuated cardiac lipid peroxidation overall. Although the 4-week treatment of H4CBD was not suffcient to ameliorate MetS-associated hypertension, the reduction of 4HNE suggests that the attenuation of cardiac damage is independent of arterial pressure. These data indicate that H4CBD and its derivatives hold promise for therapeutic use in managing CVD and related metabolic syndrome-associated pathologies. Undergraduate Research Training Initiative for Student Enhancement (U-RISE), Center for Medical Cannabis Research. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Co-Fe bimetallic oxides derived from Prussian blue analogs to activate peracetic acid for eliminating sulfamethazine: Contribution and identification of radical species

Peracetic acid (PAA), as a disinfectant with powerful oxidation and exceptional antimicrobial efficiency, has gained considerable attention for its application in advanced oxidation processes (AOPs). However, leaching of metal ions and low recovery efficiency limited the application of heterogeneous AOPs. Herein, we synthesized a CoFe bimetallic oxide (Co-Fe-O) derived from Prussian blue analogs to serve as an activator for PAA, efficiently eliminating sulfamethazine (SMZ) in a wide pH range (5–9). Electron paramagnetic resonance and quenching test revealed the coexistence of radical species in the system, and R-O· were the main factors of SMZ elimination. The steady-state model evaluation showed that 3.1 × 10−14 M R-O· and 2.05 × 10−14 M ·OH existed in the system. CoFe bimetallic synergies expedite the generation of radical species. Based on density functional theory, the aniline ring and heterocyclic ring of SMZ were regarded as the susceptible sites for radical attack and electron transfer. Furthermore, the elimination pathway of SMZ was proposed by combining the results of intermediate products. Additionally, the toxicity of SMZ and intermediates as well as the reaction conditions, water matrices, stability, and oxidation capacity of Co-Fe-O/PAA were subjected to evaluation. Results indicate that the Co-Fe-O/PAA system has significant application potential in the elimination of micropollutants.

Fenton-mediated solar-driven photocatalysis of industrial dye effluent with polyaniline impregnated with activated TiO2-Nps

Various integrated technologies have been investigated for the remediation of heavily polluted industrial dye effluent. Also, more than 70 % of these dyes are known to be solely azo dyes used in the textile industry with 5–30 % presence in the effluent as loose dye molecules which are recalcitrant to treatment. These challenges led to the investigation of energy-efficient processes (solar) and the fabrication of high-performance nano-photocatalysts for proficient photocatalysis of dye effluent while mediating the process with Fenton reagents. The study fabricated nanopolymeric catalyst composites (P-AKT) via novel in situ coupling and impregnation of the polyaniline (PANI) with surface-activated TiO2 NPs. This fabrication is aimed at developing a high-performance catalyst with rapid and proficient photocatalytic activities to photons from sunlight irradiation. The photocatalytic process was mediated using a novel Fenton reagent to enhance the generation of radical species for dye degradation. Various instrumental characterization methods were used to study the structural, molecular, elemental, functional and optoelectronic properties of the fabricated nanocomposite photocatalysts. The result reveals functional groups aiding dye-catalyst bonding and morphological interaction reveal a surface-activated tetragonal crystalline mixture of anatase and rutile from TiO2−Nps embedded in the macromolecular chain of PANI. It also reveals the optimal conditions of 20 mg dosage, 10 mg/L initial concentration with substantial effectiveness at pH of 5 and 7. However, the most efficient photocatalyst recorded was P-AKT-2 % and P-AKT-3 % having 95 % and 94 % efficiencies at 90 min of solar irradiation. The photocatalyst equally demonstrated its capacity for effluent treatability up to 4 cycles of use.

Cation Recognition by Dibenzoarsacrowns

AbstractWe recently reported dibenzoarsacrowns as a novel class of host molecules, and in this work, prepared four dibenzoarsacrowns:12‐dibenzoarsacrown‐4, 15‐dibenzoarsacrown‐5, 18‐dibenzoarsacrown‐6, and 21‐dibenzoarsacrown‐7, and investigated their guest recognition behaviors for alkali metal and ammonium cations (Li+, Na+, K+, and NH4+). It was found that the triphenylarsine moiety of the dibenzoarsacrowns could be electrochemically oxidized and that their oxidation potentials shifted in response to perturbation because of the weak interaction between the arsenic atom and guest cations. Thus, dibenzoarsacrowns could electrochemically detect cations with sizes that fit the host cavity. Electron spin resonance measurements revealed the generation of cation radical species of arsenic under the application of voltage and supported the idea that the interaction between the arsenic atom and guest cations played a crucial role in the detection of cations. In addition, ion chromatography studies showed that size‐selective cation recognition by dibenzoarsacrowns was achievable even in aqueous solutions.

Spatial confinement-regulated peroxymonosulfate activation to boost the generation of high-valent cobalt and radical species for achieving rapid removal of organic pollutants

It is of great significance to establish simple and effective methods to tackle water pollution problems. Herein, Co-loaded hollow carbon sphere (namely Co-HCS-1) served as PMS activation mediator was synthesized. The construction of hollow structure can improve specific surface areas and offer more active sites, thereby reducing electron transfer resistance and increasing contact among PMS, pollutant and catalyst. Hence, the Co-HCS-1-mediated direct electron-transfer oxidation between PMS and pollutant was enhanced. After embedding Co-based catalyst in the shell of hollow carbon sphere, hollow carbon shell will provide spatial confinement for Co-based catalyst, which shortened mass transfer process. Thus, spatial confinement effect originating from carbon sphere can accelerate the charge transfer between PMS and active sites of Co-HCS-1, thereby promoting O-O bond cleavage of PMS. As a result, the generations of radicals and high-valent metal complexes (namely Co-HCS-1≡Co4+) were boosted. Under the combined effects of electron-transfer oxidation, reactive oxygen species and Co-HCS-1≡Co4+, more than 90 % of typical organic pollutants can be removed from simulated wastewater within 5 min by Co-HCS-1/PMS system, and a high removal efficiency of total organic carbon can also be realized. To sum up, current work provided a valuable reference for the preparation and application of catalyst with high activity in PMS activation.

Packed OV-SnO2-Sb bead-electrodes for enhanced electrocatalytic oxidation of micropollutants in water

Electrocatalytic oxidation is an appealing treatment option for emerging micropollutants in wastewater, however, the limited reactive surface area and short service lifetime of planar electrodes hinder their industrial applications. This study introduces an innovative electrochemical wastewater treatment technology that employs packed bead-electrodes (PBE) as a dynamic electrocatalytic filter on a dimensionally stable anode (DSA) acting as a current collector. By using PBE, the electroactive volume is expanded beyond the vicinity of the common planar anode to the thick porous media of PBE with a vast electrocatalytic surface area. This greatly enhances the efficiency of electrochemical degradation of micropollutants. The OV-SnO2-Sb PBE filter achieved a nearly 100 % degradation of moxifloxacin (MOX) in under 2 min of single-pass filtration, with a degradation rate over an order of magnitude higher than the conventional electrochemical oxidation processes. The generation of abundant radical species (•OH) and non-radical species (1O2 and O3), along with the enhanced direct oxidation, led to the outstanding performance of the charged PBE system in MOX degradation. The OV-SnO2-Sb PBE was remarkably stable, and the separation between the electroactive PBE layer and the base Ti anode allows for easy renewal of the bead-electrode materials and scaling up of the system for practical applications. Overall, our study presents a dynamic electroactive PBE that advances the electrocatalytic oxidation technology for effective control of emerging pollutants in the water environment. This technology has the potential to revolutionize electrochemical wastewater treatment and contribute to a more sustainable future environment.

Fe-doped kelp biochar-assisted peroxymonosulfate activation for ciprofloxacin degradation: Multiple active site-triggered radical and non-radical mechanisms

In this study, a novel iron-doped kelp-derived biochar (KBC) (Fe-KBC) was prepared via a combination of hydrothermal carbonization and pyrolysis, characterized, and tested for ciprofloxacin (CIP) degradation via peroxymonosulfate (PMS) activation. The CIP removal in KBC800/PMS was remarkably improved in Fe-KBC800/PMS from 63.38% to 97.48%, under optimised condition (CIP 10 mg L−1, KBC800/Fe-KBC800 0.1 g L−1, PMS 0.5 mM). It was demonstrated that the CIP degradation in Fe-KBC800/PMS was dominantly attributed to the enhanced electron transfer and the generation of radical (SO4−) and non-radical (1O2) species, on the surface reactive sites of Fe-KBC800, such as defects, O−C=O in graphitic structures, and Fe-oxides, which were induced by the doped Fe. Those also suggest that the Fe was doped via substituting H+ in CHx and K+, as well as bonding with O in C−O. The Fe-KBC800/PMS showed an excellent degree of mineralization of CIP and the possible CIP degradation pathways were proposed based on identified intermediates. The performance of Fe-KBC800/PMS was not significantly affected by reuses and co-existing ions, i.e., K+, Na+, Ca2+, Cl−, and SO42−, while it was inhibited by Mg2+, HCO3−, H2PO4−, HA, and in natural groundwater, which may affect PMS activation. However, it was greatly enhanced by simply increasing PMS dose. The results in this study provides new insights into the reactions in metal-biochar composites and PMS activation thereby, emphasizing the great potential of Fe-KBC800/PMS in the control of refractory organics in aqueous phase.

Harnessing Radicals in Confined Supramolecular Environments Made Possible by MOFs.

Researching and utilizing radical intermediates in organic synthetic chemistry have innovated discoveries in methodology and theory. Reactions concerning free radical species opened new pathways beyond the frame of the two-electron mechanism while commonly characterized as rampant processes lacking selectivity. As a result, research in this field has always focused on the controllable generation of radical species and determining factors of selectivity. Metal-organic frameworks (MOFs) have emerged as compelling candidates as catalysts in radical chemistry. From a catalytic point of view, the porous nature of MOFs entails an inner phase for the reaction that could offer possibilities for the regulation of reactivity and selectivity. From a material science perspecti ve, MOFs are organic-inorganic hybrid materials that integrate functional units in organic compounds and complex forms in the tunable long-ranged periodic structure. In this account, we summarized our progress in the application of MOFs in radical chemistry in three parts: (1) The generation of radical species; (2) The weak interactions and site selectivity; (3) Regio- and stereo-selectivity. The unique role of MOFs play in these paradigms is demonstrated in a supramolecular narrative through the analyses of the multi-constituent collaboration within the MOF and the interactions between MOFs and the intermediates during the reactions.

Radical Afterglow Emission Harnessed by Doping N,N’‐Diaryl‐5,10‐Dihydrophenazines to Epoxy Resins

AbstractDeveloping radical‐induced afterglow emission under ambient conditions is challenging since newly formed radical species are susceptible to air and water. In this work, long afterglow materials (up to 4 s) are realized by doping a series of N,N’‐diaryl‐5,10‐dihydrophenazine (DPP)derivatives into rigid cycloaliphatic epoxy resins (CER). The afterglow is found to result from the interaction between the matrix and the excited states of the dopants through the generation of radical species under continuous UV excitation, which can be regulated by the peripheral functional groups of the N‐phenyl substituents. Density functional theory (DFT) calculations predict that the introduction of electron‐withdrawing groups hinders the afterglow emission, which may be related to the reducing reduction potential and inefficient spin‐orbit coupling (SOC) coefficients. The afterglow emission of the radical‐based systems demonstrates a bright opportunity for information encryption, anti‐counterfeiting, and photolithography.

Multimodal Biofilm Inactivation Using a Photocatalytic Bismuth Perovskite-TiO2-Ru(II)polypyridyl-Based Multisite Heterojunction.

Infectious bacterial biofilms are recalcitrant to most antibiotics compared to their planktonic version, and the lack of appropriate therapeutic strategies for mitigating them poses a serious threat to clinical treatment. A ternary heterojunction material derived from a Bi-based perovskite-TiO2 hybrid and a [Ru(2,2'-bpy)2(4,4'-dicarboxy-2,2'-bpy)]2+ (2,2'-bpy, 2,2'-bipyridyl) as a photosensitizer (RuPS) is developed. This hybrid material is found to be capable of generating reactive oxygen species (ROS)/reactive nitrogen species (RNS) upon solar light irradiation. The aligned band edges and effective exciton dynamics between multisite heterojunctions are established by steady-state/time-resolved optical and other spectroscopic studies. Proposed mechanistic pathways for the photocatalytic generation of ROS/RNS are rationalized based on a cascade-redox processes arising from three catalytic centers. These ROS/RNS are utilized to demonstrate a proof-of-concept in treating two elusive bacterial biofilms while maintaining a high level of biocompatibility (IC50 > 1 mg/mL). The in situ generation of radical species (ROS/RNS) upon photoirradiation is established with EPR spectroscopic measurements and colorimetric assays. Experimental results showed improved efficacy toward biofilm inactivation of the ternary heterojunction material as compared to their individual/binary counterparts under solar light irradiation. The multisite heterojunction formation helped with better exciton delocalization for an efficient catalytic biofilm inactivation. This was rationalized based on the favorable exciton dissociation followed by the onset of multiple oxidation and reduction sites in the ternary heterojunction. This together with exceptional photoelectric features of lead-free halide perovskites outlines a proof-of-principle demonstration in biomedical optoelectronics addressing multimodal antibiofilm/antimicrobial modality.

Synthesis and Characterization of New Tetradentate N2O2-Based Schiff’s Base Cu (II) Complexes for Dye Photodegradation

We have reported tetradentate ligands (salophen) coordinated with N and O atoms that led to the Cu (II) complexes. These Cu (II) complexes (C-1 and C-2) were firstly established by using elemental analysis and confirmed by mass spectra. At the same time, the characterization of C-1 and C-2 complexes is performed by using several spectroscopic methods and morphological analysis. The bandgap values of the C-1 and C-2 complexes are evaluated with UV-vis DRS spectra. The PL spectral data and photocurrent curves clearly indicated the small recombination rate of the hole–electron pair. The synthesized C-1 and C-2 complexes’ photocatalytic properties were examined for the degradation of cationic dyes such as methylene blue (MB λmax.= 654 nm) and methyl violet (MV λmax.= 590 nm) below visible-light action. The C-2 complex is more active than the C-1 complex because of its high photostability, small band-gap energy, and low recombination rate for hole–electron pair separation, and improved visible-light character, which encourages the generation of hydroxyl radical species throughout the photodegradation process. Scavenger probes were used to identify the dynamic species for the photodegradation of dyes, and a mechanism investigation was established.

Bifunctional photocatalytic nanofiltration membranes with immobilized BaTiO3/Ti3C2Tx catalysts for the simultaneous separation and degradation of azo compounds

Bifunctional photocatalytic nanofiltration (NF) membranes are becoming increasingly popular because of their ability to separate and degrade azo compounds (azos) in water. However, several serious drawbacks limit their practical implementation. In this study, a polyamide (PA) layer formed by interfacial polymerization on the polyvinylidene fluoride membrane surface and polydopamine (PDA) were combined with BaTiO3/Ti3C2Tx (BT) nanoparticles to prepare photocatalytic BT@PDA (BTPP) membranes, which integrated physical separation and photocatalytic degradation into a single process. By optimizing synthesis conditions, a BTPP membrane with high water permeability (34.0 L·m–2·h–1·bar–1) and Na2SO4 rejection rate (94.7%) was produced. The photocatalytic activity of this membrane was examined by studying the photocatalytic degradation efficiency of several azos. After 180 min of irradiation with a 300 W Xe lamp (λ ≥ 420 nm), the degradation rate of methyl orange (MO) reached 95.3%, while the degradation rates of alizarin yellow GG and methyl red were 92.7% and 83.5%, respectively. The photocatalytic performance of the BTPP membranes for azos degradation was verified by studying the charge transfer process and generation of reactive radical species (·OH and·O2–), and possible structures of the main intermediates formed during MO degradation were identified. This work provides new insights into the synthesis and degradation properties of bifunctional photocatalytic NF membranes.

Sulfonium Salts as Acceptors in Electron Donor‐Acceptor Complexes

AbstractThe photoactivation of electron donor‐acceptor complexes has emerged as a sustainable, selective and versatile strategy for the generation of radical species. Electron donor‐acceptor (EDA) complexation, however, imposes electronic constraints on the donor and acceptor components and this can limit the range of radicals that can be generated using the approach. New EDA complexation strategies exploiting sulfonium salts allow radicals to be generated from native functionality. For example, aryl sulfonium salts, formed by the activation of arenes, can serve as the acceptor components in EDA complexes due to their electron‐deficient nature. This “sulfonium tag” approach relaxes the electronic constraints on the parent substrate and dramatically expands the range of radicals that can be generated using EDA complexation. In this review, these new applications of sulfonium salts will be introduced and the areas of chemical space rendered accessible through this innovation will be highlighted.

Sulfonium Salts as Acceptors in Electron Donor-Acceptor Complexes.

The photoactivation of electron donor-acceptor complexes has emerged as a sustainable, selective and versatile strategy for the generation of radical species. Electron donor-acceptor (EDA) complexation, however, imposes electronic constraints on the donor and acceptor components and this can limit the range of radicals that can be generated using the approach. New EDA complexation strategies exploiting sulfonium salts allow radicals to be generated from native functionality. For example, aryl sulfonium salts, formed by the activation of arenes, can serve as the acceptor components in EDA complexes due to their electron-deficient nature. This "sulfonium tag" approach relaxes the electronic constraints on the parent substrate and dramatically expands the range of radicals that can be generated using EDA complexation. In this review, these new applications of sulfonium salts will be introduced and the areas of chemical space rendered accessible through this innovation will be highlighted.

Whose Oxygen Atom Is Transferred to the Products? A Case Study of Peracetic Acid Activation via Complexed MnII for Organic Contaminant Degradation.

Identifying reactive species in advanced oxidation process (AOP) is an essential and intriguing topic that is also challenging and requires continuous efforts. In this study, we exploited a novel AOP technology involving peracetic acid (PAA) activation mediated by a MnII-nitrilotriacetic acid (NTA) complex, which outperformed iron- and cobalt-based PAA activation processes for rapidly degrading phenolic and aniline contaminants from water. The proposed MnII/NTA/PAA system exhibited non-radical oxidation features and could stoichiometrically oxidize sulfoxide probes to the corresponding sulfone products. More importantly, we traced the origin of O atoms from the sulfone products by 18O isotope-tracing experiments and found that PAA was the only oxygen-donor, which is different from the oxidation process mediated by high-valence manganese-oxo intermediates. According to the results of theoretical calculations, we proposed that NTA could tune the coordination circumstance of the MnII center to elongate the O-O bond of the complexed PAA. Additionally, the NTA-MnII-PAA* molecular cluster presented a lower energy gap than the MnII-PAA complex, indicating that the MnII-peroxy complex was more reactive in the presence of NTA. Thus, the NTA-MnII-PAA* complex exhibited a stronger oxidation potential than PAA, which could rapidly oxidize organic contaminants from water. Further, we generalized our findings to the CoII/PAA oxidation process and highlighted that the CoII-PAA* complex might be the overlooked reactive cobalt species. The significance of this work lies in discovering that sometimes the metal-peroxy complex could directly oxidize the contaminants without the further generation of high-valence metal-oxo intermediates and/or radical species through interspecies oxygen and/or electron transfer.

Isocyanide-Based Multicomponent Reactions Promoted by Visible Light Photoredox Catalysis.

Isocyanide-based multicomponent reactions claim a one century-old history of flourishing developments. On the other hand, the enormous impact of recent progresses in visible light photocatalysis has boosted the identification of new straightforward and green approaches to both new and known chemical entities. In this context, the application of visible light photocatalytic conditions to multicomponent processes has been promoting key stimulating advancements. Spanning from radical-polar crossover pathways, to photoinduced and self-catalyzed transformations, to reactions involving the generation of imidoyl radical species, the present literature analysis would provide a general and critical overview about the potentialities and challenges of exploiting isocyanides in visible light photocatalytic multicomponent reactions.

Unraveling the complex electrochemistry of serotonin using engineered graphitic sensors.

Fast-scan cyclic voltammetry (FSCV) with micron-sized carbon sensors is a promising approach for monitoring the fast dynamics of serotonin (5-HT) neuromodulatory signals in the brain. However, sensor performance using FSCV can be compromised by complex chemical reactions associated with the reduction and oxidation of 5-HT, posing considerable challenges to detection of 5-HT in vivo. Herein we describe the use of engineered graphitic sensors to characterize the complex electrochemistry of 5-HT under a wide range of measurement conditions, with the aim of optimizing the FSCV conditions for in vivo quantitative 5-HT detection. These measurements reveal that water plays a significant role in driving side reactions during low-voltage FSCV measurements, leading to the observation of a well-defined secondary redox couple we associated with the redox reaction of tryptamine 4,5-dione. Remarkably, these side reactions can persist subsequent to the primary redox events associated with 5-HT. Furthermore, the results reveal a critical deviation from this ideal redox behavior if the FSCV anodic limit exceeds +0.8 V, which can be attributed to the generation of radical species from water oxidation. These new insights could lead to new FSCV protocols for more reliable 5-HT detection.