Specific Redox Reaction Research Articles

A Piezocatalysis Strategy to Enable Efficient Redox in Solid‐State Battery

AbstractPiezocatalysis is considered to be a favorable catalytic technology by utilizing external mechanical stimulation to promote the specific redox reactions. The application of piezocatalysis in batteries is promising but faces formidable challenges. Herein, the operation principles of piezocatalysis were successfully demonstrated by constructing solid‐state Li−Se and Li−S battery models with interfacial stress accumulation. Lead zirconate titanate with an ultra‐high piezoelectric coefficient was applied as the piezoelectric catalyst. The uniformity of the dipole orientation in materials was essential for achieving piezocatalysis in batteries. The accumulated high‐stress converts to piezopotential for catalyzing most reaction processes in batteries, while the rapid stress change prevents the internal charge reorganization, ensuring continuous efficient catalysis. The internal stress change alters the internal polarisation strength, driving excess screening charge to participate in the electrochemical reaction. Under piezocatalysis, solid‐state Li−Se batteries exhibited a initial discharge capacity of 670.9 mAh g−1 (99.4 % of the theoretical value) at 0.1 C, and Li−S batteries showed a capacity of 1463 mAh g−1 at 0.2 C, which was still maintained up to 1084 mAh g−1 at an elevated rate of 0.5 C. This piezocatalysis strategy provides a strong theoretical basis and design specification for enhancing Li−Se and Li−S battery reaction kinetics.

A Piezocatalysis Strategy to Enable Efficient Redox in Solid-State Battery.

Piezocatalysis is considered to be a favorable catalytic technology by utilizing external mechanical stimulation to promote the specific redox reactions. The application of piezocatalysis in batteries is promising but faces formidable challenges. Herein, the operation principles of piezocatalysis were successfully demonstrated by constructing solid-state Li-Se and Li-S battery models with interfacial stress accumulation. Lead zirconate titanate with an ultra-high piezoelectric coefficient was applied as the piezoelectric catalyst. The uniformity of the dipole orientation in materials was essential for achieving piezocatalysis in batteries. The accumulated high-stress converts to piezopotential for catalyzing most reaction processes in batteries, while the rapid stress change prevents the internal charge reorganization, ensuring continuous efficient catalysis. The internal stress change alters the internal polarisation strength, driving excess screening charge to participate in the electrochemical reaction. Under piezocatalysis, solid-state Li-Se batteries exhibited a initial discharge capacity of 670.9 mAh g-1 (99.4 % of the theoretical value) at 0.1 C, and Li-S batteries showed a capacity of 1463 mAh g-1 at 0.2 C, which was still maintained up to 1084 mAh g-1 at an elevated rate of 0.5 C. This piezocatalysis strategy provides a strong theoretical basis and design specification for enhancing Li-Se and Li-S battery reaction kinetics.

Exploring the Role of Redox-Shuttle Mediators in Lithium-Sulfur Batteries

The lithium-ion battery (LIB) is widely acknowledged as the state-of-the-art battery technology today and is used in consumer electronics, stationary storage, and electrified transportation1,2. However, there is a drive towards developing technologies with higher energy densities. The lithium-sulfur battery is one of the most promising next-generation batteries for high-energy applications, due to its high theoretical gravimetric energy density of 2567 W h kg-1, low raw material costs, and reduced environmental impact3. Despite these potential advantages, lithium-sulfur batteries are still beset with difficulties, one of the most significant is the so-called “polysulfide shuttle effect.” Operation of the battery involves the conversion of sulfur to polysulfide species, which dissolve into the electrolyte and diffuse to the lithium metal electrode, leading to loss of active material. This results in poor cycle life, rapid capacity fading and low coulombic efficiencies4.The use of dissolved, electrochemically active redox mediators could mitigate these effects by catalysing sulfur redox reactions during cell cycling. While it is generally agreed that the redox potential of the mediators is a key factor in their operation, no report to date has conclusively demonstrated how mediators of varying potentials can target specific sulfur redox reactions. Herein, we report a study of the mediators 9-fluorenone (9-FO), duroquinone (DQ), 2,6-di-tert-butyl-1,4-benzoquinone (TBBQ) and 1,5-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)anthra-9,10-quinone (AQT) to understand their interactions with sulfur, lithium polysulfides, lithium sulfide and lithium metal5. We use liquid-chromatography mass spectrometry (LC-MS) to isolate various polysulfide chain lengths after reaction with mediators. It is observed that high potential redox mediators, such as TBBQ, are better able to drive Li2S oxidation to higher polysulfide chain lengths, and low potential redox mediators such as 9-FO push sulfur towards lower chain polysulfides. This offers a novel and effective approach to screening suitable redox-active molecules. Galvanostatic cycling is employed to relate these chemical interactions to enhanced cell performance. Developing a fundamental understanding of how redox mediators operate in a cell will aid in the molecular design of novel redox-active compounds.[1] J. Vetter, P. et al: Ageing mechanisms in lithium-ion batteries, J. Power Sources, 2005, 147, 269–281.[2] D. Castelvecchi: Electric cars: the battery challenge, Nature, 2021, 596, 336–339.[3] P. G. Bruce et al: Li-O2 and Li-S batteries with high energy storage, Nat. Mater., 2012, 11, 19–29.[4] S. Zhang et al: Recent advances in electrolytes for lithium-sulfur batteries, Adv. Energy Mater., 2015, 5, 1–28.[5] Y. Tsao et al: Designing a quinone-based redox mediator to facilitate Li2S oxidation in Li-S batteries, Joule, 2019, 3, 872–884.

Rapid redox-response featured visual ascorbic acid sensor based on simple-assembled europium metal-organic framework

A facile, fast and visible sensing platform for ascorbic acid (AA) detection has been developed based on self-assembled hydrangea-like europium metal-organic framework (HL-EuMOF). HL-EuMOF was synthesized through a simple one-step mixing process with Eu3+ and 1, 10-phenanthroline-2, 9-dicarboxylic acid at room temperature, which exhibited excellent properties including strong red fluorescence, long decay lifetime (548.623 μs) and good luminescent stability. Based on the specific redox reaction between Fe3+ and AA, the HL-EuMOF@Fe3+ was fabricated with “turn-off” response for AA, where the resulting Fe2+ displayed effective fluorescence quenching ability toward HL-EuMOF. The sensor demonstrated low detection limit (31.94 nM), rapid response time (30 s) and high selectivity. Integration of smartphone-assisted RGB analysis with HL-EuMOF@Fe3+ permitted convenient and visible quantitative determination of AA level. This approach also presented good detection performances in complex human serum and beverage samples, which could provide a valuable tool for AA detection in biomedical research and food industry.

Iron(III)-salophene catalyzes redox cycles that induce phospholipid peroxidation and deplete cancer cells of ferroptosis-protecting cofactors

Ferroptosis, a lipid peroxidation-driven cell death program kept in check by glutathione peroxidase 4 and endogenous redox cycles, promises access to novel strategies for treating therapy-resistant cancers. Chlorido [N,N′-disalicylidene-1,2-phenylenediamine]iron (III) complexes (SCs) have potent anti-cancer properties by inducing ferroptosis, apoptosis, or necroptosis through still poorly understood molecular mechanisms. Here, we show that SCs preferentially induce ferroptosis over other cell death programs in triple-negative breast cancer cells (LC50 ≥ 0.07 μM) and are particularly effective against cell lines with acquired invasiveness, chemo- or radioresistance. Redox lipidomics reveals that initiation of cell death is associated with extensive (hydroper)oxidation of arachidonic acid and adrenic acid in membrane phospholipids, specifically phosphatidylethanolamines and phosphatidylinositols, with SCs outperforming established ferroptosis inducers. Mechanistically, SCs effectively catalyze one-electron transfer reactions, likely via a redox cycle involving the reduction of Fe(III) to Fe(II) species and reversible formation of oxo-bridged dimeric complexes, as supported by cyclic voltammetry. As a result, SCs can use hydrogen peroxide to generate organic radicals but not hydroxyl radicals and oxidize membrane phospholipids and (membrane-)protective factors such as NADPH, which is depleted from cells. We conclude that SCs catalyze specific redox reactions that drive membrane peroxidation while interfering with the ability of cells, including therapy-resistant cancer cells, to detoxify phospholipid hydroperoxides.

A multicolor aptasensor based on target-induced anti-etching gold nanorod for visible detection of aflatoxin B1

Foods contaminated with aflatoxin B1 (AFB1) pose a serious threat to humans, so rapid and sensitive detection of AFB1 plays an important role in public health. In this work, we developed a multicolor aptasensor based on target-mediated anti-etching of gold nanorods (AuNRs) for on-site visible detection of AFB1. The target was used as a competitor that competed with a cDNA probe labeled by horse radish peroxidase (cDNA-HRP) to bind with the aptamer coated in a microplate. The sensing mechanism was based on regulating the etching process of AuNRs upon the addition of different concentrations of AFB1. In the absence of AFB1, the AuNRs solution undergoes a distinct change from red to pink due to the etching effect of TMB2+ generated by a specific redox reaction catalyzed by the cDNA-HRP. However, in the presence of AFB1, the specific binding between AFB1 and aptamer made cDNA-HRP free out of the microplate, inhibiting the etching of AuNRs. Consequently, a redshift of longitudinal localized surface plasmon resonance (LSPR) and color alterations can be observed along with increasing the concentration of AFB1. The LSPR for visual estimation limits were 0.46 ng/mL. A good linear relationship between the wavelength shift and the concentration of AFB1 was achieved from violet to light green in the range of 1–1000 ng/mL. The established aptasensor displayed excellent detection performance, which was suitable for on-site analysis of AFB1 in actual food samples, and provided a new idea of immediate visualization detection for food hazardous factors.

Rational Design of Naphthol Groups Functionalized Bipolar Polymer Cathodes for High Performance Alkali-Ion Batteries.

Redox-active organic compounds gather significant attention for their potential application as electrodes in alkali ion batteries, owing to the structural versatility, environmental friendliness, and cost-effectiveness. However, their practical applications of such compounds are impeded by insufficient active sites with limited capacity, dissolution in electrolytes, and sluggish kinetics. To address these issues, a naphthol group-containing triarylamine polymer, namely poly[6,6'-(phenylazanediyl)bis(naphthol)] (poly(DNap-OH)) is rationally designed and synthesized, via oxidative coupling polymerization. It is capable of endowing favorable steric structures that facilitate fast ion diffusion, excellent chemical stability in organic electrolytes, and additional redox-active sites that enable a bipolar redox reaction. By exploiting these advantages, poly(DNap-OH) cathodes demonstrate remarkable cycling stability in both lithium-ion batteries (LIBs) and potassium-ion batteries (PIBs), showcasing enhanced specific capacity and redox reaction kinetics in comparison to the conventional poly(4-methyltriphenylamine) cathodes. Overall, this work offers insights into molecular design strategies for the development of high-performance organic cathodes in alkali-ion batteries.

Doping Strategy to Improve the Electrochemical Behavior of Lithium Rich Transition Metal Oxides As Cathodes for Lithium-Ion Batteries

Lithium-rich transition metal oxides are considered a promising cathodic solutions in Li-ion batteries to meet the growing energetic demand, thanks to their high specific capacity and operational voltage [1-2]. Li-rich layered materials have a general stoichiometry Li1+xTM1-xO2, in which TM is a blend of transition metals, as Ni, Mn, Co [2]. They stand out due to their high lithium concentration and specific capacity [1-2]. The higher capacity of Lithium-Rich can be attributed to the specific anionic redox reaction in the bulk at above 4.5 V. Nevertheless, large irreversible capacity loss in the first cycle, poor rate capability, mean working potential decay upon cycling and cobalt content are still major drawbacks that are hindering commercialization. In order to make these materials up scalable to industrial production, it is important to consider the reduction of costs and the toxicity of raw materials, in particular cobalt. Cobalt reduction has been identified as major driver to improve the environmental benignity of batteries and the sustainability of the overall production-consumption-recycling lifecycle. Several efforts to reduce these problems have been made, including the development of different synthetic strategies, doping and surface modification. The most, widely explored, chemical strategy to mitigate the voltage decay and structural degradation in Lithium Rich cathodes is the doping. Elemental doping can be divided into cation and anion doping. As an example, incorporation of redox inactive metals, such as Al, Zr, Ti, has been proposed in order to stabilize the lattice as well as the partial replacement of lithium ions with other alkali cations, e.g. K and Na; or doping the oxygen anion sublattice. In this communication, we present our doping approaches. In particular, the simultaneous replacement of cobalt in the layered structure with aluminum and lithium (over-lithiation). Moreover, we present over-lithiated Co-free materials where the introduction of different amount of iron has been investigated. The characterization of these novel layered materials is reported in terms of composition, structure, morphology and electrochemical performances. These approaches can be applied as a strategy to mitigate the voltage decay and reduce the Cobalt content.[1] Ji, X. et al. Journal of Power Sources 487, (2021).[2] Zhao, S. et al. Angewandte Chemie - International Edition 60, 2208–2220 (2021).

Enhanced Charge Separation in Nanoporous BiVO4 by External Electron Transport Layer Boosts Solar Water Splitting.

The optimization of charge transport with electron-hole separation directed toward specific redox reactions is a crucial mission for artificial photosynthesis. Bismuth vanadate (BiVO4 , BVO) is a popular photoanode material for solar water splitting, but it faces tricky challenges in poor charge separation due to its modest charge transport properties. Here, a concept of the external electron transport layer (ETL) is first proposed and demonstrated its effectiveness in suppressing the charge recombination both in bulk and at surface. Specifically, a conformal carbon capsulation applied on BVO enables a remarkable increase in the charge separation efficiency, thanks to its critical roles in passivating surface charge-trapping sites and building external conductance channels. Through decorated with an oxygen evolution catalyst to accelerate surface charge transfer, the carbon-encased BVO (BVO@C) photoanode manifests durable water splitting over 120h with a high current density of 5.9mAcm-2 at 1.23V versus the reversible hydrogen electrode (RHE) under 1sun irradiation (100mWcm-2 , AM 1.5G), which is an activity-stability trade-off record for single BVO light absorber. This work opens up a new avenue to steer charge separation via external ETL for solar fuel conversion.

Network-wide thermodynamic constraints shape NAD(P)H cofactor specificity of biochemical reactions

The ubiquitous coexistence of the redox cofactors NADH and NADPH is widely considered to facilitate an efficient operation of cellular redox metabolism. However, it remains unclear what shapes the NAD(P)H specificity of specific redox reactions. Here, we present a computational framework to analyze the effect of redox cofactor swaps on the maximal thermodynamic potential of a metabolic network and use it to investigate key aspects of redox cofactor redundancy in Escherichia coli. As one major result, our analysis suggests that evolved NAD(P)H specificities are largely shaped by metabolic network structure and associated thermodynamic constraints enabling thermodynamic driving forces that are close or even identical to the theoretical optimum and significantly higher compared to random specificities. Furthermore, while redundancy of NAD(P)H is clearly beneficial for thermodynamic driving forces, a third redox cofactor would require a low standard redox potential to be advantageous. Our approach also predicts trends of redox-cofactor concentration ratios and could facilitate the design of optimal redox cofactor specificities.

Unlocking the potential of KI as redox additive in supercapacitor through synergistic enhancement with H2SO4 as a co-electrolyte

Adding potassium iodide (KI) as a redox additive to any non-faradaic electric double layer forming aqueous electrolyte (EE) has been shown to significantly enhance the charge storage capacity in a supercapacitor. However, whether the choice of EE is immaterial, or if there are advantages with any specific EE when used with KI is an open question. Herein, we demonstrate that the extent to which performance enhancement can be attained is dependent on the EE used in conjugation with KI. EEs as co-electrolyte in KI-EE systems influence (inhibit/promote) the specific redox reactions, their kinetics, solution conductivity as well as the wettability that dictates its pore penetration. While the pH of the electrolyte dictates the participating redox reactions, the kinetics and the solution conductivity are determined by the characteristic ions constituting the EEs. Our investigations reveal that H2SO4 (acidic) as EE when used with KI showed a synergistic enhancement in charge storage capacity, which was otherwise not obtained for other commonly used EEs such as Na2SO4 and KOH. The synergistic enhancement was found emanating from the enhanced reaction kinetics of the iodine-iodide redox reactions and augmented pore penetration through enhanced wetting resulting in the access to an increased electrochemical surface area. Conversely, Na2SO4 (neutral) as EE with KI offers impeding effect on the charge storage through iodine-iodide redox reactions along with poor wetting of the electrode, thereby resulting in a lower specific capacitance. While KOH (basic) as EE with KI, leads to suppression of the iodine-iodide redox reactions offered by KI thereby lowering the charge storage capacity as compared to KI.

Introducing GO/CuI nanostructure as active electrode matter for supercapacitors: A comparative investigation within two aqueous electrolytes

The construction, energy storage capacity and characterization of a Graphene oxide/Copper iodide (GO/CuI) as electrode materials, which are perfect in transferring ions/electrons, are being studied within this work as high-efficiency supercapacitors (SCs). This electrode material is fabricated via two simple and facile Sonochemistry and Co-precipitation techniques. In order to investigate morphology, evaluating the specific surface area, phase and purification of synthesized nanocomposite, X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman spectroscopy, Energy dispersive X-ray spectroscopy (EDX), Field emission scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller (BET) and identification techniques were exerted. Cyclic Voltammetry (CV), Galvanostatic Charge-Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS) were used in order to evaluate specific capacity, redox reaction, diffusion electron-ion and cyclic stability of nanocomposites. The capacitive performance of this electrode is observed in both acidic and neutral aqueous electrolytes. The GO/CuI electrode shows a highly specific capacity 115C g−1 (413 F g−1) and 95C g−1 (283 F g−1) for H2SO4 and Na2SO4, respectively at a current density of 1.5 A g−1. We are hereby hoping to present a novel and noble work, which is unprecedented in its approach, in introducing a new electrode in two different electrolytes as applied supercapacitors.

Soil water status shapes nutrient cycling in agroecosystems from micrometer to landscape scales

AbstractSoil water status, which refers to the wetness or dryness of soils, is crucial for the productivity of agroecosystems, as it determines nutrient cycling and uptake physically via transport, biologically via the moisture‐dependent activity of soil flora, fauna, and plants, and chemically via specific hydrolyses and redox reactions. Here, we focus on the dynamics of nitrogen (N), phosphorus (P), and sulfur (S) and review how soil water is coupled to the cycling of these elements and related stoichiometric controls across different scales within agroecosystems. These scales span processes at the molecular level, where nutrients and water are consumed, to processes in the soil pore system, within a soil profile and across the landscape. We highlight that with increasing mobility of the nutrients in water, water‐based nutrient flux may alleviate or even exacerbate imbalances in nutrient supply within soils, for example, by transport of mobile nutrients towards previously depleted microsites (alleviating imbalances), or by selective loss of mobile nutrients from microsites (increasing imbalances). These imbalances can be modulated by biological activity, especially by fungal hyphae and roots, which contribute to nutrient redistribution within soils, and which are themselves dependent on specific, optimal water availability. At larger scales, such small‐scale effects converge with nutrient inputs from atmospheric (wet deposition) or nonlocal sources and with nutrient losses from the soil system towards aquifers. Hence, water acts as a major control in nutrient cycling across scales in agroecosystems and may either exacerbate or remove spatial disparities in the availability of the individual nutrients (N, P, S) required for biological activity.

Amino-functionalized perylenediimide derivative with dual fluorescence emission for the detection of ascorbic acid in vivo and in vitro.

The rapid, sensitive, and selective detection of ascorbic acid (AA) is of significance in medical assays and diagnostics. In this work, a new aminoperylenediimide (APDI) derived ratiometric fluorescent probe based on the specific redox reaction of cobalt oxyhydroxide (CoOOH) and AA was constructed. APDI exhibited dual fluorescence emission peaks at 549 and 596 nm with an excitation wavelength of 494 nm. In the presence of CoOOH, the dual fluorescence could be quenched. The dominant fluorescence quenching mechanism was caused by the inner filter effect. Using the red emission as a reference, the fluorescence intensity ratio (F549 /F596 ) was linearly correlated with the concentration of AA over a range of 0.05 to 1μM. The limit of detection for AA was found to be 17 nM. Importantly, the probe was successfully used to detect AA in living cells. Therefore, this high sensitivity and selectivity strategy could directly survey the AA levels in real samples.

ALOX15-launched PUFA-phospholipids peroxidation increases the susceptibility of ferroptosis in ischemia-induced myocardial damage

Myocardial ischemia/reperfusion (I/R) injury is a classic type of cardiovascular disease characterized by injury to cardiomyocytes leading to various forms of cell death. It is believed that irreversible myocardial damage resulted from I/R occurs due to oxidative stress evoked during the reperfusion phase. Here we demonstrate that ischemia triggers a specific redox reaction of polyunsaturated fatty acids (PUFA)-phospholipids in myocardial cells, which acts as a priming signaling that initiates the outbreak of robust oxidative damage in the reperfusion phase. Using animal and in vitro models, the crucial lipid species in I/R injury were identified to be oxidized PUFAs enriched phosphatidylethanolamines. Using multi-omics, arachidonic acid 15-lipoxygenase-1 (ALOX15) was identified as the primary mediator of ischemia-provoked phospholipid peroxidation, which was further confirmed using chemogenetic approaches. Collectively, our results reveal that ALOX15 induction in the ischemia phase acts as a “burning point” to ignite phospholipid oxidization into ferroptotic signals. This finding characterizes a novel molecular mechanism for myocardial ischemia injury and offers a potential therapeutic target for early intervention of I/R injury.

An inner filter effect-based nitrogen-doped carbon dots-CoOOH nanoflakes fluorescence probe for detection of ascorbic acid by chemical redox modulation.

Ascorbic acid (AA) is an essential nutrient for humans, which must be obtained from vegetables, fruits, and other foods. The content of AA has become an important standard to evaluate the quality and nutritional value of food. The fluorescence sensing method based on nanomaterials is a good alternative for the rapid detection of AA. In this study, we developed an inner filter effect-based fluorescent probe that hybridized nitrogen-doped carbon dots (NCDs) with cobalt oxyhydroxide nanoflakes (CoOOH NFs). An optimal NCDs was successfully selected because it has a strong fluorescence at 430 nm and the most significant quenching phenomenon with CoOOH NFs due to the inner filter effect. When adding AA into the NCDs-CoOOH NFs probe solution, a specific redox reaction will occur between the enediol group of AA and the CoOOH NFs to interfere with the quenching ability of CoOOH NFs and recover the fluorescence of NCDs. The recovered fluorescence intensities demonstrated a linear relationship with the concentrations of AA. The assay based on the NCDs-CoOOH NFs probe allows AA to be tested in a wide range of 5-200 μmol L-1 with a detection limit of 2.31 nmol L-1 . Furthermore, to evaluate its practical application, the NCDs-CoOOH NFs fluorescence probe was utilized to analyze AA in vegetable, fruit, and serum matrixes with satisfactory results. An inner filter effect-based fluorescence probe for the rapid detection of AA was developed, and it has a good potential to be applied in both food and clinical testing. © 2022 Society of Chemical Industry.

Chemical Oxidation and Reduction Pathways of Mercury Relevant to Natural Waters: A Review

Mercury (Hg) pollution in the environment is a global issue and the toxicity of mercury depends on its speciation. Chemical redox reactions of mercury in an aquatic environment greatly impact on Hg evasion to the atmosphere and the methylation of mercury in natural waters. Identifying the abiotic redox pathways of mercury relevant to natural waters is important for predicting the transport and fate of Hg in the environment. The objective of this review is to summarize the current state of knowledge on specific redox reactions of mercury relevant to natural waters at a molecular level. The rate constants and factors affecting them, as well as the mechanistic information of these redox pathways, are discussed in detail. Increasing experimental evidence also implied that the structure of natural organic matter (NOM) play an important role in dark Hg(II) reduction, dark Hg(0) oxidation and Hg(II) photoreduction in the aquatic environment. Significant photooxidation pathways of Hg(0) identified are Hg(0) photooxidation by hydroxyl radical (OH•) and by carbonate radical (CO3−•). Future research needs on improving the understanding of Hg redox cycling in natural waters are also proposed.

Core-shell “loading-type” nanomaterials towards: Simultaneous imaging analysis of glutathione and microRNA

A novel type of core-shell “loading-type” nanomaterials, which integrated excellent biocompatibility, high loading capacity, efficient delivery, dual target recognition and response all-in-one, was fabricated for simultaneous imaging analysis of glutathione and microRNAs in living cells. Specifically, the core-shell “loading-type” nanomaterials (termed as MSNs@MnO2) were formed with mesoporous silica nanoparticles (MSNs) as core and a two-dimensional manganese dioxide nanosheets (MnO2) as outer layer. Based on the excellent loading capability, the core MSNs was utilized as carriers for signal molecules of rhodamine 6G (R6G). Meanwhile, the shell MnO2 acted as carriers for nucleic acid compounds, the locker for blocking R6G in the pore of MSNs, and reactant for reacting with redox species. Upon entering the cells, the specific redox reaction between the MnO2 nanosheets and cellular glutathione (GSH) induced the removal of the locker layer from the MSNs, thereby triggering unlocking, releasing, and recovering the corresponding fluorescence of R6G. While encounter with miRNAs, the molecular beacons (MB) adsorbed on the MnO2 nanosheets hybridized with target miRNA, which induced the conformational transition of the hairpin molecules, formed new secondary structures, and then recovered the fluorescence signal. Due to the each recovered fluorescence intensity was correlated with the corresponding target molecules, simultaneous detection of dual biomarkers was successfully achieved via the core-shell “loading-type” nanomaterials, which can provide more precise data guidance for diagnosis and disease treatment, and also own promising application in such research area.

MnO2-DNA nanomaterials toward the dual signal detection of P-aminophenol micropollutants.

P-Aminophenol (PAP), a potentially toxic and mutagenic compound, is widely distributed in water and soil and has serious side effects on human health. This study presents a convenient, sensitive, and effective dual-signal assay for the detection of PAP in the environment. Two-dimensional manganese dioxide (MnO2) nanosheets were used as the carrier and quencher for fluorophore-labelled DNA to form a dual-signal nanoprobe, MnO2-DNA. Based on a specific redox reaction between the MnO2 nanosheets and target PAP, the corresponding absorption intensity of the product and the fluorescence intensity were both "turn-on" and also exhibited excellent correlation with the concentration of PAP. This strategy not only remarkably simplifies the detection process but also improves the reliability of results due to the dual-signal response, which has promising applications in environmental, clinical, and industrial research fields.

Two fluorescent cerium metal-organic frameworks for the “turn-on” sensing of AA with high sensitivity as well as biological and electrochemical properties

Two new cerium metal-organic frameworks (CUST-502 and CUST-505) for ascorbic acid (AA) switching on fluorescence sensing were successfully designed and synthesized. CUST-502 and CUST-505 all exhibit 3D frameworks and crystallize in the monoclinic space group. The specific redox reaction between AA and Ce4+ cause the increased fluorescence intensity for detecting AA, and the detection limits of CUST-502 and CUST-505 are 0.0283 ​μM and 0.3055 ​μM, respectively. The recyclability experiments display that CUST-502 and CUST-505 can be used to detect AA for at least four cycles. Moreover, they also exhibit unique biological characteristics. Among them, CUST-505 can also be used as a potential electrochemical sensor material for monitoring formaldehyde. This will have a positive impact on the field of sensing in the future.