A review on optical sensors based on layered double hydroxides nanoplatforms.

In recent years, significant efforts have been devoted towards the fabrication and application of layered double hydroxides (LDHs) due to their tremendous features such as excellent biocompatibility with negligible toxicity, large surface area, high conductivity, excellent solubility, and ion exchange properties. Most impressive, LDHs offer a favorable environment to attach several substances such as quantum dots, fluorescein dyes, proteins, and enzymes, which leads to strengthening the catalytic properties or increasing the sensing selectivity and sensitivity of the resulted hybrids. With the extensive ongoing research on the application of nanomaterials, many studies have led to remarkable achievements in exploring LDHs as sensing nanoplatforms. In optical sensors, for instance, many sensing strategies were tailored based on the enzyme-mimicking properties of LDHs, including colorimetric and chemiluminescence procedures. Meanwhile, others were designed based on intercalating some fluorogenic substrates on the LDHs, whereby the sensing signal can be acquired by quenching or enhancing their fluorescence after the addition of analytes. In this review, we aim to summarize the recent advances in optical sensors that use layered double hydroxides as sensing platforms for the determination of various analytes. By outlining some representative examples, we accentuate the change of spectral absorbance, chemiluminescence, and photoluminescence phenomena triggered by the interaction of LDH or functionalized-LDH with the indicators and analytes in the system. And finally, current limitations and possible future orientation in designing further LDHs-based optical sensors are presented. It is hoped that this review will be helpful in assisting the establishment of more improved sensors based on LDHs features. Optical sensors based on layered double hydroxides (LDHs) nanoplatforms were reviewed. The sensing system and detection approaches were rationally reviewed. Possible future orientations were highlighted.

Chemodynamic/photothermal synergistic therapy based on Ce-doped Cu-Al layered double hydroxides.

The combination of chemodynamic therapy (CDT) with photothermal therapy (PTT) is an efficacious strategy in cancer treatment to acquire satisfactory therapy efficiency in the endogenous redox reaction and external laser induction. In this work, we have designed Ce doped Cu-Al layered double hydroxide (CAC-LDH) ultrathin them through a bottom-up synthesis method, and further loaded them with indocyanine green (ICG). The synthesized ICG/CAC-LDH was used as a Fenton-catalyst and photothermal agent. With the Fenton activity, the ICG/CAC-LDH nanosheets could decompose H2O2 and exhibit a low KM value (1.57 mM) and an ultra-high Vmax (4.88 × 10-6 M s-1) value. Due to the presence of oxidized metal ions, ICG/CAC-LDH could induce intracellular GSH depletion and reduce Cu2+ and Ce4+ to Cu+ and Ce3+, respectively. The generated Cu+ and Ce3+ further reacted with local H2O2 to generate toxic hydroxyl radicals (˙OH) via the Fenton reaction. Owing to the obviously enhanced absorption of ICG/CAC-LDH at 808 nm, the photothermal efficiency of ICG/CAC-LDH increased significantly compared with ICG (ΔT = 34.7 °C vs. 28.3 °C). In vitro studies substantiate the remarkable CDT/PTT efficacy, with complete apoptosis of HepG2 cancer cells (the cell viability is less than 2%) treated with 25 µg mL-1 of ICG/CAC-LDH. Furthermore, ICG/CAC-LDH could also act as a contrast agent for cancer magnetic resonance imaging (MRI) and photoacoustic imaging (PAI). These results demonstrate the potential of ICG/CAC-LDH as an integrated agent for dual-modal imaging and synergistic CDT/PTT.

Dihydroartemisinin loaded layered double hydroxide nanocomposites for tumor specific photothermal-chemodynamic therapy.

With the inspiration to develop new cancer nanotherapeutics by repurposing old drugs, in the current study, a novel two dimensional nanomedicine namely Mn doped, dihydroartemisinin (DHA) loaded layered double hydroxide (MnMgFe-LDH/DHA) with peroxide self-supplying properties for enhanced photothermal-chemodynamic therapy was proposed. Such nanostructures could be synthesized by a simple coprecipitation method, and the as-prepared MnMgFe-LDH/DHA exhibits excellent photothermal properties with a photothermal conversion efficiency up to 10.7%. Besides, the in situ reaction between the released DHA and Fe2+/Mn2+ produced by the degradation of LDH can lead to a burst of intracellular reactive oxygen species (ROS) by Fenton-like reactions. Furthermore, the in vivo experiments demonstrate that MnMgFe-LDH/DHA exhibits a remarkable chemodynamic/photothermal therapy (CDT/PTT) synergistic effect on tumor treatment with negligible damage to normal tissues. Finally, this research provides a smart strategy to construct a DHA repurposing nanomedicine for tumor specific treatment.

FeMn layered double hydroxides: an efficient bifunctional electrocatalyst for real-time tracking of cysteine in whole blood and dopamine in biological samples.

A peculiar clock-regulated design of FeMn-LDHs (FMH) with specific physiochemical attributes has been developed and used for highly sensitive detection of cysteine (CySH) and dopamine (DA). The FMH nanoparticles were synthesized via a facile hydrothermal approach clocked at various (6 h, 12 h and 18 h) operating periods. Under optimal conditions, FMH were obtained in three unique morphologies such as hexagonal plate like, cubic, and spherical structures corresponding to the clocked periods of 6 h, 12 h, and 18 h, respectively. Among these, FMH-12 h possess the minimal particle size (54.45 nm), a large surface area (7.60 m2 g-1) and the highest pore diameter (d = 4.614 nm). In addition to these superior physiochemical attributes, the FMH nanocubes exhibit excellent electrochemical behaviors with the lowest charge transfer resistance (Rct; 96 Ω), a high heterogeneous rate constant (7.81 × 10-6 cm s-1) and a good electroactive surface area (0.3613 cm2), among the three. The electrochemical biosensor based on the FMH nanocubes exhibits a remarkable catalytic activity toward CySH and DA with a low detection limit (9.6 nM and 5.3 nM) and a broad linear range (30 nM-6.67 mM and 20 nM-700 µM). The FMH based biosensor is also feasible for the real-world detection of CySH in whole blood and DA in biological fluids with satisfactory results. The proposed sensor possessed high selectivity, good repeatability, and reproducibility toward CySH and DA sensing.

[Evaluation of Interaction between Phosphate Ion and Metal Complex-layered Hydroxide].

A nickel-aluminium-zirconium complex-layered hydroxide (NAZ), which was synthesized using each inorganic sulfate mixing ratio of 0.9 : 1.0 : 0.1, was prepared and calcined at different temperatures. The physicochemical properties of the NAZ were analyzed by scanning electron microscopy, specific surface area, number of hydroxyl groups, and pore volume. The specific surface area, number of hydroxyl groups, and pore volume of NAZ was 51.9 m2/g, 1.08 mmol/g, and 0.27 µL/g, respectively. The amount of phosphate ion adsorbed onto NAZ was higher than that onto calcined NAZ at different temperatures. Therefore, the interaction between phosphate ions and NAZ was assessed using the elemental distribution analysis and the binding energy. After adsorption, the intensity of phosphorus atoms increased, indicating that the phosphate ions were adsorbed onto the NAZ surface. Additionally, phosphorus peaks (189 eV for 2s and 130 eV for 2p), which were not detected before adsorption, were clearly detected after adsorption. On the other hand, the intensity of the sulfur peak (165 eV for 2p) decreased after adsorption. Thus, we evaluated the ion exchange between phosphate ion and sulfate ion in the interlayer space of the NAZ. As a result, the correlation coefficient between the amount of phosphate ion adsorbed and the amount of sulfate ion released was positively correlated (r=0.960). Therefore, it can be clearly stated that one of the adsorption mechanisms of phosphate ions was related to ion exchange in the interlayer space of the NAZ. These findings are useful for preventing the eutrophication and recovery of phosphate ion in water environments.

Utilization of two modified layered doubled hydroxides as supports for immobilization of Candida rugosa lipase.

In this study, two synthetic layered doubled hydroxides (LDH), including Mg/Al-CO3-LDH (LDH1) and Zn/Al-CO3-LDH (LDH2), were prepared using the co-precipitation method and modified with sodium dodecyl sulfate to be utilized as carriers for immobilization of Candida rugosa lipase via the adsorption. The activity of prepared biocatalysts was measured in the olive oil hydrolysis. The effects of lipase concentration, pH, storage stability and thermal resistance of the samples were also studied. The maximum activity was obtained at pH 6.0 for immobilized lipase on modified LDHs with monolayer surfactants, including MLDH1 (0.922 U/mg) and MLDH2 (0.744 U/mg), respectively. The remained activities for immobilized lipase on MLDH1 and MLDH2 after 24 h incubation at 60 °C were 85% and 81%, respectively. During the 25days of storage at 4 °C, immobilized lipases on MLDH1, MLDH2, and free lipase kept 87%, 86%, and 70% of their initial activities. The residual activities for immobilized lipase on MLDH1 and MLDH2 after reusing for ten cycles were 72% and 67% of their initial activities. Adsorption parameters for sorption of lipase on all supports were fitted to the Freundlich and Langmuir isotherms. Kinetic parameters obtained from the Michaelis-Menten equation on MLDH1 and MLDH2 were comparable to free enzyme.

Design of γ-AlOOH, γ-MnOOH, and α-Mn2O3 nanorods as advanced antibacterial active agents.

In the current study, γ-AlOOH, γ-MnOOH, and α-Mn2O3 nanorods (NRs) were easily synthesized and applied as advanced antibacterial materials. γ-AlOOH NRs with 20 nm width, [100] crystal plane, and 200 nm length were fabricated through a surfactant-directed solvothermal method. γ-MnOOH NRs with 20 nm width, [101] crystal direction and 500 nm length were fabricated through a hydrothermal method. The prepared γ-MnOOH NRs were calcinated (for 5 h) at 700 °C to produce α-Mn2O3 NRs with 20 nm average width and increased surface area. The NRs' structures were confirmed through FT-IR, XRD, XPS, FESEM, and FETEM. The antibacterial activity of the NRs was studied against different Gram-negative and Gram-positive bacterial strains and yeast. The three NRs exhibited antibacterial activity against all of the used strains. Biological studies indicated that the NRs' antimicrobial activity increased in the order of γ-MnOOH < γ-AlOOH < α-Mn2O3 NRs. The α-Mn2O3 NRs exhibited the lowest MIC value (39 µg mL-1) against B. subtilis, B. pertussis, and P. aeruginosa. The prepared NRs exhibited a higher antimicrobial potential toward Gram-positive bacteria than Gram-negative bacteria. The higher antimicrobial activity of the α-Mn2O3 NRs is highlighted based on their larger surface area and smaller diameter. Consequently, uniform NR architectures, single crystallinity, small nanoscale diameters, and more highly exposed [110] Mn-polar surfaces outwards are promising structures for α-Mn2O3 antibacterial agents. These NRs adhered firmly to the bacterial cells causing cell wrapping and morphology disruption, and microbial death. The designed NRs provide a great platform for microbial growth inhibition.

Deep eutectic solvent-assisted facile synthesis of copper hydroxide nitrate nanosheets as recyclable enzyme-mimicking colorimetric sensor of biothiols.

In the quest for alternative products that would conquer natural enzyme drawbacks, enzyme-like nanomaterials with controllable morphology, high catalytic activity, excellent stability, and reusability have gained extensive attention in recent years. Herein, a simple and versatile strategy based on basic deep eutectic solvents was used to create layered copper hydroxide nitrate (Cu2(OH)3NO3) with a well-structured nanosheet-like morphology. The present nanosheets exhibited extraordinary oxidase and peroxidase-like activity. More importantly, these nanosheets have shown the ability to operate at low and high temperatures with appreciable stability and multiple reusabilities. Based on inhibiting the oxidase-like activity of the prepared Cu2(OH)3NO3, we designed a colorimetric sensing technique with a high-efficiency detection of biothiols in serum samples. Because of the simplicity and low-cost fabrication approach, our findings would be beneficial to the artificial enzyme research community as another facile and green tactics to fabricate heterogeneous artificial enzymes. Graphical abstract.

A closer look into the physical interactions between lipid membranes and layered double hydroxide nanoparticles.

Layered double hydroxide nanoparticles (LDH-NPs) constitute promising nanocarriers for drug and gene delivery. Although their cell internalization has been studied, the interaction between LDH-NPs and biological membrane models, such as giant unilamellar vesicles (GUVs), remains unexplored. These vesicles are widely-used membrane models that allow minimizing the complexity and uncertainty associated with biological systems to study the physical interactions in the absence of cell metabolism effects. With such an approach the physicochemical properties of the membrane can be differentiated from the biological functionalities involved in cell internalization and the membrane-mediated internalization can be directly understood. In this work, we describe for the first time the interaction of LDH-NPs with freestanding negatively charged POPC:POPS GUVs by fluorescence microscopy. The experiments were performed with fluorescein labeled LDH-NPs of about 100 nm together with different fluorophores in order to evaluate the NPs interactions with the vesicles as well as their impact on the membrane morphology and permeability. Positively charged LDH-NPs are electrostatically accumulated at the GUVs membrane, altering its lateral phospholipid distribution and increasing the stiffness and permeability of the membrane. The adsorption of albumin (LDH@ALB) or polyacrylic acid (LDH@PA) passivates the surface of LDH-NPs eliminating long-range electrostatic attraction. The absence of membrane-mediated internalization of either LDH@ALB or LDH@PA, represents an advantage in the use of LDH-NPs as drug or nucleic acids nanocarriers, because suitable functionalization will allow an optimal cell targeting.

Adsorption of Phosphate Ions on Novel Mg/Fe/Al Hydroxides (MFA) Prepared at Different Mg2+/Fe3+/Al3+ Ratios.

In this study, we prepared novel Mg/Fe/Al hydroxides (MFA series: denoted by MFA1, MFA2, MF, and MA) and investigated their properties using scanning electron microscopy, X-ray diffraction, the specific surface area, and amount of hydroxyl groups. Additionally, the phosphate adsorption capabilities of the MFA series or Fe-Mg type hydrotalcites (FHT3.0 and FHT5.0) were evaluated by examining the effects of the solution pH and contact time, and analyzing the adsorption isotherm and desorption characteristics. In MFA1, a strong correlation exists between the amount of adsorbed phosphate ions and surface hydroxyl groups, with a correlation coefficient of 0.95. The adsorption kinetics data fitted using the pseudo-second-order model performs better than the pseudo-first-order model. The adsorption isotherm data were also fitted using both the Freundlich and Langmuir models. Finally, the phosphate ions adsorbed on the MFA1 surfaces were desorbed using sodium hydroxide solution. These results indicate that MFA1 offers great potential for phosphate ion adsorption from aqueous solutions and functions as a renewable adsorbent.

Colorimetric determination of As(III) based on 3-mercaptopropionic acid assisted active site and interlayer channel dual-masking of Fe-Co-layered double hydroxides with oxidase-like activity.

A colorimetric method is described for the determination of As(III). It is based on the use of 3-mercaptopropionic acid (3-MPA) assisted active site and interlayer channel dual-masking of oxidase-like Fe-Co-layered double hydroxides (Fe-Co-LDH). The Fe-Co-LDH acts as an oxidase-mimicking nanozyme with high activity. It catalyzes the oxidation of colorless 3,3'5,5'-tetramethylbenzidine (TMB) to form a blue product (oxTMB) with an absorption maximum at 652 nm. It is found that As(III) firmly anchors onto the Fe* sites of the 3-MPA-modified Fe-Co-LDH via forming a stable Fe─As(III)─3-MPA─As(III)─Fe structure. This results in masking the active sites and interlayer channels of the Fe-Co-LDH nanozyme. As a result, the presence of As(III) as well as 3-MPA specifically inhibit the LDH-catalyzed chromogenic reaction. Based on the above principle, a colorimetric assay was designed for the determination of As(III). It provided linear response in the 0.10~8.33 µM As(III) concentration range and a detection limit as low as 35 nM. The assay was applied to the quantitation of As(III), even in the presence of potential interferents including As(V), Hg(II) and Pb(II), in environmental and drinking water samples. Graphical abstractSchematic illustration of the As(III) sensing mechanism based on 3-mercaptopropionic acid (3-MPA) assisted active site and interlayer channel dual-masking of Fe-Co-layered double hydroxides (Fe-Co-LDH) with oxidase-like activity. 3-MPA with sulfhydryl and carboxyl groups can assist As(III) to firmly anchor onto the Fe* sites inside the interlayer channels of the Fe-Co-LDH via forming a Fe─As(III)─3-MPA─As(III)─Fe structure, thus selectively resulting in a significant suppression of the chromogenic reaction.

Dissolvable layered double hydroxide as a sorbent in dispersive micro-solid phase extraction for the determination of acidic quinolones in honey by HPLC.

This study presents a simple and green dispersive micro-solid phase extraction method for preconcentration of acidic quinolones from honey prior to high performance liquid chromatography determination. A two-dimensional nanostructured zinc-aluminum layered double hydroxide was synthesized and used as the sorbent for dispersive micro-solid phase extraction. Its different characteristics from conventional sorbents is that it is dissolvable in acidic solution (pH < 4). After the extraction, the analyte elution step was omitted and thus the use of organic solvents was avoided. The key parameters influencing the extraction efficiency such as the amount of sorbent, pH of sample solution, vortex time, type and volume of acidic solution were investigated and optimized. The method exhibited low limits of detection (3.0-5.0 ng/g), good linearity (10-2000 ng/g) with coefficients of determinations higher than 0.9991, acceptable precision (RSD<9.1%) and accuracy (RE<5.8%). The proposed method is fast, efficient, eco-friendly, and suitable for the determination of acidic quinolones in honey samples.

Efficient synthesis of multiply substituted 7H-indeno[2,1-c]quinoline using 7-aminonaphthalene-1,3-disulfonic acid supported on LDHs as catalyst.

The LDHs@Propyl-ANDSA was used as a new catalyst for synthesizing 7H-indeno[2,1-c]quinoline derivatives. The catalyst was integrated according to three-step synthesis. Zn-Cr layered double hydroxides (LDHs) were synthesized with molar ratio 2:1 by the co-precipitation method.

Synthesis and characterization of a novel biocompatible pseudo-hexagonal NaCa-layered double metal hydroxides for smart pH-responsive drug release of dacarbazine and enhanced anticancer activity in malignant melanoma.

Layered metal hydroxides have exhibited remarkable benefits in drug delivery, days or even weeks of continuous drug release with improved bioavailability and minimized adverse effects. Here, we report synthesis of a new M+ (Na+) and M2+ (Ca2+) layered double metal hydroxide-based phases with the general formula of [Na0.2Ca0.8(OH)1.4] (NO3)0.4, and 3D pseudo-hexagonal morphology. NaCa layered double metal hydroxide (NaCa-LDH), which is biodegradable, biocompatible, and pH-sensitive, could have broad applicability in drug release and other biomedical applications. Dacarbazine (DAC) is one of the most commonly used chemotherapy drugs for treating various cancers. However, its poor water solubility, short half-life in blood circulation, low response rate and high side effects limit its application. This study aimed to increase its half-life and anticancer activity; minimize its side effects; and prolong its drug release by intercalating of DAC in biodegradable NaCa-LDH (DAC-LDH). Results from the intercalation process show that NaCa-LDH is able to intercalate DAC with a simple procedure and with a good drug loading (38% w/w) through a one pot reaction. The DAC shows a sustained and pH-sensitive release, and the release rate of DAC from DAC-LDH at pH 7.4 is remarkably lower than that at pH 6.0 due to its different release mechanisms. In the latter case, the release was not complete at 24 h. We show that DAC-LDH anticancer efficacy on malignant (A-375) melanoma and breast cancer (MCF-7) cell lines is higher than that of free DAC. These nanoparticles may open a significant way toward the development of a pH-sensitive drug release system that minimizes drug side effect for a wide range of applications.

Proton-consumed nanoarchitectures toward sustainable and efficient photophosphorylation.

At present, photophosphorylation in natural or artificial systems is accomplished by the production of protons or their pumping across the biomembranes. Herein, different from this strategy above, we demonstrate a designed system which can effectively enhance photophosphorylation by photo-induced proton-scavenging through molecular assembly. Upon the introduction of photobase generators, a (photo-) chemical reaction occurs to produce hydroxyl ions. Accompanying the further extramembranous acid-base neutralization reaction, an outbound flow of protons is generated to drive the reconstituted adenosine triphosphate (ATP) synthase to produce ATP. That is, contrary to biochemistry, the proton gradient to drive photophosphorylation derives from the scavenging of protons present in the external medium by hydroxyl ions, produced by the partially photo-induced splitting of photobase generator. Such assembled system holds great potential in ATP-consuming bioapplications.

Sonocatalytic reduction of nitrate using magnetic layered double hydroxide: Implications for removal mechanism.

In this study, magnetic layered double hydroxides (mag-LDHs) were synthesized through compositing magnetite with three different metals (Mg, Cu and Al) under ultrasound (US, 100 kHz frequency and 50 W power). For the first time, mag-LDHs were applied to sonocatalytic reduction of nitrate (NO3-) and the reduction mechanism were determined by conducting kinetic tests and various spectroscopic analyses. Based on the kinetic data, NO3- reduction and the selectivity for N2 highly depends on the ratio between Mg/Al, solution pH and sonication frequency. The best condition for sonocatalytic denitrification was found to be pH 7 operated under 100 kHz (50% power) using the catalyst with lowest amount of Al (mag-LDH-Al0.3Mg1.5). As a proposed mechanism, NO3- is initially reduced to NO2- by Cu0, and then further reduced to N2/NH4+ by Mg0. Hypothetically Al0 could provide sorption sites for hydrogen radicals (·H) dissociated from ultrasound, hence served as reducing sites in denitrification process. The XPS analysis showed an increased peak of Cu0 after the sonocatalytic reduction when catalyst has lower amount of Al. The excessive hydrogen adsorbed on Al0 might spill-over to the adjacent Cu, thus reducing the CuO into Cu0 at high temperature created by the implosion of the microbubbles. Without the use of consumable reducing agents (i.e. H2 gas), sonocatalytic reduction could be a potential candidate of remediation method to treat NO3- polluted water with high N2 selectivity and easy magnetic recovery.

Self-stacking of exfoliated charged nanosheets of LDHs and graphene as biosensor with real-time tracking of dopamine from live cells.

This study introduces a new strategy for periodic stacking of positively charged NiAl layered double hydroxides (LDHs) nanosheets with negatively charged monolayers of graphene (G) by systematically optimizing several parameters in a controlled co-feeding fashion and resultant heterostacked NiAl LDH/G LBL nanocomposites have been practically applied in sensitive detection of dopamine released from live cells as early Parkinson's disease (PD) diagnostic tool. PD is the second most chronic neurodegenerative disorder with gradual progressive loss of movement and muscle control causing substantial disability and threatening the life seriously. Unfortunately majority of dopaminergic neurons present in substantia nigra of PD patients are destroyed before it is being clinically diagnosed, so early stages PD diagnosis is essential. Because of direct neighboring of extremely conductive graphene to semiconductive LDHs layers, enhanced intercalation capability of LDHs, and huge surface area with numerous active sites, good synergy effect is harvested in heteroassembled NiAl LDH/G LBL material, which in turn shows admirable electrocatalytic ability in DA detection. The interference induced by UA and AA is effectively eliminated especially after the modifying the electrode with Nafion. The outstanding electrochemical sensing performance of NiAl LDH/G LBL modified electrode has been achieved in terms of broad linear range and lowest real detection limit of 2 nM (S/N = 3) towards DA oxidation. Benefitting from superior efficiency, biosensor has been successfully used for real-time in-vitro tracking of DA efflux from live human nerve cell after being stimulated. We believe that our biosensing platform of structurally integrated well-ordered LBL heteroassembly by inserting graphene directly to the interlayer galleries of LDHs material will open up new avenue in diseases determination window.

A review on electrochemical biosensing platform based on layered double hydroxides for small molecule biomarkers determination.

The development of layered double hydroxides (LDHs), also known as anionic clays with uniform distribution of metal ions and facile exchangeability of intercalated anions, are now appealing an immense deal of attention in synthesis of multifunctional materials. In electrochemical biosensors, LDHs provide stable environment for immobilization of enzymes or other sensing materials and play crucial roles in development of clinical chemistry, point-of-care devices through analysis of various small molecule metabolites excreted by biological processes which in turn serve as molecular biomarkers for medical diagnostics. In this review, we summarize the recent development in fabrication of LDH based nanoarchitectures and their electrocatalytic applications in ultrasensitive in vitro determination of conventional biomarkers, i.e., H2O2, glucose, dopamine and other biomolecules. Moreover, detailed discussion has been compiled to differentiate electrochemical enzymatic and nonenzymatic biosensors, to evaluate useful concentration ranges of H2O2 and glucose for analytical circumstances and to distinguish tumorigenic and normal cells via quantifying the released H2O2 efflux from living cells. Here, we envision that electrochemical sensing platform based on structurally integrated LDH nanohybrids with highly conducting substrates will assist as diseases diagnostic probe further enhancing diagnosis as well as therapeutic window for chronic diseases. Finally, the perspective for fabrication and assembly of LDH electrode is proposed for the future innovation of electrochemical biosensors with high performance making them more reliable for in vitro diagnostics.

Rhodium(iii)-catalyzed C-H allylation of indoles with allyl alcohols via ß-hydroxide elimination.

An efficient Rh(iii)-catalyzed dehydrative C-H allylation of indoles with allyl alcohols via ß-hydroxide elimination under oxidant-free conditions has been developed. This method features very mild reaction conditions, excellent regioselectivity and stereoselectivity, and compatibility with various functional groups. In addition, the directing group can be removed under mild reaction conditions, which further underscores the synthetic utility of this method.

Enhanced degradation of isoproturon in soil through persulfate activation by Fe-based layered double hydroxide: different reactive species comparing with activation by homogenous Fe(II).

Phenylurea herbicide residuals in soil may continuously contaminate surface water and groundwater due to unregulated and improper use. Herein, we reported a stable and active oxidation system including heterogeneous Fe-based layered double hydroxide materials as persulfate (PS) activators. Under mild conditions, 1% LDH in weight and 70 mM PS can completely degrade 500 mg/kg isoproturon in soil within 10 h, during which less than 0.1 ppm heavy metal leaching was detected. This remarkable performance was consistent in a broad pH range (3~11) and was resistant to various inorganic anions (Cl-, Br-, NO3-, HCO3-) and humic acid. Mechanism studies from scavenging tests, EPR, and fluorescence spectra collectively proved that besides •OH and •SO4-, singlet oxygen (1O2) and superoxide (•O2-) were also generated and were accounted for the oxidative degradation. This unique mechanism of generating diverse radicals was clearly distinguished from classic Fe(II)/PS system, significantly reduced the influence of varying parameters in water and soil matrix, and was suggestive to chemical oxidation system in soil remediation to avoid scavenging effects by background electrolytes or other components in water/soil matrix. Graphical abstract ᅟ.