Rapidly and simply detecting Cr (VI) in aqueous media via a diketopyrrolopyrrole-based chemosensor with both high selectivity and low LOD.

BACKGROUND: The high toxicity of hexavalent chromium [Cr (VI)] could not only cause harmful effects on humans, including carcinogenicity, respiratory issues, genetic damage, and skin irritation, but also contaminate drinking water sources, aquatic ecosystems, and soil, impairing the reproductive capacity, growth, and survival of organisms. Due to these harmful effects, detecting toxic Cr (VI) is of great significance. However, the rapid, simple, and efficient detection at a low Cr (VI) concentration is extremely challenging, especially in an acidic condition (existing as HCrO4-) due to its low adsorption free energy. RESULTS: A diketopyrrolopyrrole-based small molecule (DPPT-PhSMe) is designed and characterized to act as a chemosensor, which allows a high selectivity to Cr (VI) at an acidic condition with a low limit of detection to 10-8 M that is two orders of magnitude lower than the cut of limit (1 µM) recommended by World Health Organization (WHO). Mechanism study indicates that the rich sulfur atoms enhance the affinity to HCrO4-. Combining with favorable features of diketopyrrolopyrrole, DPPT-PhSMe not only allows dual-mode detection (colorimetric and spectroscopic) to Cr (VI), but also enables disposable paper-based sensor for naked-eye detection to Cr (VI) from fully aqueous media. The investigation of DPPT-PhSMe chemosensor for the quantification of Cr (VI) in real life samples demonstrates a high reliability and accuracy with an average percentage recovery of 102.1 % ± 4 (n = 3). SIGNIFICANCE: DPPT-PhSMe represents the first diketopyrrolopyrrole-derived chemosensor for efficient detection to toxic Cr (VI), not only providing a targeted solution to the bottleneck of Cr (VI) detection in acidic conditions (existing as HCrO4-) caused by its low adsorption free energy, but also opening a new scenario for simple, selective, and efficient Cr (VI) detection with conjugated dye molecules.

A Comprehensive Study of NF3-Based Selective Etching Processes: Application to the Fabrication of Vertically Stacked Horizontal Gate-All-around Si Nanosheet Transistors.

In this paper, we demonstrate a comprehensive study of NF3-based selective etching processes for inner spacer formation and for channel release, enabling stacked horizontal gate-all-around Si nanosheet transistor architectures. A cyclic etching process consisting of an oxidation treatment step and an etching step is proposed and used for SiGe selective etching. The cyclic etching process exhibits a slower etching rate and higher etching selectivity compared to the direct etching process. The cycle etching process consisting of Recipe 1, which has a SiGe etching rate of 0.98 nm/cycle, is used for the cavity etch. The process achieved good interlayer uniformity of cavity depth (cavity depth ≤ 5 ± 0.3 nm), while also obtaining a near-ideal rectangular SiGe etch front shape (inner spacer shape = 0.84) and little Si loss (0.44 nm@ each side). The cycle etching process consisting of Recipe 4 with extremely high etching selectivity is used for channel release. The process realizes the channel release of nanosheets with a multi-width from 30 nm to 80 nm with little Si loss. In addition, a selective isotropic etching process using NF3/O2/Ar gas mixture is used to etch back the SiN film. The impact of the O2/NF3 ratio on the etching selectivity of SiN to Si and the surface roughness of SiN after etching is investigated. With the introduction of O2 into NF3/Ar discharge, the selectivity increases sharply, but when the ratio of O2/NF3 is up to 1.0, the selectivity tends to a constant value and the surface roughness of SiN increases rapidly. The optimal parameter is O2/NF3 = 0.5, resulting in a selectivity of 5.4 and a roughness of 0.19 nm.

A hydroxyl-rich covalent organic framework for the precisely selective fluorescence sensing of explosives with high sensitivity.

Covalent organic Frameworks (COFs) have become a new platform for functional research and material design. A novel covalent organic skeleton (DHB-TFP COF) was synthesized from 2-hydroxybenzene-1,3,5-tricarbaldehyde and 3,3'-dihydroxybenzidine using Schiff base reaction. DHB-TFP COF is a highly stable porous crystalline material and exhibits exceptional thermal and chemical resistance. DHB-TFP COF exhibited a selective and sensitive "turn-off" fluorescence response to 4-NP in ethanol, and TNP not only significantly quenched the fluorescence of DHB-TFP COF but also caused the obvious red-shift. The fluorescence intensity of DHB-TFP COF exhibited a linear correlation with the concentration of 4-NP with a detection limit of 0.40 µM. Furthermore, the maximum fluorescence peak observed for DHB-TFP COF demonstrated a linear relationship with TNP concentration with a detection limit of 11.15 µM. DHB-TFP COF exhibited satisfactory recovery in the detection of 4-NP and TNP in actual water sample indicating its practical application potential. The O atoms of rich hydroxyl and N atoms of C = N present on the surface of DHB-TFP COF scaffold can establish strong hydrogen bonds with 4-NP and TNP, facilitating their mutual interaction. The spectra studies indicated that the fluorescence quenching mechanism can be attributed to the absorption competitive quenching (ACQ) and fluorescence resonance energy transfer (FRET) mechanism. This study not only proposed the approach for synthesizing novel structured organic frameworks, but also developed a highly selective and sensitive fluorescence chemical sensor for identifying and detecting 4-NP and TNP.

The dual-configured hydrogen bonds induced by polymerized deep eutectic solvents-modified magnetic biochar enhanced the selectivity for 3,4-methylenedioxymethamphetamine.

The accurate discovering and monitoring of 3,4-methylenedioxymethamphetamine (MDMA) are especially important because of its substantial toxicity and potential harm to human and the ecological systems. Three types of polymerized deep eutectic solvents functionalized magnetic biochar (MBC@poly (AA/AAC/AAm-ChCl)) were successfully synthesized to adsorb MDMA. The isotherm and kinetic data confirmed that MBC@poly (AAm-ChCl) had the strongest adsorption capacity, and the order of adsorption capacity is as follow: MBC@poly(AAm-ChCl) > MBC@poly(AA-ChCl) > MBC@poly(MAA-ChCl), which also revealed that the adsorption was heterogeneous multi-layer chemisorption. The findings of the characterizations manifested that MBC@poly(AAm-ChCl) was the optimal adsorbent owning to its higher nitrogen content, resulting in the formation of a greater number of hydrogen bonds. Due to the strong hydrogen bonding effect of CO and -NH2 functional groups, MBC@poly(AAm-ChCl) exhibited the high selectivity towards MDMA under the coexistence of multiple chemical substances, and excellent adsorption performance over the pH range of 4-11. Urea as a hydrogen bond inhibitor further confirmed MBC@poly(AAm-ChCl) had high-density active hydrogen bonding sites. Furthermore, utilizing density functional theory (DFT) for simulating adsorption both before and after the process verified that the high selectivity of MBC@poly(AAm-ChCl) attributed to the formation of the dual-configured hydrogen bonds. This study provides support for the production of highly selective biochar for use in pretreatment during drug detection.

A Multi-Interface Structure of Graphdiyne/Cobalt Oxides for Chlorine Production.

A challenge facing the chlor-alkali process is the lack of electrocatalyst with high activity and selectivity for the efficient industrial production of chlorine. Herein the authors report a new electrocatalyst that can generate multi-interface structure by in situ growth of graphdiyne on the surface of cobalt oxides (GDY/Co3O4), which shows great potential in highly selective and efficient chlorine production. This result is due to the strong electron transfer and high density charge transport between GDY and Co3O4 and the interconversion of the mixed valence states of the Co atoms itself. These intrinsic characteristics efficiently enhance the conductivity of the catalyst, facilitate the reaction kinetics, and improve the overall catalytic selectivity and activity. Besides, the protective effect of the formed GDY layer is remarkable endowing the catalyst with excellent stability. The catalyst can selectively produce chlorine in low-concentration of NaCl aqueous solution at room temperature and pressure with the highest Faraday efficiency of 80.67% and an active chlorine yield rate of 184.40 mg h-1 cm-2, as well as superior long-term stability.

Synthesis of ultrathin hybrid membranes via the co-polymerization of acrylic acid, styrene and molybdenum disulfide and their high adsorption selectivity for lead(II) in the mixture of metal ions.

Lead(II) is a potential carcinogen of heavy-metal ions (HIs). With the wide application of Pb-bearing products including lead alloy products, and new-energy lead-ion batteries, lead pollution has become a tricky problem. To solve such a difficulty, novel ultrathin MoS2-vinyl hybrid membranes (MVHMs) with a "spring" effect were synthesized via co-polymerization of acrylic acid, styrene and molybdenum disulfide (MoS2) and their adsorptions for HIs were explored. The "spring" effect derived from the interaction between the tendency of the short polyacrylic acid (PAA) chain connected with MoS2 to spread outward and the coulomb force between layers from MoS2 (s-MoS2), which enlarge the spacing of MoS2 layers without changing the number of layers after membrane formation, which changes the swelling membrane to a dense membrane and reduces the original thickness from 0.5 cm to 0.011 mm in the thickness direction. The adsorption experiment revealed that these MVHMs had super adsorption performance and high selectivity for Pb2+ by comparison with other five metal ions: Cu2+, Cd2+, Ni2+, Cr3+ and Zn2+. Especially, the adsorption quantity of MVHMs for Pb2+ could approach 2468 mg/g and the maximum adsorption ratio of qe[Pb2+]/qe[Cu2+] can reach 10.909. These values were much larger than the data obtained with the adsorbents reported in the last decade. A variety of models are applied to evaluate the effect of ionic groups. It was confirmed that -COOH plays a key role in adsorption of HIs and s-MoS2 also has a certain contribution. Conversely, ion exchange plays only a minor role during the period of adsorption process. Effective diffusion coefficient (Deff) of Pb(II) had the largest values among these metal ions. Hence, these hybrid membranes are promising adsorbents for the removal of Pb2+ from water containing various ions.

Achieving high selectivity and activity of CO2 electroreduction to formate by in-situ synthesis of single atom Pb doped Cu catalysts.

Exploring highly selective and stable electrocatalysts is of great significance for the electrochemical conversion of CO2 into fuel. Herein, a three-dimensional (3D) nanostructure catalyst was developed by doping Pb single-atom (PbSA) in-situ on carbon paper (PbSA100-Cu/CP) through a low-energy and economical method. The designed catalyst exhibited abundant active sites and was beneficial to CO2 adsorption, activation, and subsequent conversion to fuel. Interestingly, PbSA100-Cu/CP showed a prominent Faraday efficiency (FE) of 97 % at -0.9 V versus reversible hydrogen electrode (vs. RHE) and a high partial current density of 27.9 mA·cm-2 for formate. Also, the catalyst remained significantly stable for 60 h during the durability test. The reaction mechanism was investigated by density functional theory (DFT), demonstrating that the doping PbSA induced the electrons redistribution, promoted the formate generation, reduced the rate-determining step (RDS) energy barrier, and inhibited the hydrogen evolution reaction. The study aims to provide a new strategy for developing of single-atom catalysts with high selectivity and stability, which will help reduce environmental pressure and alleviate energy problems.

Enhanced removal of phosphate from aqueous solutions by oxygen vacancy-rich MgO microspheres: Performance and mechanism.

The efficient removal of phosphate from water environments was extremely significant to control eutrophication of water bodies and prevent further deterioration of water quality. In this study, oxygen vacancy-rich magnesium oxide (OV-MgO) microspheres were synthesized by a simple solvothermal method coupling high-temperature calcination. The effects of adsorbent dosage, contact time, initial pH and coexisting components on phosphate adsorption performance were examined. The physicochemical properties of OV-MgO microspheres and the phosphate removal mechanisms were analyzed by various characterization techniques. The maximum adsorption capacity predicted by the Sips isotherm model was 379.7 mg P/g for OV-MgO microspheres. The phosphate adsorption in this study had a fast adsorption kinetics and a high selectivity. OV-MgO microspheres had a good acid resistance for phosphate adsorption, but their adsorption capacity decreased under alkaline conditions. The electrostatic attraction, ligand exchange, surface precipitation, inner-sphere surface complexation and oxygen vacancy capture were mainly responsible for efficient removal of phosphate from aqueous solutions. This study probably promoted the development of oxygen vacancy-rich metal (hydr)oxides with potential application prospects.

In Situ Growth of Conductive Metal-Organic Framework onto Cu2O for Highly Selective and Humidity-Independent Hydrogen Sulfide Detection in Food Quality Assessment.

The sensitivity of chemiresistive gas sensors based on metal oxide semiconductors (MOSs) has been inherently affected by ambient humidity because their reactive oxygen species are easily hydroxylated by water molecules, which significantly reduces the accuracy of the gas sensors in food quality assessment. Although conventional metal organic frameworks (MOFs) can serve as coatings for MOSs for humidity-independent gas detection, they have to operate at high working temperatures due to their low or nonconductivity, resulting in high power consumption, significant manufacturing inconvenience, and short-term stability due to the oxidation of MOFs. Here, the conductive and thickness-controlled CuHHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene)-coated Cu2O are developed by combining in situ etching and layer-by-layer liquid-phase growth method, which achieves humidity-independent detection of H2S at room temperature. The response to H2S only decreases by 2.6% below 75% relative humidity (RH), showing a 9.6-fold improvement than the bare Cu2O sensor, which is ascribed to the fact that the CuHHTP layer hinders the adsorption of water molecules. Finally, a portable alarm system is developed to monitor food quality by tracking released H2S. Compared with gas chromatography method, their relative error is within 9.4%, indicating a great potential for food quality assessment.

Oxygen-Activated Boron Nitride for Selective Photocatalytic Coupling of Methanol to Ethylene Glycol.

The controllable photocatalytic C-C coupling of methanol to produce ethylene glycol (EG) is a highly desirable but challenging objective for replacing the current energy-intensive thermocatalytic process. Here, we develop a metal-free porous boron nitride catalyst that demonstrates exceptional selectivity in the photocatalytic production of EG from methanol under mild conditions. Comprehensive experiments and calculations are conducted to thoroughly investigate the reaction mechanism, revealing that the OB3 unit in the porous BN plays a critical role in the preferential activation of C-H bond in methanol to form ⋅CH2OH via a concerted proton-electron transfer mechanism. More prominent energy barriers are observed for the further dehydrogenation of the ⋅CH2OH intermediate on the OB3 unit, inhibiting the formation of some other by-products during the catalytic process. Additionally, a small downhill energy barrier for the coupling of ⋅CH2OH in the OB3 unit promotes the selective generation of EG. This study provides valuable insights into the underlying mechanisms and can serve as a guide for the design and optimization of photocatalysts for efficient and selective EG production under mild conditions.

A novel ethylene linkage-based covalent organic framework for turn-on fluorescence sensing for Al3+ with excellent selectivity and sensitivity.

Covalent organic Framework (COFs) has become a new platform for functional research and material design. A novel covalent organic framework (CN-COF) was first synthesized with p-xylylene dicyanide and 2-hydroxy-1,3,5-benzenetrialdehyde through the Knoevenagel condensation reaction. CN-COF is a porous crystal material with strong thermal and chemical stability. CN-COF exhibits a selective "turn-on" fluorescence response to Al3+ in ethanol with blue-shifted emission spectra over the other tested metal ions. The color changes from pink to earth yellow, and the fluorescence effect is clearly visible. The fluorescence intensity of CN-COF was linearly related to the concentration of Al3+, and the detection limit was 1.815 µM. Importantly, CN-COF exhibits a satisfactory recovery for detecting Al3+ in drinking water and fish samples. CN-COF also showed the intuitive semi-quantitative detection ability for Al3+ via the color change with the naked eyes. The special pore structure is conducive to allow Al3+ enter to coordinate with O and N atoms on the wall of CN-COF scaffold. The revisable fluorescence change upon the selective addition of Al3+ and XRD, EDTA, XPS and DFT results demonstrated the complex process. The inhibition of the photoinduced electron transition from O atoms to Al3+ induced the fluorescence enhancement. This study not only presents a synthesis idea for a new structural organic framework, but also offers a highly selective and sensitive fluorescence chemical sensor for the identification and detection of Al3+.

A Highly Selective Implantable Electrochemical Fiber Sensor for Real-Time Monitoring of Blood Homovanillic Acid.

Homovanillic acid (HVA) is a major dopamine metabolite, and blood HVA is considered as central nervous system (CNS) dopamine biomarker, which reflects the progression of dopamine-associated CNS diseases and the behavioral response to therapeutic drugs. However, facing blood various active substances interference, particularly structurally similar catecholamines and their metabolites, real-time and accurate monitoring of blood HVA remains a challenge. Herein, a highly selective implantable electrochemical fiber sensor based on a molecularly imprinted polymer is reported to accurately monitor HVA in vivo. The sensor exhibits high selectivity, with a response intensity to HVA 12.6 times greater than that of catecholamines and their metabolites, achieving 97.8% accuracy in vivo. The sensor injected into the rat caudal vein tracked the real-time changes of blood HVA, which paralleled the brain dopamine fluctuations and indicated the behavioral response to dopamine increase. This study provides a universal design strategy for improving the selectivity of implantable electrochemical sensors.

Efficient and selective capture of various mercury species from water using an exfoliated thiocellulose.

The primary challenge in mercury (Hg) adsorbents for large-scale practical applications is to achieve the balance between performance and economy. This work attempts to address this issue by synthesizing an exfoliated thiocellulose (CU-SH) with high thiol density and hierarchical porosity using in-situ ligands grafting combined with chemical stripping. The prepared CU-SH shows remarkable physical stability and chemical resistance, and the micron sized fiber is conducive to separation from water. Hg(II) adsorption tests in water demonstrate that CU-SH has broad working pH range (1-12), fast kinetics (0.64 g/(mg‧min)), high adsorption capacity (652.9 mg/g), outstanding selectivity (Kd = 6.2 × 106 mg/L), and excellent reusability (R > 95 % after 20 cycles). Importantly, CU-SH exhibits good resistance to various coexisting ions and organic matter, and can efficiently remove Hg(II) from different real water. CU-SH can be made into a Point of Use (POU) device for continuous and efficient removal of Hg(II) from drinking water. 0.1 g CU-SH filled device can purify 3.2 L of Hg(II) (0.5 ppm) contaminated tap water before the breakthrough point of 2 ppb. Moreover, CU-SH also reveals good adsorption affinity for Hg-dissolved organic matter complexes (Hg(II)-DOM) in water, chloro(phenyl)mercury (PMC) in organic media and Hg0 vapor in air, suggesting the great practical potential of CU-SH.

Highly selective detection and removal of mercury ions in the aquatic environment based on magnetic ZIF-71 multifunctional composites with sufficient chlorine functional groups.

The development of both detection and removal technologies for heavy metal ions is of great importance. Most of the existing adsorbents that contain oxygen, nitrogen or sulfur functional groups can remove heavy metals, but achieving both selective detection and removal of a single metal ion is difficult because they bind to a wide range of heavy metal ions. Herein, we selected zeolite imidazolium hydrochloride framework-71 (ZIF-71) with sufficient chlorine functional groups to fabricate magnetic ZIF-71 multifunctional composites (M-ZIF-71). M-ZIF-71 had a large specific surface area, excellent water stability, and good magnetic properties, which made M-ZIF-71 conducive to the separation and recovery of adsorbents and the assembly of electrodes. M-ZIF-71 exhibited high selectivity, wide linear range (1-500 µg/L), and low detection limit (0.32 µg/L) for electrochemical detection of mercury ions (Hg2+). Meanwhile, M-ZIF-71 demonstrated rapid Hg2+ adsorption with a high capacity of 571.2 mg/g and excellent recyclability. The high selectivity for Hg2+ was attributed to the powerful affinity of highly electronegative chlorine and Hg2+. Moreover, XPS spectra demonstrated the interaction between chlorine and Hg2+. This work provides a new inspiration for applications in the targeted monitoring and removal of heavy metal pollution.

High-Selectivity Laminated Gas Sensor Based on Characteristic Peak under Temperature Modulation.

Aiming at the bottleneck problem of insufficient selectivity of metal oxide gas sensors, a reliable scheme to improve selectivity is proposed, that is, a laminated sensor structure of a gas-sensitive membrane plus catalytic membrane combined with the temperature modulation technology. It is presented as a highly selective ethanol sensor as an example for verification. The laminated gas sensor is made of Sr@SnO2 as the gas-sensing membrane and ZSM-5 as the catalytic membrane by the microelectro mechanical system. The results indicate that in temperature modulation mode, the Sr@SnO2/ZSM-5-laminated sensor has good resistance gas-sensing response to most different types of gases but only shows a characteristic peak on the time-resistance and temperature-resistance curves of ethanol gas response. By defining and calculating this characteristic peak, the selectivity of ethanol gas response signal is improved. The Sr@SnO2/ZSM-5 sensor also exhibits high sensitivity to ethanol gas at the parts per billion level, fast response/recovery time in seconds, excellent anti-interference, and stability, indicating the reliability and practicality of this highly selective scheme. This scheme is of great significance for the study of high selectivity of a metal oxide gas sensor and promotes its wide application.

Phosphorescence approach based on silica protected carbon dots for autofluorescence interference-free and highly selective detection of fluoride.

BACKGROUND: Fluoride (F-), an anion with the smallest ionic radius and highest charge density, plays an important role in biomedical and environmental processes, making the development of accurate F- detection methods of great importance. Fluorometric methods with simplicity and sensitivity have gained considerable attention in F- detection. However, their accuracy faces challenges due to issues like autofluorescence interference during real-time light excitation and limited selectivity. Therefore, it is important to establish a simple, real-time light excitation-free, and highly selective method for the accurate determination of F- in complicated samples. RESULTS: Herein, a novel phosphorescent approach is developed for the selective and accurate detection of F- in complex samples. Phosphorescence emission CDs@SiO2 is fabricated by confining CDs in a silica protective layer. This design retains the favorable water solubility of silica while benefitting from its inertness, making it resistant to most substances. Furthermore, phosphorescent analysis without real-time light excitation eliminates autofluorescence interference, significantly improving the signal-to-noise ratio (SNR) and simplifying sample pretreatment. The specific interaction between F- and the Si-O bond can lead to the degradation of the silica protective layer, exposing the CDs to the solution, resulting in phosphorescence quenching, achieving the highly accurate and sensitive detection of F- with a linear range of 0.001-4 mM and a limit of detection (LOD) of 1 µM. SIGNIFICANCE: This novel F- phosphorescence method based on the metal-free phosphorescent nanomaterial CDs@SiO2 integrates the benefits of no autofluorescence interference, high selectivity, and full aqueous compatibility, and its combination with a smartphone provides a simple, portable, and cost-effective detection platform for accurate and highly sensitive determination of F- in complex samples.

Quaternization drives spleen-to-lung tropism conversion for mRNA-loaded lipid-like nanoassemblies.

Background: As the overwhelming majority of advanced mRNA delivery systems are preferentially accumulated in the liver, there is an accelerating growth in the demand for the development of non-liver mRNA delivery platforms. Methods: In this study, we prepared cationic lipid-like nanoassemblies through a N-quaternizing strategy. Their physicochemical properties, in vitro mRNA delivery efficiency, and organ tropism in mice were investigated. Results: Introduction of quaternary ammonium groups onto lipid-like nanoassemblies not only enhances their mRNA delivery performance in vitro, but also completely alters their tropism from the spleen to the lung after intravenous administration in mice. Quaternized lipid-like nanoassemblies exhibit ultra-high specificity to the lung and are predominantly taken up by pulmonary immune cells, leading to over 95% of exogenous mRNA translation in the lungs. Such mRNA delivery carriers are stable even after more than one-year storage at ambient temperature. Conclusions: Quaternization provides an alternative method for design of new lung-targeted mRNA delivery systems without incorporation of targeting ligands, which should extend the therapeutic applicability of mRNA to lung diseases.

Confinement Effect and 3D Design Endow Unsaturated Single Ni Atoms with Ultrahigh Stability and Selectivity toward CO2 Electroreduction.

Developing single-atomic catalysts with superior selectivity and outstanding stability for CO2 electroreduction is desperately required but still challenging. Herein, confinement strategy and three-dimensional (3D) nanoporous structure design strategy are combined to construct unsaturated single Ni sites (Ni-N3) stabilized by pyridinic N-rich interconnected carbon nanosheets. The confinement agent chitosan and its strong interaction with g-C3N4 nanosheet are effective for dispersing Ni and restraining their agglomeration during pyrolysis, resulting in ultrastable Ni single-atom catalyst. Due to the confinement effect and structure advantage, such designed catalyst exhibits a nearly 100% selectivity and remarkable stability for CO2 electroreduction to CO, exceeding most reported state-of-the-art catalysts. Specifically, the CO Faradaic efficiency (FECO) maintains above 90% over a broad potential range (-0.55 to -0.95 V vs. RHE) and reaches a maximum value of 99.6% at a relatively low potential of -0.67 V. More importantly, the FECO is kept above 95% within a long-term 100 h electrolyzing. Density functional theory (DFT) calculations explain the high selectivity for CO generation is due to the high energy barrier required for hydrogen evolution on the unsaturated Ni-N3. This work provides a new designing strategy for the construction of ultrastable and highly selective single-atom catalysts for efficient CO2 conversion.

Chemo- and Regioselective Catalytic Cross-Coupling Reaction of Ketones for the Synthesis of ß, γ-Disubstituted ß, γ-Unsaturated Ketones.

C-C bond forming reaction of ketone with aldehyde is well-studied for the synthesis of α, ß-unsaturated ketones, however, the reaction with two different ketones to unsaturated carbonyl compound has not yet been systematically studied. Probably due to the relatively low reactivity of ketones as electrophiles (aldol acceptors), its propensity for retro-aldol reaction. The reactions often suffer from unsatisfactory chemoselectivity (self- vs. crossed aldol products) and regioselectivity (thermodynamic vs. kinetic enolate). In this quest, we report here for the first time selective cross-coupling reaction of ketones to ß-branched ß, γ-unsaturated ketones by using ruthenium catalysis. Interestingly, single crossed aldol condensation products are formed even in reactions where a mixture of products is possible. Reaction is highly chemoselective, regioselective and produces H2 O as the only byproducts making the protocol environmentally benign. Method is compatible with a wide variety of sensitive functional group and applicable for even problematic aliphatic ketones as substrates. Notably, acetone was found as a three-carbon feedstock for the syntheses of simple ß, γ-unsaturated ketone compounds. The process can further be extended to the gram-scale reaction and late-stage functionalization of natural products. With the help of DFT calculations, several control experiments, and deuterium-labeling experiments, the mechanistic finding demonstrated that initial aldol-condensation of ketones to a ß, ß-disubstituted α, ß-unsaturated ketone, which further isomerizes to a ß, γ- unsaturated ketone via η3 -allyl ruthenium complex.

Implementation of a Wideband Microwave Filter Design with Dual Electromagnetic Interference (EMI) Mitigation for Modern Wireless Communication Systems with Low Insertion Loss and High Selectivity.

By leveraging the advantages of the uniform transmission line, this manuscript presents a broadband high-selectivity filter range starting from 2.5 GHz to 16.8 GHz, utilizing a simple uniform transmission line structure loaded with three-quarter-wavelength stubs. The proposed UWB filter is studied using the ABCD network parameter method. After that, a shorted T-shaped stub-loaded resonator is coupled with the transmission line of the UWB filter to obtain dual-notch features at 4.4 GHz (for long distance wireless ISPs (WISPs), 4G/5G operator for LTE backhaul) and 7.5 GHz (for X-band downlink communication). The overall footprint is specified as 22.5 mm × 12 mm or 1.12 λg × 0.6 λg, where λg represents the wavelength at the central frequency. The operating principle of such a filter is explained, and its controllable broadband response, as well as controllable stopband frequencies, are optimized to show some of the attractive features of the new scheme, such as a super wideband response of about a 148.18% fractional bandwidth; an out-of-band performance up to 25 GHz; five single-resonator transmission poles filtering behaviour at different frequencies, with highly reduced radiation losses greater than 10 dB; a simple topology; a flat group delay; a low insertion loss of 0.4 dB; and high selectivity. Additionally, the filter is fabricated and evaluated, and the results show a good match for experimental validation purposes.