Acrylate‐derived RAFT Polymers for Enzyme Hyperactivation – Boosting the α‐Chymotrypsin Enzyme Activity Using Tailor‐Made Poly(2‐Carboxyethyl)acrylate (PCEA)

Posted on by
Acrylate-derived RAFT Polymers for Enzyme Hyperactivation – Boosting the α-Chymotrypsin Enzyme Activity Using Tailor-Made Poly(2-Carboxyethyl)acrylate (PCEA)

We study the hyperactivation of α-chymotrypsin (α-ChT) here, using acrylate-derived PCEA polymer. Enzyme activity assays revealed a pronounced enzyme hyperactivation capacity being superior to widespread PAA polymers. In a combined experimental and computational study, we investigate α-ChT/polymer interactions to elucidate the hyperactivation mechanism.


Abstract

We study the hyperactivation of α-chymotrypsin (α-ChT) using the acrylate polymer poly(2-carboxyethyl) acrylate (PCEA) in comparison to the commonly used poly(acrylic acid) (PAA). The polymers are added during the enzymatic cleavage reaction of the substrate N-glycyl-L-phenylalanine p-nitroanilide (GPNA). Enzyme activity assays reveal a pronounced enzyme hyperactivation capacity of PCEA, which reaches up to 950 % activity enhancement, and is significantly enhanced to PAA (revealing an activity enhancement of approx. 450 %). In a combined experimental and computational study, we investigate α-ChT/polymer interactions to elucidate the hyperactivation mechanism of the enzyme. Isothermal titration calorimetry reveals a pronounced complexation between the polymer and the enzyme. Docking simulations reveal that binding of polymers significantly improves the binding affinity of GPNA to α-ChT. Notably, a higher binding affinity is found for the α-ChT/PCEA compared to the α-ChT/PAA complex. Further molecular dynamics (MD) simulations reveal changes in the size of the active site in the enzyme/polymer complexes, with PCEA inducing a more pronounced alteration compared to PAA, facilitating an easier access for the substrate to the active site of α-ChT.

Cyanide Bridged Framework Nanoplates Catalytic Interlayer for High Performance Zinc‐iodine Battery

Posted on by
Cyanide Bridged Framework Nanoplates Catalytic Interlayer for High Performance Zinc-iodine Battery

A novel CoNi(CN)4 nanosheets/CNT interlayer is designed to prevent shuttle effect by adsorption-catalysis process. The iodine species can be adsorbed and catalyzed on the dual-metal centers of the cyanide bridged coordination polymer. The zinc-iodine dual-plating battery with the interlayer shows impressive areal capacity of 3.6 mAh cm−2 with high cycle stability.


Abstract

Iodine is a promising candidate among the cathode materials in zinc-ion battery. However, iodine cathode suffers from serious shuttle effect by spontaneous generated polyiodide species. In this work, we developed a CoNi(CN)4/CNT interlayer to prevent shuttle effect by adsorption-catalysis process. The adsorption of the iodine species on CoNi(CN)4/CNT interlayer is justified by UV-vis spectroscopy and X-ray photoelectron spectroscopy, where the concentration of polyiodides is significantly reduced, and the binding energy of cobalt, nickel, and nitrogen is remarkably reduced by binding with polyiodides. The zinc-iodine dual-plating battery shows significantly higher areal capacity and cycle stability with CoNi(CN)4/CNT. Moreover, battery with impressive areal capacity of 3.6 mAh cm−2 and negligible fading over 100 cycles is also achieved, which outperforms state-of the art literatures on zinc-iodine batteries.

Transition‐Metal Catalyzed C−H Alkylation Using Epoxides as Alkylating Reagents

Posted on by
Transition-Metal Catalyzed C−H Alkylation Using Epoxides as Alkylating Reagents

This review highlights the recent advances in utilizing epoxides as alkylating reagents in transition-metal-catalyzed C−H alkylation, along with its associated synthetic applications in organic synthesis.


Abstract

The alkylation of arenes is one of the most fundamental transformations in synthetic chemistry and the transition-metal-catalyzed direct C−H alkylation represents a straightforward and attractive approach from both atom and step-economy perspectives. Epoxides, the smallest three-membered saturated O-heterocycles that can be easily prepared in racemic or enantioenriched forms, are highly useful building blocks for the synthesis of complex organic molecules. Owing to their inherent high ring-strain, epoxides readily undergo ring-opening reactions and have been used as alkylating reagents for C−H alkylation catalyzed by transition metals. This review summarizes recent advances in utilizing epoxides as alkylating reagents in transition-metal-catalyzed C−H alkylation as well as their synthetic applications in organic synthesis.

Atropisomeric N‐Heterocyclic Carbene‐Palladium(II) Complexes: Influence of the Backbone Substitution

Posted on by
Atropisomeric N-Heterocyclic Carbene-Palladium(II) Complexes: Influence of the Backbone Substitution

The influence of the NHC backbone substitution was investigated for palladium-NHC complexes containing axial chirality. The two new series of atropisomeric Pd(NHC) complexes enabled the introduction of bulky moieties as ortho substituents of N-aryl groups. After resolution by chiral HPLC at preparative scale, enantiopure complexes successfully catalyzed the α-arylation of amides (up 96 % ee).


Abstract

In order to facilitate the synthesis of NHC precursors as well as to incorporate new moieties, the influence of the NHC backbone substitution was investigated within the concept of atropisomeric NHC-metal complexes. A series of NHC precursors was prepared from new anilines and used to synthesize the corresponding Pd(allyl)Cl(NHC) complexes, most of the time as a mixture of diastereomers (meso and chiral). Chiral HPLC at preparative scale enabled to obtain enantiopure complexes in low to excellent yields. These complexes displayed good activity in the intramolecular α-arylation of amides and, as a function of the structure of the chiral catalyst, excellent enantioselectivities were reached (up to 96 % ee).

Unleashing the Potential of Boron Nitride Spheres for High‐Performance Thermal Management

Posted on by
Unleashing the Potential of Boron Nitride Spheres for High-Performance Thermal Management

The thermal conductivity of micro-sized boron nitride spheres (BNSs), which is challenging to measure directly, was approximated to be that of the BNS pellet in the cross-plane direction, measured by laser flash method. BNSs exhibit a high, isotropic thermal conductivity of 37.2±2.5 W m−1 K−1 and outperform h-BN pellets in heat dissipation for LED lights due to the isotropic structures.


Abstract

Highly integrated and miniaturized electronic devices require advanced thermal management techniques to improve reliability and performance. Thanks to their high thermal conductivity and electrical insulation, boron nitride nanosheets (BNNSs) are commomly used as fillers to construct thermally conductive polymer composites for heat dissipation. However, the BNNS reinforced composites exhibit anisotropic thermal conductivity due to the anisotropic structure of BNNSs. Micro-sized boron nitride spheres (BNSs) with isotropic thermal conductivity are considered one of the best solutions. Nevertheless, precisely measuring the thermal conductivity of BNSs remains a challenge, limiting the understanding of the thermal transport mechanism. Herein, we have successfully estimated the thermal conductivity of BNSs using the laser flash method. Factors influencing BNSs’ thermal conductivity, including precursor, polymer binder and sintering temperature, are also investigated. Under optimized conditions, BNSs exhibit high, isotropic thermal conductivity of 37.2±2.5 W/(m ⋅ K), and the BNS pellet outperforms its h-BN counterpart in heat dissipation for an LED light. This superiority is attributed to outstanding heat transfer performance in the cross-plane direction, in addition to high in-plane thermal conductivity. This study provides a feasible method to estimate the thermal conductivity of spherical materials and highlights promising boron nitride materials with isotropic thermal conductivity for heat dissipation in advanced electronics.

Multi‐electron Oxidation of Ce(III) Complexes Facilitated by Redox‐Active Ligands

Posted on by
Multi-electron Oxidation of Ce(III) Complexes Facilitated by Redox-Active Ligands

Cerium(III) complexes with redox-active ligands in oxidation states L1− and L2− have been synthesized and fully characterized. Multielectron movement has been achieved by redox chemistry at the ligands. Sequestering counterions also introduces exciting reactivity, forming Ce(IV) species with dioxygen and oxidative addition of hexamethyldisiloxane to form a bis(siloxide) cerium(IV) species.


Abstract

A family of cerium complexes featuring a redox-active ligand in different oxidation states has been synthesized, including the the iminosemiquinone (isq)1− compound, Ce(dippisq)3 (1-Ceisq), and the amidophenolate (ap)2− species CeIII(dippap)3K3 (2-Ceap), [CeIII(dippap)3K][K(18-c-6)]2 (2-Ceap 18c6), and [CeIII(dippap)3K][K(15-c-5)2]2 (2-Ceap 15c5). Treating 2-Ceap 15c5 with dioxogen furnishes the cerium(IV) derivative [CeIV(dippap)3][K(15-c-5)2]2 (3-Ceap 15c5), and an analogous synthesis can be used to generate [CeIV(dippap)3][K(crypt)]2 (3-Ceap crypt). Similarly, addition of hexamethyldisiloxane produces an interesting bis(amidophenolate) species, [(Me3SiO)2CeIV(dippap)2][K(15-c-5)2]2 (4-CeOSiMe3 ). Full spectroscopic and structural characterization of each derivative was performed to establish the oxidation states of both the ligands and the cerium ions.

Transition Metal‐Cross‐Linked‐Starch Aerogel‐Derived Porous Carbon‐Based Monolithic Chainmail Electrodes for High‐Current‐Density and Durable Alkaline Water Splitting

Posted on by

A porous carbon-based monolithic chainmail electrode, namely Co2P@CSA, is fabricated via direct carbonization of Co2+-cross-linked-starch aerogel (Co2+-SA) followed by low-temperature vapor phosphorization. During successive carbonization-phosphorization, the SA framework is formulated into 3D hierarchically porous carbon membrane matrix comprising hollow open carbon microspheres while the cross-linked Co species are converted into uniformly distributed carbon-encapsulated Co2P nanoparticles on carbon microspheres. Thanks to the high porosity, excellent electrolyte wettability, unique chainmail structure, and good mechanical strength, the monolithic Co2P@CSA can be directly used as a binder-free bifunctional electrocatalyst for alkaline water splitting, and it can afford a high current density of 100 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at low overpotentials of 140.0 and 305.5 mV, respectively, with outstanding stability at 50 mA cm-2 for >30 h. More significantly, an alkaline electrolyzer assembled using Co2P@CSA achieves a current density of 100 mA cm-2 for overall water splitting (OWS) at a cell voltage of 1.94 V with unit Faradaic efficiency and provides a high solar-to-hydrogen (STH) conversion efficiency of 13.4 % when driven by a commercial silicon solar cell. This work offers an effective strategy towards cost-effective fabrication of high-performance carbon-based monolithic chainmail electrocatalysts for energy conversion reactions.

Dual‐Emissive Iridium(III) Complexes and Their Applications in Biological Sensing and Imaging

Posted on by

Phosphorescent iridium(III) complexes are widely recognized for their unique properties in the excited triplet state, making them crucial for various applications including biological sensing and imaging. Most of these complexes display single phosphorescence emission from the lowest-lying triplet state after undergoing highly efficient intersystem crossing (ISC) and ultrafast internal conversion (IC) processes. However, in cases where these excited-state processes are restricted, the less common phenomenon of dual emission has been observed. This dual emission phenomenon presents an opportunity for developing biological probes and imaging agents with multiple emission bands of different wavelengths. Compared to intensity-based biosensing, where the existence and concentration of an analyte are indicated by the brightness of the probe, the emission profile response involves modifications in emission color. This enables quantification by utilizing the intensity ratio of different wavelengths, which is self-calibrating and unaffected by the probe concentration and excitation laser power. Moreover, dual-emissive probes have the potential to demonstrate distinct responses to multiple analytes at separate wavelengths, providing orthogonal detection capabilities. In this concept, we focus on iridium(III) complexes displaying fluorescence-phosphorescence or phosphorescence-phosphorescence dual emission, along with their applications as biological probes for sensing and imaging.

Co doping induced phase transition and its distinct effects on the catalytic performance of MnO2 toward toluene oxidation

Posted on by
Co doping induced phase transition and its distinct effects on the catalytic performance of MnO2 toward toluene oxidation

In this work, Co was selected to modify the structure of MnO2, which forced the catalyst to transform from α-MnO2 to spinel phase CoMn2O4. During this process, the metal–oxygen bonds were significantly weakened, inducing the massive generation of oxygen defects. As a result, the redox property and ability to adsorb and activate gaseous oxygen of Co modified catalysts was significantly enhanced, endowing the Co doped catalysts with strongly improved catalytic performance.


Manganese oxides are very important and conventional catalysts that have demonstrated appreciable catalytic activity for the oxidation of volatile organic compounds (VOCs). Nevertheless, pure manganese oxides suffer from poor activity especially at low temperatures, making it difficult to meet industrial applications. In this work, Co species were successfully doped into the lattice of MnO2 aiming at constructing defects to boost its catalytic performance for VOCs oxidation. In combination with the results of systematic characterizations, we found that Co doping forced the catalyst to transform from α-MnO2 to spinel phase (Co,Mn)(Co,Mn)2O4. During this process, the metal–oxygen bonds are significantly weakened, which induces the massive generation of oxygen defects, endowing the Co modified catalysts with enhanced redox property and improved ability to adsorb and activate gaseous oxygen. As a result, Co doped catalysts show much better catalytic activity compared with pristine α-MnO2, among which Mn10Co10 exhibits the best performance showing a decrease of 41°C and 51°C in T 50 and T 90 compared with the raw sample, respectively. Furthermore, Mn10Co10 demonstrates excellent stability, water resistance, and reusability, illustrating a great potential for industrial applications. Moreover, path of toluene decomposition over Co10Mn10 was revealed by in situ DRIFTS experiment, which complies with the sequence of toluene → benzyl alcohol → benzaldehyde → benzoate → maleic anhydride → CO2 and H2O.

Modified electrodes: Utilizing Cu‐modified graphene oxide nanosheets as a cathode in electro‐oxidation synthesis of mild Suzuki–Miyaura cross‐coupling reaction under green and sustainable conditions

Posted on by
Modified electrodes: Utilizing Cu-modified graphene oxide nanosheets as a cathode in electro-oxidation synthesis of mild Suzuki–Miyaura cross-coupling reaction under green and sustainable conditions

This study focuses on utilizing copper-modified graphene oxide nanosheets as a cathode for the electro-oxidation synthesis of mild Suzuki–Miyaura cross-coupling reactions. The research emphasizes environmentally conscious and sustainable conditions for electrochemical processes. By exploring copper-modified graphene oxide as a catalyst, the study aims to enhance catalytic efficiency, offering insights into eco-friendly approaches for cross-coupling reactions in organic synthesis.


This study presents an eco-conscious approach to enhance the efficiency of the Suzuki–Miyaura cross-coupling reaction. We first synthesized graphene oxide nanosheets using the Hummers method and then coated them to incorporate metallic copper on their surface. Following this, we conducted various analyses, including Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) analysis, cyclic voltammetry (CV), and energy-dispersive X-ray spectroscopy (EDS) identification, to characterize these modified nanosheets. Subsequently, we utilized Cu-modified graphene oxide nanosheets as cathode catalysts in an electro-oxidation synthesis setup. To verify the effectiveness of this novel approach, we utilized bromobenzene and phenylboronic acid as model substrates to synthesize biphenyl compounds. The reaction yielded impressive product yields ranging from 87% to 93%. Operating under environmentally friendly conditions, this electro-oxidation synthesis not only enhances selectivity but also significantly reduces the environmental impact of the reaction. Our findings highlight the potential of this green chemistry strategy, offering a promising avenue for sustainable and efficient organic synthesis, as evidenced by the successful coupling of bromobenzene and phenylboronic acid with consistently high yields.