Molecular Cooperative Assembly-Mediated Synthesis of Ultra-High-Performance Hard Carbon Anodes for Dual-Carbon Sodium Hybrid Capacitors

Although sodium hybrid capacitors (NHCs) have emerged as one of the most promising next-generation energy storage systems, further advancement is delayed primarily by the absence of high-performance battery-type anodes. Herein, we report a nature-inspired synthesis route to prepare hard carbon anodes with high capacity, rate capability, and cycle stability for dual-carbon NHCs. Shape- and size-controllable crystal aggregates of inexpensive triazine molecules are utilized as reactive templates that perform triple duties of structure-directing agent, porogen, and nitrogen source. This enables the fine control of microstructure/morphology/composition and thereby electrochemical reactions toward Na-ion. The resulting hard carbon optimized in terms of lateral size, interlayer spacing, and surface affinity of graphene-like layers achieves a specific capacity of ∼380 mAh/g after 100 cycles at a current density of 250 mA/g mainly via intercalation, the current record of hard carbons. Combined with a commercial microporous carbon fiber cathode, the full cell is able to deliver a volumetric energy density of 2.89 mWh/cm3 and a volumetric power density of 160 mW/cm3, outperforming NHCs based on inorganic Na-ion anode materials. More importantly, such performance could not only be retained for 10000 cycles (4.5 F/cm3 at 10 mA/cm3) with 0.000 028 6% loss per cycle at >97% Coulombic efficiency but also successfully transferred to flexible pouch cells without significant performance loss after 300 bending cycles or during wrapping at a 10R condition. Simple preparation of hard carbon anodes using organic crystal reactive templates, therefore, demonstrates great potential for the manufacture of high-performance flexible NHCs using only carbon electrode materials

Surface-Enhanced Raman Scattering Based Ligase Detection Reaction

Genomics provides a comprehensive view of the complete genetic makeup of an organism. Individual sequence variations, as manifested by single nucleotide polymorphisms (SNPs), can provide insight into the basis for a large number of phenotypes and diseases including cancer. The ability rapidly screen for SNPs will have a profound impact on a number of applications, most notably personalized medicine. Here we demonstrate a new approach to SNP detection through the application of surface-enhanced Raman scattering (SERS) to the ligase detection reaction (LDR). The reaction uses two LDR primers, one of which contains a Raman enhancer and the other a reporter dye. In LDR, one of the primers is designed to interrogate the SNP. When the SNP being interrogated matches the discriminating primer sequence, the primers are ligated and the enhancer and dye are brought into close proximity enabling the dye’s Raman signature to be detected. By detecting the Raman signature of the dye rather than its fluorescence emission, our technique avoids the problem of spectral overlap which limits number of reactions which can be carried out in parallel by existing systems. We demonstrate the LDR-SERS reaction for the detection of point mutations in the human K-ras oncogene. The reaction is implemented in an electrokinetically active microfluidic device that enables physical concentration of the reaction products for enhanced detection sensitivity and quantization. We report a limit of detection of 20 pM of target DNA with the anticipated specificity engendered by the LDR platform

Palladium Supported on an Amphiphilic Triazine–Urea-Functionalized Porous Organic Polymer as a Highly Efficient Electrocatalyst for Electrochemical Sensing of Rutin in Human Plasma

Metal nanoparticle-containing porous organic polymers have gained great interest in chemical and pharmaceutical applications owing to their high reactivity and good recyclability. In the present work, a palladium nanoparticle-decorated triazine–urea-based porous organic polymer (Pd@TU-POP) was designed and synthesized using 1,3-bis­(4-aminophenyl)­urea with cyanuric chloride and palladium acetate. The porous structure and physicochemical properties of the electrode material Pd@TU-POP were observed using a range of standard techniques. The Pd@TU-POP material on the electrode surface showed superior sensing ability for rutin (RT) because the Pd dispersion facilitated the electrocatalytic performance of TU-POP by reducing the overpotential of RT oxidation dramatically and improving the stability significantly. Furthermore, TU-POP provides excellent structural features for loading Pd nanoparticles, and the resulting Pd@TU-POP exhibited enhanced electron transfer and outstanding sensing capability in a linear range between 2 and 200 pM having a low detection value of 5.92 × 10–12 M (S/N = 3). The abundant porous structure of Pd@TU-POP not only provides electron transport channels for RT diffusion but also offers a facile route for quantification sensing of RT with satisfactory recoveries in aqueous electrolyte containing human plasma and red wine. These data reveal that the synthetic Pd@TU-POP is an excellent potential platform for the detection of RT in biological samples

3D Macroporous Graphene Frameworks for Supercapacitors with High Energy and Power Densities

In order to develop energy storage devices with high power and energy densities, electrodes should hold well-defined pathways for efficient ionic and electronic transport. Herein, we demonstrate high-performance supercapacitors by building a three-dimensional (3D) macroporous structure that consists of chemically modified graphene (CMG). These 3D macroporous electrodes, namely, embossed-CMG (e-CMG) films, were fabricated by using polystyrene colloidal particles as a sacrificial template. Furthermore, for further capacitance boost, a thin layer of MnO₂ was additionally deposited onto e-CMG. The porous graphene structure with a large surface area facilitates fast ionic transport within the electrode while preserving decent electronic conductivity and thus endows MnO₂/e-CMG composite electrodes with excellent electrochemical properties such as a specific capacitance of 389 F/g at 1 A/g and 97.7% capacitance retention upon a current increase to 35 A/g. Moreover, when the MnO₂/e-CMG composite electrode was asymmetrically assembled with an e-CMG electrode, the assembled full cell shows remarkable cell performance: energy density of 44 Wh/kg, power density of 25 kW/kg, and excellent cycle life

Tweaking Behavior of Hydrogen Bond Donor in Choline Chloride-Based Deep Eutectic Solvents for Regulating the Phase Transition of Poly(<i>N</i>‑vinylcaprolactam): A Sustainable Medium for an Early Hydrophobic Collapse

Deep eutectic solvents (DESs) are recognized as a “green” alternative to conventional ionic liquids and organic solvents owing to their specific properties. In this study, the influence of DESs containing choline chloride (ChCl) as a hydrogen bond acceptor (HBA) and urea, ethylene glycol (EG), and lactic acid (LA) as hydrogen bond donors (HBD) on the thermoresponsive behavior of poly­(N-vinylcaprolactam) (PVCL) is investigated using various techniques. Spectroscopic investigations indicate biased interactions of the HBD group present in the DESs with a hydration layer of PVCL. Dynamic light scattering and temperature-dependent fluorescence spectroscopy results clearly show a decrease in the lower critical solution temperature of PVCL in the presence of the DESs. The hydrophobic collapse of PVCL in the presence of the DESs follows the order ChCl:urea > ChCl:EG > ChCl:LA. It is proposed that the presence of DESs does not interfere with the functional groups present in PVCL; however, it ruptures the hydrogen bonding between PVCL and the water molecules and destabilizes the water gradient around PVCL. The DESs have provided an alternative platform for low-temperature dehydration of PVCL, which can be useful as a drug carrier agent

On-site detection of sub-mg/kg melamine mixed in powdered infant formula and chocolate using sharp-edged gold nanostar substrates

<p>We report a facile method for sample preparation and sensitive on-site detection of melamine in powdered infant formula and chocolate using Raman spectroscopy on sharp-edged gold nanostars (AuNSs). The aggregation of AuNSs by sodium chloride (1.2 M) facilitates the more sensitive detection of melamine in comparison with spherical gold nanoparticles (AuNPs). Density functional theory quantum mechanical calculations were performed to determine the energetic stability on gold cluster atoms. Our spectroscopic data indicated that AuNSs are an efficient platform for detecting melamine in food mixtures. The detection limits of melamine in powdered infant formula and chocolate were found to be ~0.1 mg/kg and ~1 mg/kg respectively on AuNPs, whereas they were observed to be ~0.01 mg/kg and ~0.1 mg/kg respectively on AuNSs,. Using a hand-held Raman spectrometer, a sub-mg/kg detection of melamine in both powdered infant formula and chocolate could be achieved within a few minutes.</p

Green Diacetoxylation of Alkenes in a Microchemical System

The palladium-catalyzed diacetoxylation and trifluoromethanesulfonic acid-catalyzed diacetoxylation using inexpensive and environmentally friendly hydrogen peroxide and peracetic acid were successfully conducted with the help of microchemical technology. Excellent yield and selectivity were achieved in significantly shortened reaction times without the decomposition of explosive oxidants and further transformation of unstable products, offering a safe and efficient alternative to traditional methods for alkene diacetoxylation

Temperature-Switchable Polymer: Uniting Deep Eutectic Solvents with Poly(<i>N</i>‑isopropylacrylamide) and Poly(<i>N</i>‑vinyl caprolactam)

As analogs of ionic liquids (ILs), deep eutectic solvents (DESs) have attracted considerable attention as benign liquid formulations in the fabrication of polymeric materials because of the numerous advantages and functionalities of these liquid formulations, along with their ability to satisfy the principle of sustainability. Herein, the effectiveness of choline chloride (ChCl)-based DESs as a cosolvent was studied in the development of a versatile platform for regulating the thermal behavior of poly­(N-isopropylacrylamide) (PNIPAM) solutions. The hydrogen bond donor (HBD) groups in DESs selectively influence the dehydration mechanism of PNIPAM. UV–visible spectroscopy, steady-state fluorescence, Fourier transform infrared spectroscopy (FTIR), and dynamic light scattering (DLS) analyses demonstrated the predisposition of HBD groups toward complex hydration network around PNIPAM. Furthermore, the lower critical solution temperature (LCST) was investigated using temperature-dependent fluorescence spectroscopy, demonstrating a decrease in the LCST of PNIPAM in the presence of DESs. The LCST declined most steeply in the presence of choline chloride/lactic acid (ChCl/LA), whereas only negligible variations were observed for choline chloride/urea (ChCl/urea) and choline chloride/ethylene glycol (ChCl/EG). PNIPAM and poly­(N-vinyl caprolactam) (PVCL) were compared to understand the unique molecular interactions of DESs, which clarified the involvement of eutectic solvents in altering hydrogen bonding between the polymers and surrounding water molecules. Disruption of the hydrogen bond interactions resulted in early hydrophobic collapse of the polymers. Moreover, this change depended on the nature of the HBD groups in the DESs. This study highlights the fundamental spectroscopic insights of thermoresponsive polymers in sustainable eutectic solvents for potential use as pulsatile drug carriers

Electrochemical Sensors Based on Au-ZnS Hybrid Nanorods with Au-Mediated Efficient Electron Relay

Development of a novel and stable electrochemical sensor electrode for the sensitive and reliable determination of p-nitrophenol (p-NP) is of great importance to environment. In the present work, electrocatalysts of Au/ZnS hybrid nanorods were prepared via a facile photoassisted reduction process for an efficient detection of p-NP. The microscopic analysis revealed the uniform adherence of Au onto ZnS nanorods. As-fabricated AZS nanorods were evaluated for the efficient sensing of p-NP by modifying a glassy carbon electrode (GCE). The cyclic voltammetry analysis revealed the unique oxidative sensing ability of AZS for p-NP at 0.14 V with a low ΔEp (118 mV) when compared to that of bare GCE. On the basis of the notable sensing ability of AZS, a reliable and sensitive electrochemical method was anticipated for the determination of p-NP. Moreover, the effects of scan rate and pH level were examined to find out the optimized conditions at which there were a higher sensitivity and low detection limit. At optimal conditions, the p-NP oxidation current was found to follow linear relationships in the concentration range of 150–2000 nM, and the lowest detection limit for p-NP was obtained for 8AZS with a value of 320 nM and a signal-to-noise ratio of 3. The proposed electrochemical method was further evaluated in the presence of other inorganic cations and anions, and it was found that the interference was almost negligible. The real sample analyses confirmed the acceptable recovery levels