Shahriar Al Hossain

Conductive polymers for next-generation energy storage systems: recent progress and new functions

Conductive polymers are attractive organic materials for future high-throughput energy storage applications due to their controllable resistance over a wide range, cost-effectiveness, high conductivity (>103 S cm−1), light weight, flexibility, and excellent electrochemical properties. In particular, conductive polymers can be directly incorporated into energy storage active materials, which are essential for building advanced energy storage systems (ESSs) (i.e. supercapacitors and rechargeable batteries). This review summarizes the synthesis of conductive polymers with different chemical structures in various ways and also addresses their widespread applications for a broader range of ESSs. Moreover, we introduce recent progress in ESS development, including new electroactive polymers, new approaches (i.e. flexible, stretchable, binder-free, hybrid, etc.), and new functions (e.g. color changeable electrochromic materials for displays).

All-in-one energy harvesting and storage devices

Currently, integration of energy harvesting and storage devices is considered to be one of the most important energy-related technologies due to the possibility of replacing batteries or at least extending the lifetime of a battery. This review aims to describe current progress in the various types of energy harvesters, hybrid energy harvesters, including multi-type energy harvesters with coupling of multiple energy sources, and hybridization of energy harvesters and energy storage devices for self-powered electronics. We summarize research on recent energy harvesters based on the piezoelectric, triboelectric, pyroelectric, thermoelectric, and photovoltaic effects. We also cover hybrid cell technologies to simultaneously generate electricity using multiple types of environmental energy, such as mechanical, thermal, and solar energy. Energy harvesters based on the coupling of multiple energy sources exhibit enhancement of power generation performance with synergetic effects. Finally, integration of energy harvesters and energy storage devices is introduced. In particular, self-charging power cells provide an innovative approach to the direct conversion of mechanical energy into electrochemical energy to decrease energy conversion loss.

Towards Vaporized Molecular Discrimination: A Quartz Crystal Microbalance (QCM) Sensor System Using Cobalt-Containing Mesoporous Graphitic Carbon

A recent study on nanoporous carbon based materials (J. Am. Chem. Soc. 2012, 134, 2864) showed that the presence of abundant graphitized sp(2) carbon species in the frameworks led to higher affinity for aromatic hydrocarbons than their aliphatic analogues. Herein, improved understanding of the sensitive and selective detection of aromatic substances by using mesoporous carbon (MPC)-based materials, combined with a quartz crystal microbalance (QCM) sensor system, was obtained. MPCs were synthesized by direct carbonization of mesoporous polymers prepared from resol through a soft templating approach with Pluronic F127. The carbon-based frameworks can be graphitized through the addition of a cobalt source to the precursor solution, according to the catalytic activity of the cobalt nanoparticles formed during the carbonization process. From the Raman data, the degree of the graphitization was clearly increased by increasing the cobalt content and elevating the carbonization temperature. From a QCM study, it was proved that the highly graphitized MPCs exhibited a higher affinity for aromatic hydrocarbons than their aliphatic analogues. By increasing the degree of graphitization in the carbon-based pore walls, the MPCs showed both larger adsorption uptake and faster sensor response towards toxic benzene and toluene vapors.

Fabrication of an MOF-derived heteroatom-doped Co/CoO/carbon hybrid with superior sodium storage performance for sodium-ion batteries

Metal–organic frameworks (MOFs) have gained significant attention as precursors for the fabrication of porous hybrid materials due to their highly controllable composition, structure and pore size. However, at present, MOF-derived materials have rarely been investigated as anode materials for sodium-ion batteries. In this work, we report the fabrication of a Ni-doped Co/CoO/N-doped carbon (NC) hybrid using bimetallic Ni–Co-ZIF as the starting precursor. The resulting Ni-doped Co/CoO/NC hybrid is highly microporous with a high specific surface area of 552 m2 g−1. When employed as an anode material for sodium-ion batteries, the Ni-doped Co/CoO/NC hybrid exhibited both good rate performance with a high discharge capacity of 218 mA h g−1 at a high current density of 500 mA g−1 and good cycling stability, as a high discharge capacity of 218.7 mA h g−1 can be retained after 100 cycles at 500 mA g−1, corresponding to a high capacity retention of 87.5%. The excellent electrochemical performance of the Ni-doped Co/CoO/NC hybrid for SIBs may be attributed to the synergistic effects of various factors, including: (i) the presence of a carbon matrix which provides protection against aggregation and pulverization during sodiation/desodiation; (ii) the highly microporous nature along with the presence of a few mesopores which facilitates better insertion/de-insertion of Na+ ions; (iii) the Ni-doping which introduces defect sites into the atomic structure of CoO via partial substitution, thus enhancing the conductivity of the cobalt oxide (CoO) component and hence, the overall hybrid material, and (iv) the N-doping which promotes a faster migration speed of sodium ions (Na+) across the carbon layer by creating defect sites, thereby improving the conductivity of the carbon frameworks in the hybrid material.

Facile potentiostatic preparation of functionalized polyterthiophene-anchored graphene oxide as a metal-free electrocatalyst for the oxygen reduction reaction

The development of new catalysts for high-performance, cost-effective oxygen reduction is crucial in the commercialization of fuel cells. We demonstrate here the use of functionalized polyterthiophene-anchored graphene oxide (GO) composites as new non-metal catalysts for the oxygen reduction reaction. Different functional groups containing the monomers 3′-(2-aminopyrimidyl)-2,2′:5′,2′′-terthiophene (APT), 3′-(p-benzoic acid)-2,2′:5′,2′′-terthiophene (TBA) and 3′-(carboxylic acid)-2,2′:5′,2′′-terthiophene (TCA) were synthesized and polymerized with as-prepared GO to form complexes by a potential cycling method. The aminopyrimidyl groups on the poly(APT) backbone served as effective functional groups in the oxygen reduction reaction. The APT–GO complex was formed through hydrogen bonding and a ring-opening reaction of the epoxide group with the amine to form a new C–N bond. It was observed that the C–N bond in the polymer matrix was involved in the direct electrocatalytic reduction of O2 to H2O. The poly(APT–GO) composite showed much better tolerance to fuel cross-over and long-term electrode stability than commercially available Pt/C electrodes.

Electrochemical biosensing strategies for DNA methylation analysis

DNA methylation is one of the key epigenetic modifications of DNA that results from the enzymatic addition of a methyl group at the fifth carbon of the cytosine base. It plays a crucial role in cellular development, genomic stability and gene expression. Aberrant DNA methylation is responsible for the pathogenesis of many diseases including cancers. Over the past several decades, many methodologies have been developed to detect DNA methylation. These methodologies range from classical molecular biology and optical approaches, such as bisulfite sequencing, microarrays, quantitative real-time PCR, colorimetry, Raman spectroscopy to the more recent electrochemical approaches. Among these, electrochemical approaches offer sensitive, simple, specific, rapid, and cost-effective analysis of DNA methylation. Additionally, electrochemical methods are highly amenable to miniaturization and possess the potential to be multiplexed. In recent years, several reviews have provided information on the detection strategies of DNA methylation. However, to date, there is no comprehensive evaluation of electrochemical DNA methylation detection strategies. Herein, we address the recent developments of electrochemical DNA methylation detection approaches. Furthermore, we highlight the major technical and biological challenges involved in these strategies and provide suggestions for the future direction of this important field.

Evaluation of persistent-mode operation in a superconducting MgB2 coil in solid nitrogen

We report the fabrication of a magnesium diboride (MgB2) coil and evaluate its persistent-mode operation in a system cooled by a cryocooler with solid nitrogen (SN2) as a cooling medium. The main purpose of SN2 was to increase enthalpy of the cold mass. For this work, an in situ processed carbon-doped MgB2 wire was used. The coil was wound on a stainless steel former in a single layer (22 turns), with an inner diameter of 109 mm and height of 20 mm without any insulation. The two ends of the coil were then joined to make a persistent-current switch to obtain the persistent-current mode. After a heat treatment, the whole coil was installed in the SN2 chamber. During operation, the resultant total circuit resistance was estimated to be <7.4 × 10−14 Ω at 19.5 K ± 1.5 K, which meets the technical requirement for magnetic resonance imaging application.

A new generation of in situ MgB2 wires with improved Jc and Birr values obtained by cold densification (CHPD)

By means of Cold High Pressure Densification (CHPD), the critical current density, <i>J</i>_c, of binary and alloyed MgB₂ wires has been enhanced by more than a factor 2 at 4.2 K and at fields up to 19 T. The relative MgB₂ mass density of binary MgB₂ wires was enhanced to ~ 54% after applying 2.5 GPa at 300 K before reaction. In C₄H₆O₅ (malic acid) alloyed wires, densification also caused the enhancement of <i>B</i>_irr, as a consequence of a slightly enhanced C content, determined by X ray diffraction. Almost isotropic <i>J</i>_c values were obtained for C₄H₆O₅ added wires of 1 × 0.6 mm² cross section, the values of <i>J</i>_c(4.2 K)=1 × 10⁴ A/cm² for parallel and perpendicular fields being obtained at 13.8 and 13.4 T, respectively (1 μV/cm criterion). The corresponding values for 20 K were both close to 6.2 T. The value of <i>B</i>_irr^// at 20 K was 11 T. The positive effects of cold densification on J_c and <i>B</i>_irr on MgB₂ was also observed on 150 mm long wires alloyed with C₄H₆O₅ (malic acid) or with SiC, by the succession of 6 overlapping pressure steps. This process can be extended to long wire lengths: by means of a newly developed prototype machine with an automatic press/release/advance sequence, a first wire length of 1 m was densified at 1.5 GPa, yielding J_c(4.2 K) = 1 x 10⁴ A/cm² at 13.1 T. Further improvements are expected after optimization.

MgB2 superconducting joints for persistent current operation

High-performance superconducting joints are essential for realizing persistent-mode magnets. Herein, we propose a concept and fabrication of such superconducting joints, which yielded reliable performance in the operating temperature range of 4.2–25 K. MgB2–MgB2 joints in magnets are known to result in deterioration of localized electrical, thermal, and mechanical properties. To overcome these problems, the ends of the two wires are inserted into a pellet press, which is then filled with a mixture of unreacted magnesium and boron powders, followed by heat treatment. The critical current capacity and joint resistance were precisely evaluated by the standard four-probe method in open-circuit and by field-decay measurements in a closed-loop, respectively. These joints demonstrated up to 66% of the current-carrying capacity of unjoined wire at 20 K, 2 T and joint resistance of 1.4 × 10−12 Ω at 4.2 K in self-field.

Direct Production of Furfural in One-pot Fashion from Raw Biomass Using Brønsted Acidic Ionic Liquids

The conversion of raw biomass into C5-sugars and furfural was demonstrated with the one-pot method using Brønsted acidic ionic liquids (BAILs) without any mineral acids or metal halides. Various BAILs were synthesized and characterized using NMR, FT-IR, TGA, and CHNS microanalysis and were used as the catalyst for raw biomass conversion. The remarkably high yield (i.e. 88%) of C5 sugars from bagasse can be obtained using 1-methyl-3(3-sulfopropyl)-imidazolium hydrogen sulfate ([C3SO3HMIM][HSO4]) BAIL catalyst in a water medium. Similarly, the [C3SO3HMIM][HSO4] BAIL also converts the bagasse into furfural with very high yield (73%) in one-pot method using a water/toluene biphasic solvent system.