Hatem R. Alamri

Tailored Design of Bicontinuous Gyroid Mesoporous Carbon and Nitrogen-Doped Carbon from Poly(ethylene oxide-b-caprolactone) Diblock Copolymers

Highly ordered mesoporous resol-type phenolic resin and the corresponding mesoporous carbon materials were synthesized by using poly(ethylene oxide-b-caprolactone) (PEO-b-PCL) diblock copolymer as a soft template. The self-assembled mesoporous phenolic resin was found to form only in a specific resol concentration range of 40-70u2005wtu2009% due to an intriguing balance of hydrogen-bonding interactions in the resol/PEO-b-PCL mixtures. Furthermore, morphological transitions of the mesostructures from disordered to gyroid to cylindrical and finally to disordered micelle structure were observed with increasing resol concentration. By calcination under nitrogen atmosphere at 800u2009°C, the bicontinuous mesostructured gyroid phenolic resin could be converted to mesoporous carbon with large pore size without collapse of the original mesostructure. Furthermore, post-treatment of the mesoporous gyroid phenolic resin with melamine gave rise to N-doped mesoporous carbon with unique electronic properties for realizing high CO2 adsorption capacity (6.72u2005mmolu2009g-1 at 0u2009°C).

Gold-Loaded Nanoporous Ferric Oxide Nanocubes with Peroxidase-Mimicking Activity for Electrocatalytic and Colorimetric Detection of Autoantibody

The enzyme-mimicking activity of iron oxide based nanostructures has provided a significant advantage in developing advanced molecular sensors for biomedical and environmental applications. Herein, we introduce the horseradish peroxidase (HRP)-like activity of gold-loaded nanoporous ferric oxide nanocubes (Au-NPFe2O3NC) for the development of a molecular sensor with enhanced electrocatalytic and colorimetric (naked eye) detection of autoantibodies. The results showed that Au-NPFe2O3NC exhibits enhanced peroxidase-like activity toward the catalytic oxidation of 3,3,5,5-tertamethylbenzidine (TMB) in the presence of H2O2 at room temperature (25 °C) and follows the typical Michaelis-Menten kinetics. The autoantibody sensor based on this intrinsic property of Au-NPFe2O3NC resulted in excellent detection sensitivity [limit of detection (LOD) = 0.08 U/mL] and reproducibility [percent relative standard deviation (% RSD) = <5% for n = 3] for analyzing p53-specific autoantibodies using electrochemical and colorimetric (naked eye) readouts. The clinical applicability of the sensor has been tested in detecting p53-specific autoantibody in plasma obtained from patients with epithelial ovarian cancer high-grade serous subtype (EOCHGS, number of samples = 2) and controls (benign, number of samples = 2). As Au-NPFe2O3NC possess high peroxidase-like activity for the oxidation of TMB in the presence of H2O2 [TMB is a common chromogenic substrate for HRP in enzyme-linked immunosorbent assays (ELISAs)], we envisage that our assay could find a wide range of application in developing ELISA-based sensing approaches in the fields of medicine (i.e., detection of other biomarkers the same as p53 autoantibody), biotechnology, and environmental sciences.

Gold-loaded nanoporous ferric oxide nanocubes for electrocatalytic detection of microRNA at attomolar level

A crucial issue in microRNA (miRNA) detection is the lack of sensitive method capable of detecting the low levels of miRNA in RNA samples. Herein, we present a sensitive and specific method for the electrocatalytic detection of miR-107 using gold-loaded nanoporous superparamagnetic iron oxide nanocubes (Au-NPFe2O3NC). The target miRNA was directly adsorbed onto the gold surfaces of Au-NPFe2O3NC via gold-RNA affinity interaction. The electrocatalytic activity of Au-NPFe2O3NC was then used for the reduction of ruthenium hexaammine(III) chloride (RuHex, [Ru(NH3)6]3+) bound with target miRNA. The catalytic signal was further amplified by using the ferri/ferrocyanide [Fe(CN)6]3-/4- system. These multiple signal enhancement steps enable our assay to achieve the detection limit of 100aM which is several orders of magnitudes better than most of the conventional miRNA sensors. The method was also successfully applied to detect miR-107 from cancer cell lines and a panel of tissue samples derived from patients with oesophageal squamous cell carcinoma with excellent reproducibility (% RSD = < 5%, for n = 3) and high specificity. The analytical accuracy of the method was validated with a standard RT-qPCR method. We believe that our method has the high translational potential for screening miRNAs in clinical samples.

Enhanced Charge Collection in MOF-525–PEDOT Nanotube Composites Enable Highly Sensitive Biosensing

Abstract With the aim of a reliable biosensing exhibiting enhanced sensitivity and selectivity, this study demonstrates a dopamine (DA) sensor composed of conductive poly(3,4‐ethylenedioxythiophene) nanotubes (PEDOT NTs) conformally coated with porphyrin‐based metal–organic framework nanocrystals (MOF‐525). The MOF‐525 serves as an electrocatalytic surface, while the PEDOT NTs act as a charge collector to rapidly transport the electron from MOF nanocrystals. Bundles of these particles form a conductive interpenetrating network film that together: (i) improves charge transport pathways between the MOF‐525 regions and (ii) increases the electrochemical active sites of the film. The electrocatalytic response is measured by cyclic voltammetry and differential pulse voltammetry techniques, where the linear concentration range of DA detection is estimated to be 2 × 10−6–270 × 10−6 m and the detection limit is estimated to be 0.04 × 10−6 m with high selectivity toward DA. Additionally, a real‐time determination of DA released from living rat pheochromocytoma cells is realized. The combination of MOF5‐25 and PEDOT NTs creates a new generation of porous electrodes for highly efficient electrochemical biosensing.

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.

Prussian Blue-Derived Synthesis of Hollow Porous Iron Pyrite Nanoparticles as Platinum-Free Counter Electrodes for Highly Efficient Dye-Sensitized Solar Cells

Iron pyrite has long been an attractive material for environmental and energy applications, but is hampered by a lack of control over morphology and purity. Hollow porous iron pyrite nanoparticles were synthesized by a direct sulfurization of iron oxide derived from Prussian blue. The high efficiencies of these hollow porous iron pyrite nanoparticles as effective dye-sensitized solar cell counter electrodes were demonstrated, with an efficiency of 7.31u2009%.

Facile Synthesis of SnS2 Nanostructures with Different Morphologies for High-Performance Supercapacitor Applications

SnS2 is an emerging candidate for an electrode material because of the considerable interlayer spaces in its crystal structures and the large surface area. SnS2 as a photocatalyst and in lithium ion batteries has been reported. On the other hand, there are only a few reports of their supercapacitor applications. In this study, sheetlike SnS2 (SL-SnS2), flowerlike SnS2 (FL-SnS2), and ellipsoid-like SnS2 (EL-SnS2) were fabricated via a facile solvothermal route using different types of solvents. The results suggested that the FL-SnS2 exhibited better capacitive performance than the SL-SnS2 and EL-SnS2, which means that the morphology has a significant effect on the electrochemical reaction. The FL-SnS2 displayed higher supercapacitor performance with a high capacity of approximately ∼431.82 F/g at a current density of 1 A/g. The remarkable electrochemical performance of the FL-SnS2 could be attributed to the large specific surface area and better average pore size. These results suggest that a suitable solvent is appropriate for the large-scale construction of SnS2 with different morphologies and also has huge potential in the practical applications of high-performance supercapacitors.

Lignocellulosic biomass-derived, graphene sheet-like porous activated carbon for electrochemical supercapacitor and catechin sensing

We synthesize graphene sheet-like porous activated carbon (GPAC) with a high specific surface area by using Bougainvillea spectabilis as a precursor with the assistance of a facile and reliable chemical activation method. The as-synthesized GPAC materials were characterized with a variety of physico-chemical and analytical techniques to investigate their structural and porous properties. In addition, we apply the synthesized GPAC as an electrode material for supercapacitor and catechin sensing, and corresponding electrochemical studies were carried out using cyclic voltammetry, galvanostatic charge–discharge and differential pulse voltammetry. For supercapacitor application, the GPAC exhibits a specific capacitance of 233 F g−1 (at a current density of 1.6 A g−1) and an energy density of 7.2 W h kg−1 (for a symmetric cell). For the sensing application, the GPAC exhibits sensitive detection of catechin (CA). We achieved good sensitivity, an extensive linear range, and a low limit of detection for the CA sensor, with values of 7.2 μA μM−1 cm−2, 4–368 μM, and 0.67 μM, respectively. We further test the GPAC sensor in green tea leaves for real time CA detection. This work demonstrates the successful conversion of waste biomass to useful electrochemical devices.

Fabrication of Mesoporous Cu Films on Cu Foils and Their Applications to Dopamine Sensing

We previously succeeded to prepare stable mesoporous Cu films on Au-coated conductive working electrodes by using polystyrene-b-poly(oxyethylene) (PS63u2009000 -b-PEO26u2009000 ) micelles as template and sulfuric acid to increase ionic conductivity. In the present study, we report the preparation of mesoporous Cu films on Cu foil. By changing the Cu salts and electrodeposition potentials, we discuss how these parameters influence the final product. Without having to filtrate interefering species, such as uric acid, ascorbic acid and glucose, the dopamine concentration can be precisely determined by applying a suitable potential. Therefore, non-invasive electrochemical sensing based on mesoporous films will be useful for daily diagnosis of mental disorder.

Electronic structure and magnetic properties of rare-earth perovskite gallates from first principles

The density functional calculation is performed for centrosymmetric (La–Pm) GaO3 rare earth gallates, using a full potential linear augmented plane wave method with the LSDA and LSDA exchange correlation to treat highly correlated electrons due to the very localized 4f orbitals of rare earth elements, and explore the influence of U=0.478 Ry on the magnetic phase stability and the densities of states. LSDA calculation shows that the ferromagnetic (FM) state of RGaO3 is energetically more favorable than the anti-ferromagnetic (AFM) one, except for LaGaO3 where the NM state is the lowest in energy. The energy band gaps of RGaO3 are found to be in the range of 3.8–4.0 eV, indicating the semiconductor character with a large gap.