Novel direct synthesis of mesoporous tin dioxide network intact up to 500°C

This project is supported by PAAET project no. BE-­‐13-­‐08 in collaboration with Kuwait University and the University of York. The support of the research administration of Kuwait University to the XPS instrument (Project No. GS02/08) is acknowledged.We present a direct soft templating method to synthesise mesoporous tin dioxide network that maintains a porous structure after calcination at 400 °C and 500 °C and has a relatively high BET surface area of 220 and 100 m2 g-1, respectively. TEM, BET and XRD results confirm that both crystal and pore sizes increase as a result of increasing the temperatures during the calcination step. This method is highly reproducible.PostprintPeer reviewe

Bioprospecting autochthonous marine microalgae strain from the Arabian Gulf Seawater, Kuwait for biofuel feedstocks

Bioprospecting programs are the key to increasing the current portfolio of indigenous microalgal strains accessible for different applications in microalgal biotechnology. In this work, nine fast-growing microalgal strains isolated from Kuwait's Arabian/Persian Gulf coastal waters were evaluated for their potential as biofuel feedstocks. 18S rRNA gene sequencing showed that the strains belong to five different genera: Chlorella, Nannochloris, Scenedesmus, Tetraselmis, and Nannochloropsis. In terms of the total lipid content, in comparison to the other strains, Tetraselmis sp. KUBS13G and Tetraselmis sp. KUBS16G displayed higher lipid contents of 29.56% dry weight (DW) and 26.13% DW, respectively, dominated by palmitic and oleic acids. Fuel properties calculated from the fatty acid methyl esters (FAMES) by empirical equations were compared with EN14214 (European) and ASTM D6751--02 (American) biodiesel standards. Multicriteria decision analysis (MCDA) methods, such as the Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE) and Graphical Analysis for Interactive Assistance (GALA), were used to select suitable microalgae for biofuel feedstock based on their biodiesel fuel properties. Overall, the results suggested that the indigenous microalgal strain Tetraselmis, particularly Tetraselmis sp. KUBS37G, and Scenedesmus sp. KUB Sl7R are the most suitable strains for biofuel feedstock owing to their improved fuel properties, such as density (rho) (0.88 g cm-3), low kinematic viscosity (3.1 mm2 s-1), high cetane number (54 and 56, respectively), high oxidation stability (14.6 hr and 14.8 hr), and cold filter plugging point (1.0 degrees C and -6.1 degrees C).info:eu-repo/semantics/publishedVersio

Nitrogen-enriched activated carbon derived from plant biomasses: a review on reaction mechanism and applications in wastewater treatment

As a key kind of evolving carbonaceous adsorbent, nitrogen-enriched activated carbon has drawn a lot of focus due to its better physiochemical ability to eliminate an extensive range of wastewaters contaminants under severe conditions. Its environment-friendly character is one more reason behind this focus. Nitrogen also has immense effect on activated carbon structures’ pollutants adsorption capability; therefore, it is an area of interest. Reports concerning the reaction pathway of C-N (carbon-nitrogen) bond creation on AC surface are limited. Determining such mechanisms is challenging but critical to understand bond characteristics after carbonization. Moreover, it is vital to ascertain real-time kinetics concerning adsorption phenomena in liquid phase. Such a latest trend indicates that regulated nitrogen uses for carbonaceous substances having a biomass-based origin can provide the desired morphological characteristics produced through interconnections, production of enclosed holes, enhanced surface area, better adsorption ability, and many other benefits in contrast to conventional carbon-based substances. This review points out the developments in the main processes to introduce nitrogen atoms into the carbon matrix by utilizing different N-comprising chemical compounds. The nitrogen enrichment processes, reaction mechanisms and effects of nitrogen incorporation on the plant biomass-derived activated carbons (NEACs) are presented in brief. On the basis of their established physicochemical attributes, the adsorption performances of different biomass-derived NEACs have also been dealt with. More significantly, the review covers the technical issues in the present phase, topical trends, research gaps, economic viability along with a technical alignment recommendation to address the prevailing disadvantages

Nanoparticles of antimony doped tin dioxide as a liquid petroleum gas sensor: effect of size on sensitivity

The gas sensitivity exhibited by nanoparticles of 1 wt% Pd catalysed antimony doped tin dioxide (ATO) prepared by a citrate-nitrate process is reported here. The reduction of particle size to 55% > 47%, for CNP > SP > CP samples having crystallite sizes of the order of 2.4 nm to 18 nm to 25 nm, respectively. The ATO nanoparticles exhibited not only a remarkable increase in gas sensitivity of around 98% towards 1000 ppm butane at 350 degrees C, but also a preferential selectivity to butane compared to other gases such as CO, CO(2), SO(2), CH(4) and H(2). In addition to the exceptionally high sensitivity and selectivity, the developed sensors also exhibited an improved response time and long term stability, which are of paramount importance for practical device development

Efficient one-pot synthesis of antimony-containing mesoporous tin dioxide nanostructures for gas-sensing applications

Currently, wide-bandgap metal oxide nanomaterials with attractive chemical and physical properties are intensively used for the fabrication of chemiresistive gas sensors and other catalytic devices. However, the low electrical conductance of sensors based on wide bandgap metal oxides is an issue that limits their application in small-scale systems to read out electrical signals and the manufacturing of portable sensing devices. In this regard, combining oxide nanostructures with other elements could be an effective strategy for enhancing their electrical and sensing performances. In this work, we attempted to improve the conductivity and sensitivity of porous tin dioxide to certain gases. Herein, we report a cost-effective and simple method for synthesizing antimony-containing mesoporous tin dioxide (Sb-SnO2) under ambient pressure and temperature. The X-ray diffraction, N2 sorption, transmission electron microscopy, energy-dispersive X-ray, and photoelectron spectroscopy analyses indicate that the prepared Sb-SnO2 material is a nanocrystalline powder with a large surface area. Meanwhile, the successful incorporation of Sb into the SnO2 framework results in increased electrical conductance by at least one order of magnitude or more compared to that of pure SnO2 and other doped SnO2 materials, respectively. The structure shows a very effective sensing response to volatile organic compounds and nitrogen dioxide. Hence, we developed an efficient method for synthesizing highly conductive oxide nanomaterials for use in chemical gas sensing devices

Enhanced gas sensing performance of tin dioxide-based nanoparticles for a wide range of concentrations of hydrogen gas

Nanocrystalline tin dioxide doped with antimony Sn(Sb)O-2 and catalyzed by 1 wt% palladium has been synthesized by a sonochemical process. On calcination at 600 degrees C, the as-precipitated powder produced 8-10 nm sized Sn(Sb)O-2 nanoparticles. The calcined powder characterized by X-ray diffraction, transmission electron microscopy, specific surface area and X-ray photoelectron spectroscopy was used for thick film sensor unit fabrication. The percentage response of the sensor was more than 78% at and above 200 degrees C for a wide range of concentrations of hydrogen gas. Most of the commercially available sensors are for low ppm values of hydrogen, whereas we were able to establish the response of our sensors for a wide range of concentrations of hydrogen gas from a concentration below 1/10 of the lower explosive limit of hydrogen (4%) in air to a concentration as high as 8% by volume. At 250 degrees C operating temperature, the sensor exhibited nearly 85.5% response towards 0.1% (1000 ppm) hydrogen and 94% response towards 8% hydrogen gas. The fabricated sensor also exhibited better selectivity towards hydrogen than towards other reducing gases like methane and butane. Our results demonstrated that 1% Pd loading has improved the sensor response, lowered the operating temperature and allowed detection of hydrogen in the concentration range of 0.1-8% even in an environment with a relative humidity as high as 88%

Inducing solid-state isolation of the phthalocyanine macrocycle by its incorporation within rigid, randomly shaped oligomers

The synthesis and properties of two non-planar and highly rigid pentamers containing four phthalocyanine units linked, via a spirocyclic fused ring system, to a central phthalocyanine or porphyrin core is described. It is shown that the rigidity of these novel oligomers, together with the large number of structural isomers of irregular shape induced by the presence of the four spiro-centres, inhibits efficient packing of the macrocycles in the solid state. Therefore, the UV–visible absorption spectrum of spin-coated films of these materials is almost identical to that obtained from the non-aggregated oligomers in dilute solution. Nitrogen adsorption measurements indicate a high surface area for one of the pentamers, which is consistent with some degree of microporosity

In-Situ Preparation of Aramid-Multiwalled CNT Nano-Composites: Morphology, Thermal Mechanical and Electric Properties

In this work in-situ polymerization technique has been used to chemically link the functionalized multiwalled carbon nanotubes (CNTs) with aramid matrix chains. Phenylene diamine monomers were reacted in the first stage with the carboxylic acid functionalized CNTs and then amidized in-situ using terephthaloyl chloride generating chemically bonded CNTs with the matrix. Various proportions of the CNTs were used to prepare the hybrid materials. The functionalization procedure was studied by Fourier transform infrared (FTIR) spectroscopy and composite morphology investigated by scanning electron microscopy (SEM). Thermal mechanical properties of these hybrids, together with those where pristine CNTs with similar loadings were used, are compared using tensile and dynamic mechanical analysis (DMA). The tensile strength and temperature involving α-relaxations on CNT loading increased with CNT loading in both systems, but much higher values, i.e., 267 MPa and 353 °C, respectively, were obtained in the chemically bonded system, which are related to the nature of the interface developed as observed in SE micrographs. The water absorption capacity of the films was significantly reduced from 6.2 to 1.45% in the presence pristine CNTs. The inclusion of pristine CNTs increased the electric conductivity of the aramid films with a minimum threshold value at the loading of 3.5 wt % of CNTs. Such mechanically strong and thermally stable aramid and easily processable composites can be suitable for various applications including high performance films, electromagnetic shielding and radar absorption