Mohamad Amran Mohd Salleh

Investigations on the development of the permeability properties of binary blended concrete with nano-SiO2 particles

Water permeability of cement-based concrete has been recognized as a critical intrinsic property highly affecting the durability of reinforced concrete. An experimental study was done, designed to examine the water permeability and setting time of Portland cement mortar with nano-SiO2 admixed at 0.5, 1, 1.5, and 2 wt% of cement. The percentage, velocity, and coefficient of water absorption tests results showed that the incorporation of nano-SiO2 particles improved the water penetration resistance of the binary-blended concrete. Such improvements were especially significant when using 2 wt% of nano-SiO2. The experimental results revealed that the admixing of nano-SiO2 particles not only led to denser cement mortar but also changed the morphology of cement hydration products. Mechanisms were proposed to explain the physicochemical changes induced by the nano-SiO2 particles and the specific surface area of them is demonstrated as one of the key factors. Considering the higher strength and durability is promising their use in binary-blended concrete.

Effect of short carbon fiber surface treatment on composite properties

The effects of whiskerized carbon fibers (WCF) embedded as filler into polymer matrix were investigated. In this respect, composites consisting of pure polypropylene and also carbon fiber (CF)/polypropylene (PP) was fabricated and compared. Polypropylene matrix was reinforced with 2% concentration of WCF and prepared by a melt-mixing method. The tensile test indicated that the addition of 2% WCF enhanced the tensile strength and Young’s modulus by 38.1% and 28.2%, respectively. Besides that, the elongation was decreased for that sample. Dynamic mechanical analysis showed an increase of 39.2% in the stiffness of the WCF/PP composite and an improvement in the storage modulus. The tan δ for the sample was also smaller than unfilled PP and CF/PP composites. Furthermore, thermogravimetric analyses in an inert atmosphere showed a shift of temperature to the higher temperature with the addition of fillers.

A review on emerging diagnostic assay for viral detection: the case of avian influenza virus

Biotechnology-based detection systems and sensors are in use for a wide range of applications in biomedicine, including the diagnostics of viral pathogens. In this review, emerging detection systems and their applicability for diagnostics of viruses, exemplified by the case of avian influenza virus, are discussed. In particular, nano-diagnostic assays presently under development or available as prototype and their potentials for sensitive and rapid virus detection are highlighted.

Development of sandwich-form biosensor to detect Mycobacterium tuberculosis complex in clinical sputum specimens

Mycobacterium tuberculosis, the causing agent of tuberculosis, comes second only after HIV on the list of infectious agents slaughtering many worldwide. Due to the limitations behind the conventional detection methods, it is therefore critical to develop new sensitive sensing systems capable of quick detection of the infectious agent. In the present study, the surface modified cadmium-telluride quantum dots and gold nanoparticles conjunct with two specific oligonucleotides against early secretory antigenic target 6 were used to develop a sandwich-form fluorescence resonance energy transfer-based biosensor to detect M. tuberculosis complex and differentiate M. tuberculosis and M. bovis Bacille Calmette-Guerin simultaneously. The sensitivity and specificity of the newly developed biosensor were 94.2% and 86.6%, respectively, while the sensitivity and specificity of polymerase chain reaction and nested polymerase chain reaction were considerably lower, 74.2%, 73.3% and 82.8%, 80%, respectively. The detection limits of the sandwich-form fluorescence resonance energy transfer-based biosensor were far lower (10 fg) than those of the polymerase chain reaction and nested polymerase chain reaction (100 fg). Although the cost of the developed nanobiosensor was slightly higher than those of the polymerase chain reaction-based techniques, its unique advantages in terms of turnaround time, higher sensitivity and specificity, as well as a 10-fold lower detection limit would clearly recommend this test as a more appropriate and cost-effective tool for large scale operations.

Effects of the surface modification of carbon fiber by growing different types of carbon nanomaterials on the mechanical and thermal properties of polypropylene

The potential usage of different types of carbon nanoparticles in the herringbone, tubular and sheet structures of graphene plates, such as carbon nanofibers (CNF), carbon nanotubes (CNT) and graphene (G) flakes and also CNF–G and CNT–G on the carbon fiber (CF) surface as fillers in composite materials, is discussed in this paper. The combination of 2D graphene of high charge density and 1D CNTs or CNFs of large surface areas generates a versatile 3D hybrid network with synergic properties. A one-step process, chemical vapour deposition technique has been applied to synthesis these carbon nanoparticles (1D, 2D and 3D structures) by use of bimetallic catalyst (Ni/Cu). The morphology and chemical structure of the fibers, which have an effect on the polymer properties, were characterized by means of scanning electron microscopy, transmission electron microscopy, and specially Raman spectroscopy. These techniques were used to identify carbon nanoparticles, access their dispersion in polymers, evaluate filler/matrix interactions and detect polymer phase transitions. Compared with the neat CFs, the synthesized hybrid fibers led to an increase of the BET surface area from 0.7 m2 g−1 to 46 m2 g−1. Besides that, polypropylene (PP) composites with different carbon-based fillers, such as G on CF (CF–G), CNF on CF (CF–CNF), CNT on CF (CF–CNT) and also CF–CNF–G and CF–CNT–G were prepared by the melt mixed method, and the effects of these particles on the mechanical and thermal properties were analyzed. The mechanical results were confirmed by a mathematical model that state the mechanical reinforcement of the resultant composites strongly depends on the type of filler used. Noteworthy, composites based on combination of G and CNT presented the highest mechanical and thermal properties than those based on other carbon nanoparticles.

Effect of growing graphene flakes on branched carbon nanofibers based on carbon fiber on mechanical and thermal properties of polypropylene

A one-step process, the chemical vapor deposition method, has been used to fabricate graphene flakes (G) on branched carbon nanofibers (CNF) grown on carbon fibers (CF). In this contribution, the G–CNF–CF fibers have been used as reinforcing fillers in a polypropylene (PP) matrix in order to improve the mechanical and thermal properties of the PP. A bimetallic catalyst (Ni/Cu) was deposited on a CF surface to synthesize branched CNF using C2H2/H2 precursors at 600 °C followed by growing G flakes at 1050 °C. The morphology and chemical structure of the G–CNF–CF fibers were characterized by means of electron microscopy, transmission electron microscopy, and Raman spectroscopy. The mechanical and thermal behaviors of the synthesized G–CNF–CF/PP composite were characterized by means of tensile tests and thermal gravimetric analysis. Mechanical measurements revealed that the tensile stress and Youngs modulus of the G–CNF–CF/PP composites were higher than the neat PP with the contribution of 76%, 73%, respectively. Also, the thermal stability of the resultant composite increased about 100 °C. The measured reinforcement properties of the fibers were fitted with a mathematical model obtaining good agreement between the experimental results and analytical solutions.

Particle size effect on the permeability properties of nano-SiO2 blended Portland cement concrete

In this study, nano-SiO2 has been used as a high reactive pozzolan to develop the microstructure of the interfacial transition zone between the cement paste and the aggregate. Mechanical tests of blended cement-based concretes exposed that in addition of the pozzolanic reactivity of nano-SiO2 (chemical aspect), its particle grading (physical aspect) also revealed considerable influences on the blending effectiveness. It was concluded that the relative permeability reduction (relative to the control concrete made with plain cement) is higher for coarser nano-SiO2 after 90 days of moisture curing. However, finer nano-SiO2 particles showed better effects in early ages. These phenomena can be due to the free spacing between mixture particles that was associated with the global permeability of the blended cement-based concretes. This article presents the results of the effects of particle size ranges involved in nano-SiO2 blended Portland cement on the water permeability of concrete. It is revealed that the favorable results for coarser nano-SiO2 reflect enhanced particle packing formation accompanied by a reduction in porosity and particularly in particle spacing after 90 days.

Bulk Production of High-Purity Carbon Nanosphere by Combination of Chemical Vapor Deposition Methods

A simple method to produce pure carbon nanosphere (CNS) in high yield using continuous chemical vapor deposition (CVD) technique (combination of floating catalyst CVD and fluidized bed CVD) is proposed. Carbon fiber substrate, acetylene precursor, and Fe catalyst are employed to produce CNS. X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectrometry confirm the formation of a high percentage of hexagonal carbon. The scanning electron microscopy images reveal spheres that confirm uniform structures. Thermal gravimetric analysis implies that the CNS are free from the carbon fiber substrate as they start to decompose at a lower temperature compared to that of carbon fiber substrate. Under the optimal conditions of 700°C in ambient pressure at 60 min of reaction time and 300 mL/min of acetylene flow rate, CNS with an average diameter of less than 200 nm, 98% purity and yield of 3.07 mg/mg is obtained.

Influence of 15 and 80 nano-SiO2 particles addition on mechanical and physical properties of ternary blended concrete incorporating rice husk ash

This study demonstrates the effects of SiO2 nanoparticles as additives with two different sizes of 15 and 80 nm on compressive strength and porosity of rice husk ash (RHA) blended concrete. Up to 20% of ordinary Portland cement (OPC) was replaced by RHA with average particle size of 5 micron. Also, SiO2 nanoparticles were added to the above mixture at four different weight percentages of 0.5, 1.0, 1.5 and 2.0 and cured in lime solution. The results indicated that compressive strength of Portland cement–nano SiO2–rice husk ash (PC–NS–RHA) ternary blended concrete was considerably increased. Moreover, the total amount of porosity decreased to a minimum with respect to the control concrete. This improvement was observed at all the curing ages and replacement levels, but there was a gain in the optimal point with 20% of RHA plus 2% of 80 nm SiO2 particles at 90 days of curing.

Fluorometric immunoassay for detecting the plant virus Citrus tristeza using carbon nanoparticles acting as quenchers and antibodies labeled with CdTe quantum dots

AbstractCadmium-telluride quantum dots (QDs) were conjugated to an antibody (Ab) against Citrus tristeza virus (CTV), while the coat protein (CP) of the CTV was immobilized on the surface of carbon nanoparticles (CNPs). Following immunobinding of the QD-Ab and the CP-loaded CNPs, the fluorescence of the CdTe QDs was quenched by the CNPs. This effect was exploited to design a detection assay for the CTV which was found more sensitive and specific than the existing enzyme linked immunosorbent assay (ELISA). The limit of detection was measured at about 220 ng⋅ mL‾1 of CTV. The Stern-Volmer plot of the CNPs-QD quencher pair showed a positive deviation from linearity which was ascribed to the presence of both static and dynamic quenching. Graphical abstractCadmium-telluride quantum dots (QDs) were conjugated to an antibody (Ab) against Citrus tristeza virus (CTV), while the coat protein (CP) of the CTV was immobilized on the surface of carbon nanoparticles (CNPs). Following immunobinding of the QD-Ab and the CP-loaded CNPs, the fluorescence of the CdTe QDs was quenched by the CNPs. This effect was exploited to design a detection assay for the CTV which was found more sensitive and specific than the existing enzyme linked immunosorbent assay (ELISA).