Graphene oxide and gold nanoparticle based dual platform with short DNA probe for the PCR free DNA biosensing using Surface Enhanced Raman Scattering (SERS)

Surface-enhanced Raman scattering (SERS) based DNA biosensors have considered as excellent, fast and ultrasensitive sensing technique which relies on the fingerprinting ability to produce molecule specific distinct spectra. Unlike conventional fluorescence based strategies SERS provides narrow spectral bandwidths, fluorescence quenching and multiplexing ability, and fitting attribute with short length probe DNA sequences. Herein, we report a novel and PCR free SERS based DNA detection strategy involving dual platforms and short DNA probes for the detection of endangered species, Malayan box turtle (MBT) (Cuora amboinensis). In this biosensing feature, the detection is based on the covalent linking of the two platforms involving graphene oxide-gold nanoparticles (GO-AuNPs) functionalized with capture probe 1 and gold nanoparticles (AuNPs) modified with capture probe 2 and Raman dye (Cy3) via hybridization with the corresponding target sequences. Coupling of the two platforms generates locally enhanced electromagnetic field ‘hot spot’, formed at the junctions and interstitial crevices of the nanostructures and consequently provide significant amplification of the SERS signal. Therefore, employing the two SERS active substrates and short-length probe DNA sequences, we have managed to improve the sensitivity of the biosensors to achieve a lowest limit of detection (LOD) as low as 10 fM. Furthermore, the fabricated biosensor exhibited sensitivity even for single nucleotide base-mismatch in the target DNA as well as showed excellent performance to discriminate closely related six non-target DNA sequences. Although the developed SERS biosensor would be an attractive platform for the authentication of MBT from diverse samples including forensic and/or archaeological specimens, it could have universal application for detecting gene specific biomarkers for many diseases including cancer

Mo3VOx catalyst in biomass conversion: A review in structural evolution and reaction pathways

Mo3VOx heterogeneous catalyst is among the complex metal oxides that have piqued recent interest due to its superior ýcatalytic properties. Its synthesis via sol gel or hydrothermal methods focused on the production of pentagonal polyoxomolybdate unit in the reaction precursor assembles with other V and Mo ions to form crystalline MoV oxides with pentagonal, hexagonal, and heptagonal units in either trigonal or orthorhombic phases. Moreover, the orthorhombic structure of Mo3VOx catalyst exhibited particularly high catalytic activity for selective oxidation of ethane, propane, and acrolein, whereby the reaction can take place not only in the mouth of heptagonal channels, but also in the entirety of the Mo3VO4 channel. Indeed, the Vanadyl groups with vanadium at the crystallographic positions are accountable for C–H activation of propane in the rate determining abstraction of the first H2 atoms. The molybdenum surface enrichment is detrimental with respect to the selectivity of the reaction. With that advantage, Mo3VOx has been applied as a catalyst for the acrolein oxidation to acrylic acid, selective oxidative activation of alkanes, ammoxidation of propane to acrylonitrile, or to acrylic acid, oxidation of n-butane to maleic acid or anhydride, oxidative of dehydrogenation of ethane to ethylene, or oxidation of ethane to acetic acid and partial oxidation of alcohols/aromatic hydrocarbon. Abundant metal components, such as Fe, W, Cu, Nb, and Te, have been used with the intention of optimizing the structure and catalytic performance, elucidating structural peculiarities, and improving catalytic performance

Modified iron oxide nanomaterials: Functionalization and application

Iron oxide magnetic nanoparticles have aroused the interest of researchers of materials' chemistry due to its exceptional properties such as decent magnetic, electric, catalytic, biocompatibility, and low toxicity. However, these magnetic nanoparticles are predisposed towards aggregation and forming larger particles, due to its strong anisotropic dipolar interactions, particularly in the aqueous phase, consequently depriving them of dispersibility and particular properties, ultimately degrading their performance. Hence, this review focuses on modified magnetic nanoparticles that are stable, easily synthesized, possess a high surface area and could be facile-separated via magnetic forces, and are of low toxicity and costs for applications such as catalyst/catalyst support, food security, biomedical, and pollutant remediation

Magnetite hybrid photocatalysis: Advance environmental remediation

One of the main public concerns is the aquatic habitat and its corresponding issues because of the incessant contamination of the ecological water systems. In recent years, research attention has been focused on processes that lead to an improved oxidative degradation of organic pollutants. Therefore, semiconductor photocatalysis technology has aroused scientists' interest in environmental remediation. Although several semiconductors have proven to be ideal candidates for the treatment of water pollution, the efficient separation and recycling of this finepowdered photocatalyst is still a scientific problem when applied in practice, including separation process, selectivity, and dispersion. A photocatalyst with magnetic properties allows the use of the technique of magnetic separation, which is one of the most effective and simple methods for removing suspended solids from wastewater without the need for further separation processes. The magnetic photocatalyst allows its use as a suspended material, providing the advantage to have a high surface area for reaction. This review highlights the advantages and disadvantages of current photocatalyst systems. Moreover, it focuses on hybrid magnetic photocatalysts, including metals and nonmetals, metal oxides, carbon-based materials, and ceramics

Controlled acid catalyzed sol gel for the synthesis of highly active TiO2-chitosan nanocomposite and its corresponding photocatalytic activity

For the synthesis of a highly active TiO2-chitosan nanocomposite, pH plays a crucial role towards controlling its morphology, size, crystallinity, thermal stability, and surface adsorption properties. The presence of chitosan (CS) biopolymer facilitates greater sustainability to the photoexcited electrons and holes on the catalysts’ surface. The variation of synthesis pH from 2 to 5 resulted in different physico-chemical and photocatalytic properties, whereby a pH of 3 resulted in TiO2-chitosan nanocomposite with the highest photocatalytic degradation (above 99 %) of methylene orange (MO) dye. This was attributed to the efficient surface absorption properties, high crystallinity, and the presence of reactive surfaces of –NH2 and –OH groups, which enhances the adsorption-photodegradation effect. The larger surface oxygen vacancies coupled with reduced electron-hole recombination further enhanced the photocatalytic activity. It is undeniable that the pH during synthesis is critical towards the development of the properties of the TiO2-chitosan nanocomposite for the enhancement of photocatalytic activity

A study on growth formation of nano-sized magnetite Fe3O4 via co-precipitation method

A simple and cost-effective chemical co-precipitation of aqueous ferrous and ferric salts was used to synthesis controlled size of magnetite iron oxide nanoparticles. The titration reactions between the aqueous Fe2+/Fe3+ salt solutions were controlled by an autotitrator unit with continuous addition of 1 M sodium hydroxide under different heating temperatures from 30 up to 80 degrees C in oxidising atmosphere. Then, further investigation on the degree of crystallinity of magnetite iron oxide nanoparticles was conducted by altering the concentration of Fe2+/Fe3+ ions in the ratio of 1:1, 1:1.25, 1:1.5 and 1:2. The resultant magnetite iron oxide nanoparticles were characterised by using X-ray diffraction, field emission scanning electron microscopy and Fourier transform infrared spectroscopy. The ratio of Fe2+/Fe3+ salt solutions and heating temperatures played a crucial role in controlling the morphology, crystallinity and particle sizes of magnetite magnetite iron oxide

Facile synthesis of magnetite iron oxide nanoparticles via precipitation method at different reaction temperatures

The nano-scale magnetite iron oxide particles have been synthesised by a facile precipitation method. Magnetite iron oxide nanoparticles were synthesised in a bath with electrolytes composed of 0·10 M of iron (II) chloride with 0·45 M of sodium hydroxide at different reaction temperatures under oxidising environment. In the present study, the influence of reaction temperatures (30, 45 and 80°C) on the morphology, particle size and crystallinity of the iron oxide particles were investigated in detail. Based on the Malvern Zetasizer analysis, the iron oxide particles with variable size from ∼250 to ∼70 nm could be achieved when increasing the reaction temperature up to 80°C. The magnetite phase of iron oxide particles was determined by using X-ray diffraction analysis. In addition, field emission scanning electron microscopy micrographs were further affirmed that our synthesised iron oxide particles were in nano-scale with a spherical shape. It was found that the high reaction temperature is helpful in controlling the formation of uniform magnetite iron oxide nanoparticles