Saadat Majeed

Electrochemical cholesterol sensor based on carbon nanotube@molecularly imprinted polymer modified ceramic carbon electrode.

A monolithic molecular imprinting sensor based on ceramic carbon electrode (CCE) has been reported. The sensor can be renewed simply by smoothing. It was fabricated by thoroughly mixing multiwalled carbon nanotube@molecularly imprinted polymer (MWCNT@MIP), graphite powder, and silicon alkoxide, and then packing the resulting complex mixture of components firmly into the electrode cavity of a Teflon sleeve. The incorporated MWCNT@MIP in CCEs functioned as a recognition element for cholesterol determination. The MWCNT@MIP-CCEs were tested in the presence or absence of cholesterol by cyclic voltammetry and linear sweep voltammetry. The cholesterol sensor has excellent sensitivity with a linear range of 10-300nM and a detection limit of 1nM (S/N=3). The monolithic molecular imprinting sensor exhibits good stability, high sensitivity, and user-friendly reusability for cholesterol determination. This study shows that CCE is a promising matrix for MIP sensors.

An amperometric sensor for the determination of benzophenone in food packaging materials based on the electropolymerized molecularly imprinted poly-o-phenylenediamine film

Benzophenone is one of the most commonly used photoinitiators of UV-cured inks on food packaging materials and can migrate into foodstuffs. In this study, an amperometric benzophenone sensor based on molecularly imprinted polymer (MIP) was successfully constructed for the first time. The sensor was prepared by electropolymerizing o-phenylenediamine (o-PD) on a glassy carbon electrode (GCE) in the presence of template benzophenone, and then removing the template by immersing the poly-o-phenylenediamine film-modified GCE in ethanol. The molecularly imprinted sensor was tested in the presence or absence of benzophenone by cyclic voltammetry and linear sweep voltammetry to verify the changes in the redox peak currents of potassium ferricyanide. The sensor responded sensitively to benzophenone over a linear range of 0.05-5 μM with a detection limit of 10 nM. The imprinted sensor showed high recognition ability for benzophenone and was successfully applied to the determination of benzophenone in food packaging material samples.

Electrochemiluminescence Detection of TNT by Resonance Energy Transfer through the Formation of a TNT-Amine Complex

2,4,6-Trinitrotoluene (TNT) is a widely used nitroaromatic explosive with significant detrimental effects on the environment and human health. Its detection is of great importance. In this study, both electrochemiluminescence (ECL)-based detection of TNT through the formation of a TNT-amine complex and the detection of TNT through electrochemiluminescence resonance energy transfer (ECRET) are developed for the first time. 3-Aminopropyltriethoxysilane (APTES)-modified [Ru(phen)3](2+) (phen=1,10-phenanthroline)-doped silica nanoparticles (RuSiNPs) with uniform sizes of (73±3) nm were synthesized. TNT can interact with APTES-modified RuSiNPs through charge transfer from electron-rich amines in the RuSiNPs to the electron-deficient aromatic ring of TNT to form a red TNT-amine complex. The absorption spectrum of this complex overlaps with the ECL spectrum of the APTES-modified RuSiNPs/triethylamine system. As a result, ECL signals of the APTES-modified RuSiNPs/triethylamine system are turned off in the presence of TNT owing to resonance energy transfer from electrochemically excited RuSiNPs to the TNT-amine complex. This ECRET method has been successfully applied for the sensitive determination of TNT with a linear range from 1×10(-9) to 1×10(-6) M with a fast response time within 1 min. The limit of detection is 0.3 nM. The method exhibits good selectivity towards 2,4-dinitrotoluene, p-nitrotoluene, nitrobenzene, phenol, p-quinone, 8-hydroxyquinoline, p-phenylenediamine, K3[Fe(CN)6], Fe(3+), NO3(-), NO2(-), Cr(3+), Fe(2+), Pb(2+), SO3(2-), formaldehyde, oxalate, proline, and glycine.

Synthesis and electrochemical applications of nitrogen-doped carbon nanomaterials

Abstract Nitrogen doping is an effective way to tailor the properties of the shaped carbon materials, including the nanotubes, nanocups, nanofibers, as well as the nanorods, and render their potential use for various applications. The common bonding configurations obtained on the N insertion is the pyridinic N and pyrrolic N, which impart the characteristic properties to these carbon materials. This review will focus on the nitrogen-doped carbon materials, the doping effect on the electrochemistry of the doped nanomaterials, and the various synthetic methods to introduce N into the carbon network. The potential applications of the N-doped materials are also reviewed on the basis of the experimental and theoretical studies in electrochemistry.

Aqueous Synthesis of Tunable Highly Photoluminescent CdTe Quantum Dots Using Rongalite and Bioimaging Application

Abstract Rongalite is a cheap, strong and stable reducing agent with broad industrial applications. Herein we report novel method for the preparation of water-soluble and small-size CdTe quantum dots (QDs) using rongalite to produce Te 2− species in reaction medium for the first time. The synthesized QDs were characterized with transmission electron microscopy, spectroscopy, and confocal laser scanning microscopy. The influence of parameters such as the pH value of the precursor solution and the molar ratio of Cd 2+ to TGA and Cd 2+ to Te 2− on the quantum yields of CdTe QDs was systematically investigated. Under the optimal conditions at pH 11.6 and selecting thioglycolic acid as capping agent, the as-synthesized CdTe QDs possessed 66% quantum yield with narrow bandwidth of 24 nm. Moreover, methyl thiazolyl tetrazolium (MTT) assays were employed to evaluate the cytotoxicity of the as-prepared semiconductor nanocrystals on HeLa cell lines. Bioimaging studies showed that the as-synthesized QDs were quickly taken up by HeLa cells and did not have obvious damage to the cells within an incubation period of 24 h. The results show that Rongalite is a very promising agent for the synthesis of a variety of quantum dots and Rongalite-based QDs may find broad applications.

Synthesis, Designing and Analytical Applications of Nanostructured Ceria Based Materials

Cerium-based materials possess redox properties due to the presence of dual valence states of Ce3+ and Ce4+. In the last few years, the scientific community has paid much attention to designing and synthesizing cerium-based materials through advantageous routes for widespread catalytic and sensing applications in many fields. Cerium materials have been synthesized in many different forms, shapes and sizes. The catalytic and sensing capabilities of cerium nanostructures are highly dependent on their morphologies and can be improved significantly by modifying the sizes and shapes of the nanostructures to develop sensing scaffolds with improved sensing performance. These nanostructures provide a basis for applications in many fields. From a literature survey (2010 to 2015), it can be concluded that the fundamental morphologies, ratios, and capping of cerium nanostructures (CeNSs) constructively affect their properties and applications. Designed sensors utilizing CeNSs exhibit outstanding stability, high selectivity and eminent reproducibility in relation to time and temperature. This review will provide a perspective insight on the future trends in the design of different morphologies of CeNSs and their promising applications.