Tahmineh Mahmoudi

Recent advances in nanowires-based field-effect transistors for biological sensor applications

Abstract Nanowires (NWs)-based field-effect transistors (FETs) have attracted considerable interest to develop innovative biosensors using NWs of different materials (i.e. semiconductors, polymers, etc.). NWs-based FETs provide significant advantages over the other bulk or non-NWs nanomaterials-based FETs. As the building blocks for FET-based biosensors, one-dimensional NWs offer excellent surface-to-volume ratio and are more suitable and sensitive for sensing applications. During the past decade, FET-based biosensors are smartly designed and used due to their great specificity, sensitivity, and high selectivity. Additionally, they have the advantage of low weight, low cost of mass production, small size and compatible with commercial planar processes for large-scale circuitry. In this respect, we summarize the recent advances of NWs-based FET biosensors for different biomolecule detection i.e. glucose, cholesterol, uric acid, urea, hormone, proteins, nucleotide, biomarkers, etc. A comparative sensing performance, present challenges, and future prospects of NWs-based FET biosensors are discussed in detail.

Highly Efficient Non-Enzymatic Glucose Sensor Based on CuO Modified Vertically-Grown ZnO Nanorods on Electrode

There is a major challenge to attach nanostructures on to the electrode surface while retaining their engineered morphology, high surface area, physiochemical features for promising sensing applications. In this study, we have grown vertically-aligned ZnO nanorods (NRs) on fluorine doped tin oxide (FTO) electrodes and decorated with CuO to achieve high-performance non-enzymatic glucose sensor. This unique CuO-ZnO NRs hybrid provides large surface area and an easy substrate penetrable structure facilitating enhanced electrochemical features towards glucose oxidation. As a result, fabricated electrodes exhibit high sensitivity (2961.7 μA mM−1 cm−2), linear range up to 8.45 mM, low limit of detection (0.40 μM), and short response time (<2 s), along with excellent reproducibility, repeatability, stability, selectivity, and applicability for glucose detection in human serum samples. Circumventing, the outstanding performance originating from CuO modified ZnO NRs acts as an efficient electrocatalyst for glucose detection and as well, provides new prospects to biomolecules detecting device fabrication.

Evaluation of relaxation spectra of linear, short, and long-chain branched polyethylenes

The frequency dependent rheological data of several different linear, short- and long-chain branched metallocene catalyzed polyethylenes are assessed with respect to the relaxation spectra. For linear mLLDPEs with Mw/Mn≈ 2, a “master spectrum” is established by normalizing on the molar mass. For samples with a distinctly different molar mass distribution, deviations from the “master spectrum” can be observed. It is also demonstrated how the long-chain branches in polyethylenes of different structure influence the spectrum. Depending on the length of branches in long chain branched materials, it is shown that an increasing in the degree of long-chain branching can be clearly observed in the slow relaxation modes, while the fast ones are only affected by high degrees of long-chain branching.

Fabrication of sensitive non-enzymatic nitrite sensor using silver-reduced graphene oxide nanocomposite

There are increasing demands of more sensitive sensors for monitoring potential hazards in real water that may cause serious problems to human health. Herein, we report the development of a non-enzymatic nitrite sensor using nanocomposite of reduced graphene oxide decorated with silver nanoparticle (Ag-rGO). First, Ag-rGO nanocomposite was synthesized using a facile and cost-effective microwave-assisted approach. Then, as-synthesized Ag-rGO nanocomposite was used to modify glassy carbon electrode (GCE) and applied for the sensitive and selective detection of nitrite in the aqueous medium with increasing concentration of nitrite. Under optimized conditions, sensor achieved high sensitive response (18.4 μA/μM·cm2) in a wide linear range (0.1-120 μM), low limit of detection (∼0.012 μM), and good selectivity using differential pulse voltammograms (DPV). The applicability of fabricated non-enzymatic nitrite sensor was checked in real sample with satisfactory results.

Fabrication of a solution-gated transistor based on valinomycin modified iron oxide nanoparticles decorated zinc oxide nanorods for potassium detection

There are considerable interests to detect and monitor the abnormal level of minerals in water for avoiding/preventing any toxic effects after consumption. Herein, we report the fabrication of solution-gated field-effect-transistor (FET) based potassium sensor using iron oxide nanoparticles (Fe2O3 NPs) modified directly grown zinc oxide nanorods (ZnO NRs). The Fe2O3 NPs modification of ZnO NRs provided stability to nanorods surface and improved surface area for valinomycin immobilization. As-fabricated potassium sensor (valinomycin-Fe2O3 NPs-ZnO NRs/SiO2/Si) provided enhanced current response with increasing potassium concentration. During sensing measurements, FET sensor showed high sensitivity (4.65 μA/μM/cm2) in the linear range of 0.1 μM to 125 μM, low limit of detection (∼0.04 μM), good stability, excellent reproducibility, and favorable selectivity. Thus, good sensing performance of the FET based potassium sensor presents it as simple, low-cost, and convenient device for selective detection of potassium in solution.