Nanotechnology contribute to significant impacts in every way in our daily life. Recently,
the application of nanotechnology in biosensors has been a trend in developing a highly
sensitive, selective, quick response, inexpensive, high volume production, great reliability
and miniaturized sensors. High demands on the production of rapid sensors for food safety
and quality control purposes are increasingly become the interest for researchers all over the
world. This is because, in food sector, the quality of a certain product is based on their periodic
chemical and microbilogical analysis. The uses of nanomaterials in biosensors are very
promising because they mediate current flow. Surface modification of the electrode based on
various nanomaterials including nanoparticle, nanofiber, nanowire and nanotube significantly
increase the performance of the biosensor. Ultimately, this implementation will enhance the
sensor’s sensitivity and stability. This review explores the previous research and development
work on nanomaterials-based sensors for food applications.
Template-assisted growth is an important nanoelectrochemical deposition technique for synthesizing one-dimensional (1-D) nanostructures with uniformly well-controlled shapes and sizes. A good template with well-defined dimensions is imperative for realizing this task. Porous anodic alumina (PAA) has been a favorable candidate for this purpose as it can be tailor-made with precise pore geometries, such as pore length and diameter as well as inter-pore distances, via the anodisation of pure aluminium. This paper reports the fabrication of PAA templates and electrochemical synthesis of functional nanostructures in the form of nanowires using PAA templates as scaffolds. Axial heterostructured and homogeneous nanowires formed by engineering materials configuration via composition and/or layer thickness variations were fabricated for different functionalities. X-ray diffraction and imaging techniques were used to elucidate the microstructures, morphologies and chemical compositions of the nanowires produced. Due to their large surface area-to-volume ratios, and therefore high sensitivities, these functional nanostructures have useful applications as critical components in nanosensor devices and various areas of nanotechnology. Potential applications include as hydrogen gas sensors in nuclear power plant for monitoring structural integrity of reactor components and containment building, as well as environmental monitoring of air pollution and leakages of toxic gases and chemicals.
One-dimensional nanostructure materials are very attractive because of their electronic and optical properties depending on their size. It is well known that properties of material can be tuned by reducing size to nanoscale because at the small sizes, that they behave differently with its bulk materials and the band gap will control by the size. The tunability of the band gap makes nanostructured materials useful for many applications. As one of the wide band gaps semiconductor compounds, zinc selenide (ZnSe) nanostructures (nanoparticles, nanowires, nanorods) have received much attention for the application in optoelectronic devices, such as blue laser diode, light emitting diodes, solar cells and IR optical windows. In this study, ZnSe nanostructures have been synthesized by reduction process of zinc selenate using hydrazine hydrate (N2H4.2H2O). The reductive agent of hydrazine hydrate was added to the starting materials of zinc selenate were heat treated at 500 o C for 1 hour under argon flow to form onedimensional nanostructures. The SEM and TEM images show the formation of nanocompositelike structures, which some small nanobars and nanopellets stick to the rod. The x-ray diffraction and elemental composition analysis confirm the formation of mixture zinc oxide and zinc selenide phases.
Diabetes is a metabolic disease with a prolonged elevated level of glucose in the blood leads to long-term complications and increases the chances for cardiovascular diseases. The present study describes the fabrication of a ZnO nanowire (NW)-modified interdigitated electrode (IDE) to monitor the level of blood glucose. A silver IDE was generated by wet etching-assisted conventional lithography, with a gap between adjacent electrodes of 98.80 μm. The ZnO-based thin films and NWs were amended by sol-gel and hydrothermal routes. High-quality crystalline and c-axis orientated ZnO thin films were observed by XRD analyses. The ZnO thin film was annealed for 1, 3 and 5 h, yielding a good-quality crystallite with sizes of 50, 100 and 110 nm, and the band gaps were measured as 3.26, 3.20 and 3.17 eV, respectively. Furthermore, a flower-modeled NW was obtained with the lowest diameter of 21 nm. Our designed ZnO NW-modified IDE was shown to have a detection limit as low as 0.03 mg/dL (correlation coefficient = 0.98952) of glucose with a low response time of 3 s, perform better than commercial glucose meter, suitable to instantly monitor the glucose level of diabetes patients. This study demonstrated the high performance of NW-mediated IDEs for glucose sensing as alternative to current glucose sensors.
This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA detection on indium tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using self-assembly monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance in electrochemical sensors. The hybridization of complementary DNA was monitored by differential pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides. The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of 9.0-178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to 8 times and its stability was up to 10 weeks at 4°C in silica gel.
There are no methods sensitive enough to detect enzymes within cells, without the use of analyte labeling. Here we show that it is possible to detect protein ion signals of three different H2S-synthesizing enzymes inside microglia after pretreatment with silver nanowires (AgNW) using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Protein fragment ions, including the fragment of amino acid (C4H8N+ = 70 amu), fragments of the sulfur-producing cystathionine-containing enzymes, and the Ag+ ion signal could be detected without the use of any labels; the cells were mapped using the C4H8N+ amino acid fragment. Scanning electron microscopy imaging and energy-dispersive X-ray chemical analysis showed that the AgNWs were inside the same cells imaged by TOF-SIMS and transformed chemically into crystalline Ag2S within cells in which the sulfur-producing proteins were detected. The presence of these sulfur-producing cystathionine-containing enzymes within the cells was confirmed by Western blots and confocal microscopy images of fluorescently labeled antibodies against the sulfur-producing enzymes. Label-free TOF-SIMS is very promising for the label-free identification of H2S-contributing enzymes and their cellular localization in biological systems. The technique could in the future be used to identify which of these enzymes are most contributory.