M. Kashif

Analysis of pork adulteration in commercial meatballs targeting porcine-specific mitochondrial cytochrome b gene by TaqMan probe real-time polymerase chain reaction

A test for assessing pork adulteration in meatballs, using TaqMan probe real-time polymerase chain reaction, was developed. The assay combined porcine-specific primers and TaqMan probe for the detection of a 109 bp fragment of porcine cytochrome b gene. Specificity test with 10 ng DNA of eleven different species yielded a threshold cycle (Ct) of 15.5 ± 0.20 for the pork and negative results for the others. Analysis of beef meatballs with spiked pork showed the assay can determine 100-0.01% contaminated pork with 102% PCR efficiency, high linear regression (r(2) = 0.994) and ≤ 6% relative errors. Residuals analysis revealed a high precision in all determinations. Random analysis of commercial meatballs from pork, beef, chicken, mutton and goat, yielded a Ct between 15.89 ± 0.16 and 16.37 ± 0.22 from pork meatballs and negative results from the others, showing the suitability of the assay to determine pork in commercial meatballs with a high accuracy and precision.

Nanobiosensor for detection and quantification of DNA sequences in degraded mixed meats

A novel class of nanobiosensor was developed by integrating a 27-nucleotide AluI fragment of swine cytochrome b (cytb) gene to a 3-nm diameter citrate-tannate coated gold nanoparticle (GNP). The biosensor detected 0.5% and 1% pork in raw and 2.5- h autoclaved pork-beef binary admixtures in a single step without any separation or washing. The hybridization kinetics of the hybrid sensor was studied with synthetic and AluI digested real pork targets from moderate to extreme target concentrations and a sigmoidal relationship was found. Using the kinetic curve, a convenient method for quantifying and counting target DNA copy number was developed. The accuracy of the method was over 90% and 80% for raw and autoclaved pork-beef binary admixtures in the range of 5-100% pork adulteration. The biosensor probe identified a target DNA sequence that was several-folds shorter than a typical PCR-template. This offered the detection and quantitation of potential targets in highly processed or degraded samples where PCR amplification was not possible due to template crisis. The assay was a viable alternative approach of qPCR for detecting, quantifying and counting copy number of shorter size DNA sequences to address a wide ranging biological problem in food industry, diagnostic laboratories and forensic medicine.

Effect of different seed solutions on the morphology and electrooptical properties of ZnO nanorods

The morphology and electrooptical properties of ZnO nanorods synthesized on monoethanolamine-based seed layer and KOH-based seed layer were compared. The seed solutions were prepared in monoethanolamine in 2-methoxyethanol and potassium hydroxide in methanol, respectively. Zinc acetate dihydrate was as a common precursor in both solutions. The nanorod-ZnOs were synthesized via the spin coating of two different seed solutions on silicon substrates followed by their hydrothermal growth. The scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), and Raman studies revealed that the ZnO nanorods obtained from monoethanolamine-based seed layer had fewer defects, better crystals, and better alignment than those realized via KOH-based seed layer. However, the current-voltage (I-V) characteristics demonstrated better conductivity of the ZnO nanorods obtained via KOH-based seed layer. The current measured in forward bias was 4mA and 40 µA for ZnO-nanorods grown on KOH-based seed layer and monoethanolamine-based with the turn on voltage of approximately 1.5 V and 2.5V, respectively, showing the feasibility of using both structures in optoelectric devices.

A potentiometric indirect uric acid sensor based on ZnO nanoflakes and immobilized uricase

In the present work zinc oxide nanoflakes (ZnO-NF) structures with a wall thickness around 50 to 100 nm were synthesized on a gold coated glass substrate using a low temperature hydrothermal method. The enzyme uricase was electrostatically immobilized in conjunction with Nafion membrane on the surface of well oriented ZnO-NFs, resulting in a sensitive, selective, stable and reproducible uric acid sensor. The electrochemical response of the ZnO-NF-based sensor vs. a Ag/AgCl reference electrode was found to be linear over a relatively wide logarithmic concentration range (500 nM to 1.5 mM). In addition, the ZnO-NF structures demonstrate vast surface area that allow high enzyme loading which results provided a higher sensitivity. The proposed ZnO-NF array-based sensor exhibited a high sensitivity of ∼66 mV/ decade in test electrolyte solutions of uric acid, with fast response time. The sensor response was unaffected by normal concentrations of common interferents such as ascorbic acid, glucose, and urea.

Impact of hydrogen concentrations on the impedance spectroscopic behavior of Pd-sensitized ZnO nanorods

ZnO nanorods were synthesized using a low-cost sol-gel spin coating technique. The synthesized nanorods were consisted of hexagonal phase having c-axis orientation. SEM images reflected perpendicular ZnO nanorods forming bridging network in some areas. The impact of different hydrogen concentrations on the Pd-sensitized ZnO nanorods was investigated using an impedance spectroscopy (IS). The grain boundary resistance (Rgb) significantly contributed to the sensing properties of hydrogen gas. The boundary resistance was decreased from 11.95 to 3.765 kΩ when the hydrogen concentration was increased from 40 to 360 ppm. IS gain curve showed a gain of 6.5 for 360 ppm of hydrogen at room temperature. Nyquist plot showed reduction in real part of impedance at low frequencies on exposure to different concentrations of hydrogen. Circuit equivalency was investigated by placing capacitors and resistors to identify the conduction mechanism according to complex impedance Nyquist plot. Variations in nanorod resistance and capacitance in response to the introduction of various concentrations of hydrogen gas were obtained from the alternating current impedance spectra.

Morphological, Structural, and Electrical Characterization of Sol-Gel-Synthesized ZnO Nanorods

ZnO nanorods were grown on thermally oxidized p-type silicon substrate using sol-gel method. The SEM image revealed high-density, well-aligned, and perpendicular ZnO nanorods on the oxidized silicon substrate. The XRD profile confirmed the c-axis orientation of the nanorods. PL measurements showed the synthesized ZnO nanorods have strong ultraviolet (UV) emission. The electrical characterization was performed using interdigitated silver electrodes to investigate the stability in the current flow of the fabricated device under different ultraviolet (UV) exposure times. It was notified that a stable current flow was observed after 60 min of UV exposure. The determination of stable current flow after UV exposure is necessary for UV-based gas sensing and optoelectronic devices.

Fabrication and characterization of ZnO thin films by sol-gel spin coating method for the determination of phosphate buffer saline concentration

The fabrication, characterization and application of nanostructured zinc oxide (ZnO) thin films on interdigitated silver elec- trodes were described for the determination of phosphate buffer saline (PBS) concentration. The ZnO thin films were synthesized on a silicon dioxide wafer using a sol-gel spin coating technique. Two different seed solutions were prepared by dissolving Zn-acetate dihy- drate in methanol and isopropanol in presence of a stabilizer, monoethanolamine. The field emission scanning electron microscope, atomic force microscope, X-ray diffractometer and Fourier transform infrared characterization revealed the presence of hexagonal ZnO nano-crystals in all thin films. However, the smaller sized and homogeneous ZnO nano-crystals were observed in isopropanol derived thin films. These thin films were used to discriminate the concentrations of different PBS solutions and the discriminatory signals were captured using a low-cost dielectric analyzer and a source meter. The frequency-capacitance curve reflected 2.85 fold increase in capaci- tance values when the sensor was exposed to 1000-fold diluted PBS in deionized water. A change in PBS concentration from 1000 fold to 10 fold increased the current flow from 6uF to 122uF. Thus the capacitance and current flow demonstrated a proportional relationship with the concentration of PBS, suggesting the application of the fabricated sensor in the determination and discrimination of chemical- species concentration in various solutions.

Structural and impedance spectroscopy study of Al-doped ZnO nanorods grown by sol-gel method

Purpose – The purpose of this paper is to investigate the electrical transport mechanism of the Al‐doped ZnO nanorods at different temperatures by employing impedance spectroscopy.Design/methodology/approach – Al‐doped ZnO nanorods were grown on silicon substrate using step sol‐gel method. For the seed solution preparation Zinc acetate dihydrate, 2‐methoxyethanol, monoethanolamine and aluminum nitrite nano‐hydrate were used as a solute, solvent, stabilizer and dopant, respectively. Prior to the deposition, P‐type Si (100) wafer was cut into pieces of 1 cm×2 cm. The samples were then cleaned in an ultrasonic bath with acetone, ethanol, and de‐ionized (DI) water for 5 min. The prepared seed solution was coated on silicon substrate using spin coater at spinning speed of 3000 rpm for 30 s and then dried at 250°C for 10 min followed by annealing at 550°C for 1 h. The hydrothermal growth was carried out in a solution of zinc nitrate hexahydrate (0.025M), Hexamethyltetramine (0.025M) in DI water.Findings – Al‐do...

Study of Zinc Oxide Films on SiO2/Si Substrate by Sol–Gel Spin Coating Method for pH Measurement

This In this work, zinc oxide film was deposited onto the SiO2/Si substrate with low-cost sol-gel spin coating method. Zinc oxide thin film was deposited on the silver interdigit elctrodes for the pH measurement. The surface morphology and microstructures of the deposited zinc oxide films were analyzed by field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). Whereas the crystallinity and structure of the zinc oxide films were determined by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The measurement at various pH values, which were ±1 above and below of the neutral pH had been conducted with a real time dielectric analyzer measurement. It was observed that the increase in pH would decrease the capacitance of the device.

Area-selective ZnO thin film deposition on variable microgap electrodes and their impact on UV sensing

ZnO thin films were deposited on patterned gold electrodes using the sol-gel spin coating technique. Conventional photolithography process was used to obtain the variable microgaps of 30 and 43 µm in butterfly topology by using zero-gap chrome mask. The structural, morphological, and electrical properties of the deposited thin films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and Keithley SourceMeter, respectively. The current-voltage (I-V) characterization was performed to investigate the effect of UV light on the fabricated devices. The ZnO fabricated sensors showed a photo to dark current (Iph/Id) ratios of 6.26 for 30 µm and 5.28 for 43µm gap electrodes spacing, respectively. Dynamic responses of both fabricated sensors were observed till 1V with good reproducibility. At the applied voltage of 1V, the response time was observed to be 4.817s and 3.704 s while the recovery time was observed to be 0.3738 s and 0.2891 s for 30 and 43 µmgaps, respectively. The signal detection at low operating voltages suggested that the fabricated sensors could be used for miniaturized devices with low power consumption.