Novel green-chemistry synthesis of silver nanoparticles (AgNPs) is introduced as a low-cost, rapid and easy-to-use analytical method for mercury ion detection. Aqueous fruit extract of water apple (Syzygium aqueum) was used for the first time as bioreductant to synthesize stable AgNPs. The prepared AgNPs have a yellowish-brown color with a surface plasmon resonance peak at 420 nm. The addition of Hg(II) ions then changes the AgNPs color to colorless. The color change was in proportion to the concentration of Hg(II) ions. The presence of other metal ions in the system was also evaluated. The proposed method shows good selectivity and sensitivity towards Hg(II) ions. Using UV-visible spectrophotometry, the detection limit of the developed method was 8.5 × 10-7 M. The proposed method has been successfully applied for determination of Hg(II) ions in tap and lake water samples with precision better than 5%.

The chromium (VI) and chromium (III) depositions on the gold nanoparticles (AuNPs)-modified glassy carbon electrode (GCE) from aqueous solutions were studied by means of cyclic voltammetry technique. The deposition processes were investigated at +25°C. The anodic and cathodic scannings were recorded within the potential range of -500 to 1500 mV. The scan rate and multiple cycling were carried out to examine the behavior of the electroactive species on the electrode surface. The logarithmic of the plot between Ip and V reflected a diffusion controlled by the irreversible redox reaction of Cr (III) and an adsorption-driven process. These results strongly suggested that the irreversible redox reaction of Cr (VI) was controlled by the diffusion step

We investigated graphene like material named reduced graphene oxide (RGO) as an electrode material by employed graphene oxide (GO). Thin film of GO was prepared on the indium thin oxide (ITO) substrate by spin-coating method using varied concentration of GO that dispersed in water. In order to remove its oxygen contained, GO film was thermally reduced at 200 0 C for 1 hour. We used cyclic voltammetry to measure its CV characteristic and estimated its specific capacitance. We obtained the highest specific capacitance of 6.53 mF g-1 that measured from 4 mg ml-1 RGO thin film at scan rate 25 mVs-1 .

Fast, sensitive, and easy-to-use methods for detecting DNA related to food adulteration, health, religious, and commercial purposes are evolving. In this research, a label-free electrochemical DNA biosensor method was developed for the detection of pork in processed meat samples. Gold electrodeposited screen-printed carbon electrodes (SPCEs) were used and characterized using SEM and cyclic voltammetry. A biotinylated probe DNA sequence of the Cyt b S. scrofa gene mtDNA used as a sensing element containing guanine substituted by inosine bases. The detection of probe-target DNA hybridization on the streptavidin-modified gold SPCE surface was carried out by the peak guanine oxidation of the target using differential pulse voltammetry (DPV). The optimum experimental conditions of data processing using the Box–Behnken design were obtained after 90 min of streptavidin incubation time, at the DNA probe concentration of 1.0 µg/mL, and after 5 min of probe-target DNA hybridization. The detection limit was 0.135 µg/mL, with a linearity range of 0.5–1.5 µg/mL. The resulting current response indicated that this detection method was selective against 5% pork DNA in a mixture of meat samples. This electrochemical biosensor method can be developed into a portable point-of-care detection method for the presence of pork or food adulterations.

Human epidermal growth factor receptor 2 (HER2) is a biomarker of breast cancer plays a major role in the proliferation of breast cancer cells. The determination of HER2 concentration is one of the ways of early detection of breast cancer. In this study we have developed a label free immunosensor for the detection of HER2 using an anti HER2-gold nanoparticles (GNP) bioconjugates. Anti HER2-GNP bioconjugates synthesized by adding anti HER2 on the GNPs that already reacted with APTMS and PEG-NHS-Maleimide. GNP-APTMS characterized using FTIR and cyclic voltammetry with a potassium ferrisianide system. The anti HER2-GNP bioconjugates immobilized on the screen printed carbon electrode-GNP (SPCE-GNP) surface with covalent bonding systems (amine coupling). The result of this study showed FTIR spectra that anti HER2-GNP bioconjugates successfully synthesized. The cyclic voltammograms of GNP-SPCE without and with anti HER2-GNP bioconjugates showed the increase of fericyanide redox pair peak current from 51.946 µA to 121.891 µA. The anti HER2 bioconjugates binds HER2 then the fericyanide peak current decreases in proportion with the addition of HER2. Optimal response of current signal was generated at concentration 5.0 µg/mL anti HER2 and the incubation time of anti HER2-GNP was 1 hour. Limit of detection of HER2 from developed immunosensor is 1.02 x 10⁻² ng/mL.