Ag nanostructures on a poly(3,4-ethylenedioxythiophene) film prepared with electrochemical route: A controllable roughened SERS substrate with high repeatability and stability

A simple, reliable and reproducible one-step electrochemical method for the preparation of surface-enhanced Raman-active polymer-mediated silver nanoparticles (Ag NPs) on planar indium tin oxide (ITO) coated glass substrates was reported. Poly(3,4-ethylenedioxythiophene) (PEDOT) film was used as a support material for dispersing nanostructured silver nanostructures on the surface homogeneously, since 3,4-ethylenedioxythiophene (EDOT) monomer polymerizes regioregularly. The optical properties and morphologies of the silver substrates have been investigated by ultraviolet-visible (UV-vis) spectroscopy and field emission scanning electron microscopy (FE-SEM). The UV-vis and FE-SEM results revealed that the Ag nanostructures separately appeared on the PEDOT coated ITO after reduction. The effect of the thickness of PEDOT polymer film, reduction potential of silver, the concentration of silver ion solution and the amount of silver particle on the polymer film on the SERS response were studied as well as repeatability and temporal stability of prepared substrates. Brilliant cresyl blue (BCB) has been used as Raman probes to evaluate the properties of the new SERS substrates. Signals collected over multiple spots within the same substrate resulted in a relative standard deviation (RSD) of 9.34%, while an RSD of 11.05% was measured in signals collected from different substrates. The SERS-active substrates were robust and stable which lost only 5.71% of initial intensity after 1 month

Nanoparticle embedded chitosan film for agglomeration free TEM images

Cetin, Demet/0000-0003-1186-4229; SULUDERE, ZEKIYE/0000-0002-1207-5814WOS: 000393956500001PubMed: 27739130Transmission electron microscopy (TEM) is a very useful and commonly used microscopy technique, used especially for the characterization of nanoparticles. However, the identification of the magnetic nanoparticle could be thought problematic in TEM analysis, due to the fact that the magnetic nanoparticles are usually form aggregates on the TEM grid to form bigger particles generating higher stability. This prevents to see exact shape and size of each nanoparticle. In order to overcome this problem, a simple process for the formation of well-dispersed nanoparticles was conducted, by covering chitosan film on the unmodified copper grid, it was said to result in aggregation-free TEM images. It is also important to fix the magnetic nanoparticles on the TEM grids, due to possible contamination of TEM filament which is operated under high vacuum conditions. The chitosan film matrix also helps to protect the TEM filament from contact with magnetic nanoparticles during the imaging process. The proposed procedure offers a quick method to fix the nanoparticles in a conventional copper TEM grid and chitosan matrix prevents agglomeration of nanoparticles, and thus getting TEM images showing well-dispersed individual nanoparticles.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [CA15114-114Z793]The work was supported by The Scientific and Technological Research Council of Turkey (TUBITAK) with the project number Cost CA15114-114Z793

Amperometric glucose sensor based on the glucose oxidase enzyme immobilized on graphite rod electrode modified with Fe3O4-CS-Au magnetic nanoparticles

Cetin, Demet/0000-0003-1186-4229WOS: 000450111000030In this report, an amperometric detection method for blood glucose level was developed benefiting from glucose oxidase (GO) enzyme immobilization on nanoparticle modified graphite rod (GR) electrode. Fe3O4-CS-Au magnetic nanoparticles were synthesized, characterized by TEM, UV-Vis, magnetometry, FTIR, and zeta potential measurements and used for the modification of GR electrode. This modified electrode was used for the detection of glucose level amperometrically at 0.6 V. The obtained calibration graph was linear in the range of 5-30mM glucose concentration with a coefficient of determination (R-2) 0.9971. The limit of detection (LOD) and limit of quantification (LOQ) values were calculated as 0.55 and 1.83mM, respectively. The modified GR electrode showed excellent selectivity in the presence of dopamine, ascorbic acid, and uric acid. The applicability of the developed method was examined in real blood samples by comparing the results obtained from commercial glucose sensor. This novel glucose detection method exhibited fast amperometric response, long storage time, and good selectivity

Multiplex enumeration ofEscherichia coliandSalmonella enteritidisin a passive capillary microfluidic chip

Multiplex detection and quantification of bacteria in water by using portable devices are particularly essential in low and middle-income countries where access to clean drinking water is limited. Addressing this crucial problem, we report a highly sensitive immunoassay sensor system utilizing the fluorescence technique with magnetic nanoparticles (MNPs) to separate target bacteria and two different types of quantum dots (CdTe and Ni doped CdTe QDs) incorporated into a passive microfluidic chip to transport and to form sandwich complexes for the detection of two target bacteria, namelyEscherichia coli(E. coli) andSalmonella enteritidis(S. enteritidis) in less than 60 min. The assay is carried out on a capillary driven microfluidic chip that can be operated by merely pipetting the samples and reagents, and fluorescence measurements are done by using a handheld fluorescence spectrophotometer, which renders the system portable. The linear range of the method was found to be 10(1)to 10(5)cfu mL(-1)for bothE. coliandS. enteritidis. The limit of detection (LOD) was calculated to be 5 and 3 cfu mL(-1)forE. coliandS. enteritidis, respectively. The selectivity of the method was examined by testingEnterobacter dissolvens(E. dissolvens) andStaphylococcus aureus(S. aureus) samples, and no significant interference was observed. The method was also demonstrated to detect bacteria in tap water and lake water samples spiked with target bacteria